Gas Leakage Diffusion Research And Safety Evaluation Based On Laser Detection

Laser detection technology has the characteristics of high sensitivity,fast response time,wide coverage and high precision.Compared with traditional gas sensors,it has great advantages in natural gas leak detection.The laser detection technology has a direct relationship with the spatial distribution of leakage gas.This paper analyzes the pipeline leakage diffusion law to propose an engineering solution and safety evaluation method combined with the characteristics of laser detection.The main research contents and results of the thesis include the following points:First of all,the thesis first analyzes common leaks in natural gas stations,including flange leakage,pipeline leakage,thread leakage and valve leakage.The most common location is static sealing point.The influence of leakage velocity,wind and obstacles on gas leakage and diffusion was analyzed by FLUENT software.The diffusion law was characterized by the length and height of the leaking cloud.The results show that the larger the leakage velocity,the wider the gas leakage diffusion range;with the increase of wind speed,the length of the cloud cluster can reach a long distance,and the vertical height of the cloud cluster shows a decreasing trend,and the change is faster;the obstacle has a greater influence on the vertical height distribution of the cloud cluster,and makes a higher concentration of gas gathers on the windward side of the obstacle.Then,According to the detection characteristics of laser telemetry,a scanning laser gas sensor with a three-dimensional cloud platform as the carrier is designed.The sensor consists of a cloud platform module,a laser detection module and a video monitoring module.And the laser gas monitoring system consists of three parts: the scanning laser gas sensor,the data transmission system and the early warning terminal.The data transmission system uses the form of “optical terminal & optical cable” to convert the signal,and simultaneously transmits the data from the front-end sensor and the early warning monitoring terminal;the system's early warning monitoring terminal is developed and designed based on the force control configuration software and the programmable logic controller(PLC),including the functions of PTZ control,video monitoring and data acquisition.Thirdly,combined with the characteristics of laser detection and gas leakage diffusion,a scanning laser gas sensor arrangement method is proposed.The method mainly considers the horizontal length and vertical height of the leakage cloud cluster distribution,and analyzes the problems that need to be paid attention to when setting the sensor scanning path.The variation of laser detection value under different optical paths and different working conditions is calculated.The different optical paths take into account the angle and the distance between them and the leakage.And the different conditions consider the influence of wind and obstacles.Then,the evaluation method of the detection is proposed,including the setting of the alarm value and the data analysis method.Finally,the application of laser gas monitoring system in CS6 gas station of SinoKazakhstan natural gas pipeline is introduced.A total of four scanning laser gas sensors were installed in the process area of the station.The installation height of sensors was 9 meters,which was responsible for monitoring pipeline equipment in filtration separation zone,air-cooling zone and compressor process area.The detection effect of the sensor in the leak state was tested in the field and used as a reference for the safety warning value.By analyzing the test data of the sensor in one day,the results show that the filter separation zone and the air-cooling zone have high micro-leakage due to the large number of connecting parts such as pipeline valves and flanges,and the micro-leakage level in the booster zone is low.The above monitoring results are in line with the actual situation of the compressor station.