A method for treating stainless steel dust

Abstract

The present invention belongs to the field of metallurgical technology, and provides a method for treating stainless steel dust ash, comprising: first, modifying an ash melting furnace, attaching a refractory protective layer to the lining of the furnace shell, and using a water-cooled furnace cover and a corundum sleeve combination for the furnace cover; then, mixing the stainless steel dust ash with carbon and silicon reducing agents in proportion and sending them into the modified ash melting furnace; controlling the ash melting furnace, setting the furnace temperature and smelting time, and feeding and replenishing the ash melting furnace at any time through the furnace front silo and the screw conveyor under the silo according to the reduction smelting situation; finally, tapping and casting, and completing the treatment and reuse of the stainless steel dust ash; the present invention eliminates the sintering process of the stainless steel dust ash, directly performs reduction smelting on it, realizes the short-process disposal of the stainless steel dust ash, and avoids the environmental pollution and waste of other resources caused by the sintering process of the stainless steel dust ash.

Description

Technical Field

[0001] The invention belongs to the technical field of reduction metallurgy, relates to the treatment of stainless steel dust ash, and specifically is a method for treating stainless steel dust ash in a sintering-free ash melting furnace. Background Art

[0002] Stainless steel dust is the polluted waste discharged by the dust collector during the steelmaking process of stainless steel plants. Its production accounts for about 4% of the stainless steel output. The components of dust are mainly FeO, Cr2O3, NiO, SiO2, and CaO. The utilization of stainless steel dust is mainly reduction, extracting the metal components, especially the precious metal components, such as nickel and chromium; at the same time, through the metallurgical process, eliminate the hazardous waste components, such as hexavalent chromium.

[0003] The traditional methods of reducing and smelting stainless steel dust are blast furnace smelting and submerged arc furnace smelting; specifically, the stainless steel dust and reducing agent are mixed in proportion, sintered, and then the sintered block is sent to the blast furnace or submerged arc furnace, and other auxiliary materials are added for reduction smelting, and finally the metal components in the stainless steel dust are extracted. In this process, the sintering part has a great impact on the environment, and the pollution problem is very prominent. Summary of the invention

[0004] The purpose of the present invention is to provide a method for treating stainless steel dust ash, eliminating the sintering process, directly reducing and smelting the stainless steel dust ash, realizing a short-process disposal of the stainless steel dust ash, and avoiding environmental pollution and waste of other resources caused by the sintering process of the stainless steel dust ash.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0006] A method for treating stainless steel dust removal ash comprises the following steps:

[0007] Step 1, transform the ash melting furnace; increase the diameter of the furnace shell and furnace cover by 10-15%. Under the condition that the diameter of the electric furnace pole circle remains unchanged, the dust ash mixture layer that cannot be melted around the furnace lining and the liquid slag splashed during the smelting process adhere to the surface of the furnace lining to form a 50-100mm slag layer, forming a protective layer for the furnace shell and furnace lining; the furnace cover adopts a combination of a water-cooled furnace cover and a corundum sleeve, that is, the top surface of the furnace cover adopts a water circulation zone, and the position of the electrode water cooling sleeve is replaced by a corundum sleeve;

[0008] Step 2, batching: uniformly batch the stainless steel dust, carbon reducing agent, and silicon reducing agent, and feed them into the modified ash melting furnace;

[0009] Among them, the mass percentage of carbon reducing agent to dust ash raw material is 6-10%, and the mass percentage of silicon reducing agent to dust ash raw material is 3-6%;

[0010] The carbon-based reducing agent is coke particles with a fixed carbon content greater than 80%, and the particle size of the coke particles is 1-6mm; the silicon-based reducing agent is metallic ferrosilicon slag with a silicon content greater than 20%, and the silicon content can be greater than 20%.

[0011] Step 3, reduction smelting process: before the electrode is buried in the arc, a low voltage and low power operation mode is adopted; after the electrode is buried in the arc, a high voltage and high power operation mode is adopted. The smelting time is 6 hours per furnace, and the furnace temperature is measured in front of the furnace and the temperature is controlled within 1550 degrees.

[0012] Step 4: Casting.

[0013] Beneficial effects of the present invention: Compared with blast furnaces and submerged arc furnaces, the use of ash melting furnaces to reduce and smelt stainless steel dust removal ash has the following advantages:

[0014] The entire reduction process does not require a sintering step, which shortens the process steps and eliminates the environmental pollution caused by the dust ash sintering process.

[0015] Saves factory floor space.

[0016] It is easier to respond to process requirements and equipment failures, and the ash melting furnace can be shut down and started at any time.

[0017] In addition to circulating water cooling, the ash melting furnace does not require any additional water, which avoids the water use in the sintering process of the blast furnace or the electric arc furnace, saves water resources and reduces production costs. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the embodiments.

[0019] Example 1

[0020] A five-ton electric arc furnace was modified to reduce the dust from smelting stainless steel.

[0021] First, the furnace shell and furnace cover of the electric arc furnace were modified to meet the needs of dust removal for reduction smelting of stainless steel. The diameter of the furnace shell and furnace cover was increased by 10%, and the material layer was used as the refractory protection layer of the furnace shell, that is, a 50mm layer of raw materials was attached to the furnace lining as the refractory protection layer of the furnace shell; the erosion of the furnace lining by the arc and acidic slag was reduced.

[0022] The specific method of adhering the raw material layer is: increase the diameter of the furnace shell and the furnace cover by 10%, add the stainless steel dust ash and reducing agent mixture into the ash melting furnace while keeping the diameter of the electric furnace pole center circle unchanged, and the dust ash mixture layer that cannot be melted around the furnace lining and the liquid slag splashed during the smelting process will adhere to the surface of the furnace lining to form a slag layer of about 50mm, forming a protective layer for the furnace shell and lining.

[0023] The furnace cover adopts the combination of water-cooled furnace cover and corundum sleeve, that is, the water circulation cooling zone is adopted on the top surface of the furnace cover, and the corundum sleeve is used instead of the electrode water cooling sleeve;

[0024] Then, the batching is carried out; the batching system is equipped with a 700-square-meter bag dust collector to evenly batch the stainless steel dust ash, carbon reducing agent, and silicon reducing agent, and the mixed material is sent to the modified ash melting furnace front silo using elevators, FU scraper conveyors and other sealing equipment.

[0025] Among them, the mass percentage of the carbon reducing agent to the dust ash raw material is 6-10%, and the mass percentage of the silicon reducing agent to the dust ash raw material is 3-6%.

[0026] The carbon-based reducing agent is coke particles with a fixed carbon content greater than 80% and a particle size between 1 and 6 mm.

[0027] The silicon reducing agent is metallic ferrosilicon slag with a silicon content greater than 20%.

[0028] Next, reduction smelting is carried out; the reduction smelting process of the ash melting furnace is controlled: before the electrode is buried in the arc, low voltage and low power operation is adopted; after the electrode is buried in the arc, high voltage and high power operation is adopted; the smelting time is generally 6 hours per furnace, and the output of nickel-chromium pig iron can reach the rated output of the electric furnace or above; the furnace temperature is measured in front of the furnace, and the temperature is controlled within 1550 degrees.

[0029] According to the reduction smelting situation, the ash melting furnace is fed and supplemented at any time through the silo in front of the furnace and the screw conveyor under the silo, so that the ash melting furnace can continuously carry out reduction smelting. At the same time, a 2,000 square meter bag dust collector is added to ensure that there is no dust during the reduction smelting process of the ash melting furnace.

[0030] Finally, the iron is tapped and cast. The steel tapping process is carried out in a dust removal hood by using a steel tapping battery car to avoid environmental pollution during the steel tapping process. A bag dust collector is used above the molten steel casting area to smoothly absorb the smoke and dust during casting. Example 2

[0031] Another five-ton electric arc furnace was modified to reduce the dust from smelting stainless steel.

[0032] First, the furnace shell and furnace cover of the electric arc furnace were modified by increasing the diameter of the furnace shell and furnace cover by 15%, using the material layer as a refractory protection layer for the furnace shell, and attaching a raw material layer of about 100 mm to the furnace lining to reduce the erosion of the furnace lining by the electric arc and acidic slag.

[0033] The specific method of attaching the raw material layer is: increase the diameter of the furnace shell and the furnace cover by 15%, add the stainless steel dust ash and reducing agent mixture into the ash melting furnace while keeping the diameter of the electric furnace pole center circle unchanged, and the dust ash mixture layer that cannot be melted around the furnace lining and the liquid slag splashed during the smelting process will adhere to the surface of the furnace lining to form a slag layer of about 100mm, forming a protective layer for the furnace shell and lining.

[0034] The furnace cover also adopts the combination of water-cooled furnace cover and corundum sleeve, that is, the water circulation cooling zone is adopted on the top surface of the furnace cover, and the corundum sleeve is used instead of the electrode water cooling sleeve;

[0035] Then, the batching is carried out; the batching system is equipped with a 700-square-meter bag dust collector to evenly batch the stainless steel dust ash, carbon reducing agent, and silicon reducing agent, and the mixed material is sent to the modified ash melting furnace front silo using elevators, FU scraper conveyors and other sealing equipment.

[0036] Among them, the mass percentage of carbon reducing agent to dust ash raw material is 6-10%, and the mass percentage of silicon reducing agent to dust ash raw material is 3-6%;

[0037] The carbon-based reducing agent is coke particles with a fixed carbon content greater than 80% and a particle size between 1 and 6 mm.

[0038] The silicon reducing agent is metallic ferrosilicon slag with a silicon content greater than 20%.

[0039] Next, reduction smelting is carried out; the reduction smelting process of the ash melting furnace is controlled: before the electrode is buried in the arc, low voltage and low power operation is adopted; after the electrode is buried in the arc, high voltage and high power operation is adopted; the smelting time is generally 6 hours per furnace, and the output of nickel-chromium pig iron can reach the rated output of the electric furnace or above; the furnace temperature is measured in front of the furnace, and the temperature is controlled within 1550 degrees.

[0040] Finally, the iron is tapped and cast. The steel tapping process is carried out in a dust removal hood by using a steel tapping battery car to avoid environmental pollution during the steel tapping process. A bag dust collector is used above the molten steel casting area to smoothly absorb the smoke and dust during casting.

[0041] The benefits of modifying the furnace shell and furnace cover are: on the one hand, because the specific gravity of dust removal ash is relatively small, the smelting process requires multiple feedings. In order to reduce the number of feedings, avoid heat loss, and improve the smelting efficiency of the ash melting furnace, the diameter of the furnace shell and furnace cover is increased; on the other hand, because the pole circle diameter of the electric furnace remains unchanged, the slag material can form a slag protective layer on the surface around the furnace shell and lining during the early smelting process, enhancing the tolerance of the furnace lining and avoiding corrosion of the furnace lining by electric arc and acidic slag.

[0042] The ash melting furnace modified as described in Example 1 and Example 2 processes a furnace of 5 tons of stainless steel dust ash to produce approximately 2 tons of stainless steel ingots. The processed stainless steel dust ash contains about 1.5% nickel and about 9% chromium; the produced nickel-chromium pig iron has a nickel content of about 3.2% and a chromium content of about 15%.

Claims

1. A method for treating stainless steel dust, characterized in that: The steps include: Step 1, transform the ash melting furnace; enlarge the furnace shell and furnace cover of the electric arc furnace, and attach the raw material layer to the furnace lining as a protective layer of the furnace shell; the furnace cover adopts a combination of a water-cooled furnace cover and a corundum sleeve, that is, the top surface of the furnace cover adopts a water circulation cooling zone, and the position of the electrode water cooling sleeve is replaced by a corundum sleeve; The method for forming the furnace shell protective layer is as follows: the diameter of the furnace shell and the furnace cover of the electric arc furnace is increased by 10-15%, and the stainless steel dust removal ash and the reducing agent mixture are added to the ash melting furnace for smelting while the electric furnace pole center remains unchanged, and the dust removal ash mixture layer that cannot be melted around the furnace lining and the liquid slag splashed during the smelting process are attached to the surface of the furnace lining to form a 50-100mm thick slag layer, that is, the furnace shell and lining protective layer is formed; Step 2, batching; uniformly batch the stainless steel dust ash, carbon reducing agent, and silicon reducing agent, and feed them into the ash melting furnace modified in step 1; wherein the mass percentage of the carbon reducing agent to the dust ash raw material is 6-10%, and the mass percentage of the silicon reducing agent to the dust ash raw material is 3-6%; Step 3, reduction smelting; controlling the ash melting furnace, and according to the reduction smelting situation, feeding and replenishing the ash melting furnace through the silo in front of the furnace and the screw conveyor under the silo, so that the ash melting furnace can continuously perform reduction smelting; Step 4: Casting.

2. The method for treating stainless steel dust according to claim 1, characterized in that: The carbon-based reducing agent is coke particles with a fixed carbon content of more than 80% and a particle size of 1-6 mm; the silicon-based reducing agent is ferrosilicon slag with a silicon content of more than 20%.

3. The method for treating stainless steel dust according to claim 1, characterized in that: In the step 3, the reduction smelting process of the ash melting furnace is controlled: before the electrode is buried in the arc, low voltage and low power operation is adopted; after the electrode is buried in the arc, high voltage and high power operation is adopted; the smelting time is controlled within 6 hours per furnace, and the furnace outlet temperature is controlled within 1550 degrees by measuring the temperature in front of the furnace.