Device and method for detecting gas

Abstract

The invention provides a device and a method for detecting a gas. The device for detecting the gas comprises an FID detector; a negative pressure generation unit generates negative pressure relative to an upstream of a detection unit on a gas path at a downstream of the detection unit; the detection unit is provided with a first gas channel and a second gas channel which are arranged in parallel,and a sample gas sequentially penetrates through a first porous plate, an inner cavity and an outlet in the first gas channel; in the second gas channel, the sample gas sequentially penetrates throughthe second porous plate and an outer cavity; and the FID detector is arranged in the inner cavity, and the inner cavity is communicated with a fuel gas. The device and the method have advantages of high sensitivity, high accuracy and the like.

Description

technical field [0001] The invention relates to gas detection, in particular to a gas detection device and method. Background technique [0002] Hydrogen flame ionization detector (Flame ionization detector, FID) is considered as an ideal universal online detector due to its high sensitivity, strong anti-pollution ability and long service life. In the application scenario of online real-time monitoring of VOCs in petrochemical enterprises, in order to ensure an extremely fast response time of the system, it is a routine analysis idea to use large-flow direct sample injection and FID real-time detection. However, this analysis method has the following problems: [0003] 1. Since the analysis system samples and analyzes in real time, the pressure change of the sample gas will greatly affect the accuracy of the detection. [0004] 2. Since the FID is a micro-flow detector, direct large-flow sampling cannot guarantee the stable combustion of the hydrogen flame, and the detecto...

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Problems solved by technology

[0003] 1. Since the analysis system is real-time sampling and real-time analysis, the pressure change of the sample gas will greatly affect the accuracy of the detection

[0004] 2. Since the FID is a micro-flow detector, direct large-flow sampling cannot guarantee the stable combustion of the hydrogen flame, and the detector is difficult to work normally

Therefore, if you want to obtain a satisfactory response time in real-time monitoring, you must cooperate with a complex front-end sampling design, including large-flow sampling and sample splitting devices, which makes the overall gas path structure more complicated, increasing the volume, weight and cost of the instrument

[0005] 3. Many real-time monitoring conditions belong to continuous heavy pollution conditions, and FIDs are precision detectors, which cannot avoid periodic maintenance; and most FIDs generally have high requirements for on-site maintenance capabilities due to their complex designs

[0007] 1. Install a voltage stabilizing device at the FID injection port to ensure a stable injection volume; however, the accuracy of voltage stabilizing, the stability of the voltage stabilizing device, and the ability of the device to resist pollution and adsorption will directly affect the accuracy of FID detection. A voltage regulation scheme that perfectly integrates the above three appears

[0008] 2. The use of a suitable FID negative pressure sampling method can avoid the influence of sample gas pressure fluctuations on the accuracy of FID detection, but in order to ensure a fast enough response time, it is usually necessary to cooperate with a multi-stage sampling device to ensure both large flow sampling and micro flow Sampling, the overall flow path of the sampling device becomes quite complicated, and the requirements for the stability of the device are extremely high, and the risk of flow drift or even device failure is accompanied by long-term use

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