CN1155513A

CN1155513A - Method for producing calcium hydrophosphate and monocalcium phosphate as feeds

Info

Publication number: CN1155513A
Application number: CN96100337A
Authority: CN
Inventors: 魏如铎
Original assignee: Individual
Current assignee: Li Guangchun
Priority date: 1996-01-23
Filing date: 1996-01-23
Publication date: 1997-07-30
Anticipated expiration: 2016-01-23
Also published as: CN1044458C

Abstract

A process for producing feed-grade calcium hydrogen phosphate and calcium dihydrogen phosphate includes such steps as decomposing phosphorus ore powder with inorganic acid, filtering, purifying to obtain diluted phosphoric acid, neutralizing the diluted phosphoric acid with alkali to prepare calcium hydrogen phosphate, and mixing the calcium hydrogen phosphate with the diluted phosphoric acid and drying the mixture to obtain calcium dihydrogen phosphate.

Description

Novel method for producing feed-grade calcium hydrogen phosphate and calcium dihydrogen phosphate

The invention relates to an inorganic chemical production process, in particular to a novel method for producing feed-grade calcium hydrogen phosphate and calcium dihydrogen phosphate.

Feed grade calcium hydrogen phosphate and monocalcium phosphate, both feed additives to supplement animals with both phosphorus and calcium nutrients, have long been known for their effect and have been widely used in modern feed as compared to calcium hydrogen phosphate (CaHPO)₄2H2O) has a low solubility in water, with a solubility product KSP of 1 × 10^-7Belongs to a compound which is difficult to dissolve, and the absorption rate of the compound by general animals is only 47 percent; the calcium dihydrogen phosphate has high solubility in water, and 15.4 g of calcium dihydrogen phosphate can be dissolved in 100g of water at 25 ℃. Experiments prove that the absorption rate of the animals to the phosphorus in the feed is as high as 98 percent, so the feed additive is a very promising feed additive. However, theoretical analysis has proved that more than 60% phosphoric acid must be used to prepare monocalcium phosphate (see Dalian connection)The content P225-226 of "chemical fertilizer" in inorganic chemical engineering technology (III) compiled by Chenyaoshi of academy of industry, is due to calcium dihydrogen phosphate (Ca (H)₂PO₄)₂.H₂O) has a high solubility in water, and in order to sufficiently crystallize the product from the mother liquor, an organic solvent such as alcohol or acetone is generally used as a reaction medium. In 1991 Ma tomato proposes ethanol solution method for producing food-grade Ca (H)₂PO₄)₂.H₂O, and preparing the composite food leavening agent; a one-step method for producing feed-grade Ca (H) without returning charge is proposed in the application of 93110806.3 by Wanpu in 1993₂PO₄)₂.H₂O, the method uses thermal phosphoric acid with the concentration of more than 60 percent and 100-mesh CaCO in theoretical amount₃Reacting, and drying the reactant in hot air flow to obtain the product.

The reason why the amount of calcium dihydrogen phosphate with excellent performance currently used in the feed industry is less than one percent of that of calcium hydrogen phosphate is that: firstly, the production raw material of calcium dihydrogen phosphate is hot-process phosphoric acid, which is expensive and high in cost; secondly, the production of the thermal phosphoric acid consumes a large amount of energy and is insufficient in the total supply of the society.

The invention aims to overcome the problems in the production of monocalcium phosphate by hot-process phosphoric acid, and provides a new method for producing feed-grade calcium hydrogen phosphate and monocalcium phosphate, namely a new process for producing phosphoric acid by a low-cost wet process.

The purpose of the invention is realized by the following technical scheme:

the selected raw materials comprise Ca (OH)₂、CaCO₃The alkaline substance of (a), phosphoric acid of relatively low concentration, such as 30-60% (by weight) phosphoric acid;

the adopted method comprises the following steps: reacting alkaline substance with phosphoric acid to produce feed grade calcium hydrogen phosphate (CaHPO)₄.2H₂O) as neutralizing agent to react with phosphoric acid to prepare phosphoric acidCalcium dihydrogen;

the theoretical basis and the specific reaction operating conditions of the method are as follows:

theoretically, Ca (OH)₂、CaCO₃Reacting alkaline substances with phosphoric acid to generate feed-grade CaHPO₄.2H₂O (I), which is used as a neutralizing agent to react with purified dilute phosphoric acid to prepare calcium dihydrogen phosphate;

... (1) but in practice, CaHPO₄.2H₂O products tend to contain some more calcium than the theoretical amount and are present in the form of: ca (OH)₂、CaCO₃、Ca₃(PO₄)₃Therefore, the two raw materials can be mixed to generate the following reaction:

......(2)

.....(4)

in fact, since phosphoric acid with a relatively low concentration (for example, about 30% to 50%) is used, reaction formula (1) cannot proceed substantially completely in the mixing operation except that reactions (2), (3) and (4) may occur, but a mixture is formed by three reactions (2), (3) and (4), and then when this mixture is dried in a high-temperature gas stream, the concentration of phosphoric acid present in free form increases continuously as moisture evaporates, and when the concentration of phosphoric acid reaches 60% or more, reaction formula (1) starts to react rightward, and the entire reaction is completed with the completion of drying.

One of the characteristics of the invention is that the wet-process diluted phosphoric acid is used for production, thus saving energy consumption;

for realizing the purpose of the invention, the specific process flow provided by the invention which embodies the remarkable characteristics of the invention is as follows:

after the typical process of producing feed-grade precipitated calcium phosphate, three procedures of mixing, drying and pulverizing are added to dilute H₃PO₄And CaHPO₄.2H₂O is atMixing in a mixing tank, drying to gradually increase the concentration of dilute phosphoric acid until reaction (1) can occur to obtain Ca (H)₂PO₄)₂.H₂And (4) O products. In fact, dilute H will be₃PO₄With diluteH₃PO₄The neutralized product of (2) CaHPO₄.2H₂O is mixed and H is evaporated by a hot gas stream₃PO₄Excess water, Ca (H)₂PO₄)₂.H₂O is generated. Crushed Ca (H)₂PO₄)₂The granularity is less than 0.44mm, thus obtaining the finished product.

The invention can simply obtain Ca (H) with excellent performance after adding the three steps₂PO₄)₂.H₂O, make the utilization rate of phosphorus from CaHPO₄.2H₂47% of O is increased to Ca (H)₂PO₄)₂.H₂98% of O. With the improvement of the utilization rate of the phosphorus, the selling price of the product is greatly improved, so that the invention has good economic benefit and huge social benefit.

The technical scheme of the invention can show that the invention has the following advantages:

1. in the implementation of the invention, organic solvent is not needed, and expensive thermal phosphoric acid is not used, so that the cost is low, the process is simple, the equipment investment is saved, the utilization rate of phosphorus is high, and almost all phosphorus in the crude phosphoric acid is converted into the product.

2. When phosphoric acid having a concentration of about 50% is used, the reaction mixture can be directly dried to obtain a product. In using lower concentrations of H₃PO₄In the case of using the returned material for dilution, Ca (H) can also be directly prepared₂PO₄)₂.H₂And O or controlling the total phosphorus content to be 20 percent to obtain the calcium phosphate rich. It is also a good commercial variety of feed additives. It is therefore a further advantage of the present invention that a wide range of dilute phosphoric acid concentrations can be used to obtain a variety of phosphocalcium products.

FIG. 1 is a simplified process flow diagram of the present invention.

As shown in FIG. 1, the ground phosphate rock is mixed with H in the decomposition tank₂SO₄Reacting, filtering to separate phosphogypsum to obtain crude phosphoric acid with low impurity concentration, and filtering to remove As, Pb and F impurities by using comprehensive purification technology to obtain purified dilute H₃PO₄This is dilute H₃PO₄Two sections, one section is connected with Ca (OH)₂、CaCO₃Neutralizing in a neutralizing tank, filtering, and discharging mother liquor to obtain CaHPO₄.2H₂Precipitating with O, drying and dewatering the precipitate with air flow, and mixing with dilute H₃PO₄Mixing in a mixing tank, drying to obtain precipitate Ca (H)₂PO₄)₂.H₂O。

Example 1

100g of purified wet-process diluted phosphoric acid (containing 9.5% phosphorus, corresponding to 30% H) was added to a 400ml beaker equipped with a stirrer₃PO₄0.306mol, F0.10%), start the stirrer slowly with 8-9% Ca (OH)₂The lime milk is neutralized until the PH value is 5.4-5.8, the lime milk is stopped to be added, the stirring is continued for half an hour, the PH value is increased to 6-6.5, the vacuum filtration is adopted, the weight of the Hu cake is 132.5g, the Hu cake is detected to contain about 60 percent of water, the Hu cake is dried at the temperature of 60 ℃ to obtain 57g of a product, the P content is 16.5 percent, the Ca content is 25 percent, the water content is about 20 percent, the F content is 0.15 percent, and the As and the Pb are qualified.

Example 2

10g of the dried sample obtained in example 1 was weighed out using an evaporating dish, and 13g of 50% wet H was added₃PO₄(containing F ═ 0.12%) are thoroughly mixed and stirred to obtain a loose reaction mixture, which is dried in an oven at 98-100 ℃ for 1 hour, and the product weight is 15.6g, which is detected to contain 4% of water, 23.78% of P, 16.0% of Ca16, and 0.2% of F ═ 0.2% of Pb and As are qualified.

Example 3

The dried sample of example 1 was weighed 20g and dried in an oven at 140 ℃ for 45 minutes to obtain crystal waterMostly lost, 50% H was added₃PO₄25.5g, stirring to form a reaction mixture in loose powder shape, drying at 98-100 ℃ for 1 hour, taking out and weighing 30.5g, analyzing the product to contain 2% of water, 23.6% of P, 0.20% of F, and qualified As.

Claims

1. A process for preparing feed-class calcium hydrogen phosphate and calcium dihydrogen phosphate includes decomposing phosphorus ore powder with sulfuric acid, filtering, and purifying to obtain diluted phosphoric acid. Then the dilute phosphoric acid is divided into two sections, one section is neutralized with alkali in a neutralization tank to prepare calcium hydrophosphate, the other section is mixed with the prepared calcium hydrophosphate in a mixing tank, and then the mixture is dried to prepare the calcium dihydrogen phosphate.

2. The method of claim 1, wherein the dilute phosphoric acid is 30% to 60% phosphoric acid. Preferably 45% -55%.

3. The process of claim 1, wherein the base is Ca (OH)₂Or CaCO₃。