US2057919A

US2057919A - Method of influencing the chemical and physical properties of blast furnace slags

Info

Publication number: US2057919A
Application number: US45145A
Authority: US
Inventors: Roll Josef
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-10-15
Filing date: 1935-10-15
Publication date: 1936-10-20
Anticipated expiration: 1953-10-20

Description

Get. 20, 1936 J. ROLL ETHOD OF FLUENCING THE CHEM L AND PHYSIC SLAGS PR RTIES OF BLAS UR E Filed Oct. 1935 JOSEF FoLL,

ATTORNEY Patented a.. 20, 1936 PATENT OFFICE METHOD OF INFLUENCING THE CHEMICAL AND PHYSICAL PROPERTIES OF BLAST FURNACE SLAGS Josef Roll, Hamborn-Bruckhausen, Germany I Application October 15, 1935, Serial No. 45,145 Claims. (01. 75-41) The slag which is accumulated when working the blast furnace has gained more and more in importance during recent years and now represents an important lay-product of every blast furnace. The slags can be used among other purposes for the manufacture of road making materials, such as road metal and foundation material, and for ballast and the like and railroad tracks and also in the manufacture of tarmacadam. The slag can also be used in the man- ,ufacture of paving stones and the like. Owing to the high requirements which modern street and railway traffic imposes on the materials, only blast furnace slags of a uniform and basaltic character can be used for the purposes mentioned.

Now dense and homogeneous blast furnace slags of this kind have a definite chemical composition and must contain an excess of silicic acid. For metallurgical reasons, however, slags with a suitably high content of $102 are not usually melted in the blast furnace. The slags frequently have a pronounced basic character, that is they have a high content of CaO for binding the sulphur. Basic slags, however, are inclined to crumble and they therefore cannot be employed for the production of a dense, basalt-like and resist- Y ant material which is suitable for road making for example.

Experiments have previously been made with a view to improving these useless basic slags. Thus, attempts have been made to make these slags acid and useful by the addition of substances containing silicic acid or alumina after the slag was tapped from the blast furnace. These experiments, however, did not lead to any satisfactory result because the slag cooled down too rapidly and the substances which were added outside the blast furnace after the slag had,been tapped could o no longer be brought completely into solution.

Likewise processes in which the slag was de-sulphurized and made thinly liquid by blowing compressed air through it have, up to the present, not proved successful because the slag solidified too rapidly with such treatment.

By the process of the present invention, the chemical and physical properties of blast furnace slags are influenced in the following manner and the slags are made useful for the purposes indicated.

For carrying out the metallurgical process in the blast furnace, a relatively basic slag, the character of which depends upon the quality of the pig iron which it is desired to produce, is

melted. In the manufacture of Thomas pig-iron for example such a slag normally has approximately the following composition:31-32% SlOz,

42-43% CaO, 11-12% A1203, 5-6% MgO. Now a slag of this composition, owing to the unfavorable ratio of SlOziCaO contained in it is inclined to crumble and does not have a sufiiciently basaltlike character for use as road-making material. Therefore, according to the present invention, a definite quantity of silic acid (silica), for example in the form of fine dried sand, is blown into the 10 hearth-casing of the blast furnace during the blast period. The sand is introduced into the hearth-casing of the blast furnace below the main twyers, for example, by means of an apparatus similar to a sand blasting apparatus. For con- 15 veying the sand, compressed air or gases, for ex,- ample blast furnace gas, can be employed. It has been found by experience that, on the one hand, the temperatures prevailing in the hearth are suflicient to bring the material which is blownin into solution and that, on the other hand, no reaction by which the quality of the pig-iron is impaired takes place between the slag and the molten pig-iron.

The slags which are obtained in the manner 25 described have, after solidification, a dense and quite homogeneous structure and, owing to their uniform basalt-like character, are able to satisfy all the requirements demanded from them. At the same time, the new process of improving the slag can be carried out easily and at a relatively small expense.

The accompanying drawing illustrates, by way of example, a blast furnace provided with an apparatus which can be used for carrying out the process according to the invention.

Referring to the drawing, a nozzle 2 is introduced into the furnace through the casing l of the hearth. The mouth 3 of the nozzle is situated below the plane I--I which passes through the twyers 4. The slag is tapped 011 through the tap hole 5. The sand which is blown into the blast furnace is conducted to the nozzle 2 through a pipe 6 which is connected at 1 to an air or gas compressor. The sand falls into the pipe 6 45 from a container 8, the upper part of which is in connection through the pipe 9 with the conduit for the compressed air or gas.

The described apparatus for supplying the sand has proved to be very suitable but it will be un- 50 derstood that other methods of supplying the material to be blown in can also be employed.

I claim:

1. The method of influencing the chemical and physical properties of blast furnace slags which 55 4. The method of influencing the chemical and physical properties of blast furnace slags which consists in blowingsand by means of blast furnace gasunder pressure into the hearth-casing of the blast furnace below the plane passing through the twyers.

5. The method of influencing the chemical and physical properties of blast furnace slags which consists in blowing sand by means of compressed air into the hearth casing of the blast furnace 10 below the plane passing through the twyers.

J OSEF ROLL.