The small amount of hydrogen sulfide gas generated during the oil exploitation process is enough to cause great harm to the human body and mining equipment. It is necessary to detect hydrogen sulfide gas timely and accurately. Based on the principle of spectral absorption, a new method for detecting the concentration of hydrogen sulfide gas with high sensitivity is studied. According to Lambert Beer's law, increasing the optical path can enhance the intensity of the absorbed signal, thereby proposing a method using a long path gas absorption cell and increasing the sensitivity of the system detection. The improved Herriot absorption cell is used to make multiple round trips of light in the air chamber, which can obtain a longer absorption path and improve detection accuracy. The chamber is designed and simulated to test the practicality and accuracy. The light source part uses a Bragg fiber grating to modulate the LED broadband light source into a narrow-band light source, thereby reducing cost and enhancing practicability. The obtained light source is modulated and filtered, and the reference optical path is set, and then the dual optical path difference method is combined to eliminate the systematic error caused by noise interference and source fluctuation. The second harmonic in output signal is extracted by the lock-in amplifier, and then the gas concentration is inverted. At the same time, an adaptive algorithm is used to maintain the stability of the light source temperature, which can avoid the effects of temperature changes. The simulation experiments show that the long-range high-sensitivity measurement method of hydrogen sulfide greatly improves the measurement accuracy, and can be effectively applied to the on-line accurate detection of low-concentration hydrogen sulfide gas.
The traditional differential absorption spectroscopy method has simple detection principle for H2S gas concentration detection, accurate detection and fast reaction speed, but it will produce large errors in low concentration and short optical path environment. Differential absorption spectroscopy requires a very complex super-definite equation to solve for concentration, which is easy to generate solution errors. Based on the traditional differential absorption algorithm, this paper uses genetic algorithm to invert low-concentration H2S gas, but the genetic algorithm is prone to premature convergence and thus falls into local optimum. A genetic algorithm based on catastrophe optimization is designed to retrieve H2S gas concentration. The use of catastrophic will significantly improve the ability of the algorithm to develop in the solution space. By preserving the local optimal solution obtained before the disaster, the algorithm can be avoided as a random search, which ensures the stability of the algorithm. The optimization of the differential absorption algorithm mainly includes data acquisition, data processing and data presentation. Data acquisition is the collection of changes that occur after gas molecules absorb photons. Data processing is based on the collected data and the optimization algorithm to calculate the optimal concentration. The data presentation is to display the calculated concentration on the computer. The concentration of H2S gas was inversed by the traditional DOAS algorithm and the optimized DOAS algorithm. The results were compared. The results show that the method has high measurement accuracy for low concentration H2S gas, and combines with traditional differential absorption spectroscopy to obtain a wider measurement range.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.