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Research On Ammonia Escape Monitoring System Based On Tunable Diode Laser Absorption Spectroscopy

Posted on:2013-02-27Degree:MasterType:Thesis
Country:ChinaCandidate:Y ZhenFull Text:PDF
GTID:2212330362961643Subject:Instrument Science and Technology
Abstract/Summary:PDF Full Text Request
Ammonia is a kind of common gas in industry and life, which plays an important role in the production of agriculture and industry. In the field of industrial combustion, the total NOx can be decreased effectively through flue gas denitrification with NH3. However, the ammonia leakage may happen during the process of denitration. The unreacted ammonia is discharged from the system, which causes second contamination, it will affect the region air quality and atmospheric visibility, and it is the important source of acid subsidence. The chemical compound which is generated by ammonia will precipitate in the surface of the boiler. That will cause serious corrosion and bring expensive maintenance costs. It is very important to monitor and control the escaped ammonia in denitration process.TDLAS is an important method to measure the density of gas, which has many advantages, such as non-contact, high resolution, high sensitivity and can realize real-time on-line monitoring, and so on. This paper takes aim at on-line detection of the ammonia leakage in the industrial field. The measuring principle of TDLAS is introduced, and its universality and specific characteristic are declared. Considering the characters of the low concentration for the gas and the weak signal, we optimized the functions of detection system, which includes the choices of the laser source and detector, the composition of the optical system, the application of wavelength modulation spectroscopy and harmonic detection technology, the signal processing of the measurement results and so on. And on this basis we completed experimental prototype. Experimental results indicate that the detection system has many advantages such as: high sensitivity, high resolution, high speed of responsibility and excellent repeatability. This paper selectively analyzes the influence of pressure changes on the measurement results existing in the industrial field. The compensation method is emphasized. The final experimental results validate the feasible of the empirical equation. The accuracy of system can be improved significantly after being corrected by pressure compensation. The features of high precision and fast response would lead to a potential extensive application in industry for real time measurement and control of gas pollution emission in the future.According to the requirements of lower ammonia concentration detection and the deficiency still exists in experiment system, this paper finally puts forwards the further improvement ideas and makes plan for the next work.
Keywords/Search Tags:Tunable diode laser absorption spectroscopy, wavelength modulation, detection of NH3, compensation algorithm
PDF Full Text Request
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