Note: Descriptions are shown in the official language in which they were submitted.
CA 02686099 2009-11-19
1892
OIL IMPREGNATED PARTICULATE BIOMASS, METHODS OF
MANUFACTURE AND USES THEREOF
FIELD OF THE INVENTION
This invention relates to torrefaction processes for the production of
torrefied
products, particularly, wood, bark and agricultural biomass using plant and
animal oils; said
torrefied products and uses thereof.
BACKGROUND OF THE INVENTION
Torrefaction is the process of turning biomass material into a charcoal-like
state by
super-heating the material in a non-oxygen environment.
To-date, torrefaction has involved the use of hot gases. However, such
processes
result in the loss of significant amounts of torrefied product. Further, the
resultant product
does not have an enhanced BTU value per unit volume.
There is a need, therefore, for an improved efficacious process of producing a
torrefied biomass product that has an enhanced BTU value per unit volume.
SUMMARY OF THE INVENTION
The present invention provides a more efficacious torrefaction process of
producing a
biomass product of enhanced heat value.
Accordingly, in one aspect, the invention provides a method for the production
of a
torrefied biomass material from a particulate biomass material, comprising
treating said
material with a bio-liquid selected from an animal fat and plant oil at an
effective temperature
to provide said torrefied biomass material.
Preferably the temperature is greater than 200 C, and, more preferably,
selected from
240 C-375 C.
Preferred biomass material is selected from hardwoods and softwoods in the
form of
chips. pellets or bark; cellulosic waste agricultural materials, peat moss,
and industrial sludge.
Preferably, the liquid is a vegetable oil, for example, canola oil and soybean
oil.
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The torrefied biomass product, preferably, has a vegetable oil content of at
least 1%
w/w, most preferably, 4-12% w/w.
Preferably, the particulate biomass material of use in the practice of the
invention has
a particle size selected from 6mm to 1-2cm.
In a further aspect, the invention provides a torrefied particulate biomass
material
comprising at least 1% w/w vegetable oil, preferably, 4-12% w/w vegetable oil.
Surprisingly, I have discovered that the torrefaction process according to the
invention
is effected in a relatively short period of time, dependent on the temperature
and nature and
particle size of the biomass material. For example, times of less than 10
minutes can be
readily achieved. Pinewood pellets can be torrefied in canola or soybean oils
at about 240 C
in about 6 minutes. Pine and a hardwood was torrefied in canola oil at about
280 C within 6
minutes. At a temperature of about 320 C in canola oil, pine wood was
completely torrefied
in about 1 minute.
In a further aspect, the invention provides a method for the production of a
torrefied
wood product from a wood source, said method comprising
(i) subjecting said wood source to mechanical means to produce particulate
wood;
(ii) heating said particulate wood in a bio-liquid selected from an animal fat
and
plant oil at an effective temperature for an effective period of time to
effect torrefaction and
produce torrefied wood;
(iii) removing said torrefied wood from excess said bio-liquid; and
(iv) collecting said torrefied wood product.
In a further aspect, the invention provides, a method as hereinabove defined
wherein
said mechanical means comprises a chipper to produce particulate wood having
dimensions
created by conventional wood chipping apparatus.
In a further aspect, the invention comprises a pelletizing method that
virtually
eliminates fine, wood particles or dust that would otherwise be created after
the pellets are
extruded, because the bio-oil creates a binding agent for the material that
precludes the
creation of these dust particles during the pelleting process.
Thus, in yet a further aspect, the invention provides, a method as hereinabove
defined
wherein said mechanical means comprises a mill to produce milled particulate
wood; and
further comprising
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(v) treating said milled particulate wood with a first bio-liquid selected
from an
animal fat and plant oil to produce a bio-liquid-milled particulate wood
admixture;
(vi) treating said wood admixture in a pellet mill extruder to produce pellets
having dimensions; and
effecting steps (ii), (iii) and (iv) as defined in claim 1 wherein said
pellets constitute
said particulate wood.
The pellets have a particle size of about 4-6mm in diameter and 1-2cm in
length.
In a yet further aspect, the invention provide a process for producing a
torrefied
particulate biomass material comprising at least 4-12% w/w vegetable oil.
In a further aspect, the invention provides a torrefied particulate biomass
material.
In a further aspect, the invention provides a torrefied particulate biomass
material
made according to the invention, as hereinabove defined.
Preferably, the bio-liquid is a vegetable oil: and an oil content of at least
1% w/w
vegetable, preferably, 4-12%.
Thus. I have found that torrefaction of biomass material with a bio-oil
selected from
plant oils and animal fats, preferably, vegetable oil, gives a BTU boost
compared to
traditional torrefaction methods because of the penetration of the oil through
the strata of
biomass material, preferably, wood fibre.
Vegetable oil provides an anaerobic oxygen-free super heated environment to
allow
torrefaction. Further, by using new or used vegetable oil in the method of the
invention,
torrefied pellets maintain a low pollution emission level, are water
resistant, and reduced
organic materials found in non-torrefied biomass. Advantageously, the pellets,
according to
the invention, can be shipped and stored safely because the gases released by
normal wood
pellets are not present in consequence of the removal of the organics in the
present
torrefaction process. Further, the pellets can be used for energy production
in co-fired coal
burning facilities due to their extremely low moisture level and similar BTU
values. The
torrefied pellets can be crushed to dust and blown into existing coal fired
furnaces with
minimal changes to the furnace and coal feeding process being needed.
Torrefying methods
using hot oil versus traditional hot gases allow the biomass material to
retain more mass,
since traditional torrefaction methods experienced large volume loss due to
the removal of
carbon molecules. During hot oil torrefaction, the carbon molecules are
sequestered and
maintain more mass.
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The pelletized product as hereinabove defined can be used to generate heat in
residential or commercial pellet stoves and/or other industrial uses, such as,
energy creation
or bulk heating applications.
Preferably, the torrefied particulate biomass material is burnt in admixture
with
particulate coal.
In a further aspect, the invention provides a torrefied biomass material as
hereinabove
defined for use as a soil modifier.
The world is currently focused on the global warming crisis and the
development of
carbon neutral fuel sources. The present invention not only produces a carbon-
neutral hybrid
energy pellet, it also diverts waste agricultural and/or forestry materiel
from the waste stream
and creates a product that can be used for energy production. Using bio-oils
such as those
derived from plants and animals, e.g. new vegetable oil, refined, used
vegetable oil, animal
fats and the like. The method according to the invention allows for virtually
total use of the
oil. This is in contrast to historical usage for biodiesel production wherein
conventional use
utilizes only 60% of the total weight of material because the unwanted soaps
and other
delirious substances are discarded.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be better understood, preferred embodiments
will now
be described, by way of example only, with reference to the accompanying
drawings,
wherein
Fig. 1 is a block diagram of a torrefaction process according to the
invention;
Fig. 2 is a block diagram of an alternative torrefaction process according to
the
invention: and wherein the same numerals denote like parts.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Fig. 1 shows generally as 10, a process and apparatus for the production of
torrefied
wood chips.
Fig. 10 shows a conditioning chamber 12 linked by a conveyor 14 to mill
chipper 16
which is linked to a secondary conditioner 18 by conveyor 20. Above
conditioner 18 is
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located a spray tank 22 containing a vegetable oil 24. Conditioner 18 is
connected to a screw
conditioner 26 which is connected to torrefaction tank 28, which is connected,
via a conduit
31 to cooling tower 30 via a screen unit 32 which is above an oil recovery
unit 34. A cooling
tower 30 is located above a packaging unit 36.
In operation, wood biomass material is initially fed to conditioning chamber
12, by
conveyor 14 and then to chipper 16 wherein the material is reduced to less
than 6mm in
diameter and a maximum length of 10cm. Chipped material is transferred on
conveyor 20 to
secondary conditioner 18 and treated with vegetable oil 24 at a temperature of
about 240 C
from spray tank 22. The oil sprayer chips are mechanically mixed in screw
conditioner 26
and subsequently submerged and cooked in torrefaction tank 28 at a temperature
of at least
240 C for a sufficient period of time to effect torrefaction. A temperature of
between 240 C-
300 C is preferred.
The torrefied wood chips are removed from tank 28, excess oil removed by
screen 30,
and transferred to tower 32 via conveyer 34 to cool and harden and
subsequently packaged in
unit 36 in bulk or in bags.
Fig. 2 shows generally as 50 an alternative process and apparatus for the
production
of torrefied pellets.
The process and apparatus is essentially that shown in Fig. 1 except that
chipper 16 is
substituted with hammer mill 52 and a pellet mill extruder 54 inserted between
screw
conditioner 26 and torrefaction tank 28.
In operation, hammer mill 52 reduces the wood biomass material to less than
6mm in
diameter; and extruder 54 produces pellets of about 6mm to 10mm in diameter.
The process described in Fig. 2 provides the torrefaction of chipped biomass
before
pelletization to enable the removal of the traditional drying procedure
currently being used to
dry biomass so that pellets may be extruded.
RESULTS
EXAMPLE 1
Table 1 gives the results for two oil torrefied wood chips referred to as
Light and
Dark.
LIGHT
Prepared by torrefying pine wood pellets in canola oil at NOT for 6 minutes.
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DARK
Prepared by torrefying pine wood pellets in soybean oil at 280 C for 6
minutes.
TABLE 1
Light Dark
Sample ID (Log-in #7441/1 (Log-in #7442/2)
Moisture Content(Wet Basis)% 3.51 0.72
Moisture Content(Dry Basis)% 3.64 0.73
Ash% 0.18 0.18
Higher Heating Value BTU/lb bone dry 11783 12337
Higher Heating Value BTU/lb at MC received 11369 12247
Procedures:
Moisture Content - ASTM E871-82
Ash Content - ASTM D1102-84
Heating Value - ASTM E711-87
EXAMPLE 2
In additional experiments, the following tests were performed and the results
presented.
The first test was heating canola oil to 200 C and putting pine wood pellets
in the oil
to expel moisture. The moisture level went from 7.01% down to 1.4% after 4
minutes in
submersion. The pellets were removed and tested for BTU value.
The second test was heating canola oil to 280 C and placing the wood pellets
that had
been previously exposed to the 200 C oil into the higher temperature oil. The
pellets were
submerged for an additional 4 minutes. The moisture level was checked and a
level reduction
from 1.4% to a new low level of 1.2% was experienced. The BTU level was
checked and has
increased from 8098 btu/pound (original at 7.01%) to a level of 9299
btu/pound.
The second set of tests were completed using the same procedure as above,
however,
wherein wood pellets made of a 80%hardwood and 20% pine mixture were used.
The control pellets received were 7.04% moisture with a btu level of 8167
btu/pound. After
the process a moisture value of 1.63% and a 9591 btu/pound level was achieved.
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During the experiment the pellets were observed to first turn light brown in
color at
the 200 C heat level then dark brown to black as they were torrefaction was
experienced
during the 280 C to 320 C heat level.
Both types of pellets were observed to maintain the same physical
characteristics for
hardness and durability after the torrefaction process. It was observed during
the cooling
process the residual oil on the pellets was absorbed by the pellet and a
miniscule film of oil
was left present.
When the pellets were broken apart it was noted that the material had been
torrefied
throughout the strata of the pellet.
A test to determine if the torrefied pellets would re-absorb the moisture lost
was
effected by submersion in water. After a lengthy period of time of submersion
the pellets
were observed and noted that they did not reabsorb moisture where normal
pellets re-absorb
and crumble in minutes.
EXAMPLE 3
Test Method
An analysis was conducted on burn rate and energy content of vegetable oil -
heat
treated wood pellets. The main purpose of this analysis was to determine how
much longer
the heat treated pellets burned compared to untreated conventional wood
pellets. Also
included in this analysis was a visual comparison of the residue left behind
after burning heat
treated and unheat-treated wood pellets. Two different heat treated samples of
wood pellets
and two samples of untreated pellets from the same bags were used for heat
treatment.
An additional object was to determine the heat value (Btu/1b) of the heat
treated
pellets according to standard test method ASTM E711-87 and the moisture
content according
to standard test method ASTM E871-82.
Two groups of oil torrefied pellets were analyzed. The first group of pellets
consisted
entirely of softwood, while the second group, called mixed wood, was made up
of 80 percent
hardwood and 20 percent softwood. To make a valid comparison, the two groups
were
compared to untreated pellets of the same type.
A pellet stove, Enviro EFIIIi BayTM, was provided with thermal couple
temperature
sensors to monitor temperatures at the following locations, (1) air into heat
exchanger (stove
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supply air), (2) out of heat exchanger (room heat), (3) combustion air (air to
firebox) and (4)
combustion exhaust to stack.
The first step was to run some pellets through the stove to warm it up. Next,
the feed
rate was set at a constant rate and a 0.50 kg sample of untreated softwood
pellets was passed
through the stove and the difference between the average temperature out of
the stove heat
exchanger and the average temperature of the stove supply air was calculated.
Also noted was
the run time to bum the 0.50 kg sample. Next, a 0.50 kg sample of heat treated
softwood
pellets was burned and the run time noted. In this case, the feed rate was
adjusted to maintain
the same temperature differential as was noted for the first run. By using
this approach, a
direct comparison of the burn times between the heat treated and untreated
wood pellets can
be made since the sample mass and temperature differential were held constant.
The same method was followed for the mixed wood group as is described above
for
the softwood group.
Results
Table 1 summarizes the results comparing the burn times of the heat treated
versus the
untreated wood pellets for both the softwood and mixed wood groups.
Table 1 - Results summary of wood pellet burn test (sample size = 0.50 kg)
Pellet type Run time, min Temp, 4C ~l I
Softwood, untreated 46 43
Softwood, heat treated 60 42
Mixed wood, untreated 54.5 40
Mixed wood, heat treated 65 40
Temperature differential between the average temperature out of the stove heat
exchanger
and the average temperature of the stove supply air.
Based on the results given above, the heat treated softwood pellets burned 30
percent
longer than the untreated softwood control. The heat treated mixed wood
pellets burned 19
percent longer than the untreated mixed wood control. It is noted that the
temperature
differential of the heat treated softwood group was one degree cooler than the
control, which
would result in a slight increase in the burn time.
Visual assessment of the residue after burning revealed no apparent difference
between the heat treated and untreated pellets for both the softwood and mixed
wood groups.
The results from the heat value tests are given in Table 2 for all four groups
of pellets
tested.
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Table 2 - Heat value (Btu/]b) test results
Pellet type As received moisture Higher Heating Value, BTU/lb
content (MC), % 111 Oven dry [2' @ as received MC
Softwood, untreated 7.01 8,665 8,098
Softwood, heat treated 1.70 9.455 9,299
Mixed wood, untreated 7.04 8,742 8,167
Mixed wood, heat treated 1.63 9,750 9,591
[1] Moisture content calculated on an oven-dry basis.
121 Higher heating value test conducted on oven dried material. Higher heating
value @ as
received moisture content calculated from oven dry and as received moisture
content result.
Based on these results the oven dry heating value of the heat treated softwood
pellets
was 9 percent higher than the untreated softwood pellets. The oven dry heating
value of the
heat treated mixed wood pellets was 11.5 percent greater than the untreated
mixed wood
pellets. The as received moisture content of the heat treated pellets was over
four times lower
than that of the untreated control for both softwood and mixed wood groups.
The energy
needed to dissipate the moisture in the pellets is accounted for in the `@ as
received MC'
heating values. The heating value `@ as received MC' of the heat treated
softwood pellets
was 15 percent greater than the untreated softwood pellets. The heating value
`@ as received
MC' of the heat treated mixed wood pellets was 17 percent greater than the
untreated mixed
wood pellets.
Conclusion
The following conclusions are based on the findings from this analysis which
consider
the results from one set of tests, as follows:
= The heat treated softwood pellets and mixed wood pellets burned at least 19
percent
longer than the untreated wood pellets they were made from.
= Based on a visual assessment, there was no apparent difference in the amount
of
residue after burning between the heat treated and untreated pellets for both
the
softwood and mixed groups.
= The `as received' moisture content of the heat treated softwood and mixed
wood
pellets was 4.1 and 4.3 times lower than that of the untreated softwood and
mixed
wood control groups, respectively.
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= The higher heating value (@ as received moisture content) of the heat
treated
softwood pellets was 15 percent greater than the heat value of the untreated
softwood
pellets.
= The higher heating value (@ as received moisture content) of the heat
treated mixed
wood pellets was 17 percent greater than the heat value of the untreated mixed
wood
pellets.
EXAMPLE 4
Pine wood chips treated in canola oil at 320 C produced total torrefaction
within 1
minute.
Although this disclosure has described and illustrated certain preferred
embodiments
of the invention, it is to be understood that the invention is not restricted
to those particular
embodiments. Rather, the invention includes all embodiments which are
functional or
mechanical equivalence of the specific embodiments and features that have been
described
and illustrated.
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