RAMAN PROCESS ANALYZER FOR in-situ AND REAL- TIME MEASUREMENT OF CHEMICAL COMPOSITION

摘要

A new process instrument design based on Raman Stokes scattering is described. The instrument quantifies species concentrations in liquid or gas production facilities at any point throughout a given process, from feedstock to exhaust. The Raman in-situ process analyzer (RPA) is an emerging tool for measuring chemical concentration in situ at the sampling point. The analyzer is comprised of an optical interface head with laser source, integrated detection optics, signal processing circuitry, custom calibration models for specific applications, and is integrated into a single package suitable for mounting directly at the pipe. The RPA was tested using several different concentrations of Chlorine (CI2), Oxygen (O2), and Carbon Dioxide (CO_2) in the gas phase and Bromine (Br_2), Hexane (C6H_(14)), and Carbon Tetrachloride (CCI_4) in the liquid phase. Nominal laser power was 370mW. Normalized to standard atmospheric pressure, the 3-sigma detection limits for CI_2, CO_2, and O_2, are 800ppm, 9000ppm, and 1.9%, respectively. For liquid measurements, mixtures of Br2 in hexane and CCI_4 were investigated and the three sigma detection limit for those measurements is approximately 60ppm. The RPA has been developed for process control at chemical production facilities. It is intended to replace process Gas Chromatographs (GC) and Fourier Transform Infrared spectrometers (FTIR) for cost sensitive process applications. Analyzers for at-line use in chemical manufacturing plants must operate safely, be robust and reliable, compact in size, and low cost. The RPA has been developed specifically to address these needs.