Fiber-containing slurry can use slurry electromagnetic flowmeter

　　Precautions for measuring coal slurry with slurry electromagnetic flowmeter:

　　1. The complex composition of coal slurry makes it easy for measurement-related equipment to be damaged, which brings difficulties to measurement. Since coal contains metals such as iron wire and copper wire during mining, it is conveyed to the rod mill or ball mill through a belt and ground with additives such as papermaking waste liquid and methanol wastewater. The content is 60%~70% and the working density is 12500. When the rod mill or ball mill grinds the coal, some metal particles will fall off further, and subsequent equipment cannot filter and remove the metal particles contained in the water-coal slurry. The impact and wear during the metering process can easily cause damage to the main and auxiliary metering equipment such as the pressure pump.

　　2. Measurement difficulties caused by the characteristics of water-coal slurry When measuring the flow of liquid-solid mixed conductive media such as water-coal slurry and slurry, when solid particles or fiber media rub against the electrode surface, the contact electrochemical potential of the electrode surface changes suddenly, resulting in sharp pulse slurry (interference) noise in the electrode detection signal output by the sensor, which will cause fluctuations in display and signal output, which is equal to 1 times the sensor excitation current frequency. The friction of metal particles will produce more serious instantaneous sharp pulse interference, which will cause serious signal interference and lead to unstable measurement.

　　3. Measurement difficulties caused by booster pumps When booster pumps are working, pulsating flow is inevitable. It is basically used in the pressurization link of water-coal slurry manufacturing and ordinary boiler combustion. Due to its structure and working mode, the pulsating flow of the screw pump fluctuates very little at different speeds (the fluctuation is generally 0.5%~5%), which generally does not affect the measurement and control application. Due to its working principle and structure, even when working at full load, the pulsating flow of the pressurized liquid fluctuates greatly (the fluctuation is generally 6%~15%). If a working chamber of the coal slurry pump has a problem after long-term operation, its pulsation will further increase, and the working status of each working chamber cannot be monitored in the central control room, and can only be reflected in the instantaneous display and signal output fluctuations.

　　4. Measurement difficulties caused by coal slurry pipeline factors The coal slurry pipeline of the gasifier is generally made of 20# carbon steel. When the coal slurry transportation stops, the inner wall of the pipeline will oxidize and produce a large amount of rust. The friction of the water-coal slurry on the inner wall of the pipeline will fall off fine carbon steel particles, which will be wrapped in the coal slurry. When working, the magnetic field generated in the sensor measurement cavity will magnetize the metal particles, causing the metal particles in the coal slurry to adsorb near the measuring electrode, forming a polarization voltage on the electrode, increasing the measurement accuracy and further increasing the fluctuation. This problem basically does not exist in stainless steel pipelines.