Methyl Mercaptan from Natural Gas, Methanol and Sulfur (Carbon Disulfide Co-Product)

The process under analysis comprises four major sections: (1) H2S Synthesis; (2) CS2 Separation; (3) Methyl Mercaptan Synthesis; and (4) Methyl Mercaptan Separation.

H2S Synthesis. The process begins with pre-heating natural gas and sulfur in a furnace. The heated stream is then fed to packed bed tubular reactors where methane reacts with sulfur to produce carbon disulfide (CS2) and hydrogen sulfide (H2S). The product stream is then cooled in a waste heat boiler to recover heat as steam, and the cooled gases proceed to the CS2 Separation section.

CS2 Separation. Excess sulfur is removed from the product stream using a scrubbing system with light oil as the scrubbing fluid. The sulfur is separated from the oil and recycled to the furnace. The scrubbed stream, containing CS2 and H2S, then proceeds to an absorption step where CS2 is absorbed in light oil and separated from H2S. The absorbed CS2 is further purified through a series of distillation steps and a caustic wash, resulting in pure CS2 as a by-product.

Methyl Mercaptan Synthesis. H2S is compressed along with methanol in a two-stage compressor. The vaporized methanol is then mixed with the compressed H2S to achieve the desired molar ratio. The mixture is preheated and fed to a packed bed tubular reactor where it reacts to form methyl mercaptan (MSH) and water. The reactor effluent is cooled and sent to the purification stages.

Methyl Mercaptan Separation. The reactor effluent is first condensed, creating an organic and an aqueous condensate; the uncondensed stream being washed with methanol, which is then mixed with the aqueous condensate. Unreacted H2S is recycled to the compressor. Both condensates undergo distillation to recover Methyl Mercaptan, methanol, and remove impurities. Methyl mercaptan is further distilled, separating it from dimethyl sulfide and other components. The purified MSH is then stored as the final product.