JP2008519958A - Apparatus and method for controlling boiler superheat temperature - Google Patents

Abstract

【Task】
A boiler (10) designed or modified to reduce greenhouse gases produced by using a substantially pure oxygen atmosphere to burn fuel. A boiler comprising a main burner (14) and a water pipe (13a) is provided. The boiler further comprises at least one auxiliary burner (24), optionally positioned in a zone (26) above the main burner region (15) and below the boiler steam outlet. The auxiliary burner provides heat or energy to increase the temperature and quality of the steam. The auxiliary burner provides heat or energy lost due to the reduced flow rate of exhaust through the boiler as a result of using oxygen rather than compressed air.

Description

  The present invention relates to a steam boiler designed or modified to operate with oxygen and fuel in the absence of normal combustion air, and to control the superheat and / or reheat temperature of steam over a conventional combustion zone in the boiler. Requires advanced heating and / or reheat steam temperature control. More particularly, the present invention provides a method for enhancing the heat and energy in the superheat and / or reheat zone and the convection zone as needed to maintain the proper steam temperature at the steam boiler outlet. The present invention relates to a boiler with at least one additional burner that uses oxygen and fuel in the absence of normal combustion air.

  For example, power plants and steam plants used by power companies, businesses and local authorities to generate steam and electricity can generally supply various processes and other applications and turbines that run generators and other equipment. Includes small to large boiler systems used to generate steam. Boilers generally have a basic design dating back to the 19th century and have a myriad of tubes through which water circulates. In addition, boilers generally include one or more burners that are supplied with various carbon-based fuels (including fossil fuels) that are ignited and burned in the presence of air. The burner and water tube are close to each other, and the heat generated by the burner heats the water in the water tube. The hot water rises above the boiler burner portion in the same way as the gas heated by the burner, so that the hot water continues to rise in temperature as it rises through countless tubes. In general, the tube is under pressure, so water (boiling at about 100 ° C. at atmospheric pressure) will only continue to rise in temperature without boiling.

  Such boilers are usually several feet to several floors in height, and near the top there is a part that releases hot water from the water tube confinement and vaporizes it into steam. The hot water is suddenly released and converted into steam, thereby providing a large turbine rotational force. Such boilers are designed to generate and / or exceed the necessary heat and energy for the work assigned to the boiler.

  Improvements to such boiler systems may include superheat and reheat zones, which are used to pass steam through superheat and reheat tubes located in the high-speed exhaust stream. A means to further increase the temperature is provided. These devices use the waste energy of combustion to raise the temperature of the steam above its saturation point. In addition to the advantage that steam has high energy, it has been found that superheated steam is dry and that the dry steam has less harmful effects on turbine blades than steam rich in moisture. It has been found that dry steam has more energy per unit volume than saturated steam.

  In general, boilers are designed to produce more energy than needed and attenuate this energy by cooling the steam to the desired temperature. In prior art systems using about 18 percent oxygen, the air flow rate must be increased to achieve a stoichiometric ratio of oxygen that completely burns the fuel. When air is used at high flow pressures, hot gases are quickly flowed from the boiler burner area across the height of the water tube. As a result, the heat and energy necessary for continuously applying energy to water and steam in the superheater can be obtained up to the top of the boiler. However, with this advantage, it has been found that burning fuel in the presence of nitrogen-rich air produces nitrogen oxides (NOx) (a harmful greenhouse gas). In prior art boilers, increasing the flow of air required in the boiler to provide stoichiometric oxygen for burning the air in the boiler and providing complete combustion results in a corresponding increase in flow rate and large amounts of NOx. Is generated.

  One way to reduce greenhouse gases is described in US Pat. No. 6,436,737 entitled “Oxy-Fuel Combustion System and Uses Therefor”, which is owned by the assignee of the present invention. And the whole is incorporated as if shown here. The '737 patent discloses a system for supplying substantially pure oxygen to the burner so that excessive NOx is not produced. This system can be used in both new and existing boiler improvements.

  However, the use of uncompressed flow of pure oxygen provides the stoichiometric ratio required to consume the fuel without the use of the fast and forced flow used in air, which is associated with heat and Energy is not forced to the height of the boiler (usually by the pressure used to pump air into the boiler). As a result, for certain boilers as known by those skilled in the art in such oxygen supply systems, the appropriate amount of water in the tube that is not immersed in the heated gas at the higher level in the boiler It begins to cool before heat and energy are generated. Furthermore, in such boilers, the flow of hot gas after passing through the superheat element does not occur to the extent necessary to produce superheated steam as needed. As a result, such boilers cannot provide an effective alternative to prior art furnaces that produce greenhouse gases.

  It is desirable to obtain larger quantities of high quality steam while preventing NOx formation.

  According to the present invention, at least one main burner that uses oxygen and fuel in the absence of normal combustion air for the initial heating of water, and a first end near the at least one main burner; A boiler is provided with a collection of water tubes each having a second end remote from the first end and near the boiler steam outlet. The boiler may further comprise a superheater and / or a reheater connected to move the steam outlet and steam. At least one auxiliary burner is provided over the normal burner position to generate a lot of heat or energy to increase the temperature and quality of the steam in the boiler body and boiler overheating and / or reheating zones.

  In one embodiment of the present invention, existing prior art boilers are modified to provide substantially pure oxygen rather than compressed air. Such boiler improvements include the strategic placement of at least one auxiliary burner over the main burner area to provide the heat and energy necessary to produce the desired amount and quality of steam. . In a preferred embodiment, the auxiliary burner is supplied with substantially pure oxygen regardless of whether it is an improved prior art system or a newly designed boiler.

  In the operation of the boiler, the main burner heats the water flowing in the water pipe and raises the heated water in the boiler. The heated water is vaporized into steam at the steam outlet, and the steam is sent to the superheater. As a result of convection, heat is added to the steam in the superheated region, raising the temperature of the steam above the saturation point. The auxiliary burner adds heat and allows for more constant and consistent control throughout the heating of the steam. In this way, properly heated steam is provided to the turbine, allowing the turbine to operate efficiently and properly. In other embodiments, more than one auxiliary burner is provided so that the heat applied to the superheater element can be more carefully controlled when needed. In this embodiment, using oxygen at a lower flow rate than air reduces the flow rate of the heated gas, so the energy from the main burner is at least one auxiliary to eliminate heat and energy deficiencies. Supplemented by burners. At least one auxiliary burner located between the height of the main burner and the steam outlet provides heat or energy to the water in the tube and the steam in the superheat zone to provide the energy lost by the use of low flow oxygen To do.

  In yet another embodiment, the auxiliary burner is supplied with oxygen from the oxygen generation system in a stoichiometric ratio instead of normal combustion air, resulting in minimal greenhouse gases. Normal combustion air consisting of about 80% nitrogen consumes a large amount of heat, which is lost to the exhaust, but using oxygen from the oxygen generation system reduces the heat lost to the exhaust, Heat can be added to the superheater more efficiently. In another embodiment, both the auxiliary burner and the main burner are supplied with stoichiometric oxygen from an oxygen generation system.

  The heated water vaporizes into steam at the steam outlet, where the steam is sent to a superheater where the auxiliary burner continues to provide heat and energy to enhance the quality of the steam produced. The steam from the superheater can then be sent to the turbine. In one embodiment, the steam is returned from the turbine to the reheater where it is reheated and re-energized by both the main and auxiliary burners and sent back to the turbine. As a result of the convection generated by the auxiliary burner, the burner supplied with low flow of oxygen will generally add heat or energy to an area with a heat-energy gap, otherwise the water in the boiler will cool. . This convection causes the steam temperature to rise above the saturation point, producing the desired amount and quality of steam. The auxiliary burner adds heat or energy that allows more constant and consistent heating of the steam. In this way, properly heated steam is provided to the turbine, and the turbine can operate efficiently and properly.

  In other embodiments of the present invention, more than one auxiliary burner is provided so that the heat or energy applied to the superheater element can be more carefully controlled when needed. Furthermore, in a preferred embodiment, the boiler of the present invention can be made to generate more heat or energy than is required. In such embodiments, cooling elements and other elements known to those skilled in the art can be provided to bring the steam to (or attenuate) the desired heat and energy levels. Those skilled in the art will appreciate that using a cooling element to produce steam having the desired characteristics is more efficient than using a heating element in a boiler to attempt to heat the steam to a desired level. I will.

  In another embodiment of the invention, the burner is used as a nozzle or port that controls the superheat temperature of the steam by introducing recycled flue gas. It will be appreciated that recycled flue gas is most useful when combined with the use of carbon-based fuels, including oxygen and fossil fuels, in combustion burners in the furnace section of the boiler. It may be advantageous to use recycled flue gas to control the temperature of superheated steam as the flue gas from the combustion process is reduced and the radiant heat transfer through the process is increased. In this example, the recycled flue gas is used in controlling the steam temperature in the boiler by adding a volume effect or tempering effect to the convection area of the boiler.

  Another way to control the superheated steam temperature (or supercritical) is to introduce recycled flue gas at the auxiliary burner tip. By using the flue gas as a carrier gas for other carbon-based fuels including pulverized coal or fossil fuel, a part or all of the flue gas necessary for tempering the gas can be introduced to the tip of the auxiliary burner. Again, this is in concert with the burner mode in which oxygen and carbon-based fuels burn. With these systems, it is desirable to completely eliminate the introduction of nitrogen.

  In addition, by using recycled flue gas (substantially free of nitrogen if the product used is from an oxygen and carbon based fuel combustion system) to facilitate the combustion of coal This system can still achieve temperature control of superheated steam. In another embodiment, another portion of flue gas is introduced into the upper burner or nozzle to complete control of the system.

  A more detailed description of the invention is provided in the following description and claims, and is illustrated in the accompanying drawings.

  While the invention is susceptible to various embodiments, the drawings illustrate several presently preferred embodiments that are described in more detail below. It should be understood that this disclosure is to be regarded as illustrative of the invention and is not intended to limit the invention to the particular embodiments shown. In addition, the heading in this section of the application (“Detailed Description of an Illustrative Embodiment”) relates to the provisions of the US Patent Office and limits the subject matter disclosed herein. It should be understood that this should not be interpreted.

  Referring to the figure, a boiler 10 having a series of water tubes 12 with water cooling walls 13 is shown. The boiler 10 further includes at least one main burner 14 disposed in the main burner zone 15 and connected to a fuel supply source 16 and an air supply source 18. In a preferred embodiment of the present invention, instead of using air 18 that must be pumped at a high flow rate (to produce stoichiometric oxygen and fuel in the burner), substantially pure oxygen is used. provide. It will be appreciated that when oxygen is used, a compressed flow is not necessary because a stoichiometric ratio to fuel can be more easily created. Such a system requires only oxygen with a purity such that complete combustion of the fuel takes place. In such a system, nitrogen, which is a substantial component of air but not a substantial component of pure oxygen, is not burned and NOx is not generated, thereby reducing the production of harmful greenhouse gases. It will be appreciated that if there is a need to further reduce greenhouse gases, higher purity oxygen is required. Although the term “substantially pure oxygen” is used in various places throughout the specification, one of ordinary skill in the art will understand that the fuel and oxygen in the right ratio for the desired combustion and oxygen and without departing from the novel scope of the present invention. It will be appreciated that the purity of oxygen can be varied as needed to provide a byproduct.

  The water cooling wall 13 in the boiler 10 is composed of an infinite number of water pipes 13 a extending from the main burner zone 15 to the upper region of the boiler 10. The boiler 10 may further comprise a superheater 20 and / or a reheater 21 of a type well known in the art. In general, such superheater 20 is supplied with steam generated in the boiler 10 in the steam transfer region 22. The steam passes through the superheater 20, and heat or energy from combustion and heat and energy radiated from the water pipe 13 a are transmitted to and around the superheater 20 by convection, and the steam sent into the superheater is heated. The The reheater 21 is typically fed with steam returning from the turbine to the boiler, which must be heated before returning to the turbine for further use. This heat or energy is transferred to the steam, raising the temperature of the steam above the saturation point of the steam, which makes the steam more suitable for use in the turbine. It will be appreciated that a cooling function can be provided so that steam having a temperature and / or too much energy for the required work can be attenuated as needed.

  As an additional feature, the boiler 10 has an auxiliary burner 24 that can be placed above the normal burner zone 15 and below the steam transfer area 22. In one embodiment, at least one auxiliary burner 24 is disposed in the superheat region 26. In other embodiments, the auxiliary burner 24 is disposed at a number of locations around the boiler 10 to allow for better control of heat or energy.

  In this way, heat or energy is applied to produce larger quantities and / or higher quality steam. Further, by adding an auxiliary burner 24 in the superheat or reheat zone 26, a greater amount of burner energy can be used to heat only the steam rather than heating the water. Because less energy is required to add heat or energy to the steam than to add heat or energy to the water, the energy of the auxiliary burner 24 is generated in the turbine at or near the zone where the main burner 14 is located. It is more easily converted into electric power than heat or energy.

  As will be appreciated by those skilled in the art, the auxiliary burner 24 may be much smaller than the main burner 14, and yet in an oxygen environment is of higher quality and volume than the larger additional main burner 14 disposed in the main burner zone 15. Produces steam. It will also be appreciated that a large main burner 14 can be used both in the main burner zone and above without departing from the novel scope of the present invention. Furthermore, the number of main burners 14 and auxiliary burners 24 in the boiler 10 can be changed without departing from the novel scope of the present invention. The type, size and number of burners depend on the steam application, requirements and quality. Although FIG. 1 illustrates the use of a single burner 24, it will be understood from the foregoing description that one or any number of burners 24 may be used instead without departing from the novel scope of the present invention. Such deformations may be made, such as by adding more heat or energy when needed to make the temperature easier to control, allowing less heat or energy to be used as needed or desired. It will be understood that

  Also, in normal boilers, and in the present invention, boiler steam is produced at higher and higher temperatures than required or required, and then, as known to those skilled in the art, the novel scope of the present invention. It will be appreciated that by using cooling means such as a device that contacts the steam conduit with cooling water without departing from the above, it can be cooled to the desired heat, energy and saturation point.

  Recycled flue gas is used to control the superheat temperature when the flue gas is reduced due to the use of combustion of oxygen and carbon-based fuels (such as fossil fuels) or the radiant heat transfer rate is too high, and the combustion gas Adjust the temperature to cool the superheater tube or increase the amount of flue gas in the superheated section to properly disperse. Both applications allow control of the superheated steam temperature in the tube. Flue gas can be introduced to control the superheat temperature at the proposed location 24 of the additional burner (when the superheat temperature is too low) by using a nozzle or port device. Alternatively, the fuel source 16 in this example includes a pulverized coal machine as an additional tool that eliminates the introduction of nitrogen into the oxygen and carbon fuel combustion system.

  As those skilled in the art will appreciate, the exact location and amount requirements for additional heating or cooling of the superheated steam tube will vary with the size and configuration of the boiler. Embodiments of the present invention focus on controlling the temperature of superheated steam by adding or removing heat in the convection path of the boiler. More particularly, flue gas tempering or increased flue gas volume in the boiler superheat zone may be advantageous when used in conjunction with an oxygen and carbon based fuel combustion system.

  While illustrative embodiments of the present invention have been shown and described, it should be understood that various modifications and alternatives can be made by those skilled in the art without departing from the novel spirit and scope of the invention.

1 is a schematic view of a boiler embodying the apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Boiler 12, 13a Water pipe 14 Main burner 15 Main burner zone 16 Fuel supply source 18 Air 20 Superheater 21 Reheater 22 Steam transfer area 24 Auxiliary burner 26 Superheat or reheat area

Claims (13)

A boiler,
At least one main burner for the initial heating of water, the main burner being arranged in the main burner zone and supplied with a low flow of substantially pure oxygen in a stoichiometric ratio to the boiler fuel;
A collection of water pipes each having a first end near the at least one main burner and a second end away from the first end and near the boiler steam outlet;
A boiler comprising at least one auxiliary burner in the zone above the main burner zone and below the boiler steam outlet for generating energy for higher quality steam.   The boiler according to claim 1, wherein the at least one auxiliary burner is two auxiliary burners.   The boiler of claim 1, wherein the auxiliary burner is provided with substantially pure oxygen in a stoichiometric ratio to fuel.   The boiler according to claim 1, comprising at least one of a superheater and a reheater.   The boiler according to claim 4, wherein the at least one auxiliary burner is disposed near the superheater.   The boiler of claim 4, wherein the at least one auxiliary burner is disposed near the reheater. A boiler,
At least one main burner for the initial heating of the water;
A collection of water tubes each having a first end near the at least one main burner and a second end away from the first end and near the boiler steam outlet;
At least one of a superheater or a reheater connected to move the steam outlet and steam;
A boiler comprising two auxiliary burners arranged in a zone above the main burner region in the boiler and the steam outlet for enhancing the quality of steam in the boiler.   The boiler of claim 7, wherein the auxiliary burner is provided with substantially pure oxygen in a stoichiometric ratio to fuel. A method of modifying an existing burner to remove a substantial portion of greenhouse gases,
Supplying substantially pure oxygen to one or more main burners of the boiler;
Providing the boiler with at least one auxiliary burner located above the main burner area of the boiler;
Operating the boiler such that fuel is burned in the presence of substantially pure oxygen in both the main burner and the auxiliary burner to substantially consume the fuel.   The method of claim 9, comprising providing a superheater in a superheated area in the boiler and placing the at least one auxiliary burner near the superheated area. A boiler,
At least one main burner for the initial heating of water, the main burner being arranged in the main burner zone and supplied with a low flow of substantially pure oxygen in a stoichiometric ratio to the boiler fuel;
A collection of water pipes each having a first end near the at least one main burner and a second end away from the first end and near the boiler steam outlet;
A convection superheater connected to move the steam outlet and steam;
A boiler with at least one nozzle or port in the vicinity of the convective superheater for changing the temperature to control the temperature of the steam in the superheater. A boiler,
At least one main burner for the initial heating of water, the main burner being arranged in the main burner zone and supplied with a low flow of substantially pure oxygen in a stoichiometric ratio to the boiler fuel;
A collection of water pipes each having a first end near the at least one main burner and a second end away from the first end and near the boiler steam outlet;
A convection superheater connected to move the steam outlet and steam;
A boiler that uses high-concentration CO ₂ and nitrogen-free carrier gas for fuel transportation as a process for controlling the temperature of the steam in the superheater. A boiler,
At least one main burner for the initial heating of water, the main burner being arranged in the main burner zone and supplied with a low flow of substantially pure oxygen in a stoichiometric ratio to the boiler fuel;
A collection of water tubes each having a first end near the at least one main burner and a second end away from the first end and near the boiler steam outlet;
A convection superheater connected to move the steam outlet and steam;
A boiler that uses highly concentrated CO ₂ and a carrier gas not containing nitrogen for fuel transportation as a process for eliminating the introduction of nitrogen into the carrier gas for carbon-based fuels.

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