Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22G—SUPERHEATING OF STEAM
  • F22G1/00—Steam superheating characterised by heating method
  • F22G1/16—Steam superheating characterised by heating method by using a separate heat source independent from heat supply of the steam boiler, e.g. by electricity, by auxiliary combustion of fuel oil
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B21/00—Water-tube boilers of vertical or steeply-inclined type, i.e. the water-tube sets being arranged vertically or substantially vertically
  • F22B21/34—Water-tube boilers of vertical or steeply-inclined type, i.e. the water-tube sets being arranged vertically or substantially vertically built-up from water tubes grouped in panel form surrounding the combustion chamber, i.e. radiation boilers
  • F22B21/348—Radiation boilers with a burner at the top
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
  • F22B31/04—Heat supply by installation of two or more combustion apparatus, e.g. of separate combustion apparatus for the boiler and the superheater respectively

Definitions

• the present invention relates to a thermal generator intended for the production of steam.
• a steam generator more commonly called a boiler, operating from the combustion of a fuel, in particular that containing sulfur and nitrogen, in the presence of an oxidizer, more particularly of an oxidizer with a high oxygen content, generally greater than 80%.
• a generator can be used, in particular to drive rotating machines, such as steam turbines of thermal power plants, for which it is necessary to produce steam at high temperature, called superheated steam, with a temperature of the order of 560 ° C.
• superheated steam with a temperature of the order of 560 ° C.
• Another possible application of this generator is the production of steam in a refinery to meet the needs of petroleum transformation processes. It is also possible to use such a generator for the production of steam for the extraction of crude oil.
• a steam generator operating from the combustion of a fuel in the presence of air.
• This generator comprises a combustion hearth (or combustion chamber) provided with at least one. burner and includes; successively one after the other, a vaporization zone comprising at least one vaporization exchanger called a vaporizer or evaporator screen, a superheating zone comprising a superheating exchanger or superheater, a preheating zone comprising a preheating exchanger or economizer and a smoke evacuation zone and / or a smoke recirculation zone.
• a means of storing water in the gaseous phase and in the liquid phase called a balloon, which supplies, in heated water, the evaporator and, in water vapor, the superheater.
• This type of generator generally implements two circuits, a first circuit, called the water circuit, which includes the exchangers of the vaporization, superheating, preheating zones as well as the tank and a second circuit, called the smoke circuit, which uses the fumes resulting from the combustion of a fuel with an oxidizer and which is intended to transfer the thermal energy released by the combustion to the various exchangers, during their journeys from the burner to the smoke evacuation zone.
• the fumes resulting from combustion are high temperature fumes which pass through the exchangers to transfer their heat by convection and / or by radiation to the different exchangers so as to heat the water then to vaporize it and finally to overheat the vapor of water resulting from vaporization. Additionally, this smoke can then pass through a complex treatment installation, such as a dust collector followed by a smoke treatment unit, before being discharged into the atmosphere through a chimney. In the water circuit, the water available on site is pumped to be injected into the economizer where it is preheated.
• the preheated water is then directed either to the tank (in the case of a natural circulation generator) from which the preheated water then feeds the evaporator, or directly to this evaporator (for forced circulation generators) thanks to which the preheated water is largely vaporized.
• the two-phase liquid water-water vapor mixture is sent to the. flask where the separation of the liquid phase and the vapor phase takes place.
• the water vapor from tank feeds the superheater which produces steam at very high temperatures.
• the vaporization of water takes place largely in the evaporator of the combustion chamber, because it is in this zone that the highest thermal level of the fumes is located as well as the need for it. greater in energy to ensure the transformation of water into a two-phase fluid in the evaporator. Then there is a thermal transfer of the smoke energy to the superheater in the superheating zone, which transfer also requires a high temperature level to obtain superheated steam. Finally, when leaving the superheating zone, the fumes exchange their thermal energies with the economizer which uses the fumes at their lowest temperature levels to preheat the water. All these heat exchange operations make it possible to maximize the output of the generator by making maximum use of the heat of the fumes.
• this type of generator may also be advantageous to operate this type of generator using an oxidizer with a high oxygen content, preferably greater than 80%, and to take advantage of such combustion, in particular by reducing the nitrogen ballast contained in this oxidizer.
• the thermal losses at the stack of a generator operating in air and discharging fumes at 250 ° C. are of the order of 10% of the thermal power supplied by the fuel whereas, for identical operating conditions, the heat losses are reduced to 3% when using, as oxidant, pure oxygen, which generates an increase in energy efficiency of the order of 7%.
• the smoke flow is reduced by a factor of at least four.
• oxygen combustion the pollutant emissions are greatly reduced. More particularly, the emissions of nitrogen oxides (NOx), resulting both from the thermal dissociation of molecular nitrogen and from the reaction of the nitrogen contained in the fuel, are reduced by a factor of one to five for the same burner technology.
• the treatment of the fumes with a view to eliminating the sulfur oxides can also be simplified in view of the increase in the concentration of the sulfur oxides in the combustion fumes. Significant savings can therefore be made in the costs of equipment for treating sulfur oxides.
• Figure 1 which is a graph showing, on the abscissa, the smoke temperatures (in ° C) and, on the ordinate, the combustion efficiency (in%), shows the difference in efficiency between a combustion at l 'air (curve l) and oxycombustion (curve II).
• Figure 1 gives a thermal efficiency of 90.2% for a smoke temperature of 250 ° C (point A) at the outlet of the economizer.
• Figure 1 shows that the temperature of the fumes at the outlet of an evaporator consuming 43.8% of the power delivered by an oxycombustion generator operating with an oxidizer whose composition is of the order of 95% of oxygen, of the order of 3% of nitrogen and of the order of 2% of argon, is much greater than 2000 ° C. (line B) .
• Such a temperature is detrimental to the emission of pollutants, such as nitrogen oxides (NOx). More particularly, it has been possible to demonstrate that there is an exponential dependence between the rate of formation of NOx and the temperature of the flue gases with a very rapid increase in the conversion of molecular nitrogen from the oxidizer to NO from a temperature smoke in the range of 1500 ° C. In addition, the fumes return to the superheater at a temperature above 2000 ° C and the tubes generally constituting the superheater are therefore subjected to very high smoke temperatures. This solution poses a problem of thermal behavior for the tubes of the superheater inside which already circulates dry steam.
• pollutants such as nitrogen oxides (NOx). More particularly, it has been possible to demonstrate that there is an exponential dependence between the rate of formation of NOx and the temperature of the flue gases with a very rapid increase in the conversion of molecular nitrogen from the oxidizer to NO from a temperature smoke in the range of 1500 ° C. In addition, the fumes return to the superheater at a temperature
• FIG. 1 shows that the thermal efficiency associated with this temperature is of the order of 80.9% (point C) for a combustion chamber operating with oxy-fuel combustion, which is much higher than the efficiency required by the evaporator which is 43.8% for a temperature of approximately
• the present invention proposes to overcome the drawbacks mentioned above by means of a generator in which the temperature level of the fumes for obtaining superheated steam at a required temperature is obtained in a simple manner and this by using the techniques and materials commonly used in boilers.
• the present invention relates to a steam generator comprising at least two successive combustion stoves with at least one burner supplied with fuel and oxidizer, a vaporization zone comprising a vaporization exchanger, a superheating zone comprising a heat exchanger superheating, a preheating zone comprising a preheating exchanger and a collecting tank, characterized in that each hearth comprises at least one vaporization exchanger.
• each household can comprise at least one superheating exchanger.
• Each hearth can also include at least one preheating exchanger.
• One of the fireplaces can include at least one vaporization exchanger and the other of the fireplaces can include at least one superheat exchanger.
• One of the hearths can comprise at least one vaporization exchanger whereas the other of the hearths can comprise at least one superheating exchanger and at least one preheating exchanger.
• one of the hearths can comprise at least one vaporization exchanger and at least one superheating exchanger and the other of the hearths can comprise at least one superheating exchanger and at least one preheating exchanger.
• the steam generator may include a chamber for decontaminating fumes from combustion stoves.
• the smoke pollution control chamber can be accommodated upstream of the preheating zone.
• the smoke depollution chamber may include means for injecting absorbent.
• the smoke depollution chamber may include means for injecting a reducing agent.
• the smoke depollution chamber can comprise at least one vaporization zone.
• the absorbent injected into the smoke depollution chamber can be of the calcium or magnesian type.
• the reducing agent injected into the smoke depollution chamber can be of the urea or ammonia type.
• the oxidizer is an oxidizer with a high oxygen content whereas the fuel is a solid, liquid or gaseous fuel, such as a heavy fuel oil, a petroleum residue, a gas, petroleum coke or coal.
• the walls of at least one hearth may consist of a ferrule or of membrane walls.
• the steam generator 10 more commonly referred to as a boiler, comprises two successive combustion foci F1 and F2, in which a fuel burns in the presence of an oxidant.
• the fuel is a solid, liquid or gaseous fuel containing in particular sulfur and nitrogen, such as a heavy fuel oil, a petroleum residue, a gas, petroleum coke or coal, while the oxidant is preferably a gas with a very high oxygen content, preferably greater than 80 %, or pure oxygen.
• the primary combustion furnace F1 preferably arranged vertically, is placed, in the upper part as shown in the figure, at least one burner 12 supplied with fuel by a channel 14 and by combustion by a channel 16.
• the arrangement and the number burners will be determined by those skilled in the art so as to obtain combustion with low emissions of pollutants while avoiding contact of the burner flame with the walls 18 of this hearth.
• This combustion can also be carried out by any other means, such as grates, fluidized beds.
• an auxiliary fluid will be judiciously used to optimize combustion, such as water vapor or a gas or a mixture of gases, such as in particular C0 2 or O 2 , this so provide for recycling of fumes that could be used for vaporizing the fuel.
• This primary combustion furnace F1 comprises a vaporization zone V comprising at least one vaporization exchanger or vaporizer screen 20, called in the following description of the evaporator, which, in the example described, consists of the walls of the primary combustion chamber F1 which are preferably of the "membrane wall" type. As is known, these membrane walls are made up of tubes connected together by fins welded to form a heat exchanger. This evaporator thus obtained is a high temperature exchanger which ensures at least partial vaporization of the fluid circulating inside the tubes.
• the arrangement and the number of burners will be determined by a person skilled in the art so as to obtain combustion with low emissions of pollutants while avoiding contact of the burner flame with the walls of the secondary fireplace F2.
• This secondary combustion hearth comprises a high temperature superheating zone S1 comprising at least one superheating exchanger or superheater 30, called high temperature superheater, for raising the temperature of the fluid, generally in the vapor phase, which traverses it.
• the walls of this hearth consist of a ferrule 32, preferably metallic, protected from thermal radiation by an insulating material, such as concrete, bricks or a fibrous material.
• bundles of tubes 34 are installed in which water vapor circulates.
• This superheater is a high temperature exchanger ensuring the superheating of the vapor phase fluid which flows through it.
• the outlet 36 of the high temperature superheating zone communicates, in the upper part, with an envelope E in which is located an additional superheating zone S2, called the low temperature superheating zone, and preferably a preheating zone P.
• the superheating zone low temperature S2 comprises at least one convective type exchanger 38, called a low temperature superheater.
• the preheating zone P also includes at least one convective exchanger 40, called an economizer. These convective exchangers 38 and 40 are formed, in a manner known per se, of bundles of tubes connected to manifolds.
• the steam generator includes two fireplaces. successive combustion, the primary combustion focus F1 and, in series with this primary combustion focus, the secondary combustion focus F2.
• the primary hearth F1 comprises the burner 12 and the evaporator 20 while the hearth F2 comprises the burner 24, the high temperature superheater 30 and is followed by the casing E consisting of the low temperature superheater 38 as well as the economizer 40.
• the output 42 of the preheating zone leads to a zone exhaust fumes F that communicates to any known processing means such smoke or to a chimney (not shown).
• the economizer 40 comprises an inlet 44 for water and an outlet 46 for preheated water which ends in a pipe 48 at a fluid collecting means 50, such as a balloon usually used in this type of generator.
• the low temperature superheater 38 includes a steam inlet 52 from the balloon 50 via a pipe 54 and a steam outlet 56 to the high temperature superheater 30.
• the high temperature superheater 30 includes a steam inlet 58 from the low temperature superheater 38 conveyed by a pipe 60 and a steam outlet 62, preferably superheated, which is directed, by a pipe 64, to any means using such superheated steam, such as a thermal power plant turbine.
• the economizer and the low-temperature superheater can be provided with devices for increasing thermal transfers, such as fins, if the fumes passing through them are not too laden with dust.
• the evaporator 20 comprises an inlet 66 supplied with water preheated by a line 68 connecting the balloon 50 to this inlet and an outlet 70 of a water emulsion in two-phase form (liquid water-water vapor) to the balloon 50 through a pipe 72.
• the water is introduced into the economizer 40 by the inlet 44, circulates in this economizer while being preheated there, then is collected in the balloon 50 by means of the pipe 48 connecting this balloon to the output 46 of the economizer.
• This hot water is then sent from the tank 50 to the inlet 66 of the evaporator 20 via the pipe 68 to be at least partially transformed therein into a water emulsion, two-phase at its outlet 70.
• the emulsion leaving the evaporator is directed through line 72 into the flask 50 where it undergoes separation of the gas phase and the liquid phase.
• the water vapor contained in this balloon is then sent via line 54 to the inlet 52 of the low-temperature superheater 38 in which a rise in temperature of this vapor takes place so as to obtain, at its outlet 56, dry steam at a first temperature level.
• dry steam is meant steam at a temperature above the water saturation temperature at the pressure considered.
• the inlet 58 of the high temperature superheater 30 receives the steam from the low-temperature superheater 38 via the pipe 60 and this steam comes out through the outlet. 62 in the form of superheated steam, that is to say at a temperature higher than that of the steam coming from the low temperature superheater 38.
• the fumes generated by combustion pass through the vaporization zone V and exchange part of their thermal energy with the preheated water circulating in the tubes of the evaporator 20 so as to obtain at the outlet 70 of this evaporator a fluid in two-phase form liquid water-water vapor.
• the fumes are directed towards the secondary combustion hearth F2 in which the combustion of the remaining fraction of the total quantity of the fuel and of the oxidant is carried out by means of the burner 24 supplied with fuel and oxidizer via channels 26 and 28.
• the temperature of the fumes is then increased and these fumes pass through the high temperature superheating zone S1 which includes the high temperature superheater 30.
• the temperature of the water vapor circulating in the tubes of this superheater is then increased and this superheated steam is. then discharged through line 64 to be used by known means, such as a turbine or any method.
• the fumes leaving the high temperature superheating zone S1 through the outlet 36 are sent to the low temperature superheating zone S2 comprising the low temperature superheater 38 in which the water vapor which undergoes a temperature rise circulates.
• the fumes are sent to a fume treatment zone with injection of absorbent before passing through the low temperature superheater 38.
• These fumes then pass through the preheating zone P in which the water circulating in the economizer 40 undergoes a temperature increase by heat exchange with the fumes while cooling these fumes to an appropriate temperature, generally of the order of 250 ° C.
• the burner 12 generates fumes whose temperature at the outlet 22 of the hearth F1 is of the order of 1300 ° C. These fumes then enter the secondary combustion furnace F2. Thanks to the burner 24, they undergo a rise in temperature to reach a temperature of the order of 1000 ° C., after exchange in the focus F2, at the outlet 36 of the zone S1. These fumes thus heated penetrate into the secondary superheating zone S2 by exchanging their thermal energies with the low temperature superheater 38 from which they emerge at a temperature of approximately 600 ° C. then sweep the economiser 40 present in the preheating zone P to be evacuated by exit 42 to zone F to. an approximate temperature of 250 ° C.
• water is introduced into the economizer 40 at a temperature of approximately 150 ° C. to come out at approximately 290 ° C.
• This preheated water is then partially vaporized in the evaporator 20, after passing through the flask 50, and comes out at a temperature of about 305 ° C to be sent to the flask 50.
• the water vapor leaving this flask this same temperature is injected into the low temperature superheater 38 by means of which it increases its temperature up to approximately 375 ° C approximately at the outlet 56 to then be sent to the high temperature superheater 30 from which it emerges at approximately 480 ° C .
• a multiplicity of combustion stoves are installed one after the other and being in series with each other.
• at least one vaporization and / or superheating and / or preheating zone comprising at least one exchanger, such as an evaporator and or a superheater and / or an economizer, connected in series with the exchangers located after the other combustion hearths, is arranged in each combustion hearth.
• the entire generator has walls of the "membrane wall” type so as to take advantage of the thermal energy contained in the fumes which circulate from the primary focus F1 to the outlet 42.
• This generator comprises a primary combustion furnace F1, a secondary combustion furnace F2 comprising a low temperature superheating zone S2. This zone leads to a preheating zone P ending in a smoke evacuation zone F.
• the primary hearth F1 of the "membrane wall” type, as described above, comprises a burner 12, a vaporization zone V with an evaporator 20 and a smoke outlet 74 which leads to a high temperature superheating zone S1 contained in an envelope E1.
• This substantially vertical elongated envelope is also of the “membrane wall” type and contains a high temperature superheater 30, which is of the convective type, with a steam inlet 58 and a superheated steam outlet 62.
• the outlet 22 of this superheating zone arrives in the secondary combustion furnace F2 which comprises a burner 24, as described in relation to FIG. 2, and which also consists of membrane walls.
• the smoke outlet 36 leads, as already described, to a low temperature superheating zone S2 with a low temperature superheater 38 comprising an inlet 52 and an outlet 56 for steam, said zone communicating with a preheating zone P with an economizer 40 provided a water inlet 44 and a water outlet preheated 46, this preheating zone communicating with a smoke evacuation zone F by an outlet 42.
• the low temperature superheating S2 and preheating P zones comprise walls of the "membrane wall" type.
• the admission of preheated water into the evaporator and the outlet of the two-phase fluid (liquid water-water vapor) can be done at different levels.
• the evaporator 20 comprises an intake of preheated water 66 at the level of the primary focus F1 and an outlet 70 of the two-phase fluid (liquid water-water vapor) located at the level of the outlet 42 of the preheating zone while being connected by a pipe 72 to the tank 50.
• the fires of combustion F1 and F2 as well as the high temperature superheating zones S1, low temperature superheating zones S2 and preheating P each comprise a part of the evaporator 20 divided into the evaporation zones referenced in the drawings V, V1, V2 and V3.
• the outlet 70 of the two-phase fluid will be located at the outlet of the secondary focus F2, this outlet being connected by line 72 to the balloon 50 as shown in dotted lines on the figure, and only the evaporation zones V, V1 and V2 will remain.
• the primary focus F1 comprises the burner 12, the evaporation zone V with the evaporator 20, the high temperature superheating zone S1 with the high temperature superheater 30 and the vaporization zone V1 comprising the tubes of the membrane wall of the envelope E1 while the secondary hearth F2 comprises the burner 24, the low temperature superheating zone S2 with the low temperature superheater 38, the preheating zone P with l economizer 40 and the vaporization zones V2 and V3 comprising the tubes of the membrane walls.
• the burner 12 of the primary focus F1 is supplied by a proportion of the total amount of the gaseous fuel, liquid or solid, and a proportion of the total amount of the oxidant with high oxygen content. .
• the fumes from the hearth F1 pass through the vaporization zone V and exchange their thermal energies with the preheated water circulating in the tubes of the evaporator'20 so as to obtain at the outlet of this exchanger a fluid in a first two-phase form of liquid water -water vapour.
• the fumes pass through the high temperature superheating zone S1 where they transmit their heat energies, on the one hand, to the high temperature superheater 30 so as to obtain, at the output of this superheater, water vapor at a first temperature level and, on the other hand, to the fluid circulating in the tubes of the vaporization zone V1.
• the fumes leaving the superheating zone S1 are directed by the outlet 22 to the secondary combustion furnace F2 in which the combustion of the remaining fraction of the total quantity of the fuel and of the oxidant is carried out via the burner 24.
• the temperature of these fumes is then increased and they are evacuated, via outlet 36, to the secondary superheating zone S2 by exchanging their thermal energies with the low temperature superheater 38.
• the fumes also transmit part of their energies to the tubes of the vaporization zone V2.
• the water entering the economizer 40 through the inlet 44 is sent, after being heated by passage through this economizer, to the balloon 50 via line 48.
• the hot water is then directed through line 68 of this balloon to the inlet 66 of the evaporator 20.
• the two-phase fluid water liquid-water vapor from the outlet 70 which has absorbed the calories of the fumes throughout their paths in the generator, from the burner 12 to outlet 42, is directed by line 72 to the tank 50.
• the two-phase fluid is subjected to a separation between the vapor phase and the liquid phase and the water vapor is sent via line 54 to the inlet 52 of the low temperature superheater 38 where the temperature of this water vapor is increased to a first level.
• the steam is sent via a line 60 to the inlet 58 of the high temperature superheater 30 in which the temperature of this steam is further increased to a level higher than that of the low temperature superheater 38 and then is evacuated via outlet 62 to any device as described above.
• the burners 12 and 24 are supplied as described in relation to FIG. 2.
• the smoke temperatures are approximately 1300 ° C. at the exit from the evaporation zone V, approximately 500 ° C. at the exit from the high temperature superheating zone S1, approximately 1300 ° C at the entrance to the low temperature superheating zone S2, around 350 ° C at the exit of this zone and around 200 ° C at exit 42 towards the smoke evacuation zone F.
• temperatures of the fluids in the different exchangers are of the order of 150 ° C at the inlet 44 of the economizer 40, of the order of 165 ° C at the outlet 46 of this economizer, of the order of 304 ° C at the outlet 70 of the evaporator and at the inlet 52 of the low temperature superheater 38, of the order of 360 ° C at the outlet 56 of this superheater and at the inlet 58 of the high temperature superheater 30 and the 'order of 480 ° C at outlet 62 of this high temperature superheater.
• FIG. 4 shows an alternative embodiment of the invention according to Figure 3 and which for this also includes the same references as this figure.
• This variant is essentially distinguished from FIG. 3 by the presence of an envelope E2 containing a smoke depollution chamber 76 as well as a medium temperature overheating zone S3.
• the smoke depollution chamber 76 like a desulfurization chamber, is arranged after the outlet 36 of fumes generated by the burner 24 so as to take advantage of the temperature of the fumes which is at a high level given the action of this secondary focus.
• the primary hearth F1 of the "membrane wall" type comprises a burner 12, a vaporization zone V with an evaporator 20, a high temperature superheating zone S1 with a high temperature superheater 30 and a smoke outlet 22.
• the outlet 22 of this superheating zone arrives in the secondary combustion hearth F2.
• the outlet 36 of the fumes generated by the burner 24 of the hearth F2 leads to a medium temperature superheating zone S3 with a medium temperature superheater 78 comprising an inlet 80 connected by a line 82 to the outlet 56 of the low temperature superheater 38 and an outlet 84 of steam connected by a line 86 to the inlet 58 of the high temperature superheater 30.
• the outlet of this zone communicates with the depollution 76 which, in the example shown, is a desulfurization chamber.
• This chamber is equipped with at least one absorbent injector 88 allowing rapid and homogeneous dispersion of a jet of absorbents in the fumes passing through this chamber.
• the absorbent injected can be of the calcium, magnesium or any other type allowing the reaction with the sulfur oxides contained in the fumes to limit their formation.
• the particle size and the quantities of absorbents injected will be determined by a person skilled in the art so as to obtain desulfurization rates in accordance with the regulations in force.
• a reducing agent such as urea or ammonia.
• This reducing agent will be homogeneously dispersed in the depollution chamber by means similar to the absorbent injector 88.
• the number and arrangement of the absorbent and / or agent injectors (15 reducer will be determined by the skilled person so as to ensure a good distribution of the absorbent and / or the reducing agent in the chamber pollution.
• This depollution chamber advantageously consist of walls of the "membrane wall” type and also participate in the evaporation of the water circulating in the evaporator by forming an evaporation zone V4.
• the outlet 90 of the depollution chamber communicates, as has already been described in relation to FIG. 3, with a low temperature superheating zone S2 and a preheating zone P which opens via the outlet 42 towards the treatment zone for the fumes F.
• the fumes generated by the primary hearth F1 successively pass through the primary vaporization zone V, then the high temperature superheating zone S1. At the exit from this superheating zone, the temperature of the fumes is then increased by means of the burner 24. These 30 fumes then pass through the medium temperature superheating zone S3 • - to reach the depollution chamber 76 where they are desulphurized and / or denitrified by the injection of absorbents and / or reducing agents.
• the fumes thus treated end up at the outlet 90 from which they enter the low temperature superheating zone S2 and the preheating zone P to reach the smoke evacuation zone F.
• the water admitted into the economizer 40 is heated by passage through this economizer, then is directed to the tank 50.
• the hot water present in the tank is sent to the evaporator 20, then the two-phase fluid liquid water - water vapor from this evaporator is then directed to the balloon 50 through line 72.
• the water vapor present in this balloon is sent to the low temperature superheater 38 from which it emerges to be sent through line 82 in the medium temperature superheater 78.
• the steam from this medium temperature superheater is then sent via line 86 to the high temperature superheater, from which it exits via outlet 62 and line 64.
• the fumes which pass through the depollution chamber 76 are at a temperature preferably between 600 ° C and 1100 ° C so as to obtain a required desulfurization rate in adequacy with the residence time of the fumes in this depollution chamber. It can be observed that this temperature range also allows denitrification of the fumes in the case where this chamber is fitted with reducing agent injectors as previously described.
• the fumes transmit their thermal energies to the tubes of the different vaporization zones V, V1, V2, V3 and V4.
• the fuel used consists, in percentage by mass, of approximately 84% of carbon, approximately 9% of hydrogen, approximately 6% of sulfur and approximately 1% of sulfur.
• the volume composition of the oxidizer is of the order of 95% of oxygen, of the order of 3% of nitrogen and of the order of 2% of argon.
• the fuel and oxidizer flow rates are approximately 1.29 kg / s and 4.24 kg / s for the primary combustion furnace F1 whereas they are approximately 1.39 kg / s and 4.56 kg / s for the secondary combustion furnace F2.
• the temperature of the water at the inlet of the economizer 40 being 150 ° C.
• the temperature of the heated water leaving the economizer is approximately 180 ° C.
• the temperature of the flue gases upstream of the preheating zone P is approximately 450 ° C and approximately 250 ° C downstream of this same zone.
• the temperature of the two-phase liquid water-water vapor fluid, after passing through the evaporator 20, is approximately 305 ° C. at the outlet 70 of this evaporator.
• the temperature of the water vapor at the inlet of the low-temperature superheater 38 is of the order of 305 ° C and of the order of 330 ° C at its outlet while the temperature of the fumes is of the order of 750 ° C upstream of the S2 low temperature overheating zone and around 450 ° C downstream of this same zone.
• the temperature of the water vapor at the inlet 80 of the medium temperature superheater 78 is of the order of 330 ° C and of the order of 420 ° C at its outlet 84 while the temperature of the fumes is of the around 1300 ° C upstream of the medium temperature overheating zone S3 and around 1000 ° C downstream of this zone and at the entrance to the depollution chamber 76.
• the temperature of the water vapor the admission of the high temperature superheater 30 is of the order of 420 ° C and of the order of 480 ° C at its outlet 62 while the flue gas temperature is of the order of 1300 ° C upstream of the zone high temperature superheating S1 and of the order of 500 ° C downstream of this superheating zone.
• the primary combustion furnace F1 below the stoichiometry with a fuel in excess relative to the oxidizer, so as to limit the emissions of nitrogen oxides.
• the secondary combustion furnace F2 can operate above the stoichiometry with the oxidant in excess relative to the fuel.
• it can advantageously be envisaged to dispense with the use of the economizer and to carry out the preheating of the water by the evaporator which will admit water at the site temperature. This water will be preheated during the circulation of this water at the start of this evaporator and then evaporated in the rest of the evaporator.

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