JP5872204B2 - How to remove scale - Google Patents

Description

  The present invention relates to a method for removing scale on a surface of a hard material.

  Conventionally, scales (lime scale) such as calcium carbonate derived from hardness components of tap water are deposited on the hard material surface inside the device using tap water, and the heat transfer of the device is reduced due to steam generation, or Since it causes clogging of the water or steam piping system, removal treatment with an acidic cleaning agent is periodically performed to remove it. Moreover, even when using water other than tap water (for example, pure water, groundwater, seawater, alcohol), a scale containing dirt, calcium, and the like derived from additives and solutes may adhere.

  These scales include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, or citric acid, malic acid, acetic acid, sulfamic acid, gluconic acid, glycolic acid, tartaric acid, lactic acid, adipic acid, succinic acid, succinic acid, fumaric acid It is conventionally known that it can be removed by a cleaning treatment with an acidic cleaning agent containing as a main component an organic acid.

  Patent Document 1 (Japanese Patent Publication No. 9-508930) discloses a composition in which a maleic acid is mixed with a nonionic, anionic, cationic, amphoteric surfactant as an improved acidic detergent. It is also publicly known that the product is effective, and it is also possible to use a composition containing sulfamic acid, methanesulfonic acid, citric acid, phosphoric acid, hydrochloric acid or a mixture thereof as maleic acid as the acid component. Has been.

  Further, Patent Document 2 (Japanese Patent Application Laid-Open No. 2011-32396) discloses methane as a special scale soil removing agent containing starch, wheat flour protein, calcium, etc., which is attached to a noodle device using a stainless steel koji or phosphate. It is disclosed that an acidic detergent containing sulfonic acid, nitric acid and phosphoric acid and having a nitric acid content of 1 to 20% by weight is effective. Further, in this published patent, in order to efficiently remove the adhesion scale, it is also mentioned that a method of washing the scale adhesion surface with the above-mentioned acidic detergent and then washing with an alkaline detergent is preferable. Yes.

  Furthermore, Patent Document 3 (Japanese Patent Application Laid-Open No. 2008-266562) describes 1 to 14% by weight of sulfamic acid and 5 to 10% by weight of methanesulfonic acid for the purpose of removing solid deposits (iron clogging) in drinking water piping. , 0.075-0.15 wt.% Phosphonobutane-tricarboxylic acid, 0.3 wt.% 2-propanol and a softener necessary to make 100 wt.

Special table hei 9-508930 JP2011-32396 JP2008-266562

The present invention relates to a method for efficiently removing scale adhered to a hard material surface.
When tap water is used in the device, the hardness component contained in the tap water is a hard material of the device as a carbonate scale mainly composed of calcium carbonate or magnesium carbonate (generally, stainless steel plate, chrome-plated bronze heater tube) ) Is a common phenomenon.

  Although these carbonate-based inorganic scales are easily removed by a cleaning treatment with a generally known acidic cleaning agent, in actual usage, the characteristics of water used, the heating conditions, the influence of the type of piping used, the process of use In many cases, the scale formed due to the influence of the additive agent conditions in the mixture is a mixture of carbonate, water-insoluble silicate compound (hereinafter referred to as silica), iron rust, phosphate compound, These mixed inorganic scales are in a state where there are many so-called hard-to-removable inorganic scales that are not easily removed by a cleaning treatment with a conventionally known acidic detergent.

  Further, even when a liquid other than tap water is used in the apparatus, the scale may adhere due to its solute, such as starch, protein, metal ions, calcium, and the like.

  The present invention does not cause deterioration of the hard material surface, which is inconvenient for reuse of processing equipment, and can be removed at a high level and quickly even with inorganic scales that are difficult to remove as described above. The method to do is proposed.

The subject of the present invention is achieved by the following three processing steps.
1st step: Execution of the cleaning process by the acidic cleaning agent with respect to the hard material surface to which the scale adheres. It is particularly preferable to use a mixed liquid of methanesulfonic acid and hydroxycarboxylic acid as the acidic cleaning agent.
Second step: The drying process is performed on the first step processing surface.
3rd step: Implementation of a cleaning process with an alkaline cleaning agent on the 2nd step processing surface.

  The inventor of the present application has an efficient problem of adding a drying process to the processing surface as the second step between the cleaning process using the acidic cleaning agent as the first step and the cleaning process using the alkaline cleaning agent as the third step. The present invention has been found to be extremely useful as a solution, and the present invention has been completed.

  As the acidic detergent used in the first step, generally known acidic detergents can be used. However, strong acids such as hydrochloric acid, sulfuric acid, and sulfamic acid exhibit excellent descaling effect, but material corrosion. It is a group of detergents that lack general versatility due to its high possibility of causing odors, and its use is limited, but the group of detergents mainly composed of citric acid organic acid is less affected by corrosion, etc. Excellent in versatility.

  In particular, as a detergent exhibiting excellent characteristics for the purpose of the present invention, one or two selected from methanesulfonic acid, glycolic acid, tartaric acid, lactic acid, citric acid, DL-malic acid, gluconic acid and the like It is an acidic detergent containing the above hydroxycarboxylic acid, and among these hydroxycarboxylic acids, glycolic acid, tartaric acid, and citric acid can be particularly preferably used because they have a quick effect on the manifestation of the intended effect and less influence on member deterioration. .

  The mixed acidic cleaning agent may be a mixture of a generally used metal corrosion inhibitor, a surfactant for reinforcing cleaning power, and a chelating agent.

  The use of a mixture of hydroxy carboxylic acid and methane sulfonic acid as an acidic detergent provides a synergistically high level of removal effect on the scale to be removed, and ultimately the high removal effect level and coverage. It is possible to simultaneously minimize the effects of corrosion and deterioration of the processing material.

About the mixing ratio of hydroxycarboxylic acid and methanesulfonic acid, it is the range of 99: 1 to 1:99 by weight ratio, and the range of 70:30 to 30:70 is especially preferable.
In addition, another factor for optimizing the performance of the mixed acidic detergent is to optimize the pH of the cleaning solution, and the optimum pH range of the actual processing solution is preferably 0.3 to 2.5, preferably Is in the range of 0.8 to 2.0. If it is 0.3 or less, the influence on the member deterioration becomes large, and if it is 2.5 or more, the scale removal effect tends to decrease.

The pH of the actual processing solution can be adjusted by using an alkali hydroxide such as sodium hydroxide or potassium hydroxide immediately before use. The method of adjusting the pH in advance is more preferable because the complexity during the cleaning operation can be avoided.
In general, the mixed acidic detergent is generally prepared by preparing a concentrated solution as a concentrated solution and diluting with water to an optimum concentration at which the target performance is appropriately exhibited in actual use.

The drying process performed in the second step is a process that is performed when the scale adheres and remains on the treated surface after the cleaning process using the acidic detergent. This is an important process to be carried out in order to facilitate easy peeling at the time of washing with an alkaline detergent.
This drying treatment may be natural drying, blow drying (room temperature to 300 ° C.), or heat drying.

  The effect that the drying scale easily peels off due to this drying treatment is that voids are generated inside the scale due to the washing treatment with the acidic detergent, the scale itself shrinks due to drying, and the shrinkage force is the adhesion point of the scale material interface. This is performed with the aim of reducing the adhesion force (occurrence of floating) to the material interface of the scale.

The alkaline detergent used in the third step can be used as long as it is an alkaline detergent, and its composition is not particularly limited.
Examples of cleaning agents include sodium hydrogen carbonate (sodium bicarbonate), sodium carbonate based, sodium hydroxide and / or potassium hydroxide, and alkaline, including silicates, nonionic surfactants, chelating agents A cleaning agent can be preferably used.

  Another main point constituting the present invention is to combine the cleaning process with the acidic detergent as the first step, the drying process as the second step, and the cleaning process with the alkaline detergent as the third step in this order. If the order of application is different, the purpose and effect will be insufficient. The reason why this application order is effective is not necessarily clear at present, but the scale structure is loosened by the acidic cleaning agent treatment, the scale structure is shrunk by the drying treatment, and the adhesion force to the material interface of the adhesion scale is reduced by the shrinkage force. It can be inferred that this reduction is due to the formation of a favorable circulation system for removing adhered foreign substances such as increasing the effectiveness of the peeling effect from the material interface of the adhesion scale by the alkaline cleaning agent treatment.

  The scale removal method of the present invention is a scale that can remove scales adhering to the surface of a hard material at a high level and quickly, and has become difficult to remove due to the influence of water characteristics, additives, and usage conditions. Similarly, it can be removed at a high level and quickly.

FIG. 1 is a diagram showing the relationship between the pH of an acidic detergent and the degree of scale removal. FIG. 2 is a diagram illustrating the relationship between the scale removal degree and the cleaning processing time.

Hereinafter, the removal method of the present invention will be described for each step.
The cleaning treatment with the acidic cleaning agent performed in the first step is performed by contacting the surface of the hard material on which the scale is adhered with the optimal concentration of the acidic cleaning agent under the optimal conditions. Liquid contact means holding the cleaning liquid in contact with the surface of the hard material. Specific methods include a method of immersing a hard material having a surface to be treated in the cleaning liquid, a surface of the hard material. It is carried out by a method of filling and holding a cleaning agent solution in a container having the above, or a method of spraying or applying a cleaning agent on the surface of a hard material. A generally preferred method is a method of filling and holding a cleaning liquid in a container having a hard material surface. The optimum concentration of the cleaning agent varies depending on the amount of scale adhesion and the conditions in contact with the liquid, but as a general application condition, the concentration of the drug is 0.1 to 10 wt% as an active ingredient, preferably in the range of 0.5 to 2 wt%. The liquid temperature is 10 to 100 ° C., and the treatment time is 10 minutes to 24 hours. Moreover, in order to achieve descaling quickly, a method of applying a high liquid temperature condition by setting the applied drug concentration high is advanced.

  Substantial drug processing involves replacing the liquid supplied to the device with chemical liquid, performing normal operation processing, discharging the chemical liquid after the end of processing, injecting rinse water, and performing short-time operation processing. By repeating the process once, rinsing is performed so that no cleaning agent remains on the cleaning surface.

  As another treatment method, a chemical solution tank having a heat retaining function is prepared, and the treatment solution prepared therein is circulated for a specified time between the surface to be treated (in the tank) and the chemical solution tank by a circulation pump (chemical solution circulation method). ) Can be processed by the method.

  The drying process performed in the second step can be performed by any method of natural drying, forced drying by blowing air, or forced drying by heating. Here, the term “drying” as used in the present invention means that the liquid is reduced to such an extent that the liquid does not transfer to the hand even if at least the portion to be cleaned is touched by hand.

  The cleaning treatment with the alkaline cleaning agent performed in the third step is basically applied by a method according to the processing method with the acidic cleaning agent.

  Examples are shown below to describe the present invention more specifically, but the present invention is not limited to these Examples.

(Examples 1-7 and Comparative Examples 1-14)
The compound detergent (A-1-7) shown in Table 1 was used as a test cleaning agent as an acidic cleaning agent.

  As an alkaline cleaner, the blend composition B-1 shown in Table 2 was used.

  As the objects to be cleaned, the inner wall of the stainless steel can of the towel steamer (Electric towel steamer manufactured by Niita Kogyo Co., Ltd.) that has been confirmed to adhere to the scales of constituent elements shown in Table 3 below after long-term use of tap water. A large number of 3 cm × 3 cm pieces were cut out from the washed product 1), and an approximate scale adhering amount piece was selected from them, and subjected to a washing test.

The cleaning of the object piece to be cleaned (hereinafter referred to as “test piece”) is performed by a method in which the test piece is allowed to stand for 1 hour in a specified cleaning solution, and the same test piece is subjected to primary cleaning with an acidic cleaning solution or an alkaline cleaning solution. Based on the method of carrying out the treatment, followed by the drying treatment and then the secondary washing treatment with the acidic washing solution or the alkaline washing solution.
The number of test pieces was three for each cleaning treatment, the amount of the cleaning solution was 200 ml, and the cleaning solution container was stored in a thermostat so that the temperature of the cleaning solution was 60 ° C. ± 1 ° C.
The test piece after the cleaning treatment was rinsed by repeating the immersion treatment for 2 minutes in 200 ml of fresh water (tap water) three times, and the attached cleaning solution was washed away.

  The test piece drying process was implemented by the method of either D-1 or D-2. D-1 is a method of leaving it naturally in an indoor space having an air temperature of about 25 ° C. and a relative humidity of about 65% (air drying treatment). D-2 is a method of standing in hot air at 80 ° C. for 30 minutes (forced drying treatment).

The removal state of the adhesion scale on the test piece was evaluated by the following method.
The state of scale adhesion on the test piece after each cleaning treatment is observed with the naked eye, and the state is assigned a numerical value between 1 (state without attached scale removal (state before cleaning)) to 5 (state completely removed with attached scale), The average value of the three test piece evaluation values was taken as the degree of scale removal under the cleaning treatment conditions.

Table 4 shows the results of the cleaning treatment test carried out by combining various treatment conditions.
From the Table 4 test result table, the methods of Examples 1 to 7 (primary cleaning treatment with an acidic detergent, then drying treatment, and then secondary washing treatment with an alkaline detergent) are the same as the methods of Comparative Examples 1 to 7 (alkaline Primary cleaning treatment with a cleaning agent, followed by drying treatment, then secondary cleaning treatment with an acidic cleaning agent) and the methods of Comparative Examples 8 to 13 (primary cleaning treatment with an acidic cleaning agent, then no drying treatment, then with an alkaline cleaning agent) (Execution of secondary cleaning process) It was confirmed that the adhered foreign matter removal effect was more excellent.
Moreover, Examples 2-5 using the acidic cleaning agent which mix | blended methanesulfonic acid and hydroxycarboxylic acid are methanesulfonic acid independent (Example 1), or hydroxycarboxylic acid independent mixing type acidic cleaning agent (Example 6- 7) It was confirmed that a higher adhering foreign matter removing effect was exhibited.

(Examples 8-9 and Comparative Examples 15-18)
As the object 2 to be cleaned, a number of 5 cm × 5 cm pieces are cut out from the container transport container (carrier) member in the continuous retort sterilization apparatus made of stainless steel to which the scales of the constituent elements shown in Table 5 are attached. A scale adhering piece was selected and subjected to a cleaning test.

  As the test detergent, A-8 and A-9 of the blending composition shown in Table 6 were used as the acidic detergent, and the blending composition B-2 shown in Table 2 was used as the alkaline detergent.

The cleaning treatment is performed as an acidic cleaning agent treatment at a treatment liquid temperature of 50 ± 1 ° C. and an immersion time of 3 hours, and as an alkaline cleaning agent treatment is carried out at a treatment liquid temperature of 50 ± 1 ° C. and a treatment time of 3 hours, followed by drying The treatment was carried out by D-1 (air drying treatment) described above.
As a characteristic evaluation method, it implemented by the method applied in Examples 1-7 and Comparative Examples 1-14.

  The result of characteristic evaluation was as shown in Table 7.

Table 7 From the test result table, the degree of descaling on the final object to be cleaned by the methods of Examples 8 and 9 (primary washing treatment with acidic detergent, then drying treatment, and then secondary washing treatment with alkaline detergent). Corresponding to the methods of Comparative Examples 15 to 16 and 17 to 18 (primary washing treatment with an alkaline detergent, then drying treatment, then secondary washing treatment with an acidic detergent, or primary washing treatment with an acidic detergent, then drying treatment) It was confirmed that the level was clearly higher than that in the case of none and then a secondary cleaning treatment with an alkaline detergent.
It was also confirmed that the degree of scale removal when using an acidic detergent containing methanesulfonic acid and tartaric acid was generally higher than when methanesulfonic acid alone was used as the acidic detergent.

The effect of methanesulfonic acid-containing acidic cleaning solution pH on scale removal was evaluated by the following method.
As the test washing solution, the amount of blended NaOH was changed so that the pH of the diluted solution of 15 times water was 0.62, 0.95, 1.22, 1.41, 1.72, 1.99, 2.30 A -9 15-fold water dilution was used. As an object to be cleaned, a 3 cm × 3 cm cut piece of the object to be cleaned 1 was used. As a cleaning test method and a property evaluation method, the cleaning solution immersion treatment was performed at a treatment solution temperature of 50 ° C. and an immersion time of 1 hour, and the other implementation methods and conditions were in accordance with the methods implemented in Examples 1 to 7.
As a result of the evaluation, the relationship between the cleaning solution pH and the degree of scale removal is shown in FIG. As is clear from FIG. 1, it was confirmed that when the cleaning solution pH exceeds 2, the degree of scale removal clearly decreases.

The method of the present invention and the evaluation of the scale removal characteristics during the long-time immersion treatment of the acidic cleaning agent were carried out as follows.
The conditions of the test cleaning solution and the drying treatment were as follows: A-3, 6-fold water dilution solution was used as the acidic cleaning treatment; B-1, 6-fold water dilution solution was used as the alkaline cleaning treatment; 30 minutes in a hot air dryer. The article to be cleaned, the scale deposition amount was used the cleaning object 2 that is 14.3 g / ^{m 2.} As an actual cleaning method, each continuous treatment was carried out for 3 hours, 12 hours, and 24 hours at a liquid temperature of 50 ° C. as a pickling method alone. Then, as a method of the present application, washing with an acidic cleaning agent at a liquid temperature of 50 ° C. for 3 hours, followed by a drying treatment, and then a washing treatment with an alkaline cleaning agent for 1 hour at a liquid temperature of 50 ° C. As a conventional method, washing with an acidic detergent for 3 hours at a liquid temperature of 50 ° C., followed by washing with an alkaline detergent for 1.5 hours and 3 hours of immersion at a liquid temperature of 50 ° C. were performed.
As a characteristic evaluation method, the method performed in Example 8 was used. FIG. 2 shows the relationship between the scale removal degree and the total processing time as an evaluation result. As is clear from FIG. 2, it was confirmed that the method of the present application can completely remove the scale in a shorter time than the pickling method and the conventional method.

Claims (1)

A method of sequentially performing a cleaning process with an acidic cleaning agent, then a drying process, and then a cleaning process with an alkaline cleaning agent in this order on the surface of the hard material to which the scale is attached, and the methanesulfonic acid is used as the acidic cleaning agent. And a hydroxycarboxylic acid mixed in a mixing ratio of 30:70 to 70:30, and having a pH in the range of 0.8 to 2.0. .

Images