CA1097059A - Roller dryer - Google Patents
Roller dryerInfo
- Publication number
- CA1097059A CA1097059A CA284,519A CA284519A CA1097059A CA 1097059 A CA1097059 A CA 1097059A CA 284519 A CA284519 A CA 284519A CA 1097059 A CA1097059 A CA 1097059A
- Authority
- CA
- Canada
- Prior art keywords
- gas
- drying chamber
- chamber
- seal chamber
- housing
- 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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- Drying Of Solid Materials (AREA)
Abstract
ROLLER DRYER
ABSTRACT
Apparatus for reducing the moisture content of rigid and/or semi-rigid material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends and including a material drying chamber or dryer and a gas seal chamber or section at the material discharge end of the dryer. Material to be dried is conveyed through the dryer and through the seal section on generally horizontal tiered single roll conveyors or on tiered "pinch roll" conveyors extending through the housing. Hot gases are forced under pressure through the dryer from the "wet" end to the "dry" end.
The gases are withdrawn from the "dry" end of the dryer and returned through a recirculating duct to the "wet" end of the dryer by a fan adjacent to the "dry" end of the dryer. During return of the drying gases to the entrance end of the dryer the temperature of the gases being circulated is increased. Pressure sensors within the "dry" end of the dryer and within the seal section adjust an exhaust damper in the seal section to maintain predetermined relative pressures of the gases in the adjoining ends of the dryer and the seal section.
ABSTRACT
Apparatus for reducing the moisture content of rigid and/or semi-rigid material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends and including a material drying chamber or dryer and a gas seal chamber or section at the material discharge end of the dryer. Material to be dried is conveyed through the dryer and through the seal section on generally horizontal tiered single roll conveyors or on tiered "pinch roll" conveyors extending through the housing. Hot gases are forced under pressure through the dryer from the "wet" end to the "dry" end.
The gases are withdrawn from the "dry" end of the dryer and returned through a recirculating duct to the "wet" end of the dryer by a fan adjacent to the "dry" end of the dryer. During return of the drying gases to the entrance end of the dryer the temperature of the gases being circulated is increased. Pressure sensors within the "dry" end of the dryer and within the seal section adjust an exhaust damper in the seal section to maintain predetermined relative pressures of the gases in the adjoining ends of the dryer and the seal section.
Description
109'70S9 ROLLER DRYER
__ _ _ _ The invention relates to apparatus for drying rigid or semi-rigid sheet material having one or a plurality of tiered horizontal conveyors and utilizing force circulated, horizontal flow, gases in contact with the material to be dried for drying the same.
Single and multiple deck roller dryers for reducing the moisture content of rigid and semi~rigid material in sheet form, such as, green veneer, wet plasterboard, fiberboard and Masonite mat, and the like, wherein the material being dried ls conveyed through a stationary housing on one or a plurality of tiered single or double roll conveyors while heated gases are force circulated through the housing or a part thereof are known, Such devices have many disadvantages one of which is loss of efficiency because of the entrance of air at ambient temperature into the dryer through the material discharge opening or openings in the dryer.
Roll conveyors are typically employed in dryers of the -i ~: .
`~ type with which the present invention is particularly concerned.
,~ Single roll conveyors are usually employed in so-called "board"
~20 dryers used in the manufacture of such products as fiberboard, plasterboard, and the like, and double or pinch roll conveyors are typically employed in so-called "veneer" dryers because veneer tends to warp upon drying. In either single or double roll dryers the material can be typically discharged through ~ 25 pinch rolls at the discharge openings thus making it easier to , ~` ::: .
seal the discharge end than when a single roll is employed~ The loss of effic~en~y in dryers employing pinch roll,at the discharge end is nevertheless subst~ntial~ A typical pinch r~ll type dryer is disclosed in United States patent Morris No~ 3,299,533~
;
__ _ _ _ The invention relates to apparatus for drying rigid or semi-rigid sheet material having one or a plurality of tiered horizontal conveyors and utilizing force circulated, horizontal flow, gases in contact with the material to be dried for drying the same.
Single and multiple deck roller dryers for reducing the moisture content of rigid and semi~rigid material in sheet form, such as, green veneer, wet plasterboard, fiberboard and Masonite mat, and the like, wherein the material being dried ls conveyed through a stationary housing on one or a plurality of tiered single or double roll conveyors while heated gases are force circulated through the housing or a part thereof are known, Such devices have many disadvantages one of which is loss of efficiency because of the entrance of air at ambient temperature into the dryer through the material discharge opening or openings in the dryer.
Roll conveyors are typically employed in dryers of the -i ~: .
`~ type with which the present invention is particularly concerned.
,~ Single roll conveyors are usually employed in so-called "board"
~20 dryers used in the manufacture of such products as fiberboard, plasterboard, and the like, and double or pinch roll conveyors are typically employed in so-called "veneer" dryers because veneer tends to warp upon drying. In either single or double roll dryers the material can be typically discharged through ~ 25 pinch rolls at the discharge openings thus making it easier to , ~` ::: .
seal the discharge end than when a single roll is employed~ The loss of effic~en~y in dryers employing pinch roll,at the discharge end is nevertheless subst~ntial~ A typical pinch r~ll type dryer is disclosed in United States patent Morris No~ 3,299,533~
;
2-~"
, . . .
1~97059 The present inven~ion provides apparatus for re-ducing the moisture content of material in sheet form com-prising a dryer including a drying chamber wherein hot gases are longitudinally circulated from the "wet" end to the "dry" end from which they are withdrawn, reheated and re-- turned to the "wet" end, a seal chamber or section at the discharge end of the drying chamber, and means for sensing gas pressure in the dryer and in the seal chamber or section and causing the pressure in the discharge end of the dryer to slightly exceed the pressure in the seal chamber thereby causing flow from the dryer into the seal section thus eliminating the leakage of air at ambient temperature into the drying chamber at the dry end thereof thus increasing the efficiency of the dryer.
More specifically the invention provides apparatus for reducing the moisture content of material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends, a con-tinuous conveyor extending through the housing which includes a material drying chamber intermediate its ends and through ~which the conveyor extends, means externally of the drying chamber for producing a flow of gas lengthwise therethrough in the direction in which the material i9 conveyed through the drying chamber and maintaining a gas pressure less than : ~ atmospheric in the material exit end of the drying chamber, :~ means for heating the gas, a gas seal chamber at the material discharge end of said drying chamber, means adjacent to the . material discharge end of the seal chamber for restricting ~he flow of gas into the seal chamber, power actuated means connected to the seal chamber for exhausting gas from the seal chamber, and means for controlling the amount of gas B ~
- ~ .
~0970~9 ... .
e~hausted from the seal chamber by the exhaust means whereby the gas pressure in the seal chamber may be maintained less than that of the subatmospheric gas pressure in the material e~it end of the drying chamber.
The invention further provides an apparatus of the character described in the preceding paragraph in which the exhaust fan discharges through a stack having an adjustable damper used to maintain the gas pressure in the seal chamber less than that of the gas pressures in the discharge end of the drying chamber.
The invention further provides an apparatus as described in the preceding paragraph in which the control means for maintaining the gas pressure in the seal chamber ~ -less than the gas pressure in the discharge end of the drying chamber includes means for sensing a gas pressure in the dryer operative to adjust the damper.
The invention resides in certain constructions and combinations and arrangements of parts and further objects and advantages of the invention will be hereinafter referred and/or will become apparent from the following description of ; the preferred embodiment shown in the accompan~ing drawing.
FIGURE 1 is a ~ragmentary plan view of a dryer `~ embodying the present invention;
FIGURE 2 is a side elevation view with part of the housing broken away of the apparatus shown in FIGURE l;
FIGURE 3 is a fragmentary enlarged view of a portion of FIGURE 2; and FIGURES 4 and 5 are diagrammatic views of controls used with the apparatus shown in FIGURES 1 to 3~
Although the invention is applicable to various types of dryers for drying material in sheet form including ~A ~ 4.
109~059 "board" dryers, that is, dryers especially designed for drying board material, such as fiberboard, plasterboard and the like, it is herein shown and described as embodied in a horizontal gas flow multiple deck, double or pinch roll conveyor type dryer in which the flow of drying gases in the material drying chamber or zone of the single air system dryer depicted or the last drying chamber or zone of a multiple air system dryer is from the material entrance end to the material discharge end, that is, from the "wet"
end to the "dry" end.
The exemplary drying apparatus shown in the drawings is designated generally by the reference character A and comprises an elongated horizontal housing 10 comprising a dryer or drying chamber 12, a gas seal chamber or section 14 and a material cooling section or chamber 16. The drying section or chamber 12 is similar to the drying part or chamber of the apparatus disclosed in aforesaid Morris patent No.
, . . .
1~97059 The present inven~ion provides apparatus for re-ducing the moisture content of material in sheet form com-prising a dryer including a drying chamber wherein hot gases are longitudinally circulated from the "wet" end to the "dry" end from which they are withdrawn, reheated and re-- turned to the "wet" end, a seal chamber or section at the discharge end of the drying chamber, and means for sensing gas pressure in the dryer and in the seal chamber or section and causing the pressure in the discharge end of the dryer to slightly exceed the pressure in the seal chamber thereby causing flow from the dryer into the seal section thus eliminating the leakage of air at ambient temperature into the drying chamber at the dry end thereof thus increasing the efficiency of the dryer.
More specifically the invention provides apparatus for reducing the moisture content of material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends, a con-tinuous conveyor extending through the housing which includes a material drying chamber intermediate its ends and through ~which the conveyor extends, means externally of the drying chamber for producing a flow of gas lengthwise therethrough in the direction in which the material i9 conveyed through the drying chamber and maintaining a gas pressure less than : ~ atmospheric in the material exit end of the drying chamber, :~ means for heating the gas, a gas seal chamber at the material discharge end of said drying chamber, means adjacent to the . material discharge end of the seal chamber for restricting ~he flow of gas into the seal chamber, power actuated means connected to the seal chamber for exhausting gas from the seal chamber, and means for controlling the amount of gas B ~
- ~ .
~0970~9 ... .
e~hausted from the seal chamber by the exhaust means whereby the gas pressure in the seal chamber may be maintained less than that of the subatmospheric gas pressure in the material e~it end of the drying chamber.
The invention further provides an apparatus of the character described in the preceding paragraph in which the exhaust fan discharges through a stack having an adjustable damper used to maintain the gas pressure in the seal chamber less than that of the gas pressures in the discharge end of the drying chamber.
The invention further provides an apparatus as described in the preceding paragraph in which the control means for maintaining the gas pressure in the seal chamber ~ -less than the gas pressure in the discharge end of the drying chamber includes means for sensing a gas pressure in the dryer operative to adjust the damper.
The invention resides in certain constructions and combinations and arrangements of parts and further objects and advantages of the invention will be hereinafter referred and/or will become apparent from the following description of ; the preferred embodiment shown in the accompan~ing drawing.
FIGURE 1 is a ~ragmentary plan view of a dryer `~ embodying the present invention;
FIGURE 2 is a side elevation view with part of the housing broken away of the apparatus shown in FIGURE l;
FIGURE 3 is a fragmentary enlarged view of a portion of FIGURE 2; and FIGURES 4 and 5 are diagrammatic views of controls used with the apparatus shown in FIGURES 1 to 3~
Although the invention is applicable to various types of dryers for drying material in sheet form including ~A ~ 4.
109~059 "board" dryers, that is, dryers especially designed for drying board material, such as fiberboard, plasterboard and the like, it is herein shown and described as embodied in a horizontal gas flow multiple deck, double or pinch roll conveyor type dryer in which the flow of drying gases in the material drying chamber or zone of the single air system dryer depicted or the last drying chamber or zone of a multiple air system dryer is from the material entrance end to the material discharge end, that is, from the "wet"
end to the "dry" end.
The exemplary drying apparatus shown in the drawings is designated generally by the reference character A and comprises an elongated horizontal housing 10 comprising a dryer or drying chamber 12, a gas seal chamber or section 14 and a material cooling section or chamber 16. The drying section or chamber 12 is similar to the drying part or chamber of the apparatus disclosed in aforesaid Morris patent No.
3,299,533, the disclosure of which is incorporated herein by reference, and will not be described in detail.
The material conveying pinch roll type conveyors~
of which there are five (5) in the embodiment shown located one above the other are designated generally by the reference characters 26(a) to 26(e) and extend through the apparatus.
The pairs of pinch rolls 34a to 34e at the exit end of the seal section 14 are in vertical alignment. The arrangements of the other pinch rolls are a matter of choice. In fact the other conveying parts of the conveyors may be of any suitable construction including the single roll type. The reference characters 36a to 36f represent baffles between the respective pairs of pinch rolls at the discharge end of the seal section and the upper and lower walls thereof t~ ~ 5.
- . .
10970~S9 to restrict the flow of air or other gases through the exit end of the seal section. Baffles at the discharge end of the drying chamber 12 to restrict the flow of gas therethrough are indicated by the reference characters 38a to 38f. These baffles, however, are not as critical or important as the baffles 36a to 36f at the material exit end of the seal -chamber.
Reference characters 40, 42 designate gas pressure sensors in the dry or exit end of the drying chamber 12 and in the entrance end of the seal section 14, respectively.
The pressure sensors are connected through moisture traps 44, 46, respectively, to a differential pressure gauge 50, such as~ a 2000 series magnehelic pressure gauge Model No.
2302 manufactured by Dwyer Instruments. If the gas pressures at the respective pressure sensors are different an operator can adjust a stack damper 52 in a stack 54 by a pneumatic ; positioner 56 to control the discharge of air from the seal chamber or section through the stack 54 which air is normally discharged by a fan located in the stack 54 and driven by a motor 60. The positioner 56, for example, may be a Hogan type thrust power positioner No. 478749-2. The damper 52 ~ .:
can be controlled manually or alternatively, it can be con-nected to the pressure sensors 40, 42 so that equal or other predetermined relative pressures are automatically maintained at the discharge end of the drying chamber 12 and the entrance ~ !~
end of the seal chamber 14. Pressure sensors of the type referred to and the other control equipment mentioned are commercially available and are not herein shown and described in detail.
3Q By maintaining equal pressures, which are normally less than atmospheric, or other suitable relative pressures . ~
.~
: B 6.
~)97~.S9 at the dry end of the dryer or drying chamber and the en-trance end of the seal section, the ingress of gases into the dryer or drying chamber through the material discharge openings and/or the space between conveyors is prevented.
This will increase the efficiency of the apparatus. In a prototype installation the saving in B.T.U. per pound of water removed was over 200 B.T.U. which is in the order of 10% of the gross thermal input to the dryer.
From the foregoing description of the preferred embodiment it will be apparent that the objects heretofore enumerated have been accomplished and that the present in-vention provides means for reducing or preventing the ingress of air at ambient temperatures into a dryer of the character to which the invention relates, thus increasing the effi-ciency of the dryer. While the preferred embodiment of the invention has been illustrated and described it is to be understood that the invention is not limited to the con-struction shown but may be otherwise embodied and it is the intention to hereby cover all adaptations, modifications and uses of the invention which come within the practice of the art to which the invention relates and the scope of the appended claims.
7.
The material conveying pinch roll type conveyors~
of which there are five (5) in the embodiment shown located one above the other are designated generally by the reference characters 26(a) to 26(e) and extend through the apparatus.
The pairs of pinch rolls 34a to 34e at the exit end of the seal section 14 are in vertical alignment. The arrangements of the other pinch rolls are a matter of choice. In fact the other conveying parts of the conveyors may be of any suitable construction including the single roll type. The reference characters 36a to 36f represent baffles between the respective pairs of pinch rolls at the discharge end of the seal section and the upper and lower walls thereof t~ ~ 5.
- . .
10970~S9 to restrict the flow of air or other gases through the exit end of the seal section. Baffles at the discharge end of the drying chamber 12 to restrict the flow of gas therethrough are indicated by the reference characters 38a to 38f. These baffles, however, are not as critical or important as the baffles 36a to 36f at the material exit end of the seal -chamber.
Reference characters 40, 42 designate gas pressure sensors in the dry or exit end of the drying chamber 12 and in the entrance end of the seal section 14, respectively.
The pressure sensors are connected through moisture traps 44, 46, respectively, to a differential pressure gauge 50, such as~ a 2000 series magnehelic pressure gauge Model No.
2302 manufactured by Dwyer Instruments. If the gas pressures at the respective pressure sensors are different an operator can adjust a stack damper 52 in a stack 54 by a pneumatic ; positioner 56 to control the discharge of air from the seal chamber or section through the stack 54 which air is normally discharged by a fan located in the stack 54 and driven by a motor 60. The positioner 56, for example, may be a Hogan type thrust power positioner No. 478749-2. The damper 52 ~ .:
can be controlled manually or alternatively, it can be con-nected to the pressure sensors 40, 42 so that equal or other predetermined relative pressures are automatically maintained at the discharge end of the drying chamber 12 and the entrance ~ !~
end of the seal chamber 14. Pressure sensors of the type referred to and the other control equipment mentioned are commercially available and are not herein shown and described in detail.
3Q By maintaining equal pressures, which are normally less than atmospheric, or other suitable relative pressures . ~
.~
: B 6.
~)97~.S9 at the dry end of the dryer or drying chamber and the en-trance end of the seal section, the ingress of gases into the dryer or drying chamber through the material discharge openings and/or the space between conveyors is prevented.
This will increase the efficiency of the apparatus. In a prototype installation the saving in B.T.U. per pound of water removed was over 200 B.T.U. which is in the order of 10% of the gross thermal input to the dryer.
From the foregoing description of the preferred embodiment it will be apparent that the objects heretofore enumerated have been accomplished and that the present in-vention provides means for reducing or preventing the ingress of air at ambient temperatures into a dryer of the character to which the invention relates, thus increasing the effi-ciency of the dryer. While the preferred embodiment of the invention has been illustrated and described it is to be understood that the invention is not limited to the con-struction shown but may be otherwise embodied and it is the intention to hereby cover all adaptations, modifications and uses of the invention which come within the practice of the art to which the invention relates and the scope of the appended claims.
7.
Claims (9)
1. In a dryer for reducing the moisture content of material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends, a continuous conveyor extending through the housing which includes a material drying chamber inter-mediate its ends and through which the conveyor extends, means externally of the drying chamber for producing a flow of gas lengthwise therethrough in the direction in which the material is conveyed through said drying chamber and maintaining a gas pressure less than atmospheric in the material exit end of the drying chamber, and means for heat-ing the gas, the improvement comprising providing a gas seal chamber at the material discharge end of said drying chamber, means adjacent to the material discharge end of said seal chamber for restricting the flow of gas into said seal chamber, power actuated means connected to said seal chamber for exhausting gas from said seal chamber, and means for controlling the amount of gas exhausted from said seal chamber by said exhaust means whereby the gas pressure in said seal chamber may be maintained less than that of the subatmospheric gas pressure in the material exit end of the drying chamber.
2. In a dryer for reducing the moisture content of material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends, a continuous conveyor extending through the housing for conveying material to be processed through the housing which includes a material drying chamber intermediate its ends and through which the conveyor extends, means ex-ternally of the drying chamber for producing a flow of gas lengthwise through said drying chamber in the direction in which the material is conveyed therethrough and main-taining a gas pressure less than atmospheric in the material exit end of said drying chamber, and means for heating the gas, the improvement comprising providing a gas seal chamber at the discharge end of said drying chamber, means adjacent to the material discharge end of said seal chamber for restricting the flow of gas into said seal chamber, an exhaust fan connected to said seal chamber, means for sensing a condition in said housing upstream from said seal chamber, and means for controlling the amount of gas exhausted from said seal chamber by said exhaust fan to maintain a gas pressure in said seal chamber less than that of the sub-atmospheric gas pressure in the material discharge end of said drying chamber.
3. In a dryer for reducing the moisture content of material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends, a continuous conveyor extending through the housing for conveying material to be processed through the housing which includes a material drying chamber inter-mediate its ends and through which the conveyor extends, means externally of the drying chamber for producing a flow of gas lengthwise therethrough in the direction in which the material is conveyed through said drying chamber and maintaining a gas pressure less than atmospheric in the material exit end of said drying chamber, and means for heating the gas, the improvement comprising providing a gas seal chamber adjacent to the material discharge end of said drying chamber, means adjacent to the discharge end of said seal chamber for restricting the flow of gas into said seal chamber, an exhaust fan connected to said seal chamber and discharging through a stack having an adjustable damper, and power means operatively connected to said damper for adjusting said damper to control the amount of gas discharged from said seal chamber by said exhaust fan whereby the gas pressure in said seal chamber may be maintained less than that of the subatmospheric gas pressure in the material exit end of the drying chamber.
4. In apparatus for reducing the moisture content of material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends, a continuous conveyor extending through the housing for conveying material to be processed through the housing which includes a material drying chamber intermediate its ends and through which the conveyor extends, means ex-ternally of the drying chamber for producing a flow of gas lengthwise through said drying chamber and maintaining a gas pressure less than atmospheric in the material exit end of said drying chamber, and means for heating the gas, the improvement comprising providing a gas seal chamber adjacent to the material discharge end of said drying chamber, means adjacent to the material discharge end of said seal chamber for restricting the flow of gas thereinto, an exhaust fan connected to said seal chamber and discharging through a stack having an adjustable damper, and control means opera-tively connected to said damper for adjusting said damper to control the amount of gas exhausted from said seal chamber by said exhaust fan to maintain a gas pressure in said seal chamber less than that of the subatmospheric gas pressure in the material discharge end of said drying chamber, said control means including means for sensing a gas pressure condition in said dryer.
5. In apparatus for reducing the moisture content of material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends, a continuous conveyor extending through the housing for conveying material to be processed through the housing which includes a material drying chamber inter-mediate its ends and through which the conveyor extends, means externally of the drying chamber for producing a flow of gas lengthwise through said drying chamber in the direction in which the material is conveyed through said drying chamber and maintaining a gas pressure less than atmospheric in the material exit end of said drying chamber, and means for heating the gas, the improvement comprising providing a gas seal chamber adjacent to the material discharge end of said drying chamber, said conveyor having pinch rolls at least at the material discharge end of said seal chamber, means adjacent to said pinch rolls at the material discharge end of said seal chamber for restricting the flow of gas into said seal chamber, an exhaust fan connected to said seal chamber, and means to control the amount of gas discharged from said seal chamber by said exhaust fan whereby the gas pressure in said seal chamber may be maintained less than the subatmospheric gas pressure in the discharge end of the drying chamber.
6. In apparatus for reducing the moisture con-tent of material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends, a continuous conveyor extending through the housing for conveying material to be processed through the housing which includes a material drying chamber intermediate its ends and through which the conveyor extends, means externally of the drying chamber for producing a flow of gas lengthwise through said drying chamber in the direction in which the material is conveyed through said drying chamber and maintaining a gas pressure less than atmospheric in the material exit end of said drying chamber, and means for heating the gas, the improvement comprising providing a gas seal chamber adjacent to the material discharge end of said drying chamber, said conveyor having pinch rolls at least at the material discharge end of said seal chamber for restricting the flow of gas thereinto, an exhaust fan connected to said seal chamber, and means to control the amount of gas exhausted from said seal chamber by said exhaust fan to maintain a gas pressure in said seal chamber less than that of the subatmospheric gas pressure in the material discharge end of said drying chamber, said control means including means for sensing a gas pressure condition in said housing upstream from said seal chamber.
7. In apparatus for reducing the moisture content of rigid and/or semi-rigid material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends, a plurality of tiered roll-type generally horizontal, continuous conveyors extending through said housing for conveying material to be processed in linear paths through said housing which includes a material drying chamber intermediate its ends and through which the conveyor extends, means externally of the drying chamber for producing a flow of gas lengthwise through said drying chamber in the direction in which the material is conveyed through said drying chamber and maintaining a gas pressure less than atmospheric in the material exit end of said drying chamber, and means for heating the gas, the improve-ment comprising providing a gas seal chamber adjacent to the material discharge end of said drying chamber, said conveyor having pinch rolls at least at the material dis-charge end of said seal chamber, means adjacent to the material discharge end of said seal chamber for restricting the flow of gas into said seal chamber, an exhaust fan connected to said seal chamber and discharging through a stack having an adjustable damper, means for sensing a condition in housing upstream from said seal chamber, and means for adjusting said damper to control the amount of gas discharged from said seal chamber by said exhaust fan whereby the gas pressure in said seal chamber may be main-tained less than the subatmospheric gas pressure in the discharge end of the drying chamber.
8. In a dryer for reducing the moisture content of material in sheet form comprising an elongated generally horizontal stationary housing having material entrance and discharge ends, a plurality of tiered roll-type generally horizontal, continuous conveyors extending through said housing for conveying material in sheet form to be processed in linear paths through said housing, said housing including a material drying chamber intermediate its ends and through which the conveyors extend, means externally of the drying chamber for producing a flow of gas lengthwise through said drying chamber in the direction in which the material is conveyed through said drying chamber and maintaining a gas pressure less than atmospheric in the material exit end of said drying chamber, and means for heating the gas, the improvement comprising providing a gas seal chamber adjacent to the material discharge end of said drying chamber, said conveyor having pinch rolls at least at the material dis-charge end of said seal chamber, means adjacent to the material discharge end of said sela chamber for restricting the flow of gas into said sela chamber, and exhaust fan connected to said seal chamber and dischargng through a stack having an adjustable damper, and control means opera-tively connected to said damper for adjusting said damper to control the amount of gas exhausted from said seal chamber by said exhaust fan to maintain a gas pressure therein not greater than that at the material discharge end of said seal chamber less than that of the subatmospheric gas pres-sure in the material discharge end of said drying chamber, said control means including means for sensing a condition in said housing upstream from said seal chamber.
9. A method for reducing the moisture content of material in sheet form which comprises providing an elongated generally horizontal stationary housing having material entrance and discharge ends, a continuous conveyor extending through the housing for conveying material to be processed through the housing which includes a material drying chamber intermediate its ends and through which the conveyor extends, means externally of the drying chamber for producing a flow of gas lengthwise through the drying chamber in the direction in which the material is conveyed through the drying chamber, means for heating the gas, a gas seal chamber at the material discharge end of the drying chamber, means adjacent to the material discharge end of the seal chamber for restricting the flow of gas into the seal chamber, and an exhaust fan connected to the seal chamber; operating the means for producing the flow of gas through the drying chamber to maintain a gas pressure less than atmospheric in the material exit end of the drying chamber, and operating the exhaust fan connected to the seal chamber to maintain a gas pressure in the seal chamber less than the subatmospheric gas pressure in the material discharge end of the drying chamber.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US74375976A | 1976-11-22 | 1976-11-22 | |
| US743,759 | 1976-11-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1097059A true CA1097059A (en) | 1981-03-10 |
Family
ID=24990050
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA284,519A Expired CA1097059A (en) | 1976-11-22 | 1977-08-11 | Roller dryer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1097059A (en) |
-
1977
- 1977-08-11 CA CA284,519A patent/CA1097059A/en not_active Expired
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Legal Events
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| MKEX | Expiry |