Patent GB-935463-A (GB)
Title: Control apparatus for waste heat boiler
Inventor: TOWNSEND ALBERT JOHN
IPC: F01K1/00
Filed: 1960-12-12
Abstract: 935,463. Waste heat steam boilers. HEAD WRIGHTSON & CO. Ltd. March 9, 1962 [Dec. 12, 1960], No. 42735/60. Class 123 (2). In a control apparatus for maintaining the output of superheated steam from a waste heat boiler heated intermittently, for example, by the blow gas from a steel making converter, at a constant flow rate to a site main, which installation includes an accumulator for the storage of steam in excess of the site main requirements and a control valve normally closed for diverting excess steam to the accumulator, rate of flow measuring mechanisms are arranged in the main steam supply line, one mechanism being located up-stream of the boiler superheater to monitor the rate of flow of saturated steam leaving the boiler and the other being located down-stream of the diversion to the accumulator to monitor the rate of flow of superheated steam to the site main and a computer is provided for co-ordinating a signal received from each measuring mechanism and for transmitting a signal to the diversion control valve, whereby said valve, when an excess of steam occurs, will open to admit steam to the accumulator. In the form shown, the control apparatus is applied to the waste heat boiler system for a steel making converter described in Specification 935,462. The control means consists of a flow transmitter 11 positioned in the saturated steam line 1 and a flow controller 12 positioned in the section 2c of the site main 2, both adapted to transmit signals to a computer 13 the output signal of which actuates a control valve 4 in a diversion line 3 to an accumulator, the valve being normally closed. At the commencement of the converter blow the rate of increase of the heat input to the boiler is high, an anticipatory signal is transmitted by the flow transmitter 11 to the computer 13, as the rate of steam output rises so as to cause the control valve 4 to open a proportional amount, thus diverting the excess steam to the accumulator. As the steam proceeds through the circuit it reaches the flow controller 12. This controller compares continuously the actual rate of flow in the site main to the desired rate of flow and sends a signal to the computer 13 which will trim, if necessary, its output signal to the valve 4. Should a large amount of excess steam be generated and the accumulator approach a full condition a pressure-controlled valve 5 will limit the flow into the accumulator. As a result the rate of flow of steam will momentarily increase in the section 2B of the steam main 2. This increase will be sensed by the controller 12 and the computer 13 will give out a split range signal which will cause the valve 4 to open fully and also cause the valve 10 in the flow-down line 9 to open a controlled amount according to the strength of the signal. As the rate of flow decreases the valves 4 and 10 will return to their normal position. The control valve 8 is governed to discharge the accumulator over a predetermined period by means of a temperature controller 14 which receives a signal from a temperature transmitter 15 in the boiler drum feed water line 7. In order to control the supply of superheated steam at a constant temperature an attemperator controlled by a valve 17 is provided. A temperature controller 19 downstream of the superheaters sends a signal to a computer 20 which also receives a signal from the flow transmitter 11. The computer 20 co-ordinates these signals and transmits a signal to actuate the valve 17 admitting water to the attemperator.