CA1136563A - Crystallization via porous tube heat transfer - Google Patents
Crystallization via porous tube heat transferInfo
- Publication number
- CA1136563A CA1136563A CA000351254A CA351254A CA1136563A CA 1136563 A CA1136563 A CA 1136563A CA 000351254 A CA000351254 A CA 000351254A CA 351254 A CA351254 A CA 351254A CA 1136563 A CA1136563 A CA 1136563A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- wax
- porous
- crystallization
- chilled liquid
- 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.)
- Expired
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
- F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
- F28D21/0015—Heat and mass exchangers, e.g. with permeable walls
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/0004—Crystallisation cooling by heat exchange
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/005—Selection of auxiliary, e.g. for control of crystallisation nuclei, of crystal growth, of adherence to walls; Arrangements for introduction thereof
-
- 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
- F28F19/008—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using scrapers
Abstract
S-78-089 Chaunce/McGinley INVENTORS: RICHARD W. CHAUNCE
803 Joeck Drive West Chester, Chester County Commonwealth of Pennsylvania, 19380 THOMAS J. MCGINLEY
1110 N. Dolton Court Darley Woods Wilmington, New Castle County State of Delaware, 19810 TITLE OF THE INVENTION: CRYSTALLIZATION VIA POROUS
TUBE HEAT TRANSFER
ABSTRACT OF THE DISCLOSURE
In crystallization units such as wax crystallization units where a scraped surface double pipe heat exchanger type chiller is used, the improvement of replacing the scraped surface chiller tube with a porous tube to provide positive flow of coolant through the tube wan to prevent crystal deposition on the process side of the tube, whereby crystal degradation is eliminated and increased filter rate is obtained.
803 Joeck Drive West Chester, Chester County Commonwealth of Pennsylvania, 19380 THOMAS J. MCGINLEY
1110 N. Dolton Court Darley Woods Wilmington, New Castle County State of Delaware, 19810 TITLE OF THE INVENTION: CRYSTALLIZATION VIA POROUS
TUBE HEAT TRANSFER
ABSTRACT OF THE DISCLOSURE
In crystallization units such as wax crystallization units where a scraped surface double pipe heat exchanger type chiller is used, the improvement of replacing the scraped surface chiller tube with a porous tube to provide positive flow of coolant through the tube wan to prevent crystal deposition on the process side of the tube, whereby crystal degradation is eliminated and increased filter rate is obtained.
Description
~136S63 Wax crystallization processes are well known in the art and the most common systems employ scraped surface double pipe (e.g. concentric tubesl heat exchangers to crystallize the wax from a wax-oil-solvent mixture. In such systems crystal degradation of the crystallized wax frequently occurs due to the shearing action of the scrapers. This, in turn, adversely affects the filtration rate on filters downstream of the crystallizer because of filter plugging by the smaller, degraded crystals. A similar problem is present also in the crystallization of other materials where similar equipment is used (e.g. p-xylene crystallization).
A novel technique and apparatus has now been found to remedy such crystallization problems wherein a scraper no longer is employed. In accord with the invention which is il-lustrated by reference to wax crystallization, a process for crystallization of wax from a solvent is provided by chilling a wax-oil-solvent solution flowing through a heat exchanger of the double pipe type or a shell and tube bundle type comprising a conduit which is porous to the chilling fluid surrounding the conduit and wherein the chilling fluid is maintained at a positive pressure sufficient to force it through the conduit, whereby when the wax crystallizes from the wax-oil-solvent solution it does not adhere to the wall of the conduit and wax crystal degradation is avoided.
With reference to the drawings:
Figure 1 is a schematic side elevational view of a 12 section chilling unit (e.g. crystallizer) utilizing the porous tube of the invention.
Figure 2 is a schematic side elevational view of a 12 section chilling unit shown in Figure 1.
Figure 3 is a sectional plan view, taken on the line 3-3 of Figure 1 showing the installation of the porous tubing
A novel technique and apparatus has now been found to remedy such crystallization problems wherein a scraper no longer is employed. In accord with the invention which is il-lustrated by reference to wax crystallization, a process for crystallization of wax from a solvent is provided by chilling a wax-oil-solvent solution flowing through a heat exchanger of the double pipe type or a shell and tube bundle type comprising a conduit which is porous to the chilling fluid surrounding the conduit and wherein the chilling fluid is maintained at a positive pressure sufficient to force it through the conduit, whereby when the wax crystallizes from the wax-oil-solvent solution it does not adhere to the wall of the conduit and wax crystal degradation is avoided.
With reference to the drawings:
Figure 1 is a schematic side elevational view of a 12 section chilling unit (e.g. crystallizer) utilizing the porous tube of the invention.
Figure 2 is a schematic side elevational view of a 12 section chilling unit shown in Figure 1.
Figure 3 is a sectional plan view, taken on the line 3-3 of Figure 1 showing the installation of the porous tubing
-2-` 113~563 of the invention.
Figure 4 ~s an enlarged transverse sectional view through a heat transfer tube, taken on the line 4-4 of Figure
Figure 4 ~s an enlarged transverse sectional view through a heat transfer tube, taken on the line 4-4 of Figure
3.
Figure 5 is a greatly enlarged fragmentary sectional view of the details enclosed ~y the dot and dash box of Figure 4.
In Figure 1, the flow o~ refrigerant through the heat exchange tubes is shown. The liquid refrigerant flows from a storage tank ll through line 12 and heated 12a to enter the shell side of the heat exhanger through lines 12b and exit the heat exchanger through lines 12c (see Figure 3). The solvent solution of wax and oil enters the system at 13 (Figures 1 and 3), flows through the porous tubes 14 within the shells, being conducted from tube to tube by means of elbows 15, and exits from the system at 13a. The refrigerant is conducted through headers 12 an stated and exits the system at 12d (Figure 1) usually in the vapor state as it returns to the stoarage tank 11 .
Referring now to Figure 4, the chilling liquid 16 circulates through shell 17 and effects precepitation of wax 18 from wax-oil-s~lvent solution l9 which flows within porous tube 14. As ~ls in m~re detail in Figure 5, as the refrigerant liquid 16 5CCpS through pcrous tube 14, it forms a fluid layer 20 (liquid or gas dep3~ing on the refigerant and temperature) adjacent the inside wall of the p~rous tube and this fluid layer 20 serves to prevent wax particles 18 from adhering to the tu~e's surface. Thus, the wax is effectively removed from solution-w~thout wax build-up.
The porous conduit used in the apparatus will have, prefera~ly, as shown, a circular cross-section and be concentric with an outer conduit also preferably of circular cross-section, ~lthou~, of course, conduits of other cross-section configura-. . . ~, tions may be used. The inside porous conduit mav be made of any of numerous materials and a preferred material will be a sintered metal, which materials are made by the techniques of powder metallurgy and are known to have porosity for vapor and liquids (see for example the Kirk-Othmer "Encyclopedia of Chemical Tech-nology", Vol. lb, pages 401-402, 415-418, and 425-426). Typical sintered metals useful are sintered brass, bronze, iron, copper, stainless steel and the like and are commercially available.
Sintered stainless steel is a preferred material as it is easier - 10 to handle in constructing the heat exchanger for the system; e.g.
it is readily welded and therefore the unit can be constructed without the need for gaskets which tend to leak. Other preferred materials are laminated alloys having microscopic holes such as "Lamilloy" which is a product of General Motors corporation.
Other useful materials include ceramic materials (e.g. a porous alumina, porous graphite~, and the like. The chilling liquid flowing through the porous conduit may be a refrigerant or even chilled solvent. If the chilling liquid is a refrigerant, a material such as propane, liquid ammonia or other conventional refrigerant will be used. As the refrigerant passes through the porous conduit wall it vaporizes to some extent and provides a vapor film adjacent the outer wall of the porous conduit, thus preventing precipitated wax from adhering to the wall. In the event that vaporization does not occur, or to the extent that it is incomplete, a liquid film is formed along the external wall of of the conduit. Similarly, if a solvent material such as acetone, methylethylketone, methylisobutylketone, or other typical ketone or other solvent is used as chilling fluid, the liquid passes through the porous conduit and forms a fluid film on the wall surface to prevent wax adherence.
As indicated the chilling liquid is under sufficient positive pressure to force it through the wall of the porous X ~4~
:1~36563 conduit. The pressure need not he Very great, only sufficient to provide a fil~ of the refrigerant or its vapor on the inside wall of the conduit. Usually the pressure differential of the chil-ling liquid will be on the order of about 5 to about 50 psig, preferably about 20 psig, the actual pressure difference depending, of course, on the specific type of conduit and chilling liquid used. In order to achieve and maintain this pressure it may be helpful to provide one or more pumps in the lines through which refrigerant passes (not shown on drawings).
As the wax crystallizes from its solvent solution a wax-oil-solvent slurry is formed which is readily filtered by means of conventional filtration equipment to separate the wax crystals.
This wax, either as slack wax or deoiled wax, as it is known in the art, is, of course, subsequently handled in the usual manner (typically filtration or centrifugation)to obtain the desired wax product. The filtrate from the wax filtration will, of course, contain both the wax solvent and the chilling liquid and these components are readily separated by conventional techniques (e.g. distillation) and recycled to the system. Also not shown in the drawings but of possible benefit to the system is a mixer (say of the screw or static type) concentric with the inner tubular conduit to effect mixing of the wax crystals in the wax-oil-solvent slurry and provide a thoroughly mixed system which is fed to the filters.
~ -5-
Figure 5 is a greatly enlarged fragmentary sectional view of the details enclosed ~y the dot and dash box of Figure 4.
In Figure 1, the flow o~ refrigerant through the heat exchange tubes is shown. The liquid refrigerant flows from a storage tank ll through line 12 and heated 12a to enter the shell side of the heat exhanger through lines 12b and exit the heat exchanger through lines 12c (see Figure 3). The solvent solution of wax and oil enters the system at 13 (Figures 1 and 3), flows through the porous tubes 14 within the shells, being conducted from tube to tube by means of elbows 15, and exits from the system at 13a. The refrigerant is conducted through headers 12 an stated and exits the system at 12d (Figure 1) usually in the vapor state as it returns to the stoarage tank 11 .
Referring now to Figure 4, the chilling liquid 16 circulates through shell 17 and effects precepitation of wax 18 from wax-oil-s~lvent solution l9 which flows within porous tube 14. As ~ls in m~re detail in Figure 5, as the refrigerant liquid 16 5CCpS through pcrous tube 14, it forms a fluid layer 20 (liquid or gas dep3~ing on the refigerant and temperature) adjacent the inside wall of the p~rous tube and this fluid layer 20 serves to prevent wax particles 18 from adhering to the tu~e's surface. Thus, the wax is effectively removed from solution-w~thout wax build-up.
The porous conduit used in the apparatus will have, prefera~ly, as shown, a circular cross-section and be concentric with an outer conduit also preferably of circular cross-section, ~lthou~, of course, conduits of other cross-section configura-. . . ~, tions may be used. The inside porous conduit mav be made of any of numerous materials and a preferred material will be a sintered metal, which materials are made by the techniques of powder metallurgy and are known to have porosity for vapor and liquids (see for example the Kirk-Othmer "Encyclopedia of Chemical Tech-nology", Vol. lb, pages 401-402, 415-418, and 425-426). Typical sintered metals useful are sintered brass, bronze, iron, copper, stainless steel and the like and are commercially available.
Sintered stainless steel is a preferred material as it is easier - 10 to handle in constructing the heat exchanger for the system; e.g.
it is readily welded and therefore the unit can be constructed without the need for gaskets which tend to leak. Other preferred materials are laminated alloys having microscopic holes such as "Lamilloy" which is a product of General Motors corporation.
Other useful materials include ceramic materials (e.g. a porous alumina, porous graphite~, and the like. The chilling liquid flowing through the porous conduit may be a refrigerant or even chilled solvent. If the chilling liquid is a refrigerant, a material such as propane, liquid ammonia or other conventional refrigerant will be used. As the refrigerant passes through the porous conduit wall it vaporizes to some extent and provides a vapor film adjacent the outer wall of the porous conduit, thus preventing precipitated wax from adhering to the wall. In the event that vaporization does not occur, or to the extent that it is incomplete, a liquid film is formed along the external wall of of the conduit. Similarly, if a solvent material such as acetone, methylethylketone, methylisobutylketone, or other typical ketone or other solvent is used as chilling fluid, the liquid passes through the porous conduit and forms a fluid film on the wall surface to prevent wax adherence.
As indicated the chilling liquid is under sufficient positive pressure to force it through the wall of the porous X ~4~
:1~36563 conduit. The pressure need not he Very great, only sufficient to provide a fil~ of the refrigerant or its vapor on the inside wall of the conduit. Usually the pressure differential of the chil-ling liquid will be on the order of about 5 to about 50 psig, preferably about 20 psig, the actual pressure difference depending, of course, on the specific type of conduit and chilling liquid used. In order to achieve and maintain this pressure it may be helpful to provide one or more pumps in the lines through which refrigerant passes (not shown on drawings).
As the wax crystallizes from its solvent solution a wax-oil-solvent slurry is formed which is readily filtered by means of conventional filtration equipment to separate the wax crystals.
This wax, either as slack wax or deoiled wax, as it is known in the art, is, of course, subsequently handled in the usual manner (typically filtration or centrifugation)to obtain the desired wax product. The filtrate from the wax filtration will, of course, contain both the wax solvent and the chilling liquid and these components are readily separated by conventional techniques (e.g. distillation) and recycled to the system. Also not shown in the drawings but of possible benefit to the system is a mixer (say of the screw or static type) concentric with the inner tubular conduit to effect mixing of the wax crystals in the wax-oil-solvent slurry and provide a thoroughly mixed system which is fed to the filters.
~ -5-
Claims (7)
1. In the process of crystallizing a material from a solvent solution by conducting said solution through a heat exchanger of the double pipe or shell and tube bundle type where-in a chilled liquid surrounds the solution flowing through a tube to crystallize said material, the improvement of constructing said tube of a material porous to said chilled liquid and main-taining said chilled liquid under a positive pressure, whereby said liquid flows through the walls of said tube and forms a fluid layer to prevent crystallized material from adhering to the sur-face of said tube.
2. In the process of crystallizing wax from a wax-oil-solvent solution by conducting said wax solution through a heat exchanger of the double pipe or shell and tube bundle type wherein a chilled liquid surrounds the wax solution flowing through a tube to precipitate said wax, the improvement of constructing said tube of a material porous to said chilled liquid and main-taining said chilled liquid under a positive pressure, whereby said liquid flows through the walls of said tube and forms a fluid layer to prevent precipitated wax from adhering to the surface of said tube.
3. The process of Claim 2 wherein the heat ex-changer is of the double pipe type.
4. The process of Claim 2 wherein the heat ex-changer is of the shell and tube bundle type.
5. The process of Claim 2 wherein the porous tube is made from a sintered metal.
6. The process of Claim 5 wherein the porous tube is made of stainless steel.
7. The process of Claim 5 wherein the porous tube is made of a ceramic material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/044,292 US4252549A (en) | 1979-05-31 | 1979-05-31 | Crystallization via porous tube heat transfer |
| US44,292 | 1979-05-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1136563A true CA1136563A (en) | 1982-11-30 |
Family
ID=21931552
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000351254A Expired CA1136563A (en) | 1979-05-31 | 1980-05-05 | Crystallization via porous tube heat transfer |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4252549A (en) |
| JP (1) | JPS55162306A (en) |
| BE (1) | BE883339A (en) |
| CA (1) | CA1136563A (en) |
| DE (1) | DE3020650A1 (en) |
| FR (1) | FR2457705A1 (en) |
| GB (1) | GB2053964B (en) |
| IT (1) | IT1130752B (en) |
| NL (1) | NL8002934A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0859235A1 (en) * | 1997-02-14 | 1998-08-19 | Bp Chemicals S.N.C. | Analytical system |
| EP0892033A1 (en) * | 1997-07-16 | 1999-01-20 | Sulzer Chemtech AG | Process and device for the production of paraffin and paraffin fractions |
| US8272431B2 (en) * | 2005-12-27 | 2012-09-25 | Caterpillar Inc. | Heat exchanger using graphite foam |
| DE102007020671A1 (en) | 2007-05-01 | 2008-11-06 | Justus-Liebig-Universität Giessen | Growth of inorganic, organic, bioorganic or biological object e.g. tissue or embryos from saturated/supersaturated nutrient solution, comprises flowing growth object in flow direction of the solution and then regulating the flow direction |
| US8069912B2 (en) | 2007-09-28 | 2011-12-06 | Caterpillar Inc. | Heat exchanger with conduit surrounded by metal foam |
| US11358878B2 (en) | 2016-11-14 | 2022-06-14 | William H. Mitchell, JR. | Systems and methods for separating soluble solutions |
| CN106895624B (en) * | 2017-04-17 | 2022-10-18 | 广州高菱机电工程有限公司 | Device for preventing ice crystals from spreading in supercooled water flow and ice making method |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR723926A (en) * | 1930-12-22 | 1932-04-18 | Vessel walls for solutions separating crystals | |
| US2137373A (en) * | 1936-09-29 | 1938-11-22 | Vogt & Co Inc Henry | Double pipe chiller |
| US2224109A (en) * | 1938-07-02 | 1940-12-03 | Sun Oil Co | Process for dewaxing petroleum oils |
| DE702607C (en) * | 1938-11-02 | 1941-02-12 | Meyer Fa Rud Otto | Device to prevent and eliminate crystal deposits on overflow pipes |
| US2898271A (en) * | 1954-07-06 | 1959-08-04 | Phillips Petroleum Co | Crystal purification apparatus |
| US3702658A (en) * | 1971-02-24 | 1972-11-14 | Du Pont | Permeation separation apparatus |
| US3846279A (en) * | 1972-09-18 | 1974-11-05 | Marathon Oil Co | Method for making and slurrying wax beads |
| NL52674C (en) * | 1973-11-02 |
-
1979
- 1979-05-31 US US06/044,292 patent/US4252549A/en not_active Expired - Lifetime
-
1980
- 1980-05-05 CA CA000351254A patent/CA1136563A/en not_active Expired
- 1980-05-14 FR FR8010838A patent/FR2457705A1/en active Granted
- 1980-05-16 BE BE0/200645A patent/BE883339A/en not_active IP Right Cessation
- 1980-05-21 NL NL8002934A patent/NL8002934A/en not_active Application Discontinuation
- 1980-05-23 IT IT22306/80A patent/IT1130752B/en active
- 1980-05-27 JP JP6969380A patent/JPS55162306A/en active Granted
- 1980-05-30 GB GB8017742A patent/GB2053964B/en not_active Expired
- 1980-05-30 DE DE19803020650 patent/DE3020650A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE3020650A1 (en) | 1980-12-11 |
| NL8002934A (en) | 1980-12-02 |
| FR2457705B1 (en) | 1984-11-30 |
| US4252549A (en) | 1981-02-24 |
| IT1130752B (en) | 1986-06-18 |
| JPS55162306A (en) | 1980-12-17 |
| JPS6348561B2 (en) | 1988-09-29 |
| GB2053964B (en) | 1983-01-26 |
| IT8022306A0 (en) | 1980-05-23 |
| BE883339A (en) | 1980-11-17 |
| DE3020650C2 (en) | 1988-07-14 |
| GB2053964A (en) | 1981-02-11 |
| FR2457705A1 (en) | 1980-12-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |