Method of and means for safeguarding installations for collecting gas in the unburnt state at the exit from an oxygen blast convertor

摘要

1,006,436. Metallurgical converters; chimneys. INSTITUT DE RECHERCHES DE LA SIDERUGIE FRANCAISE. July 2, 1962 [July 27, 1961], No. 25211/62. Headings F4B and F4J. At starting and stopping of the oxygen blowing of a converter 1 a plug of inert gas is formed to separate the streams of air and carbon monoxide in the exhaust system leading from the converter hood 4. The converter is blown through a lance 5, the flow of oxygen being controlled by a valve 14 regulated by a pneumatic regulator 15 in conjunction with a flowmeter 16, and during blowing exhaust gases pass through the hood 4, a duct 5, a filter 6 and a blower 7 to a burner 8. Pressure in the hood 4 is maintained at atmospheric to prevent ingress of air by a butterfly valve 9 in the exhaust system controlled by a pneumatic regulator 10 associated with a differential pressure gauge 12 which compares atmospheric pressure with the pressure in the hood 4. At stoppage a timer 17 causes valve 9 to open fully and oxygen valve 14 to close, and opens a duet by-passing the valve 14 to give a reduced flow of oxygen. Under these conditions air is admitted to the hood and combines with carbon monoxide from the converter to form carbon dioxide. After a few seconds the timer 17 stops the flow of oxygen so that air alone passes through the exhaust system, separated from the carbon monoxide stream preceding it by a plug of carbon dioxide. At starting, the timer 17 holds valve 9 fully open so that air is admitted to the hood 4 thus forming carbon dioxide. After a few seconds valve 9 is placed under control of the regulator 10 so that carbon monoxide alone passes through the exhaust system. If at any time an emergency stoppage of oxygen blast is necessary, the inert plug is formed by admitting nitrogen to the hood from cylinders 19 through valves 20 controlled by the emergency stoppage mechanism (not shown). In an alternative construction (not shown) the pressure in the hood is always maintained below atmospheric and a sliding sleeve forms a seal between the hood and the converter which sleeve is opened for a few seconds at starting and stopping to allow air to enter the hood. Control system.-The timer 17 has four cams A, B, C and D driven by an electric motor 17a. Fig. 2 shows the positions of the cams immediately before starting. A button 17b is pressed to energize the motor 17a and cam A then closes contacts 17c to maintain energization of the motor for half a revolution of the cam-shaft. Cam C closes contacts 17d which opens the pneumatically operated valve 14 in the oxygen supply by opening a valve 26 to place valve 14 in communication with the regulator 15, and closing a valve 27 in a line connecting valve 14 with atmosphere. Initially the pneumatically operated butterfly valve 9 is in communication with an air line 28 which maintains valve 9 fully open and a valve 30 is closed to prevent communication with regulator 10, during which time air is drawn into the hood. After a few seconds cam B closes contacts 17c which closes a valve 29 in the air line 28 and opens valve 30 thus placing the valve 9 under the control of the regulator 10. The motor 17a stops when cam A has completed half a revolution. To stop oxygen blowing, the motor is again started when cam B fully opens butterfly valve 9, cam C places oxygen valve 14 in communication with the atmosphere thus closing it and cam D closes contacts 17f thus opening a valve 33 in a duct by-passing the oxygen valve 14. After a few seconds cam D closes valve 33.