Abstract:
A method for preparing a pressed article comprises providing a first and a second pressing ram in a compression chamber; supplying biomass particles in the chamber closing the chamber; extending the first pressing ram; displacing the biomass particles with the first pressing ram towards the second pressing ram; detecting abutment of the biomass particles on the second pressing ram; applying pressure to the biomass particles with the first pressing ram and with the second pressing ram detecting a pressure applied to match a predetermined pressure and continuing to extend the first and the second pressing ram until a predetermined time at the matched compression pressure has elapsed; stopping the extension of the second pressing ram when a predetermined extension length is reached; continuing to extend the first pressing ram until a predetermined additional time has elapsed after the stopping; ejecting a pressed article.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 USC §119(e) of U.S. provisional patent application No. 61/376,037 filed Aug. 23, 2010, the specification of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The invention relates to a method and a mechanical press system for the generation of densified cylindrical briquettes, ingots or pucks from various fiber materials, including residual waste. 
     BACKGROUND OF THE ART 
     Densification systems generally have two broad goals. The first goal is to reduce the volume of a certain material to facilitate its transportation. The second goal is to normalize the shape and size of the densified product, called briquettes, to facilitate its handling and often to make it compatible with mechanized handling equipment. 
     In the case of biomass and waste material destined for energy production, an additional goal of the densification is to improve the combustion or gasification of the material, by generating fuel briquettes of a certain size, shape and density. For example a pile of wood sawdust does not burn very well, but a briquette made of the same sawdust can make an excellent solid fuel. 
     The densification of biomass and waste material is somewhat more difficult to achieve than the densification of inert or inorganic material such as metal chips. This is because biomass and waste material are heterogeneous mixtures and the successful generation of briquettes with this material is influenced by its composition, moisture content and particle size distribution. Presses designed for the densification of biomass and waste material have certain characteristics in order to reliably process these materials into briquettes. 
     Biomass briquettes made of woody fibers generally fall in three categories: logs (or ingots), pucks and pellets. Fuel ingots vary in diameter from 50 mm to 100 mm, and are usually 60 mm to 150 mm long. They are generally used as a cleaner and more consistent alternative to residential firewood logs, offering a higher energy density and steady combustion. Fuel pucks have similar diameters to ingots but can be 25 mm to 50 mm in length. Fuel pucks are used in co-firing coal-powered electric generation as well as in institutional heating, greenhouse heating, and combined heat and power (CHP) applications. Fuel pellets are smaller cylinders usually with a 6 mm to 8 mm diameter and with a length that is variable around 10-15 mm. Pellets are almost exclusively made from wood sawdust and have been developed relatively recently as an alternative to fossil fuels such as natural gas and heating oil. Their size is such that they can be conveniently blown from a tanker to a storage silo and they can be fed to a burner by a simple auger feeding. A broad range of pellet stoves, central heating furnaces, and other heating appliances have been developed recently. 
     Ingot or puck briquetting systems provide flexibility and advantages with respect to pellet plants. Ingot or puck briquetting systems accept a wider range of feedstock, which is especially useful when wood sawdust feedstock is scarce. Ingot or puck briquetting feed stock particle size does not need to be ground as fine as pellet operations and they are more tolerant with respect to humidity content. Pellets are more expensive to produce than briquettes and excessive handling causes them to degrade and become dustier. The extreme pressures used in pelletizing systems (1.7 GPa) causes wear and parts such as dies need replacing regularly. This can represent a significant operating cost. Periodic, replacement of motor drives within pellet mills is also common. Because of their larger surface to volume ratio, pellets need to be kept dry and can only be stored for a relatively short period of time. Moreover, pelletizing of materials containing contaminants such as lime, clay and/or other low temperature melting point constituents is a severe operational production limitation. The high operating temperatures cause the material to liquefy and plug the orifice of the pellet press dies. For the most part pelletizing is applied to woody biomass waste and they are not suitable for agro-food waste or other types of waste. 
     The majority of the high throughput (&gt;500 kg/hr), industrial briquette presses require high capital acquisition costs, are constructed from costly proprietary components and are subject to high operational and maintenance fees. 
     The prior art systems and method for the generation of densified logs or briquettes from various fiber materials have many drawbacks 
     SUMMARY 
     The current invention aims to provide a small-scale, low-entry price briquette press to facilitate the conversion of a broad range of urban waste to a normalized solid fuel. Compared to pellet presses, the current invention minimizes the front-end processing of the feedstock to improve system reliability and reduce operating costs per ton of solid fuel processed. 
     According to one broad aspect of the present invention, there is provided a method for preparing a pressed article from compressible and cohesive biomass particles. The method comprises providing a first pressing ram and a second pressing ram operating in opposite directions and disposed in a compression chamber, in retracted position; supplying a quantity of biomass particles in a space in the compression chamber between the first and second pressing rams; closing the compression chamber; extending the first pressing ram towards the biomass particles in the compression chamber; displacing the biomass particles with the first pressing ram towards the second pressing ram; detecting abutment of the biomass particles on the second pressing ram once the biomass particles are displaced by the first pressing ram to touch the second pressing ram; applying pressure to the biomass particles with the first pressing ram by extending the first pressing ram to abut the biomass particles on the second pressing ram and with the second pressing ram by extending the second press ram to abut the biomass particles on the first pressing ram; detecting a pressure applied to match a predetermined compression pressure and continuing to extend the first pressing ram and the second pressing ram until a predetermined time at the matched compression pressure has elapsed, thereby forming a pressed article; stopping the extension of the second pressing ram when a predetermined extension length for the second pressing ram is reached; continuing to extend the first pressing ram until a predetermined additional time has elapsed after the stopping; ejecting a pressed article made of compressed biomass particles from the compression chamber. 
     According to another broad aspect of the present invention, there is provided a press for preparing a pressed article from compressible and cohesive biomass particles. The press comprises a housing; a first pressing ram and a second pressing ram operating in opposite directions and disposed in a compression chamber; a first pressure detector for the first pressing ram; a second pressure detector for the second pressing ram; a first actuator for the first pressing ram; a second actuator for the second pressing ram; an electronic control circuit adapted to control the first and second pressing rams using the first and second actuators and to receive signals from the first and second pressure detectors, the electronic control circuit being programmed to control the first and second pressing rams for: extending the first pressing ram towards the biomass particles in the compression chamber; displacing the biomass particles with the first pressing ram towards the second pressing ram; detecting abutment of the biomass particles on the second pressing ram once the biomass particles are displaced by the first pressing ram to touch the second pressing ram; applying pressure to the biomass particles with the first pressing ram by extending the first pressing ram to abut the biomass particles on the second pressing ram and with the second pressing ram by extending the second press ram to abut the biomass particles on the first pressing ram; detecting a pressure applied to match a predetermined compression pressure and continuing to extend the first pressing ram and the second pressing ram until a predetermined time at the matched compression pressure has elapsed, thereby forming a pressed article; stopping the extension of the second pressing ram when a predetermined extension length for the second pressing ram is reached; continuing to extend the first pressing ram until a predetermined additional time has elapsed after the stopping; ejecting a pressed article made of compressed biomass particles from the compression chamber. 
     In this specification, the term briquette is intended to mean any product of a press, namely a pressed article, regardless of the size or shape of this product. 
     The term ingot is used to designate a briquette of diameter around 50 mm and of length 1 to 4 times its diameter. 
     The term puck is used to designate a briquette of diameter around 50 mm and of length around half of its diameter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration an example embodiment thereof and in which 
         FIG. 1  is a perspective view of an example press with its industrial casings; 
         FIG. 2  is a perspective broken-away view of the example press of  FIG. 1  with some of its industrial casings removed to show the internal components of the press; 
         FIG. 3  is a system diagram of the main components of the example press; 
         FIG. 4  is a control diagram of the example press; 
         FIG. 5  is a flow chart of the main steps of the example method; 
         FIG. 6  is a flow chart of the sub-steps of the pre-compression stage of  FIG. 5 ; 
         FIG. 7  is a flow chart of the sub-steps of the compression stage of  FIG. 5 ; 
         FIG. 8  is a flow chart of the sub-steps of the ejection stage of  FIG. 5 ; 
         FIG. 9  is a flow chart of the sub-steps of the sawing stage of  FIG. 5 ; 
         FIG. 10  is an example timing diagram for the compression stage, the ejection stage and the pre-compression stage; 
         FIG. 11  is an example timing diagram for the sawing stage; 
         FIG. 12  is a top plan view of the example press of  FIG. 1  in which the raw material has fallen from the hopper to the pre-compression ram; 
         FIG. 13  is a top plan view of the example press of  FIG. 1  in which the pre-compression ram has completed its extension and there is resulting pre-compressed material; 
         FIG. 14  is a top plan view of the example press of  FIG. 1  in which the compression stage has begun with a simultaneous motion of long cylinder and the short cylinder towards the compression chamber; 
         FIG. 15  is a top plan view of the example press of  FIG. 1  in which the eject ram is fully extended at the beginning of the eject stage; 
         FIG. 16  is a side elevation view of the example press of  FIG. 1 , in which the ingot floor is present; 
         FIG. 17  is a side elevation view of the example press of  FIG. 1 , in which the ingot floor is absent; 
         FIG. 18  is a perspective view of the sawing stage of the example press of  FIG. 1  in which the align cylinder pushes the ingot towards the left along its axis until the ingot is pressed against the sawing wall reference; 
         FIG. 19  is a side elevation view of the example press of  FIG. 1 , in which the sawing ram pushes the ingot toward the array of blades; and 
         FIG. 20  is a side elevation view of the example press of  FIG. 1 , in which the pucks are seen exiting in the puck chute. 
     
    
    
     It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
     DETAILED DESCRIPTION 
     Multiple fiber feedstock can be converted to solid briquette ingots using the present invention, including: wood sawdust, wood sanding dust, wood cut-offs, wood pruning residue, peat moss, construction &amp; demolition wood waste, wood &amp; mixed plastics fines resulting from recycling, food-grade waxed cardboard, milk and juice containers, ordinary corrugated cardboard, paper, non-recyclable hard cover books, short &amp; long fiber paper sludge, cotton, linen, synthetic fibers, fibers from old rug waste, waste magnetic tape, agro-food waste fiber, solid digestive byproduct resulting from anaerobic digestion, and dry sludge from waste water treatment plants. 
       FIG. 1  shows an example embodiment of the mechanical press  101 . The press is constructed on two main levels, the upper level  103  and the lower level  105  arranged respectively above and below a main horizontal frame  107 . The horizontal frame  107  is resting on four legs, three of which  109 ,  111  and  113  are visible in  FIG. 1 . The front  115  and the right side  117  of the press  101  are most visible in  FIG. 1 , while the left side  118  and the back  119  are partially visible. Apart from the various protective covers  120 ,  121 ,  123  and  125 , six actuators  127 ,  129 ,  131 ,  133 ,  135  and  137  are shown in  FIG. 1 . 
     The hopper  139  has a rectangular cross-sectional shape and extends vertically from the upper level. The top of the hopper  139  is open ended to allow filling with compressible material. The hopper  139  acts as a bulk material reserve or receptacle of a generally rectangular prismatic shape. The hopper  139  is equipped with an internal vertically extending rectangular panel  141  facing the right side  117  of the press  101  with dimensions that nearly fit inside the hopper  139  rectangular volume. The moving panel  141  can be translated horizontally in a direction normal to its surface within the hopper  139  using a screw  143 . 
     The hopper  139  is equipped with high-level  145 ,  146  and low-level  147 ,  149  photocell sensors, to allow sensing the level of the compressible material. 
       FIG. 2  provides a broken-away and internal view of the example mechanical press  101  shown in  FIG. 1 . 
     The pre-compression ram  203  is located in the upper level  103  of the press  101 . The pre-compression ram  203  is a rectangular pushing device terminated with a concave cylindrical end  205  and can move in and out along an axis perpendicular to the hopper  139 . The pre-compression ram  203  is displaced using a linear actuator  127  which extends toward the back of the machine  119 . 
     The width of the pre-compression ram  203  is matched with the width of the hopper  139 . When fully extended the pre-compression ram  203  forms the bottom of the hopper  139 . When the pre-compression ram  203  is fully retracted, the bottom of the hopper  139  is the pre-compression ram floor  207 , thereby increasing the volume capacity of the hopper  139 . 
     The pre-compression chamber  209  is located in the front side of the upper level  103  of the press  101 . The pre-compression chamber  209  is formed by a hollow cylindrical cavity with an axis oriented in the left-right direction, perpendicular to the pre-compression ram  203  actuator  127  axis. 
     The long cylinder (not visible in  FIG. 2 ) is a pushing cylinder oriented and aligned on the same axis as the pre-compression chamber  209 . The long cylinder can be displaced using a linear actuator  129  which extends toward the left of the machine  118 . 
     The compression chamber  211  (represented with dash lines in  FIG. 2 ) is located in the front side of the upper level  103  of the press  101 . The compression chamber  211  is directly to the right and precisely aligned with the pre-compression chamber  209 . 
     The eject ram  213  is a rectangular object located on the front side of the upper level  103  of the press  101  and extending towards the front  115  of the press  101 . The eject ram  213  can be displaced using a linear actuator  133  which extends toward the front  115  of the press  101 . The eject ram  213  is oriented along a front-back axis perpendicular to the compression chamber  211 , but a small distance below the compression chamber  211  centerline. This allows the full movement of the eject ram  213 , even when objects protrude out of the compression chamber  211 . 
     The eject ram  213  is equipped with a brush  215  on the back end of its rectangular section and extends vertically higher than the bottom level of the compression chamber  211 . 
     An eject floor  217  is located under the eject ram  213 . The eject floor  217  is not fixed permanently and can be removed by an operator. 
     The ingot chute  219  is a plane surface meeting with the back end of the eject floor  217  and inclined towards the back to allow objects to roll down its surface if placed on it. 
     The sawing chute  221  is a vertically oriented rectangular funnel located just underneath the eject floor  217 . Its top is located in the upper level  103  of the press  101  and its bottom is located in the lower level  105  of the press  101 . 
     The sawing ram  223  is a rectangular object terminated with an off-center cylindrical concave cavity. The sawing ram  223  is located on the front side of the lower level  105  of the press  101  and extending towards the front  115  of the press  101 . The saw ram  223  can be displaced using a linear actuator  137  which extends toward the front  115  of the press  101 . The sawing ram  213  is oriented along a front-back axis parallel to the eject ram  213  but underneath the eject ram  213 . 
     The saw assembly  225  is composed of a series of circular blades  227 , a sawing reference wall  229  and a saw floor  231 . The saw module  225  is located . . . 
     The puck chute  233  is a plane surface meeting with the back end of the saw floor  231  and inclined towards the back to allow objects to roll down its surface if placed on it. 
       FIG. 3  shows system diagram  301  of the input fiber material  303 , an input transport mechanism  305 , the proposed mechanical press  307  and the output densified ingots or puck transport mechanism  309 . 
     The input transport mechanism  305  can be a belt or a screw conveyor or any other appropriate means of transporting the input material to the hopper. The input transport mechanism  305  receives stop and go signals from the controller  347 . 
     The hopper  311  is a rectangular prism volume used as a small reserve to feed the next step in the press. The hopper  311  is equipped with high-level and low-level fill sensors  315 . The controller  313  uses to the fill sensors  315  to send receives stop and go signals to the input transport mechanism  305  to keep the amount of material in the hopper  311  approximately constant. This ensures that the level of compaction at the bottom of the hopper  311  is approximately constant. 
     The pre-compression ram  317  pushes the layer of material at the bottom of the hopper  311  towards the pre-compression chamber  319 , thus forming a cylinder of material with a moderate level of densification. The pre-compression ram  317  may be equipped with position sensors  321  to allow changing the pressure profile of its actuator as a function of position, if required. 
     The final densification stage is performed in part by the long cylinder  323 . This cylindrical push rod is used to push the pre-compressed material out of the pre-compression chamber  319  and into the compression chamber  325 . The compression chamber  325  is a cylindrical hollow cavity where the long cylinder  323  can enter from one end and when the compression is completed can push the compressed material out the other end. The long cylinder is equipped with several position sensors  327  to allow changing the pressure profile of its actuator as a function of position and to allow optimal control of other actuators. 
     In order to keep the pre-compressed material inside the compression chamber  325  during the compression stage, a short cylinder  329  is inserted at the end of the compression chamber  325  opposite from where the long cylinder  323  enters. The short cylinder  329  actually performs a compression movement synchronized and in the opposite direction of the compression movement of the long cylinder  323 . This double-sided compression approach maximizes the uniformity of the compressed material. Once the compression is complete, the short cylinder  329  retracts and allows the compressed material to be ejected in the eject zone  331 . The short cylinder  329  is equipped with several position sensors  333  to allow changing the pressure profile of its actuator as a function of position and to allow optimal control of other actuators. 
     The eject ram  335  has two purposes. First it is used to nudge the compressed material from the long cylinder  323  and/or the short cylinder  329 , in cases of sticking. Second the eject ram  335  is used as ram to push the ingot down the ingot chute  337 , in the cases where the final product are ingots rather than pucks. The ingots fall down the chute where an output transport mechanism  309 , usually a belt conveyor, collects the final product. 
     The press  307  can be configured to produce pucks instead of ingots. In this case rather than being pushed to the ingot chute  337 , the ingots go to a saw assembly  339 . In the saw assembly  339 , the ingots are first aligned against a cutting guide using an align cylinder  341 . Next the ingot is pushed through an array of cutting blade using a sawing ram  343 . The pucks then fall into the puck chute  345  where the output transport mechanism  309  collects the final product. 
     An electronic controller  347  is used to automate the operation of the press  307 . 
       FIG. 4  is the control diagram of the example press. The controller  403  can be a programmable logic controller or any other type of suitable controller. The controller  403  receives inputs from the user in the form of input parameters and mode selection  405  as well as emergency stop  407  inputs. The input parameters are variables such as actuator pressure, moving speed as well as wait times that the user can change according to the type of feed material. The mode selection allows operating in an automatic mode or a manual mode. The manual mode is necessary for troubleshooting and re-initialization in case of an anomalous stop. 
     The controller  403  also receives inputs from several sensors installed in the press, including the hopper fill sensors  315 , the pre-compression ram position sensors  321 , the long cylinder position sensors  327  and the short cylinder position sensors  333 . 
     The controller  403  utilizes a sequencer to control its output signals according to a predetermined chain of events. The sequencer advanced through it various steps according to the inputs signals and expected behavior of the system. According to the expected step in the sequence, the controller  403  changes the state of its outputs which are used to control the motion of the actuators such as the input transport mechanism  305 , the pre-compression ram  317 , the long cylinder  323 , the short cylinder  329 , the eject ram  335 , the align cylinder  341  and the saw ram  343 . 
     As shown in  FIG. 5 , there are three main stages of the sequence  501  of the press: the pre-compression  503 , the compression  505  and the ejection  507 . The optional sawing  509  stage is used to produce pucks instead of ingots. 
     The nominal ingot-producing automated mode is represented by the solid line loop in  FIG. 5 . The nominal puck-producing automated mode is represented by a feedback loop in dashed lines n  FIG. 5 . 
     The start and stop points are somewhat arbitrary in an infinite loop. In the example flow chart, the start point  511  is at the beginning of the compression  505  stage, because the most critical actuators, namely the long cylinder  323  and the short cylinder  329  are completely retracted at this point in the cycle, allowing for visual inspection and maintenance if required. 
     The pre-compression stage  503  is illustrated in  FIG. 6 . The main step  603  of the pre-compression stage  503  is the motion of pre-compressing ram  317  pushing input material towards pre-compression chamber  319 . In most case this completes the pre-compression stage  503 . In some cases of very low density material there may not be enough material admitted in the pre-compression chamber  319 , even if the hopper is adjusted to its maximum volume using the moving panel  141 . In these cases the system can use the optional step  605 , where the pre-compressing ram  317  retract to its home position, so an additional quantity of input material can be used. Step  603  is repeated and the quantity of pre-compressed material can be doubled, tripled, etc. The number of times the pre-compressing ram  317  introduces material in the pre-compression chamber  319  is input by the user as an input parameter  405 . 
     The compression stage  505  is illustrated in  FIG. 7 . During compression, both the long cylinder  323  and the short cylinder  329  move towards the center of the compression chamber  325 , in steps  703  and  705  thereby compressing further the pre-compressed material. Step  707  indicates that when the long cylinder  323  has closed the pre-compression chamber  319 , the pre-compression ram  317  can leave its extended position and retracts to its home position. 
     The ejection stage  507  is illustrated in  FIG. 8 . After the start of the ejection stage  507 , the long cylinder  323  and the short cylinder  329  move synchronously to bring the compressed material to the eject zone  331 , as illustrated in steps  803  and  805 . As seen in  FIG. 2 , the eject ram  335  is lower than the height of the compression chamber  325  and is equipped with an eject brush  215  that extends higher than the lower level of the compression chamber  325 . In step  807 , the eject brush  215  nudges the compressed material and frees it from the tip of the long cylinder  323  and/or the short cylinder  329 . As indicated in step  809 , if the ingot floor  227  is present, the eject ram  335  reverses direction and pushes the compressed ingot down the ingot chute  337 . If the ingot floor  227  is not present, the compressed ingot falls into the saw module  339  and the eject ram  335  goes to its extended home position. 
     The optional sawing stage  509  is illustrated in  FIG. 9 . In the first step  903 , the align cylinder  341  pushes the ingot against saw reference wall  229 . In the second step  905 , the align cylinder  341  retracts to its home position. Next in step  907 , the sawing ram  343  pushes the ingot through the saw array  227 , thereby generating pucks which fall to the puck chute  345 . In the final step  909 , the sawing ram  343  retracts to its home position. 
       FIG. 10  illustrates an example timing diagram  1001  covering the compression stage  1003 , the ejection stage  1005  and the pre-compression stage  1007 . The timing diagram  1001  plots along its vertical axis (Y-axis) the displacement of the four following linear actuators: pre-compression ram  1009 , the long cylinder  1011 , the short cylinder  1013  and the eject ram  1015 , against a common time scale  1017  (X-axis). The convention for the displacement of the linear actuators along the vertical axis (Y-axis) is the following: Extension is in the upward direction and retraction is in the downward direction. Note that  FIG. 10  is a simplification and that the scales both in the Y-axis and the X-axis are arbitrary and not to scale. 
     At the beginning  1019  of the compression stage  1003 , the long cylinder  323  represented by line  1011  and the short cylinder  329  represented by line  1013  both move in extension towards the center of the compression chamber  325 . At time  1021  when the long cylinder  323  has expelled the pre-compressed material from the pre-compression chamber  319 , as illustrated by the reference position  1021 , the pre-compression ram  317  represented by line  1009  is allowed to leave its extended position  1025  at the pre-compression chamber  319  and starts retracting towards its home position  1027 . 
     At time  1029  when the short cylinder  329  represented by line  1013 , clears the eject zone and reaches its position  1031  where it caps the compression  325  with a small adjustable offset depending on the material being densified, the short cylinder  329  is stopped and allowed to be locked in position. For an push-pull hydraulic system, for example, this can be achieved by shutting off the cylinder hydraulic valves. This stop position  1031  is sensed by the controller  347  using a contact-less position sensor on the short cylinder  329 . 
     The short cylinder  329  waits at this position  1031  until the material being pushed by the long cylinder  323  reaches the tip of the short cylinder  329 . At this moment  1033 , the long cylinder  323  represented by line  1011  is at position  1035 . Position  1035  is not a fixed position in space as it vary according to the quantity of pre-compressed material admitted in the compression chamber  325 . Starting at position  1035 , the speed of the long cylinder  323  will decrease due to the extra resistance caused by the compression of the material, as illustrated by the lower slope in line  1011  in the time interval  1033  to  1037 . At time  1033 , the system controller  347  senses the extra resistance on the long cylinder  323  as a pre-set pressure on the digital hydraulic pressure sensor and signals short cylinder  329  to continue its extension. Cylinders  329  and  323  are activated for the distinct programmable time interval  1033  to  1037  when the hydraulic pressure has reached the given set pressure setpoint, thereby effecting an adequate compression at the short cylinder end of the compressed material. At the end of this compression motion at time  1037 , the short cylinder  329  is commanded again to hold its position  1039  for a pre-determined time interval  1037  to  1041 . During this time interval  1037  to  1041  the long cylinder  323  continues compressing the material until is reaches position  1043 . 
     At time  1041 , the short cylinder  329  is commanded to retract. The speed of displacement of short cylinder  329  is adjusted to match the speed of displacement of the long cylinder  323 , so they move together transporting the compressed ingot, until time  1045  when the ingot has cleared the compression chamber  325 . The relative speed control is effected by the use of a bypass hydraulic valve enabling the flow of hydraulic fluid from actuator C 2  to actuator C 3 . At this time  1045 , the long cylinder  323  stops at its extended position  1047 , just outside the compression chamber. 
     The short cylinder  329  moves an additional short distance and stops at its fully retracted position  1049 , helping to release the compressed ingot. At this moment  1051 , the eject ram  325  retracts starting from its fully extended position  1053  towards its fully retracted position  1055 . During the time interval  1051  to  1057 , the eject brush XXX mounted on the eject ram  325  pushes the compressed ingot in the upwards direction allowing it to unstick from the long or short cylinder tip if required. The eject ram is enabled only if the signal from the photocell in the ejection chamber confirms that a fuel ingot is indeed present at the exit of the compression chamber. The eject ram  325  reaches it fully retracted position  1055  at time  1057 . At time  1057 , the long cylinder  323  is moved towards its fully retracted position  1059 . 
     Before the long cylinder  323  reaches its fully retracted position  1059 , the precompression ram  317  is moved from its fully contracted position  1027  towards the pre-compression chamber  319  to perform pre-compression of the input material its pushes from the hopper. 
       FIG. 11  illustrates a generic timing diagram  1101  covering the sawing stage. The timing diagram  1101  plots along its vertical axis (Y-axis) the displacement of the two following linear actuators: the align cylinder  1103  and the sawing ram  1105 , against a common time scale  1107  (X-axis). The convention for the displacement of the linear actuators along the vertical axis (Y-axis) is the following: Extension is in the upward direction and retraction is in the downward direction. Note that  FIG. 11  is a simplification and that the scales both in the Y-axis and the X-axis are arbitrary and not to scale. 
     At the beginning  1109  of the sawing stage the align cylinder  341  represented by line  1103  and the sawing ram  343  represented by line  1105  are both in the retracted end-of-course positions  1111  and  1113 , respectively. At time  1019  the sawing ram  1105  move in extension until it contacts the ingot and aligns it against the sawing wall reference  229 . The align cylinder  341  does not need a high pressure to accomplish this action and pneumatic actuators are suitable for this purpose. The align cylinder  341  stops at a position  1115  corresponding to the length of the ingot. After a short waiting period  1117 - 1119  to prevent any bouncing, the align cylinder  341  can go to it end-of-course home position  1111 . When the align cylinder  341  reaches its end-of-course home position  1111  at time  1121 , the sawing ram  1105  can begin to push the ingot against the blades  227 . The sawing ram  1105  advances slowly to avoid damage on the saw blades and to perform nice cuts until time  1123  when it reaches its end-of-course extended position  1127 . After waiting a time interval from  1123  to  1125  to ensure that the pucks fall down the puck chute, the sawing ram  1105  retracts towards is end-of-course home position  1113  at time  1129 . 
     Pre-compression Stage 
     As described in  FIG. 10 , the pre-compression stage starts with the pre-compression ram fully extended. The first action is for the pre-compression ram to retract to its fully retracted position. As shown in  FIG. 12 , the pre-compression ram  203  is fully retracted and a certain volume of compressible material  1203  has fallen from the hopper  139  to the pre-compression ram  203  by gravity. 
     The pre-compression ram  203  pushes the compressible material towards the pre-compression chamber  209 .  FIG. 13  shows the pre-compression ram  203  having completed its extension and the resulting pre-compressed material  1303 . 
     Compression Stage 
     The compression stage begins with a simultaneous motion of long cylinder  1205  and the short cylinder  1207  towards the compression chamber  211  as illustrated in  FIG. 14 . The short cylinder  1207  enters through the right hand entrance of the compression chamber  211  and stops a short distance inside the compression chamber  211 . This distance is calibrated using a movable position sensor that detects the presence of a reference attached to the short cylinder  1207 . The short cylinder  1207  is held stationary in this position until the pre-compressed material gets in contact with the short cylinder  1207 . 
     The long cylinder  1205  pushes the pre-compressed material out of the pre-compression chamber  209  and into the compression chamber  211 . After a short moment, the pre-compressed material reaches the end of the short cylinder  1207  and the compression action starts as illustrated in  FIG. 14 . The material  1403  is undergoing compression and is confined by the walls of the compression chamber  211 . 
     When fiber material is being compressed into an ingot by a piston mechanism, friction is generated against the walls, thereby creating a spatial pressure gradient inside the ingot. The pressure is highest close to the pushing piston and diminishes monotonously inside the ingot with the distance from the piston. The decrease of pressure is a function of the diameter of the ingot and material used. The method proposed in this invention is to use a pushing motion from both ends of the ingot to flatten the pressure distribution, resulting in a more uniform compaction and enabling longer ingots to be manufactured. The bi-directional compression provides the necessary pressure to compact the material in a fashion that permits the proper distribution of lignin and natural binders within the media when using simple standard hydraulic cylinders. 
     As the material gets compressed, the pressure required by the long cylinder actuator  129  for the long cylinder  1205  to continue advancing increases. When a threshold level of pressure applied to the long cylinder actuator  129  is exceeded, then the short cylinder  1207  is also commanded to advance towards the center of the compression chamber  211  in order to perform a compressive action in the right hand side of the material  1403 . Eventually the pressure required by the short cylinder actuator  131  for the short cylinder  1207  to advance also reaches a threshold level of pressure. When both levels of pressure exceed predetermined thresholds, then the compression is considered to have been completed and the system moves to the eject stage. 
     Eject Stage 
     At the beginning of the eject stage, the eject ram  213  is fully extended as shown in  FIG. 15 . The eject ram  213  is located a few centimeters lower than the centerline of the compression chamber  211  as shown in  FIG. 16 , so the compressed can be ejected above the eject ram  213 . 
     The eject stage begins by commanding both the long cylinder  1205  and the short cylinder  1207  to move towards the right (towards the eject zone), with the same velocity in order to maintain the integrity of the compressed ingot. The motion of the long cylinder  1205  continues until it has reached its own end-of-course position adjusted with a reference sensor so that the tip of the long cylinder  1205  exceeds the compression chamber  211  by a small amount. The short cylinder  1207  continues its motion until it reaches its own end-of-course position, a short instant after the long cylinder  1205  has stopped.  FIG. 15  shows the compressed ingot  1503  ejected from the compression chamber  211  and in the eject zone  1505 . 
     Because of the high pressures applied and the nature of the compressible material, the compressed ingot  1503  tends to adhere to the tip of the long cylinder  1205 , as illustrated in  FIG. 15 . A brush  215  extending a short amount above the bottom of the compression chamber  211  is installed on the eject ram  213  to help free the ingots that bind to the tip of either cylinder. This motion is performed on the retracting stroke of the eject ram  213 . When the brush  215  passes by the ingot  1503 , it applies a shearing force to the ingot  1503 , allowing it to come free and fall. 
     In the case where the ingot floor  217  is present, as shown in  FIG. 16 , the ingot  1503  falls on the ingot floor  217 . After the retract motion, the eject ram  213  extends towards the back of the press  101 . The motion pushes the ingot  1503  down the sawing chute  219 . 
     In the case where the ingot floor  217  is absent, after the retracting stroke of the eject ram  213 , the ingot  1503  falls down the sawing chute  221  at the lower level  105  of the press  101  as illustrated in  FIG. 17 . The next step for this ingot  1503  is to be cut into pucks. 
     Sawing Stage 
     After falling down the sawing chute  221 , the ingot  1503  lands on the sawing floor  231 . Next, the align cylinder  1803  pushes the ingot  1503  towards the left along its axis until the ingot  1503  is pressed against the sawing wall reference  229 , as illustrated in  FIG. 18 . The align cylinder  1803  then retracts away from the ingot  1503 . Next, the sawing ram  223  pushes the ingot  1503  toward the array of blades  227  as shown in  FIG. 19 . The sawing ram  223  guides the ingot  1503  all the way through the sawing blades since it has slots corresponding to individual blades as seen in  FIG. 2 . The ingot is thus cut into multiple pucks of length equal to the separation between blades. 
     With an adequate choice of blade positioning and the use of the alignment mechanism composed of the align cylinder  1803  and the sawing wall reference  229 , pucks  2005  of equal length are produced except for one shorter puck  2003  at the end opposite to the sawing wall reference  229 . The pucks are seen exiting in the puck chute  233  in  FIG. 20 . 
     In one example the press  101  is configured to produce 50 mm diameter fuel briquettes. The briquettes are either uncut 38 to 225 mm long ingots or 25 mm long pucks as cut by the saw module  225 . This example press possesses various actuators, cylinders and rams. The press uses a 50 mm diameter cylinder with a 560 mm stroke (called the long cylinder  1205 ) and a 50 mm diameter cylinder with a 290 mm stroke (called the short cylinder  1207 ). The pre-compression ram  203  is a rectangular prism of 50 mm height and 228 mm width terminated by a concave cylindrical section with a radius of 51.25 mm as shown in  FIG. 2 . The hopper  139 , used to admit the compressible input material in the press  101 , is a rectangular prism with nominal dimensions of 490 mm (height) by 205 mm (depth). The width of the hopper can be continuously varied from 15 mm to 150 mm, yielding a hopper volume from 1470 cm 3  to 14 7000 cm 3 . The hopper has a high-level indicator  145 ,  146  and a low-level indicator  147 ,  149  located 230 mm and 380 mm from the bottom of the hopper, respectively. The pre-compression chamber  209  has a length of 240 mm and an internal diameter of 50 mm. The compression chamber  211  has a length of 280 mm and an internal diameter of 50 mm. The eject zone  1505  in  FIG. 15  offers a 185 mm clearance, sufficient to eject the longest logs. Finally, when the saw module  225  is enabled, the logs are pushed against an array of circular saws, for example 8 circular saws, with a diameter of 203 mm and a width of 2.8 mm. The saws are separated by 27.8 mm in order to produce pucks that measure exactly 25 mm in length. 
     Feedstock fibers may need pre-processing to achieve proper humidity and particle size input feed requirements. 
     Although referred to as long and short cylinders, the cylinders could be of a similar length and need not have a length difference. They can be simply a first and a second cylinder. 
     The embodiments described above are intended to be exemplary only. The scope of the invention is therefore intended to be limited solely by the appended claims.