Application of electromagnetic flowmeter in chlor

2022-06-09
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Application of electromagnetic flowmeter in chlor alkali industry

1 Principle and advantages of electromagnetic flowmeter

1.1 measurement principle of electromagnetic flowmeter

electromagnetic flowmeter works based on Faraday's law of electromagnetic induction of compressive strength/flexural strength and is composed of sensor and converter. The sensor is mainly composed of measuring tube lined with insulating material It is composed of a pair of electrodes installed through the wall of the measuring pipe, a pair of coils and iron core used to generate working magnetic field. When the conductive medium flows through the measuring tube of the sensor, there is a stable magnetic field with magnetic induction intensity generated by the transmitter in an interval perpendicular to the flow direction of the medium. When the conductive fluid with average flow velocity flows through the magnetic field area, it moves to cut the magnetic line of force. Therefore, the induced potential is generated on the two detection electrodes parallel to the cross-section of the pipeline and perpendicular to the direction of the magnetic line of force. According to the law of electromagnetic induction, the instrument constant is a constant when the pipeline diameter D has been determined and the magnetic induction intensity remains unchanged. At this time, the induced potential has a linear relationship with the volume flow, that is, the induced potential E and the volume flow Q of the medium are measured

1.2 main technical parameters

maximum flow rate: 15m/S; Accuracy: DN15 ~ DN600, ± 0.3% of the indicated value, DN700 ~ dn24000, ± 0.5% of the indicated value; Fluid conductivity: not less than 5p. S/cm; Maximum fluid temperature: ordinary type, 70oC; Parting type: PTFE lining, 100oC, neoprene lining, 80 ℃, polyurethane lining, 80 ℃, polypropylene lining, 100 ℃

① the flowmeter has the advantages of small measurement of energy and suspended particles, and can measure the pressure of

2 Application of electromagnetic flowmeter in chlor alkali measurement

2.1 suitability of electromagnetic flowmeter in chlor alkali measurement

chlor alkali industry mainly measures brine and caustic soda, which have common characteristics: ① the composition of brine is complex, sometimes acidic and sometimes alkaline, and may contain free chlorine due to unclean dechlorination of ionic membrane, both of which have strong corrosivity. ② Both are conductive media. ③ In the chlor alkali plants in the north, due to the low temperature in winter, the salt deposition phenomenon occurs in the brine pipeline, and the salt will be precipitated with the decrease of temperature during the escort process; Ionic membrane caustic soda will crystallize at about 3 ~ C; When the pipeline is long and intermittently escorted, our factory also showed 32% caustic soda crystallization in winter, resulting in pipeline infarction, so both measured media will contain solid particles. ④ The temperature of both media is below 100oC.

according to the characteristics of the measured media and the advantages of electromagnetic flowmeter, it can be seen that electromagnetic flowmeter is very suitable for chlor alkali metering. Although the price of electromagnetic flowmeter is expensive, it has high precision, small maintenance, long service life and high cost performance

differential pressure flowmeter, turbine flowmeter and elliptical gear flowmeter are affected by fluid working state, fluid density, viscosity and other parameters, which increases the measurement error. Due to the wear of solid particles, the service life of the measuring element is reduced, and even the blockage can not be used, and the corrosivity can not be solved. Our factory used elliptical gear flowmeter to measure diaphragm electrolyte, but it was stopped due to the precipitation and blockage of salt in electrolyte, and finally replaced with electromagnetic flowmeter

2.2 selection of electromagnetic flowmeter

2.2.1 selection principle of electromagnetic flowmeter: ① considering the diameter and range, although the range of electromagnetic flowmeter is set arbitrarily, its setting range is limited by the diameter. The setting of measuring range should consider that the normal flow exceeds half of the full range, so that the measurement accuracy is high. The flow rate is generally 2 ~ 4rn/s. for example, if the medium wears the electrode or the medium flows by itself according to the level difference of the high-level tank, a slightly lower flow rate in 2013 can be selected; If the medium is easy to adhere, the appropriate high flow rate can be selected. After comprehensive consideration, the diameter of the instrument shall be selected according to the flowmeter

② the measured fluid must be conductive liquid or slurry, and its conductivity should not be less than 5 ~ s/cm. The measured fluid should not contain more ferromagnetic substances or bubbles; The corresponding pressure grade, lining material, electrode material and instrument structure shall be selected according to the temperature, working pressure, corrosivity, abrasiveness and other characteristics of the measured fluid. (end)

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