Technical paper
Decreasing Contactor Temperature Could Increase Performance
Gas treating process variables such as solvent type and concentration, pressure, and circulation can be manipulated to produce specification quality hydrocarbon products. Interest has increased recently in exploring the effects of inlet gas and solvent temperatures as an aid in meeting these specifications. In general, lower temperatures tend to promote absorption of lower molecular weight components based on vapor-liquid equilibrium. Physical solvents exploit this principle by absorbing acid gases and water at lower temperatures. If the absorption process is reactive and allowed to reach equilibrium, lower temperatures still favor the absorption of low molecular weight components. However, if the reactive absorption is kinetically limited as is the case with CO2 and certain amines, it is impossible to determine how temperature affects the absorption in the absence of additional information. This ambiguity results from the competing phenomena and opposite effect temperature has on reaction rates and solubility. For absorption of H2S and CO2 in alkanolamines or mixtures of amines with physical solvents, H2S absorption reaches equilibrium conditions while CO2 absorption is kinetically limited in some situations. The performance of various amines and physical solvents are compared based on solvent and feed gas temperatures. Understanding the competing phenomena of equilibrium and kinetics may yield situations where this effect can be exploited for more profitable operation.
Gas treating process variables such as solvent type and concentration, pressure, and circulation can be manipulated to produce specification quality hydrocarbon products. Interest has increased recently in exploring the effects of inlet gas and solvent temperatures as an aid in meeting these specifications. In general, lower temperatures tend to promote absorption of lower molecular weight components based on vapor-liquid equilibrium. Physical solvents exploit this principle by absorbing acid gases and water at lower temperatures. If the absorption process is reactive and allowed to reach equilibrium, lower temperatures still favor the absorption of low molecular weight components. However, if the reactive absorption is kinetically limited as is the case with CO2 and certain amines, it is impossible to determine how temperature affects the absorption in the absence of additional information. This ambiguity results from the competing phenomena and opposite effect temperature has on reaction rates and solubility. For absorption of H2S and CO2 in alkanolamines or mixtures of amines with physical solvents, H2S absorption reaches equilibrium conditions while CO2 absorption is kinetically limited in some situations. The performance of various amines and physical solvents are compared based on solvent and feed gas temperatures. Understanding the competing phenomena of equilibrium and kinetics may yield situations where this effect can be exploited for more profitable operation.