GB1017505A - Process and apparatus for the non-combustible recovery of waste gases emanating from the refinery of pig iron by oxygen - Google Patents

Abstract

1,017,505. Controlling draught; confining and removing dust and fumes in industrial processes. INSTITUT DE RECHERCHES DE LA SIDERURGIE FRANCAISE. July 20, 1962 [July 28, 1961; Aug. 18, 1961; March 15, 1962], No. 27952/62. Headings F4B and F4X. [Also in Division G3] In a process for the non-combustible recovery of gases from the refining of pig iron by pure oxygen using a hood 2 at a predetermined distance above a converter 1, and a discharge pipe 5 for the collected gases wherein the draught is regulated to prevent air leaks and gas escapes at the hood, the temperature at at least one level in the lower part of the hood is measured to determine the position of the gas level, and the draught controlling means in the discharge pipe is operated so as to maintain the measured temperature within predetermined limits, and thus maintain the gas level at a substantially constant position. As shown, oxygen, possibly with pulverulent materials in suspension, is blown on to the pig iron 4 through a water-cooled lance 3, the resulting gases passing from the converter 1 into the hood 2, also water cooled, and through the discharge pipe 5 to a wet dust collector 6, and an exhauster fan 7 to a combustion chimney 8. Tubes 17 rising from points spaced around the lower part of the hood 2 are connected to a common suction pipe 18 and contain two inertia thermocouples 10a. The signals from the thermocouples are used to control a damper 9 in the discharge pipe, by means of a suitable control system (see Division G3) so that if the draught is insufficient, and the hot gases from the converter tend to impinge lower down in the hood and to spill into the atmosphere, the increased temperature at the thermocouples causes the damper to open, while excessive draught, which would tend to draw in ambient air and lead to combustion in the recovery system, causes lower thermocouple temperatures and hence, an increased blocking of the draught by the damper 9. To prevent spurious signals to the control system due to local heating caused by overflowing slag, thermocouples may be arranged to sense the temperatures at two levels in the hood, control being in response to one level only, except when the temperature difference between the two levels becomes zero, or of opposite sign to normal, in which case the control is blocked, e.g. by an electromagnet which cuts the damper 9 off from the control system and holds it in position. An alternative method of detecting gas leakage from the hood is to place flame-detecting means, such as thermocouples, round the outside of the lower portion of the hood 2, Fig. 1, not shown, so that when these detect a higher than normal temperature the damper 9 opening is increased. The signals from the thermocouples are summed, and control is only effected when the total e.m.f. rises above a predetermined value.