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Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis
Journal of Cleaner Production xxx (xxxx) xxx
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Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis Teng Wang a, b, Yuchi Chen c, Jinping Li a, b, Yongjie Xue d, Jingxin Liu a, b, Meng Mei a, b, Haobo Hou c, Si Chen a, b, c, * a
School of Environmental Engineering, Wuhan Textile University, Wuhan, 430073, China Engineering Research Centre for Clean Production of Textile Dyeing and Printing, Ministry of Education, Wuhan Textile University, Wuhan, 430073, China School of Resource and Environment Science, Wuhan University, 430070, Hubei, Wuhan, China d State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, 430070, Hubei, Wuhan, China b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 August 2019 Received in revised form 23 October 2019 Accepted 3 December 2019 Available online xxx
Co-pyrolysis sewage sludge (SS) and rice husk (RH) is a promising method for reusing the waste. In this study, thermogravimetry and mass spectrometry (TG-MS) were used to investigate the thermal degradation behavior and the evolution of gaseous species during co-pyrolysis. The interactions of SS and RH on gas and biochar products were explored. The results reveal that the introduction of RH can improve the pyrolysis reactivity and CO2 production of SS, but reduce the cumulation of H2, CH4 and C2H2. The interaction inhabited the main gases generation, while promoted carbonization and aromatization of the corresponding biochar, especially under 30%RH addition. The addition of RH can lead to pore development and a sharp improvement in specific surface area under high dose. Overall, co-pyrolysis of RH and SS captures more gaseous hydrocarbons and provides biochar with remarkable adsorption potential. © 2019 Elsevier Ltd. All rights reserved.
Handling editor: Jin-Kuk Kim Keywords: Sewage sludge Rice husk Co-pyrolysis Synergistic effect Gas emissions Biochar
1. Introduction Recently, sewage sludge (SS), a complex by-product produced in the wastewater treatment process, exceeds 60 million tons in China. SS contains not only many organic substances of renewable energy, but also harmful substances, such as heavy metals, toxic organic substances and pathogenic microorganisms (Huang and Yuan, 2016). Thus, the environmental and economical disposal of SS has attracted more and more attention (Zhu et al., 2018). The main methods used to treat SS include landfill, agricultural utilization, and thermochemical conversion (Soria-Verdugo et al., 2017). Statistics (Arlabosse et al., 2014) show that 40%e50% of SS from the European Union and the United States is used for agriculture. Only 14% and 17% of the total produced quantity of SS with strict rules and instructions was allowed to landfill. About 27% and
* Corresponding author. School of Environmental Engineering, Wuhan Textile University, Wuhan, 430073, China. E-mail address: [email protected] (S. Chen).
22% of SS was treated by thermal treatment (Bennamoun et al., 2013). Among these technologies, pyrolysis is considered a promising method for sludge valorization due to volume minimization, zero-waste conversion and energy/multipurpose materials recovmez et al., 2017; Tang et al., 2018). However, the monoery (Go pyrolysis of SS still faces serious drawbacks, such as high ash content, low energy efficiency, pyrolysis reactor instability and low value-added products. In contrast, biomass is a renewable and clean resource that can be made into high-quality pyrolysis products due to its high volatility and low ash content (Deng et al., 2017). Rice husk (RH) is one of the major sources of biomass, and the RH production in China exceeds 40 million tons per year (Pode, 2016). Such a large amount of RH also needs urgent treatment, otherwise it will cause serious environmental hazards (Khan et al., 2009). Therefore, the copyrolysis of SS and RH may be an effective method for disposing such large scale solid waste, improving energy utilization and the quality of pyrolysis products. Studies have tried to investigate the co-pyrolysis process of sludge and RH. Lin et al. (2018) found that co-pyrolysis of oil sludge and RH improved the quality of oil
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Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
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Abbreviations TG-MS SS RH 20RH 30RH 40RH VM FC H/C O/C SSC 20RHC 30RHC 40RHC CPI Ti Tf
thermogravimetric mass spectrometry sewage sludge rice husk mixture of 20% rice husk þ80% sewage sludge mixture of 30% rice husk þ70% sewage sludge mixture of 40% rice husk þ60% sewage sludge volatile matter fixed carbon the molar ratio of H and C the molar ratio of O and C the biochar produced from sewage sludge the biochar produced from mixture of 20% rice husk þ80% sewage sludge the biochar produced from mixture of 30% rice husk þ70% sewage sludge the biochar produced from mixture of 40% rice husk þ60% sewage sludge comprehensive pyrolysis index ignition temperature Burnout temperature
product and promoted the formation of H2, CO and C1eC2 hydrocarbons. Zhang et al. (2015) revealed a remarkable synergetic effect on gas production. Naqvi et al. (2019) provided in-depth studies of kinetics and thermodynamics of co-pyrolysis of SS and RH, indicating that the interactions facilitated the recovery of organic materials. These studies have focused on the effects of RH on gas or tar generation and the interactions of thermal decomposition. In our previous study (Chen et al., 2019), the feasibility of biochar derived from co-pyrolysis of SS and RH as adsorbent was preliminarily verified. However, in-situ monitoring of gas product evolution was unnoticed during the co-pyrolysis of SS and RH, and no literature has explained the impact of synergistic effects on gas generation. In addition, the synergistic effects on the characteristics of biochar derived from co-pyrolysis of SS and RH are currently unknown. Therefore, this study used thermogravimetric analysis coupled with mass spectrometry (TG-MS) method to simultaneously investigate the effects of RH on the thermal decomposition and the gaseous product evolution during pyrolysis of SS. Furthermore, the effects of the interactions between SS and RH on the properties of multiphase products (gas and biochar) were investigated. 2. Materials and methods
Table 1 Proximate analysis data for raw materials.
RH SS a
Proximate analysis (%)
Ultimate analysis (%)
Atomic Ratio
Ash
VM
FC
C
H
N
Oa
H/C
O/C
15.09 70.06
70.98 29.08
13.94 0.86
41.43 12.68
5.72 1.38
0.69 1.85
37.07 14.03
1.66 1.31
0.67 0.83
Calculated by O ¼ 100-Ash-C-H-N.
Tan et al., 2014). Interestingly, although SS has less hydrogen and oxygen contents, it has higher aromatic and hydrophilic (higher H/ C ¼ 1.31 and lower O/C ¼ 0.83). High aromaticity and hydrophilicity indicate the presence of more aromatic substances and reactive oxygen groups. (Tran et al., 2017).
2.2. Thermogravimetric analysis Pyrolysis of the individuals and the mixtures (SS and RH) was carried out in a TG-MS analyzer (STA 449-QMS 403, NETZSCH, Germany). During the pyrolysis process, approximately 10 ± 0.5 mg sample with particle size less than 0.075 mm was heated from room temperature to 1000 C at a heating rate of 20 C/min. Highpurity nitrogen (99.999%) was used as the carrier gas at a flow rate of 20 ml/min. Evolved gaseous products were monitored, including H2 (m/z ¼ 2), CH4 (m/z ¼ 16), C2H2 (m/z ¼ 26), CH2O (m/z ¼ 30), C3H6 (m/z ¼ 42), CO2 (m/z ¼ 44), HCOOH (m/z ¼ 46) and C4H10 (m/ z ¼ 58), according to the database of National Institute of Standards and Technology (NIST). The temperature section corresponding to different reactions could be segmented based on DTG and gas emission curves.
2.3. Interaction calculation Theoretical TG and gas emission curves of SS-RH mixtures were used to clarify the interactions between the individual components (Kai et al., 2019; Vamvuka et al., 2015). To investigate whether there is an interaction effect occurring in the co-pyrolysis of SS with RH, the theoretical values were calculated using Equation (1) according to weight losses and the cumulative gas amounts. The deviation levels (%) were calculated by Equation (2) and used to evaluate the degree of interaction (Huang et al., 2017b).
Ytheo ¼ x1 Y1 þ x2 Y2 Deviationð%Þ ¼
Ytheo Yexp Yexp
(1) 100
(2)
2.1. Materials RH and SS collected from Wuhan Hubei were used for the study. Details and pre-treatment procedures were shown in our previous research work (Wang et al., 2017a). In order to investigate the effect of biomass additives on thermal decomposition and gaseous product evolution during co-pyrolysis process, RH was mixed with SS in a ratio of 20e40%. The sample was named according to the proportion of RH, for example, 20RH refers to the mixture of 20 wt% RH and 80 wt% SS. To ensure proper mixing, the mixtures were placed in a ball mill (XQM-4L) until the particle size of the particles was less than 0.075 mm. The characteristics of SS and RH are summarized in Table 1. SS is characterized by high ash (70.06%), while RH is characterized by a high volatile matter (VM) ratio (70.98%). The molar ratio of H/C and O/C was used to characterize the degree of aromatization and hydrophilicity (Jung et al., 2019;
where Y1, Y2 are the corresponding mass losses (%) or gas outputs (A$ C/g), and Ytheo and Yexp are the theoretical and experimental values, respectively.
2.4. Preparation of bio-char The mixtures of SS and RH were carbonized in a vacuum tube furnace. In order to obtain biochar with excellent adsorbability, a detailed method was introduced in our previous study (Chen et al., 2019). The biochar was named as mixing ratio, for example, SSC and 20RHC represent the residual products of SS and 20RH, respectively. The char yield was calculated by using the ratio of the char weight/dry raw material weight determined by Equation (3), as follows:
Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
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M Char yield ð%Þ ¼ 1 100% M2
(3)
where M1 is the char weight, and M2 is the dry raw materials weight. The surface functional groups and morphology of the biochar products were determined by Fourier transform infrared spectrometry (FTIR, NicoletiS10, USA) and Scanning electron microscopy (SEM, Hitachi S-4800, Japan), respectively. 3. Results and discussion 3.1. Pyrolysis characteristics TG and DTG curves of the resulting blends are shown in Fig. 1. Clearly, three obvious peaks could be observed in the DTG curve of RH: vaporization of moisture (30e150 C), followed by devolatilization of hemicellulose and cellulose (167e407 C) and lignin decomposition (407e667 C) (Minh Loy et al., 2018; Zhou et al., 2019). The decomposition of cellulose/hemicelluloses and lignin resulted in mass loss of 53.16% and 10.57%, respectively. For SS and its mixtures, the pyrolysis patterns were completely different due to the complex composition of SS (Naqvi et al., 2019). The decomposition is divided into five regions: Region I - drying (30e150 C),
3
Region II - volatile (150e600 C), Region III - char (600e700 C) and Region IV - mineral decomposition (700e1000 C). The initial stages of all samples occurred between 30 and 150 C mainly due to water evaporation, while the final stages ranged from 700 to 1000 C, mainly including thermal decomposition of inorganic substances, e.g., carbonates (Ledakowicz et al., 2019), thus, according to our previous study, they are not worth discussing further here (Wang et al., 2019a). The second stages of the samples (SS, 20RH, 30RH and 40RH) occurred in the range of 166e580 C, 175e578 C, 178e573 C and 182e564 C, which corresponded to the mass loss of 21.33%, 29.10%, 33.07% and 36.58%, respectively. This stage mainly includes pyrolysis of hemicelluloses, cellulose, polysaccharides, carboxylic acids lipids and proteins (Lin et al., 2017). As shown in Fig. 1, peak 1 continues to become narrower and higher with the addition of RH, indicating that volatile decomposition was promoted by RH addition. The third stages occurred between 580 and 674 C, 578e684 C, 573e679 C and 564e666 C, corresponding to further mass loss of 1.35%, 1.44%, 1.48% and 1.57%, respectively. At this stage, the mass loss of the samples (SS, 20RH, 30RH and 40RH) was significantly reduced, which corresponded to the charring action of lignin and the remaining hydrocarbons (Fang et al., 2017; Vassilev and Vassileva, 2016). It is worth noting that there were shoulder peak appearing between peak 1 and peak 2 in DTG curves of SS-RH mixtures, which illustrated the overlap of the decomposition process of volatile and char during co-pyrolysis. This can be also stated as an indicator of the synergistic effect between the different components (Buyukada, 2017). In order to evaluate the pyrolysis characteristics of SS, RH and their mixtures, a comprehensive pyrolysis index (CPI) was introduced and calculated as follows (Wei et al., 2018):
CPI ¼
Dmax Dmean 1 Mf
(4)
Ti Tmax DT1=2
where, Dmax is the maximum mass loss rate, Dmean is the average mass loss rate, Tmax is the temperature corresponding to Dmax, and DT1/2 is the temperature range corresponding to D/Dmax ¼ 0.5 (halfpeak width). Table 2 shows the pyrolysis characteristic parameters of all samples, where Ti of SS and RH were measured as 197 C and 268 C, and their Tf were determined as 975 C and 939 C, respectively. Obviously, SS exhibits lower Ti and higher Tf than RH, which is consistent with our previous study under air atmosphere (Wang et al., 2019a). It can be explained that SS consists of micromolecular organic matter (Kulikowska, 2016) and is rich in reactive oxygen groups, as shown in Table 1, while the ash component of SS hinders its high-temperature pyrolysis. With the introduction of RH, the Ti of the mixtures increases, while the Tf decreases slightly. This means that the devolatilization of RH and the mineral decomposition of SS dominated the initial and terminative decomposition of the mixtures, respectively. As the addition of RH increased, the residue mass decreased from 66.91 to 26.89%, which
Table 2 Pyrolysis characteristic parameters for samples at heating rate 20 C/min.
Fig. 1. TG-DTG curves at the heating rate of 20 C/min.
Samples
Ti ( C)
Tf ( C)
Mf (%)
CPI (1013/min2$ C3)
SS RH 20RH 30RH 40RH
197 268 231 254 262
975 939 973 971 969
66.91 26.89 59.47 54.25 51.21
7.64 565.52 49.15 75.41 117.99
Ti: temperature for initial mass loss, Tf: temperature for final mass loss, Mf: the residue mass.
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was mainly related to the high ash content of SS. The larger the CPI value, the more intense the sample reaction. It can be observed that the addition of RH promotes a sharp increase in the CPI value, that is, the reactivity can be effectively improved by co-pyrolysis.
that the addition of RH reduces the cumulative amounts of H2, CH4, and C2H2, but increases the level of CO2 production. This means that biomass additives can inhibit hydrocarbon release and then enrich more hydrogen component in biochar.
3.2. Gaseous emissions during pyrolysis
3.3. Interaction investigation of co-pyrolysis
The ion fragments of the main gaseous products (m/z ¼ 2e60) produced during pyrolysis were monitored by TG-MS analysis (see Fig. 2). Hydrogen (m/z ¼ 2) is a key gaseous product in terms of pyrolysis reaction. As can be seen from Fig. 2a, H2 emissions occur continuously over a wide temperature range (single peak) for each component. Interestingly, the evolution curves of H2 turns into two stages after co-pyrolysis. The emissions of H2 at the lower temperature (250e450 C) and high temperature (450e700 C) are due to the primary degradation of the compounds enriched in hydrogen and the condensation or dehydrogenation of aromatic structures (Wang et al., 2015; Zhao et al., 2011), respectively. Abundant hydrogen and less aromatic substances in RH (Table 1) may be responsible for the cleavage of the H2 emission peak during the copyrolysis process. The dominant gas product (CH4) in the pyrolysis process (compare to Fig. 2) is produced by multi-step reactions (Fermoso and Masek, 2018), so the emission curves of CH4 (except for RH) can be divided into 4 stages. The second (the foremost) stage may be attributed to the decomposition of the species containing eCH3, while the third and fourth stages correspond to the secondarily cracks of the stable chemical bonds and the condensation of the aromatic molecules (Wang et al., 2015), respectively. CH4 presented below 200 C (first stage) can be considered a signal associated with the evolutionary CHþ 3 fragmentation ion. CnHm (n ¼ 2, 3, 4) has a similar decomposition mechanism to H2 with two peaks (except RH). The mechanisms for the two peaks can be proposed: the lowtemperature (200e400 C) peak represents that the large molecular functional group is decomposed into recombined small molecular compounds, and the high-temperature (400e600 C) peak represents the decomposition of the aromatic structures or oxygencontaining polymethylene compounds (Zou et al., 2017). It is worth noting that the temperature corresponding to both the maximal release and the fragmented ion intensity of C2H2 are the highest, compared to other hydrocarbon products. It is reasonable to conclude that C2H2 (one of the main products) is formed by the decomposition of the hydrocarbons having a large number of carbon atoms. CO2 emissions distributed over a wide temperature range were observed. The prominent peak of the CO2 profile is around 200e500 C, which is facilitated by the decarboxylation/ decarbonylation reaction of the macromolecules, such as aliphatic groups (Yu et al., 2007). The second peak at around 500e650 C may be derived from the breakage of carbonates, carbonyls, ethers, quinones, oxygen-containing heterocycles and other oxygencontaining functional groups with high thermal stability (Luo et al., 2017). The emission of hydrocarbons such as CH2O and HCOOH can be negligible, so the formation mechanism will not be discussed in detail. The gas output produced during the pyrolysis process was obtained using an integrating method, and the cumulative amounts of the gas products are shown in Fig. 3. As can be seen from Fig. 3, H2, CH4, C2H2 and CO2 are the major pyrolysis gases produced. Obviously, the cumulative amounts of all evolved gaseous products (except CH4) of RH are higher than that of SS. Previous research (Marco et al., 2011) has set CHþ 3 as a probable precursor of CH4, and more CHþ 3 formed in SS results in more CH4 release than that in RH (as shown in Fig. 2b). The main gas output sequence is: CH4 > CO2 > H2 > C2H2 for the mixtures, at least an order of magnitude higher than other gaseous products. It can be observed
Fig. 4 shows the deviations of weight loss and accumulations of the major gas emissions (H2, C2H2, CH4 and CO2) during the copyrolysis process. As can be seen from Fig. 4a, when RH dose is 30%, the deviations between the theoretical and experimental TG curves remain positive, while the deviations of the other mixtures (20RH and 40RH) are negative. This indicates that the interaction between SS and RH is an inhibition of degradation when 30% RH is added. However, the interaction turns to promote the effect regardless of whether the RH addition is decreased or increased. The mechanism of the saltation can be determined: (1) biomass can contribute additional heat to overcome the barriers of the decomposition of SS (Chen et al., 2016). (2) RH char producing a porous structure (Zhang et al., 2018) can capture the volatile substances (including gaseous and liquid products), resulting in slow release of volatile substances (Kai et al., 2017). The biochar formed by 30RH has outstanding adsorption ability for volatile substances and is a key controlling factor for determining the interaction. When the RH additive dose is higher or lower, the thermal effect dominates the interaction. In addition, the deviation curves of the weight losses of 20RH and 40RH have almost the same trends, and there are two maximum peaks with an increase in temperature, corresponding to about 300 C and 910 C, respectively. Obviously, 20RH has a lower peak at low temperatures and a higher peak at high temperature. It can also prove that the more char formed, the stronger the inhibition of thermal degradation, which is similar to Yuan’s research (Yuan et al., 2018). As shown by the deviation curves for the main gaseous products (Fig. 4b-e), there are gas-generation interactions during the copyrolysis process. The deviations of H2, C2H2, CH4, and CO2 emissions from all mixtures are positive (except C2H2 emission of 30RH), indicating that the release of H2, C2H2, CH4 and CO2 was inhibited by the interaction. Overall, the synergistic effect is to inhibit the production of gases. It is important to note that the maximum absolute deviation of all mixtures occurs at the low-temperature stage (<450 C), indicating that the degree of inhibition is most pronounced at low temperature. These results indicate that the copyrolysis of SS and RH promotes the interactions of free radicals or intermediates from liquefaction, resulting in the increased tar production (Leng et al., 2018). The resulting sticky tar may coat the residue and prevent the release of gaseous products. As the temperature increases, the tar is decomposed or volatilized, resulting in a decrease in the inhibitory effect. Liu et al. (2018) reported similar observations. However, as the temperature further increases, the inhibitory effect reappears, indicating that the formed char mainly restrains the release of the gaseous product. Fig. 4c shows that the release of CH4 can be restrained by the interaction between SS and RH, and the inhibition is most pronounced for 30RH. And the interactions in the 40RH sample resulted in the greatest inhibition of H2, C2H2 and CO2. In summary, the interaction between SS and RH restrains the generation of gaseous products, especially at high RH ratios. Namely, the interaction may affect on biochar performance, combing with our previous research (Chen et al., 2019). 3.4. Characterization of bio-char The physicochemical characteristics of biochars from SS and RH are summarized in Table 3. It can be found that the yield of char decreases as the RH ratio increases, which is consistent with that in
Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
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Fig. 2. Gas emission curves during pyrolysis process.
Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
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Fig. 3. Normalized integral values of gaseous emission produced during co-pyrolysis.
Section 3.1. The ash content in biochar decreases as the RH ratio increasing, while the VM increases. It is worth noting that the percentages of the fixed carbon (FC), C and H of 30RHC reach the maximum (Table 3), which contradicts the ultimate and approximate analysis of the raw materials. This contradiction can be explained by the synergistic effect of the addition of 30% RH which hinders the release of gaseous products and leads to the deposition of these hydrocarbons on biochar. Regarding SSC, H/C and O/C decrease from 1.32 to 0.93/0.80/0.81 and 0.39 to 0.12/0.16/0.33 for biochar of SS-RH mixtures (20RHC, 30RHC and 40RHC), respectively. The lower H/C ratio shows higher carbonization and aromaticity (Parshetti et al., 2013). In other words, RH additive promotes the sludge carbonization and aromaticity. However, carbonization and aromatization do not result in a continuous decrease in H/C when RH is added, as it moderately rises to 0.81 when the RH dose rises to 40%. This indicates that 30RHC has the most condensed aromatic structures and a sufficient degree of carbonization (Sun et al., 2013). A higher O/C ratio means the presence of a more stable carbon-oxygen complex in biochar (Liu et al., 2010), i.e., biochar with higher RH introduction can provide
Fig. 4. Deviation of TG and gas integral due to co-pyrolysis of SS and rice husk.
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Table 3 Basic characteristic of bio-char. Sample
SSC 20RHC 30RHC 40RHC a
Char yield (%)
80.21 70.12 64.6 58.32
Proximate analysis (%)
Ultimate analysis (%)
Atomic Ratio
Ash
VM
FC
C
H
N
Oa
H/C
O/C
84.36 81.24 75.99 73.13
9.33 10.02 11.93 14.89
6.31 9.74 12.08 11.98
8.98 14.98 17.80 17.11
0.99 1.16 1.18 1.15
1.01 1.18 1.17 1.06
4.66 2.44 3.86 7.55
1.32 0.93 0.80 0.81
0.39 0.12 0.16 0.33
SBET (m2g1)
19.80 25.57 47.40 68.07
Calculated by O ¼ 100-Ash-C-H-N.
more activation sites. As shown in Table 3, during the pyrolysis of SS, the surface area of the biochar increases as the RH dose increases. Interestingly, the rate of increase rises rapidly after 30% and 40% RH addition. Such significant increase may result from the adequate volatilization of volatile substances in the SS-RH mixtures (Wang et al., 2017b) and the porous structure in the RH residue, which has been proved in previous study (Pode, 2016). The FTIR spectra of the biochars are similar, indicating that RH addition does not lead to significant changes in surface functional groups (Fig. 5). The peak range of 3205e3429 cm1 corresponds to eOH stretching vibration, while the peak near 1440 cm1 is related to eOH bending vibration (Krishnani et al., 2008; Yang et al., 2010). The characteristic peaks of the eOH bending vibration of different biochars are located at 1444 cm1 (SSA and 20RHC) and 1435 cm1 (30RHC and 40RHC), respectively. The peak redshift indicates that the hydroxyl groups tend to be stable, which also clarifies the improvement of the adsorbability of the biochars after the addition of 30% and 40% RH (Feng et al., 2011). The peak around 2800e3000 cm1 corresponds to the aliphatic CHn groups (CeH stretching). After the addition of 30% and 40% RH, the peak near 2950 cm1 almost disappeared, indicating breakings in the aliphatic chains. The results show that a large number of RH additives can promote the transformation of fatty hydrocarbons into aromatic structures in biochars (Wang et al., 2019b), which is inferred from the H/C ratio in Table 3. The peaks at 1619e1624 cm1 reflect the amide bonds and the aromatic ring stretching (C]O, eCONHe, and C]C stretching vibration) (Jin et al., 2016), while the peak at 694 cm1 corresponds to the vibrations of the aromatic compounds and the hetero-aromatic compounds (Huang et al.,
Fig. 5. FTIR spectra of different biochars.
2017a). The appearance of these functional groups suggests that the biochar possesses an aromatization structure, which can give the biochar a strong adsorption capacity (Harvey et al., 2011). It is known that the absorption peaks observed in the vicinity of 460e1100 cm1 are the characteristic silica region. For all biochars, the silica absorption bands appear around 470, 780 and 1035 cm1 (Magdziarz et al., 2016). SEM analysis of the biochars at different RH dose is shown in Fig. 6. The biochars with different RH doses possess a porous structure with small granules coated on the surface, mainly due to the generation and the release of gaseous products during the pyrolysis process (Sun et al., 2018). Differences among different biochars were observed. As shown in Fig. 6a and b, there is insufficient pore structure in the biochar (SSC and 20RHC). Pore development is observed in biochars (30RHC and 40RHC) (Fig. 6c and d), which is consistent with the specific surface area of different biochar samples. Overall, based on the above discussion, 30RHC has remarkable adsorption potential.
4. Conclusion TG-MS analysis of the co-pyrolysis of SS and RH showed that the volatile decomposition was promoted by the addition of RH while inhibiting the char reactions. The addition of RH improved the Ti and CPI value of blends while reducing the Tf. This meant that the thermal degradation of RH and SS dominated the initial and terminative decomposition of the mixtures respectively, and RH introduction motivated the reactivity sharply. The major pyrolysis gas products were H2, CH4, C2H2 and CO2 for the SS-RH mixtures, in the order: CH4 > CO2 > H2 > C2H2. The RH additive can reduce the accumulation of H2, CH4, and C2H2 in SS, but increase the CO2 content. Namely, RH additive can inhibit hydrocarbon release and enrich hydrogen component in biochar during co-pyrolysis. The maximum deviations (%) value between TG-MS results of the mixtures and the theoretical results reached 18.08%, which indicates there existed interaction between SS and RH. The interaction inhabited the thermal degradation of 30RH, however, it turned to accelerate the degradation of 20RH and 40RH. It can be explained by formation of the biochar with outstanding adsorption ability for volatile substances under 30% RH addition. Meanwhile, the interactions inhibited the main gas (H2, C2H2, CH4 and CO2) generation for all mixtures. It also indicated that hydrocarbon can enrich in the formed biochar during co-pyrolysis. RH additive promoted carbonization and aromaticity of biochar derived from the copyrolysis of SS and RH, while the pore development and the specific surface area were improved as the RH ratio increases. It is worth noting that 30RHC possessed maximum FC, C and H content, while had the most condensed aromatic structure and sufficient degree of carbonization. Overall, biochar derived from the copyrolysis of SS and RH has remarkable adsorption potential, especially for 30RHC.
Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
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Fig. 6. SEM analysis of bio-char with different RH dose, (a) SSC; (b) 20RHC; (c) 40RHC; (d) 40RHC.
Declaration of competing interest The authors declared that they have no conflicts of interest to this work. Acknowledgements This research was supported by a grant from National Natural Science Foundation of China (No. 51908433) and Natural Science Foundation of Hubei Province-China (No.2019CFB236). The authors would also like to thank reviewers for commenting on this paper. References onard, A., 2014. Arlabosse, P., Ferrasse, J.H., Lecomte, D., Crine, M., Dumont, Y., Le Efficient Sludge Thermal Processing: from Drying to Thermal Valorization. Wiley-VCH Verlag GmbH & Co. KGaA. onard, A., 2013. Review on fundamental aspect of Bennamoun, L., Arlabosse, P., Le application of drying process to wastewater sludge. Renew. Sustain. Energy Rev. 28, 29e43. Buyukada, M., 2017. Uncertainty estimation by Bayesian approach in thermochemical conversion of walnut hull and lignite coal blends. Bioresour. Technol. 232, 87e92. Chen, J., Liu, J., He, Y., Huang, L., Sun, S., Sun, J., Chang, K., Kuo, J., Huang, S., Ning, X., 2016. Investigation of co-combustion characteristics of sewage sludge and coffee grounds mixtures using thermogravimetric analysis coupled to artificial neural networks modeling. Bioresour. Technol. 225, 234e245. Chen, S., Qin, C., Wang, T., Chen, F., Li, X., Hou, H., Zhou, M., 2019. Study on the adsorption of dyestuffs with different properties by sludge-rice husk biochar: adsorption capacity, isotherm, kinetic, thermodynamics and mechanism. J. Mol. Liq. 285, 62e74. Deng, S., Tan, H., Wang, X., Yang, F., Cao, R., Wang, Z., Ruan, R., 2017. Investigation on the fast co-pyrolysis of sewage sludge with biomass and the combustion reactivity of residual char. Bioresour. Technol. 239. S0960852417305710ss. Fang, S., Yu, Z., Ma, X., Lin, Y., Lin, Y., Chen, L., Fan, Y., Liao, Y., 2017. Co-pyrolysis
characters between combustible solid waste and paper mill sludge by TG-FTIR and Py-GC/MS. Energy Convers. Manag. 144, 114e122. Feng, Y., Yang, F., Wang, Y., Ma, L., Wu, Y., Kerr, P.G., Yang, L., 2011. Basic dye adsorption onto an agro-based waste material e Sesame hull (Sesamum indicum L.). Bioresour. Technol. 102, 10280e10285. Fermoso, J., Masek, O., 2018. Thermochemical decomposition of coffee ground residues by TG-MS: a kinetic study. J. Anal. Appl. Pyrolysis 130, 358e367. mez, N.R., Quispe, V., Garrue s, J.A., Martínez, M.A., Murillo, M.B., Gea, G., 2017. CoGo pyrolysis of sewage sludge and manure. Waste Manag. 59, 211. Harvey, O.R., Herbert, B.E., Rhue, R.D., Kuo, L.J., 2011. Metal interactions at the biochar-water interface: energetics and structure-sorption relationships elucidated by flow adsorption microcalorimetry. Environ. Sci. Technol. 45, 5550. Huang, H.J., Yang, T., Lai, F.Y., Wu, G.Q., 2017a. Co-pyrolysis of sewage sludge and sawdust/rice straw for the production of biochar. J. Anal. Appl. Pyrolysis. Huang, H.J., Yuan, X.Z., 2016. The migration and transformation behaviors of heavy metals during the hydrothermal treatment of sewage sludge. Bioresour. Technol. 200, 991e998. Huang, L., Xie, C., Liu, J., Zhang, X., Chang, K., Kuo, J., Sun, J., Xie, W., Zheng, L., Sun, S., 2017b. Influence of catalysts on co-combustion of sewage sludge and water hyacinth blends as determined by TG-MS analysis. Bioresour. Technol. 247, 217e225. Jin, J., Li, Y., Zhang, J., Wu, S., Cao, Y., Liang, P., Zhang, J., Wong, M.H., Wang, M., Shan, S., 2016. Influence of pyrolysis temperature on properties and environmental safety of heavy metals in biochars derived from municipal sewage sludge. J. Hazard Mater. 320, 417e426. Jung, H., Sewu, D.D., Ohemeng-Boahen, G., Lee, D.S., Woo, S.H., 2019. Characterization and adsorption performance evaluation of waste char by-product from industrial gasification of solid refuse fuel from municipal solid waste. Waste Manag. 91, 33e41. Kai, X., Li, R., Yang, T., Shen, S., Ji, Q., Zhang, T., 2017. Study on the co-pyrolysis of rice straw and high density polyethylene blends using TG-FTIR-MS. Energy Convers. Manag. 146, 20e33. Kai, X., Yang, T., Shen, S., Li, R., 2019. TG-FTIR-MS study of synergistic effects during co-pyrolysis of corn stalk and high-density polyethylene (HDPE). Energy Convers. Manag. 181, 202e213. Khan, A.A., Jong, W.D., Jansens, P.J., Spliethoff, H., 2009. Biomass combustion in fluidized bed boilers: potential problems and remedies. Fuel Process. Technol. 90, 21e50. Krishnani, K.K., Meng, X., Christodoulatos, C., Boddu, V.M., 2008. Biosorption
Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
T. Wang et al. / Journal of Cleaner Production xxx (xxxx) xxx mechanism of nine different heavy metals onto biomatrix from rice husk. J. Hazard Mater. 153, 1222e1234. Kulikowska, D., 2016. Kinetics of organic matter removal and humification progress during sewage sludge composting. Waste Manag. 49, 196e203. Ledakowicz, S., Stolarek, P., Malinowski, A., Lepez, O., 2019. Thermochemical treatment of sewage sludge by integration of drying and pyrolysis/autogasification. Renew. Sustain. Energy Rev. 104, 319e327. Leng, L., Leng, S., Chen, J., Yuan, X., Li, J., Li, K., Wang, Y., Zhou, W., 2018. The migration and transformation behavior of heavy metals during co-liquefaction of municipal sewage sludge and lignocellulosic biomass. Bioresour. Technol. 259, 156. Lin, B., Huang, Q., Chi, Y., 2018. Co-pyrolysis of oily sludge and rice husk for improving pyrolysis oil quality. Fuel Process. Technol. 177, 275e282. Lin, Y., Liao, Y., Yu, Z., Fang, S., Ma, X., 2017. A study on co-pyrolysis of bagasse and sewage sludge using TG-FTIR and Py-GC/MS. Energy Convers. Manag. 151, 190e198. Liu, C., Liu, J., Sun, G., Xie, W., Kuo, J., Li, S., Liang, J., Chang, K., Sun, S., Buyukada, M., Evrendilek, F., 2018. Thermogravimetric analysis of (co-)combustion of oily sludge and litchi peels: combustion characterization, interactions and kinetics. Thermochim. Acta 667, 207e218. Liu, Z., Zhang, F.-S., Wu, J., 2010. Characterization and application of chars produced from pinewood pyrolysis and hydrothermal treatment. Fuel 89, 510e514. Luo, L., Liu, J., Zhang, H., Ma, J., Wang, X., Jiang, X., 2017. TG-MS-FTIR study on pyrolysis behavior of superfine pulverized coal. J. Anal. Appl. Pyrolysis 128, 64e74. Magdziarz, A., Wilk, M., Gajek, M., Nowak-Wo zny, D., Kopia, A., Kalemba-Rec, I., ski, J.A., 2016. Properties of ash generated during sewage sludge comKozin bustion: a multifaceted analysis. Energy 113, 85e94. Marco, I., Roberto, D.M., Maurizio, G., Marco, B., 2011. Clay-sewage sludge copyrolysis. A TG-MS and Py-GC study on potential advantages afforded by the presence of clay in the pyrolysis of wastewater sewage sludge. Waste Manag. 31, 71e77. Minh Loy, A.C., Yusup, S., Fui Chin, B.L., Wai Gan, D.K., Shahbaz, M., Acda, M.N., Unrean, P., Rianawati, E., 2018. Comparative study of in-situ catalytic pyrolysis of rice husk for syngas production: kinetics modelling and product gas analysis. J. Clean. Prod. 197, 1231e1243. Naqvi, S.R., Hameed, Z., Tariq, R., Taqvi, S.A., Ali, I., Niazi, M.B.K., Noor, T., Hussain, A., Iqbal, N., Shahbaz, M., 2019. Synergistic effect on co-pyrolysis of rice husk and sewage sludge by thermal behavior, kinetics, thermodynamic parameters and artificial neural network. Waste Manag. 85, 131e140. Parshetti, G.K., Liu, Z., Jain, A., Srinivasan, M.P., Balasubramanian, R., 2013. Hydrothermal carbonization of sewage sludge for energy production with coal. Fuel 111, 201e210. Pode, R., 2016. Potential applications of rice husk ash waste from rice husk biomass power plant. Renew. Sustain. Energy Rev. 53, 1468e1485. Soria-Verdugo, A., Goos, E., Morato-Godino, A., García-Hernando, N., Riedel, U., 2017. Pyrolysis of biofuels of the future: sewage sludge and microalgae e thermogravimetric analysis and modelling of the pyrolysis under different temperature conditions. Energy Convers. Manag. 138, 261e272. Sun, K., Kang, M., Zhang, Z., Jin, J., Wang, Z., Pan, Z., Xu, D., Wu, F., Xing, B., 2013. Impact of deashing treatment on biochar structural properties and potential sorption mechanisms of phenanthrene. Environ. Sci. Technol. 47, 11473e11481. Sun, S., Huang, X., Lin, J., Ma, R., Fang, L., Zhang, P., Qu, J., Zhang, X., Liu, Y., 2018. Study on the effects of catalysts on the immobilization efficiency and mechanism of heavy metals during the microwave pyrolysis of sludge. Waste Manag. 77, 131e139. Tan, C., Zhang, Y., Wang, H., Lu, W., Zhou, Z., Zhang, Y., Ren, L., 2014. Influence of pyrolysis temperature on characteristics and heavy metal adsorptive
9
performance of biochar derived from municipal sewage sludge. Bioresour. Technol. 164, 47e54. Tang, S., Zheng, C., Zhang, Z., 2018. Effect of inherent minerals on sewage sludge pyrolysis: product characteristics, kinetics and thermodynamics. Waste Manag. 80, 175e185. Tran, H.N., You, S.-J., Chao, H.-P., 2017. Insight into adsorption mechanism of cationic dye onto agricultural residues-derived hydrochars: negligible role ofp-pinteraction. Korean J. Chem. Eng. 34, 1e13. Vamvuka, D., Sfakiotakis, S., Saxioni, S., 2015. Evaluation of urban wastes as promising co-fuels for energy production e a TG/MS study. Fuel 147, 170e183. Vassilev, S.V., Vassileva, C.G., 2016. Composition, properties and challenges of algae biomass for biofuel application: an overview. Fuel 181, 1e33. Wang, M., Li, Z., Huang, W., Yang, J., Xue, H., 2015. Coal pyrolysis characteristics by TGeMS and its late gas generation potential. Fuel 156, 243e253. Wang, T., Hou, H., Ye, Y., Rong, H., Li, J., Xue, Y., 2019a. Combustion behavior of refuse-derived fuel produced from sewage sludge and rice husk/wood sawdust using thermogravimetric and mass spectrometric analyses. J. Clean. Prod. 222, 1e11. Wang, T., Xue, Y., Zhou, M., Yuan, Y., Zhao, S., Tan, G., Zhou, X., Geng, J., Wu, S., Hou, H., 2017a. Comparative study on the mobility and speciation of heavy metals in ashes from co-combustion of sewage sludge/dredged sludge and rice husk. Chemosphere 169, 162e170. Wang, X., Chi, Q., Liu, X., Wang, Y., 2019b. Influence of pyrolysis temperature on characteristics and environmental risk of heavy metals in pyrolyzed biochar made from hydrothermally treated sewage sludge. Chemosphere 216, 698e706. Wang, X., Gu, L., Zhou, P., Zhu, N., Li, C., Tao, H., Wen, H., Zhang, D., 2017b. Pyrolytic temperature dependent conversion of sewage sludge to carbon catalyst and their performance in persulfate degradation of 2-Naphthol. Chem. Eng. J. 324, 203e215. Wei, X., Ma, X., Peng, X., Yao, Z., Yang, F., Dai, M., 2018. Comparative investigation between co-pyrolysis characteristics of protein and carbohydrate by TG-FTIR and Py-GC/MS. J. Anal. Appl. Pyrolysis 135, 209e218. Yang, H., Yan, R., Chen, H., Dong, H.L., Zheng, C., 2010. Characteristics of hemicellulose, cellulose and lignin pyrolysis. Fuel 86, 1781e1788. Yu, J., Lucas, J.A., Wall, T.F., 2007. Formation of the structure of chars during devolatilization of pulverized coal and its thermoproperties: a review. Prog. Energy Combust. Sci. 33, 135e170. Yuan, H., Fan, H., Shan, R., He, M., Gu, J., Chen, Y., 2018. Study of synergistic effects during co-pyrolysis of cellulose and high-density polyethylene at various ratios. Energy Convers. Manag. 157, 517e526. Zhang, K., Sun, P., Faye, M.C.A.S., Zhang, Y., 2018. Characterization of biochar derived from rice husks and its potential in chlorobenzene degradation. Carbon 130. Zhang, W., Yuan, C., Xu, J., Yang, X., 2015. Beneficial synergetic effect on gas production during co-pyrolysis of sewage sludge and biomass in a vacuum reactor. Bioresour. Technol. 183, 255e258. Zhao, Y., Hu, H., Jin, L., He, X., Wu, B., 2011. Pyrolysis behavior of vitrinite and inertinite from Chinese Pingshuo coal by TGeMS and in a fixed bed reactor. Fuel Process. Technol. 92, 780e786. Zhou, Y., Chen, Z., Gong, H., Chen, L., Yu, H., Wu, W., 2019. Characteristics of dehydration during rice husk pyrolysis and catalytic mechanism of dehydration reaction with NiO/g-Al2O3 as catalyst. Fuel 245, 131e138. Zhu, J., Yang, Y., Yang, L., Zhu, Y., 2018. High quality syngas produced from the copyrolysis of wet sewage sludge with sawdust. Int. J. Hydrogen Energy 43. S0360319918303148. Zou, C., Ma, C., Zhao, J., Shi, R., Li, X., 2017. Characterization and non-isothermal kinetics of Shenmu bituminous coal devolatilization by TG-MS. J. Anal. Appl. Pyrolysis 127, 309e320.
Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
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Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro
Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis Teng Wang a, b, Yuchi Chen c, Jinping Li a, b, Yongjie Xue d, Jingxin Liu a, b, Meng Mei a, b, Haobo Hou c, Si Chen a, b, c, * a
School of Environmental Engineering, Wuhan Textile University, Wuhan, 430073, China Engineering Research Centre for Clean Production of Textile Dyeing and Printing, Ministry of Education, Wuhan Textile University, Wuhan, 430073, China School of Resource and Environment Science, Wuhan University, 430070, Hubei, Wuhan, China d State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, 430070, Hubei, Wuhan, China b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 August 2019 Received in revised form 23 October 2019 Accepted 3 December 2019 Available online xxx
Co-pyrolysis sewage sludge (SS) and rice husk (RH) is a promising method for reusing the waste. In this study, thermogravimetry and mass spectrometry (TG-MS) were used to investigate the thermal degradation behavior and the evolution of gaseous species during co-pyrolysis. The interactions of SS and RH on gas and biochar products were explored. The results reveal that the introduction of RH can improve the pyrolysis reactivity and CO2 production of SS, but reduce the cumulation of H2, CH4 and C2H2. The interaction inhabited the main gases generation, while promoted carbonization and aromatization of the corresponding biochar, especially under 30%RH addition. The addition of RH can lead to pore development and a sharp improvement in specific surface area under high dose. Overall, co-pyrolysis of RH and SS captures more gaseous hydrocarbons and provides biochar with remarkable adsorption potential. © 2019 Elsevier Ltd. All rights reserved.
Handling editor: Jin-Kuk Kim Keywords: Sewage sludge Rice husk Co-pyrolysis Synergistic effect Gas emissions Biochar
1. Introduction Recently, sewage sludge (SS), a complex by-product produced in the wastewater treatment process, exceeds 60 million tons in China. SS contains not only many organic substances of renewable energy, but also harmful substances, such as heavy metals, toxic organic substances and pathogenic microorganisms (Huang and Yuan, 2016). Thus, the environmental and economical disposal of SS has attracted more and more attention (Zhu et al., 2018). The main methods used to treat SS include landfill, agricultural utilization, and thermochemical conversion (Soria-Verdugo et al., 2017). Statistics (Arlabosse et al., 2014) show that 40%e50% of SS from the European Union and the United States is used for agriculture. Only 14% and 17% of the total produced quantity of SS with strict rules and instructions was allowed to landfill. About 27% and
* Corresponding author. School of Environmental Engineering, Wuhan Textile University, Wuhan, 430073, China. E-mail address: [email protected] (S. Chen).
22% of SS was treated by thermal treatment (Bennamoun et al., 2013). Among these technologies, pyrolysis is considered a promising method for sludge valorization due to volume minimization, zero-waste conversion and energy/multipurpose materials recovmez et al., 2017; Tang et al., 2018). However, the monoery (Go pyrolysis of SS still faces serious drawbacks, such as high ash content, low energy efficiency, pyrolysis reactor instability and low value-added products. In contrast, biomass is a renewable and clean resource that can be made into high-quality pyrolysis products due to its high volatility and low ash content (Deng et al., 2017). Rice husk (RH) is one of the major sources of biomass, and the RH production in China exceeds 40 million tons per year (Pode, 2016). Such a large amount of RH also needs urgent treatment, otherwise it will cause serious environmental hazards (Khan et al., 2009). Therefore, the copyrolysis of SS and RH may be an effective method for disposing such large scale solid waste, improving energy utilization and the quality of pyrolysis products. Studies have tried to investigate the co-pyrolysis process of sludge and RH. Lin et al. (2018) found that co-pyrolysis of oil sludge and RH improved the quality of oil
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Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
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Abbreviations TG-MS SS RH 20RH 30RH 40RH VM FC H/C O/C SSC 20RHC 30RHC 40RHC CPI Ti Tf
thermogravimetric mass spectrometry sewage sludge rice husk mixture of 20% rice husk þ80% sewage sludge mixture of 30% rice husk þ70% sewage sludge mixture of 40% rice husk þ60% sewage sludge volatile matter fixed carbon the molar ratio of H and C the molar ratio of O and C the biochar produced from sewage sludge the biochar produced from mixture of 20% rice husk þ80% sewage sludge the biochar produced from mixture of 30% rice husk þ70% sewage sludge the biochar produced from mixture of 40% rice husk þ60% sewage sludge comprehensive pyrolysis index ignition temperature Burnout temperature
product and promoted the formation of H2, CO and C1eC2 hydrocarbons. Zhang et al. (2015) revealed a remarkable synergetic effect on gas production. Naqvi et al. (2019) provided in-depth studies of kinetics and thermodynamics of co-pyrolysis of SS and RH, indicating that the interactions facilitated the recovery of organic materials. These studies have focused on the effects of RH on gas or tar generation and the interactions of thermal decomposition. In our previous study (Chen et al., 2019), the feasibility of biochar derived from co-pyrolysis of SS and RH as adsorbent was preliminarily verified. However, in-situ monitoring of gas product evolution was unnoticed during the co-pyrolysis of SS and RH, and no literature has explained the impact of synergistic effects on gas generation. In addition, the synergistic effects on the characteristics of biochar derived from co-pyrolysis of SS and RH are currently unknown. Therefore, this study used thermogravimetric analysis coupled with mass spectrometry (TG-MS) method to simultaneously investigate the effects of RH on the thermal decomposition and the gaseous product evolution during pyrolysis of SS. Furthermore, the effects of the interactions between SS and RH on the properties of multiphase products (gas and biochar) were investigated. 2. Materials and methods
Table 1 Proximate analysis data for raw materials.
RH SS a
Proximate analysis (%)
Ultimate analysis (%)
Atomic Ratio
Ash
VM
FC
C
H
N
Oa
H/C
O/C
15.09 70.06
70.98 29.08
13.94 0.86
41.43 12.68
5.72 1.38
0.69 1.85
37.07 14.03
1.66 1.31
0.67 0.83
Calculated by O ¼ 100-Ash-C-H-N.
Tan et al., 2014). Interestingly, although SS has less hydrogen and oxygen contents, it has higher aromatic and hydrophilic (higher H/ C ¼ 1.31 and lower O/C ¼ 0.83). High aromaticity and hydrophilicity indicate the presence of more aromatic substances and reactive oxygen groups. (Tran et al., 2017).
2.2. Thermogravimetric analysis Pyrolysis of the individuals and the mixtures (SS and RH) was carried out in a TG-MS analyzer (STA 449-QMS 403, NETZSCH, Germany). During the pyrolysis process, approximately 10 ± 0.5 mg sample with particle size less than 0.075 mm was heated from room temperature to 1000 C at a heating rate of 20 C/min. Highpurity nitrogen (99.999%) was used as the carrier gas at a flow rate of 20 ml/min. Evolved gaseous products were monitored, including H2 (m/z ¼ 2), CH4 (m/z ¼ 16), C2H2 (m/z ¼ 26), CH2O (m/z ¼ 30), C3H6 (m/z ¼ 42), CO2 (m/z ¼ 44), HCOOH (m/z ¼ 46) and C4H10 (m/ z ¼ 58), according to the database of National Institute of Standards and Technology (NIST). The temperature section corresponding to different reactions could be segmented based on DTG and gas emission curves.
2.3. Interaction calculation Theoretical TG and gas emission curves of SS-RH mixtures were used to clarify the interactions between the individual components (Kai et al., 2019; Vamvuka et al., 2015). To investigate whether there is an interaction effect occurring in the co-pyrolysis of SS with RH, the theoretical values were calculated using Equation (1) according to weight losses and the cumulative gas amounts. The deviation levels (%) were calculated by Equation (2) and used to evaluate the degree of interaction (Huang et al., 2017b).
Ytheo ¼ x1 Y1 þ x2 Y2 Deviationð%Þ ¼
Ytheo Yexp Yexp
(1) 100
(2)
2.1. Materials RH and SS collected from Wuhan Hubei were used for the study. Details and pre-treatment procedures were shown in our previous research work (Wang et al., 2017a). In order to investigate the effect of biomass additives on thermal decomposition and gaseous product evolution during co-pyrolysis process, RH was mixed with SS in a ratio of 20e40%. The sample was named according to the proportion of RH, for example, 20RH refers to the mixture of 20 wt% RH and 80 wt% SS. To ensure proper mixing, the mixtures were placed in a ball mill (XQM-4L) until the particle size of the particles was less than 0.075 mm. The characteristics of SS and RH are summarized in Table 1. SS is characterized by high ash (70.06%), while RH is characterized by a high volatile matter (VM) ratio (70.98%). The molar ratio of H/C and O/C was used to characterize the degree of aromatization and hydrophilicity (Jung et al., 2019;
where Y1, Y2 are the corresponding mass losses (%) or gas outputs (A$ C/g), and Ytheo and Yexp are the theoretical and experimental values, respectively.
2.4. Preparation of bio-char The mixtures of SS and RH were carbonized in a vacuum tube furnace. In order to obtain biochar with excellent adsorbability, a detailed method was introduced in our previous study (Chen et al., 2019). The biochar was named as mixing ratio, for example, SSC and 20RHC represent the residual products of SS and 20RH, respectively. The char yield was calculated by using the ratio of the char weight/dry raw material weight determined by Equation (3), as follows:
Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
T. Wang et al. / Journal of Cleaner Production xxx (xxxx) xxx
M Char yield ð%Þ ¼ 1 100% M2
(3)
where M1 is the char weight, and M2 is the dry raw materials weight. The surface functional groups and morphology of the biochar products were determined by Fourier transform infrared spectrometry (FTIR, NicoletiS10, USA) and Scanning electron microscopy (SEM, Hitachi S-4800, Japan), respectively. 3. Results and discussion 3.1. Pyrolysis characteristics TG and DTG curves of the resulting blends are shown in Fig. 1. Clearly, three obvious peaks could be observed in the DTG curve of RH: vaporization of moisture (30e150 C), followed by devolatilization of hemicellulose and cellulose (167e407 C) and lignin decomposition (407e667 C) (Minh Loy et al., 2018; Zhou et al., 2019). The decomposition of cellulose/hemicelluloses and lignin resulted in mass loss of 53.16% and 10.57%, respectively. For SS and its mixtures, the pyrolysis patterns were completely different due to the complex composition of SS (Naqvi et al., 2019). The decomposition is divided into five regions: Region I - drying (30e150 C),
3
Region II - volatile (150e600 C), Region III - char (600e700 C) and Region IV - mineral decomposition (700e1000 C). The initial stages of all samples occurred between 30 and 150 C mainly due to water evaporation, while the final stages ranged from 700 to 1000 C, mainly including thermal decomposition of inorganic substances, e.g., carbonates (Ledakowicz et al., 2019), thus, according to our previous study, they are not worth discussing further here (Wang et al., 2019a). The second stages of the samples (SS, 20RH, 30RH and 40RH) occurred in the range of 166e580 C, 175e578 C, 178e573 C and 182e564 C, which corresponded to the mass loss of 21.33%, 29.10%, 33.07% and 36.58%, respectively. This stage mainly includes pyrolysis of hemicelluloses, cellulose, polysaccharides, carboxylic acids lipids and proteins (Lin et al., 2017). As shown in Fig. 1, peak 1 continues to become narrower and higher with the addition of RH, indicating that volatile decomposition was promoted by RH addition. The third stages occurred between 580 and 674 C, 578e684 C, 573e679 C and 564e666 C, corresponding to further mass loss of 1.35%, 1.44%, 1.48% and 1.57%, respectively. At this stage, the mass loss of the samples (SS, 20RH, 30RH and 40RH) was significantly reduced, which corresponded to the charring action of lignin and the remaining hydrocarbons (Fang et al., 2017; Vassilev and Vassileva, 2016). It is worth noting that there were shoulder peak appearing between peak 1 and peak 2 in DTG curves of SS-RH mixtures, which illustrated the overlap of the decomposition process of volatile and char during co-pyrolysis. This can be also stated as an indicator of the synergistic effect between the different components (Buyukada, 2017). In order to evaluate the pyrolysis characteristics of SS, RH and their mixtures, a comprehensive pyrolysis index (CPI) was introduced and calculated as follows (Wei et al., 2018):
CPI ¼
Dmax Dmean 1 Mf
(4)
Ti Tmax DT1=2
where, Dmax is the maximum mass loss rate, Dmean is the average mass loss rate, Tmax is the temperature corresponding to Dmax, and DT1/2 is the temperature range corresponding to D/Dmax ¼ 0.5 (halfpeak width). Table 2 shows the pyrolysis characteristic parameters of all samples, where Ti of SS and RH were measured as 197 C and 268 C, and their Tf were determined as 975 C and 939 C, respectively. Obviously, SS exhibits lower Ti and higher Tf than RH, which is consistent with our previous study under air atmosphere (Wang et al., 2019a). It can be explained that SS consists of micromolecular organic matter (Kulikowska, 2016) and is rich in reactive oxygen groups, as shown in Table 1, while the ash component of SS hinders its high-temperature pyrolysis. With the introduction of RH, the Ti of the mixtures increases, while the Tf decreases slightly. This means that the devolatilization of RH and the mineral decomposition of SS dominated the initial and terminative decomposition of the mixtures, respectively. As the addition of RH increased, the residue mass decreased from 66.91 to 26.89%, which
Table 2 Pyrolysis characteristic parameters for samples at heating rate 20 C/min.
Fig. 1. TG-DTG curves at the heating rate of 20 C/min.
Samples
Ti ( C)
Tf ( C)
Mf (%)
CPI (1013/min2$ C3)
SS RH 20RH 30RH 40RH
197 268 231 254 262
975 939 973 971 969
66.91 26.89 59.47 54.25 51.21
7.64 565.52 49.15 75.41 117.99
Ti: temperature for initial mass loss, Tf: temperature for final mass loss, Mf: the residue mass.
Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
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was mainly related to the high ash content of SS. The larger the CPI value, the more intense the sample reaction. It can be observed that the addition of RH promotes a sharp increase in the CPI value, that is, the reactivity can be effectively improved by co-pyrolysis.
that the addition of RH reduces the cumulative amounts of H2, CH4, and C2H2, but increases the level of CO2 production. This means that biomass additives can inhibit hydrocarbon release and then enrich more hydrogen component in biochar.
3.2. Gaseous emissions during pyrolysis
3.3. Interaction investigation of co-pyrolysis
The ion fragments of the main gaseous products (m/z ¼ 2e60) produced during pyrolysis were monitored by TG-MS analysis (see Fig. 2). Hydrogen (m/z ¼ 2) is a key gaseous product in terms of pyrolysis reaction. As can be seen from Fig. 2a, H2 emissions occur continuously over a wide temperature range (single peak) for each component. Interestingly, the evolution curves of H2 turns into two stages after co-pyrolysis. The emissions of H2 at the lower temperature (250e450 C) and high temperature (450e700 C) are due to the primary degradation of the compounds enriched in hydrogen and the condensation or dehydrogenation of aromatic structures (Wang et al., 2015; Zhao et al., 2011), respectively. Abundant hydrogen and less aromatic substances in RH (Table 1) may be responsible for the cleavage of the H2 emission peak during the copyrolysis process. The dominant gas product (CH4) in the pyrolysis process (compare to Fig. 2) is produced by multi-step reactions (Fermoso and Masek, 2018), so the emission curves of CH4 (except for RH) can be divided into 4 stages. The second (the foremost) stage may be attributed to the decomposition of the species containing eCH3, while the third and fourth stages correspond to the secondarily cracks of the stable chemical bonds and the condensation of the aromatic molecules (Wang et al., 2015), respectively. CH4 presented below 200 C (first stage) can be considered a signal associated with the evolutionary CHþ 3 fragmentation ion. CnHm (n ¼ 2, 3, 4) has a similar decomposition mechanism to H2 with two peaks (except RH). The mechanisms for the two peaks can be proposed: the lowtemperature (200e400 C) peak represents that the large molecular functional group is decomposed into recombined small molecular compounds, and the high-temperature (400e600 C) peak represents the decomposition of the aromatic structures or oxygencontaining polymethylene compounds (Zou et al., 2017). It is worth noting that the temperature corresponding to both the maximal release and the fragmented ion intensity of C2H2 are the highest, compared to other hydrocarbon products. It is reasonable to conclude that C2H2 (one of the main products) is formed by the decomposition of the hydrocarbons having a large number of carbon atoms. CO2 emissions distributed over a wide temperature range were observed. The prominent peak of the CO2 profile is around 200e500 C, which is facilitated by the decarboxylation/ decarbonylation reaction of the macromolecules, such as aliphatic groups (Yu et al., 2007). The second peak at around 500e650 C may be derived from the breakage of carbonates, carbonyls, ethers, quinones, oxygen-containing heterocycles and other oxygencontaining functional groups with high thermal stability (Luo et al., 2017). The emission of hydrocarbons such as CH2O and HCOOH can be negligible, so the formation mechanism will not be discussed in detail. The gas output produced during the pyrolysis process was obtained using an integrating method, and the cumulative amounts of the gas products are shown in Fig. 3. As can be seen from Fig. 3, H2, CH4, C2H2 and CO2 are the major pyrolysis gases produced. Obviously, the cumulative amounts of all evolved gaseous products (except CH4) of RH are higher than that of SS. Previous research (Marco et al., 2011) has set CHþ 3 as a probable precursor of CH4, and more CHþ 3 formed in SS results in more CH4 release than that in RH (as shown in Fig. 2b). The main gas output sequence is: CH4 > CO2 > H2 > C2H2 for the mixtures, at least an order of magnitude higher than other gaseous products. It can be observed
Fig. 4 shows the deviations of weight loss and accumulations of the major gas emissions (H2, C2H2, CH4 and CO2) during the copyrolysis process. As can be seen from Fig. 4a, when RH dose is 30%, the deviations between the theoretical and experimental TG curves remain positive, while the deviations of the other mixtures (20RH and 40RH) are negative. This indicates that the interaction between SS and RH is an inhibition of degradation when 30% RH is added. However, the interaction turns to promote the effect regardless of whether the RH addition is decreased or increased. The mechanism of the saltation can be determined: (1) biomass can contribute additional heat to overcome the barriers of the decomposition of SS (Chen et al., 2016). (2) RH char producing a porous structure (Zhang et al., 2018) can capture the volatile substances (including gaseous and liquid products), resulting in slow release of volatile substances (Kai et al., 2017). The biochar formed by 30RH has outstanding adsorption ability for volatile substances and is a key controlling factor for determining the interaction. When the RH additive dose is higher or lower, the thermal effect dominates the interaction. In addition, the deviation curves of the weight losses of 20RH and 40RH have almost the same trends, and there are two maximum peaks with an increase in temperature, corresponding to about 300 C and 910 C, respectively. Obviously, 20RH has a lower peak at low temperatures and a higher peak at high temperature. It can also prove that the more char formed, the stronger the inhibition of thermal degradation, which is similar to Yuan’s research (Yuan et al., 2018). As shown by the deviation curves for the main gaseous products (Fig. 4b-e), there are gas-generation interactions during the copyrolysis process. The deviations of H2, C2H2, CH4, and CO2 emissions from all mixtures are positive (except C2H2 emission of 30RH), indicating that the release of H2, C2H2, CH4 and CO2 was inhibited by the interaction. Overall, the synergistic effect is to inhibit the production of gases. It is important to note that the maximum absolute deviation of all mixtures occurs at the low-temperature stage (<450 C), indicating that the degree of inhibition is most pronounced at low temperature. These results indicate that the copyrolysis of SS and RH promotes the interactions of free radicals or intermediates from liquefaction, resulting in the increased tar production (Leng et al., 2018). The resulting sticky tar may coat the residue and prevent the release of gaseous products. As the temperature increases, the tar is decomposed or volatilized, resulting in a decrease in the inhibitory effect. Liu et al. (2018) reported similar observations. However, as the temperature further increases, the inhibitory effect reappears, indicating that the formed char mainly restrains the release of the gaseous product. Fig. 4c shows that the release of CH4 can be restrained by the interaction between SS and RH, and the inhibition is most pronounced for 30RH. And the interactions in the 40RH sample resulted in the greatest inhibition of H2, C2H2 and CO2. In summary, the interaction between SS and RH restrains the generation of gaseous products, especially at high RH ratios. Namely, the interaction may affect on biochar performance, combing with our previous research (Chen et al., 2019). 3.4. Characterization of bio-char The physicochemical characteristics of biochars from SS and RH are summarized in Table 3. It can be found that the yield of char decreases as the RH ratio increases, which is consistent with that in
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Fig. 2. Gas emission curves during pyrolysis process.
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Fig. 3. Normalized integral values of gaseous emission produced during co-pyrolysis.
Section 3.1. The ash content in biochar decreases as the RH ratio increasing, while the VM increases. It is worth noting that the percentages of the fixed carbon (FC), C and H of 30RHC reach the maximum (Table 3), which contradicts the ultimate and approximate analysis of the raw materials. This contradiction can be explained by the synergistic effect of the addition of 30% RH which hinders the release of gaseous products and leads to the deposition of these hydrocarbons on biochar. Regarding SSC, H/C and O/C decrease from 1.32 to 0.93/0.80/0.81 and 0.39 to 0.12/0.16/0.33 for biochar of SS-RH mixtures (20RHC, 30RHC and 40RHC), respectively. The lower H/C ratio shows higher carbonization and aromaticity (Parshetti et al., 2013). In other words, RH additive promotes the sludge carbonization and aromaticity. However, carbonization and aromatization do not result in a continuous decrease in H/C when RH is added, as it moderately rises to 0.81 when the RH dose rises to 40%. This indicates that 30RHC has the most condensed aromatic structures and a sufficient degree of carbonization (Sun et al., 2013). A higher O/C ratio means the presence of a more stable carbon-oxygen complex in biochar (Liu et al., 2010), i.e., biochar with higher RH introduction can provide
Fig. 4. Deviation of TG and gas integral due to co-pyrolysis of SS and rice husk.
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Table 3 Basic characteristic of bio-char. Sample
SSC 20RHC 30RHC 40RHC a
Char yield (%)
80.21 70.12 64.6 58.32
Proximate analysis (%)
Ultimate analysis (%)
Atomic Ratio
Ash
VM
FC
C
H
N
Oa
H/C
O/C
84.36 81.24 75.99 73.13
9.33 10.02 11.93 14.89
6.31 9.74 12.08 11.98
8.98 14.98 17.80 17.11
0.99 1.16 1.18 1.15
1.01 1.18 1.17 1.06
4.66 2.44 3.86 7.55
1.32 0.93 0.80 0.81
0.39 0.12 0.16 0.33
SBET (m2g1)
19.80 25.57 47.40 68.07
Calculated by O ¼ 100-Ash-C-H-N.
more activation sites. As shown in Table 3, during the pyrolysis of SS, the surface area of the biochar increases as the RH dose increases. Interestingly, the rate of increase rises rapidly after 30% and 40% RH addition. Such significant increase may result from the adequate volatilization of volatile substances in the SS-RH mixtures (Wang et al., 2017b) and the porous structure in the RH residue, which has been proved in previous study (Pode, 2016). The FTIR spectra of the biochars are similar, indicating that RH addition does not lead to significant changes in surface functional groups (Fig. 5). The peak range of 3205e3429 cm1 corresponds to eOH stretching vibration, while the peak near 1440 cm1 is related to eOH bending vibration (Krishnani et al., 2008; Yang et al., 2010). The characteristic peaks of the eOH bending vibration of different biochars are located at 1444 cm1 (SSA and 20RHC) and 1435 cm1 (30RHC and 40RHC), respectively. The peak redshift indicates that the hydroxyl groups tend to be stable, which also clarifies the improvement of the adsorbability of the biochars after the addition of 30% and 40% RH (Feng et al., 2011). The peak around 2800e3000 cm1 corresponds to the aliphatic CHn groups (CeH stretching). After the addition of 30% and 40% RH, the peak near 2950 cm1 almost disappeared, indicating breakings in the aliphatic chains. The results show that a large number of RH additives can promote the transformation of fatty hydrocarbons into aromatic structures in biochars (Wang et al., 2019b), which is inferred from the H/C ratio in Table 3. The peaks at 1619e1624 cm1 reflect the amide bonds and the aromatic ring stretching (C]O, eCONHe, and C]C stretching vibration) (Jin et al., 2016), while the peak at 694 cm1 corresponds to the vibrations of the aromatic compounds and the hetero-aromatic compounds (Huang et al.,
Fig. 5. FTIR spectra of different biochars.
2017a). The appearance of these functional groups suggests that the biochar possesses an aromatization structure, which can give the biochar a strong adsorption capacity (Harvey et al., 2011). It is known that the absorption peaks observed in the vicinity of 460e1100 cm1 are the characteristic silica region. For all biochars, the silica absorption bands appear around 470, 780 and 1035 cm1 (Magdziarz et al., 2016). SEM analysis of the biochars at different RH dose is shown in Fig. 6. The biochars with different RH doses possess a porous structure with small granules coated on the surface, mainly due to the generation and the release of gaseous products during the pyrolysis process (Sun et al., 2018). Differences among different biochars were observed. As shown in Fig. 6a and b, there is insufficient pore structure in the biochar (SSC and 20RHC). Pore development is observed in biochars (30RHC and 40RHC) (Fig. 6c and d), which is consistent with the specific surface area of different biochar samples. Overall, based on the above discussion, 30RHC has remarkable adsorption potential.
4. Conclusion TG-MS analysis of the co-pyrolysis of SS and RH showed that the volatile decomposition was promoted by the addition of RH while inhibiting the char reactions. The addition of RH improved the Ti and CPI value of blends while reducing the Tf. This meant that the thermal degradation of RH and SS dominated the initial and terminative decomposition of the mixtures respectively, and RH introduction motivated the reactivity sharply. The major pyrolysis gas products were H2, CH4, C2H2 and CO2 for the SS-RH mixtures, in the order: CH4 > CO2 > H2 > C2H2. The RH additive can reduce the accumulation of H2, CH4, and C2H2 in SS, but increase the CO2 content. Namely, RH additive can inhibit hydrocarbon release and enrich hydrogen component in biochar during co-pyrolysis. The maximum deviations (%) value between TG-MS results of the mixtures and the theoretical results reached 18.08%, which indicates there existed interaction between SS and RH. The interaction inhabited the thermal degradation of 30RH, however, it turned to accelerate the degradation of 20RH and 40RH. It can be explained by formation of the biochar with outstanding adsorption ability for volatile substances under 30% RH addition. Meanwhile, the interactions inhibited the main gas (H2, C2H2, CH4 and CO2) generation for all mixtures. It also indicated that hydrocarbon can enrich in the formed biochar during co-pyrolysis. RH additive promoted carbonization and aromaticity of biochar derived from the copyrolysis of SS and RH, while the pore development and the specific surface area were improved as the RH ratio increases. It is worth noting that 30RHC possessed maximum FC, C and H content, while had the most condensed aromatic structure and sufficient degree of carbonization. Overall, biochar derived from the copyrolysis of SS and RH has remarkable adsorption potential, especially for 30RHC.
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Fig. 6. SEM analysis of bio-char with different RH dose, (a) SSC; (b) 20RHC; (c) 40RHC; (d) 40RHC.
Declaration of competing interest The authors declared that they have no conflicts of interest to this work. Acknowledgements This research was supported by a grant from National Natural Science Foundation of China (No. 51908433) and Natural Science Foundation of Hubei Province-China (No.2019CFB236). The authors would also like to thank reviewers for commenting on this paper. References onard, A., 2014. Arlabosse, P., Ferrasse, J.H., Lecomte, D., Crine, M., Dumont, Y., Le Efficient Sludge Thermal Processing: from Drying to Thermal Valorization. Wiley-VCH Verlag GmbH & Co. KGaA. onard, A., 2013. Review on fundamental aspect of Bennamoun, L., Arlabosse, P., Le application of drying process to wastewater sludge. Renew. Sustain. Energy Rev. 28, 29e43. Buyukada, M., 2017. Uncertainty estimation by Bayesian approach in thermochemical conversion of walnut hull and lignite coal blends. Bioresour. Technol. 232, 87e92. Chen, J., Liu, J., He, Y., Huang, L., Sun, S., Sun, J., Chang, K., Kuo, J., Huang, S., Ning, X., 2016. Investigation of co-combustion characteristics of sewage sludge and coffee grounds mixtures using thermogravimetric analysis coupled to artificial neural networks modeling. Bioresour. Technol. 225, 234e245. Chen, S., Qin, C., Wang, T., Chen, F., Li, X., Hou, H., Zhou, M., 2019. Study on the adsorption of dyestuffs with different properties by sludge-rice husk biochar: adsorption capacity, isotherm, kinetic, thermodynamics and mechanism. J. Mol. Liq. 285, 62e74. Deng, S., Tan, H., Wang, X., Yang, F., Cao, R., Wang, Z., Ruan, R., 2017. Investigation on the fast co-pyrolysis of sewage sludge with biomass and the combustion reactivity of residual char. Bioresour. Technol. 239. S0960852417305710ss. Fang, S., Yu, Z., Ma, X., Lin, Y., Lin, Y., Chen, L., Fan, Y., Liao, Y., 2017. Co-pyrolysis
characters between combustible solid waste and paper mill sludge by TG-FTIR and Py-GC/MS. Energy Convers. Manag. 144, 114e122. Feng, Y., Yang, F., Wang, Y., Ma, L., Wu, Y., Kerr, P.G., Yang, L., 2011. Basic dye adsorption onto an agro-based waste material e Sesame hull (Sesamum indicum L.). Bioresour. Technol. 102, 10280e10285. Fermoso, J., Masek, O., 2018. Thermochemical decomposition of coffee ground residues by TG-MS: a kinetic study. J. Anal. Appl. Pyrolysis 130, 358e367. mez, N.R., Quispe, V., Garrue s, J.A., Martínez, M.A., Murillo, M.B., Gea, G., 2017. CoGo pyrolysis of sewage sludge and manure. Waste Manag. 59, 211. Harvey, O.R., Herbert, B.E., Rhue, R.D., Kuo, L.J., 2011. Metal interactions at the biochar-water interface: energetics and structure-sorption relationships elucidated by flow adsorption microcalorimetry. Environ. Sci. Technol. 45, 5550. Huang, H.J., Yang, T., Lai, F.Y., Wu, G.Q., 2017a. Co-pyrolysis of sewage sludge and sawdust/rice straw for the production of biochar. J. Anal. Appl. Pyrolysis. Huang, H.J., Yuan, X.Z., 2016. The migration and transformation behaviors of heavy metals during the hydrothermal treatment of sewage sludge. Bioresour. Technol. 200, 991e998. Huang, L., Xie, C., Liu, J., Zhang, X., Chang, K., Kuo, J., Sun, J., Xie, W., Zheng, L., Sun, S., 2017b. Influence of catalysts on co-combustion of sewage sludge and water hyacinth blends as determined by TG-MS analysis. Bioresour. Technol. 247, 217e225. Jin, J., Li, Y., Zhang, J., Wu, S., Cao, Y., Liang, P., Zhang, J., Wong, M.H., Wang, M., Shan, S., 2016. Influence of pyrolysis temperature on properties and environmental safety of heavy metals in biochars derived from municipal sewage sludge. J. Hazard Mater. 320, 417e426. Jung, H., Sewu, D.D., Ohemeng-Boahen, G., Lee, D.S., Woo, S.H., 2019. Characterization and adsorption performance evaluation of waste char by-product from industrial gasification of solid refuse fuel from municipal solid waste. Waste Manag. 91, 33e41. Kai, X., Li, R., Yang, T., Shen, S., Ji, Q., Zhang, T., 2017. Study on the co-pyrolysis of rice straw and high density polyethylene blends using TG-FTIR-MS. Energy Convers. Manag. 146, 20e33. Kai, X., Yang, T., Shen, S., Li, R., 2019. TG-FTIR-MS study of synergistic effects during co-pyrolysis of corn stalk and high-density polyethylene (HDPE). Energy Convers. Manag. 181, 202e213. Khan, A.A., Jong, W.D., Jansens, P.J., Spliethoff, H., 2009. Biomass combustion in fluidized bed boilers: potential problems and remedies. Fuel Process. Technol. 90, 21e50. Krishnani, K.K., Meng, X., Christodoulatos, C., Boddu, V.M., 2008. Biosorption
Please cite this article as: Wang, T et al., Co-pyrolysis behavior of sewage sludge and rice husk by TG-MS and residue analysis, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.119557
T. Wang et al. / Journal of Cleaner Production xxx (xxxx) xxx mechanism of nine different heavy metals onto biomatrix from rice husk. J. Hazard Mater. 153, 1222e1234. Kulikowska, D., 2016. Kinetics of organic matter removal and humification progress during sewage sludge composting. Waste Manag. 49, 196e203. Ledakowicz, S., Stolarek, P., Malinowski, A., Lepez, O., 2019. Thermochemical treatment of sewage sludge by integration of drying and pyrolysis/autogasification. Renew. Sustain. Energy Rev. 104, 319e327. Leng, L., Leng, S., Chen, J., Yuan, X., Li, J., Li, K., Wang, Y., Zhou, W., 2018. The migration and transformation behavior of heavy metals during co-liquefaction of municipal sewage sludge and lignocellulosic biomass. Bioresour. Technol. 259, 156. Lin, B., Huang, Q., Chi, Y., 2018. Co-pyrolysis of oily sludge and rice husk for improving pyrolysis oil quality. Fuel Process. Technol. 177, 275e282. Lin, Y., Liao, Y., Yu, Z., Fang, S., Ma, X., 2017. A study on co-pyrolysis of bagasse and sewage sludge using TG-FTIR and Py-GC/MS. Energy Convers. Manag. 151, 190e198. Liu, C., Liu, J., Sun, G., Xie, W., Kuo, J., Li, S., Liang, J., Chang, K., Sun, S., Buyukada, M., Evrendilek, F., 2018. Thermogravimetric analysis of (co-)combustion of oily sludge and litchi peels: combustion characterization, interactions and kinetics. Thermochim. Acta 667, 207e218. Liu, Z., Zhang, F.-S., Wu, J., 2010. Characterization and application of chars produced from pinewood pyrolysis and hydrothermal treatment. Fuel 89, 510e514. Luo, L., Liu, J., Zhang, H., Ma, J., Wang, X., Jiang, X., 2017. TG-MS-FTIR study on pyrolysis behavior of superfine pulverized coal. J. Anal. Appl. Pyrolysis 128, 64e74. Magdziarz, A., Wilk, M., Gajek, M., Nowak-Wo zny, D., Kopia, A., Kalemba-Rec, I., ski, J.A., 2016. Properties of ash generated during sewage sludge comKozin bustion: a multifaceted analysis. Energy 113, 85e94. Marco, I., Roberto, D.M., Maurizio, G., Marco, B., 2011. Clay-sewage sludge copyrolysis. A TG-MS and Py-GC study on potential advantages afforded by the presence of clay in the pyrolysis of wastewater sewage sludge. Waste Manag. 31, 71e77. Minh Loy, A.C., Yusup, S., Fui Chin, B.L., Wai Gan, D.K., Shahbaz, M., Acda, M.N., Unrean, P., Rianawati, E., 2018. Comparative study of in-situ catalytic pyrolysis of rice husk for syngas production: kinetics modelling and product gas analysis. J. Clean. Prod. 197, 1231e1243. Naqvi, S.R., Hameed, Z., Tariq, R., Taqvi, S.A., Ali, I., Niazi, M.B.K., Noor, T., Hussain, A., Iqbal, N., Shahbaz, M., 2019. Synergistic effect on co-pyrolysis of rice husk and sewage sludge by thermal behavior, kinetics, thermodynamic parameters and artificial neural network. Waste Manag. 85, 131e140. Parshetti, G.K., Liu, Z., Jain, A., Srinivasan, M.P., Balasubramanian, R., 2013. Hydrothermal carbonization of sewage sludge for energy production with coal. Fuel 111, 201e210. Pode, R., 2016. Potential applications of rice husk ash waste from rice husk biomass power plant. Renew. Sustain. Energy Rev. 53, 1468e1485. Soria-Verdugo, A., Goos, E., Morato-Godino, A., García-Hernando, N., Riedel, U., 2017. Pyrolysis of biofuels of the future: sewage sludge and microalgae e thermogravimetric analysis and modelling of the pyrolysis under different temperature conditions. Energy Convers. Manag. 138, 261e272. Sun, K., Kang, M., Zhang, Z., Jin, J., Wang, Z., Pan, Z., Xu, D., Wu, F., Xing, B., 2013. Impact of deashing treatment on biochar structural properties and potential sorption mechanisms of phenanthrene. Environ. Sci. Technol. 47, 11473e11481. Sun, S., Huang, X., Lin, J., Ma, R., Fang, L., Zhang, P., Qu, J., Zhang, X., Liu, Y., 2018. Study on the effects of catalysts on the immobilization efficiency and mechanism of heavy metals during the microwave pyrolysis of sludge. Waste Manag. 77, 131e139. Tan, C., Zhang, Y., Wang, H., Lu, W., Zhou, Z., Zhang, Y., Ren, L., 2014. Influence of pyrolysis temperature on characteristics and heavy metal adsorptive
9
performance of biochar derived from municipal sewage sludge. Bioresour. Technol. 164, 47e54. Tang, S., Zheng, C., Zhang, Z., 2018. Effect of inherent minerals on sewage sludge pyrolysis: product characteristics, kinetics and thermodynamics. Waste Manag. 80, 175e185. Tran, H.N., You, S.-J., Chao, H.-P., 2017. Insight into adsorption mechanism of cationic dye onto agricultural residues-derived hydrochars: negligible role ofp-pinteraction. Korean J. Chem. Eng. 34, 1e13. Vamvuka, D., Sfakiotakis, S., Saxioni, S., 2015. Evaluation of urban wastes as promising co-fuels for energy production e a TG/MS study. Fuel 147, 170e183. Vassilev, S.V., Vassileva, C.G., 2016. Composition, properties and challenges of algae biomass for biofuel application: an overview. Fuel 181, 1e33. Wang, M., Li, Z., Huang, W., Yang, J., Xue, H., 2015. Coal pyrolysis characteristics by TGeMS and its late gas generation potential. Fuel 156, 243e253. Wang, T., Hou, H., Ye, Y., Rong, H., Li, J., Xue, Y., 2019a. Combustion behavior of refuse-derived fuel produced from sewage sludge and rice husk/wood sawdust using thermogravimetric and mass spectrometric analyses. J. Clean. Prod. 222, 1e11. Wang, T., Xue, Y., Zhou, M., Yuan, Y., Zhao, S., Tan, G., Zhou, X., Geng, J., Wu, S., Hou, H., 2017a. Comparative study on the mobility and speciation of heavy metals in ashes from co-combustion of sewage sludge/dredged sludge and rice husk. Chemosphere 169, 162e170. Wang, X., Chi, Q., Liu, X., Wang, Y., 2019b. Influence of pyrolysis temperature on characteristics and environmental risk of heavy metals in pyrolyzed biochar made from hydrothermally treated sewage sludge. Chemosphere 216, 698e706. Wang, X., Gu, L., Zhou, P., Zhu, N., Li, C., Tao, H., Wen, H., Zhang, D., 2017b. Pyrolytic temperature dependent conversion of sewage sludge to carbon catalyst and their performance in persulfate degradation of 2-Naphthol. Chem. Eng. J. 324, 203e215. Wei, X., Ma, X., Peng, X., Yao, Z., Yang, F., Dai, M., 2018. Comparative investigation between co-pyrolysis characteristics of protein and carbohydrate by TG-FTIR and Py-GC/MS. J. Anal. Appl. Pyrolysis 135, 209e218. Yang, H., Yan, R., Chen, H., Dong, H.L., Zheng, C., 2010. Characteristics of hemicellulose, cellulose and lignin pyrolysis. Fuel 86, 1781e1788. Yu, J., Lucas, J.A., Wall, T.F., 2007. Formation of the structure of chars during devolatilization of pulverized coal and its thermoproperties: a review. Prog. Energy Combust. Sci. 33, 135e170. Yuan, H., Fan, H., Shan, R., He, M., Gu, J., Chen, Y., 2018. Study of synergistic effects during co-pyrolysis of cellulose and high-density polyethylene at various ratios. Energy Convers. Manag. 157, 517e526. Zhang, K., Sun, P., Faye, M.C.A.S., Zhang, Y., 2018. Characterization of biochar derived from rice husks and its potential in chlorobenzene degradation. Carbon 130. Zhang, W., Yuan, C., Xu, J., Yang, X., 2015. Beneficial synergetic effect on gas production during co-pyrolysis of sewage sludge and biomass in a vacuum reactor. Bioresour. Technol. 183, 255e258. Zhao, Y., Hu, H., Jin, L., He, X., Wu, B., 2011. Pyrolysis behavior of vitrinite and inertinite from Chinese Pingshuo coal by TGeMS and in a fixed bed reactor. Fuel Process. Technol. 92, 780e786. Zhou, Y., Chen, Z., Gong, H., Chen, L., Yu, H., Wu, W., 2019. Characteristics of dehydration during rice husk pyrolysis and catalytic mechanism of dehydration reaction with NiO/g-Al2O3 as catalyst. Fuel 245, 131e138. Zhu, J., Yang, Y., Yang, L., Zhu, Y., 2018. High quality syngas produced from the copyrolysis of wet sewage sludge with sawdust. Int. J. Hydrogen Energy 43. S0360319918303148. Zou, C., Ma, C., Zhao, J., Shi, R., Li, X., 2017. Characterization and non-isothermal kinetics of Shenmu bituminous coal devolatilization by TG-MS. J. Anal. Appl. Pyrolysis 127, 309e320.
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