In the process of biogas engineering operation, it is necessary to use instruments to sense the state of the production process. In biogas engineering, there are mainly two kinds of measuring instruments: thermodynamic measuring instruments for detecting temperature, pressure, flow rate and liquid level; physical properties and composition instruments for detecting solid suspended matter concentration, turbidity, PH, COD, acid-proof volatile lipids, biogas composition, etc. The following biogas biological desulfurization equipment manufacturers give you a brief introduction to several commonly used automatic control system testing instruments, hoping to help you.
1. Pressure measuring instruments
Electrical pressure measuring instrument is to use the physical characteristics of metal or semiconductor to directly convert pressure into voltage or current signal output. The deformation of elastomer under pressure can also be transformed into voltage or current signal output by resistance strain gauge. In order to ensure that the elastic element works within the effective deformation range, the maximum pressure measured should not exceed 3/4 of the full range, and the minimum pressure should not be less than 1/3 of the full range.
Pressure information acquired by pressure sensor can be converted from pressure transmitter or pressure switch to standard electrical signal output, which can be output remotely. The pressure detector composed of sensors, transmitters or pressure switches can be used to monitor the pressure in pipelines, biogas fermentation devices and gas storage devices. Pressure measurements are often used as alarm parameters.
2. Flow meter
Flow detection instruments include flow meters for measuring unit time flow and accumulator for measuring total flow of fluid. Most flow detectors have the function of measuring both flow and total flow.
There are many ways to detect the flow rate, among which the electromagnetic flowmeter has advantages in detecting the flow rate of liquid-solid two-phase media because of its smooth sensor without obstruction components, which makes the pressure loss of the instrument very small and is not easy to block. Therefore, the sewage flow with certain conductivity is suitable for the detection of electromagnetic flowmeter, but if the sewage contains more ferromagnetic substances and a large number of bubbles, it will affect the measurement. Quantity accuracy. The installation of electromagnetic flowmeter requires that there are straight pipe sections before and after installation, whose length is not less than 5 times and its diameter is 3 times respectively.
For the detection of biogas flow, the commercial flow meter of natural gas is usually used. Because biogas is corrosive, there is a contradiction between the anti-corruption and the price of the instrument. At present, the leading technology in the world is the ultrasonic gas measurement technology. Compared with the traditional pressure differential flowmeter, vortex flowmeter and thermal flowmeter, the ultrasonic flowmeter has stronger corrosion resistance, wider range ratio and smaller pressure loss. It can meet the requirements of gas measurement with high pressure and large flow rate, and there is no mechanical movable parts which are easy to wear and tear. Long-term use accuracy is unchanged, with high measurement accuracy. It is worth mentioning that the BF-3000B ultrasonic biogas flowmeter, which is designed to be self-controlled and independently developed, also has the function of simultaneously measuring CH4 concentration and biogas flow rate.
3. Temperature Measuring Instrument
Temperature is one of the main factors affecting microbial activity. The fermentation process of biogas needs temperature control. Therefore, temperature detection instrument is indispensable. In temperature sensor, thermal resistance is a typical temperature measuring element suitable for detecting the temperature of biogas fermentation liquid, and its temperature measuring circuit adopts unbalanced bridge.
The temperature sensor is directly installed on the biogas fermentation device, which may be far away from the transmitter. The sensor and the transmitter are usually connected by three wires, one of which is connected in series in the power supply branch, and the other two are connected on two adjacent bridge walls. The three-wire connection method can basically eliminate the measurement errors caused by the connecting wires.
The secondary instruments connected with temperature sensors mainly include temperature transmitter, digital temperature display instrument and temperature patrol instrument.
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