CZ336297A3 - Pipe for heat-exchange apparatus - Google Patents

Description

Technical field

The invention relates to a corrosion-resistant heat exchanger tube intended for use in an environment such as that found in air heaters in heavy oil or coal-fired boilers, gas heaters in smoke desulphurisation plants, various chemical plants, for example acid generators sulfuric.

BACKGROUND OF THE INVENTION

Pipes intended for use in air heaters, boilers firing heavy oils or coal, gas heaters in smoke desulphurisation plants and sulfuric acid plants shall be corrosion resistant as they are exposed to highly concentrated sulfuric acid at high temperatures. The pipes used hitherto are therefore made of Ni-based materials and contain a special fluorine-based component or molded parts of graphitized carbon.

Heat exchangers in which tubes made of the above-mentioned different materials are used are therefore very expensive, since. these materials are not only difficult to process but also expensive. Since the graphitized carbon molded parts do not have the required mechanical properties, such as impact resistance and flexural strength, the pipe provided with the graphitized carbon molded parts must have a very large wall thickness. However, the heat exchanger made up of such tubes is very large.

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SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a heat exchanger tube that is cheaper than known tubes, which is easier to manufacture and yet resistant to heat, corrosion and mechanical stress, at least as known tubes.

SUMMARY OF THE INVENTION

This object is achieved by the heat exchanger tube according to the invention, the principle of which is to produce a layer of carbon fabric with phenolic resin.

DETAILED DESCRIPTION OF THE INVENTION

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic cross-section of a first embodiment of a pipe according to the invention for use in a heat exchanger, FIG. 2 schematically a cross-sectional view of a second embodiment of a pipe according to the invention for use in a heat exchanger; 3 shows schematically a cross-section of a third embodiment of a pipe according to the invention for use in a heat exchanger.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a first embodiment of a pipe 10 according to the invention in cross-section. In this cross-section of FIG. 1, the arrangement of the individual layers is shown.

As shown in Fig. 1, the tube 10 consists of a layer of carbon fabric 11 woven of high strength or high resilience carbon fibers using a thermoset phenolic resin 12 in the form of a novolak or a resole applied to the inside and outside of the carbon fabrics ··

The pipe 10 of this embodiment can be easily produced by a drawing technique.

When the phenolic resin 12 used is in the form of a resole, more advantageous results are obtained because it more easily soaks into the center of the carbon fabric 11.

Alternatively, a prepreg obtained by pre-impregnating the carbon fabric 11 with a phenol resin 12 and half-curing the impregnated carbon fabric 11 may be used.

The pipe 10 of this embodiment makes it possible to reduce the size of the heat exchanger and its cost, because it is cheaper than conventional pipes and surpasses or is comparable to at least these known pipes with respect to their workability and higher heat resistance, corrosion resistance and mechanical strength.

FIG. 2 shows a second embodiment of a pipe 20 according to the invention for use in a heat exchanger. FIG. 2 is a schematic cross-sectional view of a pipe 20. In this second embodiment, the same components as in the first embodiment are provided with the same reference numerals. The same facts as the first embodiment are not described.

As shown in Fig. 2, the tube 20 is provided with a layer consisting of strips of carbon fabric 21 arranged circumferentially into a cylindrical shape, the inner and outer sides of the carbon fabric 21 being coated with phenolic resin 12. The tube 20 according to the second embodiment can easily produced by the drawing technique as well as the tube 10 according to the first embodiment described above. Since the tube 20 according to the second embodiment is provided with a plurality of carbon fabric strips 21, namely, carbon fabric strips 21 disposed on its periphery, its drawing by dragging is more advantageous than the manufacture of the tube 10

4 according to the first embodiment.

The pipe 20 of the second embodiment, similar to the pipe 10 of the first embodiment, allows the heat exchanger size and cost to be reduced because it is cheaper than conventional pipes and exceeds their workability and higher heat resistance, corrosion resistance and mechanical strength, or is at least with these known pipes comparable in terms of these properties.

FIG. 3 shows a third embodiment of a pipe 30 according to the invention for use in a heat exchanger. FIG. 3 is a schematic cross-sectional view of a pipe 30. In this third embodiment, the same components as in the preceding embodiments have the same reference numerals. The same facts as in the previous embodiments are not described.

As shown in FIG. 3, the tube 30 is provided with a layer consisting of strips of carbon fabric 21 arranged circumferentially into a cylindrical shape, with a phenolic resin 12 applied to the inside and outside of the carbon fabric 21, while being around the outside of the layer. a carbon fiber 33 of high strength or high elasticity is wound on the outer side of the carbon fabric 21, wherein the outer side of the carbon fiber 33 is provided with a layer of phenolic resin 34 so that a carbon layer is arranged on the outside 33 and phenolic resin 34; The pipe 30 of the third embodiment is manufactured by impregnating the carbon fiber 33 with phenol resin 34 and placing the carbon fiber 33 either parallel or helically around the outside of the tube 20 of the second embodiment, either by a laying or winding technique.

When the aforementioned phenolic resin 34 is in the form of a resole, more advantageous results are obtained, because it more easily penetrates the carbon roving 33 to the center. Alternatively, a prepreg formed by pre-impregnating carbon fiber 33 with phenolic resin 34 and half-curing the impregnated carbon fiber 33 may be used. The number of stacked layers of carbon roving 33 and phenolic resin 34 and their thickness are selected as needed depending on the expected quality of the tube to be produced.

The pipe 30 of the third embodiment allows the production of a heat exchanger having better properties than a heat exchanger made using the pipe 20 of the second embodiment, since the pipe 30 of the third embodiment surpasses the pipe 20 of the second embodiment in heat resistance, corrosion resistance and in mechanical strength.

The pipe according to the invention for use in a heat exchanger is inexpensive and surpasses or is at least comparable to the workability, heat resistance, corrosion resistance and mechanical strength of a conventional pipe. When the pipe according to the invention is used, for example, in heat exchangers intended for operation in harsh environments, such as heaters in boilers firing heavy oils or coal, gas heaters in a smoke desulphurisation plant and various chemical plants such as sulfuric acid production plant, corrosion resistance is required, the heat exchangers made with this pipe may be smaller in size and cheaper.

The following tests were carried out to demonstrate the effect of the heat exchanger tube according to the invention.

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[Test 1] <Test Method>

Samples 1-3 according to the following data were produced several times and kept in different aqueous solutions of sulfuric acid under the following conditions for 720 hours, after which they were checked for change in appearance, weight and flexural strength.

<Test conditions>

«Sample 1»

A tube made by drawing carbon fabric with a phenolic resin (in the form of a resol) (manufactured by Fuj i Resin Kogyo K.K. and sold under the trade name Fujikemekku # 10) in such a way that the carbon fabric is provided with a resin (first embodiment type).

Sample dimensions

Diameter mm

Length

120 mm

Wall thickness mm «Sample 2»

A tube made by drawing three circumferentially arranged strips of carbon fabric with the same phenolic resin as in Sample 1 in such a way that the carbon fabric is provided with a resin (type according to the second embodiment).

Sample 2 dimensions as for Sample 1.

«Sample 3»

A tube made by drawing three circumferentially arranged carbon fabric strips with the same phenolic resin as in Sample 1 in such a way that the carbon fabric is resin-coated, then a phenolic resin-impregnated carbon portion (podle of the third embodiment) is wound on the outside of the impregnated carbon fabric.

The dimensions of Sample 3 are the same as those of Sample 1, except for a wall thickness of 2 mm.

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«Aqueous sulfuric acid solution»

Two solutions were used, i.e. solution A having a concentration of 75% and a temperature of 120 ° C and solution B having a concentration of 82% and a temperature of 140 ° C.

<Test results>

As is clear from Table 1 below, Samples 1 and 2 showed no damage by layer separation, especially in solution A, but in solution B, which was a more harsh environment than solution A, there was separation at the fabric interface. However, sample 3 showed better physical properties in both solutions A and B than samples 1 and 2a, and no solution of any kind in solution B.

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• 9 • 9 (Table 1)

TI -------------------- II II II II II ok B in σ> Ο ~ η II II II II II II • H +> CN γΗ ! —1 II II 4-> N II II cn 0 II II 0 - Pi II II β O \ O II II > II II Φ II II ix d II II Λ AI II II Honors> 1 0 II II β XI • P CN Ο ιη II II > 0) 0 N rH γΗ II II E 0 II II N> Pi II II II II II II Ιι II II II C4 II II β II II O ω II II Ν ' 00 Γ- II II tP AND! κ *. II II E 0 cn σι CN II II P CN rH γΗ II II N II II • H O II II 4-1 Pi II II cn II II 0 II II β II II 4-> II II 0 II II E and: CN WHAT II II Λ 0 *. *. II II P O σ PD II II honors N i — 1 II II £ O II II > <1) Pi II II β II II N II r WHAT honors II II β β II II vú 'Honors II II E > > II II Ή and: 0 Ο II II β O P honors Ρ honors > 1 II II r — I • P 0 β Ο β φ β II II 'Honors N N > φ Ν > φ Ν > φ II II b O 0 G 0 β φ β II II N g Pi ÍX N fX Ν Λ Ν II II Rl M II II > β II II - 'Honors II II II II Ό o AI II II CD P O > 1 > 1 II II H 0 -P Φ β φ β Φ β II II Λ N N N > φ Ν > φ Ν > Φ II II N O O Φ β Φ β Φ β II II II > IX Pi Λ Ν Λ Ν η Ν II II il II IIι II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II II r-H (Ν m II II II II AI Α! ΑΙ II II Φ Φ Φ II II P Ρ Ρ II II 0 0 0 II II N Ν Ν II II > > > II IL. ιι

φ • ο Ή > cn β β φ 0 > Ρ Α! 0 Ν β ο 0 ÍX IX honors β Λ Λ ο > 1 0 Λ 1—1 Ο 'Χ 4-> cn 0 0 ο α: β ο > cn > Ή Ρ Φ ο ÍX Μ ΑΙ Ν 1 Γ-ι Ό β Ρ 0 Φ 0 ΑΙ > Ρ Α! > ω ÍX > cn ρ Ρ Ρ ο Ο ΑΙ cn AND! Ν ο Ν β Ό + J Ό Φ 0 Φ> Ρ β > Ρ ÍX Λ ÍX 1 Ρ Ρ Λ φ Λ> ι ίΡ, β ο Λ 0 > cn 0 Ρ 4-> Ο 4J cn Α! cn ο Ν 0 β 0 β>> Φ (X Φ IX JJ ÍX cn dl 0 β II 4-> 0 β β Λ Μ > 1 Λ II • Η 4-> 0 > • Η cn • Ρ Ο cn β 0 4-> β 0 > β Φ Λ ίΧ

ΰ ΰ ΰ Φ

Observed change: Separation at the fabric interface.

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9 ·· 99 9999 99

The results of the tests have shown that tubes of the types of samples 1 and 2, namely tubes of the types described in the first and second embodiments, can be effectively used in the environment similar to solution A described above and tubes of the type 3, namely tubes of the type described in the third embodiment can be used in solution similar to solution B.

[Test 2] <Test Method>

Samples 1-3 were made as in Test 1. A sample heat exchanger was made using Samples 1-3, which was subjected to a test operation, and then opened and examined to determine the occurrence of possible changes. In the manufacture of this heat exchanger, Sample 3 was used to form the parts to be heated to a temperature above 135 ° C, and Sample 1 and 2 were used to produce the parts to be heated to a temperature below 135 ° C.

<Test conditions>

Heat exchanger heat exchange capacity: 70000 kcal / h

Heating source: exhaust gas (supplied from Shell) Folders: h ₂ ° 11% co ₂ 10% Sat ₂ 50 ppm S0 ₃ 10 ppm

Inlet temperature: 150 ° C

Outlet temperature: 120 ° C

Flow rate: 15000 m ³ N / h

Heat receiver: water (flowing inside the pipes)

Activity time: six months (continuous) <Test results>

When the heat exchanger was opened and examined after testing under the conditions described above, no abnormality was detected on any of the tubes in the heat exchanger.

The conclusion derived from the test results is that a heat exchanger using the pipes described above can operate safely, even under very harsh conditions causing corrosion.

Claims (6)

PATENT CLAIMS CLAIMS 1. A heat exchanger tube, characterized in that it is produced by applying a layer of carbon fabric with a phenolic resin. Tube according to claim 1, characterized in that the production is carried out by a drawing technique. A pipe according to claim 1, characterized in that it is provided on its outside with a layer comprising a carbon base and a phenolic resin. A pipe according to claim 1, characterized in that the manufacture is carried out by a drawing technique, wherein the pipe is provided on its outside with a layer comprising a carbon base and a phenolic resin. A pipe according to claim 1, characterized in that it is provided on its outside with a layer comprising a carbon base and a phenolic resin and the layer is applied by a winding technique. A pipe according to claim 1, characterized in that the manufacture is carried out by a drawing technique, the pipe being provided on its outside with a layer comprising a carbon base and a phenolic resin and the layer being applied by a winding technique.