As is well known, in order to ensure the safe and stable operation of the RTO incineration device, an LEL online analyzer needs to be installed to measure the volume fraction of combustible gas components in VOCs before entering the RTO furnace, in order to monitor in real time whether the VOCs concentration exceeds 25% LEL. When the concentration of VOCs exceeds the set value, it will trigger a high alarm or even a high high interlock, causing the pneumatic cut-off valve on the VOCs collection exhaust gas pipeline to close and the emergency bypass valve for exhaust gas to open, preventing production accidents caused by untimely operation.

At present, the analyzers that can be used to measure the volume fraction of combustible gas components in mixed combustible gases mainly include flame temperature analyzers (FTA), catalytic combustion gas detectors (CAT), hydrogen ion flame gas chromatographs (FID), and infrared gas analyzers.

Today we will talk about the most expensive LEL instrument among them, which is the FTA type LEL monitoring instrument.

Depth principle

The flame temperature analyzer (FTA) is equipped with an accurately calculated combustion flame inside. The sample gas enters the combustion chamber through the sampling pipeline from the process pipeline. As the temperature rise is proportional to the concentration of the combustible gas at the lower limit of combustion (LFL or LEL) from 0 to 100%, the thermocouple located near the sensing flame will convert the generated temperature rise into an electrical signal, which will be displayed intuitively on the instrument panel for easy data reading and operation by relevant personnel.

The controller is an electronic measurement and control device installed inside the sensor housing, used to condition and convert signals from thermocouples and sensors, and perform control, alarm, and output functions. The controller amplifies the thermocouple signal and processes the digital signal to obtain the final calibrated flammability reading, and promptly issues an alarm, adjusts the flame chamber temperature, monitors the sample flow rate, and sends a fault signal when improper operation is detected. The FTA analyzer has a rapid response time (<1 s) and can directly measure the VOCs/combustible gas concentration of samples in VOCs exhaust gas pipelines. Therefore, using an FTA analyzer before VOCs waste gas enters the RTO furnace is more accurate and reasonable, and has higher safety performance.