Pyrolysis Oil Stabilization: Hot-Gas Filtration; Cooperative Research and Development Final Report, CRADA Number CRD-09-333

The hypothesis that was tested in this task was that separation of char, with its associated mineral matter from pyrolysis vapors before condensation, will lead to improved oil quality and stability with respect to storage and transportation. The metric used to evaluate stability in this case was a 10-fold reduction in the rate of increase of viscosity as determined by ASTM D445 (the acceleratedaging test). The primary unit operation that was investigated for this purpose was hot-gas filtration. A custom-built heated candle filter system was fabricated by the Pall Corporation and furnished to NREL for this test campaign. This system consisted of a candle filter element in a containment vessel surrounded by heating elements on the external surface of the vessel. The filter element andhousing were interfaced to NREL's existing 0.5 MTD pyrolysis Process Development Unit (PDU). For these tests the pyrolysis reactor of the PDU was operated in the entrained-flow mode. The HGF test stand was installed on a slipstream from the PDU so that both hot-gas filtered oil and bio-oil that was not hot-gas filtered could be collected for purposes of comparison. Two filter elements from Pallwere tested: 1) porous stainless steel (PSS) sintered metal powder; 2) sintered ceramic powder. An extremely sophisticated bio-oil condensation and collection system was designed and fabricated at NREL and interfaced to the filter unit.