Method of manufacturing densified, torrefied biomass particulates

Abstract

A method of manufacturing densified, torrefied biomass particulates is disclosed. The method comprises at least : a torrefaction step of torrefying a particulate biomass material under torrefaction conditions; a densification step of densifying the torrefied particulate biomass material from the torrefaction step, thereby obtaining densified torrefied biomass particulates; and a thermal post treatment step of heat treating the densified and torrefied biomass material particulates from the densification step under torrefaction conditions. The thermal post treatment step improves the durability of the densified, torrefied biomass particulates.

Description

[0001] METHOD OF MANUFACTURING DENSIFIED, TORREFIED BIOMASS PARTICULATES

[0002] Technical Field

[0003] The present invention relates to a method of torrefying biomass material, in particular to a method of manufacturing densified, torrefied biomass particulates.

[0004] Technical Background

[0005] Torrefaction of biomass may be described as a mild form of pyrolysis at torrefaction temperatures typically as low as 180-200 up to 340 °C or even more, under low oxygen conditions. Biomass subjected to torrefaction is transformed into a hydrophobic, decayresistant material that may be used for various applications, such as a fuel for combustion or gasification. During torrefaction moisture and light volatiles are removed from the biomass material, while biopolymers including cellulose, hemicellulose and lignin partly decompose thereby forming additional volatiles. Therefore torrefaction is accompanied by loss of mass and loss of chemical energy with respect to the solid matter. Torrefaction is frequently combined with densification, such as pelletising or briquetting, in order to increase the energy density and the hydrophobic properties. The densified, torrefied biomass is more convenient to handle and transport than the original biomass from which it is derived.

[0006] Production of densified torrefied products is generally carried out along one of the following processes. In one of such processes biomass is torrefied and subsequently the torrefied biomass is densified. In another process biomass as received is densified and thereafter the densified biomass is subjected to torrefaction. Hybrid processes are also known from patent literature.

[0007] E.g. US2020 / 0181516A1 has disclosed a method for producing a water-resistant, compressed biomass product. This known method comprises sizing and optionally milling torrefied biomass to provide particulate matter, typically having an average particle size of 0.1-5 mm; adjusting the moisture content of the particulate matter by adding water to provide a humidified biomass, typically having an average moisture content of 5-15 wt.%, based on total mass of the torrefied biomass and water present; adjusting temperature of the humidified biomass to have an average bulk temperature of at least 80 °C, typically in the range of 80- 140 °C; compressing the humidified, finely ground torrefied biomass to a provide a compressed biomass, typically having a density of 1.0-1.4 g / cm3; re-heating the compressed biomass to a temperature greater than 120 °C, typically in the range of 120-230 °C for a time period of at least 5 minutes, typically about 30-60 minutes; and cooling the biomass to ambient temperature. EP4186589A1 has disclosed a plant and method for manufacturing hydrophobic granules of biomass, comprising pelletising biomass in order to obtain biomass granules at a first predetermined temperature T1, inserting the biomass at the first temperature T1 in an oven, torrefying at a second temperature T2 in the oven while simultaneously conveying the biomass granules in order to achieve a predetermined residence time, and discharging the biomass granules thus treated.

[0008] US2016 / 244686A1 has disclosed methods and systems for forming densified lignocellulose biomass. In an embodiment thereof a lignocellulose biomass is torrefied, whereafter the torrefied lignocellulose biomass is fed to a compression die, wherein this lignocellulose biomass is densified and extruded. Following compression, the lignocellulose biomass can be maintained at high temperature and pressure conditions for a period of time, e.g. by conveyance through a sequential series of extension dies that are immediately downstream of the compression die. Water can be added to the compression die for improving lubrication of the densified lignocellulose. The densified lignocellulose can thereafter be cooled under increased pressure to a temperature below the Tg of the lignin in the biomass.

[0009] A drawback of simultaneous torrefaction and densification is that heavy devolatilisation occurs (P.C.A. Bergman, Qombined torrefaction and pelletisation The TOP process (July 2005).

[0010] When densified biomass, e.g. pellets are torrefied under high pressure, the gases resulting from torrefaction will remain in the voids of the densified biomass. Upon release of the pressure, these gases escape from the pellets causing bursts and cracks, which deteriorate the quality, such as integrity and strength of the pellets.

[0011] Furthermore, the addition of water in view of lubrication is believed to deteriorate the efficiency of torrefaction due to hydrolysis of hydrocarbons instead of desired repolymerisation thereof.

[0012] Hydrophobicity is an important characteristic property of torrefied biomass products, that is improved upon torrefaction and densification, compared to untreated biomass. However, this hydrophobic character is limited. This is significant, when the torrefied biomass products are stored in a humid environment, e.g. outdoors where they are subjected to the prevailing weather conditions. This exposure to humidity such as (rain) water, may result in damage to and disintegration of the torrefied biomass products, which results in formation of dust and fines, e.g. during storing and predominantly during handling and transport and thus loss of biomass material. In practice, the torrefied biomass products may still have some hydrophilic character allowing to absorb water thereby decreasing the energy density. Also upon exposure to water certain organic compounds may be leached, to some extent, from the torrefied products, and entrained with (rain) water, resulting in a potential hazard to the environment. The present invention aims at manufacturing torrefied biomass products that reduces at least partially the above disadvantages. More particularly, an object of the present invention is to improve the durability of densified torrefied products. Another aim is to improve the water resistance at low water absorption.

[0013] Brief Description of the Invention

[0014] According to the invention a method of manufacturing densified, torrefied biomass particulates, comprises a torrefaction step of torrefying a particulate biomass material under torrefaction conditions; a densification step of densifying the torrefied particulate biomass material from the torrefaction step, thereby obtaining densified torrefied biomass particulates; and a thermal post treatment step of heat treating the densified torrefied biomass material particulates from the densification step under torrefaction conditions, typically at atmospheric pressure.

[0015] In the method according to the invention biomass material, optionally after a pre-drying step, is subjected to torrefaction, thereby obtaining a torrefied biomass material. In a subsequent step the biomass material thus subjected to torrefaction, typically after cooling, is subjected to a densification step, such as pelletising or briquetting, wherein densified, torrefied biomass particulates like pellets or briquets, are obtained. Thereafter the densified, torrefied biomass particulates are again treated with heat under mild torrefaction conditions, typically at atmospheric pressure.

[0016] It has been experimentally evidenced that the durability (resistance to disintegration, in particular in a humid environment) of the torrefied, densified biomass products can be improved by an additional heat treatment under torrefaction conditions.

[0017] Brief description of the drawing

[0018] The invention is illustrated by the attached drawing, wherein

[0019] Fig. 1 is a diagram of an embodiment of a method according to the invention;

[0020] Fig. 2-4 are a series of photographs of wood pellets of different origin without and with a post treatment according to the invention; and

[0021] Fig. 5 diagrammatically shows a system for performing an embodiment of the invention.

[0022] Detailed description of the invention

[0023] The method according to the invention comprises at least three process steps, comprising a torrefaction step of biomass material, a densification step of torrefied biomass material and a thermal post treatment step of densified, torrefied biomass particulates. In this technical area the term ‘biomass’ is to be understood as all organic matter originating from photosynthesis and may include wood, plants, vegetable oils, green waste, manure, sewer sludge or any other form of material of organic nature.

[0024] Biomass material as received may contain a moisture content that varies from batch to batch. In view thereof in an embodiment the biomass material is subjected to a drying step of drying biomass material with a drying gas, such as preheated ambient air, typically under relatively mild conditions, wherein water adhered on the outside of the biomass, as well as intracellular and intercellular water is removed, e.g. using a dryer having a basic design as disclosed in WO 2020 / 190135A1. The biomass material fed to the torrefaction step optionally after drying, typically has a moisture content up to 15 wt.%, preferably 10 wt.% or less. Then biomass material that optionally has been dried, is torrefied under torrefaction conditions. Typical torrefaction conditions include a torrefaction temperature in the range of 180-320 °C or even more. In an embodiment the torrefaction temperature is 230-320 °C, such as 260-300 °C. In an embodiment the biomass material is kept at the desired torrefaction temperature for 3-30 minutes. In an embodiment the biomass material is indirectly heated. Alternatively, the biomass material is directly heated by an inert gas stream, which in turn is indirectly heated. Optionally the heat source is flue gas originating from the combustion of volatile gases released during the torrefaction process. E.g. volatiles released from the biomass material during torrefaction may be combusted. The flue gas of combustion may be used for indirect heating the torrefaction reactor, wherein the torrefaction is performed. An example of a torrefaction reactor is a longitudinal tube reactor wherein a screw conveyor is arranged that is configured for conveying the biomass material from an entry for feeding the biomass material to an exit for discharging the torrefied biomass material. Generally the torrefaction atmosphere is a low oxygen (less than 3 vol. % O2) atmosphere. An inert atmosphere essentially free of oxygen can also be applied.

[0025] Generally the torrefied biomass material from the torrefaction step is cooled. The end temperature of such a cooling step is dependent on the densification characteristics. In an embodiment the torrefied particulate biomass material is cooled from the torrefaction exit temperature to a densification feed temperature of 80 °C or more, preferably 90 or 100 °C or more. In an embodiment the moisture content of the torrefied particulate biomass material upon entering the densification step is in the range of up to 12 wt.%. Typically the moisture content will be about 0 % if the densification feed temperature is above 100 °C. In the densification step the torrefied biomass material is densified, e.g. pelletised or briquetted, thereby obtaining a densified, torrefied particulate biomass. The shape of the densified torrefied biomass particulates may vary and is not limited. E.g. cylindrical pellets may have a length in the order of 10-50 mm and a diameter of 4-20 mm. In an embodiment the torrefied biomass is extruded under pressure through a plate having at least one, generally a plurality of orifices. During densification the presence of heavier volatiles on the torrefied biomass material may act as a kind of lubricant. Typically densification due to friction will raise the temperature of the torrefied biomass, e.g. up to 130 °C or more. The higher the exit temperature of the densified torrefied biomass particulates, the less heat is to be supplied in the downstream thermal post treatment step.

[0026] In an embodiment the method further comprises a cooling step of cooling the densified torrefied biomass particulates from the densification step. It has appeared that sometimes the densified torrefied biomass particulates, which leave the densification step in a hot state, are fragile and brittle and may have insufficient mechanical strength to withstand the torrefaction conditions in the thermal post treatment step thereby provoking the risk of some degree of undesired disintegration. By cooling down the densified and torrefied biomass particulates from the densification step the mechanical properties of the densified torrefied biomass particulates are improved allowing the subsequent thermal post heat treatment under torrefaction conditions without deterioration of the biomass particulates. The final temperature of this cooling step is dependent upon sufficient recovery of these mechanical properties. E.g. the densified and torrefied biomass particulates may be cooled to a cooling end temperature of 100 °C or less. In an embodiment cooling to a final temperature equal to or below 60 °C may be required, preferably less than 40 °C, In the thermal post treatment step the biomass particulates now densified and torrefied are subjected to an additional heat treatment under mild torrefaction conditions in relation to temperature, such as 235-300 °C, preferably 240-290 °C, more preferably 240-265 °C, at atmospheric pressure, and in a low oxygen (less than 3 vol. % O2) atmosphere, advantageously in the absence of oxygen, for example in an inert nitrogen flow. In an embodiment reheating of the densified, torrefied biomass particulates is carried out in a device as disclosed in WO 2020 / 190135A1 , followed by the post heat treatment in a separate device. Typically the post treatment step is performed on the densified and torrefied particulate biomass in a free flowing state, like all process steps. Typically the thermal post treatment is carried out in an indirectly heated reactor similar to the torrefaction reactor described above. Alternatively, the post-treatment may be performed using direct contact with a heated gas flow. Flue gas originating from the combustion of volatile gases released during the torrefaction process may be used as a heat source. Generally, the torrefied and densified biomass material is kept at the post-treatment temperature for a period of time in the range of 2-15 minutes. Typically the post-treatment conditions are milder than the torrefaction conditions in the torrefaction step preceding the densification step. E.g, post-treatment temperature is lower and / or the residence time is smaller.

[0027] Distribution of the total degassing / mass loss over the torrefaction step and thermal posttreatment step offers the advantage that the densification following torrefaction is improved and requires less energy because the amount of carbonization in the torrefaction step is reduced compared to a process wherein the same total degassing / mass loss is achieved in a single torrefaction step, prior to densification. Typically the total degassing / mass loss based on the dry biomass material fed to the torrefaction step, is in the range of up to 40%, such as 10-35 %, corresponding to a mass yield of 60 % and higher, such as 65-90%, based on the dry material fed to the torrefaction. Typically the operating window of mass yield in the method according to the invention is in the range of 70-90%, based on the dry starting biomass material. Lower and higher percentages are feasible, depending on the required specifications of the final pellets such as fixed carbon content, the energy balance and efficiency of the equipment used. E.g. if the starting biomass is wet and the required energy for drying is to be derived from the combustion of volatiles and heat exchange with air for drying, more degassing might be required than in case of a drier starting material. Inefficient (operation of the) equipment used may also require additional energy, which may be derived from the combustion of additionally released volatiles, requiring more degassing. A higher degree of degassing may also be beneficial when the volatiles can be used for the production of energy, e.g. by combusting thereof for the production of steam by heat exchange of the flue gas resulting from combustion with a water flow.

[0028] In a particular embodiment the degree of degassing / mass loss in the thermal post treatment step is less than 35 wt. % of the total degassing / mass loss, based on the dry biomass material fed to the torrefaction step, more preferably in the range of 10-30 wt. % of the total degassing / mass loss. For example if the desired total mass loss is set at 25%, about 80% thereof (about 20% total mass loss) may be established in the torrefaction step by setting appropriate average torrefaction temperature and residence time for the biomass material, while in the thermal post treatment step an additional mass loss of 5 wt.% (about 20% of the combined loss) occurs due to appropriate setting of temperature and residence time in the thermal post treatment step. After the thermal post treatment the biomass particulates thus obtained are allowed to cool to ambient for further processing such as storage, transport or final application in combustion and / or gasification.

[0029] In an embodiment the method further comprises recycling condensable volatiles released during the torrefaction step and / or thermal post treatment step to the biomass particulates. In an embodiment the method further comprises combusting volatiles released during the torrefaction step and / or thermal post treatment step.

[0030] In an embodiment (light) condensables volatilised in the drying step before torrefaction and / or during torrefaction are at least partially recycled (the other part may be used for combustion) to the torrefied biomass material or to the densified, torrefied biomass material, advantageously after optional cooling and / or preheating thereof, so that these condensables are deposited thereon and repolymerize and devolatilize to a solid component of the densified, torrefied biomass during the subsequent post heat treatment step, thereby improving the strength and hydrophobicity throughout the densified, torrefied biomass material. Depositing the released condensables on the particulate biomass is also beneficial for the energy content per mass unit.

[0031] In an embodiment the released condensables, or at least part thereof are deposited onto the torrefied biomass material, acting as a lubricating agent, which reduces the energy consumption during the subsequent densification step.

[0032] Cooling of the torrefied biomass material may be performed in two steps. The first step thereof comprises water quenching to a temperature, typically to final biomass temperature above 100 °C such that the water used is converted to steam and the biomass material does not become wet. Thereby sticking of the torrefied biomass particulates together, as well as to surfaces of the apparatuses and thus fouling is substantially reduced. In the second cooling step the thus quenched biomass particulates are allowed to cool down, e.g. using a forced flow of gas like air. A forced gas flow also contributes to stopping the torrefaction reactions, which are believed to have ceased completely at a temperature of 100 °C or lower.

[0033] Detailed description of the drawing

[0034] Fig. 1 shows a process diagram of an embodiment of the method according to the invention, wherein biomass as received is dried in drying step 10, then heated and torrefied in torrefaction step 20, intermediately cooled in optional cooling step 30, densified in densification step 40, cooled in optional cooled step 50, reheated and torrefied in additional thermal treatment step 60, and finally cooled to ambient in final cooling step 70.

[0035] Fig. 2 shows from left to right

[0036] 1A : torrefied (torrefaction conditions; 300 C, 4 min, 6% moisture in pellets after conditioning and pelletization) Dutch waste wood class A pellets, not subjected to a thermal post treatment, after 30 hrs stagnant immersion in water.;

[0037] 2A: torrefied (torrefaction conditions; 300 C, 4 min, 6% moisture in pellets after conditioning and pelletization) Dutch waste wood class A pellets, subjected to a thermal post treatment (conditions: 250 C, 10 min, <1 % moisture after post treatment and cooling), after 30 hrs stagnant immersion in water;

[0038] 3W: torrefied (torrefaction conditions; 285 C, 4 min, 6% moisture in pellets after conditioning and pelletization) willow pellets, not subjected to a thermal post treatment, after 30 hrs stagnant immersion in water and;

[0039] 4W: torrefied (torrefaction conditions; 285 C, 4 min, 6% moisture in pellets after conditioning and pelletization) willow pellets, subjected to a thermal post treatment (conditions: 250 C, 10 min, <1 % moisture after post treatment and cooling), after 30 hrs immersion in water. Fig. 3 shows from left to right torrefied (torrefaction conditions; 300 C, 4 min, 6% moisture in pellets after conditioning and pelletization) Dutch waste wood class A pellets, not subjected to a thermal post treatment, after 30 hrs stagnant immersion in water; and torrefied (torrefaction conditions; 300 C, 4 min, 6% moisture in pellets after conditioning and pelletization) Dutch waste wood class A pellets, subjected to a thermal post treatment (conditions: 250 C, 10 min, <1 % moisture after post treatment and cooling), after 30 hrs stagnant immersion in water.

[0040] Fig. 4 shows from left to right torrefied (torrefaction conditions; 275 C, 4 min, 6% moisture in pellets after conditioning and pelletization) EFB (Empty Fruit Bunches (type of biomass waste from palm oil industry (Asia)) pellets, subjected to a thermal post treatment (conditions: 250 C, 10 min, <1% moisture after post treatment and cooling), after 30 hrs stagnant immersion in water, and torrefied (torrefaction conditions; 275 C, 4 min, 6% moisture in pellets after conditioning and pelletization) EFB, not subjected to a thermal post treatment, after 30 hrs stagnant immersion in water.

[0041] As shown the samples that were once torrefied and then pelletised showed more disintegration evidenced by the presence of fines in the water, as well as leaching evidenced by the discoloration of the water than the samples that were manufactured according to the method of the invention that retain their surface shape and show less discoloration.

[0042] Examples

[0043] Example 1

[0044] Biomass of various origin was dried to a moisture content of 6-10 wt.% and then torrefied at 265-310 °C for a period of time of 4 minutes. The torrefied biomass was allowed to cool to 20 °C and then pelletized to cylindrical pellets having a length 5-25 mm and 0 of 5.8-6.0 mm. At the entry of the pelletizer the torrefied biomass had a moisture content of 9-11 wt.%. The torrefied pellets thus obtained were subjected to a thermal post treatment at the temperatures and times presented in Table 1..

[0045] Durability was qualitatively and quantitatively PDI = pellet durability index) assessed after immersion in water during different times. The results are summarized in the below table. Table 1 .

[0046] A-wood = Dutch waste wood class A EFB = Empty Fruit Bunches

[0047] From these test results it appears that the immersed pellets shows only a very limited decrease in pellet strength (PDI) compared to the non-immersed ones, and therefore evidence the strong hydrophobic character.

[0048] Example 2

[0049] A sample of torrefied douglas fir pellets (torrefaction conditions: 300 C, 4 min - not post- treated) was subjected to a water sorption test according to ISO 23343, followed by a durability test according to ISO 17831. The below Table 2 shows the results.

[0050] Table 2 Test results douglas fir wood pellets

[0051] Example 3

[0052] A sample of torrefied pine wood pellets (torrefaction conditions: 300 C, 4 min - not posttreated) to a water sorption test according to ISO 23343, followed by a durability test. In this example the durability test was performed by manually tumbling by hand for 30 seconds, followed by sieving on a 3.15 mm sieve for 30 seconds. The below Table 3 shows the results.

[0053] Table 3 Test results pine wood pellets

[0054] Fig. 5 shows an embodiment of a preferred process according to the invention. Particulate biomass is subjected to a pretreatment (pretreatment step 100), such as size reduction and / or sieving, in order to obtain a particulate biomass having physical properties, such as dimensions, within a predetermined range. The pretreated particulate biomass is dried / preheated in drying / preheating step 110 to a temperature of about the torrefaction temperature, typically in a device as disclosed in WO 2020 / 190135A1. In torrefaction step 120 the particulate biomass is torrefied, generally in an indirectly heated screw reactor, under torrefaction conditions at atmospheric pressure. The torrefied particulate biomass is cooled in cooling step 130, typically to a temperature suitable for densification in the subsequent densification step 140, e.g. in a pellet mill. Thereafter the densified and torrefied particulate biomass is optionally cooled in cooling step 150 to strengthen the densified, torrefied particulate biomass and then again preheated in preheating step 160, typically in a device as disclosed in WO 2020 / 190135A1, to the temperature of the post heat treatment, that is carried out in thermal post treatment step 170 at torrefaction conditions at atmospheric pressure. After the thermal post treatment the thus post heat treated particulate biomass is cooled by water quenching to a temperature above 100 °C in cooling step 180 and then down to ambient temperature by e g, (forced) air cooling in cooling step 190.

[0055] In this embodiment volatiles released during drying / preheating step 110, if any, and during the torrefaction step 120 are recovered and a part thereof is combusted in combustion step 200 with air. The flue gas resulting from combustion is used to reheat another part of the condensable volatiles released during drying / preheating step 110 and torrefaction step 120 in heat exchange step 210, which heat exchanged volatiles are recycled to the drying / preheating step 110. In heat exchange step 210 typically also the air used for drying is heated to the operating temperature. A similar loop is provided over the post heat treatment step 170. A part of the volatiles released during thermal post treatment are combusted in combustion step 220 with air and the flue gas resulting from combustion is heat exchanged in heat exchange step 230 with another part of the condensable volatiles released during thermal post treatment, which are recycled to the thermal post treatment step 170. Generally the air required for preheating step 160 is also heated by heat exchange in heat exchange step 230. The volatiles released during thermal post treatment may also be recycled directly to the densified and torrefied particulate biomass entering the thermal post treatment step 170.

[0056] Part of the volatiles released torrefaction step 120 are also recycled to the torrefied particulate biomass entering the densification step 140.

[0057] In Fig. 5 the heat exchange step 210 and 230 are shown in cocurrent. Typically, they will be arranged in countercurrent. It is also feasible that combustion step 200 and 220 are combined into one unit operation. The same applies to heat exchange steps 210 and 230.

[0058] Generally, the steps except the densification step are performed at atmospheric pressure (no additional pressure applied) on free flowing biomass particulates.

Claims

CLAIMS1. Method of manufacturing densified, torrefied biomass particulates, comprising a torrefaction step of torrefying a particulate biomass material under torrefaction conditions; a densification step of densifying the torrefied particulate biomass material from the torrefaction step, thereby obtaining densified torrefied biomass particulates; and a thermal post treatment step of heat treating the densified torrefied biomass particulates from the densification step under torrefaction conditions.

2. Method according to claim 1, wherein in the thermal post treatment step the densified torrefied biomass particulates are heat treated under torrefaction conditions at atmospheric pressure.

3. Method according to claim 1 or 2, wherein the degree of degassing / mass loss in the thermal post treatment step is less than 35 wt.% of the total degassing / mass loss, based on the dry biomass material fed to the torrefaction step.

4. Method according to claim 3, wherein the degree of degassing / mass loss in the thermal post treatment step is in the range of 15-30 wt.% of the total degassing / mass loss, based on the dry biomass material fed to the torrefaction step.

5. Method according to any one of the preceding claims, wherein the thermal post treatment step is performed under torrefaction conditions in the range of 235-300 °C, preferably in the range of 240-290 °C, more preferably in the range of 240-265 °C.

6. Method according to any one of the preceding claims, wherein in the thermal post treatment step the densified and torrefied biomass particulates are kept at the post-treatment temperature in the range of 2-15 minutes.

7. Method according to any one of the preceding claims, wherein the thermal post treatment step is performed in the absence of oxygen.

8. Method according to any one of the preceding claims, wherein the torrefied particulate biomass material has a feed temperature to the densification step in the range of 80 °C or more, preferably in the range of 100 °C or more.

9. Method according to any one of the preceding claims, wherein the torrefied particulate biomass material has a feed moisture content to the densification step in the range of up to 12 wt. %.

10. Method according to any one of the preceding claims, wherein the torrefaction step is performed at a torrefaction temperature in the range of 180--320 °C.

11. Method according to any one of the preceding claims, further comprising a cooling step of cooling the densified torrefied biomass particulates from the densification step prior to the thermal post treatment step .

12. Method according to any one of the preceding claims, further comprising recycling condensable volatiles released during the torrefaction step and / or thermal post treatment step to the biomass particulates.

13. Method according to any one of the preceding claims, further comprising combusting volatiles released during the torrefaction step and / or thermal post treatment step to the biomass particulates.

Images