Gas Technology Symposium, 17–18 April, Shreveport, Louisiana

Introduction

Despite an apparent abundance of elemental sulfur at this time, a recent survey and forecast of sulfur supply and demand by Stanford Research Institute, reported in Chemical and Engineering News, indicates that reserves of Fraschsulfur may reach a peak and decline in the face of a rising demand for brimstone during the next decade. There is little doubt that economic pressure will dictate that sulfur be recovered from sources now considered uneconomical.

For example, consider the sweetening of sour natural gas as practiced by the petroleum industry. At present and for many years past, producers and transporters of natural gas have removed hydrogen sulfide by a variety of processes, notably water-amine, glycol-amine, phenolate, hot carbonate, iron sponge, etc. But sulfur is recovered from these acid gas streams only when it can be produced at rates of 10 tons per day or more by various modifications of the Claus process. As a result, a large volume of sour gas is processed daily in hundreds of small sweetening plants. The off-gases, containing hydrogen sulfide, are vented and burned, representing a substantial loss of a valuable, exhaustible resource. Obviously, improvement is a matter of economics made possible by a higher price for sulfur, or recovery process improvement, or a combination of both.

The purpose of this paper is to present a new process development for sweetening sour gas and for effecting simultaneous recovery of elemental sulfur. Based on a reaction mechanism discovered by F. M. Townsend, the process has been developed by the authors to the pilot plant stage and it is known as the "Townsend Process". This process has several notable features:

  • Gas is sweetened and its sulfur compounds are converted to elemental sulfur in one step,

  • the sweet residue gas is effectively dehydrated,

  • the process is virtually insensitive to carbon dioxide,

  • it appears to be adaptable to a complete range of H2S content regardless of whether gas sweetening or sulfur recovery is the prime objective, and

  • it can replace the Claus process in converting off-gases from sweetening processes of various types, and it promises to be especially effective where the CO2 and/or heavier hydrocarbon content of such mixtures is excessively high.

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