ABSTRACT

Natural gas is the most important and popular fossil fuel in the current era and in the future as well. However, because natural gas exist in deep underground reservoirs it may contain several non- hydrocarbon components, for example, hydrogen sulphide and carbon dioxide. Thee impurities are undesirable compounds and cause several technical problems, for example, corrosion and environmental pollution.Pirkoh gas field,which is also one of the largest gas field, located in Balochistan. Laboratory analysis has shown that the Pirkoh field natural gas contains H2S (about 0.1%) and C2O (about 4%). Therefore, this study aims to simulate the prospective Pirkoh gas sweetening process by using the Aspen HYSYS V.7.1 program. The study is based on the processes used for the natural gas sweetening which involves removal of acid gases hydrogen sulphide and carbon dioxide, these processes are commonly called amine processes because amine are used as solvents in these processes.The primary amines form the most stable bond with the acid gas, followed by the secondary amines. The least stable bond is formed by the tertiary amine. Although MEA has been extensively used by the natural gas industry in the past, because of its corrosivity it has, in large part, been supplanted by the less corrosive DEA. Both of these solvents are also degraded by COS, with DEA showing less degradation than MEA. The latter forms a non-regenerable degradation compound with COS. Thus, unless COS is removed or hydrolyzed to H2S ahead of the amine scrubber, neither one of these two amines would be suitable for synthesis gas.MDEA has become popular with the natural gas industry because it has a high H2S/CO2 selectivity is very stable against degradation and is the least corrosive of the amines. So we based our study on the MDEA selective process on behalf of several reasons which are discussed in chapter no. 3.Our feed specifications for H2S were 0.01 Mole% which is in product reduced upto just 4 PPMV and specifications for CO2 in Feed were 4 Mole% which is reduced to 2 Mole% in the product stream.