基于生物质灰和沼液可再生吸收剂体系的沼气-CCS新机制

实施沼气CO2捕集与储存（沼气-CCS）不仅可生产生物天然气，还能实现CO2净负排放。基于化学吸收法的沼气-CCS关键在于降低CO2分离成本，重点是降低富CO2吸收液的热解吸能耗。基于此，本项目提出了应用生物质灰和沼液可再生吸收剂体系的沼气-CCS新机制，即在舍弃CO2解吸过程的一次吸收工艺中，从生物质灰强化沼液中分离回收可再生氨水，作为沼气CO2吸收主体，保证CO2吸收性能，并以富CO2生物质灰和沼液为载体，将部分CO2转移到植物和土壤中，实现低成本CO2农业封存。通过解析生物质灰中有效组分在沼液中的定向浸出机制，构建生物质灰减量添加策略；探索氨水回收中水蒸气传质的参数耦合调控机制，厘清可挥发性杂质对氨水CO2化学反应的影响途径，强化CO2吸收性能；掌握CO2以生物质灰和沼液载体时在植物和土壤中的迁移转化机制，揭示CO2农业封存潜力，期望为低成本沼气-CCS提供一种新思路和新方法。

Implementing the biogas-based CO2 capture and storage (biogas-CCS) can not only obtain the bio-natural gas, but also achieve negative CO2 emission. When the typical CO2 chemical absorption method is adopted in the biogas-CCS, the key issue is determining how to reduce the cost of CO2 separation, especially reduce the CO2 regeneration heat consumption of CO2-rich solvent greatly. So a new biogas-CCS mechanism is put forward in this proposal in which a renewable CO2 solvent derived from biogas slurry and biomass ash is adopted. In this mechanism, the so-called once-through CO2 absorption process is adopted to capture CO2 from biogas where CO2 regeneration stage is rejected. In this process, the biomass ash is firstly added into biogas slurry to increase its initial pH value. Then the renewable ammonia aqueous solution is recovered and enriched from biogas slurry to act as the main solvent to capture CO2 from biogas slurry. Due to the high CO2 absorption rate and high CO2 absorption capacity of ammonia, high CO2 capture performance can be achieved. Additionally, the biomass ash and biomass slurry are also CO2-saturated to adjust their pH values to about 7 for meeting the requirements of agricultural applications. A cost-effective CO2 sequestration can be obtained because CO2 is easily fixed into the plants and soil when using the CO2-rich biomass ash and CO2-biogas slurry as CO2 carriers. After analyzing the directional leaching mechanism of effective components contained in the biomass ash into the biogas slurry, the tactics in decreasing the dosage of biomass ash into biogas slurry can be erected. Through exploring the adjustment mechanism of operation conditions to control water vapor transfer, the renewable ammonia aqueous solution with high concentration can be obtained. And the negative effects of volatile impurities in the renewable ammonia aqueous solution on CO2 absorption performance are clarified as well for enhancing the CO2 absorption performance. Moreover, the migration and transformation mechanism of CO2 contained in the CO2-rich biogas slurry and biomass ash into the plants and soil can also be analyzed. When these mechanisms are determined, the energy saving and emission reduction potentials of this new biogas-CCS can be explored. On the basis of these constructive results, a novel and positive concept might be developed for reducing the cost of biogas-CCS greatly in the future.