Densified fuel pellets

• US 8,377,153 B2
• Filed: 02/13/2012
• Issued: 02/19/2013
• Est. Priority Date: 02/15/2008
• Status: Active Grant

• Current Assignee: Renewable Densified Fuels, LLC
• Original Assignee: Renewable Densified Fuels, LLC
• Inventors: Kluko, Milan
• Primary Examiner(s): WEISS, PAMELA HL
• Application Number:
  US13/371,962
• Publication Number:
  US 20120145054A1
• Time in Patent Office: 372 Days
• Field of Search: 445/08, 445/89, 445/90, 445/94, 445/95, 446/05, 446/06, 481/97.FM
• US Class Current: 44/553
• 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 method of generating heat in a boiler such as by combusting a fuel material which includes a plurality of densified fuel pellets is provided. The densified fuel pellets may be formed by a process which includes compacting a mixture which includes about 5 to 15 wt. % molten thermoplastic polymeric material and at least about 75 wt. % cellulosic material. Many embodiments of the method are suitable for use in a coal-fired furnace and/or in other industrial boiler applications.

Claims

1. A method of generating heat in a boiler comprising combusting a fuel material which includes a plurality of densified fuel pellets;

wherein the densified fuel pellets are 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;

such that the densified fuel pellets have 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 method of claim 1 wherein the fuel material includes coal pieces and the plurality of the densified fuel pellets have substantially similar size characteristics as the coal pieces.

3. The method of claim 1 wherein the boiler is designed for burning coal.

4. The method of claim 1 wherein the densified fuel pellets have a heat value of 9,500 to 12,000 Btu/lb (as is basis).

5. The method of claim 1 wherein the thermoplastic polymeric material has a melting point of about 130 to 150°

C.

6. The method of claim 1 wherein the thermoplastic polymeric material comprises polyethylene, polypropylene or a mixture thereof.

7. The method of claim 1 wherein the thermoplastic polymeric material comprises high density polyethylene, low density polyethylene or a mixture thereof.

8. The method of claim 1 wherein the densified fuel pellets have a sulfur content of no more than about 0.5 wt. % and an ash content of no more than about 2 wt. %.

9. The method of claim 1 wherein a batch of the densified fuel pellets has a bulk density of about 25 to 35 lb/ft³.

10. The method of claim 1 wherein the cellulosic material comprises sawmill residuals, pulp mill residuals, paper mill residuals, agricultural residues or a mixture thereof.

11. The method of claim 1 wherein the densified fuel pellets have a pellet durability index of at least about 90.

12. The method of claim 1 wherein the thermoplastic polymeric material comprises high density polyethylene, low density polyethylene or a mixture thereof;

the cellulosic material is comminuted into particulate form having a maximum dimension of no more than about 20 mm; and

the densified fuel pellets have a pellet durability index of at least about 90 and a heat value of 9,500 to 12,000 Btu/lb (as is basis).

13. The method of claim 12 wherein the mixture comprises

about 5 to 15 wt. % thermoplastic polymeric material having a melting point of about 120 to 150°

C.; and

at least about 85 wt. % comminuted cellulosic material having a moisture content of no more than about 15 wt. %.

14. The method of claim 12 wherein the fuel pellets have a specific gravity of about 1.0 to 1.2 g/cm³.

15. The method of claim 12 wherein the fuel pellets have a moisture content of no more than about 3 wt. %, a sulfur content of no more than about 0.5 wt. % and an ash content of no more than about 2 wt. %.

16. The method of claim 1 wherein the fuel pellets are in the form of cylindrical pellets about 1.5 to 2 cm in diameter and about 1 to 3 cm in length.

17. The method of claim 1 wherein the mixture comprises at least about 85 wt. % comminuted cellulosic material;

wherein the densified fuel pellets have a pellet durability index of at least about 90 and a heat value of 9,500 to 12,000 Btu/lb (as is basis); and

the thermoplastic polymeric material has a melting point of about 120 to 150°

C.

18. The method of claim 17 wherein the densified fuel pellets have a moisture content of no more than about 3 wt. %;

a sulfur content of no more than about 0.5 wt. %; and

an ash content of no more than about 2 wt. %.

19. The method of claim 17 wherein the densified fuel pellets are in the form of cylindrical pellets about 1.5 to 2 cm in diameter and about 1 to 3 cm in length;

and the cellulosic material is in particulate form having a maximum dimension of no more than about 20 mm.

20. The method of claim 17 wherein the thermoplastic polymeric material comprises high density polyethylene, low density polyethylene or a mixture thereof;

and the comminuted cellulosic material comprises sawmill residuals, pulp mill residuals, paper mill residuals, agricultural residues or a mixture thereof.