阅读说明：本技术 一种同时从粉煤灰和赤泥两种含铝废渣中提取氧化铝的方法 (method for simultaneously extracting aluminum oxide from two aluminum-containing waste residues of fly ash and red mud ) 是由 卫国强 杨彬彬 陶亚男 段东红 张忠林 刘世斌 于 2019-08-19 设计创作，主要内容包括：一种同时从粉煤灰和赤泥两种含铝废渣中提取氧化铝的方法,属于固体废弃物综合利用技术领域,可解决粉煤灰和赤泥的再利用难度大,成本高的问题,本发明利用赤泥提高粉煤灰中的铝硅比,将脱硫石膏或硫酸钙与粉煤灰和赤泥混合煅烧,活化粉煤灰,提高氧化铝的提取率,同时煅烧释放出来的三氧化硫和二氧化硫可回收制备硫酸,用于后续酸浸工艺,同时在硫酸铝除杂过程可回收硫酸钙实现活化剂的循环使用,该发明不仅能够同时处理三种固废,同时还可以降低提取成本。(the invention relates to a method for simultaneously extracting aluminum oxide from two aluminum-containing waste residues of fly ash and red mud, which belongs to the technical field of comprehensive utilization of solid wastes and can solve the problems of high difficulty and high cost in recycling of fly ash and red mud.)

1. a method for simultaneously extracting aluminum oxide from two aluminum-containing waste residues of fly ash and red mud is characterized by comprising the following steps: the method comprises the following steps:

Firstly, mixing fly ash, red mud and desulfurized gypsum or calcium sulfate in proportion, and uniformly grinding to obtain a mixed material, wherein the mass ratio of aluminum to silicon in the mixed material is 0.8-1.3:1, and the molar ratio of calcium to aluminum is 0.5-1.6: 1;

Secondly, placing the mixed material in a tube furnace, calcining for 10-150min at 800-1400 ℃ to obtain clinker, and recovering gas to prepare sulfuric acid for the subsequent leaching process;

Grinding the clinker, and leaching with sulfuric acid, wherein the concentration of the sulfuric acid is 0.5-5mol/L, the liquid-solid ratio is 5-40ml/g, the leaching temperature is 60-95 ℃, and the leaching time is 10-120 min;

Fourthly, after leaching, carrying out solid-liquid separation, washing filter residues obtained by separation for four times, and collecting filtrate of the aluminum sulfate crude liquid;

step five, refining and removing impurities from the crude aluminum sulfate liquid:

(1) Calcium removal: concentrating and crystallizing the crude aluminum sulfate solution, filtering and recovering calcium sulfate precipitate, and realizing the recycling of the activating agent;

(2) Iron removal: adding hydrogen peroxide into the solution after calcium removal to oxidize Fe2+ into Fe3+, adjusting the pH of the solution to keep the pH between 2.8-3.2, precipitating Fe3+, and filtering to remove Fe (OH)3 precipitate to obtain refined filtrate;

sixthly, concentrating and crystallizing the refined filtrate, keeping the concentration temperature at 110-;

And seventhly, calcining the aluminum sulfate crystals for 4-6 hours at the temperature of 780-850 ℃, completely decomposing to obtain aluminum oxide and sulfur trioxide, and recovering sulfur trioxide to prepare sulfuric acid so as to realize cyclic utilization.

2. the method for simultaneously extracting aluminum oxide from two aluminum-containing waste residues of fly ash and red mud according to claim 1, which is characterized in that: in the first step, the mass ratio of aluminum to silicon in the mixed material is 0.8-1.2:1, and the molar ratio of calcium to aluminum is 0.8-1.5: 1.

3. the method for simultaneously extracting aluminum oxide from two aluminum-containing waste residues of fly ash and red mud according to claim 1, which is characterized in that: in the second step, the calcination temperature is 1000-1300 ℃, and the calcination time is 30-120 min.

4. the method for simultaneously extracting aluminum oxide from two aluminum-containing waste residues of fly ash and red mud according to claim 1, which is characterized in that: in the third step, the concentration of the sulfuric acid is 1-4mol/L, the liquid-solid ratio is 15-35ml/g, the leaching temperature is 70-95 ℃, and the time is 15-90 min.

Technical Field

The invention belongs to the technical field of comprehensive utilization of solid wastes, and particularly relates to a method for simultaneously extracting aluminum oxide from two aluminum-containing waste residues of fly ash and red mud.

Background

with the continuous and rapid increase of the demand of aluminum materials, the aluminum industry in China develops rapidly, and the exploitation amount of bauxite is greatly increased. By 2015, the yield of bauxite reaches 6000 million tons, and the bauxite becomes the largest alumina producing country in the world, so that the bauxite resources face the increasingly exhausted crisis in China.

the fly ash is solid particles collected by a dust remover at the tail part of a boiler in the process of discharging flue gas after pulverized coal is combusted in the boiler. The fly ash discharged from the coal-fired power plant is transported to an ash yard for stockpiling, one part is utilized, and the rest part is accumulated for stockpiling. Among them, the comprehensive utilization rate in areas such as Shanxi and inner Mongolia is low, hundreds of millions of tons of accumulated stockpiles are accumulated at present, and serious environmental pollution and ecological damage are caused due to the lack of scientific and effective treatment and protection measures.

red mud is an industrial solid waste produced in the process of producing alumina from bauxite in the aluminum production industry. At present, 1.0-2.0 tons of red mud is generated when 1 ton of alumina is produced from bauxite, and the utilization difficulty is high. The accumulated piling of the red mud occupies a large amount of land resources and also poses potential threats to the ecological environment.

at present, the industrial by-product gypsum in China mainly comprises phosphogypsum, desulfurized gypsum, titanium gypsum, fluorgypsum, salt gypsum and the like, wherein the desulfurized gypsum and the phosphogypsum are the most main industrial by-products gypsum in China. According to the Chinese industry byproduct gypsum market depth research and prediction report (2018), it is shown that: at present, the production amount of industrial byproduct gypsum in China is about 1.18 hundred million tons, and the comprehensive utilization rate is only 38 percent. Wherein, the desulfurized gypsum is about 4300 ten thousand tons, and the comprehensive utilization rate is about 56%; the phosphogypsum is about 5000 ten thousand tons, and the comprehensive utilization rate is about 20 percent. At present, the accumulated quantity of industrial by-product gypsum exceeds 3 million tons, wherein the quantity of desulfurized gypsum is more than 5000 million tons, and the quantity of phosphogypsum is more than 2 million tons. The industrial byproduct gypsum is massively stockpiled, which not only occupies land, but also wastes resources, and the contained acidity and other harmful substances easily cause pollution to the surrounding environment, thus becoming an important factor for restricting the sustainable development of the coal-fired unit flue gas desulfurization and phosphate fertilizer enterprises in China.

the main components of the fly ash are alumina and silicon dioxide, the mass fraction of the alumina and the silicon dioxide is about 80%, and the mass fraction of the silicon dioxide can reach 90% in some regions. The red mud mainly comprises Al2O3, Fe2O3, SiO2, Na2O, CaO and the like, and the content of each component is different according to the production place of bauxite and the mode of dissolving out alumina. At present, the extraction of alumina from fly ash can be summarized into four methods, namely an acid method, an alkali method, an acid-alkali combination method and an ammonium method. The process flow for extracting the alumina by the acid method is simple, the energy consumption is low, the acid can be recycled, but the acid system has strong corrosivity, high requirement on equipment and large investment. The limestone sintering method has cheap raw materials and low cost, but has high reaction temperature, which causes higher energy consumption. In addition, a large amount of calcium silicate slag is generated, 8-9 t of calcium silicate slag is generated every 1 t of alumina is produced, and a new solid waste treatment problem is formed. Compared with the lime sintering method, the energy consumption for extracting alumina by the soda lime sintering method is reduced, the generated slag amount is relatively reduced, but the problems of high energy consumption and large slag amount of the sintering method can not be avoided generally, and the method has complex reaction and difficult control of process conditions. In addition, although the sintering efficiency is improved and the amount of slag is reduced by the "pre-desiliconization" treatment, aluminum loss is caused in the process, and the alkaline slag formed in the production process is difficult to treat. Although the acid-base combination method has high extraction rate of alumina, the method is complex, the acid-base consumption is high, and acid and base cannot be recycled after acid-base neutralization. The ammonium sulfate sintering method is simple, the reaction temperature is low, but the roasting side reaction is more, the raw material consumption is large, the whole process is in an ammoniacal system, a large amount of waste gas is generated, and if leakage occurs, the environment is seriously polluted. These methods are difficult and costly.

disclosure of Invention

the invention provides a method for simultaneously extracting aluminum oxide from two aluminum-containing waste residues of fly ash and red mud, aiming at the problems of high recycling difficulty and high cost of the fly ash and the red mud. The method can treat three solid wastes simultaneously, has high extraction rate of alumina and low cost, and can recycle the activating agent.

the invention adopts the following technical scheme:

A method for simultaneously extracting aluminum oxide from two aluminum-containing waste residues of fly ash and red mud comprises the following steps:

firstly, mixing fly ash, red mud and desulfurized gypsum or calcium sulfate in proportion, and uniformly grinding to obtain a mixed material, wherein the mass ratio of aluminum to silicon in the mixed material is 0.8-1.3:1, and the molar ratio of calcium to aluminum is 0.5-1.6: 1;

Secondly, placing the mixed material in a tube furnace, calcining for 10-150min at 800-1400 ℃ to obtain clinker, and recovering gas to prepare sulfuric acid for the subsequent leaching process;

Grinding the clinker, and leaching with sulfuric acid, wherein the concentration of the sulfuric acid is 0.5-5mol/L, the liquid-solid ratio is 5-40ml/g, the leaching temperature is 60-95 ℃, and the leaching time is 10-120 min;

fourthly, after leaching, carrying out solid-liquid separation, washing filter residues obtained by separation for four times, and collecting filtrate of the aluminum sulfate crude liquid;

step five, refining and removing impurities from the crude aluminum sulfate liquid:

(1) calcium removal: concentrating and crystallizing the crude aluminum sulfate solution, filtering and recovering calcium sulfate precipitate, and realizing the recycling of the activating agent;

(2) Iron removal: adding hydrogen peroxide into the solution after calcium removal to oxidize Fe2+ into Fe3+, adjusting the pH of the solution to keep the pH between 2.8-3.2, precipitating Fe3+, and filtering to remove Fe (OH)3 precipitate to obtain refined filtrate;

sixthly, concentrating and crystallizing the refined filtrate, keeping the concentration temperature at 110-;

and seventhly, calcining the aluminum sulfate crystals for 4-6 hours at the temperature of 780-850 ℃, completely decomposing to obtain aluminum oxide and sulfur trioxide, and recovering sulfur trioxide to prepare sulfuric acid so as to realize cyclic utilization.

furthermore, the mass ratio of aluminum to silicon in the mixed material in the first step is 0.8-1.2:1, and the molar ratio of calcium to aluminum is 0.8-1.5: 1.

Further, the calcination temperature in the second step is 1000-1300 ℃, and the calcination time is 30-120 min.

further, in the third step, the concentration of the sulfuric acid is 1-4mol/L, the liquid-solid ratio is 15-35ml/g, the leaching temperature is 70-95 ℃, and the time is 15-90 min.

the principle of the invention is as follows:

。

The invention has the following beneficial effects:

the invention utilizes the characteristic that the ratio of aluminum to silicon in the red mud is more than 1, improves the ratio of aluminum to silicon of the fly ash, reduces the difficulty of extracting aluminum oxide, and can extract the aluminum oxide in the red mud to achieve the purpose of simultaneously treating two solid wastes; desulfurized gypsum or calcium sulfate is selected as an activating agent, the fly ash and the red mud are roasted and activated, and gas recovery can be used for the subsequent sulfuric acid leaching process; sulfuric acid is used as a solvent, aluminum is extracted into the solution, and calcium sulfate can be recovered in the impurity removal process of the crude aluminum sulfate solution; concentrating and crystallizing the solution after impurity removal to obtain aluminum sulfate crystals, and calcining at high temperature to obtain an aluminum oxide product. The method can realize the efficient extraction of alumina in the fly ash and the synergistic effect of the fly ash, the red mud and the desulfurized gypsum (calcium sulfate), recover the calcium sulfate, realize the recycling of the activating agent, achieve the aim of treating wastes with processes of wastes against one another, and is an economic, green and efficient solid waste treatment method.

drawings

FIG. 1 is a flow chart of the present invention for extracting alumina from fly ash and red mud using calcium sulfate;

FIG. 2 is a flow chart of the present invention for extracting alumina from fly ash and red mud using desulfurized gypsum;

FIG. 3 is a comparative XRD diagram of fly ash, red mud and activated coal ash, wherein, 1-Mullite; 2-SiO 2; 3-Ca3Al2 (SiO 4) (OH) 8; 4-Na6Ca2Al6Si6O24 (CO 3) 2.2H2O; 5-Fe2O 3; 6-Na6Ca2Al6Si6O24 (SO 4) 2; 7-CaAl2Si2O 8; 8-SiO 2; 9-Al2O 3.

Detailed Description