The Optimization Of Hydrogen Production And Heat Exchanger Networks In Biomass Fast Pyrolysis And Hydroupgrading System Based On Exergetic Analysis

Biomass is the only renewable carbon resources for liquid fuel production.Producing high quality liquid fuels from biomass and achieving the replacement of fossil fuel partly will help to solve energy and environment problems.Some techno-economic analyses have indicated that the production of liquid fuels via biomass fast pyrolysis and upgrading is promising and economically feasible.The optimization of hydrogen production process and heat exchanger networks in the system is conducted in this paper.At the same time,the exergetic analysis is carried out to realize further improvement of the system.The comparison between steam reforming(SR)and sorption enhanced steam reforming(SESR)system indicated that higher purity and yield of hydrogen was obtained via SESR reactor than SR reactor.As for SESR reactor,when S/C is equal to or greater than 3,the mole fraction of hydrogen in the equilibrium mixture on dry basis exceeds 98.67%and the hydrogen yield is more than 98.54%at 450-600?.Furthermore,coke formation is relieved in the SESR reactor.The exergy efficiency of acetic acid SR and SESR systems are 61.80%and 66.80%,respectively.The main exergy loss is caused by irreversibility in the system.The influence of the heat capacity flow rate variation causing by temperature on the results of pinch analysis was investigated.Then the heat exchanger network for maximum energy recovery was obtained based on the pinch analysis principles and the adjustment was made to reduce heat exchanger number.The results showed that the position of pinch point and the utility targets were changed when heat capacity flow rate variation was considered.The heating and cooling utility is reduced by 58.72%and 33.08%respectively compared with the non-integrated system.Finally,the exergetic analysis on the system of biomass fast pyrolysis and hydroupgrading was conducted and the comparison between the system with and without heat integration was made.The exergy efficiency of the system with and without heat integration were 69.61%and 63.04%revealing big benefits of heat integration.The main exergy loss was caused by irreversibility in the system.