NZ618672B2 - Apparatus and process for continuous carbonisation of wood chips or wastes and other charring organic materials - Google Patents
Apparatus and process for continuous carbonisation of wood chips or wastes and other charring organic materials Download PDFInfo
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- NZ618672B2 NZ618672B2 NZ618672A NZ61867212A NZ618672B2 NZ 618672 B2 NZ618672 B2 NZ 618672B2 NZ 618672 A NZ618672 A NZ 618672A NZ 61867212 A NZ61867212 A NZ 61867212A NZ 618672 B2 NZ618672 B2 NZ 618672B2
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B1/00—Retorts
- C10B1/02—Stationary retorts
- C10B1/04—Vertical retorts
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B39/00—Cooling or quenching coke
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B49/00—Destructive distillation of solid carbonaceous materials by direct heating with heat-carrying agents including the partial combustion of the solid material to be treated
- C10B49/02—Destructive distillation of solid carbonaceous materials by direct heating with heat-carrying agents including the partial combustion of the solid material to be treated with hot gases or vapours, e.g. hot gases obtained by partial combustion of the charge
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B53/00—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form
- C10B53/02—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form of cellulose-containing material
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/10—Biofuels, e.g. bio-diesel
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/141—Feedstock
- Y02P20/145—Feedstock the feedstock being materials of biological origin
Abstract
Disclosed is a process for the autogenous production of charcoal, the process comprising: adding dry organic material to a first end of a reaction vessel whereby the organic material progresses along a flow path through the reaction vessel and is removed from a discharge port at a second end of the reaction vessel; heating the organic material in a heating zone of the reaction vessel as it progresses through the reaction vessel to a reaction zone where the temperature of the organic material has reached a sufficient temperature for exothermic autogenous decomposition of the organic material to occur; allowing the organic material in the reaction zone to undergo autogenous decomposition into charcoal and pyroligneous gases; and cooling the charcoal in a cooling zone of the reaction vessel prior to discharge, wherein pyroligneous gases are removed from a reaction zone outlet in the periphery of the reaction vessel such that gases move substantially transversely across the material in the reaction zone towards the reaction zone outlet. Also disclosed is an associated apparatus for the autogenous production of charcoal comprising: a feeder for supplying a heated organic material to a reaction vessel, the reaction vessel for supporting a reaction bed of organic material, and at least one discharge port for discharging thermally decomposed organic material from the reaction vessel, the reaction vessel defining a flow path in which the thermal decomposition of the organic material progresses with the organic material through the reaction vessel; the reaction vessel comprising: a reaction zone for autogenous pyrolysis reaction of organic material in the reaction bed to form pyroligneous gases, a cooling zone having at least one cooling zone inlet for supplying cooling gas into the reaction bed and a cooling zone outlet to extract heated gas from the reaction bed, and at least one lance extending through the reaction bed into the reaction zone to supply a gas into the reaction vessel through a reaction zone inlet in the lance; and a reaction zone outlet provided in the periphery of the reaction zone to remove gas supplied to the reaction zone by the lance, wherein the reaction zone outlet is located transversely from the reaction zone inlet such that gases move substantially transversely across the material in the reaction zone towards the reaction zone outlet. reaction vessel; heating the organic material in a heating zone of the reaction vessel as it progresses through the reaction vessel to a reaction zone where the temperature of the organic material has reached a sufficient temperature for exothermic autogenous decomposition of the organic material to occur; allowing the organic material in the reaction zone to undergo autogenous decomposition into charcoal and pyroligneous gases; and cooling the charcoal in a cooling zone of the reaction vessel prior to discharge, wherein pyroligneous gases are removed from a reaction zone outlet in the periphery of the reaction vessel such that gases move substantially transversely across the material in the reaction zone towards the reaction zone outlet. Also disclosed is an associated apparatus for the autogenous production of charcoal comprising: a feeder for supplying a heated organic material to a reaction vessel, the reaction vessel for supporting a reaction bed of organic material, and at least one discharge port for discharging thermally decomposed organic material from the reaction vessel, the reaction vessel defining a flow path in which the thermal decomposition of the organic material progresses with the organic material through the reaction vessel; the reaction vessel comprising: a reaction zone for autogenous pyrolysis reaction of organic material in the reaction bed to form pyroligneous gases, a cooling zone having at least one cooling zone inlet for supplying cooling gas into the reaction bed and a cooling zone outlet to extract heated gas from the reaction bed, and at least one lance extending through the reaction bed into the reaction zone to supply a gas into the reaction vessel through a reaction zone inlet in the lance; and a reaction zone outlet provided in the periphery of the reaction zone to remove gas supplied to the reaction zone by the lance, wherein the reaction zone outlet is located transversely from the reaction zone inlet such that gases move substantially transversely across the material in the reaction zone towards the reaction zone outlet.
Description
Apparatus and process for continuous carbonisation of wood chips
or wastes and other charring organic materials
Field of the invention
The invention relates to an apparatus and process for low-cost production of charcoal
from wood chips or wastes or other particulate organic material, which can be embodied .
in wide range of sizes and capabilities; with the quality of charcoal produced to be
suitable for use in applications including chemical reagents, fuels and absorbents.
Background of the invention
Replacement of coal products by charcoal in metallurgical, chemical and other
industries has many advantages, particularly in regard to the improvement of product
quality and environmental benefits. However, the current use of charcoal by industry is
limited by its relatively high price, which is mainly due to the cost associated with its
production as well as the cost of raw materials. Current charcoal production
technologies cannot produce charcoal at prices that are competitive with coal products
in most economic environments throughout the world. As such, there is a clear need to
develop a new and economically viable method of charcoal production, which is also
capable of utilising low-grade ligno-cellulosic material.
The main factors affecting the price of charcoal include: capital costs of plant
installation, the type of process (i.e. batch or continuous), the scale of the reactor, the
residence time required by material in the reactor, maintenance costs, the cost of raw
materials, the energy efficiency of the process and the value retained with by-products.
It is preferable to use wood chips/waste, rather than quality timber logs, as a raw
material. While use of quality wood generally results in a high quality charcoal product,
use of wood chips and waste is more economically viable and cost effective.
Furthermore, the use of wood chips and wood waste decreases the residence time in a
reactor, in comparison with wood logs, as the heating time for wood chips is shorter.
However, with the use of wood chips/waste heat transfer to the core of a large mass of
wood chip/waste material is slow due to the bulk material possessing low gas
permeability and low thermal conductivity. Thus neither heating, by blowing through a
hot gas nor externally is efficient for large volumes of material.
There are many large scale commercial processes for producing charcoal. Some of the
main processes include the Lambiotte/Lurgi retort system (US 2289917), tubular reactor
systems with material driven by a screw e.g. Thomsen Retort (US 3110652), rotating
tube retort systems e.g. Seaman retort (US 1115590), multiple heath furnace systems
e.g. the Herreshoff furnace (Handbook of charcoal making. Solar Energy R&D in the
European Community. Series E, Energy from biomass, v. 7 (1985)), fluidised bed
pyrolysis reactors, and the Badger-StaffOrd process (Nelson, W.G. Waste Wood
Distillation by the Badger-Stafford Process. Ind. Eng. Chem. (1930). No.4, Vol. 22,
pp.312-315.).
Many of these systems have limitations which prevent synthesis of charcoal at the
desired quality for an economically viable price, that is competitive with the cost of coal.
Figure 1 shows an embodiment of one charcoal production technique known as the
Stafford process (US 1380262). Stafford found that when wood chips are bone dry (with
a moisture content of less than 0.5%) and pre-heated to at least 150°C, the thermal
decomposition of sufficiently large masses of material can be fully autogenous even in
the oxygen-free atmosphere (US 1380262). Thus, in comparison to other processes,
neither the blowing of hot gasses through the material nor the external heating is
needed in order to conduct pyrolysis, in the context of • the invention, the term
"autogenous" is used herein to describe a process, which spontaneously generates a
sufficient amount of heat to be self-sufficient in an oxygen-free atmosphere.
2mm x 50mm in
The Stafford process is preferably conducted in .a vertical cylindrical continuously
operating retort, in which the ingress of gas is prevented during loading and extraction
of materials (US 1380262).
Wood in the cooler zone of the retort is heated by pyroligneous vapours and gases
ascending from the hotter zone. The wood is heated to a temperature corresponding to
the point at which the carbonisation reaction becomes vigorously exothermic (this
occurs at a temperature of approximately 300°C for wood). Even limited gas
permeability is sufficient for this heating mechanism to proceed, as the overpressure of
vapours evolved in the hot zone pushes them towards the gas/vapour outlet located at
the top of the reactor. The maximum temperature reached in the Badger-Stafford
process is approximately 515°C
Due to the exothermic nature of the process, once the process is operating heat is only
required initially to dry the wood and preheat it to 150°C prior to the wood entering the
retort. Charcoal leaves the retort at approximately 255°C and is transported straight into
a charcoal conditioner, which is a rotating tube with water cooled walls.
The Badger-Stafford process is able to convert wood chips/waste, but not sawdust into
charcoal, as maintaining minimum required level of the gas permeability of material is
important. The smallest wood pieces that.can be processed are approximately 2mm x
size; the estimated residence time for material in the reactor ranges
from between 1.5 to 3 hours.
Whilst the Badger-Stafford process offers advantages over the other previously
mentioned methods of charcoal synthesis, it also has several shortcomings.
• There is no heat recovery from the charcoal as it is cooled i.e. the energy
efficiency of the process can be improved.
The process has limited flexibility and controllability i.e. there are no means to
increase the temperature to substantially above 515°C or to reliably maintain a
lower temperature, e.g. at 450°C, if required.
There is no efficient control of the heating rate and residence time for every
portion of material within the reactor.
Vapours migrate upwards from warmer layers to cooler layers of material and are
then extracted, as a result some valuable high boiling point fractions are
condensed within these cooler layers of material and cannot be extracted from
the reactor.
• As organics escape the retort, if maximising the charcoal yield is desirable, there
is no opportunity to recycle the organics into the reaction zone to increase the
charcoal yield.
The present invention provides an apparatus for the synthesis of charcoal and offers
improvements over the Badger-Stafford process. In particular the present invention
allows at least one of improved flexibility and controllability of the process, expanded
scalability of the process, improved energy efficiency, increased productivity of the
reactor, increased charcoal yield, improved quality of liquid products and faster
conditioning of charcoal.
Reference to any prior art in the specification is not, and should not be taken as, an
acknowledgement or any form of suggestion that this prior art forms part of the common
general knowledge in Australia or any other jurisdiction or that this prior art could
reasonably be expected to be ascertained, understood and regarded as relevant by a
person skilled in the art.
Summary
Some embodiments relate to an apparatus for the autogenous production of charcoal
comprising:
a feeder for supplying a heated organic material to a reaction vessel,
the reaction vessel for supporting a reaction bed of organic material, and
at least one discharge port for discharging thermally decomposed organic
material from the reaction vessel, the reaction vessel defining a flow path in which the
thermal decomposition of the organic material progresses with the organic material
through the reaction vessel;
the reaction vessel comprising:
a reaction zone for autogenous pyrolysis reaction of organic material in the
reaction bed to form pyroligneous gases,
a cooling zone having at least one cooling zone inlet for supplying cooling gas
into the reaction bed and a cooling zone outlet to extract heated gas from the reaction
bed, and
at least one lance extending through the reaction bed into the reaction zone to
supply a gas into the reaction vessel through a reaction zone inlet in the lance; and
a reaction zone outlet provided in the periphery of the reaction zone to remove
gas supplied to the reaction zone by the lance,
wherein the reaction zone outlet is located transversely from the reaction zone
inlet such that gases move substantially transversely across the material in the reaction
zone towards the reaction zone outlet.
Thermal decomposition of the organic material is preferably carbonisation of the organic
material and the discharged product is carbonised organic material (charcoal).
Condensable pyroligneous vapours and non-condensable pyroligneous gas may also
be produced and removed from the apparatus through gas outlets in the reaction
vessel.
process.
In some embodiments, the reaction vessel may include additional gas inlets for the
introduction of carrier or cooling gases and gas outlets for the removal of condensable
vapours and non-condensable gases therefrom. This may provide enhanced control
over the flow of pyroligneous vapours and heat as compared with the Badger-Stafford
In some embodiments, gases may enter the reaction zone substantially at a central
location in the reaction chamber and move transversely across the flow of material to
the periphery of the reaction chamber. In some embodiments, additional gas inlets may
also be formed on the lance downstream from the initial gas inlets on the lance or
lances. The gases may be an inert or non-oxidising gas which is intended to carry both
the pyroligneous vapours and heat generated in the reaction zone of the reactor. This
may be done to control the reactor temperature to less than the temperature which
would otherwise be obtained and also to extract a desirable fraction of pyroligneous
vapours generated at a chosen temperature range.
A first gas outlet may be provided in the periphery of the reaction zone. The first gas
outlet is to remove the pyroligneous vapours and heat generated in the reaction zone of
the reactor and carrier gas supplied to the reaction zone by the lance.
This embodiment can be used when it is desirable to produce charcoal at lower
temperature, i.e. with higher than usual content of volatile matter, and also to increase
the yield of condensable pyrolysis products.
The additional gas inlets and gas outlets may also be provided at other locations of the
reactor shaft, if required.
In alternative embodiments, a heating zone exists above the reaction zone and the
pyroligneous gases may be extracted from the heating zone of the reactor at a
predetermined temperature and introduced into the reaction zone via the lance outlet. In
this way the gaseous organic materials otherwise escaping the reactor and forming a
of liquid product yield.
substantially above 515 °
vessel,
condensable phase may be partially converted into additional charcoal at the expense
The gas introduced through the lance may be heated to control the temperature in the
reaction zone to a desired predetermined level. Due to the autogenous nature of the
carbonisation process, apart from initial start up procedures, injection of heated gas will
generally not be required, unless there is a specific need to heat charcoal to
C to obtain a low volatile matter product.
Another gas outlet may be supplied in the region of the cooling zone of the reactor to
remove hot gases. The cooling zone is preferably in a progressive flow path of the
organic material from the reaction zone. The cooling gas is preferably a non oxidising
gas which may be circulated in a counter flow direction to the material.
Some embodiments relate to an apparatus for the thermal decomposition of organic
material comprising a feeder for supplying a heated organic material to a reaction
the reaction vessel having a reaction chamber for supporting a reaction bed of
organic material, a flow path along which the organic material progresses through the
reaction vessel, the thermal decomposition of the organic material progressing with the
organic material through the reaction vessel,
the reaction vessel comprising
a reaction zone for autogenous reaction of organic material in the reaction bed
having a first gas inlet to supply a first gas into the reaction zone, and a first gas outlet
located transversely from the first gas inlet for removing gas from the reaction zone
a cooling zone having a second gas inlet for supplying a second gas into the
reaction bed and a gas outlet for removing heated gas from the cooling zone of the
reaction bed, and
reaction vessel.
a discharge port for discharging thermally decomposed organic material from the
In some embodiments, the first gas inlet may be located centrally of the reaction zone
and the first gas outlet peripherally. The first gas inlet may take the form of an outlet in a
lance but may also include other forms of gas delivery apparatus which delivers gas
centrally directly into the reaction zone. In these embodiments, sufficient amounts of
gases and vapours may be produced into the reaction zone to pressurise the reaction
vessel to such an extent, that the outflow of gases and vapours through the first gas
outlet are spontaneous.
Some embodiments relate to a process for the autogenous production of charcoal, the
process comprising:
adding dry organic material to a first end of a reaction vessel whereby the organic
material progresses along a flow path through the reaction vessel and is removed from
a discharge port at a second end of the reaction vessel;
heating the organic material in a heating zone of the reaction vessel as it
progresses through the reaction vessel to a reaction zone where the temperature of the
organic material has reached a sufficient temperature for exothermic autogenous
decomposition of the organic material to occur;
allowing the organic material in the reaction zone to undergo autogenous
decomposition into charcoal and pyroligneous gases; and
cooling the charcoal in a cooling zone of the reaction vessel prior to discharge,
wherein pyroligneous gases are removed from a reaction zone outlet in the
periphery of the reaction vessel such that gases move substantially transversely across
the material in the reaction zone towards the reaction zone outlet.
If a high-volatile-content charcoal is needed, a cool gas may be introduced into the
exothermic reaction zone. This is because the maximum temperature in the reaction
zone needs to be limited to below the maximum autogenously attained temperature.
If the charcoal needs to be heated above the maximum autogenously attained
temperature to obtain a low-volatile charcoal, then the hot gas may be introduced below
the exothermic zone, but above the cooling zone. It may not be desirable to introduce
hot gases into the exothermic reaction zone, as this may reduce the yield of charcoal
and the amount of heat generated in the exothermic zone, and hence reduce the
efficiency of the reaction.
In some embodiments, the external gases may be injected through an internal lance
having at least one gas outlet in the exothermic or heating zones of the reaction vessel.
The external gases may be inert gases, such as nitrogen. Alternatively or additionally,
gases removed from other parts of the process such as from the heating zone of the
reaction vessel may be introduced into the exothermic zone or other zones of the
process.
The process may further provide cooling gas entering the cooling zone of the reaction
vessel. The cooling gas heated in the cooling zone of the reaction zone may be
removed through secondary gas outlets in the vicinity of the cooling zone of the reaction
vessel. These gases may then be used to preheat the organic material prior to loading
into the reaction vessel in an apparatus such as a pre-heater or used in other ways to
recover heat therefrom.
In some embodiments, secondary gas outlets may be positioned in an internal lance
placed axially in the reaction vessel and/or in the reaction vessel wall in the vicinity of
the cooling zone. The internal lance may be the same internal lance which is used to
inject external gases into the exothermic zone of the reaction vessel.
Brief description of the drawings
Figure 1 shows the embodiment of the Stafford process.
Figure 2 is a side sectional view of an embodiment of the invention.
Figure 3 is a bottom view of the whole vessel shown in figure 2.
Detailed description of the embodiments
It will be understood that the invention disclosed and defined in this specification
extends to all alternative combinations of two or more of the individual features
mentioned or evident from the text or drawings. All of these different combinations
constitute various alternative aspects of the invention.
The apparatus for the production of charcoal of the invention is considered well adapted
for an autogenous process for the synthesis of charcoal. In the context of the invention,
the term 'autogenous process' is used herein to describe a process, which
spontaneously generates a sufficient amount of heat to be self-sufficient in an oxygen-
free atmosphere. An autogenous process for the synthesis of charcoal is considered to
be the most suitable process for producing large volumes of charcoal from chipped
and/or waste wood because;
no external supply of heat to the material is needed in order for the
pyrolysis reaction to proceed, as a result, the transfer of heat to the material core does
not limit the size of reactor;
the residence time of material in the reactor is reasonably short;
the process is energy efficient, as no high-grade external heat energy is
required for the pyrolysis reaction to occur;
(D) the yield of charcoal is high, due to a combination of the high
concentration of pyroligneous vapours and their sufficient residence time allowing
secondary charcoal formation reactions to proceed to a considerable extent;
(E) vapours and gases leaving the reactor have a higher economic value and
are easier to collect, as they are not diluted with circulating hot gases, as is the case
with many other processes;
(F) since the process is conducted in oxygen-free atmosphere, there is no
burn-out of charcoal, vapours or gases;
(G) the embodiment of this invention is mechanically simple, hence it has low
installation and maintenance costs.
The present invention provides an apparatus for producing charcoal from an organic
raw material. An embodiment of the invention is shown in Figure 2. The apparatus of
this embodiment comprises: a feeder [1] for supplying material to a reaction vessel [2].
The apparatus may further comprise appropriate monitoring and control systems.
The feeder comprises a raw material hopper (4) for receiving dried, preferably bone dry
and preheated organic raw material from a drier located upstream of the feeder (4) (not
shown in Fig. 2); and a conveyance shown as a screw conveyor [6] for supplying the
dried and heated organic raw material to an gas-tight cone valve [7] above the reaction
vessel [2]. In the context of the invention, bone-dry organic material has a moisture
content of less than 0.5wt%
The reaction vessel [2] comprises a tapered reaction vessel [2] which diverges from the
cone valve towards the base of the reactor. The gas-tight cone valve [7] is mounted for
rotation about a central axis to distribute raw material uniformly across the top of the
reaction vessel [2]. The reaction vessel [2] is provided with thermal insulation [5],
around the external surfaces. The reaction vessel generally has a first section
containing a heating zone [21], an exothermic reaction zone [22] and a second section
containing a cooling zone [23]. A gas and vapour outlet [8], lateral wall vents [9] in the
exothermic reaction zone [22], and lateral wall vents [10] in the cooling zone [23] are
provided to remove gas from the reaction vessel.
The reaction vessel [2] is further provided with an initial gas inlet, shown in the form of
an internal lance [12] which protrudes from the exterior below the base of the reaction
vessel [2] and extends into the exothermic reaction zone for introducing gases into the
exothermic zone [22]. In this embodiment, the lance [12] comprises an outer conduit
[15] with an inner concentric conduit [16], whereby the outer conduit [15] extends into
the cooling zone, and the inner conduit [16] extends into the exothermic reaction zone
. While this embodiment shows 'a single lance, larger vessel designs may require
more than one lance. While the embodiment of the invention has been described with
reference to a lance, other forms of gas delivery apparatus may be used within the
broad scope of the invention. The other forms include a conduit or pipe generally of
refractory material which deliver gas centrally into the exothermic reaction zone.
The outer pipe [15] of the lance of the preferred embodiment contains an extraction vent
to the cooling zone and is connected to a gas extraction system [19]. The inner
conduit [16] contains a supply vent 1181 to the exothermic reaction zone [22] and is
connected to a gas supply system [20]. The gas supplied through inner conduit [16] may
be a non-reactive gas that is not reactive with the contents of the reaction vessel [2].
Alternatively the gas supplied through the inner conduit [16] may be recycled
condensable vapours returned to the reaction vessel to increase the yield of charcoal.
The lower section of the reaction vessel further comprises a perforated-wall cone valve
to support the reaction bed and to discharge the material when it attains an appropriate
level of the thermal decomposition. The outer part of the cone valve is slidable between
an open and closed position to allow a predetermined amount of charcoal to drop into
the fixed-volume chamber formed by the cylinder [24] attached to the moving part of the
cone valve.
The lower section of the reaction vessel also includes cooling gas inlets [11] and at least
one charcoal discharge port (13] with associated gate valves [14]. The charcoal carriage
is provided and comprises. means such as a hopper for receiving charcoal
discharged from the charcoal discharge port [13].
Operation
The feeder [1] comprises a hopper [4] for receiving pre-treated organic raw material.
Pre-treatment of the organic raw material occurs in a dryer located upstream of the
hopper [4] (not shown in Fig. 2) and comprises drying and preheating the material to a
moisture content and temperature conducive to the thermal decomposition of the
organic raw material in the reaction vessel [2]. Ideally this is a moisture content of less
than 0.5 wt% and a temperature greater than 150°C. The organic materials are
preferably wood chips or wood waste. The minimum size of the wood chips/waste is the
generally the same as that of the Badger-Stafford process discussed earlier. A feeder
supplies the dried heated organic raw material to the gas-tight cone valve [7]
preceding the reaction vessel [2] by screw conveyor [6] which then passes by gravity
into the reaction vessel [2]. To distribute material uniformly across the top of the reactor
the cone valve [7] can rotate.
reaction vessel [2].
Conversion of organic raw material to carbonised organic material (charcoal) occurs in
Start up procedure
• The main purpose of the start-up procedure is to heat the material in the reactor.and the
walls of the reactor to the temperature, which is adequate for the process to run
autogenously in an oxygen free atmosphere. In order to initiate the autogenous
decomposition, the temperature of dry material placed into exothermic zone of the
C. For start-up both
reaction .vessel needs to be raised to approximately 400 to 500 °
oxidising (e.g. air) and non-oxidising gas may be blown into the reactor to raise its
temperature, However, blowing air may be more efficient/viable, as combustion of
material will provide heat, which otherwise has to be taken from an external source. Hot
gas with the temperature of approximately 500 °C is introduced into exothermic reaction
zone [22] preferably through the external gas ports [16] in the lance or conduit [15] and
gas outlets [10] in the walls of the reaction vessel may be used to introduce hot gases
and combust part of the organic material during the start up phase. The preferred hot
gat is heated air.
The outflow of the gas rising up the reaction vessel through the heating zone preferably
occurs through the gas outlet [8]. In the case of blowing hot air, when combustion of the
dry wood in the exothermic reaction zone is initiated, the combustion products can also
be removed from the reactor through the gas outlet [8]. The cooling gas inlets [11] need
to be closed during this operation to prevent the combustion process spreading
downwards instead of spreading upwards. It is preferable to close the vapour outlets [9]
and the inert gas inlet [20] as well, so the combustion products will sweep through and
pre-heat the material placed in the heating zone instead of leaving the reactor through
the vapour outlets [9] and inert gas Inlet [20]. The amount of air (gas) injected needs to
be tightly controlled to prevent the overheating of the reaction vessel. When the
temperature of the material placed in the reaction zone [22] reaches approximately
500 C, the flow of start-up gas into the reactor should be stopped and any ingress of air
into
into the reactor should be prevented. The reaction vessel [2] then may be operated in
the autogenous continuous mode.
Under 'normal operation' mode, the temperature in the exothermic reaction zone is not
controlled by any means, i.e. the temperature rises to the maximum level it can attain
for the given reactor design and the chemical properties of the material used (e.g. wood
species). However, the circulation of nitrogen gas within the cooling zone is used to
accelerate cooling, to cool the charcoal to lower temperatures (than those otherwise
would be, thus reducing the requirements to the conditioning of charcoal) and to recover
the heat from the charcoal being cooled.
To enable the heat recovery (and cooling) of charcoal, cool nitrogen gas enters through*
the inlets [11], in counter-flow with the charcoal in the discharge compartment (below
the valve (24]) and the charcoal in the cooling zone. The heated nitrogen leaves the
reactor through the gas outlets [17] and [19].
The nitrogen leaving the reactor through the outlets [17] and [19] may be heated up to
500C, and therefore it may be a source of reasonably high-grade heat for various
purposes. This is contrast to the Badger-Stafford process where charcoal was cooled by
natural heat loss through the walls of the reactor and hence had no effective recovery of
heat from the charcoal.
In continuous mode, the reaction vessel [2] converts the organic raw material
charcoal through an autogenous decomposition process whereby the decomposition
process is a carbonisation process that progresses as the organic raw material
advances from the entrance to the exit of the reaction vessel. The reaction vessel
comprises a series of reaction zones that the material passes through. In this
embodiment, three reaction zones have been designated; a heating zone [21], an
exothermic reaction zone [22] and a cooling zone [23].
The organic material is fed into the heating zone of the reaction vessel where the
material is heated by rising gases so that as it progresses to the exothermic zone of the
reaction vessel [2], it is at a temperature where autogenous decomposition of the
organic material to charcoal takes place.
Hot gas is introduced into exothermic reaction zone [22] preferably through the external
gas ports [17] in the lance or conduit [15]. Pyroligneous gases and heated external
gases introduced through gas ports [17] may be removed through gas outlets [10] in the
walls of the reaction vessel in the vicinity of the exothermic•reaction. The flow of gases
from the gas ports [17] in the lance to the gas outlets [10] provides a means to control
the temperature in the exothermic zone, allows for the removal of pyroligneous gases
which may be a by-product and maintains permeability in the reaction bed. This assists
in preventing over compaction of the reaction bed and maintains the ability to control the
product quality and the temperature in the reaction bed.
Cooling gas enters the cooling zone of the reaction vessel. The cooling gas heated in
the cooling zone of the reaction zone is removed through secondary gas outlets in the
vicinity of the cooling zone of the reaction vessel. These gases may then be used to
preheat the organic material prior to loading into the reaction vessel in an apparatus
such as a pre-heater or used in other ways to recover heat therefrom. The secondary
gas outlets may be positioned on the internal lance positioned axially in the reaction
vessel and/or in the reaction vessel wall in the vicinity of the cooling zone. The internal
lance may be the same internal lance which is used to inject external gases into the
exothermic zone of the reaction vessel.
The present invention allows control of gas and vapour flow throughout the reaction
vessel [2]. The gas and vapour outflow can be controlled by any combination of the gas
and vapour outlet [8] in the first section. of the reaction vessel in the region of the
heating zone [21], lateral wall vents [9] in the exothermic reaction zone [22], lateral wall
vents in the cooling zone [10] and the extraction of gasei from the cooling zone [23]
through the extraction vent [17] of the outer conduit [15] of the lance [12]. The gaS inflow
may be controlled using the cooling gas inlets [11], and the supply of the non-reactive
gas through the supply vent [18] of the inner conduit [16] of the lance [12]. This control
over the gas flow throughout the various reaction stages of the reaction vessel [2]
of the final carbonised organic product.
allows the temperature profile and pressure in the reaction vessel and the reaction bed
to be controlled. This control also permits the utilisation of heat withdrawn from the
cooling zone otherwise wasted as well as the extraction of a desirable fraction of
pyroligneous vapours generated at a chosen temperature range. As such, this
production method has high energy efficiency and allows control over the composition
The gas inlets and gas outlets may also be provided at other locations of the reactor
shaft, if required. For example, the gas may be extracted from the heating zone of the
reactor at a predetermined temperature and introduced into the reaction zone via the
lance outlet 18. This way the organic materials otherwise escaping the reactor and
forming a condensable phase will be partially converted into additional charcoal in
expense of liquid product yield.
As material passes through the heating zone [21], it is heated to a temperature at which
the carbonisation reaction becomes exothermic. The organic material in the 'heating
zone' is heated by pyroligneous vapours that may ascend from subsequent zones.
Thermal energy from an external source is not required to progress the reaction in the
reaction vessel [2]. The heat energy conveyed to the heating zone [21] can be
controlled by controlling the flow of pyroligneous vapours to that zone.
As material passes through the exothermic reaction zone [22], the organic material
.20 decomposes through an autogenous carbonisation process. This converts the organic
material into carbonised organic material (charcoal), pyroligneous vapour and thermal
energy. The pyroligneous vapour can ascend to higher zones in the reactor conveying
thermal energy. The pyroligneous vapour can be extracted from the exothermic zone
through lateral wall vents [9] that line the walls of the reaction vessel [2] in the
exothermic reaction zone [22]. This allows extraction of the pyroligneous vapour in the
radial direction as viewed from the top. This control over the direction of the mass flow
of pyroligneous vapour allows the rate and degree of heating to be controlled. The
pyroligneous vapour conveys a portion of the thermal energy generated as a result of
the exothermic decomposition of the organic material. Extraction of a high proportidn of
the pyroligneous vapour through the lateral wall vent [9] results in a low proportion of
pyroligneous vapour ascending to the preceding stages of the reaction vessel [2],
resulting in a low proportion of the thermal energy ascending to the preceding stages of
the reaction vessel [2]. Conversely, extraction of a low proportion of the pyroligneous
vapour through the lateral wall vents results in a higher proportion of the pyroligneous
vapour ascending to the preceding stages of the reaction vessel [2], resulting in a higher
proportion of thermal energy ascending to the previous stages of the reaction vessel [2].
Pyroligneous vapours are usually extracted from the reactor after they have migrated
upwards from warmer layers to cooler layers. As a result, some valuable high boiling
point fractions of these vapours are condensed within the cooler layerS of material and
cannot be extracted from the reactor, Therefore, an additional benefit ,of extracting the
pyroligneous vapours directly from the exothermic reaction zone is that, selected
valuable fractions of pyroligneous vapours generated within certain temperature range
may be extracted 'from the reactor through the shortest possible path. Such an
arrangement will avoid recycling of theSe fractions of vapour within the reactor. This
mode of operation is advantageous in the situation when the required treatment
temperature is below the maximum possible temperature the reactor can develop
autogenously and also if some reduction of the charcoal yield in favour of obtaining
higher-value liquid products is viable.
As material passes through the cooling zone [23], it is cooled to a desired temperature
by heat exchange with cooling gases. Generally the gas is air or mixtures with air. The
cooling zone is provided with a perforated-wall cone valve at its bottom to allow the
reaction bed to be formed in the reaction vessel and hold up the progression of the
organic material until it attains a sufficient level of decomposition to progress to the final
product. Charcoal is discharged from the reaction vessel periodically. To discharge the
material the outer part of the cone valve slides down and a predetermined amount of
charcoal drops into the fixed-volume chamber formed by the cylinder [24] attached to
the moving part of the cone valve. When the outer part of the cone valve returns to the
upper "closed" position, the charcoal discharged spreads over the bottom of the lover
section of the reaction vessel, where it is exposed to the flow of cooling gas. The
cooling zone [23] has cooling gas inlets [11] for supplying cooling gas into the reaction
bed. As the cooling gas rises through the cooling zone [23], the cooling gas extracts
thermal energy from the carbonised organic material through direct heat exchange and
becomes heated cooling gas. The carbonised organic material is cooled to the desired
temperature by controlling the flow rate of the cooling gas. The heated cooling gas can
be extracted through the lateral wall vent [10] in the cooling zone and through the
extraction vent [17] in the outer pipe [15] of the lance [12]. The thermal energy in the
extracted heated cooling gas can be recovered for use in drying and preheating the
organic raw material in the dryer. This increases the energy efficiency of the process.
To insure that no cooling gas penetrates into the exothermic reaction zone of the
reactor and that there is no reciprocal flow of pyroligneous vapours downwards into the
cooling zone [23] the pressures at the cooling gas inlets [11] and the gas and vapour
outlet [8] are carefully controlled. The best ratio of the pressures at the inlets [11] and
the outlet [8] is considered to be when a very little amount of smoke (aerosol formed by
the condensation of pyroligneous vapours) can be observed at the exit of the hot gas'
outlet [10].
The carbonised organic material is removed from the reaction vessel [2] through at least
one charcoal discharge port [13]. In this embodiment, the discharge from the discharge
port is controlled by a series of gate valves [14] and the carbonised organic material is
discharged into a charcoal carriage [3].
The residence time of the material within the reaction vessel [2] may be optimised in
each region as the material progresses through the reaction vessel. This may be
achieved by varying the horizontal cross sectional area of the reaction vessel [2]. By
inclining the walls of the reactor and/or of the lance to make the horizontal cross section
of the reaction vessel (2] either expanding or shrinking as the reaction material
progresses through the system, the residence time of every portion of the material with
the reaction vessel [2] is as close to the optimal residence time as is practicably
possible.
The reaction vessel [2] also comprises a method for monitoring the state variables
within the system. The monitored state variables may include the temperature and the
pressure at various stages throughout the reaction vessel [2]. The monitored state
variables may be used to control the flow of pyroligneous vapours throughout the
reaction vessel [2], the flow of the non-reactive gas through the outlet vents [18] of the
lance [12], and the flow of the cooling gas through the cooling gas inlets [11] in the
cooling zone.
Product quality control
The presence of the lance [12] in conjunction with the lateral wall vents [9 and 10]
allows the floW of pyroligneous vapours and the temperature to be controlled in both the
horizontal and vertical directions throughout the reaction vessel. This allows a number
of product quality control strategies to be realised. These control strategies include, but
are not limited to:
(A) Extraction of pyroligneous gases from a chosen temperature zone within the
reaction vessel allows products and by-products of a 'desired quality to be obtained. For
example, if it is desirable to maximise the charcoal yield, the pyroligneous gases
extracted from selected colder temperature zones of the reaction vessel can be
recycled into the higher temperature zones to increase conversion of the pyroligneous
gases into charcoal.
(B) If a charcoal product with a high content of volatiles than that produced in a normal
operation (e.g. in charcoal with greater flammability, as it may be required for the
injection of pulverised carbon into a blait furnace), hot gases from the hot zone of the
reactor can be extracted so that the reaction vessel temperature is maintained below a
particular value. When producing higher-volatile charcoal, the .maximum temperature of
the treatment has to be reduced (say, to 450C). The maximum temperature is the factor
primarily affecting the volatile content of the charcoal. The maximum temperature in the
reaction zone can be reduced by extracting a fraction of hot pyrolysis vapours through
the outlets [22] made to the exothermic reaction zone, therefore extracting heat froM
that zone. This can be done to certain limits only as the efficiency of .pre-heating of the
material in the heating zone will be reduced too, however, the reactor should have some
spare capacity to withstand medium heat loss, particularly if the maximum required
temperature is reduced (e.g. to 450C). Vapours should be able to flow out through the
outlets [22] spontaneously, as their pressure in the exothermic zone is above ambient.
However, blowing non-oxidizing gas through the inlet [20] may increase the outflow of
vapours from the reactor, if required, or increase the flow of the gas through the heating
zone to compensate for the reduced flow of pyrolysis gases/vapours through that zone,
if pre-heating becomes insufficient. In this mode of operation the amount of liquid
pyrolysis products will be increased in expense of the* amount of fixed carbon
associated with the charcoal and of the amount of gas. This mode of operation is
particularly
favourable if the increase in the yield of liquid products is desirable and
economically viable.
On, the other hand, the reduction of the temperature in the exothermic reaction zone to
produce higher-volatile charcoal can be achieved by recycling a fraction of the pyrolysis
gases and vapours escaping the reactor from the outlet [8]) back into the reaction zone
through the vents [22]. These gases have the temperature of 180 to 200C and carry
pyrolysis vapours (aerosol of pyrolysis tars). Pyrolysis tar aerosols, when injected into
the reaction zone, will crack on the surface of fresh hot char (this is an established
reaction) and generate additional charcoal. As the vapours extracted from the outlet [8]
have the temperature of 180 to 200C, their injection onto the exothermic reaction zone
will reduce the temperature there. At the same time, recycling of the fraction of the
pyrolysis gases back into the reaction zone will increase the overall flow rate of gas
through the heating zone (as the amount of gas leaving the reactor should stay
approximately the same to avoid the pressure build up). As a result, the relative height
of the exothermic reaction zone as well as the temperature of the gases leaving the
reactor may increase slightly.
(C) If a charcoal product with a low degree of volatiles is required, specific need for a
low-volatile charcoal (i.e. for steel re-carburisation), it can be made in the proposed
process/reactor by circulating hot nitrogen gas through the same cycle as that for the
special purposes.
cooling cycle (described above).increasing the temperature in the reaction vessel Hot
nitrogen (e.g. at 850C) should enter the reactor through the inlets [11] and then leave
the reactor through the outlets [17] and [19] slightly cooled (to, about 550C). The
maximum temperature of the hot nitrogen may be limited by the hot strength of the
materials the reactor is made from. Cooling and conditioning of charcoal produced this
way (and the extraction of heat, if desired) should be done in a separate apparatus. This
mode of operation is expected to be less energy efficient than the previous mode, but it
may be worthwhile when there is a need in small amounts of low-volatile charcoal for
As used herein, except where the context requires otherwise the term "comprise" and
variations of the term, . such as "comprising", "comprises" and "comprised", are not
intended to exclude other additives, components, integers or steps.
Claims (21)
1. An apparatus for the autogenous production of charcoal comprising: a feeder for supplying a heated organic material to a reaction vessel, the reaction vessel for supporting a reaction bed of organic material, and at least one discharge port for discharging thermally decomposed organic material from the reaction vessel, the reaction vessel defining a flow path in which the thermal decomposition of the organic material progresses with the organic material through the reaction vessel; the reaction vessel comprising: a reaction zone for autogenous pyrolysis reaction of organic material in the reaction bed to form pyroligneous gases, a cooling zone having at least one cooling zone inlet for supplying cooling gas into the reaction bed and a cooling zone outlet to extract heated gas from the reaction bed, and at least one lance extending through the reaction bed into the reaction zone to supply a gas into the reaction vessel through a reaction zone inlet in the lance; and a reaction zone outlet provided in the periphery of the reaction zone to remove gas supplied to the reaction zone by the lance, wherein the reaction zone outlet is located transversely from the reaction zone 20 inlet such that gases move substantially transversely across the material in the reaction zone towards the reaction zone outlet.
The apparatus of claim 1, further comprising a heating zone for heating the organic material by the pyroligneous gases formed in the reaction zone, and a heating zone outlet to extract gases from the heating zone.
The apparatus of claim 1 or 2, further comprising a second cooling zone outlet to 5 remove hot gases from the cooling zone.
The apparatus of any one of claims 1 to 3, comprising more than one reaction zone outlet to remove gas supplied to the reaction zone by the lance.
5. The apparatus of any one of claims 1 to 4, wherein the first gas inlet is located centrally of the reaction zone. 10
6. The apparatus of any one of claims 1 to 5, wherein the cooling zone outlet is disposed in the lance.
7. The apparatus of any one of claims 1 to 6, wherein reaction vessel comprises more than one lance extending through the reaction bed into the reaction zone to supply a gas into the reaction vessel. 15 8.
The apparatus of any one of claims 1 to 7, wherein the reaction vessel has a cross sectional area which decreases or increases at least in or in the vicinity of the reaction zone.
The apparatus of any one of claims 1 to 8, wherein the apparatus does not include an external heat source for heating the bed of organic material, or for 20 maintaining the temperature of the bed of organic material.
A process for the autogenous production of charcoal, the process comprising: adding dry organic material to a first end of a reaction vessel whereby the organic material progresses along a flow path through the reaction vessel and is removed from a discharge port at a second end of the reaction vessel; 15 13. heating the organic material in a heating zone of the reaction vessel as it progresses through the reaction vessel to a reaction zone where the temperature of the organic material has reached a sufficient temperature for exothermic autogenous decomposition of the organic material to occur; allowing the organic material in the reaction zone to undergo autogenous decomposition into charcoal and pyroligneous gases; and cooling the charcoal in a cooling zone of the reaction vessel prior to discharge, wherein pyroligneous gases are removed from a reaction zone outlet in the periphery of the reaction vessel such that gases move substantially transversely across 10 the material in the reaction zone towards the reaction zone outlet.
The process of claim 10, wherein the external gases are injected through an internal lance into the reaction zone of the reaction vessel.
12. The process of claim 10 or 11, wherein cooling gas enters the cooling zone of the reaction vessel through cooling zone inlets.
The process of claim 12, wherein cooling gas heated in the cooling zone of the reaction zone is removed through cooling zone outlets in the vicinity of the cooling zone of the reaction vessel.
14. The process of claim 13, wherein the cooling zone outlets are positioned on an internal lance. 20
15. The process of claim 14, wherein the lance is positioned axially in the reaction vessel.
16. The process of any one of claims 13 to 15, wherein at least some of the cooling zone outlets are positioned in the reaction vessel wall in the vicinity of the cooling zone. cooling zone to be used elsewhere.
The process of any one of claims 12 to 16, wherein the cooling zone inlets are positioned on in the vicinity of the cooling zone to provide cooling gas to the cooling zone.
The process of any one of claims 10 to 17, wherein the process is performed 5 without application of an external heat source to heat the organic material, or for maintaining the temperature of the bed of organic material.
The process of any one of claims 10 to 18, wherein heat is recovered from the
20. The process of claim 18, wherein the recovered heat is used to heat organic 10 material before adding the organic material to the first end of the reaction vessel.
21. The process of any one of claims 11 to 19, wherein a portion of the external gases and the pyroligneous gases that are removed from the reaction vessel, are recirculated to the reaction zone.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2011902445A AU2011902445A0 (en) | 2011-06-21 | Apparatus and process for continuous carbonisation of wood chips or wastes and other charring organic materials | |
AU2011902445 | 2011-06-21 | ||
PCT/AU2012/000704 WO2012174587A1 (en) | 2011-06-21 | 2012-06-19 | Apparatus and process for continuous carbonisation of wood chips or wastes and other charring organic materials |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ618672A NZ618672A (en) | 2015-12-24 |
NZ618672B2 true NZ618672B2 (en) | 2016-03-30 |
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