22 to 24 hours, and with natural gas about 26 hours. From the foregoing it seems apparent that powdered coal gives results which are thermally satisfactory.

There is an accumulation of fine ash which must be removed from these furnaces at intervals. The length of these intervals will depend on the percentage of ash in the coal. When the coal has a low ash content the accumulation is removed once a month. In the standard type of furnace, where the heating chamber floor level is at general floor level, the disposal of the ash is of small moment, due to greater accessibility of both heating chamber and flues.

As is well known, in annealing malleable castings a fluctuating temperature must be avoided and at no time is it permissible to allow the temperature to fall below the critical range. To secure this control of the heat requires close regulation of both the fuel and the air to burn it. No trouble has been encountered in holding these conditions

constant.

A comparative record of costs for three fuels is as follows: Natural gas, 14,000,000 cu. ft., at 35c per 1000..$4900.00 Fuel oil, 105,000 gals. at 8c... .$8400.00 Powdered coal, 525 tons at $5.00 per ton.. ..$2625.00

The figure $5.00 given as the cost of powdered coal includes besides the coal all labor, power, etc. These costs are taken from actual practice and cover three separate months during each of which one of these fuels was burned.

In another malleable iron foundry where powdered coal is now burned in the annealing furnaces, a saving of 48 per cent has been effected in the quantity of fuel consumed. In this case the amount of powdered coal burned per ton of output is 450 pounds. The time to bring the furnace to temperature has been reduced from 24 to 36 hours required for hand firing, to 11 to 14 hours. When hand fired, there was always a difference in temperature in these furnaces of from 200 to 300 degrees between the front and rear. Today, when fired with powdered coal, this temperature is uniform. This is accounted for by the fact that the pressure in the furnace is equalized as it is impossible to obtain a uniform

temperature throughout the chamber unless the furnace is under a slight pressure. With stack draft and hand firing it is exceedingly difficult to avoid pulling in some cold air, especially at the door. This makes a cold streak and naturally it is impossible to secure a uniform temperature inder such conditions.

Statement of Advantages

The advantages of powdered coal for annealing may be ummarized as follows:

First. A reduction in fuel cost is obtained in comparison vith other fuels.

Second. It is easy to control the feed of coal which orresponds in this respect to gas or oil.

Third. There is a very considerable saving in labor ver hand-fired furnaces.

Fourth. The supply of coal is more abundant than oil r natural gas.

Besides malleable castings, the Pressed Steel Car Co. Iso manufactures steel castings. They are annealed in the ame furnace as the malleable castings. The temperature arried when annealing steel is 1660 degrees Fahr. One of iese furnaces was lighted at 3 p. m., July 15, and firing disontinued at 11 a. m., July 16, so that the total time required r the annealing was 20 hours. The coal consumption was 0 pounds per ton of metal.

Fig. 3 shows the tops of the furnaces and the pipes trough which the coal and air are delivered to the burners. he large spiral riveted pipe on top carries the coal, while te secondary air flows through the lower one. From both tese branch 2-inch wrought iron pipes. The latter are conted at their upper ends to the control valves, shown in te illustration, which regulate the flow of coal and air to the brners. Their lower ends terminate at the burner.

Principle of Distribution

The coal which passes through the upper pipe is of crse very fine, as it must be held in suspension throughout tl length of the pipe. The principle of distribution is as fows:

The coal is received in cars and after being dried is pulverized and then conveyed pneumatically to a substation at the foundry building. Here it is separated from the high pressure air and falls into a 25-ton bin. Two spiral screws feed the coal from this bin into a pipe connected to the suction side of fan. This fan has a capacity of 6000 cubic feet of air per minute. In the fan the fine coal is mixed with air in the proportion of 1 pound of coal to 60 cubic feet of air. This mixture is then forced through the pipes and delivered to the burners as desired by the furnace attendant. As is w we known, it requires at least 200 cubic feet of air to form a combustible mixture with one pound of coal.

There is, therefore, no danger of combustion until th necessary additional 140 cubic feet has been added at th burner. The ratio of 1 pound of coal to 60 cubic feet of ar is maintained automatically by a very simple electrical cor trivance. If desired, the ratio can be changed and the m chinery set to hold it constant.

There have been spasmodic attempts to apply powdere coal to air furnaces, but none of these have progressed b yond the experimental stage. I believe there is a very profitab field open in this connection and from what information can gather I do not see any insurmountable obstacles to i successful application. W. R. Bean presented a paper this subject at the Boston meeting. The results from t experiments cited in this paper substantiate the opinion th we will before long be burning powdered coal in melti furnaces.

A movement is now on foot, I believe, to standard and improve malleable iron annealing furnace constructio This certainly is a laudable movement, and if carried throu should insure beside a high quality of product an increa: efficiency of operation. It should lower the quantity and cof fuel per unit of output. Those behind this movement i find powdered coal admirably suited to fulfill the fuel: quirements in these furnaces.

For the information contained in this paper, I desire extend my thanks to C. H. Gale, superintendent of t foundry of the Pressed Steel Car Co.

Efficient Use of Pulverized Coal in Malleable Foundry Practice

By MILTON W. ARROWOOD, Chicago

There is probably no branch of industry that can realize greater benefit from the proper application of pulverized fuel than the malleable iron foundry. The economy in annealing ovens is very considerable and has been recognized for a number of years. The advantage of any efficient means of eliminating hand firing on air melting furnaces, is a matter that is hardly open to debate with any foundry superintendent. It is of interest, therefore, to examine the elements of the matter, considering the difficulties, in order to reach a rational conclusion as to what means may be employed to utilize pulverized fuel in annealing ovens and on melting furnaces, with maximum efficiency and satisfactory working conditions.

Preparation of the Fuel

It will not be the purpose of this paper to discuss in any detail the general processes of preparing coal for use in pulverized form, as it will be assumed that the coal has been properly prepared and brought to the furnace in proper condition and of approximately the recognized commercial standard of fineness such that 85 per cent will pass through a 200-mesh screen. Notwithstanding the claims that have been made, from time to time, that it is not necessary to grind the coal to such a degree of fineness, the weight of experience seems to indicate that best results are secured with finely-ground fuel. Let us take it for granted, therefore, that suitable receiving, crushing, drying, pulverizing, distributing and storing facilities have been provided to furnish fine, dry fuel at the furnaces. To accomplish this, with a clean plant and elimination of hazards, it will have been necessary to have designed the plant with great care;