GB1190450A - Hydrogen Compression by Centrifugal Compressors - Google Patents

Abstract

1,190,450. Hydrocracking; hydrodesulphurization. FLUOR CORP. Ltd. 28 Dec., 1967, No. 58966/67. Heading C5E. [Also in Division F1] The hydrogen compression of a gaseous stream comprising a predominant proportion by volume of hydrogen is increased by adding to the stream, prior to compression, hydrocarbon in the 30 to 80 molecular weight range so that the stream contains about 1% to 12% by volume of the hydrocarbon, and compressing the stream by passage through a multi-stage centrifugal conpressor, the added hydrocarbon acting to increase the hydrogen compression above the level otherwise attainable under the same operating conditions but in the absence of the added hydrocarbon. An oil feed, such as gas oil in the boiling range of diesel oil needing reduction in sulphur content or increase in cetane number, is introduced through a line 10 and pumped through a heater 11 to a hydrocracking or hydrotreating unit comprising one or more reactors 13, where it is converted at high pressure (500 to 4000 lb. per square inch) and temperatures of 500‹ to 900‹ F., the hydrogen required for the conversion being compressed to the high pressure in a multi-stage centrifugal compressor 15. After conversion, the resultant liquid and gaseous, or entirely gaseous mixture is cooled in a heat exchanger 19 and an air cooler 20 and, after removal of excess hydrogen in a separator 21, passes to a fractionation stage 27, in which a fraction having an average molecular weight in the 30 to 80 range and desirably largely butane is produced. The product hydrocarbon leaves at 28, while separated butane or equivalent is taken via a line 29 to a contactor 31 in which it is added to hydrogen (which may be by-product hydrogen containing hydrocarbons in the range methane to butane) from a line 30. The resultant gaseous mixture, containing up to 12% by volume of butane or equivalent, is used as impure hydrogen input to the compressor 15. Because the butane or equivalent increases the density, the required compression is obtained with three stages instead of the six which would be required if pure hydrogen were used. Unvaporized material from the contactor 31 may be returned via line 32 to the fractionation stage 27. Surplus hydrogen is returned from the separator 21 via a compressor 23. Instead of being introduced into the cycle at a point upstream of the heater 11, the compressed hydrogen may be introduced via line 25 at, say, the suction side of the compressor 23.