JPH0322523B2 - - 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, a super heater 3, a high-pressure evaporator 1, and an economizer 2 are arranged in an exhaust gas conduit 12 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 steam is evaporated by natural circulation within a large number of heat transfer tubes connected to the water drum 5, and the steam accumulates in the upper part of the steam drum 4. This steam is further superheated by the super heater 3 and becomes high temperature and high pressure steam into the main steam pipe 13.
It is then used for in-house steam, for example for power generation.

In this conventional waste heat recovery boiler, the steam for heating used in the deaerator 6 is used in the plant and becomes low pressure and low temperature, and is used as steam 9 (hereinafter referred to as backup steam) and steam in the steam drum 4. The mixture is mixed with 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 uses the steam generated by a separate low-pressure evaporator, which reduces waste. In a waste heat recovery device consisting of a super heater, a high-pressure evaporator, and an economizer arranged from the high-temperature side of the gas, a low-pressure evaporator is provided on the waste gas outlet side of the economizer, and the degassed feed water in the deaerator is transferred to the low-pressure evaporator. The present invention is characterized in that it is equipped with a deaerator heating steam system that introduces the vapor into the deaerator and supplies the vapor 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 deaerated by a deaerator 6 is heated by an economizer 2 and guided to a steam drum 4, evaporated by a high-pressure evaporator 1, and this steam is further heated by a super heater 3. The waste heat boiler, in which high-temperature, high-pressure steam is supplied into the plant from the main steam pipe 13, is the same as the conventional example explained in FIG. In addition, 7 is a water supply pump, 19 is a flow control valve, and the signals of three elements, a drum level detector 29, a flow rate detector 23 provided in the main steam pipe 13, and a water supply flow rate detector 30, are calculated by a calculator 31. The valve opening degree is adjusted based on the generated signal.

In this embodiment, the following items are added to this conventional waste heat boiler. That is, 14 is a low-pressure evaporator provided on the exhaust gas outlet side of the economizer 2. 16 is a steam system for heating the deaerator;
The deaerated water in the deaerator 6 is transferred to the low pressure evaporator 14 by the low pressure evaporator water supply pump 15.
This vapor is mixed with backup vapor 9 and supplied to the deaerator 6. 17 and 18 are check valves, and 10 is a control valve for adjusting the internal pressure of the deaerator 6, and the valve opening degree is adjusted by a signal from the pressure detector 22.

As shown in FIG. 3, the deaerator heating steam system 16 separates steam and water using a flash tank 24 provided in the deaerator 6 via a communication pipe 26, and degass only the steam. It is also possible to guide the air to the air chamber 6. 25 is a check valve.

In addition, 20 in FIG. 1 is a deaerator water level control valve, and the valve opening degree is adjusted by the signal of the water level detector 21 so that the water level of the deaerator 6 is kept constant. 27 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 feed water pump 7, heated, and sent to the steam drum 4. This feed water is heated and evaporated in the high-pressure evaporator 1, and the steam is further led to the super heater 3, where it is converted into high-temperature and high-pressure steam into the main steam pipe.
3 will be supplied to the facility.

Therefore, economizer 2, high pressure evaporator 1
All of the energy absorbed by the superheater 3 is supplied into the plant through the main evaporation pipe 13.

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

That is, the degassed feed water in the deaerator 6 is guided to the low pressure evaporator 14 by the low pressure evaporator water pump 15 and evaporated. This steam passes through the deaerator heating steam system 16, joins 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.
It is recovered as deaeration steam in the deaerator 6 through the deaerator 6.

In the embodiment shown in FIG. 4, in addition to the first embodiment, a low-pressure economizer 28 is further provided, and the retained heat of the waste gas at the outlet of the low-pressure evaporator 14 is recovered by the deaerator water supply. This is to further reduce the amount of steam consumed to raise the temperature of the deaerator by raising the temperature of the feed water in 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 exhaust 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, by installing a low-pressure economizer on the exhaust gas outlet side of the low-pressure evaporator and raising the temperature of the feed water sent to the deaerator, it is possible to reduce the amount of steam used to raise the temperature of the deaerator, and also to reduce 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 the drawing]

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, partially showing the case where a flash tank is provided in the middle of the steam system for heating the deaerator. FIG. 4 is a diagram showing another embodiment of the present invention. 1... High pressure evaporator, 2... Economizer, 3... Super heater, 6... Deaerator, 14...
...Low pressure evaporator, 16... Steam system for heating the deaerator.

Claims (1)

[Scope of 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 the waste gas, a low pressure evaporator is provided on the waste gas outlet side of the economizer, and a low pressure evaporator is provided in the deaerator. A waste heat recovery device characterized by being provided with a deaerator heating steam system that guides deaerated feed water to a low-pressure evaporator, evaporates it, and supplies this steam to the 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. A steam system for heating the deaerator leads the deaerated feed water in the deaerator to a low-pressure evaporator, evaporates it, and supplies this steam to the deaerator, and a deaerator feed water pump evaporates the feed water to a low pressure. A waste heat recovery device equipped with a deaerator water supply system that leads to an economizer, raises the temperature, and supplies water to a deaerator.