A collaborative disposal method for high-salt steel solid waste

Abstract

A method for the coordinated disposal of high-salt steel solid waste comprises the following steps: 1) washing sinter ash to obtain a sinter ash water wash and a sinter ash water wash filter cake; 2) mixing the sinter ash water wash filter cake with blast furnace ash to form pellets and heat treat the mixture to obtain kiln slag and kiln tail flue gas; 3) cascade cooling the kiln tail flue gas to obtain high-chlorine dust and zinc-containing flue gas; washing the high-chlorine dust to obtain a high-chlorine dust water wash and a dechlorination filter cake; and removing the zinc-containing flue gas to obtain zinc suboxide and clean flue gas; 4) mixing the high-chlorine dust water wash with the sinter ash water wash, and adjusting the ammonia nitrogen concentration and pH of the solution to obtain a lead hydroxide precipitate and a lead-free clear liquid; 5) adding a hardness removal agent and a precipitant to the lead-free clear liquid to obtain a purified liquid and a zinc-containing residue; and 6) subjecting the purified liquid to an evaporation and salt separation treatment to obtain ammonia-containing condensed water, potassium salt, and sodium salt. Based on the characteristics of sinter ash and blast furnace ash, the present invention significantly reduces the scale of water washing and the amount of wastewater, reduces the pollution load of dust washing, and reduces the difficulty of wastewater treatment.

Description

Technical Field

[0001] The present invention relates to a collaborative disposal method, in particular to a collaborative disposal method for high-salt steel solid waste, and belongs to the technical field of metallurgical solid waste treatment. Background Art

[0002] Steel mills generate large amounts of high-salt solid waste, such as sintering third and fourth field ash and blast furnace bag filter ash. These wastes contain high levels of alkali and chlorine metals and cannot be directly returned to the system for disposal. Alkali and chlorine metals are typically removed through water washing, and the wastewater is then treated and treated by evaporation and crystallization to recover the crystalline salt.

[0003] Currently, sintered ash and blast furnace bag dust are typically washed and recycled separately. For example, Chinese patent CN103435073A, "Method for Producing Potassium Chloride from Blast Furnace Gas Ash in Steel Enterprises," reports on using tap water to leach blast furnace gas ash, significantly reducing the potassium and chloride content. The leachate is then used to produce potassium chloride and sodium chloride. Chinese patent CN101234766A, "Method for Producing Potassium Chloride from Sintered Electrostatic Precipitator Ash in Steel Enterprises," describes leaching sintered ash using a mixture of tap water and an SDD inhibitor solution, achieving potassium and sodium leaching rates of 95-99.5%.

[0004] Alternatively, the two ashes can be washed separately before the wastewater is treated together. For example, in Chinese Patent 202111388607.8, "A Method for Improving the Strength of Iron-Rich Slag from a Rotary Kiln," blast furnace bag ash and sintered ash are washed and dechlorinated separately before being mixed to produce a mixed slurry. After the slurry is dehydrated, the solids are roasted in a rotary kiln, while the liquids are treated together.

[0005] In addition, the low-chloride characteristic of blast furnace bag ash washing liquid is utilized to wash blast furnace bag ash and sintered ash in series, such as Chinese patent 202210726603.4 "A process for washing and extracting salt from blast furnace bag ash and sintering machine head ash", which uses water to countercurrently rinse the blast furnace bag ash and obtain the filtrate for countercurrent rinsing of the sintered ash.

[0006] It is known that both blast furnace bag dust and sinter ash produced by steel mills are high-chloride solid wastes that require water washing and dechlorination. Co-treatment of these wastes is a promising approach to reduce investment and operational costs. However, existing methods simply mix blast furnace bag dust and sinter ash for disposal, without optimizing the mixed disposal method based on the characteristics of the solid wastes. This mixed disposal method also suffers from issues such as large water washing scale, high concentrations of ammonia nitrogen and iron in the wastewater after washing, and greater difficulty in wastewater treatment. Furthermore, the lead in blast furnace bag dust has a high recovery value. However, in the prior art, after direct water washing and subsequent pyrolysis, the lead in the blast furnace bag dust exists as oxides and cannot be dissolved, resulting in a waste of resources. Summary of the Invention

[0007] Aiming at the problems in the prior art that the concentrations of ammonia nitrogen and iron in the water-washing wastewater are high, the wastewater treatment is difficult, and the resources in sintering ash and blast furnace bag ash are not fully utilized, resulting in waste of resources. The present invention proposes a method for the coordinated disposal of high-salt solid waste from steel. The chlorine content in blast furnace bag ash is generally 4-10%, which is lower than that in sintering ash, but the amount of blast furnace bag ash is generally 3 times that of sintering ash. The blast furnace bag ash is pyrometallurgically enriched, and the chlorine in the dust is extracted by gradient cooling and water washing of the kiln tail flue gas, thereby reducing the difficulty of wastewater treatment. At the same time, the large amount of ammonia nitrogen contained in the sintering ash is mixed with the water washing liquid of the high-chlorine dust to achieve the purpose of selective precipitation of lead. This method combines the characteristics of sintering ash and blast furnace bag ash, reduces the difficulty of resource recovery, and improves the treatment efficiency of high-chlorine solid waste.

[0008] According to an embodiment of the present invention, a method for the coordinated disposal of high-salt steel solid waste is provided.

[0009] A method for collaboratively disposing of high-salt steel solid waste, comprising the following steps:

[0010] 1) washing the sintered ash with water to obtain a sintered ash washing liquid and a sintered ash washing filter cake;

[0011] 2) mixing the sintered ash washed filter cake obtained in step 1) with blast furnace bag ash to form pellets, and then feeding the green pellets into a rotary kiln for heat treatment to obtain kiln slag and kiln tail gas;

[0012] 3) performing a step cooling treatment on the kiln tail flue gas obtained in step 2) to obtain high-chlorine dust and zinc-containing flue gas; washing the high-chlorine dust with water to obtain a high-chlorine dust washing liquid and a dechlorination filter cake; and removing the zinc-containing flue gas from the dust to obtain secondary zinc oxide and clean flue gas;

[0013] 4) mixing the high-chloride dust washing liquid obtained in step 3) with the sintered ash washing liquid obtained in step 1) to obtain a mixed solution, adjusting the ammonia nitrogen concentration and pH of the mixed solution, and performing solid-liquid separation after standing to obtain a lead hydroxide precipitate and a lead-free clear solution;

[0014] 5) adding a hardness removal agent and a precipitant to the lead-free clear solution obtained in step 4), performing solid-liquid separation after the reaction is completed, and obtaining a purified solution and a zinc-containing residue;

[0015] 6) The purified liquid obtained in step 5) is subjected to evaporation and salt separation treatment to obtain ammonia-containing condensed water, potassium salt and sodium salt respectively.

[0016] Preferably, the method further comprises: 7) refluxing the ammonia-containing condensed water obtained in step 6) to step 4) for adjusting the ammonia nitrogen concentration of the mixed solution and / or directly returning it for use in the sintering process.

[0017] Preferably, the method further comprises: 8) returning the dechlorination filter cake obtained in step 3) to step 2) for mixing and pelletizing.

[0018] Preferably, the water washing of the sintered ash in step 1) is a multi-stage countercurrent water washing, preferably a three-stage countercurrent water washing; preferably, the water-ash ratio during the water washing process is 1 to 5:1, preferably 2 to 4:1.

[0019] Preferably, the mixing and pelletizing in step 2) is to prepare spherical particles with a particle size of 3 to 10 mm, preferably spherical particles with a particle size of 4 to 6 mm; preferably, the pelletizing is carried out using a disc pelletizer.

[0020] Preferably, the temperature of the heat treatment in step 2) is 1000-1500° C., preferably 1100-1300° C., and the heat treatment time is 1-2 hours; preferably, the direction of gas flow during the heat treatment is opposite to the direction of material flow;

[0021] Preferably, the slag obtained from the heat treatment is sent to a sintering process.

[0022] Preferably, the step 3) of subjecting the kiln tail flue gas obtained in step 2) to a step cooling treatment is specifically as follows: cooling the kiln tail flue gas to 300-400°C (preferably 320-380°C), and then cooling it to 150-200°C (preferably 160-180°C) to separate and obtain high-chlorine dust and zinc-containing flue gas; preferably, the kiln tail flue gas is passed through a waste heat boiler and a surface cooler in sequence, cooled to 300-400°C (preferably 320-380°C) in the waste heat boiler, and then cooled to 150-200°C (preferably 160-180°C) in the surface cooler to obtain high-chlorine dust and zinc-containing flue gas.

[0023] Preferably, the zinc-containing flue gas in step 3) is subjected to dust removal treatment to obtain secondary zinc oxide and clean flue gas, specifically: the zinc-containing flue gas is separated by a bag dust collector to obtain secondary zinc oxide dust, and the remaining flue gas is purified by a flue gas purification device and then discharged.

[0024] Preferably, the water washing of the high-chloride dust in step 3) is a multi-stage countercurrent water washing, preferably a three-stage countercurrent water washing; preferably, the water-to-cement ratio during the water washing process is 1 to 5:1, preferably 2 to 4:1;

[0025] Preferably, the three-stage countercurrent water washing is specifically as follows: after the sintered ash and / or high-chloride dust is washed with the first stage water, it is dehydrated through the first stage filter press, the first stage filtrate is discharged from the system, the first stage filter residue enters the second stage water washing, the water source of the second stage water washing is the water produced by the third stage filter press, after the second stage water washing, it is dehydrated through the second stage filter press, the second stage filtrate enters the first stage water washing for use, the second stage filter residue enters the third stage water washing, the water source of the third stage water washing is industrial water and / or condensate, after the third stage water washing, it is dehydrated through the third stage filter press, the third stage filtrate is discharged to the second stage water washing for use, and the third stage filter residue is discharged from the system.

[0026] Preferably, in step 4), the ammonia nitrogen concentration and pH of the mixed solution are adjusted as follows: first, ammonia-containing condensed water is added to the mixed solution to make the ammonia nitrogen concentration in the mixed solution 0.4-1.5 mol / L, preferably 0.6-1 mol / L; and then, a base is added to the mixed solution to control the pH value of the mixed solution to 7-12, preferably 8-10; preferably, the base is one or both of sodium hydroxide and potassium hydroxide.

[0027] Preferably, the hardness removing agent in step 5) is sodium carbonate; the amount of sodium carbonate added is 2 to 15 g / L, preferably 3 to 10 g / L;

[0028] Preferably, the precipitant is sodium sulfide or a heavy capture agent; preferably, the amount of the precipitant added is 0.8 to 8 g / L, preferably 1 to 5 g / L; preferably, the heavy capture agent is a dithiocarbamate substance.

[0029] Preferably, the precipitation reaction time after adding the precipitant is 0.5 to 2 hours, preferably 0.8 to 1.5 hours.

[0030] Preferably, the evaporation and salt separation in step 6) is temperature-variable evaporation and salt separation, preferably countercurrent multi-effect salt separation; preferably, the purified liquid undergoes triple-effect, double-effect, and single-effect evaporation in sequence, the temperature of the triple-effect evaporation is controlled at 20 to 60° C. (preferably 30 to 50° C.), and the vacuum degree is -150 to -50 kPa (preferably -100 to -70 kPa), the temperature of the second-effect evaporation is controlled at 40 to 90° C. (preferably 50 to 80° C.), and the vacuum degree is -100 to -30 kPa (preferably -70 to -40 kPa), and the temperature of the single-effect evaporation is controlled at 70 to 105° C. (preferably 80 to 100° C.), and the vacuum degree is -50 to -10 kPa (preferably -40 to -5 kPa).

[0031] Preferably, the condensed water from the triple-effect reactor is collected separately to obtain ammonia-containing condensed water, and refluxed to the water washing step 3).

[0032] Preferably, the step 1) specifically comprises: performing multi-stage countercurrent water washing on the sintered ash with a water-ash ratio of 1 to 5:1 (preferably 2 to 4:1), and obtaining a sintered ash water washing liquid and a sintered ash water washing filter cake after the water washing is completed.

[0033] Preferably, the step 2) is specifically as follows: the sintered ash washed filter cake obtained in step 1) is mixed with blast furnace bag ash, and prepared into spherical particles of 3 to 10 mm (preferably 4 to 6 mm) by a disc granulator, and sent to a rotary kiln for heat treatment at a heat treatment temperature of 1000 to 1500° C. (preferably 1100 to 1300° C.) for 1 to 2 hours. During the heat treatment, the direction of gas flow is opposite to the direction of material flow, and kiln slag and kiln tail flue gas are obtained, and the kiln slag is sent to the sintering process.

[0034] Preferably, the step 3) is specifically as follows: the kiln tail flue gas obtained in step 2) is sequentially passed through a waste heat boiler, a surface cooler, a dust collector and a flue gas purification device; the roasting flue gas is cooled to 300-400°C (preferably 320-380°C) in the waste heat boiler, and cooled to 150-200°C (preferably 160-180°C) in the surface cooler to separate high-chlorine dust, and secondary zinc oxide dust is separated by a dust collector, and the remaining flue gas is purified by a flue gas purification device and then discharged; the high-chlorine dust is subjected to multi-stage countercurrent water washing with a water-to-cement ratio of 1-5:1 (preferably 2-4:1), and after the washing is completed, a high-chlorine dust water washing liquid and a dechlorination filter cake are obtained.

[0035] Preferably, the step 4) is specifically: mixing the high-chlorine dust water washing liquid obtained in step 3) with the sintered ash water washing liquid obtained in step 1) to obtain a mixed solution, adding ammonia-containing condensed water (preferably the ammonia-containing condensed water obtained in step 6)) to the mixed solution, adjusting the ammonia nitrogen concentration of the mixed solution to 0.4-1.5 mol / L (preferably 0.6-1 mol / L), and then adding sodium hydroxide and / or potassium hydroxide to the mixed solution after adjusting the ammonia nitrogen concentration, adjusting the pH of the mixed solution to 7-12 (preferably 8-10), to obtain lead hydroxide precipitate and lead-free clear solution.

[0036] Preferably, the step 5) is specifically as follows: adding a de-hardening agent in an amount of 0.8 to 8 g / L (preferably 1 to 5 g / L) to the lead-free clear solution obtained in step 4), and adding a precipitant in an amount of 2 to 15 g / L (preferably 3 to 10 g / L) to obtain a zinc-containing residue and a purified solution.

[0037] Preferably, the step 6) is specifically: passing the purified liquid obtained in step 5) through a triple-effect reactor, a second-effect reactor and a first-effect reactor in sequence, and the high-temperature steam and the flow direction of the purified liquid are opposite; wherein the temperature in the triple-effect reactor is 20-60°C (preferably 30-50°C), and the vacuum degree is -150-50kPa (preferably -100-70kPa), the temperature in the second-effect reactor is controlled to be 40-90°C (preferably 50-80°C), and the vacuum degree is -100-30kPa (preferably -70-40kPa), the temperature in the first-effect reactor is controlled to be 70-105°C (preferably 80-100°C), and the vacuum degree is -50-10kPa (preferably -40-5kPa); the condensed water in the triple-effect reactor is collected separately to obtain ammonia-containing condensed water, and the solution in the first-effect reactor is subjected to potassium and sodium concentration detection, and is subjected to cooling crystallization, a thickener, and centrifugal separation to obtain potassium salt, and a thickener and centrifugal separation to obtain sodium salt.

[0038] In existing technology, the chlorine content of blast furnace bag ash is generally 4-10%, lower than that of sintered ash. However, the amount of blast furnace bag ash is generally three times that of sintered ash. Direct water washing for dechlorination requires larger equipment and consumes significant water resources. Furthermore, blast furnace bag ash contains approximately 1-2% lead, which has a high recovery value. However, existing technology generally uses direct water washing followed by pyrometallurgical treatment. However, the lead in blast furnace bag ash exists as an oxide and cannot be dissolved. The lead concentration in the wastewater from direct water washing of blast furnace bag ash is 5-20 mg / L, resulting in the lead ash entering the pyrometallurgical treatment products, where it coexists with secondary zinc oxide, resulting in a waste of resources.

[0039] In the present invention, the characteristics of sintered ash and blast furnace bag ash are combined. The sintered ash is first washed separately with water, and the resulting filter cake is directly mixed with the blast furnace bag ash for heat treatment, thereby enriching chlorine while reducing the scale of water washing. The kiln tail flue gas obtained after heat treatment is then cooled by gradient cooling, and the different phase transition temperatures of the various compounds in the flue gas are utilized to separate secondary zinc oxide. The high-chlorine dust is then washed with water, mixed with the sintered ash washing liquid, and then ammonia-containing water is added to adjust the ammonia nitrogen content in the mixed solution to precipitate the lead in the mixed solution. The zinc in the mixed solution is then extracted using a hardness removal agent and a precipitant. Finally, the purified liquid is subjected to temperature-variable evaporation and salt separation to obtain ammonia-containing condensed water, sodium salt, and potassium salt. Various resources in sintered ash and blast furnace bag ash are collected, the resource recovery rate is improved, the effective substances in sintered ash and blast furnace bag ash are fully utilized, the respective characteristics of sintered ash and blast furnace bag ash are brought into play, and truly coordinated disposal is achieved.

[0040] In the present invention, since direct water washing of blast furnace bag ash consumes more resources, the scheme of blast furnace bag ash being subjected to pyrometallurgical enrichment (rotary kiln) is adopted, and by gradient cooling of kiln tail flue gas, the enrichment of chlorine and lead in dust is realized. According to measurement, the high chlorine dust obtained after pyrometallurgical enrichment has a chlorine content of 20-30%, which is 2-8 times the chlorine content in the initial blast furnace bag ash. The high chlorine dust is then washed, which can significantly reduce the scale of washing and the amount of wastewater compared to directly washing blast furnace bag ash. At the same time, the water quality of the dust after pyrometallurgical treatment is better, and the ammonia nitrogen and iron concentrations in the wastewater are significantly reduced. The difficulty of wastewater treatment is reduced, and iron enters the slag phase during the thermal treatment process and is sent to the sintering process, effectively preventing the waste of iron resources.

[0041] In the present invention, after heat treatment, elements such as zinc, lead, sodium, and potassium enter the kiln tail flue gas from the blast furnace bag dust. The kiln tail flue gas is then subjected to a gradient cooling process using a waste heat boiler and a surface cooler. The kiln tail flue gas is cooled to 300-400°C (preferably 320-380°C) in the waste heat boiler and to 150-200°C (preferably 160-180°C) in the surface cooler. By utilizing the fact that PbO, PbCl2, and ZnCl2 have lower precipitation temperatures than ZnO, PbO, PbCl2, and ZnCl2 are preferentially cooled and precipitated, entering the high-chloride dust in large quantities, while ZnO is collected by a subsequent bag dust collector to obtain a secondary zinc oxide product. Furthermore, the high-chloride dust is washed and dechlorinated, causing the PbCl2 and ZnCl2 therein to dissolve into the washing liquid, while PbO is returned to the rotary kiln with the filter residue for a chlorination reaction, thereby improving resource utilization.

[0042] In the present invention, after the sintered ash is washed with water, the sintered ash water-washed filter cake is mixed with blast furnace bag ash to form pellets, and heat treated simultaneously. The sintered ash water wash liquid is mixed with a high-chlorine dust water wash liquid to obtain a mixed solution. Because the sintered ash contains a high concentration of ammonia nitrogen, lead is selectively precipitated under high ammonia conditions (i.e., lead forms Pb(OH)2 under alkaline conditions, while Zn complexes with ammonia and does not form a precipitate, thereby achieving the purpose of selectively precipitating lead), reducing the amount of additional ammonia-containing condensed water added. Preferably, the ammonia-containing condensed water collected in the subsequent evaporation and salt separation step is used to adjust the ammonia nitrogen content in the mixed solution, constructing an ammonia circulation system and reducing the addition of additional ammonia nitrogen.

[0043] In the present invention, after the lead hydroxide in the high-chlorine dust wash is precipitated and separated, a hardness removal agent and a precipitant are added to the lead-free clear solution to convert heavy metals such as Zn into insoluble precipitates (such as zinc sulfide) for recovery. Through the aforementioned pyrometallurgical enrichment, step-by-step cooling, and selective lead precipitation steps, the present invention achieves the extraction of lead and zinc from high-salt steel solid waste, improving product purity, fully utilizing the properties of sintered ash and blast furnace bag dust, reducing the difficulty of wastewater treatment, and extracting effective resources from the solid waste, achieving true collaborative processing.

[0044] In the present invention, a multi-stage evaporation process first introduces a purified liquid into a triple-effect reactor, collects the dirty condensed water from the multiple-effect reactor, and returns the dilute ammonia solution to the mixed solution composed of a high-chlorine dust washing solution and a sinter ash washing solution during the ammonia nitrogen content adjustment process, thereby forming an ammonia cycle. The purified liquid is then sequentially introduced into a second-effect reactor and a first-effect reactor. Taking advantage of the different precipitation temperatures of sodium and potassium salts, the potassium and sodium concentrations of the solution in the first-effect reactor are detected, and the potassium salt is obtained through cooling crystallization, a thickener, and centrifugation, while the sodium salt is obtained through a thickener and centrifugation.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. The present invention provides a method for the coordinated disposal of high-salt steel solid waste. According to the characteristics of sintered ash and blast furnace bag ash, the sintered ash is washed separately, and the blast furnace bag ash is mixed with the sintered ash water-washed filter cake and then directly enriched by pyrometallurgy, which greatly reduces the scale of water washing and the amount of wastewater, improves the water quality of the dust after pyrometallurgy treatment, and reduces the difficulty of wastewater treatment.

[0047] 2. The present invention provides a method for the coordinated disposal of high-salt solid waste from steel, which realizes the selective separation of lead and zinc through the rational series connection of pyrolysis and hydrolysis, scientifically recovers resources in flue gas and solution, gives full play to the characteristics of sintered ash and blast furnace bag ash, and truly realizes coordinated disposal.

[0048] 3. The method for collaborative disposal of high-salt steel solid waste provided by the present invention has simple process equipment, wide applicability and strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a flow chart of a method for collaborative disposal of high-salt steel solid waste provided by the present invention. DETAILED DESCRIPTION

[0050] The technical solutions of the present invention are illustrated below with examples, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0051] According to an embodiment of the present invention, a method for the coordinated disposal of high-salt steel solid waste is provided.

[0052] A method for collaboratively disposing of high-salt steel solid waste, comprising the following steps:

[0053] 1) washing the sintered ash with water to obtain a sintered ash washing liquid and a sintered ash washing filter cake;

[0054] 2) mixing the sintered ash washed filter cake obtained in step 1) with blast furnace bag ash to form pellets, and then feeding the green pellets into a rotary kiln for heat treatment to obtain kiln slag and kiln tail gas;

[0055] 3) performing a step cooling treatment on the kiln tail flue gas obtained in step 2) to obtain high-chlorine dust and zinc-containing flue gas; washing the high-chlorine dust with water to obtain a high-chlorine dust washing liquid and a dechlorination filter cake; and removing the zinc-containing flue gas from the dust to obtain secondary zinc oxide and clean flue gas;

[0056] 4) mixing the high-chloride dust washing liquid obtained in step 3) with the sintered ash washing liquid obtained in step 1) to obtain a mixed solution, adjusting the ammonia nitrogen concentration and pH of the mixed solution, and performing solid-liquid separation after standing to obtain a lead hydroxide precipitate and a lead-free clear solution;

[0057] 5) adding a hardness removal agent and a precipitant to the lead-free clear solution obtained in step 4), performing solid-liquid separation after the reaction is completed, and obtaining a purified solution and a zinc-containing residue;

[0058] 6) The purified liquid obtained in step 5) is subjected to evaporation and salt separation treatment to obtain ammonia-containing condensed water, potassium salt and sodium salt respectively.

[0059] Preferably, the method further comprises: 7) refluxing the ammonia-containing condensed water obtained in step 6) to step 4) for adjusting the ammonia nitrogen concentration of the mixed solution and / or directly returning it for use in the sintering process.

[0060] Preferably, the method further comprises: 8) returning the dechlorination filter cake obtained in step 3) to step 2) for mixing and pelletizing.

[0061] Preferably, the water washing of the sintered ash in step 1) is a multi-stage countercurrent water washing, preferably a three-stage countercurrent water washing; preferably, the water-ash ratio during the water washing process is 1 to 5:1, preferably 2 to 4:1.

[0062] Preferably, the mixing and pelletizing in step 2) is to prepare spherical particles with a particle size of 3 to 10 mm, preferably spherical particles with a particle size of 4 to 6 mm; preferably, the pelletizing is carried out using a disc pelletizer.

[0063] Preferably, the temperature of the heat treatment in step 2) is 1000-1500° C., preferably 1100-1300° C., and the heat treatment time is 1-2 hours; preferably, the gas flow direction is opposite to the material flow direction during the heat treatment.

[0064] Preferably, the slag obtained from the heat treatment is sent to a sintering process.

[0065] Preferably, the step 3) of subjecting the kiln tail flue gas obtained in step 2) to a step cooling treatment is specifically as follows: cooling the kiln tail flue gas to 300-400°C (preferably 320-380°C), and then cooling it to 150-200°C (preferably 160-180°C) to separate and obtain high-chlorine dust and zinc-containing flue gas; preferably, the kiln tail flue gas is passed through a waste heat boiler and a surface cooler in sequence, cooled to 300-400°C (preferably 320-380°C) in the waste heat boiler, and then cooled to 150-200°C (preferably 160-180°C) in the surface cooler to obtain high-chlorine dust and zinc-containing flue gas.

[0066] Preferably, the zinc-containing flue gas in step 3) is subjected to dust removal treatment to obtain secondary zinc oxide and clean flue gas, specifically: the zinc-containing flue gas is separated by a bag dust collector to obtain secondary zinc oxide dust, and the remaining flue gas is purified by a flue gas purification device and then discharged.

[0067] Preferably, the water washing of the high-chloride dust in step 3) is a multi-stage countercurrent water washing, preferably a three-stage countercurrent water washing; preferably, the water-to-cement ratio during the water washing process is 1 to 5:1, preferably 2 to 4:1.

[0068] Preferably, the three-stage countercurrent water washing is specifically as follows: after the sintered ash and / or high-chloride dust is washed with the first stage water, it is dehydrated through the first stage filter press, the first stage filtrate is discharged from the system, the first stage filter residue enters the second stage water washing, the water source of the second stage water washing is the water produced by the third stage filter press, after the second stage water washing, it is dehydrated through the second stage filter press, the second stage filtrate enters the first stage water washing for use, the second stage filter residue enters the third stage water washing, the water source of the third stage water washing is industrial water and / or condensate, after the third stage water washing, it is dehydrated through the third stage filter press, the third stage filtrate is discharged to the second stage water washing for use, and the third stage filter residue is discharged from the system.

[0069] Preferably, in step 4), the ammonia nitrogen concentration and pH of the mixed solution are adjusted as follows: first, ammonia-containing condensed water is added to the mixed solution to make the ammonia nitrogen concentration in the mixed solution 0.4-1.5 mol / L, preferably 0.6-1 mol / L; and then, a base is added to the mixed solution to control the pH value of the mixed solution to 7-12, preferably 8-10; preferably, the base is one or both of sodium hydroxide and potassium hydroxide.

[0070] Preferably, the hardness removing agent in step 5) is sodium carbonate; the amount of sodium carbonate added is 2 to 15 g / L, preferably 3 to 10 g / L;

[0071] Preferably, the precipitant is sodium sulfide or a heavy capture agent; preferably, the amount of the precipitant added is 0.8 to 8 g / L, preferably 1 to 5 g / L; preferably, the heavy capture agent is a dithiocarbamate substance.

[0072] Preferably, the precipitation reaction time after adding the precipitant is 0.5 to 2 hours, preferably 0.8 to 1.5 hours.

[0073] Preferably, the evaporation and salt separation in step 6) is temperature-variable evaporation and salt separation, preferably countercurrent multi-effect salt separation; preferably, the purified liquid undergoes triple-effect, double-effect, and single-effect evaporation in sequence, the temperature of the triple-effect evaporation is controlled at 20 to 60° C. (preferably 30 to 50° C.), and the vacuum degree is -150 to -50 kPa (preferably -100 to -70 kPa), the temperature of the second-effect evaporation is controlled at 40 to 90° C. (preferably 50 to 80° C.), and the vacuum degree is -100 to -30 kPa (preferably -70 to -40 kPa), and the temperature of the single-effect evaporation is controlled at 70 to 105° C. (preferably 80 to 100° C.), and the vacuum degree is -50 to -10 kPa (preferably -40 to -5 kPa).

[0074] Preferably, the condensed water from the triple-effect reactor is collected separately to obtain ammonia-containing condensed water, and refluxed to the water washing step 3).

[0075] Preferably, the step 1) specifically comprises: performing multi-stage countercurrent water washing on the sintered ash with a water-ash ratio of 1 to 5:1 (preferably 2 to 4:1), and obtaining a sintered ash water washing liquid and a sintered ash water washing filter cake after the water washing is completed.

[0076] Preferably, the step 2) is specifically as follows: the sintered ash washed filter cake obtained in step 1) is mixed with blast furnace bag ash, and prepared into spherical particles of 3 to 10 mm (preferably 4 to 6 mm) by a disc granulator, and sent to a rotary kiln for heat treatment at a heat treatment temperature of 1000 to 1500° C. (preferably 1100 to 1300° C.) for 1 to 2 hours. During the heat treatment, the direction of gas flow is opposite to the direction of material flow, and kiln slag and kiln tail flue gas are obtained, and the kiln slag is sent to the sintering process.

[0077] Preferably, the step 3) is specifically as follows: the kiln tail flue gas obtained in step 2) is sequentially passed through a waste heat boiler, a surface cooler, a dust collector and a flue gas purification device; the roasting flue gas is cooled to 300-400°C (preferably 320-380°C) in the waste heat boiler, and cooled to 150-200°C (preferably 160-180°C) in the surface cooler to separate high-chlorine dust, and secondary zinc oxide dust is separated by a dust collector, and the remaining flue gas is purified by a flue gas purification device and then discharged; the high-chlorine dust is subjected to multi-stage countercurrent water washing with a water-to-cement ratio of 1-5:1 (preferably 2-4:1), and after the washing is completed, a high-chlorine dust water washing liquid and a dechlorination filter cake are obtained.

[0078] Preferably, the step 4) is specifically: mixing the high-chlorine dust water washing liquid obtained in step 3) with the sintered ash water washing liquid obtained in step 1) to obtain a mixed solution, adding ammonia-containing condensed water (preferably the ammonia-containing condensed water obtained in step 6)) to the mixed solution, adjusting the ammonia nitrogen concentration of the mixed solution to 0.4-1.5 mol / L (preferably 0.6-1 mol / L), and then adding sodium hydroxide and / or potassium hydroxide to the mixed solution after adjusting the ammonia nitrogen concentration, adjusting the pH of the mixed solution to 7-12 (preferably 8-10), to obtain lead hydroxide precipitate and lead-free clear solution.

[0079] Preferably, the step 5) is specifically as follows: adding a de-hardening agent in an amount of 0.8 to 8 g / L (preferably 1 to 5 g / L) to the lead-free clear solution obtained in step 4), and adding a precipitant in an amount of 2 to 15 g / L (preferably 3 to 10 g / L) to obtain a zinc-containing residue and a purified solution.

[0080] Preferably, the step 6) is specifically: passing the purified liquid obtained in step 5) through a triple-effect reactor, a second-effect reactor and a first-effect reactor in sequence, and the high-temperature steam and the flow direction of the purified liquid are opposite; wherein the temperature in the triple-effect reactor is 20-60°C (preferably 30-50°C), and the vacuum degree is -150-50kPa (preferably -100-70kPa), the temperature in the second-effect reactor is controlled to be 40-90°C (preferably 50-80°C), and the vacuum degree is -100-30kPa (preferably -70-40kPa), the temperature in the first-effect reactor is controlled to be 70-105°C (preferably 80-100°C), and the vacuum degree is -50-10kPa (preferably -40-5kPa); the condensed water in the triple-effect reactor is collected separately to obtain ammonia-containing condensed water, and the solution in the first-effect reactor is subjected to potassium and sodium concentration detection, and is subjected to cooling crystallization, a thickener, and centrifugal separation to obtain potassium salt, and a thickener and centrifugal separation to obtain sodium salt.

[0081] Example 1

[0082] The existing 30t / d sinter ash (containing 25% chlorine) and 84t / d blast furnace bag ash (containing 5% chlorine) are treated as follows:

[0083] 1) 30t / d sintered ash is washed with three-stage countercurrent water washing, with a water-ash ratio of 3:1. After washing, 3.75m 3 / h sintered ash water washing liquid and 20.25t / d sintered ash water washing filter cake.

[0084] 2) The 20.25t / d sintered ash washed filter cake obtained in step 1) was mixed with 84t / d blast furnace bag ash, and prepared into 5mm spherical particles using a disc granulator. The particles were then sent to a rotary kiln for heat treatment at a temperature of 1200°C for 1.5h. During the heat treatment, the direction of gas flow was opposite to that of material flow, and 78.19t / d of kiln slag and 17201m 3 / h of kiln tail gas, and sends the kiln slag to the sintering process.

[0085] 3) The flue gas from the kiln tail obtained in step 2) is passed through the waste heat boiler, surface cooler, dust collector and flue gas purification device in sequence; the roasting flue gas is cooled to 320°C in the waste heat boiler, cooled to 150°C in the surface cooler, and cooled to room temperature in the dust collector, and 7.14t / d of high chlorine dust (chlorine content 26%) is separated, and 13.26t / d of secondary zinc oxide is separated in the dust collector. The remaining flue gas is purified by the flue gas purification device and discharged. The 7.14t / d high chlorine dust is washed with three-stage countercurrent water with a water-cement ratio of 3:1. After the washing is completed, 0.89m 3 / h high-chlorine dust washing liquid and 3.57t / d dechlorination filter cake.

[0086] 4) The 0.89m obtained in step 3) 3 / h high chlorine dust washing liquid and 3.75m 3 / h sinter ash water washing liquid mixed to obtain 4.64m 3 / h mixed solution, add 1.5m 3 / h ammonia-containing condensed water, adjust the ammonia nitrogen concentration of the mixed solution to 0.8mol / L, then add 103kg / d of sodium hydroxide to the mixed solution after adjusting the ammonia nitrogen concentration, adjust the pH of the mixed solution to 9, and obtain 442kg / d of lead hydroxide precipitate and 6m 3 / h lead-free liquid.

[0087] 5) Return the 6m obtained in step 4) 3 / h lead-free clear liquid was added with 3g / L of sodium sulfide and 6g / L of sodium carbonate to obtain 2.88t / d of zinc-containing residue and 6m 3 / h purification liquid.

[0088] 6) The 6m obtained in step 5) 3 / h purified liquid passes through the three-effect reactor, the two-effect reactor and the first-effect reactor in turn, and the evaporated high-temperature steam flows in the opposite direction. Among them, the temperature in the three-effect reactor is 40℃, the vacuum degree is -90kPa, the temperature in the two-effect reactor is 65℃, the vacuum degree is -65kPa, and the temperature in the first-effect reactor is 85℃, the vacuum degree is -25kPa. The condensed water in the three-effect reactor is collected separately to obtain 2m 3 / h dilute ammonia water, collecting 15.12t / d of sodium chloride with a purity of 90.5%, and obtaining 24.47t / d of potassium chloride with a purity of 93.7%.

[0089] Example 2

[0090] The existing 27t / d sinter ash (containing 25% chlorine) and 73t / d blast furnace bag ash (containing 5% chlorine) are treated as follows:

[0091] 1) 27t / d sintered ash was washed with three-stage countercurrent water washing, with a water-ash ratio of 3:1. After washing, 3.39m 3 / h sintered ash water washing liquid and 18.17t / d sintered ash water washing filter cake.

[0092] 2) The 18.17t / d sintered ash washed filter cake obtained in step 1) was mixed with 73t / d blast furnace bag ash, and prepared into 5mm spherical particles using a disc granulator. The particles were sent to a rotary kiln for heat treatment at a temperature of 1200°C for 2.0h. During the heat treatment, the direction of gas flow was opposite to that of material flow, and 70.31t / d kiln slag and 15800m 3 / h of kiln tail gas, and sends the kiln slag to the sintering process.

[0093] 3) The kiln tail flue gas obtained in step 2) is passed through the waste heat boiler, surface cooler, dust collector and flue gas purification device in sequence; the roasting flue gas is cooled to 320°C in the waste heat boiler, cooled to 150°C in the surface cooler, and cooled to room temperature in the dust collector, and 6.05t / d of high chlorine dust (chlorine content 28%) is separated, and 11.29t / d of secondary zinc oxide is separated in the dust collector. The remaining flue gas is purified by the flue gas purification device and discharged. The 6.05t / d high chlorine dust is subjected to three-stage countercurrent water washing with a water-cement ratio of 3:1. After the washing is completed, 0.71m 3 / h high-chlorine dust washing liquid and 2.93t / d dechlorination filter cake.

[0094] 4) The 0.71m obtained in step 3) 3 / h high chlorine dust washing liquid and 3.39m 3 / h sinter ash water washing liquid mixed to obtain 4.1m 3 / h mixed solution, add 1.32m 3 / h ammonia-containing condensed water, adjust the ammonia nitrogen concentration of the mixed solution to 0.7mol / L, then add 89kg / d of sodium hydroxide to the mixed solution after adjusting the ammonia nitrogen concentration, adjust the pH of the mixed solution to 9, and obtain 396kg / d of lead hydroxide precipitate and 5m 3 / h lead-free liquid.

[0095] 5) Return the 5m obtained in step 4) 3 / h lead-free clear liquid was added with sodium sulfide at a rate of 4g / L and sodium carbonate at a rate of 5g / L to obtain 2.56t / d zinc-containing residue and 5m 3 / h purification liquid.

[0096] 6) The 5m obtained in step 5) 3 / h purified liquid passes through the three-effect reactor, the two-effect reactor and the first-effect reactor in turn, and the evaporated high-temperature steam flows in the opposite direction. Among them, the temperature in the three-effect reactor is 35℃, the vacuum degree is -80kPa, the temperature in the two-effect reactor is 70℃, the vacuum degree is -55kPa, and the temperature in the first-effect reactor is 90℃, the vacuum degree is -30kPa. The condensed water in the three-effect reactor is collected separately to obtain 1.7m 3 / h dilute ammonia water, collecting 13.22t / d of sodium chloride with a purity of 89.6%, and obtaining 21.86t / d of potassium chloride with a purity of 92.1%.

[0097] Comparative Example

[0098] The existing 30t / d sinter ash (containing 25% chlorine) and 84t / d blast furnace bag ash (containing 5% chlorine) are treated as follows:

[0099] 1) 30t / d sintered ash is washed with three-stage countercurrent water washing, with a water-ash ratio of 3:1. After washing, 3.75m 3 / h sintered ash water washing liquid and 20.25t / d sintered ash water washing filter cake.

[0100] 2) 84t / d blast furnace bag ash was washed with three-stage countercurrent water washing, with a water-ash ratio of 1:1. After washing, 3.5m 3 / h blast furnace bag ash washing liquid and 96.6t / d blast furnace bag ash washing filter cake.

[0101] 3) Mix the sinter ash washing liquid and blast furnace ash washing liquid to obtain 7.25m 3 / h mixed solution (chlorine content 9%), adjust the pH of the mixed solution to 11 with NaOH, and add 7.25m 3 / h mixed solution was added with 7.25kg / h sodium sulfide and 13.05kg / h sodium carbonate, and filtered after reaction to obtain 0.73t / d heavy metal sludge and 7.1m 3 / h high salt solution;

[0102] 4) The high-salt solution after adjusting the pH is then passed into a multi-stage temperature-variable evaporation device for evaporation and salt separation, wherein the high-salt solution passes through a triple-effect reactor, a second-effect reactor and a first-effect reactor in sequence. The temperature in the triple-effect reactor is 40°C and the vacuum degree is -90kPa, the temperature in the second-effect reactor is 65°C and the vacuum degree is -65kPa, and the temperature in the first-effect reactor is 85°C and the vacuum degree is -25kPa. The condensed water in the triple-effect reactor is collected separately to obtain 18g / L of 2.37m 3 / h dilute ammonia water. At the same time, evaporation and separation of salts yielded 7.84t / d of sodium chloride with a purity of 83.4% and 16.99t / d of potassium chloride with a purity of 88.6%.

[0103] It can be seen from the above experiments that compared with the comparative example, the method for the coordinated disposal of high-salt steel solid waste provided by the present invention can enrich chlorine, reduce water consumption and the difficulty of wastewater treatment, and at the same time, the recovered product has a higher purity, thereby realizing scientific recycling of resources.

Claims

1. A method for the coordinated disposal of high-salt steel solid waste, characterized by: The method comprises the following steps: 1) washing the sintered ash with water to obtain a sintered ash washing liquid and a sintered ash washing filter cake; 2) mixing the sintered ash washed filter cake obtained in step 1) with blast furnace bag ash to form pellets, and then feeding the green pellets into a rotary kiln for heat treatment to obtain kiln slag and kiln tail gas; 3) performing a step cooling treatment on the kiln tail flue gas obtained in step 2) to obtain high-chlorine dust and zinc-containing flue gas; washing the high-chlorine dust with water to obtain a high-chlorine dust washing liquid and a dechlorination filter cake; and removing the zinc-containing flue gas from the dust to obtain secondary zinc oxide and clean flue gas; 4) mixing the high-chloride dust washing liquid obtained in step 3) with the sintered ash washing liquid obtained in step 1) to obtain a mixed solution, adjusting the ammonia nitrogen concentration and pH of the mixed solution, and performing solid-liquid separation after standing to obtain a lead hydroxide precipitate and a lead-free clear solution; 5) adding a hardness removal agent and a precipitant to the lead-free clear solution obtained in step 4), performing solid-liquid separation after the reaction is completed, and obtaining a purified solution and a zinc-containing residue; 6) The purified liquid obtained in step 5) is subjected to evaporation and salt separation treatment to obtain ammonia-containing condensed water, potassium salt and sodium salt respectively.

2. The method according to claim 1, wherein: The method further comprises: 7) refluxing the ammonia-containing condensed water obtained in step 6) to step 4) for adjusting the ammonia nitrogen concentration of the mixed solution and / or directly returning it for use in the sintering process; and / or The method further comprises: 8) returning the dechlorination filter cake obtained in step 3) to step 2) for mixing and pelletizing.

3. The method according to claim 1 or 2, characterized in that: The water washing of the sintered ash in step 1) is a multi-stage countercurrent water washing.

4. The method according to claim 3, wherein: The water washing of the sintered ash in step 1) is a three-stage countercurrent water washing.

5. The method according to claim 3, wherein: The water-cement ratio during the water washing process is 1 to 5:

1.

6. The method according to claim 5, characterized in that: The water-cement ratio during the water washing process is 2 to 4:

1.

7. The method according to claim 1 or 2, characterized in that: The mixing and pelletizing in step 2) is to prepare spherical particles with a particle size of 3 to 10 mm; and / or Step 2) The heat treatment temperature is 1000-1500° C., and the heat treatment time is 1-2 hours.

8. The method according to claim 7, wherein: The mixing and pelletizing in step 2) is to prepare spherical particles with a particle size of 4 to 6 mm; and / or Step 2) The temperature of the heat treatment is 1100-1300°C.

9. The method according to claim 7, wherein: The mixing and pelletizing in step 2) is performed using a disc pelletizer; and / or In step 2), the direction of gas flow during the heat treatment is opposite to the direction of material flow.

10. The method according to claim 7, wherein: The slag obtained from the heat treatment is sent to the sintering process.

11. The method according to claim 1 or 2, characterized in that: The step 3) of step 2) of cooling the kiln tail flue gas is specifically as follows: cooling the kiln tail flue gas to 300-400° C., then cooling it to 150-200° C., and separating the high chlorine dust and zinc-containing flue gas; and / or The zinc-containing flue gas described in step 3) is subjected to dust removal treatment to obtain secondary zinc oxide and clean flue gas. Specifically, the zinc-containing flue gas is separated by a bag dust collector to obtain secondary zinc oxide dust, and the remaining flue gas is purified by a flue gas purification device and then discharged.

12. The method according to claim 11, characterized in that: The step 3) of performing the step cooling treatment on the kiln tail flue gas obtained in step 2) is specifically as follows: cooling the kiln tail flue gas to 320-380° C., and then cooling it to 160-180° C. to separate the high chlorine dust and zinc-containing flue gas.

13. The method according to claim 11, wherein: The kiln tail flue gas is sequentially passed through a waste heat boiler and a surface cooler, cooled to 300-400° C. in the waste heat boiler and then cooled to 150-200° C. in the surface cooler to obtain high-chlorine dust and zinc-containing flue gas.

14. The method according to claim 12, wherein: The kiln tail flue gas is sequentially passed through a waste heat boiler and a surface cooler, cooled to 320-380° C. in the waste heat boiler and then cooled to 160-180° C. in the surface cooler to obtain high-chlorine dust and zinc-containing flue gas.

15. The method according to claim 1 or 2, characterized in that: The water washing of high-chlorine dust in step 3) is a multi-stage countercurrent water washing.

16. The method according to claim 15, characterized in that: The water washing of high-chlorine dust in step 3) is a three-stage countercurrent water washing.

17. The method according to claim 15, characterized in that: The water-to-cement ratio in the water washing process in step 3) is 1 to 5:

1.

18. The method according to claim 17, wherein: The water-to-cement ratio in the water washing process in step 3) is 2 to 4:

1.

19. The method according to claim 16, wherein: The three-stage countercurrent water washing is specifically as follows: after the sintered ash and / or high-chloride dust is washed with the first stage water, it is dehydrated through the first stage filter press, the first stage filtrate is discharged from the system, the first stage filter residue enters the second stage water washing, the water source of the second stage water washing is the water produced by the third stage filter press, after the second stage water washing, it is dehydrated through the second stage filter press, the second stage filtrate enters the first stage water washing for use, the second stage filter residue enters the third stage water washing, the water source of the third stage water washing is industrial water and / or condensate water, after the third stage water washing, it is dehydrated through the third stage filter press, the third stage filtrate is discharged to the second stage water washing for use, and the third stage filter residue is discharged from the system.

20. The method according to claim 1 or 2, characterized in that: Step 4) The ammonia nitrogen concentration and pH of the mixed solution are adjusted as follows: first, ammonia-containing condensed water is added to the mixed solution to make the ammonia nitrogen concentration in the mixed solution 0.4-1.5 mol / L; then, alkali is added to the mixed solution to control the pH value of the mixed solution to 7-12.

21. The method according to claim 20, characterized in that: Step 4) The ammonia nitrogen concentration and pH of the mixed solution are adjusted as follows: first, ammonia-containing condensed water is added to the mixed solution to adjust the ammonia nitrogen concentration in the mixed solution to 0.6 to 1 mol / L; and then, alkali is added to the mixed solution to control the pH value of the mixed solution to 8 to 10.

22. The method according to claim 20, wherein: The alkali is one or both of sodium hydroxide and potassium hydroxide.

23. The method according to claim 1 or 2, characterized in that: The hardness removing agent in step 5) is sodium carbonate; the amount of sodium carbonate added is 2 to 15 g / L; The precipitant is sodium sulfide or a heavy capture agent.

24. The method according to claim 23, wherein: The amount of sodium carbonate added is 3-10 g / L; the amount of the precipitant added is 0.8-8 g / L.

25. The method according to claim 24, wherein: The amount of the precipitant added is 1-5 g / L.

26. The method according to claim 23, wherein: The heavy capture agent is a dithiocarbamate substance.

27. The method according to claim 23, wherein: The precipitation reaction time after adding the precipitant is 0.5 to 2 hours.

28. The method according to claim 27, wherein: The precipitation reaction time after adding the precipitant is 0.8 to 1.5 hours.

29. The method according to claim 1 or 2, characterized in that: The evaporation and salt separation in step 6) is temperature-variable evaporation and salt separation.

30. The method according to claim 29, wherein: The evaporation salt separation in step 6) is a countercurrent multi-effect salt separation.

31. The method according to claim 29, wherein: The purified liquid is sequentially subjected to triple-effect, double-effect, and single-effect evaporation. The temperature of the triple-effect evaporation is controlled at 20-60°C and the vacuum degree is -150-50kPa. The temperature of the second-effect evaporation is controlled at 40-90°C and the vacuum degree is -100-30kPa. The temperature of the single-effect evaporation is controlled at 70-105°C and the vacuum degree is -50-10kPa.

32. The method according to claim 31, wherein: The temperature of the triple-effect evaporation is controlled at 30-50°C and the vacuum degree is -100-70kPa. The temperature of the second-effect evaporation is controlled at 50-80°C and the vacuum degree is -70-40kPa. The temperature of the first-effect evaporation is controlled at 80-100°C and the vacuum degree is -40-5kPa.

33. The method according to claim 31, wherein: The condensed water from the three-effect reactor is collected separately to obtain ammonia-containing condensed water, and refluxed to the water washing step 3).

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