JPH10274412A - Rotary heat-exchanger for annealing furnace of metal band - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart the sensible heat of a heating band combustion exhaust gas to a metal band through the preheat band of an annealing furnace by providing a passage for removing the residual heating band combustion exhaust gas from a heat storage body and passing a circulation gas for collecting the sensible heat of the heat storage body and a purging gas for removing foreign matters adhering thereto repeatedly. SOLUTION: A section (a) is coupled with a heating band exhaust gas passage 3 and the heat of combustion exhaust gas is absorbed to a heat storage body and stored therein thereat. At a stage where starting points O1 makes a transition to O2 through rotation of a heat-exchanger body 1, the section (a) makes a gradual transition to a current section (b) where a purge gas is blown in from a purge gas passage 4 in order to remove residual exhaust gas and foreign matters being left after the combustion exhaust gas was passed. At a stage where the section (a) made a transition from the starting points O1 through O2 to O3 , a circulation gas is from a circulation gas passage 5 into the section (a) where the circulation gas collects the heat from the heat storage body 2 and the temperature thereof is elevated before being fed to a preheat band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary exchanger for an annealing furnace, and more particularly, to an annealing treatment of a metal strip such as a cold-rolled steel sheet, an electromagnetic steel sheet or a stainless steel sheet, in the pre-tropical zone of the metal strip. The temperature of the circulating gas to be blown is efficiently raised by utilizing the heat of the exhaust gas in the heating zone.

[0002]

2. Description of the Related Art In a continuous annealing furnace or the like for performing an annealing treatment of a metal strip, heat is given to a circulating gas by passing a combustion exhaust gas such as a heating zone exhaust gas through a heat exchanger, and the heat is applied to a metal passing through a pre-tropical zone. The temperature is raised by blowing on the belt,
Conventionally, a convection type heat exchanger for recovering heat through a tube, or a regenerative burner as disclosed in Japanese Patent Publication No. 4-80969, furthermore, Japanese Patent Application Laid-Open Nos. 6-257938 and 6-257724. A regenerative radiant tube burner (hereinafter referred to as a regenerative R / T burner) as disclosed in Japanese Unexamined Patent Publication (Kokai) No. H11-157, and the like has been used.

[0003]

However, the above-mentioned conventional heat exchanger has the following problems. 1) Convection type heat exchanger: Most heat exchangers that recover the sensible heat of the flue gas have little effect on the circulating gas of the flue gas. Because it recovers heat, a large temperature difference and a large heat transfer area are required between the exhaust gas temperature and the circulating gas, and in order to maintain the required performance, it is inevitable that the scale will be large, On the other hand, when a sufficient space cannot be obtained due to a demand for downsizing of equipment, it has been difficult to improve the heat recovery rate. 2) Regenerative burners: Compensate for the drawbacks of convective heat exchangers, and can provide a high heat recovery rate for each pair of burners. (By the way, near 300 R / T in continuous annealing line with a processing capacity of 80,000 t / month)
However, it is not economical to convert all burners to regenerative burners because of the large investment amount, and there are many installations in narrow spaces, so there is a problem in terms of maintenance and practical application is difficult. Met. 3) Thermal storage type R / T burner: The heat burned by the burner is transmitted to the steel strip via the R / T burner. However, the R / T burner is exposed to high temperatures, and is caused by thermal stress and high temperature creep. There was a lifetime problem.

SUMMARY OF THE INVENTION It is an object of the present invention to efficiently recover the sensible heat of flue gas from a heating zone of a metal zone annealing furnace (including an open flame furnace or the like) using a large number of burners, and to use the recovered heat in the annealing furnace. Is to propose a new rotary heat exchanger that can be applied to a metal zone passing through the pre-tropical zone.

[0005]

SUMMARY OF THE INVENTION The present invention is a rotary heat exchanger which is arranged in an annealing furnace and raises the temperature of a circulating gas circulating in a pre-tropical zone through a heat storage body. A heat exchanger body having a plurality of sections and heat storage bodies arranged in all of them, and the sensible heat of the exhaust gas is stored in each section according to the continuous or intermittent rotation of the heat exchanger body. The heating zone exhaust gas to be applied, the heating zone combustion exhaust gas remaining when applying the sensible heat of the heating zone exhaust gas is removed, and a purge gas for removing foreign substances attached to the heat storage element and the sensible heat of the heat storage element are recovered. A path for sequentially and repeatedly passing a circulating gas for spraying a metal band passing through the pre-tropical zone of the annealing furnace to raise the temperature thereof, the rotary heat exchanger for a continuous annealing furnace for a metal band. And the sec As the tio emission was more, those consisting of at least three is convenient, also, the regenerator,
A material made of a material having good heat resistance and corrosion resistance such as Al ₂ O ₃ or SUS310 or SUS316 is advantageously suitable.

[0006] In the above configuration, the inlet path of the section through which the purge gas passes is connected to the outlet path of the section through which the circulating gas passes, and the outlet path is connected to the outlet path of the section through which the exhaust gas passes. And

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the main body of the heat exchanger is divided into a plurality of sections, and the sensible heat of the exhaust gas is applied to each section in accordance with the continuous or intermittent rotation of the heat exchanger main body. Cyclic repetition of a heat storage zone for applying heat to the heat storage body, a purge zone for removing foreign matter adhering to the heat storage body when applying the sensible heat of exhaust gas, and a heating zone for raising the temperature by passing circulating gas to the heat storage body after purging. Since it is formed, the sensible heat of the high-temperature exhaust gas can be efficiently recovered, and the number of pipes and the number of valves can be reduced because the heat storage body itself rotates. Also, by connecting the inlet path of the section through which the purge gas passes through to the outlet path of the section through which the circulating gas passes, and connecting the outlet path to the outlet path of the section through which the exhaust gas passes, the path of the purge gas can be obtained. It is not necessary to provide an exit route among the above, and there is an advantage that the equipment can be simplified.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to the drawings. FIG. 1 schematically shows a rotary heat exchanger for a metal strip annealing furnace according to the present invention. In the figure, reference numeral 1 denotes a shaft center L which is accommodated in a casing (indicated by a two-dot chain line). A heat exchanger body rotatable around
This heat exchanger body 1 has three sections a,
b and c, and the heat storage body 2 is arranged in all of them. 3 is a heating zone exhaust gas path leading to a heating zone such as a continuous annealing furnace, 4 is a purging gas path, and 5 is a circulating gas path leading to a pre-tropical zone such as a continuous annealing furnace. These paths are heat exchangers. It is fixed and held in the casing of the main body 1.

To recover the sensible heat of the exhaust gas of the heating zone while the heat exchanger body 1 is continuously rotated in the regenerative heat exchanger having the above configuration, the following procedure is followed.

First, when attention is paid to the heat storage element 2 of the section a, this section is connected to the heating zone exhaust gas path 3, where the heat of the combustion exhaust gas is absorbed (heat storage) by the heat storage element 2.

Next, when the starting point 0 ₁ shifts to 0 ₂ due to the rotation of the heat exchanger body 1, the section a gradually shifts to the current position of the section b. In this area, the purge gas flows from the purge gas passage 4. Exhaust gas and foreign substances remaining when the fuel gas is blown and passed through the combustion exhaust gas are removed. Here, the purge gas is blown into the heat storage body heated by the exhaust gas directly, and when it is blown into the pre-tropical metal zone through the circulating gas, foreign substances etc. contained in the exhaust gas adhere and the surface quality of the product deteriorates. Depending on the reason.

At the stage where the starting point 0 _{1 of the} section a shifts from 0 ₂ to 0 ₃ , the circulating gas is blown into the section a from the circulating gas path 5. It is collected, heated, and sent to a pre-tropical zone such as a continuous annealing furnace.

In the above description, the case where the temperature of the circulating gas is raised with focus on the section a has been described. However, the circulating gas is also applied to the other sections, that is, the sections b and c in the same manner as the section a. The temperature of the circulating gas is increased in such a manner that the heat exchanger body 1 rotates and the gas is supplied from each of the paths 3, 4, and 5, and the cycle is repeated cyclically.

In this type of heat exchanger, each gas pressure is set so as to satisfy (exhaust gas) <(purge gas) ≦ ((circulating gas)). Is not so significant, but it is also possible to provide a buffer area adjacent to sections a, b, c, especially if strictness is required.

The cycle pitch t of the heat exchanger body 1 is t = P / V (, where P (m) is the length of the section shown in FIG. 1 and V (m / s) is the rotation speed. It can be adjusted by changing the rotation speed. The rotation method of the heat exchanger body can adopt continuous rotation by an electric motor, discontinuous rotation using a cylinder and a rod, etc., and the type is not particularly limited. Also about 0.5-4rpm
And the value of the water equivalent of the regenerator / the value of the smaller of the water equivalent of the exhaust gas and the circulating gas> 4.
Here, the water equivalent is defined as mass flow rate of fluid (kg / sec) × specific heat of fluid (J / kg · K).

FIG. 2 schematically shows an example in which the heat exchanger S of the present invention is applied to a pre-tropical zone (PHS) of a continuous annealing furnace. In the figure, 6 is a hot air circulation fan (for circulating gas), 7 is an existing convection heat exchanger, and HS exhaust gas indicates heating zone exhaust gas.

For the heat storage element, Al ₂ O ₃ or SUS31
0, a material having good heat resistance and corrosion resistance, such as SUS316, is advantageously adapted, and may be a ball-shaped material or a honeycomb structure, and is not particularly limited. As the purge gas, any clean gas such as N ₂ or Ar gas can be applied. However, in view of cost, it is preferable to use pre-tropical circulating air.

FIG. 3 shows a section 4 of the passage 4 through which the gas for purging is passed is connected to the exit path 5b of the path 5 through which the circulating gas passes, and the exit path 4b of the section through which the exhaust gas passes. In such a configuration, it is not necessary to provide an outlet side path of the purge gas path 4, and the purge is performed using the circulating gas that has already been heated. Therefore, there is an advantage that the temperature drop of the heat storage body during purging is small.

FIG. 4 shows the apparatus shown in FIG. 3 in more detail, including the pre-tropical zone of the annealing furnace. In FIG. 4, 8 is a pre-tropical zone, 9 is a circulating air fan, and 10 is an exhaust fan. The fan 11 is a chimney. FIG. 5 is a plan view showing a heat exchanger according to the present invention. In the figure, reference numeral 12 denotes a sector plate for rotatably holding the main body of the heat exchanger. A purge gas blowing port 13 can be provided adjacent to the sector plate 12.

[0020]

[Embodiment] The equipment shown in FIG.
When performing continuous annealing of cold-rolled steel sheets of 0.5 to 2.3 mm and width of 700 to 1850 mm under the following conditions, the recovery rate of exhaust heat from the exhaust gas of the heating zone (heat rising heat of pre-tropical circulating air / sensible heat of exhaust gas), heating zone Conventional convection type heat exchanger for steel strip temperature, fuel consumption rate, furnace temperature in heating zone, burner burning load in heating zone, radiant tube life, number of switching valves, equipment cost, etc. And a comparative survey was conducted. The results are shown in Table 1 (adaptation is with the heat exchanger according to the invention).

Treatment conditions Exhaust gas in heating zone Flow rate: 35310 Nm ³ / hr Fluid: M gas combustion exhaust gas Inlet temperature of heat exchanger: 627 ° C Outlet temperature of heat exchanger: 403 ° C Heat exchange existing side pressure: -330 mmAq Pre-tropical circulation Gas Flow rate: 66365Nm ³ / hr Fluid: Air Inlet temperature of heat exchanger: 360 ° C Outlet temperature of heat exchanger: 575 ° C Heat exchange existing pressure: +240 mmAq Purge gas Fluid: Air (circulating gas) Specifications of heat exchanger Applicable example: Rotary heat storage type heat exchanger (Heat exchange amount: 4.8 x 10 ⁶
kcal / hr, Fig. 1) Comparative example: Plate type heat exchanger (in tube: air, outside tube: exhaust gas, heat exchange amount: 5.4 × 10 ⁶ Kcal / hr) Heat storage material: SUS304 honeycomb structure

[0022]

[Table 1]

As is clear from Table 1, the regenerative heat exchanger according to the present invention (adapted example) has no adverse effect due to the combustion exhaust gas, and has a waste heat recovery rate of 15% or more than the conventional convective heat exchanger. It was confirmed that the temperature of the steel strip on the heating side increased by about 100 ° C, and that all other items were improving.

The operation results when the plate heat exchanger (Comparative Example 1), the rotary heat exchanger without using purge gas (Comparative Example 2), and the heat exchanger according to the present invention (Compatible Example) are used are as follows. Met.

COMPARATIVE EXAMPLE 1 Air temperature 260 on the heat exchanger inlet side
℃ (107000Nm ³ / hr) Air temperature 310 ° C (107000Nm ³ / hr) at the outlet of the heat exchanger 656 ° C (60600Nm ³ / hr) of the exhaust gas at the inlet of the heat exchanger 560 ° C (60 ° C at the outlet of the heat exchanger) 60600Nm ³ / hr) Applicable example: Air temperature at the heat exchanger inlet side is 365 ° C (62240Nm ³
/ hr) Air temperature at the outlet of the heat exchanger 575 ° C (54550Nm ³ / hr) Exhaust gas temperature at the inlet of the heat exchanger 635 ° C (51240Nm ³ / hr) Exhaust gas temperature at the outlet of the heat exchanger 430 ° C (58930Nm ³ / hr) )

[0026]

[Table 2]

[0027]

According to the present invention, not only the number and the number of pipes and valves attached to the heat exchanger are small, but also the apparatus itself can be made compact, and the heat loss of the combustion exhaust gas can be efficiently reduced. Can be collected. In addition, the effective recovery of the heat loss of the combustion exhaust gas allows the metal zone to be heated effectively in the pre-tropical zone. Therefore, the set temperature of the heating zone should be set to the minimum temperature required for the treatment of steel sheets. Can
(The furnace temperature can be set low.) As a result, the equipment cost can be reduced, the combustion load of the burner can be reduced, and the life of the radiant tube can be significantly extended. In addition, by changing the outlet hood and the inlet hood of the heat exchanger, the passage area of the exhaust gas and the air can be selected relatively freely.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of a main body of a rotary heat exchanger according to the present invention.

FIG. 2 is a diagram showing an example in which a rotary heat exchanger according to the present invention is applied to a pre-tropical zone of a continuous annealing furnace.

FIG. 3 is a diagram schematically showing another example of the rotary heat exchanger according to the present invention.

FIG. 4 is a view more specifically showing an apparatus including the heat exchanger main body shown in FIG. 3, including a pre-tropical zone.

FIG. 5 shows a plan view of a rotary heat exchanger according to the invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat exchanger main body 2 Heat storage body 3 Heating zone combustion exhaust gas path 4 Purging gas path 5 Circulating gas path 6 Hot air circulation fan 7 Convection type heat exchanger 8 Pretropical zone 9 Sector plate 10 Purging gas inlet a section b section c Section L axis

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Futhiko Nakagawa 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. 1-chome (without address) Mizushima Works, Kawasaki Steel Corporation (72) Inventor Yoshiharu Fujiwara 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Prefecture (without address) Mizushima Works, Kawasaki Steel Corporation

Claims (3)

[Claims] 1. A rotary heat exchanger disposed in an annealing furnace for raising the temperature of a circulating gas circulating in a pre-tropical zone through a heat storage body, the heat exchanger having a plurality of sections, all of which have a plurality of sections. The heat exchanger body in which the heat storage body is arranged, and the combustion exhaust gas that applies the sensible heat of the combustion exhaust gas to the heat storage body in each of the sections according to the continuous or intermittent rotation of the heat exchanger body. A purging gas that removes the combustion exhaust gas remaining in the heat accumulator when applying sensible heat and removes foreign matter adhering to the heat accumulator, and a metal band that passes through the pre-tropical zone of the annealing furnace by collecting the sensible heat of the heat accumulator And a path for sequentially and repeatedly passing a circulating gas for increasing the temperature by blowing the gas to the rotary heat exchanger for a metal strip annealing furnace. 2. The heat storage body is made of Al ₂ O ₃ or SUS310, SUS3
The rotary heat exchanger for an annealing furnace according to claim 1, comprising a material having good heat resistance and corrosion resistance, such as 16. 3. An inlet path of the section through which the purging gas passes is connected to an outlet path of the section through which the circulating gas passes.
The rotary heat exchanger for an annealing furnace according to claim 1, wherein the outlet path is connected to an outlet path of a section through which the combustion exhaust gas passes.