JP3467759B2 - Control method of outlet temperature of reformer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an outlet temperature of a reformer for reforming a fuel gas and supplying the reformed fuel gas as an anode gas to a fuel cell. 2. Description of the Related Art Molten carbonate fuel cells have features that are not present in conventional power generation devices, such as high efficiency and little impact on the environment. Attention has been paid to the system, and intensive research is currently being conducted in various countries around the world. FIG. 3 is a diagram showing an example of a power generation facility using a molten carbonate fuel cell using natural gas as a raw material gas and fuel gas obtained by adding steam to the fuel gas. In the figure, a power generation facility is a reformer 10 for reforming a fuel gas 1 in which natural gas and steam are mixed into an anode gas 2 containing hydrogen.
And a fuel cell 12 that generates power from the anode gas 2 and the cathode gas 3 containing oxygen. The fuel gas 1 is heated by the preheater 11 and then reformed into the anode gas 2 by the reformer 10 and supplied to the fuel cell. The fuel gas 12 consumes most of the fuel gas and becomes the anode exhaust gas 4. Is supplied to the combustion chamber Co of the vessel 10. A part of the cathode exhaust gas 7 is also supplied to the reformer 10, and combustible components (hydrogen, carbon monoxide, methane, etc.) in the anode exhaust gas 4 are burned in a combustion chamber Co to generate a high-temperature combustion gas. This heat causes the reforming chamber Re of the reformer 10 to be heated.
Is reformed by the reforming catalyst filled in the reforming chamber Re to form an anode gas 2. The combustion exhaust gas 5 discharged from the reformer 10 is mixed with the air 6 and supplied to the circulation line 19, where it is mixed with a part of the cathode exhaust gas 7 to form the cathode gas 3. The cathode gas 3 reacts in the fuel cell 12 to become a high-temperature cathode exhaust gas 7, a part of which is supplied to the circulation line 19, a part of which is supplied to the combustion chamber Co of the reformer 10, and the remaining part compresses the air 6. After the power is recovered by the turbine compressor 16, the heat energy is further recovered by a waste heat recovery steam generator (not shown) and discharged outside the system. [0005] The temperature of the anode gas supplied to the anode of the fuel cell 12 has a planned value determined by the load conditions and the like, and the efficiency is highest when operating at this temperature. . When the temperature is lowered to about 490 ° C. or less, the electrolyte is solidified. However, for example, 600
When there is a plan value such as ° C., the temperature of the anode gas at the outlet of the reformer 10 is reduced due to variations in the performance of the reformer, deviations of the process conditions from the plan, deviations of the partial load characteristics from the plan values, and the like. In many cases, the planned value at the exit does not become the planned value, causing an inconvenient state in the fuel cell 12. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. A temperature sensor is provided at an outlet of a reformer, and a heater provided at an inlet side is controlled so that a temperature of an anode gas at an outlet of the reformer is controlled. It is an object of the present invention to provide a method for controlling the outlet temperature of a reformer in which the temperature is set within a predetermined range. In order to achieve the above object, an anode exhaust gas (4) of a fuel cell is burned, and the fuel gas is used to reform the fuel gas (1) to an anode gas (2). In the method for controlling the outlet temperature of a reformer (10) to be supplied to a battery (12), a temperature sensor (25) provided at an outlet side of the reformer and detecting a temperature of an anode gas is provided at an inlet side of the reformer. A heat exchanger (20) provided for heating the fuel gas by the anode exhaust gas ;
And a bypass line (23 ) through which exhaust gas flows , so that the detection value of the temperature sensor falls within a predetermined temperature range.
The flow rate of the bypass line is controlled. The temperature and heat exchange of the anode gas at the outlet of the reformer
The relationship with the amount of heat applied to the heat exchanger (20) is determined for each operating condition of the fuel cell, such as load conditions, and when the operating conditions are determined, the corresponding amount of heat is added to the heat exchanger, and the outlet temperature of the reformer is determined. The temperature of the anode gas supplied to the fuel cell can be controlled within the range of the planned value by controlling the heating amount while feeding back the temperature. [0009] It is effective use of the anode exhaust gas by using the anode exhaust gas of the fuel cell as a heating gas, thereby improving the efficiency of the fuel cell. Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a first embodiment of the present invention. FIG.
The same reference numerals denote those having the same function. Reformer 1
A heat exchanger 20 is provided on the inlet side of the zero. The heat exchanger 20 has a supply line 21 for supplying a heating gas, an exhaust gas line 22 for discharging exhaust gas heat-exchanged with the fuel gas 1, and a bypass line 23 connecting the supply line 21 and the exhaust gas line 22.
The bypass line 23 is provided with a flow control valve 24. A temperature sensor 25 for detecting the temperature of the anode gas is provided at the outlet of the reformer 10, and a temperature sensor 26 for detecting the temperature of the exhaust gas is provided in the exhaust gas line 22 in order to suppress an abnormal temperature rise in this line. . The temperature controller 27 receives the detection values of the two temperature sensors 25 and 26 and performs feedback control of the flow control valve 24 so that the temperature of the anode gas is predetermined according to the operating conditions. Since a preheater 11 for preheating the fuel gas 1 is provided at the inlet of the reformer 10 as shown in FIG. 3, the heat exchanger 20 has a capacity which also functions as the preheater 11. By doing so, it is possible to reduce the cost increase without increasing the number of devices. The supply line 21 uses the anode exhaust gas 4 from the fuel cell 12. The anode exhaust gas 4 has a temperature of about 700 ° C. at the outlet of the fuel cell 12 and the temperature of the fuel gas 1 at the outlet of the heat exchanger 20 is about 450 ° C., so that it is suitable as a heating source, and the overall efficiency of the plant is improved. Next, a related embodiment will be described. FIG. 2 shows the configuration of an embodiment related to the present invention. 3 have the same functions. In this embodiment, the preheater 11 is used.
An electric heater 30 is provided between the fuel cell and the reformer 10. At the outlet of the reformer 10, a temperature sensor 21 for detecting the temperature of the anode gas is provided, and the temperature controller 31 inputs the detected value of the temperature sensor 21 to reach a predetermined anode gas temperature according to the operating conditions. The electric heater control device 32 is controlled as follows. When the temperature of the anode gas at the outlet of the reformer 10 is controlled, it is conceivable to provide a heater on the outlet side, but by providing the heater on the inlet side as in the present invention,
There are the following advantages. The temperature of the anode gas on the outlet side of the reformer 10 is about 600 ° C., while the temperature on the inlet side is about 450 ° C. For this reason, the temperature design conditions of the heater are relaxed, and low-quality materials can be used. When the fuel gas 1 obtained by adding steam to natural gas is reformed into an anode gas by the reformer 10, the volume is doubled. That is, the heater provided on the inlet side only needs to handle half the flow rate of the heater provided on the outlet side, so that the heater can be designed to be compact. When natural gas mainly composed of methane and steam are heated together with the reforming catalyst in the reformer 10, an anode gas mainly composed of hydrogen and carbon monoxide is obtained. This reaction equation is represented by the following equation. CH ₄ + H ₂ O → 3H ₂ + CO In the above formula, the left side is 2 mol and the right side is 4 mol. Therefore fuel gas 1
Is reformed to twice the volume of anode gas. As is apparent from the above description, the present invention provides a temperature sensor on the outlet side of the reformer, a heater on the inlet side, and the temperature of the anode gas at the outlet of the reformer. Is controlled within a predetermined range, so that the fuel cell can be operated efficiently and the fuel cell can be safely operated. Further, by providing the heater on the inlet side of the reformer, the temperature condition of the heater is relaxed, the volume of the gas to be heated can be reduced, and it is possible to integrate with the existing preheater. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention. FIG. 2 is a diagram showing a configuration of an embodiment related to the present invention. FIG. 3 is an overall configuration diagram of a power generation facility using a conventional molten carbonate fuel cell. [Description of Signs] 1 Fuel gas 2 Anode gas 3 Cathode gas 4 Anode exhaust gas 5 Combustion exhaust gas 6 Air 7 Cathode exhaust gas 10 Reformer 11 Preheater 12 Fuel cell 16 Turbine compressor 19 Circulation line 20 Heat exchanger (heater) Reference Signs List 21 supply line 22 exhaust gas line 23 bypass line 24 flow control valve 25, 26 temperature sensor 27, 31 temperature controller 30 electric heater (heater) 32 electric heater control device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-82463 (JP, A) JP-A-4-32163 (JP, A) JP-A-61-183102 (JP, A) JP-A-6-183102 342669 (JP, A) JP-A-6-176786 (JP, A) JP-A-1-63072 (JP, U) JP-A-1-1322062 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/04 H01M 8/06

Claims (1)

(57) [Claims 1] An anode exhaust gas (4) of a fuel cell is burned, and the fuel gas reforms the fuel gas (1) into an anode gas (2) to produce a fuel cell (12). In the method for controlling the outlet temperature of the reformer (10) to be supplied, a temperature sensor (25) provided on the outlet side of the reformer and detecting the temperature of the anode gas, and an anode exhaust gas provided on the inlet side of the reformer. A heat exchanger (20) for heating the fuel gas and bypassing the heat exchanger
And a bypass line (23) through which anode exhaust gas flows to control the flow rate of the bypass line so that the value detected by the temperature sensor falls within a predetermined temperature range. Method.