The paper presents available process solutions aimed at improving the efficiency of nonchemical hydrogen sulphide removal from stock tank oil. Based on the results of comparative performance analysis of chemical and physical methods, a number of approaches are proposed to enhance the efficiency of oil desorption during hot stage separation and inside stripping columns.
Chemicals-aided crude oil scavenging, oil treatments in stripping column, and catalytic liquid-phase oxidation with atmospheric oxygen have been found to be the most efficient technologies for removal of hydrogen sulphide. Application of chemical scavengers is the simplest process and does not require large capital investments. Physical hydrogen sulphide stripping method is also not associated with substantial material costs and does not affect oil quality. Improved performance of nonchemical processes is one of top-priority tasks, and successful solution of this task enables reduction of oil treatment costs. To reduce chemical consumption hot vacuum separation technology is proposed. It ensures improved desorption of hydrogen sulphide from oil into gas through application of liquid-ring pumps to create vacuum inside gas boots. Hydrogen sulphide stripping technology with hydrocarbon gases exhibits the highest performance as a physical hydrogen sulphide removal method at Tatnneft’s facilities. The key parameters of the desorption process are pressure, temperature, flow rate and composition of the stripping gas. Changes in the composition of crude oil upstream of the stripping column at the return of condensate or the entire gas volume downstream of the compressor station into liquid stream upstream of the separation stage ensure significant reduction of chemical consumption and increase efficiency of the process.
Under conditions of restricted gas pipeline capacity or lack of Devonian gas, feeding the gas stream from the first-stage separator can provide reduction of material costs without compromising the efficiency of the process given that molar concentration of hydrogen sulphide is below the equilibrium (primarily, not more than 1.6%).
References
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