To investigate the distribution rules of ash and sulfur in tail flue of high sulfur coal-fired boiler

an ultra low temperature economizer test bench for high sulfur coal-fired power unit was built up

on which the mass concentration of fly ash and SO3 on different sections at inlet and outlet flue of the ultra low temperature economizer were tested. The results show that

the fly ash mass concentration in horizontal flue pipe in front of the ultra low temperature economizer was high at the bottom and low at the top

while the SO3 mass concentration was high at the top and low at the bottom

and the ash-sulfur ratio was high at the bottom and low at the top. There was no significant difference in SO3 mass concentration in different sections of the horizontal flue pipe behind the ultra low temperature economizer. The SO3 mass concentration in vertical flue pipe behind the ultra low temperature economizer was high at the side and low in the center. The recommended safe ash-sulfur ratio is 150 when the ultra low temperature economizer is arranged in horizontal flue pipe and 100 when it is arranged in vertical flue pipe. The physical adsorption rate of fly ash to SO3 was 15.69%～32.45%. The physical adsorption rate of fly ash to SO3 was proportional to the mass concentration of fly ash. The higher the total SO3 mass concentration

the lower the physical adsorption rate of fly ash to SO3.