JPS5933525B2 - Method for producing phosphoric acid with high fertilizer nutrient content - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides phosphoric acid and P-separable calcium sulfate hemihydrate, which has a high content of fertilizer nutrients, by converting the raw phosphate into nitric acid with the addition of sulfate ions in the form of ammonium sulfate or sulfuric acid. ,
The present invention relates to a method for producing calcium sulfate hemihydrate by dissolving it while maintaining optimal acid concentration and working temperature conditions for precipitation.

The dissolved P solution can be processed into multinutrient fertilizers in a conventional manner with the addition of additional nutrients or dissolved substances.

In the production of multinutrient fertilizers by the conventional nitro-phosphate process, the raw phosphate is dissolved with a mixture of nitric acid and phosphoric acid, thus with nitrogen-containing phosphoric acid, and then with ammonia. This dissolved mixture is neutralized by the addition of .

This mushy sap is then granulated, optionally after addition of potash salt or other salts.

Although this nitro-phosphate process is easy to operate, it has the disadvantage that phosphoric acid must be available and its relatively high cost negatively impacts the economics of the process in the final product.

In order to reduce this economic disadvantage, various processes are already known for producing multinutrient fertilizers, which processes can be operated with reduced phosphate addition or without phosphate addition. Ru.

In this way, the raw phosphate dissolution can be accomplished simply with nitric acid, and then by cooling a portion of the calcium ions can be separated in the form of calcium nitrate, which can later be used in the production of calcium ammonium nitrate. known (Otsuzu method).

Furthermore, calcium ions that appear when the raw material phosphate is dissolved in nitric acid are removed from gypsum Ca50 using ammonium sulfate.
It is also known to precipitate in the form of 4X 2 H20, in which case the gypsum is usually thrown away as waste;
The nitrogen-containing phosphoric acid produced is further processed into multinutrient fertilizer.

This process has the advantage that ammonium sulfate can be used, the sulfate content of which is usually cheaper than the sulfate content of industrial sulfuric acid, and therefore cost savings are achieved in this manner.

This known process requires an elaborate purification of gypsum from soluble sulfates.

This requires considerable amounts of water, which must later be evaporated again during the production of the fertilizer.

The required amount for the F plane is 2.5 to 5 in this method.
m2/ton gypsum is extremely high.

As already mentioned, the residual impurities usually impair the gypsum thus obtained so strongly that it can no longer be used as a building material.

By the way, the present inventor has discovered a method that does not require complicated purification methods by using ammonium sulfate and/or sulfuric acid as a precipitant for calcium ions in a raw phosphate solution.

That is, the present invention provides a method for producing phosphoric acid containing a large amount of fertilizer nutrients by dissolving raw phosphate and precipitating calcium ions with sulfate ions using nitric acid and sulfuric acid, which includes: a) dissolving the raw phosphate; 7 per mole of P2O5 for
using ~17 equivalents of H+, b adjusting the water content of the dissolved acid mixture by addition of filter washing water such that the water content of the nitrogen-containing phosphoric acid made is 25-40% by weight; C after precipitation 1 adding sulfate ions in the form of sulfuric acid or ammonium sulfate to the dissolution solution during or after dissolution in such an amount that there are from 10 to 1507 free S2 per liter of solution; d. the molar ratio of H2SO4:HNO3 in the dissolved acid; The dissolution of raw phosphate and the separation of calcium sulfate hemihydrate are carried out exclusively by H2
When precipitating Ca2+ ions with SO4, 60~
When Ca2+ ions are precipitated exclusively with (NH4)2SO4 at 110°C, H2SO4 is precipitated at 60-100°C.
When precipitating Ca2+ ions with (NH4)2SO4, this method is characterized in that it is carried out at a temperature intermediate to the above.

In this specification, all % means % by weight.

The process of the present invention takes full advantage of the availability of inexpensive ammonium sulfate while avoiding the disadvantages mentioned above.

The invention also includes a method in which the addition of ammonium sulfate is replaced by the addition of an equivalent amount of sulfuric acid to achieve the same objective.

First, a case where ammonium sulfate is used will be described.

According to the working conditions of the method of the present invention, calcium ions liberated during dissolution of raw phosphate in nitric acid are dissolved in gypsum Ca SO
Rather than being precipitated as 4X 2 H20, the hemihydrate Ca SO4X! Precipitation as AH20 can be achieved.

In that case, very pure calcium sulfate can be produced without the inclusion of any significant amounts of ammonium sulfate.

By adding the raw phosphate to the solution, ammonium sulfate is simultaneously added to the solution in a targeted manner.
It is added in such an amount that an excess of I- is present.

Free SO2,- ions should be present at a minimum concentration of 10 fSO2/liter of dissolved solution.

Generally, this excess will be somewhat higher, e.g. about 5 ofs
Around /'J would be retained in the solution.

Under the above-mentioned conditions, well-formed calcium sulfate hemihydrate crystals are formed after a short time and, since these crystals are large, can be separated very well from P.

This separation usually consists of a mixture of large crystals that are stuck together, but also partly of single crystals.

Owing to the favorable surface to volume ratio, the precipitate can be separated and purified from adhering impurities with a small amount of water.

This makes the method of the invention very simple and economical.

The separation of the nitrogen-containing phosphoric acid from the calcium sulfate hemihydrate takes place via a filter, but it is also possible to use a centrifuge.

In order to make do with as little amount of washing water as possible, it is appropriate to perform the opposing washing in multiple stages.

As a result of good crystal formation, little water sticks to the hemihydrate crystals.

When filtered with a vacuum filter, the actual calcium sulfate is 2
It only has a total water content of 0-25%, which corresponds to about 15-20% free water (and 53-5.0% bound water).

If separated with the aid of a centrifuge, even a total water content of about 15% can be reached.

The time of condensation of calcium sulfate hemihydrate to calcium sulfate trihydrate proceeds very slowly under the conditions according to the invention, so that crusting on the filter is avoided.

The filtration speed is extremely high, so even in the case of a 4-stage filter, a filter surface of 0.8 m2/) of hemihydrate is sufficient, and in that case, a filter surface of about 0.3 m is sufficient for filtration, unless cleaning is considered. Only 100 ml/ton hemihydrate is required.

A separate recycle is not necessary, contrary to the known trihydrate process.

This means that a recirculation pump is not required) and thus energy is saved.

Nitric acid concentration and solubility temperature can be matched in the process of the invention so that calcium sulfate hemihydrate is produced.

The initial nitric acid concentration generally depends on the existing nitric acid plant, where the nitric acid fed into the reactor is adjusted by addition of recycled filter wash water to a concentration such as 35-60% HNO3, preferably 45-55%. .

When calculating the nitric acid concentration, substances present in the wash water such as ammonium nitrate and phosphoric acid are not taken into account.

In that case, the reaction temperature is appropriately 60 to 100°C, preferably 7°C.
~so'c is selected.

In that case, relatively high temperature ranges are preferred at low HNO3 concentrations, whereas at relatively high acid concentrations lower temperature ranges can also be used with the highest yields.

However, the process of the present invention is generally carried out within the above-described ranges of temperature and concentration.

Although the reaction scheme uses 2 moles of NO3 per mole of CaSO4, if CaSO4 with a total water content of 23% is to be separated, at least 0.7131-ton HNO3/ton P residue is used.

If 0.080 tons of HNO3/t of p-residue (equivalent to about 7.5 mol of HNO3 and 1 mol of P2O5) is used, then depending on the concentration of nitric acid used (column a of the table below), column b should be used. The amount of acid specified in 1 must be used, or in that case the amount of water listed in column C is supplied.

Table: o, so ton HNO3/ton P residue, Pm with 23% total water content to use a wash water-nitric acid mixture (WSG) of 48 wt% HNO3 with respect to the raw phosphate melt.
Allowable amount of washing water that can be added per i ton 2 (liter H
20) and the concentration of nitric acid (S) used from 40 to 88% by weight. Evaporation loss during dissolution and NH4NO3, (NH4)2-xH1+XP returned with the washing water.
When ignoring the amounts of O4, (NH4)2SO4, etc., (867 liters/ton P for a 48% concentration acid)
48 in column d), taking into account the moisture content of the residue.
The amount of water that can be added to prepare a dissolved mixture having % by weight of HNO3 is known.

Other desired HNO3 concentrations, other HNO3 availability per mole P2O5 or ton S/ton F or other average total water content in the r residue, etc. can be derived from equivalent tables without difficulty.

Experiments have shown that a complete multistage cleaning of 1 ton of calcium sulfate hemihydrate with a total moisture content of 23% requires at least 400
It was found that liters of washing water were required to obtain a virtually (NH4) 2804-free product.

As can be seen from the table above, all the wash water can be re-fed to the reactor up to a nitric acid concentration of 64%.

If only relatively low HNO3 concentrations of nitric acid are available, it may be appropriate to return only a small portion of the wash water or no wash water to the reactor.

Optionally, the wash water P solution can be concentrated to an acceptable volume and then combined again with the nitrogen-containing phosphoric acid product and used in the usual manner for the production of multinutrient fertilizers.

As ammonium sulfate, products of industrial purity can be used.

The method of production has virtually no effect on the yield achieved.

The phosphoric acid produced in this way can be used to produce fertilizers such as HNO3, NH4NO3 and (
NH4) 2 It is industrially pure except for impurities such as SO4.

In a further development of this process, it has been found that the addition of sulfate in the form of ammonium sulfate can be replaced by the addition of an equivalent amount of sulfuric acid.

However, this is the case if at the same time the total water content of the dissolved acid mixture is adjusted by addition of filter washing water such that the nitrogen-containing phosphoric acid produced has a water content of between 25 and 40% by weight.

This added sulfuric acid is generally used with dissolved acid to replace an equivalent amount of nitric acid.

It has been found that the range of water concentrations allowed in the acid mixture must be varied during the dissolution process while adding the amount of sulfate ions necessary for precipitation in the form of sulfuric acid.

In fact, from 65 to 40% by weight to 40 to 25% by weight H2
must be changed to 0.

Furthermore, it has been found to be advantageous to carry out the dissolution and separation of the hemihydrate gypsum at a temperature approximately 10 DEG higher than in the case of a process which relies exclusively on the addition of ammonium sulfate.

The dissolution method using sulfuric acid in combination as sulfate ion for precipitation consists of a combination of the following measures, and according to this combination, a, (al) (7-2X ) to (17-2X) moles of H
If NO3 and X moles of H2SO4 are used per mole of P2O5, (C2) then is constrained by
(C3) In addition, in the dissolved solution into which ammonium sulfate may be brought in depending on the case, after precipitation of hemihydrate gypsum, at least 1
07 maximum of 150 g, preferably about 507 free 5OI
- can take on all possible values between the maximum value The acidic dissolved mixture - preferably 25 to 40% by weight of nitrogen-containing phosphoric acid produced by tear reuse.
The total water content is adjusted to have a water content of
It will be carried out in C.

By using concentrated sulfuric acid, the high temperatures required for the separation of calcium sulfate hemihydrate can be reached without additional steam supply.

This is because the high heat of dilution of this acid in water or in aqueous nitric acid provides the necessary heat.

Moreover, the selective use of sulfuric acid and/or soluble sulfates, such as ammonium sulfate, allows economic adaptation in an optimal manner to the current price level and raw material grade.

As sulfuric acid, industrial acids from any source can be used.

Concentrated sulfuric acid, ie about 96% sulfuric acid content, will normally be used.

However, it is of course also possible to use lower concentrations of sulfuric acid, for example 80% by weight.

Of course, the addition of sulfate ions to precipitate calcium in solution can also be carried out with any mixture of sulfuric acid or ammonium sulfate (or other water-soluble sulfates).

However, this is the case if the total amount of sulfate ions does not exceed the maximum value X defined above.

The permissible amount of water in the wash water-acid mixture as well as the optimum precipitation and separation temperatures emerge accordingly from the mixing laws and the corresponding data in extreme cases.

The method of the present invention is characterized by the following features:
That is, a, (7-2X) to (17
-2X) moles of HNO3 are used per mole of P2O5, where X is moles of H2SO4 versus P20. and X is O (as characterized by the following conditions and that the molar ratio H2SO4:HNO3 is never allowed to be greater than 8:1) sulfuric acid in such an amount that 10 to 1507, preferably 51/1, 1 liter of free 5OI- is present per liter of solution. The ions are added to the lysis solution in the form of ammonium sulfate or sulfuric acid, and the lysis solution used or the acid-washing solution mixture added therefor - optionally increases the amount of filter washing water added. d. The dissolution and separation of calcium sulfate hemihydrate is carried out at a temperature of 60 to 110°C, preferably 70 to 90°C, so that the total water content of the dissolved acid mixture is 25 to 40% by weight.
This is what is carried out in.

The sulfate ion content in the raw phosphate-dissolved mixture is monitored analytically, preferably by nephelometry (using barium chloride solution).

Optionally then H2SO4 addition or (N)L
l) The amount of 2SO4 addition will be increased or decreased.

Generally speaking, however, it will suffice to add the amount calculated from the analysis of the raw phosphoric acid used at that time, in particular from its P2O5 content.

When ammonium sulfate and sulfuric acid are used as precipitants, the dissolution of raw material phosphoric acid is carried out according to the following reaction formula.

This formula thus establishes the minimum required amount of acid in the form of nitric acid and/or sulfuric acid to dissolve the raw phosphate (such as those consisting predominantly of hydroxyl apatite).

The total amount m' of sulfate ions to be added necessary to precipitate the calcium ions of the respective raw phosphate solution
is determined from y in the form of sulfate ions, y' in the form of ammonium sulfate, and the excess (in the form of sulfate ions or ammonium sulfate).

The excess is necessary in order to produce an excess of 10 to 150 g SO/l (corresponding to 0.1 to 1.57 mol SO/l) in the respective volume of lysis solution.

That is, m' - y + y' + m' = (10 + d), as can be seen from the above reaction equation applicable to the case of dissolving 13 moles of P2O5.
Mol SO: /3 mole P2O5 or, in a corresponding manner, when applied to 1 mole P2O, m' m--1 (3,33+△) mole soj 1 mole P2O
5 where m and Δ represent the corresponding amounts applied to the dissolution of only 1 mole of P2O5.

According to the above formula, 20 moles of H+ ions (I-INO
3 and/or in the form of H2SO4), applied to 3 mol of P2O5.

That is, 6.67 moles + 1 mole P2O5.

7 to 17 mol H+/5 mol P2O are used in the process using mostly ammonium sulfate as precipitating ion.

Although this excess HNO3 dissolves some subcomponents,
Or HNO due to the presence of cyclic substances in the raw phosphate.
It helps to compensate for the nitrogen loss caused by the decomposition of 3 and to accelerate the rate of dissolution.

The amount of acid applied in excess of the equivalent amount remains in the P solution in the form of HNO3 and - together with the added (NH4) 2 SO4 or) formed NH4N03 - defines its nitrogen content.

If we ignore the other subcomponents of the raw phosphate and the possible decomposition reactions, as well as the amount of sulfuric acid or ammonium sulfate necessary to adjust the excess of sulfate ions, such as 50 to 150 fsoj-/liter solution, then As the basis for the dissolution treatment according to the invention per mole P205 of raw phosphate, the following conditions must exist:

During processing into multinutrient fertilizers, excess acid is transferred to ammonium nitrate with a corresponding amount of ammonia, thereby further increasing the N content of the product.

According to the reaction equation given above, at values of a such as 2 6- (which is itself forbidden), and when X=10/3 and
'=(10/3-X)=0, dissolution in concentrated sulfuric acid is carried out without addition of nitric acid.

In this case, the separation of the hemihydrate gypsum also proceeds in relatively concentrated sulfuric acid.

That is, the purifying effect of nitric acid on the precipitated hemihydrate cannot be utilized.

When using nitric acid quantities on the order of magnitude of 7 to 9 mol HNO3 1 mol P2O5, the permissible sulfuric acid quantity of
(The NO3 molar ratio can only be increased to 8:1 at most.

For a total acid content of 7H + 1 mole P2O5, then at most 3- = 3.294 moles of 7 H2SO4 and 7/17 = 0.412 moles of l-lNO3
It may be added to 8+1 mol P20. When , the number of people is 3- = 3.765 moles of H2SO4 is 8/1
″7 = 0.471 mol of HNO3 and also 9 H+/−
When ElP2O5, up to 4-=4.235 moles of 7H2SO4 may be added after 9/17=0.529 moles of I(NO3).

According to equation (2), the raw phosphate would have to have a P2O5 content of approximately 42.4% J.

The raw phosphate containing 28-40% by weight P2O5 has a ballast content of 34-5.7% and 32-36%
Those containing P2O5 will have a ballast content of 24.5 to 15%.

This ballast material is either dissolved in variable amounts by the dissolving acid or remains undissolved - analogous to the CaF2 component of fluoroapatite.

This insoluble residue is separated out along with the hemihydrate gypsum during filtration.

For example, a raw phosphate containing 355% by weight of P2O5 would therefore have 1. 1/4 mole of P2O5 per ooya
(or 2.5 moles of P2O5 per kg) <1
16 per 01'. Contains :l of ballast material.

1.00 corresponding to equation (2)? 1 per raw material phosphate group
0/3/1/4 mol of calcium sulfate hemihydrate (145
1,5/12? 1217) are separated.

This is 1287 dry residues with 2 to 14 grams of undissolved ballast material, especially for example 7 grams, with an average moisture content of about 25%.
1 of 160y with y free water and 757 bound water
A residue is given, of which 4.57% of the water is taken from the water of the added aqueous acid solution.

7 to 17 moles per mole of P2O5) (5 to 17 moles of N03 per mole of P2O5)
11 for 1007 raw phosphoric acid containing 35.5% by weight P2O5 when applied in acid form with 0% concentration by weight.
When 0 to 2687 HNO3 and the same amount of water are provided and the specified sulfate ion excess is ignored, approximately 110
7 ammonium sulfate will be used.

The total lysate thus amounts to:

That is, in this case, as inferred earlier, about 1607 is removed by r, and when water loss due to evaporation is ignored, 2
70 or 5867 lees, but equivalent to 27.2% by weight 1 10-36.5 = 73.5f moisture content or 39.5
A P liquid having a water content of 268-36.5=23157, which corresponds to % by weight, is obtained.

5 of the mixture of sulfuric acid, nitric acid and washing water used for dissolution
If a portion of the nitric acid is replaced by sulfuric acid while maintaining a total water content of 0% by weight, then the total dissolved solution (e.g. ammonium sulfate) is equivalently replaced by I2SO4, or 867
-36.5 = 50.27 (equivalent to 44% by weight) or 113.41 or 4 with a moisture content of 244.7 - 36.5 = 208.2f (equivalent to 48.5% by weight)
29.4y of P solution is obtained.

In this pair of examples, the first one is 8:1 H2SO
Although not allowed by the present invention due to excess of the 4:HNO3 ratio, it is still found that the total acid content has only a small influence on the total water content of the acid produced.

Since the replacement of ammonium sulfate by sulfuric acid corresponds to a reduction in the secondary component content, the water content in the phosphoric acid produced increases as the sulfuric acid addition increases while the water content in the dissolved acid mixture remains unchanged.

For a dissolved acid with a total water content of 65% by weight, there may be a solution such as that in the case of the above-mentioned example, that is, it contains a P solution with ξ 187.7 or 639.7P,
Hashira et al. 161-36.5=124. Moisture content equivalent to 66.3% by weight in El - or 455-36.5 = 4
It would have a moisture content of 18.57% and equivalent to 65.4% by weight H20.

It is clear that nitrogen-containing phosphoric acid with a water content of less than 55% by weight cannot be produced in this way, even with evaporative losses of 2-3% water.

It is thus permissible to limit the addition of washing water to such an amount as to leave the total water content of the product phosphoric acid below 55%, in accordance with methods that mostly involve the addition of ammonium sulfate. means a limitation on the water content of the dissolved mixture, P2O6
In the weight percent raw phosphate and the insoluble ballast material assumed in the example above, only dissolved acids having a total water content of 53.5 to 51.3 weight percent are allowed.

Due to the required excess of sulfate ions and due to partial evaporation of water during the dissolution process, 7 to 17 mol H + 1 mol P2O5
The permissible limit range for may shift to slightly higher values, while losses due to decomposition of HNO3 to gaseous components will lower the limit range.

In the widening of the range of analytical values of the raw phosphates used, the permissible water content is therefore related to the nitrogen-containing phosphoric acid of the product and is less obvious to the H20 content of the acid-washing Mito liquor mixture than itself. It seems to me that not being able to make a connection is not only appropriate, but even necessary.

At lower acid concentrations or lower temperatures than those specified by the present invention, dihydrates may precipitate, whereas at higher concentrations or lower temperatures, anhydrides may be formed with greater acid consumption.

The Karl-Fischer reagent is used to determine the water content in nutrient-rich phosphoric acid.

Under certain working conditions, namely HNO3, H2SO4
, in the case of approximately equivalent concentrations of ammonium sulfate and raw phosphate and mixed component proportions, the moisture content of the product phosphoric acid also, provided that suitable prior calibration measurements (in relation to temperature) are carried out: It is quickly known by the so-called "spindle method".

Recalibration may be necessary if the type of raw phosphate or other changes occur.

Although the permissible amount of washing water is limited compared to the method in which ammonium sulfate is added, it is necessary to estimate the amount of water used in Accordingly - otherwise similar considerations such as those mentioned above (see table relations above) arise.

Compared to the phosphoric acid initially generated in the process that involves the addition of ammonium sulfate, the products produced by the process that use sulfuric acid as a precipitant have a lower content of non-nitrogen; mole NH4N031 mole P2O5 or 4y
The content is lower than mol N1 mol P2O5.

For the simplified case a=7 and △−〇, X=
3.294 mol H2SO4 to sometimes 1 mol P20. 0.076 mol NH4NO3 and 0.076 mol per NH4NO3.
33 mol HNO3, i.e. 0.491:1 N:P
A 2O5 molar ratio is obtained.

The nitrogen-containing phosphoric acid produced accordingly is therefore 0.09
It has a N:P2O5 weight ratio of 7:1, and NH3
The mixture obtained therefrom by neutralization (to NH4NO3 and (NH4)21(PO4)) is 2
．． N:P2O5 molar ratio such as 824:1, or 0
．． It has a N:P2O5 weight ratio of 558:1.

According to the present invention, one way to increase the amount of HNO3 supplied is the highest (17-
X) mol HNO31 mol P20. The N:P2O5 molar ratio or weight ratio increases both in the acid and also in the fertilizer premix obtainable therefrom.

For phosphoric acid produced by the process of the invention (as well as X-0) with a=7, N:P of 13.667:1, 20
There is a corresponding weight ratio of 5 molar ratio or 2.7:1,
On the other hand, for the fertilizer mixtures that can be obtained accordingly there is an N:P2O5 molar ratio of 16.0:1 or an N:P2O5 weight ratio of about 3.16:1.

1:1 or 2:1 to fertilizers produced with the aid of nitrogen-rich phosphoric acid obtained by methods that use mostly ammonium sulfate additions.
Phosphoric acid must still be added from time to time to adjust the N:P2O5 weight ratio of Such a product can be obtained directly by appropriate selection of the amount of acid.

For the purpose of producing fertilizers, it is also possible to add P2O, which is not water-soluble, as a component to the NP acid in order to additionally achieve a long-lasting fertilizer effect.

In this case, the raw phosphate and inorganic acid, as appropriate, are added to the raw acid, dissolved in the usual manner, neutralized, and then the potash component and/or any other desired additions are added and granulated. The product thus obtained is dried.

As inorganic acids for dissolution, in particular nitric acid, sulfuric acid or phosphoric acid can be used, each alone or in the form of any desired mixtures.

Fully water-soluble multinutrient fertilizers can also be produced from this nitrogen-containing phosphoric acid (NP acid) by direct treatment with ammonia, with optional addition of potassium salts or other nutrients as well as trace components. .

In processes using exclusively or partially sulfuric acid, an N:P ratio of 1:1 is particularly conveniently obtained, but this ratio is also still a fairly high percentage.

Thus, for example, the present Example 3 represents a 17/17/17 type fertilizer.

Compared to the known process, the following advantages are obtained when the process according to the invention is carried out with the addition of ammonium sulfate as a precipitant.

1. Less (washing) water is used, thereby 2. Washing water-nitric acid mixtures having a higher I (NO3 content (as well as a more favorable dissolving action) or 3. , NP acids with higher P2O5 content and lower water content can be produced, and 4. relatively lower investment costs (because the required filters and/or centrifuges are smaller and the circulation No pumps (as they are not required); 5. Lower energy requirements due to savings in pumps and agitators and shorter filtration and washing times; 6.
These include better utilization of the P2O5 fraction of the available raw material phosphate in the product NP acid; 7. Direct acquisition of usable gypsum and thus saving of complex and wasteful refining operations.

Embodiments of the process according to the invention by partially or completely replacing ammonium sulfate by (equivalent) sulfuric acid have the following additional features.

8. More favorable heat balance: energy supply is virtually unnecessary. 9. Higher total P2O5 content in N-containing phosphoric acid, 1.
0. P2O in the form of H3PO4, which is necessary for the production of multinutrient fertilizers with advantageous adjustment of low N:P2O6 weight ratios or low N:P2O5 weight ratios.

11, an advantageous adaptation to the feedstock situation by selective exchange of sulfuric acid and ammonium sulfate.

Example 1 5 tons of cola phosphate containing 39% P2O5 and 52% CaO are fed in a continuous process to a 50 d capacity reactor together with 6.65) 77 hours of ammonium sulfate.

At the same time, 64% concentration of nitric acid 8yy? addition and recirculation mixing of the filtered calcium sulfate washing solution.

The soluble 5OX content of the reactor solution is 50yso2. 'It will be in liters.

The resulting thick liquid juice is filtered using a 977+2 filter press and washed in a countercurrent manner with 3.2i water.

The washed calcium sulfate hemihydrate obtained (6 tons per hour) has the following composition: The nitrogen-containing phosphoric acid, which has been distributed separately, has the following composition: Density at 20° C. 1.41? /ml Amount obtained: Approximately 12.8yyf', equivalent to 18 tons of this 1
2.8771" of NP acid is used together with 8.7 m" of 64% strength nitric acid to dissolve an additional 4.3 tons of cola phosphate.

After ammonia treatment of the dissolved mixture to pH 5,6,
12 tons of KCI was mixed in and stirred, and this thick liquid was granulated and dried, resulting in 50% water-soluble P2O5.
40 tons of complete fertilizer with composition 18/9/18 containing ingredients are produced.

Example 2 One ton of cola phosphate as in Example 1 was mixed with 0.16
) 64% HNO3 and 0.95 tons H2SO at 77 hours
4 (96% concentration) is fed into the reactor together with 3. Simultaneously, the washing water r.liquid from the calcium sulfate r.liquid is added.

The soluble 5OI content of this reactor solution is 50ySO:/
The temperature is 90°C.

The generated thick liquid is processed door to door, and the separated calcium sulfate is washed in a countercurrent manner with 800 liters of water.

The obtained calcium sulfate hemihydrate ((1.7)n) was thoroughly washed and the following analytical values were obtained. 3 4.4 tons of cola phosphate as in Example 1 were mixed with 4.5 tons of 60% concentrated HNO3, 2 and 6 tons of concentrated H2 per hour.
The reactor is fed with SO4 and 2.2 tons of ammonium sulfate.

At the same time, a washing water solution from filtration of calcium sulfate hemihydrate is added.

The reactor temperature was brought to 85 °C and the soluble S of the reactor mixture
O4a ri is 607/liter.

The resulting mushy sap is washed separately and the calcium sulfate hemihydrate is washed with 35,001.1 mt of water in a countercurrent manner.

The obtained calcium sulfate hemihydrate (7,5 tons) contains the following components: The nitrogen-containing phosphoric acid (9,5) ton), which was distributed separately, has the following composition: The produced acid is treated with ammonia. ammoniacal to a pH value of 5.8 and 295 tons KCI (20 to 58%)
per hour and the mixture is granulated and then dried.

10 tons of 17/17/17 complete fertilizer are obtained per hour.

The following analytical values were found for this product: In summary, the subject matter of the present invention is a method for producing phosphoric acid with a high content of fertilizer nutrients as defined in the claims above, and its implementation. The following conditions may be attached to the embodiment.

(1) In the process according to the claims, the hemihydrate produced is separated from the nitrogen-containing phosphoric acid with the aid of an irrigator or a centrifuge, and optionally countercurrently with water. (to be washed cleanly)

(2) In the method according to the claims or 1) above, the filter washing water or the centrifugation-like washing water is re-supplied in whole or in part to the reactor depending on the nitric acid concentration.

(3) Scope of Claims In a method according to (1) or (2) above, the produced nitrogen-containing phosphoric acid is added, as the case may be, to a raw material phosphate, an inorganic acid, or an appropriate additional dissolved substance.
Neutralize with ammonia and process the thick sap into a multinutrient fertilizer in the usual way, possibly after adding potassium salts and other additives.

(4) In a method for producing phosphoric acid containing a large amount of fertilizer nutrients by dissolving raw material phosphate with nitric acid and precipitating calcium ions with sulfate ions, a. Mol HNO
3 per mole of P2O5, b. The nitric acid used or the nitric acid-washing solution mixture used therefor is adjusted to an HNO3 concentration of 35-60% by weight, C. Ammonium sulfate is added to this dissolved solution. , the amount of free 5OI- present is 10-150y per liter of solution, and d.
To be carried out at a temperature of °C.

Claims (1)

[Scope of Claims] 1. A method for producing phosphoric acid containing a large amount of fertilizer nutrients by dissolving raw material phosphate and precipitating calcium ions with sulfate ions using nitric acid and sulfuric acid, comprising: a. 7 per mole of P2O5 for dissolution
using ~17 equivalents of H+, b adjusting the water content of the dissolved acid mixture by addition of filter washing water such that the water content of the nitrogen-containing phosphoric acid made is 25-40% by weight, after C precipitation. Adding sulfate ions in the form of sulfuric acid or ammonium sulfate to the dissolution solution during or after dissolution in such an amount that there are from 10 to 1501 free 5OI- per liter of solution. d The molar ratio of H2SO4:HNO3 in the dissolved acid varies only between O and 8:1, and e The dissolution of the raw phosphate and the separation of calcium sulfate hemihydrate are carried out exclusively by H2
When precipitating Ca2+ ions with SO4, 60~
When Ca2+ ions are precipitated exclusively with (NH4)2SO4 at 110°C, H2SO4 is precipitated at 60-100°C.
and (NH4)2SO, in which case the Ca2+ ions are precipitated at temperatures intermediate to those mentioned above.