Page 134 - Advances in bioenergy (2016)

demonstrated that if these vapors are sent to a steam reformer, they exist in sufficient quantity
to supply the hydrogen required to sustain the reactions in the first and second stages of the
process. The entire stream of non-condensable vapors (comprising light hydrocarbons, as well
as CO and CO ) is sent to a steam reformer in industrial-scale facilities based on the process.
2
The reformer produces a product vapor stream comprising H and CO , and no CO remains.
2
2
After separation, a stream of nearly pure CO is vented to the atmosphere, and a stream of
2
nearly pure H is sent back into the process (see Figure 5.1). Another attractive feature of this
2
process is that some or all of the water required for steam reforming is produced within the
process.

In an initial experimental investigation, 16-18 the first and second stages of the process were
demonstrated in a laboratory-scale pilot unit. The feedstock was wood, and the experiment
involved a proprietary catalyst developed by CRI Catalyst Company. A condensed liquid
hydrocarbon product was obtained, and analyzed in detail. The liquid hydrocarbons were
found to consist of gasoline and diesel-range hydrocarbons and found to contain less than 1%
by mass oxygen. The liquid hydrocarbons were nonreactive, with a total acid number (TAN)
less than 2. The vapor stream from the first stage of the process was sent through a hot
sintered-metal barrier filter in order to remove char. Significantly, no increase in pressure drop

across the filter was observed as the experiments proceeded, and solids collected by the filter
were easily removed from the filter surface. This is not possible when similar filters are used
to remove solids from vapor streams produced by traditional fast pyrolysis systems.

Other aspects of the process have been investigated, in the course of subsequent work carried
out using the same laboratory-scale pilot unit. 19-21 The temperature of the fluidized bed in the
first stage of the process was varied to study the effect of this process variable on char
production. An increase in bed temperature was found to reduce char production. However, the
maximum allowable first-stage temperature is ultimately limited by the properties of the
catalyst in the bed and by the observation that, as the temperature of the first stage is increased,
more noncondensable vapors are formed. In consequence, the yield of condensable liquid
hydrocarbons is reduced. In this study, conversion of an aquatic plant (lemna) was addressed,
and promising yields of liquid hydrocarbons were documented.

Work on feedstocks has expanded to include a wide range of biomass-derived materials. 22-26
Results obtained in the course of continued laboratory-scale pilot unit testing are shown in
Table 5.1.

Tests were conducted using feedstocks consisting of wood, lemna, micro-algae, bagasse,
macro-algae, and corn stover. Every test demonstrated the production of commercially viable
yields of liquid hydrocarbon fuels, along with the consistent deoxygenation of liquid
hydrocarbon products. The effect of catalyst composition on the boiling-point range of liquid
products was demonstrated, and proprietary catalysts that shift liquid hydrocarbon production
into more desirable ranges have been identified. For example, in a comparison of two catalysts
employed under identical experimental conditions, one was found to produce significantly
more diesel and significantly less gasoline product, although the overall yield of liquid