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Publication Date: 2017-Feb-28
Document File: 3 page(s) / 32K

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The Prior Art Database


The present invention generally provides a method of recycling of the H2S scavengers in natural gas sweetening applications. Once the scavenging activity has been depleted, the spent scavenger is discarded as a hazardous waste. This can pose serious environmental concerns. The above invention solves this problem by recovering and recycling the H2S scavenger, thus further leading to cost savings and environmental benefits.

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Natural gas is a mixture of hydrocarbons and non-hydrocarbon gases found in geologic formations beneath the earth's surface, often in association with petroleum. As obtained from the ground, raw gas contains a number of impurities which must be removed at some point. The principal impurities in natural gas are water, carbon dioxide, hydrogen sulfide, organic sulfides and condensable hydrocarbons, such as propane, butane and pentane. Hydrogen sulfide, because of its corrosiveness and toxicity, is removed in the field prior to introduction to a pipeline for transport to a market or off-site processing plant. H2S, like hydrocarbon components of natural gas, exists in the gaseous state at normal temperatures and pressures.

Natural gas containing sulfides is referred to as being "raw" or "sour," due to its strong malodorous smell. In oil refineries or natural gas processing plants, the removal of organosulfur compounds and hydrogen sulfide is referred to as "sweetening". For many applications, it is desirable to remove some or substantially all the sulfides from the gas. For example, since hydrogen sulfide in the presence of water is corrosive to steel, it is desirable to remove substantially all of the hydrogen sulfide from natural gas before its use and preferably before transporting the gas or processing the gas in oil field equipment, pipelines and refineries. Because of this, many pipeline specifications limit the amount of hydrogen sulfide. Accordingly, removal of hydrogen sulfide from hydrocarbons, such as natural gas, crude oil and refined oil products, is an important concern. Further, because of the large quantities of hydrocarbon materials that contain sulfides, it is important to have a means of removal that does not harm the environment and is economically efficient.

The gas processing plants are provided with a solution containing a sulfide scavenging component which contacts the natural gas stream and reacts with the sulfides contained in the gas. Scavenging components, otherwise known as scavengers, that have been used to date have included formaldehyde, sodium nitrite, triazines and imines. However, certain of these scavengers have proven unsatisfactory for a variety of reasons. For example, formaldehyde has been found to be carcinogenic and requires careful handling and expensive disposal. Presently the products which are present in the market contain significant amounts of methyl-dialkylamines. The recycling of such a product is problematic, since recovered amines cannot be used to reduce fresh batches of scavenger.

There are several method/approaches for removing H2S from, or at least substantially reducing the amount of H2S in natural gas, i.e., “sweetening” natural gas. Amine gas treating process is used to remove H2S from raw natural gas.  One general approach is to expose the raw natural gas to a treatment liquid containing an agent...