Application Case of VOCs Online Monitoring with Miniature Pump

Background introduction:

VOCs, volatile organic compounds, refer to chemical substances with a melting point below room temperature and a boiling point between 50 and 260°C. VOCs are extremely harmful to the human body. When the concentration of volatile organic compounds in indoor air is too high, it is easy to cause acute poisoning. In recent years, with the continuous deepening of people’s green environmental protection awareness, governments and factories and enterprises have attached more importance to online monitoring, prevention and control of VOCs. VOCs monitoring is currently a key project in atmospheric monitoring. Due to the complex composition of waste gas VOCS and the harsh monitoring environment, the requirements for monitoring equipment are also very high.

Application introduction:

As the power part of VOCs online monitoring instrument gas sampling, miniature gas pump is a crucial equipment. The miniature pump transports the environmental waste gas to the analysis unit for analysis and detection through the sampling gas path. In addition, the pretreatment link of VOCs online monitoring instrument equipment also involves the condensation and water removal part, which requires the use of miniature liquid pump to discharge the water in the condenser.

1.Main links of VOCs online monitoring:

• Brief explanation of VOCs online monitoring principle:
• The sample gas is transported to the analysis unit by a miniature gas pump, which includes two links: sampling and pretreatment. The pretreatment link filters and removes water from the sample gas, while the liquid pump is responsible for discharging the liquid after condensation;
• The analysis unit detects and analyzes the processed sample gas and then discharges it, while feeding back the analysis results to the acquisition module, which is then uploaded to the monitoring system or mobile APP through wireless DTU module;

(3) The monitoring system can give signals to the control module through DTU module to indirectly control the start-stop of sampling pump, adjust flow rate or control other units.

3.Precautions:

 (1) The selected sealed container needs to have a certain negative pressure resistance ability, and it is best that there is a discharge channel at the bottom of the container;

(2) The selected liquid level sensor needs to have a certain corrosion resistance, some use scenarios and cannot pollute medium.

Project difficulties:

1.Online monitoring requires miniature pumps to run continuously day and night without stopping for long life and maintenance-free;

2.The complex composition of sample gas requires miniature pumps to have certain corrosion resistance, with extremely high requirements for pump quality and material;

3.The harsh monitoring environment requires miniature pumps to be able to work at high temperatures and tolerate high-temperature media;

4.Miniature pumps need to be remotely controlled for start-stop, flow adjustment and online feedback on pump operation.

Solutions:

1.Hilin Technology’s product system includes: miniature vacuum pump, compressor and miniature liquid pump, and the liquid pump can dry run. For example, Hilin Technology can provide both sampling pump and liquid pump at the same time in this case;

2.Hilin Technology’s full range of miniature pumps have strict life testing, each model is divided into roughly three versions according to life and performance: “Simplified version”, “Standard version” and “Premium version”. The premium version of some models can work continuously for up to 10,000 hours. Miniature pump life test conditions: “In a clean non-corrosive laboratory environment, full load operation (sealing suction port, exhaust port connected with atmosphere), continuous operation day and night; ambient temperature: 5°C～33°C, fluctuating with climate; relative humidity 30%～90%, fluctuating with climate.” At the same time, all series pumps have self-protection functions such as overload protection and overheat protection;

3.Hilin Technology’s full range of miniature diaphragm pumps use reinforced nylon and EPDM rubber materials for gas contact materials, which have good corrosion resistance for common acid-base gases and liquids;

4.The working temperature and medium temperature tolerance ability of Hilin Technology’s full range of miniature pumps are around 0-50°C for conventional models, but our company can also provide customized services for high-low temperature tolerance within 100°C or above 60°C high-temperature environment;

5.Hilin Technology’s full range of miniature pumps have versions with adjustable speed functions. The pump speed adjustment methods are diverse, and customers can choose different speed adjustment versions according to their usage. The speed adjustment methods are generally divided into voltage speed control, frequency speed control, touch control, and PWM speed control.

For the above case, frequency adjustment, voltage adjustment or PWM adjustment can be selected to facilitate remote flow rate adjustment. Most models have a remote start-stop version, which can be combined with the user’s on-site control unit to achieve remote control of the pump start-stop. In addition, some model versions also have RS-485 communication function to realize remote monitoring of working conditions, such as the top configuration of the 50 series and 60 series