JPH0322524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a waste heat recovery device that efficiently recovers the heat retained in waste gas.

[Prior art]

For example, high-temperature exhaust gas is discharged from steel plants and the like. A waste heat recovery boiler is usually provided to recover the heat of this exhaust gas.

The conventional waste heat recovery boiler was constructed as shown in FIG. In the figure, exhaust gas pipe 1
A super heater 3, a high pressure evaporator 1, and an economizer 2 are arranged in the exhaust gas in this order from the high temperature side of the exhaust gas.

First, the water supply from the water supply system 11 is led into the deaerator 6, where dissolved oxygen in the water supply is removed (hereinafter referred to as deaeration) in order to prevent oxidation corrosion of the high-pressure evaporator 1, economizer 2, and super heater 3. ).

The feed water thus deaerated is guided to the economizer 2 by the feed water pump 7, heated, and then supplied to the steam drum 4. This water supply is supplied to the steam drum 4
The water is naturally circulated within a large number of heat transfer tubes connected to the water drum 5, evaporates, and accumulates in the upper part of the steam drum 4.
This steam is further superheated by the super heater 3 to become high-temperature, high-pressure steam, which is supplied through the main steam pipe 13 for in-house steam, for example, power generation.

In this conventional waste heat recovery boiler, the steam for raising the temperature used in the deaerator 6 is steam 9 that has been used in the plant and has become low pressure and low temperature (hereinafter referred to as backup steam) and the steam drum 4. The steam 8 from the deaerator 6 is mixed with the steam 8 and introduced into the deaerator 6, and the temperature of the feed water in the deaerator 6 is raised to perform deaeration.

In this case, the heat recovered by the economizer 2 and high-pressure evaporator 1 is transferred to the deaerator 6.
This means that the heat consumed for raising the temperature inside the main steam 13 and provided to the main steam 13 will decrease accordingly.

Furthermore, the exhaust gas that exits the economizer 2 is released as is, and the heat retained in the exhaust gas cannot be sufficiently recovered.

[Purpose of the invention]

The present invention aims to provide a waste heat recovery device that can recover heat even better than the conventional waste heat recovery boiler described above.

[Summary of the invention]

The present invention does not use the steam generated by a high-pressure evaporator as the steam for heating and superheating the deaerator, but instead installs a separate low-pressure evaporator and uses the steam generated thereby. In a waste heat recovery device, a superheater, a high-pressure evaporator, and an economizer are installed from the high-temperature side of the economizer. It is characterized by the provision of a deaerator heating steam system for supplying water to the low pressure evaporator and guiding the steam evaporated in the low pressure evaporator to the deaerator.

The second invention further provides a low-pressure economizer on the waste gas outlet side of the low-pressure evaporator of the first invention, and uses the waste gas at the outlet of the low-pressure evaporator to raise the temperature of the water supplied to the deaerator, thereby increasing the temperature of the water supplied to the deaerator. It is characterized by the addition of a deaerator water supply system that recovers the heat retained in the air.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below. In FIG. 1, feed water in a deaerator 6 is sent to an economizer 2 by a feed water pump 7, heated, and then fed to a steam drum 4. This feed water is heated and evaporated by the high-pressure evaporator 1. This steam is further superheated by the super heater 3, becomes high temperature and high pressure steam, and is supplied into the plant through the main steam pipe 13.

Reference numeral 14 denotes a low-pressure evaporator installed on the waste gas outlet side of the economizer 2, which branches off from the middle of the water supply piping from the water supply pump 7 to the economizer 2, so that a part of the supplied water is sent to the low-pressure evaporator 14. There is. This low pressure evaporator 14
The amount of water sent to is controlled by the low pressure evaporator inlet valve 18. 15 is a deaerator heating steam system for supplying the vapor evaporated in the low-pressure evaporator 14 to the deaerator 6.

In addition, the deaerator heating steam system 15 separates steam and water by a flash tank 26 provided in the deaerator 6 via a communication pipe 26' as shown in FIG. It is also possible to send it to the deaerator 6. 25 is a check valve.

In FIG. 1, reference numeral 10 denotes a control valve for adjusting the flow rate of backup steam 9 provided to adjust the internal pressure in the deaerator 6, and the valve opening degree is determined by a signal from the pressure detector 23. is adjusted. 2
Reference numeral 2 denotes a deaerator feed water flow control valve for adjusting the water level in the deaerator 6, and the valve opening degree is adjusted by a signal from the water level detector 21. 19 and 20 are check valves, and 19 is a safety valve.

[Action of the invention]

In this embodiment configured as described above, the feed water deaerated in the deaerator 6 is sent to the economizer 2 by the water pump 7, heated, and sent to the evaporation drum 4. This water supply is supplied to high pressure evaporator 1
The evaporated water is further guided to the super heater 3 and supplied as high temperature and high pressure steam into the plant through the main steam pipe 13.

Therefore, all of the thermal energy absorbed by the economizer 2, high-pressure evaporator 1, and superheater 3 is supplied into the plant through the main steam pipe 13.

On the other hand, steam for heating the deaerator is generated and supplied independently from the waste heat boiler by utilizing the heat retained in the waste gas at the exit of the economizer 2.

That is, the water supply branched from the discharge side of the water supply pump 7 is guided to the low pressure evaporator 14 and evaporated.
This steam passes through the deaerator heating steam system 15, joins with the backup steam 9, and is supplied to the deaerator 6.

In this case, the heat retained in the waste gas at the exit of the economizer 2, which was previously released, is transferred to the low-pressure evaporator 14.
The water is recovered for use in raising the temperature of the feed water in the deaerator 6.

In the embodiment shown in FIG. 4, a low-pressure economizer 27 is further provided in addition to the first embodiment, and the heat retained in the waste gas at the outlet of the low-pressure evaporator 14 is recovered by water supplied to the deaerator, and deaeration is performed. The temperature of the feed water in the vessel 6 is raised to further reduce the amount of steam consumed to raise the temperature of the deaerator.

〔Effect of the invention〕

As detailed above, in the waste heat recovery device of the present invention, a low-pressure evaporator is provided on the waste gas outlet side of the economizer, and a steam system for heating the deaerator is formed independently. Thermal energy was not used for heating the deaerator, but was all effectively used for internal purposes, and it was also possible to recover the heat retained in the waste gas at the economizer outlet, which had previously been discarded.

In addition, a low-pressure economizer is installed on the exhaust gas outlet side of the low-pressure evaporator to raise the temperature of the feed water sent to the deaerator, thereby reducing the amount of steam used to raise the temperature of the deaerator and further reducing the heat retained in the waste gas. Therefore, it is possible to comprehensively improve the recovery efficiency of the heat retained in the waste gas, and it has an excellent effect in terms of energy saving.

[Brief explanation of drawings]

FIG. 1 is a flow diagram showing an embodiment of the present invention;
Figure 2 is a flow diagram of a conventional waste heat boiler, and Figure 3 is an embodiment of the present invention, which is a flow diagram partially showing the case where a flush tank is provided in the middle of the steam system for heating the deaerator. FIG. 4 is a flow diagram showing another embodiment of the present invention. 1... High pressure evaporator, 2... Economizer, 3... Super heater, 6... Deaerator, 14...
...Low pressure evaporator, 15... Steam system for heating the deaerator.

Claims (1)

[Claims] 1. In a waste heat recovery device comprising a super heater, a high pressure evaporator, and an economizer arranged from the high temperature side of waste gas, a low pressure evaporator is provided on the waste gas outlet side of the economizer, and the economizer is A waste heat recovery device characterized by being provided with a deaerator heating steam system for branching off from the middle of water being sent to a low-pressure evaporator and guiding the steam evaporated in the low-pressure evaporator to a deaerator. 2. In a waste heat recovery device comprising a super heater, a high-pressure evaporator, and an economizer arranged from the high-temperature side of the waste gas, a low-pressure evaporator is provided on the waste gas outlet side of the economizer, and a low-pressure economizer is further provided on the waste gas outlet side of the low-pressure evaporator. The water is branched from the middle of water being sent to the economizer by the boiler feed pump and sent to the low pressure evaporator, and the steam evaporated in the low pressure evaporator is provided as a steam system for heating the deaerator, while the water is sent to the low pressure economizer by the deaerator feed water pump. A waste heat recovery device characterized by comprising a deaerator water supply system that guides and heats water and supplies the water to a deaerator.