WO2025215517A1 - Système et procédé de séchage améliorés - Google Patents

Système et procédé de séchage améliorés

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Publication number
WO2025215517A1
WO2025215517A1 PCT/IB2025/053676 IB2025053676W WO2025215517A1 WO 2025215517 A1 WO2025215517 A1 WO 2025215517A1 IB 2025053676 W IB2025053676 W IB 2025053676W WO 2025215517 A1 WO2025215517 A1 WO 2025215517A1
Authority
WO
WIPO (PCT)
Prior art keywords
dryer
primary
feed material
heating fluid
drying
Prior art date
Legal status (The legal status 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 status listed.)
Pending
Application number
PCT/IB2025/053676
Other languages
English (en)
Inventor
David Kenneth Pinches
Dilip Kumar Desai
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pinches Industries Pty Ltd
Original Assignee
Pinches Industries Pty Ltd
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 AU2024900968A external-priority patent/AU2024900968A0/en
Application filed by Pinches Industries Pty Ltd filed Critical Pinches Industries Pty Ltd
Publication of WO2025215517A1 publication Critical patent/WO2025215517A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B23/00—Heating arrangements
    • F26B23/001—Heating arrangements using waste heat
    • F26B23/002—Heating arrangements using waste heat recovered from dryer exhaust gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B23/00—Heating arrangements
    • F26B23/10—Heating arrangements using tubes or passages containing heated fluids, e.g. acting as radiative elements; Closed-loop systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B11/00—Machines or apparatus for drying solid materials or objects with movement which is non-progressive
    • F26B11/12—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in stationary drums or other mainly-closed receptacles with moving stirring devices
    • F26B11/16—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in stationary drums or other mainly-closed receptacles with moving stirring devices the stirring device moving in a vertical or steeply-inclined plane
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B15/00—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form
    • F26B15/26—Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form with movement in a helical path
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
    • F26B17/18—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by rotating helical blades or other rotary conveyors which may be heated moving materials in stationary chambers, e.g. troughs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
    • F26B17/28—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by rollers or discs with material passing over or between them, e.g. suction drum, sieve, the axis of rotation being in fixed position
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B21/00—Arrangements for supplying or controlling air or other gases for drying solid materials or objects
    • F26B21/40—Arrangements for supplying or controlling air or other gases for drying solid materials or objects using gases other than air
    • F26B21/45—Arrangements for supplying or controlling air or other gases for drying solid materials or objects using gases other than air using steam
    • F26B21/452—Arrangements for supplying or controlling air or other gases for drying solid materials or objects using gases other than air using steam characterised by the steam generating means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B23/00—Heating arrangements
    • F26B23/001—Heating arrangements using waste heat
    • F26B23/002—Heating arrangements using waste heat recovered from dryer exhaust gases
    • F26B23/004—Heating arrangements using waste heat recovered from dryer exhaust gases by compressing and condensing vapour in exhaust gases, i.e. using an open cycle heat pump system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
    • F26B25/04—Agitating, stirring, or scraping devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
    • F26B3/04—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour circulating over or surrounding the materials or objects to be dried
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
    • F26B3/06—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/18—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact
    • F26B3/22—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact the heat source and the materials or objects to be dried being in relative motion, e.g. of vibration
    • F26B3/24—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact the heat source and the materials or objects to be dried being in relative motion, e.g. of vibration the movement being rotation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying goods
    • F26B2200/02—Biomass, e.g. waste vegetative matter, straw
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying goods
    • F26B2200/06—Grains, e.g. cereals, wheat, rice, corn
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying goods
    • F26B2200/08—Granular materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying goods
    • F26B2200/18—Sludges, e.g. sewage, waste, industrial processes, cooling towers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
    • F26B3/06—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried
    • F26B3/08—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried so as to loosen them, e.g. to form a fluidised bed
    • F26B3/092—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour flowing through the materials or objects to be dried so as to loosen them, e.g. to form a fluidised bed agitating the fluidised bed, e.g. by vibrating or pulsating

Definitions

  • the present invention relates to an improved drying system and method. More particularly, but not exclusively, it relates to an industrial drying system for the drying of wet bulk materials.
  • Drying of bulk materials is a task which is important across many industries, and is accomplished by industrial dryer systems of various types.
  • Common bulk materials requiring drying include minerals (e.g. ore or sand), polymers (e.g. plastic granules), agricultural products (e.g. grains, cereals, or coffee beans), and animal by-products (e.g. meat or bone meal).
  • Industrial dryers are also used in the drying of other materials that might not necessarily be characterised as 'bulk', such as sludge. In general, industrial dryers are continuously or intermittently supplied with wet feed material, which is conveyed through the dryer and subsequently discharged with some amount of moisture content removed.
  • Industrial dryers generally utilise a heat source of some kind to transfer heat into the feed material and cause evaporation of the trapped moisture.
  • Industrial dryers can be broadly classified into direct- heat dryers, where a hot gas stream makes direct contact with the feed material, and indirect- heat dryers, where a hot fluid indirectly transfers heat to the feed material e.g. through the walls of a shell, discs, or some other structure.
  • the two types of dryers each have certain advantages and may be better suited for different applications. For example, direct-heat dryers are typically more efficient, but indirect-heat dryers can avoid contaminating the feed material and may be better suited for heat-sensitive materials.
  • a superheated steam (SHS) dryer may use a combustor and a heat exchanger to continuously cycle a flow of superheated steam through the dryer shell to contact the feed material directly.
  • a disc dryer may use a steam boiler to supply steam into a series of hollow discs shaft-mounted within the dryer shell, the discs transferring heat into the feed material and discharging condensate.
  • An SHS dryer is typically configured as a rotary dryer, where the shell is continuously rotated to convey the feed material towards the discharge end, whereas a disc dryer is typically configured as a rotary disc dryer where the discs are rotated to convey the feed material.
  • Dryer efficiency is generally measured in terms of energy input via the heat source, versus the latent heat of vaporisation for moisture removed from the feed material. Typical efficiencies from common types of dryers are 40-75%. Because the vapour coming off the feed material during drying still carries a portion of the heat energy transferred, if this heat can be recovered somehow then it is in fact possible for a drying system to achieve efficiency of greater than 100% under the above definition.
  • Some drying systems utilising heat recovery techniques are known, and generally involve multiple dryers with some fluid connection. However, the efficiency of known drying systems that utilise heat recovery remains far from the theoretical maximum, and it is desirable to develop drying systems which achieve further improvements in efficiency. Given the scale at which such drying operations are conducted in industry, even relatively small efficiency improvements could provide considerable cost savings and substantially reduce the quantity of fossil fuels burned to heat the fluids used for drying.
  • the invention broadly comprises a drying system for drying wet feed material, the drying system comprising: a primary heating fluid source; a primary dryer operatively connected to the primary heating fluid source to receive heating fluid therefrom; a secondary dryer, being an indirect-heat dryer, operatively connected to a venting port of the primary dryer to receive waste steam as heating fluid, the waste steam resulting from drying of the wet feed material in the primary dryer; a compressed air source operatively connected to the secondary dryer to inject compressed air into the secondary dryer and thereby agitate feed material passing therethrough; and a feed material conveyor connecting the primary dryer and the secondary dryer, such that partially dried material feed material exiting the secondary dryer is conveyed into the primary dryer, or vice-versa.
  • the drying system further comprises a heat exchanger connected between the compressed air source and the secondary dryer, and connected to a heating fluid outlet of the primary dryer, such that heat remaining in the heating fluid after exiting the primary dryer is transferred into the compressed air to be injected into the secondary dryer.
  • the secondary dryer comprises a body having a plurality of nozzles formed in an underside of the body, the plurality of nozzles being operatively connected to the compressed air source.
  • the partially dried material feed material exiting the secondary dryer is conveyed into the primary dryer, such that the secondary dryer is a predryer.
  • the secondary dryer is a rotary disc dryer.
  • the primary dryer is an indirect-heat dryer.
  • the primary dryer is a rotary disc dryer.
  • the primary dryer is a direct-heat dryer.
  • the primary dryer is a superheated steam dryer.
  • the heating fluid source is a steam boiler.
  • the heating fluid source is an indirectly-fired heat exchanger.
  • the compressed air source is an air compressor.
  • drying system further comprises an air dryer connected to the compressed air source.
  • the drying system further comprises a mesh filter connected between the venting port of the primary dryer, and the secondary dryer.
  • the drying system further comprises a bag filter connected between the mesh filter and the secondary dryer.
  • drying system further comprises a fan connected between the venting port of the primary dryer, and the secondary dryer.
  • drying system further comprises a condenser operatively connected to a venting port of the secondary dryer to condense moisture out of gas vented from the secondary dryer.
  • the drying system further comprises a cyclone separator operatively connected between the venting port of the secondary dryer and the condenser.
  • the primary dryer is also a cooker, and comprises an outlet for tallow released from the feed material.
  • the invention broadly comprises a method of drying wet feed material, the method comprising: a primary drying step comprising heating the wet feed material using a primary heating fluid; a secondary drying step comprising indirectly heating the wet feed material using waste heat extracted from the primary drying step; agitating the wet feed material with compressed air during the secondary drying step; and conveying partially dried feed material from the secondary drying step to the primary drying step, or vice-versa.
  • the method further comprises heating the compressed air using waste heat before using it to agitate the wet feed material.
  • waste heat used to heat the compressed air is extracted from the primary drying step and transferred via condensate of the primary heating fluid.
  • heating in the primary drying step is indirect heating such that the primary heating fluid does not contact the wet feed material.
  • the primary heating fluid is steam which is introduced in the primary drying step at between 140-180°C.
  • heating in the primary drying step is direct heating such that the primary heating fluid contacts the wet feed material.
  • the primary heating fluid is superheated steam which is introduced in the primary drying step at between 200-400°C.
  • the method further comprises drying the compressed air before using it to agitate the wet feed material.
  • the waste heat extracted from the primary drying step is transferred via steam vented from the primary drying step, at least part of which is evaporated from the wet feed material during the primary drying step.
  • the method further comprises separating solid particles out of the steam vented from the primary drying step.
  • the steam vented from the primary drying step is at 120-125°C.
  • the method further comprises condensing moisture out of gas exiting the secondary drying step.
  • the invention broadly comprises an indirect-heat dryer for drying wet feed material, the dryer comprising: a body within which wet feed material is to be indirectly heated by a heating fluid; a heating fluid inlet, a heating fluid outlet, and a heating fluid channel connected therebetween and configured to pass the heating fluid through or about the body without directly contacting the wet feed material; a wet material infeed for introducing the wet feed material into the body; a dried material outfeed; a conveying mechanism for conveying the wet feed material through the body as it dries, and subsequently out of the dried material outfeed; a plurality of nozzles formed in an underside of the body to allow an agitation gas to be injected into the body and thereby directly contact and agitate the wet feed material; a venting port for venting steam evaporated from the wet feed material, and agitation gas introduced through the plurality of nozzles.
  • the indirect-heat dryer is a rotary disc dryer such that the heating fluid channel is provided within a plurality of discs mounted within the body, and the discs act as the conveying mechanism.
  • the nozzles are provided on a modular nozzle plate removably attached to the underside of the body.
  • the nozzles are formed as a grating.
  • the nozzles are formed as individual spouts.
  • nozzles are swivelable to create a swirling effect.
  • Figure 1 shows a schematic of a drying system wherein the primary dryer and the secondary dryer are both indirect-heat dryers
  • Figure 2 shows a schematic of a drying system wherein the primary dryer is a direct- heat dryer instead of an indirect-heat dryer;
  • Figure 3 shows a schematic of the drying system of figure 1, wherein the compressed air is heated by waste heat from condensate;
  • Figure 4 shows a simplified cross-section of an indirect-heat dryer having nozzles to introduce an agitation gas.
  • the drying system 100 comprises a primary heating fluid source 102 and a primary dryer 104 operatively connected to the primary heating fluid source 102 to receive heating fluid therefrom.
  • the primary dryer 104 may be any suitable industrial dryer as known in the art, but figure 1 shows an indirect-heat dryer in which the heating fluid does not contact the feed material. The specific example depicted is a rotary disc dryer. Other possibilities for the primary dryer 104 will subsequently be described.
  • the drying system 100 further comprises a secondary dryer 106, being an indirect- heat dryer, operatively connected to a venting port 108 of the primary dryer 104.
  • the venting port 108 is used to vent waste steam that results from drying of the wet feed material in the primary dryer 104.
  • the secondary dryer 106 thus receives waste steam from the primary dryer 104 as heating fluid. In this way, waste heat is extracted from the primary dryer 104, allowing the overall efficiency of the drying process to be improved.
  • the drying system 100 further comprises a compressed air source 110 operatively connected to the secondary dryer 106.
  • the compressed air source 110 is an air compressor taking in ambient air (at e.g. 20°C).
  • the compressed air source 110 is used to inject compressed air into the secondary dryer 106 and thereby agitate feed material passing therethrough.
  • the compressed air is injected via a plurality of nozzles formed in the secondary dryer 106 - structure of the secondary dryer 106 will later be described in more detail.
  • the injected air is dry air to avoid introducing moisture into the secondary dryer 106, which (dependent on ambient humidity) may require an air dryer as will subsequently be described.
  • Injection of compressed air into the secondary dryer 106 is preferably done in such a manner to fluidise the feed material, i.e. agitating it sufficiently to behave like a fluid.
  • the compressed air is preferably introduced from underneath the secondary dryer 106, at a sufficiently high flow rate, and from a sufficient number of locations (e.g. nozzles).
  • the ideal parameters will be dependent on application, in particular the properties of the wet feed material e.g. density, viscosity, particle size, pore size, and other such properties used in the characterisation of bulk/granular materials.
  • overall efficiency of the drying system 100 (by the metrics as discussed in the background) can exceed 100%.
  • the efficiency may be in the range of 130-150%.
  • the drying system 100 further comprises a feed material conveyor 112 connecting the primary dryer 104 and the secondary dryer 106.
  • the feed material conveyor 112 conveys feed material between the two dryers, but the dryers may be arranged either way around.
  • Figure 1 depicts the preferred arrangement wherein the partially dried feed material exiting the secondary dryer 106 is conveyed into the primary dryer 104, such that the secondary dryer 106 is a pre-dryer. This arrangement may be more efficient than the reverse, but an arrangement where the primary dryer 104 is the pre-dryer and the secondary dryer is still viable.
  • the improved efficiency of the preferred arrangement of the dryers may be due to the temperature of the feed material being raised in the pre-dryer while the moisture content is still relatively high, with the primary heating fluid of the primary dryer 104 being at a higher temperature still.
  • the feed material conveyor 112 depicted in figure 1 is a screw conveyor driven by a motor 114, which may be provided with a variable speed drive for process control.
  • the feed material conveyor 112 could be of any other type which serves to transfer the material while preventing clogging .
  • the dryers could be placed in a stacked configuration where the feed material conveyor 112 is a rotary gate valve, preferably configured to prevent oxygen transfer into the primary dryer 104.
  • Stacking the dryers may be especially useful where floor area is limited, for example when the secondary dryer 106 is being retrofitted to a primary dryer 104 which is part of an existing floor layout.
  • the primary heating fluid source 102 is a steam boiler such that the heating fluid for the primary dryer 104 is steam.
  • the steam boiler preferably provides steam to the primary dryer 104 at between 140-180°C and at high pressure, for example the steam boiler may operate at approximately 6 bar.
  • the steam may condense into water.
  • the heating fluid which exits the primary dryer 104 may be condensate which is drained as waste.
  • the heating fluid does not make contact with the feed material, the heating fluid could be another substance such as thermal oil, and it could be continuously reheated and cycled through the primary dryer 104 instead of being drained away after exiting.
  • the ideal heating fluid may depend on the type of indirect-heat dryer.
  • the steam evaporated from the wet feed material will generally be at approximately 100°C and at atmospheric pressure.
  • the waste steam vented from the primary dryer 104 and introduced to the secondary dryer 106 is at approximately 100°C.
  • a mesh filter 116 may be connected between the venting port 108 of the primary dryer 104, and the secondary dryer 106.
  • a bag filter 118 may also be connected between the mesh filter 116 and the secondary dryer 106.
  • various other filtering arrangements may be suitable to achieve the removal of particulates from the waste steam, and the ideal type may depend on factors such as the pressure and flow rate.
  • a fan 120 may be connected between the venting port 108 of the primary dryer 104, and the secondary dryer 106.
  • the fan 120 may help to drive the waste steam into the secondary dryer 106.
  • the fan 120 is connected after the mesh filter 116 and/or bag filter 118.
  • a condenser 122 may be operatively connected to a venting port 124 of the secondary dryer 106 to condense moisture out of gas vented from the secondary dryer 106, as the vented gas will be a mixture of waste steam and air. The resulting condensate can be drained away, and the air can be vented to atmosphere.
  • a cyclone separator 126 is operatively connected between the venting port 124 of the secondary dryer 106, and the condenser 122, to separate out solids which may have entered the gas stream from the feed material. This can prevent clogging of the condenser 122.
  • an air dryer 128 is connected to the compressed air source 110 to remove moisture from the air before it is injected into the secondary dryer 106. This can help prevent corrosion or other wear of system components, as well as potentially providing a slight increase in drying efficiency. Preferably it is connected in between the compressed air source 110 and the secondary dryer 106, but it might also be connected to dry air before it enters the compressed air source 110.
  • the primary dryer 104 may also be a cooker and cause the release of tallow from the feed material during drying.
  • the primary dryer 104 may therefore comprise an outlet for discharging tallow, in addition to that for discharging the dried feed material.
  • the primary dryer 104 of the drying system 100 may alternatively be a direct-heat dryer, in which the primary heating fluid directly contacts the feed material, rather than an indirect-heat dryer.
  • the example shown is a rotary superheated steam dryer.
  • the drying system 100 may be substantially unchanged compared to the arrangement of figure 1, except for select differences as outlined below.
  • the primary dryer 104 When the primary dryer 104 is a rotary superheated steam dryer, steam is continuously reheated and cycled directly through a body of the dryer to dry the wet feed material, and the body of the dryer is rotated to convey the feed material therethrough.
  • the primary heating fluid source 102 is an indirectly-fired heat exchanger. Part of the steam vented from the primary dryer 104, which will be a mix of the input steam and the steam evaporated from the feed material, is cycled back through the heat exchanger for reheating and reintroduced into the primary dryer 104. The excess steam, arising from the evaporation from the feed material, is the waste steam sent to the secondary dryer 106.
  • An additional cyclone separator 126 may be operatively connected to the venting port 108 of the primary dryer 104, to separate solids out of the vented steam before the steam is recycled and the waste steam is split off.
  • An additional fan 120 may also be connected between that cyclone separator 126 and the indirectly-fired heat exchanger to help move steam through the system.
  • the indirectly-fired heat exchanger introduces superheated steam into the primary dryer 104 at between 200-400°C, for example at approximately 300°C, and at close to atmospheric pressure. Operation at different pressure may change the temperature range accordingly.
  • Heat from the superheated steam is transferred to the wet feed material as the steam moves through the body, and when the steam is vented it is preferably at between 120- 125°C (it may be slightly hotter than when the primary dryer 104 is an indirect-heat dryer). This ensures no water particles are suspended in the steam i.e. the steam will not be wet steam.
  • the waste steam introduced into the secondary dryer 106 may be at the same temperature or slightly lower due to heat losses, for example approximately 115°C.
  • Flue gas exiting the indirectly-fired heat exchanger will be at a lower temperature than the superheated steam, for example approximately 200°C.
  • the ideal parameters of the input superheated steam may depend on the amount of wet feed material being passed through the body of the primary dryer 104, as increased feed material throughput increases heat loading proportionally (if the same level of drying is to be achieved).
  • the input parameters such as temperature and flow rate may be control variables in a closed loop control system where the temperature of the vented steam is the process variable to be maintained at a setpoint (this setpoint correlating to a desired level of drying). This type of control allows dynamic adjustment to different heat loading conditions.
  • Closed loop control of the primary heating fluid parameters can be provided by a controller which forms part of the drying system 100.
  • a superheated steam dryer will generally exhibit a faster control response time than an indirect-heat dryer such as a disc dryer, because disc dryers carry large amounts of heat in the discs.
  • closed loop control can nevertheless be applied to a disc dryer in a similar way. It will be appreciated that for either type of dryer, the controller may also receive input from various other sensors/input devices and perform other process control functions.
  • the heating fluid remains steam.
  • the direct contact with the feed material means that the vented gas would then be a mix of steam and a different heating fluid, which may not be ideal for use in the secondary dryer 106. Heated air for example may nevertheless be suitable if the secondary dryer 106 is configured to receive a hot air and steam mixture.
  • the drying system 100 may be able to achieve greater overall efficiency with a direct- heat dryer as the primary dryer 104, given that they are typically more efficient than comparable indirect-heat dryers.
  • an indirect-heat dryer may be preferable for its other advantages, at least with certain types of feed material.
  • the compressed air injected into the secondary dryer 106 may optionally be heated prior to injection, instead of being injected at ambient temperature.
  • this is done using waste heat in order to further improve the overall efficiency of the drying system 100 - if a dedicated combustion process was used to heat the compressed air, there may be no benefit, or efficiency may even be decreased.
  • the waste heat used could be taken from a source external to the drying system 100, for example waste heat from another industrial process in the same plant. However, the waste heat is preferably extracted from the primary dryer 104.
  • the source of waste heat for heating the compressed air is heating fluid condensate exiting the primary dryer 104.
  • Such condensate is generally only a by-product of certain types of indirect-heat drying.
  • the drying system 100 may further comprise a heat exchanger 130 connected between the compressed air source 110 and the secondary dryer 106, and connected to a heating fluid outlet of the primary dryer 104.
  • heat exchanger 130 is preferably a liquid-to-air heat exchanger of any suitable type, where one flow is condensate and the other is compressed air.
  • the drying system 100 as described above also illustrates a method of drying wet feed material, corresponding to the operation of the drying system 100, that is not necessarily specific to any particular hardware mentioned.
  • the corresponding method can be considered to comprise a primary drying step which corresponds to the function of the primary dryer 104, a secondary drying step which corresponds to the function of the secondary dryer 106, agitating the wet feed material with compressed air during the secondary drying step, and conveying partially dried feed material between the two drying steps in one direction or the other.
  • the drying system 100 of the present invention may be retrofit into the plant by installation of the secondary dryer 106 in the manner described.
  • the invention may also reside in a structure of the secondary dryer 106 which enables its use in the drying system 100.
  • the secondary dryer 106 may comprise various features typical of known indirect-heat dryers. It comprises a body 132 within which wet feed material is to be indirectly heated by a heating fluid, a heating fluid inlet 134, a heating fluid outlet 136, and a heating fluid channel 138 connected therebetween and configured to pass the heating fluid through or about the body 132 without directly contacting the wet feed material.
  • the heating fluid inlet 134 is configured to receive waste steam, such that the secondary dryer 106 can be used to improve the overall efficiency of a drying system by extracting waste heat.
  • the heating fluid outlet 136 allows for condensate of the waste steam to be drained after heat is indirectly transferred into the wet feed material.
  • the secondary dryer 106 further comprises a wet material infeed 135 for introducing the wet feed material into the body 132, a dried material outfeed 137, and a conveying mechanism 138 for conveying the wet feed material through the body 132 as the feed material dries and subsequently out of the dried material outfeed 137.
  • the infeed 135 and the outfeed 137 are preferably located at opposite ends of the body 132.
  • the conveying mechanism 138 preferably comprises a motor which rotates some part of the secondary dryer 106, but which part is rotated depends on the specific type of indirect-heat dryer.
  • the motor may be provided with a variable speed drive for process control.
  • the wet material infeed 135 may comprise a motor-driven screw conveyor, which may also have a variable speed drive for process control.
  • the secondary dryer 106 further comprises a plurality of nozzles 140 formed in an underside of the body 132 to allow an agitation gas to be injected into the body 132 and thereby directly contact and agitate the wet feed material, and preferably to fluidise the material in the manner previously described.
  • the nozzles 140 will be capable of admitting many types of gases other than compressed air, many of which may also serve to agitate the wet feed material in the desired way.
  • air is the generally preferred gas due to its ready availability at no cost.
  • the nozzles 140 are preferably adapted to inject air to the extent that their design is adapted for any particular gas.
  • the secondary dryer 106 further comprises a venting port 124 for venting steam evaporated from the wet feed material and agitation gas introduced through the plurality of nozzles.
  • the heating fluid channel 138 is provided within a plurality of discs 142 mounted within the body 132, and the discs 142 act as the conveying mechanism 139 in combination with the motor.
  • the discs 142 are mounted on a hollow shaft 144, also forming part of the heating fluid channel 138, which is coupled to the motor and thereby rotated.
  • the discs 142 comprise paddles 146 which serve to convey the feed material as the discs 142 rotate.
  • the heating fluid channel 138 may be configured as a jacket about the body 132.
  • the conveying mechanism 139 may therefore be independent of the heating fluid channel 138.
  • nozzles is meant in a broad sense, and the nozzles 140 may be formed as a grating or as individual spouts, which may or may not be convergent to increase the velocity of the agitation gas.
  • the nozzles 140 may be spaced intermediate of the discs 142 to better agitate the feed material. They may be arranged in a grid format, such that at least one row of nozzles 140 is located between each disc 142.
  • the nozzles may be swivelable, such that they can be actuated to create a swirling effect of the injected air and achieve better agitation.
  • the ideal number and placement of nozzles 140 injecting agitation gas may depend on the feed material to be dried.
  • the nozzles 140 may be configured to be selectively pluggable so as to adjust the number and placement of nozzles 140 which are actually used, allowing a given secondary dryer 106 to be adapted to different feed materials.
  • the nozzles 140 may be provided on a modular nozzle plate removably attached to the underside of the body 132, such that different modular nozzle plates can be adapted to different feed materials and easily swapped as needed.
  • the primary dryer 104 or the secondary dryer 106 could be configured such that steam enters through nozzles in the underside and agitates the feed material as well as heating it.
  • the primary dryer 104 is a superheated steam dryer
  • it may be modified such that the superheated steam is introduced through a plurality of nozzles in the underside, instead of at a conventional inlet.
  • the secondary dryer 102 may be configured as a direct-heat dryer rather than an indirect-heat dryer, with the waste steam introduced via nozzles in the underside.
  • drying system 100 may comprise various components including valving, regulators, gauges, safety devices, and the like which are not shown. However, such components would be well understood by a person skilled in the art and easily incorporated as necessary to work the invention.
  • This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Microbiology (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Drying Of Solid Materials (AREA)

Abstract

L'invention concerne un système de séchage pour le séchage d'une matière d'apport humide, le système de séchage ayant une source de fluide de chauffage primaire ; un séchoir primaire raccordé de manière fonctionnelle à la source de fluide de chauffage primaire pour recevoir un fluide de chauffage en provenance de celle-ci ; un séchoir secondaire, qui est un séchoir à chaleur indirecte, raccordé de manière fonctionnelle à un orifice d'aération du séchoir primaire pour recevoir de la vapeur résiduelle en tant que fluide de chauffage, la vapeur résiduelle résultant du séchage de la matière d'apport humide dans le séchoir primaire ; une source d'air comprimé raccordée de manière fonctionnelle au séchoir secondaire pour injecter de l'air comprimé dans le séchoir secondaire et ainsi agiter la matière d'apport qui le traverse ; et un transporteur de matière d'apport raccordant le séchoir primaire et le séchoir secondaire, de telle sorte que de la matière d'apport à matière partiellement séchée sortant du séchoir secondaire soit transportée jusque dans le séchoir primaire, ou vice-versa.
PCT/IB2025/053676 2024-04-08 2025-04-08 Système et procédé de séchage améliorés Pending WO2025215517A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AU2024900968A AU2024900968A0 (en) 2024-04-08 Improved drying system and method
AU2024900968 2024-04-08

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WO2025215517A1 true WO2025215517A1 (fr) 2025-10-16

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4602438A (en) * 1985-04-26 1986-07-29 Westinghouse Electric Corp. Method and apparatus for fluidized steam drying of low rank coals with wet scrubbing
US4687546A (en) * 1985-07-19 1987-08-18 Georgia Kaolin Company, Inc. Method of concentrating slurried kaolin
AU2012248415A1 (en) * 2011-04-28 2013-08-01 Mitsubishi Heavy Industries, Ltd. Fluidized bed drying apparatus and integrated coal gasification combined cycle system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4602438A (en) * 1985-04-26 1986-07-29 Westinghouse Electric Corp. Method and apparatus for fluidized steam drying of low rank coals with wet scrubbing
US4687546A (en) * 1985-07-19 1987-08-18 Georgia Kaolin Company, Inc. Method of concentrating slurried kaolin
US4687546B1 (en) * 1985-07-19 1996-06-04 Anglo American Clays Corp Method of concentrating slurried kaolin
AU2012248415A1 (en) * 2011-04-28 2013-08-01 Mitsubishi Heavy Industries, Ltd. Fluidized bed drying apparatus and integrated coal gasification combined cycle system

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