Method for disposing sodium-based desulfurization ash by using a roller method steel slag treatment process system

Abstract

The application discloses a method for disposing sodium-based desulfurization ash by using a roller method steel slag treatment process system, which comprises the following steps: firstly, placing the sodium-based desulfurization ash in a pretreatment pool, adding water into the pretreatment pool by using a water supplement system, and introducing compressed air into the pretreatment pool to prepare a desulfurization ash aqueous solution; according to the production rhythm and backwater condition of the roller slag treatment process, detecting the pH value of the circulating water in a sedimentation tank for treatment, and after the sedimentation process is completed, inputting the upper clean water into a clean water pool, supplementing the water loss in the process into the clean water pool by using the water supplement system; the water is transported to a roller cooling and flue gas dust removal system for use; and the backwater after being used by the roller cooling and flue gas dust removal system is introduced into the sedimentation tank through a backwater ditch to complete the turbid circulating water circulation process of the roller process. The method utilizes the characteristics of the existing roller slag treatment process to cooperatively dispose the sodium-based desulfurization ash, is simple, does not need to add a large number of equipment, has strong implementability, reduces solid waste emission, and reduces environmental protection disposal cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid waste resource utilization, and in particular to a method for disposing of sodium-based desulfurization ash by using a drum method steel slag treatment process system. BACKGROUND

[0002] With the implementation of the national steel enterprise atmospheric ultra-low emission requirement, the sodium-based flue gas desulfurization system is widely used in steel plant dry quenching coke oven, gas boiler and other process systems, which has the characteristics of high efficiency and low cost. However, the by-product of desulfurization, sodium-based desulfurization ash, is difficult to be resourcefully utilized, which has become a problem of solid waste resource utilization for steel enterprises.

[0003] The sodium-based desulfurization ash mainly contains Na2SO4, Na2SO3, NaHCO3 and other substances, and there are few reports on the resource utilization of sodium-based desulfurization ash. A Chinese invention patent with publication number CN109881019A discloses a method for resource utilization of vanadium-containing desulfurization slag. The method mixes the vanadium-containing desulfurization slag with water, adds a precipitating agent and heats, then separates the solid-liquid material, and the vanadium enters the solid phase slag. The liquid phase is crystallized to obtain sodium sulfate. The method is used for the desulfurization slag generated in the pretreatment process of molten iron for smelting of specific steel grades, and the raw material used is different from the desulfurization ash described in the present application. A Chinese invention patent with publication number CN102530997A discloses a desulfurization product recovery process. The collected waste slag is subjected to dissolution and oxidation, flocculation and clarification, evaporation and crystallization, thickening, centrifugation and drying to obtain anhydrous mirabilite product. The method is suitable for the recovery and utilization of by-products obtained from the sodium alkali method glass furnace flue gas desulfurization. Two Chinese invention patents with publication numbers CN110451532A and CN110697738A report a resourceful treatment method for sodium-based desulfurization ash. The method completely dissolves the desulfurization ash, uses a flocculating agent to precipitate and filter the suspended solids and other impurities, adjusts the pH value by adding sulfuric acid, and then recovers sodium sulfate through evaporation and crystallization, centrifugation and other steps. The centrifugal liquid is recovered for desulfurization ash dissolution. Although these methods can realize the disposal and resource utilization of sodium-based desulfurization ash, they have the problems of complex process, high equipment investment and high treatment cost, which are difficult to be used in steel plants. SUMMARY

[0004] The present application provides a method for disposing of sodium-based desulfurization ash by using a direct cooling water system of a drum method steel slag treatment process, which combines the drum method steel slag treatment process with the physical and chemical characteristics of sodium-based desulfurization ash, uses the steel slag treatment process to cooperatively dispose of the desulfurization ash, and uses water treatment reagents for sodium-based desulfurization ash. The present application not only reduces the reagent cost of the drum method steel slag treatment process, but also realizes the in-plant environmental protection disposal of sodium-based desulfurization ash of steel enterprises, and reduces the solid waste discharge.

[0005] To achieve the above object, the technical scheme of the present application is as follows:

[0006] The present application provides a method for disposing sodium-based desulfurization ash by using a drum method steel slag treatment process system, comprising the following steps:

[0007] 1) The sodium-based desulfurization ash is placed in a pretreatment pool, water is added to the pretreatment pool by using a water supplementing system, compressed air is introduced into the pretreatment pool, and a desulfurization ash aqueous solution is prepared;

[0008] 2) According to the production rhythm and backwater condition of the drum slag treatment process, after the periodic backwater is completed, the pH value of the circulating water in the sedimentation pool is detected,

[0009] When pH≥12.0, the desulfurization ash aqueous solution prepared in the pretreatment pool is used to supplement water to the sedimentation pool, and the pH value in the sedimentation pool is adjusted to ≤11.6; the supplement of the desulfurization ash aqueous solution is immediately stopped;

[0010] When pH<12.0,

[0011] 3) After the sedimentation process is completed, the upper clear water is input into a clear water pool, the pH value of the clear water pool is adjusted to 6-9, and the water loss in the process is supplemented to the clear water pool by using a water supplementing system;

[0012] 4) The water in the clear water pool is transported to the drum cooling and flue gas dust removal system by using a water supply pump;

[0013] 5) The backwater after the drum cooling and flue gas dust removal system is used is introduced into the sedimentation pool through a backwater channel to complete the turbid circulating water circulation process of the drum process.

[0014] Further, in the step 1), the percentage of the chemical components of the sodium-based desulfurization ash is as follows:

[0015] Na2SO4 30-60%;

[0016] Na2SO3 10-20%;

[0017] NaHCO3 20-60%;

[0018] The balance is crystallization water and trace amounts of other impurities; and the content of Na2SO4 is more than 2 times the content of Na2SO3.

[0019] Further, the content of the particle with a particle size of 200 mesh (75 μm) or less in the sodium-based desulfurization ash is ≥90%.

[0020] Further, in the step 1), the water added by the water supplementing system is pure water, industrial water or steel enterprise water; and the amount of the water is 6-10 times the mass of the sodium-based desulfurization ash; and the time for introducing the compressed air is 30-60 min.

[0021] Further, in the step 2), the production rhythm cycle of the drum slag treatment process is 40-50 min; and the pH value of the periodic backwater is 12.0-13.0.

[0022] Further, in the step 3), the water supplementing amount of the water supplementing system in one production cycle is 0.2-0.3 t / t slag.

[0023] Further, in the step 3), the pH value of the clean water pool is adjusted to 6-9 by adding a mass fraction of 15-25% of dilute sulfuric acid solution into the clean water pool.

[0024] Further, in the step 3), the mass fraction of the dilute sulfuric acid solution is 20%.

[0025] The main chemical principle of the preparation process of the method is as follows:

[0026] 2Na2SO3+O2=2Na2SO4 (reaction 1)

[0027] 2NaHCO3+Ca(OH)2=Na2CO3+CaCO3↓+2H2O (reaction 2)

[0028] Na2CO3+H2SO4=Na2SO4+CO2↑+H2O (reaction 3)

[0029] Ca(OH)2+H2SO4=Ca2SO4+2H2O (reaction 4)

[0030] 2NaHCO3+2Ca(OH)2+H2SO4=Na2SO4+2CaCO3↓+4H2O (reaction 5)

[0031] The drum method steel slag treatment process utilizes the heat exchange between the steel balls and the hot molten slag to realize the rapid cooling of the molten slag, the turbid circulating water and the steel balls are used for heat exchange to cool the steel balls, and the cold steel balls are contacted with the hot molten slag again. At the same time, in the heat exchange process, dust is generated and enters the flue gas, and the turbid circulating water is also used for wet dust removal of the drum flue gas. The backwater after the turbid circulating water is used for drum cooling and flue gas dust removal is a suspension liquid, which contains a large amount of slag dust generated in the cooling and dust removal process, and the slag dust contains a certain amount of f-CaO, which reacts with water to generate Ca(OH)2. The backwater is usually a saturated solution of Ca(OH)2, so the pH value of the backwater is usually about 12.6 (the pH of the saturated Ca(OH)2 solution). In the sedimentation tank, the slag dust naturally settles to form sludge, and is periodically discharged from the sedimentation tank by the excavator. The upper clean water is sent into the clean water pool, and the Ca(OH)2 is neutralized by the sulfuric acid solution, such as reaction 4, and the pH is adjusted to 6-9, and then pumped into the water system for drum cooling and flue gas dust removal.

[0032] The present application utilizes NaHCO3 in sodium-based desulfurization ash to neutralize Ca(OH)2(reaction 1), neutralize Ca(OH)2 in backwater, generate Na2CO3 dissolved in water, generate CaCO3 precipitate into sludge, and be discharged with sludge. After Ca(OH)2 in water is consumed, Ca(OH)2 in slag dust is dissolved in water again to react, and finally Ca(OH)2 is completely consumed. Ca(OH)2 is a strong base, completely ionized, and releases OH - , Na2CO3 and NaHCO3 are weak bases, partially ionized, and the pH of saturated Na2CO3 solution is about 11.6, and the pH of saturated NaHCO3 solution is about 8.3. When pH >= 11.6, it indicates that there is still OH - ionized by Ca(OH)2 in the solution. When pH <= 11.6, the solution enters HCO3 - -CO3 2- buffer system, OH - is mainly controlled by the carbonate content, and there is no need to continue adding the water solution of pretreated sodium-based desulfurization ash, otherwise, sulfuric acid will be added in the clean water tank to neutralize NaHCO3, increasing the cost. Adding sulfuric acid in the clean water tank will neutralize part of Na2CO3 (reaction 3), but the total reaction in the two tanks is still reaction 5. It can be seen that NaHCO3 plays a role in neutralizing about half of Ca(OH)2, thereby saving half of H2SO4.

[0033] Na2SO3 is oxidized to Na2SO4 by air, and the obtained NaHCO3 and Na2SO4 aqueous solution is to avoid the generation of CaSO3, thereby affecting the further resource utilization of sludge in downstream industries.

[0034] In the present application, the water supplementing amount of the roller process water supplementing system in a production cycle is about 0.2-0.3 t / t slag, and a production cycle is brought by the roller cooling and dust removal amount of about 0.02-0.05 t / t slag, and the amount of f-CaO in the slag dust is about 4-10% of the total amount of slag dust. The solubility of Ca(OH)2 is about 0.165 g per 100 g of water, and the amount of f-CaO in the slag dust is always dominant to the total water supplementing amount, so that under normal circumstances, Ca(OH)2 in the backwater is always in a saturated state, and the pH value of the backwater is generally maintained at about 12.6. At the same time, under the technical requirements, the NaHCO3 concentration of the desulfurization ash solution obtained in the pretreatment process is at least one order of magnitude greater than the Ca(OH)2 concentration in the backwater, and the water supplementing amount in the pretreatment process is much smaller than the total water supplementing amount of the system, so under the technical requirements, the situation that the water supplementing amount is too much during the desulfurization ash cooperative disposal process and exceeds the process requirements of the system will not occur.

[0035] Table 1: Standard solubility of each substance

[0036] Compound Solubility (g / 100 g, room temperature) NaHCO3 9 Na2SO4 19.5 Na2SO3 67.8 Na2CO3 20 CaSO4 0.202 Ca(OH)2 0.165 CaCO3 0.000529

[0037] Advantages of the present application:

[0038] 1. The method of the present application utilizes the characteristics of the existing roller slag treatment process for the co-disposal of sodium-based desulfurization ash. The method is simple, does not require the addition of a large number of equipment, and has strong implementability. It solves the environmental protection problem of resource utilization of sodium-based desulfurization ash, reduces solid waste discharge, and reduces environmental protection disposal costs.

[0039] 2. The roller turbid circulating water process is used to replace part of H2SO4 with NaHCO3, reducing sulfuric acid consumption and slag treatment costs. If the cost of 98% mass fraction sulfuric acid is 500-600 yuan / ton, the slag treatment cost is reduced by 0.21-1.53 yuan / t slag. If 2 million tons of steel slag are treated per year, the annual cost reduction is 42-306 million yuan.

[0040] 3. Compared with the prior art, the technical scheme of the present application is flexible and is constrained by external boundary conditions. It has wide application potential.

[0041] In summary: The present application is aimed at the internal disposal problem of sodium-based desulfurization ash in steel plants. The composition characteristics of sodium-based desulfurization ash are combined with the turbid circulating water process of the roller steel slag treatment process. Part of H2SO4 is replaced with NaHCO3, reducing production costs and solving the solid waste discharge problem of steel enterprises. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 A process flow diagram for a method of disposing sodium-based desulfurization ash using a roller steel slag treatment process system. DETAILED DESCRIPTION

[0043] The present application will be further described in detail below with reference to specific examples, so that those skilled in the art can understand it.

[0044] Example 1

[0045] A method of disposing sodium-based desulfurization ash using a roller steel slag treatment process system, comprising the following steps:

[0046] 1) Place the sodium-based desulfurization ash in a pretreatment tank. Add water to the pretreatment tank at a rate of 6 times the mass of the sodium-based desulfurization ash using a water supply system. Introduce compressed air into the pretreatment tank for 35 minutes to prepare a desulfurization ash aqueous solution;

[0047] 2) After one production cycle of the roller slag treatment, the pH value of the circulating water in the sedimentation tank is 12.6. Add the aqueous solution from the pretreatment tank to the sedimentation tank to adjust the pH value of the sedimentation tank to 11.4. Immediately stop adding the desulfurization ash aqueous solution;

[0048] 3) After the end of the precipitation process, the upper clear water is input into the clear water tank, a 20% mass fraction dilute sulfuric acid solution is added to adjust the pH of the clear water tank to 8.0, and the water loss in the process is supplemented to the clear water tank by using the water supplementing system;

[0049] 4) The water in the clear water tank is transported to the drum cooling and flue gas dust removal system by using the water supply pump;

[0050] 5) The used backwater enters the precipitation tank through the backwater ditch to complete the turbid circulating water circulation process of the drum process.

[0051] In this embodiment, the slag treatment amount in one production cycle is 37 tons, the slag dust entering the circulating water system is 0.962 tons (0.026 t / t slag), and the amount of f-CaO is 0.04329 t (4.5%). The 20% sulfuric acid solution is prepared from 98% concentrated sulfuric acid (the price is 500-600 yuan / t). If the desulfurization ash solution is not used, 0.044 t of 98% concentrated sulfuric acid needs to be consumed, and the cost is 22.1-26.4 yuan. If the desulfurization ash solution is used, 0.022 t of 98% concentrated sulfuric acid needs to be consumed, and the cost is 11.0-13.2 yuan, that is, the sulfuric acid consumption cost is reduced by 11.1-13.2 yuan, which is equivalent to a reduction of 0.30-0.36 yuan / t slag in the treatment cost of one ton of slag.

[0052] Example 2

[0053] A method for disposing sodium-based desulfurization ash by using a drum method slag treatment process system, comprising the following steps:

[0054] 1) The sodium-based desulfurization ash is placed in a pretreatment tank, water with a mass of 8 times the sodium-based desulfurization ash is added to the pretreatment tank by using a water supplementing system, and compressed air is introduced into the pretreatment tank for 45 min to prepare a desulfurization ash aqueous solution;

[0055] 2) After the backwater of the drum slag treatment in one production cycle is completed, the pH value of the circulating water in the precipitation tank is detected to be 12.4, the water in the pretreatment tank is used to supplement the water in the precipitation tank until the pH in the precipitation tank is 11.5; and the supplement of the desulfurization ash aqueous solution is immediately stopped;

[0056] 3) After the end of the precipitation process, the upper clear water is input into the clear water tank, a 20% mass fraction dilute sulfuric acid solution is added to adjust the pH of the clear water tank to 7.2, and the water loss in the process is supplemented to the clear water tank by using the water supplementing system;

[0057] 4) The water in the clear water tank is transported to the drum cooling and flue gas dust removal system by using the water supply pump;

[0058] 5) The used backwater enters the precipitation tank through the backwater ditch to complete the turbid circulating water circulation process of the drum process.

[0059] In this embodiment, the slag treatment capacity of one production cycle is 42 tons, the slag dust entering the circulating water system is 1.512 tons (0.036 t / t slag), and the amount of f-CaO is 0.1089 t (7.2%). The 98% concentrated sulfuric acid (price 500-600 yuan / t) is configured into a 20% sulfuric acid solution. If desulfurization ash solution is not used, 0.111 t of 98% concentrated sulfuric acid needs to be consumed, with a cost of 55.5-66.6 yuan. If desulfurization ash solution is used, 0.056 t of 98% concentrated sulfuric acid needs to be consumed, with a cost of 27.8-33.3 yuan, that is, the sulfuric acid consumption cost is reduced, 27.7-33.3 yuan, which is equivalent to a reduction of 0.66-0.79 yuan / t slag treatment cost per ton of slag.

[0060] Example 3

[0061] A method for disposing sodium-based desulfurization ash by using a roller method steel slag treatment process system, comprising the following steps:

[0062] 1) Put the sodium-based desulfurization ash into the pretreatment pool, add water with a mass of 10 times the sodium-based desulfurization ash to the pretreatment pool by using the water supplementing system, and introduce compressed air into the pretreatment pool for 55 min to prepare a desulfurization ash aqueous solution;

[0063] 2) After the water recycling of the roller slag treatment for one production cycle is completed, the pH value of the circulating water in the sedimentation pool is detected to be 12.6, the water solution in the pretreatment pool is used to supplement water to the sedimentation pool until the pH value of the sedimentation pool is 11.3, and then the supplement of the desulfurization ash aqueous solution is immediately stopped;

[0064] 3) After the sedimentation process is completed, the upper clear water is input into the clear water pool, a 20% dilute sulfuric acid solution is added to the clear water pool to adjust the pH value of the clear water pool to 6.3, and the water loss in the process is supplemented to the clear water pool by using the water supplementing system;

[0065] 4) The water in the clear water pool is transported to the roller cooling and flue gas dust removal system by using the water supply pump;

[0066] 5) The used backwater enters the sedimentation pool through the backwater channel to complete the turbid circulating water circulation process of the roller process.

[0067] In this embodiment, the slag treatment amount of one production cycle is 51 tons, the slag dust entering the circulating water system is 2.499 tons (0.049 t / t slag), and the amount of f-CaO is 0.2424 t (9.7%). The 98% concentrated sulfuric acid (the price is 500-600 yuan / t) is configured into a 20% sulfuric acid solution. If the desulfurization ash solution is not used, 0.2473 t of 98% concentrated sulfuric acid needs to be consumed, and the cost is 123.6-148.4 yuan. If the desulfurization ash solution is used, 0.1236 t of 98% concentrated sulfuric acid needs to be consumed, and the cost is 61.8-74.2 yuan, that is, the sulfuric acid consumption cost is reduced, 61.8-74.2 yuan, which is equivalent to a reduction of 1.21-1.45 yuan / t slag in the treatment cost of ton of slag.

[0068] Other parts not described in detail are prior art. Although the above embodiment describes the present application in detail, it is only a part of the embodiment of the present application, not all embodiments, and other embodiments can be obtained according to the embodiment without creativity, which belongs to the protection scope of the present application.

Claims

1. A method for disposal of sodium-based desulfurization ash using a roller method steel slag treatment process system, characterized by: It comprises the following steps: 1) Put the sodium-based desulfurization ash into a pretreatment pool, add water to the pretreatment pool by a water supplement system, and introduce compressed air into the pretreatment pool to prepare a desulfurization ash water solution; wherein the percentage of chemical components of the sodium-based desulfurization ash is as follows: Na2SO4 30~60%; Na2SO3 10~20%; NaHCO3 20~60%; the balance is crystal water and trace amounts of other impurities; and the content of Na2SO4 is more than twice the content of Na2SO3; the water added by the water supplement system is pure water, industrial water or steel plant reclaimed water; and the amount of the water is 6~10 times the mass of the sodium-based desulfurization ash; and the time for introducing the compressed air is 30~60 min; 2) According to the production rhythm and backwater condition of the roller slag treatment process, after the periodic backwater is completed, the pH value of the circulating water in the sedimentation pool is detected, the production rhythm cycle of the roller slag treatment process is 40~50 min; and the pH value of the periodic backwater is 12.0~13.0; when the pH is greater than or equal to 12.0, the desulfurization ash water solution prepared in the pretreatment pool is used to supplement water to the sedimentation pool until the pH in the sedimentation pool is less than or equal to 11.6; and the supplement of the desulfurization ash water solution is immediately stopped; 3) After the sedimentation process is completed, the upper clear water is input into a clear water pool, the pH of the clear water pool is adjusted to 6~9, and the water supplement system is used to supplement the water loss in the process to the clear water pool; 4) The water in the clear water pool is delivered to the roller cooling and flue gas dust removal system by a water supply pump; 5) The backwater after the roller cooling and flue gas dust removal system is used is introduced into the sedimentation pool through a backwater channel to complete the turbid circulating water circulation process of the roller process.

2. The method for disposing sodium-based desulfurization fly ash using a steel slag treatment process system with a roller method according to claim 1, characterized by: In the sodium-based desulfurization ash, the content of particles with a particle size of 200 mesh or less is greater than or equal to 90%.

3. The method for disposing sodium-based desulfurization fly ash using a steel slag treatment process system with a roller method according to claim 1, characterized in that: In the step 3), the water supplement amount of the water supplement system in one production cycle is 0.2~0.3 t / t of slag.

4. The method for disposing sodium-based desulfurization fly ash using a steel slag treatment process system with a roller method according to claim 1, characterized in that: In the step 3), the adjustment of the pH of the clear water pool to 6~9 is achieved by adding a dilute sulfuric acid solution with a mass fraction of 15~25% to the clear water pool.

5. The method for disposing sodium-based desulfurization fly ash using a steel slag treatment process system with a roller method according to claim 4, characterized in that: The mass fraction of the dilute sulfuric acid solution is 20%.

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