Filter presses smarter just to put a collapsible shelter with shutters. As for the vacuum-filter, then to conclude such a shelter is almost completely fails, because in some cases it is necessary to periodically remove the drum filter with a crane.
Local suction from the vacuum filter can be implemented in two ways. The most effective suction, if the drum filter and part of its trough on the side opposite the device for removal of filtered sediment covered with a removable (convertible) housing, usually consisting of several sections. The casing is made of steel or plastic. One of the designs of such shelters is schematically shown in Fig. 33. In the fixed parts of the shelter there are two openings for connecting ducts.
If you can not install a local suction casing is carried out by the slit, is located on the long side / troughs in front of the device for removal of sediment.
The amount of air exhausted from one filter to filter surface from 30 to 45 m2, in the presence of the casing can be made about 3000 - 6000 Martyrs, depending on the solution temperature, casing design and toxicity of the discharge. When the local suction slit exhaust air volume for the same filters can be administered in the range from 5000 to 8000 m3 / h.
In addition to rotary vacuum filters, belt filters are used, under certain conditions is also a source of hazards.
Belt filters are not usually cover the entire length, but only in the part, the PA which is an allocation of hazards. Secrete most rationally filters housings with hinged shutters. Such a cover is shown in Fig. 34. Dimensions folding curtains can take 600x250 mm. With a length of sheltered part of the filter 6 m number of curtains with two one hundred-
swarms is found to be twenty. For most cases the practice can be considered simultaneously open up to eight openings.
In determining the amount of exhaust air, except for open apertures, you must take into consideration the area of cracks. For this cover, bearing in mind the existence of gaps in its ends, securely take the coefficient k = 1,3-7-1,4.
For shelter with eight simultaneously open aperture when v = \ m / s and h = 1.4 volume of air exhausted will be
L = 3600 вЂў 0,6 вЂў 0,25 вЂў 8 вЂў 1 вЂў 1,4 6 000 m3 / h.
Allocation of gas and dust hazards of rotary kilns is possible in areas of the drum with stationary parts of the furnace. Although the furnaces of the last designs hold special seals from blowing air at the furnace operating under vacuum, the breakthrough of gas and dust is still possible, especially when a deviation from the normal course of the process.
To avoid breaks in the premises of gases and dust from furnaces recommended Semiring slotted suction device of the type shown in Fig. 35. Such local pumps are usually arranged in the combustion head, at least - at both ends of a rotating drum.
Amount of air that is necessary to extract the local suction of a rotary kiln, depending on the diameter of the drum, the degree of sealing joints rotating and stationary parts and the toxicity of pollutant emitted. The slit width is usually given between 100 to 250 mm. speed aspirated into the slit made of 3 to 5 m / sec. Under these conditions the furnace diameter of 1,5 m and a slit width of 150 mm and a speed of aspirated 3 m / sec the amount of air will be removed
L = 3600-3,14-0,75-0,15-33800 m3 / h.
The chemical industry is often used tunnel kiln and dryer. Evolved in these reaction gases and vapors discharged out process piping by mechanical or natural draft. In such furnaces and heating the dried usually electric or infrared emitters, chimneys they do not have. Air velocity in the openings oven or dryer, created by the technological stretch, it is often insufficient to prevent knocking hazards in the room. Have to resort to additional ventilation measures.