Process for comprehensively utilizing sintering machine head ash

Abstract

The invention discloses a process for comprehensively utilizing sintering machine head ash, which comprises the following steps of: preparing the sintering machine head ash, oxidizing and leaching, carrying out filter pressing, and washing chlorine and dehydrating a filter cake to obtain fine iron powder; the method comprises the following steps: preparing metal cesium by replacing and recovering valuable metal from filtrate, performing primary heavy metal removal, performing secondary impurity removal, performing evaporative crystallization, crystallizing potassium chloride and sodium chloride, extracting cesium, concentrating and crystallizing a cesium chloride solution, preparing metal cesium, extracting rubidium from cesium extraction raffinate, and concentrating and crystallizing a rubidium chloride solution, thereby preparing metal rubidium; after the metal replacement powder is dissolved by a certain concentration of acid, copper, zinc, gold, silver and bismuth in the metal replacement powder are recovered step by step, and toxic and harmful elements such as thallium, chromium and cadmium are concentrated from a system. The method can comprehensively and efficiently recover sylvite, sodium salt and valuable metal in the sintering machine head dedusting ash, solves the problem that the normal production of a blast furnace is influenced by overhigh alkali metal content accumulation, and solves the environmental pollution caused by machine head ash stacking and burning.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and particularly relates to a process for comprehensive utilization of sintering machine head ash in iron and steel metallurgy. Background Art

[0002] Sintering machine head ash is the dust captured by the sintering flue gas electrostatic precipitator during the sintering process, with a bulk density of about 0.56 - 0.77 g / cm 3 , and its main components are Fe 3 O 4 , Fe 2 O 3 , SiO 2 , PbCl 2 , ZnCl 2 , ZnSiO 3 , and various alkali metal chlorides, with the most abundant elements being iron, potassium, sodium, lead, chlorine, etc. In addition, there are also small amounts of toxic and harmful elements such as thallium (about 0.02%), chromium, cadmium, etc. The output of sintering machine head ash accounts for about 0.12 - 0.25% of the sinter. Direct landfill not only causes serious waste of resources but also pollutes the environment, which is a major obstacle to the green and sustainable development of the iron and steel industry. Currently, most domestic iron and steel plants mainly use the method of directly returning to sintering to treat the machine head ash, but this method will cause the enrichment of alkali metals and heavy metals such as zinc, copper, and lead in the sintering machine and blast furnace, resulting in the thickening of the furnace wall, equipment corrosion, seriously affecting the equipment life, and increasing the operating cost. In addition to directly returning to sintering, many iron and steel plants also use pyrometallurgical disposal technology to treat sintering machine head ash, that is, through high-temperature roasting in a kiln, mainly by adding a reducing agent and a binder to a rotary hearth furnace, a rotary kiln, a converter and other kilns, and mixing the machine head ash for high-temperature melting to recover iron. Although this method has a short process and is easy to operate, the exhaust gas discharged will cause environmental pollution, and the equipment is prone to corrosion, and the equipment maintenance cost is very high, and it can no longer meet the needs of the environment and production.

[0003] At present, the treatment of sintering machine head ash mainly focuses on recovering elements such as potassium, sodium, and iron through the method of water washing - ore dressing, with less mention of the processes for comprehensive utilization of other valuable metals. Chinese Patent CN 111250260A published a "Method for Comprehensive Utilization of Sintering Machine Head", which can obtain 85% potassium chloride, 48% iron ore material, and 30% lead material by using the method of flotation for lead extraction - synchronous leaching of potassium salt. However, the degree of comprehensive utilization of the machine head ash by this method is not high, and the grades of the obtained iron ore and lead ore are relatively low, requiring further processing to be used as products. Chinese Patent CN 117758009A published a "Method for Co - treating Sintering Machine Head Ash by High - Temperature Melting in a Converter", which uses a binder to make cold - pressed green balls from raw materials such as quicklime and fly ash and the machine head ash, and then mixes it with high - temperature liquid slag to solidify the heavy metal ions in it, making a mixed slag material for use as a backfill for building materials. This method does not mention the recovery and utilization of valuable metals, resulting in a great waste of resources. Chinese Patent CN 117682537A published a "Process for Extracting Potassium Salt and Sodium Salt from Sintering Machine Head Ash and Ore - Dressing Wastewater", which uses ore - dressing wastewater to rinse the sintering machine head ash, and after subjecting the rinse liquid to three - stage impurity and heavy - metal removal, the feed liquid is sent to a multi - effect evaporator for evaporation and crystallization to obtain potassium salt and sodium salt with a purity of over 90%. However, this invention does not mention the recovery and utilization of other valuable metals, causing a large waste of resources. Chinese Patent CN116287732A published a "Treatment Process for Sintering Machine Head Electrostatic Precipitation Ash", which uses water to dissolve the soluble potassium salt and sodium salt in the machine head ash, then performs solid - liquid separation, and after impurity removal and decolorization of the separated feed liquid, it is sent to a multi - effect evaporator for evaporation and crystallization to obtain potassium salt and sodium salt. However, the feed liquid after this process contains a large amount of calcium, magnesium ions, and sulfate radicals, which will cause pipeline scaling and affect the normal operation of the equipment. Moreover, a part of thallium will dissolve in the feed liquid during the water - washing process, which will make the product potassium and sodium salts contain toxic and harmful substances, affecting the use of the product salts. Chinese Patent CN 108277357B published a "Method for Separating and Recovering Silver and Lead from Sintering Machine Head Dust in a Steel Plant", which uses ammonium carbonate as a conversion agent and precipitant to convert lead and silver in the machine head ash into lead carbonate and silver carbonate under oxidant conditions. However, this method has a complex process, high cost, and will introduce ammonium ions into the system, consuming a large amount of oxidant. At the same time, the leaching feed liquid contains a large amount of heavy metal ions, which will cycle and accumulate in the system, corroding the equipment and possibly causing secondary environmental pollution.

[0004] In summary, the existing processes for treating machine head ash have the following problems:

[0005] 1. Only the recovery and utilization of elements such as potassium, sodium, and iron in the sintering machine head ash are solved, while the precious metals, rare metals, and heavy metals with high value are not comprehensively utilized. These harmful elements re-enter the sintering system with the selected iron ore, continuously enriching during the process, causing a huge load on the sintering equipment and reducing the grade of the finished ore, bringing great negative impacts to iron and steel metallurgy.

[0006] 2. The treatment of the feed liquid is incomplete. The feed liquid sent to the evaporation system contains a large amount of calcium and magnesium ions and sulfate radicals, which will deteriorate the evaporation and crystallization conditions. At the same time, it will result in relatively low purity of the crystallized potassium and sodium salts, mixed with other impurities, affecting the use of the products.

[0007] 3. None of them mention the treatment and utilization of toxic and harmful elements such as thallium, chromium, and cadmium in the machine head ash, and the trend of these heavy metals cannot be controlled, bringing secondary pollution to the environment. Summary of the Invention

[0008] The present invention provides a process for comprehensive utilization of sintering machine head ash in iron and steel metallurgy, which can comprehensively and efficiently recover potassium salts, sodium salts, and valuable metals in the sintering machine head dust, solve the problem that the normal production of blast furnaces is affected by the excessive accumulation of alkali metal content, and at the same time solve the environmental pollution caused by the landfill and combustion of the machine head ash.

[0009] To achieve the above technical objectives, the technical solution of the present invention is: a process for comprehensive utilization of sintering machine head ash. The process flow for disposing of sintering machine head ash is: sintering machine head ash → oxidation leaching → pressure filtration → the filter cake is washed with chlorine and dehydrated to obtain iron concentrate powder, the filtrate is subjected to replacement to recover valuable metals → primary heavy metal removal → secondary impurity removal → evaporation crystallization → crystallized potassium chloride and sodium chloride → cesium extraction → concentrated crystallization of cesium chloride solution and preparation of metallic cesium, the cesium extraction raffinate is subjected to rubidium extraction → concentrated crystallization of rubidium chloride solution and preparation of metallic rubidium; the metal replacement powder is dissolved in acid with a certain concentration, and copper, zinc, gold, silver, and bismuth are recovered step by step, and toxic and harmful elements such as thallium, chromium, and cadmium are concentrated from the system.

[0010] Specifically, it includes the following steps:

[0011] (1) Oxidation leaching: The sintering machine head ash is rinsed with water, and then an acid solution and an oxidant are added to the rinsed sintering machine head ash for leaching.

[0012] (2) Replacement of the feed liquid: The solid after leaching in step (1) is pressure-filtered, the solid is rinsed with distilled water, dehydrated, and the rinse liquid is returned to step (1), and the filter cake is returned to sintering as a raw material for ironmaking; the filtrate enters the next heavy metal removal process after being replaced by a replacement agent.

[0013] (3) Primary deweighting: The liquid material from step (2) is subjected to primary deweighting using a deweighting agent. After the reaction is complete, solid-liquid separation is carried out using a plate and frame filter press or a centrifuge. The solid is washed with clear water or distilled water. The filter cake is a precipitate of zinc, iron, and a small amount of heavy metal hydroxides, and is returned to sintering according to its composition or combined with the replacement alloy powder for treatment;

[0014] (4) First-stage impurity removal: The liquid after primary deweighting is subjected to impurity removal and residual heavy metal removal. After solid-liquid separation, the solid is washed. The water can be used as the raw material for rinsing the sintering machine head ash. The solid after treatment is crude magnesium hydroxide, which is returned to the sintering batching for use;

[0015] (5) Second-stage impurity removal: A precipitant is added to the liquid after the first-stage impurity removal, stirred at room temperature for 0.5 - 1 h, aged for 0.5 - 1 h, and after solid-liquid separation, a filter cake and the liquid after the second-stage impurity removal are obtained;

[0016] (6) Concentration and crystallization: The liquid after impurity removal in step (5) is subjected to concentration and crystallization. First, potassium chloride is produced, and then after 2 - 3 times of forced circulation, sodium chloride is produced, ensuring that the yield and purity of potassium chloride meet the first-class product standard; For the mother liquor after crystallization of potassium chloride and sodium chloride, rubidium and cesium are respectively extracted and purified from the system using an extractant; After extraction, oil removal is carried out and then evaporation crystallization is carried out to prepare the corresponding rubidium and cesium salts; The purity of rubidium and cesium is controlled by the number of extraction and washing stages. The product purity is controlled at 99 - 99.995%.

[0017] Among them, in step (1), the water used for rinsing is tap water, industrial wastewater, or ore dressing wastewater; The acid solution used is hydrochloric acid solution or sulfuric acid solution, and the concentration of the acid solution used is 0.5 - 2.5 mol / L; The leaching conditions are: liquid-solid ratio is 2 - 5:1; The Cl - concentration of the slurry during leaching is 1 - 6 mol / L, the leaching time is 3 - 8 h, the leaching temperature is 50 - 90 °C, and the pH value at the end of leaching is 3 - 7; The oxidant is one or a mixture of two of chlorine, sodium hypochlorite, calcium hypochlorite, sodium chlorate, potassium chlorate, potassium hypochlorite, and chlorine dioxide, and the potential during leaching is controlled at 0.6 - 1.5 V; The amount of the oxidant added is 0.5% - 20% of the sintering machine head ash.

[0018] Among them, in step (2), the liquid-solid ratio of the rinse is 1 - 3:1, and countercurrent washing is carried out 2 times; Diaphragm plate and frame filter press is used for pressure filtration; The replacement agent used is any one or two of zinc powder, iron powder, and lead powder, and the dosage of the replacement agent is 1 - 18 g / L to ensure complete recovery of valuable metals in the liquid after replacement.

[0019] The de-weighting agent used in step (3) is sodium hydroxide, lime slurry or potassium hydroxide, the amount of de-weighting agent added is 5-10 g / L, the end point pH value is controlled to be 6-9, stirring is performed at room temperature for 0.5-1.5 h, and aging is performed for 0.5-1 h; during washing, the liquid-to-solid ratio is maintained at 1-3:1, and washing is performed 2-3 times.

[0020] Wherein, in step (4), the impurity remover used for removing impurities and residual heavy metals is any one or two of sodium hydroxide, sodium carbonate, and lime slurry; the amount of impurity remover added is 8-12 g / L, and the control conditions are: endpoint pH value 11-13, stirring at room temperature for 1-1.5 hours, aging for 1 hour; liquid-to-solid ratio during washing is 1-3:1, and washing is performed 2-3 times.

[0021] Wherein, in step (5), the precipitant used is one or more of sodium carbonate, sodium hydroxide, and carbon dioxide, and the amount of the precipitant added is 100-120% of the measured value; after solid-liquid separation, the filter cake obtained is calcium carbonate; the calcium carbonate product can be returned to the sintering ingredients for use, or it can be dissolved in hydrochloric acid or nitric acid and then used with one or both of potassium sulfate or sodium sulfate to prepare high-purity calcium sulfate whiskers.

[0022] The concentration of the dissolving acid is 1.0-4.0 mol / l, the liquid-to-solid ratio is 1-3:1, and the dissolving time is 0.5-1h.

[0023] When preparing high-purity calcium sulfate whiskers, potassium sulfate or sodium sulfate ground into 100-500 mesh fine powder is put into an acid-soluble calcium-containing solution at 40-95°C within 1.5-3.5 hours; or potassium sulfate or sodium sulfate or a mixture of the two is quantitatively dissolved according to a liquid-to-solid ratio of 1-3:1, and the mixing ratio is the potassium-to-sodium ratio in the leaching solution, which is generally 1.5-6.5; after fully mixing, it is stirred for 1-2 hours, and after solid-liquid separation, calcium sulfate solid is obtained, and distilled water or anhydrous ethanol and a mixture of the two are used to wash the calcium sulfate, and the liquid-to-solid ratio during rinsing is 1-3:1, and the washing is performed 2-3 times; a calcium sulfate whisker product with a purity of 99%-99.99% and an aspect ratio greater than 50 can be prepared.

[0024] Wherein, in step (6), the crystallizer used is an MVR evaporator, a triple-effect evaporator, a TVR evaporator or a low-temperature crystallization evaporator; the extractant is t-BAMBP, the extraction method is countercurrent extraction, the extraction order is first extracting cesium and then extracting rubidium, and hydrochloric acid, sulfuric acid or nitric acid is used to strip the loaded organic phase according to the situation, the extraction level is 3-15, the washing level is 5-10, and the stripping level is 2-3.

[0025] Among them, the crystallized cesium chloride, rubidium chloride, cesium sulfate, rubidium sulfate, cesium nitrate, or rubidium nitrate in step (6) is used to prepare cesium carbonate or rubidium carbonate by the oxalic acid conversion method, or to prepare metallic cesium or metallic rubidium by the metallothermic reduction method. The equipment used is a vacuum tube reduction furnace, the reducing agents used are metallic calcium, metallic magnesium, metallic lanthanum, or metallic cerium, and the internal temperature of the tube furnace is 700 - 1150°C.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The present invention provides a treatment process for the sintering machine head ash in a homogeneous system. While extracting potassium salts and sodium salts from the head ash, precious metals such as gold and silver, and valuable metals such as zinc, lead, and copper in the head ash are also recovered. Product development with high-value utilization of some elements is carried out, achieving the maximum utilization of resources. Detailed implementation manners

[0028] The following embodiments are provided to better understand the present invention. It is not limited to the best implementation manner, and does not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by inspiration from the present invention or by combining the features of the present invention with other prior art features falls within the protection scope of the present invention.

[0029] Example 1:

[0030] The element contents of the sintering ESP head ash of a certain steel plant are shown in Table 1 below:

[0031] Table 1 Element contents of the sintering ESP head ash of a certain steel plant

[0032]

[0033] This example provides a process for comprehensive utilization of the sintering machine head ash, including the following steps:

[0034] (1) Oxidative leaching: The sintering machine head ash is rinsed with tap water, and then leached with 0.5 mol / L hydrochloric acid under the condition of a liquid-solid ratio of 2:1. During leaching, ensure that the chloride ion concentration in the slurry is 1 mol / L, and at the same time add calcium hypochlorite as an oxidant, with the addition amount being 0.5% of the mass of the head ash. Control the potential of the system during leaching to be 0.6 V, the leaching time to be 3 h, the leaching temperature to be 90°C, and adjust the pH value of the slurry to 3 to ensure the full leaching of valuable metals in the head ash. After leaching, perform pressure filtration for liquid-solid separation. The filtrate enters the next process, and the filter cake is rinsed with distilled water to recover the residual leaching solution in the filter cake. After the filter cake is washed and dewatered, it can be used as iron concentrate for sintering raw materials, and the rinsing solution is returned to the first step for continued leaching. The element contents of the washed ash after oxidative leaching are shown in Table 2 below:

[0035] Table 2 Element contents in the washed ash after oxidative leaching

[0036]

[0037] (2) Displacement of the feed liquid: Recover the valuable metals in the leaching solution of Step 1. The main key steps are as follows: Pump the leached feed liquid into the displacement tank, then add zinc powder at a dosage of 1 g / L for displacement. The displacement time is 0.5 h and the displacement temperature is 25°C to ensure complete recovery of the valuable metals in the leaching solution. After the reaction is completed, carry out pressure filtration. The filter cake after pressure filtration is rinsed with distilled water with a liquid-solid ratio of 2:1 to remove the chloride ions therein, and then the alloy displacement powder is leached with an acid solution to recover the valuable metals therein and make high-value-added products. The filtrate enters the next process. The element component contents after displacing the feed liquid are shown in Table 3 below:

[0038] Table 3 Element component contents after displacing the feed liquid

[0039]

[0040] (3) Heavy metal removal treatment: Carry out heavy metal removal treatment on the feed liquid of Step 2. The main key steps are as follows: Add lime slurry as the heavy metal removal agent to the feed liquid for heavy metal removal treatment. The addition amount of the heavy metal removal agent is 5 g / L, stir at room temperature for 0.5 h, keep the solution pH at 6. After the reaction is completed, carry out aging. After aging for 0.5 h, carry out pressure filtration. The filter cake after pressure filtration is rinsed 2 times with distilled water with a liquid-solid ratio of 2:1 to remove the chloride ions therein, and then return to sintering batching or combine with the alloy displacement powder for treatment. The filtrate enters the next process. The component composition of the feed liquid after heavy metal removal is shown in Table 4 below.

[0041] Table 4 Component composition of the feed liquid after heavy metal removal

[0042]

[0043] (4) First-stage impurity removal: Carry out the impurity removal process on the feed liquid of Step 3. The main key steps are as follows: Add sodium hydroxide as the impurity removal agent to the feed liquid for impurity removal treatment. The addition amount of the impurity removal agent is 8 g / L, stir at room temperature for 1.5 h, keep the solution pH at 11. After the reaction is completed, carry out aging for 1 h, and then use a filter press for pressure filtration. The filter cake after pressure filtration is rinsed 3 times with water with a liquid-solid ratio of 1:1 to remove the chloride ions therein. The filter cake returns to sintering batching, and the filtrate enters the next process. The component composition of the liquid after the first-stage impurity removal is shown in Table 5 below.

[0044] Table 5 Component composition of the liquid after the first-stage impurity removal

[0045]

[0046] (5) Secondary impurity removal: The post-liquid from the first-stage impurity removal is subjected to secondary impurity removal treatment. The main key steps are as follows. Sodium carbonate, the precipitant, is added to the post-liquid from the first-stage impurity removal. The addition amount of the precipitant is 100% of the measured value in the liquid. The reaction is carried out at room temperature for 1 h, aged for 0.5 h, and then pressure filtration is carried out. The filter cake after pressure filtration is rinsed with water to remove chloride ions therein. The filter cake is dissolved with hydrochloric acid or nitric acid to prepare calcium sulfate whiskers, and the filtrate enters the next process. The composition of the post-liquid after secondary impurity removal is shown in Table 6 below.

[0047] Table 6 Composition of the post-liquid after secondary impurity removal

[0048]

[0049] The post-liquid after secondary impurity removal in step 5 is subjected to evaporation crystallization using an MVR evaporator. During evaporation, potassium chloride is produced first, and then sodium chloride is produced after 2 times of forced circulation, ensuring that the yield and purity of potassium chloride meet the first-class product standard.

[0050] (6) Concentration crystallization: A large amount of alkali metals are enriched in the mother liquor after evaporation crystallization. The main key steps for extraction are as follows: Use the configured extractant t-BAMBP and a mixture of sulfonated kerosene and diethylbenzene, with a concentration of 0.2 mol / L, the phase ratio (O / A) is 1:1, the volume fraction ratio of sulfonated kerosene to diethylbenzene is 3:5, the stripping liquid is 1 mol / l hydrochloric acid, the phase ratio (O / A) is 2:1, extract for 3 stages, wash for 5 stages, strip for 2 stages, and carry out countercurrent extraction of cesium chloride. The recovery rate of cesium is 98.1%;

[0051] Adjust the alkali concentration of the raffinate and washing liquid from the extraction of cesium chloride to 0.8 mol / L, the stripping liquid is 1 mol / l hydrochloric acid, the phase ratio (O / A) is 2:1, use the same extractant as for the extraction of Cs, extract for 3 stages, wash for 5 stages, strip for 2 stages, and carry out countercurrent extraction of rubidium chloride. The recovery rate of rubidium is 95.6%. The raffinate can be returned to steps 1-5 for rinsing, oxidative leaching, and filter cake washing.

[0052] The crystallized cesium chloride and rubidium chloride are reduced to metallic cesium and metallic rubidium using the calcium reduction method. The equipment used is a vacuum tube reduction furnace, and the reducing agent used is metallic calcium. First, preheat, evacuate, introduce argon, and put in the cesium chloride or rubidium chloride crystal; when the temperature rises to 400 °C, put in metallic calcium particles, and then raise the internal temperature of the furnace to 700 °C, reduce for 0.5 h, and reduce metallic cesium and metallic rubidium.

[0053] Example 2:

[0054] The content of each element in the sintering ESP header ash of a certain steel plant is shown in Table 7 below:

[0055] Table 7 Content of each element in the sintering ESP header ash of a certain steel plant

[0056]

[0057] This embodiment provides a process for comprehensive utilization of sintering machine head ash, including the following steps:

[0058] (1) Oxidative leaching: The sintering machine head ash is rinsed with industrial wastewater as shown in step 1, and then 1.5 mol / L hydrochloric acid is added for leaching under the condition of a liquid-solid ratio of 4:1. During leaching, ensure that the chloride ion concentration in the slurry is 4 mol / L, and at the same time add calcium hypochlorite as an oxidant, with the addition amount being 10% of the mass of the head ash. Control the potential of the system during leaching to be 1.3 V, the leaching time to be 5 h, the leaching temperature to be 70 °C, and adjust the pH value of the slurry to 5 to ensure the full leaching of valuable metals in the head ash. After leaching is completed, press filtration is carried out for liquid-solid separation. The filtrate enters the next process, and the filter cake is rinsed with distilled water to recover the residual leaching solution in the filter cake. After the filter cake is washed and dehydrated, it can be used as iron concentrate for sintering raw materials, and the washing solution is returned to the first step for continuous leaching. The content of each element in the washed ash after oxidative leaching is shown in Table 8 below.

[0059] Table 8 Content of each element in the washed ash after oxidative leaching

[0060]

[0061] (2) Displacement of the feed liquid: Recover the valuable metals in the leaching solution of step 1. The main key steps are as follows: Pump the leached feed liquid into the displacement tank, and then add iron powder for displacement at a dosage of 9 g / L. The displacement time is 0.8 h, and the displacement temperature is 50 °C to ensure the complete recovery of valuable metals in the leaching solution. The filter cake after pressure filtration is rinsed with water at a liquid-solid ratio of 1:1 to remove the chloride ions therein, and then the alloy displacement powder is leached with an acid solution to recover the valuable metals therein and make high-value-added products. The filtrate enters the next process. The component composition of each element after displacement of the feed liquid is shown in Table 9 below:

[0062] Table 9 Component composition of each element after displacement of the feed liquid

[0063]

[0064] (3) Heavy metal removal treatment: Carry out heavy metal removal treatment on the feed liquid of step 2. The main key steps are as follows: Add sodium hydroxide as a heavy metal removal agent to the feed liquid for heavy metal removal treatment. The addition amount of the heavy metal removal agent is 7 g / L, stir at room temperature for 1.5 h, keep the pH of the solution at 7, carry out aging for 0.8 h after the reaction is completed, and carry out pressure filtration after aging is completed. The filter cake after pressure filtration is rinsed 3 times with water at a liquid-solid ratio of 1:1 and clean water to remove the chloride ions therein, and then returned to sintering batching or combined with the alloy displacement powder for treatment. The filtrate enters the next process. The component composition of the heavy metal removal feed liquid is shown in Table 10 below.

[0065] Table 10 Component composition of the heavy metal removal feed liquid

[0066]

[0067] (4) Primary impurity removal: Conduct primary impurity removal on the feed liquid from Step 3. The main key steps are as follows: Add sodium carbonate as the impurity remover to the feed liquid for impurity removal treatment. The addition amount of the impurity remover is 10 g / L. Stir at room temperature for 1.5 h, maintain the solution pH at 12. After the reaction is completed, perform pressure filtration. The filter cake after pressure filtration is rinsed twice with water with a liquid-solid ratio of 3:1 to remove the chloride ions therein. The filter cake is returned to the sintering batching, and the filtrate enters the next process. The component composition of the liquid after primary impurity removal is shown in Table 11 below.

[0068] Table 11 Component Composition of the Liquid after Primary Impurity Removal

[0069]

[0070] (5) Secondary impurity removal: Conduct secondary impurity removal treatment on the liquid after primary impurity removal. The main key steps are as follows: Add sodium hydroxide as the precipitant to the feed liquid after primary impurity removal. The addition amount of the precipitant is 110% of the measured value. React at room temperature for 0.5 h and age for 1 h, then perform pressure filtration. The filter cake after pressure filtration is rinsed with water to remove the chloride ions therein. The filter cake is dissolved with hydrochloric acid or nitric acid and then calcium sulfate whiskers are prepared. The filtrate enters the next process. The component composition of the liquid after secondary impurity removal is shown in Table 12 below.

[0071] Table 12 Component Composition of the Liquid after Secondary Impurity Removal

[0072]

[0073] (6) Evaporation and crystallization: Use a triple-effect evaporator to perform evaporation and crystallization on the liquid after secondary impurity removal in Step 5. During evaporation, potassium chloride is produced first, and then sodium chloride is produced after 3 times of forced circulation to ensure that the yield and purity of potassium chloride meet the first-class product standard.

[0074] A large amount of alkali metals are enriched in the mother liquor after evaporation and crystallization. The main key steps for extraction are as follows: Use a mixture of the configured extractant t-BAMBP and sulfonated kerosene and diethylbenzene with a concentration of 0.5 mol / L, the phase ratio (O / A) is 1:1, the volume fraction ratio of sulfonated kerosene to diethylbenzene is 3:5, the stripping liquid is 2 mol / l hydrochloric acid, the phase ratio (O / A) is 2:1, extract for 7 stages, wash for 10 stages, strip for 3 stages, and perform countercurrent extraction of cesium chloride. The recovery rate of cesium is 98.4%.

[0075] The raffinate and washing solution for extracting cesium chloride are adjusted to an alkali concentration of 1.0 mol / L, the stripping solution is 2 mol / L hydrochloric acid, the phase ratio (O / A) is 2:1, the same extractant as that for extracting Cs is used, and the phase ratio (O / A) is 1:1 for 7-stage extraction, 5-stage washing, and 2-stage stripping to perform countercurrent extraction of rubidium chloride. The recovery rate of rubidium is 95.7%. The raffinate can be returned to steps 1-5 for rinsing, oxidative leaching, and filter cake washing.

[0076] The crystallized cesium chloride and rubidium chloride are reduced to metallic cesium and metallic rubidium using the calcium reduction method. The equipment used is a vacuum tube reduction furnace, and the reducing agent used is metallic calcium. First, preheat, evacuate, introduce argon, and place the cesium chloride or rubidium chloride crystals; when the temperature rises to 400 °C, add metallic calcium particles, then raise the internal temperature of the furnace to 900 °C, and reduce for 0.8 h to reduce metallic cesium and metallic rubidium.

[0077] Example 3:

[0078] The elemental contents of the sintering ESP head ash of a certain steel plant are shown in Table 13 below:

[0079] Table 13 Elemental Contents of the Sintering ESP Head Ash of a Certain Steel Plant

[0080]

[0081] This example provides a process for comprehensive utilization of sintering head ash, including the following steps:

[0082] (1) Oxidative leaching: Rinse the sintering head ash with ore dressing wastewater as shown in step 1, then add 2.5 mol / L sulfuric acid for leaching under the condition of a liquid-solid ratio of 5:1. During leaching, ensure that the chloride ion concentration in the slurry is 6 mol / L, and at the same time add the oxidant calcium hypochlorite, with the addition amount being 20% of the mass of the head ash. Control the potential of the system during leaching to be 1.5 V, the leaching time to be 8 h, the leaching temperature to be 50 °C, adjust the pH value of the slurry to 7 to ensure the full leaching of valuable metals in the head ash. After leaching, perform pressure filtration for liquid-solid separation. The filtrate enters the next process, and the filter cake is rinsed with distilled water to recover the residual leaching solution in the filter cake. After the filter cake is washed and dewatered, it can be used as iron concentrate for sintering raw materials, and the rinsing solution is returned to the first step for continued leaching.

[0083] The elemental contents of the washed ash after oxidative leaching are shown in Table 14 below:

[0084] Table 14 Elemental Contents of the Washed Ash after Oxidative Leaching

[0085]

[0086] (2) Replacement of the feed liquid: Recover valuable metals from the leaching solution in Step 1. The main key steps are as follows: Pump the leached feed liquid into the replacement tank, then add lead powder at a dosage of 18 g / L for replacement. The replacement time is 1 h and the replacement temperature is 70 °C to ensure complete recovery of valuable metals in the leaching solution. The filter cake after pressure filtration is rinsed with water at a liquid-solid ratio of 3:1 to remove chloride ions therein, and then the alloy replacement powder is leached with an acid solution to recover valuable metals therein and make high-value-added products. The filtrate enters the next process. The component contents of each element after replacing the feed liquid are shown in Table 15 as follows:

[0087] Table 15 Component Contents of Each Element after Replacing the Feed Liquid

[0088]

[0089] (3) Heavy metal removal treatment: Conduct heavy metal removal treatment on the feed liquid in Step 2. The main key steps are as follows: Add lime slurry as the heavy metal removal agent to the feed liquid for heavy metal removal treatment. The dosage of the heavy metal removal agent is 10 g / L, stir at room temperature for 2 h, keep the solution pH at 9, conduct aging for 1 h after the reaction is completed, conduct pressure filtration after aging is completed. The filter cake after pressure filtration is rinsed twice with distilled water at a liquid-solid ratio of 3:1 to remove chloride ions therein, and then return to sintering batching or be combined with the alloy replacement powder for treatment. The filtrate enters the next process. The component composition of the heavy metal removal feed liquid is shown in Table 16 as follows.

[0090] Table 16 Component Composition of the Heavy Metal Removal Feed Liquid

[0091]

[0092] (4) First-stage impurity removal: Conduct first-stage impurity removal on the feed liquid in Step 3. The main key steps are as follows: Add lime slurry as the impurity removal agent to the feed liquid for impurity removal treatment. The dosage of the precipitant is 12 g / L, stir at room temperature for 1 h, keep the solution pH at 13, conduct aging for 1 h after the reaction is completed, conduct pressure filtration after aging is completed. The filter cake after pressure filtration is washed twice with distilled water at a liquid-solid ratio of 3:1 and rinsed with water to remove chloride ions therein, and then return to sintering batching. The filtrate enters the next process. The component composition of the liquid after the first-stage impurity removal is shown in Table 17 as follows.

[0093] Table 17 Component Composition of the Liquid after the First-stage Impurity Removal

[0094]

[0095] (5) Secondary impurity removal: The liquid after primary impurity removal is subjected to secondary impurity removal treatment. The main key steps are as follows. Carbon dioxide, the precipitant, is added to the liquid after primary impurity removal, and the addition amount of the precipitant is 120% of the measured value. After reacting at room temperature for 0.5 h and aging for 1 h, pressure filtration is carried out. The filter cake after pressure filtration is rinsed with water to remove chloride ions therein. The filter cake is dissolved with hydrochloric acid or nitric acid to prepare calcium sulfate whiskers, and the filtrate enters the next process. The composition of the liquid after secondary impurity removal is shown in Table 18 below.

[0096] Table 18 Composition of the liquid after secondary impurity removal

[0097]

[0098] (6) Evaporation and crystallization: The liquid after secondary impurity removal in step 4 is subjected to evaporation and crystallization using a TVR evaporator. During evaporation, potassium chloride is produced first, and then sodium chloride is produced after 3 times of forced circulation, ensuring that the yield and purity of potassium chloride meet the first-class product standard.

[0099] A large amount of alkali metals are enriched in the mother liquor after evaporation and crystallization. The main key steps for extraction are as follows: Use a configured extractant of t-BAMBP and a mixture of 1,2-dichloroethylene and xylene with a concentration of 0.8 mol / L, the phase ratio (O / A) is 1:1, and the volume fraction ratio of 1,2-dichloroethylene to xylene is 3:7; the stripping solution is 3 mol / l hydrochloric acid, the phase ratio (O / A) is 2:1, extract for 15 stages, wash for 10 stages, strip for 3 stages, and carry out countercurrent extraction of cesium chloride. The recovery rate of cesium is 99.3%.

[0100] The concentration of the alkali in the raffinate and washing solution of cesium chloride extraction is adjusted to 1.4 mol / L. The stripping solution is 3 mol / l hydrochloric acid, the phase ratio (O / A) is 2:1. Use the same extractant as for Cs extraction, with a phase ratio (O / A) of 2:1 for extraction, extract for 15 stages, wash for 10 stages, strip for 3 stages, and carry out countercurrent extraction of rubidium chloride. The recovery rate of rubidium is 97.1%. The raffinate can be returned to steps 1-5 for rinsing, oxidative leaching, and filter cake washing.

[0101] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention. The protection scope of the present invention is defined by the claims and their equivalent technical solutions.

Claims

1. A process for comprehensive utilization of sintering machine head ash, characterized in that The steps include: (1) Oxidation leaching: The sintering machine head ash is rinsed with water, and then an acid solution and an oxidant are added to the rinsed sintering machine head ash for leaching; (2) replacing the feed liquid: the solid after leaching in step (1) is filtered, the solid is rinsed with distilled water, dehydrated, the rinse liquid is returned to step (1), the filter cake is returned to sintering as an ironmaking raw material, and the filtrate is replaced by a replacement agent and enters the next weight removal process; (3) Primary deweighting: The feed liquid of step (2) is subjected to primary deweighting using a deweighting agent. After the reaction is complete, a plate-and-frame filter press or a centrifuge is used to separate the solid and the liquid. The solid is washed with clean water or distilled water. The filter cake is a hydroxide precipitate of zinc, iron and a small amount of heavy metals. Depending on its composition, it is returned to sintering or combined with the substitution alloy powder for treatment; (4) One-stage impurity removal: the liquid after the first stage of weight removal is subjected to impurity removal and residual heavy metal removal. After solid-liquid separation, the solid is washed. The water can be used as a raw material for rinsing the sintering machine head ash. The solid is treated to become crude magnesium hydroxide, which is returned to the sintering ingredients for use; (5) Second stage impurity removal: add a precipitant to the first stage impurity removal liquid, stir at room temperature for 0.5-1h, age for 0.5-1h, and obtain a filter cake and a second stage impurity removal liquid after solid-liquid separation; (6) Concentration and crystallization: After the impurity removal in step (5), the second stage impurity removal liquid is concentrated and crystallized to produce potassium chloride first, and then sodium chloride after 2-3 forced circulations; the mother liquor after the crystallization of potassium chloride and sodium chloride is used to extract and purify rubidium and cesium from the system respectively by using an extractant; after extraction, the oil is removed and then evaporated and crystallized to prepare the corresponding rubidium and cesium salts.

2. The process for comprehensive utilization of sintering machine head ash according to claim 1, characterized in that: In step (1), the rinsing water is tap water, industrial waste water or mineral processing waste water; the acid solution is hydrochloric acid solution or sulfuric acid solution, and the concentration of the acid solution is 0.5-2.5 mol / L; the leaching conditions are: liquid-to-solid ratio is 2-5:1; the slurry Cl during leaching is - The concentration is 1-6 mol / L, the leaching time is 3-8h, the leaching temperature is 50-90°C, and the leaching end point pH value is 3-7; the oxidant is one or a mixture of chlorine, sodium hypochlorite, calcium hypochlorite, sodium chlorate, potassium chlorate, potassium hypochlorite, and chlorine dioxide, and the potential during leaching is controlled to be 0.6-1.5V; the amount of the added oxidant is 0.5%-20% of the sintering machine head ash.

3. The process for comprehensive utilization of sintering machine head ash according to claim 1, characterized in that: In step (2), the liquid-to-solid ratio of rinsing is 1-3:1, and the countercurrent washing is performed twice; the filter press adopts a diaphragm plate and frame filter press; the displacing agent used is any one or two of zinc powder, iron powder, and lead powder, and the amount of the displacing agent used is 1-18 g / L.

4. The process for comprehensive utilization of sintering machine head ash according to claim 1, characterized in that: In step (3), the de-weighting agent used is sodium hydroxide, lime slurry or potassium hydroxide, the amount of de-weighting agent added is 5-10 g / L, the endpoint pH value is controlled to be 6-9, stirring is performed at room temperature for 0.5-1.5 h, and aging is performed for 0.5-1 h; during washing, the liquid-to-solid ratio is maintained at 1-3:1, and washing is performed 2-3 times.

5. The process for comprehensive utilization of sintering machine head ash according to claim 1, characterized in that: In step (4), the impurity remover used for removing impurities and residual heavy metals is any one or two of sodium hydroxide, sodium carbonate, and lime slurry; the amount of impurity remover added is 8-12 g / L, and the control conditions are: endpoint pH value 11-13, stirring at room temperature for 1-1.5 hours, aging for 1 hour; liquid-to-solid ratio during washing is 1-3:1, and washing is performed 2-3 times.

6. The process for comprehensive utilization of sintering machine head ash according to claim 1, characterized in that: In step (5), the precipitant used is one or more of sodium carbonate, sodium hydroxide, and carbon dioxide, and the amount of the precipitant added is 100-120% of the measured value; after solid-liquid separation, the filter cake obtained is calcium carbonate; the calcium carbonate product can be returned to the sintering ingredients for use, or it can be dissolved in hydrochloric acid or nitric acid and then used with one or both of potassium sulfate and sodium sulfate to prepare high-purity calcium sulfate whiskers.

7. The process for comprehensive utilization of sintering machine head ash according to claim 6 is characterized in that: The acid concentration for dissolution is 1.0-4.0 mol / l, the liquid-to-solid ratio is 1-3:1, and the dissolution time is 0.5-1h.

8. A process for comprehensive utilization of sintering machine head ash according to claim 6, characterized in that: When preparing high-purity calcium sulfate whiskers, potassium sulfate or sodium sulfate ground into 100-500 mesh fine powder is put into an acid-soluble calcium-containing solution at 40-95°C within 1.5-3.5 hours; or potassium sulfate or sodium sulfate or a mixture of the two is quantitatively dissolved according to a liquid-to-solid ratio of 1-3:1, and the mixing ratio is the potassium-to-sodium ratio in the leaching solution; after fully mixing, it is stirred for 1-2 hours, and after solid-liquid separation, calcium sulfate solid is obtained, and distilled water or anhydrous ethanol and a mixture of the two are used to wash the calcium sulfate, and the liquid-to-solid ratio during rinsing is 1-3:1, and the washing is performed 2-3 times; a calcium sulfate whisker product with a purity of 99%-99.99% and an aspect ratio of more than 50 can be prepared.

9. The process for comprehensive utilization of sintering machine head ash according to claim 1, characterized in that: In step (6), the crystallizer used is an MVR evaporator, a triple-effect evaporator, a TVR evaporator or a low-temperature crystallization evaporator; The extractant is t-BAMBP, the extraction method is countercurrent extraction, the extraction order is to extract cesium first, then extract rubidium, and hydrochloric acid, sulfuric acid or nitric acid is used to back-extract the loaded organic phase according to the situation. The extraction level is 3-15, the washing level is 5-10, and the back-extraction level is 2-3.

10. The process for comprehensive utilization of sintering machine head ash according to claim 1, characterized in that: The cesium chloride, rubidium chloride or cesium sulfate, rubidium sulfate or cesium nitrate, rubidium nitrate crystallized in step (6) is used to prepare cesium carbonate, rubidium carbonate by oxalic acid conversion method, or to prepare metallic cesium, metallic rubidium by metal thermal reduction method; the equipment used is a vacuum tube reduction furnace, the reducing agent used is metallic calcium, metallic magnesium, metallic lanthanum, metallic cerium, and the internal temperature of the tube furnace is 700-1150°C.

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