Page 133 - Advances in bioenergy (2016)

This process involves two reactors, the first of which contains a fluidized bed of proprietary
catalyst, and the second containing a fixed bed of a second catalyst. Both reactors operate at
pressures that are high enough to sustain exothermic deoxygenation reactions ( 200–500 psig
or 13.6–34.0 barg). It should be noted that these pressures are much lower than those needed
for upgrading of condensed liquid pyrolysis oil. 13

The temperature of the fluidized bed in the first-stage reactor is sufficiently high to enable
rapid devolatilization of biomass ( 400–500C). The fluidizing gas is primarily hydrogen. A

stream of biomass feedstock is introduced into this reactor, where it undergoes rapid
devolatilization, releasing the oxygenated vapors that are central to this process. Owing to the
operating conditions, very little of the carbon present in the feedstock is converted to a solid
char product (approximately 10% or less). Once oxygenated vapors have been generated from
the feedstock, the vapor molecules are brought into immediate contact with the catalyst and the
hydrogen atmosphere in the first-stage reactor. In this context, this process is referred to as
hydropyrolysis, and it differs from more traditional pyrolysis, as the species generated during
devolatilization are reacted primarily with hydrogen, not with each other. The majority of the
chemically bonded oxygen associated with the product vapors is immediately converted to
H O, CO, and CO . Significantly, the deoxygenation reactions occurring in the first stage are
2
2
exothermic, and will generate more than enough heat to sustain the endothermic initial
pyrolysis of biomass occurring in this reactor. The catalyst system also promotes and regulates
2
polymerization and hydrogenation in the first stage of the IH process, so that greater yields of
desirable hydrocarbon products can be obtained.

In order for this process to operate in a balanced and economically viable manner, the
proportion of each of the product vapors must be controlled, so that the amount of hydrogen
needed for deoxygenation can be provided via reforming of noncondensable hydrocarbon
products.

The char produced in the first stage is elutriated from the catalyst bed, and is separated from
the process in a downstream cyclone, barrier filter, or gravimetric separator. The product
vapor stream is then conveyed to the second stage of the process, where any remaining
heteroatoms (including species such as nitrogen and sulfur) can be removed. In this integrated
process, this stage is referred to as hydroconversion.

The stream of product vapor (consisting of hydrogen, condensable hydrocarbons,
noncondensable hydrocarbons, and other vapors such as H O, CO, CO , H S, and NH ) is then
2
3
2
2
cooled and streams of condensed liquid hydrocarbon products, water with certain dissolved
species, and noncondensable vapors, are obtained. The hydrocarbons produced by this IH 2
process are almost completely deoxygenated and the water produced in the process contains
almost no carbon, as the hydrocarbons remaining after hydrotreating are not water soluble. As
a result, a very significant proportion of the energy content of the biomass is recovered in the
liquid hydrocarbon fuel.

2
In addition, the IH process produces noncondensable hydrocarbon vapors, which are not
suitable for use as liquid transportation fuel (CH , C H , C H ). Bench-scale experiments have
4
3 8
2 6