CA2686099A1

CA2686099A1 - Oil impregnated particulate biomass, methods of manufacture and use thereof

Info

Publication number: CA2686099A1
Application number: CA2686099A
Authority: CA
Inventors: Mark A. Lowe
Original assignee: Mark A. Lowe; Southern Biomass, Llc
Current assignee: SOUTHERN BIOMASS LLC
Priority date: 2009-10-05
Filing date: 2009-11-19
Publication date: 2011-04-05
Also published as: WO2011041880A1; WO2011041881A1

Abstract

A method for the production of a torrefied biomass product from a particulate biomass material, comprising treating the biomass material with a bio-liquid selected from an animal fat and plant oil at an effective temperature to provide the torrefied product. The bio-oil is selected from plant oil and animal fat, preferably, vegetable oil, such as, canola or soybean oil. The biomass material is, preferably, a hardwood, softwood or wood bark.

Description

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.
I

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 (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.

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 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

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.

DARK
Prepared by torrefying pine wood pellets in soybean oil at 280 C for 6 minutes.

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 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.

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.

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 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.

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.

= 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.

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.

Claims

1. 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.

2. 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 to produce torrefied wood for an effective period of time to effect torrefaction;
(iii) removing said torrefied wood from excess said bio-liquid; and (iv) collecting said torrefied wood product.

3. A method as claimed in claim 2 wherein said mechanical means comprises a chipper to produce particulate wood having dimensions of about 6mm to 2cm.

4. A method as claimed in claim 2 wherein said mechanical means comprises a mill to produce milled particulate wood;
further comprising (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 of about 6mm to 2cm: and effecting steps (ii), (iii) and (iv) as defined in claim 1 wherein said pellets constitute said particulate wood.

5. A method as claimed in any one of claims 1 to 4 wherein said bio-liquid is a vegetable oil

6. A method as claimed in any one of claims 1 to 5 wherein said temperature is greater than 200°C.

7. A method as claimed in claim 6 wherein said temperature is selected from 240°C-375°C.

8. A method as claimed in any one of claims 1, 5, 6 or 7 wherein said biomass material is selected from wood material, cellulosic agricultural material, peat moss and industrial sludge.

9. A method as claimed in claim 8 wherein said wood material is in the form of chips, pellets or bark.

10. A method as claimed in any one of claims 1 to 9 wherein said bio-liquid is selected from canola or soybean oil.

11. A method as claimed in any one of claims 1 to 10 wherein said torrefied biomass product has a vegetable oil content of at least 1% w/w.

12. A method as claimed in claim 8 wherein said torrefied biomass product has a vegetable oil content selected from 4-12% w/w.

13. A torrefied particulate biomass material made according to any one of claims 1 to 12.

14. A torrefied particulate biomass material comprising at least 1% w/w bio-liquid.

15. A torrefied particulate biomass material comprising at least 1% w/w vegetable oil.

16. A torrefied particulate biomass material comprising at least 4-12% w/w vegetable oil.

17. A torrefied particulate biomass material as claimed in any one of claims 13 to 16 wherein said vegetable oil is selected from canola and soybean oil.

18. A process for producing heat energy comprising burning a torrefied particulate material as claimed in any one of claims 13 to 17.

19. A process as claimed in claim 18 wherein said torrefied particulate material is admixed with particulate coal.

20. Use of a torrefied particulate biomass material as claimed in any one of claims 13 to 17 as a soil modifier.