JPH06269602A - Device and method for removing calcium sulfate scale from evaporation device - Google Patents

Abstract

PURPOSE:To provide a device and method for removing calcium sulfate scale from an evaporation device incorporating heating elements, which can be operated safely and easily, and does not permit a chemical compound to contaminate a treated liquid. CONSTITUTION:The device for removing a calcium sulfate scale has a high- pressure liquid ejection nozzle 3 provided at the end of a heating element 2. The method for removing the calcium sulfate scale comprises 1) heating/drying the scale, 2) cooling the scale and the heating element, 3) washing the scale using a liquid, and blowing a high-pressure liquid to the residual scale from the nozzle. The method is performed at least once.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calcium sulfate scale removing device for a heating element built-in type evaporator and a method for removing calcium sulfate scale using the removing device.

[0002]

2. Description of the Related Art An evaporator is used to evaporate water in a processing liquid to produce pure water or to concentrate the processing liquid. , The liquid flowing outside the heating element is concentrated, and crystals are easily formed. Such crystals tend to adhere to the surface of the heating element as scales, and if scales are formed, the thermal conductivity decreases and the original evaporation ability cannot be exhibited. Therefore, it is necessary to suppress the scale formation or to remove the deposited scale, but calcium sulfate, which is the object of the treatment of the present invention, is a hard crystal and is firmly attached to the surface of the heating element. It is very difficult to process because it has a property that it hardly dissolves in acid and alkali. Conventionally, as measures against calcium sulfate scale, a) a jet cleaning method in which an operator or the like sprays a high-pressure fluid to remove the scale while the evaporator is stopped, b) a chemical method in which the scale is leached with a chemical, c) Crystal seed addition method to supply crystal seeds to the liquid to be treated so as not to oversaturate crystal components, d) Method of adding scale inhibitor to suppress scale precipitation, and e) Evaporation side and condensation side There is known a Rosenblad method or the like in which the cycle is periodically switched to suppress scale growth. Among these measures for calcium sulfate scale, it is reused by circulating like plating solution,
When it is necessary to control chemical components sufficiently, undesired chemical components may be mixed in the processing liquid in the above b) and d), and crystal seeds may be mixed in the processing liquid in c) above. However, in the case of (e), calcium sulfate cannot be removed from the system when the liquid to be treated is circulated and reused. There are drawbacks such as being inevitable. Therefore, the jet cleaning method described in (a) above is generally performed, but this method also requires a considerable amount of labor for humans to remove the scales in every corner of the heating element, and also removes strong scales. There is a problem in that human beings handle the high-pressure liquid for the purpose.

[0003]

Therefore, the present invention is
It is an object of the present invention to provide a calcium sulfate scale removing device and a removing method for a heating element built-in type evaporation device, which can be safely and easily operated, and in which a chemical component is not mixed in a treatment liquid.

[0004]

The object of the present invention is:
The outline of the heating element built-in type evaporation device in which the heating source is passed through the heating element and the processing liquid is passed through the outside is as shown in FIG. 1, and the appearance of the heating element is shown in FIG. There is. In this evaporator, the supplied processing liquid flows through the circulation pump and the distributor box, flows on the outer surface of the heating element, and is evaporated or concentrated by the heating source (usually steam) flowing inside the heating element. Is.

The present inventors have used a small device simulating such a heating element built-in type evaporation device to calculate a calcium sulfate scale (hereinafter, simply referred to as "scale").
Say. ), The scale and heating element are water-cooled after heating and drying the scale to make it easier to peel off the scale by taking advantage of the difference in thermal expansion between the scale and the heating element. However, the scale could not be completely removed, and as shown in FIG. 3, the scale remained firmly at the end of the heating element. Therefore, as a result of intensive studies on a method for efficiently removing scale, the present invention has been completed.

That is, according to the present invention, (1) in a calcium sulfate scale removing device of a heating element built-in type evaporator, a nozzle for spraying a high pressure liquid to the end of the heating element is provided on the side of the end of the heating element. An apparatus for removing calcium sulfate scale (hereinafter referred to as "first invention"), and (2) a method for removing calcium sulfate scale in a heating element built-in type evaporator, wherein the scale is heated. Drying, cooling the scale and heating element, washing the scale with a liquid,
Then, the step of spraying a high-pressure fluid to the scale remaining on the end of the heating element from a nozzle provided on the side of the end of the heating element of the evaporator is performed once or more. It relates to a method for removing calcium scale (hereinafter referred to as "second invention").

The present invention will be described in detail below with reference to FIGS. FIG. 4 shows a state in which the scale removing device according to the first aspect of the invention is provided for the evaporation device with a built-in heating element. Where 1 is a nozzle and high-pressure fluid piping,
2 is a heating element. EE of FIG.
A top view of the nozzle in line is shown in FIG. 5 and a side view in FIG. 5 and 6, 3 is a nozzle and 4 is a high pressure fluid pipe.

As shown in FIGS. 4-6, the nozzle is provided laterally to the end of the heating element. It is preferable to arrange the nozzles centrally at a place where scale is likely to occur. Further, the number of nozzles and the installation density are selected according to the remaining state of the scale. Therefore, it can be understood that the installation location, the number and the installation density of the nozzles can be changed depending on the design of each heating element or the area where the processing liquid flows, the property of the processing liquid, the operation period of the evaporator, and the like. Will.

Further, in the first aspect of the present invention, in designing the nozzle and the high-pressure fluid pipe, the flow of the treatment liquid outside the heating element is not hindered and the formation of scale is not promoted. It is necessary to consider engineering.

Next, the second invention will be described. In the evaporator immediately after the stop, scale is deposited on the entire surface of the heating element as shown in FIG. In order to remove such scale, first, the evaporation device on which the scale is deposited is stopped and the scale is dried by heating. For heating and drying, for example, a method is used in which after the treatment liquid is drained, dry air is allowed to flow outside the heating element.

The scale and heating element are then cooled. This cooling is to make cracks and the like in the scale by using the difference in thermal expansion between the scale and the heating element, and to facilitate separation from the heating element. Therefore, it is preferable to cool immediately after heating and drying. As the cooling medium, a gas such as cold air may be used, but cold water having a large heat capacity is preferable, and since the cooling medium does not necessarily need to dissolve the scale, in addition to cold water, particularly in terms of the quality of the treatment liquid. Various liquids can be used as long as they do not cause a problem, but it is preferable that they can be easily removed after use.

Further, the scale after cooling is washed with a liquid. As a result, the scale easily peeled by the above-mentioned treatment or the scale already peeled is washed off.
As the cleaning medium, liquids such as those mentioned above can be used in addition to water.

Although the scales deposited on the flat surface of the heating element can be considerably removed by the treatments up to the above, as shown in FIG. 8, only these treatments significantly increase the end portion of the heating element. Scale remains attached. This scale is strong and cannot be easily removed even if the treatments of to are repeated.

Therefore, in the second invention, in order to remove the scale left on the end of the heating element, the scale removing device of the first invention incorporated in the evaporator is used. The treatment consists of spraying a high-pressure fluid onto the scale remaining on the end of the heating element from a nozzle provided on the side of the end of the heating element, whereby the residual scale is knocked off. Become. As the high-pressure fluid, air, gas such as nitrogen gas and carbon dioxide gas, water, and liquids such as those mentioned above are used. The pressure of high pressure fluid is usually 2kg
・ About f / cm ² is sufficient.

In the second aspect of the invention described above,
The amount of scale, properties,
If necessary, it may be repeated twice or more depending on the deposition location and the like.

[0016]

The scale removing device according to the first aspect of the present invention has a simple structure and can be attached to the evaporation device at low cost and easily. Further, since it is easily incorporated into the evaporation device, even an operator who is unfamiliar or inexperienced in the scale removing operation can appropriately remove the scale. Further, the scale removing method of the second invention can be safely carried out because the operation using the high-pressure fluid can be automatically performed. Also, since each operation with different action is properly combined,
It is possible to remove the scale efficiently and at low cost without damaging the device parts, and it is possible to contribute to the extension of the service life of the evaporator.

[Brief description of drawings]

FIG. 1 is a schematic view of an evaporation device with a built-in heating element.

FIG. 2 is an outline view of a heating element.

FIG. 3 is a diagram showing the residual state of scale after treatment according to and of the present invention.

FIG. 4 is a diagram showing a state in which the scale removing device of the first invention is provided to the evaporation device with a built-in heating element.

5 is a plan view of the nozzle taken along the line EE of FIG.

6 is a plan view of the nozzle taken along the line EE of FIG.

FIG. 7 is a photograph showing a state in which the scale is deposited on the entire surface of the heating element.

FIG. 8 is a photograph showing a state in which a scale remains on the end of the heating element.

[Explanation of symbols]

 1 Nozzle and high pressure fluid piping 2 Heating element 3 Nozzle 4 High pressure fluid piping

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hirotaka Miyai 4-53-3 Kitahama, Chuo-ku, Osaka City Sumitomo Metal Industries Co., Ltd. (72) Atsushi Murata 4-53-3 Kitahama, Chuo-ku, Osaka No. Sumitomo Metal Industries Co., Ltd.

Claims (2)

[Claims] 1. A device for removing calcium sulfate scale of an evaporator with a built-in heating element, characterized in that a nozzle for spraying a high-pressure liquid to the end of the heating element is provided on the side of the end of the heating element. Calcium sulfate scale removal device. 2. A method for removing calcium sulfate scale in an evaporator with a built-in heating element, comprising:
The scale is heated and dried, the scale and the heating element are cooled, the scale is washed with a liquid, and then the scale remaining on the end of the heating element is attached to the side of the heating element end of the evaporator. A method for removing calcium sulfate scale, which comprises performing a step of spraying a high-pressure fluid from a nozzle provided on one side once or more.