RU2079556C1 - Apparatus for cooling hearth and lower portion of blast furnace - Google Patents

Abstract

FIELD: metallurgical industry, particularly, cooling of furnace cover in zone of hearth and well. SUBSTANCE: according to invention lower portion of furnace cover is made of separate panels. Said panels are cooled by means of shield of vertical tubes in the form of steel braces passing through cover and welded to it by solid seam. Lower and upper ends of tubes are mutually joined by air feeding and draining manifolds. Spacing between axes of cooling tubes consists 1.6-3.0 of their outer diameter. Cooling medium is air pumped by fan. EFFECT: enhanced efficiency of cooling.

Description

 The invention relates to the metallurgical industry, in particular, to a cooling structure for a casing of a blast furnace in the hearth and bream region.

 Known for the traditional design of cooling the hearth and periphery of the bream in typical blast furnaces.

 In a traditional design, water-cooled cast-iron stove refrigerators are installed along the forge and bream casing. A layer of thermal insulation with a thickness of approximately 30 mm is provided between the casing of the oven and the refrigerators. Between the refrigerator and the carbon blocks of the hearth and the periphery of the bream there is a layer of compensating carbon mass with a thickness of about 150 mm.

This standard solution does not provide reliable casing service. Water periodically falls on the carbon blocks of the hearth and on the periphery of the bream during burn-outs of the coolers of the shoulders, steams, shafts and cooled elements of air-tuyere appliances. This water, falling onto a heated carbon lining of a hearth and bream, evaporates and its vapors oxidize the carbon of carbon blocks. This process begins at a block temperature of 600 ^o C and proceeds very actively at temperatures above 1000 ^o C. When carbon blocks burn out, carbon blocks form voids. Over time, these voids are filled with cast iron. Thus, cast iron is suitable for peripheral cast-iron refrigerators for hearth and bream. With a large mass of suitable cast iron, a "heat transfer crisis" occurs in the water-cooled pipes of the refrigerators. A stable vapor film forms between the cooling water and the pipe walls, due to which the cooling of the cast-iron stove plate of the refrigerator deteriorates sharply. As a result, the refrigerator overheats, melts, molten iron reaches the casing of the furnace, the latter collapses and molten iron rushes into the hole formed (breakthrough of the hearth).

 This is a relatively rare accident, but its ability to keep the blast furnace staff on standby all the time. Despite this, accidents occur, as a rule, all of a sudden during the normal technological mode of the furnace.

 An analysis of the conditions of the furnace breakthroughs shows that the carbon lining of the furnace and the periphery of the bream with cast-iron plate coolers with water or evaporative cooling cannot ensure the trouble-free operation of the furnace.

 There are attempts to increase the reliability of cooling the furnace casing by means of its external watering, however, in this case, due to the outer surface of the casing with scale and rust, it is difficult to control the safety of the casing and the danger of side breakthrough of the hearth is not eliminated, since the conditions for burning carbon blocks remained the same.

 Attempts are known to increase the reliability of the casing service by arranging a casing (jacket) around the casing with water supplying to the gap zone between the casing and the casing. This measure also excludes any control over the condition of the furnace casing (the furnace skin is hidden by a shell) and does not change the burnout conditions of carbon blocks.

 The invention is further known in which supply air is used as a cooling medium. In this design, along the casing in the area of the hearth and bream, a shell is set up, divided into a number of compartments. Cooling air feeds into the box made in the form of a half ring adjacent to the casing of the furnace. From this duct, air is distributed over the drains and is sent from them to the air cooling of the bottom of the bottom.

 This proposal does not exclude the oxidation of carbon peripheral blocks with water vapor coming from the heated steam coolers, shoulders and cooled elements of air-tuyere devices. Consequently, during the destruction (oxidation) of carbon blocks, molten iron will fit the casing of the furnace. No protective wall and refractory bricks or refractory concrete are provided between the casing of the furnace with carbon blocks in this invention. Therefore, when approaching the case of molten iron, the case will be destroyed, i.e. hearth breakthrough.

 To eliminate the disadvantages inherent in these cooling systems, it is envisaged to apply the design shown in FIG. one.

 In FIG. Figure 1 shows the design of a hearth with a carbon glass, air-cooled, as recommended in a typical design of blast furnaces with the addition of air-cooled hearth and the periphery of the bream.

 In FIG. shown is a furnace casing 1, a layer of horizontal peripheral carbon blocks 2, a lower layer of vertically mounted graphite blocks 3, several layers of aluminosilicate refractory brick 4, to be air-cooled 5, consisting of cast-iron plate coolers filled with air-cooled pipes, a layer of carbon lining 6.

 A front view of the air-cooled panel is shown in FIG. 2. The horn and the lateral surface of the bream are composed of separate tsars. The height of the king is equal to the sum of the heights of the horn and the bream. The number of drawers is from 6 to 8, depending on the design of the furnace.

 Each casing includes a furnace casing 1, a layer of refractory concrete 7, in which steel pipes are placed 8. The pipes are bent in the form of brackets and brought out through the furnace casing. Pipes are welded to the casing of the furnace with a tight seam. Outside, the pipes are combined by a lower distribution manifold 9 and an upper collecting manifold.

 Air is injected into the collector 9 by a fan, and it is emitted from the collector 10 into the atmosphere. There is also the option of supplying air from the collector 10 to the system to be cooled 5.

 This system (air cooling of the hearth and the periphery of the bream) works as follows.

 Air is supplied from the fan to the distributing manifold 9, distributed between the vertical pipes 8 embedded in the concrete 7, exiting through these pipes to the collecting manifold 10 and discharged into the atmosphere (or fed to the system of the subject air cooling).

With preserved carbon masonry of the hearth and bream, thermal loads on the hearth air cooling system are not large (about 3 kW / m ² ). With completely destroyed carbon blocks, when molten iron approaches the layer of refractory concrete, the heat flux increases to 10 15 kW / m2.

The temperature of the concrete from the side of molten iron reaches 1400 ^o C, and from the side of the air-cooled pipes 400 500 ^o C.

 After the destruction of the carbon blocks, molten iron will be stopped by the wall of the panel made of refractory concrete.

 Indeed, water vapor, even when heated to a high temperature, does not oxidize refractory concrete and the latter can work reliably in an oxidizing atmosphere.

 Liquid cast iron also does not destroy refractory concrete, which will protect the casing from heating for a long time. Thus, when liquid cast iron approaches the concrete panel, an instant breakthrough of the hearth will not occur, and the personnel servicing the blast furnace will be able to proceed without emergency in normal production conditions to turn off the emergency situation (switching off a number of tuyeres, transferring cast iron to another grade, adding Ti compounds to furnace hearth, etc.) with subsequent preparation for repair.

The signal of the approach of molten iron to the concrete panel is received from the sensors by the temperature of the air leaving the air-cooled pipes. When approaching molten iron to the concrete panel, the temperature of the exhaust air from the brackets increases by about 40 ^o C.

 For good cooling staples with air, the distance between the axes of the pipes 8 should be within 1.5 to 3 of the outer diameter of the pipes.

The air velocity in the pipes is selected based on the permissible temperature for the steel grade used. For example, for unalloyed steel 400 - 450 ^o C. (temperature of heating pipes when liquid cast iron approaches concrete panels).

Claims (1)

 A device for cooling the hearth and the lower part of the blast furnace, including blocks mounted between the furnace casing and its inner lining with cooled elements forming a vertical row, characterized in that the blocks are made of refractory panels, and the cooled elements are in the form of steel tubular brackets cooled by fan air , the ends of the brackets are brought out through the casing and connected to the air distributing and collecting manifolds, while the distance between the axes of the tubular brackets is 1.5 - 3.0 of the outer diameter of the bracket.

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