Chapter 7 - Acid gas treating

Abstract

Natural gas contains large amounts of acid gases, such as hydrogen sulfide and carbon dioxide. This chapter describes the processes of treatment of natural gas to remove the acid gases, carbon dioxide, and hydrogen sulfide. There are many variables in treating natural gas. The precise area of application of a given process is difficult to define. Several factors are considered: types and concentrations of contaminants in the gas, the degree of contaminant removal desired, the selectivity of acid gas removal required, the temperature, pressure, volume, and composition of the gas to be processed, the carbon dioxide-hydrogen sulfide ratio in the gas, and the desirability of sulfur recovery due to process economics or environmental issues. In addition to hydrogen sulfide and carbon dioxide, gas may contain other contaminants, such as mercaptans and carbonyl sulfide. The presence of these impurities may eliminate some of the sweetening processes as some processes remove large amounts of acid gas but not to a sufficiently low concentration. Process selectivity indicates the preference with which the process removes one acid gas component relative to (or in preference to) another.