A method for utilizing metallurgical solid waste

Abstract

The present invention provides a method for utilizing metallurgical solid waste, which comprises: step A: utilizing solid waste generated in the production process of steel enterprises as raw materials, step B: processing into iron slag through high-temperature roasting in a rotary kiln, and step C: screening the iron slag, after the iron slag is screened, the iron slag with a particle size of ≥150mm is added to scrap steel as a steelmaking raw material into a converter; the iron slag with a particle size of <150mm is used as a coolant to replace the iron ore or sintered ore originally used in converter steelmaking for cooling. The iron slag product of the present invention has a large amount of iron slag used, and the use effect is not significantly different from that of sintered ore, while reducing the amount of waste emissions, realizing the transformation of waste into treasure and resource recycling.

Description

Technical Field

[0001] The invention relates to the field of recycling of metallurgical solid waste, and in particular to a method for utilizing metallurgical solid waste. Background Art

[0002] The output of carbon- and iron-containing wastes such as converter primary ash, converter secondary ash, coking coal powder, blast furnace ash, etc. generated in the production process of steel enterprises is relatively large. If they are piled up for a long time, they will cause environmental pollution. As steel companies pay more attention to energy conservation and emission reduction and attach importance to ultra-low emissions, the recycling of metallurgical waste has become increasingly important. Secondary recycling can not only reduce emissions, but also achieve economic benefits.

[0003] The quality of steelmaking in the converter steelmaking process depends on the slag making. The main purpose of slag making is to remove impurities such as sulfur, phosphorus, and zinc in the steel, transfer oxygen to the molten pool through the slag, and reduce the erosion of the slag on the furnace lining. The requirements for slag in the steelmaking process are high basicity, strong oxidizability, appropriate slag amount, good fluidity, and appropriate foaming.

[0004] At present, the coolants used in converter slag making in steel plants mainly include: scrap steel, iron oxide scale, iron ore, sintered ore, limestone, etc., and the above coolants all cause high steelmaking costs, which is not conducive to cost reduction for steel companies. At present, the industry usually disposes of metallurgical waste by adding a certain amount of adhesive to various wastes and pressing them into metal pellets, and then using them as converter coolants. As a coolant, this product has high requirements for the strength of its metal pellets. If it cannot reach a certain strength, it is not conducive to the use of the converter, resulting in less use. At the same time, the quality of the adhesive determines the strength of the metal pellets, and it also increases the cost and difficulty of disposal for enterprises.

[0005] In summary, the prior art has the following problems: metallurgical solid waste is made into metal pellets, which are then used as converter coolants, resulting in poor cooling effects, increased usage of other coolants, and increased disposal costs and difficulties for enterprises. Summary of the invention

[0006] The invention provides a method for utilizing metallurgical solid waste, so as to solve the problem that metallurgical solid waste is made into metal pellets and then used as converter coolant, resulting in poor converter steelmaking quality.

[0007] To this end, the present invention proposes a method for utilizing metallurgical solid waste, the method comprising:

[0008] Step A: using solid waste generated in the production process of steel enterprises as raw materials, mixing one or more mixtures of converter primary ash, secondary ash, converter tertiary dust ash, coking coal powder, blast furnace ash, environmental dust ash, underground silo ash, etc., to prepare a powdery mixture (powdery iron-containing material); not bonding together with an adhesive, and not pressing into metal pellets;

[0009] Step B: After being processed by high-temperature roasting in a rotary kiln, the iron slag is processed into iron slag. The main technical standards of the iron slag are as follows by weight percentage: TFe≥55%, metallization rate≥65%, Na<1%, K<1%, Pb<1%, Zn<1%; if it does not meet the standards, it is returned to the feeding end of the rotary kiln for mixing with other raw materials and then roasted at high temperature; the above-mentioned iron-containing materials are placed in a rotary kiln and roasted into molten iron at high temperature. As the furnace rotates, the non-iron materials are wrapped into irregular block materials of varying sizes. There is cooling circulating water at the discharge end of the rotary kiln to cool down. The state of the iron-containing materials is changed from the previous high-temperature liquid state to a solid state after cooling, that is, iron slag, which has a higher strength and is added to the converter as a coolant without crushing or falling into powder;

[0010] Step C: Screening the iron slag. The iron slag from the rotary kiln is screened, for example, the iron slag is cooled by industrial circulating water and then screened. After the iron slag is cooled by circulating water and screened, the fine dust (particle size is less than or equal to 1mm, accounting for 0.5-1% by weight of all iron slag) coming out with the iron slag directly enters the circulating water, and is used as a raw material after precipitation through the circulating water system. Among the remaining granular or block slag, the iron slag with a particle size ≥150mm (accounting for about 30% of the total) is added to scrap steel as a steelmaking raw material and enters the converter; the iron slag with a particle size of 1mm<particle size<150mm (accounting for about 70% of the total) is used as a coolant to replace the iron ore or sintered ore originally used in converter steelmaking for cooling. Among the iron slag with particle size of 1mm<<150mm, the content of iron slag with particle size of 1mm<<5mm is 15%-40%; the content of iron slag with particle size of 5mm≤<100mm is 50%-70%; the content of iron slag with particle size of 100mm<<150mm is 15%-40%; in the process of adding to the converter, the iron slag with these particle sizes is larger and is already granular or blocky, which can be fully and effectively utilized and will not be sucked away by the bag dust collector of the converter like dust.

[0011] Furthermore, the prepared mixture has: 30%≤TFe≤40%, C content 20%-30%, and Zn≤5%.

[0012] Furthermore, the coking coal powder has a carbon content of more than 75%.

[0013] Furthermore, the blast furnace ash is one or a mixture of more than one of dry process ash, trough ash, top ash and gravity ash.

[0014] Furthermore, the mixture is transported to the rotary kiln via a belt conveyor. After high-temperature roasting in the rotary kiln, harmful substances such as zinc and cadmium are reduced into the gas phase, and are oxidized into oxide dust in the air, and then collected by a bag filter.

[0015] Furthermore, in step B, the high temperature roasting temperature of the rotary kiln is 900-1050°C.

[0016] Furthermore, in step B, the high temperature roasting time in the rotary kiln is 15-20 minutes.

[0017] The present invention also provides a converter coolant, which is made according to the above-mentioned method for utilizing metallurgical solid waste, wherein the converter coolant is iron slag with a particle size of less than 150 mm. (Iron slag with a particle size of ≥150 mm can be used as scrap steel raw material)

[0018] The present invention utilizes solid waste generated in the production process of steel enterprises as raw materials, which may be dry or wet materials. The wet materials need to be uniformly mixed with the dry materials, and the products obtained after roasting in a rotary kiln have a particle size of ≥150mm (accounting for about 30% of the total amount) and are added to scrap steel and fed into a converter. The particles of <150mm (accounting for about 70% of the total amount) replace the original sintered ore for cooling. The present invention has good use effect, and the raw materials, auxiliary materials, etc. are all waste materials of steel enterprises with low cost. The amount of product iron slag used is large, and the use effect is not significantly different from that of sintered ore. No adhesive is required, and no metal pellets need to be made, which reduces the production and use requirements of coolants, while reducing waste emissions, realizing the transformation of waste into treasure and resource recycling, with specific good environmental protection benefits and economic benefits, and is worthy of vigorous promotion. DETAILED DESCRIPTION

[0019] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the present invention is now described.

[0020] The present invention provides a method for utilizing metallurgical solid waste, also referred to as: a process method for making a converter coolant using metallurgical solid waste, or: a method for making a converter coolant using metallurgical solid waste, the method for utilizing metallurgical solid waste mainly comprises:

[0021] (1) Batching: The batching is calculated based on the converter primary ash, converter secondary ash, coking coal powder and blast furnace ash, so that the chemical composition of the solid waste mixture after batching mainly meets the following requirements: 30% ≤ TFe ≤ 40%, C content is 20% to 30%, and Zn ≤ 5%. If the carbon content is too low, the calorific value of the kiln cannot be met, and external energy supplement is required, resulting in high costs. If the carbon content is too high, the calorific value of the kiln will be too high, causing iron to melt, which is prone to ring formation or "red kiln" phenomenon. If the TFe (total iron) content is too low, it will be detrimental to the metal recovery rate, and if the TFe content is too high, it will cause fluctuations in production operations. If the Zn content is too high, it will easily cause corrosion of the refractory materials of the kiln.

[0022] (2) After the mixed material prepared in the first step is sent to the rotary kiln and roasted at a high temperature of 900-1050℃ for 15-20 minutes, harmful substances such as zinc and cadmium are reduced and enter the gas phase at this high temperature, and are oxidized in the air to become zinc oxide dust, which is then collected by the bag filter. After the harmful elements are separated from the raw materials, a product iron slag with a high total iron content (TFe ≥ 55%) can be obtained. The main indicators of the iron slag are: TFe ≥ 55%; metallization rate ≥ 65%, Na, K, Pb, Zn and other harmful substances < 1%; the iron slag is screened and the particle size ≥ 150mm. The iron slag is mixed with scrap steel and fed into the converter. The iron slag with a particle size < 150mm is transported to the converter to replace the iron ore or sintered ore originally used in converter steelmaking for cooling, which is different from the original converter cooling process (one ton of sintered ore) The coolant produced by the present invention has no significant difference from the coolant produced by the existing converter in producing iron ore or sintered ore as a coolant. At the same time, the use of sintered ore is reduced (generally, 1-4 tons of sintered ore can be saved in normal steelmaking (240-ton converter), and about 10,000-40,000 tons of sintered ore can be saved in producing 2.4 million tons of steel a year, and about 40,000-160,000 tons of sintered ore can be saved in producing 10 million tons of steel), thereby realizing the recycling of solid waste resources.

[0023] (3) The technical standards of the converter coolant of the present invention are shown in Table 1

[0024] (4) Table 1 Physical and technical standards of converter coolant of the present invention

[0025]

[0026] (4) Implementation 1: The present invention uses solid wastes from steel enterprises, such as primary converter ash, secondary converter ash, coking coal powder, and blast furnace ash, as raw materials. The raw material components are shown in Table 2.

[0027] Table 2: Raw material composition of the coolant used in this embodiment

[0028]

[0029] (5) Coolant formulation scheme is shown in Table 3

[0030] Table 3 Coolant proportion scheme of this embodiment

[0031]

[0032] (6) Manufacturing method: First, the above-mentioned various types of solid waste are loaded into the corresponding silo by a forklift, mixed according to the proportion of ingredients in Table 3 by a quantitative feeding scale, and then transported to a rotary kiln by a belt conveyor. After being roasted at a high temperature of 900-1050°C for 15-20 minutes in the rotary kiln, for example, roasted at 950°C for 15 minutes, harmful substances such as zinc and cadmium are reduced at this high temperature, and then collected by a bag filter. The obtained iron slag is sieved, and the steel slag greater than or equal to 150 mm is added to the scrap steel and added to the converter. The steel slag less than 150 mm (the iron slag content of 1 mm < particle size < 5 mm is 18%; the iron slag content of 5 mm ≤ particle size < 100 mm is 56%; the iron slag content of 100 mm < particle size < 150 mm is 26%) replaces the original sintered ore, which fully meets the production requirements of the converter.

[0033] (7) Implementation 2: The present invention uses solid wastes from steel enterprises, such as primary converter ash, secondary converter ash, and coking coal powder, as raw materials. The raw material composition is shown in Table 4.

[0034] Table 4: Raw material composition of the coolant used in this embodiment

[0035]

[0036] (8) Coolant formulation scheme is shown in Table 5

[0037] Table 5 Coolant proportion scheme of this embodiment

[0038]

[0039] (9) Manufacturing method: First, the above-mentioned various types of solid waste are loaded into the corresponding silo by a forklift, mixed according to the proportion of ingredients in Table 4 by a quantitative feeding scale, and then transported to a rotary kiln by a belt conveyor.

[0040] After roasting at 900-1050℃ for 15-20 minutes, for example, roasting at 1000℃ for 20 minutes, harmful substances such as zinc and cadmium are reduced at this high temperature, and then collected by a bag dust collector. The obtained iron slag is screened, and the iron slag greater than or equal to 150mm is added to the scrap steel as a steelmaking raw material or other. In the steelmaking plant, it is grabbed by an overhead crane and put into the converter. The iron slag less than 150mm (1mm<particle size<5mm iron slag content is 21%; 5mm≤particle size<100mm iron slag content is 61%;

[0041] The iron slag with particle size of 100mm<particle size<150mm has a content of 18%) replaces the original sintered ore as coolant and is added to the scrap steel through the coolant adding hopper and chute (the adding channel is different from that of the iron slag greater than or equal to 150mm, and the function is different), which fully meets the production requirements of the converter.

[0042] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. The components of the present invention can be combined with each other without conflict, and any equivalent changes and modifications made by any technician in the field without departing from the concept and principle of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for utilizing metallurgical solid waste, characterized in that: The method for utilizing the metallurgical solid waste includes: Step A: using solid waste generated in the production process of steel enterprises as raw materials, mixing two or more of the following: primary converter ash, secondary converter ash, tertiary converter dust removal ash, coking coal powder, blast furnace ash, environmental dust removal ash, and underground silo ash to prepare a mixture; not bonding together with an adhesive, and not pressing into metal pellets; Step B: After being processed by high-temperature roasting in a rotary kiln, iron slag is formed. The main technical standards of iron slag are as follows by weight percentage: TFe ≥ 55%, metallization rate ≥ 65%, Na < 1%, K < 1%, Pb < 1%, Zn < 1%; Step C: Screening the iron slag. After screening, the iron slag with a particle size of ≥150 mm is mixed with scrap steel as a raw material for steelmaking and fed into the converter; the iron slag with a particle size of 1 mm <150 mm is used as a coolant to replace the iron ore or sintered ore originally used in converter steelmaking for cooling; Prepared mixture: 30%≤TFe≤40%, C content 20%~30%, Zn≤5%; In step B, the high temperature roasting temperature of the rotary kiln is 900-1050°C; In step B, the high temperature roasting time in the rotary kiln is 15-20 minutes.

2. The method for utilizing metallurgical solid waste according to claim 1, characterized in that: The coking coal powder has a carbon content of more than 75%.

3. The method for utilizing metallurgical solid waste according to claim 1, characterized in that: Blast furnace ash is dry ash, trough ash, top ash, gravity ash or a mixture of more than one of them.

4. The method for utilizing metallurgical solid waste according to claim 1, characterized in that: The mixture is transported to the rotary kiln via a belt conveyor. After high-temperature roasting in the rotary kiln, harmful substances such as zinc and cadmium are reduced into the gas phase and oxidized into oxide dust in the air, which is then collected by a bag dust collector.

5. The method for utilizing metallurgical solid waste according to claim 1, characterized in that: The mixing proportions of the mixed materials are as follows by weight: primary converter ash: 50-70%, secondary ash: 3-9%, coking coal powder: 5-35%, and blast furnace ash: 25-35%.

6. The method for utilizing metallurgical solid waste according to claim 1, characterized in that: The mixing proportions of the mixture by weight are: converter primary ash: 55%, secondary ash: 5%, coking coal powder: 7%, blast furnace ash: 33%.

7. The method for utilizing metallurgical solid waste according to claim 1, characterized in that: The mixing proportions of the mixture are as follows by weight: converter primary ash: 65%, secondary ash: 5%, coking coal powder: 30%.

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