JPH04345766A - Heat supplying power generating system for fuel cell power generating plant - Google Patents

Abstract

PURPOSE:To provide an optimum system in view of a demand by combining a thermoelectric ratio judging device capable of detecting a change in thermoelectric ratio over a wide range, a fuel generating plant and a exhaust heat recovery system. CONSTITUTION:In a battery cooling system, a heat exchanger 4b for recovering exhaust heat is interposed between another heat exchanger 4a for discharging exhaust heat and a circulating pump 3, and is connected onto a demand side 7, thus constituting an exhaust heat recovery system 8. A heat ratio judging device calculates a ratio of a heat load requiring value on the demand side to a power transmission load requiring value thereon to set a target generating load and a target load in addition to an exhaust heat discharging command, and sends them to the heat exhaust recovery system 8. Flow rates, temperatures and the like of the heat exchanger 4a connected to a cooling tower 5 and the heat exchanger 4b of the recovery system 8 are controlled on the basis of the command. Consequently, only the load required for the demand is supplied from the exhaust heat of a fuel cell generating plant. Moreover, extra exhaust heat is discharged to outside air so that a stable heat supplying generating system can be obtained and a heat load and an electric load which are widely changed can be supplied.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined heat and power generation system for a fuel cell power generation plant.

0002

2. Description of the Related Art FIG. 3 shows a schematic system diagram of a conventional fuel cell power generation plant, and FIG. 4 shows a system diagram of a cell cooling water system of the fuel cell power generation plant.

As shown in FIG. 3, natural gas supplied from a tank or pipeline 10 is passed through a compressor 11.
After being pressurized and desulfurized in the hydrodesulfurizer 12, it is mixed with steam sent from the steam separator 2 and introduced into the reformer 13.

In the reformer 13, the natural gas mixed with steam is reformed into hydrogen, carbon monoxide and carbon dioxide by an endothermic reaction, and then further converted into a carbon monoxide high-stage/low-stage shift converter 14; 15 and a contact cooler 16 for reformed gas, carbon monoxide is converted into carbon dioxide and sent to the fuel electrode (anode) 17 of the fuel cell main body 1 together with hydrogen.

In the battery body 1, the hydrogen necessary for power generation is consumed, and the surplus hydrogen at that time is used again as a combustion source in the reformer 13, and then becomes combustion exhaust gas to drive the turbo compressor 20. It is reused as a source and released into the outside air from the exhaust stack 21.

[0006] Also, air is introduced from outside air into the turbo compressor 20 driven by the exhaust gas from the reformer 13, and after being pressurized, air is transferred to the air electrode (cathode) 1 of the battery body 1.
8 and is consumed. The surplus air at that time is sent to the reformer 13 via the cathode exhaust contact cooler 19,
After being used as an oxidizing agent for combustion in the reformer 13, it becomes combustion exhaust gas, is reused as a driving source for the turbo compressor 20, and is then released into the atmosphere.

The battery body 1 generates DC power through an electrochemical reaction between supplied hydrogen and air (oxygen). The DC electricity generated by the battery body 1 is distributed to the demand side through an orthogonal converter 22 and a transformer 23. At this time, in order to remove the heat generated, cooling water is circulated around the battery body 1 as shown in FIG. It becomes a two-phase flow and is sent to the steam/water separator 2, where it is separated into steam and hot water. The steam is used as a steam source for the reformer 13, while hot water is circulated from the steam-water separator 2 by the circulation pump 3, cooled in the exhaust heat exchanger 4 on the inlet side of the battery body 1, and then It is used as cooling water for the battery body 1. The heated refrigerant in the heat exchanger 4 passes through the cooling tower 5 and is exhausted to the outside air. Furthermore, the cooling water is treated in a water treatment device 9 (FIG. 3).

Furthermore, since the battery main body 1 generates heat only after starting power generation, it is necessary to supply other energy to the power generation plant when starting up the fuel cell power generation plant. In Figure 3, a steam separator 2 is used as another energy source.
An electric heater 6 is provided inside to raise the temperature of the battery body 1 at startup and to supply steam to the reformer 3.

[0009] In the above explanation, battery cooling water was taken as an example of exhaust heat recovery. However, when actually implementing exhaust heat recovery, there are many points to consider, such as recovering steam directly from the steam separator 2 and recovering exhaust heat from the contact cooler 16 and turbo compressor 20. Its appearance varies widely depending on the system configuration.

As described above, when exhaust heat is recovered from a fuel cell power generation plant, the overall thermal efficiency is generally about 80%, and the heat /
The power ratio is 1 (exhaust heat recovery efficiency: 40%/power generation efficiency: 40%), which is a major feature, and its practical application is highly anticipated.

[0011]

[Problems to be Solved by the Invention] However, when considering a fuel cell power generation plant from the consumer side of a combined heat and power generation system, the heat load requirement and power transmission load that are required on a daily/moment basis depending on the season, weather, or time of day. The required values often vary independently of each other. As a result, when the heat/electricity ratio is approximately 1 over the entire load, which is a basic characteristic of fuel cells, this characteristic may actually be detrimental to the practical use of power generation plants.

[0012] In particular, in a fuel cell power generation plant, as mentioned above, due to the characteristic that the heat/electricity ratio is approximately 1, that is, it can only be operated at a heat/electricity ratio of 1 (constant). In application, it was necessary to solve the following problems.

(1) To provide a combined heat and power generation system that can satisfy the required values independently according to the heat load request value/power transmission load request value requested from the demand side to the combined heat and power generation system. Ratio 1 or less range), (2)
To provide a combined heat and power generation system with a heat/electricity ratio of 1 or more, taking into consideration the demand for air conditioning in the summer.

Therefore, the objects of the present invention are (1) to have the function of releasing all of the exhaust heat of the fuel cell power plant to the atmosphere when the required heat load value is zero;
It has a function of calculating the ratio between the demand-side heat load request value and the power transmission load request value, and a function of distributing the exhaust heat of the fuel cell power generation plant into a recovered portion and an exhaust portion according to the ratio, and (
3) A fuel cell power generation plant that has a system that reduces the power transmission load of the fuel cell power generation plant, increases exhaust heat, or both at the same time in order to increase the heat/electricity ratio to 1 or more. The aim is to provide a combined heat and power generation system.

[0015]

[Means for Solving the Problems] The combined heat and power generation system for a fuel cell power generation plant of the present invention includes a heat converter for exhaust heat discharge and a heat converter for exhaust heat recovery connected in series in the cell cooling water system of the fuel cell power generation plant. The heat converter for waste heat recovery is connected to the heat load demand side to form an exhaust heat recovery system, and a thermoelectric ratio judgment device is installed so that the power transmission load request value on the demand side is adjusted to the heat load demand side. If the required load value is greater than or equal to the required power transmission load value, the target power generation load of the fuel cell power generation plant is set corresponding to the required power transmission load value, and conversely, the required thermal load value is set as the required power transmission load value. If the heat load is large, set the target power generation load of the fuel cell power generation plant in accordance with the required heat load value, and set the difference between the target power generation load and the power transmission load request value as the internal load of the fuel cell power generation plant. It is characterized by consumption.

[0016]

[Operation] According to the present invention, the thermoelectric ratio determination device calculates the ratio (thermoelectric ratio) between the input heat load request value from the demand side and the power transmission load request value, and calculates the ratio (thermoelectric ratio) between the input heat load request value from the demand side and the power transmission load request value. If the value is large, the requested power transmission load value is directly used as the target power generation load of the fuel cell power generation plant. In addition, the target internal load is set to zero and the exhaust heat exhaust command is set to the difference between 1 and the thermoelectric ratio and transmitted to the fuel cell power plant. Set it as is and transmit it as a heat recovery command.

On the other hand, when the thermoelectric ratio is 1 or more, that is, the required heat load value is larger than the required power transmission load value, the target power generation load that can output exhaust heat that can satisfy the required heat load value is determined as a function of the required heat load value. Then, the difference between the target power generation load and the requested power transmission load is set as the target in-station load. Further, the exhaust heat exhaust command is set to zero and transmitted to the fuel cell power generation plant, and the heat load request value on the demand side is set and transmitted to the exhaust heat recovery system as the exhaust heat recovery command.

[0018]

[Embodiment] An embodiment of a cogeneration system for a fuel cell power generation plant according to the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows an overall configuration diagram of an embodiment of a cogeneration power generation system for a fuel cell power generation plant according to the present invention. Here, an exhaust heat recovery heat exchanger 4b is newly added to the battery cooling water system shown in FIG. 4 used in the description of the conventional technology to supply heat load to the demand side. That is, an exhaust heat recovery heat exchanger 4b is disposed between the exhaust heat exhaust heat exchanger 4a and the circulation pump 3, and is connected to the heat load demand side 7 to configure the exhaust heat recovery system 8. .

That is, as shown in the figure, the battery main body 1 generates DC power through an electrochemical reaction between supplied hydrogen and air (oxygen). The generated DC electricity is distributed to the demand side through the orthogonal converter 22 and transformer 23 shown in FIG. At that time, cooling water circulates around the battery body 1 to remove the generated heat, and the cooling water that has undergone heat exchange within the battery body 1 becomes hot water or a two-phase flow of hot water and steam. After being sent to the steam separator 2 and separated into steam and hot water, the separated steam is used as a steam source for the reformer 13. On the other hand, the separated hot water is circulated by the circulation pump 3 from the steam separator 2, and is cooled in the exhaust heat recovery heat exchanger 4b and the exhaust heat discharge heat exchanger 4a arranged on the inlet side of the battery body 1. After that, it is used again as cooling water for the battery body 1. Further, the warmed refrigerant of the exhaust heat recovery heat exchanger 4b is supplied to the heat load demand side 7 as a heat source. The refrigerant in the exhaust heat exhaust heat exchanger 4a passes through the cooling tower 5 and is exhausted to the outside air.

[0021] Since the battery main body 1 generates heat only after power generation, it is necessary to supply other energy when starting up the fuel cell power generation plant. Therefore, an electric heater 6 is provided in the steam separator 2 to raise the temperature of the battery body 1 at startup and to supply steam to the reformer 13.

FIG. 2 is a system diagram of a control system using the thermoelectric ratio determination device of the combined heat and power generation system of the present invention. In this system, a thermoelectric ratio determination device 30 equipped with means for inputting a heat load request value V1 and a power transmission load request value V2 of the heat load demand side 7 calculates the ratio of these request values V1 and V2, and calculates the ratio of the request values V1 and V2. Based on the results, a means for setting a target power generation load L1, a target internal load L2, and an exhaust heat exhaust command D1 in the fuel cell power generation plant and transmitting them to the fuel cell power generation plant 40, and setting an exhaust heat recovery command D2 in the exhaust heat recovery system 8. and means for transmitting the information. Further, the fuel cell power generation plant 40 has a means for operating the power generation plant according to the transmitted targets L1 and L2 and the specification D2, and the exhaust heat recovery system 8 recovers exhaust heat according to the transmitted exhaust heat recovery command D2. and means to do so.

By adding this exhaust heat recovery system 8,
Based on the exhaust heat exhaust command D2 determined by the thermoelectric ratio calculated and set in the thermoelectric ratio determination device 30, on the one hand, in the fuel cell power generation plant, the exhaust heat of the exhaust heat exhaust heat exchanger 4a connected to the existing cooling tower 5 is The recovery system 8 controls the flow rate, temperature, etc. of the exhaust heat recovery heat exchanger 4b based on the exhaust heat recovery command D2. This control provides only the necessary heat load for the demand side from the exhaust heat of the fuel cell power generation plant, and discharges excess exhaust heat to the outside air, resulting in a more stable cogeneration system for the fuel cell power generation plant. It will be done.

When the thermoelectric ratio is 1 or more, the electric heater 6 in the steam/water separator 2 shown in FIG. ) can provide a heat load with a thermoelectric ratio of 1 or more.

Although the exhaust heat recovery system 8 described above relates to a battery cooling water system, it can be implemented in a wide variety of ways in an actual power plant as described above. However, by making the exhaust heat recovery and exhaust method of the fuel cell power generation plant exactly the same system configuration as the battery cooling water system, it becomes possible to easily recover waste heat from other systems as well. Therefore, their explanation will be omitted.

Furthermore, although the electric heater 6 in the steam/water separator 2, which is the most obvious means for increasing the amount of exhaust heat, has been described as an embodiment of the present invention, other systems may be provided with an electric heater. Of course, it is possible to set up a system using an electric heater. Furthermore, if there is an energy source that replaces the electric heater, the present invention can be similarly applied to, for example, an auxiliary boiler.

[0027]

Effects of the Invention According to the present invention, by configuring a co-generation power generation system for a fuel cell power generation plant by combining a heat and power ratio determination device having the above-mentioned functions, a fuel cell power generation plant, and an exhaust heat recovery system, From this point of view, it is possible to obtain an optimal combined heat and power generation system for a fuel cell power generation plant. Furthermore, the present invention can replace the constant operation with a thermoelectric ratio of 1, which has been disadvantageous in the conventional combined heat and power generation system of a fuel cell power generation plant, by providing a heat load and an electric load that vary widely based on the demands of the demand side. A combined heat and power generation system for a fuel cell power generation plant can be obtained.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of a combined heat and power generation system for a fuel cell power generation plant according to the present invention.

FIG. 2 is a system diagram of a control system using a thermoelectric ratio determination device for a combined heat and power generation system of a fuel cell power generation plant according to the present invention.

FIG. 3 is a schematic diagram of a conventional fuel cell power generation plant.

FIG. 4 is a system diagram of a battery cooling water system of the conventional fuel cell power generation plant shown in FIG. 3;

[Explanation of symbols]

1 Fuel cell main body 2　Steam water separator 3 Circulation pump 4a　Heat exchanger for exhaust heat discharge 4b Heat exchanger for exhaust heat recovery 6 Electric heater 7 Demand side heat load 8　Exhaust heat recovery system 30 Thermoelectric ratio judgment device 40 Fuel cell power generation plant

Claims (1)

[Claims] Claim 1: A heat converter for exhaust heat discharge and a heat converter for exhaust heat recovery are arranged in series in a battery cooling water system of a fuel cell power generation plant, and the heat converter for exhaust heat recovery is connected to the heat load demand side. is connected to constitute an exhaust heat recovery system, and is equipped with a power generation ratio determination device, and when the demand-side power transmission load request value is greater than or equal to the demand-side heat load request value, the power transmission load request value is The target power generation load of the fuel cell power generation plant is set in response to A heat generation plant for a fuel cell power generation plant, characterized in that a target power generation load of the power generation plant is set, and the difference between the target power generation load and the power transmission load request value is consumed as an internal load of the fuel cell power generation plant. Combined power generation system.