CA2075889A1 - Regenerator - Google Patents
RegeneratorInfo
- Publication number
- CA2075889A1 CA2075889A1 CA002075889A CA2075889A CA2075889A1 CA 2075889 A1 CA2075889 A1 CA 2075889A1 CA 002075889 A CA002075889 A CA 002075889A CA 2075889 A CA2075889 A CA 2075889A CA 2075889 A1 CA2075889 A1 CA 2075889A1
- Authority
- CA
- Canada
- Prior art keywords
- regenerator
- layer
- temperature
- hot
- accumulator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
- F28D20/02—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using latent heat
- F28D20/023—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using latent heat the latent heat storage material being enclosed in granular particles or dispersed in a porous, fibrous or cellular structure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S20/00—Solar heat collectors specially adapted for particular uses or environments
- F24S20/20—Solar heat collectors for receiving concentrated solar energy, e.g. receivers for solar power plants
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D17/00—Regenerative heat-exchange apparatus in which a stationary intermediate heat-transfer medium or body is contacted successively by each heat-exchange medium, e.g. using granular particles
- F28D17/02—Regenerative heat-exchange apparatus in which a stationary intermediate heat-transfer medium or body is contacted successively by each heat-exchange medium, e.g. using granular particles using rigid bodies, e.g. of porous material
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/40—Solar thermal energy, e.g. solar towers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/14—Thermal energy storage
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E70/00—Other energy conversion or management systems reducing GHG emissions
- Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Combustion & Propulsion (AREA)
- Building Environments (AREA)
- Laminated Bodies (AREA)
- Compositions Of Oxide Ceramics (AREA)
Abstract
ABSTRACT
A regenerator, for example, in a hot-blast stove or a heat accumulator in a solar system, with an accumulator core (1) that is built up from ceramic or metal or natural material and which is used to accumulate "sensible" heat. The accumulator core (1) is acted upon by a hot charging flow on one, "hot" side so as to become charged, until such time as on the other, "cold" side, a maximally permissible charging flow outlet temperature is reached. In order to be discharged, the accumulator core (1) is acted upon from the other, "cold" side by a cold discharge flow until such time as a minimally permissible discharge outlet temperature is reached on the "hot" side. In order to increase the heat absorption capacity for (sensible) heat without increasing the volume, on the hot side and/or the cold side of the accumulator core (1) there is a layer (3, 4) that serves as a temperature buffer and which delays achievement of the maximally permissible outlet temperature super-proportionally, or else increases the heat absorption capacity super-proportionally.
(Figure 1)
A regenerator, for example, in a hot-blast stove or a heat accumulator in a solar system, with an accumulator core (1) that is built up from ceramic or metal or natural material and which is used to accumulate "sensible" heat. The accumulator core (1) is acted upon by a hot charging flow on one, "hot" side so as to become charged, until such time as on the other, "cold" side, a maximally permissible charging flow outlet temperature is reached. In order to be discharged, the accumulator core (1) is acted upon from the other, "cold" side by a cold discharge flow until such time as a minimally permissible discharge outlet temperature is reached on the "hot" side. In order to increase the heat absorption capacity for (sensible) heat without increasing the volume, on the hot side and/or the cold side of the accumulator core (1) there is a layer (3, 4) that serves as a temperature buffer and which delays achievement of the maximally permissible outlet temperature super-proportionally, or else increases the heat absorption capacity super-proportionally.
(Figure 1)
Description
The present invention relates to a regenerator, for example, for a hot-blast stove or a heat accumulator in a solar system, with an accumulator core that is built up from ceramic material and which is used to accumulate "sensible'l heat, the accumulator core being acted upon by a hot charging flow on one, "hot" side so as to become charged, until such time as a maximally permissible charging flow outlet temperature is reached on the other, "cold"
side, and in order to be discharged the accumulator core is acted upon from the other, "cold" side by a cold discharge flow until such time as a minimally permissible discharge outlet temperature is reached on the "hot" side.
In such regenerators, as a rule, the charging flow and the discharge flow are air or gas flows. The maximally permissible charge flow outlet temperature is, for example, below 400C. The minimally permissible discharge flow outlet temperature is, for exam~ e, above 600C, in order that it can be utilized in a subs/equent system.
Different types of hot blast stoves and the construction of their accumulator cores are described in the journal Stahl u. Eisen [Steel and Iron], 95 ~1975) No. 17, pages 802 to 806. The accumulator cores are built of blocks of various ceramic materials in order that they can adapt to the temperatures that occur at the various levels in the core.
DE 37 25 450 A1 describes a hot blast stove system with three hot blast stoves that are associated with a blast furnace. These work alternately in the charging and in the discharging mode.
"
DE-PS 971 943 describes special air duct shapes of the lining blocks of the accumulator core of a hot-blast stove. These help improve thermal transfer.
side, and in order to be discharged the accumulator core is acted upon from the other, "cold" side by a cold discharge flow until such time as a minimally permissible discharge outlet temperature is reached on the "hot" side.
In such regenerators, as a rule, the charging flow and the discharge flow are air or gas flows. The maximally permissible charge flow outlet temperature is, for example, below 400C. The minimally permissible discharge flow outlet temperature is, for exam~ e, above 600C, in order that it can be utilized in a subs/equent system.
Different types of hot blast stoves and the construction of their accumulator cores are described in the journal Stahl u. Eisen [Steel and Iron], 95 ~1975) No. 17, pages 802 to 806. The accumulator cores are built of blocks of various ceramic materials in order that they can adapt to the temperatures that occur at the various levels in the core.
DE 37 25 450 A1 describes a hot blast stove system with three hot blast stoves that are associated with a blast furnace. These work alternately in the charging and in the discharging mode.
"
DE-PS 971 943 describes special air duct shapes of the lining blocks of the accumulator core of a hot-blast stove. These help improve thermal transfer.
2~ 7~s~
DE-PS 847 179 describes a particular arrangement of multi-hole lining blocks for hot-blast stoves, in which all of the holes that pass through the blocks in the layers of lining blocks are connected to each other.
DE-PS 960 489 describes a regenerator in which the heat absorption capacity of the accumulator core :is to be increased.
This proposes specially shaped lining blocks in zones that lie one above the other.
The "PHOEBUS" research project concerns a solar system in which a receiver is heated by way of mirrors. The thermal energy ~rom this receiver is stored in a regenerator of the type described hereto~ore, using air as a thermal carrier, and drives a steam turbine by way of a steam generator in order to generate electricity. It is intended that the accumulator core be charged during the day and discharged at night.
It is the task of the present invention to improve the heat absorption capacity of a regenerator of the type described heretofore without increasing the volume oP the said regenPrator or else to reduce the volume and thus the installed size of the regenerator for an equal heat absorption capacity.
According to the present invention, this problem has been solved by a regenerator of the type described heretofore, such that on the hot side and/or on the cold side of the accumulator core there is a layer that acts as a temperature buffer, and which delays the achievement of the maximally parmissible charqing flow outlet temp~rature and/or the minimally permissible discharge flow outlet temperature super-proportionally or else increases the heat absorption capacity super-proportionally.
Surprisingly, the incorporation of these temperature-buffering layers results in the fact that not only do the layers of .
~7~$~
modified material display a greater heat absorption capacity, but also that, in particular, the heat absorption capacity of the unmodified material between the modified materials also increases considerably so that the overall absorbing capacity increases super-proportionally.
These temperature-buffering layers can have the following modified properties:
- An increased heat capacity as a result of a greater density and/or higher specific heat capacity.
- An increased heat capacity by the incorporation of a latent material (e.g., salt ceramic) by exploiting the phase conversion by, for example, the fusion enthalpy of the salt~
- An increased heat capacity by using a material which undergoes a chemical reaction~
- A modification of geometric data, e.g., increasing the specific surface area.
Various solutions or combinations thereof are preferred for different applications.
In a preferred embodiment of the present invention, the layer consists of a material that accumulates latent heat. In particular, fusion enthalpy is exploited when this is done. The latent heat of the layer leads to an increase of the heat capacity of the regenerator without, however, increasing the volume of said generator. However, it has been shown that this effect is less important than the fact that the latent heat accumulator material a~ts as a temperature buffer, so that the accumulator core that i5 of conventional material--and contains no latent heat accumulator material--can store more (sensible) 2~7~
heat than in the normal case, when no temperature buffer is provided.
By using materials that have only been modified relatively slightly (higher value materials) (e.g., salt ceramic, modified structure, ...), the cited heat absorption capacity of the regenerator is improved super-proportionally. This can mean that, according to today's calculations, the price ~or the system increases at a slower rate than the heat absorption capacity for the same installed volume.
It is preferred that the layers that act as temperature buffers be provided on both the hot side and on the cold side. However, in the case of existing regenerators it can be difficult to install a layer that acts as a temperature bu~fer. But even the incorporation of only one layer will bring about an increase of the heat absorption capacity.
Further advantageous configurations of the present invention are set out in the sub-claims and in the description that follows.
The drawings appended hereto show the following:
igure 1: a hot-blast stove, shown diagrammatically in cross-section;
Figure 2: a regenerator as a heat accumulator for a solar system;
Figure 3: a salt ceramic block for building up the temperature-buffer layer;
Figure 4: the curve for gas inlet and outlet temperatures plotted against time during the charging and discharging modes of a heat accumulator for a solar system;
Fi~ure 5: the curve for the outlet temperature plotted against discharge time for an accumulator for (sensible) heat (prior art) and an accumulator, improved as in the present invention, with two layers of latent material;
Figure 6: time temperature curves during the charging mode of a regenerator for a solar system, to its total height as in the prior art;
Figure 7: time temperature curves as in figure 6, when improved according to the present invention;
Figure 8: accumulated heat to the accumulator height for the two cases shown in figures 6 and 7.
A hot-blast stove shown in figure 1 has an accumulator coxe 1 and an external combustion chamber 2. On the upper hot side of the accumulator core 1 there is a layer 3. on the lower cold side of the accumulator 1 there is a layer 4. One of the layers 3, 4 can be eliminatedO Together, the accumulator core and the layexs 3, 4 form a regenerator.
The accumulator core 1 is built of blocks that are of ceramic material. In the normal way, the blocks can consist of different ceramic materials at the different levels of the accumulator core 1, in order to ensure adaptation to the various thermal and mechanical loads that occur at the different levels.
The regenerator shown in figure 2 is built up in a similar way as that shown in figure l; this is intended as an accumulator for a solar system. Such regenerators are usually in the order o~ 20 to 40 m high, with, fox example, temperatures over 600C to 1550~C predominate at the top and, for example, temperatures are under 400~C at the bottom.
The upper layer 3 and the lower layer 4 are built up, for example, of several layers of blocks. Figure 3 shows one of these blocks. The block 5 incorporates a plurality of continuous holes 6 for the charging airflow L and the discharge airflow E.
The ceramic material of the block 5 has a microporous structure, in contrast to the blocks used for the accumulator core l, and salts are incorporated in this =tructure as a latent heat ,~ , - .
~7~3~
accumulator material. All in all, the block 5 consists of a salt/ceramic material. One suitable ceramic material is, for example, MgO. Approximately 30%-vol to 60%-vol, and in particular 45%-vol of salts are added to this. Carbonates, sulfates or fluorides can be used as the sal~s.
Because of the fact that widely differing temperatures predominate in the area of the upper layer 3 and of the lower layer 4, both in the discharge mode and in the charging mode, a different salt has to be selected for the blocks 5 in the upper layer 3 and for those in the lower layer 4, in order to permit exploitation of fusion enthalpy.
A salt with a melting temperature that lies between the temperature of the charging flow L and the minimally permissible outlet temperature of the discharge flow E must be selected for the upper layer 3, in order to ensure that the salt melts during the charging mode and hardens during discharge mode. In the same way, a salt whose ~usion temperature is between the discharge temperature and the maximally permissible outlet temperature of the charging airflow during charging is used for the lower layer 4.
The thickness, or height, respectively, of the layers 3, 4 and the dimensions of their continuous holes 6 are so selected that the salts are brouqht to the particular melting or hardening temperature. Comparatively narrow through holes 6 can improve the transfer of heat to the salts.
Together, the depth or height of the layers 3, 4 amount to approximately 10 to 35% of the height of the accumulator core 1.
At a total height of the accumulator core 1 with the layers 3, 4 of 20 m, it has been shown that a height of 2 m is suitable for the upper layer 3 and for the lower layer 4. In principle, an effort is made to ensure that the upper layer 3 and the lower layer 4 are kept as small as possible since the blocks that are used for them are considerably more costly khan the blocks that make up the accumulator core 1. A greater thickness of the layers 3 and 4 leads to only a limited improvement for the thickness of the layers 3 and 4 should be only so great that the salts that are contained in them melt and harden as the temperature changes.
In figure 4, the continuous lines show temperature curves of the charging airflow passing through the regenerator for the charging period both above and below, over time, and the dashed line shows the temperature of the discharge airflow E passing through the regenerator during the discharge period, without the present invention. The improvement achieved by using the upper layer 3 and the lower layer 4 is recorded with respect to the discharge airflow E in figure 5.
For the charging mode, provision is made for a maximally permissible charging flow outlet temperature GL at the lower end of the regenerator, and this is not to be exceeded, in order that the components in this area do not become damaged. This limiting outlet temperature GL is approximately 250~C in the diagram shown in figure 4.
For discharge mode, there is a minimally permissible discharge flow outlet temperature GE as a limiting temperature. This must be sufficiently high to deliver the charging flow at a sufficiently high temperature to a unit, such as a blast furnace or steam turbine, that follows the regenerator. In the case of the hot-blast stove shown in figure 1 this i5 the minimal temperature that is required for the blast furnace that follows the hot-blast stove. In the case of the regenerator shown in figure 2, this is the minimal temperature that i~ required to operate a heat exchanger that precedes a steam turbine.
According to figure 4, this limiting temperature GE is B
~7~
approximately 650C. In the particular application, the limiting temperature GL, GE can be either higher or lower. Ths same applies to the temparature-time relationships shown in figure 4, which will be described below.
In figure 4 at the top of the regenerator there is a charging airflow L at 700C. Below, the emerging charging airflow increases from approximately 185C. When the charging airflow that is emerging below reaches the limiting outlet temperature GL, the charging flow L is cut off by means of a control system.
Discharging can then begin.
During discharge, a discharge airflow E at a temperature oP
approximately 185C is introduced into the underside of the regenerator. This leads to the fact that the temperature ak the upper side of the regenerator gradually decreases from approximately 700C. The discharge airflow E initially leaves the regenerator at approximately 700C and cools down. Once it reaches the limiting temperature GE, the discharge mode is terminated.
In figure 5, the dashed line shows the discharge of the accumulator as in figure 4, which accumulates only (sensible) heat, from 700C to the limiting temperature GE of 650~C. The continuous line shows the discharge for an accumulator according to the present invention for purposes of comparison. As can be seen, the layers 3, 4 lead to a retention effect with respect to the temperature, so that the limiting temperature is first reached much later.
Fi~ure 6 shows nine temperature curves measured at different times to the hei~ht of the accumulator core according to the prior art~ The continuous line shows the temperature of the material in the accumulator core. The dotted lines show the charging flow temperature. If, for example, one examines the ~ ~ ~ 3 ~
temperature curve at the mid-height, at lO m, it can be seen that at the beginning of the charging process there is a temperature of approximately 370C at this point and at the end of the charging mode there is a temperature of approximately 500C at the same point. Thus, there is a temperature differential for the storable (sensible~ heat of only approximately 130C.
In contrast to this, if one examines the diagram shown in figure 7, one can see that because of the layers 3, 4 there are two areas I, II that equalize the temperatures. Between these zones I, II the temperature curve bifurcates without any change in the limiting temperatures GE, GL in the zone III that corresponds to the accumulator core 1; the result of this bifurcation is that the accumulator core 1 can absorb considerably more (sensihle) heat (and can thus give it off as well) than in the usual case according to the prior art, in which neither the layer 3 nor the layer 4 are used.
If one examines the temperature, for example, in figure 7 at th~
mean height of 10 m, then it can be seen that in the curve for the charging time the temperatures lie between approximately 230C and 840C. The temperature differential in the accumulator core 1 is not only at approximately 130C, as in the prior art shown in figure 6, but is approximately 600C. Thus, because of the layers 3, 4, or because of these zones I, II that are in contact with them, there is a considerable increase of the heat absorption capacity ~or (sensible) heat of the accumulator core 1 that is made of conventional ceramic material.
In particular, in figure 8, this is recorded for the whole of the accumulator at its dif~erent levels.
DE-PS 847 179 describes a particular arrangement of multi-hole lining blocks for hot-blast stoves, in which all of the holes that pass through the blocks in the layers of lining blocks are connected to each other.
DE-PS 960 489 describes a regenerator in which the heat absorption capacity of the accumulator core :is to be increased.
This proposes specially shaped lining blocks in zones that lie one above the other.
The "PHOEBUS" research project concerns a solar system in which a receiver is heated by way of mirrors. The thermal energy ~rom this receiver is stored in a regenerator of the type described hereto~ore, using air as a thermal carrier, and drives a steam turbine by way of a steam generator in order to generate electricity. It is intended that the accumulator core be charged during the day and discharged at night.
It is the task of the present invention to improve the heat absorption capacity of a regenerator of the type described heretofore without increasing the volume oP the said regenPrator or else to reduce the volume and thus the installed size of the regenerator for an equal heat absorption capacity.
According to the present invention, this problem has been solved by a regenerator of the type described heretofore, such that on the hot side and/or on the cold side of the accumulator core there is a layer that acts as a temperature buffer, and which delays the achievement of the maximally parmissible charqing flow outlet temp~rature and/or the minimally permissible discharge flow outlet temperature super-proportionally or else increases the heat absorption capacity super-proportionally.
Surprisingly, the incorporation of these temperature-buffering layers results in the fact that not only do the layers of .
~7~$~
modified material display a greater heat absorption capacity, but also that, in particular, the heat absorption capacity of the unmodified material between the modified materials also increases considerably so that the overall absorbing capacity increases super-proportionally.
These temperature-buffering layers can have the following modified properties:
- An increased heat capacity as a result of a greater density and/or higher specific heat capacity.
- An increased heat capacity by the incorporation of a latent material (e.g., salt ceramic) by exploiting the phase conversion by, for example, the fusion enthalpy of the salt~
- An increased heat capacity by using a material which undergoes a chemical reaction~
- A modification of geometric data, e.g., increasing the specific surface area.
Various solutions or combinations thereof are preferred for different applications.
In a preferred embodiment of the present invention, the layer consists of a material that accumulates latent heat. In particular, fusion enthalpy is exploited when this is done. The latent heat of the layer leads to an increase of the heat capacity of the regenerator without, however, increasing the volume of said generator. However, it has been shown that this effect is less important than the fact that the latent heat accumulator material a~ts as a temperature buffer, so that the accumulator core that i5 of conventional material--and contains no latent heat accumulator material--can store more (sensible) 2~7~
heat than in the normal case, when no temperature buffer is provided.
By using materials that have only been modified relatively slightly (higher value materials) (e.g., salt ceramic, modified structure, ...), the cited heat absorption capacity of the regenerator is improved super-proportionally. This can mean that, according to today's calculations, the price ~or the system increases at a slower rate than the heat absorption capacity for the same installed volume.
It is preferred that the layers that act as temperature buffers be provided on both the hot side and on the cold side. However, in the case of existing regenerators it can be difficult to install a layer that acts as a temperature bu~fer. But even the incorporation of only one layer will bring about an increase of the heat absorption capacity.
Further advantageous configurations of the present invention are set out in the sub-claims and in the description that follows.
The drawings appended hereto show the following:
igure 1: a hot-blast stove, shown diagrammatically in cross-section;
Figure 2: a regenerator as a heat accumulator for a solar system;
Figure 3: a salt ceramic block for building up the temperature-buffer layer;
Figure 4: the curve for gas inlet and outlet temperatures plotted against time during the charging and discharging modes of a heat accumulator for a solar system;
Fi~ure 5: the curve for the outlet temperature plotted against discharge time for an accumulator for (sensible) heat (prior art) and an accumulator, improved as in the present invention, with two layers of latent material;
Figure 6: time temperature curves during the charging mode of a regenerator for a solar system, to its total height as in the prior art;
Figure 7: time temperature curves as in figure 6, when improved according to the present invention;
Figure 8: accumulated heat to the accumulator height for the two cases shown in figures 6 and 7.
A hot-blast stove shown in figure 1 has an accumulator coxe 1 and an external combustion chamber 2. On the upper hot side of the accumulator core 1 there is a layer 3. on the lower cold side of the accumulator 1 there is a layer 4. One of the layers 3, 4 can be eliminatedO Together, the accumulator core and the layexs 3, 4 form a regenerator.
The accumulator core 1 is built of blocks that are of ceramic material. In the normal way, the blocks can consist of different ceramic materials at the different levels of the accumulator core 1, in order to ensure adaptation to the various thermal and mechanical loads that occur at the different levels.
The regenerator shown in figure 2 is built up in a similar way as that shown in figure l; this is intended as an accumulator for a solar system. Such regenerators are usually in the order o~ 20 to 40 m high, with, fox example, temperatures over 600C to 1550~C predominate at the top and, for example, temperatures are under 400~C at the bottom.
The upper layer 3 and the lower layer 4 are built up, for example, of several layers of blocks. Figure 3 shows one of these blocks. The block 5 incorporates a plurality of continuous holes 6 for the charging airflow L and the discharge airflow E.
The ceramic material of the block 5 has a microporous structure, in contrast to the blocks used for the accumulator core l, and salts are incorporated in this =tructure as a latent heat ,~ , - .
~7~3~
accumulator material. All in all, the block 5 consists of a salt/ceramic material. One suitable ceramic material is, for example, MgO. Approximately 30%-vol to 60%-vol, and in particular 45%-vol of salts are added to this. Carbonates, sulfates or fluorides can be used as the sal~s.
Because of the fact that widely differing temperatures predominate in the area of the upper layer 3 and of the lower layer 4, both in the discharge mode and in the charging mode, a different salt has to be selected for the blocks 5 in the upper layer 3 and for those in the lower layer 4, in order to permit exploitation of fusion enthalpy.
A salt with a melting temperature that lies between the temperature of the charging flow L and the minimally permissible outlet temperature of the discharge flow E must be selected for the upper layer 3, in order to ensure that the salt melts during the charging mode and hardens during discharge mode. In the same way, a salt whose ~usion temperature is between the discharge temperature and the maximally permissible outlet temperature of the charging airflow during charging is used for the lower layer 4.
The thickness, or height, respectively, of the layers 3, 4 and the dimensions of their continuous holes 6 are so selected that the salts are brouqht to the particular melting or hardening temperature. Comparatively narrow through holes 6 can improve the transfer of heat to the salts.
Together, the depth or height of the layers 3, 4 amount to approximately 10 to 35% of the height of the accumulator core 1.
At a total height of the accumulator core 1 with the layers 3, 4 of 20 m, it has been shown that a height of 2 m is suitable for the upper layer 3 and for the lower layer 4. In principle, an effort is made to ensure that the upper layer 3 and the lower layer 4 are kept as small as possible since the blocks that are used for them are considerably more costly khan the blocks that make up the accumulator core 1. A greater thickness of the layers 3 and 4 leads to only a limited improvement for the thickness of the layers 3 and 4 should be only so great that the salts that are contained in them melt and harden as the temperature changes.
In figure 4, the continuous lines show temperature curves of the charging airflow passing through the regenerator for the charging period both above and below, over time, and the dashed line shows the temperature of the discharge airflow E passing through the regenerator during the discharge period, without the present invention. The improvement achieved by using the upper layer 3 and the lower layer 4 is recorded with respect to the discharge airflow E in figure 5.
For the charging mode, provision is made for a maximally permissible charging flow outlet temperature GL at the lower end of the regenerator, and this is not to be exceeded, in order that the components in this area do not become damaged. This limiting outlet temperature GL is approximately 250~C in the diagram shown in figure 4.
For discharge mode, there is a minimally permissible discharge flow outlet temperature GE as a limiting temperature. This must be sufficiently high to deliver the charging flow at a sufficiently high temperature to a unit, such as a blast furnace or steam turbine, that follows the regenerator. In the case of the hot-blast stove shown in figure 1 this i5 the minimal temperature that is required for the blast furnace that follows the hot-blast stove. In the case of the regenerator shown in figure 2, this is the minimal temperature that i~ required to operate a heat exchanger that precedes a steam turbine.
According to figure 4, this limiting temperature GE is B
~7~
approximately 650C. In the particular application, the limiting temperature GL, GE can be either higher or lower. Ths same applies to the temparature-time relationships shown in figure 4, which will be described below.
In figure 4 at the top of the regenerator there is a charging airflow L at 700C. Below, the emerging charging airflow increases from approximately 185C. When the charging airflow that is emerging below reaches the limiting outlet temperature GL, the charging flow L is cut off by means of a control system.
Discharging can then begin.
During discharge, a discharge airflow E at a temperature oP
approximately 185C is introduced into the underside of the regenerator. This leads to the fact that the temperature ak the upper side of the regenerator gradually decreases from approximately 700C. The discharge airflow E initially leaves the regenerator at approximately 700C and cools down. Once it reaches the limiting temperature GE, the discharge mode is terminated.
In figure 5, the dashed line shows the discharge of the accumulator as in figure 4, which accumulates only (sensible) heat, from 700C to the limiting temperature GE of 650~C. The continuous line shows the discharge for an accumulator according to the present invention for purposes of comparison. As can be seen, the layers 3, 4 lead to a retention effect with respect to the temperature, so that the limiting temperature is first reached much later.
Fi~ure 6 shows nine temperature curves measured at different times to the hei~ht of the accumulator core according to the prior art~ The continuous line shows the temperature of the material in the accumulator core. The dotted lines show the charging flow temperature. If, for example, one examines the ~ ~ ~ 3 ~
temperature curve at the mid-height, at lO m, it can be seen that at the beginning of the charging process there is a temperature of approximately 370C at this point and at the end of the charging mode there is a temperature of approximately 500C at the same point. Thus, there is a temperature differential for the storable (sensible~ heat of only approximately 130C.
In contrast to this, if one examines the diagram shown in figure 7, one can see that because of the layers 3, 4 there are two areas I, II that equalize the temperatures. Between these zones I, II the temperature curve bifurcates without any change in the limiting temperatures GE, GL in the zone III that corresponds to the accumulator core 1; the result of this bifurcation is that the accumulator core 1 can absorb considerably more (sensihle) heat (and can thus give it off as well) than in the usual case according to the prior art, in which neither the layer 3 nor the layer 4 are used.
If one examines the temperature, for example, in figure 7 at th~
mean height of 10 m, then it can be seen that in the curve for the charging time the temperatures lie between approximately 230C and 840C. The temperature differential in the accumulator core 1 is not only at approximately 130C, as in the prior art shown in figure 6, but is approximately 600C. Thus, because of the layers 3, 4, or because of these zones I, II that are in contact with them, there is a considerable increase of the heat absorption capacity ~or (sensible) heat of the accumulator core 1 that is made of conventional ceramic material.
In particular, in figure 8, this is recorded for the whole of the accumulator at its dif~erent levels.
Claims (17)
1. A regenerator, for example, in a hot-blast stove or a heat accumulator in a solar system, with an accumulator core that is built up from ceramic or metal or natural material and which is used to accumulate "sensible" heat, the accumulator core being acted upon by a hot charging flow on one, "hot"
side so as to become charged, until such time as on the other, "cold" side, a maximally permissible charging flow outlet temperature is reached, and in order to be discharged the accumulator core is acted upon from the other, "cold"
side by a cold discharge flow until such time as a minimally permissible discharge outlet temperature is reached on the "hot" side, characterized in that on the hot side and/or on the cold side of the accumulator core (1) there is a layer (3, 4) that serves as a temperature buffer that delays the achievement of the maximally permissible charging flow outlet temperature (GL) and/or the minimally permissible discharging flow outlet temperature (GE) super-proportionally or increases the heat absorption capacity super-proportionally.
side so as to become charged, until such time as on the other, "cold" side, a maximally permissible charging flow outlet temperature is reached, and in order to be discharged the accumulator core is acted upon from the other, "cold"
side by a cold discharge flow until such time as a minimally permissible discharge outlet temperature is reached on the "hot" side, characterized in that on the hot side and/or on the cold side of the accumulator core (1) there is a layer (3, 4) that serves as a temperature buffer that delays the achievement of the maximally permissible charging flow outlet temperature (GL) and/or the minimally permissible discharging flow outlet temperature (GE) super-proportionally or increases the heat absorption capacity super-proportionally.
2. A regenerator as defined in claim 1, characterized in that the layer (3, 4) consists of a material of increased heat capacity because of greater density and/or greater specific heat capacity.
3. A regenerator as defined in claim 1, characterized in that the layer (3, 4) consists of a latent heat storage material.
4. A regenerator as defined in claim 1, characterized in that the layer (3, 4) consists of a material that goes through a chemical reaction.
5. A regenerator as defined in claim 1, characterized in that the layer (3, 4) consists of material having modified geometric data.
6. A regenerator as defined in claim 5, characterized in that the flow cross-sections (6) of the layer (3, 4) are smaller than those of the accumulator core (1).
7. A regenerator as defined in claim 3, characterized in that fusion enthalpy is exploited in the latent heat storage material.
8. A regenerator as defined in claim 3 and claim 7, characterized in that the layer (3, 4) consists of a salt/ceramic material.
9. A regenerator as defined in claim 8, characterized in that the layer (3, 4) consists of blocks (5), in the ceramic structure of which salts are incorporated as latent heat storage material.
10. A regenerator as defined in claim 9, characterized in that the blocks (5) incorporate continuous holes (6) for the discharge flow and for the charging flow.
11. A regenerator as defined in one of the preceding claims 3 and 7 to 10, characterized in that the layer (3) of the hot side has a higher phase conversion temperature than the layer (4) of the cold side.
12. A regenerator as defined in claim 11, characterized in that the phase conversion temperature of the latent heat storage material for the layer (3) on the hot side lies between the temperature of the charging flow and the minimally permissible outlet temperature of the discharge flow during discharge.
13. A regenerator as defined in one of the preceding claims 11 or 12, characterized in that the phase conversion temperature of the latent heat storage material of the layer (4) of the cold side lies between the discharge temperature of the discharge flow and the maximally permissible outlet temperature of the charging flow.
14. A regenerator as defined in one of the preceding claims, characterized in that the layers (3, 4) are in the form of a filling.
15. A regenerator as defined in one of the preceding claims, characterized in that the storage material is made up of metals or naturally occurring materials.
16. A regenerator as defined in one of the preceding claims, characterized in that the thickness of the layers (3, 4) lies between 10% and 35% of the height of the accumulator core (1).
17. A regenerator as defined in one of the preceding claims, characterized in that the layers (3, 4) are of equal thickness.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4126646A DE4126646C2 (en) | 1991-08-13 | 1991-08-13 | Regenerator with storage core and a layer provided on the storage core |
| DEP4126646.3 | 1991-08-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2075889A1 true CA2075889A1 (en) | 1993-02-14 |
Family
ID=6438155
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002075889A Abandoned CA2075889A1 (en) | 1991-08-13 | 1992-08-12 | Regenerator |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0527306A1 (en) |
| CA (1) | CA2075889A1 (en) |
| DE (1) | DE4126646C2 (en) |
| RU (1) | RU2057995C1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102011003441A1 (en) * | 2011-02-01 | 2012-08-02 | ZAE Bayern Bayerisches Zentrum für angewandte Energieforschung e.V. | A method for determining the state of charge of a latent heat storage and latent heat storage with such a state of charge indicator |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1226047A (en) * | 1958-05-29 | 1960-07-06 | Scient Design Co | Apparatus forming a heat accumulator, usable in the chemical industry |
| LU43049A1 (en) * | 1962-01-26 | 1963-03-21 | ||
| AT251164B (en) * | 1963-08-02 | 1966-12-27 | Nikex Nehezipari Kulkere | Regenerative heat exchanger |
| DE1533861B1 (en) * | 1966-04-16 | 1972-03-09 | Nippon Kokan Kk | Cowper heater |
| GB1281782A (en) * | 1970-02-25 | 1972-07-12 | Kureha Chemical Ind Co Ltd | Stationary regenerative heating apparatus |
| DE2748576C3 (en) * | 1977-10-28 | 1981-03-26 | Central'nyj naučno-issledovatel'skij i proektnyj institut stroitel'nych metallokonstrukcij CNIIPROEKTSTALKONSTRUKCIJA, Moskau/Moskva | Regenerative heater |
| DE3038723A1 (en) * | 1980-10-14 | 1982-05-06 | L. & C. Steinmüller GmbH, 5270 Gummersbach | HEAT STORAGE FOR REGENERATIVE HEAT EXCHANGE |
-
1991
- 1991-08-13 DE DE4126646A patent/DE4126646C2/en not_active Expired - Fee Related
-
1992
- 1992-06-12 EP EP92109883A patent/EP0527306A1/en not_active Withdrawn
- 1992-08-12 CA CA002075889A patent/CA2075889A1/en not_active Abandoned
- 1992-08-13 RU SU925052337A patent/RU2057995C1/en active
Also Published As
| Publication number | Publication date |
|---|---|
| RU2057995C1 (en) | 1996-04-10 |
| DE4126646A1 (en) | 1993-02-18 |
| DE4126646C2 (en) | 1995-05-24 |
| EP0527306A1 (en) | 1993-02-17 |
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