WO2013040861A1 - 一种利用粉煤灰生产氧化铝的方法 - Google Patents

一种利用粉煤灰生产氧化铝的方法 Download PDF

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WO2013040861A1
WO2013040861A1 PCT/CN2012/001288 CN2012001288W WO2013040861A1 WO 2013040861 A1 WO2013040861 A1 WO 2013040861A1 CN 2012001288 W CN2012001288 W CN 2012001288W WO 2013040861 A1 WO2013040861 A1 WO 2013040861A1
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fly ash
separation
aluminum
solution
iron
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PCT/CN2012/001288
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English (en)
French (fr)
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李来时
廖新勤
刘瑛瑛
吴玉胜
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中铝国际工程股份有限公司
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Publication of WO2013040861A1 publication Critical patent/WO2013040861A1/zh

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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01FCOMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00Compounds of aluminium
    • C01F7/02Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/20Preparation of aluminium oxide or hydroxide from aluminous ores using acids or salts
    • C01F7/26Preparation of aluminium oxide or hydroxide from aluminous ores using acids or salts with sulfuric acids or sulfates

Definitions

  • the present invention relates to a process for producing alumina using industrial solid waste, and more particularly to a process for producing alumina using fly ash. Background technique
  • Fly ash is solid waste discharged from coal-fired power plants.
  • China's annual output of fly ash reached 300 million tons, and the total stock of fly ash in China was 50,000 billion to six billion tons.
  • the discharge of a large amount of fly ash not only encroaches on a large amount of land, but also seriously pollutes the environment, which constitutes a double destruction of ecology and environment. Therefore, the comprehensive utilization of fly ash has great practical significance and long-term strategic significance.
  • China is a country where bauxite resources are not rich. According to the current growth rate of alumina production and the speed of bauxite mining, even considering the prospective reserves, the age of bauxite in China is difficult to reach 30 years.
  • Alumina is one of the main components of fly ash, and its mass fraction is generally 15% ⁇ 40°/o, up to 58%. Therefore, the research work on extracting alumina from fly ash can solve the pollution of fly ash and turn waste into treasure.
  • the methods for extracting alumina from fly ash mainly include alkali method, acid method and ammonia method. More mature ones are limestone sintering and soda lime sintering, both of which are commonly referred to as alkali processes.
  • the Inner Mongolia Autonomous Region Science and Technology Department held a scientific and technological achievement appraisal meeting of the “Fly Ash Extraction and Alumina Co-production Cement Industrialization Technology” project researched and developed by Mengxi High-tech Group Co., Ltd., using the limestone sintering method, Datang International
  • the company uses a modified soda lime sintering process to treat fly ash to produce alumina.
  • fly ash Since the aluminum-to-silicon ratio of fly ash is very low, it is generally less than 1, so it is more reasonable to treat fly ash with acid.
  • An aluminum salt formed by the reaction of an acid or an acidic compound with aluminum telluride in fly ash. The aluminum salt dissolves and enters the solution. The silicon does not react with the acid or the acidic compound, and remains completely in the solid. In the slag. Acid treatment of fly ash can overcome the shortcomings of the sintering method, and will not produce more solid waste than the raw material fly ash. After the alumina is extracted, the silica will be enriched, and the content of the slag can reach 80 ⁇ 90% ( According to the alumina extraction rate of 85%, this is more conducive to its utilization.
  • the alumina extraction rate in fly ash refers to the ratio of alumina dissolved in the solution to alumina in the fly ash after calcination.
  • the acid method includes a sulfuric acid method and a hydrochloric acid method, wherein the fluorine ammonia-assisted acid leaching method is relatively mature, and a high alumina extraction rate can be obtained, but due to the addition of fluorine ammonia, ammonia gas and hydrogen fluoride toxic gas are generated in the production process. , adversely affecting the surrounding environment and labor safety, and has not been industrialized due to problems such as severe corrosion of acid equipment and high cost.
  • the ammonia method is a mixed calcination method of ammonium sulfate fly ash, and has the following advantages: 1.
  • the high silicon slag after extracting alumina can be used as a high silicon filler after being processed, and can also be used for preparing a silicon series product such as white carbon black, since no alkali can be used. It is directly used in the production of cement; the high iron slag produced in the process of extracting alumina can be used as the raw material for iron making, and the aluminum, silicon and iron in the fly ash are effectively utilized; 2 the reaction system is a weak acid system, and the equipment is easier to solve, which is beneficial to the process. Industrialization; 3 The preparation process is a reduction process with a small amount of slag.
  • the present invention provides a method for producing alumina by treating fly ash by ammonia method, aiming at eliminating high-energy calcination activation without adding any auxiliary agent, and ensuring that the alumina extraction rate in fly ash is not lowered.
  • the invention adopts the iron removal technology of the eluent, simplifies the process flow and cancels the subsequent alkali liquid treatment, adopts the advanced aluminum hydroxide desulfurization technology, so that the aluminum hydroxide roasting process does not produce sulfur trioxide, reduces the difficulty of flue gas treatment and the requirements of the roasting furnace material shield.
  • the calcined clinker product of the present invention is aluminum sulfate, and the product is ammonium aluminum sulfate which can be eluted with less water.
  • the present invention provides a method for preparing alumina by using fly ash, which comprises Including the following steps:
  • Raw material preparation mixing fly ash with ammonium sulfate to prepare raw material, wherein the weight ratio of ammonium sulfate to alumina in fly ash is 4.5 ⁇ 8:1;
  • Clinker burning The raw material is heated to 230 ⁇ 600 °C, the firing time is controlled at 0.5 ⁇ 5h, and the clinker containing aluminum sulfate and ammonia gas are prepared.
  • the ammonia gas is used to prepare ammonia water or pass through the decomposition process of aluminum sulfate.
  • Clinker dissolution Clinker is dissolved in hot water, the dissolution time is 0.1 ⁇ 5h, the dissolution time can also be 0.1 ⁇ 2h, aluminum enters the solution in the form of aluminum sulfate, and silicon remains in the residue to form high silicon slag; ammonia recovery:
  • the ammonia gas generated during the clinker burning process is recovered by water or washing liquid, or sent to the decomposition process by a compressor after dust removal;
  • the slurry after dissolution is subjected to solid-liquid separation and counter-current washing, the solution is aluminum sulphate solution, and the washed slag is high silicon slag; the separated stone aluminum-alkali solution is preferably subjected to iron removal and secondary
  • the aluminum sulfate solution is iron-removed at one time: the iron sulfate solution is eluted once by the goethite method by adding an oxidizing agent, and the iron ion concentration is lowered to 4 g/L or less, and the solution is twice subjected to iron removal once.
  • one iron slag is high iron slag;
  • the aluminum sulphate solution is second iron removal (low iron purification): ⁇ Using oxygen purification and iron removal method for secondary iron removal refining solution In addition to iron, the iron ion concentration is reduced to less than 30 mg/L, and the obtained iron slag is returned to the raw material preparation process;
  • Decomposition of aluminum sulfate solution Ammonia gas or ammonia water obtained by the clinker burning process is passed to the aluminum sulfate solution to obtain aluminum hydroxide and ammonium citrate solution;
  • Aluminium hydroxide separation and washing The slurry after decomposition of aluminum sulfate is subjected to solid-liquid separation and aluminum hydroxide washing, the liquid is ammonium sulfate solution (circulating liquid), and the solid is aluminum hydroxide; then it is preferably produced by a crude aluminum hydroxide desulfurization process.
  • Desulphurization of aluminum hydroxide The crude aluminum hydroxide obtained by the decomposition of aluminum sulfate refining liquid contains a large amount of sulfate. Sulfate will generate sulfur trioxide gas in the subsequent roasting process, causing environmental pollution and increasing the burden of exhaust gas treatment. Desulfurization is carried out to obtain an acid-free aluminum hydroxide;
  • Aluminium hydride roasting Aluminium hydroxide is calcined at 950 ⁇ 1200 °C to obtain finished alumina; Ammonium sulphate solution (recycling liquid) Evaporation: The ammonium sulphate solution obtained by separating aluminum hydroxide is evaporated to obtain a suitable ammonium sulphate solution or Ammonium sulfate crystals.
  • the raw meal is prepared by mixing fly ash with ammonium sulphate by direct mixing or grinding, and the grinding and mixing can be carried out by wet or dry grinding.
  • the clinker is eluted by one of a mill dissolution or a stirred solution, and the mill is dissolved by one-stage grinding or two-stage grinding, and stirred and dissolved by intermittent stirring or One of the continuous stirring is dissolved.
  • the high silicon slag separation washing employs one of vacuum separation, sedimentation separation or pressurized separation.
  • the high silicon slag separation washing uses one of primary, secondary or multistage countercurrent washing.
  • the aluminum sulfate solution in one time removes iron from the oxidant by using one of compressed air, oxygen or hydrogen peroxide.
  • the neutralizing agent used in the goethite method in the primary iron removal solution of the aluminum sulfate solution is one of ammonia water, ammonia gas, lime or coal ash.
  • the oxidizing agent in the secondary iron removal (low iron purification) of the aluminum sulfate solution is one of oxygen or hydrogen peroxide.
  • the neutralizing agent used in the secondary iron removal (low iron purification) of the aluminum sulfate solution is one of ammonia water, ammonia gas or aluminum hydroxide washing liquid.
  • the aluminum sulfate solution is subjected to secondary iron removal and aluminum sulfate solution secondary iron removal (low iron purification).
  • the separation and washing of the high iron slag is one of vacuum separation, sedimentation separation or pressurized separation.
  • the crude aluminum hydroxide separation washing employs one of vacuum separation, sedimentation separation or pressurized separation.
  • the crude aluminum hydroxide is desulfurized by using one of sodium carbonate, sodium hydroxide, lime milk or ammonia water as a decalcification charge.
  • the aluminum hydroxide separation washing employs one of vacuum separation, sedimentation separation or pressurized separation.
  • the aluminum hydroxide is calcined by one of rotary kiln calcination, fluidized calcination or gaseous suspension roasting.
  • ammonium sulfate solution is evaporated by one or a combination of falling film evaporation, forced circulation steaming or natural circulation evaporation.
  • the ammonium sulfate crystal produced by evaporation of the ammonium sulfate solution is one of centrifugal separation, vacuum separation, sedimentation separation or pressurized separation.
  • the high silicon slag is mainly composed of silica and is used to prepare white carbon black or other high silicon filler.
  • the main component of the high iron slag is iron oxide, which is used for iron making.
  • the invention does not add any auxiliary agent, and the fly ash does not need high temperature roasting activation, and can effectively extract alumina in the fly ash, and the extraction rate of the alumina can reach more than 85%, and the iron removal technology by using the eluate , simplify the process to cancel the subsequent lye treatment, adopt the first
  • the advanced aluminum hydroxide desulfurization technology makes the aluminum hydroxide roasting process not produce sulfur trioxide, which reduces the difficulty of flue gas treatment and the material requirements of the roaster.
  • the calcined clinker product of the present invention is aluminum sulfate, and the product is ammonium aluminum sulfate, which can be eluted with less water.
  • the ammonium sulfate cycle is realized, and the alumina in the fly ash can be extracted by batch batching through the circulation, and the exhaust gas and the waste liquid are not discharged in the whole process, and the main component of the high silicon slag after the fly ash is extracted from the alumina is Silica, easy to use, high iron slag can be used as ironmaking raw material for the iron making industry.
  • the reaction system of the invention is a weak acid system, and the equipment is easy to solve, which is beneficial to industrialization.
  • FIG. 1 is a schematic flow chart of a process (Examples 1 - 5) of the present invention
  • FIG. 2 is a schematic flow chart of another alternative process (Examples 6 - 10) of the present invention.
  • composition of the raw fly ash is: A1 2 0 3 : 41%, Si0 2 : 48%, Fe 2 0 3 : 3.3%, CaO:
  • the constituents of the raw material fly ash may also be other constituents, which are not intended to limit the scope of protection of the present invention.
  • 1000g of the raw material fly ash composed in the first embodiment 1000 g of the raw material fly ash and ammonium sulfate crystals are mixed and dry to obtain a raw material, wherein the weight ratio of ammonium sulfate to alumina in the fly ash is 6:1;
  • the material is heated to 500 ° C, kept for 0.5 h, the mature material is prepared, and the exhaust gas is used for the decomposition of aluminum sulfate; the clinker is dissolved in hot water for 0.5 h, and the aluminum enters the solution in the form of aluminum sulfate, and the silicon remains.
  • the high silicon slag is formed in the residue; after the dissolution, the slurry is separated by sedimentation and three-stage countercurrent washing, the liquid is aluminum sulfate solution, and the solid is high silicon slag; the ammonia gas generated by firing the clinker into the aluminum sulfate solution is used to make the solution
  • the aluminum hydroxide solid is decomposed, and the liquid is ammonium sulfate solution; after decomposition, the slurry is separated and washed by a filter to obtain an aluminum hydroxide solid and an ammonium sulfate solution; the ammonium sulfate solution is evaporated and returned to the raw material for grinding, recycling; aluminum hydroxide
  • the solid was calcined at 150 ° C to obtain alumina.
  • the alumina extraction rate in fly ash was 87%.
  • Example 1 Take 1000g of the raw material fly ash composed in Example 1, and mix the fly ash with the ammonium sulfate solution to obtain the raw material, wherein the weight ratio of ammonium sulfate to alumina in the fly ash is 7:1;
  • the raw material is heated to 300 °C, kept for 3 hours, and the mature material is prepared.
  • the exhaust gas is absorbed by water to obtain ammonia water, and the ammonia water is decomposed in aluminum sulfate; the clinker is dissolved in hot water for 2 hours, and aluminum enters the solution in the form of aluminum sulfate, and the silicon remains in the solution.
  • High silicon slag is formed in the residue; after the dissolution, the slurry is separated and washed by a filter, the liquid is an aluminum sulfate solution, and the solid is a high silicon slag; the ammonia water generated by the clinker firing is added to the aluminum sulfate solution to decompose the solution into the aluminum hydroxide solid.
  • the liquid is an ammonium sulfate solution; after decomposition, the slurry is separated and washed by a settling tank to obtain an aluminum hydroxide solid and an ammonium sulfate solution; the ammonium sulfate solution is evaporated and returned to the raw material for grinding, and recycled; aluminum hydroxide solid 1 150 ° C Calcination gives alumina.
  • the alumina extraction rate in fly ash was 85%.
  • Example 1 Take 1000g of the raw material fly ash composed in Example 1, and mix the raw material with fly ash and ammonium sulfate solution to obtain raw material, wherein the weight ratio of ammonium sulfate to alumina in fly ash is 8:1;
  • the raw material is heated to 550 °C, kept for 0.5h, and the mature material is prepared.
  • the exhaust gas is absorbed by water to obtain ammonia water, and the ammonia water is decomposed in aluminum sulfate; the clinker is dissolved in hot water for 1.5 hours, and aluminum enters the solution in the form of aluminum sulfate.
  • Example 1 Take 1000g of the raw material fly ash composed in Example 1, and mix the raw material with fly ash and ammonium sulfate solution to obtain raw material, wherein the weight ratio of ammonium sulfate to alumina in fly ash is 6.5:1;
  • the raw material is heated to 400 °C, kept for 1.5h, the mature material is used, and the exhaust gas is used.
  • Absorbing ammonia water ammonia water is decomposed in aluminum sulfate; clinker is dissolved in hot water for 1 hour, aluminum enters the solution in the form of aluminum sulfate, and silicon remains in the residue to form high silicon slag; after dissolution, the slurry is separated by sedimentation and three-stage countercurrent washing.
  • the liquid is an aluminum sulphate solution, and the solid is a high silicon slag; the ammonia water produced by the clinker firing is added to the aluminum sulphate solution to decompose the solution into the aluminum hydroxide solid, and the liquid is an ammonium sulfate solution; after the decomposition, the slurry is filtered.
  • the machine is separated and washed to obtain an aluminum hydroxide solid and an ammonium sulfate solution; the ammonium sulfate solution is returned to the raw material for grinding after evaporation, and recycled; the aluminum hydroxide solid is calcined at 1150 ° C to obtain alumina.
  • the alumina extraction rate in fly ash was 86%.
  • Example 2 Take 1000g of the raw material fly ash composed in Example 1, and mix the fly ash with the ammonium sulfate solution to obtain the raw material, wherein the weight ratio of ammonium sulfate to alumina in the fly ash is 5:1; Heating to 450 ° C, holding lh, making clinker containing aluminum sulfate and ammonia gas, ammonia gas is washed by washing liquid to prepare ammonia water; fired clinker is dissolved in hot water for 0.5 h with a mill, aluminum is sulfuric acid The form of aluminum enters the solution, and the silicon remains in the residue to form a high silicon slag.
  • the slurry is washed and separated by pressure, the liquid is an aluminum sulfate solution, and the solid is a high silicon slag; the aluminum sulfate solution is subjected to iron removal once, and the compressed air is used as a
  • the oxidant uses lime as a neutralizing agent to reduce the iron ions in the solution to less than 4g/L.
  • the slurry is vacuum-separated and washed, the solid is high-iron slag, the liquid is subjected to secondary iron removal, the oxygen is used as the oxidant, and the ammonia is used as the neutralizing agent.
  • the iron ion in the solution is reduced to 30 mg/L or less.
  • the ammonium sulfate is returned to the raw material for preparation and recycling; the sulfur-free aluminum hydroxide is calcined at 950 ° C in a rotary kiln to obtain alumina.
  • the alumina extraction rate in fly ash was 86%.
  • the slurry is washed by pressure separation, the solid is high iron slag, the liquid is subjected to secondary iron removal, the hydrogen peroxide is used as the oxidant, and the ammonia gas is used as the neutralizing agent.
  • the iron ion in the solution is reduced to less than 30 mg/L, and the slurry is removed after the iron removal.
  • Vacuum separation and washing the solids are returned to the raw material ingredients, and the ammonia gas recovered by the ammonia gas generated by the clinking of the clinker is added to the aluminum sulfate solution after the iron removal, and the solution is decomposed to obtain an aluminum hydroxide slurry, which is separated and washed by pressure.
  • the solid is aluminum hydroxide
  • the liquid is ammonium sulfate solution
  • the aluminum hydroxide is desulfurized by sodium carbonate, and the desulfurized aluminum hydroxide slurry is obtained, and the sulfur-free aluminum hydroxide is obtained by sedimentation separation and washing;
  • the ammonium sulfate solution is subjected to forced circulation evaporation, Vacuum separation gave ammonium sulfate back to the raw material preparation and recycling;
  • sulfur-free aluminum hydroxide was calcined at 1150 ° C to obtain alumina.
  • the alumina extraction rate in fly ash was 87%.
  • Example 1 1000g of the raw material fly ash composed in Example 1 was taken, and the fly ash was directly mixed with ammonium sulfate, wherein the weight ratio of ammonium sulfate to alumina in the fly ash was 7:1; the raw meal was heated to 30 (TC) , 3h, 3h, made clinker containing aluminum sulfate and ammonia, ammonia is used to recover ammonia water; the clinker is fired in hot water for 2h with continuous stirring, aluminum enters the solution in the form of aluminum sulfate, silicon remains High silicon slag is formed in the residue; after the dissolution, the slurry is washed and separated by vacuum, the liquid is aluminum sulphate solution, the solid is high silicon slag; the aluminum sulphate solution is subjected to iron removal once, hydrogen peroxide is used as oxidant, and coal ash is used for neutralization.
  • TC 30
  • 3h, 3h made clinker containing aluminum sulfate
  • the agent reduces the iron ion in the solution to below 4g/L. After the iron is removed, the slurry is separated and washed by sedimentation, the solid is high iron slag, the liquid is subjected to secondary iron removal, hydrogen peroxide is used as the oxidant, and the aluminum hydroxide washing liquid is used as the neutralizing agent. The iron ion in the solution is reduced to less than 30mg/L. After the iron is removed, the slurry is separated and washed by sedimentation, and the solid is returned to the raw material. The ammonia produced by the clinker is added to the aluminum sulfate solution after the iron removal.
  • the obtained ammonia water is recovered, the solution is decomposed to obtain an aluminum hydroxide slurry, and the sedimentation is separated and washed.
  • the solid is aluminum hydroxide and the liquid is ammonium sulfate solution; the aluminum hydroxide is desulfurized with sodium hydroxide to obtain a desulfurized aluminum hydroxide slurry, ⁇
  • the sulfur-free aluminum hydroxide is obtained by pressure separation and washing; the ammonium sulfate solution is evaporated by natural circulation, and the ammonium sulfate is returned to the raw material to prepare and recycle by sedimentation; the sulfur-free aluminum hydroxide is used for fluidization roasting at 1050 ° C. , obtaining alumina.
  • the alumina extraction rate in fly ash is 85%.
  • the ammonia gas is recovered by washing liquid to prepare ammonia water; the cooked clinker is dissolved in the washing liquid with intermittent stirring for 1.5 hours, aluminum
  • the solution enters the solution in the form of aluminum sulfate, and the silicon remains in the residue to form a high silicon slag; after the dissolution, the slurry is washed by vacuum separation, the liquid is an aluminum sulfate solution, and the solid is a high silicon slag; the aluminum sulfate solution is subjected to iron removal once, and compressed air is used as a
  • the oxidant uses lime as a neutralizing agent to reduce the iron ions in the solution to less than 4g/L.
  • the slurry is vacuum-separated and washed, the solid is high-iron slag, the liquid is subjected to secondary iron removal, the hydrogen peroxide is used as the oxidant, and the ammonia gas is used as the neutralizing agent.
  • the iron ion in the solution is reduced to less than 30 mg/L, and the slurry is vacuumed after removing the iron. Separating and washing, returning the solids to the raw material ingredients, adding the ammonia water recovered by the ammonia gas generated by the clinker burning to the aluminum sulfate solution after the iron removal, decomposing the solution to obtain an aluminum hydroxide slurry, vacuum separation and washing, and the solid is hydrogen.
  • the liquid is ammonium sulfate solution
  • aluminum hydroxide is desulfurized by using lime milk to obtain desulfurized aluminum hydroxide slurry, and vacuum separation and washing are used to obtain sulfur-free aluminum hydroxide
  • ammonium sulfate solution is combined by falling film evaporation and forced circulation evaporation.
  • the ammonium sulfate is returned to the raw material by vacuum separation to prepare and recycle; the sulfur-free aluminum hydroxide is calcined at 1150 ° C to obtain alumina.
  • the alumina extraction rate in fly ash was 88%.
  • the slurry is washed by vacuum separation, the liquid is aluminum sulfate solution, the solid is high silicon slag; the aluminum sulfate solution is subjected to iron removal once, and compressed air is used as
  • the oxidant uses lime as a neutralizing agent to reduce the iron ions in the solution to less than 4g/L.
  • the slurry is vacuum-separated and washed, the solid is high-iron slag, the liquid is subjected to secondary iron removal, the hydrogen peroxide is used as the oxidant, and the ammonia gas is used as the neutralizing agent.
  • the iron ion in the solution is reduced to less than 30 mg/L, and the slurry is removed after the iron removal.
  • washing with vacuum separation returning the solids to the raw material ingredients, adding the ammonia water recovered from the ammonia gas generated by the clinker burning to the aluminum sulfate solution after the iron removal, decomposing the solution to obtain an aluminum hydroxide slurry, vacuum separation and washing, solid
  • the liquid is ammonium sulfate solution
  • the aluminum hydroxide is desulfurized with lime milk to obtain desulfurized aluminum hydroxide slurry, and vacuum separation and washing are used to obtain sulfur-free aluminum hydroxide
  • ammonium sulfate solution adopts falling film evaporation and forced circulation evaporation.
  • sulfur-free aluminum hydroxide at 1150 ° C Calcination by fluidization gives alumina.
  • the alumina extraction rate in fly ash is 85%.

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Abstract

本发明公开了一种利用工业固体废弃物生产氧化铝的方法,尤其涉及一种利用粉煤灰制备氧化铝的方法。它包括下述步骤:生料磨制、熟料烧成、熟料溶出、氨气回收、高硅渣分离洗涤、硫酸铝溶液分解、氢氧化铝分离洗涤、氢氧化铝焙烧、循环液硫酸铵溶液蒸发等过程,产品为氧化铝。本发明不添加任何助剂,可有效提取粉煤灰中氧化铝,氧化铝的提取率可达到85%以上。

Description

一种利用粉煤灰生产氧化铝的方法 技术领域
本发明涉及一种利用工业固体废弃物生产氧化铝的方法, 尤其涉 及一种利用粉煤灰制备氧化铝的方法。 背景技术
粉煤灰是燃煤电厂排出的固体废弃物。 2008 年我国粉煤灰年排放 量高达 3 亿吨, 我国粉煤灰的总堆存量有五、 六十几亿吨。 大量粉煤 灰的排放不仅侵占大量土地, 而且严重污染环境, 构成了对生态和环 境的双重破坏。 因此开展粉煤灰的综合利用具有重大现实意义和长远 战略意义。 同样, 我国是一个铝土矿资源不富有的国家, 按目前氧化 铝产量的增长速度和铝土矿开采速度, 即使考虑到远景储量, 我国的 铝土矿的年限也很难达到 30年。 所以, 解决这种资源危机的方法有两 种: 一是合理利用现有铝土矿资源; 二是积极找寻并利用其他含铝资 源。 而氧化铝是粉煤灰的主要成分之一, 其质量分数一般为 15%〜40°/o, 最高可达 58%。 所以, 开展从粉煤灰中提取氧化铝的研究工作可以解 决粉煤灰的污染, 变废为宝。
目前, 从粉煤灰中提取氧化铝的方法主要有碱法、 酸法和氨法。 比较成熟的有石灰石烧结法和碱石灰烧结法,此两者通称为碱法。 2004 年 12月内蒙古自治区科技厅召开了蒙西高新技术集团有限公司研究开 发的 "粉煤灰提取氧化铝联产水泥产业化技术" 项目科技成果鉴定会, 采用的就是石灰石烧结法, 大唐国际有限公司则采用改进的碱石灰烧 结法处理粉煤灰生产氧化铝。 但碱法提取粉煤灰中氧化铝存在一些问 题, 主要是① 烧结法产生的硅钙渣, 只能用做水泥原料, 每生产 1吨 的氧化铝要产生数倍于粉煤灰的硅钙渣, 而水泥有其相应的销售半径, 如果当地没有大型的水泥工业支持将会造成二次污染; ② 烧结法只提 取了粉煤灰中的氧化铝, 其二氧化硅的利用价值低。 ③烧结法处理粉 煤灰设备投资大, 能耗高, 成本高。
由于粉煤灰的铝硅比很低, 一般都小于 1 , 所以釆用酸法处理粉煤 灰原则上更合理。 酸或酸性化合物与粉煤灰中的氡化铝反应生成的铝 盐, 铝盐溶解后进入溶液, 硅不与酸或酸性化合物反应, 完全留在固 相渣中。 酸法处理粉煤灰可以克服烧结法的不足, 不会产生多于原料 粉煤灰的固体废物, 而且提取氧化铝后, 二氧化硅会富集, 渣中其含 量能达到 80〜90% (按氧化铝提取率 85%计) , 这样更有利于其利用。 粉煤灰中氧化铝提取率是指焙烧后溶解在溶液中的氧化铝与粉煤灰中 氧化铝的比值。 酸法包括硫酸法和盐酸法, 其中氟氨助溶酸浸法比较 成熟, 可以获得较高的氧化铝提取率, 但由于要加入氟氨, 在生产的 过程中会产生氨气和氟化氢有毒气体, 对周围环境和劳动安全带来不 利影响, 而且由于酸法设备腐蚀严重, 造价高昂等问题的影响, 一直 未产业化。
氨法为硫酸铵粉煤灰混合焙烧法, 具有以下优点①提取氧化铝后 的高硅渣经过处理可以作为高硅填料, 也可以用来制备白炭黑等硅系 列产品, 由于不含碱可以直接用于生产水泥; 提取氧化铝过程中产生 的高铁渣可以作为炼铁原料, 粉煤灰中的铝、 硅、 铁均得到了有效利 用; ②反应体系为弱酸体系, 设备较容易解决, 利于产业化; ③制备 过程为减量过程, 渣量小。 但目前形成的氨法均存在一些不足和问题: 比如专利 CN100457628C "粉煤灰中提取氧化铝同时联产白炭黑" 中提 到采用在 600〜700°C焙烧 l〜2h进行活化, 这样虽然可以是粉煤灰中氧 化铝提取率较高, 但粉煤灰的加热升温和降温过程能耗高, 而且后续 采用 "碱溶一碳分" 工艺处理氨水或氨气沉淀出的氢氧化铝和氢氧化 铁的混合物, 将氢氧化铝重新溶解在沉淀, 造成流程长成本高; 其它 一些专利中熟料产物为硫酸铝铵, 硫酸铝铵溶解度小, 需要大量的水 进行溶出, 这些水都需要蒸发排出, 蒸发能耗和成本高。 发明内容
为解决上述技术问题本发明提供一种氨法处理粉煤灰生产氧化铝 的方法, 目的是不添加任何助剂, 取消高耗能的焙烧活化, 同时保证 不降低粉煤灰中氧化铝提取率。 本发明采用溶出液除铁技术, 简化工 艺流程取消后续碱液处理, 采用先进的氢氧化铝脱硫技术, 使氢氧化 铝焙烧过程不产生三氧化硫, 降低烟气处理难度和焙烧炉材盾要求。 本发明焙烧熟料产物为硫酸铝, 产物为硫酸铝铵相比可以用较少水进 行溶出。
为实现上述目的本发明一种利用粉煤灰制备氧化铝的方法, 它包 括下迷步骤:
生料制备: 将粉煤灰与硫酸铵混合, 制备成生料, 其中硫酸铵与 粉煤灰中的氧化铝的重量比为 4.5 ~ 8: 1 ;
熟料烧成: 将生料加热至 230~600 °C , 烧成时间控制在 0.5~5h, 制 成含硫酸铝的熟料和氨气, 氨气用于制备氨水或通入硫酸铝分解工序; 熟料溶出: 熟料用热水溶出, 溶出时间 0.1〜5h, 溶出时间也可以 为 0.1〜2h, 铝以硫酸铝的形式进入溶液, 硅留在残渣中形成高硅渣; 氨气回收: 熟料烧成过程产生的氨气采用水或洗液回收, 或通过 除尘后用压缩机送至分解工序;
高硅渣分离洗涤: 溶出后的浆液进行固液分离和逆流洗涤, 溶液 为石克酸铝溶液, 洗后渣为高硅渣; 分离后的石充酸铝溶液优选经过一次 除铁和二次除铁工艺, 其中硫酸铝溶液一次除铁: 采用加入氧化剂的 针铁矿法对溶出的硫酸铝溶液进行一次除铁, 将铁离子浓度降低至 4g/L 以下, 一次除铁后溶液进行二次除铁(低铁净化) 或进行还原, 一次除铁渣为高铁渣; 其中硫酸铝溶液二次除铁 (低铁净化) : 釆用 通氧净化除铁方式对一次除铁精制液进行二次除铁, 是铁离子浓度降 至 30mg/L以下, 所得到的除铁渣返回生料制备工序;
硫酸铝溶液分解: 向硫酸铝溶液通入熟料烧成工序得到的氨气或 氨水, 得到氢氧化铝和 υ酸铵溶液;
氢氧化铝分离洗涤: 硫酸铝分解后的浆液进行固液分离和氢氧化 铝洗涤, 液体为硫酸铵溶液 (循环液) , 固体为氢氧化铝; 随后优选 采用粗氢氧化铝脱硫工艺对产生的氢氧化铝脱硫: 硫酸铝精制液分解 得到的粗氢氧化铝中含有大量的硫酸根, 硫酸根会在后续焙烧过程中 产生三氧化硫气体, 造成环境污染和增加尾气处理负担, 采用碱性溶 液进行脱硫, 得到无疏酸根氢氧化铝;
氢氧化铝焙烧: 氢氧化铝在 950~1200°C下焙烧得到成品氧化铝; 硫酸铵溶液 (循环液) 蒸发: 氢氧化铝分离得到的硫酸铵溶液进 行蒸发, 得到适合配料的硫酸铵溶液或硫酸铵晶体。
所述的生料制备是采用直接混合或磨制混合的方式将粉煤灰与硫 酸铵混合在一起, 所述磨制混合可以采用湿磨或干磨得以实施。
所述的熟料溶出采用磨机溶出或搅拌溶出中的一种, 磨机溶出采 用一段磨溶出或两段磨溶出中的一种, 搅拌溶出采用间断搅拌溶出或 连续搅拌溶出中的一种。
所述的高硅渣分离洗涤采用真空分离、 沉降分离或加压分离中的 一种。
所述的高硅渣分离洗涤采用一级、 二级或多级逆流洗涤中的一种。 所述的硫酸铝溶液一次除铁中氧化剂采用压缩空气、 氧气或双氧 水中的一种。
所述的硫酸铝溶液一次除铁中针铁矿法采用的中和剂为氨水、 氨 气、 石灰或煤灰中的一种。
所述的硫酸铝溶液二次除铁 (低铁净化) 中氧化剂采用氧气或双 氧水中的一种。
所述的硫酸铝溶液二次除铁(低铁净化) 中采用的中和剂为氨水、 氨气或氢氧化铝洗液中的一种。
所述的硫酸铝溶液一次除铁和硫酸铝溶液二次除铁 (低铁净化) 中高铁渣的分离洗涤采用真空分离、 沉降分离或加压分离中的一种。
所述的粗氢氧化铝分离洗涤采用真空分离、 沉降分离或加压分离 中的一种。
所述的粗氢氧化铝脱硫采用碳酸钠、 氢氧化钠、 石灰乳或氨水中 的一种作为脱石充剂。
所述的氢氧化铝分离洗涤采用真空分离、 沉降分离或加压分离中 的一种。
所述的氢氧化铝焙烧采用回转窑焙烧、 流态化焙烧或气态悬浮焙 烧中的一种。
所述的硫酸铵溶液蒸发采用降膜蒸发、 强制循环蒸或自然循环蒸 发中的一种或几种的组合。
所述的硫酸铵溶液蒸发产生的硫酸铵晶体采用离心分离、 真空分 离、 沉降分离或加压分离中的一种。
所述的高硅渣的主要成分为二氧化硅, 用于制备白炭黑或其它高 硅填料。
所述的高铁渣的主要成分为氧化铁, 用于炼铁。
本发明的优点效果: 本发明不添加任何助剂, 粉煤灰不需高温焙 烧活化, 可有效提取粉煤灰中氧化铝, 氧化铝的提取率可达到 85%以 上, 采用溶出液除铁技术, 简化工艺流程取消后续碱液处理, 采用先 进的氢氧化铝脱硫技术, 使氢氧化铝焙烧过程不产生三氧化硫, 降低 烟气处理难度和焙烧炉材质要求。 本发明焙烧熟料产物为硫酸铝, 产 物为硫酸铝铵相比可以用较少水进行溶出。 本发明工艺流程中实现了 硫酸铵循环, 通过循环可以一批批的提取粉煤灰中氧化铝, 整个过程 没有废气、 废液的排出, 粉煤灰提取氧化铝后的高硅渣主要成分是二 氧化硅, 易于利用, 高铁渣可作为炼铁原料供给炼铁行业。 本发明反 应体系为弱酸体系, 设备容易解决, 利于产业化。 附图说明
图 1为本发明的一种工艺 (实施例 1 - 5 ) 的流程示意图; 和 图 2为本发明的另一种可选工艺 (实施例 6 - 10 ) 的流程示意图。 具体实施方式
实施例 1
原料粉煤灰组成为: A1203: 41%、 Si02: 48%、 Fe203: 3.3%、 CaO:
3.3%、 Ti02: 1.3%、 MgO: 0.2%。 原料粉煤灰的成分也可以采用其它 组成成分, 这不能用于限定本发明的保护范围。
取 1000g 上述组成的粉煤灰, 将粉煤灰与硫酸铵溶液混合湿磨得 到生料, 其中硫酸铵与粉煤灰中的氧化铝的重量比为 5: 1 ; 将生料加 热至 450 °C , 保温 lh, 制成熟料, 排出气体用于硫酸铝分解; 熟料在 热水中溶出 0.5h, 铝以硫酸铝的形式进入溶液, 硅留在残渣中形成高 硅渣; 溶出后浆液经沉降分离和三级逆流洗涤, 液体为石克酸铝溶液, 固体为高硅渣; 向硫酸铝溶液中通入熟料烧成产生的氨气, 使溶液分 解出氢氧化铝固体, 液体为硫酸铵溶液; 分解后浆液经过滤机分离洗 涤, 得到氢氧化铝固体和硫酸铵溶液; 硫酸铵溶液经蒸发后返回生料 磨制, 循环使用; 氢氧化铝固体 1 150°C焙烧得到氧化铝。 粉煤灰中氧 化铝提取率为 86%。
实施例 2
取 1000g实施例 1 中组成的原料粉煤灰, 将原料粉煤灰与硫酸铵 晶体混合干磨得到生料, 其中硫酸铵与粉煤灰中的氧化铝的重量比为 6: 1 ; 将生料加热至 500°C , 保温 0.5h, 制成熟料, 排出气体用于硫酸 铝分解; 熟料在热水中溶出 0.5h, 铝以硫酸铝的形式进入溶液, 硅留 在残渣中形成高硅渣; 溶出后浆液经沉降分离和三级逆流洗涤, 液体 为硫酸铝溶液, 固体为高硅渣; 向硫酸铝溶液中通入熟料烧成产生的 氨气, 使溶液分解出氢氧化铝固体, 液体为硫酸铵溶液; 分解后浆液 经过滤机分离洗涤, 得到氢氧化铝固体和硫酸铵溶液; 硫酸铵溶液经 蒸发后返回生料磨制, 循环使用; 氢氧化铝固体 1 150 °C焙烧得到氧化 铝。 粉煤灰中氧化铝提取率为 87%。
实施例 3
取 1000g实施例 1 中组成的原料粉煤灰, 将原料将粉煤灰与硫酸 铵溶液混合湿磨得到生料, 其中硫酸铵与粉煤灰中的氧化铝的重量比 为 7: 1 ; 将生料加热至 300 °C , 保温 3h, 制成熟料, 排出气体用水吸 收得到氨水, 氨水于硫酸铝分解; 熟料在热水中溶出 2h, 铝以硫酸铝 的形式进入溶液, 硅留在残渣中形成高硅渣; 溶出后浆液经过滤机分 离洗涤, 液体为硫酸铝溶液, 固体为高硅渣; 向硫酸铝溶液中加入熟 料烧成产生的氨水, 使溶液分解出氢氧化铝固体, 液体为硫酸铵溶液; 分解后浆液经沉降槽分离和洗涤, 得到氢氧化铝固体和硫酸铵溶液; 硫酸铵溶液经蒸发后返回生料磨制, 循环使用; 氢氧化铝固体 1 150 °C 焙烧得到氧化铝。 粉煤灰中氧化铝提取率为 85%。
实施例 4
取 1000g实施例 1 中组成的原料粉煤灰, 将原料将粉煤灰与硫酸 铵溶液混合磨制得到生料, 其中硫酸铵与粉煤灰中的氧化铝的重量比 为 8: 1 ; 将生料加热至 550 °C , 保温 0.5h, 制成熟料, 排出气体用水 吸收得到氨水, 氨水于硫酸铝分解; 熟料在热水中溶出 1.5h, 铝以硫 酸铝的形式进入溶液, 硅留在残渣中形成高硅渣; 溶出后浆液经沉降 分离和三级逆流洗涤, 液体为石克酸铝溶液, 固体为高硅渣; 向石 酸铝 溶液中加入熟料烧成产生的氨水, 使溶液分解出氢氧化铝固体, 液体 为硫酸铵溶液; 分解后浆液经过滤机分离洗涤, 得到氢氧化铝固体和 硫酸铵溶液; 硫酸铵溶液经蒸发后返回生料磨制, 循环使用; 氢氧化 铝固体 1 15CTC焙烧得到氧化铝。 粉煤灰中氧化铝提取率为 88%。
实施例 5
取 1000g实施例 1 中组成的原料粉煤灰, 将原料将粉煤灰与硫酸 铵溶液混合磨制得到生料, 其中硫酸铵与粉煤灰中的氧化铝的重量比 为 6.5 : 1 ; 将生料加热至 400 °C , 保温 1.5h, 制成熟料, 排出气体用水 吸收得到氨水, 氨水于硫酸铝分解; 熟料在热水中溶出 lh, 铝以硫酸 铝的形式进入溶液, 硅留在残渣中形成高硅渣; 溶出后浆液经沉降分 离和三级逆流洗涤, 液体为石克酸铝溶液, 固体为高硅渣; 向石克酸铝溶 液中加入熟料烧成产生的氨水, 使溶液分解出氢氧化铝固体, 液体为 硫酸铵溶液; 分解后浆液经过滤机分离洗涤, 得到氢氧化铝固体和硫 酸铵溶液; 硫酸铵溶液经蒸发后返回生料磨制, 循环使用; 氢氧化铝 固体 1150°C焙烧得到氧化铝。 粉煤灰中氧化铝提取率为 86%。
实施例 6
取 1000g实施例 1 中组成的原料粉煤灰, 将粉煤灰与硫酸铵溶液 混合湿磨得到生料, 其中硫酸铵与粉煤灰中的氧化铝的重量比为 5: 1 ; 将生料加热至 450°C , 保温 lh, 制成含硫酸铝的熟料和氨气, 氨气采 用洗液回收制备氨水; 烧成的熟料在热水中用一段磨机溶出 0.5h, 铝 以硫酸铝的形式进入溶液, 硅留在残渣中形成高硅渣; 溶出后浆液经 加压分离洗涤, 液体为硫酸铝溶液, 固体为高硅渣; 硫酸铝溶液进行 一次除铁, 釆用压缩空气作为氧化剂, 采用石灰作为中和剂, 将溶液 中铁离子降低到 4g/L以下。 除铁后浆液采用真空分离洗涤, 固体为高 铁渣, 液体进行二次除铁, 釆用氧气作为氧化剂, 采用氨水作为中和 剂,溶液中铁离子降低到 30mg/L以下,除铁后浆液采用加压分离洗涤, 固体返回生料配料, 向除铁后的硫酸铝溶液中加入熟料烧成产生的氨 气回收得到的氨水, 使溶液分解得到氢氧化铝浆液, 采用真空分离和 洗涤, 固体为氢氧化铝, 液体为硫酸铵溶液; 氢氧化铝采用氨水进行 脱硫, 得到脱硫氢氧化铝浆液, 采用沉降分离和洗涤得到无硫氢氧化 铝; 硫酸铵溶液采用降膜蒸发后, 经加压分离得到硫酸铵返回生料制 备, 循环使用; 无硫氢氧化铝在 950°C采用回转窑进行焙烧, 得到氧化 铝。 粉煤灰中氧化铝提取率为 86%。
实施例 Ί
取 1000g实施例 1 中组成的原料粉煤灰, 将粉煤灰与硫酸铵溶液 混合干磨得到生料, 其中硫酸铵与粉煤灰中的氧化铝的重量比为 6: 1 ; 将生料加热至 50(TC , 保温 0.5h, 制成含硫酸铝的熟料和氨气, 氨气回 收; 烧成的熟料在洗液中用二段磨机溶出 0.5h, 铝以硫酸铝的形式进 入溶液, 硅留在残渣中形成高硅渣; 溶出后浆液经沉降分离洗涤, 液 体为硫酸铝溶液, 固体为高硅渣; 硫酸铝溶液进行一次除铁, 采用氧 气作为氧化剂, 采用氨水作为中和剂, 将溶液中铁离子降低到 4g/L以 下。 除铁后浆液采用加压分离洗涤, 固体为高铁渣, 液体进行二次除 铁, 采用双氧水作为氧化剂, 采用氨气作为中和剂, 溶液中铁离子降 低到 30mg/L以下,除铁后浆液采用真空分离洗涤, 固体返回生料配料, 向除铁后的硫酸铝溶液中加入熟料烧成产生的氨气回收得到的氨气, 使溶液分解得到氢氧化铝浆液, 采用加压分离和洗涤, 固体为氢氧化 铝, 液体为硫酸铵溶液; 氢氧化铝采用碳酸钠进行脱硫, 得到脱硫氢 氧化铝浆液, 采用沉降分离和洗涤得到无硫氢氧化铝; 硫酸铵溶液采 用强制循环蒸发后, 经真空分离得到硫酸铵返回生料制备, 循环使用; 无硫氢氧化铝在 1150°C采用流态化焙烧, 得到氧化铝。 粉煤灰中氧化 铝提取率为 87%。
实施例 8
取 1000g实施例 1 中组成的原料粉煤灰, 将粉煤灰与硫酸铵直接 混合, 其中硫酸铵与粉煤灰中的氧化铝的重量比为 7: 1 ; 将生料加热 至 30(TC , 保温 3h, 制成含硫酸铝的熟料和氨气, 氨气采用水回收制 备氨水; 烧成的熟料在热水中用连续搅拌溶出 2h, 铝以硫酸铝的形式 进入溶液, 硅留在残渣中形成高硅渣; 溶出后浆液经真空分离洗涤, 液体为^ 酸铝溶液, 固体为高硅渣; 石克酸铝溶液进行一次除铁, 采用 双氧水作为氧化剂 ,采用煤灰作为中和剂,将溶液中铁离子降低到 4g/L 以下。 除铁后浆液采用沉降分离洗涤, 固体为高铁渣, 液体进行二次 除铁, 采用双氧水作为氧化剂, 釆用氢氧化铝洗液作为中和剂, 溶液 中铁离子降低到 30mg/L以下, 除铁后浆液釆用沉降分离洗涤, 固体返 回生料配料, 向除铁后的硫酸铝溶液中加入熟料烧成产生的氨气回收 得到的氨水, 使溶液分解得到氢氧化铝浆液, 采用沉降分离和洗涤, 固体为氢氧化铝, 液体为硫酸铵溶液; 氢氧化铝采用氢氧化钠进行脱 硫, 得到脱硫氢氧化铝浆液, 釆用加压分离和洗涤得到无硫氢氧化铝; 硫酸铵溶液采用自然循环蒸发后, 经沉降分离得到硫酸铵返回生料制 备, 循环使用; 无硫氢氧化铝在 1050°C采用流态化焙烧, 得到氧化铝。 粉煤灰中氧化铝提取率为 85%。
实施例 9
取 1000g实施例 1 中組成的原料粉煤灰, 将粉煤灰与硫酸铵溶液 混合干磨得到生料, 其中硫酸铵与粉煤灰中的氧化铝的重量比为 8: 1 ; 将生料加热至 550°C , 保温 3h, 制成含硫酸铝的熟料和氨气, 氨气采 用洗液回收制备氨水; 烧成的熟料在洗液中用间断搅拌溶出 1.5h, 铝 以硫酸铝的形式进入溶液, 硅留在残渣中形成高硅渣; 溶出后浆液经 真空分离洗涤, 液体为硫酸铝溶液, 固体为高硅渣; 硫酸铝溶液进行 一次除铁, 采用压缩空气作为氧化剂, 采用石灰作为中和剂, 将溶液 中铁离子降低到 4g/L以下。 除铁后浆液采用真空分离洗涤, 固体为高 铁渣, 液体进行二次除铁, 采用双氧水作为氧化剂, 采用氨气作为中 和剂, 溶液中铁离子降低到 30mg/L以下, 除铁后浆液采用真空分离洗 涤, 固体返回生料配料, 向除铁后的硫酸铝溶液中加入熟料烧成产生 的氨气回收得到的氨水, 使溶液分解得到氢氧化铝浆液, 采用真空分 离和洗涤, 固体为氢氧化铝, 液体为硫酸铵溶液; 氢氧化铝采用石灰 乳进行脱硫, 得到脱硫氢氧化铝浆液, 采用真空分离和洗涤得到无硫 氢氧化铝; 硫酸铵溶液采用降膜蒸发和强制循环蒸发组合, 经真空分 离得到硫酸铵返回生料制备, 循环使用; 无硫氢氧化铝在 1150°C采用 流态化焙烧, 得到氧化铝。 粉煤灰中氧化铝提取率为 88%。
实施例 10
取 1000g实施例 1 中组成的原料粉煤灰, 将粉煤灰与硫酸铵溶液 混合湿磨得到生料, 其中硫酸铵与粉煤灰中的氧化铝的重量比为 6.5: 1 ; 将生料加热至 400°C, 保温 1.5h, 制成含硫酸铝的熟料和氨气, 氨 气采用洗液回收制备氨水; 烧成的熟料在洗液中用间断搅拌溶出 1.5h, 铝以石克酸铝的形式进入溶液, 硅留在残渣中形成高硅渣; 溶出后浆液 经真空分离洗涤, 液体为硫酸铝溶液, 固体为高硅渣; 硫酸铝溶液进 行一次除铁, 采用压缩空气作为氧化剂, 采用石灰作为中和剂, 将溶 液中铁离子降低到 4g/L以下。 除铁后浆液采用真空分离洗涤, 固体为 高铁渣, 液体进行二次除铁, 釆用双氧水作为氧化剂, 采用氨气作为 中和剂, 溶液中铁离子降低到 30mg/L以下, 除铁后浆液釆用真空分离 洗涤, 固体返回生料配料, 向除铁后的硫酸铝溶液中加入熟料烧成产 生的氨气回收得到的氨水, 使溶液分解得到氢氧化铝浆液, 采用真空 分离和洗涤, 固体为氢氧化铝, 液体为硫酸铵溶液; 氢氧化铝采用石 灰乳进行脱硫, 得到脱硫氢氧化铝浆液, 采用真空分离和洗涤得到无 硫氢氧化铝; 硫酸铵溶液采用降膜蒸发和强制循环蒸发组合, 经真空 分离得到硫酸铵返回生料制备, 循环使用; 无硫氢氧化铝在 1150°C采 用流态化焙烧, 得到氧化铝。 粉煤灰中氧化铝提取率为 85%。
上文中对本发明申请的具体实施方式进行了示例性描述, 但本发 明的保护范围是由下面的权利要求书来限定的, 而不受本发明申请中 实施例所限。

Claims

权 利 要 求
1. 一种利用粉煤灰生产氧化铝的方法,其特征在于包括下述步骤: 生料磨制: 将粉煤灰与硫酸铵混合, 磨制成生料, 其中硫酸铵与 粉煤灰中的氧化铝的重量比为 4.5 ~ 8: 1 ;
熟料烧成: 将生料加热至 350〜700。C , 烧成时间控制在 0.5〜5h, 制 成含硫酸铝的熟料和氨气, 氨气用于制备氨水或通入硫酸铝分解工序; 熟料溶出: 熟料用热水溶出, 溶出时间 0.1~2h, 铝以硫酸铝的形 式进入溶液, 硅留在残渣中形成高硅渣;
氨气回收: 熟料烧成过程产生的氨气采用水或洗液回收, 或通过 除尘后用压缩机送至分解工序;
高硅渣分离洗涤: 溶出后的浆液进行固液分离和逆流洗涤, 溶液 为硫酸铝溶液, 洗后渣为高硅渣;
硫酸铝溶液分解: 向硫酸铝溶液通过熟料烧成工序得到的氨气或 氨水, 得到氢氧化铝和硫酸铵溶液;
氢氧化铝分离洗涤: 硫酸铝分解后的浆液进行固液分离和氢氧化 铝洗涤, 液体为循环液硫酸铵溶液, 固体为氢氧化铝;
氢氧化铝焙烧: 氢氧化铝在 900〜1300°C下焙烧得到成品氧化铝; 循环液硫酸铵溶液蒸发: 氢氧化铝分离得到的硫酸铵溶液进行蒸 发, 得到适合配料的硫酸铵溶液或硫酸铵晶体。
2. 根据权利要求 1所述的利用粉煤灰制备氧化铝的方法, 其特征 在于所述的生料磨制是采用湿磨或干磨中的一种。
3. 根据权利要求 1所述的利用粉煤灰制备氧化铝的方法, 其特征 在于所述的熟料溶出采用湿磨溶出或搅拌溶出中的一种。
4. 根据权利要求 1所述的利用粉煤灰制备氧化铝的方法, 其特征 在于所述的高硅渣分离洗涤采用过滤机分离或沉降槽分离中的一种。
5. 根据权利要求 1所述的利用粉煤灰制备氧化铝的方法, 其特征 在于所述的高硅渣分离洗涤采用一级、 二级或多级逆流洗涤中的一种。
6. 根据权利要求 1所迷的利用粉煤灰制备氧化铝的方法, 其特征 在于所述的硫酸铝分解采用通入氨气分解或加入氨水分解中的一种。
7. 根据权利要求 1所述的利用粉煤灰制备氧化铝的方法, 其特征 在于所述的氢氧化铝分离洗涤采用过滤机分离或沉降槽分离中的一 种。
8. 根据权利要求 1所述的利用粉煤灰制备氧化铝的方法, 其特征 在于所述的高硅渣的主要成分为二氧化硅, 用于制备白炭黑或其它高 硅填料。
9. 一种利用粉煤灰生产氧化铝的方法,其特征在于包括下述步骤: 生料制备: 将粉煤灰与硫酸铵混合, 制备成生料, 其中硫酸铵与 粉煤灰中的氧化铝的重量比为 4.5 ~ 8: 1 ;
熟料烧成: 将生料加热至 350~700°C , 烧成时间控制在 0.5~5h, 制 成含硫酸铝的熟料和氨气, 氨气用于制备氨水或通入疏酸铝精制液分 解工序;
熟料溶出: 熟料用热水或洗液进行溶出, 溶出时间 0.1〜5h, 铝以 硫酸铝的形式进入溶液, 硅留在残渣中形成高硅渣;
氨气回收: 熟料烧成过程产生的氨气采用水或洗液回收, 或通过 除尘后用压缩机送至硫酸铝溶液分解工序;
高硅渣分离洗涤: 溶出后的浆液进行固液分离和逆流洗涤, 溶液 为硫酸铝溶液, 洗后渣为高硅渣;
硫酸铝溶液一次除铁: 采用加入氧化剂的针铁矿法对溶出的硫酸 铝溶液进行一次除铁, 将铁离子浓度降低至 2g/L以下, 一次除铁后溶 液进行二次除铁或进行还原, 一次除铁渣为高铁渣;
硫酸铝溶液二次除铁: 采用通氧净化除铁方式对一次除铁精制液 进行二次除铁, 是铁离子浓度降至 30mg/L以下, 所得到的除铁渣返回 生料制备工序;
一次除铁精制液还原: 在一次除铁精制液中加入还原剂, 进行除 铁精制液还原, 使其中的三价铁离子全部转化为二价铁离子;
硫酸铝精制液溶液分解: 向二次除铁后的硫酸铝精溶或一次除铁 还原后精制液中液通过熟料烧成工序得到的氨气或氨水, 得到粗氢氧 化铝和充酸铵溶液;
粗氢氧化铝分离洗涤: 硫酸铝分解后的浆液进行固液分离和粗氢 氧化铝洗涤, 液体为循环液硫酸铵溶液, 固体为粗氢氧化铝;
粗氢氧化铝脱硫: 硫酸铝精制液分解得到的粗氢氧化铝中含有大 量的硫酸根, 采用碱性溶液进行脱硫, 得到无疏酸根氢氧化铝;
氢氧化铝分离洗涤: 脱硫后的浆液进行固液分离和氢氧化铝洗涤, 固体为氢氧化铝, 液体为碱性溶液送制硫酸铝精制液分解工序; 氢氧化铝焙烧: 氢氧化铝在 900~1300°C下焙烧得到成品氧化铝; 循环液硫酸铵溶液蒸发: 氢氧化铝分离得到的硫酸铵溶液进行蒸 发, 得到适合配料的硫酸铵溶液或硫酸铵晶体。
10. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的生料制备是采用直接混合或磨制混合的方式将粉煤灰与硫 酸铵混合在一起。
11. 根据权利要求 10所述的利用粉煤灰制备氧化铝的方法, 其特 征在于所述的磨制混合采用湿磨或干磨得以实施。
12. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的熟料溶出采用磨机溶出或搅拌溶出中的一种。
13. 根据权利要求 12所迷的利用粉煤灰制备氧化铝的方法, 其特 征在于所述的磨机溶出采用一段磨溶出或两段磨溶出中的一种。
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14. 根据权利^求 1^2所述的利用'粉煤灰制备氧 铝的方法, 其特
15. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的高硅渣分离洗涤釆用真空分离、 沉降分离或加压分离中的 一种。
16. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的高硅渣分离洗涤采用一级、 二级或多级逆流洗涤中的一种。
17. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的硫酸铝溶液一次除铁中氧化剂采用压缩空气、 氧气或双氧 水中的一种。
18. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的硫酸铝溶液一次除铁中针铁矿法釆用的中和剂为氨水、 氨 气、 石灰或煤灰中的一种。
19. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的硫酸铝溶液二次除铁中氧化剂采用氧气或双氧水中的一 种。
20. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所迷的硫酸铝溶液二次除铁中采用的中和剂为氨水、 氨气或氢氧 化铝洗液中的一种。
21. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的硫酸铝溶液一次除铁和硫酸铝溶液二次除铁中高铁渣的分 离洗涤采用真空分离、 沉降分离或加压分离中的一种。
22. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的一次除铁精制液还原采用的还原剂为硫化铁、 单质硫、 三 氧化疏、 硫化氢或硫化亚铁中的一种。
23. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所迷的硫酸铝精制液分解采用通入氨气分解或加入氨水分解中的 一种。
24. 根据权利要求 23所述的利用粉煤灰制备氧化铝的方法, 其特 征在于所述的氨气或氨水来自熟料烧成工序产生的尾气氨回收。
25. 根据权利要求 9所迷的利用粉煤灰制备氧化铝的方法,其特征 在于所述的粗氢氧化铝分离洗涤采用真空分离、 沉降分离或加压分离 中的一种。
26. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的粗氢氧化铝脱硫采用碳酸钠、 氢氧化钠、 石灰乳或氨水中 的一种作为脱硫剂。
27. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的氢氧化铝分离洗涤采用真空分离、 沉降分离或加压分离中 的一种。
28. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的氢氧化铝焙烧采用回转窑焙烧、 流态化焙烧或气态悬浮焙 烧中的一种。
29. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的氧化铝符合冶金级氧化铝标准。
30. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的硫酸铵溶液蒸发采用降膜蒸发、 强制循环蒸或自然循环蒸 发中的一种或几种的组合。
31. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的硫酸铵溶液蒸发产生的硫酸铵晶体采用离心分离、 真空分 离、 沉降分离或加压分离中的一种。
32. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的高硅渣的主要成分为二氧化硅, 用于制备白炭黑或其它高 硅填料。
33. 根据权利要求 9所述的利用粉煤灰制备氧化铝的方法,其特征 在于所述的高铁渣的主要成分为氧化铁, 用于炼铁。
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