REDUCING ENVIRONMENTAL IMPACTS AND INCREASING ENERGY EFFICIENCY IN KILN DRYING OF SOFTWOOD TIMBER: ANALYSIS AND CONDENSATION OF VOC EMISSIONS, AND CONDENSATE TREATMENT

摘要

Kiln drying of timber has become a common practice in wood processing industry.However, timber drying consumes substantial energy and generates emissions of volatile organic compounds (VOCs). This keynote paper firstly presents the VOC emission analysis and then a newly developed technology for elimination of the VOC emissions and recovery of exhaust heat in drying of softwood timber. The major components in VOC emissions are pinenes, acetone, acetaldehyde, methanol and formaldehyde. The condensate collected from the new system is analysed and it is found that the environmental parameters including the chemical oxygen demand (COD), the total organic carbon (TOC) and pH exceeded the regulation requirements, thus the condensate needs to be treated before it can be discharged to the environment.After numerous trials, it has been found that the most effective treatment is to use Fenton’s reagent in the appropriate ratio of chemicals followed by activated carbon adsorption.With this treatment, COD is reduced by 93% to 19mg/L, TOC is reduced by 86% to 8mg/L, and pH is increased from 4 to about 6.