ES294054A1 - Method of firing with fluid fuels - Google Patents

Abstract

The burners of a steam power or gas-turbine plant are supplied with a mixture of two fuels, one of the fuels being supplied at a rate which is independent of the amount of heating required and the other at a rate depending on the amount of heating required. Fig. 1 shows a steam generator having two burners 10, 11, each having a spring-urged piston 14 carrying a throttle cone 15. Blast furnace gas A and methane B are delivered to a mixing station 21 by pipes 20, 30. A valve 22 controlled by a pressure measuring unit 23 via a P.I. (proportional plus integral) controlling unit 24 maintains a desired pressure of the blast furnace gas. The pressure at an orifice 25 in the pipe 20 acts upon a measuring element 26 and a signal therefrom is corrected in a multiplication element 35 in accordance with the calorific values of the two fuels. The pressure at an orifice 32 in the other pipe 30 acts upon a measuring element 33 and the signal therefrom is superimposed at 34 upon the signal from the multiplication element 35. The sum of the two signals then acts on a P.I. controlling unit 36 acting on a valve 31 controlling the supply of methane. The controlling unit 36 is also connected by a line 37 to a load controlling unit 38 controlled via a P.I. unit 51 by a pressuremeasuring unit 39 measuring the steam pressure in the live steam pipe 4. The measuring elements 26, 33 also act on multiplication elements 40, 41, the outputs of which are combined and passed via a further multiplication element 43 to a controlling unit 44 which also receives a signal from a measuring orifice 45 in an air supply pipe 13. The controlling unit 44 controls a motor 47 driving a blower 48. The multiplication element 43 receives a correction signal via an I-controlled unit 52, the unit has integral action from a unit 49 measuring the content of oxygen in the flue gases. A pilot signal is transmitted by the load controlling unit 38 via a line 50 to the controlling unit 44 and acts proportionally or with a combined proportional and differential action on the blower motor 47. A line 53 supplies a signal in the event of change in the calorific values of the gases and lines 54, 55 supply signals corresponding to the air requirements of the gases. A multiplication element may be provided to multiply the output of the measuring element 33 and one of the multiplication elements 40, 41 may be omitted. In a simplified construction, Fig. 2 (not shown), the air supply to the burners is not controlled by the fuel flows. The gas valve 31 may be replaced by a fuel mixer, Fig. 3, comprising an ejector 62 supplied with one fuel through a pipe 60 and with a second fuel from a reservoir 63 through a line 64 containing a non-return valve 65 and a control valve 31a actuated by elements 34a, 36a &c. performing the same function as the elements 34, 36 &c. of Fig. 1. The pressure of the fuel in the pipe 60 acts on a spring-biased piston 68 which moves the ejector tube relative to the end of the second fuel line 64. In the apparatus shown in Fig. 4, the two fuels are supplied by pipes 89, 91 and the pressure of the mixture in pipe 93 is measured by a unit 94 connected to a P-controlling unit 95 (the unit has proportional action) controlling a valve 92 in the fuel pipe 91 and receiving a signal from a unit 96 receiving a signal from a unit 97 measuring the steam pressure in a pipe 81 extending from the furnace to a turbine 82. Compressed air is supplied to the burner through a valve 99 regulated by a P.I.D. controlling unit 100 (the unit has proportional plus integral plus derivative action) connected to a flow-measuring element 101 in the steam pipe 81, and to a measuring element 103 responsive to an orifice 102 in the air line, and to a differentiator 104 connected to a point between the control unit 95 and the pressure-measuring unit 94. A tachometer 85 on the turbine shaft acts via a P.I.D. controlling unit 86 on a valve 87 in the steam line. A gas turbine can be controlled in a similar way.