Development of the Process Model and Optimal Drying Conditions of Biomass Power Plants

Abstract

An empty fruit bunch (EFB) is a byproduct of the palm oil production process with an undried moisture content of 60−70%, which is too high for use as direct combustion fuel. Drying processes are generally considered essential for the recent use of EFBs as power plant fuels because their high moisture content decreases the boiler efficiency. The lower moisture content of dried EFBs increases the heating value and boiler efficiency but creates a trade-off with the energy required for the drying process. This study developed an EFB-based 10 MW power plant model by integrating economic evaluations in order to obtain optimal drying conditions. A hot air dryer was used in the drying process. The EFB evaporation behavior was predicted by reflecting the drying kinetics of EFBs in Aspen Plus. The optimum drying conditions were found to be a steam recirculation ratio of 0.25 and drying time of 23 min, creating dried EFBs with a 9.91% moisture content, which reduced costs by 5.48% relative to the undried base scenario. In addition, the developed model was compared to the drying process of a real power plant currently under construction in Indonesia. This drying process reduces the EFB moisture content from 48 to 20%.

An integrated gasification plant for electric power generation from wet biomass: toward a sustainable production in the olive oil industry

“…Rotary drum dryers can be divided into co-current and counter-current types, depending on the flow direction of the drying gas. Although counter-current rotary drum dryers can lead to products with a lower moisture content, their risk of catching fire and releasing volatiles to the environment is substantially higher [59,60]. Moreover, the vast majority of industrial rotary drum dryers operate in a co-current or parallel flow direction [61,62].…”

“…moisture content (X e ) and the drying curve of a falling-rate drying period [59,60,66]. The kinetic data for drying of wet olive pomace were obtained from [9].…”

“…In order to calculate the Sherwood, Lewis, Schmidt and Reynolds numbers, the drying gas diffusivity (δ eg ), density (ρ eg ) dynamic viscosity (μ eg ), specific heat (c p,eg ) and thermal conductivity (k eg ) were obtained by using the stream analysis of Aspen Plus. The diameter required to calculate the mass transfer coefficient and Reynolds number was replaced with Sauter mean diameter (d 32 ) and the median particle diameter (d m ) of wet olive pomace, respectively [59,60]. The velocity of the drying gas for calculation of heat and mass transfer coefficients (typical range from 0.5 to 2.5 m/s) was selected as the average value of 1.5 m/s [59].…”

“…The diameter of the dryer drum or shell was estimated at approximately 2 m by considering the volume flow rate of hot exhaust gas at the dryer inlet. As rotary drum dryers typically have a length to diameter (L/D) ratio ranging between 4 and 10, the selected L/D ratio was 7, the average value [57,60]. Consequently, a 14-m long rotary drum dryer was modeled in this work [66].…”

Pulp and paper production from oil palm empty fruit bunches: A current direction in Malaysia

“…The paper sheet formation was performed when the EFB fibres were consolidated into a thin layer. The heated cast-iron cylinders were used during the drying process to reduce the water content by up to 8 % through moving fabric belts (Han et al, 2020).…”