Method for complex processing of nepheline raw materials

Abstract

FIELD: alumina production.SUBSTANCE: invention relates to a technology for producing alumina by sintering during the processing of alkali aluminosilicates, including nepheline ores and concentrates, to obtain alumina and by-products. Nepheline sludge obtained after leaching the sinter and separating the aluminate solution is subjected to hydrochemical treatment, which is carried out until a lime component is obtained, which is divided into two parts. One part is mixed with unprocessed nepheline slurry until the required lime modulus of the raw Portland cement mixture is achieved, and the second part of the lime component is mixed with the components of the limestone-nepheline batch until the lime modulus is equal to 2. The indicated techniques ensure an equivalent reduction in the consumption of natural limestone and provide the possibility of achieving economically justified ratios of the main and by-products associated with the utilization of nepheline sludge in the production of Portland cement.EFFECT: efficiency of complex processing of nepheline raw materials is increased.1 cl, 3 dwg, 2 tbl, 5 ex

Description

[0001] The invention relates to a technology for producing alumina by sintering during the processing of alkali aluminosilicates, including nepheline ores and concentrates, to obtain alumina and by-products.

[0002] A method for producing alumina from nepheline raw materials is known (RU Patent No. 2165888, published on April 27, 2001), the essence of which lies in the addition of kaolin clays to the limestone-nepheline charge in an amount of 1 to 50% in order to increase the extraction of Al2O3 from sinters during the processing of nepheline ores with a Fe2O3 content of about 4.6%. In this case, the increase in extraction ranges from 0.1 to 0.8% with a base value of Al2O3 extraction of 88.5%.

[0003] The disadvantage of this method is minor changes in the degree of Al2O3 extraction from sinters, complication of the process of preparing a multi-component charge, complication of logistical solutions for introducing additional components, an increase in the volume of nepheline sludge output per ton of production alumina, as well as an increase in carbon dioxide emissions into the atmosphere.

[0004] A method for processing nepheline ores is known (RU Patent No. 2225357, published on March 10, 2004), the essence of which lies in adding waste fireclay refractory bricks to the limestone-nepheline charge in an amount of 0.11 to 11 wt.% of the weight of the nepheline ore, which makes it possible to reduce the consumption of nepheline ore and utilize production waste by involving them in the technological process of charge preparation.

[0005] The disadvantage of this method is the complication of the batch preparation processes, the emission of carbon dioxide into the atmosphere and the low efficiency of nepheline sludge utilization.

[0006] A method for processing nepheline ore is known (RU Patent No. 2606821, published on 10.01.2016), the essence of which lies in adding ash and slag waste to the limestone-nepheline charge in an amount of 0.1 to 10% of the mass of nepheline ore, which ensures a reduction in the consumption of the raw material component of the charge - nepheline ore, and the disposal of ash and slag waste with additional extraction of valuable components from them.

[0007] The disadvantage of this method is the emission of carbon dioxide into the atmosphere and the low efficiency of utilization of nepheline sludge, despite some compensation of natural limestone due to the introduction of CaO in the composition of ash and slag waste, the share of which in the limestone-nepheline charge is limited due to the low content of calcium oxide in them.

[0008] A method for processing nepheline ores and concentrates is known (RU Patent No. 2340559, published on 10.12.2008), the essence of which lies in adding waste slag from the aluminothermic production of ferrotitanium to the limestone-nepheline charge in an amount of 0.5 to 25% of the mass of the nepheline ore, which makes it possible to increase the extraction of alumina from the sintered charge into a solution, utilize ferrotitanium production waste and reduce the amount of waste from the complex processing of nephelines.

[0009] The disadvantage of this method is the complication of the charge preparation processes, the complication of logistical solutions for introducing additional additives, and the limitation of the possibility of using this technical solution to small volumes of accumulated slag.

[0010] A known method for processing nepheline ores to obtain alumina and soda products (RU Patent No. 2450066, published May 10, 2012) involves preparing a limestone-nepheline charge and sintering it using brown coal as fuel, the solid residue of which contains at least 30 wt.% calcium oxide and no more than 40 wt.% silicon oxide. This reduces limestone consumption during charge preparation, decreases the silicon oxide content in the aluminate solution, and allows the use of cheaper fossil coal as fuel. A 1.6% reduction in limestone consumption increases sintering furnace productivity by 0.66%.

[0011] The disadvantage of this method is the complication of the batch preparation process, the preservation of significant carbon dioxide emissions into the atmosphere and the low efficiency of nepheline sludge utilization.

[0012] A method for the comprehensive processing of nepheline raw materials is known (Abramov V.Ya., Alekseev A.I., Badal'yants H.A. Comprehensive processing of nepheline-apatite raw materials. Moscow: Metallurgy, 1990. pp. 36-46), adopted as a prototype, which consists of the preparation and sintering of a limestone-nepheline batch, leaching of the sinter to obtain an aluminate solution intended for obtaining aluminum hydroxide, alumina, soda, potash and other by-products, as well as nepheline sludge, which is used for the production of Portland cement. The method eliminates the need for the preparation of complex multi-component limestone-nepheline batches, which ensures the stability of the preparation and sintering of the batch, as well as the need for complex logistical solutions for the introduction of additional components into the composition of the batch.

[0013] The disadvantage of this method is the unreasonably high yield of Portland cement, 10-12 tons per 1 ton of production alumina, and, as a consequence, a significant carbon footprint of production from the decomposition of limestone, the accumulation of unclaimed quantities of nepheline sludge in sludge storage facilities.

[0014] The technical result is to increase the efficiency of complex processing of nepheline raw materials.

[0015] The technical result is achieved by dividing the washed nepheline sludge into two parts, one part is sent to prepare a raw Portland cement mixture, and the second part is repulped with water in a system of reactors with mechanical mixing and subjected to hydrochemical treatment with carbon dioxide, which results in the conversion of calcium orthosilicate into calcium carbonate with the following stoichiometry of chemical interaction:

[0016] Ca2SiO4+ 2СО2+ 2H2O = 2CaCO3+ SiO2⋅2H2O,

[0017] then, the resulting pulp is filtered on a vacuum filter to obtain liquid and solid products of hydrochemical processing, the liquid product - recycled solution, is fed to dilute the flow of nepheline sludge before hydrochemical processing, and the solid product - lime-silicate sludge is sent to a reactor with a mixing device, where it is mixed with an alkali solution that dissolves the resulting silicate component, to obtain a lime component containing SiO2 up to 3.0%, then the pulp is filtered to obtain a liquid product - a silicate-alkaline solution, which is sent for subsequent disposal and a solid product - a lime component, which is washed on the filter with hot water, while the wash water is sent for disposal, and a sample is taken from the lime component and a chemical analysis is performed for the content of CaO and SiO2, after this lime component is divided into two parts,one part is sent to the preparation of raw Portland cement mixture with a lime module of 3, and the second part is sent to the preparation of limestone-nepheline batch.

[0018] The method is explained by the following figures:

[0019] Fig. 1 - graph of the theoretical dependence of the SiO2 content in the lime component on the degree of conversion of calcium orthosilicate during hydrochemical treatment of nepheline sludge;

[0020] Fig. 2 - graph of the theoretical dependence of the lime modulus of the solid product - the lime component, on the degree of conversion of calcium orthosilicate during hydrochemical treatment of nepheline sludge;

[0021] Fig. 3 - graph of the theoretical dependence of the share of the flow of regenerated lime component for the production of Portland cement and the preparation of limestone-nepheline batch on the share of nepheline slurry used for the preparation of raw Portland cement mixture of alite composition.

[0022] The method is as follows.

[0023] Limestone and nepheline concentrate are wet-ground in ball mills and sent to sintering in rotary kilns. The resulting sinter is leached with water from the nepheline slurry wash in reactors with mechanical or pneumatic stirring. The resulting pulp is sent to a thickener, where the aluminate solution is separated from the nepheline slurry. The aluminate solution is used to produce alumina, soda, potash, and other by-products. The nepheline slurry is sent for multiple counter-current washing in a system of wash thickeners. The wash water is sent to leach the sinter. The washed nepheline slurry is divided into two parts. One part of the slurry, in the amount required for producing Portland cement, is sent to the preparation of raw Portland cement mixture.The second part of the nepheline sludge is repulped with water in a system of reactors with mechanical mixing and subjected to hydrochemical treatment with carbon dioxide, which ensures the conversion of calcium orthosilicate into calcium carbonate according to the following stoichiometry of chemical interaction:.

[0024] Ca2SiO4+ 2CO2+ 2H2O = 2CaCO3+ SiO2⋅2H2O.

[0025] The resulting pulp is then vacuum filtered to obtain liquid and solid hydrochemical treatment products. The liquid product, a recycled solution, is used to dilute the nepheline slurry stream prior to hydrochemical treatment. The solid product, a lime-silicate slurry, is mixed with an alkali solution in a reactor with a stirrer to dissolve the resulting silicate component and produce a lime component with a SiO2 content of up to 3.0%. After alkali treatment, the pulp is filtered to obtain liquid and solid products. The liquid product, a silicate-alkaline solution, is sent for subsequent disposal. The solid product, a lime component, is washed on the filter with hot water. The wash water is sent for disposal. Next, a sample is taken from the lime component and a chemical analysis is performed to determine the content of CaO and SiO2.

[0026] The lime component is divided into two parts. One part is used to prepare a raw Portland cement mixture with a lime modulus of 3. The second part is used to prepare a limestone-nepheline blend.

[0027] The method is explained by the following examples.

[0028] Example 1. An air-dry sample of nepheline sludge with the following chemical composition, wt.%, was used: CaO - 57.62; SiO2 - 30.68; Al2O3 - 2.83; Fe2O3 - 2.38; R2O - 1.75; loss on ignition (LOI) - 3.1. The nepheline sludge was diluted with water, heated in a reactor and supplied with carbon dioxide of the established concentration. Then the pulp was filtered, the precipitate was mixed in the reactor with an alkaline solution. Treatment with an alkaline solution was carried out for the time required to dissolve the formed silicate component. The resulting pulp was filtered using a vacuum filter and the precipitate - the lime component, was washed with hot water on the filter until the wash water was slightly alkaline. According to the analysis results, the degree of conversion of nepheline sludge was 74.8%, which ensured the production of a lime component with α изв= 8.12 with a CaO content of 53.10% and SiO2 of 7.01%. Thus, the sample of the lime component in terms of SiO2 content does not meet the requirements for limestone for alumina production, which establish a SiO2 content of no more than 3.0%.

[0029] Example 2 is similar to Example 1, but the hydrochemical treatment of nepheline sludge was carried out at elevated temperatures and a reduced process time. According to the analysis results, the conversion rate of nepheline sludge was 87.3%, which ensured the production of a lime component with α изв = 16.63 with a CaO content of 52.32% and SiO2 - 3.37%. Thus, despite the sufficiently high calcareous modulus of the sample, which ensures the possibility of its effective use in the production of Portland cement, as in example 1, it does not meet the requirements for SiO2 content for use in alumina production and, consequently, for the preparation of limestone-nepheline batch.

[0030] Example 3 is similar to example 2, but the hydrochemical treatment of nepheline sludge was carried out with an increased liquid-to-solid ratio in the pulp. Analysis showed that the conversion rate of the nepheline sludge was 91.5%, which ensured the production of a lime component with α изв = 26.3 with a CaO content of 52.06% and SiO2 - 2.13%. Thus, the obtained sample of the lime component meets the requirements for the preparation of both limestone-nepheline batch and raw Portland cement mixture. For the conditions of example 3, the content of the main components in the nepheline slurry: CaO - 57.62 and SiO2 - 30.68%, which determines its lime modulus α" изв = 2.012. Accordingly, the composition of the obtained lime component is: CaO - 52.06 and SiO2 - 2.13%, which determines its lime modulus α" изв= 26.2. These initial data allow us to calculate the distribution of the nepheline slurry flow depending on the proportion of the lime component intended for the preparation of the raw Portland cement mixture and the limestone-nepheline batch. In this example, the calculation was performed for the following proportions of the lime component supplied for the preparation of the raw Portland cement mixture of alite composition: 1.0; 0.5; 0.0. This distribution of the lime component corresponds to the following proportions of the nepheline slurry flow for the preparation of the raw Portland cement mixture of alite composition, respectively: 0.6433; 0.4742; 0.0. The available data allow us to calculate the composition of the raw Portland cement mixture and its quantity per unit of utilized nepheline slurry. For example, when disposing of 100 g of sludge in accordance with the given distribution of components, the following will be required: nepheline sludge / lime component, g / g: 64.33 / 39.48; 47.42 / 29.10; 0.0 / 0.0.According to these data, the amount of raw mix for the production of Portland cement clinker is, respectively, g: 103.81; 76.52; 0.0. In this case, the first option corresponds to the complete use of the lime component for the production of Portland cement, the second - to a 50% distribution of the lime component, and the third option involves hydrochemical treatment of the entire flow of nepheline slurry using the obtained lime component at the stage of preparation of the limestone-nepheline batch, which excludes the by-product production of Portland cement.

[0031] The quantitative calculation of the limestone-nepheline batch was performed for the previously adopted distribution of the lime component during the utilization of 100 g of nepheline slurry, with regard to the use of a limestone sample of the following composition, %: CaO - 53.3; SiO2 - 2.01; Al2O3 - 0.41; Fe2O3 - 0.56. The nepheline concentrate sample had the following composition, wt.%: Al2O3 - 28.8; SiO2 - 44.5; Na2O - 12.9; K2O -7.3; Fe2O3 - 3.3. In this case, the compositions of the limestone-nepheline batch were determined depending on the proportion of the used recycled lime component. When using only natural limestone in the batch, there is no limestone recycle, and the calculated composition includes 64.49 g of nepheline concentrate, 108.11 g of natural limestone, and 1.19 g of soda. When using 50% of the recycled limestone in the batch, the calculated composition includes 64.41 g of nepheline concentrate, 79.77 g of natural limestone, and 1.36 g of soda.With a complete transition to the recycled lime component in the batch, the calculated composition will include 64.07 g of nepheline concentrate, 110.69 g of lime component and 1.84 g of soda.

[0032] The correctness of the raw mix and batch sample preparation was verified experimentally using components pre-dried to a constant weight and ground to a residue of no more than 5-7% on a +80 µm sieve. The raw components were weighed to the nearest hundredth of a gram and then subjected to compositional averaging using a laboratory rotary mixer. The chemical composition of the resulting mixtures and batches was then determined to calculate the specified modulus values, which should not deviate from the specified alkaline and limestone modulus of the batch, 1.0 and 2.0, respectively, with an accuracy of 1%.

[0033] The results of determining the indicators of hydrochemical treatment of nepheline sludge, its proportional distribution taking into account the distribution of the lime component, as well as the calculated and experimentally established compositions of mixtures and batches are summarized in Tables 1 and 2.

[0034] Example 4 is similar to example 3, but due to the increase in the duration of the hydrochemical treatment process of nepheline sludge, the degree of conversion was 94.1%, which ensured the production of a lime component with α изв= 35.56 with a CaO content of 51.77% and SiO2 - 1.56%. Thus, the obtained sample of the lime component meets the requirements for the preparation of both the limestone-nepheline batch and the raw Portland cement mixture. The proportional distribution of nepheline slurry, the composition of the raw Portland cement mixture and the limestone-nepheline batch were calculated and experimentally determined with respect to the following proportions of the lime component for the preparation of the raw Portland cement mixture of alite composition: 0.9; 0.5; 0.1. The results of their implementation are summarized in Tables 1 and 2.

[0035] Example 5 is similar to example 4, but due to the increase in the liquid / solid ratio at the stage of hydrochemical treatment of nepheline sludge, the degree of conversion was 97.8%, which ensured the production of a lime component with α изв= 153.78 with a CaO content of 51.67% and SiO2 - 0.36%. Thus, the obtained sample of the lime component meets the requirements for the preparation of both the limestone-nepheline batch and the raw Portland cement mixture. The proportional distribution of nepheline slurry, the composition of the raw Portland cement mixture and the limestone-nepheline batch were calculated and experimentally determined with respect to the following proportions of the lime component for the preparation of the raw Portland cement mixture of alite composition: 0.75; 0.5; 0.25. The results of their implementation are summarized in Tables 1 and 2.

[0036] Table 1 - Indicators of hydrochemical treatment of nepheline sludge and preparation of raw Portland cement mixture

[0037] № Conversion rate, % Composition indicators of the lime component Indicators for the preparation of raw Portland cement mixture CaO, % SiO2, % lime module the proportion of lime component required for the preparation of raw Portland cement mixture, units. share of nepheline sludge flow for preparation of raw Portland cement mixture, units yield of raw semi-finished product mixture in % of the mass of nepheline sludge lime module of raw Portland cement mixture 1 74,8 53,10 7,01 8,12 - - - - 2 87,3 52,32 3,37 16,63 - - - - 3 91,5 52,06 2,13 26,3 1,0 0,6433 103,81 3,02 0,5 0,4742 76,52 3,03 0,0 0,0 0,0 - 4 94,1 36,02 1,56 35,36 0,9 0,6265 100,29 3,01 0,5 0,5176 77,15 3,02 0,1 0,1571 25,13 3,02 5 97,8 51,67 0,36 153,78 0,75 0,5996 93,45 3,00 0,5 0,4996 77,86 3,01 0,25 0,3333 51,92 3,01

[0038] Table 2 - Indicators for the preparation of limestone-nepheline mixture using a lime component from the hydrochemical treatment of nepheline sludge.

[0039] № The proportion of lime component for the preparation of limestone-nepheline mixture, units. Component composition and yield of limestone-nepheline slurry in % of the mass of nepheline slurry The degree of replacement of limestone by the lime component, % Alkaline batch module Lime batch module nepheline concentrate limestone lime component soda batch yield 3 0,0 64,49 108,11 - 1,19 173,79 0,0 0,99 1,99 0,5 64,41 79,77 29,1 1,36 174,64 26,15 1,00 2,01 1,0 64,07 - 110,69 1,84 176,60 100,0 1,01 2,02 4 0,1 64,52 104,05 4,17 1,24 173,98 3,80 1,00 1,99 0,5 64,74 80,03 28,91 1,59 175,27 26,27 1,00 2,00 0,9 65,23 25,81 84,73 2,36 178,13 76,40 1,01 2,01 5 0,25 64,88 97,29 11,16 1,35 174,68 10,56 0,99 2,00 0,5 65,48 81,06 27,90 1,60 176,04 26,16 1,00 2,01 0,75 68,92 54,04 55,77 2,04 180,77 51,51 1,01 2,02

[0040] Increased efficiency of integrated nepheline raw material processing is achieved by subjecting the nepheline slurry obtained after sinter leaching and aluminate solution separation to hydrochemical treatment, which is carried out to obtain a lime component with an SiO2 content of 2.0 to 3.0%. This component is then divided into two parts. One part is mixed with untreated nepheline slurry until the required lime modulus of the raw Portland cement mixture is achieved, while the second part of the lime component is mixed with the components of the limestone-nepheline batch until a lime modulus of 2 is achieved. This ensures an equivalent reduction in natural limestone consumption and makes it possible to achieve economically viable ratios of primary and by-products associated with the utilization of nepheline slurry in Portland cement production.

Claims

A method for the integrated processing of nepheline raw materials, including the preparation and sintering of a limestone-nepheline charge, leaching of the sinter to obtain an aluminate solution intended for the production of aluminum hydroxide, alumina, soda, potash, and nepheline sludge, which is sent for multiple counter-current washing in a system of washing thickeners, the wash water is returned to the leaching of the sinter, characterized in that the washed nepheline sludge is divided into two parts, one part is sent to the preparation of a raw Portland cement mixture, and the second part is repulped with water in a system of reactors with mechanical mixing and subjected to hydrochemical treatment with carbon dioxide, wherein the conversion of calcium orthosilicate into calcium carbonate occurs with the following stoichiometry of chemical interaction: Ca2SiO4+ 2СО2+ 2H2O = 2CaCO3+ SiO2⋅2H2O, then the resulting pulp is filtered on a vacuum filter to obtain liquid and solid products of hydrochemical processing, the liquid product - recycled solution, is fed to dilute the flow of nepheline sludge before hydrochemical processing, and the solid product - lime-silicate sludge is sent to a reactor with a mixing device, in which it is mixed with an alkali solution that dissolves the resulting silicate component, to obtain a lime component containing SiO2 up to 3.0%, then the pulp is filtered to obtain a liquid product - a silicate-alkaline solution, which is sent for subsequent disposal, and a solid product - a lime component, which is washed on the filter with water, while the wash water is sent for disposal, and a sample is taken from the lime component and a chemical analysis is performed for the content of CaO and SiO2, after which the lime component is divided into two parts,one part is sent to the preparation of raw Portland cement mixture with a lime module of 3, and the second part is sent to the preparation of limestone-nepheline batch.

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