UV Camera Sensing Detection Device And Its Application To Detection Of Sulfur Dioxide In Ports

The emission of atmospheric pollutants is increasing,that has caused great damage to the atmospheric environment.Taking SO₂as an example,a large amount of SO₂is emitted globally every year,which forms acid rain,smoke,and damages ecosystems.At the same time,the requirements for pollution detection and monitoring technology are getting higher and higher,requiring higher detection accuracy and more convenient and rapid detection methods.Taking SO₂monitoring of port ship exhaust as an example,due to the limitations of traditional boarding sampling detection technology,It is necessary to develop a technology that enables rapid remote detection at the site.Most of the pollutants in the atmosphere,such as SO₂,NO_x,H₂S,etc.,have UV-specific absorption of different wavelength bands,and the UV camera could quickly capture the change of UV light from a long distance.This feature can be combined with an UV camera to develop UV camera sensing detection technology.At present,UV camera sensing detection technology has been researched in the fields of volcanic flue gas,factory exhaust gas and ship exhaust gas detection due to its rapid and convenient detection and long-distance（≦3 km）detection.After years of development,UV camera sensing detection technology is getting more and more attention.In this paper,the UV camera sensing detection device was developed,and the optical path system,air chamber system and concentration detection system of the device were designed to adjust the optimal detection performance of the device.The rapid detection of gaseous pollutants with UV absorption characteristics was obtained.The device was applied to the detection of SO₂,and a new method for rapidly detecting SO₂in gas was established.Under the optimal detection conditions,the preliminary detection and analysis of SO₂in the main outdoor and port pollution sources was realized.The main work is as follows:1.The UV camera sensing detection device was designed and developed,and the detection performance of the device for the detection of gaseous pollutants was optimized.The UV camera sensing detection device is mainly composed of four parts:the optical path system,the air chamber system,the gas adjusting device and the concentration detecting system.（1）Optical path system:it mainly includes UV light source,light-incident optical fiber and optical path converter;200-400 nm UV light generated by UV light source is introduced into the gas absorption pool by optical fiber;optical path converter can realize UV camera or spectrometer under the same optical path detection.（2）Air chamber system:it mainly includes White structure gas absorption pool,gas temperature controller and air pressure monitor;the multiple-returned White-pool structure can reduce the volume of the gas absorption pool and reduce the sample usage,and greatly increase the optical path.The length improves the detection accuracy;the temperature controller and the air pressure monitor can realize the control of the temperature of the gas to be tested and the monitoring of the air pressure.（3）Gas regulating device:it mainly includes a gas mixer,a humidity generator,a humidity detector,a temperature controller,a standard gas,etc.;the large concentration of the standard gas is adjusted by the gas mixer to adjust the concentration and the flow rate,and is adjusted by the humidity generator.The humidity of the gas is finally detected by the conduit to pass the gas to be tested with a certain concentration,humidity and flow rate into the gas absorption cell.（4）Concentration detection system:it mainly includes UV camera,filter set and spectrometer;high-sensitivity UV camera with multiple filters of different bands can realize high-precision fast sensing detection of the object to be tested;the spectrometer realizes synchronous correction detection of the entire detection device.By optimizing the equipment,the gas reservoir with a volume of 362 ml has an optical path length of 4.2 meters.The gas can be precisely adjusted to a concentration of2.62 mg/m³,the temperature is adjusted to 5-45℃,and the relative humidity is adjusted to35-85%RH.Filters were obtained suitable for SO₂detection.They have five band:270 nm,280 nm,300 nm,310 nm,and 340 nm,and the 340 nm band filter can removes black carbon interference from the exhaust.Performance test results show that the device has good air tightness.Within 1.5 hours after sealing the gas,the change of the spectrometer test result was 7.41%,and the change of the UV camera test result within 1 hour was 6.98%;the spectrometer test result proves that the device can be stabilized within 50 seconds.Within the next 30 minutes,the UV camera sensing results were also stable.The standard deviation of the four detection results of the spectrometer was 0.54%,and the UV camera repeats 9times to detect different concentrations of SO₂,the standard deviation was less than 3.53%,which proves that the device has good repeat-ability in detection and could detect gaseous pollutants.2.A new method of SO₂rapid sensing detection was established by using a UV camera to capture the detection device.According to the characteristics of SO₂in the actual pollution source,this work used the device to obtain SO₂with different concentration,temperature and humidity and detected it.Set the SO₂detection concentration interval to 0-2617 mg/m³,the concentration interval was 261.7 mg/m³;the temperature was set between 5-45℃,the temperature interval was 10℃;the relative humidity changes range from 35-85%RH,and the variation interval was 10%RH.The standard deviation of the 30 sets of detection data for each concentration under each filter was within 7.65%.The results of the 270 nm and280 nm bands were fitted by quadratic polynomial,and the results of the 30 0nm and 310 nm bands were linearly fitted.Their R²were 0.9991,0.9991,0.9909,and 0.9986,and they all have good fit.The standard deviation of each filter in each group of 30 temperatures was within 4.70%,and was detected in the 270 nm,280 nm,300 nm,and 310 nm bands.The results showed that R²was 0.9501,0.9596,0.9764 and 0.9752 after linear fitting.For the relative humidity of gas between 35-85%RH,the detection method for the SO₂detection results of different humidity,the RSD of different band filters was less than 4.67%,the effect of humidity on the test results could be ignored.By using partial least squares modeling for 11 sets of test data,the R²obtained by verifying the randomly selected verification set was greater than 0.98.The result proves that under the action of the detection device,the new detection method of SO₂has higher detection accuracy.3.The newly established SO₂rapid sensing detection method was applied to the detection of simulated pollution sources and port pollution sources.The simulated pollution source is two quartz glass boxes with a side length of 50 cm,which are filled with 1300mg/m³of sulfur dioxide and nitrogen.They were placed on the roof of the Chengdu area and the Shenzhen Sea;the port pollution source was the exhaust of three ships from Hong Kong ports.In the actual environment,the UV light source was sunlight,the detection equipment was the UV camera and the filter group in the concentration detection system;the UV camera sets appropriate exposure time,focal length and aperture according to environmental conditions,the hood was used larger than 11 mm to avoid the influence of different solar elevation angles.The sky was used as a background to achieve a uniform background.At different sensing points with a distance of less than 200 meters,the detection method can detect the SO₂gas in the simulated pollution source.In this work,three ships entering and leaving the port of Hong Kong were detected.The results show that the experiment can select the appropriate parameters to estimate the SO₂content in the ship’s exhaust gas.And the SO₂concentration of the exhaust gases of the three ships did not exceed the standard.