FR2875265A1 - Device for separating exhaust gases from energy production unit supplied with liquefied natural gas comprises low-temperature collector through which gas pipes pass and in which exhaust gases are condensed - Google Patents

Abstract

A device for separating exhaust gases from an energy production unit supplied with liquefied natural gas from a low-temperature tank (12) comprises a low-temperature collector (35) through which pipes (13, 14) for supplying gas to the production unit pass and in which exhaust gases are condensed. An independent claim is also included for separating exhaust gases from an energy production unit supplied with liquefied natural gas by storing the exhaust gases in a low-temperature collector, effecting heat exchange between the exhaust gases and liquefied gas supply pipes to condense the exhaust gases, and recovering the condensate.

Description

Device and method for separating exhaust gases from a

  power generation unit, in particular an internal combustion engine of a motor vehicle.

  The present invention relates to a device and a method for separating the exhaust gases from a power generation unit, in particular an internal combustion engine of a motor vehicle.

  The present invention more particularly relates to a device for separating the exhaust gas from a power generation unit supplied with liquefied natural gas, the liquefied natural gas being stored inside a low temperature tank.

  At present, it is sought to minimize the pollutant emissions of power generation units, including internal combustion engines of motor vehicles, for example by replacing fuels such as gasoline or diesel with gas. liquids generating, at the time of combustion, lower levels of emissions of particulate pollutants, and / or using fuel cells for electrochemical generation of electricity.

  Internal combustion engines are known comprising an exhaust gas filtering device provided with a filter element capable of allowing chemical trapping of particles contained in the exhaust gases before the said gases are released into the atmosphere. Such filtration devices have the disadvantage of having a relatively high cost and being, in addition, particularly difficult to implement on motor vehicles.

  The present invention aims to overcome these disadvantages by providing a separation device to substantially reduce the exhaust emissions of a particularly simple and compact power generation unit.

  For this purpose, the device for separating the exhaust gases from an energy production unit, in particular an internal combustion engine of a motor vehicle, supplied with liquefied natural gas, said liquefied natural gas being stored at the inside a low temperature tank. According to one aspect of the invention, the device comprises a low temperature exhaust manifold inside which is stored a portion of the condensed exhaust gas, the manifold being traversed by at least one gas supply pipe. the production unit allowing condensation of said collected exhaust gas.

  Such a device has the advantage of comprising a collector crossed by at least one supply line carrying gas at low temperature in order to generate, at the level of the collector, a cooling system capable of allowing the liquefaction of the exhaust gases, in particular the carbon dioxide, emitted by the production unit. It thus becomes possible to recover, in liquid or solid form, the carbon dioxide emitted in order to facilitate its storage, treatment or reuse.

  In other words, the collector makes it possible not only to store a part of the exhaust gases emitted by the production unit, but also to generate, in cooperation with the gas supply line, a chemical transformation of said gases for separate the carbon dioxide from the other exhaust gases emitted. The collector thus allows a heat exchange between the gas supplying the production unit and the exhaust gas produced.

  Furthermore, the use of the gas supply pipe as a cooling element of the exhaust gases makes it possible to dispense with the use of a refrigerant, generating a particularly high additional energy cost in order to obtain the condensation of said gas.

  The device may comprise, upstream of the collector, a heat-coupling exchanger traversed by an exhaust gas outlet pipe and by the liquefied gas supply pipe.

  Such a heat-coupling exchanger makes it possible to cool the exhaust gases before they are introduced into the collector. When the separation device is mounted on an energy production unit comprising a fuel cell, the heat-coupling exchanger can also make it possible to recover the water vapor contained in the exhaust gas to obtain a production of water at least equal to the water consumption of the stack so as to achieve an autonomous unit.

  A main supply line for liquefied natural gas may comprise two secondary supply lines supplying respectively said main supply line with gas and liquefied gas, said secondary supply lines passing through the collector.

  Advantageously, the collector and the reservoir are mounted inside a single low temperature storage member insulated under vacuum so as to obtain a substantially zero heat exchange between the collector and the reservoir.

  Such a device has the advantage of including a single member for storing, separately, the fuel of the power generation unit and the liquefied exhaust gas. The storage member allows the use of the energy necessary to maintain the fuel temperature of the production unit in order to carry out the treatment of the exhaust gas. It thus becomes possible to cool the exhaust gas at a very low temperature by avoiding generating a particularly high energy surcharge, in particular by the addition of an additional storage member requiring clean cooling.

  Preferably, the collector and the reservoir have different storage temperatures.

  The storage member may advantageously comprise a specific compartment inside which is mounted a coolant storage element so as to increase the condensation of the exhaust gas. The coolant may comprise liquid nitrogen.

  Preferably, the device comprises an exhaust gas separation element, mounted between the heat-coupling exchanger and the collector, so as to separate the carbon dioxide from the other gases contained in the exhaust gas. Preferably, the collector comprises a heating element.

  In one embodiment, the collector comprises at least one purge element capable of allowing recovery of the collected and condensed gases outside the device.

  The invention also relates to a method for separating the exhaust gases from a power generation unit, in particular an internal combustion engine of a motor vehicle, supplied with liquefied natural gas, comprising the steps in which - stores at least a portion of the exhaust gas inside a low-temperature manifold, - heat exchange is effected between the exhaust gases of the production unit and at least one gas supply line liquefied to obtain the condensation of the exhaust gases collected, and - the condensed exhaust gases are recovered.

  The invention will be better understood on studying the detailed description of embodiments described by way of non-limiting examples, and illustrated by the appended drawings in which: FIG. 1 schematically represents a power generation unit provided with a separation device according to a first embodiment of the invention, and - Figure 2 shows schematically a power generation unit provided with a separation device according to a second embodiment of the invention.

  FIG. 1 schematically shows a power generation unit comprising a fuel cell, referenced 1 as a whole, an internal combustion engine 2 and a gas turbine 3. Of course, the power generation unit may comprise only one of these elements.

  The fuel cell 1 comprises an anode 4 and a cathode 5 separated by an electrolytic membrane 6 (shown schematically). The fuel cell 1 may advantageously be of the proton exchange membrane (PEMFC) type with solid electrolyte. Of course, another type of fuel cell can be used. Such a fuel cell 4 is actually constituted by a stack of elementary cells electrically connected in series and separated by bipolar plates (not shown in the figure).

  A main supply line 7 supplies air to the cathode 5 of the fuel cell 1, via a compressor 7a. On the main supply duct 7 are mounted two secondary air supply ducts 8 and 9, the secondary duct 9 being situated upstream of the secondary duct 8, considering the direction of flow of the air through the duct. supply line 7. The secondary supply line 8 comprises a plurality of derived lines referenced 8a to 8e, here five in number. The lines 8a to 8d supply the motor 2, the line 8e feeding the turbine 3. The secondary supply line 9 feeds a reformer 10, of conventional design.

  The separation device comprises a storage member 11 at low temperature or cryogenic, cooled for example by a cryogenic fluid circulation, and inside which is disposed a low temperature reservoir 12 capable of allowing the storage of liquefied natural gas. Of course, it may also be possible to use other types of gas, for example hydrogen. The storage member 11 is isolated under vacuum.

  The temperature of the tank 12 is approximately -160 C. The tank 12 can be fed via a filling line 12a passing through a side wall of the storage member 11 and opening into said tank 12 The pipe 12a is provided with a solenoid valve (not shown). The reservoir 12 comprises respectively two supply lines 13, 14 of gas and liquid gas. The feed pipe 13 carries the gas contained in the tank 12. A portion of the feed pipe 14 is immersed inside the liquefied natural gas contained in the tank 12. Each supply pipe 13, 14 respectively comprises a valve 15, 16, for example a solenoid valve, to allow a liquid gas mixture to be produced. The valves 15, 16 are mounted outside the storage member 11. It is also conceivable to mount them in a specific thermally insulated valve box. The gas-liquid mixture thus formed is conveyed by a main supply line 17 connected to the secondary supply lines 13, 14, downstream of said valves 15, 16.

  The main supply line 17 comprises supply lines 18, 19 supplying the engine 2, the turbine 3, and the reformer 10. The supply line 18 comprises five branch lines, respectively referenced 18a to 18e. The ducts 18a to 18d feed the engine 2, the duct 18e supplying the turbine 3. The supply duct 19 feeds the reformer 10.

  During the production of electricity, the exhaust gases from the fuel-burning unit 1, the engine 2, and the turbine 3 are directed by outlet pipes, referenced 20 to 26. The exhaust gases from the anode 4 and the cathode 5 of the fuel cell 1 are respectively directed towards a burner 27 via the anode outlet line 20, and outwards via the cathode outlet line 21 The burner 27 supplies thermal energy to the reformer 10. The anode gases thus burned are then transported, via a pipe 29, to a heat-coupling exchanger 28, for example a condenser. condensates such as water being directed outwards. The exchanger 28 is traversed by the supply line 17 of the liquid gas and makes it possible to recover the water contained in the anode exhaust gases burned.

  It may also be possible to directly send the cathode gases from the fuel cell 1 to the burner 27 to mix the anode and cathode gases before they enter the interior of said burner 27 in order to recover a larger amount of fuel. water, for example to feed the reformer 10.

  The exhaust gas outlet pipes 22 to 25 from the engine 2 as well as the gas outlet pipe 26 from the turbine 3 are connected to a main outlet pipe 30 provided with a catalytic converter 31. The catalytic converter 31 may comprise a perforated core whose walls are coated with catalytic materials, for example based on platinum and rhodium, so as to reduce the emission of polluting particles into the atmosphere. Downstream of said catalytic converter 31, the outlet pipe 30 passes through the heat-transfer exchanger 28 and then a separating element 32. The heat-transfer exchanger 28 allows the cooling and condensation of the exhaust gases emitted by the anode 4 of the fuel cell 1, but also exhaust gases emitted by the engine 2 and the turbine 3 and transported by the pipe 30.

  The separating element 32 is provided with a membrane 32a, schematically represented in dotted lines. The membrane 32a is preferentially permeable to carbon dioxide (CO2) so as to separate the carbon dioxide from the other gases that may be contained in the exhaust gases transported by the pipe 30, for example nitrogen (N 2), oxides of nitrogen (NOx), carbon monoxide (CO), hydrocarbons (HC), to reject them directly to the outside through an outlet pipe 33. A pipe 34 connected to the element separation 32, downstream of the membrane 32a, thus carries exhaust gases whose carbon dioxide content is increased. The pipe 34 is connected to a low-temperature collector 35 mounted inside the storage member 11. The collector 35 and the low-temperature tank 12 are thermally insulated with respect to each other for example, disposing, between the collector 35 and the reservoir 12, a high vacuum and heat shields consisting of insulations and reflective sheets reducing thermal losses by heat emission.

  The circulation of cryogenic fluid inside the storage member 11 and the circulation of gas in the lines 13 and 14 make it possible to maintain the collector 35 at a relatively low temperature, for example of the order of -161. C. The exhaust gases thus collected inside the storage member 11, mainly carbon dioxide, are cooled without the need for a specific cooling fluid circuit generating an additional energy cost.

  In order to allow the liquefaction of the exhaust gases collected, the supply lines 13, 14 pass through the collector 35 so as to obtain a large heat exchange between the stored exhaust gas and the supply lines 13, 14. to obtain a significant heat exchange between the stored exhaust gas and the liquefied natural gas passing through the supply line 14, it is possible to provide as illustrated schematically in the figure, a pipe 14 provided with a coil-shaped portion.

  The cooling capacity of the gases transported by the lines 13 and 14, at a temperature of about -161 C, allows the exhaust gases to be cooled to a temperature below -78.5 C, liquefaction temperature of the carbon dioxide . This cooling thus makes it possible to obtain a condensation of a part of the exhaust gases, and more particularly of carbon dioxide. Indeed, the liquefaction temperatures of nitrogen and oxygen being lower than the temperature of the gases transported by lines 13 and 14, oxygen and nitrogen do not condense. Inside the collector 35, the carbon dioxide is found to a large extent in liquid or solid form.

  Recovery of the carbon dioxide found in liquid form can be done by withdrawal at an outlet pipe 36 provided with a purge element such as a valve 37, for example a solenoid valve, able to close or open 36. The exhaust gases are in gaseous form, the residual gases low in carbon dioxide can be discharged to the outside via the outlet pipe 38 also provided with a gas control element. pressure such as a valve 39, for example a solenoid valve.

  The collector 35 also comprises a heating element 40 supplied via electrical connections 41, 42 to a power supply unit (not shown). The heating element 40, supplied with heat transfer fluid or with electricity, thus makes it possible to eliminate any accumulation of condensates at the bottom of the collector 35 by vaporizing them and then discharging them outwards by pressure withdrawal via the valve 37 having previously closed the valve 39.

  The collector 35 also comprises a temperature probe 43 capable of making it possible to measure the temperature of the exhaust gases collected. Depending on the measurement taken, the valves 15, 16 are controlled so as to effect the composition of the gas-liquid mixture transported respectively by the supply line 17.

  The embodiment illustrated in Figure 2, differs in that the storage member 11 comprises a specific compartment inside which is mounted a storage element 44 of a cooling liquid, for example liquid nitrogen. (N2). The storage element 44 is thermally insulated from the low temperature reservoir 12 and the manifold 35. The storage element 44 is fed through a fill line 45 provided with a solenoid valve (not shown) .

  The feed pipe 17 passes through a heat-coupling exchanger 46, in particular making it possible to increase the cooling of the exhaust gases conveyed by the pipe 34 and emitted by the engine 2 and the turbine 3. The heat-coupling exchanger 46 is also passed through the outlet pipe 38 before the outward discharge of carbon dioxide-deficient residual gases stored in the manifold 35.

  Between the collector 35 and the storage element 44, a pipe 46 is mounted to allow the flow of nitrogen gas inside the collector 35. The cold nitrogen from the storage element 44 allows a total condensation carbon dioxide collected in the manifold 35. In other words, the use of liquid nitrogen in the storage member 44 allows for an improved condensation of the carbon dioxide present in the manifold 35. In addition, addition of the heat-coupling exchanger 46 makes it possible to recover an additional amount of water coming from the outlet gases coming from the pipe 38 and from the exhaust gases of the pipe 34.

  Whatever the embodiment, the present invention offers many advantages, among which storage in liquid or solid form of particularly polluting emissions that can be produced by a gas-fed energy generating unit using the supply lines. in gas of the production unit and the storage member of said gas to obtain a separation and recovery device with a reduced manufacturing cost.

Claims (10)

  1 / Apparatus for separating the exhaust gases from an energy production unit, in particular from an internal combustion engine of a motor vehicle, supplied with liquefied natural gas, said liquefied natural gas being stored inside a reservoir (12) at low temperature, characterized in that the device comprises a collector (35) at low temperature inside which is stored a portion of the condensed exhaust gas, the collector being traversed by at least one conduit d supply (13, 14) of gas from the production unit for condensing said collected exhaust gas.   2 / Apparatus according to claim 1, characterized in that it comprises, upstream of the collector, a heat-coupling exchanger (28) traversed by an outlet pipe (30) of the exhaust gas and by the supply line (14) in liquefied gas.   3 / Apparatus according to claim 1 or 2, characterized in that a main supply line (17) liquefied natural gas comprises two secondary supply lines (13, 14) respectively supplying said main gas supply line and in liquefied gas, said secondary supply lines passing through the collector (35).   4 / Apparatus according to any one of the preceding claims, characterized in that the collector (35) and the reservoir (12) are mounted inside a single storage member (11) at low temperature insulated vacuum of in order to obtain a substantially zero heat exchange between the collector (35) and the reservoir (12).   5 / Apparatus according to any one of the preceding claims, characterized in that the collector (35) and the reservoir (12) have different storage temperatures.   6 / Apparatus according to any one of the preceding claims, characterized in that the storage member (11) comprises a specific compartment inside which is mounted a storage element (44) of a cooling liquid so to increase the condensation of the exhaust gases.   7 / Apparatus according to claim 6, characterized in that the cooling liquid comprises liquid nitrogen.   8 / Apparatus according to any one of claims 2 to 7, characterized in that it comprises a separating element (32) of the exhaust gas, mounted between the thermal coupling heat exchanger (28) and the collector (35). ), so as to separate the carbon dioxide from the other gases contained in the exhaust gas.   9 / Apparatus according to any one of the preceding claims, characterized in that the collet comprises at least one purge element (37, 39) adapted to allow recovery outside the device of the collected gas and condensed.   10 / A process for separating the exhaust gases from an energy production unit, in particular an internal combustion engine of a motor vehicle, supplied with liquefied natural gas, characterized in that it comprises the steps in which at least a portion of the exhaust gases are stored inside a low temperature collector, a heat exchange is carried out between the exhaust gases of the production unit and at least one feed pipe of the liquefied gas to obtain the condensation of the exhaust gases collected, and the condensed exhaust gases are recovered.