Optimal Gas Analysis Decisions Improve Ethylene Plant Operation

 One astonishing statistic regarding the oil and petrochemical industry is that 200 million tons of ethylene will be produced this year, much with 99.99% purity. This high level of performance is possible thanks to analyzers helping control the process and verifying the result.

Creating this much product with such a high level of purity depends on more than 30 gas analysis measurement points in a full ethylene production unit, from feedstock to delivery of multiple product and byproduct streams. Installing and maintaining these analyzers can be challenging, but answers are at hand.

 Gas analyzers are arguably the most complex and often misunderstood instruments in a chemical plant. There are many technologies with different capabilities, which can cause confusion as to which is best for what purpose. Michael Kamphus and I tried to help clear this up in our article in the January 2020 issue of Hydrocarbon Processing, Optimal Gas Analysis Decisions Improve Ethylene Plant Operation. Much hinges on the demand for high purity. 

These stringent purity requirements must be verified in production and at custody transfer points because the presence of impurities can poison catalysts and affect downstream processes, leading to costly repairs and downtime. Stringent environmental requirements relating to gas emissions also exist. Since purity is essential, the precision and reliability of the measurement is of key importance. Speed of response to any potential issues—along with cost reduction—are also critical to prevent potential process upsets and to ensure optimum throughput.

There’s no question this reality puts enormous pressure on effective analyzers, which means selecting the right types and using them in the right process points. The question quickly emerges, how do you make the right selections? That’s a tough thing to answer in one article, but we did our best to review the different gas analysis measurement points in the process and offer suggestions for specific gas analyzer technologies based on how each is designed to better perform at various points in the process. We started by defining three general technology categories:

The measurement of purity and process optimization in ethylene plants is accomplished by gas analysis systems, principally gas chromatographs (GCs), laser spectroscopy analysis systems, and conventional continuous gas analyzers. The latter use a variety of measurement technologies such as photometric nondispersive infrared (NDIR) and nondispersive ultraviolet (NDUV), thermal conductivity, paramagnetic and electrochemical oxygen. While virtually every ethylene plant uses some combination of these technologies, not all use them optimally. Applying the right specific gas analysis system in each process and unit will help companies thrive in the competitive petrochemical industry.

Using a gas analyzer optimally depends on the type of measurement needed, the gas being measured or the relative concentration to be sensed. Gas analysis measurements at an ethylene plant have traditionally been predominantly made by infrared and gas chromatograph analysis techniques, supported by techniques for emissions analysis. However, recent advances in tunable diode laser and quantum cascade laser spectroscopy have expanded the measurement technologies available for faster and more accurate control of the process at certain points.

If you are struggling with consistency in meeting purity requirements, complying with emissions levels, controlling production costs, or having access to real-time process analytics, it is critical to assess the performance of each gas analyzer technology.

Tell us about your situation and how you have applied gas analysis technologies. You can share with others about your implementations and experiences at the Emerson Exchange365 community forum, a place where you can share ideas and experiences with others in the same situation. It’s a site where you can communicate with experts and peers in different industries around the world. Look for the Gas Analysis and Analytical Communities, plus other specialty areas for opportunities to provide input, suggestions, and answers.