Method of phosphate ore processing

FIELD: chemistry.

SUBSTANCE: method of phosphate ore processing includes one-step counterflow process of phosphate ore decomposition, characterised by P2O5 content exceeding 20% in weight, by processing it with water solution of hydrochloric acid, which has HCl concentration lower than 10% in weight, with formation of processing solution, consisting of water phase, in which calcium phosphate is in dissolved state, and of solid phase, which contains admixtures; preliminary neutralisation of processing solution, containing calcium phosphate in solution, to first pH value, which is lower than pH value, at which essential part of said dissolved calcium phosphate precipitates in form of calcium monohydrophosphate (DCP), with precipitation of admixtures; first separation of insoluble solid phase and water phase of processing solution; repeated neutralisation of water phase obtained during first separation to second pH value, exceeding said first pH value, with DCP precipitation; and second separation of repeatedly neutralised water medium, which represents water solution of calcium chloride and precipitated DCP.

EFFECT: method allows optimising ratio between dissolved P2O5 output and purity degree of final product and ensure economically profitable process, which can be realised on simple equipment.

14 cl, 3 dwg, 2 tbl, 1 ex

 

The present invention relates to a method of processing phosphate ore, including:

the reaction of decomposition of phosphate rock with an aqueous solution of hydrochloric acid with formation of a solution treatment consisting of a water phase, in which the calcium phosphate is dissolved and solid phase containing impurities;

the first separation of the insoluble solid phase and the aqueous phase solution treatment;

- preliminary neutralization of the aqueous medium containing calcium phosphate in solution with the first pH lower than the pH at which a significant part of this dissolved calcium phosphate precipitates in the form of monohydrogenphosphate calcium (DCP), with the deposition of impurities;

- allocation of precipitated impurities from the pre-neutralized water environment;

- subsequent neutralization of the specified pre-neutralized aqueous medium at the second pH is greater than said first pH, precipitation of the DCP; and

the second division held further neutralization of the water environment, which is an aqueous solution of calcium chloride, and precipitated DCP.

Known methods involving the processing of phosphate ore with hydrochloric acid (see, for example, patents US-3304157, GB-1051521, ES-2013211 and SU-A-1470663).

The disadvantage of these methods is that them for processing, as a rule, use a solution of HCl, the concentration of which can access the gat 20 wt.% and even 30 wt.%. Used ore must be of good quality, i.e. with a high content of P2O5and , as a rule, requires fine grinding, which leads to increased cost. During processing, there is intense heat associated not only with an isothermal reaction, but also with the release of energy of dissolution, therefore, insoluble substances are very difficult to separate, as the resulting solution is viscous and contains organic matter of mineral origin. High temperature and concentration of the HCl solution cause significant corrosion problems.

There is also known a method of processing hydrochloric acid, in which the ore is subjected to a first, limited processing of diluted hydrochloric acid (see US-A-3.988.420). The only purpose of this method is the dissolution of using this acid a substantial portion of the calcium carbonate contained in the rock, and at the same time, the minimum part phosphates, resulting in getting a solid phase with a high content of P2O5for further processing.

In addition, the above-mentioned processing method with hydrochloric acid (see FR-A-2115244). This method consists in processing ore with a low phosphate content during counter-current process with the help of several consecutive hydrochloric acid solutions of different koncentracije method requires complex and expensive equipment for the removal of huge quantities of sand and other insoluble substances, polluting ore. As a result, when the processing of insoluble substances is the loss of P2About5that should be possible to compensate by using the washing steps.

When phosphate ore decomposes in dilute HCl, the feasibility of processing is determined by two results:

output R2O5dissolved in the liquid phase. Any R2O5remaining in the solid residue, is a loss and reduces output. This output is expressed in % P2O5present in the processed ore;

- the degree of purity of the final product, which is raised if the content of impurities dissolved in the liquid phase processing is reduced. In the framework of the present invention, impurities are any components (anions, cations and heavy metals, etc. that are not water, P2O5and ions of calcium and chlorine. In further description of the invention as standards of purity of the final product selected two elements, namely, fluoride and iron. In the future, the final product will be monohydratefast calcium (DCP), which provided the maximum content will be 0.2% for F and 0.05% for Fe.

It should be noted that the greater the release of dissolved P2O5the lower the degree of purity, as, when all R2O5dissolved as CR is usually most of the impurities are also dissolved. Therefore, you should make a compromise between the degree of purity required for the final product, and a minimum value of dissolved P2O5that can allow the method remained profitable, which mainly depends on the cost of raw materials.

If the original ore is of sufficient quality, I have used the method that uses the reaction of decomposition of phosphate rock with an aqueous solution of HCl with a maximum concentration of 10% by weight, separation of insoluble substances and the aqueous phase containing phosphate ions, chloride ion and calcium ions, and the neutralization of the aqueous phase to precipitate DCP (see international application number PCT/VE 03/00111, not yet published at the priority date of this application).

In fact, if you can provide the conditions under which the minimum output R2O5dissolved in dilute HCl, 75%, and the minimum degree of purity of the final product is 40%, depending on the variable the way you can define the conditions under which the method can be carried out. Such an example is represented by the graph in figure 1 for the phosphate ore. Interest on the axis of ordinates represent either the degree of purity of the final product (solid curve), or the release of dissolved P2O5(dotted curve), and the scale on the axis of absti is with reflect any variable method. In the shaded area between the two endpoints a and b are the conditions necessary for the above minimum values, according to the application PCT/VE 03/00111.

Figure 2 shows a similar graph, but for other phosphate ore. As you can see, for this ore is impossible to achieve conditions under which it is possible to obtain the minimum output P2O5(point a) and the minimum degree of purity (point b).

In this regard, the present invention is to provide a method of treatment of the ore with hydrochloric acid in which the ratio between the output of dissolved P2O5and degree of purity of the final product is optimized in such a way as to ensure efficient processing of ore that can be done on a regular, simple and relatively inexpensive equipment.

This problem in accordance with the present invention is solved using the method described at the beginning of the application, which includes in a single step when using a counter-current process, the reaction of decomposition of phosphate ore, characterized by a content of P2O5in excess of 20 mass% aqueous solution of hydrochloric acid having a concentration of HCl below 10% by weight, and in which to obtain the first LV carry out the specified preliminary neutralization mentioned before the first division in the specified solution processing, which is an aqueous medium containing a solution of calcium phosphate, precipitation of impurities deposited during this first separation specified insoluble solid phase and the aqueous medium, after the first neutralization and subsequent neutralization of the aqueous phase obtained in the first division.

Since the treatment with hydrochloric acid is diluted and, therefore, not a viscous medium, the separation of insoluble substances is better and faster in processing time, which is preferably carried out at ambient temperature, not heat, and it is possible to avoid corrosion problems caused by hydrochloric acid.

Thus, for the processing of phosphate ores are relatively simple reactor, equipped with stirrer working at a temperature and ambient pressure, which is relatively inexpensive equipment.

In the preliminary neutralization occurs prior to the deposition of heavy metals, in particular Fe and Mg, and other impurities, such as fluorine, which provides a valid output of dissolved P2O5during processing. Thus obtained DCP is particularly clean, which cannot be achieved by treatment in dilute hydrochloric acid.

Significant part of phosphate ions trace the em understand that deposited more than 10% of the dissolved P2O5.

The above preliminary neutralization can be accomplished, for example, in a separate tank, located directly at the outlet of the tank in which the reaction occurs decomposition. Preferably the pH should be adjusted to values ranging from 0.8 to 4, preferably from 1.3 to 1.5, in order to avoid any untimely deposition DCP. Precipitated heavy metals are preferably separated during one stage of separation together with obtained during the processing of insoluble components.

Agent neutralization, designed for pre-neutralization, in accordance with the present invention, is preferably a strong base selected from the group comprising a hydroxide, oxide and water-soluble salts of calcium, sodium, potassium and/or ammonium.

The reaction of the decomposition, in particular, and the whole process of processing hydrochloric acid can preferably be carried out at ambient temperature. You can also apply a temperature from 20 to 80°C.

Finally, the concentration of aqueous HCl used for processing, is preferably from 3 to 8%, more preferably from 5 to 7.4%.

Diluted hydrochloric acid used in the method according to the invention, may be of any origin, for Example, you can use such a dilute aqueous solutions of HCl, obtained as liquid wastes of other processes. You can also dissolve in water, commercially available concentrated hydrochloric acid. You can also process the sulfuric acid aqueous solution of calcium chloride to precipitate calcium sulphate and allocation of aqueous HCl. Such an aqueous solution of calcium chloride can be obtained as a liquid waste other processes, for example, some processes for the production of sodium carbonate.

In the method according to the present invention is insoluble phosphate obtained in the course of subsequent neutralization is monohydratefast calcium (DCP) with a very high degree of purity and with a sufficient content of P2O5. The content of P2O5may, for example, be from 40 to 50% by weight with any of the original ore with a content of P2O5more than 20% by weight. Preferably the phosphate ore may have a content of P2O5from 25 to 35 mass%.

During the subsequent neutralization preferably the pH is adjusted to a value at least equal to 4.5, preferably at least equal to 5. At this pH all phosphate ions dissolved in the aqueous phase in the form of dihydrophosphate calcium (MCP), pass into the state of insoluble DCP. This neutralization suppose the equipment carried out by means of a strong base, selected from the group comprising a hydroxide, oxide and water-soluble salts of calcium, sodium, potassium and/or ammonium.

According to the private option of implementing the present invention, the method includes processing the specified aqueous solution of calcium chloride aqueous solution of sulfuric acid with the formation of insoluble calcium sulfate, which precipitates, and the aqueous phase on the basis of hydrochloric acid, separation of precipitated calcium sulphate and at least partial recirculation of the aqueous phase on the basis of hydrochloric acid on the stage of the decomposition reaction for the formation of the indicated aqueous solution of hydrochloric acid.

According to an improved variant of implementation of the present invention the method further comprises the additional neutralization specified aqueous solution of calcium chloride by adding a neutralizing agent so to correct this aqueous solution pH in excess of pH further neutralization, and to achieve deposition of residual impurities, and removing these impurities from the specified aqueous solution, the processing of the aqueous solution of sulfuric acid with the formation of insoluble calcium sulfate, which precipitates, and the aqueous phase on the basis of hydrochloric acid, separation of the precipitate of calcium sulphate and recycling of the aqueous phase on the basis of hydrochloric acid on the stage of reaction RA the provisions for education specified aqueous solution of hydrochloric acid. With this step of the method can precipitate all the unwanted impurities, for example, amphoteric metals, and implement a closed recirculation system without a gradual increase of the content of these impurities during the cycle.

Other distinguishing features of the method of processing in accordance with the present invention shown in the accompanying claims.

Other details and features of this method will be more apparent from the following description of non-restrictive examples, with reference to the accompanying drawings.

Figure 1 and 2 shows the above-described graphics.

Figure 3 in the form of a block diagram shows an example implementation of a production module for receiving the DCP, which used the method of processing phosphate ore in accordance with the present invention.

As shown in figure 3, mined phosphate ore with a content of P2O5from 28 to 32% by weight, line 1 serves in the reaction tank 2, where it is during one stage processed countercurrent solution of hydrochloric acid with a concentration of about 5% by weight, coming into this tank through the pipeline 3. Under phosphate ore in the form in which it is extracted, it should be understood that it is not subjected either to calcination or fine grinding, in particular, in the mines, where the mined ore is in powder form. If we are talking about ores is of volcanic origin, it is possible to provide a simple split up the grain size of the order of 150-500 μm.

In the reaction tank 2 carry out the dissolution of calcium phosphate at ambient temperature, which is fast and intense, and get the H3PO4and soluble MCP.

You can then enter a neutralizing agent such as hydrated lime in tank 9 preliminary neutralization installed at the outlet of the reaction tank 2, with which it is connected by a pipe 8. This introduction of the neutralizing agent are carried out through the pipe 10, and it is intended to maintain in the tank pH 9, for example, in the range of 1.3 to 1.5. At such high pH heavy metals, such as Fe and other impurities such as F, dissolved from the ore during processing hydrochloric acid, precipitate, and thus obtain a suspension of the solid particles. Thus obtained slurry is sent through the pipeline 11 in the separating device 6, for example, filter press, where the solid, i.e. the insoluble matter obtained by treatment with hydrochloric acid, and precipitated in the tank 9 substances are separated through line 7, after the preferred add the corresponding known additives for filtration and discarded.

The liquid phase obtained in the separation, contains dissolved in hydrochloric acid as monocal the Nations phosphate MCP, calcium chloride and some residual impurities.

The separated aqueous phase containing phosphate ions, calcium and chloride coming from the separator device 6 to line 12, is directed into the tank 13 subsequent neutralization, where the precipitated dicalcium phosphate DCP by introducing into the liquid phase through the pipeline 14 neutralizing agent of the type that was specified above, for example, calcium carbonate or lime milk. Here, preferably pH reaches a value of about 5, in which the MCP is converted into insoluble in water and DCP.

To the precipitate, for example, be removed through the pipe 15 neutralized environment and direct it, in particular, on a belt filter 16, which separates the solid, i.e. the wet sediment DCP 17, containing about 40-50% by weight of P2O5measured on the dry product, 25-28% CA and minimal residual impurities. The filtrate is removed through line 18. It consists of an aqueous solution of CaCl2that is to be removed easily because it is not strong pollutant and can even be used in the future. Calcium chloride, for example, be used as a reagent for dealing with ice on the roads.

During this treatment with hydrochloric acid it is possible to obtain an output of dissolved P2O5more than 75%, preferably greater than 90% and sharedfoldername - 95% by weight. Even with such a high output during processing in DCP obtained in 17, reaching a degree of purity greater than normally required minimum value, for example, the maximum content of F is 0.2%, a Fe - 0,05%.

Instead of removing aqueous solution of CaCl2coming from a band filter 16, it is also possible to provide the feed pipes 19 and 20 in the reactor 21, in which the pipe 22 enters an aqueous solution of sulfuric acid. In this reactor by stirring at a temperature of about 60°C for one hour insoluble calcium sulfate is precipitated in a very pure form. Through line 23 is obtained by treatment with sulfuric acid, the solution passes through the phase separation, for example by filtration device 24. The formed solid phase of calcium sulfate is removed by line 25, and the liquid phase formed ultrapure water with HCl solution through the pipeline 26 is sent to the feed line 3 with diluted hydrochloric acid.

Because sulfuric acid occurs in the presence of more often and in larger quantities than hydrochloric acid, this recycling allows to further improve the processing performance of hydrochloric acid and even to envisage the possibility of its implementation in places where HCl is difficult to get.

In an alternative embodiment, prior to being fed into the reactor for about what abode sulfuric acid, you can send an aqueous solution of CaCl 2coming from a band filter 16 in the tank 27 additional neutralization through line 28.

In this tank 27 through line 29 to again enter the neutralizing agent, preferably gidratirovannuyu lime or calcium carbonate, to obtain a pH of about 9-10, resulting in a precipitate any residual impurities such as amphoteric metals, etc. Obtained slurry through the pipeline 30 is sent to the separator 31. The separated precipitate is removed through 32, and ultrapure filtrate formed CaCl2in solution, through the pipes 33 and 20 is directed into the reactor 21 treatment with sulphuric acid.

Of course, that it is possible to provide a feed source of a dilute hydrochloric acid aqueous solution of CaCl2obtained as the result of another process, pre-subjecting, if necessary, this aqueous solution treatment with sulfuric acid, as in the reactor 21, after neutralization device 27 neutralization.

Hereinafter the invention will be described in more detail by means of embodiment, not shown, in order restrictions.

Example

A. Used phosphate ore of Syrian origin, characterized by a content of P2O5equal to 30% by mass.

The ore processing is carried out in a continuous mode using an aqueous solution with a mass content of HCl to 7.4% at which the temperature of 25°C. In this example, the decomposition reaction occurs prototechno in a reactor equipped with a stirrer, and lasts about 30 minutes for each batch of ore.

The number of added HCl to determine the molar ratio between added to the ore HCl and present it Sa (ratio of HCl/CA=1 is defined as the HCl additive necessary to the whole Sa ore is dissolved in the form of CaCl2in the aqueous phase). In this example, the processing of ore is carried out at different ratios of HCl/Sa, ranging from 0.6 to 0.9.

After the decomposition reaction, the suspension is filtered, and the filtrate is subjected to neutralization of hydrated lime to get the DCP in the form of sediment.

Conducted an analysis of the release of dissolved P2O5and the contents of F-and Fe++in DCP, which gave the following results:

The ratio of HCl/CAThe release of dissolved P2O5, wt.%The share of the ore in the form of residue, wt.%Fluoride in DCP, wt.%The iron in the DCP, wt.%
0,6
0,7
0,8
0,9
80
92
95
96
55
52
48
47
0,41
0,48
0,65
0,78
0,06
0,064
0,096
0,12

How is one to note, although the release of dissolved P2O5is acceptable, the values of Fe and F in the DCP are too high (F>0.2 wt.% and Fe>0,05 wt.%).

B. Make processing of this ore. The ore processing carried out continuously by means of an aqueous solution with a mass content of HCl to 7.4% at 25°C. In this example, the decomposition reaction takes approximately 30 minutes for each batch, and the molar ratio of HCl/CA set equal to 0.9.

Before the first separation of liquids from solids pH regulate using gidratirovannoi lime to achieve different values, and then produce a filtered and re-neutralization to precipitate DCP, which is removed in the filtration of sediment.

The result of the analysis gives the following results:

pHThe release of dissolved P2O5, wt.%Fluoride in DCP, wt.%The iron in the DCP, wt.%
0,6
1,3
1,5
1,7
1,9
95
78
77
67
54
0,79
0,25
0,074
0,047
0,055
0,12
0,05
0.04
being 0.036
being 0.036

As can be noted, adjusting pH in the range from 1.3 to 1.5 before being filtered at the first separation of liquids and solid substances ore lead in the state in which it can be used, which cannot be achieved without prior neutralization, in the processing of ore, diluted hydrochloric acid. The release of dissolved P2O5is also valid, and the degree of purity of the final product is excellent. This requires only one stage of separation of the impurities.

Of course, that the present invention is by no means the case is not limited to this embodiment and it is possible to make changes, without leaving the scope of the attached claims.

1. The method of processing phosphate ore, including:
single-stage countercurrent process for the decomposition of phosphate ore, characterized by a content of P2O5exceeding 20 wt.%, treatment with an aqueous solution of hydrochloric acid having a concentration of HCl below 10 wt.% with the formation of a solution treatment consisting of a water phase, in which the calcium phosphate is dissolved and solid phase containing impurities;
pre-neutralization of the solution treatment containing calcium phosphate in solution, prior to the first pH that is less than the pH at which a significant part of this dissolved calcium phosphate precipitates in the form of monohydrogenphosphate calcium (DCP), with the deposition of impurities;
the first separation of the insoluble solid phases and aqueous phase solution processing;
re-neutralization of the aqueous phase obtained in the first division to the second pH values greater than a specified first value pH, precipitation of the DCP; and
the second division last re-neutralization of the water environment, which is an aqueous solution of calcium chloride, and precipitated DCP.

2. The method according to claim 1, characterized in that the first value is the pH of the solution processing adjusted by the specified preliminary neutralization is in the range of 0.8 to 4, preferably from 1.3 to 1.5.

3. The method according to one of claim 1 or 2, characterized in that the second value of the specified pH of the aqueous phase resulting from the first division, adjusted by a specified subsequent neutralization to a value at least equal to 4.5, preferably at least equal to 5.

4. The method according to claim 1, characterized in that the said prior and subsequent neutralization is carried out with the aid of a strong base selected from the group comprising a hydroxide, oxide or water-soluble salts of calcium, sodium, potassium and/or ammonium.

5. The method according to claim 1, characterized in that the decomposition reaction is carried out at ambient temperature.

6. The method according to claim 1, characterized in that it includes a preliminary stage of education specified water rastvoritelei acid by dilution of concentrated hydrochloric acid with water.

7. The method according to claim 1, characterized in that it includes a preliminary stage of education specified aqueous solution of hydrochloric acid by treatment with sulfuric acid aqueous solution of calcium chloride and removal of the precipitate of calcium sulfate.

8. The method according to claim 1, wherein the phosphate ore is the content of P2O5from 25 to 35 wt.%.

9. The method according to claim 1, characterized in that the aqueous solution of hydrochloric acid used for the decomposition reaction, is the concentration of HCl in the order of 3-8%, preferably 5-7,4 wt.%.

10. The method according to claim 1, characterized in that it includes processing the specified aqueous solution of calcium chloride aqueous solution of sulfuric acid with the formation of insoluble calcium sulfate, which precipitates, and the aqueous phase on the basis of hydrochloric acid, separation of the precipitate of calcium sulfate and at least partial recirculation of the aqueous phase on the basis of hydrochloric acid on the stage of the decomposition reaction for the formation of the indicated aqueous solution of hydrochloric acid.

11. The method according to claim 1, characterized in that it further includes an additional neutralization specified aqueous solution of calcium chloride thus, to correct this aqueous solution a pH value above the pH value of re-neutralization, and to achieve deposition of residual impurities, and removing these impurities sukasana aqueous solution, the processing of the aqueous solution of sulfuric acid with the formation of insoluble calcium sulfate, which precipitates, and the aqueous phase on the basis of hydrochloric acid, separation of the precipitate of calcium sulphate and recycling of the aqueous phase on the basis of hydrochloric acid at the stage of the decomposition reaction for the formation of the indicated aqueous solution of hydrochloric acid.

12. The method according to claim 11, characterized in that the pH value of the specified aqueous solution of calcium chloride adjusted by specified additional neutralization to a value of at least 8.5, preferably at least equal to 9.

13. The method according to claim 11, characterized in that the additional neutralization is carried out with the aid of a strong base selected from the group comprising a hydroxide, oxide or water-soluble salts of calcium, sodium, potassium and/or ammonium.

14. The method according to claim 1, characterized in that the decomposition reaction is carried out in a reactor equipped with a stirrer.



 

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FIELD: production of pure phosphoric acid and calcium monohydrophosphate.

SUBSTANCE: proposed method includes decomposition of phosphate ore by first hydrochloric acid solution at concentration not exceeding 10 mass-%, separation of liquid decomposition product into insoluble solid phase containing admixtures and separate aqueous phase containing phosphate, chloride and calcium ions in form of solution, neutralization of aqueous phase separated from liquid decomposition product by adding calcium compound for obtaining insoluble settled-out calcium phosphate by means of phosphate ions, separation of neutralized aqueous phase into aqueous phase containing calcium and chloride ions in form of solution and settled solid phase on base of water-insoluble calcium phosphate and dissolving of at least part of separated settled solid phase in second aqueous hydrochloric acid solution containing hydrochloric acid in the amount exceeding its content in first hydrochloric acid solution, thus forming aqueous solution containing phosphate, chloride and calcium ions extracted by organic extracting agent at extraction in "liquid-liquid" system. Proposed method makes it possible to avoid fine grinding or roasting of ore.

EFFECT: enhanced efficiency of extraction for production of pure concentrated phosphoric acid solution with no contamination of surrounding medium.

24 cl, 2 dwg, 1 tbl, 4 ex

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