U.S. patent application number 13/503049 was filed with the patent office on 2012-08-09 for method and device for producing power by means of oxidation of fuel in a chemical loop.
This patent application is currently assigned to L'Air Liquide Societe Anonyme Pour L'Etude L'Exploitation Des Procedes Georges Claude. Invention is credited to Bruno Alban, Simon Jallais, Ivan Sanchez-Molinero.
Application Number | 20120199054 13/503049 |
Document ID | / |
Family ID | 42224604 |
Filed Date | 2012-08-09 |
United States Patent
Application |
20120199054 |
Kind Code |
A1 |
Alban; Bruno ; et
al. |
August 9, 2012 |
Method And Device For Producing Power By Means Of Oxidation Of Fuel
In A Chemical Loop
Abstract
The invention relates to a method for producing power from at
least one fuel, said method including: a step of oxidizing said
fuel by means of placing it in contact with at least one oxygen
loaded solid compound and of concomitantly reducing said solid
compound.
Inventors: |
Alban; Bruno; (Massy,
FR) ; Jallais; Simon; (Chaville, FR) ;
Sanchez-Molinero; Ivan; (Versailles, FR) |
Assignee: |
L'Air Liquide Societe Anonyme Pour
L'Etude L'Exploitation Des Procedes Georges Claude
Paris
FR
|
Family ID: |
42224604 |
Appl. No.: |
13/503049 |
Filed: |
October 6, 2010 |
PCT Filed: |
October 6, 2010 |
PCT NO: |
PCT/FR2010/052102 |
371 Date: |
April 20, 2012 |
Current U.S.
Class: |
110/267 ;
110/342 |
Current CPC
Class: |
Y02E 20/346 20130101;
F23C 2900/99008 20130101; F23C 10/00 20130101; Y02E 20/34
20130101 |
Class at
Publication: |
110/267 ;
110/342 |
International
Class: |
F23B 90/00 20110101
F23B090/00; F23K 1/00 20060101 F23K001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 22, 2009 |
FR |
0957406 |
Claims
1-7. (canceled)
8. A process for the production of energy from at least one fuel,
comprising: a. the oxidation of at least one fuel by bringing into
contact with at least one oxygen-charged solid compound and of the
concomitant reduction of said solid compound; b. recovering said
reduced solid compound; c. the exothermic oxidation of a non-zero
fraction of said recovered solid compound by bringing said
recovered solid compound into contact with at least one
oxygen-comprising gas; and d. recovering said oxidized solid
compound, and of using a non-zero fraction of said oxidized solid
compound in step a); the heat given off in step c) being at least
partially recovered in order to carry out a production of energy;
wherein the oxygen-comprising gas is alternately, according to the
energy power desired, air or a gas comprising a concentration by
volume of oxygen of between 22% and 100%.
9. The process of claim 8, wherein the oxygen-comprising gas is
alternately, according to the energy power desired, air or a gas
comprising a concentration of oxygen by volume of between 23% and
40%.
10. The process of claim 8, wherein: during the period during which
the oxygen-comprising gas is air, said fuel is of a first given
type; and during the period during which the oxygen-comprising gas
is a gas comprising a concentration of oxygen by volume of between
22% and 100% or 23% and 40%, said fuel is of a second given type
which is more reactive in step a) than said first type.
11. The process of claim 10, wherein said first type of fuel is sub
bituminous coal and said second type of carbon-based fuel is
lignite or coal or HFO (heavy fuel oil) or LPG (liquefied petroleum
gas) or natural gas.
12. The process of claim 8, wherein: during the period during which
the oxygen-comprising gas is air, use is made of a first flow rate
of said solid compound in step a) and of a second flow rate of said
solid compound in step c); and during the period during which the
oxygen-comprising gas is a gas comprising a concentration of oxygen
by volume of between 22% and 100% or 23% and 40%, use is made of a
third flow rate of said solid compound in step a) and of a fourth
flow rate of said solid compound in step c), the ratio of said
third flow rate to said first flow rate and the ratio of said
fourth flow rate to said second flow rate being greater than or
equal to the ratio of a second power (P2) to said first power
(P1).
13. A device for the production of energy, comprising: one reactor
for the oxidation of fuel connected at the inlet to one or more
sources of fuel and to at least one pipe suitable for conveying and
intended to convey an oxygen-transporting solid compound to said
oxidation reactor, said reactor having at least one outlet for
gases resulting from the oxidation of said fuel; one reactor for
regeneration of said oxygen-transporting solid compound, connected
at the inlet to a source of air and to at least one pipe suitable
for conveying and intended to convey said oxygen-transporting solid
compound from an outlet of said oxidation reactor to said
regeneration reactor, said reactor having at least one outlet for
gases resulting from the regeneration of said oxygen-transporting
solid compound; means for recovery of said solid compound at the
outlet of said oxidation and regeneration reactors; and heat
exchangers capable of converting and intended to convert, into
energy, the heat given off in said regeneration reactor; said pipe
capable of conveying and intended to convey an oxygen-transporting
solid compound to said oxidation reactor being connected to an
outlet of said regeneration reactor; said device being
characterized in that it additionally comprises: a source of a gas
having a concentration of oxygen by volume of between 22% and 100%
connected to an inlet of said regeneration reactor; and means which
make it possible to selectively open or close said connections
between said regeneration reactor and said source of air, on the
one hand, and said regeneration reactor and said source of a gas
having a concentration of oxygen by volume of between 22% and 100%,
on the other hand.
14. The device of claim 13, wherein said source of a gas having a
concentration of oxygen by volume of between 22% and 100% is
capable of providing and is intended to provide a gas for which the
concentration of oxygen by volume is between 23% and 40%.
Description
[0001] The present invention relates to a process and a device for
the production of energy by oxidation of a fuel in a chemical
loop.
[0002] Chemical looping techniques have appeared comparatively
recently in the field of the oxidation of fuels. They employ a
solid active compound, generally a metal, which chemically fixes
atmospheric oxygen and is subsequently used to oxidize a solid,
liquid or gaseous compound, generally carbon-based. Generally, said
active compound circulates in a loop, from a reactor where it is
oxidized on contact with air to at least one other reactor where it
is reduced during the oxidation reaction of the fuel. This
oxidation of the compound regenerates it. It can again be used to
fix oxygen. The active compound is generally used in the form of a
fluidized and circulating bed of particles. It is easily separated
from gas mixtures, for example by a cyclone. The regeneration of
the solid active compound is generally highly exothermic. The heat
given off is converted to energy (steam, mechanical or electrical
power, for example). In other configurations, the same principle is
employed, not by fluidized beds of the particles of these compounds
but by regenerative fixed beds comprising these compounds.
Oxidizing or reducing gases are then passed alternately over these
beds. One possible implementation consists in using rotating
compartments (which are brought into contact alternately with
oxidizing or reducing gases).
[0003] Mention may in particular be made of the document
WO2007104655A1, which describes a power plant including a
thermochemical loop, comprising oxidation and reduction chambers,
cyclones for separating solid particles from the effluent gases,
heat exchangers and means for producing electrical energy from the
thermal energy given off. Application WO2008036902, "Chemical
looping combustion", exhibits an implementation of the chemical
looping principle, in particular by virtue of a reactor composed of
rotating compartments.
[0004] The advantage of the chemical looping techniques applied to
the oxidation of a fuel lies in the fact that the products of the
oxidation (mainly water and carbon dioxide or CO.sub.2) readily
lend themselves to capture of the CO.sub.2 as they comprise no or
little nitrogen, if the system is airtight with respect to the
surroundings. In contrast, a large amount of this nitrogen is found
in the effluent products from a conventional combustion with air.
Another specific advantage of the chemical loops is that they
require only air as oxidant, in comparison with other techniques
for the oxidation of fuels which facilitate the capture of
CO.sub.2, such as oxy-combustion or pre-combustion, which can use a
flow concentrated in oxygen.
[0005] For a plant for the production of energy (electricity, work
or heat), the main element in the design is the maximum power which
has to be produced. The size of the chemical loop is deduced
therefrom (capacity of the reactors, amount of oxygen-transporting
active compound, size of the items of equipment, and the like).
Once this design has been implemented, the maximum power, the
"peak" power, of the plant is set at a value which can no longer be
exceeded. In fact, the plant will in general produce a lower power,
that is to say that it is most of the time oversized. It will
possibly be pushed to its production maximum only at certain times
and this maximum will not change over time unless the plant is
significantly modified, with consequent capital costs.
[0006] An aim of the present invention is to overcome all or part
of the disadvantages of the prior art, in particular the
unalterable aspect of the maximum power produced (related to the
size of the items of equipment installed) and the oversizing of the
plants which may result therefrom.
[0007] The invention relates first to a process for the production
of energy from at least one fuel, comprising: [0008] a stage a) of
oxidation of said fuel by bringing into contact with at least one
oxygen-charged solid compound and of concomitant reduction of said
solid compound; [0009] a stage b) of recovery of said solid
compound reduced in stage a); [0010] a stage c), which is
exothermic, of oxidation of a non-zero fraction of said solid
compound recovered in stage b) by bringing it into contact with at
least one oxygen-comprising gas; and [0011] a stage d) of recovery
of said oxidized solid compound resulting from stage c) and of use
in stage a) of a non-zero fraction of said oxidized solid compound;
the heat given off in stage c) being at least partially recovered
in order to carry out said production of energy; said process being
characterized in that the oxygen-comprising gas 6 is alternately,
according to the energy power desired, air or a gas comprising a
concentration by volume of oxygen of between 22% and 100%.
[0012] In other words, during a period T of production of energy,
there is: [0013] a first period T1 of production during which the
oxygen-comprising gas 6 is air; energy at a power P1 is produced
during this period T1; and [0014] a second period T2 of production
during which the oxygen-comprising gas 6 is a gas comprising a
concentration by volume of oxygen of between 22% and 100%; energy
at a power P2 is produced during this period T2; with T=T1+T2 and
P2>P1.
[0015] The fuel can be solid, liquid or gaseous, or polyphase. It
can be a conventional fuel, such as natural gas or naphtha, or a
bleed or flue gases from another process, or also charcoal, coke,
petroleum coke, biomass and its derivatives or oil residues.
[0016] In stage a), the fuel is brought into contact with at least
one oxygen-transporting solid compound. This contacting operation
can be carried out in several installments and/or with a sufficient
residence time, and/or with a given excess of one of the reactants
(fuel or transporting solid compound), until a certain degree of
reaction is obtained. This solid compound can in particular be
metal, in a sometimes oxidized, sometimes reduced form. The fuel
reacts with an oxidized form of the solid compounds. In this
instance, a relative meaning should be given to "oxidized" and
"reduced". The essential point is that at least a fraction of the
solid compound can release oxygen on changing to a lower oxidation
state. The oxidation/reduction reactions may not be complete. The
oxidation/reduction reaction results, on the one hand, in the solid
compound in a reduced form and, on the other hand, in effluent
products which are the products of the oxidation of said fuel.
[0017] In stage b), the solid compound is recovered in a reduced
form, for example by virtue of a solid/gas physical separation.
[0018] In stage c), at least a portion of the reduced solid
compound, optionally supplemented by an extra contribution of solid
compound, is brought into contact with an oxygen-comprising gas. In
the prior art, this gas is air. On contact with this gas, the solid
compound changes to a higher oxidation state and for this reason
fixes oxygen. This contacting operation can be carried out in
several installments and/or with a sufficient residence time,
and/or with a given excess of one of the reactants
(oxygen-comprising gas or transporting solid compound), until a
certain degree of reaction is obtained. This reaction results, on
the one hand, in the solid compound in an oxidized form and, on the
other hand, in effluent products which are the incoming gas
depleted in oxygen with respect to its initial content.
[0019] On conclusion of this regeneration, after a recovery forming
the subject of stage d), it is again ready, optionally after being
supplemented with solid compound, to be used for the oxidation of
said fuel (stage a)).
[0020] It is seen that stages a) to d) form a loop from the
viewpoint of the oxygen-transporting solid compound or compounds.
At certain stages, they are oxidized and, at others, reduced.
Generally, the solid compound or compounds is/are circulated from
one reactor to another and thus the loop is also physical (the
solid compounds are transported). It would also be possible to
leave them in place and to circulate the other compounds. Various
means known to a person skilled in the art can be employed to
ensure airtightness during stages a) and d), such as robust
siphons, airtight intermediate chambers having an alternative
opening (lock hoppers), or others.
[0021] Said oxygen-transporting solid compound or compounds are
generally employed in the form of solid particles. These particles
are composed of the solid compound or compounds, optionally
agglomerated by a binder material according to techniques known to
a person skilled in the art. This attempts in particular to: [0022]
give them a specific capacity (per unit of weight) to fix and to
release the oxygen which is as high as possible, [0023] confer on
them a good mechanical strength, in particular towards attrition,
[0024] promote the kinetics of reaction between said particles and
said fuel, and between said particles and the oxygen-comprising
gas.
[0025] The particles are generally employed in the form of a
fluidized bed, for example fluidized by injections of steam or gas
rich in CO.sub.2 or fuel gas or recycled effluent products into a
reactor (stage a)), and injections of air or another
oxygen-comprising gas or steam into another reactor (stage b)).
This steam can be produced in the heat exchangers. This fluidized
bed circulates from the regions where the reduction of said
particles, that is to say the oxidation of said fuel, takes place
towards the regions where the regeneration of said particles, that
is to say the oxidation of the active compounds present therein,
takes place.
[0026] The particles are generally separated from the other
products of the oxidation of the fuel by physical separation, for
example in a cyclone. They are also separated from possible other
solids originating from the oxidation of the fuel (ash and/or soot
and/or unconverted solid fuel). It is the same during the
regeneration of said particles. Other separation elements can be
provided in order to separate the possible solid products of the
reactions from the oxygen-transporting active compound, so as to
recover the carrier material and increase the conversion
efficiency.
[0027] In general, the oxidation of the oxygen-transporting solid
compound is exothermic, just like that of the fuel. Nevertheless,
it takes place at high temperature.
[0028] A portion of the heat given off by the chemical reactions
carried out is recovered by heat exchange. There may be many heat
exchanges, so as to recover the heat at the place where it occurs.
The heat can be recovered in particular in or around the reaction
media or else in the primary, secondary and/or regeneration
effluent products. The thermal energy is partly transferred to one
or more heat-exchange fluids, such as steam or hot oil, according
to methods known to a person skilled in the art. These fluids,
optionally produced at different pressure and/or temperature
levels, can be used as is or to produce mechanical and/or
electrical energy.
[0029] During a first period of time where it is desired to produce
a given energy power, use is made, in stage c), of air, optionally
pretreated, in order to regenerate the oxygen-transporting solid
compound or compounds. The power delivered is adjusted by using
other parameters, in particular the flow rate of fuel and solid
compound in the loop. The inventors have established that if,
during a second given period, it is desired to increase the power
produced, it is advantageous to use, in stage c), at least one gas
comprising between 22% and 100% of oxygen by volume. In this gas,
the remainder to 100% by volume is composed of gases which do not
react with the solid compound or compounds (nitrogen, argon,
CO.sub.2, and the like). This gas can be a mixture of air and
relatively pure oxygen. In stage c), the solid compound can be
brought into contact with several oxygen-comprising gases, some
being air and others being gases comprising between 22% and 100% of
oxygen by volume.
[0030] The first period and the second period are not necessarily
successive. The second period is not necessarily subsequent to the
first period.
[0031] All this implies having available a source of gas richer in
oxygen than air, which has a capital cost, if a source is not
available, and an operating cost. On the other hand, this makes it
possible to increase the maximum power produced, without having to
enlarge the plant in which the process is carried out. Thus, the
plant can be designed not with regard to a peak power but with
regard to a lower power. In this way, the initial capital cost of
the energy production unit may be reduced.
[0032] The gaseous effluent products resulting from stage a) of the
oxidation of the fuel are analogous to the flue gases from a
conventional combustion using air as oxidant, but comprise little
or no nitrogen. Their CO.sub.2 concentration is also greater. After
condensation of the water (for example by cooling), they are thus
particularly suitable for subjecting to capture of the CO.sub.2 by
any technique known to a person skilled in the art (washing with
amines, adsorption, permeation, cryogenic distillation, and the
like).
[0033] Furthermore, the gaseous effluent products resulting from
the regeneration of the solid compounds in stage c) are depleted in
oxygen. By producing a sufficient depletion, the invention exhibits
the additional advantage of providing a residual gas which can be
used in inerting applications.
[0034] According to specific embodiments, the invention can in
addition comprise one or more of the following characteristics:
[0035] during said second period of production of energy, said
oxygen-comprising gas has a concentration of oxygen by volume of
between 23% and 40%. [0036] during said first period of production
of energy, said fuel is of a first given type and, during said
second period of production of energy, said fuel is of a second
given type which is more reactive in stage a) than said first type.
In order to determine if one fuel is more reactive than another,
the following calorimetric experiment is carried out successively
on the two test fuels. An amount of fuel equivalent in NCV (net
calorific value) to a value chosen in advance is placed in a bomb
calorimeter. The oxygen-transporting compound, in the form under
which it is employed in stage a) of the process according to the
invention, that is to say an oxidized form, is added thereto in a
stoichiometric amount. The two reactants are initially at
20.degree. C. The curve of rise in the temperature as a function of
the time is subsequently measured. The curves obtained for the two
fuels are compared on the same graph. It will be said that the more
reactive is that for which the initial rise in the temperature is
faster, that is to say that for which the curve of temperature is
higher during at least a certain interval of time. [0037] said
first type of fuel is sub-bituminous coal and said second type of
carbon-based fuel is lignite or coal or HFO (heavy fuel oil) or LPG
(liquefied petroleum gas) or natural gas. [0038] during said first
period (T1) of production of energy at said first power (P1), use
is made of a first flow rate of said solid compound in stage a) and
of a second flow rate of said solid compound in stage c) and,
during said second period (T2) of production of energy at said
second power (P2), use is made of a third flow rate of said solid
compound in stage a) and of a fourth flow rate of said solid
compound in stage c), the ratio of said third flow rate to said
first flow rate and the ratio of said fourth flow rate to said
second flow rate being greater than or equal to the ratio of said
second power (P2) to said first power (P1). The first and second
flow rates are generally similar values. If they differ, it is
because the solid compound has been bled or an extra contribution
has been made. It is the same for the third and fourth flow rates
of solid compound.
[0039] During said second period of production of energy, more
energy per unit of time is released by the chemical reactions in
the oxidation and reduction reactors. Adaptations known to a person
skilled in the art can be produced in the plant in order to remove
this additional power. For example, there may be additional heat
exchangers which come into operation during this second period, in
a heat-exchange fluid circuit shared or not shared with the main
circuit. In another example, the flow rate by weight of
heat-exchange fluid passing through the same heat exchangers may be
accordingly increased during this second period. In another
example, the control parameters of the heat-exchange fluid circuit
change in this second period, so that the heat-exchange fluid is
hotter on exiting from the heat exchangers than during the first
period (thus storing up more thermal energy). In another example,
the pressure of the heat-exchange fluid circuit increases during
this second period, so as to promote the presence of liquid phase
in this circuit, with a higher specific heat, which may be better
in removing the additional power produced.
[0040] The advantage of using a gas for which the concentration of
oxygen by volume is between 23% and 40% is that of limiting the
risk of an excessively high rise in the temperature during stage
c). This might necessitate adapting the reactor or reactors in
which the exothermic regeneration (stage c)) of the solid compound
or compounds is carried out, with negative effects on the capital
costs.
[0041] The invention also relates to a device for the production of
energy, comprising at least: [0042] one reactor for the oxidation
of fuel connected at the inlet to one or more sources of fuel and
to at least one pipe suitable for conveying and intended to convey
an oxygen-transporting solid compound to said oxidation reactor,
said reactor having at least one outlet for gases resulting from
the oxidation of said fuel; [0043] one reactor for regeneration of
said oxygen-transporting solid compound, connected at the inlet to
a source of air and to at least one pipe suitable for conveying and
intended to convey said oxygen-transporting solid compound from an
outlet of said oxidation reactor to said regeneration reactor, said
reactor having at least one outlet for gases resulting from the
regeneration of said oxygen-transporting solid compound; [0044]
means for recovery of said solid compound at the outlet of said
oxidation and regeneration reactors; and [0045] heat exchangers
capable of converting and intended to convert, into energy, the
heat given off in said regeneration reactor; said pipe capable of
conveying and intended to convey an oxygen-transporting solid
compound to said oxidation reactor being connected to an outlet of
said regeneration reactor; said device being characterized in that
it additionally comprises: [0046] a source of a gas having a
concentration of oxygen by volume of between 22% and 100% connected
to an inlet of said regeneration reactor; and [0047] means which
make it possible to selectively open or close said connections
between said regeneration reactor and said source of air, on the
one hand, and said regeneration reactor and said source of a gas
having a concentration of oxygen by volume of between 22% and 100%,
on the other hand.
[0048] Connection by pipe between the reactors means that there is
connection by a system of pipes capable of transporting a material
stream. This connection system can comprise valves, intermediate
storages, bypasses, heat exchangers or compressors but not chemical
reactors. "Reactor" shall be taken in the definition of the
invention in the broad sense of "unit". They can thus have a
complex structure known to a person skilled in the art and in
particular can comprise several receivers.
[0049] The device can also comprise means for injection of an extra
contribution of oxygen-transporting solid compound, or bleeding
means, for example on the pipes connecting the reactors.
[0050] The means for recovery of the oxygen-transporting solid
compound can be of any nature capable of isolating solid particles
in gas streams, for example systems known as "cyclones". The means
which make it possible to select one or other of the sources of
oxygen-comprising gas to be injected into the regeneration reactor,
or to mix the gases resulting from these sources, are generally
valves subjected to a control system.
[0051] According to specific embodiments, the invention can
additionally comprise the following characteristic: said source of
a gas having a concentration of oxygen by volume of between 22% and
100% is capable of providing and is intended to provide a gas for
which the concentration of oxygen by volume is between 23% and
40%.
[0052] Other distinctive features and advantages of the invention
will become apparent on reading the following description, made
with reference to the figures, where:
[0053] FIG. 1 represents a plant employing the process according to
the invention,
[0054] FIG. 2 is a diagram illustrating the choice of the
oxygen-comprising gas employed in stage c).
[0055] In the example illustrated by FIG. 1, a fuel oil 4 and
ilmenite 5a are introduced into a reactor 2. The oxidation of the
fuel oil 2a on contact with the ilmenite 2b in the reactor 2
produces primary effluent products 8 and ilmenite in reduced form
9. These primary effluent products are favorable to the capture of
CO.sub.2 in the sense that they comprise little or no nitrogen.
This capturing can be carried out by one or more known techniques
for the separation of CO.sub.2, optionally preceded by condensation
of the water present in the effluent products 8. A non-zero
fraction 9a of this ilmenite 9, preferably of approximately 100%,
is introduced into the reactor 3, where an oxygen-comprising gas 6
is also introduced. Highly exothermic oxidation of the ilmenite 3b
takes place on contact with this gas 3a in the reactor 3. This
reaction produces a gas 7 which is depleted in oxygen with respect
to the gas 6 entering the reactor 3. The ilmenite 3b is recharged
with oxygen and is recovered in an oxidized form 5. A non-zero
fraction 5a of the latter, preferably of approximately 100%, is
introduced into the reactor 3.
[0056] The oxygen-transporting compound, in this instance ilmenite,
produces a chemical loop by passing through the states 5a, 2b, 9,
9a, 3b and 5. The ilmenite is recovered at the outlet of the
reactors 2 and 3 by techniques known to a person skilled in the
art, for example cyclones (not represented). An extra contribution
of product, or a bleeding, may prove to be necessary in order to
maintain the amount (weight) and the quality of the oxygen
transporter.
[0057] The heat given off by the reactions in the reactor 2 is
recovered by heat exchange in the reactor 2. In addition, it can
also be recovered in the reactor 2 and/or on the hot solid or
gaseous products which circulate between the reactors. In practice,
this heat is used to heat water in order to produce steam, which
can subsequently be completely or partially converted to mechanical
and/or electrical energy.
[0058] The oxygen-comprising gas 6 can be prepared from a source of
air 6a and/or by mixing this air 6a with relatively pure oxygen
produced by an air separation unit 6b. The change from feeding the
reactor 3 with air 6a to feeding with a mixture of air and oxygen
will regenerate a greater amount of ilmenite 9a. More oxidized
ilmenite 5 is obtained and it is possible to inject a greater
amount 5a thereof into the reactor 2. Thus, all things otherwise
being equal, the change from feeding the reactor 3 with air to
feeding with oxygen makes it possible to oxidize more fuel and to
generate more energy.
[0059] In a specific configuration of the example illustrated in
FIG. 1, the fuel 4 is natural gas and the content of oxygen by
volume in the flow 6 is 30%. In comparison with a configuration in
which the flow 6 would be exclusively air, the invention makes it
possible to oxidize 60% more natural gas and thus to produce
approximately 60% more energy in the same plant.
[0060] The increase in the production of energy made possible by
the change in nature of the oxygen-comprising gas 6 can be further
increased by changing the nature of the fuel 4 sent to the reactor
2.
[0061] A diagrammatic representation has been given, in FIG. 2, of
a possible change as a function of the time in the concentration of
oxygen by volume C in the gas 6 sent to the reactor 3 and in the
power P, in kW or MW (amount of energy produced per unit of time),
produced by the plant. Thus, during a period of time T1, the gas 6
sent to the reactor 3 is air (C1) originating from the source 4a
(air, optionally pretreated). The plant then produces a power P1.
This period T1 generally corresponds to the normal operation of the
plant. If, for one reason or another, it is desired to satisfy a
peak in consumption corresponding to a power P2 during a period of
time T2, the nature of the gas 6 sent to the reactor 3 is changed.
The gas 6 (C2) then originates from a source of oxygen 6b or from a
mixture of 6a and 6b. During this time T2, the amount of fuel 4
injected into the reactor 2 is also increased, in order to deliver
this power P2 to the system. The period T2 is not necessarily
subsequent to the period T1. T2 is simply a period of time during
which it is desired to produce a power P2 greater than that which
is obtained under conditions of operating with air. P2 is often
referred to as peak power. Thus, the plant can be designed in order
to satisfy the need for power P1. The change to gas comprising
between 22% and 100% of oxygen by volume makes it possible to
satisfy a greater need P2 without having to modify the plant.
[0062] For example, a power plant using natural gas as fuel 4
produces, during the period T1, a useful thermal power P1=200 MWth
(thermal megawatts) with air as oxidant 6 (C1=21%). In this case,
the amount of natural gas 4 consumed is 21 635 Sm.sup.3/h (cubic
meters per hour taken under standard temperature and pressure
conditions, i.e. 0.degree. C. and 1 atmosphere) on entering the
reactor 2. The amount of air 6 is 206 049 Sm.sup.3/h, including 43
270 Sm.sup.3/h of oxygen.
[0063] During the period T2, additional oxygen (26 492 Sm.sup.3/h)
is added to these 206 049 Sm.sup.3/h of air, so that the
concentration of oxygen by volume of 6 is equal to 30% (C2=30%). In
this case, the total flow rate of oxidant 6 is 232 541 Sm.sup.3/h.
The amount 4 of natural gas to be oxidized in the reactor 2 can
increase to 34 881 Sm.sup.3/h. The power plant will then be capable
of thus producing P2=322 MWth of useful thermal power.
[0064] During the period T2, the flow rates of solid compound
employed in (entering) the reactors 2 and 3 are increased by 65%
with respect to the same flow rates considered during the period
T1. This increase is greater than the P2/P1 ratio of increase in
the power produced, which is approximately 60%.
* * * * *