Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
  • F28F1/12—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element
  • F28F1/24—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending transversely
  • F28F1/26—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending transversely the means being integral with the element
  • F28F1/28—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending transversely the means being integral with the element the element being built-up from finned sections
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
  • F28F21/04—Constructions of heat-exchange apparatus characterised by the selection of particular materials of ceramic; of concrete; of natural stone

Definitions

• the invention relates to a ceramic recuperative high-temperature heat exchanger, in which all components that come into contact with the primary and / or secondary media are made of high-temperature resistant material which consists of a mixture of SiC and MoSi 2 .
• the ceramic material made from a mixture of SiC and MoSi 2 which is available on the market under the Siamant brand, is known from DE 44 35 866 AI, in which processes for the production of SiC / MoSi 2 are described. Processes are also described in DE 43 31 307 A1 with which composite materials based on SiC / MoSi 2 are produced, which are reinforced with carbon fibers.
• a disadvantage of this heat exchanger construction is the heat exchanger size limited by the size of the perforated plate.
• the perforated plate / tube component system also requires a very complex construction with exact guides and fits, which is very difficult, especially with regard to the maximum temperature conditions.
• Another disadvantage of this construction is the transport of the heat exchanger due to the mechanical loads. To eliminate this problem, special transport devices must be provided or developed.
• the technical problem underlying the invention is to design the generic ceramic recuperative high-temperature heat exchanger so that its design is suitably tailored to the materials used and suitable for the highest temperature level intended for operation, and its components in a simple manner can be produced with the required accuracy and dimensional accuracy.
• the mutually delimited flow channels and flow areas are formed by plates into which a matching grid of truncated cone-shaped depressions with an open base is formed, the plates being stacked one above the other in such a way that the tubular lower one End of the shell of the recesses of the upper plate rests on the conical shell of the recess of the plate arranged below such that flow channels are formed by the recesses which are essentially aligned with one another.
• Such a heat exchanger has the advantage that it can be produced from very simple components which are unproblematic in their structural design is, which are tailored in a very advantageous manner to the possibilities of the highest temperature-resistant materials used.
• the two subsystems for the heat-emitting primary and the heat-absorbing secondary media which are to be demarcated from one another according to the recuperative system, are formed by a single component. Because of its simple and robust shape, this construction principle allows the material's inherent high temperature resistance to be exploited in a favorable manner, so that temperatures of around 1650 degrees Celsius are permanently manageable for the primary medium when it enters the system.
• the temperature level that is possible with this heat exchanger system is also particularly important because the heat exchange is based not only on conduction and convection, but increasingly also on radiation transmission with increasing temperature.
• the proportion of radiation in heat transfer increases with the fourth power of the temperature.
• the disproportionate effectiveness of the heat fraction in heat transfer essentially begins at temperatures above the annealing temperature.
• the height of the flow area is less than the height by which the depressions protrude below the horizontal plate part.
• the tubular depressions penetrate the flow area in a columnar manner and are surrounded by an annular depression at their base point.
• the resulting cross-sectional profile of the flow area leads to an intense Whirling of the flowing medium and to an advantageous
• the flow areas formed in this way have inflow and outflow openings only on opposite sides, since they are simply closed on the intermediate sides.
• the media flow is led from the outflow opening through a deflection device into the inflow opening of the flow area in which the flow runs in the opposite direction. If at least two flow areas are combined for parallel flow, there is an additional swirling of the gas flows in the deflection spaces, the turbulence of the flow increasing the efficiency of the heat transfer.
• a particularly favorable form of the configuration of the deflection seal is the extension of the plate, which on the inflow side delimits the downstream flow region at the bottom in the direction of flow. It thus forms the deflection plate. Because of the matching grid of the frusto-conical depressions, the entire heat exchanger can be represented in this way with two plate formats, in the case of only one flow area in one flow direction, even with only one plate format, if the elongated side is alternately laid opposite one another.
• An embodiment in which at least two plates lying one on top of the other form a plate package and the packages are separated from one another by a space into which the flow channels open and from which they emerge has the particular advantage that the upper and lower boundaries of the space to the below and above flow areas represent an additional heat transfer surface. In this way it is possible to intensify and accelerate the heat exchange process. They do Advantageously influencing the heat transfer by flow turbulence, which has been mentioned several times, can also be achieved in that the outer jacket of the depressions has a shape which leads to a swirling of the flowing media.
• the formation of the inner surface of the flow channels is determined by the profile of the lower recess end. In the description of the exemplary embodiments shown in the drawing, it is shown in detail how this profile can look. In any case, it can be assumed that the inner channel wall does not have a smooth surface that would be comparable to the inside of a pipe. As a result, an influence in the sense of a turbulent flow can also be expected here.
• the MoSi 2 component makes the material used electrically conductive. This results in the favorable possibility of applying electric current to the plates, particularly in the areas which are in the outflow area of the primary or in the inflow area of the secondary gas stream, and therefore are not at the highest temperature level, and to be heated to such temperatures by resistance heating that, if appropriate slag that becomes tougher or even solidifies is melted again in a thin liquid so that it can drip downwards. In this way it is possible to use the heat exchanger even during continue to operate intermittent cleaning phases. This has advantages over overheating by burning additional fuels or temporarily reducing the secondary gas flow. That kind of
• An embodiment in which an inertia separator made of SiC / MoSi is connected upstream of the heat exchanger for the slag-containing primary gas stream offers particular advantages with high slag fractions in the gas stream.
• Inertia separators made of the highest temperature-resistant materials can be produced in a particularly favorable form as a ball pile, baffle plate or cyclone separator.
• the novel material allows channels to be formed in the jacket of the inertia separator, in which the secondary gas stream preheated in the heat exchanger can be directed further towards the primary gas stream, which leads to a further increase in the temperature level.
• a particularly favorable form of training is provided if the channels in the jacket of the inertial separator run in a spiral.
• the proposed heat exchanger can advantageously arrange a fine filter between the inertial separator and the heat exchanger, which in particular also advantageously produced on the basis of SiC / MoSi 2 and is therefore extremely temperature-resistant.
• the heat exchanger can not only be used as a mere heat exchanger, but also because of the very high temperature levels possible due to the use of the highest temperature-resistant materials and the construction principle according to the invention, in a particularly favorable form as a reformer.
• the secondary system uses gaseous hydrocarbons that are thermally split.
• the use of a Stirling engine offers a particularly favorable option for the energy network with the maximum temperature heat exchanger.
• the flue gas heats air on the secondary side.
• the temperature of the air leaving the heat exchanger varies between 1,200 and 1,400 degrees Celsius, depending on the firing material.
• the air is accelerated by a fan to a speed of about 10 to about 50 m / s before entering the heat exchanger.
• the speed of the air depends on the size of the heat exchanger, i.e. the mass flow. For thermal reasons, it goes directly into the calculation of the convective heat transfer.
• the appropriate air speed must be set for the respective heat exchanger in order to optimize the system.
• the air can be pre-cleaned and dried before entering the heat exchanger. To prevent the secondary air from mixing with the flue gas, the secondary side is operated with a slight overpressure.
• the heated air is passed on to a Stirling engine after leaving the maximum temperature heat exchanger.
• the Stirling engine is a heat and power machine, in which the drive energy is supplied from the outside via the heater heat exchanger.
• a second, lower temperature is also set externally via the cooler heat exchanger.
• Mechanical work is done from the difference between the high and low temperature levels, taking into account the thermodynamic efficiency. In contrast to the petrol or diesel engine, this system has no internal combustion and no charge change; rather, two constant temperatures are set from the outside.
• a corresponding generator is connected in the Stirling engine, which converts the mechanical work into electrical energy.
• the air leaving the Stirling engine has a temperature of 400 degrees to 700 degrees Celsius. This hot air can be used energetically in various ways, some of which are briefly outlined here.
• the 400 to 700 degree hot air is mixed with outside air and used as combustion air in the furnace. This measure significantly increases the efficiency of the furnace.
• the hot air can be introduced as secondary air into the combustion chamber, for example into the afterburning zone.
• significantly higher flue gas temperatures can be generated.
• the result of this measure is that the flue gases reach a significantly higher temperature after leaving the afterburning zone and the air on the secondary side of the heat exchanger also has a higher heat content.
• the connected heat engine also works at a higher energy level, which has a positive effect on its efficiency.
• the flammability can be increased by supplying hot air, which has a positive effect on the combustion processes and thus on the efficiency of the furnace. Another possible use is to dry the
• the combustion stage can be used for the thermal use of moist fuel, for example damp wood or sludge
• Drying stage upstream the hot air can be directed over the material to be dried.
• the moist air is dewatered in a condenser and cleaned depending on the material to be dried.
• the air can then be released into the atmosphere or directed into the furnace as combustion air.
• a condenser for example fluidized bed dryer etc., other process variations can also be implemented.
• pyrolysis of the fired material can also be very effective.
• the actual combustion can be preceded by pyrolysis.
• the fuel is heated in the absence of air by the hot air and divided into a solid, liquid and gaseous fraction. If metallic contaminants are contained in the firing material, pyrolysis can be followed by magnetic separation, through which metallic foreign substances are separated. The three fractions can then be fed to the furnace as solid, liquid and gaseous fuels.
• the hot air can also be used for another downstream drying process.
• the clean, hot air allows, for example, large quantities of wood to be dried when used in sawmills or foods such as fruit and pasta.
• the hot air is led directly into the drying room.
• the hot air can be mixed in with the appropriate dosage.
• the air leaving the drying room can vary depending on the degree the cooling either in the atmosphere or after admixing to the flue gas stream from the heat exchanger in a water heater.
• the separation of the flue gas and air flow has significant advantages for the operation of the Stirling engine.
• the difficulties in integrating a Stirling engine into a solid fuel heating system and the direct loading of the Stirling heat exchanger with flue gases require a flue gas that is as dust-free as possible, which was previously not possible.
• the residual dust in the flue gas pollutes the heat exchanger and shortens the service life due to chemical reactions of some components of the flue gas with the metallic components of the heat exchanger.
• the heat transfer characteristic of this caloric apparatus is impaired in such a way that the efficiency of the Stirling engine deteriorates considerably over long periods of operation, so that cleaning is necessary.
• the air is compressed before entering the heat exchanger, in the heat exchanger to a temperature of Heated 1200 degrees Celsius and then relaxed in an appropriately dimensioned gas turbine.
• the gas turbine drives a generator to generate the electrical energy.
• the relaxed hot air can be used for further energy in a downstream heat exchanger, for example in drying, fuel or hot water preparation.
• a steam power process can be added to larger systems.
• the inlet temperature cannot be increased arbitrarily due to the material-specific properties of the metals. Since the overall efficiency of the system depends on the level of the turbine inlet temperature, the efficiency inherent in the process, that is, Carnot's efficiency, can only be increased by increasing the inlet temperature. If an oxygen-free gas, for example noble gases or nitrogen, is used as the working gas instead of the air, alternative turbine materials can be used. In this case, the use of carbon fiber reinforced carbon (CFC) is conceivable. This material can be used up to temperatures of around 2000 ° C in non-oxidizing atmospheres. By using this material you are independent of the turbine inlet temperature, which can be increased to up to 1600 degrees Celsius when burning carbon-rich fuels. Correspondingly high temperatures can also be achieved by using appropriately preheated or oxygen-enriched air.
• CFC carbon fiber reinforced carbon
• the inert gas is compressed before entering the heat exchanger, heated in the heat exchanger and expanded in the CFC turbine.
• the hot gas leaving the turbine is cooled to room temperature to minimize compressor performance and then compressed again.
• the flue gas can be cooled by a downstream steam power process take place. In the case of smaller units, the cooling process can be carried out in several stages. The heat flows diverted during this process can continue to be used for energy. Other possible applications include preheating the combustion air or an inert gas flow or drying fuel or foreign materials.
• This hot gas charger which is normally used as a compressor, but can also be operated as a relaxation machine in the case described, must also be produced from ceramic materials at temperatures above 1000 degrees Celsius.
• the integration into the system corresponds to that of the turbine and has already been explained above.
• FIG. 1 shows an apparatus in a sectional side view, in which a heat exchanger and an inertial separator are arranged one above the other;
• Figure 2 is a plate from which the heat exchanger is built, in a sectional side view and in plan view.
• Fig. 3 in a stylized representation of a heat exchanger segment from four stacked plates;
• Fig. 4 is a plan view of a flow area according to the
• FIG. 5 shows an embodiment with plate packs and perforation spaces arranged between the packs in a schematic
• FIG. 6 is a very simplified system sketch for plant concepts with integrative integration of the maximum temperature heat exchanger.
• Fig. 1 an apparatus is shown in principle, in which the heat exchanger 1 is arranged above a cyclone 2 as an inertial separator and in which - with dashed lines - the contours for the possible installation point of a fine filter 3 are indicated.
• the entire apparatus is surrounded by a high-temperature-resistant, heat-insulating jacket in which the inlets and outlets of the primary media P, the secondary media S and the ash drain A are formed.
• the slag-laden primary gas stream is initially passed approximately in the middle of the left side into cyclone 2, in which the coarser liquid slag particles are separated off and discharged downward in liquid form.
• the pre-cleaned primary gas flow P is then conducted upwards and, if necessary after passing through a fine filter 3, is passed into the vertical flow channels of the heat exchanger 1.
• the secondary gas flow S is introduced into the apparatus on the upper right-hand side and is counter-sensed to the upward directed primary gas flow P by four flow areas connected in parallel in a cross flow.
• the secondary gas flows S are detected in deflection chambers 9 and introduced into the flow areas below in the opposite direction.
• the secondary gas stream S is alternatively discharged after passing through the heat exchanger 1 as a secondary gas stream S 'or, for further overheating, the inertia separator 2 is directed towards the inertial separator 2 via corresponding channels 12 in the jacket of the inertial separator designed here as a cyclone 3.
• the secondary gas flow S is discharged to the right at the lower end of the apparatus.
• a plate 6 is shown, in which a regular grid of frustoconical depressions 7 is formed.
• the plate 6 is shown in a sectional side view and in the lower part of the illustration in a top view. If these plates 6 are stacked one on top of the other in such a way that the tubular lower end of the jacket of the Veitiefept 7 in the upper plate rests on the conical jacket of the Veitiefept 7 of the plate arranged below it, a heat exchanger 1 results, as shown in FIG.
• the plates 6 form the flow areas 5 in a horizontal orientation and the flow channels 4 in a vertical orientation.
• the primary medium P for example flue gas
• the flow channels 4 are clearly visible in this illustration. Since the inner wall of the flow channels 4 is formed by the lower end of the depressions 7, their shape and structure depends on the design of the lower jacket end of the recesses 7. Three examples of such a termination are indicated in the left part of FIG. 3, the upper and lower ends having a termination parallel to the plate surface and the two underlying plates having an inwardly beveled foam which increasingly adapts to the jacket surface of the underlying plate 6 . In this adapted form, a higher density of the delimitation from flow channel 4 to flow area 5 is to be expected.
• FIG. 4 shows a plan view of the lower end of a flow area 5 corresponding to the viewing clearing IV indicated in FIG. 3.
• the secondary gas flow S is indicated by arrows, while the primary gas flow P flows through the openings of the vee depressions 7, as it were, towards the viewer. It can be clearly seen that the recessed jackets projecting into the flow area 5 in a columnar manner oppose the secondary gas flow S and lead to its swirling.
• FIG. 5 very schematically shows an exemplary embodiment in which plates 6 are combined to form plate packs 10 and these are arranged at a distance from one another such that spaces 11 result between the packets 10.
• the flow channels 4 open into these spaces 11, in order to again flow into the flow channels 4 of the package 10 above them on the other side. Except for these inflow and outflow openings, the rooms 11 are closed on all sides. In the rooms 11 there is a swirling of the partial flows P, which touch the lower and upper end of the room 11 with the respective outer plates. Large areas of additional heat transfer surfaces are thus provided with these surfaces, which leads to an intensification and acceleration of the heat transfer. It is indicated that the secondary gas flow S is countercurrently directed through three flow areas 5 and around the spaces 11 by deflection spaces 9. In Fig.
• the cleaned flue gas P can be felt for the applications described, of which a process water exchanger and an air / gas exchanger for drying are indicated.
• Two secondary gas flows S are indicated.
• secondary media S] are air or inert gases such as nitrogen, which, after appropriate heating, are fed to a Stirling engine, a CFC turbine or a hot gas charger, for example.
• the second secondary gas stream S 2 indicates the heating up of hydrocarbons and their splitting at a correspondingly high temperature level.
• the fission products can be fed to a fuel cell, where they can generate electricity and be used for further useful heat.
• the secondary gas stream 1 is indicated by a solid line and the secondary gas stream 2 by dashed lines.
• the use of the modified heat exchanger 1 as a reformer makes it possible to produce synthesis gases from biomass, oil or gas at the prevailing high temperatures. It serves as a kind of cracking furnace in which the hydrocarbons are cracked.
• the synthesis gas is further processed using conventional methods that have been tried and tested in technology.
• the advantage over the prior art is that you do not have to work with catalysts, as was the case with the previously achievable temperature level of about 900 degrees Celsius. Rather, a temperature level of up to 1300 degrees Celsius is achieved here and thus better efficiency levels without the use of complex and sensitive catalyst systems.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Geometry (AREA)
• Ceramic Engineering (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Ceramic Products (AREA)

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• 1997
  • 1997-06-03 DE DE19723159A patent/DE19723159C2/de not_active Expired - Fee Related
• 1998
  • 1998-05-22 WO PCT/DE1998/001451 patent/WO1998055814A1/fr active IP Right Grant
  • 1998-05-22 DE DE59800939T patent/DE59800939D1/de not_active Expired - Lifetime
  • 1998-05-22 EP EP98934812A patent/EP0986727B1/fr not_active Expired - Lifetime
  • 1998-05-22 AT AT98934812T patent/ATE202629T1/de not_active IP Right Cessation

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