TWI241323B - Heat-emitting paint for coating inner surface of industrial furnace - Google Patents

Abstract

Disclosed is a heat-emitting paint coated on an inner surface of an industrial furnace such as a thermal cracking furnace, a thermal treating furnace, an annealing furnace, and a heating furnace to improve fuel efficiency. The heat-emitting paint comprises a composition consisting of 96 to 98.9 wt% ilmenite with fineness of 150 meshes or less as a main component, 1 to 4 wt% clay as a binder, and 0.1 wt% sodium phosphate as a dispersion agent, and used in a mixed slurry form of 40 to 60 wt% composition and 40 to 60 wt% water. Mostly comprising ilmenite, the heat-emitting paint has an advantage of higher emissivity than a conventional heat refractory material. In particular, when applied to the furnace operating under an oxidative atmosphere at 1000 DEG C or higher, the heat-emitting paint is not reduced in emissivity for a long period, thereby reducing fuel consumption of the furnace.

Description

1241323 玖 发明, description of the invention. (The description of the invention should state: the technical field to which the invention belongs, the prior art, the content, the embodiments, and the drawings.) The technical scope is generally speaking. The present invention relates to the use in the coating industry. Furnacees such as thermal cracking furnaces, heat treatment furnaces, annealing furnaces and heating furnaces have thermally diffusing coatings on their inner surfaces to improve fuel efficiency, especially regarding ceramic coatings with high emissivity, mainly composed of ilmenite with high blackness, It is stable under high temperature oxidizing atmosphere. The background technology is well known to those skilled in the art. It can be used as a heat source in various industrial furnaces such as the thermal cracking furnace used in the petrochemical industry, the calcining furnace in the ceramic industry or the heating furnace and the annealing furnace in the steel industry. The total energy produced by the fuel is classified into three types of energy: the energy transferred to the heating body in an industrial furnace, the energy transferred to a thermal refractory material in an industrial furnace, and some other energy such as preheating energy and dissipation energy. In particular, most of the energy generated from the fuel is absorbed into the heat-to-fire material. The hot refractory materials constituting industrial furnaces absorb energy and re-emit energy to the heated body in the form of radiant heat in accordance with Kirchihoff's radiation law. According to Kirchhoff's law, if the energy absorbing object is an ideal black body, the emissivity ε is equal to the absorption rate α, that is: ε = α. However, a true ideal black body does not actually exist. Therefore, the emissivity of a material is expressed as a ratio to the ideal black body, and all materials have characteristic emissivity. At the same time, the proportion of radiant energy in industrial furnaces increases rapidly as the temperature in the furnace increases. In particular, most of the heat transfer is achieved by radiant energy at high temperatures. 1241323 (2) For example, when the temperature in an industrial furnace is about 800 ° C, the near-infrared and far-infrared rays in an industrial furnace exist at equal ratios. On the other hand, when the temperature is increased to 1000 to 1300 ° C, the ratio of near-infrared rays (0.8 to 4 # m) is increased to 90% or higher and generates about 5% visible light. Therefore, if a material does not absorb near-infrared, it is difficult to expect that the material can radiate heat to emit the absorbed near-infrared to itself, thereby improving fuel efficiency. However, there are very few substances that absorb near-infrared on the earth, and some substances that absorb near-infrared will be rapidly oxidized when heated, and therefore cannot be subjected to heat stress for a long time. Refractory bricks and ceramic fibers have been widely used as heat refractory materials customarily used on the inner surface of industrial furnaces, but these materials cannot absorb near-infrared rays and therefore cannot sufficiently emit the required radiant heat. The absorption rate of refractory bricks is 75 to 80%, in other words, the emissivity of refractory bricks is 0.75 to 0.80 at relatively low temperatures, but when the temperature in the furnace exceeds 1000 ° C, the absorption rate of refractory bricks decreases rapidly. In addition, refractory bricks deteriorate rapidly at high temperatures. In addition, ceramic fibers have the disadvantage that their surfaces become vitrified when heated. When the surface of the ceramic fiber is vitrified, the surface develops gloss and decreases, and the absorption rate of the ceramic fiber reaches about 30%. Therefore, it is not desirable to obtain the required radiant heat from the vitrified ceramic fiber. As described above, the refractory monument or ceramic fiber used as a conventional thermal refractory material in an industrial furnace has an emissivity of 0.7 5 to 0.8 0 at a relatively low temperature, and thus an improved fuel efficiency is obtained at this temperature. However, when industrial furnaces are operated at high temperatures, the emissivity decreases rapidly, and due to the refractory brick 1241323 (3)

Or the vitrification and deterioration of ceramic fibers, the blackness gradually decreases, avoiding a reduction in fuel efficiency. Therefore, there is still a need to develop a technology in which a heat-dissipative coating is applied to the inner surface of an industrial furnace to change the expected life of a heat-resistant material. In consideration of color and emissivity, graphite and silicon carbide are used as the present invention. Graphite has the highest emissivity but oxygen reacts quickly and is carbonized, so it is best not to use it as a divergent coating. At the same time, most of the heat-radiating coatings used to coat the interior surfaces of industrial furnaces have been commercialized and are selectively applied. The coating based on silicon carbide includes a hydrocarbon powder having a 200 sieve as a main component and a small amount of a binder and a composition, and in the form of a mixed slurry of the composition and water, at this time, a spray gun is used. The mixed slurry is applied industrially to a thickness of 0.5 to 1.0 mm. As mentioned above, it is advantageous to use a silicon carbide-based heat-dissipating industrial furnace system, because the time required to heat the industrial furnace is shortened, and it is intended to increase the amount of energy emitted to the heating source and reduce the amount of energy dissipated outside the industrial furnace. , Borrowing rate. At this time, the efficiency of the type and operating conditions of the industrial furnace is improved by about 2 to 20%. ^ Therefore, it is not possible to have good energy efficiency and high thermal emissivity for high emissivity coatings. The heat from the atmosphere of the present invention is composed of silicon carbide (S i C) used in certain industrial pores or smaller fineness additives. And use. The amount of energy to reach the required temperature on the inner surface of the furnace. Fuel based on improved fuel efficiency

1241323 (4) The main reason why silicon carbide-based heat-divergent coatings provide improved fuel efficiency for industrial furnaces is the desire to increase the heat-divergence rate on the interior surface of the furnace. However, silicon carbide is easily oxidized at 800 ° C or higher in an oxidizing atmosphere. If oxidized, silicon carbide (SiC) is converted to silicic acid (Si02), and the color of the coating based on silicon carbide is whitened to reduce the blackness (emissivity) of the coating. Therefore, the fuel efficiency is poor. Therefore, it is not advisable to apply a heat-dissipative coating based on carbonized carbide to an industrial furnace operating at 80 ° C or higher. For example, when a coating based on silicon carbide is applied to a batch forging furnace used in the steel industry that operates at 1200 to 1250 ° C, the silicon carbide is completely oxidized and after a 72-hour operating time, Its color is whitened, so that improved fuel efficiency cannot be obtained. SUMMARY OF THE INVENTION Therefore, the present invention keeps in mind the above-mentioned problems occurring in conventional heat-dissipative coatings for coating the inner surface of industrial furnaces, and an object of the present invention is to provide a heat-dissipative coating having excellent durability, which is more industrially applicable. The heat-divergent coating on the inner surface of the furnace has a high emissivity. It has physical and chemical stability under the oxidizing atmosphere at high temperatures and firmly adheres to the inner surface of industrial furnaces. According to the present invention, a heat-dissipative coating for coating an inner surface of an industrial furnace includes a composition including ilmenite as a main component, a small amount of clay as a binder, and a small amount of sodium canister as a dispersant. Best Mode for Carrying Out the Invention According to the present invention, there is provided a heat coating 1232123 for coating an inner surface of an industrial furnace (5) a divergent coating comprising titanium having a mesh size of 150 or finer 9 8.9% by weight of titanium Iron ore, 1 to 4% by weight sodium clay. The heat-dissipative coating is based on the weight-% composition of the mixed slurry and 40 to 60% by weight of the mixed slurry. Why the component of the heat-dissipative coating is particularly limited, J is included in the coating of the present invention as the main component. A type of natural ore that must be treated separately, usually containing 4 and Fe203 as the main component and a small amount of inorganic matter, which is slightly changed according to the iron ore. Because it contains Fe203 as the main component, the color of ilmenite is much higher than that of conventional hot-fire materials. It is physically and chemically stable at high temperatures, so it is used as the material for the inner surface of industrial furnaces for operation. At the same time, heat-divergent coatings have been developed, which mainly include the second obtained from the extraction or refining of titanium slag from ilmenite. This is because the heat-divergent coating based on Ding 02 is being finalized. Unwanted components precipitate at high temperature and rapidly reduce the base rate of Ti02. Therefore, coatings based on Ti02 have not been able to deal with the chemical reaction of chemical smelting process to obtain Ti02 from ilmenite. The components that make up titanium dioxide make the coatings based on Ti02 physically and chemically. Why is Ti02 based? Thermal Diffusive Coatings at High Temperatures

The sieve fineness is 96 to 0.1 and 0.1% by weight phosphoric acid as a reference, and is used in the form of 40 to 60. Maine will be described as follows. Ilmenite (FeTi02) is a tongue-like amount of Ti〇2 even though the group of ilmenite has black at two temperatures and is coated at 1000 ° C or more at high temperature by chemically smelting titanium (Ti02), But chemically unstable compounds at high temperatures, and the launch of coatings on the bottom of metal groups is industrialized. The bonding forces that occur during the sequence are weakened and stabilized, which is considered to be a chemically unstable 1241323 ⑺ plane with a thickness of 1 to 2 mm. According to the present invention, the thermal divergent coating has an emissivity of 0.85 to 0.95, which is much higher than the conventional thermal refractory materials. As mentioned above 'because of its high emissivity, the heat-divergent coating of the present invention coated on the inner surface of an industrial furnace allows the coated inner surface to emit much less light than the uncoated ... Energy and ideally increase the energy to be applied to the body, so quickly reach the required temperature of the heated body and reduce the use of bright materials. A better understanding of this month can be obtained according to the following examples, specifically the following examples ir, for the purpose of illustrating the present invention but should not be construed as limiting the present invention. Examples: V, ilmenite with 0 mesh or less fineness, clay and acid-filled sodium are mixed at the mixing ratio of 歹 to produce the group of heat-divergent coatings of the present invention, and the combination The materials were mixed with water at the same ratio (group •) to obtain mixed slurries used in the respective examples and comparative examples. At this time, 吏 π was used by Kentucky-Tennessee Clay Co. and included SlC> 2 and Al203 as the main component and a small amount of clays of Ti02, Fe203, CuO, and MgO. Table Comparative composition Jgj Comparative composition jifr 1 Composition (wt%). Ilmenite clay sodium phosphate ~ 97.0 2.9 0.1 _ 98.0 1.9 0.1 96.5 3.4 0.1 98.7 Bu 1.2 0.1 95.0 4.9 0.1 99.2 0.7 0.1 Example 2 -11-(8) 1241323

; According to the mixed slurry of each of A and comparative examples, and the conventional hydrocarbons are:-each of the heat-generating coatings (see examples) is placed in a high-temperature box furnace with Z body as a heat source, and the heating calendar For a predetermined period, the emissivity is measured at different temperatures.

In other words, after coating the body on a second brick sample having a volume of 65mm × 50mm × 10mm, the brick sample obtained was placed in an industrial furnace and heated to 600 ° C with a constant jealousy / knowledge rate, maintained at 6001. : The emissivity is measured for 30 minutes, ..., and later. Then, the obtained brick sample is heated to 200 C in this manner so as to heat the sample to another work, and then maintained at the increased temperature. After 30 minutes, repeat this step. The temperature in the furnace is measured using a radiation temperature positioned at a horizontal distance of 2 meters from the surface of the brick sample. In addition, after the temperature in the furnace is stabilized, the temperature at each temperature is measured. Emissivity (ε:%) was measured by using a pyrometer (MQ1310C-3B) made by American Micron through a window positioned on the front of the furnace. The results are listed in Table 2 below. Table 2 Temperature (° c) Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Common examples 600 86.1 86.3 85.7 87.1 85.2 87.3 65.0 700 85.7 86.1 85.1 86.8 83.9 86.8 66.4 800 84.8 85.8 84.6 86.1 82.7 86.3 67.8 900 84.1 85.3 83.6 85.9 85.9 81.8 86.1 68. 0 1000 85.2 85.9 84.4 87.2 83.4 87.7 72,3 1100 87.2 87.7 86.7 87.9 85.6 87.8 73.4 1200 87.9 80.0 87.1 88.1 86.7 87.9 75.7 1200 ° C After 50 hours 87.9 88.0 87.1 88.1 86.7 84.2 69.2 -12-

1241323 (9) From the results in Table 2, it can be seen that in the case of the emissivity of the sample left at 1200 ° C for 50 hours, according to the example of the present invention, the emissivity of each sample only slightly changes, but it is the same as 1 2 0 Compared to the initial measurement at 0 ° C, the emissivity of the sample coated with the hydrocarbon-based coating (comparative example) was reduced. This phenomenon appears to be caused by the fact that silicon carbide is oxidized on its surface after being exposed to a high-temperature oxidizing atmosphere to reduce its blackness (emissivity). Furthermore, after the operation of the furnace was stopped and the inside of the furnace was sufficiently cooled, the surface of each sample was observed through a first-class linear tube, leading to the discovery that the sample according to the example of the present invention maintained its original black color but used a hydrocarbon-based substrate. The paint-coated sample (the conventional sample) lost its original black color and vitrified its surface. Industrial Applicability As mentioned above, most heat-emission coatings composed of ilmenite have the advantage of higher emissivity than conventional thermal refractory materials. In particular, when applied to a furnace operating in an oxidizing atmosphere at 1000 ° C or higher, the heat-divergent coating did not reduce its emissivity after a long time, shortening the heating of a receptor body to the required The time required for temperature, and ideally increasing the amount of energy emitted to the heated body, thereby reducing the fuel consumption of the furnace. For example, in the case of a heating furnace used in the iron and steel and non-ferrous metal industries, the fuel reduction effect is desirably increased by about 8 to 10% due to the use of the heat-dissipative coating according to the present invention, while in petroleum refining and In the case of heating furnaces used in the petrochemical industry, about 2 to 3%. In addition, the heat-dissipative coating of the present invention is advantageous because the coating layer is formed on the surface of the hot refractory material of an industrial furnace to prevent the hot refractory material from being invaded. -13-

1241323 (10) Corrosion and heat shield effect are obtained, so as to extend the service life of thermal refractory materials and improve their durability. In addition, the heat-dissipative coating of the present invention can be sprayed with a spray gun to form a slurry having a desired viscosity, which is easy to apply on the entire inner surface of an industrial furnace, and due to the agglomeration of clay added to the slurry as a binder. The sprayed slurry is firmly attached to the inner surface of the furnace, thereby obtaining excellent processability during the coating of the inner surface of the industrial furnace with the heat-diffusing coating. The invention has been described by way of illustration, and it should be understood that the terminology used is intended to be narrative in nature and not restrictive. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it should be understood that, within the scope of the accompanying accompanying patent application, the present invention can be used as if it were a specific revealer.

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Claims (1)

1241323 Patent application scope 1. A heat-dissipative coating for coating the inner surface of industrial furnaces, comprising: from 9 6 to 9 8.9% by weight ilmenite with a mesh size of 150 or less, A composition consisting of 1 to 4% by weight of clay and 0.1% by weight of sodium phosphate. The heat-dissipating coating is based on the weight of the mixed slurry, 40 to 60% by weight of the composition and 40 to 60% by weight of water. Use as a slurry. "J2413 rhyme; ^ (6 ^ Patent Application No. 091134800 ... one) Chinese specification replacement (April, 1994) However, as contained in the heat-divergent coating of the present invention, the iron ore has not undergone any chemical reaction procedures. It is obtained from natural ilmenite ore, which is only used as a material, so it has physical and chemical properties and has a continuous high emissivity in a high temperature atmosphere. In addition, the ilmenite is crushed into a dispersant and water that can be uniformly dispersed. The mixed slurry has 150 meshes or powders, and is intended to be attached to the inner surface of industrial furnaces. At the same time, the function of using clay as a binder increases the bonding strength and stably coats the mixed slurry for industrial use. The furnace slurry does not flow down and also acts as a dispersant. When the content of the thermal dispersion coating is less than 1%, it is impossible to ideally adhere to the surface of the mixed slurry body. On the other hand, when the content exceeds 4%, the amount It is relatively reduced and reduces the saving effect by increasing the inner surface of the furnace. Therefore, the range of the clay content is preferably from 1 when sodium phosphate is used as a dispersant, and its function is to uniformly divide the clay into the slurry. With regard to various dispersants, the coating of the phosphorous invention is most useful and has the required dispersibility and is most economically efficient at 0.1%. When the composition of the heat-dissipative coating according to the present invention is mixed with the raw slurry, it is best to The total weight of the mixed slurry is based on the weight% of the composition mixed with 40 to 60% by weight of water so that the sprayed slurry can be smoothly sprayed onto the surface of the industrial furnace and the mixed slurry will not flow down the surface of the industrial furnace. Furthermore, it is preferable to apply the heat-dissipative coating material of the present invention to a process. The main component of the titanium material is crushed and chemically stable-with a binder, a smaller fineness on the inner surface of the mixed slurry, and the clay in the material to the industrial furnace, the ilmenite-containing fuel to 4 %. Powder of ilmenite powder Sodium is produced when the content is mixed with water. The mixture is dried with a 40 to 60 shotgun and the furnace is used in the industrial furnace table 81907-940421.doc -10-