Mechanism And Integration Of Polygeneration Systems Based On Natural And Biomass Individually And As Co-feed

Synthetically combining the power generation,the chemical production andenvironment protection is the trend and character of the development of energy science.Searching the effective methods to make good use of resources and energy has becomevery important for continuous development.Focusing on this objective,the main study ofthis dissertation proposes the novel polygeneration systems based on natural gas andbiomass individually and on both of them as co-feed.The work was supported by theNational Natural Science Foundation of China and the Hi-tech Research and DevelopmentProgram of China,the researches include the mechanism of natural reforming,which willreveal the cascaded utilization of chemical energy during the chemical reaction,and theproposal of the novel polygeneration systems based on that principle.From the viewpoint of chemical kinetics and thermodynamics,the relation formula ofthe energy and time consumption supplied by outside with the extend of reaction was setup;moreover,from the viewpoint of Gibbs free energy,the relation of the change of Gibbsfree energy and the extend of reaction was also analysied.The results of calculation andanalysis shown that,when the extend of reaction over 0.6,the energy and timeconsumption will grow rapidly,and at the same time,the Gibbs free energy will decreasevery quickly.That is to say,the costs for per mole methane reforming will grow very highwith a higher extend of reaction.The phenomenon is very common in many reactionswhose elementary reaction with nonzero capital,thus the mechanisms can be extended itsrange of application,such as the chemical industry and power field.Coupling the chemicalprocess and power generation,can reduce the high energy and time consumption of perproduct in traditional chemical process for purchasing very high conversion ratio of rawmaterials,and realize the cascaded utilization of fuel.A new polygeneration system based on natural gas partial reforming is proposed, which produces methanol and power with tandem type.The characters of this systemincludes:Based the principle of cascaded utilization of chemical energy,this systemadopts partial reforming of natural gas,which aims to reduce the energy consumption forper mole syngas production;Based on the principle of cascade conversion of materialaccording to the compositions,a part of syngas that suites for chemical production is usedin the chemical process and the left is sent to gas turbine as fuel.By the analysis of systemexergy balance,found out that,the key processes are reforming process and methanolsynthesis process,more over,the EUD methodology is selected in order to reveal the innerenergy release,exchange and energy saving potential.Comparing with individual systems,this polygeneration system can realize 5-10% energy saving potential.According to thecomposition characters of biomass,a new polygeneration system based on biomassgasification is proposed,which produces methanol and power.This system coupled themethanol syntheis subsystem and power generation subsystem,so as to realize the cascadeutilization of the chemical energy in gasification gas.Comparing with the individualsystems,this polygeneration system can realize 7%-10% energy saving potential andobtain exergy efficiency between 44%-49%.The energy in biomass can be released stepby step in this system,which will bring the high effective utilization of bio energy.Taking into account of the different carbon and hydrogen ratio in natural gas andbiomass,a new polygeneration system with two schemes based on biomass and naturalgas as co-feed is presented here.By coupling the partial reforming of natural gas andgasification of biomass to produce syngas,the best ratio of carbon to hydrogen formethanol production can be obtained easily without any energy penalty.More over,thissystem can realize not only the complementation of natural gas and biomass but also thecascaded utilization of syngas by coupling chemical process and power generation.Thesystem performance shown that,the system with the syngas once through scheme,cansave 8%-10% energy when the input ratio of natural gas to biomass range from 0.5 to 8;with the partial recycling of unreacted syngas scheme,the system can realize energysaving ratio at least 9.5%.