A method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent.

Abstract

This invention relates to a method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent, belonging to the technical field of mineral resource utilization and soil conditioner preparation. The method includes the following steps: reacting urea with 98% concentrated sulfuric acid, cooling and crystallizing to prepare a solid acid hydrolysis agent; activating the solid acid hydrolysis agent with phosphate rock powder in a mechanical grinding mill to obtain a solid acidic material; mixing the solid acidic material with alkaline materials and functional conditioning aids, and then extruding into granules to obtain the granular soil conditioner. The solid acid hydrolysis agent prepared by this invention is safe to store, convenient to transport and use, and employs mechanical grinding activation technology to efficiently activate phosphorus, magnesium, and calcium elements in phosphate rock, with phosphorus activation rate ≥90%, calcium activation rate ≥85%, and magnesium activation rate ≥80%. The production process is simple, low-cost, and produces no waste. The prepared granular soil conditioner has good dispersibility and strength, enabling the full and high-value utilization of medium- and low-grade phosphate rock and flotation phosphate tailings resources.

Description

Technical Field

[0001] This invention relates to the field of mineral resource utilization and soil conditioner preparation technology, specifically to a method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent. Background Technology

[0002] About 90% of my country's phosphate rock resources are of medium to low grade, making them unsuitable for direct production of wet-process phosphoric acid and high-concentration phosphate fertilizers. The flotation process for phosphate concentrate generates a large amount of phosphate tailings, with an annual output of up to 10 million tons, but its utilization efficiency is only 10%. The large accumulation of phosphate tailings not only occupies land but also pollutes groundwater, causes soil desertification, and generates secondary dust pollution. Currently, phosphate tailings are mostly used as building materials, failing to utilize the valuable elements such as phosphorus, calcium, and magnesium, resulting in resource waste.

[0003] Sulfuric acid is commonly used as an acid hydrolysis agent in the wet processing of phosphate rock. It is a highly corrosive acid that is inconvenient to store, transport and use. If it is made into a solid acid hydrolysis agent, it will be easier to store, transport and use safely. At the same time, the wet sulfuric acid decomposition of phosphate rock to produce compound fertilizer is a complex process and will also produce a large amount of by-products such as phosphogypsum, residual acid, and sludge acid, which will cause resource waste and environmental pollution.

[0004] The soil conditioner prepared in this invention uses sandy raw materials such as calcium magnesium phosphate fertilizer and yellow phosphorus slag. The granulation of these sandy raw materials can be achieved through processes such as extrusion granulation and drum granulation, which have relatively low technical barriers. However, a technical problem often arises after granulation: the particles do not dissolve in water or soil. This lack of dissolution hinders nutrient release and affects the soil conditioner's effectiveness. Therefore, the dissolution rate of the particles must meet certain requirements to ensure rapid dissolution when applied to the soil.

[0005] Invention patent CN1113934A mentions preparing a sulfuric acid-containing solid composition product by combining sulfuric acid solution, urea, and certain additives. In application, the solid composition is mixed with phosphate rock using a "dry method" or granulated by spraying or sprinkling while the solidified acid is still uncured. The solid acid hydrolysate of this invention differs in that it requires no additives and can be made into a solid product through cooling and crystallization. The reaction with phosphate rock is activated by mechanical grinding, greatly improving the activation rate of the phosphate rock, and subsequent granulation is performed by extrusion. Invention patent CN87103006A involves mixing solidified nitric acid with phosphate rock powder and then molding, while the solid acid hydrolysate prepared in this invention differs from this method.

[0006] A method for producing soil conditioners by activating phosphate rock with a solid acid hydrolysis agent is simple, produces no waste, and is clean and environmentally friendly. The prepared solid acid hydrolysis agent is safe to store, convenient to transport and use. Combined with mechanical grinding technology, it can efficiently activate phosphorus, magnesium, and calcium nutrients in phosphate rock, enabling the direct, full, and high-value utilization of medium- and low-grade phosphate rock resources and flotation tailings. The granular soil conditioner produced has good particle strength and dissolution properties and can be used to supplement medium-quantity elements such as calcium, magnesium, and sulfur in the soil, thereby improving soil fertility. Therefore, developing a method for activating phosphate rock with a solid acid hydrolysis agent to prepare soil conditioners has significant practical significance and application value for the comprehensive utilization of phosphate rock resources and soil improvement. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention aims to provide a method for activating phosphate rock with a solid acid hydrolysis agent to produce granular soil conditioner. The prepared solid acid hydrolysis agent is safe to store, convenient to transport and use. Using mechanical grinding technology, it can efficiently activate medium and low grade phosphate rock and flotation phosphate tailings to produce functional soil conditioner containing nutrients such as nitrogen, phosphorus, calcium, magnesium, and sulfur. The production process is simple, low-cost, and produces no waste. The phosphorus activation rate is ≥90%, the calcium activation rate is ≥85%, and the magnesium activation rate is ≥80%. The particle dissolution rate of the prepared granular soil conditioner is ≥70%, and the average crushing resistance of the particles is ≥10N.

[0008] To achieve the above objectives, the present invention provides a method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent, comprising the following steps:

[0009] (1) Urea was reacted with 98% concentrated sulfuric acid solution. After the urea was completely dissolved, it was poured into a cooler and allowed to stand and cool to crystallize, thus preparing a solid acid hydrolysate.

[0010] (2) The solid acid hydrolysate is mechanically ground and activated with phosphate rock powder to obtain a solid acidic material containing multiple nutrients such as nitrogen, phosphorus, calcium, magnesium and sulfur;

[0011] (3) Mix solid acidic materials, alkaline materials, and functional conditioning agents evenly in a mixer, then add them to an extrusion granulator to extrude them into granules, and dry them to obtain granular soil conditioner products.

[0012] This invention proposes using low- to medium-grade phosphate rock and flotation tailings as raw materials, and employing a solid acid hydrolysis agent and mechanical activation with phosphate rock powder to prepare a solid acidic material, achieving efficient activation and full utilization of phosphorus, calcium, and magnesium elements in the phosphate rock. The solid acidic material, along with alkaline materials and functional conditioning agents, is extruded into granules in an extrusion granulator to prepare a functional soil conditioner with a particle dissolution rate ≥70% and an average particle crushing resistance ≥10N. This method efficiently activates phosphorus, magnesium, calcium, and other nutrients in low- to medium-grade phosphate rock and flotation tailings, achieving phosphorus activation rates ≥90%, calcium activation rates ≥85%, and magnesium activation rates ≥80%.

[0013] As a preferred embodiment, the proportion of -200 mesh phosphate rock powder in the phosphate rock is not less than 80 wt%. More preferably, it is 80-90 wt%.

[0014] As a preferred option, the medium- and low-grade phosphate rock contains 18-26 wt% P2O5, 35-40 wt% CaO, 0.5-2 wt% MgO, and 18-23 wt% SiO2.

[0015] As a preferred option, the flotation tailings contain 6-13 wt% P2O5, 30-35 wt% CaO, 15-20 wt% MgO, and 5-10 wt% SiO2.

[0016] As a preferred embodiment, the solid acid hydrolysate is obtained by reacting urea with 98% concentrated sulfuric acid.

[0017] As a preferred embodiment, the molar ratio of urea to 98% concentrated sulfuric acid is 1.5 to 2.5:1.

[0018] As a preferred embodiment, the cooling crystallization temperature of the solid acid hydrolysate is 14~20℃.

[0019] As a preferred embodiment, the mass ratio of the solid acid hydrolysis agent to phosphate rock powder is 7-9:10. Insufficient solid acid hydrolysis agent will result in a low phosphate rock decomposition rate and incomplete reaction; excessive amount will lead to excessive acidity, causing the phosphate rock conversion rate to remain constant and resulting in a waste of acid resources.

[0020] As a preferred embodiment, the mechanical activation time is 5-20 min; the mechanical grinding speed is 200-400 r / min.

[0021] As a preferred embodiment, the indicators for the high-efficiency activation of phosphate rock by the solid acid hydrolysis agent are: phosphorus activation rate ≥90%, calcium activation rate ≥85%, and magnesium activation rate ≥80%.

[0022] As a preferred embodiment, the mass ratio of the solid acidic material to the alkaline material is 1:0.3~0.8.

[0023] As a preferred embodiment, the amount of the functional conditioning agent added is 3 to 5% of the sum of the mass of the solid acidic material and the alkaline material.

[0024] As a preferred embodiment, the granulation process of the solid acidic material, alkaline material, and functional conditioning agent specifically includes: mixing the three materials evenly in a mixer and then extruding them into granules in an extrusion granulator. This granulation method is simple to operate and has low production costs.

[0025] As a preferred embodiment, the granulated soil conditioner material after granulation is dried at 60-80°C.

[0026] As a preferred embodiment, the soil conditioner has a particle size range of 1~4.75mm, an average crushing resistance ≥10N, and a particle dissolution rate (soaked in still water for 20min at room temperature) ≥70%.

[0027] Compared with the prior art, the present invention has at least the following advantages:

[0028] (1) The present invention provides a method for producing granular soil conditioner by activating phosphate rock with solid acid hydrolysis agent. It can directly and fully utilize medium and low grade phosphate rock and flotation phosphate tailings resources to produce functional soil conditioner containing nutrients such as nitrogen, phosphorus, calcium, magnesium and sulfur. The production process is simple, the cost is low and there is no discharge of "three wastes".

[0029] (2) Solid acid hydrolysate is safer to store and easier to transport and use than liquid sulfuric acid.

[0030] (3) Solid acid hydrolysis agent can efficiently activate phosphorus, calcium and magnesium elements in phosphate rock, so that the activation rate of phosphorus in phosphate rock is ≥90%, the activation rate of calcium is ≥85% and the activation rate of magnesium is ≥80%.

[0031] (4) The prepared granular soil conditioner was tested for dispersibility and average crushing force. The particle dispersibility was ≥70% and the average crushing force was ≥10N. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of the present invention;

[0033] Figure 2 The solid acidic material prepared in Example 1;

[0034] Figure 3 The dispersibility diagram is shown for the granular soil conditioner product prepared in Example 2. Detailed Implementation

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0038] Example 1

[0039] (1) Preparation of solid acid hydrolysate

[0040] Weigh out 221.4 kg of urea and 245.8 kg of 98% concentrated sulfuric acid. Slowly add the urea to the concentrated sulfuric acid. After the urea is completely dissolved, transfer it to a cooler and control the system temperature at 20°C. Allow it to stand and cool to crystallize, and a solid acid hydrolysate is obtained.

[0041] (2) Activation of phosphate rock powder with solid acid hydrolysis agent

[0042] 100 kg of flotation phosphate tailings powder and 70 kg of solid acid hydrolysis agent were weighed and ground at room temperature using a mechanical grinder at a grinding speed of 200 r / min and a grinding time of 5 min to obtain solid acidic material.

[0043] The activation rates of phosphorus, calcium, and magnesium in solid acidic materials were determined. The results showed that the activation rate of phosphorus was 90.8%, the activation rate of calcium was 85.5%, and the activation rate of magnesium was 84.3%.

[0044] (3) Preparation of granular soil conditioner products

[0045] Take 640 kg of solid acidic material, 128 kg of alkaline calcium magnesium phosphate fertilizer, 192 kg of ammonium bicarbonate, and 40 kg of humic acid. Mix them evenly by mechanical stirring, then extrude them into granules using an extrusion granulator. Dry them at 80℃, and then cool, sieve, and package them to obtain the final product.

[0046] The soil conditioner was tested for N and available P2O. 5、The results of calcium, magnesium, and sulfur content tests showed that the soil conditioner contained 11.5% N, 4.2% available P2O5, 8.0% calcium, 3.0% magnesium, and 6.0% sulfur.

[0047] Example 2

[0048] (1) Preparation of solid acid hydrolysate

[0049] Weigh out 221.4 kg of urea and 185.5 kg of 98% concentrated sulfuric acid. Slowly add the urea to the concentrated sulfuric acid. After the urea is completely dissolved, transfer it to a cooler and control the system temperature at 15°C. Allow it to stand and cool to crystallize, and a solid acid hydrolysate is obtained.

[0050] (2) Activation of phosphate rock powder with solid acid hydrolysis agent

[0051] 100 kg of flotation phosphate tailings and 80 kg of solid acid hydrolysis agent were weighed and ground at room temperature using a mechanical grinder at a grinding speed of 300 r / min and a grinding time of 10 min to obtain solid acidic material.

[0052] The activation rates of phosphorus, calcium, and magnesium in the acidic material were determined, and the results showed that the activation rate of phosphorus was 93.8%, the activation rate of calcium was 88.5%, and the activation rate of magnesium was 86.4%.

[0053] (3) Preparation of granular soil conditioner products

[0054] Take 640 kg of solid acidic material, 100 kg of alkaline calcium magnesium phosphate fertilizer, 52 kg of dolomite, 160 kg of limestone, 20 kg of alginic acid, and 28 kg of bentonite. After mechanically stirring and mixing evenly, granulate the mixture using an extrusion granulator, dry it at 70℃, and then cool, sieve, and package it to obtain the final product.

[0055] The soil conditioner was tested for N and available P2O. 5、 The results of calcium, magnesium, and sulfur content tests showed that the soil conditioner contained 8.5% N, 4.0% available P2O5, 14.0% calcium, 3.5% magnesium, and 4.5% sulfur.

[0056] Example 3

[0057] (1) Preparation of solid acid hydrolysate

[0058] Weigh out 221.4 kg of urea and 147.6 kg of 98% concentrated sulfuric acid. Slowly add the urea to the concentrated sulfuric acid. After the urea is completely dissolved, transfer it to a cooler and control the system temperature at 18°C. Allow it to stand and cool to crystallize, and a solid acid hydrolysate is obtained.

[0059] (2) Activation of phosphate rock powder with solid acid hydrolysis agent

[0060] 100 kg of medium-low grade phosphate rock powder and 90 kg of solid acid hydrolysis agent were weighed and ground at room temperature using a mechanical grinder at a grinding speed of 400 r / min and a grinding time of 20 min to obtain solid acidic material.

[0061] The activation rates of phosphorus, calcium, and magnesium in the acidic material were determined, and the results showed that the activation rate of phosphorus was 91.5%, the activation rate of calcium was 86.3%, and the activation rate of magnesium was 81.8%.

[0062] (3) Preparation of granular soil conditioner products

[0063] Take 571 kg of solid acidic material, 114 kg of alkaline calcium magnesium phosphate fertilizer, 171 kg of yellow phosphorus slag, 114 kg of lightly calcined magnesium, 10 kg of amino acids, 10 kg of alginic acid, and 10 kg of attapulgite. After mechanically stirring and mixing evenly, granulate the mixture using an extrusion granulator, dry it at 60℃, and then cool, sieve, and package it to obtain the final product.

[0064] The soil conditioner was tested for N and available P2O. 5、 The results of calcium, magnesium, and sulfur content tests showed that the soil conditioner contained 8.0% N, 8.0% available P2O5, 14.5% calcium, 7.0% magnesium, and 3.8% sulfur.

[0065] Test case

[0066] Dissolution performance test: Take 5.00 g of the granular soil conditioner prepared in the above example, distribute it evenly on a 1.00 mm test sieve, place it in a water tank with a water depth of about 30 mm, and ensure that the water surface is submerged above the surface of the sample; let it stand for 10 min, then gently lift the test sieve up and down 3 to 5 times to allow the dissolved sample to pass through the sieve holes; place the test sieve and the remaining sample on it in a clean tray of appropriate size, and then place it in an electric thermostatic drying oven at 130℃±2℃ for 30 min to dry. Remove it, place it in a desiccator to cool to room temperature, weigh it, and calculate the dissolution rate.

[0067] Average crushing force test: 30 samples with an aperture of 1.00 mm to 4.75 mm were randomly selected, and the crushing force of each sample was measured with a particle strength tester. The average crushing force was then calculated.

[0068] The granular soil conditioner prepared in Example 1 had a dissolution rate of 83% and an average crushing resistance of 18N.

[0069] The granular soil conditioner prepared in Example 2 had a dissolution rate of 78% and an average crushing resistance of 16 N.

[0070] The granular soil conditioner prepared in Example 3 had a dissolution rate of 75% and an average crushing resistance of 23 N.

[0071] It can be seen that the granular soil conditioner product provided by the present invention has good dispersibility and average crushing resistance.

[0072] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent, characterized in that: Includes the following steps: (1) Urea was reacted with 98% concentrated sulfuric acid solution. After the urea was completely dissolved, it was poured into a cooler and allowed to stand and cool to crystallize, thus preparing a solid acid hydrolysate. (2) The solid acid hydrolysate is mechanically ground and activated with phosphate rock powder to obtain a solid acidic material containing multiple nutrients such as nitrogen, phosphorus, calcium, magnesium and sulfur; (3) Mix solid acidic materials, alkaline materials, and functional conditioning agents evenly in a mixer, then add them to an extrusion granulator to extrude them into granules, and dry them to obtain granular soil conditioner products.

2. The method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent according to claim 1, characterized in that: The molar ratio of urea to 98% concentrated sulfuric acid is 1.5~2.5:

1.

3. The method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent according to claim 1, characterized in that: The cooling crystallization temperature of the solid acid hydrolysate is 14~20℃.

4. The method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent according to claim 1, characterized in that: The mass ratio of the solid acid hydrolysis agent to phosphate rock powder is 7~9:

10.

5. The method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent according to claim 1, characterized in that: The mechanical activation equipment is a mechanical grinder; the mechanical activation time is 5~20 min; the mechanical grinding speed is 200~400 r / min.

6. The method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent according to claim 1, characterized in that: The alkaline material is two or more of the following: calcium magnesium phosphate fertilizer, ammonium bicarbonate, lightly calcined magnesium, magnesium hydroxide, quicklime, limestone, calcium hydroxide, yellow phosphorus slag, and dolomite.

7. The method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent according to claim 1, characterized in that: The mass ratio of the solid acidic material to the alkaline material is 1:0.3~0.

8.

8. The method for producing granular soil conditioner by activating phosphate rock with a solid acid hydrolysis agent according to claim 1, characterized in that: The functional conditioning agent is two or more of the following: humic acid, alginic acid, amino acids, bentonite, attapulgite, and potassium humate; the amount of functional conditioning agent added is 3 to 5% of the sum of the mass of the solid acidic material and the alkaline material.

9. A granular soil conditioner prepared by any one of claims 1 to 8.

Images