Pilot-scale Experimental Study On Separation Of CO₂/N₂ By Absorption-Adsorption Slurry Method

At present,climate change is one of the most important environmental issues in the world,and the main content is to control greenhouse gas emissions.In recent years,with the rapid development of the world economy,people’s demand for fossil energy has been increasing.The burning of a large amount of fossil fuels has emitted a large amount of CO₂,which has aggravated the greenhouse effect.It is of great significance to effectively capture and separate CO₂.Although there are many methods for capturing and separating CO₂,each has its own drawbacks.Therefore,we still need to research and develop new capture and separation technologies.In this paper,we firstly made a slurry system by suspending ZIF-8 into 2-methylimidazole and water and compared the absorption and desorption characteristics of the slurry for separating CO₂ with 2-methylimidazole/water solution and ethanolamine/water solution.Then,a pilot-scale experimental unit was built and the absorption-adsorption slurry method was used to separate CO₂ from flue gas.In addition,the influences of different operating conditions on the CO₂ capture performance were investigated.The main contents are summarized as follows:（1）The absorption rate and capture capacity of ethanolamine/water solution,ZIF-8/2-methylimidazole-water slurry,and 2-methylimidazole/water solution for carbon dioxide were measured at 303.15 K.The results show that the CO₂ capture capacity and capture rate of ethanolamine/water solution,ZIF-8 slurry,and 2-methylimidazole/water solution decreased successively,and all these three systems had good capture ability for CO₂.（2）The desorption characteristics of CO₂ in ethanolamine/water solution,ZIF-8/2-methylimidazole-water slurry,and 2-methylimidazole/water solution were studied.The results show that ZIF-8 slurry and 2-methylimidazole/water solution have good regeneration performance and mild regeneration conditions at the same desorption temperature,while the ethanolamine/water solution has a very poor desorption effect,which is not conducive to continuous operation.The desorption heat of ZIF-8 slurry is significantly lower than that of 2-methylimidazole/water solution,so the regeneration energy of ZIF-8 slurry is small.In addition,the influence of desorption pressure was investigated.The results show that the lower desorption pressure,the better desorption effect,and the pressure has the most significant effect on ZIF-8 slurry.Finally,the re-use performance of ZIF-8 was tested.The results show that ZIF-8 has good stability and regeneration performance in 2-methylimidazole/water solution.（3）Through the analysis of the results of the small test,a pilot-scale continuous separation unit was built according to the experimental requirements.（4）The effects of different operating conditions including inlet flow,absorption pressure,absorption temperature,and inlet CO₂ concentration on the CO₂separation performance of ZIF-8 slurry were studied by pilot-scale experiments.The results show that increasing the absorption pressure,reducing the inlet flow,decreasing the absorption temperature,and decreasing the CO₂ concentration of the feed gas mixtures are beneficial for improving the separation of CO₂ from ZIF-8 slurry.