REFINERY hydrocarbon streams contain sulphur compounds as impurities that can contaminate catalysts and cause operational problems. Sour gas feed streams contain hydrogen sulphide, ammonia, water and total hydrocarbons.
The sour gas feed stream is sent to the oxidation furnace of a sulphur recovery plant, where the hydrogen sulphide is converted to elemental sulphur and sulphur dioxide. The ammonia present in the sour gas stream needs to be completely destroyed in order to avoid the formation of ammonium salts in the sulphur recovery plant.
The use of a sour gas feed analyser system measures the composition of hydrogen sulphide, ammonia and total hydrocarbons in the feed steam.
These compositional measurements are used to calculate a total air demand for the sour gas feed. The system controls the ratio of sour gas to airflow for changes in composition of the sour gas feed.
ABB’s Multiwave photometer is a multiple channel fixed filter photometer, which can accommodate up to eight different optical filters.
The sour gas feed analyser utilises optical filters in the infrared (IR) region of the electromagnetic spectrum. The photometer features a “cell-in-oven” design that ensures that the sample stays above the dew point of the sour gas stream.
The major benefit of this design is the sample cell and sample handling components are in one common heated enclosure. The photometer has established an excellent reputation for reliability and stable performance in refinery applications.
The fast response time of the IR photometer allows for feedforward control of the airflow valve to the combustion furnace. This maximises the efficiency of the sulphur recovery plant, protects the catalysts, ensures that environmental regulations are achieved, and reduces sulphur plant operating problems.
This measurement technology can also be applied to “clean” acid gas streams that do not contain ammonia. www.abb.com/au