JP2000306592A - Solid oxide fuel cell burner system and method for generating heat from it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high efficiency and heat generation by composing a burner system with a partial reform means before the introduction of a fuel, a preheating means before the introduction of the air, and a recovery means of heat energy from an exhaust air all of which are connected to a fuel cell. SOLUTION: A solid oxide fuel cell 15 such as a low-temperature fuel cell stack and a monolithic battery generates electricity and heat by the use of the mixture of partially reformed fuel and preheated air. Preferably, a non stoichiometric reform providing a great fuel portion is carried out with a partial reform means 20 of fuel comprising a POX reform device 110, and the need of an additional preheater for raising the fuel temperature with steam or the like is obviated, so that the overall efficiency of the system is improved. Preferably, a predetermined quantity of around 23-30% of the fuel is fed to an air preheating means 25 provided with a nonstoichiometric burner requiring a little fuel portion, and part of the preheated air is used for the partial reform of the fuel. The exhaust portions of an anode and a cathode are stoichiometrically burned in a heating device small combustion chamber 48, and the exhaust gas is discharged after the recovery of energy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to solid oxide fuel cells (SOFCs), and more particularly to partially combusted (or incompletely combusted) integrated SOFCs used as electrochemical burners.

[0002]

BACKGROUND OF THE INVENTION SOFCs have the potential to convert all heating systems using gas burners to cogeneration systems. To accomplish that, the heating capacity must not be affected in the coupling system (or combined system). Therefore, if the heating capacity has to be maintained, the SOFC must maintain the duty cycle of the replaced burner.
In addition, to maintain thermal efficiency, deviations in air, fuel, and heating rates, as well as the temperature of the combustion products, should be minimized. In such applications (or applications), the efficiency of the fuel cell is not important, as heat is the main product and power is a by-product. In fact, energy that is not converted to electricity will be transferred as heat. However, the additional cost of the fuel cell system should be offset by the value of the power generated in the thermal system's duty system.

Many features attributed to electrochemical burners differ substantially from those of fuel cell power plants. Specifically, fuel cell power plant designs allow for significantly longer start-up times, with less demanding thermal cycling and near 100% duty cycle. Electricity efficiency is a requirement because electricity is the only product and competes based on the price of electricity. In particular, such high-efficiency designs incorporate a recuperative air preheater and a heat treatment machine that improve electrical efficiency.

[0004]

The preheater is a heat exchanger that uses, for example, stack heat to reform the fuel or heat the fluid to a desired high temperature. including. Components such as these heaters, however, add cost and complexity to the system. Moreover, these components provide the system with a substantial amount of heat, which makes frequent or fast thermal cycling impractical.

[0005] Furthermore, the temperature of the exhaust gas is too low to allow effective recovery of waste heat in conventional heating systems. An additional factor that hinders waste heat recovery is the amount of excess air required to control the temperature gradient of the fuel cell stack. Whereas conventional burners generally operate with air to provide a near stoichiometric supply of fuel, fuel cells require five times or more stoichiometric air flows.

[0006] It is an object of the present invention to solve these problems and to provide an efficient (or even capable) solid oxide fuel cell burner system and a method for producing heat therefrom.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a burner system including a SOFC, a means for partially reforming a fuel, a means for preheating air, and a means for recovering thermal energy. Become. The reforming means uses fuel SOFC
The fuel is partially (or incompletely) reformed prior to introduction (or input) to the fuel. Preheating means is air SOF
Preheat air before introduction into C. The thermal energy recovery means recovers energy from the exhaust (or exhaust heat) of the SOFC. In such an embodiment, the means of partial reforming heats the fuel sufficiently to eliminate the need for any pre-heater for the fuel, which is detrimental to overall system efficiency.

[0008]

DETAILED DESCRIPTION OF THE INVENTION In a preferred embodiment, SOF
C would consist of a low temperature fuel cell stack or monolithic cell and the reforming means would consist of a POX reformer.

In another preferred embodiment, the air preheating means comprises means for supplying the preheating means with a predetermined amount of fuel. In such a preferred embodiment, the supply means delivers between about 23% and 30% of the fuel supplied to the burner system to the preheating means.

[0010] The thermal energy recovery means comprises at least one combustor, and the air preheating means comprises (low in fuel content).
Equipped with an off-stoichiometric combustor. Further, the reforming means may include means for receiving a predetermined amount of air released from the preheating means.

[0011] The invention further comprises a method for generating heat. The method includes: preheating a predetermined amount of air with air preheating; reforming at least a portion of the fuel stream with a reformer; passing at least a portion of the fuel stream and air through the SOFC. And burning at least a portion of the SOFC emissions.

In a preferred embodiment of the method, the means for preheating further comprises: diverting (or sending) a predetermined amount of fuel to the preheater; and burning the fuel at the preheater. And, as a result, preheating a predetermined amount of air. In such a preferred embodiment, the means for burning the fuel further comprises means for burning the fuel with a non-stoichiometric burner.

[0013] In another preferred embodiment, the means for reforming the fuel stream comprises means for delivering a predetermined amount of preheated air from the preheater to the reformer.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS While the present invention may be embodied in a variety of different configurations, certain specific embodiments are shown and described herein with reference to the drawings. It is to be understood that this disclosure is to be considered as illustrative of the principles of the present invention, and not as limiting the present invention to examples.

Solid oxide fuel cell (SOFC) 15, means 20 for partially (or incompletely) reforming the fuel, means 25 for preheating air, and for recovering thermal energy FIG. 1 shows a burner system 10 comprising the means 30 of FIG. As explained later,
The SOFC (15) mixes the air from the pre-heating means with the fuel from the reforming means to generate electricity and heat, followed by product recovery to a recovery means 30 which captures some additional thermal energy from the discharge. To discharge.

The fuel injection port 32 includes a fuel inlet 32, an air inlet 34, an anode outlet 36, and a cathode outlet 38.
OFC (15) is shown in FIG. SOFC (1
5) may include, but is not limited to, any different number of SOFCs, including monolithic designs and low temperature stacks.

A partial reforming (or incomplete reforming) means 20 comprising a POX reformer 40 having an air inlet 51, a fuel inlet 50 and an outlet 52 is shown in FIG. The fuel inlet 50 is connected to a fuel supply source, and the air inlet 51 is connected to the outlet 46 of the preheating means 25. The POX reformer consists of a (stoichiometric) non-stoichiometric reformer, but other reformers may be considered as well. The use of such partial reforming means to preheat the fuel eliminates the need for an additional preheater, for example, utilizing steam or the like, to increase the temperature of the fuel. In this system, by utilizing partial reforming means for heating the fuel, the additional cost and energy loss associated with conventional heaters is eliminated, thereby increasing the overall system capacity and Efficiency improves.

An air preheating means 25 comprising an air inlet 42, a fuel inlet 44 and an outlet 46 is shown in FIG. The fuel inlet 44 is connected to the fuel supply of the system, and the air inlet 42 is connected to the air supply of the system. The air preheating means 25 will comprise a non-stoichiometric combustor that raises the temperature of the air supply (lean in fuel).

A heat recovery means 30 comprising a heating device combustion chamber 48 is shown in FIG. The heating device combustion chamber 48 is
It includes a cathode inlet 54 connected to the cathode outlet 38 of the SOFC (15), an anode inlet 56 connected to the anode outlet 36 of the SOFC (15), and an outlet 58.

In operation, a fuel supply and an air supply are supplied to the burner system 10. In detail, the fuel supplied is made from natural gas such as methane (CH _4), other fuels may be similarly examined. In such an embodiment, the air supply consists of the ambient air, however, for different fuels, different gas mixtures with different configurations in different ratios may be required. .

The fuel supply is separated such that a predetermined amount is sent to the air preheating means 25. The part sent to the air preheating means depends on the particular configuration utilized and the SO
It will change depending on FC. For low temperature SOFCs, about 23-30% of the fuel will be sent to the air preheating means. As will be appreciated by those of ordinary skill in the art, the requirement for high preheating is about 35-40.
% Or more of the fuel will need to be sent to the air preheating means.

As fuel enters the air preheating means 25, it will mix with air and will partially burn (or incompletely burn). Since combustion is out of stoichiometry,
Combustion causes the fuel to react only with a portion of the air. Thereby, the air and the combustion exhaust gas are discharged from the outlet 46 at a temperature higher than the temperature of the air inlet.

When the preheated air is discharged from the outlet 46, a part of the air is sent to the inlet 51 of the POX reformer 40. The POX reformer receives fuel from the inlet 50 and air from the inlet 51 and partially reforms the fuel. The partially reformed fuel is supplied to the POX reformer 4
It is discharged from 0 through the outlet 52.

The fuel from the outlet 52 is SOFC (15)
Is sent into the suction port 32. Similarly, part of the air from the outlet 46 of the air preheating means 25 is also
It is sent to the suction port 34 of (15). As is known in the art, air and fuel react in an SOFC to generate electricity. Discharge from the cathode side of the SOFC is sent to the cathode outlet 38, and discharge from the anode side of the SOFC is sent to the anode outlet 36.

Next, the cathode is discharged from the combustion chamber 4 of the heating device.
8 and the anode exhaust is sent to the inlet 56 of the heating device combustion chamber 48. The streams from the two inlets are further combusted in the compartment 48 and the remaining exhaust gas is discharged through the outlet 58. Small room 4 of heat recovery means 30
8 will consist essentially of a stoichiometric combustor.

To support the foregoing, an analysis of one embodiment of the method was performed. In such an example, about 23% fuel was required for air preheating. In this analysis, 4 phi (phi is the fuel /
POX with an equivalence ratio of air
A reformer and pre-heating means with a phi of 0.21 were utilized. When such a POX reformer was used, it was observed that about 58% of the fuel stream 61 remained due to the reaction in the SOFC (15). The remaining fuel utilization entering the SOFC was limited to about 50%. Fuel limiting was performed by conventional techniques for limiting stack current, but other limiting techniques could be used. The remaining fuel is 3.4 gas stoichiometric (3.
4 air stoichs). "Excess air"
Stack heat is conducted-radiated (cond
uction-radiation), which is removed by a mechanism of partial internal reforming. In such an example, the SOFC
(15) As a part of the cooling configuration of the SOFC as a whole, 60% so as to take advantage of partial internal reforming.
Operates in the range 0 ° C to 800 ° C. In such an example, the overall electrical efficiency (ignoring the loss of fan and power conversion) is calculated to be about 20% for a battery operating at a voltage of 0.70V. of course,
Other embodiments may have low-grade applications where such applications have low electrical and thermal requirements. Such a low-grade application is the use of reduced SOFCs and, thereby, cheaper SFCs.
Enable OFC (to be used).

The above description and drawings merely describe and illustrate the invention, as those skilled in the art, having read this disclosure, can make improvements and modifications thereto without departing from the scope of the invention. The present invention is not limited thereto except insofar as the claims are limited.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the configuration of the improved equipment of the present invention.

FIG. 2: Ratio of the fuel of the preheating burner to the change of the preheating temperature (in absolute temperature [k]) [mol / mol]
FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Burner system 20 Partial reforming means 25 Air preheating means 30 Heat recovery means 32 Inlet 32 SOFC fuel inlet 34 SOFC air inlet 36 SOFC anode outlet 38 SOFC cathode outlet 40 Reforming Apparatus 42 Preheater air inlet 44 Preheater fuel inlet 46 Preheater outlet 48 Heating device combustion chamber 50 Reformer fuel inlet 51 Reformer air inlet 52 Reformer Outlet 54 Cathode inlet of heat recovery means 56 Anode inlet of heat recovery means 58 Outlet of heat recovery means

Claims (15)

[Claims] 1. Solid oxide fuel cell; means connected to the solid oxide fuel cell for partially reforming the fuel prior to introduction of the fuel into the solid oxide fuel cell; solid oxide oxidation of air Means connected to the solid oxide fuel cell for preheating the air prior to introduction into the solid fuel cell; and a solid oxide fuel cell for recovering thermal energy from the exhaust of the solid oxide fuel cell. Burner system consisting of connected means. 2. The burner system according to claim 1, wherein the solid oxide fuel cell comprises a low temperature fuel cell stack. 3. The burner system according to claim 1, wherein the solid oxide fuel cell comprises a monolithic cell. 4. The burner system according to claim 1, wherein the partial reforming means comprises a POX reformer. 5. The burner system according to claim 1, wherein the fuel comprises natural gas. 6. The burner system according to claim 1, wherein the air preheating means includes means for supplying a predetermined amount of fuel to the preheating means. 7. The burner system according to claim 6, wherein the supply means delivers between about 23% and 30% of the fuel supplied to the burner system to the preheating means. 8. The burner system according to claim 1, wherein the recovery means comprises at least one combustor. 9. The air preheating means is off-stoichiometric.
The burner system according to claim 1, comprising a chiometric combustor. 10. The method of claim 1, wherein the recovery means is substantially stoichiometric.
The burner system according to claim 1, comprising an iometric combustor. 11. The burner system according to claim 1, wherein the reforming means includes means for receiving a predetermined amount of gas exiting the preheating means. 12. A method for generating heat, comprising: preheating a predetermined amount of air with a preheater; partially reforming a fuel stream with a reformer; Passing air through at least a portion of the solid oxide fuel cell; and burning at least a portion of the exhaust gas of the solid oxide fuel cell. 13. The means for preheating includes: deflecting a predetermined amount of fuel to a preheater; and burning the fuel with the preheater, thereby preheating a predetermined amount of air. 13. The method of claim 12, comprising the step of: 14. The means for burning fuel comprises means for burning fuel with a non-stoichiometric burner.
The method described in. 15. The apparatus of claim 12, wherein the means for reforming at least a portion of the fuel stream comprises: sending a predetermined amount of preheated air from the preheater to the reformer.
The method described in.