(2) "Total absence of smoke." Certainly this is not true inside of the shop, for powdered-coal furnaces, due to their non uniform feed, smoke worse than oil. Powdered coal, as is well known, must be very dry to be pulverized and, when pulverized and allowed to remain quiet for 48 hours, it cakes and requires that a man knock on the bins to loosen it. This leads to uneven combustion in the furnace with large quantities of smoke when there is a large amount of coal coming through the burner and no smoke when the coal is sticking back in the bins. No doubt this is largely due to inefficient handling of the feeder and burner ; even so, a total absence of smoke cannot be claimed when such conditions are met.
(3) "A cheaper grade of coal may be used." The best coal for powdered fuel has a volatile content of not less than 30 per cent, not more than 8 percent ash, and 1 percent sulphur. I think the readers will agree that coal meeting these specifications is of no very cheap grade. Pulverized coal must be handled with great care, for if it is mixed with any quantity of air, it is highly explosive, as the records of accidents in cement plants will prove.
Another very serious objection to powdered coal, due to the incomplete combustion of all the coal ejected into the furnace, is that this coal lies on the work, and when the work is taken out of •the furnace, if not cleaned off, it is apt to be hammered into the work and make flaws which later are likely to be more or less serious according to the nature of the work. This is a fact
seen from personal observation and cannot be denied. Powdered coal is not good for small as it requires too large a chamber for combustion, and from the experience of users of powdered coal it is not desirable to have a combustion chamber separated by a bridgewall from the working chamber. It is found that the lesser of two evils is to remove the bridgewall and blow the powdered coal directly upon the work, which aggravates the condition mentioned above. If the large furnaces are changed from fuel oil to powdered coal, there will remain the small fur naces, and especially the portable ones, which will have to work on fuel oil. Then there would be the expense of handling two kinds of fuel where before there was but one. The pulverizing plant is to be considered. When it is reported that it costs only 30 to 50 cents a ton to perform a multitude of operations, I feel that some one has misplaced the decimal points, as will be shown later on.