Method and system for producing fuel from compressed biomass

Abstract

The invention relates to a method for producing fuel from compressed biomass, said method comprising the following: providing biomass; washing the biomass; comminuting, in particular finely comminuting, the biomass; mechanically dewatering the biomass; drying the biomass; and shaping the biomass; wherein at least some of the waste heat is fed back into the method, in particular into another method step. The invention also relates to a corresponding system (100) for producing fuel from compressed biomass, to a computer-readable medium, and to a program element.

Description

[0001] Process and system for producing fuel from pressed biomass

[0002] AREA OF INVENTION

[0003] The present invention relates to a method and a system for producing fuel from pressed biomass. The present invention further relates to a computer-readable medium and a program element.

[0004] BACKGROUND AND STATE OF THE ART

[0005] The production of fuel, for example in the form of pellets or briquettes, from biomass such as green waste or leaves is a well-known process. For example, WO 2004 / 067685 Al describes a process for producing fuel from pressed biomass, in which the biomass undergoes a comminution and a drying process before being pressed into pellets. Further details on the comminution process are described, among others, in DE 10 2008 035 222 Al and DE 10 2008 064 803 B3. The use of a waterjet cutter and washing the biomass has also proven advantageous, as described in DE 10 2012 203 148 B3. For drying, a contact dryer can be used, for example, as described in DE 10 2016 213 956 Al.

[0006] However, the shredding, cleaning, dewatering, and drying of the biomass used requires a considerable amount of resources (water, energy). Currently, no functioning heat recovery systems exist that meet the specific requirements of pellet production (e.g., energy-optimized pellets).

[0007] Removal of contaminants while maintaining the calorific value of the pellets).

[0008] There is therefore still a need for improvements and optimizations in a process for producing fuel from pressed biomass and in a system used or suitable for this purpose.

[0009] TASK OF INVENTION

[0010] One object of the present invention is therefore to provide an optimized process and system for the production of fuel from pressed biomass, which in particular has a lower energy consumption or improved energy efficiency in the production of the fuel while maintaining a high calorific value of the fuel.

[0011] SUMMARY OF THE INVENTION

[0012] The inventors of the present invention have conducted extensive investigations and have found that this problem can be solved by heat recovery (HR), in particular HR that is tailored to the components of the biomass and the system and optimized taking into account the quality (mechanical strength, calorific value, impurities) of the fuel. In particular, the biomass itself can transport thermal energy from one process step to another during processing; thus, the heat capacity of the biomass can be used for intermediate storage during processing.

[0013] The individual components of the system, such as a washing unit, a comminution device, in particular a fine comminution device, a mechanical dewatering device, a drying device, and a shaping device, introduce energy into the biomass (for example, heating the biomass through pressure in a press during dewatering) and also heat wastewater (for example, press water from the mechanical dewatering device) or exhaust air (for example, during thermal drying). Additionally, they produce waste heat (for example, electric motors with an efficiency of less than 100%, warm exhaust air from drying processes, etc.). According to the invention, all this energy or heat can be fed back into the process and thus recovered, taking into account the product- and process-specific details.

[0014] The present invention relates accordingly to a process for producing fuel from pressed biomass, wherein the process comprises the following steps: providing (storing) biomass, feeding the (provided) biomass, washing the (fed) biomass, comminution, in particular fine comminution, of the (washed) biomass, mechanical dewatering of the (compressed) biomass, (thermal) drying of the (mechanically dewatered) biomass, and shaping (optionally including compaction) of the (dried) biomass. At least a portion of the waste heat from a process step (in particular the waste heat or other energy released during a process step) is fed back into the process, in particular to another process step.

[0015] Furthermore, the present invention relates to a system (arrangement, device) for producing fuel from pressed biomass, in particular for carrying out a process as described herein, wherein the system comprises a washing unit, a comminution device, in particular a fine comminution device, a mechanical dewatering device, a drying device, and a shaping device (optionally including a compaction device). The system further comprises a heat recovery device. The heat recovery device can, in particular, be configured such that at least a portion of the waste heat from a component of the system, such as a washing unit, a comminution device, in particular a fine comminution device, a mechanical dewatering device, a drying device, a shaping device, or another component of the system, is recovered (recirculated).

[0016] Furthermore, the present invention relates to a computer-readable medium on which a computer program is stored, wherein the computer program is configured such that, when executed on a processor, it controls and / or regulates a method and / or a system for producing fuel from compressed biomass as described herein.

[0017] Furthermore, the present invention relates to a program element which, when executed on a processor, controls and / or regulates a method and / or a system for producing fuel from pressed biomass as described herein.

[0018] Further tasks and advantages of embodiments of the present invention will become apparent from the following detailed description and the accompanying illustration.

[0019] BRIEF DESCRIPTION OF THE IMAGE

[0020] Figure 1 is a schematic representation of a system for producing fuel from compressed biomass according to an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Further details of the present invention and other embodiments thereof are described below. However, the present invention is not limited to the following detailed description, which merely serves to illustrate the teachings of the invention.

[0022] It should be noted that features described in connection with one exemplary embodiment can be combined with any other exemplary embodiment. In particular, features described in connection with one exemplary embodiment of a method according to the invention can be combined with any other exemplary embodiment of a method according to the invention, as well as with any exemplary embodiment of a system according to the invention, as well as with any exemplary embodiment of a computer-readable medium according to the invention and any exemplary embodiment of a program element according to the invention, and vice versa, unless expressly stated otherwise.

[0023] When a term is used with an indefinite or definite article, such as "ein," "eine," "eines," "der," "die," and "das" in the singular, this also includes the plural form, and vice versa, unless the context clearly indicates otherwise. The expressions "aufweisen" and "umfassen," as used here, do not only include the meaning of "contain" or "include," but can also mean "consist of" and "essentially consist of."

[0024] Unless explicitly stated otherwise, the terms "at least partially" or "at least a part" as used here can mean at least 1% of it, at least 2% of it, at least 5% of it, at least 10% of it, at least 15% of it, at least 20% of it, at least 25% of it, at least 30% of it, at least 35% of it, at least 40% of it, at least 45% of it, at least 50% of it, at least 55% of it, at least 60% of it, at least 65% of it, at least 70% of it, at least 75% of it, at least 80% of it, at least 85% of it, at least 90% of it, at least 95% of it, at least 98% of it, at least 99% of it, and can also mean 100% of it.

[0025] In a first aspect, the present invention relates to a method for producing fuel from pressed biomass. The fuel from pressed biomass can, in particular, be pellets and / or briquettes.

[0026] For the purposes of this application, "biomass" refers in particular to plant products that can be used to generate heating energy, electrical energy and as fuels.

[0027] For the purposes of this application, "pellets" are understood to mean, in particular, small bodies made of compressed material in the shape of balls or cylinders. These can be, in particular, combustible granules used as a heating fuel. The typical diameter of pellets is between 6 and 25 mm. Pellets are mostly used in automatically fed combustion systems and pellet stoves, which offer a similar level of convenience to oil or gas heating systems; however, they are also suitable for firing large-scale systems (e.g., thermal power plants, steam boilers, etc.).

[0028] For the purposes of this application, "briquettes" are understood to mean in particular compressed fuel material with a larger size than pellets, for example with a diameter greater than 25 mm.

[0029] The steps of providing, washing, crushing, in particular fine crushing, mechanical dewatering, drying and shaping (including compaction) can in principle be carried out in an analogous manner as in the literature mentioned at the outset.

[0030] In connection with the present invention, it is important that at least some of the waste heat from a process step (in particular the waste heat or other energy released during a process step) is fed back into the process, in particular to another process step. In other words, heat recovery takes place in the process.

[0031] For the purposes of this application, "waste heat" is understood to mean in particular heat or, more generally, energy that is released during a process step or that was formed as a by-product.

[0032] For the purposes of this application, "heat recovery" is understood to mean any type of heat recovery (HR), including both active and passive HR. Heat recovery particularly includes the reuse of the thermal energy of a mass flow leaving the process.

[0033] In the context of this application, "active heat recovery" refers in particular to the use of a heat pump-like energy recovery system, which is also often referred to as mechanical heat recovery.

[0034] Within the scope of this application, "passive heat recovery" refers in particular to the heating of one mass flow by means of another mass flow of a higher temperature, which is exiting the process (typically by means of a heat exchanger or also by means of simple thermal coupling, e.g., by housing two mass flows with different temperatures within the same containment). Despite the term "passive," only pumping or conveying energy may be required. Heating in passive heat recovery can be achieved either by thermal coupling (i.e., while maintaining the separation of the two mass flows, for example, by means of a plate heat exchanger) or by mixing (e.g., increasing the temperature of one mass flow by mixing it with a mass flow of a higher temperature).

[0035] According to an exemplary embodiment, at least a portion of the (provided) biomass is selected from the group consisting of water hyacinths, seagrass, algae, grass clippings, leaves, green waste, and combinations thereof. It has been found that the type, biological properties, and mechanical form of the biomass components are relevant for maintaining a high calorific value (despite the removal of concentrated press water containing organic compounds). It has also been found that biomass from seagrass, water hyacinths, algae, grass clippings, and / or leaves does not have such a high proportion of substances that can be squeezed out at moderate temperatures (e.g.,The lack of readily soluble resins – unlike spruce, fir, or pine needles, which have a high resin content but are not shed as leaves in autumn – means that these resins are particularly readily precipitated by the temperature increase according to the invention during mechanical dewatering, thereby significantly reducing the calorific value of the remaining biomass. Furthermore, it was found that the mechanical properties of the listed materials (especially when finely cut) greatly facilitate heat transfer. This is because the predominantly flat material (e.g., a leaf) has a large contact area relative to its volume when in contact with another flat leaf, which greatly enhances heat conduction. This increases the efficiency of heat transfer, i.e., thermal coupling.

[0036] According to an exemplary embodiment, the waste heat or the energy to be recovered originates from at least one of the following heat sources: warm exhaust air (from thermal drying (especially moisture-laden, which means an increase in latent heat per standard volume)),

[0037] Press water at high temperature (press water from the second mechanical drainage, which has absorbed a relatively large amount of energy, since a great deal of energy is introduced into the second mechanical drainage),

[0038] Low-temperature press water (press water from the first mechanical dewatering, which makes up a relatively large volume for pollutant removal but has only experienced a small temperature increase), cooling air (air for cooling process components (e.g. motors), which is heated and thus represents a heat source),

[0039] Residual heat from drying (waste heat / side heat from thermal drying) and / or finished fuel (which is still warm after shaping and can be cooled by means of a heat exchange process, making the heated mass flow available again as a heat transfer medium). In particular, two, preferably three or more of these heat sources can be used.

[0040] According to an exemplary embodiment, the drying process comprises thermal drying of the biomass by heating it to a temperature above 60 °C, particularly above 80 °C, and preferably above 95 °C. During thermal drying, the biomass is heated to an elevated temperature and dried. To ensure the efficiency of this phase of fuel production, it is advantageous for the biomass temperature to be above 60 °C, particularly above 80 °C, and preferably above 95 °C. The higher the temperature, the faster the residual moisture remaining in the biomass is reduced by being released into the surrounding air. However, this requires heating the biomass to the required temperature. The higher the temperature of the biomass when it is subjected to thermal drying, the lower the thermal energy requirement for the drying process.

[0041] According to an exemplary embodiment, the mechanical dewatering of the biomass is carried out in two stages (for example, in two stages of a dewatering unit or in two process steps in two different dewatering units). If the biomass (or substances added to the biomass, for example, for moistening or washing the biomass) is heated with waste heat from the process, it is advantageous to reduce the mass of the biomass as early as possible. This can be optimized by removing moisture from the biomass in several, preferably early, steps. This reduces the mass to be heated and saves energy throughout the entire production process. This can be achieved, for example, by adding one, preferably two (i.e., two mechanical dewatering systems sequentially) mechanical dewatering systems downstream of the washing process (and any fine grinding).

[0042] According to an exemplary embodiment, at least some of the waste heat from a process step is passively and / or actively, and in particular both passively and actively, fed back into the process. As mentioned above, heat recovery can be passive (for example, by means of a heat exchanger) or active (for example, by means of a heat pump), and in particular a combination of both. Mass flows can also be used for active heat recovery; for example, a heat pump can be used to cool the press water or wastewater (or the outside air) to contribute thermally to the drying process, but this requires a corresponding primary energy input. Under certain conditions, however, the combination of active and passive heat recovery has proven to be more energy-efficient overall. Furthermore, a partially closed air circuit can also be implemented within the thermal drying process, so that, for example,Circulating air is dehumidified and kept at temperature.

[0043] According to an exemplary embodiment, the process further comprises increasing the temperature of the biomass before (thermal) drying, in particular before mechanical dewatering, preferably before, during, and / or after comminution. The greater the temperature difference between two mass streams, the more heat energy can be transferred. It is therefore advantageous if the temperature of the biomass is increased not only before (thermal) drying, but, for example, before mechanical dewatering and / or between mechanical dewatering stages (in the case of multiple mechanical dewatering stages), preferably before or during comminution.

[0044] According to an exemplary embodiment, after mechanical dewatering (especially after the final mechanical dewatering in the case of multiple mechanical dewatering), the temperature of the biomass is above 60 °C, particularly above 70 °C, preferably above 80 °C. Preferably, the temperature of the biomass is below 130 °C. At these temperatures, an energetically efficient preheating of the biomass can be achieved without leaching out too many substances (e.g., lignins) and thus affecting the mechanical strength of the pellets.

[0045] According to an exemplary embodiment, the process further comprises increasing the moisture content of the biomass prior to mechanical dewatering, particularly before, during, and / or after the comminution of the biomass. Within the scope of this application, "moisture" or "moisture content" of a biomass is understood to mean not only water or aqueous components, but the entire residue that does not constitute the dry matter (DM) of the biomass. Thus, moisture = 100% minus DM in %. In addition to water or aqueous components, the moisture therefore also includes other fluids such as volatile oil components, etc. The dry matter can be measured in the laboratory. A weighed sample of the mixture is taken and heated to over 100 °C in a drying chamber to evaporate the residual moisture (usually water). The remaining dry residue is weighed and compared to the dry matter content. This yields the dry matter content of the mixture.The liquid that evaporates during this measurement is referred to as the moisture content (in %).

[0046] According to an exemplary embodiment, press water generated during mechanical dewatering is used to increase the moisture content of the biomass. In particular, in the case of multiple mechanical dewatering processes, press water generated during the first mechanical dewatering can be used. Preferably, the moisture content of the biomass is increased before, during, and / or after shredding. This allows the heat from the press water of the first mechanical dewatering to be used particularly efficiently. If the moisture increase occurs precisely in the last step before mechanical dewatering, the least amount of heat recovery heat is lost through cooling.

[0047] According to one exemplary embodiment, condensate from a heat recovery device is used to increase the moisture content of the biomass. In particular, moisture-laden exhaust air can be used to heat the biomass via a heat exchanger. As the exhaust air cools against the cooler biomass, moisture condenses. This condensate can then be collected for humidifying the biomass and / or the water cutter, thus saving resources. The additional increase in the moisture content of the biomass allows for more efficient or improved removal of contaminants.

[0048] According to an exemplary embodiment, by recirculating a portion of the waste heat, at least a portion of the biomass is heated by more than 2 °C, in particular more than 5 °C, preferably more than 10 °C. This ensures that heat recovery can be carried out economically, in particular that the energy savings achieved through heat recovery exceed its investment costs.

[0049] According to an exemplary embodiment, by recirculating a portion of the waste heat, at least a portion of the biomass is heated after washing, particularly after comminution, and preferably after the first mechanical dewatering in the case of multiple mechanical dewatering. It is advantageous to heat the biomass in the process only after a volume reduction through moisture reduction using heat recovery, because the resulting mass reduction of the biomass relative to the pellet volume produced allows for better utilization of the recovered energy. The first process step for volume reduction is the recirculation of the wash water into the washing circuit at the washing unit. This means that heating the biomass using heat recovery is particularly beneficial if it is carried out before comminution, especially before the first mechanical dewatering, and preferably before the second mechanical dewatering.

[0050] According to an exemplary embodiment, the extent (or degree) of heat recovery is influenced by the type of biomass, and in particular, controlled or regulated depending on the biomass, preferably with further heat recovery-independent process parameters also being (co-)controlled depending on this. The degree of heat recovery is influenced by the type and properties of the biomass – either because its starting temperature varies or its moisture content or content of resins, lignins, and oils differs. For this reason, it is energetically advantageous to also selectively control or even regulate (in particular automatically or semi-automatically) the heat recovery (process parameters).

[0051] According to an exemplary embodiment, the cooling system is used to...

[0052] Air used by motors is utilized as waste heat. In particular, the airflow from the motor cooling system can be used for this purpose. The temperature of this air is preferably more than 10 °C, more preferably more than 20 °C, and more preferably more than 40 °C, higher than the ambient temperature of the system. A typical large electric drive (asynchronous motor with gearbox, 45 kW electrical), such as can be used in a method according to the invention, has an efficiency of slightly over 90%, meaning that 4 kW of waste heat is generated, which can be used for heat recovery. For a medium-sized system with a typical connected load of 150 kW, this is typically 20 kW. Asynchronous motors may be operated up to a housing temperature of 80 to 100 °C. By selectively collecting the cooling air and, if necessary, appropriately adjusting the airflow (e.g.,By reducing the airflow (ensuring the air actually heats up to the required high temperature), a high-quality thermal waste heat source can be utilized. This relatively warm air can then further heat biomass (ideally preheated with pressurized water), thus achieving a relatively high temperature boost for the biomass using passive heat recovery. In this way, it can be ensured that the cooling air for engines is more than 10 or 20 °C, and especially more than 40 °C, above the ambient temperature of the system.

[0053] According to one exemplary embodiment, the water used for washing circulates at least partially within the system. Fresh water supplied is typically relatively cold (in relation to temperatures in pellet production). If the washing water is at least partially integrated into an internal system circuit, energy conservation can be achieved, thus largely preventing (unnecessary) cooling of the biomass by the fresh water.

[0054] According to an exemplary embodiment, the method further comprises measuring the temperature of at least one mass flow. The measured temperature can then be used to control and / or regulate the recovery of a portion of the waste heat, preferably semi-automatically or fully automatically. By measuring the temperature of a mass flow, the efficiency of the heat recovery system can be optimized. For example, in staggered heat recovery systems, it can prevent pump energy from being used for heat recovery when a still-cold system is started up, or prevent the biomass from being cooled instead of heated due to an excessively cold mass flow. Data processing can trigger the control and / or regulation of the heat recovery system based on the temperature of one (or more) mass flows. This process can be implemented semi-automatically or fully automatically, thus preventing errors.

[0055] According to an exemplary embodiment, the extent (or degree) of recovering a portion of the waste heat (for example, the extent of the temperature increase) is determined, at least in part, based on data, particularly measured values, that provide information about the composition of the biomass's constituents and / or contaminants. Depending on this data, the heat recovery (HR) and / or energy consumption can be optimized. For heavily contaminated biomass, more liquid (e.g., fresh water) can be added to remove contaminants, which worsens the overall energy balance and reduces the HR effects, as more water needs to be heated. Conversely, reducing the use of wash water or humidifying agents (in the sense of resource optimization) leads to an improvement in the overall energy balance.

[0056] According to an exemplary embodiment, some of the waste heat is recovered to biomass after washing and / or to biomass towards the end of the washing step (i.e., in particular, that the biomass is heated only after the first gravimetric removal of contaminants). It is rather energy-inefficient for a passive heat recovery system to heat the biomass before gravity-based (gravimetric) removal of contaminants has taken place, as energy is then wasted heating foreign material (e.g., sand and gravel delivered with the leaves). A particularly suitable location for this initial removal of contaminants is the washing unit. It is therefore advantageous if the biomass is heated only after the washing unit (where the energy supplied to the washing unit (e.g., by a high-pressure water jet cutter) can be retained, for example, by external insulation of the washing unit or by housing the washing unit in an external containment).

[0057] According to an exemplary embodiment, the biomass is moistened before mechanical dewatering, particularly before washing. It can be especially advantageous if the time interval between moistening and mechanical dewatering is at least 10 minutes, particularly at least 30 minutes, particularly at least 2 hours, and particularly at least 6 hours. This time interval can also be referred to as the moistening exposure time. Such a procedure allows, for example, the dissolution (or partial dissolution) of salts in addition to the actual washing process. In particular, the dissolution process of salts is also relatively slow, meaning that the throughput through the washing unit is limited by the dissolution time of the salts.If this humidification is carried out more than 10 minutes, more than 30 minutes, more than 2 hours or even more than 6 hours before washing, different contaminants can dissolve and the removal of contaminants is optimized.

[0058] According to an exemplary embodiment.

[0059] According to one exemplary embodiment, the mechanical dewatering of the biomass is carried out in multiple stages (for example, in several stages of a dewatering system or in several process steps in different dewatering systems). In particular, the shear forces acting on the biomass in the different dewatering systems can differ. Consequently, the wastewater compositions of the different dewatering systems can also differ. In multi-stage dewatering, for example, the different dewatering systems can be designed such that they exert different shear forces on the biomass. This results in different degrees of cell disruption of the biomass, leading, for example, to the wastewater from the two dewatering systems exhibiting different protein concentrations and levels of contaminants.

[0060] According to one exemplary embodiment, a biomass is used which (before being fed in) has been stored under mechanical pressure for at least one day. This can increase the homogeneity of the biomass used, particularly with regard to moisture distribution and / or the degree of microbial decomposition.

[0061] According to an exemplary embodiment, at least a portion of the waste heat from a process step is actively recovered and fed back into the process, wherein the temperature difference of the actively recovered heat is less than 60 °C, in particular less than 45 °C, preferably less than 30 °C. Additionally or alternatively, the residual heat from the fuel, extracted from pressed biomass, can be passively recovered and fed back into the process, in particular to another process step, after shaping. The temperature of the thermal drying process can be supported by active heat recovery. Active heat recovery (e.g., using a heat pump) achieves its best efficiency when the temperature difference between the condensation temperature in the condenser and the evaporation temperature in the evaporator is as small as possible. The absolute value and the operating point of such a system can be optimized relatively well by selecting the refrigerant and the internal pressure conditions.However, to operate with the smallest possible temperature difference, it is highly advantageous if the material to be dried is already at an elevated temperature. The solution according to the invention, in particular the combination of active and passive heat recovery, is helpful in this regard and, as already described, can be optimized for the specific characteristics of pellet production. Investigations have shown that this makes it possible to operate thermal drying with a temperature difference of less than 60 °C for active heat recovery, in particular less than 45 °C, preferably less than 30 °C, while maintaining pellet quality. Optimization of thermal drying has also shown that an overall energy reduction is achieved when the residual heat from the pellets / briquettes is fed back into the system after shaping using passive heat recovery (e.g., for preheating the biomass).It has been shown that heat recovery from finished pellets / briquettes is not trivial: If they are subjected to excessive mechanical movement (e.g., to transfer heat via conduction through contact), their strength decreases (even to the point of disintegration). Conversely, air circulation presents the problem of the dew point: Even before the dew point of the blown-through gas is reached, moisture absorption occurs, which significantly reduces product quality. One possible solution involves passing dried air through the heated pellets and subsequently using this heated air to, for example, heat the biomass.

[0062] According to one exemplary embodiment, heat (thermal energy) from the biomass and / or the fuel is fed back into the process during and / or after (thermal) drying (passively and / or actively). Heat from the biomass and / or the pellets / bricks can be used during and / or after thermal drying. This can occur before, during, or after the shaping of the biomass. If the heat of the biomass is reduced before or during shaping (for example, the shaping tool can be liquid-cooled, e.g., with supplied fresh water or press water, which subsequently reheats the biomass), this can lead to better dimensional stability of the resulting biomass because the viscous components remaining in the biomass become more viscous (e.g., lignins and resins). In addition to the described passive heat recovery, the corresponding residual heat can, of course, also be utilized by means of active heat recovery.

[0063] According to an exemplary embodiment, at least some of the waste heat from mechanical dewatering, in particular the heat from the press water generated during mechanical dewatering, and / or the heat from the biomass (heated by the mechanical dewatering, especially pressing), is (passively and / or actively) fed back into the process. For example, press water from the mechanical dewatering (heated by the dewatering process) can be fed to the washing unit and / or used to increase the moisture content of the biomass. This increases the temperature of the biomass for subsequent drying. Especially when feeding press water back into the washing process, it can be particularly advantageous to use multi-stage mechanical dewatering – this allows for a press water stream with a lower content of impurities (salts, OH compounds, etc.).(from biomass) and are at least partially reintroduced into the process as a cycle component with higher heat.

[0064] According to an exemplary embodiment, the process further comprises passing air through the biomass (aerating the biomass) between mechanical dewatering and (thermal) drying. This can be carried out in such a way that the moisture content of the biomass decreases by more than 5%, particularly more than 10%, preferably more than 15%. If intermediate storage is provided for the transition between mechanical dewatering and thermal drying, passing air through the biomass (aerating) can lead to a reduction in the absolute moisture content of more than 5%, particularly more than 10%, preferably more than 15%. When the biomass heated by mechanical dewatering is permeated with air, a drying effect occurs. High efficiency is achieved because the air is used primarily not (only) as a heat transfer medium, but (also) as a moisture transporter.By increasing the humidity of the air flowing through it, better moisture coupling is achieved due to the increased biomass temperature, without the need to heat the biomass additionally.

[0065] According to an exemplary embodiment, the fresh water used for washing and / or increasing the moisture content of the biomass is warmer than 1 °C, in particular more than 2 °C, in particular more than 4 °C, in particular more than 5 °C, in particular more than 8 °C, than the (average) temperature of the biomass, and / or the biomass is preheated with external heat. With fresh water, the inlet temperature is typically around 15 °C, which is at least somewhat warmer than the average air temperature of approximately 10 °C (which roughly corresponds to the biomass temperature) for most applications – especially in winter, the temperature differences are even greater. Thus, the use of fresh water preheats the biomass, and with good thermal insulation of the production area, this temperature increase can be maintained until drying, which reduces the amount of drying energy required.It can be particularly advantageous to preheat the fresh water using residual heat from another, especially external, industrial process. There are few suitable uses for waste heat below 60 °C. Furthermore, data centers with warm water cooling (waste heat temperature typically 55 °C) could be used to preheat the tap water and / or biomass. This would allow, for example, the wash water, including the biomass, to be heated to 40 °C or more, while the return temperature for the data center remains below 30 °C (for warm water cooling).

[0066] A process according to the invention for producing fuel from pressed biomass can in particular be carried out by means of a system for producing fuel from pressed biomass according to the second aspect explained in more detail below.

[0067] In a second aspect, the present invention relates to a system for producing fuel from compressed biomass. The system may be particularly suitable for carrying out a process for producing fuel from compressed biomass according to the first aspect explained in more detail above. Descriptions of features already given above in connection with the first aspect apply analogously to the same or similar features in connection with the second aspect, even if they are not explicitly repeated.

[0068] The individual components of the system, such as a washing unit, a comminution device, in particular a fine comminution device, a mechanical dewatering device, a drying device, a shaping device (possibly including a compaction device), can in principle correspond to the components as disclosed in the aforementioned literature.

[0069] In connection with the second aspect of the present invention, it is important that the system further comprises a heat recovery device. The heat recovery device is configured, in particular, such that at least a portion of the waste heat from a component of the system, such as a washing unit, a comminution device, especially a fine comminution device, a mechanical dewatering device, a drying device, a forming device, or another component of the system, is recovered (recirculated).

[0070] According to an exemplary embodiment, the mechanical dewatering device comprises a two-stage dewatering device or at least one, preferably two, dewatering devices. If the biomass (or substances added to the biomass, for example, for moistening or washing the biomass) is heated with waste heat from the process, it is advantageous to reduce the biomass mass as early as possible. This can be optimized by removing moisture from the biomass in several, preferably early, steps. This reduces the mass to be heated and saves energy throughout the entire production process. This can be achieved, for example, by placing one, preferably two, mechanical dewatering devices (sequentially) downstream of the washing unit (and any fine grinding device).

[0071] According to an exemplary embodiment, the system is designed to produce more than 50 kg / h of fuel from pressed biomass, particularly more than 150 kg / h, and preferably more than 500 kg / h. For the heat recovery system to operate efficiently, a certain minimum throughput is required. Otherwise, despite any thermal insulation of the mass flows, the biomass will cool down too much before thermal drying, thus reducing efficiency. Very good results have been achieved when the system produces more than 50 kg, particularly more than 150 kg, and preferably more than 500 kg of fuel per hour.

[0072] According to an exemplary embodiment, the heat recovery device comprises an active heat recovery device and / or a passive heat recovery device. In particular, it can be advantageous to use both an active and a passive heat recovery device. As explained above, heat recovery can be passive (for example, by means of a heat exchanger) or active (for example, by means of a heat pump), and especially a combination of both. Mass flows can also be used for active heat recovery; for example, a heat pump can be used to make a thermal contribution to thermal drying by cooling the pressurized or wastewater (or the outside air). However, this requires a corresponding primary energy input. Under certain conditions, however, the combination of active and passive heat recovery has proven to be more energy-efficient overall.Furthermore, a partially closed air cycle can also be implemented within the thermal drying process, so that, for example, circulating air is dehumidified and kept at temperature.

[0073] According to an exemplary embodiment, the system further comprises a device for increasing the moisture content of the biomass, wherein the device is configured to increase the moisture content of the biomass before the biomass is fed to the mechanical dewatering unit. The system is specifically designed such that press water from the mechanical dewatering unit is routed to the device for increasing the moisture content of the biomass. In particular, in the case of multiple mechanical dewatering units, press water from the first mechanical dewatering unit can be routed to the device for increasing the moisture content of the biomass. Preferably, the device for increasing the moisture content of the biomass is arranged before, during, and / or after the shredding unit. This allows the heat from the press water of the first mechanical dewatering unit to be used particularly effectively.If the increase in humidity occurs in the last step before mechanical drainage, the least amount of heat recovery heat is lost through cooling.

[0074] According to one exemplary embodiment, the system is designed such that condensate from the heat recovery device is routed to the device for increasing the moisture content of the biomass. Specifically, moisture-laden exhaust air can be used to heat the biomass via a heat exchanger. As the exhaust air cools against the cooler biomass, moisture condenses. This condensate can then be collected for humidifying the biomass and / or the water cutter, thus saving resources. The additional increase in the moisture content of the biomass allows for more efficient or improved removal of contaminants.

[0075] According to an exemplary embodiment, the heat recovery device is designed such that the temperature of a portion of the biomass processed in the system increases by more than 2 °C, in particular more than 5 °C, preferably more than 10 °C. This ensures that heat recovery can be carried out economically, and in particular that the energy savings achieved through heat recovery exceed its investment costs.

[0076] According to an exemplary embodiment, the heat recovery device is designed such that a portion of the biomass processed in the system is heated after the washing unit, particularly after the shredding unit, and preferably after a first mechanical dewatering unit in the case of multiple mechanical dewatering units. It is advantageous to heat the biomass in the system only after a volume reduction through moisture reduction using heat recovery, because the resulting mass reduction of the biomass relative to the pellet volume produced allows for better utilization of the recovered energy. The first process step for volume reduction is the return of the wash water to the washing circuit at the washing unit.This means that heating the biomass using heat recovery is particularly advantageous when it is implemented upstream of the shredding unit, especially upstream of the first mechanical dewatering unit, and preferably upstream of the second mechanical dewatering unit. According to an exemplary embodiment, one or more components (such as the washing unit, shredding unit, especially the fine shredding unit, the mechanical dewatering unit, the (thermal) drying unit, and the shaping unit) and / or parts of the system are thermally insulated for transport (such as pipes or conveying equipment) and / or the temporary storage of biomass. This significantly reduces the cooling of the biomass, which is heated relative to the ambient temperature.

[0077] According to an exemplary embodiment, the system is housed in several individual enclosures, in particular wherein these are compatible with transport systems and / or provide at least one of the following additional benefits: sound insulation, energy optimization, odor reduction, installation simplification, logistics optimization and / or transport simplification.

[0078] According to one exemplary embodiment, the system is housed in several individual containments. These containments can be compatible with transport systems and / or offer at least one of the following additional benefits: sound insulation, energy optimization, odor reduction, simplified installation, optimized logistics, and / or simplified transport. The containments can be designed for relatively easy relocation to another site. A typical implementation involves installation in sea freight containers or using containments of compatible dimensions, allowing the individual modules to be easily transported and deployed by truck. These containments can provide additional benefits: 1) Certain areas can be additionally soundproofed. In particular, extensive containment of the functional system components inherently provides sound insulation. 2) The same applies to potential odor emissions.Targeted airflow within the enclosure (possibly with activated carbon filters) reduces potential odor emissions. 3) The enclosure also allows for the collection of waste heat and its targeted use for heat recovery or reuse. 4) Pre-assembly and adjustment of the subsystem components within the enclosure simplifies installation. The components can be pre-leveled on a support frame, so that only the entire frame needs to be leveled during installation, and the subcomponents are automatically aligned. 5) Housing the components in individual subsystems facilitates replacement in case of malfunctions, as a replacement container, for example, only needs to be delivered and connected from a central location, eliminating the need for specialists, especially in remote areas.

[0079] According to an exemplary embodiment, the mechanical dewatering device is a multi-stage dewatering device or comprises several dewatering devices. In particular, the different dewatering devices can be configured such that different shear forces act on the biomass. The different dewatering devices can also be configured such that the wastewater compositions differ from one another. In a multi-stage dewatering process with different dewatering systems designed to exert different shear forces on the biomass, different degrees of cell disruption of the biomass can be achieved, resulting, for example, in wastewater from the two dewatering systems exhibiting different protein concentrations and levels of contaminants.

[0080] According to an exemplary embodiment, the system further comprises one or more storage units configured to store biomass, at least partially, under mechanical pressure for at least one day. This increases the homogeneity of the biomass used, particularly with regard to moisture distribution and / or the degree of microbial decomposition. According to an exemplary embodiment, the heat recovery device is designed such that the coupling temperature difference is below 5 °C, particularly below 4 °C, particularly below 3 °C, particularly below 2 °C, and particularly below 1 °C. Within the scope of this application, "coupling temperature difference" is understood to mean, in particular, the sum of the heat exchange-related temperature differences of a heat recovery process. Heat recovery processes depend primarily on the respective coupling of the thermally utilized heat sources and heat sinks (especially in passive heat recovery).The efficiency of heat energy transfer depends primarily on the factors of temperature difference, thermal conductivity, exposure time, and contact area. It is important to keep the temperature difference as small as possible, as this represents a lost potential use of a heat source. The efficiency of heat recovery processes can be categorized as follows, where 1)-3) are examples of passive heat recovery and 4) represents active heat recovery.

[0081] 1) The most efficient method is the direct use of a heat source without a heat exchanger. In this process, a volume fraction of a warmer medium is mixed with a volume fraction of a colder medium, thus achieving the highest efficiency in utilizing the thermal energy of the warmer medium. Here, the aforementioned coupling temperature difference (apart from insulation and radiation losses) is 0 °C, meaning that the potential of the temperature differences between the two media is almost completely exploited.

[0082] 2) One step less efficient (in terms of a full cost accounting of operating and investment costs, i.e., taking into account pumping energy, temperature difference, heat exchanger size, proportion of reused energy, etc.) is the coupling of two mass flows in liquid form (for example, a water-to-water heat exchanger, a tube bundle, a reactor, or a plate heat exchanger). Typical coupling temperature differences of 2 to 5 °C are achieved in this case.

[0083] 3) Heat transfer is even less efficient when one or both mass flows are gaseous. This is because the power required to move an airflow through a heat exchanger in a pipe system with a fan is greater than in a water circuit with a pump and the same power output. For example, the efficiency of axial fans up to 10 kW power input averages between 25 and 45%, and that of free-running fans with backward-curved blades up to 10 kW power input is between 35 and 60%, while the efficiency of liquid pumps can reach up to 90%. With this type of heat transfer, the coupling temperature difference in typical industrial applications is between 3 and 7 °C, and this energy calculation also includes the pumping energy.

[0084] 4) The least efficient method, in terms of the aforementioned coupling temperature difference and the lost utilization potential due to the temperature difference of thermal coupling processes, is the heat pump, as it is typically operated with a heat transfer medium for the Carnot cycle, which must be decoupled from the two thermal mass flows. This necessitates two heat exchangers (one on the thermal source side and one on the thermal sink side), effectively doubling the lost thermal utilization potential. While a heat pump can achieve a temperature lift for heat transfer by utilizing external energy, this is irrelevant for the purposes of this analysis. Heat recovery processes, which require media separation for technical reasons (e.g., safety), also fall into this category.In this process, energy is transferred from one thermal mass flow to another thermal mass flow by means of a closed fluid circuit.

[0085] In a third aspect, the present invention relates to a computer-readable medium on which a computer program is stored, wherein the computer program is configured such that, when executed on a processor, it controls and / or regulates a method and / or a system for producing fuel from pressed biomass according to the first or second aspect.

[0086] In a fourth aspect, the present invention relates to a program element which is configured such that, when executed on a processor, it controls and / or regulates a method and / or a system for producing fuel from pressed biomass according to the first or second aspect.

[0087] Further considerations and embodiments relating to the present invention include the following:

[0088] Unlike a simple heat recovery system from the industrial or HVAC sector, for this process it is important to find, adjust, and, in particular, regulate the correct level of temperature increases in the biomass or the energy input for thermal drying in such a way that process parameter fluctuations or differences in the properties of the biomass do not lead to quality fluctuations in pellets or briquettes - and yet the process remains resource-optimized.

[0089] In addition to the fundamental mechanisms of mass flow interaction relevant to this process, which have already been discussed, there are further factors that significantly increase the complexity of heat recovery: Temperature has a (sometimes massive) influence on the biomass itself. Therefore, determining optimal heat recovery cannot be based solely on the heat recovery aspect derived from the balancing of thermal mass flows; the following relationships must also be considered:

[0090] 1) As the temperature of the biomass increases, the energy requirement for mechanical dewatering decreases (the biomass becomes less viscous / slippery, i.e., less mechanical energy is needed for cell disruption and wringing out the mass -> lower motor torque -> less current draw, but higher cos phi [reactive power component] for asynchronous motors without frequency converters).

[0091] 2) As the temperature increases, more and more components of the biomass transition into a liquid state (e.g., resins, lignins, oils, etc.). If these high-calorific-value materials are separated via mechanical dewatering, the calorific value of the pellets decreases (depending on the biomaterial). With an increase in temperature, these substances become more liquid, allowing them to be washed out more effectively, thus reducing the calorific value.

[0092] 3) If substances that are solid or sticky at room temperature are precipitated during dewatering due to the increased temperature of the biomass caused by heat recovery, the mechanical strength of the pellets may decrease (the binder that holds the powdery mass together as a pellet is missing).

[0093] 4) The extent and rate of separation of viscous components (e.g., resins, lignins, and oils) depend not only on the temperature but also on the residence time in the press: A material with a given viscosity flows through a sieve at a resulting velocity – this is not linear with the residence time. Therefore, less calorific value is reduced at a high conveying velocity in a press than at a long residence time. However, a high conveying velocity also means additional energy consumption. This can be partially recovered through the heat utilization according to the invention (e.g., using heat in the press water, maintaining the elevated biomass temperature until the next process step). (These relationships apply not only to press water separation but also to pellet pressing.)

[0094] 5) The energetically ideal dewatering volume of a mechanical dewatering process shifts with the temperature and the system throughput. 6) Depending on the efficiency (which in turn also depends on the throughput) of the thermal drying, the ideal operating point of the final mechanical dewatering process shifts, because the energy requirement of the mechanical dewatering increases non-linearly with the degree of drying.

[0095] 7) Since proteins in biomass begin to degrade at temperatures as low as 40 °C, the maximum temperature for biomass utilization for gasification or protein extraction differs from that required for energy-rich processes, due to the desired properties of these processes.

[0096] Pellets / briquettes. In particular, prior art known from the fermentation or anaerobic digestion context is not relevant to the problem underlying the invention - different priorities of heat recovery, as well as operating values ​​of the processes and the heat recovery operating points, must be selected for pellet production.

[0097] DETAILED DESCRIPTION OF THE IMAGE

[0098] Figure 1 is a schematic representation of a system 100 for producing fuel from pressed biomass according to an exemplary embodiment.

[0099] The system 100 shown in Figure 1 for producing fuel from pressed biomass comprises an optional storage unit 160, an optional feeding device 170, a washing unit 110, a comminution device 120, which may in particular be a fine comminution device, one or more mechanical dewatering devices 130, a drying device 140 and a shaping device 150. These components may, in principle, be such as those described in the literature cited above.The system 100 for producing fuel from pressed biomass has a heat recovery device 190, which is configured in particular to recover at least part of the waste heat from a component of the system 100, such as the washing unit 110, the crushing device 120, the mechanical dewatering device 130, the drying device 140, the shaping device 150 or another component of the system 100 (such as the storage unit 160 or the feeding device 170).

[0100] The fuel production system 100 shown in Figure 1 further comprises an optional device for increasing the moisture 166 of the biomass, which is set up (and arranged) to increase the moisture of the biomass before the biomass is fed to the mechanical dewatering device 130.

[0101] The present invention has been described with reference to specific embodiments and examples. However, the invention is not limited to these, and various modifications are possible without departing from the scope of the present invention.

[0102] List of symbols

[0103] 100 Systems for producing fuel from pressed biomass

[0104] 110 Washing unit 120 Shredding unit

[0105] 130 mechanical drainage equipment

[0106] 140 drying equipment

[0107] 150 shaping equipment

[0108] 160 Storage unit 166 Device for increasing humidity

[0109] 170 Feed device

[0110] 190 Heat recovery device

Claims

REQUIREMENTS 1. A process for producing fuel from compressed biomass, the process comprising: Providing biomass; Washing of the biomass; Shredding, especially fine shredding, of biomass; Mechanical dewatering of the biomass; Drying of the biomass; Shaping of the biomass; characterized in that at least part of the waste heat from one process step is fed back into the process, in particular to another process step.

2. The method according to claim 1, wherein at least a part of the biomass is selected from the group consisting of water hyacinths, seagrass, algae, grass clippings, leaves, green waste and combinations thereof.

3. Method according to one of the preceding claims, wherein the waste heat originates from at least one of the following heat sources: warm exhaust air, high-temperature press water, low-temperature press water, cooling air, residual heat from drying and / or finished fuel, in particular wherein two, preferably three or more of these heat sources are used.

4. Method according to one of the preceding claims, wherein the drying comprises thermal drying of the biomass by heating the biomass to a temperature above 60 °C, in particular above 80 °C, preferably above 95 °C.

5. Method according to one of the preceding claims, wherein the mechanical dewatering of the biomass is carried out in two stages.

6. Method according to one of the preceding claims, wherein at least a part of the waste heat of a process step is passively and / or actively returned to the process, in particular both passively and actively.

7. Method according to one of the preceding claims, wherein the method further comprises increasing the temperature of the biomass before drying, in particular before mechanical dewatering, preferably before, during and / or after comminution.

8. Method according to one of the preceding claims, wherein after mechanical dewatering the temperature of the biomass is above 60 °C, in particular above 70 °C, preferably above 80 °C.

9. A method according to one of the preceding claims, wherein the method further comprises increasing the moisture content of the biomass prior to mechanical dewatering, in particular before, during and / or after the comminution of the biomass, in particular wherein press water generated during the mechanical dewatering is used for increasing the moisture content of the biomass, in particular in the case of multiple mechanical dewatering, press water generated during the first mechanical dewatering is used.

10. Method according to claim 9, wherein a condensate from a heat recovery device (190) is used to increase the moisture content of the biomass.

11. Method according to one of the preceding claims, wherein by recirculating a portion of the waste heat at least a portion of the biomass is reduced by is heated to more than 2 °C, in particular more than 5 °C, preferably more than 10 °C.

12. Method according to one of the preceding claims, wherein at least a part of the biomass is heated by recirculating a portion of the waste heat after washing, in particular after shredding, preferably after the first mechanical dewatering in the case of multiple mechanical dewatering.

13. Method according to one of the preceding claims, wherein the extent of the recovery of part of the waste heat is influenced by the type of biomass, in particular controlled depending on the biomass, and especially preferably regulated.

14. Method according to one of the preceding claims, wherein the air used for cooling motors is used as waste heat, wherein in particular the airflow of the motor cooling is directed, wherein preferably this air is more than 10 °C, more preferably more than 20 °C, in particular more than 40 °C above the outside temperature of the system (100).

15. Method according to one of the preceding claims, wherein the water used for washing is at least partially circulated within the system and / or originates from a process within the system.

16. Method according to one of the preceding claims, wherein the method further comprises measuring the temperature of at least one mass flow, in particular wherein the measured temperature is used to control and / or regulate the recovery of part of the waste heat, preferably being carried out semi-automatically or fully automatically.

17. Method according to one of the preceding claims, wherein the extent of the recovery of part of the waste heat is determined at least partially depending on data, in particular measured values, which provide an indication of the composition of the constituents and / or contaminants of a biomass.

18. Method according to one of the preceding claims, wherein the recovery of part of the waste heat to biomass takes place after washing and / or to biomass towards the end of the washing step.

19. Method according to one of the preceding claims, wherein the biomass is moistened before mechanical dewatering, in particular wherein the time interval between moistening and mechanical dewatering is at least 10 minutes, in particular at least 30 minutes, in particular at least 2 hours, in particular at least 6 hours.

20. Method according to one of the preceding claims, wherein the mechanical dewatering of the biomass is carried out in multiple stages, in particular wherein the shear forces acting on the biomass of the different mechanical dewatering devices (130) differ from one another, preferably wherein the wastewater compositions of the different mechanical dewatering devices (130) differ from one another.

21. Method according to one of the preceding claims, wherein the biomass was stored at least partially under mechanical pressure for at least one day.

22. A method according to one of the preceding claims, wherein at least a portion of the waste heat from a process step is actively fed back into the process, wherein the temperature rise of the actively fed back into the process is less than 60 °C, in particular less than 45 °C, preferably less than 30 °C and / or the residual heat of the fuel from pressed biomass is passively returned to the process, in particular to another process step, after shaping.

23. A method according to any of the preceding claims, wherein heat from the biomass and / or the fuel is returned to the method during and / or after drying.

24. Method according to one of the preceding claims, wherein at least a part of the waste heat from the mechanical dewatering, in particular the heat of the press water generated during the mechanical dewatering, and / or the heat of the biomass, is fed back into the process.

25. Method according to one of the preceding claims, wherein the method further comprises passing air through the biomass between mechanical dewatering and drying, in particular such that the moisture content of the biomass decreases by more than 5%, in particular more than 10%, preferably more than 15%.

26. Method according to one of the preceding claims, wherein the fresh water for washing and / or increasing the moisture content of the biomass is warmer than the temperature of the biomass by more than 1 °C, in particular more than 2 °C, in particular more than 4 °C, in particular more than 5 °C, in particular more than 8 °C, and / or wherein the biomass is preheated with external heat.

27. System (100) for producing fuel from compressed biomass, the system (100) comprising: a washing unit (110); a comminution device (120), in particular a fine comminution device; a mechanical drainage device (130); a drying device (140); a shaping device (150); characterized in that the system (100) further comprises a heat recovery device (190).

28. System (100) according to claim 27, wherein the mechanical drainage device (130) is a two-stage drainage device (130) or comprises at least one, preferably two, drainage devices (130).

29. System (100) according to claim 27 or claim 28, wherein the system (100) is designed to have a production quantity of fuel from pressed biomass of more than 50 kg / h, in particular more than 150 kg / h, preferably more than 500 kg / h.

30. System (100) according to one of claims 27 to 29, wherein the heat recovery device (190) comprises an active heat recovery device and / or a passive heat recovery device, in particular both an active heat recovery device and a passive heat recovery device.

31. System (100) according to any one of claims 27 to 30, wherein the system (100) further comprises a device for increasing the moisture (166) of the biomass, wherein the device is configured to increase the moisture of the biomass before the biomass is fed to the mechanical dewatering device (130), in particular wherein the system (100) is designed such that press water from the mechanical dewatering device (130) is fed to the device for increasing the moisture (166) of the biomass, in particular in the case of several mechanical drainage devices (130) press water from the first mechanical drainage device (130) is directed to the device for increasing the moisture (166) of the biomass.

32. System (100) according to claim 31, wherein the system (100) is designed such that a condensate from the heat recovery device (190) is directed to the device for increasing the moisture content (166) of the biomass.

33. System (100) according to one of claims 27 to 32, wherein the heat recovery device (190) is designed such that the temperature of a part of the biomass processed in the system (100) increases by more than 2 °C, in particular more than 5 °C, preferably more than 10 °C.

34. System (100) according to one of claims 27 to 33, wherein the heat recovery device (190) is designed such that a portion of the biomass processed in the system (100) is heated after the washing unit (110), in particular after the comminution device (120), preferably after a first mechanical dewatering device (130) in the case of several mechanical dewatering devices (130).

35. System (100) according to any one of claims 27 to 34, wherein one or more components and / or parts of the system (100) are thermally insulated for the transport and / or intermediate storage of biomass.

36. System (100) according to any one of claims 27 to 35, wherein the system (100) is housed in several individual enclosures, in particular wherein these are compatible with transport systems and / or provide at least one of the following additional benefits: sound insulation, energy optimization, odor reduction, installation simplification, logistics optimization and / or transport simplification.

37. System (100) according to one of claims 27 to 36, wherein the mechanical drainage device (130) is a multi-stage drainage device (130) or comprises several drainage devices (130), in particular wherein the shear forces acting on the biomass of the different drainage device stages or of the different drainage devices (130) differ from one another, preferably that the wastewater compositions of the different drainage device stages or of the different drainage devices (130) differ from one another.

38. System (100) according to any one of claims 27 to 37, wherein the system (100) further comprises a storage unit (160) configured to store biomass at least partially under mechanical pressure for at least one day.

39. System (100) according to one of claims 27 to 38, wherein the heat recovery device (190) is designed such that the coupling temperature difference is below 5 °C, in particular below 4 °C, in particular below 3 °C, in particular below 2 °C, in particular below 1 °C.

40. Computer-readable medium on which a computer program is stored, wherein the computer program is configured such that, when executed on a processor, it controls and / or regulates a method according to any one of claims 1 to 26 and / or a system (100) according to any one of claims 27 to 39.

41. Program element which, when executed on a processor, controls and / or regulates a method according to any one of claims 1 to 26 and / or a system (100) according to any one of claims 27 to 39.

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