Fast Pyrolysis Process Development Unit for Validating Bench Scale Data

Brown, Robert C.¹  Jones, Samuel T.² 

[1] Iowa State Univ., Ames, IA (United States). Biorenewables Research Lab.. Center for Sustainable Environmental Technologies. Bioeconomy Inst.;Iowa State Univ., Ames, IA (United States). Biorenewables Research Lab.. Cen

关键词: Pyrolysis;    biomass;    biofuel;   

DOI  :  10.2172/1035783
RP-ID  :  DOE/FE/87003--Final
PID  :  OSTI ID: 1035783

学科分类：燃料技术

美国|英语

来源: SciTech Connect

【 摘 要 】

The purpose of this project was to prepare and operate a fast pyrolysis process development unit (PDU) that can validate experimental data generated at the bench scale. In order to do this, a biomass preparation system, a modular fast pyrolysis fluidized bed reactor, modular gas clean-up systems, and modular bio-oil recovery systems were designed and constructed. Instrumentation for centralized data collection and process control were integrated. The bio-oil analysis laboratory was upgraded with the addition of analytical equipment needed to measure C, H, O, N, S, P, K, and Cl. To provide a consistent material for processing through the fluidized bed fast pyrolysis reactor, the existing biomass preparation capabilities of the ISU facility needed to be upgraded. A stationary grinder was installed to reduce biomass from bale form to 5-10 cm lengths. A 25 kg/hr rotary kiln drier was installed. It has the ability to lower moisture content to the desired level of less than 20% wt. An existing forage chopper was upgraded with new screens. It is used to reduce biomass to the desired particle size of 2-25 mm fiber length. To complete the material handling between these pieces of equipment, a bucket elevator and two belt conveyors must be installed. The bucket elevator has been installed. The conveyors are being procured using other funding sources. Fast pyrolysis bio-oil, char and non-condensable gases were produced from an 8 kg/hr fluidized bed reactor. The bio-oil was collected in a fractionating bio-oil collection system that produced multiple fractions of bio-oil. This bio-oil was fractionated through two separate, but equally important, mechanisms within the collection system. The aerosols and vapors were selectively collected by utilizing laminar flow conditions to prevent aerosol collection and electrostatic precipitators to collect the aerosols. The vapors were successfully collected through a selective condensation process. The combination of these two mechanisms has created the ability to effectively fractionate the bio-oil into distinct fractions with improved characteristics. The fractions of bio-oil each contained different properties. Bio-oil properties that were improved included the energy content, water content, acid content and distribution of certain carbohydrates (levoglucosan and acetic acid). The improved properties that are associated with the fractionated bio-oil could allow bio-oil to be used in new markets, preferably without further upgrading. The decreased water and acid contents in the first four (of five) fractions could allow for easier upgrading of the bio-oil into transportation fuels or other valuable products. Char and solid particulate content of bio-oil must be minimized. Solid particulate can erode surfaces, leading to decreased equipment and component life and increased maintenance. Char can contribute to the instability of bio-oil by acting as a catalyst and causing secondary reactions. To continuously remove char from the pyrolysis reactor product stream, two cyclonic gas separators (cyclones) were designed and constructed. The design of the two gas cyclones was based on gas flow rate, particulate density, desired efficiency and desired pressure drop.