U.S. patent application number 13/256081 was filed with the patent office on 2012-03-15 for method and apparatus for a constant steam generation from the waste heat of an alkane dehydrogenation.
This patent application is currently assigned to UHDE GMBH. Invention is credited to Max Heinritz-Adrian, Sascha Wenzel.
Application Number | 20120060824 13/256081 |
Document ID | / |
Family ID | 42338328 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120060824 |
Kind Code |
A1 |
Heinritz-Adrian; Max ; et
al. |
March 15, 2012 |
METHOD AND APPARATUS FOR A CONSTANT STEAM GENERATION FROM THE WASTE
HEAT OF AN ALKANE DEHYDROGENATION
Abstract
The invention relates to a process and a device for an as
constant as possible supply of steam flow from an alkane
dehydrogenation, the process being carried out by passing a
hydrocarbonaceous gas through reaction tubes loadable with a
catalyst, and the reaction tubes, which are sealed towards the
outside, running through a heating chamber which is heatable by
means of burners, and the catalyst being regenerated for the
reaction in a cyclic operating mode, in which the reaction is
endothermic and the regeneration of the catalyst non-endothermic,
and the capacity of the main burners is reduced during the
regeneration of the catalyst, in which auxiliary burners, which
serve to keep up the production of hot flue gas during the
regeneration of the catalyst, are installed at the inlet of the
flue gas duct to produce additional hot flue gas which is used for
generating an as constant as possible amount of steam from the
waste heat of the process.
Inventors: |
Heinritz-Adrian; Max;
(Muenster, DE) ; Wenzel; Sascha; (Bochum,
DE) |
Assignee: |
UHDE GMBH
Dortmund
DE
|
Family ID: |
42338328 |
Appl. No.: |
13/256081 |
Filed: |
March 1, 2010 |
PCT Filed: |
March 1, 2010 |
PCT NO: |
PCT/EP2010/001238 |
371 Date: |
October 24, 2011 |
Current U.S.
Class: |
126/263.01 |
Current CPC
Class: |
Y02P 20/584 20151101;
C01B 2203/84 20130101; C07C 5/333 20130101; F22B 1/18 20130101;
C01B 3/26 20130101; B01J 8/062 20130101; B01J 2208/0053 20130101;
Y02P 20/129 20151101; C01B 2203/142 20130101; C07C 5/333 20130101;
C07C 11/02 20130101; C01B 2203/0277 20130101; B01J 2208/00504
20130101 |
Class at
Publication: |
126/263.01 |
International
Class: |
F24J 1/00 20060101
F24J001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 13, 2009 |
DE |
10 2009 012 663.5 |
Claims
1.-11. (canceled)
12. A process for the generation of a constant amount of steam for
the waste heat of an alkane dehydrogenation process, comprising:
arranging a fixed-bed catalyst in one or more reaction tubes and
carrying out therein an endothermic reaction by passing a reaction
gas mixture through the reaction tube(s); heating the reaction
tube(s) from the outside by combustion of a fuel gas in a heating
chamber housing the reaction tubes, forming a flue gas stream;
performing the reaction in the reaction tube(s) in a temporally
cyclic operating mode, a period of time not used for the reaction
being used for the regeneration of the catalyst by passing an
oxygen-containing gas, water vapour-containing gas, or mixture
thereof across the catalyst, and utilizing the flue gas stream for
steam generation by a steam generator having a heat exchange
surface; and increasing the quantity of the flue gas stream which
contacts the heat exchange surface of the steam generator during
regeneration by activating at least one auxiliary burner installed
in the flue gas stream behind the reaction tubes to be heated, this
burner producing a flue gas stream which does not contact the
reaction tubes.
13. The process of claim 12, wherein the auxiliary burner(s) are
used to increase the temperature of the flue gas stream on the heat
exchange surfaces of the steam generator during the
regeneration.
14. The process of claim 12, wherein the auxiliary burners are
equipped with a control device and the flue gas duct which is
heated by means of the auxiliary burner is provided with a
temperature measuring device to control the auxiliary burners by
means of the temperature in the flue gas duct.
15. The process of claim 12, wherein the auxiliary burners are
equipped with a control device and the steam generators which are
heated by the auxiliary burner are equipped with a steam flow meter
to control the auxiliary burners by the amount of produced
steam.
16. The process of claim 12, wherein the endothermic process with
the catalyst to be regenerated is an alkane dehydrogenation process
in which an alkane is converted into an alkene by the release of
hydrogen.
17. The process of claim 12, wherein the endothermic process with
the catalyst to be regenerated is an alkane dehydrogenation process
in which an alkane is converted into an alkene by the release of
hydrogen and the hydrogen is oxidised in a subsequent process step
in which a further dehydrogenation of not yet converted alkane is
achieved.
18. A facility for the generation of a constant amount of steam
from the waste heat of an alkane dehydrogenation process,
comprising: a reactor with heating chamber for carrying out an
endothermic reaction with integrated reaction tubes which are
loaded with a catalyst; an inlet for a reaction gas and an outlet
for a product gas in the reaction tubes; one or more main burners
which do not contact the catalyst or the reaction gas and which
heat the reaction tubes in the heating chamber from the outside; a
flue gas duct at the end of the heating chamber and one or more
steam generator(s) in the flue gas duct; and one or more auxiliary
burner(s) installed in the inlet of the flue gas duct in the flue
gas stream behind the reaction tubes and upstream of the entry into
the steam generator or generators.
19. The facility of claim 18, wherein the auxiliary burner(s) are
equipped with an ignition device.
20. The facility of claim 18, wherein the auxiliary burner(s) are
equipped with a control device which serves to control the capacity
of the auxiliary burner(s).
21. The facility of claim 18, wherein the flue gas duct is equipped
with a device for measuring the flue gas temperature in the flue
gas duct, by which the capacity of the auxiliary burner(s) is
controlled.
22. The facility of claim 18, wherein the steam generators which
are heated by the auxiliary burner(s) are equipped with a steam
flow meter to control the capacity of the auxiliary burner(s).
Description
[0001] The invention relates to one or more burners used as
additional heating in the flue gas duct of a reactor for the
performance of an endothermic reaction by which it is possible to
produce a nearly constant amount of flue gas, the reactor being
equipped with a steam generator located in the outlet of the flue
gas duct of the heating chamber, and the burners being used as
auxiliary burners for balancing the flue gas reduction in the flue
gas duct of the heating chamber which normally occurs during the
regeneration phase of the exothermic regeneration of the catalyst
in use. The invention also refers to a device comprising one or
more auxiliary burners installed in a reactor for the performance
of an endothermic reaction including the necessary equipment by
which it is possible to control the amount of flue gas in the
outlet of the flue gas duct housing the steam generator. In this
way, the steam flow obtainable from the steam generator is
equalised to a substantial degree, which is of advantage in the
operation of turbines or compressors. This device is especially
suited for reactors typically used for alkane dehydrogenation
processes.
[0002] A common process for performing an alkane dehydrogenation is
to pass an alkane-containing hydrocarbon mixture across a
dehydrogenation catalyst which causes the alkane contained in the
gas mixture to react to the corresponding alkene. The catalyst is
provided in a typical configuration in downward reaction tubes
which the reaction gas enters through an inlet duct so that the
product gas which contains, as a component, the required alkene can
be obtained at the outlet of the reaction tubes. The reaction is
endothermic so that it is required to heat the reaction tubes from
the outside. This is normally accomplished by means of a reactor
with a heating chamber with integrated reaction tubes, which can be
heated with fuel gas. The reaction tubes are sealed towards the
heating chamber. The heating chamber ends in a flue gas duct where
the hot flue gas is thermally utilised and finally discharged into
a stack.
[0003] A typical embodiment of the alkane hydrogenation process
with an appurtenant device is described in WO 2004/039920 A2. A
selection of various dehydrogenation processes and the
corresponding catalysts involved is given in the publication by F.
Buonomo, D. Sonfillipo, F. Trifir , Handbook of Heterogeneous
Catalysis, 1.sup.st Edition, VCH, Weinheim, 1997 p. 2140 ff. and
the literature references made therein.
[0004] The flue gas from the heating is discharged from the heating
chamber via flue gas ducts. Its temperature is around 1000.degree.
C. depending on the respective constructional design. To further
utilise the heat from the heating of the reaction tubes, a steam
generator is typically installed for the flue gas in or downstream
of the outlet of the flue gas duct.
[0005] An alkane dehydrogenation is typically accompanied by the
formation of carbonaceous by-products which deposit on the catalyst
after a certain reaction period. This will reduce the reaction
yield and the production of required alkene. The reaction is, for
this reason, interrupted after a certain period of time and the
reaction gas flow across the catalyst stopped. In a typical
embodiment an oxygen-containing gas is subsequently passed across
the catalyst. It serves to remove the carbonaceous deposits and to
regenerate the catalyst. After the regeneration, the alkane
dehydrogenation in the respective reaction tube or reactor is
resumed. According to this procedure the process is carried out in
a cyclic operating mode.
[0006] As the dehydrogenation of alkanes is endothermic and the
regeneration of the catalyst exothermic, the reactor requires a
significantly lower amount of heat during the regeneration period
than during normal operation. For this purpose, the burners are
normally operated with less fuel gas during the regeneration phase
resulting in an analogously lower production of flue gas.
[0007] WO 2007/118825 A1 describes a process for the production of
olefins from hydrocarbons and a device for running the process. By
switching off the burners during the regeneration phase the heat
supply into the catalyst bed is interrupted so that no more heat is
fed to the catalyst bed when oxygen-containing gas is passed across
it during regeneration and the catalyst is prevented from
overheating and degradation. For running the process the burners
are provided with a switch-off device and are re-ignited for
re-start by means of pilot burners after the regeneration. Both the
heating burners and the pilot burners may be equipped with a
monitoring device. No indications are made with reference to the
generation of steam by the use of a steam generator and a
compensation of the interrupted heating.
[0008] EP 179322 B1 describes a process for the exothermic
regeneration of a catalyst which has been deactivated during an
endothermic catalytic conversion in the course of a discontinuous
process. By reducing the burner capacity to below 50 percent of the
original capacity, preferably below 10 percent of the original
burner capacity, which is accomplished by reducing the supply of
heating fuel, savings in heating medium and combustion air can be
achieved. As suitable application processes, special reference is
made to the dehydrogenation of i-butane, n-butane or mixtures
thereof. If several reactors are used, it is possible to operate
them alternately so that there is in total no change in the supply
of heating media, combustion streams and no load change in the
waste heat system. This teaching as well does not give any
indications with reference to the generation of steam by the use of
a steam generator or to the compensation of the interrupted
heating.
[0009] When the heating process output is decreased for the
regeneration of the catalyst, the flue gas feed to the steam
generators installed in the flue gas duct is reduced. This is
problematic as in an important embodiment the steam generated by
the steam generators is used for driving a compressor by means of a
steam turbine. The dehydrogenation process works such that steam is
supplied to serve as turbine steam during normal operation and also
during regeneration. During the regeneration phase the unit itself
produces less steam. At the same time, however, the steam
consumption level in the regeneration mode is almost as high as
during normal operation. The amount of steam supplied during the
regeneration phase therefore determines the amount of steam
supplied to the dehydrogenation unit.
[0010] It is therefore the aim to provide a process for the
production of alkene by endothermic catalytic reaction making
available as high an amount of flue gas as possible for the
operation of a steam generator during the regeneration phase so
that a constant amount of steam is provided throughout the whole
"Production-Regeneration" cycle. It is another aim of the invention
to provide a device for this purpose. The latter is also expected
to allow monitoring and remote control of the process.
[0011] The invention achieves this aim by a process for the
constant or controlled supply of flue gas from an endothermic
catalytic reaction, by which it is possible to use this flue gas to
produce a steam flow which is as high as possible in quantity by
means of a steam generator, in which at least one auxiliary burner
is installed in the outlet of the flue gas duct, the burner being
used to generate a flue gas stream which does not get into contact
with the reaction tubes to be heated and by which the flue gas
stream is increased in quantity on the heat exchange surfaces of
the steam generator during the regeneration. The invention achieves
this aim also by a device made up by one or more auxiliary burners
at the inlet of the flue gas duct of a reactor for the performance
of an endothermic catalytic reaction, the auxiliary burners being
arranged in the flue gas stream behind the reaction tubes. The
device also includes a monitoring and control device for the
auxiliary burners.
[0012] By the present invention it is possible to reduce the
quantity of steam supplied. In this way, no additional costs are
incurred by heat-exchange devices as equipment and internals
dimensioned for normal operation are used. The auxiliary burners,
which are mainly required for the regeneration mode, are
comparatively inexpensive.
[0013] Typical endothermic catalytic processes suitable for the
application of the invention are alkane dehydrogenation processes.
These are, in any case, reactions which are performed in reaction
tubes loadable with catalyst, the reaction tubes being arranged in
a heatable reaction chamber and the reaction chamber being heated
with fuel gas from burners. A typical process for the
dehydrogenation of alkanes suited for the application of the
invention is described in WO 2004/039920 A2. This document also
describes a reactor in which the hydrogen generated in the alkane
dehydrogenation is incinerated in a separate process step.
[0014] Especially claimed is a process for the regeneration of a
fixed-bed catalyst with temporally constant generation of steam
from the heating of the reactor, in which [0015] a fixed-bed
catalyst is arranged in one or several reaction tubes where an
endothermic reaction is carried out by passing through a reaction
gas mixture, and [0016] the reaction tube or tubes are heated from
the outside by combustion of a fuel gas in a heating chamber
housing the reaction tubes for carrying out the endothermic
reaction, and [0017] the reaction in the reaction tube or tubes is
performed in a cyclic operating mode over a limited period of time,
the period not used for the reaction being used for the
regeneration of the catalyst by passing an oxygen-containing or
water vapour-containing gas or a mixture of both across the
catalyst, and [0018] the flue gas stream produced by the heating of
the reaction tubes is discharged from the heating chamber and
utilised for steam generation by a steam generator, and
characterised in that [0019] at least one auxiliary burner is
installed in the outlet of the flue gas duct, this burner producing
a flue gas stream not getting into contact with the reaction tubes
to be heated and increasing the flue gas stream in quantity on the
heat exchange surfaces of the steam generator during the
regeneration.
[0020] By the increased amount of flue gas in the flue gas duct it
is possible to use the heat exchange surfaces in the flue gas duct
during the regeneration period of the catalyst more efficiently. In
this way, the amount of produced steam can be kept nearly constant
throughout the whole duration of the process. For this purpose, the
auxiliary burners are equipped with a control device by which it is
possible to control the amount of combustion gas. This can be
achieved by controlling the auxiliary burners by means of the flue
gas temperature in the flue gas stream downstream of the auxiliary
burners. The control device adjusts the supply of fuel gas or
combustion air into the auxiliary burners.
[0021] To further increase the steam amount generated during the
regeneration, the auxiliary burners are used advantageously such
that the temperature of the flue gas stream at the inlet of the
flue gas duct is increased on the heat exchange surfaces of the
steam generator. The temperature in the flue gas duct and on the
heat exchange surfaces can be controlled via the fresh air supply
into the flue gas duct if this is required.
[0022] The auxiliary burners are advantageously equipped with a
control device so as to control the fuel gas supply and thus the
production of flue gas. The control device is governed by a
temperature sensor provided near the heat exchange surfaces of the
steam generator so that it is possible to control the auxiliary
burners by means of the temperature in the flue gas duct. In a
simpler embodiment it is also possible to provide for a manual
control of the auxiliary burners.
[0023] The control device of the auxiliary burners can also be
controlled by the amount of produced steam. In such case, a steam
flow meter for the amount of steam produced is installed in a
suitable position of the steam generator so that the auxiliary
burners can be controlled by the amount of steam produced.
[0024] Processes which are qualified for the process according to
the invention are in particular alkane dehydrogenation processes
used to convert an alkane into an alkene by releasing hydrogen.
This may be carried out in a single process. It is, however, also
common practice to carry out the alkane dehydrogenation converting
an alkane into an alkene by releasing hydrogen and oxidising the
hydrogen in a subsequent separate process step in which a further
dehydrogenation of not yet converted alkane is achieved. The
auxiliary burners may then be installed in one or more reactors. In
this way the whole endothermic process is supported by the
regeneration of the catalyst.
[0025] Also claimed is a device by which it is possible to run the
process according to the invention. Especially claimed is a device
for the generation of a constant amount of steam from the waste
heat of an alkane dehydrogenation process, comprising [0026] a
reactor with heating chamber for carrying out an endothermic
reaction with integrated reaction tubes which can be loaded with a
catalyst, an inlet for the reaction gas and an outlet for the
product gas in the reaction tubes, one or more main burners which
do not get into contact with the catalyst or the reaction gas and
heat the reaction tubes in the heating chamber from the outside,
and a flue gas duct with outlet for the flue gas at the end of the
heating chamber, and one or more steam generator/s in the flue gas
duct, and characterised in that [0027] one or more auxiliary
burners are installed at the outlet of the flue gas duct behind the
reaction tubes and upstream of the entry into the steam generator
or generators.
[0028] Reactors for the performance of endothermic processes which
are equipped with auxiliary burners for bridging the start-up
procedure are known according to the state of the art. US
2003/0101651 A1 describes a device for an endothermic catalytic
reaction by which a hydrocarbonaceous gas is passed through tubes
which can be loaded with catalyst and are heated from the outside,
the reaction gas being heated by convection in counter-current
flow. By the reaction arrangement it is possible to significantly
reduce the size of the reactor and to design the complete assembly
as a mobile unit. The device describes auxiliary burners used to
start the reaction by installing them in the heating chamber for
combustion of the fuel gas. Not described is a regeneration of the
catalyst or interruption of the heating process. Neither mentioned
is a control device for the auxiliary burners.
[0029] In most embodiments of the invention the auxiliary burners
are provided with control devices by which it is possible to
control the capacity of the burners. Suitable control devices are,
for instance, valves, gate valves, flaps or stems which serve to
control the supply of fuel gas into the auxiliary burners. The
control device may also be used to control the supply of combustion
air into the auxiliary burners.
[0030] The auxiliary burners may also be controlled by parameters
measured in the outlet of the flue gas duct. Devices required
according to the related process claims are especially sensors
measuring the flow rate of the combustion gas or the temperature of
the combustion gas. To serve this purpose, these are installed in
the outlet of the flue gas duct. If the aim is to control the
auxiliary burners by the combustion gas flow rate, the flue gas
ducts are equipped with a measuring device which serves to measure
the combustion gas flow rate of the flue gas in the flue gas duct,
by which it is possible to control the auxiliary burner.
[0031] If the aim is to control the auxiliary burner/s by the
temperature of the flue gas stream, the flue gas ducts are provided
with a device for measuring the temperature of the flue gas in the
flue gas duct by which it is possible to control the auxiliary
burner. If a comparison measurement in comparison to the overall
flow rate or temperature of the flue gas is required, appropriate
sensors can be installed in the flue gas duct itself or on the heat
exchange surfaces of the steam generator. In another embodiment it
is also possible to use Lambda probes for measuring the oxygen
content in the flue gas duct, should the auxiliary burners be
controlled by the oxygen content in the flue gas duct.
[0032] The reactor for integrating the device according to the
invention is typically configured as is common practice according
to the state of the art. For carrying out the invention this
includes a reactor for carrying out an endothermic reaction with
integrated reaction tubes which can be loaded with a catalyst,
burners which do not get into contact with the catalyst or the
reaction gas and heat the reaction tubes from the outside, an inlet
for the reaction gas and an outlet for the product gas in the
reaction tubes, an inlet for the fuel gas and a flue gas duct, and
a steam generator with heat exchange surfaces in or downstream of
the outlet of the flue g as duct. The main burners and the
auxiliary burners according to the invention may be installed in
any position in the heating chamber or in the flue gas duct. This
applies analogously to the heat exchange surfaces to be heated. The
burners, reaction tubes or steam generators can be provided as
single or as multiple units. The auxiliary burners are, in any
case, arranged such that the escaping flue gases do not get into
contact with the reaction tubes and the enclosed catalyst.
[0033] To control the auxiliary burners especially such devices may
be used that serve the purpose of burner control according to the
state of the art. These are typically valves, gate valves, flaps or
stems which serve to control the supply of fuel gas or combustion
air into the auxiliary burners. To measure control data, especially
thermocouples, pressure gauges, gas flow meters and oxygen probes
may be used.
[0034] Used as auxiliary burners may be gas burners, liquid-fuel
burners, rocket burners or solid-fuel blower burners. The type is
determined by the size of the flue gas duct and of the heat
exchange surfaces. The auxiliary burner device according to the
invention also includes suitable ignition devices as there are, for
example, electric or electronic igniters, pilot burner or flint
stones. The auxiliary burners are preferably equipped with a
control device by which the capacity of the auxiliary burner/s can
be controlled. This can be implemented such that the flue gas duct,
for example, is equipped with a device for measuring the flue gas
temperature in the flue gas duct and by which the capacity of the
auxiliary burner/s can be controlled.
[0035] To additionally utilise the waste heat, steam generators are
used which may be arranged as desired and provided in any number
desired. Typically these are steam generators which are arranged as
indirect heat exchangers with heat exchange surfaces. These may be
of optional design. These may also include measuring devices for
measuring the amount of steam produced. The steam generators which
are heated by means of the auxiliary burner/s may be equipped with
a steam flow meter by which it is possible to control the capacity
of the auxiliary burner/s. Furthermore included in the device
according to the invention is ancillary equipment such as
pipelines, for example. These may be of optional design and
number.
[0036] The device according to the invention involves the advantage
that an amount of steam which is as constant as possible throughout
the duration of the process can be generated from the waste heat of
an alkane dehydrogenation. By the device and the process according
to the invention the generation of steam from the waste heat of the
before-mentioned processes can be optimised and used to recover
mechanical energy.
* * * * *