JP2008139021A - Heat exchanger for food process - Google Patents

Abstract

An object of the present invention is to prevent food residue from adhering to the surface of a heat exchange part and to improve the chemical cleaning properties of the adhering substance.
A heat exchanger for a food process in which a surface side in contact with food is coated with an engineering plastic such as PEEK, PP, PET, PVDF, PFA, and PTFE. The surface that comes into contact with food is coated with a plastic that has a lower thermal conductivity than metal, so the heat conduction is relaxed and the temperature of the food on the surface of the heat exchanger is prevented from rising suddenly. However, food residues are difficult to adhere. In addition, the adhering food residue is prevented from sticking, and the cleaning property is improved. Since engineering plastics are excellent in heat resistance, they can be applied without problems to the operating temperature as a heat exchanger for food processes.
[Selection] Figure 1

Description

  TECHNICAL FIELD The present invention relates to a heat exchanger used for preparation of food, heating for sterilization, and the like in processes such as preparation and processing of food such as milk, mayonnaise, cheese, soy sauce, various beverages, and fat products.

  Conventionally, in food processes such as milk, mayonnaise, cheese, soy sauce, various beverages, fat products, etc., the heat exchange surface of the heat exchanger used for food preparation and sterilization, heating for processing, etc., heat exchange efficiency, From the point which is excellent in corrosion resistance etc., it is comprised with metals, such as stainless steel (for example, patent document 1).

  However, in a conventional food process heat exchanger having a heat exchange part surface made of metal, protein or the like, which is a component in food, can be obtained by directly contacting the food with the metal heat exchange part surface. There was a problem that it adheres to the surface of the heat exchanging part, and is easily solidified and fixed by being further heated on the attached surface.

  Thus, if food residues such as proteins adhere to the surface of the heat exchanger of the heat exchanger, the heat exchange efficiency of the heat exchanger is lowered and the temperature control of the heat exchanger becomes difficult. In this step, the heating conditions and the like cannot be accurately controlled.

  For this reason, conventionally, in order to prevent such problems caused by the deposits, the operation of the process is periodically stopped and chemical cleaning of the heat exchanger is performed. This cleaning is usually carried out through steps such as drug injection, heating, immersion, circulation, and drug extrusion cleaning using an appropriate acid, alkali or the like according to the composition and form of the deposit. In addition, when contamination by these deposits is severe and cannot be removed by chemical cleaning, the heat exchanger is disassembled, and cleaning work is directly performed to remove deposits on the surface of the heat exchange part by brushing or the like.

  However, it is necessary to interrupt the continuous operation for chemical cleaning of such heat exchangers, and it takes a lot of time and effort, and further cleaning for dismantling the heat exchanger is much more necessary. Therefore, there is no problem of the adhesion of food residue to the surface of the heat exchanging part or the adhesion is reduced, and the heat exchanger for food process is excellent in cleaning with chemicals. Is required.

Note that in heat exchangers for the production of ultrapure water, not for food processing, in order to prevent metal impurities from eluting from the surface of the heat exchange section and reducing the purity of ultrapure water, ultrapure water and The thing which provided the coating layer of PEEK in the heat exchange part surface which contacts is proposed (patent document 2).
“Fruit and fruit beverage encyclopedia” (supervised by the Japan Juice Association (Asakura Shoten), published in September 1978), page 47 Japanese Patent No. 3172730

  As described above, conventional food process heat exchangers have a problem of food residue adhering to the surface of the heat exchanging part, and it is necessary to prevent or reduce such adhering substances and to improve the cleaning properties of adhering substances. It was done.

  Accordingly, an object of the present invention is to provide a food process heat exchanger that has no problem of adhesion of food residues to the surface of the heat exchange section or has reduced adhesion and is excellent in cleanability.

  The food process heat exchanger of the present invention (Claim 1) is characterized in that the surface side in contact with food is covered with engineering plastic.

  The food process heat exchanger according to claim 2 is characterized in that the engineering plastic is at least one selected from the group consisting of PEEK, PP, PET, PVDF, PFA, and PTFE.

  In the heat exchanger for food processing of the present invention, the surface side that comes into contact with food is coated with engineering plastic, so that the adhesion of food residues to the surface of the heat exchange part is prevented, and the detergency is also improved.

  In other words, in a conventional food process heat exchanger whose surface is made of metal, a large amount of heat is instantaneously conducted to the food side due to the high thermal conductivity of the metal. This has caused food residue to adhere to the surface of the heat exchanging portion and further cause solidification and fixation.

  In the heat exchanger for food processing of the present invention, the surface that comes into contact with food is coated with a plastic having a lower thermal conductivity than metal, so that the heat conduction is relaxed, and the food on the surface of the heat exchange section as described above is abrupt. The temperature rise is prevented, and as a result, the food residue hardly adheres even at the same heating temperature as before. In addition, the adhering food residue is prevented from sticking, and the cleaning property is improved.

  In addition, since it is excellent in heat resistance if it is an engineering plastic, it can apply without a problem to the use temperature as a heat exchanger for food processing.

  In the present invention, PEEK (polyetheretherketone), PP (polypropylene), PET (polyethylene terephthalate), PVDF (polyvinylidene fluoride), PFA (perfluoroalkoxyfluoropolymer), PTFE (polytetrafluoroethylene) In particular, PEEK is preferable in terms of performance and durability.

  Embodiments of the food process heat exchanger of the present invention will be described in detail below.

  The heat exchanger for a food process of the present invention is generally used in a food process except that the surface that comes into contact with food is covered with engineering plastic, including the surface of the heat exchange part that comes into contact with food. The type is not particularly limited, and a plate type heat exchanger, a tube type heat exchanger, or the like can be adopted.

  The engineering plastic that covers the surface of the heat exchanger that comes into contact with the food is preferably PEEK, PP, PET, PVDF, PFA, PTFE, or two or more of these.

  When the temperature is gradually raised, the plastic eventually burns through a non-change region (endothermic region), a melting region, and a decomposition region (combustion region: change from burning region to combustion). In order to coat the heat exchanger, it is preferable that the plastic has a wide melting temperature range. FIG. 1 shows the thermal characteristics of various plastics. As is apparent from this graph, PEEK is a plastic having a wide melting temperature range and is suitable as a coating material. PEA, PVDF, and PTFE also have a wide melting temperature range, but PEEK is preferable as a coating material from the viewpoint of coating performance and durability (life).

  HT-PVC (heat resistant polyvinyl chloride), PPS (polyphenylene sulfide), etc. are not preferable as a coating material because they have a narrow melting temperature range and may burn immediately as the temperature rises.

  In the present invention, the surface of a metal heat exchange member or the like of a heat exchanger made of stainless steel, titanium, aluminum, copper or the like is covered with the engineering plastic as described above. As a method of coating the surface of such a metal heat exchange member with engineering plastic, a method in which powdered plastic is attached to the surface of these heat exchange members, heated and melted, and fused to the surface, melting There are a method of applying the applied plastic to the metal surface and attaching it, or a method of attaching a heat exchange member to the molten plastic and attaching it, and engineering plastics such as PEEK can employ any method. In addition, when forming the coating layer with an engineering plastic, you may perform pre-processing, such as a primer process, with respect to these heat exchange members.

  Although there is no restriction | limiting in particular as thickness of the coating layer formed with such an engineering plastic, It is preferable to set it as about 10-100 micrometers. If the thickness of this coating layer is too thin, it will not be possible to sufficiently obtain the effect of mitigating rapid heat conduction due to the formation of the coating layer, and thus sufficient effects for preventing adhesion of food residues and improving cleaning properties will be obtained. Can't get to. If the coating layer is excessively thick, the heat conduction efficiency may be lowered, and the formation cost is high, which is disadvantageous.

  Such a heat exchanger for food process of the present invention is useful as a heat exchanger for heating for preparation, sterilization, processing, etc. of foods such as milk, mayonnaise, cheese, soy sauce, various beverages, fat products, The effect of preventing adhesion to the surface of the heat exchange part and the effect of improving the cleaning performance reduce the chemical cleaning frequency and chemical cleaning time, and continuously operate for a long time with high heat exchange efficiency and high-precision heat exchange control. It can be carried out.

  Hereinafter, the present invention will be described more specifically with reference to experimental examples and examples.

Example 1
The test which investigates the peelability after foodstuffs adhered using the metal plate and the PEEK coating plate was done.

  A SUS-304 plate used in a normal plate heat exchanger as a test material and a plate having a 50 μm thick PEEK coating on the surface of the SUS-304 plate were used.

In the test, various foods listed in Table 1 were dropped on each plate surface in order to make the food attached, and the food was dried from the back so that the plate surface was 140-150 ° C. Next, the cellophane adhesive tape was affixed to the dried surface and peeled off instantaneously after 1-2 minutes (based on JIS-K-5400 8.5.2 (4) (e)). The state of deposits on the plate surface after peeling was visually observed and evaluated according to the following criteria, and the results are shown in Table 1.
[Evaluation criteria]
(Double-circle): The deposit remaining amount is 0%. A state in which there is no deposit remaining ○: A state in which less than 10% of the deposit remains △: A state in which more than 10% but less than 50% of the deposit remains ×: A state in which 50% or more of the deposit remains

  As is clear from Table 1, even a deposit that is difficult to peel off with a SUS-304 plate can be easily peeled off with a PEEK coated plate. From this result, it is understood that the adhesion of food residue can be greatly reduced by coating the surface of the heat exchanger that contacts the food with engineering plastic.

Example 2
In order to confirm the adhesion of food, a mini heat exchanger (inner surface size: 20 cm × 5 cm × 0.5 cmH, surface area: 100 cm ² ) shown in FIG. 2 was prototyped and tested. In this heat exchanger, a sample circulation side member 1 and a steam circulation side member 2 are integrated by a bolt 4 and a nut 5 via a heat exchange plate 3, and the vapor circulation side member 1 has a sample inlet 1A. And a sample outlet 1B. The steam distribution side member 2 is provided with a steam inlet 2A and a steam outlet 2B.

  As the heat exchange plate 3, a SUS-304 plate 3B provided with a PEEK coating (coating thickness 50 μm) 3A was provided such that the surface of the PEEK coating 3A was on the sample side.

  A steam at about 140 ° C. is vented to the steam circulation side of the heat exchanger, and a soy milk solution (20 wt%) is passed through the sample circulation side as a sample at 20 mL / min. The adhesion to the (PEEK coating 3A surface) side was evaluated.

  For comparison, a similar test was performed using an uncoated SUS-304 plate as the heat exchange plate 3.

  The adhesion of the sample was evaluated by measuring the increasing time of the inlet pressure (differential pressure) due to the sample passing time and the food residue adhering to the heat exchanger surface.

  As shown in FIG. 3, when the SUS-304 plate is used, the test results show a pressure increase tendency in about 8 hours from the start of liquid flow, whereas in the case where the PEEK coating plate is used, the pressure rises slowly in about 30 hours. The pressure increased.

  From these results, it can be seen that by coating the surface of the heat exchanger that comes into contact with food with engineering plastic, the maintenance frequency (cleaning frequency) is reduced and the apparatus operating efficiency can be greatly improved.

It is a graph which shows the thermal characteristic of various plastics. 3 is a schematic cross-sectional view showing a test heat exchanger used in Example 2. FIG. 10 is a graph showing the results of Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample distribution side member 2 Steam distribution side member 3 Heat exchange plate 3A PEEK coating 3B SUS-304 plate

Claims (2)

  A heat exchanger for food processing, characterized in that the surface side in contact with food is coated with engineering plastic.   The heat exchanger for food processing according to claim 1, wherein the engineering plastic is at least one selected from the group consisting of PEEK, PP, PET, PVDF, PFA, and PTFE.

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