Method for preparing a feed from waste materials

Abstract

The present invention relates to a method for producing a feed body capable of providing free-flowing granules and / or powders suitable for combustion in one or more burners in an industrial furnace, the method comprising the following steps: (i) providing waste material comprising more than 40% of one or more thermoplastic materials based on the total dry weight of the waste and more than 30% of one or more cellulosic materials based on the total dry weight of the waste; (ii) processing the waste material in an extruder, wherein the extruder is equipped with a transfer element, a kneading element and a heating element so that the waste material is mixed and the thermoplastic material melts; (iii) the material reaches a temperature of about 110-200°C for more than about 2 seconds before cooling; and (iv) pressing the processed waste material through a die having a hole of 2-200 mm to provide a feed body with a thickness of about 2-200 mm and a length of about 2-500 mm.

Description

Technical Field

[0001] The present invention relates to a method for preparing a feedstock from waste materials and its use. The feedstock can be used as an alternative fuel, for reactions from waste to chemicals, a reducing agent in steel manufacturing, and the like.

Background Art

[0002] Burning an industrial furnace is a process used for power generation and / or heat generation, for example, through the generation and use of steam, hot water, high-temperature gas, heat transfer oil, or direct radiation / convection heating. The furnace for power generation is the most demanding and efficient furnace currently in use. Modern industrial furnaces that require high process stability include furnaces for steam generation in power plants, blast furnaces for steel production, cement kilns, and lime kilns.

[0003] In these sectors, furnaces are generally supplied with powdered (fine) coal, oil, or gas (as the main fuel). The fuel is generally supplied through several burners, lances, or tuyeres. When the furnace is used for power generation, the heat of combustion is used to generate steam used to drive a turbine.

[0004] The amount of fine coal that can be injected depends on the quality of coal and coke, the shape of the furnace, and operating practices. Furthermore, fine coal has a low bulk density and poor storage characteristics. Therefore, coal is generally pulverized immediately before use. The main drawback of using fine coal is that it is from a non-renewable source, and thus the net CO2 emissions per unit of heat released during combustion are high.

[0005] To reduce the burden of net CO2 emissions, alternative or secondary fuels are also used to some extent. Such alternative fuels need to achieve certain characteristics in order to enable seamless processing using known processes. Furthermore, alternative fuels need to be able to be injected into the flame, and therefore, they need to exhibit good combustion characteristics such as rapid ignition and short-duration complete combustion, and to undergo complete combustion in the high-temperature furnace space.

[0006] Alternative fuels proposed for use in high-end industrial furnaces include plastic pellets, plastic / biomass mixed pellets, wood pellets, and sewage sludge pellets.

[0007] One advantage of using only plastic waste is that, generally, plastic waste has low thermal conductivity and high energy content. A disadvantage of using only plastic waste is that such mixtures, for example, derived from household waste, urban waste, or municipal waste, are relatively valuable products that can be used to make (recycled) plastic products. A further disadvantage is that, despite the high calorific value, it is difficult to process waste plastic pellets in a way that yields a particle size distribution suitable for injection into and combustion within such furnaces. Milling causes a temperature rise and rubbery behavior of the plastic, to the extent that cryogenic milling is required. However, cryogenic milling is expensive. Furthermore, handling such materials is typically considered problematic due to poor flow behavior.

[0008] The feeding of waste-derived alternative fuels into furnaces can vary depending on the nature of the waste material and the type of furnace supplied. Several methods exist for directly using waste-derived alternative fuels in furnace technology. Such techniques include direct use by injecting powdered alternative fuel through or at the level of the lance, co-pulverization of pellets and coal as described in WO2015 / 155193, or mixing coal and powdered alternative fuel before injecting the mixture into the furnace. In general, waste-derived alternative fuel products that have not been adequately processed cannot be supplied to burner sections through existing equipment used for fossil fuels.

[0009] Preferably, such waste-derived alternative fuels are made from selected non-recyclable waste portions of household waste, urban waste, or municipal waste. However, such waste portions (also called "fluff") often result in fuels with unsatisfactory properties and are usually not suitable for use with existing dosing systems and burners. For example, the fuel may form lumps or have large variations in particle size distribution, which can lead to inefficient or incomplete combustion, poor handling behavior, and blockage of the feeding equipment. These properties impose limitations on the operation of industrial furnaces. Therefore, these alternative fuels are practically used only to partially replace fossil fuels in high-end furnaces. In practice, the amount of alternative fuel is generally less than 50%, and in most cases, less than 30% of powdered coal in high-end furnaces for power generation, for example. Powdered coal suppresses the performance variability of waste-derived alternative fuels. To increase or enable the use of alternative fuels, the properties of powdered fuels need to be improved.

[0010] US2010 / 116181 describes the pelletization of plastic / cellulose-based materials with a relatively low plastic content (less than 40% by weight), which, according to WO2008 / 107042, can be milled into mostly particles smaller than 2 mm and used as an alternative fuel in combination with powdered coal. Alternative fuels with a low plastic content have relatively low combustion values, which is disadvantageous when such fuels are required to completely replace coal. In addition, such milled pellets also have poor flow properties, meaning their transport is impaired.

[0011] Therefore, there is a need in the field for a process that can produce waste-derived alternative fuels so that the furnaces can completely replace the amount of fossil fuels used, preferably using existing equipment used to supply (fine) fossil fuels, so that the waste-derived alternative fuels are suitable for supplying to industrial furnaces. The inclusion of multiple thermoplastic materials, not to mention multiple cellulosic materials, generally leads to increased heterogeneity of the material flux. Therefore, there is also a need for a process that produces alternative fuels containing multiple thermoplastic materials and multiple cellulosic materials, preferably in a single system, without adversely affecting high density, handling and flow behavior, and combustion characteristics.

[0012] US6635093 describes a method for producing pellets that can be used to partially replace fossil fuels in a furnace after milling. The process and products are commercially used. Empirical evidence shows that milling, especially when milled to small particle sizes, results in a powdery product with inferior flow properties. Therefore, the powder is generally fed into the furnace through a separate dosing mechanism to avoid these flow properties.

[0013] WO2020 / 127473 describes a process for producing pellets that can be ground into particulate material, enabling 100% combustion of high-end furnaces with alternative fuels. This process requires two-stage pelletization to achieve improved pellet properties. Although the two-stage pelletization step brings about improvements in pellet properties, the milling properties, and thus the combustion properties, can be further improved. In particular, good flow properties of the milled powder can be achieved, although the milled powder is relatively coarse, with 25-70% by weight of the powder having a diameter of 2-3.15 mm.

[0014] WO2022 / 248626 is an improvement on WO2020 / 127473, and by a modified process for two-stage pelletization, the powder obtained by grinding the pellets in a hammer mill passing through a 3 mm screen is capable of producing a powder with good flow properties in which more than 60% by weight of the powder is smaller than 2 mm.

[0015] Pelleted waste, which can be milled into a highly fluid powder, can be used to replace reducing agents in fossil fuels, waste-to-chemical processes, steelmaking, and other processes.

[0016] A process for generating feedstock from waste materials is desired, and if pulverized, handling and flow properties are improved. A fine powder product with high fluidity offers further advantages, such as enabling reliable downstream processing in furnaces (e.g., improved combustion properties), steel manufacturing (as a reducing agent), and waste-to-chemical processes. [Prior art documents] [Patent Documents]

[0017] [Patent Document 1] International Publication No. 2015 / 155193 [Patent Document 2] U.S. Patent Application Publication No. 2010 / 116181 [Patent Document 3] International Publication No. 2008 / 107042 [Patent Document 4] U.S. Patent No. 6635093 [Patent Document 5] International Publication No. 2020 / 127473 [Patent Document 6] International Publication No. 2022 / 248626 [Overview of the project]

[0018] The object of the present invention is to provide a feed comprising a mixture of a thermoplastic material and a cellulosic material, which can be used after milling or disintegration to reliably replace fossil fuels, particularly in high-end industrial furnaces used in state-of-the-art equipment. Preferably, the feed can be used to replace 70% or more of the energy requirements of an industrial furnace, preferably more than 90%, and more preferably more than 95% of the energy requirements of the furnace, of fossil fuels. The feed can be used to completely replace fossil fuels in an industrial furnace.

[0019] Fuel quality significantly impacts the successful replacement of fossil fuels. However, operational implementations that depend on production characteristics are also crucial for seamlessly integrating alternative fuels into existing industrial furnaces.

[0020] In a first aspect, the present invention relates to a method for producing a feed capable of providing free-flowing granules and / or powders suitable for combustion in one or more burners in an industrial furnace, wherein the method comprises the following steps: i. A step of optionally providing waste material in the form of pellets, comprising one or more thermoplastic materials making up more than 40% based on the total dry weight of the waste, and one or more cellulosic materials making up more than 30% based on the total dry weight of the waste. ii. A step of processing waste material in an extruder, wherein the extruder is equipped with a transfer element, a kneading element, and a heating element so that the waste material is mixed and a thermoplastic material is melted. iii. A step in which the material reaches a temperature of about 120 to 200 °C for at least about 2 seconds before being cooled, iv. A step of pressing the processed waste material through a die having holes of 2 to 200 mm, v. A step of providing a supply body having a thickness of about 2 to 200 mm and a length of about 2 to 500 mm, relating to a method.

[0021] Several documents describe an extrusion process for treating plastic waste materials. However, using an extruder with the parameters described herein using a mixture of plastic and cellulosic materials as the source material results in a supply body having very effective powdering characteristics, which also unexpectedly results in fine particle size and good flowability characteristics.

[0022] The supply body can have any cross-sectional shape. When the supply body has a non-circular cross-section, the thickness relates to the main cross-sectional distance. When the cross-section of the supply body is circular, the thickness is the diameter. When the supply body has an irregular shape, the diameter of such a body refers to the maximum distance within the particle.

[0023] Document GB2237028A discloses a solid fuel comprising a mixture of plastics derived from municipal waste and wooden materials together with an inert material. The municipal plastic waste is shredded, mixed with the wooden material, and subjected to an extrusion process, whereby continuous rods and bars having a diameter of 5 to 10 cm are produced and can subsequently be cut to the desired length. The rods are used as such in a stove.

[0024] Document EP1428642A1 discloses a method for compression molding waste plastics through a molding machine having extrusion holes with a diameter of 5 to 80 mm. In this process, only plastics are utilized and the molding is carried out at 110 °C or 120 °C.

[0025] Document CA2658030A1 discloses the production of solid fuels by solidifying plastics, waste paper, and food waste. Water is added to increase the moisture content to 15% by weight or more, and the mixture is then subjected to blending, compression, and extrusion within three turns and extruded from a molding nozzle. The moisture content of the material to be processed is approximately 15% by weight in order to control the temperature to remain within the temperature range of 100°C to 140°C.

[0026] Document RU2729638C1 discloses a method for processing municipal solid waste into waste-derived fuel by thermoplastic extrusion. Selected waste is dried to a moisture content of approximately 5% to 15%, and then crushed into fractions of 5 to 50 mm. The lumps are then heated to a temperature of 180 to 250°C to decompose the PVC, and subjected to thermoplastic extrusion to obtain pellets or briquettes to be used as fuel, etc. [Modes for carrying out the invention]

[0027] In a first aspect, the present invention relates to a method for producing a feed capable of providing free-flowing granules and / or powders suitable for combustion in one or more burners in an industrial furnace, wherein the method comprises the following steps: i. A step of optionally providing waste material in the form of pellets, comprising one or more thermoplastic materials making up more than 40% based on the total dry weight of the waste, and one or more cellulosic materials making up more than 30% based on the total dry weight of the waste. Preferably, the step of providing the material to be fed into the extruder while preheating it, ii. A step of processing waste material in an extruder, wherein the extruder is equipped with a transfer element, a kneading element, and a heating element so that the waste material is mixed and a thermoplastic material is melted. iii. The step of bringing the material to a temperature of approximately 120-200°C for at least approximately 2 seconds before it cools down. iv. A step of pressing the processed waste material through a die having a hole of 2 to 200 mm, v. A method comprising the step of providing a supply body having a thickness of approximately 2 to 200 mm and a length of approximately 2 to 500 mm.

[0028] The process of the present invention produces a feed with high homogeneity. By providing a feed with high homogeneity, the feed can be ground into homogeneous particles (granules) or powder without the problem of having threads or other relatively long plastic film particles, and without causing problems when transferring the powder. Homogeneity relates to the continuous phase within the particles, i.e., the molten plastic phase.

[0029] The waste material can be supplied to the extruder in any shape or form. The advantage of using an extruder is that the dependence on the main composition and form has less impact on the feed quality than conventional pelletizing methods. In addition, moisture content is less critical to the final feed composition. Trials have shown substantial cost savings in energy requirements and maintenance compared to die pressing.

[0030] It should be noted that the extruder forms a cake that is shaped into strands having a diameter or intersection of feed bodies. The shape of the feed body can be freely selected by shaping the cake into a chosen form, which is determined by the shape of the extruder die.

[0031] In one embodiment, the strands are cut directly into a feed body by a die. The feed body is then collected, for example, on a conveyor belt and (further) cooled, for example, with forced air.

[0032] In another embodiment, the strand is brought onto a conveyor belt or the like and cooled, for example, with air, to a temperature that allows the strand to be split and / or cut into pieces. The resulting feed generally has a thickness of about 2 to 200 mm and a length of about 2 to 500 mm.

[0033] Therefore, a feeder with high homogeneity allows for the production of relatively homogeneous granules and / or powders that provide good flow characteristics. That is, for example, if the powder is introduced into the furnace through multiple smaller tubes, the powder will not clump together and will not clog the tubes, so that the alternative fuel can be accurately administered using existing feed systems and burners.

[0034] Alternatively, it can be used directly in the furnace without the need to grind the small feed into powder. Suitable applications include cement kilns, lime kilns, and blast furnaces.

[0035] In this invention, the temperature of at least a portion of the extruder body is preferably about 110 to 240°C.

[0036] A temperature range of approximately 110–240°C, preferably 120–200°C, within the extruder ensures that the temperature is low enough to prevent substantial devolatilization or combustion of the waste material components, and high enough to provide sufficient ductility of the thermoplastic material during mixing. If the temperature is too low, a feed body will form, but it will lack the homogeneity necessary for efficient use in industrial furnaces, such as poor flow properties after grinding. However, some exhaust may be useful in improving the extrusion process. Preferably, the temperature of the mixture within the extruder is 140–190°C, more preferably 150–190°C.

[0037] The (average) residence time in the extruder is generally about 10 seconds or more, preferably about 20 seconds or more, more preferably about 0.5 minutes or more, for example, 1 minute or more. Generally, the residence time is 20 minutes or less, preferably 10 minutes or less, and even more preferably about 5 minutes or less. The upper limit of the residence time is determined mainly for economic reasons. The residence time is greatly influenced by the feed rate, and for economic reasons, a higher feed rate is preferred. In the present invention, it is important to sufficiently melt the thermoplastic material and allow sufficient time in the extruder to obtain a feed having a substantially homogeneous continuous phase.

[0038] The feed material according to the present invention typically has a nearly homogeneous dark color. In contrast, pellets produced by the prior art are lighter in color and generally appear heterogeneous when viewed from the outside. Milling the product from the prior art reveals very large differences in the particle size distribution of both, as well as in the particle flow behavior.

[0039] In a preferred embodiment, at least a portion of the heating elements of the extruder are located within the die of the extruder.

[0040] In embodiments of the present invention, the extruder body is preferably heated to achieve effective melting and mixing within the extruder. Forced mixing of the mass releases heat into the extruder, and the feed is also preferably heated. Generally, the average temperature of the extruder body is about 140 to 240°C, preferably about 150 to 220°C, more preferably about 160 to 220°C, and even more preferably about 170 to 220°C.

[0041] The average heating temperature is defined as the average temperature of the extruder body in the region actively heated by one or more heating elements located within the extruder body. Heating can also occur indirectly. At least a portion of the heating is caused by the molding of the material by the extruder.

[0042] In a preferred embodiment, the extruder body is divided into at least two sections, with the first upstream section heated to a higher temperature than the second downstream section, or vice versa. Heating the separate sections of the extruder body allows for improved control over the melting properties of the waste material, so that the material is efficiently mixed and melted in a homogeneous manner without burning the waste material. The gradual increase in temperature creates a homogeneous cake, which can be shaped to a desired form at the end of the extruder. In addition, the presence of a second section in the downstream region of the extruder increases the viscosity of the partially mixed and melted waste material, leading to an increase in pressure at the die. By increasing the pressure, the density of the feed formed from the waste material is improved.

[0043] Extruders may be equipped with vacuum evacuation to remove vapors and other volatile gaseous compounds. Applying vacuum can improve the homogeneity of the continuous phase and generally improve the characteristics of the feed material. Generally, the vacuum evacuation is located in the front half of the extruder, such as at a position 1 / 5, 1 / 4, or 1 / 3 of the way along the extruder length, as viewed from the feed side of the extruder.

[0044] In preferred embodiments, extrusion is carried out for about 10 seconds to 10 minutes, more preferably about 40 seconds to 8 minutes, and even more preferably about 1 minute to 6 minutes. Such processing times are advantageous in that they result in a homogeneous feed having a sufficiently molten plastic material, allowing for proper mixing of the cellulosic material and the thermoplastic material, and as a result, the fibers achieve improved properties, particularly with respect to pulverability and the flow properties of the powder achieved after pulverization. Insufficient heating and / or mixing results in insufficient melting of the material and, therefore, insufficient flow properties after pulverization.

[0045] In a preferred embodiment, the waste material comprises at least one of the following in an amount of 40–70% by weight, based on the total dry weight of the feed: one or more thermoplastic materials, and at least one of the following in an amount of about 30–50% by weight, based on the total dry weight of the feed: one or more cellulosic materials. By mixing the cellulosic materials with the plastic, the fibers of the cellulosic materials achieve improved properties with respect to pulverability.

[0046] In the embodiment, the waste has a particle size distribution in which more than 80% are larger than 5 mm and preferably more than 20% are larger than 20 mm, and the waste has a particle size distribution in which more than 95% are smaller than 60 mm and preferably more than 90% are smaller than 40 mm.

[0047] In an alternative embodiment, the entire pelletized waste may be included as waste material as input to a method for producing a feedstock. When the waste is provided in the form of pelletized waste, such pellets may have a thickness of about 3 to 40 mm, preferably about 5 to 20 mm, and more preferably about 6 to 10 mm. The thickness is the average thickness over the entire length of the pellet and is defined by the main distance of the cross-section of the pellet. Such pellets may be produced using the above-mentioned waste material by a process known in the art, such as, for example, US6635093.

[0048] In this embodiment, the waste has a moisture content of less than about 15% by weight, preferably less than about 10% by weight, and more preferably less than 8% by weight. Providing waste with a low moisture content reduces gas generation during extrusion.

[0049] The waste material, whether in the form of fluff or pellets, can be used as is or preheated before being fed into the extruder. In one embodiment, the feed is preferably preheated before being fed into the extruder. Heating is preferably carried out with heated air or oxygen-deficient air. When the waste material is heated, it is heated to a temperature below 180°C, preferably below 150°C, to prevent (chemical) decomposition of the waste components. More preferably, the waste is heated to a temperature of about 40°C to 140°C, for example, 50°C to 90°C.

[0050] The feed produced using the method of the present invention may have shapes other than the usual cylindrical shape, such as squares, triangles, rectangles, or semicircles.

[0051] In the embodiment, the feeder has a length of 3 to 400 mm, preferably 3 to 200 mm, more preferably 4 to 60 mm, and even more preferably 5 to 30 mm. Such a feeder can be easily cooled and is also suitable for handling and transport.

[0052] The thickness and length of the feedstock can define a length ratio of about 0.5 or more, preferably about 1 or more, and more preferably about 2 to 10. The length ratio (or aspect ratio) of the feedstock is determined as the length of the feedstock divided by its thickness or diameter. For example, a feedstock with a length of 32 mm and a diameter of 8 mm has a length ratio of 4. If the length and / or thickness of the feedstock are not constant, the average value is used to determine the length ratio. Generally, the length ratio is about 10 or less.

[0053] In a preferred embodiment, the temperature of the feed material at the die outlet is about 100 to 200°C, preferably about 120 to 180°C. When using a heated or uncooled die, the temperature may be about 120 to 210°C, more preferably about 130 to 200°C. Such temperatures exhibit sufficient melting behavior within the extruder. When a cooled die is used, the temperature may be lower, for example, 40 to 140°C, preferably 60 to 110°C. Such temperatures can improve the cutting of the feed material directly outside the die.

[0054] In a preferred embodiment, an uncooled or unheated die is used.

[0055] In the embodiment, the die temperature is about 140 to 250°C, preferably about 140 to 200°C. At such temperatures, the molded material flows relatively easily through the die, and the pressure accumulated in the extruder is relatively limited. In an alternative preferred embodiment, the die includes a cooled die, which has a temperature of about 0 to 120°C, preferably about 10 to 100°C, more preferably about 15 to 80°C, and even more preferably about 20 to 70°C. The cooled die reduces the temperature of the feed material, which in turn can be cut more easily directly outside the die.

[0056] In a preferred embodiment, the method further includes the step of cooling the feed to a temperature of about 50°C or lower, preferably about 40°C or lower, and more preferably about 30°C or lower. Cooling can be achieved by natural or forced cooling, preferably using air. The strands of material exiting the die can be taken up by a conveyor belt or the like and cooled. After cooling, the strands are hard and brittle enough to be coarsely ground, cut, or crushed into granules or pellets to achieve the feed of the present invention.

[0057] In a preferred embodiment, the feed body has a Kahl hardness of more than 22 kgf, preferably more than 30 kgf, and more preferably more than 35 kgf. In a preferred embodiment, the Kahl hardness of an 8 mm diameter feed body is about 60 kgf or less, but more than 35 kgf, preferably 40 kgf or more.

[0058] The feed material preferably has a bulk density of more than 250 kg / m³, more preferably more than 300 kg / m³, and more preferably about 350 kg / m³ or more. Generally, the density is less than about 500 kg / m³, for example, less than 450 kg / m³. The bulk density (tap) of the feed material is preferably about 350 kg / m³ to 450 kg / m³.

[0059] In this embodiment, the calorific value (LCV) of the feed is approximately 19–28 GJ / ton. This reflects the composition of the feed containing both plastic and bio-based (cellulose-type) materials.

[0060] In the embodiment, the hydrogen content of the feed is in the range of 7-8 w% of the dry weight of the feed. In the embodiment, the oxygen content of the feed is in the range of 20-30 w% of the dry weight of the feed.

[0061] According to aspects of the present invention, a feed is provided which can be obtained by any of the methods discussed above herein, preferably obtained by any of the methods discussed above herein.

[0062] According to an aspect of the present invention, a powder is provided which can be obtained by milling the feed material of the present invention, the powder preferably obtained by milling the feed material according to the present invention.

[0063] According to an aspect of the present invention, a method for producing powder is provided, comprising the steps of: providing a feed body according to the present invention; and milling the feed body in a mill to produce a powdery feed in the form of particles.

[0064] In the embodiments, the mill is one or more of a hammer mill, jet mill, roller mill, or ball mill. Preferably, the mill is a hammer mill. Hammer mills generally have size-limited screens such as 3 mm screens, 5, 6, or 8 mm screens. When milling pellets made from waste, it has been found to be very difficult to produce such pellets in a way that yields powder with good flow properties using a minimum screen of 3 mm. The present invention makes it possible to obtain a feed that can be milled in a hammer mill passing through a 3 mm screen, thereby yielding powder with good flow properties.

[0065] The feed material can be milled in a hammer mill with a screen other than 3 mm, and with larger screens such as 5 mm, 6 mm, or 8 mm, somewhat larger particles can be obtained, and the powder will have very good flow characteristics. Larger screen diameters allow for greater throughput through the mill and / or less energy input.

[0066] In one embodiment, the feed material is milled in a hammer mill equipped with a 3 mm screen to achieve a particle size such that more than 95% by weight of the particles are smaller than 3.15 mm and more than 80% are smaller than 2 mm. This milled material still has good flow properties. In a preferred embodiment, the feed material is milled in a hammer mill equipped with a 3 mm screen to have a particle size distribution such that more than about 85% are smaller than 2 mm, and preferably more than 90% are smaller than 2 mm.

[0067] In a preferred embodiment, the powdered product obtained by grinding the feed material in a hammer mill through a 3 mm screen has a bulk density of more than 180 kg / m³, preferably more than 200 kg / m³. Generally, the bulk density of the powder is about 400 kg / m³ or less, for example, about 350 kg / m³ or less. Preferably, the powder has a bulk density of about 200 to about 300 kg / m³.

[0068] Powder from the milled feed can be analyzed for particle size distribution according to the methods of DIN18123:2011-04 and DIN-EN15149-1&-2:2011-01. Generally, sieve fractions passing through sieves of 0.5 mm, 1 mm, 2 mm, 3.15 mm, and over 5 mm have been reported.

[0069] Flow properties are not easy to measure. However, a practical method is as follows: Flow properties were measured by sieving the milled product through a 2 mm sieve manually (without using forced air to pass through the sieve), and determining whether the product remaining on the sieve consisted of homogeneous particles or tangled balls. Regardless of this test, milling pellets produced according to different processes generally results in a powder where fibrous material is visible, which causes a deterioration in flow properties.

[0070] In another embodiment, the feed is cut, crushed, or coarsely ground to supply granules. Such granules may have an average length of 1 to 5 mm, where the length is the maximum dimension of the granules. Such granules may contain powdery products, preferably in an amount of about 10% by weight or less (without degrading the flow properties). The process for providing the granular material includes the steps of providing the feed according to the present invention to a granulator, crusher, cutter, etc., and reducing the diameter of the feed to granules having a diameter such that more than 90% is greater than 0.5 mm, more than 90% is less than 10 mm, and preferably has an average diameter of 1 to 5 mm.

[0071] According to aspects of the present invention, a process for burning an industrial furnace is provided, comprising the steps of: providing a feed body according to the present invention; grinding the feed body in a mill to produce a powder fuel in the form of particles, preferably achieving a particle size such that more than 90% by weight of the particles have a particle size smaller than 3.15 mm, and more preferably more than 40% have a particle size smaller than 2 mm; and supplying the powder fuel to the flame or burner of the furnace. Any amount of alternative fuel may be used in the furnace, for example, 5% or more of the energy requirement, or 10% or more. In a preferred embodiment, the fuel is used in an amount that provides more than 50% of the energy requirement of the furnace, preferably more than 70% of the energy requirement of the furnace, and more preferably more than 80% of the energy requirement of the furnace.

[0072] In preferred embodiments, particularly for fine fuel-fired boilers, the preferred particle size is such that more than 90% have a particle size of 2 mm or less, and about 50% or more have a particle size of 1 mm or less.

[0073] According to an aspect of the present invention, the use of the feed material according to the present invention as fuel for an industrial furnace is provided. In the embodiment, the feed material is used after being crushed into particles, preferably so that more than 80%, more than 90% by weight of the particles have a particle size smaller than 3.15 mm, preferably more than 40% have a particle size smaller than 2 mm, and more than 60% have a particle size smaller than 2 mm.

[0074] In another preferred embodiment, the particle size is such that more than 90% have a particle size of 2 mm or less, and about 50% or more have a particle size of 1 mm or less.

[0075] In another or additional embodiment, the feed is used without being ground into particles. Such feed is generally relatively small, preferably having a diameter of 2–8 mm, more preferably 3–6 mm. The length is preferably about the same as the diameter, or slightly larger, up to about twice the diameter.

[0076] In another embodiment, as described above, the fuel is optionally used as granules in which powder is present.

[0077] In one embodiment, the industrial furnace is used in a process for power generation. In a preferred embodiment, the industrial furnace is used in a lime furnace, a cement furnace, or a steel manufacturing furnace.

[0078] The feed, granules, and / or powders can also be used in other processes that utilize a recycling stream, such as roasting or waste-to-chemical processes. [Examples]

[0079] Examples 1-3, and comparative experiments A and B The series of tests were conducted using separated municipal waste containing approximately 45-60% plastic, 30-45% biomass, 5-15% other materials, and 5% moisture.

[0080] Four tests were conducted. These tests were comparative experiments A and B, and examples 1-3. Examples 1 and 2 used pellets described in WO2020 / 127473 as the feed for the extruder, while comparative experiments A and B, and example 3, used the fluff directly.

[0081] Extrusion was carried out using a KM (Example 1) or DEX500 extruder (Examples 2 and 3) having a heating system in the extruder body and die. The DEX500 device has a production capacity of approximately 4-5 Tn / hour. The die has an opening with a diameter of 8 mm. The die can be heated to a maximum of 280°C, and the extruder body can be heated to a maximum of 250°C. The electricity consumption of the extruder was approximately 40-50 kWh / Tn. The extruder has a maximum mechanical output of 200 kW at 1500 rpm and a nominal speed of 23 rpm. The extruder was used for 0.45 Tn / m 3 A feedstock with a density of 5.8 Tn / hour was used with a production capacity of 38.63 kWh / Tn. Therefore, approximately 0.1 Tn / m 3For a fluff with this density, this corresponds to a production rate of 1.29 Tn / hour.

[0082] The extrusion step was performed through a die with an 8 mm hole. The die thickness was approximately 5 cm. The residence time was approximately 2 minutes. In these experiments, the feed temperature at the die outlet was approximately 130°C. The temperature of the extruder body (in front of the die) was approximately 170°C during these tests.

[0083] Comparative experiments A and B were carried out by two-stage pelletization as described in Example 3 of WO2020 / 127473, with A being milled to pass through a 3 mm screen and B being milled to pass through a 6 mm screen.

[0084] The feed materials of Examples 1-3 were milled using a hammer mill with a flow rate of 108 m / s and a 3 mm screen. The powder from the milled feed materials was analyzed for particle size distribution according to the methods of DIN18123:2011-04 and DIN-EN15149-1&-2:2011-01. The results reported in the table below were obtained for sieve fractions passing through 0.5 mm, 1 mm, 2 mm, 3.15 mm, and over 5 mm. The flow characteristics were measured by sieving the milled product through a 2 mm sieve manually (without using forced air to pass through the sieve) and determining whether the product remaining on the sieve consisted of homogeneous particles or tangled balls. [Table 1]

[0085] As shown in the table above, the powder fraction is superior to comparative experiments A and B because it is milled to a smaller particle size while maintaining good flow characteristics. The product according to the present invention can be supplied to industrial furnaces without agglomeration and without impairing combustion characteristics.

[0086] The products of Examples 1-3 had the following characteristics: - Kahl hardness of 8mm pellets: 40-60kgf - Density of the supply material: 350-450 kg / m³ - Powder density: 200-300 kg / m³ Examples 4-6 and Comparative Experiments C-E

[0087] Further tests were conducted as follows: Waste material was milled and sieved through a 30 mm screen. This waste contained approximately 50 wt% plastic and approximately 40 wt% cellulose waste with a moisture content of 4%, and was extruded, where the die outlet temperature was measured to be 150-170°C. The product obtained after extrusion (8 mm in diameter, approximately 15-20 mm in length) was milled in a hammer mill using three different sieves, 3, 6, and 8 mm. The powder properties were compared to milled pellets produced according to US6635093. Particle size distribution and flow properties were measured. Flow properties were measured by sieving the milled product through a 2 mm sieve manually (without using forced air to pass through the sieve), and determining whether the product remaining on the sieve consisted of homogeneous particles or tangled balls.

[0088] The results are as follows: [Table 2]

[0089] Examples 7-10 Further tests were performed in an extruder. Examples 7 and 9 were performed using waste material (fluff) as the feed source, and Examples 8 and 10 were performed using standard pre-pelletized Subcoal® material (such material is available from N&P, Netherlands and produced according to US6635093). The material was preheated to 110-130°C with hot air just before entering the extruder, while the extruder was heated to 150-160°C. The die temperature was maintained at 170-190°C.

[0090] As shown in the table below, material strands were fabricated with diameters of 16 mm and 8 mm. The temperature of the strand material at the die exit was measured to be 150–170°C. The results show that the 16 mm diameter material has the advantage of higher throughput while still achieving very good properties.

[0091] The strands were brought onto a conveyor belt, cooled by an airflow to below approximately 80°C, preferably below approximately 40°C, and crushed in a mill to obtain pelletized or granulated material having a length of 2 to 40 mm. [Table 3]

[0092] The product was milled in a hammer mill through a 5mm screen. Milling through a larger screen offers the advantages of higher throughput and / or lower energy input compared to using a 3mm screen. [Table 4]

[0093] The present invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those skilled in the art.

[0094] In addition to the foregoing, further modifications may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Therefore, while specific embodiments are described, these are merely examples and do not limit the scope of the invention.

Claims

1. A method for producing a feed capable of providing free-flowing granules and / or powders suitable for combustion in one or more burners in an industrial furnace, wherein the method comprises the following steps: i. A step of providing waste material comprising one or more thermoplastic materials making up more than 40% based on the total dry weight of the waste, and one or more cellulosic materials making up more than 30% based on the total dry weight of the waste. ii. A step of processing the waste material in an extruder, wherein the extruder is equipped with a transfer element, a kneading element, and a heating element so that the waste material is mixed and a thermoplastic material is melted. iii. The step of the material reaching a temperature of approximately 120-200°C for more than approximately 2 seconds before it is cooled. iv. A step of pressing the processed waste material through a die having a hole of 2 to 200 mm, v. A method comprising the step of providing a supply body having a thickness of approximately 2 to 200 mm and a length of approximately 2 to 500 mm.

2. The method according to claim 1, wherein the waste has a particle size distribution in which more than 80% is larger than 5 mm and preferably more than 20% is larger than 20 mm, and more than 95% is smaller than 60 mm and preferably more than 90% is smaller than 40 mm.

3. The method according to claim 1 or 2, wherein the waste material is pelletized before being supplied to the extruder.

4. The method according to any one of claims 1 to 3, wherein the waste material is preferably heated to a temperature of about 150°C or lower before processing the material in the extruder.

5. The method according to any one of claims 1 to 4, wherein the body of the extruder is heated to an average temperature of about 110 to 240°C, preferably about 130 to 220°C.

6. The method according to any one of claims 1 to 5, wherein the process is carried out for about 20 seconds to 10 minutes, preferably about 0.5 minutes to 8 minutes.

7. The method according to any one of claims 1 to 6, wherein the temperature of the extruded material at the exit side of the die is about 100 to 200°C, preferably about 140 to 200°C.

8. The method according to any one of claims 1 to 7, further comprising the step of cooling the extruded material to a temperature of about 80°C or lower, preferably about 60°C or lower, and more preferably about 40°C or lower.

9. The method according to any one of claims 1 to 8, wherein the extruded material is cut, crushed, or broken into a feed body having a length of 3 to 400 mm, preferably 3 to 200 mm, more preferably 4 to 60 mm, and even more preferably 5 to 30 mm.

10. The supply body is approximately 300 kg / m³ ３ Preferably about 350 kg / m ３ In addition, approximately 500 kg / m ３ Preferably about 450 kg / m ３ The method according to any one of claims 1 to 9, having the following bulk density.

11. A feeder that can be obtained by the method of any one of claims 1 to 10, preferably obtained by the method of any one of claims 1 to 10.

12. A method for providing a granular material, comprising the steps of: providing the feed body described in claim 11 to a granulator, crusher, cutter, etc.; and reducing the diameter of the feed body to granules having a diameter of more than 90% greater than 0.5 mm and more than 90% less than 10 mm.

13. A method for producing powder, comprising the steps of: providing a feeder according to claim 11 or a granular material according to claim 12; and grinding the material in a mill, preferably a hammer mill, to produce a powdery feeder in particle form.

14. The obtained powder has a particle size such that more than 80% by weight of the particles are smaller than 3.15 mm, and more than 40% are smaller than 2 mm, and preferably the powder has a density of about 200 kg / m³. ３ The method according to claim 13, having the above bulk density.

15. Use of the feed body according to claim 11, the granular material according to claim 12, or a powder obtained from the method according to claim 13 or 14, as fuel for industrial furnaces, preferably industrial furnaces for power generation, industrial furnaces used in the production of lime, cement, or steel, or as a feed in a waste-to-chemical process.

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