Flammability in a Biofuel Process? Assuring Safety is a Must!

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For every industrial process, especially when working with combustible gases, human health and safety is the top priority. For a startup biofuel processor creating renewable fuels, this necessitated addressing the risks associated with flammable vapor releases from its fermentation processes.

The processer needed to implement a system to monitor combustibility of the gases in its fermentation broths to ensure safety for personnel working in downstream separations units, with the capability to halt production if process conditions approached hazardous levels.

To lead this effort and increase the safety of its operations, the processor engaged engineers at Avid Solutions to design and deliver a system for protecting its personnel and processes. With vast experience in bioprocessing operations of many sizes, the team of engineers at Avid possessed the skillset to assure proper and successful completion of this critical project.

Locking in the Calculation

Leading off the effort, the chemical components of flammable vapors released from the facility fermentation process were analyzed. A conservative lower flammability limit (LFL) calculation based on the LeChatelier principle for flammable plus inert gases was then implemented in the DCS for continuous use during processing.

<em>Ref Calculation of Flammability and Lower Flammability Limits of Gas Mixtures for Classification purposes VSchroeder Sec 422 Eqns 5 6 and Example 4 pp 11 14<em>

Using a Thermo Fisher Prima Pro Mass Spectrometer—an instrument that determines the molecular makeup of gases— equipped with a rotary sampling system to measure multiple process sample streams, analytical values for the gas concentrations were then fed to the LFL calculation.

This type of mass spectrometry process analyzer generates a visual output of data, presented as a plot of relative abundance versus ion mass-to-charge ratio. This information when compared against reference spectra from calibration gases results in concentration values for the sampled gases as analyzed by the Gasworks software.

Feedback Loop Provides Rapid Interlock

By comparing the continuously calculated total vapor flammability of the gas mixture with the predetermined LFL alarm limit, the system rapidly determines when vapors approach hazardous levels of flammability.

This information along with the mass spectrometers instrument status data is sent to an Emerson DeltaV DCS via Modbus

Safety interlocks were built to stop downstream processing if the LFL alarm threshold was exceeded. The DCS would shut off a transfer pump and generate an appropriate alarm, protecting personnel and notifying operators of the issue. Alarms with an option to shutdown were provided if there was a communication failure occur within the analyzer to DCS signal chain. 

When it Comes to Safety, Trust the Experts

The design, programming, and implementation of this safety system took about 4 months to complete including design of the sample conditioning system and commissioning of the mass spectrometer and Gasworks software. At its conclusion, the processor could rest easy, with safety assured by the rigid monitoring and tight interlock control for the potentially hazardous downstream processes.

No matter the process, Avid is ready to provide its engineering expertise to design your system from the ground up, help you modernize, or implement safety assurance measures to keep your facility running profitably and safely.  To begin a conversation on improving the safety and performance of your critical process systems, contact us here!

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