| Organic chemical industry characterized high resources consumption and large amount of pollutants emission is one of earliest industries which are practising circular economy, therefore many successful experiences of developing circular economy have been achieved in this industry. As a fundamental and leading branch piece of chemical industry, the theory and practice of circular economy in this field has important guide and reference role for the whole chemical industry. At initial stage, the practice of circular economy in organic chemical industry has formed spontaneously on the basis of long-term the practice accumulation, which demonstrates a powerful advantages and vitality of circular economy mode. However with the deepening of development and expanding of practice range in circular economy, the development mode which has formed spontaneously based only on practice accumulation can not meet the requirements in the industry development further. It is a focus that the study on design, modification and perfection for the circular economy industrial chain and web with the help of mature theory and technology to establish highly-efficient, stable circular economy development mode. The enterprise as main body of a practising circular economy, the construction and development of business chain and web in enterprise scale has crucial influence on the development of circular economy in larger scale.In this paper, based on systemic consultation literature and all-around review on the achievements on industrial chain construction and development of circular economy in chemical industry, both a analysis method of substance flow metabolism efficient and a design method on factory-level circular economy industrial chain and web in organic chemical industry has been studied by applying Substance Flow Analysis (SFA) and system integration method. Also, the connotation and effecting factors on the stability of factory-level circular economy industrial chain and web has been analyzed from these perspectives of economy, ecology and industrial structure features, subsequently a practicable evaluation indicator system and evaluation model on the stability of circular economy industrial chain and web has been established. Consequently a evaluation method on the stability of factory-level circular economy industrial chain and web in organic chemical industry has been proposed and tested by a case, the study results are as follows:(1) Scientifically identified current situation and limitation of developing circular economy in enterprisesIdentifying the factors restraining enterprises from developing circular economy on basis of analysis of the input and output of production process which integrated the cleaner production audit and practice of circular economy construction in Shandong JinYiMeng Group. The factors are as follows: high resource consumption and simple recycling, low utilization of raw materials, high water consumption with a low utilization efficiency, unidirectional industry-chains with a low relatedness degree, main production process with high energy consumption, low utilization of resources and a large quantity of waste generation and emissions.(2) Material flow analysis method of organic chemical industry chain and web of circular economy on factory-levelConsidering the characteristics of material flows of organic chemical industry chain and web on factory-level, the method of SFA was improved. The new method of the analysis on factory-level was put forward which contained research objective definition, system and system scope definition, inventory analysis, model establishment and interpretation. Three indicators, source efficiency, environmental efficiency, and reuse efficiency, were set. The conception of available substance flow in working procedures was put forward.The four organic chemical industry chains were studied. On the basis of the establishment of carbon SFA model in indifferent chains, the key links which restricted the carbon source efficiency and the sources of waste generation and emission were identified.①The results based on analysing the carbon flows of the alcohol fermentation production chain shows that the carbon system source efficiency in alcohol fermentation production process was 39.1%, and fermentation process and saccharification process were the key links which restricted the carbon source efficiency. To improve the carbon environmental efficiency and reuse efficiency, most important is to utilize the CO2 resource form cassava stillage and fermentation process.②The results based on analysing carbon flows of the acetic acid production shows that the carbon system source efficiency in acetic acid production process was 85.7%, and alcohol oxidation process were the key links which restricted the carbon source efficiency. At the same time, ameliorating the acetic acid production technics and condensing the production process are the key to improve the carbon system source efficiency and environmental efficiency.③The results based on analysing the carbon flows of ethyl acetate production chain show that the carbon system source efficiency in ethyl acetate production process was 98.1%, and dehydration process and esterification process were the key links which restricted the carbon source efficiency.④The results based on analysing the carbon flows of ammonia and methanol integrated production chain show that the carbon system source efficiency in ammonia and methanol integrated production process was 98.1%. The exising chain did not aim to improve the carbon source efficiency. As a result, the carbon source efficiency is low, most of carbon source flows, and decarbonizing desorption gas and slag of gasification have better utilization value.(3) Establishing a method for factory-level circular economy industrial chain in organic chemical industryBased on the connotation of circular economy industrial chain, the four structure types of chain, cycle, tree, network, and their evolution have been analyzed. Further a method for constructing factory-level circular economy industrial chain and web has been put forward from the perspectives of assembly, extension, complement, improvement and coupling of industrial chains. Take the four organic chemical industrial chains of JINYIMENG Group as a tested case, the method proposed has been applied. ①At industrial chain assembly. On basis of existing coal gasification, new processes of decarburization, CO extraction and carbonyl synthesis, a new chain have been developed and assembled in which use efficiency of carbon is 0.501 and the value come to 0.662 by the industrial coupling.②At industrial chain extension. Urea synthesis chain has been extended using liquid ammonia from ammonia and methanol integrated production and CO2 from decarbonization desorption gas as raw material, which makes use efficiency of carbon in the system of ammonia and methanol integrated production up to 0.644, equivalent to 16.5% increased.③At industrial chain complement. Firstly, adding a purification step of exhaust gas from alcohol fermentation is to reclaim high concentration CO2 to produce food-grade CO2, which can recycle exhaust CO2 up to 7.5×104t. Consequently, utilization efficiency of carbon in the system of alcohol fermentation has been increased to 0.591, equivalent to 51.2% increased. Next, recycling fly ash and slag of gasification as boiler fuel increases the level of carbon use and reclaims the energy.④At industrial chain improvement, the carbon content of slag of gasification decreased 2.6% and coal consumption per ton of ammonia decreased 6.0% by reconstructing configuration of gasifier and optimizing the operating parameters of blowing and gasification processes.⑤At industrial chain coupling. By the flows of methanol, acetic acid, decarbonizing desorption gas, decarbonizing exhaust and exhaust separated CO in different industrial chain, and 6 industrial chains (carbonyl synthesis, ammonia and methanol integrated production, urea synthesis, alcohol fermentation production, acetic acid production and ethyl acetate production) were mutually coupled. Then factory-level circular economy industrial chain in organic chemical industry was established. The industrial chain coupling also enriched resource flowing routes in the industrial chain, improved the carbon source efficiency and strengthened the stability of industrial chain and web.The results based on analysing the carbon flows of designed factory-level circular economy industrial chain in organic chemical industry show that the carbon utilization level was improved in every process of ammonia and methanol integrated production chain. In gasification process, it was improved 10.5% and to 0.747. In decarbonizing process, it was improved 16.1% and to 0.975. In methanol synthesis process, it was improved 18.2% and to 0.793. The carbon source efficiency of the designed circular economy industrial chain and web was improved 22.1% than the existing and to 0.675. The carbon environmental efficiency was 2.2 times than the existing ammonia and methanol integrated production chain.(4) Establishing circular economy industrial chain and web of regional water resources cascade utilizationBased on the water-saving technology of high gravity continuous fermentation process and carbonyl synthesis process, source reduction was achieved. According to various water resources of fresh water, secondary water and condenser water, classification using scheme was proposed by water type and the model of water resources cascade utilization in enterprise was established. Disposal process of different qualities was studied and propounded based on the wastewater quality. The wastewater which reached the standard could be as the replenishment of circulating cooling water system. Through the above measures, the fresh water input can be cut 4.23 billion tons and the amount of wastewater generated can be cut 1.24 billion tons, which improved the water resource utilization efficiency effectively.(5)Establishing the stability analysis and evaluation methods of factory-level circular economy industrial chain and web in organic chemical industryOn the basis of principles of value chain, life-cycle theory and openess of industrial chain, the connotation and effecting factors on the economic, ecologic and structural stability of circular economy industrial chain has been analyzed. A stability evaluation indicator system of factory-level circular economy industrial chain and web was established, which included 4 layers (arget layer, criteria layer, element layer and index layer). The evaluation indicator system was assembled and determining weights subjectively and objectively using AHP amendmented by entropy technology. Also an integrated evaluation method on the stability was studied, and the stability of circular economy industrial chain and system of the enterprise was evaluated scientifically. Results show that, compared with 2005, the stability of industrial chain and web after establishing the factory-level circular economy industrial chain and web in 2008, was enhanced from basically stable to stable. Sources consumption and pollutant emission were also greatly reduced.In words, the methods including analysis, establishment, perfection and stability evaluation for factory-level circular economy industrial chain were built by systematically studying the theory, model and technology and successfully applying in the enterprise. The study played roles of technical support, theoretical guidance and model development on the implementation of circular economy. Compared with 2005, the implementation effects of the new built circular economy industrial chain and web in 2008 included: the rate of starch liquor was improved 2.4%, industrial water recycling rate was improved 18.5%, COD emission intensity reduced 82.2%, SO2 emission intensity reduced 77.6%, comprehensive energy consumption per ton of ammonia reduced 2.2%, comprehensive energy consumption per ton of ethanol reduced 10.4%, fresh water consumption per ton of ammonia reduced 8.5%, and fresh water consumption per ton of ethanol reduced 15.7%.
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