关键词: 二氧化碳捕集, 吸收, 解吸, 生物质灰, 沼气提纯

Abstract:

In the ammonia-based CO₂ chemical absorption process, CO₂-rich ammonia aqueous solution is generally regenerated at the high temperature and pressure conditions for inhibiting the ammonia volatilization, in which a high energy input is necessary. To minimize the energy inputs, biomass ash was adopted into the CO₂-rich ammonia aqueous solution (i.e., rich ammonia solution) in this study for CO₂ desorption and CO₂ fixation through CO₂ mineralization. The feasibility of CO₂ desorption by adding biomass ash, CO₂ reabsorption performance of CO₂-lean ammonia aqueous solution and cyclic stability of ammonia during CO₂ absorption-CO₂ desorption induced by biomass ash addition were experimented. The results showed that the rich ammonia solution can be desorbed effectively through adding biomass ash to form the CO₂-lean ammonia aqueous solution with a maximum net CO₂ absorption capacity of 0.32mol/mol. Under the ambient pressure, the decrement of CO₂ loading of rich ammonia solution increased with the biomass ash dosage and reaction temperature. When the dosage of biomass ash added into the rich ammonia solution with an initial CO₂ loading of 0.6mol/mol varied from 50g/L to 250g/L, the decrement of CO₂ loading of rich ammonia solution increased gigantically from 18.83% to 94.17%. Compared to the case adopting CaO, adopting biomass ash to desorb rich ammonia solution could achieve a relatively lower cyclic CO₂ absorption performance. However, an averaged net CO₂ absorption capacity of ammonia with 0.24mol/mol could still be achieved in five "absorption-desorption" cycles.

Key words: CO₂ capture, absorption, desorption, biomass ash, biogas upgrading