An anti-freezing solution for a heat source tower

Abstract

The application discloses an anti-freezing solution for a heat source tower, which is composed of organic salt, acrylic acid polymer, quaternary ammonium salt, benzotriazole, sodium molybdate, alcohol and water. The anti-freezing solution is obtained by mixing organic salt, acrylic acid polymer, quaternary ammonium salt, benzotriazole, sodium molybdate, alcohol and water, and is used in the anti-freezing process of the heat source tower system in the north. The organic salt is used as an anti-low-temperature agent, and the pyridine quaternary ammonium salt, benzotriazole and sodium molybdate mainly play a corrosion protection role. The anti-freezing solution has obvious synergistic effect among the components, and the freezing point of the obtained anti-freezing solution is lower and more stable. The anti-freezing solution has the characteristics of corrosion resistance to carbon steel, stainless steel and copper, so as to meet the technical requirements of the anti-freezing solution used in the heat source tower heat pump in the north. In addition, the obtained anti-freezing solution also has the characteristics of low cost and good environmental protection.

Description

Technical Field

[0001] This invention relates to the field of energy technology, and in particular to an antifreeze for heat source towers. Background Technology

[0002] Heat source tower heat pump systems, as a relatively new type of heat pump system, have attracted widespread attention. Compared with air source heat pumps, heat source tower heat pumps have significant advantages in terms of winter frosting and operating costs. Current research indicates that heat source tower heat pumps are mainly distributed in southern my country, with very little use in northern my country, and their application is extremely immature due to the climatic differences between the north and south. Because winter temperatures in northern regions are much lower than in southern regions, it is necessary to select suitable antifreeze for the heat source tower to ensure efficient, safe, and stable operation of the heat source tower heat pump system in northern regions.

[0003] The main functions of antifreeze are heat dissipation and freeze prevention. Currently, antifreeze systems primarily consist of calcium chloride, silicate, and organic alcohol systems. However, in practical applications, all three systems present several problems: calcium chloride antifreeze systems can severely corrode metal materials and readily generate precipitates; silicate antifreeze systems are unstable during circulating cooling, easily forming flocculent insoluble substances and exhibiting poor stability; and organic alcohol antifreeze systems are volatile and prone to oxidation over time. Therefore, commonly used antifreeze systems are generally unstable. Since heat source tower circulation systems are typically made of carbon steel, stainless steel, or copper, and the aforementioned three antifreeze systems are unsuitable for such systems due to their instability.

[0004] Therefore, in energy technology, finding a stable antifreeze suitable for the circulation system of northern heat source towers made of carbon steel, stainless steel, and copper has become an urgent technical problem to be solved. Summary of the Invention

[0005] To address the above problems, the present invention provides an antifreeze for a heat source tower, the antifreeze being composed of organic salts, acrylic polymers, quaternary ammonium salts, benzotriazole, sodium molybdate, alcohols, and water.

[0006] Preferably, the organic salt is one of sodium formate, potassium formate, magnesium formate, lithium formate, ammonium formate, sodium lactate, potassium lactate, sodium acetate, potassium acetate, sodium citrate, and potassium citrate.

[0007] Preferably, the acrylic polymer is polyacrylic acid or polyacrylic acid-sodium acrylate copolymer; wherein the average molecular weight of the acrylic polymer is 1000 g / mol to 2000 g / mol.

[0008] Preferably, the quaternary ammonium salt is a pyridine quaternary ammonium salt or an imidazoline quaternary ammonium salt; wherein the pyridine quaternary ammonium salt is benzylpyridine chloride, and the imidazoline quaternary ammonium salt is one of imidazoline 2-(2-(octadecyl-9-enyl)-4,5-dihydroimidazoline-1-methyl)ethylenediamine quaternary ammonium salt.

[0009] Preferably, the alcohol is one of glycerol, ethylene glycol, polyethylene glycol-200 to polyethylene glycol-2000; wherein the mass fraction of the alcohol is 0.06% to 0.1%.

[0010] Preferably, the organic salt has a mass fraction of 5% to 35%.

[0011] Preferably, the mass fraction of the acrylic polymer is 0.001% to 0.008%.

[0012] Preferably, the mass fraction of the quaternary ammonium salt is 0.003% to 0.015%.

[0013] Preferably, the benzotriazole has a mass fraction of 0.03% to 0.10%.

[0014] Preferably, the sodium molybdate has a mass fraction of 0.002% to 0.01%.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] This invention discloses an antifreeze for heat source towers, comprising organic salts, acrylic polymers, quaternary ammonium salts, benzotriazole, sodium molybdate, alcohol, and water. By mixing organic salts, acrylic polymers, quaternary ammonium salts, benzotriazole, sodium molybdate, alcohol, and water, this invention obtains an antifreeze for use in the circulating heat exchange process of heat source tower systems in northern regions. The organic salts act as low-temperature resistant agents, while the pyridine quaternary ammonium salt, benzotriazole, and sodium molybdate primarily provide corrosion protection. The synergistic effect among the components of this antifreeze is significant, resulting in a lower and more stable freezing point and corrosion-resistant properties against materials such as carbon steel, stainless steel, and copper, thus meeting the technical requirements for antifreeze used in heat pumps in northern heat source towers. Furthermore, the obtained antifreeze is low-cost and environmentally friendly.

[0017] This invention aims to obtain an antifreeze for use in the circulating heat exchange process of a northern heat source tower system. Organic salts are used as low-temperature inhibitors, while pyridine quaternary ammonium salt, benzotriazole, and sodium molybdate primarily provide corrosion protection. Added alcohols improve the dispersion and dissolution of the three corrosion inhibitors, and added polyacrylic acid disperses trace corrosion products, preventing deposition. The resulting antifreeze exhibits antifreeze properties, stability, low corrosion rates on carbon steel, stainless steel, and copper, high thermal conductivity, and low surface tension. Its freezing point is -12℃ to -33℃, thermal conductivity is 0.50 to 0.60 W / mK, and surface tension is 66 to 75 mN / m. Between -25℃ and 125℃, the corrosion rate on carbon steel, stainless steel, and copper is <0.075 mm / a. The synergistic effect of the components is significant, making the antifreeze system sufficient to meet the technical requirements of northern heat source towers. Furthermore, the obtained antifreeze is simple, low-cost, and environmentally friendly. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the heat source tower heat pump system in an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the heat source tower in an embodiment of the present invention.

[0020] Figure Labels

[0021] 1. Antifreeze circulation; 2. Heat source tower; 3. Circulating liquid circulation; 4. Refrigerant circulation; 5. User-end water circulation; 6. User terminal; 7. Evaporator; 8. Compressor; 9. Condenser; 10. Expansion valve. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the examples, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0023] In summer, the heat source tower also functions as a cooling tower, working in conjunction with a water-cooled unit to remove indoor heat and cool the room; in winter, the cooling tower absorbs low-grade heat from the air and transfers it to the main unit via circulating fluid to provide indoor heating. Figure 1The diagram shows a heat pump air conditioning system with a heat source tower, including four water (solution) circulations (antifreeze circulation, circulating fluid circulation, refrigerant circulation, and user-end water circulation) and air circulations at both ends (heat source tower and user terminal). The technical principle of the heat source tower heat pump system is as follows: the heat source tower utilizes the contact between a solvent and air, employing a carrier medium with a freezing point below zero, to efficiently extract low-grade heat energy from the relatively humid air in a low-temperature environment. This high-grade heat energy is then input into the heat pump unit in the heat source tower, achieving the transfer of low-grade heat energy to high-grade heat energy in a low-temperature environment, thus providing heating and hot water to the building.

[0024] Heat source tower heat pumps are mainly distributed in southern my country, and are rarely used in northern my country. Furthermore, their application is extremely immature due to the climatic differences between the north and south. Compared to the south, the use of heat source tower heat pumps in the north faces more restrictions. Specifically, the technical requirements for antifreeze used in northern heat source tower heat pumps are: the antifreeze needs a lower freezing point (due to the low temperatures in the north) and greater stability (because the materials used in the circulation system of northern heat source towers are carbon steel, stainless steel, and copper, i.e., corrosion resistance). In addition, the thermal conductivity of the antifreeze can be further improved.

[0025] In view of this, this application proposes an antifreeze for heat source towers, which uses organic salts as low-temperature agents and pyridine quaternary ammonium salt, benzotriazole and sodium molybdate as corrosion inhibitors. The synergistic effect of each component is obvious, so that the obtained antifreeze system is sufficient to meet the technical requirements of heat source towers in the north, so as to solve the technical problem that there is no stable antifreeze in energy technology that is suitable for the circulation system of heat source towers made of carbon steel, stainless steel and copper.

[0026] The present invention provides an antifreeze for a heat source tower, the antifreeze being composed of organic salts, acrylic polymers, quaternary ammonium salts, benzotriazole, sodium molybdate, alcohols, and water.

[0027] The embodiment of this invention yields an antifreeze solution required for the circulating heat exchange process in a northern heat source tower system, referring to... Figure 2 , Figure 2This is a schematic diagram of the heat pump system for the heat source tower in an embodiment of the present invention. Antifreeze is used in the antifreeze circulation process of the heat source tower. A certain proportion of organic salt acts as a low-temperature resistant agent; a certain proportion of pyridine quaternary ammonium salt, benzotriazole, and sodium molybdate mainly play a role in corrosion protection; a certain proportion of alcohol improves the dispersion and dissolution of the three corrosion inhibitors; and a certain proportion of polyacrylic acid disperses trace amounts of corrosion products, preventing deposition. The resulting antifreeze is characterized by its antifreeze properties, stability, low corrosion rate against carbon steel, stainless steel, and copper, high thermal conductivity, and low surface tension. The individual effects of each component work together (significant synergistic effect), and this synergistic effect makes the antifreeze system sufficient to meet the technical requirements of heat source towers in northern regions. Furthermore, the resulting antifreeze also features low dosage, low cost, and good environmental performance. It should be noted that in this application, the additive mass fraction is less than 0.2%, referring to the mass percentage of the three corrosion inhibitors, polyacrylic acid, and alcohol.

[0028] Antifreeze is characterized by its low freezing point (antifreeze properties), with tests showing that the freezing point of the antifreeze system ranges from -12℃ to -33℃. Specifically, this low freezing point is due to the organic salt components in the antifreeze system.

[0029] The antifreeze is characterized by its stability and low corrosion rate on carbon steel, stainless steel, and copper within a temperature range of -25℃ to 125℃. Specifically, during the antifreeze circulation and heat exchange process, the antifreeze solution absorbs moisture from the air and exchanges heat with the air. The lowest temperature at which the antifreeze solution exists during this process is -25℃. During system operation, the antifreeze solution needs to boil, with its highest temperature between 110℃ and 125℃. Therefore, the temperature range used for the antifreeze during the entire heat exchange process of the heat source tower system is -25℃ to 125℃. Experimental tests show that the obtained antifreeze is stable within this temperature range, and the corrosion rate on carbon steel, stainless steel, and copper within this temperature range is <0.075mm / a. Furthermore, it should be noted that ethylene glycol and water will evaporate during the boiling process, but alcohol and water only act as solvents in the antifreeze system of this invention, used to dissolve and disperse the corrosion inhibitor. The corrosion inhibitor is completely dispersed before the antifreeze is used, therefore it will not affect the performance of the antifreeze.

[0030] Antifreeze is characterized by high thermal conductivity and low surface tension. Specifically, tests have shown that antifreeze has a thermal conductivity of 0.50–0.60 W / mK and a surface tension of 66–75 mN / m. Since antifreeze absorbs moisture from the air and exchanges heat with it, a higher thermal conductivity is better. Because antifreeze needs to circulate, it requires an appropriate surface tension. It should be noted that surface tension is only related to the properties and temperature of the liquid. Generally, the higher the liquid temperature, the lower its surface tension.

[0031] Furthermore, it should be noted that the heat source tower system provided in this invention does not foam, therefore no defoamer needs to be added to the antifreeze.

[0032] Preferably, the organic salt is one of sodium formate, potassium formate, magnesium formate, lithium formate, ammonium formate, sodium lactate, potassium lactate, sodium acetate, potassium acetate, sodium citrate, and potassium citrate.

[0033] Organic salts such as formate act as solutes in antifreeze systems, and their main function is to resist low temperatures and lower the freezing point.

[0034] In specific implementation, the antifreeze system of this invention is mainly composed of organic salts such as sodium formate, thus the resulting antifreeze has the characteristics of low freezing point and low volatility. Since the antifreeze is used in a heat source tower in this invention, and is exposed to air, directly contacting the air to absorb heat, a matrix with low volatility, such as formate, is used in this invention.

[0035] Preferably, the acrylic polymer is polyacrylic acid or polyacrylic acid-sodium acrylate copolymer; wherein the average molecular weight of the acrylic polymer is 1000 g / mol to 2000 g / mol.

[0036] In this system, the role of acrylic polymers is to disperse trace amounts of corrosion products and prevent their deposition.

[0037] In practice, although corrosion inhibitors are added to the antifreeze in this invention, the antifreeze will still corrode the heat source tower to a certain extent, producing trace amounts of corrosion products.

[0038] Preferably, the quaternary ammonium salt is a pyridine quaternary ammonium salt or an imidazoline quaternary ammonium salt; wherein the pyridine quaternary ammonium salt is benzylpyridine chloride, and the imidazoline quaternary ammonium salt is one of imidazoline 2-(2-(octadecyl-9-enyl)-4,5-dihydroimidazoline-1-methyl)ethylenediamine quaternary ammonium salt.

[0039] Preferably, the alcohol is one of glycerol, ethylene glycol, polyethylene glycol-200 to polyethylene glycol-2000; wherein the mass fraction of the alcohol is 0.06% to 0.1%.

[0040] In this system, alcohol and water act as solvents to dissolve and disperse corrosion inhibitors.

[0041] In specific implementation, deionized water is used. Since the antifreeze is used in the heat source tower in this invention, and the antifreeze is exposed to air, it absorbs heat through direct contact with the air; therefore, the alcohol content as a solvent in this invention is low. The values ​​of a% to b% mentioned above can be any values ​​within the range [a, b], and this embodiment of the invention does not impose specific limitations on this.

[0042] Preferably, the organic salt has a mass fraction of 5% to 35%.

[0043] In practice, the freezing point of antifreeze mainly depends on the concentration of organic salts; different concentrations of organic salts correspond to different freezing points. The higher the concentration of organic salts, the more beneficial it is to lower the freezing point.

[0044] Preferably, the mass fraction of the acrylic polymer is 0.001% to 0.008%.

[0045] Preferably, the mass fraction of the quaternary ammonium salt is 0.003% to 0.015%.

[0046] Preferably, the benzotriazole has a mass fraction of 0.03% to 0.10%.

[0047] Preferably, the sodium molybdate has a mass fraction of 0.002% to 0.01%.

[0048] Among them, quaternary ammonium salt, benzotriazole and sodium molybdate act as corrosion inhibitors in the antifreeze system, playing a role in corrosion protection, and the resulting antifreeze has good stability.

[0049] In practical implementation, since 20%–25% of organic salts such as sodium formate are used as low-temperature resistant components in the antifreeze, and these organic salts themselves can cause corrosion to the heat source towers made of copper, carbon steel, or stainless steel, this invention adds three corrosion inhibitors to eliminate the harmful effects of sodium formate and other organic salts on the heat source towers. The values ​​of a% to b% mentioned above can be any values ​​within the range [a, b], and this embodiment of the invention does not impose specific limitations on this.

[0050] In practice, the total mass percentage of organic salts, acrylic polymers, quaternary ammonium salts, benzotriazole, sodium molybdate, and alcohols is taken as the total mass percentage, and the remaining percentages are all deionized water, with the sum of the percentages of all components being 100%.

[0051] The present invention also provides a method for preparing antifreeze for heat source towers, comprising the following steps:

[0052] Step 1: Dissolve the organic salt in deionized water while stirring;

[0053] Step 2: After stirring evenly, add a certain proportion of acrylic polymer, quaternary ammonium salt, benzotriazole, sodium molybdate, and alcohol in sequence and dissolve completely;

[0054] Step 3: Add deionized water to make up the total mass of the antifreeze to obtain the antifreeze.

[0055] The antifreeze compounding method in this invention is simple and requires no complex preparation process to obtain an antifreeze system that meets the technical requirements of northern heat source towers. In the compounding process, this invention does not require stirring at temperatures between 30°C and 80°C; the antifreeze can be obtained by stirring at room temperature.

[0056] In the following examples, the total mass of the antifreeze is set to 1000.00g. In actual use, the total mass of the antifreeze can be adjusted according to the requirements.

[0057] Example 1:

[0058] 200.00g of industrial-grade sodium formate was dissolved in 660.00g of deionized water under stirring. After stirring evenly, 50mg of polyacrylic acid, 100mg of pyridine quaternary ammonium salt, 400mg of benzotriazole, 20mg of sodium molybdate, and 600mg of ethylene glycol were added in sequence. The total mass was then made up with deionized water to obtain an antifreeze solution.

[0059] Example 2:

[0060] Dissolve 200.00g of industrial-grade potassium formate in 660.00g of deionized water under stirring. After stirring evenly, add 50mg of polyacrylic acid, 100mg of pyridine quaternary ammonium salt, 400mg of benzotriazole, 20mg of sodium molybdate, and 600mg of ethylene glycol in sequence. Make up the total mass to 100.00g with deionized water to obtain the antifreeze.

[0061] Example 3:

[0062] 150.00g of industrial-grade sodium lactate was dissolved in 660.00g of deionized water under stirring. After stirring evenly, 50mg of polyacrylic acid, 100mg of pyridine quaternary ammonium salt, 400mg of benzotriazole, 20mg of sodium molybdate, and 600mg of ethylene glycol were added in sequence. The total mass was then made up with deionized water to obtain an antifreeze solution.

[0063] Example 4:

[0064] Dissolve 150.00g of industrial-grade potassium lactate in 660.00g of deionized water under stirring. After stirring evenly, add 50mg of polyacrylic acid, 100mg of pyridine quaternary ammonium salt, 400mg of benzotriazole, 20mg of sodium molybdate, and 600mg of ethylene glycol in sequence. Make up the total mass to 100.00g with deionized water to obtain the antifreeze.

[0065] Example 5:

[0066] 200.00g of industrial-grade sodium citrate was dissolved in 660.00g of deionized water under stirring. After stirring evenly, 50mg of polyacrylic acid, 100mg of pyridine quaternary ammonium salt, 400mg of benzotriazole, 20mg of sodium molybdate, and 600mg of ethylene glycol were added in sequence. The total mass was then made up with deionized water to obtain an antifreeze solution.

[0067] Example 6:

[0068] 200.00g of industrial-grade sodium formate was dissolved in 660.00g of deionized water under stirring. After stirring evenly, 80mg of polyacrylic acid, 30mg of pyridine quaternary ammonium salt, 800mg of benzotriazole, 50mg of sodium molybdate, and 800mg of ethylene glycol were added in sequence. The total mass was then made up with deionized water to obtain an antifreeze solution.

[0069] Example 7:

[0070] 200.00g of industrial-grade sodium formate was dissolved in 660.00g of deionized water under stirring. After stirring evenly, 80mg of polyacrylic acid, 150mg of pyridine quaternary ammonium salt, 1000mg of benzotriazole, 100mg of sodium molybdate, and 1000mg of ethylene glycol were added in sequence. The total mass was made up with deionized water to obtain an antifreeze.

[0071] Example 8:

[0072] 200.00g of industrial-grade sodium formate was dissolved in 660.00g of deionized water under stirring. After stirring evenly, 80mg of polyacrylic acid-sodium polyacrylate, 150mg of imidazoline quaternary ammonium salt, 1000mg of benzotriazole, 100mg of sodium molybdate, and 1000mg of polyethylene glycol 200 were added in sequence. The total mass was made up with deionized water to obtain antifreeze.

[0073] Example 9:

[0074] 200.00g of industrial-grade sodium formate was dissolved in 660.00g of deionized water under stirring. After stirring evenly, 80mg of sodium polyacrylate, 150mg of imidazoline quaternary ammonium salt, 1000mg of benzotriazole, 100mg of sodium molybdate, and 1000mg of polyethylene glycol 800 were added in sequence. The total mass was then made up with deionized water to obtain an antifreeze solution.

[0075] The antifreeze obtained in Examples 1 to 9 above was tested for its physical properties according to the national standard test method.

[0076] The corrosion inhibition performance was tested using a 5°C air-blowing test. The test steps were as follows: The test piece was hung on a stirring paddle and immersed in the test solution (antifreeze). A constant stirring speed was maintained; the stirring speed should not be too fast to avoid splashing of the antifreeze. Simultaneously, air was continuously blown into the test solution using an air pump. After 72 hours, the test piece was removed, washed, dried, and weighed. The corrosion rate was then calculated. The formula for calculating the corrosion rate is:

[0077]

[0078]

[0079]

[0080] Where 87600 is the constant for calculating the corrosion rate; weight loss is (W1-W2), which is the weight of the test piece before the test minus the weight of the test piece after the test (in grams); 28 is the surface area of ​​the test piece (in cm²). 2 ); 7.85 or 8.50 is the density of the sample material (unit: g / cm³). 3 The time period was 72 hours. The results of the corrosion rate calculation are shown in Table 1 below.

[0081] In addition, the freezing point, surface tension, and thermal conductivity of the antifreeze in Examples 1 to 9 were tested and calculated, and the results are shown in Table 1 below.

[0082] Table 1 Performance Tests of Examples

[0083]

[0084] As can be seen from Table 1 above, the antifreeze system developed in this invention exhibits excellent performance indicators. Its freezing point and corrosion resistance (especially against carbon steel, stainless steel, and copper) meet the requirements for efficient and safe operation of heat pump systems in northern regions. Furthermore, the antifreeze prepared in this invention also possesses good surface tension and thermal conductivity, sufficient to meet the primary function of heat dissipation in antifreeze systems.

[0085] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0086] The above provides a detailed description of an antifreeze for a heat source tower provided by the present invention. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An antifreeze for a heat source tower, characterized in that, The antifreeze is composed of organic salts, acrylic polymers, quaternary ammonium salts, benzotriazole, sodium molybdate, alcohol, and water. The organic salts are one of sodium formate, potassium formate, magnesium formate, lithium formate, ammonium formate, sodium lactate, potassium lactate, sodium acetate, potassium acetate, sodium citrate, and potassium citrate. The alcohol is one of glycerol, ethylene glycol, and polyethylene glycol-200 to polyethylene glycol-2000. The mass fraction of the alcohol is 0.06% to 0.1%. The mass fraction of the organic salt is 5% to 35%. The mass fraction of the acrylic polymer is 0.001% to 0.008%. The mass fraction of the quaternary ammonium salt is 0.003% to 0.015%. The mass fraction of the benzotriazole is 0.03% to 0.10%. The mass fraction of the sodium molybdate is 0.002% to 0.01%.

2. The antifreeze according to claim 1, characterized in that, The acrylic polymer is polyacrylic acid or polyacrylic acid-sodium acrylate copolymer; wherein the average molecular weight of the acrylic polymer is 1000 g / mol to 2000 g / mol.

3. The antifreeze according to claim 1, characterized in that, The quaternary ammonium salt is a pyridine quaternary ammonium salt or an imidazoline quaternary ammonium salt; wherein the pyridine quaternary ammonium salt is benzylpyridine chloride, and the imidazoline quaternary ammonium salt is 2-(2-(octadecyl-9-enyl)-4,5-dihydroimidazoline-1-methyl)ethylenediamine quaternary ammonium salt.

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