EP-3638754-B1 - STRUCTURED COMPOSITE WOOD PELLETS FOR DUST/FINES MITIGATION AND METHOD OF PRODUCING THEM

Inventors

• CHEN, FRANK BOR-HER
• NAOULI, NABIL
• WILLIAMS, PAUL A.

Dates

Publication Date

20260506

Application Date

20180601

Claims (10)

1. A treated wood pellet comprising: a wood pellet; and a coating at least partially covering the wood pellet, where the coating is concentrated at the surface of the pellet and the coating comprises less than 1 wt. % of the total weight of the treated wood pellet, wherein the coating comprises two or more ingredients, where the ingredients comprise crude tall oil, distilled tall oil, tall oil pitch, tall oil fatty acids, tall oil heads, non-food use sustainable wax, or a combination thereof, wherein the coating comprises tall oil pitch and tall oil heads in a range from 90 wt. % tall oil pitch and 10 wt. % tall oil heads to 55 wt. % tall oil pitch and 45 wt. % tall oil heads, or where the coating comprises approximately 60 wt. % tall oil pitch and approximately 40 wt. % tall oil heads, and wherein the coating reduces the generation of dust/fines of the wood pellet upon impact and/or abrasion.
2. The treated wood pellet of Claim 1, wherein preferably either the coating ingredients are pine chemicals comprising crude tall oil and/or one or more fractions from crude tall oil, and preferably the coating does not comprise chemicals that are not crude tall oil or one or more fractions from crude tall oil, or where the coating does not comprise ingredients that come from seeds or comprise triglyceride, or where the coating does not comprise lignin.
3. The treated wood pellet of Claim 1 where the wood pellet comprises compressed wood, where the wood pellet does not comprise torrified wood.
4. A method of producing a treated wood pellet, the method comprising at least partially covering the wood pellet with a coating, where the coating is concentrated at the surface of the pellet and the coating comprises less than 1 wt. % of the total weight of the treated wood pellet, wherein the coating comprises two or more ingredients, where the ingredients comprise crude tall oil, distilled tall oil, tall oil pitch, tall oil fatty acids, tall oil heads, non-food use sustainable wax, or a combination thereof, wherein the coating comprises tall oil pitch and tall oil heads in a range from 90 wt. % tall oil pitch and 10 wt. % tall oil heads to 55 wt. % tall oil pitch and 45 wt. % tall oil heads, or where the coating comprises approximately 60 wt. % tall oil pitch and approximately 40 wt. % tall oil heads, and wherein the coating is configured to reducing the generation of dust/fines of the wood pellet upon impact and/or abrasion.
5. The method of Claim 4 where at least partially covering the wood pellet with the coating comprises spraying, dripping, and/or dipping, or where the coating is applied to the wood pellet in a rotary drum mixer, a ribbon blender with soft ribbon and soft wall, or a continuous dip coater or is sprayed onto wood pellet on a moving belt or while falling.
6. The method of Claim 4, wherein preferably either the coating ingredients are pine chemicals comprising crude tall oil and/or one or more fractions from crude tall oil, an preferably the coating does not comprise chemicals that are not crude tall oil or one or more fractions from crude tall oil, or where the coating does not comprise ingredients that come from seeds or comprise triglyceride, or where the coating does not comprise lignin.
7. The method of Claim 4 where the wood pellet comprises compressed wood, where the wood pellet does not comprise torrified wood,
8. A coating for reducing the generation of dust/fines of the wood pellet upon impact and/or abrasion when the coating at least partially covers the wood pellet and is concentrated at the surface of the pellet and the coating comprises less than 1 wt. % of the total weight of the treated wood pellet, wherein the coating comprises two or more ingredients, where the ingredients comprise crude tall oil, distilled tall oil, tall oil pitch, tall oil fatty acids, tall oil heads, non-food use sustainable wax, or a combination thereof, wherein the coating comprises tall oil pitch and tall oil heads in a range from 90 wt. % tall oil pitch and 10 wt. % tall oil heads to 55 wt. % tall oil pitch and 45 wt. % tall oil heads, or where the coating comprises approximately 60 wt. % tall oil pitch and approximately 40 wt. % tall oil heads.
9. The coating of Claim 8 where the coating ingredients are pine chemicals comprising crude tall oil and/or one or more fractions from crude tall oil, preferably the coating does not comprise chemicals that are not crude tall oil or one or more fractions from crude tall oil.
10. The coating of Claim 8 where the coating does not comprise ingredients that come from seeds or comprise triglyceride, or where the coating does not comprise lignin.

Description

BACKGROUND OF THE INVENTION Cross Reference. This application is based on and claims priority to U.S. Provisional Application No. 62/518,723, filed June 13, 2017, and U.S. Conversion Utility Patent Application No. 15/990,205, filed May 25, 2018, titled "Structured Composite Wood Pellets for Dust/Fines Mitigation and Method of Producing Them". Field of the Invention. This invention relates generally to structured composite wood pellets for dust/fines mitigation and method of producing them, and more particularly, but not by way of limitation, to a coating for the surface and/or subsurface of wood pellets that improves the resistance to dust/fines generation of the wood pellets upon impact and abrasion. Description of the Related Art. Wood pellets are often used as fuel for industrial power plants and for residential uses, such as barbeque grill fuel and other uses. Such wood pellets, however, break easily and tend to generate dust upon impact and abrasion, such as during shipping and handling. In fact, for industrial use, such wood pellets are designed to be ground up prior to use. This can be a major hazard at places where wood pellets are handled in bulk, such as at ports during loading and unloading, causing concerns about human safety, fire hazard, and fines by the port authority. Examples of prior art are described in EP2325289A1 and in WO2010/017108A2. EP2325289A1 relates to a method and device for processing a solid fuel, such as a wood pellet. An additive in the form of oil, melted or fluid wax, or fat, is added. WO2010/017108A2 describes an emulsion of pitch, such as tall oil pitch, in water useful for reducing the development of fugitive dust, especially the loss of coal dust. Based on the foregoing, it is desirable to provide a structured composite wood pellet that is resistant to dust/fines generation upon impact and abrasion. It is further desirable for such resistance to come from a coating at the wood pellet's surface and/or subsurface. It is further desirable for such a coating to be easily applied for mass production of the structured composite wood pellet for dust/fines mitigation. It is further desirable for such a coating to be green and sustainable. SUMMARY OF THE INVENTION In general, in a first aspect, the invention relates to a treated wood pellet comprising a wood pellet and a coating at least partially covering the wood pellet, where the coating reduces the generation of dust/fines of the wood pellet upon impact and/or abrasion. The coating comprises less than 1 wt. % of the total weight of the treated wood pellet. The coating comprises tall oil pitch and tall oil heads in a range from 90 wt. % tall oil pitch and 10 wt. % tall oil heads to 55 wt. % tall oil pitch and 45 wt. % tall oil heads, or where the coating comprises approximately 60 wt. % tall oil pitch and approximately 40 wt. % tall oil heads. The coating may increase the durability of the wood pellet. The coating may be capable of reacquiring fugitive dust from the wood pellet. The coating may be capable of maintaining the reduction of the generation of dust/fines of the wood pellet upon impact and/or abrasion after 30 days of storage. The coating comprises two or more ingredients, where the ingredients comprise crude tall oil, distilled tall oil, tall oil pitch, tall oil fatty acids, tall oil heads, non-food use sustainable wax such as natural alcohol bottoms, or a combination thereof. The coating ingredients may be pine chemicals, which may comprise crude tall oil and/or one or more fractions from crude tall oil. The coating may not comprise chemicals that are not crude tall oil or fractions of crude tall oil. The coating may not comprise ingredients that come from seeds or comprise triglyceride. The coating may not comprise lignin. The wood pellet may comprise compressed wood and may be coated with fines. The wood pellet may not comprise torrified wood. The coating may be located at a surface and/or subsurface of the wood pellet, but not throughout the wood pellet. The coating may not be a binder or a constituent of a binder within the wood pellet. The coating may particularly comprise less than approximately 0.8 wt. % of the wood pellet, less than approximately 0.6 wt. % of the wood pellet, or less than approximately 0.4 wt. % of the wood pellet. The treated wood pellet may have an average abraded dust level reduction of at least 90% compared to the abraded dust level of the wood pellet. The average abraded dust level reduction of the treated wood pellet may not reduce by more than 3% after 30 days of storage. The treated wood pellet may have an average respirable dust level of less than 2.5 mg/m3. In a second aspect, the invention relates to a method of producing the treated wood pellet described above, the method comprising at least partially covering the wood pellet with the coating. The coating may be applied through spraying, dripping, and/or dipping, and may be applied in a rotary drum mixer, a ribbon blender with