JP5780807B2 - Exhaust gas economizer soot blow system - Google Patents

Description

  The present invention relates to a soot blow system for an exhaust gas economizer in a waste heat recovery system of a ship mainly equipped with an electronically controlled diesel main engine.

  The electronically controlled diesel main engine is a so-called environment-friendly diesel engine that reduces emissions of nitrogen oxides and dust. In the following, unless otherwise specified, the term “diesel main engine” including the electronically controlled diesel main engine is also used.

Conventionally, various methods have been taken for a waste heat recovery system of a diesel main engine. One method is to use an exhaust gas economizer, and soot is removed from the heat exchanger tube group for heat exchange called soot blow for the purpose of preventing sootfire and improving the efficiency of waste heat recovery equipment. (For example, refer to Patent Document 1).
In addition, when installing a system that combines an exhaust gas economizer and a turbo generator plant as a waste heat recovery system for a diesel main engine, the exhaust gas economizer is equipped with a soot blower for removing soot. The following countermeasure examples are taken to increase the safety of the plant or to ensure the safe operation of the plant.

(Ensuring plant safety)
(1) In order to avoid blackout of the turbo generator due to the steam pressure drop in the operation sequence of the soot blower, an interlock for preventing the steam pressure drop is provided.
(2) Instead of the interlock for preventing the steam pressure drop during the soot blower operation, additional cooking with an oil-fired boiler or parallel operation of a turbo generator and a diesel generator is performed.

(Improved soot blow effect)
(3) At the time of soot blower operation, an operation manual for increasing the load of the main engine in advance in order to mitigate the increase in the flow rate of exhaust gas and the decrease in steam pressure.
(4) Instead of steam injection, air injection is used to improve the soot removal effect. Some aim to increase the soot removal effect by the difference in the specific gravity of the injection medium or the difference in the injection pressure, but a certain decrease in steam pressure is inevitable.
(5) In order to increase the exhaust gas flow rate as much as possible, the design flow rate of the exhaust gas economizer and the pressure loss of the exhaust gas are set to the limit values so that there is no margin in terms of main engine back pressure.
(6) When the main engine is under a low load, that is, when the gas flow rate is reduced, the exhaust gas economizer is bypassed to reduce soot adhesion.

JP-A-7-217815

Some of the above conventional countermeasures involve the following problems and inconveniences.
[1] Steam pressure interlock, boiler reheating, parallel operation of turbo generator and diesel generator, etc. as effective measures to reduce steam pressure drop during soot blower operation are effective in ensuring safe operation of the plant. There are the following issues.
(B) The interlock for preventing the steam pressure drop takes time to recover the pressure, and the soot blower operation cycle inevitably becomes long. When the standby is made in the middle of the cycle, the soot blow effect is reduced.
(B) Boiler cooking for each soot blow, and parallel operation of a turbo generator and a diesel generator are not preferable because of frequent operation.
[2] An increase in the load of the main engine for increasing the flow velocity of the exhaust gas involves a change in the rotational speed, which is not necessary on actual ship operation, but may change the ship speed, which may impair the safety of the ship operation. In addition, the soot blow operation is automatic, but the rotation speed change of the main engine is not automatic, which impairs the unmanned operation system.

  In view of the above, the present invention provides a soot blow system for an exhaust gas economizer that avoids these problems and inconveniences, improves safety, has a high soot blow effect, and thus has high waste heat recovery efficiency for main engines. It is an object.

The soot blow system of the exhaust gas economizer according to the present invention is
An exhaust gas economizer that uses the exhaust heat of the diesel main engine as a heat source;
A soot blower for blowing off the soot adhering to the heat transfer tube of the exhaust gas economizer;
Steam supply means for supplying steam to the soot blower;
A turbo generator plant for generating electricity by introducing a part of the steam from the steam supply means;
A soot blow system of an exhaust gas ecomizer equipped with a main engine combustion control device that performs combustion control of the diesel main engine,
The main engine combustion control device has a set main engine load check means for checking a set level of the main engine load and a set steam pressure check means for checking a set level of the steam pressure. Combustion control is performed so as to bring about an increase in temperature.

  Also, if the main engine load is less than the set value and the steam pressure is greater than or equal to the set value, the amount of exhaust gas is increased by delaying the fuel injection timing of the main engine before the start of soot blow, and the exhaust gas flow rate in the exhaust gas economizer is increased. The main engine combustion control is performed to raise the fuel injection timing after the soot blow operation.

  In addition, when the main engine load is less than the set value and the steam pressure is less than the set value, the exhaust valve opening timing of the main engine is advanced before the start of the soot blow, or the close timing is delayed to increase the exhaust gas temperature, The main engine combustion control is performed to increase the steam pressure of the economizer and reduce the decrease in the steam pressure during the soot blow operation.

  Also, if the main engine load is greater than or equal to the set value and the steam pressure is less than the set value, the exhaust gas temperature is raised by bypassing part of the exhaust gas at the turbocharger turbine inlet before the start of soot blow, and the exhaust gas economizer The steam pressure of the engine is increased, and main engine combustion control is performed to reduce the decrease in steam pressure during the soot blow operation.

  If the main engine load is greater than or equal to the set value and the steam pressure is less than the set value, the compressed air at the outlet of the turbocharger blower is blown into the atmosphere before the soot blow starts, the exhaust gas temperature is increased, and the exhaust gas economizer The main engine combustion control is performed to increase the steam pressure and reduce the decrease in the steam pressure during the soot blow operation.

  According to the present invention, the main engine combustion control device has the set main engine load check means for checking the set level of the main engine load and the set steam pressure check means for checking the set level of the steam pressure, and at the time of soot blow, the exhaust gas Combustion control is performed to increase the flow velocity and exhaust gas temperature, so that the safety of the plant is improved, soot blower efficiency is high, and the exhaust heat economizer soot blow system with high waste heat recovery efficiency for the main engine Can be provided.

It is a block diagram which shows the structure of the soot blow system of the exhaust gas economizer which concerns on embodiment of this invention. It is a flowchart of the soot blow system of the exhaust gas economizer which concerns on embodiment of this invention.

FIG. 1 is a block diagram showing a configuration of a soot blow system of an exhaust gas economizer according to an embodiment of the present invention. Here, a soot blow control system using steam is shown. The diesel generator is installed separately from this system.
In FIG. 1, reference numeral 1 denotes an electronically controlled diesel main engine (hereinafter referred to as “main engine” or “main engine”), and an exhaust gas economizer 3 is connected to the main engine 1 via a turbocharger turbine 2. The exhaust gas economizer 3 recovers the exhaust heat from the main engine 1. Further, the exhaust gas economizer 3 and the drum 5 of the boiler 4 (steam supply means) are connected by a steam pipe 6. A plurality of branch pipes are provided at the tip of the steam pipe 6, and steam is supplied to each branch pipe. A soot blower 7 for injection is provided. Then, steam is injected from each soot blower 7 to remove the soot adhering to the heat transfer tube (not shown) of the heat exchanger inside the exhaust gas economizer 3. The steam pipe 6 is connected to a generator turbine 9 of a turbo generator 8 that generates power by introducing a part of the steam from the boiler 4. In the figure, 10 is a gas bypass pipe for bypassing exhaust gas from the main engine 1, 11 is a supercharger driven by the supercharger turbine 2 for scavenging and supplying air to the main engine 1, and 12 is a water circulation pump. A water supply pipe that supplies water in the drum 5 to the exhaust gas economizer 3 by 13, 14 is a water pipe that returns the brackish water in the exhaust gas economizer 3 to the drum 5, and 15 is a condenser.

Moreover, in this system, in order to improve the soot blow effect (soot removal effect) by steam, the combustion control of the main engine 1 is performed. In order to increase the soot blow effect, it is important that the injection steam pressure is at a certain pressure level, and that there is a certain gas flow rate (gas amount) to take out the blown soot out of the machine. In order to ensure this, the combustion control of the main engine 1 is performed.
The main engine combustion control device adjusts the fuel injection amount based on the number of revolutions, the fuel injection timing by the opening / closing valve, the opening / closing timing of the exhaust valve, the gas bypass timing, and the scavenging blow timing. In addition, the boiler control device controls the vapor pressure.

The combustion of the main engine 1 changes the exhaust gas temperature and the exhaust gas amount by adjusting the fuel injection timing and the exhaust valve opening / closing timing. The load of the main engine 1 depends on the control of the fuel injection amount, which is achieved by adjusting the fuel injection valve opening / time.
The fuel injection timing and the exhaust valve opening / closing timing are programmed in advance and are adjusted by the respective control valves.
For the combustion of the main engine 1, programming corresponding to the normal operation mode and the soot blow mode is prepared.
As will be described with reference to the flowchart of FIG. 2, the main engine load and the steam pressure are checked after the soot blow command, and the main engine combustion control mode is automatically selected depending on the respective situations. Here, after changing the combustion control mode, soot blow is started after a certain amount of combustion follow-up time (in units of several minutes) has elapsed.
The soot blow is automatically operated at intervals of 4 to 6 hours by a timer, and during that time, the main engine combustion control maintains the soot blow mode.
Upon completion of the soot blow, the main engine combustion mode is returned to the normal operation mode.

  FIG. 2 is a flowchart of the soot blow system of the exhaust gas economizer according to the embodiment of the present invention, and shows a flowchart of the main engine combustion control. However, this flowchart corresponds to case E described later.

  First, in step S1, it is checked whether or not a soot blow instruction has been issued, and the main engine 1 is performing normal operation while the soot blow instruction has not been issued (step S0).

  When the soot blow instruction is issued in step S1, it is checked whether the load of the main engine 1 is equal to or higher than the set value before driving the soot blower 7 (step S2). Since the main engine load is linked to the amount of exhaust gas, it is judged that there is a sufficient gas flow rate if it is higher than the regular plan. If there is no problem with the gas flow rate, then the vapor pressure is checked (step S3). Further, even if the main engine load is less than the set value, the steam pressure is checked (step S4). Since the balance pressure varies depending on the amount of heat of exhaust gas and the steam consumption destination, confirm that the steam pressure is at the planned pressure level effective for peeling off the soot and proceed to the next step.

  Here, it is assumed that the combustion control of the main engine 1 is performed in the following cases depending on the state of the main engine load and the steam pressure.

Case A: When the main engine load is less than the set value and the steam pressure is equal to or greater than the set value By delaying the fuel injection timing of the main engine 1 (step A1) before the start of soot blow (step S11), the amount of exhaust gas is increased. Increase the exhaust gas flow rate in the economizer 3. Further, after the end of the soot blow (step S12), the adjustment of the fuel injection timing is canceled and the original opening timing is restored (step A2).

Case B: When the main engine load is less than the set value and the steam pressure is less than the set value Before the soot blow start (step S11), the exhaust valve opening timing of the main engine 1 is advanced (step B1) or the close timing is delayed (step B2). ) To increase the exhaust gas temperature, increase the steam pressure of the exhaust gas economizer 3, and reduce the decrease in steam pressure during the soot blow operation, soot blow steam pressure interlock, boiler cooking, parallel by diesel generator Driving is unnecessary. After the end of the soot blow (step S12), the fuel injection timing and the exhaust valve opening timing are respectively returned to the original (steps A2 and B3).

Case C: When the main engine load is greater than or equal to the set value and the steam pressure is less than the set value The exhaust gas temperature is increased by partially bypassing the exhaust gas at the turbocharger turbine inlet (Step C1) before the start of soot blow (Step S13) In addition, by increasing the steam pressure of the exhaust gas economizer 3 and reducing the decrease in the steam pressure during the soot blow operation (up to step S14), the soot blow steam pressure interlock, boiler additional cooking, and parallel operation by the diesel generator are performed. Make it unnecessary. After the end of the soot blow (step S14), the bypass operation is canceled (step C2).

Case D: When the main engine load is greater than the set value and the steam pressure is less than the set value Before the soot blow start (step S13), the compressed air at the outlet of the turbocharger blower is blown to the atmosphere, the exhaust gas temperature is raised, and the exhaust gas econo By increasing the steam pressure of the miser 3 and reducing the decrease in the steam pressure during the soot blow operation (up to step S14), the soot blow steam pressure interlock, the boiler additional cooking, and the parallel operation by the diesel generator become unnecessary. After the end of the soot blow (step S14), the bypass operation is canceled (step C2).

Case E: A configuration in which case A to case D are combined.
Cases C and D can be used in the mechanically controlled diesel main engine. Here, the major difference between a mechanically controlled diesel main engine and an electronically controlled diesel main engine is the presence or absence of a fuel adjustment cam and an exhaust adjustment cam.
In the case of the machine control type, the cam drives the fuel injection pump, and the adjustment is fixed by the cam angle. The exhaust valve is also opened and closed by a cam, and is fixed once adjusted.
On the other hand, in the electronic control type, there is no cam and the hydraulic control has an independent hydraulic pump. Both the fuel injection timing and the exhaust valve opening / closing timing are controlled by having control valves, and these control valves can be freely adjusted (adjusted by software).
Since the machine control type is a cam type, cases A to C by software are not applicable.

The sootblow steam pressure interlock will be described.
In the case of a steam-type soot blower, soot is peeled off and blown off on the heat transfer tube of the exhaust gas economizer 3 with the pressure of the steam. However, the steam pressure in the plant plan cannot be made too high from another point of view (increasing exhaust heat recovery), so it is planned around 6K from the efficiency of the generator turbine, the temperature level of the heating service, and the like.
On the other hand, since soot blowers inject a large amount of steam, the steam pressure tends to decrease. If the soot blower decreases too much, it causes troubles in the stable operation of the generator turbine and the heating service.
Therefore, the soot blow steam pressure interlock has a function to stop (wait) soot blow when the steam pressure is too low from the viewpoint of soot blow effect, generator turbine, and heating service. . It stops and resumes when the steam pressure recovers.

According to this embodiment, the following effects can be expected.
(1) Depending on the main engine load (proportional to the amount of exhaust gas) and the steam pressure of the exhaust gas economizer (changes depending on the main engine load, steam demand, and ambient temperature) You can select whether to focus on temperature rise.
(2) When the load on the main engine is low, the aim is to improve the soot blow effect and to ensure plant safety by adjusting the exhaust gas volume and exhaust gas temperature (adjusting the exhaust valve opening and closing timing and fuel injection timing). Can respond.
(3) If the main engine load is higher than the set value, but the steam pressure is lower than the set value, plant safety is ensured by adjusting the exhaust gas temperature to increase the steam pressure (preparation by gas bypass or scavenging bypass). It is possible to respond with the focus on.
(4) Basically, the adjustment of the exhaust gas amount and the exhaust gas temperature increase sacrifices the main engine fuel efficiency, but by properly using the preparation method depending on the operating state, the deterioration of the fuel efficiency can be suppressed to a minimum.

  In the above-described embodiment, the soot blow method is described for the steam injection method, but the present invention can be expected to have the same effect even in the case of the air injection soot blow method.

1 Electronically controlled diesel main engine 2 Turbocharger turbine 3 Exhaust gas economizer 4 Boiler 5 Drum 6 Steam pipe 7 Soot blower 8 Turbo generator 9 Generator turbine 10 Gas bypass pipe S2 Set main engine load check means S3, S4 Set steam pressure check means

Claims (4)

An exhaust gas economizer that uses the exhaust heat of the diesel main engine as a heat source;
A soot blower for blowing off the soot adhering to the heat transfer tube of the exhaust gas economizer;
Steam supply means for supplying steam to the soot blower;
A turbo generator plant for generating electricity by introducing a part of the steam from the steam supply means;
A soot blow system of an exhaust gas economizer comprising a main engine combustion control device for controlling combustion of the diesel main engine,
The main engine combustion control device has a set main engine load check means for checking a set level of the main engine load and a set steam pressure check means for checking a set level of the steam pressure. Combustion control is performed to bring about an increase in temperature,
If the main engine load is less than the set value and the steam pressure is greater than or equal to the set value, delay the main engine fuel injection timing before the start of the soot blow to increase the exhaust gas volume and increase the exhaust gas flow velocity in the exhaust gas economizer. , soot blowing system of the exhaust gas economizer you and performing main engine combustion control to undo the fuel injection timing after the soot-blowing operation. An exhaust gas economizer that uses the exhaust heat of the diesel main engine as a heat source;
A soot blower for blowing off the soot adhering to the heat transfer tube of the exhaust gas economizer;
Steam supply means for supplying steam to the soot blower;
A turbo generator plant for generating electricity by introducing a part of the steam from the steam supply means;
A soot blow system of an exhaust gas economizer comprising a main engine combustion control device for controlling combustion of the diesel main engine,
The main engine combustion control device has a set main engine load check means for checking a set level of the main engine load and a set steam pressure check means for checking a set level of the steam pressure. Combustion control is performed to bring about an increase in temperature,
If the main engine load is less than the set value and the steam pressure is less than the set value, the exhaust gas temperature is increased by increasing the exhaust valve opening timing or delaying the closing timing before the start of soot blow. the vapor pressure is raised, soot blowing system of the exhaust gas economizer you and performing main engine combustion control to reduce the decrease in the steam pressure in the soot-blowing operation. An exhaust gas economizer that uses the exhaust heat of the diesel main engine as a heat source;
A soot blower for blowing off the soot adhering to the heat transfer tube of the exhaust gas economizer;
Steam supply means for supplying steam to the soot blower;
A turbo generator plant for generating electricity by introducing a part of the steam from the steam supply means;
A soot blow system of an exhaust gas economizer comprising a main engine combustion control device for controlling combustion of the diesel main engine,
The main engine combustion control device has a set main engine load check means for checking a set level of the main engine load and a set steam pressure check means for checking a set level of the steam pressure. Combustion control is performed to bring about an increase in temperature,
When the main engine load is greater than or equal to the set value and the steam pressure is less than the set value, the exhaust gas temperature is raised by bypassing a part of the exhaust gas at the turbocharger turbine inlet before the start of soot blow, and the exhaust gas economizer steam the pressure was raised, soot blowing system of the exhaust gas economizer you and performing main engine combustion control to reduce the decrease in the steam pressure in the soot-blowing operation. An exhaust gas economizer that uses the exhaust heat of the diesel main engine as a heat source;
A soot blower for blowing off the soot adhering to the heat transfer tube of the exhaust gas economizer;
Steam supply means for supplying steam to the soot blower;
A turbo generator plant for generating electricity by introducing a part of the steam from the steam supply means;
A soot blow system of an exhaust gas economizer comprising a main engine combustion control device for controlling combustion of the diesel main engine,
The main engine combustion control device has a set main engine load check means for checking a set level of the main engine load and a set steam pressure check means for checking a set level of the steam pressure. Combustion control is performed to bring about an increase in temperature,
If the main engine load is higher than the set value and the steam pressure is lower than the set value, the compressed air at the outlet of the turbocharger blower is blown into the atmosphere before the soot blow starts, the exhaust gas temperature is increased, and the exhaust gas economizer steam pressure increasing the soot blowing system of the exhaust gas economizer you and performing main engine combustion control to reduce the decrease in the steam pressure in the soot-blowing operation.

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