NOVEL TWO-INTERCONNECTED FLUIDIZED BED SYSTEM FOR SELECTIVE SOLID CIRCULATION

A novel two-interconnected fluidized bed system was developed to separate fine and coarse particles by means of particle size difference. Coarse (212~300 μm) and fine (63~106 μm) particles were separated perfectly using the solid separator. The effects of the fluidizing velocity, solid injection velocity, diameter of solid injection nozzle, and solid height on the solid separation rate were investigated. Moreover, continuous solid separation and circulation test up to 20 hours was performed to check feasibility of stable operation

THE EFFECT OF GAS TEMPERATURE AND VELOCITY ON COAL DRYING IN FLUIDIZED BED DRYER

The objective of this research work is to develop fluidized bed coal dryer to overcome the disadvantages of low rank coal with high moisture such as low calorific values, costly transportation, high emissions of pollutants, and operational problem. In this paper, laboratory scale bubbling fluidized bed was used to dry high moisture, low-rank Indonesian coal to produce low moisture, high-rank coal. The effects of temperature, gas velocity and bed height to diameter ratio (L/D) on drying rate were studied to obtain information relating to optimum operating conditions. Coal characterizations (proximate analysis, ultimate analysis, Thermogravimetric Analysis (TGA), BET, Higher Heating Value (HHV), Lower Heating Value (LHV)) were performed to identify the effect of the change of moisture content. This investigation aims to study the drying process under moderated heating conditions. As a result of the experiments the conclusion is that the thermal fluidized bed process can be successfully applied to reducing moisture in Indonesian coal. Results also indicate that about 80~90% of total moisture could be reduced, including some of the inherent moisture, yielding high heating value product. The drying rate of coal in a fluidized bed is increased by increasing the temperature and velocity of the drying gas. However gas temperature had limitations causing from the spontaneous combustion and gas velocity has to be decided considering energy efficiency

A Study on the Co-Combustion Characteristics of Coal and Bio-SRF in CFBC

Bio-SRF based on livestock waste has low heating value and high moisture content. The concentration of toxic gases such as SOx, NOx, and HCl in the flue gas is changed according to the composition of fuel, and it has been reported. Therefore, the study of fuel combustion characteristics is necessary. In this study, we investigated combustion characteristics on the blended firing of coal and Bio-SRF (bio-solid refused fuel) made from livestock waste fuel in CFBC (circulating fluidized bed combustor). The raw materials for manufacturing Bio-SRF include agricultural waste, herbaceous plants, waste wood, and vegetable residues. Bio-SRF, which is formed from organic sludge, has a low heating value and a high moisture content. Bio-SRF of livestock waste fuel is blended with different ratios of coal based on heating values when coal is completely combusted in CFBC. In the result of experiment, the combustor efficiency of calculated unburned carbon concentration in the fly ash shows 98.87%, 99.04%, 99.64%, and 99.71% when the multi co-combustion ratio of livestock waste fuel increased from 100/0 (coal/livestock waste) to 70/30 (coal/livestock waste). In addition, the boiler efficiency is shown to be 86.23%, 86.30%, 87.24% and 87.27%. Through the experimental results, we have identified that co-combustion of livestock waste fuel does not affect boiler efficiency. We have systematically investigated and discussed the temperature changes of the internal combustor, compositions of flue gases, solid ash characteristics, and the efficiency of combustion and of the boiler during co-combustion of coal and Bio-SRF

Fuel characteristics of molasses-impregnated low-rank coal produced in a top-spray fluidized-bed reactor

<p>Upgrading low-rank coal (LRC) through various strategies is always an important issue. Here, we report the production of hybrid coals and an evaluation of their characteristics for use as a fuel in power plants. The hybrid coals (HCKs) were prepared by a combination of drying and biomass impregnation into an Indonesian LRC followed by a precarbonization process. We used a top-spray fluidized-bed reactor for drying, biomass impregnation, and precarbonization to produce hybrid coals that have improved fuel characteristics in terms of heating value, moisture readsorption, and combustion patterns. A systematic study reveals that experimental parameters, such as a bed temperature, bioliquid spraying procedure, and precarbonization temperature strongly influence the characteristics of the resulting hybrid coal, meaning that they have an important role in upgrading LRC. In particular, the hybrid coal prepared by a process of simultaneous drying and bioliquid spraying followed by precarbonization at 200–300°C showed high contents of fixed carbon, an improved heating value, lower moisture adsorption, and single combustion patterns in which the characteristics were dramatically upgraded for practical use as a fuel in power plants. In addition, the simultaneous process using a fluidized-bed reactor has great potential because it can achieve process simplification, reduce manufacturing costs, and handle coal particles easily.</p