Background
The invention relates to a biomass gasification reactor. In addition, the
present disclosure relates to a system and method of carrying out biomass
gasification.
Biomass gasification is a flexible and efficient technology for utilizing
a widely available domestic renewable resource. Gasification of biomass is another
energy generation option. It uses renewable feedstock - biomass. Biomass
encompasses a wide spectrum of materials. Some examples of biomass include wood,
grass, com stoves and other plant derived feedstocks. If biomass is utilized in
gasification, the amount of CO2 released in the environment due to gasification,
corresponds to the amount of CO2 consumed during growth of plants. Thus
gasification or combustion of plant biomass does not add extra CO2 to the
environment. Therefore, use of biomass is considered carbon neutral. The plant
biomass can be grown relatively quickly as compared to other carbonaceous
feedstocks. Utilization of biomass feedstocks helps reduce dependence on fossil fuel
since they are renewable and can be grown relatively quickly. Thus, the use of
biomass for power generation is attractive from the perspective of sustainability and
environmental impact. Syngas production from biomass has become increasingly
important in terms of sustained and economic co-generation (co-gen) of power and
heat or biofuels from renewable resources, especially for the rural economy and
agricultural industry as a whole.
Biomass contains a large amount of oxygen and moisture as compared
to coal. The ash content can also be significantly higher; the exact quantity of ash
depends on the source of biomass employed. The syngas produced contains high
concentrations of tar and the gasification technology relies on a series of complicated
units for syngas cleaning/conditioning to remove the tar. Tars easily condense at
reduced temperatures and block or foul particulate filters, other equipment and
subsequent gas engines or turbines. High operating temperatures of the gasifier such
9
as an oxygen blow gasifier require expensive air separation unit, in addition to having
to use a large quantity of biomass feed. At lower operating temperature of the gasifier
the conversion of tar to syngas is reduced and an elaborate clean up process may be
required to remove the tar from the syngas produced. Tars are also present in
wastewater and physical methods of wet or dry scrubbing for their removal are cost
prohibitive and present an environmental liability. However, operational issues and
process complexity resulting from the removal of tars and other impurities from the
biomass syngas stream have been major barriers for commercialization of biomass
gasification based power generation systems. Unsuccessfiil removal of tars and
overloading of tar filters have been responsible for unreliable system operations and
frequent system shut-downs.
Therefore, further improvements are required for tar removal in the
biomass gasification process. In particular further improvements are needed to
provide efficient conversion of tar and produce syngas with less amount of tar, ash
and impurities. In addition, further improvements are required to obtain pressurized
gasifier operations with biomass, increasing operational flexibility in terms of system
efficiency and/or throughput, as well as reducing the cost of the overall system. The
present invention provides additional solutions to these and other challenges
associated with biomass gasification.
BRIEF DESCRIPTION
In one aspect, the present invention provides a biomass gasifier
comprising a reactor. The reactor includes (i) an inlet for biomass, (ii) an inlet for an
oxygen - containing gas, (iii) an inlet for steam, (iv) an outlet for reactor product gas,
(v) an outlet for ash, (vi) a biogas exit conduit coupled to the outlet for the reactor
product gas and (vii) an inlet for a secondary oxygen source. The biogas exit conduit
includes a catalytic partial oxidation unit, the catalytic partial oxidation unit is
substantially restricting the biogas exit conduit.
In another aspect, the present invention provides a biomass gasifier
comprising (a) a reactor. The reactor includes (i) an inlet for biomass, (ii) an inlet for
3
an oxygen - containing gas, (iii) an inlet for steam, (iv) an outlet for reactor product
gas, (v) an outlet for ash, (vi) a cyclone coupled to the outlet for the reactor product
gas and (vii) an inlet for a secondary oxygen source. The cyclone includes a catalytic
partial oxidation unit and the catalytic partial oxidation unit is substantially restricting
the biogas exit conduit.
In yet another aspect, the present invention provides a system
comprising: a biomass feed unit; a biomass gasifier; a gas cleanup unit; and a power
production unit. The biomass gasifer comprises a reactor. The reactor includes (i) an
inlet for biomass, (ii) an inlet for an oxygen - containing gas, (iii) an inlet for steam,
(iv) an outlet for reactor product gas, (v) an outlet for ash, (vi) a biogas exit conduit,
and (vii) an inlet for a secondary oxygen source. The biogas exit conduit is coupled
to the outlet for the reactor product gas. The biogas exit conduit includes a catalytic
partial oxidation unit, and the catalytic partial oxidation unit substantially restricting
the biogas.
In yet another aspect, the present invention provides a method for
biomass gasification. The method comprising (a) heating biomass in the presence of
steam and oxygen to produce a biogas; (b) flowing a substantial amount of the biogas
through the catalytic partial oxidation unit to produce a reactor product gas; and (c)
collecting the reactor product gas. The heating of the biogas is carried out in a reactor
comprising (i) an inlet for biomass, (ii) an inlet for an oxygen - containing gas, (iii) an
inlet for steam, (iv) an outlet for reactor product gas, (v) an outlet for ash, (vi) a
biogas exit conduit and (vii) an inlet for a secondary oxygen source. The biogas exit
conduit is coupled to the outlet for the reactor product gas, and the biogas exit conduit
includes a catalytic partial oxidation unit. The catalytic partial oxidation unit
substantially restricting the biogas exit conduit.
These and other features, aspects, and advantages of the present
invention may be understood more readily by reference to the following detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects, and advantages of the present
invention will become better understood when the following detailed description is
read with reference to the accompanying drawings, in which like characters represent
like parts throughout the drawings, wherein:
FIG. 1 is a schematic representation of a biomass gasifier reactor, in
accordance with one aspect of the invention.
FIG. 2 is a schematic representation of a biomass gasifier reactor, in
accordance with one aspect of the invention.
FIG. 3 is a schematic representation of a biomass gasifier reactor with
clean-up system, in accordance with one aspect of the invention.
DETAILED DESCRIPTION
In the following specification and the claims, which follow, reference
will be made to a number of terms, which shall be defined to have the following
meanings.
The singular forms "a", "an" and "the" include plural referents unless
the context clearly dictates otherwise.
"Optional" or "optionally" means that the subsequently described
event or circumstance may or may not occur, and that the description includes
instances where the event occurs and instances where it does not.
It is also understood that terms such as "top," "bottom," "outward,"
"inward," and the like are words of convenience and are not to be construed as
limiting terms. Furthermore, whenever a particular feature of the invention is said to
comprise or consist of at least one of a number of elements of a group and
combinations thereof, it is understood that the feature may comprise or consist of any
of the elements of the group, either individually or in combination with any of the
other elements of that group.
5
Approximating language, as used herein throughout the specification
and claims, may be applied to modify any quantitative representation that could
permissibly vary without resulting in a change in the basic function to which it is
related. Accordingly, a value modified by a term or terms, such as "about", is not to
be limited to the precise value specified. In some instances, the approximating
language may correspond to the precision of an instrument for measuring the value.
Similarly, "free" may be used in combination with a term, and may include an
insubstantial number, or trace amounts, while still being considered free of the
modified term.
The term "zone" used herein refers to a region of the reactor. The
zones arc not physically separated with a separation baffle unless specifically noted.
Thus, a zone corresponds to a processing region within the reactor. Tt is also
conceivable that a zone may further include sub-zones or regions that include, for
example, typical unit processes and operations involved in gasification such as drying,
devolatilization and carbon conversion reactions. These sub-zones may be
overlapping with each other. The zones on the other hand may be fairly distinct. In
one embodiment, there is a partial overlap of the successive zones.
As noted, in one embodiment the present invention provides a biomass
gasifier comprising a reactor. The reactor includes (i) an inlet for biomass, (ii) an
inlet for an oxygen - containing gas, (iii) an inlet for steam, (iv) an outlet for reactor
product gas, (v) an outlet for ash, (vi) a biogas exit conduit coupled to the outlet for
the reactor product gas and (vii) an inlet for a secondary oxygen source. The biogas
exit conduit includes a catalytic partial oxidation unit, the catalytic partial oxidation
unit is substantially restricting the biogas exit conduit.
The term biomass covers a broad range of materials that offer
themselves as fuels or raw materials and are characterized by the fact that they are
derived from recently living organisms (plants and animals). This definition clearly
excludes traditional fossil fuels, since although they are also derived from plant (coal)
or animal (oil and gas) life, it has taken millions of years to convert them to their
current form. Thus the term biomass includes feedstocks derived from materials such
c
as wood and tree based materials, forest residues, agricultural residues and energy
crops. The wood and tree materials and forest residues may include materials such as
wood, woodchips, sawdust, bark, seeds, straw, grass, and the like, from naturally
occurring plants, It includes agricultural and forestry wastes. Agricultural residue
and energy crops may further include short rotation herbaceous species, husks such as
rice husk, coffee husk etc., maize, com stover, oilseeds, residues of oilseed extraction,
cellulosic fibers like coconut, jute, and the like. The oilseeds may be typical oil
bearing seeds like soybean, camolina, canola, rapeseed, com, cottonseed, sunflower,
safflower, olive, peanut, and the like. Agricultural residue also includes material
obtained from agro-processing industries such as deoiled residue, for example, a
dcoilcd soybean cake, dcoilcd cottonseed, dcoilcd peanut cake, and the like, gums
from oil processing industry such as gum separated from the vegetable oil preparation
process- e.g. lecithin in the case of soybean, bagasse from sugar processing industry,
cotton gin frash and the like. It also includes other wastes from such industries such
as coconut shell, almond shell, walnut shell, sunflower shell, and the like. In addition
to these wastes from agro industries, biomass may also include wastes from animals
and humans. In some embodiments, the biomass includes municipal waste or yard
waste, sewage sludge and the like. In some other embodiments, the term biomass
includes animal farming byproducts such as piggery waste or chicken litter. The term
biomass may also include algae, microalgae, and the like.
Thus, biomass covers a wide range of materials, characterized by the
fact that they are derived from recently living plants and animals. All of these types
of biomass contain carbon, hydrogen and oxygen, similar to many hydrocarbon fuels;
thus the biomass can be used to generate energy. Biomass includes components such
as oxygen, moisture and ash and the proportion of these depends on the type and
source of the biomass used. Due to the presence of these components, the gasification
characteristics of biomass are much different than that of coal. Due to the presence of
these components that do not add to the heating value, the calorific value of biomass
is much lower than that of coal. The calorific value and composition of biomass also
depend on other factors such as seasonal and geographical variability.
7
Gasification involves a thermal processing of the biomass with an
oxygen-containing gas and steam to produce a reactor product gas. In one
embodiment, the reactor product gas is a synthesis gas. Synthesis gas or syngas is a
mixture of gases, containing carbon monoxide (CO) and hydrogen (H2). The oxygen
-containing gas is an oxygen source also referred to as an oxygen-supplying
compound - this may be oxygen itself, air, steam, carbon dioxide, or some
combination of these.
Gasification involves a number of reactions such as oxidation
reactions,
C+'/a O2 =C0 (Reaction 1)
C0+1/2 O2 =C02 (Reaction 2)
H2 +V2 O2 =H20 (Reaction 3)
the Boudouard reaction,
C+CO2 o 2 CO (Reaction 4)
the steam gasification reaction,
C+H2O <=> CO+H2 (Reaction 5)
the water-gas shift reaction,
CO+H2O <» CO2+H2 (Reaction 6)
and the methanation reaction
C+2 H2 o CH4 (Reaction 7)
A typical biomass can be represented by a chemical formula such as
CxHyOz, where x~l, y~2, and z~l. The gasification process of such biomass can be
generically represented as
CH2O o CO + H2 (Reaction 8)
The oxygen content of the biomass can be advantageously used to
minimize the amount of the externally added oxidant. However, in order for biomass
gasification to proceed accordingly to Reaction 8, additional heat must be supplied.
Thermal processing involves processing of the biomass by processes
such as pyrolysis, partial oxidation, complete oxidation, or a combination of these
processes. The term "Pyrolysis" refers to the heating of biomass in the absence of any
oxygen. "Partial oxidation" refers to the heating of the biomass in the presence of
sub-stoichiometric oxygen. "Complete oxidation" refers to the heating of the biomass
in the presence of stoichiometric or excess amounts of oxygen. Depending upon the
configuration of the reactor in which the thermal processing is carried out, more than
one of these reactions may be taking place in a single reactor. Hence, although the
term gasification used herein refers predominantly to oxygen-starved reactions such
as pyrolysis and partial oxidation, the conditions for complete oxidation may also be
present in the gasification reactor. Gasification also involves reaction of the biomass
with steam.
The term "gasifier" as used refers to a reaction vessel in which the
gasification is carried out. The gasifiers, based on gas velocities and configuration,
can be fixed bed, fluidized bed or entrained flow gasifiers or some variation of these.
The types and extent of reactions in a gasifier depends upon design and operating
conditions in the gasifier. Entrained flow gasifiers are generally employed for largescale
gasification operations. Typically, these gasifiers use pure oxygen as a
gasifying medium instead of air. Additionally, use of pure oxygen results in high
temperatures, enabling almost complete tar conversion, and the ash to be melted as
slag. However, the oxygen blow gasifier require expensive air separation unit, in
addition to having to use a large quantity of biomass. In one embodiment, the gasifier
9
is an oxygen blow gasifier. In another embodiment, the gasifier is an air blown
gasifier.
In one embodiment, the gasifier is operated at relatively high
temperatures so that at least a substantial portion of the tar component is eliminated
by cracking. In some embodiments, it is preferred to operate the gasifiers at
temperatures higher than about 1000°C. In one embodiment, the temperatures in the
gasifier are maintained in the range from about 1000°C to about I400°C. In another
embodiment, the gasifier temperature is advantageously maintained between about
1300°C and about 1400°C. In yet another embodiment, the gasifier may be
maintained at even higher temperatures. For example, operation of the oxygen blown
gasifier at temperatures of at least about 1500°C resulting in tar levels of only about 1
ppm in the product gas. However, operation at such high temperatures requires a lot
of energy and use of expensive refractory materials in the gasifier section, which may
not be economically favorable. In one embodiment, the gasifier is operated at
temperature a range fi"om about 300 °C to about 850 °C. In another embodiment, the
gasifier is operated at temperature a range from about 650 °C to about 850 °C In one
embodiment, the gasifier may be operated under pressure. In one embodiment, the
gasifier may be operated at a pressure at a range from about 30 bars to about 85 bars.
In another embodiment, the gasifier is operated at atmospheric pressure. In one
embodiment, the tar conversion to syngas is carried out in-situ in the gasifier.
In one embodiment, the biomass and the oxygen-containing gas come
in contact in the gasifier in the pre-gasification zone. The gasification of the biomass
can produce biogas, tar, ash and other impurities. The biogas as used herein includes
among others unreacted biomass particles, ash, tar, oxygen-containing gas, steam,
carbon monoxide, hydrogen. In one embodiment, the biogas passed through an exit
conduit which is coupled to the outlet for the reactor product gas. In one
embodiment, the reactor includes baffles that allow a large amount of biogas to enter
the exit conduit. The exit conduit includes a catalytic partial oxidation unit. The
catalytic partial oxidation unit includes a catalytic partial oxidation catalyst. In one
embodiment, the catalytic partial oxidation catalyst is at least one selected from the
)0
group consisting of supported Ni, Co, Fe, Ru, Rh, Pd, Pt or Ir catalysts. In one
embodiment, the catalytic partial oxidation unit is maintained at a temperature in a
range from about 600 °C to about 1150 °C. In one embodiment, the biogas exit
conduit is a cyclone. In another embodiment, the biogas exit conduit is coextensive
with the catalytic partial oxidation unit. By a proper choice of reactor geometry and
particle size of the feedstocks, flowrates and pressures of gases, gasification agents
etc., the flow field inside the gasifier can be organized in such a way that all the
biogas generated in the reactor is made to pass through the catalytic partial oxidation
unit. In one embodiment, a secondary air stream can be introduced in the biogas exit
conduit.
In one embodiment, the catalytic partial oxidation unit converts the tar
to produce a clean reactor product gas. In one embodiment, the catalytic partial
oxidation unit is a filter for the ash present in the biogas and does not allow the ash to
penetrate through the catalytic partial oxidation catalyst. In another embodiment, the
high temperature of the catalytic partial oxidation unit can melt the ash. In one
embodiment, the melted ash can be dripped back to the gasification zone where the
ash agglomeration occurs. In one embodiment, the gasifier includes an ash
agglomeration and an ash rejection zone. The agglomerated ash can be collected at an
outlet for the ash. In one embodiment, the outlet for ash is at the bottom of the
gasifier. For example, the agglomerated ash can be separated and collected at the
bottom of the gasifier via a lock-hopper. In one embodiment, when the unreacted
biogas comes in contact with the catalytic partial oxidation catalyst is further reacted
to produce reactor product gas. In one embodiment, the reactor product gas includes
H2, CO, CO2, H2O, N2, CH4, hydrocarbons containing fix)m about C2 to about C6
carbon atoms. In another embodiment, the reactor product gas includes primarily H2
and CO. In yet another embodiment, the reactor product gas comprises from about 5
to about 45 percent by volume hydrogen.
FIG. 1 is a biomass gasifier reactor (10) according to one embodiment
of the present invention. The reactor includes an inlet for biomass (12) and inlet for
oxygen containing gas and steam (14). The baffles (18) force the biomass and the
mixture of oxygen containing gas and steam to the gasification zone via the pregasification
zone (22). The biogas generated is led to the biogas exit conduit, which
is a cyclone (20) where the biogas is contacted with the catalytic partial oxidation unit
(30) and a stream of secondary air (34). The ash (24) does not pass through the
catalytic partial oxidation unit and falls at the bottom zone of the reactor, which is the
ash agglomeration zone (26). The agglomerated ash is collected via an outlet for ash
(28). The reactor product gas (36) is then let out of the biomass gasifier reactor via an
outlet (32).
FIG. 2 is a biomass gasifier reactor (40) according to one embodiment
of the present invention. The reactor includes an inlet for biomass (42) and inlet for
oxygen containing gas and steam (44). The biomass and the mixture of oxygen
containing gas and steam arc let to the gasification zone via the prc-gasification zone
(48). All the biogas generated (46) is led to the biogas exit conduit which is
coextensive with the catalytic partial oxidation unit (56). The ash (62) does not pass
through the catalytic partial oxidation unit and falls at the bottom zone of the reactor
which is the ash agglomeration zone (50). The agglomerated ash (52) is collected via
an outlet for ash (54). The tar present in the biogas on coming in contact with the
catalytic partial oxidation unit is converted into the reactor product gas. The reactor
product gas (58) is then let out of the biomass gasifier reactor via an outlet (60).
In one embodiment, the biomass may need a feed preparation step in a
feed preparation unit, where it undergoes pre-processing prior to introcucing the
biomass in the gasifier. The feed preparation of the biomass can involve a single step
or multiple steps. The feed preparation can optionally include sizing of the biomass
to a particle size range appropraite for thermal processing. The sizing operation may
include cutting, grinding, attrition, shearing etc. The lower particle size results in
better reaction rates in thermal processing operations. However, more energy is
required for the size reduction itself Thus, there is a balance involved in the particle
size used for thermal processing, and the power required for size reduction. In the
case of biomass such as sawdust, the particles are of a lower size than the preferred
size range. In such cases, the biomass may be subjected to agglomeration,
densification or briquetting, to meet the required size and density criteria, by
increasing the average size of the feedstock particles.
/ 2_
Apart from sizing the feed preparation of biomass may involve other
pre-processing steps, such as, but not limited to, moisture removal, volatile reduction,
and carbonization. Drying or moisture removal can be a separate preprocessing step
in locations where waste heat is available. The step is especially preferred in the case
of high-moisture content biomass, such as algae. In the case of other biomass with
less than about 20% moisture, sufficient moisture removal can often occur in the preheating
zone of the reactor in gasification step.
The feed preparation step may involve carbonization, wherein the
biomass is heated to a temperature in a range from about 200°C to about 400°C. This
removes substantially all of the moisture and low volatile compounds from the
biomass. The volatiles removed from the biomass may be condensed to a liquid -
sometimes referred to as "pyrolysis oil". This material has a good energy value that
may be subsequently recovered. Usually, the volatile compounds in the biomass are
responsible for the tar formation. Hence, the removal or reduction in quantity of the
volatiles results in the desirable reduction of tar during gasification step.
In one embodiment, the resultant stream of reactor product gas, can be
fed to a power production unit. In one embodiment, the stream of reactor product gas
can be used for combustion in an internal combustion engine or a gas turbine, for
generating mechanical or electrical power. The resultant stream may also be fed to
fuel cells for the generation of power. The resultant stream of reactor product gas can
also be used as a hydrogen source in chemical synthesis reactions. As non-limiting
examples, the resultant stream of reactor product gas can be used as a hydrogen
source in the hydrogenation reaction of oils; in hydrotreating processes; for
hydrodesulfurization; or for other reactions which consume hydrogen.
The reactor product gas can be directly used in applications like power
generation, mechanical work, or chemical synthesis. Typically the chemical synthesis
reactions, such as the Fischer Tropsch synthesis reaction, are used to form synthetic
hydrocarbons from synthesis gas. These reactions require the conditioning of reactor
product gas, so as to maintain a desired proportion of carbon monoxide and hydrogen.
The appropriate ratio of these compounds can be achieved by selective removal of
/3
either of the compounds. For example, if the amount of carbon monoxide in the
reactor product is higher than the desired range, it can be selectively removed by
membranes, or by preferential oxidation of CO.
In one embodiment, the reactor product gas can be used for heating
applications. As an example, the reactor product gas can be used to fire a heater to
produce thermal energy. In another embodiment, the reactor product gas can be used
in a boiler to produce steam. The steam can be further used for heating purposes,
process applications, or in a steam turbine or a gas turbine, to produce power. In
another embodiment, the reactor product gas may be introduced in a F-T reactor for
liquid biofUel production.
In one embodiment, the reactor product gas can be used in
applications, at a desired location adjacent to the site of preparation. In another
embodiment, the reactor product gas can be transported to other sites (sometimes
distant), for storage, further processing, or use in a selected application. Those skilled
in the art are familiar with storage and transportation techniques for such materials.
FIG. 3 shows a schematic representation of a distributed biomass to
biofuel and/or biomass to power and heat co-generation system (70) according to one
embodiment of the invention. The biomass (74) is fed into a dry feeding system (72)
such as for example a Posimetric® solid pump or a lock-hopper system. The biomass
feed particles (76) from the feeding system is introduced into a biomass gasifier (78)
that may be mainatined either at atmospheric or high pressure. The gasifier (78)
includes a catalytic partial oxidation unit (80) that contains the catalytic partial
oxidation catalyst. The reactor product gas and the unreacted biogas are contacted to
the catalytic partial oxidation unit. In one embodiment, catalytic gasification of
biogas and biomass particle occurs at the catalytic partial oxidation unit. Further tar
that comes in contact with the catalytic partial oxidation unit is converted to the
reactor product gas. The ash and other particulate matter that may be present in the
biogas are not allowed to pass through the catalytic partial oxidation unit. The
temperature of the catalytic partial oxidation unit aids to melt the ash. The melted ash
is then taken back to the gasification zone where the ash gets agglomerated (84) and is
collected at the bottom of the gasifler at an ash collection outlet (92). The reactor
product gas (86) is substantially free of tar, ash and particulate matter is fed into a gas
engine (90) for power generation.
The foregoing examples are merely illustrative, serving to exemplify
only some of the features of the invention. The appended claims are intended to claim
the invention as broadly as it has been conceived and the examples herein presented
are illustrative of selected embodiments from a manifold of all possible embodiments.
Accordingly, it is the Applicants' intention that the appended claims are not to be
limited by the choice of examples utilized to illustrate features of the present
invention. As used in the claims, the word "comprises" and its grammatical variants
logically also subtend and include phrases of varying and differing extent such as for
example, but not limited thereto, "consisting essentially of and "consisting of"
Where necessary, ranges have been supplied; those ranges are inclusive of all subranges
there between. It is to be expected that variations in these ranges will suggest
themselves to a practitioner having ordinary skill in the art and where not already
dedicated to the public, those variations should where possible be construed to be
covered by the appended claims. It is also anticipated that advances in science and
technology will make equivalents and substitutions possible that are not now
contemplated by reason of the imprecision of language and these variations should
also be construed where possible to be covered by the appended claims.

WE CLAIM :
1. A biomass gasifier comprising:
(a) a reactor comprising (i) an inlet for biomass, (ii) an inlet for an oxygen -
containing gas, (iii) an inlet for steam, (iv) an outlet for reactor product gas, (v) an
outlet for ash, (vi) a biogas exit conduit coupled to the outlet for the reactor product
gas, the biogas exit conduit comprising a catalytic partial oxidation unit, the catalytic
partial oxidation unit substantially restricting the biogas exit conduit, and (vii) an inlet
for a secondary oxygen source.
2. The biomass gasifier of claim 1, wherein the biogas exit conduit is a
cyclone.
3. The biomass gasifier of claim 1, wherein the biogas exit conduit is
coextensive with the catalytic partial oxidation unit.
4. The biomass gasifier of claim 1, wherein the reactor comprises a pregasification
zone.
5. The biomass gasifier of claim 1, wherein the reactor comprises an ash
agglomeration zone.
6. The biomass gasifier of claim 1, wherein the reactor comprises baffles.
7. A biomass gasifier comprising:
(a) a reactor comprising (i) an inlet for biomass, (ii) an inlet for an oxygen -
containing gas, (iii) an inlet for steam, (iv) an outlet for reactor product gas, (v) an
outlet for ash, (vi) a cyclone coupled to the outlet for the reactor product gas, the
cyclone comprising a catalytic partial oxidation unit, the catalytic partial oxidation
unit substantially restricting the biogas exit conduit, and (vii) an inlet for a secondary
oxygen source.
8. The biomass gasifier of claim 7, wherein the reactor comprises a pregasification
zone.
9. The biomass gasifier of claim 7, wherein the reactor comprises an ash
agglomeration zone.
10. The biomass gasifier of claim 1, wherein the reactor comprises baffles.
11. A system comprising:
a biomass feed unit;
a biomass gasifier comprising (a) a reactor comprising (i) an inlet for
biomass, (ii) an inlet for an oxygen - containing gas, (iii) an inlet for steam, (iv) an
outlet for reactor product gas, (v) an outlet for ash, (vi) a biogas exit conduit coupled
to the outlet for the reactor product gas, the biogas exit conduit comprising a catalytic
partial oxidation unit, the catalytic partial oxidation unit substantially restricting the
biogas exit conduit, and (vii) an inlet for a secondary oxygen source;
a gas clean up unit; and
a power production unit.
12. The system of claim 11, wherein the biomass feed unit further comprises
a feed preparation unit.
13. The system of claim 11,wherein the biogas exit conduit comprises a
cyclone.
14. The system of claim 11, wherein the power production unit comprises a
turbine.
15. The system of claim 11, wherein the power production unit comprises an
internal combustion engine.
16. The system of claim 11, wherein the power production unit comprises a
fuel cell.
17. A method for biomass gasification comprising:
|7
(a) heating biomass in the presence of steam and oxygen to produce a
biogas, said heating being carried out in a reactor comprising (i) an inlet for biomass,
(ii) an inlet for an oxygen - containing gas, (iii) an inlet for steam, (iv) an outlet for
reactor product gas, (v) an outlet for ash, (vi) a biogas exit conduit coupled to the
outlet for the reactor product gas, the biogas exit conduit comprising a catalytic partial
oxidation unit, the catalytic partial oxidation unit substantially restricting the biogas
exit conduit, and (vii) an inlet for a secondary oxygen source;
(b) flowing a substantial amount of the biogas through the catalytic
partial oxidation unit to produce a reactor product gas; and
(c) collecting the reactor product gas.
18. The method according to claim 17, wherein said heating is carried out at
a temperature in a range of from about 300 °C to about 850 °C.
19. The method according to claim 17, wherein said catalytic partial
oxidation unit is operated at a temperature in a range from about 600 °C to about 1150
T.
20. The method according to claim 17, wherein said reactor product gas
comprises from about 5 to about 45 percent by volume hydrogen.
21. The method according to claim 17, wherein said biomas is non-edible
agricultural waste.