Puddling furnace

“ The “Reverberatory furnace” is a modification of the wind furnace, and is used to throw heat on to the surface of substances, as in roasting ores of metals, to drive off the sulphur, arsenic, &c., or in the making of soda, litharge, and other processes where the admission of hot air with the flame is either beneficial, or at least not detrimental; fig. 1 shows the construction of this kind of furnace. Blast furnaces are for the production of the very highest degrees of temperature, and in these the air is forced into the fire by blowing machines or bellows, often worked by steam-engines ”

“ Two years ago No. 1 broke out and the molten metal caught and burned to death one of our men and injured several others. ‘Hanging’ does not occur when the furnace is working right, but failure of the charge to come down evenly is very serious sometimes. A blast furnace is like a coquette ”

“ A blast-furnace, once lit, remains burning till the end of its existence. I got inside her, and was delighted to satisfy a deep-seated curiosity: we crawled in the cinder notch. The hearth of the furnace lay six or eight feet below the brick flooring, and the effect of standing inside, with the fourteen round blowpipe holes admitting a little sunlight, was like being in a round ship's cabin, with fourteen portholes, except that the hollow furnace shot up to dark distances that the light didn't penetrate. ”

“ When they got ready to draw the charge,—that's when the red-hot iron is about to flow out of the furnace, you know, the outlet got clogged. That's a bad thing to happen to a furnace; for if a chill should set in, the whole plant would be ruined. ”

“ Each is charged with its covered pot full of blistered steel with coal to match. Their lidded mouths dull the roaring sound of the terrible combustion, but the furnace-men show by their looks the intensity of the heat. The pouring-off sight is really thrilling. When the lid is removed from each furnace, and the pot of molten metal lifted out by a pair of long-handled tongs with rounded jaws, even a spectator must have steady nerves to look at it. ”

“ The burners should be so located that the flames from individual burners do not interfere nor impinge to any extent on the side walls of the furnace, an even distribution of heat being secured in this manner. ”

“ The heat that the worker about these furnaces must face may be divided in general into two classes: there is first that heat due to the flame and hot gases that the blast in the furnaces forces out onto a man's body and face. In the majority of furnaces Page 193 this is by far the most discomforting, and care must be taken to fend it and turn it behind a suitable shield. The second class is the radiant heat, discharged as light from the glowing interior of the furnace. ”

“ Everybody douses his face and hands with water to cool off, and sits down for twenty minutes. Making back-wall has affinities with stoking, only it's hotter while it lasts. The day is made up of jobs like these—shoveling manganese at tap-time, "making bottom," bringing up mud and dolomite in wheelbarrows for fixing the spout, hauling fallen bricks out of the furnace. ”

“ The first-helper gives her that, passing up and down every few minutes to look through the peepholes in her furnace-doors. He puts his glasses down on his nose, inspects the brew, and notices if her stomach's in good shape. If the bricks get as red as the gas flame, she's burning the living lining out of her. But he keeps the gas blowing in her ends, as hot as she'll stand it without a holler. On [Pg 34] either end the gas, and on top of it the air. The first-helper, who is cook of the furnace, makes a proper mixture out of them. ”

“ I picked up my shovel, and shoved it into the dolomite pile, with a slight pressure of knee against right forearm that eases your back. The thermometer in the shade outside was 95°. I wondered vaguely how much it was where Nick stood, with the doors open in his face.
We walked back together after the front-wall to the trough of water.
"Not bad when you get good furnace, good first-helper," he said. "Fred good boy, but furnace no good. A man got to watch himself on this job," he went on bitterly; "he pull himself to pieces." ”

“ The withdrawal of the hot slag and matte abstracts much of the heat of the furnace, and the cold charge which is fed in, not only cools the furnace hearth on which it rests, but being a poor conductor, prevents the heat from again penetrating through it to the hearth and to the undermost portion of the charge. ”

“ It can be applied in a working pit, and is certain and steady in its operation. The only defect of the furnace is, its liability to explosion when the current of air by which it is supplied, becomes so charged with inflammable air, in its passage through the workings, as to be explosive. This objection to the furnace is, however, greatly obviated by what I call the system of double ventilation. The principle of this system is to supply the furnace with a current of air, which is not exposed to the hazard of being contaminated by an admixture of inflammable air. ”

“ The air previously passes through a series of cast-iron pipes, heated by the combustion of the carbonic oxide obtained from the upper parts of the furnace, where it is formed as in a ‘gas-producer.’ The blast furnace acts continuously until it is worn out; the iron is tapped off twice a day, and the furnace is allowed to cool a little from time to time so as not to be spoilt by the increasing heat, and to enable it to withstand long usage. ”

“ But in the crucible and the open-hearth processes the temperature attainable is limited by the danger of melting the furnace itself, both because some essential parts of it, which, unfortunately, are of a destructible shape, are placed most unfavourably in that they are surrounded by the heat on all sides, and because the furnace is necessarily hotter than the steel made within it. ”

“ The burning mine, hundreds of feet down in the ground, was in effect to be his subsidiary furnace—his gas-producer.
These unburned gases, from the producer, pass, hot, into the furnace proper; either directly or sometimes after being conveyed a considerable distance—as they would have to be according to Jimmy’s plan. In this latter event they cool off, but are heated up again by the waste heat of the furnace. ”

“ At the same time, the effect of this peculiarity of construction is to cause the gases themselves to move slowly through the flues, so that they may part with their useful heat before escaping into the atmosphere. The force of draught at the furnace is such that a high and constant temperature is obtained and efficiency of combustion insured, while all unpleasant odors inherent in town garbage are destroyed. ”

“ Small articles are readily fired in a Fletcher's crucible furnace supplied with a gas blow-pipe; the furnace is heated gradually to begin with. When a dull red heat is attained, the full power of the blast may be turned on, and the furnace kept at its maximum temperature for three or four hours at least, though on an emergency shorter periods may be made to do. ”

“ You pick up a shovel and run into a spell of fairly hot work for three quarters of an hour. On another day you may loaf for fifteen minutes before anything starts. After front-wall, you take a drink from the water fountain behind your furnace, and wash your arms, which have got burned a little, and your face, in a trough of water. A "clean-up" [Pg 146] job follows in front of the furnace, which means shoveling slag—still hot—down the slag-hole for ten minutes, and loading cold pieces of scrap, which have fallen on the floor, into a box. ”

“ In houses heated by furnaces or other modern systems, lack of a damper in the fireplace flue may interfere with uniform heating, particularly in very cold windy weather, whether or not there is a fire on the hearth. When air heated by the furnace is carried up the chimney there is a waste of the furnace fuel, but a damper partially open serves a slow fire of hardwood without smoking the room or wasting heated air from the main heating system. ”

“ But fortunately these older types of furnaces are being rapidly replaced by the newer forms in which the danger to life, at least from gas and explosions, is minimized. And even in the older furnaces, improvements in the structure of the bell and in methods of filling have greatly lessened the dangers.
In the modern type of blast-furnace the work at the top formerly performed by men on the staging is accomplished entirely by machinery. The general appearance of these furnaces is that of huge iron pipes or kettles mounted on several iron legs. ”

“ As these particles ascend it leaves a space which the cooler air eagerly hastens to fill; in the boiler furnace, the hot air pushing its way up the chimney, is replaced through the grate bars with cool, fresh air.
It is the mingling of this fresh air with the combustibles that produces heat, and the power of the draught is absolutely necessary to the reliable operation of the furnace.
An excess of draught can be corrected by the use of a damper or even by the closing of the ash pit doors, but no more unhappy position for an engineer can be imagined than a deficiency of draught. ”

“ The furnace should be of brick, with double iron doors, and a damper above in the first part of the flue, and a valve in the door of the ashpit for regulating the draught. In determining the dimensions it is well to remember that a comparatively large fire burning slowly is to be preferred to a small fire with a brisk draught. But here, again, the nature of the fuel to be burnt must also be considered, for if it is of a kind that produces little smoke, the opening in front may be dispensed with. ”

“ Owing to the great danger from fire incident to burning charcoal or sulphur in open pans, a special furnace provided with means for forcing the gas into the compartments of vessels or buildings is generally employed. ”

“ In the melting furnaces the gas is admitted at each end of the furnace and mixes with air which has previously been heated by passing through flues in the brickwork. The combustion thus takes place in the melting chamber directly above the crucible pots, and produces an intense and easily regulated heat. The blowing furnaces are even simpler. They merely provide a chamber of brickwork with suitable openings in the sides, and immediately under each opening a large Bunsen burner supplied with natural gas and drawing the requisite air directly from the atmosphere. ”

“ The gas on leaving the producer passes along fire-brick flues or passages to the furnace proper; the path which it is now caused to take varies somewhat according to the arrangement of the furnace in question. Modern gas-fired furnaces usually belong to one of two distinct types according to the manner in which the heat of the escaping products of combustion is utilised for heating the incoming gas and air ”

“ The forehearth is that part of the crucible projecting in front of the fire-walls of the furnace. Crucible furnaces are those shaft furnaces in which the curcible is entirely one the inside. They are divided into eye-crucible furnaces and tap-crucible furnaces. The former have an eye in the front wall from which the slag flows continuously, the metal and matter being tapped off at intervals into basins. ”

“ The difficulty is that with furnaces of the “open-fire” type the rise of dust is so great that the gauze screens soon become clogged, especially as the slight tarry matter in the smoke condenses on the gauze, causing the dust to adhere. With the better types of furnaces, the employment of gauze screens is not necessary, as there should be very little rise of dust. It is sufficient to use only expanded metal, to prevent any displaced pieces of rubber falling into the furnace chamber. ”

“ In the exterior wall, near its bottom, and opening on the lead flat, is a furnace of the commonest possible construction, and capable, from its free draught, of burning the commonest combustible material—such as inferior coal, coal screenings, coke, cinders, and sawdust. This furnace, encased in brickwork, is carried obliquely for a distance of four or five feet into the Calidarium; and its flue, following the angle of the floor, makes the circuit of the apartment. ”

“ The furnace is made to rock forward, and spill out a few hundred pounds of the slag that floats on top. A short "buggy" car runs under, to catch the flow. But somebody had blundered—no buggy was there when the slag came.
"Get him up queek, and let buggy come back for nex' time," explained an Italian with moustachios, who carried the pick. "Huh, whatze matter goddam first-helper, letta furnace go?" ”

“ The hotter he can let the gas through, the quicker the brew is cooked, and the more "tonnage" he'll make that week.
"Get me thirty thousand pounds," said the first-helper when I was on the furnace that first night. Fifteen tons of molten metal! I was undecided whether to bring it in a dipper or in my hat. But it's no more than running upstairs for a handkerchief in the bureau. You climb to a platform near the blower, where the stuff is made, and find a man there with a book. ”

“ I have learned, of late, from men of experience in these matters, why it is desirable to continue the heat—it is because no furnace can be heated up for two or three weeks, and then blow out, or stop, without risk of spoiling the furnace, or destroying its lining; and it frequently so injures the furnace, that it has to be rebuilt, or at least a portion of it. Hence, when it costs from one to five thousand dollars to prepare a furnace to bear a long blast, it is a great loss to any company to have it blow out in a short time. ”