WO2016025520A1 - Procédé et appareil de densification de matériau - Google Patents

Procédé et appareil de densification de matériau Download PDF

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Publication number
WO2016025520A1
WO2016025520A1 PCT/US2015/044714 US2015044714W WO2016025520A1 WO 2016025520 A1 WO2016025520 A1 WO 2016025520A1 US 2015044714 W US2015044714 W US 2015044714W WO 2016025520 A1 WO2016025520 A1 WO 2016025520A1
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WIPO (PCT)
Prior art keywords
log
logs
heating
pressure
barrel
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PCT/US2015/044714
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English (en)
Inventor
John T. Kelly
Nehru CHEVANAN
George Miller
Original Assignee
Altex Technologies Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US14/459,157 external-priority patent/US20140346702A1/en
Application filed by Altex Technologies Corporation filed Critical Altex Technologies Corporation
Publication of WO2016025520A1 publication Critical patent/WO2016025520A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
    • B30B15/34—Heating or cooling presses or parts thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B11/00—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses
    • B30B11/22—Extrusion presses; Dies therefor
    • B30B11/224—Extrusion chambers
    • B30B11/225—Extrusion chambers with adjustable outlet opening
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B9/00—Presses specially adapted for particular purposes
    • B30B9/02—Presses specially adapted for particular purposes for squeezing-out liquid from liquid-containing material, e.g. juice from fruits, oil from oil-containing material
    • B30B9/04—Presses specially adapted for particular purposes for squeezing-out liquid from liquid-containing material, e.g. juice from fruits, oil from oil-containing material using press rams
    • B30B9/06—Presses specially adapted for particular purposes for squeezing-out liquid from liquid-containing material, e.g. juice from fruits, oil from oil-containing material using press rams co-operating with permeable casings or strainers
    • B30B9/067—Presses specially adapted for particular purposes for squeezing-out liquid from liquid-containing material, e.g. juice from fruits, oil from oil-containing material using press rams co-operating with permeable casings or strainers with a retractable abutment member closing one end of the press chamber
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L5/00—Solid fuels
    • C10L5/02—Solid fuels such as briquettes consisting mainly of carbonaceous materials of mineral or non-mineral origin
    • C10L5/34—Other details of the shaped fuels, e.g. briquettes
    • C10L5/36—Shape
    • C10L5/363—Pellets or granulates
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L5/00—Solid fuels
    • C10L5/02—Solid fuels such as briquettes consisting mainly of carbonaceous materials of mineral or non-mineral origin
    • C10L5/34—Other details of the shaped fuels, e.g. briquettes
    • C10L5/36—Shape
    • C10L5/365—Logs
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L5/00—Solid fuels
    • C10L5/40—Solid fuels essentially based on materials of non-mineral origin
    • C10L5/44—Solid fuels essentially based on materials of non-mineral origin on vegetable substances
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/10—Biofuels, e.g. bio-diesel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel

Definitions

  • the present invention relates to densification of material, such as lignocellulosic biomass.
  • Densification is an important unit operation involved in utilization of initially lower density material, because it reduces handling, storage and transportation costs.
  • Lignocellulosic biomass material is one material type that benefits from densification.
  • biomass is densified for production of Solid Fuel (eg. Wood pellets) used in stoves for heating in the US and elsewhere, for use in utility
  • Solid Fuel eg. Wood pellets
  • the pelleting and cubing process starts with the drying of biomass to required moisture content followed by sizing. Drying and sizing are two high energy consumption processes. Sizing requirements for these two processes vary. For small pellets, the biomass must be ground to small particles that are then reconstituted in the pellet mill. Most existing cubers/briquetters are used to make cubes of size less than 3". For cubing lignocellulosic materials must be reduced in size to about twice the width of a cube. Therefore, in both processes, the basic biomass structure is broken down so that air can be expelled and a high density form can be achieved in the compaction step.
  • Table 1 compares the mechanical energy requirement for compressing the biomass in pelleting and cubing processes. In addition a lot of heat energy is required for activating the inherent binder or externally added binder. In typical pelleting and cubing operations, the inherent lignin is activated by frictional heating with the die of the biomass to greater than 70C, where lignin binding properties are good. Frictional heating is wasteful, since the expensive electric power driving the machine is the source of heat. Therefore, these processes are high energy
  • a novel process and apparatus for densification of material such as lignocellulosic biomass material has been defined and developed.
  • the process is flexible in that it can be easily adapted to densify a range of materials that have either an inherent or added binder that is activated by heat.
  • Examples of such material include lignocellulosic materials that consist of fibrous materials with lignin that can be used to bind the fibrous material together into logs, or densified structures.
  • Materials that have been densified include corn stover, wheat straw, rice straw, switchgrass, miscanthus and alfalfa. In all cases, these fibrous materials were densified at up to 50 Ib/cf, starting from ⁇ 1 Olb/cf raw material.
  • the invention provides a process that can be used to densify materials that contain only minor amounts, or do not contain lignin.
  • Examples include cardboard, paper, municipal solid waste, cellular plastic material residues and cellular inorganic materials and like materials.
  • a heat activated binder needs to be added in sufficient quantities to yield the required strength and durability for the densified product.
  • the added binder could be lignin based, or a hydrocarbon-based material that has the needed binding at the desired activation temperature. While the lignocellulosic materials typically experience binding activation at approximately 70C, the added binder activation temperature could be different.
  • the compaction pressure and residence time at pressure, heating and cooling may be adjusted to yield optimal results.
  • densification of biomass material (a) requires no preprocessing such as drying and size reduction; (b) in the case of lignocellulosic material takes advantage of an inherent shear, tensile and/or compressive strength in the compacted material to provide structural integrity; (c) requires only moderate mechanical energy (as compared to pelleting or cubing) to remove air spaces inside and between the material during compaction; (d) uses external heat to activate binder, rather than heat energy generated from mechanical work; and (e) requires heating only near the surface to activate binder in a thick enough surface layer to encase the material with sufficient strength to maintain densification and resist handling, storage and transport stresses without degradation and (f) requires cooling only near the surface of the compacted product for setting binder and producing a densified product with the sufficient structural strength and/or integrity for storage and transportation
  • lignocellulosic biomass is
  • the biomass may arrive at a compactor (according to the invention) in the form of bales, or other portions of biomass.
  • the material is initially available on fields at a density of about 1 -2 Ibs/cf. In many cases, it is then compressed to any required format having approximately 10-15 Ibs/cf using a baler or any other equipment. According to the preferred embodiment, the biomass is then compressed into logs of density between about 30 to 60 Ibs/cf for reducing the storage, handling and transportation cost. In this process, there is no size reduction or drying necessary for making logs.
  • durable densified logs of size ranging from 6" to 15" in diameter having densities ranging from 30 Ibs/cf to 60 Ibs/cf can be produced.
  • log sizes and/or densities can be greater or less than the values given, depending on need.
  • Logs produced in accordance with one aspect of the invention are larger than pellets and have lower surface area per volume than pellets. As such, logs produced in accordance with this aspect of the invention are far less dependent on frictional effects, or mechanical work done on the material to raise the temperature, which correspondingly lowers power requirements for log making. Heating is used as a replacement for mechanical work, with the overall energy cost for densification of material into logs being substantially lower than pelleting. The high cost of electric power heating (or mechanical working of material) is replaced by a much lower cost of heat provided by biomass or other low cost fuel combustion.
  • a densified biomass material is produced that has a protective shell along the periphery of the material.
  • the shell is formed by heat activated binder material that may be added to, or inherent in the material.
  • the shell of strengthening binder material is formed by heating the compacted biomass material (to activate the binder) then cooling while the biomass material is held in its compacted state (setting the binder).
  • the densified product is a log that is relatively large (as compared to pelleting or cubing) and that derives its structural integrity from an encapsulating shell of set binder material and the fibrous nature of the material forming the core of the log.
  • compaction and heating times or phases are adjusted or varied depending on the material type and binder properties.
  • a compression and heating zone are de-coupled from each other, i.e., occurring at separate times and/or places, to simplify control over the process or reduce overall complexity. Or these zones may be de-coupled for purposes of maximizing throughput such as when a heat activation time for the binder is much higher than the time needed to compress the material in a controlled manner.
  • densification equipment for performing one or more of the aforementioned processes makes densified logs of 1 1 " diameter having density ranging from 30 Ib/cf to 60 Ibs/cf.
  • the main parts of the equipment may include a feeding section, heating section, cooling section, pusher or piston, and gate.
  • a hydraulic circuit may be used to operate a door of the feeding section, gate and pusher.
  • a system of circulated oil may be used to activate binder (heat) and set binder (cool) for purposes of forming stable logs in a low-energy manner.
  • stable logs are produced in the following steps:
  • Bales having density of about 10 Ib/cf are discharged from a conveyor into the feeding section.
  • the door of the feeding section closes and may modestly compress the bale into the needed cylindrical shape ahead of primary compaction.
  • a heated piston ram/pusher is actuated and moves the bale into the heated zone and compresses the biomass to a preset density level of about 40 Ib/cf against the gate and the compacted biomass is preheated for about 15 seconds.
  • the heating section can accommodate > 4 logs which will increase the binder activation time to 5 X preheating time.
  • a compactor is configured to accept baled formats of material including lignocellulosic material, utilizes a continuous heating and cooling section, uses a variable load and speed compacting piston for minimal energy consumption, and operates a heated gate for compaction of material.
  • the gate may include internal oil flow lines and may be fitted with Teflon coating for friction reduction.
  • the compactor may utilize circumferential flow of oil for increasing the velocity of oil flow for rapid heat transfer.
  • the compression section may include tie rods for increasing the life of the compression and feeding section.
  • a control unit for controlling operation of the compactor.
  • Test results for different material indicate that in order to produce high quality logs of a consistent density, as well as good durability, including resistance to breakage and abrasion, a measured hydraulic backpressure on the compaction piston cylinder may be managed between a pressure that is high enough for good compaction, but low enough to prevent overstressing the machine and/or wasting power.
  • a feedback system can be implemented that would be able to operate a piston (used to compact biomass) at a selected pressure, to produce more consistent logs, even as feed material moisture, loading weight and initial density vary. Given the great variability of biomass materials, this would be an important feature.
  • densification of a material comprising the steps of: compressing the material to form a log; and while maintaining the log in a compressed state, heating the log to activate a binder, and then cooling the log to set the binder.
  • an apparatus for compacting biomass material comprising: a barrel including a heating section and cooling section; a heat source coupled to the heating section; and a piston ram configured for being actuated to compress the material into a first log and push the first log into a second log disposed in one of the heating and cooling sections.
  • a system for densifying material comprising a press for compressing the material into logs; and a structure, coupled to the press and holding under compression a plurality of such logs that were received from the press, the structure including a heating section and a cooling section for simultaneously activating and setting binder in the logs.
  • the material is baled, lignocellulosic biomass material; wherein the material has a density of less than about 10 lb / cf and the logs have a density of at least about 30 lb / cf; wherein the system has a total energy usage of about 25 Kwh per ton of logs produced.
  • FIGS. 1 -2 are first and second views of a compactor for densification of biomass material.
  • FIG. 3 is a first cross-sectional side view of the compactor showing a bale of biomass material being loaded into a receiving section of the compactor.
  • FIG. 4 is a second cross-sectional side view of the compactor showing a door or bale press being closed, in preparation for a compression of the biomass material.
  • FIG. 5 is a third cross-sectional side view of the compactor showing a compression of the material into a log.
  • FIG. 6 is a fourth cross-sectional side view of the compactor showing the formed log being moved into a downstream heating section of a barrel of the compactor.
  • FIG. 7 is a fifth cross-sectional side view of the compactor showing the loading of a second bale into the compactor.
  • FIGS. 8A-8D show flow processes for densification of biomass material according to the disclosure.
  • FIGS. 9A and 9B are isometric and cross-sectional views, respectively, of a switchgrass log made in accordance with the disclosure.
  • FIG. 10 is a plot showing temperature profile verses depth during heating and cooling of logs constructed in accordance with the disclosure.
  • FIG. 1 1 is a plot showing a theoretically determined temperature profile inside a log during a densification process.
  • FIG. 12 shows the cooling load needed for a log.
  • FIG. 13 plots capacity verses process time.
  • FIG. 14 plots density of logs versus process time.
  • FIG. 15 is a block diagram for a control system for monitoring a
  • FIG. 16 is a process flow diagram for monitoring a compaction pressure using the system of FIG. 15.
  • FIG. 17 is an example of a constrictor and actuator for automatically adjusting the constrictor and thereby the compaction pressure in response to control signals received from a control unit.
  • FIGS. 1 -7 depict a compactor and steps associated with the densification of a lignocellulosic biomass material according to the disclosure.
  • the compactor receives the lignocellulosic biomass material in the form of a bale and converts the bale into a compacted, densified form which, for the sake of convenience shall be called a log.
  • the term "log" is not intended to be limiting as to its final form. Rather, a log is simply intended to mean the densified product of a densification process according to the disclosure.
  • throughput for the compactor can be varied from 1 to 4 tons per hour (TPH).
  • a bale 10 rides a conveyor 5 that loads the bale 10 into a hopper 12 aligned with an opening in a barrel 20 of the compactor (FIG. 3).
  • the compactor barrel 20 has a receiving section 22, compression and heating section 24, heating section 26, cooling section 28 and constrictor section 21 .
  • bale 10 enters the barrel 20 at the receiving section 22.
  • a bale press 22a (or hinged door) moves downward or closes to modestly compress the bale 10 into a cylindrical shape ahead of primary compaction, which occurs at the compression section 24 (FIG. 4).
  • a cylinder 31 Located to the left end of the receiving section 22 is a cylinder 31 that holds a heated piston ram 30 for compressing the bale 10.
  • the piston ram 30 is actuated and moves the bale 10 into the compaction section 24 where the bale 10 is then compressed between the heated head 32 of the piston ram 30 and a heated barrier gate 40 which is located at the right hand side of the compression section24.
  • the bale 10 is compressed into a log 1 1 having density of about 40 Ib/cf ( Figure 5).
  • the compression section 24 walls are heated by a jacket 25 containing circulating oil to soften the biomass material and/or start activating binder.
  • the barrier gate 40 is lifted and the log 1 1 is moved forward against earlier compacted logs located in the downstream heating section 26 and cooling section 28 of the barrel 20 (eight such logs are shown).
  • the heating section has walls heated by a jacket 27 containing circulating hot oil.
  • the cooling section may have radiating fins or the like for passive cooling, or have a jacket 29 containing a circulating oil for dissipating heat. Through the length of the multiple logs in these heating and cooling zones, respectively, of the compactor the logs are maintained in a compressed state. Movement of log 1 1 into the heating section 26 by the actuated piston ram 30 forces a log 1 1 ' out of the barrel 20 at the discharge end 21 (FIG. 6). The piston ram 30 is retracted and the barrier gate 40 closed to restart the compaction process.
  • the log 1 1 As later logs are pushed downstream the log 1 1 is eventually moved beyond the heating section 26 and into the cooling section 28, where the log 1 1 periphery is cooled to the needed depth to set the binder and prevent loss of compaction after the log is discharged from the end 21 of the compactor.
  • the heating of the logs may occur at different stages along the barrel 20, and/or in different ways during the process depending on the biomass material and needed binder activation to provide structural integrity to the log.
  • Mode 1 heating is done only to the left of the gate 40 (ends and sides heated) so that both compaction and heating occur at the compaction section 24 (field tests were conducted using this arrangement). Heating during the compaction phase softens the biomass material to make compaction less dissipative, but the added heating time can limit throughput. This mode of heating and compaction may be preferred for binders that require similar heating time to the compaction time.
  • Mode 2 some heating is done to the left of the gate 40 and more to the right of the gate 40 ( side heated). This mode is preferred for binders that require more heating than compaction time. Mode 2 yields some beneficial softening and decouples heating time from compaction time, which maximizes throughput for those binders that require more heating than compaction time. For example, for an arrangement of four logs to the right of the gate 40 and located in the heating section 26 zone before the next log is pushed beyond the gate 40 (as shown), the heating time would be four times the compaction timescale for the material. It is desirable to limit heat to the periphery of the log, particularly in the right of the gate 40 as this limits the cooling time needed to set the binder.
  • Mode 3 log heating occurs only to the right of the gate 40 in the heating section 26, for decoupling the compaction from the heating time (sides-only are heated). This mode may be preferred as it is simpler to control the heat added to the log than mode 2, but it only heats the cylindrical periphery, and thereby has less binding on the log faces. This may be acceptable for some material.
  • FIGS. 8A-8D provides flow charts summarizing Modes 1 -4.
  • the low density material is preferably lignocellulosic biomass material, but it need not be limited to lignocellulosic or even biomass material.
  • these processes may be adapted to densify material that contains only minor amounts, or do not contain, lignin. Examples include cardboard, paper, municipal solid waste, cellular plastic material residues, cellular inorganic materials and like materials.
  • a heat activated binder is added in sufficient quantities to yield the required strength and durability for the densified product.
  • the added binder could be lignin based, or a hydrocarbon-based material that has the needed binding at the desired activation temperature.
  • the lignocellulosic materials experience binding activation at approximately 70C, the added binder activation temperature could be different.
  • the compaction pressure and residence time at pressure, heating and cooling may be adjusted to yield optimal results, as will be further appreciated in view of the discussion that follows.
  • logs may be produced at a needed rate with a very modest amount of mechanical work needed, i.e., mostly the work done by the piston head 32.
  • the piston axially compresses the material in a single motion, and then pushes logs along the barrel 20 into heating and cooling areas using this same motion.
  • upstream bales are heated to activate binder.
  • the piston pushes everything further along the barrel 20 until they eventually exit the barrel as finished logs with set binder.
  • the process by design, requires only a very modest amount of mechanical / electrical energy.
  • Ram forces for the piston head 32 may be produced by a high pressure cylinder fed by a positive displacement hydraulic fluid pump. Moreover, the head 32 hydraulic force, and hydraulic forces for activating the gate 40 and door 22a may be controlled through a single hydraulic circuit.
  • the walls of the heating section 26 (and, optionally, the walls of the compression section 24), head 32 and face of the gate 40 may be heated using a hot oil system fired by low- cost biomass in the production system. Thermal oils satisfying a 150C maximum oil temperature requirement and having adequate flow rates at this temperature are readily available for providing sufficient heat transfer to surfaces of the compactor for binder activation.
  • a positive air flow over the cooling section 28 shell may be used to augment cooling produced by heat soaking into the log interior, thereby promoting evaporation of water.
  • Sufficient vapor exit paths may be included over the cooling section 28 length to allow vapor to escape while still retaining the solid material at the required compression level.
  • Air cooling may be used for cooling logs in the cooling section 28, although it is preferred to remove heat more quickly using a circulating fluid, such as a cooling oil.
  • Air cooling may be used if the cooling section 28 is lengthened (or provided with increased surface area for radiating heat) so that a log is sufficiently cooled to set binder before being discharged from the channel 20.
  • a circulating fluid such as a cooling oil.
  • Air cooling may be used if the cooling section 28 is lengthened (or provided with increased surface area for radiating heat) so that a log is sufficiently cooled to set binder before being discharged from the channel 20.
  • an oil cooled jacket fitted around the cylindrical cooling section 28 to extract heat. The oil flows through a radiator where a fan cools the circulating oil. This system may be designed to yield any needed cooling requirement.
  • a biomass material (switchgrass) was loaded into the first compression die and compacted using the hydraulic press. The compacted material was then placed in the second compression die and pressed again using the hydraulic press. As the switchgrass is pressed in the second die, it is heated to the required temperature using band heaters. The temperature is controlled through a rheostat and is measured by a thermocouple. As the temperature of switchgrass reaches the required level, heating is stopped and the switchgrass is cooled using a fan mounted on the press frame. Once cooled to the required level, the switchgrass is expelled from the second die as a switchgrass log. [0061] In contrast to a pelleting or cubing operation, the switchgrass was not sized ahead of compaction.
  • the initial moisture content of the switchgrass was found to be 12%, using the ASABE standard procedure. To increase the moisture content to 15% and 30%, a known quantity of switchgrass and moisture was transferred to a polyethylene bag, stored overnight and used in the experiments. The log formation process was then followed with the high moisture content switchgrass. Test results using the higher moisture-content switchgrass suggest that moisture content below about 20% are best for making logs.
  • Tests were also conducted with a second stage compaction pressure set at 650psi and a biomass peak temperature at the periphery of the log set to 100C. Given that the die heats the log from the outside, the interior of the log was probably much less than 100C. Once the periphery temperature reached 100C, the die heater was shut off and the die cooled by the fan. Once the log temperature reached the target cool-down temperature, the log was ejected from the die and the density measured. For conditions where the cool-down temperature was too high and the binder had not solidified, the log would experience spring-back and the density would decrease. For the case where the binder did reach a solid and strong condition, the log did not spring-back, and density was higher.
  • Tests were also conducted on the activated binder, which occurs mostly along the outer surface of the log. Activation of binder in the material along the outer surface, rather than throughout the material, reduces energy costs. With this objective in mind, the process seeks to limit use of binder to a log's periphery, which can provide strength to the log in the form of a shell that encapsulates the log. Shell strength is much more important to log integrity than core strength. Essentially, by producing a strong shell, the bulk biomass may have the necessary strength and weather resistance. In support of this objective, tests were conducted to determine the ranges of minimal thermal energy input to the log that would be needed to activate binder at the log's periphery to form the shell.
  • the wall temperature of the compression die was maintained at either 150°C or 175°C, before the biomass was compressed.
  • Top and bottom plates used for compressing the biomass were also heated to the same temperature along with die section.
  • the biomass was heated for a specified time under compression.
  • the log was pushed into a downstream cooling section, where the die was maintained at room temperature.
  • a fan was used to dissipate heat in the log in the cooling section. After cooling, the formed log was pushed out of die.
  • the bottom plate and top plate were placed in contact with the biomass for the entire period of both thermal activation and setting.
  • the density (or specific weight) of logs is measured as the ratio of weight to volume of the log.
  • the volume of logs was measured by considering the logs as cylinders. All the density measurements were made after cooling the logs to room temperature and allowing for any spring back or recoil. Hence, the measured densities are a relaxed density of logs.
  • the measured density of cylindrical logs when heating only one end and the round sides is shown in TABLE 1 . Densities for logs heated on all sides are shown in TABLE 2.
  • the density of logs formed by activation of binder on the top and bottom surfaces of the logs and sides was much higher than logs without activation on both the top and bottom end surfaces.
  • the density of logs produced by activation of binder on both sides of the log was found to be around 30 Ibs/cf at a compressive pressure of 300 psi.
  • the density of logs produced at a pressure of 900 psi, without activation of binder on the top and bottom surfaces was around 30 Ibs/cf.
  • the compressive strength of logs was measured by inserting a load cell in the compression testing equipment to determine log compressive force.
  • An Omega model load cell having a capacity of 50,000 lbs, was used to measure the log compressive strength.
  • the load cell was fixed between the compression rod and the bottom frame of the press.
  • Logs were placed in such a way that the radial direction aligns with the direction of compression. When compressing the logs in the radial direction, the recorded resistance force was found to increase continuously, reach a maximum value and then start to decrease. The maximum force during the
  • Log drop strength is measured by dropping the log from a height of 10 feet onto a concrete surface. During drop tests, it was observed that the logs do not disintegrate or break into pieces after many drops. This is due to the strength of binder as well as the configuration of raw switchgrass used for the production of logs. Since the switchgrass was used without sizing, long stalks of the grass were contained within the logs and this material tended to add significant strength to the log. Essentially, the log consisted of stalks that have strength that are "glued" together by the binder, somewhat like a composite material (e.g. fiberglass) construction. In contrast, if the switchgrass was ground to a fine dust and compacted with binder, it would lose this composite strength.
  • a composite material e.g. fiberglass
  • any breakage would result in the release of dust that could be a nuisance.
  • the drop strength is defined as the number of drops after which the log becomes more flexible and weight is reduced by approximately 10%.
  • FIG. 9A A switchgrass log produced during testing is shown in FIG. 9A.
  • a similarly- made switchgrass log was cut in half to examine is cross-sectional characteristics.
  • the cross-section of the log is shown in FIG. 9B.
  • the biomass was heated on the periphery of the log for a very short duration. But a close observation of the log shows good binding inside the log.
  • the melting of natural binder components in the log occurs due to high temperature as well as pressure. Even though the inside temperature is below the glass transition point of lignin, good binding was observed inside the logs, potentially due to the migration of active binder.
  • thermocouples were located at varies places on and within the biomass. These temperatures were plotted verses time to better understand the changes in temperature occurring on and within the log. Additionally, detailed heat transfer analysis was carried out to determine the unsteady state heat transfer inside the compressed switchgrass.
  • the thermal diffusivity is calculated using the temperature profile recorded during heating and cooling of logs. From the temperature profile over the total process time, the diffusivity is calculated, using the method described by Adams et al. (1976). The thermal diffusivity is given by the equation:
  • the total heat requirement for a demonstration scale log making machine was determined from the recorded temperature data at different depths collected in the lab testing equipment. A typical temperature profile inside the log during heating process is shown in FIG. 10, which plots temperature verses depth from the log surface. Based on the temperature data obtained from the test apparatus, the total heat requirement was determined.
  • the biomass was considered to be a series of concentric annular cylinders having a thickness of 1/8". Based on the temperature in these concentric annular cylinders, the total sensible heat and latent heat of vaporization of around 10% of water present in the biomass was added to get the total heat requirement. Based on experimental data, the heat requirement was 1 100 Btu/min (-20 kw).
  • the heating section 24 and 26 of the barrel 20 are both formed as a jacketed cylindrical section and oil flows through the jacket (as noted earlier, the compression section 24 need not include a heating jacket, in which case only ends are heated during the compression step).
  • the hot oil from the hot oil system runs through the jacket and heat is transferred from the oil to the biomass.
  • circumferential channels are formed by rolling thin tubes over the inner cylinder. This forms circumferential oil flow lines in the heating section which increases the velocity of flow of oil inside the channel. This increased velocity effectively increases the heat transfer coefficient and the biomass is heated at much faster rates.
  • the diffusivity number calculated and noted above was used to determine the temperature profile inside the logs using unsteady state heat transfer analysis.
  • a Heisler chart was used to determine the temperature profile inside the log using unsteady state analysis.
  • the thin layer on the surface was considered as an infinite slab having a particular thickness.
  • the Biot number (hL/K) was determined and used to determine the Fourier number at different temperature ratios. Based on the Fourier Number (at/L 2 ) the time required to reach the predetermined temperatures of 70°C, 1 10°C and 150°C were determined and given in FIG. 1 1 . These data were very close to the measured temperature profile inside the biomass during the heating process.
  • the time required to reach a temperature of 70°C at a depth of 1/8" is 28.4 sec. This then sets the heating time to reach binder activation within the 1/8-inch layer. After that time, the heating can be halted, but the heat will continue to migrate inward, heating deeper layers in the log to a lower than 70C level.
  • the cooling section 28 was designed as per the procedure followed in the heating system design.
  • the measured temperature profile inside the log during cooling was given in FIG. 10.
  • the temperature profile inside the log during testing was used to determine the cooling rate and cooling system capacity.
  • equipment cooling load was determined based on the amount of heat to be removed for reducing the temperature profile during heating to the temperature profile during cooling as shown in FIG. 12.
  • the heat removal rate from the biomass was
  • the cooling oil circulating in the cooling section 28 cools the logs.
  • the cooling section is a jacketed cylindrical section and oil flows through the jacket. Inside the jacket, oil circumferential channels are formed by rolling thin tubes over the inner cylinder. This forms circumferential oil flow lines in the cooling section which increases the velocity of flow of oil inside the channel, which effectively increases the heat transfer coefficient and heat removal rate.
  • the piston 30, door 22a and gate 40 may be actuated using a hydraulic circuit. During testing, it was observed that the compressive force needed for initial compression of switchgrass in the die was small. Maximum force is required only toward the end of compression. Hence in order to minimize power needs, the actuator for the piston 30 may be designed to work at three stages, using different operating conditions, as shown in TABLE 5.
  • the operating sequence for the hydraulic system may be as follows. Initially, the piston 30 is fully retracted, the door 22a is open and gate 40 is closed. After the bale is received in the receiving section 22, the door or cover 22a closes (step 1 ) and the piston 30 pressure is increased to a level 1 which begins the compression of the biomass material (step 2). The piston 30 hydraulic pressure is increased to level 2 to increase the compression force on the biomass material (step 3). The log is formed. The gate 40 is lifted or opened (step 4). The piston 30 pressure is increased to level 3 to push the log into the heating section 26 (step 5). The piston 30 is retracted (step 6). The gate 40 closes (step 7) and the cover 22a opened to receive the next bale (step 8).
  • Tests were conducted to assess the relative importance of controlling these operating conditions to arrive at the desired result. Tests were carried out to define operating conditions for producing good quality logs. Operating parameters, such as heating time, cooling time, level of compression and level of back pressure etc., were tested.
  • the system of FIGS. 1 -7 included a heating jacket at only the compression section 24 and cooling in sections 26 and 28. Operating conditions may be determined from tests conducted using the test parameters.
  • Methods of loading (a) Sized bale flakes, and (b) Direction of straw parallel and perpendicular to the direction of pressing.
  • Process time 90 sec, 120 sec, 210 sec and 360 sec for log compression, heating and cooling.
  • Level of heating 350°F and 400°F oil temperature.
  • thermocouples were used to hold 1/8" thermocouples. The temperature was measured using an OMEGA RD 9000 model paperless recorder, connected with the thermocouples on the test equipment.
  • the oil pressure in the hydraulic system was measured using a 0-3000 psi pressure gauge attached to the manifold.
  • the pressure gauge was located directly in front of the operator or conveyor 5 feeding the biomass into the machine. The pressure at different conditions, such as beginning of compression, end of
  • the log density was measured as a ratio of weight of the log to the volume of the log.
  • the weight of each log was measured using a pan balance having a sensitivity of 0.04 lbs.
  • the volume of the log was calculated from the diameter and height of the log measured using vernier calipers.
  • vernier calipers During experiments, we observed that there was no radial expansion of logs once ejected from the test equipment, and the diameter of the logs was always 1 1 ", equivalent to the cylinder internal diameter in the cooling section 28.
  • the height of the logs was measured at 3 points using the vernier caliper. The average of the height and diameter was used to arrive at the volume of the logs, assuming the logs to have a perfectly cylindrical shape. The measured weight and volume were used to calculate the density of logs.
  • FIG. 13 plots the effects of process time on capacity. As the process time increases, the field capacity decreases. However, the two are not linearly correlated. Among the various correlations tried, such as logarithmic, power, and exponential relationship, the power relationship was found to fit well with maximum R 2 value of 0.98.
  • the log density reported was calculated as the average of density of all the logs made under a specific condition. As explained in subsequent sections, the density of logs made before reaching a steady state (i.e., full back pressure in the final cooling section) was much lower than the density of logs made during steady state conditions. The steady state conditions are reached once the entire cooling section is filled with biomass logs and the maximum back pressure has been reached for that test condition. Depending upon the level of compaction in the compression section 24, 8 to 12 logs could fit inside the cooling section 28 at steady state conditions.
  • the piston head 32 movement beyond the gate 32 is important.
  • the distance beyond the gate 40 was adjusted to 1 ".
  • the spring back was greater than 1 ", closing the gap to the gate 40.
  • the biomass could move between the gate 40 and cooling section 28 flange, which could jam the gate 40.
  • the distance was increased to 2" even though the gate 40 jamming stopped, it gave more space for spring back in the cooling section. This spring back in the cooling section resulted in reduced log density.
  • TABLE 1 1 is an example of density of logs made during initial startup period. From the table, the density of a first log made was only 25 Ibs/cf compared to the density of 46 l/cf made during steady state condition. As the number of logs present inside the cooling section 28 increases, the density of logs also increases until reaching a steady state condition. The steady state condition was attained as the entire cooling section 28 was filled with biomass logs. From this, the level of back pressure in the cooling section 28 has a very significant effect on the log density. [00112] TABLE 1 1 : Effect of back pressure in cooling section on log density
  • a comparison of log forming process for compacting biomass material is compared to pelleting and cubing processes is set forth in TABLE 16. As shown in the table the log forming process provides a substantial reduction in total energy for production of logs.
  • the cubing system can produce densified biomass with lower density compared to the pelleting process and log forming process under field test conditions. Pelleting and log formation can produce densified biomass of similar density but the formats are different, with pellets typically smaller than logs.
  • the compactor illustrated in FIGS. 3-7 may be configured without the gate 40. Without the movable gate 40, effective compaction relies on friction between the wall and the chain of logs in the heating and cooling sections
  • the compaction is a complex function of many parameters and would benfit from some pressure sensing and feedback control to adjust this pressure to the optimal level.
  • the back pressure developed on the piston head 32 which then translates into the hydraulic pressure needed to move the head 32 forward, then depends on friction inside the barrel 20, the lateral pressure inside the biomass, resulting from applied axial normal pressure, temperature of biomass by heating and subsequent biomass cooling over the complete chain of logs, e.g., 20 logs of about 5 inch length each.
  • Test results for different material indicate that in order to produce high quality logs of a consistent density, as well as good durability and integrity, the back pressure on the head 32 has to be managed between a pressure that is high enough for good compaction, but low enough to prevent overstressing the machine and/or wasting power. If a feedback system can be implemented that would be able to operate the piston 30 at a selected pressure, then optimal logs could be produced, even as feed material moisture, loading weight and initial density vary. Given the great variability of biomass materials, this would be an important feature.
  • FIG. 15 is a schematic illustration of a control system for densification of material in accordance with another aspect of the disclosure. More specifically, the control system monitors the pressure of compaction of logs 1 1 produced by a compactor, e.g., the compactor of the illustrated embodiments, to ensure good density of logs and avoidance of excessive pressure and stress on the piston 30 when producing logs. Additionally, the control system is helpful for making
  • the control system includes a main control unit 100, which may be based on any programmable logic controller, or other well-known industrial controllers that support digital and analog inputs and outputs.
  • the control unit 100 monitors the hydraulic pressure of compaction of a log 1 1 and is able to send actuation signals to the constrictor 21 for increasing or decreasing the hydraulic pressure, if necessary, during the compaction process.
  • the control unit 100 receives as input the position of the piston head 32 and hydraulic pressure of the piston. From this information the control unit is able to determine the amount of compaction pressure that is being used to make a log 1 1 .
  • control unit may be used to control only the pressure of compaction (as described below) or it may be used to control the entire operation of the compactor, including monitoring the quality of compaction, and the sequence of loading and compaction of material as described earlier in connection with FIGS. 3-7.
  • the position of the piston head 32 may be determined using a linear encoder, which continuously measures the position of the piston head 32 relative to its end of travel.
  • the control unit begins to collect pressure data on the hydraulic pressure within the piston 30. Computed from these pressure readings (collected over a stroke length) is an average hydraulic pressure (Peff), which is compared to a target pressure (Pset) for making the log 1 1 .
  • pressure readings are taken when the head 32 is within 15 cm of its end of travel for a 100 inch barrel and 20 logs each having a 5 inch compacted length are held in the barrel before exiting from the constrictor.
  • the control unit 100 collects pressure values continuously over the 15 cm stroke then average over these values to obtain Peff.
  • the control unit 100 sends a control signal to an actuator adapted to modify the size of the constrictor opening upon receiving this control signal. If Perr is less than zero (indicating that the pressure of compaction is too high) the constrictor 21 diameter is increased, thereby reducing the pressure of compaction. If Perr is greater than zero more pressure is needed to compact logs. The diameter of the constrictor is therefore decreased when Perr is greater than zero so that the compaction pressure increases.
  • the control unit 100 checks the compaction pressure at regular intervals, e.g., every 15, 30 or 45 seconds, 1 minute, less than 10, 15, 30 or 45 seconds, or less than 1 minute. The updated pressure difference may be used as feedback for adjusting the size of the opening to help ensure convergence to Pset or acceptable errors (an example of such a feedback loop is illustrated in FIG. 16).
  • actuation signal for the constrictor actuator for adjusting the size of the constrictor 21 in response to the pressure error.
  • An actuation signal for correcting the error in compaction pressure may be determined using a software implemented Proportional-lntegral-Derivative (PID) type controller.
  • PID Proportional-lntegral-Derivative
  • the PID controller generates a control signal for increasing the constrictor 21 opening if Perr > 0 and decreasing the constrictor opening if Perr ⁇ 0.
  • FIG. 16 there is shown an example of a flow process for feedback control of the constrictor 21 opening.
  • errorjimit the PID controller is called to generate a suitable actuation signal for the constrictor activation unit for reducing the error.
  • the actuation signal from the main control unit is sent to a constrictor activation unit or actuator 130, which is adapted to decrease or increase the size of an opening 123 of a tubular constrictor body 122 (by tightening or loosening a belt clamp 134 surrounding an end of the body 122) in response to the control signal received from the PID controller.
  • the control signal to the servo motor may be one of the following:
  • FIG. 17 is a perspective view of an example of a constrictor 120 with an actuator 130 for automatically adjusting an opening 123 or diameter 123 size in response to control signals from the control unit 100.
  • the opening 123 is increased or decreased in response to actuation by the actuator 130.
  • the actuator 130 reduces or increases the opening 123 in response to signals received from the control unit 100 using a belt 134, possibly constructed of metal, operated by, e.g., a screw received in a threaded collar 132 attached to the belt 134 and coupled to a servo motor 136, which is controlled by the control unit 100.
  • the servo motor and screw and threaded collar 132 tighten or loosen the belt 134 around a cylindrical constrictor body 122 (the screw and belt operate in a similar fashion to a tube clamp).
  • the constrictor body 122 has deflectable fingers 122a. When the body 122 is squeezed by the belt 134 the fingers 122a deflect inward, thereby decreasing the opening 123 and increasing the pressure of compaction. When the belt 134 is loosened by the gearing 132 the fingers 122a, which want to spring back to their original uncompressed position, deflect outward to reduce the pressure of compaction.
  • the structure shown in FIG. 17 is mounted to the end of the barrel 20 by way of a flange 124.
  • the pieces 120 and 130 were assembled to provide automatic control of the opening 123 of the constrictor 21 .
  • the flange 124 of the constrictor 120 was bolted to the cooling section of the barrel 20 (FIG. 3).
  • a nine inch long constrictor body 122 has 24 fingers 122a of thickness 0.125". Tightening of the belt 134 reduces the baseline tube diameter of 1 1 " at the flange end to 10" or 10% reduction in diameter and 20% reduction in cross sectional area at the outlet end of tube. This small variation will lead to a large increase in compaction pressure and a large rise in hydraulic fluid pressure.
  • adjustments to the compaction pressure may be made upstream of the exit of a compactor.
  • the adjustment capability need not necessarily exist only at the exit opening of a compactor as in the case of illustrated embodiments.
  • a constrictor may be located between an initial compaction zone and the exit, e.g., a constrictor may be located in a cooling zone, heating zone, or between the two zones.
  • the constrictor may be assembled in a similar fashion as in FIG. 17 with deformable or deflectable fingers forming a cylindrical passage for logs, where the fingers are deflectable by a clamping mechanism operated by an actuator, which responds to control signals received form the control unit 100.

Abstract

La présente invention concerne un procédé et un appareil destinés à la densification de matériau, qui compriment le matériau, puis chauffent et refroidissent le matériau comprimé pour assurer l'intégrité structurale et la durabilité du produit densifié ainsi obtenu. Un liant inhérent est utilisé pour un matériau à base de biomasse lignocellulosique. Le liant est activé sensiblement uniquement le long de la périphérie du matériau comprimé de sorte à augmenter le rendement et à réduire l'énergie utilisée au cours du procédé de densification. Pour optimiser le rendement et la densité ainsi que la durabilité du matériau densifié, le procédé et l'appareil font appel à une mesure de pression de compactage qui fournit un signal à un dispositif d'étranglement situé à la sortie, ou entre la sortie et l'emplacement de compactage initial, en vue de réguler automatiquement la pression de compactage à mesure que varient le type de matériau, la densité initiale, l'humidité et le poids de charge.
PCT/US2015/044714 2014-08-13 2015-08-11 Procédé et appareil de densification de matériau WO2016025520A1 (fr)

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Publication number Priority date Publication date Assignee Title
RU196537U1 (ru) * 2019-12-12 2020-03-04 Федеральное государственное бюджетное образовательное учреждение высшего образования "Кубанский государственный аграрный университет имени И.Т. Трубилина" Пресс для изготовления строительных элементов
CN111001487A (zh) * 2019-12-11 2020-04-14 陶伟 一种生物质燃料颗粒挤出机

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GB945874A (en) * 1958-09-09 1964-01-08 Coal Industry Patents Ltd Improvements in or relating to briquetting
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US5611268A (en) * 1992-09-26 1997-03-18 Hamilton; Robin Compactor with expanding and contracting nozzle
US20130319261A1 (en) * 2012-06-01 2013-12-05 Altex Technologies Corporation Method and Apparatus for Material Densification

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US1490162A (en) * 1919-11-28 1924-04-15 Fred T Dow Machine for briquetting peat
GB875441A (en) * 1956-10-18 1961-08-23 Coal Industry Patents Ltd Improvements in and relating to extrusion apparatus
GB945874A (en) * 1958-09-09 1964-01-08 Coal Industry Patents Ltd Improvements in or relating to briquetting
GB1539970A (en) * 1976-04-12 1979-02-07 Union Carbide Corp Refuse pelletizer
US5611268A (en) * 1992-09-26 1997-03-18 Hamilton; Robin Compactor with expanding and contracting nozzle
US20130319261A1 (en) * 2012-06-01 2013-12-05 Altex Technologies Corporation Method and Apparatus for Material Densification

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CN111001487A (zh) * 2019-12-11 2020-04-14 陶伟 一种生物质燃料颗粒挤出机
CN111001487B (zh) * 2019-12-11 2021-04-27 唐山泽坤新能源科技开发有限公司 一种生物质燃料颗粒挤出机
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