阅读说明：本技术 粉煤灰或煤矸石热熔盐法全元素回收利用工艺 (Full-element recycling process of coal ash or coal gangue by hot-melt salt method ) 是由 胡长春 龚景仁 卢伟 胡晓雪 于 2020-07-27 设计创作，主要内容包括：本发明公开了一种粉煤灰或煤矸石热熔盐法全元素回收利用工艺,属于粉煤灰或煤矸石回收利用技术领域。其技术方案为：对粉煤灰或煤矸石进行氯化铵工艺和/或硫酸铵工艺,提取其中的稀有元素及钙镁元素。本发明不使用盐酸、硫酸和碱,解决了设备的防腐问题,在提取粉煤灰或煤矸石中的稀有元素的同时分解铵盐,还能够提取其中的钙、镁、铝、硅、钛,实现了粉煤灰或煤矸石中各个元素非常经济合理地回收利用。(The invention discloses a full-element recycling process of fly ash or coal gangue by a hot-melt salt method, belonging to the technical field of fly ash or coal gangue recycling. The technical scheme is as follows: and (3) carrying out an ammonium chloride process and/or an ammonium sulfate process on the fly ash or the coal gangue to extract rare elements and calcium and magnesium elements in the fly ash or the coal gangue. The method does not use hydrochloric acid, sulfuric acid and alkali, solves the corrosion prevention problem of equipment, decomposes ammonium salt while extracting rare elements in the fly ash or coal gangue, can also extract calcium, magnesium, aluminum, silicon and titanium in the fly ash or coal gangue, and realizes the economic and reasonable recycling of each element in the fly ash or coal gangue.)

1. The full-element recycling process of the fly ash or coal gangue by the hot-melt salt method is characterized by comprising an ammonium chloride process and/or an ammonium sulfate process, wherein the ammonium chloride process comprises the following steps:

s11: performing high-temperature decarburization on the fly ash or coal gangue and the coal ash or coal gangue in a rotary kiln under the condition of pure oxygen or oxygen enrichment to generate hot fly ash or hot coal gangue and carbon dioxide, and washing and pressurizing the carbon dioxide and then feeding the carbon dioxide into a carbonization tower;

s12: carrying out primary hot-melt salt reaction on the hot fly ash or the hot coal gangue obtained in the S11 and an excessive saturated ammonium chloride solution in a leaching tank to generate liquid chlorate, solid acid insoluble substances and ammonia gas; ammonia gas generates ammonia water in an ice maker and then enters a carbonization tower to generate ammonium bicarbonate together with carbon dioxide;

s13: carrying out solid-liquid separation on the product of S12 to obtain solid acid insoluble substances and liquid chlorate, adsorbing and extracting rare elements in the liquid chlorate by resin, reacting the residual liquid chlorate with ammonium bicarbonate in S12, and carrying out solid-liquid separation on the product to obtain solid calcium carbonate, magnesium bicarbonate and liquid ammonium chloride;

the ammonium sulfate process comprises the following steps:

s21: performing high-temperature decarburization on fly ash or coal gangue or solid acid insoluble substances generated by S12 and calcium fluoride in a rotary kiln under the condition of pure oxygen or oxygen enrichment to generate hot fly ash or hot coal gangue or acid insoluble substances, hot calcium fluoride and carbon dioxide;

s22: carrying out secondary hot-melting salt reaction on hot fly ash or hot coal gangue or acid insoluble substances, hot calcium fluoride and an excessive saturated ammonium sulfate solution in a leaching tank, and carrying out solid-liquid separation to obtain solid calcium sulfate, acid insoluble substances, liquid sulfate and silicon fluoride gas; adsorbing the liquid sulfate by resin, extracting to extract rare elements, allowing the silicon fluoride gas to enter an ammonia washing tower to react with ammonia water, and performing solid-liquid separation on the product to obtain solid white carbon black and liquid ammonium bifluoride;

s23: s22, heating the residual liquid sulfate, carrying out hydrolysis reaction, and carrying out solid-liquid separation on the product to obtain solid titanium dioxide and liquid aluminum ammonium sulfate;

s24: and (3) reacting the liquid aluminum ammonium sulfate in the S23 with ammonia water, and performing solid-liquid separation on the product to obtain solid aluminum hydroxide and liquid ammonium sulfate, or concentrating and evaporating the liquid aluminum ammonium sulfate in the S23 to generate solid aluminum ammonium sulfate, and performing high-temperature decomposition on the solid aluminum ammonium sulfate to generate solid high-purity superfine alumina and ammonium sulfate decomposition gas.

2. The fly ash or coal gangue hot-melt salt method full-element recycling process as claimed in claim 1, wherein: before the ammonium chloride process and/or the ammonium sulfate process are carried out on the fly ash or the coal gangue, the fly ash or the coal gangue is subjected to pretreatment of levigating, magnetic separation for removing iron, removing glass beads and gravity separation for large-specific gravity elements.

3. The fly ash or coal gangue hot-melt salt method full-element recycling process as claimed in claim 1, wherein: in S11, the temperature of high-temperature decarburization is 400-600 ℃; in S21, the temperature of high-temperature decarburization is 450-900 ℃; in S22, the temperature of the secondary hot melt salt reaction is 280-400 ℃, and the reaction temperature in the ammonia washing tower is 50-95 ℃.

4. The fly ash or coal gangue hot-melt salt method full-element recycling process as claimed in claim 1, wherein: the residual heat of the rotary kiln in S11 and S21 is used for drying calcium carbonate and magnesium bicarbonate obtained in S13, concentrating, evaporating and crystallizing liquid aluminum ammonium sulfate in S24, and pyrolyzing solid aluminum ammonium sulfate in S24 to generate solid high-purity superfine alumina and ammonium sulfate decomposed gas.

5. The fly ash or coal gangue hot-melt salt method full-element recycling process as claimed in claim 1, wherein: the liquid ammonium chloride in the S13 is returned to the leaching tank of the S12 for recycling.

6. The fly ash or coal gangue hot-melt salt method full-element recycling process as claimed in claim 1, wherein: the carbon dioxide in the S21 enters a carbonization tower in the S11 after being washed and pressurized.

7. The fly ash or coal gangue hot-melt salt method full-element recycling process as claimed in claim 1, wherein: and the solid ammonium bifluoride obtained by concentrating and evaporating the liquid ammonium bifluoride in the S22 is returned to the leaching tank of the S22 for recycling and participates in the secondary hot-melt salt reaction.

8. The fly ash or coal gangue hot-melt salt method full-element recycling process as claimed in claim 1, wherein: the ammonium sulfate decomposed gas in the S24 is absorbed by water to generate liquid ammonium sulfate, and the liquid ammonium sulfate returns to the S22 for recycling.

Technical Field

The invention relates to the technical field of recycling of fly ash or coal gangue, in particular to a full-element recycling process of fly ash or coal gangue by a hot-melt salt method.

Background

The fly ash or coal gangue is fine ash collected from flue gas generated after coal combustion, and the fly ash or coal gangue is main solid waste discharged from a coal-fired power plant. The main oxide composition of the fly ash or coal gangue of the thermal power plant of China is as follows: SiO 2₂、Al₂O₃、FeO、Fe₂O₃、CaO、TiO₂And the like. Along with the development of the power industry, the discharge amount of fly ash or coal gangue of a coal-fired power plant is increased year by year, and the fly ash or coal gangue becomes one of industrial waste residues with larger discharge capacity in China at present. A large amount of fly ash or coal gangue can generate dust without treatment, thereby polluting the atmosphere; if discharged into a water system, the river can be silted, and toxic chemicals in the river can cause harm to human bodies and organisms.

According to related data, many coal fields have higher rare earth level, the average content of rare earth elements in the global fly ash or coal gangue is estimated to be 445ppm preliminarily, and a plurality of reports about the content of the rare earth elements in the fly ash or coal gangue show that the content of the rare earth elements far exceeds the global average content. The yield of the fly ash or coal gangue in the world per year is considerable, particularly, the specific gravity of Chinese coal power generation is very large, so that the formed fly ash or coal gangue is increased day by day, if the rare earth elements can be successfully extracted from the fly ash or coal gangue in a large scale, the waste fly ash is changed into valuable, the ecological environment is protected, the resources can be effectively recycled, and the strategic significance, the environmental benefit, the social benefit and the economic value are huge.

The high-alumina fly ash or coal gangue is generally referred to as A1₂0₃+SiO₂+Fe₂O₃Not less than 80% of fly ash orCoal gangue characterized by containing A1₂0₃High, generally greater than 38%, high even more than 50%, corresponding to A1 of gibbsite ore abroad₂0₃And (4) content. The high-alumina fly ash or coal gangue in China contains a large amount of kaolin, orthoclase, bauxite and other minerals, and the high-alumina fly ash or coal gangue is obtained after raw coal used in a power plant is pulverized and combusted in a power plant coal powder boiler through fine grinding. The high-alumina fly ash or coal gangue contains 37-48 percent of A1₂0₃，35％-52％SiO₂The total content of oxides of Fe, Ti, Ca, Mg, etc. is 8-12%, and also contains trace amount of rare earth metals and rare earth metals.

The most valuable of the fly ash or the coal gangue is rare earth elements, because coal components in different regions are greatly different, the adopted boiler combustion systems are different, the physical and chemical properties of the fly ash or the coal gangue are greatly different, and the extraction and separation of each element are hindered by the formation of a glass body of an amorphous substance.

Both acid extraction and alkaline extraction have disadvantages: the equipment investment is large, the equipment corrosion prevention problem always restricts the development of the high-alumina fly ash or coal gangue, wherein the corrosion prevention is the great problem of aluminum and titanium recovery, the investment economic cost is high, the operation cost is high, and the economic benefit is not satisfactory. Meanwhile, the three wastes generated by acid extraction and alkaline extraction are more, and more than ten tons of silicon-calcium waste residues exist in producing one ton of alumina. The content values of rare earth elements such as lithium, potassium, neodymium, cerium, scandium, gallium, germanium, vanadium, titanium and the like in the fly ash or coal gangue are high, and the recovery, decomposition and utilization of the rare earth elements have great value according to the principles of reduction, reclamation and no waste. The production cost of the alumina is far lower than that of the Bayer process, and cheap economic resources are provided for the production of the aluminum and the titanium. The popularization and application of the hot molten salt process technology promote the development of the coal gasification liquid slag removal technology.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the defects of the prior art are overcome, the process for recycling all elements in the fly ash or coal gangue by the hot-melt salt method is provided, hydrochloric acid, sulfuric acid and alkali are not used, the corrosion prevention problem of equipment is solved, the rare elements in the fly ash or coal gangue are extracted, ammonium salt is decomposed, calcium, magnesium, aluminum, silicon and titanium in the fly ash or coal gangue can be extracted, and all elements in the fly ash or coal gangue can be recycled economically and reasonably.

The technical scheme of the invention is as follows:

the full-element recycling process of the fly ash or coal gangue by a hot-melt salt method comprises an ammonium chloride process and/or an ammonium sulfate process, wherein the ammonium chloride process comprises the following steps:

s11: performing high-temperature decarburization on the fly ash or coal gangue and the coal ash or coal gangue in a rotary kiln under the condition of pure oxygen or oxygen enrichment to generate hot fly ash or hot coal gangue and carbon dioxide, and washing and pressurizing the carbon dioxide and then feeding the carbon dioxide into a carbonization tower;

s12: carrying out primary hot-melt salt reaction on the hot fly ash or the hot coal gangue obtained in the S11 and an excessive saturated ammonium chloride solution in a leaching tank to generate liquid chlorate, solid aluminosilicate titanate insoluble substances and ammonia gas; ammonia gas generates ammonia water in an ice maker and then enters a carbonization tower to generate ammonium bicarbonate with carbon dioxide, and the reaction formula is as follows:

s13: carrying out solid-liquid separation on the product of S12 to obtain solid acid insoluble substances and liquid chlorate, adsorbing and extracting rare elements from the liquid chlorate by resin, reacting the residual liquid chlorate with ammonium bicarbonate in S12, and carrying out solid-liquid separation on the product to obtain solid calcium carbonate, magnesium bicarbonate and liquid ammonium chloride, wherein the reaction formula is as follows:

wherein the calcium carbonate is superfine high-whiteness 90-96 min calcium carbonate, and the selling price per ton is 1000-1800 Yuan. The superfine high-whiteness colloid calcium carbonate can be further deeply processed and produced according to market demands, and is mainly used in the industries of building internal and external wall coatings, printing coatings, rubber, ceramics, glass, electrical appliances, papermaking, paint and the like. The aluminosilicate titanic acid insoluble substance can be used as a high-alumina refractory material to enter the market, and the selling price is more than 500 yuan/ton.

The ammonium sulfate process comprises the following steps:

s21: performing high-temperature decarburization on fly ash or coal gangue or solid acid insoluble substances generated by S12 and calcium fluoride in a rotary kiln under the condition of pure oxygen or oxygen enrichment to generate hot fly ash or hot coal gangue or acid insoluble substances, hot calcium fluoride and carbon dioxide;

s22: carrying out secondary hot-melting salt reaction on hot fly ash or hot coal gangue or acid insoluble substances, hot calcium fluoride and an excessive saturated ammonium sulfate solution in a leaching tank, and carrying out solid-liquid separation to obtain solid calcium sulfate, acid insoluble substances, liquid sulfate and silicon fluoride gas; the solid calcium sulfate can react with ammonium bicarbonate and then is subjected to solid-liquid separation to obtain solid calcium carbonate, magnesium bicarbonate and liquid ammonium sulfate, and the liquid ammonium sulfate is recycled; the liquid sulfate is absorbed by resin and extracted to extract rare elements, the silicon fluoride gas enters an ammonia washing tower to react with ammonia water, and the solid white carbon black and liquid ammonium bifluoride are obtained after the solid-liquid separation of the product, wherein the reaction formula is as follows:

s23: s22, heating the residual liquid sulfate, carrying out hydrolysis reaction, and carrying out solid-liquid separation on the product to obtain solid titanium dioxide and liquid aluminum ammonium sulfate, wherein the reaction formula is as follows:

s24: reacting the liquid aluminum ammonium sulfate in the S23 with ammonia water, and performing solid-liquid separation on the product to obtain solid aluminum hydroxide and liquid ammonium sulfate, wherein the reaction formula is as follows:

or the liquid aluminum ammonium sulfate in the S23 is concentrated and evaporated to generate aluminum ammonium sulfate crystals, the solid aluminum ammonium sulfate is decomposed at high temperature to generate solid high-purity superfine alumina and ammonium sulfate decomposed gas, and the reaction formula is as follows:

preferably, before the ammonium chloride process and/or the ammonium sulfate process are/is carried out on the fly ash or the coal gangue, the fly ash or the coal gangue is subjected to pretreatment of levigating, magnetic separation for removing iron, removing glass beads and gravity separation for separating elements with large specific gravity.

Preferably, in S11, the temperature of the high-temperature decarburization is 400-600 ℃; in S21, the temperature of high-temperature decarburization is 450-900 ℃; in S22, the temperature of the secondary hot melt salt reaction is 280-400 ℃, and the reaction temperature in the ammonia washing tower is 50-95 ℃.

Preferably, the residual heat of the rotary kiln in S11 and S21 is used for drying calcium carbonate and magnesium bicarbonate obtained in S13, concentrating, evaporating and crystallizing liquid aluminum ammonium sulfate in S24, and pyrolyzing solid aluminum ammonium sulfate in S24 to generate solid high-purity ultrafine alumina and ammonium sulfate decomposition gas.

Preferably, the liquid ammonium chloride in S13 is returned to the leaching tank of S12 for recycling.

Preferably, the carbon dioxide in S21 enters the carbonization tower in S11 after being washed and pressurized.

Preferably, the liquid ammonium bifluoride in the S22 is concentrated and evaporated by utilizing the waste heat of the rotary kiln to obtain solid ammonium bifluoride, the solid ammonium bifluoride is returned to the leaching tank of the S22 for recycling, and participates in the secondary hot-melt salt reaction, and the reaction formula is as follows:

preferably, the ammonium sulfate decomposition gas in S24 is absorbed by water to generate liquid ammonium sulfate, and the liquid ammonium sulfate is returned to S22 for recycling.

Compared with the prior art, the invention has the following beneficial effects:

1. the process of the invention is characterized in that the hot fly ash or coal gangue reacts with the ammonia salt, the rare elements in the fly ash or coal gangue are extracted, simultaneously the ammonium salt is decomposed, and the calcium, magnesium, aluminum, titanium and silicon in the fly ash or coal gangue can also be extracted, thereby realizing the economic and reasonable recycling of each element in the fly ash or coal gangue. In addition, the process does not use hydrochloric acid, sulfuric acid and alkali, saves the cost of acid and alkali, solves the corrosion prevention problem of equipment, fully recycles the ammonia generated in the recycling process, fully recycles the fly ash or coal gangue ammonia salt, increases the value, and really realizes low-carbon green recycling operation. The alumina has high purity and quality, and the production cost is far lower than the Bayer process cost. Meanwhile, the production cost of the titanium dioxide is lower than the production process cost of the titanium dioxide by the sulfuric acid method, and the production cost of the titanium dioxide is greatly reduced. The alumina is within 1000 yuan/ton, and the titanium dioxide is within 5000 yuan/ton, so that the method has high commercial competitiveness.

2. The process can flexibly arrange the process scheme according to the components of the fly ash or the coal gangue, when the content of calcium in the fly ash or the coal gangue is lower than 5 percent, the ammonium sulfate process can be independently used for extracting silicon, aluminum, titanium and rare elements in the fly ash or the coal gangue, and when the content of calcium in the fly ash or the coal gangue is higher, the fly ash or the coal gangue can be subjected to the ammonium chloride process and then the ammonium sulfate process. The whole process does not generate new three wastes, gas, solid and liquid can be utilized, and the carbon dioxide gas is fully utilized in a value-added manner.

Drawings

FIG. 1 is a flow diagram of the ammonium chloride process of the present invention.

Figure 2 is a flow diagram of an ammonium sulfate process of the present invention.

Detailed Description

As shown in figures 1 and 2, the invention provides a full-element recycling process of fly ash or coal gangue by a hot-melt salt method, which comprises an ammonium chloride process and an ammonium sulfate process, wherein the ammonium chloride process comprises the following steps:

s11: firstly, carrying out the pretreatment of levigating, magnetic separation and deferrization, removing glass beads and gravity separation of elements with large specific gravity on the fly ash or coal gangue, carrying out high-temperature decarburization (400-plus-600 ℃) on the pretreated fly ash or coal gangue and a rotary kiln under the condition of pure oxygen or oxygen enrichment to generate hot fly ash or hot coal gangue and carbon dioxide, washing the carbon dioxide by a washing tower, and pressurizing by a compressor to enter a carbonization tower;

s12: carrying out primary hot-melt salt reaction on the hot fly ash or the hot coal gangue obtained in the S11 and an excessive saturated ammonium chloride solution in a leaching tank to generate liquid chlorate, solid aluminosilicate titanate insoluble substances and ammonia gas; ammonia gas generates ammonia water in an ice maker and then enters a carbonization tower to generate ammonium bicarbonate with carbon dioxide, and the reaction formula is as follows:

s13: carrying out solid-liquid separation on the product of S12 to obtain solid acid insoluble substances and liquid chlorate, adsorbing and extracting rare elements in the liquid chlorate by resin, reacting the residual liquid chlorate with ammonium bicarbonate in S12, carrying out solid-liquid separation on the product to obtain solid calcium carbonate, magnesium bicarbonate and liquid ammonium chloride, and returning the liquid ammonium chloride to the leaching tank of S12 for recycling; the reaction formula is as follows:

the ammonium sulfate process comprises the following steps:

s21: carrying out high-temperature decarburization (450-;

s22: carrying out secondary hot-melting salt reaction (280-; the liquid sulfate is adsorbed by resin and extracted to extract rare elements again, the silicon fluoride gas enters an ammonia washing tower to react with ammonia water (50-95 ℃), solid white carbon black and liquid ammonium bifluoride are obtained after solid-liquid separation of products, and the solid ammonium bifluoride obtained by concentrating and evaporating the liquid ammonium bifluoride by utilizing the waste heat of a rotary kiln is returned to the leaching tank of S22 for recycling and participates in secondary hot molten salt reaction; the reaction formula is as follows:

s23: s22, heating the residual liquid sulfate to carry out hydrolysis reaction, and carrying out solid-liquid separation on the product to obtain solid titanium dioxide and liquid aluminum ammonium sulfate, wherein the reaction formula is as follows:

s24: reacting the liquid aluminum ammonium sulfate in the S23 with ammonia water, and performing solid-liquid separation on the product to obtain solid aluminum hydroxide and liquid ammonium sulfate, wherein the reaction formula is as follows:

or the liquid ammonium aluminum sulfate in the S23 is concentrated and evaporated to generate ammonium aluminum sulfate crystals, the solid ammonium aluminum sulfate is decomposed at high temperature to generate solid high-purity superfine aluminum oxide and ammonium sulfate decomposed gas, the ammonium sulfate gas is absorbed by water to generate liquid ammonium sulfate, and the liquid ammonium sulfate returns to the S22 for recycling, wherein the reaction formula is as follows:

in the invention, the residual heat of the rotary kiln in S11 and S21 is used for drying calcium carbonate and magnesium bicarbonate obtained in S13, concentrating, evaporating and crystallizing liquid aluminum ammonium sulfate in S24, and pyrolyzing solid aluminum ammonium sulfate in S24 to generate solid high-purity superfine alumina and ammonium sulfate decomposition gas.