Submitted to: Journal of Analytical & Applied Pyrolysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2018
Publication Date: 1/1/2019
Citation: Boateng, A.A., Schaffer, M.A., Mullen, C.A., Goldberg, N.M. 2019. Mobile demonstration unit for fast- and catalytic pyrolysis: the combustion reduction integrated pyrolysis system (CRIPS). Journal of Analytical & Applied Pyrolysis. 137:185-194. https://doi.org/10.1016/j.jaap.2018.11.024.
Interpretive Summary: Fast pyrolysis is a thermochemical process to convert biomass such as agricultural and forestry residues into an energy dense liquid by rapidly heating them in the absence of oxygen. This liquid called bio-oil or bio-crude can be used as a renewable fuel for industrial boilers or further refined into drop in transportation fuels (gasoline, diesel, and jet fuel). Because fast pyrolysis is a relatively simple process, amenable to small footprints, and able to rapidly densify biomass, it is thought that a biorefinery concept based on distributed scale on-farm or in-forest pyrolysis for conversion of biomass to bio-oil is economically viable. In this model, significant transportation cost savings are realized because only the high density liquid is transported to a large centralized refining facility, eliminating the need to transport low density biomass from a large radius. Although hypothetical studies have shown the potential for this scenario to be economical, production of bio-oil on-farm or in-forest has yet to be demonstrated. Therefore, a trailer mounted mobile fast pyrolysis demonstration unit was designed, built and operated to fill this research gap. The design was based on a USDA patented process called the combustion reduction integrated pyrolysis system (CRIPS) meaning it was capable of producing heat in on reactor (via combustion) and transferring it to another reactor for biomass processing. Furthermore, the electricity required for this system was produced right on the trailer by a gasifier-generator run on wood chips. These features allowed for “off the grid” operation, for example on a farm field or in the forest. Using this unit, production of on-spec bio-oil at operation rates of one ton per day was achieved. An advanced pyrolysis operation called catalytic pyrolysis which produces a higher fuel value product was also demonstrated on this unit, and continual regeneration of deactivated catalysts was achieved, demonstrating the possibility for more advanced field operations to be possible. This information will be extremely valuable to those considering the development of biorefineries and those considering methods to add value to agricultural by products.
Technical Abstract: A two metric ton per day (2 MTPD) mobile pyrolysis unit has been developed, constructed and demonstrated operation for on-farm or in-forest production of pyrolysis oil (bio-oil). The trailer -mounted pyrolysis apparatus is based on the combustion reduction integrated pyrolysis system (CRIPS), a patented, dual fluidized bed, biomass pyrolysis design developed by USDA and the University of Pretoria. The mobile design goal was to demonstrate efficacy of on-farm production and coordinate station-to-station operation to simulate a collective system of several unit operations within a distributed/satellite system of pyrolysis biorefinery. Key design features that provide utility for remote operations including in-situ (on-trailer) generation of heat and electric power required for self-sufficiency were tested at this scale. Extensive trials on three feedstocks important to US agriculture, namely woody biomass, switchgrass and horse litter, were conducted. The results show that up to 1 MTPD biomass processing was successful and easily achievable for the said biomass on the trailer; beyond which, however, operational problems such as pressure imbalance between the dual-bed reactors were encountered, hampering process control. The operation of the CRIPS under catalytic pyrolysis was even more successful with catalyst regeneration readily achievable with the design. Bio-oil yield for neat/traditional and catalytic pyrolysis were in the 45% and 5-10% ranges respectively, similar to lab scale, demonstrating production of large volumes of bio-oil on-farm. Bio-oil quality for catalytic pyrolysis was consistent over several hours on stream due to continuous catalyst regeneration that the design affords yielding high levels of BTX compounds; however, deactivation due to alkali contamination was noticeable at cumulative biomass to catalyst ratios of >6/1. Compared with the laboratory scale results, non-catalytic pyrolysis product quality wavered between that of regular pyrolysis oil produced under nitrogen atmosphere and that of the tail-gas reactive pyrolysis (TGRP) as partial recycle of effluent gas was possible with the mounted CRIPS design. With successful demonstration at the 1 MTPD capacity the mobile system meets the technology readiness level for pre-commercial design suggested for blueprints (i.e. development of full-scale prototype), however more testing is underway to remove the bottlenecks impeding operation at the full scale design.