US3149932A

US3149932A - Drying kiln

Info

Publication number: US3149932A
Application number: US93795A
Authority: US
Inventors: Jakob L Bachrich
Original assignee: Galbraith and Sulley Ltd
Current assignee: Galbraith and Sulley Ltd
Priority date: 1961-03-06
Filing date: 1961-03-06
Publication date: 1964-09-22
Anticipated expiration: 1981-09-22

Description

J. 1.. BACHRICH Sept. 22 1964 DRYING KILN 4 Sheets-Sheet 1 Filed March 6, 1961.

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DRYING KILN Filed March- 6, 1961 I i v I 4 Sheets-Sheet 3 INVA'NTOR (IA/(O 8 L. BAG/ RICH Sept. 22, 1.964

J. L. BACHRICH DRYING KILN 4 Sheets-Sheet 4 Filed March 6; 1961 nwewrok JAKOB 1.. BACHRKH United States Patent Canada Filed Mar. 6, 1961, Ser. No. 93,795 3 Claims. '(Cl. 34191) This invention relates to kilns for drying lumber and other hygroscopic materials.

This kiln is designed particularly for drying lumber, but it may be used for drying any materials that may be stacked and through which air may be circulated, such as peat moss. The material may be stacked on itself, or it may be stacked in trays or other supporting means. For the sake of convenience, the invention will be described in connection with drying lumber.

Lumber is dried in kilns in order to make it available to the market in a shorter time than it would be if it were allowed to dry naturally. However, with the drying kilns of the prior art, it has not been possible to dry the lumber reasonably evenly throughout the kiln. In order to be economically possible, the kilns have to be large enough to hold a considerable quantity of lumber in stacked form. The lumber is stacked in layers with spaces therebetween in order to permit heated air to move therethrough. The problem has been that the heated air always tends to take the easiest and shortest route through the stacks so that some portions of them are dried faster and to a greater degree than other portions thereof.

One of the main objects of the present invention is the provision of a dry kiln with air circulating means therein which will dry the lumber evenly throughout the stack. This is accomplished by providing a kiln consisting of a drying chamber including drying sections extending side by side longitudinally thereof and open to each other. Circulating means is provided at each drying section and arranged to move air transversely of its section in a direction opposite to that of the circulating means of the other section. The kiln also includes baffle means for directing air from both circulating means vertically along sides of stacks in their respective drying sections, and additional baflie means for directing air from the opposite vertical sides of the stacks back to the circulating means. Each of said circulating means is positioned to circulate air past the bafiie means and through the stack in its drying section and back to said circulating means. The air moving vertically between the stacks acts as a curtain between the drying sections. ing the direction of flow of the air from the circulating means so as to balance the heating effect through the stack in a transverse direction. This arrangement ensures an even distribution of the air circulating through the stacks and, therefore, results in even drying of the lumber or other material.

The circulating system of this kiln makes it possible to attain further advantages. It makes it possible in eifect to divide the drying chamber of the kiln longitudinally into a plurality of drying area. Each area has its own circulating system, heating means and controls so that stacks of lumber of different types or diiferent moisture conditions may be simultaneously dried and each brought to a desired moisture state.

A drying kiln according to the present invention may have means for heating the circulating air either within the drying chamber or externally thereof.

Two examples of the present invention are illustrated in the accompanying drawings, in which:

FIGURE 1 is a plan view of a preferred form of drying kiln,

Means is provided for reversice FIGURE 2 is a vertical cross section taken on the line 2-2 of FIGURE 1,

FIGURE 3 is a longitudinal vertical section taken on the line 33 of FIGURE 2,

FIGURE 4 is a vertical cross section similar to FIG- URE 2 through an alternative form of drying kiln, and

FIGURE 5 is an isometric view of the drying air system for the kiln of FIGURE 4, part of said kiln also being shown.

Referring to FIGURES 1 to 3, 10 is a drying kiln particularly for drying stacks of lumber. The kiln may be only one stack long, but it is preferable to make it long enough to accommodate several stacks placed end to end. Kiln 10 includes a base 12,

side Walls

13 and 14 and a roof 15. The kiln constitutes a drying chamber 18 which includes

drying sections

20 and 22 extending side by side longitudinally of the chamber and opening to each other at 23, said opening 23 extending longitudinally and centrally of the drying chamber. Drying section 20 is adapted to receive one or more stacks of lumber 26, while section 22 is adapted to receive one or more stacks of lumber 28. These are standard lumber stacks in which the lumber is piled with transverse spacers so that air may circulate therethrough. The stacks may be moved into and out of drying sections 21 and 22, the standard meth 0d of doing this being illustrated in the drawings. A plurality of dollies 32 support each stack 26 and ride on rails 33 extending into and, usually, through section 20. Similarly, each stack 28 is carried by a plurality of dollies 36 riding on rails 37 extending through section 22. Kiln 10 includes

end walls

40 and 41 having doors 42 and 43 therein. This arrangement makes it possible to extend

rails

33 and 37 right through the drying sections and out of both ends of the kiln. However, it is obvious that one end of the kiln may be completely closed, in which case, the rails would extend out of the opposite end thereof.

By referring to FIGURE 2, it Will be seen that

stacks

26 and 28 are spaced respectively from

side walls

13 and 14 to form therebetween

outer passages

46 and 47. The opposite sides of the stacks are spaced from each other to form a common central vertical passage 49.

A cover 52 extends longitudinally of drying section 20 just above the level of the top of stack 26, said

cover having flanges

53 and 54 depending therefrom along its longitudinal edges. Similarly, another cover 58 extends longitudinally of section 22 above the stack level and has

side flanges

59 and 60 depending therefrom. Cover 52 defines the bottom of a circulating chamber 63 above the stack area 64 beneath said cover. Cover 58 also forms a circulating chamber 67 above stack area 68 in drying section 22. A bafiie 71 extends downwardly from roof 15 midway between

side Walls

13 and 14 of chamber 18 and projects downwardly a little into central passage 49, terminating near the level of the tops of

stacks

26 and 28. Baffle 71 also forms a divider between circulating

chambers

63 and 67.

Circulatin chamber 63 communicates at one end with outer passage 46 and at its opposite end with central passage 49. Suitable circulating means is mounted in chamber 63, and in this example, the circulating means comprises one or more fans 75 located substantially midway between Wall 13 and bafiie 71. It is preferable to provide a bulkhead 76 extending the length of the kiln above cover 52 and dividing chamber 63 into two parts. This bulkhead has an opening 77 for each fan 75 and in which said fan is located, see FIGURES l and 2. The number of fans depends upon the length of the drying kiln, and there usually are a plurality of these fans spaced from each other in a longitudinal direction relative to the kiln, see FIGURE 1. The fan 75 is preferably of the type having reversible and variable pitch blades. As this type of fan and its controls are well-known, it does not need detailed description herein. When fan 75 is in operation, it draws air from outer passage 46 and directs it into central passage 49, or it draws air from said central passage and directs it into said outer passage.

Circulating chamber 67 is provided with circulating means in the form of one or more fans 78, there being one of these fans for every fan 75, and they are of the same type as the latter. Fans 78 are located in openings 79 in a bulkhead 80 extending longitudinally of the kiln above cover 53 and dividing chamber 67 into two parts. The blades of fan 78 are always set to oppose the blades of fan 75 or, in other words, these fans are always blowing in directions opposite to each other, and their controls are synchronized so that when the direction of one fan is changed, that of the other is also changed.

Fans

75 and 78 may be mounted and driven in any desired manner. Each may have its own motor, but is preferable to mount each pair of

fans

75 and 78 on a common shaft 80 which extends transversely of drying chamber 18 and through circulating

chambers

63 and 67 and is carried by suitable bearings 81. One end of each shaft 80 projects outwardly through wall 13 and has a pulley 32 on said outer end which is connected by a belt 83 to a double pulley 84 mounted on the drive shaft of a suitable source of power, such as an electric motor 85 mounted on the top of kiln 111. By having a double pulley 8 motor 85 may be used to drive two shafts 80 in the kiln. As there are usually many of these shafts in a kiln, several motors 85 are required.

Fan 75 moves air longitudinally through circulating chamber 63, the direction of movement depending upon the setting of the fan blades. It is desirable constantly to add fresh air to and to remove some stale air from the stream of air circulated by the fan. For this purpose, pipes 91) and 91 extend through the kiln roof 15 above and on opposite sides of fan 75 to provide air passages through said roof. Pipe 91 preferably has an opening 94 at its lower end facing the fan, while pipe 91 has an opening 95 at its lower end also facing the fan.

Control dampers

98 and 99 are located in pipes "Ni and 91 respectively, and these are operated in any desired manner, and they are preferably interconnected so that they open and close together. For this purpose, linkage 11111 is provided for controlling both of these dampers, said linkage in this example being operated by a suitable source of power, such as a pneumatic motor 1131. The air travelling through circulating chamber 63 is heated in any convenient manner, such as by means of groups 1115 and 1% of steam coils located in the chamber above passages 46 and 19. These steam pipes are connected to a suitable source of supply, not shown. It is desirable at times to inject moisture into the circulating air, such as at the beginning of a drying cycle, and for this purpose, a spray pipe 16% is provided in the circulating stream of air, and in this example, pipe 108 is located at the end of chamber 63 above outer passage 46.

The air travelling through circulating chamber 67 is conditioned in the same manner as that travelling through chamber 63.

Pipes

112 and 113 extend through roof 15 on opposite sides of fan 78 and have

dampers

116 and 117 therein controlled by linkage 118 operated by a pneumatic motor 121). Steam coils 125 and 126 are located in chamber e7 above

passages

49 and 47, and a spray pipe 128 is provided in said chamber above outer passage 47.

The condition of the air circulated by

fans

75 and 78 may be regulated manually or automatically by controlling the temperature thereof by means of the steam coils in the circulating chambers, but adding moisture to the air by means of the spray pipes, and/ or controlling the amount of air entering and leaving the circulating chambers through the pipes in the kiln roof at the two fans. As the actual means of effecting these controls through wet and dry bulbs in the drying chambers is done according to standard practice, this does not need description herein.

However, the actual apparatus for regulating the condition of the circulating air is such that kiln 10 may be divided lengthwise into a plurality of drying areas and the condition of the circulating air may be controlled in each area in accordance with the necessities for the lumber in that area. For example, the illustrated kiln 10 is divided longitudinally into two drying

areas

132 and 133. Each of these areas includes a pair of drying

sections

20 and 22 located side by side, and a pair of circulating

chambers

63 and 67. Each of the

areas

132 and 133 also includes a plurality of fans and 78;

steam pipes

105, 106, and 12.6; spray pipes ms and 128; and vent

pipes

90, 91, 112 and 113. With this arrangement, the condition of the air circulating in drying area 132 may be different from that circulating in drying area 133.

The general operation of drying kiln 10 is quite simple.

Fans

75 and 78 are operated to circulate air through drying

sections

20 and 22 in which they are located. These fans move the air in opposite directions, that is, they either move the air in their respective circulating chambers to wards each other or away from each other. In FIGURE 2, arrows 136 and 137 indicate that the fans are blowing the air towards each other. This air is deflected downwardly by baffle 71 vertically through central passage 49 between

stacks

26 and 28. The air passes through the stacks and up

outer passages

46 and 47 and back to the fans. This circulated air travels through the heating coils during its course from the fans and back thereto. With this set-up, the fans create a high pressure area in passage 49, and low pressure areas in

outer passages

46 and 47, and this causes the air to travel transversely through the lumber stacks. After the fans have operated in this direction for a predetermined period, they are reversed so that they direct the air away from each other, as indicated by

arrows

138 and 139 in FIGURE 2. This air strikes

side walls

13 and 14 of the kiln which act as baffles and direct it downwardly into

passages

46 and 47. After travelling through the lumber stacks, the air travels upwardly in central passage 49 back to the fans. This change of the direction of flow of the air eliminates the possibility of the stacks drying more on one side thereof than on the other side.

Regardless of which way the fans are moving the air, the combined stream of air moving vertically through passage 49 in either an upward or downward direction forms a curtain between drying sections 20 and 21 and, therefore, the stacks in said sections. When this central curtain of air is moving upwardly, baffie 71 divides it between the circulating

chambers

63 and 67.

FIGURES 4 and 5 illustrate an alternative form of drying kiln 10a which functions in the same manner as kiln 111, the only difference being in the apparatus for conditioning the air circulated by the fans through the lumber stacks in the drying sections.

Vents

90, 91, 112 and 113;

coils

105, 1116, 125 and 126; and baflle 71 have been omitted from kiln 16a. The apparatus for controlling the condition of the circulating air may be designed for a kiln having only one drying section, but the illustrated apparatus is for two drying areas 132a and 133a. As the apparatus for these sections is identical, one only will now be described, namely, apparatus for drying area 132a.

FIGURE 5 more or less diagrammatically illustrates the apparatus for this purpose.

The air to be circulated in the drying kiln is heated in a suitable heating device, such as a furnace or heat exchanger 150. Heated air is drawn from the furnace through a duct 152 in any desired manner, such as by a blower 153 driven by a suitable source of power, not shown, and is directed through another duct 156 that extends inwardly beneath kiln 10a and communicates at its inner end with a longitudinal duct or plenum chamber 157 extending along the kiln beneath central passage 49a. A plurality of pipes 160 extend upwardly from duct 157 through passages 49a, there usually being two of these pipes for each pair of fans 75a and 78a. Each pipe 160 has

branch pipes

162 and 163 extending laterally from its upper end in opposite directions to circulating chambers 63a and 67a, said branch pipes terminating respectively adjacent fans 75a. and 78a. It is preferable to provide the outer ends of

pipes

162 and 163 with T-

sections

166 and 167 which extend substantially parallel to the vertical planes of their respective fans.

In place of baffle 71 of kiln 1t}, kiln 1111a has a central bathe 171) depending from root a of the kiln between chambers 63a and 67a. This baffle is formed at its upper end with a hollow section or duct 171 which extends longitudinally of the kiln. This duct is formed by

walls

173 and 174 that diverge from bafiie 170 upwardly to roof 15a. Duct 171 is actually V-shaped in cross section, see FIGURE 5, and opens through the kiln roof. This duct communicates with another duct or plenum chamber 177 which extends longitudinally of the kiln and communicates with the intake of furnace 158 through a duct 179.

Duct walls

173 and 174 are formed with

holes

181 and 182 throughout the length thereof which bring

ducts

171 and 177 into communication respectively with circulating chambers 63a and 67a. Suitable control means is provided in this duct system for venting some or all of the wet air therein to atmosphere outside the kiln and this is preferably in the form of a damper 186 located in duct 187 extending from duct 179 to heat exchanger 158 and positioned to control an opening 188 in said duct 187, said damper being manually or automatically controlled in any convenient manner. Damper 186 may be swung from one position closing opening 188 downwardly to an inclined position completely closing duct 187, said damper when open directing some or all of the air moving along duct 187 out of the system through opening 188.

As stated above, drying kiln 10a functions in the same manner as kiln 10. The air circulated by fans 75a and 78a travels through the stacks in drying sections a and 22a. The difference between the two kilns is that in kiln 10a, the air for the circulating system is heated outside the kiln by furnace 150, and fresh air is supplied to the drying sections through

ducts

152, 156 and 157; central pipes 160,

branch pipes

162 and 163; and T-

sections

166 and 167. This air is discharged into the circulating chambers 63a and 670: adjacent fans 75a: and 78a. Some of the circulating air passes through

openings

181 and 182 into duct 171 at the upper part of baflie 170, and this air travels along

ducts

177, 179 and 187 back to furnace 150. If desired, some of this air may be directed out of the system through duct opening 188, while new air may be added to the system near the furnace in any convenient manner, such as through a controlled opening 189 in duct 187. The temperature of the air being supplied to the drying kiln is controlled through the furnace or heat exchange unit. If it is desired to increase the humidity of the air being circulated through the drying sections of the kiln, moisture may be added to said air by means of spray pipes 108a and 128a in circulating chambers 63a and 670.

What I claim as my invention is:

1. In a dry kiln for lumber and the like stacked for circulation of air therethrough, an elongated drying chamber having a base, side walls, roof and end Walls, said chamber including first and second elongated drying sections extending side by side longitudinally thereof and open to each other, each of said first and second drying sections being adapted to receive at least one lumber stack supported by the base thereof and spaced from a side wall of the chamber, a circulating fan at the top of each drying section arranged to blow air transversely of its section, the fan at the top of the first drying section being adapted to blow air in a direction opposite to that of the fan of the second section, a central hollow baffie of substantially V-shape cross section extending the length of the drying chambers and extending downwardly from the chamber roof between the fans and terminating near the top level of the lumber stacks, said central bailie having holes in the V thereof facing generally towards the fans, outlet bafie means communicating with said central duct and extending to a hot air heating device, inlet duct means extending from the heating device to and throughout the length of the drying sections, circulating means in the baffle means adapted to move air from the outlet duct means through the heating device and through the inlet duct means, a plurality of inlet pipes extending from said inlet duct means upwardly between the drying sections throughout the length of the latter, branch pipes extending laterally from an upper end of each inlet pipe in opposite directions and terminating near the fans to supply hot air from the heating device to said fans, said fans being positioned selectively to circulate air drawn from between the stacks towards the chamber side walls that act as battles to direct said air downwardly or to circulate air drawn from between the stacks and the chamber side walls towards the central baflie which is positioned to direct said air downwardly in two streams side by side between the stacks, in either case the air being circulated transversely through the stacks and the air moving between said stacks acting as a curtain between the drying sections, and means for reversing the direction of flow of the air from the fans, some of said circulating air from the stacks being drawn into the central duct through the holes thereof by the circulating means in the duct means and into the outlet duct means, passing through the heating device and returning through the inlet duct means and the inlet and branch pipes.

2. A drying kiln as claimed in claim 1 including a T- section at the end of each branch pipe near a fan and extending across the path of air moved by said fan.

3. A drying kiln, and control means in the duct means operable to permit some air to enter said duct means as claimed in claim 1 including adjustable control means in the duct means for venting some air from said duct means to atmosphere outside the kiln.

References Cited in the file of this patent UNITED STATES PATENTS 1,541,443 Thelen June 9, 1925 1,840,523 Mueller Jan. 12, 1932 2,085,634 Cobb June 29, 1937 2,315,285 Dennington Mar. 30, 1943 2,538,888 Smith Jan. 23, 1951 FOREIGN PATENTS 9,173 Australia Sept. 13, 1932 66,155 Norway Apr. 27,. 1943

Claims

1. IN A DRY KILN FOR LUMBER AND THE LIKE STACKED FOR CIRCULATION OF AIR THERETHROUGH, AN ELONGATED DRYING CHAMBER HAVING A BASE, SIDE WALLS, ROOF AND END WALLS, SAID CHAMBER INCLUDING FIRST AND SECOND ELONGATED DRYING SECTIONS EXTENDING SIDE BY SIDE LONGITUDINALLY THEREOF AND OPEN TO EACH OTHER, EACH OF SAID FIRST AND SECOND DRYING SECTIONS BEING ADAPTED TO RECEIVE AT LEST ONE LUMBER STACK SUPPORTED BY THE BASE THEREOF AND SPACED FROM A SIDE WALL OF THE CHAMBER, A CIRCULATING FAN AT THE TOP OF EACH DRYING SECTION ARRANGED TO BLOW AIR TRANSVERSELY OF ITS SECTION, THE FAN AT THE TOP OF THE FIRST DRYING SECTION BEING ADAPTED TO BLOW AIR IN A DIRECTION OPPOSITE TO THAT OF THE FAN OF THE SECOND SECTION, A CENTAL HOLLOW BAFFLE OF SUBSTANTIALLY V-SHAPE CROSS SECTION EXTENDING THE LENGTH OF THE DRYING CHAMBERS AND EXTENDING DOWNWARDLY FROM THE CHAMBER ROOF BETWEEN THE FANS AND TERMINATING NEAR THE TOP LEVEL OF THE LUMBER STACKS, SAID CENTRAL BAFFLE HAVING HOLES IN THE V THEREOF FACING GENERALLY TOWARDS THE FANS, OUTLET BAFFLE MEANS COMMUNICATING WITH SAID CENTRAL DUCT AND EXTENDING TO A HOT AIR HEATING DEVICE, INLET DUCT MEANS EXTENDING FROM THE HEATING DEVICE TO AND THROUGHOUT THE LENGTH OF THE DRYING SECTIONS, CIRCULATING MEANS IN THE BAFFLE MEANS ADAPTED TO MOVE AIR FROM THE OUTLET DUCT MEANS THROUGH THE HEATING DEVICE AND THROUGH THE INLET DUCT MEANS, A PLURALITY OF INLET PIPES EXTENDING FOM SAID INLET DUCT MEANS UPWARDLY BETWEEN THE DRYING SECTIONS THROUGHOUT THE LENGTH OF THE LATTER, BRANCH PIPES EXTENDING LATERALLY FROM AN UPPER END OF EACH INLET PIPE IN OPPOSITE DIRECTIONS AND TERMINATING NEAR THE FANS TO SUPPLY