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Using a hybrid of green chemistry and industrial ecology to make chemical production greener
Resources, Conservation and Recycling 122 (2017) 106–113
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Using a hybrid of green chemistry and industrial ecology to make chemical production greener Qiao Hao a , Jinping Tian a,b,∗ , Xing Li a , Lujun Chen a,c a
School of Environment, Tsinghua University, Beijing 100084, China Key Laboratory of Solid Waste Management and Environment Safety (Tsinghua University), Ministry of Education, Tsinghua University, Beijing 100084, China c Zhejiang Provincial Key Laboratory of Water Science and Technology, Department of Environment, Yangtze Delta Region Institute of Tsinghua University, Zhejiang, Jiaxing 314006, China b
a r t i c l e
i n f o
Article history: Received 14 December 2016 Received in revised form 3 February 2017 Accepted 5 February 2017 Keywords: Chemical industrial park Eco-industrial park Green chemistry Industrial ecology Model
a b s t r a c t We proposed a model to extend green chemistry beyond the boundary of a single product by hybridizing it with the concept of industrial ecology in a chemical industrial park. The model works at three levels: single product, product food web, and infrastructure sharing. At the single product level, the core measures are cleaner production, the design of a green process that employs the “24 principles” of green chemistry and green chemical engineering in condensed forms, PRODUCTIVELY and IMPROVEMENTS respectively. The food web level is the key to extending the system boundary of a single product. At this level, collaboration among different firms in the chemical industrial park can be facilitated through designing, uncovering, and fostering horizontal and vertical integration among different stakeholders. Infrastructure sharing is an essential characteristic of eco-industrial development of chemical industrial parks. The model is exemplified in-depth in a typical Chinese chemical industrial park. We assessed the performance of disperse dyestuff manufacturing in the park and found that the park showed substantial reduction in its sulfuric acid consumption, water pollutants emission, and hazardous solid waste generation in disperse dyestuff production from 2011 to 2015. Integrating green chemistry and industrial ecology in the context of chemical industrial parks will be insightful for other chemical industrial parks aiming to facilitate green development. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Sustainable industry is essential to addressing the challenges of climate change and resource deterioration. One of the targets proposed in the Sustainable Development Goals (SDG) is, by 2030, to “upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and industrial processes” (UN, 2015). China’s chemical industry has undergone rapid development (Eissen et al., 2002). However, this industry is both energy-intensive and emission-intensive. Green chemistry is widely recognized as a key strategy that can facilitate the sustainable development of the chemical industry (Anastas and Lankey, 1998). It is characterized by dual twelve principles that fall into two general categories
∗ Correspondence to: Room 717, School of Environment, Tsinghua University, Beijing 100084, China. E-mail address: [email protected] (J. Tian). http://dx.doi.org/10.1016/j.resconrec.2017.02.001 0921-3449/© 2017 Elsevier B.V. All rights reserved.
in condensed forms: PRODUCTIVELY (Tang et al., 2008) in green chemistry and IMPROVEMENTS (Tang et al., 2008) to Green Chemical Engineering. Myriad methods of green synthesis have been devised, and several have been honored with the “Presidential Green Chemistry Challenge Award”. In most cases, Green chemistry targets the synthetic process of a single product by designing novel methods of synthesis; it aims to enhance selectivity, improve the conversion rate and yield of core reactants, and decrease wastes, and it aims to achieve all of this simultaneously whenever possible. In general, diverse reactants and auxiliary materials are used in a synthetic reaction; however, many of these components, particularly the auxiliary materials, generally become waste. This can be partially proven by the high E factors of 5–50 and 25–1000 (Sheldon, 2007) for fine chemicals and pharmaceuticals, respectively; these high E factors are due to the multi-step synthesis and diverse material inputs in the synthesis and intensive workup processes. There are some limits on Green Chemistry’s ability to decrease the E factor because it only targets single products.
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Graedel first introduced the idea of Green Chemistry in an industrial ecology context in the inaugural issue of the Green Chemistry Journal and proposed the expansion of green chemistry from merely green synthesis to the greening of entire life cycles (Graedel, 1999). Anastas proposed the methods and principles by which each process in product synthesis could be analyzed “through life cycle analysis (LCA), which combined with the Green Chemistry theory closely, to enhance the whole process’s environmental benefits” (Anastas and Lankey, 2000). In 2001, Graedel made further progress in the practice of green chemistry and proposed a method of achieving the optimal state of an entire system in the context of the environment. Graedel’s green chemistry system was based on “products, enterprises, infrastructures, and social level promotion” (Graedel, 2009). This study proposes a model of how to apply green chemistry beyond the limits of a single product by creating a hybrid system with the methods of industrial ecology in the context of a chemical industrial park; the goal is to improve the material efficiency of chemical production. A typical Chinese chemical industrial park is used as a case study. The underlying idea is to enlarge the traditional product-specific boundary of Green Chemistry and create a boundary based on systematic thinking. Industrial ecology is a subject concerning the flows of materials and energy in industrial and consumer activities, the effects of these flows on the environment, and the influences of economic, political, regulatory, and social factors on the flow, use, and transformation of resources (Lifset and Graedel, 2010). Industrial Ecology can operate at different levels, including the firm level, inter-firm level, and regional/global level (Lifset and Graedel, 2010). An eco-industrial park is an important experimental field for industrial ecology and operates at the inter-firm level. As common feature of the global landscape, an industrial park is “a large tract of land, sub-divided, and developed for the use of several firms simultaneously, distinguished by its shareable infrastructure and close proximity of firms ”(UNEP, 1997). An eco-industrial park is a type of industrial park that fosters an industrial ecosystem within an industrial park. In such a park, the key feature is that “effluents of one process serve as the raw material for another process” (Frosch and Gallopoulos, 1989). One popular definition of an eco-industrial park (EIP) comes from the Environmental Protection Agency (EPA) (Chertow, 2000a,b), which defines the park as “a community of manufacturing and service businesses seeking enhanced environmental and economic performance through collaboration in managing environmental and resource issues including energy, water, and materials. By working together, the community of businesses seeks a collective benefit that is greater than the sum of the individual benefits each company would realize if it optimized its individual performance only”. EIP development is currently being intensively discussed and piloted in China (Shi et al., 2012a, 2012b) and around the world; the most recent review can be found in ref (Chertow and Park, 2016). Chemical industrial parks are common in the development of the chemical industry around the world. There are already many well-developed chemical industrial parks, including those in Germany (Graedel, 2009; Anonymous, 2011), the Singapore Petrochemical Complex on Jurong Island (Yang and Lay, 2004), and the ARRR cluster in Europe (EPCA, 2007). China has approximately 500 chemical industrial parks, which, collectively, play a crucial role in facilitating the development of the chemical industry (Tremblay, 2001; Fringuelli et al., 2010). In chemical industrial parks that specialize in petrochemical production, efficient use of both materials and energy can be improved by the integration of materials, products, and energy (Sterr and Ott, 2004). This integration is partially responsible for the small E factor of petrochemical production, which is generally below 1.0 (Sheldon, 2007). However, fine chemical products, such as dyestuffs and intermediates of pharmaceuticals, require multistep synthetic processes and diversified production volume, and
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Fig. 1. Schematic diagram of the production of a single product.
Fig. 2. Conceptual model of a hybrid of green chemistry and industrial ecology in the context of a chemical industrial park.
thus these products have much higher E factors (Sheldon, 2007). We propose that, in a fine chemical industrial park, there is great potential to improve the material efficiency of chemical production by extending the system boundary of single chemical production and integrating it into the industrial ecosystem. This paper is organized as follows: Section 2 introduces the models and provides a brief introduction to the fine chemical industrial park that is used as a case study; Section 3 presents the practices of green chemistry in the park; Section 4 illustrates the park’s performance in hybridizing green chemistry with industrial ecology, and Section 5 presents conclusions. 2. Methodology 2.1. A conceptual model of a hybrid of green chemistry and industrial ecology in the context of a chemical industrial park Fig. 1 illustrates the conceptual model of green chemistry at the single-product level, and the process of synthesizing a single product is defined as the system boundary. In a single-product model, the inputs include raw materials, auxiliary materials, energy, and water; the outputs are the target product(s), byproduct(s), and wastes (gaseous/liquids/solid wastes). The application of green chemistry technologies at the single-product level can, to some extent, improve the efficiency of core materials. But, inevitably, some auxiliary materials and by-products cannot achieve full atom economy because they are not combined in the structure of the final products. Fig. 2 illustrates the conceptual model of a hybrid of green chemistry and industrial ecology in the context of a chemical industrial park. It is derived from in-depth observation of the greening practice implemented in the chemical industrial park under consideration in this study and some other chemical industrial parks in China (Ding and Hua, 2012; Yune et al., 2016). The model aims to
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integrate greening practice of chemical industrial park from three levels: product, food web, and infrastructure sharing. The model considers not only the manufacturing process of a single product but also the food web that exists among different firms, as well as infrastructure sharing in the chemical industrial park. The geographic proximity of the different firms in the chemical industrial park will offer some benefits (Porter, 1998; Jensen, 2016) that may help expand the boundary of single products. The three levels in Fig. 2 are further illustrated as follows. 2.1.1. Products level At this level, the core measures are cleaner production and design of green process towards individual product, which in general employs the “24 principles” of green chemistry and green chemical engineering, PRODUCTIVELY and IMPROVEMENTS (Tang et al., 2008) respectively, aiming to improve the atom economy of chemical synthesis and efficiency of key raw materials. An end-ofpipe measure is also a necessary component at this level. 2.1.2. Food web level This level is the key to extending the system boundary of a single product. At this level, collaboration among different firms in the chemical industrial park can be facilitated via designing, uncovering, and fostering horizontal and vertical integration among different stakeholders. This may include food webs, supply chains, and industrial ecosystems in which “waste from one company may become the raw materials of another one”(Frosch and Gallopoulos, 1989) due to the clustering of chemical production and geographic proximity of different stakeholders. As a result, high cumulative material efficiency and energy efficiency can be achieved in the chemical industrial park as a whole. The material loop close is one of the benefits of food web facilitation, particularly for the auxiliary materials. 2.1.3. Infrastructure sharing level Infrastructure sharing is an essential characteristic of industrial parks, and combined heat and power (CHP) is widely employed in EIP practice (Chertow, 2000a,b) (Guo et al., 2016a,b). Besides CHP, other energy and environmental infrastructure such as centralized wastewater treatment plants, reclaimed water plants, and hazardous waste incinerators are not unusual in most Chinese eco-industrial parks. Compared with separate and self-serviced small-scale equipment, infrastructure sharing has positive effects on enhancing energy efficiency and addressing environmental issues (Porter, 1998; Yuan et al., 2010; Govindan, 2015). 2.2. Implementation of the model and performance assessment A typical Chinese fine chemical industrial park, Hangzhou Bay Shangyu Economic and Technology Development Area (HSEDA, formerly abbreviated as SYIA), is used as a case study to illustrate the implementation and performance of the model shown in Fig. 2. HSEDA, established in 1998, mainly produces dyestuffs, pharmaceutics, and other fine chemicals. It ranks No. 1 in its volume of dyestuff production, both in China and globally. Their dyestuffs outputs include disperse dyes, reactive dyes, acid dyes, vat dyes, pigments, intermediates, and dyestuff additives, such as surfactants and lignin. In 2013, HSEDA accounted for 65% of national disperse dye outputs and 45% of local gross industrial output value. Based on long-term observation of HSEDA, we have reported its one-year static metabolism of sulfur (Tian et al., 2012a,b) and carbon (Tian et al., 2013), its energy saving measures and potentials (Tian et al., 2012a,b), and the evolution of its policies targeting green development. This basic information on HSEDA can be found in previous works (Tian et al., 2012a,b, 2013).
We carefully analyzed HSEDA’s practices at the three levels listed in Fig. 2 by targeting one of its pillar industries, dyestuff production. Then, performance is qualitatively assessed by focusing on: (1) hazardous waste generation in dyestuff production, (2) water pollutants generation with the proxy of chemical oxygen demand and ammonia-nitrogen in wastewater before treatment, and (3) sulfuric acid consumption for dyestuff production. As shown in our previous work, HSEDA has two big dyestuff manufacturers, the Company L and Company R. We analyzed the hazardous waste generated by both of these groups, which accounted for 91% of HSEDA’s total hazardous waste in 2011. 2.3. Data collection The data came from two sources. On the one hand, we sent out questionnaire with the same procedure of data collection as our previous work (Tian et al., 2013). We sent out questionnaire from March to July 2014 to collect the data of material consumption and chemical production of HSEDA in 2013. We collected around 80 samples. Then we carefully checked the reliability of the data and uncover the food web of chemical production within the HSEDA. On the other hand, we collected data in the environmental statistic database from local bureau of environmental protection, including (1) waste generation of the 28 dyestuff producers in HSEDA, such as chemical oxygen demand, ammonia-nitrogen in wastewater before treatment, and hazardous waste generation, and (2) the first three products and first three raw materials in volume in each producer. 3. Hybrid of green chemistry and industrial ecology practice in HSEDA This section carefully reviews HSEDA’s hybrid of green chemistry and industrial ecology from the perspective of the three levels illustrated in Fig. 2. 3.1. Practice of greening chemical production at the products level Green chemistry practice at HSEDA at the product level is summarized in Table 1 in the condensed form of the dual 12 principles of “PRODUCTIVELY” for green chemistry and “IMPROVEMENTS” for green chemical engineering. 3.2. Facilitating food web establishment A food web of disperse dyestuff production has been established in HSEDA (Fig. 3), and all of its processes are finished within HSEDA. The food web consists of dyestuff intermediates, disperse dyes, inorganic sulfur chemicals, hydrochloric acid, and sulfuric acid (Fig. 3). Disperse dyes, sulfuric acid, and by-products of inorganic salts are the main products of the dyestuff food web. A sulfuric acid manufacturing facility also provides steam and electricity by recovering chemical reaction heat. Nitrosyl sulfuric acid has been widely applied in diazo dyestuff production by replacing most of the traditional complex “NaNO2 + HCl or H2 SO4 ”. HSEDA took advantage of the two sulfuric acid manufacturing facilities to tackle the longstanding challenge of disposing of spent sulfuric acid (Fig. 4). Spent sulfuric acid from nitration reactions has a concentration of about 69% and is concentrated to approximately 88% through vacuum concentration; it then reaches a concentration of 98% with SO3 and is recycled back to dyestuff production. A large amount of spent sulfuric acid from diazotization is neutralized with carbide slag, and the calcium sulfate goes to a landfill in the park. In 2008, the calcium sulfate associated with disperse dye production was categorized as hazardous waste in China. From that point on, HSEDA placed great importance on reducing calcium sulfate generation. Since 2012, spent sulfuric acid from diazotization has been
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Table 1 Examples of the “Dual 12 Principles” implemented in HSEDA. Green chemistry
Examplesa implemented in HSEDA
Green chemical engineering
Examples implemented in HSEDA
P-Prevention waste
(1) Implementing mandatory cleaner production auditing every three years for all chemical producers; (2) Set threshold for new chemical production projects to prevent HSEDA from adopting pollution-intensive processes and high toxicity chemicals (1) Establishing biomass-to-energy infrastructure; (2) Recovery of chemical reaction heat in sulfuric acid manufacturing, hydrogenation of nitro-aromatics, and high-temperature distilling Developing ‘one-pot’ or short synthetic processes, such as resorcinol, o-diaminobenzene, and alaninol production. Developing ecologically friendly dyes created with the OTEX standard
I-Inherently non-hazardous and safe
M-Minimize material diversity
(1) Phasing out toxic materials and solvents, such as CCl4 , CHCl3 , and Benzene as solvents; (2) Replacing dipole non-proton solvents, such as THF and DMF, with toluene; (3) Using the Distributed Control System (DCS) to improve the reliability of operation Using one solvent in multi-step synthetic processes
P-Prevention instead of treatment
Implementing mandatory cleaner production audits
R-Renewable material and energy input
(1) Establishing biomass-to-energy infrastructure; (2) Partly shifting coal-fired combined heat and power (CHP) to municipal solid waste (MSW)-to-energy; and (3) Recovery of chemical reaction heat in sulfuric acid manufacturing, hydrogenation of nitro-aromatics, and high-temperature distilling. (1) Rearranging layout of process vertically to reduce pumping of liquid materials; (2) decreasing redundant intermediate links in material transfers
R-Renewable materials
O-Omit derivation steps D-Degradable chemical products
U-Use safe synthetic methods
(1) Using continuous and adiabatic nitration technology; (2) Phasing out application or production of ODS, such as CCl4 ; (3) Replacing some odorous or hard-to-recover dipolar aprotic solvents, such as THF and DMF; and (4) Full implementation of DCS in chemical production. Employing catalytic hydrogenation technology in nitro-aromatics reduction, amino-acid reduction instead of iron powder hydrogenation and NaBH4 reduction, respectively.
O-Output-led design
T-Temperature, pressure ambient
Improving the temperatures of diazo reaction from <−5 ◦ C to 0–5 ◦ C to reduce cooling consumption.
E-Efficient use of energy, materials, and space
I-In-Process monitoring
Application of DCS and emergency stopping devices (ESD) in all chemical producers
M-Meet the need
V-Very few auxiliary substances
(1) Using NOSO3 H instead of “NaNO2 + HCl” as diazo reaction agent in disperse dyestuff synthesis; (2) Using one solvent in multi-step reactions The E factor is a key metric to assess the performance of chemical reactions in the park.
E-Easy to separate by design
C-Catalytic reagents
E-E-factor, maximize feed in product L-Low toxicity of chemical products a
(1) Phasing out ODS; (2) Releasing negative list of toxic chemicals and mandatorily disabling their utilization in the park
V-Very simple
N-Networks for exchange of local mass & energy T-Test the life cycle of the design
(1) Continuous production; (2) Avoiding manual operation; (3) Simplifying multi-step synthetic processes with one-pot or short processes, and (4) establishing supply chains in the park to reduce purification or desiccation of some intermediates (1) Energy infrastructure sharing; (2) Recovering and cascading utilization of process heat; (3) Fostering industrial symbiosis in the park; and (4) Rearranging layout of the process vertically to reduce pumping materials Using high-performance dye (e.g., 300% disperse dye instead of 100%) to reduce the dosage of dye while meeting the same function. Using spray drying instead of “salt-out + spray drying” process in reactive dye production
Cooperation among producers due to geographical proximity and supply chain integration within the park Tailored policy on experimenting with LCA-based eco-design of process and products was issued by the Chinese government in 2015
Due to space limits, only some examples are presented.
gradually transformed into ammonium sulfate. Spent sulfuric acid with a concentration of 30% or above is neutralized with ammonia to make ammonium sulfate instead of using the old process of neutralization with carbide slag. The rest, with a concentration of 10–15% is pretreated and recycled back to process. Thus the landfill of calcium sulfate has declined rapidly, as discussed in Section 4. Now, most of the spent sulfuric acid ends up as ammonium sulfate, a by-product that is useful as fertilizer. Note: The functional group in blue refers to the coupling part of diazo dye, and the red refers to the diazotization part. The process heat from the nitration and hydrogenation processes is also delicately recovered as shown in Fig. 5. Aromatics nitration and hydrogenation of nitro-aromatics are both exothermic reactions. The reaction heat is recovered in situ to produce
hot water for disperse dye work-up (washing) and to make cooling water using lithium bromide cooling technology, which can be used for dye synthesis. Furthermore, sensible heat associated with the vacuum distillation of aromatic amine is also recovered to produce low-pressure steam for solvent recovery. As a result, energy efficiency is substantially enhanced.
3.3. Infrastructure sharing in the park The energy and environmental infrastructure in HSEDA is characterized by its diversified functions, which include the following: (1) coal-fired combined heat and power (CHP) utilities with a total capacity of 30 MW; (2) a centralized wastewater treatment plant (WWTP) with a capacity of 300,000 t per day; (3) municipal solid
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Fig. 3. Food web of disperse dye production in HSEDA.
Fig. 4. Schematic illustration of disperse dye production in HSEDA.
waste incineration for electricity, with a total capacity of 650 t per day and an 18 MW electricity generator; (4) WWTP-sludge incineration for steam, with a total capacity of 750 t of sludge per day; (5) hazardous waste incineration, with a capacity of 14400 t per year; and (5) a biomass-to-energy utility, with a capacity of 150,000 t per year. The recovery of chemical reaction heat, particularly from sulfuric acid manufacturing with sulfur as a raw material, is also a key element of HSEDA’s infrastructure. There are two sets of sulfuric
acid manufacturing utilities, with a total capacity of 400,000 t of sulfuric acid per year. Furthermore, HSEDA also performs steam and electricity production and spent sulfuric acid regeneration. One of the coal-fired CHP plants also incinerates the odorous offgasses from one company’s wastewater treatment plant by mixing them with fresh air and injecting them into a boiler. The company built a 1.4-m diameter and 1.5-kilometer-long pipeline between the wastewater treatment station and the CHP plant (an investment
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Fig. 5. Cascading utilization of process heat in the dye intermediate production.
of 7 million Chinese Yuan (CNY)) in 2011. More detailed information on HSEDA’s energy metabolism can be found in our previous work (Tian et al., 2012a,b; Guo et al., 2016a,b) and the energy flow diagram can be found in the supporting information. Energy infrastructure plays a crucial role in addressing HSEDA’s environmental issues and improving its greenness accordingly. 4. Performance assessment and discussion The performance of disperses dye production in HSEDA is assessed mainly based on hazardous waste generation and water pollutants generation. Fig. 6 presents the evolution of waste generation in dyestuff production in HSEDA from 2011 to 2015. One of the characteristic solid wastes is calcium sulfate, which accounts for a large part of the solid waste generated in disperse dye production and was categorized as hazardous waste in China in 2008. The cost of calcium sulfate landfills thus increased markedly. In HSEDA, the cost of a general solid waste landfill is approximately 200 CNY per ton, but this rises to approximately 3000 CNY per ton for hazardous waste treatment. There was a buffer period during which dyestuff manufacturers were requested to develop new process to substantially reduce their calcium sulfate generation. The dyestuff companies in HSEDA took this issue very seriously, and a systematic retrofitting approach was developed to address this challenge by neutralizing spent dilute sulfuric acid with ammonia instead of carbide slag, as shown in Fig. 4. Ammonia neutralization is expensive and energy-intensive even when applying multi-effect evaporation. By inserting ammonia neutralization into the total system of disperse dye production, the spent sulfuric acid with a concentration above a certain threshold can be refurbished and recycled, while the rest can be neutralized with ammonia. The process heat in sulfuric acid manufacturing and disperse dye production is also recovered as much as possible for ammonium sulfate evaporation. The large-scale application of this new neutralization process was put into practice in 2012. Even though the cost of ammonia neutralization process is high, the whole system of dye production is profitable with positive environmental performance. Fig. 6(a) clearly shows that the hazardous waste generated in dyestuff production decreased by 52% in 2013 compared with 2012. Hazardous waste generation per unit of dyestuff output was also reduced markedly from 2013. This achievement of such a large reduction in the generation of hazardous solid waste is largely due to the adoption of the ammonia neutralization process and systematic optimizations of disperse dye production. Carbon and nitrogen make the key functional groups in the structure of dyestuff as shown in Fig. 4. Organic carbon and nitrogen emission to water will cause severe water pollution. Two indicators,
namely chemical oxygen demand (COD) and ammonia-nitrogen, are generally employed to monitor water pollution. COD is generally used to indirectly measure the amount of organic compounds in water. Ammonia-nitrogen refers to the nitrogen in water in the form of ammonia and ammonium ion, which can cause eutrophication of water. Fig. 6(b) illustrates the evolution of the two pollutants generated in dyestuff production from 2011 to 2015. Chemical oxygen demand and ammonia-nitrogen generation, which refers to the amount of pollutants just generated from the facility and without any treatment, can partly present the greenness of dyestuff production. After neutralization with carbide slag was replaced by ammonia neutralization in 2013, some organic pollutants once adsorbed by calcium sulfate and landfilled were kept in wastewater, which partly contributed to the increase of COD in wastewater in 2012. The rebound of hazardous waste generation in 2015 (Fig. 6(a)) was mainly due to three reasons: (1) startup of a new chloroalkali facility in one of the top dyestuff producers, the Group R; (2) capacity of some key intermediates of disperse dyestuff increased markedly associated with large amount of waste salts generation, such as sodium chloride and sodium sulfate; and (3) while ammonia was added to neutralize spent sulfuric acid and recovering ammonium sulfate as byproduct, ammonia-nitrogen in wastewater increased markedly, thus intensified wastewater treatment was requested to further remove ammonia-nitrogen in the effluent. Thus, more sludge was generated in wastewater treatment plant. Because the data of each category of hazardous waste generation was unavailable, the reason of the rebound could not be thoroughly uncovered in this study. Moreover, there are additional benefits to the horizontal and vertical integration of the food web of disperse dye production in HSEDA. Most spent sulfuric acid was recovered or made into useful byproducts, and nitrogen oxides generated in nitration were also recovered to produce nitrosyl sulfuric acid. Compared with the regular production process of disperse dye in China, the average yield of disperse dyestuff in HSEDA increased from 91% to 95%, the dosage of sulfuric acid decreased from 1.5 to 1.1 t per ton of disperse dye filtration cake, and average water consumption decreased from 110 to 50 t per ton of disperse dye filtration cake, which was further made into commercial dyestuff. 5. Conclusion Taking disperse dye production in HSEDA as a case study, waste generation in dyestuff production are reduced markedly by expanding the system boundary from single product synthesis to food web development in the chemical industrial park. It can be
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1.60
120,000 104,168
1.40 HW generation/product outputs (t/t)
100,000 89,423
1.20
80,850 76,189
1.00
80,000
84,100
77,531
53,662
0.80 0.60
60,000
50,139 37,867
40,000 0.40 0.20
1.34
0.66
0.42
0.66
1.34
2011
2012
2013
2014
2015
Hazardouswaste generation (t/a)
112,955
20,000
-
Hazardous waste generation per unit of product output
Hazardous waste generation
Disperse dye outputs
(a) Hazardous waste generation 25,000,000
1,200,000
19,771,840 20,000,000
1,000,000
914,945 913,438 15,204,134
15,000,000
800,000
680,649
22,110,387
600,000 21,586,970 546,427
10,000,000
400,000
16,141,860 5,000,000
200,000
-
Ammonia nitrogen generation (kg/a)
Chemical oxygen demand generation (kg/a)
1,091,284
2011
2012
2013
Chemical oxygen demand generation
2014
2015
Amonia-nitrogen generation
(b) Water pollutants generation Fig. 6. Waste generation in dyestuff production from 2011 to 2015.
observed that such symbiotic linkage of material supply, spent sulfuric acid recovery, and process heat reutilization cannot be established for a single product. The practices used in HSEDA support the argument of this paper that a hybrid of green chemistry and industrial ecology in the context of a chemical industrial park can substantially and simultaneously improve material efficiency and reduce waste generation. The food web does not stand alone in HSEDA, many chemical industrial parks have established their own featured food webs, as in Shanghai chemical industrial park (Yune et al., 2016) in China, a sugar making industrial park (Zhu et al., 2006), a coal chemical industrial park, and a sea salt and phosphorbased chemical industrial park (Ding and Hua, 2012). There are
approximately 500 chemical industrial parks in China. Actions similar to those piloted in HSEDA could be implemented in these CIPs to achieve better environmental and economic performance.
Acknowledgements The authors acknowledge the National Natural Science Foundation of China for financial support through projects 41471468 and 41671530. We also thank the administrative bureau and enterprises in HSEDA and Bureau of Environmental Protection for their assistance in data collection.
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Using a hybrid of green chemistry and industrial ecology to make chemical production greener Qiao Hao a , Jinping Tian a,b,∗ , Xing Li a , Lujun Chen a,c a
School of Environment, Tsinghua University, Beijing 100084, China Key Laboratory of Solid Waste Management and Environment Safety (Tsinghua University), Ministry of Education, Tsinghua University, Beijing 100084, China c Zhejiang Provincial Key Laboratory of Water Science and Technology, Department of Environment, Yangtze Delta Region Institute of Tsinghua University, Zhejiang, Jiaxing 314006, China b
a r t i c l e
i n f o
Article history: Received 14 December 2016 Received in revised form 3 February 2017 Accepted 5 February 2017 Keywords: Chemical industrial park Eco-industrial park Green chemistry Industrial ecology Model
a b s t r a c t We proposed a model to extend green chemistry beyond the boundary of a single product by hybridizing it with the concept of industrial ecology in a chemical industrial park. The model works at three levels: single product, product food web, and infrastructure sharing. At the single product level, the core measures are cleaner production, the design of a green process that employs the “24 principles” of green chemistry and green chemical engineering in condensed forms, PRODUCTIVELY and IMPROVEMENTS respectively. The food web level is the key to extending the system boundary of a single product. At this level, collaboration among different firms in the chemical industrial park can be facilitated through designing, uncovering, and fostering horizontal and vertical integration among different stakeholders. Infrastructure sharing is an essential characteristic of eco-industrial development of chemical industrial parks. The model is exemplified in-depth in a typical Chinese chemical industrial park. We assessed the performance of disperse dyestuff manufacturing in the park and found that the park showed substantial reduction in its sulfuric acid consumption, water pollutants emission, and hazardous solid waste generation in disperse dyestuff production from 2011 to 2015. Integrating green chemistry and industrial ecology in the context of chemical industrial parks will be insightful for other chemical industrial parks aiming to facilitate green development. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Sustainable industry is essential to addressing the challenges of climate change and resource deterioration. One of the targets proposed in the Sustainable Development Goals (SDG) is, by 2030, to “upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and industrial processes” (UN, 2015). China’s chemical industry has undergone rapid development (Eissen et al., 2002). However, this industry is both energy-intensive and emission-intensive. Green chemistry is widely recognized as a key strategy that can facilitate the sustainable development of the chemical industry (Anastas and Lankey, 1998). It is characterized by dual twelve principles that fall into two general categories
∗ Correspondence to: Room 717, School of Environment, Tsinghua University, Beijing 100084, China. E-mail address: [email protected] (J. Tian). http://dx.doi.org/10.1016/j.resconrec.2017.02.001 0921-3449/© 2017 Elsevier B.V. All rights reserved.
in condensed forms: PRODUCTIVELY (Tang et al., 2008) in green chemistry and IMPROVEMENTS (Tang et al., 2008) to Green Chemical Engineering. Myriad methods of green synthesis have been devised, and several have been honored with the “Presidential Green Chemistry Challenge Award”. In most cases, Green chemistry targets the synthetic process of a single product by designing novel methods of synthesis; it aims to enhance selectivity, improve the conversion rate and yield of core reactants, and decrease wastes, and it aims to achieve all of this simultaneously whenever possible. In general, diverse reactants and auxiliary materials are used in a synthetic reaction; however, many of these components, particularly the auxiliary materials, generally become waste. This can be partially proven by the high E factors of 5–50 and 25–1000 (Sheldon, 2007) for fine chemicals and pharmaceuticals, respectively; these high E factors are due to the multi-step synthesis and diverse material inputs in the synthesis and intensive workup processes. There are some limits on Green Chemistry’s ability to decrease the E factor because it only targets single products.
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Graedel first introduced the idea of Green Chemistry in an industrial ecology context in the inaugural issue of the Green Chemistry Journal and proposed the expansion of green chemistry from merely green synthesis to the greening of entire life cycles (Graedel, 1999). Anastas proposed the methods and principles by which each process in product synthesis could be analyzed “through life cycle analysis (LCA), which combined with the Green Chemistry theory closely, to enhance the whole process’s environmental benefits” (Anastas and Lankey, 2000). In 2001, Graedel made further progress in the practice of green chemistry and proposed a method of achieving the optimal state of an entire system in the context of the environment. Graedel’s green chemistry system was based on “products, enterprises, infrastructures, and social level promotion” (Graedel, 2009). This study proposes a model of how to apply green chemistry beyond the limits of a single product by creating a hybrid system with the methods of industrial ecology in the context of a chemical industrial park; the goal is to improve the material efficiency of chemical production. A typical Chinese chemical industrial park is used as a case study. The underlying idea is to enlarge the traditional product-specific boundary of Green Chemistry and create a boundary based on systematic thinking. Industrial ecology is a subject concerning the flows of materials and energy in industrial and consumer activities, the effects of these flows on the environment, and the influences of economic, political, regulatory, and social factors on the flow, use, and transformation of resources (Lifset and Graedel, 2010). Industrial Ecology can operate at different levels, including the firm level, inter-firm level, and regional/global level (Lifset and Graedel, 2010). An eco-industrial park is an important experimental field for industrial ecology and operates at the inter-firm level. As common feature of the global landscape, an industrial park is “a large tract of land, sub-divided, and developed for the use of several firms simultaneously, distinguished by its shareable infrastructure and close proximity of firms ”(UNEP, 1997). An eco-industrial park is a type of industrial park that fosters an industrial ecosystem within an industrial park. In such a park, the key feature is that “effluents of one process serve as the raw material for another process” (Frosch and Gallopoulos, 1989). One popular definition of an eco-industrial park (EIP) comes from the Environmental Protection Agency (EPA) (Chertow, 2000a,b), which defines the park as “a community of manufacturing and service businesses seeking enhanced environmental and economic performance through collaboration in managing environmental and resource issues including energy, water, and materials. By working together, the community of businesses seeks a collective benefit that is greater than the sum of the individual benefits each company would realize if it optimized its individual performance only”. EIP development is currently being intensively discussed and piloted in China (Shi et al., 2012a, 2012b) and around the world; the most recent review can be found in ref (Chertow and Park, 2016). Chemical industrial parks are common in the development of the chemical industry around the world. There are already many well-developed chemical industrial parks, including those in Germany (Graedel, 2009; Anonymous, 2011), the Singapore Petrochemical Complex on Jurong Island (Yang and Lay, 2004), and the ARRR cluster in Europe (EPCA, 2007). China has approximately 500 chemical industrial parks, which, collectively, play a crucial role in facilitating the development of the chemical industry (Tremblay, 2001; Fringuelli et al., 2010). In chemical industrial parks that specialize in petrochemical production, efficient use of both materials and energy can be improved by the integration of materials, products, and energy (Sterr and Ott, 2004). This integration is partially responsible for the small E factor of petrochemical production, which is generally below 1.0 (Sheldon, 2007). However, fine chemical products, such as dyestuffs and intermediates of pharmaceuticals, require multistep synthetic processes and diversified production volume, and
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Fig. 1. Schematic diagram of the production of a single product.
Fig. 2. Conceptual model of a hybrid of green chemistry and industrial ecology in the context of a chemical industrial park.
thus these products have much higher E factors (Sheldon, 2007). We propose that, in a fine chemical industrial park, there is great potential to improve the material efficiency of chemical production by extending the system boundary of single chemical production and integrating it into the industrial ecosystem. This paper is organized as follows: Section 2 introduces the models and provides a brief introduction to the fine chemical industrial park that is used as a case study; Section 3 presents the practices of green chemistry in the park; Section 4 illustrates the park’s performance in hybridizing green chemistry with industrial ecology, and Section 5 presents conclusions. 2. Methodology 2.1. A conceptual model of a hybrid of green chemistry and industrial ecology in the context of a chemical industrial park Fig. 1 illustrates the conceptual model of green chemistry at the single-product level, and the process of synthesizing a single product is defined as the system boundary. In a single-product model, the inputs include raw materials, auxiliary materials, energy, and water; the outputs are the target product(s), byproduct(s), and wastes (gaseous/liquids/solid wastes). The application of green chemistry technologies at the single-product level can, to some extent, improve the efficiency of core materials. But, inevitably, some auxiliary materials and by-products cannot achieve full atom economy because they are not combined in the structure of the final products. Fig. 2 illustrates the conceptual model of a hybrid of green chemistry and industrial ecology in the context of a chemical industrial park. It is derived from in-depth observation of the greening practice implemented in the chemical industrial park under consideration in this study and some other chemical industrial parks in China (Ding and Hua, 2012; Yune et al., 2016). The model aims to
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integrate greening practice of chemical industrial park from three levels: product, food web, and infrastructure sharing. The model considers not only the manufacturing process of a single product but also the food web that exists among different firms, as well as infrastructure sharing in the chemical industrial park. The geographic proximity of the different firms in the chemical industrial park will offer some benefits (Porter, 1998; Jensen, 2016) that may help expand the boundary of single products. The three levels in Fig. 2 are further illustrated as follows. 2.1.1. Products level At this level, the core measures are cleaner production and design of green process towards individual product, which in general employs the “24 principles” of green chemistry and green chemical engineering, PRODUCTIVELY and IMPROVEMENTS (Tang et al., 2008) respectively, aiming to improve the atom economy of chemical synthesis and efficiency of key raw materials. An end-ofpipe measure is also a necessary component at this level. 2.1.2. Food web level This level is the key to extending the system boundary of a single product. At this level, collaboration among different firms in the chemical industrial park can be facilitated via designing, uncovering, and fostering horizontal and vertical integration among different stakeholders. This may include food webs, supply chains, and industrial ecosystems in which “waste from one company may become the raw materials of another one”(Frosch and Gallopoulos, 1989) due to the clustering of chemical production and geographic proximity of different stakeholders. As a result, high cumulative material efficiency and energy efficiency can be achieved in the chemical industrial park as a whole. The material loop close is one of the benefits of food web facilitation, particularly for the auxiliary materials. 2.1.3. Infrastructure sharing level Infrastructure sharing is an essential characteristic of industrial parks, and combined heat and power (CHP) is widely employed in EIP practice (Chertow, 2000a,b) (Guo et al., 2016a,b). Besides CHP, other energy and environmental infrastructure such as centralized wastewater treatment plants, reclaimed water plants, and hazardous waste incinerators are not unusual in most Chinese eco-industrial parks. Compared with separate and self-serviced small-scale equipment, infrastructure sharing has positive effects on enhancing energy efficiency and addressing environmental issues (Porter, 1998; Yuan et al., 2010; Govindan, 2015). 2.2. Implementation of the model and performance assessment A typical Chinese fine chemical industrial park, Hangzhou Bay Shangyu Economic and Technology Development Area (HSEDA, formerly abbreviated as SYIA), is used as a case study to illustrate the implementation and performance of the model shown in Fig. 2. HSEDA, established in 1998, mainly produces dyestuffs, pharmaceutics, and other fine chemicals. It ranks No. 1 in its volume of dyestuff production, both in China and globally. Their dyestuffs outputs include disperse dyes, reactive dyes, acid dyes, vat dyes, pigments, intermediates, and dyestuff additives, such as surfactants and lignin. In 2013, HSEDA accounted for 65% of national disperse dye outputs and 45% of local gross industrial output value. Based on long-term observation of HSEDA, we have reported its one-year static metabolism of sulfur (Tian et al., 2012a,b) and carbon (Tian et al., 2013), its energy saving measures and potentials (Tian et al., 2012a,b), and the evolution of its policies targeting green development. This basic information on HSEDA can be found in previous works (Tian et al., 2012a,b, 2013).
We carefully analyzed HSEDA’s practices at the three levels listed in Fig. 2 by targeting one of its pillar industries, dyestuff production. Then, performance is qualitatively assessed by focusing on: (1) hazardous waste generation in dyestuff production, (2) water pollutants generation with the proxy of chemical oxygen demand and ammonia-nitrogen in wastewater before treatment, and (3) sulfuric acid consumption for dyestuff production. As shown in our previous work, HSEDA has two big dyestuff manufacturers, the Company L and Company R. We analyzed the hazardous waste generated by both of these groups, which accounted for 91% of HSEDA’s total hazardous waste in 2011. 2.3. Data collection The data came from two sources. On the one hand, we sent out questionnaire with the same procedure of data collection as our previous work (Tian et al., 2013). We sent out questionnaire from March to July 2014 to collect the data of material consumption and chemical production of HSEDA in 2013. We collected around 80 samples. Then we carefully checked the reliability of the data and uncover the food web of chemical production within the HSEDA. On the other hand, we collected data in the environmental statistic database from local bureau of environmental protection, including (1) waste generation of the 28 dyestuff producers in HSEDA, such as chemical oxygen demand, ammonia-nitrogen in wastewater before treatment, and hazardous waste generation, and (2) the first three products and first three raw materials in volume in each producer. 3. Hybrid of green chemistry and industrial ecology practice in HSEDA This section carefully reviews HSEDA’s hybrid of green chemistry and industrial ecology from the perspective of the three levels illustrated in Fig. 2. 3.1. Practice of greening chemical production at the products level Green chemistry practice at HSEDA at the product level is summarized in Table 1 in the condensed form of the dual 12 principles of “PRODUCTIVELY” for green chemistry and “IMPROVEMENTS” for green chemical engineering. 3.2. Facilitating food web establishment A food web of disperse dyestuff production has been established in HSEDA (Fig. 3), and all of its processes are finished within HSEDA. The food web consists of dyestuff intermediates, disperse dyes, inorganic sulfur chemicals, hydrochloric acid, and sulfuric acid (Fig. 3). Disperse dyes, sulfuric acid, and by-products of inorganic salts are the main products of the dyestuff food web. A sulfuric acid manufacturing facility also provides steam and electricity by recovering chemical reaction heat. Nitrosyl sulfuric acid has been widely applied in diazo dyestuff production by replacing most of the traditional complex “NaNO2 + HCl or H2 SO4 ”. HSEDA took advantage of the two sulfuric acid manufacturing facilities to tackle the longstanding challenge of disposing of spent sulfuric acid (Fig. 4). Spent sulfuric acid from nitration reactions has a concentration of about 69% and is concentrated to approximately 88% through vacuum concentration; it then reaches a concentration of 98% with SO3 and is recycled back to dyestuff production. A large amount of spent sulfuric acid from diazotization is neutralized with carbide slag, and the calcium sulfate goes to a landfill in the park. In 2008, the calcium sulfate associated with disperse dye production was categorized as hazardous waste in China. From that point on, HSEDA placed great importance on reducing calcium sulfate generation. Since 2012, spent sulfuric acid from diazotization has been
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Table 1 Examples of the “Dual 12 Principles” implemented in HSEDA. Green chemistry
Examplesa implemented in HSEDA
Green chemical engineering
Examples implemented in HSEDA
P-Prevention waste
(1) Implementing mandatory cleaner production auditing every three years for all chemical producers; (2) Set threshold for new chemical production projects to prevent HSEDA from adopting pollution-intensive processes and high toxicity chemicals (1) Establishing biomass-to-energy infrastructure; (2) Recovery of chemical reaction heat in sulfuric acid manufacturing, hydrogenation of nitro-aromatics, and high-temperature distilling Developing ‘one-pot’ or short synthetic processes, such as resorcinol, o-diaminobenzene, and alaninol production. Developing ecologically friendly dyes created with the OTEX standard
I-Inherently non-hazardous and safe
M-Minimize material diversity
(1) Phasing out toxic materials and solvents, such as CCl4 , CHCl3 , and Benzene as solvents; (2) Replacing dipole non-proton solvents, such as THF and DMF, with toluene; (3) Using the Distributed Control System (DCS) to improve the reliability of operation Using one solvent in multi-step synthetic processes
P-Prevention instead of treatment
Implementing mandatory cleaner production audits
R-Renewable material and energy input
(1) Establishing biomass-to-energy infrastructure; (2) Partly shifting coal-fired combined heat and power (CHP) to municipal solid waste (MSW)-to-energy; and (3) Recovery of chemical reaction heat in sulfuric acid manufacturing, hydrogenation of nitro-aromatics, and high-temperature distilling. (1) Rearranging layout of process vertically to reduce pumping of liquid materials; (2) decreasing redundant intermediate links in material transfers
R-Renewable materials
O-Omit derivation steps D-Degradable chemical products
U-Use safe synthetic methods
(1) Using continuous and adiabatic nitration technology; (2) Phasing out application or production of ODS, such as CCl4 ; (3) Replacing some odorous or hard-to-recover dipolar aprotic solvents, such as THF and DMF; and (4) Full implementation of DCS in chemical production. Employing catalytic hydrogenation technology in nitro-aromatics reduction, amino-acid reduction instead of iron powder hydrogenation and NaBH4 reduction, respectively.
O-Output-led design
T-Temperature, pressure ambient
Improving the temperatures of diazo reaction from <−5 ◦ C to 0–5 ◦ C to reduce cooling consumption.
E-Efficient use of energy, materials, and space
I-In-Process monitoring
Application of DCS and emergency stopping devices (ESD) in all chemical producers
M-Meet the need
V-Very few auxiliary substances
(1) Using NOSO3 H instead of “NaNO2 + HCl” as diazo reaction agent in disperse dyestuff synthesis; (2) Using one solvent in multi-step reactions The E factor is a key metric to assess the performance of chemical reactions in the park.
E-Easy to separate by design
C-Catalytic reagents
E-E-factor, maximize feed in product L-Low toxicity of chemical products a
(1) Phasing out ODS; (2) Releasing negative list of toxic chemicals and mandatorily disabling their utilization in the park
V-Very simple
N-Networks for exchange of local mass & energy T-Test the life cycle of the design
(1) Continuous production; (2) Avoiding manual operation; (3) Simplifying multi-step synthetic processes with one-pot or short processes, and (4) establishing supply chains in the park to reduce purification or desiccation of some intermediates (1) Energy infrastructure sharing; (2) Recovering and cascading utilization of process heat; (3) Fostering industrial symbiosis in the park; and (4) Rearranging layout of the process vertically to reduce pumping materials Using high-performance dye (e.g., 300% disperse dye instead of 100%) to reduce the dosage of dye while meeting the same function. Using spray drying instead of “salt-out + spray drying” process in reactive dye production
Cooperation among producers due to geographical proximity and supply chain integration within the park Tailored policy on experimenting with LCA-based eco-design of process and products was issued by the Chinese government in 2015
Due to space limits, only some examples are presented.
gradually transformed into ammonium sulfate. Spent sulfuric acid with a concentration of 30% or above is neutralized with ammonia to make ammonium sulfate instead of using the old process of neutralization with carbide slag. The rest, with a concentration of 10–15% is pretreated and recycled back to process. Thus the landfill of calcium sulfate has declined rapidly, as discussed in Section 4. Now, most of the spent sulfuric acid ends up as ammonium sulfate, a by-product that is useful as fertilizer. Note: The functional group in blue refers to the coupling part of diazo dye, and the red refers to the diazotization part. The process heat from the nitration and hydrogenation processes is also delicately recovered as shown in Fig. 5. Aromatics nitration and hydrogenation of nitro-aromatics are both exothermic reactions. The reaction heat is recovered in situ to produce
hot water for disperse dye work-up (washing) and to make cooling water using lithium bromide cooling technology, which can be used for dye synthesis. Furthermore, sensible heat associated with the vacuum distillation of aromatic amine is also recovered to produce low-pressure steam for solvent recovery. As a result, energy efficiency is substantially enhanced.
3.3. Infrastructure sharing in the park The energy and environmental infrastructure in HSEDA is characterized by its diversified functions, which include the following: (1) coal-fired combined heat and power (CHP) utilities with a total capacity of 30 MW; (2) a centralized wastewater treatment plant (WWTP) with a capacity of 300,000 t per day; (3) municipal solid
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Fig. 3. Food web of disperse dye production in HSEDA.
Fig. 4. Schematic illustration of disperse dye production in HSEDA.
waste incineration for electricity, with a total capacity of 650 t per day and an 18 MW electricity generator; (4) WWTP-sludge incineration for steam, with a total capacity of 750 t of sludge per day; (5) hazardous waste incineration, with a capacity of 14400 t per year; and (5) a biomass-to-energy utility, with a capacity of 150,000 t per year. The recovery of chemical reaction heat, particularly from sulfuric acid manufacturing with sulfur as a raw material, is also a key element of HSEDA’s infrastructure. There are two sets of sulfuric
acid manufacturing utilities, with a total capacity of 400,000 t of sulfuric acid per year. Furthermore, HSEDA also performs steam and electricity production and spent sulfuric acid regeneration. One of the coal-fired CHP plants also incinerates the odorous offgasses from one company’s wastewater treatment plant by mixing them with fresh air and injecting them into a boiler. The company built a 1.4-m diameter and 1.5-kilometer-long pipeline between the wastewater treatment station and the CHP plant (an investment
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Fig. 5. Cascading utilization of process heat in the dye intermediate production.
of 7 million Chinese Yuan (CNY)) in 2011. More detailed information on HSEDA’s energy metabolism can be found in our previous work (Tian et al., 2012a,b; Guo et al., 2016a,b) and the energy flow diagram can be found in the supporting information. Energy infrastructure plays a crucial role in addressing HSEDA’s environmental issues and improving its greenness accordingly. 4. Performance assessment and discussion The performance of disperses dye production in HSEDA is assessed mainly based on hazardous waste generation and water pollutants generation. Fig. 6 presents the evolution of waste generation in dyestuff production in HSEDA from 2011 to 2015. One of the characteristic solid wastes is calcium sulfate, which accounts for a large part of the solid waste generated in disperse dye production and was categorized as hazardous waste in China in 2008. The cost of calcium sulfate landfills thus increased markedly. In HSEDA, the cost of a general solid waste landfill is approximately 200 CNY per ton, but this rises to approximately 3000 CNY per ton for hazardous waste treatment. There was a buffer period during which dyestuff manufacturers were requested to develop new process to substantially reduce their calcium sulfate generation. The dyestuff companies in HSEDA took this issue very seriously, and a systematic retrofitting approach was developed to address this challenge by neutralizing spent dilute sulfuric acid with ammonia instead of carbide slag, as shown in Fig. 4. Ammonia neutralization is expensive and energy-intensive even when applying multi-effect evaporation. By inserting ammonia neutralization into the total system of disperse dye production, the spent sulfuric acid with a concentration above a certain threshold can be refurbished and recycled, while the rest can be neutralized with ammonia. The process heat in sulfuric acid manufacturing and disperse dye production is also recovered as much as possible for ammonium sulfate evaporation. The large-scale application of this new neutralization process was put into practice in 2012. Even though the cost of ammonia neutralization process is high, the whole system of dye production is profitable with positive environmental performance. Fig. 6(a) clearly shows that the hazardous waste generated in dyestuff production decreased by 52% in 2013 compared with 2012. Hazardous waste generation per unit of dyestuff output was also reduced markedly from 2013. This achievement of such a large reduction in the generation of hazardous solid waste is largely due to the adoption of the ammonia neutralization process and systematic optimizations of disperse dye production. Carbon and nitrogen make the key functional groups in the structure of dyestuff as shown in Fig. 4. Organic carbon and nitrogen emission to water will cause severe water pollution. Two indicators,
namely chemical oxygen demand (COD) and ammonia-nitrogen, are generally employed to monitor water pollution. COD is generally used to indirectly measure the amount of organic compounds in water. Ammonia-nitrogen refers to the nitrogen in water in the form of ammonia and ammonium ion, which can cause eutrophication of water. Fig. 6(b) illustrates the evolution of the two pollutants generated in dyestuff production from 2011 to 2015. Chemical oxygen demand and ammonia-nitrogen generation, which refers to the amount of pollutants just generated from the facility and without any treatment, can partly present the greenness of dyestuff production. After neutralization with carbide slag was replaced by ammonia neutralization in 2013, some organic pollutants once adsorbed by calcium sulfate and landfilled were kept in wastewater, which partly contributed to the increase of COD in wastewater in 2012. The rebound of hazardous waste generation in 2015 (Fig. 6(a)) was mainly due to three reasons: (1) startup of a new chloroalkali facility in one of the top dyestuff producers, the Group R; (2) capacity of some key intermediates of disperse dyestuff increased markedly associated with large amount of waste salts generation, such as sodium chloride and sodium sulfate; and (3) while ammonia was added to neutralize spent sulfuric acid and recovering ammonium sulfate as byproduct, ammonia-nitrogen in wastewater increased markedly, thus intensified wastewater treatment was requested to further remove ammonia-nitrogen in the effluent. Thus, more sludge was generated in wastewater treatment plant. Because the data of each category of hazardous waste generation was unavailable, the reason of the rebound could not be thoroughly uncovered in this study. Moreover, there are additional benefits to the horizontal and vertical integration of the food web of disperse dye production in HSEDA. Most spent sulfuric acid was recovered or made into useful byproducts, and nitrogen oxides generated in nitration were also recovered to produce nitrosyl sulfuric acid. Compared with the regular production process of disperse dye in China, the average yield of disperse dyestuff in HSEDA increased from 91% to 95%, the dosage of sulfuric acid decreased from 1.5 to 1.1 t per ton of disperse dye filtration cake, and average water consumption decreased from 110 to 50 t per ton of disperse dye filtration cake, which was further made into commercial dyestuff. 5. Conclusion Taking disperse dye production in HSEDA as a case study, waste generation in dyestuff production are reduced markedly by expanding the system boundary from single product synthesis to food web development in the chemical industrial park. It can be
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1.60
120,000 104,168
1.40 HW generation/product outputs (t/t)
100,000 89,423
1.20
80,850 76,189
1.00
80,000
84,100
77,531
53,662
0.80 0.60
60,000
50,139 37,867
40,000 0.40 0.20
1.34
0.66
0.42
0.66
1.34
2011
2012
2013
2014
2015
Hazardouswaste generation (t/a)
112,955
20,000
-
Hazardous waste generation per unit of product output
Hazardous waste generation
Disperse dye outputs
(a) Hazardous waste generation 25,000,000
1,200,000
19,771,840 20,000,000
1,000,000
914,945 913,438 15,204,134
15,000,000
800,000
680,649
22,110,387
600,000 21,586,970 546,427
10,000,000
400,000
16,141,860 5,000,000
200,000
-
Ammonia nitrogen generation (kg/a)
Chemical oxygen demand generation (kg/a)
1,091,284
2011
2012
2013
Chemical oxygen demand generation
2014
2015
Amonia-nitrogen generation
(b) Water pollutants generation Fig. 6. Waste generation in dyestuff production from 2011 to 2015.
observed that such symbiotic linkage of material supply, spent sulfuric acid recovery, and process heat reutilization cannot be established for a single product. The practices used in HSEDA support the argument of this paper that a hybrid of green chemistry and industrial ecology in the context of a chemical industrial park can substantially and simultaneously improve material efficiency and reduce waste generation. The food web does not stand alone in HSEDA, many chemical industrial parks have established their own featured food webs, as in Shanghai chemical industrial park (Yune et al., 2016) in China, a sugar making industrial park (Zhu et al., 2006), a coal chemical industrial park, and a sea salt and phosphorbased chemical industrial park (Ding and Hua, 2012). There are
approximately 500 chemical industrial parks in China. Actions similar to those piloted in HSEDA could be implemented in these CIPs to achieve better environmental and economic performance.
Acknowledgements The authors acknowledge the National Natural Science Foundation of China for financial support through projects 41471468 and 41671530. We also thank the administrative bureau and enterprises in HSEDA and Bureau of Environmental Protection for their assistance in data collection.
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