Patent GB-756842-A (GB)
Title: Improvements in or relating to vapour generating and vapour heating units
IPC: F22G5/00
Filed: 1952-06-27
Abstract: 756,842. Liquid, gas and pulverulent fuel fired furnaces. BAILEY METERS & CONTROLS, Ltd. June 27, 1952 [June 29, 1951], No. 16304/52. Class 51(1). [Also in Groups XIII and XXIX] In a vapour generating and vapour heating unit, the temperature of the vapour is con-, trolled from a determination of the heating gas temperature. In an embodiment, the temperature of the gas in the vicinity of steam superheaters is measured by a bolometer 16, Fig. 6, and applied to a recorder-controller 22 which actuates a pilot valve 24, as described in Specification 425,507, to give a fluid pressure in line 25 corresponding to the gas temperature. The final steam temperature is also measured and applied to a recorder-controller 28 which actuates a pilot valve 30 to give a fluid pressure in line 31 corresponding to the steam temperature. The pressure in line 31 is applied through a relay 32 to a relay 34 to which the pressure in line 25 is also applied. The output from relay 34 is applied through manual-automatic selector valves 38, 39 to fluid-actuated driving devices 19, 20 which actuate, respectively, a throttle valve 18 in a gas by-pass around the superheater and tilting, tangentially-firing burners 10 by means of which the combustion zone can be moved over the tubes of the generating section of the boiler towards or away from the gas outlet. The fuel and air supplies are controlled in accordance with the pressure of the steam at the outlet. The control may be such that the valve 18 is not actuated until the burners have been tilted to the limit position. In a modification, the gas by-pass is replaced by a spray attemperator, as disclosed in Specification 656,551, and the drive 19 actuates a valve controlling the supply of water to the attemperator. In a modification of this last arrangement, the flow of the water passing to the attemperator is measured by passing it through a restriction and applying the pressure at the two sides thereof to a meter. The latter then actuates a pilot valve to give a fluid pressure which is passed to a relay where it is combined with the other pressures controlling the valve in the attemperator water supply line. When the steam generator supplies a turbine, a further, reheater, section 5, Fig. 10, for steam returned from the turbine, or supplied from another source, may be included and both superheater and reheater sections has each its own attemperator 42, 60, respectively. The controlling variables in this modification are the gas temperature taken at the point 16, the temperature of the superheated steam, and the temperature of the reheated steam, these temperatures being applied through recordercontrollers, and pilot valves, to relays 32, 34, 67, 69. The resulting fluid pressure corresponding to the main steam supply temperature is, after passing through relay 32, combined in relay. 34 with the fluid pressure corresponding to the gas temperature, and, similarly, the output pressure from relay 69 corresponds to the combined gas and reheater steam temperatures. The output pressures from the combining relays 34, 69 control the water supplies to the spray attemperators 42, 60 as previously described and they are also applied to a relay 95 which selects the lower of the two pressures to control the amount of tilt of the burners 10. This last effect is obtained by feeding the input pressures in lines 35, 70 to the opposite sides of a diaphragm 96 and selecting, by means of valves 97, 98 actuated by diaphragm 96, the appropriate one of these pressures for application to the drive 20 of the burners. As the non- controlling steam temperature would then rise above its desired value, it is reduced by the action of the appropriate attemperator. Where a control according to the total heat available on a rate basis is desired, the air flow, as measured by a meter 75, Fig. 11, positions a movable core 76 of a transformer 77 fed with alternating current. The secondary coils 78 ... 80 of the transformer, of which 79 and 80 are in opposition, are shunted by potentiometers 81, 83, and the movable contacts of the potentiometers are connected through an amplifier 85 and are positioned by a gas temperature controller 22 and a reversible motor 86, respectively. When the network is driven from its normal balanced condition, the unbalanced signal is amplified and drives the motor to position contact 84 to rebalance the network and also actuate a pilot valve 88 which gives a control pressure in line 89. This pressure is combined in relay 34 with a pressure corresponding to the final steam temperature to give an output pressure in line 35 which actuates the driving device 20 to tilt the burners 10. The gas temperatures may be determined by the thermocouples instead of bolometers. The various relays are the same as, or modifications of, the relay described in Specification 461,389 [Group XXIX]. The vapour generator and vapour heating units may be fired by pulverized fuel, by gas or by atomized oil. Specifications 654,976 [Group XXXVII], 683,696 [Group XXIX], 707,225, 707,226 [both in Group XL(b)] and 756,919 [Group XXIX] also are referred to.