Heat treatment of firewood

Heat treating firewood in basket using a kiln having a burner side placement area and an opposite side placement area for receiving baskets containing firewood. The two placement areas separated by a set of downcomers that provide heated air. Loading the kiln with baskets of firewood through the use of at least one of the first end wall and the second end wall. Applying a charge to heat the baskets of firewood. The application of the charge circulating heated air for the kiln from the mixing chamber and returning the heated air to the kiln through the supply duct till the dry bulb temperature reaches an initial target temperature above 230 degrees Fahrenheit. After reaching the initial target temperature for dry bulb temperature, increasing the wet bulb temperature depression target while working to maintain the dry bulb temperature within a selected tolerance with respect to the initial target temperature.

BACKGROUND

Field of the Disclosure

This disclosure relates generally to batch kilns that are used to heat and dry firewood (alternatively called cordwood).

Background

Firewood (also known as cord wood or cordwood) is typically made from oak or other hardwoods, cut into lengths 12 to 18 inches long and split to form sticks 2 to 4 inches in diameter. To make firewood safe for interstate transportation, the USDA requires that the innermost fibers of firewood must be heated to a minimum of 60° C. (140° F.) for a minimum of 60 minutes to assure the destruction of Emerald Ash Borer (Agrilus plantpennis), as specified under 7 CFR § 301.53. Lumber harvested for firewood from living trees must also be dried from an initial moisture content near 100% water content by weight on a dry basis to a moisture content level less than the 20% water to make the firewood suitable for burning in hearths and wood stoves.

A Wisconsin Forest Products Laboratory study, titled “Kiln-Drying Time of Split Oak Firewood” (Simpson, W. T., Boone, R. S., Chem, J., and Mace, T., 1987), provides the anticipated treatment hours required to attain 20% moisture content. At temperatures of 140° F., 180° F., and 220° F., the respective treatment times are given as 260, 90, and 30 hours. This study also showed no difference in drying time between random and oriented fire wood stacking arrangements.

Firewood is typically randomly loaded in large metal baskets that have short legs so that the basket can be moved by fork lift. The basket has an open top and four corner extensions that extend upward beyond the top. These four corner extensions receive the legs from a basket placed above and prevent the basket legs from an upper basket from slipping off the lower basket. Alternatively, the basket could have an integrated pallet which receives the forks of a fork lift.

The four side walls of the basket have openings to allow movement of heated air through the basket walls to heat treat the firewood. The dimensions of the baskets shown in these drawings are about five feet tall (plus the height of the legs).

SUMMARY OF THE DISCLOSURE

Aspects of the teachings contained within this disclosure are addressed in the claims submitted with this application upon filing. Rather than adding redundant restatements of the contents of the claims, these claims should be considered incorporated by reference into this summary.

This summary is meant to provide an introduction to the concepts that are disclosed within the specification without being an exhaustive list of the many teachings and variations upon those teachings that are provided in the extended discussion within this disclosure. Thus, the contents of this summary should not be used to limit the scope of the claims that follow.

Inventive concepts are illustrated in a series of examples, some examples showing more than one inventive concept. Individual inventive concepts can be implemented without implementing all details provided in a particular example. It is not necessary to provide examples of every possible combination of the inventive concepts provide below as one of skill in the art will recognize that inventive concepts illustrated in various examples can be combined together in order to address a specific application.

Other systems, methods, features and advantages of the disclosed teachings will be immediately apparent or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within the scope of and be protected by the accompanying claims.

DETAILED DESCRIPTION

The teachings of the present disclosure may be used to create a kiln with the ability to dry 42 cords of firewood comprised of variable hardwood tree species and possessing unknown initial water contents to a certified pest-free heat treated condition with a moisture content less than 20% on a dry basis in less than 24 hours. The time may be driven down to 22 hours when baskets are used with basket walls that provide less resistance to the movement of the heated air, and additional steps are taken to minimize or prevent air bypassing the containerized wood. Having a kiln drying time on the order of 22 hours allows a kiln to be unloaded, reloaded, and restarted approximately 24 hours after the last start so that the routine from day to day is consistent.

The teachings of the present disclosure call for use of high temperature drying to heat treat the firewood. Thus, rather than using the temperature settings normally used for oak lumber or firewood, (temperatures not exceeding 220 degrees Fahrenheit dry bulb temperature with unregulated wet bulb), the kiln is operated at dry bulb temperatures that exceed 220 degrees Fahrenheit. The dry bulb temperature may be set in a range of 230 to 260 degrees Fahrenheit dry bulb temperature with a web bulb temperature of set 60 to 100 degrees Fahrenheit less than the dry bulb temperature. It is important to remember that it is difficult to maintain uniform temperatures throughout the kiln given the impact of evaporative cooling and other factors. So an average measured temperature of 260 degrees Fahrenheit should be deemed to include the possibility that some localized hot spots exist that are warmer than 260. Thus, to avoid risk of fire or setting off fire suppression sprinklers, the dry bulb set point is not likely to be set significantly above 260 degrees Fahrenheit.

The firewood kiln may be used as shown below without the inclusion of tracks. Such a kiln may be used with baskets loaded by forklift. The baskets may contain firewood or other small random wood lengths such as finger joint boards. Baskets of firewood and separate baskets containing finger joints can be dried at the same time.

One example is discussed in detail below. Those of skill in the art will appreciate that kilns of other sizes could be made using the teachings of the present disclosure. There is no requirement that the capacity of the kiln be at or near 42 cords.

FIG. 1is the top view of a kiln100that may be used for drying and heat treating firewood. To make relevant components visible, the roof220(FIG. 2) is not shown inFIG. 1.FIG. 2is a front side view of kiln100with the front wall212removed. Many major components of kiln100are visible inFIG. 1andFIG. 2.

The kiln100has internal dimensions of 34 feet across (from burner side wall204to opposite side wall208) and 33 feet deep (between front wall212and rear wall216) with a peak ceiling height near 28 feet tall. The kiln100is designed with a level area of concrete floor sufficient for package loading 84 baskets304stacked three high in four rows of seven baskets per row. Dimensions for the basket304are 5 feet wide (loading face), 4 feet deep (parallel to set of downcomers124), and 64 inches high (including the short legs), with each basket304holding approximately one half cord of firewood. Details of baskets304are discussed in connection ofFIG. 7,FIG. 8, andFIG. 9.

FIG. 1andFIG. 2show a burner104connected to the kiln100by a return duct108which returns air from the kiln100to the mixing chamber106and the mixture of hot gas from the burner104is combined with the return air from the kiln100in the mixing chamber106. The mixture of hot gas from the burner104with the return air from the kiln100is pushed back to the kiln100through a supply duct112by the recirculation blower116. Inside the kiln100, the heated air is distributed through a heat distribution duct124and disbursed into the kiln100through openings120with adjustable slide gates. The heat distribution duct124which also serves as the fan deck126. Additional openings in the bottom plate of this heat distribution duct124supply air downward through downcomers128that inject a curtain of heated air below the fan deck126, between the two stacks of baskets304. The downcomers128and upward facing openings120in the heat distribution duct124are sized so that about half the heated air is delivered through the downcomers128. A series of fans150in the fan wall154above the fan deck126are driven by long rotating shafts158which penetrate through sealed openings in the kiln wall and are connected with belt drives to fan motors162located external to the kiln. The burner side wall204of the kiln100is on the side of the kiln100closest to the burner104. In this kiln100, the fan motors162are located so that the shafts158go through the opposite side wall208to avoid requiring the shaft of the fan in-line with the supply duct from penetrating the supply duct. Other layouts are possible.

FIG. 1includes two open burner side doors140and two closed opposite side doors144. The kiln100inFIG. 1is loaded via doors140and144on the front wall212between the burner side wall204and the opposite side wall208.

To promote uniformity in the processing of the firewood, the direction of rotation of the fans150in the fan wall154may be periodically reversed. When the fans150are operated to push air from the burner side164of the fan wall154to the opposite side168of the fan wall154, the air pressure on the opposite side168of the fan wall154is sufficiently high that little flow comes out the openings120of the distribution duct124on the opposite side168of the fan wall154. In this fan direction, air pressure is low on the burner side164of the fan wall154and thus heated air comes out of the openings120of the distribution duct124. While some warm air leaves through the return duct108and comes back to the kiln100via the supply duct112, much of the air is circulated:from the fans150in the fan wall154over the fan deck126,down the opposite side plenum gap228between the opposite side edge of the fan deck126and the opposite side wall208;through the baskets304on the opposite side168of the fan wall154;through plenum gaps between adjacent downcomers128;through the baskets304on the burner side164of the fan wall154;up the burner side plenum gap224between the burner side edge of the fan deck126and the burner side wall204; andacross the burner side portion of the fan deck to the burner side164of the fan wall154.

When the fan motors162are operated in the opposite direction, the fans150in the fan wall154push air from the opposite side168of the fan wall154to the burner side164of the fan wall154. When the opposite side168of the fan wall154is the low pressure side, the bulk of the heated air delivered though upward facing openings120in the heat distribution duct124will pass through openings in the top of the distribution duct124on the opposite side168of the fan wall154. The flow of air circulating through the kiln100by the fans150will be the reverse of the path described above.

The kiln100shown in these drawings is equipped with a 15 MMBtu/hr natural gas burner104, a 75 HP recirculation blower116, and four 72 inch kiln fans150, each with 25 HP fan motors162mounted outside of the kiln walls. The burner104projects heat into a mixing chamber, which is located near the inlet of the recirculation blower116.

FIG. 3shows a cross section of the kiln100that reveals the fan wall154with fans150and the downcomers128below the heat distribution duct124. The heated air exits slots (not visible here) on both sides of each downcomer128along a centerline of the row of downcomers128. The downcomer128may also have openings132at the bottom of the downcomer128. The heated air forms an air curtain to optimize mixing of heated air with the fan driven air circulating through the baskets304(not shown here). There may be adjustable baffles to allow the flow rate to be adjusted in the entrance to each downcomer128. Likewise, the upward facing openings120in the heat distribution duct124may be adjustable through the use of slide gates which can be set to partially cover each upward facing opening120so that the distribution of heated air may be balanced. Note that there are significant open spaces between adjacent downcomers128to allow for heated air circulated by the fans150to move through the row of downcomers128. Overhead baffles (discussed below) help keep the circulating air from passing above the baskets304and below the heat distribution duct124. One of skill in the art might cover the tops of the top baskets304to reduce or eliminate air bypassing the wood through the air space above the baskets.

Returning toFIG. 2, the curbs232keep air from circulating between the legs of the lowest set of baskets304. As noted, the short legs are used to allow a fork lift to place forks between the legs and under the flat bottom of the basket304containing firewood. As noted below, an alternative basket design has fork pockets facing the door and sidewalls to prevent the circulating heated air from flowing under the firewood. When using baskets that block air flow from passing beneath the basket, there is not a benefit in adding curbs to the kiln.

In addition to the curbs232mentioned above, a set of baffles may be used to decrease the amount of air circulating within the kiln that does not pass through the baskets304. Air that is not passing through the baskets304is not assisting with the drying and heat treatment of the firewood in the baskets.FIG. 4is the same top view asFIG. 1but has the baffle components highlighted. A pair of rear baffles236extends out from the rear wall216. The rear baffles236may be immobile as they are aligned with a set of end stops240on the kiln floor which limit the movement of baskets304towards the rear wall216. The use of the rear baffles236keeps air from moving from the fan outlet to the fan inlet along the rear wall216without engaging the firewood in the baskets304.

FIG. 5is side view of a rear baffle236and positioned to be adjacent to a stack of three baskets304. The rear baffle236may include a gap above the floor as that pathway for airflow substantially obstructed by the end stops240which would decrease the flow of air under the rear baffles236.

Returning toFIG. 4, a pair of side wall baffles244and248is shown. Side wall baffle244is shown in the engaged position. Side wall baffle248is shown in the loading position. The side wall baffles244,248near the kiln doors may be spring loaded or secured with chains to press the baffle edges against the nearby baskets304but can be moved from the engaged position shown by side wall baffle244to a loading position as shown by side wall baffle248that is out of the way of forklifts loading or unloading baskets304into the kiln. The spring force or other placement mechanism is sufficient to maintain the position of the side wall baffle244(or248when moved to the engaged position) against the baskets304even when the circulating air presses to move the side wall baffle244or248away from the basket304.

FIG. 6is a front end view of kiln100with the front wall212removed (seeFIG. 1). Overhead baffles260and262are noted inFIG. 6. The overhead baffles260and262run the length of the set of baskets (seven baskets in this example). The overhead baffle260near the burner side wall204is shown in its engaged position resting across the frames of the upper baskets304. The overhead baffle262near the opposite side wall208is shown in the loading position where the overhead baffle262is elevated out of the way of the fork lifts that lift and move the baskets304to load and unload the kiln100. One arrangement of a cable266and pulleys270to lift the distal end of overhead baffle262around a hinge274is shown. The corresponding cable, pulleys, and hinge are not shown and labeled for overhead baffle260to avoid clutter in the drawing. Other tools such as electric winches could be used to lift and lower the overhead baffles260and262.

The overhead baffles260and262prevent large amounts of circulating air from passing above the top set of baskets304and below the heat distribution duct124. Note that as these baskets304are being moved into and out of the kiln by forklifts rather than via carts on tracks, there needs to be ample room for the baskets304to be manipulated without hitting the heat distribution duct124or downcomers128.

The kiln100disclosed is a package kiln but with a non-traditional spacing of baskets304with wood to be heat treated. The circulating heated air comes down a plenum on one side (204or208) of the kiln100, traverses a relatively short depth of baskets304with wood, is reheated by the heated air exiting the downcomers128, and traverses another relatively short depth of baskets304with wood before exiting by the plenum on the other side wall (208or204) to return to the inlet side of the fan wall154.

The speed and uniformity of drying of the firewood is promoted by having the heated air traverse no more than 12 feet and preferably no more than 10 feet across the firewood before receiving additional heat. This is in sharp contrast to the practice in prior art package kilns which typically had depths of wood to be treated of 16 to 24 feet.

A preferred material for the interior of the kiln100is stainless steel or aluminum alloy surfaces and structural components with corrosion resistant material properties suitable for exposure to the corrosive acid condensates that are present when drying hardwoods at temperatures above 212 degrees Fahrenheit. The baskets304and ductwork may be made of mild steel rather than stainless steel or aluminum alloys as these surfaces are less likely to receive condensation and thus less likely to corrode.

The kiln could be equipped with programmable logic controller (“PLC”) kiln controls to monitor, record, and certify heat treatment compliance with interstate or international transportation regulation.

The controls may be linked to roof vents that may be opened as needed to release heated air with substantial humidity in order to keep the wet bulb temperature below the desired set point, resulting in a lower humidity associated with a greater difference between dry bulb temperature and wet bulb temperature. The kiln will have roof vents on the burner side and the opposite side of the fan wall but only the roof vents on the discharge side of the fans will be opened to vent.

The process may work to heat a set of green firewood as quickly as possible to get the circulating air to the desired dry bulb temperature. After the initial achievement of the dry bulb set point, the wet bulb depression may be increased so that the wet bulb temperature is moved down to final wet bulb set point without prolonged venting that would depress the dry bulb temperature below a tolerance of the desired set point.

At the end of the process, the kiln100may be cooled rapidly by opening the roof vents and loading doors so that the kiln100may be cooled sufficiently for removal of the baskets304of firewood.

Set Point Examples.

The teachings of the present disclosure may be used with a range of dry bulb set points. Table A provides examples of dry bulb set point, and two different levels of web bulb depression.

Thus a kiln may be operated to initially ramp the dry bulb temperature up to 260 degrees Fahrenheit. Once the dry bulb temperature has been maintained for a prescribed period of time, the kiln may be vented to rid the kiln of humid air in order to slowly increase wet bulb depression. The roof vents are opened only on the fan outlet side of the fan wall. The venting process may be limited so that the dry bulb temperature does not dip below the target by more than an allowable tolerance (perhaps 5 or 10 degrees Fahrenheit). This process continues with the burner operating at full capacity until the wet bulb set point is reached. Once the wet bulb temperature is being maintained, the amount of venting will decrease. The burner may need to be operated at below full capacity in order to keep the dry bulb temperature from exceeding the target temperature of 260 degrees Fahrenheit.

A wet bulb depression of 60 degrees for a wet bulb temperature of 200 degrees Fahrenheit may be suitable for one application. An operator seeking a quicker treatment time (such as wanting to get the treatment time down to 22 hours) may choose a higher wet bulb depression to hasten the drying process. Thus an operator may choose a wet bulb depression of 100 degrees rather than 60 degrees Fahrenheit to hasten the process.

Another kiln may be set to a dry bulb set point of 230 degrees Fahrenheit rather than 260 degrees Fahrenheit. The process could be similar to the one described above with an initial target to achieve the dry bulb set point followed by a target to achieve the dry bulb set point and the desired wet bulb depression. The wet bulb depression can be gradually increased by venting while maintaining the dry bulb set point within a tolerance until a final state of dry bulb set point and desired wet bulb depression. After this state is reached, it may be necessary to reduce the burner output to avoid exceeding the dry bulb set point. This final state may be maintained for the duration of the heat treatment process.

Those of skill in the art will recognize that a range of dry bulb set points between 230 and 260 degrees may be used. The target wet bulb depression could be in the range of 60 to 100 degrees.

Optionally, for a process that uses an elevated dry bulb set point and a large wet bulb depression (120 degrees rather than 100 degrees), the process may reduce the dry bulb temperature after reaching the desired wet bulb temperature in order to minimize the risk of fire as the wood is dried.

Significant Energy Savings.

A kiln built and operated consistent with the teachings of the present application may have a heat treatment time (“charge time”) of less than 24 hours. This is about a quarter of the prior art package kiln processing that used a charge time of 96 hours. The increase in throughput for the kiln is a significant benefit of the teachings of the present disclosure.

A second benefit is a reduction in the energy costs to process a cord of wood.

Costs Associated with Processing 42 Cords via Prior Art.

A conventional side loaded package kiln was loaded with 84 baskets that were 5 feet wide, 4 feet deep, and 64 inches high (including the short legs), with each basket holding approximately one half cord of firewood. The baskets were stacked four wide, seven deep, and three high.

The prior art package kiln was heated to a dry bulb temperature of not exceeding 180 degrees Fahrenheit with the heated air making a single pass through the kiln and vented out rather than having a fraction recirculate to a burner mixing chamber. A powered exhaust continuously expelled spent gases to the surrounding atmosphere. The charge was held for 96 hours before opening the kiln doors to allow the kiln and the heat treated firewood to cool so that the baskets of firewood could be removed from the kiln.

In contrast a kiln created in accordance with the drawings set forth above and loaded with a set of baskets two wide, three high, and seven deep on a first side of the downcomers, and another set of baskets two wide, three high, and seven deep on the opposite side of the downcomers was operated to have a dry bulb temperature of 250 degrees Fahrenheit and operated to depress the wet bulb temperature via roof vents without significant depression of the dry bulb temperature. The charge was for 24 hours. Both kilns were used by the same operator and thus the source firewood is assumed to be comparable. Assuming a cost for natural gas at $5.35 per MCF and using $0.07 per Kilowatt hour. A standard cubic foot of natural gas is the amount found in a cubic foot at 60 degrees Fahrenheit and 14.73 pounds per square inch. A comparison of energy use is set forth below.

The table above shows a 14.15% savings per charge in total energy costs despite the use of a 75 HP recirculation blower, where this feature is totally absent in the prior art kiln. There will also be instruments and controls that consume some power. However, the significant cost savings in energy used to heat and dry the firewood will be much appreciated by kiln operators. With the potential for 6 times the weekly production capacity, this savings of $138.39 per charge could potentially be $41,517 per year (6 charges per week×$138.39 per charge×50 weeks per year).

Doors on both the front and rear of the kiln. The drawings discussed above had doors that opened on one end of the kiln and a rear wall without doors. A kiln could be built with doors on both the front and rear wall. The rear baffles would be replaced with a second set of side baffles that can be moved out of the way during loading or unloading of the kiln.

One door could be on a first end wall (212or216) and used to load the space between the burner side wall204and the downcomers128and a second door on the opposite end wall (216or212) could be used to load the space between the opposite side wall208and the downcomers128.

The present design uses a set of one or more end doors as opposed to doors on the side walls (walls parallel to the fan wall and to the set of downcomers).

More than One Set of Downcomers.

The teachings of the present disclosure could be used in a kiln with more than one set of downcomers. A first end-loaded treatment space could be filled with baskets between the opposite side wall and a first set of downcomers. A second end-loaded treatment space could be filled with baskets between the first set of downcomers and a second set of downcomers. A third end-loaded treatment space could be filled with baskets between the second set of downcomers and the burner side wall.

As with the example discussed above, this kiln with more than one downcomer would reheat air after the circulating air passes through a set of baskets. The number of sets of downcomers could be more than two if desired.

One of skill in the art will appreciate that as circulating air needs to traverse more than two sets of baskets, that the fans may need to operate to provide a larger pressure differential between the outlet and inlet side of the fan wall.

An alternative to use of legs to elevate the flat bottom of the basket to allow lifting by a fork lift, one could use baskets with integrated metal pallets. It is common for pallets to have fork pockets to receive the forks of a fork lift to allow the fork lift to lift the pallet. The walls of the fork pockets or other walls parallel with the fork pockets will impede air flow perpendicular to the fork pockets. Fork pockets aligned with the doors on the end walls will be perpendicular to the circulation direction of heated air within the kiln. Baskets with fork pockets end loaded into the kiln will not provide a bypass path for circulating heated air.

Baskets should securely nest without interfering with the ability to lift an upper nested basket from a lower nested basket. In other words the baskets should be set to reversibly nest. Baskets with pallet sections that block the flow of air circulated by the fans could be used in kilns that do not have curbs.

Basket side screening would preferably have more than 60% open area and ideally more than 80% open area (more is better). Ample open area is needed to minimize resistance to air flow through the baskets.

Baskets would preferably have a relatively light weight sheet metal covers that could be installed and removed by fork lifts. This cover may extend slightly down the four side walls. This cover could be used to cover the top baskets in a stack to avoid air entering one side of the basket and passing out the top of the basket rather than passing through small gaps between pieces of the firewood. The cover may also be used to protect firewood in baskets from rain when the baskets are outside before and after the heat treating process.

The example discussed above used baskets that were 5 feet wide (facing the door), 4 feet deep (parallel to set of downcomers124), and 64 inches high (including the short legs), with each basket304holding approximately one half cord of firewood. Thus, the circulating air passing through adjoining two baskets was passing through only ten feet of firewood.

Other basket sizes may be used with the teachings of the present disclosure. Having larger baskets may mean that a forklift must carry only one basket at a time rather than a stack of several baskets. With a large enough basket, a larger forklift may be required.

While the example set forth above had baskets arranged two across in the direction of air circulation, this is not a requirement. Likewise, it is not a requirement that the stack of baskets be three high or seven deep. The length of the treatment area or the height of the treatment area could be more or less than shown in the example shown above. The ratio of length of the treatment area to the height of the treatment area could be different from the example shown above. The ratio of length of the treatment area to the width of the treatment area could be different from the example shown above. The ratio of width of the treatment area to the height of the treatment area could be different from the example shown above.

The teachings of the present disclosure do call for limiting the length of traverse of firewood by circulating air to approximately twelve feet or less, preferably ten feet or less.

Illustrated Basket Example.

FIG. 7shows a stack of three baskets304as viewed from one of the two loading sides320.FIG. 8shows the same stack of three baskets304fromFIG. 7but from one of the two non-loading sides350that are ninety degrees offset from the loading sides320. As shown inFIG. 7, on each basket304, there are two fork pockets324and328to receive fork lift forks so that the basket304can be lifted and stacked. The fork lift pockets324and328include solid sidewalls332and336. With the fork lift pockets324and328aligned towards the loading door or doors, the solid sidewalls332and336preclude airflow below a firewood portion346of the basket304and in the fork portion348of the basket304. The width344of the loading side320may be wider than the width354of the non-loading side350. The basket side screening358is relatively open. Preferably have more than 60% open area and ideally more than 80% open area (more is better).

FIG. 8shows the basket side screening358extending down to cover the three fork portions348to cover sidewall336. As noted above, airflow will not be able to pass through solid sidewall336and bypass firewood portion346.

FIG. 7andFIG. 8show that the top of stack of baskets304is covered with a lid370. The lid may have fork pockets374and378so that the lid370may be placed upon a basket304through the use of a fork lift. This lid may extend slightly down the four side walls of the basket304with lid side walls382. This lid370could be used to cover the top basket304in a stack of baskets304to avoid air entering one side of the basket304and passing out the top of the basket304rather than passing through small gaps between pieces of the firewood.

FIG. 9is a top side, loading side, and non-loading side perspective view of the stack of three baskets304and a lid370.

FIG. 8shows the lid370as viewed from the non-loading side. Note that lid side wall382and the lid fork pocket378at least partially block air from passing over the uppermost pieces of firewood.

The use of baffles to diminish the flow of heated air around the baskets rather than through the baskets is desirable. Examples of suitable baffles have been provided. These specific baffle details are not required in order to enjoy at least some of the benefits of the present disclosure. A kiln without any baffles at all would still benefit from the other teachings of this disclosure.

A kiln may be designed to use scrap conveyer belt material or some other pliable material to provide a baffle that may be used without moving the baffle out of the way during loading of kiln as the pliable baffle would move when contacted by forklift or a basket being moved by a forklift.

The heat source shown in the drawings was a natural gas burner. Other fuels may be used. The heat source could be indirect rather than direct through use of heat exchangers heated with steam, hot water, oil, or other working fluids.

Alternatives to Roof Vents.

Although roof vents are a common tool for removing humidity from the kiln, other options are known to those of skill in the art. While the roof is the typical location for kiln vents to release humid air, the kiln could be vented in a location other than the roof. Another example of a tool to remove humidity is that dehumidifier units may be placed in the kiln to remove water vapor. The term dehumidifying means includes the use of kiln vents, including roof vents, and the use of dehumidifying units.

Integrated USDA Test Instruments.

As noted above, to make firewood safe for interstate transportation, the USDA requires that the innermost fibers of firewood must be heated to a minimum of 60° C. (140° F.) for a minimum of 60 minutes to assure the destruction of Emerald Ash Borer (Agrilus plantpennis), as specified under 7 CFR § 301.53. The USDA has a testing protocol which inserts one or more temperature probes within one or more pieces of firewood to ensure that the kiln and the treatment process used by that kiln results in bringing the core temperature into the prescribed range for the prescribed period. The USDA test equipment is temporary but similar temperature probes with permanent wiring could be added to the kiln. The process would need to have a way for the baskets to be moved into and out of the kiln without damage to the probe wiring.

While this disclosure had a focus on the drying of firewood within baskets, the teachings of the present disclosure, including the improved basket designs could be used in kilns that did not dry firewood at all but used baskets for other small random wood lengths such as finger joint boards or any other product that does not lend itself to stacking.

One of skill in the art will recognize that some of the alternative implementations set forth above are not universally mutually exclusive and that in some cases additional implementations can be created that employ aspects of two or more of the variations described above. Likewise, the present disclosure is not limited to the specific examples or particular embodiments provided to promote understanding of the various teachings of the present disclosure. Moreover, the any claims based upon this disclosure should be interpreted to cover the range of variations, modifications, and substitutes for the components described herein as would be known to those of skill in the art.