JPS6359073B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for increasing radiation heating efficiency in various heating furnaces and a radiator used in the method.

Improving thermal efficiency has always been called for since ancient times, but
Recently, general energy saving issues have been widely discussed, and as a result, there is a strong interest and desire for effective use of heat.

In order to improve the thermal efficiency of a heating furnace, the furnace wall,
Attention is being paid to reducing heat dissipation from the entrance and exit of the heated object, reducing exhaust gas temperature, and recovering such dissipated heat. Increasing the amount of heat transferred to the object to be heated in the heating furnace is most effective because it directly contributes to achieving the main purpose of the heating furnace and also reduces the temperature of the exhaust gas. Heat transfer by high-temperature gas to objects to be heated in a heating furnace is mainly by radiation, and convection and conduction account for the entire heat transfer.
In many cases, it is less than 10% or can be ignored. Therefore, in the design of heating furnaces, various measures are generally taken to improve the efficiency of radiant heat transfer.

This is a method of increasing the amount of heat transferred to the heated object in the heating furnace. A radiator is placed in the exhaust gas flow path on the exit side of the heating chamber, the radiator absorbs the heat held in the exhaust gas, and the absorbed heat is transferred to the heated object. The method of heating an object by radiating radiation toward the object is an extremely effective method and is currently well known. A specific typical example of this method is to provide a radiator made of a wire mesh or a heat-resistant fibrous material in the exhaust gas flow path on the exit side of the heating chamber, and use the radiator to absorb the heat retained in the exhaust gas to heat the exhaust gas. This is a method of heating an object by emitting radiation toward the object.

However, the wire mesh used as the radiator used in this method has high air permeability, making it difficult to sufficiently recover heat from exhaust gas, and has low heat resistance, making it difficult to use at high temperatures. In addition, many conventional products are made of metal, so their emissivity is low. When ceramic fiber is used, heat resistance and emissivity are improved, but the operating temperature is limited to 1400°C and it is expensive.

An object of the present invention is to provide a method for improving the radiation heating efficiency of a heated object using high-temperature gas in a heating furnace, and a radiator suitable for use in the method.

There are various heating furnaces to which the present invention can be applied, such as ceramic furnaces (glass, bricks, cement, etc.), metal furnaces (steel, non-ferrous metals, etc.), garbage incinerators, generation furnaces, etc. It is a furnace used for applying heat to an object, and may also be a furnace in which the unheated object itself generates heat. Further, the object to be heated is not limited to one that remains stationary during heating, but may be one that moves continuously or intermittently during heating.

The radiation heating method according to the present invention includes a ceramic block having a large number of parallel through-holes as a radiator in a high-temperature gas flow path in a heating chamber, the through-hole direction being inclined with respect to the flow direction of the high-temperature gas; This method is characterized in that it is performed by arranging it toward the object to be heated.

The radiant body according to the present invention is a radiant body suitable for use in the above-mentioned radiant heating method, and has a large number of parallel through holes in the opening of a heat-resistant frame having one or more openings. The ceramic block is mounted with the through-hole extending in a direction inclined with respect to the frame surface.

In a preferred embodiment of the radiation heating method and radiator of the present invention, the diameter of the through hole in the ceramic block is 1 to 200 mm, and the thickness of the through hole in the ceramic block in the penetrating direction is at least twice the diameter of the through hole. be.

In another preferred embodiment of the radiation heating method of the present invention, the ceramic block is arranged so that the direction of the through-holes in the ceramic block is inclined by 5 to 20 degrees with respect to the flow direction of the high-temperature gas.

In another preferred embodiment of the radiator of the present invention, the ceramic block is arranged so that the through-hole passing direction of the ceramic block is 5 to 50 mm perpendicular to the frame surface.
It is installed so that it is tilted 20 degrees.

In a further preferred embodiment of the radiator of the present invention, the frame body is provided with a plurality of openings, and the two ceramic blocks are attached to each opening symmetrically to the intermediate plane of both sides of the frame body. There is.

The material of the ceramic block used in the present invention may be arbitrarily selected from heat-resistant materials such as cordierite, zircon, zirconia, aluminum titanate, mullite, and alumina.

In addition, the shape of the through hole in the ceramic block is
Various shapes such as hexagonal, square, triangular, circular, etc. are possible.

FIG. 1 schematically shows, in sectional view, an example of a heating furnace in which the method of the present invention is carried out. 1 is a burner port to which a combustion burner of heavy oil or the like is attached, and high-temperature combustion gas is sent to the heating chamber 2. It may be arranged such that high-temperature exhaust gas, etc. from other equipment is taken in from a location corresponding to the burner port 1 and sent to the heating chamber 2. The heating chamber 2 accommodates an object 3 to be heated, such as a brick or the like. The object to be heated 3 is heated mainly by flame radiation of high-temperature gas and solid radiation through the furnace wall, and the high-temperature gas is heated and discharged into the exhaust gas passage 4 as shown by the arrow. At the entrance of the exhaust gas passage 4, a ceramic block 5 serving as a radiator is placed facing the object 3 to be heated. The ceramic block 5 is made of a honeycomb-shaped ceramic block made of cordierite, for example, and has a large number of parallel through holes 5A.
The penetrating direction of A is inclined with respect to the flow direction of the high temperature gas shown by the arrow.

When the direction of the through hole 5A matches the direction of the gas flow, the efficiency of heat transfer from the gas to the ceramic block 5 decreases, and since the direction of the through hole 5A faces the object to be heated 3, The radiation efficiency towards object 3 decreases. The inclination with respect to the gas flow direction depends on the structure of the furnace, the condition of the object to be heated, etc., but is generally about 5 to 20 degrees.

Regarding the diameter of the through-holes 5A, it is preferable to have a small diameter and a large number of holes because this will improve the efficiency of heat transfer to the ceramic block than the gas, and increase the unevenness of the radiation surface, increasing the radiation efficiency. However, it tends to become clogged with dust. In a normal gas-fired furnace,
A through hole with a hole diameter of about 1 to 5 mm may be sufficient, but in a heavy oil combustion furnace or a heating furnace for heating objects that cause carryover, the hole diameter needs to be made even larger. For glass furnaces, it is appropriate to use ceramic blocks with through holes with a diameter of 100 mm or more;
200mm is sufficient. In addition, when the thickness of the through-hole in the ceramic block is thin, a gap is created in the radiation surface facing the object to be heated that penetrates all the way to the back surface, reducing the emissivity. The thickness of the through hole is preferably at least twice the diameter of the through hole.

FIG. 2 shows an example of the shape and arrangement of a ceramic block as a radiator. The object to be heated is on the right side of the drawing, and the hot gas flows approximately horizontally from the right to the left of the drawing. As described above, the ceramic block 5 is arranged so that the direction of the through-hole 5A is inclined with respect to the gas flow direction, so as to face the object to be heated. In order to improve the radiation efficiency, it is desirable to have the radiation surface of the ceramic block directly facing the object to be heated. In addition, since the direction of the object to be heated and the direction in which the hot gas flows are generally the same, a ceramic block with through holes provided in it should face the object to be heated so that the direction of penetration is perpendicular to the radiation surface. This is not desirable because the direction of passage through the through hole coincides with the direction of gas flow. In such a case, it is necessary to tilt the ceramic block to face the object to be heated as shown in FIG. 2a. Although the ceramic block shown in FIG. 2b can solve the above-mentioned problems, it is somewhat complicated to manufacture the ceramic block in a honeycomb shape or the like. Furthermore, when two honeycomb-shaped ceramic blocks are combined to form a single radiator with their through holes aligned as shown in Fig. 2c and d, the through holes are refracted, so the heat absorption rate and emissivity of the radiator decrease. improves. In reality, furnaces and objects to be heated have various shapes, and the flow direction of hot gas also differs. Place in the state.

In an actual furnace, it is quite difficult to form a radiator that covers the outlet of the heating chamber with a single honeycomb-shaped ceramic block. Therefore, a radiator is formed by attaching a plurality of honeycomb-shaped ceramic blocks to a heat-resistant frame having a required area. An example of such a radiator is shown in FIGS. 3 and 4. 6A is a frame made of ceramics, heat-resistant metal, or the like. The frame 6A of the embodiment is provided with 16 square openings. Each opening has a cordierite ceramic block 5 similar to that used in the embodiment shown in FIG.
is attached and bonded to the frame 6A with adhesive, ceramic bolts, etc. to form the radiator 6. In this example, the size of the ceramic block is approximately 75 x 75 x 15 mm (thickness) and the size of the through hole is 1.8 x 1.8 mm. The ceramic block 5 is provided with holes passing through it at right angles on both sides. Therefore, since the frame surface of the radiator 6 is often directly opposed to the object to be heated, the ceramic block 5 is mounted so that the direction through which the through hole passes through the ceramic block 5 is inclined by 10 degrees from the right angle to the surface of the frame 6A. Moreover, two similar ceramic blocks 5 are attached to each opening symmetrically on the intermediate plane of both sides. As a result, the through hole is bent, and the heat absorption rate and radiation rate of the radiator 6 are improved. However, in this case, unlike Figure 2 c and d, 2
Since the two ceramic blocks 5 are isolated,
The absorbed heat of the ceramic block on the downstream side is transferred to the ceramic block on the upstream side by radiation and conduction through the frame 6A, and is radiated from the ceramic block on the upstream side. The illustrated radiators have grooves and protrusions formed on their upper and lower edges for fitting so that a larger area can be obtained by combining a plurality of radiators.

In a heating furnace as shown in Figure 1, when the temperature of the exhaust gas discharged from the heating chamber to the exhaust gas passage is 900°C, a hole diameter of 10 mmφ, an open area ratio of 40%, and a thickness of By installing a radiator with a ceramic block of 80 mm in diameter, the temperature of the exhaust gas was reduced to 870°C. This resulted in a 12% fuel savings. In another example 1200
By installing a radiator, we were able to reduce the temperature of exhaust gas from 1120°C to 1120°C.

As described above, in the method of the present invention, the radiator of the ceramic block is placed in the high-temperature gas flow path with the through hole inclined with respect to the gas flow direction, so that the radiator absorbs heat from the high-temperature gas. It has a high radiation rate and radiation rate to the heated object, and is extremely useful for improving thermal efficiency. Furthermore, the radiator is not limited to the vicinity of the exit of the heating chamber, but may be placed anywhere as long as it can face the object to be heated. for example,
The position may be as shown by the dashed line in FIG. However, since lowering the exhaust gas temperature as much as possible will improve thermal efficiency, in such cases,
It is best to install it in two places, one near the heating chamber exit. In addition, the radiator in the method of the present invention is a ceramic block, which has excellent heat resistance, can be mass-produced, and has excellent advantages such as high strength, low pressure loss during ventilation, and high emissivity. .

Furthermore, since the radiator suitable for use in the method of the present invention is formed by attaching a ceramic block to a heat-resistant frame in an appropriate state, the radiator exhibits the above-mentioned advantages of being a ceramic block. At the same time, it can easily meet the demands for large-area radiators.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an example of a heating furnace for carrying out the method of the present invention, FIG. 2 is a cross-sectional view of an example of a ceramic block used in the method of the present invention, and FIGS. 4 is a partially omitted plan view of an embodiment of a radiator using a ceramic block, and a sectional view taken along the line A--A in FIG. 3. FIG. 1...Burner port, 2...Heating chamber, 3...Heated object, 4...Exhaust gas passage, 5...Ceramic block, 5A...Through hole, 6...Radiator, 6A...Frame.

Claims (1)

[Scope of Claims] 1. A ceramic block having a large number of parallel through-holes as a radiator is placed in a high-temperature gas flow path in a heating chamber, and the through-hole direction is inclined with respect to the high-temperature gas flow direction. A radiation heating method characterized by being placed facing the object to be heated. 2 The diameter of the through hole of the ceramic block is 1 to
2. The radiation heating method according to claim 1, wherein the thickness of the ceramic block in the direction of passing through the through hole is 200 mm or more than the diameter of the through hole. 3. The radiation heating method according to claim 1 or 2, which is carried out by arranging the ceramic block so that the direction through which the through hole of the ceramic block passes is inclined by 5 to 20 degrees with respect to the flow direction of the high-temperature gas. . 4. A ceramic block having a large number of parallel through-holes is attached to the opening of a heat-resistant frame having one or more openings, with the penetration direction of the through-holes being inclined with respect to the frame surface. A radiant body. 5 The diameter of the through hole of the ceramic block is 1 to 1.
5. The radiator according to claim 4, wherein the thickness of the ceramic block in the direction of passing through the through hole is 200 mm or more than the diameter of the through hole. 6. Set the ceramic block so that the through-hole passing direction of the ceramic block is 5 to
The radiator according to claim 4 or 5, which is mounted so as to be inclined at 20 degrees. 7. A plurality of openings are provided in the frame, and two ceramic blocks are attached to each opening symmetrically with respect to the intermediate plane of both sides of the frame. Radiator in term or term 6.