A synchronous detection system for a trace nitrogen-oxygen compound based on photoacoustic spectrometry, comprising a NOx (Nitrogen Oxide) detection air channel, a dust detection air channel and a double-photoacoustic spectrometry detection mechanism which are mutually connected in parallel;
- wherein:
- the NOx detection air channel comprises a front air pipe, a background interference detection air pipe, a NO2 detection air pipe and a NO detection air pipe that communicate with the front air pipe through a four-way control valve and are mutually connected in parallel, a rear air pipe communicating with the background interference detection air pipe, the NO2 detection air pipe and the NO detection air pipe through a four-way pipe, and a NOx photoacoustic detection cavity communicating with the rear air pipe;
- and a filtering membrane is mounted on the front air pipe, a NOx activated carbon adsorbent is filled in the background interference detection air pipe, and a mercury lamp is mounted on the NO detection air pipe;
- the dust detection air channel comprises a dust detection air pipe and a dust photoacoustic detection cavity communicating with the dust detection air pipe;
- the double-photoacoustic spectrometry detection mechanism comprises a laser device configured to emit laser to the NOx photoacoustic detection cavity and the dust photoacoustic detection cavity, a signal modulator connected with the laser device, a lock-in amplifier connected with the signal modulator, a computer connected with the lock-in amplifier, a rheomicrophone I mounted on the NOx photoacoustic detection cavity and connected with the lock-in amplifier, and a rheomicrophone II mounted on the dust photoacoustic detection cavity and connected with the lock-in amplifier;
- the NOx photoacoustic detection cavity and the dust photoacoustic detection cavity are arranged side by side, the laser device aligns with the NOx photoacoustic detection cavity, the double-photoacoustic spectrometry detection mechanism further comprises two reflecting mirrors separately arranged on rear sides of the NOx photoacoustic detection cavity and the dust photoacoustic detection cavity, and the laser, emitted from the NOx photoacoustic detection cavity, irradiates into the dust photoacoustic detection cavity through the two reflecting mirrors;
- front ends of the NOx detection air channel and the dust detection air channel are connected with an air inlet pipe through a three-way pipe while rear ends of the NOx detection air channel and the dust detection air channel are connected with an air outlet pipe through the three-way pipe, and a sampling pump is mounted on the air outlet pipe;
- a detection method for a gas mass content by the synchronous detection system for the trace nitrogen-oxygen compound based on the photoacoustic spectrometry comprises the following steps of:
- synchronously inputting to-be-tested gas to the NOx detection air channel and the dust detection air channel;
- starting the double-photoacoustic spectrometry detection mechanism, wherein:
- the to-be-tested gas entering the NOx detection air channel enters the NOx photoacoustic detection cavity through the background interference detection air pipe, the NO2 detection air pipe and the NO detection air pipe in respective under the control of the four-way control valve, a local interference gas content Sbackground, a NO2 gas content SNO2 and a NO gas content SNO in the to-be-tested gas are separately obtained upon the detection of the double-photoacoustic spectrometry detection mechanism, and the to-be-tested gas entering the dust detection air channel enters the dust photoacoustic detection cavity and is subjected to the detection of the double-photoacoustic spectrometry detection mechanism, to obtain a dust content Sdust in the to-be-tested gas;
- and a rear end of the ONx detection air channel is provided with a flowmeter I configured to control a gas flow of the NOx photoacoustic detection cavity, a rear end of the dust detection air channel is provided with a flowmeter II configured to control a gas flow of the dust photoacoustic detection cavity, and the NO detection air pipe is provided with a flowmeter III configured to control a gas flow that flows through the mercury lamp and participates in a reaction.