Patent GB-467644-A (GB)
Title: Improvements in and apparatus for the regeneration of alkaline washing liquids iaden with hydrogen sulphide
IPC: C10K1/12
Filed: 1935-12-21
Abstract: Alkaline washing liquids laden with hydrogen sulphide are regenerated by heating the liquid in admixture with a washing liquid having the same chemical composition but which has previously been laden with carbon dioxide.  Suitable alkaline washing liquids are aqueous or non-aqueous solutions of inorganic substances such as alkali or alkaline earth carbonates, and tri-potassium phosphate, or organic substances such as alkylolamines, especially those containing two or more amino groups, or salts of weak organic acids with strong organic or inorganic bases, e.g. amino or imino acids, especially those described in Specification 457,343.  The liquid charged with hydrogen sulphide and/or that charged with carbon dioxide may be in part freed from these gases before they are mixed.  In these instances the regeneration may be effected in a boiler having two sections.  If the liquid containing carbon dioxide has a low content of this gas, the mixture of carbon dioxide and hydrogen sulphide obtained in the regeneration can be passed over a gas purifying mass and the gas now containing only carbon dioxide can be returned to the regeneration boiler.  The washer in which the hydrogen sulphide is absorbed may be divided into two parts, the gas passing upwards therethrough, the upper half of the washer being charged with a washing liquid which has been charged with carbon dioxide while the lower part is charged with a liquid which has served for the removal of hydrogen sulphide and which has been partially freed therefrom.  The washer in which carbon dioxide is absorbed may also be divided into two parts, the gas being treated in the lower part with a partially regenerated solution and in the upper part with a solution substantially freed from carbon dioxide.  The washing liquid laden with carbon dioxide (but preferably partially freed therefrom), may also be mixed, before the absorption of the hydrogen sulphide, with the liquid intended for that purpose.  The washing liquid laden with carbon dioxide may be obtained from the same gas as that from which the washing liquid laden with hydrogen sulphide is obtained.  According to one example, water gas containing carbon dioxide and hydrogen sulphide is washed with a solution of the potassium salt of methyl alanine, the solution being regenerated by first boiling it in the upper part of a regenerating column, allowing it to flow down while still hot through the middle part of the column and heating it in the lowest part of the column together with an equal part of the same solution saturated with carbon dioxide.  According to a second example, water gas is freed from hydrogen sulphide with a solution of diaminopropanol, is catalysed with steam and is freed from carbon dioxide with another solution of diaminopropanol, the solution charged with hydrogen sulphide being first regenerated in part in one boiler and then being led to a second boiler in which it is regenerated in admixture with the solution charged with carbon dioxide.  According to a third example, coke oven gas containing hydrogen sulphide and carbon dioxide is washed with a solution of the potassium salt of diethylene-triamino-acetic acid and the preheated solution is regenerated in a boiler formed by a tower consisting of several sections.  The solution having been partially regenerated in the top section, is in part withdrawn from the tower and treated with carbon dioxide, being then led back to the lower part of the tower where it is mixed with the remaining solution and subjected to a final regeneration.  The gas evolved during regeneration consisting of steam, hydrogen sulphide and carbon dioxide is treated in a superheated condition with a dry iron-oxide purifying mass whereby pure carbon dioxide is obtained for the above treatment. Specifications 427,394 and 444,327 also are referred to.