(219h) Capture CO2 Using Diluted Aqueous Ammonia From Coal Chemicals Plant | AIChE

(219h) Capture CO2 Using Diluted Aqueous Ammonia From Coal Chemicals Plant

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After coal carbonization, a large volume of coke oven gas (COG) is produced. The COG is treated by removing corrosive and valuable components in a coal chemicals plant to provide clean flue for the iron and steel production plant. In the coal chemicals plant, diluted ammonia solutions have been used to scrub H2S and NH3 from COG. Therefore, in the sustainable perspective, it is more reasonable to use the existent solutions to capture the greenhouse gas, rather than using the ammine-based solutions, which need to be imported from the outside of the steel-making plant. In addition, there exist considerable low and medium pressure steams that are not reused due to the economic consideration in the steel-making plant. The temperature of regenerating the diluted ammonia absorbent is much lower than the ammine counterparts, which means that the unrecovered waste heats can be used as the regeneration energy for the CO2 absorption process. However, the drawback of using the diluted ammonia absorbent is that the ammonia slips from the tops of the absorber and the stripper should be concerned. Additional ammonia scrubbers and an ammonia concentrator, which is used to regenerate the recycling water for the scrubbers, may be needed. The extra water and energy usages are the burden for developing the diluted ammonia process to capture CO2. In the coal chemicals plant, there exist ammonia scrubbers removing ammonia from COG and an ammonia still process regenerating the recycling water. Therefore, if the existent processes are capable of dealing with the ammonia leakages of the CO2 removal process, the burden of using the diluted ammonia solution can be effectively relieved.

The presented work evaluates the feasibility of integrating the CO2 removal process with the existent processes in the coal chemicals plant. The CO2 absorption experiment is conducted using the diluted ammonia solution from the coal chemicals plant in a laboratory pilot plant. The CO2 removal efficiency affected by the impurities in the ammonia solution, such as: H2S and HCN, is investigated. In addition, the absorption model is developed using the rate-based distillation module of Aspen Plus and validated by the experimental data. After that, the model is scaled up to the capacity for capturing CO2 from blast furnace gas (BFG) in the steel-making plant. The models of the ammonia still and the ammonia scrubbers in the coal chemicals plant are also built using Aspen Plus. The feasible designs for integrating the existent processes with the CO2 capture process are investigated.

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