Deutsch-Anderson Equation

Deutsch-Anderson Equation
Probably the best way to gain insight into the process of electrostatic precipitation is
to study the relationship known as the Deutsch-Anderson equation. This equation is
used to determine the collection efficiency of the precipitator under ideal conditions.
The simplest form of the equation is given below.

This equation has been used extensively for many years to calculate theoretical collection

efficiencies. Unfortunately, while the equation is scientifically valid, a number of

operating parameters can cause the results to be in error by a factor of 2 or more. The

Deutsch-Anderson equation neglects three significant process variables. First, it completely

ignores the fact that dust reentrainment may occur during the rapping process.

Second, it assumes that the particle size and, consequently, the migration velocity are

uniform for all particles in the gas stream. As stated previously, this is not true; larger

particles generally have higher migration velocity rates than smaller particles do.

Third, it assumes that the gas flow rate is uniform everywhere across the precipitator

and that particle sneakage (particles escape capture) through the hopper section does

not occur. Particle sneakage can occur when the flue gas flows down through the hopper

section instead of through the ESP chambers, thus preventing particles from being

subjected to the electric field. Therefore, this equation should be used only for making

preliminary estimates of precipitator collection efficiency.

More accurate estimates of collection efficiency can be obtained by modifying the

Deutsch-Anderson equation. This is accomplished either by substituting the effective

precipitation rate, we, in place of the migration velocity, w, or by decreasing the calculation

of collection efficiency by a factor of k, which is constant (Matts-Ohnfeldt

equation). These calculations are used in establishing preliminary design parameters

of ESPs.