Furnace 1)" of the Edgar Thomson works, built in 1882, was of different construction from either of the preceding. It was constructed with special regard to the better protection of the brick-work of hearth and bosh. The general dimensions were as follows: Ileight, 80 ft.: diameter of bosh, 23 ft.; diameter of hearth, 11 ft. 6 in. ; stock-line., 17 ft. ; bell, 11 ft.: cubical capacity, 21,478 ft. The bosh is placed at about the center of the stack. making very steep walls. The hearth is also made wider by 6 in. than in furnaces previously described. The hearth-walls are surrounded by east-iron plates with a coil inside for the circulation of water. Around the bottom of these plates is a gutter. through which waste water from the cooling plates flowed, affording better protection to the bottom of the hearth. Above this row of plates, at the tuyere breasts, is another circle of cooling plates, partially inserted in the brick-work. The walls of the bosh are incased in a jacket of wrought iron, in. in thickness. This jacket is bolted on to the mantle. The bosh-walls inside the jacket were made but 22i in. thick, so that the cooling effect of the air-currents on the jacket wonld prevent any very rapid wear of the brick-work. This furnace was put in blast in 1882. In the first 12 full months the output was 65,947 tons, on an average of 2.570 lbs. of coke per ton of iron, thus exceeding, by over 11,000 tons, the best output that had previously been obtained in the same time from any furnace at these works, and with a much smaller consump tion of fuel. The record for the best month dur ing this period was 6,131 tons, on a coke consump tion of 2,887 lbs. per ton of iron. The amount of air blown was 27,000 cub. ft. per min„ which was heated to an average temperature of 1,000°. The pressure, of blast. at the tuyeres varied between 9 and 10 lbs. After a blast. of 17 months' duration this furnace was blown out, having made a total output of 90,317 tons, on an average coke consump tion of 2.613 lbs. per ton of iron, Furnace " " was reconstructed in 1885. with the following dimensions: Height. 80 ft.; diameter of bosh. 20 ft.; diameter of hearth, 111 ft.: diameter of stock-line, 16 ft. 3 in. The bosh-walls had ant angle of 79°. and all the lines were joined by CIII'VeS. The cubic capacity was 10,680 ft. In February, 1885, the furnace was blown in.'' The volume of blast wits rapidly increased until, in the following month, it reached 31.000 cub. ft. per min. The blast entered the furnace through eight tnyeres. in. in diameter, :Ind was heated to an average tem perature of 1,2110 pressure at the luyeres was 81 lbs. The average monthly output fruin 'March to August, inclusive, sive, was 5,12 tons, 011 a coke con sumptirm of 2,871 lbs. per ton of iron. Attempts were made later to increase the economy by reduc ing the volume of blast to 28,000 cub. ft. As a result the output increased to an average of 6,050 tons per Month, on it coke consumption of 2,4911 lbs. per ton of iron.
This furnace was again reconstructed in 1887, the hearth being widened to 11 ft. diam eter, the bosh to 21 ft., and the stock-line reduced to 15 ft. The cubic capacity was increased to 17,230 ft. The furnace was " blown in " in March, 1887. On account of the brick-work in the bosh being very much worn, the furnace was blown out after a run of 2 years 7 months and 17 days—exclusive of the time the furnace was banked. The output for the blast was 203,050 tons, on an average coke consumption of 2,342 lbs. per ton of iron. The output for the first 12 full months was 72,554 tons, on a coke consumption of 2,230 lbs. For the second 12 months, during which no stoppage occurred, the output was 83,219 tons. The best output made in any one month was 7,680 tons. The furnace shown in Fig. 1 was built in 1886. The
total height is 80 ft.; the diameter of hearth, 11 ft.; the diameter of bosh, 23 ft. The bell is 12 ft. in diameter, and the stock-line 16 ft. The cubic capacity is 19,800 ft. There are 7 tuyems, each 6 in. in diameter. The furnace was started in October, 1886, and was in blast— exclusive of two stoppages-2 years 7 months and 10 days, and made in that time 224,795 tons of iron, on en average coke consumption of 2,317 lbs. The output for the first 12 full months was 88,940 tons on 2,150 lbs. of coke. The efficiency of the cooling plates on the bosh walls was very marked in this case. The exterior brick-work was in as good condition at the end of the blast as at the beginning. The interior of the boshes had widened out 18 in., but with such uniformity that the greatest variation did not exceed 2 in. From the bosh-line to the top of the furnace the wear was much greater. The furnace was relined and blown in again in September, 1889. The construction was the same in every particular, except that the diameter of the bosh was reduced to 22 ft., and the stock-line to 15 ft. 6 in. The lining runs straight from bosh to stock-line. This change reduced the cubic capacity to 18,200 ft. The same number and size of tuyeres are used. The volume of air blown is 25,000 cub. ft. per min., a reduction of 2.000 cub. ft. from that used in previous blast. The best output for any one week is 2,462 tons. The temperature of blast averages 1,100' and the pressure 9i lbs. The temperature of the escaping gases is 340°. Counting the time the furnace was running in the first blast, and up to the end of May, 1890, in the second blast, including also the time spent in relining, the period covered is 3 years and 5 months; and in that time this furnace has made an output of 301,205 tons, a record which is unparalleled. The ores used were from the Lake Superior region, and yield through the furnace 62 per cent of iron. The proportion of limestone carried was 28 per cent of the ore burden, and about 1,200 lbs. of cinder was made per ton of iron. The average analysis of the cinder is as follows: silica. 33 per cent ; alumina. 13 per cent.
In the period covered by the last decade there are three steps in the development of American blast-furnace practice that might be mentioned : first, in 1880, the introduction of rapid driving, with its large outputs and high fuel consumption ; second, in 1885, the produc tion of an equally large amount of iron with a low fuel consumption, by slow driving ; and third, in 1890, theproduction of nearly double that quantity of iron, on a low fuel consump tion, through rapid driving. An abstract of the results given by Mr. Gayley is shown in the following table: A Modern Blast-Furnace Plant.—One of the most recent complete blast-furnace plants is that of four furnaces built in 1890 at the South Chicago Works of the Illinois Steel Co., and known as Nos. 5, 6, 7. and 8. The furnaces are built in a line extending east and west, with the cast-houses branching off to the south, and they may be considered as constituting two separate plants of two furnaces each. The individuals of each pair are side by side, mid 126 ft. from center to center. Each furnace is 80 ft. high. Nos. 5 and 0 are similarly con structed, each having a bosh of 22 ft., hearth of 121 ft., and a stock-line of 16 ft. In No. 7 the bosh is 20 ft., but in other respects the lines are the same as in Nos. 5 and 6. No. 8 is considered, so far as the lines are concerned, as quite a radical change from the other three, for its bosh is only 194 ft.. hearth 13 ft., and stock-line 13i ft.. thus showing a tendency to spread out at the hearth and contract in the upper portions. Nos. 5 and 6 are built with five and No. 7 with nine rows of bosh-plates. Each furnace is supported by eight columns 20 ft.