WO2014064949A1

WO2014064949A1 - Boiler system

Info

Publication number: WO2014064949A1
Application number: PCT/JP2013/053097
Authority: WO
Inventors: 立季小林; 智浩大久保; 和弘上永; 宏之畑中; 草平秋永
Original assignee: 三浦工業株式会社
Priority date: 2012-10-22
Filing date: 2013-02-08
Publication date: 2014-05-01
Also published as: JP6056371B2; JP2014085038A

Abstract

Provided is a boiler system having improved heat efficiency when a closed-type condensate recovery apparatus and a boiler are combined. A boiler system (1) provided with: a through-flow boiler (10) for generating steam by heating feed water using combustion gas; a closed-type condensate recovery apparatus (20) for recovering, at high temperature and high pressure, condensate produced by condensing steam generated by the through-flow boiler (10), and supplying the condensate to the through-flow boiler (10); and a feed water heater (30) for performing heat exchange between combustion gas discharged from the through-flow boiler (10) and condensate supplied to the through-flow boiler (10), the boiler system further provided with an air heater (40) for causing the combustion gas heat-exchanged by the feed water heater (30) and combustion air supplied to the through-flow boiler (10) each to circulate in the reverse direction to perform heat exchange.

Description

Boiler system

The present invention relates to a boiler system. This application claims priority based on Japanese Patent Application No. 2012-233265 for which it applied to Japan on October 22, 2012, and uses the content here.

2. Description of the Related Art Conventionally, there has been proposed a drain recovery apparatus that supplies steam generated by a boiler to a load device, recovers drain generated from the steam used as a heat source in the load device, and reuses it as water supply to the boiler.
As such a drain recovery device, the drain generated in the load equipment is recovered in an open drain recovery tank that is open to the atmosphere and supplied to the boiler, and a sealed type having pressure resistance There is known a closed-type drain recovery device that recovers drain in a high-temperature and high-pressure state in this drain recovery tank and supplies the drain to a boiler (for example, see Patent Document 1).
In the closed drain recovery device, water can be supplied at a higher temperature than in the open drain recovery device, so that the fuel consumption of the boiler can be reduced and the operating cost of the boiler can be reduced.

By the way, when a boiler system is configured by combining a closed-type drain recovery device and a boiler, heat recovery from the combustion gas used to generate steam in the boiler cannot be sufficiently performed, and the thermal efficiency of the boiler system May fall. In other words, in a boiler system, by providing an economizer that exchanges heat between water supplied to the boiler and the combustion gas that has been used to generate steam, heat recovery from the combustion gas can be achieved. It is improving. However, when drain is supplied to the boiler, the temperature of the feed water introduced into the economizer is high, so that heat cannot be sufficiently recovered from the combustion gas.

Therefore, in order to improve the thermal efficiency of the boiler system, an air heater for exchanging heat between the combustion gas and the combustion air supplied to the boiler as disclosed in Patent Document 2 is provided together with the economizer. Can be considered.

JP 2006-105442 A JP-A-61-59114

However, when the boiler system includes an economizer and an air heater, the air heater may not be able to sufficiently recover heat from the combustion gas whose temperature has been recovered by the economizer.

Therefore, an object of the present invention is to provide a boiler system that can further improve thermal efficiency when a closed type drain recovery device and a boiler are combined.

The present invention relates to a once-through boiler that generates steam by heating feed water with combustion gas, and a drain that is generated by agglomeration of steam generated by the once-through boiler is recovered in a high-temperature and high-pressure state, and the drain is recovered from the once-through boiler. A boiler system comprising: a closed-type drain recovery device that supplies heat to the combustion gas discharged from the once-through boiler, and a feed water heater that exchanges heat between the drain supplied to the once-through boiler. The present invention also relates to a boiler system further comprising an air heater that performs heat exchange by circulating the combustion gas heat-exchanged in the feed water heater and the combustion air supplied to the once-through boiler in opposite directions.

The heat recovery rate of the air heater is preferably 10% or less.

The temperature of the combustion air introduced into the air heater is −20 ° C. to 80 ° C., and the temperature of the combustion air after heat exchange in the air heater is 200 ° C. or less. It is preferable.

In addition, the once-through boiler is a rectangular parallelepiped can body, and a plurality of can bodies disposed in the longitudinal direction and the width direction of the can body at predetermined intervals while being arranged extending in the vertical direction inside the can body. A water pipe, a burner which is provided on a first side surface located on one end side in the longitudinal direction of the can body, and injects and burns fuel in a substantially horizontal direction, and is located on the other end side in the longitudinal direction of the can body It is preferable to provide an exhaust pipe that is provided on the second side surface and discharges combustion gas generated inside the can body.

The exhaust pipe is connected to the combustion gas discharge part, and is provided with an upward discharge path part through which the combustion gas flows upward, and provided downstream of the upward discharge path part, and the combustion gas is directed downward. A downward discharge passage portion that circulates, wherein the feed water heater is provided in the upward discharge passage portion, the air heater is provided in the downward discharge passage portion, and combustion air is directed from below to above It is preferable to distribute toward.

According to the drain system of the present invention, when a closed type drain recovery device and a boiler are combined, the thermal efficiency can be further improved.

It is a figure showing the composition of the boiler system concerning one embodiment of the present invention. It is the figure which showed typically the once-through boiler, feed water heater, and air heater which comprise a boiler system. It is a vertical direction sectional view of the can of a once-through boiler. FIG. 4 is a sectional view taken along line AA in FIG. 3. It is a figure which shows the temperature distribution of the combustion gas and the combustion air in a countercurrent type heat exchange and a parallel flow type heat exchange.

Hereinafter, a preferred embodiment of a boiler system of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a boiler system 1 according to an embodiment of the present invention. FIG. 2 is a diagram schematically illustrating the configuration of the once-through boiler 10, the feed water heater 30, and the air heater 40.
The boiler system 1 of this embodiment is provided with the boiler apparatus 70 comprised including the some once-through boiler 10, and the closed-type drain collection | recovery apparatus 20, as shown in FIG.

As shown in FIGS. 1 and 2, the boiler device 70 is generated by a plurality of once-through boilers 10, a feed water heater 30 and an air heater 40 attached to each of the plurality of once-through boilers 10, and a plurality of once-through boilers 10. And a connecting pipe 72 that connects the plurality of once-through boilers 10 and the steam header 71 to each other.

The once-through boiler 10 generates steam by heating the feed water supplied to the inside with combustion gas. In the present embodiment, the drain recovered by a drain recovery device 20 described later is supplied as feed water to the once-through boiler 10 (a plurality of water pipes).
Details of the once-through boiler 10 and the feed water heater 30 and the air heater 40 will be described later.

As shown in FIG. 1, the steam generated by the plurality of once-through boilers 10 is supplied to the steam header 71 through a connecting pipe 72. The steam header 71 stores the steam generated by the plurality of once-through boilers 10 and supplies the steam to the load device 50.
The load device 50 uses the steam generated by the once-through boiler 10 as a heat source, and performs heat exchange with the object to be heated.

The drain recovery device 20 recovers the drain produced by agglomeration of the steam generated by the once-through boiler 10 in the load device 50 in a high-temperature and high-pressure state, and again uses the recovered drain as feed water to supply the once-through boiler 10 again. To supply.
The drain recovery device 20 includes a drain tank 21, an open tank 22, a first steam supply line L1, a first drain supply line L2, a second drain supply line L3, a second steam supply line L4, and flash steam. A discharge line L5 and a makeup water supply line L6 are provided.

The drain tank 21 collects and stores the drain produced by agglomeration of part of the steam used for heat exchange in the load device 50. The drain tank 21 is constituted by a pressure vessel that has pressure resistance and can be sealed.

The open tank 22 is open to the atmosphere. The open tank 22 stores makeup water supplied to the once-through boiler 10. Further, the open tank 22 is introduced with flash steam generated from the drain in the drain tank 21.

The first steam supply line L <b> 1 connects the steam header 71 and the load device 50, and supplies the steam generated by the once-through boiler 10 to the load device 50.
The first drain supply line L <b> 2 connects the load device 50 and the drain tank 21, and supplies the drain generated in the load device 50 to the drain tank 21. In the first drain supply line L2, a steam trap 61, a check valve 62, and a motor valve 63 that discharge drain generated in the load device 50 and prevent discharge of steam are disposed.

The second drain supply line L3 connects the drain tank 21 and the once-through boiler 10 and supplies the drain accommodated in the drain tank 21 to the once-through boiler 10. In the present embodiment, the upstream end of the second drain supply line L <b> 3 is connected to the lower portion of the drain tank 21. Further, the downstream side of the second drain supply line L3 is branched so as to be connected to each of the plurality of cans 11.

A drain pump 64 and a drain supply valve 65 are arranged in the second drain supply line L3. The drain pump 64 boosts the drain supplied from the drain tank 21 and supplies it to the once-through boiler 10. The drain supply valve 65 is constituted by a motor valve and adjusts the amount of drain supplied from the drain tank 21 to the once-through boiler 10.

The second steam supply line L4 connects the steam header 71 and the drain tank 21. The second steam supply line L4 supplies the steam generated in the once-through boiler 10 to the drain tank 21 and adjusts the pressure inside the drain tank 21. A pressure adjustment valve 66 and a motor valve 67 are disposed in the second steam supply line L4.

The flush steam discharge line L5 connects the drain tank 21 and the open tank 22, and discharges the flash steam generated in the drain tank 21 to the open tank 22. A pressure regulating valve 68 is disposed in the flash steam discharge line L5. When the pressure inside the drain tank 21 exceeds a predetermined pressure, the pressure regulating valve 68 releases the flash vapor to the open tank 22 side and reduces the pressure inside the drain tank 21.

The makeup water supply line L6 connects the open tank 22 and the drain tank 21 and supplies the water stored in the open tank 22 to the drain tank 21. A pump 69 is disposed in the makeup water supply line L6.

Next, the details of the once-through boiler 10 and the feed water heater 30 and the air heater 40 will be described. FIG. 3 is a vertical cross-sectional view of the can 11 of the once-through boiler 10. 4 is a cross-sectional view taken along line AA of FIG. 3, and is a horizontal cross-sectional view of the can 11.
As shown in FIGS. 3 and 4, the once-through boiler 10 includes a can 11, a plurality of water pipes 12, a connecting wall 13, a lower header 14, an upper header 15, a duct 16, a burner 17, And a cylinder 18.

The can body 11 is configured in a rectangular parallelepiped shape in a plan view.
The plurality of water pipes 12 are arranged extending in the vertical direction inside the can body 11 and are arranged at predetermined intervals in the longitudinal direction and the width direction of the can body 11.
In the present embodiment, the plurality of water tubes 12 are disposed along the longitudinal direction at the outer water tube group 12 a disposed along the side portion extending in the longitudinal direction of the can body 11 and at the center portion in the width direction of the can body 11. The central water pipe group 12b and the intermediate water pipe group 12c disposed between the outer water pipe group 12a and the central water pipe group 12b are classified.
The connection wall 13 connects the water pipes 12 arranged adjacent to each other in the outer water pipe group 12a.

The lower header 14 is configured by a rectangular parallelepiped container having a rectangular shape in plan view, and is disposed at the lower portion of the can 11. The lower header 14 is connected to lower ends of the plurality of water pipes 12. Drain is supplied to the lower header 14 from the drain recovery device 20, and drain is supplied from the lower header 14 to the plurality of water pipes 12.

The upper header 15 is configured by a rectangular parallelepiped container having a rectangular shape in plan view, and is disposed on the upper portion of the can 11. The upper header 15 is connected to the upper ends of the plurality of water pipes 12. Steam generated in the plurality of water pipes 12 is collected in the upper header 15. A connecting pipe 72 (see FIG. 1) is connected to the upper header 15, and the steam collected in the upper header 15 is supplied to the steam header 71 through the connecting pipe 72.

The duct 16 is connected to a lower portion of the first side surface 11 a located on one end side in the longitudinal direction of the can body 11. Connected to the upstream side of the duct 16 are a fuel supply unit 161 to which fuel gas is supplied and an air supply line AL (see FIG. 2) to which combustion air is supplied. The duct 16 mixes the fuel gas supplied from the fuel supply unit 161 and the combustion air supplied from the air supply path AL and supplies the mixed gas toward the inside of the can 11.

The burner 17 is disposed at a connection portion between the duct 16 and the can body 11 on the first side surface 11a. The burner 17 ejects a mixed gas in which combustion air and fuel are mixed from the duct 16 into the can 11 and burns the mixed gas.

The exhaust cylinder 18 is connected to the second side surface 11b located on the other end side in the longitudinal direction of the can body 11 (the side opposite to the side where the duct 16 is provided). The exhaust cylinder 18 discharges the combustion gas generated by burning the mixed gas inside the can 11.

In the present embodiment, as shown in FIG. 2, the exhaust cylinder 18 is bent from a first upward exhaust passage portion 181 extending upward from a connection portion with the can body 11 and an upper end portion of the first upward exhaust passage portion 181. A downward exhaust passage portion 182 extending downward, and a second upward exhaust passage portion 183 that is bent from the lower end portion of the downward exhaust passage portion 182 and extends upward.
According to the exhaust cylinder 18 described above, the combustion gas discharged from the can 11 circulates upward through the first upward exhaust passage portion 181, then flows downward through the downward exhaust passage portion 182, and It flows through the second upward exhaust passage 183 upward and is discharged to the outside.

The feed water heater 30 and the air heater 40 are provided in the exhaust pipe 18.
The feed water heater 30 performs heat exchange between the combustion gas discharged from the once-through boiler 10 and the drain supplied to the once-through boiler 10. In the present embodiment, the feed water heater 30 is disposed in the first upward exhaust path portion 181. More specifically, the feed water heater 30 is configured by disposing a part of the second drain supply line L3 (see FIG. 1) for supplying drain to the once-through boiler 10 in the first upward exhaust passage portion 181. The Moreover, in the feed water heater 30, the 2nd drain supply line L3 is arrange | positioned so that a drain may distribute | circulate from upper direction toward the downward direction.

The air heater 40 performs heat exchange between the combustion gas heat-exchanged in the feed water heater 30 and the combustion air supplied to the once-through boiler 10. In the present embodiment, the air heater 40 is disposed in the downward exhaust path portion 182. More specifically, as shown in FIG. 2, the air heater 40 is configured such that a part of the air supply line AL that supplies combustion air from the blower 80 to the once-through boiler 10 (duct 16) has a downward exhaust path portion 182. It is comprised by arranging in. Further, in the air heater 40, the air supply line AL is arranged so that the combustion air flows from below to above. That is, in the air heater 40 of the present embodiment, countercurrent heat exchange is performed in which the combustion gas and the combustion air flow in opposite directions to exchange heat.

Here, in the present embodiment, the heat recovery rate from the combustion gas is set to 3% to 7% by causing the air heater 40 to perform countercurrent heat exchange. In this way, by setting the heat recovery rate in the air heater 40 to 3% to 7%, the air heater is used when air having an outside air temperature (for example, 0 ° C. to 50 ° C.) is used as the combustion air. The temperature of the combustion air after heat exchange at 40 can be made 200 ° C. or lower.
It should be noted that the heat recovery rate from the combustion gas includes the inlet temperature of the combustion gas to the air heater 40, the outlet temperature of the combustion gas from the air heater 40, the flow rate of the combustion gas, and the air heater of the combustion air. It is determined based on the inlet temperature to 40, the outlet temperature of the combustion air from the air heater 40, and the flow rate of the combustion air.

Next, operation | movement of the boiler system 1 of this embodiment is demonstrated.
In the present embodiment, first, steam is generated in the once-through boiler 10. Specifically, first, the fuel gas and the combustion air are mixed in the duct 16, and the mixed gas of the combustion gas and the combustion air is ejected from the burner 17 into the can 11 and burned. Next, the plurality of water pipes 12 are heated by the combustion gas generated by the combustion of the mixed gas, and steam is generated from the feed water (drain) supplied to the inside of the plurality of water pipes 12. The steam generated inside the plurality of water pipes 12 is collected in the upper header 15 and then supplied to the steam header 71 via the connecting pipe 72.
The steam supplied to the steam header 71 becomes drain after being used in the load device 50 and is stored in the drain tank 21 in a high temperature and high pressure state. The drain stored in the drain tank 21 is supplied as feed water to the once-through boiler 10 through the second drain supply line L3.

On the other hand, the combustion gas G1 used for generating steam inside the can 11 flows upward through the first upward exhaust passage portion 181 (see G2 in FIG. 2), and then downwards through the downward exhaust passage portion 182. 2 (see G3 in FIG. 2), further flows upward through the second upward exhaust passage portion 183 (see G4 in FIG. 2), and is discharged to the outside (see G5 in FIG. 2).

Here, in the present embodiment, the feed water heater 30 is disposed in the first upward exhaust passage portion 181, and the air heater 40 is disposed in the downward exhaust passage portion 182. The air heater 40 is designed so that the heat recovery rate is 10% or less, preferably 3% to 7%. As a result, the combustion gas (for example, 250 ° C. to 350 ° C.) discharged from the can 11 is first drained (for example, 140 ° C. to 170 ° C.) through the feed water heater 30 in the first upward exhaust passage 181. ) And heat is recovered. Further, the combustion gas (for example, 140 ° C. to 200 ° C.) recovered by heat in the feed water heater 30 passes through the air heater 40 in the downward exhaust passage 182 (for example, −20 ° C. to 80 ° C.). ) And heat is recovered. Then, the combustion gas (for example, 80 ° C. to 120 ° C.) recovered by heat in the air heater 40 is discharged to the outside.

As described above, in this embodiment, the feed water heater 30 is disposed in the first upward exhaust passage portion 181, and the air heater 40 is disposed in the downward exhaust passage portion 182, thereby using high-temperature drain as the feed water. Even in such a case, the heat of the combustion gas that could not be recovered by the feed water heater 30 is given to the combustion air, so that the thermal efficiency (boiler efficiency) of the boiler system 1 can be improved.

Further, in the air heater 40 disposed in the downward exhaust passage portion 182, the air supply line AL is disposed so that the combustion air flows from the lower side to the upper side. Thereby, since the flow of the combustion gas in the downward exhaust passage 182 and the flow of the combustion air in the air heater 40 can be opposed to each other, in the air heater 40, the combustion gas and the combustion air are made to be opposite to each other. Counterflow heat exchange is performed. Therefore, the heat recovery rate from the combustion gas can be increased as compared with the parallel flow type heat exchange in which the combustion gas and the combustion air flow in the same direction. That is, as shown in FIG. 5 (a), according to the countercurrent heat exchange, the combustion air first exchanged heat with the coldest portion T4 of the combustion gas in the coldest portion T1. Thereafter, heat exchange is performed with the hottest portion T3 of the combustion gas in the hottest portion T2. As a result, as shown in FIG. 5 (b), first, more than the parallel flow heat exchange in which heat exchange is performed between the coldest portion T1 of the combustion air and the hottest portion T3 of the combustion gas. Heat recovery. Further, the temperature of combustion air after heat exchange (combustion air outlet temperature) T2 can be made higher than the temperature of combustion gas after combustion (combustion gas outlet temperature) T4 (FIG. 5). (See (a)).
Note that the vertical axis in FIG. 5 indicates the temperature of the combustion air and the combustion gas, and the horizontal axis indicates the heat exchange distance that is the distance from the inlet of the combustion air in the air heater 40.

Specifically, according to the air heater 40 of the present embodiment, the temperature of the combustion gas heat recovered in the feed water heater 30 can be lowered from about 140 ° C. to 200 ° C. to about 80 ° C. to 120 ° C., This allows 3% to 7% heat recovery.

Further, since the heat recovery rate in the air heater 40 is set to 10% or less, preferably 3% to 7%, the temperature of the combustion air heated in the air heater 40 and supplied to the once-through boiler 10 becomes high. You can prevent too much. Therefore, the thermal efficiency of the boiler system 1 can be improved and an increase in NOx contained in the combustion gas (exhaust gas) discharged from the once-through boiler 10 can be suppressed.

Further, it has been found that NOx contained in the combustion gas greatly increases when the temperature of the combustion air supplied to the once-through boiler 10 exceeds 200 ° C. And in the once-through boiler 10, the air of the environment where the boiler system 1 is installed is used as combustion air. Therefore, when the temperature of the combustion air introduced into the air heater 40 (that is, the outside air temperature) is 0 ° C. to 50 ° C., the temperature of the combustion air subjected to heat exchange becomes 200 ° C. or less. The air heater 40 was arranged in the. Thereby, it is possible to suppress an increase in NOx contained in the exhaust gas discharged from the once-through boiler 10 while improving the thermal efficiency of the boiler system 1 by performing heat recovery with the air heater 40.

Further, the once-through boiler 10 is fueled from a rectangular parallelepiped can body 11, a plurality of water pipes 12 arranged in the can body 11 at predetermined intervals in the longitudinal direction and the width direction, and a side surface of the can body 11. And a burner 17 for injecting and burning gas. Thereby, compared with the boiler which has a combustion chamber in the center part of the can 11, the time after the fuel gas combusts in the burner 17 until heat transfer to the several water pipe 12 can be shortened. Therefore, since the combustion temperature (flame temperature) of the fuel gas in the burner 17 can be lowered, the generation of NOx can be further reduced.

Further, in the feed water heater 30 disposed in the first upward exhaust passage portion 181, the second drain supply line L <b> 3 is disposed so that the drain flows from the upper side to the lower side. Thereby, since the flow of the combustion gas in the first upward exhaust passage 181 and the flow of the drain in the feed water heater 30 can be opposed to each other, the efficiency of heat recovery in the feed water heater 30 can be further improved.

As mentioned above, although one preferable embodiment of the boiler system 1 of this invention was described, this invention is not restrict | limited to embodiment mentioned above and can change suitably.
For example, in the present embodiment, the exhaust pipe 18 includes the first upward exhaust passage portion 181, the downward exhaust passage portion 182, and the second upward exhaust passage portion 183, but is not limited thereto. That is, the exhaust pipe may be configured by a downward exhaust passage portion whose upper end portion is connected to the can body and an upward exhaust passage portion connected to the lower end portion of the downward exhaust passage portion. In this case, a feed water heater may be disposed in the downward exhaust passage and an air heater may be disposed in the upward exhaust passage.

DESCRIPTION OF SYMBOLS 1 Boiler system 10 Through-flow boiler 11 Can 11a 1st side surface 11b 2nd side surface 12 Water pipe 17 Burner 18 Exhaust pipe 20 Drain collection device 30 Feed water heater 40 Air heater 181 1st upward discharge path part (upward discharge path part)
182 Downward discharge passage

Claims

A once-through boiler that generates steam by heating feed water with combustion gas;
A closed-type drain recovery device that recovers the drain produced by agglomeration of the steam generated by the once-through boiler in a high-temperature and high-pressure state, and supplies the drain to the once-through boiler;
A boiler system comprising a combustion gas discharged from the once-through boiler and a feed water heater that performs heat exchange between the drain supplied to the once-through boiler,
A boiler system further comprising an air heater for exchanging heat by circulating the combustion gas exchanged in the feed water heater and the combustion air supplied to the once-through boiler in opposite directions.
The boiler system according to claim 1, wherein a heat recovery rate of the air heater is 10% or less.
The temperature of combustion air introduced into the air heater is -20 ° C to 80 ° C, and the temperature of the combustion air after heat exchange in the air heater is 200 ° C or less. The boiler system according to 1 or 2.
The once-through boiler is
A rectangular parallelepiped can,
A plurality of water pipes arranged in the can body so as to extend in the vertical direction and arranged at predetermined intervals in the longitudinal direction and the width direction of the can body,
A burner which is provided on a first side surface located on one end side in the longitudinal direction of the can body and which burns by burning fuel in a substantially horizontal direction;
The boiler according to any one of claims 1 to 3, further comprising: an exhaust pipe that is provided on a second side surface located on the other end side in the longitudinal direction of the can body and discharges combustion gas generated inside the can body. system.
The exhaust pipe includes an upward discharge passage portion through which the combustion gas flows upward, and a downward discharge passage portion that is provided downstream of the upward discharge passage portion and through which the combustion gas flows downward.
The feed water heater is provided in the upward discharge path part,
The boiler system according to claim 4, wherein the air heater is provided in the downward discharge passage portion, and combustion air circulates from below to above.