Patent GB-919262-A (GB)
Title: Steam generators
IPC: F22B29/10
Filed: 1959-06-12
Abstract: 919,262. Regulating steam temperature in boilers. SULZER FRERES S.A. June 12, 1959 [June 13, 1958], No. 20258/59. Class 123 (3). [Also in Group XXIX] In a steam generator the temperature of steam in intermediate superheaters 21, 21<SP>1</SP> of two separate tube systems, including primary and secondary superheaters 12, 121 and 17, 17<SP>1</SP> and heat-exchanger tubes 15, 15<SP>1</SP>, is regulated by influencing, in the same direction, the heat transmission to the two systems first by rocking burners 31, 311 which are disposed in a common combustion chamber and, in addition, preferably after the lower limit of the burner adjustment has been reached, by means of water injection from a line 71 feeding through control valves 72, 72<SP>1</SP> into pipes 13, 13<SP>1</SP> of the two tube systems. Partially expanded steam is led through lines 19, 19<SP>1</SP> to the outer tubes 16, 16<SP>1</SP> of the heat-exchangers 14, 14<SP>1</SP> before it is passed to the intermediate superheaters 21, 21<SP>1</SP>, the temperature of the high-pressure steam leaving a supply line 18<SP>1</SP> being regulated by a valve 24<SP>1</SP> which controls the injection of water from a line 23<SP>1</SP> into the secondary superheater 17<SP>1</SP> and is controlled by temperature pick-offs 25<SP>1</SP>, 26<SP>1</SP> located at either side of the secondary superheater 17<SP>1</SP>. The high pressure steam output from a line 18 is controlled in a similar manner, the high-pressure steam of both systems passing through the central pipes 15, 15<SP>1</SP> of the heat-exchangers 14, 14<SP>1</SP>. Temperature deviations from required values are measured by temperature pick-offs 41, 42 located in the output lines 22, 22<SP>1</SP> of the intermediate superheaters 21, 21<SP>1</SP> and produce corresponding pressures in lines 43, 44 which are added in a unit 45 and passed through a control slide 51 to the control valve 53 of a servomotor 54, the piston-rod 56 of which influences the cross-member 33 of a linkage 32, 33, 34, interconnecting burners 31, 31<SP>1</SP>, through a plate 57 and a spring 58. The rod 56 is also connected to a spring-loaded lostmotion mechanism 75, 76 joined to the centre of a lever 74 which interconnects the operating- rods of the two injection valves 72, 72<SP>1</SP> so that after the cross-member 33 has engaged a limit stop 61 the lost motion in the mechanism 75, 76 has been all taken up and the valves 72, 72<SP>1</SP> are opened to increase the amount of water injected into the two tube systems. A regulating signal, corresponding to the difference between the two intermediate superheating temperatures t 1 , t 2 , is obtained in a unit 81 a pressure dependent upon the temperature difference being transferred, through a control slide 88, to a servomotor 90 the rod 93 of the piston 91 of which is connected by a linkage 94, 95 to an arm 96 of the lever 74 to superimpose on the latter movements which control the injection valves separately and oppositely 72, 72<SP>1</SP> to maintain the temperature t<SP>1</SP> of the reheated steam 18<SP>1</SP> substantially at the required value. The temperature t 1  remains at the predetermined level since the sum of the two temperatures has, at the same time, correspondingly varied to cause the burners to have been adjusted accordingly. In a modification, the rocking burners 31, 31<SP>1</SP> are influenced only by the temperature t 1  at the intermediate superheater 21 and the lost-motion mechanism 75, 76 between the servomotor 54 and the valves 72, 72<SP>1</SP> is omitted. The regulating signal dependent on the intermediate superheating temperature t 1 <SP>1</SP> is superimposed on the injection control valves. In a further modification the water injection 71 is replaced by lines which by-pass the intermediate superheaters and which incorporate valves which are influenced by the regulating signals which serve the rocking burners. Alternatively valvecontrolled by-passes are provided for the highpressure pipes in the heat-exchangers 14, 14<SP>1</SP>. Fig. 5, not shown, describes a flue gas recirculation system in which adjustable quantities of flue gas can be reintroduced into the furnace.