Urea particles containing bio-based polymer, and process for their preparation

Abstract

The invention relates to urea particles which contain at least 20% by weight of urea in relation to the total mass of the particles and which contain a bio-based polymer that is distributed in the urea particles, preferably homogeneously, wherein the urea particles have a weight-average particle size in the range of 0.1 to 10 mm, preferably determined by test sieving according to DIN EN 1235:2003-08. The invention further relates to a process for preparing such particles. The bio-based polymer is preferably a polysaccharide or a polysaccharide derivative. The polysaccharide is preferably selected from cellulose, starch, pectin, alginate, chitin and chitosan.

Description

Urea particles containing bio-based polymer and methods for their production

[0001] The priorities of German patent application no. 10 2024 210 784.0 of November 8, 2024; Luxembourg patent application no. LU103450 of November 8, 2024; German patent application no. 10 2024 210 783.2 of November 8, 2024; Luxembourg patent application no. LU 103449 of November 8, 2024; German patent application no. 10 2025 105 782.6 of February 17, 2025; Belgian patent application no. BE 2025 / 5092 of February 17, 2025; and German patent application no. 10 2025 105 784.2 of February 17, 2025 are listed. claimed in Belgian patent application no. BE 2025 / 5093 of 17 February 2025; Belgian patent application no. BE 2025 / 5108 of 24 February 2025; German patent application no. 10 2025 106 835.6 of 24 February 2025; and German patent application no. 10 2025 137 495.3 of 17 September 2025.

[0002] The invention relates to hygroscopic particles containing at least 20 wt% urea, based on the total mass of the particles, and containing a bio-based polymer dispersed, preferably homogeneously, within the hygroscopic particles, wherein the hygroscopic particles have a weight-average particle size in the range of 0.1 to 10 mm, preferably determined by sieve analysis according to DIN EN 1235:2003-08. The invention also relates to a method for producing such particles. The bio-based polymer is preferably a polysaccharide or a derivative of a polysaccharide. The polysaccharide is preferably selected from cellulose, starch, pectin, alginate, chitin, and chitosan.

[0003] Commercial hygrotherm particles and the processes for their manufacture must typically meet minimum quality standards. The minimum quality standards for the hygrotherm particles themselves relate in particular to their mechanical strength and storage stability. The particles must exhibit sufficient fracture toughness (composite hardness) and should not generate dust through abrasion during storage and transport. Furthermore, the particles should not clump together during storage and transport; that is, their free-flowing properties should be maintained. The minimum quality standards for the manufacturing processes relate in particular to the prevention of dust formation, good particle growth during granulation (granulation or pricking), and the prevention of agglomeration.

[0004] In conventional processes for producing ham particles by granulation or pricking, formaldehyde-containing additives, such as ham-formaldehyde solutions, are typically added to a ham melt or ham solution. This serves to improve particulate matter and also the quality of the ham particles themselves, i.e., compliance with the aforementioned minimum quality standards.

[0005] However, the use of formaldehyde-containing additives in the production of ham particles is problematic for several reasons.

[0006] On the one hand, formaldehyde is considered a harmful substance and is known to be carcinogenic. Its volatile nature causes additional safety concerns. Certain grades of urea must not contain formaldehyde, e.g., technical-grade urea, urea for diesel exhaust fluid (DEF), and urea for animal feed.

[0007] On the other hand, formaldehyde-containing additives also cause difficulties in the production of urea particles intended for use as fertilizer. To counteract the undesirable degradation of urea by ureases in the field, urease inhibitors are usually added to the urea particles, in particular thiophosphoric triamides such as n-butylthiophosphoric triamide (NBPT) and n-propylthiophosphoric triamide (NPPT). Currently, urea particles are primarily coated with a urease inhibitor formulation, individually and in small quantities, by wholesalers as a separate treatment process in mixing stations / plants.

[0008] Due to new regulations requiring higher nitrogen uptake efficiency (NUE) and reduced ammonia and greenhouse gas emissions, the demand for ham particles stabilized with urease inhibitors against enzymatic degradation is increasing and is expected to rise significantly in the future. Regarding storage stability, a minimum concentration of the urease inhibitor in the ham particles must be ensured at the time of application to guarantee sufficient nitrogen uptake efficiency. In most regions, the potential to reduce nitrogen losses must be demonstrated / verified.

[0009] Urease inhibitors such as thiophosphoric triamides, like NBPT and NPPT, exhibit only comparatively low storage stability after application to conventional ammonium particles. It has been found that these thiophosphoric triamides react with formaldehyde and ammonium formaldehyde during storage. These reactions reduce the residual thiophosphoric triamide content below the required minimum concentration. Therefore, ammonium particles produced with formaldehyde-containing additives are unsuitable, or at least significantly disadvantageous, for the production of storage-stable fertilizers.

[0010] For applications of urea in aqueous urea solutions for exhaust aftertreatment in diesel engines using selective catalytic reduction (SCR) (Diesel Exhaust Fluid (DEF)), formaldehyde-containing additives are also disadvantageous or not permitted. The urea used for the production of these aqueous urea solutions is subject to special requirements according to EN ISO 22241. Purity requirements are specified. According to ISO 22241-1:2019, the urea must be technically pure (CAS 57-13-6) and may contain only traces of biuret and ammonia. The urea must be free of aldehydes and free of impurities such as sulfur and its compounds, chloride, nitrate, or other compounds.

[0011] For the reasons mentioned above, there is a need to replace formaldehyde-containing additives with other additives. These other additives should improve the particulate formation (e.g., granulation or prilling) of urea as well as the quality of the urea particles themselves, while also being safe, environmentally friendly, and inert to agronomic substances such as urease inhibitors.

[0012] Certain bio-based polymers can meet these criteria. However, due to their often low solubility in water, their tendency to gel, and their propensity to foam, their large-scale application remains a challenge.

[0013] US 2008 0041131 A1 relates to a process for improving the fracture toughness and reducing dust formation and clumping tendency of urea particles by adding an organic compound to molten urea, wherein at least one carbohydrate and optionally a polyvinyl compound are added to the urea. The carbohydrate can be an oligosaccharide or polysaccharide, for example, starch, guar gum, or xanthan gum. The carbohydrates can be added to a urea melt as solids, or they can be dissolved in a solvent, in an aqueous solution of polyvinyl alcohol, or in a urea solution before being added to the urea melt.

[0014] US Patent 2022 0089529 A relates to a urea production process using a first and a downstream second evaporator in an evaporation section, a finishing section, and a scrubber for treating the exhaust gas from the finishing section. Condensate from the condenser of the second evaporator is fed to the scrubber.

[0015] US 2024 0051888 Al and US 2024 0300864 Al relate to processes for the production of a homogeneous, solid, particulate, urea-based composition comprising urea and an additive in a urea production plant. The additive is preferably a urease inhibitor based on a thiophosphoric triamide or a nitrification inhibitor.

[0016] WO 2023 242383 Al relates to a process for producing a solid, particulate fertilizer composition comprising a nitrogen source selected from the group consisting of urea and ammonium salts, and an additive selected from the group consisting of biostimulants and micronutrients, in a production plant comprising at least one synthesis unit, one evaporation unit, one particle unit, one exhaust gas treatment unit comprising a scrubber, and optionally a scrubber evaporator.

[0017] It is also known to use certain bio-based polymers in coatings of urea particles to delay the release of urea from these particles. For example, MM Femändez-Perez et al., Journal of Applied Polymer Science, Vol. 108, 3796-3803 (2008), discusses the use of lignin and ethylcellulose as polymers in controlled-release urea formulations. B. Beig et al., Journal of Plant Nutrition, https: / / doi.org / 10.1080 / 01904167.2020.1744647, is a review of coating materials for the slow release of nitrogen from urea-containing fertilizers. D. Lawrencia et al., Plants 2021, 10, 238. https: / / doi.org / 10.3390 / plantsl0020238, is a review of coating materials and release mechanisms of controlled-release fertilizers.

[0018] EP 3 594 194 Al relates to a process for granulating a urea-containing liquid, comprising: adding a first additive containing carboxymethyl starch to one or more first stages of the granulation process to form a carboxymethyl starch-containing inner layer of urea granules, and adding a second additive containing calcium lignosulfonate to one or more second stages of the granulation process, downstream of the first stages, to form granules with a calcium lignosulfonate-containing coating.

[0019] CN 109 369 265 A relates to a coated cellulose-based fertilizer and a process for its production, in particular a coated cellulose-based fertilizer with water retention and long-term release properties and a process for its production.

[0020] WO 2018 193344 Al concerns fertilizer particles containing urease inhibitors and nitrification inhibitors. The fertilizer particles may contain a Kemp article comprising a urease inhibitor and an outer layer comprising a nitrification inhibitor.

[0021] EP 1 761 484 B 1 relates to a process for improving the compressive strength and reducing dust formation and the tendency to clump of urea particles by adding an organic compound to molten urea, wherein at least one carbohydrate and optionally a polyvinyl compound is added to the urea.

[0022] WO 2014 032131 Al relates to a sugar-containing additive comprising (a) glycerol, (b) a sugar-containing solution and (c) optionally raffinate from citric acid production, suitable for controlling dust emissions of particulate materials during manufacture, handling, storage or transport.

[0023] It is an object of the invention to overcome the disadvantages of the prior art and to provide improved processes for the production of improved ham particles. The use of formaldehyde-containing additives such as ham formaldehyde (UFC; UF80; UF85; UF) should be avoided. Minimum qualitative standards for the ham particles themselves, as well as for the processes for their production, should be met. The ham particles should be suitable for various applications, preferably - for use as a fertilizer, optionally with inhibitors and / or additives, preferably (i) urease and / or nitrification inhibitors and / or (ii) additives selected from ammonium sulfate, sulfur, micronutrients, trace elements, etc. and mixtures thereof; or - for the production of aqueous ammonium solutions for exhaust aftertreatment in diesel engines by means of selective catalytic reduction (SCR), preferably according to EN ISO 22241, e.g. AdBlue®.

[0024] This problem is solved by the subject matter of the patent claims.

[0025] It was surprisingly found that water-soluble or dispersible bio-based polymers, when added to a urea-containing melt and / or solution instead of formaldehyde-based additives, have positive effects on the formation of ham particles (e.g., low dust formation, good particle growth) and particle quality (e.g., good hardness, low tendency to clump).

[0026] Even with small amounts of bio-based polymers, ham particles with a narrow size distribution can be produced that exhibit sufficient mechanical strength comparable to conventional ham particles, without the need for formaldehyde-based additives. Unlike ham particles containing formaldehyde additives, the bio-based polymers improve the environmental compatibility of the ham particles and also reduce their hazard potential during production, storage, and use.

[0027] It has proven particularly advantageous if the bio-based polymers are first dispersed or dissolved in an aqueous composition before being added to a solution and / or melt of urea and subsequently particulated.

[0028] Furthermore, it was surprisingly found that the problems associated with the handling, storage and transport of aqueous solutions of the bio-based polymers can be circumvented by first using the bio-based polymers in solid form, whereby the dissolving / dispersing of these bio-based polymers in solid form is then integrated into the process of urea particulate matter removal.

[0029] An aqueous urea-containing solution, which is generated during the conventional operation of a urea particulate matter collection system, e.g., as a washing solution during dust washing, is preferably used as the solution dispersion medium. The aqueous urea-containing solution can also be taken from a urea synthesis system upstream of the particulate matter collection system.

[0030] Ham matter particles:

[0031] A first aspect of the invention relates to methane particles comprehensively - at least 20% by weight urea, based on the total mass of the particles; and - a bio-based polymer, preferably homogeneously distributed within the ham particles; wherein the urea particles have a weight-average particle size in the range of 0.1 to 10 mm, preferably determined by sieve analysis according to DIN EN 1235:2003-08.

[0032] For descriptive purposes, "particle" means a physical form that may be granulated, prilled, crystalline, compacted, pulverized, or the like. The particles can exist as numerous individual particles, for example, in small, uniform forms of small size (e.g., as granules, prills, crystallites, pellets, powder, or flakes). Preferably, the particles are in the form of granules, i.e., as a granular substance (granular matter, grains).

[0033] For the purposes of description, "bio-based polymer" means a polymer as defined in the IUPAC Recommendation: "composed or derived wholly or partly from biological products from biomass (including plant, animal, marine, or forestry materials)" (M. Vert et al., Terminology for biorelated polymers and applications (IUPAC Recommendations 2012), Pure and Applied Chemistry, https: / / doi.org / 10.1351 / PAC-REC-10-12-04, page 381). A bio-based polymer preferably occurs as such in nature, preferably in polymeric form, and is usually obtained from a natural source, or it is derived as a derivative of such a polymer and is usually obtained starting from such a polymer, typically by polymer-analogous reactions. According to the invention, bio-based polymers preferably include native polymers, biogenic polymers, biopolymers, and their respective derivatives.

[0034] The ham particles according to the invention comprise a bio-based polymer which is distributed within the ham particles. The distribution is preferably homogeneous. However, according to the invention, it is also possible for the distribution to be inhomogeneous; for example, an inner nucleus of the ham particles can have a comparatively low or no content of bio-based polymer, and an outer shell of the ham particles surrounding the inner nucleus (nucleus shell) can have a comparatively high content of bio-based polymer.

[0035] Preferably, the urea, the bio-based polymer, and optionally the urease inhibitor and / or nitrification inhibitor are granulated or prilled and contained within the urea particles. More preferably, the urea, the bio-based polymer, and optionally the urease inhibitor and / or nitrification inhibitor are mixed and homogeneously distributed within the urea particles. The urea particles are thus preferably not in the form of core-shell particles, with the particle core comprising the inhibitor and the particle shell the urea. In other preferred embodiments, the urea and the bio-based polymer are granulated or prilled together and subsequently brought into contact with a composition comprising the urease inhibitor and / or nitrification inhibitor.

[0036] In preferred embodiments, the ham particles do not exist in the form of core-shell particles, i.e., not in the form of coated cores. Instead, the ham particles preferably consist of a homogeneous mixture of all ingredients and components (monoliths).

[0037] In other preferred embodiments, the ham particles are in the form of core-shell particles, i.e., coated cores. In this case, preferably at least a subset, and more preferably the entire amount, of the bio-based polymer is contained in the cores. If the coating contains any bio-based polymer at all, then preferably only a subset thereof.

[0038] For the purposes of description, core-shell particles according to the invention have an inner core and a coating (shell) surrounding this inner core, the coating preferably completely surrounding the inner core. The chemical composition of the core differs from the chemical composition of the coating in at least one property, preferably in its chemical nature and / or in the weight fraction of at least one ingredient. Preferably, the core and the coating are each formed from chemical compositions that independently contain all of their respective ingredients in a homogeneous distribution. If the core and the coating have the same chemical composition, they are therefore not core-shell particles within the meaning of the invention.

[0039] In particularly preferred embodiments, the ham particles are not in the form of core-shell particles.

[0040] In other particularly preferred embodiments, the ham particles are in the form of core-shell particles, wherein the chemical composition of the core and the coating (shell) differs only in the weight fraction of the nitrification inhibitor and / or the urease inhibitor and / or their formulation.

[0041] Preferably, the content of bio-based polymer is at most 5.0 wt.%, more preferably at most 4.0 wt.%, more preferably at most 3.0 wt.%, even more preferably at most 2.0 wt.%, most preferably at most 1.0 wt.%, and in particular at most 0.5 wt.%, in each case based on the total mass of the ham particles.

[0042] Preferably, the content of bio-based polymer is at most 0.25 wt.%, more preferably at most 0.10 wt.%, more preferably at most 0.075 wt.%, even more preferably at most 0.050 wt.%, most preferably at most 0.040 wt.%, and in particular at most 0.030 wt.%, in each case based on the total mass of the ham particles.

[0043] Preferably, the content of bio-based polymer is at least 10 ppmw, more preferably at least 20 ppmw, more preferably at least 50 ppmw, more preferably at least 100 ppmw, most preferably at least 175 ppmw, and in particular at least 250 ppmw, in each case based on the total mass of the ham particles.

[0044] Preferably, the bio-based polymer has a weight-average molecular weight of at most 250,000 g / mol, preferably at most 200,000 g / mol, more preferably at most 150,000 g / mol. more preferably not more than 100,000 g / mol, most preferably not more than 75,000 g / mol, and particularly not more than 50,000 g / mol, each determined by gel permeation chromatography.

[0045] Preferably, the bio-based polymer is water-soluble. Preferably, the solubility of the pure bio-based polymer in pure water at 23°C is at least 10 g / l, more preferably at least 20 g / l, more preferably at least 40 g / l, even more preferably at least 60 g / l, most preferably at least 80 g / l, and particularly at least 100 g / l. It is primarily a true solution (this may gel later, but is initially a solution – possibly viscous).

[0046] Preferably, the bio-based polymer is a polysaccharide or a polysaccharide derivative. If the bio-based polymer is a polysaccharide derivative, it is preferably selected from ethemes and esters, preferably ethemes. In principle, (further) linkages are also possible for derivation, for example via glycosidic bonds.

[0047] Preferably, the polysaccharide is selected from the group consisting of cellulose, hemicellulose, starch, pectin, xanthan gum, guar gum, gellan gum, gum arabic, locust bean gum, alginate, chitin, and chitosan; cellulose is particularly preferred. This also applies if the bio-based polymer is a derivative of such a polysaccharide. Other possible polysaccharides are heparin, chondroitin, keratan, or hyaluronic acid.

[0048] In preferred embodiments, the bio-based polymer is a cellulose ether; preferably selected from the group consisting of methylcellulose (MC), ethylcellulose (EC), methylethylcellulose (MEC), hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), hydroxyethylmethylcellulose (HEMC), hydroxypropylmethylcellulose (HPMC), carboxymethylcellulose (CMC).

[0049] In other preferred embodiments, the bio-based polymer is a cellulose ester; preferably cellulose acetate.

[0050] Even with comparatively small amounts of bio-based polymers, such as cellulose ethers or cellulose esters, the quality standards of the resulting hygroscopic particles can be met, such as good hygroscopicity, low dust tendency and prevention of clumping.

[0051] The bio-based polymers are generally non-acidic and not very reactive, making them ideal candidates for use in combination with urease inhibitors and / or nitrification inhibitors.

[0052] Bio-based polymers such as cellulose ethers are available in many purity grades, which means that limit values, such as technical grade urea, for aqueous compositions for exhaust aftertreatment in diesel engines can be met.

[0053] In other preferred embodiments, the bio-based polymer is modified starch.

[0054] The inventive hemp particles can contain a single bio-based polymer or a mixture of several different bio-based polymers (including bio-based cop- polymers, e.g., also bio-based block copolymers). If the ham matter particles according to the invention contain several different bio-based polymers, all information refers, unless expressly stated otherwise, to the entirety of all bio-based polymers contained in the ham matter particles.

[0055] In preferred embodiments, an additional coating of the urea particles retards the release of urea from the particles. Suitable materials for such a coating are known to those skilled in the art and include, for example, wax and polymers such as polylactic acid.

[0056] Preferably, the hygroscopic particles according to the invention have a hygroscopic strength of at least 30 N, preferably at least 32.5 N, more preferably at least 35 N, even more preferably at least 37.5 N, most preferably at least 40 N, in each case determined according to the method "7T74 procedures for determining physical properties of fertilizers", Special Report No. 12, page 444, September 1970; or "Manual for determining physical properties of fertilizer", International Fertilizer Development Centre, 1984.

[0057] The urea particles according to the invention comprise at least 20 wt.% urea, based on the total mass of the particles.

[0058] Preferably the urea content is at least 40 wt.%, preferably at least 50 wt.%, more preferably at least 60 wt.%, even more preferably at least 70 wt.%, most preferably at least 80 wt.%, and in particular at least 90 wt.%, in each case based on the total mass of the urea particles.

[0059] The ham matter particles according to the invention have a weight-average particle size in the range of 0.1 to 10 mm, preferably determined by sieve analysis according to DIN EN 1235:2003-08.

[0060] Preferably, the hygroscopic particles according to the invention have a weight-average particle size in the range of 0.5 to 8.0 mm, more preferably 0.5 to 6.0 mm, and more preferably 0.5 to 4.0 mm. The mean particle size (D50 (mass-averaged)) of the hygroscopic particles according to the invention is preferably in the range of 0.5 mm to 5.0 cm; more preferably 1.0 mm to 1.0 cm, more preferably 1.0 mm to 6.0 mm, even more preferably 2.0 mm to 5.0 mm, and most preferably 2.0 mm to 4.0 mm; preferably determined by sieve analysis according to DIN EN 1235:2003-08.

[0061] The hamstoff particles according to the invention are preferably intended for use - as fertilizer; or - in the production of aqueous ammonium solutions for exhaust aftertreatment in diesel engines using selective catalytic reduction (SCR), preferably according to EN ISO 22241, e.g. AdBlue®.

[0062] Depending on the application, the ham particles according to the invention may optionally contain inhibitors and / or additives, preferably (i) urease inhibitors, nitrification inhibitors or mixtures thereof. gen; and / or (ii) additives selected from ammonium sulfate, sulfur, micronutrients, trace elements and mixtures thereof.

[0063] In particularly preferred embodiments, the ham particles contain no formaldehyde and / or ham-formaldehyde.

[0064] Ham particles with inhibitors for use as fertilizer:

[0065] Preferably, the urea particles according to the invention contain a urease inhibitor and / or a nitrification inhibitor. Urea treated with a urease and / or nitrification inhibitor is also referred to as "stabilized urea." The respective inhibitor counteracts the undesired microbiological degradation and thus stabilizes the urea. It is also possible for the urea particles according to the invention to contain several urease inhibitors and / or several nitrification inhibitors independently of one another. For example, combinations of NBPT and NPPT as urease inhibitors are preferred.

[0066] A urease inhibitor is a substance that reduces or completely prevents the chemical activity of the enzyme urease. A nitrification inhibitor is a substance that delays or completely suppresses the bacterial oxidation of ammonium ions (nitrification).

[0067] Preferred urease inhibitors are selected from the group consisting of N-(n-butyl)thiophosphoric triamide (NBPT), N-(n-propyl)thiophosphoric triamide (NPPT), hydroquinone, phosphorus triamide, p-benzoquinone, cyclohexyl phosphate triamide, and hexaamidocyclotriphosphazene; preferably N-(n-butyl)thiophosphoric triamide and N-(n-propyl)thiophosphoric triamide.

[0068] Preferably, the inventive ham particles comprise a urease inhibitor; preferably a thiophosphoric triamide; preferably N-(n-butyl)thiophosphoric triamide (NBPT) and / or N-(n-propyl)thiophosphoric triamide (NPPT).

[0069] Preferred nitrification inhibitors are selected from the group consisting of dicyandiamide, 1-methylpyrazole-1-hydroxyamide, 3-methylpyrazole, ethyleneham, chlorazole, 4-aminotriazole, thioham, acetylene, 2-ethinylpyridine, sulfathiazole, amidinothioham, 1-amino-2,4-dimethylpyrazole phosphate, thiosulfates, for example sodium thiosulfate, calcium carbide, 2,5-dichloroaniline, 3-acetanilide, toluene, carbon disulfide, phenylacetylene, 2-propyn-1-ol and phenethylphosphoniumdiamide.

[0070] In preferred embodiments, the total content of urease inhibitor and / or a nitrification inhibitor is at most 1.0 wt.%; preferably at most 0.5 wt.%, more preferably at most 0.1 wt.%, and even more preferably at most 0.05 wt.%; in each case based on the sum of all inhibitors contained in the hemp particles and relative to the total mass of the hemp particles.

[0071] In preferred embodiments, the total content of urease inhibitor and / or a nitrification inhibitor is in the range of 0.005 to 0.5 wt.%; preferably 0.01 to 0.1 wt.%, more preferably 0.02 to 0.08 wt.%, and even more preferably 0.04 to 0.06 wt.%; in each case based on the Sum of all inhibitors contained in the ham particles and relative to the total mass of the ham particles.

[0072] In preferred embodiments, urease inhibitor and / or nitrification inhibitor are distributed in the hygroscopic particles, preferably homogeneously.

[0073] In preferred embodiments, the ham particles comprise a nucleus and optionally a coating, wherein the bio-based polymer is distributed in the nucleus, preferably homogeneously.

[0074] When homogeneously distributed, the ham particles form a phase in which the bio-based polymer is uniformly distributed. The amount and concentration of the bio-based polymer are essentially the same in every part of the phase, so there are no significant differences or deviations.

[0075] Preferably includes (i) the nucleus of the ham particles a urease inhibitor and the coating of the ham particles a nitrification inhibitor; or (ii) the nucleus of the ham particles is a nitrification inhibitor and the coating of the ham particles is a urease inhibitor.

[0076] The quality requirements for stabilized urea (with urease and / or nitrification inhibitors) are preferably analogous to the respective quality requirements for fertilizer-grade urea (see below), particularly with regard to cohesion (cohesion hardness), prevention of clumping, and discoloration. A key additional quality requirement for stabilized urea is its compatibility with the urease and / or nitrification inhibitors, especially concerning pH and reactivity. Preferably, the stabilized urea contains no or only very small amounts of functional groups such as aldehydes, acetals, or free carboxylic acids. Furthermore, the pH is preferably non-acidic, with the final pH of the urea particles (e.g., the granules) being the determining factor.

[0077] Ham matter particles with additives for use as fertilizer:

[0078] In preferred embodiments, the inventive hammock particles comprise one or more additives; preferably, the additives contain one or more of the following components: - Sulfur; - Ammonium sulfate; - at least one micronutrient; - at least one trace element.

[0079] The additive can comprise either (elemental) sulfur or ammonium sulfate, or at least one trace element. Likewise, the additive can comprise any possible combination of the aforementioned components or may also contain other constituents. The sulfur Trace elements can be present in their elemental form or as components of compounds. For example, the additive sulfur can be in the form of sulfates. Trace elements are those elements that are essential for living organisms and typically occur in mass fractions of less than 50 mg / kg. Examples of trace elements include aluminum, boron, chlorine, iron, copper, manganese, molybdenum, and / or zinc. An expert recognizes that the term "trace element" encompasses both a single element and any possible mixture of two or more elements.

[0080] In preferred embodiments, the inventive ham particles comprise ammonium sulfate.

[0081] Preferably, the ammonium sulfate content is at most 1.0 wt.%; preferably at most 0.75 wt.%, more preferably at most 0.5 wt.%, and even more preferably at most 0.3 wt.%; in each case relative to the total mass of the ammonium particles.

[0082] The quality requirements for fertilizer-grade urea are relatively uncritical with regard to purity. The purity only needs to meet fertilizer specifications. Discoloration, while undesirable, is less critical. The requirements for fracture toughness (particle hardness) and the prevention of clumping are comparatively high. The fracture toughness is preferably at least 35 N, more preferably at least 37.5 N, and even more preferably at least 40 N. The prevention of clumping is preferably at least as good as, and preferably better than, that of conventional urea particles with formaldehyde-containing additives.

[0083] Ham matter particles for exhaust aftertreatment in diesel engines

[0084] The quality requirements for urea in aqueous compositions for exhaust aftertreatment in diesel engines are comparatively stringent with regard to purity and color. The urea used must be of high purity (technical grade urea). Ideally, the limit values ​​according to EN ISO 22241 are met. Discoloration must be avoided, so the bio-based polymer used should not cause any discoloration of the granules. The requirements for diaphragm strength and prevention of clumping are somewhat lower, as the urea particles are preferably packaged soon after production to prevent contamination during storage and transport. A diaphragm strength of at least 30 N is often sufficient.

[0085] Introducing solid or liquid starting materials:

[0086] Preferably, solid starting materials, i.e., any solids to be introduced, such as solid additives, solid excipients, solid active ingredients, solid bio-based polymers, etc., are introduced, preferably independently of one another, either separately or as a mixture, using solid-liquid mixing. The solid starting material is then preferably contained within the ham particles, preferably homogeneously distributed.

[0087] The solid starting material is preferably first introduced into a fluid. Preferably, the fluid is aqueous. Preferably, the fluid contains urea. Preferred fluids include water, aqueous urea solutions, urea melts, the urea-containing aqueous solution, the aqueous polymer preparation, the melt and / or solution comprising freshly synthesized urea, and the mixture. Compared to using an aqueous solution of the solid starting material, directly introducing the solid starting material into the fluid reduces the amount of additional water that needs to be evaporated. Preferably, the fluid is generated in a plant for the production of the urea particles, for example, as process condensate, during the evaporation of the synthesis of fresh urea, during separate evaporation, in a tank, as a scrubbing solution in an exhaust gas scrubber, or in a pipeline.Optionally, the fluid is conveyed to the solid-liquid mixer by a feed pump, the feed pump being preferably arranged upstream of the solid-liquid mixer in the direction of fluid flow.

[0088] The solid feedstock to be introduced into the fluid is preferably stored in a reservoir (e.g., silo, big bag, hopper). Preferably, a defined quantity of the solid feedstock is fed to the solid-liquid mixer using a solid feed device. The feed can be carried out, for example, gravimetrically or volumetrically. Examples of suitable solid feed devices are metering screws or rotary valves. Preferably, the solid feedstock has a particle size of < 1 mm.

[0089] In a solid-liquid mixer, the solid feedstock is mixed with the fluid. An example of a suitable solid-liquid mixer is the MHD2000 from IKA Werke GmbH. The resulting mixture can be a solution and / or a suspension. It can also be an emulsion, for example, if the melting point of the solid feedstock is below the temperature of the fluid or if a complex mixing ratio is present. The solid feedstock and the fluid are mixed in a defined ratio, which can be controlled and regulated using the optional feed pump and / or the solid dosing device. The ratio can be set manually or automatically controlled.

[0090] Optionally, the resulting mixture is then passed through a degassing unit, which may remove any gas that was previously introduced by the solid starting material or the solid-liquid mixer.

[0091] Optionally, the pressure of the generated mixture is subsequently increased using a pressure boosting device, preferably a pump. Such a pressure increase may be necessary if the back pressure downstream is higher than the outlet pressure of the solid-liquid mixer or the optional degassing unit. Since the generated mixture may be viscous, the pump is preferably suitable for pumping liquids of varying viscosities (e.g., a progressive cavity pump or a screw pump). The pump is also preferably suitable for pumping suspensions. The pump's delivery rate is preferably in a defined ratio to the Outlet of the solid-liquid mixer. This ratio can be set manually or automatically controlled by wiring.

[0092] The degassing unit and pressure boosting device can be separate or combined. Depending on the type of pressure boosting device, degassing and pressure boosting can be combined.

[0093] In preferred embodiments, the generated mixture is subsequently introduced into a solution and / or melt of urea, preferably at a feed point. The solution and / or melt of urea is preferably the main stream supplied to the particle aggregation unit. Preferably, the flow rate of the solution and / or melt of urea is greater than the flow rate of the generated mixture. The generated mixture is introduced into the solution and / or melt of urea in a defined ratio. This ratio can be set manually or automated by means of a circuit. Preferably, the distance between the solid-liquid mixer and the feed point is as short as possible. Preferably, the residence time of the mixture between the solid-liquid mixer and the feed point is as short as possible. The feed point is preferably located upstream of the particle aggregation unit (e.g., fluidized bed granulation, pricking, drum granulation).Optionally, intensified mixing of the generated mixture and the urea solution and / or melt can take place downstream of the feed point and upstream of the particulate unit. A pump can be used for this mixing, particularly if the feed point is located upstream of a pump for the particulate unit. Alternatively, a static mixer, such as a filter, can be located downstream of the feed point and upstream of the particulate unit.

[0094] In other preferred embodiments, the generated mixture is subsequently introduced into a liquid composition obtained through evaporation or in a recycling system (e.g., exhaust gas scrubber). This liquid composition is preferably aqueous. The liquid composition preferably contains urea.

[0095] Preferably, liquid starting materials, i.e., any liquids to be introduced, such as liquid additives, liquid excipients, liquid active ingredients, etc., are introduced, preferably independently of one another, either separately or as a mixture, preferably with the aid of liquid-liquid mixtures. The liquid starting material is then preferably contained within the ham particles, preferably homogeneously distributed.

[0096] For liquid starting material, an additional dosing device can optionally be provided.

[0097] In preferred embodiments, the liquid feed material is fed upstream or downstream of the optional feed pump, downstream of the solid-liquid mixer, into or downstream of the degassing unit, upstream or downstream of the pressure boosting device, introduced upstream or downstream of the injection point, or directly upstream of the particular unit.

[0098] Use:

[0099] Another aspect of the invention relates to the use of the ham matter particles described above as fertilizer.

[0100] Another aspect of the invention relates to the use of the above-described ham material particles for the production of aqueous compositions for exhaust aftertreatment in diesel engines, preferably according to EN ISO 22241.

[0101] Production:

[0102] Another aspect of the invention relates to a method for producing the above-described ham matter particles according to the invention, wherein the method comprises the steps: (a) Providing an aqueous polymer preparation comprising a bio-based polymer; (b) optionally evaporating at least some of the water from the polymer preparation; (c) Providing a melt and / or solution comprising freshly synthesized urea; (d) Mixing the polymer preparation with the melt and / or solution to produce a mixture; (e) Producing ham particles from the mixture.

[0103] Preferably the method according to the invention comprises one or more of the following additional steps (f) optional pre-cooling of the ham matter particles; (g) Classifying the ham particles; and (h) optional post-cooling of the ham particles.

[0104] In step (a) of the process according to the invention, an aqueous polymer preparation is provided which comprises a bio-based polymer.

[0105] The aqueous polymer preparation is preferably in the form of a solution or dispersion, more preferably as a solution or suspension. The bio-based polymer may be swollen and contain water deposits and / or water inclusions. In addition to water, the aqueous polymer preparation may also contain other solvents, such as water-miscible organic solvents or monomers. However, water is preferably the only solvent contained in the aqueous polymer preparation.

[0106] Preferably, the bio-based polymer is mixed as a solid into a (partial) stream of an aqueous composition, preferably dissolved or dispersed therein. A dosing and mixing unit for solid bio-based polymer is preferably used for this purpose, more preferably a solid / liquid mixer.

[0107] Preferably, step (a) comprises the following sub-steps (ai) Providing an aqueous composition; (a2) optionally, evaporation of at least some of the water from the aqueous composition; and (a3) Dissolving or dispersing the bio-based polymer, which is preferably in solid form, in the aqueous composition to produce the aqueous polymer preparation.

[0108] The aqueous polymer preparation produced in sub-step (a3) ​​differs from the aqueous composition provided in sub-step (ai) at least in the bio-based polymer, and possibly also in the water content, provided that at least some of the water is evaporated from the aqueous composition in the optional sub-step (a2).

[0109] Preferably, the aqueous composition provided in step (ai) is obtained as a by-product during the production of the ham particles.

[0110] The aqueous composition provided in step (ai) and optionally concentrated in step (a2) by evaporating water, in which the bio-based polymer is dissolved or dispersed in step (a3), preferably already contains urea. The aqueous composition may also optionally contain ammonium sulfate. Preferably, the urea contained in the aqueous composition is not fresh urea, but rather unreacted, excess, and / or sorted-out material.

[0111] In preferred embodiments, the aqueous composition provided in step (ai) is a urea-containing aqueous solution. Preferably, the urea-containing aqueous solution contains unreacted, excess, and / or sorted-out material.

[0112] In other preferred embodiments, the aqueous composition provided in step (ai) is an aqueous urea-containing solution and / or melt, e.g., a hydrated urea melt. Preferably, the urea-containing aqueous solution and / or melt contains unreacted, excess, and / or rejected material.

[0113] For the purposes of this description, "unreacted, excess, and / or rejected material" includes urea that is recovered during the production of the ham particles and recycled (recycled urea). For the purposes of this description, such recovered urea differs from "freshly synthesized urea." Preferably, "unreacted, excess, and / or rejected material" includes any urea-containing material that arises in or after passing through the particle generation unit and is not directly incorporated into ham particles of the desired type and quality within the particle generation unit. For example, The system contains "unreacted, excess, and / or rejected material" such as urea-containing washing solutions from gas scrubbing (gas purification unit) or granulator scrubbing (particle unit), oversized urea particles that are rejected and subsequently dissolved, steam / process condensate, etc. Oversized urea particles (> 10 mm) are collected directly after the particle unit (e.g., the granulator) on a safety screen (also referred to as the "recycling system" according to the invention) and are typically rejected immediately after exiting the particle unit (e.g., the granulator). In addition to urea, the material may contain solvents, particularly water, as well as impurities, particularly NH3.

[0114] Preferably, the aqueous composition provided in sub-step (ai) and possibly concentrated in sub-step (a2) by evaporating water is obtained as a by-product during the production of the ham particles.

[0115] In preferred embodiments, the aqueous composition is at least partially generated as a washing solution during aqueous exhaust gas scrubbing, preferably in a gas purification unit. Preferably, the aqueous composition originates directly from aqueous exhaust gas scrubbing, i.e., it is not subjected to any further processing before the solid bio-based polymer is dispersed or dissolved in it.

[0116] In preferred embodiments, the aqueous composition is at least partially derived as a washing solution from a granulator washing process, preferably in a particulate unit. Preferably, the aqueous composition originates directly from the particulate unit, i.e., it is not subjected to any further processing before the solid bio-based polymer is dispersed or dissolved therein.

[0117] In preferred embodiments, the aqueous composition is at least partially composed of oversized ham particles, which are sorted out and subsequently dissolved.

[0118] In preferred embodiments, the aqueous composition is at least partially formed as steam / process condensate.

[0119] In preferred embodiments, the aqueous composition has been temporarily stored, preferably in a tank. Preferably, the aqueous composition originates directly from the tank, i.e., it is not subjected to any further processing before the solid bio-based polymer is dispersed or dissolved in it.

[0120] In further preferred embodiments, the aqueous composition is a mixture of several byproducts, each generated independently of the others. Preferably, these byproducts were combined and then temporarily stored, preferably in a tank.

[0121] Preferably, at least one of the by-products of the mixture is obtained as a washing solution during aqueous exhaust gas scrubbing, preferably in a gas cleaning unit.

[0122] Preferably, at least one of the by-products of the mixture is obtained as a washing solution from a granulator washing process, preferably in a particulate unit.

[0123] Preferably, at least one of the by-products of the mixture is present as oversized methane particles, which are sorted out and then dissolved.

[0124] Preferably, at least one of the by-products of the mixture is obtained as vapor / process condensate.

[0125] A difference between step (b) and the optional sub-step (a2) of the inventive process lies in the presence or absence of the bio-based polymer. The evaporation of water from the aqueous composition in sub-step (a2) prior to the evaporation of at least some of the water from the polymer preparation in step (b) is preferably carried out if the aqueous composition is itself already a urea-containing aqueous process fluid, but is too diluted, i.e., contains too high a water load.

[0126] Step (b) and sub-step (a2) are optional. In preferred embodiments, the method according to the invention includes sub-step (a2) but not step (b). In other preferred embodiments, the method according to the invention includes step (b) but not sub-step (a2). In further preferred embodiments, the method according to the invention includes both sub-step (a2) and step (b). However, it is also possible that the method according to the invention includes neither sub-step (a2) nor step (b).

[0127] Preferably, in step (a3), the bio-based polymer is initially stored in solid form, e.g., as a powder or in the form of pellets, and is subsequently dissolved or dispersed in the aqueous composition. Dissolving or dispersing the bio-based polymer may involve mixing or swelling, provided that the aqueous polymer preparation generated in step (a3) ​​is ultimately obtained as a solution or dispersion. The aqueous composition provided in step (a3) ​​and optionally concentrated in step (a2) may already be relatively viscous, but is preferably pumpable using conventional equipment. This preferably also applies to the aqueous polymer preparation generated in step (a3).

[0128] Preferably, the aqueous polymer preparation produced in step (a3) ​​is fed directly to step (d) after its production; i.e., preferably no intermediate storage of the aqueous polymer preparation takes place. Preferably, the residence time of the aqueous polymer preparation after completion of step (a3) ​​and before the start of step (d) is at most 10 minutes, more preferably at most 5 minutes, and even more preferably at most 2 minutes. Undesired gel formation and an undesired further increase in viscosity can thus be avoided.

[0129] Preferably, the unreacted, excess and / or sorted material is generated during one or more of steps (e), (f), (g) and (h). Preferably, this unreacted, excess and / or sorted material is generated as dust, as a solution from the gas scrubbing (gas purification unit) and / or as oversized ham particles, which, after sorting, are preferably dissolved in an aqueous solution (see Recycling System 1).

[0130] Preferably, the material occurs as dust and is separated from a gas phase by wet separation, producing the urea-containing aqueous solution.

[0131] Preferably, step (g) comprises separating excessively large and / or excessively small ham particles as reject material and returning the separated reject material as solid to step (e).

[0132] In the optional step (b) of the inventive process, at least some of the water from the polymer preparation provided in step (a) is evaporated.

[0133] In step (c) of the inventive process, a melt and / or solution comprising freshly synthesized urea is provided.

[0134] For the purposes of description, a urea-containing "melt and / or solution" comprises a urea-containing fluid containing urea and preferably water. This may be a melt, an aqueous solution, a hydrated melt, a hydrated melt, or the like.

[0135] For the purposes of description, "freshly synthesized urea" differs from recycled, i.e., recovered, urea. Preferably, "freshly synthesized urea" has been synthesized immediately beforehand in a synthesis and recovery unit (ham synthesis plant), typically from CO2 and NH3, and is preferably still in liquid form due to the manufacturing process. The liquid urea has preferably not remained in the liquid state for too long in order to avoid the formation of biuret. However, according to the invention, it is also possible to allow the freshly synthesized urea to cool down first and only then use it. Prefabricated and, if necessary, temporarily stored urea is also "freshly synthesized urea" within the meaning of the invention, provided it is not recovered urea.

[0136] In step (d) of the inventive process, the polymer preparation is mixed with the melt and / or solution to produce a mixture.

[0137] Preferably, the aqueous polymer preparation generated in step (a3) ​​is mixed with the melt and / or solution. Preferably, the melt and / or solution is a mass stream from a synthesis and recovery unit for the production of freshly synthesized urea. Preferably, the mass stream originates from a main urea feed, which is preferably located directly downstream of the synthesis and recovery unit.

[0138] In step (e) of the inventive process, ham particles are produced from the mixture. For this purpose, a particulate unit (prilling, granulation) is preferably used.

[0139] In the optional step (f) of the inventive process, the ham particles are pre-cooled.

[0140] In the preferred step (g) of the inventive process, the ham particles are classified, preferably by sieving.

[0141] In the optional step (h) of the process according to the invention, the ham particles are post-cooled, i.e., in addition to the pre-cooling in step (f), there is also a post-cooling step in step (h). Preferably, this is cooling before storage, typically as a separate cooling step after sieving / classifying in step (g).

[0142] The inventive method efficiently solves the following technical problems that arise when using bio-based polymers:

[0143] Low solubility of the bio-based polymer: By using the bio-based polymer in solid form, no pre-prepared solutions or dispersions are required. These would otherwise incur high transport costs because they have a low polymer content and a high solvent content, necessitating the transport of larger volumes and masses. This problem is eliminated by the invention's use of a solid bio-based polymer, which is only processed into an aqueous polymer preparation (solution or dispersion) at the point of use.

[0144] High viscosity or gel formation of the bio-based polymer: Aqueous solutions of many bio-based polymers are highly viscous or form gels. This is a physical process that is temperature- and time-dependent. By generating the aqueous polymer preparation on-site and then using it promptly, no intermediate storage is required, and the residence time in pipelines can be minimized. During its preparation and subsequent use, the aqueous polymer preparation is a relatively low-viscosity solution or dispersion that can be handled and processed with conventional equipment. Problems that would arise when handling gels can thus be avoided according to the invention.

[0145] Preferably, at least one additive selected from sulfur, ammonium sulfate, micronutrients and trace elements is added before or during particle formation, so that it is preferably distributed in the particles.

[0146] Preferably, the urease inhibitor and / or the nitrification inhibitor is added before or during particle formation, so that it is preferably distributed throughout the particles.

[0147] In preferred embodiments, a urease inhibitor and / or a nitrification inhibitor is added to the melt and / or solution provided in step (c). In other preferred embodiments, a urease inhibitor and / or a nitrification inhibitor is added to the mixture produced in step (d). In further preferred embodiments, a urease inhibitor and / or a nitrification inhibitor is added to the ham particles during their production in step (e). Combinations of these embodiments are also possible.

[0148] Preferably, the urease inhibitor and / or the nitrification inhibitor is added after particle formation, so that it is preferably present in a coating of the particles.

[0149] In preferred embodiments, the ham particles produced in step (e) are treated with a composition containing a urease inhibitor and / or a nitrification inhibitor. In other preferred embodiments, the urea particles pre-cooled in step (f) are treated with a composition containing a urease inhibitor and / or a nitrification inhibitor. In further preferred embodiments, the urea particles classified in step (g) are treated with a composition containing a urease inhibitor and / or a nitrification inhibitor. In additional preferred embodiments, the urea particles post-cooled in step (h) are treated with a composition containing a urease inhibitor and / or a nitrification inhibitor. Combinations of these embodiments are also possible.

[0150] Images:

[0151] Preferred embodiments of the invention are explained below with reference to the illustrations, which, however, are not to be interpreted as restrictive.

[0152] Figure 1 schematically illustrates a preferred embodiment according to the invention, in which the addition of the bio-based polymer, preferably in solid form, takes place in a tank in which a urea-containing aqueous solution is stored, which is produced during the recovery of urea.

[0153] According to the flow diagram shown in Figure 1, urea is synthesized from NH3 and CO2 using a conventional process in a specially configured synthesis and recovery unit (1). An evaporation stage of the synthesis and recovery unit (1) serves to concentrate the freshly synthesized urea and the urea recovered from particulateation. Recovery can be carried out as a separate process step, for which the synthesis unit is equipped with a recovery unit. The concentrated urea solution is then transferred to a particulateation unit (2), in which urea-containing particles (P) are produced, preferably by pricking or granulation. The urea-containing particles (P) leaving the particulateation unit (2) are then cooled in a pre-cooling unit (3) before being classified by sieving in a classification unit (4).Subsequently, the classified urea-containing particles (P) are preferably cooled further in a post-cooling process (5) and then fed to a product storage area (10).

[0154] A mass stream, which arises alongside the actual product stream of urea-containing particles (P) in the classification unit (4), preferably comprises urea-containing particles (P) that are too small (or possibly too large) and are preferably returned to the particulate unit (2) (possibly after comminution). Further streams, which arise in the particulate unit (2), the pre-cooling unit (3), the classification unit (4), and / or the post-cooling unit (5), preferably comprise urea-containing dust (S), which is fed to a gas purification unit (6). In this unit, urea-containing dust (S) is separated from the gas phase by wet scrubbing. Preferably, for this purpose, the urea-containing dust (S) is brought into contact with a liquid stream, preferably water or an aqueous solution, in a gas stream or as an aerosol stream in the gas purification unit (6) to remove ham- The substance and, if applicable, other components of the urea-containing dust (S), such as gases (NH3), biuret, impurities, traces of additives, inhibitors, sulfur, ammonium sulfate, etc., are absorbed into the liquid (washing solution). The urea-containing aqueous solution (L) thus produced is fed to a tank (7). Preferably, additional recovered urea (R) from other plant components or mass streams is also fed to the tank (7). The urea-containing aqueous solution (L) therefore preferably comprises both the washing solution produced during wet separation in the gas cleaning unit (6) (i.e., a urea-containing aqueous solution that is produced during the washing of the exhaust air from the particulate unit (2), preferably the granulator) and at least one of the following streams: - Material from a safety sieve at the outlet of the particle unit (2), preferably a granulator (recycling system 1); - Material from a roller crusher (recycling system 2); - a urea-containing aqueous solution which is generated during washing of the particulate unit, preferably the granulator, as part of maintenance (e.g., discontinuous maintenance every 1 to 3 months) (recycling system 3); - Steam (recycling system 4); and / or - Material from other sources. Accordingly, the tank (7) preferably stores a urea-containing aqueous solution (L) which contains urea that has been recovered from various plant components or mass streams.

[0155] The urea recovered from the urea-containing dust (S), which is present in the urea-containing aqueous solution (L), is preferably also returned to the particulate unit (2). For this purpose, however, the urea-containing aqueous solution (L) is preferably first concentrated in an evaporation unit (8), or the liquid phase is evaporated, or it is directed to the synthesis and recovery unit 1 for evaporation.

[0156] In the preferred embodiment shown schematically in Figure 1, the bio-based polymer is added to the tank (7) according to the invention. The bio-based polymer is preferably in solid form, for example, as a powder or pellets. The bio-based polymer can be in pure form or mixed with any desired additives. According to this embodiment, the tank (7) is equipped with a metering and mixing unit for the solid bio-based polymer. Adding the solid bio-based polymer to the tank (7) is advantageous because the concentration of urea in the urea-containing aqueous solution (L) is comparatively high, and urea promotes the dissolution of bio-based polymers such as cellulose and related compounds in aqueous solutions.

[0157] The dosing and mixing unit according to the invention for solid bio-based polymer can be any device capable of adding a specific quantity of solid bio-based polymer to a liquid and producing a homogeneous dispersion and / or dissolving the solid bio-based polymer in this mass stream. Suitable devices are widely used, for example, in the food industry, such as the YTRON®-ZC powder dissolving system or the guided beam mixer. scher YTRON®-Y (YTRON Process Technology, Bad Endorf, DE) or the solid / liquid mixer MHD200 (IKA Werke, Staufen im Breisgau, DE).

[0158] Optionally, according to the embodiment shown in Figure 1, a urease inhibitor and / or a nitrification inhibitor can be added (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0159] In further embodiments of the invention, the solid bio-based polymer is added via a dosing and mixing unit for the solid bio-based polymer (9) into other plant components or streams (Figures 2 to 20). Unless otherwise specified, the units and material streams, as well as their reference numerals and functions, correspond to those previously mentioned in connection with Figure 1.

[0160] Figure 2 schematically illustrates a preferred embodiment according to the invention, in which the solid bio-based polymer is added to a mass stream from the tank (7). The residence time of the urea-containing aqueous solution (L) in the tank (7) is not specified according to the invention. Since solutions of bio-based polymers such as cellulose can have a limited shelf life due to, for example, gel formation, it can be advantageous to prepare the bio-based polymer solution immediately before its further use. For this purpose, according to the embodiment of the invention schematically illustrated in Figure 2, solid bio-based polymer is mixed in a separate dosing and mixing unit (9) with a partial stream of the urea-containing aqueous solution (L) from the tank (7).Another partial stream of the urea-containing aqueous solution (L) from tank (7) is concentrated in the evaporation unit (8) and then combined with the solution containing the bio-based polymer. The combined mixture is then directed into the main urea feed immediately upstream of the particulate unit (2).

[0161] Optionally, a urease inhibitor and / or a nitrification inhibitor can also be added according to the embodiment shown in Figure 2 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0162] The urea-containing aqueous solution (L) from the tank (7) can have different compositions. Therefore, it may be advantageous to supply the dosing and mixing unit (9) with a concentrated urea-containing aqueous solution (L) from the evaporation unit (8) or from the main urea feed to ensure a desired composition of the mixture containing the bio-based polymer (Figure 3 and Figure 4).

[0163] Figure 3 schematically illustrates a preferred embodiment according to the invention, in which the solid bio-based polymer is fed into the dosing and mixing unit (9) with a mass flow rate of The urea-containing aqueous solution (L) from the tank (7) is mixed with a mass flow from the evaporation unit (8) to adjust or maintain a desired urea concentration. The mixture is then fed into the main urea feed immediately upstream of the particulate unit (2).

[0164] Optionally, a urease inhibitor and / or a nitrification inhibitor can also be added according to the embodiment shown in Figure 3 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0165] Figure 4 schematically illustrates a preferred embodiment of the invention in which the solid bio-based polymer is mixed in the dosing and mixing unit (9) with a mass stream of the urea-containing aqueous solution (L) from the tank (7) and a mass stream from the main urea feed immediately downstream of the synthesis and recovery unit (1) to establish or maintain a desired urea concentration. In principle, any partial stream originating from the synthesis and recovery unit (1) (other than the main stream) can also originate from a part of the synthesis and recovery unit (1), e.g., a first evaporation stage (1a), an intermediate tank (1b), and / or a second evaporation stage (1c) (not shown in Figure 4). The mixture is then fed into the main urea feed immediately upstream of the particulate unit (2).

[0166] Optionally, a urease inhibitor and / or a nitrification inhibitor can also be added according to the embodiment shown in Figure 4 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0167] Not all urea particulateation plants have a separate evaporation unit. Therefore, another evaporation unit, integrated into the synthesis and recovery unit (1) (Figure 5), is often used to concentrate urea-containing solutions.

[0168] Figure 5 schematically illustrates a preferred embodiment of the invention in which the solid bio-based polymer is added to the urea-containing aqueous solution (L) without separate evaporation. To avoid impurities during urea synthesis, it is advantageous in such systems without a separate evaporation unit to feed a partial stream of the urea-containing aqueous solution (L) from the tank (7) to the dosing and mixing unit (9) and mix it with the solid bio-based polymer. The mixture is then directed into the main urea feed immediately upstream of the particulate unit (2). Another partial stream of the Urea-containing aqueous solution (L) from the tank (7) is concentrated in the evaporation unit, which is integrated into the synthesis and recovery unit (1).

[0169] Optionally, a urease inhibitor and / or a nitrification inhibitor can also be added according to the embodiment shown in Figure 5 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0170] To ensure better control over the urea concentration in the urea-containing aqueous solution, it may be advantageous to supply an additional partial stream from the main urea supply to the dosing and mixing unit (9) (Figure 6).

[0171] Figure 6 schematically illustrates a preferred embodiment of the invention in which the addition of the solid bio-based polymer to the urea-containing aqueous solution (L) also takes place without separate evaporation. A partial stream of the urea-containing aqueous solution (L) from the tank (7) and a partial stream from the main urea feed are fed to the dosing and mixing unit (9) and mixed therein with the solid bio-based polymer. The mixture is then directed into the main urea feed immediately upstream of the particulate unit (2). Another partial stream of the urea-containing aqueous solution (L) from the tank (7) is concentrated in the evaporation unit, which is integrated into the synthesis and recovery unit (1).

[0172] Optionally, a urease inhibitor and / or a nitrification inhibitor can also be added according to the embodiment shown in Figure 6 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0173] To reduce the amount of water in the urea-containing aqueous solution of the bio-based polymer, it can be advantageous to concentrate the mixture or solution in the evaporation unit (8). The dosing and mixing unit for the solid bio-based polymer (9) is preferably arranged downstream of the tank (7) and upstream of the evaporation unit (8). This also shortens the residence time of the bio-based polymer in the urea-containing aqueous solution before its further use in particulateation (Figure 7).

[0174] Figure 7 schematically illustrates a preferred embodiment of the invention, in which the solid bio-based polymer is added to the urea-containing aqueous solution (L) from the tank (7) and then concentrated in a separate evaporation unit (8). The concentrated mixture is then fed into the main urea feed immediately upstream of the particulate unit (2).

[0175] Optionally, a urease inhibitor and / or a nitrification inhibitor can also be added according to the embodiment shown in Figure 7 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0176] In order to reduce the amount of water in the urea-containing aqueous solution of the bio-based polymer, it may also be advantageous to supply a partial stream of the urea-containing aqueous solution (L) previously concentrated in the evaporation unit (8) to the dosing and mixing unit (9) and mix it with the solid bio-based polymer (Figure 8).

[0177] Figure 8 schematically illustrates a preferred embodiment of the invention in which the solid bio-based polymer is added to a partial stream from a separate evaporation unit (8). For this purpose, a partial stream of the urea-containing aqueous solution (L) concentrated in the evaporation unit (8) is fed to the metering and mixing unit (9) and mixed therein with the solid bio-based polymer. The mixture is then combined with another partial stream of the urea-containing aqueous solution (L) concentrated in the evaporation unit (8) and finally directed into the main urea feed immediately upstream of the particulate unit (2).

[0178] Optionally, a urease inhibitor and / or the nitrification inhibitor can also be added according to the embodiment shown in Figure 8 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0179] Alternatively, the entire mass flow of the urea-containing aqueous solution (L), previously concentrated in the evaporation unit (8), can be fed to the dosing and mixing unit (9) and mixed therein with the solid bio-based polymer. In this case, no division into partial flows occurs (Figure 9).

[0180] Figure 9 schematically illustrates a preferred embodiment of the invention in which the solid bio-based polymer is added to the entire mass flow from a separate evaporation unit (8). For this purpose, the entire mass flow of the urea-containing aqueous solution (L), previously concentrated in the evaporation unit (8), is fed from the tank (7) to the dosing and mixing unit (9) and mixed therein with the solid bio-based polymer. The mixture is then directed into the main urea feed immediately upstream of the particulate unit (2).

[0181] Optionally, a urease inhibitor and / or the nitrification inhibitor can also be added according to the embodiment shown in Figure 9 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the precooling unit (3), in the pre-cooling (3), immediately downstream of the pre-cooling (3), immediately upstream of the post-cooling (5), in the post-cooling (5), and / or immediately upstream of the product storage (10).

[0182] In order to reduce the amount of water in the urea-containing aqueous solution of the bio-based polymer, it may also be advantageous to supply a partial stream of the urea main feed to the dosing and mixing unit (9) (Figure 10).

[0183] Figure 10 schematically illustrates a preferred embodiment of the invention in which the solid bio-based polymer is added to a partial stream from the main hemp feed. For this purpose, a partial stream from the main hemp feed is fed to the dosing and mixing unit (9) and mixed therein with the solid bio-based polymer. The mixture is then returned to the main hemp feed immediately upstream of the particulate unit (2).

[0184] Optionally, a urease inhibitor and / or the nitrification inhibitor can also be added according to the embodiment shown in Figure 10 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0185] Alternatively, the entire mass flow of the hemp main feed can be fed to the dosing and mixing unit (9) and mixed therein with the solid bio-based polymer. In this case, no division into partial flows occurs (Figure 11).

[0186] Figure 11 schematically illustrates a preferred embodiment of the invention in which the solid bio-based polymer is added to the main hemp feed, e.g., by an in-line dispersion system. For this purpose, the entire mass flow of the main hemp feed is fed to the dosing and mixing unit (9) and mixed therein with the solid bio-based polymer. The mixture is preferably then combined with the urea-containing aqueous solution (L) concentrated in the evaporation unit (8) and directed to the particulate unit (2).

[0187] Optionally, a urease inhibitor and / or the nitrification inhibitor can also be added according to the embodiment shown in Figure 11 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0188] In the embodiments according to the invention as shown in Figures 1-4 and 7-9, the evaporation unit (8) can each consist independently of one or more evaporation stages. In the case of multiple evaporation stages, further variations are preferred according to the invention (Figures 12-14).

[0189] Figure 12 schematically illustrates a preferred embodiment of the invention in which the addition of the solid bio-based polymer takes place between different evaporation stages (8a) and (8b). A partial stream of the urea-containing aqueous solution (L) concentrated in the first evaporation stage (8a) is fed to the dosing and mixing unit (9) and mixed therein with the solid bio-based polymer. The mixture is then combined with another partial stream of the urea-containing aqueous solution (L) concentrated in the first evaporation stage (8a) and fed to the second evaporation stage (8b). After further concentration in the second evaporation stage (8b), the mixture is directed into the main urea feed immediately upstream of the particulate unit (2).

[0190] Optionally, a urease inhibitor and / or the nitrification inhibitor can also be added according to the embodiment shown in Figure 12 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0191] Alternatively, the entire mass flow from the first evaporation stage (8a) can be fed to the dosing and mixing unit (9) and mixed therein with the solid bio-based polymer. In this case, no division into partial flows occurs (Figure 13).

[0192] Figure 13 schematically illustrates a preferred embodiment of the invention in which the metering and mixing unit (9) is integrated into the evaporation section, downstream of the first evaporation stage (8a) and upstream of the second evaporation stage (8b). For this purpose, the entire mass flow from the first evaporation stage (8a) is fed to the metering and mixing unit (9) and mixed therein with the solid bio-based polymer. The mixture is then further concentrated in the second evaporation stage (8b) and finally fed into the main urea feed immediately upstream of the particulate unit (2).

[0193] Optionally, a urease inhibitor and / or the nitrification inhibitor can also be added according to the embodiment shown in Figure 13 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0194] Figure 14 schematically illustrates a preferred embodiment of the invention, in which the metering and mixing unit (9) is arranged downstream of the first evaporation stage (8a), wherein the urea-containing aqueous solution concentrated in the first evaporation stage (8a) is subsequently divided into two partial streams. One partial stream from the first evaporation stage (8a) is fed to the metering and mixing unit (9) and mixed therein with the solid bio-based polymer. The mixture is then combined with another partial stream from the first evaporation stage (8a), which was previously further concentrated in the second evaporation stage (8b). The dosing and mixing unit (9) is thus arranged in a bypass around the second evaporation stage (8b). The mixture is finally fed into the main urea feed immediately upstream of the particulate unit (2).

[0195] Optionally, a urease inhibitor and / or the nitrification inhibitor can also be added according to the embodiment shown in Figure 14 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0196] If the evaporation unit (8) has more than two evaporation stages, the embodiments illustrated in Figures 12 to 14 can preferably be extended analogously to each of the evaporation stages between the first evaporation stage and the last evaporation stage.

[0197] Figure 15 schematically illustrates a preferred embodiment of the invention, in which the solid bio-based polymer is added to a mass stream from the tank (7) and a mass stream from the first evaporation stage (8a). For this purpose, the urea-containing aqueous solution (L) from the tank (7) is divided into partial streams, one of which is fed to the metering and mixing unit (9) and another of which is fed to the first evaporation stage (8a) and concentrated therein. In the first evaporation stage (8a), a concentrated urea-containing aqueous solution is obtained, which is in turn divided into partial streams, one of which is also fed to the metering and mixing unit (9) and another of which is fed to the second evaporation stage (8b) and further concentrated therein, resulting in a further concentrated urea-containing aqueous solution.The dosing and mixing unit (9) receives the partial stream of the urea-containing aqueous solution (L) from the tank (7) as well as the partial stream from the first evaporation stage (8a) and mixes it with the solid bio-based polymer. The mixture is then directed into the main urea feed immediately upstream of the particulate unit (2). The further concentrated urea-containing aqueous solution from the second evaporation stage (8b) is also directed into the main urea feed immediately upstream of the particulate unit (2).In this way, a constant concentration of urea can be maintained in the urea-containing aqueous solution of the bio-based polymer because the partial stream from the first evaporation stage (8a), which is fed to the dosing and mixing unit (9), has a higher concentration of urea than the partial stream of the urea-containing aqueous solution (L) from the tank (7), which is fed to the dosing and mixing unit (9).

[0198] Optionally, a urease inhibitor and / or the nitrification inhibitor can also be added according to the embodiment shown in Figure 15 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0199] Figure 16 schematically illustrates a preferred embodiment of the invention in which the addition of the solid bio-based polymer to the main hemp feed takes place without a separate evaporation unit (8).

[0200] Optionally, a urease inhibitor and / or the nitrification inhibitor can also be added according to the embodiment shown in Figure 16 (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0201] Figure 17 schematically illustrates a preferred embodiment of the invention, in which the synthesis and recovery unit comprises, in addition to the urea synthesis stage (H₂N-C(=O)-NH₂), a recovery stage with multi-stage evaporation, which includes a first evaporation stage (1a), an intermediate tank (1b), and a second evaporation stage (1c). In the first evaporation stage (1a), synthesized urea from the urea synthesis stage (H₂N-C(=O)-NH₂) and urea-containing aqueous solution (L) from tank (7) are fed to the recovery stage and concentrated there by evaporation. The urea-containing aqueous solution thus concentrated in the first evaporation stage (1a) is fed to an intermediate tank (1b) in which the concentrated urea-containing aqueous solution can be temporarily stored.From the intermediate tank (1b), a first and a second partial stream are drawn off. The first partial stream is fed to the dosing and mixing unit (9) and mixed there with the solid bio-based polymer. The resulting mixture is then fed into the main urea feed immediately upstream of the particulate unit (2). The second partial stream drawn off from the intermediate tank (1b) is fed to the second evaporation stage (1c), further concentrated there, and finally also fed into the main urea feed immediately upstream of the particulate unit (2), so that both partial streams are recombined.

[0202] Instead of diverting the first partial stream in the intermediate tank (1b) and feeding it into the dosing and mixing unit (9), the first partial stream can also be diverted in the first evaporation stage (1a) or between the first evaporation stage (1a) and the intermediate tank (1b) or between the intermediate tank (1b) and the second evaporation stage (1c) and fed from this diversion to the dosing and mixing unit (9) to be mixed there with the solid bio-based polymer. to be. The mixture thus obtained is then also fed into the main ham feed immediately upstream of the particulate unit (2). In other preferred embodiments (not shown in Figure 17), the first evaporation stage (1a) is integrated into the ham synthesis. In these cases, the stream from tank (7) is fed downstream of the first evaporation stage (1a), i.e., upstream of the intermediate tank (1b), into the intermediate tank (1b), upstream of the second evaporation stage (1c), or into the second evaporation stage (1c). The location of the branch for the partial stream to the metering and mixing unit (9) then preferably remains the same as described above.

[0203] Optionally, according to this embodiment, a urease inhibitor and / or a nitrification inhibitor can also be added (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0204] Figure 18 schematically illustrates a preferred embodiment according to the invention as shown in Figure 17, wherein the first evaporation stage (1a) is integrated into the urea synthesis stage (H2N-C(=O)-NH2). The urea-containing aqueous solution (L) is introduced from the tank (7) into the stream between the integrated first evaporation stage (1a) with urea synthesis stage (H2N-C(=O)-NH2) and the intermediate tank (1b).

[0205] Optionally, according to this embodiment, a urease inhibitor and / or a nitrification inhibitor can also be added (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0206] Figure 19 schematically illustrates a preferred variant of the embodiment according to Figure 18. In this case, the urea-containing aqueous solution (L) from the tank (7) is introduced into the stream between the intermediate tank (1b) and the second evaporation stage (1c).

[0207] Optionally, according to this embodiment, a urease inhibitor and / or a nitrification inhibitor can also be added (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0208] In the embodiments illustrated in Figures 17 to 19, the synthesis and recovery unit (1) is a separate system located upstream of the particulate unit (2). Fresh urea is produced in the synthesis and recovery unit (1), typically as an aqueous solution. This aqueous solution is preferably evaporated for concentration in a first evaporation stage (1a). This first evaporation stage (1a) can be integrated into the synthesis unit. An intermediate tank (1b) preferably serves to store the freshly synthesized urea. This occurs when the downstream particulate unit (2) fails. Therefore, the solution containing the freshly synthesized urea is preferably passed through the intermediate tank (1b). Preferably, further concentration then takes place in a second evaporation stage (1c), which brings the solution to the desired final concentration. The stream exiting the second evaporation stage (1c) then corresponds to the main urea stream. In preferred embodiments of the invention, this first evaporation stage (1a) and / or this second evaporation stage (1c) are additionally used for recycling aqueous urea solution containing recovered urea.

[0209] If the first evaporation stage (1a) is integrated into the urea synthesis (H2N-C(=O)-NH2), the aqueous urea solution containing the recovered urea (i.e., the urea-containing aqueous solution (L) from tank (7)) is preferably fed downstream of the first evaporation stage (1a) to avoid contamination of the urea synthesis (H2N-C(=O)-NH2). This can be done upstream of the intermediate tank (1b), into the intermediate tank (1b), downstream of the intermediate tank (1b), or into the second evaporation stage (1c). Taking a partial stream downstream of the first evaporation stage (1a), from the intermediate tank (1b) or downstream of the intermediate tank (1b) for the production of the aqueous polymer preparation with the bio-based polymer is advantageous because the urea concentration is typically higher (and thus the water content lower) than in the urea-containing aqueous solution (L) from the tank (7).

[0210] Figure 20 schematically illustrates a preferred embodiment of the invention as shown in Figure 17. As already explained above in connection with Figure 1, urea-containing dust (S) is separated from the gas phase in the gas purification unit (6) by wet scrubbing. Preferably, the urea-containing dust (S) is brought into contact with a liquid stream, preferably water or an aqueous solution, in the gas purification unit (6) in a gas stream or as an aerosol stream, in order to absorb urea and optionally other components of the urea-containing dust (S), such as gases (NH3), biuret, impurities, traces of additives, inhibitors, sulfur, ammonium sulfate, etc., into the liquid (washing solution). The resulting urea-containing aqueous solution (L) is divided into a first partial stream and a second partial stream.

[0211] The first partial stream from the gas purification unit (6) is fed to the tank (7) as in the embodiment schematically illustrated in Figure 17. Synthesized urea from the urea synthesis stage (H₂N-C(=O)-NH₂) and urea-containing aqueous solution (L) from the tank (7) are fed to the first evaporation stage (1a) and concentrated there by evaporation. The urea-containing aqueous solution thus concentrated in the first evaporation stage (1a) is fed to the intermediate tank (1b). In contrast to the embodiment schematically illustrated in Figure 17, the stream exiting the intermediate tank (1b) is not divided, but is fed entirely to the second evaporation stage, as schematically illustrated in Figure 20. fed to the evaporation stage (1c), further concentrated there and finally directed into the main ammonium feed immediately before the particulate unit (2).

[0212] The second partial stream from the gas purification unit (6) is fed to the dosing and mixing unit (9) and mixed therein with solid, bio-based polymer. The mixture is then directed into the main ammonium feed immediately upstream of the particulate unit (2).

[0213] Optionally, according to this embodiment, a urease inhibitor and / or a nitrification inhibitor can also be added (not shown), preferably upstream of the particulate unit (2), in the particulate unit (2), immediately upstream of the pre-cooling unit (3), in the pre-cooling unit (3), immediately downstream of the pre-cooling unit (3), immediately upstream of the post-cooling unit (5), in the post-cooling unit (5), and / or immediately upstream of the product storage unit (10).

[0214] Reference symbol list: P: urea-containing particles; R: recovered urea from other plant components or mass flows; S: urea-containing dust, typically mixed with air, H2O and NH3; L: urea-containing aqueous solution; 1: Synthesis and recovery unit; 1a: First evaporation stage 1b: Intermediate tank 1c: second evaporation stage 2: Particular unit; 3: Pre-cooling; 4: Classification unit; 5: Post-cooling; 6: Gas purification unit; 7: Tank; 8: Evaporation unit; 8a: first evaporation stage; 8b: second evaporation stage; 9: Dosing and mixing unit for solid bio-based polymer; and 10: Product warehouse.

[0215] The following examples serve to illustrate preferred embodiments of the invention, but are not to be interpreted restrictively.

[0216] Attempt 1:

[0217] In a pilot plant, a cellulose derivative was dissolved in a mixture of urea and water. The resulting mixture was added to a 97% urea solution via a metering pump. The 97% urea solution was added at a constant rate. It was fed into a fluidized bed granulator and granulated there. The proportion of the solution containing the cellulose derivative was 0.4 wt% of the 97% urea solution.

[0218] The cellulose derivative content in the granules was 0.02 wt.%.

[0219] The granules exhibited a breaking strength of more than 30 N. The bulk density was more than 700 kg / m³. 3 The dust levels were within acceptable limits.

[0220] As the data demonstrate, satisfactory mechanical strengths of the ham particles can be achieved with the cellulose derivative used according to the invention, even at low dosages. The observations are qualitatively consistent with studies using cellulose and other cellulose derivatives.

[0221] Attempt 2:

[0222] In a pilot plant, a cellulose derivative was dissolved in a mixture of urea and water. The resulting solution was added to a 97% urea melt in a melting vessel. The proportion of the cellulose derivative-containing solution in the urea melt was 0.4 wt%. The solution and the melt were mixed in a closed loop for 3 minutes until homogeneous and then granulated in a fluidized bed granulator.

[0223] The cellulose derivative content in the granules was 0.02 wt.%.

[0224] The granules exhibited a breaking strength of more than 35 N. The bulk density was more than 700 kg / m³. 3 The dust levels were within acceptable limits.

[0225] As the data show, satisfactory mechanical strengths of the ham particles can be achieved with the cellulose derivative according to the invention, even at low dosages.

[0226] Attempt 3:

[0227] In an industrial fluidized bed granulation plant for urea (ThyssenKrupp UFT® technology), a cellulose derivative was continuously mixed with a urea-containing aqueous solution using a solid / liquid mixer (IKA MHD 2000) and injected into a 97% urea melt upstream of the granulator. The cellulose derivative content was 0.01 to 0.03 wt%.

[0228] The granules exhibited a breaking strength of more than 30 N. Dust generation and particle size distribution were within acceptable limits.

[0229] Particle size distribution

[0230] The particle size distribution obtained by granulation according to experiment 1 was investigated and compared with the particle size distribution obtained by granulating conventional ham particles with an additive based on ham formaldehyde (UF85). The granulation conditions were identical in both cases. Exclusion criteria were set as a particle size > 4 mm for overcomponents and a particle size < 2 mm for undercomponents.

[0231] The results are summarized in the table below:

[0232] As the data in the table above demonstrate, comparable particle size distributions can be achieved with the inventive cellulose derivative at a significantly lower dosage than with granulation using a conventional additive based on urea-formaldehyde (UF85). The amount of reject material to be separated during classification due to excessively small or large particle sizes is also comparable.

[0233] Compatibility of the use of bio-based polymers with inhibitors:

[0234] For the production of stabilized ham particles, a mixture of NB PT and NPPT was added as a urease inhibitor.

[0235] The resulting granules were coated with a solution of the inhibitor and stored at 20, 30, and 40°C. The stability of the inhibitor was measured monthly as a percentage of the original inhibitor concentration after coating.

[0236] The results are shown in Figure 21, which depicts the change in inhibitor concentration during storage time, i.e., the relative amount of inhibitor compared to the inhibitor concentration immediately after the production of the ham particles and thus at the beginning of storage.

[0237] When using bio-based polymers, the change in inhibitor concentration during storage is qualitatively and quantitatively comparable to, or even lower than, the change in inhibitor concentration for pure urea (i.e., without polymer or formaldehyde-containing additives). This suggests comparable or even higher stability of the inhibitor in the sample and demonstrates that the inhibitor is not degraded by the cellulose derivative. Adding the inhibitor to the urea melt is also possible and the preferred option.

Claims

Patent claims:

1. Comprising ham particles - at least 20% by weight urea, based on the total mass of the particles; and - a bio-based polymer dispersed in the ham particles; wherein the ham particles have a weight-average particle size in the range of 0.1 to 10 mm, preferably determined by sieve analysis according to DIN EN 1235:2003-08.

2. The ham particles according to Annex 1, wherein the content of bio-based polymer is at most 0.25 wt.%, preferably at most 0.10 wt.%, more preferably at most 0.075 wt.%, even more preferably at most 0.050 wt.%, most preferably at most 0.040 wt.%, and in particular at most 0.030 wt.%, in each case based on the total mass of the ham particles.

3. The ham particles according to Annex 1 or 2, wherein the bio-based polymer is water-soluble; preferably wherein the solubility of the pure bio-based polymer in pure water at 23 °C is at least 10 g / l, more preferably at least 20 g / l, more preferably at least 40 g / l, more preferably at least 60 g / l, most preferably at least 80 g / l, and in particular at least 100 g / l.

4. The ham matter particles according to any of the preceding claims, wherein the bio-based polymer is a polysaccharide or a derivative of a polysaccharide; wherein the derivative is preferably selected from etheme and esters, preferably etheme.

5. The ham particles according to specification 4, wherein the polysaccharide as such or the polysaccharide of a derivative of a polysaccharide is selected from the group consisting of cellulose, hemicellulose, starch, pectin, xanthan gum, guar gum, gellan gum, gum arabic, locust bean gum, alginate, chitin and chitosan; preferably cellulose.

6. The hygroscopic particles according to any of the preceding claims, wherein the bio-based polymer is a cellulose ether; preferably selected from the group consisting of methylcellulose (MC), ethylcellulose (EC), methylethylcellulose (MEC), hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), hydroxyethylmethylcellulose (HEMC), hydroxypropylmethylcellulose (HPMC), carboxymethylcellulose (CMC).

7. The hygroscopic particles according to one of the preceding claims, which contain a urease inhibitor and / or a nitrification inhibitor; preferably wherein the urease inhibitor and / or nitrification inhibitor are homogeneously distributed in the particle.

8. The urea particles according to any of the preceding claims, wherein the urea content is at least 40 wt.%, preferably at least 50 wt.%, more preferably at least 60 wt.%, more preferably at least 70 wt.%, most preferably at least 80 wt.%, and in particular at least 90 wt.%, in each case based on the total mass of the urea particles.

9. The ham particles according to one of the preceding claims, which have a weight-average particle size in the range of 0.5 to 8.0 mm, preferably 0.5 to 6.0 mm, more preferably 0.5 to 4.0 mm, preferably determined by sieve analysis according to DIN EN 1235:2003-08.

10. The ham matter particles according to any of the preceding claims, which do not contain formaldehyde and / or ham matter formaldehyde.

11. A method for producing ham particles according to any one of the preceding claims, wherein the method comprises the steps: (a) Providing an aqueous polymer preparation comprising a bio-based polymer; (b) optionally evaporating at least some of the water from the polymer preparation; (c) Providing a melt and / or solution comprising freshly synthesized urea; (d) Mixing the polymer preparation with the melt and / or solution to produce a mixture; (e) Producing ham particles from the mixture.

12. The method of claim 11, comprising one or more of the following additional steps (f) optional pre-cooling of the ham matter particles; (g) Classifying the ham particles; and (h) optional post-cooling of the ham particles.

13. The method according to Annex 11 or 12, wherein step (a) comprises the sub-steps (ai) providing an aqueous composition; (a2) optionally, evaporation of at least some of the water from the aqueous composition; and (a3) Dissolving or dispersing the bio-based polymer in the aqueous composition to produce the aqueous polymer preparation.

14. The method according to claim 13, wherein the aqueous composition provided in partial step (ai) - is produced as a byproduct during the manufacture of the ham particles; and / or - a urea-containing aqueous solution; and / or - is a urea-containing aqueous melt.

15. The method according to claim 14, wherein the urea-containing aqueous solution and / or melt contains unreacted, excess and / or sorted-out material.

16. The method according to claim 15, wherein the material is generated in one or more of steps (e), (f), (g) and (h).

17. The method according to claim 14 or 15, wherein the material is obtained as dust and is separated from a gas phase by wet separation, producing the urea-containing aqueous solution.

18. The method according to any one of claims 11 to 17, wherein - the melt and / or solution provided in step (c), - the mixture produced in step (d), or - in step (e) a urease inhibitor and / or a nitrification inhibitor is added to the ham particles during their production.

19. The method according to any one of claims 11 to 18, wherein - the ham particles produced in step (e), - the ham particles pre-cooled in step (f), - the ham particles classified in step (g), or - the ham particles cooled in step (h) be treated with a composition containing a urease inhibitor and / or a nitrification inhibitor.

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