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Research And System Design Of Gas On Line Monitoring In Industrial Process Research And System Design Of Gas On Line Monitoring In Industrial Process

Posted on:2017-04-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:T PangFull Text:PDF
GTID:1318330485453638Subject:Optics
Abstract/Summary:PDF Full Text Request
Tunable diode laser absorption spectroscopy has a significant advantage compared with other gas detection techniques,such as:high sensitivity,no cross interference,short response time,no need to intervene in the flow field,so it can realize industrial in situ real-time measurement and has been developed rapidly.With the development of semiconductor laser technology,TDLAS technology has widely used in atmospheric chemistry research,gas pollution monitoring,medical diagnosis,industrial process monitoring,combustion diagnosis,detection of food safety and other various fields,more than that,it develops in a direction of multi-parameter,multicomponent simultaneous measurement,and constantly opens up new areas of application.Research and development of gas analysis instrument based on this technology has great social benefit and economic benefit.First,TDLAS technology is used in the industrial process of oxygen concentration online detection.The on-line gas analyzer based on wavelength modulation spectroscopy(Modulation Spectroscopy Wavelength)was designed,which realized online detection of 0?21%range oxygen.The hardware circuit design and related test of each part of the system were described in detail;In the software part,the data preprocessing,background noise sources and deductions were discussed,and the effects of concentration inversion algorithms and light intensity correction methods on the measurement results were compared and analyzed.Effect of optical design on the measurement accuracy of the system has been emphasized in this paper.optics and fine mechanic repeatability test and a series of instrument performance test showed that the oxygen detection system has the same performance compare with the mainstream product on the market,so it can be used for industrial security monitoring and process control.According to the new edition of "coal mine safety regulations" promulgated by the State Administration of production safety supervision and administration in 2016,it is recommended clearly to use optical full range methane sensor in coal mine safety monitoring system.Taking into account the laser absorption spectra of methane sensor has irreplaceable advantages,so the paper pioneered the combination of wavelength modulation spectroscopy(WMS)and direct absorption spectroscopy(Absorption Spectroscopy Direct)technology,to find a balance point between precision and the whole range,not only ensured the accuracy of measurement,but also achieved a full range measurement.The system hardware design was introduced in detail,including how to realize laser driver and modulation,harmonic signal detection,concentration inversion and the infrared communication.The software design of methane sensor was relatively simple,mainly considering the system reliability and the ability of rapid recovery after abnormal;According to the special application of methane sensor,response time,linearity,detection limit and stability test were carried out in the paper.Finally,the reason of the error of the sensor in high concentration measurement was analyzed.Performance test showed that design of the sensor meet the specification requirements of B type sensors in AQ6211-2008(non-dispersive infrared methane sensor in coal mine).In addition,methane sensor designed in this paper has a detection limit of 150ppm,which is better than the vast majority of full scale methane sensor on the market.At last,the paper summarizes the performance of the two instruments,points out the deficiency of the current test,and discusses how to improve the measurement precision and expand the scope of application.
Keywords/Search Tags:industrial process, on line monitoring, tunable diode laser absorption spectroscopy, direct absorption, wavelength modulation, second harmonic, full range
PDF Full Text Request
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