FR2906299A1 - Diesel quantity reducing system for motor vehicle, has separation unit e.g. glass type porous membrane, removing volatile linear hydrocarbons from lubricating oil, and separated hydrocarbons reception unit in contact with membrane - Google Patents

Abstract

The system has an exhaust line (5) with a depolluting unit (6) that is associated to a regeneration unit implementing post injections of fuel in cylinders. A four-cylinder diesel engine (1) is associated to a lubricating oil pan (17) and to a diesel/oil separation condenser (18). The condenser is provided with a gas vapour recirculation conduit (19). A separation unit e.g. porous membrane such as glass type membrane, removes volatile linear hydrocarbons from the lubrication oil. A reception unit for receiving the separated volatile light hydrocarbons is in contact with the membrane.

Description

1 System for reducing the amount of qazole in the oil of

  lubrication of an engine. The present invention relates to a system for reducing the amount of diesel fuel in the lubricating oil of a motor vehicle diesel engine. More particularly, the invention relates to such a diesel engine whose exhaust line is provided with depollution means associated with regeneration means implementing fuel post-injections in the cylinders thereof and wherein the engine is also associated with an oil tank and a diesel / oil separation condenser provided with means of evacuation of diesel vapors. It is known that motor vehicle diesel engines are associated with means for treating their polluting emissions, these treatment means comprising, for example, NOx traps, particulate filters, oxidation catalysts, etc. These different systems have been developed to allow these vehicles, and more particularly these engines, to operate in compliance with increasingly stringent pollution control standards. For example, exhaust gas pollution control systems comprising means of NOx trap type are currently very promising. However, the management of their efficiency requires generating an alternately poor and rich gas atmosphere to purge gaseous NOx and SOx species present in the exhaust line and they adsorb in their structure. For this purpose, one or more diesel injections are used in the combustion chambers of the engine. This results in almost total consumption of oxygen from the exhaust gases, thus making it possible to increase the richness of these exhaust gases passing through the trap, beyond 1, but also a gradual dilution of the lubricating oil. engine with diesel. This phenomenon of dilution of the lubricating oil is essentially due to the late phasing of the post-injection or post-injections to be used, to pass in richness greater than 1, and the condensation of gas oil in the gas phase on the cylinder walls. The diesel jets then reach the walls of the combustion chambers and dilute the film of oil present thereon. The resulting oil / diesel mixture 2906299 2 then easily passes through the seal of piston segmentation and thus reaches the engine oil tank. This dilution phenomenon is similar to that which is the consequence of the engine control strategies implemented to allow, for example, the regeneration of particulate filters, since post-injection is also required to heat the exhaust gases to a level of temperature sufficient to achieve the combustion temperature carbon soot retained on such a particulate filter. After 20000 kilometers, the dilution rate measured on the 10 serial applications in vehicle, is generally between 4 and 6%. A motor vehicle engine comprising a particulate filter and a NOx post-treatment system is therefore highly subject to the phenomenon of dilution of its lubricating oil, because of the high NOx purge frequency that it is necessary to put (in relation to the regeneration frequencies of a particulate filter), to maintain the NOx conversion efficiency of the catalyst (on average one purge every 1 to 3 minutes) and the need to add purge sulphates. For the latter, the purge frequencies are less important than those of the regenerations of the particulate filter, but the post-injection levels must both make it possible to mount the exhaust gases at a high temperature (above 650 ° C.) and at a richness greater than 1. The resultant of the purging effects of NOx + SOx purges + FAP regeneration leads to a dilution of the lubricating oil with diesel which generally exceeds 30% by mass over 30000 kilometers, if no correction is This is done to reduce it during engine operation, while the acceptable limit for the lubricating oils of diesel engines currently in use is below 9%. These levels of dilution of fuel in the oil then have several consequences: a drop in viscosity of the oil which has recoveries on the oil pressure (oil shear, engine seizure or engine failure), accelerating the aging of the oil (oxidation), - corrosion of the materials having an impact on the tightness of the oil circuit, and - dilution of the additive content introduced into the lubricating oil to increase its physical performance and chemical.

The object of the invention is to solve these problems. The invention is based on the observation that these problems, in particular the drop in the viscosity of the lubricating oil, can be solved by removing the molecules of small bulk from the oil. The subject of the invention is therefore a system for reducing the amount of diesel fuel in the lubricating oil of a motor vehicle diesel engine, whose exhaust line is provided with depollution means associated with regeneration means. implementing post-injections of fuel in the cylinders thereof and wherein the engine is also associated with an oil tank and a diesel / oil separation condenser provided with means for evacuation of diesel vapors, characterized in that it comprises selective separation means for removing the volatile linear hydrocarbons from the lubricating oil and, arranged in contact therewith, means for receiving the separated volatile linear hydrocarbons. Volatile linear hydrocarbons are understood to mean saturated or unsaturated aliphatic hydrocarbons generally having less than 25, and preferably 10 to 20, carbon atoms. These species are small and therefore are the lightest components of diesel. They therefore contribute the most to modify the properties of the lubricating oil, particularly in terms of viscosity.

In general, the separation means will be chosen so that they have, in addition to the desired selectivity, also sufficient permeability. Suitable means of separation include porous membranes, also known as molecular sieves, which are capable of separating molecules on the basis of their size and molecular form.

The porous membranes will be selected from an oil-inert and sinter-resistant material. By way of example, mention may be made of metals, metal oxides, organic or inorganic polymers, ceramics, glasses, graphites. The porous membranes may consist of a single or multiple materials, in which case they are referred to as composite membranes. Several types of porous membranes are known, in particular porous membranes of the carbon, glass, ceramic and zeolite type.

The carbon membranes are generally prepared by decomposing a polymeric organic compound which produces a carbonaceous layer having a porous structure. Carbon granules have been used commercially for many years for adsorptive molecular separation. However, these membranes have limited resistance to oxidizing atmospheres. Porous glass membranes can be prepared with pore diameters of 3 to 300 nm, for example by the Vycor process. Although the heat resistance of the porous glass is no longer ensured beyond 575 K, it can be used in the present system, the average temperature of the oil being 285K. The ceramic membranes are essentially composed of metal oxides such as SiO2, Al2O3, ZrO2, TiO2, CaO. They are generally asymmetrical systems comprising a macroporous and mesoporous multilayer support ensuring the mechanical strength of the assembly, which carries a thin microporous or mesoporous layer. This thin layer is the membrane that will control virtually the transfer of material. In general, the thin layer is obtained by sol-gel type processes, the pores then being formed by intergranular voids. Zeolite-based membranes can also be used. Zeolites are hydrated aluminosilicates containing alkali or alkaline earth ions. The crystalline structure of dehydrated zeolites comprises channels whose diameter is in the range of micropores or ultramicropores (pore diameter <0.7 nm). The pore diameter distribution is narrow, which renders these membranes more selective and therefore particularly attractive for the described application. The selectivity of the porous membranes results essentially from their porosity and their chemical affinity.

In fact, apart from convection, the transfer of matter through the porous membranes obeys the laws of diffusion of the gases in the porous media. They therefore strongly depend on the shape, size and pore distribution at the membrane texture.

In terms of pore size, microporous membranes (pore diameter> 50 nm), mesoporous (pore diameter 2 to 50 nm) and microporous membranes (pore diameter <2 nm) are distinguished. The diesel fuel molecules most affecting the viscosity of the lubricating oil are unbranched linear molecules having an atomic chain of less than 20 carbon atoms. These molecules can be selectively retained in microporous membranes, preferably having an internal pore diameter of less than 0.5 nm, and in particular less than 0.4 nm. The pore inlet diameter of a material can be reduced, if necessary, by grafting the membrane with bulky molecules, such as chloroisopentane. These molecules block by their conformation a part of the pores causing a decrease in the input diameter of the molecules. On the other hand, a surface of the membrane can be treated to modify its molecular affinity, especially its polarity. Such a treatment may be advantageous in the present system in that it allows for example to prevent the passage of aromatic molecules. The shape and size of the porous membrane can be adapted by known techniques to the diameter of the lubricating oil circulation pipes. In order to prolong its lifetime, the porous membrane is preferably associated with a particle filtering means. For this purpose, one can for example have upstream of the porous membrane one or more traps for submicron particles.

According to the invention, the separating means are associated with means for receiving the separated volatile linear hydrocarbons.

The purpose of the reception means is to trap the separated volatile linear hydrocarbons and thus to avoid the emission of the molecules captured in the atmosphere and the risks of leakage. The means of reception may in particular be a miscible liquid with the volatile light hydrocarbons separated from a C 6 to C 12 alkanol substituted with one or more C 3 to C 6 branched alkyl groups, such as di-1,10-isopropyldecanol. Alternatively, the receiving means may be a porous material, especially in the form of beads.

The reception means are arranged in contact with the separation means. For example, they may be contained in a pocket of suitable material forming an envelope of separation means. The described system can be assembled as a cartridge. It is then easily implantable, without external connectique.

Advantageously, the separation means do not interfere with the operation of the diesel engine. In particular, the composition of the lubricating oil is not impaired, especially as regards the additives. In this regard, the system advantageously selectively eliminates the compounds from the diesel without affecting the presence of the other compounds in the lubricating oil. The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which: FIG. 1 represents a block diagram illustrating the structure and operation of a diesel engine of the state of the art; and - FIG. 2 is a block diagram illustrating the structure and operation of a reduction system embodiment according to the invention; and FIG. 3 is a detail view of the block diagram of FIG.

In fact, FIG. 1 shows a motorization system of the state of the art, which comprises a motor designated by the general reference 1, which, in the example described, is a four-cylinder diesel engine. . The exhaust outlet 2 of this engine is associated with the turbine portion 3 of a turbocharger 4 integrated in an exhaust line 5 of this engine, this exhaust line being provided with pollution control means 6 comprising, for example a NOx 7 catalyst associated with a particulate filter 8. The compressor portion 9 of the turbocharger 4 is associated at input with an air filter, for example 10, and at the outlet with an intake air cooler designated by the general reference 11, the output of which is connected to a gas intake manifold at the engine inlet and designated by the general reference 12. The exhaust outlet of the engine 2 is also associated with a recirculation EGR circuit designated by the general reference 13, comprising an EGR valve designated by the general reference 14, optionally an EGR oxidation catalyst designated by the general reference 15 and an EGR cooler designated by the a general reference 16, whose output is also connected to the intake manifold 12.

This conventionally makes it possible to recirculate part of the exhaust gas at the engine inlet. In addition, the engine is also associated with a lubricating oil tank designated by the general reference 17 in this figure and a diesel fuel / oil separation condenser 18 provided with means for evacuation of the diesel vapors, such as for example a conduit 19 for recirculating these vapors in the engine and an oil filter 20. It will be recalled that the lubricating oils consist of heavy hydrocarbons whose distillation temperatures are generally between 340 and 500 C. They also contain additives Specific whose role is to enhance its antioxidant properties, maintain or increase its viscosity, etc ..., and whose vaporization temperatures are generally located above 380 C.

In the system according to the invention, it is intended to separate from the lubricating oil the light linear compounds derived from diesel, so as to maintain the properties of the lubricating oil. Thus, in the system according to the invention, there are provided means for separating volatile linear compounds to improve the gas oil / oil separation and, arranged in contact with the separation means, means for receiving the separated volatile light hydrocarbons. Of course, different embodiments of these separation and reception means can be envisaged.

Thus, for example, as illustrated in FIG. 2, these separation means may be a porous membrane 22, advantageously associated with one or more submicron particle traps 21 located upstream, making it possible to extend the duration of operation of the membrane. In this FIG. 2, identical reference numerals denote parts identical or similar to those illustrated in FIG. 1. Thus, in this figure, the engine 1, the turbocharger 4 and the exhaust line 5 are recognized. , the depollution means 6, the EGR circuit 13, the oil tank 17, the condenser 18 and the evacuation means 19. In this case, is located downstream of the condenser 18 an oil filter 20 and 20 a trap for submicron particles 21 and a porous membrane, designated by reference number 22 in this figure. The porous membrane 22 may be of the type described above. Preferably, it is a porous membrane of zeolite type also called molecular sieve.

The lubricating oil then passes from the condenser 19 through the oil filter 20, and the trap (s) for submicron particles 21 before reaching the porous membrane 22. The molecules having a bulk less than the Pore inlet size is preferentially adsorbed in the porous membrane. Thus, a porous membrane having an inlet size of 0.5 nm can adsorb molecules smaller than 0.5 nm. The adsorbed molecules can then migrate along the porous system of the porous membrane.

Advantageously, the porous membrane is formed and arranged in such a way that the molecules thus adsorbed can be easily removed from the oil circuit. Such an embodiment is illustrated in FIG. 3. The porous membrane 22 is arranged in such a way that one of its surfaces is in contact with the oil circuit and another with the receiving means 23. the porous membrane are connected by pores. The adsorbed molecules migrate through the porous membrane system under the effect of osmotic pressure due to the concentration gradient across the membrane. They then migrate through the porous membrane to be captured, in particular by dissolution or absorption, in the receiving means 23. The receiving means may comprise in particular a mis-target liquid with the volatile light hydrocarbons. Advantageously, its constitution does not allow migration to the oil circuit. Such a liquid may be in particular a hydrocarbon carrying one or more polar functions, such as hydroxyl, amine, nitrile or carboxyl groups, in particular a C 6 to C 12 alkanol. The hydrocarbon is, moreover, preferably substituted by one or more branched C 3 to C 6 alkyl groups, preferably isopropyl. Particularly preferred is di-1,10-isopropyldecanol.

According to another embodiment, the receiving means may be a porous material, preferably divided, especially in the form of porous beads. The porous material may comprise or consist of metal, metal oxide, such as silica, alumina or zircon, organic or inorganic polymer, ceramic, glass, graphite or clay.

The reception means are arranged in contact with the separation means. For example, they may be contained in a pocket of suitable material forming an envelope around the separation means. The system according to the invention associating the two means described makes it possible to further limit the emission of the light molecules captured in the atmosphere and the risks of leakage and thus to improve the possibilities of implantation of this molecular sieve. The system operates autonomously because the concentration gradient through the membrane allows via osmotic pressure to migrate the light hydrocarbons of diesel to the receiving means.

Thus, the light diesel fuel molecules responsible for the viscosity drop of the engine oil by dilution are eliminated. It goes without saying of course that other embodiments of these separation and reception means described can be envisaged.

The described system allows the selective separation of the most important gas oil molecules in the lubricating oil for maintaining the properties of the oil, especially in terms of viscosity. It also has the following advantages: no modification of the motor architecture for a better life of the powertrain unit using a submicron trap; prolongation of the physical and chemical characteristics of oil; prolonging the life of the engine by reducing the wear of parts; ease of integration ; No increase in oil backpressure; economical solution with inexpensive materials; versatility in terms of oil types; exchange of separation means possible during a conventional oil change; The possibility of eliminating certain organic or organometallic compounds considered critical in the future; -limitation of the emission of molecules captured in the atmosphere and risks of leaks; and the possibility of implanting the system without external connectors, especially in the form of a cartridge.

Claims (10)

  1. A system for reducing the amount of diesel fuel in the lubricating oil of a motor vehicle diesel engine, whose exhaust line (5) is provided with depollution means (6) associated with regeneration means in the case of fuel injections into the cylinders thereof and in which the engine (1) is also associated with an oil tank (17) and with a diesel / oil separation condenser (18) provided with means ( 19) for evacuating diesel vapors, characterized in that it comprises selective separation means (22) for removing from the lubricating oil the volatile linear hydrocarbons and disposed in contact with said separation means, means for receiving (23) separated volatile light hydrocarbons.   2. System according to claim 1, characterized in that it further comprises upstream separation means a trap for submicron particles (21).   3. System according to claim 1 or 2, characterized in that the separation means (22) comprise a porous membrane.   4. System according to claim 3, characterized in that the porous membrane is selected from a membrane of carbon, glass, ceramic and zeolite type.   5. System according to any one of claims 1 to 4, characterized in that the receiving means (23) comprise a target liquid with separated volatile light hydrocarbons.   6. System according to claim 5, characterized in that the liquid is a hydrocarbon bearing one or more polar groups, such as hydroxyl groups, amine, nitrile or carboxyl.   7. System according to one of claims 5 or 6, characterized in that the liquid is a hydrocarbon bearing one or more branched alkyl groups C3 to C6, especially isopropyl.   8. System according to any one of the preceding claims, characterized in that the receiving means comprise a porous material. 2906299 12   9. System according to claim 8, characterized in that the porous material is in the form of beads.   10. System according to one of claims 1 to 9, characterized in that it is assembled in the form of a cartridge.