Torrefaction process is the innovation to improve the properties of biomass. Residence time is one of the parameters that affects the properties of torrefied biomass. The residence time of a rotary kiln is the time of biomass drop into the cylinder until getting out of the cylinder. So, the propose of this study is the effect of lifters, inclination angle and rotational speed on the residence time of a rotary kiln for the torrefaction process. Palm kernel shell was used in this research. Palm kernel was chopped and minced to reduce size. The rotary kiln (0.3 meters diameter 6 meters in length) was used in this research. The number of lifters in this research were 0, 1 and 2. The rotational speed were 1, 2 and 3 rpm. The inclination angle was 1, 3 and 5 degrees. The hopper was used for the feeding system. The time was collected from biomass drop into the cylinder until getting out of the cylinder. The results reveal that the number of lifters, rotational speed and inclination angle affects the residence time of the rotary kiln. The residence time of rotary kiln was an increase when the number of lifters increase. The residence time of the rotary kiln was decreased when the rotational speed and inclination angle increase. It can be concluded that the least residence time of rotary kiln was 86.94 minute at 0 lifters, 3 rpm and 5 degrees. The most residence time was 9.22 minute at 2 lifters, 1 rpm and 1 degree.

This research studies the effect of the torrefaction process by using a rotary kiln on torrefied biomass properties. The torrefaction rotary kiln and palm kernel shell were used in this research. An investigation focused on and studied the palm kernel shell in the torrefaction process using a torrefaction rotary kiln. The solid phase (biochar), liquid phase (condensed liquid), and gas-phase ratio were clarified. The feasibility of a palm kernel shell as renewable energy was investigated. Palm kernel shell waste is abundant in the southern region of Thailand. The waste from palm kernel shells is around 500,000 tons per year and increasing every year. The palm kernel shell (raw material) has an advantage as high calorific value. Moreover, the palm kernel shell is potentially fuel in the boiler (instead of charcoal) and is widely used in many power plants. The value of the palm kernel shell depends on the quality of biomass. To find an optimum condition in the palm kernel shell industrial process, the temperature of the torrefaction process and rotation speed were set at 230, 250, 270°C, and 1, 2, 3 rpm, respectively. The product yield, characteristics of torrefied biomass, moisture content, particle distribution, mass yield, and energy yield were reported. From the result, the solid phase product was decreased when the torrefaction temperature increased, the fluid phase product and gas-phase product were increased. The particle size after torrefaction was smaller than raw biomass. The mass yield and energy yield decreased when the torrefaction was increased. On the other hand, the mass yield and energy yield increased when rotation speed was increased. It was concluded that the optimum condition for palm kernel shell in torrefaction process was 230°C with 3 rpm. The torrefaction process can improve the properties and combustion performance of biomass. The palm kernel shell was a suitable fuel and co-burning in the economic energy plant in the torrefaction process with the optimum condition.