Amines and rainfall. Impact of amines on rainfall from plume clouds (Task 5.3).
Abstract
Growth of droplets by water vapour condensation is a very effective mechanism for the initial growth of particles from sub micrometre sizes to cloud droplets of 10-20 μm size within a few minutes. The growth of water droplets in the atmosphere strongly depends on the surface tension. An important effect of amines is to lower the surface tension. Thus amines enhance the probability that very small water droplets can grow to cloud droplet size (10-20 μm) and cause cloud formation in the plume of the CO2 capture plant at a lower ambient humidity. Added amines promote the formation of supercritical droplets that can cause rainfall from the plume, thus amines act as a trigger of rain. Drops containing MEA will grow and become larger than the majority of cloud droplets. During growth, the curvature of the droplet decreases and thereby the surface tension also decreases. As the droplet reaches the critical size, the water vapour pressure becomes high enough to enable free growth. If sufficient humidity is available in the surrounding air, the droplet can continue to grow into a rain drop; this may be the case during cold spells with fog events. Rain drops falling from the plume cloud contain dissolved amines and might cause effects on buildings, materials and human health in the vicinity of the CO2 capture plant.