SYSTEM AND METHOD FOR DRYING WOOD PRODUCTS WITH RECOVERED FLUE GAS

• US 20110219640A1
• Filed: 03/11/2010
• Published: 09/15/2011
• Est. Priority Date: 03/11/2010
• Status: Active Grant

• Current Assignee: Weyerhaeuser NR Company (Weyerhauser)
• Original Assignee: Weyerhaeuser NR Company (Weyerhauser)
• Inventors: Latos, Philip
• Granted Patent: US 8,881,425 B2
• Time in Patent Office: Days
• US Class Current: 34/487
• CPC Class Codes: F26B 2210/16 Wood, e.g. lumber, timber
• CPC Class Codes: F26B 23/02 using combustion heating F26B3/305, F26B13/186, F26B21/001, F26B23/10 take precedence
• CPC Class Codes: F26B 23/10 using tubes or passages containing heated fluids , e.g. acting as radiative elements; Closed-loop systems for combustion gases F26B3/305

Abstract

The present disclosure is directed generally to systems and methods for drying wood products in one or more kilns with recovered flue gases. In some embodiments, methods for drying wood products include firing a fuel in the one or more combustion devices, thereby producing a heated fluid and a flue gas. The heated fluid is circulated to provide a primary heat source to the one or more indirect fired kilns. An amount of flue gas is recovered and transferred to provide a secondary heat source to the one or more indirect fired kilns.

Claims

1. A method for drying wood products with recovered flue gas comprising the steps of:

providing an indirect fired kiln containing the wood products, the indirect fired kiln comprising;

one or more chambers;

one or more heating zones within the one or more chambers;

one or more heating elements located in the one or more chambers; and

a ventilation system;

providing one or more combustion devices, each of the one or more combustion devices comprising an exhaust stack;

firing a fuel in the one or more combustion devices, thereby producing a heated fluid and a flue gas;

circulating the heated fluid in one or more heating elements, thereby providing a primary heat source to the kiln;

recovering an amount of the flue gas before the flue gas is discharged from the exhaust stack in each of the one or more combustion devices;

transferring the amount of flue gas to one or more of the ventilation systems to provide a secondary heat source to the indirect fired kiln; and

drying the wood products in the indirect fired kiln.

2. The method of claim 1 wherein the indirect fired kiln is a continuous kiln or a batch kiln.

3. The method of claim 1 wherein the one more combustion devices are selected from the group consisting of:

a steam boiler, a water boiler, and a thermal fluid heater.

4. The method of claim 1 wherein:

a total heat source for the indirect fired kiln is provided by the primary heat source and the secondary heat source;

wherein the primary heat source provides approximately 70% of the total heat source to approximately 80% of the total heat source; and

wherein the secondary heat source provides approximately 30% of the total heat source to approximately 20% of the total heat source.

5. The method of claim 1 wherein the fuel in the one or more combustion devices is selected from the group consisting of:

bio residual fuels, natural gas, coal, and oil.

6. The method of claim 1, wherein the step of transferring the amount of flue gas to the ventilation system to provide the secondary heat source to the indirect fired kiln includes providing insulated piping which connects the ventilation system of the indirect fired kiln to the one or more combustion devices.

7. The method of claim 6 wherein the step of transferring the amount of flue gas to the ventilation system to provide the secondary heat source to the indirect fired kiln further comprises equipping the insulated piping with one or more fans.

8. The method of claim 1, further comprising the step of:

regulating the amount of flue gas transferred to the ventilation system using one or more dampers.

9. A method for drying wood products with recovered flue gas comprising the steps of:

placing a first group of wood products in a first kiln, the first kiln comprising;

one or more first chambers;

one or more heating zones within the one or more first chambers;

one or more first drying mechanisms, the one or more first drying mechanisms configured to dry the first group of wood products in the one or more first chambers; and

one or more first inlet mechanisms, the one or more first inlet mechanisms configured to allow fluid to pass into the one or more first chambers;

placing a second group of wood products in a second kiln, the second kiln comprising;

one or more second chambers;

one or more second heating zones within the one or more second chambers;

one or more second drying mechanisms, the one or more second drying mechanisms configured to dry the second group of wood products in the one or more second chambers; and

one or more second inlet mechanisms, the one or more inlet mechanisms configured to allow fluid to pass into the one or more second chambers;

providing one or more combustion devices, each of the one or more combustion devices comprising an exhaust stack;

firing a fuel in the one or more combustion devices, thereby producing a flue gas;

recovering a first portion of the flue gas from the one or more combustion devices before the first portion of the flue gas is discharged via the exhaust stack;

transferring the first portion of the flue gas from the one or more combustion devices to the one or more first inlet mechanisms;

drying the first group of wood products in the one or more first chambers with the one or more first drying mechanisms and the first portion of the flue gas;

recovering a second portion of the flue gas from the one or more combustion devices before the second portion of the flue gas is discharged via the exhaust stack;

transferring the second portion of the flue gas from the one or more combustion devices to the one or more second inlet mechanisms; and

drying the second group of wood products in the one or more second chambers with the one or more second drying mechanisms and the second portion of the flue gas.

11. The method of claim 10 wherein the one or more first drying mechanisms is selected from the group consisting of:

a steam boiler, a water boiler, and a thermal fluid heater.

12. The method of claim 10 wherein the one or more second drying mechanisms is selected from the group consisting of:

a steam boiler, a water boiler, and a thermal fluid heater.

13. The method of claim 10 wherein the first kiln is a continuous kiln or a batch kiln.

14. The method of claim 10 wherein the second kiln is a continuous kiln or a batch kiln.

15. The method of claim 10 wherein the fuel in the one or more combustion devices is selected from the group consisting of:

bio residual fuels, natural gas, coal, and oil.

16. A system for drying wood products with recovered flue gas comprising:

one or more combustion devices, the one combustion devices each having an exhaust stack;

one or more indirect fired kilns, the one or more indirect fired kilns each comprising;

one or more chambers;

one or more heating zones within each of the one or more chambers;

an opening for receiving wood products into the one or more chambers;

one or more discharge mechanisms configured to discharge humid air from the one or more chambers;

one or more inlets vents configured to let dry air into the one or more chambers; and

one or more heating elements in fluid communication with the one or more combustion devices; and

a flue gas recovery mechanism configured to deliver flue gas from the one or more combustion devices to the one or more indirect fired kilns before the flue gas exits through the exhaust stack in each of the one or more combustion devices.

17. The system of claim 16 wherein the indirect fired kiln is a continuous kiln or a batch kiln.

18. The system of claim 16 wherein the flue gas recovery mechanism comprises one or more strings of insulated piping which connect the exhaust stack on the one or more combustion devices to the one or more inlet vents on the one or more indirect fired kilns.

19. The system of claim 16 wherein the flue gas recovery mechanism further comprises one or more dampers arranged on the one or more strings of insulated piping, the one or more damper being configured to regulate recovery of the flue gas.

20. The system of claim 16 wherein each of the one or more indirect fired kilns are located between approximately 50 feet and approximately 300 feet away from each of the one or more combustion devices.