Abstract: Because of the low concentration and active chemical properties, it has always been difficult to detect SO₃ in the coal burning flue gas for pollutant inspection domestically and abroad. Aiming at the problem of the low collection efficiency of SO₃ detection by control condensation method, the experiment was conducted based on the homegrown SO₃ calibration system. Study results show that:the collection efficiency can be effectively improved to over 90% through the application of the D-type condenser and filter membrane filter device with borosilicate glass fiber membrane, if the optimal sampling flow rate was kept at 20 L/min, and the heating temperature of sample tube, condenser pipe and filter was controlled precisely. Hence both the collection efficiency of SO₃ detection and the accuracy of test result are guaranteed. The enhanced control condensation method has been widely used in computer simulations under the conditions of low dust content with certain moisture and various concentrations of SO₃, and consequently can be implemented to examine the SO₃ concentration in fume for the entire coal-fired power industry.

Key words: SO₃ test, control condensation, capture efficiency, sampling flow, snake pipe, membrane filter