There are at present two reverberatory furnaces, 19x12, constructed on a concrete base, 3 ft. 6 in. thick, on top of which are 24 in. of silica. The walls of the furnaces are made of silica brick 2 ft. 10 in. thick, outside of which are 5 in. of fire clay brick.
These furnaces have shown a capacity of 400 tons per day of 10 hours, making 40 to 42 per cent of matte, the slag averaging from 43 to 45 per cent SiO2, 28 to 30 per cent Fe, and 7 to 10 per cent CaO.
Three oil burners of the Steptoe type are required, the oil being atomized with air, supplied by two Root blowers, having a capacity of 3600 cu. ft. per minute at 48 oz. pressure.
Two charges of 5% tons each are dropped in the furnace every 30 minutes without interfering with the operation of the burners.
The draft is regulated so as to have the flame reach the middle of the furnace, the shaft readings in inches of water being 0.2 at the doors, .08 at the throat, 1.6 in the main flue and 0.9 at the base of the stack.
The oil consumption per furnace is from 12,500 to 13,500 gal. per day when smelting from 350 to 400 tons of charge.
The gases from the furnaces pass into a silica brick flue, 8x19 ft., and are then distributed to a bat tery of Sterling waste heat boilers. There are six boilers, five of which are in use when the two furnaces are in operation.
A thermal efficiency of about 35 per cent is ob tained in steam from the oil burned in the furnaces.
At the El Paso smelter oil is used as fuel in the reverbatory furnaces. They are 19x100 ft., and have a capacity of about 350 tons per day. The burners are "Home-Made Type," and from general appearances are not very efficient. No data could be obtained re garding the oil used per charge.
The matte averages 42 to 45 per cent copper, and has run as high as 55 per cent.
Fettling of the reverbatories is done with high silica, copper sulphides, ores averaging 70 per .cent S102, 2 per cent Fe, 3 per cent S, 7 per cent Cu. The fettling is thrown in at the side doors, except at the bridge, where there are fettling hoppers that permit the material to be dropped in through the roof.
Mining companies as a rule are quick to adopt new and improved machinery, but they do not seem to "get on to" the latest developments in oil burning machinery. The pressure type of oil burner would show wonderful savings, and improve the furnace con ditions in reverbatory furnace to such an extent as to surprise the general managers, but the writer has no knowledge of any being in use at this writing.
In the roasting furnaces the old type burners are still in use, while we have a new rotary oil burner that might have been made to order for such furnaces. Still the mining companies have evidently not discov ered this type of burner. The users of mechanical roasting furnaces would do well to investigate the rotary burner.
As explained in a previous installment, it is dif ficult to use oil as a fuel for blast furnaces. Many engineers have attempted to design a blast furnace in which this cheap fuel could be used, one of the first of these experiments to come to the attention of the writer was conducted at Los Angeles by Mr. E. Riverall. Fig. 68 shows sectional views of his fur nace for smelting ore with oil.
The ore and flux are introduced through a charg ing door directly under the stack, and pass down the inclined bottom of the furnace, the molten metal and slag being collected in the crucible at the lower end, from which they can be capped off. The oil is intro duced with steam, through a number of jets placed on the top of the furnace as shown. The furnace de scribed is 40 ft. in length and 2 ft. in the clear, inside. The inventor points out that during the past decade numerous attempts have been made to accomplish this process. It is true, pig iron has been secured by ex perimenters with oil as fuel, but in no case has more than 150 lb. of the charge been reduced at one time, and even then coke or charcoal had to be introduced to the extent of 10 per cent, or thereabouts, in order to bring about the necessary chemical reaction. Here tofore all effort to produce this important material in commercial quantities, using only crude oil as fuel, have failed, became of the apparently insurmount able difficulties in the way. Chief among these was the getting rid of oxygen in the iron ores, and the application of the heat directly upon the entire body of the ore to be reduced. This process is both simple and inexpensive, being less complicated than the cupola or upright smelter, and requiring none of the cumbersome machinery incidental to the hoisting of both ore and fuel to the top of the flue.
furnace is first brought up to the required tempera ture, all burners being used. The air required for the blast is furnished by means of an electrically driven No. 4 Root blower, an air pressure of 8 oz. being used while heating up the furnace. After about 40 minutes the charge is introduced in the regular manner, and the air pressure increased to 14 oz. The tempera ture of the furnace can be easily regulated ; white cast iron requires about 2100 degrees F., and gray cast iron about 2300 degrees F. The capacity of this fur nace is 4 tons per hour ; the amount of oil consumed is 20 gal. per ton of castings. The operation has been completely successful, melting each day the amount of iron required. Not only is money saved, but val uable space and labor as well. The molders do not have to wait for a heat, for by the use of the auxiliary burner the charge can be kept ready to pour for many hours.