6th mineral waste utilization symposium

Conference

reports

6th Mineral Waste Utilization Symposium The buff-coloured volumes of collected papers of the biennial symposia jointly sponsored by the US Bureau of Mines and the Illinois Institute of Technology Research

Institute

of resource in scope

are now essential

recovery.

and

the

reference

Since their inception

6th

symposium

tools for all workers

in 1968,

included

47

sessions, over a period of two days. 6th Mineral Chicago,

2-3

May

papers

Waste

delivered

IJtilization

in the field

have widened during

six

Symposium,

19 78.

The proceedings were opened by the Assistant Director - Metallurgy, US Bureau of Mines, who took as his theme a definition of conservation as the sum of maximum utilization with minimum waste. Citing as example practice at a zinc mine in Tennessee, where an ore containing about 4% of zinc and more than 95% limestone was processed into zinc, stone and agricultural limestone as fractions, the speaker saleable proceeded to examine the current status mineral extraction of the primary industries. The fact that the average grade of copper ore mined has fallen 1900 to 3% in around from considerably less than 1% in 1978, makes clear the need for development of uses for the byproducts of extraction. in other obtain Similar situations extraction processes, notably in the iron industry. The crucial question is whether the increased amounts of energy and effort required to produce metals from ores whose grades fall inexorably may partially be offset by the perceived values for byproducts formerly discarded. Some 870 million tonnes of waste are generated annually by the copper industry, and 320 million tonnes by the phosphates industry. The wastes of all the primary metal extraction operations in the USA are probably more than 2 x lo9 tonnes, exceeding by an order of magnitude the arising of municipal solid waste. For the most economical total operation it is essential that useful applications be developed for fractions now discarded. Iron slags containing 25-30% iron are

RESOURCES

the events

POLICY

useful copper potentially for cementation, and sulphur recovery from smelter gases could far exceed the possible market for the element. One may look forward to the time when scrap will be a major and not a minor source of materials. This, of already applies to certain course, specialized areas of industry such as steel production in minimills, operating on a 100% scrap charge.

Legislative help Whilst the materials secondary achieve recovery industries often recovery rates, praiseworthy performance in some sectors is still rather poor. Congressional legislation has already proved a spur to the development of recovery technologies, but the industry may expect further interference both by the lawyers and the politicians. The unusually speedy progress of the 1976 Resource Recovery Act is evidence enough of the seriousness with which the Congress views the question of resource recovery. However, the complexity of government interest is exemplified by the fact that no fewer than 18 federal agencies are currently involved in problems of resource recovery. A movement towards maximum use of recycled materials may prove significant in the context of more than 9 000 federal facilities that may in future be required, in their ordering. to specify a minimum content of secondary materials. In the final analysis, the acceptability

December

1978

of any material. primary or secondary, depends upon its meeting the specified performance data for a particular application. The American Society for the Testing of Materials is examining the whole question of specifications for secondary materials. Whilst concerned primarily with wastes destined for disposal, as compared with scrap metals for which recycling channels are already well established. subcommittees of the main E38 committee deal with glass, metals. paper and with both ferrous and non-ferrous metals. Amid the wealth of operating data on the treatment of municipal solid waste (MSW), little is written on the day-today problems of the plant. In one contribution, however, attention was drawn to the hazards attendant upon the presence in the waste stream of items such as cans of combustible materials. quantities of blasting powder, and even dynamite. Up until April 1976 the shredding of 7.5 million tons of MSW had been accompanied by 97 explosions. of which 69 did significant damage, averaging about $50000 per incident. The use of devices that flood the shredder halogenated with hydrocarbons, or that damp the refuse with controlled moisture additions, were only two of the measures described in a paper dealing with a much neglected facet of the subject. Often overlooked by all but the more optimistic conservationists is the fact that world resources of many materials are. to all intents and purposes, practically inexhaustible. The crust of the earth contains vast tonnages of almost all metals. It has been calculated, for instance, that the first 2 000 m depth of the crust sufficient contains aluminium to last for 1 500 million years at current rates of consumption. The key to the exploitation of these riches is energy. and the cost of the finished metals will reflect the cost of the energy required to extract them.

Energy costs It is an Article of Faith that secondary materials may be produced from scrap at a fraction of the energy investment required for corresponding primary supplies. That this is not invariably the case may be demonstrated if one reflects upon the

295

Cortferetrce energy

reports

required

to

collect

dispersed

wastes such as beverage cans discarded over a wide area, or to beneficiate as would

be necessary

of aluminium used

to

from

bchoves

us

analyses

of

proccdurcs

wrappings

cigarettes.

lo

them

for the recovery

the foil

package

make

If

careful

collection

to establish

thus

energy

and

data

were

types

reference

to

the

scrap

operation.

for

deficient

can almost form

an

world

were outlined systetn

them.

and where

times as much energy drosses,

that required

with

iron.

some

versus an

Anti-pollution that

the

on

more

cost

pollution

refuse than

an

has

the

Such

can

incinerator

enrichment referred

of

Economics The

dramatic

rise in oil prices

1973-74

has changed

resource

reclamation

of

refuse-

Significant

the economics and

now

comparable A town

and the current

fabrication

that

which

form of the waste product, albeit

similar.

less

Further

variations

choice

of

were for

presented

could the

the

clean

be pot-melted

product,

and

consume

virgin

material,

energy

possible.

Efforts

directed

towards

winning methods

296

generation

complete

of

avoid as

the

required

be new

is

daily

many speakers

pitfalls

of

designing

are fossil of the

that

of

surprising

the

processing

differences

are,

compound

evaluation

any

Only gradually has it been widely recognized that the steady markets that must be enjoyed

by recovered

criteria.

exceeds

that

$1.5 x 10y will be required. Some 35% of the systems currently under proposal

3.0%

and

sell

costs

markets suggested

RDF,

ranging

and from

need for guaranteed

recovered

the

idea

products of

was cited

of the city

tonnes/day.

burn,

for

initially,

of refuse and that will developed to 1 800

Ferrous

be the products

will

The

of Albany,

where boilers are under construction that

has

partnerships

between city and state in the USA. cast

will $4.4.

being

Data

metals and fuel wilt

of a separation

system

to

recovery average were

and

of 6%. also

l-23%

lead,

tin

remains recovered Similar

to

be

of

of much

make

the

acceptable. in

the

degradation

paper

of paper of fibre

of the properties.

Here, the aim of recovery

POLICY

eddy-

capable to

exist

length to the detriment

RESOURCES

and,

or

where the re-pulping

paper

refuse

bismuth

are

done

causes successive

separate

the

generally

problems

industry,

In

improvement,

metal

an

picks up silicon,

and

some

0.16. with

lead and tin

heavy-medium techniques

effecting

mobile

zinc

Bismuth.

aluminium

although

showing in

contain

problems.

incinerator

current

presented

could

on

specification

reclaimed

centres

silicon

products depend

meet

were

aluminium

copper, for

of a

projected

system.

estimated

at

by

which

Meeting specifications

$12 x 10’ and the peak year for investment will probably be 1985, when

extract

of

the difficulty of

able

will

however,

all

their

investment

large

in similar samples examined

in 1970 to 444 000 tonnes by 2000. The capital

as MSW that

in ash and moisture are from different samples.

laboratories,

recovery

of

will

for an eight

estimated

a material

not

is to continue,

680 tonnes/day ultimately be

such

of

people

(MSW),

capacity

reclamation

from fossil fuels

different

will rise from 333 000 tonnes

an installation

less than 30% efficient,

but rises are

those

waste

It

The general that,

reported

100 000

The paramount

such electro-

fact

the

if recovery

27ltonne.

are

have

of RDF

to 34 tonnes/h

equipment

since

these

with of

solid

shift.

operate

design

electrical obscure

as a

hour

exist for the

though,

that steps

of

since power is usually

the

zinc

10% of

savings

or electro-refining. may

tin,

high-purity

should,

routes

convenience

lead,

showing,

for

otherwise

energy-intensive

data

for only about

would

reclamation

and

die-cast

Since markets

pot-melted

by the

and reclaimed

required

redistillation.

influence.

industries

that

energy

serious

from

degraded product

equivalent

method,

and zinc

example,

affects the may exert a

prices

generate about 6 I 000 tonnes/annum municipal

are introduced

refining

titanium,

paper

type

Oil

now more or less stabilized.

of

the

operation,

the

(RDF).

of

fuels.

product,

to

metal

in a field where so many

differences reported

cost

of the

fuels

during

variations

re-emphasized

or implicitly,

it is perhaps

where the economics

finished

heavy

of the effluent gases.

In so heterogeneous

of waste disposal

for

entering

has been shown

the real costs have yet to be determined.

point

actually

pre-

three

with

ie that percentage

in

non-combustibles.

prevent

to

seen in the prices of coal and gas to the

material

and

has exhibited

advantage the

or

loss of profitability yield,

of MSW

a procedure

derived

product

reclaims

of

of

reduce

the fabrication industries which, in turn, have a backward link to the designer. It has been shown that a most serious

incoming

year

of combustibles,

environmental

Explicity

Such

is associated

city

20

the ultimate of 27 elements contained in

separation

control

incinerators

separation

examination

the combustibles

populated

legislation

the

a

to the state, which

destination

rise to $20.

densely

case

under

in

fees of

equipment

one third

have serious implications

is

more expensive.

can now

and tipping this

by

Analyses continue to emerge of the respective merits of direct incineration

rather

disposal

will,

$550 000

from

where the arising is heavily

contaminated

agreement

the large,

Waste

the city

metals and burns the residue.

is

as from clippings

but only

in

meant now

is

than to

is the rule

progressively

equipment itself.

it

be saving

$2.75/tonne. In supplies refuse

costs that only a few years ago

areas.

the

may consume

car

the exception.

30/tonne

the

where

by high oil prices. It the system

that

fuel costs annually.

in a paper

burning

made feasible only is calculated 1980.

in an energy-

to leave lights

Landfill

for

Recovery

borings

than

to

out some of the absurdities

economic

becoming

triple

of the arising

important.

disclosures

of

energy

available

countries

that pointed of

options

were $2-4/tonne

melting

requirements

The

aluminium

special industry.

economics

regulations

energy

or from

with

can arise from restrictions; pollution

abatement aluminium

on the

aluminium in

reclamation environmental

also

the

industrialized

extinguish

metals from

of arising, the

changes

total

of

there is

presented

costs of reclaiming

Major

Some

cheaper

whether

particularly

single-passenger

Useful different

are

refining

a net gain. energy

methods intensive.

is generally

adequate

December

purity

to to

1978

Corzjerence reports blend

with

analysis

new

stock.

showed

that

paper

from

of

equivalent/tonne

oil

scrap

I 008/tonne This

of

traditionall)

of virgin

pulp.

of $52/tonne

wh0

have

remarkable

expertise

in

by methods

that

of sparks skills rising

arc

to

both

and

mechanization.

One

using

currents

eddy

the

transported or

to

to central

the

separators Positive

by removal

another.

is also

eddy-current

of

its

produce

more

plants,

of

the

operating

one from

attempted

of caustic on

material.

using

separators.

out

Hopefully

Any bc

exposed

simply

to

oil

and

paint.

simple

materials

that

become

irretrievable.

Scrap

under

the

cumulatively the melt

to which

evidence

already

build

of

mention

it are or

and

and tin are under

most

are, moreover,

not

is a recirculating

load

conditions,

the

impurity

it is added. exists

of

copper

and

but

two

can level

of

The an

ferrous MSW

undesirable

Associated, food it

metal has

in steel,

fraction

form

of

as it is likely

wastes,

lacquers

contaminates

RESOURCES

costs

of

inflated and

steel paper

commercial

POLICY

as

scrap. ash,

labels,

de-tinning

the

industry

with

the

wastes.

The

the

economics

the

installation will

from

in This

derive RDF

from

products. to

came

County.

plant

come

of

plant

Landfill the

whose

construction

million

will

start-up, to

as

of

meeting

Data

performance

deteriorating reported

some

by the National

Recycling

December

in

is

1978

Industries

areas.

(NARI)

needed

on

the

will

were

drawn

European of

the

before

on

charge.

but in

of

showed

losses

this

an

in

scale

scrap

in is only

liquors.

an

89%

40(X) in water,

and

in air

86%

pollution.

seem destined in

the

estimated

1.4% Japan, 3.3%

obvious ranging a

tiny

to slags

and

benefits

than

iron

74%

in

in

by

1980. costs

Costs 1975 In have

of ore

virgin

in energy

to rise from

USA

conscious reached

one

saving

materials. latter

furnace

The

rather

coke

a

material,

steel

as

practice

comprising

pickle

common

metallurgical

each

of oxidizing

at

the

spectrum

pellet

or

Examples

entire

sparks,

loss energy

American

of

from

GNP

Data

and

incorporation

appear

that

of

and North

quenching

waste

evidently

Association

arc

manufacture.

emphasis

the

makers,

ic the politicians.

of

spares

speaker from

decision

stage

be

every

The absence

overall

of

heat,

with

every

$50-53

to learn

of the

of loss

as sensible

of

Trends in recovery performance current

the

be those

disposal

associated

of

where

may

residuals.

complained

as a case

biggest

only

energy

tonne

using

it was depressing

not

costs

materials

probably

costs.

of total

of

residuals

wastes

steel industry,

degradation

sale

handle

IO%

and

all is energy.

only

and the

the

the iron

took

intractable

but

solid

Canada

associated

million.

our

from

be

to

the

use tow-grade

the

experiments

by

develop

must

not

treatment

the

it

secondary

recognized

materials.

A paper

of

of

well

will

by management

all

that

to

as its raw

use

is also

extrapolate

plant.

recovery.

the

It

by

discriminatory

who

contingency

For

recovered regarded

in

on

materials,

of its markets of

example

other

$28

the expansion

policies

for and

rates

primary

elimination

to

of

to be, with

and

the

is now

to

cases

been

from

to permit

a long-term

tin

long

and

for

freight

ris-&is

materials.

batches

Monroe

be needed

and the

asked

treatment

about

of its revenues

metals

equitable

secondary

industry tax

tonnes.

of

will

more

materials

economically

seems to be in view.

the

135

tonne/day

remainder

No

favourable

is

the valuable

structural

more

of the metal.

galvanizing

corrosion. alternative

is, it

the

of protecting

of

a description

50%

of most

in

study

on

at

used

the

zinc

of

it performs

carried

an MSW

1 800

since

scale.

data

uses

the

a viewpoint

service

capacity

beaker-scale

construction

is vital

Disturbing

contamination. from

in

still

steelmaking

worst

raise

More building

to the properties

during

processes.

up

arc.

that

eliminated

that.

Copper

that

its

eliminate,

co-mingled

detrimental

of steel and two

of

life, be

which

to

are

elements

conditions.

service

contamination,

comparatively

two

during

subsequent

a yield

of

from practical

is by

in the light

tests were

those

full commercial may,

and

tin.

showed

the Bureau

sample

by

results

material

fabrication

residual

solution.

this

ignored

Contamination

product

levels

dissipative

Predictably.

metal

substantial

a

in

simultaneously

Commercial

on

zinc Iost,

optimum

as

low,

be examined

ine\,itably

removal

that

must

to

factory

consumed

disastrously

felt.

that

own

Recovery

Although

of the cans

It is significant

industry.

of total

requires

staionary.

scrap

that

Preparation

facilitates

of

M;IS

portion

his

almost

refuse

solutions

recovery

the seams

ingress

of non-metallics.

being

Y 1%. these

is

pcrccntagc

raw

together.

tests

supplement

many

could,

combustibles,

opening

aluminium

of metals,

than

to

primary

materials,

(ic that

the steelmaker

initial

to minimize

rinse

0.06%

re-shredding

being

and

washed

in attaining

use that

copper

to

ferrous

scrap

the

to assure

melting

on

produce

claimed

product

a

Subsequent of

to

its

contact

containing

by

a view

final

to

and

shredding

metal-caustic

heavy-medium

segregation

in

plant,

of tin-bearing

method,

of

from

obtained

adequate

reported

from

baled

processing

upgrading

concentrate

of Mines

retention

capable

to

fractions

scrap

and

relative

I I1

paper

programme

the

non-magnetic

prior

usable fractions

its

that

with of

reject

in

now

has been evaluated

beneficiation

shredder

Bureau

progress

are

induced

configurations

US

de-

impossible.

with

promising

magnets.

in scvcral

is then

that

aluminium

slipping

purchased

scrap)

alloying

such

both

buy

organic

steel

secondary

niatcrial. of

a refuse

causes

and

were

passage

through

but

tin

that

react

solution.

The

eliminates

bctwccn

easy-

use

stripping

frothing. tin cans

separation

Such

techniques

less subjective

soda

to

post-consumer

tinning

aluminium

common

and,

efforts

to develop

permanent

by the

its surface.

Los&.

made

such

emitted

acquire

rise

The

alloys

on criteria

from

long

labour

being

by

and on the appearance

struck

take

in

the caustic

giving

developed

of the note

on impact

has

grading

depend

with

the

now

contaminants

scrap

performed

operatives

ends

incinerator

of IO cents/l. metallic

been

as the timbre

I

48.5 with

case

oil price

Scgrcgation

metal

about

Moreover,

open

of

compared

to a saving

at a notional

baths.

energy

production

consumed

in the

translates

An

the

of the 0.8%

of

to

an

pollutionalready

of GNP.

297

Corference

reports

Whilst zinc used for galvanizing may be irrecoverable, work continues to recover oxides from the wastes of the galvanizing process itself. Such drosses contain about 65% zinc and are generated in the USA at the rate of over 73 000 tonnes annually. The zinc oxide product is claimed to be suitable for metallurgical and chemical uses, again virgin metal for more releasing demanding applications. This was only one example cited of recovery from a fairly unattractive arising or of the use of entire fractions in less critical capacities. Among the latter were the recycling of pot linings in the primary aluminium industry to recover carbon, lluoride or alumina, exploitation of power station fly ash for alumina, and the use of various kinds of refractories for civil engineering applications.

Constraints in scrap use Many barriers exist to the use of secondary materials; these may be laws, that place regulations. or policies secondary material at a competitive disadvantage compared with their primary counterparts. Of an identified

ferrous scrap in the USA at the end of I975 would support the total purchased scrap requirements of the US steel and foundry industries, plus the export demand. for nearly 14 years. The arguments supported by the reports are now well known. They relate to the aspirations of the scrap consumers who, not unnaturally. seek to ensure the ready availability of inexpensive scrap for the domestic market. a condition encouraged by export embargo. The scrap industry, equally naturally, insists that the fluctuating home market forces it to rely on overseas sales. Thus, it seeks to protect its right to export scrap. This dispute is not new. Indeed, it has for many industrialized countries a familiar ring and re-emphasizes, if any emphasis be needed, the desirability of improving the status of secondary materials. Only when these cease to be regarded as a last resort will the market in them be stabilized and the scrap industry innovate and invest.

41 barriers. 5 have been classified as high priority and include freight rate differentials. that create an $0.79/tonne barrier to the use of scrap iron and steel and $3.65/tonne to the use of scrap aluminium. Data were also presented on depletion allowances and vehicle titling laws. Procurement policies were not found to create barriers to the use of secondary metals, perhaps implying that the economic level of secondary utitiLation has already been reached. Similarly. pollution control requirements were claimed to present no noticeable barrier since, as suggested elsewhere, secondary materials may be produced with minimal damage to the environment. A final reminder of the political overtones of the scrap business came from the Institute of Scrap Iron and Steel. Inc (ISIS). The background to the paper is to be found in two voluminous reports on ferrous scrap. That sponsored by the American Iron and Steel Institute projects that the supply of obsolete scrap will fall short of US domestic demand during the next quinquennium. The ISIS report maintains that the pool of obsolete

Michael The University

E. Henstock

of Nottingham Nottingham,

UK

adding to the capitalization plights that most domestic materials industries face. A number of basic questions have arisen from the advent of this crisis. These include:

Materials policy - planning for consensus

0

The 1978

Henniker

of participants brought

together

researchers August

1978,

Conference

from

from

the USA

on materials and abroad.

1 10 high-level government

Henniker,

materials and

private

administrators, sectors.

a record number biennial

gathering

policy makers,

Henniker

V, 30

and

July-4

New Hampshire.

This was the fifth in the series of weeklong materials policy conferences hosted by the Engineering Foundation in Henniker, New Hampshire, which has become the dean of materials policy gatherings. The theme of Henniker V was ‘Building a consensus on legislation for national materials policy’. However, the economic prominence of the USA in materials matters, combined with the level of attendees and fundamental issues addressed, made the meeting one

298

policy attracted The week-long

of significant international interest. Henniker V documented the critical period which the US materials sector has entered. The continuing energy crisis has brought some recognition of the intimacy of energy and materials and effective policy, yet coherent government policy toward materials is still lacking. Competition from abroad has posed serious threats to US materials industries. At the same time continued environmental constraints are

Do we need a materials policy per se, or do we need an integration of materials needs into overall economic and environmental policies? . Is it time for the USA and other market economies to rely more heavily on central, long-range planning to alleviate materials problems? . Is it inherently dangerous for the USA to let its role as a major materials producer diminish? 0 What are the major factors threatening US materials industries? 0 Are environmental protection and economic health of materials industries incompatible? The question of whether a materials policy per se is desirable provoked

RESOURCES

POLICY

December

1978