Patent Application
20110203290
1. Field of the Invention
The present invention relates to a control method and a control device for an exhaust heat recovery system for a marine vessel, in particular, a control method and a control device for an exhaust heat recovery system which changes an operation state of an auxiliary generator based on a reserve heat amount of the exhaust gas economizer.
2. Description of the Related Art
As an exhaust heat recovery system for vessels, there is a power generation system wherein a steam turbine is driven by performing heat exchange with exhaust gas discharged from a main engine with use of an exhaust gas economizer which utilizes the exhaust gas from the main engine, and a system wherein the supply power is generated by rotating a shaft generator by engine output so as to compensate for electric power demand within the vessel. These types of systems have been proposed in view of saving power in the vessel.
The exhaust heat recovery system generates electricity within the vessel by using the exhaust heat from the main drive unit of the vessel, e.g. an engine. Thus, once the power demand (electricity demand within the vessel) suddenly decreases, the electricity having been generated becomes surplus. Then, the rotation of the steam turbine and the gas turbine gets accelerated, which may causes damage to the turbines.
In contrast, a sudden stop of the engine causes a supply power shortage within the vessel, and in the worst case, the vessel can experience a blackout.
To take measure against the surplus power, it is possible to bypass the exhaust gas from the main drive unit (diesel engine) of the vessel to discharge the exhaust gas outside, or to release surplus steam having been generated in the exhaust gas economizer to a condenser so as to suppress production of electricity. In such case that the engine stops abruptly and there is supply power shortage, a power demand with low necessity is shut down and an auxiliary diesel generator is actuated while waiting for the power supply. However, this still leaves an issue that the vessel inevitably still goes into blackout when the power generation by the exhaust heat recovery system decreases before the power is supplied by the diesel generator.
The change of the supply power within the vessel due to the sudden stop of the main drive unit is illustrated in
As shown in
To prevent the blackout due to the sudden decline of the power generation by the generator such as the main generator, it is possible to perform the control described below. For instance, Patent Document 1 (JP 3804693B) proposes to suppress control delay by focusing on a temperature change of cooling water in response to a change of a recovered amount of the exhaust heat. Specifically, the invention of Patent Document 1 comprises: a temperature sensor which is arranged in a circulation pipe of the load side on a downstream side of an exhaust heat recovery unit and detects a temperature of circulating water on the load side; an amount detector which compares the temperature of the circulating water detected by the temperature sensor and a first preset temperature and output a heat-discharge signal depending on whether or not there exists an abnormal fluid state; a fluid state detector which is arranged in the circulation pipe of the load side and detects whether the fluid state of the circulation water on the load side is normal or abnormal and then outputs a heat discharge signal according to the fluid state; a holding means which outputs a heat discharge signal till a temperature of cooling water detected by a cooling water temperature sensor becomes below a second preset temperature; a feedforward-side control unit which outputs a control signal in response to the heat discharge signal so that an opening of a heat-discharge amount adjusting means is smaller than a preset opening in which the engine operates at a rated power and requisite amount of the cooling water is supplied to a heat exchanger for heat-discharge when the exhaust heat of a heat exhaust recovery load is not needed; and a feedback control means which output a signal to control the heat-discharge amount adjusting means based on the detected temperature of the cooling water so that the heat discharge amount increases as the detected temperature becomes higher, wherein the heat-discharge amount adjusting means is controlled by sum of the control output from the feedforward control means and the control output from the feedback control means.
However, the exhaust heat recovery system of Patent Document 1 focuses on the temperature of the cooling water to control the system, and fails to focus on the amount of heat (the amount of reserve heat) stored in the exhaust gas economizer on the vessel.
[Patent Document]
[PATENT DOCUMENT 1] JP 3804693B
In view of the problem above, an object of the present invention is to provide a control method and a control device for an exhaust heat recovery system which can prevent blackout within the vessel due to the sudden load change of the main engine.
To solve the problem, as a first specific example of a first aspect of the present invention, the present invention proposes a control method for an exhaust heat recovery system which comprises an exhaust gas economizer to which exhaust gas generated in a main engine of a vessel is introduced via a turbocharger, a steam turbine powered by steam generated in the exhaust gas economizer, a gas turbine driving a generator together with the steam turbine, and an auxiliary generator compensating for a decline in electricity based on power generation by the generator, and in which a portion of the exhaust gas generated in the main engine is supplied to the gas turbine so as to discharge the exhaust gas from the gas turbine to the exhaust gas economizer, the control method comprising the steps of:
acquiring an estimated or calculated current reserve heat amount (Q) based on a heat energy detection signal of the exhaust gas economizer;
acquiring, based on an operation state of the auxiliary generator and power demand within the vessel, a reference heat amount (Qmin) which is required to maintain requisite power needed until the auxiliary generator is actuated; comparing the current reserve heat amount (Q) and the reference heat amount (Qmin); and
selecting an operation state of the auxiliary generator based on a result of the comparing step, from a shutoff state, a standby state and a driving state.
The exhaust gas economizer is a device specifically for vessels and may be installed in a chimney of the vessel. For instance, heat exchanging pipes are closely installed in the chimney and water is introduced through the pipes so as to produce steam or heat water by performing heat exchange with the exhaust gas discharged from the main engine.
The current reserve heat amount Q may be calculated from (amount and temperature of) cooling water introduced to the exhaust gas economizer from a cooler (ref.
Moreover, the auxiliary generator includes an auxiliary generator body and a drive unit such as a diesel engine being directly or indirectly connected to the auxiliary generator body. The auxiliary generator has three operation states: a shutoff state in which the drive unit is shutoff; a standby state in which the auxiliary generator is disconnected from the drive unit which is still actuated and the auxiliary generator is not rotating (commonly called, an idling operation); and a driving state in which the auxiliary generator body and the drive unit are connected to transmit the energy of the drive unit side to the auxiliary generator side.
According to the present invention, the current reserve heat amount (Q) and the reference heat amount (Qmin) are compared, and the operation state of the auxiliary generator is selected based on a result of the comparing step, from the shutoff state, the standby state and the driving state so that the current reserve heat amount (Q) becomes greater than the reference heat amount (Qmin). As a result, it is possible to start up the auxiliary generator before the supply power within the vessel becomes lower than the requisite power even when there is a sudden output decline of the main engine and thus, the requisite power generation (the power generation corresponding to the minimal requisite power within the vessel needed for a security reason to avoid the blackout) can be secured and the blackout within the vessel can be avoided.
More specifically, as a second specific example, it is preferable that the auxiliary generator is shut off when the current reserve heat amount (Q) reserved in the exhaust gas economizer is greater than the reference heat amount (Qmin) and a reserve heat amount (Qstop) which is required to maintain requisite power until the auxiliary generator gets in a state to generate power from the shutoff state when the main engine stops, i.e. Q≧Qstop>Qmin.
By this, the requisite power generation can be maintained without generating surplus power within the vessel, thereby saving the auxiliary generator from the non-stop operation.
Furthermore, as a second specific example, it is preferable that the auxiliary generator is set in the standby state when the current reserve heat amount (Q) reserved in the exhaust gas economizer is smaller than the reserve heat amount (Qstop) and greater than a reserve heat amount (Qstby) which is required to maintain requisite power until the auxiliary generator get in a state to generate power from the standby state when the main engine stops, i.e. Qstop>Q≧Qstby>Qmin.
In this manner, it is possible to actuate the auxiliary generator by keeping the auxiliary generator in the standby state. Thus, the blackout within the vessel can be avoided even when the output of the main engine declines suddenly.
Moreover, as a third specific example, it is also preferable that the auxiliary generator is set in the driving state when the current reserve heat amount (Q) reserved in the exhaust gas economizer is smaller than both the reserve heat amount (Qstop) and the reserve heat amount (Qstby), i.e. Qstop>Qstby≧Q≧Qmin.
When the current reserve heat amount (Q) reserved in the exhaust gas economizer is smaller than both the reserve heat amount (Qstop) and the reserve heat amount (Qstby), the auxiliary generator is actuated immediately from the standby state to avoid the blackout within the vessel.
Therefore, the present invention is unique in the points described below.
1.Qmin≧Q is avoided by controlling the operation state of the auxiliary generator when the main engine is still operating (before the sudden stop of the main engine). By this, the power generation which corresponds to the minimal requisite power needed within the vessel for a security reason to avoid the blackout, can be promptly obtained even when the main engine stops (the sudden drop of the output of the main generator caused by the sudden energy drop of the exhaust gas).
In this case, the current reserve heat amount Q is obtained by the calculation or estimation. And it is determined which one of the operation states 2-4 listed below the estimated/calculated current reserve heat amount is in, and the operation state is selected. 2. Qstop>Qstby≧Q≧Qmin→continuing the driving state 3. Qstop>Q≧Qstby>Qmin→the standby state (idling operation state) 4. Q≧Qstop>Qmin→the shutoff state
As a second aspect of the present invention, the above control method may further comprise the step of:
By this, even when the output of the main engine drops suddenly, the reserve heat amount Q reserved in the exhaust gas economizer can be increased and thus, it is possible to maintain the requisite power needed till the auxiliary generator is actuated, thereby preventing the blackout within the ship.
Further, as a first specific example of the second aspect of the present invention, it is preferable that the opening of the bypass valve is reduced when the current reserve heat amount (Q) reserved in the exhaust gas economizer is greater than a reserve heat amount (Qstop) which is required to maintain requisite power until the auxiliary generator gets in a state to generate power from the shutoff state when the main engine stops.
By this, the requisite power can be maintained without causing power surplus within the vessel.
Furthermore, as a second specific example of the second aspect of the present invention, it is also preferable to increase the opening of the bypass valve when the current reserve heat amount (Q) reserved in the exhaust gas economizer is smaller than the reserve heat amount (Qstop) which is required to maintain requisite power until the auxiliary generator gets in a state to generate power from the shutoff state when the main engine stops.
By this, the reserve heat amount Q reserved in the exhaust gas economizer is increased and thus the heat recovery in the steam turbine can be increased as well. As a result, the period when the auxiliary generator can be inactive is increased, thereby saving fuel.
As a device to perform the above method in a preferable manner, the present invention also proposes a control device for an exhaust heat recovery system which comprises an exhaust gas economizer to which exhaust gas generated in a main engine of a vessel is introduced via a turbocharger, a steam turbine powered by steam generated in the exhaust gas economizer, a gas turbine driving a generator together with the steam turbine, an auxiliary generator compensating for a decline in electricity based on power generation by the generator and a portion of the exhaust gas generated in the main engine is supplied to the gas turbine so as to discharge (amount of heat of) the exhaust gas from the gas turbine to the exhaust gas economizer, the control device comprising:
an acquiring unit which estimates or calculates a current reserve heat amount (Q) based on a heat energy detection signal of the exhaust gas economizer;
an acquiring unit which obtains, based on an operation state of the auxiliary generator and power demand within the vessel, a reference heat amount (Qmin) which is required to maintain requisite power until the auxiliary generator is actuated; and
a control unit which controls the auxiliary generator by selecting an operation state of the auxiliary generator from a shutoff state, a standby state and a driving state so that the current reserve heat amount (Q) becomes greater than the reference heat amount (Qmin).
Further, the above-mentioned control device may preferably comprise:
a bypass line which bypasses the gas turbine to supply a portion of the exhaust gas generated in the main engine to the exhaust gas economizer;
a bypass valve adjusting unit which adjusts an opening of the bypass valve so that the current reserve heat amount (Q) reserved in the exhaust gas economizer becomes greater than the reference heat amount (Qmin).
By this, in the same manner as the above-described method, the blackout within the vessel can be prevented against the sudden load change of the main engine by accelerating the actuation of the auxiliary generator or by maintaining the requisite power until the actuation of the auxiliary generator.
According to the present invention, the vessel can be operated for a while by the heat amount reserved in the exhaust gas economizer even if the engine stops suddenly and thus, it is possible to avoid the blackout within the vessel by keeping the reserve heat amount of the exhaust economizer not less than a predetermined amount.
The present invention successfully provides the control method and the control device for the exhaust heat recovery system, which can prevent the blackout within the vessel against the sudden load change of the main engine.
A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. It is intended, however, that unless particularly specified, dimensions, materials, shape, its relative positions and the like shall be interpreted as illustrative only and not limitative of the scope of the present.
First, a configuration of an exhaust heat recovery system in relation to the present invention is explained in reference with
Further, the exhaust heat recovery system of the present invention is equipped with an exhaust gas economizer 24. The exhaust gas discharged from the engine 18 is supplied to the exhaust gas economizer 24 via the turbocharger 22 or the gas turbine. The exhaust gas economizer 24 produces steam out of the exhaust gas and the steam turbine 8 is then driven by the steam and rotates the generator 6 together with the output of the gas turbine 10.
The dotted line in
Furthermore, the auxiliary generator 4 functions as an auxiliary diesel generator (DG) having a diesel engine connected to a body thereof. The auxiliary generator has three operation states: a shutoff state in which the diesel engine is shutoff; a standby state in which the auxiliary generator 4 is disconnected from the diesel engine which is still actuated and the auxiliary generator is not rotating (commonly called, an idling operation at a low speed); and a driving state in which the auxiliary generator body and the diesel engine are connected so as to generate power.
During the operation of the auxiliary generator 4, the auxiliary generator 4 generates at least minimal requisite power required within the vessel for a security reason to avoid the blackout.
A control circuit 30 for the auxiliary generator 4 includes a calculation circuit 31, an estimation circuit 32, a comparison unit 33, a judging circuit 34, an auxiliary generator operation control unit 35, and a bypass valve control unit 36. The calculation circuit 31 sets a period of time needed to actuate the auxiliary generator based on requisite power required within the vessel for a security reason (hereinafter simply referred to as the requisite power) and the operation state of the auxiliary generator, and then calculates a reference heat amount Qmin of the exhaust gas economizer needed to generate enough steam energy to drive the steam turbine so as to drive the main generator for the period previously set. The estimate circuit 32 estimate a current reserve heat amount Q of the exhaust gas economizer 24 from an outlet temperature Ts of the steam and/or an outlet temperature Tg of the exhaust gas from the exhaust gas economizer 24. The comparison unit 33 compares the current reserve heat amount Q and the reference heat amount Qmin and the obtained result of the comparison is sent to the judging circuit 34. An appropriate operation state is selected by the auxiliary generator operation control unit 35 and the bypass valve control unit 36 by the control of the judging circuit.
The auxiliary generator operation control unit 35 controls the auxiliary generator during the normal operation of the main engine (before the sudden stop of the main engine) to avoid the reserve heat amount Q reserved in the exhaust gas economizer being smaller than the reference heat amount Qmin, i.e. Qmin≧Q by selecting an operation state of the auxiliary generator from the shutoff state, the standby state and the driving state or by forcibly starting (actual driving) the auxiliary generator at a point when the sudden stop of the engine is detected by a detection sensor arranged on the engine side to detect the sudden stop of the main engine (the engine 18).
Moreover, the electricity within the vessel is generated with use of the exhaust gas of the main engine (engine) of the vessel and thus, when there is a sudden decline in the load, the power being generated becomes surplus. Therefore, the rotation of the gas turbine is accelerated, thereby causing damage thereof. To take measure against the issue caused by power surplus, the bypass valve control unit 36 is provided to open the bypass valve 11 fully and/or control the opening of the bypass valve 11 to bypass the gas turbine to supply the exhaust gas from the main engine (diesel engine). The current reserve heat amount Q estimated during the process is compared with Qstop to perform the control of
To prevent the blackout of the vessel against the sudden demand power change of the vessel being equipped with the above exhaust heat recovery system, it is preferable to set control values listed below in advance.
Pmin: Minimal requisite power needed within the vessel for a security reason to avoid the blackout
Sstop: Time needed for the auxiliary generator to get to a state capable of generating power from the shutoff state (time that takes to reach the drive load corresponding to the minimal requisite power Pmin from a point at which the auxiliary generator is actuated)
Sstby: Time needed for the auxiliary generator to get to a state capable of generating power from the idling state (time that takes to reach the drive load corresponding to the minimal requisite power Pmin by actual-driving from the idling state)
Qstop: Heat amount needed for power generation Ps by the steam turbine to reach the minimal requisite power Pmin from the shutoff state of the engine for the time Sstop, or longer Qstby: Heat amount needed for power generation Ps by the steam turbine to reach the minimal requisite power Pmin from the shutoff state of the engine for the time Sstop or longer
In
Next, a control method for the exhaust heat recovery system in relation to the first preferred embodiment is explained in reference to
As illustrated in
Therefore, in the preferred embodiment, the control is performed so as to accelerate the actuation of the auxiliary generator (DG) as indicated by the arrow S of
The control method for the exhaust heat recovery system of the first preferred embodiment is explained in reference to
First, in a step S1, the current reserve heat amount Q of the exhaust gas economizer is estimated from the steam temperature Ts or the outlet temperature Tg of the exhaust gas. The steam temperature Ts and the outlet temperature Tg of the exhaust gas are measured at the outlet of the exhaust gas economizer 24 as shown in
In a step S2, the current reserve heat amount Q estimated in S1 is compared with Qstop. If Q>Qstop, the auxiliary generator is set in the shutoff state in a step S3. Then, in a step S4, the time is counted and the process returns to the step S1.
If the inequality of Q>Qstop is not satisfied, Q is compared with Qstby in a step S5. If it is determined that Q>Qstby in the step S5, the auxiliary generator is set in the standby state in a step S6. Then, in the step S4, the time is counted and the process returns to the step S1. In contrast, if it is determined that the inequality of Q>Qstby is not satisfied in the step S5, the auxiliary generator is set in the driving state in a step S7. Then, in the step S4, the time is counted and the process returns to the step S1.
In this manner, the operation state of the auxiliary generator is selected from the shutoff state, the standby state and the driving state so that the auxiliary generator can be actuated faster even when the sudden decline of the engine output such as the sudden stop of the engine takes place. As a result, it is possible to avoid the blackout within the vessel.
Next, a control method for the exhaust heat recovery system in relation to a second preferred embodiment is explained in reference to
The electricity within the vessel is generated with use of the exhaust gas of the main engine (engine) of the vessel and thus, when there is a sudden decline of the power demand, the power having been generated becomes surplus. Then, the rotation of the gas turbine is accelerated, thereby causing damage thereof. To take measure against the issue caused by power surplus, a bypass valve opening control unit 36 controls the opening of the bypass valve 11 based on the power demand within the vessel by opening the bypass valve 11 fully and/or controlling the opening of the bypass valve 11 to bypass the gas turbine to supply the exhaust gas from the main engine (diesel engine).
In this state, the current reserve heat amount Q for the exhaust heat recovery system is compared with Qstop to perform the control of
A control method for the exhaust heat recovery system in relation to the second preferred embodiment is explained in reference to
First, in a step S11, the current reserve heat amount Q of the exhaust gas economizer is estimated from the steam temperature Ts or the outlet temperature Tg of the exhaust gas.
In a step S12, the current reserve heat amount Q estimated in S11 is compared with Qstop. If Q>Qstop, the opening amount of the bypass valve is reduced in a step S13. The bypass valve here is a gas turbine bypass valve 11 shown in
If the inequality of Q>Qstop is not satisfied in the step S12, Q is compared with Qstby in a step S16. If it is determined that (Qstop>) Q>Qstby in the step S16, it is determined in a step S17 whether or not the gas turbine bypass valve 11 is full-open. When it is determined that the bypass valve 11 is full-open, the auxiliary generator is set in the standby state in a step S18. Then, in the step S15, the time Sstby is counted and the process returns to the step S11 so that the supply power reaches the requisite power Pmin.
Further, if it is determined that the inequality of Q>Qstby is not satisfied in the step S16, it is still determined in a step S19 whether or not the gas turbine bypass valve 11 is full-open. When it is determined that the bypass valve 11 is full-open, the auxiliary generator is set in the driving state in a step S20 by actuating the auxiliary diesel engine and connecting the auxiliary generator body thereto. Then, in the step S15, the time Sstop is counted and the process returns to the step S11 so that the supply power reaches the requisite power Pmin.
In contrast, if it is determined in the step S17 or S19 that the gas turbine bypass valve 11 is not full-open, the opening amount of the bypass valve 11 is increased. Then, in the step S15, the time is counted and the process returns to the step S11 so that the supply power reaches the requisite power Pmin.
In this manner, the operation state of the auxiliary generator is changed among the shutoff state, the standby state and the driving state so as to achieve Q>Qmin. Further, the opening amount of the gas turbine bypass valve is increased to enhance heat recovery in the steam turbine so that the current reserve heat amount Q of the exhaust gas economizer becomes greater than Qstop. Thus, the steam turbine generates more power than the gas turbine.
As a result, it is possible to maintain the requisite power needed until the auxiliary generator is actuated as shown in
Furthermore, in both the first preferred embodiment and the second preferred embodiment, the sudden decline of the power demand within the vessel causes power surplus within the vessel, and thus an opening amount of a gas turbine inlet valve 13 (ref.
According to the present invention, the blackout within the vessel against the sudden load change of the main engine is successfully prevented. Therefore, it is beneficial to apply the present invention to a control method and device for an exhaust heat recovery system.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-331595 | Dec 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/070993 | 12/16/2009 | WO | 00 | 5/6/2011 |
