Development Of Innovative Process Configurations And Solvents With Low Energy Consumption And Studies Of Amine Degradation Performance For Carbon Dioxide ?CO₂? Capture

The large amount anthropogenic emission of carbon dioxide?CO₂?created by fossil fuel?e.g.coal,oil,and natural gas?combustion has been blamed for the occurrence of a string of environmental problems such as global warming,which has been concerned by the whole world.Fossil fuel-fired power generation has been considered to be the largest contributor to anthropogenic CO₂ emission.Carbon capture and storage?CCS?is regarded as an effective method to remove large quantities of CO₂ and combat global mean temperature change.Post-combustion CO₂ capture by amine absorption,as a leading contender for application in CCS,has a big potential for large-scale implementation in the retrofitting existing power plants.However,amine-based CO₂ capture suffers from high regeneration energy consumption and other undesirable problems such as amine degradation and equipment corrosion.Therefore,how to develop effective process configurations solvents that can be applied in industry is one of research hotspots of CO₂ capture.The energy consumption for the amine-based CO₂ capture can be further reduced by utilizing heat from the overhead vapor,which accounts for approximately 60% of the total waste heat of the whole absorption-stripping process.Two innovative processes configurations were developed in the present work and five absorption-stripping process configurations associated with CO₂ intercooling compression system were simulated including two innovative configurations,which were designed to utilize energy of the overhead vapor at the stripper top.It is effective using packing column to evaluate the regeneration performance of amine solvents.N,N-Diethylethanolamine?DEEA?as a tertiary amine has relatively fast absorption rate,higher CO₂ capacity and lower absorption heat,and diethylenetriamine?DETA?has faster kinetics and a higher solubility capacity.In addition,it is important for the solvents with high thermal stability in the industrial application.Based on the research significance above,the study content and research results of this thesis are listed below:?1?An effective split flow with with vapor recompression process was developed and simulated by the simulation software ProMax3.2.The sensitivity analysis of the process with 90% CO₂ removal efficiency was performed in order to reduce the energy consumption.The influences of Rich2 feed fraction?6-30 mol%?,Rich2 feed location?6-12N?and outlet pressure of compressor?185-245 k Pa?on the reboiler heat duty and total equivalent work were investigated in this work.The simulation results for the split flow with with vapor recompression process showed that the lowest reboiler heat duty of 1.982 GJ/t CO₂ and total equivalent work of 0.392 GJ/t CO₂ were obtained while the Rich2 feed fraction was 18 mol%,Rich2 feed location was 11 and outlet pressure of compressor was 195 k Pa.It leads to a very significant reduction of total equivalent work by 29.24%.However,this process is limited in the industrial application by the complex configuration.?2?An innovative heat pump distillation with split flow process was also developed and simulated by the simulation software ProMax3.2.Under 90% CO₂ removal efficiency,the sensitivity analysis for various operation conditions were studied on the the reboiler heat duty and total equivalent work of this innovative process.The simulation results showed that the total equivalent work firstly decreased and then increased with the increase of Rich2 feed fraction and outlet pressure of compressor was 195 k Pa.When the Rich2 feed fraction was 10 mol%,Rich2 feed location was 12 and outlet pressure of compressor was 205 k Pa,the lowest reboiler heat duty were obtaioned with the values of 1.841 GJ/t CO₂ and 0.365 GJ/t CO₂,respectively.It leads to a very significant reduction of total equivalentwork by 34.12%.The energy consumption was reduced by effective utilization of the heat of over-head vapor at the stripper.?3?Five process configurations associated with CO₂ intercooling compression system including traditional MEA-based process were simulated and optimized by the simulation software ProMax3.2.The sensitivity analysis for four improved process configurations has been conducted in order to effectively utilize the heat of over-head vapor at the stripper.The simulation results showed that the total equivalent works of these configurations were in the following order: Improved split flow with vapor recompression < Split flow with vapor recompression < Split flow with over-head exchanger < Conventional process < Simple vapor recompression process.The split flow with vapor recompression and the improved split flow with vapor recompression were both the best configurations,and the total equivalent work was significantly reduced by 17.21% and 17.52%,respectively,compared to the baseline configuration.?4?Carbon dioxide?CO₂?stripping from CO₂-loaded aqueous solution of DEEA was comprehensively investigated in a laboratory scale regeneration column packed with 316 L Dixon ring random packing.The experimental results from this study showed that Qreb decreased as the lean CO₂ loading,rich CO₂ loading,rich amine stripper feed temperature,and DEEA concentration;Qreb first decreases and then begins to increase as the increase of solvent flow rate;additionally,the synergistic effects of ??×L and C×L on Qreb were also investigated.Compared to the Qreb of MEA?4.201 GJ/t CO₂?and DETA?3.439 GJ/t CO₂?,the lowest Qreb for aqueous DEEA solution was obtained approximately 2.171 GJ/t CO₂.?5?The thermal degradation of aqueous DEEA and DETA solutions were investigated in a stainless steel autoclave.The experimental results showed that an increase in CO₂ loading,temperature and DEEA concentration all resulted in a reduction in the fraction of DEEA and DETA remaining.Although the fraction of DEEA remaining decreased due to thermal degradation experiments,the degraded solution still has a relatively high CO₂ absorptive capacity,indicating that some of the by-products have the ability to absorb the CO₂.A DEEA thermal degradation rate/kinetics model based on Power Law and RBFNN model were successfully formulated.A possible general pathway for the thermal degradation of DEEA has been proposed based on the experimental observed degradation products.