Stainless steel base material and method for resourceful treatment of stainless steel dedusting ash

Abstract

The invention relates to the technical field of solid waste resource utilization, in particular to a stainless steel base material and a method for resource treatment of stainless steel dedusting ash. The method for resourceful treatment of the stainless steel dedusting ash comprises the following steps: carrying out reduction smelting on the stainless steel dedusting ash, monatomic silicon powder and lime powder, and carrying out slag-iron separation to obtain molten iron and slag; and casting the molten iron to obtain a stainless steel base material, and carrying out water quenching treatment on the slag to obtain water-quenched slag. According to the method, the monatomic silicon powder is used as a reducing agent to carry out reduction smelting on the stainless steel dedusting ash, so that carbon emission and energy consumption are reduced, the harmless treatment process is short, the investment of environment-friendly equipment is small, the recovery rate of Ni in the stainless steel dedusting ash is larger than or equal to 95%, the recovery rate of Cr is larger than or equal to 95%, and the recovery rate of Fe is larger than or equal to 90%.

Description

Technical Field

[0001] The invention relates to the technical field of resource utilization of solid waste, and in particular to a stainless steel base material and a method for resource processing of stainless steel dust ash. Background Art

[0002] The stainless steel smelting industry produces a large amount of stainless steel dust ash containing heavy metal waste every year (class HW23 hazardous waste in the "National List of Hazardous Wastes" (2023 edition)). The dust ash generated during the smelting process of each ton of stainless steel is 40-60 kg. Stainless steel dust ash contains heavy metal elements such as nickel and chromium. If not handled properly, it will not only cause waste of resources, but also seriously pollute the environment, especially chromium pollution, which will pose a serious threat to environmental safety and human health.

[0003] At present, the main methods for treating stainless steel dust ash are: (1) directly returning it to the stainless steel smelting production system, but this will affect the control of stainless steel production process indicators and thus affect product quality; (2) treating stainless steel dust ash with raw materials such as laterite nickel ore or pickling sludge through batching, homogenization, sintering, high-temperature melting reduction and other processes for harmless disposal and comprehensive resource utilization. However, this disposal process has problems such as long process flow, high energy consumption, large investment in environmental protection equipment, and low metal element recovery rate. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the existing stainless steel dust ash treatment process, such as long process flow, high energy consumption, large investment in environmental protection equipment, and low metal element recovery rate, thereby providing a stainless steel base material and a method for resource-based treatment of stainless steel dust ash to solve the above problems.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for recycling stainless steel dust, comprising: reducing and smelting the stainless steel dust, elemental silicon powder and lime powder, and separating slag and iron to obtain molten iron and slag;

[0007] The molten iron is cast to obtain a stainless steel base material, and the slag is water-quenched to obtain water-quenched slag.

[0008] Preferably, the mass ratio of the stainless steel dust, silicon in elemental silicon powder and calcium oxide in lime powder is 7:2:1.

[0009] Preferably, the components of the stainless steel dust ash include Ni: 2wt%, FeO: 53wt%, CaO: 15wt%, SiO: 6wt%, Cr2O: 14wt%, MgO: 2wt%, and C: 1.5wt%.

[0010] Preferably, the elemental silicon powder is silicon wafer cutting waste.

[0011] Preferably, in the silicon wafer cutting waste, metallic silicon accounts for 83-84%, silicon dioxide accounts for 13-14%, and diamond accounts for 1-1.5%.

[0012] Preferably, the CaO content in the lime powder is ≥ 80wt%.

[0013] Preferably, the reduction smelting temperature is 1600-1700°C, preferably 1650°C;

[0014] And / or, the reduction smelting is carried out in a tilting refining furnace;

[0015] And / or, the stainless steel dust, elemental silicon powder and lime powder are stored in a closed storage bin and pneumatically transported through a closed pipeline for feeding.

[0016] Preferably, a heat exchange tube is arranged in the closed storage bin and the raw and auxiliary materials are subjected to heat exchange treatment using the reducing smelting flue gas.

[0017] Preferably, the temperature of the reducing smelting flue gas is 850-900°C.

[0018] The present invention also provides a stainless steel base material, which is prepared by the above-mentioned method for resource-based treatment of stainless steel dust ash.

[0019] In the present invention, the tilting refining furnace uses electric energy to reduce and melt the stainless steel dust. After the raw materials are added to the electric furnace, they can be powered on for heating. The three-phase alternating current is delivered to three carbon electrodes by the transformer through the soft busbar and the electrode clamp. The electrodes are inserted into the slag layer, and the current generates an arc at the air pocket between the end of the electrode and the slag, and heat is generated by the resistance of the charge and the slag at the same time. The electrode is a conductor that releases electric energy in the form of an arc to heat and melt the charge, and does not participate in the reduction reaction. Generally, the electrode is discharged once per shift, and the power is supplied after the electrode is discharged. The current increases step by step from small to large.

[0020] The technical solution of the present invention has the following advantages:

[0021] 1. A method for recycling stainless steel dust, comprising: reducing and smelting stainless steel dust, elemental silicon powder and lime powder, separating slag and iron to obtain molten iron and slag; casting the molten iron to obtain stainless steel base material, and water quenching the slag to obtain water-quenched slag. This method uses the fact that silicon has a greater affinity for oxygen than chromium, iron and nickel, thereby seizing oxygen from the oxides of chromium, iron and nickel in the stainless steel dust and directly reducing them, while calcium, aluminum and magnesium have a greater affinity for oxygen than silicon, so the calcium, aluminum and magnesium oxides in the stainless steel dust are not reduced by silicon but are enriched in the slag. In addition, the reducibility of silicon is greater than that of carbon, and silicon is an exothermic reaction when used as a reducing agent, which can achieve the purpose of saving energy. Based on the above technical concept, this method uses elemental silicon powder as a reducing agent to reduce and smelt stainless steel dust ash, thereby reducing carbon emissions and energy consumption. The harmless treatment process is short and the investment in environmental protection equipment is small. The recovery rate of Ni in stainless steel dust ash is ≥95%, the recovery rate of Cr is ≥95%, and the recovery rate of Fe is ≥90%.

[0022] 2. In the method for recycling stainless steel dust of the present invention, raw and auxiliary materials are stored in a closed storage bin and transported through a closed pipeline for feeding, thereby avoiding the problem of difficult control of environmental protection during the production process. In addition, the method also sets a heat exchange tube in the closed storage bin and uses the reduction smelting flue gas to perform heat exchange treatment on the raw and auxiliary materials, thereby utilizing waste heat and further reducing energy consumption.

[0023] 3. In the method for recycling stainless steel dust of the present invention, a tilting refining furnace is used for reduction smelting to improve the uniformity of the mixing of raw and auxiliary materials, so that the quality of the stainless steel substrate is improved, and the tilting refining furnace is used to improve the smelting efficiency. The mechanism is that the furnace body of the tilting refining furnace can be tilted during the smelting process, and the tilting operation can achieve the uniformity of the components in the metal melt and the reduction smelting speed to a certain extent, thereby shortening the smelting cycle and improving product quality. DETAILED DESCRIPTION

[0024] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0025] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0026] Example 1

[0027] This embodiment provides a method for recycling stainless steel dust, and the specific steps are as follows:

[0028] (1) Stainless steel dust, silicon powder and lime powder are transported to a closed storage tank by a closed tank truck, and then transported to the upper metering tank of a tilting refining furnace by pneumatic means through a closed pipeline. A heat exchange pipe is arranged in the closed silo, and the high-temperature flue gas (850°C) of the tilting refining furnace is used to exchange heat with the raw and auxiliary materials for waste heat utilization; wherein the components in the stainless steel dust include Ni: 2wt%, FeO: 53wt%, CaO: 15wt%, SiO: 6wt%, Cr2O: 14wt%, MgO: 2wt%, and C: 1.5wt%; the silicon powder is silicon wafer cutting waste, in which metal silicon accounts for 83%, silicon dioxide accounts for 14%, and diamond accounts for 1.2%; and CaO in the lime powder accounts for 80wt%.

[0029] (2) According to the mass ratio of stainless steel dust, silicon in elemental silicon powder and calcium oxide in lime powder of 7:2:1, the materials are added into the tilting refining furnace through the feeding pipe. With the melting reduction and slag making in the furnace, intermittent operation is implemented, and the charging, heating and discharging are alternated. The smelting temperature is controlled at 1650℃. After the smelting is completed, the tilting device of the refining electric furnace is started, and the slag and iron are discharged from the outlet at the same time and transferred to the iron ladle for slag and iron separation. The specific gravity of the molten metal is relatively large (about 7.5t / m 3 ), deposited in the lower part of the ladle; the slag has a small specific gravity (about 1.8t / m 3 ), floats on the top of the molten metal, and is physically separated. The molten metal in the ladle flows into the ingot mold by gravity and is cast into a stainless steel base material for nickel-chromium-iron alloy products (metal content: Ni is 2.92%, Cr is 14.01%, Fe is 60.22%; recovery rate Ni is 95%, Cr is 95%, Fe is 90%), and demolded after natural cooling. The slag enters the water quenching system through the chute, and the liquid slag is impacted with high-pressure water to form fine granular slag, namely water-quenched slag (glass slag).

[0030] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for recycling stainless steel dust, characterized in that: include: Stainless steel dust, elemental silicon powder and lime powder are reduced and smelted, and slag and iron are separated to obtain molten iron and slag; The molten iron is cast to obtain a stainless steel base material, and the slag is water-quenched to obtain water-quenched slag.

2. The method according to claim 1, characterized in that The mass ratio of the stainless steel dust, silicon in the elemental silicon powder and calcium oxide in the lime powder is 7:2:

1.

3. The method according to claim 1 or 2, characterized in that: The components of the stainless steel dust ash include Ni: 2wt%, FeO: 53wt%, CaO: 15wt%, SiO: 6wt%, Cr2O: 14wt%, MgO: 2wt%, and C: 1.5wt%.

4. The method according to any one of claims 1 to 3, characterized in that: The elemental silicon powder is waste from silicon wafer cutting.

5. The method according to claim 4, characterized in that Among the silicon wafer cutting waste, metallic silicon accounts for 83-84%, silicon dioxide accounts for 13-14%, and diamond accounts for 1-1.5%.

6. The method according to any one of claims 1 to 5, characterized in that: The lime powder contains CaO≥80wt%.

7. The method according to any one of claims 1 to 6, characterized in that: The reduction smelting temperature is 1600-1700°C, preferably 1650°C; And / or, the reduction smelting is carried out in a tilting refining furnace; And / or, the stainless steel dust, elemental silicon powder and lime powder are stored in a closed storage bin and pneumatically transported through a closed pipeline for feeding.

8. The method according to claim 7, characterized in that Heat exchange tubes are arranged in the closed material storage bin and the raw and auxiliary materials are subjected to heat exchange treatment using the reducing smelting flue gas.

9. The method according to claim 8, characterized in that The temperature of the reducing smelting flue gas is 850-900°C.

10. A stainless steel base material, characterized in that: The stainless steel dust ash is prepared by the method for resource recovery treatment of stainless steel dust ash as described in any one of claims 1 to 9.