US2380518A - Kiln drying - Google Patents

Description

July 31 1945- F. wfGOTTscHALK ETALf 2,380,518

KILN DRYING Filed April 18, 1942 2 Sheets-Sheet 1 arzgeZZ. M

July 31, 1945.

F. W. GOTTSCHALK ET AL KILN DRYING Fil-ed April 18, 1942 v 2 Sheets-Sheet 2 ,me w,

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Patented July 3 1, 1945 zsosia KILN DRYING Frederick W. Gottschalk and Herbert W. Angell. ,Chicago, Ill., assignors to American Lumber 8:

Treating Co., a corporation of Delaware Application April 18, 1942, Serial No. 439,518

(Cl. 34--86l 4 Claims.

This invention relates to an improvementI in apparatus for drying lumber in dry kilns.

."The object of the invention is to economize on heat consumption by more fully utilizing the available heat contained in the circulating air before discharging it to the atmosphere.

I Heretofore, lumber dry kilns have been built rather looselygparticularly around the doors and Because of this loose construction it has been an exclusive practice to place the exhaust vents on the outlet or pressure side of the fans or circulating means/'so that the exhaustion of air was certain and more than suflicient. Likewise, the intake vents were situated on the intake or vacuum side of th'e/ fans or circulating means so that the intake of fresh air was -possible. This was the ideal lo/cation for exhaust and intake vents as far as mere discharging and taking in air were concerned; however, having the exhaust vents on the outlet side of the lans meant that part of the newly-conditioned air was discharged from the kiln before it ever passed through the lumber pile. This meant that B. t. u.s which rwere available for drying were being wasted;

hence, more expensive lumber drying resulted.

It is the purpose of this invention to place both the exhaust and intake vents on the intake or vacuum side of the fans and operate them si' multaneously as a single unit. It has been found that if the kiln is of fairly tight construction, intake of fresh air and exhaustion of used air on the intake or vacuum side of the fans is very easily and eniciently done by having the vents open inward. In this manner all discharged air will rst have passed through the lumber pile, thus becoming thoroughly spent. By having the vents open inward, used air is virtually trapped and forced out of the kiln, and to compensate for this lost air an equal, amount of fresh air enters through the intakevent.

Another purpose oi/this invention is to' provide for lheat exchangers on the outside of the kiln at the vent openin/gs. The discharged air, although saturated and partially cooled, stili has a considerable B. t. u. content and part of this can be reclaimed by the incoming cool air. The heat exchangers are preferably made up of several highly conductive metal plates that "will transmit heat from the discharging hot air on one side/to the incoming cool air on the other side.

lTh'e specic construction of the invention will be more fully explained in connection with the accompanying drawings, which illustrate the same in its preferred form.

yrectangular or otherwise.

Figure l is a vertical cross section of the kiln showing the pile of lumber inserted. The kiln' and the pile of lumber are preferably circular in cross section as'shown, is not limited to circulai'I kilns and circular lumber piles but may be applied to kilns and lumber piles of any shape,

Figure 2 is a longitudinal vertical section of the device. Fig. 3. is a. section taken along liney 3 3 of Fig. l. Fig. 4 is a section taken along line 4-4 of Fig. 3. Fig. 5 is a section taken alongline 5-*5 of Fig. 3.

As shown in the drawings the kiln comprises the shell I within which the pile of lumber 2 is mounted on the truck 3 which runs on the track 4. A fan 5 is provided in the apex of the kiln and carries a baillev 6. The .chamber is adapted to contain a. stack of lumber 2 of generally circular-cross section having its apex immediately below the fan and having a portion thereof substantially in contact with the ballie. It will be observed that the inner wall of the shell I and y the outer wall of lumber 2 form a free path for air movement of gradually diminishing cross section. This path is located on one side of the drying chamber only, extending from the pressure side of the ian at the apex of the chamber around to the base of the carriage near the bottorny of the chamber. At one side of the kiln an air inlet 'I is provided with a closure means 8. Immediately below the air` inlet is an air outlet 9 provided with a closure means I0. Between the fan andthe air inlet is a series of heatingcoils II which are' provided with steam in any suitable manner. A'heat exchange box I2 is arranged over the air inlet and air outlet having any desired heat exchange system.

The heat exchanger I2 operates as follows: The elongated box-like structure of substantially square cross section is positioned on the outside of the kiln and in communication with the inlet 1 and outlet 9 air passages. The heat exchanger is made up of flat metal sections, preferably of copper arranged side by side, with alternate sections communicating with the inlet air passages and 'others communicating with the outlet air passages, and with each section sealed off from its neighbors. The inlet sections Il are closed at the outer side so that inlet air enters the heat exchanger at the bottom and leaves at the top. The outlet sections I5 are sealed at the1 bottom and top so that outlet air enters the heat exchanger at the side next to the kiln and leaves at the opposite side. Thusfwhile the two streams of air arein the heat exchanger, there einplilyd'f l irolled heating coilsfmay is an exchange of heat from the outgoing air to the ingoing air.

In the operation of the device air enters the inlet 8 and passes through the heating coils Il, then through the fan 5 and returns 'through the pile of lumber 2. The sticker openings in the pile of lumber are adjusted to provide uniform circulation of air therethrough as explained in my copending application. Serial No. 393,818. filed May 1G, 1941, of which this application is a continuation-in-part.

It will be observed that the barile, the inner shell wall, the lumber, the- -f track, and, to a certainextent, the truck upon which the lumber is mounted, all serve to direct the air uniformly through the sticker openings=. 4 The direction of movement of the air from the -lzian 'is1originally.substantially tangentialto'` the Thev `baillel i 6 initially servesj sto `separate thefaiizirom .the wood and-prenant short circuit-grv wood.

. freni anfing-etherwiturtneiremaimespent air f' infine kiln,pa'sses'-'over'l the' heating oils' ligandVr becomes'lconditioned.

ebndently conseparate 'wet and dry bi'ilbcoiitrol thermometers. 1 vIlhe wetand dr-ybulbthermoineters are used to 'controlftheuheat input,. h midifying :and amount of ventinginaccordanc with es bli'shedprinl12d-inchinternal ldiameter"kiln the fans vare 'preferablyl: about ,24 inchgwith y28 inch rims. A

seresiof sprays f3I maybeprovided between the heatingcoils and't-hevents in "order" to-a'dd suii-V cient-)humidity to' thegfncoming faire; However,

.with the present system vitis..pi oper to control i withgreataccuracy the amount of `spent air ydisf.

used in various sec-v given for clearness of understanding only, and no lunnecessary limitations should be understood therefrom. l

We claim:

l. A dry kiln for treating elongated wood prod ucts comprising an elongated horizontal chamber of generally circular cross-section, at least one ian facing transversely of the chamber and located inside the apexthereof, a small baflie below and immediately adjacent the fan, means for mounting a stack of wood of substantially circuf- ,lar cross-section having its center below the center of the kiln with the long axis of the wood parallel with the axis of thc chamber, the mounting f means, the shell, and said baille being shaped to direct the air currentfrom the faninitially substantially tangentially of the 'stack of wood'in a l lpath'oi free air movement of graduallyidiminis'hingv cross-section,an air; exhaust -vent in the chamber wall,an.air intake vent in the chamber wallI immadiatelyadj acent` the' airfexhaust vent arid rbetween it, an d tireufyanA Vand a lheating coil :waitin the-"c h'amber'ipcate inthe air' stream TireV incorn'ing` mana bef y Vthem may be chargedtandf`v fresh-airfadmitted andv xtherefore the steam spray maybe eliminated in most operatins since theV bulkroi, the-moisture required. is provided by the'lumberitself.` "In this way the r h processes ix'rwh'ich" the wastage Iof `fair was .so great that moistureha'd to `liefadded in consider-.1

present` process is distinguishd n from the other ablefq-uantities to the-.drying process. f Y l .The ventsfonainfmayl be controlledmanually or automatically as desired. 'Sweetman ielatinatolthe present dis# 'l between .the intake ventan'dthefan.:

` 2L Afdry kiln for:treatingfelongated wood prodriots comprising an' elongatedhorizontal chamber ol generally circular cross-sectiong-atf least 1 one gian.` facing .transversely Yof. :the lchamber `andA lofv. catedinside the apex thereof, af small baille below A.and immediately a'd`jacentthey a fan, means Y for mounting@ stackofwoodpf substantially circular',cross-section him/'ing thelcenterv below the center of the kiln with'the'long axis of the wood parallel with the axis of the ciiamoer, the mounting means, the shell,-and said baille beingshaped 4to directthe aircurre'nt rorrifthe ian initially substantially tangentiallyof the stack of Wood in apath of free ainmovement of gradually diminshing cross-sectionan air exhaust vent in the chamber ;wallan air 'intake vent in thechamber wall immediately adjacent the air exhaustvent and between it' and the fan, and a heating coil within the chamber located in the air stream be- .tween'the intakeven't and tlie'fan,v said air exhaust vent and air intake vent respectively ventingandadmittingair solely by -actionjof the cir-L y `culatingair-streani'witl'iin the chamber.

n 3*.;A kiln as setiorth in` claimvZ; in .which means vare provided within the chamber which cooperate with vthe fa-n and baiiieto'pass Aair substantially uniformly vthrough tnewood.

ensure is shownjirimy appiiatmiiasassz, [new 'deterred 'description' been f '4.'.Adry, kiln asset forth'- in claim 1', in which heat'exchange means are" provided 'outside the .kilnl-atlthe ventopenings for transmitting heat from thedischarging ,hot airitothe incoming cool air. n f FREDERICKW, 1GOTTSCHALK.

' HERBERT WeMami.k

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