Densified fuel pellets

• US 8,137,420 B2
• Filed: 05/10/2011
• Issued: 03/20/2012
• 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): Toomer, Cephia D
• Assistant Examiner(s): WEISS, PAMELA HL
• Application Number:
  US13/104,884
• Publication Number:
  US 20110306002A1
• Time in Patent Office: 315 Days
• Field of Search: 445/08, 445/89, 445/90, 44594-595, 446/05, 446/06
• 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 producing 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 method commonly includes compressing a feed mixture to form a densified material, where the feed mixture includes about 5 to 15 wt. % of the thermoplastic polymeric material and at least about 75 wt. % cellulosic material. 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 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 feedstock material;

such that the densified material 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 method of claim 1 wherein the cellulosic feedstock has a moisture content of no more than about 15 wt. % and is in particulate form having a maximum dimension of no more than about 20 mm.

3. The method of claim 1 further comprising, prior to the compressing step, blending the feed mixture in a mixer for a time period sufficient for substantially all of the thermoplastic polymeric material to be melted.

4. The method of claim 1 further comprising:

preblending comminuted thermoplastic polymeric material and comminuted cellulosic feedstock material in a mixing station to provide a preblended feed mixture;

transferring the preblended feed mixture into a preheating system where the preblended feed mixture is heated to a temperature of at least about 140°

C.

5. The method of claim 1 further comprising blending the feed mixture in a heated mixer for a time period sufficient for substantially all of the thermoplastic polymeric material to be melted.

6. The method of claim 1 wherein the feed mixture is maintained at a temperature of at least about 140°

C. during the compressing step.

7. The method of claim 6 wherein the thermoplastic polymeric material comprises high density polyethylene, low density polyethylene or a mixture thereof.

8. The method of claim 1 wherein the feed mixture is compressed sufficiently to increase the specific gravity of the feed mixture by a factor of at least about three.

9. The method of claim 1 wherein the densified material is extruded as columnar ribbons of compressed material;

and further comprising comminuting the compressed material into pieces; and

blowing air over the comminuted material to provide cooled comminuted pieces of the compressed material.

10. The method of claim 1 wherein the feed mixture is subjected to a compaction pressure of 1,500 to 2,500 psi during the compression step.

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

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

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

14. The method of claim 1 wherein the thermoplastic polymeric material comprises a mixture of high density polyethylene and low density polyethylene.

15. The method of claim 1 wherein the method produces a densified fuel pellet having a pellet durability index of at least about 90 and a bulk density of about 25 to 35 lb/ft³.