No abstract

No abstract

Three gray models for the radiative properties of gases were examined for their usage in oxy-combustion simulations of a full scale boiler with flue gas recycle. Fully coupled computational fluid dynamic (CFD) simulations of a full scale boiler were carried out employing the weighted-sum-of-gray-gases model (WSGGM) at air burn, dry-recycle and wet-recycle conditions. The resulting thermal and composition fields were then frozen and the radiative properties of the gaseous media recomputed employing the Exponential Wide Band Model (EWBM) and correlations for total emissivities of gas mixtures. It is shown that when high CO2/H2O ratios were encountered within the boiler such as in dry-recycle scenarios, employing emissivity correlations developed for purely CO2 media within the models can result in incorrect gas properties. The errors associated with this can be significant when there are large pockets within the furnace where the gas radiation dominates the particle radiation.

Tightening of air quality standards for populated urban areas has led to increasing attention to assessment of air quality management areas, where violation of air quality standards occurs, and development of control strategies to eliminate such violation of air quality standards. The Quetta urban area is very densely built and has heavy motorized traffic. The increase of emissions mainly from traffic and industry are responsible for the increase in atmospheric pollution levels during the last years. The dust examined in the current study was collected by both deposit gauge and Petri dish methods at various sites of Quetta Valley. Smoke particles were obtained by bladder method from the exhausts of various types of motor vehicles. The concentration of lead found in the smoke ranged from 1.5x10(-6) to 4.5x10(-6).

No abstract