CA1254737A - Control of drying operation - Google Patents
Control of drying operationInfo
- Publication number
- CA1254737A CA1254737A CA000428613A CA428613A CA1254737A CA 1254737 A CA1254737 A CA 1254737A CA 000428613 A CA000428613 A CA 000428613A CA 428613 A CA428613 A CA 428613A CA 1254737 A CA1254737 A CA 1254737A
- Authority
- CA
- Canada
- Prior art keywords
- gas
- drying
- moisture
- air
- moisture content
- 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.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
- F26B21/06—Controlling, e.g. regulating, parameters of gas supply
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
- F26B25/22—Controlling the drying process in dependence on liquid content of solid materials or objects
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Drying Of Solid Materials (AREA)
- Drying Of Gases (AREA)
Abstract
ABSTRACT
Control of Drying Operation An improved technique for the drying of materials or otherwise controlling the moisture content thereof consists in passing air over or through the materials, the specific enthalpy of the input air being controlled independently of its drying potential.
Control of Drying Operation An improved technique for the drying of materials or otherwise controlling the moisture content thereof consists in passing air over or through the materials, the specific enthalpy of the input air being controlled independently of its drying potential.
Description
~q~5~7;37 1 Control of Drying Operation The invention relates to the control of drying or other moisture control operations by the circulation of air or other suitable gas over or through the material the moisture in or on which is to be controlled.
The ability of relatively dry air to extract water from surfaces with which it makes contact is employed in a wide range of industrial and other drying operations. The drying capacity or drying potential of air being determined solely by its temperature and existing moisture content, drying operations can be and often are precisely thermally controlled in an attempt to optimise efficiency.
However important the thermal efficiency may be, the prime consideration must always be product quality, and the present invention arose from a consideration of, but is not necessarily confined to, circumstances in which control of drying potential of the drying air is of supreme importance to the quality of the product.
According to one aspect of the invention there i5 provided a method of controlling moisture in or on materials when passing gas over or through the materials wherein the specific enthalpy of the gas is controlled independently of the drying poten~ial thereof. The value of specific enthalpy relative to drying capacity may be controlled by monitoring the temperature and moisture content adding heat and moisture as required.
- la -1 According to another aspect of the invention there is provided a method of drying a material by passing a gas over or through the material wherein the specific enthalpy of the gas is controlled independently of the drying potential thereof, comprising the successive steps of:
(a) warming the material without substantial removal of water therefrom by the use of gas at a first enthalpy level and a first drying potential and (b) removing a first quantity of water from the material by increasing the drying potential of the gas relative to that utilised in step (a) and by increasing the enthalpy level above said first enthalpy level.
~'~5~737 1 The method may be applied to the drying of material or, alternatively, to the maintenance of a controlled property of moisture on or in materials.
According to a further aspect of the invention there is provided a method of controlling the moisture on or in materials when passing gas over or through the materials comprising means for controlling the specific enthalpy of the gas independently of the drying potential thereof.
Preferably the addition of heat and moisture is controlled automatically by signals representing temperature and moisture content.
Before discussing a specific embodiment of the present invention, a brie review of some basic concepts will follow.
Specific enthalpy H is the quantity of recoverable energy available in a certain mass. Basically, specific enthalpy H
is defined as follows:
H = U + PV (1) where U is the internal energy, P is pressure and V is volume. ~ore particularly, specific enthalpy H can broken down into different components as follows:
a g g (2) where H is the specific enthalpy of moist air per kilogram of dry air, Ha is the specific enthalpy of dry air, Hg is the specific enthalpy of water vapor, all measured in kJ/kg, and g is the moisture content per kilogram of dry air, measured in kg/kg.
,~.. ,~
1~5~73t~
- 2a -l In the present invention, the method of drying a material is used with a fixed pressure and volume. Since the internal energy U is a function of pressure and temperature, that is, U = f(P,T), from equations (1) and (2), the following are derived:
Ha=f(U,P,V)=f(P,V,T) (3) Hg=f(U,P,V)=f(P,V,T) (4) Combining equations (2), (3) and (4), the specific enthalpy of the system is derived as follows:
H=f'(Ha Hg g)=f'(P,V,T,g) (5) Since the present invention utilizes a constant pressure and volume, equation (5) is reduced as follows:
H=constant x f"(g,T)(6) (6) From equation (6), it is readily seen that specific enthalpy H is a function of moisture content g and temperature T. It will be remembered that drying potential of air is also dependent on the moisture content and temperature of the air. However, the enthalpy and drying potential thereof vary differently, although depending on the same quantities, that i9, temperature T and moisture content g. A simple example readily illustrates this concept. For example, saturated air at 10C. has approximately the same enthalpy H
as air at 20C. and 25~ humidity, since the air in both situations has the same heat content and the same potential for recoverable heat. However, the 10C. air has no drying potential, since it is saturated, while the 25C. air does have a drying potential. The values of enthalpy H as a function of temperature T and moisture content g are readily obtainable from prepared tables, such as those published in the "IHVE Guide, Cl & 2, Properties of Humid Air, Water and Steam", 1975, by The Institution of Heating and Ventilating Engineers, ~9 Cadogan Square, London SWlXOJB, and printed by the Curwen Press Ltd., London E13.
.
~S~37 - 2b -1 The invention will now be further described by reference to a number of non-limiting examples and the accompanying drawings of which the single figure shows schematically an installation for the drying of material by the circulation of air therethrough.
In the non-limitlng example described, the material to be dried consists of green malt, which is a substance which is susceptible to damage if subjected to incremental changes in enthalpy and drying rate greater than predetermined values. It will be assumed that the initial moisture content of the malt is 45% and that it is required to reduce this to something like 4~.
For the sake of the example, it will also be assumed that the ambient air has a temperature of 15C and a dew point of 10C, though if the drying cycle continues into the night, the moisture content may drop to a dew point of 0C and the temperature, having also dropped to around 0C may, typically, recover to some 3C by morning.
In the present example, the method of drying will be described, for the sake of simplicity, as comprising three .~
'73~
distinct phases, thougll it should be understood that in pract:ice the phases may overlap at. least. to some exten~.
As shown in ~he figure the installation for drying 05 comprises a chamber 2 for containing a quanti-ty of material 4 to be driecl, in this example green malt. Air i5 passe~1 int.o the chamber 2 through an inle-t 6 by means of a fan ~, and having passed over or t~rough -the material 4 the air is exhausted through outlet 10 and either voided to atmosphere ~0 at opening 12 or ret.urned to the fan 8 via branch ~ipe 14 for recirculation. A valve 16 controls the ~roportion of air recirculated with respect. to the proportion voided ~o atmosphere.
lS In its passage from the fan 8 to the inlet 6 the air is capable of being heated by means of a heater 18. A mixing unit 20 is also provided in the path between the fan 8 and the inlet 6 providing facility for the introduction of moisture, for example in the form of steam or liquid water through moisture inlet 22 controlled by valve 24.
The rate oE air flow produced by the Ean 8 is controlled by means of a con-troller 26, and to the extent that the exhaust side of the fan is not satisfied with recirculated air from branch pipe 14, air is introduced through inlet 28 via valve 30~ The air in~roduced through inlet 28 will normally be moist ambient air hut in certain circumstances may be rela-~ively or absolutely dry air.
The temperatures t. of the air circula~ing in the apparatus is determined at various posit.ions by means of sensors Tl, T2, T3 and T4. The moisture conten-t m of the circulating air is similarly determined at corresponding locations by moisture meters Ml, M2, M3 and M4.
In t~he first, initia~ion, phase of drying, ambient air is drawn from inlet 28 through valve 30 ~y fan 8 and, heated 73~
1 in heating unit 18 and moistened as required in the mixing unit 20 so as to produce the desired enthalpy and drying potential, is introduced into the material 4 in chamber 2 via inlet 6.
As the initiation phase continues, the enthalpy of the input air is increased gradually whilst controlling the drying potential so as not to damage the material 4.
The warming of the material 4 increases the transpiration of moisture within the material but, although the specific enthalpy of the air is increased, the drying capacity of the air is not allowed to increase in this example. The process is infinitely variable and in other examples the drying capacity may be allowed to increase but not in correspondence with increasing specific enthalpy.
This can be contrasted with normal drying where, for example, ambient air with a temperature of 15C and a dew point of 10C is merely warmed prior to passing through the malt. During the night the dew point may be reduced to 0C, and under these conditions the control of input temperature alone fails to control the drying process adequately and damage to the product can occur.
The control of drying capacity independently of specific enthalpy is effected by introduction into the air entering the chamber of quantities of moisture controlled by signal ml provided by sensor Ml. The moisture introduced may originate from the atmosphere, any recirculated exhaust air or, predominantly at this phase, by injection into the mixing unit 20, and the input air moisture signal is therefore used to control the valves 16, 24, and 30.
The initiation phase therefore proceeds with gradual 3S warming of the material without drying. The exhaust air leaving the chamber 2 via outlet 10 may be recirculated or B
~Z5~ 7 voided to atmosphere. The process is continued un~..il the conditions recorded by sensors M3 and T3 h~ve reached predetemlined values or until the condi-tions at a predetermined zone within the material 4, as determinecl by 05 sensors M2 and T2, have reached prede-termined values. In practice, the temperature and the moisture content of the air within the material 4 may be determined by a series of probes at dif~erent levels, and the sensors T2 and M2 shown in the figure are to be taken as representative of such probe~.
The second phase of the process is one of free drying. The specific entllalpy is furtl~er increased, but now the drying capacity of the air is also allowed to increase according ]5 to the requirements of the process and the material, for example as to whether the main requirement is for thermal efficiency or the safety of the product. It is to be understood that the requirements may vary throughout the process.
During this phase, the increase of drying capacity is still controlled independently of the increase of specific enthalpy. At least some of the exhaust air is conveniently recirculated during this process, and the requirement for the injection of moisture through valve 24 is accordingly adjusted. In excep-tional circumstances dry air will be introduced through inlet 28. Data used in the control of ~dle valves accordingly may include signals indicative of the moisture content for the time being of bo~h illpU~: and recirculated exhaust air.
During the phase of free drying, evaporative cooling generally means that the t-emperat-ure of ~he product does not rise t.o t.he value of t.he input air. Conversely, when t.he t:emperature of the produc~: as measured by probe T2 begins to increase without any correspondin~ increase in t~le moist.ure con~ent. of -~.he air in the material as ~LZ~ 3~7 de~ermined by M2, the end of free drying is indicat.ed and t.he inset of the t.hird phase - restric~ed drying - in which water removal cannot continue at the former rate. At this st.age, ~he moisture content of the material may be, 05 typically, 7~, and in order to reduce this to the 4~
required, it is convenien-t to increase the drying potential of the air so as to shorten the process. ~is may be effected by:-I0 (a) increasing the t.emperature of t.he circulating airfurther by operat.ion oE the heater )8 whils-t maintaining its moisture cont.ent;
(b) main~aining the temperat.ure and, for example by int.roducing dry air through inlet 28, reducing the moisture con~ent; or (c) varying the temperature, the moisture content, and the flow rate o the circulat.ing air by means oE controller 26.
Whilst in the above example the ~hree phases of the operation have been described as being quite distinct from one anot.her, in practice the free drying phase may be integra~ed with the initiation phase lnasmuch as some drying could take place from the outset. Nevertheless, the drying capacity o~ the air will be controlled together with, but independently of, specific enthalpy.
If the process of free drying cont.inues to a point at which the mois~ure content of the material is reduced to the required Level, the third phase will of course be dispensed with.
The example described above is one of batch drying wherein t~le three drying phases - distinct or overlapping - take place in the sarne spatial zone but at. different (distinct ~L~5~737 or overlapping) periods of time. However, -the inven-tion is equally applicable to con-tinuous processing wherein a por~.ion of a mat.erial is made subject to the conditions of the first. phase in a first zone and is then moved 05 successively to second and third zones maintained at the conditions respectively-of the second and third phases.
Successive portions of the material follow the first mentioned portion t.hrough the three zones. In the continuous process the e~uivalent of the overlapping of the )0 phases in the batch process can be afforded by providing zones int.ermediate the above-mentioned ~ones and providing in the intermediat.e zones conditions int.ermediate those of t.he adjacent zones.
The invention has been described primarily in relat.ion to drying and this is likely to be it.s ma~or application.
However, in the storage of cert.ain products 5UC}l as fruit or vegetables, it may be required to maintain or even increase the moisture content of the product whilst circulating air or other gas over or through it, and the invention is to be underst.ood as extending to such application.
Again, ~he above descriptions have related primarily to cont.rol of moisture within materials, but it i9 to be understood that the invention is equally applicable to the control of moisture on the sur~ace of materials~
The ability of relatively dry air to extract water from surfaces with which it makes contact is employed in a wide range of industrial and other drying operations. The drying capacity or drying potential of air being determined solely by its temperature and existing moisture content, drying operations can be and often are precisely thermally controlled in an attempt to optimise efficiency.
However important the thermal efficiency may be, the prime consideration must always be product quality, and the present invention arose from a consideration of, but is not necessarily confined to, circumstances in which control of drying potential of the drying air is of supreme importance to the quality of the product.
According to one aspect of the invention there i5 provided a method of controlling moisture in or on materials when passing gas over or through the materials wherein the specific enthalpy of the gas is controlled independently of the drying poten~ial thereof. The value of specific enthalpy relative to drying capacity may be controlled by monitoring the temperature and moisture content adding heat and moisture as required.
- la -1 According to another aspect of the invention there is provided a method of drying a material by passing a gas over or through the material wherein the specific enthalpy of the gas is controlled independently of the drying potential thereof, comprising the successive steps of:
(a) warming the material without substantial removal of water therefrom by the use of gas at a first enthalpy level and a first drying potential and (b) removing a first quantity of water from the material by increasing the drying potential of the gas relative to that utilised in step (a) and by increasing the enthalpy level above said first enthalpy level.
~'~5~737 1 The method may be applied to the drying of material or, alternatively, to the maintenance of a controlled property of moisture on or in materials.
According to a further aspect of the invention there is provided a method of controlling the moisture on or in materials when passing gas over or through the materials comprising means for controlling the specific enthalpy of the gas independently of the drying potential thereof.
Preferably the addition of heat and moisture is controlled automatically by signals representing temperature and moisture content.
Before discussing a specific embodiment of the present invention, a brie review of some basic concepts will follow.
Specific enthalpy H is the quantity of recoverable energy available in a certain mass. Basically, specific enthalpy H
is defined as follows:
H = U + PV (1) where U is the internal energy, P is pressure and V is volume. ~ore particularly, specific enthalpy H can broken down into different components as follows:
a g g (2) where H is the specific enthalpy of moist air per kilogram of dry air, Ha is the specific enthalpy of dry air, Hg is the specific enthalpy of water vapor, all measured in kJ/kg, and g is the moisture content per kilogram of dry air, measured in kg/kg.
,~.. ,~
1~5~73t~
- 2a -l In the present invention, the method of drying a material is used with a fixed pressure and volume. Since the internal energy U is a function of pressure and temperature, that is, U = f(P,T), from equations (1) and (2), the following are derived:
Ha=f(U,P,V)=f(P,V,T) (3) Hg=f(U,P,V)=f(P,V,T) (4) Combining equations (2), (3) and (4), the specific enthalpy of the system is derived as follows:
H=f'(Ha Hg g)=f'(P,V,T,g) (5) Since the present invention utilizes a constant pressure and volume, equation (5) is reduced as follows:
H=constant x f"(g,T)(6) (6) From equation (6), it is readily seen that specific enthalpy H is a function of moisture content g and temperature T. It will be remembered that drying potential of air is also dependent on the moisture content and temperature of the air. However, the enthalpy and drying potential thereof vary differently, although depending on the same quantities, that i9, temperature T and moisture content g. A simple example readily illustrates this concept. For example, saturated air at 10C. has approximately the same enthalpy H
as air at 20C. and 25~ humidity, since the air in both situations has the same heat content and the same potential for recoverable heat. However, the 10C. air has no drying potential, since it is saturated, while the 25C. air does have a drying potential. The values of enthalpy H as a function of temperature T and moisture content g are readily obtainable from prepared tables, such as those published in the "IHVE Guide, Cl & 2, Properties of Humid Air, Water and Steam", 1975, by The Institution of Heating and Ventilating Engineers, ~9 Cadogan Square, London SWlXOJB, and printed by the Curwen Press Ltd., London E13.
.
~S~37 - 2b -1 The invention will now be further described by reference to a number of non-limiting examples and the accompanying drawings of which the single figure shows schematically an installation for the drying of material by the circulation of air therethrough.
In the non-limitlng example described, the material to be dried consists of green malt, which is a substance which is susceptible to damage if subjected to incremental changes in enthalpy and drying rate greater than predetermined values. It will be assumed that the initial moisture content of the malt is 45% and that it is required to reduce this to something like 4~.
For the sake of the example, it will also be assumed that the ambient air has a temperature of 15C and a dew point of 10C, though if the drying cycle continues into the night, the moisture content may drop to a dew point of 0C and the temperature, having also dropped to around 0C may, typically, recover to some 3C by morning.
In the present example, the method of drying will be described, for the sake of simplicity, as comprising three .~
'73~
distinct phases, thougll it should be understood that in pract:ice the phases may overlap at. least. to some exten~.
As shown in ~he figure the installation for drying 05 comprises a chamber 2 for containing a quanti-ty of material 4 to be driecl, in this example green malt. Air i5 passe~1 int.o the chamber 2 through an inle-t 6 by means of a fan ~, and having passed over or t~rough -the material 4 the air is exhausted through outlet 10 and either voided to atmosphere ~0 at opening 12 or ret.urned to the fan 8 via branch ~ipe 14 for recirculation. A valve 16 controls the ~roportion of air recirculated with respect. to the proportion voided ~o atmosphere.
lS In its passage from the fan 8 to the inlet 6 the air is capable of being heated by means of a heater 18. A mixing unit 20 is also provided in the path between the fan 8 and the inlet 6 providing facility for the introduction of moisture, for example in the form of steam or liquid water through moisture inlet 22 controlled by valve 24.
The rate oE air flow produced by the Ean 8 is controlled by means of a con-troller 26, and to the extent that the exhaust side of the fan is not satisfied with recirculated air from branch pipe 14, air is introduced through inlet 28 via valve 30~ The air in~roduced through inlet 28 will normally be moist ambient air hut in certain circumstances may be rela-~ively or absolutely dry air.
The temperatures t. of the air circula~ing in the apparatus is determined at various posit.ions by means of sensors Tl, T2, T3 and T4. The moisture conten-t m of the circulating air is similarly determined at corresponding locations by moisture meters Ml, M2, M3 and M4.
In t~he first, initia~ion, phase of drying, ambient air is drawn from inlet 28 through valve 30 ~y fan 8 and, heated 73~
1 in heating unit 18 and moistened as required in the mixing unit 20 so as to produce the desired enthalpy and drying potential, is introduced into the material 4 in chamber 2 via inlet 6.
As the initiation phase continues, the enthalpy of the input air is increased gradually whilst controlling the drying potential so as not to damage the material 4.
The warming of the material 4 increases the transpiration of moisture within the material but, although the specific enthalpy of the air is increased, the drying capacity of the air is not allowed to increase in this example. The process is infinitely variable and in other examples the drying capacity may be allowed to increase but not in correspondence with increasing specific enthalpy.
This can be contrasted with normal drying where, for example, ambient air with a temperature of 15C and a dew point of 10C is merely warmed prior to passing through the malt. During the night the dew point may be reduced to 0C, and under these conditions the control of input temperature alone fails to control the drying process adequately and damage to the product can occur.
The control of drying capacity independently of specific enthalpy is effected by introduction into the air entering the chamber of quantities of moisture controlled by signal ml provided by sensor Ml. The moisture introduced may originate from the atmosphere, any recirculated exhaust air or, predominantly at this phase, by injection into the mixing unit 20, and the input air moisture signal is therefore used to control the valves 16, 24, and 30.
The initiation phase therefore proceeds with gradual 3S warming of the material without drying. The exhaust air leaving the chamber 2 via outlet 10 may be recirculated or B
~Z5~ 7 voided to atmosphere. The process is continued un~..il the conditions recorded by sensors M3 and T3 h~ve reached predetemlined values or until the condi-tions at a predetermined zone within the material 4, as determinecl by 05 sensors M2 and T2, have reached prede-termined values. In practice, the temperature and the moisture content of the air within the material 4 may be determined by a series of probes at dif~erent levels, and the sensors T2 and M2 shown in the figure are to be taken as representative of such probe~.
The second phase of the process is one of free drying. The specific entllalpy is furtl~er increased, but now the drying capacity of the air is also allowed to increase according ]5 to the requirements of the process and the material, for example as to whether the main requirement is for thermal efficiency or the safety of the product. It is to be understood that the requirements may vary throughout the process.
During this phase, the increase of drying capacity is still controlled independently of the increase of specific enthalpy. At least some of the exhaust air is conveniently recirculated during this process, and the requirement for the injection of moisture through valve 24 is accordingly adjusted. In excep-tional circumstances dry air will be introduced through inlet 28. Data used in the control of ~dle valves accordingly may include signals indicative of the moisture content for the time being of bo~h illpU~: and recirculated exhaust air.
During the phase of free drying, evaporative cooling generally means that the t-emperat-ure of ~he product does not rise t.o t.he value of t.he input air. Conversely, when t.he t:emperature of the produc~: as measured by probe T2 begins to increase without any correspondin~ increase in t~le moist.ure con~ent. of -~.he air in the material as ~LZ~ 3~7 de~ermined by M2, the end of free drying is indicat.ed and t.he inset of the t.hird phase - restric~ed drying - in which water removal cannot continue at the former rate. At this st.age, ~he moisture content of the material may be, 05 typically, 7~, and in order to reduce this to the 4~
required, it is convenien-t to increase the drying potential of the air so as to shorten the process. ~is may be effected by:-I0 (a) increasing the t.emperature of t.he circulating airfurther by operat.ion oE the heater )8 whils-t maintaining its moisture cont.ent;
(b) main~aining the temperat.ure and, for example by int.roducing dry air through inlet 28, reducing the moisture con~ent; or (c) varying the temperature, the moisture content, and the flow rate o the circulat.ing air by means oE controller 26.
Whilst in the above example the ~hree phases of the operation have been described as being quite distinct from one anot.her, in practice the free drying phase may be integra~ed with the initiation phase lnasmuch as some drying could take place from the outset. Nevertheless, the drying capacity o~ the air will be controlled together with, but independently of, specific enthalpy.
If the process of free drying cont.inues to a point at which the mois~ure content of the material is reduced to the required Level, the third phase will of course be dispensed with.
The example described above is one of batch drying wherein t~le three drying phases - distinct or overlapping - take place in the sarne spatial zone but at. different (distinct ~L~5~737 or overlapping) periods of time. However, -the inven-tion is equally applicable to con-tinuous processing wherein a por~.ion of a mat.erial is made subject to the conditions of the first. phase in a first zone and is then moved 05 successively to second and third zones maintained at the conditions respectively-of the second and third phases.
Successive portions of the material follow the first mentioned portion t.hrough the three zones. In the continuous process the e~uivalent of the overlapping of the )0 phases in the batch process can be afforded by providing zones int.ermediate the above-mentioned ~ones and providing in the intermediat.e zones conditions int.ermediate those of t.he adjacent zones.
The invention has been described primarily in relat.ion to drying and this is likely to be it.s ma~or application.
However, in the storage of cert.ain products 5UC}l as fruit or vegetables, it may be required to maintain or even increase the moisture content of the product whilst circulating air or other gas over or through it, and the invention is to be underst.ood as extending to such application.
Again, ~he above descriptions have related primarily to cont.rol of moisture within materials, but it i9 to be understood that the invention is equally applicable to the control of moisture on the sur~ace of materials~
Claims (8)
1. A method of drying a material by passing a gas over or through the material wherein the specific enthalpy of the gas is controlled independently of the drying potential thereof, comprising the successive steps of:
(a) warming the material without substantial removal of water therefrom by the use of gas at a first enthalpy level and a first drying potential and (b) removing a first quantity of water from the material by increasing the drying potential of the gas relative to that utilised in step (a) and by increasing the enthalpy level above said first enthalpy level.
(a) warming the material without substantial removal of water therefrom by the use of gas at a first enthalpy level and a first drying potential and (b) removing a first quantity of water from the material by increasing the drying potential of the gas relative to that utilised in step (a) and by increasing the enthalpy level above said first enthalpy level.
2. A method according to claim 1 comprising a third step of removing a second quantity of water from said material by increasing the drying potential of the gas from the level utilised in step (b) and by varying the enthalpy in accordance with desired characteristics of the material.
3. A method of drying according to claim 1, wherein said step of warming includes:
(i) the step of monitoring temperature and moisture content of said gas at different positions with respect to said material, (ii) the step of varying the moisture content of said gas in response to said sensed temperatures and moisture contents, and (iii) the step of adding heat to said gas in response to said sensed temperatures and moisture content.
(i) the step of monitoring temperature and moisture content of said gas at different positions with respect to said material, (ii) the step of varying the moisture content of said gas in response to said sensed temperatures and moisture contents, and (iii) the step of adding heat to said gas in response to said sensed temperatures and moisture content.
4. A method according to claim 3, wherein said step of varying the moisture content of said gas includes at least one of a step of recirculating said gas, adding gas from an external source and adding moisture to said gas from a source of moisture.
5. A method according to claim 3, wherein said step of adding heat to said gas includes a step of increasing the temperature of said gas by at least one of a heater, recirculating said gas and adding gas from an external source.
6. A method according to claim 1, wherein said step of removing a first quantity of moisture includes:
(i) the step of monitoring temperature and moisture content of said gas at different positions with respect to said material, (ii) the step of varying the moisture content of said gas in response to said sensed temperatures and moisture contents, and (iii) the step of adding heat to said gas in response to said sensed temperatures and moisture contents.
(i) the step of monitoring temperature and moisture content of said gas at different positions with respect to said material, (ii) the step of varying the moisture content of said gas in response to said sensed temperatures and moisture contents, and (iii) the step of adding heat to said gas in response to said sensed temperatures and moisture contents.
7. A method according to claim 6, wherein said step of varying the moisture content of said gas includes at least one of a step of recirculating said gas, adding gas from an external source and adding moisture to said gas from a source of moisture.
8. A method according to claim 6, wherein said step of adding heat to said gas includes a step of increasing the temperature of said gas by at least one of a heater, recirculating said gas and adding gas from an external source.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8214951 | 1982-05-21 | ||
| GB8214951 | 1982-05-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1254737A true CA1254737A (en) | 1989-05-30 |
Family
ID=10530543
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000428613A Expired CA1254737A (en) | 1982-05-21 | 1983-05-20 | Control of drying operation |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0095265A3 (en) |
| JP (1) | JPH0663702B2 (en) |
| CA (1) | CA1254737A (en) |
| GB (1) | GB2120120A (en) |
| NO (1) | NO831732L (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8719470D0 (en) * | 1987-08-18 | 1987-09-23 | British Res Agricult Eng | Grain drying |
| DE4037443A1 (en) * | 1990-11-24 | 1992-05-27 | Mann & Hummel Filter | DEVICE FOR DRYING SCHUETTGUT |
| FR2681673A1 (en) * | 1991-09-19 | 1993-03-26 | Semada Ingenierie | Process and plant for drying granular materials |
| IE940232A1 (en) * | 1994-03-15 | 1995-09-20 | Midland Malting Res Ltd | Malt production |
| FR2775076B1 (en) * | 1998-02-16 | 2000-04-14 | Eric Verheecke | METHOD AND DEVICE FOR CONTROLLING THE WATER CONTENT OF PRODUCTS STORED IN AN ENCLOSURE |
| NL1011760C2 (en) * | 1999-04-09 | 2000-10-10 | Tno | Method and device for drying products. |
| FR2824757B1 (en) * | 2001-05-21 | 2003-08-15 | Oddeis | AIR PROCESSING PROCESS, PRODUCT PROCESSING DEVICE, AND PROCESSED PRODUCTS |
| DE10229521A1 (en) * | 2002-07-01 | 2004-01-29 | Kolb, Regina | Method for controlling low-temperature drying of moist material |
| AU2006352202B2 (en) * | 2006-12-22 | 2010-08-12 | Gea Process Engineering A/S | A method of controlling a spray dryer apparatus by regulating an inlet air flow rate, and a spray dryer apparatus |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB245263A (en) * | 1924-12-09 | 1926-01-07 | Vivian Elkington | Improvements in or relating to the drying of agricultural or horticultural products such as hops, seeds or the like |
| GB647336A (en) * | 1948-12-15 | 1950-12-13 | Hope S Heating & Engineering L | Air-conditioning apparatus |
| ES379040A1 (en) * | 1969-05-12 | 1972-08-01 | Termoelectronica Genia Ltda | Procedure for desecating food. (Machine-translation by Google Translate, not legally binding) |
| FR2045189A5 (en) * | 1969-06-18 | 1971-02-26 | Ebersohl Friederich | Food drying device |
| GB1332116A (en) * | 1969-10-17 | 1973-10-03 | Michnik H E A | Kiln drying |
| US3614074A (en) * | 1969-11-14 | 1971-10-19 | Moore Dry Kiln Co | Direct-fired kiln furnace control system |
| JPS498855U (en) * | 1972-04-25 | 1974-01-25 | ||
| JPS5057856A (en) * | 1974-02-05 | 1975-05-20 | ||
| JPS5436104A (en) * | 1977-08-26 | 1979-03-16 | Nec Corp | Tripartite communication circuit |
| JPS6021315B2 (en) * | 1978-06-02 | 1985-05-27 | 株式会社 サタケ | Grain humidity control device |
| JPS55123980A (en) * | 1979-03-16 | 1980-09-24 | Satake Eng Co Ltd | Automatic controller for grain drier |
| JPS55150473A (en) * | 1979-05-07 | 1980-11-22 | Satake Eng Co Ltd | Low temperature dehumidifying drying method of and apparatus for grain drying |
| DE3022067A1 (en) * | 1979-06-14 | 1981-01-08 | Hoover Ltd | CONTROLS FOR DRYING MACHINES |
-
1983
- 1983-05-05 EP EP83302532A patent/EP0095265A3/en not_active Withdrawn
- 1983-05-16 NO NO831732A patent/NO831732L/en unknown
- 1983-05-18 GB GB08313709A patent/GB2120120A/en not_active Withdrawn
- 1983-05-20 JP JP58089900A patent/JPH0663702B2/en not_active Expired - Lifetime
- 1983-05-20 CA CA000428613A patent/CA1254737A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB8313709D0 (en) | 1983-06-22 |
| NO831732L (en) | 1983-11-22 |
| EP0095265A2 (en) | 1983-11-30 |
| JPH0663702B2 (en) | 1994-08-22 |
| JPS58217183A (en) | 1983-12-17 |
| EP0095265A3 (en) | 1984-11-14 |
| GB2120120A (en) | 1983-11-30 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |