The plasmadust process for recovery of metals from waste oxides

Resources and Conservation, 9 (1982)191-198 Elsevier Scientific Publishing Company,Amsterdam -F'rintedin The Netherlands

THE PLASMADUST

PROCESS

FOR RECOVERY

OF METALS

191

FROM WASTE

OXIDES

H.G. HERLITZ SKF Steel

Engineering

AB, Hofors

(Sweden)

ABSTRACT Considerable

quantities

and steel

industry.

these,and

there

with

their

With

dumping

to produce

coal powder

provided

with

is efficient,

losses

methods.

specific

investment

Successful arc heater

iron,

making

A centra1 most

Because

associated

can be treated

as metallic

where

in a normal

shaft

is injected

and gaseous

metals

condenser. of electrical

are wel1

of the simple

filled

the material

and liquid

the utilization costs

zinc and

is pneumatically

competitive

equipment

energy

with

required,

con-

the

is low. have been

carried

out in a smal1

1.5 MW electric

300 kg/h.

steelmaking

Tests

resulted Similar

in a liquid

in metal

PLASMADUST

plant

plant

with

a plasma

and a feed rate of waste baghouse

yields

tests with

iron alloyed

high metal

oxides

power

with normal

again with

of the waste

problem

are extracted

zinc and lead.

resulted

molybdenum,

wastes

the fine material

reduced,

are small,

of maximum

of about

arc furnace both

tests

of these

arc heaters

and the operating

ventional

for recycling

into the lower part of a coke

plasma

The latter

As the heat

in the iron

suited

problems

iron as wel1

sintering

are instantaneously

are formed.

oxides

many

a liquid

injected furnace

environmental

process,

previous

The oxides

are generated

are not wel1

or stockpiling.

lead. Without with

oxides

methods

are increasing

the PLASMADUST

economically

of waste

Present

with

dust

dust

of more from

from electric than

97 % for

stainless

chromium,

nickel

steel-

and

yields.

in each

steelmaking

from that area,

and at the same time recovering

thus

area

solving

valuable

co,uld recycle an environmental

metals

material.

Publishing Company 0166-3097/82/0000-0000/$02.75 0 1982 Elsevierscientific

from waste

192

INTRODUCTION The

iron and steel

containing these

valuable

wastes

siderable

to several

percent

The steel

companies

incur

The situation much

rising

rapidly

A similar other

THE PLASMADUST

should

be a need

wastes

back

process

by SKF Steel.

in powder

form

an energy 3500°C

a cavity

is formed

reducing

agent

Practically when

plasma

of each

al1 metal

iron thus produced

electric

are

metals.

industries

that could

econo-

enter melts

generator

of this gas to

the gas through

(Fig. 2). The shaft part

leve1

of a hot gas

The preheating

occurs.

al1 heat

Waste

at the tuyere

quantity

in the lower

15% coke)

oxides

an elecis filled

of the coke

column

reaction

between

As there

is no admission

required

oxide

for the reduction

in the feed material

the reaction

and

ema-

as from

steelmaking,

are vaporized

a blast

frequently

in the bottom

furnace.

The

of the shaft.

furnace.

occurring

are reduced

(completely

are instantaneously

zone in the shaft

and is collected

of zinc and lead, arc furnace

a smal1

sheet.

and

gas.

Iron and slag are tapped

the metals

or stock-

costs

was developed

flow

are injected

the endothermic

free oxygen,

they

recycling

by passing

tuyere

in which

from the plasma

Oxides

from

last

metals.

the process

with

is performed

(85% coal,

of air or other

oxide

1 shows

together

tric arc in a so-called

reduced

dump

valuable

for a process

of 4 - 8 kWh/Nm3.

(6330OF)

In front

for waste

Fig.

density

nates

many

oxides

to useful

and coal powder

with

coke.

companies

the associated

dust,

States

PROCESS

furnace,

with

which

arc furnace

steel

States,

each year.

stockpiling,

in the United

waste

there

of a low shaft

about

many

and

contain

these

The PLASMADUST

oxide

with

In the United

are generated

Electric

although

amounts

iron and steel.

convert

patented

that many

industry

waste

the wastes

exists

produced.

for dumping

reasons.

oxides,

and although

Consequently, mically

waste

situation

than

quantity

but con-

they cannot

1-2).

from the steel

a hazardous

is thus

of their

(refs.

Some of

processes,

because

tons of such waste

for environmental was declared

metallurgical

oxides

costs

of wastes

in the form of oxides.

or stockpiled

of the steel million

rapidly

large quantities

be recycled

of waste

several

for example,

pile

usually

are dumped

quantity

for example,

generates

in various

or economically

The total

year.

metals,

are recycled

quantities

technically

grow

industry

in baghouse in the same

dust

from

fashion,

in the case of zinc and partly

and in

193 the case qases

of lead) . The metal

and are col lected

The condensation content

as metals

leave

present

and consequently

process

different

since

there

the furnace

when

is no carbon

no reoxidation

from competirig methods

risk.

there

This

2 Principle

of a plasma

generator

or water

feature

process

Insulation

Fig.

the off-

is a low zinc

dioxide

(refs. 3-8).

1 Flow sheet of the PLASMADUST

with

outs ide the furnace.

in a condenser

of zinc is also efficient

in the charge,

Fig.

vapors

makes

vapor this

194 Part of the lead produced iron

in the bottom

during

of the furnace.

as liquid

The lead

The only

gases

formed

ly return top have

in presence

(from the coal);

of the suspended

particles

of coke

in the column

should

in the reaction

zone were

accurately

controlled

the feed of materials would

occur

The excess

riations

lY, when

which

heat

are reduced.

the coke

result

is absorbed

the hot coke

surface

monoxide and most

and eventual-

the furnace

dioxide

be discussed. Even

at the

material

brought vapor

and the reoxidation

and thus

either

consumed,

energy,

temperature

va-

of

or is eventual-

into the reaction

are eliminated

of zinc vapor

fluc-

collector

melts

back

be-

of the tempera-

as a good

and water

coke

by the equivalente

of electrical

by the coke

First,

if the temperature

in an elevation

the coke acts

Second,

is slowly

carbon

Third,

and the input may

and the collected

flue particles,

with

the iron

are carbon

in the shaft,

leaving

material.

zone.

from

the

and can thus be used.

refractory

tuations

coke

rise

on the coke

The gases

zone.

heat value

importante

gases

are caught

to the reaction a high

of excess

these

and cheap

ture.

beneath

is separated

is an excellent

tween

metal

tapping.

and hydrogen

The

is collected

by reaction

deterred.

APPLICATIONS Al1

steel

enriched. steel

furnaces

This

furnace

flue dusts Such dust

generate

flue dust

is especially

valid

in galvanized

containing

more

is an economie

scrap. than

in which

volatile

elements

for zinc and lead which Consequently,

10 % Zn and

feed material

electric

enter

are

the

arc furnace

1-4 % Pb are not uncommon.

for the PLASMADUST

process

as

just described. Of course,

the

zinc content

10 % for the material from

the steel

and dusts verters. main

PLASMADUST

have much

blast

plants,

These

materials

are equally

from

requirement for pneumatic stainless

nickel

yielding

Many waste

zinc contents, furnaces

wel1

suited

to be more

and basic

than

oxides

e.g. mi11 oxygen

for the process,

that they are sufficiently

scales conthe

dry and

feeding.

steelmaking

and molybdenum.

process,

ing elements.

being

not have

in the process.

lower

sintering

fine to allow

chromium,

to be treated

industry

from

technical

Wastes

in the feed does

usually

These

contain

wastes

a hot metal

high

contents

can be treated

containing

of

in the

the valuable

alloy-

195

Although probably einder

there

not yet tested, be economically

from

sulphuric

lead;

TEST

RESULTS

In a pilot

plant

having

able

materials

than

oxide

to process

in so smal1 a unit,

it wil1

furnace.

composition

was

Pb0 Balance yields

test a dust

from

hot metal

Al1

typical yield been

- as hot metal

oxides

dust

steelmaking

was processed:

13% 5% 1% 43% 38%

%

Yield,

%

>85 99 99 98

or cold pigs

plant

have

from steelmaking

in the PLASMADUST encountered.

losses higher

- would

be an attractive

raw

steelmaking.

in the pilot

waste

heat

is much

In one test a baghouse

15 8 2 68 4 3

in stainless

tests

Since

was obtained:

Cr Ni Mo Fe C Balance

material

tested.

consumption

treated:

Composition,

alloy

used at

up to 0.3 Mg of dust per hour,

stainless

Fe2o3 Balance

This

(normally

99% >97% >97%

Cr203 Ni0 Mo02

An alloyed

of metals,

were: Fe Zn Pb

In another

that can

50% 25% 2% 23%

;;$"3

The metal

wastes

Some examples:

from production

generator

has been

the energy

be in a fullsize

of the following

slags

a 1.5 MW plasma

0.7 - 0.8 MW) and being

are large

oxidic

sludges.

a series

of waste

other

in the same way.

acid production;

and grinding

e.g.

are many

processed

process.

shown

that the valuable

can be recovered

NO serious

operational

with

metals

in

a high

problems

have

196

ECONOMICS Assumptions A plant

is built

for treatment

of flue dust with free of charge

22% zinc,

power

Reduction I,

charge

to the plasma

of 100,000

The dust

furnace

Mg

is delivered

amounts

at an efficiency

Fe at

"

Pb at Zn at at

1500°c

550 kWh/Mg

"

II gaseous slag

as an average

with

to the

of 85% of the

generators:

to molten

in a plant

%

25% iron.

in a plasma-heated

on a cold

of one Mg of fuel

renders

Quantities

Metal

input

of silicate

Consumption furnace

based

of Fe203 II Pb0 ,I Zn0

II Melting

of energy

figures

electric

5% lead and

quantity

at the plant.

The consumption following

of an annual

1500°C

2150 kWh/Mg

Fe

8OOOC

400 kWh/Mg

Pb

1000°C

2300 kWh/Mg

(coal or coke)

gases

with

an annual

Zn slag

in the plasma-heated

a combustion

value

capacity

of 100,000

in 1000 Mg

Energy

requirement,

content

per Mg metal

saleable

of 4535 kWh.

Mg of dust kWh

per Mg dust

quantity

Zinc

22

22

Lead

5

5

Iron

25

25

20

2300

4.5 22

506

400

20

2150

538

Others

173

550 Sum

The plant

should

be dimensioned

put in 6000 hours,

i.e.

for treatment

16.7 Mg/h.

The furnace

1237

of the annual capacity

should

throughbe 22 MW.

Investment The total included

investment

in this

wil1

be about

$ 22 million.

The following

figure:

Dust

handling

equipment

Lime

handling

equipment

Coal

handling

equipment

Coke

handling

equipment

Shaft

furnace

Plasma Process

generators, gas

system,

including including

power

supply

condenser

is

197

Iron and slag handling Proces5

control

Planning, The following

is not

design,

erection

included:

Raw material Cooling

equipment

equipment

stock yard

water

Utilities Genera1

supply

such as compressed electric

power

air, oxygen,

steam

supply

Buildings Production

costs

Al1 costs price

and prices

levels

in this paper

in the United

are expressed

at August,

1981,

States.

Materials Quantity

Item Furnace

dust

Electrical

100,000

energy

1237

106 $ per year Sum Cost

Price Mg

- 105kWh $ O.OQ/kWh

Coal

15,300

Coke

4200 Mg

Mg

4.95

$ 5O/Mg

0.77

$ 12O/Mg

0.50 1.50

Misc.

7.7

Labor 50 workers

at $ 30,000

per year

1.50

5 staff

at $ 35,000

per year

0.18

1.7

Repairs 4 % of investment Capita1

tost,

0.9 20 % of investment

4.4 Sum

14.7

Revenues Price

Item 20,000

Mg zinc

$ 9OO/Mg

Value,lO'$ 18.0

4500

Mg lead

$ 8OO/Mg

3.6

22,000

Mg iron

$ lOO/Mg

2.2

75,000

MWh

$ 12/MWh

0.9

in gas

24.7 Differente

$ 10.0 x 106

198

This under

calculation the assumed

COMMERCIAL

nace

be able

baghouse

dust would

wil1

dust with

wil1

be profitable

an average from

above,

annually

zinc content

the various

of steelworks

located

100,000

in the Pittsburgh

Mg of electric approaching

steel mills

in this district,

arc fur-

20 %. The

in the area.

Due

the transportation

be limited.

A PLASMADUST

plant

Pittsburgh,

Chicago

arc furnace

dusts

vironmental

problems.

in each major and Houston

that

In the end,

ed, too.

in the exampel

to process

be collected

to the concentration costs

plant

OPERATION

of the size

would

that a PLASMADUST

conditions.

PLASMADUST

A plant area,

indicates

today

a nationwide

city between

10,000

process

of the wastes

most

- could

cause

Gradually

and 200,000 being

steelmaking recycle

increasing

other

waste

system

- for example

most

of the electric

disposal oxides

oxides

costs

could

of plants,

Mg of waste dumped

area

varying per year,

or stockpiled

and en-

then be treatin capacould

today.

REFERENCES S.B. Floyd and L. Pasztor, Managing and Disposing of Residues from Environmental Control Facilities in the Steel Industry, EPA Report 600/2-76-267, EPA Office of Research and Development, Research Triangle Park, N.C., 1976. R.P. Leonard, R.C. Ziegler, W.R. Brown, J.Y. Yang and H.G. Reif, Assessment of Industrial Hazardous Waste Practices in the Metal EPA Smelting and Refining Industry, EPA Report 53O/SN-145C.1, Hazardous Waste Management Division, Office of Solid Waste, Washington, D.C., 1977. L.'fl.Higley and M.M. Fine, Electric Furnace Steelmaking Dusts 8209, US Bureau of a Zinc Raw Material, Report of Investigations D.C., 1977. Mines, Washington, P.G. Barnard, W.M. Dressel and M.M. Fine, Arc Furnace Recycling of Chromium-Nickel from Stainless Steel Wastes, Report of InvestigaD.C., 1977. tions 8218, US Bureau of Mines, Washington, K. Sugasawa, Y. Yamada, S. Watanabe, K. Kato, K. Masuda, Y. SutO and T. Kawabato, Stahl und Eisen 96 (1976):24, pp. 1239-1244. Washington, M. Harris, in Proc. 1st Process Technology Conference, D.C., March 25-26, 1980, Vol. 1, The Iron and Steel Society of AIME, Book Crafters, Chelsea, MI, 1980, pp. 62-71. H. Maczek and R. Kola, Jour. of Metals 32 (1980):1, pp. 53-58. J.K. Pargeter and H.J. Weil, in Proc. 1st Process Technology ConD.C., March.25-26, 1980, Vol. i, The Iron and ference, Washington, Steel Society of AIME, Book Crafters, Chelsea, MI, 1980, pp.172-177.