Thermo-Physical Properties Of CO₂ Mixture And Analysis Of Techno-Economic Performance Of Capturing CO₂ From Bioenergy By Chemical Absorption

As the 14th Five-Year Plan begins,Carbon capture,transport and storage technology（CCS）will usher in greater development under the national policy support,and"carbon peak"and"carbon neutral"goals.However,there are some knowledge gaps in the thermo-physical properties of CO₂ mixtures,which hinder the design,operation and optimization of the process of CCS.This thesis aims to identify these gaps and then some contributions are expected to be made in the development of modelling,which is significant for the safe,efficient and economic operation of CCS.In order to achieve the peak of carbon dioxide emissions by 2030 and carbon neutrality by 2060,China needs to reduce the carbon emission intensity significantly.It is necessary to develop carbon negative emission technologies on a large scale,especially Bioenergy and Carbon Capture and Storage（BECCS）,to remove CO₂from the atmosphere.However,it will bring some opportunities and challenges to apply the carbon capture technology to the process of bioenergy conversion.This thesis aims to explore the techno-economic performance of capturing CO₂ from bioenergy by chemical absorption,which is the most mature technology.The results will provide guidelines for the application of carbon capture technology to bioenergy conversion and promote the development and deployment of BECCS.Therefore,this thesis covers two parts,including modelling of thermo-physical properties of CO₂ mixtures and analysis of techno-economic performance of capturing CO₂ from bioenergy by chemical absorption.The main research conclusions are as follows:（1）For the thermal conductivity of CO₂/Ar and CO₂/N₂.Compared with the theoretical white box models,it was found that the accuracy of black box models is higher,and the accuracy of gray box models is lower.When the thermal conductivity is less than0.015W/（m·K）,almost all models have poor performance due to the lack of the experimental data at low temperature.It is essential to obtain more data by experiment measuring to improve the accuracy and applicability of the model.The black SVR model should be prioritized to develop due to its good performance.（2）For the process of the combustion,torrefaction and pyrolysis of biomass,CO₂ is usually captured from the flue gas after the combustion of biomass or syngas.For the process of the gasification,anaerobic digestion of biomass,CO₂ can be captured from the flue gas after the combustion of biogas and syngas;or from the biogas and syngas directly.The scale of biomass combustion is the largest,but the concentration of CO₂ in flue gas is low;while the scale of biomass anaerobic digestion is the smallest,but the concentration of CO₂ in biogas is the highest.In addition,the scale of biomass gasification and CO₂ concentration in syngas are both high;the scale of biomass torrefaction and pyrolysis and CO₂ concentration in flue gas are both low.（3）It was found that the energy consumption of carbon capture from different bioenergy conversion processes by both MEA and aqueous ammonia ranked as,carbon capture from the flue gas of pyrolysis>carbon capture from the flue gas of gasification combined cycle combustion>carbon capture from the flue gas of combustion>carbon capture from the syngas of gasification>carbon capture from the biogas of anaerobic digestion.It is also same with carbon capture cost.（4）Considering both energy consumption and capture cost,it will bring great opportunity to carbon capture for the both solvents if CO₂is captured from syngas of gasification and biogas of anaerobic digestion.The energy consumption and capture cost are3.77-4 MJ/kg CO₂ and 53-63 USD/t CO₂ for MEA system;3.17-3.78 MJ/kg CO₂ and 53-62USD/t CO₂ for aqueous ammonia system.（5）When the concentration of CO₂ is lower,the energy consumption and capture cost of aqueous ammonia system are higher than those of MEA system.Under 90%of capture rate,the energy consumption and capture cost of capturing CO₂ from pyrolysis process are4.58 MJ/kg CO₂ and 224 USD/t CO₂for MEA system;7.08 MJ/kg CO₂ and 337 USD/t CO₂ for aqueous ammonia system.When the concentration of CO2 is higher,the energy consumption of aqueous ammonia system is lower than that of MEA system;and there is no big difference in the capture cost.Under 90%of capture rate,the energy consumption and capture cost of capturing CO2 from biogas are 3.77 MJ/kg CO₂ and 53 USD/t CO₂for MEA system;3.17MJ/kg CO₂ and 53 USD/t CO₂ for aqueous ammonia system.（6）Consideration both energy consumption and capture cost,aqueous ammonia is recommended to capture CO₂ from syngas of gasification and biogas of anaerobic digestion due to its lower energy consumption.MEA is recommended to capture CO₂ from the flue gas generated by the combustion of pyrolysis gas,biogas or gasified syngas by gas turbine,due to its lower energy consumption and capture cost.