dispersion of gases and dust in the atmosphere
Knowing at least approximately, how many are released into the atmosphere harm exhaust ventilation, is extremely essential was to establish the laws of their dispersal in the air surrounding industrial enterprise. Unfortunately, the problem of scattering of dust and gases in the atmosphere lit yet far from complete. Research in this area are ongoing, but the practical results are not entirely satisfactory, at least if it is not about process emissions, and on the air.
We note a significant difference between the process and ventilation exhausts: First, process emissions, tend to have significantly higher concentrations of harmful substances, and secondly, these emissions are carried out mainly by high (about 60-100 m) tubes, concentrated. For process plants diameter exhaust pipe of 5 m is not an exception, but for air emissions from the exhaust pipe diameter of 1.5 m are rare, if not speak, of course, central air emissions of large free-standing tubes that take air out of several ventilation systems. Such centralized emissions occur, particularly in the manufacture of artificial silk, which must observe the vent pipes with a diameter of 5 m and a height of 100 m. However, this exception only confirms the customary rule of thumb: the ventilation exhaust is always less powerful and lower than technological.
For the tall chimneys and power scab process emissions in relation to the chimney thermal power developed "Guidelines for the calculation of atmospheric dispersion of hazardous substances" CH 369 - -67.
The basic formula used to determine the maximum concentration of pollutant in surface area, suitable only for pipes with a minimum height of 50 m, with the number of emitted gases of at least 20 m / sec on one pipe and the temperature difference between emitted gases and ambient air is not less than 30 " C. From these conditions it is clear that for air emissions, this formula is not intended. Nu can be used, of course, but to a limited extent and with a relative accuracy of calculation.
In addition to the mentioned formula for determining the maximum single concentration of surface hazards, we have yet another empirical formula, the calculation accuracy of which is also questionable. This is the formula proposed by Andreev and PI derived by him on the basis of foreign experiments and studies in the late forties and a few refined at the present time.