U.S. patent application number 12/088437 was filed with the patent office on 2009-01-15 for method for producing a hot gas by oxidation comprising a delay prior to scavenging.
Invention is credited to Etienne Lebas, Didier Pavone.
Application Number | 20090017405 12/088437 |
Document ID | / |
Family ID | 36617181 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090017405 |
Kind Code |
A1 |
Pavone; Didier ; et
al. |
January 15, 2009 |
Method for Producing a Hot Gas By Oxidation Comprising a Delay
Prior to Scavenging
Abstract
The invention relates to an optimized method for producing a hot
gas by oxidation of an active material having an oxidized form and
a reduced form using a rotary reactor or a simulated-rotation
reactor. According to the invention, the production cycle comprises
a flow interruption between an oxidation stage and a scavenging
stage.
Inventors: |
Pavone; Didier; (Ecully,
FR) ; Lebas; Etienne; (Vienne, FR) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
36617181 |
Appl. No.: |
12/088437 |
Filed: |
September 28, 2006 |
PCT Filed: |
September 28, 2006 |
PCT NO: |
PCT/FR2006/002194 |
371 Date: |
September 8, 2008 |
Current U.S.
Class: |
431/29 |
Current CPC
Class: |
F23C 2900/99008
20130101; F23C 99/00 20130101; Y02E 20/34 20130101 |
Class at
Publication: |
431/29 |
International
Class: |
F23N 5/00 20060101
F23N005/00; F23N 5/26 20060101 F23N005/26; F23L 7/00 20060101
F23L007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2005 |
FR |
0509969 |
Claims
1) A method for producing a hot gas by oxidation of an active
material contained by at least one reaction module working as a
function of time successively in oxidation, scavenging and
reduction stages by contacting through successive circulation
respectively of an oxidizing gas, a scavenging gas or a reducing
gas, characterized in that the contacting stages by circulation of
the oxidizing and scavenging gas are separated by a flow
interruption of predetermined duration of the oxidizing gas prior
to circulating the scavenging gas.
2) A method as claimed in claim 1, wherein said duration is
determined so as to increase the contacting time of the oxidizing
gas on the active material.
3) A method as claimed in claim 1, wherein the rate of circulation
of the scavenging gas is higher than the rate of circulation of the
oxidizing gas.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of energy
production, gas turbines, boilers and furnaces, notably for the
petroleum industry, the glass-making industry and in cement plants.
The field of the invention also covers the use of these various
means for producing electricity, heat or steam.
[0002] The field of the invention is more particularly the devices
and the methods allowing, through oxidation-reduction reactions of
an active phase, to produce a hot gas by means of a hydrocarbon or
a hydrocarbon mixture and to isolate the carbon dioxide produced so
as to be able to capture it. The invention also applies to the
field of hydrogen or oxygen production.
[0003] The growing worldwide energy demand leads to build new
thermal power plants and to emit increasing amounts of carbon
dioxide that are harmful to environment. Capture of carbon dioxide
with a view to its sequestration has thus become an imperative
necessity.
BACKGROUND OF THE INVENTION
[0004] One of the techniques that can be used for capturing carbon
dioxide consists in carrying out oxidation-reduction reactions of
an active phase so as to decompose the combustion reaction commonly
used into two successive reactions:
[0005] an oxidation reaction of the active phase with air allows,
through the exothermic nature of the oxidation, to obtain a hot gas
whose energy can be used,
[0006] a reduction reaction of the active phase thus oxidized by
means of a reducing gas then allows to obtain a reusable active
phase, as well as a gaseous mixture essentially comprising carbon
dioxide and water.
[0007] The uncoupling thus achieved between the oxidation stage and
the reduction stage allows easier later separation of the carbon
dioxide from a gaseous mixture practically free of oxygen and
nitrogen.
[0008] Document U.S. Pat. No. 5,447,024 describes a process
comprising a first reactor for a reduction reaction of a metallic
oxide by means of a reducing gas, and a second reactor producing
said metallic oxide through an oxidation reaction with moistened
air. The exhaust gases from these two reactors are fed into the gas
turbines of an electric power plant. However, implementation of
such a process requires two distinct reactors and transport means
for an active phase in form of solid particles. Such a process is
therefore relatively complicated to implement and it involves high
operation and maintenance costs. Furthermore, fine active phase
particles carried along in the exhaust gas can be a source of
drawbacks for later treatment of this gas.
[0009] Document FR-2,846,710 describes a real rotary reactor in the
sense that the reactor exhibits a material rotation between a
stationary part and a moving part so as to carry out successive
oxidation, then reduction reactions of an active mass.
[0010] Document FR-04/08,549 filed by the applicant describes a
reactor type allowing to carry out the same reactions as the
reactor described in patent application FR-2,846,710, but without a
real rotation. Rotation, or more precisely switching from a reactor
configuration to another, is obtained through a delay applied, with
a fixed periodicity, to a set of modules, preferably identical,
each one of which can be supplied by specific means with an
oxidizing gas, a reducing gas or an inert gas (referred to as
scavenging gas).
[0011] These specific means essentially consist of a system of
valves allowing to deliver to each module, according to the time
period considered, the oxidizing gas, the scavenging gas or the
reducing gas. These means are specific to each module.
SUMMARY OF THE INVENTION
[0012] The object of the invention is to provide an optimized
method for implementing a device allowing oxidation and reduction
reactions of an active phase in order to produce a hot gas by means
of a hydrocarbon, or a mixture of hydrocarbons, and to jointly
isolate the carbon dioxide produced so as to readily capture
it.
DETAILED DESCRIPTION
[0013] The invention thus relates to a method for producing a hot
gas by oxidation of an active material contained by at least one
reaction module working as a function of time successively in
oxidation, scavenging and reduction stages by contacting through
successive circulation respectively of an oxidizing gas, a
scavenging gas or a reducing gas.
[0014] According to the invention, the contacting stages by
circulation of the oxidizing and scavenging gas are separated by a
flow interruption of predetermined duration of the oxidizing gas
prior to circulating the scavenging gas.
[0015] The flow interruption duration can be determined so as to
increase the contacting time of the oxidizing gas with the active
material.
[0016] The rate of circulation of the scavenging gas can be higher
than the rate of circulation of the oxidizing gas.
[0017] The progress of an oxidizing cycle, then of a reducing cycle
on an active mass is reminded hereafter.
[0018] The oxidation-reduction cycle of the oxido-reducing active
mass comprises a stage of injection of the combustible gas. During
this stage, the combustible gas comes into contact with the
oxido-reducing active mass that is in a partly oxidized state. The
oxygen collected by this mass is transferred to the gas that
oxidizes while releasing carbon oxides and water.
[0019] The devices according to document FR-2,846,710 or
FR-04/08,549 mentioned here by way of reference comprise a set of
reaction modules, each module comprising an active material working
as a function of time successively in an oxidation, scavenging and
reduction stage by contacting respectively with an oxidizing,
scavenging or reducing gas. Contacting with the active mass is
achieved using either a feed system specific to each module, able
to receive as a function of time an oxidizing, scavenging or
reducing gas, or a rotary set rotating with respect to a
distribution set.
[0020] At the start of the fuel injection stage, the gas oxidation
reaction (and therefore the reduction of the oxido-reducing mass)
is mainly located near the inlet of the module in form of a
monolith for example. In the course of time, this
oxidation-reduction moves downstream from the module since the
upstream oxido-reducing mass has been reduced and therefore no
longer contains the oxygen required for combustion.
[0021] The applicant has observed a problem relative to unburnt
combustible gases. The more the reaction occurs downstream from the
monolith, the greater the proportion of combustible gas that can
flow through the monolith without having the time to come into
contact with the oxido-reducing mass, which increases the volume of
unburnt gas.
[0022] A simulation was carried out considering a 1-meter long
cylindrical channel 2 mm in inside diameter, coated with a 50-.mu.m
thick active mass (washcoat). In this oxidation-reduction cycle
simulation, the gases are injected at about 500.degree. C., at a
pressure of 30 bars. The standard cycle considered comprises the
following successive injection durations: 3 s air-0.5 s steam-1.5 s
methane-0.5 s steam. The respective injection rates for the air,
steam and methane are: 20 m/s, 5 m/s and 1 m/s. The steam is
introduced to clean the channel from the oxidizer or the fuel prior
to the next introduction of oxidizer or fuel.
[0023] In FIG. 1, curve 1 shows the flow rate of combustible gas
injected and curve 2 the amount of unburnt gas (in mol/s as
ordinate) as a function of time (as abscissa), for a channel. It
can be noted that, during the gas oxidation stage (between the
times 14.5 and 16 s), a first amount of unburnt gas appears at the
channel outlet (curve 2). Then, a "puff" of unburnt gas is produced
between 16 s and 16.5 s as illustrated by peak 3.
[0024] This "puff" is very harmful to the process yield because it
involves a large amount of unburnt gas. Furthermore, it appears
concomitantly with a similar carbon dioxide "puff". Now, according
to the method, this CO.sub.2 stream must be directed towards the
CO.sub.2 collecting device and not towards the gas turbine. This
therefore also applies for this combustible gas "puff" (unburnt
gas). The consequence thereof is that a quite considerable amount
of unburnt gas has to be sent into the gaseous fluid used for
collecting the CO.sub.2. Now, this gas cannot be burnt thereafter
since the gaseous fluid selected for CO.sub.2 collection contains
no oxygen.
[0025] Thus, the reaction yield drops, and CO.sub.2 collection and
separation becomes more complicated.
[0026] According to the present invention, what is provided is a
method or a process that reduces by about 25% the amount of unburnt
gas present in said unburnt gas "puff" (peak 3 of FIG. 1). A short
period during which nothing is injected is therefore added between
the end of the combustible gas injection stage and the next stage
of scavenging by steam. The combustible gas trapped in the channel
then has the time to oxidize on the oxido-reducing mass, thus
reducing the amount of unburnt gas.
[0027] FIG. 2 illustrates the new cycle of the process according to
the invention. Curve 1 shows as above the rate of injection of the
fuel in a cycle and identical conditions for the standard cycle,
except for the addition of a 0.5-s injection interruption after
injection of the fuel and before injection of the scavenging steam.
This pause is shown by reference number 4 in FIG. 2. With this new
cycle, curve 2' shows the unburnt flow rate during the combustion
and peak 3' corresponds to the unburnt gas "puff".
Numerical Results
[0028] The numerical simulations of the method show the efficiency
of the solution provided. Table 1 synthesizes the results
corresponding to the cycle according to the invention, illustrated
by FIG. 2.
TABLE-US-00001 TABLE 1 Synthesis of the numerical results According
Standard to the in mol/cycle/channel case invention gain/cycle
gain/cycle Unburnt gas in the puff 440 10.sup.-6 325 10.sup.-6 115
10.sup.-6 26% (peaks 3, 3') Unburnt gas during the 467 10.sup.-6
393 10.sup.-6 74 10.sup.-6 15% injection of combustible gas (curves
2, 2') Total unburnt gas per 907 10.sup.-6 718 10.sup.-6 189
10.sup.-6 21% cycle
[0029] The last line of the table gives the total amount of unburnt
gas for a cycle, i.e. the integral below curves 2+3 and 2'+3'. It
can be noted that the cycle according to the invention provides an
overall unburnt gas reduction of 21% per cycle. The goal of the
invention being however to act upon the volume of said "puff", the
contribution of this invention will be clearer by comparing its
volume, according to the invention or according to the standard
case. This comparison is shown in the second line of the table. It
appears that the invention reduces the volume of unburnt gas of the
puff by 26%.
[0030] It can also be noted that this better combustion provides a
wider use of the oxido-reducing mass, which is translated into an
additional 15% decrease on the volume of unburnt gas that has
appeared during the combustible gas injection stage (first line in
the table).
[0031] The present invention advantageously applies to the devices
described in documents FR-2,846,710 or FR-04/08,549.
* * * * *