Abstract:

Efficient and deep utilization of low-grade waste heat is one of the key measures to promote further energy saving and emission reduction in coal-fired power stations. The low temperature saturated wet flue gas after wet desulphurization contains a large amount of latent heat and water resources, and the temperature of a large amount of desulphurization slurry rises after absorbing the flue gas heat. The flue gas and slurry have huge potential for waste heat utilization and water recovery, but discharging the flue gas and the slurry directly, will cause waste of resources and easily lead to "white plume" pollution. This paper takes the saturated wet flue gas and desulphurization slurry after wet desulphurization as the research object, and summarizes the domestic and foreign technologies and development directions for flue gas water heat recovery and slurry waste heat recovery after desulphurization, in response to the problems of low waste heat recovery efficiency and difficulty in matching cold sources in current wet desulfurization technology. Among them, direct condensing of flue gas and slurry, and heat pump technology are mature and widely used; solution absorption technology has high energy utilization rate and low corrosiveness of flue gas; flue gas membrane separation technology, slurry flash, heat pump technology are clean and environmentally friendly with high recovery quality. Direct condensing of flue gas and slurry, and membrane separation technology need to further improve corrosion resistance and exchange efficiency; slurry flash and heat pump technologies have high energy consumption; and membrane separation technology still needs to find efficient, safe and environmentally friendly non-toxic refrigerant. Finally, the main ways and problems of the current flue gas desulphurization (FGD) slurry waste heat utilization are discussed, and the recovered waste heat is mainly used for heating and internal heat utilization in power plants, with a view to further promoting the recovery and utilization of flue gas and slurry waste heat after wet FGD and realizing the deep energy saving and emission reduction in coal-fired power plants.

Key words: desulphurization slurry, saturated wet flue gas, waste heat recovery, low temperature waste heat, water and electricity saving

摘要：

低品位余热高效深度利用是促进燃煤电站进一步节能减排的关键之一，湿法脱硫后的低温饱和湿烟气蕴含大量潜热和水资源，大量脱硫浆液吸收烟气热量后温度升高。烟气与浆液具有巨大的余热利用和水资源回收的潜力，若直接排放烟气，直接排出浆液，不但造成资源浪费，还容易引发“白色烟羽”污染环境。本文以湿法脱硫后饱和湿烟气和脱硫浆液为研究对象，针对目前湿法脱硫技术余热回收效率低、利用难以匹配冷源等困境，总结了国内外针对脱硫后烟气水热回收和浆液余热回收技术及发展方向，研究中针对浆液余热利用仍待发展。其中，直接冷凝烟气和浆液技术和热泵技术成熟，应用广泛；溶液吸收技术能源利用率高，烟气腐蚀性低；烟气膜分离技术、浆液闪蒸、热泵技术清洁环保，回收质量高。直接冷凝烟气、浆液技术和膜分离技术需要进一步提高抗腐蚀性和转换效率；浆液闪蒸、热泵技术能耗较高，吸收式热泵技术仍需寻找高效安全环保无毒的吸收溶液。最后，探讨了目前脱硫浆液余热利用的主要方式及存在问题，回收余热主要用于供暖和电厂内部热利用，以期进一步推动湿法脱硫后烟气与浆液余热回收利用，实现燃煤电站的深度节能减排。

关键词: 脱硫浆液, 饱和湿烟气, 余热回收, 低温余热, 节水节电