аэродинамика воздухоочистных устройств с зернистым слоем

318 Summary
to 200 Pa. The vitality of microorganisms also depends on aerodynamic resistance.
Where pressure is high, they may die which results in considerably decreased treatment
efficiency of the device. However, as practice shows, microorganisms are
capable of withstanding the pressure of up to 50 atmospheres. Biological air treatment
devices are not likely to be exposed to such aerodynamic pressure. After five
layers of the charge composed of wood chips, barks, natural zeolite granules and
foam cubes, 75 mm high bio-filter aerodynamic resistance at the supplied airflow
rate of 0.1 m/s reached 741 Pa. Upon increasing the rate of the airflow supplied to
the device up to 0.3 m/s after five layers charge’s aerodynamic resistance reaches
1 226 Pa. The carried out investigations show that the aerodynamic resistance of
synthetic-origin charges depends on time. The resistance of the charge composed
of ceramic rings reached 1 500 Pa. Bio-filter aerodynamic resistance of 1 700 Pa/m
was achieved upon using other materials such as a mixture of peat and bark. The
lowest aerodynamic resistance, 200 Pa/m, was obtained using wood chips for biological
treatment.
Chapter 7 Aerodynamic Peculiarities in Devices with a Granulated Charge
Layer discusses devices of different structures used by industries, presents the peculiarities
of devices aimed at reducing the aerodynamic resistance of charging and
analyses technologies for gas distribution in devices with a thin layer of granulated
charge. It presents airflow directions in devices with an equalising partition of gas
flow and in devices with an extended air supply branch pipe which initially diverts
airflow in the flow-reverse direction. Currently, different technologies are being developed
in order to achieve a uniform distribution of gas flow within the entire layer
of granulated charge. In order to achieve the uniform distribution of gas flow within
the entire layer of the charge, device cassettes with granulated charge are shifted
from 0 to 11° angle. Cassette height, length and width can reach 95×600×300 mm
respectively. The directions of gas flow in the charge were identified upon adding
soot particles to gas flow which coloured the respective places of gas flowing. The
preciseness of this method, in terms of quality and quantity, was proved by subsequently
applied thermoanemometers. The chapter presents the directions of gas
flows on the basis of the research methods. The distribution of airflow rate within
the entire width of a cassette was discussed. To achieve the uniform distribution of
airflow, diffusive systems were used in the device and cone-shaped diffusers were
investigated. Subject to the type and length of a diffuser, the ratio of airflow rates
W/W 0
(when W 0
= 2.5 m/s) may vary from 0.7 to 1.4. It is recommended to use
granulated charges composed of silica gel balls of 3–5 mm diameter in cassette filters.
In order to reduce the aerodynamic resistance of charging, attempts are made to
develop the structure of a uniform layer of the cylinder-shaped charge. This chapter
also focuses on the analysis of reactors operating on the catalytic principle of cleaning
the air from gaseous pollutants.