الفهرس 
chapter 1Only 14 pages are availabe for public view
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Abstract
Biomass fuel is a renewable source to produce energy, because biomass can re-grow over a relatively short period of time. There are several kinds of biomass conversion techniques for producing energywhere thermo-chemical and bio-chemical conversions are the two main process technologies. Direct combustion is the best established and most commonly thermo-chemical technology used for converting biomass to heat.
The cycloneisusually used asatwo-phase flow separator. Furthermore, it can be used as a combustor that is developed for the combustion of materials which are difficult to be burnt efficiently, such as biomass fuel, by taking the advantages of dual benefits of the combustion process followed by the separation process using the gravitational effect.
The work presented herein is devoted to study experimentally two parts: the first part involved cold tests (isothermal) in which the separation efficiency of the cyclone and the different dominant parameters affect it were studied, such as the vortex finder length to the cyclone height ratio (S/H), the air flow rate and the biomass mass flow rates. Also different types of biomass particles were used such as; sawdust, rice straw and rice husk with different particles sizes. The second part of this work is the combustion test, results from the cold tests were taken as a base of the combustion tests in order to identify the optimum operating conditions. The combustion tests characterized the gas radial and axial temperature distributions along the cyclone and the biomass separation efficiencies.
In addition the combustion characteristics of the cyclone were studied in case of burning a mixture of Liquefied Petroleum Gas (LPG) fuel and biomass fuel and compared with the behavior of the combustion of LPG fuel only.
To carry out this experimental study, a test rig was especially constructed and manufactured including a vertical water cooled cyclone combustor. The test rig consists of three main lines; the air supply line, the gaseous fuel supply line and the biomass feeding system.
The experimental results showed that, by increasing the air flow rate and decreasing the biomass mass flow rates the separation efficiency increased. Also, by increasing the vortex finder ratio the separation efficiency increased for vortex finder ratios greater than 8% up to a vortex finder ratio of 16% where the separation efficiency reached its maximum value. After that the separation efficiency started to decrease by the further increase of the vortex finder ratio. Furthermore, by increasing the biomass particles size the separation efficiency increased. However it is worth stating that, the fine biomass particles with small sizes gave lower separation efficiency than the coarse particles at whole ranges of biomass flow rates.
In addition, the separation efficiency of the cold tests is higher than the separation efficiency of the combustion tests. Also, the saw dust type with particles size of 6 mm gave the maximum separation efficiency under geometrical conditions of vortex finder ratio of 16% and operating conditions of air flow rate and biomass flow rateof 38 L/s and 20 g/s respectively.
For all particles sizes, the maximum centerline axial temperature was obtained at the top of the cyclone. For coarse particles sizes, the centerline axial temperature started to decrease until axial distance of y/D = 3. After that, the centerline axial temperature increased slightly until the exit of the cyclone. For fine particles sizes the centerline axial temperature decreased until the bottom of the cyclone. Also, the peak values of the radial temperatures were found at the centerline of the cyclone.
In a comparison between the radial temperature distribution of the combustion of LPG fuel only and a mixture of LPG and biomass fuel at the same thermal load, the combustion of LPG and biomass fuel mixture revealed higher values of radial temperatures than those obtained from the combustion of the LPG only. Furthermore, there was a noticeable discrepancy in the radial temperatures measured for coarse particles. However this was not the case for the results obtained from the fine particles for all biomass types.