| Popis: |
To evaluate the potential environmental impacts of waste heat released by future dry cooling towers, an oil burning system which emits sensible heat at a rate of the order of 1000 MW into the atmosphere has been built up at the Centre de Recherches Atmospheriques . The project involved development of an oil burner device and experiments to quantify the amounts of heat and other matters released from oil combustion, such as gas and aerosol, that are not present in the case of cooling towers but may interact with heat and cause complications. The burner produces a flame of 3–5 m in height and 0.5–1.5 m in diameter. Fuel is consumed at a rate of 3.5–16.5 l min −1 at a pressure of 30–60 bars to develop a thermal output of 3–11 MW. The thermal power is distributed into three parts: sensible heat (82%), radiative energy (7–13%) and forced convection energy ( ~ 6 %); the two latter energy forms also heat the ambient air and so increase the real sensible heat output which eventually reaches 90 % of the thermal power. When the plume rises to some tens of meters, the combustion gas density is not very different from the air density and the additional water vapor does not exceed 5 % of the ambient water vapor. Smoke aerosol produced at the rate of 2–6gkg −1 of fuel-oil exhibits a maximum concentration of 10 7 particles cm −3 with a mean diameter of 0.5μm. The aerosol consists essentially of hydrophobic carbon (97%), while other elements, that may form hygroscopic or ice nuclei are present only in trace concentrations. The gaseous sulfur content may be higher but the SO 2 oxidation rate is very slow and then the cloud condensation nuclei amounts injected by the plume are neglegible in comparison with the natural nuclei. Thus the thermal impact on the atmosphere of the fuel oil combustion is essentially due to its thermodynamic characteristics, and our 105-burner system (Meteotron) should correctly simulate in full scale a dry cooling tower. The smoke particles are quite useful as they make the plume visible and are used as passive tracers of the thermal disturbance. |
