Patent Application
20120125240
1. Field
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.
2. Description of Related Art
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.
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.
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.
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.
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.
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.
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.
The above described and other features are exemplified by the following figures and detailed description.
Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike:
In one embodiment, as shown in
Referring generally to
The oxidant stream 134 generally contains oxygen (O2), 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.
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.
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.
As shown in
In one embodiment, the flue gas stream 124 may include contaminants such as, but not limited to, sulfur oxides (SOx), mercury (Hg), carbon dioxide (CO2), particulates, nitrous oxide (N2O) 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.
Downstream of the combustion system 120 is a contaminant control system, shown generally at 140. In one embodiment, as shown in
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.
Still referring to
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.
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.
Now referring to
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.
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, CO2, 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.
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.
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.
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.
As shown in
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
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.
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
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
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.
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.
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.
In another embodiment, as shown in
In yet a further embodiment, and as shown in
As shown in
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.
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.
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.
