ES2357831T3 - COMBUSTION SYSTEM FOR VAPOR GENERATION AND PROCEDURE FOR EMISSION CONTROL THAT USES OXYGEN ENRICHMENT. - Google Patents

Abstract

A combustion process for steam generation, comprising: providing a stream (42) of oxygen-enriched gas with an oxygen content of 21 to 100%; create an oxidizing stream (46) containing the oxygen enriched gas stream (42); combustion of a fuel in the oxidant stream (42) in a combustion chamber (10) that generates steam and that generates combustion gas (22) having a mass flow of combustion gas that is less than a mass flow of gas of combustion generated by the combustion chamber (10) when operating with the same mass flow of fuel and with air as the oxidizing current; and reduction of the amount of at least one particulate matter, SOx, NOx and mercury in the combustion gas (22) with a combustion gas contaminant control system (20), in which the stage of creating an oxidizing stream (46) comprises the release of a dilution gas (80) in the oxygen enriched gas (42) forming the oxidizing stream (46), and the dilution gas comprises recirculated wet or dry combustion gas.

Description

Field of the Invention

The invention relates to a method for improved emission control of a combustion system for steam generation using a combination of an improved combustion process and combustion gas treatment systems. 5

Description of the related technique

Industrial combustion systems are the main source of sulfur dioxide (SO2), nitrogen oxides (NOx) and mercury (Hg) emissions, as well as carbon dioxide (CO2). Whether by the Kyoto Protocol or by recent initiatives by the United States government, these industrial combustion plants will now have to comply with increasingly demanding regulations related to these pollutants. 10

The combustion of fossil fuels in boilers of power plants, industrial boilers, furnaces, dryers, etc. It results in the formation of significant levels of contaminants. The combustion of coal, for example, leads to the generation, among others, of SOx, NOx, Hg and particulate matter. All these substances have been shown to be detrimental to human health.

The typical procedure for reducing particulate, Hg, NOx and SO2 emissions from steam generation boilers 15 used in power plants is with the use of combustion gas treatment equipment, including electrostatic precipitators (ESP), bag filters , catalytic systems or wet and dry scrubbers. These devices are large and very expensive to acquire and operate, significantly increase the investment costs of the installation and increase operating costs. Typically, they require large amounts of space at the plant site and increase the cost of electricity produced at a power plant up to fifty percent. twenty

In glassmaking furnaces, oxygen-enriched combustion has been used mainly for two reasons: it increases the efficiency of the process and reduces the generation of NOx. For example, glass manufacturing efficiency is increased by providing approximately 20-25% fuel savings with oxy-combustion compared to air combustion.

However, the use of oxygen-enriched combustion in glass furnaces does not affect the volume of combustion gas that is treated, because the high temperature combustion gas leaving the oven is diluted in air to reduce its temperature before flue gas treatment to eliminate harmful emissions. Therefore, the cost of combustion gas treatment, based on the volume of combustion gas to be treated, remains substantially constant when switching from combustion with combustion air enriched with oxygen in glass manufacturing furnaces. Finally, the cost of oxygen generation must be taken into account. Therefore, the improved NOx emissions and energy efficiency resulting from oxygen-rich combustion in glass furnaces do not always translate into associated cost savings in these furnaces.

 In contrast in boilers for steam generation, such as those used in power generation facilities, the amount of pollution produced by the boiler is usually high because the fuels used and the cost of pollution control is a very significant part of the cost of producing 35 energy.

One way to reduce the costs of combustion gas treatment for combustion systems for power generation is to combine the various pollutant reduction techniques in a single operation, known as multi-pollutant control. In Alix et al. (U.S. Patent Nos. 6,132,692; 6,117,403; and 5,871,703) and McLarnon et al. (McLarnon, CR, Jones, MD, “Electro – Catalytic Oxidation Process for Multi – Pollutant Control at 40 FirstEnergy's RE Burger Generating Station”, presented at Electric Power 2000, Cincinnati, OH, April 5, 2000), a procedure is proposed for the reduction of NOx, SO2, Hg and particulate emissions in a single system that uses a plasma-based discharge barrier reactor to oxidize NOx, SO2, and Hg in HNO3, H2SO4 and HgO respectively. In this reactor a pulse discharge between two electrodes separated by a dielectric produces radical species such as OH, O and H at relatively low temperatures 65 to 148.9 ° C (150 to 300 F). These 45 radicals quickly transform SOx, NOx and Hg into higher oxides. Acids, HgO, and particles are subsequently removed in a wet electrostatic precipitator. However, due to the significant amount of gas to be treated, the reactor's energy consumption can be high, up to about 5% of the power plant. This procedure is described only for combustion applications with air combustion, and no reference is made to oxygen enriched systems. fifty

Document US-A-5,590,519 describes a combustion system for steam generation comprising a dilution gas release system (recirculated combustion gas) in the combustion chamber.

It would be desirable to provide an improved emission control procedure in boilers that produce energy and / or steam through the use of oxygen-enriched combustion.

55

Summary of the invention

The present invention relates to a combustion process with a gas stream enriched with oxygen and a pollutant control system to achieve improved emissions at a reduced cost.

According to an embodiment of the present invention, a combustion process for steam generation includes providing a stream of oxygen-enriched gas with an oxygen content of 21% to 100%, which generates an oxidizing vapor containing the stream of oxygen enriched gas, combustion of a fuel in the oxidizing steam in a combustion chamber for steam generation and generation of the combustion gas having a mass flow of combustion gas that is less than a mass flow of combustion gas generated by the combustion chamber when operating with the same mass flow of fuel and with air as the oxidizing current and reducing the amount of at least one between particulate matter, SOx, NOx and mercury in the combustion gas with a control system of combustion gas contamination.

Brief description of the figures

The invention will now be described in greater detail with reference to the preferred embodiments illustrated in the accompanying drawings, in which analogous elements are indicated by analogous reference numbers, and in which:

Figure 1 is a schematic diagram of an embodiment of a combustion system for steam generation 15 capable of implementing a method according to the invention.

Figure 2 is a schematic diagram of an embodiment of the oxidant release system of Figure 1 with a dilution gas release system.

Figure 3 is a schematic diagram of another embodiment of a combustion system for steam generation with a dilution gas release system using recycled combustion gas. twenty

Figure 4 is a schematic diagram of a further embodiment of the oxygen enriched steam generation system of Figure 1.

Figure 5 is a schematic diagram of an embodiment of the combustion gas treatment system of Figure 1.

Figure 6 is a schematic diagram of another embodiment of the flue gas treatment system of Figure 1.

Detailed description of the invention

The invention relates to a combustion process for steam generation for emission control using oxygen enrichment. The procedure of replacing at least a part of the combustion air with a combustion system for steam generation with an oxidant resulting from a gas enriched with oxygen diluted 30 or not with recirculated combustion gas, air, N2, CO2 or steam According to the present invention, it reduces the volume and mass flow rate of the combustion gas leaving the combustion chamber or plant when combustion takes place, thus creating favorable conditions for a more efficient and less expensive control of combustion gas contaminants. A significant advantage of the addition of a gas stream enriched with oxygen is that the reduction in the volume of combustion gas will allow the implementation of much smaller contaminant control equipment, since the size of all these units is mainly based on the volumetric or mass flow rate of the combustion gas to be treated.

To comply with increasingly restrictive emission control standards, pulverized coal combustion boilers and other combustion systems for steam generation are now required to be equipped with a variety of combustion gas treatment systems. For a power plant these devices represent 40 significant cost increases, both in terms of investment spending and operating costs. In a typical coal-fired power plant, the emission control equipment could consist of a bag filter and / or an ESP (electrostatic precipitator) for particle removal, a flue gas desulfurizer (FGD) for SOx control , a SCR system (selective catalytic reduction) for effective NOx control, and a mercury reduction system. A main benefit of the addition of an oxygen enriched gas stream is the fact that the mass flow rate of combustion gas is significantly reduced and consequently the volume of combustion gas is significantly reduced compared to a volume of combustion gas generated by the combustion chamber when it operates with the same mass flow of fuel, the same ratio of oxygen to fuel (or the same mass flow of oxygen) and with air as the oxidizing current.

Because the size and costs of the emission control systems mentioned above depend on the mass flow rate or volume of the flue gas, the addition of a gas stream enriched with oxygen can lead to significant cost savings. The use of an oxygen-enriched gas also presents CO2 capture capabilities inherent in when it produces, when it contains high levels of oxygen and very low nitrogen content, a CO2-rich combustion gas, which can be conditioned, compressed and ultimately easily release in a

kidnapping place. CO2 capture is provided as an added value when compared to the combustion operation with traditional air.

The embodiments described below offer the potential to reduce emissions of SOx, NOx, mercury and particulate matter to acceptable levels at an attractive cost. Furthermore, when carbon sequestration becomes a necessity, it will be possible to release CO2-rich combustion gas to a sequestration site with a relatively low level of additional processing.

Figure 1 illustrates an embodiment of a combustion system for steam generation that includes a combustion chamber 10 and a post-treatment combustion gas contaminant control system 20 designed for oxygen enrichment operation. The terms "oxygen enrichment" and "oxygen-enriched combustion" refer to combustion with an oxidizing current, at least part of it being a gas stream 10 enriched with oxygen. The term "oxygen enriched gas" refers to a gas stream containing from 21% to 100% oxygen.

In the embodiment of Figure 1, a fuel stream 32 of a fuel release system 30 and an oxidizing stream 46 of an oxidant release system 44 are fed to the combustion chamber 10. The oxidant release system 44 receives a stream 42 of oxygen-enriched gas from an oxygen-enriched gas generating system 40. The stream 42 of oxygen-enriched gas has an oxygen content of 21% to 100%. According to one embodiment, the oxygen content of the oxygen enriched gas stream is about 90% or more, preferably about 95% or more. The fuel is burned in the combustion chamber 10 by heating water from a water supply 50 and generates steam 52. The steam 52 can be fed to an electric generator 54 for the generation of electrical energy. twenty

In Figure 1, the combustion gas stream 22 leaving the combustion chamber 10 has a volume of combustion gas that is smaller than a volume of combustion gas generated by the boiler when operating with air such as the oxidizing stream. The flue gas pollutant control system 20 receiving the combustion stream 22 of the combustion chamber 10 reduces at least one of particulate matter, SOx, NOx and mercury in the flue gas to meet the emission standards. Due to the reduction in the volume of combustion gas, the pollutant control system 20 is of a lower cost due to the smaller size reaching similar or better pollution control when compared to a pollution control system necessary for the combustion operation with traditional air. The combustion gas 24 leaving the contaminant control system 20 can be fed to block 60 and / or a CO2 conditioning and sequestration system 70.

Figures 2 and 3 illustrate embodiments of the invention in which the combustion system includes an oxidant release system 30 that includes a dilution gas release system 48, for supplying the oxidant stream 46 to the combustion chamber 10.

The dilution gas release system 48 releases a controlled amount of dilution gas, such as air, H2O, CO2, N2 or combustion gas. The dilution gas stream 49 is combined with the oxygen enriched gas stream 42 forming the oxidizing stream 46. The oxidizing stream 46 can be released into the combustion chamber 10 in one or more streams. When the oxidizing stream 46 is released in more than one stream the plurality of streams may be the same or different, the described oxidant stream being the average of all oxidizing streams as if the oxidizing streams are mixed together in a single stream.

As shown in Figure 3, the dilution gas release system may include a stream of recycled or recirculated combustion gas 80 that is incorporated into the stream 42 of oxygen-enriched gas either alone or in combination with other gases of dilution. The dilution gas release system 48 controls the release of the dilution gas to achieve an oxidizing stream 46 in the form of synthetic air with an oxygen content optimized for the particular combustion application. When the dilution gas used is recirculated combustion gas, the mass flow rate of oxidant injected into the combustion chamber may be equivalent to the mass flow rate of oxidant in a case of combustion with air, but the final mass flow rate treated in the systems Pollution control is really inferior due to the recirculation that eliminates a part of the flue gas. Whereas if the dilution gas used is air, N2, CO2, or steam, the amount of this dilution gas should be such that the overall oxidizing mass flow rate is less than the mass air flow rate required in a case of combustion with air .

The combustion chamber 10 can include any combustion system for industrial steam generation where oxygen-enriched combustion can be carried out such as, but not limited to, power generation plants or steam generation plants in general, coal combustion boilers, gas combustion boilers, and industrial boilers. These combustion chambers for steam generation do not generally use oxygen enrichment due to the cost of implementing enriched oxygen systems as long as strong financial constraints are not associated with some pollutant emissions. 55

The invention is useful for combustion chambers 10 using gaseous, liquid and solid fuels, including natural gas, industrial process waste gases, other gaseous fuels, oil, liquid heavy waste, other liquid fuels, coal, coke, burner coke, heavy solid waste, and other solid fuels.

Solid fuels are normally ground, such as pulverized coal, and transported as the fuel stream 32 to the combustion chamber 10 with a transport gas that may include air, combustion gas, oxidant, or other gas. Liquid fuels can be atomized in steam before entering combustion chamber 10.

In the embodiment of Fig. 4, a stream 90 of air is first separated in the air separation unit 40 such as, but not limited to, cryogenic, membrane units or a PSA or VSA adsorption system to produce a stream of high purity oxygen, producing nitrogen as a byproduct. According to one example, the oxygen stream 42 has a purity of about 90% or more, preferably 95% or more, and the nitrogen stream 94 has a purity of about 90% or more, preferably 98% or more. An argon stream can also be produced that can include a mixture of argon and oxygen that requires an additional separation device to produce a substantially pure argon stream.

The stream 42 of substantially pure oxygen or oxygen enriched gas from the air separation unit 40 may be injected directly into the combustion chamber 10 or, the stream enriched with oxygen 42 may be mixed with one or more dilution gases with the 48 dilution gas release system. The oxygen enriched gas generation system may alternatively include a liquid oxygen tank or liquid oxygen release ducts.

The combustion gas stream 22 resulting from the combustion process is sent to a series of contaminant control units that constitute the post-treatment contaminant control system 20 of the combustion gas. The contaminant control system 20 allows the elimination of part or all of the amount of one or more between particulate matter, SOx, NOx, and mercury (each of these species being optional, depending on the process) before the subsequent use (such as heat recovery systems) or removal in block 60.

According to an example, shown in Figure 5, the contaminant control system 20 includes a site 70 of particulate matter removal system 100, a SOx removal system 102, a mercury removal system 104, and a NOx removal system 106.

In addition, as shown in the figures, the invention may also include a site 70 for sequestration and conditioning or reuse of optional CO2 (reuse through recovery of additional oil, methane in coal bed, etc.). Clean CO2-rich combustion resulting from this process is released to the sequestration site 70 providing the added value of CO2 capture. If the combustion gas stream is to be sequestered or reused, the required combustion gas treatment could be reduced to the level of CO2 conditioning and duct requirements (maximum allowable content for acid gases resulting from NOx, SOx etc. ). 30

The systems of the present invention can be implemented by converting existing combustion systems or into new systems. A major interest of this invention is that in any configuration (reconversion or new design), the partial removal of nitrogen in the oxidant stream 46 will reduce the volume of combustion gas and therefore, the mass flow rate, by a factor of two to a factor of four compared to the case of air flow, which offers significant advantages. An advantage of the removal of the nitrogen ballast in the oxidant stream 46, without compensating the entire amount eliminated with an additional dilution, is the increase in the adiabatic flame temperature. This phenomenon is the main characteristic of oxygen-enriched combustion and can be exploited to increase the efficiency of various combustion systems.

An advantage of the addition of the oxygen enriched gas stream to the combustion system, in addition to this first advantage, is that the reduction in volume of combustion gas (by removing nitrogen) will allow the implementation of a system 20 of Pollutant control much smaller, because the size of the combustion gas treatment units is mainly based on the volumetric or mass flow rate of the combustion gas to be treated. In addition in oxygen combustion applications such as in the context of the invention, the absence of diluent nitrogen will lead to concentrated levels of contaminants in the flue gas. The high concentrations of pollutant will improve its absorption in the different pollutant control systems, improving the elimination efficiency for all species.

An example of a cost reduction achieved with oxygen enrichment is the example of gas desulfurization washers (FGD), this type of units offer excellent SO2 removal efficiencies and are flexible processes, but are relatively demanding in investment and expensive to operate One way to reduce FGD costs, while still maintaining at least the same SO2 removal efficiency, is to reduce the volume of combustible gas that needs to be treated. This is exactly what is achieved with oxygen enrichment. Assuming that the cost of the scrubber follows an exponential increase of 0.6, it can be shown that when the oxygen enrichment reaches 100%, reductions in investment expenses from 50 to 60% can be achieved. A major reduction in the mass flow of combustion gas will therefore result in significant FGD savings for plant operators. 55

Another advantage of oxygen enrichment is the fact that the removal of nitrogen from the oxidant streams, together with the recirculation of a part of the NOx when the combustion gas is recirculated, will significantly reduce the formation of NOx or destroy something of the previously formed NOx. A NOx reduction strategy

which combines oxygen enrichment with, for example, a lower NOx burner and / or an effective combustion technique and / or a combustion gas recirculation scheme, will reduce NOx formation rates substantially. In fact, these techniques could even replace conventional NOx removal processes such as selective catalytic reduction (SCR).

Alternatively, if the level of NOx emissions is maintained above the permitted levels, the reduced volume 5 of the flue gas will allow at least the use of deNOx units 106 of substantially reduced size. Considering SCR investment expenses that reach approximately 80 dollars / kW, the savings in investment expenses will be very significant.

Likewise, oxygen enrichment will offer important advantages in terms of CO2 capture. The continuous increase in atmospheric CO2 concentrations can drive new measures to reduce CO2 emissions from fossil fuel combustion power plants. The combustion of fossil fuels is considered to be a major contribution to the increase in CO2 concentrations and potential CO2 regulations are expected to eventually address industrial combustion procedures using these types of fuel.

Current techniques for CO2 capture, transport and disposal require intensive energy consumption and are expensive. Most of the costs are associated with the CO2 separation process rather than with transport and sequestration. The most widely accepted technique for removing CO2 from combustion gas involves the use of absorbents such as monoethanolamine (MEA) or other chemical reagents. The regeneration of the absorbent is extremely intensive in energy consumption and leads to degradation of the reagent causing corrosion problems. The removal of CO2 from the combustion gas or a stream of oxygen-enriched gas could be greatly facilitated if the combustion air is replaced with oxygen, as proposed in the present invention, eliminating the effects of dilution of the nitrogen component and the need to wash flue gas. For cases of high oxygen enrichment, the clean combustion gas will contain high levels of CO2, which can be liquefied, compressed, and if necessary marketed as a product or released to a sequestration point such as in improved oil recovery ( EOR). In these cases the combustion gas treatment system 20 also serves as a CO2 purification system. 25

An economic assessment of the oxygen enrichment concept may also show the viability of the improved combustion system and process with oxidant described above. Of course, the different costs and their distribution will vary from one industrial application to another, but a global evaluation can be carried out nonetheless. The base case in one example would be a conventional air flow procedure with an FGD unit, a deNOx unit, mercury and particulate matter removal systems (such as electrostatic precipitators, 30 bag filters, washers, SCR, etc.) . The CO2 capture scenario is also considered. In the case of CO2 capture, the basal plant includes a washing system based on MEA. This will not be required in the case of oxy-combustion as it inherently produces an effluent rich in CO2.

The investment expense of the oxygen-enriched combustion system is reduced by at least about 40%. This estimate is conservative and considers the fact that some of the components will not be affected by the lower volumes of flue gas. Likewise, with regard to the control of emissions of SOx, mercury and particulate matter, related equipment costs are reduced by a conservator by approximately 33%. Due to the very low NOx formation rates expected for a new oxygen-enriched combustion plant, the SCR unit is removed from the process.

These estimates indicate that the investment costs of the air separation unit (ASU) or other 40 gas generation system 40 will be more than offset by the cost reduction related to the reduction of combustion system size and system 20 Contaminant control and removal of the SCR unit. In the CO2 capture scenario, the oxygen-enriched system has an even clearer cost advantage over the baseline.

Above all this, the air separation unit 40 of Figure 4 is a multi-product system, which generates a substantially pure nitrogen stream 94 in addition to the oxygen stream 42. In a given application, ASU 45 will be optimized to produce oxygen, nitrogen, and possibly argon at the desired purities and pressures. In a particular case, the ASU can be optimized to produce low pressure gaseous oxygen for the combustion process, and a high value nitrogen stream. In this way, the income of nitrogen as a product can compensate for the production costs of oxygen. This analysis suggests that the technique when applied to a new commercial plant at real scale is economically viable. fifty

Therefore, this combustion system for steam generation involves a new approach for multi-pollutant control in industrial combustion processes since it allows a more efficient and more cost effective removal of SOx, NOx, mercury and particulate matter, achieving this high efficiency with the implementation of oxygen-enriched combustion in the combustion system and the drastic reduction resulting from the amount of combustion gas being treated. 55

Additionally, when carbon sequestration becomes a reality, the described procedure allows the release of CO2-rich combustion gas 24 at a sequestration point with a relatively low level of processing, thus offering another enormous cost advantage over the current air combustion systems.

The proposed integrated procedure will thus lead to a new generation of combustion processes, characterized not only by low / zero emissions but also by high efficiency and reduced investment expenditure, which will dramatically improve your competitiveness in an increasingly industrial world regulated in terms of emissions.

Figure 6 illustrates an alternative embodiment of a contaminant control system by post-treatment of combustible gas 20b including a plasma-based combustion gas treatment device 112. The flue gas stream 22 5 in Figure 6 is fed to a contaminant control system 20b that includes a particle removal system 110 and a plasma-based device 112 such as a barrier discharge reactor. The purpose of this device 112 is to generate radical species that oxidize contaminants at relatively low temperatures. Hence it does NOT oxidize to NO2 and HNO3, SO2 to SO3 and H2SO4, and Hg to HgO. These higher oxides and particles are subsequently removed in an absorption vessel, ESP wet, etc. With the use of oxidizers 10 enriched with oxygen, the volume of the combustion gas that is fed to the combustion gas treatment system is reduced, whereby more compact equipment is used, and the energy consumption of the device is reduced. Also the injection of an oxygen-enriched oxidant upstream of the plasma-based device 112 could improve the formation of radical oxidant species. This system offers the advantage of reducing the cost of combustion gas treatment, and in cases of high oxygen enrichment, it produces a stream of concentrated clean CO2, which can be marketed or released at a sequestration site.

The embodiment of Figure 6 includes a particle removal system 110, such as an ESP or bag filters. The plasma-based combustion gas treatment device 112 may be any of the known systems, such as one of those described in US Pat. Nos. 6,132,692; 6,117,403; and 5,871,703, which is used to remove most of the remaining contaminants. In the first stage of this system a barrier discharge reactor 20 or similar device generates radical species (OH, O, etc.) capable of oxidizing contaminants at relatively low temperatures. Hence, NO is oxidized to NO2 and HNO3, SO2 to SO3 and H2SO4, and Hg to HgO. The addition of an oxygen-enriched oxidant to the inlet stream would increase the oxygen concentration and potentially increase the rate of radical species formation. The oxidized species and particles that remain are then removed from the combustion gas in an absorption container and electrostatic precipitator by wet route. The removal of SO2 and NO2 can be improved with the addition of a reagent such as ammonia. By-products that can be sold such as sulfuric acid, nitric acid, ammonium nitrate or ammonium sulfate are recovered. This system is also capable of eliminating metallic species such as Ni, As, Cu, Pb, Zn etc. (McLarnon et al.). This feature will be beneficial for combustion systems that burn fuels that contain metals, for example, petroleum coke with its high vanadium and nickel contents. 30

The mass flow of the reduced combustion gas is transferred to smaller and / or shorter electrodes in the barrier discharge system 112, a smaller absorption vessel, and ESP by smaller wet route. The reduced electrode zone will also reduce the energy consumption of the discharge plasma. Oxygen enrichment by the addition of an oxygen or oxygen enriched stream 114 to the current entering the barrier discharge reactor 112 could also improve the formation of the oxidizing species, potentially reducing the size and energy consumption required by the device.

Therefore this system provides a low-cost multi-contaminant control process, and in cases of high oxygen enrichment, it produces a clean concentrated CO2 stream, which can be marketed or released at a sequestration site.

Another embodiment of the invention relates to a process of reconversion or re-energization of a combustion system for steam generation, combustion with commercial air, to reduce the overall cost of emission control. The process includes the steps of adding an oxygen enriched gas generation system to the combustion system for steam generation to release an oxygen enriched stream with 21% to 100% oxygen, release of the oxygen enriched stream to a system of oxidant release to produce an oxidizing current for the combustion chamber of the combustion system, and to achieve a reduced mass flow rate of the combustion gas leaving the combustion chamber due to the enrichment of the oxidant with the oxygen enriched gas stream . The combustion gas contaminant control system is modified to be advantageous with the reduction of the volume of combustion gas and the lower emission levels of the system for the generation of oxygen-enriched steam by: a) replacement of at least one device in the combustion gas pollutant control system of the combustion system with a control device of 50 pollutants of a smaller size that achieves similar or better pollution control for control devices for exit pollutants when the pollutant still has to eliminate to comply with the same regulations, b) for new control devices required due to the most demanding regulations, adding at least one device in the flue gas pollutant control system with a smaller size than the size needed to treat the combustion gas generated by this combustion system when operating with ai re, and / or c) removal of the device dedicated to NOx reduction when the oxygen-enriched combustion system reaches very low levels of NOx and the device is not required due to the emission reduction achieved.

EXAMPLE

Tables 1, 2 and 3 below compare the costs of three boilers of pulverized coal combustion with oxygen with the costs of combustion boilers with conventional air, in a range of plant sizes. 60 form

In particular, the impact of complete oxy-combustion on the costs of treatment of combustion gas in coal boilers has been examined, with the assumption that oxy-combustion results in the reduction in volumes of flue gas, and in consequently a reduction in emission control costs. For a representative comparison, cost reductions are compared with the costs of investment and operating costs of an air separation unit (ASU) that provides oxygen. The tables illustrate that the cost of the ASU is compensated 5 with post-treatment savings so that the cost of the entire plant is reduced with this invention, and would even be reduced more if the examples were compared with the air stream plant with system CO2 removal.

  Investment, operating and total costs are calculated for air and oxygen power plants, for four plant sizes: 30, 100, 200 and 500 MWe of output power. More than the determination of costs for complete power plants, only those elements of the power plants that differ between combustion with air and oxygen are included in the analysis. These elements include the following:

a) combustion gas treatment equipment: wet FGD for SOx, SCR for NOx, activated carbon injection for mercury, and ESP for particle control;

b) air separation unit (for cases of combustion with O2);

c) boiler (existing unit for cases of combustion with air and reconverted O2, new unit for new cases of combustion with O2).

Each of the three cases described below includes a conventional air stream boiler with FGD, SCR, ESP and Hg control. Three combustion scenarios with O2 (oxygen enriched gas = almost pure O2) were considered:

 Case 1: The boiler is a reconverted O2 current system with flue gas recirculation (FGR). FGD, SCR, ESP and Hg systems are used.

Case 2: the boiler is a reconverted O2 current system with flue gas recirculation (FGR). FGD, ESP and Hg systems are used. SCR is not required because NOx reductions result from oxy-combustion.

Case 3: The boiler is a new compact complete O2 current unit without FGR or any other dilution gas. FGD, ESP and Hg systems are used. SCR is not used because NOx reductions result from oxy-combustion.

TABLE 1 - Investment costs (millions of dollars) of air combustion systems versus oxygen combustion system in three cases

 PLANT SIZE (MWe)

 500 200 100 30

 Oxidizer

 Air O2 Air O2 Air O2 Air O2

 Post-treatment unit costs

 FGD $ 129.60 $ 83.30 $ 78.50 $ 55.10 $ 59.50 $ 41.70 $ 36.70 $ 25.80

 SCR $ 30.70 $ 11.40 $ 16.90 $ 6.30 $ 10.80 $ 4.00 $ 4.90 $ 1.80

 Hg (carbon injection) $ 0.75 $ 0.21 $ 0.36 $ 0.10 $ 0.21 $ 0.06 $ 0.08 $ 0.02

 ESP $ 25.00 $ 8.90 $ 13.60 $ 4.80 $ 8.60 $ 3.10 $ 3.90 $ 1.40

 Total post-treatment costs

 $ 186.05% 104.31 $ 109.36 $ 66.30 $ 79.11 $ 48.86 $ 45.58 $ 29.02

 Post-treatment costs vs. base case

    –44% –39% –38% –36%

 Generation cost of oxygen enriched gas (ASU)

    $ 89.80 $ 35.90 $ 22.10 $ 9.50

Case 1

 Combustion system for steam generation (boiler)

 $ 210.00 $ 210.00 $ 84.00 $ 84.00 $ 42.00 $ 42.00 $ 12.60 $ 12.60

 Plant investment cost

 $ 396.05 $ 404.11 $ 193.36 $ 186.20 $ 121.11 $ 112.96 $ 58.18% 51.12

 Plant investment cost vs base case

    2% –4% –7% –12%

Case 2

 Combustion system for steam generation (boiler)

 $ 210.00 $ 210.00 $ 84.00 $ 84.00 $ 42.00 $ 42.00 $ 12.60 $ 12.60

 Plant investment cost

 $ 396.05 $ 392.71 $ 193.36 $ 179.90 $ 121.11 $ 108.96 $ 58.18% 49.32

 Plant investment cost vs base case

    –1% –7% –10% –15%

Case 3 5

 Combustion system for steam generation (boiler)

 $ 210.00 $ 126.00 $ 84.00 $ 50.40 $ 42.00 $ 25.20 $ 12.60 $ 7.60

 Plant investment cost

 $ 396.05 $ 308.71 $ 193.36 $ 146.30 $ 121.11 $ 92.16 $ 58.18% 44.32

 Plant investment cost vs base case

    –22% –24% –24% –24%

TABLE 2 - Operating costs (millions of dollars / year) of the three cases in table 1

 PLANT SIZE (MWe)

 500 200 100 30

 Oxidizer

 Air O2 Air O2 Air O2 Air O2

 Post-treatment

 FGD $ 8.70 $ 6.80 $ 4.30 $ 3.40 $ 2.60 $ 2.10 $ 1.30 $ 1.10

 SCR $ 1.89 $ 1.46 $ 0.86 $ 0.63 $ 0.48 $ 0.33 $ 0.18 $ 0.12

 Hg (carbon injection) $ 1.61 $ 0.34 $ 0.64 $ 0.13 $ 0.32 $ 0.07 $ 0.10 $ 0.02

 ESP $ 9.20 $ 3.20 $ 4.90 $ 1.70 $ 3.10 $ 1.10 $ 1.40 $ 0.50

 Total post-treatment costs

 $ 21.40% 11.80 $ 10.70 $ 5.86 $ 6.50 $ 3.60 $ 2.98 $ 1.74

 Post-treatment costs vs. base case

    –45% –45% –45% –42%

 Generation of oxygen enriched gas (ASU)

    $ 15.60 $ 6.30 $ 3.10 $ 0.90

Case 1

 Plant operating cost

 $ 21.40 $ 27.40 $ 10.70 $ 12.10 $ 6.50 $ 6.70 $ 2.90 $ 2.7

 Plant operating cost vs base case

    28% 13% 3% –7%

Cases 2 and 3

 Plant operating cost

 $ 21.40 $ 25.90 $ 10.70 $ 11.50 $ 6.50 $ 6.40 $ 2.90 $ 2.50

 Plant operating cost vs base case

    21% 7% –2% –14%

TABLE 3 - Total annual costs (millions of dollars / year) of the three cases of tables 1 and 2 5

 PLANT SIZE (MWe)

 500 200 100 30

 Oxidizer

 Air O2 Air O2 Air O2 Air O2

 Post-treatment

 FGD $ 37.20 $ 25.30 $ 21.50 $ 15.50 $ 15.70 $ 11.30 $ 9.40 $ 6.80

 SCR $ 8.60 $ 4.00 $ 4.60 $ 2.00 $ 2.90 $ 1.20 $ 1.30 $ 0.50

 Hg (carbon injection) $ 1.80 $ 0.40 $ 0.70 $ 0.20 $ 0.40 $ 0.10 $ 0.10 $ 0.00

 ESP $ 14.70 $ 5.10 $ 7.90 $ 2.80 $ 5.00 $ 1.70 $ 2.20 $ 0.80

 Total post-treatment cost

 $ 62.30 $ 34.80 $ 34.70 $ 20.50 $ 24.00 $ 14.30 $ 13.00 $ 8.10

 Post-treatment cost vs. base case

    –44% –41% –40% –38%

 Generation of oxygen enriched gas (ASU)

    $ 35.40 $ 14.20 $ 8.00 $ 3.00

Case 1

 Combustion system for steam generation (boiler)

 $ 46.20 $ 46.20 $ 18.50 $ 18.50 $ 9.20 $ 9.20 $ 2.80 $ 2.80

 Annual cost of the plant

 $ 108.50 $ 116.40 $ 53.20 $ 53.20 $ 33.20 $ 31.50 $ 15.80% 13.90

 Annual cost of the plant vs base case

    7% 0% –5% –12%

Case 2

 Combustion system for steam generation (boiler)

 $ 46.20 $ 46.20 $ 18.50 $ 18.50 $ 9.20 $ 9.20 $ 2.80 $ 2.80

 Annual cost of the plant

 $ 108.50 $ 112.40 $ 53.20 $ 51.20 $ 33.20 $ 30.30 $ 15.80% 13.40

 Annual cost of the plant vs base case

    4% –4% –9% –15%

Case 3

 Combustion system for steam generation (boiler)

 $ 46.20 $ 27.70 $ 18.50 $ 11.10 $ 9.20 $ 5.50 $ 2.80 $ 1.70

 Annual cost of the plant

 $ 108.50 $ 93.90 $ 53.20 $ 43.80 $ 33.20 $ 26.60 $ 15.80% 12.30

 Annual cost of the plant vs base case

    –13% –18% –20% –22%

Claims (18)

1. A combustion process for steam generation, comprising: providing a stream (42) of oxygen-enriched gas with an oxygen content of 21 to 100%; create an oxidizing stream (46) containing the oxygen enriched gas stream (42); combustion of a fuel in the oxidant stream (42) in a combustion chamber (10) that generates 5 steam and that generates combustion gas (22) having a mass flow of combustion gas that is less than a mass flow of combustion gas generated by the combustion chamber (10) when operating with the same mass flow of fuel and with air as the oxidizing current; Y reduction of the amount of at least one particulate matter, SOx, NOx and mercury in the combustion gas (22) with a combustion gas contaminant control system (20), in which the stage of creating an oxidizing stream 10 (46) comprises the release of a dilution gas (80) in the oxygen enriched gas (42) forming the oxidizing stream (46), and the dilution gas comprises recirculated wet or dry combustion gas. 2. The method of claim 1, wherein the oxygen enriched gas stream (42) has an oxygen content of about 90% or more. fifteen 3. The method of claim 1, wherein the oxidizing stream (46) has an oxygen content of about 90% or more. 4. The method of claim 1, wherein the oxygen enriched gas stream is generated with an air separation unit (40) configured to separate air into at least a first stream (42) of gaseous oxygen having a purity of approximately 90% or more and a second current (94). twenty 5. The method of claim 4, wherein the second stream (94) is nitrogen having a purity of about 90% or more. 6. The method of claim 1, wherein the oxygen enriched gas stream (42) is generated by an air separation unit (40) configured to separate air into at least a first stream (42) of gaseous oxygen which has a purity of approximately 95% or more and a second current (94). 25 7. The method of claim 6, wherein the second stream (94) is nitrogen having a purity between about 98% or more. 8. The method of claim 1, further comprising generating steam electricity from the combustion chamber (10). 9. The method of claim 1, wherein the fuel (32) comprises natural gas, waste gases from industrial processes, or other gaseous fuels. 10. The method of claim 1, wherein the fuel (32) comprises coal, coke, burner coke, solid heavy waste or other solid fuels. 11. The method of claim 1, wherein the fuel (32) comprises oil, heavy liquid waste or other liquid fuels. 35 12. The method of claim 1, wherein the flue gas pollutant control system (20) includes separate devices (100, 102, 104, 106) for the reduction of particulate matter, SOx, NOx and mercury. 13. The method of claim 1, wherein the flue gas contaminant control system (20) includes a combined device for the reduction of at least two between particulate matter, SOx, NOx and mercury. 14. The method of claim 1, wherein the flue gas contaminant control system (20) includes a plasma-based flue gas treatment device (112) for the oxidation of at least one of NO , SO2 and Hg, in water soluble oxides. 15. The method of claim 14, wherein the plasma-based flue gas treatment device (112) is improved by oxygen injection (114). 16. The method of claim 14, comprising a container of absorrtp753685enesB45 tion and an electrostatic precipitator that receives the water soluble oxides from the plasma-based flue gas treatment device (112) and reduces the amount of the water soluble oxides. 17. The method of claim 1, wherein the mass flow of combustion gas leaving the chamber (10) of combustion is at least a factor of twice less than the mass flow of combustion gas leaving the combustion chamber (10) when the combustion chamber operates in the same conditions except with air as the oxidizing current. 18. The method of claim 1, wherein the flue gas pollutant control system (20) includes devices that have flue gas flow capacities less than the flue gas capacity needed to treat a gas of combustion generated by the combustion chamber (10) when operating with air as the oxidizing current.