Assessment And Scenario Analysis Of Exergy,carbon Emissions,and Water Footprint For Coking Network Evolution

As a key upstream supplier for the most energy-intensive industries,the coking industry is a typical high energy-consumption and high emission industry.Limited by the non-renewable resource,coking industry is facing serious challenges in improvement of energy efficiency and carbon reduction.Based on the evolution of coking industrial network,this study introduced the quantitative indicators of exergy,life cycle carbon emissions,and water footprint to evaluate the benefits of industrial symbiosis measures,moreover analyze the availability of different scenarios achieving carbon reduction target.In the case study,which is composed of real production for the coking plant coupled with iron and steel industry in Gansu Province,the exergy and emissions evolution were analyzed at temporal scale.While the location of reduction potential for exergy loss and emissions were identified.Furthermore,the embodied water in the coking industry was analyzed,identifying the adjustment processes of water use and preliminarily explored the nexus between exergy losses and water footprint for the coking industry.Thus,the effect of water utilization way on exergy efficiency was analyzed.To provide a reasonable forecast of development patterns,four key scenarios were examined using scenario analysis,including industrial symbiosis,bio-production,carbon capture and storage and energy recovery.The results were illustrated as follows:（1）The exergy efficiency was enhanced from 26.08%of the initial stage to 77.53%of the last stage.When the coking plant was coupled with the iron and steel industry,the ammonium sulfate work zone had the maximum value of specific exergy losses in2012,followed by the desulfurization work zone,coke oven battery,crude benzene work zone,and cold work zone.（2）For life cycle greenhouse gases emissions,in the case carbon emissions was decreased from 25.36 t CO₂eq/t coke to 0.91 t CO₂eq/t coke.Moreover,coking has the highest emissions in the coking plant.It contributes to 76.7%of the total emissions from the network in 2012.（3）In case study of typical coking enterprise,the results showed the linear relationship between blue water footprint and exergy efficiency of coking sub-processes.Water use for ammonia distillation is 6.4 times greater than the rest water use in the cold work zone,thus there is great potential for blue water savings for ammonia distillation.At coking industry level,the results showed a significant positive correlation between the total water footprint and the exergy loss of the coking industry.It is verified that indirect water footprint contributing most of the total water footprint and the water footprint of the coking industry shows a net input trend.（4）The scenario analysis showed independent coking enterprises has the lowest exergy efficiency and the highest emissions.The best practice scenario indicated the improvement potentials of sustainable development in the coking industry,which shows 81.39%of the exergy efficiency and 0.58 t CO₂eq/t coke.To further decrease the emissions,electricity decarbonization displays a great potential for cleaner industrial production.Furthermore,expanding scenario analysis to industry scale,the results showed structure adjustment of the coking industry alone could not achieve the 2030climate target.Combined bio-coke production,power equipped with carbon capture and storage（CCS）,and further energy recovery would benefit to achieve emissions reduction target.