Emerson Exchange 365

The global push to reduce greenhouse gas emissions, particularly within the aviation sector, is driving a rapid expansion of sustainable aviation fuel (SAF) production. SAF or biojet is a renewable fuel approved for commercial airlines and can be blended up to 50% with conventional jet fuel. However, SAF production presents unique operational challenges associated with feedstock variability and conversion processes.

In an article published in Hydrocarbon Processing magazine, Lara Petrishchev and Julie Valentine share measurement instrumentation strategies for navigating the complexities of biofuel production, especially within the hydrotreatment process unit of the refining process.

SAF Production Challenges

SAF is produced through lipid conversion processes, utilizing renewable feedstocks rich in oil, such as used cooking oil, oil-bearing plants like rapeseed and soybeans, and tallow. These feedstocks undergo pretreatment to eliminate contaminants that can harm reactor catalysts and to break them down into consistent intermediates that feed the hydrotreating and isomerization reactors.

Despite the pretreatment process of bio-based feedstocks, SAF feedstocks present unique challenges:
• They tend to be more corrosive, leading to operational issues.
• Their variability adds another layer of complexity.

In addition, the SAF refining process demands significantly more hydrogen (H₂) and operates at elevated pressures and temperatures.

The hydrotreatment unit is the heart of the plant where fatty acid feedstocks are converted into hydrocarbons, so maximizing yields depends on optimizing reactor operations to handle feedstock variability and meet quality standards.

Improving Process Control

To optimize the operation of the hydrotreatment and isomerization unit, strategically deploying measurement sensors is critical to improving visibility into process conditions for better decision-making.

Critical bed temperature transmitters (left) should utilize dual sensors and detect sensor drift. Remote electronic pressure transmitters measuring catalyst bed differential pressure (dP) (right) will require gold-plated diaphragms for H2 service. Both must be SIL-2 or SIL-3 capable.

Controlling Highly Exothermic Reactions:

• • Temperature transmitters with advanced diagnostics and dual hot backup capabilities are vital for monitoring reactor temperatures and ensuring process safety.
  • Quad vortex flow meters provide redundant flow measurements for hydrogen treat gas, purge streams, and reactor recycle flow, preventing temperature excursions. With a two-out-of-three (2oo3) voting SIL-3 configuration, they enhance both safety and process control.
  • Differential pressure transmitters monitor pressure drop across reactor beds, indicating potential catalyst fouling.

Monitoring Yields and Catalyst Deactivation Rate:

• • Coriolis meters are crucial for the main feed, hydrogen, and product streams. Their ability to measure both mass flow and density enables accurate mass balance data for yield monitoring and catalyst evaluation.

Corrosion Monitoring:

Wireless corrosion and erosion sensors can be placed in strategic areas throughout the process to detect and monitor corrosion. Their wireless design allows them to be added or moved easily to meet service needs.

• • Wireless ultrasonic corrosion sensors provide real-time indication of metal loss and monitoring of pipe wall thickness. This helps ensure equipment integrity given the variable and often more corrosive nature of renewable feedstocks. Check out this article for more insights on managing corrosion risk in biofuels processing.

Hydrogen Purity Monitoring

• • Continuous gas analyzers and gas chromatographs play a critical role in monitoring the purity of hydrogen streams for optimal conversion rates. They also track H₂S in the recycle stream for better reaction control.

Energy Efficiency & Emissions

• • Continuous gas analyzers and Continuous Emissions Monitoring Systems (CEMS) provide real-time data to quantify greenhouse gas emissions.
  • Real-time monitoring of flows, temperatures, and pressures of both process and transfer fluids in heat exchangers provides early detection of equipment fouling. The measurements optimize heat transfer and significantly reduce energy waste and emissions.

Simplifying Regulatory Reporting

• • Automated level and flow metering instrumentation with onboard diagnostics facilitates accurate fluid transfer measurements and reporting, ensuring compliance with regulations. This includes custody chain documentation, invoices, transportation, and audit trails critical to securing government subsidies.

Read the article for more information on how careful selection of measurement instrumentation and control strategies can help refiners optimize SAF production, meet stringent regulatory requirements, and advance sustainability initiatives.

The post Optimizing the Hydrotreatment Process in Sustainable Aviation Fuel Production appeared first on the Emerson Automation Experts blog.