Abstract: Scaling and wearing tend to happen on the sampling probe of pH meters and density meters used in lime-gypsum FGD system of thermal power plants, which leads to frequent clogging in the measuring pipeline and deviation, even distortion in pH value and density measurement for the desulfurization tower slurry. Therefore, an improved pH sampling device is designed, adopting the diaphragm pressure transmitter instead of the traditional densimeter. Combined with the FGD project for three 75-t/h circulating fluidized bed boilers in the No.1 combined heat and power plant for Shanxi Datuhe Coking and Chemical Co., Ltd., the principle and application of the design is introduced. The experimental results show that the improved pH sampling device can effectively protect the sampling probe with better practicability and economics. The diaphragm pressure transmitter also has dual functions, i.e., monitoring the density and liquid level of the slurry in the desulfurization tower, which requires less maintenance work and is more suitable for engineering application.

Key words: FGD, pH meter, density meter, diaphragm pressure transmitter