The Empirical Research Of The Structure And Function In A Typical Iron And Steel Industrial Symbiosis Network

With producing more than 900 million tons of steel at the end of 2018 in China,accounting for 50 percent of the world’s total output,the steel industry faces increasing chanllenges of resource,energy and environments.Building the industry symbiotic relationship inside and outside the iron and steel industry,the industrial ecological transformation and high-quality sustainable development can be realized only by evaluating,optimizing and regulating the industrial symbiosis network.How to evaluate,optimize,regulate and manage the network is still an opened problem.The structure,function in a typical iron and steel industry symbiosis network are investigated by using exergy and ecological network analysis and are quantitatively characterized by ecological indicators in this paper.The main findings are as follows:The construction of the network should not only truly and objectively represent the technological process and production operation characteristics of the steel industry production system,but also reflect the symbiotic utilization of the upper and lower reaches of the production process,by-products and wastes,and the sharing of facilities and services.Based on the data in 2012 of a steel group company that has been in production for more than 60 years,the four scenarios of intra-firm symbiosis are surveyed since the company established.It is proposed that the boundary of the system should be set according to the boundary of land occupied coupled with the boundary of efficiency,power,ability and identity.Iron,carbon and exergy flow(Integrated Flow)were selected as the medium flow of ecological network analysis.The node scale level of symbiotic networks is distinguished by production units,processes,workshops,factories,subsidiaries and group companies and the industrial symbiosis network is constructed and quantified by coordinating and matching the symbiotic relationship between node scales and their flow data available.Coal gas,slag,scrap iron,scrap steel,desulfurization gypsum and other symbiotic recycling measures have improved the resource consumption,energy efficiency and emission of tons of crude steel.As a subsystem embedded in the external environment,the increase of industrial symbiosis measures leads to the changes of the topological structure of the symbiosis network and the changes of the influence on the external environment.The number of symbiotic network nodes,direct link,link density and link correlation degree all increased,and carbon metabolism and exergy flow all presented triangular stable structure,but iron metabolism presented trapezoidal structure in trophic structure level.The network utility analysis shows that ironmaking in iron metabolism and thermal power plant and ironmaking as well as coking in carbon metabolism has the biggest impact on the external environment and steel making and ore dressing are the key nodes affecting iron flow and thermal power plant,coking,ironmaking and waste management are the key nodes that affect carbon flow as well as the exergy flow shows the importance of ore dressing.Iron metabolism is dominated by mutualistic symbiosis and followed by commensalism and carbon metabolism is dominated by commensalism and followed by mutualism.Iron-making nodes play a dominant role in controlling the structure and function of the symbiotic network,which their control level is lower than that of the external environment,and they have a higher control level of iron metabolism,while thermal power plant and coking has a higher control level of carbon metabolism.Compared with carbon flux,iron flux has a greater influence on industrial symbiosis network and a higher level of the control to the network.The key nodes of symbiotic network optimization and control are external environment,ironmaking,thermal power plant and coking.The total system throughflow,the ascendency,and the capacity of iron and carbon metabolism are increasing with the symbiotic measures increased that shows the improvement and development of the ascendency and the characteristics of high carbon consumption and emission,but the average mutual information showed a downward trend.The average mutual information,the ascendency and organization maturity of iron metabolism were higher than that of carbon metabolism.The total system throughflow,the flow diversity,the capacity,the system redundancy and the overhead of carbon metabolism are higher than that of iron metabolism.Iron metabolism is dominated by efficiency,while carbon metabolism is dominated by resistance.The Total System Throughflow,System Capacity and Redundancy of the carbon metabolism,the iron metabolism and the exergy flow of the symbiotic network have the same distribution characteristics as well as Average Matual Information,Ascendency and Robustness.It is necessary to further optimize the iron metabolism and carbon metabolism in the sysbiotic network.The ecological network analysis combining carbon metabolism,iron metabolism and exergy flow can reflect the effects of change of symbiotic measures and the extension of industrial chains on the structure,function and behaviour of the symbiotic network.Average Path Length(APL),Finn Cycling Index(FCI),Mean Trophic Level(MTL),Detritivory to Herbivory ratio(D/H),Keystoneness,Structural Information(SI),and Flow-based Information Indices all can be used as quantitative indicators of industrial symbiosis network to display the environmental management information of the system from various views.They have great potential in studying the structure,function and environmental performace and system response of symbiotic networks to symbiotic measures.The results can be used to evaluate,optimize,regulate and manage the iron and steel industrial symbiosis network and can be further extended to other industrial systems.