Method of purification of calcium nitrate solution or melt

专利摘要:
The present invention relates to a method for purifying calcium nitrate melt/solution separated from the mixture obtained by dissolution of rock phosphate with nitric acid. The melt contains fluorine and phosphorus as main contaminants. The mol-ratio phosphorus/fluorine in the crude calcium nitrate melt/solution is adjusted to 3.5>P/F>0.3, possibly by extra addition of a phosphorus compound, and the mixture is then neutralized by ammonia to pH = 5-6. The precipitate thereby formed is removed while the filtrate, which is a purified nitrate of lime melt, is evaporated and further processed. The purification can be carried out in two stages, with a P/F-ratio in the first stage of 0.3-3 and 1-3.5 in the second stage. Phosphoric acid or a phosphoric acid containing solution is used as phosphorus compound.
公开号:SU1706384A3
申请号:SU884356609
申请日:1988-10-05
公开日:1992-01-15
发明作者:Николайсен Йохнни
申请人:Норск Хюдро А.С. (Фирма)；
IPC主号:

专利说明:

This invention relates to a method for purifying a melt or solution of calcium nitrate obtained by decomposing natural phosphate with nitric acid,
After the natural phosphate is dissolved with nitric acid, the mixture is cooled, as a result of which calcium nitrate Ca (NOj) crystallizes. These crystals are isolated, washed and melted. The melt is mainly contaminated with phosphorus, fluorine and nitric acid and, to a lesser extent, silicon, iron, manganese, magnesium, aluminum, calcium sulfate, etc. Neachi melted melt produces calcium nitrate using, as an agricultural fertilizer. Through the purification of calcium nitrate, its application areas are expanded, it can be used in greenhouses, as an additive in civilian liquid explosives, as a coagulant for natural rubber, latex, etc. Purified calcium nitrate can also be used. It can be converted by ammonia and carbon dioxide to ammonium nitrate and calcium carbonate. In addition, during processing, in particular by evaporation, purified calcium nitrate with a reduced fluorine content reduces equipment corrosion. No colored impurities in calcium nitrate
J
O 0
with
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t / 4
317
leads to better control of chemical reactions.
It is known to remove fluorine from a solution of calcium nitrate by distilling off fluorine in the form of hydrogen fluoride or tetrafluoride silicon. The mass ratio between nitrate ions and calcium ions in the solution is set below 2, 3. Silicon dioxide can be added to form tetrafluoride silicon, if natural phosphate contains too little of this component. Through this treatment, l0% fluorine is removed from the solution.
However, this method leads to a loss of nitrogen (0.2 kg per 1 kg of fluorine removed), in addition, it is less technological, t
There is also known a method for purifying and processing calcium nitrate containing approximately 2% or 0.9% phosphorus. Prior to the conversion of calcium nitrate to ammonium nitrate and calcium carbonate, phosphorus is removed by precipitation with ammonia. As a result initially
an apatite is formed which is removed by filtration. Apatite may contain some impurities, such as silicon, aluminum, iron and magnesium.
To obtain the desired degree of precipitation of apatite, as well as its easy filtration, it is necessary that the solution have a low viscosity (below 10 MPa-s), a temperature above 80 ° C and a pH value of 4.5 when measured with a dilution of 1:10. The apatite removed by filtration can be returned to the dissolution stage. Calcium carbonate, obtained from the purified calcium nitrate, contains. 0.05% fluorine, i.e. 500 ppm The calcium nitrate solution contains 150 ppm of fluorine.
The purpose of the invention is to increase the degree of purification of calcium nitrate.
The goal is achieved by keeping the ratio of phosphorus to fluorine in the initial solution or melt of calcium nitrate satisfying condition 3,, 3 by introducing a phosphorus compound, and neutralizing the initial solution with ammonia to a pH of 5-6, and the best results are obtained at pH 5 ,five.
FIG. 1 shows a process for cleaning a melt or nitrate solution.
0
five
0
five
0
five
0
five
calcium, carried out in one stage | day; in fig. 2 - the same, in two stages; in fig. 3 dependence of the content of fluorine in the purified melt on the ratio of phosphorus to fluorine in the neutralization process.
The one-step cleaning method is carried out as follows.
Calcium nitrate melt 1 (Fig. 1) is fed to storage tank 2, in which the possible content of nitric acid is established by adding it through line 3. The melt passes through the pipeline to neutralization tank 5. An additional amount of phosphorus in the form of phosphoric acid is supplied through pipelines 6 and 4 from the tank 7 for its storage. Phosphoric acid is introduced before the desired P / F ratio is established. If necessary, water can be added to the neutralizer through line 8. Ammonia is fed through line 9. Impurities are precipitated in tank 5. The mixture from the latter is fed through pipe 10 to separation unit 11. If separation is required when flocculating agents or flotation agents are added, one of them can be added through pipelines 10 and 12. The purified melt or solution is removed through line 13 for further processing into granular calcium nitrate or for conversion to ammonium nitrate and calcium carbonate. . The sludge separated from the mixture is recirculated to the stage of acidification of natural phosphate via pipeline I.
In the two-stage method of cleaning a melt or a solution of calcium nitrate (Fig. 2), the first stage of purification is carried out as described. The purified melt or solution from block 11 is then fed via conduit T to the second neutralizing tank 15. Phosphoric acid is added via conduits 6 and 1 until the desired P / F ratio is reached. Ammonia is fed into the tank 15 through the pipeline 9. In the tank 15 there is an additional precipitation of impurities. The resulting mixture is fed through conduit 16 to a second separation unit 17. Pipelines 12 and 16 can provide flocculating agents or flotation agents. The purified melt or solution is removed through conduit 18 for further processing. Slurry isolated
during the cleaning process, the pipelines 13 and 19 return to the stage of treatment with nitric acid.
FIG. Figure 3 shows the dependence of the concentration of fluorine in the purified melt, expressed in g F / kg Ca. from the atomic ratio of phosphorus to fluorine in the neutralization process. This curve is based on the results of a large number of experiments with melts of different composition, obtained using different types of natural phosphate. The curve shows the results obtained in one- and two-step purification at pH 5.2 in the first and second stages of neutralization. The pH value is measured in a solution consisting of 1 part of the melt and 10 parts of water. The concentration of fluorine includes both dissolved fluorine and fluorine in the solid phase.
Example 1. The purification of a melt of calcium nitrate is carried out in one stage. 16200 kg / h, of calcium nitrate melt containing 8.2 g of P per 1 kg of Ca and 16.7 g of F per 1 kg of Ca and having a P / F ratio of 0.3, are fed into container 2 (Fig. 1). 1300 kg / h, yody and 3 & 3 kg / h are added through pipe 6. phosphoric acid. In this case, the P / F ratio varies and is 2. The mixture is kept at an ejection of 268 kg of ammonia and a pH of 5 is maintained. A precipitate is obtained having B mainly large crystals. Then, 0.2 kg / h of polyelectrolyte is added to the calcium nitrate solution, and then centrifuged.
Analysis of the filtrate (calcium nitrate solution) dgl the following results:
g P / kg Ca 0.10
g F / kg Ca 0.10
Insoluble in
water impurity - h / mln. AOO
Iron, hours / million 10
Silicon, ppm 15
In accordance with this method, 99% of fluorine and 99.8% of phosphorus are removed from the melt of calcium nitrate by using 25 kg of phosphoric acid per 1 ton of Ca (HY) g.
When phosphoric acid is replaced by 26 kg / h, primary ammonium phosphate produces similar results in the purification of calcium nitrate.
Cleaning the melt of calcium nitrate, the above composition
50
5 0 5
0
five
0
five
According to the prototype method, in one stage, at pH 5.2, temperature 60 ° C and ratio, 3 allows to obtain a filtrate containing 0.25 g P per 1 kg of Ca, 1, 2 g F per 1 kg of Ca, 3000 h ./million water-insoluble impurities and 0 ppm iron.
PRI mme R 2. Purification of a melt of calcium nitrate is carried out. in two stages in accordance with the scheme shown in FIG. 2
16200 kg / h of molten calcium nitrate containing 15 g of F / kg of Ca and 8 g of P / kg of Ca are fed into container 2, and phosphoric acid of 91 kg / ton is added through pipe 5. Thereafter, the P / F ratio in the mixture becomes 0.8. This mixture is fed to the first neutralization tank 5, to which 175 kg / h of ammonia is added, so that the pH of the mixture is kept at 5.2 at 70 C. Then 0.6 kg / h of polyelectrolyte is added to the mixture and converted it in the first centrifuge 11. Phosphoric acid is added in such quantities that the effluent filtrate has a ratio of 5.
This mixture is transferred to a second neutralization tank 15, to which 5 kg / h of ammonia is added, phosphorus and fluorine are precipitated at pH. The calcium nitrate solution containing the precipitate is transferred to the second centrifuge 17. The filtrate from this centrifuge is purified calcium nitrate, and its output is truccated to 18. 18. The sludge extracted from it together with the sludge from centrifuge 11 is mixed with 215 kg / h. nitric acid to partially dissolve precipitated apatite. This mixture is then returned to the stage of dissolution of natural phosphate with nitric acid,
Analysis of the purified calcium nitrate solution gave the following results:
g P / kg Ca0.10
g F / kg Ca0,10
Insoluble in
water impurity
h / m
Iron, hours / million ten
Silicon, hours / million 15
Manganese, ppm 2
In order to reduce the water content in the filtrate, it is removed by evaporation.
From the presented examples, it follows that the invention allows more efficiently than in the prototype to clear
melt or solution of calcium nitrate from impurities. Moreover, the degree of purification in examples 1 and 2 is the same, but the amount of phosphoric acid used in the two-stage process is 2.3 kg P per 1 ton Ca (M03) 24H20, and in the one-stage process - 7.9 kg P per ton t Ca (H05) 2-4NaO.
The amount of impurities in the product decreases with an increase in the P / F ratio during neutralization. When cleaning is carried out at a P / F ratio, is equal to 3 ~ 1.0, the product — calcium nitrate — may contain 0.07–0, water-insoluble impurities. With an increase in the amount of phosphorus to the ratio, 0 in the purified solution contains 0.03-0.1% of insoluble a
170638 8

权利要求:
Claims (3)
[1]
1. A method for purifying a melt or calcium nitrate solution obtained by dissolving natural phosphate with nitric acid, including neutralizing the melt or solution with ammonia and separating the impurity sediment, characterized in that the phosphorus ratio is maintained in the starting melt or solution to fluorine satisfying condition 3,, 3 by introducing a phosphorus compound, and neutralization is carried out to a pH of 5-6.
[2]
2. The method according to p. 1, about tl and h a- o y and with the fact that the cleaning is carried out in two stages, and maintain the relationship, 3 on the first step of the water impurities. Relevant tendency-- 0 J h. Yun
chi is also manifested for some friends 3, in the second stage.
[3]
3. The method according to paragraphs. 1 and 2, which is based on the fact that the separation of impurities is carried out in the presence of a polyelectrogite in a centrifuge.
gih components (see table).
Thus, the invention makes it possible, in a simple way, to obtain a melt or a solution of calcium nitrate, which is cleaner than in the known method, and be used in various technical and agricultural fields.
wearing, 3 on the first step J h. un
and 3, in the second stage.
3. The method according to paragraphs. 1 and 2, which is based on the fact that the separation of impurities is carried out in the presence of a polyelectrogite in a centrifuge.
1. The method according to paragraphs. 1-3, which is used in such a case that phosphoric acid or a solution containing phosphoric acid is used as a phosphorus compound.
0.05-0.3
0, 20
0.02
O.OA-0.15
0.08-0.15
ABOUT
0.04
 I
P.
one
12
ten
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Fig. (
 .
. 30 PI

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法律状态:
2010-07-20| REG| Reference to a code of a succession state|Ref country code: RU Ref legal event code: MM4A Effective date: 20071006 |

优先权:

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申请号 | 申请日 | 专利标题

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NO874186A|NO162714C|1987-10-06|1987-10-06|PROCEDURE FOR PURIFICATION OF CALCIUM NITRATE MELT / SOLUTION SEPARATED FROM THE MIXTURE PHASED ON DISSOLUTION OF RAA PHOSPHATE WITH NITROGEN ACID.|

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