SU1143690A1 - Method of obtaining fodder dicalciumphosphate - Google Patents

Abstract

The method of producing dietary phosphate phosphate from phosphate solutions, including their purification by neutralization, followed by separation of impurities and precipitation of the finished product with a calcium-containing reagent in the presence of gaseous ammonia, melt and heat, and to increase the flow rate of the product with an increase in ammonia gas, and increase the amount of impurities in the presence of ammonia gaseous ammonia in the presence of ammonia gas. product and increase the removal of the washed precipitate, the deposition of the finished product is carried out in the bottom of the stage, and the calcium-containing reagent is introduced in the first stage to the ratio of CaO: P O

Description

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The invention relates to a technique for the production of feed dicalcium phosphate in the acid processing of natural phosphates.

There are known methods for producing feed dicalcium phosphate on the basis of thermal or extraction phosphoric acid p. ,

However, the use of thermal phosphoric acid is not very economical. In addition, in the production of dicalcium phosphate from phosphate nitrate extraction with freezing of calcium nitrate from it during purification of a nitrate solution, along with sesquioxides and fluorine compounds, a significant amount of calcium phosphates is deposited in the solid phase, with which an additional amount of phosphoric anhydride is lost . The main disadvantage of methods for producing feed dicalcium phosphate -ia on the basis of extraction phosphoric acid is the low yield of the target product and its poor filtering properties due to the use of lime or chalk as a calcium-containing reagent.

The closest to the proposed technical essence and the achieved result is a method of obtaining pure di-calcium phosphate from phosphate solutions by pre-cleaning them with gaseous ammonia or a gas containing arviMHaK at pH 2-3, separating the precipitate of impurities by filtration and then precipitating the desired product in the presence of calcium. The latter is introduced in an amount that provides the stoichiometric mass ratio of CaO2 O. necessary for the precipitation of CaHRO and is 0. This stage is carried out upon ammonization of the solution. The precipitated sediment of fodder dicalcium phosphate is separated from the solution by filtration. The yield of 2 phosphate solution in the feed product is 85-90% due to the low solubility of dicalcium phosphate in these solutions. Removal of the dry washed precipitate is 300-500 2,

The disadvantage of this method is the low content of the final product and not enough high removal of the washed precipitate.

The aim of the invention is to increase the content of the finished product and increase the removal of the washed sludge,

The goal is achieved by the proposed method of obtaining feed dicalcium phosphate from phosphate solutions, including their purification by neutralization with

the subsequent separation of impurities and the precipitation of the finished product with a calcium-containing reagent in the presence of gaseous ammonia, according to which the precipitation of the finished product is carried out in two steps, with the calcium-containing reagent being introduced in the first step to the ratio CaO: P2O5 (0.4-0.65): 1, O and the remainder of the reagent is introduced in a second stage.

Ammonia gas is introduced into the purification stage of the phosphorus-containing solution in an amount that provides a process pH value from 2 to 3, as a result of which iron and aluminum compounds are almost completely precipitated. A cleaned solution along with calcium nitrate serves ammonia in an amount that ensures the precipitation of all contained in the liquid phase of phosphates in the form of dicalcium phosphate, and part of the calcium nitrate to the ratio Cao: P2O5- 0.4-0.5: 1. For the second precipitation stage, only the amount of calcium nitrate, calculated for the total precipitation, is fed. of title produkta.Formirovanie dicalcium phosphate crystals in the present process is determined primarily stepwise feeding the calcium-containing reagent. Therefore, in order to simplify the process, the feed of the ashlet into the purified phosphorus-containing solution is performed in one step, i.e. on the first stage.

The calcium-containing reagent, in particular the salt or calcium nitrate solution, is fed into two reactors connected in series. Using the dosing unit, so much calcium-containing reagent is supplied to the first one in order to provide the CaOiP-jOg ratio in suspension equal to 0.4-0.65: 1. The remaining amount of calcium nitrate, calculated for the complete precipitation of phosphates from solution, is introduced into the second reactor.

The supply of calcium-containing reagent in two steps allows the crystallization of the main mass of dicalcium phosphate (at the first stage in an excess of phosphate ions, which ensures the production of larger, well-filtering crystals. The second stage crystallizes the remaining amount of dicalcium phosphate on the already formed large crystals This technique makes it possible to obtain large and, most importantly, homogeneous crystals of dicalcium phosphate with a size of 30-50 microns. The filtration capacity of the finished product in terms of the washed sediment is 1150-1300 kg / mh, which is 2

times higher than the famous spssobu. The duration of the first and second stages of precipitation is fixed by the time of formation of dipotassium di-phosphate and is 3060 minutes at each stage of the process. The yield of P 0 to the final product according to the proposed method is increased compared with the known process due to more complete binding of the solution to dicalcium phosphate. As a result, at the same mass ratio of CaOrPjOj. in the proposed method, practically all phosphates are precipitated from the initial solution, while, in a known manner, the amount of calcium injected is not sufficient for complete binding, since tricalcium phosphate is precipitated along with dicalcium phosphate. Due to this, in the proposed process, the yield of PjO in the finished product is higher by 7–9%.

Example 1. 100 kg of phosphorus-containing solution (P 25.8% CaO - 1.5%; - 1.2%; F- 1.3%) are treated with 3.1 kg of gaseous ammonia in the presence of 13.6 kg of nitrate calcium. At the same time, impurities precipitate - phosphates are one and a half oxides and calcium fluoride. The precipitate also co-precipitates a part in the NANO SanHRO. The precipitate is separated from the liquid phase by filtration. With a mixture of impurities (16.7 kg), 3.8 kg is lost. Purified solution. (100 kg) containing 22% 0.1% CaO; 0.04% F and 0.5%, are treated with 76.5 kg of a 50% calcium nitrate solution to maintain the CaO: P 05 ratio of 0.4: 1 and 5.3 kg of gaseous ammonia at the first stage. The obtained 181.8 kg of suspension after 30 minutes of stirring is treated in the second stage with the remaining amount (76.5 kg) of calcium nitrate solution to maintain the CaO: P2O5 ratio of 0.79: 1, the resulting suspension (258.3 kg) is stirred for 60 minutes filtered with the Department of 40.9 kg of dry washed feed dicaldiophosphate.

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The degree of purification from RoO is 95.9%, from fluorine - 97.0%. The yield of PiO in the feed product is 97.2%. CaHRO4 crystals have a size of 30-40 µm, and the removal of the dry washed precipitate is 1150 kg / m

Example 2. 100 kg of phosphorus-containing solution is subjected to purification, as presented in example 1. Purified solution (100 kg). The composition of which is indicated in example I is treated with 62.2 kg of calcium nitrate four-water nitrate (23% CaO) for

maintaining the ratio at the first stage of CaO: PO 0.65: 1 and 5.3 kg of gaseous ammonia. The resulting 167.5 kg of the suspension, after 60 minutes of stirring, is treated with 5 in the second stage with the remaining amount (14.3 kg) of calcium nitrate to maintain the CaO: P.-2O ratio of 0.79: 1; the resulting suspension (181.8 kg) is stirred 30 min

0 and filtered with the separation of 41.5 kg of dry washed fodder dicalcium phosphate.

The degree of purification from impurities is the same as in example 1. Output

5, the feed product is 98.5%. The CaHRO crystals have a size of 40-50 microns, and the removal of the dry, washed sludge is 1300 kg / m.h.

PRI me R 3. 100 kg of a forcing-containing solution is subjected to purification, as in Example 1. The purified solution (100 kg), the composition of which is indicated in Example 1, is treated with 52.6 kg of tetrabasic nitrate

5 calcium (23%. СаО) to maintain the ratio at the first stage of CaO: P? 05 0;; 55: 1 and 5.3 kg of gaseous ammonia. The resulting 157.9 kg of the suspension, after 50 minutes of mixing, is treated

in the second stage, the remaining amount (23.9 kg) of calcium nitrate to maintain CaO: P About 0.79: 1, the resulting suspension (181.8 kg)

5 is stirred for 40 min and filtered with the separation of 41.2 kg of dry washed fodder dicalcium phosphate.

The degree of purification from impurities is the same as in example 1. Exit

0 feed product is 98.0%. The CaHP04 crystals have a size of 30-50 µm, and the removal of the dry washed precipitate is 1200 kg / m -h.

The table shows the results of the process in the proposed range of parameters (examples 1-3) and beyond.

From the table it is clear that. when the values of the parameters are outside the foregoing limits, the yield of P O J to the feed product decreases.

Reduced CaO- ratio. 0.3 in the first stage (Example 4) leads to a decrease in the yield of PjOj in the feed product and removal of the precipitate due to the formation of small crystals due to the lack of calcium-containing reagent and a sharp decrease in the solubility of CaHRO in these 0 solutions.

An increase in the ratio to 0.7 in the first stage (example) leads to a decrease in the process performance due to the formation of crystals under the conditions of low solubility of dicalcium phosphate.

When feeding the calcium-containing reagent in one step (by a known method, example 6), small and non-uniform crystals are formed.

dicalcium phosphate due to local supersaturation and low solubility.

The use of the proposed method makes it possible to increase the productivity of existing shops for the production of dicalcium phosphate.

Claims (1)

METHOD FOR PRODUCING FODDER DICALCIUMPHOSPHATE from phosphoric acid solutions, including their purification by neutralization with the subsequent isolation of impurities and precipitation of the finished product with a calcium-containing reagent in the presence of gaseous ammonia, distinguishing with the fact that, in order to increase the content of P _r 0 and ₅ in the finished product increase the removal of the washout of the precipitate, the precipitation of the finished product is carried out in two stages, and the calcium-containing reagent is introduced in the first stage to the ratio CaO: P ₂ O ₅ = (0.4-0.65): 1.0, and the rest of the reagent introduced in the second stage. Color Co O Оρ F