US2754198A - Steel-making - Google Patents

Description

United States Patent STEEL-MAKING Ernest S. Starkman, El Cerrito, Calif, and Stanley S. Sorem, Brombrough, Wirral, England, assignors to Shell Development Company, San Francisco, Calif, a corporation of Delaware N0 Drawing. Application June 24, 1950, Serial No. 170,249

3 Claims. (Cl. 75-43) This invention relates to the production of steel, particularly by the open hearth processes, and to fuels for use in such processes.

One of the most frequent reasons for interrupting open hearth furnace operations is the necessity for cleaning out the regenerative heating chambers, known as checker chambers, so that such may function properly. The cleaning consists primarily of removing slag, dirt, soot or carbon deposits, etc., the amounts and types of these deposits depending largely upon the type of fuel used. When liquid hydrocarbon fuels, such as residual fuel oils, are burned, there are large quantities of soot and carbon deposited in said chambers.

It has been known for some time that carbon and soot resulting from the burning of liquid hydrocarbon fuels could be eliminated, or substantially reduced, by incorporating relatively small amounts of base metal compounds, such as, for example, sodium or calcium naphthenates, into the fuel. However, in situations where the fuels were being burned in furnaces containing acidic refractories, such as the silica brick in open hearth furnaces, it has not been possible to use these base metals because of their deleterious effects upon the acidic refractories.

Another problem which has recently arisen in the steelmaking industry is a result of the increasingly high sulfur content of residual, or bunker, fuel oils. When these high sulfur content fuels are used, it has been found that the time required to complete a heat is increased by as much as ten or twenty percent because of difficulty in reducing the sulfur content of the metallic charge to required specifications. In order to avoid this latter difi'iculty, it has been necessary to include a maximum sulfur concentration limitation in the specifications for such fuels, the general result of which has been to make such fuels more expensive-an obviously undesirable result.

It has now been found that the combined presence of base metal compounds and sulfur will substantially eliminate the deleterious effects of both of such substances. More particularly, it has been found that the use of such materials in open hearth furnaces will not adversely afiect the acidic refractories, and, at the same time, will not increase the time required to reduce the sulfur content of the steel to the desired concentration.

The term base metal, or alkaline metal, as used herein, is meant to embrace only alkali metals and alkaline earth metals, such as sodium, potassium, cesium, calcium, magnesium, barium, etc. The alkali metals, and sodium in particular, are preferred for use according to this invention.

The base metal compound may be added at any point of the operation prior to that where the fuel combustion products contact the charge in the hearth, so long as the sulfur is also present at the time that such base metal compounds are exposed to the heated acidic refractories. Thus, the metal compounds may be injected directly into the flame, may be controllably injected into the fuel stream just prior to combustion, or may be originally blended into the fuel as an integral component thereof.

The particular type of base metal compound is not critical, and will usually depend upon the manner in which it is utilized. If it is to be blended into the fuel as a permanent component, it will usually be convenient to use an oil-soluble form, such as the base metal salt of a naphthenic acid, of a sulfonic acid, of a phenol, or the like. However, inorganic forms may also be used, for example, by suspending the solid compound in the oil or dissolving it by means of a suitable co-solvent. Thus, sodium hydroxide may be incorporated into the oil by first dissolving in alcohol and then adding the alcohol solution to the fuel. Where an injection is made in the fuel stream or directly into the combustion chamber, any fluid form may be used, such as oil, alcohol, acetone or Water solutions, etc. Even when injecting into the fuel stream it is not necessary that the injected fluid be soluble in the oil, especially if the fuel is in turbulent flow.

The sulfur which is required to overcome the deleterious effects of the sodium may be present in any form, for example, as mercaptans, sulfides, disulfides, as elemental sulfurs, etc. The most practical method of obtaining the sulfur will generally be by securing unusually high sulfur content fuels; however, if it is desired to enjoy the benefits of this invention while burning low sulfur fuels, the sulfur may be added in any form and in any manner, just as in the case of the base metal compound addition.

The relative quantities of sulfur and base metal are closely related and quite critical. In general, these amounts should be controlled by the relation:

wherein S and M are weight percent of sulfur and alkaline metal, respectively, based upon the quantity of fuel burned, A is the hydrogen equivalent of the alkaline metal, and m. w. is the molecular weight of said metal. For best results, the last term of the above relationship should be limited to :025.

From this relationship it may be readily seen that when the sulfur content of the fuel is in the lower ranges of about 0.5% or below, there is no need for the presence of the base metal in the furnace, and consequently that there is no advantage to be derived from the present invention in such cases. In order to derive the benefits of this invention it is necessary to use at least about 0.05% of the metal, and preferably more than about 0.1%, based upon the fuel consumption, and, of course, a commensurate amount of sulfur. On the other hand, not more than about 2%, or at the most, 3%, of the alkaline metal may be used because of the unduly high amounts of sulfur which would be required to counteract the effect of greater quantities of metal. From the above equation it will be evident that for a base metal concentration range of 0.1 to 1% by weight and in the case of the preferred base metal, sodium, the sulfur content of the finished fuel oil composition should be from about 0.8% to about 1.9% by weight for best results. The minimum sulfur content of the finished fuel oil in this case, 0.8%, is derived by substituting a base metal concentration of 0.1%, and the constants for sodium, into the above equation with the last term being 0.25. Thus, this minimum sulfur content The maximum sulfur content of the finished fuel oil in this case, 1.9%, is derived by substituting a base metal concentration of 1.0%, and the constants for sodium,

into the above equation with the last term being +0.25. Thus, this maximum sulfur content While the present invention is primarily directed to the method of refining pig iron in an open hearth furnace, it will be readily apparent that the fundamental concepts involved are applicable to many other operations, which are intended to be included within the scope of this application. Moreover, it is believed that the fuel compositions formed when the present invention is practiced by adding the base metal to a suitable sulfur content residual fuel are novel compositions, and such are also contemplated as a part of the invention.

In confirming the advantages set forth hereinbefore, samples of silica refractory brick were exposed to flames containing varying amounts of sulfur and sodium. The results were as set forth in the table.

Table Weight percent, based on fuel Appearance of silica S Na 0.25 1.0 Heavily glazed. 1. 1.0 Slightly glazed. 1. 0 0. 5 Substantially unchanged.

The invention claimed is:

1. A liquid residual fuel oil composition comprising a a predominant amount of a bunker fuel oil, more than 0.10% up to about 1% by weight of sodium in the form of sodium naphthenate and between about 0.8% and about 1.9% by Weight of sulfur, the weight percent of sulfur present also being equal to 0.7 M+0.99i0.25,

wherein M is equal to the weight percent of sodium present.

2. A liquid residual fuel oil composition comprising a predominant amount of a bunker fuel oil and containing about 1.0% by weight of sulfur and about 0.5% by weight of sodium in the form of sodium naphthenate.

3. In a process of reducing carbon and soot deposition on the surfaces of the regenerative heating chambers of an open hearth furnace provided with an acidic refractory lining by the use of a residual fuel oil containing a compound of an alkali or alkaline earth metal, the improvement comprising the reduction of the chemical attack on the acidic refractory material in said furnace by the combustion, as the only fuel in said furnace, of a residual fuel oil containing about 1.0% by weight of sulfur and about 0.5% by Weight of sodium in the form of sodium naphthenate.

References Cited in the file of this patent UNITED STATES PATENTS 1,419,801 Basset June 13, 1922 2,045,788 Maverick June 30, 1936 2,141,848 Adams et a1 Dec. 27, 1938 2,167,345 Crandall et al. July 25, 1939 2,205,126 Seeley et al June 18, 1940 2,230,642 Fischer et al. Feb. 4, 1941 2,230,817 Shoemaker Feb. 4, 1941 2,360,584 Risk Oct. 17, 1944 2,361,054 Pevere Oct. 24, 1944 2,362,085 Morgan Nov. 7, 1944 2,460,700 Lyons Feb. 1, 1949 FOREIGN PATENTS 12,401 Great Britain of 1888 496,692 Great Britain Dec. 5, 1938

Claims (1)

1. A LIQUID RESIDUAL FUEL OIL COMPOSITION COMPRISING A PREDOMINANT AMOUNT OF A BUNKER FUEL OIL, MORE THAN 0.10% UP TO ABOUT 1% BY WEIGHT OF SODIUM IN THE FORM OF SODIUM NAPHTHENATE AND BETWEEN ABOUT 0.8% AND ABOUT 1.9% BY WEIGHT OF SULFUR, THE WEIGHT PERCENT OF SULFUR PRESENT ALSO BEING EQUAL TO 0.7 M+0.99$0.25, WHEREIN M IS EQUAL TO THE WEIGHT PERCENT OF SODIUM PRESENT.