(24f) Cold Flow Validation of Catalyst-Biomass Hydrodynamics in Catalytic Fast Pyrolysis

Catalytic Fast Pyrolysis (CFP) is a promising technology for producing renewable transportation fuels and chemicals from lignocellulosic biomass. In the CFP process, circulating fluidized beds (CFBs) of catalyst particles (ranging from dilute-phase (risers) to dense-phase bubbling beds) are used to simultaneously pyrolyze biomass and catalytically upgrade the vapors to a thermally stable, partially deoxygenated bio-oil. The bio-oil is subsequently upgraded and fractionated to produce valuable fuels and chemicals.

Inaeris Technologies (formerly KiOR) is a world leader in development and commercialization of the CFP process. There are many commercial applications of CFBs, but because of the special requirements of biomass pyrolysis, the applicability of the large and well-established body of CFB learnings to CFP is quite limited. For this reason, Inaeris has been executing an aggressive research program into the relevant physics and chemistry of the CFP process, with parallel development of a CFD model capable of reactor design, scale-up, troubleshooting and optimization. To achieve the model development objectives at an accelerated pace, Inaeris has been collaborating with CPFD Software, utilizing the Barracuda Virtual Reactor® software.

The Inaeris-CPFD collaboration has investigated, modeled and reported on catalyst fluidization and catalyst-biomass mixing in fixed fluidized beds [1], followed by catalyst circulation in CFBs[2]. The current stage of the program is investigating and modeling catalyst-biomass hydrodynamics in CFBs, specifically addressing:

(1) Pneumatic transport, agglomeration and deagglomeration of biomass, and

(2) Mixing of catalyst and biomass under dynamic conditions

Both these objectives involve generating experimental validation data under cold flow conditions against which CFD predictions are compared and verified. A lab-scale cold-flow CFB unit has been constructed such that catalyst and biomass can be independently pneumatically conveyed from separate, positive displacement feeders through transport lines to mock reactors under differential pressure conditions. This unit is flexible enough to test different geometries for mock reactors, different configurations for catalyst-biomass contacting and mixing, and wide ranges of catalyst, biomass and gas flows. Existing measurement capabilities include mass holdups of catalyst and biomass in the mock reactor, pressure profiles, particle size distribution (PSD) analysis, quality of mixing, bed-building kinetics, residence time distributions, and visual observations.

Both experimental and CFD results for catalyst only circulation confirm transition from dense regime to dilute regime as a function of transport gas flowrate. This transition is evident in solids holdup in the mock reactor and the corresponding pressure drop across the unit. Furthermore, such flow regime shifts are determined to be sensitive to catalyst PSD and solids feed rate. We will present the CFD models for catalyst circulation and detail model applicability for a range of configurations, feed rates and flow ranges. Next, we will report on biomass incorporation and co-feeding configurations in the experimental setup. Experimental methods to ascertain catalyst-biomass mixing in the mock reactor will be discussed and corresponding CFD models will be presented.

References

[1] B. Adkins, N. Kapur, J. Pendergrass, J. Parker, P. Blaser, KiOR Update: Incorporating Barracuda in our CFP Development Process, Proceedings of the Inaugural Barracuda Virtual Reactor Usersâ?? Conference, Santa Ana Pueblo, New Mexico, 2015.

[2] B. Adkins, N. Kapur, T. Dudley, S. Webb, P. Blaser, Experimental validation of CFD hydrodynamic models for catalytic fast pyrolysis (CFP), Fluidization XV, May 22-27, 2016, Quebec, Canada.