U.S. patent application number 12/234844 was filed with the patent office on 2009-03-26 for process and device for gasification of crude glycerol.
Invention is credited to Axel Behrens, Wibke Korn, Anton Wellenhofer, Hans Jorg ZANDER.
Application Number | 20090077888 12/234844 |
Document ID | / |
Family ID | 40384181 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090077888 |
Kind Code |
A1 |
ZANDER; Hans Jorg ; et
al. |
March 26, 2009 |
PROCESS AND DEVICE FOR GASIFICATION OF CRUDE GLYCEROL
Abstract
The invention relates to a process as well as a device for
continuous thermal decomposition (pyrolysis) of a mixture of
substances (crude glycerol) (1) that contains glycerol, salts and
water, whereby the crude glycerol (1) is heated in a reactor
(pyrolysis reactor) (R) to a temperature (pyrolysis temperature) of
more than 100.degree. C. The pyrolysis of the crude glycerol (1) is
performed at a pressure (pyrolysis pressure) that is higher than
the vapor pressure of the water, present in the pyrolysis reactor
(R), at pyrolysis temperature, and salts and other higher-boiling
substances together with water are drawn off continuously from the
pyrolysis reactor (R) as waste water (3).
Inventors: |
ZANDER; Hans Jorg; (Munchen,
DE) ; Wellenhofer; Anton; (Hohenschaftlarn, DE)
; Behrens; Axel; (Munchen, DE) ; Korn; Wibke;
(Munchen, DE) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD., SUITE 1400
ARLINGTON
VA
22201
US
|
Family ID: |
40384181 |
Appl. No.: |
12/234844 |
Filed: |
September 22, 2008 |
Current U.S.
Class: |
48/78 ;
48/206 |
Current CPC
Class: |
C01B 2203/0272 20130101;
C01B 2203/1217 20130101; C01B 3/22 20130101; C01B 2203/0277
20130101 |
Class at
Publication: |
48/78 ;
48/206 |
International
Class: |
C10J 3/68 20060101
C10J003/68; C10L 3/00 20060101 C10L003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2007 |
DE |
10 2007 045 360.6 |
Claims
1. A process for continuous thermal decomposition of a crude
glycerol mixture containing glycerol, salts and water, comprising:
heating said crude glycerol mixture (1) in a pyrolysis reactor (R)
to a pyrolysis temperature of more than 100.degree. C., wherein
pyrolysis of the crude glycerol mixture (1) is performed at a
pyrolysis pressure that is higher than the vapor pressure of water
present in said pyrolysis reactor (R), at said pyrolysis
temperature, and withdrawing continuously salts and other
higher-boiling substances, together with water, from the pyrolysis
reactor (R) as waste water (3).
2. A process according to claim 1, wherein said process is
performed at a pyrolysis temperature of 290.degree. C.-370.degree.
C.
3. A process according to claim 1, wherein said process is
performed at a pyrolysis temperature of 290.degree. C.-340.degree.
C.
4. A process according to claim 1, wherein said process is
performed at a pyrolysis temperature of 290.degree. C.-310.degree.
C.
5. A process according to claim 1, wherein said crude glycerol
mixture (1) is thermally decomposed in the presence of acids and/or
Lewis acids.
6. A process according to claim 1, wherein the heat required for
the pyrolysis is introduced into the pyrolysis reactor (R) by
indirect heating via heating surfaces and/or by direct heating via
high-pressure vapor (2).
7. A process according to claim 1, wherein a pyrolysis gas,
produced by pyrolysis of crude glycerol mixture in said pyrolysis
reactor (1) is superheated to cleave long-chain compounds contained
therein and thereby form hydrogen and/or carbon monoxide.
8. An apparatus for thermal decomposition of a crude glycerol
mixture (1) containing glycerol, salts and water, said apparatus
comprising: a pyrolysis reactor (R) having a feed inlet (Z) for
feeding of a crude glycerol mixture, a gas discharge outlet (H) for
discharging a gaseous pyrolysis product, means for heating the
crude glycerol mixture (1) to a pyrolysis temperature of more than
100.degree. C., wherein said pyrolysis reactor (R) is a pressure
vessel, in which a crude glycerol mixture (1) is gasifiable at a
pressure higher than the vapor pressure of water present in the
pyrolysis reactor, at the pyrolysis temperature, and wherein said
pyrolysis reactor (R) has a second discharge outlet for discharging
waste water (A), via which salts and other higher-boiling
substances together with water can be drawn off continuously from
pyrolysis reactor (R) as waste water (3).
9. An apparatus according to claim 8, wherein between the crude
glycerol feed inlet (Z) and the second discharge outlet for
discharging waste water (A), the pyrolysis reactor further
comprises built-in components (T) that ensure a sufficiently long
dwell-time of crude glycerol (1) in the pyrolysis reactor (R) to
avoid premature removal of glycerol with the waste water (3).
10. An apparatus according to claim 8, wherein said apparatus
further comprises a device for superheating (U) the pyrolysis gas,
in which pyrolysis gas can be heated to a temperature higher than
the pyrolysis temperature.
11. An apparatus according to claim 8, wherein said apparatus
further comprises a feed means for introducing high-pressure vapor
(D) into the pyrolysis reactor (R), whereby energy required for
pyrolysis can be introduced into the pyrolysis reactor (R) via
high-pressure vapor.
Description
[0001] The invention relates to a process for continuous thermal
decomposition (pyrolysis) of a mixture of substances (crude
glycerol) that contains glycerol, salts and water, whereby the
crude glycerol is heated in a reactor (pyrolysis reactor) to a
temperature (pyrolysis temperature) of more than 100.degree. C., as
well as a device for performing the process.
[0002] In an attempt to reduce the input of carbon dioxide into the
Earth's atmosphere or at least not allow it to increase further,
and as alternatives to the shrinking crude oil and natural gas
reserves, energy sources from renewable raw materials will be
increasingly produced in the future. 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 by 2010. In this connection,
biodiesel, which is already now added at a concentration of up to
five percent to diesel fuel available to German gas stations, plays
a tremendous role.
[0003] Biodiesel is a standardized fuel that is obtained primarily
from rapeseed oil, but also from other vegetable oils and fats.
Vegetable oils and fats consist of triglycerides, i.e., compounds
in which three fatty acids are bonded to glycerol. As a result of
this chemical structure, vegetable oils and fats are viscous to
solid at normal ambient temperatures, i.e., they have a much higher
viscosity than the fuels for which a current diesel engine is
designed. Thus, vegetable oils and fats behave differently in the
injection process, and also the combustion of vegetable oils and
fats runs less cleanly. These drawbacks can be compensated only
incompletely by powered interventions - such as, for example, the
preheating of the vegetable oil.
[0004] Biodiesel is produced from vegetable oils and fats by
replacement of glycerol with methanol. The viscosity of biodiesel
corresponds to the commercially available diesel fuel, and thus it
can easily be burned even in non-modified diesel engines.
[0005] The glycerol that is separated from vegetable oils and fats
during biodiesel production is not obtained in pure form, but
instead the glycerol accumulates as part of a mixture of substances
which, in addition to glycerol, contains larger amounts of
contaminants. Such a mixture of substances, for example, so-called
crude glycerol, has a glycerol content of 80-85%, but, moreover,
also contains water and salts in still larger amounts as well as
residual substances from the production process. According to prior
art processes, crude glycerol is purified in expensive process
steps by vacuum distillation, deodorization, and filtration to the
extent that the purified glycerol satisfies the strict requirements
of the European Pharmacopeion and can be purchased with a purity of
at least 99.5% as a pharmaglycerol in the pharmaceutical industry.
At present, the entire amount of glycerol accumulating in biodiesel
production can be used in this way. However, with the foreseeable
expansion of biodiesel production, this will become increasingly
difficult in the future, such that still other methods of use of
the crude glycerol must be sought.
[0006] In several patent applications filed with the German Patent
and Trademark Office (1020060178888.2, 102006020985.0,
102006051262.6, 102006056641.6), the disclosures of which are
hereby incorporated by reference in the entirety, alternative
processes for using crude glycerol are proposed, in which the crude
glycerol is reacted by thermal decomposition (pyrolysis) to form a
gaseous pyrolysis product (pyrolysis gas). While in one of these
patent applications (102006056641.6), the glycerol is separated
from the crude glycerol before pyrolysis, for example by vacuum
distillation, the other patent applications describe processes in
which the crude glycerol is fed to a pyrolysis without preliminary
treatment.
[0007] To decompose glycerol thermally, the glycerol is fed to a
reactor (pyrolysis reactor) according to the prior art and heated
to temperatures of more than 100.degree. C., optionally in the
presence of acids or Lewis acids. Under these conditions, pure
glycerol, for examples glycerol separated from crude glycerol, is
reacted without residue in pyrolysis gas. Water contained in the
pyrolysis reactor is evaporated and conveyed together with the
pyrolysis gas discharged from the pyrolysis reactor. However, if
untreated crude glycerol is reacted in this way, higher-boiling
substances, in particular salts, remain as residues in the
pyrolysis reactor.
[0008] So as not to impair the functionality of the pyrolysis
reactor (e.g., by forming deposits), the residues must be removed.
For this purpose, either the pyrolysis reactor is shut down and
purified at intervals, or the higher-boiling substances are drawn
off continuously from the pyrolysis reactor during the pyrolysis
process together with a portion of the glycerol. Separation of the
glycerol from the crude glycerol, purification of the pyrolysis
reactor itself, and the associated unit shut-down as well as loss
of glycerol in a continuous removal of the residues produce high
costs and considerably impair the economic efficiency of the
described types of crude glycerol use.
[0009] Therefore, an aspect of this invention is to provide a
process of the type described above, as well as an apparatus for
performing the process, by which the problems and/or disadvantages
of the prior art in the pyrolysis of crude glycerol are
overcome.
[0010] In the process according to the invention, pyrolysis of the
crude glycerol is performed at a pressure (pyrolysis pressure) that
is higher than the vapor pressure of the water present in the
pyrolysis reactor at the pyrolysis temperature, and salts and other
higher-boiling substances together with water are drawn off
continuously from the pyrolysis reactor as waste water.
[0011] Higher-boiling substances are defined as those substances
that do not pass into the gaseous state under the conditions
prevailing in pyrolysis, but rather accumulate as residues.
Higher-boiling substances, such as salts, can already be contained
in the crude glycerol fed to the pyrolysis reactor, or are formed
only during pyrolysis.
[0012] The idea on which the invention is based is to produce
residues that accumulate during the pyrolysis of crude glycerol in
a flowable and sufficiently viscous form. By providing the residues
in such a form, the residues can be continuously drawn off or
removed from the pyrolysis reactor--even during the pyrolysis
process and without shutting down the unit--and without loss of
valuable glycerol from the pyrolysis reactor. In accordance with
the invention, this is achieved by performing pyrolysis at a
pressure that is higher than the vapor pressure of the water,
contained in the pyrolysis reactor, at pyrolysis temperature. The
liquid water thus also represents a residue, in which other
residues are present in dissolved form (e.g., salts) or suspended
form (e.g., carbon black).
[0013] In performing the process according to the invention, at
least a portion of the water present in the pyrolysis reactor
unavoidably changes into the gas phase and is drawn off from the
pyrolysis reactor with the pyrolysis gas. To avoid the accumulation
of the residues formed during the pyrolysis as a result of this
water loss--with a viscosity by which their continuous removal from
the pyrolysis reactor is prevented, an embodiment of the process
according to the invention provides for the addition of water to
ensures that the water content of the crude glycerol is raised to a
value that is high enough to produce residues from pyrolysis in a
sufficiently viscous form.
[0014] The pyrolysis temperature, together with the dwell time, is
decisive for the achievable crude glycerol conversion: the higher
the temperature, the greater the conversion. Pyrolysis temperatures
of more than 290.degree. C. have proven suitable. Since water
cannot be heated higher than up to 373.degree. C., it is proposed
to perform processes according to the invention at pyrolysis
temperatures of between 290 and 370.degree. C., preferably between
290 and 340.degree. C., and especially preferably between 290 and
310.degree. C.
[0015] To be able to perform the pyrolysis of pure glycerol more
effectively, acids and/or Lewis acids (subsequently referred to
only as acids) are fed to the pyrolysis reactor according to the
prior art, so that the pyrolysis of glycerol is carried out in
direct contact with these acids. The acids, which are liquids or
solids (e.g., Al.sub.2O.sub.3), act as catalysts in this connection
and are not consumed. Since it is to be expected that acids also
have an effectiveness-increasing effect on pyrolysis of crude
glycerol, it is proposed according to the invention that acids be
fed to the pyrolysis reactor so that the pyrolysis of the crude
glycerol is also carried out in direct contact with these acids.
The acids, in particular liquid acids, are drawn off from the
pyrolysis reactor with the waste water and, therefore, must be
continuously replaced by fresh acids. To keep operating costs low
and to avoid problems in disposal of waste water, the acids are
separated from the waste water in a suitable way and fed again
(recycled) to the pyrolysis reactor.
[0016] One purpose of using crude glycerol as a feed to a pyrolysis
reactor is to cleave the glycerol--contained in the crude
glycerol--completely into hydrogen and carbon monoxide and produce
a pyrolysis gas that can be used in the chemical industry as
synthesis gas for the production of a number of products. Because
of the relatively low pyrolysis temperatures, in which the process
according to the invention is performed, the pyrolysis gas produced
contains, in addition to hydrogen and carbon monoxide, long-chain
hydrocarbons. However, these long-chain hydrocarbons must be
cleaved in additional process steps. A further development of the
process according to the invention, therefore, is to superheated
the pyrolysis gas produced in the pyrolysis reactor, i.e., heated
to a temperature that is higher than the pyrolysis temperature in
order to cleave long-chain hydrocarbons contained in the pyrolysis
gas into hydrogen and carbon monoxide.
[0017] To remove entrained particles, for example, carbon black,
from the pyrolysis gas before further treatment, in particular
before superheating, according to another embodiment of the process
according to the invention the pyrolysis gas is subjected to a gas
scrubbing, which is suitably a water scrubber. The charged washing
water is preferably introduced into the pyrolysis reactor, from
which it is drawn off again with the waste water.
[0018] In accordance with another aspect of the process according
to the invention, energy required for pyrolysis is introduced
indirectly into the pyrolysis reactor via heating surfaces. As
experience has shown, there is a risk of the heating surfaces
carbonizing in this type of energy introduction. To eliminate this
risk or to at least reduce it, according to another aspect of the
process according to the invention the energy required for
pyrolysis is introduced with high-pressure vapor into the pyrolysis
reactor and is transferred to the mixture of substances (crude
glycerol mixture) that is to be decomposed thermally by direct
contact. Process variants ensure that the high-pressure vapor is
introduced into the gas chamber of the pyrolysis reactor, i.e.,
into the pyrolysis gas, and/or into the mixture of substances
(crude glycerol mixture) that is to be decomposed thermally.
[0019] The invention also relates to an apparatus for thermal
decomposition (pyrolysis) of a mixture of substances (crude
glycerol) that contains glycerol, salts and water, the apparatus
comprising a reactor (pyrolysis reactor) with a feed device (crude
glycerol feed) for the feeding of crude glycerol, and a discharge
device (gas discharge) for discharging a gaseous pyrolysis product
(pyrolysis gas), wherein the crude glycerol can be heated to a
temperature (pyrolysis temperature) of more than 100.degree. C. in
the reactor.
[0020] According to an aspect of the invention, the pyrolysis
reactor is designed as a pressure vessel, in which the crude
glycerol is gasifiable at a pressure (pyrolysis pressure) that is
higher than the vapor pressure of the water, present in the
pyrolysis reactor, at pyrolysis temperature, and in that it has a
second discharge device (waste water discharge), via which salts
and other higher-boiling substances together with water can be
drawn off continuously from the pyrolysis reactor as waste
water.
[0021] The device according to the invention is designed so that
the crude glycerol can be run through the pyrolysis reactor at a
dwell time that is long enough to react the entire amount of
glycerol fed with the crude glycerol and convert it into pyrolysis
gas.
[0022] In a suitable way, the pyrolysis reactor is equipped with
suitable built-in components, between the crude glycerol feed and
the waste water discharge, that ensure a sufficiently narrow
dwell-time distribution and thus prevent a premature glycerol
removal with the waste water.
[0023] To cleave long-chain components of the pyrolysis gas and for
conversion into hydrogen and carbon monoxide, an embodiment of the
apparatus according to the invention provides a means for
superheating pyrolysis gas (superheater), into which pyrolysis gas
formed in the pyrolysis reactor can be introduced, and in which the
pyrolysis gas can be heated to a temperature higher than the
pyrolysis temperature.
[0024] A variant of the apparatus according to the invention
provides heating surfaces, arranged inside and/or outside of the
pyrolysis reactor, via which energy required for pyrolysis can be
introduced by indirect heating into the pyrolysis reactor and can
be transferred to the mixture of substances (crude glycerol
mixture) to be decomposed thermally. Another variant of the
apparatus according to the invention is equipped with at least one
feed device for high-pressure vapor, via which energy required for
pyrolysis can be introduced via high-pressure vapor into the
pyrolysis reactor and can be transferred directly to the mixture of
substances (crude glycerol mixture) to be decomposed thermally. In
a suitable way, the feed device for high-pressure vapor is designed
as pipe connections or lances, via which the high-pressure vapor
can be introduced directly into the mixture of substances (crude
glycerol mixture) to be decomposed, or into the gas chamber of the
pyrolysis reactor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The invention and further details, such as features and
attendant advantages, of the invention are explained in more detail
below on the basis of exemplary embodiments which are
diagrammatically depicted in the drawing, and wherein:
[0026] FIG. 1 shows an embodiment of the device according to the
invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0027] In the embodiment of FIG. 1, a pyrolysis gas is produced by
pyrolysis of crude glycerol in a pyrolysis reactor designed as a
horizontal pipe. The pyrolysis gas is subsequently subjected to
water scrubbing and superheating to form a hydrogen- and carbon
monoxide-rich gas.
[0028] The pump P suctions off crude glycerol 1 and conveys it with
pyrolysis pressure into the pyrolysis reactor R via the crude
glycerol feed Z. The pyrolysis reactor R is designed essentially as
a horizontal pipe and is embodied with the compressive strength and
temperature stability necessary for the process. The interior
chamber of the pyrolysis reactor R has built-in components T that,
in this respect, ensure that the crude glycerol remains in the
pyrolysis reactor R with a uniform dwell time that is long enough
to completely thermally decompose the glycerol present in the crude
glycerol. Via line 2 and the pipe sockets D, high-pressure vapor is
introduced into the gas chamber G of the pyrolysis reactor R. The
high-pressure condenses on the surfaces of the mixture of
substances, i.e., S1-S6 (the mixture primarily being made up of
crude glycerol), and releases a majority of the energy stored
therein to the mixture of substances S1-S6, thereby heating the
latter to a pyrolysis temperature of about 300.degree. C. At this
temperature, the glycerol molecules contained in the crude glycerol
1 decompose, and a pyrolysis gas is formed that is further conveyed
via the gas discharge H into the gas scrubbing unit W (e.g., a
water scrubber). The pyrolysis pressure that prevails in the
pyrolysis reactor R prevents evaporation of the water portion in
the mixture of substances S1-S6. With progressive pyrolysis, the
glycerol content in the mixture of substances S1-S6 is reduced, and
salts and other higher-boiling substances accumulate in the water.
The free-flowing mixture of substances S6, which accomplishes the
removal of waste water A, is ultimately free of glycerol to a large
extent and is drawn off via line 3 from the pyrolysis reactor
R.
[0029] Undesirable solids (e.g., carbon black) are also extracted
from the pyrolysis reactor R with the pyrolysis gas. To separate
these solids, the pyrolysis gas in the gas scrubbing unit W is
subjected to gas scrubbing with water 4, which is heated in the
heat exchanger E from the hot waste water 3. The washing water that
is charged in the gas scrubbing unit W flows downward into the
mixture of substances S1-S6 that is to be decomposed, and is drawn
off with the waste water 3 from the pyrolysis reactor R. In
connection to the gas scrubbing unit W, the purified pyrolysis gas
is introduced into the superheater U and is further heated there to
the starting temperature of a reformer (not shown) that is arranged
downstream. Long-chain components that are present in the pyrolysis
gas decompose at this temperature and are converted into hydrogen
(H.sub.2) and carbon monoxide (CO). The gas produced in superheater
U, which in addition to H.sub.2 and CO primarily contains water and
carbon dioxide, is drawn off via line 5 and fed to, for example, a
separating device (not shown) to produce an H.sub.2 product and a
CO product.
[0030] 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.
[0031] The entire disclosure of all applications, patents and
publications, cited above and below, and of corresponding German
Application No. 102007045360.6, filed Sep. 22, 2007, is hereby
incorporated by reference.
* * * * *