US20190003789A1 - Heat exchanger for heating gas and use of the heat exchanger - Google Patents
Heat exchanger for heating gas and use of the heat exchanger Download PDFInfo
- Publication number
- US20190003789A1 US20190003789A1 US16/064,021 US201616064021A US2019003789A1 US 20190003789 A1 US20190003789 A1 US 20190003789A1 US 201616064021 A US201616064021 A US 201616064021A US 2019003789 A1 US2019003789 A1 US 2019003789A1
- Authority
- US
- United States
- Prior art keywords
- heat exchanger
- gas
- drying
- exchanger according
- heat
- 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
- 238000010438 heat treatment Methods 0.000 title claims description 17
- 238000001035 drying Methods 0.000 claims description 45
- 239000002245 particle Substances 0.000 claims description 25
- 238000004519 manufacturing process Methods 0.000 claims description 14
- 239000007921 spray Substances 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 6
- 229910000831 Steel Inorganic materials 0.000 claims description 3
- 239000002608 ionic liquid Substances 0.000 claims description 3
- 150000003839 salts Chemical class 0.000 claims description 3
- 239000010959 steel Substances 0.000 claims description 3
- 239000007789 gas Substances 0.000 description 66
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 13
- 229910052725 zinc Inorganic materials 0.000 description 13
- 239000011701 zinc Substances 0.000 description 13
- 239000000463 material Substances 0.000 description 11
- 239000011248 coating agent Substances 0.000 description 7
- 238000000576 coating method Methods 0.000 description 7
- 239000000376 reactant Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 239000012530 fluid Substances 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 229920000193 polymethacrylate Polymers 0.000 description 3
- 238000004026 adhesive bonding Methods 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical class C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 239000004971 Cross linker Substances 0.000 description 1
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000010981 drying operation Methods 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- KFZAUHNPPZCSCR-UHFFFAOYSA-N iron zinc Chemical compound [Fe].[Zn] KFZAUHNPPZCSCR-UHFFFAOYSA-N 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 229920000058 polyacrylate Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 229920000247 superabsorbent polymer Polymers 0.000 description 1
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
- F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
- F28F19/02—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings
- F28F19/06—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings of metal
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
- C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
- F26B17/02—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by belts carrying the materials; with movement performed by belts or elements attached to endless belts or chains propelling the materials over stationary surfaces
- F26B17/04—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by belts carrying the materials; with movement performed by belts or elements attached to endless belts or chains propelling the materials over stationary surfaces the belts being all horizontal or slightly inclined
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
- F26B21/02—Circulating air or gases in closed cycles, e.g. wholly within the drying enclosure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B3/00—Drying solid materials or objects by processes involving the application of heat
- F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
- F26B3/04—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour circulating over or surrounding the materials or objects to be dried
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B3/00—Drying solid materials or objects by processes involving the application of heat
- F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
- F26B3/10—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air the gas or vapour carrying the materials or objects to be dried with it
Definitions
- the invention proceeds from a heat exchanger for heating gas to a temperature in the range from 150 to 400° C., wherein the gas is heated by indirect heat transfer.
- Heating gas to a temperature of more than 150° C. is required, for example, when the gas is being used as drying gas.
- Applications of this kind are, for example, driers in superabsorbent production.
- Two different processes are known for production of superabsorbents: firstly production in a mixing kneader, in which case the superabsorbent thus produced is dried in a belt drier in a next step, and secondly in a spray tower, in which the monomer solution is introduced by spraying in countercurrent to a drying gas, polymerized to superabsorbent particles while falling within the spray tower and simultaneously dried.
- the zinc coating has a tendency to delaminate. This effect is also known as the Kirkendall effect. This can result in detachment of zinc particles and contamination of the superabsorbent. However, this leads to an unwanted reduction in quality of the superabsorbent.
- the object is achieved by a heat exchanger for heating gas to a temperature in the range from 150 to 400° C., wherein the gas is heated by indirect heat transfer, wherein all the surfaces of the walls of the heat exchanger which come into contact with the gas have been hot dip galvanized and the surfaces which come into contact with the gas, after the hot dip galvanization, have been heat treated at a temperature in the range from 400 to 750° C.
- the components of the heat exchanger to be galvanized are first dipped into a bath of molten zinc.
- zinc accumulates on the surface of the heat exchanger and bonds to the surface.
- the material from which the heat exchanger is manufactured is stable to the hot dip galvanization temperatures.
- good heat transfer is possible, for which the material should have a very low coefficient of heat transfer. Suitable materials are therefore especially metals.
- the walls of the heat exchanger are manufactured from sheet steel.
- the heat exchanger in accordance with the invention, is subjected to a heat treatment at a temperature in the range from 400 to 750° C., preferably in the range from 525 to 575° C., for example at a mean component temperature of 550° C.
- the duration of the heat treatment at a temperature of more than 525° C. is preferably in the range from 1 to 5 min, especially in the range from 2 to 3 min.
- the duration of the heat treatment is extended up to 90 min.
- the required duration of the heat treatment should be adjusted correspondingly and decreases with increasing temperature.
- the heat treatment can be conducted in any desired furnace known to those skilled in the art. Suitable furnaces are, for example, continuous furnaces.
- the heat exchanger may have any desired design known to those skilled in the art for heat exchangers in which indirect heat transfer is effected.
- the gas can be heated in cocurrent, in countercurrent, in crosscurrent or in any desired combination thereof.
- Standard variants are, for example, cross-countercurrent or cross-cocurrent.
- Suitable heat exchangers are, for example, plate heat exchangers, shell and tube heat exchangers or spiral heat exchangers.
- Indirect heat transfer is understood to mean that heat is transferred from a hot fluid to a colder fluid, the hot fluid and the colder fluid being separated from one another by a wall. This results in heat transfer through the wall of the heat exchanger.
- the gas is the colder fluid.
- the hot fluid used is a suitable heat transfer medium having a temperature above the temperature to which the gas is to be heated.
- Suitable heat transfer media are, for example, superheated steam, a thermal oil suitable for the temperature, an ionic liquid or a salt melt.
- a preferred heat transfer medium is superheated steam.
- the surface area which comes into contact with the gas to be heated is at a maximum.
- the fins are preferably soldered to the wall or welded to the wall.
- Adhesive bonding of the fins to the wall is generally less advantageous since standard polymer-based adhesives firstly do not withstand the temperatures and polymers secondly have poorer thermal conductivity than metals, such that the effect of the increased heat transfer area as a result of the fins is only very small in the case of adhesive bonding. Attachment of the fins by screws or rivets is not advantageous either, since it cannot be ensured in this case that the fins are fully aligned with the wall. If a gap is established between wall and fin, the gas to be heated will flow through it, the gas to be heated having much poorer thermal conductivity than metal, such that the fins in these regions cannot assume the surface temperature of the wall and so the effect resulting from the fins likewise does not occur. In the case of galvanization, even zinc does generally flow into a possible gap between fins and the wall, but it cannot be ensured thereby that the gap will be closed by the galvanization.
- the invention further relates to the use of such a heat exchanger.
- the heat exchanger is used for drying superabsorbent particles.
- Superabsorbents are materials that can absorb and store several times their mass of liquid.
- superabsorbents are polymers based on polyacrylate or polymethacrylate, also referred to as poly(meth)acrylate hereinafter. These are typically prepared from esters of acrylic acid or methacrylic acid and suitable crosslinkers known to those skilled in the art. The reactants used for preparation of the poly(meth)acrylates and the conversion thereof in a mixing kneader is described, for example, in WO 2006/034853 A1.
- the heat exchanger is used in a belt drier for drying superabsorbent particles.
- the superabsorbent is produced in a reactor, withdrawn from the reactor and then dried in a belt drier.
- the reactor used in this case is typically a mixing kneader.
- the reactants for production of the superabsorbent are added thereto.
- the reactants are converted to the superabsorbent in the mixing kneader, forming a high-viscosity mass. This mass is broken up with suitable kneading bars in the mixing kneader.
- the product formed is a coarse-grain material.
- This coarse-grain material is added to the belt drier.
- the superabsorbent material is distributed on a drying belt of the belt drier, and a gas is passed over it at a temperature of preferably at least 50° C., more preferably at least 100° C., even more preferably at least 150° C., and preferably up to 250° C., more preferably up to 220° C., most preferably up to 200° C.
- the gas used may, for example, be air or gases that are inert towards the superabsorbent material, for example nitrogen. Preference is given, however, to the use of air as drying gas.
- the drying gas is heated in the heat exchanger of the invention to the temperature required for the drying.
- the heat exchanger may be disposed within the belt drier, for example beneath the drying belt.
- the drying gas is conducted in a circuit.
- a suitable particle separator can be positioned between the belt drier and heat exchanger, in order to remove entrained superabsorbent particles from the gas stream.
- Suitable particle separators are, for example, cyclones or filters.
- the superabsorbent particles Downstream of the belt drier, the superabsorbent particles are ground and fed to a postcrosslinking operation and a drying operation. Finally, the superabsorbent particles are classified by size, for which it is customary to use a sieving machine having several sieve decks. Superabsorbent particles that are too small are introduced back into the mixing kneader, such that they mix with the superabsorbent mass which forms and sufficiently large particles can thus be produced. Superabsorbent particles that are too large are recycled into the mill and subjected once again to the grinding operation in order to comminute them further.
- the superabsorbent particles are produced in a spray tower.
- the reactants used for the production of the superabsorbents are first mixed and then dropletized in a spray tower, producing droplets having a size which is chosen such that the superabsorbent particles formed in the spray tower from the droplets by reaction of the reactants meet the desired specification.
- the droplets fall from the top downward, while a drying gas is fed in simultaneously.
- This drying gas has been heated to a temperature required for the production of the superabsorbent and the subsequent drying thereof.
- the drying gas can be added in cocurrent or in countercurrent.
- drying gas is fed in at the top of the spray tower above the addition point for the reactants.
- the liquid reactants in the droplets are converted to the superabsorbent polymer. This gives rise to superabsorbent particles having a size corresponding essentially to the size of the droplets.
- the droplets fall into a fluidized bed in the lower region of the spray tower, in which drying gas is fed in from the bottom. Further polymerization is effected in the fluidized bed.
- drying gas Since drying gas is fed in both from the top and from the bottom, there is a gas withdrawal point above the fluidized bed, in which the drying gas is drawn off from the spray tower. Since superabsorbent particles entrained in the drying gas are present, the drying gas is freed of solids present therein. For this purpose, it is possible to use, for example, cyclones and/or filters.
- the drying gas is typically circulated, it being necessary to remove a portion of the drying gas in order to keep the water content in the drying gas constant.
- this requires a lot of energy, and so this is viable only when a gas other than air, for example nitrogen, is being used as drying gas.
- air is being used as drying gas, it is possible to remove a portion from the process as offgas and, at the same time, to replace the amount removed with fresh air.
- the drying gas Before the drying gas is fed to the spray tower, either at the top or in the fluidized bed, it has to be heated to the necessary temperature.
- the above-described heat exchanger is used.
- the heat exchanger is preferably at a position in the drying gas circuit beyond the removal of the solids.
- the heating of the drying gas for the belt drier or for the spray drier is effected by heat transfer from a heat transfer medium to the drying gas in the heat exchanger.
- Suitable heat transfer media are, for example, a thermal oil, an ionic liquid, a salt melt or steam.
- a particularly preferred heat transfer medium is steam, it being possible to use either saturated steam or superheated steam.
- the heat exchanger of the invention in any other processes in which a gas has to be heated to a temperature of more than 150° C., the gas comprising constituents that are corrosive or abrasive with respect to the materials typically used for heat exchangers, and coating with zinc providing a surface which is not attacked by the constituents present in the gas, such that, firstly, no impurities are introduced into the gas by the material removed from the heat exchanger and, secondly, corrosion of the heat exchanger is prevented and hence the lifetime of the heat exchanger is extended.
Abstract
Description
- The invention proceeds from a heat exchanger for heating gas to a temperature in the range from 150 to 400° C., wherein the gas is heated by indirect heat transfer.
- Heating gas to a temperature of more than 150° C. is required, for example, when the gas is being used as drying gas. Applications of this kind are, for example, driers in superabsorbent production. Two different processes are known for production of superabsorbents: firstly production in a mixing kneader, in which case the superabsorbent thus produced is dried in a belt drier in a next step, and secondly in a spray tower, in which the monomer solution is introduced by spraying in countercurrent to a drying gas, polymerized to superabsorbent particles while falling within the spray tower and simultaneously dried.
- Especially in the case of use in superabsorbent production, standard heat exchangers have a tendency to corrosion. It is therefore necessary to protect the surfaces of the heat exchanger against corrosion. For this purpose, it is possible to manufacture the heat exchanger from stainless steel. However, this has the disadvantage that, because of the poorer thermal conductivity of stainless steel, a much larger heat exchanger is required. A further option would be production of the heat exchanger from aluminum. However, this has the disadvantage in superabsorbent production that superabsorbent particles can still be present in the gas, especially in the case of circulation of the gas, and the superabsorbent has an abrasive effect, especially with respect to aluminum, which is soft compared to steel. Alternatively, it is also possible to provide the surfaces which come into contact with the gas with a suitable coating. For this purpose, the surfaces can be provided, for example, with a zinc coating by hot dip galvanization.
- At the temperatures of more than 200° C. that occur in the heat exchanger, the zinc coating, however, has a tendency to delaminate. This effect is also known as the Kirkendall effect. This can result in detachment of zinc particles and contamination of the superabsorbent. However, this leads to an unwanted reduction in quality of the superabsorbent.
- It is therefore an object of the present invention to provide a heat exchanger which does not have the disadvantages known from the prior art.
- The object is achieved by a heat exchanger for heating gas to a temperature in the range from 150 to 400° C., wherein the gas is heated by indirect heat transfer, wherein all the surfaces of the walls of the heat exchanger which come into contact with the gas have been hot dip galvanized and the surfaces which come into contact with the gas, after the hot dip galvanization, have been heat treated at a temperature in the range from 400 to 750° C.
- It has been found that, surprisingly, as a result of the heat treatment which follows on from hot dip galvanization, the zinc coating remains stable and the Kirkendall effect does not occur even when the gas is heated to a temperature in the range from 150 to 400° C. and the coating remains undamaged. Especially when the heat exchanger is used in the production of superabsorbents, this prevents the superabsorbent particles from becoming contaminated by detachment of zinc layers.
- For production of the galvanized surface, the components of the heat exchanger to be galvanized, after an appropriate pretreatment, are first dipped into a bath of molten zinc. In the course of this, zinc accumulates on the surface of the heat exchanger and bonds to the surface. In order to obtain a stable bond and to be able to conduct a hot dip galvanization, it is necessary that the material from which the heat exchanger is manufactured is stable to the hot dip galvanization temperatures. In addition, it is necessary that good heat transfer is possible, for which the material should have a very low coefficient of heat transfer. Suitable materials are therefore especially metals. In a particularly preferred embodiment, the walls of the heat exchanger are manufactured from sheet steel.
- After the dipping and holding of the components of the heat exchanger to be galvanized in the bath of molten zinc, these components are removed from the zinc bath and cooled under air. This results in formation of a zinc-iron diffusion layer and of a pure zinc layer on the surface of the walls of the heat exchanger. The hot dip galvanization is conducted by the standard methods known to those skilled in the art.
- After the cooling and solidification of the zinc coating produced by the hot dip galvanization, the heat exchanger, in accordance with the invention, is subjected to a heat treatment at a temperature in the range from 400 to 750° C., preferably in the range from 525 to 575° C., for example at a mean component temperature of 550° C. The duration of the heat treatment at a temperature of more than 525° C. is preferably in the range from 1 to 5 min, especially in the range from 2 to 3 min.
- When the heat treatment is conducted at a temperature in the range from 400 to 450° C., the duration of the heat treatment is extended up to 90 min. At temperatures between 450° C. and 525° C., the required duration of the heat treatment should be adjusted correspondingly and decreases with increasing temperature.
- In this context, the heat treatment can be conducted in any desired furnace known to those skilled in the art. Suitable furnaces are, for example, continuous furnaces.
- The heat exchanger may have any desired design known to those skilled in the art for heat exchangers in which indirect heat transfer is effected. The gas can be heated in cocurrent, in countercurrent, in crosscurrent or in any desired combination thereof. Standard variants are, for example, cross-countercurrent or cross-cocurrent. Suitable heat exchangers are, for example, plate heat exchangers, shell and tube heat exchangers or spiral heat exchangers. Indirect heat transfer is understood to mean that heat is transferred from a hot fluid to a colder fluid, the hot fluid and the colder fluid being separated from one another by a wall. This results in heat transfer through the wall of the heat exchanger. For the heating of the gas to a temperature in the range from 150 to 400° C., the gas is the colder fluid. The hot fluid used is a suitable heat transfer medium having a temperature above the temperature to which the gas is to be heated. Suitable heat transfer media are, for example, superheated steam, a thermal oil suitable for the temperature, an ionic liquid or a salt melt. A preferred heat transfer medium is superheated steam.
- In order to obtain good heat transfer, it is preferable when the surface area which comes into contact with the gas to be heated is at a maximum. For this purpose, it is possible, for example, to provide the walls which come into contact with the gas with fins. Because of the good heat conduction of the material from which the walls are manufactured, the fins mounted on the wall are also heated. It is necessary here for the bond of the fins to the wall to have good thermal conductivity. For this purpose, the fins are preferably soldered to the wall or welded to the wall. Adhesive bonding of the fins to the wall is generally less advantageous since standard polymer-based adhesives firstly do not withstand the temperatures and polymers secondly have poorer thermal conductivity than metals, such that the effect of the increased heat transfer area as a result of the fins is only very small in the case of adhesive bonding. Attachment of the fins by screws or rivets is not advantageous either, since it cannot be ensured in this case that the fins are fully aligned with the wall. If a gap is established between wall and fin, the gas to be heated will flow through it, the gas to be heated having much poorer thermal conductivity than metal, such that the fins in these regions cannot assume the surface temperature of the wall and so the effect resulting from the fins likewise does not occur. In the case of galvanization, even zinc does generally flow into a possible gap between fins and the wall, but it cannot be ensured thereby that the gap will be closed by the galvanization.
- The invention further relates to the use of such a heat exchanger. Advantageously, the heat exchanger is used for drying superabsorbent particles.
- Superabsorbents are materials that can absorb and store several times their mass of liquid. Typically, superabsorbents are polymers based on polyacrylate or polymethacrylate, also referred to as poly(meth)acrylate hereinafter. These are typically prepared from esters of acrylic acid or methacrylic acid and suitable crosslinkers known to those skilled in the art. The reactants used for preparation of the poly(meth)acrylates and the conversion thereof in a mixing kneader is described, for example, in WO 2006/034853 A1.
- In one embodiment of the invention, the heat exchanger is used in a belt drier for drying superabsorbent particles. In this case, the superabsorbent is produced in a reactor, withdrawn from the reactor and then dried in a belt drier. The reactor used in this case is typically a mixing kneader. The reactants for production of the superabsorbent are added thereto. The reactants are converted to the superabsorbent in the mixing kneader, forming a high-viscosity mass. This mass is broken up with suitable kneading bars in the mixing kneader. The product formed is a coarse-grain material.
- This coarse-grain material is added to the belt drier. For this purpose, the superabsorbent material is distributed on a drying belt of the belt drier, and a gas is passed over it at a temperature of preferably at least 50° C., more preferably at least 100° C., even more preferably at least 150° C., and preferably up to 250° C., more preferably up to 220° C., most preferably up to 200° C. The gas used may, for example, be air or gases that are inert towards the superabsorbent material, for example nitrogen. Preference is given, however, to the use of air as drying gas.
- The drying gas is heated in the heat exchanger of the invention to the temperature required for the drying. The heat exchanger may be disposed within the belt drier, for example beneath the drying belt. Alternatively, it is also possible to position the heat exchanger outside the belt drier and feed the gas heated in the heat exchanger to the belt drier on one side, and to remove it again from the belt drier at another position and feed it back to the heat exchanger. In this case, the drying gas is conducted in a circuit. When the heat exchanger is disposed outside the belt drier, this has the advantage that a suitable particle separator can be positioned between the belt drier and heat exchanger, in order to remove entrained superabsorbent particles from the gas stream. Suitable particle separators are, for example, cyclones or filters.
- When the heat exchanger is positioned beneath the drying belt, the heated drying gas ascends and thus flows around superabsorbent particles from below. In the course of this, the gas cools down and flows back downward again, such that a gas flow in the belt drier is established. This has the advantage over a heat exchanger positioned outside the drier that no large gas flows have to be circulated with the aid of a suitable blower and conducted through the heat exchanger, since natural convection is established. A disadvantage, however, is that it is impossible to separate superabsorbent particles from the gas which flows through the heat exchanger and is heated therein.
- In both variants, however, it is necessary to remove a portion of the gas from the process, in order to remove the water absorbed in the course of drying. If all the gas is circulated, the water released in the course of drying accumulates in the gas and the water concentration becomes ever higher until effective drying is no longer possible.
- Downstream of the belt drier, the superabsorbent particles are ground and fed to a postcrosslinking operation and a drying operation. Finally, the superabsorbent particles are classified by size, for which it is customary to use a sieving machine having several sieve decks. Superabsorbent particles that are too small are introduced back into the mixing kneader, such that they mix with the superabsorbent mass which forms and sufficiently large particles can thus be produced. Superabsorbent particles that are too large are recycled into the mill and subjected once again to the grinding operation in order to comminute them further.
- In an alternative embodiment, the superabsorbent particles are produced in a spray tower. For this purpose, the reactants used for the production of the superabsorbents are first mixed and then dropletized in a spray tower, producing droplets having a size which is chosen such that the superabsorbent particles formed in the spray tower from the droplets by reaction of the reactants meet the desired specification.
- In the spray tower, the droplets fall from the top downward, while a drying gas is fed in simultaneously. This drying gas has been heated to a temperature required for the production of the superabsorbent and the subsequent drying thereof. The drying gas can be added in cocurrent or in countercurrent. Typically, drying gas is fed in at the top of the spray tower above the addition point for the reactants. During the fall, the liquid reactants in the droplets are converted to the superabsorbent polymer. This gives rise to superabsorbent particles having a size corresponding essentially to the size of the droplets. The droplets fall into a fluidized bed in the lower region of the spray tower, in which drying gas is fed in from the bottom. Further polymerization is effected in the fluidized bed. Since drying gas is fed in both from the top and from the bottom, there is a gas withdrawal point above the fluidized bed, in which the drying gas is drawn off from the spray tower. Since superabsorbent particles entrained in the drying gas are present, the drying gas is freed of solids present therein. For this purpose, it is possible to use, for example, cyclones and/or filters.
- The drying gas is typically circulated, it being necessary to remove a portion of the drying gas in order to keep the water content in the drying gas constant. Alternatively, it is also possible first to condense the moisture out of the drying gas and then to reheat the drying gas. However, this requires a lot of energy, and so this is viable only when a gas other than air, for example nitrogen, is being used as drying gas. When air is being used as drying gas, it is possible to remove a portion from the process as offgas and, at the same time, to replace the amount removed with fresh air.
- Before the drying gas is fed to the spray tower, either at the top or in the fluidized bed, it has to be heated to the necessary temperature. For this purpose, the above-described heat exchanger is used. In order to avoid damage as a result of abrasion because of the superabsorbent particles entrained by the drying gas, the heat exchanger is preferably at a position in the drying gas circuit beyond the removal of the solids.
- The heating of the drying gas for the belt drier or for the spray drier is effected by heat transfer from a heat transfer medium to the drying gas in the heat exchanger. Suitable heat transfer media are, for example, a thermal oil, an ionic liquid, a salt melt or steam. A particularly preferred heat transfer medium is steam, it being possible to use either saturated steam or superheated steam.
- As well as use for heating the drying gas used in superabsorbent production, it is also possible to use the heat exchanger of the invention in any other processes in which a gas has to be heated to a temperature of more than 150° C., the gas comprising constituents that are corrosive or abrasive with respect to the materials typically used for heat exchangers, and coating with zinc providing a surface which is not attacked by the constituents present in the gas, such that, firstly, no impurities are introduced into the gas by the material removed from the heat exchanger and, secondly, corrosion of the heat exchanger is prevented and hence the lifetime of the heat exchanger is extended.
Claims (13)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP15202312 | 2015-12-23 | ||
EP15202312.3 | 2015-12-23 | ||
PCT/EP2016/082073 WO2017108888A1 (en) | 2015-12-23 | 2016-12-21 | Heat exchanger for heating gas and use of the heat exchanger |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2016/082073 A-371-Of-International WO2017108888A1 (en) | 2015-12-23 | 2016-12-21 | Heat exchanger for heating gas and use of the heat exchanger |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US17/688,032 Continuation US11933552B2 (en) | 2015-12-23 | 2022-03-07 | Heat exchanger for heating gas and use of the heat exchanger |
Publications (1)
Publication Number | Publication Date |
---|---|
US20190003789A1 true US20190003789A1 (en) | 2019-01-03 |
Family
ID=55077361
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US16/064,021 Abandoned US20190003789A1 (en) | 2015-12-23 | 2016-12-21 | Heat exchanger for heating gas and use of the heat exchanger |
US17/688,032 Active US11933552B2 (en) | 2015-12-23 | 2022-03-07 | Heat exchanger for heating gas and use of the heat exchanger |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US17/688,032 Active US11933552B2 (en) | 2015-12-23 | 2022-03-07 | Heat exchanger for heating gas and use of the heat exchanger |
Country Status (6)
Country | Link |
---|---|
US (2) | US20190003789A1 (en) |
EP (1) | EP3394310B1 (en) |
JP (1) | JP6877436B2 (en) |
KR (1) | KR20180097578A (en) |
CN (1) | CN108541274B (en) |
WO (1) | WO2017108888A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11154832B2 (en) | 2017-05-31 | 2021-10-26 | Basf Se | Fluidizing plate and apparatus comprising such a fluidizing plate |
US11933552B2 (en) | 2015-12-23 | 2024-03-19 | Basf Se | Heat exchanger for heating gas and use of the heat exchanger |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE202018102525U1 (en) * | 2018-05-07 | 2019-08-13 | Ram Engineering + Anlagenbau Gmbh | Heat exchanger arrangement for immersion bath in hot dip galvanizing |
CN114935247B (en) * | 2022-03-25 | 2023-09-05 | 重庆和创简一科技有限公司 | Intelligent pulse type airflow grain drying equipment |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4971842A (en) * | 1987-02-27 | 1990-11-20 | Rasmet Ky | Method for controlling the thickness of an intermetallic layer on a continuous steel product in a continuous hot-dip galvanizing process |
US5042574A (en) * | 1989-09-12 | 1991-08-27 | Modine Manufacturing Company | Finned assembly for heat exchangers |
US6177140B1 (en) * | 1998-01-29 | 2001-01-23 | Ispat Inland, Inc. | Method for galvanizing and galvannealing employing a bath of zinc and aluminum |
US20020152630A1 (en) * | 2001-04-20 | 2002-10-24 | Lindsay Jeffrey Dean | Systems for tissue dried with metal bands |
US20060235141A1 (en) * | 2003-04-03 | 2006-10-19 | Ulrich Riegel | Mixtures of compounds comprising at least two double bonds and use thereof |
DE102008033222A1 (en) * | 2008-07-15 | 2010-01-21 | Behr Gmbh & Co. Kg | Producing a part of a heat exchanger comprising aluminum and/or aluminum alloy and having a corrosion protected surface, comprises applying zinc or zinc-containing layer to the surface or part of the surface |
US20110059329A1 (en) * | 2009-09-04 | 2011-03-10 | Basf Se | Water-Absorbent Polymer Particles |
US20170037520A1 (en) * | 2014-04-22 | 2017-02-09 | Green Future Ltd. | Method and formulations for removing rust and scale from steel and for regenerating pickling liquor in hot-dip galvanization process |
US10208170B2 (en) * | 2012-11-21 | 2019-02-19 | Basf Se | Process for producing surface-postcrosslinked water-absorbent polymer particles |
Family Cites Families (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2326418A1 (en) * | 1973-05-24 | 1974-12-12 | Gea Luftkuehler Happel Gmbh | Heat treating ribbed tubes - for improving adhesion of zinc dip coatings |
US4891275A (en) * | 1982-10-29 | 1990-01-02 | Norsk Hydro A.S. | Aluminum shapes coated with brazing material and process of coating |
NO177405C (en) * | 1993-03-04 | 1995-09-06 | Sinvent As | Process and apparatus for drying materials containing volatile constituents |
DE4319828A1 (en) * | 1993-06-16 | 1994-12-22 | Henkel Kgaa | Modified drying process using superheated steam in the drying medium and its application |
US6276872B1 (en) * | 1999-10-22 | 2001-08-21 | Envirosolve Corporation | Low temperature heat-assisted evaporation impoundment |
EP1796823B1 (en) | 2004-09-28 | 2009-07-22 | Basf Se | Kneader mixer and method for the production of poly(meth)acrylates using said kneader mixer |
JP5553611B2 (en) * | 2007-01-16 | 2014-07-16 | ビーエーエスエフ ソシエタス・ヨーロピア | Production of superabsorbent polymer |
DE102008000237A1 (en) * | 2007-02-06 | 2008-08-07 | Basf Se | Mixtures, useful e.g. as an inhibitor or retarder for the stabilization of polymerizable compound, preferably swellable hydrogel-forming polymers, comprises a phenol imidazole derivative and a polymerizable compound |
CN102459368B (en) * | 2009-06-03 | 2014-08-27 | 巴斯夫欧洲公司 | Method for producing water-absorbing polymer particles |
CN101702333B (en) * | 2009-11-05 | 2013-05-29 | 周宏伟 | Compound copper conductor with decoration and antiseptic effect and manufacturing method thereof |
EP2539382B1 (en) * | 2010-02-24 | 2014-10-22 | Basf Se | Method for producing water-absorbing polymer particles |
BR112012023789B8 (en) * | 2010-03-24 | 2021-07-27 | Basf Se | process for removing residual monomers from water absorbent polymeric particles |
EP2550306B1 (en) * | 2010-03-24 | 2014-07-02 | Basf Se | A process for producing water-absorbent polymer particles by polymerizing droplets of a monomer solution |
EP2620466B1 (en) * | 2012-01-27 | 2014-09-10 | Evonik Degussa GmbH | Heat-treatment of water-absorbing polymeric particles in a fluidized bed |
US10005064B2 (en) * | 2013-11-22 | 2018-06-26 | Basf Se | Process for producing water-absorbing polymer particles |
AT14471U1 (en) * | 2014-03-06 | 2015-11-15 | Lasco Heutechnik Gmbh | furnace |
US20150299882A1 (en) * | 2014-04-18 | 2015-10-22 | Lam Research Corporation | Nickel electroplating systems having a grain refiner releasing device |
US11150037B2 (en) * | 2014-10-10 | 2021-10-19 | Baltimore Aircoil Company, Inc. | Heat exchange apparatus |
CN108541274B (en) | 2015-12-23 | 2021-01-15 | 巴斯夫欧洲公司 | Heat exchanger for heating a gas and use of the heat exchanger |
-
2016
- 2016-12-21 CN CN201680076130.0A patent/CN108541274B/en active Active
- 2016-12-21 EP EP16825390.4A patent/EP3394310B1/en active Active
- 2016-12-21 WO PCT/EP2016/082073 patent/WO2017108888A1/en active Application Filing
- 2016-12-21 KR KR1020187017695A patent/KR20180097578A/en active IP Right Grant
- 2016-12-21 US US16/064,021 patent/US20190003789A1/en not_active Abandoned
- 2016-12-21 JP JP2018533056A patent/JP6877436B2/en active Active
-
2022
- 2022-03-07 US US17/688,032 patent/US11933552B2/en active Active
Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4971842A (en) * | 1987-02-27 | 1990-11-20 | Rasmet Ky | Method for controlling the thickness of an intermetallic layer on a continuous steel product in a continuous hot-dip galvanizing process |
US5042574A (en) * | 1989-09-12 | 1991-08-27 | Modine Manufacturing Company | Finned assembly for heat exchangers |
US6177140B1 (en) * | 1998-01-29 | 2001-01-23 | Ispat Inland, Inc. | Method for galvanizing and galvannealing employing a bath of zinc and aluminum |
US20020152630A1 (en) * | 2001-04-20 | 2002-10-24 | Lindsay Jeffrey Dean | Systems for tissue dried with metal bands |
US20060235141A1 (en) * | 2003-04-03 | 2006-10-19 | Ulrich Riegel | Mixtures of compounds comprising at least two double bonds and use thereof |
DE102008033222A1 (en) * | 2008-07-15 | 2010-01-21 | Behr Gmbh & Co. Kg | Producing a part of a heat exchanger comprising aluminum and/or aluminum alloy and having a corrosion protected surface, comprises applying zinc or zinc-containing layer to the surface or part of the surface |
US20110059329A1 (en) * | 2009-09-04 | 2011-03-10 | Basf Se | Water-Absorbent Polymer Particles |
US10208170B2 (en) * | 2012-11-21 | 2019-02-19 | Basf Se | Process for producing surface-postcrosslinked water-absorbent polymer particles |
US20170037520A1 (en) * | 2014-04-22 | 2017-02-09 | Green Future Ltd. | Method and formulations for removing rust and scale from steel and for regenerating pickling liquor in hot-dip galvanization process |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11933552B2 (en) | 2015-12-23 | 2024-03-19 | Basf Se | Heat exchanger for heating gas and use of the heat exchanger |
US11154832B2 (en) | 2017-05-31 | 2021-10-26 | Basf Se | Fluidizing plate and apparatus comprising such a fluidizing plate |
Also Published As
Publication number | Publication date |
---|---|
WO2017108888A1 (en) | 2017-06-29 |
JP6877436B2 (en) | 2021-05-26 |
US11933552B2 (en) | 2024-03-19 |
JP2019505673A (en) | 2019-02-28 |
KR20180097578A (en) | 2018-08-31 |
CN108541274A (en) | 2018-09-14 |
EP3394310B1 (en) | 2023-12-06 |
US20220187034A1 (en) | 2022-06-16 |
EP3394310A1 (en) | 2018-10-31 |
CN108541274B (en) | 2021-01-15 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US11933552B2 (en) | Heat exchanger for heating gas and use of the heat exchanger | |
US3231413A (en) | Method and apparatus for granulating melted solid and hardenable fluid products | |
KR101475549B1 (en) | Method for the production of polyester granules low in hydrolysis made of high-viscosity polyester melts, and device for the production of the polyester granules | |
JP5676471B2 (en) | Process and system for producing silicon tetrafluoride from fluorosilicate in a fluidized bed reactor | |
TWI415826B (en) | Distillative workup of acetone cyanohydrin and process for preparing methacrylate and conversion products | |
TW200902495A (en) | Process for adsorptively purifying alkyl methacrylates | |
EP2431697A1 (en) | Device for recovering heat of molten slag | |
CN109110813B (en) | Method for preparing multi-valence vanadium oxide by dynamic calcination | |
JP7197732B2 (en) | Treatment of offgas from urea finishing | |
JP2018016516A (en) | Method for producing nickel oxide and fluidized roasting furnace | |
TWI657859B (en) | Regeneration method of carbon dioxide absorbent material | |
AT504996B1 (en) | METHOD AND DEVICE FOR DRYING CRYSTALLINE CARBOXYLIC ACIDS | |
CN1040831C (en) | Making dry coffee aroma gas with improved aroma charactics | |
RU2016150937A (en) | PRODUCTS FROM GRANULATED SLAG AND METHODS OF PRODUCING THEM | |
UA121333C2 (en) | Process and system for thermal treatment of granular solids | |
CN106504976B (en) | The cleaning method of reflux board cavity | |
JP4363940B2 (en) | Method for removing vinyl chloride monomer from vinyl chloride resin slurry | |
JP6942942B2 (en) | Nickel oxide manufacturing method, fluid roasting furnace | |
JPH0138844B2 (en) | ||
CN108187436A (en) | A kind of method of the dry method quenching removing and recycling of arsenic in flue gas during smelting | |
RU2460579C2 (en) | Method of producing granular calcium chloride | |
JPS62170411A (en) | Converter exhaust gas treatment device | |
RU2520453C2 (en) | Plant for feed thermal treatment and coke cooling | |
CN103980952A (en) | Gas generator with dry distillation section single exit and gas purifying, cooling and oil-water separation process thereof | |
JPS60118609A (en) | Removal and purification of dust in sulfur compound- containing gas |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: BASF SE, GERMANY Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WEISMANTEL, MATTHIAS;SCHNEIDER, KARL-FRIEDRICH;STEPHAN, OSKAR;SIGNING DATES FROM 20170130 TO 20170209;REEL/FRAME:046137/0017 |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NON FINAL ACTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NON FINAL ACTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: FINAL REJECTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NON FINAL ACTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: FINAL REJECTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: ADVISORY ACTION MAILED |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |