RU2532773C1 - Method of processing rare-earth phosphate concentrate - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of processing a rare-earth phosphate concentrate separated when neutralising a nitric-phosphoric acid solution obtained after breaking down apatite with nitric acid, includes treating rare-earth phosphate concentrate with nitric acid and separating the undissolved residue from the obtained rare-earth element nitrate-phosphate solution. After treatment, the undissolved residue is washed and rare-earth elements are extracted from the rare-earth element solution. The undissolved residue is washed with ammonium nitrate solution with concentration of 40-70 wt % in amount of 25 pts.wt per 1 pts.wt of the undissolved residue. The wash solution is combined with the rare-earth element solution fed for extraction, and the undissolved residue is taken for production of compound fertilisers.

EFFECT: high degree of extraction of rare-earth elements from the rare-earth phosphate concentrate while reducing consumption of ammonia at the step of neutralising the nitric-phosphoric acid solution, consumption of nitric acid and hydrogen peroxide when dissolving the rare-earth phosphate concentrate.

3 cl, 3 tbl, 4 ex

Description

The invention relates to a technology for the processing of phosphate rare-earth concentrate (or FRZK) obtained in the process of complex nitric acid processing of apatite into complex fertilizers.

The separation of rare earth elements from apatite during its nitric acid decomposition is carried out from a nitric phosphate solution with its partial neutralization in the form of a phosphate rare earth concentrate (FRZK), during the subsequent processing of which rare earth elements are obtained.

Known methods for the processing of PRZK by dissolving it in nitric or hydrochloric acids, followed by precipitation of oxalates of rare earth elements with oxalic acid (Complex nitric acid processing of phosphate raw materials. Edited by A. Goldinov and B. A. Kopyleva - L .: Chemistry 1982, p. 157-159; RU 2148019, 11/23/1998).

The disadvantages of the methods:

- the use of scarce expensive reagent - oxalic acid;

- during processing, solutions are formed containing excess oxalic acid, the utilization of which in the production of complex fertilizers leads to a deterioration in the quality of fertilizers.

A known method of producing nitrate-phosphate solution of rare-earth elements (hereinafter REE) from FRZK, suitable for subsequent extraction of REE extraction method. SUBSTANCE: method involves pulverizing a flask with a solution from the washing stage of an extractant, treatment with nitric acid, separating the obtained solution of a rare-earth element from an insoluble residue and subsequent washing of an insoluble residue with a diluted solution of nitric acid with a concentration of 1.5 N (Moiseev S.D. et al. Extraction purification of rare-earth phosphate concentrate obtained by processing apatite. Chemical industry, No. 8, 1981, S. 472-475). Of great importance in the extraction extraction of REE from nitric phosphate solutions is the concentration of REE in the solution, the presence of salting out agents in the solution, and the content of free nitric acid.

The disadvantage of this method is the use for washing an insoluble residue containing a significant amount of REE-rich liquid phase, a solution with a high water content, which leads to an increase in water content and a decrease in the REE content in the solution supplied to the extraction, and requires the creation of additional equipment for its further processing.

The closest in technical essence (prototype) to the proposed method is a method of processing a phosphate rare-earth concentrate, isolated when neutralizing a nitric-phosphate solution obtained after opening apatite with nitric acid, including treating a phosphate rare-earth concentrate with nitric acid, separating the insoluble residue from the resulting nitrate-phosphate solution rare earth elements and washing the insoluble residue with a nitric phosphate solution with a flow rate within 100 m to 710 parts by weight per 1 part by weight insoluble residue. After washing, the solution is fed to the ammonization stage for precipitation of the PPC (patent RU 2086507, 05.26.1992). The practical implementation of the method consists in mixing an insoluble precipitate with the initial nitric phosphate solution. The disadvantages of the method are:

- the need to separate insoluble sediment from significant volumes of suspensions, which require a long sludge (more than 8 hours) and filtering the thickened portion of the resulting suspension;

- the separated residue from the dissolution stage of the FEC contains a significant amount of REE in the form of water-soluble nitrate salts - more than 10% of the REE of its amount in the FER; this amount of REE is returned to the beginning of the technological cycle for preparing the REED (recycling), in connection with which the consumption of reagents for the deposition of an additional amount of REE from the nitric phosphate solution and obtaining a solution of nitrate salts of REE increases; recycle REE flow requires an increase in the consumption of ammonia at the stages of deposition of the FRAZ, nitric acid and hydrogen peroxide at the stages of the dissolution of the FER;

- separation of the insoluble residue in the form of “collective” precipitates together with sodium or calcium silicofluorides will lead to a deterioration in the quality of these products and the inability to obtain marketable products without additional purification steps.

The objective of the invention is to increase the efficiency of the method of processing phosphate rare-earth concentrate due to its simplification and lower consumption of reagents with a high degree of extraction of REE from FRZK.

The technical result of the invention is to achieve a degree of extraction of REE from FRZK to 99% while reducing the consumption of ammonia at the stage of neutralization of nitric phosphate solution, the flow rate of nitric acid and hydrogen peroxide to dissolve the FRZK by 10%.

The proposed method allows to eliminate the disadvantages of the method of the prototype, namely:

- no additional equipment is required for settling and filtering large volumes of a suspension of insoluble sediment in a nitrogen-phosphoric acid solution;

- the insoluble residue from the stage of dissolution of the FRZK after washing the water-soluble REE from it is sent to the technological cycle for producing complex fertilizer;

- the insoluble residue from the stage of dissolution of the FRZK is not fed to the stage of defluorination, and therefore, additional purification steps will not be required to obtain salable sodium or calcium silicofluoride salts;

- for washing the insoluble residue does not require special equipment, it is carried out by filtering the decomposition solution of the FRZK;

- excludes the return (recycling) of REEs to the beginning of the technological cycle of obtaining REEDs, that is, the consumption of reagents for precipitation of an additional amount of REEs from a nitric phosphate solution and the production of a solution of nitrate salts of REEs, which is approximately 10% of the total reagent consumption, are excluded.

The task is achieved in that the processing of the rare-earth phosphate concentrate separated during neutralization of the nitric-phosphate solution obtained after opening apatite with nitric acid includes the treatment of the rare-earth phosphate concentrate with nitric acid, the separation of the insoluble residue from the obtained nitrate-phosphate solution of rare-earth soluble and non-soluble elements. While washing the insoluble residue is carried out with a solution of ammonium nitrate at a concentration of 40-70% by weight, the flow rate of the solution of ammonium nitrate during washing of the insoluble residue is maintained within 2-5 parts by weight. per 1 part by weight insoluble residue. The washing solution is combined with the target REE solution fed to the extraction, the insoluble precipitate is returned to the production of complex fertilizers, the spent nitric phosphate solution is used to transport the insoluble precipitate after separation of the rare-earth phosphate concentrate from it.

In this case, a solution of ammonium nitrate obtained by the conversion of calcium nitrate, isolated by crystallization from a solution of decomposition of apatite with nitric acid, with a solution of ammonium carbonate can be used as a washing solution.

The use of a solution of ammonium nitrate for washing an insoluble precipitate with a liquid-solid ratio (hereinafter referred to as L / T) (2 ÷ 5) / 1 by weight reaches up to 95% degree of washing REE from insoluble precipitate and, accordingly, up to 99% degree of extraction of REE from FRZK.

The washing solution (filtrate) is combined with the main solution (filtrate) and then, after adjusting the composition according to the content of the salting out agent, it is directed to the extraction separation of REE by known methods.

According to the claimed method, there is no need for additional equipment for preliminary sedimentation and filtration of significant volumes of a suspension of an insoluble residue in a nitrogen-phosphoric acid solution. Washing of the insoluble residue is carried out directly on the filter. That is, the recycle stream of REE is excluded and, accordingly, the additional consumption of reagents for precipitation of REE from the washing solution and their subsequent dissolution is excluded.

The insoluble residue, which is silicon dioxide with impurities of iron and titanium compounds, is returned to receive complex fertilizer. At the same time, nitric-phosphate solution can be used as a transport fluid after separation of a rare-earth concentrate from it. A portion of the solution or the entire stream may be used to transport the insoluble residue.

Due to the fact that the insoluble residue is not supplied to the stage of purification of the nitric phosphate solution from fluorine, which is a necessary stage for obtaining high-quality FRSK, contamination of fluorine salts (sodium fluoride, potassium, calcium, etc.) is not observed even after washing these salts from water-soluble impurities, these salts can be produced as commercial products.

The combination of the washing solution with the main REE filtrate eliminates the return (recycling) of REE to the beginning of the production cycle of the FRSK, that is, the reagent consumption for the stage of neutralization (ammonia) of the nitric phosphate solution, the solution for dissolving the FRZK (nitric acid and hydrogen peroxide) is reduced by about 10 % compared with the prototype.

Ammonium nitrate, which is part of the washing solution, is a strong salting out component, which allows to increase the separation coefficients during extraction methods of purification of nitrate-phosphate REE solutions from phosphates and other impurities.

Ammonium nitrate solutions with a concentration of 40-70% wt. they are intermediate technological environments in the production of complex fertilizers obtained by the decomposition of apatite with nitric acid; no additional costs are required for their production.

Implementation of the proposed method in an industrial environment, unlike the prototype, will reduce raw materials and energy and obtain a nitrogen-phosphorus REE solution of the required quality for subsequent extraction of REE from it by an extraction method.

Tables 1, 2, 3 show examples illustrating the possibility of obtaining a solution of the required quality for extraction by the content of the amount of rare earth elements in terms of oxides (hereinafter REO), acidity and the content of a salting-out agent using ammonium nitrate solutions to wash the insoluble precipitate remaining after the dissolution of the PPRC in nitric acid.

From the examples shown in table 1, it is seen that obtaining a ready-made solution for extraction with the required values for the content of the total REO (at least 65 g / l) for acidity (70-90 g / l) and the content of the salting out agent (ammonium nitrate - at least 600 g / l) is possible only under the condition that the insoluble precipitate from the stage of dissolution of the PPC does not rinse, while the loss of rare-earth elements with an unwashed precipitate is more than 10% (in example 1, table 1 11.3%). Washing the precipitate with acidified water leads to a decrease in losses of up to 2.4% at W / T = 2: 1, but at the same time the content of the total REO of the finished solution decreases to 60 g / l, which is extremely undesirable for the extraction cascade. Washing at W / T = 4: 1 leads to a decrease in the amount of REO with the finished solution decreases to 42 g / l; processing of such solutions by the extraction method will lead to large losses of REO at the extraction stage.

The examples shown in table 2 show that the use for washing an insoluble precipitate of solutions of ammonium nitrate with a concentration of 40-70% at T / W equal to 2: 1, with a loss of REO of 2.4%; allows you to get ready-made solutions for extraction with a content of REO of 70-80 g / l. A decrease in the content of ammonium nitrate in the wash solution to 20% leads to a decrease in the content of the total REO in the solution to a limit value of 65 g / l.

The examples shown in table 3 show that the use for washing an insoluble precipitate of solutions of ammonium nitrate with a concentration of 57% at T / W below 2: 1 leads to an increase in REO losses up to 5%, which is also undesirable. When the ratio T / W equal to (2 ÷ 5) / 1, losses are reduced to 1.1-2.5%, while the content of the total REO in the resulting solution is 59-76 g / l. An increase in the T / F ratio when washing the precipitate above 5: 1 leads to a decrease in the content of the total REO in the resulting solution below 55 g / L.

Examples

In all examples, the preparation of a solution of nitrate salts of the sum of rare-earth elements containing about 80 g / l of free nitric acid and about 600 g / l of ammonium nitrate from 128.5 g of FRAZ with the total amount of rare-earth ions of 22.2% and humidity of 45% is shown.

Table 1 shows data on the composition of the obtained solutions and the degree of extraction of the amount of rare-earth elements in the solution, provided that the insoluble residue from the dissolution stage of the PPC is not washed or washed with water at a T / W ratio of (2 ÷ 4): 1.

Table 2 shows data on the composition of the obtained solutions and the degree of extraction of the amount of rare-earth elements in the solution, provided that the insoluble residue from the stage of dissolving the PPC is washed with solutions of ammonium nitrate with a concentration of 0 to 70% at a T / G ratio of 2: 1.

Table 3 shows data on the composition of the obtained solutions and the degree of extraction of the amount of rare-earth elements in the solution, provided that the insoluble residue from the stage of dissolution of the PPC is washed with solutions of ammonium nitrate at a concentration of 57% and 70% at a ratio T / W equal to (0.5 ÷ 6) :one.

Example 1 (Experience 1, table 1).

125.8 g of FRAZ with a total REO content of 22.2% and a humidity of 45% are dissolved in 122.4 g of 58% nitric acid in the presence of 10 g of a 30% hydrogen peroxide solution. The resulting nitric phosphate suspension is filtered. Obtain 211.8 g of filtrate with a content of the total REO of 11.6% and 45 g of sediment with a content of retained liquid phase of 60% and a content of the sum of REO of 7.3%. The resulting precipitate is not washed. To the obtained filtrate, 181.2 g of ammonium nitrate are added and 391 g of a ready-made solution for extraction is obtained with a total content of REO of 90.2 g / l, nitric acid 80.6 g / l, and ammonium nitrate 600 g / l. The output of the amount of REE in the finished solution is 88.7%, and the loss of the amount of REE with an unwashed precipitate is 11.3%.

Example 2 (Experience 2, table 1).

125.8 g of FRSK with a total REO content of 22.2% and a humidity of 45% are dissolved in 142.6 g of 58% nitric acid in the presence of 10 g of a 30% hydrogen peroxide solution. The resulting nitric phosphate suspension is filtered. The resulting precipitate was washed with acidified water at W / T = 2: 1, and the washing filtrate was added to the main filtrate. Obtain 322.3 g of the filtrate with a content of REO of 8.4%. 300 g of ammonium nitrate are added to the total filtrate and 620 g of a ready-made solution for extraction is obtained with a content of REO of 60.1 g / l, nitric acid 79.1 g / l, and ammonium nitrate 600 g / l. The output of the amount of REE in the finished solution is 97.6%, and the loss of the amount of REE with washed precipitate is 2.4%.

Example 3 (Experience 4, table 2).

125.8 g of FRSK with a total REO content of 22.2% and a humidity of 45% are dissolved in 130.6 g of 58%) nitric acid in the presence of 10 g of a 30% hydrogen peroxide solution. The resulting nitric phosphate suspension is filtered. The resulting precipitate is washed with a solution of ammonium nitrate 57% wt. at W / T = 2: 1 and the washing filtrate is added to the main filtrate. Get 310, 2 g of the filtrate with a content of REO of 8.7%. 192.9 g of ammonium nitrate is added to the total filtrate and 501 g of a ready-made solution for extraction is obtained with a content of REO of 75.9 g / l, nitric acid 80.9 g / l, and ammonium nitrate 600 g / l. The output of the amount of REE in the finished solution is 97.5%, and the loss of the amount of REE with washed precipitate is 2.5%.

Example 4 (Experience 9, table 3).

125.8 g of FRSK with a total REO content of 22.2% and a humidity of 45% are dissolved in 130.9 g of 58% nitric acid in the presence of 10 g of a 30% hydrogen peroxide solution. The resulting nitric phosphate suspension is filtered. The resulting precipitate is washed with a solution of ammonium nitrate 70% wt. at W / T = 4: 1 and the washing filtrate is added to the main filtrate. Receive 400.8 g of the filtrate with a content of REO of 6.8%. 128.4 g of ammonium nitrate is added to the total filtrate and 527 g of a ready-made solution for extraction is obtained with a total content of REO of 72.6 g / l, nitric acid 77.8 g / l, and ammonium nitrate 600 g / l. The output of the amount of REE in the finished solution is 98.6%, and the loss of the amount of REE with washed precipitate is 1.4%.

Claims (3)

1. A method of processing a phosphate rare earth concentrate isolated during the neutralization of a nitric phosphate solution obtained after opening apatite with nitric acid, comprising treating a phosphate rare earth concentrate with nitric acid, separating an insoluble residue from the obtained nitrate phosphate solution of rare earth elements and rare-earth solids, washed the extraction of rare earth elements from a solution of REE, characterized in that the washing of the insoluble residue is carried out with a solution of nitrate ammonium concentration 40-70% by weight. with a flow rate of a solution of ammonium nitrate 2-5 wt.h. per 1 part by weight insoluble residue, the washing solution is combined with the REE solution supplied to the extraction, and the insoluble precipitate is sent to the production of complex fertilizers. 2. The method according to claim 1, characterized in that the ammonium nitrate solution is obtained by the conversion of calcium tetranitrate isolated from nitric phosphate solution by polythermal crystallization with ammonium carbonate. 3. The method according to claim 1, characterized in that for transportation of insoluble sediment use spent nitric phosphate solution after separation of phosphate rare-earth concentrate from it.