Validation of CO2 Capture

In absorbers for removal of CO2 from exhaust from natural gas fired power stations the liquid/gas flow ratio is very low. Problems may easily arise with wetting of the packing material. This reduces mass transfer. In order to counteract this effect good i nitial distribution of liquid is essential. Likewise a packing that distributes the liquid well, and which is equipped with a material with surface properties that enhances wetting of the surfaces. With the development of new and energetically less demand ing absorbent, it is very important to know how the packing material and the solvent interact. The various solvent have quite different properties as to interfacial tension, viscosity and wetting, and one cannot assume that one specific packing will be th e best one to use regardless of solvent choice. By recycle of exhaust gas the content of CO2 can be substantially increased, from about 3.5 vol% to maybe 7-9 vol%. This has many positive effects. It reduces directly the volumetric flow of gas, thus reduc ing the absorber cross sectional area proportionally to the increase in CO2 concentration. As the absorber is the element with highest cost this is important. Additionally the driving forces in the column are increased, making a shorter column possible, o r if desired, a higher rich loading. A third effect that might be very important is the increase in the liquid/gas ratio leading to improved mass transfer performance of the packing. To study these effects in a column of sufficient size that wall effects would be considered small. To check this, a larger column section is also included. The column will be in an infrastructure where surface area and packing efficiency can be measured directly in a chemically active system. Most correlations for effective surface area are obtained for distillation columns, without reactions, and these may not be well suited for absorption conditions. Typically distillation columns have much faster mass transfer than absorbers.