Title of Invention

"RECYCLING METHOD OF WASTE MATERIAL BY USING OF COAL BASED IRON MAKING PROCESS"

Abstract The present invention relates to a coal based iron making process by using a reduction-melting apparatus which includes a reduction furnace for reducing ore and supplementary raw material, a melter gasifier for reduction-melting reduced iron fed from the reduction furnace into hot metal, a cyclone for trapping fine dust in exhaust gas from the melter gasifier to circulate trapped fine dust to the melter gasifier and to feed exhaust gas cleared of fine dust to the reduction furnace as reduction gas, and a dust burner with one end connected to the cyclone and the other end connected to the melter gasifier and for executing melting condensation to and then blowing fine dust into the melting gasifier, a recycling method of waste materials comprising the following steps of collecting and drying waste material so that the total composition of T. Fe, C, Cao and MgO reaches at least 50wt% sorting dried waste material to have a particle size of 5 mm or less; and blowing sorted waste material into the melter gasifier with the dust burner.
Full Text RECYCLING METHOD OF WASTE MATERIAL BY USING OF COAL BASED IRON MAKING PROCESS
TECHNICAL FIELD
The present invention relates to a recycling method of dust and sludge produced in iron and steel works, and more particularly, to a recycling method by which waste material such as dust and sludge outputted in an iron and steel working process can be recycled as fuel and raw material in a coal based iron making process.
BACKGROUND ART
In general, by-products outputted in most iron and steel works can be mainly discriminated into slag, dust and sludge. Although dust and sludge can be recycled as raw material in some iron and steel working,, smelting or cement manufacturing processes sir.ce they are abundant with Fe and C components, a large portion of the by-products tend to be buried through solidification without recycling. Therefore, treatment and recycling of the by-products are gradually becoming important environmental problems in the ironworks.
The iron and steel works output dust and sludge in each process. Dust and sludge are mainly comprises compounds of carbon component useful as both of heat source and reducing agent, Fe component useful as raw material of iron and Ca, Mg and so on useful as supplementary raw material. Although dust and sludge have particles sizes of 1mm or less, occasionally the particle sizes thereof reach up to 8mm. Moisture content is remarkably different according to processes of outputting sludge and dust, or between dust and sludge.
Recycling of the dus and sludge is greatly dependent upon several conditions such as component difference, moisture content, particle size and so on. Therefore, dust is recycled by a large quantity since it has low moisture content and can be simply treated, whereas outputted sludge is recycled by about half only.
The COREX process, i.e. one of coal based iron making process, generally uses two reactors such as a melter gasifier 20 and a reduction furnace 10. In the iron making process, iron ore used as raw material is charged together with supplementary raw material into the top of the reduction furnace 10, where iron ore and supplementary raw material undergo reduction and sintering due to reducing gas blown through the bottom of the reduction furnace 10. Reduced iron ore and sintered
supplementary raw material are fed into the melter gasifier 20, where they are hot melted to yield pig iron. Coal is charged into the hot melter gasifier 20 to produce reducing gas, which is fed into the reduction furnace 10, in which char of the remaining coal is used as heat source as it reacts with oxygen at the bottom of the melter gasifier 20. In the meantime, reference numerals 12, 210 and 222 each indicate an ore-charging duct, a dust-recycling duct and an exhaust gas duct.
In the coal based iron making process using the above two reactors, a large quantity of reducing gas is fed into the upper reduction furnace 10 from the lower melter gasifier 20 so that fine dust of coal, reduced ore and supplementary raw material can be fed on reducing gas into the reduction furnace 10. Since this is a major reason for deteriorating the internal status of the reduction furnace, a cyclone 21 is installed between the melter gasifier 20 and the reduction furnace 10 in order to remove fine dust from gas.
Fine dust trapped by the cyclone 21 is blown again through a two-stage charging vessel into the melter gasifier 20, in which melting condensation is carried out with a dust burner 213 in order to prevent blown fine dust from dispersing again. In such melting condensation, oxygen is fed together with the fine dust into the dust burner to burn fine dust at the leading end of the
dust burner by using carbon contained in coal as fuel and blown oxygen and oxygen contained in some of reduced ore as oxidizing agent.
This makes reduced ore melt and condense thereby restricting re-dispersion. The dust burner blows again fine dust outputted from the melter, and fine dust is melting-condensed at the leading end thereof and thus restricted in its re-dispersion.
SUMMARY OF THE PRESENT INVENTION
It is therefore an object of the invention to provide a recycling method in a coal based iron making process, which allows recycling of waste material such as dust and sludge outputted from iron and steel works.
In order to obtain the above object, the invention provides a recycling method of waste material in use for a coal based iron making process by using a reduction-melting apparatus which includes a reduction furnace for reducing ore and supplementary raw material, a melter gasifier for reduction-melting reduced iron fed from the reduction furnace into hot metal, a cyclone for trapping fine dust in exhaust gas from the melter gasifier to circulate trapped fine dust to the melter gasifier and to feed
exhaust gas cleared of fine dust to the reduction turnace as reduction gas, and a dust burner with one end connected to the cyclone and the other end connected to the melter gasifier and for executing melting condensation to and then blowing fine dust into the melting gasifier, in which the method comprises the following steps of: collecting and drying waste material so that 'the total composition of T.Fe, C, CaO and MgO reaches at least 50wt%; sorting dried waste material to have a particle size of 5mm or less; and blowing sorted waste material into the melter gasifier with the dust burner.
BRIEF DESCRIPTION OF THE DRAWINGS
The above object and other advantages of the present invention will become more apparent by describing in detail the preferred embodiment of the present invention with reference to the attached drawings in which:
Fig. 1 schematically illustrates a general coal based iron making process; and
Fig. 2 is a schematic view illustrating a recycling apparatus of waste material in an iron making process according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Hereinafter the present invention will be described in detail.
As set forth above, it is a main feature of the present invention that sludge and dust outputted from iron and steel works are blown after adjusting composition and particle size thereof, thereby recycling them in an iron making reduction-melting process.
First, in the present invention, sludge and dust outputted in an iron and steel working process are collected for recycling thereof. At this time, sludge and dust are required to contain useful components in the iron working process such as Fe, C and supplementary raw material (CaO, MgO) whose total composition is at least 50wt%. It is because charging of waste material cannot be effectuated as additional charging of fuel and raw material unless the total composition of the useful components reaches 50wt%.
If collected sludge and dust contain those components such as alkaline metal compounds, Zn, S, and P by a large portion dropping the total composition of the useful components under 50wt%, such sludge and dust are not suitably used in the iron making process since those components would deposit within the
melter or act as heavy load in a hot metal pretreatment.
That is, if sludge and dust are mainly composed of those elements including Si, Al, S, P, Cl, Zn, Na and K rather than the above useful components, those elements may create severe problems in the operation of the iron making process. Specifically, Si and Al components removed as slag in the iron making process directly affect properties of slag such as melting point, viscosity, desulfurizing ability and so on. So there are a number of difficulties in recycling sludge or dust containing the Si and Al components by a large quantity. Further, in selection of fuel, raw material and supplementary raw material, those components are strictly restricted since they otherwise would yield low-grade pig iron and form deposits within the furnace while creating environmental problems.
In this regard, the invention preferably restricts the composition of waste material so that collected sludge and dust may contain Si and Al compounds each at 20wt% or less, Zn, Na and K components each at 5wt% or less and S, P and Cl components each at l wt% or less. The following Table 1 shows examples of dust and sludge applicable to the invention.
TABLE 1

(Table Removed 1)
MC: Moisture Content
Any waste material meeting the above composition standard is collected and then dried. Where the moisture content is too high, it is difficult to transport waste material on a belt or via air, and waste material is unsuitable for the iron making process.
The moisture content of dried waste material is controlled with a drier, preferably, at 10% or less.
Above dried waste material is sorted to have a certain particle size or less. Dried waste material is classified according to its particle size applicable to a dust burner, that is, for example, about 70mm or less since a blowing portion of the dust burner has an inside diameter of about 70mm.
Sludge and dust are necessarily melted and condensed' in flames of a dust burner for being recycled in the iron making process, however, the present inventors found out through researches that dust particles having a particle size of 5mm or more hardly melt or condense in the dust burner based upon iron ore regardless of their melting degrees which are varied depending on their components. Further, the inventors found out that in case where the iron ore particles have the large specific gravity and a particle size of 5mm or more, it is required to blow the air with a velocity of about at least 20m/s in order to pneumatically carry them up to a charging bin which is
installed at least 50m high from the ground, thereby not ensuring an efficient blowing.
Therefore, the invention restricts the particle size of waste material at 5mm or less, and preferably, at 3mm or less considering efficient blowing and melting.
And waste material having thus classified particle size is blown into the melter gasifier with the dust burner, and therefore, the waste material outputted in the iron and works can be efficiently recycled as fuel and raw material of the iron making process.
Hereinafter the following detailed description will discuss a detailed blowing method of the waste material prepared as above.
Fig. 2 is a schematic view illustrating a coal based iron making apparatus according to an embodiment of the invention, in which the apparatus generally comprises a reduction furnace 10 adapted for reducing ore and supplementary raw material, a melter gasifier 20 adapted for manufacturing pig iron through reduction-melting of reduced iron fed from the reduction furnace 10 and a cyclone 21 for trapping exhaust gas from the melter gasifier 20 to circulate fine dust in exhaust gas through a dust recycling duct 210 to the melter gasifier 20 and feed exhaust
gas cleared of fine dust through a gas duct 22 to the reduction furnace 10 as reduction gas.
Further, the reduction furnace 10 is connected through an ore-charging duct 12 to the melter gasifier 20 in an ore-communicating relation, and includes a dust burner 213 having one end connected to the cyclone 21 and the other end connected to the melter gasifier 10 and for executing melting condensation to and then blowing the fine dust into the melter gasifier 20.
First, waste material such as sludge and dust produced from processes in iron and steel works is collected in a storage 41. The collected waste material is dried in a drier such as a rotary kiln 42 for adjusting the moisture content suitable for recycling. Dried waste material is adjusted in a sorting machine 43 to have a particle size suitable for recycling. Coarse waste material sorted in the sorting machine 43 is sent again to a grinding machine 44, where coarse waste material is ground into a desired particle size.
In this manner, waste material having certain degrees of moisture content and particle size is stored in a storage 31, and stored waste material is fed through a rotary feeder 34 and a feeding line 35 to a temporary storage 36 which temporarily stores waste material. Waste material in the temporary storage
36 is fed through a rotor feeder 37 under the storage 36 to a storage 212 and then to the dust burner 213, by which waste material is blown into the melter gasifier 20.
In the meantime, the invention preferably mixes any material such as ore or coal, which is used as fuel or raw material in the iron making process, into above prepared waste material before feeding waste material to the dust burner 213 in order to enhance the melting condensation efficiency of waste material having the above composition and particle size distribution.
For the purpose of complete combustion of blown fine dust, at the leading end of the dust burner, the art examines the oxidation states of carbon component (raw material) and ore (regarding oxygen in metal oxide which is not completely metalized as reducing agent) while adjusting the quantity of oxygen which is blown in together with fine dust. Therefore, the degree of compounding between coal and ore can be changed into any value according to the carbon content and the oxidation degree of iron oxide in waste material to be treated. The compounding ratio is flexibly adjusted according to operating situations, that is, oxidizing agent component can be overly mixed to stop temperature elevation when the melter gasifier is so heated to excessively elevate its temperature due to complete combustion.
The following example will provide a more detailed description of the invention without restricting the extent of the invention.
EXAMPLE
The following experiment was performed in order to know whether sludge/dust can be recycled in the iron making process. The composition of sludge/dust used in this experiment is reported in the following Table 2. In Table 2, Inventive examples 1 to 3 each contain T. Fe, C, CaO and MgO components whose total composition is 50wt% or more, while Comparative examples 1 and 2 each contain the same components whose total composition is under 50wt%. In the meantime, sludge/dust particles used in this experiment are so sorted to have a particle size of 3mm or less.
TABLE 2

(Table Removed 2)
Sludge/dust waste materials having the above composition and sorted with their particle sizes were respectively blown into the melter gasifier of the reduction-melting apparatus configured as shown in Fig. 2 at a blowing speed of 5ton/hr for 3 days in order to make molten iron while evaluating any problems in operation and facilities related to blowing of the waste materials.
First, in order to determine the quantity of blown sludge/dust which leaves on reduction gas out of the melter gasifier 20 without melting condensation, it is measured the quantity of dust circulating in the dust recycling duct 210 and the air permeability of the reduction furnace 10 before and after blowing. As a result, it can be seen that both of sludge and dust waste materials have no effect on the air permeability of the reduction furnace and the quantity of circulating dust has no variation before and after blowing by the following reason. That is, since both of the sludge and dust waste materials have a particle size of 3mm or less within the inventive range, they could be effectively melted and condensed when blown into the melter gasifier.
Then, the effects for the composition of the blown sludge/dust are examined. As a result, in case where the waste materials of Inventive examples 1 to 3 within the inventive range
are blown into the raelter gasifier, there was almost no variation in the operation while increasing the yield of molten iron.
On the contrary, in blowing the waste materials of the Comparative examples 1 and 2 having composition beyond the inventive range, it is required to additionally charge certain quantities of lime and dolomite to adjust the basicity of slag thereby increasing the output of slag. That is, when blown into the melter gasif ier, sludge and dust which contain a small amount of useful components (e.g. T.Fe, C, CaO, MgO) and a large amount of Si and Al increase the output of slag by itself because they perform the same role as those components outputted as slag. Also, it is needed to further charge supplementary raw material to adjust the basicity of slag thereby dropping productivity.
As described above, in order to recycle sludge and dust outputted in the iron and steel working process in the coal based iron making process, it can be understood that sludge and dust necessarily contain T.Fe, C, CaO and MgO whose total composition is at least 50wt% as well as have particle sizes of 5mm or less by taking account of the increasing hot metal output and reduction in use of heat source and supplementary raw material.
According to the present invention as set forth above, there is a useful effect that dust and sludge produced in the iron and steel works and generally subject to burial are recycled as fuel and raw material in the iron making process.




We claim:
1. In a coal based iron making process by using a reduction-melting
apparatus which includes a reduction furnace for reducing ore and
supplementary raw material, a melter gasifier for reduction-melting
reduced iron fed from the reduction furnace into hot metal, a cyclone for
trapping fine dust in exhaust gas from the melter gasifier to circulate
trapped fine dust to the melter gasifier and to feed exhaust gas cleared of
fine dust to the reduction furnace as reduction gas, and a dust burner
with one end connected to the cyclone and the other end connected to
the melter gasifier and for executing melting condensation to and then
blowing fine dust into the melting gasifier, a recycling method of waste
materials comprising the following steps of:
collecting and drying waste material so that the total composition of T. Fe, C, Cao and MgO reaches at least 50wt%;
sorting dried waste material to have a particle size of 5 mm or less; and blowing sorted waste material into the melter gasifier with the dust burner.
2. The recycling method as claimed in claim 1 wherein waste material is
dried to have a moisture content at 10% or less.
3. The recycling method as claimed in claim 1 wherein dried waste material
is sorted to have a particle size of 3mm or less.

4. The recycling method as claimed in claim 1 wherein the blowing step of
sorted waste material comprises: mixing a proper amount of ore or coal
into sorted waste material.
5. In a coal based iron making process substantially as herein described
with reference to the foregoing description, examples, tables and the
accompanying drawings.

Documents:

IN-PCT-2002-01239-DEL-Correspondence-Others-(25-03-2010).pdf

IN-PCT-2002-01239-DEL-Correspondence-Others-(28-11-2008).pdf

IN-PCT-2002-01239-DEL-Drawings-(28-11-2008).pdf

IN-PCT-2002-1239-DEL-Abstract-(25-11-2008).pdf

in-pct-2002-1239-del-abstract.pdf

IN-PCT-2002-1239-DEL-Claims-(25-11-2008).pdf

in-pct-2002-1239-del-claims.pdf

IN-PCT-2002-1239-DEL-Correspondence-Others-(24-08-2009).pdf

IN-PCT-2002-1239-DEL-Correspondence-Others-(25-11-2008).pdf

in-pct-2002-1239-del-correspondence-others.pdf

in-pct-2002-1239-del-description (complete).pdf

in-pct-2002-1239-del-drawings.pdf

IN-PCT-2002-1239-DEL-Form-1-(25-11-2008).pdf

in-pct-2002-1239-del-form-1.pdf

in-pct-2002-1239-del-form-18.pdf

IN-PCT-2002-1239-DEL-Form-2-(25-11-2008).pdf

in-pct-2002-1239-del-form-2.pdf

in-pct-2002-1239-del-form-3.pdf

in-pct-2002-1239-del-form-5.pdf

IN-PCT-2002-1239-DEL-GPA-(25-11-2008).pdf

in-pct-2002-1239-del-pct-210.pdf

in-pct-2002-1239-del-pct-308.pdf

IN-PCT-2002-1239-DEL-Petition-137-(24-08-2009).pdf


Patent Number 240837
Indian Patent Application Number IN/PCT/2002/01239/DEL
PG Journal Number 24/2010
Publication Date 11-Jun-2010
Grant Date 03-Jun-2010
Date of Filing 13-Dec-2002
Name of Patentee RESEARCH INSTITUTE OF INDUSTRIAL SCIENCE & TECHNOLOGY
Applicant Address C/O RESEARCH INSTITUTE OF INDUSTRIAL SCIENCE & TECHNOLOGY, SAN 32, HYOJA-DONG, NAM-KU, POHANG-SI, KYUNGSANGBOOK-DO 790-330, REPUBLIC OF KOREA.
Inventors:
# Inventor's Name Inventor's Address
1 CHO, MIN-YOUNG C/O RESEARCH INSTITUTE OF INDUSTRIAL SCIENCE & TECHNOLOGY, SAN 32, HYOJA-DONG, NAM-KU, POHANG-SI, KYUNGSANGBOOK-DO 790-330, REPUBLIC OF KOREA.
2 LEE EUN-HO POSCO CO., LTD., 5 DONGCHON-DONG,NAM-KU, POHANG-SI KYUNGSANGBOOK-DO 790-360, REPUBLIC OF KOREA.
3 SHIN, MYOUNG-KYUN C/O RESEARCH INSTITUTE OF INDUSTRIAL SCIENCE & TECHNOLOGY, SAN 32, HYOJA-DONG, NAM-KU, POHANG-SI, KYUNGSANGBOOK-DO 790-330, REPUBLIC OF KOREA.
4 LEE, JUN-HYUK C/O RESEARCH INSTITUTE OF INDUSTRIAL SCIENCE & TECHNOLOGY, SAN 32, HYOJA-DONG, NAM-KU, POHANG-SI, KYUNGSANGBOOK-DO 790-330, REPUBLIC OF KOREA.
5 NAM KUNG, WON C/O RESEARCH INSTITUTE OF INDUSTRIAL SCIENCE & TECHNOLOGY, SAN 32, HYOJA-DONG, NAM-KU, POHANG-SI, KYUNGSANGBOOK-DO 790-330, REPUBLIC OF KOREA.
PCT International Classification Number C21B 13/00
PCT International Application Number PCT/KR02/00785
PCT International Filing date 2002-04-26
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2001/23113 2001-04-27 Republic of Korea