CN115974595A - A process for preparing phosphorus-magnesium-calcium compound long-acting fertilizer from wastewater containing phosphorus and fluorine - Google Patents

Abstract

The invention discloses a process for preparing a phosphorus-magnesium-calcium composite long-acting fertilizer by treating phosphorus-fluorine-containing wastewater, which comprises the following steps: step 1, calcining the dolomite type phosphorus tailings to obtain a calcined substance A, wherein the loss on ignition is not lower than 90% of the complete loss on ignition of the dolomite type phosphorus tailings; and 2, step: adding the calcined substance A obtained in the step 1 into a phosphorus-containing fluorine-containing water body in the phosphate fertilizer industry for defluorination precipitation reaction, and filtering feed liquid to obtain defluorination residues and defluorination liquid; and step 3: adding the calcined substance A obtained in the step 1 into the defluorination liquid obtained in the step 2 to carry out precipitation reaction for preparing phosphate, stopping the reaction when the pH value of slurry is 5-6, and forming two parts, namely suspension B mainly containing calcium magnesium phosphate and bottom precipitate C mainly containing fluorapatite in the slurry after the reaction is stopped; and 4, step 4: and (4) performing rotary liquid separation or sedimentation separation on the slurry obtained in the step (3) to obtain the bottom precipitate C. The method does not need to use sulfuric acid in actual use, and has the advantages of simple process and low cost.

Description

A process for preparing phosphorus-magnesium-calcium compound long-acting fertilizer from wastewater containing phosphorus and fluorine

technical field

The invention relates to the technical field of preparation of a phosphorus-magnesium-calcium compound long-acting fertilizer, in particular to a phosphorus-magnesium-calcium compound long-acting fertilizer.

Background technique

High-magnesium phosphorus tailings are low-grade phosphorus pentoxide-containing tailings discharged from phosphate ore after obtaining high-grade phosphorus pentoxide concentrate during the beneficiation process. The main phases are fluorapatite and dolomite, and The P ₂ O ₅ content is 4% to 8%, and the MgO content is 15% to 19%, which belongs to high magnesium and low grade phosphate rock. For a concentrator with an annual output of 4 million tons of phosphorous concentrate, about 1.2 million tons of high-magnesium phosphorus tailings can be produced each year, containing about 50,000 to 100,000 tons of P ₂ O ₅ and about 150,000 to 250,000 tons of MgO , rich in phosphorus and magnesium resources. For a long time, because of the low phosphorus grade in high-magnesium phosphorus tailings, they are usually treated as waste by phosphate mines and disposed of in a stockpiling manner. The phosphorus and magnesium resources in the tailings are wasted, and the effective use of resources has not been realized.

The application number is: CN201410626672.3, and the publication number is: CN104387121B (hereinafter referred to as the prior art 1) invention patent discloses a method for preparing phosphorus and magnesium fertilizers. In this method, high-magnesium phosphorus tailings are calcined at 880-1200°C , to obtain calcined white; calcined white is added to the acidic phosphorus-containing wastewater of the phosphate fertilizer industry for neutralization and precipitation reaction, and when the pH value of the feed liquid is 7-10, the feed liquid is filtered to obtain clear liquid and phosphorus-containing magnesium solid phase slag, and the clear liquid is returned Phosphate fertilizer production system or up to standard discharge; add sulfuric acid with 10%-45% dry weight of solid phase slag to react for 0.1-10h in the phosphorus-containing magnesium solid-phase slag obtained by filtration, and then dry and pulverize the reactants to obtain phosphorus-magnesium fertilizer products .

The solid-phase precipitation slag obtained in prior art 1 contains a large amount of non-citrate-soluble calcium phosphate and magnesium phosphate, which are not effective phosphorus magnesium calcium used in agricultural fertilizers, and need to be converted into effective phosphorus magnesium calcium by adding sulfuric acid, which makes the process more complicated and increases the cost.

Contents of the invention

The object of the present invention is to provide a process for preparing phosphorus-magnesium-calcium composite long-acting fertilizer by treating wastewater containing phosphorus and fluorine, which does not need to use sulfuric acid to participate in actual use, and has the advantages of simple process and low cost.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A process for preparing phosphorus-magnesium-calcium compound long-acting fertilizer by treating wastewater containing phosphorus and fluorine, comprising the following steps:

Step 1, calcining dolomite-type phosphorus tailings with a Ca content of 23% to 27%, a Mg content of 9% to 12%, and a P content of 2% to 4% at 850 to 1150°C to obtain a calcined product A and The loss on ignition rate is not less than 90% of the complete loss on ignition rate of the dolomite-type phosphorus tailings;

Step 2: Add the calcined product A obtained in Step 1 to the phosphorus-containing and fluorine-containing water body in the phosphate fertilizer industry with a P content of 0.5% to 3%, a F content of 0.1% to 0.5%, and a pH value of 0.5 to 2.3 to carry out fluoride removal precipitation reaction , stop the reaction when the pH value of the feed liquid is 2.5 to 3.5, filter the feed liquid to obtain defluorinated slag and defluorinated liquid;

Step 3: Add the calcined product A obtained in step 1 to the defluorination solution in step 2 to carry out the precipitation reaction for preparing phosphate, stop the reaction when the pH value of the slurry is 5-6, and form calcium and magnesium in the slurry after the reaction is stopped Two parts: phosphate-based suspension B and fluoroapatite-based bottom sediment C;

Step 4: The slurry obtained in step 3 is subjected to hydrocyclone separation or sedimentation separation to obtain the bottom sediment C and suspension B, the bottom sediment C is used as a phosphate rock product, and the suspension B is filtered to obtain clear liquid and calcium magnesium phosphate solid Phase slag D;

Step 5: Dry the calcium magnesium phosphate solid-phase slag D obtained in step 4 to obtain a powder of effective citrate-soluble P2O5 of 30% to 36%, effective citrate-soluble MgO of 8% to 10%, and effective citrate-soluble CaO of 12% to 15%. Phosphorus-magnesium-calcium compound long-acting fertilizer products, the above-mentioned content is a percentage by mass.

Wherein, the clear liquid obtained in step 4 returns to the production system of the factory or enters the waste water treatment system for treatment and then discharges out after reaching the standard.

It is further defined that in step 2, the defluorinated slag enters the solid waste treatment system of the factory.

Wherein, in step 2, the total amount of fluorine in the defluorination slag is not less than 85% of the total amount of fluorine in the received feed liquid.

Among them, dolomite-type phosphorus tailings are minerals containing low-grade phosphorus pentoxide and mainly composed of dolomite that are discharged after obtaining high-grade phosphorus pentoxide concentrate in the process of phosphate ore dressing.

It is further defined, and also includes step 6, granulating the powdery calcium-phosphorus-magnesium compound long-acting fertilizer product on a disc granulator or a drum granulator, drying and sieving to obtain the granular phosphorus-magnesium-calcium compound long-acting fertilizer product.

Wherein, in step 2, the reaction is stopped when the pH value of the feed liquid is 3.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention realizes the purpose of defluorination in the technique, can reduce fluorine to enter in the fertilizer, is beneficial to agricultural use; Meanwhile, in step 3 of the present invention, pH value is controlled to be 5-6, and the precipitate that generates is mainly calcium hydrogen phosphate and Magnesium hydrogen phosphate, these two kinds of materials are citrus soluble, can be used as the long-acting fertilizer of phosphorus magnesium calcium after separating and drying, and this patent flow process is short, and cost is low; Contain phosphate ore (being that Phosphorus, magnesium and calcium in the solid phase slag are mainly insoluble and non-effective forms, which need to be converted into fertilizers by reacting with sulfuric acid, the process is long and the cost is increased; more importantly, since there is no sulfuric acid used in this patent, the fertilizer The total nutrient is higher than the original patent, and it is mainly citrate-soluble nutrient, which belongs to long-acting fertilizer.

Detailed ways

In the following, only some exemplary embodiments are briefly described. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

Embodiment one

This embodiment discloses a process for preparing phosphorus-magnesium-calcium compound long-acting fertilizer by treating wastewater containing phosphorus and fluorine, including the following steps:

Step 1, calcining dolomite-type phosphorus tailings with a Ca content of 23% to 27%, a Mg content of 9% to 12%, and a P content of 2% to 4% at 850 to 1150°C to obtain a calcined product A and The loss on ignition rate is not less than 90% of the complete loss on ignition rate of the dolomite-type phosphorus tailings;

In this embodiment, dolomite-type phosphorus tailings with a Ca content of 25%, a Mg content of 10%, and a P content of 3% are preferred, and the calcination temperature is 1000°C;

The mineral composition of dolomite-type phosphorus tailings is mainly dolomite (main) and fluoroapatite (secondary). When calcined, the dolomite components become calcium oxide and magnesium oxide, which are used to treat wastewater , and the product is a substance containing effective phosphorus, magnesium and calcium, and is used as a long-term fertilizer.

Its reaction equation is as follows:

MgCO ₃ ·CaCO ₃ →MgO+CaO+CO ₂ ↑Calcination

Liquid phase reaction:

CaO+ _H2O →Ca(OH) ₂

MgO+H ₂ O→Mg(OH) ₂

The reaction of calcium ions and fluoride ions to form calcium fluoride is the main reaction in the defluorination step

Ca(OH) ₂ +H ₃ PO ₄ →CaHPO ₄ 2H ₂ O↓

Mg(OH) ₂ +H ₃ PO ₄ +H ₂ O→MgHPO ₄ 3H ₂ O↓

Step 2: Add the calcined product A obtained in Step 1 to the phosphorus-containing and fluorine-containing water body in the phosphate fertilizer industry with a P content of 0.5% to 3%, a F content of 0.1% to 0.5%, and a pH value of 0.5 to 2.3 to carry out fluoride removal precipitation reaction , stop the reaction when the pH value of the feed liquid is 2.5 to 3.5, filter the feed liquid to obtain defluorinated slag and defluorinated liquid;

In this embodiment, the calcined product A will be obtained and the loss on ignition rate is not lower than 90% of the complete loss on ignition rate of the dolomite-type phosphorus tailings, which can make the phosphorus tailings relatively completely decompose into calcium oxide, magnesium oxide, and residual Fluorapatite, if the decomposition rate is too low, the content of calcium oxide and magnesium oxide is insufficient, it is difficult to use, and the effective nutrients of the final fertilizer product will be low.

In this embodiment, preferably, the P content is 23%, the F content is 0.3%, and the phosphate fertilizer industry contains phosphorus and fluorine with a pH value of 2. Precipitation reaction is carried out, and the reaction is stopped when the pH value of the feed liquid is 3;

Step 3: Add the calcined product A obtained in step 1 to the defluorination solution in step 2 to carry out the precipitation reaction for preparing phosphate, stop the reaction when the pH value of the slurry is 5-6, and form calcium and magnesium in the slurry after the reaction is stopped Two parts: phosphate-based suspension B and fluoroapatite-based bottom sediment C;

In step 3, the reaction was stopped when the pH value of the slurry was 5.

Stop the reaction when the pH value of the slurry is 5-6, add calcined product A to the defluorination solution in step 2, the pH value of the liquid phase will rise; when the pH value of the reaction stop is in the range of 5-6, the generated The precipitates are mainly calcium hydrogen phosphate and magnesium hydrogen phosphate, which are citrate-soluble, and can be used as long-term fertilizers for phosphorus, magnesium and calcium after separation and drying.

Step 4: The slurry obtained in step 3 is subjected to hydrocyclone separation or sedimentation separation to obtain the bottom sediment C and suspension B, the bottom sediment C is used as a phosphate rock product, and the suspension B is filtered to obtain clear liquid and calcium magnesium phosphate solid Phase slag D;

Step 5: Dry the calcium magnesium phosphate solid-phase slag D obtained in step 4 to obtain a powder of effective citrate-soluble P2O5 of 30% to 36%, effective citrate-soluble MgO of 8% to 10%, and effective citrate-soluble CaO of 12% to 15%. Phosphorus-magnesium-calcium compound long-acting fertilizer products, the above-mentioned content is a percentage by mass.

The citrate-soluble effective P2O5 that present embodiment obtains is 33%, the citrate-soluble effective MgO 8.2%, the citrate-soluble effective CaO13.5%.

In actual use, the clear liquid obtained in step 4 is returned to the factory production system or enters the waste water treatment system for treatment and then discharged up to the standard, so as to realize the recycling of cleaning and achieve the purpose of environmental protection.

Among them, in step 2, the defluorination slag enters the solid waste treatment system of the factory.

It should be noted that in step 2, the total amount of fluorine in the defluorination slag is not less than 85% of the total amount of fluorine in the received feed liquid; in this way, the proportion of fluorine entering the reaction in step 2 can be controlled, and the suspended sediment in step 2 It is separated and used as fertilizer, fluorine is a harmful element in fertilizer

Among them, dolomite-type phosphorus tailings are minerals containing low-grade phosphorus pentoxide and mainly composed of dolomite that are discharged after obtaining high-grade phosphorus pentoxide concentrate in the process of phosphate ore dressing.

Embodiment two

This embodiment is further optimized on the basis of Embodiment 1. In this embodiment, it also includes step 6, granulating the powdery phosphorus magnesium calcium compound long-acting fertilizer product on a disc granulator or a drum granulator, and then After drying and sieving, the product of granular phosphorus magnesium calcium compound long-acting fertilizer is obtained.

Embodiment Three

A preparation process of phosphorus-magnesium-calcium compound long-acting fertilizer, calcining dolomite-type phosphorus tailings with a Ca content of 27%, a Mg content of 12%, and a P content of 2% at 1150°C, and the loss on ignition rate is the dolomite 98% of the complete loss-on-combustion rate of the stone-type phosphorous tailings, and the obtained calcined product A whose quality is 58% of the mass of the phosphorous tailings;

Take 21kg of calcined product A and add it to 1000kg of phosphorus and fluorine-containing water in the phosphate fertilizer industry with a P content of 3%, an F content of 0.5%, and a pH value of 0.5 to carry out the defluoridation precipitation reaction, and stop the reaction when the pH value of the feed liquid is 2.5, filter The feed liquid is defluorinated slag and defluorinated liquid, and the defluorinated slag enters the solid waste treatment system of the factory, and the F content in the defluorinated liquid is 0.1%;

Take 35kg of calcined product A and add it to the defluorination solution to carry out the precipitation reaction for preparing phosphate, stop the reaction when the pH value of the slurry is 6, and form a suspension B mainly composed of calcium magnesium phosphate and fluorophosphorus in the slurry after the reaction is stopped There are two parts of bottom sediment C mainly composed of limestone;

The resulting slurry is separated by hydrocyclone to obtain 7kg of the bottom sediment C and suspension B, the bottom sediment C is used as a phosphate rock product, the suspension B is filtered to obtain the clear liquid and calcium magnesium phosphate solid phase slag D, and the clear liquid is returned After being treated in the factory production system or in the wastewater treatment system, it meets the standard and is discharged;

The obtained calcium magnesium phosphate solid-phase slag D was dried to obtain 162 kg of powdered phosphorus, magnesium and calcium compound long-acting fertilizer whose components were citrate-soluble effective _P2O5 34%, citrate-soluble _effective MgO 9%, and citrate-soluble effective CaO 13%. product.

Phosphorus-containing wastewater in the general phosphate fertilizer industry contains fluorine, and the prior art does not have defluorination operations, causing fluorine elements to enter the fertilizer, which is not conducive to agricultural use; the invention adds a defluorination step, which can reduce the entry of fluorine elements into the fertilizer;

At the same time, the existing technology controls the pH value of the reaction end point to be 7-10, and the obtained solid-phase precipitation residue contains a large amount of non-citrate-soluble calcium phosphate and magnesium phosphate, which are not effective phosphorus, magnesium, and calcium used in agricultural fertilizers, and sulfuric acid needs to be added to react to convert them into effective Phosphate magnesium calcium, the present invention controls the pH value to 5-6, and the precipitates generated are mainly calcium hydrogen phosphate and magnesium hydrogen phosphate. These two substances are citrus soluble, and can be used as a long-term fertilizer for phosphorus magnesium calcium after separation and drying Use, the patent process is short and the cost is low;

After the reaction in the prior art, the solid phase slag contains phosphate rock (i.e. fluoroapatite), which is converted into fertilizer by reacting with sulfuric acid; the present invention obtains the bottom sediment C through separation, and converts it into a phosphate rock product; more importantly What is more interesting is that, because there is no sulfuric acid used in this patent, the total nutrient content of the fertilizer is higher than that in the prior art, and it is mainly citrus soluble nutrients, which belong to long-acting fertilizers. The nutrients in the original patent are water-soluble components, which are quick-acting fertilizers.

While preferred embodiments of the invention have been described, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is appreciated. Therefore, it is intended that the appended claims be construed to cover the preferred embodiment as well as all changes and modifications which fall within the scope of the invention.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. It should be noted that any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should include Within the protection scope of the present invention.

Claims (7)

1. A process for preparing a phosphorus-magnesium-calcium composite long-acting fertilizer by treating phosphorus-fluorine-containing wastewater is characterized by comprising the following steps:

step 1, calcining dolomite type phosphorus tailings with the Ca content of 23-27%, the Mg content of 9-12% and the P content of 2-4% at 850-1150 ℃ to obtain a calcined substance A, wherein the loss on ignition is not lower than 90% of the complete loss on ignition of the dolomite type phosphorus tailings;

and 2, step: adding the calcined substance A obtained in the step 1 into phosphorus-containing and fluorine-containing water in the phosphate fertilizer industry, wherein the P content is 0.5-3%, the F content is 0.1-0.5% and the pH value is 0.5-2.3, carrying out defluorination precipitation reaction, stopping the reaction until the pH value of feed liquid is 2.5-3.5, and filtering the feed liquid to obtain defluorination residues and defluorination liquid;

and step 3: adding the calcined substance A obtained in the step 1 into the defluorination liquid obtained in the step 2 to carry out precipitation reaction for preparing phosphate, stopping the reaction when the pH value of slurry is 5-6, and forming two parts, namely suspension B mainly containing calcium magnesium phosphate and bottom precipitate C mainly containing fluorapatite in the slurry after the reaction is stopped;

and 4, step 4: performing rotary liquid separation or sedimentation separation on the slurry obtained in the step 3 to obtain bottom sediment C and suspension B, taking the bottom sediment C as a phosphorite product, and filtering the suspension B to obtain clear liquid and calcium magnesium phosphate solid-phase slag D;

and 5: and (5) drying the calcium magnesium phosphate solid-phase slag D obtained in the step (4) to obtain a powdery phosphorus magnesium calcium compound long-acting fertilizer product with the content of citrate-soluble effective P2O 530-36%, citrate-soluble effective MgO 8-10% and citrate-soluble effective CaO 12-15%, wherein the content is the mass percentage content.

2. The process for preparing the phosphorus-magnesium-calcium compound long-acting fertilizer by treating the phosphorus-fluorine-containing wastewater according to claim 1, which is characterized in that: and (4) returning the clear liquid obtained in the step (4) to a factory production system or discharging the clear liquid after the clear liquid enters a wastewater treatment system for treatment and reaches the standard.

3. The process for preparing the phosphorus-magnesium-calcium compound long-acting fertilizer by treating the phosphorus-fluorine-containing wastewater according to claim 1, which is characterized in that: and in the step 2, the defluorinated slag enters a factory solid waste treatment system.

4. The process for preparing the phosphorus-magnesium-calcium compound long-acting fertilizer by treating the phosphorus-fluorine-containing wastewater according to claim 1, which is characterized in that: in the step 2, the total fluorine content in the defluorination residues is not less than 85% of the total fluorine content in the feed liquid.

5. The process for preparing the phosphorus-magnesium-calcium composite long-acting fertilizer by treating the phosphorus-fluorine-containing wastewater according to claim 1, which is characterized by comprising the following steps of: the dolomite phosphorus tailings are minerals which contain low-grade phosphorus pentoxide and mainly contain dolomite and are discharged after phosphate concentrate of high-grade phosphorus pentoxide is obtained from phosphorite in the ore dressing process.

6. The process for preparing the phosphorus-magnesium-calcium composite long-acting fertilizer by treating the phosphorus-fluorine-containing wastewater according to any one of claims 1 to 5, which is characterized in that: and 6, granulating the powdery phosphorus-magnesium-calcium composite long-acting fertilizer product on a disc granulator or a roller granulator, and drying and screening to obtain the granular phosphorus-magnesium-calcium composite long-acting fertilizer product.

7. The process for preparing the phosphorus-magnesium-calcium compound long-acting fertilizer by treating the phosphorus-fluorine-containing wastewater according to claim 1, which is characterized in that: and in the step 2, stopping the reaction when the pH value of the feed liquid is 3.