- Email: [email protected]
Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
JOEI291_proof ■ 16 December 2016 ■ 1/7
Journal of the Energy Institute xxx (2016) 1e7
Contents lists available at ScienceDirect
Journal of the Energy Institute journal homepage: http://www.journals.elsevier.com/journal-of-the-energyinstitute
Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield Q4
Shengdan Feng, Ping Li*, Zeyi Liu, Yue Zhang, Zhuangmei Li School of Chemistry and Chemical Engineering, Ningxia University, Yinchuan 750021, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 24 July 2016 Received in revised form 3 December 2016 Accepted 5 December 2016 Available online xxx
The thermal decomposition of coal was the essential step of many reactions, thus it was widespread concerned. In order to investigate the behaviors and kinetics of coal pyrolysis, coal samples which obtained from Ningdong coalfield of China were pyrolyzed with a tubular furnace in argon atmosphere at the heating rate of 5 K min1. The primary gaseous products including CH4, H2, N2, CO, CO2, C2H4 and C2H6 were quantified using a gas chromatogram. It can be seen that with the temperature increasing, the yields of H2 and CO increased, while the others decreased. In order to produce possibly much tar, the optimal temperature was 923 K. The characteristic of pyrolysis kinetics was determined by thermo gravimetric analysis measurement. The CoatseRedfern and FlynneWalleOzawa methods was used to obtain kinetic parameters. The activation energy range of 50e200 kJ mol1 was determined. © 2016 Published by Elsevier Ltd on behalf of Energy Institute.
Keywords: Coal pyrolysis Thermal gravimetric analysis Kinetic analysis
1. Introduction Aiming at the condition of resource distribution in china, coal resource is relatively abundant [1]. As one of the important base of energy and chemical industry in China, the coal chemical industry of Ningxia is developing rapidly. The development of Ningxia relies on coal to a great extent. It is more necessary that coal can be efficient utilized and converted for the characteristic of relatively low rank. In this study, one representative coal sample (MLT) which is selected from Maliantai coal mine, Ningdong coalfield was chosen for research. Pyrolysis is the fundamental first procedure in many coal conversation projects [2]. The conclusions of the pyrolysis behaviors may contribute to the coal upgrading. The research on the thermal decomposition of coal can contribute to the efficient utilization and conversion of coal. Therefore, pyrolysis manners have attracted extensive concern [3e6]. The heating process of coal can be divided into two steps [7]. Firstly, the coal depolymerizes while gas, water vapor, and tar are generated. The second step is the repolymerization process, in which char formed. Large quantities of pyrolytic reactions appear in the complex process [2,8,9]. At the same time, developing knowledge of the reaction kinetics is important. The kinetic parameters are necessary for accurate design of pyrolysis systems [4]. It is also necessary for the definition and optimization of the operating conditions to obtain kinetic parameters. Thermo gravimetric analysis gives a rapid quantitative method to acquire kinetic parameters. Because of the advantages of relatively higher temperature and easy operating, the TGA has been widely used for researchers [4,10,11]. The purpose of this study is to explore the devolatilization behaviors of coking coal from Ningdong coal field in low temperature. The kinetic parameters were also calculated based on different methods. Overall, this research on the MLT coking coal will be contributed to the practical effective application. 2. Experimental section 2.1. Preparation of coal samples In this experiment, we studied a kind of low rank coal. Sample with particle size from 75 mm to 100 mm was selected for the subsequent pyrolysis experiments.
* Corresponding author. E-mail address: [email protected] (P. Li). http://dx.doi.org/10.1016/j.joei.2016.12.001 1743-9671/© 2016 Published by Elsevier Ltd on behalf of Energy Institute.
Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
Q1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
JOEI291_proof ■ 16 December 2016 ■ 2/7
2
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
Ultimate analysis and proximate analysis of the sample were determined based on Chinese National Standard GB/T 476-2001 [12] and GB/T 212-2008 [13]. The results are shown in Table 1. 2.2. Experimental equipment and procedures The experiments of pyrolysis were carried out on a furnace (SK-G06123K, Zhonghuan Lab Furnace). The adopted experimental apparatus are shown schematically in Fig. 1. Sample (2 ± 0.2 g) was placed in a quartz sample tube and pushed into the center of the furnace. In order to make sure the sample reaction was without air, the high purity argon (Ar) was used as the carrier gas. A mass flow controller (CS200A, Sevenstar) was used to control the flow of carrier gas. The tube was purged continuously with Ar. The volatile matter during pyrolysis was brought out by the carrier gas from the high temperature zone to suppress the occurrence of the secondary reactions. The purpose of heating belt wrapped outside the outlet tube is to suppress the condensation of tar. Water trap was used to collect the tar. The gases were collected with a gas bag for gas chromatograph (GC) analysis. Coal samples were heated to the ultimate temperature with the heating rate of 5 K min1, and then held 40 min at ultimate temperature to insure the volatile matter release completely. Temperature difference between sample and furnace was proved to be within 5 K. The solid char was removed from the reactor and its mass was determined when the experiment was completed. Gas yield was obtained through the gas chromatographic measurements. A high sensitivity gas chromatogram (GC-2008, Guangzheng) equipped with a thermal conductivity detector (TCD) was used to quantify the main gaseous species, including H2, N2, CH4, CO, CO2, C2H4, and C2H6. The quantitative analysis of H2, N2, CH4, CO was carried out with a packed column (13) and another packed column (GDX502) was used for the other species. Due to its condensable characteristics, it is difficult to measure the yield of tar directly. In this paper, the yield of tar can be obtained by subtraction method and it equals to the mass of initial coal sample subtracts char and gas products (CH4, H2, CO, CO2, C2H4, and C2H6) from the GC. 2.3. Kinetic analysis The kinetic analysis tests were carried out on a thermal gravimetric analyzer (Setsys Evo 16, SETARAM), by which the mass loss curve (TG curve) could be obtained. Every test needed about 20 mg coal, the pressure condition was ambient pressure with an argon flow of 100 ml min1. Sample was heated to 1073 K from room temperature with heating rate of 10, 20 and 30 K min1, respectively. There are several methods available in literature that used for calculation of kinetic parameters. Both of the single-heating rate and the isoconversional method can be used to obtain the pyrolysis kinetic. The single-heating rate method, such as the CoatseRedfern method [14], needs the data obtained at only one heating rate. However, the single-heating method needs better knowledge of the reaction mechanism, while the reaction mechanism is not easy to determine. Contrary to the single-heating rate method, the isoconversional method, which is also called multi-heating rate method, needs a series experimental data acquired at three heating rates at least. The mathematical model and prior assumption are not necessary. Therefore, the multi-heating rate method has been widely used and recommended. 2.3.1. Non-isothermal single heating rate In this study, the conversion rate a is defined as follows:
a¼
w0 wt 100% w0 w∞
(1)
where w0 refers to the initial mass of the sample (g), wt refers to the mass of the sample at time t (g) and w∞ refers to the final mass of the sample (g). Under the reaction mechanism involved in a thermal conversion process, a well-established method for data analysis was applied. It is assumed the general reaction rate ddta is a function of the conversion (a) and a rate constant (k), can be expressed as follows:
da ¼ kf ðaÞ dt
(2)
where f ðaÞ is the hypothetical model of the reaction mechanism. The reaction rate constant (k) was dependent on the temperature and could be expressed as follows using the Arrhenius equation:
Table 1 Characteristic of MLT. Proximate analysis (air-dried basis, wt%) Moisture 1.53 Volatile 32.39 Fixed carbon 56.18 Ash 9.64 Ultimate analysis (air-dried basis, wt%) Carbon 72.01 Hydrogen 4.18 Oxygena 10.61 Nitrogen 1.41 Sulfur 0.62 a
By difference.
Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
JOEI291_proof ■ 16 December 2016 ■ 3/7
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
3
Fig. 1. Experimental apparatus of the reaction system.
E k ¼ A exp RT
(3)
where A refers to the pre-exponential factor (min1). E refers to the apparent activation energy (kJ mol1). R refers to the gas constant and equals 8.314 (kJ K1 mol1). T refers to the absolute temperature (K). When heating rate (b ¼ dT ) is a constant during combustion, Eq. (3) can be transformed into: dt
da A E ¼ f ðaÞ exp RT dT b
(4)
The chemical reaction model is the mostly used in many kinetic studies, it can be described as:
f ðaÞ ¼ ð1 aÞn
(5)
where n refers to the order of reaction. The equation derived for calculating the activation energy value is given as:
lnð1 aÞ AR 2RT E AR E zln 1 ¼ ln ln E RT RT bE bE T2
ðn ¼ 1Þ
(6)
"
# 1 ð1 aÞ1n AR 2RT E AR E zln 1 ln ¼ ln E RT RT bE bE ð1 nÞT 2
ðns1Þ
(7)
# " aÞ 1ð1aÞ1n against T1 [15]. In this method, TG where E and A can be acquired by the slope and intercept of the line of ln lnð1 or ln 2 2 ð1nÞT T data at only one heating rate is enough to calculate the kinetic parameters. 2.3.2. Isoconversional method In this part, different TG data were used to calculate activation energy by FlynneWalleOzawa (FWO) iso-conversional method [16], which has been widely accepted by researchers. By integration and application the function of Eq. (4), the following equation [1] is obtained.
ln b ¼ ln
AE E 5:331 1:052 RgðaÞ RT
where gðaÞ ¼
(8)
R a da
0 f ðaÞ
By assumingf ðaÞ, a series of ln b versus T1 can be obtained for each heating rate at a constant conversion ratioa. E can be obtained from the slope. 3. Results and discussion 3.1. Influence of ultimate temperature on yields The Fig. 2 indicates yields of pyrolysis products at different temperatures with the heating rate of 5 K min1, under the argon atmosphere. As it shows, at a certain temperature, the yield of char is far higher than the yield of gas. However, the yield of tar is slightly higher than that of gas. With the temperature increasing, the gas yield increases while the char decreases. The yield of tar varies relatively small, and the maximum yield occurs at the temperature of 923 K. This conclusion may be due to the existence of secondary cooking and cracking reaction Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
JOEI291_proof ■ 16 December 2016 ■ 4/7
4
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
Fig. 2. Yields of pyrolysis products at the heating rate of 5 K min1.
at temperatures higher than 923 K. The result agrees with the other researchers [17]. Because of the high contents of phenolics, the tar could used to produce many chemical products with high-added value. In order to obtain tar as much as possible, 923 K is the optimal temperature for the pyrolysis of the MLT coal. 3.2. Analysis of gaseous products We explored the influence of ultimate temperature on the release of gas. The contents of CO, CO2, CH4, H2, C2H4, C2H6 and N2 among gaseous products are plotted in Fig. 3. High purity argon was used as the carrier gas and the heating rate is 5 K min1. It is found that H2, CH4 and CO are the major products, while the contents of N2, C2H4 and C2H6 are small compared with the others. As illustrated in Fig. 3, the profile of five gases products decrease with the temperature raising, and the decrease of CH4 and CO2 is greater than that of C2H4 and C2H6. However, the amount of hydrogen increases with the temperature rising, which is caused by constant condensation of aromatic structures and the decomposition of heterocyclic compounds. Release of CO2 and CO relates to the decomposition of ether structure, oxygen-bearing heterocycles, inorganic carbonates, and carboxyl [18]. CH4 mainly comes from the break of methyl groups and aryl/aryl-ether bonds and the decomposition temperatures of these structures are low relatively. So the yield of Methane is gradually decreases when the temperature is higher than 823 K. The content of C2H4 and C2H6 are no more than 5%. The release of light hydrocarbons relates to cleavage of the aliphatic chains and bridges [19]. 3.3. Kinetic analysis Fig. 4(a) and (b) show the TG and DTG curve at three heating rates: 10, 20 and 30 K min1. As shown in Fig. 4(a), three key stages consist of the pyrolysis process by different loss rates. The initial stage finishes at 400 K and the weight loss of this stage is about 3%. The small peak about 300 K is caused by the removal of water. What is more, fracture of weak bonds and release of mobile phase in this stage is weak. The next stage is between 600 and 850 K. It is the primary process of pyrolysis. Tar and gas are liberated and semi-char is generated in this stage [20]. In the range of 600e850 K, the weight decreases dramatically with the increasing temperature. The weight loss in this stage is due to the decomposition of the carbonaceous matrix and the evolution of relatively high molecular weight species. The third stage starts at about 900 K and continues up to the final temperature. Condensation of the aromatic ring and the decomposition of mineral matter lead to the mass decrease [18].
Fig. 3. Yields of gaseous products at different temperatures.
Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
JOEI291_proof ■ 16 December 2016 ■ 5/7
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
5
Fig. 4. TG and DTG curves of different heating rates.
Characteristic temperatures during pyrolysis were explored. The initial temperature (T0), peak temperature (Tp) and final temperature (Tf) at different heating rates are summarized and listed in Table 2. As is shown in Fig. 4(b) and Table 2, the derivative thermo gravimetric curves of samples shift toward the right and the characteristic temperatures increase with the heating rate raising. This delaying decomposition is attributes to differences in heat transfer and kinetic rates [1]. The reason is that with heating rate increasing, the reaction time at a certain temperature was shortened, the reaction process moved to high temperature zone. For predicting the devolatilization of coal samples, we gained the kinetic parameters of the pyrolysis process with the single-heating rate and the isoconversional method. 3.3.1. Non-isothermal single heating rate # " aÞ 1ð1aÞ1n By drawing plots of ln lnð1 against 1/T in a range of reaction order (n ¼ 1, 2, 3), we can found that the secondorln 2 2 ð1nÞT T order reaction obtains better fitting result compared with first-order and third-order reactions in general. What is more, Sarwar et al [21] found that the first order reaction unable to represent the complex pyrolysis process. The E and A can be acquired by Eqs. (6) and (7). The consequences are presented in Table 3. The activation energies are in the range of 50 kJ mol1 to 72 kJ mol1, and the frequency factor varies between 0.4 and 27.1 min1. The frequency factor signifies the level of complexity of reaction. The lower A is, the more difficult to carry out of the reaction [22]. Values of the frequency factor increase with heating rate increasing, showing that heating rate is beneficial for the process of pyrolysis. The relative high linear correlation coefficients indicate that the second-order reaction is feasible. 3.3.2. Non-isothermal multiple heating rate Heating rate is an important factor for analysis process. In order to explore the influence of it, multiple heating rate tests were conducted. Results were obtained with FWO method expounded in 2.3.2. Fig. 5 shows the curve of lnb versus 1/T in a series of fractional conversion valued (a ¼ 0.1e0.9). Three sets of (b,T) were gained for each conversion ratio as in Fig. 5 illustrated. According to the slope of a line that fit three points for a certain conversion ratio, the E was gained from Eq. (8). The values of E are listed in Table 4 for different conversion ratios. Average value of the activation energy was determined with arithmetic average. It can be seen from Table 4 that the corresponding 1/T for the same conversion ratio has a relative good linear relation with each other in most cased at different heating rates. Compared with CoatseRedfern, which provides single overall activation energy value of the process, the non-isothermal multiple heating rate method may demonstrate the complexity of reaction mechanism through activation energy of different conversion ratios. The isoconversional method provides remarkable results of kinetic parameters compared with the single heating rate method. The average activation energy is 192.57 kJ mol1. The CoatseRedfern method needs only one thermal curve to calculate the kinetic parameters, but in data processing, some assumptions about reaction mechanism should be made. For the FWO method, the greater amount of tests has to be done, but no assumption is needed and also activation energy at different conversion ratios could be calculated easily. The activation energy obtained by the FWO method is higher compared with that obtained by CoatseRedfern method. Different kinetic analysis methods are not exclusive but mutually complementary [1]. Thus, an appropriate activation energy range should achieved by combining all observations in two methods. Consequently, an activation energy range of 50 kJ mol1 to 200 kJ mol1 is recommended for the pyrolysis process of MLT.
Table 2 Characteristic temperature during pyrolysis of different heating rates.
b (K min1)
To (K)
Tp (K)
Tf (K)
10 20 30
566.15 609.25 641.25
727.05 731.65 737.05
887.95 854.05 832.85
Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Q3
JOEI291_proof ■ 16 December 2016 ■ 6/7
6
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
Table 3 Value of E and A at different heating rates and reaction orders by method A. Reaction order
Heating rate (K min1)
E (kJ mol1)
A (min1)
R2
n¼1
10 20 30 10 20 30 10 20 30
36.24 45.39 56.46 50.58 60.15 71.37 67.92 77.58 88.61
0.01 0.15 1.43 0.36 3.23 27.13 14.00 107.64 764.74
0.8973 0.9522 0.9676 0.8985 0.9533 0.9700 0.8893 0.9464 0.9666
n¼2
n¼3
Fig. 5. Plot of lnb versus 1/T at different conversion rates.
Table 4 Values of E at different conversation rates by method B. Conversation rate
E (kJ mol1)
R2
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Average
49.28 230.31 288.65 271.73 227.42 165.71 136.92 152.86 210.24 192.57
0.9796 0.5425 0.9413 0.8766 0.9131 0.9413 0.9780 0.9914 0.9488
4. Conclusions In order to obtain the distribution characteristics of volatile, pyrolysis experiments in a tubular furnace were performed. Increasing heating rate and temperature can both increase the extent of pyrolysis. The gas yield increases while that of char decreases with temperature increasing. For obtaining more chemical products with high-added value, the optimum temperature for tar is 923 K. The evolution characteristics of gaseous products are investigated. H2, CH4 and CO are the major products and the yields of the products are changed with temperature. Relatively high temperature will be beneficial to obtain more coke oven gas. The conclusions of the pyrolysis behaviors may contribute to the coal upgrading. The pyrolysis kinetic characteristics were studied according to CoatseRedfern and FWO methods. By comparing the calculation results of different reaction orders, the second-order reaction model obtains better fitting result. The kinetic parameters obtained by the FWO method are higher than that of the CoatseRedfern method. Generally, activation energy interval of 50e200 kJ mol1 is recommended for the MLT pyrolysis process. Results of this study are helpful for the researchers to understand the process of coking and adjust the operating conditions to obtain target product as much as possible. Ultimately achieve the purpose of effective utilization of the coal. Acknowledgements This study was accomplished with both support of the External Cooperation Program of Science and Technology Department of Ningxia (2015) and Postgraduate Technology Innovation Project of Ningxia University (GIP2015017). Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
JOEI291_proof ■ 16 December 2016 ■ 7/7
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
7
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22]
Y. Lin, Q. Li, X. Li, K. Ji, H. Zhang, Y. Yu, Y. Song, Y. Fu, L. Sun, Pyrolysates distribution and kinetics of Shenmu long flame coal, Energy Convers. Manag. 86 (2014) 428e434. Y. Zhao, H. Hu, L. Jin, B. Wu, S. Zhu, Pyrolysis behavior of weakly reductive coals from northwest China, Energy Fuels 23 (2009) 870e875. M.A. Serio, D.G. Hamblen, J.R. Markham, P.R. Solomon, Kinetics of volatile product evolution in coal pyrolysis: experiment and theory, Energy Fuels 1 (1987) 138e152. C. Herce, B. de Caprariis, S. Stendardo, N. Verdone, P. De Filippis, Comparison of global models of sub-bituminous coal devolatilization by means of thermogravimetric analysis, J. Therm. Analysis Calorim. 117 (2014) 507e516. B. Li, G. Chen, H. Zhang, C. Sheng, Development of non-isothermal TGAeDSC for kinetics analysis of low temperature coal oxidation prior to ignition, Fuel 118 (2014) 385e391. L. Xu, M. Tang, B. Liu, X. Ma, Y. Zhang, M.D. Argyle, M. Fan, Pyrolysis characteristics and kinetics of residue from China Shenhua industrial direct coal liquefaction plant, Thermochim. Acta 589 (2014) 1e10. G. Wang, J. Zhang, J. Shao, S. Hui, H. Zuo, Thermogravimetric analysis of coal char combustion kinetics, J. Iron Steel Res. Int. 21 (2014) 897e904. L. Chen, C. Zeng, X. Guo, Y. Mao, Y. Zhang, X. Zhang, W. Li, Y. Long, H. Zhu, B. Eiteneer, Gas evolution kinetics of two coal samples during rapid pyrolysis, Fuel Process. Technol. 91 (2010) 848e852. H. Hu, Q. Zhou, S. Zhu, B. Meyer, S. Krzack, G. Chen, Product distribution and sulfur behavior in coal pyrolysis, Fuel Process. Technol. 85 (8) (2004) 849e861. J. Cai, W. Wu, R. Liu, An overview of distributed activation energy model and its application in the pyrolysis of lignocellulosic biomass, Renew. Sustain. Energy Rev. 36 (2014) 236e246. C. Loha, H. Chattopadhyay, P.K. Chatterjee, Three dimensional kinetic modeling of fluidized bed biomass gasification, Chem. Eng. Sci. 109 (2014) 53e64. Ultimate analysis of coal, Chinese National Standard, GB/T 476e2001. Proximate analysis of coal, Chinese National Standard, GB/T 212e2008. A.W. Coats, J.P. Redfern, Kinetic parameters from thermogravimetric data, Nature 201 (1964) 68e69. S. Ceylan, Y. Topçu, Pyrolysis kinetics of hazelnut husk using thermogravimetric analysis, Bioresour. Technol. 156 (2014) 182e188. C.D. Doyle, Series approximations to the equation of thermogravimetric data, 1965. C. Yang, S. Li, W. Song, W. Lin, Pyrolysis behavior of large coal particles in a lab-scale bubbling fluidized bed, Energy Fuels 27 (2012) 126e132. X. Li, G. Matuschek, M. Herrera, H. Wang, A. Kettrup, Investigation of pyrolysis of chinese coals using thermal analysis/mass spectrometry, J. Therm. analysis Calorim. 71 (2003) 601e612. Q. Sun, W. Li, H. Chen, B. Li, The variation of structural characteristics of macerals during pyrolysis, Fuel 82 (2003) 669e676. D.K. Seo, S.S. Park, Y.T. Kim, J. Hwang, T. Yu, Study of coal pyrolysis by thermo-gravimetric analysis (TGA) and concentration measurements of the evolved species, J. Anal. Appl. Pyrolysis 92 (2011) 209e216. A. Sarwar, M. Nasiruddin Khan, K. Azhar, Kinetic studies of pyrolysis and combustion of Thar coal by thermogravimetry and chemometric data analysis, J. Therm. Anal. Calorim. 109 (2012) 97e103. D. Wu, G. Liu, S. Chen, R. Sun, An experimental investigation on heating rate effect in the thermal behavior of perhydrous bituminous coal during pyrolysis, J. Therm. Anal. Calorim. 119 (2015) 2195e2203.
List of Nomenclature and Abbreviation TG: Thermal gravimetry TGA: Thermal gravimetric analysis Ar: Argon GC: Gas chromatograph TCD: Thermal conductivity detector w0 : Initial mass of the sample, g wt : Mass of the sample at time t, g w∞ : Final mass of the sample, g a: Conversion k: Reaction rate constant A: Pre-exponential factor, min1 E: Apparent activation energy, kJ mol1 R: Gas constant, 8.314 kJ K1 mol1 T: Absolute temperature, K b: Heating rate, K min1 n: Order of reaction T0: The initial temperature, K Tp: The peak temperature, K Tf: The final temperature, K
Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
JOEI291_proof ■ 16 December 2016 ■ 1/7
Journal of the Energy Institute xxx (2016) 1e7
Contents lists available at ScienceDirect
Journal of the Energy Institute journal homepage: http://www.journals.elsevier.com/journal-of-the-energyinstitute
Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield Q4
Shengdan Feng, Ping Li*, Zeyi Liu, Yue Zhang, Zhuangmei Li School of Chemistry and Chemical Engineering, Ningxia University, Yinchuan 750021, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 24 July 2016 Received in revised form 3 December 2016 Accepted 5 December 2016 Available online xxx
The thermal decomposition of coal was the essential step of many reactions, thus it was widespread concerned. In order to investigate the behaviors and kinetics of coal pyrolysis, coal samples which obtained from Ningdong coalfield of China were pyrolyzed with a tubular furnace in argon atmosphere at the heating rate of 5 K min1. The primary gaseous products including CH4, H2, N2, CO, CO2, C2H4 and C2H6 were quantified using a gas chromatogram. It can be seen that with the temperature increasing, the yields of H2 and CO increased, while the others decreased. In order to produce possibly much tar, the optimal temperature was 923 K. The characteristic of pyrolysis kinetics was determined by thermo gravimetric analysis measurement. The CoatseRedfern and FlynneWalleOzawa methods was used to obtain kinetic parameters. The activation energy range of 50e200 kJ mol1 was determined. © 2016 Published by Elsevier Ltd on behalf of Energy Institute.
Keywords: Coal pyrolysis Thermal gravimetric analysis Kinetic analysis
1. Introduction Aiming at the condition of resource distribution in china, coal resource is relatively abundant [1]. As one of the important base of energy and chemical industry in China, the coal chemical industry of Ningxia is developing rapidly. The development of Ningxia relies on coal to a great extent. It is more necessary that coal can be efficient utilized and converted for the characteristic of relatively low rank. In this study, one representative coal sample (MLT) which is selected from Maliantai coal mine, Ningdong coalfield was chosen for research. Pyrolysis is the fundamental first procedure in many coal conversation projects [2]. The conclusions of the pyrolysis behaviors may contribute to the coal upgrading. The research on the thermal decomposition of coal can contribute to the efficient utilization and conversion of coal. Therefore, pyrolysis manners have attracted extensive concern [3e6]. The heating process of coal can be divided into two steps [7]. Firstly, the coal depolymerizes while gas, water vapor, and tar are generated. The second step is the repolymerization process, in which char formed. Large quantities of pyrolytic reactions appear in the complex process [2,8,9]. At the same time, developing knowledge of the reaction kinetics is important. The kinetic parameters are necessary for accurate design of pyrolysis systems [4]. It is also necessary for the definition and optimization of the operating conditions to obtain kinetic parameters. Thermo gravimetric analysis gives a rapid quantitative method to acquire kinetic parameters. Because of the advantages of relatively higher temperature and easy operating, the TGA has been widely used for researchers [4,10,11]. The purpose of this study is to explore the devolatilization behaviors of coking coal from Ningdong coal field in low temperature. The kinetic parameters were also calculated based on different methods. Overall, this research on the MLT coking coal will be contributed to the practical effective application. 2. Experimental section 2.1. Preparation of coal samples In this experiment, we studied a kind of low rank coal. Sample with particle size from 75 mm to 100 mm was selected for the subsequent pyrolysis experiments.
* Corresponding author. E-mail address: [email protected] (P. Li). http://dx.doi.org/10.1016/j.joei.2016.12.001 1743-9671/© 2016 Published by Elsevier Ltd on behalf of Energy Institute.
Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
Q1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
JOEI291_proof ■ 16 December 2016 ■ 2/7
2
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
Ultimate analysis and proximate analysis of the sample were determined based on Chinese National Standard GB/T 476-2001 [12] and GB/T 212-2008 [13]. The results are shown in Table 1. 2.2. Experimental equipment and procedures The experiments of pyrolysis were carried out on a furnace (SK-G06123K, Zhonghuan Lab Furnace). The adopted experimental apparatus are shown schematically in Fig. 1. Sample (2 ± 0.2 g) was placed in a quartz sample tube and pushed into the center of the furnace. In order to make sure the sample reaction was without air, the high purity argon (Ar) was used as the carrier gas. A mass flow controller (CS200A, Sevenstar) was used to control the flow of carrier gas. The tube was purged continuously with Ar. The volatile matter during pyrolysis was brought out by the carrier gas from the high temperature zone to suppress the occurrence of the secondary reactions. The purpose of heating belt wrapped outside the outlet tube is to suppress the condensation of tar. Water trap was used to collect the tar. The gases were collected with a gas bag for gas chromatograph (GC) analysis. Coal samples were heated to the ultimate temperature with the heating rate of 5 K min1, and then held 40 min at ultimate temperature to insure the volatile matter release completely. Temperature difference between sample and furnace was proved to be within 5 K. The solid char was removed from the reactor and its mass was determined when the experiment was completed. Gas yield was obtained through the gas chromatographic measurements. A high sensitivity gas chromatogram (GC-2008, Guangzheng) equipped with a thermal conductivity detector (TCD) was used to quantify the main gaseous species, including H2, N2, CH4, CO, CO2, C2H4, and C2H6. The quantitative analysis of H2, N2, CH4, CO was carried out with a packed column (13) and another packed column (GDX502) was used for the other species. Due to its condensable characteristics, it is difficult to measure the yield of tar directly. In this paper, the yield of tar can be obtained by subtraction method and it equals to the mass of initial coal sample subtracts char and gas products (CH4, H2, CO, CO2, C2H4, and C2H6) from the GC. 2.3. Kinetic analysis The kinetic analysis tests were carried out on a thermal gravimetric analyzer (Setsys Evo 16, SETARAM), by which the mass loss curve (TG curve) could be obtained. Every test needed about 20 mg coal, the pressure condition was ambient pressure with an argon flow of 100 ml min1. Sample was heated to 1073 K from room temperature with heating rate of 10, 20 and 30 K min1, respectively. There are several methods available in literature that used for calculation of kinetic parameters. Both of the single-heating rate and the isoconversional method can be used to obtain the pyrolysis kinetic. The single-heating rate method, such as the CoatseRedfern method [14], needs the data obtained at only one heating rate. However, the single-heating method needs better knowledge of the reaction mechanism, while the reaction mechanism is not easy to determine. Contrary to the single-heating rate method, the isoconversional method, which is also called multi-heating rate method, needs a series experimental data acquired at three heating rates at least. The mathematical model and prior assumption are not necessary. Therefore, the multi-heating rate method has been widely used and recommended. 2.3.1. Non-isothermal single heating rate In this study, the conversion rate a is defined as follows:
a¼
w0 wt 100% w0 w∞
(1)
where w0 refers to the initial mass of the sample (g), wt refers to the mass of the sample at time t (g) and w∞ refers to the final mass of the sample (g). Under the reaction mechanism involved in a thermal conversion process, a well-established method for data analysis was applied. It is assumed the general reaction rate ddta is a function of the conversion (a) and a rate constant (k), can be expressed as follows:
da ¼ kf ðaÞ dt
(2)
where f ðaÞ is the hypothetical model of the reaction mechanism. The reaction rate constant (k) was dependent on the temperature and could be expressed as follows using the Arrhenius equation:
Table 1 Characteristic of MLT. Proximate analysis (air-dried basis, wt%) Moisture 1.53 Volatile 32.39 Fixed carbon 56.18 Ash 9.64 Ultimate analysis (air-dried basis, wt%) Carbon 72.01 Hydrogen 4.18 Oxygena 10.61 Nitrogen 1.41 Sulfur 0.62 a
By difference.
Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
JOEI291_proof ■ 16 December 2016 ■ 3/7
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
3
Fig. 1. Experimental apparatus of the reaction system.
E k ¼ A exp RT
(3)
where A refers to the pre-exponential factor (min1). E refers to the apparent activation energy (kJ mol1). R refers to the gas constant and equals 8.314 (kJ K1 mol1). T refers to the absolute temperature (K). When heating rate (b ¼ dT ) is a constant during combustion, Eq. (3) can be transformed into: dt
da A E ¼ f ðaÞ exp RT dT b
(4)
The chemical reaction model is the mostly used in many kinetic studies, it can be described as:
f ðaÞ ¼ ð1 aÞn
(5)
where n refers to the order of reaction. The equation derived for calculating the activation energy value is given as:
lnð1 aÞ AR 2RT E AR E zln 1 ¼ ln ln E RT RT bE bE T2
ðn ¼ 1Þ
(6)
"
# 1 ð1 aÞ1n AR 2RT E AR E zln 1 ln ¼ ln E RT RT bE bE ð1 nÞT 2
ðns1Þ
(7)
# " aÞ 1ð1aÞ1n against T1 [15]. In this method, TG where E and A can be acquired by the slope and intercept of the line of ln lnð1 or ln 2 2 ð1nÞT T data at only one heating rate is enough to calculate the kinetic parameters. 2.3.2. Isoconversional method In this part, different TG data were used to calculate activation energy by FlynneWalleOzawa (FWO) iso-conversional method [16], which has been widely accepted by researchers. By integration and application the function of Eq. (4), the following equation [1] is obtained.
ln b ¼ ln
AE E 5:331 1:052 RgðaÞ RT
where gðaÞ ¼
(8)
R a da
0 f ðaÞ
By assumingf ðaÞ, a series of ln b versus T1 can be obtained for each heating rate at a constant conversion ratioa. E can be obtained from the slope. 3. Results and discussion 3.1. Influence of ultimate temperature on yields The Fig. 2 indicates yields of pyrolysis products at different temperatures with the heating rate of 5 K min1, under the argon atmosphere. As it shows, at a certain temperature, the yield of char is far higher than the yield of gas. However, the yield of tar is slightly higher than that of gas. With the temperature increasing, the gas yield increases while the char decreases. The yield of tar varies relatively small, and the maximum yield occurs at the temperature of 923 K. This conclusion may be due to the existence of secondary cooking and cracking reaction Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
JOEI291_proof ■ 16 December 2016 ■ 4/7
4
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
Fig. 2. Yields of pyrolysis products at the heating rate of 5 K min1.
at temperatures higher than 923 K. The result agrees with the other researchers [17]. Because of the high contents of phenolics, the tar could used to produce many chemical products with high-added value. In order to obtain tar as much as possible, 923 K is the optimal temperature for the pyrolysis of the MLT coal. 3.2. Analysis of gaseous products We explored the influence of ultimate temperature on the release of gas. The contents of CO, CO2, CH4, H2, C2H4, C2H6 and N2 among gaseous products are plotted in Fig. 3. High purity argon was used as the carrier gas and the heating rate is 5 K min1. It is found that H2, CH4 and CO are the major products, while the contents of N2, C2H4 and C2H6 are small compared with the others. As illustrated in Fig. 3, the profile of five gases products decrease with the temperature raising, and the decrease of CH4 and CO2 is greater than that of C2H4 and C2H6. However, the amount of hydrogen increases with the temperature rising, which is caused by constant condensation of aromatic structures and the decomposition of heterocyclic compounds. Release of CO2 and CO relates to the decomposition of ether structure, oxygen-bearing heterocycles, inorganic carbonates, and carboxyl [18]. CH4 mainly comes from the break of methyl groups and aryl/aryl-ether bonds and the decomposition temperatures of these structures are low relatively. So the yield of Methane is gradually decreases when the temperature is higher than 823 K. The content of C2H4 and C2H6 are no more than 5%. The release of light hydrocarbons relates to cleavage of the aliphatic chains and bridges [19]. 3.3. Kinetic analysis Fig. 4(a) and (b) show the TG and DTG curve at three heating rates: 10, 20 and 30 K min1. As shown in Fig. 4(a), three key stages consist of the pyrolysis process by different loss rates. The initial stage finishes at 400 K and the weight loss of this stage is about 3%. The small peak about 300 K is caused by the removal of water. What is more, fracture of weak bonds and release of mobile phase in this stage is weak. The next stage is between 600 and 850 K. It is the primary process of pyrolysis. Tar and gas are liberated and semi-char is generated in this stage [20]. In the range of 600e850 K, the weight decreases dramatically with the increasing temperature. The weight loss in this stage is due to the decomposition of the carbonaceous matrix and the evolution of relatively high molecular weight species. The third stage starts at about 900 K and continues up to the final temperature. Condensation of the aromatic ring and the decomposition of mineral matter lead to the mass decrease [18].
Fig. 3. Yields of gaseous products at different temperatures.
Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
JOEI291_proof ■ 16 December 2016 ■ 5/7
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
5
Fig. 4. TG and DTG curves of different heating rates.
Characteristic temperatures during pyrolysis were explored. The initial temperature (T0), peak temperature (Tp) and final temperature (Tf) at different heating rates are summarized and listed in Table 2. As is shown in Fig. 4(b) and Table 2, the derivative thermo gravimetric curves of samples shift toward the right and the characteristic temperatures increase with the heating rate raising. This delaying decomposition is attributes to differences in heat transfer and kinetic rates [1]. The reason is that with heating rate increasing, the reaction time at a certain temperature was shortened, the reaction process moved to high temperature zone. For predicting the devolatilization of coal samples, we gained the kinetic parameters of the pyrolysis process with the single-heating rate and the isoconversional method. 3.3.1. Non-isothermal single heating rate # " aÞ 1ð1aÞ1n By drawing plots of ln lnð1 against 1/T in a range of reaction order (n ¼ 1, 2, 3), we can found that the secondorln 2 2 ð1nÞT T order reaction obtains better fitting result compared with first-order and third-order reactions in general. What is more, Sarwar et al [21] found that the first order reaction unable to represent the complex pyrolysis process. The E and A can be acquired by Eqs. (6) and (7). The consequences are presented in Table 3. The activation energies are in the range of 50 kJ mol1 to 72 kJ mol1, and the frequency factor varies between 0.4 and 27.1 min1. The frequency factor signifies the level of complexity of reaction. The lower A is, the more difficult to carry out of the reaction [22]. Values of the frequency factor increase with heating rate increasing, showing that heating rate is beneficial for the process of pyrolysis. The relative high linear correlation coefficients indicate that the second-order reaction is feasible. 3.3.2. Non-isothermal multiple heating rate Heating rate is an important factor for analysis process. In order to explore the influence of it, multiple heating rate tests were conducted. Results were obtained with FWO method expounded in 2.3.2. Fig. 5 shows the curve of lnb versus 1/T in a series of fractional conversion valued (a ¼ 0.1e0.9). Three sets of (b,T) were gained for each conversion ratio as in Fig. 5 illustrated. According to the slope of a line that fit three points for a certain conversion ratio, the E was gained from Eq. (8). The values of E are listed in Table 4 for different conversion ratios. Average value of the activation energy was determined with arithmetic average. It can be seen from Table 4 that the corresponding 1/T for the same conversion ratio has a relative good linear relation with each other in most cased at different heating rates. Compared with CoatseRedfern, which provides single overall activation energy value of the process, the non-isothermal multiple heating rate method may demonstrate the complexity of reaction mechanism through activation energy of different conversion ratios. The isoconversional method provides remarkable results of kinetic parameters compared with the single heating rate method. The average activation energy is 192.57 kJ mol1. The CoatseRedfern method needs only one thermal curve to calculate the kinetic parameters, but in data processing, some assumptions about reaction mechanism should be made. For the FWO method, the greater amount of tests has to be done, but no assumption is needed and also activation energy at different conversion ratios could be calculated easily. The activation energy obtained by the FWO method is higher compared with that obtained by CoatseRedfern method. Different kinetic analysis methods are not exclusive but mutually complementary [1]. Thus, an appropriate activation energy range should achieved by combining all observations in two methods. Consequently, an activation energy range of 50 kJ mol1 to 200 kJ mol1 is recommended for the pyrolysis process of MLT.
Table 2 Characteristic temperature during pyrolysis of different heating rates.
b (K min1)
To (K)
Tp (K)
Tf (K)
10 20 30
566.15 609.25 641.25
727.05 731.65 737.05
887.95 854.05 832.85
Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Q3
JOEI291_proof ■ 16 December 2016 ■ 6/7
6
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
Table 3 Value of E and A at different heating rates and reaction orders by method A. Reaction order
Heating rate (K min1)
E (kJ mol1)
A (min1)
R2
n¼1
10 20 30 10 20 30 10 20 30
36.24 45.39 56.46 50.58 60.15 71.37 67.92 77.58 88.61
0.01 0.15 1.43 0.36 3.23 27.13 14.00 107.64 764.74
0.8973 0.9522 0.9676 0.8985 0.9533 0.9700 0.8893 0.9464 0.9666
n¼2
n¼3
Fig. 5. Plot of lnb versus 1/T at different conversion rates.
Table 4 Values of E at different conversation rates by method B. Conversation rate
E (kJ mol1)
R2
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Average
49.28 230.31 288.65 271.73 227.42 165.71 136.92 152.86 210.24 192.57
0.9796 0.5425 0.9413 0.8766 0.9131 0.9413 0.9780 0.9914 0.9488
4. Conclusions In order to obtain the distribution characteristics of volatile, pyrolysis experiments in a tubular furnace were performed. Increasing heating rate and temperature can both increase the extent of pyrolysis. The gas yield increases while that of char decreases with temperature increasing. For obtaining more chemical products with high-added value, the optimum temperature for tar is 923 K. The evolution characteristics of gaseous products are investigated. H2, CH4 and CO are the major products and the yields of the products are changed with temperature. Relatively high temperature will be beneficial to obtain more coke oven gas. The conclusions of the pyrolysis behaviors may contribute to the coal upgrading. The pyrolysis kinetic characteristics were studied according to CoatseRedfern and FWO methods. By comparing the calculation results of different reaction orders, the second-order reaction model obtains better fitting result. The kinetic parameters obtained by the FWO method are higher than that of the CoatseRedfern method. Generally, activation energy interval of 50e200 kJ mol1 is recommended for the MLT pyrolysis process. Results of this study are helpful for the researchers to understand the process of coking and adjust the operating conditions to obtain target product as much as possible. Ultimately achieve the purpose of effective utilization of the coal. Acknowledgements This study was accomplished with both support of the External Cooperation Program of Science and Technology Department of Ningxia (2015) and Postgraduate Technology Innovation Project of Ningxia University (GIP2015017). Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
JOEI291_proof ■ 16 December 2016 ■ 7/7
S. Feng et al. / Journal of the Energy Institute xxx (2016) 1e7
7
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22]
Y. Lin, Q. Li, X. Li, K. Ji, H. Zhang, Y. Yu, Y. Song, Y. Fu, L. Sun, Pyrolysates distribution and kinetics of Shenmu long flame coal, Energy Convers. Manag. 86 (2014) 428e434. Y. Zhao, H. Hu, L. Jin, B. Wu, S. Zhu, Pyrolysis behavior of weakly reductive coals from northwest China, Energy Fuels 23 (2009) 870e875. M.A. Serio, D.G. Hamblen, J.R. Markham, P.R. Solomon, Kinetics of volatile product evolution in coal pyrolysis: experiment and theory, Energy Fuels 1 (1987) 138e152. C. Herce, B. de Caprariis, S. Stendardo, N. Verdone, P. De Filippis, Comparison of global models of sub-bituminous coal devolatilization by means of thermogravimetric analysis, J. Therm. Analysis Calorim. 117 (2014) 507e516. B. Li, G. Chen, H. Zhang, C. Sheng, Development of non-isothermal TGAeDSC for kinetics analysis of low temperature coal oxidation prior to ignition, Fuel 118 (2014) 385e391. L. Xu, M. Tang, B. Liu, X. Ma, Y. Zhang, M.D. Argyle, M. Fan, Pyrolysis characteristics and kinetics of residue from China Shenhua industrial direct coal liquefaction plant, Thermochim. Acta 589 (2014) 1e10. G. Wang, J. Zhang, J. Shao, S. Hui, H. Zuo, Thermogravimetric analysis of coal char combustion kinetics, J. Iron Steel Res. Int. 21 (2014) 897e904. L. Chen, C. Zeng, X. Guo, Y. Mao, Y. Zhang, X. Zhang, W. Li, Y. Long, H. Zhu, B. Eiteneer, Gas evolution kinetics of two coal samples during rapid pyrolysis, Fuel Process. Technol. 91 (2010) 848e852. H. Hu, Q. Zhou, S. Zhu, B. Meyer, S. Krzack, G. Chen, Product distribution and sulfur behavior in coal pyrolysis, Fuel Process. Technol. 85 (8) (2004) 849e861. J. Cai, W. Wu, R. Liu, An overview of distributed activation energy model and its application in the pyrolysis of lignocellulosic biomass, Renew. Sustain. Energy Rev. 36 (2014) 236e246. C. Loha, H. Chattopadhyay, P.K. Chatterjee, Three dimensional kinetic modeling of fluidized bed biomass gasification, Chem. Eng. Sci. 109 (2014) 53e64. Ultimate analysis of coal, Chinese National Standard, GB/T 476e2001. Proximate analysis of coal, Chinese National Standard, GB/T 212e2008. A.W. Coats, J.P. Redfern, Kinetic parameters from thermogravimetric data, Nature 201 (1964) 68e69. S. Ceylan, Y. Topçu, Pyrolysis kinetics of hazelnut husk using thermogravimetric analysis, Bioresour. Technol. 156 (2014) 182e188. C.D. Doyle, Series approximations to the equation of thermogravimetric data, 1965. C. Yang, S. Li, W. Song, W. Lin, Pyrolysis behavior of large coal particles in a lab-scale bubbling fluidized bed, Energy Fuels 27 (2012) 126e132. X. Li, G. Matuschek, M. Herrera, H. Wang, A. Kettrup, Investigation of pyrolysis of chinese coals using thermal analysis/mass spectrometry, J. Therm. analysis Calorim. 71 (2003) 601e612. Q. Sun, W. Li, H. Chen, B. Li, The variation of structural characteristics of macerals during pyrolysis, Fuel 82 (2003) 669e676. D.K. Seo, S.S. Park, Y.T. Kim, J. Hwang, T. Yu, Study of coal pyrolysis by thermo-gravimetric analysis (TGA) and concentration measurements of the evolved species, J. Anal. Appl. Pyrolysis 92 (2011) 209e216. A. Sarwar, M. Nasiruddin Khan, K. Azhar, Kinetic studies of pyrolysis and combustion of Thar coal by thermogravimetry and chemometric data analysis, J. Therm. Anal. Calorim. 109 (2012) 97e103. D. Wu, G. Liu, S. Chen, R. Sun, An experimental investigation on heating rate effect in the thermal behavior of perhydrous bituminous coal during pyrolysis, J. Therm. Anal. Calorim. 119 (2015) 2195e2203.
List of Nomenclature and Abbreviation TG: Thermal gravimetry TGA: Thermal gravimetric analysis Ar: Argon GC: Gas chromatograph TCD: Thermal conductivity detector w0 : Initial mass of the sample, g wt : Mass of the sample at time t, g w∞ : Final mass of the sample, g a: Conversion k: Reaction rate constant A: Pre-exponential factor, min1 E: Apparent activation energy, kJ mol1 R: Gas constant, 8.314 kJ K1 mol1 T: Absolute temperature, K b: Heating rate, K min1 n: Order of reaction T0: The initial temperature, K Tp: The peak temperature, K Tf: The final temperature, K
Please cite this article in press as: S. Feng, et al., Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.12.001