WO2014117779A2

WO2014117779A2 - A biomass pre-treatment system and a method thereof

Info

Publication number: WO2014117779A2
Application number: PCT/DK2014/050018
Authority: WO
Inventors: Henrik Kjeldgaard Hansen
Original assignee: Xergi Nix Technology A/S
Priority date: 2013-01-30
Filing date: 2014-01-30
Publication date: 2014-08-07
Also published as: WO2014117779A3

Abstract

According to an embodiment of the invention, a biomass pre-treatment system is disclosed. The system includes a chamber defined by a chamber wall, a substantially cylindrical compartment at a bottom section of the chamber, wherein the substantially cylindrical compartment includes a stirring unit. The stirring unit includes a rotatable shaft having stirring elements extending therefrom, the stirring elements being adapted to mix a biomass material received in the chamber and to propel the received biomass material along a length of the chamber in a pre-determined direction.

Description

A BIOMASS PRE-TREATMENT SYSTEM AND A METHOD THEREOF

FIELD OF THE INVENTION

The present invention relates generally to pressure cooking and, more specifically, methods and systems for pretreatment of biomass material.

DESCRIPTION OF RELATED ART

Pressure cooking is a known technology that over time has also been used in household cooking. For industrial purposes, the technology is used in various processes but despite diverse application, the technical specifications of the industrial pressure cookers are very similar and have gone through only minor improvements.

An example of pressure cooker application includes using autoclaves for producing bone meal. Production of bone meal requires stirring during the cooking process. Figures 1A-1C illustrate a convention pressure cooker 100. The conventionally available pressure cooker includes a chamber 105 with a rotating shaft 120, which is provided with very large and strong agitator arms 125 having welded stirring blades 130. Functionally, each arm and blade simply rotates along a longitudinal axis of the shaft and produces useful, but ineffective, stirring. A typical stirrer includes a very high torque stirrer, requiring a connection with a very high speed motor. As a consequence, such stirrers have very high energy consumption. Furthermore, the blades drag the received material against the inner surface of the chamber, resulting in wearing of the chamber.

Furthermore, the inlet opening 110 and outlet opening 115 of the pressure cookers/ autoclaves are such that it takes long fill-in time i.e. time required to fill the autoclave with material to be processed, and long flush time i.e. time required to remove the processed material from the autoclave. Usually, these openings are smaller than 400 mm in diameter.

Currently available pressure cookers use spade valve closures. These spade valve seals are dependent on the relatively small tolerances, and are therefore extremely vulnerable to the sedimentation during cooking.

Another industrial use of pressure cooker relates to producing biogas, which offers an alternative to finite traditional energy sources. While the biomass itself may be perceived to contain an energy reservoir, this energy reservoir may not readily be released in a convenient form. The energy potential may often be difficult to exploit and may be present in a form which may be extracted efficiently only after following a number of extensive and optimized biomass processing steps. For example, in order to increase the total energy yield of the process, the aim would be to extract as much energy as possible from the biomass, by using as little energy as possible and effectively preparing the biomass material for further biogas generation steps.

As part of the energy extraction process, the biomass material may be processed in a pre- treatment plant such as a lime-pressure cooker where hydrolysis of aqueous slurry comprising biomass material takes place. In other words, in lime-pressure cooker, the biomass material is constantly stirred and broken down into segments, which are then diverted to a chamber where the segmented biomass material is subjected to high pressure and elevated temperature. The lime-pressure cooking, thus, results in rendering the biomass material available for microbial digestion at a later stage. The significance of stirred-pressure cooking step in energy extraction process is critical, requiring efficient equipment for cooking and handling of biomass material having a very high solid content.

Typically, conventional pressure cookers have high energy consumption, high

manufacturing and maintenance cost, long fill and flush time, with vulnerable sealing means.

In order to overcome the limitation of conventional pressure cooker and to optimize the cooking process, an improved pressure cooker is required. One which is optimized with respect to the requirements which are necessary in order to achieve an effective and reliable pre- treatment of biomasses that are to be used in later stages of biogas extraction process. In particular, the improved pressure cooking unit needs to at least offer one or more optimization with respect to lowering production cost, handling biomasses with high solids content and coarse structure, increasing filling and flushing rate, consuming lower energy for stirring purposes, and having simple and robust sealing mechanism.

SUMMARY OF THE INVENTION

According to an embodiment of the invention, a biomass pre-treatment system is disclosed. The system includes a chamber defined by a chamber wall, a substantially cylindrical compartment at a bottom section of the chamber, wherein the substantially cylindrical compartment includes a stirring unit. The stirring unit includes a rotatable shaft having protruded space curved stirring elements extending from the shaft, the stirring elements being adapted to mix a biomass material received in the chamber and to propel the received biomass material along a length of the chamber in a pre-determined direction.

In another embodiment, a biomass pre-treatment method using the pre-treatment system is disclosed. The method includes actuating the stirring unit that includes a rotatable shaft having protruded space curved elements extending therefrom, the stirring elements being adapted to rotate within a substantially cylindrical compartment to mix a biomass material received in the chamber and to propel the received biomass along a length of the chamber in a pre-determined direction. This is followed by receiving the biomass material in the chamber from a top opening and controlling rotational direction of the stirring elements during operation of the system for propelling the received biomass material from one end to another end of the chamber and vice versa resulting in mixing of the receiving biomass material.

In yet another embodiment of the invention, a sealing unit having a sliding mechanism is disclosed. The mechanism includes an elevated opening that includes a cut out section for receiving a slidable lid, and a guiderail adapted to allow sliding movement of the lid along the guiderail from an open position through to a closed position and vice versa over the opening.

In yet another embodiment of the invention, a sealing unit comprising a sliding sealing mechanism is disclosed. The sealing mechanism includes a slidable lid supported on at least one slidable support means, a slidable base in connection with the at least one slidbale support means and adapted to slide over a support unit, and an actuating means adapted for sliding the slidable base such that the slidable lid is moved from an open position to a closed postion from beneath an opening.

In yet another embodiment of the invention, a pressure cooker system is disclosed. The system includes a chamber defined by a chamber wall; a substantially cylindrical compartment at a bottom section of the chamber, the substantially cylindrical compartment comprising a stirring unit; and the stirring unit comprising a rotatable shaft comprising protruded space curved stirring elements extending therefrom, the elements being adapted to mix an input material received in the chamber and/ or the compartment and to propel the received input material along a length of the chamber in a pre-determined direction. The pressure cooker system may be used as a pre- treatment system in a biogas plant with a biomass material as the input material.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The embodiments of the invention, together with its advantages, may be best understood from the following detailed description taken in conjunction with the accompanying figures in which

Figures 1A-1C illustrate a conventional pressure cooker;

Figure 2 illustrates a pre-treatment system according to an embodiment of the invention; Figures 3A-3B illustrate substantially cylindrical compartment according to an embodiment of the invention, where Figure 3A illustrates a side view of cylindrical compartment, Figure 3b illustrates side view of an almost cylindrical compartment;

Figure 4 illustrates a bottom lid when the bottom lid is in closed bottom position according to an embodiment of the invention; Figures 5A-5B illustrate a top opening in accordance with an embodiment of the invention, where Figure 5A illustrates a top open position and Figure 5B illustrates a top closed position;

Figure 6 illustrates the movement of biomass material under the influence of stirrer rotation according to an embodiment of the invention, where Figure 6A illustrates movement during operation/ processing of the biomass material and Figure 6B illustrates the movement during removal step;

Figure 7 illustrates the extension of the stirring elements from the shaft according to an embodiment of the invention;

Figure 8 illustrates a pre-treatment system with more than one stirring unit according to an embodiment of the invention;

Figure 9 illustrates the orientations/ configurations of stirring elements of adjacent stirring units according to an embodiment of the invention;

Figure 10 illustrates stirring elements according to an embodiment of the invention;

Figure 11 illustrates a first set and second set of stirring elements according to an

embodiment of the invention;

Figure 12 that illustrates positioning of compartment ends according to an embodiment of the invention, where Figure 12A illustrates a front view, Figure 12B illustrates bottom opening end side view and Figure 12C illustrates motor end side view; and

Figure 13 illustrates top sealing mechanism according to another embodiment of the invention, where Figure 13 A illustrates top lid in top open position and Figure 13B illustrates top lid in top closed position;

Figure 14 illustrates an upper movement mechanism according to an embodiment of the invention; and

Figure 15 illustrates stirring unit protrusions according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The description and accompanying figures represent different components; where same components in different figures share same numeral. The person skilled in the art would appreciate that although the invention is described in relation to a lime pressure cooking for biomass pre-treatment and with specific features like space curved stirring elements as helical elements but the disclosed features and principles are applicable in related fields, such as bone meal preparation, and with other replaceable element shapes like fan elements, where working principles such as mixing and controlling movement of inflow material in a processing container, sealing of openings, etc. are required. Figure 2 illustrates a biomass pretreatment system 200, which is a pressure cooker, according to an embodiment of the invention. The system includes a chamber 202 defined by a chamber wall 204, a substantially cylindrical compartment 206 at a bottom section 208 of the chamber. The substantially cylindrical compartment includes a stirring unit 210, which includes a rotatable shaft 212 having protruded space curved stirring elements 214 extending from the shaft. The stirring elements are adapted to mix a biomass material received in the chamber and to propel the received biomass material along a length of the chamber in a pre-determined direction. If the length of the compartment is more than that of the chamber, then the stirring unit is configured to propel the received biomass material along the length of compartment as well. The space curved may include smooth space curved stirring elements.

A space curve is defined as a curve that passes through any region of three-dimensional space, where the curve is defined as a continuously bending line. One example of such space curve is a helix or spiral.

Although the shape of the chamber may be chosen from a number of alternatives but preferably the chamber wall comprises substantially cylindrical wall and defines a substantially cylindrical chamber. The bottom section is defined as the chamber volumetric space towards which the received biomass falls under gravity. In various embodiments of the invention, the stirring elements are selected from helical elements, fan elements, spiral elements and a combination thereof. In principle, the stirring elements are configured not only to mix the received biomass material but also to propel the received biomass material in the pre-determined direction.

The biomass material is processed in the pre-treatment system prior to entering e. g. the fermentor or the biogas reactor. The biomass material may include biomass from a number of sources. However, the system is particularly effective where the biomass material has high total solid and the use of disclosed system allows for substantially homogenous mixing of biomass material and processing in the pressure cooker. In context of the present invention, the pretreatment system represents a pressure cooking system like a lime pressure cooking system. The pre-treatment system may be used for hydrolyzing aqueous slurry comprising biomass material, wherein said hydrolysis results in rendering the organic material available to microbial digestion in a bioreactor. The lime pressure cooker of the system is capable of cutting the biomass material into segments and subsequently capable of diverting the segmented biomass material to a chamber wherein said segmented organic material is heated and simultaneously exposed to a high pressure due to the elevated temperature. The biomass material to be treated in the lime pressure cooker is added with an amount of lime, including CaO and/or Ca(OH)₂ prior to or after entry into the lime pressure cooker. Preferably CaO is added to the lime pressure cooker in an amount of from 25-100 g per kg dry matter in the organic material. The system operates at a temperature of between 100°C and 220°C, such as e. g. 180°C to 200°C. The temperature is aligned according to the biomass material to be treated, a higher temperature is chosen for higher content of cellulose,

hemicellulose and lignin is in the biomass material, or a higher temperature is chosen according to the risk of infectious microbial organism or pathogenic compounds including Bovine

Spongiform Encephalopathy (BSE) prions in the biomass material such as e. g. meat and bone meal.

The pressure in the lime pressure cooker is preferably between from 2 to preferably less than 16 bar, such as from 4 to preferably less than 16 bar, for example from 6 to preferably less than 16 bar, such as from 10 to preferably less than 16 bar. The system operates at the elevated temperature for about 5 to 10 minutes, but longer treatment times may also be used.

Top Opening & Bottom Opening

The system includes a top opening 216 that is adapted to receiving biomass material. In an embodiment, the top opening is an elevated opening 218, i.e. slightly higher than the surface of the chamber wall where the opening is positioned. The top opening is defined by a cut-out section across the thickness of the chamber wall. The chamber wall is defined by a chamber facing surface and an external surface that faces the environment, the distance between the two surfaces define the thickness of the chamber wall. The chamber facing surface defines the volumetric space available in the chamber.

Similarly, the system may also include a bottom opening 220 that is adapted to removing processed biomass material. The processed biomass includes the biomass, received through the top opening, that has been mixed and already processed under a lime pressure cooking method (described in earlier section) using the disclosed system. The bottom opening is included as a cut-out section across the thickness of a side wall 230 of the compartment.

In one embodiment, the top opening 216 is proximal to a first top end 222 of an upper section of the chamber wall. In another embodiment, the top opening 216 is proximal to a second top end 224 of the upper section of the chamber wall. Similarly, in one embodiment, the bottom opening 220 is proximal to a first bottom end 226 of the compartment side wall 230 or in another embodiment; the bottom opening is proximal to a second bottom end 228 of the compartment side wall. As illustrated, the chamber and the compartment include respective first end and second end and are at two extreme ends along the length of the chamber and compartment.

The system includes the stirring unit 210 (described in detail later) that allows for controlled directional movement of the biomass material within the chamber away from chamber region proximal to the top opening. Because the chamber region proximal to the top opening is effectively cleared using the stirring unit, therefore more chamber region is available for receiving larger amount of biomass. For example, if the top opening is proximal to the first top end, the chamber region is defined by volumetric chamber space that is proximal to the first end. The stirring moves the received biomass material towards the second end, thereby continuously clearing the region proximal to first end for receiving more biomass material. The dimension of the top opening is therefore relatively large, compared to openings in conventional pressure cookers, for allowing higher inflow of biomass material, thereby increasing the filling rate.

During operation of the system, i.e. processing of the biomass material, the received biomass material is continually moved from one end of the chamber to the other end and vice versa. This not only allows in achieving relative homogenous mixing of the biomass material but also uniform processing of the received biomass material.

Because the stirring unit is adapted to move the biomass in the pre-determined direction, the stirring unit 210 is thus configured to propel the biomass toward the bottom opening 220 in order to remove the processed biomass relatively quickly, compared to the removal rate achieved in conventional pressure cookers. This allows for having a larger dimension bottom opening, which in itself increases the rate of removal of the processed biomass.

The cylindrical compartment is substantially cylindrical, which includes both arrangements shown in Figure 3 A and 3B and similar constructions. Figure 3 A illustrates a side view of cylindrical compartment 305 and Figure 3b illustrates side view of an almost cylindrical compartment, i.e. with angular inner compartment wall 310. In the former scenario (Figure 3A), there is a high friction between the inner wall of the compartment and the helical elements, resulting in higher energy consumption. However, this construction ensures superior directional movement of the biomass material. In the latter scenario (Figure 3B), the friction between the inner wall of the compartment and the helical elements is lower, thus consuming lower energy to operate. But, the resulting directional flow of biomass is relatively better than what is achieved in the former scenario. A choice may be made on the construction of the substantial compartment based on the requirement, such as type of biomass being processed, viscosity of slurry comprising biomass, energy efficiency requirement, etc.

The biomass material includes biological material from living, or recently living organisms and it includes a number of sources like garbage, wood, waste, etc. A person skilled in the art would recognize many different sources for biomass material.

Because of the use of stirring unit, a higher filling rate and flushing rate are achieved.

Therefore, the size of both the top opening and the bottom opening may be increased

significantly. For a typically circular shaped openings, the individual diameter of the bottom opening and the top opening is in the range of 400mm to 900mm, preferably 500 mm to 850 mm, more preferably, 600 mm to 800mm.

Sealing Mechanism

The system includes separate sealing units, in order to seal the top opening 216 and the bottom opening 220 respectively.

The system includes an openable bottom lid 405, which is adapted to seal the bottom opening 220 when the bottom lid is in a bottom closed position (refer Figure 4). The radial axis 410 of the bottom lid 405 is substantially perpendicular to longitudinal axis 415 of the chamber and the through-axis 420 is substantially parallel to the longitudinal axis of the chamber.

The openable bottom lid 405 may be selected from a number of configurations, for example a separate plate that is joined by way of nut-bolts or similar attaching means to the chamber side wall. The bottom lid may also be an integral part of the chamber and is attached in a door-like configuration, hinged at one of its periphery with the chamber side wall and adapted to rotate around an axis of the hinge from a bottom open position, i.e. when the bottom opening 220 is open, to a bottom closed position, i.e. when the bottom opening is completely covered with the bottom lid 405 (as shown in Figure 4).

The bottom lid 405 includes a bottom sealing means such as a bottom gasket along a periphery of compartment facing side 425 of the bottom lid. The sealing means may be provided along bottom lid facing periphery of the bottom opening 220. In another embodiment, the sealing means are provided on both the bottom lid 220 and the bottom opening 220. As the names suggest, the compartment facing periphery is the periphery of the bottom lid that faces the compartment and the bottom lid facing periphery is the periphery of the bottom opening that faces and interacts with the compartment facing periphery of the bottom lid. The interaction between the bottom lid, gasket, and the opening ensures that the bottom opening is sealed.

Sealing Top Opening - Embodiment 1

Now, referring to Figure 5, which illustrates a top opening in accordance with an

embodiment of the invention, where Figure 5A illustrates a top open position and Figure 5B illustrates a top closed position .

In one embodiment for sealing the top opening, the system includes a slidable top lid 232 for sealing the top opening 216 when the top lid is in a top closed position (refer Figure 5B). The elevated top opening 218 includes a top slidable sealing mechanism 234 that includes a cut out section 505 for receiving the slidable top lid 232 and a top guiderail 510 for allowing sliding movement of the slidable top lid along the top guiderail from a top open position (shown in Figure 5A) through to a top closed position (shown in Figure 5B) and vice versa. The cut out section includes a cut across the thickness and along partial length of periphery of the elevated top opening. The top guiderail includes lower inner periphery 510, accessible via the cut-out section 505, of the top opening along which the slidable top lid 232 may move.

A top sealing means includes a top gasket like an O-ring gasket. The top gasket may be provided along an upper periphery 515of the top lid 232 or along an upper inner periphery 520 of the top opening 216. In another embodiment, the sealing means like gasket is provided on both the upper periphery 515 of the top lid 232 and also along the upper inner periphery 520 of the top opening 516.

The top sealing mechanism 234 may include a top clearance (not shown) between the top sealing means of the top lid 232 and the upper inner periphery 520 of the top opening 216.

During operation of the system, the slurry (received biomass in combination with water or other liquid) is subjected to high temperature and pressure, creating enough outward pressure because of steam build-up in the pressure cooker system. It is understandable that in other applications, biomass and water may be replaced by other substrate material and liquid.

Therefore, the sealing of the top opening is achieved by reducing the clearance between the top sealing means and the upper inner periphery 520 of the top opening 216 through exertion of outward pressure, from inside the chamber, on the top lid. The exertion of pressure forces the top lid 232 to move away from the chamber 202, thereby forming a tight seal. When the system is depressurised, the top lid is automatically lowered vertically and the lid may then be slided to the top open position.

The system may also include a guideplate 520, which is preferably integrated with the chamber wall (as shown in Figure 5), for placing a withdrawn top lid 232 or for placing the top lid that is to be placed in the top closed position. When the lid is placed completely on the guideplate, the top opening is open (refer Figure 5A) and the top lid is in top open position. The guideplate is positioned such that the slidable top lid 232 may be slided from the guideplate 520 through the cut-out section 505 along the guiderail 510 over the top opening 216, to a top closed position (Figure 5B). Sealing Top Opening - Embodiment 2

Figure 13 illustrates top sealing mechanism according to another embodiment of the invention, where Figure 13 A illustrates top lid in top open position and Figure 13B illustrates top lid in top closed position.

The top sealing unit includes a top sealing mechanism that includes a slidable top lid 232 having a top sealing means that includes a top gasket like an O-ring gasket. The top gasket may be provided along an upper periphery 1320 of the top lid 232 or along an inner periphery 1320 of the top opening 216. In another embodiment, the sealing means like gasket is provided on both along the upper periphery 515 of the top lid 232 and also along the inner periphery 1320 of the top opening 516.

The slidable top lid 232 is supported on at least one slidable support means 1305, which are in connection with a slidable base 1310 that is adapted to move/ slide along the length of the chamber while being supported on a support unit 1315. The sliding base 1310 is connected to an actuating means that is adapted for sliding the slidable base such that the slidable top lid is moved from an open position to a closed position from beneath the top opening. The sliding of the base 1310, support members 1305 and the top lid 232 moves the lid from top open postion (Figure 13A) to top closed position (Figure 13B).

The support members 1305 may be bendable such that it may be bent before the processing step. The support means is adapted to allow positioning and establishing physical interaction between the upper periphery 515 of the top lid 232 and the inner periphery 1320 of the top opening 216. This controlled placement, along with the outward pressure created by steam build up in the pressure cooker on the top lid creating a tight seal because of the interaction of the top lid, sealing means and top opening. As in the earlier embodiment, when the system is depressurised, the top lid is automatically lowered vertically and the lid may then be slided to the top open position.

Stirring & Flushing Features

The stirring unit 210 includes a shaft 230, which is along the length of the compartment 206. The shaft is usually cylindrical or substantially cylindrical. However it may also include shapes other than cylindrical or substantially cylindrical shape. The rotatable shaft is connected to a motor 236, which is adapted to rotating the shaft 212.

In various embodiments, the motor is positioned at different positions. However, for simplicity of design construction, the connection between the shaft-motor is preferably established at the bottom section and at an end opposite to the bottom lid end (refer Figure 2). It is apparent that the motor itself is placed outside the chamber.

As mentioned earlier, the pre-determined direction includes forward and backward directions along the length of the chamber length (shown by directional lines in Figure 6A, which illustrates the movement of biomass material under the influence of stirrer rotation during processing of the biomass material). The forward direction is defined by movement of the biomass material from the first end to the second end whereas the backward direction is defined by a movement from the second end to the first end. In other words, the movement of the received biomass is along a chamber longitudinal axis (refer Figure 4, 415) of the chamber. The pre-determined direction is dependent upon and controlled by the rotational direction of the shaft 212 such that the helical mixing elements 214 move the received biomass material from one end to another. The rotational direction of the shaft is around the longitudinal axis 605 of the shaft. Because the helical elements 214 are rotated under the influence of the rotation of the shaft 212, the helical construction of the elements are thus configured to push the biomass in linear direction along the length of the chamber 202 and compartment 206. If the length of the compartment 206 is more than that of the chamber 202, the movement of the biomass is along the entire length of the compartment length.

The shape helix of helical arrangement is defined by its conventional meaning. For example, the shape may be defined as a three dimensional curve formed by a straight line drawn on a plane when that plane is wrapped around a cylindrical surface of any kind, especially a right circular cylinder. The other definition may include an object having a three-dimensional shape like that of a wire wound uniformly around a cylinder or cone. The helical arrangement may include right-handed, left-handed helices or a combination thereof.

Figure 7 illustrates the extension of the helical elements from the shaft according to an embodiment of the invention. The helical elements 214 are arranged such that they extend outwardly from the shaft 212. The extension is radially outward (refer Figures 7A and 7B) along radial axis 705 of the shaft 212. In another embodiment, the extension is longitudinally outward (refer Figure 7A) along the longitudinal axis 605 of the shaft 212 and extends beyond the length of the shaft 212.

In the former scenario of radial extension, the helical elements are supported directly and completely (Figure 7B) on the shaft 212, which typically spans through the entire length of the compartment. The helical elements 214 may extend along the entire length or part of the length of the shaft 212.

In another embodiment, the helical elements 214 are supported directly but only for a part of the helical elements (Figure 7A). For longitudinal extension, a section S of the helical elements 214 are indirectly supported, on the shaft 212, through rest section R of the helical elements 214 providing the necessary support to the indirectly supported section.

In yet another embodiment (Figure 7C), for longitudinal extension, the rest of the section R may include only an end connection at E with the shaft 212. The direct support and connection of the rest section at E provides the indirect support to the longitudinally outward section S of the helical elements 214.

For longitudinal extension, the shaft spans only to a part of the length of the compartment with rest part of the length completely or partially dedicated for the helical element section S of the indirectly supported helical elements. This arrangement may work particularly well with viscous/ sticky slurry. It is apparent that the length of indirectly supported section S is dependent upon the constructional strength and reliability of movement of biomass material during the operation of the system.

In various embodiments, the orientation of the helical elements includes right handed orientation and left handed orientations or a combination thereof along different sections of same shaft. With the line of sight along the helix's longitudinal axis, if a clockwise screwing motion the helix away from the observer, then it is called a right-handed helix; if towards the observer then it is a left-handed helix.

Figure 8 illustrates a pre-treatment system with more than one stirring unit according to an embodiment of the invention, where Figure 8A illustrates an isometric view, Figure 8B illustrating bottom lid end side view and Figure 8C illustrating motor end side view. In an embodiment illustrated in Figure 8, the system includes a plurality of stirring units (210, 210'), each stirring unit (210/ 210') comprising a rotatable shaft having helical elements extending therefrom, the helical elements being adapted to mix a biomass material received in the chamber and to propel the received biomass material along a length of the chamber in a pre-determined direction. In principle, each of the plurality of stirring units operates in same manner as the stirring unit of the system described earlier. However, each stirring unit of the plurality of stirring unit individually includes a bottom opening (220/ 200') and a bottom lid associated with respective bottom opening. Similarly, each of the stirring unit may be connected to respective motor (236/ 236'). This configuration not only facilitates more effective mixing and movement of the biomass material but also results in faster flushing time, when compared to single stirring unit systems.

Figure 9 illustrates the orientations/ configurations of helical elements of adjacent stirring units according to an embodiment of the invention. In other embodiments, where more than one stirring unit is employed (refer Figure 8), the helical elements of adjacent stirring units (220, 200') are arranged in an orientation arrangement that includes either same orientation (Figures 9B and 9C), or opposite orientation (Figure 9A). For example, same orientation includes helical elements on adjacent stirring unit having right/ left handed orientations and the opposite orientation may include one right handed and adjacent left handed orientation. However, it may even be a combination of same and opposite orientations in scenarios where three or more stirring units are used.

Similarly, in embodiments where more than one stirring unit is employed, the helical elements of adjacent stirring units are arranged in configuration that includes either engaged (refer Figure 9C) or disengaged configurations (refer Figures 9A and 9B). However, it may even be a combination of engaged and disengaged configuration in scenarios where three or more stirring units are used. The engaged configuration (Figure 9C) includes configurations where a part of helical elements of first stirring unit overlaps along the length of the compartment (as represented by region indicated by O), but without physical contact, with some part of helical elements of adjacent second stirring unit. In contrast, the disengaged configuration (Figures 9 A and 9B) includes situations where the helical elements of adjacent elements do not overlap and typically placed at some distance from each other.

In various embodiments, a first pitch P of a first stirring unit and a second pitch P' of an adjacent second stirring units (210 and 210') may include same or different pitches, where the pitch defines the distance between successive helical elements along the length of the same stirring unit. Similarly, in various embodiments, a first amplitude A of helical elements 214 of a first stirring unit 210 and a second amplitude A' of helical elements 214' of an adjacent second stirring 210' unit may include same or different amplitudes, where the amplitude is defined by perpendicular height of the element from the shaft to element crest. In other words, in referenced embodiments, the helical elements of the adjacent stirring units include same/ different pitches and/ or same/ different element amplitude.

In different embodiments, the distances D between at least two pairs of adjacent shafts are same or different. However, in another embodiment, where there are more than two pairs of adjacent shafts, the distance between adjacent shafts may even be a combination of same distance and different distances.

The system may also include a pitch varying unit for varying the pitch P/ P', i.e. distance between the helical elements on the same stirring unit. In addition, the system may also include a distance varying unit for changing the distances D between adjacent shafts.

In an embodiment, the helical elements 214 are selected from a group consisting of unsegmented helical elements (refer Figure 10A), i.e. helical elements continuous along the length of the shaft 212, and segmented helical elements, (refer Figure 10B), i.e. helical elements separated along the length of the shaft 212.

Although the amplitude A and pitch P of helical elements 214 are same along the length of the shaft 212 but, in another embodiment, the stirring unit 210 includes helical elements that may vary in amplitude and/ or pitch along the length of the shaft. For example, the amplitude of the elements in the chamber region proximal to the top opening 216 is more than those in the chamber region distal to the top opening. This allows more effective clearing of the region proximal to the top opening for receiving more biomass material, thereby positively affecting the filling rate. Or, the amplitude of the elements proximal to the bottom opening 220 is more than those distal to the bottom opening. This allows for flushing the processed biomass material more quickly, thus positively affecting the removal/ flushing rate.

Figure 11 illustrates a first set and second set of helical elements according to an embodiment of the invention. As shown in Figure 11 A, the stirring unit includes a plurality of sets of helical elements comprising a first set of helical elements 214 and a second set of helical elements 214" on same shaft 212. The first set and the second set are overlapping along the length of the same shaft. The helical elements of the first set and the helical elements of the second set may include same or different amplitudes. Similarly, in other embodiments, the helical elements of the second set include same/ different pitches and/ or same/ different orientations (see Figure 1 IB).

The helical elements 214 may include a curved shape such as in a cup-shaped, with concave side preferably facing the direction of movement of biomass material. In an embodiment, a curve changing unit (not shown) for changing direction in which the concave side of the helical elements would face, may also be used.

As mentioned earlier, the disclosed stirring unit propels the biomass by pushing the biomass in the pre-determined direction. The applied force allows for compressing the received biomass or the biomass in the system such that the density of the biomass increases substantially, for example by a factor of at least 1.25 times, such as 1.5 times, such as 1.75 times and preferably around 2 times or more. The increase in density of the biomass, especially of the received biomass during filling, allows for efficient utilization of system intake capacity as more biomass material may now be received and processed in the system, thus increasing the filling rate and processing rate of the system. The processing rate is defined as the volume of received biomass processed in the system per unit time.

In one embodiment, the stirring elements is dimensioned such that during rotation of the stirring unit, the biomass getting positioned between a periphery 1505 of the stirring elements 214 and inner wall 1515 of the bottom section gets broken down into smaller biomass particles. In another embodiment (as illustrated in Figure 15), the stirring unit includes stirring unit protrusions 1525 that extend beyond the periphery 1505 of the stirring elements 214. The protrusions extend laterally outwards from the periphery 1505 towards the inner wall 1515. During rotation of the stirring unit, the biomass getting positioned between the stirring unit protrusions 1525 and inner wall of the bottom section gets broken down into smaller biomass particles. In particular, the biomass that gets positioned in a volumetric space 1520 between the periphery 1510 of the stirring unit protrusions 1525 and inner wall 1515 of the bottom section gets broken down into smaller biomass particles. The broken down biomass particles results in a more homogenous biomass mixture, which can be processed more uniformly and consistently in the system and also results in a processed biomass that is more suitable for any further processing, for example in anaerobic digestion for production of biogas.

Now referring to Figure 12 that illustrates positioning of compartment ends according to an embodiment of the invention, where Figure 12A illustrates a front view, Figure 12B illustrates bottom opening end side view and Figure 12C illustrates motor end side view. In one embodiment, the first end 226 of the compartment and corresponding second end 228 of the compartment are positioned at same height. However, in another embodiment, the first end 226 of the compartment is positioned at a first height HI and the corresponding second end 228 of the chamber is positioned at a second height H2 such that the end proximal to the bottom opening is at a lower height. The first height and the second height are measured from the base of the system (as illustrated). This relative height difference not only increases rate of flushing because the processed biomass material moves towards the bottom opening under the influence of gravity but also facilitates movement of the received biomass away from the chamber region proximal to the top opening if the top opening and the bottom opening are at opposite ends.

In different embodiments, the relative height between the first height and the second height is selected from a fixed height difference, i.e. the relative height difference is unchanged, and a variable height difference, i.e. the relative height difference may be changed. The change in relative height difference is made possible because of the inclusion of relative height difference adjuster such as telescopic boom based supports (refer Figure 2, 238 and 238') or an adjustable slanted platform (as shown in Figure 12). For example, this may include changing the heights of supporting legs/ supports at the ends such that the end proximal to the bottom opening is at a lower height than the end distal to the bottom opening.

Upper Movement Mechanism

Figure 14 illustrates an upper movement mechanism according to an embodiment of the invention. The upper movement mechanism 1400 includes a second protruded space curved elements (upper movement elements 1405) that extend from an upper shaft 1410. In various embodiments, the upper movement mechanism may extend either at least partially along the length of the chamber (not shown) or along the length of the chamber (shown in Figure 14). In other implementation, there exist a plurality of upper movement mechanisms (comparable to the plurality of stirring units, as shown in Figure 8) with each including a second protruded space curved elements. The upper movement mechanism includes a longitudinal axis 1415 defining the extension the upper movement mechanism 1400. In different embodiments, the extension (shown 1415)/ partial extension of the upper movement mechanism along the length of the chamber is selected from an axis parallel with the longitudinal axis of the stirring unit (as shown); or an axis converging with the longitudinal axis of the stirring unit; or respective axis of a plurality of upper movement mechanisms that is parallel or converging with the longitudinal axis of the stirring unit.

In various embodiments, the upper movement mechanism comprises any feature of already disclosed stirring unit, except the second movement mechanism is positioned in the chamber. For example, the upper movement mechanism is connected to a motor that controls an upper predetermined direction of rotation of the upper movement mechanism around its longitudinal axis, and/ or the upper movement mechanism may include helical elements or fan elements or combination thereof, and/ or in case of the plurality of upper movement mechanisms, the adjacent upper movement elements are arranged in an engaged configuration and disengaged configuration, and/ or the adjacent upper movement elements of the plurality of upper movement mechanisms are arranged in an orientation arrangement selected from same orientation and opposite orientation, and/ or the adjacent upper movement elements have same/ different pitches and/ or same/ different element amplitude, etc. It is apparent to the skilled person that other similar principled comparable features of the stirring unit are easily replicable as the features of the upper movement mechanism and thus, form part of the upper movement mechanism.

The upper pre-determined direction of movement upper movement mechanism is selected from a direction that is opposite to the pre-determined direction of the stirring unit, or a direction that is same as the pre-determined direction of the stirring unit.

The upper movement mechanism is not only adapted to move the received biomass/ biomass in the upper pre-determined direction but its positioning in the middle of the chamber initiates a movement of the received biomass before the received biomass is acted upon by the stirring unit in the bottom section, thus allowing for better mixing and moveability. Method employed in the pre-treatment system

The invention also includes a method for a pre-treatment system, which is described earlier in this application. The method includes actuating a stirring unit that includes a rotatable shaft having stirring elements extending therefrom, the stirring elements being adapted to rotate within a substantially cylindrical compartment to mix a biomass material received in the chamber and to propel the received biomass along a length of the chamber in a pre-determined direction. This is followed by receiving the biomass material in the chamber from a top opening and controlling rotational direction of the stirring elements during operation of the system for propelling the received biomass material from one end to another end of the chamber and vice versa resulting in mixing of the receiving biomass material. The stirring elements may include helical elements, fan elements, and a combination thereof. In principle, the stirring elements are configured not only to mix the received biomass material but also to propel the received biomass material in the pre-determined direction. In an embodiment where the fan elements are used, the fan elements include a series of blade set sequentially arranged along the length of the shaft. Each blade set in the sequence are arranged similar to blades of an axial flow fans such that the received biomass is moved from one blade set to subsequent blade set. The number of blades in each blade set and tapering along the length of each blade may be changed for improving movement of the received biomass material.

In operation, the movement of the biomass material takes place by moving a contact volume of the received biomass from one stirring element to the subsequent stirring element in the predetermined direction, wherein the contact volume is defined by a volume of the biomass material that is being pushed by a stirring element that is in contact with the volume. It is apparent that the biomass material moves both in linear direction, i.e. along the pre-determined direction and in a direction perpendicular to the pre-determined direction within the chamber/ compartment, thus allowing mixing and movement of the biomass material.

Subsequent stirring elements of the stirring unit may define respective volumetric space around the shaft such that volumetric space of one (prior) stirring element is partly overlapping with that of the subsequent stirring element. This allows the contact volume of the biomass material to contact the subsequent stirring element in the overlapping space after the contact volume has been pushed, in the pre-determined direction, by the prior stirring element.

Thereafter, the contact volume is pushed by the subsequent stirring element to the following stirring element along the length of the shaft, thus allowing movement of the biomass material in the pre-determined direction.

The operation includes controlled temperature and controlled pressure cooking of the received biomass material in an alkaline environment. The alkalinity may be achieved by addition of lime and the disclosed device is adapted to allow for addition of the lime through the top opening. The temperature range, pressure range and nature of alkaline environment are described earlier in the description. The shaft is actuated under the influence of a motor and the pre-determined direction is controlled by the rotational direction of the shaft, as determined by motor operation, such that the helical mixing elements move the received biomass material from one end to another end of the chamber. Before the biomass material is received, a bottom opening of the chamber is sealed using a bottom lid before the biomass is received in the chamber. After receiving the biomass material, the top opening of the chamber is sealed using a top lid and the pre-treatment system is ready for operation. The sealing of the top opening includes sliding a slidable top lid along guiderails included in the top opening and placing the top lid in a closed top lid position. The top opening is sealed when an outward pressure, from inside the chamber, is exerted on the top lid during the operation of the chamber.

After the operation is performed, the bottom lid is opened and rotational direction of the helical elements is controlled in order to propel the processed biomass material towards the bottom opening during removal step (refer Figure 6B, which illustrates movement of the biomass material during the removal step).

In an embodiment, an upper movement means is actuated under an influence of an upper motor, the upper movement means includes a second protruded space curved elements that extend from an upper shaft. The upper motor controls the direction of rotation of the upper movement means and in turn determines the upper pre-determined direction. In different embodiments, the upper movement means is actuated before receiving the biomass material or after receiving the biomass material.

In an embodiment where more than one stirring unit is employed, the method includes actuating a plurality of stirring units; and controlling rotational direction of the helical elements of each of the plurality of stirring units during operation. During removal of the processed biomass material, the rotational direction of the helical elements of each of the plurality of stirring units may be controlled such that the processed biomass material is moved towards respective bottom opening of each stirring unit.

In an embodiment, relative heights of corresponding first end and a second end are adjusted such that for removal of processed biomass, the end proximal to the bottom opening is positioned lower than the end distal to the bottom opening. Seal for closure

A sealing unit having a sliding mechanism is disclosed, the sealing unit is useable in the pre- treatment system. However, the sealing mechanism may be used in any other similar application. The mechanism includes an elevated opening that includes a cut out section for receiving a slidable lid, and a guiderail adapted to allow sliding movement of the lid along the guiderail from an open position through to a closed position and vice versa over the opening.

The sealing unit includes a sealing means such as a gasket along an upper periphery of the lid and/ or along an upper inner periphery of the opening. There exists a clearance between the sealing means and the upper inner periphery of the opening. The sealing is achieved by exertion of exertion of outward pressure on the lid, from inside a chamber of a system, during operation of the system that is sealed using the sealing unit, for example pressure exerted because of steam build up during heating in a pressure cooker system.

It is important to note that Figures 1 to 15 illustrate specific applications and embodiments of the invention, and it is not intended to limit the scope of the present disclosure or claims to that which is presented therein. Throughout the foregoing description, for the purposes of explanation, numerous specific details, such as reference to biomass pretreatment system, helical elements, etc. were set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without some of these specific details and by employing different embodiments in combination with one another. The underlying principles of the invention may be employed using a large number of different combinations.

Accordingly, the scope of the invention should be judged in terms of the claims which follow.

Claims

CLAIMS:

1. A biomass pre-treatment system comprising:

a chamber defined by a chamber wall;

a substantially cylindrical compartment at a bottom section of the chamber, the substantially cylindrical compartment comprising a stirring unit; and

the stirring unit comprising a rotatable shaft comprising protruded space curved stirring elements extending from the shaft, the elements being adapted to mix a biomass material received in the chamber and/ or the compartment and to propel the received biomass material along a length of the chamber in a pre-determined direction.

2. The system according to claim 1, wherein the stirring elements include smooth space curved stirring elements.

3. The system according to any of the preceding claims, wherein the stirring elements is

selected from a group consisting of helical elements, fan elements, spiral elements and a combination thereof.

4. The system according to any of the preceding claims, wherein the wall comprises

substantially cylindrical wall defining a substantially cylindrical chamber.

5. The system according to any of the preceding claims, further comprising a top opening, comprised in the chamber wall, adapted to receiving biomass material.

6. The system according to any of the preceding claims, further comprising a bottom opening, comprised in a side section of a compartment wall, adapted to removing processed biomass material.

7. The system according to any of the preceding claims, wherein

the top opening is proximal to a first top end of an upper chamber wall or proximal to a second top end of an upper chamber wall; and/ or

the bottom opening is proximal to a first bottom end of a compartment wall or proximal to a second bottom end of the compartment wall.

8. The system according to any of the preceding claims, further comprising a slidable top lid that is adapted to seal the top opening when the top lid is in a top closed position.

9. The system according to any of the preceding claims, further comprising an openable bottom lid, the bottom lid being adapted to seal the bottom opening when the bottom lid is in a bottom closed position.

10. The system according to any of the preceding claims, wherein radial axis of the bottom lid is substantially perpendicular to longitudinal axis of the chamber and the through-axis is substantially parallel to the longitudinal axis of the chamber.

11. The system according to any of the preceding claims, wherein the top opening comprises an elevated opening comprising a top slidable mechanism comprising a cut out section for receiving the slidable top lid and a top guiderail for allowing sliding movement of the slidable top lid along the top guiderail from the top open position through to a top closed position and vice versa.

12. The system according to any of the preceding claims, further comprising

a top sealing means such as a top gasket along an upper periphery of the top lid and/ or along an upper inner periphery of the top opening; and/ or

a bottom sealing means such as a bottom gasket along a compartment facing periphery of the bottom lid and/ or along a bottom lid facing periphery of the bottom opening.

13. The system according to any of the preceding claims, further comprising a top clearance between the top sealing means of the top lid and the upper inner periphery of the top opening.

14. The system according to any of the preceding claims, wherein the sealing of the top opening is achieved by reduction of the clearance between the top sealing means and the upper inner periphery of the top opening through exertion of outward pressure, from inside the chamber, on the top lid during operation of the system for example because of steam build up during heating in a pre-treatment system.

15. The system according to any of the preceding claims, further comprising a guideplate,

preferably integrated with the chamber wall, for placing a withdrawn top lid or the top lid that is to be placed in the top closed position.

16. The system according to any of the claims , further comprising a top sealing unit

comprising a sliding sealing mechanism, comprising

a slidable top lid supported on at least one slidable support means;

a slidable base in connection with the at least one slidbale support means and adapted to slide over a support unit; and

an actuating means adapted for sliding the slidable base such that the slidable top lid is moved from an open position to a closed postion from beneath the top opening.

17. The sealing unit according to claim..., further comprising a top sealing means along an upper periphery of the lid and/ or along inner periphery of the opening.

18. The sealing unit according to any of the claims , wherein the at least one slidable means is bendable and adapted for positioning and establishing physical contact between the upper periphery of the slidable lid and the inner periphery of the top opening.

19. The sealing unit according to any of the claims , wherein the sealing of the opening is achieved by exertion of outward pressure through the creation of steam build up in the system during operation.

20. The system according to any of the preceding claims, wherein the shaft is along the length of the substantially cylindrical chamber.

21. The system according to any of the preceding claims, further comprising a motor connected with the shaft, the motor being adapted to rotating the cylindrical shaft.

22. The system according to any of the preceding claims, wherein the motor-shaft connection is established at the bottom section and at a compartment wall end opposite to the bottom lid end.

23. The system according to any of the preceding claims, wherein the pre-determined direction is controllable by the rotational direction of the shaft, as determined by motor operation, such that the helical mixing elements move the received biomass material from one end to another end of the chamber.

24. The system according to any of the preceding claims, wherein the movement of the received biomass material is along a chamber longitudinal axis of the chamber.

25. The system according to any of the preceding claims, wherein

the first end of the compartment is positioned at a first height, and

corresponding second end of the compartment is positioned at a second height, such that the end proximal to the bottom opening is at a lower height.

26. The system according to any of the preceding claims, wherein the relative height between the first height and the second height is selected from a fixed height difference and a variable height difference.

27. The system according to any of the preceding claims, further comprising a relative height adjuster for varying relative height between the first end and the second end.

28. The system according to any of the preceding claims, wherein the stirring elements of

adjacent stirring units are arranged in an orientation arrangement selected from same orientation and opposite orientation.

29. The system according to any of the preceding claims, wherein the stirring elements of the adjacent stirring units are arranged in configuration selected from engaged configuration and disengaged configuration.

30. The system according to any of the preceding claims, wherein the stirring elements of the adjacent stirring units comprise same/ different pitches and/ or same/ different element amplitude.

31. The system according to any of the preceding claims, further comprising a plurality of stirring units, each stirring unit comprising a rotatable shaft having space curved stirring elements extending from the shaft, the stirring elements being adapted to mix a biomass material received in the chamber and to propel the received biomass material along a length of the chamber in a pre-determined direction.

32. The system according to the 25, wherein each stirring unit comprises an associated bottom opening and an associated bottom lid.

33. The system according to any of the preceding claims, wherein distances between at least two pairs of adjacent shafts are same or different.

34. The system according to any of the preceding claims, further comprising

a pitch varying unit for varying the distance between the stirring elements; and/ or a distance varying unit for changing the distances between adjacent shafts.

35. The system according to any of the preceding claims, wherein the stirring elements are

directly supported by the shaft.

36. The system according to any of the preceding claims, wherein a section of the stirring

elements are indirectly supported by the shaft through rest section of the stirring elements.

37. The system according to any of the preceding claims, further comprising a plurality of sets of stirring elements comprising a first set of stirring elements and a second set of stirring elements on same shaft.

38. The system according to any of the preceding claims, wherein the amplitude and/ or pitch of stirring elements are same and/ or different along the length of the shaft.

39. The system according to any of the preceding claims, wherein the stirring elements of the first set and the stirring elements of the second set comprise same/ different amplitudes and/ or same/ different pitches and/ or same/ different orientations.

40. The system according to any of the preceding claims, wherein the stirring elements are

selected from a group consisting of unsegmented stirring elements and segmented stirring elements.

41. The system according to any of the preceding claims, wherein the stirring elements are

curved such as in a cup-shaped, with concave side facing the direction of movement of biomass material.

42. The system according to any of the preceding claims, further comprising a curve changing unit for changing facing-direction of the concave side of the stirring elements.

43. The system according to any of the preceding claims, wherein the stirring unit propels the biomass material by moving a contact volume of the received biomass from one stirring element to the subsequent stirring element in the pre-determined direction.

44. The system according to any of the preceding claims, wherein the contact volume comprises a volume of the biomass material being pushed by a stirring element that is in contact with the volume of the biomass material.

45. The system according to any of the preceding claims, wherein subsequent stirring elements of the stirring unit define respective volumetric space around the shaft such that volumetric space of one stirring element is partly overlapping with that of the subsequent stirring element.

46. The system according to any of the preceding claims, further comprising an upper movement mechanism comprising a second protruded space curved elements that extend from an upper shaft.

47. The system according to any of the preceding claims, wherein the upper movement

mechanism extends at least partially along the length of the chamber.

48. The system according to any of the preceding claims, wherein the upper movement

mechanism extends along the length of the chamber.

49. The system according to any of the preceding claims, wherein a longitudinal axis of the extension/ partial extension of the upper movement mechanism along the length of the chamber is selected from

an axis parallel with the longitudinal axis of the stirring unit; or

an axis converging with the longitudinal axis of the stirring unit; or

respective axis of a plurality of upper movement mechanism that is parallel or converging with the longitudinal axis of the stirring unit.

50. The system according to any of the preceding claims, wherein the plurality of upper

movement mechanisms, each comprising a plurality of the second protruded space curved elements.

51. The system according to any of the preceding claims, wherein the upper movement

mechanism moves the biomass in an upper pre-determined direction.

52. The system according to any of the preceding claims, wherein the upper pre-determined direction is selected from a group consisting of a direction opposite to the pre-determined direction, or a direction that is same as the pre-determined direction.

53. The system according to any of the preceding claims, wherein the upper movement

mechanism comprises any feature of the stirring unit, except the second movement mechanism is positioned in the chamber.

54. The system according to any of the preceding claims, wherein the stirring unit compresses the received biomass or the biomass already in the system such that the density of the biomass increases substantially, for example by a factor of at least 1.25 times, such as 1.5 times, such as 1.75 times and preferably around 2 times or more.

55. The system according to any of the preceding claims, wherein the biomass getting positioned between a periphery of the stirring unit and inner wall of the bottom section during rotation of the stirring unit, gets broken down into smaller biomass particles.

56. The system according to any of the preceding claims, wherein the stirring unit further

comprises stirring unit protrusions extending beyond the periphery of the stirring unit.

57. The system according to any of the preceding claims, wherein the biomass getting positioned between the stirring unit protrusions and inner wall of the bottom section during rotation of the stirring unit, gets broken down into smaller biomass particles.

58. The system according to any of the preceding claims, wherein individual diameter of the top opening and bottom opening is in the range of 400mm to 900mm, preferably 500 mm to 850 mm, more preferably, 600 mm to 800mm.

59. A method for a pre-treatment system, the method comprising

actuating a stirring unit comprising a rotatable shaft having protruded space curved stirring elements extending from the shaft, the stirring elements being adapted to rotate within a substantially cylindrical compartment to mix a biomass material received in the chamber and to propel the received biomass along a length of the chamber and/ or compartment in a pre-determined direction;

receiving the biomass material in the chamber from a top opening; and controlling rotational direction of the stirring elements during operation of the system for propelling the received biomass material from one end to another end of the chamber and vice versa resulting in mixing of the receiving biomass material.

60. The method according to claim 59, wherein the stirring elements are selected from a group consisting of helical elements, fan elements, spiral elements, and a combination thereof.

61. The method according to any of the claims 59-60, wherein the operation comprises

controlled temperature and controlled pressure cooking of the received biomass material in an alkaline environment.

62. The method according to any of the claims 59-61, wherein the alkaline environment is

achieved by addition of lime.

63. The method according to any of the claims 59-62, further comprising actuating an upper movement means under influence of an upper motor, the upper movement means comprising a second protruded space curved elements that extend from an upper shaft.

64. The method according to any of the claims 59-63, wherein the upper movement means is actuated before receiving the biomass material or after receiving the biomass material.

65. The method according to any of the claims 59-64, further comprising controlling rotational direction of the stirring elements such the processed biomass material is propelled towards a bottom opening, after the operation is performed.

66. The method according to claim 59-65, further comprising sealing the bottom opening of the chamber using a bottom lid before the biomass is received in the chamber.

67. The method according to any of the claims 59-66, wherein the shaft is actuated under the influence of a motor.

68. The method according to any of the claims 59-67, further comprising sealing the top opening of the chamber using the top lid after the biomass material is received.

69. The method according to any of the claims 59-68, wherein the sealing of the top opening comprises sliding a slidable top lid along guiderails included in the top opening and placing the top lid in a closed top lid position.

70. The method according to any of the claims 59-69, further comprising sealing the top opening when an outward pressure, from inside the chamber, is exerted on the top lid during the operation of the chamber.

71. The method according to any of the claims 59-70, wherein the pre-determined direction is controllable by the rotational direction of the shaft, determined by motor operation, such that the helical mixing elements move the received biomass material from one end to another end of the chamber.

72. The method according to any of the claims 59-71, further comprising adjusting relative

heights of corresponding first end and a second end such that for removal of processed biomass, the end proximal to the bottom opening is positioned lower than the end distal to the bottom opening.

73. The method according to any of the preceding claims 59-72, further comprising controlling the rotational direction of the stirring elements such that the processed biomass material is moved towards the bottom opening during removal stage.

74. The method according to any of the claims 59-73, further comprising

actuating a plurality of stirring units; and

controlling rotational direction of the stirring elements of each of the plurality of stirring units during operation.

75. The method according to any of the preceding claims 59-74, further comprising controlling the rotational direction of the stirring elements of each of the plurality of stirring units such that the processed biomass material is moved towards respective bottom opening during removal stage.

76. The method according to any of the preceding claims 59-75, further comprising propelling the biomass material by moving a contact volume of the received biomass from one stirring element to the subsequent stirring element in the pre-determined direction.

77. The method according to any of the preceding claims 59-76, wherein the contact volume comprises a volume of the biomass material being pushed by a stirring element that is in contact with the volume of the biomass material.

78. The method according to any of the preceding claims 59-77, further comprising any of the features included in preceding claims 1-.58.

79. A sealing unit comprising a sliding mechanism comprising:

an elevated opening comprising,

a cut out section for receiving a slidable lid; and

a guiderail adapted to allow sliding movement of the lid along the guiderail from an open position through to a closed position and vice versa over the opening.

80. The sealing unit according to claim 79, further comprising a sealing means such as a gasket along an upper periphery of the lid; and/ or along an upper inner periphery of the opening.

81. The sealing unit according to any of claims 79-80, further comprising a clearance between the sealing means and the upper inner periphery of the opening.

82. The sealing unit according to any of the claims 79-81, wherein the sealing of the opening is achieved by reduction of the clearance between the sealing means and the upper inner periphery of the top opening through exertion of outward pressure on the lid, from inside a chamber of a system, during operation of the system that is sealed using the sealing unit, for example pressure exerted because of steam build up during heating in a pressure cooker system.

83. A sealing unit comprising a sliding sealing mechanism, comprising

a slidable lid supported on at least one slidable support means;

an actuating means adapted for sliding the slidable base such that the slidable lid is moved from an open position to a closed postion from beneath an opening.

84. The sealing unit according to claim 83, further comprising a sealing means along an upper periphery of the lid and/ or along inner periphery of the opening.

85. The sealing unit according to any of the claims 83-84, wherein the at least one slidable means is bendable and adapted for positioning and establishing physical contact between the upper periphery of the slidable lid and the inner periphery of the opening.

86. The sealing unit according to any of the claims 83-85, wherein the sealing of the opening is achieved by exertion of outward pressure through the creation of steam build up in a pressure cooker during operation.

87. A pressure cooker system, comprising

a chamber defined by a chamber wall;

the stirring unit comprising a rotatable shaft comprising protruded space curved stirring elements extending from the shaft, the elements being adapted to mix an input material received in the chamber and/ or the compartment and to propel the received input material along a length of the chamber in a pre-determined direction.

88. The pressure cooker system according to claim 87, wherein the input material is a biomass material.

89. The pressure cooker system according to claims 87-88, further comprising any of the features of claims 1-86.