Fluidised bed pyrolysis apparatus and method

Abstract

A carbonaceous feed pyrolysis apparatus is provided including two or more hot particle fluidized beds, and one or more positive displacement apparatus for the transfer of hot particles between two or more of the beds, wherein one or more of the fluidized beds contains a combustion zone. A bio-oil production process is also provided, including pyrolysis of a carbonaceous bio-mass using two or more fluidized beds, including a first combustion zone carried out in one or more combustion fluidized beds in which a particulate material is fluidized and heated, and a second pyrolysis zone carried out in one or more pyrolysis fluidized beds in which the hot particles heated in the combustion zone are used for pyrolysis of the bio-mass.

Claims

1. A carbonaceous feed pyrolysis apparatus, comprising: a combustion reactor configured to contain a first fluidized bed of hot particles, the first fluidized bed containing a combustion zone; a pyrolysis reactor configured to contain a second fluidized bed of hot particles, the second fluidized bed containing a pyrolysis zone; one or more positive displacement apparatus configured for transfer of hot particles from a base portion of the pyrolysis reactor to a base portion of the combustion reactor; and one or more non-mechanical Z valves having an angle of between 120 and 150 and situated between the combustion reactor and the pyrolysis reactor, wherein the one or more non-mechanical Z valves are configured such that, in operation, hot particles flow from the combustion zone at a temperature of from 400 C. to 1100 C. to the pyrolysis zone while impeding a flow of gas in an opposite direction.

2. The carbonaceous feed pyrolysis apparatus of claim 1, further comprising hot particles, wherein the hot particles are sand particles.

3. The carbonaceous feed pyrolysis apparatus of claim 2, further comprising: first fluidized bed nozzles at the base portion of the combustion reactor, wherein the first fluidized bed nozzles are configured to inject a fluidizing gas and/or a combustion gas into the combustion reactor; and second fluidized bed nozzles at the base portion of the pyrolysis reactor, wherein the second fluidized bed nozzles are configured to inject a fluidizing gas and/or a pyrolysis gas into the pyrolysis reactor.

4. The carbonaceous feed pyrolysis apparatus of claim 3, wherein the second fluidized bed nozzles are configured to permit removal of the hot particles from the base portion of the pyrolysis reactor by the one or more positive displacement apparatus, wherein, in operation, the one or more positive displacement apparatus are configured to exhibit a smaller hold up volume as the hot particles drop past the second fluidized bed nozzles for removal.

5. The carbonaceous feed pyrolysis apparatus of claim 1, further comprising hot particles, wherein the hot particles are primarily catalyst particles.

6. The carbonaceous feed pyrolysis apparatus of claim 5, wherein the catalyst particles are cracking catalyst particles.

7. The carbonaceous feed pyrolysis apparatus of claim 1, further comprising a char separator in fluid communication with pyrolysis reactor and configured to capture char.

8. The carbonaceous feed pyrolysis apparatus of claim 1, wherein the one or more positive displacement apparatus comprise a screw feeder driven by a variable speed drive motor or a constant speed drive motor.

9. A bio-oil production process, comprising: providing the apparatus of claim 1; fluidizing and heating a first portion of hot particles in the combustion reactor to form the first fluidized bed comprising the combustion zone, wherein the combustion zone is operated at or about atmospheric pressure and at a temperature of from 400 C. to 1100 C.; transferring hot particles, via the one or more non-mechanical Z valves, from the combustion reactor to the pyrolysis reactor to form the second fluidized bed containing the pyrolysis zone, wherein the pyrolysis zone is operated at a pressure of from atmospheric pressure to 100 Barg and at a temperature of from 400 C. to 900 C.; introducing a carbonaceous bio-mass into the pyrolysis zone, whereby a bio-oil is obtained by pyrolysis of the carbonaceous bio-mass; and at least partially recycling a pyrolysis gas from the pyrolysis zone to the combustion zone as a source of fuel for heating the hot particles.

10. The bio-oil production process of claim 9, wherein the pyrolysis zone is operated at a temperature of from 500 C. to 600 C.

11. The bio-oil production process of claim 9, wherein the hot particles are catalyst particles, and wherein the catalyst particles in the pyrolysis zone increase throughput of the carbonaceous bio-mass via production of more CO.sub.2, which renders the pyrolysis reaction less endothermic.

12. The bio-oil production process of claim 11, wherein the catalyst particles are cracking catalyst particles.

13. The bio-oil production process of claim 12, wherein the catalyst particles are acid zeolite catalyst particles.

14. The bio-oil production process of claim 9, wherein the pyrolysis zone is operated at or about atmospheric pressure.

15. The bio-oil production process of claim 9, further comprising controlling or selecting a superficial gas velocity of the recycled pyrolysis gas in relation to a degree of entrainment of hot particles in the combustion zone.

16. The bio-oil production process of claim 9, further comprising controlling the temperature of the combustion zone by varying a rate of transfer of hot particles from the pyrolysis zone to the combustion zone by the positive displacement apparatus.

17. The bio-oil production process of claim 9, wherein the first fluidized bed and the second fluidized bed each comprise a disengagement zone, and wherein a pressure in each of the disengagement zones is close to atmospheric pressure.

18. The bio-oil production process of claim 9, wherein the hot particles are catalyst particles, the method further comprising regenerating, in the combustion zone, the catalyst particles by burning off coke formed in pores of the catalyst particles during pyrolysis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described, by way of non-limiting example only, with reference to the accompanying flow sheet and diagrammatic drawings, FIGS. 1 and 2.

(2) In FIG. 1 is shown a dual fluidised bed pyrolysis apparatus of the invention;

(3) In FIG. 2 is shown a nozzle arrangement for the fluidised beds of FIG. 1; and

(4) In FIG. 3 is shown another embodiment of the pyrolysis apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(5) In the flow sheet 10 of FIG. 1, representing an embodiment of this invention, a pyrolysis apparatus 12 and a pyrolysis process is provided for rapidly heating bio-mass to be pyrolysed to bio-oil by mixing it in a pyrolysis fluidised bed 14 with hot particles, in the form of hot sand 16, from a separate fluidised bed operating in combustion conditions.

(6) The combustion fluidised bed 18 has a cross sectional area 3 to 4 times that of the cross sectional area of the pyrolysis fluidised bed 14.

(7) In FIG. 1, the combustion fluidised bed 18 is kept hot, typically around 900 C., by burning combustible gas and char. The hot sand 16 moves from the combustion region 15 to the pyrolysis region 17 by means of an L valve 20 which is known in fluidised bed technology.

(8) The pyrolysis reaction cools the sand down to 500-600 C., and the cooled sand is returned by a screw conveyor 22 to the hot combustion fluidised bed 18 for re-heating.

(9) Some char is entrained with the sand although most of the char will be entrained with the gas and will be collected by the cyclone 24. The char in the sand will burn in the fluidised bed, to provide at least part of the required energy. More energy can be provided from the purge of the pyrolysis gas loop 26. of the energy required for combustion can come from the pyrolysis gases which are combustible gases. These gases are introduced directly into the fluidised bed nozzles 28 with the recycle pyrolysis gas being fed concentricly with the air supply pipe into the fluidised bed gas feed pipes to the fluidised bed nozzles. It is preferable to use the gas as the heat source thereby saving the char, because the char is a valuable resource for farmers; it improves the soil when it is worked in.

(10) As shown in FIG. 2, the air 30 may enter the fluidised bed 18 through the nozzles either downwards, as indicated, or upwards. The horizontal jets are designed to prevent sand from flowing into the air supply line. The gas line 32 enters as close as possible to the nozzle 34 (28), where it mixes with cold air, and combusts in the fluidized bed.

(11) In another embodiment represented by the same flowsheet of FIG. 1, the sand 16 that is used for the bed of the fluidised beds 14, 18 of the first embodiment is replaced with catalyst that provides a more stable bio-oil than using sand alone. The oxygen content in the oil can be reduced in this way (being removed as CO.sub.2. Without this treatment, the oils are reactive and oligomerize over time to become an unmanageable sludge. The catalytically treated oil can be blended into refinery feedstocks to form transportation fuel.

(12) At pyrolytic temperatures, catalysts are prone to coking, which deactivates them. They will last just 5 minutes at these conditions. The catalyst can be renewed by burning off the carbon. The dual fluidised bed system of the invention provides the ideal circumstances for continuous regeneration of the pyrolysis catalyst as the catalyst particles which are returned by the screw feeder to the combustion fluidised bed are heated to around 900 C. which regenerates the catalyst continuously.

(13) In FIG. 3, the flowsheet of FIG. 1 is modified in that the hot sand moves from the combustion region to the pyrolysis region by means of a Z valve which is novel in fluidised bed technology.

(14) Unlike L-valves 20 of FIG. 1, in which the bottom pipe section is at 90 from the vertical, the non-mechanical Z valve 36 design makes use of an angle between 120 and 150, e.g., closer to 135, as shown between Bed A 38 (equivalent to 18 in FIG. 1) and Bed B 40 (equivalent to 14 in FIG. 1) in FIG. 3. This allows for the unassisted transport of solids through the valve as only gravity is required as the driving force for the flow of solids.

(15) It is believed to be an advantage of the invention that more efficient pyrolisis is achieved as well as better quality bio-oil, while char which is produced can be used for other purposes.