WO2009006772A1

WO2009006772A1 - A method for producing alumina with middle and low grade bauxite

Info

Publication number: WO2009006772A1
Application number: PCT/CN2007/003721
Authority: WO
Inventors: Songqing Gu; Zhonglin Yin; Xinhua Li; Xiangmin Liu; Guobao Wu
Original assignee: Aluminum Corporation Of China Limited
Priority date: 2007-07-12
Filing date: 2007-12-21
Publication date: 2009-01-15
Also published as: RU2010104624A; RU2478574C2; AU2007356401B2; CN100532262C; CN101113001A; AU2007356401A1

Abstract

A method for producing alumina with middle and low grade bauxite is characterized in that the Bayer process digestion is performed by adding the dealuminizing residue as an additive instead of lime into middle and low grade bauxite during the Bayer process; the red mud after the Bayer process digestion is subjected to reversal washing, then mixed with recycling alkali liquor, digested after the lime being added, and the resulting red mud is discharged after it is separated, a portion of the resulting solution is used to reversal wash the red mud obtained from Bayer process digestion, then supplemented with alkali after it is sent to Bayer process system, the dealuminizing residue and the recycling alkali liquor for wet-treating the red mud obtained from Bayer process are obtained after lime is added into another portion of the resulting solution, and the dealuminizing residue , i.e. calcium aluminate hydrate, as a additive, is added to the Bayer process digestion instead of lime. The method is a wet-treating process, is suitable for middle and low grade bauxite, and has advantages of simpleness, low energy consumption, low alkali consumption, high yield of alumina, high level of resources utilization, low red mud discharging, and comprehensive utilization of red mud.

Description

Method for producing alumina from medium grade bauxite ore

The invention relates to a method for producing alumina in medium and low grade bauxite, in particular to a method for producing alumina by using a Bayer process for treating medium and low grade bauxite. Background technique

At present, the methods used in the industry to treat low-grade bauxite (A/S 8 ) include sintering method, mixing method, mineralization Bayer method, lime Bayer method, and series method. Among them, the sintering method and the mixing method have high energy consumption and complicated process; the mineralization Bayer method and the lime Bayer method have simple processes and low energy consumption, but the recovery rate of alumina is only about 70%, and the utilization rate of resources is low. The tandem method is to treat the bauxite by Bayer method first, and then to treat the Bayer red mud by sintering. The abandonment of red mud A/S and N/S is low, and the resource utilization rate is high. It is to treat medium and low grade bauxite. A better way. However, since the sintering process still exists, the process is still complicated and the energy consumption is still high.

The Bayer hydration method proposed by the former Soviet Union and other countries [Alumina production technology, edited by Yang Zhongyu, Beijing: Metallurgical Industry Press, 1982, 307] includes two parts: bauxite treatment and red mud treatment. Figure 1 shows. Although this method is purely a wet process, but the following deficiencies still exist: a) treating red mud required high a _k alkaline sodium aluminate solution was evaporated to a depth of Na ₂ 0 concentration of 500g / L or more precipitated aluminate Obtained by sodium crystallization, the evaporation is too large, the energy consumption is high, and the precipitated sodium aluminate is difficult to separate; 2) The conditions for treating red mud are too harsh, and need to be at high temperature (280 ~ 300 °C) and high alkali concentration (Na ₂ 0 Operating at 400 ~ 500g / L), the industrial implementation is difficult; 3) The process is complex. Therefore, this Bayer hydration method is difficult to apply in industry.

In view of the above deficiencies, the present invention proposes a total wet method for treating low grade bauxite to produce aluminum oxide. The advantage of this method is that the operating temperature is low, the alkali concentration is low, and the amount of slag generated is small, so that the energy consumption can be remarkably reduced, and it is industrially easy to implement. Summary of the invention

The object of the present invention is to address the deficiencies of the prior art mentioned above, and propose a method for treating the whole wet process, having a simple process, low energy consumption, low alkali consumption, high alumina recovery rate, high resource utilization rate, and red efflux. A method for producing alumina from low-grade, easy-to-use, low-grade bauxite. The method of the present invention is achieved by the following technical solutions.

According to an embodiment of the present invention, there is provided a method for producing oxidized aluminum in a medium-low grade bauxite, wherein the bauxite is first treated by a Bayer process, and then the red mud is treated with a lower concentration of lye. Wet treatment.

According to an aspect of the present invention, a method for producing alumina in a medium-low grade bauxite is provided, characterized in that in the Bayer process used, the dissolution process is to add dealuminized slag to the medium and low grade bauxite. Instead of lime as an additive, Bayer method is used for dissolution; after dissolution, the red mud is mixed with the circulating alkali liquor after reverse washing, and after adding lime, the slurry is separated, and the slurry is separated from the red mud efflux, and the obtained solution is partially reverse-washed by Bayer method. After dissolving the red mud, the Bayer method is used to replenish the alkali. After partial lime addition, the demelted slag and the Bayer process red mud wet treatment are used to treat the circulating alkali liquor. The dealuminized slag hydrated calcium aluminate is added to the Bayer process to replace the lime.

The process of the invention has reasonable and easy operation, and the existing mixed alumina plant can add a wet dissolution system to remove the sintering system with high energy consumption and complicated process, and greatly reduce the energy consumption of producing alumina. .

The method of the invention is characterized in that the content of A1 ₂ 0 ₃ and Na ₂ 0 in the red mud is lower, and the amount of lime added is less, the utilization of resources is improved, and the amount of red mud in the outer row is reduced.

The method of the invention is characterized in that the content of Na ₂ 0 in the red mud is lower, which is beneficial to the comprehensive utilization of the red mud.

The method of the invention is applicable to a factory for producing alumina by using medium and low grade bauxite, and the method of the invention plays an active role in improving the utilization rate of bauxite resources and reducing the energy consumption and alkali consumption of alumina production. Good promotion and application prospects. DRAWINGS

Figure 1 is a process flow diagram of the existing Bayer hydration method;

2 is a flow chart of a full wet process of the present invention;

3 is a flow chart of still another wet process of the present invention. Specific embodiment

The invention will be further described with reference to the drawings and specific embodiments.

As used herein, the term "de-aluminizing slag" refers to a solid obtained by adding a solution of a Bayer process red mud to a lime solution, and the main component is a small amount of silica. The hydrated tricalcium aluminate.

As used herein, the term "α _κ " refers to the molar ratio of caustic soda to alumina in solution.

As used herein, the term "abandoned red mud" refers to the red mud that is ultimately discharged after treatment of the bauxite.

As used herein, the term "circulating lye" refers to a lye used for wet processing of Bayer red mud.

According to one aspect of the invention, a method of processing a low to medium grade bauxite to produce alumina is provided. The method includes two main processes: Bayer process dissolution of bauxite and wet process of Bayer process dissolution of red mud.

According to another aspect of the present invention, in the Bayer process for the dissolution of bauxite, a medium-low grade bauxite, a circulating mother liquor, and a dealuminated slag as a dissolution additive are added. Preferably, the dissolution process of the Bayer method, the eluate by a _K of 1.35 - 1.60 with the aluminum-silicon ratio A / S is in the low grade bauxite and N _k 3 ~ 9 of 180 ~ 280g / L of circulating The amount of the mother liquor and the dealuminated slag is 3 to 15% of the added bauxite in terms of CaO. When the amount of dealumination slag is insufficient, CaO may be supplemented as a partial dissolution additive.

According to another aspect of the invention, the Bayer process can be carried out using pipe preheating-stop tank dissolution techniques, pipeline dissolution techniques, pipe preheating-compressor dissolution techniques, dual flow processes known in the art (these techniques have been It is well known to those of ordinary skill in the art, and will not be further described herein. Preferably, the dissolution treatment temperature is 240 - 290 ° C and the dissolution time is 10 - 120 min.

According to another aspect of the present invention, after the Bayer dissolution slurry is separated by dilution and sedimentation, the obtained sodium aluminate solution is decomposed into seeds to obtain a decomposition mother liquid and aluminum hydroxide, and the aluminum hydroxide is subjected to calcination to obtain final alumina. The decomposition mother liquid is evaporated to obtain the circulating mother liquid into the Bayer dissolution process; after the slurry is separated and the red mud obtained is washed by hot water, the ratio of aluminum to silicon

A/S < 1.7, sodium to silicon ratio N/S is 0.20 - 0.65.

As shown in Fig. 2, optionally, the portion of the red mud solution obtained by the Bayer red mud wet treatment (described below) is used to reversely wash the Bayer dissolved red mud. The reverse washing may be carried out by a red mud filtration washing method well known in the art, or a settling tank washing method. A portion of the excess reverse scrubbing liquid is sent to the dealuminized portion and a portion to the decomposed mother liquor.

Alternatively, as shown in Figure 3, optionally, the Bayer dissolved red mud is backwashed with a discarded red mud wash (described below). The excess reverse washing liquid is sent to the dealumination. Bayer dissolves the red mud (or after the reverse washing) into the Bayer red mud wet process, which is mixed with the medium and low concentration circulating alkali liquor and lime. Among them, the addition amount of Bayer red mud is 10 ~ 350g per liter of circulating alkali liquor; the caustic concentration of circulating alkali liquor N _k is 30 ~ 260g / L, preferably 90 ~ 220g / L, more preferably 100 ~ 190g / L, A1 ₂ 0 ₃ <20g/L; the amount of lime added is such that the ratio of calcium to silicon is C/S (C/S: mass ratio of CaO to SiO ₂ in red mud) is 0.5 ~ 2.5, preferably 1.0 ~ 2.1, and the dissolution temperature is 200 ~ 300 °C, preferably 200 ~ 280 ° C, more preferably 240 ~ ° C 270, dissolution time 5 ~ 150min. The wet treatment can be realized by a pipeline preheating-stop tank dissolution technique, a pipeline dissolution technique, a pipeline preheating-compressor dissolution technique, a double flow method, and the like.

After the Bayer red mud wet treatment, the slurry is separated to obtain a red mud solution and a red mud. Wherein, all or a portion of the red mud eluate is added to lime for dealuminization, and a portion of the red mud eluate is washed back to the Bayer red mud, as shown in FIG. 2; or, all or part of the red mud eluate is added with lime for dealuminization. Some of them go directly into the decomposition mother liquor, as shown in Figure 3. After the washed red mud is washed with hot water, the final red mud and the abandoned red mud washing liquid are obtained, wherein the discarded red mud washing liquid is used for reverse washing of the Bayer red mud, as shown in FIG. Or used to separate the slurry after the Bayer red mud wet treatment, as shown in Figure 2, or to separate the Bayer process dissolution slurry. The A/S of the final red mud is generally 0.2 to 0.8, preferably 0.4 to 0.8, and N/S is generally 0.01 to 0.30.

Part of the red mud leachate and / or part of the reverse washing solution is added with lime when dealuminizing, the lime addition amount is according to the ratio of calcium to aluminum C / A (C / A: CaO in lime and A1 ₂ 0 _{3 in} solution) The mass ratio is 1.5 to 2.5, the temperature is 40 ~ 1 10 ° C, and the time is 10 ~ 180 min. The recycled alkali liquor after dealuminization is optionally added with caustic for treating the next batch of Bayer process to dissolve red mud; the dealuminated slag obtained after dealumination is used as a Bayer process elution additive. The separation of the dealuminated slurry is carried out by a separation method such as pressure filtration or sedimentation, and pressure filtration is preferred. The addition of the new caustic is carried out in a Bayer process red mud wet processing system.

According to the embodiment of the present invention, the Bayer red mud wet treatment has a low operating temperature and a low alkalinity, so that it is easy to handle, has low energy consumption, and has low corrosion to equipment. The existing hybrid aluminum oxide plant adds a wet dissolution system to remove the high-energy, complex process sintering system, which significantly reduces the energy consumption of alumina production.

According to an embodiment of the present invention, most of the Bayer process red mud wet treatment solution adds lime, reacts with the alumina in the solution, substantially removes the alumina in the solution, and realizes the Bayer red mud wet treatment of the circulating alkali liquor. Regeneration, the obtained dealuminated slag provides a force agent for Bayer process dissolution. According to the embodiment of the present invention, the content of A1 ₂ 0 ₃ and Na ₂ 0 in the abandoned red mud is lower, the amount of lime added is less, the utilization of resources is improved, and the amount of red mud in the outer row is reduced, and at the same time Conducive to the comprehensive utilization of red mud.

The method of the invention is suitable for producing alumina by using medium and low grade bauxite. The method of the invention plays an active role in improving the utilization rate of bauxite resources and reducing the energy consumption and alkali consumption of alumina production, and has good performance. Promote application prospects.

In the following, the invention will be further described in conjunction with the following specific but non-limiting examples. Example

Example 1

The bauxite has an aluminum to silicon ratio of 3/A, the circulating mother liquor caustic concentration N _k is 230 g/L, and the additive dealuminized slag is added in an amount of 11% of the added bauxite in terms of CaO. - The residence tank dissolution technology is dissolved at 260 ° C for 60 min, the a _k is 1.48, and the red mud, aluminum, silicon and silicon ratio is 1.0, and the red mud is separated and washed. After the red mud is separated and washed, the red mud washing solution is reversed. Washing, reverse washing is achieved by filtration washing; Bayer process red mud after reverse washing is wet-processed by pipe preheating-stop tank dissolution technology, temperature is 260 °C, circulating alkali concentration is 130g/L, The amount of red mud added is 200g/L circulating alkali liquor, the total lime addition amount is 1.3, the dissolution time is 90min; the dissolution solution obtained by the Bayer process red mud wet treatment is sent to the dealumination, and the dealuminated slurry is pressed. The filter is separated by pressure filtration, the dealuminization temperature is 90 ° C, the time is 30 min. The amount of dealuminized lime added is added according to the mass ratio of calcium to aluminum of 1.6, and the resulting dealuminated slag is added to the Bayer process, and the Bayer process is obtained by the red mud wet process. The solid washed away the red mud washed the washing liquid to reverse the washing of the Bayer red mud, and finally obtained Red mud aluminum silicon ratio A / S is 0.6, the sodium silicon ratio N / S was 0.10.

Example 2

The bauxite has an aluminum to silicon ratio of 5/A, the circulating mother liquor caustic concentration N _k is 230 g/L, and the additive dealuminized slag is added in an amount of 5% of the added bauxite ore according to CaO. - The residence tank dissolution technique is dissolved at 26 (TC, dissolution for 60 min, the dissolution a _k is 1.40, and the dissolution ratio of red mud aluminum to silicon is 1.1; Bayer dissolves the red mud to separate and wash, and then reverses with the red mud washing solution. Washing, reverse washing is carried out by means of filtration washing; Bayer process red mud after reverse washing is wet-processed by pipeline preheating-stop tank dissolution technology, temperature is 260 ° C, circulating alkali concentration is 130 g / L, The amount of red mud added is 250g / L circulating lye, total lime The ratio of calcium to silicon is 1.0, and the dissolution time is 60 min. The dissolution solution obtained by the Bayer process red mud treatment is all sent to dealumination. The dealuminized slurry is separated by pressure filtration using a filter press. The dealuminization temperature is 90 ° C for 30 min. The amount of dealuminated lime added was 1.8 by mass ratio of calcium to aluminum, and the resulting dealuminated slag was added to the Bayer process system. The ratio of the obtained red mud aluminum to silicon was 0.7, and the ratio of sodium to silicon was 0.10.

Example 3

The bauxite has an aluminum to silicon ratio of 7/A, the circulating mother liquor caustic concentration N _k is 230 g/L, and the additive dealuminized slag is added in an amount of 5% of the added bauxite in terms of CaO, plus lime 2 %, using the pipe-stop tank dissolution technology at 260 ° C, dissolution for 60 min dissolution, the dissolution a _k is 1.50, the dissolution of red mud aluminum silicon ratio A / S is 1.2; Bayer dissolved red mud separation 3⁄4 polyester, with abandoned red The mud washing liquid is reversely washed, and the reverse washing is carried out by means of filtration washing; the Bayer method red mud after the reverse washing is subjected to the wet processing by the pipeline preheating-stop tank dissolution technique, the temperature is 260 ° C, and the circulating alkali concentration is 170g / L, Bayer red mud added amount of 200g / L circulating lye, total lime added amount of calcium to silicon ratio of 1.7, dissolution time of 90min.; Bayer process red mud wet treatment of all the resulting solution is sent to dealumination The dealuminized slurry is separated by pressure filtration using a filter press. The dealuminization temperature is 90 ° C. The time of dealuminization and lime addition is 30 min. The mass ratio of calcium to aluminum is 1.6, and the resulting dealuminized slag is added to the Bayer process system. The red mud aluminum to silicon ratio is 0.7% for A/S, and the sodium to silicon ratio is 0.16 for N/S.

Example 4

The bauxite has an aluminum to silicon ratio of A/S of 9, the circulating mother liquor caustic concentration N _k is 230 g/L, and the additive dealuminization slag is added by 9% of the added bauxite ore according to CaO. The tank dissolution technique was dissolved at 260 ° C for 60 min. The a _k of the eluate was 1.48, and the ratio of dissolved red mud to aluminum silicon was 1.4; after the dissolution of the red mud by Bayer, the washing was reversed with a discarded red mud washing solution. The reverse washing is carried out by means of filtration washing; the Bayer process red mud after reverse washing is subjected to wet treatment by pipe stripping technology, the temperature is 260 ° C, the circulating alkali concentration is 150 g / L, and the Bayer red mud is added. 100g / L circulating lye, total lime addition amount of calcium to silicon ratio of 1.9, dissolution time of 90min; Bayer process red mud wet process after the part of the solution is sent to dealumination, dealuminized slurry by filter press filter separation The dealuminization temperature is 90 ° C, the time of 30 min removal of dealuminized lime is added according to the mass ratio of calcium to aluminum of 1.6, and the resulting dealuminated slag is added to the Bayer process system, and the final red mud aluminum silicon ratio is 0.5, sodium. The silicon ratio N/S is 0.10.

Example 5

Bauxite, alumina-silica ratio A / S of 5, Save circulating liquor caustic concentration N _k of 230g / L, Tim The amount of de-aluminizing slag added is 13% of the added bauxite in terms of CaO. It is dissolved in a pipe-stop tank at 260 ° C and dissolved for 90 min. The a _k is 1.48, and the red mud aluminum silicon is dissolved. The ratio A/S is 1.5; after the Bayer dissolves the red mud and washes it, it uses the abandoned red mud washing liquid to reverse the washing, and the reverse washing adopts the filtering and washing method; the reverse washing of the Bayer method red mud adopts the pipeline preheating- The method of dissolving the tank is wet processing, the temperature is 260 ° C, the circulating alkali concentration is 130 g / L, the Bayer red mud is added in the amount of 50 g / L circulating lye, the total lime addition amount is 1.9, the dissolution time is 90 min. The dissolution solution obtained by the Bayer method red mud wet treatment is all sent to dealumination, and the dealuminated slurry is separated by pressure filtration using a filter press. The dealuminization temperature is 90 ° C, the time is 30 min. The amount of dealuminized lime added is determined by the mass ratio of calcium to aluminum. 1.6 Addition, the resulting dealuminated slag is added to the Bayer process, and the resulting red mud aluminum silicon has a ratio of A/S of 0.7 and a sodium to silicon ratio of N/S of 0.16.

Example 6

Bauxite, alumina-silica ratio A / S is 5, the concentration of the caustic liquor circulation N _k of 230g / L, the additive is added in an amount of dealuminated slag CaO based added 15% bauxite required using pipe - residence The tank dissolution technology was dissolved at 260 ° C for 90 min, the a _k of the eluate was 1.48, and the ratio of dissolved red mud to aluminum silicon was 1.1; Bayer dissolved red mud was separated and washed, and washed with abandoned red mud washing solution. The reverse washing is carried out by means of filtration washing; the Bayer process red mud after reverse washing is subjected to wet treatment by pipeline preheating-stop tank dissolution technology at a temperature of 280 ° C and a circulating alkali concentration of 130 g / L, Bayer Red The amount of mud added is 250g/L circulating alkali liquor, the total lime addition amount is 1.3, the dissolution time is 30min; the dissolution solution obtained by the Bayer process red mud wet treatment is all sent to the dealumination, and the dealuminated slurry is used as the filter press. Separation by pressure filtration, dealuminization temperature 90 ° C, time 30 min, the amount of dealuminized lime added is 1.7 by mass ratio of calcium to aluminum, and the resulting dealuminated slag is added to the Bayer process system, and the final red mud aluminum silicon ratio is A/S. For 0.65, the sodium to silicon ratio is 0.10 for N/S.

Example 7

The bauxite has an aluminum to silicon ratio of 5/A, the circulating mother liquor caustic concentration N _k is 230 g/L, and the additive dealuminized slag is added in an amount of 11% of the added bauxite in terms of CaO. The tank dissolution technique was dissolved at 250 ° C for 90 min, and the a _k of the eluate was 1.48. The ratio of the dissolved red mud to aluminum silicon was 1.1. After the dissolution of the red mud by Bayer, the washing was reversed with a red mud washing solution. The reverse washing is carried out by means of filtration washing; the Bayer process red mud after reverse washing is subjected to wet treatment by pipeline dissolving technology, the temperature is 250 ° C, the circulating alkali concentration is 210 g / L, and the Bayer red mud is added. 300g / L circulating lye, total lime added amount of calcium to silicon ratio of 1.9, dissolution time of 90min; Bayer method red mud wet treatment of the resulting solution is sent Dealuminization, dealuminization slurry is separated by pressure filtration using a filter press. The dealuminization temperature is 90 ° C. The time of dealuminization and lime addition is 30 min. The mass ratio of calcium to aluminum is 2.0, and the resulting dealuminized slag is added to the Bayer process system. The abandonment of red mud aluminum silicon has an A/S ratio of 0.55 and a sodium to silicon ratio of N/S of 0.16.

Example 8

Bauxite, alumina-silica ratio A / S is 5, the concentration of the caustic liquor circulation N _k of 210g / L, the additive is added in an amount of dealuminated slag CaO based required added 11% bauxite, preclude the use of tubes - The dissolution tank dissolution technology was dissolved at 280 °C for 30 min, and the eluent 3 was 1.48. The ratio of red mud aluminum to silicon was 1.1. After the Bayer dissolved red mud was separated and washed, it was washed back with a red mud washing solution. The reverse washing is carried out by means of filtration washing; the Bayer process red mud after reverse washing is subjected to wet treatment by pipeline preheating-stop tank dissolution technology at a temperature of 240 ° C, and the circulating alkali concentration is 130 g / L, Bayer Red The amount of mud added is 200g/L circulating alkali liquor, the total lime addition amount is 2.3, the dissolution time is 120min; the dissolution solution obtained by the Bayer process red mud wet treatment is all sent to dealumination, and the dealuminated slurry is used for filter press. Separation by pressure filtration, dealuminization temperature 90 ° C, time 30 min, the amount of dealuminized lime added is added according to the mass ratio of calcium to aluminum of 1.8, and the resulting dealuminated slag is added to the Bayer process system, and the final red mud aluminum silicon ratio is A/S. For 0.75, the sodium to silicon ratio is 0.10 for N/S.

Example 9

The bauxite has an aluminum to silicon ratio of 3/A, the circulating mother liquor caustic concentration N _k is 230 g/L, and the additive dealuminized slag is added in an amount of 11% of the added bauxite in terms of CaO. The tank dissolution technique was dissolved at 260 ° C for 90 min, the a _k of the eluate was 1.48, and the ratio of dissolved red mud to aluminum silicon was 1.0; the Bayer dissolved red mud was separated and washed, and washed with a discarded red mud washing solution. The reverse washing is carried out by means of filtration washing; the Bayer process red mud after reverse washing is wet-processed by pipe preheating-compressor dissolution technology at a temperature of 260 ° C and a circulating alkali concentration of 130 g / L, Bayer The amount of red mud added is 250g/L circulating lye, the ratio of total lime added to calcium and silicon is 1.3, and the dissolution time is 90min. The part of the eluate obtained after the wet treatment of Bayer red mud is sent to dealumination, and the dealuminized slurry is pressure-filtered. Machine pressure filtration separation, dealuminization temperature 90 ° C, time 30 min dealuminized lime addition amount is added according to the calcium to aluminum mass ratio of 1.6, the resulting dealuminated slag is added to the Bayer process system, and the final obtained red mud aluminum silicon ratio A / S is 0.62 and the sodium to silicon ratio is 0.14.

Example 10

The bauxite has an aluminum to silicon ratio of 5/A, the circulating mother liquor caustic concentration N _k is 230 g/L, and the additive dealuminized slag is added in an amount of 11% of the added bauxite by CaO, using a dual flow method. At 260 ° C, dissolution for 90 min dissolution, a solution of a _K is 1.48, dissolution of red mud aluminum silicon than A / S is 1.0; Bayer dissolved red mud separation and washing, reverse washing with abandoned red mud washing, reverse The washing is carried out by means of filtration washing; the Bayer process red mud after reverse washing is wet-processed by pipeline preheating-compressor dissolution technology, the temperature is 260 °C, the circulating alkali concentration is 130g/L, Bayer red mud The addition amount is 250g/L circulating alkali liquor, the total lime addition amount is 0.9, the dissolution time is 90min; the dissolution solution obtained by the Bayer process red mud wet treatment is sent to the dealumination, and the dealuminated slurry is pressed by the filter press. Filtration separation, dealuminization temperature 70 ° C, time 30 min, the amount of dealuminized lime added is added according to the mass ratio of calcium to aluminum of 1.6, and the resulting dealuminized slag is added to the Bayer process system, and the final obtained red mud aluminum silicon ratio A/S is 0.75, sodium to silicon ratio N/S is 0.10.

Example 11

The bauxite has an aluminum to silicon ratio of 5/A, the circulating mother liquor caustic concentration N _k is 260 g/L, and the additive dealuminized slag is added in an amount of 11% of the added bauxite by CaO. The technology is dissolved at 280 ° C for 30 min, and the a _k is 1.35. The red mud aluminum silicon is dissolved. The ratio A/S is 1.5; after the dissolution of the red mud by Bayer, the washing is reversed with the discarded red mud washing solution. The washing is carried out by means of filtration washing; the Bayer process red mud after reverse washing is subjected to wet treatment by a double-flow method, the temperature is 280 ° C, the circulating alkali concentration is 210 g / L, and the Bayer red mud is added in an amount of 350 g / L-cycle lye, total lime addition amount of calcium to silicon ratio is 2.5, dissolution time is 30min; Bayer method red mud wet treatment process is partially sent to dealumination, and the dealuminized slurry is separated by filter press. The aluminum temperature is 40 ° C, the time is 60 min, the amount of dealuminized lime added is added according to the mass ratio of calcium to aluminum of 1.6, and the resulting dealuminized slag is added to the Bayer process system, and the obtained red mud aluminum silicon ratio is 0.75, sodium silicon. The ratio N/S is 0.04.

Example 12

Bauxite, alumina-silica ratio A / S is 3, Bayer Process temperature 250 ° C, the caustic alkali concentration of cyclic N _k of 230g / L, a _K of 3.0, the wet red mud Bayer lye treatment cycle The dealuminization slag produced by the regeneration process is used as a dissolution additive. The dissolution time is 90 min, the a _k is 1.48, the red mud aluminum silicon ratio is 1.5, and the Bayer process red mud is 290 ° C. It is 30g/L, the total lime addition amount is 1.0, the dissolution time is 20min, the red mud aluminum silicon ratio is 0.5, and the sodium to silicon ratio N/S is 0.10.

Example 13

Bauxite, alumina-silica ratio A / S of 4, Bayer Process temperature 260 ° C, the caustic alkali concentration of cyclic N _k of 230g / L, a _K of 3.0, the dissolution time 60min, a _K eluate was 1.50, The dissolution ratio of red mud aluminum to silicon is 1.4; Bayer process red mud wet treatment temperature 260 ° C, circulating alkali The liquid concentration is 90g/L, the total lime addition amount is 1.2, the dissolution time is 90min, the red mud aluminum silicon ratio is 0.60, and the sodium to silicon ratio N/S is 0.15.

Example 14

Bauxite, alumina-silica ratio A / S of 5, Bayer Process temperature 270 ° C, the caustic alkali concentration of cyclic N _k of 230g / L, a _K of 3.0, the dissolution time 60min, 1.50 3 eluate eluted Red mud aluminum-silicon ratio A/S is 1.30; Bayer process red mud wet treatment temperature 250 ° C, circulating alkali concentration 130g / L, total lime addition amount of calcium to silicon ratio of 1.4, dissolution time 80min, dissolution of red mud aluminum The silicon ratio A/S was 0.65, and the sodium to silicon ratio N/S was 0.18.

Example 15

Bauxite, alumina-silica ratio A / S of 6, Bayer Process temperature 280 ° C, the caustic alkali concentration of cyclic N _k of 230g / L, a _K of 3.0, the dissolution time 50min, 1.50 eluate, eluted erythro The mud-aluminum-silicon ratio A/S is 1.2; the Bayer process red mud wet treatment temperature is 240 °C, the circulating alkali concentration is 170g/L, the total lime addition amount is 1.9, the dissolution time is 120min, and the red mud aluminum silicon is dissolved. The ratio A/S is 0.55, and the sodium to silicon ratio is 0.12.

Example 16

The bauxite has an aluminum to silicon ratio of A/S of 7, a Bayer process dissolution temperature of 260 ° C, a circulating alkali caustic concentration N _k of 230 g/L, a _K of 3.0, a dissolution time of 70 min, and a leachate a _K of 1.50. The dissolution ratio of red mud aluminum to silicon is 1.1; the Bayer process red mud wet treatment temperature is 250 °C, the circulating alkali concentration is 190g/L, the total lime addition amount is calcium and silicon ratio is 2.1, the dissolution time is 150min, and the red mud is dissolved. The aluminum to silicon ratio is 0.65 for A/S, and the sodium to silicon ratio is 0.12 for N/S.

Example 17

Bauxite, alumina-silica ratio A / S of 8, Bayer Process temperature 260 ° C, the caustic alkali concentration of cyclic N _k of 230g / L, a _K of 3.0, the dissolution time 90min, a _K eluate was 1.55, The dissolution ratio of red mud aluminum to silicon is 1.1; the Bayer process red mud wet treatment temperature is 280 ° C, the circulating alkali concentration is 30 g / L, the total lime addition amount is calcium and silicon ratio is 1.9, the dissolution time is 30 min, and the red mud is dissolved. The aluminum to silicon ratio is 0.66 for A/S, and the sodium/silicon ratio is 0.13 for N/S.

Example 18

The bauxite has an aluminum to silicon ratio of A/S of 9, a Bayer process dissolution temperature of 270 ° C, a circulating alkali caustic concentration N _k of 230 g/L, a _K of 3.0, a dissolution time of 60 min, and a leachate a _K of 1.50. The dissolution ratio of red mud aluminum to silicon is 1.25; Bayer process red mud wet treatment temperature 260 ° C, circulating alkali concentration 130 g / L, total lime addition amount of calcium to silicon ratio of 0.9, dissolution time 90 min, dissolution of red mud The aluminum to silicon ratio is 0.60 for A/S, and the sodium to silicon ratio is 0.15 for N/S. The invention has been described with reference to preferred embodiments thereof. Those skilled in the art will appreciate that variations and modifications can be made within the scope of the invention.

Claims

A method for producing alumina from a medium and low grade bauxite, characterized by comprising the steps of:

a) Bayer dissolution of bauxite; and

b) Wet treatment of Bayer red mud from step a).

A method for producing alumina in a medium-low grade bauxite according to claim 1, characterized in that at least a part of the solution of the red one from the step b) is subjected to dealumination to obtain a dealuminated slag and a circulating lye. The dealuminated slag is used as at least part of the dissolution additive of step a), and the circulating lye is passed to step b) for treating the next batch of Bayer red mud.

A method of producing alumina in a medium-low grade bauxite according to claim 2, characterized in that said dealumination is carried out by a pressure filtration method.

A method for producing alumina by a medium-low grade bauxite according to claim 2, characterized in that the circulating alkali liquor has N _k = 30 - 260 g / L and A1 ₂ 0 ₃ < 20 g / L.

A method for producing alumina from a medium-low grade bauxite according to claim 2, characterized in that the circulating alkali liquor has N _k = 90 - 220 g/L and A1 ₂ 0 ₃ < 20 g/L.

A method for producing alumina in a medium-low grade bauxite according to claim 2, characterized in that said circulating alkali liquor has N _k = 100 - 190 g/L and A1 ₂ 0 ₃ < 20 g/L.

A method of producing alumina from a medium-low grade bauxite according to claim 4, characterized in that said circulating alkali liquor is added with caustic before the addition of step b).

A method for producing alumina in a medium-low grade bauxite according to claim 2, characterized in that in step a), a circulating mother liquor having a N _k of 180 - 280 g/L is added, and the temperature is 240 - 30 CTC. .

A method for producing alumina in a medium-low grade bauxite according to claim 2, characterized in that said step b) is at 200 - 300 ° C, the alkali concentration is 30 - '260 g / L, and A1 ₂ 0 ₃ < 20 g /L conditions are carried out.

10. A method of producing alumina from a medium to low grade bauxite according to claim 2, characterized in that said step b) is at 200 - 300 ° C, the alkali concentration is 90 - 220 g/L, and A1 ₂ 0 ₃ < 20 g / Under the conditions of L.

A method for producing alumina from a medium-low grade bauxite according to claim 2, characterized in that said step b) is at 200 - 300 ° C, the alkali concentration is 100 - 190 g / L, and A1 ₂ 0 ₃ < 20 g /L conditions are carried out.

A method for producing alumina in a medium-low grade bauxite according to claim 2, characterized in that said step b) is at 200 - 280 ° C, the alkali concentration is 30 - 260 g / L, and A1 ₂ 0 ₃ < 20 g / Under the conditions of L.

A method for producing alumina in a medium-low grade bauxite according to claim 2, characterized in that said step b) is at 200 - 280 ° C, the alkali concentration is 90 - 220 g / L, and Al ₂ O ₃ 20 g / L Under the conditions.

A method for producing alumina in a medium-low grade bauxite according to claim 2, wherein said step b) is at 200 - 280 ° C, the alkali concentration is 100 - 190 g / L, and A1 ₂ 0 ₃ < 20 g / Under the conditions of L.

A method for producing alumina in a medium-low grade bauxite according to claim 2, wherein said step b) is at 240 - 270 ° C, the alkali concentration is 30 - 260 g / L, and A1 ₂ 0 ₃ < 20 g / Under the conditions of L.

A method for producing alumina in a medium-low grade bauxite according to claim 2, wherein said step b) is at 240 - 270 ° C, the alkali concentration is 90 - 220 g / L, and A1 ₂ 0 ₃ < 20 g / Under the conditions of L.

A method for producing alumina in a medium-low grade bauxite according to claim 2, wherein said step b) is at 240 - 270 ° C, the alkali concentration is 100 - 190 g / L, and A1 ₂ 0 ₃ < 20 g / Under the conditions of L.

18. A method of producing alumina from a medium to low grade bauxite according to claim 2, characterized in that lime is added to said step b).

A method for producing alumina in a medium-low grade bauxite according to claim 2, characterized in that lime is added during said dealumination, and the amount of lime added is such that the ratio of calcium to silicon is from 0.5 to 2.5.

A method of producing alumina from a medium-low grade bauxite according to claim 2, wherein lime is added during said dealumination, and the amount of lime added is such that the ratio of calcium to silicon is C/S

1.0 ~ 2.1.

21. A process for the production of alumina from a medium to low grade bauxite according to any of claims 1 - 20, characterized in that the Bayer red mud from step a) is subjected to a stepping of red from step b) before entering step b) The mud wash is subjected to reverse washing.

22. A method of producing alumina from a medium to low grade bauxite according to claim 21, characterized in that the solution after the reverse washing is dealuminated and then introduced into the circulating lye.

23. A method for producing alumina from a medium and low grade bauxite according to any of claims 1-20. The method is characterized in that the Bayer red mud from step a) is subjected to a reverse washing with a portion of the red mud eluate from step b) before entering step b).

A method of producing alumina in a medium-low grade bauxite according to claim 23, wherein a portion of the solution after the reverse washing is subjected to dealumination, and then into the circulating alkali liquor, and the other portion is introduced into the circulating mother liquor.

25. A method of producing alumina from a medium to low grade bauxite according to any of claims 1 to 20, characterized in that said steps a) and b) can be carried out by means of a pipe preheating-stop tank dissolution technique, a piped dissolution technique, Pipe preheating - cooker dissolution technology, dual flow method to achieve.

26. A method of producing alumina from a medium to low grade bauxite according to claim 21, characterized in that said steps a) and b) can be carried out by means of a pipeline preheating-stop tank dissolution technique, a pipeline dissolution technique, a pipeline preheating- Compressor dissolution technology, dual flow method to achieve.