FURNACE SYSTEM WITH INTERNAL FLUE GAS RECIRCULATION
A furnace system 10 including a combustion vessel 12 having an outlet end 19 and at least one aperture 20, 22 extending into an interior area 14 defined by the combustion vessel. The furnace system 10 includes a flue duct 42 coupled to the outlet end 19 and in fluid communication with the interior area. A recirculation duct 55 extends from the flue duct 42 to one or more of the apertures 20, 22 and provides fluid communication between the flue duct 42 and the interior area 14.
Latest ALSTOM TECHNOLOGY LTD. Patents:
- On-load tap-changer control method, excitation control system carrying out said control method and power excitation chain
- Flue gas heat recovery integration
- Apparatus and method for control of direct current transmission lines
- Power transformers using optical current sensors
- Current connection and/or cut-off device comprising permanent contacts with reduced wear
This application claims the benefit of U.S. provisional application No. 61/075,451 filed Jun. 25, 2008, the contents of which are incorporated herein by reference in their entirety.
TECHNICAL FIELDThe present invention relates generally to a fossil fuel fired furnace system, and more particularly, to an oxyfuel fired furnace system having an internal flue gas recirculation system.
BACKGROUNDSteam generators, also referred to as boilers or furnaces, are used in various systems. For example, boilers can be used to produce steam for use in electric turbines and in chemical processes for providing energy to initiate a chemical reaction. The combustion process employed in boilers often utilizes fossil fuels such as coal or oil. Generally, during the combustion process pollutants such as unburned fuel, particulate, ash, NOx and other combustion byproducts are generated. If allowed to enter the atmosphere in sufficient amounts, these pollutants can detrimentally impact the environment and pose health hazards to humans and animals.
SUMMARY OF THE INVENTIONAccording to aspects illustrated herein, there is provided a furnace system including a combustion vessel. A flue duct is coupled to an outlet end of the combustion vessel and is in fluid communication with an interior area defined thereby. A recirculation duct also forms a portion of the furnace system and extends outwardly from the flue duct and provides fluid communication between the flue duct and the interior area of the combustion vessel.
According to other aspects disclosed herein, a conveying device is disposed at least partially in the recirculation duct for facilitating flow of one or more fluids through the recirculation duct into the interior area of the combustion vessel in response to commands issued from a controller. The conveying device can include an eductor for conveying a fluid such as, but not limited to oxygen, steam, flue gas or combinations thereof into the interior area defined by the combustion vessel.
The above described and other features are illustrated by the following figures and detailed description.
Referring now to the Figures, which are exemplary embodiments, and wherein like elements are numbered alike:
As shown in
Still referring to
The interior area 14 of the combustion vessel 12 is also in fluid communication with flue duct 42 for facilitating the flow of flue gas FG therethrough. Similarly, flue duct 44 is in fluid communication with the flue duct 42 as well as with a second hopper section 46. A first heat exchanger, for example an economizer 45, is positioned in and is in fluid communication with the flue duct 44. During operation, the economizer 45 cools the flue gas FG flowing therethrough. A second heat exchanger 50, such as an air preheater, is positioned downstream of and is in fluid communication with the flue duct 44 via, in the illustrated embodiment, conduit 48. A second conduit 52 extends between and is in fluid communication with the flue duct 44 and the manifold 24. The second conduit 52 extends from the flue duct 44 downstream of an outlet 47 of the economizer 45.
While the economizer 45 is described as being one potential means of cooling the flue gas FG, other heat exchanger means may be employed, such as but not limited to ultra critical steam panels, steam heating means, steam production means and combinations thereof without departing from the broader aspects disclosed herein.
The second conduit 52 and the manifold 24 cooperate to define a recirculation duct 55 which provides fluid communication between the flue duct 44 and the interior area 14 of the combustion vessel 12. The second conduit 52 can be installed during initial construction of the furnace system 10 or can be installed during a retrofit operation, after initial construction. The furnace system 10 also includes a pollution control system 54 in fluid communication with, and positioned downstream of, the second heat exchanger 50.
The furnace system of
The interior area 114 of the combustion vessel 112 is in fluid communication with flue duct 142 for facilitating the flow of flue gas FG therethrough. Similarly, flue duct 144 is in fluid communication with the flue duct 142. A first heat exchanger, for example an economizer 145 is positioned in and is in fluid communication with the flue duct 144. A second conduit 152 extends between and is in fluid communication with flue duct 144 and the manifold 124. The second conduit 152 extends from the flue duct 144 downstream of an outlet 147 of the economizer 145. A second heat exchanger 150, such as an air preheater, is positioned downstream of and is in fluid communication with the flue duct 144 via, in the illustrated embodiment, conduit 148. The second conduit 152 and the manifold 124 cooperate to define a recirculation duct 155 which provides fluid communication between the flue duct 144 and the interior area 114 of the combustion vessel 112. The furnace system 110 further includes a pollution control system 154 in fluid communication with, and positioned downstream of, the second heat exchanger 150.
Still referring to
While the air separation unit 160 is shown and described as supplying oxygen to the eductor 156, it is contemplated that other means of supplying the oxygen can be employed, including but not limited to an oxygen sources such as oxygen tanks and/or cylinders in addition to or in place of the air separation unit.
Recirculation of a portion of the flue gas FG into the combustion vessel 112 helps regulate furnace temperatures and steam conditions within a predetermined range and allows a greater mass flow of gas through the combustion vessel. In addition, recirculation of the flue gas FG into the combustion vessel reduces the overall mass flow rate of flue gas flowing downstream of the flue duct 144. The introduction of oxygen (or any low nitrogen fluid) into the combustion vessel 112 reduces pollutants and the recirculation of flue gas FG into the combustion vessel 112 reduces the mass flow rate of the flue gas FG to be treated by the pollution control system 154, thus smaller, less costly second heat exchangers 150 and pollution control systems can be employed.
Although, oxygen is described as the motive fluid for use in the eductor 156, other fluids can be employed including but not limited to steam, flue gas, flue gas processed by the pollution control system 154 or a combination thereof. While the eductor 156 is shown and described as being positioned in the second conduit 152 for discharging oxygen and flue gas FG into the combustion vessel 112, other devices for conveying the flue gas into the combustion vessel can be employed including but not limited to a compressor, fan or blower as illustrated in
The furnace system of
While a fan 270 is shown and described for conveying the flue gas FG from the duct 244 into the combustion vessel 212, other devices such as, but not limited to, blowers and compressors can be employed without departing from the broader aspects disclosed herein. Although the fan 270 is shown and described as being positioned in the second conduit 252, it is contemplated that portions of the fan and/or drive unit may extend outside of the second conduit, for example into the manifold 224, into the flue duct 144 and/or protrude into the external area 159 outside of the second conduit.
The furnace system of
Referring back to
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 furnace system comprising:
- a combustion vessel having an outlet end and at least one aperture extending into an interior area defined by said combustion vessel;
- a flue duct coupled to said outlet end and in fluid communication with said interior area; and
- a recirculation duct extending from said flue duct to said at least one aperture and providing fluid communication between said flue duct and said interior area.
2. The furnace system of claim 1, further comprising conveying means disposed at least partially in said recirculation duct for causing flow of at least one fluid through said recirculation duct into said interior area in response to a command issued from a controller.
3. The furnace system of claim 2, wherein said conveying means comprises at least one of a fan and a blower and a compressor.
4. The furnace system of claim 2, wherein said conveying means comprises an eductor having a motive fluid supplied thereto for conveying said at least one fluid and said motive fluid into said interior area.
5. The furnace system of claim 4, wherein said motive fluid is oxygen.
6. The furnace system of claim 4, wherein said motive fluid is steam.
7. The furnace system of claim 4, wherein said motive fluid is flue gas.
8. The furnace system of claim 1, further comprising:
- a pollution control system in communication with said flue duct for processing flue gas discharged from said interior area;
- an air preheater in fluid communication with said flue duct; and wherein
- said recirculation duct is positioned upstream of at least one of said pollution control system and said air preheater.
9. The furnace system of claim 8, further comprising:
- conveying means disposed at least partially in said recirculation duct for causing flow of at least one fluid through said recirculation duct into said interior area in response to a command issued from a controller;
- wherein said conveying means comprises an eductor having a motive fluid supplied thereto for conveying said at least one fluid and said motive fluid into said interior area; and
- wherein said flue gas is supplied from said pollution control system.
10. The furnace system of claim 2, wherein said at least one fluid is flue gas.
11. The furnace system of claim 1, wherein said furnace is tangentially-fired for combusting a fuel in the presence of oxygen.
12. A furnace system comprising:
- a combustion vessel having an outlet end and at least one aperture extending into an interior area defined by said combustion vessel;
- a flue duct coupled to said outlet end and in fluid communication with said interior area; a recirculation duct extending from said flue duct to said at least one aperture and providing fluid communication between said flue duct and said interior area; and
- an eductor disposed at least partially in said recirculation duct and having oxygen supplied thereto for conveying at least some of said flue gas and said oxygen through said recirculation duct into said interior area.
13. The furnace system of claim 12, wherein at least one lance extends through said at least one aperture and into said interior area, said lance having a passage extending therethrough for conveying a portion of said oxygen through said lance into said interior area.
14. The furnace system of claim 12, wherein at least one nozzle extends through said at least one aperture and into said interior area, said nozzle having a passage extending therethrough for conveying a portion of said oxygen through said nozzle into said interior area.
15. The furnace system of claim 12, further comprising:
- a pollution control system in communication with said flue duct for processing flue gas discharged from said interior area;
- an air preheater in fluid communication with said flue duct; and wherein
- said recirculation duct is positioned upstream of at least one of said pollution control system and said air preheater.
Type: Application
Filed: Jun 24, 2009
Publication Date: Dec 31, 2009
Applicant: ALSTOM TECHNOLOGY LTD. (Baden)
Inventors: Shin G. Kang (Simsbury, CT), Armand A. Levasseur (Windsor Locks, CT), David G. Turek (South Windsor, CT)
Application Number: 12/490,818
International Classification: F23B 80/02 (20060101); F24H 3/12 (20060101);