NL2007206C2

NL2007206C2 - Use of torrefaction condensate.

Info

Publication number: NL2007206C2
Application number: NL2007206A
Authority: NL
Inventors: Robin Willem Rudolf Zwart; Jan Remmert Pels
Original assignee: Stichting Energie
Priority date: 2011-08-01
Filing date: 2011-08-01
Publication date: 2013-02-04

Description

Use of torrefaction condensate

Field of the invention

[0001] The invention is in the field of torrefaction of biomass. The invention is also 5 in the field of producing renewable solid fuels.

Background of the invention

[0002] Torrefaction is a technique for producing valuable materials such a fuel, from wood or biomass waste such as plant residues from agriculture or sylviculture. Torrefaction is a thermal treatment at moderate temperatures in the substantial absence 10 of oxygen. Torrefaction is distinguished from pyrolysis by the temperatures used: while pyrolysis employs temperatures of 300-700°C, in particular 400-500°C, the temperatures used in torrefaction are between 200 and 350°C.

[0003] A method for torrefaction of biomass, wherein the biomass is first dried in a co-current mode and is then torrefied in counter-current operation, is described in WO

15 2007/078199.

[0004] US 2010/083530 discloses a torrefaction process wherein wet cellulose material is cascaded down a torrefaction reactor to produce steam and volatiles, in addition to a dried solid. The volatiles can be used for their caloric value.

[0005] Torrefied fuel is densified for several reasons. Primarily, it improves 20 logistics (transport and storage), but it also leads to efficient feeding in combustion and gasification installations. Densification is done by mechanical compression, e.g. pelleting, briquetting and tabletting. In densification, binder may be added to improve the cohesion of the material and the resistance against wear or breakage. The binder also acts as a lubricant in the compression, lowering energy consumption of the machine and 25 diminishing porosity, thus increasing density.

[0006] The use of torrefied biomass as a substitute for fossil fuels, such as coal, is hampered by the fact that the currently used binders are environmentally undesired or result in products that have low strength and cannot easily be processed to pellets and briquettes.

30 Summary of the invention

[0007] It was found according to the invention, that the volatile organic fraction of a biomass torrefaction, after condensation, is excellently suitable for binding and/or 2 coating solid biomass and other carbonaceous material, resulting in high caloric and wear and water resistant, shippable solid fuel.

[0008] Hence, the invention pertains to the use of a biomass torrefaction condensate (BTC) as a binding agent or coating agent for solid material. The invention 5 furthermore pertains to a process for producing a wear- and water-resistant solid fuel, comprising combining a solid carbonaceous material with a BTC obtained by condensation of organic material volatilised during torrefaction of biomass. In one embodiment, the solid material is biomass-derived, such as torrefied biomass.

[0009] The invention in particular concerns a process for upgrading biomass 10 comprising: a. subjecting the biomass to torrefaction, to produce a torrefied solid fraction and a volatised fraction; b. cooling the volatised fraction to produce an organic condensate; c. combining the condensate with a torrefied solid fraction; 15 d. densifying the torrefied solid fraction of step (a) or step (c).

[0010] Furthermore, the invention pertains to the mass-derived solid fuel obtainable by these processes.

Description of the invention

[0011] The invention concerns the use of a biomass torrefaction condensate as a 20 binding agent or coating agent for solid biomass-derived material. The term “biomass torrefaction condensate” (BTC) is used herein to denote a condensate which can be obtained by conducting a part of the exhaust gas of a biomass torrefaction process, as further described below, containing organic volatiles and water, through a condenser and collecting organic condensate, and optionally water.

25 [0012] Alternatively, although somewhat less preferred, the BTC can also be used as a binder for other materials such as fly ash, char and/or charcoal, although not limited thereto. Such materials can be used as an acceptable alternative or additive to biomass. [0013] It is preferred that the BTC has a condensation temperature which is between 100°C above and 50°C below the condensation temperature of water, 30 preferably between 90°C above and 20°C below the condensation temperature of water, more preferably between 80°C above and 10°C below the condensation temperature of water, most preferably between 60°C above and the condensation temperature of water. The condensation temperature applies to any pressure, but for comparative reason, the 3 pressure may be converted to ambient pressure. More precisely, reference can be made to the dew point of water at the specific process conditions, but the condensation (or boiling) point can be used in practice. In other words, when cooling the torrefaction exhaust gas, the temperatures and pressure are selected in such a manner that, 5 depending on the content of water and organic molecules in the gas, most of the organic material is condensed, while most, but not necessarily all water remains in the vapour phase.

[0014] The BTC may comprise up to 80 wt% water, but preferably less, e.g. below 50 wt.%. The water content may vary depending on the condensation temperature of the 10 BTC. Where necessary to lower the water content of the agent, the BTC temperature may be between 0°C and 100°C above the condensation of water, in particular between 5°C and 80°C above the condensation of water. Alternatively, further cooling and separation of water may be used. On the other hand, where the water content is too low, water may be added before using the condensate as a binding or coating agent. The 15 amount of water can e.g. be 0.25-2.5 times the amount of (dry) condensate, preferably 0.4-1 times the amount of (dry) condensate. Water may also be added separately, directly to the densification process, for example directly into the pelletisation apparatus. Water may be added as liquid or as vapour.

[0015] If necessary, the BTC binding or coating agent may contain further 20 additives, which enhance the processability or homogeneity of the agent. Such further additives may include organic solvents, such as alcohols (e.g. ethanol, butanol), glycols (ethylene glycol propylene glycol), or higher polyols such as glycerol. However, the use of such further additives is not always necessary, and if used, their level is preferably below 50 wt.% based on the total weight of the agent, in particular between 0 and 20 25 wt.% thereof. Also if used, such additives may preferably be low-grade, i.e. contain water or further organic components, preferably excluding heteroatoms such as sulphur, halogens, metals etc.

[0016] When used as a binding or coating agent, the BTC is advantageously used in a weight ratio of below 1:3 (= <25%), especially between 1:99 and 1:4 (1-20%). When 30 used as a binding agent, it is preferably used at between 1:49 and 1:7 (2-12.5%), more preferably 1:24 to 1:9 (4-10%) to the solid material. When used as a coating agent, the ratio is preferably between 1:24 and 1:4, while ratios between 1:19 and 1:7 are preferred.

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[0017] Any solid or solid-like biomass or other (semi) solid carbonaceous material as defined below, having insufficient resistance to dusting or rupture or having insufficient wear- and/or water resistance, may be treated with the BTC as a binding or coating agent. Examples include wood dust, wood chips, as such or in compressed form, 5 agricultural waste etc. The biomass may be treated as such. Particularly useful is a solid biomass-derived material which is thermally pre-treated so as to increase its value as a biomass-derived fuel, most in particular by torrefaction of the biomass. As a result of the thermal pre-treatment, the biomass has lost part or most of the effectiveness of its natural binding agents, such as lignin and/or resin. In this way two components from the 10 same process are efficiently used, i.e. the torrefied solid mass as the basic biomass material and the condensed volatise (BTC) as the binder or coating agent. Besides torrefied biomass, other carbonaceous material with insufficient intrinsic binding agents, such as fly ash, char or charcoal, can also be advantageously treated according to the invention.

15 [0018] The term “biomass” as used herein denotes organic material derived from plant in any form, in particular wood, straw and other plant residues and the like. For the purpose of this invention, biomass also encompasses peat, manure, recycled wood, as well as algae and see weeds. A “carbonaceous material is any material which contains substantial amounts, specifically at least 10 wt.%, in particular at least 25 20 wt.%, of carbon, wherein fully oxidised carbon (i.e. in carbon dioxide or carbonate form) is excluded. In particular, carbonaceous material encompasses biomass and fossil carbon-containing materials such as coal, oil residues and other non or incompletely combusted (solid) combustibles.

[0019] Also for the torrefied material, this may originate from any type of biomass 25 as described above. Particularly useful is a biomass which consists partly or largely, say at least 50 wt% (dry weight basis), of wood, herbaceous plants or combinations thereof. Preferably at least 70 wt% consists of wood and or herbaceous plants, most preferably at least 50 wt% of wood. The wood may be hard wood (deciduous) or soft wood (coniferous) or any mixture thereof. Fast growing wood types such as poplar or willow 30 will be particularly efficient on a large scale. Any remaining part of the biomass may originate from straw or other agricultural or sylvicultural waste, or other organic waste having acceptable levels of hazardous contaminants such as halogen compounds, and the like. Non-biomass, i.e. fossil derived organic material may be admixed, but preferably at minor levels, e.g. below 25 wt.% only.

5

[0020] In another aspect, the invention concerns a process for producing a wear-and water-resistant solid biomass-derived fuel, comprising combining a solid biomass-derived material with a BTC as described above. The content of BTC may be between 1 and 25 wt.%, based on the weight of the final product.

5 [0021] When the BTC is used as a binder, it can be mixed with the solid biomass in the described ratios. The precise ratio can be determined by the skilled person as a function of the further processing steps and the ultimate use of the solid material. Likewise, the precise water level can be adjusted so as to achieve optimum results. Mixing can be done separately, in a distinct mixing equipment, or it can be part of the 10 further densification steps, such as pelleting, briquetting or tabletting.

[0022] The invention applies to torrefied or heat-treated biomass that undergoes densification. In particular it is of use in pelletisation and briquetting as described below. The invention may also be applied to tabletting or any other form of densification. Pelletisation can be carried out in conventional pelletising equipment such 15 as used for producing wood pellets from chips or animal feed pellets. The binding agent may be directly fed into the pelletiser or prior to entering the pelletiser. In a particular embodiment, the BTC is produced in situ, i.e. the gas flow, or part of it, containing the organic volatiles of the torrefaction process, is brought in contact with the solid (torrefied) biomass at relatively low temperatures, resulting in condensation of the 20 organic volatiles onto the solid biomass. Thus, in a preferred process according to the invention, the organic material volatilised during torrefaction of biomass is directly condensed onto the solid biomass-derived material. The temperature of the torrefied biomass being subjected to the stream of organic volatiles is chosen as described above for the condensation temperature of the BTC, and can be varied depending in the 25 desired amount of water condensation onto the torrefied biomass. Thus, the biomass which is subjected to the stream organic volatiles is between 100°C above and 50°C below the condensation temperature of water, especially between 90°C above and 20°C below, preferably between 80°C above and 10°C below the condensation temperature of water, most preferably between 60°C above and the condensation temperature of water. 30 [0023] Briquetting is another form of densification to be used according to the invention. For briquetting, material is enclosed in a space and subsequently force is applied from one direction. Briquettes are larger than pellets, typically more than 20 mm in diameter. The energy needed to make them is much lower than for pelleting.

6

Typically, briquetting is done cold or with heat applied from outside, while in pelleting the material is heated up substantially as a result of the friction in the die. At least three forms of briquetting can be distinguished: i) between two rolls with hemispherical spaces, ii) by compressing in a cycle where the previous briquette is immovably 5 clamped at the exit acting as a temporary fixed wall; iii) extrusion of a single strand, similar to pelleting but with a much larger diameter; the strand is cut into briquettes. In the latter two forms, the force can be generated hydraulically, from a fly wheel with an eccentrically mounted piston or a feeder screw. The way BTC is used in briquetting is analogous to its use in pelletisation (see above).

10 [0024] When the BTC is used as a coating agent, it is applied onto the solid biomass material after densification using conventional coating technique such as spraycoating, dip-coating etc. The precise amounts of coating agent are determined on the basis of routine adjustment depending on the shape and further characteristics of the final material.

15 [0025] The invention further encompasses a process for upgrading biomass comprising: a. subjecting the biomass to torrefaction, to produce a torrefied solid fraction and a volatised fraction; b. cooling the volatised fraction to produce an organic condensate; 20 c. combining the condensate with torrefied solid fraction; d. densifying the torrefied solid fraction, either after, before or during combining with the condensate in step (c); when the condensate is used as a binder for the torrefied solid fraction, combining (i.e. mixing) takes place before or during densification, and when the condensate is used as a coating agent for the 25 torrefied solid fraction, combining (i.e. coating) takes place after densification.

[0026] The torrefaction is performed at a temperature of between 200 and 350°C, preferably between 240 and 320°C. Upon combining both fractions in step (c) the weight ratio between said organic condensate and said torrefied solid fraction is preferably between 1:4 and 1:49.

30 [0027] In an advantageous embodiment, no more than 10 wt.%, of other additives than an organic torrefaction condensate is used on the basis of the dry weight of the torrefied mass fraction, preferably less than 5 wt.%. Such less desired additives include starch and other materials that would have to be abstracted from potential food supplies, and fossil-derived polymers and derivatives. If used, they are used at a level of no more 7 than 50 wt.% of the BTC. An acceptable further additive, which may be used up to e.g. 20% of the dry weight of the torrefied mass, or up to 50wt.% of the BTC, may be lignin obtained from wood in another way than as a torrefaction condensate.

[0028] The invention also pertains to a torrefied biomass-derived material, suitable 5 as a fuel, obtainable by the process as described herein. Such a biomass-derived fuel can be defined by one or more of the following characteristics: i. an outer particle size of between 2 mm and 10 cm as smallest diameter; ii. a bulk density of between 0.35 and 1.0 kg/dm3, preferably between 0.65 and 0.9 kg/dm3; 10 iii. a specific density between 0.8 and 1.5 kg/dm3, preferably between 1.1 and 1.4 kg/dm3; iv. a calorific value on dry and ash-free basis of between 15 and 28 MJ/kg especially a higher heat value (HHV, taking into account the vapour energy of water) of between 18 and 28 MJ/kg, preferably between 21 and 25, and/or a 15 lower heat value (LHV) between 18 and 23 MJ/kg; v. a moisture content of less than 5 wt.%, also after storage at ambient conditions for at least 1 month; vi. a carbon content derived from biomass of at least 75%, which can for example be determined by its 14C content of at least 5.1013 (0.5 ppt) on carbon basis; 20 vii. a grindability which is comparable to the grindability of coal, corresponding to a power consumption below 0.5 MJ/ton on a 0.25 mm mesh, and preferably above 0.05 MJ/ton (0.25 mm); viii. stability to ambient (outdoor) conditions for at least 1 month.

[0029] For the stability test, analyses are typically performed by exposing a 1 kg- 25 sized sample to a set humidity level (working range 0-95 %, typically in the range of 70-95 % relative humidity) at a desired temperature (range -40 to +80 °C, typically 5-25 °C) over a desired period of time (typically 7 days, though which can be extended to 1 month) in a climate chamber sufficiently large to accommodate several specimens. Samples are drawn after specific time intervals during the period of exposure. The 30 moisture uptake investigations are aided by standard moisture analyses. A visual observation of mold formation or other signs of biologic degradation (discoloration, effluent or gas formation) is also done to check stability. Another rapid test for sufficient stability consist in submerging particles (e.g. pellets) in water of ambient temperature for at least 24 h, in particular 1 week; if the particles can be taken from the 8 water without noticeable softening or other visible change, the stability is rated to be sufficient.

[0030] A solid fuel produced according to this invention may be made from torrefied biomass and BTC, with less than 5 wt% of other additives present, preferably 5 less than 2 wt%, in particular less than 0.5 wt%. In this embodiment, the biomass and the binder, and optionally even a part of the water or the entire water fraction, which are used in the densification process, all originate from the biomass which was fed to the torrefaction reaction, and thus less waste is produced. Hence, solid fuels produced according to the invention and a densification process according to the invention are 10 more energy and waste efficient then prior art pellets and processes.

[0031] BTC has improved properties as a binder compared to pyrolysis oil. In general, pyrolysis oil is more acidic than BTC, contains more water and it also does not harden when cooled or tempered. Pyrolysis is performed at higher temperatures than torrefaction, and the condensate of the pyrolysis gas (pyrolysis oil) comprises smaller 15 molecules, i.e. the lignin and hemicelluloses components of the biomass are degraded into smaller molecules, because of the high pyrolysis temperature. This degradation into smaller molecules comprises hydrolysis or decomposition of lignin and hemicelluloses derivatives, thereby producing phenolic and carboxylic acid moieties and molecules. These moieties render pyrolysis oil more acidic than BTC, and enable more hydrogen 20 bridges to be formed with water, which results in a higher water content of pyrolysis oil compared to BTC. Using BTC as a binder, pelletising is possible at typical temperatures in a pellet mill, around 140°C, retaining its binding characteristics, which results in hard pellets. Furthermore, in case of pyrolysis oil, the higher acidity causes gas formation during pelletisation at elevated temperatures, which induces foaming of the pellet.

25 Pellets resulting from biomass pelletisation with pyrolysis oil as binder are of low quality, i.e. have a lower hardness and are less wear and water resistant then pellets obtained with BTC as binder.

[0032] Torrefaction at elevated temperatures, such as above 240°C, preferably above 260°C, causes more lignin to break down into smaller molecules, which 30 evaporate into the gas phase. The resulting torrefied biomass has a higher calorific value and a higher carbon content than biomass torrefied at lower temperatures, due to this heat treatment. This biomass resembles charcoal more than low-temperature torrefied biomass. However, densifying torrefied biomass obtained by torrefaction at elevated temperature used to be more problematic, as a result of the lower effectiveness of the 9 lignine residues remaining in the torrefied biomass acting as a binder. Hence, after torrefaction at elevated temperatures addition of more binder is needed for easy densification, resulting in more additives in the final pellet. Addition of BTC as a binder solves this problem, as BTC originates from the same biomass as the torrefied biomass, 5 which is now low in lignin residues. Hence, no other additives are needed for processing, including pelletising or briquetting of the torrefied biomass, resulting in a solid fuel with a very low, if any, content of material which does not originate from the biomass that was fed to the torrefaction chamber.

[0033] The pellet or briquette according to the invention preferably comprises at 10 most 5 wt% other additives, preferably at most 2 wt% in particular at most 0.5 wt%.

Herein, other additives that are not present in the solid fuel or in very small amounts comprise materials that are potentially suitable as food components such as starch, fossil derived components, but also although with less drawbacks, minerals such as cement, clay, etc.. In a most preferred embodiment, the solid fuel contains at least 99.5 wt% 15 material that originates from biomass, in particular form a biomass torrefaction process.

[0034] The torrefaction process can be carried out as described in more detail below. The biomass fed to the torrefying device may be relatively wet in untreated state. The material generally contains free and bound water. The bound or loosely bound water is absorbed by the natural raw material itself. For example, biomass of plant 20 origin, such as prunings and mown grass, contains a considerable amount of moisture by nature. The organic material may for instance have a moisture content of 5-15%, i.e. an amount of residual moisture is contained in the material.

[0035] The organic material with the residual moisture is introduced into the torrefaction reactor. The material is heated in the substantial absence of oxygen, usually 25 though not necessarily under atmospheric pressure, to a temperature of 200-350 °C, preferably 240-320 °C, for example 260-300 °C. The lack of oxygen prevents the material from burning. Instead the material is torrefied, which leads to loss of mass because of the elimination of gases. This loss of mass generally amounts to about 10-50%, typically around 30%, while the energy value is only reduced by 5-20%, typically 30 10%.

[0036] The phrase “in the substantial absence of oxygen” especially indicates that the amount of oxygen is below explosion values. As will be clear to a person skilled in the art, this may depend upon temperature and pressure. Especially, the amount of 10 oxygen in the gas phase is kept below 5 vol. %, such as below 2 vol.%, in particular less than 0.5 vol. %.

[0037] In general, the torrefying chamber is flushed with a gas substantially free of oxygen, such as a CO2, N2 steam and/or recirculated process gasses. Preferably, the 5 water content of the organic material provides the majority of the process gas, so that supply of additional process can be avoided. The torrefying chamber, but also the gas transport structure may be kept at a pressure in the range of -0.5 to +20 bar, especially -0 to +5 bar respective to atmospheric pressure, and in general at a pressure near atmospheric pressure.

10 [0038] Torrefaction also causes changes to the chemical structure of the material.

The material loses its mechanical strength and elasticity, so it is much easier to grind. Furthermore, torrefied material is hydrophobic, and it therefore stays dry and is insensitive to atmospheric humidity. The risk of rotting and overheating is very small when the material which has been produced by torrefaction is stored.

15 [0039] The temperature of the material is raised in the torrefaction reactor. Before torrefaction of the material can take place, the residual moisture, however, evaporates from the material. The material may be virtually completely dried, for instance in a drying chamber of the torrefaction reactor by evaporating the residual moisture. The actual torrefaction of the material may only take place after the residual moisture has 20 been evaporated. Torrefaction may begin as soon as the temperature of the material exceeds about 200 °C.

[0040] The torrefying chamber allows transport of the organic material through the torrefying chamber (in a “first direction” or “transport direction”). The organic material may be transported under influence of gravity and/or may be transported by using a feed 25 device, such as a screw. The torrefying chamber will thus have an entrance part, where the (dried) organic material enters the reactor and an exit part, where the (torrefied) organic material leaves the reactor. Herein the torrefying chamber at least may comprise an inlet for a gas, and an outlet for a gas (i.e. the gas from the torrefying chamber).

[0041] The gas transport structure may comprise a cooling chamber and a heating 30 chamber, wherein the cooling chamber is downstream from the torrefying chamber gas outlet, the heating chamber is downstream from the cooling chamber and upstream of the torrefying chamber gas inlet. In this way, recycling may be performed of the gas in the torrefying chamber. The cooling chamber is configured to cool torrefying chamber gas that has been removed from the torrefying chamber via the torrefying chamber gas 11 outlet and has been transported through the gas transport structure to the cooling chamber. The heating chamber is configured to heat the gas that has been cooled in the cooling chamber and that has been transported via a gas transport device (such as a pump, a blower, a fan, a compressor, etc.) to the heating chamber. Especially, the 5 heating chamber is configured to heat the gas to a temperature substantially equal to the chosen torrefying chamber gas inlet temperature. In an embodiment, the gas transport structure may comprise a further heater, for instance arranged downstream of the heating chamber (but upstream of the torrefying chamber gas inlet. The heating chamber and optional further heaters are configured to heat the gas to a temperature 10 substantially equal to the chosen torrefying chamber gas inlet temperature. Hence, gas retrieved from the torrefying chamber is transported through the gas transport structure, and thereby flows through the cooling chamber and heating chamber, respectively, back to the torrefying chamber. The cooling chamber and the heating chamber may be separate chambers with different outlets, but may in an embodiment also be two zones 15 of a single device with different as well as equal outlets. In an embodiment, thermal energy released by the cooling chamber is used to heat the heating chamber.

[0042] The gas emerging from the gas outlet is cooled to allow condensables to be condensed from the gas, for example in the cooling chamber, to produce the biomass torrefaction condensate (BTC). When a gas recycle system is applied, the remaining gas 20 thus obtained from the cooling chamber is then heated again in the heating chamber (and by one or more optional downstream heaters) to reach a temperature suitable for introduction into the torrefying chamber. Herein, cooling may comprise cooling to a cooling temperature in the range of higher than about 50°C below the dew point of water and lower than the torrefying temperature in the torrefying chamber. In general, 25 the cooling temperature will be around or above the condensation temperature of water, and preferably below about 200 °C. For instance, the cooling temperature may be selected from the range of 90-180 °C, such as about 110-140 °C; this may especially apply at atmospheric conditions. At pressurised conditions, the selected temperature may be correspondingly higher. Alternatively, but less preferred, the cooling may 30 comprise cooling to a cooling temperature in the range of about 20°C below the boiling point of water and lower than the torrefying temperature in the torrefying chamber. In general, the cooling temperature will be around or above the boiling point of water, and preferably below about 200 °C.

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[0043] The gas from which the condensables (including water and BTC) have been separated by cooling, can be reheated and returned to the torrifier. Prior to heating the gas, an additional cooling step may be performed to remove water that has not condensed in the BTC, for example using a heat exchanger. The need for such a step 5 depends on the condensation temperature of the BTC and the remaining water vapour content of the gas after the first cooling step. This will be appreciated by the man skilled in the art. The cooling chamber, the heating chamber and the optional heat exchanger are preferably equipped with a system that facilitates removal of condensables from them, such as the removal of BTC. These condensables are preferably transported to a 10 single opening, the cooling chamber opening, from which the condensables are collected. Alternatively, the heating chamber may have a separate opening for the removal of condensables.

[0044] The heat exchanger may be configured to facilitate transport of liquid material to the cooling chamber opening. For instance, the heat exchanger may 15 comprise substantially vertically cooling elements. Alternatively or in addition, the cooling chamber is configured to facilitate transport of liquid material to the cooling chamber opening. For instance, the cooling chamber may have smooth walls, and the walls may be arranged to facilitate transport to the cooling chamber opening. For instance, at least part of the cooling chamber may have the shape of a funnel, with 20 preferably the cooling chamber opening at the bottom of the funnel.

[0045] The torrefying device may further comprise a receiver, arranged to receive liquid from the cooling chamber and optionally arranged to receive liquid from the heating chamber. This receiver is preferably designed to receive the BTC, which is condensed from the gas issuing form the torrefaction process (= “torgas”). The receiver 25 may act as a gas liquid separating device separating liquid droplets and/or aerosols from the gas stream. The receiver may further be connected with a storage vessel. The torrefying device may further comprise a temperature regulator, configured to control the temperature of the receiver. In this way, this may allow maintaining the receiver at a temperature of at least 30 °C and below a temperature at which the BTC might be 30 unstable by for example evaporation. For instance, this may imply in an embodiment maintaining the receiver at a temperature between 30 °C and the condensation temperature of the BTC, in particular between 30 °C and 100 °C.

[0046] As will be clear to a person skilled in the art, the entire gas transport may be heated to the (locally) desired temperature. For instance, up to the cooling chamber (i.e.

13 upstream of the cooling chamber), the gas transport structure may be kept at a temperature of over 200 °C, such as about 230 °C. Likewise, the gas transport downstream of the heating chamber may be kept at a temperature of over 200 °C, such as 240-320 °C (preferably at about the same temperature as the chosen torrefying 5 chamber gas inlet temperature).

[0047] Optionally, the torrefying device is configured to allow transport of organic material in a first direction (transport direction) and the torrefying chamber gas inlet and the torrefying chamber gas outlet are arranged to facilitate a counter-current flow of the torrefying chamber gas. The gas transport device (such as a pump, a blower, a fan, a 10 compressor, etc.) facilitates the counter-current flow of the gas in the torrefying chamber. An advantage of the counter-current flow may be a good control of the torrefying temperature. The torrefying device may comprise a feed device configured to transport the organic material through a torrefying reactor. The feed device may comprise two pistons and a supporting valve. The first piston can move through an inlet 15 to push in organic material for the second piston, which can move up and down within the torrefying chamber. The supporting valve can move between a supporting position and a free position. When the piston has reached the end of its stroke, the supporting valve moves over to the supporting position to support the organic material within the torrefying chamber. The second piston can then move downwards, after which the first 20 piston can again load a quantity of organic material on it. However, the feed device can also be designed as a conveyer screw. The design of the feed device may depend on the orientation of the torrefying chamber, which can be essentially vertical, horizontal or inclined at an angle between the two.

[0048] The reactor may in an embodiment be a moving bed reactor. In such 25 embodiment, the organic material should preferably comprise solid particles that are passed through the torrefying chamber in the form of a packed moving bed. In this case the torrefying device is operated on the principle of moving-bed technology.

[0049] The thermal treatment of organic material may comprise: a. torrefying the organic material in a torrefying chamber of a torrefying device; 30 b. removing torrefying chamber gas from the torrefying chamber, separating the condensable volatiles from the removed torrefying chamber gas, and optionally subsequently reintroducing part or all of the torrefying chamber gas into the torrefying chamber, wherein the separation may comprise a cooling and a subsequent heating; 14 c. maintaining a, preferably counter-current, flow of the torrefying chamber gas, relative to a flow of the organic material through the torrefying chamber.

[0050] The separation of the condensable volatiles is preferably performed by cooling to produce an organic liquid, also containing variable amounts of water. The 5 organic liquid is further used according to the invention is described above. As indicated above, the process may further comprise receiving liquid material from the cooling chamber and optionally from the heating chamber in a receiver.

[0051] According to the invention, the condensate (BTC), mainly originating from the lignin fraction in the biomass, is used as a binder in the production of biomass- 10 derived fuels. The BTC has a calorific value significantly higher than the original feedstock, typically between 28 and 35 MJ/kg on a dry basis, and an elemental composition similar to the elemental composition of lignins. It has a high solubility in ethanol or glycerol and less high solubility in water or hydrocarbon liquids such as diesel. Evaporation of the condensate is only possible without substantial carbonaceous 15 remainder, if it is in the form of aerosols below about 1 micron in diameter. The condensate is not stable at elevated temperatures. For atmospheric conditions, at 100 °C mass loss of around 15 % may occur over a week. At temperatures exceeding 200 °C the condensate may rapidly degrade leaving a carbonaceous residue behind, unless the condensate liquid is in the form of aerosols.

20 [0052] When quantities above a few gram are heated to a temperature that causes rapid degradation, gases that are released cannot readily escape the degrading liquid and blow it up into a foam resulting in a very low density char, that is a density below 50 g/1 and sometimes below 20 g/1. The PAH (polyaromatic hydrocarbons) content of the condensate is typically below 1 ppm and therefore significantly lower than for 25 condensate products rich in lignin fragments from slow or fast pyrolysis processes known. The viscosity of condensate that has not been significantly degraded approaches that of water at a temperature of 100 °C and is comparable to honey in the temperature range 0 to 40 °C.

[0053] A considerable amount of steam may be generated in the torrefaction reactor 30 when residual moisture is evaporated in the torrefaction reactor. This can lead to a relatively fast-moving gas stream flowing in the reactor, which increases the pressure drop over the reactor. Furthermore, the energy needed for evaporating the residual moisture may be much greater than the energy required for torrefaction. In particular, in a torrefaction reactor based on direct contact between the gas and the material, a 15 relatively large amount of hot gas may have to be introduced into the torrefaction reactor at a high inlet temperature, which may further increase the amount of gas that has to pass through the torrefaction reactor. This may hamper the implementation of the method of treatment. Hence, the torrefaction reactor may comprise a drying chamber 5 and a torrefying chamber, the organic material with the residual moisture contained in it being essentially fully dried in the drying chamber by evaporation of the residual moisture, and the torrefaction of the dried material being essentially carried out in the torrefying chamber, and the material being conveyed through the torrefaction reactor in a transport direction, and the drying of the material in the drying chamber being carried 10 out by introducing into it a hot drying gas that flows through the drying chamber in cocurrent with the material, and the torrefaction of the material in the torrefying chamber of the torrefaction reactor being carried out by introducing into it a hot torrefying gas that flows through the torrefying chamber of the torrefaction reactor in counter-current to the material.

15 [0054] When a hot gas is introduced, which is e.g. in direct contact with the material, the temperature of the material in the torrefaction reactor may rise to a torrefying temperature. In counter-current, the temperature of the hot gas "follows" the temperature of the material. The temperature of the material and the temperature of the hot gas both increase in the transport direction of the material. The inlet temperature of 20 the hot gas then is close to, and often slightly below, the temperature of the material due to the counter-current flow arrangement and the exothermicity of the torrefaction reaction. By controlling flow and inlet temperature of the hot gas, there is only a very small risk of "hot spots" developing in the dry material, or of uncontrolled torrefaction or pyrolysis taking place. Initially, only a relatively small amount of energy needs to be 25 introduced into the torrefying chamber, which allows for an improved dosing and/or fine tuning of the energy input. As a result, the torrefying temperature in the torrefying chamber can be set and controlled accurately.

[0055] The required temperatures of the hot gases introduced - drying gas and torrefying gas - are relatively low. This facilitates the production of these hot gases. For 30 example, the temperature of the hot gas introduced into the torrefying chamber is in the range of 200-400 °C, being e.g. about 300 °C. Controlled torrefaction can be carried out in the torrefying chamber at such a temperature. In addition the temperature of the hot gas introduced into the drying chamber can be in the range of 150-600 °C though depending on pressure levels, being e.g. about 350 °C. This temperature is particularly 16 suitable for the almost complete drying of the material, such as to a moisture content of < 3%. These temperatures are sufficiently low for the production using e.g. thermal oil.

[0056] It is possible for the drying gas, after it has moved in co-current with the material and has thus been cooled to leave the drying chamber and to be introduced into 5 a first heat exchanger, which heats up this drying gas, after which the drying gas heated up by the first heat exchanger is introduced into the drying chamber, and the torrefying gas after it has moved in counter-current to the material and has thus been cooled down leaving the torrefying chamber and being introduced into the cooler/heater system to separate the BTC and a second heat exchanger (especially the heat exchanger in the 10 heating chamber), which heats up this torrefying gas, after which the torrefying gas that has been heated up by the second heat exchanger is introduced into the torrefying chamber. In this case, the drying gas circulates in a first circuit, while the torrefying gas circulates in a second circuit (here indicated also as “gas transport structure”). By using two circuits, each with its own heat exchanger, it is possible to ensure an efficient 15 energy recovery from the drying gas and the torrefying gas.

[0057] The process may comprise introducing a relatively wet raw material into a dryer, and heating the material in the dryer to evaporate moisture. The material is not fully dried in the dryer, i.e. an amount of residual moisture is left in the material. The residual moisture is mainly formed by bound water in the material. In practice, energy is 20 introduced into the dryer until the moisture content of the material is about 10-15%. Further reducing the moisture content in the dryer might reduce the yield of the whole treatment method. Material with moisture content higher than 15% can of course also be fed into the torrefaction reactor without preliminary drying or pre-drying in a separate dryer. For example, straw generally has a moisture content of about 20%. This straw 25 can be directly fed into the torrefaction reactor.

[0058] During operation, the material is conveyed through the torrefaction reactor in a transport direction. The material is dried in the drying chamber by the introduction of a hot drying gas into it through one or more inlet orifices in the drying chamber. The hot drying gas flows through the drying chamber in co-current with the material. The 30 torrefaction of the material in the torrefying chamber of the torrefaction reactor is carried out by introducing into it a hot torrefying gas through one or more inlet orifices in the torrefying chamber. The hot torrefying gas flows through the torrefying chamber of the torrefaction reactor in counter-current to the material. The drying gas and the torrefying gas flow towards each other from opposite ends of the torrefaction reactor.

17

These gases meet each other at the outlet orifices located between the drying gas inlet orifices and the torrefying gas inlet orifices. This ensures a gas separation between the drying chamber and the torrefying chamber, allowing the process to be split into two stages which can be set in an optimum manner.

5 [0059] When the drying chamber and the torrefying chamber are housed in the torrefaction reactor, the drying chamber and the torrefying chamber may form two separate spaces in the same torrefaction reactor, or they may form two distinct devices. If necessary, a second dryer may be provided for an optimised, stage-wise drying.

[0060] A torrefying device to be used according to the invention may comprise: 10 a. a torrefying chamber configured to torrefy organic material, the torrefying chamber further comprising a torrefying chamber gas inlet for a gas and a torrefying chamber gas outlet for removal of torrefying chamber gas from the torrefying chamber; b. a gas transport structure, downstream of the torrefying chamber gas outlet, 15 cpmprising a cooling chamber, comprising a cooling chamber opening for the separation of BTC, and downstream from the cooling chamber optionally a heating chamber; c. optionally a gas transport device configured to remove torrefying chamber gas via the torrefying chamber gas outlet from the torrefying chamber and configured to 20 transport torrefying chamber gas through the gas transport structure (at least through the cooling chamber and optionally also through the heating chamber).

[0061] The liquid material obtained after cooling is used according to the invention as described above and illustrated below. Also the remaining gas may be used. As indicated above, it may partly be reused, and introduced (after heating) to the torrefying 25 chamber, and produced torgas may partly be taken from the loop and combusted in a combustor to provide energy for the system. The torrefying device may further comprise an additional gas source, configured to provide torrefying gas into the torrefying chamber.

[0062] Preferred embodiments of the invention include the following: 30 1. Use of a biomass torrefaction condensate (BTC) as a binding agent or coating agent for solid material.

2. Use according to embodiment 1, wherein the BTC has a condensation temperature which is between 100°C above and 50°C below the condensation temperature of water, preferably between 80°C above and 10°C below the condensation 18 temperature of water, most preferably between 60°C above and the condensation temperature of water.

3. Use according to any one of the preceding embodiments, wherein the binding or coating agent is used in an amount of between 1 and 25 wt.%, preferably between 5 2 and 12.5 wt.%, based on the combination of binding or coating agent and solid material.

4. Use according to any one of the preceding embodiments, wherein the solid material comprises at least 75 wt.% biomass-derived material and/or at least 50% of wood, herbaceous plants or combinations thereof.

10 5. Use according to the preceding embodiment, wherein the solid material comprises a material obtained by thermal treatment of semi-solid material, in particular torrefaction, pyrolysis, gasification or partial combustion, more particularly torrefaction.

6. A process for producing a wear- and water-resistant solid fuel, comprising 15 combining a solid carbonaceous material with between 1 and 25 wt.%, based on the combined weight, of a BTC obtained by condensation of organic material volatilised during torrefaction of biomass.

7. A process according to embodiment 6, wherein the BTC is added to said carbonaceous material and the material is subsequently densifred.

20 8. A process according to embodiment 6, wherein the solid carbonaceous material is densifred and the BTC is subsequently coated onto the solid material.

9. A process according to any one of embodiments 6-8, wherein the material is densified by being pelletised or briquetted.

10. A process according to any one of embodiments 6-9, wherein the organic material 25 volatilised during torrefaction of biomass is directly condensed onto the solid carbonaceous material.

11. A process according to any one of embodiments 6-9, wherein the solid carbonaceous material comprises heat treated material, in particular heat-treated biomass.

30 12. A process for upgrading biomass comprising: a. subjecting the biomass to torrefaction, to produce a torrefied solid fraction and a volatised fraction; b. cooling the volatised fraction to produce an organic condensate; c. combining the condensate with a torrefied solid fraction; 19 d. densifying the torrefied solid fraction..

13. A process according to embodiment 12, wherein the torrefaction is performed at a temperature of between 240 and 320°C.

14. A process according to any one of the preceding process embodiments, wherein 5 the weight ratio between said organic condensate and said torrefied solid fraction in step (c) is between 1:4 and 1:99.

15. A process according to any one of the preceding process embodiments, wherein the condensate is combined with the torrefied solid fraction in the presence of water in an amount of 0.25-2.5 times the amount of condensate and less than 0.5 10 times the amount of condensate of other additives selected from organic solvents.

16. A process according to any one of the preceding process embodiments, wherein torrefied solid fraction is further pelletised and/or briquetted.

17. A torrefied biomass-derived material, suitable as a fuel, obtainable by the process according to any one of the preceding embodiments.

15 18. A torrefied material according to the preceding embodiment having one or more, preferably all, of the following characteristics: a. a smallest outer particle size of between 2 mm and 10 cm; b. a bulk density of between 0.35 and 1.0 kg/dm3, preferably between 0.65 and 0.9 kg/dm3; 20 c. a specific density between 0.8 and 1.5 kg/dm3, preferably between 1.1 and 1.4 kg/dm3; d. a caloric value (HHV) of between 18 and 28 MJ/kg; e. a moisture content of less than 5 wt.%, also after storage at ambient conditions for at least 1 month; 25 f. a biomass-derived carbon content of at least 75%, i.e. a 14C content of at least 5.1 O'13 (0.5 ppt); g. a grindability corresponding to a power consumption below 0.5 MJ/ton on a 0.25 mm mesh; h. stability to ambient (outdoor) conditions for at least 1 month.

30 19. A torrefied material according to one of the preceding product embodiments, which comprises at least 95 wt%, preferably at least 99 wt.% material that originates from the biomass torrefaction process.

20 20. A torrefied material according to one of the preceding product embodiments, which comprises not more than 5 wt% other additives, which do not originate from the biomass torrefaction process.

5 Examples Example 1

In order to investigate the BTC in detail, a 50-100 kg/hr plant was operated to study the role and fate of organic components and the behaviour of these organic components during cooling of the torgas. As long as the temperature of the wall is cooler than the 10 torgas temperature and above 50 °C, the condensate is fluid, not sticky, and easily removed. As long as the temperature of the wall is cooler than the torgas temperature and above the water dew point of the gas - at atmospheric conditions almost 100°C -the condensate is fluid, non sticky, and easily removed and will contain limited amounts of water. The absence of water in the BTC for the utilization of the BTC as a binder 15 however is not crucial.

The amount of BTC produced depends on the feedstock, the cooling temperature in the torgas loop, but more importantly also on the operating temperature of the torrefaction process. When the torrefaction temperature is increased, more volatile organic components will be released, providing a different ratio of BTC versus torrefied 20 biomass. At 235°C, the amount of BTC related to the torrefied biomass will be low, in a typical experiment as presented in the table below 0.3%. When increasing the temperature of torrefaction to 245 and 255°C, this amount increases to 2.3 and 4.0%, respectively. Indicative trials at higher temperatures show that percentages above 10% can also be obtained. The results are presented in Table 1.

21

Table 1: Mass balance of test with wood chips at stable periods at three temperature setpoints (wood chips, moisture content 18.9 % as received)

| 235°C | 245°C | 255°C

Input

Wet biomass amount (kg) frli frjfl (accuracy = ± 20 kg)

Wet biomass rate (kg/h) (accuracy -- , -- = ± 0.5 kg/h)________

Dry biomass amount (kg) 579 1063 (accuracy = ± 20 kg)

Dry biomass rate (kg/h) (accuracy = ,, 7 ,-7 ,-7 ± 0.5 kg/h)__44'' _40 ' _

Output

Torrefied biomass amount (kg) [77 T77T [~ (accuracy = ± 20 kg) ooa aua 941

Torrefied biomass rate (kg/h) --, --- (accuracy = ± 0.5 kg/h) 4 ^-1 d0-b

Solid yield on dry biomass basis --- --- 0, - ,0,, yo.o oo.o oi .0 (/o)____

Torgas amount (without biomass _ ,-.

moisture) (kg) 0 d

Torgas rate (without biomass ,- „ „ 0 , . . 1.0 b.b 8.1 moisture) (kg/hr)

Gas yield on dry biomass basis (%) 3.5 14.5 18.5 BTC amount (kg) 1.5 21.2 37.3 BTC rate (kg/hr) 0.25 0.91 1.4 BTC yield on torrefied biomass -- -- , .

. • ,o/x 0.3 2.3 4.0 basis (%)___ 5 Example 2 BTC extracted from torrefaction of poplar chips was used as a binder as follows: 2.83 kg BTC was mixed with 1.12 kg ethanol at ambient temperature to produce a 72 % solution. The liquid was a thick dark fluid. 50 ml of this mixture was added to 2.5 kg of solid material torrefied at 265°C. Effectively, the batch contained 1.4 wt% BTC on the 10 torrefied material. The batch was left for several hours. A reference batch was prepared by adding 20 gram water to 400 gram solid material. The total moisture content was about 11 wt%, which was found to be suitable for making pellets in previous tests.

The tests were performed in a pelletising machine with a die of 4.8 mm. The reference material was used for flushing the machine. When continuously running, the input was 15 switched to material with added BTC. The output data are presented in Table 2.

22

Table 2 with BTC with water moisture in material [wt%] 5.72 5.72 added water [wt%] - 5.0 added BTC [wt%] C4 pellet moisture (end product) [wt%] 3.7 not determined pellet density (material) [kg/m3] 1151 1104

Running with material with BTC added, significant changes were found: • less noise in pelletisation 5 • significantly less power consumption • less wear of the machine • longer pellets • less dust.

Thus both operation and pellet quality improve. The lowering of the power consumption 10 for pelleting is of particular interest. The addition of 1.4% BTC equals to about half of the power consumption of the pelleting (taking into account 40% efficiency converting BTC to electric power).

The specific density of pellets with BTC was found to be higher, but it can be regarded as being the same as without addition of BTC, 1104 and 1151, respectively, since this 15 is within the variation found in individual pellets.

Ethanol was added only to enable mixing of the BTC and evaporated during pelleting. When operating at elevated temperatures, the BTC is sufficiently fluid enough to be blended without ethanol.

Conclusion of this test 20 The use of BTC as a supplement to torrefied material is a great improvement, with several technically advantages and no apparent disadvantages.

Claims

Use of a biomass torrefaction condensate (BTC) as a binder or coating material for solid material.

The use according to claim 1, wherein the BTC has a condensing temperature that is between 100 ° C above and 50 ° C below the condensation temperature of water, preferably between 80 ° C above and 10 ° C below the condensation temperature of water, and with most preferably between 60 ° C and the condensation temperature of water.

Use according to any one of the preceding claims, wherein the binder or coating agent is used in an amount between 1 and 25% by weight, preferably between 2 and 12.5% by weight, based on the combination of binder or coating agent and solid material.

4. Use according to any one of the preceding claims, wherein the solid material comprises at least 75% by weight of biomass-derived material and / or at least 50% of wood, grassy plants or combinations thereof.

5. Use according to claim 4, wherein the solid material is a material obtained by heat treatment of semi-solid material, in particular torrefaction, pyrolysis, gasification or partial combustion, more in particular by torrefaction.

6. Process for the preparation of a wear-resistant and water-resistant solid fuel, in which a solid carbonaceous material is combined with between 1 and 25% by weight, based on the combined weight, of a BTC obtained by condensation of a during torrefaction organic material volatilized from biomass.

The method according to claim 6, wherein the BTC is added to the carbonaceous material and the material is subsequently compacted.

The method of claim 6, wherein the solid carbonaceous material is compacted and the BTC is then applied to the solid material.

The method according to any of claims 6-8, wherein the material is compacted by pelletizing or briquetting.

The method according to any of claims 6-9, wherein the organic material volatilized during torrefaction of biomass is directly condensed on the solid carbonaceous material.

11. A method according to any one of claims 6-9, wherein the solid carbonaceous material comprises a heat-treated material, in particular a heat-treated biomass.

12. Method for upgrading biomass wherein: a. The biomass is subjected to torrefaction, thereby creating a torrefied solid fraction and a volatilized fraction; 10 b. the volatilized fraction cools, thereby forming an organic condensate; c. the condensate combines with a torrefied solid fraction; d. the torrefied solid fraction compacted.

The method according to claim 12, wherein the torrefaction is carried out at a temperature between 240 and 320 ° C.

A method according to any one of the preceding process claims, wherein the weight ratio between the organic condensate and the torrefied solid fraction in step (c) is between 1: 4 and 1:99.

15. A method according to any one of the preceding method claims, wherein the condensate is combined with the torrefied solid fraction in the presence of water in an amount of 0.25-2.5 times the amount of condensate and less than 0.5 times the amount of condensate on other additives selected from organic solvents.

A method according to any one of the preceding process claims, wherein torrefied solid fraction is also pelleted and / or briquetted.

A torrefied biomass-derived material suitable as a fuel obtainable by the method according to any one of the preceding claims.

A torrefied material according to the preceding claim, which has one or more, preferably all, of the following features: a. A smallest external particle size between 2 mm and 10 cm; 30 b. a bulk density between 0.35 and 1.0 kg / dm 3, preferably between 0.65 and 0.9 kg / dm 3; c. a specific density between 0.8 and 1.5 kg / dm 3, preferably between 1.1 and 1.4 kg / dm 3; d. a calorific value (HHV) between 18 and 28 MJ / kg; e. a moisture content of less than 5% by weight, also after storage under ambient conditions for at least 1 month; f. a biomass-derived carbon content of at least 75%, i.e. a 14 C content of at least 5.10-13 (0.5 ppt); g. a millability corresponding to an energy consumption of 0.5 MJ / tonne on sieves of 0.25 mm (mesh); h. stability under (outside) o mgcvi ng conditions for at least 1 month.

A torrefined material according to any one of the preceding product claims, comprising at least 95% by weight, preferably at least 99% by weight, of material originating from the torrefaction of biomass.

20. A torrefined material according to any one of the preceding product claims, which comprises no more than 5% by weight of other additives not originating from the torrefaction of biomass.