JPS63217107A - Feedwater-temperature regulator for waste-heat recovery boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a heat recovery boiler for recovering heat from hot exhaust gas, for example hot exhaust gas discharged from a gas turbine.

For example, there is a conventional technique as shown in FIG. 10, which is used in a single-shaft combined power generation system consisting of a steam and gas turbine and a boiler that are directly connected by a shaft.

As shown in Figure 7, single-pressure single-shaft combined cycle power generation systems generally use fuel containing sulfur, and the components on the boiler 2 side include a superheater 3, an evaporator 4, , a denitrification device 5, a carbon saver 6, a steam drum 7, a chimney 8, etc. On the other hand, the components on the turbine 9 side include a steam turbine 10, a compressor 11, a combustor 12, a gas turbine 13, and a condenser 14.
, condensate pump 15, multiple feed water heaters 16, generator 17
etc.

In addition, each line connecting these component devices includes a water supply (condensate) line 18, a steam line 19, and a fuel line 20.
, an exhaust gas line 21, and a reducing agent injection line 22 to the denitrification device.

Now, ammonia is usually injected as a reducing agent from a reducing agent injection line 22 into the denitrification device 4 built in this (heavy pressure) boiler 2.
When used, SO5 is precipitated in the exhaust gas of the gas turbine 13, and reacts with this ammonia to form acidic ammonium sulfate (NH, )IIsO.

occurs.

Since acidic ammonium sulfate has the property of becoming a solid phase at 150 to 200°C, it is necessary to release the exhaust gas to the boiler 2 side at a high temperature of 230 to 2600°C. The generated steam is under heavy pressure, and the feed water is heated with steam turbine oil air in the feed water heater IO, and the temperature is set at 200°C with two boilers, that is, six energy savers, but the plant efficiency is not very high. This is the current situation.

Next, as shown in Fig. 8, the components on the boiler 2' side of the double-pressure single-shaft combined cycle power generation system 1' generally use fuel that does not contain sulfur, such as LNG. be. The components on the (double pressure) boiler 2' side are as described above (single pressure).
E) Like the boiler t, the steam generation part, that is, the evaporator 5 and the steam drum 7 are not a single unit (heavy pressure) but are composed of two sets for high pressure and low pressure, and the upstream side of the denitrification device 5 is a high pressure evaporator 23 and a steam drum 7. A high-pressure steam drum 24 is disposed downstream of the denitrification device 5, while a low-pressure evaporator 25 and a low-pressure steam drum 26 are disposed downstream of the denitrification device 5. Furthermore, these high pressure and low pressure steam drums 2
A high-pressure economizer 27 and a low-pressure economizer 28 are disposed downstream of 4° 26, respectively.

In addition to these components, there are a mixer 29, a low pressure economizer recirculation pump 3 (1), a high pressure water supply pump 31, etc.

Now, the water is supplied to the high pressure steam drum 24 and the high pressure evaporator 23.
Before being introduced into the water supply line 18, the recirculation pump 30 connected to the low-pressure steam drum 26 is used to introduce the water into the mixer 29 disposed in the water supply line 18 on the downstream side of the low-pressure economizer 28-L. It is mixed with low-pressure steam V-ram water in the steam drum 26 and controlled at about 60° C. so that carbon dioxide corrosion does not occur.

The exhaust gas to the chimney 8 is about 100°C, and the gas turbine 13
The exhaust gas heat recovery is maximized, resulting in relatively high efficiency.

Furthermore, in FIGS. 9 and 10, the amount of heat recovered from the exhaust gas discharged by the gas turbine 13 in the components on the steam and water supply lines 19 and 18 of the vehicle pressure boiler 2 and the double pressure boiler 2', respectively, is shown. The desired exhaust gas temperature T at the boiler inlet. 0, superheated steam temperature T8o, etc. are the same for each boiler 2', the amount of recovered heat, or in other words, the plant thermal efficiency
It turns out that ′ is better. From this, the exhaust gas temperature TT at the boiler outlet and the boiler feed water temperature Tsi, Ts
Even if Gl' G2 is applied to □, it is generally lower in the double pressure boiler 2' than in the single boiler 2.

Problems to be Solved by the Invention The exhaust heat recovery boiler described above, however, had the following drawbacks.

In a combined cycle power generation system, when using fuel containing sulfur, the power of heat recovery by each component,
The exhaust gas temperature at the boiler outlet tends to be low, and as a result, as mentioned above, when the temperature drops below the precipitation temperature of acidic ammonium sulfate, the acidic ammonium sulfate adheres to the surface of the heat transfer tubes of each component, causing corrosion of the tubes and damage to the structure. This was causing dirt and clogging inside the equipment.

Furthermore, in order to freely burn both sulfur-containing fuel and sulfur-free fuel such as 1, NG, etc., it is necessary to prevent corrosion, dirt, clogging, etc. in the component equipment, as described above. From the point of view of generation, double pressure boilers have the disadvantage that they are used exclusively for combustion of sulfur-free fuel, so a single boiler (see Fig. 7) with low plant efficiency has to be used.

Furthermore, there was no boiler (plant) that could be easily switched between single-firing and co-firing.

Means for Solving the Problems In order to solve these conventional problems, the present invention has the following features:
In a feed water temperature adjustment device for a double pressure waste heat recovery boiler that has each economizer for high pressure and low pressure, an evaporator, and a steam drum,
A condensate boost pump that heats the feed water from low pressure to high pressure is connected to the water supply line upstream of the low-pressure energy saver, and a recirculation line extending from the high-pressure steam drum is connected downstream of the condensate boost pump. In addition to arranging feed water heaters respectively, the low pressure steam drum is bypassed and the low pressure steam drum 1t is
btf shi, yu 2 pressure, □ hot, average, 11. □ A bypass line is provided to connect the high pressure water supply pump installed on the population side, and a water supply return line is further provided to connect the low pressure increase and high pressure water pump outlet side to the mixer inlet side.

Effect: According to this method, in a double-pressure waste heat recovery boiler that normally uses only sulfur-free fuel, by bypassing the low-pressure evaporator (drum), it is possible to use sulfur-containing fuel on the high-pressure steam side. On the other hand, high-pressure steam drum water is used to heat the feed water, and the temperature can be controlled by recirculating this high-pressure steam drum water and mixing it with condensate.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 to 6. In addition, in these figures, the same parts as in FIGS. 7 to 10 are given the same reference numerals, and detailed explanation thereof will be omitted.

According to the present invention, as shown in FIG. 1, in a double pressure boiler 2' having high pressure and low pressure economizers 27, 28, evaporators 23, 25, and steam drums 24, 26, respectively, In the low-pressure economizer 28, a condensate boost pump 32 that pressurizes the water supply from low pressure to high pressure is installed in the middle of the water supply line 18 on the downstream side.
is located.

On the downstream side of this condensate boost pump, there is a feed water heater 3 connected to a recirculation line 33 extending from the high pressure steam drum.
4 is placed.

- Power bus ±1, bypassing the low pressure steam drum 26 and low pressure economizer 2
A bypass line 36 is provided to connect the 8 outlet side and the population side of the high pressure water supply pump 31 in which the low pressure boost water pump 35 is arranged in parallel.
A water supply return line 37 is provided that connects the 5.31 outlet side and the mixer 29 population side.

Also, as a control system, the recirculation line 33 connects to the feed water heater 34.
A feed water temperature control valve 38 for adjusting the temperature of the feed water flowing out from the mixer is provided on the way from the mixer 29 to the mixer 29, and a boiler circulation cutoff valve 39 is further provided on the recirculation line. ing. On the other hand, a return pressure regulating valve 40 for adjusting the internal pressure of the high-pressure steam drum 24 is provided in the middle of the water supply return line 37, and a water supply cutoff valve v1 and pump intake and outlet valves V, V, are provided. , an economizer recirculation line 41 connecting the low pressure steam drum 26 and the mixer 29
The low pressure economizer recirculation pump 30 in the middle of the pump is equipped with pump inlet and outlet valves V,,V.

is provided. Then, the low pressure steam drum 26 includes a low pressure steam boiler stop valve V, a drum population valve and a Yamaguchi valve V.
,, V, and the bypass line 36 are provided with a bypass valve V, and the high pressure water supply pump 31 and the low pressure water supply pump 35 are provided with a pump inlet, a Yamaguchi valve, a VIO
+ LL and Vtt + L3 are provided at the tail.

With the above basic configuration, the double pressure boiler 2' can perform double pressure operation and heavy pressure operation, and switching between these can be done by opening and closing various valves on some system lines. It's easy to do.

Although necessary, the precipitation temperature of acidic ammonium sulfate is determined by the combination of the SO2 concentration in the exhaust gas and the 1eak ammonia concentration from the denitrification device 5.

In order to burn sulfur-containing fuel freely even if there are variations in the sulfur-containing fuel, it is important to frequently increase the feed water temperature and control the exhaust gas temperature at the boiler 2' outlet to be higher than the acidic ammonium sulfate precipitation temperature. High efficiency can be achieved not only under pressure operation but also under heavy pressure operation.

In order to control the feed water temperature, for example, to a predetermined temperature of 200° C., high pressure steam drum water can be recirculated and mixed with condensate (feed water).

Now, as a premise for this heavy pressure operation, the low pressure evaporator 25 (drum 26) is closed (dry operation),
It is necessary to operate the high-pressure steam side, that is, the high-pressure evaporator 23 (drum 24) side.
Alternatively, vehicle pressure operation is enabled by functioning devices such as a low pressure boost water pump 35), bypass line 36/(high pressure drum water) recirculation line 33, water supply return line 37, etc.

Therefore, each function and function of these component devices and lines will be explained in separate sections.

(1) First, we will explain the prerequisite for closing the low-pressure side. ＼ Close the low-pressure evaporator 25 (drum 26) (the drain line 41 is not used, so the low-pressure economizer recirculation pump 30 stops, and the valves V, V Then, the bypass valve v8 on the side of the bypass line 36 is opened, and the low pressure steam drum artificial valve and outlet valve V7.V are closed to perform dry operation of the low pressure steam drum 26.

Under this bypass operation, vehicle pressure operation is performed only on the high-pressure steam side. However, the feed water passes through the low pressure economizer 28 and flows to the high pressure steam side via the bypass line 36.

I will explain. As mentioned above, since the temperature is controlled by recirculating the high-pressure steam drum water and mixing it with condensate, when the boiler feed water temperature is preset at, for example, 200°C, the condensate at the outlet of the condenser 14 Temperature approximately 30°C (vacuum 7
20 to 730 mmHgv) is mixed with saturated water (e.g., 300° C./pressure 80 ata) from the high-pressure steam drum 24.

Note that the target value of the temperature of the feed water is determined in accordance with the sulfur concentration of the sulfur-containing fuel, and normally, for example, the higher the sulfur concentration, the higher the temperature of the feed water needs to be.

(3) The condensate boost pump 32 will be explained.

The condensate boost pump 32 provided upstream of the feed water heater 34 is
In bypass operation, for example, a water supply system with a condensate outlet pressure of approximately 30°C cm' or more is used, and the water supply (
After closing the condensate shutoff valve V on the condensate line 18 and opening the inlet and outlet valves Vt, V, the condensate boost pump is operated. In addition, the condensate boost pump 32 has not only high-pressure water supply capacity but also low-pressure water supply capacity during double-pressure operation, and the set pressure of the condensate boost pump in this case is:
The outlet pressure of the condensate pump 15 (e.g. 5 K9/cx”
v) is based on a pressure (saturation pressure 16ata) or higher that does not cause flushing (evaporation) even when water is supplied at 200°C. However, flushing (evaporation of condensate) is reliably prevented by increasing the pressure to about 30 to 40 ata, for example. This pressurized feed water is then passed through the feed water heater 34 on the downstream side.

Note that if the upstream condensate pump 15 has a variable rotation speed and variable blades, the direct condensate pressure boost pump 32 can be omitted and the water supply pressure can be increased to the same level.

In addition, as another example, the condensate pump 15 may maintain its bale pressure capacity as before, and the condensate boost pump 82 may be a pump that can vary from low pressure to high pressure like the condensate pump 15, and further, Keep the condensate boost pump 32 on the high pressure side,
The recirculation line 33 on the high-pressure steam side of the condensate booster pump (4) in this state will be explained.

In the recirculation line 33 from the high pressure steam drum 24,
Steam drum water is introduced into the feed water heater 34 by opening the shutoff valve. And this drum water and condensate boost pump 3
Heat exchange is performed with high pressure (approximately 30 to 40 ata) condensate at around 30° C., which is fed from water supply heater 34 to feed water heater 34 from water heater 34. At this stage of heat exchange in the feed water heater, the condensate is heated to near a predetermined temperature while at the same time reducing the temperature and pressure of the high-pressure steam drum water that is being recirculated.

However, stabilizing the water supply temperature to the desired value is
It's not possible at this stage.

That is, within the feed water heater 34, the circulating water (steam drum water) is approximately at the drum pressure (e.g., s Oat a +ii
The temperature of the water is lowered in (after j), and once it exits the heater and enters the mixer, it is controlled by the feed water temperature control valve 38, the pressure is reduced, and then it is mixed with condensate in the mixer 29. After this mixing, the steam drum water has a condensate temperature at the outlet of the mixer 29 which is about 200 mL.
The FE force (flow rate) will be adjusted by this feed water temperature control valve so that the temperature is at ℃.

In addition, the return (feed) water pressure in this mixer 29 is planned to be slightly higher than the saturation pressure (30 to 40 ata) if the circulating water at the outlet of the feed water heater 34 is cooled to 230 to 250°C. shall be taken as a thing.

(5) The condensate (water supply) flowing from the mixer 29 to the low pressure economizer 28 will be explained.

Assuming that the feed water flows into the low pressure economizer 28 while maintaining the feed water temperature at approximately 200°C, which is approximately the same as the feed water temperature at the outlet of the mixer 29, in the heat recovery curve of the double pressure boiler 2' under vehicle pressure operation shown in Fig. 2, , for that water supply temperature T si = 200°C,
Boiler outlet exhaust gas temperature T. 1 is maintained at approximately 230°C. The horizontal axis of the figure represents the amount of heat recovered by each component that recovers heat from the exhaust gas. Of the heat, the feed water heated in the low-pressure economizer 28 continues to rise to 60 degrees Fahrenheit, and the bypass It passes through line 36 and is flowing high. Thereafter, the feed water is further heated in the high pressure economizer 27 and introduced into the steam high pressure drum 24 at T9°C.

At this time, heat recovery in conventional double pressure operation (see Figure 10)
Similarly, it can be seen that in the double pressure boiler 2' according to the present invention, the predetermined water supply temperature TD° C. to the high pressure steam drum 24 is ensured.

(6) In item (5), changes in the temperature and pressure of the feed water were described, but on the other hand, the flow rate of the feed water will be explained.

In Figure 3, the vertical axis shows the required heat transfer area S for each of the high pressure and low pressure economizers 27 and 28 for the high pressure economizer 27 during double pressure operation.
%, passing feed water flow rate G%, and boiler outlet exhaust gas temperature T.

1°C, and the horizontal axis represents the water supply temperature (°C) m.

As mentioned above, the water supply temperature is 150 to 200℃, the pressure is in the 30 to 40 ata range, and the required heat transfer area is S%.
is the sum of both high pressure and low pressure economizers 27.28.

On the other hand, as mentioned above, the passing water supply flow rate is approximately 50% compared to the main steam flow rate where the high pressure drum recirculation amount is supplied to the turbine 9 side.
~150%. From this, the amount of water supplied to the high-pressure and low-pressure economizers 27 and 28 is approximately 100% of the main steam amount from the water supply (condensate) line 18 that joins in the mixer 29 and the high-pressure drum water from the recirculation line 33. Water recirculation amount 50-150
%. As a result, the flow rate is approximately 150 to 250% of the main steam flow rate.

Therefore, in these conditions (ranges), the exhaust gas temperature at the boiler outlet is maintained at about 220 to 230°C, which can be kept above the acidic ammonium sulfate precipitation temperature on the surface of the heat exchanger tube (not shown), which satisfies the prevention of precipitation. I understand that.

(7) The high-pressure water pump 31 and the low-pressure water pump 35 will be explained.

It is assumed that the high-pressure water supply pump 31 has a constant discharge pressure regardless of an increase or decrease in the flow rate of passing water supply.

In other words, by increasing the water pump pressure, the pressure at the outlet of the low-pressure economizer 28 of the water supply is made equal to or higher than the saturation pressure, and the water supply in the section from the mixer 29 to the outlet of the low-pressure economizer 28 is achieved, which is an essential technology for switching to low-pressure operation. In order to prevent flanging, it is necessary to control the outlet pressure of the high-pressure water pump 31 during vehicle pressure operation so as to maintain it at the same value as in double-pressure operation.

However, in the high-pressure water pump characteristics shown in Fig. 4, for the double-pressure operating point (Q, H), the pump passing flow ff1Q' during vehicle pressure operation is 15 as shown in item (5) above.
In the 200°C water supply operation, which increases from 0 to 250%, when only the high-pressure water supply pump 31 is used, the pump pressure increase decreases from ■] to H'.

As a measure to keep the water supply outlet pressure constant, first, the water supply pressure of the high pressure water supply pump 31 can be increased by using the condensate pressure boosting pump 19 (backup). In other words, the pressure increase ΔP of the water supply (condensate) on the side of the condensate boost pump 19
On the other hand, by selecting a pump characteristic that satisfies ΔPz (HH'), the high-pressure water supply pump 31 can be used as is in either double-pressure or vehicle-pressure operation.

However, if the outlet pressure of the water supply is still insufficient due to this measure, a separate low-pressure water supply pump 3 for heavy pressure operation is required.
5 are arranged in parallel, and operation is performed by switching from the high-pressure water supply pump 31 to this low-pressure boost water pump side, thereby preparing for an operating point mismatch of the high-pressure water supply pump 31. Further, as an example of other measures, if the high-pressure water supply pump 31 is a variable rotation speed, variable blade type pump, the low-pressure water supply pump 35 does not need to be arranged or used as a backup.

Furthermore, as an example of other measures, there is a control valve 39 when the water supply is above a certain level.
By passing the water through the water supply return line 37 equipped with a water supply and releasing it to the mixer 29 side, the water supply outlet pressure can be kept constant at all times.

(8) The functions of the water supply return line 37 and the low pressure boost water pump 35 other than water supply in item (7) above will be explained.

First, the water supply return line is provided to keep the pressure of high-pressure water supply constant as described above, and also to keep the internal pressure in the high-pressure steam drum 24 constant regardless of whether it is in double pressure or vehicle pressure operation. .

In other words, the pressure inside the high-pressure steam drum 24 is detected by the water supply return line 374! Return pressure regulating valve product Water supply return from the iris high pressure water supply pump 31! (pressure) adjustment.

The temperature of the supplied water at this time is almost the same as the outlet temperature of the low-pressure economizer 28 +ff1TE'C (see Figure 2), and at this temperature the supplied water is passed through the water supply return line 37 to the mixer 29. will be introduced in

Therefore, since this feed water temperature TE° C. is clearly higher than 200° C., the steam drum water (circulated water) introduced into the mixer 29 through the recirculation line 33 is The amount of circulating water is restricted by the water temperature control valve 38.

The return of the feed water controlled in this way and the high-pressure steam drum water are mixed together with the condensate from the feed water (condensate) line 18 in the mixer 29 until the temperature reaches the desired 200°C.
The temperature is kept at around ℃.

In addition, in one of the low pressure boost water pumps 35, especially when the internal pressure of the high pressure steam drum 24 cannot be reliably controlled during vehicle pressure operation due to mismatch in various conditions, the high pressure water feed pump 31 is stopped and the low pressure boost By switching to a pump and operating it, the internal pressure of the steam drum can be adjusted.

(9) According to the present invention, the high-pressure steam drum water in the boiler 2' system is recirculated and used as the heating source for the feed water heater 34 during the vehicle pressure operation of the double pressure boiler 2' as described above. However, the performance, economic efficiency, etc. of heating the feed water using high-pressure steam drum water of the present invention will be compared with other heating sources.

As the heat source outside the boiler system, for example, any heat source from outside the system of the combined power generation system 1t, steam turbine 10 extraction air, gas turbine 13 cooling (compression) or regenerated air, etc. can be used, and the same function can be ensured.

First, a comprehensive comparison shows that if the feed water temperature is increased by mixing condensate at approximately 30°C with high pressure steam drum water in the double pressure boiler 2' system, the plant thermal efficiency can be maintained at a high level. It is possible to operate independently.

On the other hand, when heating source fluid such as steam, water, air, or combustion gas can be supplied from outside the system, high-pressure steam (flow rate, temperature, pressure)
is constant, so the plant thermal efficiency is the same, but the net plant thermal efficiency, which takes into account heat input from outside the system, is slightly lower than when using internal fluid.

During this plant retreat, it is necessary to use a separate heat source regularly, so the independence of the plant is low, but there is another advantage in that other surplus heat sources can be used effectively.

Next, we examine the characteristics of the heat source b for each case (A) to (D).
) will be explained.

(A) When using high-pressure steam drum water as a heat source in the boiler system, the high-pressure steam drum recirculation amount + high-pressure main steam flow rate is 2.
The outlet temperature of the high-pressure economizer 27 is covered by a portion of the 00°C water supply.

(B) When using an arbitrary heat source outside the combined power generation system 1', the flow rate of feed water passing through the economizer is the same as the flow rate of high-pressure main steam, so the total heat transfer area of the economizer is based on the above item (A). It becomes less. Basically, no heat source fluid is allowed into the system.

(C) Steam turbine 1 as an external heat source for boiler 2'
When using zero bleed air, the feed water heating system is the same water feed line 18 as in the conventional combined cycle power generation system shown in FIG.
, steam line 19.

Furthermore, if this steam turbine lO bleed air feed water heating system is adopted in the present invention, in this case, in FIG.
Recirculation line 33 and feed water return line 37 would be unnecessary. Then, the output of the steam turbine 10 decreases due to the steam turbine extraction, and the plant thermal efficiency decreases.

2' (D) When using gas turbine cooling (compressed) air or gas turbine 13 regeneration air as a heat source outside the boiler teno system, the equipment is the same as in the case of high-pressure steam drum water in item (A) above. The heating fluid is used on the turbine 9 side in the combined power generation plant 1' system, and the plant thermal efficiency is either the above item (C) or an intermediate value between items (A) to (C).

In addition, in FIG. 5, only the parts of the power generation system using the cooling (compressed) air of the gas turbine 13 as a heat source that are different from the present invention in FIG. 1 are shown. A feed water heater 16 is provided upstream of the provided cooling air cooler 42, and temperature control (adjustment) at the outlet of the mixer 29 is performed by a heater bypass control valve 43.

Depending on the amount of heat, the cooling air cooler 42 may be stopped from being used.

Furthermore, FIG. 6 similarly shows only the parts of the gas turbine regenerator 44 that are different from the present invention (see FIG. Before this, the exhaust gas is shut off with the shutoff valve V14 and used to heat the feed water, and then it is fed into the gas turbine.

In this system, the regeneration amount and high pressure steam flow rate are constant under (double pressure - heavy pressure).

Depending on the calorific value plan, the order of heat recovery for the air may be (a) first by heating the feed water, then regenerating it, then by gas turbine and then inputting it into the gas turbine 13. Then, the temperature control in the feed water heater 16 is performed by gas turbine cooling (
(compressed) air.

The following table summarizes the characteristics of the above cases (A) to (D).

It can be seen that B<C<D<A, that is, A, that is, the high-pressure steam drum water according to the present invention is the best.

Which system case to select is determined by the heat source conditions, and it is possible to use several of them together depending on the heat amount plan.

Note that in these cases, the flow rate passing through the high-pressure water supply pump 31 is 150 ml of water in a double-pressure operation in case of high-pressure steam drum water (case (A)) in a vehicle pressure operation.
~250%, and the inlet pressure is approximately 10Kg/cx'
g to about 30 to 9/crtt”g, so bo: / 7
'N The change of intention moves. Therefore, the high pressure water supply pump 31
or change the rotation speed of the low pressure water supply pump 3 for single operation.
As mentioned in item (7) above, it is necessary to separately arrange the pumps 5 in parallel in order to prepare for the malfunction of the operating point of this high-pressure water supply pump.

On the other hand, in each case (B) to (D) described above, the flow rate passing through these high-pressure water supply pumps 31 is almost the same In, and only the inlet pressure is about 10 Kg/cm"@Ga3
Since it is OK97cm''9, sufficient countermeasures for the high-pressure water supply pump 31 are required as in the case of the steam drum water (case (A)) described above.

Furthermore, in each case (A) to (D), the mixer 29
Of course, this is a requirement since measures are basically taken to prevent flushing inside the building.

2' (10) Finally, regarding each component and each line (system) etc. required for car pressure operation in double pressure boiler N,
As mentioned above, we will briefly explain switching from vehicle pressure operation in double pressure operation, that is, operation using fuel that does not contain sulfur.

Then, the closed valves on the low-pressure steam side, the inlet of the low-pressure economizer recirculation pump 30, and the Yamaguchi valves V, V5 are opened, and the bypass valve vg of the bypass line 36 is closed.
and low pressure steam boiler stop valve V6 on the low pressure steam drum 26 side
and open the inlet and outlet valves V, , V, of the low pressure steam drum 26. Furthermore, the water supply pump inlet and outlet valves VIIVI3 of the low pressure pump 24, which are used only during single pump operation, are closed. High-pressure water supply pump 3 is always on during pressure recovery operation.
1 will be used.

By only operating some of the equipment (lines) as described above,
It becomes possible to easily perform a switching operation between vehicle pressure and double pressure operation.

Effects of the Invention As described in detail above, according to the present invention, in a double pressure boiler, the feed water temperature is increased by simple switching of some equipment and lines, and the low pressure steam is closed, thereby achieving vehicle pressure operation with high pressure steam. Therefore, by this vehicle pressure operation, both the sulfur-containing fuel and the sulfur-free fuel can be freely fired in the double pressure boiler, either exclusively or mixedly.

Furthermore, the boiler feed water temperature can be controlled between N100"C1 and 200°C depending on the sulfur concentration of sulfur-containing fuels that are co-fired with clean fuels such as natural gas or exclusively fired. It has more fuel flexibility than a steam system (heavy pressure boiler).

Furthermore, by setting the feed water temperature to 200°C or higher, the exhaust gas temperature at the boiler outlet can be obtained at approximately 230°C (by setting the atmosphere on the surface of the heat exchanger tube to acidic ammonium sulfate (N11.
Since it is possible to always maintain the temperature below the precipitation temperature of SO, and to keep the surface of the heat transfer tube clean, highly efficient waste heat recovery can be reliably obtained even under double pressure operation: single-tube operation. Can be done.

In addition, when mixing high-pressure feed water and condensate, first the high-pressure steam circulating water is heat-exchanged with the condensate using a feed water heater, and then the circulating water is throttled and controlled using a feed water temperature control valve to condense water. By mixing the high-pressure saturated water, which is essential for changing vehicle pressure, from causing flashing in the valve part and especially in the mixer, it is possible to sufficiently prevent flushing. 5 (It is an essential technology.

On the other hand, by using the high-pressure steam drum water (circulated water) within the boiler system as the feedwater heating source, the feedwater heating source can be widely used regardless of whether it is inside or outside the combined power generation plant system.

However, among these heat sources, the use of high-pressure steam drum water (circulated water) can be superior to other heating sources in terms of brand thermal efficiency, operability, and economy.

Furthermore, a feed water heater (steam turbine bleed air) like a conventional single-pressure system can be made unnecessary.

[Brief explanation of the drawing]

Figure 1 is a system (line) diagram showing an example of the feed water temperature adjustment device for a (double pressure) waste heat recovery boiler according to the present invention, Figure 2 is a diagram showing the amount of heat recovered from exhaust gas at the boiler outlet, and Figure 3. Figure 4 shows the relationship between the heat transfer area of the high-pressure and low-pressure economizers and the flow rate of the passing feed water, Figure 4 shows the operating characteristics of the high-pressure water pump, and Figure 5 shows the relationship between the heat transfer area of the high-pressure and low-pressure economizers and the flow rate of the feed water. FIG. 6 is a system (line) diagram showing another embodiment, and FIGS. 7 and 8 are conventional feed water temperature control devices for vehicle pressure and double pressure exhaust heat recovery boilers, respectively. FIG. 2 is a system diagram showing the amount of heat recovered from the boiler outlet exhaust gas of the slag. ■...Exhaust heat recovery boiler, 18...Water supply line, 23...
High pressure evaporator, 24...High pressure steam drum, 25...Low pressure evaporator, 26...Low pressure steam drum, 27...High pressure economizer 1
．． 28...Low pressure energy saver, 29...Mixer, 31...High pressure feed water pump, 32...Condensate boost pump, 33...Recirculation line, 34...Feed water heater, 35...Low pressure boost water pump , 36... Bypass line, 37... Paintbrush Figure 2 Figure 3

Claims (1)

[Claims] In a feed water temperature adjustment device for a double pressure waste heat recovery boiler that has each economizer for high pressure and low pressure, an evaporator, and a steam drum,
A condensate boost pump that heats the feed water from low pressure to high pressure is connected to the water supply line upstream of the low-pressure energy saver, and a recirculation line extending from the high-pressure steam drum is connected downstream of the condensate boost pump. A bypass line is provided which bypasses the low-pressure steam drum and connects the outlet side of the low-pressure economizer with the inlet side of the high-pressure feed water pump in which the low-pressure boost water pump is arranged in parallel, and further A feed water temperature adjustment device for an exhaust heat recovery boiler, comprising a feed water return line connecting the low pressure increase and high pressure feed water pump outlet side and the mixer inlet side.