Air flow measurement of utility boilers is often liken by using venturi duct, latticed wing, multiple pilot tube and double venturi tube.

Based on the problems existed in Venturi tube throat of double Venturi tube wet cleaning system, the rectangle sizing throat is developed and designed.

Reasons of high efficiency dedusting and no settling dust and no abra-sion at the throat inlet of the system under the condition of no water With the double-Venturi Tube washing process are presented.