Dedusting ash treatment system for iron and steel plant

Abstract

The utility model relates to a steel plant fly ash treatment system which is particularly suitable for treating stainless steel fly ash of a steel plant and belongs to the field of solid waste utilization of the steel plant. The method comprises the following steps: adding carbon powder, cement and water into stainless steel dedusting ash of an iron and steel plant, uniformly mixing, pressing into a carbon brick with the height of 30-70mm and the diameter of 30-70mm and through holes by using a brick press, and adding the carbon brick and coke into a shaft furnace in batches; hot air is blown in from an air inlet of the shaft furnace, high-temperature coal gas generated by combustion of the hot air and coke heats the carbon bricks, iron oxide in the carbon bricks and carbon powder are subjected to a direct reduction reaction at the high temperature, slag and molten iron are formed at the temperature of 1400 DEG C, and the molten iron is discharged through a molten iron channel and the front furnace. The service life of a molten iron channel is prolonged by adopting preposed furnace tapping; the carbon brick size is reduced, carbon brick through holes are increased, and the heat exchange efficiency of the carbon brick and coal gas is improved; the shaft furnace is cooled by the cooling wall, so that water accumulation at the foundation of the shaft furnace during water spraying cooling of the furnace shell is avoided, and the production safety is improved.

Description

Technical Field

[0001] The present invention relates to a dust removal ash treatment system for steel plants, and particularly to a device for treating stainless steel dust removal ash in steel plants, belonging to the field of solid waste utilization in steel plants. Technical Background

[0002] The Oxycup shaft furnace treats the waste generated in the traditional steel smelting process, such as blast furnace dust sludge, scrap steel, mill scale, etc. generated in processes such as blast furnace, converter, continuous casting, and hot rolling. In particular, it can recover elements such as Cr and Ni in the waste of stainless steel enterprises, and the recovery value is very high.

[0003] Mix steel dust sludge, carbon powder, cement, etc. for batching, and use the cold consolidation technology to press the mixture into self-reducing carbon blocks with a certain strength. Then add them into the Oxycup shaft furnace together with coke, scrap steel, and flux. The iron oxide in the self-reducing carbon block starts to be reduced at 1000°C and is completely reduced at 1400°C to form sponge iron. Immediately afterwards, the reduced iron and slag start to melt. The molten iron and slag are continuously discharged from the shaft furnace and enter a siphon-type slag-iron separation device to separate the slag and iron.

[0004] A certain stainless steel enterprise in China introduced the OxyCup shaft furnace of KUTTNER to treat stainless steel dust removal ash, but there are many defects in this device.

[0005] The following problems exist in its production:

[0006] 1) In the continuous iron tapping mode, there is no molten iron stored in the furnace. During the iron tapping process, the upper part of the molten iron channel is easily scoured. After the molten iron channel expands, it cannot seal the gas, and the slag and iron cannot be discharged normally. The furnace needs to be shut down for maintenance of the molten iron channel every 10 - 15 days.

[0007] 2) The furnace body is cooled by spraying water on the furnace shell. The water is easy to splash, and there is water accumulation under the foundation of the shaft furnace, which is not conducive to safety.

[0008] 3) The OXYCUP shaft furnace uses hexagonal carbon bricks with a height of 110 mm and a diagonal of 110 mm. The block size is too large, and large-sized foundry coke (particle size is shown in the following table) must be used. Otherwise, the pressure loss of the burden column is large, and the large block size is not conducive to heating and reaction.

[0009]

[0010] The price of foundry coke is higher than that of metallurgical coke, and it is not easy to purchase.

[0011] 4) The top gas pressure of the shaft furnace is slightly positive pressure, about 0 to 1.5 mbar, and there is no sealing device, so there is a gas leakage phenomenon.

[0012] 5) The blast heating uses a tubular heat exchanger, and the temperature is only 750°C. The heat of the molten iron is low, and the carbon consumption is high.

[0013] 6) The gas purification adopts water washing, and sludge is generated during the washing process, resulting in a poor environment. Summary of the Invention

[0014] In view of the existing problems, the following solutions are proposed:

[0015] A dust removal ash treatment system for a steel plant includes the preparation of carbon bricks, a shaft furnace charging device, a shaft furnace body, an iron tapping device, a slag tapping device, a blast heating system, and gas purification; the iron tapping method of the shaft furnace is that there is an iron channel at the bottom of the body, connecting the shaft furnace and the pre-furnace to form a U-shaped iron tapping connector for continuous iron tapping; the cooling element of the shaft furnace adopts a cooling stave.

[0016] Furthermore, the carbon bricks prepared from the dust removal ash of the steel plant have the following dimensions: height: 30 - 70 mm, diameter: 30 - 70 mm, and the carbon bricks have through holes.

[0017] Furthermore, the shaft furnace charging device adopts a double-bell top.

[0018] Furthermore, the blast heating system adopts a spherical or checker brick type hot blast stove, and the heating temperature is 750 - 1200 °C.

[0019] Furthermore, the shaft furnace is provided with a slag tapping opening, and the slag tapping opening is located above the iron channel.

[0020] Furthermore, the gas purification of the shaft furnace adopts a bag filter.

[0021] Furthermore, the gas pressure at the top of the shaft furnace is ≧ 10 kPa.

[0022] Raw materials charged into the shaft furnace:

[0023] Stainless steel carbon bricks: made from stainless steel dust removal ash, dust sludge, rolling mill ash, iron scale, stainless steel red mud, etc., and then adding carbon powder and cement, mixing evenly, adding water according to the proportion and stirring. Finally, a mixed material with uniform composition and 17% water content is stirred out, and is pressed into stainless steel carbon bricks by a brick press. The pressed carbon bricks are cylindrical, with dimensions: height: 30 - 70 mm, diameter: 30 - 70 mm, and the carbon bricks have through holes. The main components of the carbon bricks are:

[0024]

[0025]

[0026] Coke: metallurgical coke, particle size 30 - 100 mm

[0027] Auxiliary materials: silica stone, limestone

[0028] The carbon bricks, coke and auxiliary materials are loaded into the charging basket, lifted to the top of the furnace by a crane, and charged into the shaft furnace in batches through the double-bell top.

[0029] The cold air is heated by the hot blast stove to 750 - 1200 °C, and then blown into the shaft furnace through the hot blast pipeline and the air inlet. The hot air burns with the coke to produce high-temperature gas. During the upward process, the carbon bricks are heated. At high temperatures, a direct reduction reaction occurs between the carbon in the carbon bricks and the iron oxides. When the carbon bricks are heated to 1000 °C, the iron oxides in the carbon bricks start to be reduced. When heated to 1400 °C, sponge iron is formed and melted, forming slag and molten iron.

[0030] The molten slag and molten iron droplets fall to the lower part of the shaft furnace. The molten iron is at the bottom and the slag is on top of the molten iron. The slag is discharged regularly through the slag outlet, and the molten iron is discharged through the molten iron channel and the forehearth.

[0031] The gas formed by combustion rises to the top of the shaft furnace. The gas pressure is controlled to 10 - 30 kPa. After being discharged from the shaft furnace, it is purified by cyclone dust removal and bag filter. The purified gas is supplied to users.

[0032] Refractory materials are laid at the lower part of the shaft furnace, and cooling walls are installed closely to the furnace shell. The cooling walls are cooled by water, effectively protecting the furnace shell from being burned out.

[0033] In the implementation of this patent, by using a forehearth for tapping iron, the service life of the molten iron channel is improved; by adopting a double-bell furnace top, the sealing effect of the furnace top is improved; by reducing the size of the carbon bricks and increasing the through holes, the heat exchange efficiency between the carbon bricks and the gas is improved; the shaft furnace is cooled by cooling walls, improving the safety. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the dust removal ash treatment system in a steel plant

[0035] Legend Marks

[0036] 1 Coke, 2 Carbon bricks, 3 Double-bell furnace top, 4 Shaft furnace, 5 Forehearth,

[0037] 6 Cooling wall, 7 Bag filter, 8 Hot blast stove, 9 Cold air, 10 Purified gas,

[0038] 11 Slag outlet, 12 Air inlet, 13 Furnace shell, 14 Molten iron channel. Detailed Implementation Manner

[0039] The furnace charge of the shaft furnace 4:

[0040] Stainless steel carbon bricks 2: Using stainless steel dust, dust sludge, rolling mill ash, iron scale, stainless steel red mud, etc., and then adding carbon powder and cement. After mixing evenly, water is added in proportion and stirred. Finally, a mixed material with uniform composition and 17% water content is stirred out. It is pressed into stainless steel carbon bricks 2 by a brick press. The pressed carbon bricks 2 are cylindrical, with dimensions: height: 30 - 70 mm, diameter: 30 - 70 mm, and the carbon bricks 2 have through holes.

[0041] Among them, cement is used as the binder for carbon bricks, and portland cement is adopted, such as blast furnace slag cement with strong adhesiveness.

[0042] Carbon brick 2: The main components are:

[0043]

[0044] Coke 1: Metallurgical coke, with a particle size of 30 - 100 mm

[0045]

[0046] Auxiliary materials: silica, limestone

[0047]

[0048] Carbon brick 2, coke 1 and auxiliary materials are loaded into the charging basket, lifted to the furnace top by a crane, and charged into the shaft furnace 4 in three batches through the double-bell furnace top 3; part of the scrap steel can be added to the charged materials, and the size of the scrap steel is ≤ 100 mm.

[0049] The cold air 9 is heated by the hot blast stove 8 to 1200 °C, blown into the shaft furnace 4 through the hot blast pipeline and the air inlet 12. The hot air burns with coke 1 to generate high-temperature gas. During the upward process, the carbon brick 2 is heated. At high temperatures, a direct reduction reaction occurs between the carbon in the carbon brick 2 and iron oxides. When the carbon brick 2 is heated to 1000 °C, the iron oxides in it start to be reduced, and when heated to 1400 °C, sponge iron is formed and melted, forming slag and molten iron.

[0050] Reaction formula of carbon and iron oxides:

[0051] Fe 2 O 3 + 3C = 2Fe + 3CO

[0052] The molten slag and molten iron drop to the lower part of the shaft furnace 4. The molten iron is at the bottom and the slag is on top of the molten iron. The slag is discharged regularly through the slag tapping hole 11, and the molten iron is continuously discharged into the molten iron ladle through the molten iron channel 14 and the forehearth 5.

[0053] The gas formed by combustion rises to the top of the shaft furnace 4. The gas pressure is controlled to 10 - 30 kPa. After being discharged from the shaft furnace 4, it is purified by a cyclone dust collector and a bag filter 7. The purified gas 10 is supplied to the hot blast stove for burning, and the remaining part is incorporated into the gas pipeline network.

[0054] Refractory materials are laid at the lower part of the shaft furnace 4. The cooling wall 6 is installed closely against the furnace shell 13. The cooling wall 6 is cooled by water, and the heat transfer surface of the cooling is sprayed with refractory materials.

Claims

1. A dust removal ash treatment system for a steel plant, comprising the preparation of carbon bricks, a vertical furnace charging device, a vertical furnace body, an iron tapping device, a slag tapping device, a blast heating system, and coal gas purification; characterized in that: The vertical furnace tapping method is to provide a molten iron channel at the bottom of the main body, connecting the vertical furnace and the front furnace to form a U-shaped tapping connecting vessel for continuous tapping; the vertical furnace cooling element adopts a cooling wall.

2. A steel plant dust treatment system according to claim 1, characterized in that: The carbon bricks prepared from steel plant dust have the following dimensions: height: 30-70 mm, diameter: 30-70 mm, and the carbon bricks have through holes.

3. A steel plant dust treatment system according to claim 1, characterized in that: The vertical furnace charging device adopts a double bell furnace top.

4. A steel plant dust treatment system as claimed in claim 1, characterized in that: The blast heating system uses a ball or checker brick hot air furnace with a heating temperature of 750-1200℃.

5. A steel plant dust treatment system as claimed in claim 1, characterized in that: The vertical furnace is provided with a slag outlet, which is located above the molten iron channel.

6. A steel plant dust treatment system according to claim 1, characterized in that: Bag dust collector is used for vertical furnace gas purification.

7. A steel plant dust treatment system as claimed in claim 1, characterized in that: The gas pressure at the top of the vertical furnace is ≧10kpa.

Images