以负碳排放为目标的生物质灰矿化CO_(2)路径研究

CO_(2)Mineralization Pathway Investigation Using Biomass Ash for Achieving Negative Carbon Emissions

将生物质能源开发利用与碳捕获、利用与封存结合,可实现CO_(2)负排放,是能源领域降低CO_(2)排放的重要技术之一。生物质直接燃烧后产生的生物质灰理论上可吸收并永久封存CO_(2),但其能否实现负碳排放还需进行深入研究。基于此,分别在自然状态(空气氛围)、中等CO_(2)初始分压(101.3 kPa)和高CO_(2)初始分压(300~1400 kPa)条件下开展了生物质灰矿化CO_(2)试验,测试了生物质灰的CO_(2)矿化量,并评估了3种矿化路径的负碳排放量。结果表明,从空气中吸收CO_(2)时,生物质灰的CO_(2)矿化性能最差,40 d内的最高CO_(2)矿化量仅为60.66 g/kg。在中等CO_(2)分压101.3 kPa条件下,可最高实现121.68 g/kg的矿化量,而初始分压1400 kPa下的CO_(2)矿化量可达216.85 g/kg。综合考虑矿化过程的能源消耗和生物质灰运输产生的碳排放及灰的固碳量等因素,评估了3种生物质灰矿化路径的实际负碳排放量。当生物质灰运输距离小于207 km时,适合选择中等CO_(2)分压矿化路径以获得最大的负碳排放效益;当运输距离大于207 km时,建议选择高CO_(2)分压矿化路径。

Combining the development and utilization of bioenergy with carbon capture,utilization and storage(BECCUS)is one of the important methods to reduce CO_(2)emissions in the energy field as it can achieve the negative carbon emissions.Biomass ash(BA)generated from the direct combustion of biomass,can be used to absorb and sequestrate CO_(2)permanently.However,the issue adopting biomass ash to achieve the negative carbon emissions should be investigated carefully.CO_(2)mineralization performance of biomass ash from atmospheric CO_(2)and CO_(2)-rich gas streams with a moderate(101.3 kPa)and high CO_(2)partial pressure(300~1400 kPa)was experimented in terms of CO_(2)sequestration capacity.Moreover,negative carbon emissions of these three mineralization pathways were evaluated as well.Results showed that among all the three pathways,the lowest CO_(2)sequestration capacity with 60.66 g/kg after 40 days was acquired when CO_(2)came from atmosphere.Comparatively,when the initial CO_(2)partial pressure was elevated to about 101.3 kPa(i.e.,the moderate CO_(2)partial pressure case),the maximum CO_(2)sequestration capacity of 121.68 g/kg can be achieved.When CO_(2)partial pressure was increased to about 1400 kPa(i.e.,the high CO_(2)partial pressure case),a CO_(2)sequestration capacity of 216.85 g/kg was obtained.The actual negative carbon emissions of three mineralization pathways of biomass ash were assessed by comparing CO_(2)emissions reduction ascribed to CO_(2)sequestration of biomass ash and CO_(2)emissions related to energy consumption in the mineralization process and biomass ash transportation.When the transportation distance of biomass ash was less than 207 km,adopting this mineralization pathway in which CO_(2)came from the CO_(2)-rich gas streams with a moderate CO_(2)partial pressure(101.3 kPa)might be reasonable for achieving a highest negative carbon emission.When the transportation distance was above 207 km,the pathway in which CO_(2)came from the gases with a high CO_(2)partial pressure should be sensible.