Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
  • F26B21/06—Controlling, e.g. regulating, parameters of gas supply
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
  • F26B21/02—Circulating air or gases in closed cycles, e.g. wholly within the drying enclosure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B23/00—Heating arrangements
  • F26B23/02—Heating arrangements using combustion heating

Definitions

• the present invention relates to a device for the heat treatment at high temperature of a load of woody material composed of stacked elements, and in particular of a load of wood, said device being provided with a treatment enclosure comprising:
• Wood is a widely used material because it has multiple advantages both aesthetically and in terms of its mechanical, acoustic and insulating properties.
• the wood in order for it to retain all of its characteristics and dimensional stability in the presence of moisture or immersed in water, the wood must be treated in order to remove all the supports that generate germs and mold.
• This treatment can be done by impregnation using chemicals which are toxic products harmful to the environment, or thermally by the process which consists in carrying out a chemical bridging between the macromolecular chains of the wood constituents by thermal means in atmosphere controlled and at a minimum temperature of 230 °.
• the second solution is clearly preferable because chemical treatments can have harmful consequences on the environment and health.
• the homogeneity and the reproducibility of the treatment are of course essential.
• the high temperature heat treatment of wood requires the use of devices which allow the wood to be brought to high temperature without igniting it. This can only be done by reducing the oxygen content of the volume of air contained in the treatment enclosure.
• Such devices are described in French patents published under Nos 2591 611 and 2 609 927 which provide ovens provided with one or more burners which, by heating the volume of air contained in the heating enclosure, reduce the oxygen content of this volume of air.
• the object of the present invention is to remedy these drawbacks encountered in the operation of the devices currently proposed by providing a device using the combustion of at least one burner to heat the volume of air in the treatment enclosure and to reduce the content thereof. in oxygen, and comprising improved means for conditioning and managing the treatment enclosure and the load of woody material to be treated.
• the device according to the invention as defined in the preamble and characterized in that it comprises means for regulating the temperature and the humidity of the treatment enclosure arranged to humidify said enclosure during its rise in temperature, stabilize its temperature during the treatment of the load of woody material and allow its cooling in successive stages after the treatment.
• the device comprises means for concentrating the heat transfer fluid.
• it also comprises means for adjusting the pressure prevailing in the enclosure, said means being arranged to maintain an overpressure in said enclosure.
• the means for conditioning the load of woody material to be treated comprise, between the stacked elements, spacing members whose dimensions are defined as a function of the dimensions of the woody material to be treated.
• the treatment enclosure of the device • comprises, in its upper part, a heating chamber arranged to heat the heat-transfer fluid after each passage through the charge of woody material to be treated and communicating, through an opening provided in the bottom of said chamber, with the lower part of the enclosure forming a treatment zone.
• the device advantageously includes means for modifying the height of the treatment zone as a function of the variation in the height of the load of woody material to be treated.
• the means for concentrating the heat transfer fluid are arranged to cooperate with the means for heating the said fluid to obtain better homogenization of the temperature and a neutral atmosphere by destruction of the oxygen in the enclosure, and are arranged in the heating chamber of the coolant.
• the means for heating the heat transfer fluid comprise at least one gas burner and the heat transfer fluid defining a neutral atmosphere is formed by a mixture of air stripped of its oxygen and the combustion gases from the burner.
• the enclosure comprises means arranged to ensure a seal around the load of woody material to be treated.
• the device may include electronic means for programmable management of temperature variations in the enclosure.
• the temperature regulation means comprise at least one water spraying ramp arranged at the outlet from the heating chamber of the heat transfer fluid.
• the heat transfer fluid concentration • means may comprise at least one concentration cone associated with at least one distribution deflector designed to homogenise the concentrated flow of hot gas, the axis of said cone merging with the axis of the flame generated by the burner.
• the means for adjusting an overpressure in the enclosure preferably include a calibrated valve disposed on a circuit for discharging the additional gas supplied by the combustion of the at least one burner.
• the means for modifying the height of the treatment zone as a function of the variation in the height of the load of woody material to be treated and ensuring a seal around said load can include a height-adjustable screen disposed vertically between the load of material woody to be treated and the bottom of the heating chamber.
• the tightness of said load is also ensured by longitudinal angles provided on the support of the load, said angles being arranged to cooperate with the edge of recovery tanks arranged at the bottom of the enclosure.
• the device also includes means arranged to introduce neutral gas into the treatment enclosure during the cooling phase of said enclosure.
• FIG. 1 represents a front view of the device according to the invention
• FIG. 2 represents a side view of the device of FIG. 1,
• FIG. 3 represents a view in vertical section along the line A-A of FIG. 2, and
• FIG. 4 represents a view in horizontal section along the line BB of FIG. 2.
• the device 10 intended for the heat treatment at high temperature of a load of woody material 11 such as wood by continuous circulation of a heat transfer fluid brought to a temperature above 230 ° comprises an enclosure 12 of treatment.
• This enclosure is in the general form of a rectangular parallelepiped and has four vertical walls 13, 14, 15 and 16 and a ceiling 17. These walls and the ceiling consist of two metal plates between which is placed a thermally material insulating.
• the interior walls of the enclosure are preferably made of a sheet of stainless steel.
• the front wall 16 of the enclosure 12 is provided with a door 18 allowing the loading of the woody material to be treated 11.
• the enclosure 12 is provided in its upper part, at a distance of between 0.20 and 1.50 meters from the ceiling 17, with a partition 19 whose width is less than that of said ceiling and which defines, between it and said ceiling, a chamber called the heating chamber 20, opening into the enclosure through the opening 21 formed by the difference in width between the partition 19 and the ceiling 17, and a zone called the treatment zone 22 in which the woody material to be treated is introduced.
• the heating chamber 20 is provided on its longitudinal wall 14 with heating means such as one or more burners 23, preferably of gas and with adjustable power, making it possible to heat the heat transfer fluid at its concentration point and to reduce the content thereof. oxygen.
• the flame 24 of each burner 23 extends horizontally between the ceiling 17 and the partition 19 and is surrounded by a means for concentrating the fluid in the form of plates 25 arranged to delimit a cone 26 whose axis coincides with that of the flame 24 generated by the burner 23.
• This cone 26 is associated with a distribution deflector 27 which makes it possible to homogenize the concentrated flow of gas emitted by the hot burner before it enters the treatment zone 22 by the opening 21 of chamber 20.
• Fluid circulation means in the form of fans 28 are also housed in the heating chamber 20 and are arranged vertically on each side of the burners 23 between the ceiling 17 and the partition 19 into which they open. These fans 28 cooperate with the opening 21 to circulate the heat transfer fluid between the upper volume of the heating chamber 20 and the lower volume delimiting the treatment zone 22.
• the underside of the partition 19, which forms the top of the treatment zone 22, comprises means for regulating the temperature and the humidity of the treatment enclosure 12.
• These means are in the form of a horizontal spray bar 30 at high water pressure, fixed at the outlet of the heating chamber 20 under the edge of the partition 19 defining the opening 21.
• This water spray bar 30 is provided with a sufficient number nozzles for spraying a mist at high flow rate and is supplied with cold water, or possibly refrigerated water, by means known per se which are not shown. It is intended to humidify the treatment zone 22 during the temperature rise of the enclosure 12, to stabilize its temperature during the treatment of the load of woody material 11, and to allow its cooling in successive stages after the treatment.
• the load of woody material to be treated 11 which, in the present case, consists of planks of wood stacked one on the other to form substantially a parallelepipedal structure placed on a movable support 31, is placed in the enclosure 12 by the loading door 18.
• the boards are placed so that their length is in the longitudinal direction of the enclosure, and they are separated from each other by spacers in the form of spacers 32 placed in their transverse direction.
• the thickness of these spacers is defined as a function of the thickness of the woods to be treated, the dimensions of the load and the physical parameters of circulation of the fluid in the enclosure and in said load.
• the support 31, on which the wood to be treated is stacked, is movable by means of wheels 33 moving on two longitudinal rails 34 disposed at the bottom of the enclosure.
• This support is further provided with two longitudinal angles 35 in the shape of an inverted L which each cooperate with the vertical edge of two trays 36 arranged at the bottom of the enclosure, on either side of the load to be treated.
• These tanks are intended for the recovery of condensation flows and runoff occurring during the treatment.
• This connection between the mobile support 31 and the recovery tanks 36 makes it possible to close the existing passage under the support and ensures sealing between the bottom of the walls of the enclosure and the load of material to be treated.
• the charge of woody material to be treated 11 defines a first volume, called overpressure chamber 40, located between said charge and the wall 13 of the enclosure defining the opening 21, and a second volume, called recovery chamber 41, located between the load and the opposite wall 14 of the enclosure 12.
• the means for concentrating the fluid and the arrangement of the opening 21 cause said fluid to flow in the transverse direction of the treatment zone 22, that is to say from the overpressure chamber 40 to the recovery chamber 41 in passing through the charge 11 of the woody material to be treated.
• the fans 28 then suck up the heat transfer fluid at the level of the partition 19 in the recovery chamber 41 and draw it from the heating chamber 20 downstream of the burners 23.
• the treatment zone 22 is provided with a screen 42 of variable height disposed vertically between the top of the load 11 of woody material to be treated and the partition 19 forming the bottom of the heating chamber 20 and, therefore, the ceiling of this treatment area.
• This screen allows the elimination of a preferential circulation of the heat transfer fluid and the maintenance of a constant pressure in the treatment zone 22.
• Ports 44 formed in the lower part of the wall 14 of the recovery chamber 41 of the enclosure and regularly distributed on this wall, allow the evacuation of the additional gas produced by the supply of combustion gases from the burners and the increase in volume of the heat transfer fluid when the temperature rises.
• These orifices 44 open into a horizontal collector 45 located outside the enclosure 12, this collector itself being connected to a series of vertical tubes 46 forming a condenser and opening into a chimney 47 by means of a evacuation circuit 48 provided with a sealed valve 49.
• This valve which is calibrated, constitutes the means for adjusting the pressure prevailing in the treatment enclosure 12.
• the treatment zone 22 is further provided with several horizontal spraying ramps 50 fixed on each longitudinal wall 13, 14 of the enclosure. These high-flow ramps are intended to be put into operation in the event of accidental ignition of the load 11 and are connected to appropriate flows 51. Furthermore, discharge orifices 52 formed at the bottom of the enclosure 12 allow the disposal of liquids recovered in recovery tanks 36.
• the enclosure 12 is made watertight by the installation of seals at the level of the door 18 and siphons at the level of the discharge ports 52.
• the temperature and humidity prevailing in the enclosure during the treatment are managed by temperature and rate sensors hygrometry (not shown) known per se and arranged on each of the longitudinal internal walls 13, 14 of the enclosure.
• Another probe also housed in the enclosure allows permanent monitoring of the oxygen content of the heat transfer fluid.
• a supply of neutral gas is made by an inlet (not shown) formed in one of the walls of the treatment enclosure 12.
• Programmable electronic means make it possible to manage the temperature variation levels and the humidity level in the treatment enclosure.
• the operating principle of the device of the invention is based on a continuous circulation of the heat transfer gas formed by the air stripped of its oxygen and mixed with the combustion gases to provide a neutral atmosphere. After having been heated in successive stages to a minimum temperature of 230 °, these stages being defined on the basis of the parameters of the woody material to be treated, the heat transfer gas circulates continuously, throughout the treatment cycle, from the point where it is heated by the burners towards the load of woody material to be treated which it crosses at a balanced rate and speed at any point of its circuit by bringing it homogeneously the calories necessary for the heat treatment.
• This circulation drawn by the fans is conditioned by the cones which concentrate the volume at a heating point and by the deflectors which homogenize the fluid before its introduction at low speed into the overpressure chamber, while a pressure of the order of 4 mmCE in the enclosure is regulated by the calibrated valve placed in the chimney.
• the fluid After passing through the charge to be treated, passage during which there is a heat exchange between the fluid and said charge, the fluid arrives in the recovery chamber at a pressure and a temperature different from those of the overpressure chamber. So he is taken up by the fans and heated and reconditioned in the heating chamber before a new passage through the load.
• the treatment cycle requires several passages of the fluid through the charge.
• the temperature is lowered in successive stages using a high-pressure cold water spray in the circuit of the heat transfer gas in the overpressure chamber by means of the spray boom.
• the pressure of the order of 4 mmCE is maintained in the treatment zone by the arrival of neutral gas which compensates for the reduction in the volume of heat-transfer fluid during this cooling phase.
• This spraying is also requested in order to avoid thermal shocks on the load of woody material to be treated during an abnormal rise in temperature in the enclosure.
• the enclosure can be equipped with a second door intended for discharging the woody material after its treatment and the movement of the load support can be automated. It is also possible to modify the positioning of the burners and fans.
• the device can also be provided with an element intended to treat air in order to lower the oxygen content.
• means may be provided in the device for modifying the height of the treatment zone as a function of the variation in the height of the load of woody material to be treated, composed of a pressure plate with a surface at less equal to the horizontal surface of said load.
• Said pressure plate is placed at the ceiling of the treatment zone and remains integral with the latter by suspension and maneuvering means such as at least one jack, not shown, making it possible to raise said pressure plate, to lower it onto the load of woody material to be treated after introduction thereof into the treatment enclosure and to apply to said load a constant pressure throughout the duration of the treatment in order to avoid deformations.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)
• Resistance Heating (AREA)
• Ink Jet Recording Methods And Recording Media Thereof (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)
• Drying Of Solid Materials (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1999
  • 1999-03-09 FR FR9903179A patent/FR2790698B1/fr not_active Expired - Fee Related
• 2000
  • 2000-02-29 EP EP00907740A patent/EP1133666B1/de not_active Expired - Lifetime
  • 2000-02-29 WO PCT/FR2000/000492 patent/WO2000053985A1/fr active IP Right Grant
  • 2000-02-29 DE DE60023444T patent/DE60023444T2/de not_active Expired - Lifetime
  • 2000-02-29 AU AU29221/00A patent/AU2922100A/en not_active Abandoned
  • 2000-02-29 AT AT00907740T patent/ATE308025T1/de active
  • 2000-02-29 ES ES00907740T patent/ES2250106T3/es not_active Expired - Lifetime

Non-Patent Citations (1)

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