Apparatuses and methods for controlling heat for rapid thermal processing of carbonaceous material

Abstract

Embodiments of apparatuses and methods for controlling heat for rapid thermal processing of carbonaceous material are provided herein. The apparatus comprises a reheater for containing a fluidized bubbling bed comprising an oxygen-containing gas, inorganic heat carrier particles, and char and for burning the char into ash to form heated inorganic particles. An inorganic particle cooler is in fluid communication with the reheater to receive a first portion of the heated inorganic particles. The inorganic particle cooler is configured to receive a cooling medium for indirect heat exchange with the first portion of the heated inorganic particles to form first partially-cooled heated inorganic particles that are fluidly communicated to the reheater and combined with a second portion of the heated inorganic particles to form second partially-cooled heated inorganic particles. A reactor is in fluid communication with the reheater to receive the second partially-cooled heated inorganic particles.

Description

FIELD OF THE INVENTION

The present invention relates generally to apparatuses and methods for thermal processing of carbonaceous material, and more particularly relates to apparatuses and methods for controlling heat for rapid thermal processing of carbonaceous material.

BACKGROUND OF THE INVENTION

The processing of carbonaceous feedstocks (e.g. biomass) to produce chemicals and/or fuels can be accomplished by fast (rapid or flash) pyrolysis. Fast pyrolysis is a generic term that encompasses various methods of rapidly imparting a relatively high temperature to feedstocks for a very short time, and then rapidly reducing the temperature of the primary products before chemical equilibrium can occur. Using this approach, the complex structures of carbonaceous feedstocks are broken into reactive chemical fragments, which are initially formed by depolymerization and volatilization reactions. The non-equilibrium products are then preserved by rapidly reducing the temperature.

More recently, a rapid thermal process (RTP) has been developed for carrying out fast pyrolysis of carbonaceous material. The RTP utilizes an upflow transport reactor and reheater arrangement, and makes use of an inert inorganic solid particulate heat carrier (e.g. typically sand) to carry and transfer heat in the process. The RTP reactor provides an extremely rapid heating rate and excellent particle ablation of the carbonaceous material, which is particularly well-suited for processing of biomass, as a result of direct turbulent contact between the heated inorganic solid particulates and the carbonaceous material as they are mixed together and travel upward through the reactor. In particular, the heated inorganic solid particulates transfer heat to pyrolyze the carbonaceous material forming char and gaseous products including high quality pyrolysis gas, which are removed from the reactor to a cyclone. The cyclone separates the gaseous products and solids (e.g. inorganic solid particulates and char), and the solids are passed to the reheater.

The reheater is a vessel that burns the char into ash and reheats the inorganic solid particulates, which are then returned to the reactor for pyrolyzing more carbonaceous material. An oxygen-containing gas, typically air, is supplied to the reheater for burning the char. The inorganic solid particulates and char are contained in the lower portion of the reheater and are fluidized by the air, forming a fluidized bubbling bed also referred to as the dense phase. The reheater also has a dilute phase that is above the dense phase and comprises primarily flue gas, entrained inorganic particles, and ash, which are the byproducts formed from combusting the char with the air. The flue gas, entrained inorganic particles, and ash are removed from the reheater to a cyclone which separates the solids from the flue gas.

Currently, higher capacity RTP arrangements are desired that are capable of handling carbonaceous feedstock rates of up to 400 bone dry metric tons per day (BDMTPD) or higher compared to previously lower feedstock rates of less than 100 BDMTPD. The increased capacity results in more char being produced in the RTP reactor, and the RTP reheater and auxiliary equipment (e.g. cyclone, air blower, etc.) need to be larger in size to support the increased feedstock rate. In particular, many newer RTP reheaters require additional volume to accommodate additional air supplied to the reheaters for cooling to control the otherwise rising temperatures from burning the additional char, and can have sizes of up to 12 meters (m) or greater in diameter and heights of up to 25 m or greater. Unfortunately, the larger sizes of these reheaters substantially increase the cost and complexity of shipping, installing, and operating the reheaters.

Accordingly, it is desirable to provide apparatuses and methods for controlling heat for rapid thermal processing that can adequately support higher carbonaceous feedstock rates without exceeding the design temperature of the reheater from burning the additional char. Moreover, it is also desirable to provide apparatuses and methods for controlling heat for rapid thermal processing without substantially increasing the cost and complexity of shipping, installing, and operating the reheaters. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.

SUMMARY OF THE INVENTION

Apparatuses and methods for controlling heat for rapid thermal processing of carbonaceous material are provided herein. In accordance with an exemplary embodiment, an apparatus for controlling heat for rapid thermal processing of carbonaceous material comprises a reheater configured to contain a fluidized bubbling bed that comprises an oxygen-containing gas, inorganic heat carrier particles, and char and to operate at combustion conditions effective to burn the char into ash and heat the inorganic heat carrier particles to form heated inorganic particles. An inorganic particle cooler is in fluid communication with the reheater to receive a first portion of the heated inorganic particles and is configured to receive a cooling medium for indirect heat exchange with the first portion of the heated inorganic particles to form first partially-cooled heated inorganic particles. The reheater and the inorganic particle cooler are cooperatively configured to combine the first partially-cooled heated inorganic particles with a second portion of the heated inorganic particles in the reheater to form second partially-cooled heated inorganic particles. A reactor is in fluid communication with the reheater to receive the second partially-cooled heated inorganic particles.

In accordance with another exemplary embodiment, an apparatus for controlling heat for rapid thermal processing of carbonaceous material is provided. The apparatus comprises a reactor and a reheater that is in fluid communication with the reactor to receive inorganic heat carrier particles and char. The reheater is configured to form a fluidized bubbling bed that comprises an oxygen-containing gas, the inorganic heat carrier particles, and the char and to operate at combustion conditions effective to burn the char into ash and heat the inorganic heat carrier particles to form heated inorganic particles. An inorganic particle cooler is in fluid communication with the reheater and comprises a shell portion and a tube portion that is disposed in the shell portion. The inorganic particle cooler is configured such that the tube portion receives a portion of the heated inorganic particles and the shell portion receives a cooling medium for indirect heat exchange with the portion of the heated inorganic particles to form partially-cooled heated inorganic particles that are fluidly communicated to the reheater.

In accordance with another exemplary embodiment, a method for controlling heat for rapid thermal processing of carbonaceous material is provided. The method comprises the steps of combining an oxygen-containing gas, inorganic heat carrier particles, and char at combustion conditions effective to burn the char into ash and heat the inorganic heat carrier particles to form heated inorganic particles. Heat from a first portion of the heated inorganic particles is indirectly exchanged to a cooling medium to form first partially-cooled heated inorganic particles. The first partially-cooled heated inorganic particles are combined with a second portion of the heated inorganic particles to form second partially-cooled heated inorganic particles.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:

FIG. 1 schematically illustrates an apparatus for rapid thermal processing of carbonaceous material in accordance with an exemplary embodiment;

FIG. 2 is a partial sectional view of the apparatus depicted in FIG. 1 including an inorganic particle cooler in accordance with an exemplary embodiment; and

FIG. 3 is a sectional view of the inorganic particle cooler depicted in FIG. 2 along line 3-3.

DETAILED DESCRIPTION

The following Detailed Description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding Background of the Invention or the following Detailed Description.

Various embodiments contemplated herein relate to apparatuses and methods for controlling heat for rapid thermal processing of carbonaceous material. Unlike the prior art, the exemplary embodiments taught herein provide an apparatus comprising a reactor, a reheater that is in fluid communication with the reactor, and an inorganic particle cooler that is in fluid communication with the reheater. The reactor rapidly pyrolyzes a carbonaceous feedstock with heated inorganic particles to form gaseous products and solids that include cooled inorganic heat carrier particles and char. A cyclone separates the gaseous products from the solids. The reheater receives the solids and fluidizes the cooled inorganic heat carrier particles and char with an oxygen-containing gas to form a fluidized bubbling bed. The reheater is operating at combustion conditions effective to burn the char into ash and reheat the cooled inorganic heat carrier particles to form heated inorganic particles.

In an exemplary embodiment, a portion of the heated inorganic particles and a cooling medium are fluidly communicated to the inorganic particle cooler. Some of the heat from the heated inorganic particles is indirectly exchanged with the cooling medium to partially cool the heated inorganic particles, forming a heated cooling medium and first partially-cooled heated inorganic particles. The heated cooling medium is removed from the inorganic particle cooler. The first partially-cooled heated inorganic particles are fluidly communicated to the reheater and combined with the remaining portion of the heated inorganic particles to partially cool the heated inorganic particles, forming second partially-cooled heated inorganic particles. The second partially-cooled heated inorganic particles are fluidly communicated to the reactor for continued rapid pyrolysis of the carbonaceous feedstock. The inventors have found that partially cooling the heated inorganic particles with the inorganic particle cooler facilitates controlling the temperatures from excessively rising in the reheater even if the fluidized bubbling bed contains higher levels of char. Accordingly, the reheater does not require additional volume that would otherwise be needed to accommodate additional air for cooling to control the reheater temperatures and therefore, the cost and complexity of shipping, installing, and operating the reheater is not substantially impacted.

Referring to FIG. 1, a schematic depiction of an apparatus 10 for rapid thermal processing of a carbonaceous material in accordance with an exemplary embodiment is provided. The apparatus 10 comprises an upflow transport reactor 12, a reheater 14, and an inorganic particle cooler 15. The reactor 12 is configured for achieving a relatively high temperature within a minimum amount of time as well as providing a relatively short residence time at the high temperature to affect fast pyrolysis of a carbonaceous feedstock 20 (e.g. biomass including biomass waste). The relatively high temperature is achieved in a lower portion 16 of the reactor 12 using heated inorganic heat carrier particles 18 (e.g., heated sand) that are supplied from the reheater 14 to drive the pyrolysis process.

As illustrated and will be discussed in further detail below, a dryer 13 removes water from a moisture-containing carbonaceous feedstock 11 to form a carbonaceous feedstock 20 that preferably has a moisture content of 6 weight percent (wt. %) or less. The carbonaceous feedstock 20 is supplied to a feed bin 22 where a reactor feed conveyor 24 introduces the carbonaceous feedstock 20 to the lower portion 16 of the reactor 12. A carrier gas 25, which can be a recirculation gas collected from a suitable location along the apparatus 10, is also introduced to the lower portion 16 of the reactor 12. The carrier gas 25 preferably contains less than 1 wt. % of oxygen, and more preferably, less than 0.5 wt. % of oxygen so that there is very little or no oxygen present thus minimizing or preventing oxidation and/or combustion of the carbonaceous feedstock 20 in the reactor 12.

Rapid mixing of the heated inorganic heat carrier particles 18 and the carbonaceous feedstock 20 occur in the lower portion 16 of the reactor 12. As the mixture advances up the reactor 12 in turbulent flow with the carrier gas 25, heat is transferred from the heated inorganic heat carrier particles 18 to the carbonaceous feedstock 20. In an exemplary embodiment, mixing and rapid heat transfer occurs within 10% of the desired overall reactor resident time. Accordingly, the mixing time is preferably less than 0.1 seconds, and more preferably within 0.015 to 0.030 seconds. In an exemplary embodiment, the temperature in the lower portion 16 of the reactor 12 is from 600 to 780° C., and the heating rate of the carbonaceous feedstock 20 is preferably 1000° C. per second or greater. The use of sand or other suitable inorganic particulate as a solid heat carrier enhances the heat transfer because of the higher heat carrying capacity of the inorganic particles, and the ability of the inorganic particles to mechanically ablate the surface of the reacting carbonaceous material.

As the heated mixture is carried towards an upper portion 17 of the reactor 12 with the carrier gas 25, fast pyrolysis of the carbonaceous feedstock 20 occurs. In an exemplary embodiment, the temperature in the upper portion 17 of the reactor 12 is from 450 to 600° C. The sand or other inorganic heat carrier particles and the carrier gas 25, along with product vapors 30 and char form a product stream 26 that is carried out of the upper portion 17 of the reactor 12 to a cyclone 28. The cyclone 28, preferably a reverse flow cyclone, removes the solids 32, e.g., sand and char, from the product vapors 30, which comprise the carrier gas 25, non-condensible product gases and the primary condensible vapor products. The product vapors 30 are removed from the cyclone 28 and passed to a Quench Tower (not shown), for example, for rapid cooling or quenching to preserve the yields of the valuable non-equilibrium products in the product vapors 30. The solids 32 are removed from the cyclone 28 and passed to the reheater 14.

The reheater 14 receives an oxygen-containing gas 34, which is typically air. The solids 32 are contained in a lower portion 36 of the reheater 14 and are fluidized by the oxygen-containing gas 34 from a gas distributor 86 (see FIG. 2) to form a fluidized bubbling bed of char, inorganic heat carrier particles, and the oxygen-containing gas 34. The reheater 14 is operating at combustion conditions to burn the char into ash and flue gas. The energy released from combustion of the char reheats the inorganic heat carrier particles to form heated inorganic particles. In an exemplary embodiment, the heated inorganic particles have a temperature of from 600 to 780° C.

The flue gas, entrained sand, and ash rise to an upper portion 37 of the reheater 14 and are carried out of the reheater 14 as an exhaust stream 41 to a cyclone 43. The cyclone 43, preferably a reverse flow cyclone, removes the sand and ash from the flue gas.

The flue gas is passed along as a gas stream 51 for exhausting, subsequent processing, recirculation, or a combination thereof, and the sand and ash are passed along as a solids-containing stream 49 for disposal or subsequent processing.

Referring also to FIG. 2, in an exemplary embodiment, a portion of heated inorganic particles 38 is removed from the reheater 14 and introduced to the inorganic particle cooler 15. As illustrated, the portion of heated inorganic particles 38 is removed from the lower portion 36 of the reheater 14 and passed along a cooler inlet pipe 40 through at least one bubble breaking grating 39 to an exchanger vessel 42. The bubble breaking grating 39 breaks up any larger air-bubbles, for example, from the fluidized inorganic particles that otherwise may be passed along countercurrent to the portion of heated inorganic particles 38, back up to the bubbling bed at the lower portion 36 of the reheater 14. Big bubbles in the fluidized bed affect the reheater's 14 performance and solid entrainment. The bubble breaking grating 39 also serves as a screener to prevent bigger chunks of material, such as refractory from directly blocking or plugging the tube portion 45 and reducing the inorganic particle cooler capacity.

In an exemplary embodiment, the exchanger vessel 42 is configured as a heat exchanger and comprises a shell portion 44 and a tube portion 45 that is disposed in the shell portion 44. The portion of the heated inorganic particles 38 is passed through the tube portion 45. The shell portion 44 of the exchanger vessel 42 receives a cooling medium 52 for indirect heat exchange with the portion of heated inorganic particles 38 passing through the tube portion 45 to form partially-cooled heated inorganic particles 54 and a heated cooling medium 53. In an exemplary embodiment, the partially-cooled heated inorganic particles 54 have a temperature of from 500 to 680° C.

Preferably, the cooling medium 52 comprises air and the heated cooling medium 53 comprises heated air. As illustrated in FIG. 1, the heated cooling medium 53 (e.g. heated air) may be passed along to the dryer 13 for removing water from the moisture-containing carbonaceous feedstock 11. Alternatively, the cooling medium 52 may be any other thermally conductive fluid known to those skilled in the art. Preferably, the cooling medium 52 has a temperature of 40° C. or less, and the heated cooling medium 53 has a temperature of 125° C. or greater.

Referring to FIG. 3, in an exemplary embodiment, the tube portion 45 comprises a plurality of tubes 58 that are juxtaposed, spaced apart, and longitudinally disposed substantially parallel to a vertical axis. Each of the tubes 58 has an outer surface with one or more cooling fins 60 that can extend, for example, radially or longitudinally outward from the outer surface. The cooling fins 60 facilitate indirect heat exchange between the portion of the heated inorganic particles 38 advancing through the tube portion 45 and the cooling medium 52 advancing through the shell portion 44.

As illustrated in FIG. 2, the partially-cooled heated inorganic particles 54 are removed from the exchanger vessel 42 and passed along a cooler standpipe 73. The cooler standpipe 73 has an expansion joint-slide valve 74 for controlling the flow rate of the partially-cooled heated inorganic particles 54. A lift riser 76 is downstream from the exchanger vessel 42 and is fluidly coupled to the cooler standpipe 73 for receiving the partially-cooled heated inorganic particles 54. Disposed in a lower portion 78 of the lift riser 76 is an air nozzle 80 that is configured to direct the partially-cooled heated inorganic particles 54 through the lift riser 76 to an upper portion 82 of the lift riser 76.

A sand-air distributor 84 is disposed in the reheater 14 and is fluidly coupled to the lift-riser 76 to receive the partially-cooled heated inorganic particles 54. The sand-air distributor 84 is configured to distribute the partially-cooled heated inorganic particles 54 in the reheater 14, preferably above the gas distributor 86, to partially cool the remaining portion of the heated inorganic particles and form the heated inorganic heat carrier particles 18. Referring also to FIG. 1, in exemplary embodiment, the heated inorganic heat carrier particles 18 have a temperature of from 600 to 780° C. and are passed along to the reactor 12 for rapidly pyrolyzing additional carbonaceous material.

Accordingly, apparatuses and methods for controlling heat for rapid thermal processing of carbonaceous material have been described. Unlike the prior art, the exemplary embodiments taught herein provide an apparatus comprising a reactor, a reheater, and an inorganic particle cooler. The reactor rapidly pyrolyzes a carbonaceous feedstock with heated inorganic particles to form pyrolysis oil and solids that include cooled inorganic heat carrier particles and char. The reheater receives the solids and fluidizes the cooled inorganic heat carrier particles and char with an oxygen-containing gas to form a fluidized bubbling bed. The reheater is operating at combustion conditions effective to burn the char into ash and heat the cooled inorganic heat carrier particles to form heated inorganic particles. The inorganic particle cooler receives a portion of the heated inorganic particles and removes some of the heat via indirect exchange to form partially-cooled heated inorganic particles that are combined with the remaining portion of the heated inorganic particles to partially cool the heated inorganic particles. It has been found that partially cooling the heated inorganic particles with the inorganic particle cooler facilitates controlling the temperatures from excessively rising in the reheater even if the fluidized bubbling bed contains higher levels of char. Accordingly, the reheater does not require additional volume that would otherwise be needed to accommodate additional air for cooling to control the reheater temperatures and therefore, the cost and complexity of shipping, installing, and operating the reheater is not substantially impacted.

While at least one exemplary embodiment has been presented in the foregoing Detailed Description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing Detailed Description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended Claims and their legal equivalents.

Claims

1. A method for controlling heat for rapid thermal processing of carbonaceous material, comprising: i) combining char obtained from a rapid thermal processing unit with inorganic particles and an oxygen-containing gas in a reheater at combustion conditions effective to burn the char into ash and heat the inorganic particles to form heated inorganic particles;ii) drying a moisture-containing carbonaceous feedstock to form a reduced-moisture carbonaceous feedstock, comprising:a) contacting an air stream and a first portion of the heated inorganic particles to form a heated air stream; andb) transferring heat to the moisture-containing carbonaceous feedstock, comprising: contacting the heated air stream with the moisture-containing carbonaceous feedstock; andiii) pyrolyzing the reduced-moisture carbonaceous feedstock in the rapid thermal processing unit, comprising: adding heat to the reduced-moisture carbonaceous feedstock in the rapid thermal processing unit, wherein the heat in the drying and the heat in the pyrolyzing consist of heat derived from the combustion of the char obtained from the rapid thermal processing unit.

2. The method of claim 1, wherein the moisture-containing carbonaceous feedstock is a biomass.

3. The method of claim 1, wherein the reduced-moisture carbonaceous feedstock has a water content of 6 wt. % or less.

4. The method of claim 1, wherein the contacting the air stream and the first portion of the heated inorganic particles comprises: introducing the first portion of the heated inorganic particles and the air stream into a heat exchanger.

5. The method of claim 4, said pyrolyzing comprising: introducing the reduced-moisture carbonaceous feedstock to a lower portion of the rapid thermal processing unit, wherein the rapid thermal processing unit is a fast pyrolysis upflow reactor.

6. The method of claim 4, wherein the contacting the air stream and the first portion of the heated inorganic particles further forms first partially-cooled heated inorganic particles, and said first partially-cooled heated inorganic particles are recirculated from the heat exchanger into the reheater and combined with a second portion of the heated inorganic particles in the reheater to form second partially-cooled heated inorganic particles, and the second partially-cooled heated inorganic particles are communicated from the reheater to said lower portion of the rapid thermal processing unit.

7. The method of claim 4, wherein the contacting the air stream and the first portion of the heated inorganic particles further forms first partially-cooled heated inorganic particles, and said first portion of the heated inorganic particles enter the heat exchanger at a temperature of between 600° C. and 780° C. and said first partially-cooled heated inorganic particles exit the heat exchanger at a temperature of between 500° C. and 680° C.

8. The method of claim 7, wherein said first portion of heated inorganic particles are recirculated from the heat exchanger into the reheater and combined with a second portion of the heated inorganic particles in the reheater to form second partially-cooled heated inorganic particles, and the second partially-cooled heated inorganic particles are communicated from the reheater to said lower portion of the reactor.

9. The method of claim 1, wherein the heated air stream is at a temperature of at least 125° C.

10. The method of claim 1, wherein the air stream is at a temperature of 40° C. or less.

11. The method of claim 1, said pyrolyzing comprising: introducing the reduced-moisture carbonaceous feedstock to a lower portion of the rapid thermal processing unit, wherein the rapid thermal processing unit is a fast pyrolysis upflow reactor.

12. The method of claim 11, wherein the lower portion of the reactor is at a temperature of between 600° C. and 780° C.

13. The method of claim 11, wherein an upper portion of the reactor is maintained at a temperature of between 450° C. and 600° C.

14. The method of claim 11, wherein said first portion of heated inorganic particles are recirculated from the heat exchanger into the reheater and combined with a second portion of the heated inorganic particles in the reheater to form second partially-cooled heated inorganic particles, wherein said introducing comprises: mixing the reduced-moisture carbonaceous feedstock with the second partially-cooled heated inorganic particles in a low-oxygen carrier gas, said second partially-cooled heated inorganic particles at an initial temperature of between 600° C. and 780° C.

15. The method of claim 14, wherein the mixing occurs under turbulent flow conditions.

16. The method of claim 15, wherein the mixing has a mixing time of less than 0.1 seconds.

17. The method of claim 15, wherein the mixing occurs within 10% of a desired reactor residence time.

18. The method of claim 14, wherein said reduced-moisture carbonaceous feedstock is heated at a rate of greater than 1000° C. per second in said lower portion of the reactor.

19. The method of claim 14, wherein the low oxygen carrier gas has an oxygen content of less than 1 wt. %.

20. The method of claim 1, wherein up to 400 bone dry metric tons per day of reduced-moisture carbonaceous feedstock are pyrolyzed.