Use of sodium bisulfate as a pelletizing aid for renewable materials

Abstract

The present invention relates to pellets which are based on organic, renewable raw materials and are obtained using sodium bisulfate as a pelletizing agent.

Description

[0001] Our reference: 250589WO EBO / scs

[0002] 09.09.2025

[0003] Pellets from renewable raw materials

[0004] The present invention relates to pellets which are based on organic, renewable raw materials and are obtained using sodium bisulfate as a pelleting aid.

[0005] Renewable raw materials are becoming increasingly popular. In times of climate change, attempts are being made to replace petrol-based raw materials with renewable raw materials in a wide variety of areas. In heating, for example, gas heating systems are being replaced by wood pellet heating systems.

[0006] Renewable raw materials provide a source of cellulose, hemicellulose or lignin, which can be processed into various products and additives. Cellulose is traditionally used in paper and pulp production. Lignin can be used as a binding and stabilizing material in concretes and cements - but also as a fertilizer or briquette as an energy raw material. Many supposed seizures, such as the cocoa fruit or coffee fruit (in each case after removal of the beans), have a high lignin content. The shells of other fruits can also be an important raw material but are often not used because transportation and storage are difficult.

[0007] The advantage of pelletizing the raw materials is that they are compact and can be stored and transported with little space requirement and little dust generation. Pellets are usually produced by pressing the material. However, especially in the case of pellets made from renewable materials, it has been shown that this is only possible to a limited extent with conventional pressing processes or that the desired qualities cannot be achieved due to the strongly fluctuating raw material qualities. Thus, there is a need for pellets that are stable to enable transportation and storage. Surprisingly, it has been shown that the use of sodium bisulfate as a pressing aid makes it possible to produce stable pellets from a wide variety of renewable raw materials, even though the raw material quality does not permit production. Sodium bisulfate has the advantage that it is non-toxic, so that the pellets can later be used in any area.

[0008] The use of sodium bisulfate is surprising, as the application of pressure required for pellet production in the presence of sodium bisulfate leads to heat development and carbonization of the pellets during production.

[0009] Surprisingly, it has been shown that it is possible to produce pellets from renewable raw materials using sodium bisulfate as a pelletizing aid by optimizing the process. Renewable raw materials in the meaning of the present invention are in particular oat husks, rapeseed husks, soy, cocoa, wood, softwood chips, coffee, pea husks, straw, spelt and / or sunflower husks. Pellets can theoretically be made from mixtures of the raw materials, but pellets made from one of the materials mentioned are common and preferred. Preferably, the raw material is at least one, preferably one, selected from oat husks, rapeseed husks, soy, cocoa, wood, softwood chips, coffee, pea husks, spelt and / or sunflower husks. In another preferred embodiment, the raw material is at least one, preferably one, selected from husks, especially oat husks, rapeseed husks, pea husks and sunflower husks. In a further preferred embodiment, the raw material is at least one, preferably one, selected from oat husks, rapeseed husks, soy, cocoa, coffee, pea husks, straw, spelt and / or sunflower husks.

[0010] In the case of cocoa and coffee, this refers in particular to the remains of the fruit, which usually remain as waste after the beans have been removed. After drying, a fibrous material is obtained, which is difficult to transport due to its volume. Until now, pelleting has only been possible with great difficulty and not with the desired quality. Oat hulls, rapeseed hulls, soy (hulls) and pea

[0011] 250589WO hulls are also regarded as waste rather than raw material. In these cases, too, pelleting enables storage and transportation and thus further use.

[0012] So that the renewable raw materials can be pelletized, the amount of sodium bisulfate in the pellets is at least 0.3% by weight relative to the total weight of the pellets. Preferably, the amount of sodium bisulfate is from 0.5 to 30% by weight, preferably from 1 to 20% by weight, in particular from 3 to 15% by weight, more preferably from 5 to 10% by weight, based on the total weight of the pellets. It has been shown that an effective result is achieved in these ranges and thus stable pellets of the desired quality can be obtained.

[0013] If the amount of sodium bisulfate is below 0.3 % by weight and in particular below 0.5 % by weight, the pellets are unstable. With amounts of more than 30% by weight, there is a risk of high heat development during pressing, so that the pressing pressure must be reduced. For this reason, pellets of the desired quality cannot be obtained in these cases either. In addition, an amount of more than 30% by weight of sodium bisulfate is not desirable, as other properties of the additive come into effect. In particular, the hygroscopic properties of sodium bisulfate can then adversely affect the properties of the pellets. Therefore, the amount of sodium bisulfate is preferably less than 28% by weight, in particular less than 25% by weight, especially preferably 23% by weight or less.

[0014] In one preferred embodiment, the raw material is straw and the amount of sodium bisulfate is 0.3% by weight to less than 5% by weight, preferably from 0.3% by weight to 4% by weight. If the raw material is one or more selected from oat husks, rapeseed husks, soy, cocoa, wood, softwood chips, coffee, pea husks, spelt and / or sunflower husks, the amount of sodium bisulfate is 0.3 % by weight to 30% by weight.

[0015] 250589WO In the before mentioned areas, the use of sodium bisulfate is also harmless in terms of further use. Some of the raw materials mentioned can also be used as animal feed. As sodium bisulfate is approved as animal feed, the claimed amount is also harmless for this application.

[0016] Surprisingly, it has also been shown that the addition of sodium bisulfate to the above-mentioned raw materials partially impairs their structural properties. Suitable parameters for this are crude fiber, NDF (Neutral Detergent Fiber), ADF (Acid Detergent Fiber), ADL (Acid Detergent Lignin), hemicellulose and cellulose. The addition of sodium bisulfate influences NDF, ADF, cellulose and hemicellulose.

[0017] It is assumed that the pelletizing aid does not negatively influence the raw material by the meaning of its usefulness as litter. Hence, one of the most important features of the obtained pellets was the suitability as litter. It is assumed that during pelletizing, the sodium bisulfate reacts with polysaccharides (cellulose and hemicellulose) of the raw material. It is assumed that the cell walls of the raw material are subjected to mechanical stress by the pelletizing aid during the mixing process. Only this then enables the presumed reaction with the polysaccharides contained in the raw material. It is likely that the combination of these two factors is what enables stable pellets to be obtained. This was surprising insofar as sodium bisulfate is known to be hygroscopic and it was assumed that contact with the residual moisture in the raw materials and air humidity would produce sulphuric acid, which would destroy the pellets during the pressing process due to the heat generated by the exothermic reaction in combination with the pressure.

[0018] Surprisingly, however, this did not happen. Instead, stable pellets were obtained despite the hygroscopic properties of sodium sulphate and the presence of water / moisture. This may be the case due to a higher internal roughness during the pelletizing process.

[0019] 250589WO However, the lignin content is not significantly affected by the addition of sodium bisulfate.

[0020] The contents of crude fiber, NDF (Neutral Detergent Fiber), ADF (Acid Detergent Fiber), ADL (Acid Detergent Lignin), hemicellulose and cellulose were determined as described below:

[0021] • Crude fiber: o Definition: Broadly refers to all fibers found in plants, including hemicellulose, cellulose and lignin. o Analysis: Determined by Weender analysis, represents the residue after extraction with diluted acids and alkalis.

[0022] • Neutral Detergent Fiber (NDF): o Definition: Represents the total content of cell wall substances in feed plants, including hemicellulose, cellulose, lignin and lignin-nitrogen compounds. o Analysis: Determined by the extended Weender analysis.

[0023] • Acid Detergent Fiber (ADF): o Definition: Represents the content of fibrous carbohydrates that are not soluble in acidic solution, mainly cellulose and lignin. o Analysis: Determined by acid-detergent analysis.

[0024] • Acid Detergent Lignin (ADL): o Definition: Indicates the amount of lignin that is not soluble in acidic solution and represents the lignin content of the plant sample. o Analysis: Also determined by acid-detergent analysis.

[0025] • Hemicellulose:

[0026] 250589WO o Definition: The amount of fiber carbohydrates, calculated by subtracting ADF from NDF, comprises complex polysaccharides in the cell walls. o Calculation-. Hemicellulose = NDF - ADF

[0027] • Cellulose: o Definition: Represents the amount of fiber carbohydrates, calculated by subtracting ADL from ADF and is the main component of plant cell walls. o Calculation-. Cellulose = ADF - ADL

[0028] These parameters serve as key indicators to describe the structural composition of plant fibers.

[0029] The stability of the obtained pellets can be further determined by measuring their abrasion resistance and hardness.

[0030] The abrasion resistance of the pellets was determined according to Ligno. This standardized test allows to measure the weight of the pellets prior and after abrasion. The loss of weight during the abrasion test shows the value of abrasion in %. To determine the pellet hardness, pressure is applied (whereby the pressure is exerted in the longitudinal direction) to a pellet until the pellet shattered. The force required to crush the pellet refers to the hardness (usually determined in newtons [N]).

[0031] When using sodium bisulfate as a pelleting aid, it is mixed with the corresponding raw material. In order to obtain a homogeneous mixture and to be able to produce pellets in standard sizes, the raw material is crushed before or at the same time as mixing if necessary. Common sizes for pellets range from a diameter of 3 mm to 10 mm, preferably from 4 mm to 7 mm, and a length of 1 cm to 5 cm. Flexible use is possible with these sizes.

[0032] 250589WO The use of sodium bisulfate according to the invention thus enables a pellet production process comprising the following steps: a) provision of the renewable raw material, b) crushing the raw material if necessary, c) providing sodium bisulfate, d) providing water, if necessary, d) homogeneous mixing of the raw material and the sodium bisulfate and water (where applicable), the raw material being optionally crushed during mixing; and e) feeding the resulting mixture into a press and producing the pellets.

[0033] The crushing of the raw material may be performed by using a roller mill or a hammer mill for example. Both methods lead to the formation of stable pellets. Nevertheless, it was surprisingly found that using a hammer mill in combination with the inventive us of the pelletizing aid resulted in the most stable pellets.

[0034] Once the pellets have been produced, they can be packaged. The packaging is particularly airtight so that the pellets cannot absorb moisture from the air.

[0035] The raw material and sodium bisulfate can be mixed, for example, in a screw conveyor on the way to the pellet press. The mixing ratio of raw material and sodium bisulfate must be adjusted in order to achieve the desired mixing ratio. This can be done in particular by adjusting the feed rates in a screw conveyor. It is also possible to adjust and homogenize the desired mixture and then feed this mixture to the mold in the press, taking into account the length of the feed section. It is also possible for the sodium bisulfate to be added directly to the press via the mold.

[0036] After the homogeneous mixture has been introduced into the mold of the press, a pellet is produced by applying pressure. Pelletizing itself is a process familiar to the skilled person.

[0037] 250589WO After the pellets have been produced, they can, if desired, be reworked into pellets using suitable techniques, e.g. a pelletizing chair.

[0038] The raw materials contain a certain amount of water before the pressing process. This is an inherent characteristic of the material itself. It is also possible that water is added to the raw material to enable better processing. After pressing in the mold, the water content (moisture) of the pellets is preferably 20% by weight or less, in particular 15% by weight or less, especially preferably 12% by weight or less and in particular 2% by weight or more and especially preferred 5% by weight or more. The percentage by weight is based on the total weight of the pellets. The water content ensures that stable pellets are obtained. A too low water content may result in instable pellets, whereas a too high water content, which may be obtained by adding water to the mixture of raw material and pelletizing aid, may also result in unstable pellets or pellets showing cracks. This results in worse stability during storage.

[0039] Therefore, to optimize the stability and properties of the pellets, it is in one preferred embodiment that the pelletizing aid is used together with water to prepare stable pellets. The amount of water added to the raw material and the pelletizing aid prior to the mixing is depending on the raw material itselt and its natural containing moisture and the amount of pelletizing aid. Preferably, the amount of water added is in the range from 0.5 % by weight to 10 % by weight, especially preferred at least 1 % by weight or more or 3% by weight or more and 8 % by weight or less or 5 % by weight or less. The amount in % by weight refers to the total weight of starting materials, i.e. the sum of raw material, pelletizing aid and water. Surprisingly, the addition of water did not lead to a formation of excess of sulfuric acid resulting in a destroying of the raw material. Instead, the addition of water enabled the control of obtaining stable pellets. At the same time, surprisingly, it has been shown that adding water reduces the machine load during mixing and especially during pressing.

[0040] 250589WO In the following embodiments, the present invention is further explained in a non-limiting manner.

[0041] Examples:

[0042] Example 1 :

[0043] Straw chaff and pellets produced from this straw using sodium bisulfate as a pelletizing aid were analyzed for crude fiber, NDF (Neutral Detergent Fiber), ADF (Acid Detergent Fiber), ADL (Acid Detergent Lignin), hemicellulose and cellulose content. For this purpose, the straw and pellet samples were dried in a drying oven at >100 °C for at least 4 hours prior to analysis.

[0044] Pellets: Straw pellets containing sodium bisulfate (80 wt.% straw, 20 wt.% sodium bisulfate) were produced using a flat mold with a pressing ratio of 1 :2. The diameter of the pellets was 6 mm. a) NDF (neutral detergent fiber) content

[0045] The samples (at least 3 straw samples and 3 pellet samples) were ground to a size of <1.0 mm using an ultracentrifuge. 1 g of the sample was weighed to the nearest 1 mg

[0046] The samples were treated in a Fibretherm (Gerhardt Analytical Systems, Ko- nigswinter, Germany). The digestion was carried out according to the corresponding method (here: method 4), which is programmed into the device. The samples were then removed from the container with demineralized water and rinsed with acetone.

[0047] Pre-annealed and cooled crucibles were filled with the sample and dried in a drying oven. The crucibles were then placed in a muffle furnace and the program

[0048] 250589WO for crude fiber (4 h at 500 °C) was started. The crucibles were placed in a desiccator to cool down to room temperature.

[0049] The mass was obtained after digestion and ashing. b) ADF (acid detergent fiber) content

[0050] The samples (at least 3 straw samples and 3 pellet samples) were ground to a size of <1.0 mm using an ultracentrifuge. 1 g of the sample was weighed to the nearest 1 mg.

[0051] The samples were treated in a Fibretherm (Gerhardt Analytical Systems, Ko- nigswinter, Germany). The digestion was carried out according to the corresponding method (here: method 3), which is programmed into the device. The samples were then removed from the container with demineralized water and rinsed with acetone.

[0052] Pre-annealed and cooled crucibles were filled with the sample and dried in a drying oven. The crucibles were then placed in a muffle furnace and the program for crude fiber (4 h at 500 °C) was started. The crucibles were placed in a desiccator to cool down to room temperature.

[0053] The mass is obtained after digestion and ashing. c) ADL (acid-detergent lignin) content

[0054] The samples (at least 3 straw samples and 3 pellet samples) were ground to a size of <1.0 mm using an ultracentrifuge. 1 g of the sample was weighed to the nearest 1 mg.

[0055] The samples were treated in a Fibretherm (Gerhardt Analytical Systems, Ko- nigswinter, Germany). The digestion was carried out according to the corresponding method (here: method 3), which is programmed into the device.

[0056] 250589WO 360 ml of 72% sulphuric acid was added to a 1-liter beaker. The samples from the Fibretherm were immersed in the sulphuric acid. After 3 h of contact with sulphuric acid, the samples were washed three times with hot (temperature at 60 °C to 90 °C) deionized water and at least once with cold (room temperature) deionized water. Washing was carried out until the sample was free of acid.

[0057] The samples were then removed from the container with demineralized water and the container was rinsed with acetone.

[0058] Pre-annealed and cooled crucibles were filled with the sample and dried in a drying oven. The crucibles were then placed in a muffle furnace and the program for crude fiber (4 h at 500 °C) was started. The crucibles were placed in a desiccator to cool down to room temperature.

[0059] The mass is obtained after digestion and ashing. d) Hemicellulose content

[0060] The hemicellulose was calculated by subtracting the ADF from the NDF. The NDF includes all fiber carbohydrates that are not soluble in neutral solution, while the ADF represents the amount of fiber carbohydrates that are not soluble in acidic solution. The difference between the two, i.e. NDF - ADF, indicates the hemicellulose content. e) Cellulose content

[0061] The cellulose content was calculated by subtracting the Acid Detergent Lignin (ADL) content from the ADF. The ADF represents the amount of fiber carbohydrates that are not soluble in acidic solution, while the ADL content indicates the amount of lignin-containing compounds that are not soluble in acidic solution. The difference between the two, i.e. ADF - ADL, indicates the cellulose content.

[0062] 250589WO The results of the analyses are shown in Tables 1 and 2 below, with the respective content given in grams. The results shown are the mean value from 2 to 3 samples.

[0063] Table 1 : Straw samples

[0064] Table 2: Pellet samples

[0065] % in dry matter : Percentage by weight in dry matter

[0066] L / H2O-Tr: Water content in the sample

[0067] A t-test was used to analyze whether the differences between the straw samples and the pellet samples were significant. It was found that the differences in 250589WO crude fiber content, ADF content, NDF content, hemicellulose content and cellulose content were significant before and after pelleting. This indicates a degradation of polysaccharides caused by the sodium bisulfate.

[0068] The ADL content is not influenced by pelletization. This indicates that the addition of salt has no direct effect on the lignin.

[0069] Example 2:

[0070] Pellets made from spelt husks, which were produced using sodium bisulfate as a pelletizing aid, were analyzed with regard to the content of crude fiber, NDF (Neutral Detergent Fiber), ADF (Acid Detergent Fiber), ADL (Acid Detergent Lignin), hemicellulose and cellulose. The spelt husks themselves were also analyzed. For this purpose, the spelt husks samples and the pellets were dried in a drying oven at >100 °C for at least 4 hours prior to analysis.

[0071] Pellets: Spelt husk pellets containing sodium bisulfate (80 wt.% spelt husks, 20 wt.% sodium bisulfate) were produced using a flat mold with a pressing ratio of 1 :2. The diameter of the pellets was 6 mm.

[0072] The components were analyzed as described for example 1. A t-test was used to analyze whether the differences between the spelt husks samples and the pellet samples were significant. This showed that the differences in crude fiber content, ADF content, NDF content, hemicellulose content and cellulose content were significant before and after pelletizing. This indicates a degradation of polysaccharides caused by the sodium bisulfate.

[0073] The ADL content is not influenced by pelletization. This indicates that the addition of salt has no direct effect on the lignin.

[0074] Example 3:

[0075] 250589WO Pellets were made from wood chips (wood chips were made of softwood (approx. 85% by weight pine / spruce and 15% by weight larch, Douglas fir, fir) which were produced using sodium bisulfate as a pelletizing aid. They were analyzed with regard to the content of crude fiber, NDF (Neutral Detergent Fiber), ADF (Acid Detergent Fiber), ADL (Acid Detergent Lignin), hemicellulose and cellulose. The wood chips themselves were also analyzed. For this purpose, the wood chip samples and the pellets were dried in a drying oven at >100 °C for at least 4 hours prior to analysis.

[0076] The stability of the pellets was determined by their abrasion resistance and hardness. The abrasion resistance of the pellets was determined according to Ligno. This was carried out using the LignoTester ( : Manufacturer: Borregaard, Norway, model LT-II Serial No. LT 275 / 0 / 0, production date of the tester 6 / 1999) abrasion testing device as a double determination. After switching on the power supply to the device, the funnel-shaped test chamber was opened. 100g of pellets were carefully filled into the test chamber. The device was closed. The fan, whose air flow causes stress on the pellets, was started using the start button. Before starting, ensure that the stress duration of 60 seconds has been set using the rotary knob on the right-hand side of the housing. After the preselected stress duration had elapsed, the fan switched off automatically. The test chamber was opened. The pellets were transferred to a pre-prepared tray by slowly tilting the test chamber through the filling funnel cover.

[0077] To determine the pellet hardness, the pellets were placed in the designated chamber of a measuring device (Manufacturer: Fa. Amandus Kahl, Germany, model K3175B002). A pressure screw was tightened, increasing the pressure of a stamp until the pellet shattered. The force required to crush the pellet was measured. The hardness was determined in newtons [N].

[0078] Moisture was determined by taking 5 g of the sample. Approximately 5 g of the sample was weighed into the tared weighing bottle to an accuracy of 1 mg and

[0079] 250589WO distributed evenly. The weighing bottle containing the sample was placed in a drying oven preheated to approximately 105 °C. After 4 hours, the weighing bottle was sealed and placed in a desiccator to cool. It was then weighed again to an accuracy of 1 mg. The difference in mass corresponds to the moisture content.

[0080] Pellets: Wood chip pellets containing sodium bisulfate (80 wt.% wood chips, 20 wt.% sodium bisulfate) were produced using a flat mold with a pressing ratio of 1 :2. The diameter of the pellets was 6 mm. Prior to pelletizing, the wood chips were milled with a hammer mill with a 6 mm sieve.

[0081] The components were analyzed as described for example 1.

[0082] Pellets were produced with addition of 20 wt% sodium bisulfate. To analyze the effect of water, pellets with 20wt.% sodium bisulfate and 0.5 wt.% water were analyzed as well.

[0083] The results are shown in the following table:

[0084] 250589WO The experiments show that addition of sodium bisulfate allows to obtain stable pellets from wood chips. Addition of water is not necessary, but the water content (moisture in the samples) should be kept low. The addition of water resulted in cracks in the pellets. This is reflected in the reduced stability of the tests.

[0085] The chemical analysis showed significant change in ADF, cellulose, and hemicellulose. This may be due to the fact that sodium bisulfate reacting with polysaccharides by means of hydrolysis.

[0086] Example 4:

[0087] Spelt husks were again used to prepare pellets. The stability of the pellets was determined by their abrasion resistance and hardness as described in Example 3. In the following table, the pellets and results are summarized (the missing amount to 100 wt.% is spelt husks):

[0088] 250589WO 4-1: no stable pellets were obtained.

[0089] 4-2: hardly any stable pellets were obtained, measurements for the stability and abrasion were not possible.

[0090] The Examples show that the addition of sodium bisulfate (NazSC ) clearly improves the stability of the pellets. Water content is another factor. But hardness and abrasion resistance were strongly improved by the sodium bisulfate. If water and sodium bisulfate are added, the quality decreases again. Hence, a low water / moisture content is preferred when using sodium bisulfate as pelletizing aid.

[0091] Examples 4-3 and 4-4 were repeated with the use of the same amounts of water and sodium bisulfate. But in the first test of both of Examples 4-3 and 4-4 (the results are separated by a in the table, whereas the left value is the first test and the right value the second on), a hammer mill was used to crush the spelt husks prior to mixing and pelletizing. In the second test, a roller mill was used. In the examples, where only sodium bisulfate was added, this difference in the milling process showed surprising differences in the hardness of the pellets.

[0092] 250589WO

Claims

Claims1. Use of sodium bisulfate as a pelletizing aid for the production of pellets from renewable raw materials, wherein the renewable raw materials are selected from at least one of oat husks, rapeseed husks, soy, cocoa, wood, softwood chips, coffee, pea husks, straw or chopped straw, lignocellulose, corn silage, rye straw, wheat straw, triticale, spelt, spelt husks, sunflower husks, hay. and grass, and wherein the proportion of sodium bisulfate in the pellets is at least 0.3% by weight, based on the total weight of the pellets.

2. The use of sodium bisulfate as a pelletizing aid according to claim 1, characterized in that the proportion of sodium bisulfate is from 0.5 to 30% by weight, preferably from 1 to 25% by weight, in particular from 3 to 15% by weight, preferably from 5 to 10% by weight, based on the total weight of the pellets.

3. The use of sodium bisulfate as a pelletizing aid according to any one of claims 1 to 2, characterized in that the diameter of the pellets produced is between 3 and 10 mm, preferably from 4 to 7 mm.

4. The use of sodium bisulfate as a pelletizing aid according to at least one of claims 1 to 3, characterized in that the length of the pellets produced is from 1 cm to 5 cm.

5. The use of sodium bisulfate as a pelletizing aid according to at least one of claims 1 to 4, characterized in that it is mixed with the raw material and the raw material is crushed before or during mixing.250589WO6. The use of sodium bisulfate as a pelletizing aid according to claim 5, characterized in that the mixing takes place in a screw conveyor.

7. The use of sodium bisulfate as a pelletizing aid according to at least one of claims 1 to 6, characterized in that it is used together with water.

8. The use of sodium bisulfate as a pelletizing aid according to claim 7, characterized in that the amount of water added is in the range from 0.5 % by weight to 10 % by weight, preferably at least 1 % by weight or more, especially preferred 3% by weight or more, and preferably 8 % by weight or less, especially preferred 5 % by weight or less250589WO

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