JPS5867813A - Manufacture for sponge iron by tunnel kiln - Google Patents

Abstract

PURPOSE:To recover with high efficiency the exhaust heat in the manufacture for sponge iron by tunnel kiln by a method in which after the raw material for iron-powder in a moving truck is preheated, reduced and sintered, the exhaust air having been used for cooling is utilized as the air for combustion in said reducing and sintering stage. CONSTITUTION:The mixed raw mateial of iron powder raw material and reducing agent on a truck 2 is moved through a preheating zone 4, a reducing and sintering zone 6 and a cooling zone 8. In this process, the cooling air to cool the truck is blown into the cooling zone 8 from a fun 24. The temperature of the cooling air is elevated in the cooling zone 8 by heat-exchange between said air and the sintered raw material on the truck 2. A part of the combustion gas from the sintering zone 6 is mixed with this high temperature air, and then the cooled exhast gas at high temperature is taken out 28 from the cooling zone 8 and is used as the air for combustion in the sintering zone 6 by a fun 26. The temperature of the sintering zone 6 is detected by a thermometer 12 and is transferred to an arithmetic unit 14B. The fuel such as coke oven gas which is necessary to keep a predetermined temperature is controlled by a flow amount controller 16 and is supplied to a burner 20.

Description

[Detailed Description of the Invention] The present invention relates to a method for producing Kaine iron using a tunnel furnace.
This invention relates to a method for manufacturing sponge iron that can effectively utilize the exhaust heat of a tunnel furnace.

Conventionally, as shown in Fig. 1, a K for manufacturing sponge iron consists of a truck 2 loaded with containers filled with mill scale, coke, etc., which are raw materials for manufacturing sponge iron, a pre-heating zone 4, a firing zone 6, and a cooling zone 8. By moving it through the tunnel furnace 10, it is preheated, reduced and fired, and finally cooled. In such a manufacturing method, an E11 degree needle 12 is installed above the firing zone 6, and the temperature indicated by the thermometer 12 is maintained at the set temperature.
The calculation unit 14A adjusts the flow rate controller 16 for fuel such as coke oven gas and the flow rate controller 18A for air, and adjusts the flow rate of the burner 2.
0 is controlled. The exhaust gas after combustion passes through the preheating zone 4 while being preheated by the sensible heat of the exhaust gas, and is discharged into the atmosphere by the exhaust fan 22.

On the other hand, cold air for cooling is supplied from the air blower 2 near the outlet of the cooling zone 8.
4 into the cooling zone 8, and is dissipated into the atmosphere from near the inlet of the cooling zone 8 as cooling exhaust by the X exhaust device 26. This diffused cooling exhaust gas is partially mixed with combustion gas from the burner 20 in addition to the cooling air.

In the conventional method for manufacturing sponge iron, the combustion air in the burner 20 of the firing zone 6 is cooled at room temperature, or the combustion exhaust gas discharged from the preheating zone 4 or the cooled exhaust gas discharged from the cooling zone 8 exchanges heat. If preheated air obtained by air is used, or if the E-air from both ministries is used, there is a problem that more fuel will be used, and if preheated air without heat exchange is used, it is necessary to install a heat exchanger. This had the disadvantage of increased installation costs and maintenance costs.

It is an object of the present invention to solve the problems of the prior art described above and to provide a method for manufacturing sponge iron using a tunnel furnace, which has a co-heat recovery effect.

The gist of the present invention is as follows.

That is, a step of preheating a mixed raw material of iron powder raw material and reduced 7c sliver stored in a moving truck, a step of reducing and firing the preheated raw material, and a step of cooling the reduced and fired cut material with air. A method for producing sponge iron using a tunnel furnace, comprising: using the cooled air exhaust as combustion air in the reduction firing step.

Oxygen # & of the cooling exhaust gas in the cooling zone 8 used in the present invention
An example of degrees and temperatures is shown in Figure 2. The surrounding air in the cooling zone 8 is a mixture of cooling air and combustion exhaust gas from the firing zone 6, so the oxygen concentration is lower than the atmospheric concentration of 21%, but
As shown in FIG. 2, on the cold air inlet side, that is, on the outlet side of the cooling zone 8, the oxygen concentration is 16% or more, which is necessary for stable combustion in the burner, so it cannot be used as combustion air as is. On the other hand, in the firing zone 6@ of the cooling zone 8, there is a lot of mixture of combustion exhaust gas, and the oxidation rate is less than 16%, but since the temperature is high, air is mixed in to increase the oxygen concentration. is used as combustion air at a rate of 16% or more required for stable combustion. In either case, the sensible heat of the cooling exhaust gas in the cooling zone 8 can be effectively utilized.

The present invention will be specifically explained with reference to FIG. The raw materials on the cart 2 are reduced and fired and cooled while moving through the preheating zone 4, the firing zone 6, and the cooling zone 8 at the times shown in FIG.

The air blower +1A24 blows cold air for cooling the truck 2 into the cooling #8. The cold air undergoes heat exchange with the firing raw material in the trolley 2 and rises in temperature in the cooling zone 8, and 1 joll of combustion gas flows in from the firing zone 6 and mixes with it to form a 4-temperature cooled exhaust air, which is passed through the cooling exhaust duct 28 by the exhaust fan 26. It is then discharged from the cooling zone 8.

An example of the temperature of the cooled exhaust gas and the temperature of the molten metal is shown in FIG. 2 above, but it will naturally vary depending on the furnace and operation.

The temperature of the firing zone 6 is detected by the thermometer 12 and transmitted to the calculation section 14B, and the fuel such as coke oven gas required to maintain the set temperature f is controlled by the flow rate controller G4 16 and supplied to the burner 20.

On the other hand, the oxygen concentration of the cooling exhaust gas is detected by the oxygen concentration meter 30, and if it is 16% or more, the constant flow sound is controlled by the flow rate controller I41 18B, and the cooling exhaust duct 28 is turned to exhaust air +f.
The air is supplied to the burner 20 of the firing zone 6 by i26 as air for burning rice.

On the other hand, if the measured value of the oxygen concentration meter 30 is less than 16%, the arithmetic unit 14B adjusts the opening degree of the mixed air flow rate control valve 34 via the mixed air TLT violet controller 32 so that the set oxygen level is reached. Air is mixed into the cooling exhaust duct 28.

The temperature of the cooled exhaust gas into which air has been mixed to control the concentration of 1 g of acid is detected by a thermometer 36 and transmitted to the calculation section 14B. The required amount of combustion air commensurate with the above-mentioned controlled fuel amount is determined by the calculation unit 1.
48 after correction for acid 111 degrees and temperature, controlled by flow controller 188 and controlled by burner 20
is supplied to

The cooling exhaust gas in the cooling zone is sucked in to keep the pressure inside the furnace constant, and if the amount of intake air is surplus to the amount of combustion air, the surplus is released into the atmosphere by the flow controller 38 and control valve 40. .

Example 1 A comparative test was conducted in which sponge iron was produced in the following tunnel furnace for making sponge iron, using 9 air for normal temperature combustion using the conventional method and the cooled exhaust air from the cooling zone according to the method of the present invention as combustion air. The results are shown in Part 1.

Table 1 As is clear from Table 1, in the method of the present invention, 115
”/hrt of coke oven gas fuel could be reduced by 8u.

Large Example 2 Under the same operating conditions as in Example 1 above, cooling υP air at 600°C and acidic concentration 13% was discharged from the cooling zone for 2 hours.
400”/hr suction, and room temperature air 4=-144
0"/hr and the total temperature is 395℃, the sales temperature is 1.
When the mixed air is 6%, 384 ON/hr and combustion air is used, the fuel injection amount is 580 kt.
”/hr, saving 135 NI&/hr of coke oven gas fuel.

As is clear from the above two examples, the method of the present invention uses the high-temperature cooled exhaust gas from the cooling zone as combustion air, so it is possible to manufacture sponge iron using a tunnel furnace without the need for equipment such as a heat exchanger. We were able to significantly reduce fuel consumption by KPA.

In addition, in the method of the present invention, if the oxygen content is 16% or more,
If the oxygen concentration is less than 16%, the oxygen concentration [1
It is also possible to appropriately mix 6% or more of the cooled exhaust gas and less than 16% of the cooled exhaust gas to make the mixture 16% or more and use it as combustion air.

[Brief explanation of the drawing]

Figure #I1 is a combustion control system diagram using the conventional sponge iron manufacturing method in a tunnel furnace, and Figure 2 is a cooling 'IK' diagram of the tunnel furnace.
Diagram showing an example of the acid concentration and temperature of the atmosphere, Part 3
The figure is a combustion I control system diagram according to the sponge iron manufacturing method of the present invention in a tunnel furnace. 2.・9 trolleys 4...preparation zone 690. Firing zone 8...Cooling zone lO...Tunnel furnace
16...Fuel flow rate mtt a device 18...Combustion air flow ii grade uIl device 20...Burner

Claims (3)

[Claims] (1) A step of preheating a mixed raw material of iron powder raw material and a reducing agent stored in a moving cart, a step of reducing and firing the preheated raw material, and a step of cooling the reduced and fired monthly charge with air. A method for producing sponge iron S using a tunnel furnace, comprising: using the cooled air exhaust as combustion air in the reduction firing step. (2) The cooling exhaust gas used as the combustion air must have an oxygen lateral variation of 16% or more.
A method for manufacturing sponge iron using a tunnel furnace as described in . (3) When the carbon concentration of the cooled exhaust gas used as the combustion air is less than 16%, air is added to make the carbon concentration higher than 16%. Iron manufacturing method.