Nicholas P. Cheremisinoff. Handbook of Solid Waste Management and Waste Minimization Technologies

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furnace). Sanitary sewage effluents require treatment in a separate facility or

discharge to a municipal sewer.

COPPER SMELTING

INDUSTRY DESCRIPTION AND PRACTICES

Copper can be produced either pyrometallurgically or hydrometallurgically. The

hydrometallurgical route is used only for a very limited amount of the world's

copper production and is normally only considered in connection with in situ

leaching of copper ores. From an environmental point of view, this is a

questionable production route. Several different processes can be used for copper

production. The traditional process is based on roasting, smelting in reverbatory

furnaces (or electric furnaces for more complex ores), producing matte (copper-

iron sulfide), and converting for production of blister copper, which is further

refined to cathode copper. This route for production of cathode copper requires

large amounts of energy per ton of copper: 30 to 40 million British thermal units

(Btu) per ton cathode copper. It also produces furnace gases with low sulfur

dioxide concentrations from which the production of sulfuric acid or other

products is less efficient. The sulfur dioxide concentration in the exhaust gas

from a reverbatory furnace is about 0.5-1.5%; that from an electric furnace is

about 2-4%. So-called flash smelting techniques have therefore been developed

that utilize the energy released during oxidation of the sulfur in the ore. The flash

techniques reduce the energy demand to about 20 million Btu/ton of produced

cathode copper. The SO

concentration in the off-gases from flash furnaces is

also higher, over 30%, and is less expensive to convert to sulfuric acid. The

INCO process results in 80% sulfur dioxide in the off-gas. Flash processes have

been in use since the early 1950s.

In addition to the above processes, there are a number of newer processes such as

Noranda, Mitsubishi, and Contop, which replace roasting, smelting, and

converting, or processes such as ISA-SMELT and KIVCET, which replace

roasting and smelting. For converting, the Pierce-Smith and Hoboken converters

are the most common processes.

The matte from the furnace is charged to converters, where the molten material

is oxidized in the presence of air to remove the iron and sulfur impurities (as

converter slag) and to form blister copper. Blister copper is further refined as

either fire-refined copper or anode copper

(99.5%

pure copper), which is used in

subsequent electrolytic refining. In fire refining, molten blister copper is placed

in a fire-refining furnace, a flux may be added, and air is blown through the

molten mixture to remove residual sulfur. Air blowing results in residual oxygen,

which is removed by the addition of natural gas, propane, ammonia, or wood.

The fire-refined copper is then cast into anodes for further refining by electrolytic

processes or is cast into shapes for sale.

In the most common hydrometallurgical process, the ore is leached with

ammonia or sulfuric acid to extract the copper. These processes can operate at

atmospheric pressure or as pressure leach circuits. Copper is recovered from

solution by electro

winning,

a process similar to electrolytic refining. The process

is most commonly used for leaching low-grade deposits in situ or as heaps.

Recovery of copper metal and alloys from copper-bearing scrap metal and

smelting residues requires preparation of the scrap (e.g., removal of insulation)

prior to feeding into the primary process. Electric arc furnaces using scrap as

feed are also common.

POLLUTION PREVENTION PRACTICES AND OPPORTUNITIES

The principal air pollutants emitted from the processes are sulfur dioxide and

paniculate matter. The amount of sulfur dioxide released depends on the

characteristics of the ore-complex ores which may contain lead, zinc, nickel, and

other metals, and on whether facilities are in place for capturing and converting

the sulfur dioxide. SO

emissions may range from less than 4 kilograms per

metric ton (kg/t) of copper to 2000 kg/t of copper. Particulate emissions can

range from 0.1 kg/t of copper to as high as 20 kg/t of copper. Fugitive emissions

occur at furnace openings and from launders, casting molds, and ladles carrying

molten materials. Additional fugitive particulate emissions occur from materials

handling and transport of ores and concentrates. Some vapors, such as arsine, are

produced in hydrometallurgy and various refining processes. Dioxins can be

formed from plastic and other organic material when scrap is melted. The

principal constituents of the particulate matter are copper and iron oxides. Other

copper and iron compounds, as well as sulfides, sulfates, oxides, chlorides, and

fluorides of arsenic, antimony, cadmium, lead, mercury, and zinc, may also be

present. Mercury can also be present in metallic form. At higher temperatures,

mercury and arsenic could be present in vapor form. Leaching processes will

generate acid vapors, while fire-refining processes result in copper and SO

emissions. Emissions of arsine, hydrogen vapors, and acid mists are associated

with electrorefining. Waste water from primary copper production contains

dissolved and suspended solids that may include concentrations of copper, lead,

cadmium, zinc, arsenic, and mercury and residues from mold release agents

(lime or aluminum oxides). Fluoride may also be present, and the effluent may

have a low pH. Normally there is no liquid effluent from the smelter other than

cooling water; wastewaters do originate in scrubbers (if used), wet electrostatic

precipitators, cooling of copper cathodes, and so on. In the electrolytic refining

process, by-products such as gold and silver are collected as slimes that are

subsequently recovered. Sources of waste water include spent electrolytic baths,

slimes recovery, spent acid from hydrometallurgy processes, cooling water, air

scrubbers, washdowns, stormwater, and sludges from wastewater treatment

processes that require reuse/recovery or appropriate disposal. The main portion

of the solid waste is discarded slag from the smelter. Discard slag may contain

0.5-0.7% copper and is frequently used as construction material or for

sandblasting. Leaching processes produce residues, while effluent treatment

results in sludges, which can be sent for metals recovery. The smelting process

typically produces less than 3 tons of solid waste per ton of copper produced.

Process-gas streams containing sulfur dioxide are processed to produce sulfuric

acid, liquid sulfur dioxide, or sulfur. The smelting furnace will generate process

gas streams with SO

concentrations ranging from 0.5% to 80%, depending on

the process used. It is important, therefore, that a process be selected that uses

oxygen-enriched air (or pure oxygen) to raise the SO

content of the process gas

stream and reduce the total volume of the stream, thus permitting efficient

fixation of sulfur dioxide. Processes should be operated to maximize the

concentration of the sulfur dioxide. An added benefit is the reduction of NO

Some pollution prevention practices for this industry include the following:

• Closed-loop electrolysis plants will contribute to prevention of pollution.

• Furnaces should be enclosed to reduce fugitive emissions, and dust from

dust control equipment should be returned to the process.

• Energy efficiency measures (such as waste heat recovery from process

gases) should be applied to reduce fuel usage and associated emissions.

• Recycling should be practiced for cooling water, condensates, rainwater,

and excess process water used for washing, dust control, gas scrubbing,

and other process applications where water quality is not a concern.

• Good housekeeping practices are key to minimizing losses and

preventing fugitive emissions. Such losses and emissions are minimized

by enclosed buildings, covered or enclosed conveyors and transfer

points, and dust collection equipment. Yards should be paved and runoff

water routed to settling ponds. Regular sweeping of yards and indoor

storage or coverage of concentrates and other raw materials also reduces

materials losses and emissions.

Pollution control technologies acceptable for this industry are as follows. Fabric

filters are used to control paniculate emissions. Dust that is captured but not

recycled will need to be disposed of in a secure landfill or other acceptable

manner. Vapors of arsenic and mercury present at high gas temperatures are

condensed by gas cooling and removed. Additional scrubbing may be required.

Effluent treatment by precipitation, filtration, and so on, of process bleed

streams, filter backwash waters, boiler blowdown, and other streams may be

required to reduce suspended and dissolved solids and heavy metals. Residues

that result from treatment are sent for metals recovery or to sedimentation basins.

Stormwaters should be treated for suspended solids and heavy metals reduction.

Slag should be landfilled or granulated and sold. Modern plants using good

industrial practices should set as targets total dust releases of 0.5 to 1.0 kg/t of

copper and SO

discharges of 25 kg/t of copper. A double-contact, double-

absorption plant should emit no more than 0.2 kg of sulfur dioxide per ton of

sulfuric acid produced (based on a conversion efficiency of 99.7%).

A SHORT REVIEW

Industry practices are shifting away from end-of-pipe treatment technologies

toward pollution prevention. The transition in general is slow, because many

companies face large-scale investments in more environmentally friendly

technologies. Large infrastructure investments into green technologies which

reduce pollution and forms of waste at the source generally are taking years of

planning and implementation and are often implemented over several stages.

Because these investments are not examined in terms of the four tiers of

environmental costs, more conservative and lengthy transitions to greener

technologies are taking place.

In the chapter to follow, the methodology behind waste minimization and

pollution prevention programs is explained in greater detail. The principles of

life-cycle costing and their application to assessing P2 technologies are described.

Chapter 8

ESTABLISHING P2 AND

WASTE MINIMIZATION

PROGRAMS

INTRODUCTION

The first overall objective of any pollution management strategy is to bring a

facility into compliance with environmental regulations. Simply stated, there are

only two choices any company faces:

• Comply with environmental regulations and remain in business, or

• Don't comply, and face heavy fines, penalties, costly interruptions, or in the

extreme, go out of business.

When a company approaches this objective with strategies based largely on end-

of-pipe treatment technologies, it is addressing only the legal requirements for

staying in business, and not growth. By repeatedly trying to meet more stringent

effluent emission standards through the use of more advanced controls, a

company is always on the defensive, i.e., playing catch-up with compliance

requirements.

P2 and waste minimization strategies achieve the same end results as the

application of control technologies (i.e., they help meet a compliance

requirement), but they are more cost effective. The reason for this is that

P2/waste minimization strategies reduce Tier 1 and 2 costs through savings not

achievable through control technologies, which are simply add-on process

components that impose additional demands on energy, materials, and labor. The

savings can be applied toward reinvesting into modernization and improvements

to operations, or in financing the implementation of an EMS (environmental

management system). This enables a company to grow its operations.

P2 strategies also reduce or eliminate costs associated with future liabilities (Tier

3) and less tangible costs (Tier 4). In the ideal case, prevention eliminates waste

and pollution altogether. Hence, issues such as third-party damages or joint and

several liabilities for off-site damages are no longer a concern. When P2

strategies are employed, the owners/operators of facilities can exceed compliance

requirements, because in the ideal case zero waste and pollution is the ultimate

goal. Another way of looking at this is that when an organization focuses on

continual reductions of waste and pollution, operating costs are steadily reduced

over time, and profitability is maximized.

A P2 program consists of a systematic approach to identifying more cost-effective

strategies and technologies for waste handling, then implementing those strategies

and tracking their environmental and economic performances for the purposes of

establishing new targets and goals, starting with the highest environmental

priorities first, and then iteratively repeating the process for and applying lessons

learned to successive pollution problems throughout the entire operation. Through

the application of this iterative process, incremental savings are achieved with

each new P2 activity. The savings are cumulative and hence, over time, represent

significant capital returns that can be reinvested into a company's operations.

Successive rounds of continual P2 improvements are what constitute the basis for

an EMS.

P2 DRIVERS

An overwhelming number of success stories illustrate the benefits of pollution

prevention strategies. Many examples for a variety of industry categories are

summarized in earlier publications devoted to this subject (Cheremisinoff, N. P.,

Handbook of Pollution Prevention Practices, 2001, and Cheremisinoff, N. P. and

A. Bendavid-Val, Green Profits: The Manager's Handbook for ISO 14001 and

Pollution Prevention, 2001). These case studies show distinct financial advantages

to companies not only by identifying reductions in pollution and the costs

associated with pollution management, but also through reduced raw material

consumption, energy savings, reductions in treatment and disposal of wastes, and

reductions in labor associated with environmental management. Many P2 and

waste minimization strategies, such as substituting toxic materials with safer

alternatives, do not require process changes, and as such are simple and cost very

little to implement. The areas in which P2 has proven effective include the

elimination and reduction of impacts from:

• Treatment, disposal, and associated labor costs

• Wildlife and habitat damage

• Property devaluation

• Remediation costs

• Civil and criminal fines

• Permitting fees

• Insurance costs

• Process outages and disruptions

There are case studies that testify to the fact that P2 benefits result in:

• Enhanced public image: consumers more favorably view businesses that

adopt and practice P2 strategies, and the marketing of these practices can

assist in increasing a company's profits.

• Increased productivity and efficiency: P2 assessments have proven helpful

in identifying opportunities that decrease raw materials use, eliminate

unnecessary operations, increase throughput, reduce off-spec product

generation, and improve yields.

• Reduced regulatory burden: improving environmental performance and

achieving performance goals that exceed compliance have been demonstrated

in many P2 programs, which in turn reduce the costs of compliance,

• Decreased liability: handling hazardous and toxic materials brings along

with it high liabilities should an accident such as a fire or explosion, or a

major spill occur.

• Improved environmental health and safety: P2 practices can be applied to

all forms of pollution media. Reductions in pollution minimize worker

exposure and conserve resources and landfill space.

DEVELOPING A P2 PROGRAM

The basic scheme for a P2 program involves the following:

Identifying and understanding the company's baseline costs for pollution and

waste management. This includes an understanding of the total costs and the

individual components contributing to overall costs for managing each

environmental aspect.

Prioritizing environmental aspects of the company's operations. With infinite

resources, all environmental aspects in even the largest companies can be

addressed simultaneously. But no corporation has this luxury, and furthermore,

there are other program priorities that compete for fixed budgets. In this regard, a

P2 investment should be able to compete for budget approval just like any other

capital project.

Working with the highest priority issues first, a company applies engineering

and management expertise and tools to identify alternative approaches to

pollution management within the hierarchy of environmental strategies.

With alternative strategies and technologies identified, a company performs

an investment analysis to determine the financial attractiveness of the P2

investment alternatives. Those alternatives that are more financially attractive

than the baseline strategies and technologies used become the recommendations

for senior management to endorse and implement.

The entire process is then repeated within the company to address additional

environmental aspects and also, as appropriate, rolled out to other parts of the

company or other environmental and waste priorities in a process of continual

improvement.

These five program elements have been organized by the authors into a three-

phase plan that is referred to as the P2 assessment.

The P2 assessment is a systematic approach to evaluating alternative strategies

that not only reduce pollution and wastes compared to baseline conditions or

status quo, but are more cost effective than current technologies and strategies

and/or reduce a company's risk in managing wastes. The assessment can be

implemented by applying three phases sequentially:

• Preassessment

• Auditing

• Life-cycle costing analysis

METHODOLOGY FOR P2 AUDITS

The following describes a step-by-step approach for carrying out the pollution

prevention/waste minimization audit. It is designed to be generic and to apply to

a broad spectrum of industries. The approach consists of three phases that are

implemented in succession:

A preassessment phase for assessment preparation

A data collection phase to derive a material balance

A synthesis phase where the findings from material balances are translated

into a waste reduction action plan

Phase 1: The Preassessment

Step 1: Assessment Focus and Preparation. A thorough preparation for a

pollution prevention audit is a prerequisite for an efficient and cost-effective

study. Of particular importance is to gain support for the assessment from top-

level management, and for the implementation of results; otherwise there will be

no real action on recommendations. The pollution prevention auditing team

should be identified. The number of people required on a team will depend on the

size and complexity of the processes to be investigated. A pollution prevention

audit of a small factory may be undertaken by one person with contributions from

the employees. A more complicated process may require at least three to four

people: technical

staff,

production employees, and an environmental specialist.

Involving personnel from each stage of the manufacturing operations will

increase employee awareness of waste reduction and promote input and support

for the program.

The audit may require external resources, such as laboratory and possibly

equipment for sampling and flow measurement. You should attempt to identify

external resource requirements at the outset. Analytical services and equipment

may not be available to a small factory. If this is the case, investigate the

possibility of forming a pollution prevention association with other factories or

industries; under this umbrella the external resource costs can be shared.

It is important to select the focus of your assessment at the preparation stage.

You may wish the audit to cover a complete process or you may want to

concentrate on a selection of unit operations within a process. The focus will

depend on the objectives of the assessment. You may wish to look at waste

minimization as a whole or you may wish to concentrate on particular wastes: for

example, raw material losses, wastes that cause processing problems, wastes

considered to be hazardous or for which regulations exist, and/or wastes for

which disposal costs are high. A good starting point for designing a pollution

prevention assessment is to determine the major problems/wastes associated with

your particular process or industrial sector.

All existing documentation and information regarding the process, the plant or

the regional industrial sector should be collated and reviewed as a preliminary

step.

Regional or plant surveys may have been undertaken; these could yield

useful information indicating the areas for concern and will also show gaps where

no data are available. The following prompts give some guidelines on useful

documentation.

Is a site plan available?

• Are any process flow diagrams available?

• Have the process wastes ever been monitored -- do you have access to

the records?

• Do you have a map of the surrounding area - indicating watercourses,

hydrology, and human settlements?

• Are there any other factories/plants in the area which may have similar

processes?

• What are the obvious wastes associated with your process?

• Where is water used in greatest volume?

• Do you use chemicals that have special instructions for their use and

handling?

• Do you have waste treatment and disposal costs ~ what are they?

• Where are your discharge points for liquid, solid, and gaseous

emissions?

The plant employees should be informed that the assessment will be taking place,

and they should be encouraged to take part. The support of the staff is imperative

for this type of interactive study. It is important to undertake the assessment

during normal working hours so that the employees and operators can be

consulted, the equipment can be observed in operation, and, most importantly,

wastes can be quantified.

Step 2: Listing Unit Operations. Your process will comprise a number of unit

operations. A unit operation may be defined as an area of the process or a piece

of equipment where materials are input, a function occurs and materials are

output, possibly in a different form, state, or composition. For example, a

process may comprise the following unit operations: raw material storage,

surface treatment, rinsing, painting, drying, product storage, and waste

treatment.

Any initial site survey should include a walk around the entire manufacturing

plant in order to gain a sound understanding of all the processing operations and

their interrelationships. This will help the assessment team decide how to

describe a process in terms of unit operations. During this initial overview, it is

useful to record visual observations and discussions and to make sketches of

process layout, drainage systems, vents, plumbing and other material transfer

areas.

These help to ensure that important factors are not overlooked.

The assessment team should consult the production staff regarding normal

operating conditions. The production or plant staff are likely to know about waste

discharge points, and unplanned waste generating operations such as spills and

washouts, and they can give the assessors a good indication of actual operating

procedures. Investigations may reveal that night-shift procedures are different

from day-shift procedures; also, a plant may disclose that actual material-

handling practices are different from those set out in written procedures. A long-

standing employee could give some insight into recurring process problems. In

the absence of any historical monitoring this information can be very useful.

Such employee participation must, however, be a nonblaming process; otherwise

it will not be as useful as it could be. During the initial survey, note imminent

problems that need to be addressed before the assessment is complete.