DE2603096A1 - PROCEDURE FOR DUST RECYCLING - Google Patents

Description

NIPPON STEEL CORPORATION No ₀ 6-3, 2-chome, Ote-machi, Chiyoda-ku, Tokyo, Japan

KOWA SEIKO COMPANY, LTD. No. 8-2, 1-chome, Marunouchi, Chiyoda-ku, Tokyo , Japan

"Procedure for treating dust"

The invention relates to a method for processing dust, in particular industrial dust, for selective Recovery of carbon and metals such as iron, zinc and lead, for example from metallurgical dust, such as furnace gas, Converter, electric furnace and sinter dust.

Metal-containing dusts, in particular smelter dusts, usually consist of particles with a diameter of 2 to 3 μm and coarse particles with a diameter of about 1 mm Coke particles.

A number of methods for processing such dusts are known. For example, a well-known technique is to to subject the dust to a zinc and lead leaching process, then filtering off the lye and adding the filter cake

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a drying process to blast furnace sinter.

A major disadvantage of the known method is the need to remove the zinc and lead before a Re-use of the dust to loosen or remove, because these metals are particularly in a "use of the dust for making pellets or sinter adversely affect the furnace aisle.

The removal of zinc and lead requires complex equipment and causes high costs, especially at low costs Yield all the dust that needs to be treated. Unlike carbon, the two metals mentioned can also be used do not separate by flotation or magnetically. For this reason, dusts containing zinc and lead are becoming industrial not reconditioned and not used again.

The invention is based on the object of creating a method for processing zinc and lead-containing dusts with a particle size of 2 to 3 μm and coarse particles of about 1 mm and for recovering zinc and lead. The solution to this problem consists in a method in which a slurry or pulp containing at most 50%, preferably about 30% dust, is hydraulically sorted. The hydraulic sorting can be done with the help of a cyclone, a vibrating sieve or an ultrasonic sifter. Over 70% of the harmful zinc and lead can be removed and at the same time over 70% of the iron and carbon can be recovered for reuse as a furnace insert.

The overflow of the hydraulic sorting is then reduced, leached, oxidized roasted and then finally optionally roasted in a chlorinating manner after flotation, while the underflow is either immediately sintered or

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Pellets are processed or leached first. In this way, zinc and lead on the one hand as well as iron and, on the other hand, recovering carbon or dusts in a non-ferrous overflow and a ferrous underflow separate. This has the advantage of much lower investment and process costs for further processing of the two factions joined,

The invention is explained in more detail in the following with reference to exemplary embodiments and the drawing Drawing show:

1 shows a family tree of the method according to the invention,

2 shows a cross section through a hydro-cyclone for the hydrosorting according to the invention and

3 shows a family tree covering the entire process.

The metal-containing dust to be processed comes from a bunker 1 into a sorting stage, for example into a hydro-cyclone, a hydro-vibrating screen or a hydro-ultrasonic sorter. The overflow is obtained from sorting stage 2 either via a flotation stage 3 or a by-pass line 4 a reduction stage 5, a leaching stage 6 or an oxidizing roasting and chlorinating evaporation 7 fed. Accordingly, the overflow is either chemically treated directly in stages 5, 6 and 7 or first in the Level 3 floats. The underflow of sorting stage 2 either arrives via a leaching stage 8 or directly via a bypass line 9 in a processing stage 10, for example for pelletizing or sintering.

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Depending on the selectivity in sorting level 2, the contents of zinc and lead in the starting dust and its use of the dust from the underflow can be the flotation, reduction and leaching stages for the overflow are not necessary and it is sufficient to roast and chlorinate the overflow exclusively in an oxidizing manner. Leaching can also do the same the discharge of the underflow of the sorting stage is omitted and the underflow is further processed directly in stage 10 will. On the other hand, it can also be useful to sort the pulp twice in this way or to repeat it in sorting stage 2.

In the hydro-cyclone shown in Fig. 2, you are the one Diameter of the underflow opening and Do is the diameter of the Overflow opening as well as IM the feed line. As part of an experiment, a moist gout dust with 18.51% total iron, 6.48% silica, 3.19% alumina, 1.60% lime, 50.0% carbon, 2.01% zinc and 0.52% lead among those in the following Table I listed conditions sorted. Where P is the feed pressure of the dusty dust, k is the dust concentration of Slurry, A the proportions of the overflow and the underflow, based on the dry weight, Ü.L the overflow and U.L the Underflow of the hydro-cyclone.

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Table I.

Try You / Do P k

(bar) (Ji)

Zn

salary

Pb

salary

0.72 1.5

CD CO OO CO

25th U.L. 71.8 0.37 13.1 0.11 15.3 I.
VJl U.L. 28.2 6.16 ' 86.9 1.50 84.7 I. 30th U.L. 67.3 0.63 21.3 0.17 22.4 Ü.L. 32.7 4.81 78.7 1.19 77o6 40 U.L. 64.5 1.03 33.2 0.28 35.6 Ü.L. 35.5 3.76 66.8 0.91 64.4 50 U.L. 61.3 1.48 45.3 0.37 45.2 Ü.L. 38.7 2.86 54.7 0.71 54.8 60 U ₀ L. 58.2 1.66 48.3 0o44 51.3 Ü.L. 41.8 2.47 51.7 0.58 48.7

O LO CD CO CD

From the data in Table I it can be seen that at one concentration over 50% the selectivity gradually deteriorates. As a result, the concentration of Preferably cloudy at about 30%. On the other hand, if the concentration of the sludge is around 10%, it is smaller in the lower reaches Enriching particles, then the zinc output in the overflow can be improved without impairing the underflow.

Similarly, when separating with the aid of a hydraulic ultrasonic sieve, particles can be separated with a Diameter less than 5 μm and particles with a diameter greater than 5 μm a 65% recovery of the underflow at 80 to Achieve 85% removal of zinc,

When sorting a pulp with a concentration of dust hydraulically of 25% according to the experiment in Table I, the underflow can be further processed directly, for example to a blast furnace sinter.

In the embodiment according to FIG. 3, the metal-containing Dust from a bunker 1 into a hydro-cyclone, the underflow of which via a line 9 to a dewatering stage 11 and from there via a dryer 12 into a bunker 13. Some of the dust escapes from the bunker 13 the underflow into a pelletizing stage 14 for mixing, grinding and pelletizing while another part is mixed with cement and a pelletizing stage 15 for mixing, grinding and Pelleting is fed, from which the pellets pass into a hardening stage 16 for a hardening period of two to three days. Another part of the output is finally mixed with slaked lime and goes to mixing, grinding and Pelleting into a pelletizing stage 17 and from there into one Carbonization tower 18, while finally another part of the discharge mixed with sinter and a sintering stage 39

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is fed. The one leaving the output stages 14, 16, 18 and 39 Good is suitable for a furnace painter

On the other hand, the melting conditions of a blast furnace allow direct processing of the underflow of experiment 4 of FIG Table I not too. Such an underflow is therefore first a leaching stage 19 for loosening the zinc and the Lead with the help of mineral acids and water and then a Filter stage 20 supplied, from which the filter cake passes into the aforementioned dewatering stage 11 and in the is further processed in the manner described above. The filtrate passes into a reaction stage 10, in which the extinguished with the help Lime zinc and lead are precipitated as a gel. The gel is filtered off in a filter stage 21 and then in a dehydration stage 22 dried

The overflow of sorting stage 2 reaches the filter stage 21 via a bypass or pipe 4 and from there to the dewatering stage 22 _O A part of the cake produced in the dewatering stage 22 is mixed with a reducing agent such as coke powder and lime in a mixed and Grinding stage 23 is offset and then passes via a drying and preheating stage 24 to a rotary kiln 25, in which reduced pellets are produced with the addition of reducing agents. The remainder of the cake passes through a turbidity stage 26 into a leach stage 27, where mineral acid and water are added to leach out zinc and lead. The lye stage 27 is followed by a filter stage 28, the filter cake of which is fed into a dewatering stage 29. After dewatering, the filter cake, like the discharge from the bunker 13, is further processed into blast furnace sinter or pellets

The zinc- and lead-containing filtrate from the filter stage 28 is converted into slaked lime in a reaction stage 30 Zinc and lead precipitated as a gel, which in a filter stage 31

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filtered off and then a dewatering stage 32 is fed. The remaining amount from the dewatering stage 22 is oxidatively roasted in a roasting stage 33 in order to remove the carbon and then mixed with a chlorine carrier such as calcium chloride and roasted in an evaporation stage 37 in a chlorinating manner. The evaporation residue is then pelletized in a mixing and pelletizing stage 34 The pellets then go to a drying stage 35 and are finally fired in a rotary kiln 36, while the zinc- and lead chloride-containing vapors are further processed wet-chemically.

The 30% dust-containing pulp from test 2 was sorted hydraulically, the overflow being used to separate the Carbon was floated. When floating, the carbon went into the flotation foam, while iron, zinc and lead remained in the residue, the carbonaceous Foam can be used as a reducing agent, while the flotation residue is reduced in the manner described, leached, oxidized and roasted with chlorine, and the residue that remains is processed into sinter or pellets will.

According to Table II, the ferrous fraction makes up in the invention Process about 70% and the NE fraction about 30% off. The ferrous fraction contains about 20% iron and about 50% carbon; it can be used as a blast furnace insert Use in the form of pellets or sinter without affecting the furnace. This is due to the low levels due to zinc and lead. The non-ferrous fraction of the gout dust contains about 6% zinc and about 1.5% lead and is thus characterized by a high NF metal yield.

The fact that the high output of iron and zinc is particularly advantageous in the process according to the invention

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and lead can be achieved in a compact processing plant without a large outlay in terms of equipment and thus inexpensively leaves.

The results of the process according to FIG. 3 can be seen from Table II below.

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CD CD CD OO

cn ~ o
m

Wet Gichxsxaub (%)

Zn

Pb

Fe

total

47.0 20.1 0.55 18.5

Unxerlauf (%)

Zn

Pb

Fe

47.7 0.43 O.19

total 18.5

Leaching (* 1)

Residue (%)

73

Overflow {%)

C zn 45.0 6.20

Fe

ges,
18.5

Zn

Fe

total

50 0.052 19.2

proportion of

69

solution

PH value

Output Anreil (%)
27

Flotation proportion of Foam (%) Anxeil Residue (fi) ¹² · ^{5 40} KOk ₃ V ⁰ - ⁸
9 I. Zn Fe coke
ses. 16.2 ^{2n Fe} _S es. 1.8 45 82

1
2 Sintered ore (%) according to fine
ore Marcona-
fine ore serpentine Application
(%) Limestone
powder Sintering time
(min.) Return
BUt Coke-
grus • 27.3
26.7 iaL Under
run 79.9
78.9 5.0
5.0 2.6
2.6 68.4
68.5 12.5
12.5 17.6
17.8 25.0
25.0 3.8
3.8 Mater 1
2 10 productivity
(t / m ² / h) processing
(%) Per-
duct 17.9
17.8

Reducing agent
for non-ferrous metals

^ Oxidizing roasting

Fe

total

0.1 9.9

29.5

H ₉ SO ₄

CaC]

CD O LiO O CD CD

CD O CO CO CJ

co t jj ed

O U

Cold pellets

Table II continued

ionverter dust

60

Underflow dust

10

dust

20th

Compressive

Keix

(kp / p)

150-200

Compressive strength after reduction (fcp / p)

100-120

Cement clinker

10

Reducibility

(Si)

70-80

Solid, liquid Leach time
(min.) Initial conc.
H ₂ SO ₄ *1 1: 3 60 40 g / l * £ 1: 4 60 20 g / l

Leaching (* 2)

Residue {%)

solution

50 0.06 18.1

proportion of

24. ρ

aisenher atstellung

PH value

Application

Ki-Metail manufacture

tr. pellets (%)

^ ⁵ O-Oe ^ ^{n Cu} Cad,

57.8 O.S. 0.7 4.2

used pellets

Fe Zn Cu CaCl ₂

61.4 0.03 0.03 -

K) CD O U) O CD CD

Claims (1)

Patent claims: 1β Process for the treatment of dust, especially mill dust, characterized in that a sludge containing at most 50% dust is hydraulic is sorted. 2. The method according to claim 1, characterized in that the overflow is a hydraulic Sorting stage is reduced, leached, oxidized and chlorinated roasted individually or one after the other. 3. The method according to claim 2, characterized in that that the overflow of a hydraulic sorting stage is fied and then reduced individually or one after the other, is leached, oxidized and roasted in a chlorinating manner. 4. The method according to claim 2 or 3, characterized in that the underflow of the hydraulic Sorting stage is processed directly into sinter or pellets. Method according to Claim 4, characterized in that the underflow is first leached. 609831/0763 Method according to one of Claims 1 to 5, characterized by a multiple hydraulic
Sort by. 7. The method according to any one of claims 1 to 6, characterized in that the pulp in a hydro-cyclone is sorted. 8. The method according to any one of claims 1 to 6, characterized in that the pulp with the aid of a hydraulic ultrasonic sieve is sorted. 9. The method according to any one of claims 1 to 6, characterized in that the pulp is eichnet with a hydraulic Vibrating sieve is sorted. 609831/0763