If you allow the technology, rationally arrange the ends of the oven or dryer (where there are openings for entry and exit of the material) the special pre-combustion chamber from which the exhaust air. Prechamber provided with similar openings, which have a stove or dryer. Performed prechamber of any material, in particular of steel sheet. Oven prechamber is shown in Fig. 36.
The amount of air removed from the plenum chamber is determined by the velocity in the openings and their size. Speed is taken, depending on the degree of harmfulness of emissions and the temperature in the range from 0,5 to 1,5 m / sec.
If the device is not plenum chamber, then to trap harmful substances used umbrellas with overhangs (sometimes without overhangs, less rational), as well as slot and onboard pumps, located above the stove opening, or along the perimeter on three sides.
Umbrellas are acceptable only under the condition that runs from the furnace is not under an umbrella. Otherwise, the umbrella can
harm rather than good, especially when the toxic secretions of opening the oven.
Slot and onboard pumps are more effective than the umbrellas, but at significant rates in the slot suction. But they are indispensable if you are working have to stay near the stove opening for a long time. At high temperature in the furnace and toxic hazards are sometimes combined with a parasol slit suction.
Suction slit width varies from 40 to 150 mm, depending on the size of the opening, in particular of its height. Velocity in the gap to make selections with the allowable concentrations of up to 100 mg/m3 in the range of 6-8 m / sec, with an allowable discharge concentration of 10 mg/m3 - 8-12 m / sec and for particularly harmful emissions with the allowable concentration of 1 mg / m3 and below - 14-20 m / sec.
Define the desired amount of air removed by suction slot located over an aperture width of 800 mm and 1000 mm, from which intensively allocated sulfur dioxide.
Slit width of 150 mm accepted as the height of the opening is significant, and the length of the gap of 900 mm.
aspirated speed of 12 m / sec. The volume of air exhausted
L = 3600 вЂў 0,9 вЂў 0,15 вЂў 12 5 800 m3 / h.
Given the intense evolution of gas, more reliable in this case to designate the amount of exhaust air 7000 m3 / h.