RU2568716C1 - Plate-type block heat exchanger with scale prevention properties - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: plate-type block heat exchanger contains a package (30) of heat-conducting plates which comprise the first heat-conducting plate (51) and the second heat-conducting plate (52). At least a part of each of the first heat-conducting plate (51) and the second heat-conducting plate (52) has coating, which: i) has the layer thickness 1-30 mcm, ii) prepared using sol-gel method, iii) contains silicon oxide (SiOx) with the atomic ratio O/Si>1 and iv) contains ≥5 or ≥10 of nuclear percentage of carbon (C).

EFFECT: preservation of coating on areas which are applied by it, within a long period of heat exchanger operation.

12 cl, 3 tbl, 6 dwg

Description

Field of Invention

The invention relates to a plate-type plate heat exchanger containing an upper head, a lower head and four side panels that are bolted to a set of corner beams to form a sealed casing. A pack of heat transferring plates is located in this sealed casing. The block-type plate heat exchanger has properties that reduce deposits and facilitate cleaning of the heat exchanger.

State of the art

Currently, there are several different types of plate heat exchangers that are used to solve various problems depending on their type. The heat exchanger of one particular type is assembled by bolting the upper head, lower head and four side panels to the corner beams to form a box casing around a stack of heat transferring plates. A plate heat exchanger of this particular type is called a block type heat exchanger. One example of a commercially available block-type heat exchanger is the heat exchanger offered by Alfa Laval AB under the name Compablock. Other block-type plate heat exchangers are described in patent documents EP 165179 and EP 639258.

In a block-type plate heat exchanger, fluid paths for two fluids between which heat exchange occurs are formed between heat transfer plates in a plate package. During operation, deposits form on the heat transfer plates, for example, as a result of sedimentation, microbial growth, the presence of contaminants, etc., in the fluid that passes between the heat transfer plates. Deposits usually reduce heat transfer efficiency and increase the pressure drop across the heat exchanger, resulting in a general decrease in performance. The problem of deposits is typically solved by removing one or more of the side panels so as to access the stack of heat exchanger plates and cleaning such plates.

For other types of heat exchangers, it is known to coat those areas of the heat exchanger that are susceptible to scale formation. Examples of coating technology are given in numerous patent documents, such as US 20090123730, US 200060196644, WO 2008119751 and WO 2009034359

Despite the fact that such coating technologies can reduce the formation of deposits, it turned out that they are not optimal for a block-type plate heat exchanger, which is usually used in aggressive environments and high pressure, where safety requirements are high. For example, after some time, the coating wears out and leaves the surface on which it is applied. Moreover, the unique structure and design of the block-type plate heat exchanger requires a different coating, which is optimized for the structural structure of the block-type plate heat exchanger.

SUMMARY OF THE INVENTION

The aim of the present invention is to find a coating that reduces the formation of deposits in the plate heat exchanger block type. Another goal is to find block-type plate heat exchanger variants that ensure that the coating remains in the areas on which it is applied for a long time the heat exchanger operates.

To achieve these goals, a block-type plate heat exchanger is proposed. The block-type heat exchanger comprises an upper head, a lower head and four side panels that are bolted to a set of corner beams to form a sealed casing, and a package of heat exchanger plates located inside the sealed casing. The heat exchanger plate package contains pairs of heat exchanger plates arranged so that a first fluid path is formed between the pairs of stacked heat exchanger plates, in which a pair of stacked heat exchanger plate pairs contains a first heat exchanger plate and a second heat exchanger plate, which are connected so that between the first and second heat exchanger plates formed a path for the second fluid. At least a portion of each of the first heat transfer plate and the second heat transfer plate contains a coating that i) has a layer thickness of 1-30 μm, ii) is prepared using sol-gel technology, iii) contains silicon oxide (SiOx) having an atomic ratio O / Si> 1, and iv) contains ≥5 or ≥10 atomic percent carbon (C).

Such a block-type plate heat exchanger has the advantage that the formation of deposits on the heat exchanger plates is significantly reduced. Therefore, no or almost no cleaning is required. This reduces the use of potent detergents and / or potentially abrasive mechanical cleaning, and also reduces the downtime of the plate heat exchanger. Moreover, this coating in comparison with known coatings is highly wear-resistant and has a relative resistance to cracking, which can occur due to the torsional and tensile forces acting on the heat exchanger plates. Essentially each side or both sides of the respective heat exchanger plate may have such a coating.

The various components that make up the plate heat exchanger may have predetermined dimensions. For example, the first heat transfer plate and the second heat transfer plate may have a thickness of 0.6-1.4 mm or 0.8-1.2 mm. Each of the first heat transfer plate and the second heat transfer plate may have a heat transfer area of 0.05-0.30 ^m2 or 0.6-1.8 m ^2. Any of the upper head and lower head may have a thickness of 45-145 mm or 190-250 mm. Each of the four side panels may have a thickness of 35-85 mm or 110-190 mm. Finally, the sealed casing may have a volume of 0.02-0.40 m ³ or 0.7-5.0 m ³ .

Empirical tests, as well as finite element analysis, have shown that each of these sizes, either one, or in combination with one or more, gives a heat exchanger structure that is particularly suitable for coating. The reason underlying this is that such dimensions give the structure of the heat exchanger plates, which prevents their intense bending during operation of the heat exchanger. This is a great advantage, since the coating in this case remains on the plates for a long time (bending leads to faster detachment of the coating or its wear). Therefore, the coating, together with one or more of a predetermined size, allows to obtain a block-type plate heat exchanger, which is optimized with respect to the resistance to deposits for a longer time.

The thickness of the coating layer can be 1.5-25 microns, or 2-20 microns, or 2-15 microns, or 2-10 microns, or 3-10 microns. Silicon oxide SiOx may have an atomic ratio O / Si = 1.5-3 or may have an atomic ratio O / Si = 2-2.5. The coating may have a carbon content of 20-60 atomic percent or 30-40 atomic percent. The heat exchanger may comprise a gasket that is at least partially coated. The first heat transfer plate and the second heat transfer plate can be made of stainless steel.

Other features, objectives, aspects and advantages of the invention will be apparent from the following detailed description with reference to the attached drawings.

Brief Description of the Drawings

The following is a description of illustrative embodiments of the present invention with reference to the attached schematic drawings, where:

FIG. 1 is an exploded view of a block-type heat exchanger with a stack of heat exchanger plates;

FIG. 2 is a top view of the pairs of heat transfer plates used in the stack of heat transfer plates of FIG. one;

FIG. 3 is a section in the plane AA in FIG. one;

FIG. 4 is a section in the plane BB in FIG. one;

FIG. 5 - fragment C of FIG. 3 on an enlarged scale;

FIG. 6 is a schematic sectional view of a coated heat exchanger plate that is part of the heat exchanger plate package of FIG. one.

Detailed description

In FIG. 1 shows a plate type plate heat exchanger 2. The plate heat exchanger 2 contains an upper head (cover) 15, a lower head (cover) 16 and four side panels 11, 12, 13 and 14, which are screwed onto a set (usually of four) of angle bars 21-24 for assembling the plate heat exchanger 2. B In the assembled state, the plate heat exchanger 2 has a box-shaped or block shape, and the upper head 15, the lower head 16 and the side panels 11-14 form a casing. Inside the casing is a stack of heat transfer plates 30, which contains, as will be described in more detail below, a plurality of pairs of heat transfer plates. The package 30 of heat transfer plates also has a box-shaped or block shape, which corresponds to the shape of the casing formed by the heads 15, 16 and side panels 11-14. The package 30 of heat transfer plates at the corners has four pads 31-34 facing the four side beams 21-24.

The plate heat exchanger 2 is typically assembled by known methods and using bolts (not shown) that fasten the listed components to each other through bolt holes, such as holes 35 and 36. In short, the assembly of the plate heat exchanger 2 includes operations in which the bag 30 is placed heat transfer plates on the lower head 16, slide the corner beams 21-24 into the linings 31-34 and fasten them with bolts with the lower head 16. On top of the package 30 of the heat transfer plates put the channel end plate 38 and to the corner beams 21-24 with bolts to hoarse the upper head. Then, side panels 11-14 are fastened to the corner beams 21-24 and to the heads 15, 16 with bolts. Essentially the plate heat exchanger 2 also has a base 17, which facilitates the installation of the plate heat exchanger 2 on the ground.

On the side panels 11-14 there are gaskets 131 located on those sections that face the corner beams 21-24 and the heads 15, 16 so that the casing formed by the heads 15, 16 and the side panels is properly sealed to prevent leakage from plate heat exchanger 2.

The first side panel 11 and the second side panel 12 of the side panels 11-14 comprise inlets and outlets for two fluids. In more detail, the first side panel 11 has an inlet 41 and an inlet 42 for the first fluid. The inlet 41 and the outlet 42 in combination with the package 30 of heat transfer plates of the first panel 11 form a path for the first fluid coming from the inlet 41 through the package 30 of the heat transfer plates and to the outlet 42. This path is shown by dashed arrows that extend in a direction parallel to the direction D1. Known baffles, such as baffles 39, are connected to the sides of the heat exchanger plate package 30 to direct the first fluid flow in multiple passages in the bag 30 (four passages in the embodiment shown).

The second side panel 12 has an inlet 43 and an outlet 44 for a second fluid. The inlet 43 and the outlet 44 of the second side panel 12, in combination with the stack of heat exchanger plates 30, form a path for the second fluid that extends from the inlet 43 through the stack of heat exchanger plates 30 and to the outlet 44. This path is indicated by dashed arrows extending in a direction parallel to direction D2. Known partitions are connected to the sides of the heat exchanger plate package 30 for directing the flow of the second fluid by a plurality of passes in the bag 30 (in this case, the same number of passes as for the first fluid).

Installation of partitions is performed by known methods. However, the first path for the first fluid passes between the pairs of heat transfer plates in the bag 30, and the second path for the second fluid passes inside the pairs of heat transfer plates in the bag 30. The pair of heat transfer plates comprises a first heat transfer plate and a second heat transfer plate, as will be described below. This means that the flow of the first fluid passes between the heat-exchange (heat-conducting) plates belonging to different pairs, and the path of the second fluid passes between the first and second heat-exchange plates of one pair, i.e. inside the couple. Pads 31-4 seal the corners of the package 30 of heat transfer plates and provide separation of the two flows of different fluids.

In FIG. 2, 3 and 4, an example of the first and second pairs 50, 60 of heat exchange (heat conducting) plates is given, where FIG. 3 is a section in the plane AA in FIG. 2, and FIG. 4 is a section in the plane BB in FIG. 2. The pairs 50, 60 of the heat exchange plates are part of the bag 30 shown in FIG. 1. The package 30 contains many pairs of heat transfer plates, which are similar to pairs 50, 60, for example 4-200 pairs or even more.

In pairs 50, 60 of the heat transfer plates shown in FIG. 2, 3 and 4, the first pair comprises a first heat exchanger plate 51 and a second heat exchanger plate 52. The second pair 60 of heat exchanger plates is typically similar to the first pair 50 of heat exchanger plates, which means that it also contains a first heat exchanger plate 61 and a second heat exchanger plate 62. Thus thus, the first heat transfer plate 61 of the second pair 60 of heat transfer plates is usually similar to the first heat transfer plate 51 of the first pair 50 of heat transfer plates, and the second heat transfer plate 62 of the second pair 60 of heat transfer plates similar to the second heat transfer plate 52 of the first pair 50 of heat exchanger plates.

In addition, the first heat transfer plate 51 and the second heat transfer plate 52 of the first pair 50 of heat transfer plates have the same shape.

Each heat transfer plate, as shown in the example of the first heat transfer plate 51 of the first pair 50 of heat transfer plates, has a rectangular shape with a first 511, a second 512, a third 513 and a fourth 514 elongated sides. When the heat exchanger plate package 30 is located in the casing of the plate heat exchanger 2, the first elongated side 511 faces the first side panel 11 and the third side 513 faces the third side panel 13. The first heat exchanger plate 51 is connected to the second heat exchanger plate 52 by a seam 78 on the first elongated side 511 and seam 79 on the third elongated side 513, as shown in FIG. 3.

The first heat exchange plate 51 contains a set of corrugations 101-106, which are located on respective sides of the elongated seams 72-76, which connect the first and second heat exchange plates 51, 52. It can also be said that the corrugations 101-106 are separated by elongated seams 72-76. The set of corrugations 101-106 extends in a direction parallel to the seams 72-76, which in the above example is parallel to the direction D2. The set of corrugations 101-106 has two external sets of corrugations 101, 106, and between the outer sets of corrugations 101, 106 and the corresponding nearest elongated sides 513, 511 additional seams 71, 77 can pass. As indicated above, since all the heat transfer plates are similar to each other, all or part of the heat transfer plates in the stack 30, for example plates 62, 61, and 62, may have the same structural properties and structural shape as the heat transfer plate 51.

Corrugations 101-106 contain ridges and grooves that extend in the direction D1, which lies at an angle of 45 ° -90 ° to the direction D2, along which elongated seams 71-77 pass. The directions D1, D2 in this case coincide with those described above with respect to the flows of the first and second fluid. The corrugations 101, 102 on the first heat exchanger plate 51 and the corresponding corrugations 201, 202 on the second heat exchanger plate 52 comprise ridges and grooves such as ridge 92 and groove 93 of the first heat exchanger plate 51 and ridge 192 and groove 193 of the second heat exchanger plate 52.

The first pair 50 of heat transfer plates includes elongated connecting grooves, shown as connecting grooves 81-87 of the first heat transfer plate 51, along which elongated seams 71-77 extend. Each corrugation of the corrugation set 101-106 comprises a ridge and a groove that extend in a direction D1 that extends transversely to a direction D2 along which elongated connecting grooves 81-87 extend.

The ridges of the first heat exchanger plate 51 can be aligned with the ridges of the second heat exchanger plate 52 when viewed in a direction parallel to the normal direction N of the first pair 50 of heat exchanger plates. This provides the advantage of obtaining efficient heat transfer and fluid flow.

As shown in the drawings, seams 71-77 are located in respective connecting grooves 81-87. Since the second heat transfer plate 52 is similar to the first heat transfer plate 51, it also contains elongated connecting grooves along which elongated seams 71-77 extend.

In FIG. 3 and in FIG. 5 illustrating fragment C in FIG. 3, it is shown that, for example, the connecting groove 82 of the first heat transfer plate 51 abuts against the corresponding connecting groove 182 of the second heat transfer plate 52. The heat transfer plates 51, 52 are connected to each other on the connecting grooves 82, 182 by a seam 72. In this context, the back surface 515 the connecting groove 82 of the first heat transfer plate 51 is in contact with the rear surface 525 of the connecting groove 182 of the second heat transfer plate 52.

Seams are usually formed by welding, but can be formed by brazing or by any other suitable method. Heat transfer plates 51, 52, 61, 62 are typically made of metal, such as stainless steel. When welding is used to form the joints, i.e. when the seams are welded, laser welding can be used, as well as other welding methods, such as resistance welding.

Each of the seams 71-77 may contain at least partially overlapped sections of the seam, as shown in the example of the first section 721 and the second section 722 of the seam 72. The sections 721, 722 of the seam can be laid one on top of another at a predetermined distance, for example 5-30 mm. These two sections 721, 722 of the seam, or sections of the weld when the seam is formed by welding, can begin at the corresponding end portion of the connecting groove, as shown by the two end sections 821, 822 of the connecting groove 82.

As shown, the connection of the first heat exchanger plate 51 with the second heat exchanger plate 52 on the first and third elongated sides 511, 513 can be performed by a first set of opposite elongated side seams 78, 79 so that between the first set of opposite elongated side seams 78, 79, i.e. . inside the first pair 50 of heat transfer plates, a path 57 for the second fluid was formed. Path 57 runs parallel to direction D2 described with reference to FIG. one.

To facilitate the connection of the plates into a pair 50, the first and second heat exchange plates 51, 52 have peripheral sections, for example, sections 53 54, bent towards each other. The peripheral sections 53, 54 are bent towards each other because the second heat transfer plate 52 is arranged as an inverted mirror image of the first heat transfer plate 51, taking into account that these plates 51, 52 are identical to each other. The corresponding weld 79 is formed on the contact surface formed between the bent sections 53, 54.

The connecting grooves 81-87 can extend continuously along a path 57 that is formed between the first and second heat exchanger plates 51, 52. In addition, since the first heat exchanger plate 51 and the second heat exchanger plate 52 are typically connected by a plurality of elongated seams 71-77, path 57 for the second a fluid formed between the first and second heat exchanger plates 51, 52 comprises a plurality of parallel flow channels 571-576.

To form a stack of heat transfer plates 30, pairs of heat transfer plates, such as a first pair of heat transfer plates 50 and a second pair of heat transfer plates 60, are joined by opposite elongated side seams. Examples of such seams are a set of opposing elongated side seams 781, 782 located between the first pair 50 of heat transfer plates and the second pair 60 of heat transfer plates. Such elongated side seams 781, 782 extend laterally with respect to the first set of elongated side seams 78, 79 and connect a pair of heat exchanger plates (e.g., pair 50) to an adjacent pair of heat exchanger plates (e.g., pair 60). To facilitate the connection, the plates 51, 52, 61 62 have corresponding peripheral sections that are bent in the direction of the heat exchange plate belonging to another pair of heat exchange plates, for example, sections 56 and 65. A corresponding weld 781 is formed on the contact surface between the bent sections 56, 65 .

When the pairs 50, 60 of heat transfer plates are connected, a path 67 for the first fluid occurs between pairs of 50, 60 of heat transfer plates. Since the pairs 50, 60 are connected only by the second set of side seams 781, 782, a so-called free channel is formed between the seams 781, 782, i.e. a free channel is formed between pairs of 50, 60 heat transfer plates. In this context, a free channel can be defined as a path without any contact points between the seams 781, 782. A substantially free channel is advantageous, since in practice it is possible to reduce or even eliminate the occurrence of deposits from the fluid or due to the presence of bacteria.

To form a complete package 30 of heat transfer plates, many pairs of heat transfer plates are stacked (stacked) next to each other and connected to each other in the manner described for the first and second pairs 50, 60 of heat transfer plates. Pairs can be joined using the same methods (welding, brazing, etc.) as for joining plates of one pair.

To effectively connect the heat transfer plates to the pads 31-34, each heat transfer plate has four protrusions located at its corners, such as the protrusions 515-518 of the first heat transfer plate 51. The protrusions are connected to the pads 31-34, for example, by welding, brazing or other in a suitable way. The pads 31-34 partially surround the set of corner beams 21-24 when the plate heat exchanger 2 is assembled so that the package 30 of heat transfer plates is firmly fixed in the casing formed by the heads 5, 16 and side panels 11-14.

The heat transfer plates 51, 52, 61, 62 can be made of a steel sheet subjected to pressure treatment on a press that forms corrugations and connecting grooves. Then, the edger cuts the extruded plates along their periphery, and the edges of the trimmed plates are bent in a bending machine to form bent peripheral portions.

The heat transfer plates in the stack of 30 heat transfer plates are coated. The coating can be called a coating that reduces the stickiness, and it makes it easy to clean the plate. Coated plates provide improved heat transfer over time compared to the known heat transfer plates, since the latter are much more quickly covered by deposits, which reduces heat transfer characteristics to a greater extent. The coating also gives a significantly more uniform surface of the plates, which improves flow characteristics. In addition, the pressure drop on the plates of the heat exchanger 2 decreases in time compared with the known plate heat exchangers of the block type, since the formation of deposits caused by impurities, microorganisms and other substances is reduced.

Coated plates can be easily cleaned using high pressure rinsing with water. In addition, there is no need for intensive, time-consuming mechanical cleaning or cleaning with strong acids, alkalis or detergents such as NaOH and HNO ₃ .

The heat transfer plates in package 30 are coated with a sol-gel process and contain organosilicon compounds. These organosilicon compounds are starting materials that are used in the sol-gel process, and are preferably silicon alkoxy compounds. In the sol-gel process, sol is converted to gel to produce nanomaterials. Using hydrolysis and condensation reactions in a liquid, a three-dimensional network of molecules with interlayers is obtained. Then, for further processing of the gel and obtaining nanomaterials or nanostructures, heat treatment steps are applied, as a result of which a finished coating is obtained. This coating containing such nanomaterials or nanostructures mainly contains silicon oxide SiOx with an atomic ratio O / Si> 1, alternatively with an atomic ratio in the range O / Si = 1.5-3 or alternatively in the range O / Si = 2-2 ,5. By "atomic ratio O / Si> 1" it is understood that the quotient of dividing the number of oxygen (O) atoms in silicon oxide (SiOx) by the number of silicon (Si) atoms in silicon oxide (SiOx) is greater than unity. Accordingly, for alternatives, the quotient of dividing the number of oxygen (O) atoms by the number of silicon (Si) atoms is in the range of 1.5-3 or in the range of 2-2.5.

Preferred silica is silica, SiO ₂ . Silicon oxide forms a three-dimensional network with excellent adhesion to the plates. All heat transfer plates of package 30, such as the first heat transfer plate 51 and the second heat transfer plate 52, may be coated. Typically, the coating on the plates is applied to those sides that face one or both of the paths for the first fluid and for the second fluid.

The coating contains carbon in hydrocarbon chains. Hydrocarbon chains may have functional groups, such as those found in hydrocarbon chains or aromatic groups, for example C = O, C — O, C — O — C, C — N, N — C — O, N — C = O, etc. Preferably, the carbon is contained in an amount of ≥10 atomic percent, or in the range of 20-60 atomic percent, or in the range of 30-40 atomic percent. Carbon gives the coating flexibility and resilience, which is important if the plates bend during operation due to the high pressure acting on the plates in the bag 30. The hydrocarbon chains are hydrophobic and oleophobic, which gives the coating anti-stick properties.

In FIG. 6 is a schematic view of a first heat exchange plate 51 with a sol-gel coating 701 of silicon oxide described above. The coating is also referred to as silicon oxide layer 701. Next to the plate 51, the silicon oxide layer 701 forms an interface 702 between the coating siloxane and the metal oxide film on the plate 51. The bulk of the coating 701 is a siloxane network 703 that has chains of organic crosslinking agent and voids that give the coating 701 flexibility. The siloxane network 703 is located "on top" of the interface 702. The silicon oxide layer 701 forms an outer layer in the form of a functional surface 704, which has hydrophobic and oleophobic properties that reduce the formation of deposits.

There is no clear boundary between the interface 702 and the siloxane network 703 and, respectively, between the siloxane network 703 and the functional surface 704, but there are smooth transitions.

All the plates of the coated package 30 may have the coating described with reference to FIG. 6. This coating is both durable and flexible and allows to obtain a plate for a plate type plate heat exchanger with excellent properties that prevent sticking, wear resistance and resistance to cracking.

In one embodiment, at least one organosilicon compound containing a sol is deposited on the surface of the coated heat transfer plate. Any suitable method can be used to wet the surface with a sol or to apply a sol to it. The surface coating can be applied, for example, by spraying, dipping or watering. Typically, a coating is applied to all surfaces of a heat exchanger plate that are in contact with a fluid, which can lead to the formation of deposits. In addition, the coating can be applied to gaskets, such as gaskets 131 on the side panels 11-14, while the coating can be of the same type as the coating on the heat transfer plates. The coating is typically applied to the surfaces of the gaskets that come in contact with the fluid, which can lead to the formation of deposits.

A method of coating a heat exchanger plate of a package 30 comprises the steps of pre-treating the surfaces of the heat exchanger plates that are coated. This pretreatment can be done by dipping, watering or spraying.

Pre-treatment is carried out to clean the surfaces on which the coating is applied, in order to provide enhanced adhesion of the coating. An example of a pretreatment is treatment with acetone and / or alkaline solutions, for example a caustic solution.

The method of coating a heat exchanger plate may comprise a step where heat treatment is performed, for example, a drying operation performed after pretreatment, and a drying and / or curing operation can be carried out after the coating is applied to the plate. The coating can be heated using a known heating device, for example, in a furnace.

The coating, which, as described above, contains SiOx, is applied to the plates of the bag 30. Coating is performed by a sol-gel process. The coating thickness is preferably 1-30 microns. A coating with a thickness of less than 1 μm is considered insufficiently wear-resistant, since the plates in the plate heat exchanger 2 may bend slightly during operation. Bending of the plates results in wear of the coating, and over time the coating wears out. At the same time, the thickness of the coating has an upper limit, since the application of substances to the heat transfer plates affects their heat transfer and thereby the overall characteristics of the heat exchanger. The upper limit of the thickness of the heat exchanger is preferably equal to 30 microns. Therefore, the thickness of the coating containing the silica sol is 1-30 microns, alternatively preferably 1.5-25 microns, preferably 2-15 microns, preferably 2-10 microns, or preferably 3-10 microns.

The material from which the heat transfer plates of package 30 are made can be selected from a variety of metals and metal alloys. Preferably, the material is stainless steel or titanium. The material can also be selected from the range containing nickel, copper and alloys of these materials and / or carbon steel.

In an attempt to create a block-type plate heat exchanger less susceptible to deposits, two glass-ceramic coatings with low surface energy were tested, both of which are of the type described above. Tests, analysis and results are presented below. Coating 1 is a polymer with terminal silane groups in butyl acetate, and Coating 2 is a polysiloxane urethane resin in a solvent consisting of kerosene and butyl acetate. The tests were carried out on coated heat exchanger plates in package 30. Further, the plate that was subjected to the tests is also referred to as a substrate.

Tests showed coating properties such as wetting of the substrate, adhesion to the substrate, contact angle, coating thickness and stability to a 1.2% solution of HNO ₃ in H ₂ O, to a 1% solution of NaOH in H ₂ O, and to crude oil. The results are summarized in Table 1.

Both coatings showed excellent spray wetting on both the stainless steel substrate and the titanium substrate.

Adhesion was determined by a mesh notch / tape test according to DIN EN ISO 2409. Ratings from 0 (excellent) to 0 (poor) or 1 are acceptable ratings and 2-5 are not acceptable. The first digit is the estimate after the mesh incision (1 mm net), and the second digit is the estimate after applying the tape and removing it.

To obtain the desired adhesion for Coating 1 and Coating 2, the substrates were pretreated. To obtain the desired adhesion of Coating 1 on a stainless steel substrate, the substrate was pretreated by immersing it in an alkaline detergent for 30 minutes. Then the substrate was washed with water and demineralized water and dried before applying Coating 1 (which was applied after half an hour to achieve optimal adhesion). Tests have shown that adhesion is reduced if the substrate is cleaned only with acetone. Stainless steel substrates were also pretreated, on which Coating 2 was applied. The adhesion of this coating was not affected by whether acetone or an alkaline detergent were used in the pretreatment or not. If the pretreatment step was not carried out or was carried out incorrectly, the adhesion of the coating is maintained.

Both coatings showed good stability in an acidic environment. The coatings were stable for 1.5 hours at 75 ° C and more than 24 hours at room temperature.

Under alkaline conditions, Coating 1 showed better results than Coating 2. Coating 1 withstood alkaline conditions for 3 hours at 85 ° C, and Coating 2 - 2 hours at 85 ° C. Both coatings did not show decomposition or reduction of oleophobic properties after treatment with crude oil for 6 months at a temperature of 20 ° C.

Then, Coating 1 and Coating 2 were applied to the heat exchanger plates in package 30. In this test, the heat exchanger plates were made of titanium, and the heat exchanger 2 was used to process crude oil. All coated heat transfer plates were pretreated with acidic and alkaline solutions to remove deposits, and then washed with high pressure water. Before coating, the plates were allowed to dry.

The pre-treatment was completed the day before Coating 1 and Coating 2 were applied to the plates. When the plates were allowed to dry at room temperature (approximately above 20 ° C), some of the plates were still wet. More precisely, Coating 1 was applied to a third of the plates, Coating 2 was applied to a third of the plates, and a third of the plates were left uncoated. The coatings were sprayed with the appropriate coating in path 57, 67, which are formed by the plates in the bag 30, so that the coating was applied to those sides of the plates that are facing the paths. The measured coating thickness was 2-4 microns. The drying / hardening of the two coatings was carried out for 1.2 hours in an oven at elevated temperatures of 200 ° C and, accordingly, 160 ° C.

A bag 30 with coated heat exchanger plates was installed in the heat exchanger of FIG. 1 and coated plates were evaluated after approximately seven months of operation of heat exchanger 2.

The plates were analyzed after seven months. In more detail, three different silica coated heat transfer plates were analyzed using X-ray spectroscopy, also known as electron spectroscopy for chemical analysis. The method of X-ray electron spectroscopy gives quantitative chemical information, including the chemical composition, expressed in atomic percent, for an external 2-10 microns surface.

The measurement principle of the method of X-ray electron spectroscopy is based on the fact that the sample (i.e. the heat transfer plate with Coating 1, the heat transfer plate with Coating 2 and the heat transfer plate without coating) is placed in deep vacuum and irradiated with a well-defined energy of x-ray radiation, which leads to emission by the sample photoelectrons. Only photoelectrons from the outer surface of the sample reach the detector. By analyzing the kinetic energy of photoelectrons, one can calculate their binding energy, which shows their origin relative to the chemical element (including the electron shell) of the sample.

X-ray electron spectroscopy gives quantitative data both on the elemental composition and on the various chemical states of the chemical element of the sample (such as various functional groups, chemical bonds, oxidation state, etc.). All chemical elements, except hydrogen and helium, are detected, and the resulting chemical composition of the sample is expressed in atomic percent.

When analyzing heat transfer plates with different types (in terms of C, O and Si) of a coating containing silicon oxide, or, more precisely, when analyzing the chemical elements of the coating, one can find the relative surface composition in atomic percent or atomic ratio O / Si. It was determined that C, O, and Si can be detected on the outer surfaces of the coating. The C content is typically 41.9-68.0 atomic percent, the O content is 19.5-34.3 atomic percent, and the Si content is typically 8.6-23.4 atomic percent. The atomic ratio O / Si is in the range of 1.46-2.30. It should be noted that the total amount of oxygen is used to determine the atomic O / Si ratio. This means that they include oxygen in functional groups with carbon. Otherwise, a theoretical O / Si ratio of 2.0 is expected for silica (i.e., silica in the form of SiO ₂ ).

After four months of operation, a preliminary inspection was carried out by obtaining a thermal image. The thermal image was obtained from the middle region of the heat exchanger 2 during operation of the heat exchanger. From the image it is obvious that part of the heat transfer plates showed increased heat transfer compared to other heat transfer plates in the heat exchanger.

The inspection showed an elevated temperature on the coated plates. Uncoated plates had a lower operating temperature. The difference in temperature arose as a result of different rates of deposition, and the coated plates had an elevated temperature.

A visual inspection revealed that Coated 1 plates had the least amount of deposits on the side facing the crude oil. In addition, Coating 2 had a reduced amount of deposits on the side of the plate facing the crude oil as compared to a bare titanium surface, but to a lesser extent than Coating 1. The bare titanium plates were completely covered with a thick layer of crude oil that the plates “sprinkled” with . The term "deposits" is used here to describe deposits formed on heat transfer plates during operation. Deposits are residues and sludge formed by crude oil, and consist of a waxy, organic, part, and mineral, inorganic, part.

Subtracting the average weight of a clean plate from the weight recorded for individual plates with deposits, the average number of deposits per surface type was calculated (see Table 2). The weight of the coating was not compensated, so the real reduction in the formation of deposits will be slightly higher. For the heat transfer plates used in the test, the heat transfer surface was 0.85 m ² , therefore, for a plate with a coating of 4 μm thickness on both sides, the total volume of the coating material is 6.8 cm ³ . If the coating consists of pure SiO ₂ (density 2.6 g / cm ³ ), then the amount of coating on each plate is approx. 20 g

For both Coating 1 and Coating 2, deposits from the plates were removed more easily than deposits on exposed titanium plates (see Table 3). The difference in cleaning requirements was verified by manually wiping the plates with a cloth and rinsing with high pressure water. A simple wipe of the wafers with a cloth showed that deposits from coated wafers are very easy to remove, unlike uncoated wafers. When washing with high pressure water, all deposits, with the exception of one or two small spots, can be removed from the surface covered by Coating 1. On the surface covered by Coating 2, after washing with a stream of water, slightly more deposits remained. These deposits were in the form of slightly burnt oil. The coating was in good condition. Crude oil was passed through the first path of heat exchanger 2, and sea water was passed through the second path. On the surfaces of the plates facing the sea water, both coatings degraded.

The cold resistance of the coatings was tested by immersing the plates in liquid nitrogen having a temperature of -196 ° C. Then the plates were washed with water under high pressure, which removed most of the deposits. Neither for Coating 1 nor for Coating 2 damage was observed.

Returning to FIG. 1, 2 and 4, the plate heat exchanger 2 has predetermined dimensions of a plurality of components contained therein. For example, the first heat transfer plate and the second heat transfer plate may have a thickness m1 in the range of 0.1-1.4 mm or 0.2-1.2 mm. Each of the first heat transfer plate and the second heat transfer plate may have a heat transfer area m2 in the range of 0.05-0.30 m ² or 0.6-1.8 m ² . Any of the upper head and lower head may have a thickness m3 in the range of 45-145 mm or 190-250 mm. Each of the four side panels can have a thickness of m4 in the range of 35-85 mm or 65-175 mm. Each of the corner beams can have a side m5 section in the range of 35-85 mm or 110-190 mm. Finally, the sealed casing may have a volume of max. 0.02-0.40 m ³ or 0.7-5.0 m ³ . As described above, these dimensions, individually or in combination, create conditions in which the heat transfer plates in the bag 30 are less bent, which extends the life of the coating applied to them. At the same time, these components are not enlarged unnecessarily, but their dimensions are optimized so that the coating remains on them longer, while at the same time ensuring that the heat exchanger 2 has a reasonable material consumption.

In more detail, the sizes m1-m5 can be optimized relative to each other. For example, in one embodiment, the first heat transfer plate and the second heat transfer plate have a thickness of 0.7-0.9 mm and a heat transfer area of 0.02-0.035 m ² , while the upper and lower heads have a thickness of 35-45 mm, each side panel can have a thickness of 35-45 mm, each of the corner beams has a section side in the range of 35-45 mm, and the sealed casing has a volume of 0.005-0.020 m ³ .

In another embodiment, the first heat transfer plate and the second heat transfer plate have a thickness of 0.7-0.9 mm and a heat transfer area of 0.05-0.07 m ² , while the upper and lower heads have a thickness of 45-55 mm, each side panel can have a thickness of 35-65 mm, each of the corner beams has a section side in the range of 45-55 mm, and the sealed casing has a volume of 0.02-0.06 m ³ .

In another embodiment, the first heat transfer plate and the second heat transfer plate have a thickness of 0.7-0.9 mm and a heat transfer area of 0.09-0.11 m ² , while the upper and lower heads have a thickness of 45-55 mm, each side panel can have a thickness of 35-65 mm, each of the corner beams has a section side in the range of 45-55 mm, and the sealed casing has a volume of 0.04-0.22 m ³ .

In another embodiment, the first heat transfer plate and the second heat transfer plate have a thickness of 0.9-1.1 mm and a heat transfer area of 0.13-0.19 m ² , while the upper and lower heads have a thickness of 60-80 mm, each side panel can have a thickness of 45-85 mm, each of the corner beams has a section side in the range of 55-65 mm, and the sealed casing has a volume of 0.12-0.26 m ³ .

In another embodiment, the first heat transfer plate and the second heat transfer plate have a thickness of 0.9-1.1 mm and a heat transfer area of 0.24-0.30 m ² , while the upper and lower heads have a thickness of 120-160 mm, each side panel can have a thickness of 45-85 mm, each of the corner beams has a section side in the range of 65-105 mm, and the sealed casing has a volume of 0.2-0.6 m ³ .

In another embodiment, the first heat transfer plate and the second heat transfer plate have a thickness of 0.9-1.1 mm and a heat transfer area of 0.50-0.80 m ² , while the upper and lower heads have a thickness of 170-230 mm, each side panel can have a thickness of 90-160 mm, each of the corner beams has a section side in the range of 100-140 mm, and the sealed casing has a volume of 1.0-2.4 m ³ .

In another embodiment, the first heat transfer plate and the second heat transfer plate have a thickness of 1.1-1.3 mm and a heat transfer area of 1.4-2.0 m ² , while the upper and lower heads have a thickness of 120-400 mm, each side panel can have a thickness of 110-250 mm, each of the corner beams has a section side in the range of 120-240 mm, and the sealed casing has a volume of 2.4-5.9 m ³ .

From the above description it follows that although various embodiments of the invention have been shown, the present invention is not limited to them, but can be implemented in other ways within the scope of the invention defined in the attached claims. For example, optimization calculations may show that heat exchanger components with other sizes can provide a structure that allows the coating to remain on the coated surface for a long time. In addition, the heat transfer plates may have a different corrugation pattern. In other embodiments, the elongated seams and corresponding connecting grooves on the heat exchanger plates may be lowered so that the corrugations cover the heat exchange regions of the plates.

Claims (12)

1. A plate heat exchanger comprising an upper head (15), a lower head (16) and four side panels (11-14), which are bolted to a set of corner beams (21-24) to form a sealed casing, and a package of heat exchanger plates (30 ) located in the sealed casing, while the package of heat transfer plates (30) contains pairs (50, 60) of heat transfer plates stacked in a stack so that a path (67) is formed between pairs of stacked heat transfer plates (50, 60) in the stack the first fluid, and the pair (50) in the folded pairs of the foot (50, 60) is warm the exchange plates comprises a first heat exchange plate (51) and a second heat exchange plate (52), which are connected so that between the first and second heat exchange plates (51, 52) a path (57) is formed for the second fluid, characterized in that
the first heat transfer plate (51) and the second heat transfer plate (52) comprise a coating (701) that:
has a layer thickness of 1-30 microns,
made by sol-gel technology,
contains silicon oxide (SiOx) with an atomic ratio O / Si> 1 and
contains ≥5 atomic percent carbon (C). 2. A heat exchanger according to claim 1, wherein the first heat exchanger plate (51) and the second heat exchanger plate (52) have a thickness (m1) in the range of 0.6-1.4 mm or 0.8-1.2 mm. 3. The heat exchanger according to any one of paragraphs. 1, 2, in which each of the first heat transfer plate (51) and the second heat transfer plate (52) has a heat transfer area (m2) in the range of 0.05-0.30 m ² or 0.6-1.8 m ² . 4. The heat exchanger according to claim 1, wherein any of the upper head (15) and the lower head (16) has a thickness (m3) in the range of 45-145 mm or 190-250 mm. 5. The heat exchanger according to claim 1, wherein each of the four side panels (11-14) has a thickness (m4) in the range of 35-85 mm or 65-175 mm. 6. The heat exchanger according to claim 1, in which each of the corner beams (21-24) has a section side (m5) in the range of 35-85 mm or 110-190 mm. 7. The heat exchanger according to claim 1, in which the sealed casing has a volume in the range of 0.02-0.40 m ³ or 0.7-5.0 m ³ . 8. The heat exchanger according to claim 1, in which the thickness of the coating layer is in the range of 1.5-25 microns, or 2-20 microns, or 2-15 microns, or 2-10 microns, or 3-10 microns. 9. The heat exchanger according to claim 1, in which silicon oxide (SiOx) has an atomic ratio O / Si = 1.5-3 or has an atomic ratio O / Si = 2-2.5. 10. The heat exchanger according to claim 1, in which the coating has a carbon content in the range of 20-60 atomic percent or 30-40 atomic percent. 11. The heat exchanger according to claim 1, containing a gasket (131), which is at least partially coated. 12. The heat exchanger according to claim 1, in which the first heat transfer plate (51) and the second heat transfer plate (52) are made of stainless steel.

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