Development of the carbon dioxide laser detection system for grain storage based on TDLAS

Abstract: During the grain storage process,microbes and all kinds of pests make up the biological field,The temperature and humidity of the grain stored in the granary constitute the abiotic field of the granary environment,the combined effects of biological and abiotic fields in granary will affect the stored grain and reduce its quality,and then affect the safety of grain storage in the grain depot. The concentration of carbon dioxide in grain storage reflects the condition of grain storage biological field and is an important index for monitoring grain storage biological field.In order to realize the high precision detection of carbon dioxide concentration of grain stored in grain depot,the study is based on Tunable Diode Laser Absorption Spectroscopy (TDLAS),the tunable semiconductor laser absorption spectroscopy is characterized by high sensitivity and fast response,a system for real-time detection of carbon dioxide concentration in grain storage was developed.In addition,the method of carbon dioxide laser spectrum analysis and data processing is also established.In order to achieve the portable requirements of the stored grain carbon dioxide detector,the carbon dioxide detection system is designed with a compact mechanism,the system can not only detect the carbon dioxide concentration of grain stored in the grain depot, but also detect the change of temperature and humidity, so that the detection of the three integrated.At the same time, the detection system designed in this study can also complete the conditioning of weak signals.Calculating carbon dioxide concentration,Finally generate multi-parameter cloud map, water potential map, etc.The volume of the carbon dioxide detector based on tunable semiconductor laser absorption spectroscopy is 338 mm×251 mm×88 mm,the power loss of the instrument is less than 1.3 W at room temperature.The test results show that:The carbon dioxide detection system can keep working steadily for long periods of time,the robustness of human-computer interaction function of the system is good, the response time of this instrument to the detection of carbon dioxide concentration in grain storage is less than 20 s. Its linear error is less than 1.2%,the detection repeatability was 0.4%,the detection accuracy of the carbon dioxide concentration of the instrument is 10 mg/m3, the detection range of the carbon dioxide concentration is 0-20 000 mg/m3.At the same time,the carbon dioxide detection system designed in this study has a temperature detection range of -40-120 ℃,the humidity detection range of the instrument is 0%-100%.In the solid warehouse inspection,The experimental results show that, The carbon dioxide detection system is designed for corn under different storage conditions under different working conditions, the response time of carbon dioxide concentration detection was 15-18 s, the temperature detection range was 25.6-26.8 ℃, and the humidity detection range was 43%-47%.Combined with the man-machine interaction function of multi-parameter cloud image and water potential diagram display analysis presented by the detection system,It can better reflect the biosafety situation of granary,Intelligent judgment of the safety of the stored grain and give reasonable suggestions based on the actual situation of grain storage. The carbon dioxide detection system is of great significance to reduce the economic losses caused by pests and mildew in the process of grain storage.