Hopper with cooling element

Abstract

The present disclosure relates to a hopper comprising a buffer compartment defined by a sidewall, a top end with an opening for receiving solid particles, and a bottom end with an opening for dispensing the solid particles from the buffer compartment. The buffer compartment comprises a plurality of essentially vertically positioned cooling plate elements for cooling the solid particles in the buffer compartment. The present disclosure further relates to a system including the hopper, a method of operating the hopper or system, and the production of solid particles.

Description

[Technical Field]

[0001] The present disclosure relates to the field of chemical manufacturing, and more particularly, the present disclosure provides a novel hopper with a cooling element. [Background technology]

[0002] A hopper, also known as a collection vessel for particles, is a device that can collect, hold, and dispense materials, especially granular or fine granular materials, on demand. A hopper is a container with a large opening at the top to easily receive the material to be held and a narrow bottom end to dispense the material in a controlled manner. A hopper can alternatively be described as a container with converging sides, i.e., a funnel-like shape. Hoppers are widely used in the production of chemicals, such as fertilizer granules.

[0003] EP0444338A1 (Cominco Ltd, 1991) discloses a device for cooling solid particles. The device comprises a plurality of parallel, spaced apart, vertically arranged heat exchanger plates, a feed hopper, and a discharge hopper. The heat exchanger plates are connected to fluid inlets and outlets located at the sides of the hopper. The device reduces wear and abrasion of the particles being cooled.

[0004] US2020 / 0017416A1 (thyssenkrupp AG, 2020) discloses a system including a fluidized bed granulator, a cooler, and a product screen, the product screen having an outlet for oversized particles that is connected to the fluidized bed granulator via one or more mills.

[0005] The functionality of currently available hoppers is limited to their primary function: collecting, storing, and dispensing material. There is a need to develop a new hopper that can cool the material it holds. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] EP0444338A1 [Patent Document 2] US2020 / 0017416A1 Summary of the Invention

[0007] It has been found possible to develop a new type of hopper that includes a cooling element in a buffer compartment, such that the temperature of particles collected and dispensed by the hopper is reduced during its stay in the hopper. The buffer compartment is an area of ​​the hopper where material, such as particles, is provided or held before use or dispensing.

[0008] The inventors have also found a way to improve conventional hoppers, i.e., hoppers without any cooling function. Improving existing devices is particularly interesting because it allows the problem to be solved by modifying only one device, the hopper, without having to change other devices, such as devices connected to the hopper. Also, the improved hopper does not use more space in the plant than the original hopper.

[0009] Retrofitting a device allows a plant to increase its capacity or functionality with minimal cost and disruption to the plant.

[0010] The present invention is defined by the following set of claims.

[0011] In a first aspect, the present disclosure relates to a hopper comprising a buffer compartment defined by a sidewall, a top end with an opening adapted to receive solid particles, and a bottom end with an opening adapted to dispense the solid particles from the buffer compartment, wherein the buffer compartment comprises a plurality of essentially vertically positioned cooling plate elements for cooling the solid particles in the buffer compartment.

[0012] In another aspect, the present disclosure relates to a method for operating a hopper according to the present disclosure, comprising the steps of: a) activating the cooling effect of a plurality of cooling plate elements; b) providing solid particles, e.g., as a feed or a stream, to a top end of the hopper, e.g., in a continuous or intermittent manner; and c) dispensing the cooled solid particles through an opening in a bottom end of the hopper, e.g., in a continuous or intermittent manner.

[0013] In another aspect, the present disclosure provides a method for operating a system according to the present disclosure, comprising: I) activating the cooling effect of a plurality of cooling plate elements of the hopper; II) directing a melt, in particular a melt comprising one or more selected from the group consisting of urea, ammonium salts, nitrates, and / or mixtures thereof, into a granulator; III) granulating the melt in a granulator, in particular in a fluidized bed granulator, thereby obtaining particles; IV) separating the resulting particles into fractions of on-spec solid particles, under-spec solid particles, and over-spec solid particles based on predetermined size ranges; V) directing any resulting oversized solid particles into the hopper; VI) providing any oversized solid particles to the top end of the hopper, e.g., in a continuous or intermittent manner; VII) dispensing the cooled solid particles through an opening in the bottom end of the hopper, e.g., in a continuous or intermittent manner; VIII) dispensing the cooled solid particles from the hopper to a grinder to reduce the particle size of the solid particles; IX) separating any resulting undersized solid particles from the mill and directing them to a granulator.

[0014] In another aspect, the present disclosure provides a method for the production of solid particles using the present hopper, comprising: a) activating the cooling effect of a plurality of cooling plate elements of the hopper; b) providing solid particles to the top end of the hopper, e.g., in a continuous or intermittent manner; c) dispensing the cooled solid particles through an opening in the bottom end of the hopper, e.g., in a continuous or intermittent manner; d) dispensing the cooled solid particles from the hopper to a grinder to reduce the particle size of the solid particles; e) separating any resulting undersized solid particles from the mill and directing them to a granulator; The solid particles provided in b) i) directing a melt, in particular a melt comprising one or more selected from the group consisting of urea, ammonium salts, nitrates, and / or mixtures thereof, into a granulator; ii) granulating the melt in a granulator, in particular in a fluidized bed granulator, thereby obtaining particles; iii) separating the resulting particles into fractions of on-spec solid particles, under-spec solid particles, and over-spec solid particles based on predetermined size ranges; iv) directing any resulting oversized solid particles into the hopper as the solid particles of step b.

[0015] In another aspect, the present disclosure relates to a method for producing solid particles in a granulator, particularly a fluidized bed granulator, using a hopper according to the present disclosure, the method comprising the steps of: a) directing a melt, particularly a melt comprising one or more selected from the group of urea, ammonium salts, nitrates, and / or mixtures thereof, to the granulator; b) granulating the melt in the granulator, thereby obtaining on-spec solid particles, undersized solid particles, and oversized solid particles; c) activating the cooling effect of a plurality of cooling plate elements of the hopper according to the present disclosure; d) directing the oversized solid particles according to the present disclosure to the hopper; e) dispensing the cooled oversized solid particles from the hopper according to the present disclosure to a mill, thereby obtaining oversized solid particles, and optionally also on-size solid particles; and f) directing the undersized solid particles obtained from the mill in step e) to the granulator.

[0016] In another aspect, the present disclosure relates to the use of a hopper according to the present disclosure for distributing solid particles to a grinder.

[0017] In another aspect, the present disclosure relates to the use of a hopper according to the present disclosure in the production of solid fertilizer particles, such as sized solid fertilizer particles. [Brief explanation of the drawings]

[0018] [Figure 1] The following description of FIG. 1 of a particular embodiment of a hopper according to the present disclosure is provided by way of example only and is not intended to limit the description, its application, or uses. [Figure 2] Figure 2 shows another view of the same embodiment as in Figure 1 after being rotated 90° about the vertical axis.In the figures, the same reference numbers refer to the same or similar parts and features. DETAILED DESCRIPTION OF THE INVENTION

[0019] Unless otherwise defined, all terms used in disclosing the present invention, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art to which this invention belongs. As a further guide, term definitions are included to better understand the teachings of the present invention.

[0020] All references cited in this description are incorporated herein by reference in their entirety.

[0021] As used herein, the following terms have the following meanings:

[0022] As used herein, "A," "an," and "the" refer to both singular and plural referents unless the context clearly dictates otherwise. By way of example, a "device" refers to one or more compartments.

[0023] As used herein, "about" in reference to a measurable value, such as a parameter, amount, temporal duration, etc., is meant to encompass a variation of + / - 20% or less, specifically + / - 10% or less, more specifically + / - 5% or less, even more specifically + / - 1% or less, and even more specifically + / - 0.1% or less of the specified value, insofar as such variations are appropriate for practicing the disclosed invention. However, it should be understood that the value to which the "about" modifier refers is itself specifically disclosed.

[0024] As used herein, the terms "comprise," "comprising," and "comprises" and "consisting of" are synonymous with "include," "including," "includes," or "contain," "containing," and are inclusive or open-ended terms that specify the presence of, for example, following components, and do not exclude or preclude the presence of additional, unrecited components, features, elements, materials, steps that are known in the art or disclosed herein.

[0025] The recitation of numerical ranges by endpoints includes not only the recited endpoints but also all numbers and fractions subsumed within that range.

[0026] The expressions "weight percent," "% weight," or "% by weight" throughout this specification and description refer to the relative weight of each component based on the total weight of the formulation, unless otherwise defined.

[0027] In a first aspect, the present disclosure relates to a hopper comprising a buffer compartment defined by a sidewall, a top end with an opening for receiving solid particles, and a bottom end with an opening for dispensing the solid particles from the buffer compartment, wherein the buffer compartment comprises a plurality of essentially vertically positioned cooling plate elements for cooling the solid particles in the buffer compartment.

[0028] Hoppers are very useful devices for regulating the flow of solid particles between two other devices in a production process. For example, they can be used to transfer solid particles or granules from a conveyor belt to a grinder. They can distribute solid particles to a precise area at a constant rate. Hoppers include a buffer compartment. The buffer compartment can be defined by the interior of the hopper. The buffer compartment can be provided by the internal volume of the hopper. The buffer compartment can be defined by the side walls, top end, and bottom end of the hopper, and can hold solid particles in the buffer compartment, for example, before distribution. The heights of the hopper and the buffer compartment can be the same. The top end of the hopper is at least partially open to allow solid particles to be received. Alternatively, the top end of the hopper can have a lid that can be opened during operation to allow solid particles to be provided to the hopper and its buffer compartment. Solid particles can be provided to the hopper or its buffer compartment in a continuous or intermittent manner. Thus, the top end is adapted to receive solid particles in a continuous or intermittent manner. The solid particles may be provided to the hopper via a conveyor belt, a heat exchanger, a pipe, or any other suitable device. A product chute or funnel may be attached above the opening at the top end of the hopper to guide the solid particles into the hopper. The bottom end or bottom section of the hopper is where the particles are distributed to other devices in the production process. The solid particles can be discharged from the hopper or its buffer section in a continuous or intermittent manner. Thus, the bottom end or bottom section is adapted to allow the solid particles to be discharged in a continuous or intermittent manner. The bottom end may be partially or completely open when dispensing solid particles such as granules. The bottom end may be equipped with a movable device, such as a lid, that can be closed, partially open, or completely open to prevent any particles from exiting the hopper.

[0029] The supply of solid particles to the hopper or its buffer compartment, and the discharge of said solid particles from the hopper or its buffer compartment, which may be adapted to be carried out in a continuous or intermittent manner, are, for example, carried out in the same manner, i.e., if the supply is carried out continuously, the discharge is also carried out, and similarly, if the supply is carried out intermittently, the discharge is also carried out. The hopper or its buffer compartment may contain solid particles at all times during its operation.

[0030] In order to distribute the particles in a more precise manner, the opening at the bottom end of the hopper or buffer compartment is often smaller, i.e., has a smaller area, than the opening at the top end of the hopper or buffer compartment. The opening at the top end must be large enough to receive all the solid particles that the hopper or buffer compartment is adapted to receive. The size and shape of the opening can be adapted to any process or any equipment that provides solid particles to the hopper. The shape and size of the bottom end can be adapted depending on the purpose of the hopper or any device that distributes solid particles.

[0031] During operation, the hopper and its buffer compartment receive and / or contain solid particles and may be kept at least partially full, meaning that there are always solid particles in the buffer compartment of the hopper. This ensures that the dispensing flow rate of the hopper is always constant. While in the hopper, the solid particles may exchange heat with the surrounding atmosphere. However, the solid particles may be densely packed, and therefore, heat exchange with the surrounding atmosphere is limited.

[0032] The inventors have encountered the problem of particles received by a hopper being too hot to allow for distribution to downstream equipment. This was particularly observed in light of the heat provided during the granulation process to generate solid particles that are subsequently fed to the hopper. For example, when particles are distributed from the hopper to a grinder, it is important that the solid particles do not exceed a temperature at which they are not adequately ground. In fact, if solid particles exceed a certain temperature in the grinder, they tend to solidify during grinding, forming a paste rather than being broken down into smaller, free-flowing solid particles. Furthermore, it was observed that some particles provided to the hopper still contained a liquid phase within them. This is possible because the particles may be generated from a hot melt, particularly in a granulator such as a fluidized bed granulator, drum granulator, or pan granulator. Such liquid then spills into the grinder as the particles are ground, solidifies in the grinder, and eventually clogs the grinder after accumulation.

[0033] To solve this problem, it was conceived and investigated to add a cooling plate element positioned essentially vertically within the buffer section of the hopper, and thus contained therein. As particles are provided to the hopper, some of them come into contact with the cooling plate element, reducing their temperature. Due to particle movement within the buffer section, the cooled particles may come into contact with other warmer particles, reducing their temperature as well. It may not be necessary for all solid particles present in the hopper to come into contact with the cooling element to achieve an overall temperature reduction of the stream of solid particles being dispensed. Although it is conceivable to cool the walls of the hopper to cool the particles inside, locating the cooling element in the buffer section allows for faster cooling, since the surface of contact with the cooled part of the solid particles is significantly larger in this solution.

[0034] Adding a cooling element to the hopper allows for cooling of the solid particles without any modification or significant impact on the devices connected to the hopper, e.g., minimizing interference and modifications to the general or original equipment setup.

[0035] The cooling plate element can have any type of shape. Commercially available products often have a square or rectangular shape. The shape of the element can be adapted to the shape of the buffer compartment of the hopper. The cooling plate element needs to fit into the buffer compartment of the hopper. The element can have a shape similar to that of the buffer compartment, i.e., if the buffer compartment has a trapezoidal cross section, as in the device of FIG. 1, the cooling plate element can also have a trapezoidal cross section. This ensures that the cooling element has as large a surface area as allowed by the shape of the buffer compartment and therefore has the highest possible cooling effect.

[0036] In one embodiment, the cooling plate element has a trapezoidal shape.

[0037] The cooling element can be a pillow plate, i.e., a plate made of two thin sheets of material, such as steel, joined together at separate locations, for example by welding, with a space or channel between the two sheets through which a cooling fluid can reside and flow.

[0038] The cooling element is positioned in the hopper, i.e., in the buffer compartment. The cooling element may be positioned in a direction extending at least partially along the distance between the top and bottom ends of the hopper or its buffer compartment. Because hoppers are often installed in processes that utilize gravity on any material contained therein, the hopper is often provided vertically, i.e., the top end is positioned vertically above the bottom end, although different embodiments can be envisioned. Similarly, the cooling element may be positioned essentially vertically, meaning that the preferred position of the cooling element is oriented vertically in the buffer compartment as viewed from the top and bottom ends of the buffer compartment. This ensures that the flow of particles is not obstructed by the element, reducing the risk of particles adhering to the element or damage to the particles. However, the cooling element may also be positioned at an angle compared to a vertical position. It may not be necessary to achieve a completely vertical position of the cooling element. The cooling element may be positioned to deviate from the vertical by up to 20°, ie, an angle of 0-20°, particularly up to 10°, ie, an angle of 0-10°, more particularly, an angle of 0-5°.

[0039] The cooling elements may be positioned along the sidewalls of the buffer compartment at a distance from the sidewalls and / or within the buffer compartment, for example, in such a manner that the cooling elements extend inward toward the center of the buffer compartment. The cooling elements may be attached directly to the wall of the hopper. Several cooling elements may be attached to each other to provide structural rigidity to the assembly of cooling elements.

[0040] In one embodiment, the height of the plate cooling element is 30-80% of the height of the hopper. The size of the plate cooling element may correspond to 30-80% of the height of the hopper. The plate cooling element may extend vertically from the bottom end of the hopper for 30-80% of the height of the hopper. The plate cooling element should be located within the buffer section of the hopper. The height of the cooling element determines the contact time between the solid particles and the cooling element; the higher the cooling element, the longer the contact time. The height of the cooling element can be determined based on the temperature of the solid particles intended for the hopper when they reach the hopper and the desired temperature of the solid particles at the bottom end of the hopper. It has been found that the cooling element can have a height of 30-80% of the height of the hopper. It has been found that it may be preferable for the height of the cooling element to be less than 80% of the height of the hopper so that the cooling element does not extend near the top end of the hopper.

[0041] In one embodiment, the height of the cooling plate element is comprised between 30 and 70%, such as between 30 and 65%, 35 and 70%, 40 and 70%, 35 and 65%, 40 and 65%, 40 and 60% of the height of the hopper.

[0042] The role of the cooling plate element is to extract heat from the solid particles. Such heat exchange can be carried out in various systems. For example, the cooling element can be a thermoelectric cooling plate, also known as a Peltier element, or alternatively, the cooling element can include pipes for a cooling liquid. The solid particles in the hopper have a higher temperature than the cooling element and transfer heat to the cooling element upon physical contact. The cooling liquid is injected into the cooling element and reduces the temperature of the plate by absorbing the heat provided by the solid particles.

[0043] In one embodiment, the hopper includes inlet and outlet pipes for the cooling liquid, and the plurality of cooling plate elements are fluidly connected to the inlet and outlet pipes. When the cooling plate elements are cooled by a cooling liquid, it may be advantageous to include inlet and outlet pipes in the hopper to supply all cooling elements with the cooling liquid. The inlet pipe may include an inlet for the cooling liquid and a fluid connection to each cooling element, such that one inlet pipe is connected to multiple cooling elements, and these cooling elements are connected in parallel with each other. Alternatively, the inlet pipe may be connected to multiple cooling elements, and these cooling elements may be connected in series with each other. The outlet pipe may be fluidly connected to each cooling element in a manner similar to that shown for the inlet pipe and include one outlet for the cooling liquid drawn from the hopper. Accordingly, the outlet pipe may include an outlet for the cooling liquid and a fluid connection to each cooling element, such that one outlet pipe is connected to multiple cooling elements, and these cooling elements are connected in parallel with each other, or alternatively, in series with each other. This provides a simpler system with one inlet and one outlet for the cooling liquid. An alternative is for each cooling element to have an inlet and an outlet for the coolant that must be individually connected to a coolant source or tank, whereby the inlet and outlet pipes consist of multiple inlet and outlet pipes, with each pair of inlet and outlet pipes being separately connected to one cooling element of the multiple cooling elements.

[0044] In one embodiment, the inlet and outlet pipes are positioned parallel to each other and at the same height in the buffer section.

[0045] In one embodiment, the inlet and outlet pipes are in the buffer section.

[0046] In one embodiment, at least one of the inlet pipe or the outlet pipe is located above the cooling plate element in the vertical direction of the hopper, i.e., the inlet pipe or the outlet pipe is located closer to the top end of the hopper than the cooling plate elements, in particular both the inlet pipe and the outlet pipe, which allows the operator to evacuate the assembly comprising the cooling plate element, the inlet pipe and the outlet pipe after the cooling element is filled with cooling liquid.

[0047] In one embodiment, the inlet and outlet pipes are located above the cooling plate elements in the vertical direction of the hopper, i.e., the inlet and outlet pipes are located closer to the top end of the hopper than the cooling plate elements. This allows for easier access to the inlet and outlet pipes during maintenance. This configuration also makes it very easy to install and remove the assembly from the hopper, since the cooling plate element and the inlet and outlet pipes can be easily inserted and removed from the buffer compartment. This configuration allows a conventional hopper, i.e., a hopper without any cooling elements, to be easily converted into a cooled hopper without any modifications to other devices, such as a conveyor belt arranged to deliver particles to the hopper. In this embodiment, the inlet and outlet pipes create additional obstacles for the particles, which may cause further damage to the particles. However, this is not necessarily a negative aspect, especially when the hopper is configured to supply particles to a grinder or when the particles are melted or dissolved in a solution.

[0048] Furthermore, hoppers with inlet and outlet pipes in the buffer section do not require additional space to accommodate new elements. Although some space is required for the inlet and outlet pipes to be connected to the coolant circuit, such connections are usually small and very flexible, so they can be installed even in places where space is limited.

[0049] The fact that the inlet and outlet pipes may be positioned on multiple cooling plate elements requires that the liquid channels contained in the cooling plate elements have a suitable pattern to ensure sufficient movement of the cooling liquid in the cooling elements.

[0050] In one embodiment, the cooling plate elements do not extend within the volume defined by a horizontal cross section of 80% of the hopper's height and the top end of the hopper. With respect to the vertical height of the hopper, the cooling plate elements may be found in the hopper up to a height of 80% of the hopper's height calculated from the bottom end of the hopper. This means that the top of the hopper cannot contain any part of the cooling plate elements, i.e., the part provided by the upper 20% of the height from the top end of the hopper and extending vertically downward, and the volume of the hopper's buffer section thereby provided. It may be preferable for the cooling elements to be located toward the bottom of the hopper, in particular, so that the cooling elements do not extend within the volume defined by a horizontal cross section of 80% of the hopper's height and the top end of the hopper. Therefore, the cooling plate elements may be found in the buffer section area extending vertically from the bottom end of the hopper up to a height of 80% of the hopper's height calculated from the bottom end of the hopper. The hopper may be adapted to be filled with solid particles to the extent that, in use, the plate cooling elements are covered with particles in the hopper, i.e., the hopper is filled with solid particles to a height from its bottom end that extends beyond the height of the plurality of plate cooling elements, thereby ensuring that the cross section of the hopper directly above the cooling elements is completely filled with solid particles in operation and that the flow of solid particles between the cooling elements is uniform or similar throughout the hopper.

[0051] In one embodiment, the area of ​​the top end is 5 to 20 times larger than the area of ​​the opening at the bottom end, such as 5 to 17 times, 7 to 20 times, 7 to 17 times, 7 to 14 times, or 5 to 14 times. The top end, which has a much larger area than the bottom end, is unique to hoppers. This means that they can accept solid particles from various devices and distribute them in a very precise manner without the need for a precise distribution mechanism such as a belt conveyor. This differs from conventional heat exchangers, which have similarly sized top and bottom ends. In one embodiment, the area of ​​the apical end is 9 to 11 times, especially about 10 times, greater than the area of ​​the bottom end.

[0052] In one embodiment, the plurality of cooling plate elements are made of a metal such as stainless steel, carbon steel, wrought iron, aluminum bronze, copper brass, aluminum, or copper, particularly stainless steel. Stainless steel may have good thermal conductivity and be resistant to corrosion. The exact selection of material can be made by one skilled in the art based on the requirements of the system, for example, the composition of the solid particles to be processed by the hopper.

[0053] In one embodiment, the hopper has a cooling capacity of 10-20° C. at a flow rate of 10-15 t / hr (metric tonnes / hour).

[0054] In one embodiment, a hopper according to the present disclosure is included in an assembly comprising a hopper and a means for transporting solid particles to the hopper.

[0055] In one embodiment, an assembly including a hopper and a means for transporting solid particles may also include a screening device. The screening device ensures that the size of particles directed into the hopper does not exceed a certain size. This allows for better control over the flow characteristics of the solid particles fed into the hopper, allowing for the design of a more efficient hopper. One risk of attaching a cooling plate element to a hopper is that the solid particles will not flow properly between the cooling elements. The screening device may be attached to the means for transporting solid particles to the hopper or between the means for transporting and the hopper.

[0056] When the means for transporting the solid particles is a conveyor belt, the screening device may be found at the start of the conveyor belt, or at any point on the belt, or at the end of the conveyor belt.

[0057] In one embodiment, the assembly includes a screening device having a desired mesh size, and the distance between the two cooling plate elements in the buffer compartment, or the distance between the cooling plate element and the wall of the hopper, is 4 to 8 times, specifically 4 to 6 times, and more specifically 5 times, the mesh size of the screening device. This means that the distance between the two cooling plate elements in the hopper, or the distance between the cooling plate element and the wall of the hopper, is significantly larger than the mesh size of the screening device. When the assembly including the hopper according to the present disclosure also includes a screening device, it has been found that maintaining the distance between the two cooling plate elements in the hopper, or between the cooling plate element and the wall of the hopper, provides a good cooling effect and does not affect the flow of particles in the buffer compartment.

[0058] In one embodiment, the hopper according to the present disclosure is included in a production system, particularly a system for producing solid particles, particularly solid fertilizer particles. The system may include a granulator adapted to transform a melt into solid particles, the hopper, a mill adapted to crush the solid particles fed to the mill into smaller particles, a first transport means adapted to transport particles from the granulator to the hopper, preferably particles transported from the granulator and classified as oversized particles in terms of a predetermined particle size range, and a second transport means adapted to transport the solid particles obtained from the mill. The system may include a granulator, such as a fluidized bed granulator, for transforming the melt into solid particles, a hopper according to the present disclosure for feeding the solid particles to the mill, which crushes the solid particles fed to the mill into smaller particles, a first means for transporting the oversized particles from the granulator to the hopper, and a second means for transporting the solid particles from the mill. When a melt or solution is transformed into solid particles in a granulator, it can be difficult to obtain only particles having the desired size or diameter. In addition to a certain amount of oversized particles, i.e., within-specification or on-size particles, i.e., particles whose size falls within a desired predetermined range, it is very common to obtain particles having a diameter larger than the required size and undersized particles, i.e., particles having a diameter smaller than the predetermined size considered to be within-specification or on-size particles. In order to reduce waste in the production process and increase the overall yield of the process, it is not desirable to simply discard the oversized particles. Instead, it is possible to crush the oversized particles into particles having a much smaller diameter and reintroduce these particles into the production process. For example, the crushed particles can be directly injected into the granulator as seed material, or can be melted or dissolved again, mixed with a melt or solution, and directed to the granulator.

[0059] On-spec particles can be directed to a storage area or further processing steps such as coating. Undersized particles can be reintroduced into the granulator to be used as seed particles, or they can be mixed in the melt and directed to the granulator. In such systems, there is a means for transporting oversized particles from the granulator to a hopper. Such means for transport can include, for example, a conveyor belt, a bucket elevator, a product chute, or a pneumatic conveyor. The end of the conveyor belt is located above the hopper and feeds the oversized particles into the hopper. The hopper then cools the particles and distributes them to a crusher located below the hopper. A second means for transporting the solid particles receives the crushed particles from the crusher to the desired location in the plant. The second means for transport can be one or more of a conveyor belt or an elevator. Installing a cooling element in the hopper in such a system ensures that the overall space occupied by the system does not change and that the production process does not require any other modifications.

[0060] In one embodiment, the system including the granulator, the hopper, the crusher, and two means for transporting solid particles also includes a screening device. The screening device ensures that the size of the particles directed into the hopper does not exceed a certain size. This allows for better control over the flow characteristics of the solid particles fed into the hopper, allowing for the design of more efficient hoppers. One risk of installing cooling plate elements in the hopper is that the solid particles will not flow properly between the cooling elements.

[0061] In one embodiment, the system includes a screening device having a desired mesh size, and in addition, the distance between two cooling plate elements in the hopper or the distance between the cooling plate element and the wall of the hopper is 4 to 8 times, specifically 4 to 6 times, and more specifically 5 times, the mesh size of the screening device. When a system including a hopper according to the present disclosure also includes a screening device, it has been found that maintaining the distance between two cooling plate elements in the hopper or between the cooling plate element and the wall of the hopper provides a good cooling effect and does not affect the flow of particles in the buffer compartment.

[0062] In another aspect, the present disclosure relates to a method for operating a hopper according to the present disclosure, comprising the steps of: a) activating the cooling effect of a plurality of cooling plate elements; b) providing solid particles to a top end of the hopper, e.g., in a continuous or intermittent manner; and c) dispensing the cooled solid particles through an opening in a bottom end of the hopper, e.g., in a continuous or intermittent manner.

[0063] Activating the cooling effect of the cooling plate elements also means turning on the process responsible for extracting heat from the cooling plate elements. The exact nature of this step may depend on the nature of the cooling elements. For example, if the cooling elements are thermoelectric plates, activating the plates requires providing power to the cooling elements. If the cooling elements are cooled via a cooling liquid, activating the cooling effect may include directing the cooling liquid to the cooling elements via an inlet pipe.

[0064] When the cooling effect in the cooling element is activated, the solid particles may be directed toward the top end of the hopper. Before starting to dispense the particles, it may be preferable to wait until the solid particles reach a certain level within the buffer section of the hopper, defined as a desired volume or height extending from the vertical bottom end of the hopper. For example, it may be preferable to wait until the solid particles completely cover the cooling plate element before dispensing the solid particles from the hopper. In other words, it may be preferable to wait while dispensing particles from the hopper until the hopper is filled with particles to the extent that the solid particles completely cover the cooling element. Alternatively, the operator may wait until the solid particles reach a certain level in the buffer section of the hopper, for example, until 80%, 90%, or 95% of the volume of the buffer section is filled with solid particles, or until the solid particles cover multiple cooling plate elements, or until the solid particles reach a vertical height of at least 80% of the hopper's height from the bottom end.

[0065] Once the desired level of particles in the hopper is achieved, the opening in the bottom end can be opened to dispense the particles.

[0066] In another aspect, the present disclosure relates to a method for the production of solid particles, particularly sized solid particles, using a hopper according to the present disclosure, the method comprising: a) activating the cooling effect of a plurality of cooling plate elements of the hopper; b) providing solid particles to the top end of the hopper, e.g., in a continuous or intermittent manner; c) dispensing the cooled solid particles through an opening in the bottom end of the hopper, e.g., in a continuous or intermittent manner; d) dispensing the cooled solid particles from the hopper to a grinder to reduce the particle size of the solid particles; e) separating any resulting undersized solid particles from the mill and directing them to a granulator; The solid particles provided in b) are i) directing a melt, in particular a melt comprising one or more selected from the group consisting of urea, ammonium salts, nitrates, and / or mixtures thereof, into a granulator; ii) granulating the melt in a granulator, in particular in a fluidized bed granulator, thereby obtaining particles; iii) separating the resulting particles into fractions of on-spec solid particles, under-spec solid particles, and over-spec solid particles based on predetermined size ranges; iv) directing any resulting oversized solid particles into the hopper as the solid particles of step b.

[0067] The present method of producing solid particles provides solid particles of a desired predetermined size in an easier and more efficient manner compared to known methods of producing solid particles. Furthermore, any undersized solid particles obtained from the separation in step iii) can be directed to a granulator and reused in the process.

[0068] In another aspect, the present disclosure provides a method of operating a system according to the present disclosure, comprising: I) activating the cooling effect of a plurality of cooling plate elements of the hopper; II) directing a melt, in particular a melt comprising one or more selected from the group consisting of urea, ammonium salts, nitrates, and / or mixtures thereof, into a granulator; III) granulating the melt in a granulator, in particular in a fluidized bed granulator, thereby obtaining particles; IV) separating the resulting particles into fractions of on-spec solid particles, under-spec solid particles, and over-spec solid particles based on predetermined size ranges; V) directing any resulting oversized solid particles into the hopper; VI) providing any oversized solid particles to the top end of the hopper, e.g., in a continuous or intermittent manner; VII) dispensing the cooled solid particles through an opening in the bottom end of the hopper, e.g., in a continuous or intermittent manner; VIII) dispensing the cooled solid particles from the hopper to a grinder to reduce the particle size of the solid particles; IX) separating any resulting undersized solid particles from the mill and directing them to a granulator.

[0069] The method of operating the system provides solid particles of a desired predetermined size in an easier and more efficient manner compared to known methods of producing solid particles. Additionally, any undersized solid particles resulting from the separation in step IV) can be directed to a granulator and reused in the process.

[0070] In another aspect, the present disclosure relates to a method for producing solid particles in a granulator, particularly a fluidized bed granulator, using a hopper according to the present disclosure, the method comprising the steps of: a) directing a melt, particularly a melt comprising one or more selected from the group consisting of urea, ammonium salts, nitrates, and / or mixtures thereof, to the granulator; b) granulating the melt in the granulator, thereby obtaining on-specification solid particles, undersized solid particles, and oversized solid particles; c) activating the cooling effect of a plurality of cooling plate elements of the hopper according to the present disclosure; d) directing the oversized solid particles according to the present disclosure to the hopper; e) dispensing the cooled oversized solid particles from the hopper according to the present disclosure to a mill, thereby obtaining oversized solid particles and, optionally, on-size solid particles; and f) directing the undersized solid particles obtained from the mill in step e) to the granulator. Furthermore, any undersized solid particles obtained from the granulation in step b) can be returned to the granulator and reused in the process.

[0071] Considering the operation of a hopper or system or the methods disclosed above related to the production of solid particles, when transforming a melt or solution into solid particles in a granulator, it can be difficult to obtain only particles having the desired size or diameter. In most cases, granulators produce on-size particles, undersized particles, i.e., particles with diameters smaller than the required range, and oversized particles, i.e., particles with diameters larger than the required range. The desired particle size can be predetermined, and the particles obtained from the methods herein can be compared to that predetermined particle size. The production process can be optimized in different ways, for example, to obtain the maximum amount of on-size particles or the minimum amount of oversized particles. To reduce waste in the production process and increase the overall yield of the process, it is not desirable to simply discard the oversized particles. Instead, it is possible to crush the oversized particles into particles with much smaller diameters and reintroduce these particles into the production process. For example, crushed particles can be injected directly into the granulator as seed material, or can be melted or dissolved again, mixed with a melt or solution, and directed to the granulator. However, the particles obtained from the granulator are typically at very high temperatures, e.g., above 80°C, and it may be undesirable to grind the particles at such high temperatures due to the risk of clogging the grinder. The use of a hopper according to the present invention provides a very compact solution to this problem.

[0072] In the present system, method of operating the system, and method for producing solid particles, a means for transporting oversized particles from the granulator to a hopper is present. Such a means for transporting may include, for example, a conveyor belt, a bucket elevator, a product chute, or a pneumatic conveyor. The end of the conveyor belt is located above the hopper and supplies the oversized particles to the hopper. The hopper then cools and distributes the particles to a crusher located below the hopper. A second means for transporting the solid particles receives the crushed particles from the crusher to a desired location in the plant. The second means for transporting may be one or more of a conveyor belt or an elevator. Installing a cooling element in the hopper in such a system ensures that the overall space occupied by the system does not change and that the production process does not require any other modifications.

[0073] In one embodiment, the method herein comprises providing a cooling liquid to a cooling plate element, wherein the relative humidity of air in contact with the solid particles at a temperature equal to the temperature of the cooling liquid is lower than the critical relative humidity of the solid particles to be cooled.

[0074] In another aspect, the present disclosure relates to the use of a hopper according to the present disclosure for distributing solid particles to a grinder.

[0075] In another aspect, the present disclosure relates to the use of a hopper according to the present disclosure in the production of (sized) solid fertilizer particles.

[0076] In another aspect, the present disclosure provides a method for improving or modifying a hopper comprising a buffer compartment defined by a sidewall, a top end with an opening adapted to receive solid particles, and a bottom end with an opening adapted to dispense the solid particles from the buffer compartment, the method comprising: a) providing an assembly comprising a plurality of cooling plate elements fluidly connected to an inlet pipe for a cooling liquid and an outlet pipe for the cooling liquid, the plurality of cooling plate elements being parallel to one another and the inlet pipe and the outlet pipe being located on the same side of the cooling plate element; b) placing the assembly provided in step a) in the buffer section of the hopper so that the inlet and outlet pipes are above the cooling plate element; c) connecting the inlet and outlet pipes of the assembly to a coolant circuit.

[0077] An advantage of the hopper design according to the present disclosure is that a conventional hopper not equipped with any cooling element can be easily modified or retrofitted into a hopper suitable for cooling solid particles.

[0078] The assembly of cooling plate elements with inlet and outlet pipes for the cooling liquid can be an element produced by fluidly connecting the inlet and outlet pipes for the cooling liquid. The cooling plate elements are parallel to each other, and the inlet and outlet pipes are located on the same side of the cooling plate elements. When the assembly is mounted on the hopper, the inlet and outlet pipes need to be connected to the upward-facing side of the cooling elements.

[0079] The assembly is then placed in the buffer section of the hopper without any major modification of the hopper. The hopper does not need to be removed from the production line. The improved method only requires enough space above the hopper so that the assembly of the cooling plate element, inlet pipe, and outlet pipe can be inserted from above the hopper into the buffer section of the hopper.

[0080] This is of great interest as it provides an easy and inexpensive solution to the problem of high temperature granules being fed to the mill. An alternative solution would be to replace the hopper with a heat exchanger for the solid particles, but this would require even more work, removing the hopper, installing a new heat exchanger, and possibly modifying the device that feeds the particles to the new heat exchanger.

[0081] Minor modifications may need to be made to the hopper, particularly to connect the inlet and outlet pipes to a coolant circuit configured to deliver coolant to the inlet pipe and remove heated coolant from the outlet pipe.

[0082] FIG. 1 shows one embodiment of a hopper according to the present disclosure as viewed from one side. The hopper 1 comprises a top end 2, a bottom end 3, and a plurality of, for example, 30-40, cooling plates 4 arranged vertically and parallel to one another. The cooling plates 4 are made of stainless steel SS316L and are connected to an inlet pipe 5 for the cooling liquid and an outlet pipe 6 for the cooling liquid. To optimize the surface area of ​​the cooling plates, the sides of the cooling plates are essentially parallel to the corresponding sides of the hopper. The top end is approximately 3.8 m 2 and is partially open to receive particles. The bottom end is approximately 0.38 m 2 and is completely open, i.e. the opening at the bottom end is 0.38m 2 The cooling liquid is process water available in the plant. The water has a temperature of 37°C at the inlet pipe of the hopper. The height of the cooling plate 4 is 56% of the height of the hopper 1.

[0083] The hopper in Figure 1 is part of a granulation unit that includes a fluidized-bed granulator, a conveyor belt for transporting oversized granules produced in the granulator to the hopper, a crusher with an opening at the bottom end of the hopper located directly above the crusher, and a conveyor belt for transporting the crushed granules from the crusher to the inlet of the granulator. The screen, with a mesh size of 10 mm, is located between the outlet for oversized granules of the granulator and the conveyor belt for transporting the oversized granules to the hopper. The distance between the two cooling plates 4 in the hopper is about 50 mm. Granules containing, for example, urea have a temperature of 60-75°C when they arrive at the hopper and a temperature of 40-45°C when they are dispensed from the hopper into the grinder.

[0084] Figure 2 shows another view of the same embodiment as in Figure 1, i.e. after a 90° rotation around the vertical axis. The hopper comprises a number of cooling plates 4 that are essentially vertical and parallel to one another and connected to an inlet pipe 5. An outlet pipe 6 is located in the same horizontal plane as the inlet pipe 5.

Claims

1. a hopper comprising: a buffer compartment defined by a sidewall; a top end with an opening adapted to receive solid particles; and a bottom end with an opening adapted to dispense the solid particles from the buffer compartment; - the buffer section comprises a plurality of essentially vertically positioned cooling plate-like elements for cooling the solid particles in the buffer section, the hopper comprises an inlet and an outlet pipe for a cooling liquid, the plurality of cooling plate elements being fluidly connected to the inlet and outlet pipes, a hopper, wherein the inlet pipe and the outlet pipe are located in the buffer compartment above the plurality of cooling plate elements.

2. 2. The hopper according to claim 1, wherein the height of the cooling plate element corresponds to 30 to 80% of the height of the hopper, and the cooling plate element extends vertically from the bottom end to the top end of the hopper.

3. 3. The hopper of claim 1, wherein the plurality of cooling plate elements do not extend within a volume defined by a horizontal cross section at 80% of the height of the hopper and the top end of the hopper.

4. A hopper according to any one of claims 1 to 3, wherein the area of ​​the top end is 5 to 20 times greater than the area of ​​the opening at the bottom end.

5. The hopper according to any one of claims 1 to 4, wherein the inlet pipe and the outlet pipe are parallel and at the same height in the buffer section.

6. The hopper according to any one of claims 1 to 5, wherein the plurality of cooling plate elements are made of stainless steel.

7. The hopper according to any one of claims 1 to 6, wherein the hopper has a cooling capacity of 10 to 20°C at a flow rate of 10 to 15 t / h.

8. 8. A system comprising: a series of granulators, hoppers, and grinders, the hoppers being as defined in any one of claims 1 to 7 and configured to supply solid particles to the grinders; first means for transporting particles from the granulators to the hoppers; and second means for transporting solid particles from the grinders.

9. The system of claim 8 , further comprising a screening device for limiting the size of particles fed into the hopper.

10. A method for operating a hopper according to any one of claims 1 to 7, comprising the steps of: a) activating the cooling effect of the plurality of cooling plate elements; b) providing solid particles to the top end of the hopper; and c) dispensing the cooled solid particles through the opening in the bottom end of the hopper.

11. 11. The method of claim 10, wherein step a) comprises providing a cooling liquid to the cooling plate element, and the relative humidity of air in contact with the solid particles at a temperature equal to the temperature of the cooling liquid is lower than the critical relative humidity of the solid particles to be cooled.

12. 12. A method according to claim 10 or 11 for operating a hopper according to any one of claims 1 to 7 in a system for producing solid particles in a granulator, comprising: a) directing a melt to a granulator; b) granulating the melt in the granulator, thereby obtaining on-spec solid particles, under-spec solid particles, and over-spec solid particles; c) activating the cooling effect of the plurality of cooling plate elements; d) directing the oversized solid particles into a hopper according to any one of claims 1 to 7; e) dispensing the cooled oversized solid particles from the hopper to a grinder, thereby obtaining undersized solid particles.

13. A method for the production of solid particles using a hopper according to any one of claims 1 to 7, comprising the steps of: a) activating the cooling effect of the plurality of cooling plate elements of the hopper; b) providing solid particles to the top end of the hopper in a continuous or intermittent manner; c) dispensing cooled solid particles through the opening in the bottom end of the hopper in a continuous or intermittent manner; d) dispensing the cooled solid particles from the hopper to a grinder to reduce the particle size of the solid particles; e) separating any resulting undersized solid particles from said grinder and directing them to a granulator; The solid particles provided in b) are i) directing the melt to a granulator; ii) granulating the melt in the granulator, thereby obtaining particles; iii) separating the resulting particles into fractions of on-spec solid particles, undersized solid particles, and oversized solid particles based on predetermined size ranges; iv) directing any resulting oversized solid particles into said hopper as said solid particles of step b.

14. A method as described in claim 12 or 13, wherein the melt comprises one or more selected from the group consisting of urea, ammonium salts, nitrates, and / or mixtures thereof.

15. 1. A method for modifying a hopper comprising: a buffer compartment defined by a sidewall; a top end with an opening adapted to receive solid particles; and a bottom end with an opening adapted to dispense the solid particles from the buffer compartment, comprising: a) providing an assembly comprising a plurality of cooling plate elements fluidly connected to an inlet pipe for a cooling liquid and an outlet pipe for the cooling liquid, the plurality of cooling plate elements being parallel to one another and the inlet pipe and the outlet pipe being located on the same side of the cooling plate element; b) placing the assembly provided in step a) in the buffer section of the hopper such that the inlet pipe and the outlet pipe are above the cooling plate element; c) connecting the inlet and outlet pipes of the assembly to a coolant circuit.

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