(583gb) Challenges in the Operation of a Fluidized Bed Reactor for Biomass Pyrolysis

Challenges
in the Operation of a Fluidized Bed Reactor for Biomass Pyrolysis

Shoucheng Du, George M. Bollas,

Department of Chemical and
Biomolecular Engineering, University of Connecticut, Storrs, CT

Although micro-pyroprobe
reactors have been widely used in studying fast (catalytic) pyrolysis of
biomass due to their easiness in operation[1¨C4], they cannot be economically scaled up [5], to satisfy industrial needs. On the contrary,
fluidized bed reactors have been extensively utilized in chemical processes
across industry due to their scalability, excellent mass and heat transfer
properties, good mixing between the solids and the suspending fluid, uniform
catalyst distribution, and so forth. Furthermore, as shown in Figure 1, by
comparing catalytic pyrolysis using ZSM-5 catalyst in fixed bed reactor and
that in fluidized bed reactor, it can be found that improvement of the bio-oil
quality of up to 10 wt% in oxygen content can be achieved by exploiting
short-contact-time fluidization technologies, such as riser reactors and
spouted bed reactors. Therefore, it is beneficial to study biomass pyrolysis in
fluidized bed reactors and focus on reflecting more realistic bench scale
simulations of an industrially relevant process and improving bio-oil quality.

Figure 1 Comparison of Bio-oil qualities between different catalysts and different reactor designs (fixed bed vs fluidized bed)

As one kind
of the fluidized bed reactors, spouted-bed reactors are ideal for the
characteristics of biomass: they can handle large particle size distributions,
larger particles, differences in particle densities, and provide excellent
mixing [6]. Moreover, spouted beds can decouple residence times
of gas and solids; thus, reducing unwanted secondary biomass reactions [7]. Considering the above advantages, a bench-scale
conical spouted-bed biomass catalytic reactor, shown in Figure 2, has been
designed, considering different particle properties, geometric factors and
important hydrodynamic parameters [8]. Further initial tests with the spouted bed reactor
have also been performed.

Figure 2 Schematic of the existing spouted bed reactor setup for biomass (catalytic) pyrolysis

However, a
variety of technical challenges during the operation of this reactor have been
encountered, such as biomass and catalyst feeding, catalyst entrainment, char
separation/filtration, and product (liquid and solid) collection/processing. These
challenges are highly possible to contribute to the experimental errors and, directly
and significantly affect the accuracy and consistency of the experimental
results. This presentation will start with a discussion of the challenges in
the operation of the existing spouted bed reactor setup, and then focus on the progress
that has been made so far to improve the reactor setup. Experimental results from
different biomass feedstocks, catalyst types and catalyst inventories will also
be presented and compared with other fluidized bed reactors in the literature,
such as spouted and bubbling bed reactors, and risers.

References:

[1]         T.R.
Carlson, J. Jae, Y.-C. Lin, G. A. Tompsett, G.W. Huber, Journal of Catalysis
270 (2010) 110.

[2]         P.R.
Patwardhan, D.L. Dalluge, B.H. Shanks, R.C. Brown, Bioresource Technology 102
(2011) 5265.

[3]         D.J.
Nowakowski, a. V. Bridgwater, D.C. Elliott, D. Meier, P. de Wild, Journal of
Analytical and Applied Pyrolysis 88 (2010) 53.

[4]         J.
Adam, M. Blazso, E. Meszaros, M. Stocker, M. Nilsen, A Bouzga, J. Hustad, M.
Gronli, G. Oye, Fuel 84 (2005) 1494.

[5]         T.R.
Carlson, Y.-T. Cheng, J. Jae, G.W. Huber, Energy & Environmental Science 4
(2011) 145.

[6]         H.
Cui, J.R. Grace, Bioresource Technology 99 (2008) 4008.

[7]         R.
Aguado, M. Olazar, M. Jose, G. Aguirre, J. Bilbao, Industrial & Engineering
Chemistry Research 39 (2000) 1925.

[8]         S.
Du, J. Valla, G.M. Bollas, in:, 2011 AIChE Annual Meeting, Conference
Proceedings, 2011.