Low-iron glass for solar thermal power generation and preparation method thereof

Abstract

The invention relates to low-iron glass for solar thermal power generation and a preparation method of the low-iron glass. Comprising the following steps: uniformly mixing 58.5 to 60 parts by weight of low-iron quartz sand, 12 to 15 parts by weight of low-iron dolomite, 3.5 to 6 parts by weight of low-iron limestone, 18.5 to 20 parts by weight of sodium carbonate, 1.7 to 2.1 parts by weight of potassium metaaluminate, 0.55 to 1.15 parts by weight of kainite, 0.25 to 0.5 part by weight of potassium bismuthate and 0.06 to 0.14 part by weight of cerium oxide to obtain a mixture; the mixture is put into a kiln to be melted, the melting temperature is set in a gradient mode, the oxidizing atmosphere is kept, and molten glass is obtained; clarifying, homogenizing, cooling, forming, annealing and cutting the molten glass to obtain the low-iron glass for solar thermal power generation. The low-iron glass for solar thermal power generation has higher sunlight direct transmittance and lower bubble defect number.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of glass production, in particular to a low-iron glass for solar thermal power generation and a preparation method thereof. BACKGROUND

[0002] Solar thermal power generation is a system that converts solar radiation into heat energy and generates electricity through a heat-power conversion process. It generally consists of three parts: a heat collection system, a heat storage and heat exchange system, and a heat-power-electricity conversion system. According to the different forms of concentration, solar thermal power generation technology mainly includes tower type, trough type, linear Fresnel type, and dish type, among which tower type and dish type are point focusing, and trough type and linear Fresnel type are line focusing. The focusing process is achieved through different shaped arrays of concentrating mirrors.

[0003] The base material of the concentrating mirror for solar thermal power stations uses low-iron float glass to meet the requirements of high solar transmittance and excellent weather resistance. The optical properties, mechanical strength, and chemical stability of low-iron float glass directly affect the light-heat conversion efficiency and equipment service life of solar thermal power stations. Therefore, under the premise of ensuring mechanical strength, chemical stability, and appearance quality, it is necessary to improve the direct solar transmittance of the glass as much as possible. The key indicator is that the direct solar transmittance of the glass (4.0mm thickness) in the 300-2500nm spectral range should not be less than 90.8%.

[0004] Currently, only a few domestic enterprises can stably produce low-iron glass for solar thermal power generation in batches. Other production attempts have problems such as not meeting the standard of direct solar transmittance and an increase in bubbles in the glass, making the glass quality unable to meet the needs of power stations. In order to achieve industrialized production of low-iron glass for solar thermal power generation, glass industry technicians have conducted a lot of innovative research, but the above problems have not been well solved.

[0005] CN 118978332 A discloses a preparation method of high-transmittance optical thermal glass, including the following preparation steps: (1) mixing batch materials, composite clarifying agent, cerium oxide, and lithium oxide, passing in ozone at 100-300mL / s, heating and melting, and when reaching two-thirds of the melting time, passing in air and increasing the gas flow rate to obtain glass liquid; (2) pouring the glass liquid into a mold, performing annealing treatment, then cooling to room temperature with the furnace, then sequentially placing in anhydrous ethanol and deionized water, performing ultrasonic cleaning, and then using nitrogen to dry to obtain intermediate A; (3) placing intermediate A in a vacuum degree of 4x10 -3In the environment of Pa, a protective gas, argon, is introduced until the gas pressure is 0.3 Pa, then a working gas, hydrogen, is introduced at 100 mL / min until the gas pressure is 3-6 kPa, plasma etching is performed, then methane is introduced at 4 mL / min and the gas pressure is kept at 4-8 kPa, reaction is performed for 20-60 min, then diamond-like deposition is performed, and high light transmission and heat glass is obtained. The method uses mold forming, and problems such as large size and uniformity are not easy to solve, and industrial production is difficult to realize.

[0006] CN 117776521 A discloses a photothermal glass and a preparation method thereof, which comprises a main glass and a trace additive. The main glass comprises the following components in percentage by mass: SiO2 58.8-63.4%; Al2O3 12.4-14.6%; Na2O 9.8-13.6%; K2O 4.6-6.8%; MgO 5.6-7.4%; ZrO2 0.6-1.2%; B2O3 0-0.3%; and Fe2O3 <0.01%. The trace additive is one or more of CaO, SrO, BaO and ZnO. The glass prepared by the method belongs to an alumino-silicate glass structure, which has better mechanical strength and thermal stability than a soda-lime-silicate glass structure. However, the alumino-silicate glass has a high melting temperature and a high production cost, and the higher the melting temperature, the more conducive to the generation of Fe 3+ The transition from high valence to low valence is not conducive to the improvement of the direct transmittance of sunlight under the condition of consistent total iron content.

[0007] CN 117361873 A discloses an ultra-white float process photothermal glass and a preparation method thereof. The raw material components further comprise a composite fining agent, and the combination given is at least two of carbon powder, mirabilite, sodium nitrate and sodium pyroantimonate. Carbon powder shows strong reducibility at high temperatures, and its common role in glass preparation is to accelerate the decomposition of mirabilite. The combination of carbon powder and mirabilite is a common combination of traditional "sulfur-carbon fining", and one of the important reactions is that sodium sulfate reacts with carbon powder in solid phase at 400-500 DEG C to generate Na2S and CO2. However, the reaction temperature is close to the decomposition temperature of sodium nitrate, and the oxygen generated by the decomposition of sodium nitrate will affect the reaction of sodium sulfate and carbon powder, which is not conducive to the fining of the glass. SUMMARY

[0008] In view of the above problems, the present application provides a low-iron glass for solar thermal power generation and a preparation method thereof. The low-iron glass for solar thermal power generation has a high direct transmittance of sunlight and a low number of bubble defects, and the preparation method can reduce the concentration ratio of Fe 2+ in the glass finished product, improve the fining effect of the glass liquid, and realize the industrial production of the low-iron glass for solar thermal power generation.

[0009] The first aspect of the application provides a preparation method of low-iron glass for solar thermal power generation, comprising the following steps:

[0010] Mixing: uniformly mixing 58.5-60 parts by weight of low-iron quartz sand, 12-15 parts by weight of low-iron dolomite, 3.5-6 parts by weight of low-iron limestone, 18.5-20 parts by weight of soda ash, 1.7-2.1 parts by weight of potassium aluminate, 0.55-1.15 parts by weight of kainite, 0.25-0.5 parts by weight of potassium bismuthate, and 0.06-0.14 parts by weight of cerium oxide to obtain a mixture; the iron content in the low-iron quartz sand is ≤60 ppm, the iron content in the low-iron dolomite is ≤100 ppm, the iron content in the low-iron limestone is ≤80 ppm, and the iron content in the kainite is ≤100 ppm;

[0011] Melting and fining: the mixture is put into a kiln for melting to obtain a glass liquid; the melting temperature is set in a gradient and sequentially includes a first melting temperature of 1500-1515℃, a second melting temperature of 1555-1580℃, a third melting temperature of 1585-1610℃, a fourth melting temperature of 1590-1610℃, a fifth melting temperature of 1567-1582℃, and a sixth melting temperature of 1522-1532℃; an oxidizing atmosphere is maintained during the melting process;

[0012] The glass liquid after melting is subjected to fining and homogenization, and is cooled to 1050-1100℃; during the fining process, the surface temperature of the glass liquid is controlled at 1450-1470℃;

[0013] Forming, annealing, and cutting: the cooled glass liquid is subjected to tin bath forming, annealing, and cutting to obtain the low-iron glass for solar thermal power generation.

[0014] The low-iron glass for solar thermal power generation is prepared from low-iron quartz sand, low-iron dolomite, low-iron limestone, soda ash, potassium metaaluminate, kainite, potassium bismuthate and cerium oxide as raw materials. The potassium oxide and aluminum oxide are introduced by potassium metaaluminate, which can reduce the reaction temperature compared with using aluminum oxide and aluminum hydroxide as raw materials to introduce aluminum oxide, and is helpful to reduce carbon emissions compared with using alkali metal carbonate as raw material to introduce potassium oxide. The halide and sulfate are introduced by kainite, which realizes halide clarification and sulfur clarification, and avoids the possibility of forming nitrous water when using mirabilite to introduce sulfate. The bismuth oxide is introduced by potassium bismuthate, which can reduce the viscosity of the glass melt, help the clarification of the glass liquid and reduce the melting temperature. The introduction of cerium oxide can prevent the variable valence metal oxides such as Fe and Bi from being reduced to low valence state or metal state by H2 and Sn in the tin bath, so that the coloring ion absorption band is in a shorter wavelength band, and the absorption of sunlight is reduced. By limiting the iron content in the four mineral raw materials of low-iron quartz sand, low-iron dolomite, low-iron limestone and kainite, the introduction of impurity metal elements is controlled, and the stability of the low-iron glass solar direct transmittance is ensured.

[0015] Through the synergistic effect of halide and sulfate in kainite, potassium bismuthate and cerium oxide, the temperature range of the clarification effect is wide, and the generation of bubble defects is reduced. Potassium bismuthate decomposes to generate potassium oxide (K2O), bismuth trioxide (Bi2O3) and oxygen (O2) at 400-500 ℃; bismuth trioxide (Bi2O3) decomposes to generate bismuth monoxide (BiO) and oxygen (O2) at 800-1000 ℃. Kainite loses crystal water after heating, starts to lose part of sulfate at 800-1000 ℃, and the sulfate decomposes into sulfur dioxide (SO2) and oxygen (O2) above 1100 ℃; above 1000 ℃, part of chlorine (Cl2) is decomposed, and part of KCl is vaporized above 1400 ℃. Cerium oxide is partially reduced to generate cerium trioxide (Ce2O3) and oxygen (O2) at 1300-1450 ℃, oxidizes the variable valence metal oxides in the low valence state in the glass melt, and oxidizes the un-discharged sulfur dioxide (SO2) in the glass liquid in the later stage of the clarification process, promoting the absorption of bubbles. The above raw material decomposition process releases oxygen, sulfur dioxide, potassium chloride vaporization and other gases gradually in the melting temperature range. These gases are different from the air mixed in the main raw materials of glass and the carbon dioxide generated by decomposition, and the partial pressure of these gases is small, which can diffuse into the bubbles, promote the growth, floating and discharge of the bubbles.

[0016] In industrial glass production, the five stages of glass melting (silicate formation, glass formation, clarification, homogenization and cooling) are often carried out at the same time. The wider the temperature range of the clarification effect, the more conducive to the clarification of the glass.

[0017] And due to the decomposition, vaporization and other reaction temperature differences (from 400 to 1450 degrees) of the above raw materials, the gas is released in turn during the melting temperature rising process, which helps to discharge the bubbles in the glass melt and reduce the generation of bubble defects, and is beneficial to the fining of the glass.

[0018] The melting temperature gradient and the fining temperature are set according to the used raw materials and the proportioning, to ensure the melting and fining effects of the glass, so as to prepare high-quality glass liquid with less bubbles and uniform composition; at the same time, the setting of the temperature gradient in the present technology is beneficial to the stable release of oxygen by the corresponding raw materials, and is beneficial to the reduction of the Fe 2+ content.

[0019] Different from the prior art, the present technical solution uses the proportioning of raw materials, especially the synergistic effect of the decomposition temperature-different potassium salt kieserite, potassium bismuthate and cerium oxide, so that the temperature range of the continuous fining effect is wide, and the temperature gradient suitable for the raw materials is used during melting to maintain the oxidizing atmosphere, so as to effectively reduce the Fe 2+ concentration ratio in the glass product, improve the fining effect of the glass liquid, and improve the direct solar light transmission ratio of the finished glass and reduce the bubble defects.

[0020] Further, in the mixing step, the weight ratio of the potassium salt kieserite, the potassium bismuthate and the cerium oxide is 59.9-67.0:26.0-31.5:7.0-8.6.

[0021] Further, in the mixing step, the potassium salt kieserite contains the following components with the mass percentage: K2O 15.7-16.0%, MgO 16.2-16.4%, SO3 32.7-33.2%, Cl 14.2-14.5%, and crystal water 20.3-20.7%.

[0022] The mixing step comprises:

[0023] 1) The potassium salt kieserite, the potassium bismuthate and the cerium oxide are sequentially put into a mixing machine, mixed uniformly, and mixed small materials are prepared and stored in a tank for standby;

[0024] 2) The low-iron quartz sand, the soda ash, the potassium metaaluminate, the low-iron dolomite, the low-iron limestone and the mixed small materials are sequentially put into a mixing machine, mixed uniformly, and the mixed materials are obtained.

[0025] The two-step mixing method can improve the uniformity of the mixed small materials, which is beneficial to the synergistic effect among the potassium salt kieserite, the potassium bismuthate and the cerium oxide.

[0026] Further, in the melting and refining step, the melting part of the kiln is sequentially provided with a first small furnace, a second small furnace, a third small furnace, a fourth small furnace, a fifth small furnace and a sixth small furnace, the first small furnace is controlled at a temperature of 1500-1515℃, the second small furnace is controlled at a temperature of 1555-1580℃, the third small furnace is controlled at a temperature of 1585-1610℃, the fourth small furnace is controlled at a temperature of 1590-1610℃, the fifth small furnace is controlled at a temperature of 1567-1582℃, and the sixth small furnace is controlled at a temperature of 1522-1532℃.

[0027] Further, in the melting and refining step, the first small furnace has an air excess coefficient of 1.25-1.35, the second small furnace has an air excess coefficient of 1.1-1.2, the third small furnace has an air excess coefficient of 1.25-1.35, the fourth small furnace has an air excess coefficient of 1.25-1.35, the fifth small furnace has an air excess coefficient of 1.3-1.4, and the sixth small furnace has an air excess coefficient of 1.45-1.55.

[0028] Further, the fuel usage of each small furnace of the kiln is distributed as follows: the total fuel usage of the first to third small furnaces accounts for 54-58%, wherein the fuel usage of the third small furnace accounts for 14-16%, and the remaining fuel usage of the first and second small furnaces is evenly distributed; the total fuel usage of the fourth to sixth small furnaces accounts for 42-46%, wherein the fuel usage of the fifth small furnace is consistent with that of the first and second small furnaces, the fuel usage of the sixth small furnace accounts for 3-5%, and the remaining fuel usage is distributed to the fourth small furnace.

[0029] Further, the melting rate of the kiln is controlled at 1.55-1.65t / m 2 ·d.

[0030] By reasonably distributing the fuel usage, air excess coefficient and melting rate of the kiln, the overall kiln is kept in an oxidizing atmosphere.

[0031] The second part of the application provides a low-iron glass for solar thermal power generation, which is prepared by the preparation method of the first part of the application.

[0032] Further, the low-iron glass for solar thermal power generation has a thickness of 4mm, and a direct solar transmission ratio of 91.1-91.4%.

[0033] Further, the low-iron glass for solar thermal power generation has an iron content of 60-80ppm.

[0034] Further, the low-iron glass for solar thermal power generation (original plate) has a bubble defect density of ≦0.02 pieces per square meter for bubbles with a diameter greater than 1.0mm.

[0035] Differing from the prior art, the technical scheme is designed by the proportioning of raw materials, especially the synergistic effect of the potassium salt of magnesium alum, potassium bismuthate and cerium oxide with different decomposition temperatures, so that the temperature range of the continuous clarification effect is wide, and the temperature gradient suitable for the raw materials is adopted during melting, the oxidation atmosphere is maintained, the concentration ratio of Fe 2+ in the glass product is reduced, the clarification effect of the glass liquid is improved, the glass has a higher direct transmittance of sunlight and a lower number of bubble defects.

[0036] The above summary of the invention is only a summary of the technical scheme of the present application. In order for those skilled in the art to more clearly understand the technical scheme of the present application, and then can be implemented according to the content of the written description in the specification, and in order to make the above-mentioned purpose and other purposes, characteristics and advantages of the present application can be more easily understood, the following is described in conjunction with the specific embodiments of the present application and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings are only used to show the principles, implementation modes, applications, characteristics and effects of the specific embodiments of the present application and other related contents, and cannot be considered as a limitation of the present application.

[0038] In the drawings:

[0039] Figure 1 The spectral transmittance curves of the 4mm-thick glass produced by different embodiments and comparative examples.

[0040] Figure 2 The spectral (wavelength range 700nm-2000nm) transmittance curves of the 4mm-thick glass of different embodiments and comparative examples. DETAILED DESCRIPTION

[0041] In order to explain the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following will be described in detail in conjunction with the specific embodiments listed and the accompanying drawings. The embodiments described in this paper are only used to more clearly illustrate the technical scheme of the present application, therefore only as an example, and cannot be used to limit the protection scope of the present application.

[0042] In this paper, the term "embodiment" means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, and does not particularly limit the independence or association between other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the technical features mentioned in each embodiment can be combined in any way to form a corresponding implementable technical scheme.

[0043] Unless otherwise defined, the meanings of technical terms used in the present application are the same as commonly understood by one of ordinary skill in the art to which the present application belongs; the use of related terms in the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0044] In the description of the present application, the phrase "and / or" is a description of the logical relationship between objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally represents that the associated objects before and after are a "or" logical relationship.

[0045] In the present application, terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual quantity, primary and secondary, or order relationship between the entities or operations.

[0046] In the present application, without more limitation, the "includes", "contains", "has" or other similar expressions used in the sentence are intended to cover non-exclusive inclusion, and these expressions do not exclude the presence of other elements in the process, method or product including the described elements, so that the process, method or product including a series of elements can not only include those limited elements, but also include other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0047] As the same understanding as in the "Guidelines for Examination", in the present application, the expressions "greater than", "less than", "exceed" and the like are understood as not including the number; the expressions "above", "below", "within" and the like are understood as including the number. In addition, in the description of the embodiments of the present application, the meaning of "multiple" is more than two (including two), and similar expressions related to "multiple" are also understood in this way, for example, "multiple groups", "multiple times" and the like, unless otherwise explicitly limited.

[0048] Example 1

[0049] The low-iron glass for solar thermal power generation described in this embodiment 1 comprises the following raw materials by weight: low-iron quartz sand 59.24 parts by weight, low-iron dolomite 13.45 parts by weight, low-iron limestone 4.88 parts by weight, soda ash 19.21 parts by weight, potassium metaaluminate 1.90 parts by weight, potassium salt sylvite 0.83 parts by weight, potassium bismuthate 0.37 parts by weight, cerium oxide 0.10 parts by weight.

[0050] Among them:

[0051] The iron content of the raw material is 58 ppm in low-iron quartz sand, 95 ppm in low-iron dolomite, 73 ppm in low-iron limestone, and 100 ppm in kainite.

[0052] The main chemical composition of the kainite, in percentage by mass, is as follows: K2O 16.0%, MgO 16.4%, SO3 32.7%, Cl 14.5%, and crystal water 20.3%.

[0053] The preparation method of the low-iron glass for solar thermal power generation in the embodiment 1 comprises the following steps:

[0054] In step one, the kainite, potassium bismuthate, and cerium oxide are weighed in the ratio of 63.8:28.5:7.7, and then sequentially added into a gravity-free mixer to mix for 3 minutes to obtain a mixed small material.

[0055] In step two, the low-iron quartz sand, soda ash, potassium meta-aluminate, low-iron dolomite, low-iron limestone, and the mixed small material prepared in step one are weighed and sequentially added into the mixer, and then uniformly mixed and delivered to a kiln for feeding.

[0056] In step three, the batch prepared in step two is fed into the kiln, and the melting part of the kiln is sequentially provided with first to sixth small furnaces. The batch is heated and melted in the melting part to form a glass liquid.

[0057] The melting temperature gradient is as follows: 1508±2℃ for the first small furnace, 1570±2℃ for the second small furnace, 1598±2℃ for the third small furnace, 1600±2℃ for the fourth small furnace, 1574±2℃ for the fifth small furnace, and 1527±2℃ for the sixth small furnace.

[0058] The fuel consumption of each small furnace is as follows: 20.7% for the first small furnace, 20.7% for the second small furnace, 14.8% for the third small furnace, 19.1% for the fourth small furnace, 20.7% for the fifth small furnace, and 4.0% for the sixth small furnace.

[0059] The excess air coefficient of each small furnace is as follows: 1.29 for the first small furnace, 1.13 for the second small furnace, 1.30 for the third small furnace, 1.31 for the fourth small furnace, 1.36 for the fifth small furnace, and 1.51 for the sixth small furnace.

[0060] The melting rate of the kiln is controlled at 1.61 t / m 2 ·d.

[0061] In step four, the glass liquid is refined (the surface temperature of the glass liquid in the refining zone of the kiln is 1459±1℃), homogenized, and cooled to 1090℃, and then formed through a tin bath, annealed in an annealing kiln, and cut at a cold end to obtain the finished low-iron glass for solar thermal power generation.

[0062] Embodiment 2

[0063] The low-iron glass for solar thermal power generation according to the present embodiment 2 comprises the following raw materials by weight: low-iron quartz sand 58.57 parts by weight, low-iron dolomite 14.94 parts by weight, low-iron limestone 3.51 parts by weight, soda ash 19.96 parts by weight, potassium metaaluminate 2.10 parts by weight, kainite 0.55 parts by weight, potassium bismuthate 0.29 parts by weight, and cerium oxide 0.08 parts by weight.

[0064] Wherein:

[0065] The iron content of the low-iron quartz sand in the raw materials is 58 ppm, the iron content of the low-iron dolomite is 95 ppm, the iron content of the low-iron limestone is 73 ppm, and the iron content of the kainite is 100 ppm.

[0066] The main chemical composition of the kainite is as follows in terms of mass percentage: K2O 16.0%, MgO 16.4%, SO3 32.7%, Cl 14.5%, and crystal water 20.3%.

[0067] The preparation method of the low-iron glass for solar thermal power generation according to the present embodiment 2 comprises the following steps:

[0068] Step one: the kainite, potassium bismuthate, and cerium oxide are weighed according to the ratio of 59.9:31.5:8.6, and then sequentially added into a gravity-free mixer to mix for 3 minutes to obtain a mixture of small materials;

[0069] Step two: the low-iron quartz sand, soda ash, potassium metaaluminate, low-iron dolomite, low-iron limestone, and the mixture of small materials prepared in step one are weighed by weight parts, sequentially added into the mixer, and then uniformly mixed and delivered to the kiln for feeding;

[0070] Step three: the batch prepared in step two is fed into the kiln, and the melting part of the kiln is sequentially provided with first to sixth small furnaces. The batch is heated and melted in the melting part to form a glass liquid.

[0071] The melting temperature gradient is as follows: the first small furnace 1502±2℃, the second small furnace 1559±2℃, the third small furnace 1587±2℃, the fourth small furnace 1594±2℃, the fifth small furnace 1569±2℃, and the sixth small furnace 1530±2℃.

[0072] The fuel consumption of each small furnace is as follows: the first small furnace 20.0%, the second small furnace 20.0%, the third small furnace 14.1%, the fourth small furnace 20.9%, the fifth small furnace 20.0%, and the fuel consumption of the sixth small furnace accounts for 5.0%.

[0073] The excess air coefficient of each small furnace is as follows: the first small furnace 1.25, the second small furnace 1.11, the third small furnace 1.25, the fourth small furnace 1.35, the fifth small furnace 1.31, and the sixth small furnace 1.55.

[0074] The furnace melting rate is controlled at 1.56 t / m 2 ·d.

[0075] Step four, the glass liquid is clarified (the surface temperature of the glass liquid in the furnace clarification zone is 1452±1℃), homogenized, cooled to 1090℃, and then formed by a tin bath, annealed in an annealing furnace, and cut at the cold end to obtain a low-iron glass product for solar thermal power generation.

[0076] Example 3

[0077] The low-iron glass for solar thermal power generation described in this embodiment 3 comprises the following raw materials by weight: low-iron quartz sand 59.92 parts by weight, low-iron dolomite 12.06 parts by weight, low-iron limestone 5.97 parts by weight, soda ash 18.62 parts by weight, potassium metaaluminate 1.72 parts by weight, kainite 1.15 parts by weight, potassium bismuthate 0.44 parts by weight, and cerium oxide 0.12 parts by weight.

[0078] Among them:

[0079] The iron content of the low-iron quartz sand in the raw materials is 58 ppm, the iron content of the low-iron dolomite is 95 ppm, the iron content of the low-iron limestone is 73 ppm, and the iron content of the kainite is 100 ppm.

[0080] The main chemical composition of the kainite is as follows in terms of mass percentage: K2O 16.0%, MgO 16.4%, SO3 32.7%, Cl 14.5%, and crystal water 20.3%.

[0081] The preparation method of the low-iron glass for solar thermal power generation described in this embodiment 3 is composed of the following steps:

[0082] Step one, the kainite, potassium bismuthate, and cerium oxide are weighed according to the ratio of 67.0:26.0:7.0, and then sequentially added into a gravity-free mixer to mix for 3 minutes to obtain a mixed small material;

[0083] Step two, the low-iron quartz sand, soda ash, potassium metaaluminate, low-iron dolomite, low-iron limestone, and the mixed small material prepared in step one are weighed by weight parts, sequentially added into the mixer, and then uniformly mixed before being conveyed to the furnace for feeding. The crushed glass is proportionally spread on the mixture during the conveying process;

[0084] Step three, the mixture prepared in step two is fed into the furnace, and the melting part of the furnace is sequentially provided with the first to sixth small furnaces. The mixture is heated and melted in the melting part to form a glass liquid;

[0085] The melting temperature gradient is: the first furnace 1512±2℃, the second furnace 1578±2℃, the third furnace 1607±2℃, the fourth furnace 1607±2℃, the fifth furnace 1580±2℃, and the sixth furnace 1525±2℃. The fuel consumption of each furnace is distributed as follows: the first furnace 21.0%, the second furnace 21.0%, the third furnace 16.0%, the fourth furnace 17.9%, the fifth furnace 21.0%, and the sixth furnace 3.1%.

[0086] The excess air coefficient of each furnace is: the first furnace 1.35, the second furnace 1.18, the third furnace 1.35, the fourth furnace 1.26, the fifth furnace 1.40, and the sixth furnace 1.45.

[0087] The melting rate of the furnace is controlled at 1.65t / m 2 ·d.

[0088] Step four, the glass liquid is clarified (the surface temperature of the glass liquid in the clarifying zone of the furnace is 1469±1℃), homogenized, and cooled to 1090℃, then formed by a tin bath, annealed in an annealing furnace, and cut at the cold end to obtain a low-iron glass product for solar thermal power generation.

[0089] Comparative Example 1

[0090] The preparation method of the low-iron glass for solar thermal power generation in Comparative Example 1 is the same as that in Example 1, and the only difference is the composition of the raw materials. Comparative Example 1 includes the following raw materials in parts by weight: low-iron quartz sand 59.49 parts by weight, low-iron dolomite 14.15 parts by weight, low-iron limestone 4.52 parts by weight, soda ash 18.96 parts by weight, potassium metaaluminate 1.91 parts by weight, mirabilite 0.49 parts by weight, potassium bismuthate 0.37 parts by weight, and cerium oxide 0.10 parts by weight.

[0091] Comparative Example 2

[0092] The preparation method of the low-iron glass for solar thermal power generation in Comparative Example 2 is the same as that in Example 1, and the only difference is the composition of the raw materials. Comparative Example 2 includes the following raw materials in parts by weight: low-iron quartz sand 59.20 parts by weight, low-iron dolomite 13.44 parts by weight, low-iron limestone 4.88 parts by weight, soda ash 19.20 parts by weight, potassium metaaluminate 1.90 parts by weight, potassium salt of magnesium sulfate 1.19 parts by weight, and cerium oxide 0.19 parts by weight.

[0093] Comparative Example 3

[0094] The preparation method of the low-iron glass for solar thermal power generation according to Comparative Example 3 is the same as that of Example 1, except that the raw material composition is different. Comparative Example 3 comprises the following raw materials in parts by weight: low-iron quartz sand 59.23 parts by weight, low-iron dolomite 13.45 parts by weight, low-iron limestone 4.88 parts by weight, soda ash 19.21 parts by weight, potassium metaaluminate 1.90 parts by weight, kainite 0.93 parts by weight, and potassium bismuthate 0.40 parts by weight.

[0095] Comparative Example 4

[0096] The raw material composition of the low-iron glass for solar thermal power generation according to Comparative Example 4 is the same as that of Example 1, except that the process parameters of the kiln in the preparation method are set as follows:

[0097] The melting temperature gradient is: the first small furnace 1492±2℃, the second small furnace 1545±2℃, the third small furnace 1578±2℃, the fourth small furnace 1598±2℃, the fifth small furnace 1554±2℃, and the sixth small furnace 1517±2℃.

[0098] The fuel usage distribution of each small furnace is: the first small furnace 20.0%, the second small furnace 21.0%, the third small furnace 20.5%, the fourth small furnace 16.5%, the fifth small furnace 21%, and the sixth small furnace 1.0%.

[0099] The excess air coefficient of each small furnace is: the first small furnace 1.05, the second small furnace 1.04, the third small furnace 1.02, the fourth small furnace 1.14, the fifth small furnace 1.31, and the sixth small furnace 1.50.

[0100] The surface temperature of the glass liquid in the clarifying zone of the kiln is 1454±1℃.

[0101] The melting rate of the kiln is controlled at 1.61t / m 2 ·d.

[0102] Comparative Example 5

[0103] The raw material composition of the low-iron glass for solar thermal power generation according to Comparative Example 5 is the same as that of Example 1, except that the process parameters of the kiln in the preparation method are set as follows:

[0104] The melting temperature gradient is: the first small furnace 1500±2℃, the second small furnace 1555±2℃, the third small furnace 1587±2℃, the fourth small furnace 1606±2℃, the fifth small furnace 1562±2℃, and the sixth small furnace 1525±2℃.

[0105] The fuel usage distribution of each small furnace is: the first small furnace 20.0%, the second small furnace 21.0%, the third small furnace 20.5%, the fourth small furnace 16.5%, the fifth small furnace 21%, and the sixth small furnace 1.0%.

[0106] The air excess coefficients of the respective small furnaces are: 1.05 for the first small furnace, 1.04 for the second small furnace, 1.02 for the third small furnace, 1.14 for the fourth small furnace, 1.31 for the fifth small furnace, and 1.50 for the sixth small furnace.

[0107] The surface temperature of the glass liquid in the clarifying zone of the furnace is 1469±1℃.

[0108] The melting rate of the furnace is controlled at 1.65t / m 2 ·d.

[0109] The following performance tests were conducted on the glass produced by the different examples and comparative examples, and the results are shown in Table 1.

[0110] 1. The iron content was tested by a physics X-ray fluorescence spectrometer ZSX Primus III+,

[0111] 2. The direct solar transmittance was tested by a Lambda950 (with a 150mm integrating sphere) of PerkinElmer Company (the testing and calculation methods were conducted according to ISO 9050:2003)

[0112] 3. The bubble number was tested by an FS-Basic online detector of ISRA VISION Company.

[0113] Table 1: Test results of the 4mm-thick glass produced by the different examples and comparative examples

[0114]

[0115] *L is the bubble size, taking the longest axis diameter of the bubble

[0116] As can be seen from the data in Table 1, in the case of using the same mineral raw materials, the iron content of each example and comparative example is basically not affected by other changes, and compared with the comparative examples, the examples in the range of the raw material composition and preparation method set by the present application have better direct solar transmittance and relatively lower bubble defect density. Figure 1 and Figure 2 As can be seen, the main difference between Examples 1, 2 and 3 and Comparative Examples 2, 3, 4 and 5 is that the transmittance in the range of 700nm-2000nm is obviously higher, indicating that the Fe 2+ content in the glass of the examples is significantly reduced. It can be seen that, by setting the raw material composition and preparation method of the present application, the direct solar transmittance of the glass can be effectively improved under the condition of basically equivalent iron content.

[0117] Comparatively, the bubble defects of Comparative Example 1 are obviously increased, and some sodium sulfate bubbles are observed, indicating that the decomposition of sodium sulfate is affected in the oxidative environment, resulting in poor clarification.

[0118] Finally, it should be noted that the above-described embodiments are described in the specification and drawings of the application, but this does not limit the patent protection scope of the application. Any equivalent structure or equivalent process replacement or modification based on the essential concept of the application, using the content described in the specification and drawings of the application, and directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, etc., are all included in the patent protection scope of the application.

Claims

1. A method for preparing low-iron glass for solar thermal power generation, characterized in that, The preparation method includes the following steps: Mixing: Mix 58.5-60 parts by weight of low-iron quartz sand, 12-15 parts by weight of low-iron dolomite, 3.5-6 parts by weight of low-iron limestone, 18.5-20 parts by weight of soda ash, 1.7-2.1 parts by weight of potassium aluminate, 0.55-1.15 parts by weight of potassium magnesium sulfate, 0.25-0.5 parts by weight of potassium bismuthate, and 0.06-0.14 parts by weight of cerium oxide evenly to obtain a mixture; wherein the iron content in the low-iron quartz sand is ≤60ppm, the iron content in the low-iron dolomite is ≤100ppm, the iron content in the low-iron limestone is ≤80ppm, and the iron content in the potassium magnesium sulfate is ≤100ppm. Melting and clarification: The mixture is fed into a furnace for melting to obtain molten glass; the melting temperatures are set in a gradient, including a first melting temperature of 1500–1515℃, a second melting temperature of 1555–1580℃, a third melting temperature of 1585–1610℃, a fourth melting temperature of 1590–1610℃, a fifth melting temperature of 1567–1582℃, and a sixth melting temperature of 1522–1532℃; the melting process is carried out in an oxidizing atmosphere; The molten glass is clarified and homogenized, and then cooled to 1050–1100°C; during the clarification process, the surface temperature of the molten glass is controlled at 1450°C–1470°C. Forming, annealing, and cutting: The cooled molten glass is formed, annealed, and cut in a tin bath to obtain the low-iron glass for solar thermal power generation.

2. The preparation method according to claim 1, characterized in that, In the mixing step, the weight ratio of potassium magnesium alum, potassium bismuthate, and cerium oxide is 59.9–67.0:26.0–31.5:7.0–8.

6.

3. The preparation method according to claim 1, characterized in that, In the mixing step, the potassium salt magnesium alum contains the following components in mass percentage: K2O 15.7-16.0%, MgO 16.2-16.4%, SO3 32.7-33.2%, Cl 14.2-14.5%, and water of crystallization 20.3-20.7%.

4. The preparation method according to claim 1, characterized in that, The mixing step includes: 1) Add potassium magnesium alum, potassium bismuthate and cerium oxide into a mixer in sequence, mix evenly to obtain a mixed material, and store it in a material tank for later use; 2) Add low-iron quartz sand, soda ash, potassium aluminate, low-iron dolomite, low-iron limestone and the mixed small materials into the mixer in sequence, mix evenly to obtain the mixed material.

5. The preparation method according to claim 1, characterized in that, In the melting and clarification steps, the melting section of the kiln is sequentially equipped with a first small furnace, a second small furnace, a third small furnace, a fourth small furnace, a fifth small furnace, and a sixth small furnace. The temperature of the first small furnace is controlled at 1500-1515℃, the temperature of the second small furnace is controlled at 1555-1580℃, the temperature of the third small furnace is controlled at 1585-1610℃, the temperature of the fourth small furnace is controlled at 1590-1610℃, the temperature of the fifth small furnace is controlled at 1567-1582℃, and the temperature of the sixth small furnace is controlled at 1522-1532℃.

6. The preparation method according to claim 5, characterized in that, In the melting and clarification steps, the excess air coefficient of the first small furnace is 1.25-1.35, the excess air coefficient of the second small furnace is 1.1-1.2, the excess air coefficient of the third small furnace is 1.25-1.35, the excess air coefficient of the fourth small furnace is 1.25-1.35, the excess air coefficient of the fifth small furnace is 1.3-1.4, and the excess air coefficient of the sixth small furnace is 1.45-1.

55.

7. A low-iron glass for solar thermal power generation, characterized in that, The low-iron glass for solar thermal power generation is prepared using the preparation method described in any one of claims 1-6.

8. The low-iron glass for solar thermal power generation according to claim 7, characterized in that, The low-iron glass used for solar thermal power generation has a direct solar transmittance of 91.1% to 91.4% when it is 4mm thick.

9. The low-iron glass for solar thermal power generation according to claim 7, characterized in that, The iron content of the low-iron glass used for solar thermal power generation is 60-80 ppm.

10. The low-iron glass for solar thermal power generation according to claim 7, characterized in that, The density of bubble defects with a diameter greater than 1.0 mm in the low-iron glass used for solar thermal power generation is ≤0.02 per square meter.

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