EP0167524A1 - A method for the control of drying of veneer - Google Patents

A method for the control of drying of veneer

Info

Publication number
EP0167524A1
EP0167524A1 EP19840900509 EP84900509A EP0167524A1 EP 0167524 A1 EP0167524 A1 EP 0167524A1 EP 19840900509 EP19840900509 EP 19840900509 EP 84900509 A EP84900509 A EP 84900509A EP 0167524 A1 EP0167524 A1 EP 0167524A1
Authority
EP
European Patent Office
Prior art keywords
veneer
kiln
speed
drying
air
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.)
Withdrawn
Application number
EP19840900509
Other languages
German (de)
French (fr)
Inventor
Olli Mahlberg
Keijo Kovala
Pauli Kuhno
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.)
Wilh Schauman Oy AB
Original Assignee
Wilh Schauman Oy AB
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
Application filed by Wilh Schauman Oy AB filed Critical Wilh Schauman Oy AB
Publication of EP0167524A1 publication Critical patent/EP0167524A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B13/00—Machines and apparatus for drying fabrics, fibres, yarns, or other materials in long lengths, with progressive movement
    • F26B13/10—Arrangements for feeding, heating or supporting materials; Controlling movement, tension or position of materials

Definitions

  • the object of this invention is a method for the control of the drying of veneer.
  • the drying takes place in a kiln, not unknown in itself, in which the drying-air circulates in the drying compartment from blowers to heat exchangers and passes the veneer, absorbing the water evaporating from the veneer.
  • the moisture of the veneer produced is controlled.
  • the veneer is lathed from roundwood in a veneer lathe, after which the veneer is dried in a kiln to attain moisture content appropriate for further processing.
  • a veneer dryer is normally a fairly large kiln with tracks carry ing the veneer, and with blowers blowing heated air into the drying compartment.
  • the drying power can be regulated through adjusting the speed and the humidity of the air circulating in the kiln and the speed of the veneer passing the dryer. The regulation of these parameters is necessary to provide constant quality of the dried veneer or to change the drying conditions deliberately.
  • the control of the quality of the veneer is traditionally carried out manually by sorters, who, by feeling the veneer with their fingers, establish its quality. As veneer that is too moist is rejected, the drying parameters are so adjusted that the dryness of the veneer is assured. The parameters are adjusted manually by trial.
  • the above method has certain disadvantages.
  • the quality of the veneer suffers from over-drying; it shakes and blisters. Over-drying also wastes energy.
  • Manual adjustment is difficult, because the exact loading of the dryer is not known. The loading of the kiln is also a factor affecting the drying-power needed, and it varies.
  • Further disadvantages of manual adjustment are the long transitional shut-off times and the large reject batches as drying conditions change, e.g. in moving over to another wood grade, when the parameters are readjusted by trial, and it takes time before the conditions of a large kiln stabilize to produce reliable evidence of the results of the change.
  • the humidity of the air in the kiln is only one of the many factors affecting the moisture of the end product. Moreover, the adjusting of the valve has to be done by hand; automation and remote control are difficult to carry out, and the gain remains doubtful.
  • the object of the present invention is to avoid the disadvantages described above. It is characteristic of the invention that, through measuring the parameters affecting the moisture of the product in the kiln, sufficient information is gained for the automatic regulation of the drying process, in which the adjust ⁇ able factors consist of the speed of the air circulating in the kiln, the outflow of air, and the speed of the veneer going through the kiln, in a way not unknown in itself, to obtain desired moisture content in the dried veneer.
  • the kiln automatically reacts to changes in the drying conditions, thus eliminating waste of energy. All the essential parameters are considered.
  • the loading can be affected, and by drawing up drying parameters for each wood grade or production type, unnecessary losses are eliminated in connection with changes in production.
  • An essential feature of this invention is also the fact that the parameters observed in the kiln are the moisture content of the incoming veneer, the loading of the kiln, the speed of the veneer in the kiln, the speed, the humidity and the temperature of the air flowing in the kiln. The knowledge of the state of these parameters produces an adequate picture of the drying process.
  • Essential of this invention is also the fact that the humidity of the air is measured through compilation of values given by various temperature sensors. This is an accurate method of moisture measurement, suitable for automatic control.
  • Another characteristic of the present invention is that, as need for adjustment arises, the adjustable factors are exploited fully, one by one, till the desired result is achieved. Thus the whole range of the adjustment can be exploited when necessary, to maintain constant moisture content of the veneer.
  • a further characteristic of the invention is the order in which the. adjustments are made: the speed of the infeed air blowers, the speed of the outflow air blowers, and the speed of the wires carrying the veneer sheet. This order is important for the economy of the drying process, because with the use of circulating air blowers primarily, heat loss is eliminated, and the speed of production is maintained.
  • Fig. 1. presents schematically a device employing the present invention, as seen from the side.
  • Fig. 2. presents the same device as seen from the head.
  • Undried veneer (2) coming from the lathe is fed into the kiln (1) in (3).
  • the veneer sheet is conveyed on a track consisting of wires (4) and folding wheels (5).
  • the kiln (1) is divided into compartments with own infeed air blowers (6).
  • the blowers blow air through heat exchangers (7) heated with steam, after which the air is led through nozzles onto the veneer.
  • the air circulates in the kiln (1) as shown in figure 2.
  • the kiln has hygrometers for incoming and outgoing veneer (14 and 15) required by the regulation system, a device measuring the humidity of the air (16), a thermometer (17) and a pulse sensor (18) for the measuring of the speed of the veneer.
  • the humidity of the air in the kiln is adjusted.
  • the speed of the veneer sheet in the kiln can be affected. This is abased on the fact that the speed of the infeed of the wet veneer (2) is not related to the operating speed of the kiln (1).
  • each of the above parameters can be adjusted independent of each other within the regulation system, or a part or all of the adjustments can be left to the computer (9).
  • the regulation system In a fully-automated mode, which is the normal form of operation, the regulation system first of all changes the speed of the circulation of air with blowers (6) as need for adjustment arises. Only if this is found insufficient, the regulation system moves over to adjust the following parameter: the speed of the outf] air blower. If desired results are still not achieved, the last possibility is the regulation of the speed of the wires (4) with the engine (13).

Landscapes

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

Abstract

Procédé de séchage d'un placage, où le séchage s'effectue dans un séchoir (10) connu en soi, dans lequel l'air de séchage circule dans le compartiment de séchage des souffleries (6) aux échangeurs thermiques et passe sur le placage en absorbant l'eau évaporée du placage. Afin d'améliorer et d'automatiser la surveillance, une caractéristique principale de la présente invention est, grâce à l'observation de la teneur en humidité du placage produit (10) et à la mesure des paramètres affectant l'humidité du produit (10) dans le séchoir, qu'une information suffisante est obtenue pour la régulation automatique du procédé de séchage, les facteurs réglables étant la vitesse de l'air circulant dans le séchoir, l'écoulement de l'air et la vitesse du placage traversant le séchoir, afin d'obtenir la teneur en humidité désirée dans le placage séché.Method for drying a veneer, where the drying takes place in a drier (10) known per se, in which the drying air circulates in the drying compartment of the blowers (6) with heat exchangers and passes over the veneer by absorbing the evaporated water from the veneer. In order to improve and automate the monitoring, a main characteristic of the present invention is, by observing the moisture content of the product plating (10) and measuring the parameters affecting the humidity of the product (10 ) in the dryer, sufficient information is obtained for the automatic regulation of the drying process, the adjustable factors being the speed of the air circulating in the dryer, the air flow and the speed of the plating passing through the dryer, to obtain the desired moisture content in the dried veneer.

Description

A METHOD FOR THE CONTROL OP DRYING OP VENEER
The object of this invention is a method for the control of the drying of veneer. In this method the drying takes place in a kiln, not unknown in itself, in which the drying-air circulates in the drying compartment from blowers to heat exchangers and passes the veneer, absorbing the water evaporating from the veneer. In this method, also the moisture of the veneer produced, is controlled.
In the plywood industry the veneer is lathed from roundwood in a veneer lathe, after which the veneer is dried in a kiln to attain moisture content appropriate for further processing.
A veneer dryer is normally a fairly large kiln with tracks carry ing the veneer, and with blowers blowing heated air into the drying compartment. The drying power can be regulated through adjusting the speed and the humidity of the air circulating in the kiln and the speed of the veneer passing the dryer. The regulation of these parameters is necessary to provide constant quality of the dried veneer or to change the drying conditions deliberately.
The control of the quality of the veneer is traditionally carried out manually by sorters, who, by feeling the veneer with their fingers, establish its quality. As veneer that is too moist is rejected, the drying parameters are so adjusted that the dryness of the veneer is assured. The parameters are adjusted manually by trial.
The above method has certain disadvantages. The quality of the veneer suffers from over-drying; it shakes and blisters. Over-drying also wastes energy. Manual adjustment is difficult, because the exact loading of the dryer is not known. The loading of the kiln is also a factor affecting the drying-power needed, and it varies. Further disadvantages of manual adjustment are the long transitional shut-off times and the large reject batches as drying conditions change, e.g. in moving over to another wood grade, when the parameters are readjusted by trial, and it takes time before the conditions of a large kiln stabilize to produce reliable evidence of the results of the change.
Prom the Finnish patent publication 58021 a method is known for regulating the outflow of air, through measuring the pressure of the air in the kiln, by a valve, to keep the humidity of the air within certain limits.
The humidity of the air in the kiln is only one of the many factors affecting the moisture of the end product. Moreover, the adjusting of the valve has to be done by hand; automation and remote control are difficult to carry out, and the gain remains doubtful.
The object of the present invention is to avoid the disadvantages described above. It is characteristic of the invention that, through measuring the parameters affecting the moisture of the product in the kiln, sufficient information is gained for the automatic regulation of the drying process, in which the adjust¬able factors consist of the speed of the air circulating in the kiln, the outflow of air, and the speed of the veneer going through the kiln, in a way not unknown in itself, to obtain desired moisture content in the dried veneer. In this method, the kiln automatically reacts to changes in the drying conditions, thus eliminating waste of energy. All the essential parameters are considered. By regulating the speed of the veneer in the kiln, also the loading can be affected, and by drawing up drying parameters for each wood grade or production type, unnecessary losses are eliminated in connection with changes in production.
An essential feature of this invention is also the fact that the parameters observed in the kiln are the moisture content of the incoming veneer, the loading of the kiln, the speed of the veneer in the kiln, the speed, the humidity and the temperature of the air flowing in the kiln. The knowledge of the state of these parameters produces an adequate picture of the drying process.
Essential of this invention is also the fact that the humidity of the air is measured through compilation of values given by various temperature sensors. This is an accurate method of moisture measurement, suitable for automatic control.
Another characteristic of the present invention is that, as need for adjustment arises, the adjustable factors are exploited fully, one by one, till the desired result is achieved. Thus the whole range of the adjustment can be exploited when necessary, to maintain constant moisture content of the veneer.
A further characteristic of the invention is the order in which the. adjustments are made: the speed of the infeed air blowers, the speed of the outflow air blowers, and the speed of the wires carrying the veneer sheet. This order is important for the economy of the drying process, because with the use of circulating air blowers primarily, heat loss is eliminated, and the speed of production is maintained.
The invention is described in further detail in an example with figure 1. and 2.
Fig. 1. presents schematically a device employing the present invention, as seen from the side.
Fig. 2. presents the same device as seen from the head.
Undried veneer (2) coming from the lathe is fed into the kiln (1) in (3). The veneer sheet is conveyed on a track consisting of wires (4) and folding wheels (5). The kiln (1) is divided into compartments with own infeed air blowers (6). The blowers blow air through heat exchangers (7) heated with steam, after which the air is led through nozzles onto the veneer. The air circulates in the kiln (1) as shown in figure 2. The kiln has hygrometers for incoming and outgoing veneer (14 and 15) required by the regulation system, a device measuring the humidity of the air (16), a thermometer (17) and a pulse sensor (18) for the measuring of the speed of the veneer.
Through the regulation of the speed of the circulation of air by means of an inverter regulator (8) to meet the parameter value in the controlling computer, the moisture content of the end product can be affected. If the circulation of the air is sped up, the drying of the veneer becomes more powerful and vice versa.
By means of the outflow air blower (11) and its regulator (12) the humidity of the air in the kiln is adjusted. The more humid the air is, i.e. the less of it is allowed to flow out, the more efficient is the transfer of heat into the veneer, and the evaporation of water from the veneer is sped up. This produces energy savings.
Through regulating the rotation speed of the engine (13) the speed of the veneer sheet in the kiln, and thereby also the loading of the kiln, can be affected. This is abased on the fact that the speed of the infeed of the wet veneer (2) is not related to the operating speed of the kiln (1).
During the operation of the kiln (1), each of the above parameters can be adjusted independent of each other within the regulation system, or a part or all of the adjustments can be left to the computer (9). In a fully-automated mode, which is the normal form of operation, the regulation system first of all changes the speed of the circulation of air with blowers (6) as need for adjustment arises. Only if this is found insufficient, the regulation system moves over to adjust the following parameter: the speed of the outf] air blower. If desired results are still not achieved, the last possibility is the regulation of the speed of the wires (4) with the engine (13).
An expert appreciates that the applications of the present invention are not limited merely to the above example, but they can vary within the limits of the claims put forward below. Therefor the structure of the dryer does not need to be the one described above; e.g. a roll dryer is possible. There are also various possibilities for the control system. In this case it is computerized, but it does not have to be.

Claims

1. A method for the control of drying of veneer, in which the drying takes place in a kiln (1), not unknown in itself, in which the drying-air circulates in the drying compartment from blowers (6 to heat exchangers (7), and passes the veneer absorbing the water evaporated from the veneer, and in which the moisture content of the veneer produced (10) is controlled, c har ac t e r iz e by that, through measuring the parameters affecting the moisture of the product (10) in the kiln, sufficient information is gained for the automatic regulation of the drying process, in which the adjustable factors consist of the speed of the air circulating in the kiln, the outflow of air, and the speed of the veneer going through the kiln, in a way not unknown in itself, to obtain desired moisture content in the dried veneer (10).
2. A method complying with claim 1, c har ac t e r i z e d by that the parameters observed in the kiln (1) are the moisture content of the incoming veneer, the loading of the kiln, the speed of the veneer sheet in the kiln, and the speed, the humidity and the temperature of the air circulating in the kiln.
3. A method complying with claims 1 and 2, c har ac t e r i z e by that the humidity of the air is measured through compilation of values given by various temperature sensors.
4. A method complying with claims 1, 2 and 3, c harac t e ri z e d by that, as need for adjustment arises, the adjustable factors are exploited fully, one by one, till the desired result is achieved.
5. A method complying with claim 4, c h a r a c t e r i z e d by that the order in which the adjustments are made, is: the speed of the infeed air blowers (8), the speed of the outflow air blowers (11) and the speed of the wires ( 4) carrying the veneer.
EP19840900509 1984-01-06 1984-01-06 A method for the control of drying of veneer Withdrawn EP0167524A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/FI1984/000003 WO1985003117A1 (en) 1984-01-06 1984-01-06 A method for the control of drying of veneer

Publications (1)

Publication Number Publication Date
EP0167524A1 true EP0167524A1 (en) 1986-01-15

Family

ID=8556349

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19840900509 Withdrawn EP0167524A1 (en) 1984-01-06 1984-01-06 A method for the control of drying of veneer

Country Status (2)

Country Link
EP (1) EP0167524A1 (en)
WO (1) WO1985003117A1 (en)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3639929A1 (en) * 1986-11-22 1988-06-01 Babcock Bsh Ag CONTINUOUS DRYER FOR VENEER BLADES
DE69017218T2 (en) * 1990-12-05 1995-06-22 Gesma Spa Device for drying textile goods.
FR2674945B1 (en) * 1991-04-04 1993-07-23 Amdes DEVICE FOR CONTROLLING THE CONTINUOUS OPERATION OF A CONVECTIVE DRYER FOR DRYING TAPE PRODUCTS, PARTICULARLY TEXTILE TYPE.
DE4431708A1 (en) * 1994-09-06 1996-03-07 Helmut Spielvogel Accurate control of final moisture in drying of veneers of different woods
DE19525545C1 (en) * 1995-07-13 1996-09-26 Babcock Textilmasch Compact drier for high throughput for textile web with heavy borders
FI114452B (en) * 2001-08-10 2004-10-29 Raute Oyj Procedure and plant for the production of uniformly moist veneers
MY151520A (en) * 2005-09-30 2014-05-30 Australian Choice Timber Supplies Pty Ltd A method of and system for controlling a kiln
CN106593527B (en) * 2016-12-27 2018-11-02 浙江恩大施福软件科技有限公司 Nitrogen protection tunnel pushed bat kiln atmosphere automatic regulating system

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE471664C (en) * 1925-02-20 1929-02-19 Martin Vermoehlen Automatic control device for fabric tensioning and drying machines
US2442148A (en) * 1945-02-20 1948-05-25 Uxbridge Worsted Co Inc Warp drier with automatic control means
US3241249A (en) * 1963-01-24 1966-03-22 Aubrey G Lavender Method and apparatus for a speed-adjustable conveyer-type dryer

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8503117A1 *

Also Published As

Publication number Publication date
WO1985003117A1 (en) 1985-07-18

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Inventor name: KUHNO, PAULI

Inventor name: MAHLBERG, OLLI

Inventor name: KOVALA, KEIJO