FR2949822A1 - Carbon dioxide release decreasing process for engine i.e. internal combustion engine, of car, involves heating carbon dioxide released from outlet side of engine with hydrocarbon in heat exchanger - Google Patents

Abstract

The process involves heating carbon dioxide released from an outlet side of an engine (1) with hydrocarbon (8) in a heat exchanger, and directly connecting a catalytic engine to an exit of engine exhaust pipes. The catalytic engine is indirectly heated by combustion gases before connecting to a muffler.

Description

It is known that internal combustion engines that are used to produce mechanical energy, especially in automobiles, operate by combustion using air and a hydrocarbon-based fuel. The resulting flue gas contains mainly water vapor and nitrogen and carbon dioxide between 12% and 14% and is released into the atmosphere after passage in a catalytic converter intended to reduce certain harmful discharges such as water. carbon monoxide and unburned fuels

The present invention provides a method and a device for recovering the carbon dioxide usually released into the atmosphere by converting it into a second additional fuel to the engine by using the CO2 which has been generated by the first limiting main fuel and the contribution of fossil carbon for the motor supply. The method includes operating an internal combustion engine with air and at least two external fuels, one referred to as a primary fuel being a conventional hydrocarbon fuel such as gasoline, diesel or diesel fuel. methane and another called additional fuel being obtained from the exhaust gas from the engine A carbon dioxide separator collects firstly a first gas enriched in carbon dioxide and depleted in nitrogen and secondly a second and wherein said first gas is mixed with at least one hydrocarbon and the resulting mixture is contacted with conversion of the mixture of carbon dioxide and hydrocarbon, led to a mixture of carbon monoxide and hydrogen, under temperature conditions for said conversion, the latter mixture being the second additional aforementioned fuel that powers the engine. The carbon dioxide separator is of a new type with controlled porosity ceramic polymer membrane whose pores of the ceramic are lined with polymers of the family -polyimide resistant to a temperature of 350 ° _400 ° C. For example, use a support aluminosilicate or metal or metal alloy porous capable of withstanding high temperatures of the order of 400 ° C and treated as previously described. These low-temperature separators may also be used under the dual condition of cooling the exhaust gas at the engine outlet before admission to the separator and then reheating them before they pass into the catalytic converter. This can be done and specifically at this location by recovering heat at the exhaust pipes through a countercurrent exchanger of hot gases exiting the engine before entering the separator, and gas from the separator before entering the separator. converter. This exchange can take place in a conventional wall-type heat exchanger. This device alone placed at this point makes it possible to maintain the catalyst at a sufficiently high temperature without resorting to electric heating. This arrangement increases the overall energy efficiency of the engine by using this source. The conversion catalysts of step (b) above are conversion catalysts such as those currently used in catalytic converters of motor vehicles, especially those based on platinum or palladium. Catalysts based on nickel or other are also described in EP 494 550 of June 15, 1994 or US 6251 30 227 of June 26, 2001. The conversion temperature is usually of the order of 450 to 600 ° C but may vary in more or less. In one embodiment, the hot gases from the engine are used to indirectly heat the catalytic conversion zone. The catalyst is then placed on a first side of a double-walled enclosure, the hot gases pass on the other side of the first wall, before joining the CO2 separator. It should be noted that the exhaust gases at the engine outlet contain, in addition to CO2 and N2, water vapor and a little carbon monoxide. Depending on the type of separator and its selectivity, the enriched carbon dioxide stream from the separator may contain, in addition to CO2, and N2 a certain amount of water vapor and carbon monoxide. This is not generally a disadvantage and the water vapor can even be useful as a reagent in the converter. The invention relates inter alia to a device for producing mechanical energy comprising an internal combustion engine of hydrocarbon by means of air, said engine producing mechanical energy characterized in that it comprises in the order flue gas discharge conduit to a carbon dioxide separator providing a combustion gas stream enriched with carbon dioxide, a catalytic converter of carbon dioxide, carbon monoxide and hydrogen mixed with a hydrocarbon and a pipe returning the mixture of carbon monoxide and hydrogen to the engine supply. The invention is illustrated by Figures 1 and 2. In Figure 1, the motor is schematically represented by a circle (1). It is fed with a main mixture of hydrocarbon and air (2) and with a stream of the second additional fuel (3). The exhaust gas (9) is sent to the carbon dioxide separator (4). The CO2-depleted gases are released to the atmosphere via line (5) while the CO2-enriched gases (6) are sent to the catalytic converter (7). It receives a quantity of hydrocarbon (8) sufficient to ensure at least partial conversion of CO2 to CO and hydrogen. The gas obtained, enriched in CO and hydrogen constitutes the second additional fuel (3). The device of Figure (2) is an improvement It allows in particular to use a membrane operating at a relatively low temperature, which requires a cooling of exhaust gas and their subsequent reheating. In this case the hot exhaust gases (9a) pass through a wall exchanger (10) countercurrent relatively cold gases (11) from the membrane separator (4) and the additional hydrocarbon (8a). After cooling the cooled gas passes through the pipe (9b) in said low temperature separator (4) and the pipe (11) and is then heated in the exchanger (10) as explained above. After reheating, they are sent via line (12) to the converter (7). They are then returned to the engine as additional fuel by the pipe (3). Alternatively the additional hydrocarbon can be injected directly into the converter, through the pipe (8b) in this case the pipe (8a) is not used, or the hydrocarbon is injected in part in each of these pipes. Although an additional hydrocarbon feed (8,8a, 8b) has been shown to the converter (7) separate from the CO2 enriched gas feed (6 or 12), it is preferred to intimately mix these two streams. before entering the converter. This can be achieved with a static mixer. The hydrocarbon used may be of the same type as the one feeding the engine, or may be different. Light, saturated or unsaturated hydrocarbons, for example from C1 to C8, are preferred.

From the foregoing description it is clear the advantage of the invention, namely that it can convert at least a portion of the carbon dioxide from the additional fuel engine for the same power delivered by the engine. We can reduce the amount of fossil fuel introduced into the engine either by direct injection or by the carburetor.

Modifications to a conventional engine are minimal. The carburetor or the usual injectors can be kept and the additional fuel gas stream can be introduced, for example, into the (or the) duct (s) for admission of air or fuel mixture to the engine. A device for regulating the various currents, for example an electronic device, will make it possible to adjust the proportions of air and fuels necessary for good combustion in the engine.

The method and the device of the invention are compatible with the use, now customary in some vehicles of catalytic converters. These can advantageously be placed between the engine and the CO2 separator or at the outlet of the separator, on the pipe (5) of FIGS. 1 and 2.

Claims (7)

Revendications1. A method of reducing the emission of CO2 emitted by an engine into the atmosphere by converting a portion of the CO2 produced into fuel. 2. Method according to claim 1, implemented in a well-defined order comprising the concentration of CO2 produced by the engine followed by passing over a conversion catalyst heated at the engine outlet with a hydrocarbon in a heat exchanger. 3. The process of claim 2 wherein the catalyst reactor is directly connected to the outlet of the engine exhaust pipes where the temperature is between 450 and 600 degrees centigrade. 4. Process according to claims 1 to 3 in that the catalytic reactor is heated indirectly by the combustion exhaust gases before connection to the exhaust pipe. 5. Process according to claims 1 to 4 characterized in that the mixture of fuels is gaseous, comes from a carbon that has already produced energy and is based on converted CO2. 25 6. Apparatus for carrying out the method according to any one of claims 1 to 5, wherein the CO2 separator is ceramic, aluminosilicate or porous metal alloy whose porosities of the surface are covered with a film polymer of the polyimidic family. 30 7. Use of the method according to any one of claims 1 to 5 on heat engines to reduce the release of CO2 into the atmosphere. 20