GB1356700A - Automatically controlling mole ratios - Google Patents

Abstract

1356700 Control of chemical composition TEXACO DEVELOPMENT CORP 25 Nov 1971 [14 Dec 1970] 54710/71 Heading G3R In the catalytic reforming of oil, or the hydrogenation of kerosine, light gas oil or lubricating oil, the mole ratio of hydrogen in the recirculating gas, to the hydrocarbon in the oil is computed on the basis of sensed parameters in the system, and maintained at a desired value to minimize coking of the catalyst, by controlling the speed of a compressor recirculating the gas. A signal means 24, see also Fig. 2 (not shown), contains meters (28), (29) measuring the boiling point and API gravity of the charge oil, whose outputs are processed in the unit 24, on the basis of disclosed algebraic equations relating the meter outputs to the average specific gravity and molecular weight of the oil, to provide signals E 2 , E 1 representing the latter quantities. Reference voltages (E a -E n ) fed to the unit represent co-efficients in algebraic analysis The signal E 2 is multiplied by signal E 14 representing oil flow rate, the resultant being divided in unit 81 by the signal E 1 , to provide an output E 16 , the denominator of an algebraic expression representing the mole ratio. Signal means 87, see also Fig. 3(not shown), contains a chromatograph (88) sensing the hydrogen, and specified hydrocarbon constituents of the recycled gas, and, on the basis of disclosed algebra, outputs a signal E 19 representing the percentage by volume of hydrogen, and a signal E 20 for the specific gravity of the gas. Such signals are multiplied in unit 102, and multiplied by a signal E 25 representing gas flow rate, to provide signal E 26 , the numerator of the mole ratio expression. E 26 is divided by E 16 in unit 110, and amplifier 112 having a gain equal to a co-efficient in the expression, outputs a signal equivalent to the actual mole ratio, which is subtracted in unit 116 from a predetermined desired value mole ratio signal E 9 , the difference signal establishing a setting of a speed controller influencing a steam flow recorder controller 125 pneumatically controlling the setting of a steam valve 130 providing steam to a turbine 20 driving recirculating gas compressor 17. Signal E 28 is an actual steam flow signal. A tachometer 120 feeds a turbine speed signal to controller 120, limiting the maximum allowable turbine speed. Clock 21, via switch 22, controls the operation of sample and hold units (34, 63 Fig. 2, 90-90H Fig. 3) in the units 24, 87. Computation may be analogue, or digital with a/d converters at the sensor locations, and a d/a converter at the speed controller input. Amplifier 112 may be replaced by a multiplier receiving a reference voltage representing the co-efficient in the mole ratio expression, and the output of divider 110. Alternatively, the mole ratio may be stabilized by controlling the oil flow to the catalytic reforming unit.