Deacidization is required before a raw natural gas or any other gaseous mixture that contains significant amounts of acid gas, such as hydrogen sulfide (H2S), carbon dioxide (CO2), NOX, SOX, or similar contaminants, can be utilized. The deacidization process reduces the acid gas impurity in the gaseous mixture to acceptable levels. This is commonly done with an amine gas treatment process. Amine gas treatment processes are common in various types of industrial settings, such as refineries, natural gas processing plants, and petrochemical plants. Amine gas treatment processes include the processes utilizing aqueous solutions of amines to remove acid gas, such as H2S and CO2, from natural gases.
A common deacidization process is gas-liquid absorption. Such process typically involves contacting a gaseous mixture containing an acid gas to be removed with an aqueous amine solution, whereby the amine solution is an absorbent that absorbs the acid gas. In industrial settings, the most commonly used amines are alkanolamines, such as monoethanolamine (MEA) and diethanolamine (DEA). The use of the alkanolamine methyldiethanolamine (MDEA) for CO2 separation has recently become notable for use in industrial settings. Diisopropanolamine (DIPA) is currently used in the Sulfinol process and in the SCOT process for Claus plant tail acid gas purification.
In the typical gas-liquid absorption process, after the acid gas is absorbed into the absorbent in an absorption unit, the gas-rich absorbent is sent to a regeneration unit, where the gas-rich absorbent is treated and separated to regenerate the absorbed gas and the gas-lean absorbent. The regenerated gas-lean absorbent is then recycled back into the absorption unit and the acid gas is either collected or discharged, depending on the purpose of the user. In this type of gas-liquid absorption, the regeneration process accounts for greater than 80% of the total energy costs because the entire volume of the absorbent effluent must be regenerated in order to be reused in the absorption unit. In addition, the typical gas-liquid absorption process is limited to the use of an absorbent in the form of one liquid phase.