JPS596330A - Optimizing method of atmospheric gas flow in batch-type coil annealing furnace - Google Patents

Abstract

PURPOSE:To effectively obtain coils having stable annealing quality, by a method wherein thermal efficiency in furnace is raised by allowing respective stage spacer put on fixedly with respective stage coil stacked by stage in furnace to be arranged in a specified ratio to an opening area on respective outer peripheral surface. CONSTITUTION:The spacer arrangement is studied by using the simulation model of batch-type coil annealing furnace so constructed as shown in the figure. Respective stacked by stage coils 1-4 of stages A-D are classified and there are a single spacer 5, respective spacers 6-8, inner and outer covers 9, 10, a diffuse 11, a base fan 12 and thermometers 13, 14 upward from the base. The spacer has general guide vane, as shown in the figure, that is, rib construction. Therefrom, the optimum arrangement of spacer when height of spacer rib is made abocet 20-60mm., is made to be a ratio of formula 1 to the opening area S on respective outer peripheral surface successively upward from the spacer 5 to upper stage. Further, the area S is given as formula II [(b) is outer diameter of spacer, (c) is width of rib, (d) is number of rib and H is height of rib].

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for optimizing atmospheric gas flow in a batch coil annealing furnace.

The cold-rolled strip is wound into tight coils and stacked in multiple stages inside the inner cover of a batch coil annealing furnace to impart mechanical properties suitable for specifications. The material is heated in a furnace using K such as a direct flame, electric heat, or radiant tube on the outside, and is subjected to annealing under an atmosphere gas flow that is indirectly heated.

However, the flow of atmospheric gas inside the inner cover is generally complicated, but in order to smooth this flow and effectively heat the coil to raise its temperature and cool it to lower its temperature, the coils must be stacked in advance. Spacers or convectors are arranged at each stage of the coils, and the heating or cooling described above is promoted mainly from the end faces of the coils by guiding the convection of atmospheric gas between the coils.

However, the selection of this spacer has traditionally been determined mainly based on empirical rules, and the relationship between the flow rate and flow velocity of the atmospheric gas has never been investigated to find a fit that will maximize the thermal efficiency within the furnace. .

Therefore, in order to ensure a predetermined annealing quality, in many cases long heating operations are always performed on the safe side, and excess input heat and operating time are generally wasted.

In recent years, there has been a strong demand for eliminating the above-mentioned waste in this type of batch coil annealing furnace from the viewpoint of energy saving.

In particular, in order to shorten the heating time of batch-type coil annealing furnaces, thereby reducing the unit consumption, and increasing the efficiency of Bell Nohka, we developed an optimal spacer arrangement using a batch-type coil annealing furnace simulation model. It was investigated.

Here, Figure 1 shows the framework of a batch type coil annealing furnace used for this type of use, numbered 1-4 and designated by A.
The coils stacked in each stage from stage to D are distinguished, 5 is a single spacer, 6 to 8 are spacers for each stage from A to C, 9 is an inner cover, 10 is an outer cover, 11 is a diffuser, 1
9 is the base fan, 1B is the base temperature needle, and 14 is the bell temperature needle. In addition, Fig. 2+a+ shows the general appearance plane of the spacer along with a partial illustration of the internal guide vane or rib configuration, and Fig. 2(b) shows the A-A cross section, and Fig.
BB cross section is shown at.

In this invention, first, a simulation model of a batch type coil annealing furnace was created as a means of estimating the internal temperature of the coil during the annealing process.

This simulation model takes into account almost all thermal phenomena inside the annealing furnace, maintains a heat balance for the combustion gas and the atmospheric gas inside the inner cover, and allows boundary conditions such as those around the coil to be calculated within the model. I made it.

The overall flow of this model is as shown in Figure 8. Initial conditions such as coil, spacer, and inner cover dimensions are input as data, and after taking into account the necessary coefficients from the initial conditions, We calculated the temperature distribution at several dozen points inside the coil, as well as the temperature distribution at several dozen points each for the spacer, inner cover, and bell.

This simulation model was compared and revised with actual temperature measurement results until it could operate just as it would in actual operation, with the aim of improving the level of accuracy to an extremely high level.

An example of comparison between this measured value and the calculated value by the model is shown in the fourth section.
As shown in Fig. 5. Here, the coldest point temperature of the stacked coil 8 of 0 stages (hereinafter simply referred to as C, F3 temperature -1-> is 6
The error between the measured value and the calculated value near 00°C is approximately ±5
It has been confirmed that it lasts for about C. In Figure 4, the stacked coils are arranged in the order of stages A to D (thickness: 1.5 m).
x width 1012mm, weight 88.66) 7), (thickness z, omx width 102 sum *'M11 B8.
80) 7), (thickness O, ? IIXI@987ml
+ weight'lK'87.88 tons), (thickness 1.611 proverbs x
@ 1008 am.

Weight @ 28.88 ) n), then tech charge weight G'
l 14Ll tons Also in Figure 5, (thickness 0.8
Width: 908 mm, 1 layer: 8 B, 62 mm), (Thickness: 9 mm)
71111X width 106611III, weight t41-70
Door ), (thickness Q, 9 mm x width 1 $ a 811 m, i
t amount 44-22 ) n), (thickness lL'7 x m x width 1
00B order 9-fold 87.501-n) and charge type needle is 1
In both figures, the bell temperature is plotted as △, the base temperature is plotted as ○, and the C and S+ severity is plotted as -, and the model calculation values are plotted as broken lines.

K K Using the above simulation model, width
When 1000mm coils are stacked in four tiers, the rib height is changed in the order of the optimal spacer arrangement in the most basic stacking configuration, that is, tier A, single, tier B, and tier 0.
We investigated the spacer arrangement that would give the highest thermal efficiency.

Considering the relationship between the flow rate of atmospheric gas and its flow velocity, which affects the improvement of thermal efficiency, for example, if the rib height of the A-stage spacer is reduced, the flow rate between the single spacer - the 9B-stage spacer and the 0-stage spacer will increase. The gas flow rate increases and the flow velocity also increases, in which case the gas flow rate flowing through the A-stage spacer decreases, but the increase in flow velocity will reduce this until the rib height reaches a certain height, that is, the optimal rib height. It is thought that the thermal efficiency of the entire furnace increases because the spacers in the B and C stages absorb more than the loss in the A stage. In order to find the optimal spacer arrangement based on this idea, we used an annealing simulation model and varied the spacer lip heights of A stage, single stage, B stage, and 0 stage. I investigated the relationship between time ■1.

Here, we performed a model simulation assuming the following conditions.

111 #l effect m = cp XΔtxW/input heat amount C
Input heat amount C heat (0-14Kcal/9. ”C) Jt
, : Temperature rise W : Coil weight.

1113 Reheating conditions Combustion gas maximum input flow rate M gas: 2885 Kcal/Nm 8.400 Nm
8/h-Coil initial temperature: 40”C Bell initial temperature: 500℃ (8+ heating pattern; free heating bell upper limit 810℃ Base upper limit 685℃ 141 coil stacking situation Large unit weight 85.74) Stacked in 4 layers with , coil width 100
0 (5) Estimated coil temperature position The position equivalent to the coldest point of each stage coil (6) Judgment of finished firing When the temperature equivalent to the coldest point of all stage coils reaches 600°C First, measure the height of the A stage spacer rib in Table 1 The results are shown in Table 1 and Figure 6.

As a result, the optimal rib height of the A-stage spacer is 20 to 6
(It has been found that a range of 1 m+ is suitable.

Below, the rib height of the A-stage spacer is set to 13 Qrm, which provides good results in thermal dynamics and baking time, and
Table 2-4 shows the changes in thermal dynamics and baking time when the height of each subaza rib of single (B), B stage, and C stage is changed. #! Shown in Figures 7-9.

As is clear from the thermal effect and baked clay time shown in these tables and figures, as well as the same curve, the spacer rib heights of the single, B tier and 0 tier are 6 to 80 mm, 16 to 60 mm, and 16 to 60 mm, respectively. We have newly discovered that 18~(%(311) is suitable.-□Synthesizing the above new knowledge, when the spacer rib height is set to about BO~fiQ*i, the optimal spacer arrangement is For the opening area in (0,8~0.Fl): l:
(o, 8-1.0): An arrangement according to (0,9-1.1) is necessary for optimizing the atmospheric gas flow in the batch coil annealing 1 furnace.

This invention proposes a spacer arrangement method consisting of spacer opening area deadening based on these findings. Each spacer on which each stage of stacked coils is mounted is sequentially moved from the single spacer on the base toward the upper stage, and the opening area on the outer peripheral surface of each spacer is as follows (0.8 to 0.a) + 1: (o,
s~1.0): (0,9~1.1) This is a concrete means for optimizing the atmospheric gas flow in a batch type coil annealing furnace.

This spacer arrangement ratio indicates the spacer opening area ratio, and the spacer opening area is calculated by the following formula ゛S=(πXb
-cXd)XH b: Spacer diameter (outer diameter) C: Rib width, d: Number of ribs, H: Rib height. 2600"'n diameter. If it is 5 widths and 40 locations, it will be 7164XH 2.

Examples are given below. When annealing each stacked coil at a temperature of 0.8.6 degrees or higher in a batch type annealing furnace, the charge organization shown in Table 5 was performed.

In the table, as a spacer, the opening area ratio of single, A stage, B stage and 0 stage is OJ! 120.8 : 1
under a free heating pattern, annealing temperature 60
By heating to 0°C, the current spacer arrangement, A stage height of 70IIIm, and single: AR: BR1
The spacer opening area ratio for the 0th stage is 0.5 g 121!
Compared to the case of 1.8, it is possible to reduce the baking time to approximately 8 hours (approximately 5% improvement due to the shortened thermal efficiency in ■), and the fuel consumption can be reduced by approximately 50 x 108 Kc modified T. The elongation of the annealed cold-rolled steel sheet is also high, and it is possible to obtain an annealed cold-rolled steel sheet of good quality η.

As described above, this invention makes it possible to significantly shorten the annealing time, improve heat efficiency, and reduce fuel consumption when performing annealing in a batch-type annealing furnace. By increasing the efficiency of the furnace, it is possible to efficiently produce cold-rolled coils with reliable annealing quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a batch-type annealing furnace, and IEZ diagram fal is a plan view of a spacer showing a part of rib arrangement positions. Qw Figure 1bl is the A-A sectional view of Figure 2-2(a), the second
Figure 1cl is a BB sectional view of Figure 2 (al), Figure 8 is a
Flowchart of the annealing simulation model. Figures 4 and 8A5 are graphs to confirm the fine changes of this simulation model. Figures 6 to 9 are changes in the height of the spacer ribs of the A, single, B, and IC stages. This is a 1° graph showing the relationship between the heat effect wheel and the baking time in the case of 1°. Patent applicant: Kawasaki Steel Corporation Figure 1 Figure 2 (b) Figure 4 Simulation E/:I; 7 Figure Nngll/Sugo Saarib IvI (7nfn) No. 8
Figure 9

Claims (1)

[Claims] L When stacking cold-rolled strip coils in a batch annealing furnace and heat-treating them, each stage spacer on which each stage of stacked coils is placed may be replaced by a single spacer on the base. For each opening area on the outer peripheral surface toward the upper stage, the following ratio (o, s ~ 0.5): 1: (o, 8 ~ i, o
): A method for optimizing the flow of atmospheric gas in a batch coil annealing furnace, comprising forming an arrangement according to (0.9 to 1.1).