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
  • F26B21/08—Humidity
  • F26B21/086—Humidity by condensing the moisture in the drying medium, which may be recycled, e.g. using a heat pump cycle

Definitions

• the present invention relates to a plant for drying moisture-containing goods and especially such goods that are enclosed in an enclosure, in which the drying process can take place using a heat- and/or cool-generating unit.
• the enclosure contains or is connected to a fan for circulating a drying gas within the enclosure (usually air), which passes the goods in such a manner that moisture transfers from the goods to the drying gas.
• a drying gas usually air
• the invention may be used for drying moisture-containing goods of different sizes and forms, and even may be used to dehumidify air/drying gas in stables, green houses, desalination plants, among other things, it may be mentioned that the unit has been developed with the intent to dry sawn and stacked wood products in the shape of planks and boards and also wood chips.
• Passively working section refers to a heat exchange using media as air, water and other media, where no active steps are taken to raise or lower the content of energy or the height of temperature in the used media and/or where the energy content can be used without any cost.
• Actively working section refers to a heat exchange using media as air, water and other media, where active steps are taken to raise or lower the energy content or the height of temperature in a controlled manner, and where those active steps are based on the use of "externally" available expensive energy.
• the invention is based on primarily using the energy and the heat content of the ambient air or the available water at the plant, while using additional "exter- nal" energy not until the need arises.
• External energy refers to such heating and/or cooling energy that has been transformed from electricity, gas or other energy into a processed form.
• drying of moisture-containing goods can be done by placing the goods into an enclosure and letting the drying process pass through a number of steps, usually two, a shorter heating period and a longer dry- ing period.
• the temperature must be raised slowly during the heating period to an adapted, maximum temperature, say 50° to 60° C to obtain a good product quality without any cracks in the goods, and afterwards pass into the drying process step, at which the drying gas is taken out from the enclosure to be dehumidified in a condensing unit before it is returned to the enclosure.
• This patent publication shows and describes a drying kiln for wood prod- ucts with a heat exchange and dehumidifying unit 16.
• This unit 16 shows in a sequenced arrangement a first passive heat exchanger 22, a second active heat exchanger 24 and a third passive heat exchanger 26 with the alternative of feeding external heat energy to said third heat exchanger.
• the active heat exchanger 24 can be controlled, so that its temperature is kept below the dew point temperature for the gas passing through.
• the fan 20, in operation, will be able to affect a portion of the total air vol- ume in the plant and get the tapped-off air volume from the interior of the plant or kiln 10 to pass an outlet duct 40, force said portion of air through three units or heat exchangers 22,24, 26, joined in series, and then return it as a dried portion of air through an inlet duct 42 to the kiln 10, in accordance with the shown arrows 21.
• the fan 20 is controlled by the need to remove moisture from the hot moisture-containing air in order to control the temperature exactly.
• the heat exchanger 22 will remove heat from the air, while a portion of the air is passing through.
• This heat lead away via the heat exchanger 22, will be transferred to the third heat exchanger 26 via known heat exchangers or heat exchange functions, which is indicated by the reference sign 44, and where the third heat exchanger 26 will transfer heat to the air stream.
• the cooled saturated air stream upon leaving the first heat exchanger 22, will pass through said second heat exchanger 24, where an additional and active cooling to a temperature considerably below the dew point occurs, causing a condensation of moisture in the second heat exchanger 24.
• the temperature of the second heat exchanger 24 is controlled by joining it, via a pipe 25, to a known device 46, such as a cooling water based heat exchanger.
• Water from the condensation of water steam in the second heat exchanger 24 is removed by using a condense water removing system 36.
• the cooled dehumidified air leaving the second heat exchanger 24 will thus pass through the third heat exchanger 26, where heat energy, lead away in the heat exchanger 22, again is brought into the air stream.
• dehumidified air stream can now be returned to the kiln 10 of the unit through duct 30 as dehumidified hot air stream to be admixed with the moisture- containing air volume within the unit or drying kiln 10.
• a first portion of the heat exchanger comprise both a passively working cooling section and a passively working heating section, in which the first passively working cooling section is arranged to work partly with the cooled drying gas portion, and partly with fresh air, water and/or the like as cooling media for said drying gas portion, while the passively working heating section is arranged to work with the out-streaming hot portion of the drying gas as a heating medium.
• the actively working section of the second portion of the heat exchanger may consist of an adjustable cooler, for example cooling elements/cooling coils, connected to the evaporation side of a heat pump.
• drying gas with the drying gas portion can circulate in a closed system, with a "by-pass" branch, through which a drying gas portion is lead through the heat exchangers, where flow and temperature are monitored and regulated in such a way that the same amount of moisture will be taken away from the "by pass" stream as is given away from the drying goods, and then returned to the enclosure for the drying goods in order to absorb new moisture.
• the present invention assumes a plant of initially described type.
• the present invention is based especially on the fact that a certain portion of the drying gas in the enclosure is arranged to pass said first as well as said second portion of the heat exchanger, and that a current dew point temperature of the drying gas portion and the coldest temperature occurring downstream the second portion of the heat exchanger are to be mutually adapted to present a con- trolled, usually decreasing, temperature difference during the drying process.
• the passively working cooling section of the heat exchanger should be adapted to use as cooling media partly the returning cold drying gas portion, and partly an addi- tional cooling medium stream
• the passively working heating section should be adapted to use as a heating medium an ambient, hot, moisture-containing and counter-flowing drying gas portion.
• the value of the coldest temperature should be adjustable, usually by controlling the speed of the drying gas portion.
• the coldest temperature should be arranged to be adjustable in a manner that an occurring temperature difference is arranged to correspond to, or at least essentially correspond, to the amount of absorbed moisture content in said drying gas portion.
• the cooling media working in said first portion of the heat exchanger should also be able to comprise an additional cooling medium stream, such as fresh air, water or the like.
• said second portion of the heat exchanger should be arranged to be activated dependent on a need to control the coldest temperature.
• the cooling section should be arranged for a larger transfer of energy than the heating section.
• the heat exchanging unit should consist of at least two joined heat exchanger sections, a first heat exchanging portion and a second heat exchanging portion.
• the first heat exchanger portion should then consist of a passive, double- acting cooling and heating section, in which the passively working cooling section is arranged to work partly on fresh air, water and/or the like, and partly on the cooled returning drying gas portion as cooling media streams for the moisture- containing drying gas portion, and the passively working heating section is ar- ranged to work on the out-streaming hot drying gas portion.
• the second heat exchanger portion consists of an actively working cooling section.
• the passively working cooling section within the first portion of the heat exchanger should be arranged and dimensioned for a lowering of the temperature of the drying gas portion to a value usually lower than the dew point temperature of the drying gas portion.
• the passively working cooling section being part of the first heat exchanger portion should be connected at its upstream end directly to the enclosure containing the drying goods, while its downstream end should be connected to the actively working cooling section of the second heat exchanger portion.
• the drying gas portion cooled in the second heat exchanger portion is ar- ranged to return to the first heat exchanger portion as a cooling medium stream for the out-streaming drying gas portion.
• Said drying gas portion is arranged to achieve a controlled low temperature downstream a condenser, in the form of a cooling unit, for example consisting of elements/cooling coils connected to the evaporation side of a heat pump unit.
• a condenser for example consisting of elements/cooling coils connected to the evaporation side of a heat pump unit.
• the drying gas portion is arranged to circulate within an enclosure comprising a closed system, and that a cooling medium stream in the heat exchanger, separated from the drying gas portion, forms part of a closed or open system, which can change between closed/open throughout the drying process by setting a valve.
• the condensed liquid should be drained via a drainage or a pump.
• said first heat exchanger portion is arranged to cool the out-streaming drying gas portion via a counter or cross flowing cooling medium, and also via the returning counter flowing and already cooled drying gas portion, thereby heating the returning drying gas portion by the out- streaming hot drying gas portion.
• first heat exchanger portions can be connected in parallel.
• Said first heat exchanger portions can be connected in series with a cooling unit for an adjustable, further lowering of the temperature of the drying gas portion before the drying gas portion is returned into the enclosure.
• a returning cold drying gas portion is to be enclosed by an out-streaming hot drying gas portion in one ore more ducts with heat exchanging duct surfaces made of metallic or plastic films.
• the flow of the drying gas portion can preferably be adjustable via a speed controlled fan and/or an adjustable valve.
• an outlet duct should be arranged so or extended in relation to an inlet duct that an out-streaming drying gas portion cannot immediately be mixed with an in-streaming drying gas portion.
• Cooling elements/cooling coils can also be installed in the first heat exchanger portion to intensify the cooling and/or to recover cooling energy which, by means of a heat pump, can be used for the purpose of heating, for example, for the drying gas in the enclosure.
• One and the same heat pump can also serve several condensing units belonging to separate drying plants.
• the flows of media, the flows of drying gas and the temperatures are functionally dependent on each other and are monitored and controlled by a computer.
• the advantages that mainly characterise a drying plant in accordance with the present invention are that the preconditions are generated for providing in a simple and energy effective way, a drying process at a speed adapted to the goods by utilising an available cooling medium stream.
• the drying process can simply be adapted to mainly use fresh air, water or the like as a cooling medium, and only when needed resort to externally available and expensive energy for heat exchanging. This is of special interest when the heating energy for the drying process is very cheap or available for other reasons, and/or when the externally available cooling energy is expensive.
• a plant in accordance with the present invention will be extra advantageous when the plant's drying capacity is at its maximum, though without detrimental effect on the quality of the goods.
• the heat exchanging portions are concentrated for co-ordination.
• the main characteristics of a plant, in accordance with the present invention, are specified in the characterising part of subsequent claim 1.
• Figure 1 illustrates a time-temperature diagram for an assumed drying pro- cess
• Figure 2 illustrates schematically a section of a plant with an externally located cooling and dehumidifying unit and an internally located air heater illustrating the characteristics of the invention
• Figure 3 illustrates schematically a view of a section, illustrating the character- istic of the invention
• Figure 4 illustrates a volume-temperature diagram applicable for an embodiment where all drying gas within an enclosure is subject to cooling and condensation
• Figure 5 illustrates a volume-temperature diagram with an embodiment in ac- cordance with the invention where only a portion of the drying gas is diverted from the enclosure for cooling-down and condensation
• Figure 6 illustrates a temperature-time diagram exemplifying the time dependent changing of the temperature difference between the dew point temperature T2 and the coldest temperature T4 of the unit.
• a time-temperature diagram is shown, principally representative for a drying process for stacked wood planks, with an initial heating step "W” working for a number of hours and ending in a temperature "TO", for example 50° C, and a subsequent drying step “D", working for a number of hours during which the temperature is kept at an appropriate interval, and where cell external and cell internal or cell bound water steam is removed gradually from the goods to be dried.
• the invention comprises in the first place designs and instructions appli- cable during the drying process, which can be considered to start during the later course of step "W” and continue during step "D".
• the present invention indicates a plant "A", suitable for drying moisture-containing goods 1 , in the form of stacked wood products, and where these goods 1 are placed in an enclosure 2.
• the walls 2a of the enclosure 2 may preferably be heat-insulated.
• the heating process itself during step "W”, and when necessary, the heat input for the drying process during step “D", may wholly or partly take place by means of a heat-generating and fan equipped unit 4.
• This unit 4 as shown here, is placed inside the enclosure 2, and in said unit 4, a fan 5 is included or connected to, adapted to run and circulate within enclosure 2 a drying gas 3, heated by the unit 4.
• the heat generation may also wholly or partly be placed outside the enclosure 2 or consist of or be complemented by a heat pump unit. Consequently, the fan 5 will run and circulate a drying gas 3, heated by the unit 4, in enclosure 2, and then past the goods 1 , such as stacked planks, in a way that moisture from the goods is transferred to the drying gas 3.
• Figure 2 is meant to illustrate that a major portion 3' of the drying gas 3 will circulate inside the enclosure 2, and that a minor portion 3a of the drying gas 3, exhausted and moisture-containing, will pass a heat exchanging unit or set of units, the design of which will be described with reference to fig. 3.
• the invention makes use of a heat exchanging unit or set of units 6 arranged or located separately from the enclosure 2 consisting of a number of heat exchanging portions 61 and 62, connected in series or, as sets, connected paral- lei.
• a first adjustable portion 3a of the drying gas is led from the enclosure 2 into the first heat exchanging portion 61A, passively cooling the drying gas portion 3b, further into the actively cooling unit 62, actively cooling the drying gas portion 3c, and then into the passively heating unit 61 B, pas- sively re-heating the drying gas portion 3d, which returns to the enclosure 2 as a dehumidified and heated portion 3e of the drying gas.
• the passively working cooling section or unit 61A is adapted to utilise as cooling media streams partly the returning drying gas portion 3d and partly an additional cooling medium stream 8, such as fresh air, water or other forms of cheap energy.
• the actively working heating section 61 B is adapted to utilise the ambient, moisture-containing counter streaming drying gas portion 3b as a heating medium stream for the drying gas portion 3d.
• the second portion 62 of the heat exchanger contains an actively working cooling section for the drying gas portion 3c.
• the passively working cooling section 61 A is furthermore adapted for lowering the temperature of the drying gas portion 3b to a value usually below that for the dew point or the dew point temperature of the drying gas.
• the heat exchanging unit 6 is connected to the enclosure 2 via an inlet duct 7 and an outlet duct 7', situated from each other at such a distance that the returning drying gas portion 3e will admix the drying gas portion 3' in the enclosure 2 and pass the goods in the enclosure.
• the speed and/or the volume of the drying gas portion 3a through the heat exchanger unit 6 is controllable by means of a fan and/or a valve device 9.
• the heat exchanger unit 6, according to the invention will consist of a number of portions or sections, functionally separated and usually connected in series. In this respect, it is obvious that a main function in the first portion of the heat exchanger may be enhanced by actions in subsequent heat exchanging portions, or vice versa.
• the passively working cooling section 61A of the first heat exchanging portion 61 is, at its upstream end via the inlet duct 7, directly connected to the enclosure 2.
• the outlet duct 7' is usually enclosed by the inlet duct and is directly connected to the downstream end of the passively working heating section 61 B.
• the actively working cooling section 62A belonging to the second heat exchanging portion 62, is at its upstream end directly connected to the passively working cooling section 61A, and at its downstream end directly connected to the passively working heating section 61 B.
• the example of the embodiment indicates more specifically that the actively working cooling section 62A of the second heat exchanging portion 62 consists of a cooling unit, for example connected to the evaporating side of a heat pump unit 65.
• one or more cooling ele- ments/cooling coils 62A, 62B and/or 62C are connected in a controlled and adjustable manner.
• a heating element 63 is connected in a controlled and adjustable way and placed inside the enclosure 2.
• the cooling coils 62B and 62C are mainly intended to enhance the con- densing cooling and/or take care of cooling and condensing energy and transfer it as heat to the heating element 63 in the enclosure 2.
• the cooling elements are placed in the hottest areas of the affected heat exchanger ducts, but may also be placed along the entire ducts or along parts of them. It is especially obvious that the actively cooling sections 62A, 62B and 62C and the actively heating section 63 are co-ordinated and connected to one and the same heat pump unit 65. This heat pump unit may also be connected to other heating and cooling units in drying plants separated from each other.
• the embodiment according to fig. 3 intends to illustrate that the necessary cooling of the moisture-containing hot drying gas portion 3b will occur not only to the greater extent in the heat exchanging portion 61 A, but when needed, also in the cooling coils 62A, connected to the evaporating side of the heat pump unit 65. Accordingly, the actively working cooling section 62A has not to be active in case the additional medium stream 8 is sufficiently cooling.
• the initial cooling medium stream 8 (usually fresh air/water) intended for heat exchanging with the drying gas portion 3b is adapted to pass the first heat exchanger portion 61A.
• the medium stream 8 may in ordinary the simplest case consist of air (fresh air), but may also consist of another gas or water, or some other available medium.
• Temperature and flow speed of the medium stream 8 are adapted to the current temperature and flow speed of the drying gas portion 3b as well as to the chosen embodiment of the heat exchanging portion 61 A, in order to cause a falling temperature in the moisture-containing drying gas portion 3b within the first heat exchanging portion 61 A, usually to a temperature below the current dew point.
• the present invention specifies that condensing liquid from the first heat exchanging portion 61 A is removed via a drainage or via a pump 61 C.
• Function and control of these heat exchanging portions 61, ( 61 A, 61 B); and 62 can briefly be described according to the following, by the following exemplified temperatures.
• the temperature of the drying gas 3 in the enclosure 2 is set to "TO"
• the temperature of the gas portion 3a at the inlet 7 is set to "T1”
• the dew point tern- perature is lower and set to "T2”
• the drying gas portion 3b is given a low temperature "T3" at the end of the heat exchanging portion 61 A.
• the drying gas portion 3c can be further cooled in an active and controlled way by the heat exchanging portion 62 to reach a temperature indicated as "T4", downstream the cooling coil 62A. This will constitute the lowest temperature for the drying gas portion 3c.
• the cooling medium stream 8 has an initial temperature of "T10".
• the medium stream 8 passes the heat exchanging portion 61A and shows at the outlet 8a an increased temperature "T11". It is suggested that the drying gas portion 3b in the heat exchanging portion 61A is cooled very rapidly to a temperature if possible below dew point temperature "T2" by the cooling medium 8.
• the initial temperature "T1" of the drying gas portion 3a, the temperatures “T3" after the heat exchanger 61 A and “T4" after the cooling element 62A respec- tively, as well as the gas flow are time dependently adjustable by the control unit 100, in a manner well known to the skilled person.
• the control unit 100 requires a number of sensors to sense current parameter values in order to control the drying process. Thus, a number of sensors are shown in fig. 3.
• a sensor 20 within the enclosure is adapted to indicate the relative humidity "RH" of the drying gas 3, and connected to the control unit 100 via a cable 20a.
• the temperature of the drying gas portion 3a is evaluated by a sensor 21 and attached cable 21a at the inlet 7 to the heat exchanging portion 61 A.
• the temperature "TO" of the drying gas 3 in the enclosure is sensed by a sensor 22.
• the sensor 22 is connected to the control unit 100 via a cable 22a.
• the temperature "T4" is measured by a sensor 23 connected to the control unit 100 via a cable 23a.
• the fan and valve arrangement 9 is controlled by the control unit 100.
• the temperature "T10” is measured by a sensor 25 connected to the control unit 100 via a cable 25A.
• Figure 3 shows also a fan and/or filter device 8B, which by means of speed control by the control unit 100 can adapt flow 8 through the heat exchanging portions 61 A.
• the control device 26 is connected via a cable 26A to the control unit 100.
• the temperature "T10” measured by a sensor 25 and a cable 25A, controls whether the actively cooling coil 62A is to be started or not. If the cooling medium 8 is sufficient cold by nature, there is no need of starting-up.
• the actively working cooling portion i.e. the cooling coil 62A
• the passively work- ing cooling section 61A may be thermally insulated 62D from the passively work- ing cooling section 61A.
• the purpose is to prevent cold from spreading from the actively working section 62A into the medium stream 8 via the passively working section 61 A.
• the fundamental function of plant A may briefly be described so that the goods to be dried 1 are to be fitted or placed in a closed or limited enclosure 2 in such a manner to be well encompassed by ambient drying gas, such as air, which can absorb moisture.
• the drying gas 3 is mixed and heated in the heating unit 4 and passes one ore more fans 5, which transport and circulate the drying gas past and through the drying goods 1.
• the fan and valve ar- rangements 9 and 8B may be entirely closed and can be started/opened and regulated when the conditions for moisture removal occur.
• the speed of fan 9, and beneficially also of fan 8B can be controlled in order to force the drying gas portion 3a and the medium stream 8 through the heat exchanger set 6.
• a minor portion 3a of the drying gas 3 will pass the heat exchanger sets 61 , 62 for dehumidifying and subsequent heating, and a major portion 3' of the drying gas 3 is circulated directly to the heating unit 4, where the enclosed portion 3' is admixed with the dehumidified and heated drying gas portion 3e.
• the drying gas 3 leaves the heating unit 4 its temperature is "TO".
• the temperature of the moisture-containing drying gas portion 3b will be lowered further when passing the remaining portion of the passively working heat exchanging section 61A and the actively working heat exchanging section 62, and when the drying gas portion 3c leaves the exchanging section 62, it has reached temperature "T4", which is so low, that the same amount of moisture having been absorbed by the drying gas 3 when passing the goods 1 , will have been removed from the gas after passing the heat exchangers.
• temperature "T4" must be controlled.
• the cooling and heating surfaces in a utilised condensing unit, as well as the flows of cooling medium and drying gas through the unit 6 have to be balanced and controlled, so that moisture removal from the drying goods per time unit is adapted to a level not damaging to the goods.
• the heat exchanger set 6 can preferably be located outside the drying house or the enclosure of drying goods (enclosure 2), but can of course also wholly or partly be placed inside if necessary or convenient. The requirements of insulation around set 6 will however be higher in that case.
• the cooling of the drying gas 3 must not entail a lowering of the gas tem- perature below the dew point temperature before passing the drying goods 1 in enclosure 2 entirely, as moisture initially separated from the gas would be precipitated on the goods and damage them (risk for mould). Moreover, the speed of the drying process decreases. Therefore, the temperature difference "TO - T1", the chosen maximum value of "TO” and the speed of the drying gas must be carefully monitored, preferably by computer control in control unit 100.
• the cooling medium 8, selected to pass the heat exchanging unit 6, may be part of an open cooling cycle, such as cooling air 8 in form of fresh air blown straight through the heat exchanging portions 61 A of the heat exchanging unit 6, or be part of a closed cycle, such as cooling gas circulated around and heated by unit 6.
• the energy of the flow 8a, recovered in heat exchanging unit 6, may e.g. be used for heating purposes, or as shown in fig. 3, an even larger amount of energy can be recovered and transferred from 62B, 62C and/or 62A to the condensing side 63 via a heat pump 65.
• Figure 4 intends to illustrate a temperature-volume relation with occurring energy losses when all drying gas 3 is used in a continuous condensation.
• the energy losses "EL" will be calculated for the entire volume of the drying gas and the condensing energy “CE” will also be valid for the entire volume of drying gas.
• the energy losses "EL" occur when all drying gas has to be cooled down to the dew point temperature "T2" before a condensation can start.
• the large volume of drying gas (large content of energy) involves also difficulties in lowering the dew point temperature causing an unnecessarily slow dry- ing process.
• Figure 5 intends to illustrate a temperature-volume relation where only a portion 3a of the drying gas is used for condensation, according to the present invention.
• Cooling all drying gas a certain number of degrees to condense a certain amount of water, or cooling a smaller volume of drying gas a larger number of degrees to get that same amount of water, is about equal considering the energy consumption throughout the condensing step. However, the same is not true for the energy losses.
• drying time means evaporating and condensing a certain amount of moisture or water, which means that a certain amount of energy is consumed.
• the energy losses are time dependent and they become smaller at a shorter drying time. To control temperatures and flows in a way that will minimise the drying time, will lead to a substantial reduction of the energy losses and also give a better utilisation of the capacity of the drying plant.
• Said heat exchanging unit 6 shown, with a number of heat exchanging portions connected in series, may, as units, be connected in parallel.
• the returning cold and dehumidified drying gas portion 3d is surrounded and re-heated by an out-streaming drying gas portion 3b in one or several ducts, where the heat exchanging surfaces consist of metallic or plastic film.
• the reheating of the drying gas will further contribute to decrease energy losses.
• the heat pump unit 65 may be used primarily for heating purposes (heating element 63) by taking energy from the heated cooling air stream 8a and the out-streaming hot drying gas 3b by means of the cooling elements 62C and 62B respectively.
• Figure 6 illustrates the time variation of the temperature difference "T2 - T4", assuming that at time "t1", the drying process has removed cell external moisture and that after that time, it is a matter of removing cell internal or cell bound moisture.
• the invention is based on the principle that a certain portion of the drying gas from the enclosure will be adapted to pass said first as well as said sec- ond portion of the heat exchanger, and that a current dew point temperature "T2" of the drying gas and the coldest temperature "T4" downstream the second heat exchanging portion are adapted to each other, according to fig. 6, to present a decreasing temperature difference during the drying process.
• the coldest temperature "T4" is adjustable in a manner that an occurring temperature difference "T2 - T4" is adapted to allow the drying gas portion to contain, or at least essentially contain, the amount of moisture equivalent to the mois- ture amount precipitated from the drying goods.
• the working cooling medium within the first heat exchanging portion consists of a returning, cold drying gas portion, and that one of the working heating medium in the first heat exchanging portion is an out- streaming hot and moisture-containing drying gas portion.
• Said second portion of the heat exchanger is to be activated dependent on the need to control the lowest temperature "T4", and the cooling section within the first heat exchanging portion is adapted for a larger energy transfer than the heating section.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Drying Of Solid Materials (AREA)

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Citations (4)

• 2000
  • 2000-05-02 SE SE0001595A patent/SE518880C2/sv not_active IP Right Cessation
• 2001
  • 2001-04-26 WO PCT/SE2001/000903 patent/WO2001084067A1/en active Application Filing
  • 2001-04-26 AU AU2001252822A patent/AU2001252822A1/en not_active Abandoned

Patent Citations (4)

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