Application of industrial ecology in water utilization of coal chemical industry: A case study in Erdos, China

Journal of Cleaner Production 135 (2016) 20e29

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Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro

Application of industrial ecology in water utilization of coal chemical industry: A case study in Erdos, China Shengyong Jia a, *, Haifeng Zhuang b, Hongjun Han c, Fengjun Wang d a

School of Water Conservancy & Environment, Zhengzhou University, Zhengzhou 450001, China Key Laboratory of Recycling and Eco-treatment of Waste Biomass of Zhejiang Province, Zhejiang University of Science and Technology, Hangzhou 310023, China c State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China d China Coal Erdos Energy & Chemical Co. Ltd, Erdos 017300, China b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 5 February 2015 Received in revised form 7 June 2016 Accepted 14 June 2016 Available online 16 June 2016

China has been accelerating coal chemical development, more and more industries have focused on the highly efficient water utilization. The water utilization in coal chemical industry was evaluated in Erdos, China. According to the industrial ecology principles, the processes in sectors of pretreatment, desalination, wastewater treatment plant, reuse, recirculation and brine have been fully discussed. The water balance was investigated to evaluate water reuse, reaching efficiencies of 70e81%. Two major cleaner production measures based on industrial ecology have been transformed: 1, the production water of pretreatment has been mainly pumped to recirculation sector as supplement; 2, production water of reuse sector has been transferred to desalination sector. Results indicated that if the production water from reuse sector to desalination sector was sufficient, 15,000 tons of pretreatment production water scheduled for desalination sector and cost of 730 United States Dollars have been saved daily. The driving forces for industrial ecology implementation in the industry mainly included the requirements of resource and environment, industrial policy, technical support and enterprise culture. And the present technologies of water utilization in this industry provided scientific guidance for the designs and operation of water utilization for the coal chemical industry. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Water utilization Coal chemical industry Cleaner production Industry ecology Coal gasification wastewater Green engineering

1. Introduction In recent years, Chinese energy industries have been focusing on accelerating the development of new coal chemical technologies mainly taking up productions of clean energy such as liquefied natural gas, synthetic methanol, ammonia, olefin and urea to reduce the resource consumption by coal-fired power generation (Chen and Xu, 2010; Yoon and Lee, 2011). Numerous coal chemical industries were building and starting operations in arid regions of China's Northwest, such as Shaanxi, Inner Mongolia and Ningxia, these provinces were characterized by abundant coal resource but less water resource, what's worse, huge water consumption of the coal chemical industries aggravated the existing fresh water scarcity. Besides, the coal chemical industries were characterized as pollution-intensive industries for high strength wastewater with

* Corresponding author. E-mail address: [email protected] (S. Jia). http://dx.doi.org/10.1016/j.jclepro.2016.06.076 0959-6526/© 2016 Elsevier Ltd. All rights reserved.

huge quantity; thus many attentions should be paid on the balance of the energy development and water consumption and environment protection. According to the national energy development strategy, new coal chemical industries must develop and promote the high-efficiency and cleaner coal utilizing technology to realize the energy sustainable development (Xie et al., 2010). And industrial ecology (IE) as the promising strategy can provide efficient approaches for water utilization to reduce the environmental impact and realize the coordinated development with the environment. The concept of IE was popularized by using the analogy between natural ecosystems and industrial systems (Boix et al., 2015), and indeed a more recent definition for IE has been expressed as “a systems-based, multidisciplinary discourse that seeks to understand emergent behavior of complex integrated human/natural systems” (Allenby, 2004, 2006). The key feature of IE relied on the integration of various components of a system to reduce the net resource input as well as pollutant and waste outputs (Despeisse et al., 2012). The main goal of implication of IE can improve the

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industries' environmental performance, preserve environment while increase business success. rt et al. (2002) evaluated the IE concept by considering its Robe application in terms of the strategic sustainable development and indicated that the applications of IE contributed five levels in the hierarchical model (Table 1). Baas and Boons (2004) suggested that IE was a label under which many linkages between production and consumption processes were grouped, and they provided an analytical framework to investigate regional IE through three phases including regional efficiency, regional learning and sustainable industrial district. There were many studies concerning IE applications in various word-wide industries. According to IE principles, more environment-friendly reagents for copper sulphide ore flotation and environmental managements for granite slab production were proposed (Mendoza et al., 2014; Reyes-Bozo et al., 2014). For the coal chemical industries, application of more advanced technologies with high efficiencies of water use and wastewater reuse was the key to reduce the water consumption and wastewater discharge (Pan et al., 2012). Liu and Zhang (2013) have demonstrated that IE provided principles for water utilization for marine chemical industry and it has achieved effective utilization of underground brine, seawater and freshwater, besides, economic and environmental benefits have been achieved. IE activities were also implemented in sugar refining industry and it has achieved the successful transition from a traditional corporation to a sustainable corporation (Yang and Feng, 2008). In addition to separated industry, planning and construction of port cities and eco-industrial parks have also been guided by IE principles and studies indicated the IE could provide significant guidance with less influences on the environment (Cerceau et al., 2014; Gibbs and Deutz, 2007). The concept of eco-industrial park, which was defined as “a system of planned materials and energy exchanges that seeks to minimize energy and raw materials use, minimize waste and build sustainable economic, ecological and social relationships” (Alexander et al., 2000), has been popularized. And Boix et al. (2012) has indicated that under the condition of an eco-industrial park, the sum of benefits achieved by working collectively was higher than working as a standalone facility. But for individual industry, the integration of tools and approaches of IE, cleaner production (CP), pollution prevention could be more practically realized at factory level (Despeisse et al., 2012). Actually, the approaches of IE and CP have been attached great importance and vigorously promoted by Chinese government (Geng et al., 2007) and IE principles on water utilization referring to this coal chemical industry were shown in Table 2, relying on the report of Liu and Zhang (2013). Coal gasification technology was the clean use of coal resources, representing large-scale and high-efficiency characteristics, which included Lurgi, Texaco, Shell, and U-gas processes (Xie et al., 2010). This paper represented a case study on China Coal Erdos Energy & Chemical Co. Ltd, a famous coal chemical industry in China, which utilized British Gas/Lurgi (BGL) gasification technology. The BGL was derived from Lurgi and represented lower requirement for oxygen, higher gasification efficiency and less wastewater quantity than Lurgi (Zheng and Furinsky, 2005). At the industry where the

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study was carried out, the water utilization virtually concerned all departments and equipments especially for the gas washing, condensing, purification and synthesis processes. Result indicated that this coal chemical industry with present technologies and CP measures was characterized by high water utilization efficiency and zero liquid discharge (ZLD) which represented a symbol of the Green Engineering. Exact descriptions of water utilization and applications of IE in a coal chemical industry were rare in the previous studies. The major goals of this paper were to show a strategy for more efficient water resource management with less water consumption and no wastewater discharge; to evaluate the effect of CP measures on the water utilization and investigate the mass balance by measurement of the water flows and calculation of water consumption; to present the driving forces of the water utilization and discuss the challenges of IE implementation and feasibility of technologies for other cases. Additionally, the reuse of salt produced from the brine in the crystallizer was discussed to reach the resources recovery and utilization. Results indicated IE and CP measures implemented in the coal chemical industry demonstrated an economyenvironment win-win situation and provided scientific guidance for the designs and operation of water utilization for other coal chemical industries. 2. Methods The water utilization at a coal chemical industry in Erdos, China was monitored for many months. The water treatment plant (WTP) included 6 sectors, and pretreatment, desalination, recirculation, wastewater treatment plant (WWTP), reuse and brine were checked in the study. Relying on the IE principles and operational experience, two major transformations have been made to improve the water utilization efficiency and save the cost. Although more efforts should be concentrated on tackling key technological problems to reach the ZLD, the driving forces for highly efficient water utilization and environment protection played the critical guiding significance to design and operate the practical engineering. Therefore, the impetus for the highly efficient water utilization has been investigated to reveal the driving forces. How to successfully achieve the purpose of cleaner production based on IE principles was still a matter, and the challenges of IE implementation in this coal chemical industry have been discussed, and the feasibility of technologies for other industries especially the coal chemical industries has also been evaluated. In addition, the key processes to realize the resource recovery and utilization of the salt produced from brine in the crystallizer were also investigated. The technology route was outlined in Fig. 1. The evaluated parameters included suspended solid (SS), turbidity, residual chlorine, silting density index (SDI), sodium ion, pH, ammonia, conductivity, urea, chemical oxygen demand (COD), Silicon dioxide (SiO2), total dissolved solids (TDS), total phenols (TPh), volatile phenol (VP), oils, total hardness, calcium hardness, phenolphthalein alkalinity, methyl orange alkalinity, total alkalinity, mixed liquid suspended solids, chloride ion, phosphate, total iron, zinc, sulfate and total heterotrophic bacteria count. Based on these parameters,

Table 1 rt et al., 2002). Concepts of industrial ecology applied to the strategic sustainable development model (Robe Level

Definition

1 2 3 4 5

Principles for the constitution of the system Principles for a favourable outcome of planning within the system; principles for sustainability as the desired outcome Principles for the process to reach the above outcome of sustainability, e.g. principles of sustainable development to reach sustainability Actions and concrete measures Tools and metrics to monitor and audit

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Table 2 Industrial ecology principles on water utilization and measures in this coal chemical industry (Liu and Zhang, 2013). Principles

Meaning

Water cascading

The step-wise use of water according to different water quality requirements The reuse sector production water was pumped to desalination sector, of different water demands between sectors. and the pretreatment production water was sent to recirculation sector. Treated or untreated wastewater was used as raw materials for making The WWTPa effluent as raw water was pumped to reuse sector. products.

Measures in this coal chemical industry

Wastewater utilized as production material Water substitution “Scarce” water should be substituted with “plentiful” water of a special region. In this way, the quantity of “scarce” water could be saved and its serviceable time could be extended. All the industry departments jointly utilize WWTP, through which the costs Wastewater of wastewater treatment facilities constructed by individual departments can treatment facility sharing be saved.

The main raw water was the mine water, thus the ground water was substituted, which represents a positive effect on the ecological environment protection. The WWTP with EBAb system was exclusively used for treating wastewater in this industry, which represents high pollutants removal efficiencies.

a

WWTP, wastewater treatment plant. EBA, System of external circulation anaerobic process (EC)-biological enhanced process (BE)-multi stage anoxic-oxic process (AO)-high density sedimentation tankadvanced oxidation process-biological aerated filter-V type filter. b

3. Results and discussion

17,914&22,362 Pretreatment sector

0&3,128

Desalination sector Turbine condensate : 15,126& 16,467

1,632&2,432 13,178&25,522 8,658&11,164

Brine sector 600&720

Boiler, turbine, coal gasification, phenols & ammonia recovery, synthesis, purification and other processes

Process condensate: 3,861&4,522 4,500&6,000 Reuse sector

0&10,056

Evaporator 100&144 Crystallizer ZLD Salt

1,496&1,974

23,904& 29,530

Recirculation sector

3,192&4,800 WWTP

1,104&1,540 Other wastewater

9,116&16,888 Coal gasification process and phenols & ammonia recovery process; synthesis, purification, air separation and boiler processes; urea production process

Fig. 1. Technology route and flowsheet of water utilization in water treatment plant (Values represent minimum value & maximum value; unit represents m3 day 1; WWTP, wastewater treatment plant; ZLD, zero liquid discharge).

efficiencies of water treatment in each sector were assessed. Collections, preservation and analysis of the samples were performed according to the Standard Methods (AHPA, 1998). The parameters in this study were determined daily in the continuous and steady operation stage. It should be emphasized that not all the water quantity could be regularly determined due to the differences of the equipments and water characteristics, such as the backwash sewage and ground flush water in each sector. In order to improve operation stability, regulating tanks have been built before or after each sector, thus the analyses of the water quantity among each sector should combine the pipe flows and liquid level variations in regulating tanks. Generally, it took a long period for coal chemical industries construction (3 yr for this coal chemical industry). During the test run, all the equipments performance should be checked to satisfy the design and production requirements. It must be paid more attention to the production index in each sector to provide guidance to improve the treatment efficiency.

There have been designed some key equipments in the WTP. Multi-media filter (MMF), dual media filter (DMF) and precision filter were used to remove SS and colloid, and backwashing would be required if the effluent quality and quantity reduced. Reverse osmosis (RO) membranes were used to produce high quality water; however, the treatment efficiency would be inhibited due to the increment of TDS, recovery limiting salts and chloride (Antony et al., 2012; Eddy and Metcalf, 2006). The use of ultrafiltration (UF) membranes as pretreatment for RO would significantly mitigate the particulate fouling (Childress et al., 2005). In order to achieve the purpose of precision desalination, mixed bed was designed in which the ions exchanged with anion and cation resins. 3.1. Processes of each sector and environmental benefits implementing IE in the WTP The whole WTP was divided into 6 sectors to better identify the individual effects, the flowsheet of the water flows was represented in Fig. 1 and the detailed original designs were as follows: 3.1.1. Pretreatment The raw water pumped to pretreatment sector was taken from an artificial reservoir in which the supplementary water was from rainfall, groundwater seepage and mine water from nearby coal mines (the main water resource). According to IE principles in Table 2, the groundwater and natural lakes water have been substituted and this played a positive effect on the environment and ecology protection in this arid region. The raw water fully mixed with polymeric aluminum chloride (PAC) in the pipeline mixer and then flowed into grid flocculating tank, where the polyacrylamide (PAM) was added to facilitate the flocculation process. In sequence, inclined plate settling tank was designed to separate the coagulation and water, and coagulation was sent to be dewatered by hydroextractor. Next, the water flowed into V type filter to remove the smaller particles. The water quality and water utilization of this sector were shown in Table 3 and Fig. 2, respectively. 3.1.2. Desalination The main effect of desalination sector was to supply pure water for the production departments. Desalination sector included 3 series to treat different water including pretreatment production water, turbine condensate and process condensate, to avoid excessive treatment for turbine and process condensate using the process treating pretreatment production water; and this satisfied

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Table 3 Water characteristics of pretreatment, desalination, reuse, wastewater treatment plant and brine sectors. Sector

Influent

Pretreatment

CODa 20 Ammonia 1.3 0.7 COD 15.3 COD 3300 Total hardness

Turbidityb 400 Conductivityc 6.8 5.9 Turbidity 21.5 Ammonia 280 Ammonia

pH 8.21 pH 9.1 8.4 Total hardness 280 VPf 320 Turbidity

pH 11.4 TPhg 700 SiO2

501.4

13.1

2.7

30

Desalination

Turbine condensate Process condensate

Reuse WWTPe Brine

a b c d e f g h i

COD, Chemical oxygen demand. Unit represents NTU. Unit represents ms cm 1. SiO2, Silicon dioxide. WWTP, wastewater treatment plant. VP, volatile phenols. TPh, total phenols. ND, not detected. TDS, total dissolved solids, unit represents g L

PAC Raw water

Pipeline mixer

Effluent

1

; Other units represent mg L

1

PAM Grid flocculating tank

Sludge

Inclined plate settling tank

Sludge dewatering machine

COD Turbidity 1.9 1.1 SiO2d Mixed bed Precision mixed bed 0.1 0.1 COD Turbidity 3.4 0.5 COD Ammonia 58 0.2 Production water COD Ammonia 8.5 6.6

pH 8.3 pH 8.7 Total hardness 30 VP NDh Brine pH Chloride ion 11.1 85,760

pH 10.5 TPh 15 TDSi 273.8

.

contrast, cation bed has been set before water pumped into precision mixed bed in this process. The water quality and water utilization of this sector were shown in Table 3 and Fig. 3, respectively.

Sludge

Backwash water V type filter Backwash Clean water tank

Other sectors

Fig. 2. Diagram of water utilization in pretreatment sector (PAC, polymeric aluminum chloride; PAM, polyacrylamide).

the IE principle of water cascading (Table 2). In addition, the chemical agents and power consumption were saved representing friendly environmental behavior. The pretreatment production water was sent to desalination sector. Before the water flowed into MMF, microbicide was added to prevent bacteria building up on the media which would taint water and negatively affect the backwash. And then, water would be sent to UF modules and precision filters to remove the residual SS and colloids. RO modules have been utilized to desalinize the major portion of the salt, decarburization devices were used to remove free carbon dioxide which would occupy the exchange capacity of anion in the mixed bed in which the residual ions exchanged with anion and cation resins, further achieving the purpose of precision desalination. Turbine condensate exchanged heat with pretreatment production water and recirculating water, and then flowed into turbine condensate tank. The cooling turbine condensate was pumped to precision filter to remove the pipeline rust and small amount of SS. Next, water would be pumped into desalination tank after removing ions in the precision mixed bed. Process condensate exchanged heat only with recirculating water and then pumped to process condensate tank. Similar to turbine condensate, precision filter and precision mixed bed were utilized to remove pipeline rust, SS and ions, respectively; by

3.1.3. Recirculation The main effect of recirculation sector was to supply cooling water for the production departments. The recirculation sector contained 3 series, series 1: to supply recirculating cooling water for synthesis, purification and air separation departments; series 2: to supply recirculating cooling water for coal gasification department; series 3: to supply recirculating cooling water for urea production department. The reason for separated series was to make the precision adjustment according to the different water quality demand in individual department, which met the fine management requirements and IE principles and to some extent, the water utilization efficiency has been improved. Furthermore, the 3 series utilized the same treatment process: part of the recirculating water with higher temperature (not exceeding 40  C) was distributed at the top of the cooling tower, filler and fan were utilized to facilitate the cooling (not lower than 30  C); in order to prevent corrosion and scale formation in the pipelines and heat exchange equipments, corrosion and scale inhibitor were added into the cooling water, additionally, chlorine dioxide as bactericide was used to kill bacteria to prevent sludge blocking devices. The other part of the recirculating water would be filtered by sand filter, and normally, this quantity took a small part of the whole water quantity. When the SS in the recirculating water got higher, more quantity of recirculating water would be filtered. As the water steam evaporated, the contaminants concentrations in recirculating water was gradually condensed, therefore, some recirculating water should be pumped to the reuse sector to be treated. In the original designs, the water supplement for recirculation sector was from the reuse sector, the pretreatment sector would supply the difference in case the reuse sector capacity was insufficient. The water quality and water utilization of this sector were shown in Table 4 and Fig. 4, respectively. 3.1.4. WWTP The wastewater mainly included coal gasification wastewater (CGW), ground flush water, sewage, laboratory wastewater and so

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Microbicide Pretreatment production water

MMF

UF tank

UF modules

Scale inhibitor Precision filter Turbine condensate

Heat exchanger RO modules Turbine condensate tank Decarburization devices Precision filter Mixed bed

Process condensate

Heat exchanger

Desalination tank

Process condensate tank

Precision mixed bed

Precision filter

Cation bed

Production departments

Fig. 3. Diagram of water utilization in desalination sector (MMF, multi-media filter; UF, ultrafiltration; RO, reverse osmosis).

Table 4 Water characteristics of the recirculation sector. Parameters

pH Turbidityc Conductivityd Calcium hardness Total alkalinity Chloride ion Residual chlorine CODf Phosphate Ammonia Total iron Zinc Sulfate Total heterotrophic bacteria countg Suspended solids Maximum concentrated ratio

Normala

Concentratedb

Synthesis, purification and air separation processes

Coal gasification process

Urea production process

8.9 10.0 3220 222 409 217 0.5 23 3.4 0.8 1.0 0.3 791 700

9.0 17.0 6140 345 631 484 NDe 32 9.2 2.7 0.5 1.0 1593 4000

8.5 27.6 4390 343 175 290 0.2 47 13.3 3.5 1.5 0.1 1365 18,200

16 5

58 5

82 3

<6.8 or >9.5 >20 >5000 >1300 <80 or >500 >500 >1.0 >30 >6.0 >30 >1.0 >4.5 >1000 >50,000 (Summer) or 10,000 (Winter) >20 e

a

Normal values represent the operating values. Concentrated values represent the values which indicate recirculating water should be discharged to reuse sector and clean water from pretreatment sector should be supplemented. c Unit represents NTU. d Unit represents ms cm 1. e ND, not detected. f COD, chemical oxygen demand. g Unit represents CFU mL 1; Other units represent mg L 1. b

on. The well-known CGW was generated in gas washing, condensing and purification processes which contained toxic and refractory compounds, including high concentrations of phenolic compounds, ammonia, heterocyclic and polycyclic aromatic hydrocarbons, long chain alkanes, thiocyanate and cyanide (Wang

and Han, 2012), which brought huge difficulty to biological treatment (Jia et al., 2014). In many coal chemical industries, the efficient treatment of CGW was the technology bottleneck needed to be broken. This WWTP was exclusively used for treating wastewater in this industry and the effluent was required to pump to reuse sector

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Water with high temperature from coal gasification department and phenols & ammonia recovery process

Cooling tower

Water with high temperature from synthesis, purification, air separation and boiler departments

Cooling tower

Water with high temperature from urea production departments Sand filter

Corrosion & scale inhibitor and chlorine dioxide Cooling water tank

Cooling tower

Production departments

Fig. 4. Diagram of water utilization in recirculation sector.

as raw water with no wastewater discharge into the environment which satisfied the IE principles (Table 2), and this sector was one of the key techniques to realize ZLD. Owing to the residual heat from the steaming ammonia in ammonia recovery department, the CGW temperature maintained 40e50  C which especially solved the problem of heating wastewater in winter, in this way, the amount of steam was saved. In the original designs, wastewater disposed into WWTP amounted to 8640 m3 day 1 with the hydraulic retention time of 161 h. Before the CGW pumped into biological treatments, flocculation-flotation was utilized as pretreatment to remove SS and oil instead of air flotation. Rubio et al. (2002) evaluated flocculation-flotation representing high efficiency in removing SS and reducing turbidity; however, the air flotation would facilitate the formation of cyclopentenone, pyridine derivatives and other heterocyclic aromatic hydrocarbons which reduced the CGW biodegradability (Han et al., 2013). Other wastewater was pretreated by primary settling tank. The WWTP applied external circulation anaerobic process (EC)biological enhanced process (BE)-multi stage anoxic-oxic process (AO)-high density sedimentation tank-advanced oxidation process (AOP)-biological aerated filter (BAF)-V type filter, which was defined as EBA system to treat the wastewater. The main characteristics of the influent and effluent of WWTP were outlined in Table 3. The effect of EC process was to improve the biodegradability of CGW with the similar mechanism of two-continuous upflow anaerobic sludge bed system (Wang et al., 2011) and methanol was added as co-substrate (Wang et al., 2010). The main effects of BE and AO processes were to remove organics and nitrogen with high efficiencies, respectively. The AOP represented a significant decrement of chromaticity and improvement of biodegradability (Zhuang et al., 2014a, 2014b). Result revealed that the EBA system was a promising technique for efficient CGW treatment. It was notable that CGW characteristics were in close relation to the coal quality and gasification process, so it was very important to culture the activated sludge before the CGW pumped into WWTP, otherwise the treatment effluent might not meet the reuse standard which threatened a great burden on the accident pool. The inoculated activated sludge was taken from aerobic tank treating similar wastewater in other WWTP and synthetic wastewater by crude phenols (mixtures of various phenols produced in the phenols recovery department) was used for microbes acclimatation. The effluent which met the discharge standard was pumped to reuse sector. Large contribution of the WWTP, about 28,010 kg COD day 1 and 2419 kg ammonia day 1 were cut down which reduced the dissolved oxygen consumption of the environment (relying on the original designs). Assessments of pollutants removal of the WWTP were made, it could be calculated from Table 3 that the removal efficiencies of COD, ammonia, VP and TPh reached 98%, 99%, 100% and 98%, respectively. High pollutants removal

25

efficiencies ensured a good and stable operation for the reuse and brine sectors, revealing that WWTP played the vital role in the ZLD achievement. The water quality and water utilization of this sector were shown in Table 3 and Fig. 5, respectively. The engineering of WWTP in this coal chemical industry was the first demonstration project in China for the purpose of realizing ZLD. The success of the long time operation boosted the confidence that the Lurgi (BGL) CGW can be efficiently treated and this made the country endorse the more applications of the coal chemical industry investment. 3.1.5. Reuse Water reuse schemes were considered to be “more green” or “eco-friendly”, as they allowed water to be treated and processed in a more nature-oriented way (Partzsch, 2009; Zaneti et al., 2012). The influent of reuse sector mainly contained WWTP effluent with activated carbon filter pretreatment, sewage from desalination, recirculation and sludge dewatering machine and brine from desalination. Thus this was the indispensable sector to transform the polluted water to clean water for reuse to other sectors which was well satisfied with the IE principles (Table 2). The mixed influent was pumped into stirring clarification pool, where the PAC, soda and calcium oxide were added to remove the hardness of calcium and magnesium and adjust the pH. And then, water was pumped into MMF to filter the SS and oil materials to meet the requirements of UF and RO modules. Before the water flowed into RO modules, reducing agents, scale inhibitor and precision filter were utilized. In the original designs, the production water would be sent to recirculation sector as supplement and the brine would be further treated by MMF, UF modules, sodium ion exchanger and RO modules, furthermore, the production water was also sent to recirculation sector and the highly concentrated brine was sent to brine sector. The water quality and water utilization of this sector were shown in Table 3 and Fig. 6, respectively. 3.1.6. Brine This sector was the last and critical process to transform the brine to salt by evaporating and crystallizing to realize the ZLD. The brine sector applied high efficiency reverse osmosis (HERO) technology with the advantages of capacities of anti-pollution caused by organics, microbe and SS; without pollution of Silicon and inorganic salts. Rapid mixing tank and contacted clarifier were used to reduce the turbidity and total hardness and increase the total

CGW

Other wastewater

Multi stage AO process

Flocculation-flotation tank

CGW regulating tank

Sewage regulating tank

BE process

Primary settling tank

EC process

Distribution well Backwash water

High density sedimentation tank

AOP

BAF process

V type filter

Backwash Clean water tank

Fig. 5. Diagram of water utilization in wastewater treatment plant (CGW, coal gasification wastewater; EC, external circulation anaerobic process; BE, biological enhanced process; AO, anoxic-oxic process; AOP, advanced oxidation process; BAF, biological aerated filter).

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Brine from desalination Sewage from desalination AC filter

Effluent of WWTP

Sewage correction tank

Sewage from recirculation

3.2. Cleaner production measures and water balance of the WTP

Sewage from sludge dewatering machine Microbicid & acid UF modules

MMF

PAC, soda and calcium oxide Stirring clarification pool

Reducing agents & scale inhibitor Precision filter

Production RO modules

Reuse water tank

Brine MMF

Recirculation sector Production

UF modules

Brine RO modules

Sodium ion exchanger

Brine sector

Fig. 6. Diagram of water utilization in reuse sector (WWTP, wastewater treatment plant; AC, activated carbon; PAC, polymeric aluminum chloride; MMF, multi-media filter; UF, ultrafiltration; RO, reverse osmosis).

alkalinity with the agents of lime cream, soda and PAC. And then, the water was pumped into DMF to remove the smaller SS to prepare for the UF modules. Before the water pumped into the RO modules, sodium ion exchanger and precision filter were applied, additionally, scale inhibitor would be added into precision filter. The RO production water would be sent to reuse water tank or desalination sector and the brine water would be sent to evaporator and crystallizer. The water quality and water utilization of this sector were shown in Table 3 and Fig. 7, respectively. In light of the study of Baas and Boons (2004), the whole WTP

Soda, PAC and Lime cream Brine from reuse sector

Rapid mixing tank

Sodium ion exchanger

UF modules

Contacted clarifier

DMF

Scale inhibitor Production Precision filter

was still in the first phase (regional efficiency) with other firms, but to some extent, the sectors in WTP were in the third phase (sustainable industrial district). And it was notable that the main parameters in Tables 3 and 4 concerned the influent and effluent of each sector, while some water parameters concerned the intermediate devices were not outlined.

RO

modules

Reuse water tank

Brine Evaporator Brine Crystallizer Fig. 7. Diagram of water utilization in brine sector (PAC, polymeric aluminum chloride; DMF, dual media filter; UF, ultrafiltration; RO, reverse osmosis).

Fig. 1 shows the water flows with quantity among each sector. It should be emphasized that the water flows in Fig. 1 have been gradually modified during the operation, based on the original designs. Specially, the results showed the largest water consumption sector of the WTP was the recirculation sector, during the cooling process, considerable quantity of water was consumed as steam. Thus, the production water of pretreatment which satisfied the requirements was mainly pumped to recirculation sector as supplement. It should be noted that the water in recirculation sector was gradually condensed with the steam consumption, if the concentrated ratios reached higher than 5, 5 and 3 for series 1, 2 and 3, respectively, the recirculating cooling water should be piped to reuse sector as sewage and this water quantity would be supplemented by the clean water from pretreatment; but the exact quantity represented no statistical regularity, due to the characteristics of the recirculating cooling water and the supplementary clean water (obviously, the quantity in summer represented higher than winter). Another CP measure was the production water of reuse sector which satisfied the requirements of RO modules in desalination sector has been transferred to the UF tank of the desalination sector, thus the MMF and UF modules were both omitted. And the pretreatment production water would not be sent to desalination sector (quantity of 0 m3 day 1) if the production water of reuse sector was sufficient (most of the time). As a result, the agents including reducing agent (2.3 g ton 1 water), microbicide (5.5 g ton 1 water), scale inhibitor (3.3 g ton 1 water) and hydrochloric acid (57 g ton 1 water), electricity consumption, loss of the equipment and backwash water consumption have been saved, and it should be noted that only the agents added into MMF and UF were saved. In this way, about 15,000 tons of pretreatment production water scheduled for desalination in original designs was saved daily and the benefit was approximately 730 USD. Therefore, the advantage of the second CP measure was to avoid the excessive water treatment, and the operation cost has been saved. Fig. 1 represents the water balance of the whole WTP. Because of the differences of the equipments and water characteristics, the sectors of pretreatment, desalination, reuse, recirculation and brine could not be regularly determined how much sewage was generated (such as the backwash water of the filters and sewage of cleaning UF and RO modules, sewage in the regeneration process of the ion exchangers and so on), thus these values were not shown in Fig. 1. In addition, the sewage of pretreatment, reuse and brine sectors could be treated in their individual sector. According to the operation situation of the industry, regulating and collecting tanks were built before or after each sector, thus the water quantity could be adjusted by regulating the tanks levels. It was notable in Fig. 1 that the water quantity transported between sectors was represented as minimum value & maximum value which performed the water utilization more objectively. During the study stage, the water reuse efficiencies of the whole industry stayed in the scope of 70e81%, higher than the original designs with 59e65%. According to the water utilization status of the industry, it can be observed that the effluent of the whole industry at the end-of-pipe was 100e144 m3 day 1 to the crystallizer, and the salt amount reached 12.5e18 t day 1 which represented the industry deserved to be an environmentally friendly project.

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What's more, as stricter requirement and higher standard have been imposed, more and more attention has been paid on the reuse of salt produced in the crystallizer in the brine sector. The salt has the characteristic of significant amount of sodium chloride and sodium sulfate, therefore, the salt separation has become the difficult problem in realizing the purpose of salt reuse. Contrast to chloride, nanofiltration (NF) process represented a superior rejection for sulfate at relatively low operating pressure. In addition, the organic matter in the brine would reduce the salt quality and negatively affect in the operation stability of evaporation and crystallization processes, and the AOP was utilized as a promising technology to remove the organics. Therefore, a novel technology with the key processes of pretreatment-UF-NF-AOP-evaporator and crystallizer has been researching in a pilot scale in this coal chemical industry. After two months operation, the pilot-scale laboratory results showed that the high-quality sodium chloride and sodium sulfate were successfully produced and they were both satisfied standard of the industrial salt. In addition, another issue of mother liquor in crystallization was further analyzed. The mother liquor contained extremely high concentrations of organic matter and various other salt, and the AOP hybrid biological process has been investigated, and the halotolerant bacteria should be inoculated. 3.3. Driving forces of highly efficient water utilization based on IE principles Boons (2008) suggested that the IE achievement should be assessed from a perspective which involved structural, cultural and political factors. Liu and Zhang (2013) investigated the impetus of water utilization of a marine chemical industry from five aspects, i.e., government, market, policy, culture and technique, therefore, it was necessary to examine IE development from a wider and more systematic perspective. Based on this idea, the study analyzed the impetus of highly efficient water utilization of this industry from four aspects: resource and environment, industrial policy, technical support and enterprise culture. 3.3.1. Resource and environment This industry was located in the interior of Mu Us Desert, characterized by lack of water resources, less natural rainfall with extreme interannual variation, strong transpiration, unequal distribution of surface water and serious shortage of groundwater. The grassland vegetation was seriously damaged by human activities during the past few decades, exposing the underlying sand; as a result, the natural ecological environment was deteriorating. Thus, the water resource supply and environmental capacity must be taken into consideration when building industry. And the situation of water resource and environment required enterprises in this region should comply with the principles of less water consumption and less pollution discharge, as far as possible to reduce the impacts on the environment. 3.3.2. Industrial policy China mid-and long term planning for coal chemical industry firstly required that strict water management should be taken in the coal chemical industries, adhering to the principle of “water capacity determining industry scale”, and it was strictly prohibited to use fresh water, agriculture and ecological water for coal chemical industry. Meanwhile, coal chemical industries should vigorously develop the circular economy, strengthen the rational circulation and cascade use of the resources, continuously improve the resources utilization efficiency and strive to achieve the ZLD or harmless treatment. Additionally, in order to achieve the sustainable development and reduction of production cost based on the

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limited resources, it was indispensable to promote scientific development and clean production technology, vigorously develop resource-saving industry and improve the level of environment protection. 3.3.3. Technical support The highly efficient water utilization in this coal chemical industry depended on two key techniques: 1, WWTP technology supported by research group of Prof. Hongjun Han (Harbin Institute of Technology), who has guided to build the first WWTP treating CGW (generated by Lurgi gasifier) as demonstration project in China. EBA system developed by research group of Prof. Han successfully removed pollutants with high efficiencies to meet the requirements of reuse sector; 2, to achieve the purpose of ZLD, HERO-evaporator-crystallizer technology by Aquatech International Corporation was applied which represented good and stable operation result. Another indispensable support was the online monitoring and automatic system on water quality and quantity, which made it easy to grasp the changes of water supply and consumption in time. This system played an important role in maintaining the stable operation of the industry. 3.3.4. Enterprise culture China Coal Erdos Energy & Chemical Co. Ltd is attached to China Coal Group (CCG) which took scientific development and win-win harmony for the enterprise's core values, building a world-class energy enterprise as the goal which has been striving toward persistently, providing high-quality energy, specially, promoting the coal transformation and clean utilization as the mission. Additionally, CCG strived to build a harmonious enterprise and strengthen the protection of the ecological environment. Advanced enterprise culture played a vital role in the enterprise development and guided CCG to build a Green Energy Enterprise. It should be emphasized that the present WTP technologies applied in this coal chemical industry especially the CP measures were taken on the basis of the above four driving forces and operation experience, which provided guiding principles for the coal chemical and similar industries. Particularly, the EBA technology applied in WWTP represented feasibility treating CGW especially generated by Lurgi gasifier and the innovative BGL gasifier. Not limited to the current state of treatment, research group of Prof. Han has made further researches on the AOP and reuse of salt produced in the crystallizer in the brine sector. 3.4. Challenges of IE implementation and feasibility for other industries The purposes of developing coal chemical industry were to change the types of energy use, improve energy utilization efficiency and reduce environmental pollution, which was satisfied with the requirements of IE. Based on the analyses of the WTP in the coal chemical industry in Erdos, four approaches were found to achieve the highly efficient water utilization: (1) more strict control of water resources exploitation especially for the groundwater; (2) enhancement of the wastewater reuse; (3) realization of ZLD of CGW; (4) resource utilization of the crystallization salt. However, there still constituted actual challenges for coal chemical industry with regard to reducing pressures on the environment influence and water resource consumption. Considering the logistic nodes centralizing material and energy flows, directly concerning issues of optimization and integration of flow management represented major drivers for the implementation of IE (Cerceau et al., 2014; Cohen-Rosenthal, 2000). It has been suggested that the industrial symbiosis would be a promising way to

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implement IE principles, which could engage separated sectors in a collective approach to enhance the cooperation involving exchanges of materials and energy (Chertow, 2000). According to the previous studies and operation experience, there were some challenges which should be concerned to achieve the IE in this coal chemical industry: 1. In the light of original design, it took a long time for operators achieving the optimum conditions. And the WTP exposed to profound influence from other production departments (such as coal gasification and phenols & ammonia recovery departments) which would directly influence the water characteristics in WTP and this could put forward more requirements to operators. 2. Up to date, the WTP has been continuously operating for many months, and the design indexes have been verified. In addition, drastic overhaul was needed when the coal chemical industry operated for a long time, during which all the departments would empty tanks and the WTP faced critical test to operate normally; furthermore, another big test to WTP was the starting-up after drastic overhaul. These required necessary solutions to maintain the operation. 3. On the one hand, on the basis of ensuring the treatment efficacy, scientific and punctilious attitudes should be taken to reduce the operation cost; on the other hand, appreciate measures should be considered and taken based on certain cost. 4. Obviously, the 6 sectors in WTP composed a networking behavior through the pipes, thus it was crucial to bolster coordination work among sectors; and this brought forward a matter, at what level (scale) could the IE be implemented, the WTP or the sector? In this study, the IE principles have been considered at the whole WTP scale to realize the maximum reduction of input cost, waste production and resource consumption. Korhonen et al. (2004) has summarized the applications of IE, they described the general tools for industrial symbiosis studies including substance flow analysis, information technology, environmental supply chain and life cycle management which represented more general for different types of industries in individual region and they were also crucial tools to improve networking and cooperation between sectors. Thus the technologies applied in WTP of this coal chemical industry would be possible to provide scientific guidance to other industrial cases especially the coal chemical industries. However, it should be noted that the current and advanced technologies applied in this coal chemical industry have covered almost all the water treatment measures, and this industry case was characterized by high quantity of water consumption and wastewater generation, and the eco-efficiency has been achieved based on the comprehensive benefit of this large industry; thus other industry cases should draw on the experience more reasonably, according to case characteristics of themselves. In addition to technologies, the levels of decision-making should be taken into account from both the local and regional factors and the outside international factors (Korhonen et al., 2004). 4. Conclusions IE provided principles for water utilization of the coal chemical industry, in which the 6 WTP sectors interacted with each other. Result demonstrated the ZLD was realized, in addition, highly efficient water utilization and economic and environmental benefit was achieved by implementing IE. The CP measures saved about 15,000 tons of pretreatment production water scheduled for desalination daily and approximate benefit of 730 USD. During the

study stage, the water reuse efficiencies of the whole industry stayed in the scope of 70e81%, higher than the original designs of 59e65%. Based on a wider and more systematic perspective of IE, resource and environment, industrial policy, technical support and enterprise culture played the key role as the driving forces for IE implementation. Four approaches including more strict control of water resources exploitation, enhancement of the wastewater reuse, realization of ZLD of CGW and resource utilization of the crystallization salt were found to achieve the highly efficient water utilization. In addition, the present technologies of this coal chemical industry provided scientific guidance and played an exemplary role for other industries. Acknowledgements This work was supported by Sino-Dutch Research Program (SDRP: 2012-2016) and the independent subject sponsored by State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (No. 2013DX10). References AHPA, 1998. Standard Methods for the Examination of Water and Wastewater, twentieth ed. American Public Health Association, American Water Works Association, Water Environment Federation, Washington, DC, p. 20. Alexander, B., Barton, G., Petrie, J., Romagnoli, J., 2000. Process synthesis and optimization tools for environmental design: methodology and structure. Comput. Chem. Eng. 24, 1195e1200. Allenby, B., 2004. Clean production in context: an information infrastructure perspective. J. Clean. Prod. 12, 833e839. Allenby, B., 2006. The ontologies on industrial ecology? Progress in industrial ecology. Annu. Int. J. 3 (1e2), 28e40. Antony, A., Subhi, N., Henderson, R.K., Khan, S.J., Stuetz, R.M., Le-Clech, P., Chen, V., Leslie, G., 2012. Comparison of reverse osmosis membrane fouling profiles from Australian water recycling plants. J. Membr. Sci. 407e408, 8e16. Baas, L.W., Boons, F.A., 2004. An industrial ecology project in practice: exploring the boundaries of decision-making levels in regional industrial systems. J. Clean. Prod. 12, 1073e1085. Boix, M., Montastruc, L., Azzaro-Pantel, C., Domenech, S., 2015. Optimization methods applied to the design of eco-industrial parks: a literature review. J. Clean. Prod. 87, 303e317. Boix, M., Montastruc, L., Pibouleau, L., Azzaro-Pantel, C., Domenech, S., 2012. Industrial water management by multiobjective optimization: from individual to collective solution through eco-industrial parks. J. Clean. Prod. 22, 85e97. Boons, F., 2008. History's lessons: a critical assessment of the desrochers papers. J. Ind. Ecol. 12, 148e158. Cerceau, J., Mat, N., Junqua, G., Lin, L., Laforest, V., Gonzalez, C., 2014. Implementing industrial ecology in port cities: international overview of case studies and cross-case analysis. J. Clean. Prod. 74, 1e16. Chen, W.X., Xu, R.N., 2010. Clean coal technology development in China. Energ. Policy 38, 2123e2130. Chertow, M.R., 2000. Industrial symbiosis: literature and taxonomy. Annu. Rev. Energ. Env. 25, 313e337. Childress, A.E., Le-Clech, P., Daugherty, J.L., Chen, C., Leslie, G.L., 2005. Mechanical analysis of hollow fiber membrane integrity in water reuse applications. Desalination 180, 5e14. Cohen-Rosenthal, E., 2000. A walk on the human side of industrial ecology. Am. Behav. Sci. 44, 245e264. Despeisse, M., Ball, P.D., Evans, S., Levers, A., 2012. Industrial ecology at factory levelea conceptual model. J. Clean Prod. 31, 30e39. Eddy, Metcalf, 2006. Water Reuse: Issues Technologies, and Applications (New York, USA). Geng, Y., Haight, M., Zhu, Q., 2007. Empirical analysis of eco-industrial development in China. Sustain. Dev. 15, 121e133. Gibbs, D., Deutz, P., 2007. Reflections on implementing industrial ecology through eco-industrial park development. J. Clean. Prod. 15, 1683e1695. Han, H.J., Zhao, Q., Xu, C.Y., Zhuang, H.F., Xu, P., 2013. Coal gasification wastewater pretreatment with coagulation and N2 flotation combined system (New Series). J. Harbin Inst. Technol. 20, 20e24. Jia, S.Y., Han, H.J., Hou, B.L., Zhuang, H.F., Fang, F., Zhao, Q., 2014. Treatment of coal gasification wastewater by membrane bioreactor hybrid powdered activated carbon (MBRePAC) system. Chemosphere 117, 753e759. Korhonen, J., Huisingh, D., Chiu, A.S.F., 2004. Applications of industrial ecologydan overview of the special issue. J. Clean. Prod. 12, 803e807. Liu, C.H., Zhang, K., 2013. Industrial ecology and water utilization of the marine chemical industry: a case study of Hai Hua Group (HHG), China. Resour. Conser. Recycl. 70, 78e85. Mendoza, J.F., Capitano, C., Peri, G., Josa, A., Rieradevall, J., Gabarrell, X., 2014.

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Glossary IE: Industrial ecology BGL: British Gas/Lurgi ZLD: Zero liquid discharge WTP: Water treatment plant WWTP: Wastewater treatment plant SS: Suspended solid SDI: Silting density index TDS: Total dissolved solids TPh: Total phenols VP: Volatile phenol MMF: Multi-media filter DMF: Dual media filter RO: Reverse osmosis UF: Ultrafiltration NF: Nanofiltration PAC: Polymeric aluminum chloride PAM: Polyacrylamide CGW: Coal gasification wastewater EC: External circulation anaerobic process BE: Biological enhanced process AO: Anoxic-oxic process AOP: Advanced oxidation process BAF: Biological aerated filter EBA: System of external circulation anaerobic process (EC)-biological enhanced process (BE)-multi stage anoxic-oxic process (AO)-high density sedimentation tank-advanced oxidation process (AOP)-biological aerated filter-V type filter AC: Activated carbon HERO: High efficiency reverse osmosis CP: Cleaner production CCG: China coal group