Wood pellets

Abstract

The subject of the invention is a wood pellet with increased resistance to biological factors and excellent mechanical strength. The wood pellet contains wood raw material with a fineness of 0 mm to 1 mm - 8% to 10%, from 1 mm to 3 mm - 75% to 77%, from 3 mm to 5 mm - 8% to 10%, and humidity up to 12% and from 0.9% to 1.3% gelatin and from 0.9% to 1.3% sugar and from 0.2% to 0.4% biocide, wherein the biocide is Acticide 14, containing a mixture of 5-chloro-2-methyl-2H-isothiazol-3 and 2-methyl-2H-isothiazol-3.

Description

[0001] Wood pellets

[0002] The subject of the invention is a wood pellet intended for use in heating, for heating houses, plants, public buildings and in district heating.

[0003] Wood pellet is known from the Japanese patent application description JP2011105922A obtained by adding wood chips and sawdust to a gelatinized substance obtained by suspending starch in water and heating it and after forming the final shape of the pellet, drying it. The proportions of mixing the pellet raw materials are: 1 kg of starch powder, 1500 to 2500 cm3 of water, 2 to 4 kg of wood chips with a thickness of 1 to 10 mm and a width of 5 to 40 mm and 10 to 70 mm and 4 to 4 kg of sawdust.

[0004] It is known from the Polish patent description of the invention PL235085B1 a fuel pellet with a moisture content of not more than 5% by weight, made of thermally processed biomass mixed with a binder consisting of modified wheat or potato starch in the amount of 0.5-0.8% by weight of the binder, beet molasses in the amount of 0.1-0.5% by weight of the binder and sodium lignosulfonate in the amount of 0.1-0.3% by weight of the binder.

[0005] A high-energy pellet is known from the Polish patent application description PL421093A1, enriched with a modifier increasing the efficiency of the combustion process, based on sawdust, having an added modifier in the form of a liquid aqueous solution with a concentration of 6% of the reaction product of acetic acid, n-butanol, 2-methylpropan-l-ol, n-propanol and isopropanol in an amount of 35% by weight, fed in the amount of 1 liter of liquid per 1 tonne of pellet.

[0006] The aim of the solution according to the invention was to develop a wood pellet composition with increased resistance to biological factors and excellent mechanical strength and light color.

[0007] The essence of the solution according to the invention, in which the wood pellet consists of crushed biomass in the form of wood raw material, binder and biocide, is that it contains wood raw material with a fineness from 0 mm to 1 mm - 8% to 10%, from 1 mm to 3 mm - 75% to 77%, from 3 mm to 5 mm - 8% to 10% and humidity up to 12% and from 0.9% to 1.3% gelatin and from 0.9% to 1.3% sugar and from 0.2% to 0.4% biocide, wherein the biocide is Acticide 14, containing a mixture of 5-chloro-2-methyl-2H-isothiazol-3 and 2- methyl-2H-isothiazol-3. Thanks to the use of the Acticide 14 biocidal additive protecting the wood raw material against the development of biological life, preferably in the amount of 0.3% by weight, a pellet with increased resistance to the development of biological life was obtained.

[0008] Thanks to the use of gelatin, preferably in the amount of 1% by weight, and sugar, preferably in the amount of 1% by weight, the mechanical strength of the pellet was improved, and the gelatin also contributed to a lighter colour of the pellets.

[0009] Example

[0010] The biomass constituting the wood raw material in the form of wood chips, shavings and sawdust was crushed in a hammer mill into particles up to 10 mm in size. The crushed wood raw material was then dried in a vortex dryer, at a drying air temperature of 200°C to 215°C. The dried wood raw material with a moisture content of 12% was removed from the dryer by means of a mechanical conveyor and transferred via a pneumatic transport system to a dry raw material silo constituting a warehouse enabling even feeding of the wood raw material to the production line and maintaining the temperature of the raw material leaving the dryer in the range of 45°C to 60°C and moisture at the level of 12%. Then the dried wood raw material was transported to the dry raw material hammer mill where it was crushed, and the crushed wood raw material was then subjected to selection in the sieve module. The arrangement of the sieve holes in the sieve module formed an arrow pattern, with the holes being 10 mm long and 4 mm wide. Then the crushed and sieved wood raw material was transported by a mechanical conveyor to the mixer and was pre-conditioned. In the mixer, using the bulk additive dispenser module and the liquid additive dispensing system, the additives were evenly distributed in the mass of the wood raw material.

[0011] The additives introduced to the mass of the wood raw material were gelatin in the amount of 1%, sugar in the amount of 1% and biocide in the amount of 0.3%. In the obtained mixture, the wood raw material was fragmented from 0mm to 1mm - 8% to 10%, from 1mm to 3mm - 75% to 77%, from 3mm to 5mm - 8% tol0%.

[0012] The biocide was Acticide 14, containing a mixture of 5-chloro-2-methyl-2H-isothiazol-3 and 2-methyl-2H-isothiazol-3. The biocide had a pH of 4.7 and contained 3.06% nitrogen and 6.99% sulfur. The content of the active substance in the biocide was 46.5 g per 100 g. The biocidal additive used in the form of Acticide 14 was intended to protect the wood raw material and then the granulate from the development of biological life, while gelatin and sugar were additives improving the mechanical strength of the pellets.

[0013] The mixture with a moisture content of 12% obtained in the mixer was subjected to granulation in a granulator after the parameters had been unified, and then the cooled and sieved granulate with a length of 3.5 mm to 50 mm was transported to the warehouse and packed.

[0014] Table 1 presents the results of tests on the mechanical strength and colour of pellets obtained using the method according to the invention, where the sugar addition was 1% and the gelatin addition was 1%.

[0015] The mechanical strength was assessed using a method of dropping approximately 10 g of the pellets produced four times from a height of 185 cm onto a metal plate and weighing pellets with a length of over 3.5 mm. The difference between the sample weight before and after the four-time drop determined the strength of the tested pellet sample. Mechanical strength tests were performed for pellets produced from biomass without additives and pellets produced from sawdust containing additives.

[0016] Table 1

[0017] The additive used Average Strength Score Additive Impact. Color Difference % sugar 99,35 10,43 D (4,0) gelatine 99,33 10,41 A+ (0,5) pellets without 88,92 0 A+(0,75) additives

[0018] In the case of pellets with 1% sugar and gelatin additives, the strength results obtained were more than 10 percentage points higher than the strength results obtained for pellet samples obtained from untreated biomass. In order to determine the color of the produced pellets, a color scale was created, which was then used to evaluate the produced samples. The color scale was prepared using different types of wood pellets obtained from the market. Each color was assigned a number of points, the lightest pellets marked on the scale with the symbol A were assigned 1.0 points, while the darkest ones marked on the scale with the symbol G - 7 points. The intermediate color of the pellets was evaluated by subtracting half a point, for example, a pellet sample with a color between C and D according to the scale should be marked as D+ and receive 3.5 points, while samples lighter than color A should be marked with the symbol A+ and receive 0.5 points.

[0019] Table 2 presents the results of tests on the growth of microorganisms in pellets with the addition of the biocide presented in the example embodiment and without additives.

[0020] A biocide suspension was introduced into the supplied biomass sample using a sprayer so that the liquid to biomass ratio was 1:2, and the concentration of the biocide in the biomass reached the assumed level. The moistened biomass was mixed and left for 48 h, and then dried in a dryer at 35 °C so that the excess water introduced with the biocide evaporated. Biocides in solid form were introduced directly into the biomass, thoroughly mixing the weighed amounts of the additive and the biomass. For the base and refined biomass samples, a microbiological analysis was carried out using the culture method on media by sowing 0.1 g of biomass directly onto the media. The starting material for the tests was a sawdust suspension obtained after mixing a specific mass of the tested product with a nine-fold amount of diluent. Then, 1 ml of the starting suspension was diluted with 9 ml of diluent, and this procedure was repeated twice. Samples from the series of dilutions obtained in this way were applied to the media. The research material was placed on Petri dishes filled with solidified medium: Tryptone Soya Agar for the cultivation of aerobic bacteria and Malt Extract Agar for the cultivation of fungi. The dishes with the applied samples were incubated at 25°C for 5 days. Table 2

[0021] Biocyd 0% share Share 0.1% Share 0.3% Share 0.5%

[0022] (without extras)

[0023] Acticide 14 +++ + - -

[0024] +++ intensive growth of microorganisms (80 - 100% of the surface of the dish)

[0025] ++ moderate growth (20 - 80% of the surface of the dish)

[0026] + weak growth (up to 20% of the surface of the dish)

[0027] - no growth

[0028] In the case of the base biomass and biomass containing the biocide Acticide 14, tests of the content of microorganisms were carried out using the 10-fold dilution method.

[0029] Table 3 presents the results of tests of the content of microorganisms in pellets with and without the biocide additive.

[0030] Table 3

[0031] The additive used content of microorganisms in 1 g of biomass:

[0032] - aerobic bacteria - fungus

[0033] Acticide 14 at 0.3% 7xl02below 10 concentration

[0034] Pellets without added biocide 3xl02below 100

[0035] The presented research results confirm the effectiveness of the biocide: the content of bacteria in the biomass protected with the additive does not exceed 10 com / g, and the content of fungi - 100 com / g, which is the lower detection limit of the method.

Claims

ClaimWood pellet consisting of crushed biomass in the form of wood raw material, binder and biocide, characterized in that it contains wood raw material with a fragmentation of from 0 mm to 1 mm - 8% to 10% from 1 mm to 3 mm - 75% to 77% from 3 mm to 5 mm - 8% to 10% and moisture content up to 12% and from 0.9% to 1.3% gelatin and from 0.9% to 1.3% sugar and from 0.2% to 0.4% biocide, wherein the biocide is Acticide 14, containing a mixture of 5-chloro-2-methyl-2H-isothiazol- 3-one and 2-methyl-2H-isothiazol-3-one.

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