Brookhaven National Laboratory (BNL) and Fulton Heating Solutions recently completed laboratory testing of a 2-million-Btuh-capacity hydronic condensing boiler that uses pure biodiesel (B100) fuel. The project proved that B100 successfully can replace traditional fossil fuels, such as natural gas, when used in properly designed and operated heating equipment.

The testing was sponsored by the New York State Energy Research and Development Authority (NYSERDA), a public-benefit corporation that administers energy and environmental programs.

Boiler Testing Program
A dual-fuel boiler originally designed to operate on gas or No. 2 heating oil, the B100-fired unit incorporates a primary and secondary (condensing) heat-exchanger design (Photo A and Figure 1). When operating on No. 2 heating oil, the commercial version of the boiler has a return-water temperature above the flue-gas dew point, a control strategy that was implemented because corrosion can occur during oil-fired operation. When B100 is utilized, this is not a factor because the fuel is sulfur-free, leaving the boiler to operate efficiently with gas and liquid fuels. Able to achieve thermal-efficiency levels greater than 94 percent, the boiler is gaining attention for its high-efficiency renewable-energy applications in schools, hospitals, office buildings, and institutional applications. The boiler can be used as a stand-alone heating unit or the lead unit in a modular boiler system to maximize operating hours and annual fuel savings.

The first biodiesel fuel used in the testing was derived from tallow (rendered animal fat). Tallow-based biodiesel fuel generally is known to have less-favorable cold-temperature characteristics (e.g., high cloud-point and cold-filter-plugging-point temperatures) than biodiesel fuels derived from many plant-based oils. Testing with tallow-based biodiesel fuel enabled the quick identification and resolution of cold-temperature operating problems that could occur with a B100-fired boiler under adverse fuel-storage and boiler-room-temperature conditions.

During laboratory testing, which was performed from September 2009 to January 2010, the boiler and surrounding mechanical room were allowed to cool to the mid-50˚F range, causing the tallow-based biodiesel fuel to gel within the piping between the fuel-storage tank and the boiler. Such gelling was resolved by warming the fuel piping, and no operational difficulties were observed within the burner and boiler system.