necessary heating of the air-blast which is used in the manufacturing of iron, and when this economy had been successfully accomplished and only a fraction of the available gas was used, the possible saving of fuel under the steam-boilers, which supplied the blast-driving engines, was recognized. From this, with nearly fifty per cent of the daily production of gas still wasting itself, the devising of other means for using this big balance became the study of the inventors. A blast-furnace which turns out a product of 400 tons of pig-iron in the course of each twenty-four hours of its operation produces gas which will furnish 10,000 horse-power. At the South Chicago plant of the Illinois Steel Company, six furnaces out of the eleven which are operated, produce twenty-six hundred tons of pig in every twentyfour hours and are capable of providing the great total of 65,000 horse-power, when the gas is completely utilized. The plant at Gary which is now under actual construction includes eight blastfurnaces, which will manufacture 3,600 tons of pig per twenty-four hours and will furnish the gas for the development of the huge power already mentionedone hundred thousand horse-power. The officials of the company are planning to double this capacity eventually, when the total power, produced at this plant, will equal half the entire gas-engine power so produced at present in Germany, or twothirds the power developed by all kinds and conditions of gas-engines at the present time in the United States. Practically all iron manufacturing plants in Germany are equipped with apparatus for utilizing the gas from the furnaces, yet her total horse-power from this source is but 400,000. England's total is now 22,000 horse-power, Belgium's 40,000, while France has 32,000. Gary alone will out-total all three of the last-named when her plant now building is completed, and this power will generate the electric energy which will roll two hundred thousand tons of steel ingots a month into rails, plates, structural shapes and merchant bars; will run hundreds of motors, ranging from the six-thousandhorse-power colossus to the little toy-like machine which only operates its big brother's controlling switches; will unload boats, put ore in stock-piles and transfer it from stock-pile to furnace; will keep scores of auxiliary machines whirring and will abundantly provide for practically all public utilities in the town itself. Gary will be virtually without a steam-engine. The method of handling the gas is the feature of the plan that has made the ONE OF THE HUGE GAS ENGINES WHICH WILL RUN THE STEEL MILLS AT GARY. enormous economy possible. In the top of each blast-furnace, where conditions necessarily attending the manufacture of the iron have caused the gas to collect and where it cannot burn because of the limited supply of oxygen, an outlet for its escape has been provided. This outlet leads into a huge pipe capable of carrying the entire gas-product of the furnace. When the gas first leaves the furnace, it is full of dust which has risen from the coke, ore and limestone in the furnace, and is quite unfit to enter the cylinders of any engine. cleansed. Its first course, therefore, is It must be downward through the huge pipe, into a great dry tank, a dry-cleaner, as it is called. Here the force of gravitation arrests the larger particles of dust and dirt, which drop to the bottom of the tank. The gas then rises and what is called the primary washer, a passes into tank similar to the first, but containing water in the lower portion, against the surface of which the gas flows, leaving upon it still more of its dust-burden. The gas then rises once more and passes through a continuation of the big main to a point where the pipe is tapped and some thirty per cent of it is turned aside to the great "stoves" where the air-blast for the furnaces is heated. Each furnace uses about forty-thousand cubic feet of air per minute under a pressure of from ten to fifteen pounds, and the first use made of the newly saved gas is to supply the heat for this blast. furnace. They are huge affairs, each alFour of the stoves are provided for each most as large as the furnace itself, and CLOSE VIEW OF THE BLAST-HEATING STOVES WITH PARTIALLY COMPLETED GAS-PIPING. one of them is constantly in use, while a second and third are heating and the fourth is being cleaned. The gas is burned inside of these stoves, till the brick lining is white-hot, when the gas is shut off and the air-blast is turned through, heating from the fiery brick. The seventy per cent of the gas in the main passes on after the stove-supply has been withdrawn, till it reaches a power-house, where it supplies fuel for the production of steam, for heating the buildings and for running the only steam-engines in the plant-insignificant compared with the main power-plantwhich operate a spare steam-blower and the pressure and other pumps. These engines are also used for starting the furnaces before the gas takes the burden of work upon itself, and the little plant con sumes about seven and one-half per cent of the gas. A third cleaning process is then provided, which, with the primary cleaners, uses up about two and one-half per cent of the gas supply. A machine called the Thiesen washer, after its inventor, gives the big gas current a scrubbing. It consists of a drum revolving inside a shield and armed with a series of paddle-like blades. The gas is turned in between the drum and the shield, while a stream of water is spread into a film on the inside of the shield by centrifugal motion. The whirling drum throws the impurities, which the gas still holds, out against the water-film, where they are caught and held. The Thiesen washer also puts the one-half per cent, and the balance remaining for the big engines is therefore forty-five per cent of the whole volume produced, which amounts to ten million cubic feet of gas per hour. The whole plant of the Indiana company which is now building at Gary is to cost $75,000,000. This includes the entire steel mills, furnaces, power-plant and buildings. If the value of a single horsepower may be roughly estimated at twenty dollars per year, the saving ac complished by the complete utilization of the blast-furnace gas and the production of 100,000 horse-power from it, is ap proximately $2,000,000, or about two and two-thirds per cent on the total investment. When the number of furnaces is CYLINDER OF ONE OF THE THIRTY-THREE 3,000 HORSE-POWER GAS ENGINES, IN BUILDING FOR THE GARY PLANT. gas under pressure to a degree which enables it, immediately after this final washing, to enter the storage tanks. The supply for the engines, both in the blastblowing plant and in the main power plant, is drawn from these storage tanks, and the gas is exploded in the cylinders, exactly as in all gas-engines. The blowing-engines consume about twelve and doubled the percentage will remain the same, and though no figures as to the cost of the power-plant itself are given out, it requires no deep reasoning to understand the tremendous importance of the economy. The plant is the largest gas-power plant of any kind in the world, and two years hence will be nearing completion, if it is not actually finished. |