CN101607259B - Method for activating fly ash at low temperature and application thereof - Google Patents

Abstract

The invention relates to a method for activating fly ash at low temperature and its application. The fly ash is pulverized until the particle size is less than 30 microns. According to the content of Ca and Al in the fly ash and the reaction characteristics of the fly ash, the calcium content is appropriately increased. And by treating under a certain moisture content condition, the fly ash can be activated at a lower calcination temperature, and the fly ash clinker with high reactivity suitable for alumina extraction can be prepared, and then acid leaching can be used. The advantages of the present invention: the ingredients are not affected by the Si content in the fly ash, and the fly ash is treated at a lower temperature of 800-950°C and a shorter time of 30-60 minutes, and the acid leaching rate of alumina can be obtained exceeding 75%. % of fly ash clinker.

Description

A method and application of low-temperature activation of fly ash

【Technical field】

The invention relates to the technical field of fly ash, in particular to a method for activating fly ash at low temperature and its application in extracting alumina.

【Background technique】

Fly ash is a kind of solid waste produced by coal combustion, accounting for 10-40% of coal. At present, my country's thermal power plants and other coal-fired boilers discharge as much as 330 million tons of fly ash every year, which is mainly used in building materials production, construction engineering, road construction, fertilizer production, soil improvement and backfilling. Due to the saturation of market demand and the activity of fly ash, there is an annual accumulation of 100 million tons of fly ash in my country. As of 2008, the cumulative accumulation of fly ash in my country has exceeded 2.7 billion tons.

my country's alumina industry has developed rapidly in recent years. In 2006, its output ranked first in the world. In 2008, its output accounted for 27.36% of the world's total output. Alumina is currently mainly produced from bauxite rich ore through the Bayer process. However, my country's bauxite resources only account for 3.12% of the world's total reserves, and most of them are of low grade. Therefore, my country currently mainly maintains the alumina industry by importing a large amount of bauxite. The development of bauxite imports increased rapidly from 880,000 tons in 2004 to 25.79 million tons in 2008. It is imperative to look for alternative resources of bauxite in our country. The average alumina content of fly ash in my country is 27%, and it is as high as 40-60% in some areas, which is a very important aluminum resource. The development of fly ash to prepare alumina technology can not only effectively solve the problems of fly ash occupation of cultivated land and environmental pollution, but also solve the dilemma of lack of raw materials for alumina production in my country, which has great environmental and economic significance.

The process of using fly ash as aluminum resource to prepare alumina is mainly divided into acid method and alkali method. The activated fly ash is reacted with acid or alkali to form aluminum salt, and then purified and separated, dried and pyrolyzed. get alumina. Related invention patents and patent applications are: Inner Mongolia Mengxi High-tech Group Co., Ltd. invented a method of using fly ash to prepare alumina for co-production of cement clinker (patent number ZL03131079.6) and using fly ash and limestone to combine A method for producing alumina and cement (patent application number 200410090949.1), a method for extracting alumina from fly ash invented by the Shuozhou Municipal People’s Government (patent application number 200510048274.9), and a method for extracting alumina from fly ash invented by Li Yu A method for simultaneously co-producing white carbon black with aluminum (patent application number 200610012780.7), a method for producing alumina from fly ash invented by Pingshuo Coal Industry Company (patent application number 200610048295.5) and a method for producing alumina from fly ash A method for extracting aluminum after silicon extraction (patent application number 200710062534.7) and a method for producing silica and alumina using fly ash 200710061662.X), a method invented by Aluminum Corporation of China to extract Alumina method (patent application number 200710118679.4), a method of extracting alumina from high-alumina fly ash and its waste residue to produce cement invented by Chang'an University (patent application number 200710017304.9) and extracting alumina from fly ash and using The method of producing cement from waste slag (patent application number 200710017453.5), a clean production process of alumina and white carbon black by using high-alumina fly ash invented by China University of Geosciences (Beijing) (patent application number 200710087028.3), a kind of invention invented by Zhejiang University A method for preparing flaky alumina from coal-measure kaolinite or fly ash (patent application number 200710068433.0), a method invented by Tsinghua University to extract silica, alumina and gallium oxide from high-alumina fly ash Method (patent application number 200710065366.7), a method for preparing alumina from fly ash invented by Shenyang Aluminum and Magnesium Design Research Institute (patent application number 200710012997.2), a new fly ash extraction alumina process invented by Inner Mongolia United Industry Co., Ltd. ( Patent Application No. 200710110423.9), Zhang Keyi invented the method of extracting alumina from fly ash to produce cement by using calcium carbide slag or cyanamide slag (patent application No. 200610092056.X), Huainan Power Plant invented the method of extracting oxidation from fly ash Aluminum simultaneously generates β-C 2S cementitious material method (patent number ZL87101461.0), a method for extracting high-purity alumina and silica gel from fly ash invented by Pan Aifang (patent application number 200810017869.1), a method invented by Guizhou University from A method for extracting alumina from fly ash (patent application number 200810302421.4), a method for extracting metallurgical grade alumina from fly ash or slag invented by Beijing Century Dihe Technology Co., Ltd. (patent application number 200810115355.X), Invented by Tianjin University from A method for extracting high-purity ultra-fine alumina from fly ash (patent application number 200710150915.0).

The key step in extracting alumina from fly ash is to activate fly ash, but the current process generally has problems such as high calcination temperature, long calcination time, and large amount of additives in the process of fly ash activation. , and due to the large amount of additives, the amount of waste residue is correspondingly large, and the secondary pollution is serious. Therefore, large-scale industrial application is restricted.

【Content of invention】

The purpose of the present invention is to overcome the deficiencies of the prior art, provide a method for activating fly ash at low temperature and its application; overcome the problems of high calcination temperature and long calcination time in the prior art, reduce energy consumption, and have environmental effects It is also economically significant, and provides a method for extracting alumina from fly ash with low energy consumption.

The concept of the present invention is: the fly ash is pulverized until the particle size is less than 30 microns, the calcium content is appropriately increased according to the Ca and Al content and the reaction characteristics of the fly ash, and the process is performed under a certain moisture content condition, and low-temperature calcination is adopted. Qualified fly ash can be obtained to prepare sintered clinker of alumina, which is then extracted by acid leaching.

The purpose of the present invention is achieved through the following technical solutions:

A method for activating fly ash at low temperature, the concrete steps are:

(1) Control the fineness of fly ash to less than 30 microns by means of grinding;

(2) Calcium-aluminum ratio control: According to the reaction characteristics of the fly ash itself, the molar ratio of Ca and Al in the fly ash mixture sample is made 0.5:1 to 0.7:1 by adding calcium;

(3) Water content control: according to the reaction characteristics of fly ash, the mass percent water content of the mixture in the control step (2) is at 5% to 50%;

(4) drying the material in step (3);

(5) Calcining at low temperature: Calcining the mixture prepared by the above steps (1), (2), (3) and (4) at 800-950° C. for 30-60 minutes, then quenching to obtain sintered clinker.

Another object of the present invention is to provide a method for low-temperature activation of fly ash in the application of alumina extraction, the specific steps are:

(1) Control the fineness of fly ash to less than 30 microns by means of grinding;

(2) Calcium-aluminum ratio control: According to the reaction characteristics of the fly ash itself, the molar ratio of Ca and Al in the fly ash mixture sample is made 0.5:1 to 0.7:1 by adding calcium;

(3) Water content control: according to the reaction characteristics of fly ash, the mass percent water content of the mixture in the control step (2) is at 5% to 50%;

(4) drying the material in step (3);

(5) Calcining at low temperature: Calcining the mixture prepared by the above steps (1), (2), (3) and (4) at 800-950° C. for 30-60 minutes, then quenching to obtain sintered clinker;

(6) Aluminum leaching: the sintered clinker prepared in step (5) is leached with dilute hydrochloric acid or dilute sulfuric acid, wherein the concentration of dilute hydrochloric acid is 0.4-0.7 mol/l, and the concentration of dilute sulfuric acid is 0.2-0.7 mol/l l; the leaching temperature is 75-120°C, and the leaching time is 10-60 minutes to obtain aluminum chloride or aluminum sulfate.

Compared with prior art, positive effect of the present invention is:

Use a lower temperature of 800-950°C and a shorter time of 30-60 minutes to treat fly ash, and use waste hydrochloric acid and waste sulfuric acid to achieve fly ash at a lower temperature of 75-120°C and a shorter time of 10-60 minutes The high-efficiency leaching of medium-sized alumina reduces energy consumption and leaves less aluminum extraction residue.

【Detailed ways】

A method for activating fly ash at low temperature of the present invention and a specific embodiment of its application are provided below.

Example 1

Grinding the fly ash with 31.47% by mass of alumina and 2.75% by mass of calcium oxide until it passes through 30 microns, adding calcium according to the molar ratio of Ca to Al of 0.6, controlling the moisture content by mass to 20%, and mixing uniform, then calcined at 800°C for 60 minutes, quenched, pulverized, and leached with hydrochloric acid with a concentration of 20% by mass at 120°C for 10 minutes, and the extraction rate of alumina was 78%.

Example 2

Grind low-calcium fly ash with a mass percentage of alumina of 31.47% and a mass percentage of calcium oxide of 2.75% until it passes through 20 microns, increase calcium at a molar ratio of Ca to Al of 0.5, and control a moisture content of 10% by mass , mixed evenly, then calcined at 900°C for 40 minutes, quenched, pulverized, and leached with sulfuric acid with a mass percent concentration of 25% at 120°C for 20 minutes, and the extraction rate of alumina was 84.70%.

Example 3

Grind the low-calcium fly ash with a mass percentage of alumina of 31.47% and a mass percentage of calcium oxide of 2.75% until all of them pass through 20 microns, increase calcium according to the molar ratio of Ca to Al of 0.7, and control the moisture content of 50% by mass , mixed evenly, then calcined at 950°C for 30 minutes, quenched, pulverized, and leached with hydrochloric acid with a concentration of 25% by mass at 75°C for 30 minutes, and the extraction rate of alumina was 87.13%.

Example 4

Grind the low-calcium fly ash with a mass percentage of alumina of 53.26% and a mass percentage of calcium oxide of 3.41% until all pass through 30 microns, increase calcium according to the molar ratio of Ca and Al of 0.6, and control the moisture content of 30% by mass , mixed evenly, then calcined at 900°C for 60 minutes, quenched, pulverized, and leached with hydrochloric acid with a concentration of 20% by mass at 120°C for 10 minutes, and the extraction rate of alumina was 92.80%.

Example 5

Grind the fly ash with a mass percentage of alumina of 19.99% and a mass percentage of calcium oxide of 18.75% until it passes through 30 microns, add calcium-based additives at a molar ratio of Ca to Al of 0.5, and control a moisture content of 5% by mass %, mixed evenly, then calcined at 800°C for 30 minutes, quenched, crushed, and leached with hydrochloric acid with a concentration of 20% by mass at 100°C for 30 minutes, and the extraction rate of alumina was 93.55%.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be considered Within the protection scope of the present invention.

Claims (2)

1. the method for an activating fly ash at low temperature is characterized in that, concrete steps are:

(1) adopt the grinding mode to control fineness of pulverized-coal ash less than 30 microns;

(2) calcium al proportion control: according to the response characteristic of flyash self, through increasing the mol ratio 0.5: 1～0.7: 1 that calcium makes Ca and Al in the flyash aggregate sample;

(3) moisture content control: according to the flyash response characteristic, the mass percent moisture content of compound is 5%～50% in the control step (2);

(4) material in the drying steps (3);

(5) low temperature calcination: under 800～950 ℃ to the compound calcining through above-mentioned steps (1), (2), (3), (4) preparation after 30～60 minutes, chilling makes sintered clinker.

2. the application of the method for an activating fly ash at low temperature in extracting aluminium oxide is characterized in that concrete steps are:

(1) adopt the grinding mode to control fineness of pulverized-coal ash less than 30 microns;

(2) calcium al proportion control: according to the response characteristic of flyash self, through increasing the mol ratio 0.5: 1～0.7: 1 that calcium makes Ca and Al in the flyash aggregate sample;

(3) moisture content control: according to the flyash response characteristic, the mass percent moisture content of compound is 5%～50% in the control step (2);

(4) material in the drying steps (3);

(5) low temperature calcination: under 800～950 ℃ to the compound calcining through above-mentioned steps (1), (2), (3), (4) preparation after 30～60 minutes, chilling makes sintered clinker;

(6) aluminium element leaching: the sintered clinker that makes through step (5) leaches through watery hydrochloric acid or dilute sulfuric acid, and wherein, watery hydrochloric acid concentration is 0.4～0.7mol/l, and dilute sulfuric acid concentration is 0.2～0.7mol/l; 75～120 ℃ of leaching temperatures, leaching time 10～60 minutes obtains aluminium chloride or aluminum sulfate.