Pyrolysis reactor and method of pyrolyzing biomass waste residue

1. A pyrolysis reactor having an inlet for biomass waste material and an outlet for products, the reactor comprising a screw for conveying biomass waste material from the inlet to the outlet, the screw comprising a shaft with a first end and a second end adjacent the outlet and a helical flight arranged about the shaft and extending between the first and second ends, wherein the pitch of the flight alters between the first and second ends of the shaft, the diameter of the shaft increases along its length towards the outlet and the depth of the flight decreases in the direction from the inlet towards the outlet, the screw having a heater extending from the first end to the second end.

2. A pyrolysis reactor according to claim 1 , wherein the pitch of the flight decreases along at least part of the length of the shaft.

3. A pyrolysis reactor according to claim 1 , wherein the outer diameter of the flight is substantially constant along the length of the shaft.

4. A pyrolysis reactor according to claim 1 , wherein the helix angle of the flight varies in correspondence to increase or decrease of the pitch of the flight along the length of the shaft.

5. A pyrolysis reactor according to claim 1 , wherein the shaft comprises one or more recesses.

6. A pyrolysis reactor according to claim 1 , wherein the screw and/or the shaft further comprises at least one of a feed section, a transition section and a metering section.

7. A pyrolysis reactor according to claim 6 , wherein:

(a) the feed section is at and/or adjacent the first end of the screw and/or the shaft,

(b) the metering section is at and/or adjacent the second end of the screw and/or the shaft, and/or

(c) the transition section is between the feed section and the metering section.

8. A pyrolysis reactor according to claim 6 , wherein the pitch of the flight for at least one of the turns is less in the metering section than in the feed section and/or in the transition section.

9. A pyrolysis reactor according to claim 6 , wherein the screw and/or the shaft further comprises an outlet section located in between the metering section and the second end, and wherein the shaft of the outlet section may have a reduced diameter with respect to the diameter of the shaft in the metering section.

10. A pyrolysis reactor according to claim 8 , wherein the pitch and/or the depth of the flight is greater at the outlet section of the screw than in the metering section.

11. A pyrolysis reactor according to claim 8 , wherein the shaft of the outlet section further comprises a conical or tapered end.

12. A pyrolysis reactor according to claim 1 , further comprising one or more apertures that extend through the flight.

13. A pyrolysis reactor according to claim 12 , wherein one or more turns of the flight in the metering section comprises the one or more apertures.

14. A pyrolysis reactor according to claim 1 , further comprising an engagement member configured to allow engagement between the shaft and an actuator for rotating the shaft.

15. A pyrolysis reactor according to claim 1 , further comprising a housing or barrel, wherein said housing or barrel is sized and/or shaped to closely surround the screw.

16. A method of pyrolyzing biomass waste residue in a pyrolysis reactor, the reactor comprising a screw for conveying biomass waste residue from a first end of the screw to an outlet at a second end of the screw, the screw comprising a shaft with a first end and a second end adjacent the outlet and a helical flight arranged about the shaft and extending between the first and second ends, wherein the pitch of the flight alters between the first and second ends of the shaft, the diameter of the shaft increases along its length towards the outlet and the depth of the flight decreases in the direction from the inlet towards the outlet, the method comprising:

a) heating biomass waste residue between the first and second ends of the screw in order to partially pyrolyze the biomass waste residue by heating the screw; and

b) increasing the pressure of the partially pyrolyzed biomass waste residue to thereby further pyrolyze the partially pyrolyzed biomass waste residue.

17. A method of pyrolyzing biomass according to claim 16 , further comprising moving or conveying the biomass waste residue and/or the partially pyrolyzed biomass waste residue.

18. A method of pyrolyzing biomass according to claim 16 , further comprising mixing phases of products of the partially pyrolyzed biomass waste residue.