U.S. patent application number 16/329786 was filed with the patent office on 2020-01-09 for resource recovery from wood wastes.
The applicant listed for this patent is The Crucible Group IP Pty Ltd. Invention is credited to Joseph George Herbertson, Kannappar Mukunthan, Lazar Strezov.
Application Number | 20200010763 16/329786 |
Document ID | / |
Family ID | 61299832 |
Filed Date | 2020-01-09 |
United States Patent
Application |
20200010763 |
Kind Code |
A1 |
Herbertson; Joseph George ;
et al. |
January 9, 2020 |
RESOURCE RECOVERY FROM WOOD WASTES
Abstract
A method and an apparatus for processing wood wastes and
producing valuable products that are safe and have economic value
is disclosed. The apparatus includes a continuous converter (3) for
a feed material that includes wood wastes containing contaminants.
The continuous converter includes a reaction chamber (5) for
producing a solid carbon-containing product, a gas product, and
optionally a liquid oil product and a separate water-based
condensate product in the chamber, via pyrolysis or other reaction
mechanisms.
Inventors: |
Herbertson; Joseph George;
(Mayfield, New South Wales, AU) ; Strezov; Lazar;
(Adamstown Heights, New South Wales, AU) ; Mukunthan;
Kannappar; (Garden Suburb, New South Wales, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Crucible Group IP Pty Ltd |
Paddington, NSW |
|
AU |
|
|
Family ID: |
61299832 |
Appl. No.: |
16/329786 |
Filed: |
September 1, 2017 |
PCT Filed: |
September 1, 2017 |
PCT NO: |
PCT/AU2017/050946 |
371 Date: |
March 1, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10B 57/10 20130101;
C10G 2300/205 20130101; C10B 7/10 20130101; C10G 2300/1014
20130101; C10B 53/02 20130101; C10G 2300/30 20130101; C10B 21/10
20130101; C10G 1/045 20130101; C10B 49/04 20130101; Y02E 50/14
20130101 |
International
Class: |
C10B 53/02 20060101
C10B053/02; C10B 57/10 20060101 C10B057/10; C10B 7/10 20060101
C10B007/10; C10B 49/04 20060101 C10B049/04; C10B 21/10 20060101
C10B021/10; C10G 1/04 20060101 C10G001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 1, 2016 |
AU |
2016903495 |
Claims
1. An apparatus for processing wood wastes and producing valuable
products that are safe and have economic value, the apparatus
including a continuous converter for a feed material that includes
wood wastes containing contaminants, with the continuous converter
including a reaction chamber for producing a solid
carbon-containing product, a gas product, and optionally a liquid
oil product and a separate water-based condensate product in the
chamber, via pyrolysis or other reaction mechanisms, an inlet for
supplying the feed material to the reaction chamber, an assembly
for moving the feed material through the reaction chamber from the
upstream end towards the downstream end of the chamber
counter-current to the flow of gas generated in the chamber as a
consequence of drying or other reactions in the chamber, and
separate outlets for the solid carbon-containing product, the gas
product, and optionally the liquid water product from the reaction
chamber, with the apparatus being adapted to decompose organic
material contaminants in the wood wastes and to incorporate the
decomposed forms into useful products, and with the apparatus being
adapted to deport heavy metal contaminants to the solid
carbon-containing product.
2. The apparatus defined in claim 1 wherein the continuous
converter includes an assembly for establishing a temperature
profile in the reaction chamber that includes the following zones
extending successively along the length of the reaction chamber
from the upstream end to the downstream end of the reaction
chamber: (a) a drying zone (Zone 1) for drying the feed
material--typically 60-80.degree. C. is the inlet end temperature
and 100-150.degree. C. is the upper temperature limit of Zone 1,
(b) a pre-heating zone (Zone 2) for heating the feed material to a
temperature that is suitable for the thermo-chemical reactions
required in the next zone--typically 250-300.degree. C. is the
upper limit of Zone 2, and (c) a thermo-chemical reaction zone
(Zone 3) for thermally decomposing the feed material and producing
a solid carbon-containing, typically char product, and gas.
3. A method for processing wood wastes and producing valuable
products that are safe and have economic value in the apparatus
described in the preceding paragraph, with the method including the
steps of: (a) supplying a solid feed material that includes wood
wastes containing contaminants to the inlet of the reaction chamber
of the apparatus; (b) moving the feed material through the reaction
chamber from the inlet to the downstream end of the chamber and
exposing the feed material to a time-temperature profile within the
chamber that dries and pyrolyses or otherwise processes the feed
material and releases water vapour and a volatile products gas
phase from the feed material as the feed material moves through the
chamber; (c) moving the water vapour phase and the volatile
products gas phase produced by heating the feed material in step
(b) through the reaction chamber in a direction counter to that of
the feed material so that at least a part of the water vapour phase
and the condensable components of the volatile products gas phase
condense in cooler upstream sections of the reaction chamber and
form liquid water and liquid oil, at least the liquid oil being
carried forward in the reaction chamber by the feed material to the
higher temperature regions of the reaction chamber and being
progressively volatilised and cracked to a non-condensable gas; and
(d) discharging (i) a gas product and (ii) a dried and pyrolysed
solid carbon-containing product from the separate outlets of the
chamber, and with the time-temperature profile within the chamber
ensuring that (i) organic material contaminants in the wood wastes
are decomposed and the decomposed forms are incorporated into
useful products and (ii) heavy metal contaminants in the wood
wastes are deported to the solid carbon-containing product.
4. The method defined in claim 3 wherein the wood wastes are in a
particulate form having a particle size of minus 25 mm, typically
minus 20 mm.
5. The method defined in claim 3 wherein less than 15 wt. %,
typically less than 10 wt. %, of the total mass of wood wastes have
a particle size of minus 1 mm.
6. The method defined in claim 3 wherein the amount of moisture in
the feed material is less than 20 wt. %, more typically less than
15 wt. %, of the total mass of the feed material.
7. The method defined in claim 3 includes controlling the gas
product composition by controlling the temperature profile in the
reactor and therefore the residence time within a required
temperature range.
8. The method defined in claim 3 includes condensing water vapour
from the gas product outside the chamber and forming a liquid water
product.
9. The method defined in claim 3 includes maintaining a required
temperature profile in the reaction chamber by supplying an
oxygen-containing gas, such as air, to the reaction chamber and at
least partially combusting combustible gases in the reaction
chamber.
10. The method defined in claim 3 wherein the temperature profile
in the reaction chamber include a plurality of zones successively
along the length of the chamber in which different reactions occur
as the feed material moves from the upstream cooler end to the
downstream hotter end of the reaction chamber.
11. The method defined in claim 10 includes establishing a
temperature profile in the reaction chamber that includes the
following zones extending successively along the length of the
reaction chamber from the upstream end to the downstream end of the
reaction chamber: (a) a drying zone (Zone 1) for drying the feed
material--typically 60-80.degree. C. is the inlet end temperature
and 100-150.degree. C. is the upper temperature limit of Zone 1,
(b) a pre-heating zone (Zone 2) for heating the feed material to a
temperature that is suitable for the thermo-chemical reactions
required in the next zone--typically 250-300.degree. C. is the
upper limit of Zone 2, and (c) a thermo-chemical reaction zone
(Zone 3) for thermally decomposing the feed material and producing
a solid carbon-containing, typically char product, and gas.
12. The method defined in claim 3 includes supplying the
oxygen-containing gas, such as air, to the reaction chamber in Zone
3, whereby the devolatilization produces combustible gases that are
combusted by the oxygen-containing gas. Supplying the
oxygen-containing gas in this region of the reaction chamber
optimises the combustion of combustible gases.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method of processing wood
wastes and producing safe products that have economic value.
BACKGROUND ART
[0002] There are considerable amounts of wood wastes that are
generated each year.
[0003] The term "wood wastes" is understood herein to mean wood
off-cuts or shavings etc. produced in the course of manufacturing
wood products, reject wood products, and discarded wood products,
for example as a result of renovating houses or offices. Wood
wastes may include composite products that include wood and other
components. One example is kitchen bench tops that comprise a wood
base and a top surface of a plastics material or other material
that is laminated or otherwise fixed to the base.
[0004] Specific examples of wood wastes are engineered timbers,
blue pine, wood wastes with plastics, painted timber, and wood
wasted with metals.
[0005] A significant proportion of wood wastes contain
contaminants. The contaminants may include organic materials such
as resins, glues, paints etc. that make it difficult to
cost-effectively process the wood wastes for use as or in new
products. The contaminants may also include heavy metals.
[0006] Organic contaminants include organic materials that are
added to wood to improve longevity of wood products--creosote,
pymetheroid treatments. Heavy metals may be in wood products as a
result of processing or use of the wood products and present in
trace amounts. Heavy metals may also be added deliberately to wood
in trace or higher amounts, such as copper, chrome, and arsenic use
to treat timber. The term "trace" is understood to mean up to 500
ppm and typically less than 100ppm.
[0007] In this context, the term "contaminant" does not necessarily
mean that the materials are toxic, although this may be the
case.
[0008] The term "contaminant" is understood herein in the wider
context of materials that have to be separated from the wood in
wood wastes to allow the wood to be used in new products.
[0009] As a consequence, it is often the case that current options
for processing wood wastes to remove contaminants are not
economically viable and the only option for the wood wastes is in
land fill.
[0010] There is a need for alternative options for processing wood
wastes than the currently-available options.
[0011] The above description is not to be taken as an admission of
the common general knowledge in Australia and elsewhere.
SUMMARY OF THE DISCLOSURE
[0012] The applicant has developed a method and an apparatus for
converting biomass or other solid organic feed materials via
pyrolysis or other mechanisms to valuable products such as but not
confined to any one or more of a liquid water product (which can be
described in general terms as a water-based condensate and in some
instances as "wood vinegar"), a liquid oil product, a gas product,
and a solid carbon-containing product such as a char product.
[0013] The method and the apparatus are hereinafter referred to
collectively as the "continuous biomass converter" technology.
[0014] The term "biomass" is understood herein to mean living or
recently living organic matter. Specific biomass products include,
by way of example, forestry products (including mill residues such
as wood shavings), agricultural products, biomass produced in
aquatic environments such as algae, agricultural residues such as
straw, olive pits and nut shells, animal wastes, municipal and
industrial residues.
[0015] The term "organic feed materials" includes biomass, peat,
coal, oil shales/sands, plastic waste materials, and also includes
blends of these feed materials.
[0016] The above-mentioned continuous biomass converter technology
is described and claimed in patent families that include
International applications PCT/AU2009/000455 (WO2009/124359) and
PCT/AU2014/001020 (WO2015/061833) in the name of the applicant. The
disclosure in the patent specifications of these patent
applications is incorporated herein by cross-reference.
[0017] The continuous biomass converter technology of the applicant
combines the functions of drying, char making, tar cracking and gas
scrubbing into a single stage, continuous and automatically
controlled reactor operating under quite unique thermo-chemical
conditions. The continuous biomass converter technology makes it
possible to achieve high efficiencies and streamlined engineering,
which has considerable advantages when compared to available
pyrolysis and gasification options.
[0018] The applicant has identified operating conditions that make
the continuous biomass converter technology particularly effective
for processing wood wastes and producing valuable products that are
safe and have economic value.
[0019] In particular, the applicant has found in research and
development work on wood wastes provided by Laminex Group that the
the continuous biomass converter technology of the applicant can:
[0020] (a) decompose organic material contaminants in these wood
wastes and incorporated decomposed products into useful products;
and [0021] (b) deport at least a significant proportion of heavy
metal contaminants in these wood wastes to a char product, with the
char product being a preferable medium for the heavy metals than
the liquid and gas products, and with the heavy metals being
recoverable from the char product if the levels are sufficiently
high to warrant recovery.
[0022] In broad terms, in accordance with the present invention, a
feed material comprising wood wastes containing contaminants is
supplied to an apparatus in the form of a continuous converter and
moved through a reaction chamber of the converter, typically in a
packed bed form, more particularly a closely packed bed form, and
exposed to a time-temperature profile within the chamber that dries
and pyrolyses or otherwise processes by another reaction mechanism
the feed material and produces a solid carbon-containing product
(such as a char product) and releases water vapour and a volatile
products gas phase, with organic material contaminants in the wood
wastes being decomposed altogether or converted into useful
products effectively, and with heavy metal contaminants in the wood
wastes being deported to the solid carbon-containing product.
[0023] Typically, the converter is positioned so that the reaction
chamber is horizontally disposed. It is noted that the converter,
and more particularly the chamber, may be slightly inclined or
vertical.
[0024] The water vapour and volatile products gas phase move
counter-current to the feed material in the chamber. At least a
part of the condensable components of the volatile products in the
gas phase condense in cooler upstream sections of the chamber and
form liquid oil (i.e. a liquid oil-based condensate) and tar.
Typically, the operating temperatures are such that water vapour
does not condense in the chamber and discharges from the chamber as
part of the gas phase and condenses as liquid water product outside
the chamber.
[0025] The condensed liquid oil and tar are carried forward in the
reaction chamber by the feed material to the higher temperature
regions of the chamber and are progressively volatilised and
cracked to hydrogen, carbon monoxide, carbon dioxide and short
chain hydrocarbons such as methane, ethane, and other light
hydrocarbons. The end result of the condensation and
cracking/volatilisation cycle is that a gas product comprising
water vapour and non-condensable gases at the temperature and
pressure within the chamber is discharged from the chamber.
[0026] There may be circumstances where it is desirable to drain a
part of the liquid oil from the chamber as a separate product.
[0027] The materials that are contaminants in wood wastes may be as
described above.
[0028] For example, contaminants in wood wastes may include organic
materials such as resins, glues, paints etc. that make it difficult
to cost-effectively process the wood wastes for use as or in new
products. By way of further example, contaminants may include heavy
metals.
[0029] The contaminants may be the result of the use of the wood
products or because the contaminants were added deliberately to
improve longevity of the wood products.
[0030] The gas generated from the feed materials is clean burning
with respect to potentially harmful organic substances, due to
internal cracking and thermal decomposition of long chain, complex
molecules in the reaction chamber of the converter. The gas exits
the continuous biomass converter at very low temperatures compared
to typical thermal processes (well below 100.degree. C.), after
flowing through the packed bed of input feed material moving
counter currently (these are distinctive features of the continuous
biomass converter technology). Consequently, there is gas scrubbing
as the gas moves towards the cold end of the reaction chamber and
minimal opportunity for metal transfer from the feed material to
the gas.
[0031] The continuous biomass converter operates under reducing
conditions (not combustion or incineration).
[0032] Whilst the continuous biomass converter technology
incorporates pyrolysis reactions, it is more than a pyrolyser,
since it includes drying, tar cracking, and gas scrubbing within
the reactor. In other pyrolysis systems, these functions typically
take place in separate unit operations, under different conditions
to those prevailing in the continuous biomass converter
technology.
[0033] The features of the continuous biomass converter technology
that the applicant has identified as being important for processing
wood wastes include the following features:
[0034] 1. The continuous biomass converter technology is a sealed
system and therefore contaminants in wood wastes are completely
contained during processing in the apparatus.
[0035] 2. The feed inlet to the main chamber of the apparatus is
maintained at a small negative pressure, .about.50 Pa, as an
additional protection against gas escaping from the apparatus.
[0036] 3. The time-temperature profile within the reaction chamber
of the apparatus, typically 200-600.degree. C. over a period of
5-20 minutes, typically 7-15 minutes, is controlled to decompose
organic contaminants in wood wastes.
[0037] 4. The thermo-chemical conditions in the reaction chamber of
the apparatus are controlled to be reducing to ensure high
carbonisation of the char product.
[0038] 5. The process conditions, such as gas exit temperatures
(typically controlled to be less than 100.degree. C. at the outlet,
typically less than 90.degree. C., typically of the order of
80.degree. C.) ensures that heavy metal contaminants present in the
wood waste are retained with the solid carbon-containing product
and not present as vapour in the gas phase and transported to the
gas and the liquid product from.
[0039] In broad terms, the present invention provides an apparatus
for processing wood wastes and producing valuable products that are
safe and have economic value, the apparatus including a continuous
converter for a feed material that includes wood wastes containing
contaminants, with the continuous converter including a reaction
chamber for producing a solid carbon-containing product, a gas
product, and optionally a liquid water product in the chamber, via
pyrolysis or other reaction mechanisms, an inlet for supplying the
feed material to the reaction chamber, an assembly for moving the
feed material through the reaction chamber from the upstream end
towards the downstream end of the chamber counter-current to the
flow of gas generated in the chamber as a consequence of drying or
other reactions in the chamber, and separate outlets for the solid
carbon-containing product, the gas product, and optionally an oil
product and a separate water-based condensate product from the
reaction chamber, with the apparatus being adapted to decompose
organic material contaminants in the wood wastes and to incorporate
the decomposed forms into useful products, and with the apparatus
being adapted to deport heavy metal contaminants to the solid
carbon-containing product.
[0040] In broad terms, the present invention also provides a method
for processing wood wastes and producing valuable products that are
safe and have economic value in the apparatus described in the
preceding paragraph, with the method including the steps of:
[0041] (a) supplying a solid feed material that includes wood
wastes containing contaminants to the inlet of the reaction chamber
of the apparatus;
[0042] (b) moving the feed material through the reaction chamber
from the inlet to the downstream end of the chamber and exposing
the feed material to a time-temperature profile within the chamber
that dries and pyrolyses or otherwise processes the feed material
and releases water vapour and a volatile products gas phase from
the feed material as the feed material moves through the
chamber;
[0043] (c) moving the water vapour phase and the volatile products
gas phase produced by heating the feed material in step (b) through
the reaction chamber in a direction counter to that of the feed
material so that at least a part of the water vapour phase and the
condensable components of the volatile products gas phase condense
in cooler upstream sections of the reaction chamber and form liquid
water and liquid oil, at least the liquid oil being carried forward
in the reaction chamber by the feed material to the higher
temperature regions of the reaction chamber and being progressively
volatilised and cracked to a non-condensable gas; and
[0044] (d) discharging (i) a gas product and (ii) a dried and
pyrolysed solid carbon-containing product from the separate outlets
of the chamber, and [0045] with the time-temperature profile within
the chamber ensuring that (i) organic material contaminants in the
wood wastes are decomposed and the decomposed forms are
incorporated into useful products and (ii) heavy metal contaminants
in the wood wastes are deported to the solid carbon-containing
product.
[0046] The wood wastes may be any suitable wood wastes having
regard to the process requirements.
[0047] One requirement for the wood wastes is to ensure the packed
bed of feed material has a structure that maintains the required
characteristics of the packed bed as it moves through the reaction
chamber of the converter. By way of example, the structure may be
to provide the packed bed with sufficient porosity for gas flow
counter-current to the direction of movement of the moving bed of
feed material through the reaction chamber.
[0048] Typically, the wood wastes are in a particulate form.
[0049] The wood wastes may be in a particulate form having a
particle size of minus 25 mm, typically minus 20 mm.
[0050] Less than 15 wt. %, typically less than 10 wt. %, of the
total mass of wastes may have a particle size of minus 1 mm. This
is regarded as a fines component of the feed material.
[0051] Typically, the amount of moisture in the feed material is
less than 20 wt. %, more typically less than 15 wt. %, of the total
mass of the feed material. There may be situations where there are
higher moisture contents.
[0052] Typically, the gas product includes water vapour and
non-condensable gases including carbon monoxide, carbon dioxide,
hydrogen, and hydrocarbons (particularly methane).
[0053] The method may include controlling gas product composition
having regard to end-use requirements for the gas product.
[0054] The gas product may contain varying amounts of hydrogen and
methane. There may be situations in which higher concentrations of
hydrogen and lower concentrations of methane are preferred. There
may be other situations, for example when the gas product is used
for electricity generation in an internal combustion engine, where
higher concentrations of methane and lower concentrations of
hydrogen are preferred.
[0055] The method may include controlling the gas product
composition by controlling the temperature profile in the reactor
and therefore the residence time within a required temperature
range.
[0056] The method may include draining some liquid oil form the
chamber as a separate product.
[0057] As described above, the method may be operated so that water
is discharged as water vapour only and there is no liquid water
discharged from the chamber. Consequently, the only "products"
discharged from the chamber are a gas product and a solid
carbon-containing product. The gas product may include water
vapour, CO, H.sub.2, CO.sub.2, N.sub.2, methane, ethane and other
light hydrocarbons.
[0058] The method may include condensing water vapour from the gas
product outside the chamber and forming a liquid water product. The
remaining gas product may be used as a fuel gas.
[0059] However, it is also noted that the method may include
forming a water-based condensate product within the chamber and
discharging the product from the chamber.
[0060] The method may be operated at a small negative pressure
relative to atmospheric pressure at the upstream feed material end
of the reaction chamber to prevent or minimise the risk of gas
leakage from the reaction chamber.
[0061] The method may include supplying water to the downstream end
of the reaction chamber to control solid carbon-containing product
characteristics such as moisture content. For example, higher
moisture contents may be desirable for solid carbon-containing
products for agricultural use. Lower moisture contents may be
suitable for industrial applications, such as char (e.g. for
metallurgy and power generation) where water needs to be limited).
Adding water helps to overcome problems associated with potentially
pyrohorric char (spontaneous combustion).
[0062] The temperature profile in the reaction chamber is an
important consideration. Operating with a required temperature
profile requires selecting appropriate operating conditions,
including feed rate along the length of the reaction chamber and
air injection rate into the chamber, having regard to the
composition and physical characteristics of the feed materials and
the need for balancing internal heating, process heat and heat
losses
[0063] Typically, the required temperature profile is an extended
temperature gradient in a countercurrent solids/gas reactor. The
term "extended" in this context means that sufficient time is
allowed for the required reactions to occur in the reaction
chamber. As is discussed further below, the applicant has realised
that appropriate processing of feed materials requires the material
to move through three zones involving drying, heating and
thermo-chemical reactions and it is necessary to allow sufficient
time for these process steps to be achieved.
[0064] The method may include maintaining a required temperature
profile in the reaction chamber by supplying an oxygen-containing
gas, such as air, to the reaction chamber and at least partially
combusting combustible gases in the reaction chamber. The
combustible gases may be generated by pyrolysis of organic material
in the reaction chamber.
[0065] The temperature profile in the reaction chamber may include
a plurality of zones successively along the length of the chamber
in which different reactions occur as the feed material moves from
the upstream cooler end to the downstream hotter end of the
reaction chamber.
[0066] The continuous converter may include an assembly for
establishing a temperature profile in the reaction chamber that
includes the following zones extending successively along the
length of the reaction chamber from the upstream end to the
downstream end of the reaction chamber: [0067] (a) a drying zone
(Zone 1) for drying the feed material--typically 60-80.degree. C.
is the inlet end temperature and 100-150.degree. C. is the upper
temperature limit of Zone 1, [0068] (b) a pre-heating zone (Zone 2)
for heating the feed material to a temperature that is suitable for
the thermo-chemical reactions required in the next zone--typically
250-300.degree. C. is the upper limit of Zone 2, and [0069] (c) a
thermo-chemical reaction zone (Zone 3) for thermally decomposing
the feed material and producing a solid carbon-containing,
typically char product, and gas.
[0070] Thermal decomposition of the feed material in Zone 3
devolatilises the feed material and generates gas. The gas includes
some combustible gas and this combustible gas combusts in Zone 3
and generates heat within the zone. Typically, 600-650.degree. C.
is the upper limit of Zone 3.
[0071] The applicant has found that the thermal decomposition
reactions are predominantly endothermic and the combustion of some
of the combustible gas released from the feed material is important
to maintain reaction temperatures in Zone 3.
[0072] The gas generated in Zone 3 inevitably moves from the hotter
downstream end to the colder upstream end of the chamber because
the downstream end has a gas seal and there is a gas outlet in the
upstream end of the chamber. There is convective heat transfer to
the feed material in Zones 1 and 2 from the comparatively hot gas
moving from Zone 3 towards the colder upstream end of the reactor
counter-current to the direction of movement of the feed material
successively through the zones.
[0073] The method may include supplying the oxygen-containing gas,
such as air, to the reaction chamber in Zone 3, whereby the
devolatilization produces combustible gases that are combusted by
the oxygen-containing gas. Supplying the oxygen-containing gas in
this region of the reaction chamber optimises the combustion of
combustible gases to where it is most beneficial.
[0074] The oxygen-containing gas may be oxygen, air, or
oxygen-enriched air.
[0075] In broad terms, the present invention also provides an
apparatus for processing wood wastes and producing valuable
products that are safe and have economic value, with the apparatus
including the apparatus described above.
[0076] In broad terms, the present invention also provides a method
for processing wood wastes and producing valuable products that are
safe and have economic value including the steps of:
[0077] (a) size reduction wood wastes;
[0078] (b) reducing the water content of the wood wastes to a
predetermined content; and
[0079] (c) processing the wood wastes in the above-described method
and producing valuable products
[0080] Step (b) of reducing the water content of the wood wastes
may include a drying step after the de-watering step.
BRIEF DESCRIPTION OF THE DRAWINGS
[0081] The present invention is described further by way of example
only with reference to the accompanying drawings, of which:
[0082] FIG. 1 is a diagram that illustrates one embodiment of a
method and an apparatus for processing wood wastes and producing
valuable products that are safe and have economic value in
accordance with the present invention;
[0083] FIG. 2 is a temperature/time profile in the reaction chamber
of a continuous converter for carrying out the method illustrated
in FIG. 1, with the profile being generated from trial data
described below;
[0084] FIG. 3 is a perspective view of one embodiment of an
apparatus in the form of a continuous converter in accordance with
the invention;
[0085] FIG. 4 is a transverse cross-section through the continuous
converter along the line 5-5 shown in FIG. 4
[0086] FIG. 5 is a temperature-time graph at a series of locations
along the length of a reactor for a trial with a feed material
comprising 100 wt. % wood waste feed material in trials of an
embodiment of the method and the apparatus of the invention, with
the graph illustrating a 1 hour period of the trial; and
[0087] FIG. 6 is a temperature-time graph at a series of locations
along the length of a reactor for a trial with a feed material
comprising contaminated wood waste including 7 wt. % plastics
material in trials of the embodiment of the method and the
apparatus of the invention mentioned in the description of FIG. 5,
with the graph illustrating a 1 hour period of the trial.
DESCRIPTION OF EMBODIMENTS
[0088] FIG. 1 is a diagram that illustrates one embodiment of a
method and apparatus for processing wood wastes and producing
valuable products that are safe and have economic value in
accordance with the invention.
[0089] With reference to FIG. 1, feed material in the form of wood
waste containing contaminants is supplied at ambient temperature to
an inlet of a reaction chamber 5 of continuous converter 3 shown
diagrammatically in FIG. 1 and in more detail in FIGS. 3 and 4 and
also described in International applications PCT/AU2009/000455
(WO2009/124359) and PCT/AU2014/001020 (WO2015/061833) in the name
of the applicant.
[0090] The feed material is moved through the reaction chamber 5
from an inlet 41 at an upstream end 7 to a downstream end 9 of the
chamber and is exposed to a temperature profile that reaches a
maximum of 650.degree. C. over a selected time period within the
chamber 5 that: [0091] (a) pyrolyses organic material in the feed
material, [0092] (b) releases water vapour and a volatile products
gas phase, [0093] (c) decomposes organic material contaminants and
incorporates decomposed products into useful products effectively,
and [0094] (d) deports at least a significant proportion of heavy
metal contaminants in these wood wastes to a char product, with the
char product being a preferable medium for the heavy metals than
the liquid and gas products, and with the heavy metals being
recoverable from the char product if the levels are sufficiently
high to warrant recovery.
[0095] The water vapour phase and the volatile products gas phase
produced by heating the feed material moves in a direction counter
to that of the feed material. At least a part of the water vapour
phase and the condensable components of the volatile products gas
phase condense in cooler upstream sections of the chamber and form
liquid water and liquid oil/tars. At least the liquid oil/tars is
carried forward in the reaction chamber by the feed material to the
higher temperature regions of the reaction chamber and is
progressively volatilised and cracked to a non-condensable gas. In
some circumstances, liquid oil may be drained from the reactor 5 as
a product.
[0096] A gas product and a dried and pyrolysed solid
carbon-containing product are discharged from separate respective
outlets 15, 35 in the reaction chamber 5.
[0097] The temperature profile in the reaction chamber 5 is
selected and controlled so that the gas product discharged from the
reaction chamber 5 is at a temperature of the order of 80.degree.
C. The gas product is transported away from the reaction chamber 5
and the water vapour phase and condensable components of the
volatile products gas phase condense in cooler upstream sections at
a temperature of the order of 30.degree. C. and form (a) a
water-based condensate product (water recovered from a pyrolysis
process is typically somewhat acidic and contains dilute smoke
chemicals and other organics; it is often referred to as
pyroligneous acid or "wood vinegar" and has beneficial applications
in horticulture) and (b) a separate fuel gas product that has
sufficient calorific value to be combusted as an energy source.
[0098] The contaminants in wood wastes may be as described above.
The contaminants may include organic materials such as resins,
glues, paints etc. that make it difficult to cost-effectively
process the wood wastes for use as or in new products. The
contaminants may also include heavy metals.
[0099] The solid char, gas and water-based condensate product
outputs are intrinsically valuable, with a wide range of potential
material and energy applications in industry and agriculture.
[0100] Embodiments of suitable temperature profile in the reaction
chamber are shown in FIG. 2.
[0101] FIG. 2 was generated from trial data described in more
detail below.
[0102] The horizontal axis of FIG. 2 is time that a unit of feed
material has been in the reaction chamber 5 measured in minutes and
the vertical axis of the Figure is temperature in .degree. C. Time
is a measure of position along the length of the reaction chamber
5.
[0103] FIG. 2 shows the results of trials with 4 different feed
materials, with the feed materials of each trial comprising wood
wastes and different amounts of plastics material.
[0104] FIG. 2 shows that the temperature of the feed material in
each trial increased steadily to approximately 250.degree. C. after
8 minutes within the reaction chamber 5.
[0105] FIG. 2 also shows that the temperature of the feed material
having 100 wt. % wood wastes then increased quickly generally
linearly during the next 4 minutes to 600.degree. C. This sharp
increase indicates thermo-chemical reactions of the feed material,
i.e. Zone 3 of the temperature profile described above.
[0106] FIG. 2 also shows similar sharp increases in temperature at
later start times for feed materials having increasing proportions
of plastics materials, with the start times being a function of the
increasing proportions of plastics materials in the feed materials.
Basically, the steady heating of the feed materials continued along
the lower gradient line shown in the Figure until the temperature
reached a point where significant thermo-chemical reactions
commenced and there was a sharp increase in temperature.
[0107] It is evident from FIG. 2 that the 4 feed materials had the
same basic temperature-time profiles, with the only differences
being the temperature and time at which the increased heating rate
commenced.
[0108] Basically, FIG. 2 shows an extended temperature-time
gradient in a countercurrent solids/gas reactor. The trial results
described below establish that the extended temperature-time
gradient shown in FIG. 2 make it possible to process wood wastes as
the only feed material and wood wastes with other components, in
the present instance plastics materials, in the feed material.
[0109] FIG. 2 illustrates that the temperature profile in the
reaction chamber includes the following zones extending
successively along the length of the reaction chamber from the
upstream end to the downstream end of the reaction chamber: [0110]
(a) a drying zone (Zone 1) for drying the feed material--typically
increasing from 60-80.degree. C. at the inlet to 100-150.degree. C.
at the upper temperature limit of Zone 1, [0111] (b) a pre-heating
zone (Zone 2) for heating the feed material to a temperature that
is suitable for the thermo-chemical reactions required in the Zone
3--typically 250-300.degree. C. is the upper limit of Zone 2, and
[0112] (c) a thermo-chemical reaction Zone 3 for thermally
decomposing the feed material and producing a solid
carbon-containing, typically char product, and gas.
[0113] With reference to FIGS. 3 and 4, the embodiment of the
apparatus in the form of a continuous converter, generally
identified by the numeral 3, for decomposing organic contaminants
in wood wastes shown in the Figures includes a reaction chamber 5
that has an upstream colder end 7, an inlet 41 for feed material
(including waste wood containing contaminants), a downstream hotter
end 9, outlets 13, 35 for discharging liquid water and gas products
respectively from the chamber 5 at the upstream end, and an outlet
15 for discharging a solid carbon-containing product, for example
in the form of char, at the downstream end of the chamber 5.
[0114] The converter 3 also comprises a feed hopper 37 for
supplying organic feed material to the upstream end of the reaction
chamber. The feed hopper may be a sealed or an open hopper.
[0115] The converter 3 also comprises an assembly that forces feed
material continuously forwardly in the reaction chamber 5 from the
upstream end 7 towards the downstream end 9. The assembly comprises
three parallel rotatable shafts 17 and screw feeders 19 on the
shaft. The screw feeders 19 are interleaved. One shaft 19 is a
motor-driven shaft via motor M4 and the other shafts 19 are linked
to rotate with the driven shaft. This is a simple and reliable
arrangement whereby rotation of the shafts 17 about their axes
forces feed material from the upstream end towards the downstream
end of the chamber 5. The feed screw arrangement can include a
single or any other suitable number of multiple screws, which may
or may not be interleaved.
[0116] The converter 3 also includes an intruder 21 (i.e. a
gas-sealed entry device) for supplying feed material to the
reaction chamber 5 and an extruder 23 (i.e. a gas-sealed discharge
device) for discharging the solid carbon-containing product from
the chamber 5. Each device includes two screws 27, 29 on the same
axis. The screws 27, 29 are mounted to counter-rotate with respect
to each other about the axis. It is noted that the screws 27, 29,
may be arranged to rotate in the same direction. The screws are
separated by an axial gap 25. The intruder 21 controls the rate of
supplying feed material to the reaction chamber 5 and compresses
feed material and forms a seal that minimises escape of gas from
the chamber 5 via the intruder. Each screw 27, 29 is independently
driven by a motor M1, M2 with variable speed capability so that in
use the downstream screw 27 runs at a slower rotation rate than the
upstream screw 29. The difference in the rates of rotation causes
feed material supplied to the upstream screw 29 from the feed
hopper 37 and transported to the gap 25 to be compressed in the gap
25 and to enter the downstream screw 27 as compressed material and
to travel forward as compressed material via the downstream screw
27.
[0117] The method and the seal quality may be controlled by setting
the motor torque of the motors M1 and M2 to a level determined to
be required to deliver a required level of compression. Typically,
motor torque and not rate of rotation is set for control purposes.
Typically, the rate of rotation of the upstream screw 29 is linked
directly to the rate of rotation of the motor-driven screw feeder
19 in the reaction chamber 5 to control throughput. Typically, the
rate of rotation of the downstream screw 27 is controlled to
maintain constant torque of the upstream screw 29 of the intruder
21 to control compression. The packing density of the feed material
to achieve a required seal may be dependent on a number of factors,
including the characteristics of the feed material. The
characteristics may include the packing characteristics of the feed
material.
[0118] It is noted that the opposite arrangement may be used for
control purposes. Specifically, the rate of rotation of the
downstream screw 27 may be linked directly to the rate of rotation
of the motor-driven screw feeder 19 in the reaction chamber 5 to
control throughput and the rate of rotation of the upstream screw
29 may be controlled to maintain constant torque of the downstream
screw 27 of the intruder 21 to control compression.
[0119] Similarly, the extruder 23 controls the rate of discharging
solid carbon-containing product from the reaction chamber 5 and
forms a seal that prevents escape of gas from the reaction chamber
5 via the extruder 23. The intruder 21 and the extruder 23 have the
same basic structural components and these are identified by the
same reference numerals in the Figures.
[0120] The converter 3 also includes a feed assembly generally
identified by the numeral 11 for controlling the flow of feed
material from the intruder 21 to the inlet 41 of the reaction
chamber 5. The feed assembly 11 includes a transfer chute that is
in the form of a distribution box 43 between an outlet 45 of the
intruder 21 and the inlet 41 of the reaction chamber 5 and a
sweeper blade 47 that is rotatable about a central vertical axis of
the distribution box 43 via operation of a motor M3 to control the
distribution of feed material to the reaction chamber inlet 41.
[0121] In use, feed material from the outlet 45 of the intruder 21
falls downwardly through the inlet 41 into an upstream end of the
reaction chamber 5 and is moved forward, for example by means of an
auger in the reaction chamber, through the reaction chamber 5 and
is thermally decomposed and then discharged as a solid
carbon-containing product from the chamber 5 via the extruder 23,
with liquid water and gas products also being produced and
discharges from the chamber 5 via the outlets 13, 35 as the feed
material moves through the chamber 5.
[0122] Typically, the feed rate to the reaction chamber 5 is
controlled to ensure that the chamber is full of feed material.
[0123] The sweeper blade 47 is important to ensuring that there is
a uniform distribution of feed material delivered to the inlet of
the reaction chamber 5, i.e. so that the reaction chamber 5 is full
of feed material.
[0124] The level of feed material in the distribution box 43 is
also an important consideration from an operational viewpoint. The
applicant has found that the apparatus may block if the level of
feed material is too high.
[0125] The method of operating the converter 3 includes measuring
the torque on the sweeper blade 47 to provide an indication of the
level of feed material in the distribution box and adjusting the
rate of rotation of the upstream screw of the intruder 21 to
control the supply rate of feed material to maintain the desired
level of feed material in the distribution box 43.
[0126] The converter 3 has structural features that make it
possible to establish and maintain a required temperature profile
in the reaction chamber 5 to operate one embodiment of the method
of the present invention in the reaction chamber 5.
[0127] In particular, important features of the converter 3
include, for example, selection of the length of the reaction
chamber 5, selection of the feed (e.g. biomass) and the feed rate
(i.e. organic material) through the chamber 5, providing targeted
injection of oxygen-containing gas into the chamber 5, providing
targeted injection of liquid water into a downstream end of the
chamber 5 for char cooling, and providing a means for achieving
internal heat transfer within the chamber.
[0128] The converter 3 is particularly suited for a method that
operates so that there is total destruction of the liquid oil
product produced in the chamber. Specifically, the method is
operated so that there is volatilization and cracking of liquid oil
and tar product that forms in the chamber to the extent that there
is total destruction of the liquid oil and tar product into a
non-condensable gas that is discharged from the upstream end of the
chamber. Having said this, there may be situations in which it is
desirable to drain some oil from the chamber 5 as a separate
product.
[0129] The method and the apparatus of the present invention create
a completely unique thermo-chemical environment compared to known
pyrolysis technologies that are commercially available or under
development.
Experimental Work--Trials
[0130] As described above, the applicant has identified operating
conditions that make the continuous biomass converter technology
particularly effective for processing wood wastes containing
contaminants and producing valuable products that are safe and have
economic value.
A. Trials on Wood Wastes--Engineered Timbers
[0131] The applicant has carried out a series of trials on wood
wastes in the form of engineered timbers provided by Laminex
Group.
[0132] The applicant found that organic material contaminants in
these wood wastes and contaminants in pyrethroid-impregnated
timbers such as H2-F Blue Pine waste can be decomposed altogether
or converted into useful products effectively by the continuous
biomass converter technology of the applicant.
[0133] In addition, the applicant found that heavy metal
contaminants in these wood wastes deported to the char product of
the converter.
1. Engineered Timbers
[0134] The Laminex wood wastes were in the form of engineered
timber wastes.
[0135] Specifically, the wood wastes comprised particle board (PB),
medium density fibreboard (MDF) and plywood timber products. MDF is
manufactured from softwood fibres, wax and resin. Wax is used to
improve the moisture resistance of the finished product while urea
formaldehyde resin bonds the fibres together in the finished
pressed board. PB is manufactured in a similar process but uses
wood particles rather than fibres.
[0136] Table 1 provides an approximate composition profile of the
PB, MDF and plywood products.
TABLE-US-00001 TABLE 1 Approximate composition of PB, MDF and
Plywood Chemical Entity PB MDF Plywood.sup.8 Wood >85% >86%
>92% Urea Formaldehyde resin <13% 1-12% <8% Melamine urea
formaldehyde <13% -- <8% resin Phenol formaldehyde resin --
-- <8% Paraffin wax <2% 0-2% --
1.1 Chemical Properties
[0137] Engineered timber product waste sample analysis (other than
the analyses for plywood samples) was undertaken by NATA accredited
LabMark Environmental Laboratories (NATA Acc. Site No. 18217,
Accreditation No. 1261) using samples collected in accordance with
a sampling plan. Fluorine and chlorine testing was subcontracted to
Amdel Ltd (NATA accreditation No. 626), while melamine and cyanuric
acid was analysed by AsureQuality.
[0138] Plywood waste sample analysis was undertaken by NATA
accredited Eurofins Environmental Testing Australia [formerly
LabMark] (NATA Acc. Site No. 14271, Accreditation No. 1261) using
samples collected in accordance with a sampling plan. Fluorine and
chlorine testing was subcontracted to Amdel Ltd (NATA accreditation
No. 626), while melamine and cyanuric acid was analysed by
AsureQuality.
[0139] The samples were tested for calorific value for the
application for use of the engineered timber product waste as
non-standard fuel. Calorific value testing was carried out by SGS
Australia Pty Ltd (NATA Accreditation No. 2562).
[0140] The number of samples taken of each type of engineered
timber product was determined by the proportion of product sold;
i.e. 82% of the product sold is decorated whilst 18% is raw
product.
[0141] A summary of the results of laboratory analysis are
presented in Table 2 along with guideline values for chemical
properties established by the NSW EPA. Where NSW EPA guidance was
not available, the Swiss Agency for the Environment, Forests and
Landscape (SAEFL) National Environment Protection Guideline on
Investigation Levels for Soil and Groundwaters--Guidelines:
Disposal of Wastes in Cement Plants was referenced.
TABLE-US-00002 TABLE 2 Summary Chemical Characterisation of
Engineered Timber Product Waste Chemical Levels for Standard
Attributes Units LOR Characterisation Minimum Maximum Average
Deviation % Moisture % 0.1 3.7 9.3 6.9 1.2 Ash % w/w 0.01 0.2 10.0
4.1 3.0 Calorific Value Kcal/kg 4.026 4.682 4.312 143 Conductivity
(1:5 dS/cm 0.005 0.1 0.7 0.3 0.1 aqueous extract) Formaldehyde
mg/kg 10 190 53.000 19.772 11.333 Loss on Ignition % 0.1 95 100 99
1.2 (550C) Melamine mg/kg 1.0 4.4 660 134 136 Nitrate & Nitrite
mg/kg 0.1 0.3 18.0 5.1 4.5 (N) pH (1:5 Aqueous units 0.1 8-11.sup.1
4.6 8.6 5.6 1.0 extract) Phosphorus mg/kg 10 5 250 76 57 Sulphur
mg/kg 100 5000.sup.1 38 770 198 203 Total Chlorine % 0.01 0.0 0.1
0.0 0.0 Total Fluorine mg/kg 20 10 10 10 0.0 Total Kjeldahl mg/kg
10 1.000 63.000 33.876 16.647 Nitrogen (N) Total Nitrogen mg/kg 10
1.000 63.000 33.894 16.664 (N) Total Oxidisable % 0.5 7.3 78.0 38.9
20.6 Organic Carbon Heavy Metals Antimony mg/kg 1 .sup. 3 6.sup.2
0.1 5.0 0.5 1.5 Arsenic mg/kg 1 10.sup.1 11.sup.2 0.1 3.6 0.3 0.6
Beryllium mg/kg 1 .sup. 3 6.sup.2 0.1 1.0 0.1 0.3 Boron mg/kg 5 2.5
24.0 5.9 5.8 Cadmium mg/kg 0.1 0.5.sup.1 1.4.sup.2 0.1 0.2 0.1 0.0
Chromium mg/kg 2 75.sup.1 72.sup.2 1.0 8.5 3.0 1.1 Cobalt mg/kg 1
14.sup.2 0.1 2.5 0.3 0.7 Copper mg/kg 2 50.sup.1 72.sup.2 1.0 27.0
2.2 3.6 Lead mg/kg 2 50.sup.1 145.sup.2 1.0 4.4 1.2 0.7 Manganese
mg/kg 5 6.3 56.0 23.2 11.6 Mercury mg/kg 0.05 0.5.sup.1 0.36.sup.2
0.0 0.2 0.1 0.1 Molybdenum mg/kg 1 0.5 5.0 0.9 1.3 Nickel mg/kg 1
40.sup.1 72.sup.2 0.5 2.5 0.8 0.7 Selenium mg/kg 2 2.sup.1
3.6.sup.2 1.0 2.5 1.1 0.4 Tin mg/kg 1 .sup. 7 1.sup.2 0.5 5.0 0.9
1.3 Vanadium mg/kg 5 72.sup.2 2.5 5.0 2.7 0.7 Zinc mg/kg 5
100.sup.1 290.sup.2 2.5 14.0 3.5 2.4 Speciated Phenols 2.4.5- mg/kg
0.5 0.5 1.3 1.2 0.2 Trichlorophenol 2.4.6- mg/kg 0.5 0.5 1.3 1.2
0.2 Trichlorophenol 2.4- mg/kg 0.5 0.3 1.3 1.2 0.3 Dichlorophenol
2.4- mg/kg 0.5 0.3 8.8 1.4 1.2 Dimethylphenol 2-Chlorophenol mg/kg
0.5 0.3 1.3 1.2 0.3 2-Methylphenol mg/kg 0.5 0.1 19.0 1.7 2.9
(o-Cresol) 2-Nitrophenol mg/kg 0.5 0.5 3.6 1.2 0.4 3&4- mg/kg 1
0.2 25.0 3.0 3.7 Methylphenol (m&p-Cresol) 4-Chloro-3- mg/kg
0.5 0.5 28.0 1.7 3.7 methylphenol Pentachlorophenol mg/kg 1 0.5 2.5
2.3 0.6 Phenol mg/kg 0.5 8500.sup.2 0.3 3.700 129.9 622.8 Phenol-d5
(surr.) % 1 71.0 104.0 92.1 5.9 Note: Where samples resulted in
less than the LOR, or where the attribute was not detected (ND),
0.5 .times. LOR was used to calculate averages, minimum, maximum
and SD. .sup.1General Exemption under Part 9, Clause 93 Protection
of the Environment Operations (Waste) Regulation (2014) - The coal
washery rejects order 2014, Table 1. p.3. .sup.2SAEFL. (2005).
Guidelines: Disposal of Wastes in Cement Plants. Swiss Agency for
the Environment, Forests and Landscape.
[0142] Formaldehyde levels for the samples ranged between 2000
mg/kg for sample #7 (HPL) to 53,000 mg/kg for sample #44 (Raw MDF).
Similarly, melamine levels for the samples ranged between 5.5 in
sample #41 (raw MDF) to 660 in sample #32 (raw PB). These
substances when heated can produce a suite of volatile organic
compounds. However, the chemical analysis of the samples must be
viewed within the context of the proposed utilisation of the
engineered timber product waste as a feedstock for the continuous
biomass converter technology.
[0143] As a consequence of decomposition, tar cracking and
scrubbing actions within the reactor, the continuous converter
produces a gas essentially free of higher molecular weight
compounds.
2. Treated Timbers--H2-F Blue Pine Waste--Pyrethroid-Impregnated
Timber
2.1 Chemical Properties
[0144] Plantation pine is considered an eligible fuel and not
subject to any environmentally based regulatory controls.
[0145] Addition of up to 0.02% pyrethroid (as either 0.02%
permethrin, using a natural oil as the delivery vector, or 0.02%
bifenthrin, using water as the delivery vector in framing timber)
or 0.0078% nicotinoid (as imidacloprid) (AS1604.1-2012) is an
entirely known and understood process not requiring full chemical
analysis in order to characterise the waste/offcuts. The AS
1604.1-2012 Specification for preservative treatment: Sawn and
round timber standard specifies the minimum concentrations of the
oven-dried active ingredients utilised for the production of H2-F
blue pine framing timbers.
[0146] The concentration of the active organo-chlorine ingredients
is of the order of tens and hundreds of parts per million (i.e.
0.02% w/w=200 ppm). Given the concentrates/starting solutions of
bifenthrin, permethrin and imidacloprid have a high concentration
of the active ingredients, the dilution effect during the
preparation and impregnation of pine timber is in the order of
1,000 times or more.
3. Initial Trial with Engineered Timbers
[0147] A preliminary trial was carried out to monitor emissions at
the flare, especially VOC's and aldehydes as an indication of the
ability of the continuous converter to break down complex organic
constituents of engineered timbers.
3.1 Gas Properties/Air Emissions
[0148] Emissions from combustion of the continuous converter gas at
the flare were measured by ETC (now Ektimo) and are summarised in
Table 3.
[0149] Clean timber was used as a reference feedstock; and the
trial feedstock was a blend of 50% clean timber and 50% decorated
particle board, referred to as the "Laminex Blend".
TABLE-US-00003 TABLE 3 Air Quality - Flare Combustion of Gas
Product Laminex Detection Group 6 Clean Timber Blend Limit .sup.16
Standards.sup.17 Emissions .sup.18 Emissions Substance (mg/m.sup.3)
(mg/m.sup.3) (mg/m.sup.3) (mg/m.sup.3) Particulates <4.0 50
<4.0 5.1 VOC's 40 4.0 and 6.1 10 Formaldehyde <0.1 <0.1
<0.1 Acetaldehyde <0.1 <0.1 <0.1 NO.sub.x 450 240 and
450 1.500
[0150] All units are mg/m.sup.3 at NTP and 3% O.sub.2
[0151] This trial was considered to have a positive outcome. The
following important facts/findings are noted from this trial with
respect to the gas product: [0152] VOC emissions well below Group 6
(Clean Air Regulation) standards, consistent with the proposition
that complex, long chain molecules do not endure the particular
thermochemical conditions of the continuous biomass converter
technology. [0153] Formaldehyde and acetaldehyde emissions were
below detection limits. Note the detection limit of 0.1 mg/Nm.sup.3
at the flare would be triggered by as little as 350 mg of aldehydes
if emitted from one tonne of engineered timber feedstock, i.e. 0.35
ppm emitted from the feedstock. The formaldehyde content of
engineered timbers is many orders of magnitude higher than this,
with formaldehyde ranging from 900 to 53,000 ppm. The fact that
aldehydes were not detectable in the emissions is therefore
considered positive evidence that continuous converter processing
of engineered timbers does not release aldehydes to air. [0154]
Particulates were found to be well below Group 6 standards, and
were not significantly compromised by 50% engineered timber in the
feed blend. [0155] There was no visible smoke during the trial,
which is typical of normal continuous converter operations. [0156]
SO.sub.2 was monitored but was undetectable in the emissions for
both the clean timber and the engineered timber blend. (Detection
limit--6 mg/Nm.sup.3).
[0157] Concentrations of NO.sub.x were monitored at the flare and
found to be rather variable during the trial. During two periods of
clean timber processing, average NO.sub.x levels were 240 and 450
mg/Nm.sup.3, whereas they were higher at 1,500 mg/Nm.sup.3 during a
period with the engineered timber blend. The extent to which NOx
performance at the flare is dependent on fuel nitrogen (e.g. urea
in the engineered timber) and/or burner design and combustion
conditions has not yet been resolved. For perspective, NO.sub.x at
1,500 mg/Nm.sup.3 meets Group 5 standards, not Group 6 for Schedule
3 and 4. Note that the interim arrangement will be flaring where
there are no NO.sub.x criteria.
3.2 Biochar Properties
[0158] Char samples were analysed from separate periods during the
trial, covering the processing of clean timber and the 50% particle
board blend ("Laminex blend"). The purpose of this preliminary
trial was to compare and contrast the two chars against the
following criteria: [0159] Type 1 and Type 2 trace metals not to
exceed 350 mg/kg; [0160] Calorific value to be determined; and
[0161] Chlorine, fluorine, copper and sulphur to be recorded.
[0162] The results are summarised in Table 4.
TABLE-US-00004 TABLE 4 Summary of Char Assays Clean Timber Laminex
Blend Properties Char (mg/kg)* Char (mg/kg)* Type 1 Metals Antimony
Sb 0.3 0.9 Arsenic As 0.3 1.4 Cadmium Cd <0.01 <0.01 Lead Pb
0.9 5.1 Mercury Hg 0.01 0.01 Total Type 1 1.5 7.4 Type 2 Metals
Beryllium Be 0.02 0.03 Chromium Cr 25 31 Cobalt Co 1.1 4.9 Maganese
Mn 47 73 Nickel Ni 17 17 Selenium Se 0.2 0.4 Tin Sn 0.2 0.1
Vanadium V 2 3 Total Type 2 92 130 Type 1 and 2 Total 94 138 Other
Elements Copper, Cu 22 29 Sulphur, S % 0.01 0.03 Chlorine, Cl %
0.011 <0.01 Fluorine, F <10 11 Calorific Value.sup.23 MJ/kg
28.35 30.8
[0163] All results are reported in mg/kg on a dry weight basis
except where otherwise noted. S and Cl concentrations are reported
as % and the Calorific Value is reported in MJ/kg.
[0164] The following important facts/findings are noted from this
trial with respect to the biochar: [0165] The clean timber char and
the engineered timber char have quite similar properties, with
respect to trace elements and energy content. [0166] Char quality
as a fuel has not been compromised with the Laminex particle board
added to the feedstock. In fact, carbonisation has progressed
somewhat further with the engineered timber blend.sup.24. [0167]
Both chars fall well below the Total Type 1 and 2 trace metal limit
currently imposed on Delta's use of alternative fuels (350 ppm). 4.
Initial Trial with Pyrethroid-Impregnated Timbers--H2-F Blue Pine
Waste
[0168] H2-F Blue Pine waste contains bifenthrin and permethrin.
These are long chain complex chlorinated/fluorinated organic
substances. A preliminary trial was therefore undertaken to test
whether the continuous converter could break down under the
thermo-chemical conditions inside the reactor, and that they would
not act as precursors for dioxins, furans or PAH formation.
[0169] The initial trials relating to the H2-F treated blue pine
framing timber. The shredded blue pine timber was 100% pre-consumer
blue pine initially sourced from the timber and frame off-cuts of
Bay Timber.
4.1 Gas Properties
[0170] It was decided to measure for the potentially toxic
substances in the gas product of the continuous converter, before
the flare, so that evidence of their presence could not be hidden
by subsequent combustion. Gas concentrations were measured by ETC
(now Ektimo), as summarised in the table below. The primary
objective with regard to the gas product was to: [0171] confirm
bifenthrin and permethrin decomposition.sup.28 under continuous
biomass converter technology thermo-chemical conditions (expected
above 250.degree. C.); and [0172] confirm that dioxin formation did
not result from the decomposition of chlorinated organics
(pyrethroids and nicotinoids).
[0173] The results of the fuel gas testing are reproduced in Table
5.
TABLE-US-00005 TABLE 5 Fuel Gas Composition - Prior to Flare
Combustion of Continuous biomass converter Technology Gas Substance
Units CBC Gas Bifenthrin mg/Nm.sup.3 <0.003 Pemethrin
mg/Nm.sup.3 <0.003 Dioxins and Furans ng/Nm.sup.3 TEQ 0.019 PAH
.mu.g/Nm.sup.3 TEQ (BaP) 17
[0174] The following facts/findings are noted from this trial and
from the cumulative trials thus far with respect to the fuel gas:
[0175] The bifenthrin and permethrin were both below detection
limits in the gas product. Note that the detection limit of 0.003
mg/Nm.sup.3 would be triggered if as little as 2.1 mg reported to
the gas per one tonne of blue pine timber. In reality, the
pyrethroid concentration in blue pine is orders of magnitude higher
than this, typically around 0.02% or 200,000 mg per tonne of
timber. This is therefore considered positive evidence that the
bifenthrin and permethrin do not survive the thermo-chemical
conditions of the continuous converter. [0176] In this initial
trial, dioxin and furan levels in the continuous biomass converter
technology gas, before flaring, were measured at 0.019 ng/Nm.sup.3
TEQ, some five times below Group 6 emission standards. Actual flare
emissions could be expected to be lower than this, given the
dilution effect of the combustion air and possible destruction of
dioxins and furans within the flare. [0177] There are no published
Group 6 emission limits for PAH's in NSW. The measured value in the
gas product, before flaring, of 17 .mu.g/Nm.sup.3 TEQ (BaP
equivalent) corresponds to a BaP based emission factor of 12
.mu.g/kg feedstock. Actual flare emission factors for the
continuous converter may be lower, if there is any PAH destruction
within the combustion zone. This initial result is in line with
measurements reported in the literature for industrial stack
emissions.
5. Initial Trial on Trace Metal Emissions
[0178] A feature of the continuous converter technology is, despite
being a thermal process with an operating set point temperature of
typically 650.degree. C., the gas exits the reactor at low
temperatures, typically around 80.degree. C., followed by further
cooling to lower the dew point of the gas and collect the water
product of the continuous converter as a condensate. At these low
gas exit temperatures, the vapour pressure of metals contained in
the feed is very low.
[0179] A preliminary trial was therefore undertaken to test whether
trace metal volatilisation from feedstocks to the product gas is
not favoured under the thermo-chemical conditions of the
reactor.
[0180] Metal concentrations were measured at the flare by Ektimo,
as summarised in Table 6. The feedstock for the monitoring period
was 40% clean timber, 40% H2-F blue pine, and 20% engineered timber
waste.
TABLE-US-00006 TABLE 6 Flare Emissions Monitoring - Trace Metals
CBC Flare Emissions Properties (mg/Nm.sup.3 at 3% (O.sub.2) Type 1
Metals Antimony Sb <0.002 Arsenic As 0.018 Cadmium Cd <0.001
Lead Pb <0.002 Mercury Hg 0.0021 Total Type 1 0.02 Type 2 Metals
Beryllium Be <0.001 Chromium Cr 0.11 Cobalt Co 0.0044 Manganese
Mn 0.014 Nickel Ni 0.17 Selenium Se 0.0037 Tin Sn <0.002
Vanadium V <0.001 Total Type 2 0.3 Type 1 and 2 Total 0.33
[0181] The results confirm that a very small proportion of metals
in the feedstock report to the gas. Importantly, for this feedstock
blend, which included 40% clean timber, 40% Blue Pine and 20%
engineered timber, heavy metal emissions are within Group 6
standards, namely Type 1 and 2 in aggregate below 1 mg/Nm.sup.3,
and Hg and Cd individually below 0.2 mg/Nm.sup.3.
6. Comprehensive Trial--Blends of Pyrethroid-Impregnated Timbers
such as H2-F Blue Pine Waste and Engineered Timber
[0182] With positive indications coming from the initial continuous
converter trials with feedstocks containing engineered timbers and
H2-F blue pine, a comprehensive trial was conducted.
[0183] The important trial considerations/parameters include:
[0184] The core feedstock was a blend of 50% H2-F Blue Pine and 50%
engineering timbers. [0185] The prime focus was measuring emissions
at the flare for the range of substances relevant waste gas
concentrations to Group 6 (Clean Air Regulation) standards. [0186]
The trial also included a preceding period of 100% H2-F Blue Pine
processing, with limited emissions monitoring. [0187] The trial was
subsequently followed by a run with 100% clean timber mill
feedstock, but with no emissions monitoring. [0188] The two
supporting runs with blue pine and clean timber feedstocks were
conducted primarily to obtain char and water samples for comparison
with the char and water made from the 50:50 blend of blue pine and
engineered timbers.
6.1 Air Emissions
[0189] Emissions at the flare were measured by Ektimo, as
summarised in Table 7.
TABLE-US-00007 TABLE 7 Air Quality - Flare Combustion of Continuous
Biomass Converter Technology Gas Group 6* CBC 50:50 CBC 100%
Pollutant/Species Limit Laminex:Blue Blue Pine Smoke Ringleman 1
Ringleman 0 None 20% Opacity None visible Visible Solid
Particulates (Total) 50 <3 Type 1 and Type II 1.0 0.027 Metals
(in aggregate).sup.c Mercury 0.2 <0.002 Cadmium 0.2 <0.001
Dioxins or Furans 0.1 0.00095 (ng/m.sup.3 TEQ) Volatile Organic 40
0.02 Compounds (VOC's as n-propane) Sulfuric Acid Mist (SO.sub.3
100 5.4 2.6 equivalent) Hydrogen Sulfide (H.sub.2S) 5.0 0.46 8.1
Fluorine (HF equivalent) 50 3.2 Hydrogen Chloride (HCl) 100 100 52
Chlorine (Cl.sub.2) 200 <0.02 <0.02
[0190] All units are mg/m.sup.3 at NTP and 3% O2, except for
dioxins in ng/m.sup.3 at NTP and 3% O2.
[0191] *Based on Protection of the Environment (Clean Air)
Regulation 2010 Schedule 3 and Schedule 4
[0192] For the suite of air quality parameters monitored in this
trial, the results are very positive, in that all are well below
Group 6 standards, except HCL (50:50 Laminex Blue) which was at the
Group 6 limit and H.sub.2S (100% Blue), which was above the Group 6
limit, although this result is questionable, since on the same day
a value of 0.46 mg/m.sup.3 with 50% blue was recorded.
[0193] For the same trial conditions, with the 50:50 Laminex:Blue
Pine blend, a detailed breakdown of the trace metal emissions at
the flare is given in Table 8.
TABLE-US-00008 TABLE 8 Flare Trace Metal Emissions Trace Metals CBC
Flare Type 1 Antimony Sb <0.001 Arsenic As 0.011 Cadmium Cd
<0.001 Lead Pb <0.001 Mercury Hg <0.002 Total Type 1 0.011
Type 2 Beryllium Be <0.001 Chromium Cr <0.04 Cobalt Co
<0.001 Manganese Mn <0.001 Nickel Ni 0.0022 Selenium Se
0.0095 Tin Sn <0.001 Vanadium V <0.001 Total Type 2 0.016
Type 1 and 2 Total 0.27
[0194] All results reported in mg/Nm.sup.3 at 3% O.sub.2
[0195] These results provide more evidence of the clean burning
properties of the gas. The results are within Group 6 standards.
Type 1 metals, other than Arsenic (0.011 mg/Nm.sup.3), and Type 2
trace metals, other than Nickel (0.0022 mg/Nm.sup.3)and Selenium
(0.0095 mg/Nm.sup.3) were below detection.
6.2 Char Properties
[0196] The trial provided the opportunity to compare the properties
of char samples manufactured from (1) the 50:50 Laminex:H2-F blue
pine blend, as well as (2) 100% blue pine and (3) 100% clean timber
for reference. The results are presented in Table 9 below.
TABLE-US-00009 TABLE 9 Continuous Biomass Converter Technology Char
Properties Properties Laminex Blue Blue Pine Clean Timber 50:50
100% 100% Date of Manufacture (2015) 7 January 7 January 15 January
Type 1 Metals Antimony Sb 0.2 0.2 0.1 ppm Arsenic As 3.3 3.8 1.6
dry basis Cadmium Cd 0.01 0.01 0.01 Lead Pb 4 6 3 Mercury Hg 0.01
0.01 0.01 Total Type 1 7.5 10 4.7 Type 2 Metals Beryllium Be 0.17
0.23 <0.01 ppm Chromium Cr 33 49 20 dry basis Cobalt Co 4.4 4.8
1.2 Manganese Mn 156 182 67 Nickel Ni 16 30 13 Selenium Se 0.4 1.1
0.5 Tin Sn 0.5 1.1 0.5 Vanadium V 10 13 2 Total Type 2 190.5 241
105 Type 1 and 2 Total 198 251 110 Other Constituents ppm dry basis
Copper. Cu 23 24 (46) Fluorine. F 30 63 (9) % dry basis Chlorine.
Cl 0.01 0.01 (0.011) Nitrogen N 2.64 0.3 0.41 Sulphur. S 0.05 0.04
(0.03) Ash .sup.37 17 30 4.6 Fuel Related Calorific Value 31.8 31.9
31.5 Properties Volatile Matter 24.7 26.9 25.6 % dry ash free Total
Carbon 83.2 85.2 82.4 basis Fixed Carbon 75.3 73.1 74.4 CV: MJ/kg
Hydrogen. H 3.25 3.07 3.15
[0197] Results in brackets for clean timber are from an earlier
char analysis made from the same source of clean timber.sup.38
[0198] The following observations are noted from this trial with
respect to the char: [0199] From a fuel perspective, the two chars
manufactured from waste wood feedstocks are essentially the same as
the char made from clean timber, in terms of calorific value,
volatile matter, and carbon and hydrogen contents. [0200] The trace
metal levels in the chars made from waste wood feedstocks are
somewhat higher than the clean timber char; the differences are
primarily driven by manganese [0201] Nitrogen is significantly
higher in the char made from the Laminex blend, presumably
reflecting the higher nitrogen levels in the engineered timber
feedstock (e.g. urea).
6.3 Water Product
[0202] The trial provided the opportunity to compare the properties
of the water product manufactured from:
[0203] 1. 50:50 Laminex:H2-F blue pine blend.
[0204] 2. 100% blue pine.
[0205] 3. 100% clean timber for reference.
[0206] The results are presented in Table 10.
[0207] The samples were taken from the continuous converter,
without filtering or significant settling time; they can be
regarded as `raw wood vinegar`.
[0208] The following observations are noted from this trial with
respect to the water product: [0209] The compositions of the three
wood vinegars are similar, with no major differences apparent.
[0210] Comparing the clean timber wood vinegar with the wood
vinegar made from the 50:50 Laminex:Blue blend, it has very similar
Total Type 1 and 2 trace metals (0.22 cf 0.27 ppm), slightly lower
total hydrocarbons (0.57 cf 0.88%) and higher BTEXN (12.6 cf 4.4
ppm). [0211] Trace metal levels are low, such that Type 1 and 2 in
aggregate are less than 1 mg/L (ppm) in all cases.
TABLE-US-00010 [0211] TABLE 10 Water Product Properties Clean
Laminex:Blue Blue Pine Timber Properties 50:50 100% 100% Date of
Manufacture (2015) 7 January 7 January 15 January Acidity pH 3.9
1.9 2.06 Acetic Acid 4.6% 5.5% 5.8% Type 1 Metals Antimony Sb 0.03
0.012 0.014 Arsenic As 0.173 0.3 0.12 Cadmium Cd 0.0002 0.0004
0.0002 Lead Pb 0.023 0.108 0.007 Mercury Hg 0.004 0.037 0.061 Total
Type 1 0.234 0.456 0.202 Type 2 Metals Beryllium Be <0.001
<0.001 <0.001 Chromium Cr -0.004 0.017 0.003 Cobalt Co
<0.001 0.001 <0.001 Manganese Mn 0.021 0.03 0.007 Nickel Ni
0.012 0.053 0.006 Seleium Se <0.001 <0.001 <0.001 Tin Sn
<0.001 <0.001 <0.001 Vanadium V <0.001 0.001 <0.001
Total 2 0.037 0.1 0.016 Type 1 and 2 Total 1 and 2 0.271 0.557
0.216 Recoverable C6-C10 78.5 105 136 Hydrocarbons >C10-C16
8.560 7.580 5.420 (excl. TBEXN) >C16-C34 136 153 101 >C34-C40
<0.15 <0.15 <0.15 Total C6-C40 0.88% 0.78% 0.57% BTEXN
Benzines 1.14 1.87 2.78 Ethylbenzene 0.098 0.142 0.125 Toluene 0.94
1.34 1.19 Xylenes 0.343 0.391 0.343 BTEX Total 2.52 3.7 4.44
Naphthalene 1.92 6.52 8.19 BTEXN Total 4.44 10.2 12.6
[0212] All units mg/L (approx. ppm) except acid and total
recoverable hydrocarbons in %
[0213] These analyses are of the water condensate direct from the
converter which is further refined by separation of any residual
oils and tars prior to application in the field. During this period
the BTEXN have been shown to be biodegradable.
6.4 Trace Metal Deportment
[0214] The distribution of trace metals between the products can be
calculated from the char, gas and water analyses presented above,
Table 8, Table 9 and Table 10, based on the relative yields of
char, gas and water.
[0215] The calculations have been carried out for the 50:50
Laminex:Blue Pine blend feedstock, since this is the one where
trace metals have been analysed for all three products.
Back-calculating from the product analyses, the estimated feedstock
trace metal concentrations are shown in the table below:
TABLE-US-00011 TABLE 11 Feedstock Trace Metals Feedstock
Concentration mg/kg Trace Metals (ppm dry weight basis) Type 1 3.1
ppm Type 2 76.3 ppm Total 1 and 2 Total 79.4 ppm
[0216] On the same assumptions, calculations of the relative
deportment of trace metals to the three co-products were made and
are shown in Table 12 below:
TABLE-US-00012 TABLE 12 Deportment of Trace Metals to the Products,
% of Original Feedstock Content Department Type 1 Type 2 Type 1 and
2 Total To Char 96.5% 99.93% 99.8% To Water 2.61% 0.017% 0.12% To
Gas 0.87% 0.052% 0.08%
[0217] The following observations are noted about trace metal
deportment: [0218] Type 1 and 2 metals report predominantly to the
char product (99.8% in total); [0219] Metals can only end up in the
gas or water products via the gas phase; Type 1 metals are
generally more volatile than Type 2 metals, hence their slightly
higher deportment to the gas and water. Even in the case of Type 1
metals, some 96.5% report to the char; and [0220] This is positive
evidence for the proposition that the low exit temperature of the
gas does not favour volatilisation of metals from the incoming
feed, and even where some volatilisation occurs, most of the metal
reports to the water product, not the gas.
B. Trials on Contaminated Wood Wastes--Impact of Plastics
Materials
Feed Preparation
[0221] Trials were conducted with wood wastes blended with
different amounts of plastics materials.
[0222] Table 13 summarises the plastics components:
TABLE-US-00013 TABLE 13 Components Proportion Components (dry
weight) Constituents Plastic 0, 3, 5, 7 wt. % 30% LDPE, 30% HDPE,
30% PP, 10% HIPS, Astron Plastics, Ingleburn
[0223] The wood waste was also prepared to the following feed
material specification of the applicant: [0224] total moisture
content <15%. [0225] size: minus 20 mm and <10% minus 1
mm.
[0226] The wood waste was blended with clean wood waste to produce
three blends, one blend having 3 wt. % plastics material, a second
blend having 5 wt. % plastics material, and a third blend having 7
wt. % plastics material.
Trial Procedure
[0227] In total, six processing trials were conducted at around 300
kg/hr, with an accumulated operating period of some 25 hours.
[0228] In each trial, after a period of at least 1 hour of stable
operation with clean wood waste in the reaction chamber 5 of the
converter 3, controlled amounts of plastic materials were added
each minute to the metering screw of the feed hopper of the
apparatus. The additions corresponded to 3 wt. %, 7 wt. % and 9 wt.
% plastics materials in the wood wastes.
[0229] It was found in the trials that, in this range of plastics
additions, stable operations and effective carbonisation were
achieved. In other words, the plastics materials did not impact
negatively on process stability.
Effective Carbonisation
[0230] The degree of carbonisation (char making) is an indicator of
the effectiveness of the apparatus in processing wood wastes. The
reason for this is that, if there is effective decomposition of the
lignin, cellulose and hemi-cellulose to char, it follows that biota
cannot survive and the various organics in the food, plastic and
paper will also decompose.
[0231] Table 14 summarises the carbonisation of the SFCW/wood
blends and a comparative example for 100% wood.
TABLE-US-00014 TABLE 14 Carbonisation Results 3% 5% 7% Char
Properties Clean plastics plastics plastics (DAF basis) Wood
materials materials materials Calorific Value 33.8 33.4 33.4 33.3
(GJ/t) Volatile Matter 10.2 9.8 12.1 13.4 (%) Carbon (%) 90 90 89
88 Hydrogen (%) 2.3 2.0 2.4 2.4 Oxygen (%) 5.6 5.8 6.4 6.7
[0232] A dry ash-free (DAF) calorific value above 30 GJ/t is a
measure of effective carbonization. The addition of plastics to
wood in wood wastes up to 7 wt. % in the wood wastes did not
compromise the carbonisation process (DAF CV >33 GJ/t in all
cases).
Process Stability
[0233] It was clear from the trial data, for example FIGS. 5 and 6,
that the addition of plastics up to 7 wt. % in the wood wastes
(i.e. up to 7 wt. % plastics materials) in the wood wastes did not
compromise process stability.
[0234] The control system of the apparatus made adjustments to the
operating parameters in response to the changes in feed properties
(composition and packing density).
[0235] For instance, the solids moved more slowly through the
apparatus with up to 7 wt. % plastics in the wood wastes) compared
to the 100% wood product, but the net production rate was higher
due to the increased packing density of the blend.
[0236] FIGS. 5 and 6 are temperature-time graphs for 1 hour periods
of trials with 0 and 7 wt. % wood wastes, i.e. 100 wt. % wood waste
and wood waste with 7 wt. % plastics material, at different
positions along the length of the reactor.
[0237] It is clear from the Figures that the temperature profiles
at the same positions are similar.
[0238] The data showed the same results with the other trials.
Temperature-Time
[0239] As discussed above, FIG. 2 shows the temperature-time
profiles of trials with four different feed materials, the feed
materials of each trial having different amounts of plastics
material. Four of the plots in FIG. 2 are for trials on 0, 3 wt. %,
5 wt. %, and 7% wood wastes.
[0240] As discussed above, FIG. 2 shows that the temperature of the
feed material in each trial increases steadily to approximately
250.degree. C. after 8 minutes within the reaction chamber 5.
[0241] The temperature of the feed material that had no quarantined
material increased quickly generally linearly from this point
during the next 4 minutes to 600.degree. C.
[0242] FIG. 2 also shows similar sharp increases in temperature at
later start times, with the start times being a function of the
increasing proportions of quarantined material (including plastics
materials) in the feed materials.
[0243] From a process management perspective, one of the key
factors is "time at temperature" for the solids travelling through
the reaction chamber 5 of the converter 3.
[0244] For perspective, the distance the solids travel from feed
entry to char discharge is some 4 m and there was a total residence
time of solids inside the apparatus is around 15 minutes.
[0245] On the journey through the reaction chamber 5, the solids
are first fully dried, then pre-heated and finally carbonised in
the reactor section.
[0246] The times at temperatures for effective thermal
decomposition of wood and the plastics and other organics in the
catering waste (300-600.degree. C.), were not compromised (ca 5
minutes) by the presence of the plastics materials).
[0247] The times at temperature are illustrated by Table 15
below.
TABLE-US-00015 TABLE 15 3% 5% 7% Plastics in wood 0% plastics
plastics plastics wastes plastics materials materials materials
Total Time in CBC 13.4 14.6 14.0 16.8 Time above 100.degree. C.
11.3 13.0 12.4 14.9 Time above 200.degree. C. 7.4 8.6 8.0 10.3 Time
above 300.degree. C. 5.0 5.2 5.0 4.6 Time above 400.degree. C. 3.5
3.3 3.0 3.4 Time above 500.degree. C. 2.3 2.0 2.3 2.6
[0248] As an approximation, and having regard to FIG. 2, the first
third of the journey through the reaction chamber 5 of the
converter 3, i.e. Zone 1, dries the feed material (with solids
reaching temperatures of 100-150.degree. C.), the second third,
i.e. Zone 2, preheats the feed material (to 250-300.degree. C.),
and the final section, i.e. Zone 3, is where the bulk of the
thermo-chemical reactions take place with peak temperatures in the
reactor reaching around 650.degree. C.
Products
[0249] The trials produced valuable solid char, wood vinegar (i.e.
a water-based condensate), and gas products. These are commercially
valuable products
[0250] In particular, the analysis of the trials showed that the
gas generated from processing 7 wt. % plastics is clean burning,
with all emission monitoring parameters, except NOx and HCl, well
below the Australian EPA Group 6 standards, without a gas cleaning
step prior to combustion. There are counter-measures available for
the NOx and HCl emissions.
[0251] The results are summarised in Table 16 below.
TABLE-US-00016 Gas Combustion EPA Emissions Parameters Group 6
Limits (7% plastics materials) Smoke (Opacity) 20% No visible smoke
Particulates 50 24 VOC's (as n-propane) 40 5.4 Chlorine 200
<0.07 Fluorides (as HF) 50 <0.08 Hydrogen Chloride 100 490
Hydrogen Sulphide 5 <0.5 Type 1 and 2 Metals Total 1 0.098
Cadmium 0.2 <0.0006 Mercury 0.2 <0.0002 Dioxins/Furans
(ng/Nm.sup.3 TEQ) 0.1 0.012 No.sub.x (as NO.sub.2) 450 560
Sulphuric Acid Mist (as SO.sub.3) 100 25 Sulphur Dioxide 1,000
140
[0252] The VOC's and dioxins/furans data in the above table is
particularly relevant to the plastics materials.
[0253] Many modifications may be made to the embodiment of the
method and the apparatus of the present invention shown in the
drawings without departing from the spirit and scope of the
invention.
[0254] By way of example, whilst the embodiment described in
relation to the drawings includes three parallel rotatable shafts
17 and interleaved screw feeders 19 on the shafts 17, the invention
is not limited to this arrangement and extends to any alternative
arrangements for moving feed material along the chamber 5 and is
not limited to this number of rotatable shafts 17 and interleaved
screw feeders 19.
[0255] By way of further example, whilst the embodiment described
in relation to the drawings includes particular forms of the
intruder 21 and the extruder 23, the invention is not limited to
this arrangement and extends to any alternative arrangements for
supplying feed material to the chamber 5 and discharging solid
product from the chamber 5 which creates effective gas seals for
the chamber 5.
[0256] By way of further example, whilst the embodiment described
in relation to the drawings includes a particular feed assembly 11
for controlling the flow of feed material from the intruder 21 to
the inlet 41 of the reaction chamber 5, the invention is not
limited to this arrangement and extends to any suitable alternative
arrangements.
[0257] Throughout this specification the word "comprise", or
variations such as "comprises" or "comprising", will be understood
to imply the inclusion of a stated element, integer or step, or
group of elements, integers or steps, but not the exclusion of any
other element, integer or step, or group of elements, integers or
steps.
* * * * *