U.S. patent application number 12/333498 was filed with the patent office on 2009-06-18 for process for pyrolysis of glycerol-containing feedstocks.
Invention is credited to Axel Behrens, Wibke Korn, Frank Wiessner, Hubertus WINKLER, Hans-Jorg Zander.
Application Number | 20090151254 12/333498 |
Document ID | / |
Family ID | 40751406 |
Filed Date | 2009-06-18 |
United States Patent
Application |
20090151254 |
Kind Code |
A1 |
WINKLER; Hubertus ; et
al. |
June 18, 2009 |
PROCESS FOR PYROLYSIS OF GLYCEROL-CONTAINING FEEDSTOCKS
Abstract
A process and apparatus for producing a hydrogen-containing
product gas (4) from a glycerol-containing feedstock (1). A product
gas (4) is produced from the glycerol-containing feedstock (1) by
separation of undesirable substances (V) and the pyrolysis of
glycerol (P).
Inventors: |
WINKLER; Hubertus; (Grainau,
DE) ; Wiessner; Frank; (Pullach, DE) ; Zander;
Hans-Jorg; (Munchen, DE) ; Behrens; Axel;
(Munchen, DE) ; Korn; Wibke; (Krailling,
DE) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD., SUITE 1400
ARLINGTON
VA
22201
US
|
Family ID: |
40751406 |
Appl. No.: |
12/333498 |
Filed: |
December 12, 2008 |
Current U.S.
Class: |
48/62R ;
48/197R |
Current CPC
Class: |
C01B 2203/1258 20130101;
C01B 2203/0233 20130101; C01B 3/22 20130101; C01B 2203/148
20130101; C01B 2203/1217 20130101; C01B 2203/025 20130101; C01B
2203/0266 20130101 |
Class at
Publication: |
48/62.R ;
48/197.R |
International
Class: |
C10J 3/48 20060101
C10J003/48; C10J 3/46 20060101 C10J003/46 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2007 |
DE |
10 2007 060 166.4 |
Claims
1. A process for producing a hydrogen-containing product gas (4)
from a glycerol-containing feedstock (1), containing impurities,
comprising the steps of (a) separating the impurities from the
glycerol-containing feedstock (1) and (b) subjecting the resultant
glycerol (P) to pyrolysis to produce a hydrogen-containing product
gas.
2. A process according to claim 1, wherein the step of separating
of impurities present in the feedstock and/or produced during the
process and the step of pyrolysis of glycerol are conducted
simultaneously in one process step.
3. A process according to claim 1, wherein the product gas (4) is
obtained from the feedstock (1) in at least two successive process
steps, whereby in each of the process steps, impurities are
separated and/or glycerol is reacted by pyrolysis.
4. A process according to claim 1, wherein the pyrolysis (P) is
conducted with water and/or steam and/or an oxidizing agent wherein
the oxidizing agent is air or oxygen-enriched air or oxygen.
5. A process according to claim 1, wherein impurities present in
the feedstock (1) are separated by distillation (V) and/or thermal
drying and/or filtering on activated carbon and/or membrane and/or
chromatography and/or ion exchange and/or ion exclusion and/or
precipitation.
6. A process according to claim 5, comprising the thermal drying of
the feedstock, said thermal drying being conducted at temperatures
sufficient to cause at least a partial pyrolysis of the glycerol
contained in the feedstock (1).
7. A process according to claim 1, wherein an aqueous mixture (3)
accumulates during the separating of impurities from the feedstock
(1) in which the separated impurities are present in dissolved
and/or suspended form, and subjecting the aqueous mixture to drying
in a thermal drying system (G), to obtain a largely anhydrous solid
fraction (6) and a gas fraction (7).
8. Apparatus for producing a hydrogen-containing product gas (4)
from a glycerol-containing feedstock (1), comprising means for
separating from the feedstock by contaminants from a feedstock and
means for subjecting resultant contaminant-depleted feedstock
containing glycerol to pyrolysis (P) of the glycerol.
9. Apparatus according to claim 8, wherein the pyrolysis system
comprises means for thermal drying of the feedstock, in which a
gas-free and a largely anhydrous solid fraction can be produced
from the feedstock, whereby glycerol that is present in the gas
fraction is at least partially pyrolyzed based on the temperatures
prevailing in the thermal drying means.
10. Apparatus according to claim 8, wherein the pyrolysis system
comprising purification means (V) and a downstream pyrolysis
reactor (P), whereby a pyrolysis feedstock (2) can be produced in
the purification system from the feedstock (1) by separation of
contaminants and can be reacted in the product gas (4) in the
pyrolysis reactor (P) by pyrolysis.
11. Apparatus according to claim 8, wherein the purification means
(V) comprises a vacuum distillation system and/or a thermal drying
system and/or a filtering system with activated carbon or membrane
and/or a chromatography system and/or an ion exchanger and/or ion
exclusion system and/or a precipitation and separation system.
12. Apparatus according to claim 8, wherein comprising means (G)
for reducing the water content of waste water comprising material
that accumulates when the glycerol-containing feedstock (1) is
purified.
13. A process according to claim 1, comprising providing a crude
glycerol feed containing salt impurities from a transesterification
reaction subjecting said crude glycerol feed to a distillation so
as to provide an overhead of purified glycerol and a bottoms of a
liquid waste product containing salts subjecting the purified
glycerol to pyrolysis so as to obtain a hydrogen-containing product
passing the liquid waste product containing salts from the
distillation to a fluidized bed granulator branching a stream of
pyrolyzed glycerol containing hydrogen into said granulator so as
to provide heat for drying, and withdrawing from said granulator
granulated salts and a stream comprising dust and primarily gases,
and scrubbing the stream comprising dust and primarily gases with
water so as to provide a water stream containing said dust as a
bottoms product and an overhead comprising mostly pyrolysis gas and
steam.
Description
[0001] The invention relates to a process for producing a
hydrogen-containing product gas (product gas) from a
glycerol-containing feedstock as well as a device for implementing
the process.
[0002] In an attempt to reduce the introduction of carbon dioxide
into the earth's atmosphere or at least to not let it increase
further, and as alternatives to the dwindling natural oil and
natural gas reserves, energy sources in enhanced form will be
produced in the future from renewable raw materials. According to
an EU guideline, at least 5.75% of the fuel requirement is to be
covered by such energy sources in the European Union until 2010. In
this connection, biodiesel, which even now is added at a
concentration of up to five percent to the diesel fuel available at
German gas stations, plays a tremendous role.
[0003] Biodiesel is a standardized fuel that is obtained from,
e.g., rapeseed oil but also from other plant oils and fats. Plant
oils and fats consist of triglycerides, i.e., fatty acid tri-esters
of glycerol. This structure causes plant oils and fats to be
viscous to solid at normal ambient temperatures, i.e., to have a
much higher viscosity than the fuels for which a commercially
available diesel engine is designed. Plant oils and fats behave
differently in the injection process, and also the combustion
proceeds less cleanly. These drawbacks can be only incompletely
compensated for even by motor-driven interventions--such as, for
example, preheating the plant oil.
[0004] Biodiesel is produced from plant oils and fats by the
replacement of glycerol by methanol. Its viscosity corresponds to
that of commercially available diesel fuel, which is why it can be
easily consumed even in unmodified diesel engines.
[0005] The glycerol that is separated from the plant oils and fats
in the biodiesel production is not obtained in pure form but rather
accumulates as a portion of the mixture of materials, which contain
larger amounts of contaminants in addition to glycerol. Such a
mixture of materials is, for example, so-called crude glycerol,
which has a glycerol content of 80-85%, but in addition also
contains water, salts e.g. potassium salts, and organic
contaminants (e.g., fatty acids or methanol) as well as residues
from the production process in still larger amounts. According to
the prior art, the crude glycerol is purified in expensive process
steps by vacuum distillation, deodorizing and filtration, to the
extent that it is sufficient for the strict requirements of the
European Pharmacopeia and can be sold to the pharmaceutical
industry with a purity of at least 99.5% as a pharmaceutical
glycerol. At present, the entire amount of glycerol that
accumulates in the biodiesel production can be used in this way.
With the foreseeable expansion of the biodiesel production, this
will be increasingly more difficult in the future, however, so that
other ways of using crude glycerol must be sought.
[0006] It is therefore the object of the invention to provide a
process of the above-mentioned type as well as apparatus for
implementing the process, which make it possible to direct
glycerol-containing by-products that accumulate in biodiesel
production to a productive use.
[0007] This object is achieved according to the process side of the
invention in that a product gas is produced from the
glycerol-containing feedstock by separation of undesirable
substances and pyrolysis of glycerol.
[0008] In this connection, pyrolysis is defined as the thermal
decomposition of glycerol in volatile molecules, whereby the
decomposition is carried out with the exclusion of oxygen and water
or--deviating from the usual definition--in the presence of oxygen
and/or water.
[0009] The invention is based on the experience that when
glycerol-containing feedstocks, such as, for example, crude
glycerol, are put to direct use by gasification, problems
arise--which cannot be overcome or can be overcome only at great
expense--owing to the high proportion of contaminants that are
present in the feedstocks. Thus, salts lead to corrosion of system
parts. Also, organic contaminants are controlled only with
difficulty and can result in deposits and the formation of carbon
black.
[0010] One embodiment of the process according to the invention
calls for the separation of undesirable substances--already present
in the feedstock and/or produced in the implementation of the
process according to the invention--and the pyrolysis of glycerol
to be implemented simultaneously in one process step.
[0011] Another embodiment of the process according to the invention
calls for a product gas to be obtained from the feedstock in at
least two successive process steps, whereby in each of the process
steps, undesirable substances are separated and/or glycerol is
reacted by pyrolysis.
[0012] To separate undesirable substances that are present in the
feedstock, the feedstock according to the invention is preferably
subjected to a distillation and/or a thermal drying and/or a
filtering on activated carbon and/or a membrane and/or
chromatography and/or an ion exchange and/or an ion exclusion
and/or a precipitation.
[0013] In a suitable way, the water or steam content in the
glycerol-containing fraction that was recovered by separating
undesirable substances from the feedstock is set at a value by
adding or removing water or steam, which makes it possible to
implement a subsequent pyrolysis without the formation of carbon
black and with simultaneously minimum energy input.
[0014] Another embodiment of the process according to the invention
calls for the water required for pyrolysis to be fed in more than
one step (in a stepped process), whereby the water is fed before
and/or during pyrolysis at a suitable location. If pyrolysis is
implemented in several successive steps (pyrolysis steps), it is
useful for water to be added in each case before a pyrolysis
step.
[0015] If the glycerol-containing fraction is fed in liquid form to
pyrolysis, water is preferably fed in the form of steam, whereby
the steam is sprayed into the glycerol-containing fraction or the
glycerol-containing fraction is sprayed into the steam. A portion
of the energy required for the subsequent pyrolysis is already
introduced with the steam, which results in a reduced heating
expense in the pyrolysis reactor and in a reduction of the
equipment cost for the pyrolysis reactor.
[0016] Since it is possible to pressurize, at low cost, the
glycerol-containing fraction in liquid form and to conduct
pyrolysis at an increased pressure, the process according to the
invention is suitable in particular for producing a product gas
under increased pressure. Thus, an expensive compression of the
product gas can be eliminated.
[0017] In this connection, thermal drying is defined as the
feedstock being introduced into a thermal drying system and being
subjected there to a thermal treatment. Volatile components, such
as water and glycerol, are evaporated and form a gas fraction
possibly with other gaseous substances, while solids, such as, for
example, salts, are converted into a largely anhydrous solid
fraction. Solid and gas fractions are then separated to a large
extent from the thermal drying system, which is equipped for this
purpose with a suitable system for separating dust and gas, such
as, for example, a gravity separator and/or a cyclone and/or a
filtering system and/or a water scrubber.
[0018] At sufficiently high temperatures, glycerol is thermally
decomposed, i.e., pyrolyzed into a gas containing hydrogen. Further
developing the process according to the invention, it is therefore
proposed that the thermal drying of the feedstock be implemented at
temperatures in which at least part of the glycerol contained in
the feedstock is pyrolyzed. Depending on how much of the glycerol
is pyrolyzed in the thermal drying, the gas fraction is subjected
to further pyrolysis downstream of the thermal drying.
[0019] An advantageous embodiment of the process according to the
invention calls for the heat that is required for thermal drying of
the feedstock to be removed from the hot product gas.
[0020] Preferably, for thermal drying of the feedstock,
fluidized-bed granulators and/or fluidized-bed dryers and/or drum
dryers and/or fluid-bed dryers and/or suspension dryers and/or
paste dryers are used.
[0021] Variants of the process according to the invention call for
the pyrolysis to be implemented while water and/or steam and/or an
oxidizing agent are being fed in, whereby the oxidizing agent is
air or oxygen-enriched air or oxygen.
[0022] The application of oxygen during the pyrolysis step refers
to another reaction option. The glycerol will react partly with the
oxygen to steam and CO/CO.sub.2. The benefit is the internally
generated heat which is used for the pyrolysis of the remaining
glycerol. This results in decreased operating costs owing to an
improved heat transfer/balance. This variant will lower the
requirement of energy from the externally applied heat (usually
methane) but will use some of the glycerol and the applied oxygen
to form CO/CO.sub.2.
[0023] Based on the process, which is selected for separating
undesirable substances from the feedstock, an aqueous mixture
(waste water), in which the separated substances are present in
dissolved and/or suspended form and whose material cannot be used
without additional treatment, can accumulate when the process
according to the invention is implemented. The waste water
represents a waste that has to be shipped to a hazardous waste site
at a dump. To keep dumping costs low, an attempt is made to keep
the volume of waste to be dumped as small as possible. An
embodiment of the process according to the invention therefore
calls for the waste water to be subjected to a treatment in which
the volume of waste to be deposited is reduced. The waste water is
preferably subjected to drying in a thermal drying system, whereby
a largely anhydrous solid fraction and a gas fraction are produced.
In the most advantageous case, the thus obtained solid fraction can
be used economically (e.g., as fertilizer), so that the volume of
waste to be dumped drops to zero.
[0024] An advantageous embodiment of the process according to the
invention therefore calls for the heat that is required for thermal
drying of waste water to be removed from hot product gas. Based on
the heat that is released from the hot product gas to the waste
water, volatile components pass from the waste water into the gas
phase, by which a gas fraction and a largely anhydrous solid
fraction--which is present, for example, as a granulate or powder
depending on the drying process that is used--are produced.
[0025] The hot gas stream that is used for thermal drying of waste
water is a part of the product gas, and its heat is transferred in
direct heat exchange to the waste water to be dried, thus a further
development of the process according to the invention calls for the
gas fraction that is produced during drying to preferably be
subjected to a water scrubbing system of a water scrubber and then
be recycled before pyrolysis. In a suitable way, the charged
scrubber water is drawn off from the water-scrubber system and
mixed in with glycerol-containing feedstock.
[0026] For thermal drying of waste water, fluidized-bed granulators
and/or fluidized-bed dryers and/or drum dryers and/or fluid-bed
dryers and/or suspension dryers and/or paste dryers are preferably
used.
[0027] The invention also relates to a device for implementing the
process according to the invention.
[0028] In terms of the device, this object is achieved in that it
comprises a pyrolysis system in which a product gas can be produced
from the feedstock by separation of contaminants and pyrolysis of
the glycerol contained in the feedstock.
[0029] A preferred embodiment of the device according to the
invention calls for the pyrolysis system to consist of a thermal
drying system, in which a gas-free and largely anhydrous solid
fraction can be produced from the feedstock, whereby based on the
temperatures prevailing in the thermal drying system, glycerol that
is present in the gas fraction is at least partially pyrolyzed. In
a suitable way, the thermal drying system comprises a suitable
system for separating dust from the gas fraction, so that a largely
dust-free product gas can be produced. Preferably, the thermal
drying system is a fluidized-bed granulator and/or a fluidized-bed
dryer and/or a drum dryer and/or a fluid-bed dryer and/or a
suspension dryer and/or a paste dryer. Such thermal drying systems
have been known to one skilled in the art for many years and are
available on the market.
[0030] Another preferred embodiment of the device according to the
invention calls for the pyrolysis system to comprise a purification
system and a downstream pyrolysis reactor, whereby a prolysis
feedstock, which can be reacted into product gas in the pyrolysis
reactor by pyrolysis, can be produced in the purification system
from the feedstock by separation of contaminants. According to the
invention, the purification system is preferably designed as a
vacuum distillation system and/or a thermal drying system and/or a
filtering system with activated carbon or membrane and/or a
chromatography system and/or an ion exchanger and/or an ion
exclusion system and/or a precipitating and separating system.
[0031] A suitable embodiment of the device according to the
invention calls for a suitable system with which the water or the
steam content of the glycerol-containing fraction--obtained by
separation of undesirable substances from the feedstock--can be
adjusted preferably to a value that is advantageous for
implementing a subsequent pyrolysis by adding or removing water or
steam.
[0032] Another embodiment of the device according to the invention
calls for a suitable system with which the water that is required
for pyrolysis can be fed to a suitable location in front of the
pyrolysis reactor and/or in the pyrolysis reactor in more than one
step (in a stepped process). If the pyrolysis is implemented in
several pyrolysis reactors that are arranged in series, water can
be fed in each case in front of a pyrolysis reactor in a useful
way.
[0033] If the glycerol-containing fraction is fed to the pyrolysis
system in liquid form, the device according to the invention
preferably comprises a system for mixing steam with the
glycerol-containing fraction (mixer), whereby steam can be injected
into the glycerol-containing fraction or the glycerol-containing
fraction can be injected into the steam. In an attempt to design
the mixer as compactly as possible, a nozzle--via which the
glycerol-containing fraction is sprayed as a fine mist into the
greatly turbulent steam--is provided, for example, at a suitable
location. A portion of the energy required for the subsequent
pyrolysis is already introduced with the steam, which results in a
reduced heat demand in the pyrolysis reactor and in a reduction of
the equipment cost for the pyrolysis reactor.
[0034] An advantageous variant of the device according to the
invention calls for a system for reducing the water content of an
aqueous mixture (waste water) whose material cannot be further used
and that accumulates when the glycerol-containing feedstock is
purified. Preferably, this system is a thermal drying system, such
as, for example, a fluidized-bed granulator and/or a fluidized-bed
dryer and/or a drum dryer and/or a fluid-bed dryer and/or a
suspension dryer and/or a paste dryer. Such thermal drying systems
have been known to one skilled in the art for years and are
available on the market, by such companies as GEA Barr-Rosin, ALL
GAIER and FIMA, for example. In a suitable way, the thermal drying
system is designed so that a largely anhydrous solid fraction and a
largely dust-free gas fraction can be produced from the waste
water.
[0035] The thermal drying system is a system in which energy can be
fed to the waste water to be dried in direct contact with hot
product gas; thus, an advantageous embodiment of the device
according to the invention calls for a water scrubbing system into
which the dust-charged gas stream that exits from the thermal
drying system can be introduced and freed from dust there by water
scrubbing before it is recycled and fed to the pyrolysis reactor as
feedstock. In a suitable way, the charged scrubbing water can be
removed from the water scrubber and mixed in with the crude
glycerol.
BRIEF DESCRIPTION OF DRAWING
[0036] Below, the invention is to be explained in more detail based
on a non-limiting preferred embodiment that is depicted
diagrammatically in the FIGURE:
[0037] This embodiment relates to a unit for producing a product
gas, whereby crude glycerol from the biodiesel production is used
as a feedstock.
[0038] Via line 1, the crude glycerol is introduced into the vacuum
distillation system V, where it is separated into two streams 2 and
3. Then, the stream 2, which consists almost exclusively of
evaporated glycerol, is sent to the pyrolysis reactor P as a
feedstock and is converted there to a hydrogen-containing product
gas, which is drawn off via line 4 from the pyrolysis reactor P.
Stream 3 from the vacuum distillation system V, which consists
primarily of water and salts, as well as residues from the
biodiesel production, is sent to the granulator G and dried there
by means of a part 5 of the hot hydrogen-containing product gas 4.
The salts and other solids contained in stream 3 are converted into
a granulate and drawn off via line 6 from the granulator G. Via
line 7, a stream, which consists primarily of gases and vapors, but
in addition also contains solids in dust form, is fed to the water
scrubbing system W and purified there. A part of the charged
scrubber water from the water scrubbing system W is drawn off via
line 8 and introduced together with the crude glycerol via line 1
into the vacuum distillation system V, while the other part 9 is
mixed with fresh water 10 and is recycled as scrubbing water in the
water scrubber system W. Via line 11, a stream that consists
largely of product gas and steam is drawn off from the water
scrubber system W and fed together with the glycerol stream 2 to
the pyrolysis reactor P.
[0039] As compared to the above described embodiment in a one-step
process, the crude glycerol is heated up to a temperature high
enough to evaporate glycerol, and hence separate it from the
impurities, and simultaneously crack the glycerol molecules in a
pyrolysis reaction.
[0040] Conversely, the first step of the two-step process is a
purification step, in which glycerol is mainly evaporated, in order
to separate it from impurities. Whether pyrolysis takes place in
the purification step depends on the applied temperature within the
purification. If the temperature is high enough, the pyrolysis of
glycerol starts in the purification step.
[0041] Without further elaboration, it is believed that one skilled
in the art can, using the preceding description, utilize the
present invention to its fullest extent. The preceding preferred
specific embodiments are, therefore, to be construed as merely
illustrative, and not limitative of the remainder of the disclosure
in any way whatsoever.
[0042] The entire disclosures of all applications, patents and
publications, cited herein and of corresponding German application
No. 10 2007 060 166.4, filed Dec. 13, 2007 are incorporated by
reference herein.
[0043] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention
and, without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *