With the acceleration of China's industrialization, the problem of environmental pollution has become more and more serious, and the society has become more and more vocal for sustainable development. The concept of harmonious coexistence between man and nature has been accepted by people, and the treatment of various kinds of pollution has become more urgent.In the process of sewage treatment, it is necessary to measure and control the discharge of sewage, additives and sludge, so the flow measurement is very important.Among the many flowmeter products used for sewage measurement, the electromagnetic flowmeter is dominant, both in terms of principle and measurement degree.

Electromagnetic flowmeter is composed of flow sensor and transmitter.The sensor measuring tube is equipped with excitation coil above and below. After the excitation current is switched on, a magnetic field is generated through the measuring tube. A pair of electrodes are installed on the inner wall of the measuring tube and in contact with the liquid, leading to the induced potential and sending it to the transmitter.The field current is provided by the transmitter.According to the assembly mode of transducer and sensor, there are two types: separable type and unibody type.In sewage treatment process, large diameter flowmeters are mostly split type, one part is installed underground, the other part is above ground.The small aperture is more than one.The principle of electromagnetic flowmeter is based on Faraday's law of electromagnetic induction.An induced voltage is generated when the conductive metal bar moves perpendicular to the magnetic field line at a certain speed.If the magnetic field strength is B, the length of the rod is L, and the velocity is V, then the induced voltage is generated.

At present, the function of electromagnetic flowmeter on the market is also very different, simple is just to measure one-way flow, only output analog signal to drive the back of the instrument;Intelligent electromagnetic flowmeter can measure two-way flow, range switch, upper and lower limit flow alarm, air tube and power cut alarm, small signal excising, flow display and total calculation, automatic check and fault self-diagnosis, communication with upper computer and motion configuration, etc.Some models of electromagnetic flowmeter serial digital communication function can be selected a variety of communication interfaces and special chip (ASIC), to connect HART protocol system, PROFTBUS, Modbus, FF field bus, etc.

The premise of using electromagnetic flowmeter is that the measured liquid must be conductive. The conductivity below the threshold will cause measurement error until it cannot be used. The measurement error beyond the threshold can be measured even if it changes.However, the conductivity of industrial water and its aqueous solution is greater than 10-4s /cm, the conductivity of acid, alkali and salt solution is between 10-4 ~ 10-1s /cm, so there is no problem with the use, and there is no problem with the low-grade distilled water being 10-5s /cm.Usually sewage conductivity is high, because it contains more ions, which is the electromagnetic flowmeter used to measure the advantage of sewage, by its measurement principle decided.

In addition, some characteristics of electromagnetic flowmeter also determine that compared with other flowmeter products, it is more suitable for sewage measurement.Electromagnetic flowmeter is not affected by the influence of external factors such as temperature, pressure, viscosity, measurements of the interior of the tube without shrinkage or bulge caused by the pressure loss, in addition, the flow element to detect the signal at the beginning, is an average flow velocity and fluid into the linear change of voltage, it has nothing to do with the other properties of the fluid, has the very big superiority.According to the sewage flow has a large change, containing impurities, corrosive small, certain conductivity characteristics, such as the measurement of sewage flow, electromagnetic flowmeter can be said to be the choice.

Moreover, the electromagnetic flowmeter is compact in structure, small in volume, convenient in installation, operation and maintenance. The measurement system adopts intelligent design, and the overall sealing is strengthened, so that it can work normally under severe environment.Compared with other flowmeter products, vortex flowmeter is difficult to enlarge its diameter due to technical reasons, and its quality and pipeline ultrasonic flowmeter lacks competitive advantage in price relative to electromagnetic.Therefore, in the water supply and drainage and sewage treatment industry, the electromagnetic flowmeter, especially the large-diameter electromagnetic flowmeter, has a great advantage and has been widely used.

Sewage treatment technology is mainly through biological oxidation, flocculation, precipitation and other processes to achieve the purpose of sewage purification, in each stage requires a certain flow meter for measurement.In the process of sewage treatment, corresponding measuring instruments should be configured according to the process requirements to form a reliable control system.

Generally, sewage treatment plants need to be equipped with flow meters in the following process testing procedures:

(1) Water inlet pipe;

(2) Detection of sludge volume from the initial settling tank to the mud storage tank;

(3) Sludge pump room surplus, sludge flow detection;

(4) Sludge flow test of the sludge pump house;

(5) Test the water flow rate of the distribution well in the secondary sedimentation tank;

(6) Detection of sludge intake in digester;

(7) Detection of sludge output from digester;

(8) Flocculation tank dosage detection, etc.

So, sewage treatment is inseparable from the electromagnetic flowmeter.With increasing attention to environmental protection, electromagnetic flowmeters used in sewage treatment will also have a booming market.

Related products: Split electromagnetic flow meter, Electromagnetic heat meter, Electromagnetic water meter