JP2019094802A - Exhaust heat recovery system of marine engine, and control method of exhaust heat recovery system of marine engine - Google Patents

Abstract

To provide an exhaust heat recovery system for a marine engine, and its control method capable of suppressing fuel costs and COemission by suppressing fluctuation of a pressure of an evaporated gas supplied to an expander, and minimizing a heat charging amount from the external, in the exhaust heat recovery system of the marine engine converting heat energy of an exhaust gas of the marine engine including a supercharger into mechanical energy by the expander.SOLUTION: A flow rate of a working medium S supplied to an expander 25 is adjusted and controlled to cope with fluctuation of a demand amount of mechanical energy converted by the expander 25, and a flow rate of an exhaust gas Gb bypassing an exhaust turbine 12t of a marine engine 10 is adjusted and controlled on the basis of a valve opening β of a first steam flow rate control valve 27 for adjusting the flow rate of the working medium S supplied to the expander 25 or the demand amount to mechanical energy, to adjust a temperature Teg of an exhaust gas G supplied to an evaporator 23.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust heat recovery system of a marine engine in utilizing exhaust heat of a ship, a floating body structure or the like, and a control method of the exhaust heat recovery system of the marine engine.

  In ships and floating structures such as floating marine oil and gas production and storage facilities (FPSO) used for shipping, exhaust heat from marine engines is used to generate steam, and the steam drives the steam turbine with this steam. Utilization of waste heat from marine engines is progressing, including power generation.

  Related to this, the water from the steam separator is converted to steam by the exhaust gas economizer having an evaporator and a superheater using the heat of the exhaust gas from the diesel engine, and this steam is transferred to the steam turbine via the steam separator An exhaust heat recovery system has been proposed in which the generator is driven by the steam turbine, the steam exiting the steam turbine is returned to water by the condenser, and returned to the steam separator by the condensate pump (for example, Patent Document 1).

  In this exhaust heat recovery system, the flow rate of the steam supplied to the steam turbine is adjusted by the governor valve, and the steam provided in the bypass passage bypassing the steam turbine so that the pressure of the steam becomes the set pressure set by the operation mode. Adjustment is made by the valve opening of the dump valve. In addition, changes in the output of the diesel engine are handled by changing the set pressure. Further, the opening degree of the governor valve is controlled such that the fluctuation of the pressure of the steam of the steam water separator per unit time becomes equal to or less than a predetermined pressure.

  Also, by adjusting the water level in the low pressure steam water separator with the feed water control valve and adjusting it with the steam inlet control valve, the amount of power generation by the turbocharger caused by the rise and fall of the exhaust gas temperature accompanying the load change of the diesel engine An internal combustion engine system has been proposed which controls the amount of power generation by a steam turbine according to the increase or decrease (see, for example, Patent Document 2).

  On the other hand, in exhaust gas driven turbochargers used in main engines for ship propulsion, compressor efficiency has been improved, and in normal operation the desired compressed air is obtained without using the entire exhaust gas for turbine drive. It is possible to generate As an example of this method, there is a control method of an internal combustion engine with a NOx removal catalyst that controls the inlet temperature of the NOx removal catalyst exhaust gas by the opening degree of a bypass valve that extracts part of the exhaust gas and bypasses the turbocharger. It is proposed (for example, refer patent document 3).

  Also in the above internal combustion engine system, a configuration is disclosed in which by opening the exhaust bypass valve, part of exhaust gas from the exhaust manifold is bypassed to the exhaust gas economizer side without being supplied to the turbocharger. However, there is no description about the control of this exhaust bypass valve.

JP, 2017-180406, A JP, 2014-84853, A JP, 2013-139733, A

As described above, a part of the exhaust gas has been bypassed without passing through the turbine, and the environment where the temperature of the exhaust gas can be controlled has been established, but in general, it is generated in the exhaust heat boiler due to the exhaust heat of the internal combustion engine In an exhaust heat recovery system that drives a steam turbine with steam to generate electricity, etc., steam is generated by the heat of the exhaust gas and the combustion heat of fuel by the auxiliary burner, and the pressure of the steam is mainly adjusted by the auxiliary burner Pressure control is performed by increasing and decreasing the heat of combustion. However, when this auxiliary burner is used for pressure control of a waste heat boiler, fuel such as heavy oil is consumed, so there is a problem that CO ₂ emissions increase in addition to the deterioration of fuel efficiency.

  In addition, in an exhaust heat recovery system that uses exhaust gas from an internal combustion engine, it is required to supply steam at a constant pressure to a steam demand (demand steam volume) that changes more rapidly than the power demand (power demand) for power generation. However, there is a problem that the pressure fluctuation of the steam is large and it is difficult to cope with it. Furthermore, in ships, the load on marine engines, particularly marine propulsion engines (main engines), changes significantly due to disturbances such as rudder operation and the effects of ship maneuvering such as ship acceleration and deceleration, and the effects of weather, waves, and ocean currents. Because the amount and temperature of exhaust gases also change, there is also a problem unique to marine engines that the pressure fluctuation of the steam is further increased.

The present invention has been made in view of the above situation, and an object thereof is a marine engine for converting thermal energy of exhaust gas from a marine engine equipped with a turbocharger into mechanical energy by an expander through a working medium. In the exhaust heat recovery system of the present invention, exhaust heat of marine engines can be suppressed by suppressing fluctuations in the pressure of evaporated gas supplied to the expander and minimizing the amount of heat input from the outside, thereby reducing fuel consumption and CO ₂ emissions. It is an object of the present invention to provide a recovery system and a control method of an exhaust heat recovery system of a marine engine.

  The exhaust heat recovery system for a marine engine according to the present invention for achieving the above objects comprises a condenser, a pump, an evaporator, and an expansion using the heat quantity of exhaust gas from a marine engine equipped with a turbocharger. In an exhaust heat recovery system for a marine engine, wherein the working medium circulating in the tank is heated by the evaporator and the thermal energy of the exhaust gas is converted into mechanical energy by the expander, the exhaust gas from the turbocharger of the marine engine The exhaust passage in which the turbine is disposed is detoured around the exhaust turbine, and a bypass passage in which an exhaust gas flow control valve is disposed is provided, and a junction where the bypass passage joins the exhaust passage An exhaust gas temperature sensor for measuring the temperature of the exhaust gas after merging is provided in the exhaust passage further downstream, and a flow path for moving the working medium in the vapor phase from the evaporator to the expander , In the gas phase The control device controls the exhaust heat recovery system of the marine engine, comprising a steam flow control valve for adjusting the flow rate of the working medium and a steam pressure sensor for measuring the steam pressure of the working medium in the gas phase. Input the measured value of the valve flow of the steam flow control valve or the demand for mechanical energy converted by the expander and the temperature of the exhaust gas after merging detected by the exhaust gas temperature sensor, and the exhaust It is comprised so that the valve-opening degree of a gas flow control valve may be controlled.

  With this configuration, control of the flow rate of the gas phase working medium required by the expander for converting thermal energy into mechanical energy to control the demand for mechanical energy (control of the opening degree of the steam flow control valve Control of the exhaust heat recovery system of the marine engine in a state where the control of the temperature of the exhaust gas supplied from the marine engine to the evaporator (control of the valve opening degree of the exhaust gas flow control valve) is associated Will be able to

  In the exhaust heat recovery system for a marine engine as described above, the controller sets the target temperature of the exhaust gas, which is set using a valve opening degree of the steam flow control valve or a demand for mechanical energy converted into the expander. If the measurement value of the temperature of the exhaust gas after merging detected by the exhaust gas temperature sensor is configured to be controlled, the target temperature for controlling the temperature of the exhaust gas after merging is a specific target temperature To control the flow rate control of the gas-phase working medium required by the expander, which converts thermal energy into mechanical energy, and the temperature control of the exhaust gas from the marine engine supplied to the evaporator through various physical quantities It is possible to control the exhaust heat recovery system of a marine engine efficiently by using a relatively simple algorithm.

  In the exhaust heat recovery system for a marine engine as described above, the controller is configured to determine a valve opening degree of the steam flow control valve or a demand amount for mechanical energy converted by the expander, a steam pressure command value, and the steam pressure sensor If the target temperature is set using the measured value of the vapor pressure detected by the target, the target temperature, the demand for mechanical energy converted by the degree of opening of the steam flow control valve or the expander Not only the parameter of quantity but also the parameter of vapor pressure of the gas phase working medium can be used to control the exhaust heat recovery system of the marine engine more efficiently.

  In the above exhaust heat recovery system of a marine engine, the control device is a first output value by feedforward control with respect to a valve opening degree of the steam flow control valve or a demand for mechanical energy converted by the expander. This feedforward is configured when the target temperature is set using a second output value by feedback control using the steam pressure command value and the measured value of the steam pressure detected by the steam pressure sensor as an input. Control and control of feedback control, the demand for mechanical energy while maintaining a moderate response speed for both the slow response to changes in steam pressure in the exhaust heat recovery system of a marine engine and the fast response to exhaust gas temperature It will be possible to control the exhaust heat recovery system of the marine engine so that it can respond to the change in quantity.

  In the exhaust heat recovery system for a marine engine described above, the control device performs PID control in the feedback control, and for the difference between the steam pressure command value and the measured value of the steam pressure detected by the steam pressure sensor. If the proportional control part is configured to include an operation of subtracting the previous value of the difference in the difference, the effect of the velocity type PID control can be exhibited.

  In the exhaust heat recovery system for a marine engine described above, the control device sets a first control unit that sets the target temperature, and the target temperature and the temperature of the exhaust gas after merging detected by the exhaust gas temperature sensor. When the second control unit is configured to control the opening degree of the exhaust gas flow control valve based on the difference, in the second control unit, the merging detected by the target temperature and the exhaust gas temperature sensor It becomes possible to use a relatively simple control of controlling the opening degree of the exhaust gas flow control valve based on the difference with the temperature of the exhaust gas later, and the second control unit is designed again. The need is eliminated and commercially available controllers can be used.

  In the exhaust heat recovery system of the above marine engine, the working medium is water, the pump is a feed pump, and the evaporator is a heat exchanger for heating and evaporating water, and steam and saturated water And a steam turbine connected to a generator, the expander being a steam turbine connected to a generator, a waste heat recovery power generation system combining a waste heat boiler and a steam turbine, which is often used on ships It becomes.

  The control method of the exhaust heat recovery system for a marine engine according to the present invention for achieving the above objects comprises: collecting a condenser, a pump, evaporation using heat quantity of exhaust gas from a marine engine equipped with a supercharger In the control method of an exhaust heat recovery system of a marine engine, a working medium which sequentially circulates through an expander and an expander is heated by the evaporator and heat energy of exhaust gas is converted into mechanical energy by the expander. The flow rate of the exhaust gas passing through the exhaust turbine of the turbocharger and the flow rate of the exhaust gas bypassing the exhaust turbine are controlled by an exhaust gas flow control valve disposed in a bypass flow passage bypassing the exhaust turbine Thus, the temperature of the exhaust gas supplied to the evaporator is adjusted, and the flow rate of the working medium in the gas phase supplied to the expander moves the working medium in the gas phase from the evaporator to the expander. To do By controlling with the steam flow control valve disposed in the flow path, the fluctuation of the demand for the mechanical energy converted by the expander is coped with, and the opening degree of the steam flow control valve or the expander Using the measured value of the demand for the mechanical energy converted by the exhaust gas temperature detected by the exhaust gas temperature sensor after the merging of the exhaust gas passing through the exhaust turbine and the exhaust gas passing through the bypass flow passage And controlling the opening degree of the exhaust gas flow control valve.

  This control method controls the flow rate of the gas phase working medium required by the expander, which converts thermal energy into mechanical energy, and supplies it to the evaporator from the marine engine, in order to meet the demand for mechanical energy. The exhaust heat recovery system of the marine engine can be controlled in association with the control of the exhaust gas temperature.

According to the exhaust heat recovery system of the marine engine and the control method of the exhaust heat recovery system of the marine engine of the present invention, the thermal energy of the exhaust gas from the marine engine equipped with the supercharger is expanded by the expander via the working medium. In a marine engine exhaust heat recovery system that converts it into mechanical energy, while suppressing fluctuations in the pressure of the evaporative gas supplied to the expander, minimizing the amount of external heat input and suppressing fuel consumption and CO ₂ emissions it can.

It is a figure showing the composition of the exhaust heat recovery system of the marine engine of an embodiment concerning the present invention. It is a figure showing the composition of the 1st control part (upper rank controller) of the exhaust heat recovery system of the marine engine of an embodiment concerning the present invention. It is a figure which shows the structure of the 2nd control part (lower order controller) of the exhaust heat recovery system of the marine engine of embodiment which concerns on this invention.

Hereinafter, an exhaust heat recovery system of a marine engine and a control method of an exhaust heat recovery system of a marine engine according to an embodiment of the present invention will be described with reference to the drawings. Here, a main engine that rotates a propeller will be described as an example of a marine engine, and a power generation system (simple Rankine cycle) using an exhaust heat boiler as an example of an exhaust heat recovery unit. Therefore, the working medium of this exhaust heat recovery unit is water and steam, and the expander is a steam turbine connected to the generator.

  However, according to the present invention, the marine engine is not necessarily limited to the main engine, the exhaust heat recovery unit is not limited to the power generation system using the exhaust heat boiler, and the Rankine cycle is also not limited to the simple Rankine cycle.

  As shown in FIG. 1, the waste heat recovery system 1 for a marine engine according to an embodiment of the present invention comprises a main engine (marine engine) 10 and a waste heat recovery unit 20 having a power generation system with a waste heat boiler. It is located in the rear engine room inside the hull. Moreover, in order to control the exhaust heat recovery system 1 of this marine engine, it has the control apparatus 40 which has 1st control part (upper level controller: C1) 41 and 2nd control part (lower level controller: C2) 42. .

  The main engine 10 for driving the propeller 2 is often constituted by a low speed diesel engine. In this main engine 10, the output shaft (crankshaft) 15 driven by the piston 14 sliding in the cylinder 13 is a propeller It is directly connected to the shaft 16 and rotates the propeller 2 located overboard. A rudder 3 is provided on the rear side of the propeller 2. The propeller shaft 16 is provided with a rotational speed sensor (N) 16 a. By changing the engine rotation speed Ne of the main engine 10 based on the rotation speed measurement value Nms detected by the rotation speed sensor 16a, the propeller rotation speed Np is controlled, and the propulsive force generated by the propeller 2 is controlled. ing.

  Next, the configuration of the main engine 10 will be described. As shown on the left side of FIG. 1, in the main engine 10, air A is pressurized by the compressor 12 c of the supercharger 12 provided in the intake passage 11, and further, air cooling (not shown) installed in the intake passage 11 The mixture is cooled by the vessel to form supercharged air A, which is introduced into the cylinder 13. By injecting fuel F into the cylinder 13 and burning it, the piston 14 is slid in the cylinder 13 to rotate the output shaft 15 to obtain a driving force for rotating the propeller 2.

  On the other hand, the exhaust gas (combustion gas) G discharged from the cylinder 13 is temporarily introduced into the exhaust receiver 18 provided in the exhaust passage 17 and further exits the exhaust receiver 18 to rotationally drive the exhaust turbine 12t of the turbocharger 12 Thereafter, heat is exchanged by an exhaust heat boiler (evaporator) 23 called an economizer or an exhaust gas boiler or the like of the exhaust heat recovery unit 20, and the heat is discharged to the atmosphere from a silencer (not shown).

  Further, in order to adjust the temperature of the exhaust gas G, a bypass flow passage 19 is provided, and an exhaust gas flow control valve 19 v is provided in the bypass flow passage 19. Further, an exhaust gas temperature sensor 17 b is disposed in the exhaust passage 17 on the downstream side of a junction 17 a where the bypass passage 19 joins the exhaust passage 17. Based on the measured value Tegm of the temperature Teg of the exhaust gas G after merging detected by the exhaust gas temperature sensor 17b, the exhaust gas flow control valve 19v controls the flow rate adjustment of the exhaust gas Gb, and the exhaust gas after merging Adjust the temperature Teg of G.

  That is, when the exhaust gas flow control valve 19v is closed, the total amount G of the exhaust gas G passes through the exhaust turbine 12t of the turbocharger 12 and is expanded by the isentropic process, and the temperature Teg of the exhaust gas G is descend. On the other hand, when the exhaust gas flow control valve 19v is opened, a part of the exhaust gas Ga passes through the exhaust turbine 12t of the turbocharger 12 and is expanded by an isentropic process, and the temperature Tga of the exhaust gas Ga decreases The remaining exhaust gas Gb is discharged from the exhaust receiver 18 to the exhaust passage 17 without passing through the exhaust turbine 12 t of the turbocharger 12 by the bypass flow passage 19. A part of the exhaust gas Gb that does not drive the exhaust turbine 12t of the turbocharger 12 is expanded by an isenthalpy process, and the temperature Tgb of the exhaust gas Gb rises.

  Therefore, by changing the valve opening degree α of the exhaust gas flow rate control valve 19v, the ratio of a part of the exhaust gas Ga to the remaining exhaust gas Gb can be changed, so the temperature Teg of the exhaust gas G downstream of the junction 17a Can be adjusted. The temperature Teg of the exhaust gas G is the temperature of the exhaust gas G flowing into the exhaust heat boiler 23 of the exhaust heat recovery unit 20, and the measurement value Tegm can be detected by the exhaust gas temperature sensor 17b.

  Next, the configuration of the exhaust heat recovery unit 20 will be described. As shown on the right side of FIG. 1, the exhaust heat recovery unit 20 is a simple Rankine cycle, and a condenser (condenser) 21, a feed water pump 22, a waste heat boiler (evaporator) 23, a brackish water separation drum Separator) 24, steam turbine (expander) 25, generator 26, first steam flow control valve (steam flow control valve) 27, steam pressure sensor 28, second steam flow control valve 29, and these are connected It has piping (flow path) 31-34 and the steam bypass flow path 35 which are configured.

  In this configuration, the water (liquid-phase working medium) W of the condenser 21 is pressurized by the feed water pump 22 by the pipe 31, and the pressurized water W enters the exhaust heat boiler 23 through the pipe 32. . In the waste heat boiler 23, the water W supplied from the condenser 21 is heated by the first heat exchange flow passage 23 a inside the waste heat boiler 23 and enters the steam separator 24. Then, the saturated water W from the steam separator 24 is heated by the exhaust gas G in the second heat exchange flow passage 23b inside the waste heat boiler 23, and is converted to steam (working gas in the gas phase) S to Return to the separation drum 24. The brackish water separation drum 24 is provided with a level sensor (L) 24a for detecting the height of the water surface, and a control system not shown based on the measurement value of the water surface level detected by the level sensor 24a. The water level in the brackish water separation drum 24 is controlled by operating the water supply pump 22.

  The steam S whose water content has been removed by the steam separation drum 24 is adjusted in flow rate by the first steam flow control valve 27 provided in the pipe (flow path) 33 and supplied to the steam turbine 25 via the pipe 33. And drive this steam turbine 25. The steam turbine 25 drives a generator 26 to generate electric power. The exhaust side of the steam turbine 25 is connected to the condenser 21 by a pipe 34, and the steam S after driving the steam turbine 25 enters the condenser 21 via the pipe 34, and is input to the condenser 21. The steam S contained therein is cooled by a cooling medium such as seawater Ws and condensed to become water W. In this way, the water W coming out of the condenser 21 returns to the condenser 21 and circulates in the circulation flow path of the exhaust heat recovery unit 20.

  Further, on the inlet side of the steam turbine 25, a steam bypass flow branched from the pipe 33 downstream of the steam pressure sensor 28 on the upstream side of the first steam flow control valve 27 and joining the condenser 21. A passage 35 is provided. The steam bypass flow path 35 is provided with a second steam flow control valve 29. Thereby, the steam S from the steam separation drum 24 can be introduced into the condenser 21 without passing through the steam turbine 25.

  The valve opening degree β of the first steam flow control valve 27 is operated by the governor (speed governor) 25c of the power controller or the controller or controller 40 (not shown) so that the rotational speed Ns of the steam turbine 25 becomes constant. To be controlled. Further, the measured value Psm of the vapor pressure Ps of the water vapor S is detected by the vapor pressure sensor 28 disposed in the pipe 33. The adjustment of the measured value Psm of the vapor pressure Ps detected by the vapor pressure sensor 28 is such that part of the steam S flows to the vapor bypass flow path 35 by adjusting the valve opening degree γ of the second vapor flow control valve 29. It takes place in Note that the control of the second steam flow control valve 29 prevents an excessive rise of the steam pressure Ps of the steam S by a control device (not shown), and discards the steam in a short time when it becomes necessary to protect the equipment. be able to.

  Then, when the power demand increases, the amount of electricity extracted from the generator 26 increases, and thus the torque of the generator 26 increases. As a result, the rotational speed Ng of the generator 26 is reduced, so the governor (speed governor) 25 c controls the valve opening degree β of the first steam flow control valve 27 to be large. On the other hand, when the power demand decreases, the amount of electricity extracted from the generator 26 decreases, so the torque of the generator 26 decreases. As a result, the rotation speed Ng of the generator 26 is increased, so the governor (speed governor) 25 c controls the valve opening degree β of the first steam flow control valve 27 to be small. By these controls, it is possible to maintain the predetermined number of revolutions Nc (related to the frequency of generated alternating current power) in which the number of revolutions Ns of the steam turbine 25 and the number of revolutions Ng of the generator 26 are preset.

  In the exhaust heat recovery system 1 of a marine engine having a power generation system using the exhaust heat boiler 23, the following four situations occur with respect to the steam pressure Ps of the steam S supplied to the steam turbine 25. The first situation is that even if the valve opening degree α of the exhaust gas flow control valve 19v is the same, the temperature Teg of the exhaust gas G does not necessarily become the same temperature because it is affected by the operating state of the main engine 10 It is. That is, in the main engine 10, the operating state of the main engine 10 changes due to a change in thrust, disturbance such as waves, wind or tidal current, and the temperature of the cooled exhaust gas Ga on the exhaust passage 17 side also The temperature of the hot exhaust gas Gb on the passage 19 side also tends to fluctuate, and moreover, there is no one-to-one correspondence between the valve opening degree α of the exhaust gas flow control valve 19v and the temperature Teg of the exhaust gas G. is there.

  The second situation is that the influence of the valve opening degree α of the exhaust gas flow control valve 19v has a great influence on the operation of the main engine 10. That is, since the main engine 10 is supercharged by the exhaust turbine 12t of the turbocharger 12, the driving force of the exhaust turbine 12t fluctuates under the influence of the valve opening degree α of the exhaust gas flow control valve 19v, The supercharging by the compressor 12c fluctuates. Therefore, the operating state of the main engine 10 fluctuates, and the temperature Teg of the exhaust gas G discharged to the exhaust passage 17 fluctuates. For example, when the exhaust gas flow control valve 19v is opened, the supercharging weakens and the scavenging pressure (pressure of air supplied to the engine) also decreases. As a result, the output of the main engine 10 is reduced, and to cope with this, the amount of fuel F supplied is increased, and the temperature of the exhaust gas G is increased. As a result, the temperature Teg of the exhaust gas G fluctuates.

  The third situation is that the waste heat boiler is designed so that the response of the steam pressure Ps becomes insensitive to the change of the flow rate of the steam S due to the design principle of the waste heat boiler 23 . That is, in a ship, since the heat source of the main engine 10 is used for applications other than the heat source of the exhaust heat boiler 23, for example, propulsion of the ship, the heat input to the exhaust heat boiler 23 tends to fluctuate. is there. Therefore, in the design policy of the exhaust heat boiler 23, in order to operate the exhaust heat recovery system 1 of the marine engine stably, the exhaust heat boiler 23 increases the saturated water amount W with respect to the generation amount of the steam S, and the exhaust gas G The steam pressure Ps of the steam S on the outlet side is made insensitive to fluctuations in the heat input from the engine.

  In the fourth situation, since the power demand on the ship fluctuates largely and rapidly due to the start and stop of the motor (not shown), the steam demand related to the required driving force of the steam turbine 25 that drives the generator is also large and It is to change rapidly.

  Here, the following first to third measures are taken for these first to fourth situations. As a first measure, before the disturbance to the main engine 10 reaches the vapor pressure Ps, the second control unit 42 uses the measured value Tegm of the temperature Teg of the exhaust gas G detected by the exhaust gas temperature sensor, The fluctuation of the temperature Teg of the exhaust gas G is suppressed, and the propagation of the influence to the exhaust heat recovery unit 20 is blocked.

  As a second measure, the temperature Teg of the exhaust gas G after merging is controlled in a short time by the operation of the exhaust gas flow control valve 19v. That is, the influence of the change in the temperature Tg of the exhaust gas G discharged to the exhaust passage 17 due to the fluctuation of the input / output of the turbocharger 12 appears in the temperature Teg of the exhaust gas G after the merging. The control of the valve opening degree α of the exhaust gas flow rate control valve 19v in the second control unit 42 reduces the influence that appears late.

  Furthermore, as a third measure, the waste heat boiler 23 is designed to reduce the response delay due to the fact that the variation of the flow rate of the steam S does not readily appear as the variation of the steam pressure Ps. A feedforward unit is provided in the control unit 41, thereby achieving good controllability.

  Next, the control device 40 will be described. The control device 40 is configured to have a first control unit 41 called an upper controller and a second control unit 42 called a lower controller. In the first control unit 41, as illustrated in FIG. 2, the valve opening degree β of the first steam flow control valve 27, the steam pressure command value Pst, and the measured value Psm of the steam pressure Ps detected by the steam pressure sensor 28 To output the target temperature Tegt of the temperature Teg of the exhaust gas G after the merging. The steam pressure command value Pst is set by the console 43 or the like, and the set value is input to the first control unit 41 as the steam pressure command value Pst.

  In other words, in the first control unit 41, the target temperature Tegt, which is the target value for controlling the temperature Teg of the exhaust gas G, is the deviation e between the measured value Psm of the vapor pressure Ps and the vapor pressure command value Pst that is the target value. Calculate and set.

  In the control circuit of FIG. 2, in the first control circuit 41a on the upper left side, the valve opening degree β of the first steam flow control valve 27 is compared with the valve opening degree β of the time T seconds ago, If the magnitude of ds is less than the preset limit value X (−X <ds <X), the output value do is set to 0, and the magnitude of the increase (or decrement) ds is preset The output value do is equal to ds when the threshold value X is equal to or higher than the threshold X (ds ≦ −X or X ≦ ds). The output value do is multiplied by the coefficient Kx to obtain a first output value doa for control, which is output to the adder 41c. The first control circuit 41 a is a feedforward control circuit having a dead zone with respect to the amount of change of the valve opening degree β of the first steam flow control valve 27.

  That is, the first control circuit 41a operates the valve opening degree α of the exhaust gas flow control valve 19v when the amount of change in the valve opening degree β of the first steam flow control valve 27 exceeds a predetermined value X. It becomes the operation route which calculates feed forward.

  T seconds is a set value obtained experimentally beforehand, or a set value artificially adjusted while observing the result of this control, or automatically adjusted while observing the result of this control. Can be set by learning.

  Further, in the second control circuit 41b on the lower left side of the control circuit of FIG. 2, the vapor pressure command value Pst and the measured value Psm of the vapor pressure Ps detected by the vapor pressure sensor 28 are input and controlled by PID control. Output the second output value dob for In this PID control, velocity type PID control is used for the deviation e (= Pst−Psm). In the second control circuit 41b, the upper stage is integral control (I control), the middle stage is proportional control (P control), and the lower stage is differential control (D control). Then, as shown in this middle stage, the difference from the previous value related to the speed is put in the proportional control (P control) portion.

  Then, the adder 41c adds up the control first output value doa and the control second output value dob to obtain a control third output value doc, which is output to the right control circuit 41d. In the third control circuit 41d, normal speed type control is performed on the third output value doc for control, that is, the previous operation amount is added to the third output value doc to obtain a new operation amount, Control to output a fourth output value dod for The fourth output value dod for control becomes the target temperature Tegt.

In summary, in the second control circuit 41b, in the integral control portion, the deviation e is multiplied by "Δt / Ti", and in the proportional control portion, "Kp" is subtracted from the difference (subtracting the previous value from the current value). In the differential control portion, the second derivative is multiplied by “T _D ”, and these are added and integrated in the third control circuit 41 d. As a result, with respect to the deviation e, the integral component is integrated in the third control circuit 41d and the proportional component is differenced and integrated in the third control circuit 41d. The component integrates the second derivative to become the value of the first derivative. Here, "f" is a function for obtaining a second-order incomplete derivative.

The coefficient Ti, the coefficient Kp, and the coefficient T _D used in the PID control are values set in advance by experiments or the like, or values set by adjustment as appropriate. It is determined and set to the set value in it, and then it is set by artificial adjustment while looking at the control result, or by set value by learning automatically adjusted by looking at the control result. can do.

  Further, it is more preferable to add a reset windup function and a bumpless function at the time of switching from the manual operation to the automatic operation to the third control circuit 41d. Since this reset windup function and its configuration, and the bumpless function and its configuration may be generally used, known techniques can be used.

  Note that the reset windup function pulls back to the upper and lower limit values when the fourth control value dod for control, which is the manipulated variable, exceeds the upper and lower limit values, and enables immediate response when the deviation is reversed. Is a function to stop the integration operation in the direction beyond.

  In addition, the bumpless function prevents a step change due to sudden change of the fourth output value dod for control when the coefficient used in automatic mode and manual mode switching or in PID control changes, and the fourth output value for control It is a function to make dod switch smoothly without bumping.

  Although a combination of feedforward control and feedback control is used in FIG. 2, the output values dod for the input values β, Pst, and Psm are converted into a database, and a control table is set and stored in advance. The output value dod may be calculated and output with reference to the control table according to β, Pst, and Psm.

  Then, the second control unit 42 inputs, as the target temperature Tegt, the fourth control value dod for control output from the first control unit 41, and the exhaust gas after merging detected by the exhaust gas temperature sensor 17b. The control value αc of the valve opening degree α of the exhaust gas flow control valve 19v is output so that the measurement value Tegm of the temperature Teg of G is input and the measurement value Tegm of the temperature Teg of the exhaust gas G becomes the target temperature Tegt. The valve opening degree α of the exhaust gas flow control valve 19v is controlled by the control amount αc. In other words, the target temperature Tegt set by the first control unit 41 is input, and the valve opening degree α of the exhaust gas flow control valve 19v is controlled by the second control unit 42, so that the temperature of the exhaust gas G after merging The measured value Tegm of Teg is made the target temperature Tegt.

  That is, when the exhaust gas G is bypassed to the bypass flow path 19, first, there is a change in the temperature Teg of the exhaust gas G after merging due to the increase or decrease of the bypass amount of the exhaust gas G. The change in the state of the turbocharger 12 caused by the change in the flow rate of G causes a change in the temperature Tg and the flow rate of the exhaust gas G discharged from the cylinder 13 to the exhaust passage 17. The temperature Teg of the exhaust gas G after the merging is detected by the exhaust gas temperature sensor 17b, and the measured value Tegm is input to the second control unit 42. By adjusting the measurement value Tegm of the temperature Teg of the exhaust gas G after merging in the control unit 42 to the target temperature Tegt, it is possible to suppress the fluctuation of the vapor pressure Ps.

  As illustrated in FIG. 3, the second control unit 42 can use feedback control of PID control. However, the second control unit 42 can use not only PID control but any control capable of temperature adjustment. However, PID control is a widely used good method that is generally used, and since adjustment of each control coefficient used in PID control can be easily adjusted in the field, PID control It is more preferable to use. In addition, "f" of FIG. 3 is a function which calculates | requires the 1st-order imperfect differential.

  Next, control of the first control unit 41 and the second control unit 42 will be described. In the control of the first control unit 41 and the control of the second control unit 42, a signal of the target temperature Tegt is appropriately transmitted from the first control unit 41 to the second control unit 42, and individual controllers simultaneously proceed in parallel. However, it is not essential to synchronize the two controls if there is no problem in the signal exchange of the target temperature Tegt, and even if they are not synchronized, the signal exchange of the target temperature Tegt is performed in a known manner be able to.

  In the exhaust heat recovery system 1 of this marine engine, exhaust gas discharged from the cylinder 13 to the exhaust passage 17 due to changes in the rotational speed Ng of the generator 26 due to changes in the power demand, changes in the operating state of the main engine 10, etc. When the temperature Tg of G changes and the rotation speed Ng of the generator 26 changes, the governor 25 c opens the first steam flow control valve 27 for adjusting the flow rate of the steam S supplied to the steam turbine 25. The degree β is controlled to return the rotational speed Ng of the generator 26 to maintain a predetermined rotational speed Nc.

  The valve opening degree β of the first steam flow control valve 27 as a result of this control, the measured value Psm of the vapor pressure Ps detected by the vapor pressure sensor 28 and the vapor pressure command value Pst are input to the first control unit 41 Be done. In the first control unit 41, a target temperature Tegt for adjusting the valve opening degree α of the exhaust gas flow control valve 19v is calculated and set, and is output from the first control unit 41 to the second control unit 42. In the second control unit 42, the target temperature Tegt and the measured value Tegm of the temperature Teg of the exhaust gas G after merging detected by the exhaust gas temperature sensor 17b are input, and the measured value Tegm of the temperature Teg of the exhaust gas G is The valve opening degree α of the exhaust gas flow control valve 19v is controlled so that the target temperature Tegt is achieved.

  In other words, in the exhaust heat recovery system 1 of the marine engine, the exhaust gas flow rate with respect to the exhaust gas G in addition to the change (slightly complicated and slow response) of the steam pressure Ps due to the heat transfer amount from the exhaust gas G to the exhaust heat boiler 23 Change in the amount of heat transfer from the exhaust gas G to the exhaust heat boiler 23 (simple and fast response) by controlling the valve opening degree α of the control valve 19v and the influence of control of the valve opening degree α of the exhaust gas flow control valve 19v The exhaust heat boiler 23 caused by the change in the temperature Tg and the flow rate of the exhaust gas G discharged from the cylinder 13 to the exhaust passage 17 in response to the change in the operating state of the turbocharger 12 and the change in the operating state of the main engine 10 A plurality of changes are combined and complicated, for example, the amount of heat transfer from the exhaust gas G changes (slightly complicated and slow response). With respect to this complexity, control of the valve opening degree β of the first steam flow control valve 27 and control of the exhaust gas flow control valve 19v by control of the first control unit 41 and the second control unit 42 Since the control is simplified by separating the control from the control of (1) and (2) separately, there is a great advantage that PID control can be used in each control.

  Further, since the valve opening degree β of the first steam flow control valve 27 has a close relationship with the power demand, that is, “power demand increase / decrease → generator torque increase / decrease → generator rotation speed decrease or increase → first steam Since there is a relationship “reduction or increase of the valve opening degree β of the flow control valve 27”, power demand is used instead of the valve opening degree β of the first steam flow control valve 27 in the control of the first control unit 41. You can also. In the method of using the electric power demand instead of the valve opening degree β of the first steam flow control valve 27, “Power demand increase / decrease → Generator torque increase / decrease → Generator rotation number decrease or increase → First steam flow control valve 27 It is possible to eliminate the delay of each part in the “decrease or increase of the valve opening degree β”.

  For example, when the power (specifically, the current) increases rapidly due to a rapid increase in power demand (for example, start of a motor (not shown)), the drive torque of the generator 26 (load torque of the steam turbine 25) increases rapidly. In this steam turbine 25, control of constant rotation speed (keeping AC frequency constant) is applied by the governor 25c, and the rotation speed Ng is slightly decreased by rapid increase of the torque of the generator 26, and steam flow is increased rapidly to compensate for this. Of the first steam flow control valve 27 is increased rapidly. As a result, in the waste heat boiler 23, a pressure drop occurs due to the rapid increase of the steam flow rate, and the heat transfer amount needs to be increased to compensate for this.

  Under these circumstances, the target temperature which is the output of the first control unit 41 including feedforward control for controlling the valve opening degree α of the exhaust gas flow control valve 19v based on the steam flow rate withdrawn from the exhaust heat boiler 23 The second control unit 42 operates using Tegt to control the vapor pressure Ps.

  According to the above configuration and control, the exhaust gas flow rate by the exhaust gas temperature sensor 17b on the inlet side of the exhaust heat boiler 23 in order to suppress the fluctuation of the steam pressure Ps of the exhaust heat boiler 23 of the main engine 10 below a certain level. The control valve 19v is operated by the second control unit 42 to control the measurement value Tegm of the temperature Teg of the exhaust gas G supplied to the exhaust heat boiler 23 to coincide with the target temperature Tegt. The operating condition of the engine 10 and the influence of disturbance, and the effect that the temperature Tg of the exhaust gas G discharged from the cylinder 13 to the exhaust passage 17 fluctuates by operating the exhaust gas flow rate control valve 19 v Therefore, it is possible to prevent the steam pressure Ss supplied to the steam turbine 25 from reaching the steam pressure Ps, and to perform effective control.

  Then, in the first control unit 41, feedforward control is applied in which the temperature Teg of the exhaust gas G after merging is directly changed from the amount of steam utilization, so that the steam pressure Ps of the steam S from the waste heat boiler 23 In order to suppress the fluctuation, the waste heat boiler 23 has a large amount of saturated water relative to the amount of steam generation, and the amount of heat possessed by the saturated water alleviates the pressure drop. Although the time delay is large, it becomes control that can cope with this.

  As a result, the target steam pressure Pst and the measured value of the steam pressure Ps of the waste heat boiler 23 are simply measured without relating the control of the temperature Teg of the exhaust gas G supplied to the waste heat boiler 23 to the control of the steam turbine 25. In the simple feedback control method of operating the valve opening degree β of the first steam flow control valve 27 from the deviation e of Psm, the following factors that could not obtain sufficient performance could be solved.

  That is, in the adjustment of the temperature Teg of the exhaust gas G supplied to the exhaust heat boiler 23 by the operation of the exhaust gas flow control valve 19v, the response of the temperature Teg of the exhaust gas G to the operation of the exhaust gas flow control valve 19v is bypassed. There is a direct quick response (variation) due to the quantity and a rather gradual response (variation) via the operating state of the main engine 10, both of which are complex and slow. For this reason, it is difficult to cope with both of the above, and as a result, it becomes either to operate at a substantially constant opening without using the exhaust gas flow rate control valve 19v flexibly, or to allow the device deterioration due to large fluctuations. It was

  If it is possible to respond to such factors directly, it is possible to respond to a somewhat gentle response, and by these responses, the fluctuation of the heat input to the waste heat boiler 23 is suppressed within a certain range. I thought I could. Then, although the steam pressure Ps fluctuates due to the change of the flow rate of the steam S from the waste heat boiler 23 to the steam turbine 25, the waste heat boiler 23 lags in the change of the steam pressure Ps. It respond | corresponds by performing control by the feedforward control part of the 1st control part 41, and was able to reduce the influence of the delay of the response of this vapor pressure Ps.

Therefore, according to the exhaust heat recovery system 1 of the marine engine and the control method of the exhaust heat recovery system of the marine engine, the first control of the valve opening degree α of the exhaust gas flow control valve 19v is performed. The effect of the valve opening degree β of the steam flow control valve 27 can be incorporated, and in the exhaust heat recovery system 1 of a marine engine, the working medium W such as water is removed by the heat of exhaust gas G of the internal combustion engine Of the steam S to be evaporated into the steam turbine (expander) 25 and to suppress fluctuations in the steam pressure Ps of the steam S introduced into the steam turbine 25. In addition to the heat of the exhaust gas G, the amount of external heat input such as the auxiliary burner 23c etc. Fuel consumption and CO ₂ emissions can be reduced.

That is, using the heat quantity of the exhaust gas G from the main engine 10 equipped with the turbocharger 12, the condenser 21, the feed water pump 22, the exhaust heat boiler (evaporator) 23, and the steam turbine (expander) 25 are sequentially In the waste heat recovery system 1 of a marine engine that heats circulating water (working medium) W by the exhaust heat boiler 23 and converts the thermal energy of the exhaust gas G into mechanical energy by the steam turbine 25, the system is supplied to the steam turbine 25. Besides suppressing the fluctuation of the vapor pressure Ps of the steam S, it is possible to minimize the amount of heat input from the outside such as the auxiliary burner 23c besides the heat of the exhaust gas G, and to suppress the fuel consumption and the CO ₂ emission.

1 Exhaust Heat Recovery System for Marine Engine 2 Propeller 3 Rudder 10 Main Engine (Marine Engine)
11 intake passage 12 supercharger 12c compressor 12t exhaust turbine 13 cylinder 14 piston 15 output shaft (crankshaft)
16 Propeller shaft 16a Speed sensor (N)
17 exhaust passage 17a joining portion 17b exhaust gas temperature sensor 18 exhaust receiver 19 bypass flow passage 19v exhaust gas flow control valve 20 exhaust heat recovery unit 21 condenser (condenser)
22 Water feed pump 23 Exhaust heat boiler (evaporator)
23a 1st heat exchange flow path 23b 2nd heat exchange flow path 23c auxiliary burner 24 steam separation drum (water steam separator)
24a Level sensor 25 Steam turbine (expander)
25c governor (speed governor)
26 Generator 27 First steam flow control valve 28 Steam pressure sensor 29 Second steam flow control valve 31 to 34 Piping (flow path)
35 steam bypass flow path 40 control device 41 first control unit (upper controller: C1)
42 Second control unit (lower controller: C2)
43 Control console A Air F Fuel G Exhaust gas Ga Partial exhaust gas Gb Residual exhaust gas Pst Steam pressure command value Psm Steam pressure S detected by a steam pressure sensor Temperature of exhaust gas after merging with steam Teg Temperature of exhaust gas Tegm Exhaust gas temperature Exhaust gas temperature after merging detected by sensor Tegt Target temperature W Water (working medium)
Ws seawater (cooling medium)
α Exhaust gas flow rate control valve opening degree β First steam flow control valve opening degree γ Second steam flow control valve opening degree

Claims (8)

Using the heat of exhaust gas from a marine engine equipped with a supercharger, the evaporator heats a working medium, which circulates through a condenser, a pump, an evaporator, and an expander in this order, to produce heat energy of the exhaust gas. In the exhaust heat recovery system of a marine engine that converts into mechanical energy by the expander,
In the exhaust passage where the exhaust turbine of the supercharger of the marine engine is disposed, a bypass passage is provided which bypasses the exhaust turbine and in which an exhaust gas flow control valve is disposed;
An exhaust gas temperature sensor for measuring the temperature of the exhaust gas after joining is provided in the exhaust passage downstream of the junction where the bypass passage joins the exhaust passage, and the evaporation medium of the gas phase is evaporated In the flow path for moving from the pressure vessel to the expander, a steam flow control valve for adjusting the flow rate of the working medium in the gas phase, and a steam pressure sensor for measuring the steam pressure of the working medium in the gas phase are provided And
The controller for controlling the exhaust heat recovery system of the marine engine concerned, the valve opening degree of the steam flow control valve or the demand for mechanical energy converted by the expander, and after merging detected by the exhaust gas temperature sensor The exhaust heat recovery system of a marine engine according to claim 1, wherein the exhaust gas flow control valve is controlled to be open by inputting a measured value of the exhaust gas temperature.   The merging is detected by the exhaust gas temperature sensor at a target temperature of the exhaust gas set using the valve opening degree of the steam flow control valve or the demand for mechanical energy converted by the expander. The exhaust heat recovery system for a marine engine according to claim 1, wherein the exhaust heat recovery system is configured to be controlled so that the measured value of the temperature of the exhaust gas later becomes.   The controller determines the valve opening degree of the steam flow control valve or the demand amount for mechanical energy converted by the expander, the steam pressure command value, and the measured value of the steam pressure detected by the steam pressure sensor. The exhaust heat recovery system for a marine engine according to claim 2, wherein the target temperature is set using the engine.   The control device detects a first output value by feedforward control with respect to a valve opening degree of the steam flow control valve or a demand for mechanical energy converted by the expander, a steam pressure command value, and the steam pressure sensor The exhaust of the marine engine according to claim 2 or 3, wherein the target temperature is set using a second output value by feedback control using the measured value of the vapor pressure as an input. Heat recovery system.   The control device performs PID control in the feedback control, and a proportional control portion for the difference between the steam pressure command value and the measured value of the steam pressure detected by the steam pressure sensor is the difference between the difference and the difference. The exhaust heat recovery system for a marine engine according to claim 4, wherein the previous value is subtracted.   The exhaust gas flow control valve based on a first control unit that sets the target temperature, and a difference between the target temperature and the temperature of the exhaust gas after merging detected by the exhaust gas temperature sensor. The exhaust heat recovery system for a marine engine according to any one of claims 2 to 5, characterized by comprising a second control unit that controls the degree of opening of the valve.   The working medium is water, the pump is a feed water pump, the evaporator is a heat exchanger for heating and evaporating water, and the evaporator is a steam water separating drum for separating water vapor and saturated water. The exhaust heat recovery system for a marine engine according to any one of claims 1 to 6, wherein the expander is a steam turbine connected to a generator. Using the heat of exhaust gas from a marine engine equipped with a supercharger, the evaporator heats a working medium, which circulates through a condenser, a pump, an evaporator, and an expander in this order, to produce heat energy of the exhaust gas. In the control method of an exhaust heat recovery system of a marine engine, wherein the expander converts mechanical energy into mechanical energy,
The flow rate of exhaust gas passing through the exhaust turbine of the supercharger of the marine engine and the flow rate of exhaust gas bypassing the exhaust turbine are controlled by an exhaust gas flow rate disposed in a bypass passage bypassing the exhaust turbine By controlling with the valve, the temperature of the exhaust gas supplied to the evaporator is adjusted;
The flow rate of the gas phase working medium supplied to the expander is controlled by a steam flow control valve disposed in a flow path for moving the gas phase working medium from the evaporator to the expander To cope with fluctuations in demand for mechanical energy converted by the expander, and
With the exhaust gas temperature sensor after the merging of the opening of the steam flow control valve or the demand for mechanical energy converted by the expander, the exhaust gas passing through the exhaust turbine and the exhaust gas passing through the bypass flow path A control method of an exhaust heat recovery system for a marine engine, comprising controlling a valve opening degree of the exhaust gas flow control valve using a measured value of a detected exhaust gas temperature.

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