Method and device for detecting trace mercury concentration based on fiber-coupled laser sum frequency technology

Abstract

The invention discloses an optical fiber-coupled laser sum frequency technology-based trace mercury concentration detection method and device. The device comprises a data acquisition card, two laser diode drivers, two diode lasers with tail fibers and different wavelengths, a 1: 2 tapering lens optical fiber, barium metaborate (BBO) crystals, a quartz lens, a beam splitter prism, two reflectors, a light splitter, a reference cell, a sample tank, two photomultipliers, two filters and a computer. The method utilizes a multiple linear regression algorithm and an automatic circuit control wavelength feedback technology to realize on-line continuous detection of a mercury vapor concentration.

Description

technical field [0001] The invention belongs to the field of detection of elemental mercury concentration in industrial exhaust gas, and in particular relates to a method and device for detecting trace mercury concentration based on optical fiber coupled laser sum frequency technology. Background technique [0002] Mercury is an element that is very harmful to the human body. Excessive intake of mercury can easily cause physical diseases and have great damage to the nervous system. Mercury in the atmosphere mainly comes from man-made and natural emissions. Natural emissions mainly include lake volatilization and volcanic eruptions. Artificial emissions mainly come from industrial smoke emissions. my country's energy mainly comes from the combustion of coal, and my country's coal mines contain relatively high levels of mercury. Therefore, mercury vapor in flue gas emissions is the main source of mercury pollution in my country. Traditional mercury vapor measurement techn...

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Problems solved by technology

Mercury vapor concentration measurement based on the Zeeman effect is equivalent to its own reference path, so it can avoid the influence of mercury lamp power changes, but the problem of mercury lamp life is also not resolved

[0003] The patent number is ZL201210055105, which discloses a continuous monitoring device and method for mercury gas based on a diode laser. Its disadvantages include: (1) The system is sensitive to vibration, and the twisting of the light source, reflector, and achromatic lens will reduce the coupling efficiency and further Reduce the power of synthetic ultraviolet light, thereby reducing the sensitivity of the system; (2) At the same time, due to the use of dichroic mirrors, the mode size of the laser beam does not match, and the efficiency of ultraviolet light synthesis in the system is low; (3) When using a data acquisition analyzer to calculate the concentration , only select individual points for I / I o Calculation, cannot collect data continuously, and is easily affected by noise to reduce accuracy; (4) The signal generator increases the volume of the analysis system as a separate module; (5) The system does not have closed-loop feedback, and cannot be adaptively adjusted when the wavelength of the laser drifts Back to the best state, manual setting is required, which reduces the automatic measurement capability of the system

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