GB951283A - Combustion air system for continuous re-heating furnace - Google Patents

Abstract

951,283. Continuous metal heating furnaces; supplying combustion air. LOFTUS ENGINEERING CORPORATION. Feb. 21, 1962 [June 8, 1961], No. 6792/62. Heading F4B. In a method of feeding combustion air to a continuous re-heating furnace having a plurality of combustion zones each with a plurality of burners, the combustion air is propelled through a heat exchanger and taken in two parallel streams longitudinally of the furnace in ducts which deliver the air into transversely extending headers spaced longitudinally of the furnace, the headers being connected to manifolds each feeding a bank of burners. In the form shown the furnace has combustion zones 2, 3, 4 fired respectively by burners 8, 9 and 10, 11 and 12. The burners are respectively connected to combustion air manifolds 31, 31A ... 31D by pipes 37. The air manifolds are respectively connected by longitudinal connector ducts 30, 34, 35 to the mid-portions of transversely extending longitudinally spaced headers 28, 29, 33 which connect with upper and lower transversely spaced ducts 26, 27 extending longitudinally on each side of the furnace. The ducts 26, 27 are fed with air which enters at an inlet 17 from a blower and passes to a cold air manifold 16 whence it flows through a number of heat exchanger sections 13 arranged in the form of a recuperator in two ducts carrying the waste gases from the furnace to an uptake stack to two manifolds 20 arranged one on each side of the furnace from which vertical headers depend and connect with the ducts 26, 27. The manifold 20 is provided with a pressure bleed off valve 23 to ensure a sufficient flow of air through the heat exchanger elements to keep the metal temperature therein at safe limits when the required air demand at the burners is low. The connector ducts 30, 34, 35 are provided with air-flow metering orifices and on the downstream side of the orifices with air control valves 36, 36A ... 36D thus enabling the air flow to each burner manifold to be measured and controlled in accordance with the desired firing rate. The pressure of the air delivered to the system is controlled by means of a butterfly valve mounted in the duct 17 or set of movable louvres (not shown) mounted either side of the inlet or outlet of the blower feeding air into the duct 17 and controlled by a suitable pressure control apparatus.