EP0168418B1 - A method and a device for drying a fibrous or granular material - Google Patents
A method and a device for drying a fibrous or granular material Download PDFInfo
- Publication number
- EP0168418B1 EP0168418B1 EP19850900250 EP85900250A EP0168418B1 EP 0168418 B1 EP0168418 B1 EP 0168418B1 EP 19850900250 EP19850900250 EP 19850900250 EP 85900250 A EP85900250 A EP 85900250A EP 0168418 B1 EP0168418 B1 EP 0168418B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- drying air
- drying
- rotary drier
- drum
- temperature
- 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
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Classifications
-
- 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
- F26B11/02—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles
- F26B11/028—Arrangements for the supply or exhaust of gaseous drying medium for direct heat transfer, e.g. perforated tubes, annular passages, burner arrangements, dust separation, combined direct and indirect heating
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10F—DRYING OR WORKING-UP OF PEAT
- C10F5/00—Drying or de-watering peat
Definitions
- This invention relates to a method for drying a fibrous or granular material, preferably peat, in a rotary drier, primary drying air being supplied to the drier axially and being substantially moisture saturated at its passage through the drier due to absorption of water from the material to be dried.
- the invention also comprises a device for drying a fibrous or granular material.
- a method and a device for drying wood chips and peat are previously known, the material being dried in a first space surrounding the space in which the final drying takes place.
- This two-step drying requires a relatively complicated device, the handling of the peat being relatively circumstantial as the peat must be transferred to the internal space for final drying after pre-drying in the external space.
- a device for continuous dewatering of peat is also known, where peat is supplied to a stationary, perforated drum, electric current being conducted through the peat, which will then give off water vapour. Air is fed into the drum, absorbs the water vapour and is pressed out through the perforations in the drum.
- US-A-892 901 discloses a method and a device for drying fibrous or granular material in a rotary drier whereby drying air is supplied radially to a drum through a great number of holes in the mantle of the rotary drier and the temperature is raised before introduction into the rotary drier by passing a number of heating pipes.
- very high air temperatures about 140°C, are used which means that the drying is carried out rapidly and efficiently.
- the drying air is substantially moisture saturated during the whole drying process the risk of so-called dust explosion is in principle eliminated.
- Fig. 1 is shown schematically a longitudinal section of a drying unit according to the invention and Fig. 2 shows a section taken on the line 11-11 in Fig. 1.
- the drying unit 1 shown in Figs 1 and 2 comprises a rotatry drier 2, which on its inside, see Fig. 2, is provided with flanges 3 ensuring good stirring of the material placed in the drum 2.
- the drum 2 is preferably cylindrical and has a great number of holes 4 on its mantle surface. These holes have preferably a diameter of about 3 mm.
- the rotary drier 2 has an inlet opening 5 and a discharge opening 6.
- a great number of finned pipes 7 surround the drum 2 and are arranged at some distance from this. In operation of the drying unit 1 hot water or some other suitable medium is circulating in these finned pipes 7.
- the drum 2 is supported by two bearings 8, which have the shape of rings running about the drum 2.
- the drum 2 is rotatable within these bearings 8. This rotation is created by a drive source, e.g. an electric motor, and suitable transmitting means.
- An insulated mantle 9 is also included in the drying unit 1, which mantle extends along the major portion of the drum 2, the inlet and outlet openings 5 and 6 however not being surrounded by the mantle 9. As is apparent from Figs. 1 and 2 the mantle 9 has an upwardly tapering inlet 10 for drying air.
- the drying unit described above works in the following way.
- the drying principle of the unit 1 is built on the fact that raw peat is dried in the rotary drier 2 by evaporation of the water bound in the peat.
- the primary drying air supplied to the drum 2 axially at the inlet opening has a relatively high temperature, about 150°C, when entering the drum 2.
- the supply of the primary drying air is preferably carried out by means of a fan not shown in the figures.
- the drying air After the drying air has left the drum 2 via the outlet opening 6 it is dehydrated, e.g. in a heat exchanger or condenser not shown in the figures. After this the secondary drying air is blown via fans or the like (not shown) into the mantle 9 through the inlet opening 10.
- the secondary drying air When the secondary drying air is supplied to the mantle 9 after the de- moistening, its temperature is down to about 50°C.
- hot water or the like is circulating in the finned pipes 7, the temperature of the host water being of the order of 200°C.
- the hot water in the finned pipes 7 can e.g. consist of cooling water from some plant, waste heat thus being utilized for heating the drying air.
- the peat granulate obtained as the result of peat drying is extraordinarily well suited for automated solid fuel systems.
- the drying air used with the drying process according to the claimed invention can be obtained in many ways.
- a so-called hot air boiler is possible, which is e.g. fired with oil.
- This boiler has then preferably a water-carried cooling system.
- the heated air is used as primary drying air, but it can be mixed with the exhaust gases formed in the oil combustion. Cooling water from the boiler can be circulated in the finned pipes 7 for heating the secondary drying air.
- the secondary drying is preheated in another way than through passage of the finned pipes.
- the temperature of the secondary drying air can e.g. be raised in such a way that it passes through a hot air boiler.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Drying Of Solid Materials (AREA)
Abstract
Description
- This invention relates to a method for drying a fibrous or granular material, preferably peat, in a rotary drier, primary drying air being supplied to the drier axially and being substantially moisture saturated at its passage through the drier due to absorption of water from the material to be dried. The invention also comprises a device for drying a fibrous or granular material.
- A method and a device for drying wood chips and peat are previously known, the material being dried in a first space surrounding the space in which the final drying takes place. This two-step drying requires a relatively complicated device, the handling of the peat being relatively circumstantial as the peat must be transferred to the internal space for final drying after pre-drying in the external space.
- A device for continuous dewatering of peat is also known, where peat is supplied to a stationary, perforated drum, electric current being conducted through the peat, which will then give off water vapour. Air is fed into the drum, absorbs the water vapour and is pressed out through the perforations in the drum.
- Thus, the known technique for drying of peat is relatively complicated and slow. Moreover, it is not especially efficient as too low air temperatures are used.
- US-A-892 901 discloses a method and a device for drying fibrous or granular material in a rotary drier whereby drying air is supplied radially to a drum through a great number of holes in the mantle of the rotary drier and the temperature is raised before introduction into the rotary drier by passing a number of heating pipes.
- It is the object of this invention to provide a method and and a device for drying preferably peat in which drying air is supplied both axially and radially to a drier whereby the drying air meets the material to be dried both in a countercurrent and cross-flow direction which results in an extraordinarily efficient heat transfer. Besides, very high air temperatures, about 140°C, are used which means that the drying is carried out rapidly and efficiently. As the drying air is substantially moisture saturated during the whole drying process the risk of so-called dust explosion is in principle eliminated.
- The object of the invention is realized by means of a method and a device given the characteristic features set out in the appended claims.
- An illustrative example of a device according to the invention will be described below with reference to the enclosed drawing, where in Fig. 1 is shown schematically a longitudinal section of a drying unit according to the invention and Fig. 2 shows a section taken on the line 11-11 in Fig. 1.
- The drying unit 1 shown in Figs 1 and 2 comprises a
rotatry drier 2, which on its inside, see Fig. 2, is provided with flanges 3 ensuring good stirring of the material placed in thedrum 2. Thedrum 2 is preferably cylindrical and has a great number of holes 4 on its mantle surface. These holes have preferably a diameter of about 3 mm. - As is apparent from Fig. 1 the
rotary drier 2 has an inlet opening 5 and a discharge opening 6. - A great number of
finned pipes 7 surround thedrum 2 and are arranged at some distance from this. In operation of the drying unit 1 hot water or some other suitable medium is circulating in thesefinned pipes 7. - The
drum 2 is supported by twobearings 8, which have the shape of rings running about thedrum 2. Thedrum 2 is rotatable within thesebearings 8. This rotation is created by a drive source, e.g. an electric motor, and suitable transmitting means. - An insulated
mantle 9 is also included in the drying unit 1, which mantle extends along the major portion of thedrum 2, the inlet and outlet openings 5 and 6 however not being surrounded by themantle 9. As is apparent from Figs. 1 and 2 themantle 9 has an upwardly taperinginlet 10 for drying air. - The drying unit described above works in the following way.
- The drying principle of the unit 1 is built on the fact that raw peat is dried in the
rotary drier 2 by evaporation of the water bound in the peat. - The primary drying air supplied to the
drum 2 axially at the inlet opening has a relatively high temperature, about 150°C, when entering thedrum 2. The supply of the primary drying air is preferably carried out by means of a fan not shown in the figures. - As the temperature of the primary drying air is so high a continuous disintegration of the particles takes place, the water in the particles being evaporated und taken up by the supplied drying air.
- When the drying air supplied at the inlet opening 5 absorbs water vapour its temperature will sink to the order of 70°C when the air leaves the
drum 2 at the outlet opening 6. At this stage the primary drying air is almost moisture saturated. - After the drying air has left the
drum 2 via the outlet opening 6 it is dehydrated, e.g. in a heat exchanger or condenser not shown in the figures. After this the secondary drying air is blown via fans or the like (not shown) into themantle 9 through the inlet opening 10. When the secondary drying air is supplied to themantle 9 after the de- moistening, its temperature is down to about 50°C. As mentioned above hot water or the like is circulating in thefinned pipes 7, the temperature of the host water being of the order of 200°C. The hot water in thefinned pipes 7 can e.g. consist of cooling water from some plant, waste heat thus being utilized for heating the drying air. - When the dehydrated drying air having a temperature of about 50°C is supplied to the
drum 2 transversely via the holes 4, said drying air will pass past thehot water pipes 7, the drying air being heated at its passage of thepipes 7. The temperature of the so-called cross-flow air is raised from the above-mentioned about 50°C to about 140°C. - The fact that the
drum 2 is rotating and that the drying air meets the peat both in a countercurrent and cross-flow direction contributes to an extraordinarily efficient heat transfer. The result of said heat transfer, in turn, is that the peat balls successively burst and are converted into peat granulate having a diameter of 4-6 mm. By the bursting the moisture transmitting surface is increased with a simultaneous increase of the dry content in the peat. Despite the increasing dry content in the peat and drying effect is constant during the entire drying process due to the continuous bursting of the particles. - The risk of so-called dust explosion in the
drum 2 is very slight when using the process of the present invention as the drying air during the whole drying process has a high moisture content due to the fact that the water released at bursting is absorbed by the drying air in the form of water vapour. As there is a possibility within the scope of the invention of using exhaust gases as drying air this is also positive considering the risk of explosion as exhaust gases always contain water vapour in principle. - The peat granulate obtained as the result of peat drying is extraordinarily well suited for automated solid fuel systems.
- The drying air used with the drying process according to the claimed invention can be obtained in many ways. A so-called hot air boiler is possible, which is e.g. fired with oil. This boiler has then preferably a water-carried cooling system. The heated air is used as primary drying air, but it can be mixed with the exhaust gases formed in the oil combustion. Cooling water from the boiler can be circulated in the
finned pipes 7 for heating the secondary drying air. - It is also possible within the scope of the invention that the secondary drying is preheated in another way than through passage of the finned pipes. The temperature of the secondary drying air can e.g. be raised in such a way that it passes through a hot air boiler.
- The invention is of course by no means restricted to the illustrative example described above and considering the generation of the primary drying air in particular the variations are numerous. Thus, the invention can be freely varied within the scope of the accompanying drawings.
Claims (7)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT85900250T ATE36552T1 (en) | 1983-12-15 | 1984-12-17 | METHOD AND APPARATUS FOR DRYING FIBER AND PARTICULATE MATERIALS. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE8306950A SE441835B (en) | 1983-12-15 | 1983-12-15 | PROCEDURE FOR DRYING FIBROST OR CORNED MATERIAL, PREFERRED PORTS |
SE8306950 | 1983-12-15 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0168418A1 EP0168418A1 (en) | 1986-01-22 |
EP0168418B1 true EP0168418B1 (en) | 1988-08-17 |
Family
ID=20353751
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19850900250 Expired EP0168418B1 (en) | 1983-12-15 | 1984-12-17 | A method and a device for drying a fibrous or granular material |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0168418B1 (en) |
DE (1) | DE3473471D1 (en) |
FI (1) | FI82860C (en) |
SE (2) | SE8306950L (en) |
WO (1) | WO1985002623A1 (en) |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE265602C (en) * | ||||
US892901A (en) * | 1906-11-22 | 1908-07-07 | Philadelphia Textile Mach Co | Rotary drying-machine. |
DE1585888A1 (en) * | 1967-09-21 | 1971-10-14 | Passat Maschinenbau Gmbh | Drum dryer for laundry or the like. |
-
1983
- 1983-12-15 SE SE8306950D patent/SE8306950L/en not_active Application Discontinuation
- 1983-12-15 SE SE8306950A patent/SE441835B/en not_active IP Right Cessation
-
1984
- 1984-12-14 FI FI844964A patent/FI82860C/en not_active IP Right Cessation
- 1984-12-17 EP EP19850900250 patent/EP0168418B1/en not_active Expired
- 1984-12-17 WO PCT/SE1984/000431 patent/WO1985002623A1/en active IP Right Grant
- 1984-12-17 DE DE8585900250T patent/DE3473471D1/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
FI82860B (en) | 1991-01-15 |
SE441835B (en) | 1985-11-11 |
EP0168418A1 (en) | 1986-01-22 |
SE8306950D0 (en) | 1983-12-15 |
FI844964L (en) | 1985-06-16 |
SE8306950L (en) | 1985-06-16 |
WO1985002623A1 (en) | 1985-06-20 |
FI82860C (en) | 1991-04-25 |
FI844964A0 (en) | 1984-12-14 |
DE3473471D1 (en) | 1988-09-22 |
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