碳捕集与封存Carbon capture and storage

燃烧后捕集最成熟，常用 30% 单乙醇胺（MEA）水溶液在约 40 °C 吸收烟气中的 CO₂，生成氨基甲酸盐和碳酸氢盐，再在 110–120 °C 加热解吸，吸收剂循环使用。燃烧前捕集先把燃料气化变换为 H₂ 和 CO₂，在高压下物理吸收 CO₂；富氧燃烧用纯氧燃烧得到高浓度 CO₂。新型吸附材料包括金属有机框架、胺功能化多孔材料等。

Post-combustion capture is the most mature: 30% aqueous monoethanolamine (MEA) absorbs CO₂ from flue gas at about 40 °C, forming carbamate and bicarbonate, and releases it on heating to 110–120 °C so the solvent can be reused. Pre-combustion capture gasifies and shifts fuel to H₂ and CO₂, then absorbs the CO₂ physically under pressure; oxy-fuel combustion burns fuel in pure oxygen to give concentrated CO₂. Newer sorbents include metal–organic frameworks and amine-functionalised porous solids.

CO₂ 被压缩为超临界流体，注入 800 m 以下的咸水层、枯竭油气藏或不可开采煤层，靠盖层构造封闭、溶解、残余捕获和矿化逐步固定。1972 年美国得克萨斯开始用 CO₂ 驱油；1996 年挪威斯莱普纳项目首次以减排为目的把 CO₂ 注入海底咸水层，至今已封存超过 2000 万吨。

CO₂ is compressed to a supercritical fluid and injected below about 800 m into saline aquifers, depleted oil and gas fields or unmineable coal seams, where structural trapping under caprock, dissolution, residual trapping and mineralisation gradually fix it. CO₂ enhanced oil recovery began in Texas in 1972, and in 1996 Norway's Sleipner project became the first to inject CO₂ into a sub-seabed aquifer for climate reasons; it has stored more than 20 million tonnes.

主要挑战是能耗和成本高（胺法解吸约占电厂出力的 20–30%）、长期泄漏风险监测和公众接受度。直接空气捕集（DAC）和生物质能结合碳捕集（BECCS）可以实现负排放。CO₂ 转化利用研究包括合成甲醇、碳酸酯、聚碳酸酯和矿化建材。

The main challenges are energy use and cost (amine regeneration takes about 20–30% of a power plant's output), long-term leak monitoring and public acceptance. Direct air capture (DAC) and bioenergy with carbon capture (BECCS) can deliver negative emissions. Research on CO₂ utilisation covers methanol, carbonates, polycarbonates and mineralised building materials.