Method for leaching alumina from coal ash generated by gasifying Shell furnace
阅读说明：本技术 一种由Shell炉煤气化粉煤灰浸出氧化铝的方法 (Method for leaching alumina from coal ash generated by gasifying Shell furnace ) 是由 杨保俊 江鸥 宛强 郑学根 王百年 朱四九 于 2019-11-19 设计创作，主要内容包括：本发明公开了一种由Shell炉煤气化粉煤灰浸出氧化铝的方法,此方法是通过在粉煤灰中添加计量的CaCl<Sub>2</Sub>和Ca(OH)<Sub>2</Sub>复合活化剂,在700～900℃下焙烧0.5～2.5h,焙烧熟料经水洗去除过量的CaCl<Sub>2</Sub>,再按液固比2～6:1加入质量浓度为20～50％的硫酸溶液,在常压、≤95℃条件下搅拌反应2～5h提取氧化铝。采用本发明技术,氧化铝浸出率高达95％以上,且过量的CaCl<Sub>2</Sub>活化剂可采用水洗焙烧熟料回收利用。与现有粉煤灰活化技术相比,本发明具有焙烧温度相对较低、氧化铝浸出率高、渣量少、活化剂成本低等多重优点。(The invention discloses a method for leaching alumina from coal ash generated by gasifying Shell coal, which is characterized in that CaCl is added into the coal ash in a metered manner 2 And Ca (OH) 2 The composite activator is roasted for 0.5 to 2.5 hours at the temperature of 700 to 900 ℃, and the roasted clinker is washed to remove excessive CaCl 2 And adding a sulfuric acid solution with the mass concentration of 20-50% according to the liquid-solid ratio of 2-6: 1, and stirring and reacting for 2-5 hours at the temperature of less than or equal to 95 ℃ under normal pressure to extract the alumina. By adopting the technology of the invention, the leaching rate of the alumina reaches more than 95 percent, and excessive CaCl 2 The activator can be recycled by washing the roasted clinker. Compared with the prior fly ash activation technology, the method has the advantages of relatively low roasting temperature, high leaching rate of alumina, less slag, low cost of the activating agent and the like.)
1. A method for leaching alumina from coal ash gasified by Shell furnace, which is characterized by comprising the following steps:
step 1: uniformly mixing coal gasification fly ash and a composite activator in a mass ratio of 1: 0.4-1, roasting at 700-900 ℃ for 0.5-2.5 h to obtain roasted clinker, and naturally cooling the roasted clinker to normal temperature at room temperature to obtain normal-temperature roasted clinker;
wherein the composite activator is Ca (OH) in a mass ratio of 1: 1-82And CaCl2Preparing;
step 2: washing normal-temperature roasted clinker with deionized water, wherein the solid-to-liquid ratio of the normal-temperature roasted clinker to the deionized water is 1: 1-4, stirring for 3-7 minutes, and filtering to obtain filtrate and filter cake;
and step 3: and (3) placing the filter cake into a reaction kettle, adding a sulfuric acid solution with the concentration of 20-50% into the reaction kettle according to the solid-to-liquid ratio of 1: 2-6, stirring and reacting for 2-5 hours under the conditions of normal pressure and the temperature of less than or equal to 95 ℃, and filtering to obtain an aluminum sulfate solution containing impurities and an acid leaching filter cake.
2. The method of claim 1, wherein the stirring time in step 2 is 5 minutes.
3. The method as claimed in claim 1 or 2, wherein the roasting temperature in step 1 is 900 ℃ and the roasting time is 2.5 hours, the solid-to-liquid ratio of the normal-temperature roasted clinker to the deionized water in step 2 is 1:1.5, the solid-to-liquid ratio in step 3 is 1:6, and the mass concentration of the sulfuric acid solution is 40%.
4. The method of claim 3, wherein the stirring reaction time in step 3 is 5 hours.
5. The method according to claim 1 or 2, wherein the roasting temperature in step 1 is 800 ℃ and the roasting time is 1.5h, the solid-to-liquid ratio of the normal-temperature roasted clinker to the deionized water in step 2 is 1:2, the solid-to-liquid ratio in step 3 is 1:4, and the mass concentration of the sulfuric acid solution is 30%.
6. The method of claim 5, wherein the stirring reaction time in step 3 is 4 hours.
7. The method according to claim 1 or 2, wherein the roasting temperature in step 1 is 850 ℃ and the roasting time is 1h, the solid-to-liquid ratio of the normal-temperature roasted clinker to the deionized water in step 2 is 1:2.5, the solid-to-liquid ratio in step 3 is 1:3, and the mass concentration of the sulfuric acid solution is 36%.
8. The method of claim 7, wherein the stirring reaction time in step 3 is 3.5 h.
Technical Field
The invention relates to a fine comprehensive utilization technology of coal ash, in particular to comprehensive utilization of coal gasification coal ash.
Background
In recent years, the alumina capacity of China is always in a high-speed increasing state, and the alumina capacity of China has reached 7,713 ten thousand tons by 2017, which accounts for more than 50% of the total global production capacity. Currently, alumina in China is still mainly produced from bauxite by a Bayer process (Qiaoxichen, Jian nationality, Zhouhuamei, and the like. a method for activating fly ash at low temperature and application thereof [ P ]. Chinese patent: 20096055013.8,2009-12-23 ]. Although the bauxite resources in China reach 40.8 hundred million tons (by 2015), the diasporic bauxite which is difficult to grind and dissolve and has an A/S (A/S) of less than 5 is mainly used, most of the diasporic bauxite has low grade, and the alumina industry needs to maintain the development of the diasporic bauxite through a large amount of imported bauxite, so how to economically and efficiently utilize the low-grade bauxite or find the alternative resources of the bauxite is always a main problem in the alumina industry in China.
The fly ash is an industrial solid waste discharged by smelting plants, chemical plants and coal-fired power plants, and the main chemical components of the fly ash are Al2O3 and SiO2 (wherein the content of Al2O3 is generally 17-35 percent), and the fly ash is an important non-traditional alumina resource. If the method can be comprehensively utilized and effectively extract the alumina in the fly ash, the problem of serious environmental pollution caused by the mass stockpiling of the fly ash can be solved, and the waste can be changed into valuable, so that better environmental benefit and economic benefit can be obtained.
The currently reported methods for extracting aluminum from fly ash mainly comprise an alkaline method and an acid method.
The alkali method includes limestone sintering process (Wuyongfeng, limestone sintering process for extracting alumina [ J ] from CFB ash, environmental protection and circular economy, 2017,37(04):38-44.), alkali lime sintering process (Wangkongdong, Dian Yuchun, Shendayi, etc.), etc. the alkali lime sintering process for extracting alumina [ J ] light metal, 2009(06): 14-16) from desiliconized fly ash, roasting, and water leaching or acid leaching to separate and extract the main valuable elements of aluminum, silicon, etc. The alkaline process has the defects of large energy consumption, large slag quantity and the like, and is difficult to realize industrialization.
An acid method (li rui ice, li xin, wu nan, etc.; a method for preparing alumina by using fly ash from power plants [ P ]. chinese patent: 201210102794.3,2013-01-02.) refers to that under a certain condition, fly ash and appropriate inorganic acid (HCl, H2SO4, HNO3, etc.) are subjected to acid leaching reaction, SO as to realize effective separation and enrichment of main valuable elements such as aluminum, silicon, etc. Because the aluminum in the fly ash exists in the chemically stable mullite and aluminosilicate glass phase, the reaction activity of soluble components such as alumina in the fly ash is lower. In order to effectively improve the leaching rate of soluble components such as alumina in the fly ash, the reported technical methods mainly comprise the following two types:
(1) acid leaching method
A method for extracting aluminum oxide from fly ash by adopting high temperature and pressurization (Chengde, Lingwen, Guoshua, and the like) [ P ] Chinese patent: 201110103782.8,2011-08-10 ], and adding cosolvent (mainly fluoride) (Zhangdong, Zhao Feiyan, Guoshua, and the like.) to research the influence of a potassium fluoride dissolution assisting method on the dissolution rate of the aluminum oxide in the fly ash [ J ] coal and chemical industry, 2017,40(01):30-33.) to improve the leaching rate of soluble components such as the aluminum oxide, wherein the former has high requirements on equipment materials and large energy consumption, and the latter easily causes secondary pollution to the environment, has certain danger in operation, and limits the industrial application of the method.
(2) Acid leaching method for roasting and activating auxiliary agent
Roasting and activating the fly ash before acid leaching, and adding different activating auxiliary agents such as chloride, sodium salt, sulfate and the like in the process to improve the leaching rate of soluble components such as alumina and the like in the fly ash. Compared with the assistant-dissolving acid leaching method, the assistant roasting activation method has the obvious advantages of high leaching rate of alumina and large-scale application.
However, the prior reported auxiliary agent roasting activated acid leaching method still has the defects of high roasting temperature, large sulfuric acid consumption and slag quantityMajor deficiency is caused. For example, the roasting temperature of the sodium carbonate roasting method is high (more than or equal to 900 ℃), the liquid-solid ratio in the acid leaching process is large, the consumption of sulfuric acid is high, and gel SiO which is difficult to filter and separate is easy to generate2(ii) a The roasting temperature of the calcium oxide roasting method is high (1300 ℃), and the added calcium oxide additive is more than that of the fly ash, so that the subsequent acid leaching treatment has large slag quantity. Therefore, the development of a medium-low temperature activated acid leaching technology with multiple advantages of relatively low roasting temperature, high alumina leaching rate, small slag amount and the like becomes a research hotspot, and the key of the technology is the research and development of a suitable activating agent or a composite activating agent.
Disclosure of Invention
The invention provides a method for leaching alumina from coal ash gasified by Shell furnace, wherein the composite activating auxiliary agent used in the method is (CaCl)2+Ca(OH)2) Low cost, environment friendship, high leaching rate up to 95%, and excessive CaCl2Can be recycled through the water washing process of the roasted clinker, so the method has the advantages of low energy consumption, small slag amount, suitability for industrial mass production and the like.
The invention provides a method for leaching alumina from coal gasification fly ash of a Shell furnace, which comprises the following steps:
step 1: uniformly mixing coal gasification fly ash and a composite activator in a mass ratio of 1: 0.4-1, roasting at 700-900 ℃ for 0.5-2.5 h to obtain roasted clinker, and naturally cooling the roasted clinker to normal temperature at room temperature to obtain normal-temperature roasted clinker;
wherein the composite activator is Ca (OH) in a mass ratio of 1: 1-82And CaCl2Preparing;
step 2: washing normal temperature roasted clinker with deionized water, and recovering excessive activating agent CaCl2And the solid-to-liquid ratio of the normal-temperature roasted clinker to the deionized water is 1: 1-4, stirring for 3-7 minutes, and filtering to obtain a filtrate and a filter cake, wherein the filtrate can be used for recycling excessive activator CaCl2；
And step 3: putting the filter cake into a reaction kettle, and adding a sulfuric acid solution with the concentration of 20-50% into the reaction kettle according to the solid-to-liquid ratio of 1: 2-6Stirring and reacting for 2-5 h under the condition of normal pressure and the temperature of less than or equal to 95 ℃, filtering to obtain an aluminum sulfate solution containing impurities and an acid leaching filter cake, wherein the acid leaching filter cake is active silicon dioxide (SiO)2·nH2O) and insoluble calcium sulfate, and subsequent treatment is used for preparing nano-silica and light calcium carbonate; the filtrate of the aluminum sulfate solution containing impurities is the aluminum sulfate solution containing soluble impurities such as iron, magnesium and the like, and can be used for preparing aluminum hydroxide or aluminum oxide.
Further, the stirring time in
Further, the roasting temperature in the step 1 is 900 ℃ and the roasting time is 2.5 hours, the solid-to-liquid ratio of the normal-temperature roasted clinker to the deionized water in the
Further, the reaction time was 5 hours with stirring in step 3.
Further, the roasting temperature in the step 1 is 800 ℃ and the roasting time is 1.5h, the solid-to-liquid ratio of the normal-temperature roasted clinker to the deionized water in the
Further, the reaction time was 4 hours with stirring in step 3.
Further, the roasting temperature in the step 1 is 850 ℃ and the roasting time is 1h, the solid-to-liquid ratio of the normal-temperature roasted clinker to the deionized water in the
Further, the reaction time in step 3 was 3.5h with stirring.
Compared with the prior art, the invention has the following advantages:
(1) the invention selects CaCl2And Ca (OH)2The composite activating agent can effectively destroy Si-O-Al bonds in the coal gasification fly ash under the medium temperature condition (700-900 ℃), realizes high-efficiency leaching of alumina (the leaching rate reaches more than 95%), and has no special requirements on the grade of the fly ash.
(2) Activators Ca (OH)2The addition of the catalyst effectively neutralizes HCl gas generated in the roasting process and chloride intermediate products gasified at high temperature, and reduces environmental pollutionWhile protecting the equipment, the comprehensive utilization rate of valuable metals is improved, and excessive activating agent CaCl2The washed roasted clinker can be recycled.
(3) After the roasted clinker is subjected to acid leaching, the obtained aluminum sulfate solution containing soluble impurities such as iron, magnesium and the like can be used for preparing aluminum hydroxide or aluminum oxide, and the acid leaching filter cake can be used for preparing nano silicon dioxide and light calcium carbonate.
(4) Compared with the prior fly ash activation technology, the method has the advantages of relatively low roasting temperature, high leaching rate of alumina, less slag, low cost of the activating agent and the like.
Drawings
FIG. 1: the process flow schematic diagram of the medium-temperature roasting, activating and leaching of the alumina from the coal gasification fly ash of the Shell furnace.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The raw material is coal gasification fly ash of a Shell furnace, and the chemical composition of the coal gasification fly ash is shown in Table 1:
composition (I)
SiO2
Al2O3
CaO
MgO
Na2O
K2O
Fe2O3
TiO2
Loss on ignition
Content (W)B％)
46.60
17.50
8.02
0.80
1.18
0.99
8.48
1.25
16.5
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