KR100902538B1 - Boiler and method of retrofitting burner for boiler - Google Patents

Abstract

Boiler 10 designed or modified to produce less greenhouse gases by using a substantially pure oxygen atmosphere to burn fuel. A boiler having a main burner 14 and a water tube 13a is provided. The boiler comprises at least one auxiliary burner 24 Fmf disposed as necessary in the zone 26 below the boiler steam outlet and above the two burner zones 15. Auxiliary burners provide heat or energy to increase the quality and temperature of the steam. Auxiliary burners provide lost heat and energy through a reduced flow rate of exhaust gas through the boiler as a result of the use of oxygen rather than pressurized air.

Burner, Water Tube, Boiler

Description

BOILER AND METHOD OF RETROFITTING BURNER FOR BOILER}

The present invention operates with oxygen and fuel in the absence of normal combustion air, and overheating and / or reheating employing an improved method of controlling the overheating and / or reheating temperature of steam in boilers superior to conventional combustion regions. A steam boiler is designed or modified to require steam temperature. More specifically, the present invention is directed to the absence of normal combustion air in the convection zone to boost heat and energy in the overheat and / or reheat zone and the convection zone as required to maintain a suitable steam temperature at the outlet of the steam boiler. A boiler with one or more additional burners using oxygen and fuel.

First of all, power plants and / or steam plants used by public companies, industries and municipalities for the generation of steam and electricity are typically large and small boiler systems for generating steam that can be used for different processes and other applications, and turbines. It includes, the turbine sequentially drives the generator and other devices. In general, boilers with a basic design up to the nineteenth century contain a myriad of tubes through which water circulates. In addition, boilers typically include burners or burners fed with various carbon based fuels, including fossil fuels, which are ignited and burned in the presence of air. The burner and water tube are in close proximity to each other and the heat generated by the burner or burners heats the water in the tube. The hot water rises above the burner section of the boiler, as does the heated gas in the presence of the burner so that the hot water is continuously hotter as it rises in the myriad of tubes. Typically, the tube is under pressure so that water boiling at about 100 ° C. under atmospheric pressure does not boil and continues to get hotter.

These boilers are typically a few bits high to several stories high and comprise a region at their upper end that allows hot water to escape the confines of the water tube and evaporate into steam. The sudden release of water and its conversion to steam provide significant turbine rotational power. Such boilers are engineered to generate and / or exceed the heat and energy requirements needed for the mission in which the boiler is designed.

Improvements to these boiler systems include the inclusion of superheat and reheat zones, which provide a means to further step the temperature of the steam by passing the steam through a superheat and reheat tube disposed within a rapid flow of exhaust gas. . These devices use the combustion waste heat of the steam to raise the temperature of the steam above its saturation point. More than the advantage of steam with increased energy, superheated steam has been found to be drier, and this drier steam has less harmful effects on turbine blades than steam with higher moisture content. Dry steam has been found to have more energy per volume than saturated steam.

In general, boilers are designed to produce more energy than is needed, which is attenuated by cooling the steam to the desired temperature. In prior art systems using air where nearly 18% is oxygen, the flow of air must be increased to provide a stoichiometric ratio of oxygen to completely burn the fuel. Using high flow pressure air causes hot gas to rise rapidly from the burner area of the boiler, throughout the height of the water tube. As such, the heat and energy required to transfer energy to the steam and water of the superheater to the top of the boiler and to continuously heat it are obtained. However, with this advantage, combustion of fuel in the presence of nitrogen rich air has been found to cause the generation of nitrogen oxides (NO _X ), which are hazardous greenhouse gases. In prior art boilers, the increased air flow into the boiler required to provide a stoichiometric ratio of oxygen for combustion and complete combustion of the air in the boiler is accompanied _by a large amount of flow and the generation of large amounts of NO _x . .

One method of reducing greenhouse gases is U.S. Patent No. 6, entitled Oxygenated Fuel Combustion System, and Uses of the Assignee of the Invention, which is hereby incorporated by reference in its entirety as described herein. 6,436,737. The '737 patent discloses a system in which the burner is supplied with substantially pure oxygen such that excess NO _x is not produced. This system can be used for both existing boiler modifications and new boilers.

However, since the use of pure oxygen at an unpressurized flow rate does not require a rapid / forced flow used with air and produces the stoichiometric ratio needed to consume fuel, heat and energy are also high in the boiler's height. It is not forced up to (otherwise by the pressure used to pump air into the boiler). As a result, for certain boilers known to those skilled in the art, in such an oxygen supply system, the water in the tube that is not bathed in the higher height heated gas in the boiler will produce an appropriate amount of heat and energy. It begins to cool before. In addition, in such boilers, no flow of hot gas passes over the superheating element to the extent necessary to produce the necessary superheated steam. This prevents such boilers from becoming an effective alternative to prior art greenhouse gas generating furnaces.

It is desirable to have higher quality steam, while avoiding the production of NO _x .

According to the invention, at least one main burner using fuel and oxygen in the absence of normal combustion air for initial heating of water, a first end adjacent to the at least one main burner and a first end adjacent to the boiler steam outlet A boiler is provided that includes a collection of water tubes each having a second end spaced from it. The boiler may further comprise a superheater and / or a reheater in a steam outlet and steam delivery connection. At least one auxiliary burner is provided above the conventional burner position to generate more heat or energy in the overheat and / or reheat zone of the boiler to adequately increase the temperature and quality of the boiler's steam.

In one embodiment of the present invention, existing prior art boilers are modified to receive substantially pure oxygen rather than pressurized air. Modification of such boilers involves strategically placing at least one secondary burner above the primary burner area to provide the heat and energy needed to produce the desired quality and amount of steam. In a preferred embodiment, the auxiliary burners, whether modified conventional systems or newly designed boilers, are supplied with substantially pure oxygen.

In operation of the boiler, the main burners or burners heat the water flowing in the water tube, causing the heated water to rise in the boiler. The heated water evaporates to steam at the steam outlet and the steam is passed to the superheater. As a result of the convection flow, heat is added to the steam in the superheated zone to raise the temperature of the steam above the saturation point. Auxiliary burners provide added heat, allowing for more consistent and consistent control of steam heating. In this way, properly heated steam is supplied to the turbine to enable the turbine to operate in an effective and appropriate manner. In another embodiment, one or more auxiliary heaters are provided so that the heat applied to the overheating element can be more carefully controlled, if necessary. In general, due to the reduced flow of the heated gas of the present embodiment due to the use of oxygen at a lower flow rate than the air, the energy from the main burner or main burners is transferred to at least one subheater to overcome insufficient heat and energy. Complemented by At least one auxiliary burner disposed between the height of the main burner (s) and the vapor outlet provides heat or energy to the steam in the water and superheat zones in the tube to provide lost energy through the use of low flow oxygen.

In another embodiment, the auxiliary burner is supplied with oxygen from an oxygen generation system instead of normal combustion gas at a stoichiometric ratio of fuel so that greenhouse gases are minimized. Since normal combustion air consisting of about 80% nitrogen consumes significant heat, which is a loss to the emissions, the use of oxygen from the oxygen generating system reduces the heat loss to the emissions, and in a more effective way the heat of the burner It can be applied to the superheater. In another embodiment, both the secondary and main burners are supplied oxygen from an oxygen production system at stoichiometric ratios.

The heated steam evaporates to steam at the steam outlet, and the steam is delivered to the superheater, where the auxiliary burner continuously provides added heat and energy to improve the quality of the steam produced. Steam from the superheater can then be supplied to the turbine. In one embodiment, the steam is returned from the turbine to the reheat device, where it is placed in the presence of heat and energy provided by both the primary and secondary burners, and is sent back to the turbine. As a result of the convective flow generated by the auxiliary burner, heat or energy is typically added to the steam in the region where the low flow oxygen supply burner has a heat and energy gap, otherwise the water in the boiler is cooled. The convection stream raises the temperature of the steam above the saturation point to produce the desired quality and amount of steam. Auxiliary burners provide added heat or energy, allowing for more consistent, consistent heating of steam. In this way, properly heated steam is provided to the turbine to allow the turbine to operate in an effective and proper manner.

In another embodiment of the present invention, one or more auxiliary burners are provided so that the heat and energy applied to the overheating element can be more carefully controlled, if necessary. In addition, in a preferred embodiment, the boiler of the present invention can be generated to produce greater heat or energy than necessary. In such an embodiment, cooling and other elements known to those skilled in the art are provided to bring the vapor to the desired heat and energy level, or to attenuate it to the desired heat and energy level. Those skilled in the art will appreciate that the use of a cooling element to produce steam with the desired specificity is more effective than trying to use a heating element that heats the steam in the boiler to the desired level.

In another embodiment of the present invention, a burner is used as a nozzle or port for controlling the superheat temperature of the steam by introducing recycled flue gas. It will be appreciated that recycled flue gas is most useful when integrated with the use of carbon-based fuels and oxygen, including fossil fuels, in which burners are ignited in the furnace section of the boiler. Due to the reduced volume of flue gas from the combustion process and the higher radiant heat transfer from the process, it may be advantageous to use recycled flue gas to control the temperature of the superheated vapor. In this embodiment, the recycled flue gas is used to control the steam temperature in the boiler by tempering or adding a volume to the boiler's convection zone.

Another way to control the superheated steam temperature (or supercritical) is to introduce recycled flue gas at the auxiliary burner tip. By using flue gas as a carrier gas for pulverized coal or other carbon based fuels including fossil fuels, some or all of the required flue gas tempering gases can be introduced at the tip of the auxiliary burner. This is also in harmony with the aspects of the oxygen and carbon based fuel combustion burners. In these systems, it is desirable to exclude the introduction of any nitrogen.

In addition, by using recycled flue gas to propel the coal (substantially no nitrogen when the product used is obtained from oxygen and carbon based fuel combustion systems), this system once again provides superheated steam temperature control. Can be achieved. In another embodiment, another portion of the flue gas is introduced at the upper burner or nozzle to complete control of the system.

Further details of the invention are provided in the following description and claims, and are illustrated in the accompanying drawings.

1 is a schematic diagram of a boiler incorporating the device of the present invention;

Although the present invention may have various forms of embodiments, there are shown a number of existing preferred embodiments which are described in detail below. It is to be understood that this disclosure is to be considered as illustrative of the invention and is not intended to limit the invention to the specific embodiments illustrated. In addition, it is to be understood that the title of this chapter ("Examples") of the present application is at the request of the United States Patent Office and does not limit the subject matter described herein.

Referring to the drawings, a boiler 10 is shown that includes a series of water tubes 12, which together include a water wall 13. Boiler 10 also includes one or more main burners 14 disposed in main burner area 15 connected to a source of fuel 16 and air 18. In a preferred embodiment of the present invention, substantially pure oxygen is provided instead of using air 18 which must be pumped into the boiler in increased amounts (to produce a stoichiometric fuel to oxygen ratio in the burner). When using oxygen, it is to be understood that the pressurized flow is not necessary because the stoichiometric ratio for the fuel is more easily produced. These systems only require pure oxygen to allow complete combustion of the fuel. In such a system, the generation of harmful greenhouse gases is reduced in that nitrogen, which is a major component of air but not pure oxygen, does not burn to produce NO _x . If further reductions in greenhouse gases are desired, it will be appreciated that greater oxygen purity is required. Although the term "substantially pure oxygen" has been used in various places herein, the skilled artisan will provide the exact ratio of fuel and oxygen for the product and the desired combustion, without the purity of the oxygen deviating from the novel scope of the invention. It will be appreciated that it may change as needed.

The water wall 13 in the boiler 10 consists of a myriad of water tubes 13a extending from the main burner area 15 to the upper area of the boiler 10. Boiler 10 may further include superheater 20 and / or reheater 21 of a type well known in the art. This superheater 20 is generally fed with steam produced in the boiler 10 in the steam delivery zone 22. The steam passes through the superheater 20, and the convection flow transfers heat and energy radiated from the water tube 13a around and on the superheater 20 and the steam delivered therein to transfer energy or heat from combustion. Heat. The reheater 21 is typically supplied with steam returning from the turbine to the boiler, which requires additional heating before returning to the turbine for further use. This heat or energy is transferred from the steam, causing its temperature to rise above the saturation point of the steam, making the steam more suitable for use in a turbine. It will be appreciated that steam having too high temperature and / or too much energy may be attenuated as needed, including a cooling feature, for the desired task.

As a further feature, the boiler 10 includes an auxiliary burner 24, which may be located above the conventional burner area 15 of the boiler 10 and below the steam delivery area 22. In one embodiment, one or more auxiliary burners 24 are disposed in the superheat zone 26. In another embodiment, the auxiliary burner 24 is disposed at various locations around the boiler 10 to allow for more appropriate control of heat or energy.

In this way, heat or energy is added to produce a greater quality and / or amount of steam. In addition, the addition of the auxiliary burner 24 in the superheated or reheated region 26 allows for greater amounts of burner energy used to heat the steam, not solely to heat the water. Since less energy is needed to add heating or energy to the steam than to water, the energy of the auxiliary heater 24 is greater than the heat or energy generated in or near the region where the main burner 14 is disposed. It is more easily converted to power within the turbine.

As will be appreciated by those skilled in the art, the auxiliary burner 24 may be significantly smaller than the main burner 14, but in an oxygen environment than the larger additional main burner 14 disposed in the main burner area 15, Resulting in a greater quantity and quality of steam. It should also be understood that the use of a large main burner 14 in both the main burner area and the above can also be used without departing from the novel scope of the present invention. In addition, the number of auxiliary and main burners 24, 14 in boiler 10 can be changed without departing from the novel scope of the present invention. The type, size and number of burners depends on the quality and quantity and application of the desired steam. Although FIG. 1 illustrates the use of one burner 24, it is understood from the above description that one burner 24 or any number of burners 24 may be replaced without departing from the novel scope of the present invention. Could be. It will be appreciated that modifications may be made to help control the temperature, such as to enable the use of less heat or energy required or desired, and to add more heat or energy as needed.

In addition, in conventional boilers and the present invention, without departing from the scope of the present invention, the steam has greater heat than desired or necessary, is produced at higher quality, and then, as will be appreciated by those skilled in the art. It will be appreciated that by using cooling means such as a device to bring the delivery conduit into contact with the coolant, it can be cooled to the desired heat, energy and saturation point.

When the reduction of flue gas from the use of oxygen and carbon based fuels (such as fossil fuels) or the increased radiant heat transfer rate is too high, to control the superheat temperature, the recycled flue gas is subjected to an increase in the gas volume of the section. To provide proper dispersion or to temper the combustion gas temperature to cool the superheated tube. Each application enables the control of superheated steam temperature in the tube. Flue gas may be introduced for superheat temperature control purposes at the proposed location 24 of the additional burner (if the superheat temperature is too low) by use of a nozzle or port device. Alternatively, in the fuel source 16, there is a coal mill in this embodiment as an additional tool to prevent the introduction of oxygen and nitrogen into the carbon based fuel combustion system.

As will be appreciated by those skilled in the art, the exact location and requirements for the amount of additional heating or cooling of the superheated steam tube will vary depending on the structure and size of the boiler. Embodiments of the present invention focus on controlling the temperature of superheated steam by adding or subtracting heat in the convection path of the boiler. In particular, the use of increased gas volume or tempering of flue gas in the superheat zone of the boiler can be beneficial when used in conjunction with oxygen and carbon based fuel combustion systems.

While illustrative embodiments of the invention have been illustrated and described, it should be understood that various changes and substitutions may be made by those skilled in the art without departing from the novel concept and scope of the invention.

Claims (13)

At least one main burner for initial heating of water, the main burner being provided with a low flow rate of oxygen to the boiler fuel; A water tube assembly located between the main burner and the boiler steam outlet, wherein one end of each water tube is adjacent to the main burner and the other end is adjacent to the boiler steam outlet; And At least one auxiliary burner located between said main burner and said boiler steam outlet for producing energy for superheated steam; Boiler comprising. The boiler of claim 1 wherein the boiler comprises two auxiliary burners. The boiler of claim 1, wherein the auxiliary burner is supplied with fuel and oxygen. The boiler of claim 1, wherein the boiler comprises one or both of a superheater or a reheater connected to the steam outlet to transfer steam. 5. The boiler of claim 4, wherein said auxiliary burner is located adjacent said superheater. 5. The boiler of claim 4, wherein the auxiliary burner is located adjacent to the reheater. At least one main burner for initial heating of water; A water tube assembly located between the main burner and the boiler steam outlet, wherein one end of each water tube is adjacent to the main burner and the other end is adjacent to the boiler steam outlet; At least one superheater or reheater connected to the steam outlet to deliver steam; And Two auxiliary burners for producing heat or energy for increased superheated steam in a boiler, comprising: an auxiliary burner located between the main burner and the steam outlet; Boiler comprising. 8. The boiler of claim 7, wherein the auxiliary burner is supplied with fuel and oxygen. In a method of retrofitting an existing burner to remove greenhouse gases, Supplying oxygen to at least one main burner of the boiler; Providing at least one auxiliary burner for the boiler, the auxiliary burner being located above the main burner area of the boiler; And Operating a boiler such that fuel of a primary burner and an auxiliary burner reacts with the supplied oxygen to combust; Burner retrofit method comprising a. 10. The method of claim 9, comprising providing superheated steam to a superheated region of a boiler and placing the at least one auxiliary burner adjacent to the superheated region. At least one main burner for initial heating of water, the main burner being located in the main burner area and having a low flow rate of oxygen supplied to the boiler fuel; A water tube assembly located between the main burner and the boiler steam outlet, wherein one end of each water tube is adjacent to the main burner and the other end is adjacent to the boiler steam outlet; A convection type superheater connected to the steam outlet to transfer steam; And At least one nozzle or port in fluid communication with the flue gas and adjacent to the superheater to control the temperature of the steam in the superheater; Boiler comprising. At least one main burner for initial heating of water, the main burner being located in the main burner area and having a low flow rate of oxygen supplied to the boiler fuel; A water tube assembly located between the main burner and the boiler steam outlet, wherein one end of each water tube is adjacent to the main burner and the other end is adjacent to the boiler steam outlet; And A convection type superheater connected to the steam outlet to transfer steam; And a recycled flue gas adjacent to said superheater for controlling the temperature of the steam in said superheater. At least one main burner for initial heating of water, the main burner being located in the main burner area and having a low flow rate of oxygen supplied to the boiler fuel; A water tube assembly located between the main burner and the boiler steam outlet, wherein one end of each water tube is adjacent to the main burner and the other end is adjacent to the boiler steam outlet; And A convection type superheater connected to the steam outlet to transfer steam; And a boiler using flue gas recycled as a carrier gas for fuel delivery as a process of avoiding introducing nitrogen into the carrier gas for the carbon-based fuel.

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