DK179734B1

DK179734B1 - Combustion engine system

Info

Publication number: DK179734B1
Application number: DKPA201770667A
Authority: DK
Inventors: Mayer Stefan
Original assignee: MAN Energy Solutions
Priority date: 2017-09-05
Filing date: 2017-09-05
Publication date: 2019-04-29
Also published as: CN109424403A; JP7030660B2; KR101939674B1; JP2019044773A; DK201770667A1; CN109424403B

Abstract

The present invention relates to a combustion engine system comprising an internal combustion engine generating an exhaust gas comprising soot, a turbocharger driven by the exhaust gas, and a NOx reduction unit arranged upstream of the turbocharger and fluidly connected with the internal combustion engine for purifying the exhaust gas from the internal combustion engine, the NOx reduction unit, in which the soot deposits, comprising a catalytic reactor housing having a chamber, an inlet pipe and an outlet pipe, and one or more catalytic element(s) arranged in the chamber of the catalytic reactor housing between the inlet pipe and the outlet pipe, wherein the combustion enginesystem further comprises a soot removing unit comprising a valve in fluid communication with an opening of the catalytic reactor housing, the valve having an open position allowing at least part of the exhaust gas in the catalytic reactor housing to escape into the soot removing unit, a receiver having a cross-sectional receiver area and a receiver inlet and a vent port, a conduit fluidly connecting the receiver inlet with the valve and having a cross-sectional conduit area which is smaller than the cross-sectional receiver area. The present invention also relates to a soot reduction method for reducing soot in a chamber of a NOx reduction unit in a combustion engine system according to the present invention.

Description

COMBUSTION ENGINE SYSTEM

Field of the invention

The present invention relates to a combustion engine system and to a soot reduction method for reducing soot in a chamber of a NO_x reduction unit in a combustion engine system according to the present invention.

Background art

Exhaust gas from an internal combustion engine are purified in order to reduce the NO_x emission in a catalytic reactor. During the purification process, soot is depositing in the reactor housing and on the surfaces of the catalytic elements in the SCR reactor. In order to clean soot off the surfaces, high pressure air is injected at predetermined intervals to loosen the soot, and the gas carries the loosened soot out of the reactor housing. However, high pressure air is not very efficient in loosening the soot and requires at lot of equipment, i.e. high pressure pipes and nozzles, which are costly and may be difficult to repair or replace. WO2006/091136 discloses an arrangement for removal of particulates in a gas flow applied to purify exhaust gas from an internal combustion engine.

Summary of the invention

It is therefore an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved combustion engine system which is more efficient in removing the soot and/or which requires less equipment.

The above objects, together with numerous other objects, advantages and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by a combustion engine system comprising:

- an internal combustion engine generating an exhaust gas comprising soot,

- a turbocharger driven by the exhaust gas, and

- a NO_x reduction unit arranged upstream of the turbocharger and fluidly connected with the internal combustion engine for purifying the exhaust gas from the internal combustion engine, the NO_x reduction unit, in which the soot deposits, comprising:

- a catalytic reactor housing having a chamber, an inlet pipe and an outlet pipe, and

- one or more catalytic element(s) arranged in the chamber of the catalytic reactor housing between the inlet pipe and the outlet pipe, wherein the combustion engine system further comprises a soot removing unit comprising:

- a valve in fluid communication with an opening of the catalytic reactor housing, the valve having an open position allowing at least part of the exhaust gas in the catalytic reactor housing to escape into the soot removing unit,

- a receiver having a cross-sectional receiver area and a receiver inlet and a vent port, and

- a conduit fluidly connecting the receiver inlet with the valve and having a cross-sectional conduit area which is smaller than the cross-sectional receiver area.

By having a conduit fluidly connecting the receiver inlet with the valve and having a cross-sectional conduit area which is smaller than the cross-sectional receiver area, an acoustic wave is provided in the catalytic reactor housing to loosen at least part of the soot.

The opening may be arranged in the chamber upstream of the one or more catalytic element(s).

Moreover, the opening may be arranged in the chamber closer to the inlet pipe than a middle part of the chamber. By having the opening closer to the inlet pipe than a middle part of the chamber, a reverse flow is created in the chamber to loosen the soot.

Also, the opening may be arranged in the chamber closer to the outlet pipe than a middle part of the chamber.

Further, the opening may be arranged in the inlet pipe.

In addition, the opening may be arranged in the middle part of the chamber between the catalytic elements.

Furthermore, the vent port may be fluidly connected with a vent pipe being fluidly connected downstream of the turbocharger.

The soot removing unit may have several openings, each opening having a valve fluidly connected to a conduit.

Additionally, all conduits may fluidly connect the openings with the receiver.

Moreover, the soot removing unit may have several receivers, each receiver being connected to one of the conduits.

Also the cross-sectional conduit area may be less than 50% of the cross-sectional receiver area, preferably less than 30%.

Further, the conduit may have a conduit length which is larger than a diameter of the cross-sectional conduit area.

In addition, the conduit may have a conduit length which is 10% larger than a diameter of the cross-sectional conduit area, preferably 25% larger than a diameter of the cross-sectional conduit area, more preferably 50% larger than a diameter of the cross-sectional conduit area.

Furthermore, the chamber may have a chamber volume and the receiver may have a receiver volume which is less than 20% of the chamber volume, preferably less than 10% of the chamber volume.

Also, a sound insulating unit may be at least partly enclosing the soot removing unit and/or the NO_x reduction unit.

The soot removing unit may have a valve control for controlling the opening of the valve.

Furthermore, the NOx reduction unit may be arranged on the high pressure side of the turbocharger.

Moreover, the valve control may comprise a timer.

Additionally, the soot removing unit may have a soot sensor.

Said soot sensor may be a pressure sensor.

The combustion engine system according to the present invention may further comprise a second turbocharger arranged upstream of the NO_x reduction unit.

Furthermore, the internal combustion engine of the combustion engine system may be a two-stroke or a four-stroke internal combustion engine.

The combustion engine system may further comprise an exhaust gas receiver.

Also, the combustion engine system may further comprise a scavenging gas receiver.

Moreover, the combustion engine system may further comprise a heat exchanger, e.g. a boiler.

A check valve may be arranged in the vent pipe.

The internal combustion engine may be powered by a fuel having a sulphur content of at least 0.05%.

Said internal combustion engine may be a large two-stroke internal combustion engine.

Also, the combustion engine system may comprise one or more catalytic reactor housing(s) having a volume of at least 200 litres.

The NOx reduction unit may further comprise a reducing agent supply unit comprising a dosing unit for dosing an amount of reducing agent to the exhaust gas in or before entering the NOx reduction unit.

Additionally, the NOx reduction unit may further comprise a control unit adapted to reduce the amount of reducing agent supplied to the NOx reduction unit.

Further, the reducing agent may comprise ammonia.

The present invention also relates to a soot reduction method for reducing soot in a chamber of a NO_x reduction unit in a combustion engine system according to the present invention, the method comprising the steps of:

- opening the valve for allowing part of the exhaust gas to escape into the conduit and further into the receiver generating an acoustic wave which is transmitted into the chamber, loosening part of the soot in the chamber,

- closing the valve, and

- venting the receiver.

Brief description of the drawings

The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of illustration show some non-limiting embodiments and in which

Fig. 1 shows a diagram of a combustion engine system having a NO_X reduction unit at the high-pressure side of the turbocharger,

Fig. 2 shows a NO_X reduction unit and a soot removing unit,

Fig. 3 shows in perspective a soot removing unit,

Fig. 4 shows another NO_X reduction unit having two openings and another soot removing unit having two conduits connected to the openings,

Fig. 5 shows another NO_X reduction unit having an opening upstream of the catalytic elements and an opening downstream of the catalytic elements, each opening being connected to a soot removing unit, and

Fig. 6 shows a diagram of another combustion engine system having a NO_Xreduction unit at the high-pressure side of the turbocharger.

All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested.

Detailed description of the invention

Fig. 1 shows a combustion engine system 1 comprising an internal combustion engine 2 generating an exhaust gas. The combustion engine system 1 comprises a turbocharger 3 driven by the exhaust gas on the high pressure side of the turbocharger 3. The combustion engine system 1 further comprises a NO_xreduction unit 4 arranged upstream of the turbocharger, i.e. on the high pressure side of the turbocharger 3, fluidly connected with the internal combustion engine 2 for purifying the exhaust gas from the internal combustion engine 2 by means of selective catalytic reduction (SCR). The NO_x reduction unit 4 comprises a catalytic reactor housing 5 having a chamber 6, an inlet pipe 7, an outlet pipe 8 and one or more catalytic element(s) 9 arranged in the chamber 6 of the catalytic reactor housing 5 between the inlet pipe 7 and the outlet pipe 8. In the NOx reduction unit 4 soot deposits on the catalytic element(s) 9 and on all surfaces inside the catalytic reactor housing 5 during purification of the exhaust gas. The combustion engine system 1 therefore further comprises a soot removing unit 10 for, at certain intervals, removing the soot. The soot removing unit 10 is fluidly connected with a valve 11in an opening 12 of the catalytic reactor housing 5, and the valve 11 has a closed position in which the opening 12 is blocked and an open position in which at least part of the exhaust gas in the catalytic reactor housing 5 is allowed to escape into the soot removing unit 10.

As shown in Fig. 3, the soot removing unit 10 comprises a receiver 14having a cross-sectional receiver area A_R and a receiver inlet 15 and a vent port 16, and further comprises a conduit 17 fluidly connecting the receiver inlet 15 with the valve 11. The conduit 17 has a cross-sectional conduit area A_C which is smaller than the cross-sectional receiver area A_R for providing an acoustic wave first in the receiver 14 and thus, as the wave travels, also in the catalytic reactor housing 5 to loosen at least part of the soot in the catalytic reactor housing 5 and on the catalytic elements 9. The exhaust gas escaping into the soot removing unit 10 creates a standing wave travelling into the NO_x reduction unit 4 to loosen the soot therein. As the valve 11 opens, the exhaust gas having a very high pressure escapes into the conduit 17 and further into the receiver 14 having a substantially lower pressure, and due to the cross-sectional conduit area AC being smaller than the cross-sectional receiver area A_R, an acoustic wave is generated similar to a Helmboltz resonator. The acoustic wave causes rapid transient variations in the local gas flow, imposing rapid changes in shear stress on the deposited soot layers on all walls in the catalytic elements 9, thereby loosening the soot from the walls.

The receiver has a vent port 16, as shown in Fig. 2, and the high pressure exhaust gas in the receiver 14 is vented through the vent port 16, which causes the pressure therein to be reduced, and the receiver 14 is prepared to receive a new portion of exhaust gas when the valve 11 opens again. The pressure in the receiver 14 is vented via a vent pipe 18 into the gas stream downstream of the turbocharger 3. The opening 12 is arranged in the chamber 6upstream of the one or more catalytic element(s) 9 and as the valve 11 opens generating the acoustic wave, a reverse flow stream is simultaneously created in the catalytic reactor housing 5. The reverse flow stream further increases the soot removal.

In Fig. 2, the opening 12 is arranged in the chamber 6 closer to the inlet pipe 7 than a middle part 36 of the chamber 6. By having the opening 12 closer to the inlet pipe 7 than a middle part 36 of the chamber 6, or by having the opening 12 in the inlet pipe 7, a reverse flow is created in the chamber 6 to loosen the soot. In Fig. 4, the soot removing unit 10 has several openings 12, each opening 12 having a valve 11 fluidly connected to a conduit 17 and the conduits 17 are fluidly connected to the receiver 14. The openings 12 are arranged in the middle part 36 of the chamber 6 between the catalytic elements 9, creating at least partly a reverse flow in the chamber 6 downstream of the openings 12 to loosen the soot. The soot is also loosened by the acoustic wave created in the soot removing unit 10.

In Fig. 5, the soot removing unit 10 may have several receivers 14, each receiver 14 being connected to one of the conduits 17 and one of the openings 12 is arranged in the chamber 6 closer to the outlet pipe 8 than a middle part 36 of the chamber 6 and another of the openings 12 is arranged in the inlet pipe 7.

In Fig. 3, the cross-sectional conduit area A_C of the conduit 17 is less than 50% of the cross-sectional receiver area A_R, preferably less than 30%. When the cross-sectional conduit area A_C of the conduit 17 is less than 50% of the crosssectional receiver area A_R of the receiver 14, a larger acoustic wave is created compared to a smaller difference in cross-sectional area. The chamber 6 has a chamber volume V_C, and the receiver 14 has a receiver volume V_R, and the receiver volume V_R is less than 20% of the chamber volume V_C, preferably less than 10% of the chamber volume V_C, depending on the chamber volume V_C and on how much soot is depositing over time during the purification of the exhaust gas. As shown, the conduit 17 has a conduit length L which is larger than a diameter of the cross-sectional conduit area A_C, and the conduit 17 is the neck in the Helmholz resonator-designed soot removing unit 10. A longer conduit/neck will result in a lower frequency of the acoustic wave generated when opening the valve 11. In one embodiment, the conduit 17 has a conduit length L which is 10% larger than a diameter of the cross-sectional conduit area A_C. In another embodiment, the conduit 17 has a conduit length L which is 25% larger than a diameter of the cross-sectional conduit area A_C, and in yet another embodiment, the conduit 17 has a conduit length L which is 50% larger than a diameter of the cross-sectional conduit area Ac. The acoustic wave created by the high pressure exhaust gas escaping into the soot removing unit 10 designed as a Helmholz resonator results in a very loud sound, and the frequency of the acoustic wave is dependent on the cross-sectional conduit area Ac where a larger cross-sectional conduit area Ac results in a higher frequency of the acoustic wave. The frequency is also dependent on the chamber volume V_C where a larger chamber volume V_Clowers the frequency.

The acoustic wave created by the high pressure exhaust gas escaping into the soot removing unit 10 results in a very loud sound, and the combustion engine system 1 therefore comprises a sound insulating unit 19 which is at least partly enclosing the soot removing unit 10 as shown in Fig. 4 and/or the NO_x reduction unit 4.

In Fig. 6, the soot removing unit 10 may have a valve control 37 for controlling the opening of the valve 11. The valve control 37 may comprise a timer (not shown) for activating the valve 11 at predetermined time intervals. The soot removing unit 10 may have a soot sensor 38 for measuring if soot is deposited in the catalytic reactor housing 5. The soot sensor 38 may be a pressure sensor for measuring the back pressure in the NO_X reduction unit 4, or the soot sensor may be an acoustic sensor for also measuring the thickness of the soot layer in the catalytic reactor housing 5. The soot sensor 38 may thus be communicating with the valve control 37. The combustion engine system 1 further comprises a second turbocharger 21 arranged upstream of the NOX reduction unit 4 and upstream of the other turbocharger 3. The NOx reduction unit 4 is fluidly connected in between the turbochargers and thus on the high pressure side of the second turbocharger 21.

The internal combustion engine 2 of the combustion engine system 1 may be a two-stroke or a four-stroke internal combustion engine 2. As shown in Fig. 1, the combustion engine system 1 may further comprise an exhaust gas receiver 31, a scavenging gas receiver 32 and a heat exchanger (not shown), e.g. a boiler. The turbocharger 3 comprises a turbine 33 driven by the exhaust gas, and the turbine 33 drives the compressor 34.

In Fig. 5, the soot removing unit 10 has two receivers 14 where one receiver 14 is fluidly connected to an opening 12 in the inlet pipe 7 via a conduit 17 and the other receiver 14 is fluidly connected to the bottom of the catalytic reactor housing 6 closer to the outlet pipe 8 than the catalytic elements 9. A check valve 35 is arranged in the vent pipes 18 for allowing the exhaust gas to flow away from the receiver 14 but preventing it from flowing back again.

The internal combustion engine 2 may be a large two-stroke internal combustion engine and powered by a fuel having a sulphur content of at least 0.05%. The catalytic reactor housing 5 has a volume of at least 200 litres. The two-stroke internal combustion engines 2 may be large two-stroke uniflow turbocharged compression-ignited crosshead internal combustion engines 2 which are used as propulsion systems for large ships or as stationary engines in power plants. The massive height, width, weight and power output make them quite different from common combustion engines and place large two-stroke uniflow turbocharged compression-ignited crosshead internal combustion engines 2 in a league of their own. The total output for a single engine 2 can exceed 100.000 BHP.

The NO_x reduction unit 4 further comprises a reducing agent supply unit (not shown) comprising a dosing unit (not shown) for dosing an amount of reducing agent to the exhaust gas in or before entering the NO_x reduction unit 4, and the reducing agent comprises ammonia.

The present invention provides a soot reduction method of reducing soot in a chamber 6 of a NO_x reduction unit 4 in a combustion engine system 1 by opening the valve 11 for allowing part of the exhaust gas to escape into the conduit 17 and further into the receiver 14, generating an acoustic wave which is transmitted into the chamber 6 to loosen part of the soot in the chamber 6. Then the valve 11 is closed. The receiver 14 is vented simultaneously.

Although the invention has been described in the above in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.

Claims

Patent claims

An internal combustion engine system (1) comprising:

an internal combustion engine (2) generating an exhaust gas comprising soot,

a turbocharger (3) powered by the exhaust gas, and

an NO _x reduction unit (4) arranged upstream of the turbocharger and fluidly connected to the internal combustion engine (2) for purifying the exhaust gas from the internal combustion engine (2), the NOx reduction unit (4) in which the soot is deposited comprises:

a catalytic reactor housing (5) with a chamber (6), an inlet pipe (7) and an outlet pipe (8), and

one or more catalytic element (s) (9) arranged in the chamber (6) of the catalytic reactor housing (5) between the inlet pipe (7) and the outlet pipe (8), wherein the internal combustion engine system (1) further comprises a soot removal unit (10) includes:

a receiver (14) having a cross-sectional receiver area (Ar) and a receiver inlet (15) and a vent port (16), and

a pipe (17) fluidly connecting the receiver inlet (15) to the valve (11) and having a cross-sectional tube area (Ac) smaller than the cross-sectional receiver area (Ar), characterized in that the soot removal unit further comprises a valve (11) in fluid communication with an opening (12) in the catalytic reactor housing (5), the valve (11) has an open position which allows at least a part of the exhaust gas in the catalytic reactor housing (5) to flow into the soot removal unit (10).

Internal combustion engine system (1) according to claim 1, wherein the opening (12) is arranged in the chamber (6) upstream of the one or more catalytic element (s) (9).

Internal combustion engine system (1) according to claim 1 or 2, wherein the vent port (16) is in fluid communication with a vent pipe (18) fluidly connected downstream of the turbocharger (3).

Internal combustion engine system (1) according to any one of the preceding claims, wherein the cross-sectional area (A _C ) is less than 50% of the cross-sectional area (A _R ), preferably less than 30%.

Internal combustion engine system (1) according to claim 4, wherein the pipe (17) has a pipe length (L) greater than a diameter of the cross-sectional pipe area (A _C ).

Internal combustion engine system (1) according to claim 4, wherein the pipe (17) has a pipe length (L) which is 10% larger than a diameter of the cross-sectional pipe area (A _C ), preferably 25% larger than a diameter of the cross-sectional pipe area (A _C ) , more preferably 50% larger than a diameter of the cross-sectional area (A _C ).

Internal combustion engine system (1) according to any one of the preceding claims, wherein the chamber (6) has a chamber volume (V _C ) and the receiver (14) has a receiver volume (V _R ) which is less than 20% of the chamber volume ( V _C ), preferably less than 10% of the chamber volume (V _C ).

An internal combustion engine system (1) according to any one of the preceding claims, wherein a sound insulating unit (19) at least partially surrounds the soot removal unit (10) and / or the NO _x reduction unit (4).

An internal combustion engine system (1) according to any one of the preceding claims, said internal combustion engine system further comprising a second turbocharger (21) located upstream of the NOx reduction unit (4).

A method for reducing soot in a chamber (6) in a NOx reduction unit (4) in an internal combustion engine system (1) according to claims 1-9, the method comprises the following steps:

opening the valve (11) to allow a portion of the exhaust gas to flow into the tube (17) and further into the receiver (14), generating an acoustic wave which is transmitted into the chamber (6), thereby releasing a part of the soot in the chamber (6),

closing the valve (11) and

venting the receiver (14).