Method for producing calcium magnesium phosphate fertilizer with high phosphorus content by using industrial byproduct magnesium ammonium phosphate

Abstract

The invention discloses a method for producing a high-phosphorus-content calcium magnesium phosphate fertilizer by using an industrial byproduct magnesium ammonium phosphate, which comprises the following steps: drying and screening magnesium ammonium phosphate, adding phosphorite, dolomite or serpentine and coke or anthracite, feeding the materials into a smelting furnace according to a ratio, melting and smelting at a high temperature, blowing air or oxygen by an air blower at the smelting temperature of 1400-1600 DEG C for 2-3 hours, and cooling to room temperature to obtain the high-phosphorus-content calcium magnesium phosphate fertilizer. The smelting time is 0.5-4 hours, discharging molten slag from a slag opening of the smelting furnace, and carrying out water quenching to obtain the calcium magnesium phosphate fertilizer; gas generated in the process enters a hot-blast stove along with smelting furnace gas, at the moment, the temperature of a hearth of the hot-blast stove reaches 900-1000 DEG C due to gas combustion, and ammonia reacts with nitrogen oxide in the tail gas to obtain nitrogen and water, and reacts with sulfur dioxide to finally obtain ammonium bisulfate. According to the invention, resource utilization of the industrial byproduct magnesium ammonium phosphate can be realized, the calcium magnesium phosphate fertilizer with high phosphorus content can be obtained, and nitrogen oxides and sulfur dioxide in the tail gas in the production process of the calcium magnesium phosphate fertilizer can be more effectively removed.

Description

TECHNICAL FIELD

[0001] The application relates to a method for producing high-phosphorus-content calcium-magnesium-phosphorus fertilizer by using industrial by-product magnesium ammonium phosphate, and belongs to the technical field of resource recycling. BACKGROUND

[0002] The industrial by-product magnesium ammonium phosphate is a by-product in the wastewater treatment process, which refers to magnesium ammonium phosphate (MAP) crystals recovered from industrial wastewater or sludge liquid rich in nitrogen (mainly in the form of ammonia nitrogen) and phosphorus through a chemical precipitation method.

[0003] For example, as a precursor of lithium iron phosphate, iron phosphate will go through synthesis, washing water and other process procedures in the production process, and the generated synthesis mother liquor and washing water are high-salt inorganic wastewater containing metal ions, sulfate ions and phosphate ions with different concentrations, which are difficult to treat. In the prior art, ammonia water is added to improve the pH of the wastewater, and the metal ions in the water are removed in the form of precipitation, and the generated main precipitate is magnesium ammonium phosphate.

[0004] Calcium-magnesium-phosphorus fertilizer contains phosphorus, calcium, magnesium, silicon, iron, aluminum and other nutrients required by crops, and has been rapidly developed and applied in agriculture in recent years. The existing method for producing calcium-magnesium-phosphorus fertilizer by a blast furnace is to use phosphate rock, dolomite and serpentine, take coke and coal as fuel, crush the raw materials, then lift the crushed raw materials into the blast furnace, blast and smelt in the blast furnace, and then obtain a semi-finished product by high-pressure water quenching, and finally produce calcium-magnesium-phosphorus fertilizer from the semi-finished product. The existing method has defects such as low phosphorus content in calcium-magnesium-phosphorus fertilizer and great difficulty in tail gas treatment. SUMMARY

[0005] In view of the above prior art, the purpose of the present application is to provide a method for producing high-phosphorus-content calcium-magnesium-phosphorus fertilizer by using industrial by-product magnesium ammonium phosphate, which can realize resource utilization of the industrial by-product magnesium ammonium phosphate, obtain calcium-magnesium-phosphorus fertilizer with high phosphorus content, and more effectively remove nitrogen oxides and sulfur dioxide in tail gas in the production process of calcium-magnesium-phosphorus fertilizer, so as to achieve the purposes of effective denitration and desulfurization.

[0006] To achieve the above purpose, the present application adopts the following technical solutions:

[0007] The application discloses a method for producing high-phosphorus-content calcium-magnesium-phosphorus fertilizer by using industrial by-product magnesium ammonium phosphate, and belongs to the technical field of fertilizer production.

[0008] The industrial by-product magnesium ammonium phosphate contains, in percentage by weight, P2O5 12-60%, MgO 0-30% and NH3 6-12%; the phosphate rock contains, in percentage by weight, P2O5 12-38%, CaO 20-48%, MgO 0.3-15% and SiO2 3-40%.

[0009] The raw materials are proportioned in a mass ratio of magnesium ammonium phosphate: phosphate rock: dolomite / snakeskin rock: coke / anthracite coal = 0.05-0.2:0.7-0.9:0.2-0.3:0.2-0.3.

[0010] The magnesium ammonium phosphate is dried and sieved, and then the block body with a particle size of less than 200 mm is taken; the phosphate rock, dolomite or snakeskin rock, coke or anthracite coal is crushed and sieved to a particle size of less than 150 mm.

[0011] The smelting furnace is a blast furnace, a shaft furnace, a flat furnace, a converter or an electric furnace.

[0012] The cooling speed of the molten slag after water quenching is greater than 100 DEG C / s.

[0013] The application has the following beneficial effects:

[0014] The application utilizes the low-value phosphorus and ammonia of the industrial by-product magnesium ammonium phosphate to produce high-phosphorus-content calcium-magnesium-phosphorus fertilizer in a smelting furnace together with phosphate rock, dolomite or snakeskin rock, etc., and removes nitrogen oxides and sulfur dioxide in tail gas by using the ammonia in the magnesium ammonium phosphate, thereby saving resources and protecting the environment.

[0015] In the application, the addition of the magnesium ammonium phosphate increases the effective phosphorus content of the calcium-magnesium-phosphorus fertilizer, and the ammonia can react with nitrogen oxides in the tail gas to obtain nitrogen and water, and finally reacts with sulfur dioxide to obtain ammonium bisulfite, thereby achieving the purposes of denitration and desulfurization. DETAILED DESCRIPTION

[0016] The application will be further described below in combination with examples.

[0017] The equipment involved in the method for producing high-phosphorus calcium-magnesium phosphate fertilizer by using industrial by-product magnesium ammonium phosphate includes a smelting furnace, a water quenching device, a hot blast furnace, and a tail gas purification system. The smelting furnace is high-temperature resistant (above 1600℃), lined with refractory bricks, and equipped with an air blower to ensure complete combustion and melting. The water quenching device is used for rapid cooling of the molten material. The hot blast furnace is the main equipment for flue gas denitrification and desulfurization. The tail gas purification system includes gravity dust removal, cyclone dust removal, bag dust removal, electric dust removal, and alkali liquor absorption tower.

[0018] The process design of the method for producing high-phosphorus calcium-magnesium phosphate fertilizer by using industrial by-product magnesium ammonium phosphate provided by the present application is as follows:

[0019] 1. Process design

[0020] The melting process of a smelting furnace such as a blast furnace, a shaft furnace, a flat furnace, a converter, or an electric furnace is selected.

[0021] (1) Raw materials and proportioning: Magnesium ammonium phosphate is mixed with phosphate rock, dolomite, or serpentine in proportion, with an appropriate amount of coke or anthracite added to provide a reducing agent and heat.

[0022] (2) Reaction temperature: The temperature in the furnace is controlled at 1400-1600℃ to ensure complete melting and reaction of the materials.

[0023] (3) Reducing atmosphere: Air or oxygen is introduced into the smelting furnace, and coke or anthracite is burned to generate heat and CO, and to provide a reducing atmosphere.

[0024] 2. Specific process:

[0025] The magnesium ammonium phosphate is formed into balls, and is mixed with phosphate rock, dolomite, or serpentine, coke, or anthracite. The materials are fed into the smelting furnace in proportion for high-temperature melting and smelting, during which complex chemical reactions occur to obtain calcium-magnesium phosphate smelting material. At the same time, ammonia generated by the magnesium ammonium phosphate at high temperature in the smelting furnace enters the hot blast furnace with the smelting furnace gas. At this time, the hearth of the hot blast furnace reaches 900-1000℃ due to the combustion of the gas, and ammonia reacts with nitrogen oxides in the tail gas to obtain nitrogen and water without the need for adding a catalyst, achieving the purpose of flue gas denitrification. At the same time, it reacts with sulfur dioxide to ultimately obtain ammonium bisulfate. On the other hand, calcium-magnesium phosphate with high phosphorus content is obtained.

[0026] 3. Reaction principle:

[0027] (1) The industrial by-product magnesium ammonium phosphate gradually decomposes and releases ammonia at 600℃ in the upper part of the smelting furnace, and reacts with phosphate rock and dolomite to obtain high-phosphorus magnesium metaphosphate, etc.

[0028] 2MgNH4PO4→Mg2P2O7+2NH3+H2O

[0029] Mg2P2O7+ P2O5→ 2Mg(PO3)2

[0030] (Phosphorus is reduced when phosphorite is smelted at high temperature in smelting furnace, and the phosphorus is combusted to obtain P2O5 when it meets oxygen)

[0031] (2) Ammonia reacts with nitrogen oxides in tail gas to obtain nitrogen and water

[0032] 4NH3+ 6NO→ 5N2+ 6H2O

[0033] (3) Ammonia reacts with sulfur dioxide in tail gas to obtain ammonium bisulfite, which is oxidized to obtain ammonium bisulfate

[0034] NH3+ SO2+ H2O = NH4HSO3

[0035] 2NH4HSO3+ O2= 2NH4HSO4

[0036] In the following examples, the sources of the raw materials used are as follows:

[0037] The by-product ammonium magnesium phosphate from iron phosphate is a solid waste obtained from the wastewater pretreatment during the production of iron phosphate. The content of the key components is given in the form of weight percentage of elements or molecules, which does not represent the actual form of existence in the raw material, for example, the content of ammonia is calculated as the mass percentage of ammonia molecules. Phosphorite, dolomite, serpentine, and anthracite are obtained from mining; coke is obtained from a coking plant.

[0038] Among them, phosphorite is used for high-temperature smelting to generate calcium magnesium phosphate fertilizer main component calcium phosphate and produce P2O5 gas. The addition of dolomite mainly helps to reduce the melting point and improve the fluidity of the smelting material, and helps to absorb P2O5 gas by providing calcium and magnesium. The particle size of the raw materials is controlled within a certain range, the purpose of which is to maintain the permeability of the smelting furnace, and the smelting time and temperature, fluidity are related, therefore, they are given in the form of numerical range, rather than a specific numerical value.

[0039] Example 1

[0040] Raw material composition and ratio:

[0041] By-product ammonium magnesium phosphate from iron phosphate: P2O5 34%, MgO 13%, NH3 6%;

[0042] Phosphorite: P2O5 16%, CaO 32%, MgO 6%, SiO2 26%;

[0043] Dolomite: CaO 30%, MgO 20%;

[0044] Anthracite: fixed carbon 80%, ash content 14%;

[0045] Magnesium ammonium phosphate: phosphate rock: dolomite: anthracite (tons) = 0.15: 0.85: 0.23: 0.23.

[0046] Process: According to the above raw material ratio, the magnesium ammonium phosphate by-product of ferric phosphate is dried, screened, and then the lumps with a particle size of less than 200mm are taken. The phosphate rock, dolomite, and anthracite are crushed to particle sizes of less than 150mm. After automatic weighing, they are sent into the blast furnace, and air is blown in by a blower. The smelting temperature is 1400-1600℃ and the smelting time is 4 hours. After the slag is discharged from the smelting furnace slag outlet, it is quickly cooled with water to obtain calcium magnesium phosphate fertilizer with high phosphorus content.

[0047] Results: 1 ton of calcium magnesium phosphate fertilizer was obtained, with an effective phosphorus content (calculated as P2O5) of 16.8%, which is about 2% higher than that without magnesium ammonium phosphate, and 9 kg of ammonia was produced. Theoretically, nitrogen oxides can be reduced by at least 4.7 kg.

[0048] Example 2

[0049] Raw material composition and proportions:

[0050] Magnesium ammonium phosphate, a byproduct of ferric phosphate production: P2O5 52%, MgO 21%, NH3 12%;

[0051] Phosphate rock: P2O5 22%, CaO 38%, MgO 4%, SiO2 15%;

[0052] Serpentine: SiO2 40%, MgO 30%;

[0053] Coke: 80% fixed carbon, 18% ash;

[0054] Magnesium ammonium phosphate: phosphate rock: serpentine: coke (tons) = 0.1:0.9:0.23:0.25.

[0055] Process: According to the above raw material ratio, the magnesium ammonium phosphate by-product of ferric phosphate is dried, screened, and then the lumps with a particle size of less than 200mm are taken. The phosphate rock, serpentine, and coke are crushed to particle sizes of less than 150mm. After automatic weighing, they are sent into the blast furnace. Oxygen is blown in by a blower. The smelting temperature is 1400-1600℃ and the smelting time is 4 hours. After the slag is discharged from the smelting furnace slag outlet, it is quickly cooled with water to obtain calcium magnesium phosphate fertilizer with high phosphorus content.

[0056] Results: 1 ton of calcium magnesium phosphate fertilizer was obtained, with an effective phosphorus content (calculated as P2O5) of 20.5%, which is about 3% higher than that without magnesium ammonium phosphate, exceeding the national first grade standard, and 12 kg of ammonia was produced. Theoretically, it can reduce nitrogen oxides by at least 6.3 kg.

[0057] In the above embodiments, the exhaust gas containing carbon monoxide, nitrogen oxides and acidic gases generated during the production process is sent to a hot air furnace for combustion to heat the air after dust removal. After combustion, the nitrogen oxides and sulfur dioxide in the exhaust gas are absorbed by ammonia and then treated with alkaline solution before being discharged in compliance with standards.

[0058] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the above embodiments have described the present invention in detail, those skilled in the art should understand that modifications or equivalent substitutions can be made to the present invention, but any modifications and partial substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for producing high-phosphorus-content calcium magnesium phosphate fertilizer using industrial by-product magnesium ammonium phosphate, characterized in that, include: Magnesium ammonium phosphate is dried and sieved, then mixed with phosphate rock, dolomite or serpentine, coke or anthracite, and fed into a smelting furnace for high-temperature melting and smelting. Air or oxygen is blown in by a blower. The smelting temperature is 1400-1600℃, and the smelting time is 0.5-4 hours. After the slag is discharged from the slag outlet of the smelting furnace, it is quenched in water to obtain calcium magnesium phosphate fertilizer. The gas generated during this process enters the hot blast stove with the smelting furnace gas. At this time, the furnace chamber of the hot blast stove reaches 900-1000℃ due to the combustion of the gas. Ammonia reacts with nitrogen oxides in the tail gas to produce nitrogen and water, and reacts with sulfur dioxide to finally produce ammonium bisulfate.

2. The method for producing high-phosphorus-content calcium magnesium phosphate fertilizer using industrial by-product magnesium ammonium phosphate according to claim 1, characterized in that, The industrial by-product magnesium ammonium phosphate contains, by weight percentage: P2O5 12-60%, MgO 2-30%, NH3 6-12%; the phosphate rock contains, by weight percentage: P2O5 12-38%, CaO 20-48%, MgO 0.3-15%.

3. The method for producing high-phosphorus-content calcium magnesium phosphate fertilizer using industrial by-product magnesium ammonium phosphate according to claim 1 or 2, characterized in that, Based on mass ratio, the proportions of raw materials are as follows: magnesium ammonium phosphate: phosphate rock: dolomite / serpentine: coke / anthracite = 0.05-0.2: 0.7-0.9: 0.2-0.3: 0.2-0.

3.

4. The method for producing high-phosphorus-content calcium magnesium phosphate fertilizer using industrial by-product magnesium ammonium phosphate according to claim 1 or 2, characterized in that, After drying and sieving, take lumps with a particle size of less than 200mm from magnesium ammonium phosphate. Crush and sieve the phosphate rock, dolomite or serpentine, coke or anthracite to a particle size of less than 150mm.

5. The method for producing high-phosphorus-content calcium magnesium phosphate fertilizer using industrial by-product magnesium ammonium phosphate according to claim 1 or 2, characterized in that, The smelting furnace is a blast furnace, vertical shaft furnace, open-hearth furnace, converter, or electric furnace.

6. The method for producing high-phosphorus-content calcium magnesium phosphate fertilizer using industrial by-product magnesium ammonium phosphate according to claim 1 or 2, characterized in that, The cooling rate of the molten slag water quenching is greater than 100℃ / s.