Development of a bi-equilibrium model for biomass gasification in a downdraft bed reactor.
This work proposes a simple and accurate tool for predicting the main parameters of biomass gasification (syngas composition, heating value, flow rate), suitable for process study and system analysis. A multizonal model based on non-stoichiometric equilibrium models and a repartition factor, simulating the bypass of pyrolysis products through the oxidant zone, was developed. The results of tests with different feedstocks (corn cobs, wood pellets, rice husks and vine pruning) in a demonstrative downdraft gasifier (350kW) were used for validation. The average discrepancy between model and experimental results was up to 8 times less than the one with the simple equilibrium model. The repartition factor was successfully related to the operating conditions and characteristics of the biomass to simulate different conditions of the gasifier (variation in potentiality, densification and mixing of feedstock) and analyze the model sensitivity.
Some recent developments in the physics of fuel combustion
The main factors limiting combustion intensity in practical solid or liquid fuel systems are macro and micro mixing of fuel and air, heating the incoming fuel and heat loss from the flame. Micro mixing leads to a combustion time proportional to the square of the initial particle or droplet diameter so that fineness of grinding or "atomization" is the prime essential. In grate firing the high relative velocity of gas and particle can give a much greater rate of micro mixing and the particles remain in the combustion chamber until they are consumed. Macro mixing can be predicted from isothermal models in the three cases of the high velocity fuel jet, the large preheated gaseous fuel jet and the low Reynolds number heating flue - the geometrical distortion to allow for the density change on combustion is different in the three cases. The first case which corresponds to the liquid fuel fired open hearth steel-melting flame has been extensively studied to throw considerable light on the optimum design. Models can also be used for predicting the erosion of walls, the distribution of fuel residence times and the effect of buoyancy. A method of calculating the heat transfer rate from various flames in the open hearth furnace is providing a link between the model work, and flame radiation measurements and practical operation.
Mite population density analysis of stored dried apricots in Turkey
The aim of this study was to determine the population density of mite species attacking stored dried apricots in Malatya, Elazig and Izmir regions of Turkey. Storage construction types and duration of storage were also considered. The samples were collected during 2000–2003 in the most important apricot producing areas (Malatya and Elazig) and the exporting center (Izmir). Frequency of occurrence and rates of intensity of infestations were determined (16.50% from Malatya, 3.19% from Elazig and 80.49% from Izmir). A total of 16 mite species belonging to 13 genera and 11 families were identified during the surveys. The pest species Carpoglyphus lactis (L.) (Astigmata: Carpoglyphidae) was the most abundant species recorded (69.14% of samples). The highest infestation value recorded was 15,534 mites per kg.