KR20120039548A - System for heating a primary air stream - Google Patents

Abstract

The system for heating the primary air stream in the steam generation process includes at least one primary air heat exchanger for heat exchange between the process fluid and the primary air stream of the primary air heat exchanger (s).

Description

System for heating the primary air stream {SYSTEM FOR HEATING A PRIMARY AIR STREAM}

The present invention relates generally to a system and method for heating a primary air stream in a steam generation process, including a steam generator, such as a coal fired boiler, which includes steam for heating the feedwater to increase efficiency. Condensate and feed heating systems extracted from the stage and part of the power plant using a steam powered turbine generator can be formed.

In the steam generation process, there is generally one or more steam generators that can be ignited by various types of fuels such as coal and biomass, boilers being one example. Such boilers for steam generation are known and may form part of a power plant that uses steam to drive one or more steam turbine generators.

In general, the steam generation process involves the supply of a large number of air streams for various purposes to and around the process, and typically, some of the air streams are more closely or more closely to the place of use. By temperature matching, it is heated before being used to ensure the best use efficiency.

Typically, the steam generation process includes a "primary air stream" for the main purpose, which is generally for use in fuel delivery and transportation. Conventionally, such primary air streams are heated by heat exchange with a hot flue gas stream in a gas-to-air heat exchanger such as a regenerative gas air heater. However, due to the high pressure characteristic of the primary air flowing therein, the leakage of primary air from the regeneration gas air heater can be as high as 30%. In addition, the temperature of the hot flue gas stream conventionally used in such air heaters is much higher than often needed, especially when the fuel water content is low. Thus, a tampering air source is needed to lower the temperature of the primary air stream after heat exchange, which is not efficient. In addition, tampering air that bypasses air heaters can cause a high backend gas temperature.

It is an object of the present invention to eliminate one or more of the above mentioned disadvantages and to provide a better system for heating the primary air stream in a steam generation process.

According to a first aspect of the present invention, a system for heating a primary air stream in a steam generation process is provided, wherein the system provides for heat exchange between the primary air stream of the primary air heat exchanger (s) and the process fluid. At least one primary air heat exchanger.

The process fluid can be water and / or steam, for example. The process fluid may be water and / or steam from the steam generator of the steam generating process. The process fluid can be, for example, water from between the condenser outlet and the economizer outlet of the steam generator in the steam generating process.

By heating the primary air stream with process fluids such as water and / or steam from the steam generation process rather than the hot exhaust gas stream, the problem of primary air leakage from the regeneration gas air heater can be avoided and heat exchange can be avoided. It can be controlled reliably.

The term "primary air stream" as used herein may include one or more primary air streams in series, in parallel, or both. Embodiments of the invention as described below may be applied to a single primary air stream, or to each primary air stream in a plurality of primary air streams, or may vary over a plurality of primary air streams. . Thus, while the invention has been described with reference to a single primary air stream, the invention is not so limited.

The primary air stream may comprise any combination in which one or more other components, such as atmospheric, regenerating gas, or quasi-oxygen or pure oxygen streams are optionally added so that their proportion is from 0 to 100%. The primary air stream is required to at least partially assist in the delivery and / or delivery of fuel into the steam generator, and optionally to support combustion.

Where the primary air stream comprises two or more primary air streams, each primary air stream is the same or includes, but is not limited to, flow rate, flow rate, temperature, pressure, oxygen content and regeneration gas content. Different properties and / or compositions.

If the primary air stream comprises two or more primary air streams, each primary air stream may be heated identically or differently, and may be heated by the same or different number of primary heat exchangers. Can be.

If the primary air stream comprises two or more primary air streams, two or more of the air streams may be at any time before, during or after their intended use or destination. It can be integrated after being heated according to the invention.

If the primary air stream comprises two or more primary air streams, the primary air streams can be passed to the steam generator individually and / or in any combination.

In one embodiment of the present invention, a plurality of primary air streams are provided, each primary air stream providing and / or delivering a separate fuel stream to a steam generator, such as a plurality of comparable fuel mills, each fuel The mill delivers the individual fuel streams to the boiler. In this way, each primary air stream can be controlled individually and can provide great control flexibility in providing, transporting and feeding the entire fuel into the steam generator.

The system may include two or more primary heat exchangers in series, in parallel, or both, such that they also exchange heat with one or more primary air streams in series, in parallel, or both, The system may include any combination of any number of primary air streams and primary air heat exchangers.

In one embodiment of the invention, the primary air heat exchanger (s) comprises at least one high pressure heat exchanger and at least one low pressure heat exchanger. The terms "high pressure" and "low pressure" are known to those skilled in the art, in particular in the context of steam generation processes, including steam generators such as boilers and feed heating / heat recovery systems.

The process fluid may be provided in one or more streams. The plurality of process fluid streams may be provided in series, in parallel, or both, and, optionally, from a single source or from a plurality of sources. Further, optionally, the process stream may be provided in one or more process fluid circuits, separated or connected, optionally in a plurality of individual circuits, each for heat exchange between the process fluid stream and the primary air stream. The circuit optionally passes through individual primary air heat exchangers.

The process fluid may be a process liquid. The process liquid can be any liquid or combination of liquids available for heat exchange, including water, ammonia, alcohols, hydrocarbons, and the like. Preferably, the process liquid is wholly or substantially water and optionally comprises one or more additives or other minor components known in the art.

The process stream may be heated by any direct or indirect process, device, unit or apparatus (to provide heat to the primary air stream of the primary air heat exchanger (s) subsequently). This may include direct heating by one or more boilers or the like, or heat exchange with a hot fluid stream, such as a hot exhaust stream or an exhaust gas stream.

Because the flow of process fluids contemplated for use in accordance with the present invention, such as process liquids, can be easily controlled, the system of the present invention can better control the heat of the primary air stream. In order to achieve the correct temperature of the primary air stream prior to use in the steam generation process, tempering air source supplies may not be needed with the primary air stream. Preferably, no primary air stream gas to air heater is required.

In one possible embodiment of the invention, the process fluid is water and / or steam from a steam generator or boiler of a steam generating process. For example, the process fluid may be water collected at a downstream point of the condensation pump of the steam generation process.

In one possible embodiment of the invention, the process liquid is feed water for a steam generator. Such a steam generator may be a boiler, optionally including one or more boilers, and optionally including an integrated steam generator economizer as is known in the art.

Such feedwater may be provided directly or indirectly from the feedwater stream to be processed by one or more steam generators of the steam generation process included in the present invention. Preferably, part of the feed stream is provided as process liquid for the system of the present invention. A portion thereof may be provided as a complete feed stream or preferably as a slip stream of the feed stream, which generally is a small portion of the complete feed stream.

According to another embodiment of the invention, the feed water is provided from the feed stream in a steam generating process between the steam condenser and the outlet of the steam generator economizer.

In another embodiment of the invention, the primary air heat exchanger (s) comprises at least one high pressure heat exchanger and at least one low pressure heat exchanger. The terms "high pressure" and "low pressure" are known to correspond to pressures downstream or upstream of the feed pump (s), respectively.

In coal fired steam generators or boilers, coal is typically ground in one or more grinders before being used in the boiler.

According to another embodiment of the invention, the primary air stream is heated by the primary air heat exchanger (s) and then passed through one or more grinders, typically through two or more grinders.

According to another embodiment of the invention, the primary air stream may be preheated by at least one separate process fluid preheat exchanger (in front of the main system for heating the primary air stream), wherein the heat for this is one or more. It may be provided by any suitable source, such as via heat exchange with an exhaust stream or an exhaust gas stream, optionally with a steam generator exhaust gas stream.

According to a second aspect of the present invention, there is provided a steam generation system comprising a steam generator, such as a boiler, and a system for heating a primary air stream as defined herein. Preferably, the steam generation system includes one or more steam generation processes as defined herein. In the steam generation system, preferably, the heated primary air stream is provided to one or more grinders of solid fuel, such as coal or biomass, for use in steam generation.

According to a third aspect of the invention, there is provided a method for heating a primary air stream in a steam generation process, wherein the heating method comprises heat from the process liquid to the primary air stream in the primary air heat exchanger (s). Passing the process fluid through at least one primary air heat exchanger for exchange.

Preferably, the method for heating a primary air stream in accordance with the present invention comprises heating the primary air stream using a system as defined herein.

The present invention includes all combinations of the various embodiments or aspects of the invention disclosed herein. It will be appreciated that any and all embodiments of the invention may be considered in conjunction with any other embodiment to describe further embodiments of the invention. In addition, any components of one embodiment may be combined with any and all other components of any other embodiment to describe further embodiments.

Hereinafter, embodiments of the present invention will be described by way of example only with reference to the accompanying drawings.
1 is a view including a first scheme of a system for heating a primary air stream according to an embodiment of the present invention,
2 is a view including a second structure of a system for heating a primary air stream according to a second embodiment of the present invention,
3 is a view including other embodiments of the present invention and a third structure of a system for heating a primary air stream.
For illustration purposes, a single reference number has been given to the line as well as to the steam delivered within that line.

1 shows a first structure A for a system for heating the primary air stream 2 in a steam generation process. In the first structure A, the steam generating process comprises a steam generator which is a boiler 4. The boiler 4 may comprise a plurality of inlets and outlets for the passage of a plurality of streams, in particular water feed into the boiler and steam out of the boiler. Most of these inlets, outlets and streams are not shown in FIG. 1 for clarity.

The fuel source for the boiler 4 in FIG. 1 is coal fed as a coal stream 6. Typically, coal stream 6 is pulverized in one or more grinders 8 to be provided to boiler 4 as pulverized coal stream 10.

In the first structure A of FIG. 1, the primary air stream 2 is used as an air stream entering the one or more mills 8. In order to realize the drying capacity in the grinding process, it is usually desirable to provide the primary air stream to the mill at elevated temperatures, such as above 150 ° C or above 200 ° C.

The first structure A of FIG. 1 shows at least one primary air heat exchanger 12 capable of heat exchange between the primary air stream 2 and the process liquid. The process liquid is provided as a process liquid stream 14 through the inlet (not shown) into the primary air heat exchanger 12 to provide a heated primary air stream 2a and a low temperature process liquid stream 14a. Do it. In addition, the first structure A of FIG. 1 shows the exhaust gas stream 16 from the boiler 4.

2 shows a second structure for heating a primary air stream according to a second embodiment of the invention. In the structure of FIG. 2, primary air with atmospheric characteristics and conditions can be provided, and / or it can be partly or substantially regenerated gas (derived from the exhaust gas), which generally reduces its pressure. Pass through a primary air fan (not shown) to raise and provide the first primary air stream 22.

The first primary air stream 22 may be preheated by at least one separate process liquid preheat exchanger 24. The process liquid preheat stream 26 for providing heat to the initial primary air stream 22 may be heated directly or indirectly by any hot stream, unit, device or device. An example of heating of the process fluid preheat stream 26 is through heat exchange in the first flue gas heat exchanger 28, so that the process fluid preheat stream 26 passes through the first flue gas heat exchanger 28. To one exhaust gas exchange stream 30. Optionally, the path of process fluid preheat stream 26 passes through one or more other heat exchangers or other units or devices.

The preheat exchanger 24 may have a primary air stream 22, such as from an ambient temperature that may be about 20 to 25 ° C. to a high temperature of at least 50 ° C. or a higher temperature, such as less than about 100 ° C., nearly 100 ° C. or more than 100 ° C. Is raised to provide a preheated primary air stream 22a.

The second structure of FIG. 2 shows that the preheated primary air stream 22a is split into two equal or unequal part streams 22b and 22c at the connection 27. Any suitable splitter or separator may be used in the connector 27 to produce the partial stream, and optionally one or more more partial streams shown in FIG. 2 may be generated, such as stream 22d.

In the path of the partial streams 22b, 22c, FIG. 2 shows two primary air heat exchangers, each of which is a first low pressure heat exchanger 32a, 32b and a subsequent high pressure heat exchanger 34a, 34b. And are arranged in series, respectively.

The low pressure heat exchangers 32a, 32b are provided with a process liquid as the first process liquid streams 36a, 36b, which streams are identical in any characteristic, composition or property, such as flow rate, flow rate, temperature, pressure, etc. Or different. Preferably, the process liquid of the first process liquid streams 36a, 36b is one or more slip streams of the main feedwater stream that are subsequently processed by the steam generator of the steam generating process. In FIG. 2, the steam generator is shown as a coal fired boiler 40.

The first process liquid streams 36a and 36b may provide heat to the preheated primary air streams 22b and 22c which enter the low pressure heat exchangers 32a and 32b through inlets, thereby providing a high temperature primary air stream. 22d, 22e, and then the hot streams 22d, 22e pass through the inlets of the high pressure primary air heat exchangers 34a, 34b. The low pressure heat exchangers 32a and 32b may further raise the temperature of one or both of the preheated primary air streams 22b and 22c by an additional 50 ° C. or 100 ° C. or more, the temperature rise being While the same or different, the first process liquid streams 36a, 36b are provided through the outlets of the low pressure heat exchangers 32a, 32b as the low temperature first process liquid streams 42a, 42b.

The high pressure primary air heat exchanger 34a, 34b is provided with process liquid as a second process liquid stream 44a, 44b through a suitable inlet. In addition, the second process liquid streams 44a, 44b may also be the same or different in any feature, composition, or nature, such as flow rate, flow rate, temperature, pressure, and the like. The streams may also be provided from the same or different sources as the first process liquid streams 36a and 36b.

Preferably, the second process liquid streams 44a, 44b are part of the main feedwater stream that is subsequently processed by the steam generator of the steam generating process, which is like a slip stream. Optionally, the second process liquid stream 44a, 44b is further processed to a generally low temperature first process liquid stream 42a, 42b, in particular after raising its pressure and / or temperature. From the first process liquid streams 42a, 42b.

In order to provide two final primary air streams 22f and 22g, respectively, from the outlets of the high pressure primary air heat exchangers 34a and 34b, the second process liquid streams 44a and 44b are the hot primary Provide heat to the air streams 22d and 22e. The final primary air streams 22f and 22g may have a temperature of 200 ° C. or higher, but not limited to this.

Each final primary air stream 22f, 22g may then provide a primary air stream into two separate mills 46a, 46b provided by two coal streams 48. The mills 46a and 46b provide two milled coal streams 50 into the boiler 40 in a manner known in the art.

In addition to individually controlling the heating of each of the partial streams 22b, 22c, any such other partial streams are delivered to one or more additional grinders, thereby providing a fuel and fuel conveyance stream into the boiler 40. Greater flexibility can be provided in the overall feed, especially in the mill exit temperature of each coal stream 50. Typically, by providing four to ten mills, the system of the present invention can provide very tight control over each fuel line connected into the boiler 40, so that other variables, such as overall steam generator demand, may vary. When the efficiency is maximized.

The high pressure primary air heat exchangers 34a, 34b provide a second, low temperature process fluid stream 52a, 52b that can be passed directly or indirectly into the boiler 40 for use as boiler feed water.

The cold first and second process fluid streams 42a, 42b and 52a, 52b are used to provide a complete feedwater stream 56 into the boiler 40. The process fluid streams 36a, 36b and 44a, 44b After providing any slip stream (s) that provide a, it may be integrated with one or more other feed streams 54, such as most or remaining main feed streams. 2 shows two schematic inlet streams 57 representing possible regression feedwater slip streams.

The boiler 40 generates steam that can be used in many processes, including, but not limited to, steam powered turbine generators. The boiler 40 also produces an exhaust or exhaust gas stream 60. The exhaust gas stream 60 may be provided in one or more heat exchangers known in the art. Any cold exhaust gas stream 66 may still have sufficient residual heat to heat another stream in the heat exchanger 28, such as the process fluid preheat stream 26, as the exchanger stream 30.

The first and second structures shown in FIGS. 1 and 2 may further comprise apparatus, devices, units, streams, conduits, etc. for completing the steam generation process, which are not shown for clarity. For example, FIG. 3 shows that flue gas 60 is split at first connection 61 to pass secondary air stream heat exchanger 62 to heat secondary air stream 63 and second connection 65. It is shown passing through one or more other heat exchangers 64, such as one or more process liquid economizers, before being reintegrated in. The cold exhaust gas stream 66 from the second connection 65 passes through an electrostatic precipitator (ESP) 82 and an induction fan 84, followed by a passage through the appropriate inlet into the downstream process fluid heat exchanger 86. do. The downstream process fluid heat exchanger 86 may extract any remaining available heat energy from the exhaust gas with the downstream process fluid in the first process circuit 100.

The first process circuit 100 passes through a suitable inlet into the downstream process fluid heat exchanger 86 through a suitable inlet to provide a hot downstream process fluid stream 104 to the second fluid conduit 104 through a suitable outlet. At least a process fluid in the first downstream process fluid conduit 102. At the first circuit connection 106, the hot downstream process fluid stream 104 is divided into secondary air heating stream 108 and primary air heating stream 110 in a range of 0 to 100% by a suitable controller. Can be.

The secondary air heating stream 108 is passed through a suitable inlet to the secondary air preheat exchanger 112 to provide heat exchange with the original secondary air stream 90, thereby regenerative gas secondary air heater 62. A portion of the preheating to the secondary air is provided prior to subsequent heating of the secondary air stream 63 by means of.

Likewise, the primary air heating stream 110 may provide a portion of the preheating for the first primary air stream 92 (after passing through the primary air fan 94) in the primary air preheat exchanger 114. Thus, by providing a primary air stream 70 which is subsequently heated in one or more primary air heat exchangers 72 by a process liquid stream 74 according to the system of the present invention. To provide a preheated primary air stream 76 that passes into the mill 80.

The downstream process fluid of the downstream process fluid circuit 100 may be any suitable liquid, gas or combination thereof and is generally low pressure and is generally circulated by one or more suitable circulation pumps in the circuit 100. Can be.

The primary and secondary air preheat exchangers 112 and 114 provide the cold return streams 116 and 118, respectively, which may be recombined to provide process fluid in the first downstream process fluid conduit 102. The downstream process fluid heat exchanger 86 provides a low temperature flue gas stream 88.

The first primary air stream 92 and the secondary air stream 90 may be provided from a single air source stream 94 before being split by a suitable controller. The source of the stream 94 may be atmospheric, regeneration gas, or any combination thereof, optionally wherein the regeneration gas is optionally at least partially by the cold exhaust gas 88 after other processing. Is provided.

In a first alternative, the hot downstream process fluid stream 104 in the second fluid conduit 104 uses a heat exchanger on the single air source stream 94 for heating before the primary and secondary air are split. To pass.

The downstream process fluid circuit 100 increases the use of available thermal energy in the flue gas to provide part of the preheating to the primary and secondary air streams in order to maximize the efficiency of the steam generation system shown in FIG. 3. Do it.

The structures of FIGS. 1-3 show the heating of the primary air stream by the use of process liquid, optionally provided in one or more streams, optionally with one or more individual process liquid preheating streams. In this way, the system of the present invention is any primary, which is a gas-to-air heater, in particular a regenerative air heater, capable of leaking about 30% of the primary air stream at the air heater inlet due to the high pressure of the primary air stream. The use of an air heat exchanger can be avoided. In addition, since the temperature of the primary air stream can be precisely controlled by the use of process liquid (s), a tempering air source or a tempering air system can be avoided.

In addition, process liquids, in particular water, are used in the structure shown in FIGS. 1-3 to provide heat to all heat exchangers for the primary air stream. Water can provide significant advantages over steam, even with small pipes, which can be transported, such as around the circuit, with minimal pressure loss over distance. By carefully selecting and controlling the temperature difference and the flow of water in the first air heat exchangers, it is possible to optimize the heat exchange from the process liquid such as water to the primary air stream.

In addition, since the specific heat capacity of water is much higher than the specific heat capacity of gases such as air, the flow of process liquids such as water can be minimized as well as the OPEX of the system can be reduced.

In addition, corrosion, erosion and adhesion are not potential problems for these process liquid PA heaters because the process liquid PA heaters are not exposed to ash borne corrosive flue gases.

In an exemplary embodiment, boiler feed water is used from the condenser outlet to the economizer outlet as the heat source. The primary air heaters are water PA heaters.

If the system is considered in conjunction with a once through boiler with a no pump start up system, the economizer outlet water temperature may be much lower than the saturation temperature during boiler startup. As a heat source it is also possible to consider not only water to the economizer outlet, but also to include both water and steam from a boiler to a point. In this case, the primary air heaters are water / vapor PA heaters.

Another interesting advantage can arise from the early service of coal milling systems. In general, the boiler is started with oil to raise the boiler load to a certain level so that the exhaust gas temperature is high enough to heat the primary air to a temperature sufficient for the drying process of the milling system. By means of a water / steam PA heater, the required primary air temperature can be realized at lower loads compared to conventional designs in which primary air is generated from a gas / air heater. By early service of the milling system, the pulverized coal can be burned at a low boiler output instead of oil, so that the oil consumption can be further reduced. Since the oil price is considerably higher than coal, this is very advantageous if the boiler is frequently started and stopped.

Claims (22)

A system for heating a primary air stream in a steam generation process,
One or more primary air heat exchangers for heat exchange between the process fluid and the primary air stream in the primary air heat exchanger (s),
Heating system.
The method of claim 1,
Comprising two or more primary air heat exchangers,
Heating system.
The method of claim 2,
The primary air heat exchangers include one or more high pressure heat exchangers and one or more low pressure heat exchangers,
Heating system.
The method according to any one of claims 1 to 3,
The process fluid comprises two or more streams,
Heating system.
The method of claim 4, wherein
Each process fluid stream passes through a separate primary air heat exchanger,
Heating system.
6. The method according to any one of claims 1 to 5,
No tempering air source supply is provided into the primary air stream,
Heating system.
The method according to any one of claims 1 to 6,
The primary air stream comprises two or more primary air streams, each primary air stream including, but not limited to, the same including flow rate, flow rate, temperature, pressure, oxygen content and regeneration gas content. Or include different features, properties and / or compositions,
Heating system.
The method of claim 7, wherein
Each primary air stream is delivered to an individual mill
Heating system.
The method according to claim 7 or 8,
Each primary air stream is individually heated by separate primary air heat exchanger (s),
Heating system.
The method according to any one of claims 1 to 9,
The process fluid is water and / or steam from the boiler of the steam generation process,
Heating system.
The method according to any one of claims 1 to 10,
The process fluid is a process liquid,
Heating system.
The method of claim 11,
Wherein the process liquid is water,
Heating system.
The method of claim 12,
The process liquid is a feedwater for a steam generator,
Heating system.
The method of claim 13,
Wherein the process liquid is part of a feedwater stream processed by a steam generator of a steam generating process,
Heating system.
15. The method of claim 14,
Wherein said process liquid is a slip stream of a feedwater stream processed by a steam generator of a steam generation process,
Heating system.
The method according to any one of claims 13 to 15,
The feed water is provided from the feed stream in the steam generation process between the outlet of the steam generator economizer and the steam condenser.
Heating system.
The method according to any one of claims 1 to 16,
The primary air stream is heated by the primary air heat exchanger (s) and then sent to one or more grinders,
Heating system.
The method according to any one of claims 1 to 17,
The primary air heat exchanger (s) is not a gas to air heater,
Heating system.
The method according to any one of claims 1 to 18,
Wherein the primary air stream is preheated by one or more separate process fluid preheat exchangers,
Heating system.
A steam generator, such as a boiler and a primary air stream heating system as defined in any of claims 1 to 19,
Steam generation system.
A method for heating a primary air stream in a steam generation process,
At least passing the process fluid through the one or more primary air heat exchangers for heat exchange from the process liquid to the primary air stream in the primary air heat exchanger (s),
Heating method.
The method of claim 21,
18. The method comprising heating the primary air stream using a system as defined in any of claims 1 to 17,
Heating method.

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