Parameter analysis on SO₃ measurement in coal-fired flue gas with controlled condensation method

The accurate, repeatable, and verifiable measurement of SO3/H2SO4 is significant to the reliability operation of coal-fired power plants, as well as environment protection and human health. Although the amount of SO3 in flue gas is very small, and its chemical property is extremely active, the measurement of SO3/H2SO4 is difficult and problematic. The measurement errors of controlled condensation method for SO3/H2SO4 in flue gas were evaluated with a sampling system based on dilute sulfuric acid heating method. In order to improve the test accuracy of this method, the effects of water bath temperature, flue gas sampling flow rate, and spiral condensing tube structure parameters (inner diameter and length of spiral condensing tube) on the recovery efficiency of SO3/H2SO4 were investigated. The results indicate that the recovery efficiency fluctuates in the range between 84.1% and 91.6%, with the water bath temperature increasing from 40 degrees C to 90 degrees C. As the flue gas sampling flow rate increases from .5 L/min to 4 L/min, the recovery efficiency of SO3/H2SO4 shows a gradual tendency of increasing, and the recovery efficiency can be high up to 98.4%. When the inner diameter of the spiral condensing tube increases from 3 mm to 10 mm, the recovery efficiency of SO3/H2SO4 decreases gradually. The recovery efficiency of SO3/H2SO4 increases gradually with the spiral condensing tube length increasing from 900 mm to 2000 mm.