Utilization of Biomass Energy in Drying of Glutinous Rice Crackers

Fried glutinous rice cracker or Khaotan is a popular Thai traditional snack, which is economically important for local entrepreneurs in the north of Thailand. Drying process is an important step in acquiring good quality for final products. Without sufficient solar radiation, drying of Khaotan is usually performed in a drying cabinet with multidirectional flow of hot flue gas from burning of liquefied petroleum gas (LPG). This traditional dryer is usually inefficient. The present research work aims to improve energy efficiency and decrease operating cost of Khaotan drying by utilizing biomass energy instead of LPG. The dryer was completely re-designed and constructed with biomass combustor and flue gas to air heat exchanger. Hot air recirculation was employed as drying medium, instead of flue gas. A number of test runs were carried out on site. The dryer capacity was about 250 kg. Drying time was about 20 h to reduce original moisture content of the rice cracker from about 85-90 % dry basis to below 10 % dry basis. On average, 60-70 kg of biomass was used. Physical properties of dried Khaotan being analyzed were color, shrinkage ratio, expansion ratio, hardness and crispness. From the findings, while the product quality was similar, the energetic analysis results were better than those fueled by LPG. Energy consumption and operating cost of the biomass fired, hot air dryer were lower.