Article pubs.acs.org/EF
Fast Pyrolysis of Stem Wood in a Pilot-Scale Cyclone Reactor Henrik Wiinikka,* Per Carlsson,† Ann-Christine Johansson, Marcus Gullberg, Calle Ylipaä ,̈ Mattias Lundgren, and Linda Sandström SP Energy Technology Center AB, Box 726, SE-941 28, Piteå, Sweden ABSTRACT: Fast pyrolysis of stem wood was performed in a pilot-scale cyclone reactor with a reactor wall temperature of ∼750 °C. Wood powder was introduced to the pyrolyzer at 20 kg/h during the experiments. Stable operation of the pyrolyzer was easily achieved, and the resulting yields of the products were 54.6 wt % of pyrolysis oil, 15.2 wt % of solid residue, and 20.1 wt % of gases. From the ingoing raw material, 3.4 wt % of the mass could be recovered as deposits, mainly on the walls of the reactor and in the oil condensing part of the plant. The mass and energy balance closures were approximately 93% and 89%, respectively. The physicochemical properties of the pyrolysis oil, solid residue, and noncondensable gas were measured and compared to values in the literature. The results also show that it is possible to produce an oil with a very low concentration of ash-forming elements because particle separation has already occurred in the cyclone reactor.
1. INTRODUCTION Fast pyrolysis is a promising technology for upgrading solid biomass to the liquid form (pyrolysis oil or bio-oil). The oil has a larger field of application (e.g., as an energy source and feedstock for chemical production) and also has an energy density that is higher than that of the original raw material. Fast pyrolysis is a thermal process in the absence of oxygen in which the biomass is converted to pyrolysis gas and char. A typical process temperature in the reactor is ∼500 °C with a vapor/gas residence time of less than 2 s. After pyrolysis, the solid material is separated from the gas, and thereafter, the pyrolysis gas is rapidly cooled (quenched) to form pyrolysis oil and a noncondensable gas. The pyrolysis oil, a dark brown mobile liquid, is made up of a complex mixture of oxygenated hydrocarbons with an appreciable amount of water from both the original moisture found in the biomass and that formed as a reaction product.1 Pyrolysis oil produced from biomass-based raw materials is a renewable fuel and has, in techno-economic studies, proven to be a very competitive fuel, especially for integrated concepts.2 Areas of applications, considering direct use, are substitutes for heating oil and diesel in several different applications (e.g., boilers, engines, and gas turbines for generating heat and power).3 There is also ongoing research for upgrading pyrolysis oil to a motor fuel by means of a catalyst.4 Common to all of these applications are that the combustion technique (or the catalyst) demands an oil with a very low content of particles and metals, because ash-related operational problems (particle emissions, particle deposits on heat transfer surfaces, and high temperature corrosion) are closely related to the initial concentration of ash-forming elements in the fuel. Therefore, Lehto et al.5 recently recommended reduction of the solid content of the pyrolysis oil to
