KR100658569B1 - Titanium oxide-based thermal radiation paint - Google Patents

Abstract

Conventionally, coating and coating materials for coating and coating the inner wall surfaces of industrial furnaces to increase radiant heat transfer include those based on silicon carbide and those based on chromite. Known. The former is whitened by thermal oxidation at a temperature of 800 ° C. or higher, and the effect is lost. The latter is ineffective at 600 ° C. or lower, and may change to hexavalent chromium at 1000 ° C. or higher.

The present invention is based on titanium oxide and reduced titanium oxide. Titanium oxide (TiO ₂ ) changes into reduced titanium oxide when heated to a high temperature in a furnace in a CO ₂ or H ₂ atmosphere. The reduced titanium oxide absorbs near infrared rays and is highly radioactive. When a coating film of reduced titanium oxide is formed on the inner wall surface of the heating furnace, the radiation heat in the furnace is greatly increased. The reduced titanium oxide is excellent in high temperature stability, does not corrode in acids, bases, and organic solvents, and has strong corrosion resistance to various gas components in the furnace.

Titanium oxide, reduced titanium oxide, thermal radiation, paint, industrial heating furnace, coating, fuel saving

Description

Titanium oxide based heat radiating coating material

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the formation of a film by coating or coating on the inner wall surface of an industrial heating furnace, and relates to an increase in radiant heat in a furnace.

By coating or coatings on the inner wall surface of the industrial heat in the art, as the coating material and coating material to increase the radiation heat in the furnace, and the coating material and the coating material to the silicon carbide (SiC) as a substrate (基材), chromite (Cr ₂ O ₃ The coating material and coating material based on) are known. The latter is patented as Japanese Patent No. 1480360.

The coating and coating materials based on the former silicon carbide effectively work up to a temperature of up to 800 ° C. However, in the vicinity of the temperature exceeding this temperature, the silicon carbide is blushed by thermal oxidation. The absorption and emissivity of the radiant energy are rapidly lowered and lose their effect.

The coating and coating material based on the latter chromite have no effect when the furnace temperature is 600 ° C or lower. In addition, chromite has a fatal defect which produces a hexavalent chromium compound which is toxic in a high temperature furnace over 1000 degreeC.

Since the oil shock of the late 1970s, this kind of product has appeared on the market quite a lot, but these products are now without exception. The reason is that it is ineffective at a high temperature of 1000 ° C. or higher, and is not able to withstand thermal oxidation and thermal shock, and is unstable, eroded, and harmful.

The most important physical property required for the furnace material to which high temperature is applied is

(1) In the high temperature range of 1000 ℃ or higher, the absorption and emissivity of radiation energy is high.

(2) Low thermal conductivity.

(3) Be physically and chemically stable.

(4) It shall not be eroded by various gas components in contact with the surface of the furnace materials.

(5) Harmless and German.

Basic physical properties such as are required.

However, the conventional coating / coating material coated and coated on the inner wall surface of an industrial heating furnace lacks any of these basic physical properties and has no effect in a furnace at a high temperature of 1000 ° C. or higher.

This invention makes titanium oxide and reduced titanium oxide the base material of a coating material and a coating material.

The present invention utilizes the physical properties of titanium oxide and reduced titanium oxide and changes thereof. Hereinafter, the properties of titanium oxide and reduced titanium oxide and changes thereof will be described in detail.

In a furnace in which carbonaceous fuel is burned and heated, the oxygen partial pressure in the furnace becomes extremely low when the furnace temperature reaches a high temperature of 1000 ° C or higher. When the oxygen partial pressure decreases in a high temperature furnace, the oxygen atom in the titanium dioxide (TiO ₂ ) crystal is released out of the system as shown in Reaction Formula 1 below, and the titanium dioxide is changed to reduced titanium oxide.

The reduced titanium oxide can be expressed as Ti _n O _2n-1 .

The crystal of TiO ₂ is Ti ⁴⁺ O ₂ ^2- . When the oxygen atom is released from the crystal of TiO ₂ , Ti ³⁺ with one electron reduced in Ti ⁴⁺ is produced. As a result, TiO ₂ , which was originally an insulator, changes into an n-type semiconductor. Therefore, the reduced titanium oxide is conductive.

When one oxygen atom leaves the system in the TiO ₂ crystal, two electrons leave the crystal. The remaining two electrons reduce two adjacent Ti ⁴⁺ to Ti ³⁺ . The reduced Ti ³⁺ strongly polarizes and large deformation occurs in the outer shell electrons, so that energy absorption is increased. When molecules and atoms absorb energy, the reactivity becomes high and becomes active.

1 shows light absorption and transmittance in rutile single crystal (TiO ₂ ) and reduced titanium oxide.

In rutile single crystals, most of light having a wavelength of 0.4 to 7 µm is transmitted. In reduced titanium oxide, light having a wavelength of 0.78 to 3 µm (near infrared) has a transmittance of 10% or less, and the remaining 90 % Absorbs or reflects. Ti ₂ O ₃ and Ti ₃ O _{5, which} are the substrates of the present invention, have a blue-black color, and are excellent in absorbing radiation energy.

Table 1 shows the properties of the reduced titanium oxide.

Properties of Reduced Titanium Oxide Molecular formula rescue color Melting Point (℃) ΔfH ⁰ / (KJmol ^-1 ) Property TiO NaCl bronze 1760 -518 Significantly indeterminate, basic, soluble in acids when heated Ti ₂ O ₃ Al ₂ O ₃ Celadon 2130 -1536 Irregular, positive, stable Ti ₃ O ₅ Single yarn Blue Black 2210 -2458 Irregular, acid, stable

※ ΔfH ⁰ is the standard production enthalpy. Negative (-) signs dissipate heat.

In addition, there are also crystals having a blue-black color of a triclinic system such as Ti ₄ O ₇ and Ti ₅ O ₉ , and the composition range is extremely narrow, making it intentional and artificial. In other words, the product may be a coincidence in a high temperature furnace.

TiO becomes TiO when Ti and TiO ₂ are mixed in chemical equivalents and calcined at 1600 ° C. in an inert gas. However, TiO is not produced because there is no metal Ti in the furnace.

Similarly for Ti ₂ O ₃ , when the hydrogen concentration in the furnace becomes high, TiO ₂ is reduced to Ti ₂ O ₃ near 1300 ° C.

TiO ₂ is reduced to Ti ₃ O ₅ at 800 to 1200 ° C. in a CO ₂ or H ₂ atmosphere.

In addition to these, in a high-temperature furnace, a composition of an ideal coexistence (also called a mixed phase), that is, Ti ₂ O ₃ -Ti ₃ O ₅ , Ti ₃ O ₅ -Ti ₄ O ₇ , Ti ₄ Although O ₇ -Ti ₅ O _{9 and the like} also appear, the compositions of these abnormal coexistences are the most dark and opaque, and have the highest energy absorption and emissivity.

When TiO ₂ is supported with fine metal particles or oxides thereof, or is added in chemical equivalents and heated, high-charge metal ions are generated to replace Ti ⁴⁺ in the TiO ₂ crystals. Color appears, and energy absorption increases. The color that appears depends on the type of metal.

In general, when a divalent impurity is added to an ionic solid, lattice defects occur to maintain electrical neutrality. Alternatively, when one atom is separated from the crystal, vacancies are formed in the place, resulting in lattice defects. Since the lattice defects disturb the period of lattice vibration, the thermal conductivity decreases and the internal energy becomes large.

The element Ti exists in the oxidized state at the earth's surface. Currently, actual materials used for titanium are ilmenite ore and rutile ore, and anatase ore is mainly used as a raw material for TiO ₂ photocatalysts, all of which have different oxides. It is mixed with and does not exist as pure titanium.

Ilmenite varies depending on the region of origin, but its main component is about 50-70% of TiO ₂ , and the rest of oxides such as FeO, FeO ₃ , SiO ₂ , Cr ₂ O ₃ , MnO, Al ₂ O ₃ It is mixed.

Rutile contains 75% or more of TiO ₂ , and other oxides such as FeO, SiO ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ are mixed.

Ilmenite is black and rutile is bluish black.

These ore is pulverized as it is and used for the base material of this invention. Alternatively, the heating of the furnace within a H ₂ atmosphere at 800~1200 ℃, by changing the reduction of titanium oxide is used as a base material of the present invention.

The same is true of rutile projection.

Titanium and may be taken out from yonggwang surface of the as blast furnace slag (titanium slag) is to remove iron in a low Ilmenite content of the TiO _2, grade and up (grade up) the content of the TiO _2, which It is used as a description of the present invention without any process.

Titanium oxide is the most stable physically and chemically. It is known that other similar semiconductor materials except titanium oxide, such as cadmium selenide (CdSe), niobium oxide (Nb ₂ O ₅ ), etc., all cause self-dissolution upon absorption of high energy. This phenomenon is common to oxide semiconductors, and the semiconductor absorbs energy above the band gap, and electron holes (H ⁺ ) after electrons escape by the excitation reaction. ) Causes self-erosion. Incidentally, only titanium oxide does not cause magnetic erosion.

Titanium oxide is not eroded by acids, bases, and organic solvents, and wets well with water, but does not dissolve.

In furnaces filled with high temperatures and various gas components, the furnace material is large or small, or its surface erodes as the reaction proceeds. Titanium oxide absorbs H ₂ and CO ₂ well. H ₂ and CO ₂ adsorbed on the surface of titanium oxide in a high temperature furnace act as a reducing agent (electron donor) to change TiO ₂ to reduced titanium oxide. Thus, the reduced titanium oxide has strong corrosion resistance.

In the above description, it has been described that raw ore, such as ilmenite and rutile, is used as the substrate of the present invention. However, in a high-temperature furnace with low oxygen partial pressure, TiO ₂ is changed to reduced titanium oxide, and thus the present invention, Finally, it can be said that it is a technique using the physical property of reduced titanium oxide.

The key point of this invention is the discovery of the phenomenon that radiant heat energy remarkably increases when a film is formed on the inner wall surface of an industrial heating furnace by reduction titanium oxide. However, in a high temperature furnace, the reactor mechanism in which this phenomenon occurs is very complicated, so it is not easy to clarify this sufficiently.

The increase in the radiant heat energy when a film made of reduced titanium oxide is formed on the inner wall surface of the furnace,

(1) The energy absorption in the near infrared region is significantly higher than that of titanium dioxide (see FIG. 1) (D. C. Cronemeyer, Phys. Rev., 87, 876 (1952)).

(2) Emissivity is high (when the temperature in the furnace is 1050 ° C, the emissivity reaches 96-98% (see Fig. 2C)).

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(3) In the reaction between the reactant and the product, the reduced titanium oxide acts as a catalyst (catalysis of the reduced titanium oxide: in a furnace at 1000 ° C., CO ₂ adsorbed to TiO ₂ is only deformed, but Ti ₂ O ₃ , CO ₂ adsorbed on Ti ₃ O ₅ is dissociated In recent studies, SMSI (Strong Metal Suport Interaction) has attracted attention, and in the case of reduced titanium oxide with oxygen defects, the interaction becomes stronger. Being).

Although some explanation is possible, etc., the whole picture of the reactor port has no choice but to wait for further study.

Moreover, one of the side effects of this invention is that the exhaust gas temperature of a gas exhaust port falls remarkably. This phenomenon is called "charge transfer transition" because electrons move from a ligand to a metal of CO ₂ (or NO and NO ₂ ) adsorbed on the reduced titanium oxide surface. The reaction between and metals is generally an oxidation reaction, that is, the extraction of electrons, which in the coordinating magnetic field donate electrons, which are called oxidization and the latter are called oxygenation. It can be explained that dissociation of CO ₂ occurs by the action, but this phenomenon refers to the reduction of the emission of CO ₂ . Reductions in CO ₂ emissions have not, at present, resulted in quantitative identification.

Radical reactions are also involved in the reduction of CO ₂ emissions.

For example, a hydroxyl radical (.OH) oxidizes and dissociates CO ₂ by drawing electrons. Anyway, future explanations are awaited for these reactors.

1 is a diagram showing the wavelength and the transmittance of light in the titanium dioxide (TiO ₂₎ and the reduction of titanium oxide.
It is a figure which shows the emissivity of the sample at the time of setting the temperature in the furnace of a test furnace to 1050 degreeC as the sample (sample 1) used as the fireproof lead used as the inner wall material of an industrial furnace.
FIG. 2B is a sample (Sample 2) coated with a chromite (Cr ₂ O ₃ ) -based thermal radiation coating (trade name: HRC) on the surface of the sample, and the emissivity of the sample under the same temperature conditions. The figure shown.
Fig. 2C is a diagram showing the emissivity of a sample under the same temperature conditions by applying the titanium oxide-based heat-radiating paint of the present invention to the surface of the same refractory lead to obtain a sample (sample 3).

In the practice of the present invention, the first choice of titanium oxide as the substrate becomes a problem.

If the description of the present invention is broadly classified,

(1) In the case where natural ore such as ilmenite ore or rutile ore is pulverized and used as it is,

(2) When the content of TiO _2, using a high-quality titanium oxide of 95% or more,

(3) when using reduced titanium oxide with reduced ilmenite, rutile and anatase,

(4) When using titanium slag

Divided into

In the case of (1), while it is the lowest cost, there is a difference in the content of components depending on the place of origin, and therefore also in the performance. Further, the rate of reduction reaction varies depending on the H ₂ concentration and the CO ₂ concentration in the furnace until the change from TiO ₂ to reduced titanium oxide, and when these concentrations are low, the reduction of TiO ₂ takes a long time.

In the case of (2), high cost cannot be avoided. On the other hand, it is easy to control various kinds of metals on titanium oxide, or to add or support various kinds of metals to impart catalytic functions to the purpose.                 

In case of (3), high cost is inevitable, and in case of (4), it is low cost. Among them, titanium slag discharged from the blast furnace is most preferable.

Titanium slag may be quenched or slow cooled when taken out of the furnace, and quenching in an inert gas results in complete reduction titanium oxide of the oxygen-deficient structure. It accepts and part of it changes to TiO ₂ .

The same applies to the reduction of ilmenite, rutile and anatase by H ₂ .

Next, the particle size of the titanium oxide which is the substrate of the present invention becomes a problem. Generally, absorption, reflection, and transmission of infrared energy in reduced titanium oxide have a large particle size dependency. It is important to select a particle size that can absorb near infrared energy to the maximum.

Next, an example of implementation of the present invention will be described.

Titanium slag is used as a base material, and the components thereof are as shown in Table 2 below.

Ingredients Ti ₃ O ₅ Ti ₂ O ₃ FeO SiO ₂ Al ₂ O ₃ CaO ₂ MgO ratio(%) 80 to 85 8 to 13 3 to 5 3 to 4 2-3 0.4 to 0.6 0.5 to 0.8

The titanium slag shown in Table 2 was pulverized, adjusted to a particle size distribution of 0.8 to 3 µm, and a coating and coating material composition containing a binder and an inorganic adhesive was prepared. In some cases, a small amount of chromite (Cr _{2) was used.} O ₃ ) and silica (SiO ₂ ) are added. Al ₂ O ₃ , SiO ₂ , and Cr ₂ O ₃ form a spinel compound on the surface of a high-temperature furnace wall, resulting in a strong bonding force and adhesion. However, the bonding material is SiO _2, as compared to the Al ₂ O ₃ the high thermal expansion, the amount thereof shall require that the titration.

The coating composition consisting of titanium, slag, binder, and inorganic adhesive is finally suspended and dispersed in an aqueous solution to form a slurry in a slurry state. The mixing ratio of the aqueous solution and the solid component is 50:50 (weight ratio).

Although the film-forming operation of the coating film and the coating film on the furnace wall surface is mainly carried out by a spray coating method using a spray gun, in some cases, a film may be formed by a water plasma spraying method.

After forming a coating film by the spray coating method by a spray gun, it heats at 150-180 degreeC, and bakes. When forming a film by a thermal spraying method, the process of applying heat and baking is unnecessary.

When the present invention is applied to the inner wall surface of an industrial heating furnace, the radiant heat energy is remarkably increased, and as a result, fuel can be greatly reduced. In the actual furnace test results, the savings of 8 to 10% in the fuel raw unit in the whole furnace, and 3 to 3.5% in the fuel raw unit in the ethylene cracking furnace were shown. . Test results in the actual furnace will be reported and submitted through the calibration procedure.

As a side effect of the present invention, a significant drop (about 10%) of the exhaust gas temperature at the exhaust port of the furnace is recognized, which is a phenomenon of dissociation of carbon dioxide (CO ₂ ) and nitrogen oxides (NO _x ) by ligand action. Can be assumed to be an advanced result, but at present it has not been possible to obtain quantitative identification by precise analysis.

As described above, the present invention can be immediately implemented in an industrial heating furnace, and the effect appears as a significant saving of fuel. Incidentally, the emission of carbon dioxide in the industrial heating furnace can be significantly reduced.

Claims (3)

Based on reduced titanium oxide (lower titanium oxide, which can be represented by Ti _n O _2n-1 , such as Ti ₂ O ₃ , Ti ₃ O ₅ , Ti ₄ O ₇ , Ti ₅ O ₉ , Ti ₆ O _11, etc.) In this case, a binder and an inorganic adhesive are blended, and in some cases, chromite (Cr ₂ O ₃ ), alumina (Al ₂ O ₃ ) and silica (SiO ₂ ) are added. Titanium oxide thermal radiation paint. delete A coating material for forming a coating film composed mainly of reduced titanium oxide on the inner wall surface of an industrial furnace, based on a powder obtained by pulverizing a raw material mineral (including titanium ore and titanium slag) of metal titanium, wherein the binder, inorganic An adhesive is used, and in some cases, chromite (Cr ₂ O ₃ ), alumina (Al ₂ O ₃ ) and silica (SiO ₂ ) are added to the titanium oxide-based thermal radiation coating material for industrial furnaces.

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