JPH07217802A - Waste heat recovery boiler - Google Patents

Abstract

PURPOSE:To prevent low temperature corrosion of an economizer and generation of steam of feed water in the economizer. CONSTITUTION:A conduit 13 for supplying part of hot water of a steam drum 1 to a feed water tube 3 via a circulating pump 14 and a first control valve 17 is provided. A first feed water temperature detector 18 is mounted at a feed water inlet of an economizer 4. A first controller 18a for controlling the inlet temperature of the economizer 4 by so controlling an opening of the valve 17 that a detected temperature of the detector 18 becomes an inlet set temperature S1 is provided. Further, a bypass conduit 20 for feeding hot water of the drum 1 discharged from the pump 14 to a condenser 12 via a second control valve 19 is provided. A second feed water temperature detector 21 is mounted at a feed water outlet of the atomizer 4. A second controller 21a for controlling an entire amount of the feed water by so controlling the opening of the valve 19 that the detected temperature of the detector 21 becomes an outlet set temperature S2 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust heat recovery boiler for recovering heat of exhaust gas used for power.

[0002]

2. Description of the Related Art An example of a conventional exhaust heat recovery boiler will be described with reference to FIG.
Water is supplied from the water supply pump 2 through the water supply pipe 3, the economizer 4, and the valve 5. An evaporator 6 and a superheater 7 are attached to the steam drum 1, and the superheater 7
Is connected to a steam power unit 8 such as a steam turbine.

The aforementioned economizer 4, evaporator 6 and superheater 7 are
The exhaust gas at a temperature of about 500 ° C. discharged from the gas turbine 9 is housed in the exhaust gas passage 10 to absorb the heat of the exhaust gas.

Water entering the economizer 4 from the water supply pump 2 through the water supply pipe 3 is heated by the economizer 4 and then supplied to the steam drum 1 through the valve 5. The water in the steam drum 1 is heated by the evaporator 6 to become steam, and after returning to the steam drum 1, it is supplied to the steam power unit 8 through the superheater 7.

The steam power unit 8 drives, for example, a generator 11, the steam used in the steam power unit 8 is returned to water by a condenser 12, and is circulated again as water supply to the steam drum 1 by a water supply pump 2. At this time, the water supply pump 2 is controlled by the detection value of the molten metal level gauge 1a provided in the steam drum 1 so that the molten metal level is always constant.

The hot water temperature of the economizer 4 is 40 to 50 ° C.
If the amount is less than a certain level, there is a problem that moisture in the exhaust gas from the gas turbine 9 is condensed on the surface of the economizer 4 to cause low temperature corrosion.

Therefore, the pipe line 13 is provided at the bottom of the steam drum 1.
Is attached, and this pipe line 13 is connected to the water supply pipe 3 via the circulation pump 14 and the control valve 15. Further, a feedwater temperature detector 16 is attached to a portion of the water supply pipe 3 connected to the inlet of the economizer 4, so that the feedwater temperature at the inlet of the economizer 4 is detected. Further, the feed water temperature at the inlet of the economizer 4 detected by the feed water temperature detector 16 has a lower limit set to prevent the low temperature corrosion.
(° C) or less, the control valve 15 is opened so that the opening of the control valve 15 is increased to raise the temperature of the economizer 4.
The controller 16a is provided to control the opening of the.

[0008]

However, in the above-mentioned conventional apparatus, the temperature control of the feed water entering the economizer 4 from the water supply pipe 3 is maintained at the inlet set temperature S1 or higher to prevent low temperature corrosion of the economizer 4. Since only the prevention is performed, the temperature of the feed water by the economizer 4 rises, for example, when the level of the molten metal in the steam drum 1 rises, and the pressure in the steam drum 1 rises, for example, to 30 Kg / cm ^2. When the temperature of the hot water in the economizer 4 becomes 235 ° C. or higher at that time, steaming occurs in the economizer 4, resulting in vibration and pressure fluctuation.

The present invention overcomes these conventional drawbacks,
It is an object of the present invention to provide an exhaust heat recovery boiler capable of simultaneously preventing low temperature corrosion and steaming in a economizer.

[0010]

The present invention is directed to a steam drum, a water supply pipe, a economizer provided between the steam drum and the water supply pipe, and water supplied to the steam drum to steam. An evaporator, a steam power unit, a superheater provided between the steam drum and the steam power unit, an exhaust gas passage containing the economizer, the evaporator, and the superheater, and the steam power unit. In an exhaust heat recovery boiler equipped with a condenser provided between the water supply pipe and a pipe, a part of the hot water of the steam drum is supplied to the water supply pipe through a circulation pump and a first control valve. A first feedwater temperature detector attached to the feedwater inlet of the economizer, a second feedwater temperature detector attached to the feedwater outlet of the economizer, and steam discharged from the circulation pump Bypass for sending hot water from the drum to the condenser via the second control valve A pipe is provided, and when the detected temperature of the first feed water temperature detector is lower than the inlet set temperature, the opening of the first control valve is increased so that the detected temperature of the first feed water temperature detector is the inlet. A first controller for controlling the opening degree of the first control valve to be smaller when the temperature is higher than the set temperature, and the second control when the temperature detected by the second feed water temperature detector is lower than the outlet set temperature. A second controller that controls the opening of the second control valve to be small when the opening of the valve is small and the temperature detected by the second feed water temperature detector is higher than the outlet set temperature. The present invention relates to an exhaust heat recovery boiler.

[0011]

When part of the hot water in the steam drum is supplied to the water supply pipe through the circulation pump and the first control valve, the temperature of the water supply in the water supply pipe rises. The first feed water temperature detector detects the feed water temperature at the feed water inlet of the economizer, and when the temperature detected by the first feed water temperature detector is lower than the inlet set temperature, the opening of the first control valve is increased. First, increase the amount of hot water entering the water supply pipe
When the temperature detected by the water supply temperature detector is higher than the inlet set temperature, the opening of the first control valve is reduced to reduce the amount of hot water entering the water supply pipe.

Further, when the temperature detected by the second feed water temperature detector is lower than the outlet set temperature, the opening degree of the second control valve is reduced so that the amount of hot water discharged from the circulation pump to the condenser. The temperature of the hot water in the economizer is increased by decreasing the total amount of water supplied by the water supply pipe by
When the temperature detected by the water supply temperature detector is higher than the outlet set temperature, the opening degree of the second control valve is increased to increase the amount of hot water sent from the circulation pump to the condenser to supply water by the water supply pipe. The temperature of the hot water in the economizer is lowered by increasing the total amount.

[0013]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a system diagram of an embodiment of the present invention, in which the same parts as those of the conventional apparatus shown in FIG. 2 are designated by the same reference numerals.

As shown in FIG. 1, a pipe line 13 is attached to the bottom of the steam drum 1, and this pipe line 13 is connected to the circulation pump 1.
4, connected to the water supply pipe 3 via the first control valve 17. Further, a first feedwater temperature detector 18 is attached to a portion of the water supply pipe 3 which is connected to the inlet of the economizer 4,
The inlet water temperature can be detected.

When the feed water temperature at the inlet of the economizer 4 detected by the first feed water temperature detector 18 is lower than the inlet set temperature S1 such as 100 ° C., the opening of the first control valve 17 is increased. , The feed water temperature at the inlet of the economizer 4 detected by the first feed water temperature detector 18 is an inlet set temperature S such as 100 ° C.
When it is higher than 1, a first controller 18a for controlling the opening degree of the first control valve 17 to be small is provided.

Further, the discharge side of the circulation pump 14 is connected to the condenser 12 by a bypass line 20 having a second control valve 19, and a second feed water temperature detector 21 is provided at the outlet of the economizer 4. It is attached so that the feed water temperature at the outlet of the economizer 4 can be detected.

When the feed water temperature at the outlet of the economizer 4 detected by the second feed water temperature detector 21 is lower than the outlet set temperature S2, the opening degree of the second control valve 19 is reduced to make the second feed water. When the feed water temperature at the inlet of the economizer 4 detected by the temperature detector 21 is higher than the outlet set temperature S2, a second controller 21a for controlling the opening degree of the second control valve 19 to be increased is provided. .

Next, the operation of the above embodiment will be described.

Water that has entered the economizer 4 from the water supply pump 2 through the water supply pipe 3 is heated by the exhaust gas in the exhaust gas passage 10 in the economizer 4, and then is supplied to the steam drum 1 through the valve 5. It The water in the steam drum 1 is heated by the evaporator 6 to become steam, and after returning to the steam drum 1, it is supplied to the steam power unit 8 through the superheater 7.

A part of the hot water in the steam drum 1 enters the pipe line 13, is pressurized by the circulation pump 14, and is supplied to the first control valve 17
And is supplied to the water supply pipe 3. Therefore, in the water supply pipe 3, the hot water in the steam drum 1 is mixed with the water sent from the water supply pump 2, and the water having a temperature raised by the mixing of the hot water enters the economizer 4.

The temperature of the feed water entering the economizer 4 is detected by the first feed water temperature detector 18, and when the temperature detected by the first feed water temperature detector 18 is lower than the inlet set temperature S1 such as 100 ° C., The first control valve 17 is controlled by the first controller 18a so that the opening degree becomes large. Therefore, the amount of hot water in the steam drum 1 supplied to the water supply pipe 3 through the first control valve 17 increases, and the temperature of the water supply entering the economizer 4 rises.

When the temperature detected by the first feed water temperature detector 18 is higher than the inlet set temperature S1 such as 100 ° C., the first control valve 17 is controlled so that its opening becomes small. Therefore, the amount of hot water in the steam drum 1 supplied to the water supply pipe 3 through the first control valve 17 is reduced, and the economizer 4
The temperature of the incoming water supply drops.

Therefore, the temperature of the feed water entering the economizer 4 is kept substantially at the inlet set temperature S1 such as 100 ° C., and low temperature corrosion does not occur in the economizer 4.

The water supplied to the economizer 4 is supplied to the exhaust gas passage 10
After being heated by the exhaust gas of the steam, it is supplied to the steam drum 1 through the valve 5, but the amount of water supplied to the economizer 4 is reduced due to the high level of the molten metal in the steam drum 1. If the feed water temperature at the outlet of the economizer 4 becomes too high, steaming of the feed water will occur, causing vibrations and pressure fluctuations, which may cause problems.

Therefore, as described above, when the feed water temperature at the outlet of the economizer 4 detected by the second feed water temperature detector 21 is higher than the outlet set temperature S2, the second control valve 21a controls the second control valve. The opening degree of 19 is controlled to be large. As a result, the amount of hot water in the steam drum 1 discharged from the circulation pump 14 that flows through the bypass pipe 20 to the condenser 12 increases, and the total amount of water supplied by the water supply pipe 3 increases. Therefore, by increasing the amount of feed water flowing into the economizer 4, the feedwater temperature on the exit side of the economizer 4 is lowered.

The control for increasing the opening degree of the second control valve 19 is continued until the feed water temperature at the outlet of the economizer 4 becomes equal to or lower than the outlet set temperature S2. Therefore, if the outlet set temperature S2 is set to be slightly lower than the temperature at which the water supply on the outlet side of the economizer 4 starts steaming, vibration and pressure fluctuation due to steaming of the water supply on the outlet side of the economizer 4 are prevented. You can

When the feed water temperature at the outlet of the economizer 4 detected by the second feed water temperature detector 21 is lower than the outlet set temperature S2, the opening degree of the second control valve 19 is controlled to be small. Therefore, the amount of hot water in the steam drum 1 discharged from the circulation pump 14 that flows through the bypass line 20 to the condenser 12 decreases, and the total amount of water supplied by the water supply pipe 3 decreases. Therefore, by reducing the amount of feed water flowing into the economizer 4, the feed water temperature on the exit side of the economizer 4 is increased.

[0029]

According to the exhaust heat recovery boiler of the present invention, the occurrence of low temperature corrosion due to the temperature of the feedwater entering the economizer is too low, and the steaming of the feedwater at the exit side of the economizer is prevented. It is possible to obtain an excellent effect that the problem of occurrence of vibration and pressure fluctuation due to the above can be prevented.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the invention of claim 1;

FIG. 2 is a system diagram showing an example of a conventional exhaust heat recovery boiler.

[Explanation of symbols]

 1 Steam Drum 3 Water Supply Pipe 4 Economizer 6 Evaporator 7 Superheater 8 Steam Power Unit 10 Exhaust Gas Passage 12 Condenser 13 Pipeline 14 Circulation Pump 17 First Control Valve 18 First Water Supply Temperature Detector 18a 1st Controller 19 Second control valve 20 Bypass line 21 Second feed water temperature detector 21a Second controller S1 Inlet set temperature S2 Outlet set temperature

Claims (1)

[Claims] 1. A steam drum, a water supply pipe, a economizer provided between the steam drum and the water supply pipe, an evaporator that turns the water supplied to the steam drum into steam, and a steam power unit. A superheater provided between the steam drum and the steam power unit, an exhaust gas passage accommodating the economizer, the evaporator and the superheater, and provided between the steam power unit and the water supply pipe. In the exhaust heat recovery boiler including a condenser, a pipe for supplying a part of the hot water of the steam drum to the water supply pipe through a circulation pump and a first control valve, and a water supply for the economizer. A first feed water temperature detector attached to the inlet, a second feed water temperature detector attached to the feed water outlet of the economizer, and a second control of the hot water of the steam drum discharged from the circulation pump. A bypass line for sending to the condenser via a valve, When the temperature detected by the water supply temperature detector is lower than the inlet set temperature, the opening of the first control valve is increased, and when the temperature detected by the first water supply temperature detector is higher than the inlet set temperature, the first control is performed. A first controller for controlling the opening degree of the valve to be small, and when the temperature detected by the second feed water temperature detector is lower than the outlet set temperature, the opening degree of the second control valve is reduced to And a second controller for controlling the opening degree of the second control valve to increase when the temperature detected by the second feed water temperature detector is higher than the outlet set temperature. .