Method and apparatus for baking process

Abstract

A torrefaction method includes transferring biomass through a process chamber; heating the biomass in the process chamber to a predetermined temperature and pyrolyzing the biomass to release syngas from the biomass, wherein the syngas comprises at least 20% of the energy contained in the biomass stream; and oxidizing the syngas to heat the biomass in the process chamber.

Description

[0001] (This application is a divisional application of application No. 202080063310.1, filed on July 24, 2020, entitled “Method and apparatus for baking process”) Technical Field

[0002] The present invention generally relates to methods and apparatus for torrefaction processes. Background Art

[0003] In countries without natural resources of fossil fuels such as coal and oil, and in countries that wish to switch to sustainable energy production, biomass is considered as an alternative source. In this regard, the use of gases produced by decomposing organic matter in the absence of oxygen, commonly known as biogas, has been practiced for quite some time. However, biogas usually requires gas tanks for storage, which greatly limits the storage capacity. In addition, some of its components are toxic or considered greenhouse gases. The production of biogas further produces digestate, which is the material left over after biogas production. This digestate is sometimes difficult to process.

[0004] It has been found that torrefaction converts biomass into biocoal or biochar, which is a solid with a low moisture content, and the amount of carbon, especially the mass percentage, is increased compared to the initial biomass. Biomass usually refers to wood chips, but a wide variety of biomass can be imagined. It has been found that the biocoal produced by torrefaction has a lighter weight than the initial biomass, especially less oxygen weight, and has a higher energy density in terms of volume and mass. Biocoal from torrefaction can be used for energy generation in conventional coal-fired power plants like traditional fossil coal. If the biocoal has a high enough grade, other applications (such as steel production) are also conceivable. Biocoal is also chemically stable and can therefore be easily stored and transported like traditional coal.

[0005] In principle, torrefaction is a pyrolysis process at essentially atmospheric pressure, in the absence of essentially any oxygen other than that contained in the biomass itself. Typically, the biomass is exposed to temperatures between 200°C and 350°C, with a residence time between 10 minutes and 120 minutes. The quality of the resulting biocoal is determined by the temperature and the residence time. In the torrefaction process, syngas is separated from the biomass. The syngas contains tar, H2, CH4 and / or CO. Although typically in the gas phase, the syngas may also contain condensed tar droplets. In principle, the syngas is cooled to condense and remove the tar from the syngas, so that the syngas can be used for conventional applications, such as gas engines for generating electrical energy.

[0006] Conventional torrefaction processes typically provide biocoal with an energy density of 20 to 21 GJ / ton. As will be discussed in more detail below, the energy density depends primarily on the temperature and residence time of the biomass in the process atmosphere, with longer residence times or higher temperatures providing biocoal with higher energy density despite a smaller amount of energy from the original biomass.

[0007] However, as energy density increases, the amount of tar produced and contained in the syngas also increases. This requires more tar to be removed from the syngas. Otherwise, the tar in the syngas will spontaneously condense, causing fouling or coking of the gas engine. In addition, when tar is used, polycyclic aromatic hydrocarbons may be released, which have been found to be associated with various forms of cancer. For this reason, tar is often replaced by pitch, which in turn makes it more difficult to utilize the tar produced in the torrefaction process.

[0008] WO2015 / 084162A1 describes an improved dryer that operates on a different principle from that used by existing torrefaction equipment. The invention uses heat conduction to torrefy biomass in a vibrating reactor, in which heated solid imperforate plates are sealed in the reactor to separate the biomass above from the gas below that is used to heat the plates. In addition, the synthesis gas produced from the process is used to power a gas engine, whose exhaust gas output is recycled to heat the reactor plates. When the gas engine is connected to a generator, the waste energy is recovered for use in other parts of the plant or directed elsewhere. Summary of the invention

[0009] While the invention is defined in the independent claim, further aspects of the invention are set out in the dependent claims, the drawings and the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 shows a baking device according to an embodiment of the present invention; and

[0011] Figure 2 is a schematic diagram of one embodiment showing reagents and products of a roasting process of varying energy contents. DETAILED DESCRIPTION

[0012] Figure 1 There is shown a baking apparatus comprising a process chamber 11a and an oxidizer 12. Before explaining the baking apparatus in detail, some general aspects of the invention will be discussed.

[0013] According to one aspect, a baking apparatus comprises:

[0014] - a process chamber configured to accommodate a torrefaction process of the biomass;

[0015] - an oxidizer arranged to heat the process chamber; and

[0016] - a conduit for syngas released from biomass during a torrefaction process; wherein the conduit is arranged to conduct the syngas from a process chamber to an oxidiser; wherein the oxidiser is configured to provide oxidation of the syngas releasing energy which is at least 20% of the energy contained in the maximum biomass flow passing through the process chamber.

[0017] The biocoal produced is hydrophobic and can therefore be easily stored without further weather protection. It can be made water-resistant with specific additives. Biocoal can be burnt as dust in existing facilities.

[0018] In the following, biomass flow refers to the amount of biomass in a specific time span. For example, biomass flow can be expressed as the mass of biomass in kilograms [kg] per hour [hrs] of time, or

[0019] Biomass [kg]

[0020] Time [hrs].

[0021] The maximum biomass flow through the process chamber represents the amount of biomass that the process chamber is dimensioned to process to the maximum extent within a certain time span. Since the biomass flow is an amount per unit time, the energy contained in this amount corresponds to energy at that time.

[0022] In some embodiments, the conduit is configured to maintain the syngas temperature above the condensation temperature of the syngas from the process chamber during operation. In various embodiments, the syngas temperature is maintained at a temperature above 330°C and / or at least 50°C above the maximum temperature of the biomass in the process chamber. In various embodiments, the maximum temperature of the biomass is the core temperature of a single particle. Typically, the core temperature adapts to the ambient temperature in a delayed manner and may be different from the surface temperature of the particle. Combusting the syngas in an oxidizer immediately adjacent to the process chamber also limits the effort required to keep the syngas temperature above the condensation temperature of the syngas.

[0023] For example, while passing through the process chamber, the biomass is heated to a temperature of at most 280° C. The conduit therefore maintains the temperature of the syngas at 330° C. In a different example, the biomass is heated to a temperature of at most 300° C. The conduit therefore maintains the temperature of the syngas at 350° C. The biomass reaches the maximum temperature before leaving the process chamber.

[0024] In some embodiments, the conduit is thermally insulated.

[0025] In some embodiments, the duct and / or process chamber includes an air inlet that allows controlled combustion of a portion of the syngas. This typically means that some of the syngas is burned before reaching the oxidizer. For example, in an apparatus with an oxidizer burning about 4 MW, the syngas burned in the duct and / or process chamber corresponds to about 100 kW.

[0026] In some embodiments, the oxidizer is configured to provide oxidation that releases energy of at least 23%, 25%, or 27% of the energy contained in the maximum biomass flow through the process chamber. In some embodiments, the oxidizer is configured to provide oxidation that releases no more than 36% or 40% of the energy contained in the maximum biomass flow through the process chamber. In some embodiments, the oxidizer is configured to provide oxidation that releases energy between 23% and 40%. In some embodiments, the oxidizer is configured to provide oxidation that releases energy between 23% and 36%. In some embodiments, the oxidizer is configured to provide oxidation that releases energy between 25% and 40%. In some embodiments, the oxidizer is configured to provide oxidation that releases energy between 25% and 36%. In some embodiments, the oxidizer is configured to provide oxidation that releases energy between 25% and 36%. In some embodiments, the oxidizer is configured to provide oxidation that releases energy between 27% and 40%. In some embodiments, the oxidizer is configured to provide oxidation that releases energy between 27% and 36%.

[0027] The more energetic the oxidizer process, the higher the energy density of the resulting biocoal. Higher energy density could make biocoal suitable for other applications such as steel production.

[0028] In some embodiments, the oxidizer is configured to combust the syngas at a temperature greater than 750°C, more preferably greater than 850°C or 1050°C. In various embodiments, the oxidizer is configured to pass the syngas through within a residence time of 1 second, preferably within 2 seconds. It has been found that for an oxidizer configured for a residence time of 1 second, a temperature of at least 850°C allows substantially complete combustion of the combustible components of the syngas. In various embodiments, the temperature of the oxidizer and the residence time of the syngas are adjusted to allow substantially complete combustion.

[0029] In some embodiments, the oxidizer is configured to maintain the process chamber at a temperature between 400° C. and 650° C., preferably at about 500° C. In another embodiment, the baking apparatus is provided with a cooling structure that dissipates some of the heat energy from the oxidation to various heat sinks to control the temperature of the process chamber. In various embodiments, this allows the factory to build a specific grade of low-cost material.

[0030] In some embodiments, the oxidizer is provided with an oxidizer air feeder configured to maintain the temperature of the process chamber below 600° C., preferably below 550° C., by generating a flow of ambient dilution air in the direction of the process chamber. In some embodiments, the warm gas is additionally or alternatively passed from the process chamber to a dryer, where the biomass is dried before entering the process chamber. In some embodiments, the oxidizer air feeder is a blower or a fan.

[0031] In some embodiments, the process chamber has a rated temperature below 600°C, preferably 550°C and below. The rated temperature refers to the temperature at which the process chamber can operate without damaging the reactor. Process chambers with higher rated temperatures require different materials and different construction, which generally makes the process chamber more expensive.

[0032] In some embodiments, the process chamber has a temperature above 500°C, up to 950°C, using higher grade materials and insulation to protect lower grade materials to help increase biomass processing capabilities to produce very high grade carbon materials such as coke.

[0033] In some embodiments, the process chamber includes a feed element, a conveying element, and / or a distribution element configured to hold a specific volume of biomass in the process chamber for a period of between 15 and 30 minutes. In some examples, this results in an output biocoal energy content of between 22 GJ / ton and 30 GJ / ton for a biomass input of 3100 kg / hr, corresponding to approximately 14.6 MW of energy, as temperature and residence time substantially determine the output of energy content.

[0034] In some embodiments, the process chamber is configured to minimize spontaneous air exchange between its contents and ambient air, wherein the process chamber preferably includes an inlet with an airlock and an outlet with an airlock to convey biomass through the inlet, process chamber and outlet, wherein the process chamber is preferably maintained at a pressure below ambient air pressure. Since the process chamber is maintained below ambient air pressure, a slight leak in the process chamber will not release syngas into the environment, which would otherwise cause health problems and safety hazards. In some embodiments, the duct includes a fan or blower to create a low pressure in the process chamber.

[0035] In some embodiments, the syngas comprises tar, H2, CH4 and / or CO, wherein the oxidizer is preferably configured to combust at least a portion of the tar.

[0036] According to another aspect, a baking method comprises:

[0037] transferring biomass through a process chamber;

[0038] heating the biomass in the process chamber to a predetermined temperature and pyrolyzing the biomass to release syngas from the biomass, wherein the syngas comprises at least 20% of the energy contained in the biomass stream; and

[0039] The syngas is oxidized to heat the biomass in the process chamber.

[0040] In some embodiments, a particular volume of biomass is maintained in the process chamber for 15 to 30 minutes.

[0041] In some embodiments, the syngas is maintained at a temperature above the condensation temperature of the syngas components. In various embodiments, the syngas temperature is maintained at a temperature above 330°C and / or at least 50°C above the maximum temperature of the biomass in the process chamber. Maintaining the syngas at this temperature can prevent tars from condensing before reaching the oxidizer that burns them.

[0042] In some embodiments, the syngas is mixed with a controlled flow of air, preferably to heat the air. Mixing the syngas with some air allows for controlled combustion, thereby maintaining the temperature of the syngas.

[0043] In some embodiments, the oxidizer burns the syngas at a temperature above 750°C, more preferably above 850°C or 1050°C, to provide thermal energy to heat the biomass in the process chamber. In some embodiments, the syngas passes through the oxidizer in at least 1 second, preferably in 2 seconds. Combustion at these temperatures can allow for oxidation of a large amount of tar.

[0044] In some embodiments, the air flow regulates the heat energy transferred to the process chamber. In some embodiments, the heat energy is further transferred to a dryer where the biomass is dried before entering the process chamber. In some embodiments, the oxidizer air feeder generates pressure to force warm air containing heat energy from the oxidizer through the process chamber and toward the dryer. This can avoid adding a fan between the oxidizer and the dryer, which would otherwise need to be configured for very high temperatures.

[0045] It has been found that the amount of tar produced in the torrefaction process can be reduced by combustion in the process chamber, ducts and / or oxidizer. The burned tar can be used to heat the biomass in the process chamber and / or oxidizer.

[0046] Back to Figure 1 As described above, the biomass 21 in various embodiments is stored and fed into the dryer 17, where it is heated (preferably by evaporation) to remove water. The dried biomass 22 is then supplied to the process chamber 11a. In operation, the oxidizer 12 provides thermal energy 25 to the process chamber 11a. By processing the dried biomass 22 in a torrefaction process, the process chamber 11a produces, on the one hand, a synthesis gas 23 such as tar, hydrogen, methane and carbon monoxide, and on the other hand, a solid component 24. Hereinafter, the solid component will be referred to as biochar or biocoal. In various embodiments, the oxidizer is configured to burn the synthesis gas 23 to provide thermal energy 25.

[0047] The syngas 23 stream in a given time frame contains at least 20% of the energy of the biomass stream in the same time frame. Therefore, the oxidizer 12 is configured to burn a corresponding amount in that time interval. As understood in the art, this means that the air feed or oxygen feed to the oxidizer is sized accordingly. At least a portion of the 20% energy content of the biomass processed during a time interval is substantially used to heat the process chamber 11a during approximately that time interval.

[0048] The torrefaction device further comprises a conduit 13 for feeding the syngas 23 to the oxidizer 12. In various embodiments, the process chamber 11a and the conduit 13 are configured to maintain the temperature of the syngas 23 above the condensation temperature of most components of the syngas. Thus, in particular components with a high condensation temperature, such as tar, remain in the gas phase and are fed to the oxidizer 12. As a result, the amount of tar released from the torrefaction device is reduced.

[0049] As will be further explained below, this allows the production of biocoal 24 with a higher energy density, particularly in terms of energy content per unit mass. In particular, the present invention contemplates the production of biocoal with an energy density of at least 22 GJ / ton, preferably 24 GJ / ton, but also up to and above 28 GJ / ton.

[0050] In order to maintain the temperature of the syngas 23, in various embodiments, the pipeline 13 is provided with an insulator to maintain the temperature of the syngas 23. In another embodiment, the pipeline 13 is provided with a first air feeder 15, and the first air feeder 15 is configured to supply heated compressed air to the pipeline 13. In various embodiments, the process chamber 11a is provided with a second air feeder 16, and the second air feeder 16 is configured to supply heated compressed air to the process chamber 11a. In various embodiments, the air of the first and second air feeders 15, 16 is heated by the oxidizer 12.

[0051] The hot air supplied to the process chamber 11a and / or the duct 13 heats the syngas 23 and allows controlled combustion of some of the tars to maintain the temperature of the syngas 23. The combustion of some of the tars reduces the tars 23 in the syngas.

[0052] In various embodiments, the first and second air feeders 15, 16 supply air having ambient temperature. In another embodiment, the first and second air feeders 15, 16 supply air heated by the oxidizer 12. In another embodiment, the first and second air feeders 15, 16 are connected to the same compressed air source. In various embodiments, the first and second air feeders are controlled in a closed loop to maintain the temperature of the syngas 23 above the condensation temperature of most components of the syngas 23.

[0053] In various embodiments, the oxidizer 12 is housed in a heating chamber 11b that is arranged adjacent to the process chamber 11a. In various embodiments, the heating chamber 11b is arranged below the process chamber 11a. The heating chamber 11b is arranged to keep the heat energy 25 adjacent to the process chamber 11a. The oxidizer 12 is further provided with an oxidizer air feeder 14. In various embodiments, the oxidizer air feeder 14 is arranged to supply oxygen for oxidizing the synthesis gas 23. In various embodiments, the oxidizer air feeder 14 is configured to supply more air than required to oxidize the synthesis gas 23. In various embodiments, the oxidizer air feeder 14 is configured to supply air to adjust the heat energy 25 supplied to the process chamber 11a, thereby controlling the temperature of the process chamber 11a. In various embodiments, the oxidizer air feeder 14 supplies ambient air. In different embodiments, a feed of oxygen from a source other than air is supplied to the oxidizer 12.

[0054] In various embodiments, the oxidizer 12 is configured to combust the syngas 23 at a temperature above 750°C, preferably above 850°C, more preferably above 950°C or 1050°C. In various embodiments, the oxidizer is configured to allow the syngas to pass through with a residence time of at least 1 second, preferably within 2 seconds or more. The residence time and oxidizer temperature are preferably configured to allow substantially complete combustion of the combustible components of the syngas 23. In various embodiments, the oxidizer air feeder 14 is configured to control the thermal energy 25 generated by the oxidizer 12 so that the process chamber 11a is heated to a temperature of not less than 400°C, preferably at 500°C.

[0055] In various embodiments, the heating chamber 11b is maintained at a temperature not exceeding 600°C, preferably at 550°C. Limiting the temperature of the process chamber 11a and / or the heating chamber 11b allows the use of cheaper materials to construct the process chamber 11a and / or the heating chamber 11b or the entire baking equipment, thereby allowing a more economically feasible design. In various embodiments, air from the oxidizer air feeder 14 is used to regulate the thermal energy 25 between the oxidizer 12 and the process chamber 11a to regulate the temperature of the process chamber 11a and / or the heating chamber 11b. In various embodiments, the oxidizer air feeder 14 includes two separate fans to supply air for oxidizing the synthesis gas 23 and to regulate the temperature of the process chamber 11a and / or the heating chamber 11b.

[0056] In various embodiments, the air supplied by the oxidizer air feeder 14 and the oxidized syngas form a warm air 26 stream used as a heat source. In various embodiments, the warm air 26 stream passes from the heating chamber 11b to the dryer 17. In the dryer 17, the warm air 26 stream dries the biomass 21 by evaporating water 27. The warm air 26 stream and the evaporated water 27 are then released from the dryer 17.

[0057] In another embodiment, the dryer 17 is arranged adjacent to the process chamber 11a. In various embodiments, the oxidizer air feeder 14 is configured to supply air to the oxidizer 12 at a sufficient pressure so that the warm air 26 flow passes from the heating chamber 11b to the dryer 17. In various embodiments, the warm air 26 flow is mixed with the biomass 21. In various embodiments, the oxidizer 12 and the dryer are arranged so that the warm air 26 flow heats the dryer 17 without contacting the biomass 21. In various embodiments, a conduit for the warm air 26 flow is arranged between the chamber including the oxidizer 12 and the dryer 17. Preferably, the dryer is a cross-flow dryer, wherein the warm air 26 flow passes through the biomass perpendicular to the biomass 21 flow. In another embodiment, the warm air 26 flow and the biomass 21 flow pass through the dryer 17 in parallel in the same direction or in countercurrent in opposite directions.

[0058] In various embodiments, an oxidizer sized to process syngas containing at least 20% of the energy of a biomass stream is substantially provided with an oxidizer air feeder 14 that provides a sufficient amount of oxygen to combust substantially all of the corresponding combustible syngas containing at least 20% of the energy of the biomass stream. In various embodiments, the oxidizer air feeder 14 supplies more oxygen than can be combusted with the syngas.

[0059] In various embodiments, the process chamber 11a is maintained at a pressure different from the ambient pressure. In some embodiments, the pressure inside the process chamber 11a is lower than the ambient pressure. This prevents the synthesis gas 23 generated in the process chamber 11a from escaping into the environment. Otherwise, the synthesis gas 23 may pose a health risk to operators and may be ignited once they escape from the process chamber 11a and come into contact with the ambient air.

[0060] In various embodiments, the process chamber 11a includes an inlet airlock 18 that allows the dry biomass 22 to enter the process chamber 11a while preventing air exchange between the interior of the process chamber 11a and the ambient atmosphere. In various embodiments, the process chamber 11a includes an outlet airlock 19 that allows the biocoal 23 to leave the process chamber 11a while preventing air exchange between the interior of the process chamber 11a and the ambient atmosphere.

[0061] The duct 13 includes a fan 20 to transfer the syngas 23 from the process chamber 11a to the oxidizer 12. In some embodiments, the pressure in the process chamber 11a transfers the syngas 23 to the oxidizer 12 and no fan is required. In another embodiment, the fan 20 creates a pressure within the process chamber 11a that is lower than the ambient pressure. Therefore, if the process chamber 11a has a leak, less syngas will leave the process chamber 11a through the leak into the environment.

[0062] Figure 2is a schematic diagram showing an embodiment of the reagents in the process chamber 11a and the products of different energy contents. In an embodiment comprising mainly biomass from wood, the reagents fed into the process chamber 11a mainly include carbon C, oxygen O and hydrogen H. In various embodiments, the reagents from the wood also contain ash, moisture contained in the wood, moisture from hydrogen if wood is supplied, and moisture in the air. In one embodiment, about 49% of the mass of the wood is carbon C, about 44% is oxygen O, about 6% is hydrogen H, and the rest (about 1%) is composed of ash, nitrogen and other elements. Other reagents are moisture from different sources, such as wood moisture, moisture from hydrogen and moisture from the air that enters the process chamber 11a together with the dried biomass and / or compressed air.

[0063] Figure 2 The three slanted solid lines in show the qualitative distribution of the biomass content in the biocoal and the syngas with different energy densities per ton in the biocoal 24 after torrefaction. In particular, the part of the figure on the left side of each slanted solid line becomes the biocoal 24, and the part of the figure on the right side of each slanted solid line becomes the syngas 23.

[0064] Therefore, the slope of the biocoal with an energy density of 21 GJ / ton provides a content distribution in the biocoal that is not much different from dry biomass. Most importantly, the syngas produced contains very little carbon C. Therefore, very little tar needs to be removed from the syngas.

[0065] The slope for a 24 GJ / ton energy density biocoal provides a distribution where the biocoal contains from about a quarter to less than half of non-carbon elements such as oxygen O and hydrogen H. Because a large amount of energy is contained in the carbon, the energy density increases when the oxygen O is removed. However, the syngas for the 24 GJ / ton energy density biocoal also contains more carbon C, and therefore more tar, than the previously discussed biocoal.

[0066] The slope of the biocoal with an energy density of 30 GJ / ton provides a profile in which the biocoal contains relatively small amounts of oxygen O and hydrogen H to achieve such a high energy density. Figure 2 It is also shown that synthesis gas with an energy density of 30 GJ / ton contains a lot of carbon and therefore a lot of tar.

[0067] In the process according to the invention, the tar is retained and burned together with the synthesis gas to operate the process chamber 11a and dry the biomass. The tar therefore does not need to be handled separately from the torrefaction plant, but rather delivers energy to operate the torrefaction plant. Typically the energy of the tar comes from the carbon and hydrogen content of the synthesis gas.

[0068] The energy density of the bio-coal depends specifically on the residence time of the torrefied biomass 22 in the process chamber 11a and the resulting final temperature of the biomass 22. For example, for a process chamber 11a at a temperature of about 500°C, a time of 15 minutes provides a bio-coal with an energy density of about 22 GJ / ton. As shown by the time arrow, an increase in residence time at the same temperature increases the energy density. For a residence time of 30 minutes, the energy density may be about 28 GJ / ton.

[0069] This also means that the amount of tar released from a specific volume of torrefied biomass increases over time. In some embodiments, the first and / or second air feeders 15, 16 are controlled to adapt the supply of hot compressed air to the process chamber 11a and / or the duct 13 to the amount of tar released from the torrefied biomass to keep the temperature of the syngas above the condensation temperature of the tar. In some embodiments, the process chamber 11a is arranged to operate continuously so that different degrees of torrefied biomass are in the process chamber 11a and the amount of tar released remains substantially constant over time.

[0070] In the following, the torrefaction process in the torrefaction apparatus according to the present invention will be described. Although the following description is based on a batch of biomass, it should be noted that the process is continuous so that the generated syngas can be used to heat the process chamber for the next batch.

[0071] The biomass 21 is fed to the dryer 17 where it is dried with the support of warm air 26 from the oxidizer 12. The dryer 17 together with the warm air 26 causes the biomass 21 to release water 27. The dryer 17 supplies the dried biomass 22. The dried biomass 22 is fed through the inlet airlock 18 to the process chamber 11a.

[0072] In the process chamber 11a, the dried biomass 22 is heated to about 280°C to 400°C so that it is torrefied and becomes biocoal 24 over time, while releasing synthesis gas 23. In various embodiments, the residence time of the dried biomass 22 in the process chamber 11a is between 15 and 30 minutes. In various embodiments, the temperature at the process chamber 11a is between 400°C and 550°C, preferably at about 500°C. Once the dried biomass 22 has become a predetermined grade of biocoal 24, i.e. after a predetermined residence time in the process chamber 11a, the biocoal 24 is released through the outlet airlock 19. The biocoal 24 is then transferred to various possible applications such as energy production, additives in steel production, or permanent carbon storage.

[0073] During the baking process, the synthesis gas 23 containing tar, H2, CH4 and / or CO is separated from the dried biomass 22 and passed through the pipeline 13. The synthesis gas 23 in the process chamber 11a and the pipeline 13 is maintained at a temperature higher than the condensation temperature of the tar to prevent the tar from condensing. In various embodiments, the condensation temperature is about 400°C. In various embodiments, the temperature is maintained by preventing temperature exchange with the environment of the process chamber 11a and the pipeline 13. In various embodiments, the temperature is maintained by burning a small amount of tar. In some embodiments, air is fed to the process chamber 11a and / or the pipeline 13 to burn the tar. In some embodiments, the air flow is controlled to keep the temperature in the synthesis gas 23 above the condensation temperature of the tar.

[0074] The syngas 23 is passed into the oxidizer 12. In various embodiments, air is fed to the oxidizer 12. In various embodiments, the air flow fed to the oxidizer 12 is at least sufficient to burn all combustible components of the syngas 23. In various embodiments, the air flow supplied to the oxidizer 12 is adjusted to burn all combustible components of the syngas 23 and to adjust the heat energy 25 provided from the oxidizer 12 to the process chamber 11a. In various embodiments, the air flow fed to the oxidizer 12 is adjusted so as to provide warm air 26 to the dryer 17 for drying the biomass 21. In various embodiments, the air flow in the oxidizer 12 is adjusted so as to adjust the temperature of the process chamber 11a to between 400°C and 550°C, preferably at about 500°C.

[0075] In various embodiments, the oxidizer air feeder 14 regulates the air flow. In various embodiments, the air flow is blocked in the oxidizer 12 and / or the oxidizer air feeder 14 to regulate the air flow. In various embodiments, the air flow in the oxidizer 12 is regulated in order to regulate the temperature of the process chamber 11a. In various embodiments, the material from which the process chamber 11a is made absorbs and dampens temperature fluctuations. This is particularly advantageous for biomass of different qualities that release different component portions of syngas during torrefaction.

[0076] Several examples of biomass input and biocoal output are provided below. Typically, biomass with a moisture content of about 10% is roughly between 16 GJ / ton and 19 GJ / ton. In the following examples, biomass is provided at a flow rate of 3100 kg / hr. This corresponds to a thermal power capacity of about 14.6 MW.

[0077] In a first example, the oxidizer 12 consumes about 3 MW in the form of synthesis gas to heat the process chamber 11a and dry the biomass. The process chamber 11a is heated to a temperature of 500°C. The residence time of the biomass in the process chamber 11a is about 15 minutes. During the residence time, the biomass is heated to about 280°C. The energy yield is about 22 GJ / ton or 11.6 MW, corresponding to about 79% of the energy contained in the original biomass.

[0078] In a second example, the oxidizer 12 consumes about 3.4 MW in the form of synthesis gas to heat the process chamber 11a and dry the biomass. The process chamber 11a is heated to a temperature of 500°C. The residence time of the biomass in the process chamber 11a is about 20 minutes. During the residence time, the biomass is heated to about 300°C. The energy yield is about 24 GJ / ton or 11.2 MW, corresponding to about 77% of the energy contained in the original biomass.

[0079] In a third example, the oxidizer 12 consumes about 4 MW in the form of synthesis gas to heat the process chamber 11a and dry the biomass. The process chamber 11a is heated to a temperature of 500°C. The residence time of the biomass in the process chamber 11a is about 25 minutes. During the residence time, the biomass is heated to about 350°C. The energy yield is about 28 GJ / ton or 10.6 MW, corresponding to about 72% of the energy contained in the original biomass.

[0080] In a fourth example, the oxidizer 12 consumes more than 4 MW in the form of synthesis gas to heat the process chamber 11a and dry the biomass. The process chamber 11a is heated to a temperature of 500°C. The residence time of the biomass in the process chamber 11a is about 30 minutes. During the residence time, the biomass is heated to more than 400°C. The energy yield is about 30 GJ / ton.

[0081] In all cases, the heat generated maintained the reaction chamber temperature while having sufficient excess energy to dry the wet biomass, which had 50% water by weight to about 10% water by weight at the process chamber inlet.

[0082] Note that biocoal can be used for steel production for high energy densities above 25 GJ / ton. In these examples, up to 100 kW of syngas 23 is combusted in process chamber 11a and / or duct 13 to keep the temperature of syngas 23 above the condensation temperature of the tar.

[0083] The table below shows several examples of processes according to different embodiments, where "Process energy yield" represents the energy retained in the biocoal after the roasting process, "Product energy ratio" represents the ratio between the energy density of the resulting biocoal and the starting biomass, "Energy input MJ / kg" represents the energy density of the starting biomass, "Energy output MJ / kg" represents the energy density of the resulting biocoal, and "Mass yield" represents the mass ratio of the resulting biocoal to the starting biomass.

[0084]

Claims

1. A baking device, comprising: - a process chamber configured to accommodate a torrefaction process of biomass; - an oxidizer arranged to heat the process chamber; and - a conduit for syngas released from the biomass during the torrefaction process; wherein the conduit is arranged to conduct the syngas from the process chamber to the oxidiser; and wherein the oxidiser is configured to provide oxidation of the syngas with a release of energy which is at least 20% of the energy contained in the maximum biomass flow passing through the process chamber. 2 . The torrefaction apparatus of claim 1 , wherein the conduit is configured to maintain a syngas temperature during operation above a condensation temperature of the syngas from the process chamber.

3. Torrefaction apparatus according to claim 2, wherein the syngas temperature is maintained at a temperature above 330°C and / or at least 50°C above the maximum temperature of the biomass in the process chamber.

4. Baking apparatus according to any one of the preceding claims, wherein the duct is thermally insulated.

5. Torrefaction apparatus according to any one of the preceding claims, wherein the duct and / or the process chamber comprises an air inlet to allow controlled combustion of a portion of the synthesis gas.

6. Baking equipment according to any of the preceding claims, wherein the oxidizer is configured to provide oxidation, which releases energy of at least 23%, 25% or 27% of the energy contained in the maximum biomass flow through the process chamber, preferably, the oxidizer is configured to provide oxidation, which releases energy not exceeding 36% or 40% of the energy contained in the maximum biomass flow through the process chamber.

7. Baking apparatus according to any one of the preceding claims, wherein the oxidiser is configured to maintain the process chamber at a temperature between 400°C and 550°C, preferably at about 500°C.

8. Baking apparatus according to any one of the preceding claims, wherein the oxidiser is provided with an oxidiser air feeder configured to maintain the temperature of the process chamber below 550°C, preferably below 500°C, by generating a flow of ambient dilution air in the direction of the process chamber.

9. Baking apparatus according to claim 7 or 8, wherein the process chamber has a rated temperature below 600°C, preferably 550°C and below.

10. Torrefaction apparatus according to any of the preceding claims, wherein the process chamber comprises a feed element, a conveying element and / or a distribution element, the process chamber being configured to hold a specific volume of biomass in the process chamber for at least 15 minutes, preferably at least 30 minutes.

11. A torrefaction apparatus according to any one of the preceding claims, wherein the process chamber is configured to minimize spontaneous air exchange between its contents and ambient air, wherein the process chamber preferably comprises an inlet with an airlock and an outlet with an airlock to convey biomass through the inlet, the process chamber and the outlet, wherein the process chamber is preferably maintained at a pressure below the ambient air pressure.

12. A torrefaction apparatus according to any one of the preceding claims, wherein the syngas comprises tar, H2, CH4 and / or CO, wherein the oxidiser is preferably configured to combust at least part of the tar.

13. A baking method, comprising: transferring biomass through a process chamber; heating the biomass in the process chamber to a temperature and pyrolyzing the biomass to release syngas from the biomass, wherein the syngas comprises at least 20% of the energy contained in the biomass stream; and The syngas is oxidized to heat the biomass in the process chamber.

14. Torrefaction method according to claim 13, wherein the specified volume of biomass is maintained in the process chamber for at least 15 minutes, preferably at least 30 minutes.

15. Torrefaction method according to any one of claims 13 to 14, wherein the syngas temperature is maintained at above 330°C and / or at a temperature at least 50°C above the maximum temperature of the biomass in the process chamber.

16. A torrefaction method according to claim 15, wherein the syngas is mixed with a controlled air flow, preferably to heat the air.

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