JPH06176786A - Method and device of controlling temperature of water supplied to boiler in fuel cell power generating facility - Google Patents

Abstract

PURPOSE:To provide a method and a device of controlling the temperature of water supplied to a boiler and increasing efficiency of power generating facilities, by preventing water supplied to the boiler from evaporating in a supplied water heater, from partially flowing in a pipe and from causing pressure loss and obtain a stable flow. CONSTITUTION:A gas cooler 60 is arranged parallel to a supplied water heater 50 on the upstream side of a gas/water separator 70 in an anode exhaust gas line 11 and a control valve 90 is provided at a branch connection on the inlet side between the supplied water heater and the gas cooler to control the flow rate of anode exhaust gas respectively flowing therein. The temperature of water supplied to a boiler on the outlet side of the supplied water heater in a boiler water supply line 83 is detected by a temperature detector 92 and the control valve 90 is controlled according to the detected temperature of water supplied to the boiler to change the flow rate of anode exhaust gas flowing in the supplied water heater 50 so that the temperature of water supplied to the boiler can be controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling boiler feed water temperature in a fuel cell power generation facility, and more specifically, heating boiler feed water using anode exhaust gas discharged from a molten carbonate fuel cell. The present invention relates to a method and an apparatus for controlling a boiler feed water temperature in a fuel cell power generation facility including a feed water heater.

[0002]

2. Description of the Related Art Molten carbonate fuel cells have characteristics that conventional power generators do not have, such as high efficiency and little impact on the environment, and they are attracting attention as a power generation system following hydropower, thermal power, and nuclear power. Is currently being researched and developed all over the world. In particular, in a power generation facility using a molten carbonate fuel cell using natural gas as a fuel, as shown in FIG. 2, reforming is performed to reform a fuel gas obtained by mixing natural gas and water vapor into an anode gas containing hydrogen. A fuel cell 20 for generating power from an anode gas and a cathode gas containing oxygen is generally provided, and the anode gas produced by the reformer is supplied to the fuel cell, and the anode gas produced by the reformer is used in the fuel cell. Part (eg 8
After consuming 0%), the water content is separated as anode exhaust gas and then supplied to the combustion chamber of the reformer as combustion gas. In the reformer, combustible components (hydrogen, carbon monoxide, methane, etc.) in the combustion gas are burned in the combustion chamber, and the high-temperature combustion gas heats the reforming pipe in the reforming chamber to pass the fuel gas through the reforming pipe. Reform. The flue gas discharged from the reforming chamber is combined with the cathode gas for the fuel cell to supply necessary carbon dioxide to the cathode side of the fuel cell. A part of the cathode gas reacts in the fuel cell, and then is discharged to the outside of the system.

The above anode exhaust gas needs to be cooled to a predetermined temperature in order to separate its water content, and therefore,
The steam separator 7 is passed through several heat exchangers (fuel preheater 30, preheater 40, feed water heater 50, and gas cooler 60).
Supplied to zero. In the steam separator, the water in the anode exhaust gas that has been sufficiently cooled is separated, and the anode exhaust gas from which the water has been removed is supplied to the combustion chamber of the reformer and used as combustion gas. On the other hand, the water separated from the anode exhaust gas is subjected to a predetermined water supply treatment, then heated as the boiler water supply by the water supply heater 50 and supplied to the boiler 80. The boiler feed water supplied to the boiler is the evaporator 8 of the boiler.
1 and steam at a predetermined temperature and pressure in the superheater 82, mixed with the above natural gas, and supplied as fuel gas to the reforming pipe of the reformer. The reason why the moisture of the anode exhaust gas separated by the steam separator passes through the feed water heater 50 is to raise the temperature of this moisture in advance to improve the efficiency of the power generation equipment. Heater 50
Boiler feed water temperature is 10-20 than saturation temperature
It is necessary to keep the temperature at ℃ lower. This is because when water partially evaporates in the feed water heater, it becomes a two-phase flow, causing uneven flow in the flow inside the pipe, resulting in pressure loss, and a stable flow cannot be obtained, resulting in efficient and stable power generation equipment. This will hinder proper driving.

[0004]

In the above-described power generation equipment, the flow rate of the anode exhaust gas emitted from the fuel cell is not always constant. For example, when the flow rate of the anode exhaust gas increases at the time of starting or load fluctuation, In the feed water heater, there is a problem that the boiler feed water temperature rises and a part of the feed water evaporates. In order to prevent such evaporation of boiler feed water in the feed water heater, it is conceivable to set the heat receiving amount of boiler feed water to a low value when the flow rate of anode exhaust gas is constant. Thus, the above situation can be avoided to some extent. However, lowering the amount of received heat of the feed water in the feed water heater cannot sufficiently achieve the purpose of improving the efficiency of the power generation equipment, and even if this is done, more than that. When the flow rate of the anode exhaust gas increases, the feed water eventually evaporates in the feed water heater, which is not a fundamental solution to the above problem.

The present invention was created to solve such a problem. That is, the present invention provides a method and an apparatus that can prevent the boiler feed water from evaporating in the feed water heater and can prevent the boiler feed water temperature from being too low, thereby improving the efficiency and operation of the power generation facility. The purpose is to stabilize the.

[0006]

According to the present invention, a reformer for reforming a fuel gas containing water vapor into an anode gas containing hydrogen, and a fuel cell for generating power from the anode gas and a cathode gas containing oxygen. In the method for controlling the boiler feed water temperature in a fuel cell power generation facility including a boiler that generates steam mixed with fuel gas, the moisture of the anode exhaust gas is separated from the steam separator to obtain boiler feed water, and the boiler feed water is at a low temperature. Is heated in the feed water heater by exchanging heat with the high temperature anode exhaust gas from the fuel cell, and a gas cooler is arranged in parallel with the feed water heater upstream of the steam separator in the anode exhaust gas line. A control valve for adjusting the flow rate of the anode exhaust gas flowing to each of the branch points on the inlet side of the heater and the gas cooler was installed to the boiler water supply line. The temperature of the outlet side of the feed water heater is detected, and the boiler feed water temperature is controlled by adjusting the control valve according to the detected boiler feed water temperature to change the flow rate of the anode exhaust gas flowing to the feed water heater. A temperature control method for a fuel cell power generation facility is provided.

Further, according to the present invention, a reformer for reforming a fuel gas containing water vapor into an anode gas containing hydrogen, a fuel cell for generating electricity from the anode gas and a cathode gas containing oxygen, and a fuel gas In a control device for boiler feed water temperature in a fuel cell power generation facility including a boiler that generates water vapor mixed with a steam-water separator that separates moisture of anode exhaust gas into boiler feed water, and A feed water heater that exchanges heat between the anode exhaust gas and low-temperature boiler feed water, a gas cooler that is arranged in parallel with the feed water heater in the anode exhaust gas line and cools the anode exhaust gas, and a feed water in the anode exhaust gas line A control valve for adjusting the flow rate of the anode exhaust gas flowing to each of the branch points on the inlet side of the heater and the gas cooler, and the boiler feed water A temperature detector for detecting the temperature of the outlet side of the feed water heater at the inlet is provided, and the flow rate of the anode exhaust gas flowing to the feed water heater is changed by adjusting the control valve according to the temperature detected by the temperature detector. There is provided a temperature control device for fuel cell power generation equipment, characterized in that the temperature is controlled.

[0008]

According to the present invention, the boiler feed water temperature discharged from the feed water heater is detected, and the control valve is adjusted based on the detected temperature to control the flow rate of the anode exhaust gas passing through the feed water heater. By controlling the flow rate of the anode exhaust gas of the feed water heater, the boiler feed water temperature passing through the inside of the feed water heater can be set to a predetermined temperature, for example, 10 to 20 ° C. lower than the saturation temperature. As a result, even if the amount of anode exhaust gas emitted from the fuel cell becomes larger than expected, the flow rate of anode exhaust gas passing through the feed water heater can be controlled, so that boiler feed water does not evaporate in the feed water heater, and It is possible to prevent uneven flow in the pipe, prevent pressure loss, and obtain a stable flow. Therefore, it is possible to improve efficiency of the power generation equipment and stabilize operation.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram showing a power generation facility for carrying out the method according to the present invention.

In the figure, natural gas is supplied through a natural gas line 1 and steam is supplied through a steam line 2, which are combined and supplied as fuel gas through a fuel gas line 3 to a power generation facility. The power generation facility includes a reformer 10 that reforms a fuel gas into an anode gas containing hydrogen,
A fuel cell 20 for generating power from the anode gas and a cathode gas containing oxygen, and a fuel for exchanging heat between the high temperature anode exhaust gas emitted from the fuel cell 20 and the low temperature fuel gas supplied to the reformer 10. Preheater 30 and fuel preheater 3
The high-temperature anode exhaust gas that has passed 0 and the preheater 40 that exchanges heat between the high-temperature anode exhaust gas and the low-temperature combustion gas that is supplied to the combustion chamber 10a of the reformer 10 and has passed through the preheater 40. A feed water heater 50 for exchanging heat between the high temperature anode exhaust gas and the low temperature boiler feed water, a gas cooler 60 arranged in parallel with the feed water heater 50 and cooling the high temperature anode exhaust gas, and an anode. A steam / water separator 70 for separating the water content of the exhaust gas into boiler feed water, and the steam / water separator 70
The exhaust gas boiler 80, which is heated to evaporate in order to mix the water separated from the anode exhaust gas with the natural gas to produce the fuel gas, is provided. The anode exhaust gas is used as a combustion gas that is burned in the combustion chamber 10a of the reformer 10. However, for convenience of description, the gas from the fuel cell 20 to the steam separator 70 is referred to as the anode exhaust gas. The path is called the anode exhaust gas line 11, and the gas from the steam separator 70 to the combustion chamber 10a of the reformer 10 is used as a combustion gas.
The path is called the combustion gas line 71.

The reformer 10 includes a combustion chamber 10a for burning the combustion gas from which water has been removed from the anode exhaust gas, and a reforming chamber 10b for reforming the fuel gas by heat transfer from the combustion gas in the combustion chamber 10a. Consists of. Moisture in the anode exhaust gas is removed by the steam separator 70 into the combustion chamber 10a, and the combustion gas is supplied with the combustion gas.
Further, the combustion chamber 10a is supplied with air 4 from an air source (not shown) so that the combustion gas is burned in the combustion chamber 10a to generate a high temperature. A reforming pipe 10c, which is usually filled with a reforming catalyst, is provided in the reforming chamber 10b so that the fuel gas is reformed by the high-temperature combustion gas generated in the combustion chamber 10a. The fuel gas reformed in the reforming pipe 10c is used as the anode gas in the anode gas line 5
Is supplied to the anode side of the fuel cell 20 via the. Further, the combustion gas whose temperature has dropped in the reforming chamber 10a merges with the cathode gas of the fuel cell 20 via the combustion exhaust gas line 6 as combustion exhaust gas.

The fuel gas supplied to the reforming pipe 10c is heated in the fuel preheater 30 by exchanging heat with the high temperature anode exhaust gas emitted from the fuel cell 20, while the anode exhaust gas is heated in the fuel preheater. The temperature is lowered slightly by 30. The temperature and flow rate of the anode exhaust gas supplied to the combustion chamber 10a are controlled by the preheater 40 and the blower 42 provided in the combustion gas line 71 between the combustion chamber 10a and the steam separator 70. ing. Preheater 4
0 is heat exchanged between the high temperature anode exhaust gas that has passed through the fuel preheater 30 and the low temperature combustion gas whose moisture has been removed by the steam separator 70, the temperature of the combustion gas is raised, and the fuel is heated. The temperature of the hot anode exhaust gas that has passed through the preheater 30 is further lowered in temperature.

The fuel cell 20 comprises an anode side (A) through which the anode gas passes and a cathode side (C) through which the cathode gas passes. Hydrogen and carbon monoxide in the anode gas and oxygen in the cathode gas are contained in the fuel cell 20. , Carbon dioxide and a chemical reaction to generate electricity. The fuel cell is preferably a molten carbonate fuel cell. Carbon dioxide necessary for the reaction is supplied to the cathode gas line 7 through the combustion exhaust gas line 6. Further, the cathode exhaust gas that has passed through the cathode of the fuel cell 20 exits from the fuel cell 20 via the cathode exhaust gas line 8, a part of it is circulated to the cathode gas line 7 via the cathode circulation line 9, and the rest is the exhaust gas boiler. It is designed to be released to the outside of the system via 80. As will be described later, the exhaust gas boiler 80 is adapted to evaporate the water removed from the anode exhaust gas to superheat it into steam, and then supply it to the steam line 2.

In the feed water heater 50, heat is exchanged between the high temperature anode exhaust gas passing through the preheater 40 and the low temperature boiler feed water, and the temperature of the high temperature anode exhaust gas passing through the preheater 40 is further lowered. . The gas cooler 60 is arranged in parallel with the feed water heater 50 in the anode exhaust gas line 11, and is adapted to sufficiently exchange heat of the high-temperature anode exhaust gas with the cooling water for sufficient cooling. 90
Is the feed water heater 50 in the anode exhaust gas line 11.
Is a three-way valve disposed at a branch point on the inlet side between the gas cooler 60 and the gas cooler 60, and the three-way valve 90 can adjust the flow rate of the anode exhaust gas flowing to the feed water heater 50 and the gas cooler 60, respectively. ing.

Reference numeral 92 denotes a temperature detector for detecting the boiler feed water temperature output from the feed water heater 50 and controlling the three-way valve 90. The temperature detector 92 detects the three-way valve 90 based on the detection result. The amount of anode exhaust gas flowing through each of the feed water heater 50 and the gas cooler 60 is controlled and adjusted. The three-way valve 90 is not limited to this, and the feed water heater 50 and the gas cooler 60 are respectively introduced from branch points on the inlet side of the feed water heater 50 and the gas cooler 60.
A flow rate control valve may be separately provided at a position close to. The steam separator 70 is arranged on the downstream side of the branch point on the outlet side between the feed water heater 50 and the gas cooler 60, and is designed to remove water from the sufficiently cooled anode exhaust gas. There is. The anode exhaust gas from which the moisture has been removed is supplied to the combustion chamber 10a of the reformer 10 as a combustion gas as described above, while the moisture removed from the anode exhaust gas serves as boiler feed water via the boiler feed water line 83 to the exhaust gas boiler. 80. The boiler feed water is subjected to a predetermined treatment by a feed water treatment facility (not shown), then pressure-fed by the feed water pump 85, and the exhaust gas boiler 8 via the feed water heater 50.
0 is supplied.

In the feed water heater 50, heat is exchanged between the boiler feed water and the high-temperature anode exhaust gas to raise the temperature, and the temperature is detected at the outlet side thereof as described above. The exhaust gas boiler 80 exchanges heat between the high-temperature cathode exhaust gas and the low-temperature boiler feed water, and includes an evaporator 81 that evaporates the boiler feed water and a superheater 82 that further superheats the evaporated steam. In the exhaust gas boiler 80, the evaporated and overheated boiler feed water is supplied to the steam line 2 and mixed with natural gas to be a fuel gas.

In the power generation equipment as described above, the boiler feed water temperature is controlled as follows, so that it does not evaporate in the feed water heater 50. That is, the boiler feed water temperature in the feed water heater 50 is sequentially detected by the temperature detector 92. Based on the detection result, for example, when the temperature is higher than the set temperature, the opening degree of the three-way valve 90 is adjusted to adjust the feed water heater 50. The amount of anode exhaust gas flowing to the gas cooler 60 is decreased, and the amount of anode exhaust gas flowing to the gas cooler 60 is increased so that the boiler feed water temperature does not rise any more. Conversely, when the temperature is lower than the set temperature, By adjusting the opening degree of the three-way valve 90 to increase the amount of anode exhaust gas flowing to the feed water heater 50 and decreasing the amount of anode exhaust gas flowing to the gas cooler 60,
The boiler feedwater temperature is prevented from falling any further. Thereby, the boiler feed water in the feed water heater 50 can be set to a predetermined temperature, for example, a temperature 10 to 20 ° C. lower than the saturation temperature, and the boiler feed water is not evaporated in the feed water heater 50. , Again, exhaust gas boiler 8
The temperature supplied to 0 can be a temperature that is not low.

When the opening degree of the three-way valve 90 is adjusted on the basis of the temperature detector 92, the amount of anode exhaust gas flowing through the feed water heater 50 and the gas cooler 60 changes and the anode enters the steam separator 70. The temperature of the exhaust gas fluctuates, which can be dealt with by changing the amount of cooling water flowing through the gas cooler 60, for example. In order to change the amount of cooling water flowing to the gas cooler 60, for example, it is possible to detect the temperature of the anode gas entering the steam separator 70 and control the amount of cooling water flowing to the gas cooler 60. .

[0019]

According to the present invention described above, the flow rate of the anode exhaust gas passing through the feed water heater is controlled by detecting the boiler feed water temperature exiting the feed water heater and adjusting the control valve based on the detected temperature. By controlling the flow rate of the anode exhaust gas of the feed water heater, the boiler feed water temperature passing through the inside of the feed water heater is set to a predetermined temperature, for example, 10 to 20 higher than the saturation temperature.
It can be set to a temperature lower by ℃. As a result, even if the amount of anode exhaust gas emitted from the fuel cell becomes larger than expected, the flow rate of anode exhaust gas passing through the feed water heater can be controlled, so that boiler feed water does not evaporate in the feed water heater, and It is possible to prevent uneven flow in the pipe, prevent pressure loss, and obtain a stable flow. Therefore, it is possible to improve efficiency of the power generation equipment and stabilize operation.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a power generation facility for implementing a method and an apparatus according to the present invention.

FIG. 2 is an overall configuration diagram showing a conventional power generation facility.

[Explanation of symbols]

 1 natural gas line 2 steam line 3 fuel gas line 4 air line 5 anode gas line 6 combustion exhaust gas line 7 cathode gas line 8 cathode exhaust gas line 9 cathode circulation line 10 reformer 10a combustion chamber 10b reforming chamber 10c reforming pipe 11 Anode exhaust gas line 20 Fuel cell 30 Fuel preheater 40 Preheater 42 Blower 50 Water heater 60 Gas cooler 70 Steam separator 71 Combustion gas line 80 Exhaust gas boiler 81 Evaporator 82 Superheater 83 Boiler water supply line 85 Water feed pump 90 Three-way valve 92 Temperature detector

Claims (2)

[Claims] 1. A reformer for reforming a fuel gas containing water vapor into an anode gas containing hydrogen, a fuel cell for generating electricity from the anode gas and a cathode gas containing oxygen, and generating water vapor mixed with the fuel gas. In the method for controlling the boiler feed water temperature in a fuel cell power generation facility including a boiler, the moisture of the anode exhaust gas is separated by a steam separator to obtain boiler feed water, and the low temperature boiler feed water is discharged from the fuel cell in the feed water heater. In addition to heating by exchanging heat with the hot anode exhaust gas, a gas cooler is installed in parallel with the feed water heater upstream of the steam separator in the anode exhaust gas line, and at the inlet side of the feed water heater and gas cooler. A control valve that adjusts the flow rate of the anode exhaust gas flowing to each branch is installed, and the boiler on the outlet side of the feed water heater in the boiler feed line is The fuel supply temperature is detected, and the boiler feed water temperature is controlled by adjusting the control valve according to the detected boiler feed water temperature to change the flow rate of anode exhaust gas flowing to the feed water heater. Control method of boiler feedwater temperature in battery power generation equipment. 2. A reformer for reforming a fuel gas containing water vapor into an anode gas containing hydrogen, a fuel cell for generating power from the anode gas and a cathode gas containing oxygen, and generating water vapor mixed with the fuel gas. In a controller for controlling boiler feed water temperature in a fuel cell power generation facility including a boiler, a steam water separator that separates moisture of anode exhaust gas into boiler feed water, a high temperature anode exhaust gas and a low temperature boiler discharged from the fuel cell. A feed water heater that exchanges heat with the feed water, a gas cooler that is arranged in parallel with the feed water heater in the anode exhaust gas line and cools the anode exhaust gas, and a feed water heater and a gas cooler in the anode exhaust gas line A control valve that adjusts the flow rate of the anode exhaust gas that flows at each branch point on the inlet side of A temperature detector for detecting the boiler feed water temperature on the outlet side of the heater is provided, and the control valve is adjusted according to the temperature detected by the temperature detector to change the flow rate of the anode exhaust gas flowing to the feed water heater to supply boiler feed water. A boiler feed water temperature control device in a fuel cell power generation facility, characterized in that the temperature is controlled.