Method for producing organomineral fertilizer

Abstract

Disclosed is a method for producing an organomineral fertilizer using a magnesium compound and a strong acid, characterized in that at ambient temperature, 25 to 80 w / w% of an organic sludge containing more than 40 to 90% of dry matter is introduced into a bioreactor, then 5 to 40 w / w% of roasted magnesite is added while stirring, and the mixture is stirred for 15 to 30 minutes, the present invention relates to a method for producing a solid-liquid mixture, characterized in that the solid-liquid mixture is introduced into a bioreactor, then while cooling it, 5 to 30 w / w% phosphoric acid at a concentration of 50 to 90% and solid potassium hydroxide in an amount of 2 to 25 w / w% are gradually added to the bioreactor, next, sulfuric acid at a concentration of 70 to 100% is added in an amount of 20 to 50 w / w%, after which the resulting mixture is cooled to a temperature of less than 40 DEG C, and the solid potassium hydroxide is added to the bioreactor in an amount of 2 to 25 w / w%. And measuring the aqueous phase reaction value of the substance withdrawn from the bioreactor, after which, if the pH value of the aqueous phase reaction is 4 to 8.0, 5 to 30% urea is added and the entire mixture is stirred until the majority of the components are completely homogenized, and on the other hand, if the pH value is below 4, 5 to 30% urea is added and the entire mixture is stirred until the majority of the components are completely homogenized. If the pH value is in the range of 4 to 8.0, a second dose of roasted magnesite in an amount of 1 / 50 of the first dose is injected into the bioreactor, and the contents of the reactor are homogenized, repeating this process until the pH value is in the range of 4 to 8.0, followed by adding 5 to 30% urea.

Description

[0001] The subject of the invention is a method for producing organic-mineral fertilizers based on industrial and non-industrial waste, which are used as fertilizers for agricultural applications.

[0002] For many years, waste from production and non-production activities has been used for further processing into fertilizers as an ecological alternative to chemical fertilizers or for recycling the minerals contained therein. For example, Polish application no. P.326127 discloses a method for obtaining a solid fertilizer from sewage treatment sludge produced mainly in municipal sewage treatment plants, according to which, in the environment of a strong acid, in particular sulfuric acid, organic structures of biological origin are partially mineralized. The resulting solution is then neutralized with a magnesium compound. As a result of the neutralization process, a salt is obtained, which, by binding water from the reaction environment, results in obtaining a stable fertilizing product.

[0003] Another method is disclosed in Polish patent application P.290774, which uses dehydrated sewage sludge with a degree of hydration of calcium oxide of 65% to 85% to obtain a fertilizer mixture, the ratio of sludge to lime being 1:4 to 3:1. Even at a significant excess (4:1) relative to the sludge, the use of quicklime is required.

[0004] It is also known from patent specification EP 283153 that a method for purifying municipal sewage by adding cement powder containing calcium oxide, magnesium oxide, potassium oxide in addition to carbonates. These cement powders are used as chemical stabilizers in the dewatering, thickening and conditioning of sewage sludge.

[0005] Polish patent specification no. PL169896 discloses a method for purifying post-digestion sludge while converting toxic metals into poorly soluble compounds, which comprises mixing 10 parts by weight of post-digestion sludge from a municipal sewage treatment plant containing 18% by weight of dry matter with 1 part by weight of cement powder from an electrostatic precipitator containing 34% by weight of calcium oxide, and then adding 1.1 parts by weight of calcined dolomite containing 12% by weight of magnesium oxide to the resulting mixture.

[0006] It is known from Russian application no. RU2013113685 that a method for obtaining an organic-mineral fertilizer from sewage sludge, which comprises preparing a mixture of sewage sludge and water, circulating the mixture, ultrasonically treating the mixture, dewatering the liquid phase, and discharging the undissolved part of the sludge. An alkaline reagent is added to the prepared mixture at 40 to 60°C, followed by ultrasonic treatment of the prepared mixture in an ultrasonic reactor while using a circulation pump for alkaline extraction. KOH or NaOH is used as the alkaline reagent. The alkaline extraction of the mixture during ultrasonic treatment is carried out for 30 to 60 minutes. The liquid phase of the method is an organic-mineral fertilizer, and the undissolved part of the sludge is sand contaminated with organic residues.

[0007] The description of another Russian patent No. RU2463280 C2 discloses a method of producing organic-mineral fertilizer based on sewage sludge, which includes treatment of the residue placed into a box with an acid solution representing a mixture of inorganic acids, and neutralization thereof with an alkaline extractant in the form of a mixture of alkali metal hydroxides. Acid treatment produces a solid fertilizer with removed heavy metals, while alkaline treatment produces a liquid organic-mineral fertilizer in the form of water-soluble humic acid salts, and after drying, a solid organic-mineral fertilizer as a final product is obtained.

[0008] The description of Chinese invention application No. CN115215703 A discloses a soil conditioner based on dry sludge, which is prepared by adding acid industrial or agricultural waste to dry sludge, adding a rotting agent for organic mass, performing aerobic composting digestion, adding humic acid, pyroligneous liquor and a microbial agent, and mixing them. Dry sludge is a solid residue after preparation of a concentrated solution of polypeptides from municipal sludge produced in municipal wastewater treatment using alkaline hydrolysis technology. The soil conditioner disclosed in this invention is used as an ecological agent for soil improvement.

[0009] Taking into account the huge amount of waste produced both by industrial and non-industrial human activities, and the fact that it often still contains a lot of valuable components, the inventors conceived their inventive goal to develop a method of producing an organic-mineral fertilizer as a more environmentally friendly alternative to chemical fertilizers. This is achieved by producing a solid fertilizer from production and non-production waste, including sewage sludge, organic waste, digestate, distillery waste, brewery waste, winery waste and bottom sediments, which contains minerals and organic matter recovered from waste, and provides an environmentally friendly alternative to chemical fertilizers.

[0010] The subject of the invention is a method for producing an organic-mineral fertilizer, said method comprising: introducing 25 w / w% to 80 w / w% of organic sludge containing 40% to 90% of dry matter as a substrate into a bioreactor at ambient temperature, followed by adding 5 w / w% to 40 w / w% of calcined magnesite while stirring, and stirring the mixture for 15 to 30 minutes, then, while cooling it, gradually adding 5 w / w% to 30 w / w% of phosphoric acid with a concentration of 50% to 90% into the bioreactor, and adding solid potassium hydroxide in an amount of 2 w / w% to 25 w / w%, and continuing the cooling and stirring process until the process temperature stabilizes, and next, adding sulfuric acid with a concentration of 70% to 100% in an amount of 20 w / w% to 50 w / w%, and said process is carried out at a temperature not exceeding 145°C for a time of 10 to 60 minutes, then cooling the resulting mixture to a temperature below 40°C, and measuring the water phase reaction value of the substance taken out from the bioreactor, followed by, if the pH value of the water phase reaction is 4 to 8.0, adding urea containing urease inhibitors in an amount of 5% to 30% in succession, and stirring the whole mixture until the bulk ingredients are completely homogenized, on the other hand, if the pH value is below 4, injecting into the bioreactor a second dose of calcined magnesite in an amount of 1 / 50 of the first dose, and homogenizing the contents of the reactor, repeating this process until the pH value is in the range of 4 to 8.0, after which urea in an amount of 5% to 30% is added, and the whole mixture is stirred until the bulk ingredients are completely homogenized.

[0011] Advantageously, the calcined magnesite has a particle size of less than 1 mm and a magnesium oxide content of 50 w / w% to 100 w / w%.

[0012] Advantageously, the magnesium oxide content is 87 w / w%.

[0013] Advantageously, the concentration of phosphoric acid is 75%.

[0014] Advantageously, the concentration of sulfuric acid is 95%.

[0015] Advantageously, the urea containing urease inhibitors is in the form of a powder having an amide nitrogen content of 44% to 46%.

[0016] Advantageously, the pH value of the aqueous solution of the fertilizer obtained by the method according to the invention is 7 + / - 0.5.

[0017] Advantageously, the fertilizer production process is carried out in a bioreactor equipped with a cooling system, a stirrer for the solid product, a batch height metrology, a dynamic scale, a cooling system for steam condensation and a full metrology device.

[0018] Advantageously, the fertilizer obtained by the method according to the application is subjected to a granulation process.

[0019] The substrate used in the method according to the application is tested each time for the content of organic substances, minerals, chemical compositions, water, pH of the bacterial flora, water extract, heavy metals. If the tests show the presence of heavy metals, they are neutralized using known methods, most commonly using heavy metal precipitants, preferably dithiocarbamate derivatives or soluble sulfides.

[0020] At ambient temperature, the prepared organic substrate containing 25 w / w% to 80 w / w% dry matter is introduced into the bioreactor in an amount of 25 w / w% to 80 w / w%, then the stirring is started, and next, 5 w / w% to 40 w / w% of loose calcined magnesite is added, which advantageously has a particle size of less than 1 mm and a magnesium oxide (MgO) content of 50% to 100%, advantageously 87%. The mixing of the two substrates is carried out for a period of 15 to 30 minutes, after which the cooling of the bioreactor is started, and a gradual addition of phosphoric acid in a concentration of 50% to 90%, advantageously in a concentration of 75%, in a concentration of 5 w / w% to 30 w / w%, and solid potassium hydroxide in an amount of 2 w / w% to 25 w / w% is started. After the addition of phosphoric acid, a strong exothermic reaction with potassium hydroxide begins, which causes a rapid temperature increase. If the temperature of the process stabilizes, the dosing of sulfuric acid in a concentration of 70% to 100%, advantageously 95%, in a concentration of 20 w / w% to 50 w / w% is started. This reaction is also highly exothermic, therefore slow, steady dosing and strict control of the process so that the reaction can remain stable, and the process can be carried out in such a way that the temperature does not exceed 145°C. The reaction with sulfuric acid produces a large amount of steam, which is condensed in a water cooler, thus preventing possible sulfuric acid aerosol emissions. Once the acid dosing is complete, the process of stirring is continued while cooling the reactor contents. The mixing and cooling process is continuously monitored to prevent uncontrolled solidification of the mixture and to keep it in powder form.

[0021] Then, the high temperature of no more than 145°C during these phases of the introduction of the acid into the process is maintained for 10 to 60 minutes, and depending on the dry matter content of the substrate, in order to evaporate a large amount of water, thus enabling the complete purification of the resulting semi-finished product, while the heat generated in the process is used for the concentration of the organic substrate, i.e. increasing the dry matter content or drying the fertilizer granules, and for other purposes.

[0022] Subsequently, the content of the bioreactor is cooled to below 40°C and a sample is taken to measure the pH. For this purpose, 10 g of the product is added to 90 g of distilled water and, once the mixture is homogenized, the reaction of the water extract can be tested, i.e. the pH value is measured. If the pH value is in the range of 4 to 8.0, advantageously 7 + / - 0.5, then the substance is added, i.e. 5% to 30% of urea containing urease inhibitors, the urea being in powder form, the powder having an amide nitrogen content of 44% to 46%, and the whole mixture is stirred until most of the components are completely homogenized. The product thus obtained can be granulated in a granulator suitable for this type of product.

[0023] However, if the pH of the water extract obtained is less than 4, another dose of magnesite is added, equivalent to 1 / 50 of the first portion of calcined magnesite, and the content of the reactor is homogenized, then the urea is added and another sample is taken to test the pH of the water extract. This procedure is carried out until the desired pH value is obtained.

[0024] The process according to the present application makes it possible to utilize all natural sources of organic matter and to transform them into a fertilizer in the form of granules that is attractive to farmers, which contains nitrogen, phosphorus, potassium, magnesium, sulfur and valuable biocidal organic matter, thus increasing the humus content of the soil. In addition to these advantages, the fertilizer also has the property of improving the water retention in the soil through its appropriate adsorption.

[0025] It should also be noted that, when reacting with the acid, the potassium hydroxide and the calcined magnesite used in the process according to the present application produce a very intense exothermic reaction, thus making the entire process take place without the need for an external supply of heat. Keeping the process at high temperatures during the stage of adding the acid makes it possible to evaporate a considerable amount of water.

[0026] The process according to the present application is illustrated in the following examples, however, which do not limit the mode of implementation thereof.

[0027] Example 1

[0028] Residual sludge from a municipal waste water treatment plant was used for the process according to the present application. Chemical analysis showed the presence of excess heavy metals, so FUROSEP CW3 / 5 was used to precipitate these heavy metals. 150 kg of residual sludge with a dry matter content of 50 w / w% and 30 kg of calcined magnesite with a particle size of less than 1 mm and a magnesium oxide content of 77% were introduced into the bioreactor at ambient temperature and the stirring process was started. This process was carried out for 25 minutes. While maintaining the stirring, the gradual cooling was started, while 7.5 kg of 85% phosphoric acid and 11 kg of solid potassium hydroxide were added in multiple small portions. Throughout the process, the temperature and stability of the process were continuously monitored. As a result of the exothermic reaction, the temperature increased and stabilized at 107°C, after which, while continuing the stirring and cooling, 74.5 kg of 98% sulfuric acid was gradually injected. As a result of the reaction with sulfuric acid, the temperature increased to 135°C. This temperature was maintained for 25 minutes. A large amount of steam was also produced and the steam was discharged into a water cooler, the amount of which was 50 kg. The stirring and cooling were continued until a temperature of 35°C was reached, while at all times the reactor contents were controlled to prevent uncontrolled solidification of the mixture. During the cooling process, samples were taken and tested, measuring the pH of the water extract, which was 5.6. Once the tests were completed, 11 kg of urea 46% N (Urea 46% N) was added and the entire mixture was stirred until the product was completely homogenized.

[0029] The resulting product was tested for nutrient content. The following results were obtained: organic matter - 41.7 w / w%; N (amide) - 1.0 w / w%; P205- 1.3 w / w%; K20 - 2.6 w / w%; MgO - 26.0 w / w%; SO3 - 14.3 w / w%.

[0030] Example 2

[0031] Compost was used in the method according to the application. The analysis performed did not indicate the presence of heavy metals. 55 kg of compost with a dry matter content of 75 w / w% and 35 kg of calcined magnesite with a particle size of less than 1 mm and a magnesium oxide content of 75% were introduced into the bioreactor at ambient temperature and the stirring process was started. This process was carried out for 20 minutes. While the mixture was still being stirred, the cooling was started, at the same time 11.7 kg of 85% phosphoric acid and 15 kg of solid potassium hydroxide were added in multiple small portions. The temperature and the process were monitored at all times. As a result of the exothermic reaction, the temperature increased and stabilized at 110°C, after which 63.8 kg of 95% sulfuric acid was gradually added to the mixture. The temperature increased to 130°C and was maintained for 25 minutes. 6 kg of steam was produced and the steam was discharged into a water cooler. The stirring and cooling process was carried out until the temperature decreased to 38°C, while the reactor contents were constantly controlled to prevent uncontrolled solidification of the mixture. During the cooling, a sample was taken and the pH of the water extract was measured, which was 3.7, therefore 0.07 kg of calcined magnesite with a magnesium oxide content of 75% was added to the reactor and stirring was continued for another 10 minutes. After re-measurement, the pH of the water extract was 6.2, therefore 10.0 kg of 46% N urea was added to the resulting powdered product and the entire mixture was stirred until the product was completely homogenized.

[0032] The nutrient content of the resulting product was tested. The following results were obtained: organic matter - 22.47 w / w%; N (amide) - 2.64 w / w%; P2O5 - 3.63 w / w%; K2O - 7.22 w / w%; MgO - 12.04 w / w%; SO3 - 23.9 w / w%.

[0033] Example 3

[0034] Digestate was used in the method according to the application. The analysis performed did not indicate the presence of heavy metals.

[0035] The 120.0 kg of digestate with a dry matter content of 45 w / w% and 30.0 kg of calcined magnesite with a particle size of less than 1 mm and a magnesium oxide content of 88% were introduced into the bioreactor at ambient temperature and the stirring process was started. This process was carried out for 30 minutes. While the mixture was still being stirred, the cooling was started and 10.0 kg of solid potassium hydroxide and 7.3 kg of 80% phosphoric acid were added in multiple small portions. Throughout the process, the temperature and stability of the process were continuously monitored. As a result of the exothermic reaction, the temperature increased and stabilized at 105°C, after which 67.6 kg of 95% sulfuric acid was gradually added. The temperature increased to 138°C and was maintained for 30 minutes. The reaction with sulfuric acid resulted in the production of a large amount of steam, which was discharged into a water cooler in an amount of 15.0 kg. The stirring and cooling process was carried out until a temperature of 38°C was reached, while at all times the reactor contents were controlled to prevent uncontrolled solidification of the mixture. During the cooling process, samples were taken and tested, measuring the pH of the water extract, which was 5.8. Subsequently, 8.0 kg of urea 46% N was added to the resulting powdered product and the entire mixture was stirred until the product was completely homogenized.

[0036] The resulting product was tested for nutrient content. The following results were obtained: organic matter - 42.2 w / w%; N (amide) - 1.3 w / w%; P2O5 - 1.5 w / w%; K2O - 2.9 w / w%; MgO - 23.7 w / w%; SO3 - 18.8 w / w%.

[0037] Example 4

[0038] Brewery waste was used in the method according to the application. The analysis carried out did not indicate heavy metals.

[0039] Example 4 100.0 kg of brewery waste with a dry matter content of 55 w / w% and 32.0 kg of calcined magnesite with a particle size of less than 1 mm and a magnesium oxide content of 88% were introduced into the bioreactor at ambient temperature and the stirring process was started. This process was carried out for 30 minutes. While the mixture was still being stirred, the cooling was started and 5.0 kg of solid potassium hydroxide and 3.6 kg of 80% phosphoric acid were added in multiple small portions. Throughout the process, the temperature and stability of the process were continuously monitored. As a result of the exothermic reaction, the temperature increased and stabilized at 103°C, after which 72.1 kg of 95% sulfuric acid was gradually added. The temperature increased to 137°C and was maintained for 30 minutes. The reaction with sulfuric acid produced 6.0 kg of steam, which was discharged into a water cooler. The stirring and cooling process was carried out until the temperature reached 40°C, while the reactor contents were constantly controlled to prevent uncontrolled solidification of the mixture. During the cooling process, samples were taken and tested, measuring the pH of the water extract, which was 5.7. Subsequently, 10.0 kg of urea 46% N was added to the resulting powdered product and the entire mixture was stirred until the product was completely homogenized.

[0040] The resulting product was tested for nutrient content. The following results were obtained: organic matter - 38.9 w / w%; N (amide) - 1.8 w / w%; P2O5 - 0.8 w / w%; K2O - 1.6 w / w%; MgO - 25.0 w / w%; SO3 - 21.7 w / w%.

[0041] Example 5

[0042] Brewery waste was used in the method according to the application. The analysis carried out did not indicate heavy metals.

[0043] The 115.0 kg of brewery waste with a dry matter content of 66 w / w% and 34.0 kg of calcined magnesite with a particle size of less than 1 mm and a magnesium oxide content of 87% at ambient temperature were introduced into the bioreactor and the stirring process was started. This process was carried out for 30 minutes. While still stirring, cooling was started and 6.0 kg of solid potassium hydroxide and 4.4 kg of 80% phosphoric acid were added in multiple small portions. Throughout the process, the temperature and stability of the process were continuously monitored. As a result of the exothermic reaction, the temperature increased and stabilized at 95°C, after which 78.8 kg of 92% sulfuric acid was gradually added. The temperature increased to 140°C and was maintained for 22 minutes. The reaction with sulfuric acid produced 15.8 kg of steam, which was discharged into a water cooler. The stirring and cooling process was carried out until a temperature of 35°C was reached, while at all times the reactor contents were controlled to prevent uncontrolled solidification of the mixture. During the cooling process, samples were taken and tested, measuring the pH of the water extract, which was 6.9. Subsequently, 15.0 kg of urea 46% N was added to the resulting powdered product and the entire mixture was stirred until the product was completely homogenized.

[0044] The resulting product was tested for nutrient content. The following results were obtained: organic matter - 38.1 w / w%; N (amide) - 2.3 w / w%; P2O5 - 0.8 w / w%; K2O - 1.7 w / w%; MgO - 26.00 w / w%; SO3 - 21.0 w / w%.

[0045] Example 6

[0046] The bottom sediment was used in the method according to the application. Analysis showed the presence of excess heavy metals, so these were precipitated using FUROSEP CW3 / 5.

[0047] The 130.0 kg of bottom sediment with a dry matter content of 71 w / w% and 29.0 kg of calcined magnesite with a magnesium oxide content of 87% and a particle size of less than 1 mm were introduced into the bioreactor at ambient temperature and the stirring process was started. This process was carried out for 30 minutes. While still stirring, cooling was started and 15.0 kg of solid potassium hydroxide and 10.9 kg of 80% phosphoric acid were added in multiple small portions. Throughout the process, the temperature and stability of the process were continuously monitored. As a result of the exothermic reaction, the temperature increased and stabilized at 109°C, after which 66.7 kg of 92% sulfuric acid was gradually added. The temperature increased to 127°C and was maintained for 30 minutes. The reaction with sulfuric acid produced 20.3 kg of steam, which was discharged into a water cooler. The mixing and cooling process was carried out until a temperature of 38°C was reached, while at all times the reactor contents were controlled to prevent uncontrolled solidification of the mixture. During the cooling process, samples were taken and analyzed, measuring the pH of the water extract, which was 7.2. Subsequently, 12.0 kg of urea 46% N was added to the resulting powdered product and the entire mixture was stirred until the product was completely homogenized.

[0048] The resulting product was tested for nutrient content. The following results were obtained: organic matter - 42.4 w / w%; N (amide) - 1.8 w / w%; P2O5 - 2.1 w / w%; K2O - 4.1 w / w%; MgO - 22.4 w / w%; SO3 - 27.2 w / w%. CLAIM (MODIFIED PURSUANT TO ARTICLE 19 OF THE TREATY) 1. A method for producing an organic-mineral fertilizer, wherein 25 w / w% to 80 w / w% of organic sludge - municipal waste water treatment plants and / or compost and / or digestate and / or brewery waste and / or distillery waste and / or bottom sediments containing 40% to 90% of dry matter are introduced into a bioreactor at ambient temperature, equipped with a cooling system, a stirrer designed for solid products, a batch height gauge, a dynamic scale, a cooling system for steam condensation and a full metering device, then, while stirring, 5 w / w% to 401 w / w% of calcined magnesite is added and the mixture is stirred for 15 to 30 minutes, characterized in that the organic-mineral fertilizer and magnesite are mixed, while cooling them, 5 w / w% to 30 w / w% of phosphoric acid with a concentration of 50% to 90% and a quantity of 2 w / w% to 25 w / w% of solid potassium hydroxide are gradually added to the bioreactor and the cooling and stirring process is carried out until the process temperature stabilizes; next, a quantity of 20 w / w% to 50 w / w% of sulfuric acid with a concentration of 70% to 100% is added and the process is carried out at a temperature not exceeding 145°C for 10 to 40 minutes; then, the resulting mixture is cooled to a temperature below 40°C and the pH of the water extract of the material taken from the bioreactor is measured; if the pH of the aqueous phase reaction is 4 to 8.0, 5% to 30% of urea in powder form is added, the powder having a particle diameter of less than 0.1 mm and an amide nitrogen content of 44% to 46%, and the entire mixture is stirred until most of the ingredients are completely homogenized, on the other hand, if the pH is below 4, a second dose of calcined magnesite is injected into the bioreactor, the second dose being 1 / 50 of the first dose, and the contents of the reactor are homogenized, this process is repeated until the pH is in the range of 4 to 8.0, after which 5% to 30% of urea is added and the entire mixture is stirred until most of the ingredients are completely homogenized. 2. The method according to claim 1, characterized in that the calcined magnesite has a particle size of less than 0.1 mm and a magnesium oxide content of 50 w / w% to 100 w / w%. 3. The method according to claim 2, characterized in that the magnesium oxide content is 87 w / w%. 4. The method according to any one of claims 1 to 3, characterized in that the concentration of phosphoric acid is 75%. 5. The method according to any one of claims 1 to 4, characterized in that the concentration of sulfuric acid is 95%. 6. The method according to any one of claims 1 to 6, characterized in that the pH of the aqueous solution of the resulting product is 7 + / - 0.5. 7. The process according to any one of claims 1 to 7, characterized in that the resulting product is subjected to a granulation process.

Claims

1. A method for producing an organic mineral fertilizer using a magnesium compound and a strong acid, characterized by, At ambient temperature, 25 w / w% to 80 w / w% of organic sludge containing 40% to 90% dry matter is introduced into a bioreactor, followed by the addition of 5 w / w% to 40 w / w% of calcined magnesite while stirring, and the mixture is stirred for 15 to 30 minutes, then 5 w / w% to 30 w / w% of phosphoric acid at a concentration of 50% to 90% and a quantity of solid potassium hydroxide of 2 w / w% to 25 w / w% are gradually added to the bioreactor while it is being cooled and the cooling and stirring process is performed until the process temperature stabilizes; next, a quantity of 20 w / w% to 50 w / w% of sulfuric acid at a concentration of 70% to 100% is added and the process is performed at a temperature not exceeding 145°C for 10 to 40 minutes; then the resulting mixture is cooled to a temperature below 40°C and the pH of the water extract of the material removed from the bioreactor is measured; if the pH of the aqueous phase reaction is 4 to 8.0, 5% to 30% of urea is added and the entire mixture is stirred until most of the ingredients are completely homogenized, on the other hand, if the pH is below 4, a second dose of calcined magnesite is injected into the bioreactor, the quantity of the second dose being 1 / 50 of the first dose, and the contents of the reactor are homogenized, this procedure is repeated until the pH is in the range of 4 to 8.0, after which 5% to 30% of urea is added and the entire mixture is stirred until most of the ingredients are completely homogenized.

2. The method of claim 1, wherein, The calcined magnesite has a particle size of less than 0.1 mm and a magnesium oxide content of 50 w / w% to 100 w / w%.

3. The method of claim 2, wherein, The magnesium oxide content is 87 w / w%.

4. The method according to any one of claims 1 to 3, characterized in that, The concentration of phosphoric acid is 75%.

5. The method according to any one of claims 1 to 4, characterized in that, The concentration of sulfuric acid is 95%.

6. The method according to any one of claims 1 to 5, characterized in that, The urea is in powder form, the powder having a particle diameter of less than 0.1 mm and an amide nitrogen content of 44% to 46%.

7. The method according to any one of claims 1 to 6, characterized in that, The pH of the aqueous solution of the resulting product is 7 + / - 0.

5.

8. The method according to any one of claims 1 to 7, characterized in that, The fertilizer production process is performed in a bioreactor equipped with a cooling system, a stirrer designed for solid products, a batch height dosing scale, a dynamic scale, a cooling system for steam condensation and a full metering device.

9. The method according to any one of claims 1 to 7, characterized in that, The resulting product is subjected to a granulation process. The resulting product is subjected to a granulation process.