Integrated gasification combined cycle and operation control method thereof

An integrated gasification combined cycle that can adjust the balance of pressure/temperature in an overall plant and can stabilize the output of a gas turbine at an early stage during load variation, and an operation control method of the integrated gasification combined cycle are provided. When a calorific abnormality of fuel gas is detected during load variation of a gas turbine (5b), a load change command value of the gas turbine (5b) is set to zero or is decreased, and based on this load change command value, a power generation output command of the gas turbine (5b) is generated.

TECHNICAL FIELD

The present invention relates to an integrated gasification combined cycle and an operation control method thereof.

BACKGROUND ART

Heretofore, an integrated gasification combined cycle (IGCC) that combines a gas turbine facility and a steam turbine facility has been known (for example, see Patent Document 1).Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2002-129910

DISCLOSURE OF INVENTION

One problem experienced in this IGCC is, for example, output variation of a gas turbine which occurs during load variation, as described below.

In general, the response speed of a steam turbine is low as compared to that of a gas turbine. Hence, as shown inFIG. 14, since the delay in response of the steam turbine is compensated for by the gas turbine during load variation, a gas-turbine output command overshoots (A inFIG. 14). During this overshoot, since a large amount of fuel gas must be supplied to the gas turbine, a large compressor extraction airflow of the gas turbine is necessary as compared to that required during normal operation, as shown by f inFIG. 14, and furthermore, the amount of powdered coal and the like to be charged in a gasification furnace is also increased (B inFIG. 14).

When the compressor extraction airflow of the gas turbine is increased, the pressure of the gasification furnace is not likely to be increased. As a result, in order to maintain a predetermined pressure, in the gasification furnace, a larger amount of air must be supplied, and hence the amount of air supplied to the gas turbine is decreased.

When the amount of air supplied to the gas turbine is decreased, the temperature therein is increased, and as a result, the operation is shifted to a temperature control mode. During this temperature control, in order to maintain an inlet temperature constant, since the output is reduced (C inFIG. 14), the amount of fuel gas flowing from the gasification furnace is decreased, and the pressure therein is concomitantly increased (D inFIG. 14).

Accordingly, in the gasification furnace, in order to lower the increased pressure to the original level, control for decreasing the amount of air supplied to the gasification furnace is performed (E inFIG. 14), and as a result, the pressure in the gasification furnace is decreased (F inFIG. 14).

In addition, concomitant with the decrease in pressure in the gasification furnace, the temperature in the gas turbine is gradually decreased, and when the operation escapes from the temperature control mode, the output of the gas turbine is increased in accordance with the required load (G inFIG. 14).

Since the steps described above are repeatedly performed, the output of the gas turbine is repeatedly varied, and the output converges to an output value in accordance with a gas-turbine output command.

In addition, since the pressure variation or the like occurs in the gasification furnace as described above, the calorific value of fuel gas output from the gasification furnace is also varied, so that a calorific abnormality may occur in some cases. When the calorific abnormality described above occurs, the range of load variation of the gas turbine is further increased, and a problem may arise in that a longer time is necessary to obtain a stable output.

The present invention has been conceived to solve the problems described above, and an object of the present invention is to provide an integrated gasification combined cycle that can adjust the balance of pressure/temperature in an overall plant and, during load variation, that can stabilize the output of a gas turbine at an early stage, and to provide an operation control method of the integrated gasification combined cycle.

In order to achieve the above object, the present invention uses the following solutions.

According to a first aspect of the present invention, there is provided an operation control method of an integrated gasification combined cycle, wherein when a calorific abnormality of fuel gas is detected during load variation of a gas turbine, a load change command value of the gas turbine is set to zero or is decreased, and based on this load change command value, a power generation output command of the gas turbine is generated.

As described above, when a calorific abnormality of fuel gas is detected during load variation of a gas turbine, since the load change command value of the gas turbine is set to zero or is decreased, the amount of fuel gas supplied to a combustor of the gas turbine can be maintained constant or can be decreased. Accordingly, since the flow rate of fuel gas output from a gasification furnace is stabilized, the gasification furnace can be operated so as to obtain a stable state. As a result, the operation of the gasification furnace can be stabilized at an early stage, and hence the calorific value of the fuel gas can be returned to a normal level at an early stage.

In the operation control method of an integrated gasification combined cycle, described above, when the load change command value is decreased, the range of decrease of the load change command value may be determined in accordance with the range of change of the calorific value of the fuel gas.

Accordingly, while an output of the gas turbine at a certain level is obtained, the gasification furnace can be stabilized.

In the above operation control method of an integrated gasification combined cycle, in the case in which the calorific abnormality is not detected when a load change demand of the gas turbine is set to zero or is decreased, the load change command value of the gas turbine may be returned to a normal level.

Accordingly, when the calorific abnormality is not detected, since the load change command value of the gas turbine is returned to a normal level, a desired output can be obtained by a stable operation control.

According to a second aspect of the present invention, there is provided an operation control method of an integrated gasification combined cycle, including: a first step of generating a power generation output command of a gas turbine using a value obtained by subtracting a power generation output of a steam turbine from a power generator output command, and in this method, a gasification furnace is controlled using the power generation output command of the gas turbine obtained in the first step.

As described above, since the power generation output command of the gas turbine is generated using the value obtained by subtracting the power generation output of the steam turbine from the power generator output command, and further the gasification furnace is controlled by using the power generation output command of the gas turbine, the delay of response of the steam turbine can be reflected in the operation control of the gasification furnace. Accordingly, the trackability of the gasification furnace with respect to the load variation can be improved, and by cooperative operation of the gasification furnace and the gas turbine, the output of the gas turbine can be stabilized at an early stage.

In the operation control method of an integrated gasification combined cycle, described above, by using a table or a relational expression in which the power generation output command of the gas turbine and required amounts of elements to be charged into the gasification furnace are related with each other, the required amounts of the elements corresponding to the power generation output command of the gas turbine obtained in the first step may be obtained, and correction amounts corresponding to the range of variation of the power generation output command of the gas turbine or the range of variation of the power generation output of the gas turbine may be added to the obtained required amounts to determine final required amounts of the elements, so that based on the final required amounts, the amounts of the elements to be charged into the gasification furnace are controlled.

As described above, the required amounts of the elements are obtained based on the table or the relational expression, and the correction amounts corresponding to the range of variation of the power generation output command of the gas turbine or the range of variation of the power generation output of the gas turbine are added to the obtained required amounts, so that the final required amounts of the elements are determined; hence, in accordance with the operating conditions of the gas turbine, the operation of the gasification furnace can be further enhanced.

Accordingly, the operation of the gas turbine can be further stabilized.

In the operation control method of an integrated gasification combined cycle, described above, while the gas turbine is in a temperature control state, the load change command value of the gas turbine may be set to zero or may be decreased, and the power generation output command of the gas turbine may be generated based on the load change command value.

During temperature control, since the load change demand of the gas turbine is set to zero or is decreased, the operating conditions of the gas turbine can be controlled so as to obtain a stable state. Accordingly, the gas turbine can escape from the temperature control state at an early stage and can return to a normal operation mode, that is, an operation mode in accordance with the load, at an early stage.

In the operation control method of an integrated gasification combined cycle, described above, while the gas turbine is in a temperature control state, the gasification furnace may be controlled by using the power generation output of the gas turbine instead of the power generation output command of the gas turbine.

During temperature control, regardless of the load, the control is performed so as to maintain an inlet temperature of the gas turbine constant. On the other hand, the gasification furnace is controlled based on the output command of the gas turbine. Accordingly, the operation of the gas turbine and that of the gasification furnace are controlled based on parameters which are completely independent of each other. Hence, the balance of temperature, pressure, and the like in a plant may be disrupted with high probability. On the other hand, according to the present invention, during temperature control, the actual output of the gas turbine is fed back to the gasification furnace so that the operation thereof is controlled; hence, cooperative operation of the gas turbine and the gasification furnace can be performed. Accordingly, since the balance of temperature, pressure, and the like in the plant can be maintained, even during temperature control, the operation control can be stably performed.

According to a third aspect of the present invention, there is provided an integrated gasification combined cycle in which when a calorific abnormality of fuel gas is detected during load variation of a gas turbine, a load change command value of the gas turbine is set to zero or is decreased, and based on this load change command value, a power generation output command of the gas turbine is generated.

According to a fourth aspect of the present invention, there is provided an integrated gasification combined cycle in which a power generation output command of a gas turbine is generated using a value obtained by subtracting a power generation output of a steam turbine from a power generator output command, and in which a gasification furnace is controlled using the generated power generation output command of the gas turbine.

In addition, the above aspects may be used in combination whenever possible.

The present invention provides advantages in that the balance of pressure/temperature in an overall plant can be adjusted and, during load variation, the output of the gas turbine can be stabilized at an early stage.

EXPLANATION OF REFERENCE SIGNS

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment

Hereinafter, an integrated gasification combined cycle (hereinafter referred to as “IGCC”) and a control operation method thereof, according to a first embodiment of the present invention, will be described with reference to the drawings.

FIG. 1is a view showing a schematic structure of the overall IGCC according to this embodiment.

As shown inFIG. 1, an IGCC1according to this embodiment primarily includes a gasification furnace3, a gas turbine facility5, a steam turbine facility7, and an exhaust heat recovery boiler (HRSG)30.

At the upstream side of the gasification furnace3, a coal supply facility10for supplying powdered coal to the gasification furnace3is provided. This coal supply facility10includes a pulverizer (not shown) which pulverizes coking coal into powdered coal of several to several hundreds of micrometers, and the powdered coal pulverized by this pulverizer is stored in a plurality of hoppers11.

The powdered coal stored in the hoppers11is transported, a fixed amount at a time, to the gasification furnace3together with nitrogen supplied from an air separation apparatus15.

The gasification furnace3includes a coal gasification unit3ain which gas flows from a lower side to an upper side and a heat exchange unit3bwhich is connected to a downstream side of the coal gasification unit3aand in which gas flows from an upper side to a lower side.

In the coal gasification unit3a, a combustor13and a reductor14are provided in this order from a lower side. The combustor13is a unit in which powdered coal and char are partly combusted, and in which the remaining is pyrolyzed to discharge volatile components (CO, H2, and lower hydrocarbons). In the combustor13, an entrained bed is used. However, a fluidized bed or a fixed bed may also be used.

The combustor13and the reductor14are provided with a combustor burner13aand a reductor burner14a, respectively, and powdered coal is supplied to the burners13aand14afrom the coal supply facility10.

It is designed that air is supplied to the combustor burner13aas a gasification agent from an extraction air pressure increasing device17together with oxygen separated by the air separation apparatus15. As described above, the combustor burner13ais designed such that air containing oxygen at an adjusted concentration is supplied thereto.

In the reductor14, powdered coal is gasified by high-temperature combustion gases from the combustor13. Accordingly, flammable gases used as a gas fuel, such as CO and H2, are generated from coal. A coal gasification reaction is an endothermic reaction in which powdered coal and carbon in char react with CO2and H2O in a high-temperature gas to generate CO and H2.

In the heat exchanger unit3bof the gasification furnace3, a plurality of heat exchangers (not shown) is disposed and is designed to generate steam by obtaining sensible heat from a gas supplied from the reductor14. Steam generated in the heat exchangers is primarily used as drive steam for driving a steam turbine7b. Gas passing through the heat exchanger unit3bis introduced into a char recovery apparatus20. This char recovery apparatus20includes a porous filter and traps char mixed in the gas for recovery by making it pass through the porous filter. The char thus trapped is deposited in the porous filter to form a char layer. In the char layer, Na and K components contained in the gas are condensed, and as a result, the Na and K components are also removed in the char recovery apparatus20.

The char thus recovered is returned to the combustor burner13aof the gasification furnace3together with nitrogen separated in the air separation apparatus15for recycling. In addition, the Na and K components returned to the combustor burner13atogether with char are finally discharged from a lower side of the coal gasification unit3atogether with molten ash of powdered coal. The molten ash thus discharged is quenched with water and is pulverized to form glassy slugs.

Gas passing through the char recovery apparatus20is supplied as fuel gas to a combustor5aof the gas turbine facility5.

Between the char recovery apparatus20and the combustor5aof the gas turbine facility5, a branched path22is provided, and a gas purification facility24is provided downstream of this branched path22. The gas purification facility is a facility performing dust removal and desulfurization.

The gas turbine facility5includes the combustor5ain which a gasified fuel is combusted, a gas turbine5bdriven by a combusted gas, and a turbo compressor5csupplying high-pressure air to the combustor5a. The gas turbine5band the turbo compressor5care connected to each other by the same rotary shaft5d. Air compressed by the turbo compressor5cis also supplied to the air pressure increasing device17as well as to the combustor5a.

A combusted exhaust gas passing through the gas turbine5bis introduced into the exhaust heat recovery boiler30.

The steam turbine7bof the steam turbine facility7is connected to the same rotary shaft5dof the gas turbine facility5, so that a so-called single-shaft type combined system is formed. High-pressure steam is supplied to the steam turbine7bfrom the gasification furnace3and the exhaust heat recovery boiler30. In addition, besides the single-shaft type combined system, a multi-shaft type combined system may also be used.

A power generator G which outputs electricity using the rotary shaft5ddriven by the gas turbine5band the steam turbine7bis provided at a side opposite to that of the gas turbine facility5with the steam turbine facility7interposed therebetween. In addition, the position of the power generator G is not limited to that described above and may be provided at any place as long as an electric output can be performed using the rotary shaft5d.

The exhaust heat recovery boiler30generates steam using a combusted exhaust gas from the gas turbine5band also discharges the combusted exhaust gas to the atmosphere from a chimney35.

Next, the operation of the integrated gasification combined cycle1having the above structure will be described.

The coking coal is pulverized by the pulverizer (not shown) and is then fed to the hoppers11for storage. The powdered coal stored in the hoppers11is supplied to the reductor burner14aand the combustor burner13atogether with nitrogen separated in the air separation apparatus15. Furthermore, besides powdered coal, char recovered in the char recovery apparatus20is also supplied to the combustor burner13a.

As a combustion gas of the combustor burner13a, air is used which is formed by adding oxygen separated in the air separation unit15to compressed air obtained by further increasing the pressure of compressed air extracted from the turbo compressor5cof the gas turbine facility5using the extraction air pressure increasing device17. In the combustor13, powdered coal and char are partly combusted by combustion air, and the remaining is pyrolyzed into volatile components (CO, H2, and lower hydrocarbons).

In the reductor14, powdered coal supplied from the reductor burner14aand char from which volatile components are discharged in the combustor13are gasified by a high-temperature gas flowing up from the combustor13, so that flammable gases, such as CO and H2, are generated.

Gas passing through the reductor14supplies its sensible heat to the heat exchangers while passing through the heat exchanger unit3bof the gasification furnace3, so that steam is generated. The steam generated in the heat exchanger unit3bis primarily used to drive the steam turbine7b.

Gas passing through the heat exchanger unit3bis introduced into the char recovery apparatus20, so that char is recovered. Na and K components in the gas are condensed in this step and are incorporated in the char. The char incorporating the Na and K components is returned to the gasification furnace3.

Gas passing through the char recovery apparatus20is introduced into the combustor5aof the gas turbine facility5and is then combusted together with compressed air supplied from the turbo compressor5c. The gas turbine5bis rotated by this combusted gas, and the rotation shaft is driven.

A combusted exhaust gas passing through the gas turbine5bis introduced into the exhaust heat recovery boiler30, and by using the sensible heat of this combusted exhaust gas, steam is generated. The steam generated in the exhaust heat recovery boiler30is primarily used to drive the steam turbine7b.

The steam turbine7bis rotated by the steam from the gasification furnace3and the steam from the exhaust heat recovery boiler30and drives the rotary shaft which is also used for the gas turbine facility5. A rotation force of the rotary shaft is converted into an electric output by the power generator G.

Next, the control of the gasification furnace3of the above-described IGCC will be described with reference toFIGS. 2 and 3.

FIG. 2is a view showing primary constituent elements relating to the control of the gasification furnace.

As shown inFIG. 2, in a supply pipe for supplying powdered coal to the gasification furnace3from the coal supply facility10, a powdered-coal flow rate control valve41is provided to adjust the amount of powdered coal to be charged in the gasification furnace3. In addition, in an air pipe for introducing air into the gasification furnace from the extraction air pressure increasing device17, an airflow rate control valve42is provided to adjust the amount of air to be supplied to the gasification furnace. Furthermore, in this air pipe, a pressure control valve43to adjust the pressure is provided.

The valve openings of the powdered-coal flow rate control valve41, the airflow rate control valve42, and the pressure control valve43are controlled by a powdered-coal requirement command, an air requirement command, and a pressure command, respectively, which are output from a gasification furnace control apparatus50. In addition, in a fuel pipe for introducing fuel gas generated in the gasification furnace3into the combustor5aof the gas turbine facility5, a pressure sensor44for measuring a gasification furnace outlet pressure is provided in the vicinity of the outlet of the gasification furnace. A value measured by this pressure sensor44is output to the gasification furnace control apparatus50.

FIG. 3is a block diagram showing a schematic structure of the gasification furnace control apparatus50.

As shown inFIG. 3, it is designed that a gas turbine output command GT_MWD obtained in a turbine control apparatus70described later is input to the gasification furnace control apparatus50. In the gasification furnace control apparatus50, this gas turbine command GT_MWD is given to a design GID (gasification furnace total command value) setting unit51and a correction value calculation unit52.

The design GID setting unit51sets a design GID in order to perform preliminary control of the gasification furnace3according to the load of the gas turbine5b. The design GID setting unit51includes, for example, a table or a relational expression in which the gas turbine output command GT_MWD and the design GID are related with each other, and by using this table or the relational expression, the design GID corresponding to the gas turbine output command GT_MWD from the turbine control apparatus70is obtained.

The correction value calculation unit52obtains a correction value to correct the above design GID from the relationship, for example, between the gas turbine output command GT_MWD and the gasification furnace outlet pressure.

In particular, the correction value calculation unit52has a table or a relational expression in which the gas turbine output command GT_MWD and an outlet pressure command value of the gasification furnace3are related with each other, and after a pressure command value corresponding to the gas turbine output command GT_MWD from the turbine control apparatus70is obtained by using this table or the relational expression, the deviation (hereinafter referred to as “pressure deviation ΔP”) between this pressure command value and the actual gasification furnace outlet pressure is obtained, so that a value obtained by performing proportional-integral control on this pressure deviation ΔP is output as a correction value.

In addition, in an adder53, the design GID set by the above design GID setting unit51and the correction value obtained by the correction value calculation unit52are added to each other, and this added value is output as the gasification furnace total command value GID to a powdered-coal required amount setting unit54, an air required amount setting unit55, and a pressure setting unit56.

The setting units54to56have respective tables or computational formulas in which the gasification furnace total correction value GID is related with the required amounts of powdered coal, air, and pressure, respectively. By using the tables or the computational formulas, the respective required amounts corresponding to the gasification furnace total command value GID are obtained, and commands corresponding to the respective required amounts are generated. These commands are output to the units shown inFIG. 2as the powdered-coal requirement command, the air requirement command, and the pressure command and are used as control values controlling the amount of powdered coal charged into the gasification furnace3, the amount of air supplied thereto, and the gasification furnace outlet pressure, respectively.

In addition, although the above three setting units are shown inFIG. 3, besides the above setting units, setting units to set the amounts of oxygen and char to be charged may also be provided.

In addition, the above gasification furnace total command value GID obtained in the gasification furnace control apparatus50is given to the turbine control apparatus70described later and is used as one of a number of important parameters also in the gas turbine facility5.

Next, the control of the gas turbine facility5shown inFIG. 1will be described with reference toFIGS. 4 and 5.

FIG. 4is a view showing a primary structure relating to the control of the gas turbine facility5.

As shown inFIG. 4, in a fuel pipe for supplying fuel gas to the combustor5a, a fuel flow rate adjustment valve60adjusting a fuel flow rate is provided. The opening of this fuel flow rate adjustment valve60is controlled by the turbine control apparatus70. In an air pipe for supplying air to the turbo compressor5c, an airflow rate adjustment valve (hereinafter referred to as “IGV adjustment valve”)61adjusting an airflow rate is provided. The opening of this IGV adjustment valve61is adjusted by the turbine control apparatus70.

In the vicinity of the gas turbine5b, a BPT sensor (not shown) measuring an exhaust gas temperature (hereinafter referred to as “blade path temperature”) of the gas turbine5bis provided. In addition, at a position further downstream in an exhaust gas flow path in which the BPT sensor is provided, an EXT sensor (not shown) measuring an exhaust gas temperature at an exhaust duct (hereinafter referred to as “exhaust gas temperature”) is provided. For example, thermocouples are used as the above sensors. The temperatures measured by the BPT sensor and the EXT sensor are output to the turbine control apparatus70.

In addition, the output of the steam turbine7band the output of the power generator G are given to the turbine control apparatus70. The output of the steam turbine7bmay be obtained, for example, by calculation from the inlet state quantity of the steam turbine7b.

The turbine control apparatus70obtains the state quantities relating to the operating conditions and the temperature condition of the gas turbine as input signals, and based on these input signals, a fuel flow-rate valve-opening command value controlling a fuel flow rate supplied to the combustor5a, a pressure command value controlling a suction pressure of the extraction air pressure increasing device17, and the like are determined. As the state quantity relating to the above operating conditions, for example, the output of the power generator G, the output of the steam turbine7b, and the rotation speed or the number of rotations of the gas turbine5bmay be mentioned by way of example. In addition, as the state quantity relating to the temperature condition, for example, an exhaust gas temperature, a blade path temperature, or the like may be mentioned by way of example.

FIG. 5is a block diagram showing a schematic structure of the turbine control apparatus70.

First, when a target load of a power generator output is set by a shaft load setting device71, a power generator command MWD is set so that the load is changed to this target load at a plant load change rate (3% per minute). This power generator command MWD is subtracted by the output of the steam turbine by a subtracter72and is then input to a rate limiting unit73as a primary output command of the gas turbine.

The rate limiting unit73adjusts the primary output command of the gas turbine so as not to exceed the change rate (load change command value) set by the rate setting unit78and outputs a final gas turbine output command (power generation output command of the gas turbine) GT_MWD.

The rate setting unit78sets the change rate to 6% per minute when the calorific value of fuel gas is normal and sets it to zero when the calorific value of the fuel gas is abnormal.

Accordingly, while the calorific value of the fuel gas is detected as abnormal, since the change rate of the gas turbine output command is set to zero, the gas turbine output command GT_MWD during this period is prevented from changing and can be made constant.

The gas turbine output command GT_MWD output from the rate limiting unit73is input to a subtracter74so that the difference from the output of the gas turbine is calculated, and PI control using a PI controller75is further performed, so that a control command value LDC based on the required load is output to a selection circuit76.

For example, a temperature control command value EXC and BPC calculated based on the temperature, and a governor control command value GVC calculated based on a governor pressure are input to the selection circuit76. The selection circuit76selects the lowest value among the control command values described above and outputs it to a valve opening setting unit77as a control command value CSO. The valve opening setting unit77is provided in advance with a table or a relational expression in which the valve opening and the control command value CSO are related with each other. The valve opening setting unit77obtains an opening corresponding to the control command value CSO input from the selection circuit76using the table or the relational expression and outputs this valve opening as the fuel flow-rate valve-opening command value.

In addition, the gasification furnace total command value GID obtained in the above gasification furnace control apparatus50is given to a pressure setting unit79setting a suction pressure of the extraction air pressure increasing device17. The pressure setting unit79has a table or a computational formula in which the gasification furnace total command value GID and a pressure set value are related with each other, and by using this table or the computational formula, a pressure set value corresponding to the gasification furnace command value GID from the gasification furnace control apparatus50is obtained, so that a pressure command corresponding to this set value is generated. This pressure command is used as a control value determining the opening of the IGV adjustment valve61shown inFIG. 4.

Next, the operation of the gasification furnace control apparatus50and that of the turbine control apparatus70when a fuel gas abnormality occurs will be described.

When the fuel gas abnormality occurs, the change rate is set to zero by the change rate setting unit78. Hence, the gas turbine output command GT_MWD output from the rate limiting unit73is maintained at a constant value.

Accordingly, since the control command value CSO selected by the selection circuit76is made constant at the same value as described above, the opening of a fuel flow rate valve is maintained, so that the fuel flow rate supplied to the combustor5ais made constant. As a result, since the gas flow rate flowing from the gasification furnace3can be stabilized, the gasification furnace3can be placed in the state in which the operation thereof can be easily stabilized. Furthermore, in the gasification furnace3, since the amounts of the respective elements, such as powdered coal, air, and char, which are to be charged into the gasification furnace3are adjusted based on the gas turbine output command GT_MWD which is maintained constant, the operation state of the gas turbine can be reflected in the operation of the gasification furnace3.

As described above, according to the IGCC and the operation control method thereof in this embodiment, when a calorific abnormality of fuel gas occurs, since the gas turbine output command GT_MWD is made constant, the fuel gas supply amount can be made constant, and the conditions of the gasification furnace3, such as the pressure, temperature, and calorific value of fuel gas, can be stabilized at an early stage. Hence, the calorific value of fuel gas supplied to the combustor5acan be returned to a normal level at an early stage, and the operation of the gas turbine can be stabilized at an early stage.

Furthermore, according to the IGCC and the operation control method thereof in this embodiment, since the gas turbine output command GT_MWD is set by subtracting the actual output of the steam turbine from the power generator command MWD, the delay in response by the steam turbine7acan be reflected in the gas turbine output command GT_MWD. In addition, since the control of the gasification furnace3is performed based on the gas turbine output command GT_MWD in which the delay in response of the steam turbine is reflected, the delay in response of the steam turbine7acan be reflected in the control of the gasification furnace3, so that the responsiveness of the gasification furnace3can be improved.

In addition, in this embodiment, although the change rate of the power generation command of the gas turbine is set to zero when the calorific abnormality occurs, instead of the above, as shown inFIG. 6, the change rate of the gas turbine output command GT_MWD may be set to a change rate α lower than the normal change rate (6% per minute in the above case) so as to decrease the change rate of the gas turbine output command GT_MWD to less than the normal change rate.

In addition, also in this case, the change rate may be set in accordance with the range of change of the calorific value of the fuel gas. In particular, as the range of change of the calorific value is increased, the change rate is preferably decreased. As described above, when the change rate is set in accordance with the range of change of the calorific value of the fuel gas, precise control can be realized in accordance with the calorific condition.

Second Embodiment

Next, an IGCC and an operation control method thereof according to a second embodiment of the present invention will be described.

When a calorific abnormality of fuel gas is detected in the above first embodiment, the change rate setting unit78sets the change rate of the gas turbine output command GT_MWD to zero.

In this embodiment, as shown inFIG. 7, a pressure deviation ΔP obtained in the gasification furnace control apparatus50, that is, the difference between the pressure command value set based on the gas turbine output command GT_MWD and the actual gasification furnace outlet pressure, is given to the change rate setting unit78of the gas turbine control apparatus70, as shown inFIG. 8, and when the pressure deviation ΔP is larger than a standard value, the change rate setting unit77sets the change rate to zero.

With the structure described above, when the deviation between the gasification furnace outlet pressure and the pressure command value is larger than the standard value, the pressure abnormality is detected, and the gas turbine output command GT_MWD is rapidly made constant; hence, the control of the gasification furnace3can be stabilized at an early stage. As a result, the gasification furnace outlet pressure can be made close to a normal value at an early stage, and a normal state can be rapidly recovered.

Besides the case in which the change rate is set to zero, as described above, the range of decrease in change rate may be changed in accordance with the pressure deviation ΔP. For example, as the pressure deviation ΔP is increased, the change rate may be decreased.

Third Embodiment

Next, an IGCC and an operation control method thereof according to a third embodiment of the present invention will be described.

In the IGCC according to this embodiment, as shown inFIG. 9, the method for generating the powdered-coal requirement command and the method for generating the air requirement command in the gasification furnace control apparatus50are different from those of the first embodiment.

Hereinafter, differences from the first embodiment will be primarily described.

As shown inFIG. 9, in this embodiment, as in the first embodiment, by using a table in which GID and a powdered-coal required amount are related with each other, a coal required amount is first obtained, and by adding a coal acceleration command GIRfuelenhancing the operating conditions of the gasification furnace3to this coal required amount, a final powdered-coal requirement command is generated. In this case, the coal acceleration command GIRfuelis a control value which is set based on the output command GT_MWD of the gas turbine or the output thereof.

For example, the coal acceleration command GIRfuelis obtained by the structure as shown inFIG. 10. As shown inFIG. 10, after the output command GT_MWD of the gas turbine or the output of the gas turbine is received as input information, an upper limit change value of the coal required amount is obtained from the differential rate of change of the input information and a predetermined equation FX1, and the coal acceleration command GIRfuelis obtained by multiplying the upper limit change value and a standard GIR obtained from the predetermined equation FX1and the output command GT_MWD of the gas turbine or the actual output of the gas turbine.

In a manner similar to that described above, as for the air requirement command, as shown inFIG. 11, the air required amount is obtained by using a table in which GID and the air required amount are related with each other, and in addition, an air acceleration command GIRairenhancing the operating conditions of the gasification furnace3is added to this air required amount, so that a final air requirement command is generated. In this case, the air acceleration command GIRairis a control value which is set based on the output command GT_MWD of the gas turbine5bor the actual output thereof.

For example, the air acceleration command GIRairis obtained by the structure shown inFIG. 12. As shown inFIG. 12, after the output command GT_MWD of the gas turbine5bor the output thereof is received as input information, an upper limit change value of the air required amount is obtained from the differential rate of change of the input information and a predetermined equation FX2, and the air acceleration command GIRairis obtained by multiplying the upper limit change value and a standard GIR obtained from the predetermined equation FX2and the output command GT_MWD of the gas turbine or the actual output thereof.

As described above, according to the IGCC and the operation control method thereof in this embodiment, to the required amounts of powdered coal and air obtained based on GID, the respective acceleration commands GIRfueland GIRairwhich are set based on the output command GT_MWD of the gas turbine or the actual output of the gas turbine are further added so as to obtain the final powdered-coal requirement command and air requirement command; hence, the operation of the gasification furnace3during load variation can be further enhanced. As a result, the influence of output variation due to the delay in response of the steam turbine7bcan be reduced, and the output of the gas turbine can be stabilized at an early stage.

Fourth Embodiment

Next, an IGCC and an operation control method thereof according to a fourth embodiment of the present invention will be described.

In the first embodiment described above, although the change rate is set to zero or is decreased by the change rate setting unit78when a calorific abnormality of fuel gas is detected, in this embodiment, when the gas turbine5bis shifted to temperature control, or the exhaust gas temperature of the gas turbine5bis close to a predetermined temperature control starting temperature or more, the change rate is set to zero or is decreased by the change rate setting unit78, so that the change of the gas turbine output command GT_MWD is suppressed.

Accordingly, when the gas turbine5bis shifted to temperature control, the operation of the gas turbine5band that of the gasification furnace3can be stabilized.

In addition, as shown inFIG. 13, during the above temperature control, by using the actual output of the gas turbine5bor an actual output of the gas turbine5b, which is obtained after noise is reduced by filtering, instead of the gas turbine output command GT_MWD, the design GID may be obtained. Accordingly, the operation of the gasification furnace3can be stabilized during load variation.

For example, during temperature control in the gas turbine facility5, regardless of a required load, that is, regardless of the gas turbine output command GT_MWD, the control is performed so that the inlet temperature of the gas turbine is maintained constant. On the other hand, in the gasification furnace3, since the operation control is performed based on the gas turbine output command GT_MWD even during temperature control, the gas turbine5band the gasification furnace3are controlled by totally different parameters from each other; hence, the controls are separately performed.

In order to avoid the situation described above, in this embodiment, during temperature control, instead of using the gas turbine output command GT_MWD, since the operation of the gasification furnace3is controlled based on the actual output of the gas turbine, the condition of the gas turbine5bcan be reflected in the operation control of the gasification furnace3.

As has thus been described, according to the IGCC and the operation control thereof in this embodiment, since the operation of the gasification furnace3can be performed by reflecting the condition of the gas turbine5btherein even during temperature control, the overall plant can be stably operated.