CN1220235A

CN1220235A - Preparation of feed synthos by using slurry concentration defluorinating method

Info

Publication number: CN1220235A
Application number: CN97107830A
Authority: CN
Inventors: 金作美; 王励生
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-12-17
Filing date: 1997-12-17
Publication date: 1999-06-23
Anticipated expiration: 2017-12-17
Also published as: CN1064646C

Abstract

The slurry concentration and defluorination method for preparing feed synthos is characterized by that it adopts the circulating phosphoric acid exceeding theoretically-calculated use level to decompose phosphorus ore, and in the course of decomposition of the phosphorus ore the phosphorus materials are completely dissolved in the circulating phosphoric acid, and at the time of decomposition and concentration the HF and SiF4 being in the slurry are escaped into gas phase, and the defluorinated calcium hydrophosphate slurry is neutralized by lime or lime cream, so that the partial calcium hydrophosphate can be made into feed-level snthos product whose fluorine content is less than or equal to 0.15, and the residual slurry is reacted with sulfuric acid to obtain the circulating phosphoric acid for secondary use to decompose phosphorus ore.

Description

Preparation of feed calcium phosphate by slurry concentration defluorination

The invention relates to a method for preparing feed calcium hydrophosphate by wet-process phosphoric acid, namely, a slurry concentration defluorination method is adopted to prepare feed calcium hydrophosphate.

The method for producing feed calcium hydrophosphate by wet-process phosphoric acid comprises two major types:

1. wet phosphoric acid concentration defluorination

(1) Wet phosphoric acid with the concentration of 28-30 percent P₂O₅Concentrating to 54%, and removing 80% of fluorine and P in phosphoric acid₂O₅F can be increased from the initial 15: 1 to 100-150: 1. Post-addition of sodium salt to remove residual fluorine and to obtain P₂O₅F is up to 250-300: 1, and then lime or lime milk is used for neutralizing the wet-process phosphoric acid, so that feed-grade calcium hydrophosphate with the fluorine content of less than 0.18 percent can be obtained.

(2) Wet phosphoric acid is concentrated by adding silicon to make H in phosphoric acid₂SiF₆With SiO₂Reaction: namely, it is Allowing the SiR to be generated₄Escape during concentration to allow P₂O₅F is up to 250-300: 1, and then lime is used for neutralizing the wet-process phosphoric acid, so that feed-grade calcium hydrophosphate can be prepared.

Because the wet-process phosphoric acid contains H in the wet-process phosphoric acid concentration method₃PO₄、HF、H₂SiF₆The device has strong corrosivity, and the concentration device only adopts a tube type graphite heat exchanger or a block-hole type graphite heat exchanger. In order to obtain higher defluorination rate in the concentration process, larger circulation volume and longer retention time are needed, so the energy consumption is high; phosphorus-containing precipitate sludge is generated during the concentration process, and the yield of phosphorus is reduced, resulting in high cost.

2. Two-time neutralization precipitation method

And (3) neutralizing the wet-process phosphoric acid by using lime milk to ensure that the pH value reaches 2.5-3.5, removing most of impurities (including fluorine) in the wet-process phosphoric acid at the moment, and neutralizing the wet-process phosphoric acid by using the lime milk to ensure that the pH value is 5-7 to obtain the feed-grade calcium hydrophosphate.

Because the twice neutralization precipitation method has long process flow, more equipment and large one-time investment, the CaHPO exists while the first neutralization defluorination is carried out₄、2H₂The defluorination residue obtained by separating out the O precipitate and filtering contains 25 to 35 percent citrate soluble P₂O₅Therefore, the defluorinated slag can only be used as a fertilizer grade product. P entering feed grade product due to fertilizer grade product produced₂O₅Is total input P₂O₅40-60%, low phosphorus yield and high consumption quota.

The invention aims to provide a method for preparing feed calcium phosphate by slurry concentration defluorination, which is characterized in that the phosphorus ore is decomposed by using circulating phosphoric acid with more than theoretical calculation amount, the phosphorus-containing substances of the phosphorus ore are completely dissolved in the circulating phosphoric acid in the decomposition process, and most of HF and SiF are dissolved in the decomposition and concentration processes₄And escaping into a gas phase, neutralizing the defluorinated calcium hydrophosphate slurry by using lime or lime milk: part of the calcium hydrogen phosphate can be made into feed grade phosphoric acidThe fluorine content in the calcium hydrogen phosphate and calcium hydrogen phosphate products is less than or equal to 0.15 percent and is better than national standard GB8258-17(F is less than 0.18 percent), and the residual part of the calcium hydrogen phosphate reacts with sulfuric acid to obtain circulating phosphoric acid for the working section of decomposing phosphorite. Thus overcoming the defects of the prior art, greatly reducing the consumption quota of raw materials, reducing the cost and having obvious economic and social benefits.

The purpose of the invention is realized by the following technical measures.

The invention provides a method for preparing feed calcium phosphate by a slurry concentration defluorination method, which is characterized in that:

1. decomposing phosphorus ore by using circulating phosphoric acid with concentration of 18-45% and over theoretical calculated amount, wherein during the decomposition process, the phosphorus-containing substance Ca of phosphorus ore₅F(PO₄)₃All dissolved in the circulating phosphoric acid, and the reaction equation is as follows:

5Ca (H) in the formula₂PO₄)₂,(m-7)H₃PO₄,HF,SiF₄,H₂SiF₆To form the fluorine-containing calcium hydrophosphate slurry. Part of HF, SiF during decomposition₄Escape into the gas phase.

2. By concentrating slurry of calcium hydrogen phosphate, fluorine (HF, SiF) contained in the slurry is obtained₄,H₂SiF₆) Most of the gas is removed and escaped into gas phase

The concentration temperature is 70-175 ℃, and the concentration temperature is P in defluorinated calcium hydrophosphate slurry₂O₅The weight ratio of F to F is more than or equal to 300 to 1, so that the fluorine content in the prepared feed-grade phosphate product is less than 0.15 percent and is better than that in international GB8258-17F and less than 0.18 percent.

3. After lime or lime milk is adopted for neutralization, concentration and defluorinationPart of the calcium hydrogen phosphate slurry [ corresponding to 5Ca (H) produced in the total reaction formula₂PO₄)₂1.5Ca (H) in (1)₂PO₄)₂]Feed-grade monocalcium phosphate (Ca (H)) can be prepared according to market demands₂PO₄)₂·H₂O) and calcium hydrogen phosphate (CaHPO)₄·2H₂O) products.

4. Using sulfuric acid (93% or 98% H concentration)₂SO₄) With the remaining part of calcium hydrogen phosphate [ corresponding to 5Ca (H) generated in the total reaction formula₂PO₄)₂3.5Ca (H) of (1)₂PO₄)₂]

n =2,0.5, 7H generated₂PO₅And (m-7) H₃PO₄mH of composition₃PO₄Used as a working section for decomposing phosphorite by recycling phosphoric acid.

5. HF, SiF escaping during decomposition and concentration₄The H is recovered by adopting a condensing and absorbing mode to obtain more than 10 percent of H₂SiF₆Solutions which can be used for the production of Na₂SiF₆,CaSiF₆And AlF₃By-products.

The invention has the following advantages:

1. the calcium hydrogen phosphate produced by slurry concentration defluorination has high defluorination rate and makes P in calcium hydrogen phosphate slurry₂O₅F is less than 300: 1 (weight ratio), the concentrated calcium hydrophosphate slurry improves the environmental condition, the production is easy to operate and control, and the corrosivity is greatly reduced.

2. The calcium phosphate slurry after defluorination is used for preparing feed-grade calcium phosphate salt, and the calcium in the phosphorite is fully utilized, so that the consumption of sulfuric acid and lime is greatly reduced, and the production cost is low.

3. No phosphate sludge and fertilizer grade phosphate are generated in the production process, the yield of phosphorus is high, and the consumption of phosphate ore is low.

4. The economic indicators of the invention are compared with the economic indicators of the prior art and are detailed in table 1.

As can be seen from Table 1, the economic indicators of the present invention are superior to the prior art.

The production process of the present invention is given by the following figures and examples.

FIG. 1 is a block diagram of a process flow for preparing feed calcium phosphate by a slurry concentration defluorination method.

Examples

1. Adopting phosphorite components as follows; p₂O₅30.81％,CaO 42.69％,MgO 1.33％,F 2.82％,SiO₂17.13 percent. Decomposing 1.42 ton phosphorus ore at 80-100 deg.C with 7.42 ton of circulatingphosphoric acid to obtain calcium hydrogen phosphate slurry, concentrating at 80 deg.C to remove most of fluorine carried by phosphorus ore, and making phosphorus-fluorine ratio P in the slurry₂O₅F is more than 312: 1, 770-800 kg of defluorinated calcium hydrophosphate slurry and 350 kg of lime (or lime milk) are used for neutralization reaction to prepare 1 ton of calcium hydrophosphate slurry containing P₂O₅More than 37 percent, more than or equal to 21 percent of Ca and less than or equal to 0.15 percent of F; 0.88 to 0.92 ton of 98 percent sulfuric acid reacts with the rest defluorinated calcium hydrophosphate slurry to prepare 7.42 tons of phosphoric acid, and the phosphoric acid is returned to decompose the phosphorite. 460-480 kg of 10% H are recovered in a fluorine absorption system₂SiF₆And can be further processed into fluoride salt by-products.

2. The adopted phosphorite comprises the following components: p₂O₅22.81％,CaO 41.65％,MgO 0.16％,Fe₂O₃0.36％,Al₂O₃,0.25％,SiO₂8.34 percent and F2.11 percent. Decomposing 1.74 tons of demagnetised phosphate rock by 7.6 tons of circulating phosphoric acid at 80-90 deg.C to obtain calcium hydrogen phosphate slurry, concentrating at 110 deg.C to remove most of fluorine carried by phosphate rock, and making phosphorus-fluorine ratio P in the slurry₂O₅F is more than 308: 1, 800-840 kg of defluorinated calcium hydrophosphate slurry is used for neutralization reaction with 400 kg of lime to prepare 1 ton of calcium hydrophosphate slurry containing P₂O₅More than 37 percent, more than or equal to 21 percent of Ca and less than or equal to 0.15 percent of F; 0.85 ton of 98% sulfuric acid is used to react with the rest calcium hydrogen phosphate slurry to obtain 7.6 ton of circular phosphoric acid, which is returned to decomposephosphorus ore. 465 kg of 10% H are recovered in a fluorine absorption system₂SiF₆And can be further processed into fluoride salt by-products.

3. The phosphorite comprises the following components: p₂O₅33.0％；CaO 44.3％,MgO 0.6％,SiO₂6.6 percent and F3.6 percent. Decomposing 1.694 tons of phosphorus ore at 80-115 deg.C with 10.14 tons of circulating phosphoric acid to obtain calcium hydrogen phosphate slurry, and removing most of fluorine from phosphorus ore during concentration at 110 deg.C to remove phosphorus and fluorine P in the slurry₂O₅F is more than 350: 1. 1.17 ton of defluorinated calcium hydrophosphate slurry was mixed with 150 kg of Ca (OH)₂Neutralization reaction to obtain 1 ton of P-containing₂O₅1.16 tons of 98% H is used as the calcium dihydrogen phosphate product with more than or equal to 52%, more than or equal to 20.5% CaO and less than or equal to 0.15% F₂SO₄The sulfuric acid reacts with the residual defluorinated calcium hydrogen phosphate slurry to prepare 10.14 tons of circulating phosphoric acid which is returned to decompose phosphorite. 600-620 kg of 10% H can be recovered in the fluorine absorption system₂SiF₆Further processing to produce fluoride salt by-product.

Table 1 shows the comparison of the economic indicators of the present invention and the prior art

Rating item	Defluorination of concentrated phosphoric acid	Two stage neutralization process	This patent
Rating item	Defluorination of concentrated phosphoric acid	Two stage neutralization process	This patent	1. Consumption of raw materials (t/t) Sulfuric acid (98% H)₂SO₄) Lime (90% CaO) Phosphorus ore (30% P)₂O₅)	1.1～1.3 0.45～0.55 1.45～1.55	1.2～1.6 0.55～0.65 1.7～1.8	0.8～1.0 0.35～0.45 1.35～1.45
2. Process flow	Short length	Is longer	Short length		1.1～1.3 0.45～0.55 1.45～1.55	1.2～1.6 0.55～0.65 1.7～1.8	0.8～1.0 0.35～0.45 1.35～1.45
2. Process flow	Short length	Is longer	Short length	3. Investment estimation	1100 yuan/t	1500 Yuan/t	1000 yuan/t
4. Fluorine recovery	Can be recycled	Can not be recycled	Can be recycled	3. Investment estimation	1100 yuan/t	1500 Yuan/t	1000 yuan/t
4. Fluorine recovery	Can be recycled	Can not be recycled	Can be recycled	5. Can produce feed-grade products	Calcium hydrogen phosphate	Calcium hydrogen phosphate	Calcium hydrogen phosphate
	Calcium dihydrogen phosphate		Calcium dihydrogen phosphate	5. Can produce feed-grade products	Calcium hydrogen phosphate	Calcium hydrogen phosphate	Calcium hydrogen phosphate
	Calcium dihydrogen phosphate		Calcium dihydrogen phosphate	6. Environmental protection ① waste gas ② waste liquid ③ waste residue	After the defluorination waste gas is recovered, the waste gas is discharged Can reach the discharge standard Little waste water and can be recycled With phosphogypsum waste residue and concentrated acid sludge Treating mud	The fluorine-containing gas is discharged in the process Is not recycled The waste water is more and can be recycled By using With phosphogypsum waste residues and defluorination residues Should be treated and can be used as fertilizer	The defluorinated gas is discharged after being recovered Discharge can reach the discharge standard Less waste water and can be recycled The application is as follows. With phosphogypsum waste residue and no others Waste slag

Claims

The preparation method of the feed calcium phosphate by the slurry concentration defluorination method is characterized in that:

1. decomposing phosphorus ore by using circulating phosphoric acid with concentration of 18-45% and over theoretical calculated amount, wherein during the decomposition process, the phosphorus-containing substance Ca of phosphorus ore₅F(PO₄)₃Is totally dissolved in the circulating phosphoric acid, and the reaction equation is

5Ca (H) in the formula₂PO₄)₂,(m-7)H₃PO₄,HF,SiF₄,H₂SiF₆To form the fluorine-containing calcium hydrophosphate slurry. Part of HF, SiF during decomposition₄The gas phase is escaped into the gas phase,
2. by concentrating slurry of calcium hydrogen phosphate, fluorine (HF, SiF) contained in the slurry is obtained₄,H₂SiF₆) Most of the gas is removed and escaped into gas phase The concentration temperature is 70-175 ℃, and P in defluorinated calcium hydrophosphate slurry₂O₅F is more than or equal to 300: 1 (weight ratio), the fluorine content in the prepared feed-grade calcium phosphate product is ensured to be less than 0.15 percent,
3. lime or lime milk is adopted to neutralize part of calcium hydrophosphate slurry after concentration and defluorination to prepare feed calcium biphosphate and calcium hydrophosphate products,
4. the sulfuric acid with the concentration of 93 percent or 98 percent is adopted to react with the other part of the calcium hydrophosphate slurry,

n =2 or 0.5, 7H produced₃PO₄And (m-7) H₃PO₄Composition mH₃PO₄Used as the circulating phosphoric acid to return to the working section of decomposing phosphorite for use,
5. HF, SiF escaping during decomposition and concentration₄Recovery by condensation and absorption to obtain>10% H₂SiF₆Solution and production of Na₂SiF₆,CaSiF₆And AlF₃By-products.