Patent Application
20060269886
The present invention generally relates to the field of combustion processes, and more particularly to combustion processes ignited by radiant heat (also referred to as radiant combustion processes). More specifically, the invention relates to a radiant combustion reactor for the use in radiant combustion processes.
As known in the art, radiant combustion is a process of combustion of a substance that is ignited by a heat source not involving the presence of a flame, but irradiating the substance, e.g. a gas or a mix of gases, to be combusted to electromagnetic radiating energy, particularly in the range of range of wavelengths from InfraRed (IR) to UltraViolet (UV).
Radiant combustion is carried out within apparatuses known as radiant combustion reactors.
In very general terms, a radiant combustion reactor consists of an enclosure within which the substance(s) to be combusted are fed. Associated with the enclosure walls, which are made of suitable materials, are heating means adapted to heat the enclosure walls up to a temperature at which the material making up the enclosure walls starts radiating electromagnetic radiation (in the way that approximates the black-body radiation), in a range of wavelengths and with an energy sufficient to cause the heating of the substance(s) to be combusted. Provided the radiated energy is sufficiently high, the substance(s) to be combusted is heated up to a temperature sufficient to ignite the combustion thereof. The combustion reactors typically take the form of tubes (also referred to as radiant tubes) of suitable material, within which the substance(s) to be combusted, typically gases, are caused to flow. The heating means are associated with the tubes and cause heating thereof, so that the gases flowing therethrough are also heated up to the desired temperature.
Typical heating means used in radiant combustion reactors are based on the Joule effect, and comprise electrical resistors, for example spiral resistors wound around radiant tubes, or embedded in heat-radiating panels between which the radiant tubes are sandwiched.
Other known heating means are based on the combustion (meaning a classical combustion, in presence of a flame) of gases.
It has been observed that the known heating means exploited in radiant combustion reactors are disadvantageous under many respects, being slow, power-consuming and (at least in the case of heating means based on the combustion of gases) polluting and possibly critic from the safety viewpoint.
In view of the state of the art briefly outlined in the foregoing, it is desired to provide a radiant combustion reactor that is not affected by the above-mentioned problems.
It has been found that significant advantages can be achieved if an optical radiation source is used as a heating means for a radiant combustion reactor, particularly a highly coherent, monochromatic and intense radiation such as a laser radiation.
In summary, the radiant combustion reactor comprises a combustion chamber delimited by walls which, when properly heated, radiate electromagnetic energy, particularly in a wavelength range from infrared to ultraviolet; a heating arrangement is operatively associated with the heat-radiating walls for heating the walls up to a prescribed, radiating temperature.
The heating arrangement comprises at least one optical radiation source generating an optical radiation that is caused to invest the heat-radiating walls and is adapted to cause heating thereof.
It is observed that, for the purposes of the present invention, optical radiation is not to be construed strictly as meaning an electromagnetic radiation in a wavelength range such as to be visible by the human's eye, but more broadly, to include for example infrared radiation.
Features and advantages of the present invention will be made apparent by the following detailed description of some embodiments thereof, provided merely by way of non-limitative examples, description that will be conducted making reference to the annexed drawings, wherein:
Hereinafter the present invention will be described in detail making reference to a particular application thereof, being intended that the invention can be applied in general to other and very different contexts.
With reference to the drawings, in
The pollutants-reduction apparatus, denoted globally as 100, is schematically depicted as placed downstream a block 105, representative of a generic apparatus of any type whose operation involves the combustion of fuels, particularly fossil fuels such as hydrocarbon fuels or hydrocarbon containing fuels such as petroleum, including natural gas, coal, or wood and the like, in general any fuel that can be combusted; for example, the apparatus 105 may be an internal-combustion engine of a vehicle, particularly but not limitatively of the Diesel type, or a burner of a heating system for buildings. Downstream the pollutants-reduction apparatus 100, a block 110 is provided, schematically representing an exhaust system of any conventional type, for example a simple muffler of a vehicle.
In greater detail, the pollutants-reduction apparatus 100 has an input manifold 115i, for receiving combustion exhaust gases from the apparatus 105; the received exhaust gases are treated by the apparatus 100 before being released in the environment; the pollutants-reduction apparatus 100 has an output manifold 1150 for delivering treated exhaust gases to the exhaust system 110 (it is however observed that the exhaust system 110 might also not be provided for, and the treated exhaust gases be released directly into the environment).
The input manifold 115i leads the exhaust gases to be treated to a gases pre-heating chamber 120, where the exhaust gases, received from the apparatus 105 at a relatively low temperature, are submitted to a preliminary heating process. Considering for example the case of exhaust gases from an internal combustion engine, particularly of the Diesel type, the temperature of the exhaust gases should in theory be around 400-450° C.; however, experimental trials conducted by the Applicant have revealed that the exhaust gases temperature is normally lower, falling in the range from approximately 150° C. to approximately 300° C. The preliminary heating process in the pre-heating chamber 120 brings the exhaust gases temperature to a suitably high value, preferably a value higher than 400° C., for example a value in the range from approximately 400° C. to 700° C. and, preferably, from approximately 550° C. or 600° C. to approximately 700° C.
The pre-heating chamber 120 comprises means adapted to submit the incoming exhaust gases to a compression, thereby the gases temperature rises. In particular, the pre-heating chamber 120 may comprise means adapted to imparting a suitable acceleration to the exhaust gases, and particularly one or more among a fan (or an arrangement of fans), a turbine (or an arrangement of turbines), a turbocompressor; these elements are schematically indicated in
Preferably, downstream the means for accelerating the exhaust gases, a Venturi tube (schematically represented in
From the pre-heating chamber 120, the pre-heated gases are conveyed to a radiant combustion reactor 125, situated just downstream the Venturi tube 123.
The radiant combustion reactor 125 comprises an enclosure or chamber with walls made of suitable material, which are heated by a heat source to a prescribed temperature, thereby the chamber walls radiate electromagnetic energy within the chamber (in the way that approximate the black-body radiation). Within the radiant combustion reactor 125, the temperature of the exhaust gases is raised further and rather quickly from the pre-heating temperature, for example the initial approximately 700° C., to a temperature in the range from approximately 900° C. to approximately 1200° C., preferably from approximately 900° C. to approximately 1100° C., suitable to determine a combustion (post-combustion) of the exhaust gases; more generally, the upper limit of the temperature of the exhaust gases is determined by the requirement that, at such a temperature, the creation of nitrogen oxides is not relevant; thus, the maximum temperature of the gases within the combustion reactor 125 may reach 1300-1400° C. The increase in temperature is achieved by radiant energy, particularly in the wavelength range from IR to UV, radiating from the walls of the radiant combustion reactor 125.
By subjecting the exhaust gases to such a fast increase in temperature, the exhaust gases post-combustion process that is automatically induced allows substantially reducing or even eliminating the harmful, uncombusted particulates present in the exhaust gases. In particular, in the exhaust gases, typically a mix of oxygen, uncombusted hydrocarbons, carbon particulate, self-combustion is automatically ignited, because the gaseous fluid in the reactor 125 travels in an environment at a temperature which is higher than the self-combustion temperature (the specific value of which depend on the substances present in the exhaust gases), and the combustion is carried out exploiting the radiant energy irradiating from the walls of the reactor 125. This substantially improves the efficiency of the combustion of the carbon particulates, which is more difficult than that of hydrocarbons because the combustion time is related exponentially to the size and shape of the particle.
It is observed that by ensuring that the gas temperature in the radiant combustion reactor 125 is sufficiently high, in particular higher than approximately 450° C., preferably in the range from approximately 900° C. to approximately 1200° C., and more preferably from approximately 900° C. to approximately 1100° C., i.e. below the temperature at which nitride oxides start forming, nitride oxides already present in the exhaust gases are reduced. To this purposes, the post-combustion process of the exhaust gases may be combined with known reduction processes, such as the Non-Selective Catalytic Reduction (NSCR) process, in presence of oxygen (by providing a suitable feed of oxygen to the radiant combustion reactor), or the Selective Catalytic Reduction (SCR) process, in presence of a noble catalyst (e.g., platinum), maintained at high temperature by the flow of the exhaust gases. It is pointed out that the NSCR and the SCR processes may be exploited in alternative to one another, or in combination, depending in particular on the structure, e.g. on the geometry, of the radiant combustion reactor 125.
It is also observed that, in the radiant combustion reactor 125, the post-combustion of the exhaust gases takes place at a constant pressure.
In
In order to avoid dispersions of energy, the radiant combustion reactor 125 is preferably thermally insulated, for example by means of refractory silicon-ceramic materials, or other suitable materials.
Optionally, a first filtering element 130a is arranged along the radiant combustion reactor 125 (for example, the radiant combustion reactor 125 may be made up of two parts in cascade, and the filtering element 130a may be arranged between the first and the second part).
Upon leaving the radiant combustion reactor 125, the exhaust gases are led to a second filtering element 130b.
Each one or both of the filtering elements 130a and 130b may comprise active filters, particularly selective filters, preferably active nanofilters in ceramic/zeolite material, and are used for trapping residual dust and Particulate Material (hereinafter, shortly, PM) still present in the exhaust gases after the post-combustion process in the radiant combustion reactor 125. In particular, the first filtering element 130a, if provided, allows trapping the residual, uncombusted dust and PM present in the exhaust gases after a first post-combustion phase, while the second filtering element 130b, positioned at the output of the radiant combustion reactor 125, serves for trapping the uncombusted dust and PM still remaining in the exhaust gases after the post-combustion. Depending on the type of nanofilters adopted, the filtering elements may act both as hot catalysts, and as pure filters,
It is pointed out that the specific arrangement, the number and the dimensions of the nanofilters making up the filtering elements 130a and 130b will depend on the specific type of apparatus 105 to which the pollutant-reduction apparatus 100 is intended to be associated with. However, as a general rule, nanofilters resistant to high temperatures should be used.
It is also observed that more than one intermediate filtering element 130a may be provided along the radiant combustion reactor.
Preferably, the filtering elements 130a and 130b are removable from the apparatus 100 and, even more preferably, they are also reconditionable or recyclable.
Optionally, means suitable to favor the exit of the post-combusted gases from the radiant combustion reactor 125 are provided, as shown in phantom and indicated by 127 in
After being passed through the second filtering element 130b, the treated exhaust gases (substantially freed of the harmful pollutants) are led to a heat exchange arrangement 135. In the heat exchange arrangement 135 the temperature of the treated exhaust gases is lowered from the 900° C.-1200° C. to values suitable to avoid thermal shocks, such as a temperature value of approximately 100° C.-150° C.
Expediently, the heat exchange arrangement 135 is arranged in such a way that at least part of the heat released by the treated exhaust gases is exploited for pre-heating the incoming gases to be treated in the pre-heating chamber 120, thereby alleviating the burden of the exhaust gases acceleration means.
Preferably, the heat exchange arrangement 135 is made of materials resistant to high temperatures, particularly sodium, lithium, titanium, etc), and it may be of the molded metal type, of the liquid metal type, of the plate type, of the spiral type; in case the apparatus 100 is intended to be installed on a vehicle, the heat exchanger shall have a compact design.
From the heat exchange arrangement 135, the treated exhaust gases, from which the harmful pollutants have been substantially eliminated, are led to the output manifold 1150, and then to the exhaust system 110 (for example, the muffler of the vehicle).
A control unit 140 is provided in the apparatus 100 for controlling the various components thereof (as schematized by the dash-and-dot lines in the drawing). In particular, the control unit 140 comprises electronic control means, preferably programmable, particularly microprocessor-based control means, adapted to execute suitable microprograms for implementing a predefined control flow, and sensors, such as pressure sensors and temperature sensors for detecting the operating temperature in the different parts of the apparatus 100, such as the pre-heating chamber 120, the radiant combustion reactor 125, the heat exchange arrangement 135.
The specific controls operated by the control unit 140 depend largely on the structure of the radiant combustion reactor 125, but in general the control unit 140 shall at least ensure that a correct temperature is maintained within the reactor 125.
The Applicant has found that the apparatus described in the foregoing, when used in any system wherein combustion of fuels is provided for, such as for example internal-combustion engines, using Diesel fuel, gasoline, methanol, mix of alcohols, natural gas, LPG, Kerosene, fuel oil, hydrocarbons mixed with water, GECAM, BLUDIESEL, fuel for planes with additives, masut for marine engines, allows eliminating approximately 90% of the carbon monoxide, carbon particulate, uncombusted hydrocarbon (CxHy) from the exhaust gases, and reducing nitrogen oxides (NOx) of up to 90%.
In the following of the present description, several different embodiments of the radiant combustion reactor 125 will be presented, being however intended that the list of presented alternatives is not to be intended as exhaustive, and several other embodiments can be devised. It is in fact pointed out that the specific spatial configuration and structure of the radiant combustion reactor 125 may depend on the specific application.
Lasers are more and more widely exploited in several applications, either in industry and in consumer products, thanks to the fact that the emitted optical radiation is highly coherent, substantially monochromatic, very homogenous, intense and concentrated, and that they have a very fast response.
In detail, the radiant combustion chamber 125 comprises a radiant combustion reactor enclosure 1000; the spatial configuration of the radiant combustion reactor enclosure is not limitative to the present invention, depending for example on the specific application: thus, in
Outside of and around the radiant combustion reactor enclosure 1000, an arrangement of optical radiation reflecting/deflecting elements 1010 is provided, such as mirrors and/or optical prisms, schematically depicted in the drawing as the internal faces of walls of a box-shaped casing 1007 containing the radiant combustion reactor 1000.
The arrangement of optical radiation reflecting/deflecting elements 1010 reflects/deflects optical radiations 1015 which are generated by one or more optical radiation sources, particularly lasers, schematically indicated in the drawing at 1020. It is observed that the number and the arrangement of the lasers 1020 is not limitative to the present invention, depending for example on the shape of the radiant combustion reactor enclosure 1000; in the drawing, just by way of example, four lasers 1020 are shown, each one located at a respective corner of the box 1007; the lasers 1020 may be fixed or movable, for example they can be partially rotated and/or angularly oriented.
The optical radiation emitted by the laser(s) 1020, controlled by the control unit 140, is reflected/deflected by the optical radiation reflecting/deflecting elements 1010, and hits the external side of the walls of the radiant combustion reactor 1000, causing a substantially uniform heating thereof. In this way, the walls of the radiant combustion reactor are brought to the radiative temperature, i.e. to a temperature such that a sufficient electromagnetic energy, in the prescribed range of wavelengths (approximately from infrared to ultraviolet) is radiated from the walls of the radiant combustion reactor into the enclosure 1000.
In the following, some possible practical embodiments of radiant combustion reactor 125 exploiting the optical-based heating mechanism, particularly the laser-based heating, will be presented, being intended that such embodiments are merely exemplary and not at all limitative.
In particular, in the embodiment schematically shown in
It is observed that in
A slightly different arrangement is schematically depicted in
The substantially spherical shape of the radiant combustion reactor 125 in the embodiment of
It is observed that by properly disaligning the inlet and the outlet of the gases into/from the radiant combustion reactor, a vortex can created inside the combustion chamber that, proximate to the chamber outlet, optimizes the gas recirculation, favoring the exit of the portion at a higher temperature. This is further helped by the Venturi accelerator 127 that may be placed at the exit of the chamber.
The use of one or more lasers for heating the radiant combustion reactor has the advantage of allowing a substantial reduction in the dimensions of the combustion reactor, because, when turned on, the laser(s) cause the reactor walls to almost instantly reach the desired operating temperature (necessary for inducing self-combustion of the exhaust gases and, in general, of the substances to be combusted), and, similarly, the laser(s) can be turned off almost instantaneously.
Additionally, using lasers as a heating means for the radiant combustion reactor involves a lower power consumption than using Joule-effect heaters such as electrical resistors, because only relatively high peak energies are required.
Compared to the known solution using combustion of gases as a heat source for heating the radiant combustion reactor, the use of lasers does not pose problems of environment pollution, and far less safety problems.
For all these and other reasons, the use of lasers thus allows reducing the operation costs of the radiant combustion reactor and of the apparatus including it.
Those skilled in the art will readily understand that the lasers used, and their optical power, may vary depending on contingent needs, according to the specific applications. The laser(s) may be operated in Continuous Wave (CW) mode or, preferably, in pulsed mode. also, the laser(s) may be of rotating type, or a laser(s) emitting multiple beams properly out of phase.
A suitable number of sensors may be associated with the walls of the radiant combustion reactor such as to enable the control unit 140 to cause the laser radiation hit the desired areas of the radiant combustion reactor walls, scanning the surface according to prescribed patterns in such a way as to cause the surface be homogeneously hit by the optical radiation.
In particular, a specific control software may be executed by the control unit 140, according to which the surface to be hit by the laser radiation is subdivided according to several different parameters, such as the temperature of the areas already hit by the optical radiation, the difference in temperature between these areas and those not yet hit (the cold areas), the target temperature. A dynamic temperature map can thus be built, and such a temperature map, in addition to being used by the control unit to control the laser(s) (and the positioning thereof), might also be displayed, on suitable display devices, to an operator, so as to enable constantly control the operation of the apparatus.
The control software may be based on variation calculations or on perturbation calculation, or on a simpler “fork shoot” (a term derived from the navy jargon and indicating a successive approximation process). The control software, in conjunction with the reflecting/deflecting arrangement, may allow to hit in a substantially random manner different areas of the walls of the radiant combustion reactor.
Moreover, the use of laser(s) allows a better controllability of the whole radiant combustion process. In fact, considering for the example the apparatus of
The further embodiments shown schematically in
In particular, in
A suitable drive arrangement is also provided, not shown in the drawings, for causing the rotor 1405 to rotate about its axis inside the radiant combustion reactor during the operation.
As in the embodiment of
The exhaust gases to be treated are conveyed into the combustion chamber through an inlet 1410i; within the chamber, the rotation of the rotor 1405 causes a dynamic partition of the internal space of the chamber into three dynamically-varying portions, and facilitates the flow of the gases towards an outlet 1410o or 1400o′; while flowing from the inlet to the outlet, the gases undergoes a post-combustion process due to the radiant energy that is irradiated by the walls of the radiant combustion reactor, heated by the laser radiation.
It is observed that the inlet 1410i and the outlet 1410o or 1400o′ to/from the radiant combustion reactor can either be axially aligned or not, and either the inlet or the outlet 1410o or 1400o′ or both may even be perpendicular to the chamber axis. Other configurations are clearly possible.
In the embodiment of
Finally, in the embodiment of
By properly controlling the motion of the rotors 1405, 1505, 1605 within the combustion chamber, the efficiency of the radiant combustion reactor heating by the laser radiation pulses may be optimized.
It is observed that the combustion process carried out in the radiant combustion chamber may be either continuous, partially continuous or discontinuous (intermittent). By continuous there is intended a process wherein there is no substantial separation between the incoming, relatively cold exhaust gases to be treated and the outgoing, hot and already treated exhaust gases: the cold phase is contiguous to the hot phase. A partially continuous post-combustion process is one in which there is a certain separation in time (for example, of the order of 106 seconds) between the cold and the hot phases, i.e. between the cold and the hot gases; this is for example the case where a combustion chamber such as those of the embodiments of
Although the present invention has been disclosed and described by way of some embodiments, it is apparent to those skilled in the art that several modifications to the described embodiments, as well as other embodiments of the present invention are possible without departing from the scope thereof as defined in the appended claims.
In particular, the radiant combustion reactor may be a mix of the solutions presented in the foregoing.
| Number | Date | Country | Kind |
|---|---|---|---|
| MI2003A002179 | Nov 2003 | IT | national |
This is a continuation-in-part application which claims priority from PCT/EP2003/51115, published in English, filed Dec. 30, 2003, which claims priority from Italian patent Application No. M12003A002179, filed Nov. 12, 2003, which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP03/51115 | Dec 2003 | US |
| Child | 11433640 | May 2006 | US |
