Process for accelerated drying of green wood

• US 5,836,086 A
• Filed: 07/01/1997
• Issued: 11/17/1998
• Est. Priority Date: 05/21/1997
• Status: Expired due to Fees

• Current Assignee: James D. Labove, Robert Keith Wade, The French Oak Trust, The Labove Family Trust
• Original Assignee: James D. Labove, Robert Keith Wade, The French Oak Trust, The Labove Family Trust
• Inventors: Elder, Danny J.
• Primary Examiner(s): Bennett, Henry
• Assistant Examiner(s): GRAVINI, STEPHEN MICHAEL
• Application Number:
  US08/886,497
• Time in Patent Office: 504 Days
• Field of Search: 34/396, 34/406, 34/413, 34/417, 34/443, 34/474, 34/475, 34/486, 34/493, 34/497, 427/254, 427/315, 427/317, 427/325, 427/398.1, 427/440, 427/444, 144/335, 144/364, 144/380, 62/331
• US Class Current: 34/396
• CPC Class Codes: F26B 21/06 Controlling, e.g. regulating, parameters of gas supply F26B21/14 takes precedence; control in general G05
• CPC Class Codes: F26B 2210/16 Wood, e.g. lumber, timber
• CPC Class Codes: F26B 3/04 the gas or vapour circulating over or surrounding the materials or objects to be dried F26B3/14 takes precedence

Abstract

A process for drying or curing green wood including the heating of green wood in a heating enclosure to a predetermined temperature over about 120° F. while maintaining the moisture content of the wood close to the original moisture content of the felled wood, and then immediately cooling the heated wood with a cooling fluid at a temperature and humidity substantially less than the temperature and relative humidity of the heating enclosure for a time period sufficient for the wood to reach substantially the reduced temperature of the cooling fluid for normally removing at least about 5% of moisture from the green wood. The green wood is conditioned by the cooling step for subsequent drying steps in which moisture removal rates are substantially higher than moisture removal rates under prior conventional drying steps.

Claims

1. A method for the rapid reduction of the moisture content of green wood utilizing a controlled heating fluid in a confined zone comprising the following steps:

applying the heating fluid at a temperature between about 120°

F. and 190°

F. to the wood in the confined zone for a predetermined period of time sufficient to provide a generally uniform heating of the green wood, the heating fluid having a predetermined moisture content sufficient to maintain substantially the moisture content of the green wood;

applying a cooling fluid after heating of said green wood for surrounding said green wood, the cooling fluid having a temperature and humidity substantially less than the temperature and moisture content of the heated wood; and

maintaining the application of the cooling fluid to said green wood for a predetermined time period sufficient for said wood to reach substantially the reduced temperature of the cooling fluid for the removal of substantial moisture from the green wood.

2. The method as set forth in claim 1 wherein the step of applying a cooling fluid includes applying a cooling fluid having a temperature at least about 30°

F. less than the temperature of the heated wood and a relative humidity at least about 10% less than the relative humidity of the heated confined zone.

3. The method as set forth in claim 1 wherein the step of applying a cooling fluid includes applying a cooling fluid having a temperature at least about 50°

F. less than the temperature of the heated wood and a relative humidity at least about 20% less than the relative humidity of the heated confined zone.

4. The method as set forth in claim 1 including the step of maintaining the moisture content of the green wood prior to placing the green wood within the confined zone for heating to a moisture loss not greater than 10% of the original moisture content of the wood when felled.

5. The method as set forth in claim 1 wherein the step of applying a cooling fluid includes applying ambient air to said green wood in an environment outside said confined zone.

6. The method as set forth in claim 1 wherein the step of applying a cooling fluid includes applying ambient air as said cooling fluid within an enclosure defining said confined zone for surrounding said green wood with outside ambient air for reducing the temperature and moisture content of said green wood after being heated by said heating fluid.

7. The method as set forth in claim 1 wherein said heating fluid comprises steam for heating and maintaining the moisture content of the green wood.

8. The method as set forth in claim 1 wherein the step of applying cooling fluid to said heated wood is provided within thirty (30) minutes after heating of said wood by said heating fluid.

9. The method as set forth in claim 1 wherein said confined zone comprises an enclosed chamber in which said green wood is positioned and heated by the heating fluid, said chamber being open at least partially to the atmosphere upon application of said cooling fluid to permit heat to escape from said enclosure upon application of said cooling fluid.

10. The method as set forth in claim 9 wherein the applying of said cooling fluid includes the application of artificially cooled air into said chamber having a temperature and humidity substantially less than the temperature and humidity of the heated enclosure.

11. A process for accelerating the drying of green wood comprising the following steps:

sawing wood from a tree containing a moisture content;

heating the wood with a heating fluid in an enclosure to a predetermined temperature at least about 120°

F. for a predetermined period of time sufficient to provide a generally uniform heating across the entire cross section of the wood and to maintain substantially the moisture content of the wood during heating;

then exposing the heated wood to a cooling environment containing cooling fluid surrounding said wood of a temperature at least 30°

F. less than the temperature of said heated wood and a relative humidity of at least 10% less than the relative humidity of the heated enclosure for the transfer of internal heat and moisture to said cooling fluid;

maintaining the exposure of said wood to said cooling fluid surrounding said wood for a period of time sufficient for the entire cross section of the wood to reach substantially the temperature of the surrounding cooling fluid with substantial moisture being removed from said wood;

then reheating said wood in an enclosure to a predetermined temperature for drying of the wood;

applying moisture within said enclosure to maintain a sufficient moisture content in the outer surface of said wood for minimizing any defects; and

maintaining the reheating of said wood for a predetermined time period sufficient to reduce the moisture content of the wood to a predetermined target amount, the wet bulb depression in said enclosure increasing during said reheating of said wood.

12. The process for accelerating the drying of green wood as set forth in claim 11 including the step of sawing lumber from a tree for placing in an enclosure for heating with the lumber having a moisture content that has been reduced an amount less than about 10% of the original moisture content of the tree when felled.

13. The process for accelerating the drying of green wood as set forth in claim 11 including the step of sawing logs from a tree for placing in an enclosure for heating with the logs having a moisture content that has been reduced an amount less than about 10% of the original moisture content of the tree when felled.

14. The process for accelerating the drying of green wood as set forth in claim 11 wherein the step of exposing said wood to a cooling environment includes the application of ambient air to said enclosure.

15. The process for accelerating the drying of green wood as set forth in claim 11 wherein the step of exposing said wood to a cooling environment includes the application of refrigerated air to said enclosure.

16. The process for accelerating the drying of green wood as set forth in claim 11 wherein the step of exposing said wood to a cooling environment including removing said wood from the enclosure and exposing said wood to ambient air forming said cooling fluid.

17. The process for accelerating the drying of green wood as set forth in claim 11 wherein the step of exposing said heated wood to a cooling environment comprising exposing said heated wood to air having a temperature at least 50°

F. less than the temperature of said heated wood and a relative humidity of at least 20% less than the relative humidity of the heated enclosure.

18. A process for accelerating the drying of green wood comprising the following steps:

a. sawing wood from a tree containing a moisture content;

b. heating the wood with steam in a heating enclosure to a predetermined temperature at least about 120°

F. for a predetermined period of time sufficient to provide a generally uniform heating across the entire cross section of the wood and to maintain the moisture content of the wood during heating;

c. then exposing said wood to a cooling environment containing cooling fluid surrounding said wood of a temperature at least 30°

F. less than the temperature of said heated wood and a relative humidity of at least 10% less than the relative humidity of the heating enclosure for the transfer of internal heat and moisture to said cooling fluid;

d. maintaining the exposure of said wood to said cooling fluid surrounding said wood for a period of time sufficient for the entire cross section of the wood to reach substantially the temperature of the surrounding cooling fluid with substantial moisture being removed from said wood; and

e. then repeating steps b, c and d in sequence for at least one time to reduce further the moisture content of the wood.

19. The process as set forth in claim 18 wherein said step of exposing said wood to a cooling environment comprises exposing said wood to ambient air.

20. The process as set forth in claim 19 wherein said step of exposing said wood to a cooling environment comprises the transfer of the wood from the heating enclosure to an outside atmosphere containing ambient air.

21. The process as set forth in claim 19 wherein said step of exposing said wood to a cooling environment comprises exposing said wood to ambient air within said heating enclosure.

22. The process as set forth in claim 18 wherein said wood comprises logs.

23. A method for pre-treating green wood to increase the permeability of the wood and to condition the wood for further drying in a kiln;

said method comprising;

sawing wood from a tree containing a moisture content that has been reduced a minimum amount from the original moisture content of the tree and is at least about 50%;

heating the wood with steam in a heating enclosure to a predetermined temperature at least about 120°

F. for a predetermined period of time sufficient to provide a generally uniform heating across the entire cross section of the wood and to maintain the moisture content of the wood during heating;

then exposing said wood to a cooling environment containing cooling fluid surrounding said wood of a temperature at least 30°

F. less than the temperature of said heated wood and a relative humidity less than the relative humidity of the heating enclosure for the transfer of internal heat and moisture to said cooling fluid;

maintaining the exposure of said wood to said cooling fluid surrounding said wood for a period of time sufficient for the entire cross section of the wood to reach substantially the temperature of the surrounding cooling fluid with substantial of moisture being removed from said wood thereby completing the pre-treatment phase; and

then transferring the pre-treating green wood to a kiln for completing the drying of said green wood.

26. The process for pre-treating green wood as set forth in claim 23 wherein said step of exposing said wood to a cooling environment comprises exposing said wood to ambient air within said heating enclosure.

24. The method for pre-treating green wood as set forth in class 23 wherein said step of exposing said wood to a cooling environment comprises exposing said wood to ambient air.

25. The method for pre-treating green wood as set forth in claim 24 wherein said step of exposing said wood to a cooling environment comprises the transfer of the wood from the heating enclosure to an outside atmosphere containing ambient air.

27. A method for conditioning green wood to increase the permeability of the wood for further drying;

said method comprising

sawing wood from a tree containing a moisture content that has been reduced less than 10% from the original moisture content of the tree and is at least about 50%;

heating the wood with steam in a heating enclosure to a predetermined temperature at least about 120°

F. for a predetermined amount of time sufficient to provide a generally uniform heating across the entire cross section of the wood and to maintain the moisture content of the wood during heating;

then exposing said wood to a cooling environment containing cooling fluid surrounding said wood of a temperature at least 30°

F. less than the temperature of said heated wood and a relative humidity at least 10% less than the relative humidity of the heating enclosure for the transfer of internal heat and moisture to said cooling fluid; and

maintaining the exposure of said wood to said cooling fluid surrounding said wood for a period of time sufficient for the entire cross section of the wood to reach substantially the temperature of the surrounding cooling fluid with at least 5% of moisture normally being removed from said wood thereby to condition said green wood for further drying.

28. The method of conditioning green wood as set forth in claim 27 wherein said wood is subjected to further drying by air drying said green wood.

29. The method of conditioning green wood as set forth in claim 27 wherein said green wood is subjected to further drying by heating said green wood in a kiln while gradually increasing the wet bulb depression during heating.

30. The method of conditioning green wood as set forth in claim 27 wherein the step of exposing said wood to a cooling environment including exposing said wood to ambient air of a temperature at least 50°

F. less than the temperature of said heated wood and a relative humidity at least 20% less than the relative humidity of the heating enclosure.

31. The method of conditioning green wood as set forth in claim 27 wherein said step of exposing said wood to a cooling environment comprising exposing said wood to a cooling environment within at least 30 minutes after completing heating of said wood.

32. A method for drying railroad cross ties comprising the following steps:

sawing the cross ties from a tree containing a moisture content;

heating the cross ties with steam in a heating enclosure to a predetermined temperature at least about 130°

F. for a predetermined amount of time sufficient to provide a generally uniform heating across the entire cross section of the cross ties and to maintain substantially the moisture content of the cross ties during heating;

then exposing said cross ties to cooling fluid surrounding said cross ties of a temperature at least 30°

F. less than the temperature of said heated cross ties and a relative humidity of at least 10% less than the relative humidity of the heating enclosure for the transfer of internal heat and moisture to said cooling fluid;

maintaining the exposure of said cross ties to said cooling fluid surrounding said cross ties for a period of time sufficient for the entire cross section of the cross ties to reach substantially the temperature of the surrounding cooling fluid with at least about 5% of moisture normally being removed from said cross ties; and

then reheating said cross ties to a low temperature less than about 150°

F.

33. The method for drying cross ties as set forth in claim 32 including the step of exposing said cross ties to a cooling environment comprising exposing said cross ties to ambient air within at least 30 minutes after completing the heating of said cross ties.

34. The method for drying cross ties as set forth in claim 32 wherein the step of exposing said cross ties to cooling fluid comprises surrounding said cross ties with ambient air of a temperature at least 50°

F. less than the temperature of said heated cross ties.

35. A process of conditioning wood comprising the following steps:

applying a controlled heating fluid at a temperature between about 120°

F. and 190°

F. to the wood in a confined zone for a predetermined period of time sufficient to provide a generally uniform heating of the wood, the heating fluid having predetermined moisture content sufficient to maintain substantially the moisture content of wood;

applying a cooling fluid after heating of the wood for substantially surrounding the wood, the cooling fluid having a temperature and humidity substantially less than the temperature and moisture content of the heated wood; and

maintaining the application of the cooling fluid to the wood for a predetermined time period.

36. The process as set forth in claim 35 wherein the step of applying a cooling fluid includes applying a cooling fluid having a temperature at least about 30°

F. less than the temperature of the heated wood and a relative humidity at least about 10% less than the relative humidity of the heated confined zone.

37. The process as set forth in claim 35 wherein the step of applying a cooling fluid includes applying a cooling fluid having a temperature at least about 50°

F. less than the temperature of the heated wood and a relative humidity at least about 20% less than the relative humidity of the heated confined zone.

38. The process as set forth in claim 35 wherein the step of applying a cooling fluid comprises applying ambient air from the outside atmosphere.