Descaling cleaning agent and application thereof

Abstract

The invention relates to the field of surface treatment of high-pressure heater heat exchange equipment, and discloses a descaling cleaning agent and application thereof. Based on the total weight of the descaling cleaning agent, the descaling cleaning agent is prepared from the following components in percentage by weight: 5 to 40 percent of oxalic acid, 0.5 to 10 percent of tartaric acid, 0.5 to 10 percent of malic acid, 0.05 to 5 percent of a surfactant, 0.05 to 5 percent of a complexing agent, 0.05 to 5 percent of a corrosion inhibitor, 0.1 to 5 percent of an additive and 40 to 93 percent of water, the surfactant is a combination of a nonionic surfactant and an anionic surfactant. The descaling cleaning agent disclosed by the invention takes the organic weak acid as a main body, is matched with the surfactant, the complexing agent and other auxiliaries, has the characteristics of high descaling efficiency, high speed, low corrosivity, no damage to a cleaning surface, low cost and the like, can be applied to surface treatment of high-pressure heater heat exchange equipment, and is particularly suitable for cleaning a scale sample in a U-shaped heat exchange tube of a high-pressure heater.

Description

Technical Field

[0001] The invention relates to the field of surface treatment of high-pressure heat exchange equipment, and in particular to a descaling cleaning agent and application thereof. Background Art

[0002] As an important heat exchange unit in thermal power plants, high-pressure heaters generally have scaling on the heat exchange surface. For U-shaped tube-type high-pressure heaters, the inner wall of the U-shaped heat exchange tube is more susceptible to corrosion and scaling under high temperature and high pressure. The diameter of the U-shaped heat exchange tube in a common U-shaped tube-type high-pressure heater is about 16mm, the tube length is about 23m, the tube openings are densely distributed, and the area is about 2m 2 There are about 800 tube openings on the tube sheet. This structure makes it difficult to clean the scale inside the U-shaped heat exchange tube by traditional mechanical methods. Incomplete cleaning of the scale will not only seriously affect the heat exchange efficiency of the high-pressure heat exchanger, but also affect its service life, cause safety hazards, and increase maintenance costs.

[0003] Research shows that the working temperature of the high-pressure heat exchanger in a thermal power plant can reach 170-250℃ and the pressure can reach 17MPa. The temperature of the U-shaped heat exchange tube can reach 265℃ and the pressure can reach 35MPa. When the medium water in the tube passes through the U-shaped heat exchange tube to exchange heat with the shell medium water and steam outside the tube, the heat exchange surface inside the tube is prone to electrochemical corrosion under the action of high temperature and high pressure, and scale samples with a certain degree of bonding with the heat exchange surface are accumulated inside the tube. The main component of the scale sample is iron oxide Fe. 2 O 3 With magnetic iron oxide Fe 3 O 4 Due to the magnetic rust Fe 3 O 4 The unique trans-spinel structure is relatively stable at room temperature and is not easy to clean by simple acid dissolution.

[0004] In the industry, inorganic strong acids such as hydrochloric acid and hydrofluoric acid are often used for chemical cleaning. However, such chemical cleaning agents will produce acid mist during the production and application process. At the same time, due to the lack of anti-rust function, corrosive chemicals such as strong acids and chloride ions can easily cause secondary damage to the cleaning surface, affecting the service life of the equipment. The scale inside the U-shaped heat exchange tube of the high-pressure heat exchanger mostly comes from electrochemical corrosion under high temperature and high pressure. The scaling process will cause certain damage to the heat exchange surface matrix, so traditional strong acid descaling cleaning agents are not suitable. Organic acids are less corrosive than inorganic acids, but their descaling rate is slow, the cycle is long, and the operating temperature is high. At the same time, the cost of fine organic acids is high and cannot meet the needs of actual applications. Therefore, it is of great significance to provide a highly efficient, environmentally friendly descaling cleaning agent suitable for U-shaped heat exchange tubes of high-pressure heaters with low substrate corrosion. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of slow descaling rate, strong corrosiveness and high cost of descaling cleaning agents in the prior art, and to provide a descaling cleaning agent and its application. The descaling cleaning agent is mainly composed of organic weak acid, combined with surfactants, chelating agents and other auxiliary agents, and has the characteristics of high descaling efficiency, fast rate, low corrosiveness, no damage to the cleaned surface, low cost, etc. It can be used in the surface treatment of high-pressure heat exchange equipment, and is particularly suitable for cleaning scale samples inside U-shaped heat exchange tubes of high-pressure heaters.

[0006] In order to achieve the above-mentioned purpose, on the one hand, the present invention provides a descaling cleaning agent, which, based on the total weight of the descaling cleaning agent, contains 5-40wt% of oxalic acid, 0.5-10wt% of tartaric acid, 0.5-10wt% of malic acid, 0.05-5wt% of a surfactant, 0.05-5wt% of a complexing agent, 0.05-5wt% of a corrosion inhibitor, 0.1-5wt% of an additive and 40-93wt% of water, wherein the surfactant is a combination of a nonionic surfactant and an anionic surfactant.

[0007] Preferably, based on the total weight of the descaling cleaning agent, the descaling cleaning agent contains 10-25wt% of oxalic acid, 3-5wt% of tartaric acid, 3-5wt% of malic acid, 0.6-1.5wt% of a surfactant, 0.6-1.5wt% of a complexing agent, 0.1-1wt% of a corrosion inhibitor, 0.5-1.5wt% of an additive and 60-80wt% of water.

[0008] Preferably, among the surfactants, the mass ratio of the nonionic surfactant to the anionic surfactant is 1:(0.5-5), preferably 1:(1-3).

[0009] Preferably, the nonionic surfactant is at least one of fatty alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether.

[0010] Preferably, the anionic surfactant is at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and sodium dodecyl polyoxyethylene ether sulfate.

[0011] Preferably, the complexing agent is at least one of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, tetrasodium hydroxyethylidene diphosphonate, sodium citrate and sodium gluconate.

[0012] More preferably, the complexing agent is a combination of disodium ethylenediaminetetraacetate and tetrasodium hydroxyethylidene diphosphonate.

[0013] Preferably, the mass ratio of the disodium ethylenediaminetetraacetate to the tetrasodium hydroxyethylidene diphosphonate is (0.5-5):1, and more preferably (1-3):1.

[0014] Preferably, the corrosion inhibitor is at least one of hexamethylenetetramine, imidazoline, quinoline and Mannich base.

[0015] Preferably, the additive is at least one of potassium chloride and sodium chloride.

[0016] The second aspect of the present invention further provides the use of the above-mentioned descaling cleaning agent in the surface treatment process of the U-shaped heat exchange tube.

[0017] Preferably, the implementation conditions of the surface treatment process include: a temperature of 15-35° C., more preferably 20-30° C.; and a soaking time of 2-10 h, more preferably 4-6 h.

[0018] The descaling cleaning agent of the present invention is mainly composed of organic weak acid, combined with a compounded surfactant and a combined chelating agent and other auxiliary agents. It has the characteristics of high descaling efficiency, fast rate, low corrosiveness, no damage to the cleaned surface, low cost, etc. It can be used in the surface treatment of high-pressure heat exchange equipment, and is particularly suitable for cleaning scale samples inside U-shaped heat exchange tubes of high-pressure heaters. DETAILED DESCRIPTION

[0019] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0020] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0021] The descaling cleaning agent of the present invention contains, based on the total weight of the descaling cleaning agent, 5-40wt% of oxalic acid, 0.5-10wt% of tartaric acid, 0.5-10wt% of malic acid, 0.05-5wt% of a surfactant, 0.05-5wt% of a complexing agent, 0.05-5wt% of a corrosion inhibitor, 0.1-5wt% of an additive and 40-93wt% of water, wherein the surfactant is a combination of a nonionic surfactant and an anionic surfactant.

[0022] Preferably, based on the total weight of the descaling cleaning agent, the descaling cleaning agent contains 10-30wt% of oxalic acid, 1-8wt% of tartaric acid, 1-8wt% of malic acid, 0.1-3wt% of a surfactant, 0.1-3wt% of a complexing agent, 0.1-3wt% of a corrosion inhibitor, 0.5-3wt% of an additive and 50-85wt% of water.

[0023] In a more preferred case, based on the total weight of the descaling cleaning agent, the descaling cleaning agent contains 10-25wt% of oxalic acid, 3-5wt% of tartaric acid, 3-5wt% of malic acid, 0.6-1.5wt% of a surfactant, 0.6-1.5wt% of a complexing agent, 0.1-1wt% of a corrosion inhibitor, 0.5-1.5wt% of an additive and 60-80wt% of water.

[0024] By adjusting and controlling the proportions of the various components of the descaling cleaning agent, the synergistic effect between the components allows the cleaning agent to exert a better combined effect. The descaling cleaning agent combined in the most optimal proportion has the best descaling efficiency and the best overall effect.

[0025] In the present invention, the surfactant is a combination of a nonionic surfactant and an anionic surfactant, and the mass ratio of the nonionic surfactant to the anionic surfactant can be 1:(0.5-5), preferably 1:(0.8-4), and further preferably 1:(1-3).

[0026] In the present invention, the nonionic surfactant is preferably at least one of fatty alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether.

[0027] In the present invention, the anionic surfactant is preferably at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and sodium dodecyl polyoxyethylene ether sulfate.

[0028] In a preferred embodiment, the mass ratio of the nonionic surfactant to the anionic surfactant is 1:(1-3), the nonionic surfactant is fatty alcohol polyoxyethylene ether, and the anionic surfactant is sodium dodecyl sulfate. Among them, fatty alcohol polyoxyethylene ether has good water solubility and stability, good compatibility with other surfactants, and low surface tension enables it to enhance the wettability of the cleaning agent on the surface of the scale sample and enhance the penetration ability of the cleaning agent; on the other hand, sodium dodecyl sulfate can form a micellar structure with a hydrophilic head group with a hydrophobic chain when dissolved in water, which can reduce the surface tension of the cleaning agent and play a dispersing role. At the same time, the small particles of oil and dirt on the heat exchange surface can be connected with the lipophilic end of the dodecyl sulfate ion and enter the water with the hydrophilic end, thereby improving the cleaning efficiency of the cleaning agent.

[0029] In the present invention, the complexing agent can be at least one of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, tetrasodium hydroxyethylidene diphosphonate, sodium citrate and sodium gluconate, preferably a combination of disodium ethylenediaminetetraacetate and tetrasodium hydroxyethylidene diphosphonate.

[0030] When the complexing agent is a combination of disodium ethylenediaminetetraacetate and tetrasodium hydroxyethylidene diphosphonate, the mass ratio of the disodium ethylenediaminetetraacetate to the tetrasodium hydroxyethylidene diphosphonate may be (0.5-5):1, preferably (0.8-4):1, and further preferably (1-3):1.

[0031] In a preferred embodiment, the complexing agent is a combination of disodium ethylenediaminetetraacetate and tetrasodium hydroxyethylidene diphosphonate, and the mass ratio of the disodium ethylenediaminetetraacetate and the tetrasodium hydroxyethylidene diphosphonate is (1-3): 1. Among them, the four oxygen atoms and two ethylenediamine groups of disodium ethylenediaminetetraacetate can form coordination bonds with iron ions in the scale sample inside the heat exchange tube, and can form stable complexes with both trivalent iron ions and divalent iron ions; on the other hand, sodium hydroxyethylidene diphosphonate can also form stable complexes with iron ions to improve the descaling efficiency, and it can also form complexes with miscellaneous ions such as calcium and magnesium in the cleaning agent, thereby inhibiting the production of calcium and magnesium salt precipitates during the cleaning process, and has a certain scale inhibition effect.

[0032] In the present invention, the corrosion inhibitor is preferably at least one of urotropine, imidazoline, quinoline and Mannich base. The above corrosion inhibitors can still maintain a good slow-release effect in an environment above 170°C, and can enhance the corrosion resistance of the high-temperature heat exchanger at high temperatures to a certain extent after use. During the cleaning process, the polar groups on the corrosion inhibitor are easily adsorbed on the heat exchange surface to form a monomolecular protective film, which effectively reduces the contact between the corrosive medium and the heat exchange surface, thereby achieving a corrosion inhibition effect.

[0033] In the present invention, the additive is preferably at least one of potassium chloride and sodium chloride.

[0034] In the present invention, the water is preferably deionized water. Using deionized water can avoid chemical reactions between impurity ions and components in the cleaning agent or heat exchange surfaces during the cleaning process, improve the descaling and cleaning effect, and protect the equipment.

[0035] In the present invention, the descaling cleaning agent can be prepared by a combination of conventional technical means in the art. In some specific embodiments, the preparation method of the descaling cleaning agent comprises: uniformly mixing 5-40wt% of oxalic acid, 0.5-10wt% of tartaric acid, 0.5-10wt% of malic acid, 0.05-5wt% of surfactant, 0.05-5wt% of complexing agent, 0.05-5wt% of corrosion inhibitor, 0.1-5wt% of additive and 40-93wt% of deionized water.

[0036] In some specific embodiments, based on the total weight of the descaling cleaning agent, the content of oxalic acid in the descaling cleaning agent is 10-25wt%, the content of tartaric acid is 3-5wt%, the content of malic acid is 3-5wt%, the content of the surfactant is 0.6-1.5wt%, the content of the complexing agent is 0.6-1.5wt%, the content of the corrosion inhibitor is 0.1-1wt%, the content of the additive is 0.5-1.5wt%, and the balance is deionized water. Wherein, the surfactant is a combination of a nonionic surfactant and an anionic surfactant, the mass ratio of the nonionic surfactant to the anionic surfactant is 1: (1-3), the nonionic surfactant is a fatty alcohol polyoxyethylene ether, and the anionic surfactant is sodium dodecyl sulfate. The complexing agent is a combination of disodium ethylenediaminetetraacetic acid and tetrasodium hydroxyethylidene diphosphonic acid, and the mass ratio of the disodium ethylenediaminetetraacetic acid to the tetrasodium hydroxyethylidene diphosphonic acid is (1-3): 1. The corrosion inhibitor is urotropine. The additive is potassium chloride. The descaling cleaning agent prepared according to the implementation method has a good descaling effect, a higher cleaning efficiency, and the cleaning agent has low corrosiveness and does not damage the cleaning surface.

[0037] In other specific embodiments, based on the total weight of the descaling cleaning agent, the content of oxalic acid in the descaling cleaning agent is 10-25wt%, the content of tartaric acid is 3-5wt%, the content of malic acid is 3-5wt%, the content of surfactant is 0.6-1.5wt%, the content of complexing agent is 0.6-1.5wt%, the content of corrosion inhibitor is 0.1-1wt%, the content of additive is 0.5-1.5wt%, and the balance is deionized water. Wherein, the surfactant is a combination of a nonionic surfactant and an anionic surfactant, the mass ratio of the nonionic surfactant to the anionic surfactant is 1: (1-3), the nonionic surfactant is fatty alcohol polyoxyethylene ether, and the anionic surfactant is sodium dodecyl sulfate. The complexing agent is disodium ethylenediaminetetraacetate. The corrosion inhibitor is urotropine. The additive is potassium chloride. The descaling cleaning agent prepared according to the implementation method has a good descaling effect, a higher cleaning efficiency, and the cleaning agent is less corrosive and does not damage the cleaning surface.

[0038] The present invention also provides the use of the above-mentioned descaling cleaning agent in the surface treatment process of the U-shaped heat exchange tube. The descaling cleaning agent of the present invention has a high descaling rate, a fast speed, low corrosiveness, no damage to the cleaning surface, and a simple method of use, and is particularly suitable for cleaning the scale sample inside the U-shaped heat exchange tube of the high-pressure heater.

[0039] In the present invention, the implementation conditions of the surface treatment process may include: a temperature of 15-35° C., preferably 20-30° C.; and a soaking time of 2-10 h, preferably 4-6 h.

[0040] The descaling cleaning agent and its application of the present invention are further described below by way of examples. The examples are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0041] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0042] Example 1

[0043] 15 g of oxalic acid, 5 g of tartaric acid, 5 g of malic acid, 0.33 g of fatty alcohol polyoxyethylene ether, 0.67 g of sodium lauryl sulfate, 0.67 g of disodium ethylenediaminetetraacetate, 0.33 g of tetrasodium hydroxyethylidene diphosphonate, 0.2 g of urotropine, 1 g of potassium chloride and 71.8 g of deionized water are mixed uniformly to obtain the descaling cleaning agent A1 of the present invention.

[0044] Example 2

[0045] 15 g of oxalic acid, 5 g of tartaric acid, 5 g of malic acid, 0.5 g of fatty alcohol polyoxyethylene ether, 1 g of sodium lauryl sulfate, 1 g of disodium ethylenediaminetetraacetate, 0.5 g of tetrasodium hydroxyethylidene diphosphonate, 0.2 g of urotropine, 1 g of potassium chloride and 70.8 g of deionized water are mixed uniformly to obtain the descaling cleaning agent A2 of the present invention.

[0046] Example 3

[0047] 15 g of oxalic acid, 5 g of tartaric acid, 5 g of malic acid, 0.2 g of fatty alcohol polyoxyethylene ether, 0.4 g of sodium lauryl sulfate, 0.4 g of disodium ethylenediaminetetraacetate, 0.2 g of tetrasodium hydroxyethylidene diphosphonate, 0.2 g of urotropine, 1 g of potassium chloride and 72.6 g of deionized water are mixed uniformly to obtain the descaling cleaning agent A3 of the present invention.

[0048] Example 4

[0049] 15 g of oxalic acid, 3 g of tartaric acid, 3 g of malic acid, 0.3 g of fatty alcohol polyoxyethylene ether, 0.6 g of sodium lauryl sulfate, 0.6 g of disodium ethylenediaminetetraacetate, 0.3 g of tetrasodium hydroxyethylidene diphosphonate, 0.2 g of urotropine, 0.8 g of potassium chloride and 76.2 g of deionized water are mixed uniformly to obtain the descaling cleaning agent A4 of the present invention.

[0050] Example 5

[0051] 15 g of oxalic acid, 3 g of tartaric acid, 3 g of malic acid, 0.2 g of fatty alcohol polyoxyethylene ether, 0.4 g of sodium lauryl sulfate, 0.4 g of disodium ethylenediaminetetraacetate, 0.2 g of tetrasodium hydroxyethylidene diphosphonate, 0.2 g of urotropine, 0.8 g of potassium chloride and 76.8 g of deionized water are mixed uniformly to obtain the descaling cleaning agent A5 of the present invention.

[0052] Example 6

[0053] 20 g of oxalic acid, 4 g of tartaric acid, 4 g of malic acid, 0.3 g of fatty alcohol polyoxyethylene ether, 0.6 g of sodium lauryl sulfate, 0.6 g of disodium ethylenediaminetetraacetate, 0.3 g of tetrasodium hydroxyethylidene diphosphonate, 0.2 g of urotropine, 0.8 g of potassium chloride and 69.2 g of deionized water are mixed uniformly to obtain the descaling cleaning agent A6 of the present invention.

[0054] Example 7

[0055] 25 g of oxalic acid, 3 g of tartaric acid, 3 g of malic acid, 0.33 g of fatty alcohol polyoxyethylene ether, 0.67 g of sodium lauryl sulfate, 0.67 g of disodium ethylenediaminetetraacetate, 0.33 g of tetrasodium hydroxyethylidene diphosphonate, 0.2 g of urotropine, 0.8 g of potassium chloride and 66 g of deionized water are mixed uniformly to obtain the descaling cleaning agent A7 of the present invention.

[0056] Example 8

[0057] 10 g of oxalic acid, 5 g of tartaric acid, 5 g of malic acid, 0.33 g of fatty alcohol polyoxyethylene ether, 0.67 g of sodium lauryl sulfate, 0.67 g of disodium ethylenediaminetetraacetate, 0.33 g of tetrasodium hydroxyethylidene diphosphonate, 0.2 g of urotropine, 0.8 g of potassium chloride and 77 g of deionized water are mixed uniformly to obtain the descaling cleaning agent A8 of the present invention.

[0058] Example 9

[0059] 10 g of oxalic acid, 2 g of tartaric acid, 2 g of malic acid, 0.04 g of fatty alcohol polyoxyethylene ether, 0.08 g of sodium lauryl sulfate, 0.08 g of disodium ethylenediaminetetraacetate, 0.04 g of tetrasodium hydroxyethylidene diphosphonate, 0.2 g of urotropine, 0.5 g of potassium chloride and 85.06 g of deionized water are mixed uniformly to obtain the descaling cleaning agent A9 of the present invention.

[0060] Example 10

[0061] A descaling cleaning agent was prepared according to the method of Example 1, except that 1 g of tetrasodium ethylenediaminetetraacetate was used as the complexing agent, to obtain the descaling cleaning agent A10 of the present invention.

[0062] Embodiment 11

[0063] A descaling cleaning agent was prepared according to the method of Example 1, except that 1 g of sodium citrate was used as the complexing agent, to obtain the descaling cleaning agent A11 of the present invention.

[0064] Example 12

[0065] A descaling cleaning agent was prepared according to the method of Example 1, except that 1 g of sodium gluconate was used as the complexing agent, to obtain the descaling cleaning agent A12 of the present invention.

[0066] Embodiment 13

[0067] A descaling cleaning agent was prepared according to the method of Example 1, except that the surfactant used was a mixture of 2 g of fatty alcohol polyoxyethylene ether and 4 g of sodium lauryl sulfate, and the deionized water was reduced to 66.8 g, to obtain the descaling cleaning agent A13 of the present invention.

[0068] Embodiment 14

[0069] A descaling cleaning agent was prepared according to the method of Example 1, except that the complexing agent used was a mixture of 4 g of disodium ethylenediaminetetraacetate and 2 g of tetrasodium hydroxyethylidene diphosphonate, and the deionized water was reduced to 66.8 g to obtain the descaling cleaning agent A14 of the present invention.

[0070] Embodiment 15

[0071] A descaling cleaning agent was prepared according to the method of Example 1, except that 4 g of oxalic acid, 0.5 g of tartaric acid, 0.5 g of malic acid, and 91.8 g of deionized water were used to obtain the descaling cleaning agent A15 of the present invention.

[0072] Comparative Example 1

[0073] A descaling cleaning agent was prepared according to the method of Example 1, except that no nonionic surfactant was added as the surfactant, and all of it was 1 g of sodium dodecyl sulfate, to obtain the descaling cleaning agent D1 of the present invention.

[0074] Comparative Example 2

[0075] A descaling cleaning agent was prepared according to the method of Example 1, except that no anionic surfactant was added as the surfactant, and all of the surfactant was 1 g of fatty alcohol polyoxyethylene ether, to obtain the descaling cleaning agent D2 of the present invention.

[0076] Comparative Example 3

[0077] A descaling cleaning agent was prepared according to the method of Example 1, except that an equal weight of aminosulfonic acid was used to replace oxalic acid, thereby obtaining the descaling cleaning agent D3 of the present invention.

[0078] Comparative Example 4

[0079] A descaling cleaning agent was prepared according to the method of Example 1, except that malic acid was replaced by an equal weight of oxalic acid, to obtain the descaling cleaning agent D4 of the present invention.

[0080] Comparative Example 5

[0081] A descaling cleaning agent was prepared according to the method of Example 1, except that tartaric acid was replaced by an equal weight of oxalic acid, to obtain the descaling cleaning agent D5 of the present invention.

[0082] Test Example 1

[0083] The descaling effects of the descaling cleaning agents in Examples 1-15 and Comparative Examples 1-3 were tested. The testing method included injecting the descaling cleaning agent into a U-shaped tube of a high-pressure heater, soaking it at 25°C for 6 hours, observing the descaling effect, and calculating the descaling rate. The results are shown in Table 1.

[0084] Table 1

[0085]

[0086] Test Example 2

[0087] The descaling effect of the descaling cleaning agents in Example 1 and Comparative Example 3 was tested. The testing method included: injecting the descaling cleaning agent into the U-shaped tube of the high-pressure heater, soaking it at 25°C for 1h and 2h, observing the descaling effect, and calculating the descaling rate. The results are shown in Table 2.

[0088] Table 2

[0089]

[0090] Test Example 3

[0091] The corrosiveness of the descaling cleaning agent of Example 1 was tested. The test method included: a U-shaped tube was made into a Φ16mm×2mm×4mm ring sample and immersed in the descaling cleaning agent at 25°C for 6 hours, and the corrosion rate was calculated. The results showed that the average corrosion rate was 0.3577g / (m 2 h), meeting the requirements of GB / T 25146-2010 for laboratory verification of corrosion rate of stainless steel materials. Therefore, the descaling agent has little damage to the substrate under experimental conditions and will not damage the cleaning surface.

[0092] It can be seen from the data of Tables 1-2 and Test Example 3 that the descaling rates of the descaling cleaning agent of the present invention are all above 45%, and the descaling rate of the descaling cleaning agent within the preferred range is as high as above 70%, which can achieve significantly better descaling effect at room temperature, and has the characteristics of high descaling rate and good descaling effect; in addition, under the same temperature conditions, the descaling cleaning agent of the present invention has a much higher descaling rate than the descaling cleaning agent in the comparative example when soaked for 1h, 2h and 6h, indicating that the descaling cleaning agent of the present invention has the characteristics of fast descaling rate and high cleaning efficiency; and the descaling agent has little damage to the substrate during the cleaning process and will not damage the cleaning surface, so it can be used in the surface treatment of high-pressure heat exchange equipment, and is particularly suitable for cleaning scale samples inside U-shaped heat exchange tubes of high-pressure heaters.

[0093] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A descaling cleaning agent, characterized in that: Based on the total weight of the descaling cleaning agent, the descaling cleaning agent contains 5-40wt% of oxalic acid, 0.5-10wt% of tartaric acid, 0.5-10wt% of malic acid, 0.05-5wt% of surfactant, 0.05-5wt% of complexing agent, 0.05-5wt% of corrosion inhibitor, 0.1-5wt% of additives and 40-93wt% of water, wherein the surfactant is a combination of a nonionic surfactant and an anionic surfactant.

2. The descaling cleaning agent according to claim 1, characterized in that: Based on the total weight of the descaling cleaning agent, the descaling cleaning agent contains 10-25wt% of oxalic acid, 3-5wt% of tartaric acid, 3-5wt% of malic acid, 0.6-1.5wt% of surfactant, 0.6-1.5wt% of complexing agent, 0.1-1wt% of corrosion inhibitor, 0.5-1.5wt% of additives and 60-80wt% of water.

3. The descaling cleaning agent according to claim 1 or 2, characterized in that: Among the surfactants, the mass ratio of the nonionic surfactant to the anionic surfactant is 1:(0.5-5), preferably 1:(1-3).

4. The descaling cleaning agent according to any one of claims 1 to 3, characterized in that: The nonionic surfactant is at least one of fatty alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether.

5. The descaling cleaning agent according to any one of claims 1 to 3, characterized in that: The anionic surfactant is at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and sodium dodecyl polyoxyethylene ether sulfate.

6. The descaling cleaning agent according to claim 1 or 2, characterized in that: The complexing agent is at least one of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, tetrasodium hydroxyethylidene diphosphonate, sodium citrate and sodium gluconate; Preferably, the complexing agent is a combination of disodium ethylenediaminetetraacetate and tetrasodium hydroxyethylidene diphosphonate; Preferably, the mass ratio of the disodium ethylenediaminetetraacetate to the tetrasodium hydroxyethylidene diphosphonate is (0.5-5):1, and more preferably (1-3):

1.

7. The descaling cleaning agent according to claim 1 or 2, characterized in that: The corrosion inhibitor is at least one of hexamethylenetetramine, imidazoline, quinoline and Mannich base.

8. The descaling cleaning agent according to claim 1 or 2, characterized in that: The additive is preferably at least one of potassium chloride and sodium chloride.

9. Use of the descaling cleaning agent according to any one of claims 1 to 8 in the surface treatment process of a U-shaped heat exchange tube.

10. The use according to claim 9, characterized in that: The implementation conditions of the surface treatment process include: temperature of 15-35° C., preferably 20-30° C.; soaking time of 2-10 h, preferably 4-6 h.

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