| 摘要 |
870,349. Cold separation of gas mixtures. JOY MANUFACTURING CO. Nov. 10, 1958 [Nov. 14, 1957], No. 35972/58. Class 8(2). In a method of separating readily condensible impurities from a gas mixture e.g., air prior to its rectification in a column 72 to produce a substantially pure product e.g., nitrogen comprising cooling compressed air in one or other of paths 16, 18 in heat exchangers 20, 22 in countercurrent to cold nitrogen in paths 86 or 88 then interrupting said air and nitrogen flows and passing a reverse flow of effluent nitrogen in say path 18, warm high pressure nitrogen is passed through a third path 102 of the exchanger being derimed and of such heat content as to sublime the condensed impurities. The cold and warm nitrogen paths are included in a refrigeration cycle comprising an expansion engine 70 exhausting a minor portion of nitrogen through a line 126, one or other of paths 86, 88 of exchangers 20, 22 to the intake of a compressor 76 where it is joined by the remaining major portion of the engine exhaust after having liquefied high pressure nitrogen in an exchanger 120 and effected preliminary cooling of said nitrogen in an exchanger 78. The minor portion of the warm compressed nitrogen issuing from compressor 76 traverses a path 114 of exchanger 78 after which it is joined by the remainder after having traversed one or other of paths 100, 102 of the exchanger being derimed, and a major portion of the combined streams passes to the intake of the expansion engine whilst the remainder traverses a path 156 of exchanger 120 where it is liquefied before beingfed through a line 158 to the column 72. Make-up for the cycle is provided by the column through a line 128. An operation change-over of exchangers 20, 22 is effected by a conventional valve arrangement once an hour, but since the warm high pressure nitrogen flow is designed to provide more heat than is necessary the flow through path 100 or 102 is shut off five minutes short of the hour and the cold nitrogen stream is allowed to flow through say path 88 of exchanger 22 near the end of its deriming period as well as through path 86 of the exchanger 20 in use, whereby exchanger 22 due to be put into use is cooled at all points to substantially those temperatures which subsist after the air flow is established therein. Low pressure liquid nitrogen product is withdrawn through a duct 188 and valve 228 whereas gaseous nitrogen product is withdrawn through ducts 189, 220 a path 222 of exchanger 78 and a line 224. The pressure of product liquid or gaseous nitrogen may be increased by a pump 212. In a modification for the production of oxygen using a conventional double column 225, Fig. 2 (not shown), the nitrogen liquefied in exchanger 120, instead of being fed direct to the column gives up its cold in a fourth exchanger to the incoming air stream just prior to its entry into the column.
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