HEAT EXCHANGER DEVICE WITH HEAT-RADIATIVE COATING

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. 13b 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. 14b 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_max⁴−T_min⁴). 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. 13b 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. 14b 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
C₃H₈

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
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

	Number	Date	Country
Parent	11815488	Aug 2007	US
Child	13369332		US

HEAT EXCHANGER DEVICE WITH HEAT-RADIATIVE COATING

Information

Publication Number

Date Filed

Date Published

Inventors

CPC

US Classifications

International Classifications

Abstract

Description

Claims

Priority Claims (1)

CROSS-REFERENCE TO RELATED APPLICATIONS

Continuation in Parts (1)