High sensitivity and high-precision ultraviolet spectrometer based on fast Fourier transform (FFT)

Direct injection measurement of high temperature and high humidity gases

EXM500-L is particularly focused on new low emission regulations (50mg/Nm3 nitrogen oxides, 30 mg/Nm3 sulfur dioxide, 5 μ g/Nm3 mercury) and extremely low levels of hydrogen sulfide required for detection in chemical processes. This new model uses a 1200 mm multi-channel analysis cell coupled with an ultra sensitive 2048 pixel CCD (charge coupled device) and a high-resolution spectrometer (0.1 nm). Has high sensitivity and longer bulb lifespan (3 years). UV spectroscopy has higher sensitivity than infrared spectroscopy and can simultaneously measure multiple gases on the same spectrometer. The internal gas circuit of the instrument, including the optional sampling pump, is heated to 240 ° C, so it can directly introduce high-temperature and humid gas without condensation and avoid the risk of sediment adhering to the quartz window and pipeline.

Principles of Optics - Main Methods: Ultraviolet Spectroscopy

By using different wavelengths and algorithms, multiple gases can be measured simultaneously, thanks to UV spectroscopy. For gases with periodic absorption spectra, such as NH3, SO2, NO, CS2, or acetylene, the FFT (Fast Fourier Transform) algorithm ensures excellent measurement selectivity. Due to the solid-state design of UV spectroscopy, the measurement system has high reliability and does not require maintenance.

UV lamp is a xenon flash lamp with a long lifespan and no thermal effect (which may cause measurement drift).

The gas flow cell has two quartz windows for transmitting UV light through the measured gas. The standard path length for a flow cell is 1200 millimeters.

The spectrometer is based on a concave grating to miniaturize the optical components, and the spectrum is read on a 2048 pixel CCD with a resolution of 0.1nm.

Automatically adjust the zero point under clean air or nitrogen (if possible, try to adjust every 2 or 4 hours, at least once a day).

The absorption spectrum is calculated based on the reference spectrum obtained during the zero step period.

The measurement principle is based on ultraviolet light, according to the Beer Lambert absorption law:

[C]=K log lref/lgas

[C]： The concentration of the sample

K： Absorption coefficient of a specific gas at a specific wavelength

Iref： Zero air light intensity

Igas： Light intensity on the sample

Main testing method: UV spectroscopy

By using different wavelengths and algorithms, multiple gases can be measured simultaneously, thanks to UV spectroscopy. For gases with periodic absorption spectra, such as NH3, SO2, NO, CS2, or acetylene, a method based on FFT (Fast Fourier Transform) ensures excellent measurement selectivity. Due to the solid-state design of UV spectroscopy, the measurement system has high reliability and does not require maintenance.

UV lamp is a long-lasting xenon flash lamp that is unlikely to produce measurement drift due to thermal effects.

The gas flow cell has two quartz windows for transmitting UV light through the measured gas. The standard path length of the flow pool is 240 millimeters.

The spectrometer is based on a concave grating to miniaturize the optical components, and the spectrum is read on a 2048 pixel CCD with a resolution of 0.1nm.

Automatically adjust the zero point under zero air or nitrogen (if possible, every 2 or 4 hours, but once a day is still acceptable).

The absorption spectrum is calculated based on the reference spectrum obtained during the zeroing step.

Heating version

The analyzer is equipped with a heating system for the gas path.

The heating temperature can be adjusted to 190 ℃. High temperature will evaporate the sediment on the quartz window.

Does not interfere with CO, CO2, and CH4

The main emission gases such as CO, CO2, and CH4 do not absorb ultraviolet radiation, so they will not interfere with the measured gas.

H2O has weak absorption in the ultraviolet range, but absorbs less at different wavelengths than combustion gases such as NH3, NO, NO2, or SO2. Therefore, H2O with concentrations typically between 5% and 20% will not interfere with the measurement.

Multiple gas configurations

If the composition of the sample gas is compatible with the selected algorithm and wavelength, multiple gases can be measured in the same analyzer.

Due to the use of proprietary algorithms to identify specific UV absorption spectra of gases, this analyzer has high measurement selectivity.

For denitrification applications, special algorithms can simultaneously measure NH3 with a range of 0-10 ppm and SO2 with a content of up to 1200 ppm, just like in coal-fired power plants.

Low maintenance and high reliability

This design is specifically designed for low maintenance and high reliability in measurement.

The specified lifespan of the ultraviolet xenon lamp is 109 flashes. Therefore, the lifespan of continuous measurements is about 3 years, and with measurements taken every minute, the lifespan can reach 10 years. This greatly reduces the risk of maintenance and incorrect measurements caused by replacing aging lamps.

Humanized user interface

The color touch screen display interface allows users to easily browse multiple windows for setting and checking the operating conditions of the instrument.

The protective film reduces the risk of damaging the touch screen surface, especially for solvents and corrosive liquids.

Time

For processes that require rapid measurement, such as electric workbench applications, due to the ultra fast electronic design based on high-speed DSP (digital signal processor), the analyzer can measure sample concentration within 200 milliseconds. However, the usual measurement of emissions is completed within 5 seconds. Special automatic averaging algorithms can be activated to improve stability without affecting response time.

Gas path

The air inlet and zero air inlet are connected to a three-way electric valve. When the automatic zero calibration starts, the solenoid valve switches to the zero gas inlet. The pressure sensor compensates for the measured gas pressure and provides flow indication.

The gas circuit is located inside the heating chamber, and the temperature can be set and controlled between 60 ℃ and 190 ℃ (± 0.5 ℃).

An optional pump can be installed before the gas analysis tank to extract air when using ambient air as the zero gas.

automatic compensation

Conduct internal measurements of sample temperature and pressure. Apply ratios related to the ideal gas law to the measured values to compensate for the effects of temperature and pressure.

EXM500-LTechnical Parameter

*Higher range products can be customized according to demand