JPS6346301A - Exhaust-heat recovery operation method in sintering facility - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention increases the amount of heat contained in the sintered cake supplied to the cooler, prevents corrosion of exhaust gas treatment equipment, and increases the amount of exhaust heat recovered in the cooler. This invention relates to an exhaust heat recovery operation method in a sintering facility that aims to achieve this.

(Prior art) The sintering reaction progresses from the upper layer to the lower layer of the pipette by the combustion of coke powder mixed in the raw materials and sucks air, and as shown in Figure 3, the maximum temperature is 1300~ 135
It reaches 0℃.

Conventionally, as a technology to increase the amount of waste heat recovered in the cooler, the overall amount of exhaust gas is adjusted and the sintering end points (hereinafter referred to as B, T, P) are managed as close to the ore discharge area as possible, and after the completion of sintering, This also prevents the sintered ore on top of the sintering machine from being cooled by the suction air, and increases the temperature of the sintered cake fed to the cooler to increase the amount of waste heat recovered. This is done as general operational management. However, due to changes in raw materials, moisture, and other conditions, fluctuations in ventilation occur, and this is accompanied by B.

T and P also change. If ventilation deteriorates, the sintering progress speed will be delayed and B, T, and P will depend on the ore discharge side.

Therefore, if B, T, and P are managed to the limit in the ore discharge section, the ore will be discharged without completing the sintering reaction, and the yield will decrease.
This will lead to deterioration in quality. Therefore, in actual operation, it is necessary to manage the optimal positions B, T, and P on the safe side, that is, on the raw material supply side, and there is a problem that the heat recovery effect cannot be obtained in the lar.

On the other hand, Japanese Patent Application No. 55-139615 proposes a method of increasing the temperature of the sintered cake fed to the sicooler by throttling the damper at the final stage of the sintering machine wind box and reducing the amount of exhaust gas. .

However, the effect of reducing the amount of heat transferred to the grate is small, and the drawback is that the amount of heat is taken away by things other than the sintered ore.

In order to solve this problem, a patent application was filed in 1983-21 to absorb the decrease in the amount of exhaust heat recovered due to changes in the balance between the sintering machine exhaust gas calorific value and the sensible heat of the sintered cake due to changes in operation.
No. 624, No. 55-43634, No. 55-89033
A method has been proposed for stably recovering waste heat from both the exhaust gas from the wind box at the final stage of the sintering machine and the heat from the sintered cake in a cooler as a total system.

According to this conventional technology, even if the sintering end point (B, T, P') changes, the amount of waste heat that can be recovered does not change, and the amount of waste heat that can be recovered does not change. Fluctuations in the amount of heat recovered are small and the effect is that the optimum and maximum amount of heat can always be recovered.

However, according to the above method, the equipment is complicated and large-scale because waste heat is recovered from two places: the exhaust gas from the sintering machine and the exhaust gas from the cooler, and the equipment cost is high, as well as the associated maintenance costs and running costs. It's covered in a large cloth.

(Problems to be Solved by the Invention) In the conventional method described above, the cooling side of the high-temperature sintering zone completely reaches the grate before the sintered cake is vented, and after this, the sintered cake is The average temperature of the fL1 sintered cake, which is cooled by suction air until it is discharged, is lowered,
As a result, the amount of heat recovered by the cooler was reduced.

Furthermore, the method of recovering exhaust heat from two locations, the exhaust gas from the sintering machine and the exhaust gas from the cooler, has the drawback that the equipment is complex and large-scale, resulting in high equipment costs, maintenance costs, and running costs.

(Means and effects for solving the problem) The present invention measures the temperature of exhaust gas sucked from a group of wind boxes of a sintering machine, and prevents the exhaust gas temperature from falling below a certain set temperature by A backing metal that adjusts the thickness of the bedding ore, exchanges the sensible heat of the exhaust gas to the bedding ore, reduces the amount of heat carried away by the exhaust gas, and increases the heat content of the sintered cake supplied to the cooler by that amount. The main feature is the exhaust heat recovery operation method in sintering equipment.

Then, the sintered cake supplied to the cooler (10 beds of sintered ore)
The purpose is to increase the amount of heat contained in the exhaust gas and prevent corrosion of exhaust gas treatment equipment while increasing the amount of exhaust heat recovered by the cooler.

Note that the bedding is sintered ore with a grain size of 10 to 20 that is laid on the grate to prevent the charged sintered raw material from falling through the gaps between the grate.

The present invention will be described in detail below based on the drawings.

First, an overview of the sintering machine and sintering machine equipment and its operation will be explained in Part 2.
This will be explained with the help of a diagram.

The sintering equipment consists of a sintering machine 1, a crusher 9 placed in its ore discharge section, and a cooler 1o placed after the sintering machine 1. On the raw material supply side, a bedding charging hopper 2, a raw material charging device There are an IIL 3, an ignition furnace 4, and a number of wind boxes 6 at the bottom of the pallet. The surface of the charged raw material is ignited by the ignition furnace 4, and air is sucked from the top to the bottom of the civet through the wind box 6 by a main blower (not shown). Then, the pallet is moved to advance sintering from the upper surface of the raw material to the lower layer. Sintering is completed when the sintered zone 5 reaches the bedding 7, and the sintered cake that has been fired is discharged to the ore discharge section.

It is then crushed by a crusher 9 placed in the ore discharge section,
It is charged into the cooler 10. In the first half of this cooler, the high-temperature sintered cake is cooled by the exhaust heat recovery blower 13.
High temperature exhaust gas is collected in a hood 11 and supplied to an exhaust heat recovery boiler 12.

Here, heat is exchanged with water supplied to the exhaust heat recovery boiler 12, and exhaust heat is recovered as steam.

To explain the sintering reaction based on the heat pattern shown in Fig. 3, the wet raw material a charged into the pallet is heated to 600 to
It is preheated and dried to OO°C to form a drying zone b. Furthermore, coke powder combustion continues, the temperature rises to 800 to 1100°C, and a sintering reaction zone C is formed. Here, QaCO
A decomposition reaction of limestone, which becomes 3→CaO + C02, and a sintering reaction, in which hematite is reduced by CO gas and becomes magnetite, are progressing. As the reaction progresses further, melting of the ore occurs, forming a melting zone d, where the sintering temperature reaches its maximum. Sintering ends when this highest temperature point F reaches the upper surface of the bedding ore. After this, a sintering completion zone θ is reached, where the zone is cooled by suctioned nitrogen gas.

If the proportion of this cooling zone is large, the high-temperature exhaust gas passes through the entire bedding, passes through a wind box (not shown), is subjected to dust collection, desulfurization, denitrification, etc., and is discharged into the atmosphere.

In the present invention, the bedding thickness is controlled based on the actual state of conventional sintering operations. This allows efficient heat exchange between the high temperature gas discharged during cooling after sintering and the bedding, forming a higher temperature bedding layer and increasing the heat content t of the sintered cake. This is intended to increase the power of the exhaust heat recovery lid in the cooler. On the other hand, the temperature of the exhaust gas sucked from the wind box will decrease. For this reason, acid corrosion in exhaust gas treatment equipment becomes a problem. Therefore, it is necessary to maintain the exhaust gas temperature so that it does not fall below a certain set temperature so that the SOx contained in the exhaust gas does not turn into mist within the exhaust gas treatment equipment. The present invention is intended to control the bedding thickness without managing the exhaust gas temperature.

An example of this control is shown in FIG.

The temperature of the exhaust gas sucked from the wind box group of the sintering machine is continuously measured, for example, by a temperature detector 15 disposed in the main duct 14.

On the other hand, the exhaust gas temperature is set to a certain temperature, such as the acid dew point (85~
Set to b.

These deviation signals are controlled by the bedding gate controller 19 so that the exhaust gas sent to the charging cut gate controller 19 has a temperature higher than the set temperature and an appropriate layer thickness.

There is no problem with this management even if it is done manually.

(Example) Next, the present invention will be explained in detail.

The embodiments were carried out under the formulation conditions shown in Table 1 and the operating conditions shown in Table 2.

The control temperature for the exhaust gas temperature was determined through experiments and was set at 85°C to control the bed thickness. FIG. 4 shows a control flow diagram.

Table 1 Table 2 The implementation results will be explained while comparing with the conventional technology.

FIG. 1 shows a comparison of the distribution of sintered zones between the conventional method and the present invention.

Here, (al is the result of the conventional method, and in this case, the cooling side (heat behind) of the high temperature sintering zone has completely reached grade K by the time the sintered cake is discharged, and after that the sintered cake is discharged. It is cooled before it is mined, and the exhaust gas temperature increases, but the average temperature of the sintered cake decreases.As a result, the amount of heat recovered by the cooler decreases.

On the other hand, when the bedding layer thickness of the present invention shown in ('b) is controlled, the advancing speed of the sintered zone is the same as that of the conventional method, but by increasing the bedding thickness (aJ In the conventional method, the amount of heat that was carried away by the grate and exhaust gas is stored in the bedding.As a result, the average temperature of the sintered cake is not high.
The exhaust gas temperature is maintained just below the lower limit of 85°C, and an increase in the amount of exhaust heat recovered by the cooler is achieved.

Further, Fig. 5 shows the exhaust gas temperature of the conventional method and the method of the present invention, and Fig. 6 shows the change in the amount of waste heat recovery steam. In addition, in the method of the present invention, the exhaust gas temperature was controlled between the lower limit of 85° C. and 87° C., and the amount of recovered steam was increased by about 10% compared to the conventional method.

Figure 7 shows the influence of yield and cold strength (TI) of sintered ore on quality. From this, it was confirmed that there was no difference in the quality of sintered ore obtained by the method of the present invention compared to the conventional method, and there was almost no effect on the quality.

Furthermore, the relationship with COG basic unit is shown in Figure 8. As a control of the present invention, the charging layer thickness is changed here as the bedding thickness changes, so in this example where the bedding thickness is increased, (3
0G basic unit decreased. These data represent average values over several days.

(Effects of the Invention) As described above, the present invention can easily increase the amount of waste heat recovered in the cooler without the need for major equipment modifications, and is very effective in terms of cost and energy for producing sintered ore. The improvement effect of waste heat recovery operation method is extremely large.
It has great industrial utility value.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the firing distribution of the present invention method and the conventional method, Fig. 2 is a schematic diagram of a sintering facility equipped with a cooler waste heat recovery device, and Fig. 3 is a diagram showing the heat pattern of the sintering reaction. Figure 4 is an example of the control flow of the present invention, Figure 5 is a diagram comparing the exhaust gas temperature of the present invention method and the conventional method, Figure 6 is a diagram comparing the amount of recovered steam, and Figure 7 is also a diagram comparing the amount of recovered steam. Figure 8 is a diagram comparing changes in concretion quality, and Figure 8 is a diagram comparing COG basic units. 1...Sintering machine 2...Bedding hopper 3...Charging device 4...Ignition furnace 5...Sintering zone 5 -1...Cooling side of high temperature sintering zone 6...Wind box 7...Bed ore 8...Cut gate 9...Crusher 10... Sintered ore cooler 11... Hood 12... Exhaust heat recovery boiler 13... Exhaust heat recovery blower 14... Main duct 15... ...Temperature detector 16...Bedding gate 17...Temperature setting device 18...Bedding gate controller 19...Charging cut gate controller Nippon Steel Corporation Figure 1/Irefu 11-L7Kf, Mouth Figure 3 Figure 4

Claims (1)

[Claims] The temperature of the exhaust gas sucked from the windbox group of the sintering machine is measured, and the thickness of the bedding ore on the sintering machine grate is adjusted so that the exhaust gas temperature does not fall below a certain set temperature to reduce the sensible heat of the exhaust gas. An exhaust heat recovery operation method in a sintering facility characterized by exchanging heat with bedding ore, reducing the amount of heat carried away by the exhaust gas, and increasing the amount of heat contained in the sintered cake supplied to the cooler. .