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

摘要：

以氨水为吸收剂进行CO₂化学吸收时，为抑制氨挥发，一般需要在高温高压条件下对富CO₂氨水进行热解吸，能耗较高。基于此，本文提出在氨水富液中添加生物质灰，通过生物质灰的CO₂矿化特性来实现氨水富液解吸与CO₂固定，并探究了生物质灰矿化解吸氨水富液的可行性、氨水贫液的沼气CO₂再吸收特性以及氨水在“CO₂吸收-生物灰矿化解吸”中的循环稳定性。结果表明，在氨水富液中添加生物质灰，能有效解吸氨水富液，且解吸后获得的氨水贫液具备良好的CO₂再吸收性能，净CO₂吸收能力最高可达0.32mol/mol。在常压条件下，氨水富液的CO₂负荷降幅随生物质灰添加量及反应温度的增加而增大。在初始CO₂负荷为0.6mol/mol的氨水富液中添加生物质灰进行解吸时，当添加量从50g/L提升至250g/L时，富液CO₂负荷降幅从18.83%急剧上升至94.17%。与直接添加CaO解吸相比，生物质飞灰矿化解吸氨水富液时，氨水的CO₂循环吸收能力略低，但在5个“吸收-解吸”循环周期里，氨水的平均净CO₂吸收能力仍能达到0.24mol/mol。

关键词: 二氧化碳捕集, 吸收, 解吸, 生物质灰, 沼气提纯