US20120208142A1

US20120208142A1 - Heat exchanger device with heat-radiative coating

Info

Publication number: US20120208142A1
Application number: US13/369,332
Authority: US
Inventors: Huimin Zhou
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-06-17
Filing date: 2012-02-09
Publication date: 2012-08-16

Abstract

A heat retainer for a hot blast stove of a blast furnace, the heat retainer adapted to function without decomposition at temperatures of about 1200° C., wherein: at least one surface of said heat retainer is coated with a high radiative and highly-emissive material forming said coating layer; the thickness of said coating layer is critically between 0.02 mm and 3 mm; the heat retainer absorbs energy or emits energy mainly by radiation; and energy of radiation is mainly at a wavelength of 1-5 μm.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 11/815,488 with a 371(c) date of Aug. 3, 2007, now pending, which is a National Phase Entry application under 35 U.S.C. 371 of International Patent Application No. PCT/CN2005/002010 with an international filing date of Nov. 25, 2005, designating the United States, now pending. This application further claims foreign priority benefits to Chinese Patent Application No. 200510043838.X, filed on Jun. 17, 2005. The contents of all of the aforementioned specifications as originally filed, and all amendment thereto, are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a heat exchanger device and more particularly to a heat storage device having a high radiative coating layer on the surface of the heat storage device, so that facilitates heat exchange.
2. Description of the Related Art
In industrial fields such as metallurgy, machinery and farm product processing, heat exchangers are commonly used. The main function of a heat exchanger is to transfer heat to air or gas. One type of heat exchangers uses coal, gas, oil or electricity as a direct heat source. Another type of heat exchangers employs secondary sources of heat. A heat source firstly transfers energy to a heat retainer of the heat exchanger, and then air or gas that needs to be heated is passed over it. During heat exchange between the heat retainer and the air or gas, heat is removed from the heat retainer, and the air or gas is heated. Generally, the heat retainer is made of a refractory material, a ceramic material, or a steel material.
Heat absorption and emission capability of heat retainers is an important factor for the heat exchange performance of a heat exchanger, and is directly associated with power savings. To improve the heat exchange efficiency of a heat exchanger, a plurality of patents, such as CN2462326Y and CN2313197Y, provide structural improvements of heat exchangers. However, a heat exchanger employing a coating layer made of high radiative material has not heretofore been proposed to improve the heat storage capability and working efficiency of the heat retainer.

SUMMARY OF THE INVENTION

To overcome the deficiencies of prior art, it is one objective of the invention to provide a highly-efficient and energy-saving heat exchanger with a coating layer on a part of or on the entire surface of the heat retainer for facilitating heat exchange.
In one aspect of the invention, provided is a heat exchanger with a coating layer for facilitating heat exchange, wherein at least one surface of the heat exchanger is coated with a coating layer.
In another aspect of the invention provided is a heat exchanger, comprising: a heat retainer and a coating layer, wherein the heat retainer is coated by the coating layer.
In certain embodiments of the invention, the matrix of the heat retainer is made of a refractory material, a ceramic material or a steel material.
In certain embodiments of the invention, the matrix of the heat retainer, i.e., the core, is made of a refractory material.
In certain embodiments of the invention, the matrix of the heat retainer, i.e., the core, is made of a ceramic material.
In certain embodiments of the invention, the coating layer made of a high radiative material.
In certain embodiments of the invention, the heat radiation of the coating layer is greater than the heat radiation of the core.
In certain embodiments of the invention, the heat emissivity of the coating layer is greater than the heat emissivity of the core.
In certain embodiments of the invention, the radiation of the high radiative material is greater than that of the substrate material of which the core of the heat retainer is made.
In certain embodiments of the invention, the high radiative material is a material having an absorption rate and an emission rate higher than those of the matrix material of which the core of the heat retainer is made.
In certain embodiments of the invention, the high radiative material is not highly-reflective.
In certain embodiments of the invention, the heat retainer is adapted for use in a high temperature heat exchanger.
In certain embodiments of the invention, the heat retainer is adapted for use in a hot blast stove of a blast furnace, or a coke battery.
In certain embodiments of the invention, the heat retainer is a heat retainer of a heat exchanger of a hot blast stove of a blast furnace, or a heat retainer of a heat exchanger of a coke battery.
In certain embodiments of the invention, the heat exchanger is adapted for use, and can be used without decomposition of the core and the coating layer, at temperatures exceeding 800° C., 825° C., 850° C., 875° C., 900° C., 925° C., 950° C., 975° C., 1000° C., 1025° C., 1050° C., 1075° C., 1100° C., 1125° C., 1150° C., 1175° C., 1200° C., 1225° C., 1250° C., 1275° C., 1300° C., 1325° C., 1350° C., 1375° C., 1400° C.
In certain embodiments of the invention the core and the coating layer will critically not decompose in a blast furnace during operation, where temperatures in the hot stove are below 1400° C.
In certain embodiments of the invention, the thickness of the coating layer is 0.02-3 mm.
In certain embodiments of the invention, the thickness of the high radiative material coating layer is critically not lower than 0.02 mm.
The thickness of the coating layer of between 0.02 and 3 mm is critical. The particular thickness of the coating has an unexpectedly beneficial effect on the adhesion between the coating and the matrix. When coatings of a smaller thickness than 0.02 mm or of greater thickness than 3 mm are used, the coating does not adhere well to the matrix.
In addition, only the particular thickness used and claimed allows the coating to properly infiltrate into the opening cavities of the core and allows for a permanent connection to form between the core and the coating.
The coating thickness combined with the shape of the retainer improves the basic mechanical properties and high temperature mechanical properties of the regenerator; it increases anti-corrosive properties with respect to high temperature flue gas; it protects the regenerator from slugging; and it prolongs the service lifetime of the regenerator compared.
In certain embodiments of the invention, the heat retainer takes the shape of a honeycomb, a fin, a rod, a brick, a ball, an ellipse or a plate.
In certain embodiments of the invention, the heat retainer is in the shape of a honeycomb.
In certain embodiments of the invention, the shape of the heat retainer is as shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, or FIG. 7.
In certain embodiments of the invention, the shape of the heat retainer is substantially as shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, or FIG. 7.
In certain embodiments of the invention, a cross section of the heat retainer is circular, square, rectangular, rhombic, hexagonal or polygonal.
In certain embodiments of the invention, the cross section of the heat retainer is in the shape of an elongated rectangle.
In certain embodiments of the invention, the cross sectional area of the core is square, rectangular, rhombic, hexagonal or polygonal.
In certain embodiments of the invention, the cross-sectional area of the core has a circumference, and the circumference comprises straight lines connected by non-straight lines.
In certain embodiments of the invention, the cross sectional area of the core is comprised of strips.
In certain embodiments of the invention, the heat retainer further comprises at least one cavity in the core.
In certain embodiments of the invention, a cavity passes through the matrix from its one end to another and the coating layer completely coats the surface of the cavity.
In certain embodiments of the invention, a plurality of inner holes is disposed within the heat retainer.
In certain embodiments of the invention, the inner holes are non-concentric with respect to one another.
In certain embodiments of the invention, the inner holes are fixed in space and immovable with respect to one another.
In certain embodiments of the invention, the cross sectional area of the cavity is square, rectangular, rhombic, hexagonal or polygonal, and the cross sectional area of the core is comprised of strips.
In certain embodiments of the invention, heat retainer is not a gauze.
In certain embodiments of the invention, the retainer is not in the shape of a gauze.
In certain embodiments of the invention, the inner holes are circular, square, rectangular, rhombic, hexagonal or polygonal.
In certain embodiments of the invention, the cross-sectional area of the inner holes is not very elongated.
In certain embodiments of the invention, when an external force is applied to the core, the individual cavities will not shift with respect to one another.
In certain embodiments of the invention, the high radiative material is any suitable high radiative far-infrared material suitable for a heat retainer made of a refractory material, a ceramic material or a steel material.
In certain embodiments of the invention, the coating layer comprises one or more of the following: Cr₂O₃, clay, montmorillonite, brown corundum, silicon carbide, TiO₂, Al₂O₃, Fe₂O₃, aluminum hydroxide, zirconium oxide, phosphoric acid, or hydrated sodium silicate gel.
In certain embodiments of the invention, the coating layer made of high radiative material is implemented by way of paste-coating, spray-coating or dip-coating, and the heat retainer having the coating layer is used directly after coating, or is used after high temperature curing.
In certain embodiments of the invention, surfaces of the substrate of the heat retainer are pre-treated with a pre-treating liquid prior to being paste-coated, spray-coated or dip-coated with the high radiative material, so as to further improve adhesion between the high radiative material and the substrate.
In certain embodiments of the invention, the pre-treating liquid is an aqueous solution containing polyamine curing agent PA80 (PA80 adhesive) or an alkali metal silicate and as a result the adhesion between the substrate and the high radiative material is increased.
In certain embodiments of the invention, the heat exchanger is prepared by coating surfaces of the substrate of the heat retainer with a pre-treating liquid and then paste-coating, spray-coating or dip-coated with the high radiative material to form a coating layer, wherein the pre-treating liquid is an aqueous solution of the polyamine curing agent PA80 or an alkali metal silicate.
The pre-treating liquid comprises one or more material that will not decompose in a blast furnace during operation, where temperatures in the hot stove are around 1200° C.
In certain embodiments of the invention, solid components in the high radiative material are hyperfinely processed, so as to enable the particle size to be between 20 and 900 nm, and to improve adhesion between the high radiative material and the substrate.
In certain embodiments of the invention, the core comprises a plurality of surfaces, the coating layer coats at least one the surface, the coating layer has been applied to at least one the surface by a process comprising: (a) coating at least one the surface with a pre-treating liquid; (b) paste-coating, spray-coating or dip-coating a high radiative material to form a coating layer; wherein the pre-treating liquid is an aqueous solution of a polyamine curing agent or an alkali metal silicate.
In certain embodiments of the invention, the core comprises a plurality of surfaces, the coating layer coats at least one the surface, the coating layer has been applied to at least one the surface by a process comprising: (a) pre-treating at least one the surface with a material increasing affinity of the core for the material to be applied in step (b); and (b) applying a material the heat emissivity of which is higher than that of the core to at least one the surface.
In certain embodiments of the invention, the coating layer increases the heat absorption and emission capability of the heat retainer, which improves heat absorption and emission of the heat retainer, and increases the heat storage capacity.
In certain embodiments of the invention, the coating layer increases the radiation efficiency of the retainer compared to what the radiation efficiency would have been if no coating layer were used.
In certain embodiments of the invention, the coating layer achieves savings of over 20% of energy compared to what the energy usage would have been if no coating layer were used.
In certain embodiments of the invention, the coating layer achieves rapid and efficient heat transfer and increases the heat storage capacity of the heat retainer.
In certain embodiments of the invention, the heat retainer is adapted to transfer heat mainly by radiation.
In certain embodiments of the invention, the heat retainer is adapted to transfer more heat by radiation than by convection.
In certain embodiments of the invention, the heat retainer is adapted to absorb and emit heat non-simultaneously.
In certain embodiments of the invention, the coating layer increases heat absorption and heat radiation ability of the core.
In certain embodiments of the invention, the heat exchanger is adapted to receive heat by gasses flowing through the inner holes.
In certain embodiments of the invention, the coating acts to increase the radiative ability of the matrix.
In certain embodiments of the invention, the heat retainer with a high radiative coating decreases the high-temperature creep rate by about 40% compared with that of conventional heat retainers.
In certain embodiments of the invention, the heat storage ability of the heat retainer with a high radiative coating is unexpectedly higher by at least about 15% at under 1300° C. compared with that of conventional heat retainers art.
In certain embodiments of the invention, the heat retainer with a high radiative coating improves the regenerator's heat absorption ability during combustion period and heat emission ability during blast period in blast furnace hot stoves.
In certain embodiments of the invention, the working efficiency and thermal efficiency of blast furnace hot stoves are increased.
In certain embodiments of the invention, the hot blast temperature is increased by at least 15° C., the exhaust gas temperature is reduced by at least 13° C., and gas consumption is decreased by at least 7%. In addition, the reduction of CO₂emission is successfully realized. Besides, the high radiative coating can prolong the blast time by at least 10%, and/or decrease the flue gas temperature by more than 10%.
When high radiative material is used on the surface of regenerators, heat storage and heat emission of the heat exchanger made of the heat retainer do not occur simultaneously. Particularly, heat storage occurs during a heat storage period, and the high radiative material improves the ability of the matrix to absorb heat. Then, heat radiation and emission takes place during heat emission period, and the high radiative material improves the ability of the matrix to release heat. For example, for hot stoves of blast furnace used for iron-making, the heat storage period of a heat retainer according to this invention is generally 110 min and the heat emission period is about 55 min, and the blast furnace hot stoves go through the two periods alternately.
Coating a heat retainer with a high radiative material achieves the goal of absorbing more heat during heat storage period as compared with uncoated retainers by increasing the thermal radiative absorption rate of the surface of the matrix, and releasing more heat during heat emission period as compared with uncoated retainers by increasing the thermal radiative emission rate of the surface of the matrix. The end temperature of the matrix is comparatively increased during heat storage period and the end temperature of the matrix is comparatively decreased during heat release period.
Most energy radiated at high temperature concentrates in the wavelength region of between 1 and 5 micron. When a heat retainer is coated with high radiative coating, the coating inherently allows heat to be absorbed and later released by radiation at a wavelength in 1 to 5 micron. (High radiative coating has high radiativity within 1 to 5 micron wavelength range.) Energy at that wavelength is more easily absorbed by the heated bodies.
In certain embodiments of the invention, the coating of high radiative material increases the heat exchange efficiency of the heat retainer and saves energy. Particularly, when a checker brick of a hot blast stove of a blast furnace is coated with the high radiative material, temperature inside the hot blast stove is uniformly distributed, and the heat storage capacity is notably increased.
In certain embodiments of the invention, when the heat retainer is placed in a hot blast stove of a blast furnace at their normal operating temperature, the heat retainer will absorb heat from hot air mainly by thermal radiation.
In certain embodiments of the invention, the heat retainer is a checker brick, or a similar type.
In another aspect of the invention provided is a method for improving the efficiency of heat transfer in a heat retainer for a heat exchanger, comprising coating a surface of the heat retainer with a high radiative material.
In another aspect of the invention provided is a method for improving the efficiency of heat transfer in a heat retainer for a heat exchanger, comprising using a heat retainer coated with a high radiative material to absorb heat during a heat absorption period and later emit heat during a heat radiation period.
In certain embodiments of the invention, steady state for heat exchange is not achieved during the heat absorption period and/or during the heat radiation period.
In another aspect of the invention provided is a method for enhancing radiative heat absorption and radiative heat emission and for simultaneously reducing heat reflection in a heat retainer for a hot blast stove of a blast furnace, comprising: placing into a hot blast stove of a blast furnace a regenerator coated with a coating layer, and operating the hot blast stove of the blast furnace at usual operating temperatures described above.
In certain embodiments of the invention, when the heat retainer absorbs heat from hot air in a hot blast stove of a blast furnace, the temperature of the heat retainer increases substantially.
In certain embodiments of the invention, the method further comprises placing the heat retainer into a hot blast stove of a blast furnace.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinbelow with reference to accompanying drawings, in which:

FIG. 1 shows a honeycomb-shaped heat retainer with a coating layer according to one embodiment of the invention;

FIG. 2 shows a honeycomb-shaped heat retainer with a coating layer according to another embodiment of the invention;

FIG. 3 shows a fin-shaped heat retainer with a coating layer according to another embodiment of the invention;

FIG. 4 is a partial cross-sectional view illustrating a plate-shaped heat retainer with a coating layer according to yet another embodiment of the invention;

FIG. 5 is a partial cross-sectional view illustrating a ball-shaped heat retainer with a coating layer according to yet another embodiment of the invention;

FIG. 6 shows an elliptical heat retainer with a coating layer according to yet another embodiment of the invention;

FIG. 7 is a partial cross-sectional view illustrating a non-metallic heat retainer with a coating layer according to yet another embodiment of the invention;

FIG. 8 shows temperature profile during a heat absorption period (temperature rising) and heat emission period (temperature falling) of a heat retainer with a coating layer according to the invention as compared to a similar uncoated retainer;

FIG. 9 shows a heat retainer in the shape of a rod with a coating layer according to another embodiment of the invention;

FIG. 10 shows physical model of checker brick passage in a regenerator according to one embodiment of the invention;

FIG. 11 shows the temperature difference between flue gas and bricks along top-to-down direction for hot stoves with coatings or without coatings at 110 minutes in the combustion period according to one embodiment of the invention;

FIG. 12 shows temperature difference between checker brick and blast during blast period along top-to-down direction for hot stoves with coatings or without coatings according to one embodiment of the invention;

FIG. 13 a shows changing curves of the blast temperature with respect to the calculation results and test results for the 3^# hot stove without coating, and FIG. 13 b shows changing curves of the blast temperature with respect to the calculation results and test results for the 1^# hot stove with coating according to one embodiment of the invention; and

FIG. 14 a shows changing curves of the temperature of flue gas with respect to the calculation results and test results for the 3^# hot stove without coating, and FIG. 14 b shows changing curves of the temperature of flue gas with respect to the calculation results and test results for the 1^#hot stove with coating according to one embodiment of the invention.

Reference list: 1—circular inner hole; 2—high radiative material coating layer; 3—circular inner hole; 4—high radiative material coating layer; 5—rectangular inner hole; 6—highly-radiative material coating layer; 7—high radiative material coating layer; 8—substrate; 9—heat exchange surface; 10—substrate; 11—high radiative material coating layer; 12—heat exchange surface; 13—substrate; 14—high radiative material coating layer; 15—heat exchange surface.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated in Table 4 below, the radiative rate of common refractory materials commonly used to make heat retainers is between about 0.6 and about 0.8 at room temperature. However, the radiative rate decreases significantly when the temperature increases. In a hot stove of a blast furnace during operation, where temperatures in the hot stove are around 1200° C., the radiative rate of common regenerative materials is only between about 0.4 and 0.5. Thus, the heat exchange efficiency is low. Much heat is lost with exhaust gases instead of being absorbed by the regenerative materials. To improve efficiency of the heat retainers, the radiative rate of the new high radiative rate coating is above about 0.9 at around 1200° C.
In addition, generally, when the temperature is over 900° C., heat radiation becomes the principal mode in heat transfer process (with over 90% of heat being transferred by radiation). Energy radiated at high temperature concentrates in the wavelength region of between 1 and 5 microns. When a heat retainer is coated with high radiative coating, the coating inherently allows heat to be absorbed and later released by radiation at a wavelength in 1 to 5 micron. (High radiative coating has high radiativity within 1 to 5 microns wavelength range.) Energy at that wavelength is more easily absorbed by the heated bodies. Therefore, a coating of a high radiative material disposed on a heat retainer effectively increases the capability of heat absorption and heat emission, and increases the heat exchange efficiency of the heat retainer at high temperatures. Beyond this, the coating layer also increases the heat absorption and heat radiation ability of the core of the heat retainer.
The heat retainer experiences the heat storage period and heat release period alternately in industrial application, and the heat retainer absorbs and emits heat non-simultaneously. In the heat storage period, the heat retainer absorbs energy which is usually generated by combustion of fuel; in the heat release period, the heat retainer emits energy to the blast which is used as air for circulation. The end temperature of the regenerator is comparatively increased during heat storage period and the end temperature of the regenerator is comparatively decreased during heat release period relative to heat retainers not coated with the coating described herein.
The heat retainer coating made of a high radiative material absorbs more heat during heat storage period as compared with an uncoated retainer by increasing the thermal radiative absorption rate of the surface of the matrix, and has higher radiation rate of the surface matrix during heat emission period as compared with uncoated retainers by increasing the thermal radiative emission rate of the surface of the matrix. Thus, the end temperature of the matrix is comparatively increased during heat storage period and the end temperature of the matrix is comparatively decreased during heat release period.
In addition, the working efficiency and thermal efficiency of the heat exchangers coating with a high radiative material are increased as compared with uncoated heat exchangers. This raises the temperature of hot blast, shortens the heat storage period, prolongs the heat release period, and reduces the gas consumption and air flow. Reduction of the gas consumption and the air flow further saves energy, reduces coke consumption and, correspondingly, reduces CO₂emissions.
In addition, the nano/micro coating materials filled the cavity on the surface of the heat retainer which protects the heat retainer and increases its service life. The coating layer of the heat retainer also operates to protect the substrate of which the core of the heat retainer is made. The following features of the heat retainer are improved after coating with a high radiative material: the volume density, the crushing strength, tensile strength and the softening temperature with loading. However, the pore rate and the distortion rate of the heat retainer are decreased after coating which are good for prolonging the service life of the heat retainer.
In addition, when the surfaces of the regenerator of a steel-rolling regenerative furnace are coated with the high radiative material, temperature of the core of the heat retainer increases significantly. The thickness of the coating layer allows the coating to infiltrate into the opening cavities of the core and allows for a permanent connection to form between the core and the coating. The coating having critically the particular thickness combined with the shape of the retainer increases the basic mechanical properties and high temperature mechanical properties of the heat retainer, increases anti-corrosive properties with respect to high temperature flue gas, protects the heat retainer from slugging, and prolongs the service lifetime of the heat retainer.
The high radiative material forming a coating layer on the heat retainer may be freely selected. The below embodiments are intended to be illustrative only, and are not meant to limit the invention.

Example 1

As shown in FIG. 1, a heat retainer used for a hot blast stove of a blast furnace is a checker brick. The checker brick (heat retainer) has a plurality of circular inner holes 1, and all surfaces (comprising those of the inner holes) of the check brick (heat retainer) are coated with a coating layer of a high radiative material 2 whose thickness is 0.02 mm. A substrate of the heat retainer is a refractory material, and the high radiative material coating layer 2 is a high radiative material whose emissivity in the far-infrared region is greater than that of a substrate material of the heat retainer.
The high radiative material coating layer 2 comprises by weight: 110 parts of Cr₂O₃, 80 parts of clays, 90 parts of montmorillonites, 300 parts of brown corundum, 100 parts of silicon carbides, 400 parts of PA80 adhesive and 100 parts of water. These components are hyperfinely processed, i.e., the mixture is grinded to particles with micro/nano-meter sizes by using superfine processing technique, so as to enable the particle size to be in the 25-700 nm range. Compared with existent heat exchangers, the heat exchanger of this example saves over 20% of energy.

Example 2

As described in example 1, except that differences are as follows: the cross section of the honeycomb-shaped heat retainer is rectangular; and the high radiative material coating layer is disposed within a plurality of circular inner holes 3 (as shown in FIG. 2).

Example 3

As shown in FIG. 3, the heat retainer for a heat exchange is fin-shaped. A plurality of rectangular inner holes 5 are disposed in the heat retainer, and all surfaces (comprising surfaces of the inner holes) of the heat retainer for the heat exchanger are paste-coated with a high radiative material coating layer 6 whose thickness is 0.03 mm. A substrate of the heat retainer is a ceramic material, and the high radiative material coating layer 4 is a high radiative material whose emissivity in the far-infrared region is greater than that of a substrate material of the heat retainer.
The high radiative material comprises by weight: 15 parts of zirconium oxide, 8 parts of Cr₂O₃, 10 parts of TiO₂, 2 parts of montmorillonites, 15 parts of Al₂O₃, 10 parts of carborundums, 30 parts of PA80 adhesives, and 10 parts of water. Compared with existent heat exchangers, the heat efficiency of the heat exchanger according to this example is improved by over 10%.

Example 4

As shown in FIG. 4, the heat retainer for use in a heat exchanger according to this example is plate-shaped; and the surfaces of the heat retainer are paste-coated with a coating layer 7 made of a high radiative material and whose thickness is 0.1 mm. A substrate 8 of the heat retainer is a steel material, and the high radiative material is a high radiative material whose emissivity in the far-infrared region is greater than that of the substrate material.
The high radiative material comprises by weight: 60 parts of Cr₂O₃, 200 parts of brown corundums, 50 parts of clays, 30 parts of montmorillonites, 200 parts of silicon carbides, 200 parts of hydrated sodium silicate gels, and 100 parts of water. The outer surface of the coating layer 7 is the heat exchange surface 9. The surfaces of the heat retainer are coated with a pre-treating liquid prior to being paste-coated with the high radiative material. The pre-treating liquid comprises 10% aqueous solution (by weight) of PA80 adhesive. Compared with existent heat exchangers, the heating efficiency of the heat exchanger of this example is improved by over 10%.

Example 5

As shown in FIG. 5, the heat retainer for a heat exchanger is ball-shaped, and the surfaces of the heat retainer are paste-coated with a high radiative material resulting in a coating layer 11 whose thickness is 0.3 mm. An outer surface of the coating layer 7 is the infiltrating layer 12 whose thickness is 2 mm. A substrate 10 of the heat retainer is a refractory material, and the high radiative material forming the coating layer 11 is a high radiative material whose far-infrared emissivity is greater than that of a substrate material.
The high radiative material comprises by weight: 5 parts of zirconium oxide, 10 parts of silicon carbides, 5 parts of titanium, 3 parts of clays, 40 parts of brown corundums, 10 parts of aluminum hydroxides, 15 parts of phosphoric acid, and 12 parts of water. Compared with existent heat exchangers, the relative temperature of the heat exchanger of this example is increased by over 15° C. The heat retainer according to this example is applicable for use as a regenerative furnace, in which the ball-shaped heat retainer exchanges heat within a heat accumulator being part of the regenerative furnace.

Example 6

As described in example 5, with the change that the heat retainer for a heat exchanger is elliptical in shape (as shown in FIG. 6).

Example 7

The surfaces of a ball-shaped heat retainer are spray-coated with a high radiative material giving rise to a coating layer whose thickness is 2.5 mm.
The coating layer comprises by weight: 15 parts of silicon carbide, 2 parts of brown corundum, 35 parts of zirconia, 2 parts of montmorillonite, 6 parts of chromium oxides, 27 parts of PA80 adhesives and parts of 13 water.
The surfaces of the heat retainer are coated with pre-treating liquid prior to being spray-coated with the high radiative material, the pre-treating liquid comprising a 10% by weight aqueous solution of hydrated sodium silicate gels.

Example 8

As shown in FIG. 7, the surfaces of a ceramic substrate 13 of a heat retainer are paste-coated with a high radiative material resulting in a coating layer 14 whose thickness is 3 mm. The outer surface of the coating layer 14 is the heat exchange surface 15.
The coating layer comprises by weight: 60 parts of Fe₂O₃, 5 parts of zirconia, 20 parts of hydrated potassium silicate gels and 15 parts of water. The surfaces of the heat retainer are coated with a pre-treating liquid prior to being paste-coated with the high radiative material coating layer. The pre-treating liquid comprises 8% aqueous solution (by weight) of PA80 adhesive.

Example 9

A checker brick is coated with a high radiative material. The material is mainly made from sintering agent, suspending agent and adhesives, etc. First, the solid component is weighed according to the designed composition. The mixture to micro/nano-size is then grinded using superfine processing technology. The micro/nano powder are mixed with adhesives and a thermoplastic polymer and a small number of surfactant are added. Finally, high-speed mechanical agitation is used to form the high radiative coating product into a viscous fluid.
The coating is applied by the following processes: cleaning dust for the checker brick→spraying adhesives→coating by soaking→drying.
The coated checker brick is heated in the furnace to 1100° C. and water quenched repeatedly. The coating layer adheres well as a result and there are no cracks or shedding after the coating process is completed.
Specifically, when the bricks were broken to expose the interface of the core and the coating layer:

- the coating did not shed;
- the interface between the coating and the brick had no cracks, which shows shat the coating and the brick can be closely integrated together;
- the small coating particles infiltrating into the matrix existed in the cracks of the bricks;
- the coating infiltrated into brick well, and
- the composition of the brick did not react chemically with other substances or generated a low melting phase.

Example 10

Heat-absorption and heat-release rates of high-alumina and silica checker bricks were conducted respectively under the same conditions. The two specimens having the same volume were prepared from the same checker brick. One of the specimens was coated with the coating, whereas the other one was not.
Both the heating speed and the cooling speed of the bricks with coating were faster than that of the uncoated specimen during the heating and cooling period. The specimen with coating has a higher capacity of heat regenerative than that of the uncoated one.
The heating and cooling curves of the specimens are shown in FIG. 8. It can be clear seen that the temperature of the specimen with coating is higher than that of the uncoated one during the heating process, and the maximum temperature difference reached 283° C., 13 minutes after the start of heating. The coated specimen reached 1142° C., whereas the uncoated specimen reached only 1067° C.
The result shows that the coated specimen with higher heat absorption capability can reach the designed temperature in a shorter time. Thus, the coating is superior for heat absorption during combustion period in hot stove and results in reducing the heating time in the BF hot stove. In addition, the initial temperature at the beginning of the heat emission period of the coated specimen is 1142° C. and that of the uncoated one is 1067° C. Also, the cooling time from the initial temperature to 390° C. for the coated specimen was 6 minutes and that for the uncoated one was 11 minutes. Thus, the coating is also superior for heat emission during blast period in hot stove and result in reducing the blast time.
Properties of the corresponding coated and uncoated checker bricks are summarized in Tables 1-3.

TABLE 1

Performance comparison between coated and uncoated
high-alumina checker brick

		Strength of
Volume	Pore	compression	Break	Distortion
density	rate	resistance	strength	rate
(g/cm³)	(%)	(MPa)	(MPa)	(%)

Without coating	2.43	25	49	5.8	−1.424
With coating	2.48	21	64	6.3	−0.623

TABLE 2

High temperature physical properties contrast between uncoated
and coated silica bricks (1300° C. × 3 h)

		Strength of
Volumn		compression	Break
density	Pore rate	resistance	strength	Distortion rate
(g/cm³)	(%)	(MPa)	(MPa)	(%)

Without	1.80	19.88	28	12.23	+0.51
coating
With coating	1.81	19.27	31	12.65	+0.33

TABLE 3

Softening temperature with loading and the distortion
rate contrast between uncoated and coated silica bricks

		Softening temperature	High temperature
		with loading	distortion rate
		(0.2 MPa, 0.6%), ° C.	(1430° C. × 50 h), %

Without	1550	+0.405
coating
With coating	>1650	−0.074

As shown in Tables 1-3, the following features of the heat retainer are improved after coating with a high radiative material: the volume density, the crushing strength, tensile strength and the softening temperature with loading. In addition, the pore rate and the distortion rate of the heat retainer are decreased after coating which is superior for prolonging the service life of the heat retainer.
The nano/micro-size particles of the coating material filled the cavity on the brick surface, which decreases the pore rate and increases the volume density. This is superior for increasing the strength of compression resistance and anti-corrosive properties with respect to high temperature flue gas, decreasing the distortion rate of the brick, and protecting the regenerator from slugging. All of these improvements help to prolong the service life of the blast furnace hot stove.

Example 11

Take the “Jie Neng Wang” Nano/Micro-Meter High-Temperature Infrared Energy-Saving Coating (HM-HRC)'s application in Shandong Shiheng Steel Company as an example, where there is a 1080 m³BF with 3 hot stoves. The 34 layers of siliceous checker bricks on the top of the high temperature region of the 1^#and 2^# hot stoves are coated with HM-HRC invented and produced by Shandong Huimin Science & Technology Co., Ltd., while the 3^# hot stove is without coating.
We analyzed the hot air flow and heat transfer process inside hot stoves with and without HM-HRC, respectively. It is well known that during the combustion period, the radiative and convective heat transfers between the high-temperature flue gas and checker bricks are the principal heat transfer modes, and the heat conduction also exists inside the check bricks simultaneously. During the blast period, the cool air is heated when it passes through the checker bricks, and the checker bricks are cooled down at the same time.
Along the altitude-direction, the temperature of checker brick surface is very high, the maximum can reach up to more than 1300° C. and the bottom is about 300° C. (the height of regenerator chamber was 31.7 m.). In order to simplify the calculation, the regenerator chamber was divided into three different zones from top to bottom. The mathematical model of the radiation and convection heat transfer inside the regenerator chamber have been set up according to the energy balance between the flue gas and the regenerator as well as heat conduction of regenerator.
Using the CFD software, we simulated the heat transfer process inside regenerator chamber; made a quantitative analysis and comparison of hot blast temperature, flue gas temperature and checker bricks' surface temperature of 1^#hot stove (with HM-HRC) with those of 3^# hot stove (without HM-HRC), then got the radiation rate influence on the hot blast temperature and the flue gas temperature. At last, we made a comparison of the numerical results with detected results in 1^#and 3^# stoves.
Physical Model of the Hot Blast Stove
Analysis of Fluid Flow Heat Transfer Inside Regenerator Chamber
During the combustion period, high temperature flue gas heats the checker bricks in the stove from top to bottom. During blast period, the cold air flows through the checker brick from bottom to top and turns into hot blast by absorbing heat from regenerators, and finally is delivered to blast furnace.
The Technology Parameters of Hot Blast Stove
The Characteristic of Hot Blast Stove
The calculation model is based on the following parameters: number of hot blast stove is 3; height of regenerator chamber is 31.7 m; cross-section area of regenerator chamber is 35.8 m²; regenerator chamber is divided into 3 regions; surface area of hot stove body is 781 m²; surface area of hot air pipe is 325 m². The checker brick has 19 holes and the inner diameter of holes is 31 mm. The bricks from top to bottom in hot stoves are: silica brick, 9.6 m; high alumina brick, 7.8 m; ordinary density clay brick, 14.3 m.
Operation Parameters of the Hot Blast Stove
The operational rule for hot blast stove is “two in combustion, one in blast”. The combustion cycle is 114 min, the blast cycle is 55 min, stove cutover takes 10 min.
During the test period, the combustion air temperature of hot blast stoves is 183° C.; the cool air inlet temperature of both 1^#and 3^# stoves is 171° C.; the average hot blast temperature of 1^#is 1198° C. and 3^# is 1173° C., the average flue gas outlet temperature of 1^#and 3^# is 300° C. and 313° C., respectively.
The dry gas component of hot stove is measured on site by flue gas analysis meter. After the beginning of test period, the analysis result is recorded every 15 minutes. Then the average result is calculated and conversed into humid components according to experiential formula.
Thermal Physical Performance of Checker Brick in Regenerator of Hot Stove
Specific Heat and the Heat Conduction Coefficient of Checker Brick
The thermal physical characteristic of checker brick is a linear function of temperature, i.e., a+b t. In this project, the checker bricks in the three different parts have different physical performance function coefficient a and b, as shown in Table 4.

TABLE 4

Thermal physical characteristics of checker bricks

Coefficient of heat

Specific heat

conductivity

	a	b	a	b

Silica brick	0.19	0.7 × 10⁻⁴	0.93	0.197 × 10⁻³
Andalusite high-	0.20	0.56 × 10⁻⁴	1.52	−0.19 × 10⁻³
alumina brick
Clay brick	0.20	0.63 × 10⁻⁴	0.836	0.58 × 10⁻³

Surface Radiativity of Checker Brick
As is known from references^[1], the radiation rate of firebricks is usually 0.6˜0.8 under room temperature; meanwhile, with stoves' temperature increasing, the radiation rate decreases dramatically. When temperature rises to 800° C.˜1000° C., the blackness is 0.5; when temperature rises to 1300° C., the blackness drops to 0.4. However, the radiation rate of Nano/Micro-Meter High Temperature Infrared Energy Saving Coating is always over 0.9 from room temperature to high temperature.
Mathematical Model
Simulation Object
The simulation object is regenerator chamber. According to the fluid flow features of flue gas inside the holes of checker bricks during the combustion and the blast period, the heat transfer process of regenerator chamber is simplified into a cluster of flow pipes, assuming that the flux speed and temperature distribution into every checker brick hole are the same during the numerical simulation calculation, as shown in FIG. 10. The inner diameter of flow pipes is the diameter of the holes. The outer diameter of bricks is:
$d_{0} = 2 \times \sqrt{\frac{A_{s}}{π N_{s}}} .$
Where A_sis upper surface area of one brick with 19 holes (including area of holes). Ns is number of the holes.
Radiative Heat Exchange Model
The radiative quantity of heat exchange is proportional to the fourth power of temperature under high temperature; radiative heat transfer is the principal way of heat transfer. The quantity of heat exchanged by radiation is: Q_rad=σ(T_max ⁴−T_min ⁴). As for the medium with absorption, emission and dispersion characteristic, the radiative transmission equation on position {right arrow over (r)}, along direction {right arrow over (s)} is:
$\frac{\partial I (\vec{r}, \vec{s})}{\partial s} + (a + σ_{s}) I (\vec{r}, \vec{s}) = {an}^{2} \frac{σ T^{4}}{π} + \frac{σ_{s}}{4 π} \int_{0}^{4 π} I (\vec{r}, {\vec{s}}^{'}) Φ (\vec{s}, {\vec{s}}^{'}) \partial Ω^{'}$
Numerical Simulation Result and Analysis
The equation is solved by CFD equation solver, the flue gas temperature and checker brick surface temperature changes during combustion period, and the blast temperature and checker brick surface temperature changes during air heating period of 3^# stove and 1^# stove are obtained, their change regularities are summarized as following.
Temperature Difference Between Flue Gas and Checker Brick During Combustion Period
FIG. 11 illustrates the temperature difference between flue gas and bricks along top-to-down direction and the comparison between hot stoves with coatings and without coatings at 110 minutes in combustion period. The temperature difference in the top is larger than that at the bottom of regenerator chamber; because of heat exchanges between the flue gas and checker bricks, the flue gas temperature gradually lowers and the temperature difference gradually decreases. The temperature difference is the lowest at the flue gas outlet.
From the comparison between regenerator chambers with and without HM-HRC, the temperature difference decreases after 34-layer silica bricks on the top of regenerator chamber in hot stoves which are coated with high radiative coating, and this indicates that the heat absorption of checker bricks was speeded up during combustion period, so heat absorption capacity increases; meanwhile, the thermal storage capacity of checker bricks increases. Although only 34 layers of checker brick in the upper region of regenerator chamber is coated, it has affected the heat transfer of the whole regenerator chamber; especially the top 80% region of regenerator chamber, the effect is more conspicuous.
Temperature difference between checker brick and blast during blast period.
From FIG. 12, it can be seen that during 55 minutes of blast period: the temperature differences between checker brick and blast are almost the same. Higher checker brick temperature means higher blast temperature. Since the heat absorption capacity and temperature of checker brick with coating are higher during combustion period, the temperature difference between the checker bricks and blast with coating is the same or less than that without coating, which indicates that the checker brick with coating has stronger heat radiativity, the heat capacity is more than that without coating, so the blast temperature is increased.
Comparison Between Calculation Results and Test Results on Site
Temperature of Blast Outlet
FIG. 13 a and FIG. 13 b show the blast temperature changed with time during the blast period for the 3^# hot stove without coating and 1^#hot stove with coating. The dashed line is the numerical simulation result, and the red line is the detected data curve on site separately. By comparing the curves for the two hot stoves, we can see that the blast temperature of 1^#hot stove is higher than that of 3^# hot stove.
The Outlet Temperature of Flue Gas
FIG. 14 a describes the temperature of exhaust gas from 3^# hot stove without coatings. The highest temperature is about 400° C., the lowest temperature is 198° C. or so, the average temperature is about 313° C. FIG. 14 b describes the temperature of flue gas from 1^#hot stove with coatings. The highest temperature does not reduce much, but the average temperature reduces 13° C. than 3^# hot stove. The calculated results are lower than the actual data, but the error is within the tolerance of 10%.
If thermal losses of stove walls and heterogeneity of regenerator materials are taken into account, the calculated results would be smaller and be closer to the actual values.
Conclusions
The numerical calculation results confirm: 1. During combustion period, in the top region of regenerator chamber, the temperature difference of checker bricks with coating is smaller than that without coating, the heat absorption speed and the heat storage capacity of checker bricks in the whole regenerator chamber is increased. 2. During blast period, the temperature differences between checker brick and blast in hot stoves with coating and without coating are almost the same. Since the regenerator with coating has stronger heat storage capacity and higher temperature, the fact that the temperature differences between checker brick and blast are the same indicates that the hot blast temperature of hot stove with coating is higher. 3. The average blast outlet temperature with coating increases more than 20° C. and the flue gas outlet temperature decreases more than 10° C., which are similar to the detected results on site.

Example 12

In order to measure the heat-using condition and thermal efficiency changing after using the high radiative coating on the checker bricks of BF hot blast stove, to evaluate the thermal characters and to have a deeper understanding of the principle—the high radiative coating improves thermal efficiency, Shandong Huimin Science & Technology Co., Ltd., University of Science & Technology Beijing, Shandong Shiheng Steel Co., Ltd., Shandong province Energy Detection Center and other units carried out the energy-saving thermal diagnostic testing and thermal process diagnosis and comparison on Shiheng steel company 1080 m³BF 1^# and 3^# hot blast stoves, and also made a diagnosis of heat flow and heat distribution of 3^# hot blast stove (without coating) and 1^#hot blast stove(with coating). According to the results, of the hot blast stove (with the high radiative coating), the blast temperature improved, exhaust air temperature decreased, and thermal efficiency improved by 5%.
Introduction
In the industrial furnace, heat transfer mainly by way of radiation. Considering the industrial furnaces' size and the important part it takes in industry, even though a small increase could take a big improvement on the thermal efficiency and energy saving effect of the whole system. According to the research result of J. C. Hellander, using high radiative infrared coating on the industrial furnace can improve the radiaitve heat transfer ability, which leads to the improvement of thermal efficiency. Generally speaking, the radiative rate of the regenerator (silica and aluminum martial) will decreased with the temperature increasing, however, the high radiative coating can make up this disadvantage.
In order to test the heat using condition and the thermal efficiency changing condition after using the high radiative coating on checker bricks, evaluate the thermal character, and reveal the application effect of the high radiative coating on Shandong Shiheng steel Co, Ltd. 1080 m³BF hot blast stoves, the heat diagnosis testing and analysis of the 1# and 3# stoves was carried out, which is good for the analysis of the energy saving effect and proposed measures for energy saving.
Detection Base of Thermal Diagnosis
Detection Cycle
Measured the complete heating cycle and the heat transfer cycle of 1# and 3# hot blast stove respectively, that is under the normal product condition of BF, measured the thermal condition between two combustion periods. Shandong Shiheng steel Co, Ltd. takes two stoves burning with another stove sending as the normal operation system, the burning time for 114 minutes, blowing time for 55 minutes, changing stove for 10 minutes, one cycle takes a total of 2 hours and 59 minutes.
The Base Temperature
Take the test-stage ambient temperature as a base temperature, this test make 10° as the base temperature.
Main Content of the Thermal Diagnosis
In this detection, the media flow and temperature is according to the average data of the inline meter records, gas component is analyzed by the flue gas analyzer on-site detection, the stoves' body heat dissipation and pipe heat dissipation used infrared thermometers. All instruments were debugged and adjusted before the test; the test results are true and reliable
Gas Parameters
(1) Gas Component Converter
The main fuel of the hot-blast stove is blast furnace gas, blast furnace gas composition analysis on-site frequently contain a small amount of oxygen, which is due to sampling and analysis, for this reason, of the blast furnace gas test results often mixed with 0.2%-0.4% oxygen, sometimes more than 0.6%. Actually, the composition of blast furnace gas should not be aerobic; you must deduct the oxygen and the corresponding nitrogen, and converted into 100%. As the blast furnace gas contain water after they wet—dust, which influence the gas heat value and theoretical combustion temperature. From this reason, we should select the wet gas component to calculate. In the thermal balance calculation, taking 5% water vapor of the amount of the gas (Be equal to 40 g/m³gas).
In the calculation, the first test of gas components in the residual oxygen Z deduction into “dry ingredients” Z^g, and then converted into “wet ingredients” Z^s.

Form 1 Hot Blast Stove Burning Gas Component (%)


Dry gas component without
Oxygen Z^g%	Wet gas conversion component Z^s%

CO	CO₂	H₂	CH₄	N₂	CO	CO₂	H₂	CH₄	N₂	H₂O

24.5	20.4	0.8	1.1	53.2	23.3	19.4	0.7	1.0	50.6	5.0

total	100.0	Total	100.0

(2) Fuel (Wet Gas) Low Heating Value
Fuel low heating value is calculated in accordance with 1% (volume)
Heat efficiency of the combustible component of wet gas, in this case, the combustible component is CO, H₂and CH₄. The low heating value is 3378.49 KJ/m³.
Gas Parameters
Dry gas component is tested by the gas analyzer on-site, from the beginning of one testing cycle, take a sample records every 15 min, and make the average, then convert to the wet component according to the empirical formula.

Form 2 Gas Components in the Test Cycle (%)


Item	O₂	CO₂	CO	NO	NO_X	SO₂	C₃ H ₈

1^#	1.85	25.82	0.0029	0.0008	0.0008	0.0003	0.0043
3^#	1.17	25.66	0.45	0.0008	0.0008	0	0.0059

Hot blast stove surface heat dissipation parameter.
Take the hot blast stove as seven segments for it has six platforms, every segment has eight measuring points. The testing results are shown in Form 3 and Form 4.

Form 3 1^#Hot Blast Stove Temperature (° C.)


	North-		North-		South-		South-
East	east	North	west	West	west	South	east	Average

1-2	51.6	50.2	50.9	51.5	45.7	58.4	65.1	58.4
platforms	67.6	55.4	41.2	34	40.3	44.1	73.7	55.8
	44	48.6	42.6	41.1	41.8	48.8	71.1	52.4
	39.8	43.9	43.4	40.3	37.8	48.7	52.2	45.1
Average	50.75	49.52	44.52	41.72	41.4	50	65.52	52.92	49.54
2-3	62.4	76.8	68.6	66.4	61.9	70.5	76.2	77.9
platforms		79.6	64.5	57.2	52.4	75.9	78.2	74.1
		60.8	65.9	46.4	48.5	67.8	68.4	74
Average	62.4	72.4	66.33	56.66	54.26	71.4	74.26	75.33	66.63
3-4	60.3	53.4	56.9	56	40.2	57	58.6	66
platforms	78.4	68.9	66	70.2	67.1	82.5	72.9	76.4
Average	69.35	61.15	61.45	63.1	53.65	69.75	65.75	71.2	64.42
4-5	51.2	39.5	53.1	54.7	42.7	57.1	52.4	51.3	50.25
platforms
5-6	25.3	20.5	19.3	18.5	16.5	32.4	39.1	31.4
platforms	41.2	36.1	37.9	38.4	23.7	41.6	44.4	38.5
Average	33.25	28.3	28.6	28.45	20.1	37	41.75	34.95	31.55
1 below	38.3	36.9	33.8	21.9	20.9	20.6	34	49.9	32.03
platform

Form 4 3^# Hot Blast Stove Temperature (° C.)


	North-		North-		South-		South-
East	east	North	west	West	west	South	east	Average

1-2	56.6	65.2	71.6	63.8	54.8	66.7	63.7	55.6
platforms	50.8	58.4	76.1	61.7	44.1	52.7	59.8	61.1
	51	63.4	74.9	61.3	43.2	53.9	51.9	56.8
	45.8	51.8	58.3	48.2	40	53.6	60.1	55
average	51.05	59.7	70.2	58.75	45.52	56.72	58.87	57.12	57.24
2-3	75.7	86.5	70	81	66.2	77.2	86.9	80.2
platforms	/	77	86.9	70.9	57.7	68.4	75.8	79.7
	/	72.3	77	53.9	49.4	47.9	66.7	63.2
average	75.7	78.6	77.96	68.6	57.76	64.5	76.46	74.36	71.74
3-4	58.6	60.9	55	55.2	48.1	47.3	48.3	57
platforms	78.2	75.4	77.5	71.6	71.2	83	87.4	76.1
average	68.4	68.15	66.25	63.4	59.65	65.15	67.85	66.55	65.67
4-5	50.6	49.9	52.8	47.6	43.7	54.5	44.7	46	48.72
platforms
5-6	14.2	14.1	24	17.2	16.2	31.6	31.9	28.3
platforms	31.6	29.3	34	26.5	33.5	45.1	41.5	37.8
average	22.9	21.7	29	21.85	24.85	38.35	36.7	33.05	28.55
1 below	51.5	54.8	39.3	28.6	25.3	21.4	31.3	44
platform	46.7	46.4	38.7	28.6	25.3	21.4	21.2	42.5
average	49.1	50.6	39	28.6	25.3	21.4	26.25	43.25	35.43

Original Data of Thermal Diagnosis Test

Form

5 1^#Stove Original Data


				Hot blast
Gas	Combustion-	Hot	Stove	pipe

Gas

Cool blast

supporting air

blast

Flue gas

superficial

Item	Temp.	flow	Temp.	Flow	Temp.	Flow	Temp.	Temp.	temp.	temp.

unit	° C.	m³/min	° C.	m³/min	° C.	m³/min	° C.	° C.	m²	m²
data	40	1299	171	2509	183	622	1198	300	781	325

Form 6 3^# Stove Original Data


					Hot blast
Gas	Combustion-	Hot	Flue	Stove	pipe

Gas

Cool blast

supporting air

blast

gas

Superficial

superficial

Item	Temp.	flow	Temp.	Flow	Temp.	flow	Temp.	Temp.	Temp.	temp.

unit	° C.	m³/min	° C.	m³/min	° C.	m³/min	° C.	° C.	m²	m²
data	40	1299	171	2509	183	622	1173	313	781	325

Thermal Diagnosis Testing Results
The thermal diagnosis process is omitted; the results are shown in Form 7

Form 7 1^#Stove Thermal-Diagnosis Form


Heat receiving	Heat consumption

Symbol	Item	KJ/m³	%	Symbol	Item	KJ/m³	%

Q₁	Chemical heat of	1899.05	86.36	Q₁′	Heat hot air	1768.29	80.05
	fuel				taken away
Q₂	Physical heat of	22.27	1.00	Q₂′	Physical	230.16	10.68
	fuel				heat fume
					taken away
Q₃	Physical heat of	65.44	2.98	Q₃′	Chemical	2.62	0.12
	combustion-				incomplete
	supporting air				combustion
					heat loss
Q₄	Heat cool air	212.24	9.66	Q₄′	Gas	23.48	1.09
	taken				Mechanical
					water
					absorption
					heat
				Q₅′	Stove	72.33	3.36
					surface
					heat
					dissipation
					capacity
				Q₆′	Hot air	58.31	2.71
					pipe heat
					dissipation
					Capacity
				ΔQ	Heat-	43.81	1.99
					balance
					difference
ΣQ		2199.00	100.00	ΣQ		2199.00	100.00

Form 8 3^# Hot Blast Stove Thermal-Diagnosis Form


Heat receiving	Heat consumption

Symbol	Item	KJ/m³	%	Symbol	Item	KJ/m³	%

Q₁	Chemical heat of	1899.05	86.55	Q₁′	Heat hot air	1665.57	74.93
	fuel				taken away
Q₂	Physical heat of	22.27	1.00	Q₂′	Physical heat	274.49	13.22
	fuel				fume taken
					away
Q₃	Physical heat of	61.97	2.83	Q₃′	Chemical	36.50	1.70
	combustion-				incomplete
	supporting air				combustion
					heat loss
Q₄	Heat cool air	212.24	9.62	Q₄′	Gas	24.03.	1.12
	taken				Mechanical
					water
					absorption
					heat
				Q₅′	Stove surface	86.60	4.04
					heat
					dissipation
					capacity
				Q₆′	Hot air pipe	54.67	2.55
					heat
					dissipation
					Capacity
				ΔQ	Heat-balance	53.67	2.44
					difference
ΣQ		2199.00	100.00	ΣQ		2195.53	100.00

Result Analysis
Hot air temperature improved in large extent, exhausted gas temperature decreased.
Seen from the testing data and heat balance form, under the same condition with 3^# hot blast stove, the hot blast temperature of 1^#hot blast stove is 25° C. higher on average and exhausted gas temperature is 13° C. lower on average than 3^# hot blast stove. These two indicators cause the energy consumption is 3% lower and the heat taken away for temperature increasing increased 5.1% compared with 3^#. The energy effect is obvious.
Gas Combustion Completely
Because of the increasing of checker bricks radiation of 1^#, the heat storage ability is improved and the gas resistant time in the regenerator during the combustion period is prolonged. Seen from the analysis, CO content in gas of 1^#hot blast stove is much more lower than 3^# hot blast stove, which reduced the heat consumption for chemical incomplete combustion to 0.12% from 1.7%. Heat utilization is more perfect.
Thermal Efficiency Increasing
{circle around (1)} Thermal efficiency of the body of hot stove η₁
$1^{#} : η_{1} = \frac{Q_{1}^{'} - Q_{4} + Q_{6}^{'}}{\sum Q - Q_{4}} = \frac{1768.29 - 212.24 + 58.31}{2199.00 - 212.24} 81.26 %$ $3^{#} : η_{1} = \frac{Q_{1}^{'} - Q_{4} + Q_{6}^{'}}{\sum Q - Q_{4}} = \frac{1665.57 - 212.24 + 54.67}{2195.53 - 212.24} 76.03 %$
{circle around (2)} Thermal efficiency of the hot stove η₂
$1^{#} : η_{2} = \frac{Q_{1}^{'} - Q_{4}}{\sum Q - Q_{4}} \times 100 = \frac{1768.29 - 212.24}{2199.00 - 212.24} 78.32 %$ $3^{#} : η_{2} = \frac{Q_{1}^{'} - Q_{4}}{\sum Q - Q_{4}} \times 100 = \frac{1665.57 - 212.24}{2195.53 - 212.24} 73.28 %$
Conclusion:
The blast temperature of the hot blast stove (without coating) is 25° C. higher on average than the one without coating, the gas temperature is reduced by 13° C., and the energy consumption reduced by 3%.
The gas combustion of the hot blast stove (with coating) is complete, and the combustible component in gas is decreased to a large extent. Heat loss decreased from 1.7% to 0.12%.
The thermal efficiency of the hot blast stove (with coating) is improved by 5% than the one without coating, the energy saving effect is obvious and stable.

Commercial Success

The heat retainers for the hot blast stoves of the blast furnaces of the present invention have been used in commerce in at least 217 blast furnace hot stoves and 3 coke batteries by more than 50 iron and steel companies, and they are commercially successful.
The heat storage ability of the heat retainer with a high radiative coating of the invention is higher by at least about 15% at under 1300° C. compared with that described in the prior art. The hot blast temperature is increased by at least 15° C., the exhaust gas temperature is reduced by at least 13° C., and gas consumption is decreased by at least 7%. In addition, the reduction of CO₂emission is successfully realized.
This invention is not to be limited to the specific embodiments disclosed herein and modifications for various applications and other embodiments are intended to be included within the scope of the appended claims. While this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and following claims.
All publications and patent applications mentioned in this specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application mentioned in this specification.

Emissivity of Common Metal and Non-Metal Materials


Metal Material	Temp ° F. (° C.)	Emissivity

Alloys

20-Ni, 24-CR, 55-FE, Oxidized	392	(200)	0.9
20-Ni, 24-CR, 55-FE, Oxidized	932	(500)	0.97
60-Ni, 12-CR, 28-FE, Oxidized	518	(270)	0.89
60-Ni, 12-CR, 28-FE, Oxidized	1040	(560)	0.82
80-Ni, 20-CR, Oxidized	212	(100)	0.87
80-Ni, 20-CR, Oxidized	1112	(600)	0.87
80-Ni, 20-CR, Oxidized	2372	(1300)	0.89

Aluminum

Unoxidized	77	(25)	0.02
Unoxidized	212	(100)	0.03
Unoxidized	932	(500)	0.06
Oxidized	390	(199)	0.11
Oxidized	1110	(599)	0.19
Oxidized at 599° C. (1110° F.)	390	(199)	0.11
Oxidized at 599° C. (1110° F.)	1110	(599)	0.19
Heavily Oxidized	200	(93)	0.2
Heavily Oxidized	940	(504)	0.31
Highly Polished	212	(100)	0.09
Roughly Polished	212	(100)	0.18
Commercial Sheet	212	(100)	0.09
Highly Polished Plate	440	(227)	0.04
Highly Polished Plate	1070	(577)	0.06
Bright Rolled Plate	338	(170)	0.04
Bright Rolled Plate	932	(500)	0.05
Alloy A3003, Oxidized	600	(316)	0.4
Alloy A3003, Oxidized	900	(482)	0.4
Alloy 1100-0	200-800	(93-427)	0.05
Alloy 24ST	75	(24)	0.09
Alloy 24ST, Polished	75	(24)	0.09
Alloy 75ST	75	(24)	0.11
Alloy 75ST, Polished	75	(24)	0.08
Bismuth, Bright	176	(80)	0.34
Bismuth, Unoxidized	77	(25)	0.05
Bismuth, Unoxidized	212	(100)	0.06

Brass

73% Cu, 27% Zn, Polished	476	(247)	0.03
73% Cu, 27% Zn, Polished	674	(357)	0.03
62% Cu, 37% Zn, Polished	494	(257)	0.03
62% Cu, 37% Zn, Polished	710	(377)	0.04
83% Cu, 17% Zn, Polished	530	(277)	0.03
Matte	68	(20)	0.07
Burnished to Brown Color	68	(20)	0.4
Cu—Zn, Brass Oxidized	392	(200)	0.61
Cu—Zn, Brass Oxidized	752	(400)	0.6
Cu—Zn, Brass Oxidized	1112	(600)	0.61
Unoxidized	77	(25)	0.04
Unoxidized	212	(100)	0.04
Cadmium	77	(25)	0.02

Carbon

Lampblack	77	(25)	0.95
Unoxidized	77	(25)	0.81
Unoxidized	212	(100)	0.81
Unoxidized	932	(500)	0.79
Candle Soot	250	(121)	0.95
Filament	500	(260)	0.95
Graphitized	212	(100)	0.76
Graphitized	572	(300)	0.75
Graphitized	932	(500)	0.71
Chromium	100	(38)	0.08
Chromium	1000	(538)	0.26
Chromium, Polished	302	(150)	0.06
Cobalt, Unoxidized	932	(500)	0.13
Cobalt, Unoxidized	1832	(1000)	0.23
Columbium, Unoxidized	1500	(816)	0.19
Columbium, Unoxidized	2000	(1093)	0.24

Copper

Cuprous Oxide	100	(38)	0.87
Cuprous Oxide	500	(260)	0.83
Cuprous Oxide	1000	(538)	0.77
Black, Oxidized	100	(38)	0.78
Etched	100	(38)	0.09
Matte	100	(38)	0.22
Roughly Polished	100	(38)	0.07
Polished	100	(38)	0.03
Highly Polished	100	(38)	0.02
Rolled	100	(38)	0.64
Rough	100	(38)	0.74
Molten	1000	(538)	0.15
Molten	1970	(1077)	0.16
Molten	2230	(1221)	0.13
Nickel Plated	100-500	(38-260)	0.37
Dow Metal	0.4-600	(−18-316)	0.15

Gold

Enamel	212	(100)	0.37
Plate (.0001)
Plate on .0005 Silver	200-750	(93-399)	.11-.14
Plate on .0005 Nickel	200-750	(93-399)	.07-.09
Polished	100-500	(38-260)	0.02
Polished	1000-2000	(5381093)	0.03

Haynes Alloy C

Oxidized

600-2000

(316-1093)

.90-.96

Haynes Alloy 25,

Oxidized

600-2000

(316-1093)

.86-.89

Haynes Alloy X

Oxidized	600-2000	(316-1093)	.85-.88
Inconel Sheet	1000	(538)	0.28
Inconel Sheet	1200	(649)	0.42
Inconel Sheet	1400	(760)	0.58
Inconel X, Polished	75	(24)	0.19
Inconel B, Polished	75	(24)	0.21

Iron

Oxidized	212	(100)	0.74
Oxidized	930	(499)	0.84
Oxidized	2190	(1199)	0.89
Unoxidized	212	(100)	0.05
Red Rust	77	(25)	0.7
Rusted	77	(25)	0.65
Liquid	2760-3220	(1516-1771)	.42-.45

Cast Iron

Oxidized	390	(199)	0.64
Oxidized	1110	(599)	0.78
Unoxidized	212	(100)	0.21
Strong Oxidation	40	(104)	0.95
Strong Oxidation	482	(250)	0.95
Liquid	2795	(1535)	0.29

Wrought Iron

Dull	77	(25)	0.94
Dull	660	(349)	0.94
Smooth	100	(38)	0.35
Polished	100	(38)	0.28

Lead

Polished	100-500	(38-260)	.06-.08
Rough	100	(38)	0.43
Oxidized	100	(38)	0.43
Oxidized at 1100	100	(38)	0.63
Gray Oxidized	100	(38)	0.28
Magnesium	100-500	(38-260)	.07-.13
Magnesium Oxide	1880-3140	(1027-1727)	.16-.20
Mercury	32	(0)	0.09
Mercury	77	(25)	0.1
Mercury	100	(38)	0.1
Mercury	212	(100)	0.12
Monel, Ni—Cu	392	(200)	0.41
Monel, Ni—Cu	752	(400)	0.44
Monel, Ni—Cu	1112	(600)	0.46
Monel, Ni—Cu Oxidized	68	(20)	0.43
Monel, Ni—Cu Oxidized	1110	(599)	0.46
at 1110° F.

Nickel

Polished	100	(38)	0.05
Oxidized	100-500	(38-260)	.31-.46
Unoxidized	77	(25)	0.05
Unoxidized	212	(100)	0.06
Unoxidized	932	(500)	0.12
Unoxidized	1832	(1000)	0.19
Electrolytic	100	(38)	0.04
Electrolytic	500	(260)	0.06
Electrolytic	1000	(538)	0.1
Electrolytic	2000	(1093)	0.16
Nickel Oxide	1000-2000	(538-1093)	.59-.86
Palladium Plate	200-750	(93-399)	.16-.17
(.00005 on .0005 silver)
Platinum	100	(38)	0.05
Platinum	500	(260)	0.05
Platinum	1000	(538)	0.1
Platinum, Black	100	(38)	0.93
Platinum, Black	500	(260)	0.96
Platinum, Black	2000	(1093)	0.97
Platinum Oxidized at 1100	500	(260)	0.07
Platinum Oxidized at 1100	1000	(538)	0.11
Rhodium Flash	200-700	(93-371)	.10-.18
(0.0002 on 0.0005 Ni)

Silver

Plate (0.0005 on Ni)	200-700	(93-371)	.06-.07
Polished	100	(38)	0.01
Polished	500	(260)	0.02
Polished	1000	(538)	0.03
Polished	2000	(1093)	0.03

Steel

Cold Rolled	200	(93)	.75-.85
Ground Sheet	1720-2010	(938-1099)	.55-.61
Polished Sheet	100	(38)	0.07
Polished Sheet	500	(260)	0.1
Polished Sheet	1000	(538)	0.14
Mild Steel, Polished	75	(24)	0.1
Mild Steel, Smooth	75	(24)	0.12
Mild Steel, liquid	2910-3270	(1599-1793)	0.28
Steel, Unoxidized	212	(100)	0.08
Steel, Oxidized	77	(25)	0.8

Steel Alloys

Type 301, Polished	75	(24)	0.27
Type 301, Polished	450	(232)	0.57
Type 301, Polished	1740	(949)	0.55
Type 303, Oxidized	600-2000	(316-1093)	.74-.87
Type 310, Rolled	1500-2100	(8161149)	.56-.81
Type 316, Polished	75	(24)	0.28
Type 316, Polished	450	(232)	0.57
Type 316, Polished	1740	(949)	0.66
Type 321	200-800	(93-427)	.27-.32
Type 321 Polished	300-1500	(149-815)	.18-.49
Type 321 w/BK Oxide	200-800	(93-427)	.66-.76
Type 347, Oxidized	600-2000	(316-1093)	.87-.91
Type 350	200-800	(93-427)	.18-.27
Type 350 Polished	300-1800	(149-982)	.11-.35
Type 446, Polished	300-1500	(149-815)	.15-.37
Type 17-7 PH	200-600	(93-316)	.44-.51
Type 17-7 PH Polished	300-1500	(149-815)	.09-.16
Type C1020, Oxidized	600-2000	(316-1093)	.87-.91
Type PH-15-7 MO	300-1200	(149-649)	.07-.19
Stellite, Polished	68	(20)	0.18
Tantalum, Unoxidized	1340	(727)	0.14
Tantalum, Unoxidized	2000	(1093)	0.19
Tantalum, Unoxidized	3600	(1982)	0.26
Tantalum, Unoxidized	5306	(2930)	0.3
Tin, Unoxidized	77	(25)	0.04
Tin, Unoxidized	212	(100)	0.05
Tinned Iron, Bright	76	(24)	0.05
Tinned Iron, Bright	212	(100)	0.08

Titanium

Alloy C110M, Polished	300-1200	(149-649)	.08-.19
Oxidized at 538° C. (1000° F.)	200-800	(93-427)	.51-.61
Alloy Ti-95A, Oxidized	200-800	(93-427)	.35-.48
at 538° C. (1000° F.)
Anodized onto SS	200-600	(93-316)	.96-.82

Tungsten

Unoxidized	77	(25)	0.02
Unoxidized	212	(100)	0.03
Unoxidized	932	(500)	0.07
Unoxidized	1832	(1000)	0.15
Unoxidized	2732	(1500)	0.23
Unoxidized	3632	(2000)	0.28
Filament (Aged)	100	(38)	0.03
Filament (Aged)	1000	(538)	0.11
Filament (Aged)	5000	(2760)	0.35
Uranium Oxide	1880	(1027)	0.79

Zinc

Bright, Galvanized	100	(38)	0.23
Commercial 99.1%	500	(260)	0.05
Galvanized	100	(38)	0.28
Oxidized	500-1000	(260-538)	0.11
Polished	100	(38)	0.02
Polished	500	(260)	0.03
Polished	1000	(538)	0.04
Polished	2000	(1093)	0.06

Non-Metals Material	Temp ° F. (° C.)	Emissivity

Adobe

68

(20)

0.9

Asbestos

Board	100	(38)	0.96
Cement	32-392	(0-200)	0.96
Cement, Red	2500	(1371)	0.67
Cement, White	2500	(1371)	0.65
Cloth	199	(93)	0.9
Paper	100-700	(38-371)	0.93
Slate	68	(20)	0.97
Asphalt, pavement	100	(38)	0.93
Asphalt, tar paper	68	(20)	0.93
Basalt	68	(20)	0.72

Brick

Red, rough	70	(21)	0.93
Gault Cream	2500-5000	(1371-2760)	.26-.30
Fire Clay	2500	(1371)	0.75
Light Buff	1000	(538)	0.8
Lime Clay	2500	(1371)	0.43
Fire Brick	1832	(1000)	.75-.80
Magnesite, Refractory	1832	(1000)	0.38
Grey Brick	2012	(1100)	0.75
Silica, Glazed	2000	(1093)	0.88
Silica, Unglazed	2000	(1093)	0.8
Sandlime	2500-5000	(1371-2760)	.59-.63
Carborundum	1850	(1010)	0.92

Ceramic

Alumina on Inconel	800-2000	(427-1093)	.69-.45
Earthenware, Glazed	70	(21)	0.9
Earthenware, Matte	70	(21)	0.93
Greens No. 5210-2C	200-750	(93-399)	.89-.82
Coating No. C20A	200-750	(93-399)	.73-.67
Porcelain	72	(22)	0.92
White Al₂O₃	200	(93)	0.9
Zirconia on Inconel	800-2000	(427-1093)	.62-.45
Clay	68	(20)	0.39
Fired	158	(70)	0.91
Shale	68	(20)	0.69
Tiles, Light Red	2500-5000	(1371-2760)	.32-.34
Tiles, Red	2500-5000	(1371-2760)	.40-.51
Tiles, Dark Purple	2500-5000	(1371-2760)	0.78

Concrete

Rough	32-2000	(0-1093)	0.94
Tiles, Natural	2500-5000	(1371-2760)	.63-.62
Brown	2500-5000	(1371-2760)	.87-.83
Black	2500-5000	(1371-2760)	.94-.91
Cotton Cloth	68	(20)	0.77
Dolomite Lime	68	(20)	0.41
Emery Corundum	176	(80)	0.86

Glass

Convex D	212	(100)	0.8
Convex D	600	(316)	0.8
Convex D	932	(500)	0.76
Nonex	212	(100)	0.82
Nonex	600	(316)	0.82
Nonex	932	(500)	0.78
Smooth	32-200	(0-93)	.92-.94
Granite	70	(21)	0.45
Gravel	100	(38)	0.28
Gypsum	68	(20)	.80-.90
Ice, Smooth	32	(0)	0.97
Ice, Rough	32	(0)	0.98

Lacquer

Black	200	(93)	0.96
Blue, on Al Foil	100	(38)	0.78
Clear, on Al Foil (2 coats)	200	(93)	.08-.09
Clear, on Bright Cu	200	(93)	0.66
Clear, on Tarnished Cu	200	(93)	0.64
Red, on Al Foil (2 coats)	100	(38)	.60-.74
White	200	(93)	0.95
White, on Al Foil (2 coats)	100	(38)	.69-.88
Yellow, on Al Foil (2 coats)	100	(38)	.57-.79
Lime Mortar	100-500	(38-260)	.90-.92
Limestone	100	(38)	0.95
Marble, White	100	(38)	0.95
Smooth, White	100	(38)	0.56
Polished Grey	100	(38)	0.75
Mica	100	(38)	0.75

Oil on Nickel

0.001 Film	72	(22)	0.27
0.002″	72	(22)	0.46
0.005″	72	(22)	0.72
Thick″	72	(22)	0.82

Oil, Linseed

On Al Foil, uncoated	250	(121)	0.09
On Al Foil, 1 coat	250	(121)	0.56
On Al Foil, 2 coats	250	(121)	0.51
On Polished Iron, .001 Film	100	(38)	0.22
On Polished Iron, .002 Film	100	(38)	0.45
On Polished Iron, .004 Film	100	(38)	0.65
On Polished Iron, Thick Film	100	(38)	0.83

Paints

Blue, Cu₂O₃	75	(24)	0.94
Black, CuO	75	(24)	0.96
Green, Cu₂O₃	75	(24)	0.92
Red, Fe₂O₃	75	(24)	0.91
White, Al₂O₃	75	(24)	0.94
White, Y₂O₃	75	(24)	0.9
White, ZnO	75	(24)	0.95
White, MgCO₃	75	(24)	0.91
White, ZrO₂	75	(24)	0.95
White, ThO₂	75	(24)	0.9
White, MgO	75	(24)	0.91
White, PbCO3	75	(24)	0.93
Yellow, PbO	75	(24)	0.9
Yellow, PbCrO₄	75	(24)	0.93
Paints, Aluminum	100	(38)	.27-.67
10% Al	100	(38)	0.52
26% Al	100	(38)	0.3
Dow XP-310	200	(93)	0.22

Paints, Bronze

Low

.34-.80

Gum Varnish (2 coats)	70	(21)	0.53
Gum Varnish (3 coats)	70	(21)	0.5
Cellulose Binder (2 coats)	70	(21)	0.34

Paints, Oil

All colors	200	(93)	.92-.96
Black	200	(93)	0.92
Black Gloss	70	(21)	0.9
Camouflage Green	125	(52)	0.85
Flat Black	80	(27)	0.88
Flat White	80	(27)	0.91
Grey-Green	70	(21)	0.95
Green	200	(93)	0.95
Lamp Black	209	(98)	0.96
Red	200	(93)	0.95
White	200	(93)	0.94
Red Lead	212	(100)	0.93
Rubber, Hard	74	(23)	0.94
Rubber, Soft, Grey	76	(24)	0.86
Sand	68	(20)	0.76
Sandstone	100	(38)	0.67
Sandstone, Red	100	(38)	.60-.83
Sawdust	68	(20)	0.75
Shale	68	(20)	0.69
Silica, Glazed	1832	(1000)	0.85
Silica, Unglazed	2012	(1100)	0.75
Silicon Carbide	300-1200	(149-649)	.83-.96
Silk Cloth	68	(20)	0.78
Slate	100	(38)	.67-.80
Snow, Fine Particles	20	(−7)	0.82
Snow, Granular	18	(−8)	0.89

Soil

Surface	100	(38)	0.38
Black Loam	68	(20)	0.66
Plowed Field	68	(20)	0.38

Soot

Acetylene	75	(24)	0.97
Camphor	75	(24)	0.94
Candle	250	(121)	0.95
Coal	68	(20)	0.95
Stonework	100	(38)	0.93
Water	100	(38)	0.67

Wood

Low

.80-.90

Beech Planed	158	(70)	0.94
Oak, Planed	100	(38)	0.91
Spruce, Sanded	100	(38)	0.89

Claims

1. A heat retainer for a hot blast stove of a blast furnace, the heat retainer adapted to function at temperatures of about 1200° C. present during operation of a hot blast stove of a blast furnace, and adapted to absorb thermal energy from air in the hot blast stove of the blast furnace, the heat retainer experiencing a heat storage period and a heat release period, the heat retainer having a coating layer,

wherein:

at least one surface of said heat retainer is coated with a high radiative material forming said coating layer;

the thickness of said coating layer is critically between 0.02 mm and 3 mm;

the heat retainer absorbs energy in the heat storage period, whereby end temperature of the heat retainer is increased during heat storage period compared to what it would have been in the absence of said coating layer;

the heat retainer emits energy in the heat release period, whereby end temperature of the heat retainer is decreased during heat release period compared to what it would have been in the absence of said coating layer;

the heat retainer absorbs energy or emits energy mainly by radiation at a wavelength of between 1 and 5 μm.

2. The heat retainer of claim 1, wherein said coating layer achieves rapid and efficient heat transfer and increases the heat storage capacity of the heat retainer.

3. The heat retainer of claim 1, wherein said high radiative material is not highly-reflective.

4. The heat retainer of claim 1, adapted to transfer more heat by radiation than by convection.

5. The heat retainer of claim 1, adapted to absorb and emit heat non-simultaneously, wherein a steady-state for heat absorption and emission is not reached during a heat absorption period or a heat emission period.

6. The heat retainer of claim 1, comprising a core and a coating layer, wherein the heat emissivity of the coating layer is greater than the heat emissivity of the core.

7. The heat retainer of claim 6, wherein said coating layer increases heat absorption and heat radiation ability of the core.

8. The heat retainer of claim 6, further comprising at least one cavity in said core.

9. The heat retainer of claim 8, wherein said cavity passes through the matrix from its one end to another and said coating layer completely coats the surface of said cavity.

10. The heat retainer of claim 1, wherein the substrate of the heat retainer is made of one of a refractory material, or a ceramic material.

11. The heat retainer of claim 1, wherein said coating layer comprises one or more of the following: Cr₂O₃, clay, montmorillonite, brown corundum, silicon carbide, TiO₂, Al₂O₃, aluminum hydroxide, zirconium oxide, phosphoric acid, or hydrated sodium silicate gel.

12. A heat retainer comprising: a core having a first heat emissivity; a plurality of inner passages in said core, said plurality of said inner passages extending from a first surface of said core to a second surface of said core, and being immovable with respect to one another; and a coating layer coating said core and said passages, said coating layer having a second heat emissivity; wherein said coating layer comprises a high radiative material; the thickness of said coating layer is critically between 0.02 mm and 3 mm; said second heat emissivity is greater than said first heat emissivity; said coating layer achieves rapid and efficient heat transfer and increases the heat storage capacity of the heat retainer; said high radiative material is not highly-reflective; said heat retainer is adapted to absorb heat from and to emit heat to air in a hot blast stove of a blast furnace mainly by thermal radiation; said heat retainer is adapted to absorb and emit heat non-simultaneously; said heat retainer is adapted for use in a high temperature heat exchanger and for use at temperatures below 1400° C. present during operation of a hot blast stove of a blast furnace; the heat retainer experiences a heat storage period and a heat release period; the heat retainer absorbs energy in the heat storage period, whereby end temperature of the heat retainer is increased during heat storage period relative to what it would have been without said coating layer; the heat retainer emits energy in the heat release period, whereby end temperature of the heat retainer is decreased during heat release period relative to what it would have been without said coating layer; and energy of thermal radiation is mainly at a wavelength of between 1 and 5 μm.

13. The heat retainer of claim 1, wherein said coating layer achieves rapid and efficient heat transfer and increases the heat storage capacity of the heat retainer.

14. The heat retainer of claim 1, wherein said high radiative material is not highly-reflective.

15. The heat retainer of claim 1, adapted to transfer more heat by radiation than by convection.

16. The heat retainer of claim 1, adapted to absorb and emit heat non-simultaneously.

17. The heat retainer of claim 1, comprising a core and a coating layer, wherein the heat emissivity of the coating layer is greater than the heat emissivity of the core.

18. The heat retainer of claim 6, wherein said coating layer increases heat absorption and heat radiation ability of the core.

19. The heat retainer of claim 6, further comprising at least one cavity in said core.

20. The heat retainer of claim 8, wherein said cavity passes through the matrix from its one end to another and said coating layer completely coats the surface of said cavity.

21. A method for enhancing radiative heat absorption and radiative heat emission and for simultaneously reducing heat reflection in a heat retainer for a hot blast stove of a blast furnace, comprising: placing into a hot blast stove of a blast furnace a core coated with a coating layer, and operating said hot blast stove or said blast furnace at usual operating temperatures about 1200° C.; wherein said core has a first heat emissivity; said coating layer has a second heat emissivity; said second heat emissivity is greater than said first heat emissivity; said coating layer comprises a high radiative material; the thickness of said coating layer is critically between 0.02 mm and 3 mm; said coating layer achieves rapid and efficient heat transfer and increases the heat storage capacity of the heat retainer; said high radiative material is not highly-reflective; said heat retainer absorbs heat from and emits heat to air in a hot blast stove of a blast furnace mainly by thermal radiation; said heat retainer absorbs and emits heat non-simultaneously; the heat retainer experiences a heat storage period and a heat release period; the heat retainer absorbs energy in the heat storage period, whereby end temperature of the heat retainer is increased during heat storage period; the heat retainer emits energy in the heat release period, whereby end temperature of the heat retainer is decreased during heat storage period; and energy of thermal radiation is mainly in a wavelength of 1-5 μm.