US 5,751,415 A · Raman spectroscopy apparatus and method for continuous chemical analysis of fluid streams

Abstract

Apparatus and methods for analyzing the chemical composition of fluid streams using Raman spectroscopy are disclosed. The invention is particularly useful in continuously analyzing a fluid stream containing petroleum products, aqueous or biological fluids. The apparatus includes a laser source for producing light having an excitation wavelength. The light is introduced into a bundle of optical fibers connected to a tubular Raman enhancement cell. A transparent optical element (lens and/or window) acts as a barrier element to isolate the flowing sample stream from the optical components. The Raman enhancement cell is configured to allow continuous sample fluid flow therethrough, and it is preferably lined with a material having an index of refraction less than the index of refraction of the fluid stream. Scattered light from the enhancement cell preferably exits the optical fibers as a linear optical signal. A Raman spectrometer passes the optical signal through an excitation wavelength filter, an optical slit, and a volume holographic transmission grating with an aberration correction device before transmitting the optical signal to a charge coupled device array which converts the optical signal into a corresponding electronic signal. The electronic signal is analyzed and converted by computer into a representation of the chemical analysis of the fluid stream.

Claims45

Dependent claims

A method for continuously analyzing the composition of a fluid stream using Raman spectroscopy comprising the steps of:

(a) introducing the fluid stream into a tubular Raman enhancement cell comprising:
a fluid stream inlet and a fluid stream outlet located adjacent the ends of the enhancement cell for continuous fluid flow through the enhancement cell;
an optical connector located at one end of the enhancement cell for connecting a bundle of optical fibers to the enhancement cell, wherein said bundle of optical fibers includes at least one excitation optical fiber and one or more collection optical fibers;
and
a transparent fluid barrier located between the bundle of optical fibers and the enhancement cell;
(b) introducing light having an excitation wavelength into the Raman enhancement cell through the excitation optical fiber;
(c) collecting backscattered Raman light from the enhancement cell with the one or more collection optical fibers;
(d) measuring the backscattered light with a Raman spectrometer comprising:
a linear array of the one or more collection optical fibers for generating an optical signal of the scattered light from the enhancement cell;
a filter for rejecting portions of the optical signal having the excitation wavelength;
a volume holographic transmission grating to disperse the light;
a transmissive aberration correction element for correcting optical aberrations introduced into optical signal by the volume holographic transmission grating, said aberration correction element comprising at least one optically transparent wedge or prism;
and
a charge coupled device array for converting the optical signal into a corresponding electronic signal;
and
(e) converting the electronic signal into a representation of the chemical analysis of the fluid stream.

13 more elements

An apparatus for analyzing the composition of a fluid stream using Raman spectroscopy comprising:

a laser source for producing light having an excitation wavelength;
a bundle of optical fibers comprising one or more excitation optical fibers and a plurality of collection optical fibers;
a tubular Raman enhancement cell comprising:
a fluid stream inlet and a fluid stream outlet located adjacent the ends of the enhancement cell for continuous fluid flow through the enhancement cell;
an optical connector located at one end of the enhancement cell for connecting the bundle of optical fibers to the enhancement cell;
and
a transparent fluid barrier located between the bundle of optical fibers and the enhancement cell;
a Raman spectrometer comprising:
a linear array of the collection optical fibers for generating a linear optical signal of the scattered light from the enhancement cell;
a filter for rejecting portions of the optical signal having the excitation wavelength;
a volume holographic transmission grating to disperse the signal and a transmissive aberration correction element for correcting optical aberrations introduced into optical signal by the volume holographic transmission grating, said aberration correction element comprising at least one optically transparent wedge or prism;
and
a charge coupled device array for converting the optical signal into a corresponding electronic signal;
and
a computer for converting the electronic signal into a representation of the chemical analysis of the fluid stream.

12 more elements

Dependencies are inferred from the claim text.

Raman spectroscopy apparatus and method for continuous chemical analysis of fluid streams

Life of this patent

Raman spectroscopy apparatus and method for continuous chemical analysis of fluid streams

Life of this patent

Abstract

Claims45