Dwiwahju Sasongko

Simulation of temperature and reaction time prediction of the torrefaction process: case of hard-wood biomass

ABSTRACT Direct utilisation of biomass for energy application is less profound due to the problems of low calorific value, high water content, and low grindability of biomass. For this reason, pre-heating treatment, sometimes called torrefaction, is necessary to improve the physical properties of biomass similar to ‘coal-like’ material. Unfortunately, only few comprehensive but simple theoretical models focused on hard-wood biomass were available to describe the torrefaction process. In this discussion, a simple proposed torrefaction model was developed and reported. The model has ability to estimate the yield of product mass and energy after the torrefaction process and determine the optimum conditions.

Fragmentation Model of Coal Devolatilization in Fluidized Bed Combustion

ABSTRACT Devolatilisation is the release of volatile compounds from coal matrix by thermal decomposition. During coal devolatilisation, fragmentation could occur due to pressure build-up of accumulated volatiles. A fragmentation model is necessary to ensure the safe operation of coal combustion and optimum process condition. In this study, the refinement of fragmentation model of coal devolatilisation was done. In order to obtain a comprehensive model, a fluidised bed combustion experiment was conducted using two Indonesian coals (Musi Banyuasin and Berau) and the results were then compared with the model simulation. Using a coal diameter of 0.8–17 mm at a combustion temperature of 850°C, it shows that the fragmentation probability and number of fragments could be affected by the coal particle diameter, convective pore diameter, and porosity. Predictions made by the developed model were close to the experimental fragmentation data, with an error range of less than 5.1%.

Effects of biomass type, blend composition, and co-pyrolysis temperature on hybrid coal quality

An experimental study on co-pyrolysis of coal with biomass wastes to produce hybrid coal was conducted to investigate the effects of important process variables, namely biomass type (rice husk and sawdust), blend composition, and co-pyrolysis temperature on the quality of hybrid coal. The experiments were carried out using a vertical tubular furnace equipped with temperature controller to maintain the co-pyrolysis reactor at a given temperature. Nitrogen gas was introduced into the furnace to create an inert environment preventing the sample from burning. A known mass of solid sample consisting of manually granulated blend of coal and biomass with binder in spherical shape was contained in a basket made of stainless sieve. After a given residence time, the sample was taken from the furnace. The blend sample prior to experiment and the produced hybrid coal were then characterized for its proximate analysis, ultimate analysis and calorific value. Experimental findings suggested that by increasing co-pyrolysis temperature from 200 to 400 °C, the calorific value of hybrid coal will increase by 14.5-17.7% to be 5585-7060 kcal/kg. It was also showed that 30% increase in the biomass content in the fuel blend would produce a hybrid coal that emitting up to 25.9% less in CO2 when used for combustion, although its calorific value decreased down to 8% compared to the biomass blend. It is shown that hybrid coal obtained from this study is comparable in calorific value to bituminous coal, thus suitable for power plant while being more environmentally friendly.An experimental study on co-pyrolysis of coal with biomass wastes to produce hybrid coal was conducted to investigate the effects of important process variables, namely biomass type (rice husk and sawdust), blend composition, and co-pyrolysis temperature on the quality of hybrid coal. The experiments were carried out using a vertical tubular furnace equipped with temperature controller to maintain the co-pyrolysis reactor at a given temperature. Nitrogen gas was introduced into the furnace to create an inert environment preventing the sample from burning. A known mass of solid sample consisting of manually granulated blend of coal and biomass with binder in spherical shape was contained in a basket made of stainless sieve. After a given residence time, the sample was taken from the furnace. The blend sample prior to experiment and the produced hybrid coal were then characterized for its proximate analysis, ultimate analysis and calorific value. Experimental findings suggested that by increasing co-pyrolys...