JPH0433751B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a method for producing quicklime for sintering raw material by burning limestone.

[Prior art and its problems]

Generally, the blast furnace charge charged into a blast furnace is supplied in the form of sintered ore, which is a mixture of powdered iron ore, coke powder, and powdered limestone of 5 mm or less, and is fired and agglomerated. However, when limestone is used, it is highly pulverized and is used as a sintering raw material, which impedes air permeability during the firing process and poses problems in terms of productivity and manufacturing costs.

When quicklime is used instead of limestone, it becomes gel-like slaked lime when mixed with water during the preparation of sintering compound raw materials, which has a granulation effect in the sintered layer, improves air permeability, and accelerates the sintering reaction. It has been confirmed that it has advantages over limestone in this respect, and that it can improve the quality of sintered ore.

In order to obtain quicklime, limestone can be fired in a rotary kiln, shaft furnace, or other kiln to cause a decarboxylation reaction. When we produced this product, there were many equipment problems due to powdering, and operation was difficult.
A fluidized torrefaction furnace is a possible method for turning pulverized limestone into quickstone ash, but it is difficult to install a new one due to the high equipment cost.

In order to deal with this situation, the applicant first charged a mixed material of limestone and coke powder into the preheater of a rotary kiln, burned it without rolling it to form quicklime, and cooled it in the rotary kiln. - Proposed a quicklimeization method for limestone that involves crushing (Patent Application No. 62-44847). Although this method solved the problems caused by pulverization, it had the disadvantage of requiring a large amount of electricity to operate the kiln or cooler, which is the main equipment of the rotary kiln.

This invention was made in view of the above circumstances. The purpose is to produce quicklime for sintering at a low cost by using only the rotary kiln's preheater, omitting the crushing and cooling steps, improving the yield of quicklime, and using low-cost coke raw materials. is to provide.

[Means and actions for solving problems]

This method for producing quicklime for sintering raw material is a method of producing quicklime for sintering raw material by burning limestone using rotary kiln equipment, and is a method of producing quicklime for sintering raw material by calcining limestone using rotary kiln equipment. The mixed material mixed with further water is supplied to the preheater of the rotary kiln, ignited by the ignition burner installed in the preheater, and combusted by air suction. The mixed material is baked within the preheater without rolling. , the quicklime obtained is taken out of the preheater without being sent to the rotary kiln, transported in gas, and supplied to the sintering process.

Another invention is characterized in that quicklime obtained by firing taken out of the preheater and quicklime dust collected in a dust collector during the firing process are transported by gas and supplied to the sintering process. do.

In this method for producing quicklime, 8 to 12% of fine coke, of which 90% or more has a grain size of 1 mm or less, is added to limestone sized to about 4 to 15 mm, and water is further added to 2 to 15 mm.
The mixed material mixed at a concentration of about 3% is supplied to a preheater of a rotary kiln. Fine coke is the conventionally used coke powder (particle size of 1 mm or less 50-60
%), there is no difference in calorific value, it easily adheres to the surface of limestone, and homogeneous mixing is possible.Furthermore, coke powder contains coarse particles of 5 mm or more, which tend to be unburned and remain as residual carbon. Fine coke does not have this fear and can achieve uniform firing.

The mixed material is supplied to the preheater, the surface is ignited by the ignition burner, and it is baked without rolling by air suction, causing a decarboxylation reaction and turning it into quicklime, which suppresses pulverization and reduces the amount of powder during baking. No problems occur due to conversion.

The mixed material burned in the preheater is calcined and converted to quicklime, which is discharged into a product tank outside the preheater system.The temperature of the quicklime after discharge is 50 to 80℃, and it is difficult to transport the quicklime using nitrogen gas. There is no problem. The particle size of quicklime is approximately the same as the limestone particle size (4 to 15 mm) because it is fired without rolling in the preheater, but since it is easily pulverized by nature, it is pulverized during gas transportation, and is particularly difficult to crush. A suitable particle size structure as a sintering raw material can be obtained by simply transporting the material by gas and sending it to the sintering process without providing any process.

During the firing process, the quicklime dust that is entrained in the suction air and collected in the dust collector has a different particle size from the quicklime discharged from the preheater, but the degree of calcination is roughly the same, so it should be treated the same as the product quicklime. It can be supplied to the sintering process by gas transport and used as a sintering raw material. As a sintering raw material, fine particle size is a preferable condition, and the particle size of quicklime dust is not a problem.

〔Example〕

The present invention will be described below based on illustrated embodiments. As shown in FIG. 1, rotary kiln equipment originally performs firing by exclusively firing C gas from a burner in a rotary kiln 11, and in a preheater 10, C gas from the rotary kiln 11 is fired.
Although it is configured to preheat with gas and cool with a cooler 12, in the present invention, firing is performed in a preheater (grate) 10 in order to avoid powdering during firing. Therefore, we changed the C gas exclusive combustion system to a coke powder exclusive combustion system, newly installed a C gas ignition burner 9 as an ignition source in the preheater 10, and used the auxiliary chimney 8 at the top of the preheater 10 for sucking combustion air.
A mixed material consisting of limestone and fine coke is used.

Fine coke c from coke tank 2 is added to limestone (CaCO ₃ ) sized to 4 to 15 mm from ore storage tank 1.
After adding 8 to 12% (excluding numbers) of (90% or more with a particle size of 1 mm or less), remove 2 to 3 ounces of water with a drum washer.
% and are mixed and deposited, sent to the furnace front raw stone tank 4, and charged into the preheater 10 via the surge hopper 6 and pH hopper 7.

In the preheater 10, the surface of the mixed material M is ignited by the ignition burner 9, and the mixed material M on the grate 10A is fired from the upper layer by air suction from the exhaust blower. The layer thickness of material M is appropriately adjusted to 300 to 700 mm, and the moving speed of the grating 10A is adjusted so that baking is completed to the lower layer at the exit of the preheater. The amount of quicklime produced and the degree of calcination can be adjusted as appropriate by adjusting the layer thickness, grate movement speed, and coke blending ratio.

The calcined quicklime is discharged from the end of the grate 10A to the product tank 13 outside the preheater 10 system, and then sent to the pneumatic tank 14, where it is gas-transported to the sintering process using nitrogen gas or the like.

In this firing process, the quicklime dust collected in the dust collector 15 attached to the preheater 10 is discharged into the dust tank 16, and then sent to the pneumatic tank 14, where it is gas-transported and sintered together with the quicklime discharged from the preheater. Supplied to the process.

The quicklime that was supplied to the firing process by gas transportation was pulverized during the transportation process and had a suitable particle size structure.

Figures 2, 3, and 4 show the results of sintering using quicklime produced by this production method. this is
Base (no quicklime) and conventional method (rotary kiln,
This is an example of comparison with C gas-fired crushed products), and both the conventional method and the method of the present invention contain 2% quicklime.

The production rate shown in Figure 2, the granulation rate shown in Figure 3, and each value shown in Figure 4 were almost the same as the conventional method, indicating that this production method is highly effective in using quicklime as a sintering raw material. I understand.

〔Effect of the invention〕

The present invention is as described above, and according to this manufacturing method, baking is performed without rolling in the preheater of a rotary kiln, so there is no problem of powdering during the baking process, and low-cost pulverized coke is used as fuel. , Since existing rotary kiln equipment is used and no kiln or cooler is used, raw material costs, equipment costs, electricity costs, etc. can be reduced, and quicklime dust can be used as the same product as quicklime, improving yield. I can do it.

Therefore, according to this quicklime production method, quicklime suitable as a sintering raw material can be produced at low cost.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a manufacturing apparatus for carrying out the quicklime production method of the present invention, Fig. 2 is a graph showing the production rate, Fig. 3 is a graph showing the granulation rate, and Fig. 4 is a graph showing various values. This is a graph showing. 1...Ore storage tank, 2...Coke tank, 3...Drum washer, 4...Rough stone tank, 5...Tank, 6...Surge hopper, 7...pH hopper,
8... Auxiliary chimney, 9... Ignition burner, 10...
Preheater, 10A...Grate, 11...Rotary kiln, 12...Cooler, 13...Product tank, 14...Pneumatic tank, 15...Dust collector, 1
6...Dust tank.

Claims (1)

[Claims] 1. A method for producing quicklime for use as a sintering raw material by calcining limestone using rotary kiln equipment, which comprises adding fine coke of 90% or more in particle size of 1 mm or less to limestone, and further adding water. In addition, the mixed material is supplied to a preheater of a rotary kiln, ignited by an ignition burner installed in the preheater, combusted by air suction, and baked without rolling the mixed material within the preheater. A method for producing quicklime for use as a sintering raw material, characterized in that the quicklime is taken out of the preheater without being sent to a rotary kiln, transported in gas, and supplied to a sintering process. 2. The sintering raw material according to claim 1, characterized in that the quicklime taken out of the preheater and the quicklime dust collected in a dust collector during the sintering process are transported by gas and supplied to the sintering process. Quicklime manufacturing method.