Degree of separation

The separation efficiency  η ( English separation efficiency in) describes process technology , the efficiency of a deposition and separation process .

definition

The degree of separation is defined as the ratio of the amount or concentration of the substance to be separated (e.g. dust ) that is separated in the system ( filter , mass force separator ) to that which has entered the system:

${\displaystyle {\begin{aligned}\eta &={\frac {c_{0}-c_{1}}{c_{0}}}\\&=1-{\frac {c_{1}}{c_{0}}}<100\%\\&=1-P\end{aligned}}}$

With

• the original concentration  c ₀
• the secluded concentration ${\displaystyle c_{0}-c_{1}}$
• the achieved concentration  c ₁
• the penetration  (see dust separation efficiency ). ${\displaystyle P={\frac {c_{1}}{c_{0}}}}$

Special degrees of separation

Fractional separation efficiency

Since the degree of separation alone does not allow a generally binding assessment of the properties of a separator, the separation properties are often viewed as a function of the particle diameter  d _{p of} the substance to be separated. This results in analogous to the degree of separation of the fraction degree of   separation η (d _p ) , as z. B. is used when dividing particle and dust filters into filter classes:

${\displaystyle \eta (d_{p})={\frac {c_{0}(d_{p})-c_{1}(d_{p})}{c_{0}(d_{p})}}}$

The fraction degree of separation is also called the degree of separation .

Single fiber separation rate

Another parameter in this context is the individual fiber separation efficiency , which describes the filtration through depth filters with fibers as a model. It makes sense to consider a single fiber, as sieve effects can usually be ruled out due to the high porosity of filter materials .

detection

Degrees of separation depend u. a. on the gas temperature and the flow velocity . They should therefore only be mentioned in connection with the respective test method .

When testing particle air filters , the degrees of separation are determined gravimetrically .

literature

• VDI 3677 Part 2: 2004-02 Filtering separators; Depth fiber filters (filtering separators). Beuth Verlag, Berlin. ( Summary and table of contents online )

Individual evidence

1. ↑ ^{a b} VDI 3677 sheet 2: 2004-02 Filtering separators; Depth fiber filters (filtering separators). Beuth Verlag, Berlin, p. 5.
2. ↑ VDI 3676: 1999-09 Inertial Separators. Beuth Verlag, Berlin. P. 5.
3. ↑ VDI 3677 sheet 2: 2004-02 Filtering separators; Depth fiber filters (filtering separators). Beuth Verlag, Berlin, p. 6.
4. ↑ VDI 3679 sheet 1: 2014-07 wet separator; Basics, waste gas cleaning of particulate matter (wet separators; Fundamentals, waste gas cleaning of particle collections). Beuth Verlag, Berlin. P. 6.
5. ↑ VDI 3677 sheet 2: 2004-02 Filtering separators; Depth fiber filters (filtering separators). Beuth Verlag, Berlin, p. 12.
6. ↑ Horst Bartz, Christoph Helsper: Theoretical calculation of the degree of separation of a filter in different operating states . In: Dust - cleanliness. Air . 47, No. 3/4, 1987, ISSN  0949-8036 , pp. 112-114.
7. ↑ DIN EN 779: 2012-10 Particle air filters for general ventilation technology; Determination of the filter performance; German version EN 779: 2012. Beuth Verlag, Berlin, p. 7.