GB519871A - Means for automatically controlling apparatus for the densityaltering treatment of aflowing material by heating - Google Patents

Abstract

519,871. Fluid-pressure servomotor control systems. BAILEY METERS & CONTROLS, Ltd. June 30, 1938, No. 18516. Convention date, July 9, 1937. [Class 135] [Also in Groups XXXV, III and XXXVIII] Fluid - flow; density. Any density - altering heating treatment of a flowing material is automatically controlled by means operating continuously in accordance with variations in the mean densities of the material before and after the heating. The invention may be applied to the heat treatment of any fluid, e.g., the generation of steam, but is described in relation to the heating or cracking of petroleum or hydrocarbon oil. In order to obtain a measurement of density of a fluid at a point such as 12A, Fig. 3, in a conduit two measurements of flow rate are made by differential flow meters, 4, 3, one at the point 12a referred to and another at an earlier point 5 at which the density is known. The quotient of these is a measure of the density at the point 12A and is obtained by means of electrical self - synchronous transmissions and an electrical differential mechanism such as 31, 32 assisted by logarithmic and antilogarithmic cams such as 39, 46 respectively. The mean density between two points 12A, 13A defining a treatment zone is obtained by summation in mechanical differential 50 and may be recorded by an indicator 51. Logarithmic records of the three flow rates may be obtained at 43, the time of detention of any particle in the treatment zone being recorded at 63 through an electrical differential mechanism driving an antilogarithmic cam and coupling logarithmic cams 39A and 60 driven by a flow rate meter 3 and the mean density recorder 51, a record of the yield per pass is obtained at 71 by a similar operation in respect of the time of detention pointer and coupled Bourdon tubes 68, 69 storing the mean temperature in the treatment zone 15. An alternative means of density measurement Fig. 1A, employs positive displacement meters 3A, 4A driving a disc 161 and a rotating contact 172 respectively. The latter mounted on a carriage 164 and a ball 162 rolls in contact with the disc and a welt spool 163 on the carriage. Contacts carried by the spool co-operate with the contact 172 to control a reversible motor which moves the carriage spool and ball to a position of balance which varies with the rate of the speeds of the flow meter and is adapted to indicate the density on a recorder 176. The automatic control of the heat treatment in accordance with variations in the mean density of the fluid in a treatment zone 15 is illustrated in Fig. 14 wherein the pointers 148, 149 correspond to the elements 48, 49 in Fig. 3 and operate valves controlling the fluid pressure in pipes 153, 150 in accordance with density changes. The fuel supply valve 94 is controlled directly in accordance with 'outlet density but the air valve 95 is controlled in accordance with the mean density of the fluid by the operation of a fluid-pressure control valve 152 subject to the sum of the pressures in pipes 153, 150. Fig. 12 (not shown) includes a modification in which the air valve is controlled in accordance with the outlet density and the fuel valve in accordance with mean density. Fig. 4 shows an arrangement in which the element 74 corresponds with 57 in Fig. 3 and an additional control in accordance with temperature at the inlet 78 of the treament zone 15 is compounded therewith to control fuel and air valves 94, 95. A modification of this Fig. 5 (not shown) uses thermo-couples at inlet and outlet to obtain a response at 83 proportional to mean temperature in the treatment zone and an additional fluid pressure control of rheostat by the combination gives a variation of the speed of a fan recirculating the combustion products in the furnace. A flow rate meter 110. Fig. 6, and a thermo-couple 115 may be installed in a median portion of the treatment zone to co-operate with a flow rate meter 3 at an earlier point in the fluid path where the density is known to obtain a similar control, the recirculation of combustion products being controlled by a damper. Fig. 9 (not shown) illustrates the manner in which the pointer 62, Fig. 3, which registers the time of detention of fluid particles in the treatment zone may be applied to control jointly the fuel valve and a flow control valve fot the treated fluid, and Fig. 10 (not shown) shows the combination with this of control in accordance with mean temperature in the treatment zone. By combining with this last arrangement a manual or automatic adjustment of the proportionality of the control in accordance with stock factor variations a desired yield per pass may be maintained constant. The Specification as open to inspection under Sect. 91, comprises also arrangements (1) for automatic control of a valve determining the back pressure on the outlet from the treatment zone or on a reaction chamber into which the fluid discharged after heat treatment, the control being effected jointly by elements responsive respectively to the density at the end of the heating zone and to the back pressure and (2) for hand control of the firing in a heat treatment utilizing indications of the weight rate of fluid flow (supply tank fluid level) and of a differential-head flow-rate meter at the end of the treatment zone. This subject-matter does not appear in the Specification as accepted.