At present, oil-based or resin-based silver powder paint is mostly used for the outer wall coating of storage tanks in petrochemical and other industries. Due to the limited reflectivity and thermal barrier properties of silver powder paint, solvent storage tanks and low-boiling point chemical product storage tanks can only be used in high temperature seasons. Use water spray to cool down to reduce the breathing loss of the product.

The water spray brings the rust in the water pipe and the sedimentary dirt of the circulating water, and the algae and mold grow on the tank wall, which causes the damage of the outer wall coating and the corrosion of the tank body, and hinders the appearance of the factory area and the reservoir area. Because water resources are relatively precious, the cost of cooling with water spray is high; the old way of water spraying cannot be used, and the use of heat reflective thermal insulation coatings can reduce the breathing loss of light oil products and reduce the surface temperature. Therefore, heat reflective thermal insulation coatings are necessary. product. At present, the domestic R&D and production of this coating started early and there are few manufacturers with good reputation in the industry. The most representative is Taiyuan Yuyuan Coatings Co., Ltd. This type of product is divided into durable and economical and practical types, both of which have high high solar reflectance, hemispheric emissivity and low thermal conductivity.

Heat-reflecting heat-insulating and anti-corrosion coatings are used for storage tanks and pipelines. Due to the low thermal conductivity of the coating, the heat conduction of the coating to the substrate is reduced, the temperature of the tank wall is small, and the efficiency of water spraying is eliminated, saving energy and water. . The use of heat-reflecting, heat-insulating and anti-corrosion coatings on the exterior walls of buildings can reflect sunlight in summer, block the transfer of heat energy to the interior, and reduce indoor temperature; in winter, it can prevent indoor heat energy from diffusing outward, play a role in indoor heat preservation, reduce the number of air conditioners turned on, and save energy. . As a new type of special functional coating, solar heat reflective thermal insulation coating has a very clear purpose. Its characteristics of reflecting sunlight, blocking thermal energy transfer, cooling, energy saving and comprehensive economic benefits determine its target market in petroleum, chemical, It has a wide range of market applications in transportation pipelines, grain storage and warehouse sectors, construction and vehicle, shipbuilding and other industries.

It is understood that there are more than 100,000 petrochemical storage tanks in China, ranging from tens of thousands of cubic meters to hundreds of cubic meters. Grain steel silos in various regions of the country have been transformed from turnover silos into storage silos. It is also very urgent to solve the problem of heat insulation. The development of this target market has great potential.

Discussion on the application of heat-reflecting and heat-insulating coatings for steel oil storage tanks

Abstract: Heat reflective thermal insulation coating, a new type of functional coating, has been successfully and widely used on the outer surface of volatile oil storage tanks and pipelines, and has achieved good results in cooling and reducing pressure, safety and efficiency, and energy saving and water saving. The classification and main technical indicators of this coating are introduced: "thermal insulation temperature difference" is not less than 10 ℃; "thermal insulation temperature difference attenuation (white)" is not more than 12 ℃. In the "artificial weathering resistance" index, "powder/grade" is not greater than 1; "discoloration" (white and light color)/grade is not greater than 2; "solar reflectance (white)" is not less than 0.81; "hemisphere" Emissivity" is not less than 0.83. The coating index reaches "solar heat reflectance" not less than 0.90 (full wave area); "hemispheric emissivity" is not less than 0.85 "solar heat reflectance" is not less than 0.90 (full wave area); "hemispheric emission rate" is not less than 0.90 The average temperature of the tank surface is lowered by 10-20 °C; the medium temperature of the tank is reduced by about 5-10 °C.

In recent years, with the advancement of science and technology and the popularization of the scientific concept of development, the economic operation mode of energy conservation, emission reduction, resource conservation, environmental friendliness and sustainable development is promoting the transformation of domestic production and life to a more reasonable and effective direction. This has also been fully confirmed in the development and progress of anti-corrosion coating engineering technology for steel oil storage tanks. At present, spray water is mainly used for cooling light oil tanks, which not only requires external power supply, wastes valuable resources such as water and electricity, but also makes it difficult to obtain the best cooling effect, which has become an urgent problem in the application of ground oil tanks. .

There are many studies on heat reflective coatings at home and abroad, but the cooling performance indicators are not uniform and the physical meaning is unclear. The evaluation methods for the heat reflectivity of heat reflective coatings are different, and the corresponding incident wavelength bands are rarely mentioned, so it is difficult to obtain data. Compare. At present, domestic researchers mainly evaluate the quality of the coating film by simulating solar radiation or the cooling performance of the coating film under measured conditions, which is bound to have certain limitations. Among the relevant standards, the implementation of the national standard for thermal insulation and cooling coatings for buildings has a certain normative effect.

The guidance of the national energy-saving and emission-reduction policy has been continuously increased, and domestic and foreign paint manufacturers have launched such products to seize the opportunity of the energy-saving and emission-reduction market. The testing standards are different, and it is generally impossible to distinguish the authenticity and quality. In order to quickly and accurately select the products that meet the objective needs, the product testing report issued by the current national authoritative testing department should be used as the main basis, and the main technical index index should be grasped. This paper firstly expounds the connotation and extension of heat reflective thermal insulation coatings from a technical point of view, and analyzes key technical indicators, hoping to provide practical guidance for the majority of users.

1. Overview of Heat Reflective Thermal Insulation Coatings

1.1 Heat analysis of oil tank surface under sunlight

The propagation of heat has three basic forms: radiation, convection and conduction. The decisive heat source that affects the temperature of various objects on the earth's surface comes from the sun, and solar heat energy is transmitted to the earth's surface in the form of electromagnetic radiation. The wavelength range of solar radiation is very wide. Thermal energy is concentrated in the 200-2600 nm wave region. The specific distribution is about 5% in the ultraviolet 200-380 nm; about 46% in the visible light 380-760 nm; about 49% in the infrared 760-2 600 nm, especially the visible and near-infrared wavelengths of 380-1 400 nm account for the sun. most of the thermal energy. Various objects receive heat radiation from the sun to heat up, and then form convection and conduction between each other, which finally manifests as the specific temperature state of each object.

Heat reflective thermal insulation coating, a new type of functional coating, has been successfully and widely used on the outer surface of storage tanks and pipelines for volatile oil products (including low-viscosity crude oil, middle distillate oil and light product oil and gas). Good effect of safety, efficiency, energy saving and water saving. Experiments show that under the sunshine conditions in summer, compared with the cans coated with silver powder paint, the surface of the cans coated with the heat-reflecting and heat-insulating paint is lowered by 10-20℃ on average, the internal temperature of the cans is reduced by 5-10℃, and the higher the ambient temperature is, the lower the temperature is. The more obvious the high temperature difference, the more the liquefied gas tank does not have over-temperature, over-pressure and other phenomena. Compared with traditional cooling methods, solar heat reflective coatings can effectively reduce the temperature of oil tanks without consuming energy, prevent the transfer of heat to the interior of the object from the source, and achieve the purpose of energy saving and cooling. application prospects.

1.2 Technical Classification of Heat Reflective Thermal Insulation Coatings

At present, domestic heat reflective and thermal insulation coating products can be roughly divided into two categories according to their technical routes:

One type is a product that uses ceramic or glass hollow microbeads as the main functional material to achieve thermal insulation effect by means of thermal radiation reflection, infrared emission and additional thermal resistance. In addition to thermal radiation, reflection and infrared emission, the thermal insulation efficacy of such products is directly related to the thermal resistance coefficient of the hollow bead material. In principle, the lower the bulk density of hollow microbeads, the higher the thermal resistance index, and the "light" quality is one of its major characteristics, that is, because of the "light" quality, hollow microbeads will be formed in a short period of time during the storage of such coating liquid products. The upward condensation phenomenon and the poor leveling of the coating during the coating process, so the coating construction should only be done by troweling or high-pressure airless spraying to obtain a thicker (generally more than 300 μm) and relatively uniform coating, and it is very It is difficult to obtain a fine and smooth surface, and the anti-fouling and self-cleaning ability is poor. In the process of using in the natural environment, the reflection and emission indicators are prone to large attenuation, resulting in a high thermal insulation temperature difference attenuation index of the coating and a large loss of thermal insulation effect. The full play of the "thermal resistance" performance of microbeads is closely related to the overlapping and seamless arrangement of microbeads in the coating and the thickness of the coating. In theory, the thickness of the coating has a considerable influence on the thermal insulation function. The thicker the coating, the thermal insulation effect. The better, but when the coating is too thin so that the microbeads cannot form a complete and seamless state, most of the thermal insulation effect brought by the thermal resistance coefficient will be lost.

The other type is the products represented by Wuxing Environmental Protection Group Co., Ltd. that use various composite high-reflection and high-emission powders as basic functional materials to achieve a certain thermal insulation effect by means of thermal radiation, reflection and infrared emission. Once the functional index is determined, its heat reflective and thermal insulation function index has been determined, as long as it is evenly painted on the surface of the object and completely covers the coating (the average thickness of the reflective thermal insulation coating of such coatings is less than 100μm), it is completed. Complete functional coating, if the coating thickness is simply increased on this basis, it will make little contribution to further improving the thermal insulation effect of the coating. Therefore, there is no need to pursue the coating thickness and increase the ineffective cost in the process of product coating. The phenomenon. To further enhance the thermal insulation effect, a corresponding thermal insulation layer can be added under the heat reflective thermal insulation coating. This thin-layer heat-reflecting and heat-insulating paint is close to traditional paint in various physical properties, so the construction can adopt various painting methods and process schemes commonly used in traditional paint. This kind of reflective thermal insulation coating has the unique effects of high reflectivity, high self-cleaning, high weather resistance, and greatly enhances the life of the anti-corrosion coating to meet the actual needs.

2. Analysis of key technical indicators of heat reflective thermal insulation coatings

2.1 Analysis of solar reflectance and hemispheric emissivity

Heat reflective thermal insulation coating is a functional coating that uses thermal radiation reflection as the main technical means and infrared emission (also called "heat dissipation") as an auxiliary means to achieve thermal insulation effect. effect. The coating formed by the heat reflective thermal insulation coating can effectively suppress the temperature rise and fall of the object to be coated. T 1040—2007 "Heat Reflective Thermal Insulation Coatings for External Surfaces of Buildings" stipulates that the indicators that the products must meet are "solar reflectance (white) ≥ 0. 83; hemispheric emissivity ≥ 0. 85", of which "solar reflectance" (200 ~ 2600 nm solar thermal radiation full band) index is the most important technical index to measure the performance of the product. This index of the product directly determines the amount of solar radiation and heat energy accepted by the coating formed by the coating. The higher the index, the lower the acceptance amount. , it will show more and more obvious "drawing wages from the bottom of the kettle"; and the "hemispheric emissivity" index is an important auxiliary technical indicator to measure the quality of product performance, its role is to determine the coating film formed by the coating has received radiant heat energy outward It can reduce the accumulation of radiant heat energy on the surface of the coating and the final conduction to the other side of the coating, which has an important auxiliary enhancement effect on the final thermal insulation effect of the coating.

2.2 Analysis of “Insulation Temperature Difference” and “Insulation Temperature Difference Attenuation” The results of the combined effect of two functional technical indicators “solar reflectance” and “hemispheric emissivity” are reflected in the standard “Insulation temperature difference” and “Insulation temperature difference”. In terms of the two technical indicators of "temperature difference attenuation", JG/T 235-2008 "Architectural Reflective Thermal Insulation Coatings" stipulates that the products must meet the following indicators: "Insulation temperature difference" ≥ 10 ℃; "Insulation temperature difference attenuation (white)" ≤12 ℃, the "thermal insulation temperature difference" index is the value of the final thermal insulation function achieved by the coating formed by the coating under laboratory standard conditions, and the index with a higher index should be selected; (white)” index is the actual functional effect value that can be achieved when the product is finally formed into a coating under the assumption of standard test conditions to simulate natural environment conditions. This index is the product functional technical index that users should pay most attention to. The "thermal insulation temperature difference" index is used for bundled comparison, and the one with the lower index is better.

2.3 Analysis of "Artificial Weathering Resistance" Index

Secondly, we should also pay attention to the technical indicators in the item column of "Artificial Weathering Resistance" in the product inspection report. Weathering resistance" (Class W 400 h; Class S 500 h) must meet the technical indicators that "appearance" is not blistered, peeled, and cracked; "Chalking/Grade" is not more than 1; Light color)/level not more than 2; "Solar reflectance (white)" is not less than 0.81; "Hemispherical emissivity" is not less than 0.83. The first three of these 5 indicators are "appearance", "chalking ", "Discoloration" test index is based on the standard test conditions to simulate the natural environment for a certain period of time after the product is formed into a coating, the degree of decay and the degree of maintenance of the basic physical state, that is, the display of the difference in the durability of the coating, and the difference between the coating and the coating. The latter two functional technical indicators such as "solar reflectance (white)" and "hemispheric emissivity" are directly related to the degree of decay and retention after use in the natural environment. Generally speaking, the longer the artificial weathering resistance, the lower the first three index indices, and the higher the last two index indices, the slower the decay process and the better the weather resistance of the product, which is more conducive to the one-time coating after the coating is completed. Durable and effective maintenance of various functions of the layer in the natural environment.

3. Main performance technical indicators of heat reflection series products

The heat-reflecting and heat-insulating coatings produced by Wuxing are based on the high-reflection composite powder independently developed by the company. According to objective needs and differences in substrates, a variety of synthetic resins or emulsions are selected, and the "solar heat reflectance ratio" is not less than 0. 90 (full wave area), "hemispheric emissivity" is not less than 0. 85, "solar heat reflectance" is not less than 0. 90 (full wave area), "hemispheric emissivity" is not less than 0. 85 as an internal control technical index, developed The key technical indicators of the new products produced are significantly higher than the technical indicators of national product standards. The company has launched a variety of high-performance and high-quality heat-reflective thermal insulation coatings and related supporting products. Relying on the original coating process, the serialized and differentiated product system has completed the market layout of heat-reflective thermal insulation coatings. It can meet the personalized selection needs of different regions, different industries and many users.

According to the special needs of anti-corrosion for steel oil storage tanks and the understanding of the basic properties of heat-reflective thermal insulation coatings, experiments show that heat-reflective thermal insulation coatings are not only a general substitute for existing anti-corrosion materials for steel oil storage tanks, but also a It can be used in combination with existing anti-corrosion materials and can protect the anti-corrosion coating. A more reasonable application method is to design and construct according to the standards stipulated in GB 50393-2008 "Technical Specification for Anti-corrosion Engineering of Steel Petroleum Storage Tanks", and then add a layer of thin heat-reflecting heat-insulating paint surface coating, which can fully absorb the corrosion resistance. To the dual effect of cooling down and reducing pressure in the high temperature season and extending the service life of the anti-corrosion coating in general, it is easy to implement and easy to popularize.

 4 Conclusion

The heat reflective thermal insulation coating required for the anti-corrosion project of steel oil storage tanks has achieved good effects of cooling and reducing pressure, safety and efficiency, energy saving and water saving. Compared with the tank body coated with silver powder paint, the surface of the tank body coated with heat reflective heat insulation coating is lowered by an average of 10 to 20 °C, and the temperature of the tank medium is reduced by about 5 to 10 °C. No over-temperature, over-pressure and other phenomena occurred. Compared with traditional cooling methods, solar heat reflective coatings can effectively reduce the temperature of oil tanks without consuming energy, prevent the transfer of heat to the interior of the object from the source, and achieve the purpose of energy saving and cooling. application prospects. When using it, it is necessary to screen out several main performance indicators, and it must be tested and approved by the relevant national authoritative departments before it can be used with confidence, otherwise it is difficult to achieve satisfactory results.