Mechanism And Integration Of Coke Oven Gas & Coal Gas Based Polygeneration Systems For Production Of Coke, Chemicals & Power

Polygeneration systems belong to cross subjects,which involve chemical field,power generation field,and even metallurgical field.They can achieve highefficiency,low investment and less environmental impact by integration chemicalproduction with power generation and innovation of key processes.They arebecoming the key sustainable development of energy technologies.Supported by theNational Key Project and the National Natural Science Foundation of China,themajor aim of this research is to investigate the principle of polygeneration systemicintegration,to reveal the integration mechanism of polygeneration systems forenergy saving,and to propose some new methods to produce or/and utilize coke ovengas(COG)more efficiently,based on the cascade utilization of physical andchemical energy.The internal mechanism of energy saving in polygeneration systems isrevealed.Firstly,this paper investigates the potentials and advantages for energysaving of the polygeneration systems,and illustrates the principle of systemintegration.Then,it studies on the mechanism of energy saving in polygenerationsystems,and finds that the exergy consumption increases nonlinearly,along with theincrease of percent conversion.A lowest exergy consumption for 1 kW of productexisted at a certain percent conversion.The moderate conversion of raw material isthe key factor for energy saving,which was disclosed by comparison method.Finally,it reveals the relationships between the energy earnings in the power side and energydestruction in the chemical side.A new kind of coke oven and a polygeneration system producing coke &power are proposed.In a conventional coke oven plant,about half of COG by-produced in the oven is burned to provide coking heat.The new kind of cokeoven burns coal rather than COG,so more COG is saved to supply the followingprocesses.The feature of flue gas and air resulted in high temperature of exhaust gasin the coke oven.And polygeneration system proposed here producing coke andpower resolves that problem,and uses COG more efficiently by combined cycle.COG and coal gas based polygeneration system was optimized by systemicintegration.This paper analysed a polygeneration system proposed by TaiyuanUniversity of Technology,and than integrated a polygeneration system based onCOG and coal gas without reforming.The results of thermal energy analyses andfeature analyses show that the new system has better performance.And the exergyanalysis is adopted to reveal reasons for energy saving in the new system,which arethe elimination of shift and reforming reactions.The new system not only simplifiesthe scheme and reduces the investment,but also gains higher energy saving ratio.Finally,based on this system,a polygeneration system with CO₂ recovery wasintegrated,which realizes CO₂ separation without energy consumption as comparedto conventional systems.Two multifunctionai systems,which produce coke,chemicals and power,areproposed.On the basis of COG rich in H₂,a multifunctional system is proposed.Inthe new system,COG produced by coal fired coke oven is fed to pressure swingadsorption(PSA)unit to separate H2 firstly,and then the PSA tail gas is fed tocombined cycle for power generation.With the same inputs and the same coking heatoutput,the new system can produce 65% more H₂ than the conventional systems.Itsoverall efficiency is about 70%,exergy efficiency is about 66%,and energy savingratio is about 12.5%.Then the reasons for the energy saving of the system are studiedby EUD method,which are coal-fired coke oven and efficient utilization of COG.The system also has good performance on economics analyses and CO₂ emissionreduction analyses.Moreover,another multifunctional system is integrated,whichcombines a coal fired coke oven and a polygeneration system based on COG andcoal gas as co-feed without reforming reaction,which is another way to use COGand coal efficiently.In short,this research provides a theoretical basis of systemic integration for the polygeneration system,and puts forward some valuable choices for the developmentof clean coal technologies.