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Boiler operators, engineers, and facility managers constantly address changing emissions regulations and sustainability objectives. Liquid biofuels continue to emerge as a compelling alternative to traditional fossil fuels. Advancements in retrofit technology have made it quicker and more affordable to make the switch.
Derived from organic waste — including used cooking oils, agricultural residues, and other biomass — these renewable fuels offer a way to reduce greenhouse gas emissions and increase sustainability while maintaining efficient boiler operations and meeting budget restrictions.
Integrating liquid biofuels into existing boiler systems can present challenges. Understanding the various biofuels, their requirements, and necessary combustion control technologies is important for successful adoption.
Types of Liquid Biofuels for Boilers
Several liquid biofuels are particularly relevant for boiler applications:
- Biodiesel (B20, B100): Produced through the transesterification of vegetable oils, animal fats, or recycled cooking oils, resulting in fatty acid methyl esters. B20, a common biodiesel blend, contains 20% biodiesel and 80% petroleum diesel. B100 is 100% biodiesel.
- Bio-Residual Oil (BRO-500): A fuel derived from biodiesel production residuals. It serves as a renewable alternative to traditional residual fuel oils, providing comparable energy content. It delivers up to 128,000 BTUs per gallon with minimal water or methanol content, surpassing coal and wood-fiber fuels with 100-125% more energy per pound than wood chips or pellets.
- Pyrolysis Oil: Produced by heating organic waste at high temperatures without oxygen, breaking down biomass into a liquid fuel rich in oxygenated compounds.
- Renewable Fuel Oil (RFO): A wood-derived pyrolysis oil that’s 100% renewable. It holds the highest RIN rating (7) and produces lower SOx emissions than heavy oil.
- Ethanol: Made by fermenting sugars from crops like corn and sugarcane. Microorganisms convert these sugars into ethanol and carbon dioxide, producing a high-oxygen liquid fuel.
CONTROLS: BMS Controls in action.
Challenges in Using Liquid Biofuels
Key challenges include variability, storage and handling, and combustion control.
- Variability: Fuel variability is a consideration when using liquid biofuels such as pyrolysis oil, biodiesel, and BRO. This issue has improved with advancements in refining and quality control.
- Storage and Handling: Proper storage and handling are critical to maintaining fuel quality and ensuring reliable boiler operation.
- Temperature consideration: Biofuels have higher cloud and pour points compared with petroleum-based fuels, making them prone to gelling in colder conditions.
- Water contamination and microbial growth: Biofuels attract water more readily than diesel or other fuel oils, which can lead to microbial growth.
- Material compatibility: Certain biofuels can react with materials commonly used in fuel systems. Biodiesel may degrade rubber components and corrode metals like copper and brass. Ethanol and pyrolysis oil aren’t compatible with carbon steel. RFO has an acidity of pH 2.5 and high ash content.
Seamless Integration with Advanced Controls and Monitoring
To successfully implement liquid biofuels, facilities require advanced control and monitoring systems for real-time monitoring and adjustments, accommodating fluctuations in biofuel properties, ensuring efficient combustion, and maintaining safety. The following systems are recommended:
- Burner Management System (BMS) Controls: A fully metered, UL-listed combined burner management and combustion controller can handle a wide range of fuel scenarios, including many renewable fuels. For facilities looking to integrate with existing control infrastructure, a PLC-based solution can match the plant’s current platform. These options continuously monitor variations and adjust fuel flow, air ratios, and burner settings to maintain stable and efficient combustion. They also automate ignition sequences, flame monitoring, and shutdown procedures, ensuring safe burner operation. The system integrates with fuel pumps, heaters, and blending skids, optimizing fuel delivery and minimizing operational disruptions.
- Cloud-Based Remote Monitoring: Secure cloud integration provides real-time notifications and system diagnostics, ensuring operational efficiency and reliability.
BIO: Biofuels in use on a college campus in Massachusetts.
Successful Case Study
A Massachusetts university achieved success with its 2020 addition of biofuel to its traditional fuel options. The university installed a 40,000 lb/hr, 300 PSIG steam boiler, including an economizer, tri-fuel burner, multiple fuel piping trains, a boiler control system, and associated fans and instrumentation. The system achieved the following thermal efficiencies with the three different fuel types:
- 83% firing natural gas
- 86% firing No. 2 oil
- 81% firing pyrolysis oil
This case study proved the effectiveness and efficiency of using renewable pyrolysis oil.
SUCCESS: In 2020, a Massachusetts university successfully expanded its energy portfolio by incorporating biofuel alongside traditional fuel sources.
Stepping into the Future
The adoption of liquid biofuels presents a viable pathway for reducing carbon emissions in boiler operations. By understanding the specific properties and challenges associated with various liquid biofuels and implementing appropriate storage, handling, and combustion strategies, facilities can transition toward more sustainable energy solutions without compromising efficiency or reliability. Proper controls, monitoring, and maintenance can ensure the efficiency and safety of your boiler system.
Preferred Utilities is committed to addressing increasing regulations and sustainability objectives with its carbon-neutral innovations. Preferred manufactures high-tech burner technology, controls, and monitoring systems that enable organizations to easily and affordably switch to a higher level of renewable fuel. Our experts understand that one size doesn’t fit all when working to achieve the best sustainability solutions.