WO2002014773A1

WO2002014773A1 - Heat reservoir

Info

Publication number: WO2002014773A1
Application number: PCT/JP2001/006985
Authority: WO
Inventors: Yutaka Suzukawa; Isao Mori; Hirokazu Katsushima; Yoshiyuki Kasai
Original assignee: Nkk Corporation; Nippon Furnace Kogyo Kaisha, Ltd.; Ngk Insulators, Ltd.
Priority date: 2000-08-14
Filing date: 2001-08-13
Publication date: 2002-02-21
Also published as: JP2004286232A; AU2001278719A1

Abstract

A heat reservoir of regenerative burner, comprising a plurality of honeycomb structural bodies stacked in a gas flowing direction and divided into a plurality of parts also in a cross section orthogonal to the gas flowing direction, wherein the honeycomb structural bodies have a relation specified in Table 9 below, whereby the cracking of the heat reservoir by a thermal stress can be prevented to use stably over a long period. In Table 6, (T) is the temperature of honeycomb in use, (h) is the height of honeycomb, (W) is the width of honeycomb, (d) is the depth of honeycomb, (w x d) is the projected area of the gas passage cross section of honeycomb, and (w x d x h) is the volume of honeycomb. Table 6 Temperature range Where, T: Temperature of honeycomb in use h: Height of honeycomb w: Width of honeycomb d: Depth of honeycomb w x d: Projected area of gas passage cross section of honeycomb w x d x h: Volume of honeycomb

Description

Technical field

The present invention relates to a heat storage element, and more particularly to a heat storage element that can be prevented from cracking due to thermal stress and can be used stably for a long period of time.

Light background technology food

Here, the prior art will be described by taking as an example a regenerator for a regenerative type burner, which is one of the purposes of using the regenerator according to the present invention.

The regenerative burner is equipped with a heat storage unit attached to each burner, and exchanges heat between the combustion exhaust gas and the combustion air, thereby obtaining high-temperature preheated air and performing highly efficient combustion. It is Pana.

Hereinafter, the regenerative parner will be described with reference to the drawings, taking an example in which it is installed in a heating furnace.

FIG. 4 is a schematic sectional view showing a heating furnace in which a regenerative parner is installed.

In Fig. 4, 1 is a heating furnace, 2a 2b is a pair of regenerative parners installed facing the furnace wall of heating furnace 1, 3a 3b is a regenerative parner 2a 2b It is a heat storage body provided inside. The heat storage bodies 3a and 3b preferably have a large specific surface area, and are composed of a plurality of honeycomb structures as disclosed in Japanese Patent Application Laid-Open No. Hei 4-251190. 4a and 4b are fuel shut-off valves, and while this valve is open, pressurized fuel is supplied from a fuel supply source (not shown) to the parner 2a 2b at a predetermined flow rate. .

5a and 5b are combustion air valves, and while this valve is open, pressurized air is supplied to the parner 2a2b at a predetermined flow rate from an air supply source (not shown). . Numerals 6a and 6b denote flue gas valves. While these valves are open, flue gas that has passed through the regenerators 3a and 3b by an exhaust blower (not shown in the figure) Is aspirated at a predetermined flow rate and released to the atmosphere. Reference numeral 7 denotes an object to be heated such as a steel slab in the heating furnace 1. D1 and D2 are thermometers, T1 is a high temperature (combustion side) thermometer, and T2 is a low temperature (anti-combustion side) thermometer.

In FIG. 4, for example, when one of the burners 2a is in a combustion state, the fuel cutoff valve 4a is opened to supply fuel. Further, the combustion air valve 5a opens, the combustion exhaust gas valve 6a closes, and air is pushed into one of the heat storage bodies 3a. The air that has passed through the heat storage body 3a deprives the heat storage body 3a of heat and is supplied to the burner 2a as high-temperature preheated air. On the other hand, at this time, in the other parner 2 b, both the fuel cutoff valve 4 b and the combustion air valve 5 are closed, and the combustion exhaust gas valve 6 b is open, and the gas in the furnace is sucked from the parner 2 b and the regenerator 3 b After heating this through b, it is exhausted by an exhaust blower.

When performing thermal storage combustion in the heating furnace 1 using the thermal storage type parners 2a and 2b, alternating combustion is performed in which the combustion between the panners 2a and 2b is alternately performed at regular intervals. The switching time is generally short, about 30 seconds to 2 minutes.

Then, when the combustion is switched and the other parner 2b is in a combustion state, the fuel cutoff valve 4b and the combustion air valve 5b are both opened, the combustion exhaust gas valve 6b is closed, and the other heat storage element 3b is closed. Air is supplied to b. The air that has passed through the high-temperature heat storage unit 3 b deprives the heat storage unit 3 b of heat and becomes high-temperature preheated air to be supplied to the parner 2 b.

On the other hand, at this time, in one parner 2a, both the fuel cutoff valve 4a and the combustion air valve 5a are closed, and the combustion exhaust gas valve 6a is open, and the gas in the furnace is sucked from the parner 2a and the regenerator After heating through 3a, it is exhausted by an exhaust blower.

In a heating furnace using such a regenerative burner, when the regenerative burner is in a thermal storage state, the furnace gas is sucked into the burner, so that the high temperature side of the regenerator is generally The furnace is heated to the gas temperature. The gas in the furnace that has passed through the regenerator heats the regenerator to a low temperature. If the suction of the furnace gas is continued, it is possible to heat the inside of the regenerator to the furnace gas temperature, but if the suction of the furnace gas is continued, it will pass through the regenerator The gas temperature on the low temperature side of the regenerator from which the in-furnace gas flows out rises. Since the gas inside the furnace that has passed through the regenerator is discharged outside the system via the flue gas valve, the gas temperature on the low temperature side of the regenerator can be obtained at the heat-resistant temperature of the flue gas valve, for example, at an economical price. In the valve

It cannot exceed 350 ° C.

There is a problem if the gas temperature in the furnace on the low temperature side of the heat storage body is too low. That is, if the combustion exhaust gas contains sulfur, etc. in the fuel component in addition to water, a part of the combustion exhaust gas may condense at a temperature of about 150 ° C or less and generate combustion water. is there. Since the combustion water corrodes the piping and the flue gas valve, the gas temperature in the furnace on the low temperature side of the regenerator may be maintained at a maximum of 350 ° C or less, and an average of about 180 ° C. preferable.

On the other hand, when the regenerative burner is in the combustion state, normal-temperature combustion air is supplied to the low-temperature side of the regenerator, and while passing through the regenerator, the high-temperature regenerator removes heat and is preheated. Supplied to PANA. When operating the heat storage parner, it is preferable to operate so that preheated air with the highest possible temperature can be obtained. The maximum temperature of the preheated air obtained by the regenerative burner is the furnace gas temperature. In practice, it is sufficient that a preheated air temperature lower by about 50 to 100 ° C. than the gas temperature in the furnace is obtained.

That is, in a heat storage element of a regeneratively-operated parner that is properly designed and operated, the temperature of the gas passing through the heat storage element on the high-temperature side of the heat storage element is 100 ° from the furnace gas temperature and the furnace gas temperature. The temperature changes within the range of the preheated air temperature which is lower by about C. On the other hand, on the low temperature side, the combustion state starts from about 350 ° C which is the maximum temperature of the outflow temperature of the furnace gas when the heat storage state is completed. At the time of completion, the temperature changes within a temperature range of about 30 ° C, which is the temperature of room temperature air. As described above, it has been empirically known that a conventional heat storage element for a regenerative burner has a large specific surface area, and a honeycomb structure having a large specific surface area is known. Used.

For example, in a regenerative burner with a combustion capacity of 100,000 kca 1 ZH, as shown in Fig. 5, the size of the regenerator 3 is such that the gas cross section is 40 It is 400 mm wide and the height of the heat storage body is about 400 mm. Conventionally, a rectangular parallelepiped honeycomb structure with a length of 100 mm, a width of 100 mm, and a height of 100 mm has a cross section of 4 x 4 = 1 _Λ

Four

Six were arranged, and four layers were stacked in the height direction. The cross-sectional area of the gas passage (thin tube) of the honeycomb structure constituting the heat storage body was the same in any of the honeycomb structures.

FIG. 6 is a schematic perspective view showing one honeycomb structure 8 constituting the heat storage body. Here, the length, width, and height dimensions of the honeycomb structure are denoted by symbols d, w, and h, respectively. Indicated by FIG. 7 is an enlarged view of the gas passage of the honeycomb structure 8. The wall thickness of the honeycomb structure 8 is indicated by a symbol t, and the distance between the walls (pitch) is indicated by a symbol P.

According to the study of the present inventors, for example, in the case of a honeycomb structure having a wall thickness t of 1.5 mm or less and a pitch P of 5 mm or less, the specific surface area of the heat storage body is 60 Οπι ² / !! ! ³ or more, the heat exchange performance is good, and if the wall thickness t is about 1.5 mm, it takes only about 1 s for the heat to be transmitted to the center of the wall by heat conduction and equalize. However, it has been found that it has excellent responsiveness to temperature changes.

As described above, in the conventional heat storage element for a heat storage type burner, a heat storage element is formed by combining a rectangular parallelepiped honeycomb structure having a length of about 100 mm, a width of about 100 mm and a height of about 100 mm. However, this method has a problem that the honeycomb structure on the high-temperature side, into which the furnace gas flows, is cracked by thermal stress at the time of heating, the exchange cycle of the heat storage material is short, and the maintenance cost is increased. Stopping the equipment for replacement caused an increase in production machine losses.

In order to achieve the above-mentioned object, the inventors of the present application have proposed a heat storage body disclosed in Japanese Patent Application Laid-Open No. H8-2476771 did. As shown in FIG. 8, the heat storage body has a plurality of stacked honeycomb structures in a direction in which the combustion air is fed, and also has a plurality of honeycomb structures divided in a cross section orthogonal to the flow of air. The gas passage on the high temperature side (combustion side) of the body has a larger area than the low temperature side (anti-combustion side). The reason for such a configuration is as follows. The cracks in the honeycomb structure occur when the thermal stress generated due to the temperature deviation in the height direction of the heat storage body-(in the axial direction of the thin tube) exceeds the material strength limit. Therefore, taking into account that the strength of the honeycomb structure decreases at high temperatures, _g

If the temperature deviation generated in the honeycomb structure is reduced, cracking can be prevented.

According to the above-mentioned prior invention, cracks due to thermal stress can be prevented, and a heat storage element that can be used stably for a long period of time can be obtained. However, the operating temperature of the honeycomb structure and the shape of the honeycomb structure, that is, the honeycomb structure, The relationship between the height (h), width (w), depth (d), projected area (cross-sectional area of thin tube) (wXd) and volume (wXdXh) of the gas passage It had not yet been specified.

Accordingly, an object of the present invention is to further improve the above-described prior invention, to prevent the cracks due to thermal stress, to use a honeycomb structure for obtaining a heat storage element that can be used stably for a long period of time, and to improve the honeycomb structure. To provide a heat storage body that quantitatively defines the relationship with the shape of the body. Disclosure of the invention

According to a first aspect of the present invention, there is provided a honeycomb structure including a porous honeycomb structure, wherein the honeycomb structure is heated by passing a high-temperature gas through the honeycomb structure for a certain period of time and heated to a high temperature for the next predetermined period of time. In the heat storage body that repeatedly heats the low-temperature gas by passing the low-temperature gas through the structure, the plurality of honeycomb structures are stacked in the direction of the gas flow, and are orthogonal to the gas flow. Also, the honeycomb structure is divided into a plurality of sections in the same cross section as described above.

Τ Honeycomb operating temperature

h /, two cam height

/, Width of two cams

d Honeycomb depth

w X d Projected area of gas passage cross section of honeycomb

x d X h is characterized by having a relationship defined by the volume of the honeycomb. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing the experimental results of the durability of the honeycomb structure.

FIG. 2 is a schematic perspective view showing the heat storage body used in the embodiment of the present invention.

FIG. 3 is a schematic perspective view showing a honeycomb structure of a hexagonal gas passage.

FIG. 4 is a schematic sectional view showing a regenerative burner heating furnace.

FIG. 5 is a schematic perspective view showing a heat storage body composed of a honeycomb structure having the same gas passage channel area.

FIG. 6 is a schematic perspective view showing a honeycomb structure of a test piece.

FIG. 7 is an enlarged view showing a gas passage.

FIG. 8 is a schematic perspective view showing the heat storage body of the prior invention. BEST MODE FOR CARRYING OUT THE INVENTION

The inventors of the present application have found that the use temperature of the honeycomb structure in the heat storage and the shape of the honeycomb structure, that is, the height of the honeycomb structure (h) can prevent cracking due to thermal stress and can be used stably for a long period of time. , Width (w;), depth (d), projected area of gas passage cross-section (cross-sectional area of thin tube) (wXd) and volume (wXdXh) Was performed.

That is, in a heating furnace equipped with a regenerative parner as shown in Fig. 4, ceramic honeycomb structures with different dimensions w, d, and h were tested on the high temperature side of the regenerator shown in Fig. 8. The average value of the furnace gas temperature measured by the thermometer T1 is changed from 1300 ° C to 400 ° C by changing the combustion load of the regenerative burner, and at the same time, the temperature is measured by the thermometer T2. The long-term durability test of the heat storage material was performed by adjusting the furnace gas flow rate so that the average value of the furnace gas temperature was constant at approximately 200 ° C. The test piece was made of ceramics containing 90% or more of alumina.

As a result, the result as shown in FIG. 1 was obtained. In FIG. 1, the horizontal axis shows the average temperature of the gas in the furnace measured by the thermometer T1, and the vertical axis shows the dimensions, w, d, and h of the honeycomb test piece. The solid line in the figure indicates the temperature range in which the honeycomb structure did not crack.

As is evident from Fig. 1, it was found that the smaller the gas passage cross-sectional area (wX d) and the height of the honeycomb (h) of the honeycomb structure, the smaller the cracks were. It was also found that (wX d) and (h) can be larger as the operating temperature is lower. The above is disclosed in the preceding invention.

The present invention further specifically relates to the use temperature of the honeycomb structure, the height (h), the width (w), the depth (d), and the projected area of the gas passage cross section (cross sectional area of the thin tube) of the honeycomb structure.

The relationship between (wXd) and volume (wXdXh) is defined as shown in Table 2, and a heat storage material that can prevent cracking due to thermal stress and can be used stably for ft period is obtained. Table 2 shows the operating temperature in the high-temperature area (1 100 ° C <T≤1200 ° C, 1200 ° C <T) where cracks are most likely to occur, and the height (h) and width (w) of the honeycomb structure. ), Depth (d), projection area of gas passage cross section (cross-sectional area of thin tube) (wX d) and volume (wX d X h).

Table 2

However, the operating temperature of T honeycomb

h /, two cam height.

w /, two cam width

d Honeycomb depth

w X d Projected area of gas passage cross section of honeycomb

w X d X h Volume of honeycomb In addition to the above-mentioned rectangular honeycomb structure having a gas passage channel, the present inventors have also considered a honeycomb structure having a hexagonal gas passage channel shown in FIG. Experimented. As a result, they found that if the dimension X in Fig. 3 was read as w and y was read as d, the results in Table 3 above would apply.

Next, the present invention will be further described with reference to examples.

(Example 1)

Combination shown in Table 3 in a continuous billet heating furnace for wire rods with a maximum furnace temperature of 125 ° C, as shown in Fig. 2, length 45 O mm x width 45 O mm X height A regenerative parner with a thermal storage of 400 mm was installed and used for two years. As a result, problems such as cracks in the honeycomb structure did not become apparent.

Table 3

(Example 2)

The continuous slab heating furnace for hot rolling with a maximum furnace temperature of 135 ° C was combined with the combination shown in Table 4. _g

Therefore, a regenerative burner having a regenerator of the same dimensions as in Example 1 was installed and used for two years. As a result, defects such as cracks in the honeycomb structure did not appear. Table 4

As described above, according to the present invention, by further improving the prior invention, by quantitatively defining the relationship between the operating temperature of the honeycomb structure and the shape of the honeycomb structure, the thermal stress is reduced. Cracks can be prevented, and a heat storage element that can be used stably for a long period of time can be obtained.In addition, maintenance costs can be reduced by extending the replacement cycle of the honeycomb structure, and production can be stopped by replacing equipment for replacement. Useful effects such as the effect of reducing mechanical loss can be obtained.

Claims

The scope of the claims

1. The honeycomb structure is made of a porous honeycomb structure. The honeycomb structure is heated by passing high-temperature gas through the honeycomb structure for a certain period of time, and then heated to a high temperature for the next predetermined period. In a heat storage body that repeatedly heats the low-temperature gas by passing gas,

A plurality of the honeycomb structures are stacked in the direction of the gas flow, and are divided into a plurality of sections also in a cross section orthogonal to the flow of the gas.

Table 5

However, the operating temperature of T honeycomb

h Honeycomb height

w The width of the honeycomb

d Honeycomb depth

w X d Projected area of gas passage cross section of honeycomb

w X d X h A regenerator characterized by having a relationship defined by the volume of a honeycomb.