KR100827334B1 - Fuel cell system shut-down method - Google Patents

Abstract

A method for shutting down the household fuel cell system is provided to prevent the discharge of toxic and combustible gas to air, to improve the efficiency of system and to simplify the constitution and control logic. A method for shutting down the household fuel cell system comprises the steps of (S1) gradually reducing the load of a stack to 30% and reducing the fuel supply amount to a fuel converter to 30% according the decrease and supplying the open gas of a stack to a burner; (S2) reducing the load of a stack to 0 to shut town the operation of a stack if the load of the stack reaches 30%, and supplying then open gas of a stack to a burner; (S3) blocking the injection of a purification gas discharged from the fuel converter into a stack if the stack is shut down, and supplying the purification gas to the burner; (S4) reducing the fuel supply amount to the fuel converter to 0 so as to shut down the operation of the fuel converter; (S5) purging the fuel converter to supply the remaining gas to the burner; and (S6) performing the purging step for a certain time and to completely shutting down the operation of system.

Description

Fuel cell system shut-down method

1 is a schematic configuration diagram of a conventional domestic fuel cell system,

2 is a flow chart of a method for ending operation of a domestic fuel cell system according to the present invention;

3 is a graph showing the relationship between the stack load and the fuel supply amount to the fuel converter at the end of the fuel cell system operation;

4 is a graph of the reformer temperature according to the fuel converter fuel supply amount;

5 is a graph of the temperature of the CO transformer according to the fuel converter fuel supply amount,

6 is a graph of the temperature of the CO remover according to the fuel converter fuel supply amount,

7 is a graph showing the relationship between stack load, fuel supply amount and steam supply amount,

8 is a schematic configuration diagram of a fuel cell system in which operation ends according to the present invention.

* Description of the symbols for the main parts of the drawings *

10: fuel converter 11: reformer

12: CO transformer 13: CO remover

14: Burner 20: Stack

The present invention relates to a method for operating a domestic fuel cell system, and more particularly, to a method for terminating an operation to prevent the release of toxic and flammable gases into the atmosphere.

A fuel cell is a power generation device that directly converts chemical energy of a fuel into electrical energy by an electrochemical reaction. Therefore, since it is not subject to the thermodynamic limitation (Carnot efficiency) of the heat engine in principle, it is more efficient than the existing power generation equipment, has no environmental problems with no pollution and noise, and can be manufactured in various capacities. It is a cutting-edge technology with high expectations in terms of power system operation, such as easy transmission and reduction of transmission and transmission facilities.

Accordingly, although it is attracting attention as a home energy system, a 1 to 3 kW fuel cell system using a polymer electrolyte membrane fuel cell (PEMFC) is mainly developed for home use.

1 schematically shows a configuration of a conventional domestic fuel cell system.

The fuel converter 10 converts the supplied fuel gas (hydrocarbons such as NG and LPG) into a gas containing a large amount of hydrogen that can be used in the stack 20 (referred to as hydrogen rich gas and susori gas). The initial reforming process is mostly done by steam reforming (SR), autothermal reforming (ATR), catalytic partial oxidation (CPOX) or non-catalytic partial oxidation (POX).

The present invention is applied to a fuel cell system using a fuel converter 10 for converting fuel gas into hydrogen-containing gas using a steam reforming reaction.

The fuel converter 10 receives a fuel gas and reformers 11 for generating a large amount of hydrogen, carbon monoxide (CO) and carbon dioxide (CO2) by steam reforming reaction, and the reformed gas generated therefrom through a shift reaction. CO transformer 12 for reducing the amount of sulfur to 1% or less, and CO remover for reducing CO to 10 ppm or less, which is a level capable of supplying CO to the stack 20 through selective oxidation by mixing the modified gas discharged therefrom with air. (13) (CO purifier) and a burner (14) for receiving the fuel gas and burning it to preheat the reactors, and in particular to supply heat required for the reforming reaction.

The fuel gas is passed through a desulfurizer to remove the sulfur component contained in the amount of about 3.5 ppm as a odorant, and then supplied to the reformer 11.

In addition, the purification gas supply pipe 30 is connected between the CO remover 13 and the stack 20, the off-gas recovery pipe 31 is connected between the stack 20 and the burner 14, purification Gas is supplied to the stack 20 for power generation, and off-gas containing unused residual hydrogen is supplied to the burner 14 to reduce the external fuel supply to the burner 14 during system rated operation, thereby improving system efficiency. To promote

In addition, the unstable gas discharge pipe 32 is connected to the purified gas supply pipe 30 to discharge the unstable purified gas that is not purified to a sufficient level at the start and end of operation to the outside (the stack due to CO ( 20) prevention of poisoning of the catalyst (platinum), the off-gas discharge pipe (33) is connected to the off-gas recovery pipe (31) to discharge the off-gas with excess heat at the beginning and end of operation to the burner (14) ), It is possible to prevent overheating of the burner 14.

In addition, the bypass pipe 34 is connected between the purge gas supply pipe 30 and the off-gas recovery pipe 31 to bypass the unstable purge gas directly to the burner 14 to poison the stack 20 catalyst. Prevented. In each of the pipelines, the valves 40, 41, 42, 43, 44 for performing the above control are installed in place.

On the other hand, after operating the stack 20 for the required time at the rated time, in order to end the operation of the fuel cell system, the operation of the stack 20 is ended by reducing the load of the stack 20 and then the fuel converter 10 The operation of the fuel converter 10 is ended by stopping the supply of fuel gas to the fuel cell 10.

However, as described above, since the off gas discharged during the load reduction of the stack 20 and the purge gas discharged from the fuel converter 10 after the operation of the stack 20 are terminated include an excessive amount of heat, the burner 14 as described above. In addition, overheating damages the burner 14 and the fuel converter 10, as well as disabling normal temperature control of the respective reactors.

Therefore, conventionally, at the end of the fuel cell system operation, off gas generated while the load of the stack 20 decreases is discharged to the atmosphere through the off-gas discharge pipe 33, and after the operation of the stack 20 ends, the fuel converter 10 is finished. Purification gas generated during the operation of the) is discharged into the atmosphere through the unstable gas discharge pipe (32).

However, since the purge gas and off gas contain CH ₄ and H ₂ , which are toxic and flammable, when released to the outside of the system, there is a risk of pollution and explosion. In order to suppress the prior art had to install a separate purification device has a problem that the configuration and control of the system is complicated.

Accordingly, the present invention has been made to solve the above problems, it is possible to prevent the emission of toxic and flammable gases into the atmosphere without the need to install additional devices to reduce the risk of environmental pollution and fire accidents. Therefore, there is no need for a purification device installed for the purification of the toxic and flammable gas, thereby simplifying the configuration of the fuel cell system, and supplying and burning off-gas and purified gas to a burner until the operation is completed. The purpose of the present invention is to provide a method of terminating the operation of a domestic fuel cell system that can increase fuel efficiency by reducing fuel consumption.

The present invention for achieving the above object,

The load of the stack is gradually reduced from rated to 30% of the rated load, and the fuel supply to the fuel converter is reduced to 30% of the rated load as the load of the stack decreases, and the off-gas of the stack is supplied to the burner. And reducing the fuel supply amount;

In the stack load and fuel supply reduction step, when the load of the stack reaches 30%, the stack operation is immediately reduced by zeroing the stack load to zero, and the stack stop step of supplying off-gas of the stack to the burner;

When the stack is stopped in the stack stop step, the stack of the purge gas discharged from the fuel converter is blocked, and the purge gas stack input blocking step of supplying the purge gas to the burner;

A fuel converter stopping step of terminating operation of the fuel converter by reducing the fuel supply amount to zero after the purge gas stack input blocking step;

A purge step of purging the fuel converter after the fuel converter stop step and supplying residual gas therein to a burner;

After the purge step for a predetermined time, the step of terminating the operation of the system completely;

It is made, including.

Therefore, the operation of the fuel cell system can be terminated without discharging off-gas of the stack and purge gas of the fuel converter to the outside of the system.

Hereinafter, with reference to the accompanying drawings the present invention will be described in detail.

Figure 2 is a flow chart showing the progress of the operation termination method of the home fuel cell system according to the present invention, the present invention is a stack load and fuel supply amount reduction step (S1), the stack stop step (S2), purge gas stack input It comprises a blocking step (S3), a fuel converter stop step (S4), a purge step (S5) and the end step (S6).

To terminate the operation of the system, first reduce the stack load by 30% (preferably by 10%) while the stack 20 is operating at nominal (C).

At this time, while the hydrogen utilization rate of the stack 20 is maintained at 70 to 80% of the hydrogen utilization rate at the rated operation, the fuel supply amount supplied to the reformer 11 of the fuel converter 10 according to the load reduction of the stack 20 is equal to the rated value. Simultaneously decreases to 30% (stack load and fuel supply reduction step (S1)).

The relationship between the load reduction of the stack 20 and the fuel supply amount of the fuel converter 10 is shown as (b) in FIG. 3. (A) shows the case of the conventional method for ending the operation of a conventional fuel cell system.

In the conventional case (a), the fuel supply amount is maintained at the rating (c) while reducing the stack load at the end of the operation, and when the stack load reaches zero, the operation of the stack 20 is terminated to stop the fuel converter ( It prevents the inflow of the stack 20 of the purge gas discharged from 10). Subsequently, the fuel supply amount was decreased to terminate the operation of the fuel converter 10 and purge the fuel cell system.

Therefore, conventionally, fuel is continuously supplied unnecessarily until the stack load is reduced and the operation of the stack 20 ends, and no off-gas is introduced into the burner 14 of the fuel converter 10. During the load reduction of 20, a large amount of additional fuel must be supplied to the burner 14 by the amount of off-gas heat, so that the fuel consumption is increased and the system efficiency is lowered.

On the other hand, in the case of the present invention (b), while reducing the stack load (C → A) at the end of the operation, the fuel supply amount is simultaneously reduced at the same rate (c → a). At this time, the fuel supply amount is adjusted so that the hydrogen of the stack 20 maintains 70 to 80% of its utilization rate. Off-gas used for power generation of the stack 20 continues to be supplied to the burner 14 of the fuel converter 10. When the load of the stack 20 is reduced to 30% (or 10%) A of the rating, the stack load is immediately reduced to zero and the operation of the stack 20 is terminated. After the stack 20 operation is completed, the purge gas is supplied to the burner 14 of the fuel converter 10, and then the operation of the fuel cell system is terminated by stopping the fuel supply to the reformer 11.

As described above, by adjusting the fuel supply amount supplied to the reformer 11 during the end of operation of the fuel cell system, the fuel supply amount used for power generation is maintained by maintaining the hydrogen utilization rate of the stack 20 at 70 to 80% as in the rated time. Is reduced.

In addition, since it is not necessary to supply an excessive amount of heat to the fuel converter 10, the content of the combustible component H ₂ in the off gas supplied to the burner 14 can be reduced as much as possible, and the fuel until the system operation is completed. Continued introduction of offgas into burner 14 of converter 10 reduces the additional fuel consumption of burner 14 for the reforming reaction. Thus, system efficiency is improved by minimizing the amount of fuel used during system operation termination.

Now, while the stack load and fuel supply amount reduction step S1 are in progress, using the change of the fuel supply amount according to the stack load in FIG. 3, and further controlling the reformer 11 temperature of the fuel converter 10. As a result, the operating temperature of each reactor of the fuel converter 10 in which the purge gas discharged from the fuel converter 10 can remove CO to 10 ppm or less so that the stack can be loaded while having the same composition at all times regardless of the stack load variation. To present.

4 is a graph showing the temperature of the reformer 11 according to the fuel supply amount of the fuel converter 10. In general, the reaction temperature at which the reforming reaction normally occurs is between 500 and 750 ° C. as shown in (c), and the reformed gas generated in this range is introduced into the stack 20 through the CO transformer 12 and the CO remover 13. Converted to possible purge gas.

As described above, the present invention operates by controlling the temperature of the reformer 11 as shown in FIG. That is, when the fuel supply amount is rated (c), the reformer 11 temperature is controlled to maintain 700 ℃. Since the fuel supply amount is reduced, the temperature of the reformer 11 is controlled at 620-640 ° C. at the intermediate stage (b), and the temperature of the reformer 11 is reduced from 570 to 620 at a time when the fuel supply amount is reduced to 30% of the rating. Controlled to 600 ° C. The reformer 11 temperature control is controlled by adjusting the amount of fuel additionally supplied to the burner 14.

As described above, the operating temperature of the reformer 11 controlled according to the stack load fluctuation is correlated with the stack load fluctuation of the composition of the purification gas in consideration of the temperature of the CO transformer 12 and the CO remover 13 mounted at the rear end of the reformer 11. It was confirmed through repeated experiments to be discharged constantly without. That is, the purge gas discharged from the CO remover 13 in all the load areas is H ₂ 70% or more, CH ₄ 2% or less, CO ₂ and N ₂ 20% and CO has a constant composition in which CO is removed to 10 ppm or less. It was confirmed that the discharge in 10).

The purge gas is used for power generation of the stack 20 and supplied to the burner 14 of the fuel converter 10 in the off-gas form and used as fuel of the burner 14. Therefore, the hydrogen utilization rate of the stack 20 and the additional fuel supply amount of the burner 14 were calculated based on the composition and the flow rate of the purge gas, and applied to the fuel cell system operation control logic using this. In particular, when the purge gas is supplied to the stack 20 in a constant composition regardless of the load variation of the stack 20, even if the load of the stack 20 varies, the hydrogen utilization rate used in the stack 20 is calculated using a calculated value. Control to keep it constant is possible. In addition, by calculating and applying the additional fuel supply amount of the burner 14 and the operating temperature fluctuation range of the reformer 11 for the reformer 11 temperature control, the end operation control of the fuel cell system is easily induced.

FIG. 5 is a graph illustrating an operating temperature range of the CO transformer 12 that is displayed as a result of adjusting the temperature of the reformer 11 according to a change in fuel supply amount to the fuel converter 10 as shown in FIG. 4. In general, the active temperature range of the catalyst mounted on the CO transformer 12 is approximately 180 ~ 250 ℃ at rated. However, as a result of reducing the fuel supply amount and adjusting the temperature of the reformer 11 as in the present invention, the operating temperature of the CO transformer 12 is maintained at 220 to 230 ° C. at the rated c, but the fuel supply amount is 30% ((a When it decreases to), it reaches 180 ~ 190 ℃.

In addition, as shown in Fig. 6, the operating temperature of the CO remover 13 is operated at 150 ° C at the rating (c) and is operated at 120 ° C reduced by 30 ° C when the fuel supply amount is reduced to 30%.

 In the applicant's prior application (2007.04.20.) 10-2007-0038651 (method for starting the operation of the home fuel cell system) when the load of the fuel cell system is operated at 30%, the CO transformer 12 of the fuel converter 10 Is 150 ℃ or more, CO remover 13 was confirmed that the normal reaction proceeds at 100 ℃ or more can be removed to a CO concentration of the purge gas below 10ppm. Therefore, since the operation temperature of the CO transformer 12 and the CO remover 13 at the end of the operation of the fuel converter 10 of the present invention is greater than the active temperature, the purge gas discharged from the CO remover 13 is sufficiently stacked 20. It can be seen that the input is possible.

Referring to Figure 7, using a change in the fuel supply amount according to the stack load, and further controls the amount of water vapor supplied to maintain a thermal balance of the fuel converter 10 and to induce a stable purge gas discharge Explain.

If the S / C ratio of the feed fuel is low in the operation of the fuel converter 10, the performance of the CO denaturation reaction is reduced and caulking the catalyst mounted on the reformer 11 and the CO transformer 12 at a high temperature. Coking occurs and durability is reduced. On the other hand, when the steam / carbon ratio is high, a large amount of heat is consumed to heat the steam, thereby reducing the efficiency of the fuel converter 10.

Therefore, there is an appropriate water vapor / carbon ratio to ensure the efficiency of the fuel converter 10 and the stability of the purge gas, and such operating conditions were confirmed through repeated experiments.

As a result, it was confirmed that the efficiency was the best when the water vapor / carbon ratio of the fuel supplied at the rating was 2.5-3.

However, when the fuel converter 10 is operated at a low load, the fuel supply amount decreases and the temperature gradient of each reactor, the burner 14, the heat exchanger, etc. in the fuel converter 10 is unstable due to the change of the reaction temperature according to the load. In this case, the composition and flow rate of the purification gas are affected. When the water vapor / carbon ratio is maintained as it is in the fuel converter 10 to which the present invention is applied, the stability of the purification gas becomes less than 50% of the stack load. It was confirmed that the decrease.

Therefore, by increasing the steam / carbon ratio (S / C ratio) of the feed fuel at 50% or less of the stack load, the stability of the purge gas discharged from the fuel converter 10 is not lowered.

As shown in FIG. 7, when the stack is operated at the rated C and the fuel supply amount supplied to the reformer 11 is also rated c, the amount of water vapor is 2.5 to 3 (S / C ratio). e).

When the stack load is reduced to 50% (B) to terminate the operation, the fuel gas and water vapor volume are also reduced together, and are supplied in amounts of 50% (fuel supply b) and water vapor supply f respectively). That is, in this section, the steam / carbon ratio is maintained at 2.5 to 3 as in the rated operation.

Then, when the load of the stack 20 is reduced from 50% (B) to 30% (A), the fuel supply amount is also 50% (b), which is the same ratio so that the hydrogen utilization rate of the stack 20 is maintained at 70 to 80%. To 30% (a).

However, the steam supply is at least 30% of the rated g. That is, the water vapor supply amount in the section of the stack load 50% (B) or less is reduced at a rate smaller than the rate of water vapor supply decrease in the section of the stack load 50% (B) or more. In the present invention, it is preferable to operate the steam / carbon ratio = 3 at a stack load of 50% and to control the amount of steam supplied according to the load reduction such that the steam / carbon ratio = 4 at the stack minimum load (30% or 10%). In other words, to reduce the amount of steam supplied to the amount of fuel supplied following the stack load, the decrease tends to be maintained but the rate of reduction is alleviated so that the amount of water supplied is reduced compared to the previous section, but the water vapor / carbon ratio is controlled to increase. .

That is, when the load is 50%, the stable purge gas is discharged, but since the purge gas is continuously supplied to the stack 20, the water vapor supply rate is supplied from 50% before reaching the load 30%, the end point of the stack 20 operation. By increasing the reaction to remove the CO from the reforming reaction as well as the CO denaturation reaction to the maximum to suppress the unstable gas emissions.

In addition, the residual gas present in the fuel converter 10 after the termination by inducing the maximum reaction as described above in the low load section (unreacted CH ₄ and Carbon causes coking phenomenon to reduce durability and performance). The amount was to be minimized.

On the other hand, when the stack stop step (S2) is carried out at 10% of the stack load, the fuel supply amount is also reduced to 10% of the rating, which is the same ratio, and at the time of increasing the water vapor / carbon ratio in controlling the steam supply amount, the stack load is indicated. You can raise it at 30% instead of 50%. That is, in this case, the load of the stack 20 gradually decreases to 10%, and then immediately decreases to zero and ends.

Next, the amount of air for selective oxidation reaction supplied to the CO remover 13 is also reduced following the stack load, but the oxygen / carbon monoxide ratio (O ₂ / CO ratio) is maintained at 1.5 to 2.5, which is a value at the rated operation.

Selective oxidation reaction is too forms a CO shift converter 12 is 1% or less, preferably by reaction with the CO of 0.5% of air removed with CO _2, but excessive generation of H ₂ and the reaction H ₂ O Due to side reactions discharged from When a large amount of air is supplied, a large amount of H ₂ is consumed in addition to CO, and as a result, the operating efficiency of the fuel cell system is reduced. Therefore, at the end of the fuel cell system operation, the oxygen / carbon monoxide ratio of the CO remover 13 maintains 1.5 to 2.5 equal to the rating as described above and reduces the load.

If the load of the stack 20 reaches 30% while the stack load and fuel supply amount reduction step S1 are performed as described above, the load of the stack 20 is immediately reduced to zero and operation of the stack 20 is stopped. (Stack stop step S2).

The offgas discharged in the above process is continuously supplied to the burner 14.

After the stack 20 is stopped in the stack stop step (S2), the purge gas discharged from the fuel converter 10 is blocked from being introduced into the stack 20, and the burner (3) is passed through the bypass pipe 34. 14) (purified gas stack input blocking step (S3).

Here, since the purge gas is supplied to the burner 14 of the fuel converter 10 without consuming a certain amount of heat, more heat than the required amount is supplied to the burner 14 to cause problems such as burning (generally the fuel converter 10). The purge gas discharged from the gas has about 2-4 times higher heat than burner 14 needs.)

However, when the load of the stack 20 reaches 30% (A), the water vapor / carbon ratio introduced to the reformer 11 is supplied at 3 to 4 higher than the rated value, so that a large amount of water is used to denature the liquid water into water vapor. The amount of heat is required, and the temperature of the reformer 11 is 570-600 ° C. at a load of 30%, which is lower than the rated temperature of 700 ° C., and the time required for the end point is very short. Even if it is supplied to 14, problems such as deterioration of the reforming catalyst and burning of the burner 14 do not occur.

Therefore, the stack stop step (S2) and the purge gas stack input blocking step (S3) may be performed at a load of 30% or less, preferably at a minimum load of 10%.

Thereafter, the fuel supply to the fuel converter 10 is reduced to zero (zero) to stop the operation of the fuel converter 10 (fuel converter stop step S4).

When the supply of fuel gas is stopped as described above, the fuel converter 10 is purged using inert gas, water vapor and fuel gas, and the remaining gas is supplied to the burner 14 to burn the combustible component as much as possible. (Purge step (S5))

The purge step S5 is sufficiently performed for 2 to 5 minutes so that the remaining gas in the fuel converter 10 can be completely discharged, and the operation of the fuel cell system is completely terminated. (End step S6)

As described above, at the end of operation of the fuel cell system, the load of the fuel converter 10 is simultaneously reduced while gradually reducing the supply amount of reactant fuel gas, water vapor, and air as the load of the stack 20 decreases. By increasing the water vapor / carbon ratio (S / C ratio) of the fuel supplied to (10) to stabilize the thermal gradient in the fuel converter 10 to ensure the stability of the purge gas discharged.

As a result, the purge gas of the fuel converter 10 is used for power generation of the stack 20 and the off gas discharged from the stack 20 is circulated / burned to the heat source of the burner 14 of the fuel converter 10 during the operation of the fuel cell system. It is possible to effectively prevent the release of toxic and flammable gases into the air, thereby preventing the risk of environmental pollution and fire accidents.

In addition, as the stack load and fuel supply are gradually reduced, the operation of the system is terminated. Therefore, when the abrupt termination is performed at the rated rate as in the past, the reduction of durability of the system is suppressed in the longer term, and at the same time, the off gas generated in the stack 20 Is recovered by the burner 14 and burned, thereby suppressing excess fuel gas consumption, thereby improving system efficiency during operation termination.

Therefore, as shown in FIG. 8, there is no need to provide a conventional unstable gas discharge pipe 32, an off gas discharge pipe 33, and valves 42 and 43 installed thereon, and further purify the system. There is no need to install the device. As such, the present invention not only simplifies the configuration of the system, but also enables a simple configuration of the controller and control logic for driving the valve.

As described above, according to the present invention, the emission of toxic and flammable gases is prevented at the end of operation of the fuel cell system, thereby eliminating the causes of environmental pollution and safety accidents.

Efficiency is improved by reducing the fuel supply at the end of the system.

Unstable gas exhaust pipes, off-gas exhaust pipes, and separate purifiers are not required, simplifying the configuration and control of the system.

Shutdown of the system proceeds gradually, avoiding the impact of sudden shutdown, thereby improving the durability of the system.

Claims (10)

The load of the stack 20 is gradually reduced from the rated to 30% of the rating, and the fuel supply amount to the fuel converter 10 is reduced to 30% of the rating as the load of the stack 20 decreases, and the stack 20 Off gas of the) is the stack load and fuel supply amount reducing step (S1) for supplying to the burner 14; When the load of the stack 20 reaches 30% in the stack load and fuel supply reduction step S1, the load of the stack 20 is immediately reduced to zero and the operation of the stack 20 ends, and the stack 20 Off gas of the stack (S2) for supplying to the burner 14; When the stack 20 is stopped in the stack stop step (S2), the stack of the purge gas discharged from the fuel converter 10 is blocked, and the purge gas stack input blocking step of supplying the purge gas to the burner 14 ( S3); A fuel converter stop step (S4) of terminating the operation of the fuel converter 10 by reducing the fuel supply amount to the fuel converter 10 after the purge gas stack input blocking step S3; After the fuel converter stop step (S4), to purge the fuel converter (10) to supply a residual gas in the burner (14) and (S5); After performing the purge step (S5) for a predetermined time, the termination step (S6) to completely terminate the operation of the system; Operation termination method of the domestic fuel cell system comprising a. The method according to claim 1, When the load of the stack 20 is reduced to 10% in the stack load and fuel supply reduction step S1, the fuel supply amount to the fuel converter 10 is reduced to 10% of the rating and the stack stop step S2 is performed. Home fuel cell system operation termination method. The method according to claim 1, Reducing the amount of fuel supplied to the reformer 11 while maintaining the hydrogen utilization rate of the stack 20 in the stack load and fuel supply amount reducing step (S1) the same as the rated operation (70 ~ 80%). How to terminate the operation of a domestic fuel cell system. The method according to claim 1, Household fuel cell, characterized in that for controlling the temperature of the reformer 11, the CO transformer 12 and the CO remover 13 so that the composition of the purification gas is kept the same in the stack load and fuel supply amount reduction step (S1). How to shut down the system. The method according to claim 4, The temperature of the reformer 11 is controlled to decrease from 700 ℃ to 570 ~ 600 ℃ while the stack load is reduced from the rated to 30% of the rating. The method according to claim 4, The temperature of the CO transformer 12 is controlled to decrease from 220 ~ 230 ℃ to 180 ~ 190 ℃ while the stack load is reduced from the rated to 30% of the rating. The method according to claim 4, The temperature of the CO remover (13) is controlled to be reduced from 150 ℃ to 120 ℃ while the stack load is reduced from 30 to 30% of the rating. The method according to claim 1, While reducing the amount of steam supplied to the reformer 11 in the stack load and fuel supply reduction step (S1), the steam / carbon ratio at the rated operation (2.5 to 3) in a section where the stack load is reduced to 50% from the rated load (2.5 to 3). Maintaining the same, and the operation termination method of the home fuel cell system, characterized in that to increase from 3 to 4 in the section of reduction from 50% to 30%. The method according to claim 2, The stack load and the amount of fuel supplied to the reformer 11 in the fuel supply amount reducing step (S1) are reduced together, while the steam / carbon ratio is rated at the time of operating the steam / carbon ratio in a section in which the stack load is reduced to 30% from the rating (2.5 to 3). ) And the operation termination method of the home fuel cell system, characterized in that the increase to 3 to 4 in the section of decreasing from 30% to 10%. The method according to claim 1, Reduction of the amount of air supplied to the CO remover 13 in the stack load and fuel supply reduction step (S1), while maintaining the oxygen / carbon monoxide ratio to the same as in the rated operation (1.5 ~ 2.5) How to shut down the battery system.

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