CN113753929A - Method for preparing high-whiteness aluminum hydroxide and silicon fertilizer from high-alumina fly ash - Google Patents
Method for preparing high-whiteness aluminum hydroxide and silicon fertilizer from high-alumina fly ash Download PDFInfo
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- CN113753929A CN113753929A CN202110991430.4A CN202110991430A CN113753929A CN 113753929 A CN113753929 A CN 113753929A CN 202110991430 A CN202110991430 A CN 202110991430A CN 113753929 A CN113753929 A CN 113753929A
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/16—Preparation of alkaline-earth metal aluminates or magnesium aluminates; Aluminium oxide or hydroxide therefrom
- C01F7/164—Calcium aluminates
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/20—Preparation of aluminium oxide or hydroxide from aluminous ores using acids or salts
- C01F7/22—Preparation of aluminium oxide or hydroxide from aluminous ores using acids or salts with halides or halogen acids
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- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05D—INORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C; FERTILISERS PRODUCING CARBON DIOXIDE
- C05D9/00—Other inorganic fertilisers
Abstract
The invention provides a method for preparing high-white aluminum hydroxide and a silicon fertilizer by using high-alumina fly ash, which is a brand-new calcium chloride process technology2·nH2Roasting the O precipitate and calcium chloride to obtain the silicon fertilizer clinker, wherein effective SiO in the silicon fertilizer clinker2More than 20 percent, therefore, the invention can lead the high-alumina fly ash to achieve the purpose of full resource utilization and open a new way for the comprehensive utilization of the high-alumina fly ash.
Description
Technical Field
The invention belongs to the technical field of comprehensive utilization of fly ash, and particularly relates to a method for preparing high-whiteness aluminum hydroxide and a silicon fertilizer from high-alumina fly ash.
Background
China has abundant coal resources and is a major coal-producing nation in the world. In 2020, the coal consumption of China is about 30 hundred million tons, which accounts for 56.8% of the total energy consumption of China. Based on abundant coal resources in China, China forms an electric power production structure mainly based on thermal power, and the thermal power proportion accounts for more than 70% of the total generated energy. More than 50% of coal in China is used for power generation of thermal power plants, and the rest is used in the industries of heating, coking, gas making and the like.
Because the fly ash is solid waste discharged after coal is combusted in a boiler of a coal-fired power plant, the fly ash is also the industrial waste residue with the largest discharge amount in China. 1 ton of coal is usually combusted to generate 20-30% of fly ash, and the average ash discharge amount of thermal power plants in China is about 25%. In addition, other industries such as heating, coal gas preparation and the like can also generate a large amount of fly ash. At present, about 6 hundred million tons of fly ash are discharged in China in year, and the fly ash accounts for 1/3 of global discharge. In northern coal-producing provinces, fly ash is generally stockpiled by a method of building an ash yard, which occupies land and pollutes the environment. The comprehensive utilization research of the fly ash is a scientific research project which is greatly supported and encouraged by the nation all the time.
The fly ash mainly comprises alumina and silicon oxide, and also comprises components such as ferric oxide, calcium oxide, magnesium oxide, titanium oxide, unburned carbon and the like, and almost does not contain heavy metal. Usually SiO in fly ash2+A12O3Accounting for about 80 percent. The other components account for about 20 percent.
In the coal producing provinces of inner Mongolia, Shanxi and Ningxia in China, the coal contains more inorganic minerals with higher aluminum content such as kaolinite, boehmite, clay minerals and the like, and Al is formed in the combustion process2O3High content of fly ash, Al2O3The content can reach 40-52% usually, which is equivalent to Al in China's middle-low grade bauxite and imported trihydrate bauxite2O3The content is known in the industry as high alumina fly ash.
Therefore, the research on the comprehensive utilization of the fly ash for extracting the alumina and the byproduct is one of the worldwide technical problems, and the foreign research mainly takes Poland, which has been about 60 years to date, has not been successful.
In China, in nearly 20 years, billions of capital are invested for research, and no technical breakthrough is made up till now. The large Tang power, China Shenhua, China aluminum industry, China middlings group and Mongolian group adopt a plurality of process technologies such as a pre-desiliconization sintering method, an acid method, a low calcium sintering method, a lime sintering method and the like in sequence to produce alumina and related byproducts, the industrial and economic utilization is not obtained, and the research is in the low valley at present.
The fly ash mainly contains alumina and silicon oxide, and is a raw material for preparing aluminum hydroxide, alumina and silicon fertilizer. In recent years, experience teaching of the coal ash comprehensive utilization research in the past is summarized, the high-alumina fly ash comprehensive utilization research work is carried out, and a great deal of experience is obtained. The invention provides a novel process technology for treating high-alumina fly ash by a calcium chloride method, and high-whiteness aluminum hydroxide and a silicon fertilizer are produced. Thereby achieving the full resource comprehensive utilization of the fly ash.
China is the largest alumina producing and consuming country in the world, and the current alumina yield is about 8000 million tons/year, which accounts for more than half of the world yield. Most of the bauxite needed by the production of alumina is solved by import, and the self-produced bauxite can not meet the domestic alumina production requirement.
95% of the alumina yield is a metallurgical-grade product used for producing electrolytic aluminum, and the remaining 5% is used as an alumina chemical, about 300 million tons or so called as various alumina, and is widely used in many industries such as petrochemical industry, building materials, power transmission, medicine, fire protection, new energy batteries and automobiles, environmental protection, daily necessities, and the like.
Although the yield of alumina chemical products is only 300-.
High-whiteness aluminum hydroxide is a large branch of alumina chemicals and is widely used in the fields of artificial marble, fire-fighting flame retardant, filler for plastic rubber papermaking, electronic components, friction agents, medicines, chemical catalysts and the like. Due to wide application, various industries have different requirements on the chemical composition and material properties of the high-whiteness aluminum hydroxide. According to different requirements of users, the high-whiteness aluminum hydroxide forms series products with different purities, different impurity contents, different particle sizes and different whiteness.
At present, the annual output of the high-whiteness aluminum hydroxide in China is 60-70 ten thousand tons, the high-whiteness aluminum hydroxide is mainly produced by China-aluminum China, Shandong branches, the total output is 50 ten thousand tons/year, and the output of other enterprises is only 20 ten thousand tons/year.
Production methodThe method is mainly a sintering process and is grafted on the existing metallurgical-grade aluminum oxide production line. Because the sintering method has a clinker sintering process at 1250 ℃ and is followed by medium-pressure desiliconization and impurity removal and decoloration processes, the sintering method product has low organic matter content and high solution purity after desiliconization and iron removal, and the decomposition rate is about 50% by adopting a seed separation process. The concentration of the sodium aluminate solution is controlled to be about 105g/l, and the causticization coefficient alpha is controlledkThe value is about 1.6, the decomposition temperature is low, the time is long, various high-whiteness aluminum hydroxide products with different properties can be produced, and the whiteness of the products is between 94 and 98 percent. The Bayer process has high organic matter content and low whiteness, usually 85-90%, and thus cannot meet the requirement of high whiteness.
In the existing production of high-white aluminum hydroxide, bauxite must be used as a raw material.
Because silicon is a necessary nutrient element for plant growth, silicon has good effects on promoting crop growth, enhancing the disease and pest resistance of crops, improving the quality of crops, increasing the yield of crops, improving the soil environment, adjusting soil components and the like. At present, silicon fertilizer is the fourth largest fertilizer after nitrogen fertilizer, phosphate fertilizer and potassium fertilizer in agriculture.
The main components of the silicon fertilizer are dicalcium silicate, monocalcium silicate, calcium magnesium silicate, calcium aluminate, sodium metasilicate and the like.
The development of the silicon fertilizer in China is about 50 years later than that in foreign countries, the silicon fertilizer is researched in the middle 70 years of the last century, and the silicon fertilizer is produced and applied in small scale in the 80 th year. After 1990, the development speed of the silicon fertilizer in China is high, and a batch of silicon fertilizer factories for industrial production are built and put into production. At present, the silicon fertilizer is popularized and used on a large scale, the yield of the silicon fertilizer is about 300 million tons in China in 2020, and the yield of the silicon fertilizer is increased year by year. But at the same time, the yield of the foreign silicon fertilizer exceeds 3000 ten thousand tons per year. Therefore, the yield of the silicon fertilizer in China and the world has a large difference.
The cultivated land area of China is nearly 18 hundred million mu, and the cultivated land with silicon element shortage is about 10 hundred million mu, which exceeds 50 percent of the cultivated land area of China. Yangtze river valley is the main rice producing area in China, and over 80% of farmlands lack silicon and need silicon fertilizer. The potential demand of the domestic silicon fertilizer market is more than 3000 million tons. The silicon fertilizer industry faces better development prospect.
Silicon is the most abundant element in the earth's crust and accounts for about one-fourth of the total mass of the earth's crust. If calculated as silica, it occupies more than half of the earth's crust. Therefore, in various tailings, smelting slag and fly ash which are industrially exploited, SiO is contained in large quantity2The waste residues occupy land and pollute environment, and are good raw materials for producing silicon fertilizer according to chemical compositions.
At present, the domestic silicon fertilizer production mainly takes industrial slag as raw materials, such as: blast furnace water-quenched slag in the steel making industry, common aluminum-silicon fly ash, waste slag in the phosphating chemical production process, waste glass and the like. The method mainly comprises the following steps: drying waste residues, crushing, removing impurities by heavy metals, adding partial local soil rare elements according to soil components, performing ball milling pulverization, and screening to obtain the commercial silicon fertilizer.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash comprises the following steps:
(1) preparing raw slurry with the water content of 36-42% by using the high-alumina fly ash and the calcium chloride powder;
(2) sintering the raw slurry in the step (1) at the temperature of 700-1200 ℃, wherein the sintering reaction time is 1-5 hours, and clinker containing calcium aluminate, calcium dialuminate, calcium silicate and dicalcium silicate is obtained;
(3) reacting the clinker in the step (2) with hydrochloric acid with the concentration of 10-20% to obtain a mixed solution of aluminum chloride and calcium chloride and SiO2˙nH2O precipitate;
(4) adding lime into the mixed solution in the step (3), and reacting for 0.5-1.0h at the temperature of 45-90 ℃ to obtain an aluminum hydroxide precipitate;
(5) sequentially separating, washing and drying the aluminum hydroxide precipitate in the step (4) to obtain a high-whiteness aluminum hydroxide product;
(6) SiO in the step (3)2˙nH2Mixing the O precipitate and calcium chloride powder to prepare a silicon raw material;
(7) and (4) roasting the silicon raw material in the step (6) at the roasting temperature of 800-.
Further, the granularity of the high-alumina fly ash is 5-60 mu, and Al2O3The content of (A) is more than 40%; al in the high-alumina fly ash2O3The sum of the mol number of CaO and CaCl in calcium chloride powder2The ratio of the number of moles of (a) is 1:1 to 1: 3.
Further, the steps (2) and (7) both comprise treating reaction tail gas, which comprises: absorbing the hydrogen chloride flue gas generated by the reaction by hydrochloric acid with the concentration of 10-20%.
Further, when the clinker in the step (2) is reacted with hydrochloric acid with the concentration of 10-20%, the method comprises the following steps:
crushing the clinker into particles with the particle size of 100-300 meshes, and reacting the particles with a hydrochloric acid solution with the concentration of 10-20% at the temperature of 45-90 ℃, wherein Al in the clinker is2O3And the ratio of the sum of the moles of CaO to the moles of HCl in the hydrochloric acid solution is 0.98 to 1.0.
Further, when lime is added to the mixed solution in the step (3), CaO and AlCl are added3The ratio of the mole number of the components is 1.8: 1-2.5: 1.
Further, when the aluminum hydroxide precipitate in the step (4) is sequentially subjected to separation, washing and drying treatment, the method comprises the following steps:
after liquid-solid separation is carried out on the solution containing the aluminum hydroxide precipitate, hot water at the temperature of 80-90 ℃ is added into the filtered aluminum hydroxide precipitate for washing, the water content of the aluminum hydroxide filter cake after washing and filtering is 5-8%, the aluminum hydroxide filter cake is dried at the temperature of 100-160 ℃, and the high-whiteness aluminum hydroxide product can be obtained after drying.
Further, after the aluminum hydroxide precipitate is sequentially separated and washed, the method further comprises the following steps:
sending a separation stock solution obtained by performing liquid-solid separation on a solution containing aluminum hydroxide precipitates and a washing solution of aluminum hydroxide to an evaporation station, evaporating and removing excessive water, and concentrating the concentrations of the separation stock solution and the washing solution within a water range required by a raw slurry preparation process so that the concentrated solution can be used as the raw slurry in the step (1).
Furthermore, the pressure of the evaporation station for evaporating the separation stock solution and the washing solution is 0.6mpa, the evaporator group of the evaporation station operates with 3-4 efficiency, the PH value is within the range of 5-6, and the heating pipe and the shell of the evaporator are made of titanium materials.
Further, SiO in the step (3)2˙nH2When the O precipitate is mixed with calcium chloride powder, SiO is formed2With CaCl2The ratio of the mole numbers between the two is 1:1-1: 4.
The invention provides a method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash, which is a brand-new calcium chloride process technology2˙nH2Roasting the O precipitate and calcium chloride to obtain the silicon fertilizer clinker, wherein effective SiO in the silicon fertilizer clinker2More than 20 percent, therefore, the invention can lead the high-alumina fly ash to achieve the purpose of full resource utilization and open a new way for the comprehensive utilization of the high-alumina fly ash.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
Fig. 1 is a schematic flow chart of a method for preparing high-whiteness aluminum hydroxide and a silicon fertilizer from high-alumina fly ash according to exemplary embodiment 1 of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention provides a method for preparing high-whiteness aluminum hydroxide and a silicon fertilizer by using high-alumina fly ash, which comprises the following steps:
(1) preparing raw slurry with the water content of 36-42% by using the high-alumina fly ash and the calcium chloride powder;
wherein the particle size of the high-alumina fly ash is 5-60 mu, and Al2O3The content of (A) is more than 40%; al in high-alumina fly ash2O3The sum of the mol number of CaO and CaCl in calcium chloride powder2The ratio of the number of moles of (a) is 1:1 to 1: 3. Wherein the calcium chloride powder is CaCl2Industrial solid calcium chloride powder II grade product with content higher than 90%.
(2) And (2) sintering the raw slurry in the step (1) at the temperature of 700-1200 ℃, wherein the sintering reaction time is 1-5 hours, and thus obtaining the clinker containing calcium aluminate, calcium dialuminate, calcium silicate and dicalcium silicate.
The step (2) specifically comprises the following steps: the raw slurry is conveyed to a rotary kiln to be fired by a pump and a spray gun in sequence, the firing fuel is fine coal powder, the coal powder is also conveyed to the kiln head in the kiln by the spray gun, the firing temperature is 700-1200 ℃, and the reaction time in the kiln is 1-5 hours. The main chemical reaction process of the clinker sintering is as follows:
Al2O3+CaCl2+H2O→CaO˙Al2O3+CaO˙2Al2O3+HCl↑
SiO2+CaCl2+H2O→CaO˙SiO2+2CaO˙SiO2+HCl↑
it can be seen that the raw slurry in step (1) is subjected to a clinker firing reaction to obtain clinker of calcium aluminate, calcium dialuminate, calcium silicate and dicalcium silicate.
Since the hydrogen chloride fume is generated during the clinker sintering reaction, the step (2) also includes the treatment of the reaction tail gas, which includes: absorbing the hydrogen chloride flue gas generated by the reaction by hydrochloric acid with the concentration of 10-20%.
Since the hydrochloric acid is recycled in the preparation method of the invention, the calcium chloride powder is also used in the raw material in the step (1), and the excessive hydrochloric acid is in the reaction system of the invention, the concentration of the hydrochloric acid solution for recovering the hydrogen chloride flue gas is controlled to be 10-20%, and the hydrochloric acid treatment solution for absorbing the hydrogen chloride flue gas can be sold as a hydrochloric acid byproduct.
(3) Reacting the clinker in the step (2) with hydrochloric acid with the concentration of 10-20% to obtain a mixed solution of aluminum chloride and calcium chloride and SiO2˙nH2And (4) precipitating O.
Specifically, when the clinker in the step (2) is reacted with hydrochloric acid with the concentration of 10-20%, the method specifically comprises the following steps: crushing the clinker into particles with the particle size of 100-300 meshes, and reacting the particles with a hydrochloric acid solution with the concentration of 10-20% at the temperature of 45-90 ℃, wherein Al in the clinker is2O3And the ratio of the sum of the moles of CaO to the moles of HCl in the hydrochloric acid solution is 0.98 to 1.0.
Wherein, when the clinker and the hydrochloric acid react, the reaction temperature is preferably 45-90 ℃, so that the reaction between the clinker and the hydrochloric acid is a strong exothermic reaction, namely, the clinker and the hydrochloric acid are not required to be heated, and the heat of the reaction between the clinker and the hydrochloric acid can be used for heating the system to 45-90 ℃; the reaction time of the clinker and the hydrochloric acid is preferably 0.5-1.0 hour, and after the clinker and the hydrochloric acid react, the dissolution rate of the obtained alumina is more than 90 percent and the dissolution rate of the obtained calcium oxide is 50-80 percent; in addition, the chemical reaction process of the clinker and the hydrochloric acid is as follows:
CaO˙Al2O3+CaO˙2Al2O3+HCl→AlCl3+CaCl2+H2O
CaO˙SiO2+2CaO˙SiO2+HCl→CaCl2+SiO2˙nH2O↓+H2O
it can be seen that the mixed solution of aluminum chloride and calcium chloride obtained by the reaction of clinker and hydrochloric acid, and amorphous SiO2˙nH2And (4) precipitating O.
(4) Adding lime into the mixed solution in the step (3), and reacting for 0.5-1.0h at the temperature of 45-90 ℃ to obtain aluminum hydroxide precipitate.
Specifically, the chemical reaction process of the aluminum hydroxide decomposition reaction between the mixed solution and the lime in the step (3) is as follows:
AlCl3+CaO+aq→CaCl2+Al(OH)3↓
formed Al (OH)3The granularity is between 17 and 50 mu, which meets the granularity requirement of high-whiteness aluminum hydroxide.
Specifically, when lime is added to the mixed solution in the step (3), CaO and AlCl are added3The ratio of the mole number of the components is 1.8: 1-2.5: 1.
(5) Sequentially separating, washing and drying the aluminum hydroxide precipitate in the step (4) to obtain a high-whiteness aluminum hydroxide product;
specifically, when the aluminum hydroxide precipitate in the step (4) is sequentially subjected to separation, washing and drying, the method comprises the following steps: after liquid-solid separation is carried out on the solution containing the aluminum hydroxide precipitate, hot water at the temperature of 80-90 ℃ is added into the filtered aluminum hydroxide precipitate for washing, the water content of the aluminum hydroxide filter cake after washing and filtering is 5-8%, the aluminum hydroxide filter cake is dried at the temperature of 100-160 ℃, and the high-whiteness aluminum hydroxide product can be obtained after drying.
Further, after the aluminum hydroxide precipitate is sequentially separated and washed, the method further comprises the following steps: sending a separation stock solution obtained by performing liquid-solid separation on a solution containing aluminum hydroxide precipitates and a washing solution of aluminum hydroxide to an evaporation station, evaporating and removing excessive water, and concentrating the concentrations of the separation stock solution and the washing solution within a water range required by a raw slurry preparation process so that the concentrated solution can be used as the raw slurry in the step (1). Wherein, in order to keep the water balance of the production circulation system, the separation stock solution and the washing solution are sent to an evaporation station, and redundant water is evaporated and removed, so that the concentration of the separation stock solution and the washing solution is concentrated to the water content of 36-42%.
Furthermore, the pressure of the evaporation station for evaporating the separation stock solution and the washing solution is 0.6mpa, the evaporator group of the evaporation station operates by 3-4 efficiency, the PH value is in the range of 5-6, and the heating pipe and the shell of the evaporator are made of titanium materials.
(6) SiO in the step (3)2˙nH2And mixing the O precipitate with calcium chloride powder to prepare the silicon raw material.
Specifically, SiO in the step (3)2˙nH2When the O precipitate is mixed with calcium chloride powder, SiO is formed2With CaCl2The ratio of the mole numbers between the two is 1:1-1: 4. Wherein the calcium chloride powder is CaCl2Industrial solid calcium chloride powder II grade product with content higher than 90%.
(7) And (4) roasting the silicon raw material in the step (6) at the roasting temperature of 800-.
Specifically, the silicon raw material is delivered into a rotary kiln for roasting at the roasting temperature of 800-.
Since calcium chloride powder reacts with silicon dioxide during the roasting process, the generated flue gas contains 8-22% of hydrogen chloride, and therefore, the step (7) comprises the treatment of the reaction tail gas, which comprises the following steps: absorbing the hydrogen chloride flue gas generated by the reaction by hydrochloric acid with the concentration of 10-20%. Preferably, the flue gas in the step (7) and the flue gas generated by sintering the clinker are sent to an acid absorption workshop together to prepare hydrochloric acid with the concentration of 10-20%.
The silicon fertilizer clinker with the components of dicalcium silicate, monocalcium silicate, calcium magnesium silicate, calcium aluminate and sodium metasilicate can be obtained by roasting the silicon raw material, wherein effective SiO is2The content is 20-30%, and the standard requirement of the silicon fertilizer industry can be met.
In some embodiments, further comprising a process of crushing and bagging the silicon fertilizer clinker, comprising: and (3) crushing the roasted silicon fertilizer clinker with the lumpiness of less than 10mm to obtain the silicon fertilizer product, wherein the granularity of the crushed silicon fertilizer clinker is less than 200 mu, and then packaging the crushed silicon fertilizer clinker with 15-25kg per bag.
The invention provides a method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash, which is a brand-new calcium chloride process technology2˙nH2Roasting the O precipitate and calcium chloride to obtain the silicon fertilizer clinker, wherein effective SiO in the silicon fertilizer clinker2More than 20 percent, therefore, the invention can lead the high-alumina fly ash to achieve the purpose of full resource utilization and open a new way for the comprehensive utilization of the high-alumina fly ash.
The following provides a specific description of the method for preparing high-whiteness aluminum hydroxide and silicon fertilizer from high-alumina fly ash according to the present invention.
Example 1
A method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash is shown in figure 1 and comprises the following steps:
(1) adding 100kg of high-alumina fly ash and 9kg of calcium chloride powder into a raw slurry preparation tank, and uniformly mixing to obtain raw slurry with the water content of 38%; wherein, Al of the high-alumina fly ash2O3Content of 52% SiO231 percent of the calcium chloride powder, the average particle size of the calcium chloride powder is 20 mu, and the calcium chloride powder is CaCl2Industrial solid calcium chloride powder II grade product with content more than 90%;
(2) feeding the raw slurry obtained in the step (1) into a rotary kiln by using a centrifugal pump and a spray gun, wherein 50.4kg of clean coal (ash content 23%) is used as rotary kiln fuel, and roasting for 3 hours at 1150 ℃ to obtain 280kg of clinker with the sintered lumpiness of 5 mm;
(3) crushing the clinker in the step (2) by a crusher to ensure that the granularity of the crushed clinker is 100 mu, reacting the crushed clinker with 800kg of 10-20% hydrochloric acid, wherein the dissolution temperature is 80 ℃, and the dissolution is carried outWithin 1.0 hour, the dissolution rate of alumina in clinker is 90 percent, the dissolution rate of calcium oxide is 50 percent, and aluminum chloride and calcium chloride mixed solution and SiO are obtained2˙nH2O precipitate;
(4) adding 50kg of lime into the mixed solution in the step (3) for decomposition reaction, wherein the content of CaO and calcium oxide in the lime powder is 88%, and reacting for 0.5-1.0h at the temperature of 45-90 ℃ to obtain 71.5kg of aluminum hydroxide precipitate with the water content of 8%;
(5) drying the aluminum hydroxide precipitate with the water content of 8% by hot air at 120 ℃, and packaging by an automatic metering packaging machine of 25 kg/bag to obtain a high-whiteness aluminum hydroxide product; wherein, the high-whiteness aluminum hydroxide product has the following properties: yield 71.5kg, Al (OH)3Purity is more than or equal to 99.6 percent, and sodium Na is added2O is less than or equal to 0.01 percent, the attached water is less than or equal to 0.2 percent, the average particle size is 11-50 mu, and the whiteness is more than or equal to 94 percent. The apparent density is more than or equal to 0.9g/cm3；
(6) The concentration of the aluminum hydroxide after decomposition, separation and washing is 135g/l CaCl2The solution adopts an evaporation mode to remove redundant moisture in the process, the evaporation adopts a 3-effect operation process, the new steam pressure is 0.6mpa, and the evaporation steam-water ratio is 0.5. Concentration after evaporation of CaCl2Sending the mother liquor of 420g/l to a raw slurry preparation process to prepare raw slurry applicable to the step (1);
(7) SiO in the step (3)2˙nH2Separating and washing the O precipitate to obtain a filter cake with the water content of 25%, wherein the mass of the precipitate is 134kg, and mixing the filtered precipitate with 45kg of CaCl2Mixing industrial solid calcium chloride powder II grade product with the content of more than 90 percent to prepare silicon raw material;
(8) the silicon-yielding raw material is roasted by adopting a rotary kiln, clean coal is used as a fuel (the ash content is 23%), and the roasting temperature is as follows: 950 ℃; roasting time: 3 hours; crushing the roasted silicon fertilizer clinker by a crusher, wherein the crushing granularity is less than or equal to 120 mu;
(9) and packaging the silicon fertilizer by an automatic packaging machine with 25 kg/bag to obtain a qualified silicon fertilizer product. The effective silicon content is more than or equal to 27 percent, and the yield of the silicon fertilizer is 140 kg.
Wherein, the flue gas generated in the process of sintering the clinker in the step (2),and SiO in step (8)2˙nH2The hydrogen chloride flue gas generated by sintering the O precipitate can be sent to an acid absorption process together, and a secondary absorption tower is adopted for absorption, so that 377kg of hydrochloric acid with the concentration of 20% is prepared. 217kg of the acid is used for clinker dissolution and is recycled in the process, and 160kg of the acid is sold as a byproduct.
800kg of 20% hydrochloric acid sent by the clinker in the acid absorption process is added into a dissolution reaction tank together with the clinker, and the dissolution rate of alumina in the clinker is 90% and the dissolution rate of calcium oxide is 50%. The dissolution temperature is 80 ℃, and the dissolution time is 1.0 hour. The reaction generates aluminum chloride, calcium chloride solution and SiO2˙nH2Slurry consisting of O precipitates, the volume of the slurry is 0.85m3The slurry is separated and washed, SiO2˙nH2The O precipitate is sent to the preparation process of silicon raw material, and the solution containing aluminum chloride and calcium chloride is sent to the decomposition process of aluminum hydroxide.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (9)
1. A method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash is characterized by comprising the following steps:
(1) preparing raw slurry with the water content of 36-42% by using the high-alumina fly ash and the calcium chloride powder;
(2) sintering the raw slurry in the step (1) at the temperature of 700-1200 ℃, wherein the sintering reaction time is 1-5 hours, and clinker containing calcium aluminate, calcium dialuminate, calcium silicate and dicalcium silicate is obtained;
(3) reacting the clinker in the step (2) with hydrochloric acid with the concentration of 10-20% to obtain a mixed solution of aluminum chloride and calcium chloride and SiO2˙nH2O precipitate；
(4) Adding lime into the mixed solution in the step (3), and reacting for 0.5-1.0h at the temperature of 45-90 ℃ to obtain an aluminum hydroxide precipitate;
(5) sequentially separating, washing and drying the aluminum hydroxide precipitate in the step (4) to obtain a high-whiteness aluminum hydroxide product;
(6) SiO in the step (3)2˙nH2Mixing the O precipitate and calcium chloride powder to prepare a silicon raw material;
(7) and (4) roasting the silicon raw material in the step (6) at the roasting temperature of 800-.
2. The method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash according to claim 1, wherein the particle size of the high-alumina fly ash is 5-60 mu, and Al is2O3The content of (A) is more than 40%; al in the high-alumina fly ash2O3The sum of the mol number of CaO and CaCl in calcium chloride powder2The ratio of the number of moles of (a) is 1:1 to 1: 3.
3. The method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash as claimed in claim 1, wherein the steps (2) and (7) comprise treating reaction tail gas, and the method comprises the following steps:
absorbing the hydrogen chloride flue gas generated by the reaction by hydrochloric acid with the concentration of 10-20%.
4. The method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash as claimed in claim 1, wherein the reaction of the clinker in the step (2) and hydrochloric acid with the concentration of 10-20% comprises the following steps:
crushing the clinker into particles with the particle size of 100-300 meshes, and reacting the particles with a hydrochloric acid solution with the concentration of 10-20% at the temperature of 45-90 ℃, wherein Al in the clinker is2O3And the sum of the CaO and the hydrochloric acidThe ratio between the moles of HCl in the liquor is between 0.98 and 1.0.
5. The method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash as claimed in claim 1, wherein CaO and AlCl are added when lime is added to the mixed solution in the step (3)3The ratio of the mole number of the components is 1.8: 1-2.5: 1.
6. The method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash according to claim 1, wherein when the aluminum hydroxide precipitate in the step (4) is sequentially subjected to separation, washing and drying treatment, the method comprises the following steps:
after liquid-solid separation is carried out on the solution containing the aluminum hydroxide precipitate, hot water at the temperature of 80-90 ℃ is added into the filtered aluminum hydroxide precipitate for washing, the water content of the aluminum hydroxide filter cake after washing and filtering is 5-8%, the aluminum hydroxide filter cake is dried at the temperature of 100-160 ℃, and the high-whiteness aluminum hydroxide product can be obtained after drying.
7. The method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash according to claim 6, wherein after the aluminum hydroxide precipitate is sequentially separated and washed, the method further comprises the following steps:
sending a separation stock solution obtained by performing liquid-solid separation on a solution containing aluminum hydroxide precipitates and a washing solution of aluminum hydroxide to an evaporation station, evaporating and removing excessive water, and concentrating the concentrations of the separation stock solution and the washing solution within a water range required by a raw slurry preparation process so that the concentrated solution can be used as the raw slurry in the step (1).
8. The method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash as claimed in claim 7, wherein the pressure for evaporating the separation stock solution and the washing solution in the evaporation station is 0.6mpa, the evaporator group of the evaporation station operates in a 3-4 effect mode, the pH value is in a range of 5-6, and the heating pipes and the shell of the evaporator are made of titanium materials.
9. The method for preparing high-whiteness aluminum hydroxide and silicon fertilizer by using high-alumina fly ash as claimed in claim 1, wherein SiO in the step (3)2˙nH2When the O precipitate is mixed with calcium chloride powder, SiO is formed2With CaCl2The ratio of the mole numbers between the two is 1:1-1: 4.
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