ITTO20120662A1 - SYSTEM FOR THE PRODUCTION OF ELECTRIC ENERGY BASED ON ACTIVE ELEMENTS SUCH AS SOLID OXIDE CELLS. - Google Patents

Description

System for the production of electricity based on active elements such as solid oxide cells

The present invention relates to the production of electrochemical systems for energy based on active elements such as solid oxide cells (SOFC). In particular, the invention relates to an innovative solution for the distribution of reagents and the discharge of reaction products inside a stack of fuel cells.

Solid oxide fuel cells generate a continuous flow of electrical energy following the oxidation-reduction reactions of a fuel, fed to an anode electrode, and an oxidizer fed to a cathode electrode (usually air). The ceramic electrolyte, usually zirconia doped with yttria or other ceramic oxide, transports oxygen ions from the cathode to the anode electrode as a function of the operating temperature. This type of technology is currently considered promising in many application sectors (for example in the field of distributed electricity generation, home micro-cogeneration, portable power generation devices, auxiliary units) due to the high efficiencies of converting fuel into electricity and possibility of integration with other devices for the generation of further electricity by exploiting the hot fumes (300-500 ° C) that come out. The operating temperature of solid oxide cells is usually in the range of 500-800 ° C depending on the geometry and cell materials used. The high temperature allows to reduce the main cell overvoltages that are dependent on thermally activated physical phenomena. In addition, the high operating temperature allows integration with reformers and flexibility for multi-fuel supply. Finally, it allows various configurations of energy systems based on solid oxide fuel cells such as systems for the cogeneration of thermal energy and heat, trigeneration systems for the further production of cooling energy, hybrid systems for the production of electricity with a plant thermoelectric in cascade.

A typical configuration of a single fuel cell provides for the presence of a solid and dense electrolyte that guarantees the transport of oxygen ions; based on the state of the art, zirconia stabilized with yttrium oxide (YSZ) is the most widely used thanks to its chemical-physical stability in reducing / oxidizing atmospheres and the excellent conduction of oxygen ions for temperatures above 650 -700 ° C; a cathode material that allows the reduction of an oxidant, which is chemically and physically stable with other functional layers and feed gas atmospheres, such as a strontium-doped lanthanum manganite (LSM); a material for the anode which allows the oxidation of a fuel which may contain hydrogen, carbon monoxide and gaseous hydrocarbons, is chemically and physically stable with the other functional layers and atmospheres of feed gas, such as for example a compound of nickel (Ni) and YSZ; an interconnection material between cells, typically consisting of a ferritic steel with excellent conduction properties in the oxide state, in contact with the surfaces of the electrodes, which guarantees a good electrical connection between adjacent cells and which favors the achievement of the anode and the cathode by the reagent fluids.

The problem faced by the present invention was how to optimize both the fuel supply and the exhaust of exhausted products to and from a generation unit in which there are a plurality of cells organized according to a predefined scheme. Furthermore, the applicant has raised the problem of how to organize a generation unit in which a plurality of cells are present. In particular, a stack or pile solution with a multi-level and multi-cell structure is proposed that allows better flexibility in setting the electrical parameters required by the various applications for which the system can be intended, thanks to the multiple configurations that can be realized on each floor.

An aspect of the present invention relates to a system for the production of electrical energy based on active elements such as solid oxide cells having the characteristics of the attached claim 1.

Other features and advantages of the invention will be described below with reference to an embodiment of the invention illustrated in the attached figures which illustrate in particular:

Figure 1 is a cross section of the integrated system according to the present invention;

• the figures. 2A and 2B respectively an enlargement of the upper and lower heads of the integrated system, with FIG. 2A which illustrates the flows of power and exhausted cathodes and FIG. 2B which illustrates the flows of power supply and anodic exhaust,

• Figure 3 the packing order of the components of a multi-cell stack plan.

• figure 4 a partial section of the plates that make up the stack in which the supply channels, the communication holes and the distribution and discharge channels are highlighted,

• figures 5A and 5B the circulation of the cathode flow respectively on the supply plate and on the distribution and discharge plate,

• figures 6A and 6B the circulation of the anode flow respectively on the supply plate and on the distribution and discharge plate,

• figure 7 details of one of the plates making up the pre-reforming unit. • figure 8 details of one of the plates making up the afterburner unit.

Figures 9A, 9B and 9C show the circulation of the anodic flow respectively on the separator plate, on the supply plate and on the distribution and discharge plate in the alternative representation of the multi-cell plane according to an alternative embodiment of the present invention.

With reference to the aforementioned figures, the system for producing electricity according to the present invention comprises an upper head 2 and a lower head 3, between which a generation unit 4 is placed.

These upper and lower heads comprise a plurality of supply ducts and chambers suitable for distributing a cathode flux and an anode flux.

For the purposes of the present invention, "anode flux" or "anode feed" means any fuel containing methane (for example, natural gas or biogas from anaerobic digestion) or other carbon-hydrogen-oxygen based fuel (for example, propane , LPG, methanol, ethanol, etc.) that can be converted into a synthesis gas mixed with water; by “cathode flow” or “cathodic supply” we mean an oxidizer, for example air.

Between the upper head and the generation unit there is a first heat exchange unit 5 (or pre-reforming) and between the lower head and the generation unit there is a second heat exchange unit 6 (or afterburner). A central duct 7 substantially crosses the entire structure and connects the two heads and allows the cathode and anode fluxes to pass from the upper head to the lower one and vice versa. This conduit in fact includes a first cathode channel 71 for the cathode flow and an anode channel 72 for the anode flow placed inside the cathode one. Both the first heat exchange unit (pre-reformer) and the second (post-burner) are conceived as the continuation, respectively upwards and downwards, of the generation unit. The first unit includes a heat exchanger that receives the cathode discharge coming out of an exhaust duct of the generation unit and the fresh anodic flow coming from the upper head. The second unit includes a combustor that also performs the task of exchanger: in fact, it receives the anodic discharge, coming from the relative discharge duct of the generation unit, which burns with a stoichiometric percentage of the cathode flux, which instead comes from the central duct. , thus heating the remaining flow.

The upper head comprises a chamber for distributing the anodic feed flow 21 and sending to the pre-reformer unit, a chamber for the inlet of the cathode flow 22 with additional function of fresh flow / cathode discharge exchanger and an ejection chamber 23 cathode discharge. The lower head, on the other hand, includes a cathode flow distribution chamber 31 and delivery to the afterburner, a collection chamber 32 and ejection of the anode exhaust and the inlet 33 of the duct which introduces the fresh anode flow mixture into the system integrated.

The circulation of the cathode flux (indicated in figure 1) occurs in the following way. The cathodic power supply enters from the entrance in communication with the exchanger located in the upper head. The cathode flow expands inside the chamber 22 where it is preheated by the ducts 24 in which the cathode discharges directed towards the expulsion chamber 23 flow, corresponding to the outer annular area of the upper floor. Once the entire exchange chamber is occupied, the cathode flow begins to flow towards the passage volume (internal area of the upper floor) through communication holes 25. From here it is immediately made to flow inside the central tie-rod 7 through as many holes 26 made on its side wall.

Entered inside the central duct 7, the cathode flux runs through it entirely until it reaches the opposite end, located in the lower head, being in the meantime heated by the surrounding generation unit 4 and at the same time heating the anode flow passing through the internal duct 72 of smaller diameter. A foil turbulator can, if necessary, be fixed on the anode flux duct to improve heat exchange. At the end of the descent, the cathodic power supply exits through other holes 341 which introduce it into an annular section chamber 34 delimited at the top by a sealing ring and, passing through further slots 35, reaches the distribution chamber 31, where it will be directed towards the post-combustion unit. The entry into the post-combustion plates takes place through small holes 36, as regards the percentage that must burn with the anodic discharge, and large holes 37 for the remaining flow that must be heated. Crossing the section where the heat exchange takes place, the cathode flux goes towards a narrow annular slot, interposed between the central area of the plates and the central tie-rod, which will feed all the floors of the stack above. The cathode discharges produced by the reactions occurring on the cells are collected by elongated ducts 41 positioned on the outer perimeter of the plates of the stack. The drains go towards the pre-reforming unit and run radially until they reach the ducts that will transport them to the ejection chamber. These ducts pass through the anodic supply flow distribution chamber and the chamber used as an exchanger, interacting thermally with them. Once in the ejection chamber 23, the cathode discharges are removed from the integrated system through the outlet conduit.

The path followed by the anode flux is the following. The anodic feed flow (see corresponding arrows in figure 1) enters the system perpendicular to the lower head by means of a thin duct 33. The flow then passes through a vaporization chamber 39 which allows the complete atomization of the quantity of water present. inside, thanks to the heat released by the collection chamber and expulsion of the surrounding combustion anodic fumes. The dose of water that is added is such as to avoid mixtures that can cause "carbon deposition" phenomena during the reactions that take place in the generation unit. Subsequently, the small duct is inserted inside the central duct 7 and runs along its entire length reaching the top of the upper head. Within this section, thermal exchange phenomena occur due to the simultaneous passage, in a counter-current direction, of the cathode flux. At this point, the anode flow, also slightly heated by the passage of the pre-reforming unit, exits the system and passes through an external mixer 8 which guarantees an additional supply of water to the anode flow in case of shortage during operation. of the device. The mixer 8 can also be used to introduce water with the aim of producing inertizing steam in the event of breakage or overheating. The anodic power supply re-enters the system through inlet 29 and goes directly to the fuel distribution chamber 21. From here the anodic feed flow moves to the underlying pre-reforming unit through passages 28 obtained on the lower base. The anodic flux radially crosses the pre-reforming unit heading towards the supply ducts 42 of the generation unit 4. During the passage, a heat exchange occurs with the cathode fluxes which flow in the opposite direction, from the periphery to the center, directed to the upper head. The anodic discharges produced inside the generation 4 unit flow into the exhaust ducts from which they will later be transported to the afterburner unit. The fumes produced by the combustion of the anodic discharges, with the incoming cathode feeding molar fraction, pass through the cathode flow distribution chamber 31 passing through the conduit that will take them to the exhaust collection chamber 32 from which they will be expelled through an outlet conduit.

The generation unit 4 according to the present invention comprises a plurality of solid oxide fuel cells which generate a continuous flow of electrical energy following the oxidation-reduction reactions of a fuel, fed to an anode electrode, and an oxidant fed to a cathode electrode. These cells are organized on superimposed planes P and on each plane P there are preferably provided a plurality of cells, for example six positioned according to a distribution of circular shape and a parallel connection is established between them. The cells are closed on the sides by two groups of metal plates, which regulate the circulation of the different reagent flows and allow an electrical connection in series to be established between the different levels. At the ends of the unit as a whole composed of a plurality of superimposed planes, two collectors are positioned respectively for the anode current 43 and the cathode current 44.

Finally, the entire stack of shelves is electrically isolated from the rest of the system by placing an insulating plate 45 above each collector. Preferably, the shelves are oriented so that the cathode of each cell faces downwards.

The number of cells in each plane can be chosen at will, but advantageously by using an even number of cells, whatever it may be, a symmetrical geometry is obtained, which makes the distribution of flows advantageous.

Considering the cathode side first and scrolling from bottom to top, it is possible to notice an AC power supply plate, a DC discharges distribution and collection plate and a plate for the DC containment of metal grids R with the purpose of allowing a better expansion and homogeneity of the flow directed to the different cells C. With the aid of FIG. 4 it is possible to see the section of an assembled plan. The feeding plate has a set of ACC channels whose depth is equal to the total thickness of the plate. As can be seen in FIG. 5A, the network of channels is also formed by secondary transverse ribs ACN, with a depth equal to half that of the plate, which connect the main channels to each other.

The section of the channels is kept constant throughout their extension and as a whole they are organized in such a way as to exactly reproduce the shape of the cells.

In particular, these channels are arranged longitudinally to each other, of which the outermost ones are slightly arched, so that the lattice takes on a particular shape that copies the shape of the cell above. In this network of channels the incoming fresh flow is distributed evenly before heading towards the DC distribution plate shown in FIG. 5B. The passage takes place through a series of DCF holes, present in variable numbers, obtained in the distribution and drain collection plate and placed exactly at the intersections of the grid of the underlying supply plate and possibly on the apex of the main ACC branches. A slight pressure gradient is created between the two ends of the holes which gives a slight acceleration to the flow that passes through them, thus ensuring that the jet coming out of them reaches the cell.

The same geometry with longitudinal channels is proposed in the DC distribution plate: these are DCC grooves half the thickness of the plate, interposed to the supply holes and used for the collection and disposal of the produced drains. Between the cells and the DC distribution plate there are metal meshes R, each positioned exactly below a cell of the surface and having its own surface area, housed within the housings present in the containment plate CC.

The texture of the network R has been chosen with a texture and passage section such as to greatly enlarge the diameter of the jet coming out of each hole, so that the overall distribution of the flow over the entire surface of the corresponding electrode is as homogeneous as possible. . Furthermore, the network acts both as an excellent heat exchanger, allowing the flow to reach suitable working temperatures before coming into contact with the cell, and as a good electrical conductor, generating low contact resistances both at the cell cathode and on the cell. distribution and waste collection plate.

The group of plates belonging to the anodic side is completely analogous to the cathodic one but inverted in order. The analogy also persists in the assembly of the plates and in the distribution of the channels on the feeding plates AA and distribution and discharge plates DA, as shown in FIGS. 6A and 6B. The anodic feeding plate, AA and consequently the channels AAC obtained in it, have been made with a lower thickness than the cathode side due to the lower flow rate of the anode flux.

Between the anodic and cathodic compartments there are three plates, two for containing DC networks and an insulating plate PI. The mesh containment plates have the function of containing the meshes, while the insulating plate, made of dielectric material, has the function of containing the cells and guarantees electrical insulation between adjacent cells and prevents the passage of gases from one electrode to another. in this way avoiding mixtures that could cause malfunctions to the entire device.

Finally, the cathode side of each plane is separated from the anodic side of the next plane by a very thin metal separator plate PS, which forms the bottom of the two adjacent power plates. A possible alternative configuration foresees the replacement of the two anode and cathode feeding plates and of the separator plate with a single bipolar plate.

FIGS. 5A and 5B show in detail the arrangement of the upper surfaces of the two plates which form the pairs relative to the cathode sides of the cells of each plane. FIG. 5A refers in particular to the cathode flux AC supply plate, while FIG. 5B shows the DC distribution plate of the fresh flow and collection of the waste product. The cathode flow comes from a narrow annular gap present between the central tie-rod 7 and the plate itself and spreads into the network of ACC power channels through a connection area also obtained in the plate and having the same depth as them. Subsequently, the flow, through the system of DCF holes, passes into the upper DC distribution plate from which it reaches the cathode and is involved in the reactions that allow the production of electric current. The products obtained from the reactions that have taken place are deposited in the DCC collection and discharge channels, while the fresh flow rises from the distribution channels and goes towards the cell, replacing the previous one in a sort of convective motion. The cathode discharge is transported by the appropriate channels to the ASC openings located on the opposite side of the inlet, on the outer edge of the plate, which represent the discharge ducts.

As regards the anode side, the dynamics of the events is the same as described for the cathode side with the only difference being the different location of the inputs and outputs of the anode flux. FIGS. 6A and 6B show that the flow reaches the supply plate through ducts of a circular shape AAF placed on the outer edge of the plate and interspersed with as many ducts ASA used for collecting the anodic discharges. Each conduit provides the amount of anode power required for the operation of two cells. The anodic flux is introduced into a large initial channel whose depth, equal to the thickness of the plate, is preferably the same as the channels and which is subsequently divided into two parts by a tab LA which separates the fluxes destined for the two adjacent cells. Similarly, in the DA distribution and waste collection plate each duct collects the discharges of two cells. Finally, also in this case, the ducts used for collecting the discharges are located in the opposite position with respect to the supply ones.

In this way, the feeding phase of the cells belonging to each floor of unit 4, anode and cathode side, is obtained through a system of channels that makes the distribution of flows on the surface of the cell homogeneous. The circulation of the gases obtained during the feeding phase, anode and cathode side, allows to have a substantially uniform temperature profile on the surface of each cell.

The phase of collection and discharge of the products generated by the reactions occurred on the cells of each plane, anodic and cathodic side, takes place separately from the feeding phase.

In an alternative representation of the multi-cell plane, the cells lying on the same plane work in series. In particular, each cell is fed by an anodic mixture composed in part of fresh fuel coming from the stack and for the remainder by a percentage of the anode exhaust produced by the preceding cell. Therefore, when the stack is operational, a recirculation is formed on each floor belonging to it in which part of the power supply of each cell is supplied by the cell that comes immediately before. The percentages with which the flows involved participate in the feed mixture depend on the working parameters, i.e. Fuel Utilization and steam-to-carbon ratio, with which it is decided to operate each single cell and are determined by the dimensions of the various ducts. Power supply. For this representation it has been chosen to keep the parameters in question constant for all the cells lying on the same plane. FIGS. 9A, 9B and 9C show the plates that make up the anodic side of this alternative representation, while as far as the cathode side is concerned, no modification is foreseen with respect to the plates shown in FIGS. 6A and 6B. In particular, FIG. 9A presents the metallic separator plate PS which separates the anodic and cathodic feeding plates of two consecutive planes.

The fresh anode flux arrives through the right duct CD of each pair present on the outer edge of the plate. It runs through a short CS channel dug into the metal plate and then enters the passage that will lead it to the underlying feed plate, visible in FIG. 9B. At this point, the fresh feed fuel flows through a convergent / divergent CDC channel with a depth equal to half that of the host plate. At the ends of this channel a pressure difference is created which accelerates the incoming flow in the direction of the network of channels located at the front. During the transit inside this channel, the fresh fuel comes into contact, mixing, with a part of the anode discharges produced by the cell that occupies the previous position. The discharges, also containing the percentage of fuel that did not participate in the reactions that took place in the previous cell due to the Fuel Utilization set, come from the distribution and collection plate of the discharges shown in FIG. 9C. Once collected by the appropriate channels, they move towards the duct in the shape of a truncated circular crown ASA and then spread into the corresponding channel present in the supply plate and dug to a depth equal to its half. From here they flow into the convergent / divergent channel, where they will mix with the fresh fuel flow and head towards the adjacent distribution area, through two lateral CLS ducts dug at half depth. Thanks to the pressure difference generated by the convergent / divergent channel, the anodic discharges are attracted towards the exact direction and there is no risk of any suction, even of the same fresh fuel, which could in some way create operating problems in the stack or pile. . The dimensions of the two side ducts are determined on the basis of the discharge flow rate of the previous cell to be reused. It is important that the mixing takes place before diffusion within the network of channels to avoid the creation of spatial inhomogeneity in the composition of the feed due to the different nature of the two participating flows. Finally, it is necessary to avoid that with the passage of time an excessive accumulation of water may be generated inside the plate due to the recirculation that has been established. For this reason, a part of the anodic discharges produced by each cell, containing a significant percentage of water, are expelled from the pile through small CEPS ducts located next to the truncated circular crowns and communicated with them through short ducts with equal depth. to that of the plate. This type of configuration allows to have, for each level of the pile, overall values of Fuel Utilization and of the steam-to-carbon ratio lower than those associated with each single cell. In this alternative representation, each plane can host any number of cells since each of them is fed independently of the others, thus eliminating any constraint on the geometry of the plates.

A first heat exchange unit 5 (or pre-reforming) is positioned on the top of the generation unit 4 preferably formed by several floors, used for the pre-reforming process of the anodic feed stream. This process consists in the decomposition of heavy hydrocarbons, present in the fuel used for the system. In general, at the exit of the pre-reformer there will be a mixture rich in methane and steam and to a lesser extent hydrogen, carbon monoxide and carbon dioxide. The quantity of water is such as to avoid carbon deposits in the ducts for feeding the fuel mixture to the cells and in the cells themselves.

Referring to FIG. 7, the pre-reforming unit is made up of a stack of identical PR plates, the dimensions of which are the same as the distribution feed plates and those that contain the cells of each floor and therefore constitutes an extension thereof. along the vertical direction. The number of plates that will make up this unit will strongly depend on the type of fuel introduced into the system and the difficulty of bringing it back to a mixture that can be fed directly to the cells. The modulation of this unit in terms of the fuel introduced can also be obtained by acting on the type of catalyst deposited in the areas where the pre-reforming reactions take place.

Since the pre-reforming process is very endothermic, the heat necessary for its activation is taken from the cathode discharge arriving from the generation unit 4. For this reason, each plate of the pre-reforming unit is made in such a way as to have counter-current heat exchangers S, each of which is composed of two channels SC for the passage of the cathode discharge interspersed with an oval-shaped section SO, where the pre-reforming reactions take place. Each element was obtained by engraving the plate to which it belongs to a depth preferably equal to half of its overall thickness. The feed flow comes from small holes located in the internal part of the plate and flows towards the AAF anodic feed holes which are located in front of the first ones and which will subsequently distribute it to the different multi-cell floors below. The path develops through an RC catalytic network positioned within each section with the aim of favoring the pre-reforming reactions. At the same time, the cathode discharge coming from the unit enters through the ASC collection duct and flows towards the center of the plate in the opposite direction to that of the anode flow. Once the journey has been completed, the discharge will enter the duct that will lead it to the cathode discharge collection plate, located inside the upper head, to then be permanently expelled from the integrated system. To maximize the heat exchange between the two flows present, the channels where the cathode discharge flows have been scattered with small cylinders with the aim of increasing the contact surface.

On the lower end of the generation unit 4 there is a second heat exchange unit 6 (post-combustor) dedicated to the combustion of the anodic exhaust with a small molar fraction taken from the fresh cathode flow coming from the central tie-rod 7.

Unit 6 includes a series of PC plates whose design is shown in FIG. 8. As in the case of the pre-reformer, the size of the plates is the same as that of the plates that make up the generation unit, and in fact it represents its downward extension. The reaction mainly produces carbon dioxide and water, while its highly exothermic nature favors the generation of a very high amount of heat which is used to heat the air flow destined for subsequent entry into the generation unit 4.

To make the most of the heat produced by the reaction, combustion sections are alternated on the plate with channels for the passage of the flow that must be heated, all made always with a depth preferably equal to half the thickness of the plate. The anodic exhaust enters the combustion section through the ASA exhaust duct of the generation unit 4 and propagates through an RC catalytic network inserted to promote the combustion reaction. The cathode flow coming from the central duct 7 is split into two flows whose flow rates are determined by the different diameters of the holes. In the small holes FP enters the molar fraction necessary to activate the combustion process, while in the larger ones FG flows the flow that will be heated. The combustion products flow into the FE duct which will lead them to the exhaust expulsion plate located in the lower head. The flow to be heated moves along a radial direction with respect to the center of symmetry moving from the inlets located on the outer edge of the plate to its inner end, where it will enter the thin annular section that leads to the different planes of the generation 4 unit Advantageously, as for the unit 5, or pre-reformer, the transit channels of the cathode feed are sprinkled with small cylinders to increase the thermal interaction with the adjacent combustion sections.

The paths of the reacting fluids have been organized in such a way as to maximize the heat exchanges between the high temperature waste streams that must be expelled from the system and the fresh low temperature streams that instead go to the generation 4 unit where they have place the expected reactions. The anodic and cathodic discharges produced follow two separate paths for a more profitable exploitation of their calorific value.

The plates that make up the central units of the system described so far are not subjected to any type of welding. Referring to FIG. 1, the perfect adherence and compactness of the parts is ensured through the pressure exerted on the device by the upper and lower heads, which are connected through the central duct which also acts as a central tie-rod. The tightening is completed on the lower head with the application of contrast plates P1 and P2 on which MT disc springs are pressed, all closed with a screw with nut D. An additional seal is inserted inside the contrast plates T, made with rubber resistant to high temperatures, which prevents the cathode flux from escaping from the lower head.

The upper head is composed of three cylindrical chambers 21, 22 and 23, of which the upper one, to which the tie rod is welded, has smaller dimensions than the plates of the central block, while the remaining ones have larger dimensions. FIG. 2A shows the order in which the three blocks are assembled. The lower chamber 21 is used for the distribution of the anodic flux towards the prereforming unit located below it. The incoming flow must make a first spiral section that slows down its expansion within the available volume, thus allowing the heat exchange with the cathode discharge ducts that cross the chamber directed towards the expulsion chamber. As an alternative to the spiral inlet, a circular grid with small holes can be inserted in the external area of the chamber, thus creating a preliminary area where the anodic flux is distributed evenly before expanding towards the central area where there are passages, also of reduced dimensions, which communicate with the pre-reforming section. The upper chamber 22, on the other hand, contains only the ducts coming from the generation unit 4, which are made by overlapping cylindrical and elliptical plates. Also in this case it is possible to introduce a circular grid in the external area of the chamber so as to make the cathode flux uniform before it enters the heat exchange area. Finally, the last chamber 23 includes two areas separated by a circular wall: the outer ring-shaped area collects the cathode discharges from unit 4 and expels them from the system; the innermost area acts as a passage for the cathode flux, before its introduction into the central tie-rod, thus also allowing a final heat exchange between the different moving flows.

The lower head comprises two cylindrical chambers 31 and 32 having larger dimensions than the plates of unit 4. Referring to FIG. 2B, the distribution chamber 31 receives the cathode flow coming from the central tie-rod tube and routes it to the post-combustion unit. Before reaching the actual sorting site, the cathode flow passes through a first volume of annular section 34 made to avoid the possible generation of friction between the distribution chamber and the pipe due to possible thermal expansion by the components of the head. inferior. This initial volume is separated from the remaining volume thanks to a ribbed wall equipped with flow passages 35 placed in perfect correspondence with those present on the tie rod 341 Furthermore, thanks to the presence of the ribs 342 in the radial direction, the wall provides rigidity to the structure of the distribution chamber which is subjected to the load exerted by the nut screwed onto the terminal part of the tie tube by means of the cup springs. A sealing ring is placed above the annular section which guarantees the separation between the fresh flow entering the chamber and the hottest one coming out of the post-combustion unit which will feed the cathode section of unit 4. The lower chamber 32 has an empty volume, except for the ribbed wall with functions similar to those of the upper floor, completely dedicated to the collection of anodic fumes from the post-combustion unit and their expulsion neither.

The central duct 7, which can be seen in FIG.1, has a double function. First of all it assumes the role of internal tie rod, acting as a connection between the two heads. This task is also completed thanks to the internal walls of the two heads which, in addition to having a containment role, give rigidity to the entire system. The position of the tube also allows the cathode flow that flows inside it to have thermal exchanges both with the generation unit 4 and with the anode flow passing through the smaller 72 duct contained within it. Any non-linear sections, which can be made with curvatures 721 of the tube itself, increase the residence time of the anode flux in the central section with a consequent increase in the thermal interaction time. In an alternative embodiment of the device it is also possible to think of modifying the surface of the external or internal wall of the duct by introducing foil turbulators or finned components, with the aim of maximizing the exchange surface.

Claims (9)

CLAIMS 1. System for the production of electrical energy based on active elements such as solid oxide cells in which following the oxidation-reduction reactions of a fuel, fed to an anode electrode of such cells and an oxidant fed to a cathode electrode of such cells, a continuous flow of electrical energy is generated at the ends of these electrodes, characterized by the fact that these cells are organized in a generation unit (4) comprising at least one plane (P) in which a plurality of cells (C) positioned according to a distribution of circular shape are organized and an electrical connection is established between them . 2 System according to claim 1, wherein said connection is a parallel connection. 3 System according to claim 1, wherein at the ends of the unit as a whole composed of a plurality of superimposed planes electrically connected in series to each other, two collectors are positioned respectively for the anode (43) and cathode current ( 44). 4. System according to claim 1, in which the entire stack of shelves is electrically isolated from the rest of the system by placing an insulating plate above each manifold (45). 5. System according to claim 1, in which the planes are oriented in such a way that the cathode of the cells of each plane is facing downwards while the anode is facing upwards. System according to claim 1, wherein each plane comprises: • a cathode compartment comprising a cathodic supply plate (AC), an exhausted cathodic distribution and collection plate (DC), • an anodic compartment comprising an anodic feeding plate (AA), an anodic exhaust distribution and collection plate (DA), • between the anodic and cathodic compartments being inserted two nets containment plates (CC) which have the function of containing the nets (R) and an insulating plate (PI), made of dielectric material, which has the function of containing the cells ( C), ensure the isolation between adjacent cells and prevent the passage of gases from one electrode to the other. System according to claim 1, wherein the cathode side of each plane being separated from the anode side of the next plane by a metal separator plate (PS) which forms the bottom of two adjacent feed plates. 8. System according to claim 7, wherein the two adjacent anode and cathode feed plates and the separator plate are formed by means of a single bipolar plate. System according to claim 1, wherein each plane comprises an even number of cells realizing a symmetrical geometry.