WO1985003117A1 - A method for the control of drying of veneer - Google Patents

A method for the control of drying of veneer Download PDF

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Publication number
WO1985003117A1
WO1985003117A1 PCT/FI1984/000003 FI8400003W WO8503117A1 WO 1985003117 A1 WO1985003117 A1 WO 1985003117A1 FI 8400003 W FI8400003 W FI 8400003W WO 8503117 A1 WO8503117 A1 WO 8503117A1
Authority
WO
WIPO (PCT)
Prior art keywords
veneer
kiln
speed
air
drying
Prior art date
Application number
PCT/FI1984/000003
Other languages
French (fr)
Inventor
Olli Mahlberg
Keijo Kovala
Pauli Kuhno
Original Assignee
Oy Wilh. Schauman 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 Oy Wilh. Schauman Ab filed Critical Oy Wilh. Schauman Ab
Priority to PCT/FI1984/000003 priority Critical patent/WO1985003117A1/en
Priority to EP19840900509 priority patent/EP0167524A1/en
Publication of WO1985003117A1 publication Critical patent/WO1985003117A1/en

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).

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

Abstract

A method for the during 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 and passes the veneer absorbing the water evaporated from the veneer. For the improvement and automation of the control, a major characteristic of the present invention is that, through observing the moisture content of the veneer produced (10) and 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 dryer, the outflow of air, and the speed of the veneer going through the kiln, to obtain desired moisture content in the dried veneer (10).

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.
PCT/FI1984/000003 1984-01-06 1984-01-06 A method for the control of drying of veneer WO1985003117A1 (en)

Priority Applications (2)

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
EP19840900509 EP0167524A1 (en) 1984-01-06 1984-01-06 A method for the control of drying of veneer

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
WO1985003117A1 true WO1985003117A1 (en) 1985-07-18

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PCT/FI1984/000003 WO1985003117A1 (en) 1984-01-06 1984-01-06 A method for the control of drying of veneer

Country Status (2)

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

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0268774A2 (en) * 1986-11-22 1988-06-01 BABCOCK-BSH AKTIENGESELLSCHAFT vormals Büttner-Schilde-Haas AG Continuous veneer dryer
EP0489190A1 (en) * 1990-12-05 1992-06-10 GESMA - Gestione Sviluppo Medie Aziende SpA Device to dry textile materials
EP0507711A1 (en) * 1991-04-04 1992-10-07 Société Anonyme dite:AMDES Apparatus for controlling the continuous operation of a convective dryer for drying products in the form of webs, in particular those of the textile type
DE4431708A1 (en) * 1994-09-06 1996-03-07 Helmut Spielvogel Accurate control of final moisture in drying of veneers of different woods
WO1997003331A1 (en) * 1995-07-13 1997-01-30 Babcock Textilmaschinen Gmbh Continuous textile web drier
FR2828430A1 (en) * 2001-08-10 2003-02-14 Raute Oyj Production method for uniformly moist veneer by moistening veneer or plywood based upon measuring results received using water or steam in one or multiple points
WO2007035995A1 (en) * 2005-09-30 2007-04-05 Australian Choice Timber Supplies Pty Ltd A method of and system for controlling a kiln
CN106593527A (en) * 2016-12-27 2017-04-26 浙江恩大施福软件科技有限公司 Nitrogen protection tunnel pusher kiln atmosphere automatic adjusting system

Citations (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

Patent Citations (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

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0268774A2 (en) * 1986-11-22 1988-06-01 BABCOCK-BSH AKTIENGESELLSCHAFT vormals Büttner-Schilde-Haas AG Continuous veneer dryer
DE3639929A1 (en) * 1986-11-22 1988-06-01 Babcock Bsh Ag CONTINUOUS DRYER FOR VENEER BLADES
EP0268774A3 (en) * 1986-11-22 1989-05-24 Babcock-Bsh Aktiengesellschaft Vormals Buttner-Schilde-Haas Ag Continuous veneer dryer
EP0489190A1 (en) * 1990-12-05 1992-06-10 GESMA - Gestione Sviluppo Medie Aziende SpA Device to dry textile materials
EP0507711A1 (en) * 1991-04-04 1992-10-07 Société Anonyme dite:AMDES Apparatus for controlling the continuous operation of a convective dryer for drying products in the form of webs, in particular those of the textile type
FR2674945A1 (en) * 1991-04-04 1992-10-09 Amdes DEVICE FOR REGULATING THE CONTINUOUS OPERATION OF A CONVICTIVE DRYER INTENDED FOR DRYING PRODUCTS IN BAND, IN PARTICULAR THE TEXTILE TYPE.
DE4431708A1 (en) * 1994-09-06 1996-03-07 Helmut Spielvogel Accurate control of final moisture in drying of veneers of different woods
WO1997003331A1 (en) * 1995-07-13 1997-01-30 Babcock Textilmaschinen Gmbh Continuous textile web drier
FR2828430A1 (en) * 2001-08-10 2003-02-14 Raute Oyj Production method for uniformly moist veneer by moistening veneer or plywood based upon measuring results received using water or steam in one or multiple points
WO2007035995A1 (en) * 2005-09-30 2007-04-05 Australian Choice Timber Supplies Pty Ltd A method of and system for controlling a kiln
CN106593527A (en) * 2016-12-27 2017-04-26 浙江恩大施福软件科技有限公司 Nitrogen protection tunnel pusher kiln atmosphere automatic adjusting system

Also Published As

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