Nov-2024

Reliable laser-based gas analysis for enhanced process safety and efficiency (ERTC 2024)

Now more than ever, European refiners are facing challenges due to shifting market dynamics and strong competition while also under pressure to comply with stricter environmental guidelines and standards. Maintaining plant uptime, improving efficiency, ensuring process safety, and producing high-quality products has never been more critical to staying competitive.

Sophia Asal
Endress+Hauser

Article Summary

A key aspect of meeting these obstacles is desulphurisation. The removal of sulphur not only prevents the formation of harmful sulphur oxides (SOx) during fuel combustion but also enhances fuel quality by improving combustion efficiency and reducing the risk of particulate matter in engines, such as diesel engines. In addition, sulphur compounds are highly corrosive and can cause significant damage to refinery equipment, resulting in higher maintenance costs and reduced operational efficiency. Hydrodesulphurisation (HDS) can effectively reduce sulphur content, enabling refineries to meet stringent environmental standards and emission limits while maintaining process reliability and product quality.

HydrodesulphuriSation process
As a crucial process unit in oil refineries, HDS ensures the removal of sulphur compounds from liquid hydrocarbon streams to reduce sulphur content in fuels, such as gasoline, diesel, jet fuel, and other refinery products, to meet environmental regulations and prevent corrosion in pipelines or poisoning of catalysts. High availability and reliability are mandatory to guarantee safe operation in the HDS process.

The preheated feedstock (crude oil fractions like gasoline, diesel, kerosene or heavy oils) is mixed with hydrogen gas and then further heated to 300°C to 400°C. The mixture is fed into the HDS reactor, which operates under high pressure of up to 100 bar and contains a solid catalyst (usually NiMoS/Al₂O₃ or CoMoS/Al₂O₃). This catalyst helps in facilitating the hydrogenation reactions: the hydrogen (H₂) reacts with the sulphur compounds to produce hydrogen sulphide (H₂S) and desulphurised hydrocarbons (R-H).
After the catalytic reaction, the mixture leaves the reactor and enters a separation section. Hydrogen sulphide (H₂S), which is now a gaseous byproduct, is separated from the desulphurised liquid hydrocarbons. This separation is typically done in a gas-liquid separator.

Unused hydrogen from the reactor effluent is usually recycled back into the system for efficiency, while the desulphurised product moves on to further refining or distribution. In the HDS process, H₂S is removed from the hydrogen using an amine unit before the hydrogen is recycled.

Importance of monitoring
Gas analysis plays a critical role in the HDS process by monitoring and controlling various aspects of the operation to ensure efficiency, safety, and compliance with environmental standards. H₂S is the main byproduct of the HDS reaction. Its concentration in the gas stream of the recycled hydrogen needs to be closely monitored to ensure the separation process is working effectively and to avoid catalyst poisoning.

By analysing the gas composition (for example, the levels of H₂S and other gases), operators can assess the performance of the HDS catalyst. A decrease in sulphur removal efficiency or an unexpected increase in H₂S may indicate that the catalyst is deactivating, requiring regeneration or replacement.

Gas analysers further provide real-time data, allowing for immediate adjustments to process variables and helping optimise the HDS process for maximum efficiency.

Advantages of TDLAS gas analysers
Endress+Hauser’s tunable diode laser absorption spectroscopy (TDLAS) analysers, based on SpectraSensors technology, are proven to be highly effective in H₂S measurement. They have an extremely fast response to changes in H₂S concentration, allowing operators to intervene quickly when necessary. The company’s patented differential spectroscopy technique enables the detection and quantitation of low ppm levels of H₂S in hydrogen recycle gas. Laser and detector components are isolated and protected from process gas and entrained contaminants, avoiding fouling and corrosion, ensuring stable long-term operation and accurate measurements. In HDS applications within the refining market, these TDLAS analysers are used to monitor the hydrogen quality to ensure there is no residual H₂S, as it can poison the catalyst.

Endress+Hauser’s newest JT33 TDLAS gas analyser is particularly robust and reliable, providing continuous, real-time H₂S measurements, even in the presence of contaminants, across both light and heavy streams. Its superior accuracy and repeatability are ensured by proven metrology and National Institute of Standards and Technology (NIST)-traceable factory calibration, delivering consistent results verified by on-site auto-validation.

With Endress+Hauser Heartbeat Technology, the JT33 offers 24/7 monitoring of the analyser health. It also features auto-stored historical data, spectrum logging, diagnostics, and verification reporting for complete system transparency. Downtime is minimised thanks to field-serviceable and interchangeable components, allowing for quick repairs without recalibration. Additionally, the system’s minimal consumables further maximise operational uptime.

The JT33 is designed for ease of use, featuring a user-friendly interface with an intuitive menu. Setup and operation are accessible remotely via integrated web server software, ensuring smooth and efficient operation at all times.

Summary
In conclusion, the JT33 TDLAS gas analyser is an indispensable tool for real-time monitoring in the refining industry. Its application in the HDS process is critical for meeting environmental regulations and preventing issues such as pipeline corrosion and catalyst poisoning. The high availability and reliability of the JT33 ensure safe and efficient operation, reducing failures and operating costs.

By enhancing the safety and integrity of refinery operations, this technology not only protects asset investments but also provides a sustainable competitive advantage in the market. Moreover, the JT33’s advanced features, such as continuous real-time H₂S measurements, robust design, and user-friendly interface, make it a preferred choice for refineries aiming to optimise their processes. This comprehensive approach to gas analysis not only supports compliance with stringent environmental standards but also drives operational excellence and long-term sustainability in the refining sector.

This short article originally appeared in the 2024 ERTC Newspaper, which you can VIEW HERE