Blast furnace plant drawings
Cross section through "A" furnace.
The skip hoist house is to the left of the furnace and a skip is shown at top and bottom positions. The skip dumped the charge into the breeches chute, McKee distributor, small bell, and big bell in sequence. The internal shape of the stock bins is shown and the scale car running on tracks 75ft1in. from the centre of the furnace. The scale car extracted materials from the bunkers according to specification and weighed them. The coke (grizzlie) screens are just to the left of the scale car, their purpose was to separate out fine coke dust (called coke breeze). If left, the dust would have a negative effect on gas flow and erosion. There were three tracks for hopper cars on top of the stock bins (bunkers).
The McKee distributor was designed by Arthur G. McKee & Co. of Cleveland Ohio. The skips dumped into a fixed receiving hopper above the rotating hopper. This and the small bell revolved via a motor driven reduction gear driving a circular rack fixed on the cast steel plate carrying the hopper. The plate is supported by a ball race. This arrangement promoted uniform distribution of the burden. The small bell and large bell were lowered alternately to drop the charge into the furnace with minimal escape of gas ad heat.
Gas Off-takes
The Replogle Steel Co. gas off-takes at the top of the furnace were an improvement on the usual arrangement of very tall off-takes which restrict the passage of solids with the gas.
These McKee designed off-takes diverted the flow of gas, with the least loss of energy, ejecting the dust out of the gas stream and into a trap from where it fell back down in to the furnace. There were four of these on each furnace.
Bosh and Hearth construction
The copper coolers were accommodated in brick housings built in the lining, and in the plan view, the relative position of the coolers are shown. Just at the tuyere level, an open water drain was arranged at intervals around the base of the furnace. Warm water from the coolers was led to these drains so that any potentially dangerous failure in the water cooling system was readily spotted.
The bustle pipe, supplying air to the tuyeres via pipe couplings surrounds the hearth. The tuyeres were water cooled copper nozzles that directed the hot air blast to the bosh. as the iron ore smelted, slag and iron collected in the bosh and were periodically drained or tapped, through the tap hole.
Cooler arrangement
This diagram represents the circular base of the furnace opened out and flattened. It represents the arrangement of copper coolers which were rather like reverse action radiators ( serving to absorb heat, not radiate it).
The cooling pipes coupled each copper cooler in groups of four, vertically. The coolers were wedge shaped copper castings with internal water channels. The bosh coolers lay horizontally in cast iron housings built in to the brickwork. The cast iron hearth coolers were arranged vertically around the hearth below the tuyere belt and were about 12 feet tall
Primary dustcatcher
The dustcatcher was a mild steel shell 25ft. in diameter with a conical bottom, domed top and refractory lining. Sometimes called a whirler the principle of operation is identical to many modern bagless domestic vacuum cleaners.
Dirty gas from the blast furnace top was guided by the downcomers to the inlet (inclined right). The sudden change of direction and reduction in velocity and pressure caused the dust to fall out of the gas flow.
Relatively clean gas exited the top through a larger diameter pipe which could be utilised in the stoves and in the boiler house.
Secondary dustcatcher
Gas was directed to the secondary unit in a horizontal direction. the gas whirled around the outer casing, 25ft. in diameter and came into contact with a sheet of water. The water curtain extended some 270 degrees around the cleaner. A central tube was fitted to take off the clean gas.
Both the dustcatchers were refractory lined to combat the action of the hard dust particles.
Refractory construction
The machine-pressed bricks used in construction measured 13.5 in. long by 3in. thick by 6in. wide. This drawing shows the size of the furnace and thickness of the refractory lining. CL Cinder notch refers to the Centre Line of the Cinder Notch (Slag Notch) through which the slag was extracted. The molten iron was tapped through a notch lower down.
General construction notes.
The diameter of the hearth is 17ft. 6in., of the bosh 21ft. 6in. and of the throat 16ft. 10in., with a total height of 90ft. The ores used are magnetites and the usual burden contains 46% iron, giving an average output of 3290 tons per week.
The approximate weights of materials charged per week are : Burden 7200 tons, Coke 3500 tons.
Good coke is available, and this, as well as all the ore, has to be transported by railroad. Stock bins are used for all materials, and scale cars are used for filling the skips. The charging gear consists of an inclined hoist carrying a double skip track. The skips discharge into a McKee distributor in which a small receiving bell is used, discharging eventually on to the large bell. The small bell with its hopper can be rotated. Owing to lack of space, the hoisting machine is arranged on the side of the furnace, remote from the hoist.
The bosh is banded with steel hoops (visible in the photo), the intermediate spaces being used to accommodate the bosh plate coolers. The hearth is protected with a strong steel casing inside which are fixed cooling plates 3 in. thick with water pipes cast in. The concrete foundation is brought up around the hearth and forms a further safeguard against break-outs. The working platform is provided by the top of the foundations, and is protected by a roof. Both iron and slag are dealt with in ladles.