BIO-FUEL AND COMBUSTION

Bio-Fuel and Combustion

Larry Richardson, Plumbing Manager

Recently I have had some discussions concerning the burning of Bio-fuels in Riello™ burners. The issue was getting the appliance to burn cleanly and the condition of the filter.

Riello was generous enough to share with me seven “features and effects of the bio-fuel used on heating plants”:

•1 - Reduction of the polluting emissions of SO2 and other by-products of the sulphur combustion (unlike the gas-oils, this bio-fuel does not have sulphur).

• 2 - Lower net calorific value (about 14%) than the light-oil net calorific value with the necessity to increase the fuel volumetric output in order to have the same burner output.

• 3 - Higher density and viscosity than the light-oil; these change the atomizing features and involve (with the same pump pressure adjustments) an increase of the volumetric burner output (on the average about 10%).

• 4 - A general consequence of the points 2 and 3, according to the burner and the adjustment, there are not significant changes of burner output (after all higher output and lower net calorific value balance each other).

• 5 - The different viscosity and density create also a compact and long flame with probable problems due to less stability and probable smoke (Bacharach) and CO presence on boilers with short combustion chamber.

• 6 - Nitrile rubbers and some black plastics soften after long contact with this fuel, therefore for the burners with standard materials, the flexible oil pipes (intake and return), the seals of the oil valves, the hydraulic jacks of the air dampers and the pump are at issue.

• 7 - The solvent power of the bio-fuel involves the melting of residual products and sludges inside the tanks. These materials remain in suspension in the fuel and could wear the components (i.e. nozzles, pump gears, etc.).

I’m told the Riello burners are UL approved for 5% Bio-fuel mixes. Some boiler manufacturers have advocated for double filtering for some time. It appears more important now than ever. The suggestion from General filter is to install a standard fiber filter such as their tried and true Model 1A25 and then follow that with a spin-on filter for optimum filtering.