GB940653A - Improvements in control installations for regeneratively heated hot blast stoves - Google Patents

Abstract

940,653. Thermal regenerators. ZIMMERMANN & JANSEN G.m.b.H. Nov. 6, 1959 [July 16, 1959], No. 37759/59. Heading F4K. In a blast furnace plant having at least two stoves supplying hot blast to the furnace, the change over from one stove to another is automatically initiated by a change in the temperature of the blast. The regulators 2, 4 for the amount of cold blast fed to the plant and the temperature of the blast at the furnace bustle pipe HWR are linked through a regulator 5 to control the gas supply valve 22 and combustion air valve 25 for each stove, as claimed in Divisional Specification 940,654 [Division F4]. Thermocouples 10, 11, and 26 in the stove hot blast outlet, the stove flue gas outlet and in the dome of the stove respectively provide signals for changing the stove state to " gas," " blast " or " boxed," as does a limit switch 6 closed when the damper 31, controlling the amount of cold air added to the stove output in accordance with the temperature in the bustle pipe HWR, is closed. When a stove I on " blast " is approaching the end of its useful blast period, the hot blast output thermocouple 10, or the stove dome thermocouple 26 provide signals which are transmitted through the central control 12 of the stove I to the programme control 13 of a second stove II, or " gas " or " boxed " to change this stove II to " blast." The closing of the switch 6 also causes the stove II to be changed to " blast." The arrangement is such that the stove I cannot be changed to " gas " until another stove is on " blast," and that the stove which has been longest on " gas " or " boxed " is selected to change to " blast." A delayed action relay prevents the stove just changed to " blast " changing back immediately to " gas " and switches operated by opening and closing of the valves of each stove ensure that these valves are operated in the correct order when the closing of a relay initiates the changeover. A relay is actuated to " box " a stove in response to an undesirable rise in temperature at the dome thermocouple 26 or the flue gas thermocouple 11. In a three stove system, each stove has an A/M switch by which the stove can be taken out of the automatic operation, so that the remaining two stoves can then operate automatically, or, by operating the A/M switches of all three stoves, they can be operated by means of push-buttons PB at each central control. Switches are provided to take a stove out of operation completely. When two stoves only are operated automatically, the automatic regulation of the gas and air supply to the stove on " gas " is taken out of circuit, so that the stoves can operate at their fullest efficiency.