Processing method of alkaline aluminosilicate raw material

Abstract

The present disclosure relates to chemical and non-ferrous metallurgy and can be used to treat alkaline aluminosilicate feedstocks by sintering to produce alumina and sodium products (soda, potash and potassium sulfate). The method of treating an alkaline aluminosilicate feedstock of the present invention comprises preparing a charge comprising nepheline ore, limestone, and a recovered soda alkaline solution and a reducing agent; coal is used as a process fuel sintering furnace material; and leaching the sinter, wherein the content of the reducing agent in the charge is 0.8-1.5 wt% of the weight of the dry charge. During the production of the charge, a recovered soda alkaline solution is added in an amount of 5.5-6.5 wt% R2O based on the weight of the dry charge, the charge is sintered at a temperature of 1, 245-1, 255 DEG C, the charge is sintered in a reducing atmosphere containing no less than 3 g / m3 of carbon oxide. The process allows for increased specific yields of alumina and sodium products and reduced specific fuel consumption.

Description

Technical Field

[0001] The present disclosure relates to chemical and nonferrous metallurgy, and it can be used to process basic aluminosilicate feedstocks to produce alumina and sodium products such as soda, potash, and potassium sulfate by sintering. Background Art

[0002] AI Lainer et al., "Alumina Production", published in Moscow: Metallurgia in 1978, and IN Kitler and Yu.A., "Lainer Nephelines as a complex raw material for the aluminum industry", published in Moscow: Metallurgia in 1962, teach on page 238 a method for producing alumina and sodium products by sintering from raw or concentrating or concentrated nepheline ore, limestone and recovered products (soda solution and desiliconized sludge (i.e., sludge obtained as a result of desiliconization)).

[0003] According to a known method, a charge from a mixture of raw or concentrating (concentrated) nepheline ore, limestone and recycled products is prepared to produce agglomerates containing aluminum and alkali metals, or simply agglomerates. The charge ground to a target size is sintered in a rotary kiln at a temperature of about 1,220 to 1,350°C. The agglomerate, which is also crushed to a target size, is leached with an alkaline solution of soda to obtain an alkaline aluminate solution. Alumina and sodium products (soda, potash and potassium sulfate) are produced from the alkaline aluminate solution by hydrolysis, carbonation, evaporation and calcination. When preparing the charge to be sintered, a target molar ratio is obtained in the charge, i.e., the amount of limestone is adjusted to a CaO / SiO2 molar ratio of 2±0.1 to obtain a poorly soluble phase of dicalcium silicate (Ca2SiO4) during sintering. The amount of soda solution recovered is adjusted to a molar ratio of R2O (the sum of Na2O and K2O, based on Na2O) / Al2O3 of 1±0.1 to obtain a poorly soluble phase of sodium aluminate (NaAlO2) in the sinter. Said ratios, also referred to as lime to silica (L / S) and alkali to alumina (A / A) ratios, respectively, are also applied when the nepheline ore is of high quality, i.e. when the content of harmful impurities (mainly iron and sulfur) in said ore is low. (e.g., nepheline concentrate from the Kola Peninsula or part of the ore from the Kia-Shayrine mine).

[0004] Unfortunately, most nepheline ores contain increased amounts of iron- and sulfur-containing minerals (hornblende and other amphibole, emerald-pyroxene, pyrite and other iron-containing sulfides, various forms of magnetite, including titanomagnetite, etc.). The iron and sulfur also interact with the alkali during the sintering process to form sodium ferrite (NaFeO2) and sodium sulfate (Na2SO4). This interaction results in a disturbance or imbalance in the alkali metal to alumina molar ratio (i.e., A / A ratio) and results in lower alumina recovery, secondary losses of alkali metal with poorly soluble sodium ferrite, etc.

[0005] In order to solve the problem of molar ratio disturbance (imbalance) in the charge due to high content of sulfur and iron, an additional amount of recovered soda solution (i.e. solution containing dissolved Na2CO3) is added when the charge is obtained to restore the molar ratio. Due to this operation, part of the soda solution is no longer used for the production of sodium products, which leads to a 10-20% reduction in the yield of said product. In addition, sulfur and iron compounds form low-melting compounds called "eutectics", which lead to emergency stops of the rotary kiln due to very large accumulations in the form of ring structures and crusts.

[0006] In nature, it is quite rare to find nepheline ores containing low iron contents. Therefore, right at the beginning of the development of the technology or method for processing (conversion) nepheline into alumina, it was proposed to carry out sintering in the presence of a reducing agent (charcoal or lignite, or brown coal), which was added in an amount required to reduce all the iron to metallic iron (E.I Khazanov, AF Khlyupina, A.S. Bessonov et al. in the article "On the Sintering of the Uzhur Nepheline Syenites with Limestone in the presence of a Reducer", abstract of a report presented at the 3rd Coordination Meeting on the Development of Light Metallurgy Based on Local Ores in Eastern Siberia, American Academy of Sciences Eastern Siberia, Irkutsk, 1956 (E.I Khazanov, AF Khlyupina, A.S. Bessonov et al. "On the Sintering of the Uzhur Nepheline Syenites with Limestone in the presence of a Reducer", abstract of a report presented at the 3rd Coordination Meeting on the Development of Light Metallurgy Based on Local Ores in Eastern Siberia, American Academy of Sciences Eastern Siberia, Irkutsk, 1956 rdCoordination Meeting regarding the Development of Light Metals Metallurgy in Eastern Siberia on the basis of local ores, Eastern Siberian Branch of the USSR Academy of Sciences, Irkutsk, 1956)). This method was developed for processing high-iron nepheline from Western Siberia. When sintered in the presence of a reducing agent, i.e. during reduction sintering, the high-iron problem is solved by converting the iron into its inert form, i.e. metallic iron. This method has its disadvantages:

[0007] - Burning of relatively large quantities of coal (more than 5% of the charge weight) results in the formation of large quantities of CO, which can lead to "pops" or explosions, and fires in electrostatic precipitators (ESPs).

[0008] -Using large amounts of coal reduces the production of the rotary kiln.

[0009] - The highly reducing atmosphere leads to the volatilization and loss of a large amount of alkali, especially potassium, due to the reduction of alkali to metal. This leads to composition problems of the sinter, that is, molar ratio problems in the sinter.

[0010] The above disadvantages significantly reduce the advantages of processing (converting) high-iron and high-sulfur nepheline into alumina; they even call into question the possibility of carrying out the sintering process in industrial rotary kilns due to the potential for explosions.

[0011] RU 2313491 dd. December 27, 2007, teaches a method of processing an aluminum-containing raw material (nepheline) by reducing (or reducing) melt processing at 1,450-1,660° C., including conversion of all iron into ferrosilicon (ferrosilicon). For further sale, the ferrosilicon (ferrosilicon) is separated from the phase containing aluminum and alkali metals, and the remaining part of the sinter is processed according to existing methods into aluminum oxide and sodium products.

[0012] Following are the main disadvantages of the above approach:

[0013] - The consumption of reducing agents increases, which leads to large carbon emissions.

[0014] - Low quality ferrosilicon (ferrosilicon) due to the impossibility of separating ferrosilicon (ferrosilicon) from sodium aluminate and Ca2SiO4 (commonly known as belite, as in Portland cement manufacturing) by melting.

[0015] -Due to the extremely high temperature of reduction sintering, the volatility of alkali is very high.

[0016] RU 2417162dd.27.04.2011 is the closest prior art. It teaches a method for treating alkaline aluminosilicate raw materials, comprising preparing a charge containing strengthening additives of fluoride and coal, sintering the charge and treating the sinter, wherein 0.2-2.5% by weight of the dry charge of aluminum production waste containing fluorine carbon is used as a strengthening additive, sintering is carried out at a temperature of 1,150-1,260° C. and the sinter is leached. This technical solution allows to reduce the sintering temperature, convert iron into its inert form and thus increase the yield of sodium products (soda and potash), but the method still has several disadvantages, including the following:

[0017] - the presence of a low melting point eutectic between CaF2 and NaF leading to extreme build-up in the kiln (i.e., crusting in the sinter formation zone), and

[0018] - Fluorine enters the soda solution from the sinter and then into commercial sodium carbonate (which is produced from nepheline), which reduces its quality and makes it impossible to produce high, premium quality soda. DETAILED DESCRIPTION

[0019] This disclosure provides the following:

[0020] - The specific yield of sodium product per ton of ore processed increases due to the reduction in the amount of soda solution returned to the beginning of the process (recovery) to bind iron and sulphur.

[0021] - Since the reducing agent (coal) locally heats the interior of the sinter 20-25°C higher than the kiln temperature, fuel consumption is reduced due to lower sintering temperatures. As a result, CO2 emissions, i.e. CO2 emissions, are lower per ton of alumina produced.

[0022] Additional benefits of the present disclosure:

[0023] - Extreme agglomeration (crust / ring formation) is reduced, with the result that the risk of emergency kiln shutdown is reduced, which is made possible by a reduction in sintering temperature of about 25°C and a reduction in the amount of melt produced, i.e. the risk of forming low-melting eutectics with the participation of ferric iron.

[0024] - Additional alumina and alkali production due to higher throughput of the sintering kiln.

[0025] - No need to use expensive flotation separation; can process high iron ore.

[0026] The method for treating alkaline aluminosilicate materials of the present invention comprises preparing a furnace charge comprising nepheline ore, limestone and a recovered soda alkaline solution and a reducing agent; sintering the furnace charge using coal as a process fuel; and leaching the sinter. The reducing agent content in the furnace charge is 0.8-1.5 wt% of the dry furnace charge weight, wherein the recovered soda alkaline solution is added during the preparation of the furnace charge in an amount of 5.5-6.5 wt% of R2O based on the dry weight of the furnace charge.

[0027] The charge is sintered at a temperature of 1,245-1,255°C, wherein the charge contains not less than 3 g / m 3 The amount of carbon oxides in the sintering process is greater than 3g / m 3 The carbon-containing oxides allow a low reducing atmosphere to be maintained in the kiln, in which the ferrous iron from pyrite and hornblende is not reduced to ferric iron. As a result, it does not combine with soda to form sodium ferrite. The presence of carbon oxides in the atmosphere is controlled by the amount of reducing agent introduced into the feed and the nature of the reducing agent. 3 The carbon-containing oxides are insufficient to keep the iron in pyrite and hornblende in ferrous form. Therefore, it is partially oxidized to ferric iron (Fe +3 ) and reacts with soda to form sodium ferrite (NaFeO2). Greater than 4.5g / m 3 The amount of carbon oxides affects the operation of the electrostatic precipitator (ESP) of the gas treatment station located downstream and is therefore not recommended. The above carbon oxide concentration is ensured by introducing 0.8 to 1.5% of a reducing agent into the feed, the reducing agent comprising a volatile matter content (VMC) of not more than 16 wt%.

[0028] The charge may contain nepheline ore containing not less than 7 wt % iron and not less than 1 wt % sulfur.

[0029] The amount of the recovered soda alkaline solution was adjusted to an alkali metal to alumina (A / A) ratio of 1.0.

[0030] A carbonaceous material may be used as the reducing agent, said material comprising a volatile content of not more than 16 wt%.

[0031] Hard coal and / or semi-coke and / or coke powder may be used as the carbonaceous material.

[0032] T-grade hard coal (GOST 25543-2013 / ISO 562) or other reducing agents with low VMC (i.e., close to T-grade coal) (e.g., semi-coke or coke powder) can be introduced into the charge during the grinding stage. When grinding, the coal rubs itself with the surface of the mineral particles of the charge. Since the coal is "rubbed" to have a high specific gravity (ρ = 2.6-2.7 g / cm 3) of the nepheline and limestone mineral particles, and coal has a hydrophobic (non-wettable) surface and a low specific gravity (ρ = 1.55 g / cm 3 ), there is no separation and floating of coal particles at a feed humidity of 28-33%. The coal as a reducing agent enters the kiln uniformly with the charge for sintering. When fed in large quantities (and not atomized by pressure through a nozzle), it is dried and granulated. When granulated, the "fried" coal remains evenly distributed within the particles of the charge and does not enter the electrostatic precipitator (ESP) with the dust (that is, there is no risk of fire and explosion). Entering the high-temperature zone, it gradually burns in the temperature range of 160 to 820°C in the absence of free O2. Due to the lack of free O2, carbon monoxide (CO) is locally discharged. The local CO concentration is 0.5 to 5 g / m3 (optimally 3 g / m3) and is sufficient to maintain a low reducing atmosphere, including taking into account the carbon dioxide emitted during the thermal decomposition of limestone and the combustion of the main part of the oxygen in the pulverized coal fuel flame. After CO diffuses from the sinter into the kiln atmosphere, it is oxidized into fire-proof and explosion-proof CO2 in the coal flame according to the following formula:

[0033] 2CO+O2→2CO2 (1),

[0034] And will not lead to critical concentrations in the ESP which could cause a "pop" or explosion due to CO combustion.

[0035] In this local low-reducing atmosphere, the iron and ferrous forms (Fe +2 ) maintains its chemical valence, i.e., it does not oxidize to Fe +3 . Ferrous iron (Fe +2 ) has a basic property, that is, it does not interact with alkali. Therefore, when preparing the charge, there is no need to feed soda solution to bind ferric iron to sodium ferrite according to the following reaction:

[0036] Fe2O3+Na2CO3→2NaFeO2+CO2↑ (2)

[0037] The recovered soda solution is not used in connection with the ferrous form (FeO) (which is inert to alkalis) and sulfur. Instead, the recovered soda solution is sent to commercial soda ash (sodium carbonate) production areas.

[0038] Furthermore, due to the reducing atmosphere, during the sintering process, iron and sulfur in the charge in the form of pyrite (FeS2) remain inert as they are converted into inert compounds such as pyrrhotite-troilite (FeS), which does not require a soda solution to bind ferric iron and sulfate into sodium ferrite and sodium sulfate.

[0039] The combustion of coal in the granular charge (sinter) results in a local temperature jump in the sinter of 20-30° C. Thus, the sinter formation temperature is reduced by 20-30° C., which allows to reduce the fuel consumption per ton of sinter by reducing the temperature of the exhaust gases from the rotary kiln.

[0040] The above reduction sintering method can be used in the Achinsk alumina refinery when switching the raw materials from the currently almost depleted Kia-Shaltyr nepheline mine to concentrate or raw ore from the Goryachogrsk nepheline mine and beneficiation plant currently under construction.

[0041] In industry, the sintering of wet charge is carried out in rotary kilns, the working principle of which is based on the counterflow of the material to be sintered, which is fed in bulk from the "cold" end to the hot gases generated during the combustion of pulverized coal fuel, which are removed through the "cold" end and sent to a gas treatment center. During the sintering process in a low reducing atmosphere, the following reactions occur:

[0042] - Pyrite and other sulfides contained in limestone and nepheline are partially desulfurized and form alkali-inert compounds such as pyrrhotite-troilite according to the following reaction:

[0043] FeS2+O2→FeS+SO2↑ (3)

[0044] - The ferric and ferrous iron contained in dark aluminosilicates such as hornblende - amphibole, omphacite - pyroxene - is released in the form of wüstite (FeO) and / or magnetite (Fe3O4).

[0045] - The interaction of alumina and the alkali contained in nepheline (Na,K)1[AlSiO4] and silicon with limestone results in the formation of sodium aluminate and dicalcium silicate according to the following reaction:

[0046] Na[AlSiO4]+2CaCO3→NaAlO2+Ca2SiO3+CO2↑ (4)

[0047] β-Dicalcium silicate (belite) formed in a reducing atmosphere is more resistant to leaching by alkaline solutions of soda, which increases the alumina yield per ton of nepheline ore due to the reduction of secondary losses during the desiliconization process.

[0048] - There is a certain decrease in the temperature of the beginning and end of the decomposition of limestone, which is explained by the combustion of carbon at 600-820 ° C, which is accompanied by an exothermic reaction and a temperature increase in the charge layer, which temperature (temperature) becomes higher than the temperature in the combustion zone of the furnace itself; the lower the temperature of the conversion of limestone to lime, the lower the temperature and the higher the rate of the main sinter formation reactions during the sintering of the charge from alkaline aluminosilicate materials, including the formation of sodium aluminate. In addition, since iron is the main alkali-inert form, solid solutions of sodium aluminate and ferrite (NaAlO2–NaFeO2) are not formed, which are poorly soluble and form ferrihydrite, which adsorbs alkalis. The absence of solid solutions has a positive effect on the recovery of alumina and alkalis from the sinter.

[0049] - All other conditions being equal, lower contents of active iron and sulfur in the agglomerate allow widening the agglomerate formation temperature range, since the risk of eutectic formation is lower and the amount of low-melting eutectic is lower. As a result, a high-quality porous mass is obtained that ensures a higher yield of alumina and alkali from nepheline, due to a more complete reaction. It provides additional output of alumina and alkali.

[0050] The method is carried out on a laboratory scale. As basic aluminosilicate raw material, nepheline concentrate from the Goryachersk nepheline mine (hereinafter referred to as Goryachersk) is used. The concentrate will be processed at the Achinsk alumina refinery (Achinsk). Other materials are used. For more information, see Table 1.

[0051] Table 1

[0052]

[0053] *LOI—Loss on Ignition.

[0054] As raw materials for the furnace charge, limestone from the Mazulsky limestone mine (hereinafter referred to as Mazulsky), recycled desiliconized sludge and a mixture of sodium carbonate and potassium carbonate (i.e. soda and potash) were used. As a reducing agent, poor hard coal (T grade) from the Kiyzassky mine (Kemerovo region) was used; it was used in Achinsk.

[0055] For sintering, two charges were prepared; the charges had different component molecular ratios:

[0056] Charge 1 - recycled soda is added to combine Al2O3 with alkali in a molar ratio (MR) of 1, i.e. (Na2O+K2O):Al2O3=1;

[0057] Feed 2 - recycled soda is added to combine Al2O3, Fe2O3 and SO3 with the alkali in a molar ratio (MR) of 1, i.e. (Na2O+K2O):ΣAl2O3+Fe2O3+SO3=1.

[0058] Sintering was carried out in a controlled atmosphere at two different temperatures with and without the addition of a reducing agent (coal) at 0.8% and 1.5% addition.

[0059] Table 2 explains that the amount of reducing agent added is 0.8-1.5%.

[0060] Table 2

[0061]

[0062] Since the optimum molecular alkali:alumina ratio is set to 1 (MR=1, i.e. (Na2O+K2O):Al2O3=1) for nepheline-based charge, the amount of alkali should be 5.5-6.5% (see Table 4) to effectively carry out the process.

[0063] The temperature range in which the agglomerate has satisfactory technological quality, i.e., it ensures the formation of sodium (potassium) aluminate and ferrite and good solidification of dicalcium silicate, is called the agglomerate formation temperature range. This range is characterized by maximum recovery of useful components (alumina and alkali) from the agglomerate during leaching, sufficient mechanical properties (strength) and sufficient porosity.

[0064] Formally, the concept of "sinter formation temperature range" corresponds to the difference between the melting (melting) temperature of the charge and the temperature at which the formation of sodium (potassium) aluminate and ferrite and dicalcium silicate is almost complete. The greater this difference, the more likely it is to produce a sintered block with sufficient porosity and to produce such a block under industrial conditions.

[0065] With the above charge composition, sintering at a temperature below 1,245°C results in insufficient sintering and secondary loss of useful components during leaching. Temperatures above 1,255°C result in the formation of clinker and then frit (melt), which also results in a reduced recovery rate of useful components. Table 3 provides some experimental data.

[0066] Table 3

[0067]

[0068] Figure 1 A schematic diagram showing a process / apparatus for sintering a charge in a controlled reducing atmosphere, including controlling the change in the atmosphere composition during combustion of the reducing agent and during other reactions, said apparatus comprising:

[0069] 1–40-dm 3Bottles, filled with gaseous nitrogen of grade 1 (according to GOST 9293-74 (ISO 2435-73)) at a pressure (T=20°C) of 150 atm, having the following characteristics: not less than 99.999 vol%, not more than 0.0005 vol%, not more than 0.0007 vol%, not more than 0.0002 vol%, not more than 0.0003 vol% of methane;

[0070] 2 – Pressure reducing valve (regulator);

[0071] 3-fine adjustment valve;

[0072] 4–PVC medical tube 6*1.5mm;

[0073] 5 – flow meter;

[0074] 6 – represents flow meter;

[0075] 7 – Gas analyzer, used to measure the atmospheric gas phase;

[0076] 8 – Gas analyzer for measuring the gas phase composition of the exhaust gases from the furnace;

[0077] 9 – Ambient air intake nozzle; and

[0078] 10 – Box furnace.

[0079] A comparative test was conducted to evaluate the effect of reducing agent in the feed on the recovery of alumina and alkali from sinter as follows:

[0080] Based on nepheline concentrate from Goryachegorsk, limestone from Mazulsky and other components, the briquettes were molded. The charge had a target particle size (100% passing through a 0.08 mm sieve) and chemical composition (MR=1, ie, (Na2O+K2O):Al2O3=1, CaO:SiO2=2 and MR=1, ie, (Na2O+K2O):ΣAl2O3+Fe2O3+SO3=1, CaO:SiO2=2), i.e. the chemical composition of the feed was based on the target A / A and L / S ratios.

[0081] The briquettes are placed on lightweight refractory clay trays and placed in a box furnace (10) at room temperature.

[0082] Start heating the box furnace at a target rate of 10°C / min, start adding nitrogen from the bottle (1) through the pressure reducing valve (2), the fine adjustment valve (3) and the flow meter (5), adjust the furnace atmosphere exchange rate to 100 times per hour, turn on the automatic gas analyzer (7) and the automatic gas analyzer (8) for the composition and amount of the furnace exhaust gas, and measure the contents of oxygen, carbon monoxide and carbon dioxide (CO and CO2), nitrogen oxides and carbon dioxide (NO and NO2).

[0083] After reaching the target sintering temperature, the sintered product was soaked at the reaction temperature for 30 minutes, and then cooled at 15°C / min for 8 hours in a closed furnace.

[0084] After the sinter was cooled to room temperature, it was crushed to -1 mm (100%) and leached with a soda alkaline solution at 75° C. The chemical composition was analyzed in the liquid phase and the mud after leaching; the recovery of alkali and alumina was calculated based on the addition of reducing agent, A / A ratio and sintering temperature.

[0085] Example

[0086] The furnace charge which had been pre-dried and ground to -0.08 mm (i.e. 100% of the material passed through a 0.08 mm sieve) was thoroughly mixed and crushed using a mechanical press at 200 kg / cm 2 The preform is molded under a specific pressure and sintered at 1,250 and 1,275°C on a light refractory clay substrate, reaching the target temperature at a rate of 10°C / minute. The target temperature is reached at a rate of 10°C per minute. Then soak for 30 minutes. The sinter is then cooled with the furnace for 8 hours, from 1,250-1,275°C to 20-25°C to prevent damage to the furnace lining. After cooling, the sinter is crushed and leached with a soda alkaline solution according to the following method:

[0087] - The obtained sinter was crushed in a metal mortar to -1.0 mm (ie 100% of the material passed through a 1.0 mm sieve);

[0088] - Leaching temperature: 75±1℃;

[0089] - Leaching time: 15 minutes;

[0090] - Composition of the soda alkaline solution used for leaching the sinter (same composition in all experiments), g / dm3: Na2O total –34.6; Na2O caust. –7.2; Na2O carb. –27.4;

[0091] - L (liquid): S (solid) ratio, during standard leaching = 4:1 (per 100 cm 3 Solution 25g sintered product);

[0092] - Use propeller stirrer for stirring, stirring speed: 200 rpm,

[0093] - The standard leached mud was filtered and vacuum washed in a Büchner funnel with hot distilled water (about 12 times the mud weight), after which the solution and mud were sampled and analyzed using known methods: Inductively Coupled Plasma Atomic Emission (ICP AS), X-ray Diffraction (XRD), X-ray Fluorescence (XRF); the remaining mud was dried to constant weight.

[0094] Alumina and alkali (see Table 4) extracted from the sinter into solution during the leaching process were calculated based on the slurry chemical analysis. Table 4 shows how the introduction of a reducing agent into the charge affects the quality of the sinter and the process parameters.

[0095] Table 4

[0096]

[0097]

[0098] From Table 4 we can see that:

[0099] - Charge 1 (MR=1, i.e. (Na2O+K2O):Al2O3=1). The introduction of 1.5% of reducing agent (based on the charge weight) allowed to reduce the sintering temperature to 1,250°C and thus reduce fuel consumption and increase the yield of sodium product. The higher alumina yield is due to the higher kiln throughput (Table 4, Example 6);

[0100] - Charge 1 (MR=1, i.e. (Na2O+K2O):Al2O3=1). Sintering at 1,250°C without a reducing agent resulted in insufficient sintering and the formation of alkaline aluminosilicates and calcium ferrites, which resulted in alumina and alkali losses (Table 4, Example 4); and

[0101] - Charge 2 (in which recycled soda is added to bind Al2O3, Fe2O3 and SO3 with alkali at MR=1, i.e. (Na2O+K2O):ΣAl2O3+Fe2O3+SO3=1). The introduction of 1.5% of reducing agent (based on the weight of the charge) allows to reduce the sintering temperature from 1,275°C to 1,250°C and thus reduce fuel consumption. The higher alumina production is due to the higher kiln throughput; the production of sodium product is not higher (Table 4, Example 12);

[0102] Therefore, the experimental data and examples confirm the above-mentioned benefits provided by the present invention.

[0103] In view of the above detailed description and embodiments of the present invention, legal protection is sought for a method of processing an alkaline aluminosilicate raw material, said method comprising preparing a charge comprising nepheline ore, limestone and a recovered alkaline solution of soda and a reducing agent, sintering the charge using coal as a process fuel, and leaching the sinter, wherein the content of the reducing agent in the charge is 0.8-1.5 wt% of the dry charge weight, and when preparing the charge, the recovered alkaline solution of soda is added in an amount of 5.5-6.5 wt% of the charge weight on a dry basis. Preferably, the charge is sintered at a temperature of 1,245-1,255°C, and the recovered alkaline solution of soda is added at a temperature comprising not less than 3 g / m 3 The charge is sintered in a reducing atmosphere of an amount of carbon oxide, the charge containing nepheline ore, the nepheline ore containing not less than 7wt% of iron and not less than 1wt% of sulfur, the amount of recovered soda alkaline solution is adjusted to an alkali to alumina (A / A) ratio of 1.0, a carbonaceous material is used as a reducing agent, the material contains a volatile matter content of not more than 16wt%, and hard coal and / or semi-coke and / or coke powder are used as the carbonaceous material.

Claims

1. A method for processing an alkaline aluminosilicate raw material, the method comprising: - preparing a furnace charge comprising nepheline ore, limestone and an alkaline solution of recovered soda and a reducing agent, - sintering the charge using coal as process fuel, and - leaching of the sinter, wherein The content of the reducing agent in the charge is 0.8 to 1.5 wt % of the weight of the dry charge. The recovered soda alkaline solution is added when preparing the charge in an amount of 5.5 to 6.5 wt % R2O based on the weight of the charge on a dry basis.

2. The method according to claim 1, wherein: The charge was sintered at a temperature of 1,245-1,255°C.

3. The method according to any one of claims 1 and 2, wherein: The charge contains not less than 3g / m 3 The amount of carbon oxides contained in the sintering is reduced in the atmosphere.

4. The method according to claim 1, wherein: The charge comprises nepheline ore, and the nepheline ore comprises not less than 7wt% of iron and not less than 1wt% of sulfur.

5. The method according to claim 1, wherein: The amount of the recovered soda alkaline solution was adjusted to an alkali to alumina (A / A) ratio of 1.

0.

6. The method according to claim 1, wherein: A carbonaceous material is used as a reducing agent, the carbonaceous material comprising a volatile content of not more than 16 wt%.

7. The method according to any one of claims 1 and 6, wherein: As the carbonaceous material, hard coal and / or semi-coke and / or coke powder are used.

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