Simulation Study On Carbon Capture Process Of Natural Gas Oxy-fuel Combustion Furnace

Natural gas is a kind of clean energy,whose share in China's energy consumption structure is gradually increasing.As a gas combustion equipment,natural gas furnace plays an irreplaceable role in industrial production.Although the carbon emission per unit energy consumption of natural gas is low,natural gas furnaces will be a source of carbon emissions with the widespread use of natural gas.Therefore,it is necessary to study the carbon reduction technology of natural gas furnace.CO₂ capture process in a natural gas oxy-fuel combustion furnace is studied and simulated based on Aspen Plus software.In order to improve the simulation accuracy,the equation of state(EOS)required for simulation is verified.Single flash separation system,Double flash separation system and Distillation separation system for CO₂ capture and recovery from flue gas are designed using EOS method.The effects of CO₂ purity,separation efficiency and oxygen concentration in oxidant on the specific comprehensive power of the three carbon capture process systems are simulated and analyzed by using Aspen Plus.Combined with the analysis results,a series of evaluation indexes are set up such as specific comprehensive energy cost.The entropy weight method and distance evaluation method are used to evaluate the three systems and to determine the reasonable carbon capture scheme.The results show that the PENG-ROB EOS with HYSYS binary parameters is more suitable for the simulation of CO₂ capture system using low temperature separation method because its accuracy is higher than that with the default EOS-LIT binary parameters.When the molar fraction of oxygen in oxidizer is 95%,separation efficiency is95.4%,CO₂ purity is 96.3%,specific comprehensive power of single flash separation system reaches the minimum of 776.9 k Wh/t CO_2.When the mole fraction of oxygen in the oxidant is 95%,the separation efficiency is 94.6%and the purity of CO₂ is 99.99%,the specific comprehensive power of the distillation separation system is 853.0 k Wh/t CO₂and reaches minimum.When the mole fraction of oxygen in the oxidant is 95%,the separation efficiency is 94.7%,and the purity of product CO₂ is 98.0%,the specific comprehensive power of double flash separation system is the lowest which is 776.2 k Wh/t CO₂.It is known that distillation separation system is a reasonable scheme for the CO₂ capture from flue gas from natural gas oxy-fuel combustion furnace due to the results of comprehensive evaluation under the current CO₂ market and policy.