Patent GB-965358-A (GB)
Title: Process for the separation of acid components from a mixture
IPC: C09K5/00
Filed: 1962-12-21
Abstract: A process for the separation of <PICT:0965358/C1/1> acid components, e.g. hydrogen sulphide, carbon dioxide and carbon oxysulphide, from a mixture which is not appreciably soluble in water or aqueous liquids, comprises contacting, preferably countercurrently, the starting mixture with an aqueous solvent for these components in a separation zone, withdrawing the purified product and the charged solvent from this zone, heating the charged solvent in a stripper to free it at least substantially from the absorbed components and returning the stripped solvent to the separation zone, and includes controlling the quantity of solvent supplied to the separation zone in dependence on the residual content of acid components in the purified product (or in dependence also on the amount of acid components supplied to the separation zone per unit of time), such that the quantity of solvent supplied increases with increasing content of acid components and vice-versa, and controlling the supply of heat to the bottom part of the stripper in dependence on the temperature at the top part of the stripper such that the supply of heat increases with a decreasing temperature at the top part of the stripper to maintain that temperature at least approximately at a desired value.  This temperature may be determined according to the pressure in the stripper and the permissible content of acid components in the returned solvent or the purified product, and may be measured by means of a probe containing a material having a vapour pressure curve which is the same as, or similar to, the vapour pressure curve of the mixture at the top part of the stripper, the pressure prevailing in the stripper is compared with the vapour pressure of the liquid in the probe, and the heat supplied to the stripper is controlled in dependence on that comparison. Specified solvents are an aqueous solution containing potassium phosphate, an alkanolamine, a cyclotetramethylene sulphone, or a mixture of an alkanolamine and a cyclotetramethylene sulphone.  A gas mixture containing light hydrocarbons and hydrogen sulphide is separated in a process shown in Fig. 1.  The mixture enters the separation zone 2 via line 1, and an aqueous solution of diisopropanolamine is supplied through 3.  The purified gas is withdrawn through 4, and the charged solvent through 5, via heat-exchanger 6 to stripper 7. The stripped solvent is returned to zone 2 via pump 8, line 3, heat-exchanger 6, and cooler 9. The hydrogen sulphide is separated from any water vapour in 12, and leaves through 14. The residual content of acid components in the purified product is measured by 22, compared with the desired value in 23, and passed to control 21, which effects valve 18, which controls the amount of solvent supplied to zone 2. The amount of acid components supplied to the separation zone per unit of time, is determined by 25 passed to 21 via 26, which again effects valve 18. The temperature at the top part of the stripper is measured by 27, compared with the desired value in 28, passed to control, 19, affecting valve 18, which controls the supply of heat to the bottom part of the stripper. Fig. 2 (not shown) shows the control system used when the pressure in the stripping column is not constant.