KR20240068043A - Method and large two-stroke uniflow scavenged internal combustion engine configured for carbon dioxide capture - Google Patents

Abstract

Supplying a carbon-based fuel to a large two-stroke turbocharged uniflow scavenged internal combustion engine and a combustion chamber, combusting the carbon-based fuel in the combustion chamber to produce a stream of exhaust gases comprising carbon dioxide, a stream of exhaust gases. recirculating a first portion of the exhaust gas stream and exhausting a second portion of the stream of exhaust gases, using the stream of heat exchange medium to cool the first portion of the stream of exhaust gases being recirculated in the exhaust gas system, thereby forming the stream of heat exchange medium. heating, supplying a stream of carbon dioxide-lean solvent to the absorber (42) and discharging a stream of carbon dioxide-rich solvent from the absorber (42) to the desorber (66) and reboiler (62) assembly; chemically absorbing carbon dioxide from the portion into a solvent, and heating the dissolver 66 by supplying at least a portion of the heated stream of heat exchange medium to a desorber 66 and reboiler 62 assembly to heat the solvent. ) and regenerating the carbon rich solvent in the reboiler (62) assembly.

Description

Large 2-stroke Uniflow scavenging internal combustion engine and method configured for carbon dioxide capture {METHOD AND LARGE TWO-STROKE UNIFLOW SCAVENGED INTERNAL COMBUSTION ENGINE CONFIGURED FOR CARBON DIOXIDE CAPTURE}

The present disclosure relates to large two-stroke internal combustion engines configured to reduce carbon dioxide emissions, particularly large two-stroke uniflow scavenged internal combustion engines with crossheads running on carbon-based fuels (gaseous or liquid fuels), and methods of operating these types of engines. It's about.

Large two-stroke turbocharged Uniflow scavenging internal combustion engines with crossheads are used, for example, for propulsion of large oceangoing vessels or as the main power source for power plants. These two-stroke diesel engines are constructed differently from other internal combustion engines in addition to their sheer size. The exhaust valve can weigh up to 400 kg, the piston has a diameter of up to 100 cm, and the maximum operating pressure in the combustion chamber is typically several hundred bar. The forces that accompany these high pressure levels and piston sizes are enormous.

DK202170181B1 discloses a large turbocharged multi-cylinder two-stroke internal combustion engine of the Uniflow type with an EGR system for transferring the flow of exhaust gases from the exhaust system to the intake system. The EGR system includes an EGR blower and an electronically adjustable EGR throttling valve. An AC electric drive motor is connected to the EGR blower to drive the EGR blower. The AC electric drive motor is configured to operate at a constant, predetermined speed. The sensor provides a signal indicating the oxygen concentration in the scavenge gas receiver, and the controller receives the signal and is coupled to an electronically adjustable EGR throttling valve. The controller is configured, as a primary action, to regulate the flow of exhaust gases through the EGR system by adjusting the position of the electronically adjustable EGR throttling valve as a function of the first signal. This engine emits CO2 generated during the combustion of carbon fuel into the atmosphere. Large two-stroke turbocharged internal combustion engines operate on liquid fuels (e.g. fuel oil, marine diesel, heavy oil, ethanol, dimethyl ether (DME)) or gaseous fuels (e.g. methane, natural gas (LNG), petroleum gas (e.g. LPG), It operates on methanol or ethane).

Engines running on gaseous fuel may operate according to the Otto cycle, in which the gaseous fuel is introduced by fuel valves arranged centrally along the length of the cylinder cover or cylinder liner, meaning that such engines start well before the exhaust valve closes. introduces gaseous fuel during the upward stroke (from BDC to TDC) of the piston and compresses the mixture of scavenge air and gaseous fuel in the combustion chamber, compressed at or near TDC by means of timed ignition, for example a liquid fuel injector. Ignite the mixture.

Engines running on liquid fuel and also engines running on gaseous fuel via high-pressure injection inject gaseous or liquid fuel when the piston is at or near TDC, i.e. when the compression pressure in the combustion chamber is at or near maximum; It operates according to the diesel cycle, i.e. compression ignition.

Liquid and gaseous fuels used in known large two-stroke turbocharged uniflow scavenging internal combustion engines generally contain carbon, i.e. they are carbon-based fuels and their combustion results in the production of carbon dioxide which is released into the atmosphere. Carbon dioxide emissions are generally considered to contribute to climate change and should be minimized or prevented.

Known carbon capture technologies typically fall into three categories: post-combustion CO2 capture, pre-combustion CO2 capture, and oxyfuel combustion. Pre-combustion means separating and capturing carbon components before combustion of fuel.

In pre-combustion carbon dioxide capture, the fuel is first reacted with oxygen and/or steam and then further processed in a water gas shift reactor to produce a mixture of H2 and CO2. CO2 is captured from a high-pressure gas mixture containing 15% to 40% CO2. The advantage of pre-combustion is that the gas volume required for processing is greatly reduced and the CO2 concentration in the gas is increased. This reduces energy consumption and equipment investment for the separation process.

In oxyfuel combustion, carbon-based fuels are burned in recycled flue gases and pure O2 rather than in air. This limits its commercialization potential due to the high cost of O2 separation. Oxygen fuel combustion technology consists of an air separation unit where nitrogen is removed from the air. The carbon-based fuel is then burned in recycled flue gases and pure oxygen. The flue gases, which mainly consist of particulate matter from combustion, CO2, sulfur oxides from fuel and water, are sent to a particulate matter removal unit, a sulfur removal unit, before condensing the water, leaving a stream of CO2 that can be compressed. The main advantage is that it enables almost 100% CO2 capture.

In post-combustion technology, carbon-based fuels are burned as in conventional energy generation and CO2 is captured from the exhaust gases. These carbon separation technologies are broadly divided into four sub-areas: absorption, adsorption, membrane, and cryogenic. Amine solvents can be used to capture CO2 by absorption from exhaust gases. Here, CO2 is captured in the solvent and the amine regeneration process follows. The downside is the large-scale expansion of the power plant and the significant energy required for the carbon dioxide capture process. In particular, a very large amount of energy is required for amine solvent regeneration.

The aim is to provide an engine and method that overcomes or at least reduces the problems mentioned above.

The above objects and other objects are achieved by the features of the independent claims. Additional embodiment forms become apparent from the dependent claims, description and drawings.

According to a first aspect there is provided a large two-stroke turbocharged uniflow scavenging internal combustion engine having a crosshead, the engine comprising:

at least one combustion chamber defined by a cylinder liner, a piston configured to reciprocate in the cylinder liner, and a cylinder cover,

a scavenging port arranged in the cylinder liner for introducing scavenging gas into the at least one combustion chamber;

a fuel system configured to supply carbon-based fuel to at least one combustion chamber;

at least one combustion chamber configured to combust a carbon-based fuel to produce a stream of exhaust gases comprising carbon dioxide;

an exhaust gas outlet arranged in the cylinder cover and controlled by an exhaust valve;

at least one combustion chamber connected to the scavenge gas receiver through a scavenge port and connected to the exhaust gas receiver through an exhaust gas outlet;

an exhaust gas system comprising a turbine of a turbocharger system driven by a stream of exhaust gases;

an air inlet system comprising a compressor of a turbocharger system, wherein the compressor is configured to supply pressurized scavenge air to a scavenge gas receiver;

an exhaust gas recirculation system configured to recirculate a portion of the exhaust gases originating from at least one combustion chamber to the scavenge gas receiver, the exhaust gas recirculation system comprising a blower to assist the flow of exhaust gases to the scavenge air receiver;

An absorber, preferably an absorption tower, for absorbing carbon dioxide into a solvent,

A desorber and reboiler assembly for desorbing carbon dioxide from the solvent,

The absorber has a solvent inlet that receives a carbon dioxide-lean solvent from the absorber and a solvent outlet that supplies a carbon dioxide-enriched solvent to the absorber,

the absorber being arranged such that a stream of exhaust gases passes therethrough for separation of carbon dioxide from the stream of exhaust gases into a solvent by chemical absorption;

The desorber and reboiler assembly has an inlet that receives carbon dioxide-rich solvent from the absorber and an outlet that supplies carbon dioxide-lean solvent to the absorber;

The desorber and reboiler assembly is configured to heat the solvent to release carbon dioxide from the solvent, and

and a heat exchange device configured to exchange heat between the solvent and the exhaust gas being recycled in the exhaust gas recirculation system.

The amount of energy required to regenerate the solvent is significant and can amount to more than 60% of the engine shaft power delivered by a large two-stroke internal combustion engine. This penalty on the energy efficiency of the engine makes operation with a carbon dioxide capture system more expensive than an engine without such a carbon dioxide capture system. However, the inventors have recognized that large two-stroke diesel engines operated with exhaust gas recirculation create a stream of excess energy because the recirculated exhaust gases are advantageously cooled using a heat exchange medium before being reintroduced to the cylinder. The inventors have also recognized that such heat exchange media (e.g. water or steam) can be heated to a temperature sufficient to use the heat exchange media directly for heating to regenerate the carbon dioxide rich solvent in the receiver and reboiler assembly.

In a possible implementation form of the first aspect, the heat exchange device is configured to exchange heat between the heat exchange medium and the exhaust gas of the exhaust gas recirculation system to cool the exhaust gas of the exhaust gas recirculation system and heat the heat exchange medium. An exhaust gas recirculation heat exchanger (32), and a heat exchanger configured to exchange heat between the heat exchange medium and the solvent to heat the solvent and cool the heat exchange medium.

In a possible implementation form of the first aspect, the exhaust gas recirculation system comprises a scrubber, preferably a wet scrubber, and the scrubber is arranged in the exhaust gas recirculation system downstream of the exhaust gas recirculation heat exchanger.

In a possible implementation of the first aspect, the heat exchange device is configured to exchange heat between the solvent of the desorber and reboiler assembly and the recirculated exhaust gas of the exhaust gas recirculation system.

In a possible implementation form of the first aspect, it includes a controller configured to adjust the mass percentage of exhaust gas recirculated in the scavenge gas to at least 40%, preferably between 40% and 55%.

In a possible implementation of the first aspect, the controller is configured to control the speed of the blower to regulate the percentage of exhaust gas that is recirculated in the scavenge gas.

According to a second aspect, a method is provided for operating a large two-stroke turbocharged uniflow scavenging internal combustion engine having a plurality of combustion chambers, the method comprising:

supplying carbon-based fuel to the combustion chamber;

Combusting a carbon-based fuel in a combustion chamber to produce a stream of exhaust gases comprising carbon dioxide;

Recirculating the first portion of the stream of exhaust gases and exhausting the second portion of the stream of exhaust gases;

supplying a stream of pressurized scavenge gas to the combustion chamber, the stream of pressurized scavenge gas comprising recycled exhaust gas;

heating a stream of heat exchange medium by using the stream of heat exchange medium to cool a stream of exhaust gases that are recirculated in the exhaust gas system;

chemically absorbing carbon dioxide from the second portion of the stream of exhaust gases into the solvent by supplying a stream of carbon dioxide-lean solvent to the absorber and discharging a stream of carbon dioxide-rich solvent from the absorber to the desorber and reboiler assembly; and

and regenerating the carbon-rich solvent in the disposer and reboiler assembly through heating by supplying at least a portion of a heated stream of heat exchange medium to the disposer and reboiler assembly to heat the solvent.

In a possible implementation form of the second aspect, the method comprises recycling at least 40 wt.% of the stream of exhaust gases, preferably between 40 and 55 wt.% of the stream of exhaust gases.

In a possible implementation of the second aspect, the method includes controlling the speed of a blower of the exhaust gas recirculation system to adjust the percentage of exhaust gas that is recirculated in the pressurized scavenging gas.

In a possible implementation form of the second aspect, the method comprises the step of supplying a stream of steam or water vapor and a gas containing carbon dioxide generated in the absorber 66 to a separator 69 to separate the carbon dioxide and water vapor or steam. and the separator is preferably a knockout drum for obtaining a stream of gas mainly comprising carbon dioxide and a stream of liquid mainly comprising water.

In a possible implementation form of the second aspect, the method comprises supplying a stream of gas mainly comprising carbon dioxide to a liquefaction unit and liquefying the stream of gas mainly comprising carbon dioxide to obtain a flow of liquefied carbon dioxide, The method preferably includes directing a stream of liquefied carbon dioxide to a liquefied carbon dioxide storage unit.

In a possible implementation form of the second aspect, the method uses an exhaust gas recirculation heat exchanger of the exhaust gas recirculation system to extract heat from the recirculating exhaust gas of the exhaust gas recirculation system and transfer it between the heat exchange medium and the exhaust gas of the exhaust gas recirculation system. cooling the exhaust gas of the exhaust gas recirculation system and heating the heat exchange medium by exchanging heat, and exchanging heat between the heated heat exchange medium and the solvent to heat the solvent and cool the heat exchange medium. These and other aspects will become apparent from the examples described below.

The aim is to provide an engine and method that overcomes or at least reduces the problems mentioned above.

In the following detailed portions of the present disclosure, aspects, embodiments and implementations will be described in greater detail with reference to example embodiments shown in the drawings.

1 is a perspective view of a large two-stroke diesel engine according to an example embodiment.
Figure 2 is a perspective view from another angle of the large two-stroke engine of Figure 1;
Figure 3 is a schematic diagram of a large two-stroke engine according to Figures 1 and 2 of the embodiment.
FIG. 4A is a schematic diagram of a first embodiment of a heat pump used in the embodiments of FIGS. 1 to 3.
FIG. 4B is a schematic diagram of a second embodiment of the heat pump used in the embodiments of FIGS. 1 to 3.
Figure 5 is a more detailed schematic diagram of an embodiment of a heat pump used in the embodiments of Figures 1-4A.
Figure 6 is a schematic diagram of a large two-stroke engine according to Figures 1 and 2 in another embodiment;

In the following detailed description, internal combustion engines will be described with reference to the large two-stroke, low-speed turbocharged internal combustion crosshead engine of an exemplary embodiment. 1, 2 and 3 show an embodiment of a large, low-speed turbocharged two-stroke diesel engine with a crankshaft (8) and a crosshead (9). 1 and 2 are perspective views from different angles. Figure 3 is a schematic diagram of an embodiment of the large, low-speed turbocharged two-stroke diesel engine of Figures 1 and 2 with intake and exhaust systems. In this embodiment the engine has six cylinders in a row. However, a large low-speed turbocharged two-stroke internal combustion engine may have 4 to 14 cylinders in line with cylinder liners provided by the engine frame 11. The engine can be used, for example, as the main engine of a marine vessel or as a stationary engine to operate a generator in a power plant. For example, the total output of the engine may be 1,000 to 110,000 kW.

The engine, in this example embodiment, is a two-stroke unit having a scavenging port (18) in the lower region of the cylinder liner (1) and a central exhaust valve (4) in the cylinder cover (22) on top of the cylinder liner (1). It is a flow scavenging type engine. Scavenging gas passes from the scavenging gas receiver (2) through the scavenging port (18) of the individual cylinder liner (1) when the piston (10) is below the scavenging port (18).

When the engine is operated as a premix engine (Otto principle), the gaseous fuel containing carbon (e.g. methanol, petroleum gas or LPG, methane, natural gas LNG or ethane) causes the piston 10 to move upwards (from BDC to TDC). When moving and before the piston 10 passes the fuel valve 50' (gas inlet valve), gaseous fuel flows in from the gaseous fuel inlet valve 50' under the control of the electronic controller 100. Gaseous or liquid carbon-containing fuel (e.g. fuel oil) is injected at high pressure (preferably above 300 bar) into the combustion chamber fuel valve 50 when the piston 10 is at or near TDC. The fuel gas is introduced at relatively low pressure, less than 30 bar, preferably less than 25 bar, more preferably less than 20 bar and is supplied by the gaseous fuel supply system 30'. A flow containing fuel for injection through the fuel valve 50 is supplied by the fuel system 30 . The high pressure can be generated by the fuel system 30 (common rail) or in the fuel valve 50. The fuel inlet valves 50' are preferably uniformly distributed around the circumference of the cylinder liner and are arranged in a central region of the length of the cylinder liner 1. The inflow of gaseous fuel occurs when the compression pressure is relatively low, i.e. much lower than the compression pressure when the piston reaches TDC, thus allowing inflow at relatively low pressure.

When the engine is operated as a compression ignition engine (diesel principle), there is no gas inlet valve 50' and carbon-containing fuel (gaseous or liquid) flows through the fuel valve 50 when the piston 10 is at or near TDC. It is sprayed at high pressure.

The piston 10 of the cylinder liner 1 compresses the charge of scavenge gas and gaseous fuel (or compresses the scavenge gas if the operation has fuel injection only at TDC) and preferably compresses the cylinder cover at or near TDC. Ignition is triggered by injection of fuel at high pressure through compression from the fuel valve 50 arranged at (22) or in the case of liquid fuel injection only at or near TDC. This causes combustion and produces exhaust gas containing carbon dioxide.

When the exhaust valve (4) is opened, combustion gases flow through the combustion gas duct associated with the cylinder (1) to the combustion/exhaust gas receiver (3) and continue to the selective catalytic reactor for the reduction of nitrous oxide (Nox) in the exhaust gases. It flows through a first exhaust gas conduit (19) comprising (33).

Via the shaft the turbine 6 drives the compressor 7 through which fresh air is supplied through the air inlet 12. The compressor (7) delivers pressurized scavenge air to the scavenge air conduit (13) leading to the scavenge air receiver (2). The scavenge air in conduit 13 passes through an intercooler 14 to cool the scavenge air.

Upstream (shown) or downstream (not shown) of intercooler 14 an exhaust gas recirculation conduit 35 is connected to a scavenge air conduit 13 . At this location, the recirculated exhaust gas mixes with the scavenge air to form scavenge gas that flows to the scavenge gas receiver (2). The controller 100 (electronic control unit) is configured to adjust the ratio between exhaust gas and scavenge air in the scavenge gas, as described in more detail below.

The cooled scavenge air or gas is used to pressurize the scavenge air flow when the compressor (7) of the turbocharger (5) does not deliver sufficient pressure to the scavenge air receiver (2), i.e. during low or partial load conditions of the engine. It passes through an auxiliary blower (16) driven by an electric motor (17). At higher engine loads the turbocharger compressor (7) delivers sufficient compressed scavenging air and the auxiliary blower (16) is bypassed via the check valve (15). The test may comprise one or more turbochargers (5) to form a turbocharger system.

The controller 100, which may consist of several interconnected electronic units including a processor and other hardware to perform the functions of the controller, generally controls the operation of the engine and controls, for example, gaseous fuel intake (amount and timing), liquid Controls are exerted over fuel injection (quantity and timing) and the opening and closing of the exhaust valve 4 (timing and degree of lift), the proportion of recirculated exhaust gases, and the operation of various coolers, pumps and other equipment. At this time, the controller 100 transmits information from the sensor to the controller 100 such as the operating conditions of the engine (engine load, engine speed), blower speed, scavenge gas temperature, exhaust gas temperature at various locations, exhaust gas temperature at various locations, It receives various signals informing the pressure of the scavenging system, combustion chamber, exhaust gas system and exhaust gas recirculation system. Preferably the engine includes a variable timing exhaust valve actuation system allowing individual control of exhaust valve timing for each combustion chamber. The controller 100 detects the angles of the fuel valve 50, the liquid fuel inlet valve 50', the exhaust valve actuator, and the crankshaft via a signal line or wireless connection and the angular position to generate a signal indicative of the position of the crankshaft. It is connected to a sensor, and preferably to a pressure sensor in the cylinder cover 22 or alternatively in the cylinder liner 1 which generates a signal indicative of the pressure in the combustion chamber.

Depending on the engine size, the cylinder liner 1 can be manufactured in various sizes, with a cylinder bore typically from 250 mm to 1000 mm and a corresponding typical length from 1000 mm to 4500 mm.

Cylinder liners 1 are mounted on a cylinder frame 23 and a cylinder cover 22 is disposed on top of each cylinder liner 1 with an airtight interface therebetween. The piston 10 is arranged to move back and forth between Bottom Dead Center (BDC) and Top Dead Center (TDC). These two extreme positions of the piston 10 are spaced apart by 180 degrees of rotation of the crankshaft 8. The cylinder liner (1) provides a supply of cylinder lubricant when the piston (10) passes through the cylinder lubrication hole (25), after which the piston ring (not shown) of the piston (10) supplies the cylinder lubricant to the cylinder liner (1). A plurality of circumferentially distributed lubrication holes are provided, connected to a cylinder lubrication line distributing to the working surface (inner surface) of the cylinder. The cylinder liner is provided with a jacket (not shown), and jacket coolant circulates in the space between the jacket and the cylinder liner.

Liquid fuel valves 50 (typically at least one per cylinder, preferably three or four) are mounted on the cylinder cover 22 and connected to a source of pressurized carbon-containing fuel 30. The liquid fuel valves 50 are preferably arranged around the exhaust valve 4, in particular around the central outlet (opening) of the cylinder cover 22 and are evenly distributed in the circumferential direction. The central outline is controlled by the exhaust valve (4). The timing and amount of apparition fuel injection are controlled by the controller 100. The fuel valve 50 is only used to inject a small amount of ignition liquid (pilot) when the engine is operating in premix mode. When the engine is operating in compression ignition mode, the amount of liquid fuel required to operate the engine at the actual engine load is injected through the liquid fuel valve 50. The cylinder 22 cover may be provided with a prechamber (not shown), and the tip of the liquid fuel valve 50, typically the tip provided with a nozzle having one or more nozzle holes, allows pilot oil (ignition liquid) to enter the prechamber. It is arranged to be injected and sprayed into and trigger ignition. The prechamber helps ensure stable ignition.

The fuel inlet valve 50' is installed in the cylinder liner 1 (or cylinder cover 22), its nozzle substantially parallel with the inner surface of the cylinder liner 1 and rear of the fuel valve 50'. The end protrudes from the outer wall of the cylinder liner 22. Typically one or two, but possibly as many as three or four fuel valves 50' are provided in each cylinder liner 1 and distributed circumferentially around the cylinder liner 1 (preferably (it is evenly distributed in the circumferential direction). The fuel inlet valve 50' is arranged substantially centrally along the length of the cylinder liner 1 in the embodiment. The fuel inlet valve 50' is connected to a pressurized source of gaseous fuel 30' (e.g. methanol, LPG, LNG, ethane or ammonia), i.e. the fuel is delivered to the fuel inlet valve 50' It is in a gaseous state. Since gaseous fuel is introduced during the stroke of the piston 10 from BDC to TDC, the pressure of the source of gaseous fuel need only be higher than the pressure present in the cylinder liner 1, and typically a pressure of less than 20 bar is required for fuel inflow. Enough for the gaseous fuel to be delivered to valve 50'. Fuel inlet valve 50' is connected to a controller 100 that determines the timing of opening and closing of fuel inlet valve 50' and the duration of opening of fuel inlet valve 50'.

The liquid fuel for ignition is in embodiments fuel oil, marine diesel, heavy oil, ethanol or dimethyl ether (DME).

The aircraft operating mode may be one of several operating modes of the engine. Other modes may include a liquid fuel operation mode in which all fuel required for operation of the engine is provided in liquid form through the liquid fuel valve 50. In the gaseous fuel mode of operation, the engine operates with the gaseous fuel flowing in during the stroke of the piston from BDC to TDC at relatively low pressure as the main fuel, i.e. the one that provides most of the energy supplied to the engine, while the liquid fuel, in comparison, provides a significant contribution to the engine. It constitutes a relatively small amount of fuel that makes a relatively small contribution to the amount of energy supplied, and its purpose is for just-in-time ignition, i.e. the liquid fuel acts as an ignition liquid.

Accordingly, the engine of this embodiment may be a dual fuel engine, that is, the engine has a mode in which it operates only with liquid fuel and a mode in which it operates almost exclusively with gaseous fuel.

In this embodiment the engine is shown as a premix engine operating according to the Otto principle. However, the engine may also be a compression ignition engine (operating on diesel principles) in which carbon-based fuel (gaseous or liquid) is injected at high pressure when the piston 10 is at or near TDC.

The engine supplies carbon-based fuel (liquid and/or gaseous fuel) to a combustion chamber, combusts the carbon-based fuel in the combustion chamber to produce a stream of exhaust gases containing carbon dioxide, preferably (or recirculates) the exhaust gases. In an embodiment in which the gases are taken directly from the combustion chamber, a first part of the flow (of combustion gases) is recirculated, and another (second) part of the flow of exhaust gases is exhausted as exhaust gases, containing the exhaust gases into the combustion chamber. supplying a pressurized scavenging gas that, in an embodiment, contains at least 40 wt.% of recycled exhaust gas, preferably 40 to 50 wt.%, and separates carbon dioxide from the exhaust gas in a carbon dioxide absorption process; , which works by storing separated carbon dioxide.

Downstream of the turbocharger's turbine 6 the exhaust gases enter a second exhaust conduit 28 which guides the exhaust gases to a boiler 20 (also known as an economizer) configured to produce steam. The steam may be used onboard, for example, marine vessels where engines are installed for a variety of purposes, or the steam may be used directly to heat the desorber 66 and regenerator 62 assemblies, which will be described in more detail below. This is because it has a temperature sufficient to be supplied directly to the regenerator 66 and reboiler 62 assembly.

Downstream of the boiler 20 a second exhaust conduit 28 leads to a first heat exchanger 40 where the exhaust gases exchange with a primary medium described in more detail below.

Downstream of the first heat exchanger 40, a second exhaust conduit 28 leads to an inlet at the bottom of the absorber 42. The absorber 42 is preferably an absorption tower, for example a packed absorption tower. Exhaust gases flow through the absorber 42 to an outlet at the top of the absorber 42.

Absorber 42 is part of a system for chemically absorbing carbon dioxide using a solvent. An example of a suitable solvent is an amine solution. Amine solutions may include primary, secondary and/or tertiary amines. Another example of a suitable solution is a NaOH/KOH solution, preferably an aqueous amine NaOH/KOH solution.

Carbon dioxide is removed from the exhaust gas by a packed absorption tower (absorber) 42. This reaction is exothermic and increases the solvent temperature along the absorption tower 42. For example, the carbon dioxide concentration of the exhaust gases from the engine ranges from 4-5 vol.% (without exhaust gas recirculation) to 9-10 vol.% (with exhaust gas recirculation) entering the top of the absorption tower 42 and in a carbon dioxide-lean solvent. It is introduced into the absorber 42 in countercurrent with a solvent called . This carbon dioxide lean solvent is supplied by the disposer 66 at ambient pressure at approximately 35°C to 55°C. A wash water section consisting of a packed bed at the top of the absorber 42 condenses and dissolves the volatile amine adsorbent escaping into the exhaust gas and removes it. The total height of the absorption tower 42 can be up to 50 m. As carbon dioxide is absorbed into absorber 42, the flow of carbon dioxide-rich solvent from the bottom of absorber 42 undergoes heat exchange with the flow of carbon dioxide-lean solvent before being introduced into the absorber 66 and reboiler 62 assembly. It is fed by pump 44 to cross heat exchanger 60, where it is heated in reboiler 62 to release carbon dioxide from the solvent. Stripping (desorption) temperatures vary between 120°C and 150°C and operating pressures reach up to 5 bar.

The water-saturated carbon dioxide stream is discharged from the top of the absorber column (66) and cooled in the heat exchanger (68) to condense most of the water content, which is separated in the knockout drum (69) and returned to the absorber column (66). do. The stream of carbon dioxide from knockout drum 69 is then compressed/liquefied in liquefaction unit 70 and temporarily stored in storage tank 88, which in this example is a cryogenic storage tank. Liquefied carbon dioxide from temporary storage tank 85 may be transported to a final storage or utility site (not shown). If the engine is installed on a marine vessel, the temporary storage tank 88 will be arranged on the marine vessel and will be emptied when the marine vessel is in a port where utilities for receiving liquefied carbon dioxide are provided.

The regeneration process of the amine solution does not remove all of the carbon dioxide from the solution, and the regenerated carbon dioxide-lean solvent is recycled to the absorption tower 42 along with the lean carbon dioxide loading by the action of the pump 64. Before reaching the absorption tower (42), the carbon dioxide-rich solvent exchanges heat with the carbon dioxide-lean solvent in the cross heat exchanger (60) and heat exchanger (67).

The carbon dioxide loading of the solvent after absorbing carbon dioxide through the column is called carbon dioxide rich solvent. The difference between this lean and rich loading is the amount of carbon dioxide captured from the exhaust gases.

The carbon dioxide concentration of the exhaust gas leaving the absorber 42 is up to 10 times lower than the carbon dioxide concentration of the exhaust gas entering the absorber 42.

Some of the amines in the solvent may still be present in the exhaust gas leaving the absorber 42, which is removed by an amine scrubber 44 arranged in the exhaust conduit 49 downstream of the absorber 42.

The engine generates many excess energy flows (Q1, Q2, Qn), also called waste heat flows, from various parts of the engine. In the embodiment of Figure 3 these include:

- Q1: Primary cooling medium (e.g. water) of the scavenge air cooler (14). Cooling water from scavenge air cooler 14 typically has a temperature of about 20 to 240 degrees Celsius.

- Q2: Primary intermediate engine lubricant typically having a temperature of 45 to 55°C.

- Q3: Primary cooling medium (e.g. water) of the cylinder jacket cooler. Cooling water from the cylinder jacket typically has a temperature of about 70 to 90 degrees Celsius.

- Q4: Primary cooling medium (e.g. water) of the exhaust gas recirculation conduit heat exchanger (cooler) 32, typically having a temperature of about 50 to 350° C.

- Q5: Boiler 20 that supplies steam typically at a temperature of about 160 to 170°C.

- Q6: Primary medium (eg water) used in the first heat exchanger 40, typically having a temperature of 160 to 170° C.

- Q7: Primary medium (e.g. water) used in the second heat exchanger 67, typically having a temperature between 100 and 170° C.

- Q8: Primary medium (e.g. water) used in the third heat exchanger 68, typically having a temperature of 95 to 105° C.

- Q9: Primary medium (e.g. water) used to cool the liquefaction unit 70, the temperature of which depends on the type of technology used for liquefaction and the type of cooling system used in the liquefaction unit 70.

This list of excess energy flows generated by engines is not exhaustive and merely serves to provide examples of such sources.

At least one of the sources of excess energy (Q1, Q2, ... Qn) listed above, especially those having a temperature lower than that required to heat the desorber (66) and regenerator (62) assemblies (at least 120° C., (preferably requiring a secondary medium having a temperature of at least 110° C.) is supplied to the heat pump 80. The heat pump 80 is configured to generate a stream of energy Qr in the form of a flow of secondary medium (eg water or steam) having a temperature of at least 120° C., preferably at least 130° C. Preferably the temperature of the secondary medium supplied to the desorber 66 and reboiler 62 assembly is between 130 and 140° C., most preferably approximately 136° C.

A first example implementation of heat pump 80 is shown in FIG. 4A. In this embodiment, a plurality of sources of excess energy (Q1, Q2, ... Qn) are applied to a single heat pump (80), and energy (Qr) is supplied to the desorber (66) and regenerator (62) assembly. A stream of is produced by pump 80.

A second embodiment of the implementation of pump 80 is shown in FIG. 4B. In this embodiment, one of the plurality of sources of excess energy (Q1, Q2, ... Qn) is applied to one of the plurality of heat pumps 80 and supplied to the desorber 66 and regenerator 62 assembly. Streams of energy Qr are generated by a plurality of heat pumps 80 and are preferably combined into one stream of energy Qr for the absorber 66 and regenerator 62 assembly.

Heat pump 80 is used to increase the temperature of the amine solution in reboiler 62. Heat pump 80 includes at least an evaporator, condenser, compressor and throttling valve. Within the heat pump 80, the heat pump (refrigeration) fluid is circulated in a cycle including an evaporator, condenser, compressor, and throttling valve, as shown in FIG. 5. Heat pump 80 functions by an evaporator receiving heat from the flow of energy Q2. Heat pump fluid evaporates in the evaporator and enters the compressor. The compressor is driven, for example, by an electric motor that receives power from an alternator or generator driven by take-off power from, for example, the crankshaft of the engine. The compressor increases the pressure and temperature of the heat pump fluid. Downstream of the compressor, the heat pump fluid enters the condenser, and heat is transferred to the heat sink, where the heat pump fluid is condensed. The heat pump fluid then expands in the throttling valve before re-entering the evaporator and repeating the cycle. A secondary medium, for example water or steam, preferably transfers heat from the condenser to the reboiler 62 in a cycle driven by a pump, the secondary medium having a temperature of at least 120° C., preferably at least 130° C. has The reboiler 62 thus forms a heat sink for the heat pump 80.

In order to increase the efficiency of the heat pump 80, the condenser portion is divided into three heat exchanger (HEX) areas: a superheater, a condenser, and a sub-cooler in the embodiment. Heat extracted from the superheater and condenser areas is sent to the heat sink. The heat extracted from the subcooler is used to preheat the heat pump fluid leaving the evaporator. Having this condenser arrangement reduces the operation required on the compressor and increases system efficiency. Furthermore, a water loop with steam HEX and electric coils is applied between the condenser, superheater and reboiler (62). The fluid entering the steam HEX is steam produced in boiler 20 in one embodiment. The steam HEX and electric coils ensure that the reboiler 62 receives sufficient energy over the entire engine load range.

In Figure 5 several energy flows (Q1, Q2, ... Qn) are utilized. If only one energy flow (Q1, Q2, ... Qn) is applied, the deaerator below the evaporator can be eliminated.

In an embodiment the engine is provided with an exhaust gas recirculation system comprising an exhaust gas recirculation conduit (35) connecting the first exhaust conduit (19) to the scavenge air conduit (13). Preferably the exhaust gas recirculation conduit 35 is connected to the first exhaust gas conduit 19 upstream of the selective catalytic reactor 33 . Preferably the exhaust gas recirculation conduit 35 is connected to the scavenge air conduit 13 upstream of the scavenge air cooler 14 . However, the exhaust gas recirculation conduit 35 may also be connected to the scavenge air conduit 13 downstream of the scavenge air cooler 14. The exhaust gas recirculation conduit 35 includes a blower 34 that forces exhaust gases from the exhaust gas conduit into the scavenge air conduit, as the pressure in the scavenge air conduit 13 typically increases with the pressure of the first exhaust gas conduit 19 during engine operation. This is because it is higher than the pressure of ). In the illustrated embodiment the blower 34 is driven by an electric motor, but the blower may be driven by any other rotary power. In the illustrated embodiment the blower 34 is arranged between the exhaust gas recirculation scrubber 36 and the exhaust gas recirculation heat exchanger 32 which cools the exhaust gases. However, the location of the blower 35 may be upstream or downstream of other elements of the exhaust gas recirculation conduit 35. An exhaust gas recirculation heat exchanger 32 is arranged upstream of the exhaust gas recirculation scrubber 36. The main purpose of the exhaust gas recirculation scrubber 36 is to remove impurities (soot). The controller 100 is configured to control the speed of the blower 34 in the exhaust gas recirculation system to regulate the percentage of exhaust gases recirculated in the pressurized scavenge gas, preferably to a percentage of at least 35 wt.%. Increases the efficiency of the carbon dioxide absorption system by increasing the concentration of carbon dioxide. The exhaust gas recirculation rate may be controlled by a valve (not shown) controlled by the controller 100. Accordingly, the controller 100 is configured to operate the engine with a percentage of recirculated exhaust gas in pressurized scavenge gas of at least 40% or at least 50% depending on operating conditions. Controller 100 is generally configured to operate with the highest percentage of recycled exhaust/combustion gases possible, as this facilitates removal of current dioxide from the exhaust gases. “Highest possible” means the highest rate that does not cause unacceptable negative effects, such as a decrease in the quality of the combustion process, its reliability, an unacceptable increase in the heat load of the engine, etc. The medium (e.g. water or steam) used to exchange heat with the exhaust gases in the exhaust gas recirculation heat exchanger 32 leaves the exhaust gas recirculation heat exchanger 32 at a temperature of approximately 130 to 170° C. and thus this medium is The sober 66 and regenerator 62 assembly may be used directly, i.e., without including the heat pump 80. The recirculated exhaust gas enters the exhaust gas recirculation heat exchanger 32 at a temperature of about 260 to 400° C. and the required temperature for the medium can be obtained by adjusting the flow rate of the medium passing through the exhaust gas recirculation heat exchanger 32. Exhaust gas recirculation increases the carbon dioxide concentration of the exhaust gas supplied to the absorber 42, resulting in lower energy consumption of the absorber 66 and regenerator 62 assembly. Higher exhaust gas recirculation rates also reduce the magnitude of the flow of exhaust gases to the absorber 42 so that if exhaust gas recirculation is used or the rate is increased, an absorber tower with a smaller diameter can be used. In addition, the energy extracted from the exhaust gas recirculation heat exchanger 32 is excess energy (waste heat) supplied to the desorber 66 and regenerator 62 assembly. Significantly reduces the amount of energy that must be supplied to operate. The medium coming from the exhaust gas recirculation heat exchanger 32 has a higher temperature compared to the other excess heat streams of the engine (since the medium is heated by the exhaust gases that have not passed through the turbine 6 of the turbocharger 5). Therefore, it can be used directly in the absorber 66 and regenerator 62 assembly.

Figure 6 shows another embodiment of the engine. In this embodiment, structures and features that are the same or similar to the corresponding structures and features previously described or shown are denoted by the same reference numerals as previously used for simplicity. In this embodiment, the engine and its operation are almost identical to the previous embodiment, so only the differences from the previous embodiment will be described in detail.

This embodiment includes an optional second scavenge air cooler 14a downstream of the scavenge air cooler 14. The scavenge air cooler 14 may be configured to produce a stream of heat exchange medium for the desorber 66 and regenerator 62 assembly at a temperature sufficient for direct use in the desorber 66 and regenerator 62 assembly. You can. The secondary scavenge air cooler (14a) requires the use of a heat pump (80) to generate a stream of secondary medium before the flow of energy can be used to the desorber (66) and regenerator (62) assembly. It creates an excess energy flow (Q10) in the form of a stream of primary medium (e.g. water) with temperature. The stream of energy Q10 generated in the second scavenge air cooler 14a is sent to the heat exchanger 80.

In this embodiment, an additional fourth heat exchanger 41 may optionally be provided downstream of the first heat exchanger 40. This additional fourth heat exchanger 41 allows the production of another excess energy stream Q11 which is supplied to the heat pump 80.

In this embodiment an additional excess energy flow Q12 may be generated from excess heat from the exhaust gas recirculation scrubber 36 which is supplied to the heat pump 80 .

Various aspects and implementations have been described in connection with various embodiments. Embodiments may be combined in various ways. Additionally, other modifications to the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed subject matter, from reference to the drawings, disclosure, and appended claims. In a claim, the word "comprising" does not exclude another element or step, and the indefinite article "a" or "an" does not exclude a plurality. A single processor, controller or other unit may perform the functions of several items recited in the claims. Just because certain measures are mentioned in different dependent claims does not mean that a combination of these measures cannot be used to advantage. Reference signs used in the claims should not be construed as limiting their scope.

Claims (11)

A large two-stroke turbocharged uniflow scavenging internal combustion engine having a crosshead, comprising:
at least one combustion chamber defined by a cylinder liner (1), a piston (10) configured to reciprocate in the cylinder liner (1), and a cylinder cover (22),
a scavenging port (18) arranged in the cylinder liner (1) for introducing scavenging gas into the at least one combustion chamber;
a fuel system (30) configured to supply carbon-based fuel to at least one combustion chamber;
at least one combustion chamber configured to combust a carbon-based fuel to produce a stream of exhaust gases comprising carbon dioxide;
an exhaust gas outlet arranged in the cylinder cover (22) and controlled by an exhaust valve (4);
at least one combustion chamber connected to the scavenge gas receiver (2) via a scavenge port (18) and to the exhaust gas receiver (3) via an exhaust gas outlet;
an exhaust gas system comprising a turbine (6) of a turbocharger system (5) driven by a stream of exhaust gases;
an air inlet system comprising a compressor (7) of the turbocharger system (5), wherein the compressor (7) is configured to supply pressurized scavenge air to the scavenge gas receiver (2);
An exhaust gas configured to recirculate a portion of the exhaust gases originating from at least one combustion chamber to the scavenge gas receiver (2), and comprising a blower (34) for assisting the flow of exhaust gases to the scavenge air receiver (2). Including a recirculation system,
An absorber (42), in particular an absorption tower, for absorbing carbon dioxide into the solvent;
A desorber (66) and reboiler (62) assembly for desorbing carbon dioxide from the solvent,
The absorber 42 has a solvent inlet for receiving a carbon dioxide-lean solvent from the absorber 66 and a solvent outlet for supplying a carbon dioxide-enriched solvent to the absorber 66.
The absorber (42) is arranged such that a stream of exhaust gases passes therethrough for separation of carbon dioxide from the stream of exhaust gases into a solvent by chemical absorption,
The desorber (66) and reboiler (62) assembly has an inlet that receives carbon dioxide-rich solvent from the absorber (42) and an outlet that supplies carbon dioxide-lean solvent to the absorber (42);
The desorber (66) and reboiler (62) assembly is configured to heat the solvent to release carbon dioxide from the solvent, and
An engine comprising a heat exchange device configured to exchange heat between the solvent and the exhaust gases being recirculated in the exhaust gas recirculation system. According to paragraph 1,
The heat exchange device includes an exhaust gas recirculation heat exchanger (32) of the exhaust gas recirculation system, which is configured to exchange heat between the heat exchange medium and the exhaust gas of the exhaust gas recirculation system to cool the exhaust gas of the exhaust gas recirculation system and heat the heat exchange medium; and an engine comprising a heat exchanger configured to exchange heat between the heat exchange medium and the solvent to heat the solvent and cool the heat exchange medium. According to claim 1 or 2,
The engine wherein the exhaust gas recirculation system comprises a scrubber (36), preferably a wet scrubber, the scrubber being arranged in the exhaust gas recirculation system downstream of the exhaust gas recirculation heat exchanger (32). According to paragraph 1,
An engine comprising a controller (100) configured to regulate the mass percentage of exhaust gases being recirculated in the scavenge gases to at least 40%, preferably between 40% and 55%. According to paragraph 4,
The controller (100) is configured to control the speed of the blower (75) to regulate the percentage of exhaust gases that are recirculated in the scavenge gas. A method of operating a large two-stroke turbocharged uniflow scavenging internal combustion engine having a plurality of combustion chambers, comprising:
supplying carbon-based fuel to the combustion chamber;
Combusting a carbon-based fuel in a combustion chamber to produce a stream of exhaust gases comprising carbon dioxide;
Recirculating the first portion of the stream of exhaust gases and exhausting the second portion of the stream of exhaust gases,
supplying a stream of pressurized scavenge gas to the combustion chamber, the stream of pressurized scavenge gas comprising recycled exhaust gas;
heating a stream of heat exchange medium by using the stream of heat exchange medium to cool a stream of exhaust gases that are recirculated in the exhaust gas system;
from the second portion of the stream of exhaust gases to the solvent by supplying a stream of carbon dioxide-lean solvent to the absorber 42 and discharging a stream of carbon dioxide-rich solvent from the absorber 42 to the absorber 66 and reboiler 62 assembly. chemically absorbing carbon dioxide, and
The carbon-rich solvent is removed from the disposer 66 and reboiler 62 assembly through heating by supplying at least a portion of a heated stream of heat exchange medium to the disposer 66 and reboiler 62 assembly to heat the solvent. A method comprising the step of regenerating. According to clause 6,
A method comprising the step of recycling at least 40 wt.% of the stream of exhaust gases, preferably between 40 and 55 wt.% of the stream of exhaust gases. According to clause 6 or 7,
A method comprising controlling the speed of a blower (36) of an exhaust gas recirculation system to regulate the percentage of exhaust gas that is recirculated in the pressurized scavenge gas. According to clause 6,
supplying a flow of gas containing steam or water vapor and carbon dioxide generated in the absorber (66) to a separator (69) to separate carbon dioxide and water vapor or steam, wherein the separator preferably mainly contains carbon dioxide. A method that is a knockout drum for obtaining a stream of gas and a stream of liquid containing mainly water. According to clause 9,
supplying a stream of gas mainly comprising carbon dioxide to a liquefaction unit (70) and liquefying the stream of gas mainly comprising carbon dioxide to obtain a flow of liquefied carbon dioxide, preferably in a liquefied carbon dioxide storage unit (85). A method comprising sending a stream of liquefied carbon dioxide into. According to clause 6,
The exhaust gas recirculation system extracts heat from the recirculating exhaust gas of the exhaust gas recirculation system using the exhaust gas recirculation heat exchanger 32 of the exhaust gas recirculation system to exchange heat between the heat exchange medium and the exhaust gas of the exhaust gas recirculation system. cooling the exhaust gas and heating the heat exchange medium, and exchanging heat between the heated heat exchange medium and the solvent to heat the solvent and cool the heat exchange medium.