Oxalic acid solution for decontamination of photovoltaic device and preparation process of oxalic acid solution

Abstract

The invention discloses an oxalic acid solution for decontamination of a photovoltaic device and a preparation process of the oxalic acid solution, and belongs to the technical field of preparation of decontamination cleaning solutions. The oxalic acid solution comprises oxalic acid, hydrofluoric acid, EDTA-2Na, ethanol and the like; the concentration of oxalic acid is 10-15%, the concentration of hydrofluoric acid is 55%, and the concentration of ethanol is 95%; the ratio of the oxalic acid to the hydrofluoric acid to the EDTA-2Na to the ethanol is 82 to 90 weight percent, 1 to 5 weight percent, 0.2 to 1 weight percent and 6 to 15 weight percent. Metal oxide and silicate scabs are efficiently removed through the synergistic effect of oxalic acid, hydrofluoric acid and ammonium bifluoride, and chelating stability of EDTA-2Na and physical enhancement of a nano-silica carrier are supplemented, so that the decontamination rate is larger than or equal to 95%, and zero damage of components is achieved. The cleaning agent is suitable for cleaning multi-element stubborn stains on the photovoltaic surface, has both environmental friendliness and economy, has the characteristics of high descaling efficiency, high speed, low corrosion, no damage to the cleaning surface, low cost and the like, and can be applied to operation and maintenance of photovoltaic power stations on a large scale.

Description

Technical Field

[0001] The present invention relates to an oxalic acid solution for decontaminating photovoltaic devices and a preparation process thereof, belonging to the technical field of preparation of decontamination cleaning solutions or cleaning technologies for photovoltaic devices. Background Art

[0002] Photovoltaic modules are exposed to sunlight, rain and various extreme harsh environments for a long time. As a result, various kinds of dirt will form on their surfaces, such as thick dust, bird droppings, white spots and golden spots caused by the mildew of the glass itself, iron oxide powder, rubber, algal attachments and oil stains, etc. In desert areas, due to being unable to withstand the blowing of sand, the film layer even falls off. In tropical and subtropical coastal areas, the salt content and water vapor in the air are high, and the surface of the film layer is also prone to become rough or even fall off. Therefore, the power generation efficiency of photovoltaic modules generally decays year by year. It can decay by more than 10% in two or three years and by more than 20% in seven or eight years. Under extreme use conditions, it can even decay by more than 40%.

[0003] The decline in the power of photovoltaic modules has attracted great attention from the industry. A lot of research has been done on the cleaning process, cleaning automation equipment and cleaning liquid formula of photovoltaic modules, and many patents have also been applied for. In the cleaning process of photovoltaic modules, the selection of the cleaning liquid is very important. The types of pollutants on photovoltaic devices are complex and are prone to react with the glass surface to form a dense "scab" (such as silicate scabs and calcium and magnesium salt deposits). The pollutants are exposed to the outdoor environment for a long time and chemically adsorb or physically adhere to the surface of photovoltaic glass, with strong adhesion. The cleaning effect of traditional cleaning agents is very limited. It is difficult to completely remove some dirt and not easy to clean. Frequent brushing itself will cause physical damage to the film surface and reduce the power generation efficiency of the module. Or there is too strong corrosiveness, which damages the anti-reflection film and metal frame of photovoltaic glass, resulting in excessive power attenuation of the module. There is also a risk of secondary pollution: unchelated metal ions (Fe3+, Ca 2 +) redeposit on the surface of the module, accelerating the atomization of the glass.

[0004] Hefei Wensheng New Energy Technology Co., Ltd. applied for a photovoltaic module cleaning liquid with a publication number of CN107488521A, which includes the following raw materials: phosphoric acid, oxalic acid, fluorosilicic acid, malic acid, linear alkylbenzene sulfonate, water; the above raw materials are uniformly mixed at room temperature and then stirred for 20 min - 30 min to obtain the cleaning liquid. However, its scale removal rate is slow, the cycle is long, and the cost is relatively high. The cleaning effect on photovoltaic modules needs to be improved and it cannot meet the actual application needs. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] The technical problem to be solved by the present invention is to solve the problem that the cleaning effect of the existing photovoltaic module cleaning solution is very limited, it is difficult to completely remove some dirt, and it is not easy to clean cleanly.

[0007] (II) Technical solution

[0008] To solve the above technical problem, the present invention provides an oxalic acid solution for decontaminating photovoltaic devices, which includes oxalic acid, hydrofluoric acid and EDTA-2Na; the concentration of the oxalic acid is 10-15%, and the concentration of the hydrofluoric acid is 55%.

[0009] Furthermore, the proportion of the oxalic acid is 96.5 wt%, the proportion of the hydrofluoric acid is 2.5 wt%, and the proportion of the EDTA-2Na is 1 wt%.

[0010] Even further, the second more preferred solution is that it further includes ethanol, and the concentration of the ethanol is 95%; and the ratio is 87.75 wt% of oxalic acid, 2 wt% of hydrofluoric acid, 0.5 wt% of EDTA-2Na, and 9.75 wt% of ethanol.

[0011] Even further, the third more preferred solution is that it further includes ethanol, ammonium bifluoride, glutathione, nano-silica, alkyl glycoside and polyglycerol ester, and the concentration of the ethanol is 95%.

[0012] Even further, for the oxalic acid solution for decontaminating photovoltaic devices according to the third more preferred solution, the component ratios thereof are as follows:

[0013]

[0014] Furthermore, for the oxalic acid solution for decontaminating photovoltaic devices according to the third more preferred solution, the component ratios can be further optimized as follows:

[0015]

[0016] The present invention also provides a preparation process for the oxalic acid solution for decontaminating photovoltaic devices according to the third more preferred solution, which includes the following steps:

[0017] Step 1: Add deionized water, oxalic acid solution and hydrofluoric acid into a corrosion-resistant reaction kettle in sequence, and stir;

[0018] Step 2: Add ammonium bifluoride, control the temperature at 20-25 °C, and then add EDTA-2Na, and adjust the pH to 2.5-3.0;

[0019] Step 3: Add ethanol and glutathione in sequence, and stir until completely dissolved;

[0020] Step 4: Pre-disperse nano-silica in ethanol, and add it to the system after ultrasonic treatment at 40 kHz for 15 minutes;

[0021] Step 5: Add alkyl polyglycoside and polyglycerol ester, and stir at a low speed of 50 rpm for 20 minutes to obtain a homogeneous solution.

[0022] More specifically, in the said Step 1, control the temperature ≤ 25°C and stir at 200 rpm for 10 minutes.

[0023] More specifically, in the said Step 4, pre-disperse the nano-silica in 5% ethanol and process it with a high-speed shear emulsifier at a rotation speed of 3000 rpm for 10 min.

[0024] More specifically, in the said Step 5, under the condition of 25°C, control the dynamic viscosity of the homogeneous solution at 15 - 20 mPa·s.

[0025] (III) Beneficial effects

[0026] The above technical solution of the present invention has the following advantages:

[0027] In the oxalic acid solution of the present invention, oxalic acid reacts with metal oxide (Fe2O3) through protonation to generate soluble ferric oxalate complex (Fe(C2O4)3 3- ), and at the same time decomposes the carboxylic acid groups in the organic stains; hydrofluoric acid (HF) and ammonium bifluoride (NH4HF2) form a buffer system to selectively etch the silicate crust (SiO2·nH2O) to generate volatile SiF4 gas, avoiding excessive corrosion of the glass. EDTA-2Na chelates Fe3+, Ca 2 + and other ions through a hexadentate coordination structure to form a stable water-soluble complex and prevent them from redepositing on the surface of the component. The nano-silica carrier (particle size D50 ≤ 50 nm) binds to the active ingredient through surface hydroxyl groups, generates micro-friction during the cleaning process, peels off stubborn crusts, and at the same time avoids scratching the glass surface.

[0028] The present invention is applicable to the cleaning of stubborn stains on the surface of photovoltaic modules, including dust, bird droppings, glass mildew, iron oxide powder, oil stains and the dense crusts formed by them, etc. This solution combines acid dissolution, chelation stabilization and physical synergistic effects, taking into account both the decontamination efficiency and device protection, and is especially suitable for the maintenance of the surfaces of photovoltaic glass, metal frames and battery chips in complex outdoor environments.

[0029] The present invention efficiently removes metal oxides and silicate crusts through the synergistic effect of oxalic acid, hydrofluoric acid and ammonium bifluoride, supplemented by the chelation stabilization of EDTA-2Na and the physical enhancement of the nano-silica carrier, achieving a decontamination rate ≥ 95% and zero damage to the components. The present invention is applicable to the cleaning of multiple stubborn stains on the photovoltaic surface, and has both environmental protection and economy, and can be applied to the operation and maintenance of photovoltaic power stations on a large scale.

[0030] Technical effects: 1. High-efficiency decontamination, with a comprehensive decontamination rate of ≥95% for multiple stains (metal oxides, silicates, organic residues); the nano-carrier improves the scab stripping efficiency by 40%. 2. Low corrosiveness: pH 2.5 - 3.0 and fluoride ion concentration ≤0.5%, glass corrosion rate ≤0.1 μm / h; glutathione inhibits the oxidation of metal components, and the annual corrosion amount of the frame ≤0.05 mm. 3. Environmental friendliness: Phosphorus-free formula, biodegradation rate (28 days) ≥90%, meeting the GB / T 28001 standard; no toxic residues after ethanol volatilization, and the COD value of the wastewater ≤50 mg / L.

[0031] The oxalic acid solution for decontaminating photovoltaic devices of the present invention has the characteristics of high decontamination and scale removal rate, good decontamination effect, fast decontamination rate, and high cleaning efficiency; and this oxalic acid solution causes little damage to photovoltaic modules during the cleaning process.

[0032] In addition to the technical problems solved by the present invention, the technical features of the technical solutions constituted, and the advantages brought by these technical features of the technical solutions described above, the other technical features of the present invention and the advantages brought by these technical features will be further described in conjunction with the accompanying drawings. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is a schematic block diagram of the process flow for preparing the solution of the present invention. Detailed Embodiments

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0036] Embodiment 1

[0037] An oxalic acid solution for decontaminating photovoltaic devices, which includes oxalic acid, hydrofluoric acid, and EDTA-2Na; the concentration of the oxalic acid is 10 - 15% (or conventional oxalic acid), and the concentration of the hydrofluoric acid is 55%.

[0038] In this embodiment, the proportion of oxalic acid is 96.5 wt%, the proportion of hydrofluoric acid is 2.5 wt%, and the proportion of EDTA-2Na is 1 wt%. Or another mixing ratio is: 500 ML of conventional oxalic acid + 13.5 grams of 55% hydrofluoric acid (accounting for 2.5%) + EDTA-2NA (accounting for 1%), and the prepared solution is C1.

[0039] Example 2

[0040] An oxalic acid solution for decontaminating photovoltaic devices, which includes oxalic acid, hydrofluoric acid, EDTA-2Na and ethanol. The concentration of oxalic acid is 10-15% (or conventional oxalic acid is used), the concentration of hydrofluoric acid is 55%, and the concentration of ethanol is 95%; and the mixing ratio is 87.75 wt% of oxalic acid, 2 wt% of hydrofluoric acid, 0.5 wt% of EDTA-2Na, and 9.75 wt% of ethanol. Or another mixing ratio is: 450 ML of conventional oxalic acid + 10 grams of 55% hydrofluoric acid + 0.5% (2.5 grams) of EDTA-2NA + 50 ML of 95% ethanol, and the prepared solution is C2.

[0041] The experimental results of the decontamination ability and pungent smell of the above C1 and C2 oxalic acid solution samples and commercially available conventional oxalic acid (currently used oxalic acid):

[0042] Decontamination ability: C2 > C1 > currently used oxalic acid

[0043] Pungent smell: currently used oxalic acid > C2 > C1 Conclusion: In the comprehensive evaluation of the decontamination ability and pungent smell of oxalic acid, sample C2 is the best.

[0044] Example 3

[0045] An oxalic acid solution for decontaminating photovoltaic devices, which includes oxalic acid, hydrofluoric acid, EDTA-2Na, ethanol, ammonium bifluoride, glutathione, nano-silica, alkyl polyglycoside and polyglycerol ester. The concentration of oxalic acid is 10-15% (or conventional oxalic acid is used), the concentration of hydrofluoric acid is 55%, and the concentration of ethanol is 95%.

[0046] For the oxalic acid solution for decontaminating photovoltaic devices in this embodiment, the component ratios are as follows:

[0047]

[0048] Among them, oxalic acid is the main acidic solvent for metal oxides and organic stains; hydrofluoric acid is used to assist in dissolving silicate crusts and synergistically enhance the decontamination efficiency with oxalic acid; EDTA-2Na is used to chelate metal ions to prevent secondary deposition; ethanol is used to accelerate solvent volatilization, assist in removing oil stains and reduce water marks; ammonium bifluoride is used to buffer the activity of hydrofluoric acid and reduce the risk of glass corrosion; glutathione is used as an antioxidant to protect the metal frame and solder tape; nano-silica is used to enhance decontamination through physical friction and load active ingredients; alkyl polyglycoside is used as a surfactant to reduce the surface tension of the solution; polyglycerol ester is used to synergistically enhance the permeability with alkyl polyglycoside.

[0049] Technical principle

[0050] Chemical synergistic dissolution:

[0051] Oxalic acid reacts with metal oxide (Fe2O3) through protonation to form soluble ferric oxalate complex (Fe(C2O4)3 3- ), while decomposing the carboxylic acid groups in organic stains;

[0052] Hydrofluoric acid (HF) and ammonium bifluoride (NH4HF2) form a buffer system to selectively etch silicate crust (SiO2·nH2O) to generate volatile SiF4 gas, avoiding excessive corrosion of the glass.

[0053] Chelation stabilization mechanism:

[0054] EDTA-2Na chelates Fe3+, Ca 2 + and other plasma through a hexadentate coordination structure to form stable water-soluble complexes, preventing them from redepositing on the surface of the component.

[0055] Physical enhancement effect:

[0056] The nano-silica carrier (particle size D50≤50nm) binds with the active ingredient through surface hydroxyl groups, generating micro-friction during the cleaning process to peel off stubborn crusts, while avoiding scratching the glass surface.

[0057] In this embodiment, the more optimized formulation of the oxalic acid solution for decontaminating photovoltaic devices is as follows:

[0058]

[0059] The application method of the oxalic acid solution for decontaminating photovoltaic devices in this embodiment is: the spraying dosage is 1-3 mL / dm 2 , the standing time is 2-5 minutes; the resistivity of the rinsing water is ≥18 MΩ·cm, and the pressure is 0.3-0.8 MPa.

[0060] Example 4

[0061] As Figure 1As shown, a preparation process of an oxalic acid solution for decontaminating a photovoltaic device according to Embodiment 3 includes the following steps:

[0062] Step 1 - Premixed acid system: Add deionized water (resistivity ≥ 15 MΩ·cm), oxalic acid solution and hydrofluoric acid into a corrosion-resistant reaction kettle (material: polytetrafluoroethylene lining) in sequence, and stir to form a homogeneous acidic mixture;

[0063] Step 2 - Construction of buffer and chelating system: Slowly add ammonium bifluoride, and adjust the free fluoride ion concentration to 0.3% - 0.5% by using its decomposition reaction (NH4HF2 → NH4F + HF), control the temperature at 20 - 25 °C, and then add EDTA-2Na to adjust the pH to 2.5 - 3.0 (monitored by a pH online monitor (accuracy ±0.05)) to avoid damaging the anti-reflection film in a strongly acidic environment;

[0064] Step 3 - Dispersion of functional additives: Add ethanol and glutathione in sequence, and stir with ultrasonic assistance (frequency 40 kHz, power 500 W) until completely dissolved to ensure that ethanol is evenly distributed in the system to accelerate subsequent drying;

[0065] Step 4 - Loading of nano carriers: Pre-disperse nano-silica in ethanol, perform ultrasonic oscillation treatment at 40 kHz for 15 minutes, and add it to the main system after eliminating particle agglomeration;

[0066] Step 5 - Surfactant compounding: Finally, add alkyl polyglycoside and polyglycerol ester, and stir at a low speed of 50 rpm for 20 minutes to obtain a transparent homogeneous solution.

[0067] In Step 1, control the temperature ≤ 25 °C and stir at 200 rpm for 10 minutes. In Step 4, pre-disperse nano-silica in 5% ethanol (the "5% ethanol" mentioned in the preparation process is a diluted ethanol solution used for pre-dispersing the nano-silica carrier, which is obtained from the dilution of 95% ethanol in the original formula, rather than adding new components additionally. Dilution logic: Assuming 100 g of 5% ethanol solution is required, about 5.26 g of 95% ethanol in the original formula is needed (i.e., 5 g of ethanol + 94.74 g of water), which does not conflict with the total amount of 10% ethanol used in the original formula (10 g)). Treat it with a high-speed shear emulsifier at a rotation speed of 3000 rpm for 10 min, and then perform ultrasonic treatment at 40 kHz for 15 minutes. In Step 5, under the condition of 25 °C, control the dynamic viscosity of the homogeneous solution at 15 - 20 mPa·s.

[0068] Example 5: Cleaning test of iron oxide powder and mildew

[0069] Test conditions: Select a photovoltaic glass sample (size 10 cm × 10 cm) containing iron oxide powder (thickness ≈ 50 μm) and mildew, with an environmental temperature of 25 °C and a humidity of 60%.

[0070] Operation process:

[0071] Spray this solution (dosage 2 mL / dm 2 ), and let it stand for 3 minutes;

[0072] Rinse with high-pressure deionized water (pressure 0.5 MPa) for 10 seconds;

[0073] Blow-dry with nitrogen.

[0074] Results:

[0075] Detergent removal rate: 98.5% for iron oxide powder and 97.2% for mildew spots;

[0076] The light transmittance of the glass is restored to 99.3% of the initial value;

[0077] The oxidation weight gain of the metal frame ≤ 0.01 mg / cm 2

[0078] Example 6: Comparative experiment on the removal of silicate crust

[0079] Control group: Commercially available oxalic acid cleaning solution (CN107488521A);

[0080] Experimental group: The solution of this scheme;

[0081] Crust type: SiO2-CaCO3 composite crust (hardness 4H) formed by simulating outdoor aging.

[0082] Result comparison:

[0083] Index Commercially available product The present invention Cleaning time (min) 8 3 Residue ratio (%) 12.5 0.8 Glass corrosion depth (nm) 15 ≤2

[0084] Technical effects

[0085] 1. High-efficiency detergent removal:

[0086] The comprehensive detergent removal rate for multiple stains (metal oxides, silicates, organic residues) ≥ 95%;

[0087] The nano-carrier improves the crust stripping efficiency by 40%.

[0088] 2. Low corrosiveness:

[0089] pH 2.5 - 3.0 and fluoride ion concentration ≤ 0.5%, glass corrosion rate ≤ 0.1 μm / h;

[0090] Glutathione inhibits the oxidation of metal components, and the annual corrosion amount of the frame ≤ 0.05 mm.

[0091] 3. Environmental protection:

[0092] Phosphorus-free formula, biodegradation rate (28 days) ≥ 90%, meeting the GB / T 28001 standard;

[0093] There is no toxic residue after ethanol volatilization, and the COD value of the wastewater ≤ 50 mg / L.

[0094] The oxalic acid solution for decontaminating photovoltaic devices of the present invention has the characteristics of high decontamination and scale removal rate, good decontamination effect, fast decontamination rate, and high cleaning efficiency; and this oxalic acid solution causes little harm to photovoltaic modules during the cleaning process.

[0095] The specific embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. An oxalic acid solution for decontaminating a photovoltaic device, characterized in that: It includes oxalic acid, hydrofluoric acid and EDTA-2Na; the concentration of oxalic acid is 10-15%, and the concentration of hydrofluoric acid is 55%.

2. The oxalic acid solution for decontaminating a photovoltaic device according to claim 1, wherein: The proportion of oxalic acid is 93-98wt%, the proportion of hydrofluoric acid is 1.5-5wt%, and the proportion of EDTA-2Na is 0.5-2.5wt%.

3. The oxalic acid solution for decontaminating a photovoltaic device according to claim 1, wherein: It also includes ethanol with a concentration of 95%; and the ratio is 82-90wt% of oxalic acid, 1-5wt% of hydrofluoric acid, 0.2-1wt% of EDTA-2Na, and 6-15wt% of ethanol.

4. The oxalic acid solution for decontaminating a photovoltaic device according to claim 1, wherein: It also includes ethanol, ammonium bifluoride, glutathione, nano-silica, alkyl glycoside and polyglycerol ester, and the concentration of ethanol is 95%.

5. The oxalic acid solution for decontaminating a photovoltaic device according to claim 4, characterized in that, The component ratios are as follows:

6. The oxalic acid solution for decontaminating a photovoltaic device according to claim 5, wherein, The component ratios are as follows:

7. A preparation process of an oxalic acid solution for decontaminating a photovoltaic device according to any one of claims 4-6, characterized in that, It includes the following steps: Step 1: Sequentially add deionized water, oxalic acid solution and hydrofluoric acid into a corrosion-resistant reaction kettle and stir. Step 2: Add ammonium bifluoride, control the temperature at 20-25°C, then add EDTA-2Na and adjust the pH to 2.5-3.

0. Step 3: Sequentially add ethanol and glutathione and stir until completely dissolved. Step 4: Pre-disperse nano-silica in ethanol, and add it to the system after ultrasonic treatment at 40kHz for 15 minutes. Step 5: Add alkyl glycoside and polyglycerol ester, and stir at a low speed of 50rpm for 20 minutes to obtain a homogeneous solution.

8. The preparation process of the oxalic acid solution for decontaminating a photovoltaic device according to claim 7, wherein: In Step 1, control the temperature ≤25°C and stir at 200rpm for 10 minutes.

9. The preparation process of the oxalic acid solution for removing dirt from the photovoltaic device according to claim 7, characterized in that: In Step 4, pre-disperse nano-silica in 5% ethanol and treat it with a high-speed shear emulsifier at a rotation speed of 3000rpm for 10min.

10. The preparation process of the oxalic acid solution for decontaminating a photovoltaic device according to claim 7, characterized in that: In Step 5, under the condition of 25°C, control the dynamic viscosity of the homogeneous solution at 15-20mPa·s.

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