JP2016508596A - Drying equipment - Google Patents

Abstract

A drying apparatus for drying fibrous material (or granular material) is disclosed. The drying apparatus includes a heater configured to heat the first gas stream and the fibrous material, the first gas stream configured to flow into the drying apparatus at an inlet, wherein the gas stream is Contains steam. A separator is provided for separating the fibrous material from the first gas stream to form a second gas stream, and a fan and duct recirculate the second gas stream to the process heater and the steam injector. It is configured to circulate. The flow rate changing device is configured to change the gas flow in the first gas flow to improve (improve) the drying function by increasing heat transfer and mass transfer between the gas flow and the tobacco product. [Selection] Figure 2

Description

  The present invention relates to a drying apparatus and method for drying fibrous or granular materials, and more particularly, but not limited to, a drying apparatus and method for drying fibrous materials such as tobacco leaves or portions of tobacco leaves.

  Tobacco leaves are processed for the manufacture of cigarettes by primary tobacco processing. To provide tobacco particles (small pieces) suitable for cigarette manufacture, the tobacco leaf stack is compressed and then cut with a cutter. In general, moisture is removed from the fibrous tobacco material to improve the handling and filling properties of the tobacco material.

  The tobacco industry uses a pneumatic conveying dryer, also known as a flash dryer, to reduce the moisture content of the cigarette filler to a level suitable for cigarette manufacture and packaging It is known to do. The general principle of such dryers is that tobacco products are transported along a passage by a flow of hot gas. The gas flow provides an environment in which the tobacco product is dispersed and dried in the passage. The tobacco product is then separated from the gas stream by any means. Product drying takes place by heat and mass transfer between the gas stream and the tobacco product. It is known to use superheated flow, air, a mixture of air and carbon dioxide, or air with other combustion components as the carrier gas.

  Because cigarettes are the most expensive component of cigarettes, manufacturers have a strong motivation to process tobacco in a way that maximizes the number of cigarettes that can be produced from a given weight of tobacco. is there. Producing chopped tobacco products at a lower density results in more output (yield) from the default weight of the starting product. Air-drying dryers, also known as flash dryers, and main drying with superheated flow as a drying medium, improve yields with lower-density chopped tobacco than results (if any) using other drying methods. Bring.

  FIG. 1 shows a conventional drying apparatus 100 (for example, an air current dryer). The drying apparatus 100 includes a process heater 10, a product supply apparatus 1, and an apparatus that controls discharge and release of materials. In this example, the release apparatus includes a rotary air lock 2, and (the drying apparatus 100 is ) Comprising a drying duct 3, a separator and another rotary airlock, and a discharge device 5; Typically, the separator is a cyclonic separator 4. The stored tobacco product passes through a drying device, and a flow of water-containing (or wet) tobacco product is generated by the supply device 1. The water-containing tobacco product then passes through the rotating airlock 2, the product is dispersed into the duct 3, and the gas and solid mixture is transported along the duct 3 to the cyclonic separator 4 by the hot gas transport stream. Is done. The hot gas gives heat to the tobacco product and evaporates some of the tobacco's moisture. The cyclonic separator 4 separates the dry solids (dry solids) of the tobacco product from the gas stream. The dried tobacco product is discharged through the airlock 5 and then transported to the next stage of the cigarette manufacturing process as needed.

  The conventional drying apparatus shown in FIG. 1 further comprises components that capture and recirculate the carrier gas stream. The drying device further includes a fan 6, an exhaust port 7, a collection duct 8, and a steam injection device. The gas stream leaving the cyclonic separator 4 is conveyed to the fan 6 for recirculation towards the process heater 10 or other heat source (heat exchanger) and again to the drying duct 3. Steam is injected into the system via a suitable control valve 9 and a flow metering system. The fan 6 operates to generate sufficient pressure to carry the gas flow along the duct 8. Excess gas (a part of the returned gas) is discharged or released at the exhaust port 7 to maintain the material balance of the system. The surplus gas is caused by inevitable internal air leakage during air lock and steam injection, and evaporation of moisture from tobacco products originally containing moisture. In the example illustrated in FIG. 1, surplus gas is shown to be vented to the atmosphere, but the gas can be treated or purified prior to release. Examples include condensation (condensation) or cleaning, such as chemical cleaning, to remove any impurities, odors, and contaminants from the vapor release.

US Patent No. 8037620 US Pat. No. 5,252,061 U.S. Pat. No. 4,859,248

  Density reduction and production increase (yield improvement) with an air-borne dryer is due to the speed (rapidity) of the drying process as a function of the rate at which heat is transferred from the drying gas to the product. High-speed heat transfer will produce higher vapor pressure in the tobacco cell matrix compared to vapor pressure generated by gentle heat transfer. When the internal vapor pressure is higher than the ambient vapor pressure, the cell matrix tends to swell, resulting in a reduced density of tobacco products during and after the drying process. The heat transfer between the drying gas and the tobacco product is determined by a number of factors of the drying gas, especially the thermodynamic properties. This is because the thermodynamic properties affect the heat transfer characteristics of the gas boundary layer surrounding each particle surface of the product as the gas is transported through the dryer.

  The drying device may be large (bulky). The physical size of the flash dryer, especially its height, is closely related to the desired throughput, moisture removal and efficiency. Therefore, there is an alternative apparatus and method for improving the heat transfer between the drying gas and the product and for drying such fibrous products, so that the overall size and capital cost of the dryer can be reduced. The purpose is to provide.

According to a first aspect, the present invention provides a drying device for drying a fibrous or granular material, the drying device comprising:
A heater configured to heat a first gas stream and a fibrous material, wherein the first gas stream is configured to enter a drying device at an inlet and includes steam And
A separator for separating the fibrous material from a first gas stream to form a second gas stream;
A fan and a duct configured to recirculate the second gas stream to the process heater and the steam injector;
A flow variation apparatus configured to change a gas flow in the first gas flow.

  U.S. Pat. No. 8,037,620, U.S. Pat. No. 5,252,061, and U.S. Pat. No. 4,859,248 describe commercial dryers that use gas flow to enhance the heat transfer of drying organic materials such as grains and chip chips. Applying pulsation (pulsation). In these dryers, the burner flow is pulsed, that is, a pulsating gas flow is generated by a pulse combustor or pulse jet engine that generates a pulsating hot gas flow that directly heats the organic material. Unlike other organic material examples, it is generally unacceptable to dry flue gas in contact with the product in tobacco drying. This is because the chemical components of the flue gas are thought to adversely affect the taste or smoking characteristics of the processed tobacco. Tobacco dryer design is influenced by the fact that higher temperatures adversely affect tobacco taste. The high temperature burns away the flavor because it burns the sugar and starch components contained in the tobacco. However, higher drying temperatures tend to increase tobacco expansion due to the increased heat transfer rate to the product.

  The present invention utilizes a flow modification device that exploits the thermodynamic and other process advantages of pulsatile gas flow without the associated use of a pulse combustor. The invention has been described with reference to an air-borne dryer or a flash dryer. The present invention and the various configurations claimed are also suitable for other drying devices where the heat transfer to the product to be dried is convective. One example is a fluidized bed dryer that uses carrier gas or fluidized gas as a method of heat transfer.

  In one embodiment, the flow changer is configured to change the flow periodically. The circulation of the gas stream has the effect of repeatedly heating the tobacco product while assisting heat transfer. This flow change (or fluctuation) may take the form of a speed change (speed fluctuation), a pressure change (pressure fluctuation), or a combination of speed and pressure.

  The flow rate changing device is configured to pulsate the flow of process gas (processing gas) and to improve heat transfer in one embodiment. The flow rate change device generates pulses in the process gas stream that decompose and agitate the gas boundary layer surrounding each particle surface of the product as the product is transported through the dryer. This increases the rate of heat transfer between process gases and to tobacco products, ensuring the above advantages of providing improved flavor characteristics to lower density tobacco, while maintaining the benefits of products at lower process gas temperatures. Improve expandability.

  Thus, the apparatus provides the thermodynamic and other process advantages of pulsatile gas flow with flow rate changes (variations) without the associated use of a pulse combustor that directly heats the process gas. It seeks to use.

  In one embodiment, the flow rate changing device is configured to change (vari) the flow in a frequency range from 0.3 Hz to 200 Hz, and is configured to change (change) the flow in a frequency range from 0.3 Hz to 5 Hz. Is done. Here, by operating at a low frequency, but not limited to, typically in the range of 0.3 Hz to 5 Hz, the tobacco flow in the dryer is periodically decelerated and then accelerated. It becomes possible to produce alternately. This periodic speed reduction (deceleration) performs two functions. That is, firstly, heat transfer is increased because the relative velocity between the tobacco product and the gas stream is increased. Secondly, the time for the tobacco product to stay in the dryer is increased, allowing the drying process to be performed at a lower temperature resulting in the resulting flavor benefits. In the present invention, the position of the device that causes the flow rate change and the periodic fluctuation may be the outlet of the cyclone exhaust device or the outlet of the heat exchanger. The flow rate change (variation) may take the form of a speed change (speed change), a pressure change (pressure change), or a combination of speed and pressure.

  In the embodiment, the flow rate changing device includes a mechanical device. In the embodiments described below, the first gas stream and the fibrous material have a process (drying) flow direction, and the flow altering device has a rotation axis perpendicular to the process flow direction. Has a rotatable disc or chopper. This allows for a straight flow rate change device and the disc comprises at least one opening for the process flow of the first gas flow. The disc can be installed in existing drying equipment. The disc of one embodiment comprises a plurality of openings for the process flow of the first gas stream. The multiple openings facilitate the passage of fibrous products such as gas streams and tobacco, and are useful, for example, if (one) opening is clogged or plugged.

  The first gas flow and the fibrous material have a process flow direction, and the flow rate changing device includes a rotatable damper plate having a rotation axis perpendicular to the process flow direction. Embodiments have also been described. The damper plate is a convenient and reliable structure for the flow rate changing device.

  In one embodiment where higher frequency flow fluctuations are required, the flow rate changer comprises a pneumatically driven sound emitter. In another embodiment, the flow changing device comprises an electrically driven sonic radiator.

  Heat transfer between the process gas and the product is related to the relevant conditions in the boundary layer of gas molecules directly adjacent to and surrounding the product particles of the fibrous material. Higher frequency flow fluctuations applied to heat exchange systems, such as acoustic vibrations, result in significantly increased heat transfer due to gas boundary layer breakdown or fracture. For example, in one embodiment, an electrically driven or pneumatically driven sonic radiator or acoustic horn is used to provide additional high frequency flow fluctuations to the dryer system, ranging from 20 Hz to 400 Hz.

In the drying apparatus, the steam generation and heating steps require a significant amount of energy input. In addition, air inflow at various points in the system results in diluting the vapor content of the dry gas, which is compensated by increasing the amount of vapor injected into the system. It has been thought that the heat energy from the exhaust gas and excess gas obtained from the drying process can be recovered using a heat exchanger. In one embodiment, the drying device condenses and separates the first vapor component and the water component from the second gas stream and further generates a second vapor component at low pressure, and A compressor configured to compress the second steam component and return the steam component to the inlet (inlet).
In one embodiment, the drying device further includes a compressor configured to compress the second gas stream, condensing and separating the vapor and water components from the second gas stream, and further reducing the second steam at low pressure. A heat exchanger is provided that is configured to generate the component and return the second vapor component to the inlet. This means that the energy content of the exhaust from the dryer or dryer can be recovered and that energy content is returned to the dryer for reuse.

  Due to product quality considerations, there was a tendency to determine the use of superheated steam as the drying medium for tobacco dryers. In these dryers, the steam in the dry gas is reduced by minimizing the inflow of air and injecting steam into the process to supplement the steam generated by evaporating the moisture of the tobacco product itself. High concentration is achieved.

  It is desirable to maintain low oxygen levels in such dryers. This is because the quality of the product is improved by preventing the risk of fire and preventing the surface oxidation of the product.

  The exhaust from the drying process includes moisture evaporated from the product, internal leaked air, and injected steam. The exhaust is at a pressure close to atmospheric pressure and has a large energy content due to the enthalpy of moisture evaporated from the product.

  The evacuation conditions of the dryer are to contain 90% steam and 10% air by volume at a temperature of about 150 ° C. and an absolute pressure of 1 bar. Using a heat exchanger, thermal energy can be recovered from such a gas stream, but the temperature of the recovered energy is relatively low, well below the process gas condensation temperature and below 100 ° C. at atmospheric pressure. Will be below.

  A system is described in which the gas stream contains superheated steam. Here, it is desirable to raise the temperature of the recovered energy to a level that is easy to use, and it is therefore necessary to introduce a compression stage into the process. A heat exchanger such as that described in co-pending International Publication No. WO 2010/094913 can be employed. The heat exchanger can generate steam from water at low pressure and then compress the resulting low atmospheric pressure steam to a pressure suitable for injection into the process. In this embodiment, the compressor is only required to handle clean steam that is not contaminated with particles or dust from the process exhaust, while the larger compressor has a lower gas density at its inlet. Is required to be adjusted. The use of heat exchangers ensures that the steam generated with the recovered heat is not contaminated with air or other substances that can affect the quality of the processed product.

  In the described drying apparatus, the drying apparatus further comprises an apparatus configured to introduce additional steam into the first gas stream. The additional steam is, in one embodiment, from an alternative source that is external to the dryer. One described embodiment is that the heat exchanger is configured to have a gas flow pressure of less than 1 bar, preferably in the range of 0.3 bar to 0.7 bar, for optimal functional properties. including. As described above, one embodiment comprises a compressor, and optimal operation is achieved by a compressor configured to compress the gas stream to a pressure greater than 1 bar, preferably in the range of 1.1 bar to 1.5 bar. Arise.

  In one embodiment, the drying apparatus changes the flow rate of the first gas flow in a state where the amplitude of the gas velocity fluctuation from the average velocity of the first gas flow is in the range of 0 to 20 m / sec. Includes equipment.

  According to the present invention as seen from the second feature, a method for drying a fibrous product using the drying apparatus of the present invention is provided.

  Further preferred features of the invention are defined in the appended claims, wherein the process gas flow in the flash dryer is periodically changed to increase the heat transfer between the drying gas and the product. Includes processes. Also included is a process in which the flow of process gas in the flash dryer is periodically changed to increase the product residence time in the dryer. Also included is a process in which the flow of process gas in the flash dryer is periodically changed using a frequency in the range of 0.3 Hz to 200 Hz.

  Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a prior art drying apparatus. FIG. 2 is a schematic view of the drying apparatus of the present invention. FIG. 3 is a schematic view of a portion of the drying apparatus of FIG. 1 in accordance with the first embodiment of the present invention. FIG. 4 is a schematic view of a portion of the drying apparatus of FIG. 3 parallel to the direction of process flow. FIG. 5 is a schematic view of a portion of the drying apparatus of FIG. 1 in accordance with the second embodiment of the present invention. FIG. 6 is a schematic view of the drying apparatus of the present invention according to the third embodiment. FIG. 7 is a graph showing gas velocity and operation according to the present invention. FIG. 8 is a schematic diagram of the drying apparatus of the present invention in an alternative configuration. FIG. 9 is a schematic diagram of the drying apparatus of the present invention in yet another alternative configuration.

  One type of conventionally known drying apparatus and the drying apparatus of the present invention will be described with reference to FIGS. Some of the details of the structure and operation of the known drying apparatus have been described above, and a summary of the detailed description follows. Moisture is removed from the wet (wet) tobacco product in a duct 3 that transports and disperses the tobacco product in a gas stream. The cyclonic separator 4 operates to separate tobacco products from the exhaust gas, which can be treated and purified or recycled.

  Since the drying apparatus 200, 300, 400, 500 of the embodiment of the present invention includes several components that are substantially similar to the apparatus 100 shown in FIG. 1, similar features use the same reference numerals. As referenced. Referring to FIG. 2, a drying apparatus 200 according to a first embodiment of the present invention is shown, which has a flow rate changing device 20 located in a process gas duct 3 prior to a rotating air lock 2. ing. The flow changing device may be located after the cyclonic separator.

  The flow rate changing device 20 is shown in the embodiment shown in FIG. 3 as comprising mechanical means of a rotatable disk 21. The disk 21 is rotatably mounted in an apparatus having an axis 22 parallel to the process gas flow direction 40. The disc is mounted about the shaft 22. A plurality of holes 23 are located on the outer periphery of the disk, and a plurality of land portions or solid regions 24 exist between these holes. The process gas duct 3 accommodates a disk 21 and a shaft 22 for installation.

  FIG. 4 shows a cross-sectional view of the flow rate changing device and shows the disk 21 with drive means 50 for driving the disk 21 and rotating the disk about the shaft 22. In this embodiment, the drive means is a variable speed motor 50. The disk 21 is directly installed on the shaft of the variable speed motor 50. The fixed housing 60 is configured to surround the disk 21 and serves to connect the disk 21 to the process gas duct 3 to prevent gas leakage into or out of the flow rate changer unit.

  In use, the disk 21 is driven by a motor 50 and intersects the process gas duct 3 laterally. Process gas moving in the direction 40 can pass through the hole 23 when the hole 23 is aligned with the duct 3 or the flow is interrupted when the solid land 24 of the disk 21 is aligned with the duct 3. The The flow waveform can vary depending on the shape or pattern of the holes on the disk 21. The frequency of change in the flow can be increased or decreased depending on the rotational speed of the disk 21.

  Another embodiment of a flow rate changing device is shown in FIG. This flow rate changing device is a damper plate 25 arranged before the product feed point of the process gas duct 3 or after the cyclonic separator, and has a rotating shaft 26 perpendicular to the process gas flow direction 40. This is a damper plate 25. The damper plate 25 is a rectangular plate having a long side L and a short side H. The shape and size are selected so as to complement each other (complementarily), but are not the same shape as the inner method of the height and width of the cut surface (intersection surface) of the process duct 3. Here, the process gas duct 3 is shown in a rectangular parallelepiped shape. The damper plate 25 is attached to and connected to a drive motor or a device that drives and rotates the damper plate 25.

  In use, the plate alternately blocks and flows the gas flow in the duct 3 as the plate rotates. If the area of the plate 25 is equal to or close to the cross-sectional area of the duct 3, the minimum flow rate will be substantially zero. If the area of the plate 25 is slightly smaller than the area of the duct 3, the minimum flow will proportionally approach the maximum flow.

  FIG. 7 illustrates the effect of changing the width dimension W on the height or diameter HH of the duct. The speed graph 27 represents the effect when the ratio of the plate width H to the duct height HH is 66%, and the graph 28 represents the effect when the plate width H is equal to 50% of the duct height HH. Represents the effect of the plate width H which is 22% of the duct height HH. In these graphs, it is assumed that the fan speed of the process gas is adjusted to provide the same average gas flow rate throughout. Similar effects can be obtained by changing the ratio of the open area to the total area of the embodiment with the disk 21 shown in FIG. The speed and time numbers in the graph are for illustrative purposes and are not limited to these values.

  As described above, by operating in a low frequency range, typically between 0.3 Hz and 5 Hz, but not limited thereto, the tobacco flow in the drying apparatus alternates between deceleration and acceleration periodically. It is possible to create a repeating situation. This periodic or cyclical speed reduction performs two functions. That is, firstly, the relative speed between the cigarette (product) and the gas flow increases, so that heat transfer increases. Secondly, the time that the tobacco (product) stays in the dryer is increased, thus allowing the drying process to be performed at a lower temperature, which is beneficial to flavor (maintenance).

  FIG. 6 shows another drying device 300 including a flow rate changing device 20 arranged in the duct 3. Here, the flow rate changing device comprises a sound emitter 90 such as a pneumatically driven sound emitter such as IKT150 / 360 manufactured by Kockum Sonics, Malmo, Sweden. Such a sound emitter can be connected to the drying duct system using a branch duct in front of the product delivery position, as shown in FIG. In use, the sonic emitter will generate a flow of radio frequency pulses that alters the process gas flow moving along the duct 3. It is envisioned that one or more of the flow rate change devices 20 described above can be used in one drying system and drying device. Thus, the low frequency vibration of the flow is generated by the mechanical means of the rotating disk 21 or the damper 25, and the higher frequency acoustic vibration is generated by the pneumatically driven sound radiator 90.

  In another embodiment, the flow changing device 20 described as disk 21, plate 25 and sonic radiator 90 may also be used in the drying devices 400, 500 shown in FIGS. The drying apparatuses 400 and 500 further include a heat exchanger 12 for condensing (condensing) the exhaust gas flow, and have an access inlet port 11, access exhaust ports 13 and 14, a compressor 16, and a steam monitoring device 17. In a preferred embodiment, the monitoring device is a steam flow meter and the compressor is a rotary lobe compressor. The drying apparatus further comprises a separate and independent steam supply 19 and a steam injection system for providing additional steam to the process steam injection line 15. The steam injection system includes a flow meter 18 and a flow control valve 9 responsive to the steam monitoring device 17.

  In order to maintain the required low oxygen concentration in the dryer, steam is injected into the system via appropriate control valves and flow metering systems. Examples thereof are well known to those skilled in the art.

  The devices 400, 500 operate in the manner described above for the conventional device 100. In contrast to the drying device 100, the exhaust gas from the drying device 400 at the point 7 generates heat that evaporates the water 11 supplied to the inlet 11 on the shell (shell, outer shell) side of the heat exchanger 12 ( The exhaust gas goes to the heat exchanger 12 that it provides. A level sensor controller (not shown) is provided in the heat exchanger 12 so that water is not released (possible) from the heat exchanger 12 to the process steam injection line 15 although the electric heating surface is covered. Maintain the water level. The pressure in the heat exchanger 12 is maintained below atmospheric pressure, and in a preferred embodiment is maintained at an absolute pressure of 0.5 bar. Negative pressure (negative pressure) is generated by the compressor 16. At this low pressure, steam is generated by a heat exchanger between 65 ° C. and 75 ° C. and a temperature around 70 ° C., thereby recovering the latent heat content of the steam in the exhaust gas. In other words, the thermal energy in the exhaust gas mixture of the drying process is used to generate low pressure steam using the heat exchanger 12.

  This low pressure steam, free of water and other contents, is then mechanically compressed by compressor 16 and injected into the process gas to maintain the desired vapor concentration. The low pressure steam is compressed by the compressor 16 to a pressure greater than 1 bar absolute pressure. Pressures above 1 bar have been found suitable for injecting steam back into the process line, drying process and process heater stage 10. The steam flow injected into the duct 3 and the separator 4 is controlled by changing the speed of the compressor 16 according to feedback from the steam flow meter 17. Independent steam injection consisting of a flow meter 18 and a flow control valve 9 to provide an appropriate flow of additional steam from a separate source 19 when the steam flow from the compressor 16 is below the desired steam flow. The system can be used. In this preferred embodiment, the separation source 19 is a central boiler facility that provides steam to bring the total steam injection flow to a predetermined desired level. Not all exhaust streams are condensed (condensed) by the heat exchanger. In particular, the air content of the exhaust gas is discharged from the condenser of the heat exchanger 12 through the exhaust port 14. The exhaust gas and excess gas at the exhaust ports 7 and 14 are discharged from the saturated heat exchanger 12 and thus contain a vapor component. As noted above, the exhaust gas may require additional processing to purify the gas and / or remove malodorous components. Moreover, water is discharged | emitted from the heat exchanger 12 in the exit 13 (in a heat exchanger, water condenses, taking out the latent heat concerning condensation). By the term “gas stream” we mean the fluid flow in a drying device that carries tobacco products, gases, vapors, impurities, and possibly water, through the system.

  Referring to FIG. 9, there is shown a drying device 500 with a flow rate changing device 20 according to a further embodiment of the present invention. The drying devices 400, 500 of embodiments of the present invention are substantially similar, and similar features are referenced using the same reference numerals. The configuration of the drying device 500 differs from the drying device 400 in that the compressor 16 is located upstream of the heat exchanger 12. The compressor 16, ie the drying compression stage, takes place before the heat exchanger 12. In this embodiment, in order to remove air from the steam, the exhaust gas is recompressed by means such as the heat exchanger 12 of this preferred embodiment just prior to being reinjected as steam into the drying process. Thus, the temperature of the recovered gas and energy is raised to a level that is beneficial for use in the drying process.

  Various modifications may be made to the above-described embodiments without departing from the scope of the present invention. There may be different numbers of drying stages, or compressors, or heat exchange means. There may be more than one separator. In addition, other types of independent steam sources may be used, such as containers or feeders that are completely external from the operating facility. The efficiency of energy recovery can be optimized as needed and depends on a number of detailed design considerations. The material to be dried may be fibrous or granular and may include organic materials. Here, the duct is indicated by a circle. Other shaped ducts may be used. For example, any easy-to-use cross section such as a circle or a rectangle may be used. Although a pneumatically driven sound emitter has been described, it may be electrically driven or driven by other means, other energy supplies, or other frequency bands.

  In FIG. 7, “Gas Velocity m / s” is the gas velocity m / s, and “Time (Seconds)” is the time (seconds).

Claims (15)

A drying device for drying a fibrous or granular material,
A heater configured to heat a first gas stream and a fibrous material, wherein the first gas stream is configured to flow into a drying device at an inlet, the gas stream including steam. A heater,
A separator that separates the fibrous material from the first gas stream to form a second gas stream;
A fan and a duct configured to recirculate the second gas stream to the process heater and a steam injector;
A flow rate changing device configured to change a gas flow in the first gas flow;
A drying apparatus comprising:   The drying apparatus according to claim 1, wherein the flow rate changing device is configured to periodically change the gas flow.   The drying apparatus according to claim 1 or 2, wherein the flow rate changing device is configured to pulsate a flow of a process gas (processing gas) and to improve heat transfer.   The drying apparatus according to any one of claims 1 to 3, wherein the flow rate changing device is configured to change the gas flow in a frequency range of 0.3 Hz to 200 Hz.   The drying apparatus according to any one of claims 1 to 4, wherein the flow rate changing device is configured to change the gas flow in a frequency range of 0.3 Hz to 5 Hz.   The drying apparatus according to any one of claims 1 to 5, wherein the flow rate changing device includes a mechanical device. The first gas stream and the fibrous material have a flow direction of the process (drying process);
The drying apparatus according to claim 6, wherein the flow rate changing device includes a rotatable disk or chopper having a rotation axis orthogonal to a process flow direction.   8. A drying apparatus according to claim 7, wherein the disk comprises at least one opening for the process flow of the first gas flow.   The drying apparatus according to claim 7 or 8, wherein the disk includes a plurality of openings for the process flow of the first gas flow. The first gas stream and the fibrous material have a flow direction of the process (drying process);
The drying apparatus according to claim 6, wherein the flow rate changing device includes a rotatable damper plate having a rotation axis orthogonal to a process flow direction.   The drying apparatus according to claim 6, wherein the flow rate changing device includes a pneumatically driven sonic radiator.   The drying apparatus according to claim 6, wherein the flow rate changing device includes an electrically driven sonic radiator.   The flow rate changing device operates to change the gas flow of the first gas flow in a state where the amplitude of the gas velocity fluctuation from the average velocity of the first gas flow is in the range of 0 to 20 m / sec. The drying apparatus according to any one of claims 1 to 12, wherein the drying apparatus is characterized in that   A method for drying a fibrous material, characterized in that the drying apparatus according to any one of claims 1 to 13 is used.   A drying apparatus substantially as herein described with reference to the accompanying drawings.

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