In further explanation of the competition in quality of Bessemer and of open-hearth steels it should be understood that in both the acid Bessemer and the acid open-hearth furnaces we get out in quality just what we put in. While for some purposes phosphorus and sulphur of 0.1 per cent is allowable, for other purposes they should not be over 0.025 or 0.03 per cent. To produce steel of the latter high quality, material containing slightly less than this of sulphur and phosphorus must be charged, and these are usually much higher in price than are pig iron and scrap containing greater percentages of these metalloids.
Charging Floor of the Battery of Gas Producers Showing Rocking Arms for Gradual Feeding of the Coal
Where materials of 2.5 to 3 per cent of phosphorus are obtainable, as, generally speaking, they are not in this country, the basic Bessemer should make as low phosphorus steel as does the basic open-hearth.
The great advantages of the basic open-hearth process, then, are that for it can be utilized a much wider variety of raw materials than is possible with the acid open-hearth or either of the Bessemer processes, and, particularly that here, at least, the proper materials are readily available.
The fuels used vary, of course, according to what is most available, considering quantity, quality, and price. Natural gas has been a favorite fuel, as also has oil. But in many localities natural gas never was available and in others which were thus blessed, the supply has been exhausted. By-product coke oven gas and tar are being experimented with with some success.
Largely because of the great size of the open-hearth furnace solid fuel, such as coal which can be used for puddling furnaces, is not adaptable.
As far back as 1839 attempts were made to gasify coal by burning it to ash and utilizing the gaseous products for industrial purposes. These attempts succeeded and the process has been brought to quite a high state of development. There are to-day a large number of efficient types of “gas producers” which furnish gas for general industrial use and it is with this “producer gas” that a great deal of the steel nowadays is made.
While endeavoring to leave out of these articles most of the chemistry and as much of the technical detail as is consistent with clearness, the chemistry of combustion and the “gas producer” is so interesting that it will be well to explain that carbon (coal, coke, wood, etc.) can burn either in one or two stages. Nearly every one has noticed the blue flame with which coal burns in the parlor coal heater or in other furnaces where little draft is used and most of us remember that the gas which is given off from such a fire has asphyxiated many who were unfortunate enough to be sleeping in a closed room, when through insufficient chimney draft or a leaky stove some of the unburnt gas filled the room.
This gas, which is carbon monoxide, is labeled CO in books on chemistry. It is the result of burning the coal with insufficient air. Chemically it is explained by the second of the chemical “equations” which follow. The third equation explains the second stage of the burning which would occur were further air or oxygen admitted to the upper part of the furnace.