US3083091A - Shaft furnace sintering method - Google Patents

Description

March 26, 1963 H. scHENcK ETAI. 3,083,091

SHAFT FURNACE SINTERING METHOD Filed Jan. 5, 1960 0 O aan INVENTORS. HERMANN scHENcK BY WERNER wENzEL,

JMJ?. M

THE/IE A7' 7' OIE/VE X ite taes The present invention relates to a method and apparatus for sintering iron ore-hearing materials into larger lumps which are suitable for a subsequent treatment in blast furnaces.

According to previous methods, the process of sintering the iron ore-bearing material was usually carried out on a movable conveyor belt by i'irst igniting a mixture of iinely granulated ore and fuel along the surface of such a belt and by then drawing combustion air through this permeable mixture. This known process has the disadvantage of requiring a relatively complicated and expensive apparatus.

The sintering process may, however, also be carried out in a shaft furnace which may be constructed much more easily and inexpensively than a sintering apparatus with a movable belt. This is true to a still greater extent if provision is made to pass the combustion air through the material to be sintered hy pressure rather than by suction.

It is an object of the present invention to provide a new method of carrying out the sintering process within a shaft furnace by forcing the combustion air by pressure through the material to be sintered.

This and other objects of the present invention as well as the features and advantages thereof will also appear from the following detailed description thereof, particularly when the same is read with reference to the accompanying diagrammatic drawing which shows a vertical cross section of a shaft furnace according to the invention.

The shaft of the sintering furnace according to the invention is generally made of a rectangular cross section, while its length may vary in accordance with the desired output of the furnace. In the drawing, in which the two sides of the shaft are symmetrical to the vertical axis A-A, the walls i. of the sintering shaft are provided with inlet passages or openings 2 for thepassage of the combustion air into the furnace. rThese air inlets may also 'ce provided by the apertures between the adjacent bars of a vertical grate. This entire grate or the individual bars thereof may be movable. The walls of a charging box 3 extend from above into the sintering shaft in a direction parallel to walls l. thereof.

The operation of the sintering shaft furnace as illustrated in the drawing is as follows:

Charging box 3 which extends substantially centrally of the shaft is supplied with a relatively coarse material 4;- which permits gases to pass easily therethrough and consists, for example, of the residue of a sintering process which is formed when the sintered material is broken up and screened to a size of approximately 5 to 2O mm., and further of ores of the same granular size which are accumulated when the ore is graded. This granular vertical central layer in the sintering shaft usually does not contain any fuel, although it is possible to add fuel theretoin order to attain special sintering effects. Such a fuel may also be applied in the form of a liquid fuel by spraying Patented Mar. 26, i933 the same upon the upper surface of the coarse granular material 4. The lateral parts of the sintering shaft be* tween walls l of the shaft and the walls of the charging box 3 are filled with the material 5 which is primarily to be sintered. This material 5 consists as usual of a mixture of ne ores or other fine-grained iron-bearing materials and fuel. The permeability of this sinter material 5 to gases is attained in the conventional manner by moisture and crumbling.

As illustrated in the drawing by the arrows 6, the corrbustion air is passed into the sinter material 5 through the air inlet passages 2 in the shaft walls either by drawing the air through the material or by forcing it through it under pressure. The latter procedure is preferred since it has particular advantages. The combustion air passes through the material 5 to be sintered in a substantially horizontal direction and then enters into the vertical central layer of a coarser material in which the combustion air and the flue gas produced in the sintering material S ow upwardly and finally leave the shaft 3 at the upper end of the central part thereof, as indicated in the drawing by arrows 7.

The material 5 to be sintered is ignited along the shaft walls l through the passages 2. The original ignition of the material may be attained in different manners depending upon whether the sintering process is to be carried out continuously or intermittently. The drawing illustrates the sintering process as being carried out in a continuous operation. The sinter material 5 which is newly supplied into the upper opening of the shaft passes at the level into the area containing the inlet openings 2 through which the combustion air enters in the direction of the arrows 6. At this point, the ignition occurs along the surface of the sinter material facing toward the openings 2 in the shaft walls, as indicated by arrow 3. The ignition maybe carried out in the conventional manner by passing hot gases into the sinter material directly adjacent to walls l. lt is, however, also possible to spray a liquid fuel upon the surface of the material, while by heating the surface of the solid fuel contained in the sinter material by radiation the temperature of this fuel should be increased at least to the ignition temperature of the liquid fuel. Furthermore, the surface of the sinter material may also be heated merely by radiation, for example, by means of electric heating elements, and to such a degree that the fuel together with the air which is passed through the sinter material will be ignited. After the ignition has started at the points S, directly adjacent the walls 1, the so-called sinter front, that is, the zone of the highest temperature, will move gradually downwardly and toward the center of the shaft as the charge 4 of the shaft 3 sinks downwardly, as shown in the drawing at 9 where the sintered material is indicated by horizontal shade lines. The speed at which the material is to be lowered may be adjusted so that the entire material will be sintered when it reaches the lowest air inlet passages 2 in the shaft walls. The part 12 of the shaft underneath these air inlet passages 2 is utilized for cooling the sintered material. For this purpose, special cooling openingsl 13 may be provided in the lower part of the shaft Walls. Finally, a continuous body of cooled sinter emerges from the shaft at ld.

If the sintering process is carried out in an intermittent operation, the charge 4 of the shaft 3 is not moved dur- Vsintering shaft.

be deposited on Vthe surface of the coarse granular mate-V ing the sintering process. The ignition occurs simultaneously or successively through all air-inlet passages 2. After the entire surface of the sinter material has been ignite-d, the ignition is discontinued and combustion air is passed through the sinter material 5 until the entire sinter material which is contained within the area of the air inlets has been sintered completely. Thereupon the entire charge 4 of the shaft is lowered until the area containing the air inlets is again filled with a fresh charge of sinter material 5. The entire proceeding as above described is then repeated. Y

It is one of the characteristic features of the present invention that not only the sinter material 5- within the outer layer will be Sintered, but that also the charge of coarser granular material 4 within the vertical central layer will be sintered to a considerable extent. The flow of the flue gases from the actual sinter layer passes through the vertical central layer and thereby preheats this central layer approximately within the area 10. W'hen the sinter front approaches this central layer, at l1, the temperature will have become so high within the central layer that the granular material therein will also be extensively sintered. This procedure is aided by lthe fact that the flue gases carry a considerable amount of dust into the granular central layer which will cement that coarser pieces thereof to each other.

According to the present invention the process of sintering the coarser central layer may be assisted and improved by special measures. These measures consist in adding fuel in a solid or liquid form also to the central layer and in sprinkling a liquid such Yas water or oil from above upon the central layer. This liquid penetrates from above through the central layer and binds the dust which is contained in the flue gases and icarried thereby in the upward direction through the central layer. Thus, after the liquid has evaporated, this dust will be deposited on the coarser particles of the central layer. According to anotherV feature of the invention, fuel dust and/ or mineral dust such as lime dust, iron-ore dust, fine dust and the like is mixed into the central layer. For this purpose it is also possible Vto utilize slurries which form the residues from other kinds of processes and contain the mentioned substances. One product which has proved to be very suitable for this purpose is, for example, the slurry which results from the cleaning of blast-furnace gases and forms a waste product which is otherwise very bothersome and difcult to be disposed of. it is even possible to utilize gas slurries containing zinc since the high fuel content of these slurries leads to a reduction of the zinc oxide and an evaporation of the zinc Within Vthe central layer of the This line granular material fmay also rial which forms the central layer of the `sintering shaft before the latter is filled into the furnace, for example, by mixing the coarse material and the slurry intimately with each other in a mixer.

rl`he sintering method in a shaft furnace according to the invention as described above may be modified in numerous ways. Thus, for example, instead of making the shaft of a rectangular shape, it may be made of a. circular or any other suitable shape. Furthermore, the heat contained in the iiueV gases may be utilized, forV example, for preheating the combustion air'. Also, the elements for the heat exchange between the flue gases and the kcombustion air may be placed into the upper part v of the charging box 3, and they may also be kept entirely separate from the 'actual sinter layer.

The machinery and other apparatus which are required for charging the shaftY furnace and for removing the sintered material therefrom do not form a part of this invention. These are numerous means known vin the art for this purpose, and it is therefore not necessary to describe or illustrate them specifically herein. .Also, the particular means for drawing or blowing the combustion known in the art.

It should, however, be mentioned particularly that the sintering process according to the invention may also be carried out by placing the vertical layer of coarser matcrial, which serves for uniformly withdrawing the flue gases, more closely toward one side wall of the shaft so that the shaft furnace will be operated unsymmetrically. If the sintering process according to the invention is carried out in this manner, the combustion air will be passed through one wai-l of the shaft into the material to be sintered and, after flowing through the latter, it will pass through the coarser layer which is disposed adjacent to the other wall. The fiue gases may then be discharged from the vertical layer of the coarser material in a Vertically upward direction, in which case the wall of the shaft adjacent to the coarser material wil not be provided with any air inlet passages. The liuc gases may, however, also be discharged through the wall of the shaft adjacent to the vertical layer of the coarser material. In this case, the combustion air as well as the flue gases will flow substantially horizontally in the transverse direction of the shaft through the entire charge of the shaft which is lowered in the vertical direction. Although this modification falls within the basic concept of the invention and may be useful in particular cases, the process as first described utilizing a symmetrical arrangement of the contents of the shaft is of a greater advantage especially because of a more economical utilization of the heat and because it maybe constructed more easily.

Although our invention has Vbeen illustrated and described with reference to the preferred embodiments thereof, We wish to have it understood that it is in no Way limited to the details of such embodiments, but is capable of numerous modications within the scope of the appended claims.

Having thus fully disclosed our invention, what we claim is:

l. A shaft-furnace sintering method comprising the steps of charging the shaft at a point near the center thereof with a material of coarse granular consistency and relatively poor in fuel, and comprising iron ore, so as to form a substantially central vertical layer, charging Vthe parts of said shaft intermediate said substantially central vertical layer and therwalls of said shaft with the actual material to be sintered comprising a gas-permeable mixture of fine ore and fuel, lowering the material to be sintered in the vertical direction, igniting said descending material through openings in the walls of said shaft at the surface of said material immediately adiacent to said walls, then further lowering'said material andV at the same time passing combustion air through further openings in said walls into said material and in a substantially horizontal flow transversely through said material into the central vertical layer, and discharging the flue gases formed by the combustion of the air and the fuel contained within the material through said central layer in a substantially vertical upward direction.

2. A sintering method as defined in claim l, in which the material to be sintered is ignited by forcing hot gases into and through the material.

3. A sintering methodV as defined in claim l, in which the material to be sintcred is ignited by first heating the outer surfaces of the material adjacent to the walls of said shaft at least to a temperature corresponding to the ignition point of a liquid fuel, and then spraying said liquid fuel'upon said outer surfaces.

4. A sintering methodes defined in claim l, in which the vertical central layer'is sprinkled with water for binding therein the dust contained in the flue gases formed duringethe sintering process.

5. A sintering method as defined in claim l, in which the vertical central Vlayer is sprinkled with a watery slurry containing fuel dust and a mineral dust.

6. A sintering method as dened in claim 1, in which the vertical central layer is sprinkled with a gas slurry containing zinc attained in the cleaning of blast-furnace flue gas.

7. A sintering method as dened in claim 4, in which a mineral dust is added to the water sprinkled upon the central vertical layer.

References Cited in the file of this patent UNITED STATES PATENTS Robinson Iune 29, 1909 Brassert Jan. 30, 1934

Claims (1)

1. A SHAFT-FURANCE SINTERING METHOD COMPRISING THE STEPS OF CHARGING THE SHAFT AT A POINT NEAR THE CENTER THEREOF WITH A MATERIAL OF COARSE GRANULAR CONSISTENCY AND RELATIVELY POOR IN FUEL, AND COMPRISING IRON ORE, SO AS TO FORM A SUBSTANTIALLY CENTRAL VERTICAL LAYER, CHARGING THE PARTS OF SAID SHAFT INTERMEDIATE SAID SUBSTANTIALLY CENTRAL VERTICAL LAYER AND THE WALLS OF SAID SHAFT WITH THE ACTUAL MATERIAL TO BE SINTERED COMPRISING A GAS-PERMEABLE MIXTURE OF FINE ORE AND FUEL, LOWERING THE MATERIAL TO BE SINTERED IN THE VERTICAL DIRECTION, IGNITING SAID DESCENDING MATERIAL THROUGH OPENINGS IN THE WALLS OF SAID SHAFT AT THE SURFACE OF SAID MATERIAL IMMEDIATELY ADJACENT TO SAID WALL, THEN FURTHER LOWERING SAID MATERIAL AND AT THE SAME TIME PASSING COMBUSTION AIR THROUGH FURTHER OPENINGS IN SAID WALL INTO SAID MATERIAL AND IN A SUBSTANTIALLY HORIZONTAL FLOW TRANSVERSELY THROUGH SAID MATERIAL INTO THE CENTRAL VERTICAL LAYER, AND DISCHARGING THE FLUE GASES FORMED BY THE COMBUSTION OF THE AIR AND THE FUEL CONTAINED WITHIN THE MATERIAL THROUGH SAID CENTRAL LAYER IN A SUBSTANTIALLY VERTICAL UPWARD DIRECTION.

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