Method for improving extraction rate of alumina in high-alumina fly ash and mineralizer thereof

Abstract

The invention discloses a method for improving the extraction rate of alumina in high-alumina fly ash and a mineralizer thereof. In the process of extracting the aluminum oxide from the high-alumina fly ash through the limestone sintering method, a mineralizer CSO is added into a raw material, and the index requirements of the mineralizer CSO are as follows: the content of SO3 is greater than 40.0%, the content of CaO is greater than 30.0%, and the content of Fe2O3 and the content of TiO2 are both less than 1.0%. According to the method, fluorite is replaced by the mineralizer CSO to serve as the mineralizer, and the firing temperature range of the fluorite mineralizer is expanded from 1270-1320 DEG C to 1280-1450 DEG C, so that the firing temperature range is further expanded, the sintering performance of the clinker can be greatly improved, and favorable conditions are provided for stable operation of a clinker kiln. The mineralizer CSO replaces fluorite to serve as the mineralizer, in the technological process, the purpose of pursuing the dissolution rate of the clinker is achieved, the pulverization rate of the clinker is not pursued deliberately, the strict requirement for a cooling system needed in the clinker pulverization process can be greatly lowered, the clinker cooling control difficulty in the clinker sintering process can be lowered, and the clinker sintering quality is improved. And a fundamental guarantee is provided for stable operation of production.

Description

Technical Field

[0001] The invention relates to a method for improving the extraction rate of aluminum oxide from high-aluminum fly ash and a mineralizer thereof, belonging to the technical field of aluminum oxide production. Background Art

[0002] With the continuous expansion of domestic electrolytic aluminum production capacity, demand for alumina has further increased. Although global bauxite reserves are abundant, with proven reserves reaching 32 billion tons, my country's bauxite reserves are relatively small, with proven reserves of only 680 million tons. With nearly 100 million tons of alumina production capacity, the domestic bauxite supply is extremely tight, forcing alumina producers to turn to imported bauxite for production, resulting in a dependence on imported bauxite exceeding 60%. To enhance the independent and controllable capabilities of my country's aluminum industry, seeking alternative bauxite resources has become a top priority.

[0003] The Zhungeer coalfield in the Ordos region has proven reserves of 26.7 billion tons of high-alumina coal. The coal contains an alumina content of 8.0% to 15.0%, making it a high-quality aluminum-bearing resource. Coal combustion produces high-alumina fly ash (alumina content ≥32.0%), with production reaching 8.0 billion tons, including 3.2 billion tons of alumina. Therefore, high-alumina fly ash is a valuable alternative to bauxite.

[0004] A lot of experimental research and technical verification work has been carried out on the extraction of alumina from high-alumina fly ash. Currently, several major high-alumina fly ash extraction and technical routes are as follows: 1. Acid extraction of alumina technology The activated fly ash is dissolved at high temperature using high-concentration hydrochloric acid, sulfuric acid or nitric acid. Since the acid reacts with the aluminum in the high-aluminum fly ash and enters the solution, while the acid does not react with silica, the purpose of separating aluminum from silicon in the high-aluminum fly ash is achieved. The produced aluminum salt solution is evaporated and crystallized, and the solid aluminum salt is calcined to obtain alumina. The acid can then be used to dissolve the high-aluminum fly ash again.

[0005] Because the dissolution process requires high acid concentrations and high temperatures, acid corrosion on equipment is a major challenge. Furthermore, the physical and chemical properties of the alumina produced do not meet the requirements for electrolytic aluminum, necessitating the Bayer process. This process is complex and costly, and is currently still in the experimental stage.

[0006] 2. Pre-desiliconization + soda lime sintering method The high-alumina fly ash is first pre-desiliconized to remove part of the silica and improve the A / S of the fly ash. It is then treated using the traditional soda-lime sintering method to obtain an alumina product.

[0007] This process has low desiliconization efficiency of high-alumina fly ash, and the A / S of desiliconized fly ash is only about 2.0. It is still not economical to use the soda-lime sintering method for treatment. At the same time, the sintering process can only adopt wet sintering, which has high energy consumption, poor economy, and poor economic benefits of industrial production.

[0008] 3. Limestone sintering The high-alumina fly ash is mixed with limestone and sintered. The sintered clinker is dissolved with sodium carbonate solution and then carbonized to produce crude aluminum hydroxide. The crude aluminum hydroxide is then desiliconized, dissolved and seeded to produce metallurgical grade alumina.

[0009] The main features of this process are: dry sintering, low sintering energy consumption, and the resulting calcium-silicon slag tailings can be used as a raw material for cement production. It is currently the most promising technology for extracting alumina from high-alumina fly ash.

[0010] The bottleneck of this process is that the sintering process has high technical requirements and the pulverization rate of the sintered clinker is less stable, resulting in a low dissolution rate of the clinker.

[0011] The following is a detailed description of the process for extracting alumina from high-alumina fly ash using the limestone sintering method. The principle of this process is as follows: at high temperatures, the calcium oxide in the limestone combines with the aluminum in the fly ash to form 7-aluminum-12-calcium. The calcium oxide in the limestone combines with the silicon in the fly ash to form dicalcium silicate. A small amount of iron in the fly ash combines with the aluminum and calcium to form tetracalcium aluminoferrite. Since dicalcium silicate is β-dicalcium silicate at high temperatures, it converts to γ-dicalcium silicate during cooling, expanding in volume and causing self-pulverization of the clinker.

[0012] The chemical formula is as follows: CaCO3=CaO+CO2 CaO+SIO2=2CaO.SiO2 12CaO+7Al2O3=12CaO.7Al2O3 CaO+Fe2O3+Al2O3=4CaO.Al2O3.Fe2O3 Since 7 aluminum 12 calcium can react with sodium carbonate solution to produce sodium aluminate solution, thus achieving solid-liquid separation, the sodium aluminate solution can be treated to obtain the product alumina.

[0013] According to the above batching scheme, sufficient limestone must be added during production. To achieve a high alumina dissolution rate, laboratory tests have shown that adding more limestone is not necessarily better. Excessive limestone production will produce tricalcium silicate, which not only increases the hardness of the clinker but also significantly reduces the alumina dissolution rate. Therefore, in actual production, the amount of limestone added is usually less than the theoretical amount. The ratio of the actual amount of limestone added to the theoretical amount is called the saturation ratio (KH).

[0014] The main difficulty faced by the limestone sintering method is that its main raw materials are limestone and fly ash, both of which have high sintering temperatures. To promote solid-solid reactions, the sintering process must produce a liquid phase, so the only way to achieve this is to increase the sintering temperature. The sintering temperature must be controlled high, generally above 1350°C. The higher the sintering temperature, the less stable the operation control. As a result, the temperature fluctuates, resulting in raw and over-burned clinker. Raw clinker is the most worrying issue in the limestone sintering method because raw clinker has a composition similar to cement clinker, which can cause hardening and blockage during the dissolution process, leading to production interruptions.

[0015] Therefore, in actual production, sintering aids, namely mineralizers, are usually added to improve the sintering properties of clinker. Fluorite mineralizer is a commonly used sintering aid.

[0016] While the addition of fluorite mineralizer can significantly reduce the firing temperature and significantly increase the amount of liquid phase in the sintered clinker, thus playing a role in lowering the sintering temperature, the addition of fluorite causes the liquid phase of the clinker to appear earlier. When the fluorite mineralizer addition level is high (greater than 2.0% of the raw meal), a liquid phase is generated in the preheater, causing blockage of the preheater. When the fluorite mineralizer addition level is low (1.0% of the raw meal), a large amount of liquid phase appears in the firing zone, causing rings in the firing zone, large lumps in the clinker, pools at the kiln mouth, and accumulation of material at the cooler mouth that cannot be removed, causing cooler blockage.

[0017] At the same time, the addition of fluorite mineralizer narrows the clinker firing temperature range, which is 1270-1320℃. The narrow temperature range can easily cause either raw material leakage or clinker over-burning, making it difficult to stabilize the clinker firing operation. Summary of the Invention

[0018] The present invention aims to provide a method and mineralizer for increasing the extraction rate of alumina from high-alumina fly ash. By using CSO (Chemical Sodium Sulfate) instead of fluorite as a mineralizer, the method significantly improves clinker sintering performance, lowering the firing temperature while further expanding the firing temperature range. This method enhances the stability of the clinker sintering operation and improves the extraction rate of alumina from the clinker.

[0019] The technical solution of the present invention is a method for improving the extraction rate of alumina from high-alumina fly ash. During the sintering process of high-alumina fly ash clinker for extracting alumina from limestone sintering method, a mineralizer CSO is added to the raw meal. The index requirements of the mineralizer CSO are: SO3 content>40.0%, CaO content>30.0%, and Fe2O3 and TiO2 contents both<1.0%.

[0020] In the aforementioned method for improving the extraction rate of alumina from high-alumina fly ash, the amount of the mineralizer CSO added is 3% to 10% of the raw material amount.

[0021] In the aforementioned method for improving the extraction rate of alumina from high-aluminum fly ash, the raw meal consists of material A and material B; Material A is one or a mixture of any of high-alumina fly ash, boiler slag, coal gangue, kaolin, metakaolin, and its index requirements are: Al2O3 content>32.0%, A / S>0.7, Fe2O3 content<5.0%, TiO2 and MgO content<1.0%; Material B is one of limestone, carbide slag or a mixture of the two, and its index requirements are: SiO2 content <5.0%, CaO content >48.0%, Fe2O3, TiO2, and MgO content all <1.0%.

[0022] In the aforementioned method for improving the extraction rate of alumina from high-alumina fly ash, the material A is high-alumina fly ash, and the material B is limestone.

[0023] In the aforementioned method for improving the extraction rate of alumina from high-aluminum fly ash, the proportions of material A and material B are 23.00% to 32.00% and 77.00% to 68.00%. The present invention uses the proportions of material A and material B to express the saturation ratio (KH) of the ingredients, and the proportions are calculated from the saturation ratio.

[0024] In the aforementioned method for improving the extraction rate of alumina from high-alumina fly ash, during the process of extracting alumina from high-alumina fly ash using the limestone sintering method, the raw material sintering temperature is 1280°C to 1450°C, and the sintering time is 20 to 40 minutes.

[0025] In the aforementioned method for improving the extraction rate of alumina from high-alumina fly ash, during the process of extracting alumina from high-alumina fly ash using the limestone sintering method, the sintered clinker is cooled to room temperature at a gradient of 5°C / min to 35°C / min.

[0026] In the aforementioned method for improving the extraction rate of alumina from high-alumina fly ash, during the process of extracting alumina from high-alumina fly ash using the limestone sintering method, the raw materials need to be ground to a residue of less than 5.0% on a 180-mesh sieve before sintering.

[0027] In the aforementioned method for improving the extraction rate of alumina from high-alumina fly ash, the sintering process is completed in a limestone sintering method clinker sintering kiln.

[0028] The present invention also claims protection for a mineralizer used in a method for improving the extraction rate of alumina from high-aluminum fly ash.

[0029] Beneficial effects of the present invention: Compared with the prior art, the present invention has the following advantages: (1) The present invention uses CSO as a mineralizer instead of fluorite, and expands the firing temperature range of the fluorite mineralizer from 1270℃ to 1320℃ to 1280℃ to 1450℃, further expanding the firing temperature range, which can greatly improve the clinker sintering performance and provide favorable conditions for the stable operation of the clinker kiln.

[0030] (2) The present invention uses CSO as a mineralizer instead of fluorite. During the process, the purpose is to pursue the dissolution rate of clinker instead of the pulverization rate of clinker. This can greatly reduce the stringent requirements of the cooling system required for the clinker pulverization process, reduce the difficulty of clinker cooling control during the clinker sintering process, and provide a fundamental guarantee for the stable operation of production.

[0031] (3) The present invention uses CSO as a mineralizer instead of fluorite, which improves the clinker sintering performance while increasing the clinker dissolution rate. When fluorite is used as a mineralizer, the clinker dissolution rate is 60.0%-70.0%, while the present invention uses CSO as a mineralizer to increase the dissolution rate to 85.0%. The increase in the clinker alumina dissolution rate can significantly reduce the clinker consumption of alumina and reduce the energy consumption of sintering, greatly improving the economic benefits and market competitiveness of alumina extraction from fly ash, and opening up broad space for the industrial application of alumina extraction from high-aluminum fly ash. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the examples, but they are not intended to limit the present invention. Example

[0033] raw material: Mineralizer CSO: CaO: 32.0%, SO3: 42.51% Limestone: CaO: 51.8%, Fe2O3: 2.42% High-alumina fly ash: Al2O3: 35.25%, A / S: 0.71 Firing process conditions: ingredient ratio: high-alumina fly ash 28.0% + limestone: 72.0%; mineralizer CSO addition amount: 3.0% of raw material amount (fly ash amount + limestone amount); sintering temperature: 1280℃; sintering time: 20 minutes, cooling gradient: 15.0℃ / minute.

[0034] Dissolution rate conditions: dissolution liquid-to-solid ratio: 5.0, dissolution temperature: 75.0°C, dissolution time: 30.0 minutes. Example

[0035] raw material: Mineralizer CSO: CaO: 32.0%, SO3: 42.51% Limestone: CaO: 51.8%, Fe2O3: 2.42% High-alumina fly ash: Al2O3: 35.25%, A / S: 0.71 Firing process conditions: ingredient ratio: high-alumina fly ash 28.0% + limestone 72.0%; mineralizer CSO addition amount: 3.0% of raw material amount; sintering temperature: 1280℃; sintering time: 40 minutes, cooling gradient: 15.0℃ / minute.

[0036] Dissolution conditions: liquid-to-solid ratio: 5.0, dissolution temperature: 75.0°C, dissolution time: 30.0 minutes. Example

[0037] raw material: Mineralizer CSO: CaO: 35.84.0%, SO3: 46.38% Limestone: CaO: 51.8%, Fe2O3: 2.42% High-alumina fly ash: Al2O3: 39.68%, A / S: 0.79 Process conditions: ingredient ratio: high-alumina fly ash 27.34% + limestone 72.66%; mineralizer CSO addition amount: 3.0% of raw material amount; sintering temperature: 1300℃; sintering time: 40 minutes, cooling gradient: 15.0℃ / minute.

[0038] Dissolution conditions: liquid-to-solid ratio: 5.0, dissolution temperature: 75.0°C, dissolution time: 30.0 minutes. Example

[0039] raw material: Mineralizer CSO: CaO: 35.84.0%, SO3: 46.38% Limestone: CaO: 51.8%, Fe2O3: 2.42% High-alumina fly ash: Al2O3: 39.68%, A / S: 0.79 Process conditions: ingredient ratio: high-alumina fly ash: 27.85% + limestone: 72.15%; mineralizer CSO addition amount: 3.0% of raw material amount; sintering temperature: 1350℃; sintering time: 40 minutes, cooling gradient: 15.0℃ / minute.

[0040] Dissolution conditions: liquid-to-solid ratio: 5.0, dissolution temperature: 75.0°C, dissolution time: 30.0 minutes. Example

[0041] raw material: Mineralizer CSO: CaO: 35.84.0%, SO3: 46.38% Limestone: CaO: 51.8%, Fe2O3: 2.42% High-alumina fly ash: Al2O3: 39.68%, A / S: 0.79 Process conditions: ingredient ratio: high-alumina fly ash: 28.06% + limestone: 71.94%; mineralizer CSO addition amount: 3.0% of raw material amount; sintering temperature: 1400℃; sintering time: 40 minutes, cooling gradient: 15.0℃ / minute.

[0042] Dissolution conditions: liquid-to-solid ratio: 5.0, dissolution temperature: 75.0°C, dissolution time: 30.0 minutes. Example

[0043] raw material: Mineralizer CSO: CaO: 35.84.0%, SO3: 46.38% Limestone: CaO: 51.8%, Fe2O3: 2.42% High-alumina fly ash: Al2O3: 39.68%, A / S: 0.79 Process conditions: ingredient ratio: high-alumina fly ash: 28.22% + limestone: 71.78%; mineralizer CSO addition amount: 3.0% of raw material amount; sintering temperature: 1450℃; sintering time: 40 minutes, cooling gradient: 15.0℃ / minute.

[0044] Dissolution conditions: liquid-to-solid ratio: 5.0, dissolution temperature: 75.0°C, dissolution time: 30.0 minutes. Example

[0045] raw material: Mineralizer CSO: CaO: 35.84.0%, SO3: 49.11% Limestone: CaO: 52.70%, Fe2O3: 2.42% High-alumina fly ash: Al2O3: 47.97%, A / S: 1.30 Process conditions: ingredient ratio: high-alumina fly ash: 26.68% + limestone: 73.32%; mineralizer CSO addition amount: 5.0% of raw material amount; sintering temperature: 1280℃; sintering time: 20 minutes, cooling gradient: 15.0℃ / minute.

[0046] Dissolution conditions: liquid-to-solid ratio: 5.0, dissolution temperature: 75.0°C, dissolution time: 30.0 minutes. Example

[0047] raw material: Mineralizer CSO: CaO: 35.84.0%, SO3: 49.11% Limestone: CaO: 52.70%, Fe2O3: 2.42% High-alumina fly ash: Al2O3: 47.97%, A / S: 1.30 Process conditions: ingredient ratio: high-alumina fly ash: 26.55% + limestone: 73.45%; mineralizer CSO addition amount: 8.0% of raw material amount; sintering temperature: 1300℃; sintering time: 20 minutes, cooling gradient: 15.0℃ / minute.

[0048] Dissolution conditions: liquid-to-solid ratio: 5.0, dissolution temperature: 75.0°C, dissolution time: 30.0 minutes. Example

[0049] raw material: Mineralizer CSO: CaO: 35.84.0%, SO3: 49.11% Limestone: CaO: 52.70%, Fe2O3: 2.42% High-alumina fly ash: Al2O3: 47.97%, A / S: 1.30 Process conditions: ingredient ratio: high-alumina fly ash: 26.32% + limestone: 73.68%; mineralizer CSO addition amount: 10.0% of raw material amount; sintering temperature: 1350℃; sintering time: 20 minutes, cooling gradient: 15.0℃ / minute.

[0050] Dissolution conditions: liquid-to-solid ratio: 5.0, dissolution temperature: 75.0°C, dissolution time: 30.0 minutes.

[0051] raw material: Mineralizer CSO: CaO: 35.84.0%, SO3: 49.11% Limestone: CaO: 52.70%, Fe2O3: 2.42% High-alumina fly ash: Al2O3: 47.97%, A / S: 1.30 Process conditions: ingredient ratio: high-alumina fly ash: 26.19% + limestone: 73.81; mineralizer CSO addition amount: 10.0% of raw material amount; sintering temperature: 1400℃; sintering time: 20 minutes, cooling gradient: 15.0℃ / minute.

[0052] Dissolution conditions: liquid-to-solid ratio: 5.0, dissolution temperature: 75.0°C, dissolution time: 30.0 minutes.

[0053] In order to verify the feasibility of the method in the above embodiment, a production experiment was conducted according to the method in the above embodiment, and corresponding observations and records were made during the experiment. The specific steps are as follows: S1: Grind the raw materials until the residue on the 180-mesh sieve is less than 5.0%, which is convenient for uniform mixing and sufficient reaction in the later stage; S2: Prepare raw material according to the percentage of fly ash and limestone; S3: Add the mineralizer CSO to the raw meal according to the corresponding raw meal amount ratio; S4: sintering the raw material according to the sintering temperature and sintering time specified in the embodiment; S5: Lower the temperature of the sintered clinker to room temperature according to the cooling gradient specified in the embodiment. Observe and record the pulverization rate of the clinker. S6: Grind the sintered clinker to a size of less than 180 mesh. Analyze the clinker composition: alumina, silicon oxide, calcium oxide, and iron oxide content; S7: dissolving the ground clinker with 50-100 g / L sodium carbonate solution; Dissolution rate conditions: The dissolution reaction was carried out according to the dissolution conditions specified in the examples, and the dissolution solution was filtered. The dissolution filtrate was analyzed for Nt and AO; the dissolution tailings - silica-calcium slag was washed and the alumina and calcium oxide content of the tailings was analyzed; S8: Calculation of dissolution rate: The dissolution rate of alumina: =100 (1-(silicon calcium slag AO / silicon calcium slag CaO) / (clinker AO / clinker CaO)).

[0054] The recorded technical indicator data are as follows:

[0055] From the above results, it can be seen that when the amount of mineralizer remains unchanged, the dissolution rate of alumina shows a trend of first increasing and then decreasing with the increase of sintering temperature, but can generally maintain a dissolution rate above 70%. However, the powdering rate shows a downward trend with the increase of sintering temperature.

[0056] When the mineralizer dosage is 3% to 10%, the sintering temperature is 1280℃ to 1450℃, and the sintering time is 20 to 40min, the dissolution rate of alumina can be kept at a high level, reaching a maximum of 85.47%, but the pulverization rate is greatly affected, with the lowest being 0.00%. However, the above scheme fully meets the technical requirements of pursuing the dissolution rate of clinker without deliberately pursuing the pulverization rate of clinker.

[0057] In the above embodiment, the sintering temperature range of 1280℃-1450℃ is selected because if the sintering temperature is lower than 1280℃, the clinker is likely to be burned raw, and 1280℃-1450℃ already provides a wider temperature range. It is easy to control the clinker burning operation within this range. Further increasing the sintering temperature will not significantly increase the dissolution rate. In addition, increasing the sintering temperature will lead to increased energy consumption, increased production costs, and higher requirements for equipment. From an economic point of view, it is not recommended to further increase the sintering temperature.

[0058] In addition, we also conducted two phases of experiments, focusing on laboratory tests to examine the effects of different mineralizer addition amounts on clinker pulverization rate and dissolution rate.

[0059] The trial is divided into two phases: Phase I: Investigate the fly ash of Company A and the limestone mix from our company’s operation center, and conduct sintering tests by adding different mineralizers.

[0060] The effects of mineralizer addition on clinker dissolution rate and pulverization rate were investigated by adding no mineralizer, adding 1.0% fluorite mineralizer, adding 1.0%, 2.0%, and 3.0% CSO, with the fly ash and limestone proportions being 23.00% to 32.00% and 77.00% to 68.00%; the sintering temperature was in a wide range from 1280℃ to 1450℃, the sintering time was 40 minutes, and the temperature was lowered to 1100℃ for cooling.

[0061] The test data are summarized as follows:

[0062] Test conclusion: In the limestone sintering fly ash extraction process, without the addition of mineralizers, the dissolution rate and pulverization rate of the sintered clinker are both low. Therefore, mineralizers must be added to improve the sintering performance of the clinker and increase the pulverization rate and dissolution rate of the sintered clinker.

[0063] Tests have shown that fluorite mineralizers can significantly increase the liquid phase volume of sintered clinker, which is beneficial for improving the pulverization rate and dissolution rate at low temperatures. However, as the temperature rises, the liquid phase volume of the sintered clinker increases significantly, which can easily cause clinker pooling and hinder the control of the sintering process.

[0064] The experiments fully demonstrated that the mineralizer CSO can improve the pulverization and dissolution rates of sintered clinker. Compared with fluorite mineralizer, the addition of 3.0% CSO outperformed fluorite mineralizer in both pulverization and dissolution rates. Within the 100°C range of 1300°C to 1400°C, the dissolution rate exceeded 80.0%.

[0065] Phase II: We examined Company B's fly ash (alumina content greater than 45.0%) and our company's operating center limestone batching, and conducted sintering tests with different mineralizers. We increased the alumina content in the fly ash to determine the optimal mineralizer dosage and the most suitable sintering temperature and time.

[0066] By adding 1.0% fluorite mineralizer as the basis for comparison, and comparing with adding 3.0%, 5.0%, 8.0%, 10.0%, 15.0%, and 12.0% mineralizer CSO, the proportion of fly ash and limestone is: 23.00%~32.00%: 77.00~68.00%. Under the same conditions, the sintering temperature ranges from 1280℃ to 1400℃, the sintering time is 20 minutes, and the temperature is cooled to 1000℃-1100℃ before being taken out for cooling. In this way, the effect of the addition of mineralizer on the dissolution rate and pulverization rate of the clinker is investigated.

[0067] The test data are shown in Table 3 below:

[0068] From the sintering test results, the following conclusions can be drawn: For clinker sintered with high-alumina fly ash (AO content greater than 45.0%), the dissolution rate gradually increases with increasing CSO addition. See the table above: at 1280°C, with 5.0% CSO added, the solid-phase dissolution rate is 76.03%; at 1300°C, with 8.0% CSO added, the solid-phase dissolution rate is 85.47%; and at 1350°C, with 10.0% CSO added, the solid-phase dissolution rate is 84.98%.

[0069] By comparing the addition of 1.0% fluorite mineralizer and the addition of CSO mineralizer above 3.0%, fluorite has no obvious advantage in the pulverization rate and dissolution rate of sintered clinker.

[0070] As the amount of CSO added increases, the dissolution rate of the sintered clinker increases, but the pulverization rate is poor, or even non-pulverization. Therefore, for clinker sintered with fly ash containing high AO content, it is not easy to pursue a high pulverization rate; instead, the dissolution rate should be the primary goal. This allows for much more relaxed control over the clinker cooling system, which helps reduce the process requirements of the clinker sintering process.

[0071] When the clinker sintering temperature is kept at 1350°C and the sintering time is controlled to be no less than 20 minutes, and the CSO mineralizer addition level is controlled within the range of 3.0% to 10.0%, the clinker dissolution rate is consistently above 82.0%, with a maximum of 84.98%. Therefore, at this temperature, fluctuations in the CSO mineralizer addition have little effect on the clinker dissolution rate.

[0072] The invention relates to a method for extracting aluminum oxide from high-aluminum fly ash using a limestone sintering process. The sintering process is completed in a limestone sintering process clinker sintering kiln.

[0073] In addition to claiming a method for increasing the alumina extraction rate from high-alumina fly ash, the present invention also claims a mineralizer used in the method, namely CSO, with the following performance requirements: SO3 content >40.0%, CaO content >30.0%, and Fe2O3 and TiO2 contents both <1.0%. The CSO is added in an amount of 3% to 10% of the raw meal.

Claims

1. A method for improving the extraction rate of alumina from high-alumina fly ash, characterized by: In the limestone sintering method, alumina clinker is extracted from high-alumina fly ash and a mineralizer CSO is added to the raw meal. The index requirements of the mineralizer CSO are: SO3 content > 40.0%, CaO content > 30.0%, and Fe2O3 and TiO2 contents are both < 1.0%.

2. The method for improving the extraction rate of alumina from high-alumina fly ash according to claim 1, characterized in that: The amount of the mineralizer CSO added is 3% to 10% of the raw material amount.

3. The method for improving the extraction rate of aluminum oxide from high-aluminum fly ash according to claim 1, characterized in that: The raw material consists of material A and material B; Material A is one or a mixture of any of high-alumina fly ash, boiler slag, coal gangue, kaolin, metakaolin, and its index requirements are: Al2O3 content>32.0%, A / S>0.7, Fe2O3 content<5.0%, TiO2 and MgO content<1.0%; Material B is one of limestone, carbide slag or a mixture of the two, and its index requirements are: SiO2 content <5.0%, CaO content >48.0%, Fe2O3, TiO2, and MgO content all <1.0%.

4. The method for improving the extraction rate of aluminum oxide from high-aluminum fly ash according to claim 3, characterized in that: The material A is high-alumina fly ash, and the material B is limestone.

5. The method for improving the extraction rate of aluminum oxide from high-aluminum fly ash according to claim 3, characterized in that: The proportion of material A and material B is: 23.00%~32.00%:77.00~68.00%.

6. The method for improving the extraction rate of alumina from high-alumina fly ash according to claim 1, characterized in that: In the process of extracting alumina from high-alumina fly ash using the limestone sintering method, the raw material sintering temperature is 1280℃~1450℃, and the sintering time is 20~40min.

7. The method for improving the extraction rate of aluminum oxide from high-aluminum fly ash according to claim 6, characterized in that: During the process of extracting alumina from high-alumina fly ash using the limestone sintering method, the sintered clinker is cooled to room temperature at a gradient of 5°C / min to 35°C / min.

8. The method for improving the extraction rate of aluminum oxide from high-aluminum fly ash according to claim 1, characterized in that: In the process of extracting alumina from high-alumina fly ash by limestone sintering method, the raw materials need to be ground to a residue of less than 5.0% on 180 mesh sieve before sintering.

9. The method for improving the extraction rate of aluminum oxide from high-aluminum fly ash according to claim 1, characterized in that: In the method, the sintering process is completed in a limestone sintering method clinker sintering kiln.

10. A mineralizer used in the method for improving the extraction rate of alumina from high-aluminum fly ash as claimed in any one of claims 1 to 9.

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