There are many factors which need to be considered when selecting a process for a given sweetening application. The system discussed in the paper is the application of chemical solvent processes to develop an economic way of reducing H2S levels in produced and fuel gas and the reduction of H2S levels from atmospheric tank systems.
The chemical solvent processes are applicable at low pressure and relatively low temperature. Most commercially available chemicals for H2S sweetening have very similar operating principles. The efficiency of the chemical conversion equipment used has t0 be oriented towards the physical gas distribution and gas-liquid contact efficiency.
Some key items to consider for the chemical reaction mechanisms in the solvent sweetening process are very essential for economic operation of the process.
Most of the chemical sweetening produ.cts used are water soluble, therefore their efficiency is very low in dry gas production systems and thus the gas should be saturated Water based sweetening products have the potential to saturate lean gases to their natural saturation point. Foaming problems have resulted in serious deterioration of the chemical solvent efficiency.
When bacteria development takes place in the produced water system, the bacteria growth is often inhibited by the use of biocides which contain aldehydes, The aldehydes forms the reaction base for the sweetening process, therefore their directed use either for bacteria or H2S sweetening is not obtained.
Hydrogen sulfide can cause serious production operation problems due to corrosion, environmental, gas quality and safety concerns.
The oil industry bas adapted two (2) methods for H2S removal. In large process systems, the use of Amine process is most common, in smaller processing systems, solvent extraction methods arc often used where a reaction product provides the opportunity for the H2S to ionize and attach to partially positive charged carbon atoms.
When the H2S is generated by bacteria such as Sulfate Reducing Bacteria (SRB), the H2S level, can be reduced, disregarding the origin of the H2S, through H2S scavenging.
This reaction products used for the H2S conversion all appear to have very fast reactions such as the glutaraldehyde and aerolein solutions. The reaction mechanisms and effects of salt and the organic phase to the reaction mechanism was studied by Elliot and Raymond.
The following provides critical equipment design Parameters which can be utilized in the H2S scavenging, the advantages and drawbacks of some commercial chemical products are also outlined.
The residual product developed in the H2S sweetening process is a very essential criteria in determining the utilization of the sweetening process for an in-line treating system.
The chemical solvent efficiency and potential absorption by the sour gas arc the two other concerns associated with the sweetening process especially for in-line process development.
Experimentation of several sweetening solvents have demonstrated drawbacks to its utilization. A detailed study was conducted by Fisher et al,.
Saturated sour gas systems can increase CaCO scale deposition. The solid scale deposit creates an excellent environment for the culture growth of Sulfate Reducing Bacteria (SRB) which results in increased H2S levels down the line.