WO2008058347A1

WO2008058347A1 - Manufacture of fuels

Info

Publication number: WO2008058347A1
Application number: PCT/AU2007/001772
Authority: WO
Inventors: Edek Choros
Original assignee: Millennium Synfuels, Llc
Priority date: 2006-11-17
Filing date: 2007-11-16
Publication date: 2008-05-22

Abstract

Disclosed is retort apparatus, for processing a carbonaceous feed material for the manufacture of hydrocarbon gases and vapours, with a heating chamber having at least one heating surface for heating the bed of carbonaceous material. The device also includes at least one steam inlet for introducing steam into the heating chamber to interact with at least a portion of the bed of carbonaceous material in the chamber. Methods for the preparation of hydrocarbon vapours and gases are also disclosed.

Description

TITLE OF THE INVENTION "Manufacture of Fuels"

FIELD OF THE INVENTION The invention generally relates to a device and methods for the generation of hydrocarbon and other fuel gases and vapours from carbonaceous material, for the preparation of fuel and chemical values.

BACKGROUND TO THE INVENTION Coal pyrolysis is a thermal process for converting carbonaceous material to (1) a char (the char often having a high calorific value depending on the nature of the feed), (2) condensable hydrocarbons and (3) non-condensable gases. After purification, the condensable gases, including gases such as: hydrogen, hydrocarbons such as Cl — C4 gases, and carbon monoxide, can be used for their heating value or as raw materials for the manufacture of chemicals or fuels, and the non-condensable gases can be utilised for their fuel or chemical values.

Condensable and non-condensable vapours may be generated from carbonaceous material in a number of ways. One method is to heat a carbonaceous material, such as coal or shale, in a retort in the absence of air, thereby partially converting the carbonaceous material to vapours (some of which condense) and to a char residue. This process is known as retorting.

Under appropriate conditions, coal can be almost completely converted to gas by continuously reacting coal in a gasifier with air and steam. This requires relatively high temperatures and pressures with temperatures typically greater than 800⁰C and commonly greater than 100O⁰C. The gas obtained in this manner, generally a mixture of CO, H₂ and other gases, has a thermal content per unit volume of gas ranging from about 100 btu/SCF to about 350 btu/SCF, depending on the exact gas composition. Processes have been developed to continuously produce such gas using steam and essentially pure oxygen as a reactant. One process, reacts coal with pure oxygen and steam at an elevated pressure of about 30 atmospheres to produce a gas that may be converted to synthetic natural gas. The coal is fed at the top with air, and steam is introduced at the bottom. The gas, air, and steam rising up the retort heat the coal in its downward flow and react with the coal to convert it to gas. Ash is removed at the bottom of the retort.

Other processes react finely powdered coal with steam and oxygen. One of these, the Winkler process, uses a fluidized bed in which the powdered coal is agitated with the reactant gases. Another, called the Koppers-Totzek process, operates at a much higher temperature, and the powdered coal is reacted while it is entrained in the gases passing through the reactor. The reacted material is removed from the bottom of the reactor. Both of these processes are used for fuel gas production and in the generation of gases for chemical and fertilizer production. As petroleum and natural gas supplies decrease, the desirability of producing gas from coal increases. It is also anticipated that costs of natural gas will increase, allowing coal pyrolysis and gasification to compete as economically viable processes.

Complete gasification of coal requires relatively high temperatures and pressures resulting in need for more expensive construction materials and concomitant higher construction costs.

Improving yields of hydrocarbon vapours generated from coal via low temperature thermal processes can increase the versatility of coal as a source of fuel.

SUMMARY OF THE INVENTION

Accordingly, the invention provides a retorting device for the manufacture of hydrocarbon vapours and gases from a bed of carbonaceous material, including: a heating chamber having at least one heating surface for heating a bed of carbonaceous material, a means for increasing surface contact area between the particles of the bed and the heating surface, and at least one inlet for introducing steam into the heating chamber to interact with at least a portion of the bed of carbonaceous material in the chamber.

Suitably, the device comprises a first opening for introducing carbonaceous material into the heating chamber and a second opening for removing the retorted carbonaceous material from the heating chamber, said carbonaceous material passing through the heating chamber from the first opening to the second opening.

Preferably, the heating chamber has an overall pressure of less than two atmospheres, more preferably atmospheric pressure or less.

Typically, the temperature of the bed of carbonaceous material increases inside the heating chamber through contact of the bed with at least one heating surface, as the bed passes from the first opening to the second opening. Generally, the carbonaceous is heated from its entry at the first opening to its exit at the second opening at a relatively slow heating rate. Preferably, the heating rate is in the range of about 2°C/min to about 50°C/min, more preferably in the range of about 4°C/min to about 20°C/min.

Generally, the temperature of the bed as it leaves the heating chamber through the second opening is from about 45O⁰C to about 65O⁰C, sometimes from about 500⁰C to 600⁰C.

Typically, the heating chamber comprises vents to allow vapours generated from heating the carbonaceous material to exit or be drawn from the heating chamber.

A suitable means for increasing surface contact area between the particles of the bed and the heating surface are flow diverters which mix the bed particles as they flow through the heating chamber by diverting the direction of a portion of the bed. Optionally, the diverters may be an arrangement of staggered chevrons or may be a screw.

Generally, the one or more inlets for introducing steam are located in the region of the heating chamber where the bed has temperature in the range of at least 25O⁰C to 65O⁰C, preferably in the region of at least 35O⁰C to 600⁰C. Typically, there is a plurality of inlets providing steam to the bed over a temperature range.

Optionally, the diverters may provide heating surfaces.

In one embodiment, the heating surface for heating the bed of carbonaceous material may be in the shape of a chevron. The underside of the chevron may form a channel to provide a path to assist gases and vapours to exit from the heating chamber. Suitably the channel is in fluid communication with a vent. Steam inlets may be disposed within channels under the chevrons.

In another aspect, the invention provides a method of manufacturing hydrocarbon vapours and gases, said method including the steps of:

(i) providing a flow of carbonaceous material through a heating chamber, (ii) heating the carbonaceous material by contacting the material with at least one heating surface to thermally generate hydrocarbon vapours and gases; (iii) contacting the bed with mechanical means for increasing surface area contact between heating surfaces and the bed; and

(iv) introducing steam into the heating chamber to interact with at least a portion of the carbonaceous material during the thermal generation of hydrocarbon vapours.

The carbonaceous material can be heated with a range of heating rate profiles. Preferably, the heating rate is in the range of about 2°C/min to about 50°C/min, more preferably in the range of about 4°C/min to about 20°C/min. The bed may be heated slowly and then more rapidly, or may be heated rapidly and then slowly. Suitably, the carbonaceous material may be held substantially isothermally for periods of time.

Generally, the process is self-inerting, with the gases generated through retorting acting as an inert blanket, thereby minimising combustion and other oxidative processes. In selected embodiments, the carbonaceous material introduced into the heating chamber is preheated.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will be described with reference to the accompanying drawings, of which:

FIG. 1 illustrates a cross-sectional view of the retorting device of one embodiment;

FIG. 2 illustrates a perspective view of chambers, diverters, baffles and a gas line of the retorting device; FIG. 3 illustrates a perspective view of a diverter and a gas line of the retorting device underneath that diverter;

FIG. 4 illustrates a perpendicular cross-sectional view of a diverter and a gas line under that diverter;

FIG. 5 illustrates a cross-sectional view of one section of the retorting device including a valved upper opening and a source for the feed material;

FIG. 6 illustrates a cross-sectional view of another section of the retorting device including a valved second opening for removing heated carbonaceous material;

FIG. 7 shows a perspective view of gas pipes on an outside wall of the retorting device; FIG. 8 shows a cross-sectional view of a section of one embodiment of the retorting device including steam inlets in the collection chambers;

FIG. 9 illustrates schematic representation of flow of the bed through the heating chamber.

FIG. 10 illustrates a cross-sectional view of another section of the retorting device; FIG. 11 illustrates a cross-sectional view of another section of the retorting device including steam lines entering through the vapour chamber; and

FIG. 12 illustrates DTA and TGA analysis of sample 001.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings it will be appreciated that the invention may be implemented in various forms, and that this description is given by way of example only. Without wishing to be bound by theory, the mixing of the bed as it flows on a pathway through the heating chamber has the effect of changing the contact surface area between the carbonaceous particles and the heating surface, thus providing a more constant heating profile to the bed and reducing the likelihood of hotspots within the bed. This also provides a more consistent contact between the introduced steam and the bed. This is in contrast to a static (i.e. non-mixed) flowing bed, which does not experience the same degree of change in surface contact area of the bed particles with the heating surfacer. Furthermore, the introduction of steam into the bed over selected temperature ranges has the effect of increasing the yield of vapours and gases generated through both physical and chemical interactions with both the bed particles and gases generated, as well as increasing the volume of the gas in the heating chamber thus increasing the gas velocity and therefore reducing the residence time of the thermally generated gases and vapours within the heating chamber.

The term "interaction" and like terms such as "interact" are meant to refer to both physical interaction and physical and chemical interactions.

Referring to FIGs 1 to 11, the retorting device (10) is usually comprised of the following major components: a heating chamber (12); heating surfaces (20); a first opening towards the top (14); a second opening towards the bottom (16); steam lines and steam inlets (18); diverters (20a); and vents for removal of the thermally generated vapours and gases (22).

Other features may include particulate collection chambers (24) which adjoin the heating chamber; baffles (26); and outlets (27) through which pass gases and other vapours for collection via pipes (28). Referring to FIG. 5, typically, raw carbonaceous material contained in a chamber (30) of an adjoining vessel (32), is introduced into the heating chamber (12) of the retorting device. The vessel (32) may be a hopper containing a carbonaceous material such as coal, lignite, carbonaceous mudstone, or the like, or may be, for example, a dryer connected in series to the heating chamber. The carbonaceous material may be introduced into the heating chamber substantially at room temperature, or substantially at the temperature to which the material was dried, for example, up to about 300⁰C. The carbonaceous feed material, for example coal, may be introduced into the heating chamber (12) through a valve (34), such as represented diagrammatically in FIG 5. Referring to FIG. 1, the feed material passes through the heating chamber from the upper opening (14) to the lower opening (16) and interacts with steam, introduced via steam lines (18), as the material passes through the heating chamber. Steam is typically introduced into the heating chamber after inherent moisture has been removed from the carbonaceous material. Inherent moisture may include hydrogen bonded water, mechanically bound water and the like. Typically, the steam is introduced into the bed of carbonaceous material, as it flows through the heating chamber, in the region of the chamber where the bed has been heated to at least 25O⁰C up until the point where the bed leaves the heating chamber. The steam may be added to the bed at different points in the bed over a range of temperatures, for example, from 25O⁰C to 600⁰C, from 35O⁰C to 500⁰C or from 400⁰C to 500⁰C. Generally, steam is introduced into the bed over that range of temperature at which the pyrolytic devolatisation of the bed material occurs. The feed material has a bulk directional flow from the upper opening towards the lower opening.

Referring to FIG. 5, if desired, the opening towards the top of the heating chamber (12) may be sealable, for example, by a valve (34). If desired, particularly during start-up or shut-down, air from around the carbonaceous material may be purged by introduction of a gas such as nitrogen, argon, methane or the like, into the heating chamber. The gas may be used to fully saturate the heating chamber. Referring to FIG. 6, if desired, the opening towards the bottom of the chamber may also be sealed by a sealable valve (36).

The retorted carbonaceous material may be subjected to further processing (indicated by the block arrow (37)) such as briquetting to form a solid fuel, combustion in a power station boiler or transfer to a coal gasifier. Referring to FIG. 3 and 4, steam (40) can be introduced into the heating chamber (12) through nozzles (38) through a manifold of pipes

(18). As shown in FIG. 7, the pipes (18) may enter into the heating chamber through an outside wall (42) of the heating chamber. As shown in FIG 4, a gas line or gas pipe (18) may be located separate to, and beneath a diverter (20a). The nozzles (38) through which steam is released are shown directed in a generally downwards direction, however steam may be encourage to flow in any direction within the heating chamber so as to interact with the bed. Referring to FIG. 1, the steam pipes may extend across (indicated by the double headed arrow x-y) the heating chamber (12) and be secured (46) on a wall (44) of the heating chamber (12). Referring to FIG. 7, steam may be generated, for example, as a by-product of a power station or a heat recovery process and piped (48) to the retorting device. Steam may also be generated by a dedicated steam generation device, such as a boiler, and piped (48) to the retorting device heating chamber (12). The temperature of the steam may vary depending on the method used to generate the steam. It is desirable, in some instances, to be able to vary the temperature of the steam used in the retorting process in order to vary the conditions and therefore vary the retorting product distribution.

The composition of the fuel gases generated from retorting of carbonaceous material may vary depending on a range of parameters, for example: whether air is allowed in the heating chamber or whether air is excluded from the chamber; the temperature to which the retorting process is conducted; the quantities of such as steam (H₂O) introduced during the retorting process; and the type of raw material used in the retorting process (e.g. the type of coal, lignite, shale, etc). Parameters such as the heat of the bed material (before contact with the gaseous reagent) and the heat of the steam when it is introduced, can also influence the product composition.

Referring to FIGs. 2, 3 and 4, once steam has been introduced into the reaction chamber (12) via nozzles (38), and the carbonaceous bed material has commenced interacting with the steam, the resulting gas can be compartmentalised, in gas compartments (50) which are formed underneath the diverters (20a). The diverters agitate the flow of material through the reaction chamber and change the particle surfaces that contact with the heating surfaces thus increasing the surface contact area between the heating surfaces and the bed. The diverters may be any mechanical means of homogenising the bed by mixing of the bed particles. For example, the bed may be homogenised with respect to its temperature or with respect to the interaction of the bed particles with steam by action of the diverters. The diverters (20a) may also be used to protect the steam nozzles from being clogged by the feed material as it flows through the heating chamber. Referring to FIGs. 2 and 3, and 10, where a gas line (18) is used together with a diverter, there may be no corresponding vent (22) at the termination of the diverter on the wall, instead there may be a dead end (54). Due to the relative low density of the gas compartment spaces, gas velocity in these compartments is reduced with respect to the bed providing a preferred path for the gases and vapours out of the heating chamber.

The diverters may be solid or may be hollow. The diverters can be formed from a metallic substance, with suitable heat transfer properties, that is rated for temperatures up to about 600⁰C - 700⁰C, for example, some kinds of stainless steel. The heat to the heating surfaces (20) may be supplied, for example, by resistive heaters (84a, 84b, and 84c) disposed within the body of a diverter (20a). Alternatively, the heat to the heating surfaces may be supplied through heat exchange. For example, heat can be retrieved from a hot gas which is passed through a diverter which is modified to have one or more internal hollow bodies (86a, 86b) for the passage of such gas.

Referring to FIG. 2, fuel gases may stream (indicated by arrows 52) from the heating chamber through vents (22) to be collected. The pyrolysis gas and vapours, once they have flowed (52) through the vent (22), enters into an adjoining chamber (24), as shown in FIGs. 1 and 2. The adjoining collection chamber contains a sloped baffle (26) which may form part of a wall of the chamber. The baffles (26) are used to completely or partially disentrain particulate matter from the gas stream (52). Accordingly, at least a portion of the particulate matter, which may be entrained in the gas stream from the heating chamber chamber (12), is collected in the collection chamber (24). The velocity of the gas stream may reduce as it passes from the heating chamber to collection chamber. Gravitational effects lead to disentrainment of particles from the gas stream. Disentrainment of particulate matter from the gas stream may depend upon one or more of the following: velocity of the gas stream, the momentum and mass of the particle and frictional effects.

As shown in FIG 1 and in FIG 2, the gas stream (24) exits the particulate matter collection chamber via the exit port (27). The particulate matter that has been collected in the collection chamber (24) may flow back into the heating chamber (12). The fuel gases, are piped via pipes (28) to be purified and collected for further use. For example, condensable hydrocarbons can be condensed from the gas stream by cooling of the stream, and nitrogenous and sulphurous by-products can be scrubbed and/or catalytically removed from the gas stream. The path of the gas stream through the retorting device may be influenced by, for example: changes in pressure - e.g. thermal expansion of materials and positive or reduced pressure applied to the device. The gas stream path may also be influenced by convection currents. Referring to FIG. 8, optionally, steam may be introduced into the collection chambers (24), piped to the chamber (24) via a main pipe line (60) which then splits into subsidiary pipelines (62) which enter into the collection chambers (24). Steam may be ejected from nozzles (64) on the pipelines (62) in order to clean the baffles (26).

The retorting process is substantially continuous with a flow of feed material passing through the heating chamber (12) from top to bottom. Referring to FIG. 1 and 5, carbonaceous feed material introduced via chamber (30) of the vessel (32) through the valve (34) into the heating chamber (12) is replaced by further feed material from the chamber (30) as pyrolysed material is removed from the opening (16) at the bottom of the heating chamber. The arrow (70) in FIG. 5 indicates the general direction of flow of the carbonaceous feed material as it makes its way through the heating chamber (12).

Referring to FIG. 9, diverters (20a) change the direction of flow of the bed as indicated by directional arrows (72), (74) and (76). Steam (40), radiates from steam lines (18), into the bed. When the retort has carbonaceous material flowing through it, the bed can be described as the bulk material that flows through heating chamber (12).

Referring to FIG. 10, Steam can be selectively introduced into different sections of the retort by use of valves (78a - 78d). This allows steam to be introduced at different temperatures. The arrow (82) indicates increasing temperature down the retort. Accordingly, steam introduced after valve (78a) will enter a cooler part of the bed than steam introduced at the steam line after valve (78d). The void spaces (80) between the diverters (20a) are typically occupied by the bed as the bed flows down through the retort. Referring to FIG. 11, the steam lines (18) may be introduced into the heating chamber (12) in a variety of ways. Pipe (48) may come into the retort from either front or side walls or may enter from the top or the bottom of the retort. In FIG. 11, the steam lines are shown coming in through the vapour chamber (24). The hot vapour in the vapour chamber may be used to heat the steam before it is released into the heating chamber (12) via pipes (18).

Referring to FIG. 12, TGA and DTA analysis of sample 001 shows the region where most devolatisation occurs is between about 400 - 500⁰C. Some devolatisation is shown to occur above and below these temperatures. The heating rate of the TGA and DTA analysis was 10°C/minute.

Table 1: Proximate, Ultimate and CV

Referring to Table 1, this table details proximate analysis, ultimate analysis and energy for seven carbonaceous samples labelled 001 - 007.

Table 2: Inert Testing Results

Table 2 details the results of pyrolysis testing with samples 001 - 007 without the addition of steam during the pyrolysis process. The reaction conditions are essentially kept inert by an initial nitrogen purge. Table 3: Hydrous Testing Results

Table 3 details the results of pyrolysis testing with samples 001 - 007 with the addition of steam during the pyrolysis process.

Table 4: Raw Analysis of Sample 010

Table 4 shows proximate, ultimate and energy data for a high ash carbonaceous sample 010. Table 5: Steam added at different Rates

Table 5 shows tests AMB17 to AMB23 which cover a range of testing conditions including different rates of steam addition and different isothermal periods at 600⁰C.

Claims

CLAIMS:

1. A retorting device for the manufacture of hydrocarbon vapours and gases from a bed of carbonaceous material, including: a heating chamber having at least one heating surface for heating the bed of carbonaceous material; a means for increasing surface contact area between the particles of the bed and the heating surface; and, at least one steam inlet for introducing steam into the heating chamber to interact with at least a portion of the bed of carbonaceous material in the chamber.

2. The device of claim 1 wherein the at least one inlet for introducing steam is located in the region of the heating chamber where the bed has been heated to a temperature from at least 25O⁰C to a temperature of 65O⁰C.

3. The device of claim 2 wherein the at least one inlet for introducing steam is located in the region of the heating chamber where the bed has been heated to a temperature from at least 35O⁰C to a temperature of 65O⁰C.

4. The device of any of the preceding claims wherein the at least one inlet is a multiplicity of inlets .

5. The device of any of the preceding claims wherein a multiplicity steam inlets are located in the region of the heating chamber where the bed is undergoing pyrolytic devolatisation.

6. The device of any of claims 1 to 5, further comprising a first opening for introducing carbonaceous material into the heating chamber and a second opening for removing the retorted carbonaceous material from the heating chamber, such that the carbonaceous material passes through the heating chamber from the first opening to the second opening.

7. The device of claim 6 wherein the temperature of the bed of carbonaceous material increases inside the heating chamber as the bed passes from the first opening to the second opening.

8. The device of claim 7 wherein the heating rate of the bed is in the range of about 2°C/min to about 50°C/min.

9. The device of claim 8 wherein the heating rate is in the range of about 4°C/min to about 20°C/min.

10. The device of claim 6 wherein the bed is held isothermally for at least a portion of its passage from the first opening to the second opening.

11. The device of any of claims 6 to 10 wherein the temperature of the bed as it leaves the heating chamber through the second opening is from about 45O⁰C to about

65O⁰C.

12. The device of claim 11 wherein the temperature of the bed is from about 500⁰C to 600⁰C.

13. The device of any of the preceding claims wherein the heating chamber comprises vents to allow vapours generated from heating the carbonaceous material to exit the heating chamber.

14. The device of any of the preceding claims wherein the means for increasing surface contact area between the particles of the bed and the heating surface are mechanical flow diverters that mix the bed particles as they flow through the heating chamber by contacting the bed and diverting the direction of a portion of the bed.

15. The device of claim 13 wherein the diverter provides a heating surface.

16. The device of either of claims 14 or 15 wherein the diverter is in the shape of a chevron.

17. The device of claim 15 wherein the underside of the chevron forms a channel to provide a path for gases and vapours to exit from the heating chamber.

18. The device of claim 17 wherein the channel is in fluid communication with a vent.

19. The device of claim 18 wherein steam inlets are disposed within channels under the chevrons.

20. A method of manufacturing hydrocarbon vapours and gases, said method including the steps of:

(i) providing a flow of carbonaceous material through a heating chamber, (ii) heating the flow of carbonaceous material by contacting the material with at least one heating surface to heat the material to a temperature sufficient to thermally generate hydrocarbon vapours and gases;

(iii) contacting the bed with mechanical means for increasing surface area contact between heating surfaces and the bed; and (iv) introducing steam into the heating chamber to interact with at least a portion of the carbonaceous material during the thermal generation of hydrocarbon vapours.

21. The method of claim 20 wherein the bed of carbonaceous material is heated at a heating rate in the range of about 2°C/min to about 50°C/min,

22. The method of claim 21 wherein the heating rate is in the range of about 4°C/min to about 20°C/min.

23. The method of any of claims 20 to 22 wherein the bed is heated slowly and then more rapidly.

24. The method of any of claims 20 to 22 where the bed is initially heated rapidly and then slowly.

25. The method of claim 20 including the further step of holding the carbonaceous material substantially at a constant temperature.

26. The method of claim 20 wherein the, the steam is introduced to the heating chamber in that region of the chamber where the bed is at a temperature of at least 250⁰C to a temperature of 65O⁰C.

27. The method of claim 20 wherein the, the steam is introduced to the heating chamber in that region of the chamber where the bed is at a temperature of at least 350O⁰C to a temperature of 600⁰C.

28. The method of claim 20 wherein the steam is introduced into the heating chamber in the region of the chamber where the bed is undergoing pyrolytic devolatisation.

29. The method of any of claims 20 to 28 wherein the steam is introduced at a temperature from about 100⁰C to about 65O⁰C.

30. Retort apparatus including: a reaction chamber having a pathway for throughput of carbonaceous material, one or more diverters arranged on the pathway for agitating the carbonaceous material, one or more heating surfaces arranged on the pathway for heating the agitated material, one or more steam inlets for introducing steam to the heating chamber to interact with the heated material, and one or more gas outlets for collecting gas produced by interactions between the heated material and the steam.

31. Apparatus according to claim 30 wherein the pathway is a vertical passage through the chamber and the carbonaceous material falls through the passage under gravity.

32. Apparatus according to claim 30 wherein a plurality of diverters are distributed along the pathway between heating surfaces.

33. Apparatus according to claim 30 wherein at least some of the diverters include heating surfaces.

34. Apparatus according to claim 30 wherein the steam inlets are located downstream of respective diverters and/or heating surfaces.

35. Apparatus according to claim 30 wherein the diverters are shaped as chevrons pointed upstream on the pathway.

36. Apparatus according to claim 35 wherein the steam inlets and/or the gas outlets are located behind or under the chevrons.

37. Apparatus according to claim 30 wherein temperature increases along the pathway to an exit temperature of about 650° C.