JP3530224B2 - Exhaust gas circulation sintering operation method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintering operation method using a Dwightroid type sintering equipment under an exhaust gas circulation operation.

[0002]

2. Description of the Related Art A sintering method in which a wind box at the bottom of a sintering bed is divided in the flow direction of raw materials (strand direction) and a part of the exhaust gas is circulated for operation is improved in thermal efficiency. There is an advantage that it contributes to the reduction of the coke amount and the exhaust gas amount. Therefore, Japanese Patent Laid-Open No. 5-
In Japanese Patent No. 43951, exhaust gas generated from the ignition furnace region of the sintering machine is supplied to the middle rear part of the sintering machine, and exhaust gas generated from the rear part of the sintering machine is supplied to the middle front part of the sintering machine for circulation. Moreover, there has been proposed a method of operating a sintering machine for the purpose of saving the energy, significantly reducing the gas fuel consumption rate, etc. by making the oxygen concentration of the circulating exhaust gas 18% or more. Further, when circulating the exhaust gas, in Japanese Patent Application No. 5-124448, the internal pressure of the hood for introducing the circulating gas installed on the sintered strand is always kept at a negative pressure, and the exhaust gas containing carbon monoxide is not leaked out. It has been reported.

[0003]

However, when the actual operation is performed by the method described in the above publication, there is no problem when the exhaust gas circulation rate is 10 to 15% as shown in FIG.
When the exhaust gas circulation rate is further increased (25 to 30%) to improve the thermal efficiency, the yield of the product is reduced, the productivity is reduced, the RDI (reduced dusting rate) and the RI (reduced rate) are reduced.
Was caused, and there was a problem that it was remarkable in the lower layer. Therefore, when the heat pattern during sintering was measured, the cooling rate decreased in any of the upper layer, the middle layer, and the lower layer as the exhaust gas circulation rate increased, and as a result, the high temperature holding time of the raw material became longer and the structure of the mineral was increased. As a result, the structure of hematite = calcium ferrite is changed to that of magnetite = slag. It has been found that this causes the deterioration of the above-mentioned RDI and RI.

Then, as shown in FIG. 9, by keeping the internal pressure of the hood for introducing the circulating gas at a negative pressure, the atmosphere intrudes into the hood through the gap between the hood and the pallet.
We found a phenomenon in which the oxygen concentration in the width direction of the pallet is high in the edge part and the oxygen concentration in the center part is low, and an oxygen concentration distribution occurs. The present inventor has conducted a detailed investigation to find that the oxygen concentration distribution causes the firing rate in the central portion to decrease and the formation of an unburned portion in the central portion causes a decrease in yield and a decrease in productivity. discovered. The present invention has been made in view of the above circumstances, and further improves the exhaust gas circulation rate to improve thermal efficiency, and further improves the product yield, productivity, and R
It is an object of the present invention to provide an exhaust gas circulation sintering operation method which is the same as or higher than the conventional one in terms of DI and RI.

[0005]

A method according to the above-mentioned object.
The exhaust gas circulation sintering operation method described is an exhaust gas circulation firing process in which exhaust gas from the front and rear portions of a wind box that is divided into a lower portion of a sintering pallet is supplied to the central portion of the sintering pallet to operate. In the operating method, when the oxygen concentration of the exhaust gas is in the range of 15% or more, the ventilation index during the exhaust gas circulation is adjusted so as to correspond to the yield, productivity and quality deterioration of the sintering equipment due to the increase of the exhaust gas circulation rate. Increase of
When adjusting, first set the operating point with an exhaust gas circulation rate of 0% as a reference.
Corrected by the decrease of oxygen concentration due to exhaust gas circulation
Calculate the amount of gas, then calculate from this required amount of gas
Derivation of pressure loss per unit bed height from ventilation index
Then, the yield estimated from the pressure loss is calculated, and the yield
Is lower than the yield of the exhaust gas circulation rate of 0%, which is the standard
Or, the yield will be lower than the target yield and productivity will decrease.
If deterioration of product quality is predicted,
Yield or aim of the exhaust gas circulation rate of 0% as a standard
The granulation water content, quick lime content, and grain size segregation with respect to the layer height or layer direction of the raw material should be small so that the yield is equivalent to
It has improved by increasing the ventilation index by also changing one.

Further, exhaust gas circulation sintering operation method of claim 2, in exhaust gas circulation sintering operation method according to claim 1, wherein, during the increase of the ventilation index, water at the time of granulation 6.5
% To 8.0 %, the pseudo-granulation of the raw material is promoted, the particle size of the pseudo-particle is expanded and the strength is improved. In addition, in order to increase the aeration index, the present invention can be applied not only when independently changing the granulation water content, the amount of quick lime, the particle size segregation with respect to the layer height or layer direction of the raw material, but also when changing two or more of these. .

[0007]

The relationship between the machine length direction (raw material flow direction) and the oxygen concentration and the water concentration in a sintering machine in which exhaust gas is not circulated is shown in FIG. As is clear from FIG. 2, the sintering raw material has a high oxygen concentration in the ignition furnace region (the front part of the sintering pallet) and the sintering completion region (the rear part of the sintering pallet).
Furthermore, the water concentration is low. Therefore, claim 1 and
In the exhaust gas circulation sintering operation method described in 2, since the exhaust gas in this portion is selectively circulated, the exhaust gas having a relatively high oxygen concentration and a low water content is circulated,
This prevents a significant decrease in oxygen concentration (oxygen concentration of 15% or less) due to exhaust gas circulation as shown in FIG.

FIG. 4 shows the coefficient (required gas amount substitution coefficient) of which it is necessary to increase the total exhaust gas amount because the oxygen concentration decreases as the exhaust gas circulation rate increases. It can be seen that this increases the air volume, and thus the overall pressure loss (and hence the pressure loss per unit length described below) is also high. On the other hand, in general, JPU (Japanes) is used to represent the aeration index of the charging raw material.
e Permeability Unit), which represents the ratio of the value of the pressure loss per unit length to the 0.6th power (hereinafter simply referred to as pressure loss index K) and the exhaust gas amount N. The relationship between the pressure loss index K and the yield is as shown in FIG. 5A from past data. Therefore, if the exhaust gas amount N and the JPU are known under the same operating conditions, the yield will inevitably be determined. Also, J
Since PU is an index of air permeability, it can be controlled by changing the pseudo-granulation index (GI) which is a function of granulation water, the amount of quicklime added and the layer height of sintering.

FIG. 5C shows the relationship with the required exhaust gas amount M when the exhaust gas circulation rate is determined from the relationship of FIG. 4, and since the oxygen concentration decreases as the exhaust gas circulation rate increases. , The required exhaust gas amount M increases. Therefore, if the circulation rate is increased from the operating condition where the actual circulation rate is 0, the required exhaust gas amount M increases, which means that the actual exhaust gas amount N is increased. It can be seen that the index K increases and the yield decreases. Therefore, in the exhaust gas circulation sintering operation method according to claims 1 and 2, the decrease in the yield due to the improvement of the exhaust gas circulation rate is caused by the granulation moisture, the amount of quick lime, the layer height of the raw material, and the particle size segregation in the layer direction. By increasing the air permeability index, which improves the yield. When the yield is improved, the productivity is naturally improved, and the product quality indicated by RDI or RI is increased by increasing the aeration index, so that the amount of air passing through the raw material layer is increased and the cooling rate is increased. By
It is improved because hematite = calcium ferrite type structure is easily generated. When the oxygen concentration is 15% or less, the absolute oxygen is insufficient even if the JPU is improved, so that the relationship shown in FIG. 5 is hard to be established.

In particular, this exhaust gas circulation sintering method is described in J.
This is for obtaining the selection of the PU from the graph, and as shown in FIG. 6 in which FIG. 5 is enlarged, the required exhaust gas amount b corrected by exhaust gas circulation based on the operating point a at which the exhaust gas circulation rate is 0%. Then, the pressure loss per unit loading layer (the pressure loss index c, which is the 0.6th power of that) is calculated from the actual JPU, and the yield d is estimated from this. Next, when the estimated yield d is lower than the yield s with an exhaust gas circulation rate of 0% or the target yield, JP
It is only necessary to change U to a higher value. Therefore, the JPU is increased by appropriately changing the granulation water content, the amount of quick lime, the layer height of the raw material, and the particle size segregation in the layer direction. As a result, the JPU for the exhaust gas circulation rate can be easily obtained.

Further, in the exhaust gas circulation sintering operation method according to claim 2 , the water content during granulation is 6.5% or more and 8.0% or more.
Since it is set as below, the degree of granulation of the fine powder increases and the pseudo-powdering index increases, which increases the JPU. That is, in order to increase the JPU, it is sufficient to change the granulation water content, the amount of quick lime, the bed height of the raw material, etc. FIG. 7 shows the degree of improvement in yield with respect to these increases. In order, increasing the granulation water content is the most efficient. Therefore, when it is necessary to increase the JPU, first increase the granulation water content, and if the water content is still insufficient, increase the quick lime. It will change the particle size segregation. If the water content is 8.0% or more, the evaporation of the water content is rate-determining and the productivity is reduced.

When the water content at the time of granulation is adjusted to increase the pseudo-granulation index, the raw material charging method shown in FIG.
That is, by increasing the amount of raw material supplied from the end of the vessel so as to keep the surface of the raw material in the raw material vessel in a V shape, a large amount of raw material having a high pseudo-granulation index of coarse particles is distributed due to the V-shaped valley portion. .
When loaded on a pallet by a drum-type raw material cutting device, a large amount of raw material having a high pseudo-granulation index is distributed in the central portion of the pallet, so that the central portion further increases the JPU than the end portion, and FIG. JPU according to the oxygen distribution in the hood shown in
A distribution of is formed.

[0013]

Embodiments of the present invention will now be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIG. 1 is a schematic explanatory view of an exhaust gas circulation sintering operation method according to an embodiment of the present invention.

As shown in FIG. 1, no. 1 to No. 33 wind boxes 11
The front wind box (for example, No. 1 to
No. Exhaust gas from the wind box 3 of FIG. 3 is circulated and supplied through the damper 12, the blower 13, and the hood 14 as combustion gas for the sintering raw material from the center to the rear.
In addition, a rear wind box (for example, No. 26 to N)
o. The exhaust gas from the wind box 32 of 32 is circulated and supplied as a combustion gas for the sintering raw material from the center through the waste heat boiler 15 for heat recovery, the dust catcher 16, the damper 17, the blower 18 and the hood 19. There is.

Then, the No. 6 located in the center of the sintering machine is used. Four
~ No. 25 and No. The exhaust gas discharged from 33 is sucked by the blower 20 and discharged from the chimney 21. Here, in the case of improving the exhaust gas circulation rate, the number of wind boxes that circulate the exhaust gas is increased and the air volumes of the blowers 13 and 18 are increased. In this case, as is apparent from FIG. 2, the exhaust gas in the central portion of the sintering machine has a low oxygen concentration. Therefore, if the exhaust gas circulation rate is improved, the degree of decrease in oxygen concentration will be large as shown in FIG. In the present embodiment, the configuration of the wind box that circulates the exhaust gas is not changed, and the air volume of the blowers 13 and 18 is increased within a range that does not hinder the operation.

[0016] When exhaust gas circulation is performed, the yield decreases as described above, so it is necessary to increase JPU in order to compensate for this. In that case, granulation water, quick lime amount, raw material The layer height will be changed. Table 1 shows an example in which these are changed independently, and it is understood that the yield, RDI, and productivity are improved by increasing the JPU.

[0017]

[Table 1]

In the above embodiment, the JPU is increased by changing the granulated water content, the amount of quick lime, and the bed height of the raw material, but other JPU increasing factors (for example, particle size segregation in the layer thickness direction) are changed. The JPU may be changed by changing two or more of these. Further, since the degree of increase in JPU with respect to the rate of increase in granulated water is large, this may be prioritized, and then the increase in quicklime and the decrease in bed height may be changed in this order.

[0019]

As is apparent from the above description, the exhaust gas circulation sintering operation method according to the first and second aspects of the present invention is effective in increasing the ventilation index even when exhaust gas circulation is performed in order to improve thermal efficiency and reduce exhaust gas. By adjusting the yield, productivity and quality (RDI or RI) can be maintained or improved. Further, in this exhaust gas circulation sintering operation method, since the ventilation index can be predicted in advance before the actual operation, it has become possible to preset the operating conditions corresponding to the ventilation index from the past data. In claim 2 exhaust gas circulation sintering operation method according, since an increase in moisture in preference so that achieved an increase in ventilation index is very inexpensive, furthermore the control is easy.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a sintering machine to which an exhaust gas circulation sintering operation method according to an embodiment of the present invention is applied.

FIG. 2 is a graph showing the oxygen concentration of exhaust gas in the machine length direction of a sintering machine.

FIG. 3 is a graph showing the relationship between exhaust gas circulation rate and hydrous oxygen.

FIG. 4 is a ratio between an exhaust gas circulation rate and a required gas amount substitution coefficient.

FIG. 5 is a graph for explaining the method of the present invention.

FIG. 6 is a graph for explaining the method of the present invention.

FIG. 7 is a graph showing the relationship between yield, water content, quick lime, and bed height.

FIG. 8 is a graph showing the relationship between the exhaust gas circulation rate and the yield, productivity, RDI and RI when exhaust gas is circulated by a conventional method.

FIG. 9 is a graph showing the oxygen concentration in the width direction of the sintering pallet.

FIG. 10 is a graph showing JPU in the width direction of a sintering pallet.

[Explanation of symbols]

10: Sintering pallet, 11: Windbox, 12:
Damper, 13: Blower, 14: Hood, 15: Waste heat boiler, 16: Dust catcher, 17: Damper, 18: Blower, 19: Hood, 20: Blower,
21: Chimney

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshiaki Shimakawa, Inventor Yoshiaki Shimakawa 1-1, Tobata-cho, Tobata-ku, Kitakyushu, Fukuoka Nippon Steel Co., Ltd., Yawata Works (72) Inventor Nakazaki, Showa, Tobata-ku, Kitakyushu, Kitakyushu, Fukuoka No. 1 in Machi Nippon Steel Co., Ltd. Yawata Works (56) References JP-A-5-247546 (JP, A) JP-A-59-93842 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) C22B 1/00-61/00

Claims (2)

(57) [Claims] 1. An exhaust gas circulation sintering operation method in which exhaust gas from a front portion and a rear portion of a wind box dividedly provided in a lower portion of a sintering pallet is supplied to a central portion of the sintering pallet to perform operation, When the oxygen concentration of the exhaust gas is in the range of 15% or more, the ventilation finger during the exhaust gas circulation is commensurate with the yield, productivity and quality deterioration of the sintering equipment due to the increase of the exhaust gas circulation rate.
When adjusting the increase in the number, set the operating point with an exhaust gas circulation rate of 0%.
First, the standard is supplemented by reducing the oxygen concentration due to exhaust gas circulation.
Calculate the corrected required gas amount, and then from this required gas amount
From the required ventilation index, the pressure loss per unit bed height
Loss, and obtain the yield estimated from the pressure loss.
Therefore, the yield with the exhaust gas circulation rate of 0%, which is the standard for the yield
Less than or less than the target yield
If deterioration of product quality or deterioration of product quality is expected,
The yield of the exhaust gas circulation rate of 0% based on the ventilation index
Granulation water content, quick lime content, particle size segregation with respect to the layer height or layer direction of the raw material so that the yield is equivalent to the target yield.
The exhaust gas circulation sintering operation method, wherein the ventilation index is increased and improved by changing at least one of the above . 2. When the air permeability index is increased, the water content at the time of granulation is adjusted to 6.5% or more and 8.0% or less to promote pseudo-granulation of the raw material to increase the particle size and strength of the pseudo-particle. claim 1 exhaust gas circulation sintering operation method according to improve.