Systems, apparatuses and methods of utilizing a Fischer-Tropsch (FT) tail gas purge stream for recycling are disclosed. One or more methods include removing an FT tail gas purge stream from an FT tail gas produced by an FT reactor, treating the FT tail gas purge stream with steam in a water gas shift (WGS) reactor, having a WGS catalyst, to produce a shifted FT purge stream including carbon dioxide and hydrogen, and removing at least a portion of the carbon dioxide from the shifted FT purge stream, producing a carbon dioxide stream and a treated purge stream. Other embodiments are also disclosed.

The invention provides a system for removing an acid gas from syngas with enhanced heat recovery, the system including an acid gas absorber containing a solvent and having an inlet positioned to receive a syngas stream, the acid gas absorber producing an acid gas enriched solvent effluent; a first heat exchanger positioned to exchange heat between the syngas stream upstream of the acid gas absorber and the acid gas enriched solvent effluent; and an acid gas stripper positioned to receive the acid gas enriched solvent effluent from the first heat exchanger, the acid gas stripper producing a lean solvent effluent having reduced acid gas content. The invention also provides a method for removing an acid gas from syngas with enhanced heat recovery, which involves heating an acid gas enriched solvent effluent through heat exchange with a syngas stream upstream of an acid gas absorber.

The present invention relates to an absorbent, an absorbent system and a process for removing acidic gas such as CO.sub.2 from exhaust gases from fossil fuel fired power stations, from natural gas streams, from blast furnace oven off-gases in iron/steel plants, from cement plant exhaust gas and from reformer gases containing CO.sub.2 in mixtures with H.sub.2S and COS. The liquid absorbent, a mixture of amine and amino acid salt is contacted with a CO.sub.2 containing gas in an absorber and CO.sub.2 in the gas stream is absorbed into the liquid. The absorbed CO.sub.2 forms more than one type of solid precipitate in the liquid at different absorption stages. In a first absorption stage solid precipitate of amine bicarbonate is formed and is withdrawn as slurry from the bottom of a first absorber section. In a second absorption stage solid precipitate of alkali metal bicarbonate is formed and withdrawn as slurry at the bottom of a second absorber section. The slurry withdrawn from the first absorption section is heated to dissolve the precipitate with CO.sub.2 release in an amine flash regeneration tank. The slurry from the second precipitation stage is withdrawn from the bottom of the second absorber section and sent to a regenerator for desorption with CO.sub.2 release. The lean amine and amino acid salt mixture from the flash regenerator and desorber are mixed and returned to the top of the absorber. This absorbent system improves carbon dioxide removal efficiency due to its higher CO.sub.2 removal ability per cycle when compared with conventional amine, absorbent from organic acid neutralized with inorganic base and carbonate based absorbent system. It exhibits less solvent vaporization loss because part of the absorbent is in salt form.

The invention relates to novel nitrogen compounds belonging to the family of tertiary diamines of general formula (I) below, wherein R is an alkanediyl radical (CH.sub.2)n- with n=2, 3, 4, 5 or 6.

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The compound according to the invention is for example N,N,N,N-(tetramethyl)-1,6-diamino-2,5-hexanediol or N,N,N,N-(tetramethyl)-1,8-diamino-2,7-octanediol. The invention also relates to the method for preparing them and to their use for removing acid compounds contained in a gaseous effluent.

The present invention relates to an aqueous alkanolamine solution for the removal of hydrogen sulfide from gaseous mixtures containing hydrogen sulfide. The aqueous alkanolamine solution comprises (i) an amino compound with the formula:

R.sup.1R.sup.2NCH.sub.2CH(OH)CH.sub.2OH

wherein R.sup.1 and R.sup.2 independently represent lower alkyl groups of 1 to 3 carbon atoms, (ii) piperazine, and (iii) optionally a physical solvent, wherein said solution does not contain a strong acid. Further, the present invention relates to a process for removing hydrogen sulfide from a gaseous mixture containing hydrogen sulfide, and additionally other acid gases, if present, for example carbon dioxide, comprising the step of contacting the gaseous mixture contain hydrogen sulfide with the aqueous alkanolamine solution, preferably wherein the temperature of the aqueous alkanolamine solution is equal to or greater than 140 F. Examples of the gaseous mixtures include natural gas, synthesis gas, tail gas, and refinery gas.

The invention relates to a process for separation or purification of gaseous streams by removal of acid gases using a liquid amine solution. The process involves the steps of contacting the gaseous stream with liquid lean amine solution in at least one continuous flow stirred-tank reactor (10; 10a, 10b; 10c); removing a sweetened gaseous flow from said continuous flow stirred-tank reactor (10); removing rich amine from said continuous flow stirred-tank reactor (10; 10a, 10b; 10c) for regeneration; passing rich amine solution through at least one flash tank stripper 20; 20a, 20b; 20c; removing acid gases and vapor from said flash tank stripper 20; 20a, 20b; 20c; removing lean amine from said flash tank stripper for recirculation to said continuous flow stirred-tank reactor (10; 10a, 10b; 10c).