Standardization of Kiln seasoning schedule for coconut (Cocos nucifera L.) wood

Abstract

Coconut palm is a versatile and commercially important palm grown in the tropical and sub-tropical regions of the world. Technological up gradation of the coconut wood processing methods can bring in improvement in quality of products and greater preference by the consumers. The purpose of the present study is to popularise the commercial value of coconut as a timber species through improved processing. This study titled aims at standardising kiln seasoning schedule for high and medium density coconut wood, which are mainly used for structural purposes. Drying is one of the most important processing techniques, because a proper drying process will be the main key to ensure high quality wood products. Freshly cut samples were collected from farmer’s plot and converted into desirable sizes. Pilodyn standardisation was done to sort the coconut wood into different density classes. The regression equation formulated for basic density and Pilodyn Penetration Depth (PPD) was Y= -0.02096 (X) + 1.077583, where Y is the density of coconut wood in g/cm3 and X is the PPD in millimetres. Fundamental physical properties of wood like moisture content, dimensional shrinkage and dimensional shrinkage were also studied. Moisture content of coconut palm wood across different density classes showed significant differences. The mean moisture content for high density wood was 52.76 per cent. Mean moisture content was 103.95 per cent for medium density coconut palm wood. In low density coconut palm wood, the moisture content averaged at 186.54 per cent. There was no significant difference in volumetric shrinkage across density classes. There was significant difference in the dimensional shrinkage between different density classes. Quick drying test was conducted in the laboratory in a hot air oven to study the degree and type of defects during drying. The major seasoning defects observed in coconut palm wood were surface cracking, end splitting, twisting, cupping and bowing. Defects were 2 graded according to Terasawa scale. Seasoning schedule treatments were determined for both high density and medium density wood. There were five treatments for high density coconut wood and three treatments for the medium density wood. Samples were given different seasoning schedule treatments in a convection kiln to determine the best treatment based on grading of defects. The best kiln conditions for high density wood were with initial Dry Bulb Temperature (DBT) of 45oC, final DBT of 80oC and initial Wet Bulb Depression (WBD) of 1.8oC. The best kiln conditions for medium density 72 wood were with initial Dry Bulb Temperature (DBT) of 49oC, final DBT of 80oC and initial Wet Bulb Depression (WBD) of 2 oC. The drying time for high density wood was 11 days whereas for medium density wood the drying time was 12 days in a convection kiln of 20 cubic meters. The regression equation for high density coconut wood is Y = (0.1335× X) + 11.737, where Y is the kiln drying time in days and X is the moisture content in percentage. The regression equation for the medium density coconut palm wood were Y = (-0.08503× X) + 11.0064. Air drying of coconut palm wood took 13 weeks for high density wood and 15 weeks for medium density wood to reach the equilibrium moisture content.