Radioactive dust should be fully captured in all cases. In the sanitary rules work with radioactive substances is said that for the capture of radioactive aerosols must be carried out two-step purification of the extracted air. For the first-stage filters are generally recommended, and for the second - long staple fabric FPP.
We now turn to the critical Armillaria some ways to clean the air of dust.
As is known, the degree of purification is the ratio of the percentage of weight collected dust to the weight of dust contained in air to clean it. Coefficient of purification to a formula expressed
= D-A1 100 [%],( 73)
where D - the amount of dust in the air to clear a mg / m, Co - the amount of dust in the air after purification in mg / m
Fractional efficiency of dust - the detention determined by the following formula
where SF - coefficient of general cleaning in%;
bp - the content of n-th fraction of dust in% by weight; e - ratio for the treatment of n-th fraction in%.
Here is an example of determining the coefficient of general cleaning of dust following fractional composition: up to 5 l / s-Si = 15% to 10 microns - b2 = 20%, to 20 microns - b3 = 35%, and 40 MK-64 = 30% - Odds treatment for these fractions, respectively: e = 80%, e2 = 95%, E3 = 97%, E4 = 100%. Coefficient of general cleaning formula (75)
15-80 -: 20-95 35-97 - - 30-100 ps0, 100
- Dust arrester on the principle of operation can be divided into dry scrubbers and wet scrubbers. The first delay and collect dust in the dry state, the second - respectively in a damp or wet. Intermediaries between these groups are the so-called oil filters, where the dust comes in contact with a viscous liquid - oil.
Universal dust collectors that are suitable for all kinds of dust and for all initial concentrations, does not exist. Each type of dust collector is designed for a certain kind or kinds of dust and for a certain range of its initial concentration.
Cyclones trap dust only I, II and III classification groups. High efficiency cyclones, such as type NIOGAZa or with a reverse cone, catch 60-80% of the dust of group III. Irrigated Dust - cyclones - washers, scrubbers, foam, etc. - and captures dust III and IV of the classification groups, holding up to 65-85% of the dust of group IV.
Fabric Filters and electro - Dust holds up to 70-95% of the dust IV classification group. Dust V group of almost captured.
Dust V classification group is delayed only filters made of special fiber fabric, such as the type of PPP. Such filters are divided into three classes:
Class III-V of the dust does not delay; II class - holds up to 85-95% of the dust of group V; I class - holds up to 99% of the dust of group V.
From the dry dust collectors are most effective fabric filters, fine dust can hold at a high purification factor, amounting to 98-99%. This factor is largely dependent on the type of tissue. The result of treatment also depends on the specific load filter, which is recommended to take between 50 to 100 m3/ch-m2 depending on the type of dust and its initial concentration.
When filtering air containing lead dust, as a filter material used canvas, cloth, bike and bike with nylon. The load on the filter was adopted in 1950 m3 / h вЂў m2.
Cloth filters work well in dry not sticky and fibrous dust. But they are totally unsuitable for the wet air. These shortcomings need to carry a large air leak, reaching in some designs up to 25%. In SNIP 1-T. 5-62 (Table 6) indicated that: in the wet dust collector and dust collector - all kinds of washer can clean the air polluted with any dust, but the fiber;
in net dust collector can clean the air polluted with only fibrous dust.
However, according to the author, strainers, used sometimes for fibrous dust, in practice, have not justified. In periods of separation of the fibrous layer of the grid there is a significant breakthrough dust out. To apply these filters to trap dust from the fiber felt and fabric circles is not recommended.