EP0744587A1 - Graphitwärmetauscher mit Siliziumkarbid-Einschubrohren und Fluorpolymerbeschichtung - Google Patents

Graphitwärmetauscher mit Siliziumkarbid-Einschubrohren und Fluorpolymerbeschichtung Download PDF

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Publication number
EP0744587A1
EP0744587A1 EP96107387A EP96107387A EP0744587A1 EP 0744587 A1 EP0744587 A1 EP 0744587A1 EP 96107387 A EP96107387 A EP 96107387A EP 96107387 A EP96107387 A EP 96107387A EP 0744587 A1 EP0744587 A1 EP 0744587A1
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EP
European Patent Office
Prior art keywords
heat exchange
exchange assembly
service
tubes
silicon carbide
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Application number
EP96107387A
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English (en)
French (fr)
Inventor
John R. Ayers Iii.
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CARBONE OF AMERICA IND CORP
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CARBONE OF AMERICA IND CORP
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Publication of EP0744587A1 publication Critical patent/EP0744587A1/de
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
    • F28F9/02—Header boxes; End plates
    • F28F9/0236—Header boxes; End plates floating elements
    • F28F9/0241—Header boxes; End plates floating elements floating end plates
    • 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
    • F28F19/04—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings of rubber; of plastics material; of varnish
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
    • F28F21/02—Constructions of heat-exchange apparatus characterised by the selection of particular materials of carbon, e.g. graphite
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
    • F28F21/04—Constructions of heat-exchange apparatus characterised by the selection of particular materials of ceramic; of concrete; of natural stone

Definitions

  • the present invention relates generally to heat exchangers and, more specifically, to a heat exchange assembly which contains a plurality of bores having silicon carbide tube inserts and which has a fluoropolymer coating deposited on certain external surfaces of the heat exchange assembly and on the ends of the silicon carbide inserts.
  • Heat exchange assemblies in which two or more fluids at differing temperatures exchange heat to raise the temperature of one fluid and to lower the temperature of the other.
  • Heat exchange assemblies are generally constructed of a container or shell and a core member positioned within the shell.
  • a first fluid is introduced into the shell, passes through or around the core member, and exits out another portion of the shell.
  • a second fluid is also introduced into the shell and passes through a multiplicity of holes or passageways in the core member which are closely adjacent those bores through which the first fluid is passing.
  • the process fluid the fluid which provides the heat or absorbs heat
  • These fluids may be gases or liquids or, as in the case of steam that condenses within the core, a mixture of both.
  • heat exchange assemblies are well-known devices; they have many different applications.
  • the chemical and pharmaceutical industries use heat exchange assemblies in chemical and pharmaceutical processing.
  • a process fluid such as a battery acid (H 2 SO 4 ) in the chemical industry or an acetone in the pharmaceutical industry is processed at high temperatures.
  • a heat exchange assembly may be used to remove heat from the process fluid in a specific processing step.
  • heat exchange assemblies In the field of heat exchange assemblies, and in many other technological fields, there are ever-increasing needs for refractory structures and surfaces which are stable and which retain strength at much higher operating temperatures than previously used. Heat exchange assemblies often operate in the presence of oxidizing or reducing atmospheres, high pressures or vacuums, and other severe and unusual environments which ordinary materials of construction will not withstand. Graphite is a material which admirably satisfies many of the necessary requirements in this field. Therefore, heat exchange assemblies are often constructed of graphite components and many are formed around a single-piece graphite block or gasket assemblies of such blocks.
  • Graphite has highly desirable properties including low density, high melting or sublimation point, and high structural strength at higher temperatures. These characteristics permit graphite to be used where most other structural materials, including common metals, are unsatisfactory. The normal properties of graphite are inadequate, however, in certain respects and in particular environments. Graphite erodes and corrodes at high fluid pressures, velocities, and temperatures. Many fluids and other materials react with graphite or are absorbed in an undesirable manner in certain environments.
  • the present practice is to apply a resin to the graphite used to construct the heat exchange assembly.
  • the resin impregnates the graphite, penetrating into the porosity of the graphite block and closing off microporosity.
  • the resin renders the graphite block impermeable to process fluids.
  • the known resins e.g., phenolics
  • heat exchange assemblies incorporating resin-impregnated graphite components achieve, for example, good hydrostatic test results, the components often do not withstand steam cycle testing due to resin deterioration.
  • Silicon carbide has long been recognized as an extremely valuable refractory material. See, for example, United States Patent Number 2,784,112 issued to Nicholson in 1957. Silicon carbide is one of the hardest engineering materials, resists abrasion, and is unreactive to most chemicals. These advantageous properties have prompted the use of silicon carbide for gas turbine and nuclear reactor components and for pipes, reaction vessels, pumps, stirrers, valves and other chemical apparatus components.
  • United States Patent Number 5,323,849 issued to Korczynski et al. discloses a corrosion resistant shell-and-tube heat exchange assembly for use with corrosive fluids.
  • the heat exchange assembly uses corrosion and erosion resistant tube sheets, tubes, and a shell.
  • the reference discloses that the corrosion resistant material of the tubes may comprise, among other materials, a sintered alpha silicon carbide ceramic.
  • the tubes are secured in apertures in the tube sheets by an epoxy adhesive.
  • United States Patent Number 4,360,057 issued to Koump discloses a high-temperature, abrasion-resistant heat exchange assembly which includes a plurality of tube sheets dividing the interior of the shell into separate consecutive chambers.
  • the tubes are made from a ceramic material, preferably dense silicon carbide.
  • United States Patent Number 5,238,057 issued to Schelter et al. discloses a finned-tube heat exchange assembly in which the tubes are silicon-infiltrated silicon carbide.
  • United States Patent Number 5,036,903 issued to Shook also discloses the use of tubes comprising corrosion resistant materials such as silicon carbide. More particularly, however, Shook teaches a graphite tube condensing heat exchange assembly for recovering heat from a corrosive gas stream.
  • the reference discloses the use of polytetrafluoroethylene (PTFE) coatings to provide corrosion-resistance and recognizes that such fluoroplastics tend to be somewhat insulative if used in thicker layers on the inside surfaces of metal tubes used in prior art heat exchange assemblies.
  • PTFE polytetrafluoroethylene
  • Also disclosed is the use of a corrosion-protective coating system for side-aperatured tube sheets through which resin-impregnated graphite tubes penetrate.
  • the coating system comprises an inner silicon-carbide impregnated coating affixed to the tube sheet and a fluoroplastic layer over the silicon carbide impregnated layer.
  • This bi-layered system provides improved corrosion-protection and erosion-resistance in protecting steel tube sheets.
  • Shook teaches impregnated graphite and silicon carbide as alternative materials for the tubes of his shell-and-tube type heat exchange assembly. The two materials are not used in combination.
  • the corrosion-protective coating system is placed on the inside surface of the metal tube sheets--neither on an external surface of the heat exchange assembly nor on the tubes themselves.
  • Silicon carbide coated graphite has also been used to construct heat exchange assemblies.
  • United States Patent Number 3,250,322 issued to McCrary, Jr. discloses a corrosive fluid heat exchange assembly comprising a graphite body having walls which are coated with beta silicon carbide in order to render the heat exchange assembly fluid-impervious. Referring to Figure 1, the assembly is constructed with a metal cylindrical shell 12 with end plates 14 and 16. A plurality of graphite elements 24, 26, 28, 30, 32, and 34 are stacked within shell 12.
  • the corrosive liquid is confined to the interior of the header elements 24 and 34 and the heat exchange elements 26, 28, 30, and 32.
  • Radial bores 64 and axial bores 70 run through the heat exchange elements.
  • the bores 64 and 70, the surfaces of the header elements 24 and 34, and the surfaces of the heat exchange elements 26, 28, 30, and 32--all are uniformly coated with fluid-impervious, beta silicon carbide which protects the base material of the elements from oxidation and corrosion.
  • the silicon carbide is also extremely hard and protects the elements from abrasive wear. Although they may be tungsten or molybdenum, the header and heat exchange elements are preferably fabricated from graphite.
  • the heat exchange array 30 is shown in Figure 2 and includes a plurality of steam or fluid tubes 31A-31N coated with a non-stick material such as Teflon® (a trademark of E.I. du Pont de Nemours Company for a tetrafluoroethylene polymer).
  • a plurality of steam or fluid tubes 32A-32N are also coated with Teflon®-like material and are placed beneath 31A-31N in order to provide an exchange of heat between two flowing liquids.
  • United States Patent Number 4,669,530 issued to Warner is directed to a heat exchange assembly which is used to cool sulfur trioxide wherein the heat exchange assembly must be protected against corrosion.
  • Various fluoroplastics are used as thin coverings on the heat exchange tubes in order to prevent corrosion while allowing good heat transfer.
  • CVD Chemical vapor deposition
  • McCrary, Jr. in the '322 patent.
  • the process involves passing, in vapor form, a halide of the metal to be deposited over the graphite body at such a temperature that the halide is thermally decomposed and the metal is deposited on the surface of the graphite.
  • an improved graphite heat exchange assembly which incorporates silicon carbide tubes and a fluoropolymer coating on the tube ends and graphite surfaces is provided.
  • One object of the invention is to provide a heat exchange assembly for handling fluids which would normally corrode graphite and most metals.
  • a related object is to provide a heat exchange assembly which can handle oxidizing and other corrosive process fluids without deleterious effects on the assembly.
  • Another object is to protect the graphite heat exchange assembly from chemical attack by many chemical media of interest to the process industry.
  • a more general object is to provide a heat exchange assembly having good thermal conductivity which may be used over a wide temperature range.
  • Yet another object of this invention is to coat a graphite heat exchange assembly with a uniform, adherent coating of fluoropolymer.
  • It is still another object of the present invention to provide a heat exchange assembly with a hard, durable surface free of microporosity and able to resist corrosion and abrasion.
  • a related object is to seal off the surface porosity of the pre-machined graphite heat exchange assembly.
  • the present invention provides a graphite heat exchange assembly for efficient heat transfer between a process fluid and a service fluid.
  • the heat exchange assembly includes a thermally conductive graphite body having an external surface and a plurality of bores receiving the process fluid.
  • a plurality of passageways receive the service fluid.
  • the bores and the passageways facilitate efficient heat transfer between the process fluid and the service fluid.
  • a multiplicity of silicon carbide tubes, having exposed ends and an internal diameter, are disposed in the bores, the passageways, or both.
  • a fluoropolymer coating is applied to the external surface of the graphite body and to the ends of the silicon carbide tubes. The internal diameter of the silicon carbide tubes is maintained free of the coating.
  • Graphite heat exchange assemblies have a number of advantages which make them especially desirable for high temperature, high chemical corrosion usage. For example, graphite withstands thermal shock to a limited extent and resists chemical corrosion, with the exception of certain strong oxidizing chemicals. Moreover, graphite structures have excellent stability at elevated temperatures, as well as good thermal conductivity.
  • graphite structures which limit their use in heat exchange assemblies.
  • graphite has relatively low tensile strength so that tubes made of graphite are relatively fragile.
  • Graphite is also porous and permeable to various fluids. This permeability may be overcome by impregnating the graphite with certain synthetic resins, but this reduces the stability of the graphite-synthetic resin compositions at high temperatures.
  • the subject invention comprises a conventional graphite heat exchange assembly and incorporates two features which, in combination, protect the heat exchange assembly against corrosion.
  • tubes made of alpha silicon carbide are inserted into bores drilled in the graphite to carry the process fluid, into passageways drilled in the graphite to carry the service fluid, or both.
  • a fluoropolymer coating is deposited on certain external surfaces of the graphite heat exchange assembly and on the ends of the silicon carbide tubes. Neither feature alone will assure the increased corrosion protection and enhanced performance characteristics provided by the two features in combination.
  • silicon carbide by nature of its chemical properties and impervious nature, protects the base graphite material of the heat transfer assembly from oxidation and corrosion.
  • the silicon carbide is also extremely hard and protects the heat transfer assembly from abrasive wear caused by solids entrained in the process fluid.
  • the thermal properties of graphite and silicon carbide combine to give the heat transfer assembly good thermal conductivity.
  • the stability of silicon carbide at high temperatures and the substantially matching coefficients of thermal expansion of the graphite and silicon carbide allow the heat transfer assembly to be used at high temperatures in high thermal gradients where efficiency is maximum.
  • the silicon carbide tubes are sufficiently hard that the heat exchange assembly can by used under severe abrasive conditions and still offer a long service life.
  • the tubes of the present invention are made of alpha silicon carbide.
  • Alpha silicon carbide is very dense and virtually impervious to fluids.
  • Alpha silicon carbide tubes may be produced by pressureless sintering an ultra-pure, sub-micron powder. The powder is mixed with non-oxide sintering aids, then formed into the tube shape and consolidated by sintering at temperatures above 3632°F.
  • the sintering process results in a single-phase, fine-grain silicon carbide tube that is pure, uniform, and virtually devoid of porosity. Whether submerged in corrosive environments, subjected to extreme wear and abrasive conditions, or exposed to temperatures in excess of 2552°F, sintered alpha silicon carbide outperforms other commercially available ceramics or metal alloys--including superalloys.
  • Alpha silicon carbide tubes have extremely high strength and excellent resistance to creep and stress rupture at temperatures up to 3000°F.
  • the flexural strength (4 pt.) of sintered alpha silicon carbide is about 58,600 psi at 1500°C; the fracture toughness is about 420 X 10 3 psi/m 1/2 at 25°C, and the modulus of elasticity is about 59 X 10 6 psi at room temperature.
  • Alpha silicon carbide is one of the hardest, high-performance materials available, behind boron carbide (B 4 C), cubic crystalline boron nitride (BN), and diamond. It has a hardness (Knoop) of about 2800 kg/mm 2 at room temperature. Alpha silicon carbide weighs less than half as much as most metal alloys (40 percent as much as steel). The densities of sintered tubes are consistently in excess of 98 percent of the theoretical density of alpha silicon carbide: 3.21 g/cm 3 . The extreme hardness and density of alpha silicon carbide make it ideal for heat exchange assemblies where components are subject to high abrasion and sliding wear. The specific wear rate and coefficient of friction (both pin on disc) of silicon carbide versus silicon carbide are 1 X 10 -9 mm 2 /kg and 0.2, respectively.
  • alpha silicon carbide tubes permit them to function in environments of hot gases and liquids, in oxidizing and corrosive atmospheres, and in strong acids and bases, even at extremely high temperatures.
  • the high thermal conductivity of alpha silicon carbide combined with its low thermal expansion, produces excellent thermal-shock resistance.
  • the thermal-shock resistance is far better than tungsten carbide, aluminum oxide, and silicon nitride. These properties allow alpha silicon carbide to replace ductile metals in high-temperature heat-exchange assemblies.
  • the as-sintered surface finish of alpha silicon carbide tubes is excellent (about 64 microinches). This surface quality, combined with tight dimensional control, yields tubes that require little or no additional machining or finish grinding.
  • a fluoropolymer coating is applied to certain external graphite surfaces of the heat exchange assembly and on the ends of the silicon carbide tubes.
  • the coating is not applied inside the silicon carbide tubes because this would hinder the heat transfer across the silicon carbide tubes and through the graphite block.
  • the fluoropolymer is preferably a fluoroelastomer polymer, such as FEP, which can be applied as a coating.
  • FEP fluoroelastomer polymer
  • a suitable example FEP is NeoflonTM coating powder, available from Daikin Industries, Ltd.
  • the coating powder is a fine powder made of tetrafluoroethylene and hexafluoropropylene copolymer.
  • the coating powder is low in melt viscosity and excellent in melt fluidity; consequently, a coating film free of pinholes can be obtained.
  • This coating is ideal for use as a corrosion resistant lining, has excellent thermal and chemical resistance, and desirable anti-stick, sliding, and electric properties.
  • the fluoropolymer coating is applied to the "raw" (i.e, un-impregnated) graphite.
  • a strong and dense grade of graphite such as the assignee's grade 2020 graphite
  • a continuous, adherent, homogeneous fluoropolymer coating of substantially uniform thickness (about 3.5 ⁇ 0.5 mils) can be achieved.
  • heat exchange assemblies have relatively complex shapes, the coating is uniform over the entire area coated at all angles and positions from the vertical and so tightly adherent and tenacious that the bond cannot be disrupted without destroying the graphite interface.
  • the fluoropolymer enters the pores and crevices of the graphite and reacts in situ to seal the graphite. Consequently, problematic microporosity is minimized.
  • Sections of the graphite which are not coated with the fluoropolymer may be impregnated with a phenolic based resin or another material.
  • the fluoropolymer coating helps to seal the graphite-to-silicon carbide tube intersection and prevent leakage.
  • the service side because it is typically free of coating, is made impervious by impregnation.
  • the specific combination of three materials (graphite, alpha silicon carbide, and a fluoroelastomer polymer coating) of the present invention offers heat transfer assemblies increased corrosion resistance and permits higher design pressures.
  • Each of the three materials of construction is inert and corrosion resistant.
  • the invention may be applied equally well to all three types of conventional heat exchange assemblies: cylindrical block, rectangular or cubic block, and shell-and-tube assemblies.
  • FIGS. 1A, 1B, and 1C show top, bottom, and side views, respectively, of a conventional cylindrical block heat exchange assembly 10.
  • Cylindrical block heat exchange assembly 10 is the most versatile of the various designs because it is best suited for a wide variety of applications.
  • Cylindrical block heat exchange assembly 10 has a top compression plate 12 and a bottom compression plate 14.
  • Compression plates 12 and 14 may be made of steel or other suitable material.
  • Mounting lugs 16 are provided (preferably 180 degrees radially opposite each other) to position cylindrical block heat exchange assembly 10 in an appropriate location for removing or applying heat from or to a process fluid.
  • Lifting lugs 18 are provided, preferably 180 degrees radially opposite each other, to facilitate transport and installation of cylindrical block heat exchange assembly 10.
  • Cylindrical block heat exchange assembly 10 can be installed vertically or horizontally, in series, parallel or in combinations to any suitable framework or floor structure.
  • a nameplate bracket 22 may be provided for identification purposes.
  • the number of intermediate blocks 20 may be varied depending upon the application; twelve is a typical number.
  • Surrounding intermediate blocks 20 is a shell 24.
  • Shell 24 has a top flange 26 and a bottom flange 28.
  • Shell 24 is preferably carbon steel but can also be lined, clad, or alloyed.
  • Block gaskets 30 may be formed of Teflon® braid, neoprene rubber, or the like.
  • intermediate blocks 20 engage shell 24 using shell baffles 32.
  • Neoprene rubber is a suitable material for shell baffles 32.
  • Block gaskets 30 and shell baffles 32 may be combined to form a block gasket and shell baffle unit 34 (see FIG. 1D).
  • An axial baffle bar 35 may also be provided and may be constructed of a metal such as stainless steel. Block gaskets 30 and shell baffles 32 prevent intermediate blocks 20 from becoming cemented either together or to shell 24 and assure that cylindrical block heat exchange assembly 10 is leak tight.
  • cylindrical block heat exchange assembly 10 may be used to form the columnar graphite block used in cylindrical block heat exchange assembly 10.
  • multiple intermediate blocks 20 are often preferable to a single, monolithic block because manufacture is made easier.
  • the heat exchange surface of cylindrical block heat exchange assembly 10 can be increased by adding more intermediate blocks 20; this can be done at the site of use. Maintenance costs are low because cleaning and servicing are simplified by the ease of dismantling (and replacing, if necessary) intermediate blocks 20 on site.
  • shape of cylindrical block heat exchange assembly 10 may be cylindrical, as shown in FIG. 1C, other shapes would be suitable.
  • a floating joint 36 is placed between top compression plate 12 and top flange 26 of shell 24.
  • Springs 40 may be steel coil springs.
  • Floating flange bolting 46 is provided to connect floating header 44 to top compression plate 12 through top header flange 48. Because graphite is inherently weak in tension and strong in compression, cylindrical block heat exchange assembly 10, with its axial spring compression principle, accommodates higher design pressures. There are no cemented joints to be attacked by process fluids.
  • a fixed joint 52 is created between bottom compression plate 14 and bottom flange 28 of shell 24.
  • a plurality (typically twelve) of fixed end bolts 54, each with a nut 56, are provided to connect bottom compression plate 14 to bottom flange 28 of shell 24.
  • Fixed flange bolting 58 is provided to connect fixed header 60 to bottom compression plate 14 through bottom header flange 62.
  • Service inlet 68 and service outlet 70 Projecting radially from shell 24 are a service inlet 68 and a service outlet 70.
  • Service inlet 68 and service outlet 70 are preferably made of graphite.
  • a multiplicity of service passageways 74 are machined radially through each intermediate block 20 of graphite.
  • Intermediate blocks 20 can be impregnated with advanced polymers (such as TFE) to resist most corrosives and solvents, up to about 450°F, with the exception of certain concentrated, strong oxidizers such as HNO 3 .
  • the number and diameter of service passageways 74 provided depends upon the application. For purposes of example only, one hundred and forty-four service passageways 74 of approximately 3/8-inch diameter are suitable for some applications.
  • Service passageways 74 define a travel path 76 (illustrated by the arrows 76 in FIGS. 1C and 1D) for the service (cooling or heating) fluid used in cylindrical block heat exchange assembly 10.
  • Water and steam are common service fluids.
  • the service fluid enters cylindrical block heat exchange assembly 10 at service inlet 68 (shown by arrows A in FIGS. 1C and 1D), follows travel path 76, and exits cylindrical block heat exchange assembly 10 at service outlet 70 (shown by arrows B in FIGS. 1C and 1D).
  • Floating header 44 defines a process outlet 64 and fixed header 60 defines a process inlet 66.
  • Process outlet 64 and process inlet 66 are preferably made of graphite.
  • the number and diameter of process bores 72 provided depends upon the application. For purposes of example only, ninety-eight process bores 72 of approximately 5/8-inch diameter are illustrated in FIG. 1E (an alternative example would be fifty-seven process bores 72 of approximately 3/4-inch diameter).
  • the process fluid to be heated or cooled by cylindrical block heat exchange assembly 10 is delivered to process inlet 66 (shown by arrows C in FIGS. 1C and 1D), travels through process bores 72, and exits cylindrical block heat exchange assembly 10 at process outlet 64 (shown by arrows D in FIGS. 1C and 1D).
  • cylindrical block heat exchange assembly 10 examples of the many different process fluids which cylindrical block heat exchange assembly 10 accommodates are battery acids (H 2 SO 4 ) and acetones. Multiple passes can be arranged, for both the process and service fluids, as desired.
  • battery acids H 2 SO 4
  • acetones Multiple passes can be arranged, for both the process and service fluids, as desired.
  • Axial process bores 72 are independent of, and are carefully sealed away from, radial service passageways 74. There is no intersection between process bores 72 and service passageways 74. Process bores 72 and service passageways 74 do lie in extremely close proximity to each other, however, and form an interlocking grid throughout cylindrical block heat exchange assembly 10. The geometric relationship between process bores 72 and service passageways 74 facilitates efficient heat transfer or exchange between the process fluid traveling in process bores 72 and the service fluid traveling in service passageways 74.
  • FIG. 1E further illustrates the geometric relationship between process bores 72 and service passageways 74.
  • FIG. 1E is an enlarged sectional view taken along the line 1E-1E of FIG. 1C.
  • the alternating rows of process bores 72 and service passageways 74 assure maximum heat transfer. Although it can be exceeded for certain applications with water-cooled heads, the typical design temperature for conventional cylindrical block heat exchange assembly 10 is about 360°F.
  • the maximum allowable working pressure is typically about 100 psig.
  • FIGS. 2A and 2B illustrate intermediate block 20 of conventional cylindrical block heat exchange assembly 10 (as discussed in detail above) in accordance with the present invention.
  • silicon carbide tubes 80 are inserted into process bores 72 after the bores are drilled in graphite intermediate blocks 20. Tubes 80 are "forced" into process bores 72, because the outside diameter of tubes 80 are equal to or slightly less than the outside diameter of process bores 72, to assure a tight fit and maximum heat exchange. Tubes 80 may have a wall thickness of about 1/16 inches. Heat transfer occurs across the silicon carbide and then through the graphite. Silicon carbide tubes 80 offer increased corrosion resistance over bare graphite process bores 72.
  • service passageways 74 may be uncoated, or may be coated with resin or other similar material having a much lower temperature capability than silicon carbide tubes.
  • Service passageways 74 may be uncoated or coated only with resin because temperatures are sufficiently low in these passageways so that protection of the graphite intermediate blocks 20 is unnecessary or decomposition of the resin does not occur.
  • Tubes 80 may be bonded in process bores 72 by an adhesive.
  • a suitable adhesive is Cotronics Corporation's ceramic cement 901(-2), Sermabond 487, or the like.
  • tubes 80 may project outside process bores 72 by a nominal amount (e.g., 0.25 inches).
  • Tubes 80 can also be made flush with the face of graphite intermediate block 20 or recessed slightly within process bores 72.
  • a frictional locking of tubes 80 in process bores 72 can be accomplished using graphite dust particles, dust also serving to maximize heat transfer.
  • a fluoropolymer coating 90 is deposited on certain external surfaces of cylindrical block heat exchange assembly 10 and on the ends 82 of silicon carbide tubes 80.
  • fluoropolymer coating 90 need be applied only to the faces 20a, 20b of intermediate block 20 from which process bores 72 exit. This is especially true when the service fluid is water.
  • fluoropolymer coating 90 may also be applied to the faces 20c, 20d of intermediate block 20 from which service passageways 74 exit.
  • a recess 92 may be provided in intermediate block 20 to allow dimensionally for the extension of tubes 80 and for fluoropolymer coating 90.
  • Cubic heat exchange assembly 110 has, as its central component, a cubic block 112.
  • Cubic block 112 is made of graphite and forms the core of cubic heat exchange assembly 110.
  • the graphite of cubic block 112 may be impregnated with a polymer such as PTFE.
  • cubic block 112 of cubic heat exchange assembly 110 has alternating rows of process bores 172 and service passageways 174 to assure maximum heat transfer.
  • Process bores 172 are independent of, and are carefully sealed away from, service passageways 174. There is no intersection between process bores 172 and service passageways 174.
  • Process bores 172 and service passageways 174 do lie in extremely close proximity to each other, however, and form an interlocking grid throughout cubic heat exchange assembly 110.
  • process bores 172 and service passageways 174 facilitates efficient heat transfer or exchange between the process fluid traveling in process bores 172 and the service fluid traveling in service passageways 174.
  • process bores are either 3/8-inch diameter or 5/32-inch diameter.
  • the smaller diameter option is generally used for condensation applications but is also suitable for clean liquids.
  • graphite tubes having a 3/4-inch or 1/2-inch diameter can be placed in process bores 172 to meet special requirements.
  • a clamping plate casting 114 provides structural support for cubic block 112.
  • Clamping bolts 116 extending from clamping plate casting 114 engage the remaining components of cubic heat exchange assembly 110 and affix those components in relation to cubic block, 112.
  • a process head liner 118 and a process return liner 120 are positioned over the two, opposing faces of cubic block 112 from which process bores 172 exit.
  • Process head liner 118 and process return liner 120 are each preferably made of graphite, coated in raw state with fluoropolymer, impregnated after coating, and mounted in metal.
  • a process head casting 122 having a process inlet 166 and a process outlet 164, seats on clamping bolts 116 and covers process head liner 118.
  • a process return head casting 124 similarly seats on clamping bolts 116 and covers process return liner 120.
  • Process head casting 122 and process return head casting 124 are preferably made of steel.
  • liners might be used on the service side of cubic block 112, they are not usually necessary (and are not shown in FIG. 3A).
  • a service head 126 Positioned over the two, opposing faces of cubic block 112 from which service passageways 174 exit are a service head 126, having a service inlet 168 and a service outlet 170, and a service return head 128.
  • Service head 126 and service return head 128 seat on clamping bolts 116 and are preferably made of steel.
  • Cubic heat exchange assembly 110 is one of the most maintenance-free types of heat exchange assemblies ever designed; all graphite is kept in compression. Cubic heat exchange assembly 110 will take overloads, including thermal, hydraulic, and external mechanical shock, without failure. Simplicity of design, ease of disassembly for mechanical cleaning, and a large number of sizes and pass arrangements all contribute to the versatility of cubic heat exchange assembly 110.
  • Conventional cubic heat exchange assembly 110 is manufactured in size ranges having heat transfer areas from 10 ft 2 to 1,000 ft 2 . Passes are available from a single pass to sixty passes depending upon the model. Shown in FIG. 3B is a three-pass configuration; FIG. 3C illustrates a four-pass configuration. The flow paths of the process fluid are indicated by arrows.
  • TFE process gaskets (not shown) are standard components. There are no internal gaskets in cubic heat exchange assembly 110. The physical size of cubic heat exchange assembly 110 will often be one-fifth the volume of the comparable shell-and-tube type graphite heat exchange assembly discussed below. Cubic heat exchange assembly 110 is especially advantageous, therefore, for applications where space constraints exist.
  • FIGS. 4A and 4B illustrate cubic block 112 of conventional cubic heat exchange assembly 110 (as discussed in detail above) in accordance with the present invention.
  • cubic block 112 may be 8.75 inches high, have a 9.5-inch depth and a 9.5-inch width, and be drilled with 1/2-inch diameter process bores 172 and 3/8-inch diameter service passageways 174.
  • Silicon carbide tubes 180 are inserted into process bores 172. Tubes 180 are "forced" into process bores 172, because the outside diameter of tubes 180 almost equals the outside diameter of process bores 172 (about 1/2-inch), to assure a tight fit and maximum heat exchange.
  • tubes 180 could also be inserted into service passageways 174, little advantage would be gained unless the service fluid were corrosive.
  • Tubes 180 may be bonded in process bores 172 by an adhesive, or frictionally locked using graphite powder. As shown in FIG. 4B, tubes 180 are flush with the face of graphite cubic block 112. Alternatively, tubes 180 may project outside process bores 172 by a nominal amount (e.g., 0.25 inches) or be recessed slightly within process bores 172.
  • a fluoropolymer coating 190 is deposited on certain external surfaces of cubic heat exchange assembly 110 and on the ends 182 of silicon carbide tubes 180. (Fluoropolymer coating 190 is shown in partial cut-away in FIG. 4A.) Typically, fluoropolymer coating 190 need be applied only to the faces of cubic block 112 from which process bores 172 exit. This is especially true when the service fluid is water. Alternatively, fluoropolymer coating 190 may also be applied to the faces of cubic block 112 from which service passageways 174 exit. Even when the four faces of cubic block 112 receive fluoropolymer coating 190, the top and bottom of cubic block 112 need not be coated.
  • the amount of fluoropolymer coating 190 applied to the faces of cubic block 112 depends on the application. Twenty-five mils of fluoropolymer coating 190 are suitable in some applications, for example, while 8-10 mils may suffice in other applications. Although ends 182 of tubes 180 are coated, no coating is applied to the inside diameters of tubes 180. A slightly deeper gasket groove may be provided in the liners 118, 120 to allow dimensionally for the extension of tubes 180 (if they extend) and for fluoropolymer coating 190.
  • the concept of the present invention may be used in heat exchange assemblies of any desired shape (as discussed above), and is also adaptable to tubular heat exchange assemblies.
  • heat exchange assemblies of a tubular configuration is highly advantageous in certain environments in which it is desired that the heat exchange take place entirely within the exchange assembly.
  • the tubular heat exchange assembly commonly in use in such an environment is of the type known in the art as "shell-and-tube" heat exchange assemblies.
  • a plurality of tubular elements conveying one heat exchange medium are arranged within a shell through which is circulating another heat exchange medium with or without the use of baffles to direct the flow. The flow is substantially axial along the tubes.
  • a conventional shell-and-tube heat exchange assembly 210 is illustrated in FIG. 5.
  • the process fluid is introduced into shell-and-tube heat exchange assembly 210 through process inlet 266, flows through the tubes 212 disposed within the outer shell 214, and exits from process outlet 264.
  • Tubes 212 are typically metal, alpha silicon carbide, glass, or impervious graphite.
  • Shell 214 is, for example, low temperature steel, stainless steel, or fiberglass.
  • the service fluid enters shell-and-tube heat exchange assembly 210 through service inlet 268, flows around tubes 212 as directed by service baffles 216, and exits from service outlet 270. In essence, the service fluid traverses shell-and-tube heat exchange assembly 210 through "passageways" defined by service baffles 216 and tubes 212.
  • Service baffles 216 are typically stainless steel, fiberglass, or polypropylene.
  • Tubes 212 are held within shell 214 by tube sheets.
  • the ends of tubes 212 nearest process inlet 266 are held in first tube sheet 218; the ends of tubes 212 nearest process outlet 264 are held in second tube sheet 220.
  • Tube sheets 218, 220 are typically metal, impervious graphite, or glass-filled PTFE. Bores are drilled in tube sheets 218, 220 to accommodate tubes 212.
  • Packing 222 may be provided between tube sheet 220 and shell 214 to secure tube sheet 220 in position.
  • Internal process gaskets 224 are provided to seal tube sheets 218, 220.
  • First process head 226 and second process head 228 engage first tube sheet 218 and second tube sheet 220, respectively, to hold tube sheets 218, 220 in position.
  • First process head 226 and first tube sheet 218 are located in the fixed end 230 of shell-and-tube heat exchange assembly 210.
  • Second process head 228 and second tube sheet 220 are located in the floating end 232 of shell-and-tube heat exchange assembly 210.
  • Tie rods 234 and split ring flanges 236 are provided on floating end 232 to apply compression to shell-and-tube heat exchange assembly 210.
  • Tie rods 234 are typically stainless steel, fiberglass, or polypropylene.
  • Tube sheets 218, 220 are graphite and tubes 280 are alpha silicon carbide.
  • a fluoropolymer coating 290 is applied on the face of tube sheets 218, 220 nearest process heads 226, 228, respectively.
  • the joint between silicon carbide tubes 280 and graphite tube sheets 218, 220 is sealed by fluoropolymer coating 290.
  • the graphite may be impregnated (e.g., with a phenolic) on the remaining faces of tube sheets 218, 220.
  • Fluoropolymer coating 290 is also applied to the ends 282 of tubes 280. Fluoropolymer coating 290 is not applied, however, inside tubes 280.
  • Process heads 226, 228 are graphite coated with fluoropolymer and encased in steel.
  • tube bundle heat exchange assembly (218, 220, 280) is a single piece construction.
  • the entire bundle (218, 220, 280) is coated with tube sheets 218, 220 and tubes 280 fully assembled.
  • tube sheets 218, 220 are impregnated.
  • the tube side-construction offers materials of construction (silicon carbide and fluoropolymer-coated graphite) which resist contamination.
  • h S (water) 299 Btu/Hr.-ft 2 -°F
  • hp(steam) 2500 Btu/Hr.-ft 2 -°F
  • the Log Mean Temperature Difference (LMTD) was 81.5 °F.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
EP96107387A 1995-05-23 1996-05-09 Graphitwärmetauscher mit Siliziumkarbid-Einschubrohren und Fluorpolymerbeschichtung Withdrawn EP0744587A1 (de)

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US447832 1995-05-23

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EP1217322A2 (de) * 2000-12-21 2002-06-26 Fujikoshi Machinery Corporation Wärmetauscher
EP2084483A2 (de) * 2006-11-20 2009-08-05 Robert G. Graham Keramikwärmetauscher, diese verwendende systeme und verfahren zur herstellung derartiger systeme
DE19922397B4 (de) * 1998-05-27 2010-03-25 Smc Corp. Kühl-/Heizvorrichtung für Halbleiterverarbeitungsflüssigkeiten
DE102010001065A1 (de) * 2010-01-20 2011-07-21 Sgl Carbon Se, 65203 Leitscheibenanordnung für einen Wärmetauscher, Wärmetauscher, Verfahren zum Herstellen eines Wärmetauschers sowie Aus- oder Nachrüstkit für einen Wärmetauscher
CN102243026A (zh) * 2010-05-11 2011-11-16 王庆鹏 微孔式空气换热器结构及典型采暖空调应用形式
US8256502B2 (en) 2007-06-08 2012-09-04 Denso Corporation Heat exchange member and heat exchange apparatus
CN104058394A (zh) * 2014-07-04 2014-09-24 龚孝祥 一种块孔式石墨再沸器及其制造方法
US20140305620A1 (en) * 2011-11-16 2014-10-16 Vahterus Oy Plate heat exchanger and method for manufacturing of a plate heat exchanger
CN105423778A (zh) * 2015-12-17 2016-03-23 贵州祥宇泵阀制造有限公司 一种石墨换热器
US20160238330A1 (en) * 2015-02-08 2016-08-18 Ronald Keith Cummins Reinforced cross drilled block
EP3309497A1 (de) * 2016-10-13 2018-04-18 Airbus Defence and Space GmbH Heissgaswaermetauscher fuer ein waermetauschertriebwerk eines luft- oder raumfahrzeugs, verfahren zur herstellung eines waermetauscherelements fuer einen heissgaswaermetauscher, verbundpulver zur generativen fertigung, verfahren zur herstellung eines verbundpulvers
WO2018227649A1 (zh) * 2017-06-15 2018-12-20 南通三圣石墨设备科技股份有限公司 碳纤维热交换器及工艺
DE102017009854A1 (de) * 2017-10-22 2019-04-25 Hochschule Mittweida (Fh) Eine Medienströme beeinflussende Mikroeinrichtung mit einem Kernstück mit voneinander getrennten Kanälen und mit wenigstens einem Anschlusselemente aufweisenden Anschlussstück am Kernstück
EP4279855A1 (de) * 2022-05-18 2023-11-22 Mersen France Py SAS Verfahren zur herstellung einer wärmetauschergraphitanordnung, entsprechende anordnung und rohrbündelwärmetauscher damit

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EP2861929A4 (de) * 2012-06-18 2016-06-22 Tranter Inc Wärmetauscher mit zugänglichem kern
JP5876601B1 (ja) * 2015-03-06 2016-03-02 中外炉工業株式会社 蒸気加熱装置

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DE3117187A1 (de) * 1981-04-30 1982-11-18 Sigri Elektrographit Gmbh, 8901 Meitingen Blockwaermeaustauscher
DE3201156A1 (de) * 1982-01-15 1983-07-28 Osrodek Badawczo-Rozwojowy Przemysłu Budowy Urządzen Chemicznych CEBEA, Kraków Blockwaermeaustauscher

Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19922397B4 (de) * 1998-05-27 2010-03-25 Smc Corp. Kühl-/Heizvorrichtung für Halbleiterverarbeitungsflüssigkeiten
EP1217322A2 (de) * 2000-12-21 2002-06-26 Fujikoshi Machinery Corporation Wärmetauscher
EP1217322A3 (de) * 2000-12-21 2005-01-19 Fujikoshi Machinery Corporation Wärmetauscher
US7163053B2 (en) 2000-12-21 2007-01-16 Fujikoshi Machinery Corp. Heat exchanger
EP2084483A2 (de) * 2006-11-20 2009-08-05 Robert G. Graham Keramikwärmetauscher, diese verwendende systeme und verfahren zur herstellung derartiger systeme
EP2084483A4 (de) * 2006-11-20 2012-08-15 Heat Transfer International Inc Keramikwärmetauscher, diese verwendende systeme und verfahren zur herstellung derartiger systeme
US8256502B2 (en) 2007-06-08 2012-09-04 Denso Corporation Heat exchange member and heat exchange apparatus
DE102010001065A1 (de) * 2010-01-20 2011-07-21 Sgl Carbon Se, 65203 Leitscheibenanordnung für einen Wärmetauscher, Wärmetauscher, Verfahren zum Herstellen eines Wärmetauschers sowie Aus- oder Nachrüstkit für einen Wärmetauscher
WO2011089189A3 (de) * 2010-01-20 2012-02-09 Sgl Carbon Se Leitscheibenanordnung für einen wärmetauscher, wärmetauscher, verfahren zum herstellen eines wärmetauschers sowie aus- oder nachrüstkit für einen wärmetauscher
RU2517468C2 (ru) * 2010-01-20 2014-05-27 Сгл Карбон Се Система направляющих дисков для теплообменника, теплообменник, способ изготовления теплообменника, а также комплект для оборудования или дооборудования теплообменника
CN102243026A (zh) * 2010-05-11 2011-11-16 王庆鹏 微孔式空气换热器结构及典型采暖空调应用形式
US20140305620A1 (en) * 2011-11-16 2014-10-16 Vahterus Oy Plate heat exchanger and method for manufacturing of a plate heat exchanger
US9714796B2 (en) * 2011-11-16 2017-07-25 Vahterus Oy Plate heat exchanger and method for manufacturing of a plate heat exchanger
CN104058394B (zh) * 2014-07-04 2016-08-24 龚孝祥 一种块孔式石墨再沸器及其制造方法
CN104058394A (zh) * 2014-07-04 2014-09-24 龚孝祥 一种块孔式石墨再沸器及其制造方法
US20160238330A1 (en) * 2015-02-08 2016-08-18 Ronald Keith Cummins Reinforced cross drilled block
US9874412B2 (en) * 2015-02-08 2018-01-23 Ronald Keith Cummins Reinforced cross drilled block
CN105423778B (zh) * 2015-12-17 2023-10-03 贵州祥宇泵阀制造有限公司 一种石墨换热器
CN105423778A (zh) * 2015-12-17 2016-03-23 贵州祥宇泵阀制造有限公司 一种石墨换热器
EP3309497A1 (de) * 2016-10-13 2018-04-18 Airbus Defence and Space GmbH Heissgaswaermetauscher fuer ein waermetauschertriebwerk eines luft- oder raumfahrzeugs, verfahren zur herstellung eines waermetauscherelements fuer einen heissgaswaermetauscher, verbundpulver zur generativen fertigung, verfahren zur herstellung eines verbundpulvers
EP4187191A1 (de) * 2016-10-13 2023-05-31 Airbus Defence and Space GmbH Verbundpulver zur generativen fertigung, verfahren zur herstellung eines verbundpulvers
WO2018227649A1 (zh) * 2017-06-15 2018-12-20 南通三圣石墨设备科技股份有限公司 碳纤维热交换器及工艺
DE102017009854A1 (de) * 2017-10-22 2019-04-25 Hochschule Mittweida (Fh) Eine Medienströme beeinflussende Mikroeinrichtung mit einem Kernstück mit voneinander getrennten Kanälen und mit wenigstens einem Anschlusselemente aufweisenden Anschlussstück am Kernstück
EP4279855A1 (de) * 2022-05-18 2023-11-22 Mersen France Py SAS Verfahren zur herstellung einer wärmetauschergraphitanordnung, entsprechende anordnung und rohrbündelwärmetauscher damit
WO2023223147A1 (en) 2022-05-18 2023-11-23 Mersen France Py Sas Method for manufacturing a heat exchange graphite assembly, corresponding assembly and tube bundle heat exchanger comprising the same

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