Method and apparatus for photometrically monitoring low level concentration of hydrogen sulfide in alkanol amine

A method for photometrically analyzing the hydrogen sulfide concentration in a stream containing at least a first predetermined concentration of bonded hydrogen sulfide-amines and ultraviolet radiation-absorbing impurities comprising the sequential steps of:

• (a) isolating a first, reference, sample of the stream;
• (b) removing the hydrogen sulfide from the first, reference, sample to lower the concentration of hydrogen sulfide therein to a second predetermined concentration;
• (c) photometrically analyzing the first, reference, sample to generate a reference signal representative of the ultraviolet radiation-absorbing characteristics of the remaining hydrogen sulfide and of the impurities in the first, reference, sample;
• (d) photometrically analyzing a second sample of the stream to generate a second signal representative of the ultraviolet radiation-absorbing characteristics of the bonded hydrogen sulfide-amines and ultraviolet radiation-absorbing impurities therein;
• and
• (e) generating a signal functionally related to the second signal and to the reference signal and representative of the concentration of hydrogen sulfide in the second sample.

In apparatus for photometrically analyzing the hydrogen sulfide concentration in a stream containing at least a first predetermined concentration of bonded hydrogen sulfide-amines and ultraviolet radiation-absorbing impurities the improvement which comprises:

• a vessel for receiving therein a reference sample of the stream;
• means for removing hydrogen sulfide from the reference sample until a second predetermined concentration of hydrogen sulfide remains therein;
• and
• a photometric analysis instrument adapted to analyze the reference sample to generate an electrical reference signal representative of the ultraviolet radiation-absorbing characteristics of the remaining hydrogen sulfide and of the impurities in the reference sample and to analyze a second sample of the stream in a manner which takes into account the reference signal to generate a signal representative of the concentration of hydrogen sulfide in the second sample.