System And Method Of Managing Energy Utilized In A Flue Gas Processing System

Abstract

A method is provided for managing an amount of energy utilized by a carbon dioxide capture system. The method includes providing a fuel and a feed stream to a combustion system. The feed stream includes oxygen and a portion of a flue gas stream generated upon combustion of the fuel. The method also includes subjecting the flue gas stream to a carbon dioxide capture system to remove carbon dioxide therefrom, measuring a concentration of oxygen present in the feed stream, and selectively adjusting an amount of the flue gas stream included in the feed stream based on the measured concentration of oxygen in the feed stream. The selective adjustment is performed such that the feed stream maintains an oxygen concentration in a range of between about 10% to 90% by volume and the carbon dioxide capture system operates at an energy load between 1.4 GJ/ton of carbon dioxide and 3.0 GJ/ton of carbon dioxide.

Description

BACKGROUND

[0001] 1. Field

[0002] The disclosed subject matter relates to a system and method of managing an amount of energy utilized by a flue gas stream processing system. More particularly, the disclosed subject matter relates to a method of optimizing an amount of energy used in a flue gas processing system that includes oxy-firing boiler combustion and a carbon dioxide capture system.

[0003] 2. Description of Related Art

[0004] Combustion of fuel, particularly carbonaceous materials such as fossil fuels and waste, results in flue gas streams that contain impurities, such as mercury (Hg), sulfur oxides (SOx) and nitrogen oxides (NOx), and particulates, such as fly ash, which must be removed or reduced prior to releasing the flue gas to the environment. In response to regulations in place in many jurisdictions, numerous processes and apparatus have been developed to remove or reduce the impurities and particulates in the flue gas.

[0005] The typical method of reducing particulates, Hg, NOx, and SOx emissions from steam generating boilers is by the use of flue gas treatment equipment including electrostatic precipitators (ESP), fabric filter bag houses, catalytic systems, or wet and dry scrubbers. Additionally, carbon dioxide capture systems (also referred to as "carbon capture systems") may be employed in a flue gas processing system if carbon dioxide emissions are to be kept at or below a certain level.

[0006] Flue gas treatment equipment, e.g., emission control devices and systems, are large and expensive to purchase and operate, which significantly increases the capital cost of the facility and operating costs. Additionally, flue gas stream treatment equipment typically requires a large amount of space at the plant site.

[0007] One way of reducing the costs of post combustion flue gas stream treatment is to combine various pollutant reduction techniques and equipment into a single operation, often referred to as "multi-pollutant control." However, combined techniques and equipment are not applicable or feasible in every flue gas stream processing system. Accordingly, other processes and/or systems that facilitate the reduction of cost or overall energy use of the flue gas stream processing system are desired.

SUMMARY

[0008] According to aspects illustrated herein, there is provided a method for managing an amount of energy utilized by a carbon dioxide capture system. The method includes providing a fuel and a feed stream to a combustion system. The feed stream includes oxygen and a portion of a flue gas stream generated upon combustion of the fuel in the combustion system. The method includes subjecting the flue gas stream to a carbon dioxide capture system to remove carbon dioxide therefrom, measuring a concentration of oxygen present in the feed stream, and selectively adjusting an amount of the flue gas stream included in the feed stream based on the measured concentration of oxygen in the feed stream. The selective adjustment is performed such that the feed stream maintains an oxygen concentration in a range of between about 10% to 90% by volume and the carbon dioxide capture system operates at an energy load between 1.4 GJ/ton of carbon dioxide and 3.0 GJ/ton of carbon dioxide.

[0009] According to an aspect illustrated herein, the method further includes subjecting the flue gas stream to a desulfurization system located downstream of the combustion system and upstream of the carbon dioxide capture system. The desulfurization system removes sulfur oxide from the flue gas stream and forms a treated flue gas stream. The method also includes directing at least one of a portion of the flue gas stream, a portion of the treated flue gas stream and combinations of the portions, to the feed stream. In one embodiment, the portion of the flue gas stream is directed from a location upstream of the desulfurization system, and the portion of the treated flue gas stream is directed from a location downstream of the desulfurization system.

[0010] In one embodiment, the feed stream is further comprised of a fresh air stream and an oxidant stream. The method includes generating the oxidant stream in an oxygen producing unit. The method further includes measuring a concentration of oxygen in the oxidant stream, and selectively adjusting a feed rate of an air stream provided to the oxygen producing unit based on the measured concentration of oxygen in the oxidant stream. In one embodiment, the method includes measuring a flow rate of the fresh air stream provided to the feed stream, and selectively adjusting the flow rate of at least one of the portion of the flue gas stream and the portion of the treated flue gas stream directed to the feed stream based on the measured flow rate of the fresh air stream provided to the feed stream. In still another embodiment, the method includes measuring a concentration of carbon dioxide present in the flue gas stream exiting the combustion system, and selectively adjusting a feed rate of the feed stream directed to the combustion system based on the measured concentration of carbon dioxide present in the flue gas stream such that the flue gas stream maintains a carbon dioxide concentration in a range of between about 10% to 60% by volume.

[0011] The above described and other features are exemplified by the following figures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike:

[0013] FIG. 1 illustrates a flue gas stream processing system according to one embodiment disclosed herein.

[0014] FIG. 2 illustrates a flue gas stream processing system according to one embodiment disclosed herein.

[0015] FIG. 3 illustrates a flue gas stream processing system according to one embodiment disclosed herein.

[0016] FIG. 4 illustrates a flue gas stream processing system according to one embodiment disclosed herein.

[0017] FIG. 5 illustrates a flue gas stream processing system according to one embodiment disclosed herein.

DETAILED DESCRIPTION

[0018] FIG. 1 illustrates a flue gas stream processing system 100 that includes a combustion system 120 in communication with oxygen producing unit 130. The combustion system 120 may be any system configured to combust a fuel 122 to produce a flue gas stream 124 at an output 121 of the combustion system 120. Examples of the combustion system 120 include, but are not limited to, pulverized coal (PC) combustion, oxy-firing boilers and circulating fluidized bed combustors (CFB). In one embodiment, illustrated in FIG. 1, the combustion system 120 is an oxy-firing boiler configured to burn the fuel 122 provided to the combustion system 120 in the presence of a feed stream 132 provided to the combustion system. The flue gas stream 124 is generated upon combustion of the fuel 122 and is provided at the output 121 of the combustion system 120.

[0019] In one embodiment, as shown in FIG. 1, the feed stream 132 is a combination of an oxidant stream 134, a fresh air stream 136 and a recycled portion 124a of the flue gas stream, which has been subjected to treatment and/or contaminant removal, e.g., the recycled portion 124a of a treated flue gas stream 124'. In another embodiment, as shown in FIG. 2, the feed stream 132 includes the oxidant stream 134, the fresh air stream 136 and a recycled portion 124b of the flue gas stream 124, which has not been treated. In a further embodiment, as shown in FIG. 3, the feed stream 132 includes the oxidant stream 134, the fresh air stream 136, the recycled portion 124a of the treated flue gas stream 124', and the recycled portion 124b of the flue gas stream 124. While not illustrated in each of FIGS. 1-3, it is contemplated that the feed stream 132 may include one or more of the oxidant stream 134, the fresh air stream 136, the recycled portion 124a of the treated flue gas stream 124', and the recycled portion 124b of the untreated flue gas stream 124. As disclosed herein, combination of the oxidant stream 134 and the fresh air stream 136 into the feed stream 132 assists in selectively maintaining a ratio of oxygen to fuel for proper combustion within the combustion system 120 as well as a feed rate of the feed stream 132 to the combustion system 120.

[0020] Referring generally to FIGS. 1-3, the oxidant stream 134 is generated by the oxygen producing unit 130, which receives an air stream 138. In one embodiment, the oxygen producing unit 130 is an air separation unit (ASU). The ASU may be, for example, an ion transport membrane (ITM), an oxygen transport membrane (OTM), or a cryogenic air separation system, e.g., a rectification column. The oxygen producing unit 130 is not limited in this regard, since the oxygen producing unit may be any equipment capable of producing the oxidant stream 134.

[0021] The oxidant stream 134 generally contains oxygen (O.sub.2), however, other elements and/or gases may be present in the oxidant stream as well. In one embodiment, the oxidant stream 134 is at least 90% wt. oxygen. In another embodiment, the oxidant stream 134 is at least 95% wt. oxygen.

[0022] The oxygen producing unit 130 typically requires a relatively large energy load to process the air stream 138 and generate the oxidant stream 134. However, in many applications, the amount of energy expended in generating the oxidant stream 134 is a benefit to the overall performance of the flue gas stream processing system 100 since a reduced volume of the flue gas stream 124 is produced by the combustion system 120 utilizing a feed stream including oxygen as compared to systems not utilizing the oxygen producing unit 130. For example, combining the oxidant stream 134 (as well as the fresh air stream 136) with the feed stream 132 and providing the combination to the combustion system 120 promotes a more complete combustion of the fuel 122 in the combustion system 120.

[0023] In one embodiment, the fresh air stream 136 is not subjected to any treatment prior to combination with the oxidant stream 134, and one or more of the recycled portion 124a of the treated flue gas stream 124' and the recycled portion 124b of the flue gas stream 124 to form the feed stream 132. Accordingly, the fresh air stream 136 may include a variety of elements and/or gases including, but not limited to, oxygen, carbon dioxide, nitrogen, water, and the like. In one embodiment, the fresh air stream 136 may be subjected to some treatment such as, for example, to remove or minimize particulates or other contaminants, if any, therefrom.

[0024] As shown in FIGS. 1-3, the feed stream 132 and the flue gas stream 124 may proceed through an air preheater (APH) 126, which facilitates an increase of temperature of the feed stream 132 by transferring heat from the flue gas stream 124.

[0025] In one embodiment, the flue gas stream 124 may include contaminants such as, but not limited to, sulfur oxides (SOx), mercury (Hg), carbon dioxide (CO.sub.2), particulates, nitrous oxide (N.sub.2O) and to a lesser extent, nitrogen oxides (NOx). The concentration of NOx present in flue gas stream 124 is dependent upon several factors, including, but not limited to, the nitrogen content of the fuel 122, and the concentration of nitrogen provided to the combustion system 120 via feed stream 132. As the percentage of oxygen present in feed stream 132 increases, the amount of nitrogen in the feed stream 132 provided to the combustion system 120 decreases, thereby decreasing the percentage of NOx present in the flue gas stream 124.

[0026] Downstream of the combustion system 120 is a contaminant control system, shown generally at 140. In one embodiment, as shown in FIGS. 1-3, the contaminant control system 140 includes an electrostatic precipitator (ESP) 142 and a flue gas desulfurization (FGD) system 144. It is contemplated that the contaminant control system 140 may include more or less devices than what is shown in FIGS. 1-3. For example, in one embodiment, the contaminant control system 140 may include only the flue gas desulfurization system 144. The flue gas desulfurization system 144 may either be a dry flue gas desulfurization (DFGD) system or a wet flue gas desulfurization (WFGD) system. While not shown in FIGS. 1-3, it is contemplated that different devices may be included in the contaminant control system 140, including, but not limited to, a bag house, a venturi-type scrubber, and the like.

[0027] The flue gas stream 124 generated and outputted by the combustion system 120 is subjected to treatment by the contaminant control system 140. In one embodiment, the flue gas stream 124 is subjected to treatment by the flue gas desulfurization system 144, which facilitates the removal, or substantial elimination or minimization, of SOx from the flue gas stream 124. After proceeding through the contaminant control system 140, the treated flue gas stream 124' is subjected to treatment by a carbon dioxide capture system 150 to remove, or substantially eliminate or minimize, carbon dioxide from the treated flue gas stream 124'. The carbon dioxide capture system 150 may be any system capable of removing or minimizing carbon dioxide from the treated flue gas stream 124' to produce a carbon dioxide stream 151 and a reduced carbon dioxide flue gas stream 152. Examples of carbon dioxide capture system 150 include, but are not limited to, systems referred to as "advanced amine" systems, "chilled ammonia" systems such as is disclosed in International Patent Application Publication No. WO2006/022885, as well as gas processing units, and the like.

[0028] Still referring to FIGS. 1-3, at least a portion of the untreated flue gas stream 124 and/or the treated flue gas stream 124' may be recycled and combined to form the feed stream 132 after exiting the combustion system 120. The recycled portion 124a of the treated flue gas stream 124' is directed to the feed stream 132 from a location A. As shown in FIG. 1, the location A is positioned downstream of the flue gas desulfurization system 144. In another embodiment, as shown in FIG. 2, the recycled portion 124b of the flue gas stream 124 is directed to the feed stream 132 from a location B, which is positioned upstream of the contaminant control system 140. In yet a further embodiment, as shown in FIG. 3, the recycled portion 124a of the treated flue gas stream 124' is directed to the feed stream 132 from the location A and the recycled portion 124b of the flue gas stream 124 is directed to the feed stream 132 from the location B. As shown in FIGS. 1-3, the recycled portions 124a and 124b may be combined with the oxidant stream 134 and the fresh air stream 136 to form the feed stream 132. While FIGS. 1-3 illustrate at least two different locations A and B for drawing off and recycling the treated or untreated portions of the flue gas stream, the system 100 is not limited in this regard as the flue gas stream may be drawn from another point within the system 100. For example, in one embodiment, a portion of the flue gas stream may be drawn from a location within the contaminant control system 140 such as between the ESP 142 and the FGD 144. It should be appreciated that locations A and B may be varied about the flue gas processing system 100 depending on, for example, the type or nature of the fuel 122 combusted in the combustion system 120. For example, the flue gas stream 124 may be recycled back to the combustion system 120 prior to treatment by the flue gas desulfurization system 144 when the fuel 122 has a low concentration of SO.sub.X.

[0029] The recycled portion 124a of the treated flue gas stream 124' and the recycled portion 124b of the untreated flue gas stream 124 may be selectively directed to combine with the feed stream 132 by any mechanism having the capability of doing so, including, but not limited to, pipes, conduits, valves, and the like, as are known in the art.

[0030] In an effort to manage an amount of energy utilized by the flue gas stream processing system 100, and particularly the carbon dioxide capture system 150, various parameters of the flue gas stream processing system are monitored, measured and analyzed.

[0031] Now referring to FIG. 4, in one embodiment, a concentration of oxygen present in the feed stream 132 is measured or sensed by, for example, a sensor or like testing or measurement device 212, disposed in a flow path of the feed stream 132. In one embodiment, the measured concentration of oxygen in the feed stream 132 is compared to a predetermined or "set-point" value programmed, stored in or provided to an integrated flow control device 210 such as, for example, a valve. The valve 210 selectively operates to vary a ratio of the recycled portion 124a of the treated flue gas stream 124' provided to the feed stream 132.

[0032] The concentration of oxygen present in the feed stream 132 may be measured at any point prior to the feed stream 132 entering the combustion system 120. In one embodiment, the concentration of oxygen present in the feed stream 132 is measured at a location C where the feed stream 132 includes the recycled portion 124a of the treated flue gas 124', the oxidant stream 134 and the fresh air stream 136. However, it is contemplated that the measurement of oxygen concentration in the feed stream 132 may occur at another location, e.g., prior to the combination of one or more of the recycled portions 124a, 124b of the flue gas stream, the oxidant stream 134, and the fresh air stream 136 with the feed stream 132.

[0033] As noted above, in one embodiment, the measured oxygen concentration in the feed stream 132 is compared to a predetermined set-point value. The set-point value may be determined by parameters of the flue gas stream processing system 100, which include, but are not limited to, the amount of contaminants, e.g., NOx, SOx, CO.sub.2, and the like, present in the flue gas stream 124. For example, the predetermined set-point value may be based on an oxygen concentration. In one embodiment, the set-point value is an oxygen concentration having a value in a range of between about 10% to about 90% by volume. In one embodiment, the set-point is calculated by a controller 260. In one embodiment, the controller 260 receives the measured oxygen concentration in the feed stream 132 from the sensor 212 and other streams (e.g., the flue gas stream 124, and the oxidant stream 134) at one or more inputs, shown generally at 262. In one embodiment, the controller 260 receives oxygen concentration measurements from various points of the flow path of the feed stream 132 at the inputs 262.

[0034] When the measured concentration of oxygen present in the feed stream 132 is not equal to the set-point value, the recycled portions 124a, 124b of the flue gas stream directed to the feed stream 132 may be adjusted such that the feed stream 132 maintains an oxygen concentration in a predetermined range, for example, in a range of between about 10% to about 90% by volume based on the total volume of the feed stream 132. Maintenance of the oxygen concentration in the feed stream 132 in a range of between about 10% to about 90% by volume allows the carbon dioxide capture system 150 to operate at an energy load of, for example, below about 3.0 gigajoule per ton of carbon dioxide (GJ/ton of carbon dioxide). For example, the energy load may be between 1.4 GJ/ton of carbon dioxide and 3.0 GJ/ton of carbon dioxide. In another example, the energy load may be between 1.4 GJ/ton of carbon dioxide and 2.5 GJ/ton of carbon dioxide.

[0035] In another embodiment, maintenance of the oxygen concentration in the feed stream 132 in a range of between about 40% to about 60% allows the carbon dioxide capture system 150 to operate at an energy load of, for example, below about 3.0 GJ/ton of carbon dioxide. For example, the energy load may be between 1.4 GJ/ton of carbon dioxide and 3.0 GJ/ton of carbon dioxide. In another example, the energy load may be between 1.4 GJ/ton of carbon dioxide and 2.5 GJ/ton of carbon dioxide.

[0036] In a further embodiment, maintenance of the oxygen concentration in the feed stream in a range of between about 40% and about 60% by volume, based on the total volume of the feed stream 132, allows the carbon dioxide capture stream 150 to operate at an energy load of, for example, between about 2.1 to about 2.9 GJ/ton of carbon dioxide.

[0037] As shown in FIG. 4, adjustment of the recycled portion 124a of the treated flue gas stream 124' directed to the feed stream 132 is performed at the valve 210 that is selectively operated based on a set-point programmed, stored or provided to the valve 210 and/or in response to signals S received from the controller 260. Accordingly, when an amount of the recycled flue gas stream 124 directed to the feed stream 132 is to be increased in order to decrease the concentration of oxygen present in the feed stream 132, the valve 210 operates to allow a greater amount of the recycled portion 124a of the flue gas stream 124' to flow to the feed stream 132.

[0038] In one embodiment, a flow of the fresh air stream 136 is sensed or measured at, for example, a location D, by, for example, a sensor or like test or measurement device 222, and compared to a set point value stored or provided to the controller 260 by, for example, an operator (indicated by arrow O) of the flue gas stream processing system 100. In one embodiment, the set point value is based on, for example, an electrical demand (e.g., load) of the combustion system 120 and is either pre-programmed, or is entered by the operator during operation of the processing system 100. For example, as the electrical demand of the combustion system 120 decreases, the concentration of carbon dioxide in the feed stream 132 may be higher than what was present when the combustion system operated at the previous electrical demand. In one embodiment, when it is desired to increase the carbon dioxide concentration in the feed stream 132, the amount of fresh air 136 provided to the feed stream 132 is reduced. As shown in FIG. 4, the flow of the fresh air stream 136 is adjusted by selectively operating a valve 220. In one embodiment, the valve 220 is selectively adjusted in response to one of the signals S from the controller 260. It should be appreciated that as the flow of the fresh air stream 136 is adjusted, the flow of the feed stream 132 to the combustion system 120 may be adjusted.

[0039] In one embodiment, as the flow of the fresh air stream 136 is adjusted by selective operation of the valve 220, a signal 51 is provided (e.g., cascaded) to the valve 210. Upon receipt of the signal 51, the valve 210 may selective operate to adjust the flow of the portion 124a of the recycled treated flue gas stream 124' to the feed stream 132. As such, the portion 124a of the recycled flue gas stream 124' directed to the feed stream 132 may be adjusted (increased or decreased) or otherwise controlled based on the flow rate of the fresh air stream 136 provided to the feed stream 132. In one embodiment, a calculation block 230 receives the signal S1. The calculation block 230 may be implemented in a variety of ways, including, but not limited to, a function capable of changing a time interval (e.g., selective delay) for providing the signal S1 (multiplexed at 232 with signal S) to the valve 210. In one embodiment, the time interval may be equal to an estimated or measured time required for an air stream to travel from the combustion system 120 to the carbon dioxide capture system 150.

[0040] In one embodiment, the concentration of oxygen present in the oxidant stream 134 (e.g., purity of the oxidant stream) may be sensed or measured at, for example, a location E by, for example, a sensor or like testing or measurement device 242, and selectively adjusted (increased or decreased). As shown in FIG. 4, in one embodiment, the concentration measurement is provided to the controller 260 to compare, calculate and/or to control adjustment of the concentration of oxygen present in the oxidant stream 134. In one embodiment, the controller 260 compares the measured oxygen concentration to an oxygen flow rate set-point value stored in or provided to the controller 260. The oxygen concentration value stored or provided to the controller 260 determines whether the amount of the air stream 138 provided to the oxygen producing unit 130 (e.g., the feed rate) should be selectively adjusted (e.g., increased or decreased) to vary the oxygen concentration in the oxidant stream 134. For example, to increase or decrease the feed rate of the air stream 138 provided to the air separation unit 130, the controller 260 provides the signal S to a valve 240. In response, the valve 240 operates to selectively adjust the feed rate of the air stream 138 provided to the oxygen producing unit 130. In one example, if the load of the combustion system 120 is reduced, the demand for oxygen in the feed stream 132 is reduced and, accordingly, the feed rate of the air stream 138 to the air separation unit 130 is reduced.

[0041] In one embodiment, the concentration of carbon dioxide present in the flue gas stream 124 may be measured or sensed at, for example, a location F, by, for example, any device capable of taking such a measurement, including, but not limited to a carbon dioxide analyzer 250. While FIG. 4 illustrates location F at a position upstream of the contaminant control system 140, it is contemplated that location F may be positioned downstream of the contaminant control system or within the contaminant control system, for example, between the electrostatic precipitator 142 and the flue gas desulfurization system 144. In one embodiment, the measured concentration of carbon dioxide present in the flue gas stream 124 is provided to the controller 260. The controller 260 compares the concentration of carbon dioxide present in the flue gas stream 124 to a predetermined set-point. When the concentration does not, for example, match or fall within a predetermined range of the set point valve, the controller 260 operates to adjust the concentration. In one embodiment, the controller 260 adjusts (increases or decreases) the concentration of carbon dioxide present in the flue gas stream 124 by, for example, adjusting an amount (e.g., feed rate) of the feed stream 132 directed to the combustion system 120 such that the flue gas stream 124 subsequently output maintains a carbon dioxide concentration in a range of between about 10% to 60% by volume. In another embodiment, the feed rate of the feed stream 132 provided to the combustion system 120 is adjusted such that the flue gas stream 124 maintains a carbon dioxide concentration in a range of between about 12% to 46% by volume. In a further embodiment, the feed rate of the feed stream 132 provided to the combustion system 120 is adjusted such that the flue gas stream 124 maintains a carbon dioxide concentration in a range of between about 30% to 50% by volume.

[0042] It should be appreciated that while it is described above to maintain a predetermined carbon dioxide concentration in the flue gas stream 124 by adjusting the feed rate of the feed stream 132, it is within the scope of the present disclosure to maintain the carbon dioxide concentration by, for example, selectively adjusting the amount of the recycled portion 124a of the treated flue gas stream 124' combined with the feed stream 132, and/or selectively adjusting the concentration of oxygen present in the oxidant stream 134 combined with the feed stream 132.

[0043] It should also be appreciated that when the carbon dioxide concentration present in the flue gas stream 124 is between about 10% to 60% by volume, the carbon dioxide capture system 150 operates at an energy load below about 3.0 GJ/ton of carbon dioxide without the load of the oxygen producing unit 130, and at an energy load of about 2.3 to 6.6 GJ/ton of carbon dioxide with the load of the oxygen producing unit 130.

[0044] In one embodiment, the controller 260 includes a microprocessor programmed to receive and send signals to and from the aforementioned integrated flow control devices, sensors and other test and measurement devices, and valves within the system 100. In one embodiment, the controller 260 receives input including data and information from an operator of the system 100 (as indicated by arrow O) or other portion of the system 100 (as indicated at inputs 262). Information provided to the controller 260 includes, but is not limited to, the electrical demand of the system 100. It is contemplated that the operator can manually control the operations of the controller 260 and various flow control and sensing and measuring devices as described herein by providing input to the controller 260. Alternatively, it is contemplated that the operator may control the system 100 by preprogramming commands, set points and other parameters of the system 100 and allow the system to proceed in an automated manner, for example, by comparing various measurement signals and controlling adjustments of feed rates and concentrations of flow streams as described herein. For example, and as described in detail above, the control signals S and S1 selectively operate valves 210, 220 and 240 to vary feed rates and concentrations of the recycled flue gas 124a and 124b, the feed stream 132, the oxidant stream 134, the fresh air stream 136 and the air stream 138.

[0045] In another embodiment, as shown in FIG. 4, the signal S may also be provided to an integrated flow control device 280, for example, a valve, which selectively adjusts an amount of steam 292 generated by steam turbine 290 and provided to the carbon dioxide capture system 150. In one embodiment, the control signal S communicates commands to the valve 280 to regulate an amount of steam 292 to be provided to the carbon dioxide capture system 150. In one embodiment, the amount of steam 292 currently provided to the carbon dioxide capture system 150 is measured by, for example, a sensor 282 at location H, and provided to the controller 260. The controller 260 compares the measured amount of steam to a predetermined or provided set point and, based on the comparison, the controller 260 operates the valve 280 to selectively adjust (increase or decrease) the amount of steam 292 provided to the carbon dioxide capture system 150.

[0046] In yet a further embodiment, and as shown in FIG. 5, the controller 260 may provide the signal S to an integrated flow control device 300 such as, for example, a valve, disposed within the flow path of the treated flue gas stream 124' to the carbon dioxide capture system 150. The controller 260 evaluates flow measurements measured or sensed by, for example, a sensor or like testing and measuring device 302. The sensor 302 is disposed at, for example, location G in the flow path of the treated flue gas stream 124' to the carbon dioxide capture system 150 and provides the measurements to the controller 260. In response, the controller 260 selectively operates the valve 300 to adjust (increase or decrease) the flow of the treated flue gas stream 124' to the carbon dioxide capture system 150. Accordingly, the controller 260 may selectively regulate the flow of the treated flue gas stream 124' to the carbon dioxide capture system 150 in relation to load on the processing system 100. For example, the controller 260 increases flow to the carbon dioxide capture system 150 as the processing system 100 increases combustion of the fuel 122 and consequently increases the amount of the output flue gas stream 124, or decreases flow to the carbon dioxide capture system 150 as the processing system 100 decreases combustion of fuel 122 and decreases the amount of output flue gas stream 124.

[0047] As shown in FIGS. 4 and 5, in a further embodiment, the controller 260 provides a combination of the control signals S and S1, which cascades to the respective valves 210, 220, 240 and 300. However, it is contemplated that controller 260 does not provide all of the signals within the flue gas stream processing system 100. For example, some control signals may originate from operator input.

[0048] In addition to the functions noted above, it is contemplated that controller 260 is programmed to contain information pertaining to the cost of compressing the air stream 138 fed to the oxygen producing unit 130 in order to generate the oxidant stream 134, the reboiler duty, as well as the desired concentration of oxygen present in the feed stream 132 provided to the combustion system 120. The controller 260 may further be programmed in a manner to compare the parameters of the flue gas stream processing system 100 in an effort to manage the costs associated with running the flue gas processing system 100. Additionally, it is contemplated that the controller 260 can manage the parameters of the flue gas stream processing system 100 in a dynamic fashion, for example, change flow rates of flue gas stream 124 and/or the feed stream 132 to adapt to the measured concentrations of oxygen, carbon dioxide, and/or a combination thereof. Such dynamic control of the flue gas stream processing system 100 allows the energy load of the processing system 100 to be more efficiently managed.

[0049] Unless otherwise specified, all ranges disclosed herein are inclusive and combinable at the end points and all intermediate points therein. The terms "first," "second," and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms "a" and "an" herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. All numerals modified by "about" are inclusive of the precise numeric value unless otherwise specified.

[0050] While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A method for managing an amount of energy utilized by a carbon dioxide capture system, the method comprising: providing a fuel and a feed stream to a combustion system, the feed stream comprising oxygen and including a portion of a flue gas stream generated upon combustion of the fuel in the combustion system; subjecting the flue gas stream to a carbon dioxide capture system to remove carbon dioxide therefrom; measuring a concentration of oxygen present in the feed stream; and selectively adjusting an amount of the flue gas stream included in the feed stream based on the measured concentration of oxygen in the feed stream such that the feed stream maintains an oxygen concentration in a range of between about 10% to 90% by volume and the carbon dioxide capture system operates at an energy load between 1.4 GJ/ton of carbon dioxide and 3.0 GJ/ton of carbon dioxide.

2. A method according to claim 1, wherein the carbon dioxide capture system operates at an energy load between 1.4 GJ/ton of carbon dioxide and 2.5 GJ/ton of carbon dioxide.

3. A method according to claim 1, further comprising: subjecting the flue gas stream to a desulfurization system located downstream of the combustion system and upstream of the carbon dioxide capture system, thereby removing sulfur oxide from the flue gas stream and forming a treated flue gas stream.

4. A method according to claim 3, further comprising directing at least one of a portion of the flue gas stream, a portion of the treated flue gas stream and combinations of the portions, to the feed stream.

5. A method according to claim 4, wherein the portion of the flue gas stream is directed from a location upstream of the desulfurization system, and the portion of the treated flue gas stream is directed from a location downstream of the desulfurization system.

6. A method according to claim 4, wherein the feed stream is further comprised of a fresh air stream and an oxidant stream.

7. A method according to claim 6, further comprising generating the oxidant stream in an oxygen producing unit.

8. A method according to claim 7, further comprising: measuring a concentration of oxygen in the oxidant stream; and selectively adjusting a feed rate of an air stream provided to the oxygen producing unit based on the measured concentration of oxygen in the oxidant stream.

9. A method according to claim 6, further comprising: measuring a flow rate of the fresh air stream provided to the feed stream; and selectively adjusting the flow rate of at least one of the portion of the flue gas stream and the portion of the treated flue gas stream directed to the feed stream based on the measured flow rate of the fresh air stream provided to the feed stream.

10. A method according to claim 1, further comprising: measuring a concentration of carbon dioxide present in the flue gas stream exiting the combustion system; and selectively adjusting a feed rate of the feed stream directed to the combustion system based on the measured concentration of carbon dioxide present in the flue gas stream such that the flue gas stream maintains a carbon dioxide concentration in a range of between about 10% to 60% by volume.

11. A method for managing an amount of energy utilized by a carbon dioxide capture system, the method comprising: providing a fuel and a feed stream to a combustion system, the feed stream comprising oxygen and including a portion of a flue gas stream generated upon combustion of the fuel in the combustion system; subjecting the flue gas stream to a carbon dioxide capture system to remove carbon dioxide therefrom; measuring a concentration of carbon dioxide present in the flue gas stream exiting the combustion system; and selectively adjusting a feed rate of the feed stream directed to the combustion system based on the measured concentration of carbon dioxide present in the flue gas stream such that the flue gas stream maintains a carbon dioxide concentration in a range of between about 10% to 60% by volume and the carbon dioxide capture system operates at an energy load between 1.4 GJ/ton of carbon dioxide and 3.0 GJ/ton of carbon dioxide.

12. A method according to claim 11, wherein the carbon dioxide capture system operates at an energy load between 1.4 GJ/ton of carbon dioxide and 2.5 GJ/ton of carbon dioxide.

13. A method according to claim 11, further comprising: subjecting the flue gas stream to a desulfurization system located downstream of the combustion system and upstream of the carbon dioxide capture system, thereby removing sulfur oxide from the flue gas stream and forming a treated flue gas stream.

14. A method according to claim 13, further comprising directing at least one of a portion of the treated flue gas stream from a location downstream of the desulfurization system, a portion of the flue gas stream from a location upstream of the desulfurization system, and combinations of the portions to the feed stream.

15. A method according to claim 13, wherein the feed stream further comprises an oxidant stream and a fresh air stream.

16. A method according to claim 15, further comprising: measuring a concentration of oxygen in the oxidant stream generated by an oxygen producing unit; and selectively adjusting a feed rate of air provided to the oxygen producing unit based on the measured concentration of oxygen in the oxidant stream.

17. A method according to claim 15, further comprising: measuring a flow rate of the fresh air stream provided to the feed stream; and selectively adjusting the flow rate of the portion of the flue gas stream directed to the feed stream based on the measured flow rate of the fresh air stream provided to the feed stream.

18. A method according to claim 11, further comprising: measuring a concentration of oxygen present in the feed stream; and selectively adjusting an amount of the flue gas stream directed to the feed stream based on the measured concentration of oxygen in the feed stream such that the feed stream maintains an oxygen concentration in a range of between about 10% to 90% by volume.

19. A method for managing an amount of energy utilized by a carbon dioxide capture system, the method comprising: providing a fuel and a feed stream to a combustion system, the feed stream comprising oxygen and including a portion of a flue gas stream generated upon combustion of the fuel in the combustion system; subjecting the flue gas stream to a carbon dioxide capture system to remove carbon dioxide therefrom; measuring a concentration of carbon dioxide present in the flue gas stream exiting the combustion system; selectively adjusting a feed rate of the feed stream directed to the combustion system based on the measured concentration of carbon dioxide present in the flue gas stream such that the flue gas stream maintains a carbon dioxide concentration in a range of between about 10% to 60% by volume; measuring a concentration of oxygen present in the feed stream; and selectively adjusting an amount of the flue gas stream present in the feed stream based on the measured concentration of oxygen in the feed stream such that the feed stream maintains an oxygen concentration in a range of between about 10% to 90% by volume and the carbon dioxide capture system operates at an energy load between 1.4 GJ/ton of carbon dioxide and 3.0 GJ/ton of carbon dioxide.

20. A method according to claim 19, wherein the carbon dioxide capture system operates at an energy load between 1.4 GJ/ton of carbon dioxide and 2.5 GJ/ton of carbon dioxide.

21. A method according to claim 19, further comprising: subjecting the flue gas stream to a desulfurization system located downstream of the combustion system and upstream of the carbon dioxide capture system, thereby removing sulfur oxide from the flue gas stream and forming a treated flue gas stream.

22. A method according to claim 21, further comprising: directing at least one of a portion of the flue gas stream from a location upstream of the desulfurization system, a portion of the treated flue gas stream from a location downstream of the desulfurization system, and combinations thereof, to the feed stream.

23. A method according to claim 21, wherein the feed stream further comprises an oxidant stream and a fresh air stream.

24. A method according to claim 23, further comprising generating the oxidant stream in an oxygen producing unit.

25. A method according to claim 24, further comprising: measuring a concentration of oxygen in the oxidant stream generated by an oxygen producing unit; and selectively adjusting a feed rate of air provided to the oxygen producing unit based on the measured concentration of oxygen in the oxidant stream.

26. A method according to claim 24, further comprising: measuring a flow rate of the fresh air stream provided to the feed stream; and selectively adjusting the flow rate of the flue gas stream directed to the feed stream based on the measured flow rate of the fresh air stream provided to the feed stream.