Method for manufacturing organic-mineral fertiliser

Abstract

A method for manufacturing an organic-mineral fertiliser, using magnesium compounds and strong acids is characteristic in that at ambient temperature from 25 to 80 w / w% of organic sludge containing over 40 to 90% of dry matter is introduced into a bioreactor and subsequently, while stirring, from 5 to 40 w / w% of roasted magnesite is added and the mixture is stirred for 15 to 30 min., and then, while cooling it, 5 to 30 w / w% of phosphoric acid with the concentration of 50% to 90% is gradually added to the bioreactor as well as solid potassium hydroxide in the amount of 2 to 25 w / w% and next, sulphuric acid with the concentration of 70% to 100 % is added in the amount of 20 to 50 w / w%, after which the resulting mixture is cooled to the temperature below 40° C and the aqueous reaction value of the substance taken from the bioreactor is measured, and subsequently, if the pH value of the aqueous reaction is between 4 and 8.0, 5% to 30% of urea is added and the whole mixture is stirred until the bulk ingredients are fully homogenised, if, on the other hand, the pH value is lower than 4, a second dose of roasted magnesite in the amount of 1 / 50 of the first dose is injected into the bioreactor and the contents of the reactor are homogenised, this procedure being repeated until the pH value is within the range of 4 to 8.0, after which 5% to 30% of urea is added.

Description

[0001] Method for manufacturing organic-mineral fertiliser

[0002] The subject of the invention is a method for manufacturing an organic- mineral fertilizer based on industrial and non-industrial waste, for use as a fertilizer for agricultural application.

[0003] For many years, waste from production and non-production activities has been used for further processing into fertilisers as an ecological alternative to chemical fertilisers or for recovering the minerals they contain. For example, Polish invention application no. P.326127 discloses a method for obtaining a solid fertiliser from sewage treatment sludge generated mainly in municipal sewage treatment plants, according to which organic structures of biological origin are partially mineralised in the environment of a strong acid, in particular sulphuric acid. The resulting solution is subsequently neutralised with magnesium compounds. As a result of the neutralisation process, a salt is obtained which, by binding the water from the reaction environment, results in obtaining a stable fertilising mass.

[0004] Another method is disclosed in Polish patent application P.290774 for obtaining a fertiliser mixture from dehydrated sewage sludge with the hydration of 65 - 85% with calcium oxide, the ratio of sludge to lime being from 1:4 to 3: 1. The use of quicklime is claimed even at a significant excess in relation to the sludge (4: 1).

[0005] Also known from patent description EP 283153 is a method of hygienizing municipal sludge by adding cement dusts containing, in addition to carbonates, calcium oxide, magnesium oxide, potassium oxide. These dusts are used as chemical stabilisers in the dewatering, thickening and conditioning of sewage sludge.

[0006] Polish patent description no. PL169896 discloses a method of hygienizing post-digestion sludge with simultaneous conversion of toxic metals into poorly soluble chemical compounds, consisting in mixing 10 parts by weight of post-digestion sludge, containing 18% by weight of dry matter, from a municipal sewage treatment plant with 1 part by weight of cement dust from an electrostatic precipitator containing 34% by weight of calcium oxide, followed by the addition of 1.1 parts by weight of roasted dolomite, at 873 K for 2K, containing 12% by weight of magnesium oxide to the resulting mixture.

[0007] From the Russian invention application No. RU2013113685, a method of obtaining an organic-mineral fertiliser from sewage sludge is known, comprising preparation of a mixture of sewage sludge and water, circulation of the mixture, ultrasonic treatment of the mixture, draining of the liquid phase and discharge of the undissolved part of the sludge. An alkaline reagent is added to the prepared mixture at 40-60°C and subsequently alkaline extraction is carried out using a circulating pump, while ultrasonic treatment of the prepared mixture is carried out in an ultrasonic reactor. KOH or NaOH is used as the alkaline reagent. The alkaline extraction of the mixture during ultrasonic treatment is carried out for 30-60 minutes. The liquid phase of the method is organic- mineral fertiliser and the undissolved part of the sludge is sand contaminated with organic residues.

[0008] Another description of Russian patent No. RU2463280C2 discloses a method of producing an organic-mineral fertiliser based on sewage sludge, consisting in treating the residue placed in a cassette with an acidic solution representing a mixture of inorganic acids and neutralising it with an alkaline extractant in the form of a mixture of alkali metal hydroxides. The acid treatment yields solid fertilisers with the heavy metals removed, while the alkaline treatment yields liquid organic-mineral fertilisers in the form of water-soluble humates and, after drying, solid organic-mineral fertilisers are obtained as the finished product.

[0009] The description of the Chinese invention application No. CN115215703A discloses a soil conditioner based on dried sludge, which is produced by adding acidic industrial or agricultural waste to the dried sludge, adding a decomposing agent for organic material, carrying out aerobic compost digestion, adding humic acid, pyromagnetic lye and microbial agent and mixing them. The dried sludge is the solid residue after the preparation of a concentrated solution of polypeptide from municipal sludge generated in the treatment of municipal wastewater using alkaline thermal hydrolysis technology. The soil conditioner disclosed in the invention is used as an ecological agent for soil reclamation.

[0010] Considering the huge amount of waste generated by both industrial and non-industrial human activities, and the fact that it generally still contains a great deal of valuable components, the inventors formulated their inventive goal as developing a method of producing an organic-mineral fertiliser as a more environmentally friendly alternative to chemical fertilisers. This was achieved by using production and non-production waste, including sewage sludge, organic waste, digestate, distillery waste, brewery waste, winery-industry waste and bottom sediments to produce a solid fertiliser containing the recovered minerals and organic matter from waste and providing an environmentally friendly alternative to chemical fertilisers.

[0011] The subject of the invention is a method for manufacturing an organic- mineral fertiliser, which consists in introducing, as the substrate, from 25 to 80 w / w% of organic sludge containing from 40 to 90% of dry matter into a bioreactor at ambient temperature and subsequently, while stirring, from 5 to 40 w / w% of roasted magnesite is added and the mixture is stirred for 15 to 30 min, then, while cooling it, 5 to 30 w / w% of phosphoric acid with the concentration of 50% to 90% is gradually added to the bioreactor and solid potassium hydroxide is added in the amount of 2 to 25 w / w% and the cooling and stirring processes are continued until the temperature of the process stabilises, and next, sulphuric acid with the concentration of 70% to 100 % is added in the amount of 20 to 50 w / w% and the process is carried out at the temperature not exceeding 145° C for a period of 10 to 60 minutes and then the resulting mixture is cooled to the temperature below 40° C and the aqueous reaction value of the substance taken from the bioreactor is measured, and subsequently, if the pH value of the aqueous reaction is between 4 and 8.0, 5% to 30% of urea containing urease inhibitor is added sequentially and the whole mixture is stirred until the bulk ingredients are fully homogenised, if, on the other hand, the pH value is lower than 4, a second dose of roasted magnesite in the amount of 1 / 50 of the first dose is injected into the bioreactor and the contents of the reactor are homogenised, this procedure being repeated until the pH value is within the range of 4 to 8.0, after which 5% to 30% of urea is added and the whole mixture is stirred until the bulk ingredients are completely homogenised.

[0012] Favourably, the roasted magnesite has the grain size of less than 1 mm and a magnesium oxide content of 50 to 100 w / w%.

[0013] Favourably, the magnesium oxide content is 87 w / w%.

[0014] Favourably, the phosphoric acid has the concentration of 75%.

[0015] Favourably, the sulphuric acid has the concentration of 95%.

[0016] Favourably, the urea containing urease inhibitor is in the form of a powder with the amide nitrogen content of 44% to 46%.

[0017] Favourably, the pH value of the aqueous solution of the fertiliser obtained by the method according to the invention is 7+ / -0.5.

[0018] Favourably, the fertiliser production process is carried out in a bioreactor equipped with a cooling system, a stirrer for solid products, batch height measurement, dynamic scales, a cooling system for steam condensation, and full metering.

[0019] Favourably, the fertiliser obtained by the method according to the invention is subjected to the granulation process.

[0020] The substrate to be used in the method according to the invention is each time subjected to tests for the content of organic substances, minerals, chemical composition, water, bacterial flora, pH of the water extract, heavy metals. If the tests reveal the presence of heavy metals, they are neutralized using known methods, most commonly using a heavy metal precipitation agent, preferably dithiocarbamate derivatives or soluble sulphides.

[0021] The prepared organic substrate, containing between 25 and 80 w / w% of dry matter, is introduced into the bioreactor at ambient temperature in the amount of 25 to 80 w / w% and then stirring is commenced, and next, 5 to 40 w / w% of loose roasted magnesite, favourably with the grain size of less than 1 mm and the magnesium oxide (MgO) content of 50% to 100%, favourably 87%, is added. The mixing of the two substrates is carried out for a period of 15 to 30 min, after which cooling of the bioreactor is initiated and 5 to 30 w / w% of phosphoric acid is gradually dosed with the concentration of 50% to 90%, favourably with the concentration of 75%, and solid potassium hydroxide is added in the amount of 2 to 25 w / w%. The addition of phosphoric acid starts a strongly exothermic reaction with the potassium hydroxide, causing a rapid rise in temperature. If the temperature of the process stabilises, a dosage of 20 to 50 w / w% of sulphuric acid with the concentration of 70% to 100%, favourably 95%, is started. This reaction, too, is highly exothermic, therefore slow, steady dosing, as well as strict control of the process, allows the reaction to remain stable and the process to be conducted in such a way that the temperature does not exceed 145° C. The reaction with sulphuric acid produces large amounts of steam, which is condensed in a water cooler, thus protecting against the possible emission of sulphuric acid aerosols. Once the acid dosing is complete, the stirring process continues simultaneously with the cooling of the reactor contents. The mixing and cooling process is continuously monitored to prevent the mixture from uncontrolled solidifying and to keep in powdered form instead.

[0022] The high temperature during the stages when acids are introduced into the process, not exceeding 145° C, however, is maintained for 10 to 60 minutes and is dependent on the dry matter content of the substrate, so that a significant amount of water is evaporated, allowing the resulting semifinished product to be fully hygienized, while the heat generated in the process is used to concentrate the organic substrates, i.e. increase the dry matter content or dry the fertiliser granules, and for other purposes.

[0023] Subsequently, the contents of the bioreactor are cooled to below 40° C and a sample is taken to measure the pH. For this purpose, 10g of the product is added to 90g of distilled water and, once the mixture is homogenised, the reaction of the aqueous extract is tested, i.e. the pH value is measured. If the pH value ranges from 4 to 8.0, favourably 7+ / -0.5, enrichment substances are then added, i.e. from 5% to 30% of urea containing the urease inhibitor, occurring in the form of a powder with 44% to 46% amide nitrogen content, and the whole mixture is stirred until the bulk components are fully homogenised. Thus obtained product can be granulated in granulators suitable for this type of product.

[0024] However, if the pH of the aqueous extract obtained is less than 4, a further dose of magnesite equivalent to l / 50th of the first portion of roasted magnesite is added and the contents of the reactor are homogenised before the urea is added, and a further sample is taken to test the pH of the aqueous extract. This procedure is carried out until the desired pH value is obtained.

[0025] The method according to the invention makes it possible to utilise all organic substances of natural origin and convert them into an attractive fertiliser for farmers in the form of granules containing nitrogen, phosphorus, potassium, magnesium, sulphur and valuable sterile organic matter, improving the humus content of the soil. In addition to these advantages, the fertiliser also has the property of improving water retention in the soil through its proper sorption.

[0026] It should also be pointed out that, when reacting with acids, the potassium hydroxide and roasted magnesite used in the method according to the invention give a very strongly exothermic reaction, so that the whole process takes place without the need to supply heat from outside. Keeping the process at a high temperature during the stages of adding acids, allows a considerable amount of water to evaporate.

[0027] The method according to the invention is shown in the following embodiments, which, however, do not limit its implementation.

[0028] Example 1

[0029] Excess sludge from a municipal wastewater treatment plant was used for the method according to the invention. Chemical analysis revealed the presence of exceeded amounts of heavy metals, so FUROSEP CW3 / 5 was used to precipitate them. 150 kg of excess sludge with a dry matter content of 50 w / w% and 30 kg of roasted magnesite with the granulation 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. The process was carried out for 25 min. While maintaining the stirring, gradual cooling was started, while adding 7.5 kg of 85% phosphoric acid and 11 kg of solid potassium hydroxide in 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 stabilised at 107° C, after which, while the stirring and cooling were continued, 74.5 kg of 98% sulphuric acid was gradually injected. As a result of the reaction with the sulphuric acid, the temperature rose to 135°C. This temperature was maintained for 25 min. A significant amount of steam was also generated and discharged into a water cooler in the amount of 50 kg. The stirring and cooling was continued until the temperature of 35° C was reached, while constantly controlling the reactor contents to prevent uncontrolled solidification of the mixture. During the cooling process, a sample was taken and tested and the pH value of the aqueous extract was measured, which was 5.6. Once the tests were completed, 11 kg of Urea 46% N was added and the whole mixture was stirred until the product was fully homogenised.

[0030] 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%; P2O5 - 1.3 w / w% ; K2O - 2.6 w / w%; MgO- 26.0 w / w%; SO3 - 14.3 w / w%.

[0031] Example 2

[0032] Compost was used for the method according to the invention. The performed analysis did not reveal the presence of heavy metals. 55 kg of compost with a dry matter content of 75 w / w% and 35 kg of roasted magnesite with the granulation of less than 1 mm and a magnesium oxide content of 75% were introduced into the bioreactor at ambient temperature and the stirring process started. The process was carried out for 20 min. While still stirring the mixture, cooling was started while adding 11.7 kg of 85% phosphoric acid and 15 kg of solid potassium hydroxide in small portions. The temperature and process were constantly monitored. As a result of the exothermic reaction, the temperature increased and stabilised at 110° C, after which 63.8 kg of 95% sulphuric acid was gradually dosed into the mixture. The temperature increased to 130° C and was maintained for 25 min. 6 kg of steam was produced and discharged into the water cooler. The stirring and cooling processes were carried out until the temperature decreased to 38° C, while constantly controlling the reactor contents to prevent uncontrolled solidification of the mixture. During the cooling, a sample was taken and the pH value of the aqueous extract was measured, which was 3.7, and so 0.07 kg of roasted magnesite with a magnesium oxide content of 75% was added to the reactor and the stirring continued for a further 10 min. After remeasuring, the pH of the aqueous extract was 6.2, so 10.0 kg of 46%N urea was added to the obtained powdered product and the whole mixture was stirred until the product was fully homogenised.

[0033] The resulting product was tested for nutrient content. 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%.

[0034] Example 3

[0035] Digestate was used for the method according to the invention. The performed analysis did not reveal heavy metals.

[0036] 120.0 kg of digestate with a dry matter content of 45 w / w% and 30.0 kg of roasted magnesite with the granulation of less than 1 mm and a magnesium oxide content of 88% were introduced into the bioreactor at ambient temperature and the stirring process started. The process was carried out for 30 min. While still stirring the mixture, cooling was started and 10.0 kg of solid potassium hydroxide was added as well as 7.3 kg of 80% phosphoric acid in 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 stabilised at 105° C, after which 67.6 kg of 95% sulphuric acid was gradually dosed. The temperature increased to 138° C and was maintained for 30 min. The reaction with the sulphuric acid resulted in a significant amount of steam produced, which was discharged into the water cooler in the amount of 15.0 kg. The stirring and cooling process was carried out until the temperature of 38° C was reached, while constantly controlling the reactor contents to prevent uncontrolled solidification of the mixture. During the cooling process, a sample was taken and tested and the pH value of the aqueous extract was measured, which was 5.8. Subsequently, 8.0 kg of Urea 46% N was added to the resulting powdered product and the whole mixture was stirred until the product was fully homogenised.

[0037] 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%. Example 4

[0038] Brewery waste was used for the method according to the invention. The analysis performed did not reveal heavy metals.

[0039] 100.0 kg of brewery waste with a dry matter content of 55 w / w% and 32.0 kg of roasted magnesite with the granulation of less than 1 mm and a magnesium oxide content of 88% were introduced into the bioreactor at ambient temperature and the stirring process started. The process was carried out for 30 min. While still stirring the mixture, cooling was started and solid potassium hydroxide was added in the amount of 5.0 kg as well as 3.6 kg of 80% phosphoric acid in 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 stabilised at 103° C, after which 72.1 kg of 95% sulphuric acid was gradually dosed. The temperature increased to 137° C and was maintained for 30 min. The reaction with the sulphuric acid resulted in 6.0 kg of steam discharged into the water cooler. The stirring and cooling processes were carried out until the temperature reached 40° C, while constantly controlling the reactor contents to prevent uncontrolled solidification of the mixture. During the cooling process, a sample was taken and tested and the pH value of the aqueous extract was measured, which was 5.7. Subsequently, 10.0 kg of Urea 46% N was added to the resulting powdered product and the whole mixture was stirred until the product was fully homogenised.

[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] Winery-industry waste was used for the method according to the invention. The analysis performed did not reveal heavy metals.

[0043] 115.0 kg of brewery-industry waste with a dry matter content of 66 w / w% and 34.0 kg of roasted magnesite with the granulation of less than 1 mm and a magnesium oxide content of 87% were introduced into the bioreactor at ambient temperature and the stirring process started. The process was carried out for 30 min. While still stirring, cooling was started and solid potassium hydroxide was added in the amount of 6.0 kg as well as 4.4 kg of 80% phosphoric acid in 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 stabilised at 95° C, after which 78.8 kg of 92% sulphuric acid was gradually dosed. The temperature rose to 140°C and was maintained for 22 min. The reaction with the sulphuric acid resulted in 15.8 kg of steam discharged into a water cooler. The stirring and cooling process was carried out until the temperature of 35°C was reached, while constantly controlling the reactor contents to prevent uncontrolled solidification of the mixture. During the cooling process, a sample was taken and tested and the pH value of the aqueous extract was measured, which was 6.9. Subsequently, 15.0 kg of Urea 46% N was added to the resulting powdered product and the whole mixture was stirred until the product was fully homogenised.

[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] Bottom sediments were used for the method according to the invention. The analysis revealed the presence of exceeded amounts of heavy metals, so FUROSEP CW3 / 5 was used to precipitate them.

[0047] 130.0 kg of bottom sediments with a dry matter content of 71 w / w% and 29.0 kg of roasted magnesite with the granulation of less than 1 mm and a magnesium oxide content of 87% were introduced into the bioreactor at ambient temperature and the stirring process started. The process was carried out for 30 min. While still stirring, cooling was started and solid potassium hydroxide was added in the amount of 15.0 kg as well as 10.9 kg of 80% phosphoric acid in 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 stabilised at 109° C, after which 66.7 kg of 92% sulphuric acid was gradually dosed. The temperature rose to 127° C and was maintained for 30 min. The reaction with the sulphuric acid resulted in 20.3 kg of steam discharged into a water cooler. The mixing and cooling processes were carried out until the temperature of 38° C was reached, while constantly controlling the reactor contents to prevent uncontrolled solidification of the mixture. During the cooling process, a sample was taken and analysed and the pH value of the aqueous extract was measured, which was 7.2. Subsequently, 12.0 kg of Urea 46% N was added to the resulting powdered product and the whole mixture was stirred until the product was fully homogenised.

[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%.

Claims

Patent claims1. A method for manufacturing an organic-mineral fertiliser, using magnesium compounds and strong acids characteristic in that at ambient temperature from 25 to 80 w / w% of organic sludge containing from 40 to 90% of dry matter is introduced into a bioreactor and subsequently, while stirring, from 5 to 40 w / w% of roasted magnesite is added and the mixture is stirred for 15 to 30 min., then, while cooling it, 5 to 30 w / w% of phosphoric acid with the concentration of 50% to 90% is gradually added to the bioreactor as well as solid potassium hydroxide in the amount of 2 to 25 w / w% and the cooling and stirring process is carried out until the process temperature stabilises; next, sulphuric acid with the concentration of 70% to 100 % is added in the amount of 20 to 50 w / w% and the process is carried out at a temperature not exceeding 145° C for 10 to 40 minutes; then the resulting mixture is cooled down to a temperature below 40°C and the pH value of the aqueous extract of the substance taken from the bioreactor is measured; if the pH value of the aqueous reaction is between 4 and 8.0, 5% to 30% of urea is added and the whole mixture is stirred until the bulk ingredients are fully homogenised, if, on the other hand, the pH value is lower than 4, a second dose of roasted magnesite in the amount of 1 / 50 of the first dose is injected into the bioreactor and the contents of the reactor are homogenised, this procedure being repeated until the pH value is within the range of 4 to 8.0, after which 5% to 30% of urea is added and the whole mixture is stirred until the bulk ingredients are fully homogenised.

2. A method according to claim 1, characteristic in that the roasted magnesite has the grain size of less than 0.1 mm and a magnesium oxide content of 50 to 100 w / w%.

3. A method according to claim 2, characteristic in that the magnesium oxide content is 87 w / w%.

4. A method according to any of the claims from 1 to 3, characteristic in that the phosphoric acid has the concentration of 75%.

5. A method according to any of the claims from 1 to 4, characteristic in that the sulphuric acid has the concentration of 95%.

6. A method according to any of the claims 1 to 5, characteristic in that the urea is in the form of a powder with grain diameter of less than 0.1 mm and amide nitrogen content of 44% to 46%.

7. A method according to any of the claims 1 to 6, characteristic in that the pH value of the aqueous solution of the obtained product is 7+ / -0.5.

8. A method according to any of the claims 1 to 7, characteristic in that the fertiliser manufacturing process is carried out in a bioreactor equipped with a cooling system, a stirrer designed for solid products, batch height measurement, dynamic scales, a cooling system for steam condensation, and full metering.

9. A method according to any of the claims 1 to 7, characteristic in that the obtained product is subjected to the granulation process.

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