GB970567A - Adsorption process - Google Patents

Abstract

<PICT:0970567/C1/1> In the purification of hydrocarbon-containing gases, e.g. natural gas, from hydrogen sulphide (see Division C5), the hydrocarbon feed gas is passed through an adsorption zone (B1) to remove H2S, a portion of the effluent is heated (at 26) and passed through a desorption zone (B4) containing an adsorbent previously used to adsorb the H2S, the H2S at increased concentration in the desorption gas is absorbed (at 35) and recovered, and the purified desorption gas is returned to an adsorption zone. The numerals refer to a preferred embodiment shown in Fig. 1 in which before being passed to absorber 35, the desorption gas is cooled to condense water, atmospheric condenser 33 and heat exchanger 16 being employed. In absorber 35 H2S is washed out with recirculating water, and carried to tank 46 from which it is vaporized and removed through line 47.ALSO:<PICT:0970567/C4-C5/1> <PICT:0970567/C4-C5/2> Acid gas, e.g. hydrogen sulphide, is removed from gases containing hydrocarbons, e.g. natural gas, by passing the hydrocarbon feed gas through a first adsorbent zone to remove acid gas, passing a part of the effluent after heating through a second adsorbent zone containing previously adsorbed acid gas, to regenerate said second zone, absorbing acid gas from the effluent from said second zone and returning the purified effluent to said first zone to obtain sweetened product gas therefrom. In a first embodiment illustrated by Fig. 1, hydrocarbon feed is introduced into separator 11 where water and liquid hydrocarbons are removed, e.g. with cooling, and then through filter 14 and heat exchanger 16 to a first adsorption bed B1. After withdrawal of a portion through line 25 as regenerating gas, the gas is passed to a second bed B2 to complete the adsorption of water and hydrogen sulphide and then to bed B3 which is thereby cooled to adsorption temperature. The product is withdrawn via heat exchanger 22. The portion withdrawn through line 25 is passed through heater 26 to bed B4 which is to be regenerated. Gas containing desorbed hydrogen sulphide is passed through atmospheric cooler 33 and heat exchanger 16 to an absorber 35 where hydrogen sulphide is washed out with recirculating water, and together with moisture condensed by 33 and 16, carried to tank 46. The gas is then returned via line 40 to join gases entering absorber B2, while hydrogen sulphide is vaporized and removed through line 47. Fig. 2 (not shown) shows how the system of Fig. 1 may be programmed to change the phase of the beds B1 to B4. This may be done on a time basis or by means of temperature-sensitive devices in lines 21 and 32. Fig. 3 shows a similar system in which two beds B1, B2, are employed to adsorb the hydrogen sulphide and regeneration gas is taken from the product line at 121 and after heating (e.g. to 550 DEG F.) passed in series through beds B3, B4 before passing to absorber 35. This system may be similarly programmed (Fig. 4, not shown) to rotate the function of the beds B1-B4. This embodiment also illustrates (a) the control of the amount of recirculating absorption water in accordance with the amount of gas entering at 10 (see line 87a); (b) the similar control of the amount of desorption gas withdrawn at 121 (see line 121 b); (c) when hydrogen sulphide desorption is complete, the operation of valve 85 to return the gas from the desorption beds directly to the adsorption beds (via line 94) and the passage of the feed gas through the absorber 35 (via line 98) by operation of valve 80. These valves are controlled by the temperature in line 132.