Patent GB-965565-A (GB)
Title: Apparatus and process for heaterless fractionation of gaseous constituents
IPC: C01B3/56
Filed: 1961-03-24
Abstract: 965,565. Separation of gaseous mixtures. ESSO RESEARCH & ENGINEERING CO. March 24, 1961 [April 12, 1960; April 20, 1960; May 18, 1960; June 16, 1960; Aug. 2, 1960], No. 10856/61. Heading B1L. Gaseous mixtures are separated by flowing the mixture at a relatively high pressure through a bed of adsorbent which is selective for at least one component of the mixture, whereby an increasing concentration of the adsorbed component moves along the bed and gaseous effluent stream is discharged from the other end. Before the adsorbed component reaches the end of the bed, the flow of feed stream is stopped and the exit end closed. The pressure is reduced and the adsorbed component is desorbed and removed from the inlet end of the bed. The pressure is then raised to the initial relatively high pressure by introducing at least a portion of the gaseous effluent stream at the exit end, and the process is then repeated. Part of the gaseous effluent may be led to a product surge tank at the relatively high pressure, and this may be used for repressurizing. The process may be carried out as above, or by using two identical beds where one is under adsorption while the other is being desorbed and vice versa. In this latter case, the desorption may be stopped when the bed under adsorption is 50-90% saturated, preferably 70-80%. Separations possible by the process include hydrogen from hydrocarbons ; moisture and other trace impurities from oxygen, nitrogen, helium or hydrogen, drying refrigerants, e.g. the freons, ammonia, SO 2 ; drying methyl chloride for use in butyl rubber manufacture; removing water, acetylene and C 3+  from ethylene ; removing water, H 2 S, CO 2 , C 4+  from natural gas ; removal of C 3+  hydrocarbons from natural gas. Adsorbents may be selected from activated carbon, activated alumina, silica gel, glass wool, adsorbent cotton, metal oxides, clays, fuller's earth, bone char, "Mobilbeads" (Registered Trade Mark), molecular sieves. In the two bed process, the following procedure may be adopted. In Fig. 5, feed gas containing moisture enters through line 202 and is led into zone 220 via valve 203. Zones 210 and 220 are filled with silica gel. Substantially dry gas is removed from the top via line 204. It passes through valve 205 since 206 is a closed check valve, and is divided into two streams. A portion passes through line 207, valve 209 and into product surge tank 211, while the remainder passes through valve 213 controlled by flow controller 214 which maintains a predetermined pressure drop across the valve, and is withdrawn as product gas. The remaining gas passes through 208, through check valve 216 (spring loaded by 221) and valve 217 and is passed into the top of zone 210. Valve 217 is controlled by flow controller 219 maintaining the required pressure drop across 217. Spring loaded valve 216 only opens after a predetermined pressure drop across 216. The gas backwashes down through 210 and is withdrawn with the desorbed constituent through valve 224, and may be further processed if desired. Zone 210 is then repressurized by opening valve 250, allowing gas to flow from surge tank 211, and closing valve 224. The rate of repressurizing is controlled by throttle valve 229. When 210 is pressurized valve 227 opens and 203 closes. Finally 226 opens, 250 closes and the cycle is continued. The valves are all controlled and interconnected by programme controller 290. The removed desorbed constituents may be further treated by passing through lines 225 and 240 to vacuum pump 241. The gases are then compressed by compressor 242, passed through cooler 243 to condense the moisture, and through trap 244 from which the moisture is removed via 245. The remaining gases are preferably recombined with the feed gas or some may be bled away through 247.