Densified fuel pellets

• US 20090205546A1
• Filed: 02/15/2008
• Published: 08/20/2009
• Est. Priority Date: 02/15/2008
• Status: Active Grant

• Current Assignee: Renewable Densified Fuels, LLC
• Original Assignee: Renewable Densified Fuels, LLC
• Inventors: Kluko, Milan
• Granted Patent: US 7,960,325 B2
• Time in Patent Office: Days
• US Class Current: 110/261
• CPC Class Codes: C10L 5/363 Pellets or granulates
• CPC Class Codes: C10L 5/44 on vegetable substances
• CPC Class Codes: C10L 5/46 on sewage, house, or town refuse C10L5/403, C10L5/406 take precedence
• CPC Class Codes: F23K 1/00 Preparation of lump or pulverulent fuel in readiness for delivery to combustion apparatus
• CPC Class Codes: F23K 1/04 Heating fuel prior to delivery to combustion apparatus
• CPC Class Codes: F23K 2201/501 with other fuels or combustible waste
• CPC Class Codes: F23K 2201/505 with additives
• CPC Class Codes: F23K 3/00 Feeding or distributing of lump or pulverulent fuel to combustion apparatus
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel

Abstract

A biomass-based fuel pellet, such as a fuel pellet which includes thermoplastic polymeric material and a substantial amount of cellulosic material, e.g. cellulosic material derived from biomass source(s), is provided. The fuel pellet commonly includes about 5 to 15 wt. % of the thermoplastic polymeric material and at least about 75 wt. % cellulosic material. Optionally, the fuel pellet may comprise a lignin additive. Many embodiments of the fuel pellets are suitable for use in a coal-fired furnace and/or in other industrial boiler applications.

Claims

1. A densified fuel pellet formed by a process comprising:

compacting a mixture which includes

a) about 5 to 15 wt. % molten thermoplastic polymeric material;

b) at least about 75 wt. % cellulosic material;

wherein the fuel pellet has a minimum dimension of at least about 1 cm and a heat value of at least about 9,500 Btu/lb (as is basis).

2. The densified fuel pellet of claim 1 wherein the thermoplastic polymeric material has a melting point of about 120 to 150°

C.

3. The densified fuel pellet of claim 1 wherein the mixture further comprises about 0.25 to 5 wt. % lignin additive (dry basis).

4. The densified fuel pellet of claim 1 wherein the fuel pellet has a moisture content of no more than about 3 wt. %.

5. The densified fuel pellet of claim 1 wherein the fuel pellet has a sulfur content of no more than about 0.5 wt. %.

6. The densified fuel pellet of claim 1 wherein the fuel pellet has a ash content of no more than about 8 wt. %.

7. The densified fuel pellet of claim 1 wherein the fuel pellet has a pellet durability index of at least about 80.

8. The densified fuel pellet of claim 1 wherein the fuel pellet has a specific gravity of about 1.0 to 1.2 g/cm3.

9. The densified fuel pellet of claim 1 wherein the fuel pellet has a density of about 20 to 45 lb/ft3.

10. The densified fuel pellet of claim 1 wherein the fuel pellet has a specific gravity which is at least about 150% of the mixture'"'"'s specific gravity.

11. The densified fuel pellet of claim 1 wherein the fuel pellet has a heat value of 9,500 to 12,000 Btu/lb (as is basis).

12. The densified fuel pellet of claim 1 wherein the cellulosic material is in particulate form having a maximum dimension of no more than about 20 mm.

13. The densified fuel pellet of claim 1 wherein the cellulosic material in the mixture has an initial moisture content of no more than about 15 wt. %.

14. The densified fuel pellet of claim 1 wherein the thermoplastic polymeric material comprises polyethylene, polypropylene, or a mixture thereof.

15. The densified fuel pellet of claim 1 wherein compacting the mixture comprises extruding the feed mixture.

16. The densified fuel pellet of claim 1 wherein the thermoplastic polymeric material comprises a mixture of high density polyethylene and low density polyethylene.

24. A method of generating heat in a boiler designed for burning coal comprising combusting a fuel material which includes a plurality of the densified fuel pellets of claim 1.

25. The method of claim 24 wherein the fuel material includes coal pieces and a plurality of the densified fuel pellets having substantially similar size characteristics as the coal pieces.

17. A densified fuel pellet comprising:

a) about 5 to 15 wt. % thermoplastic polymeric material;

b) at least about 75 wt. % cellulosic material;

wherein the fuel pellet has a minimum dimension of at least about 1 cm;

a heat value of at least about 9,500 Btu/lb; and

a PDI of at least about 80.

18. A method of producing a densified fuel pellet comprising:

compressing a feed mixture to form a densified material, wherein the mixture includes;

a) about 5 to 15 wt. % molten thermoplastic polymeric material; and

b) at least about 75 wt. % cellulosic material;

such that the densified fuel pellet has a minimum dimension of at least about 1 cm and a heat value of at least about 9,500 Btu/lb.

19. The method of claim 18 wherein the fuel pellet has a PDI of at least about 80.

20. The method of claim 18 wherein the thermoplastic polymeric material has a melting point of about 130 to 150°

C.

21. The method of claim 18 wherein the mixture further comprises lignin additive.

22. The method of claim 18 wherein compressing the mixture comprises extruding the feed mixture at a temperature sufficient to maintain the thermoplastic polymeric material in a molten state.

23. The method of claim 18 wherein compressing the mixture comprises uniaxial compaction of the feed mixture at a temperature sufficient to maintain the thermoplastic polymeric material in a molten state.