Materials Compatibility With Pyrolysis Biofuel

The conversion of biomass such as wood and wood byproducts via pyrolysis into a liquid fuel is important in maximizing the use of material resources and in providing alternative and renewable sources of energy. Pyrolysis oils (or biofuels) have good combustion characteristics but are compositionally different from conventional diesel fuels. This difference requires that materials in contact with the biofuel be tested for compatibility. Three types of biofuels were tested for compatibility with a variety of polymeric materials and metal alloys. The test temperatures were set at 80°C to represent aggressive field usage conditions. The tests were conducted using coupons, which were fully immersed in the fluid for periods up to 15 days. These tests revealed that the metals 304L stainless steel, 316L stainless steel, 430 stainless steel and 20M04 stainless steels had corrosion rates of less than 0.007 mm/y and are suitable for use with the oils tested. A non-traditional low chromium alloy steel, MASH, was also examined and was found to be highly susceptible to all fuels at the high temperature tested and corroded at rates up to 3.7 mm/y. At room temperature, the alloy showed good resistance with a corrosion rate less than <0.009 mm/y. The polymeric materials showed a wide range of properties in the oils tested. Non-elastomers such as polytetrafluoroethylene, polypropylene and high-density polyethylene in general showed little swelling or staining in the oils. The elastomeric materials were much more susceptible to swelling, weight gain and change of surface properties. The attack on elastomeric materials was quite rapid with significant volume expansion seen within 24 hours. Viton, Buna-N and EPDM had volume changes up to 100% during a 10-day test and were not considered suitable seal materials for these oils. Multiple day tests for the low alloy steel at 80°C revealed that the corrosion attack was linear in nature leaving a corrosion scale, which slowed but did not prevent further attack. Details of the material degradation will be discussed.