Quality Drying of Hardwood 11.-13. September 2000 Sopron Hungary

1. 2nd. Workshop of COST Action E15 Quality Drying of Hardwood 11.-13. September 2000 Sopron Hungary

2. Drying of Black LocustWood Marian Babiak Technical University in Zvolen Slovak Republic

3. Zvolen - location

4. Zvolen castle Zvolen castle

5. Main square

6. University campus

7. Main building – ceremony hall

8. Another view of the University

9. Why Black Locust wood? Weedy species? Low quality? Small dimensions? Difficult to process (tool blunting)? Toxic???

10. One of the traditional produts

11. Ecological species – long natural durability • Good mechanical properties • Possibility to change the color by steaming • Fast growing species

12. INCO-COPERNICUS Project No. PL 96-4114; Contract No.ERB IC15 - CT 960713Technology for High Quality Products from Black LocustRobinia pseudoacacia „TEQUBLOC“

13. Partners • Institute for Wood Biology, University of Hamburg (coordinator) • Department of Wood Science, West Hungarian University, Sopron • Department of Wood Science, Technical University, Zvolen • TNO Building and Construction Research, Delft • Robinia Kft, Budapest

14. What we know? Czech,H.-Tamásy-Banó,M: Holz Zentralblatt • above FSP max.temp.60°C < 30mm, 55°C > 30mm • below FSP 65°C • high thylosis – low permeability • requires soft drying schedule • tendency to form drying checks

15. Dry Kiln Operator's Manual, USDA, 1991 • For thicknesses of 25 to 38 mm: recommended drying schedule: T6-A3 : • For a thickness of 50 mm: recommended drying schedule is T3-A2 • Slovak ON 49 0651 15-28 mm, 32-60mm, 75-100mm soft, hard

16. MC [%] 1 Over 60 2 60-40 3 40-30 4 30-25 5 25-20 6 20-15 7 15-10 8 10-final Drying steps (T6-A3)+(T3-A2) Steps 4-8 ON 49 0651 Steps 1-8

17. Dry bulb temperature - soft

18. Dry bulb temperature - hard

19. Equilibrium MC - soft

20. Drying schedules: Hamburg – ON soft

21. Equilibrium MC - hard

22. Drying schedules: Hamburg – ON hard

23. Klement,I. – Trebula,P.: • Comparison of classic and MW drying • Black Locust 50x150x3000 mm • Schedule 15min…………P 105min…………P/2 180min…………0 • MC 33%  10% MW 145 hours classic 408 hours

24. Microwave kiln DIES 3-V f=2,42 GHz, P=2kW

25. Our experiments • Semivacuum kiln 30-40kPa • MW resonator – normal pressure • MW resonator – normal pressure lowered pressure • HF heating

26. “Vacuum” kiln

28. magnetron power 800 W, frequency 2450 MHz Microwave “oven”

29. MW in kiln

30. frequency 23 MHz, power 3,7 kW HF heating

31. Material Specimen dimensions for drying (h = 30 w = 100-150mm ; h = 60 w = 150 - 200mm)

32. Board for experimental evaluation

33. Steaming diagram - 3x each cycle pressure 0,35 MPa

34. Slow Standard Init. temp. 40 °C 50 °C Final temp. 50 °C 60 °C Init.RH 77,5% 72,5% Final RH 30% 30% Min. dr.rate 0,05 %/hour 0,1 %/hour Drying parameters for conventional heating

35. Results

36. Drying curves 30mm: MC[%]vs time[h]

37. MC[%] distribution in layers (1-6) 30 mm

38. Quality testing “vacuum” 30 mm 1 MC SD [%]; 2 Target MC; 3 End checking; 4 Internal checking; 5 Casehardening; 6 Average drying rate [%/h] 7 Drying time 8 Starting MC 9Final MC

39. Drying curves 60mm: MC[%]vs time[h]

40. MC[%] distribution in layers (1-6) 60 mm

41. Quality testing “vacuum” 60 mm 1 MC SD [%]; 2 Target MC; 3 End checking; 4 Internal checking; 5 Casehardening; 6 Average drying rate [%/h] 7 Drying time 8 Starting MC 9Final MC

42. Drying curves(MW) MC[%] vs time[h]

43. MC[%] distribution in layers (1-6; 1-7) - MW

44. Quality testing microwaves 30, 60 mm 1 MC SD [%]; 2 Target MC; 3 End checking; 4 Internal checking; 5 Casehardening; 6 Average drying rate [%/h] 7 Drying time 8 Starting MC 9Final MC

45. Drying curves(MWV) MC[%] vs time[h]

46. MC[%] distribution in layers (1-6; 1-7) - MWV

47. Drying curves(MWV,HF) MC[%] vs time[h]

48. MC[%] distribution in layers - MWV-HF

49. Quality testing microwaves + vacuum 30, 60 mm; high frequency 30mm

50. Diffusion coefficient D[m2.s-1] “vacuum”