INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY #126

1.   Headline:  Outokumpu flash smelting process for copper
     allows high sulphur recovery, efficient energy
     utilization, and flexibility in varied feed material.

2.   Background:  See below.

3.   Cleaner Production Principle:  new technology

4.   Description of Cleaner Production Application:  The
     Outokumpu flash smelting process combines the conventional
     operations of roasting, smelting and partial converting
     into one process.  Preheated oxygen-enriched air is used
     to provide heat such that additional fuel is not required
     for the reactions to proceed.  Copper concentrate is
     recovered from the slag and recycled through the smelter.
     The clean slag is sent for disposal.  Heat and dust are
     recovered from the smelter gases producing dust for
     recycle to the smelter, and SO2 gases for production of
     sulfuric acid.  The matte is further treated in
     conventional converters to obtain blister copper.

     Material/Energy Balance and Substitution

     FEEDSTOCKS: Ore concentrate, fuel, electrical energy,
     oxygen-enriched air, silica flux

     WASTES: Gaseous stream of 10-30% SO2 for use in sulfuric
     acid plant, particulates in gas stream (6-7% of the feed),
     slag from electric furnace

     MEDIUM: Gaseous, solid

5.   Economics

     OPERATION/MAINTENANCE:  61.0 cents/kg (27.7 cents/lb)

     DISPOSAL & FEEDSTOCK:  Operating costs reduced to 61.0
     cents/kg from 97.8 cents with conventional process

6.   Advantages:

     FEEDSTOCK REDUCTION:  Energy consumption is about 20 to
     30% of that required by a conventional furnace

     WASTE PRODUCTION: 50-80% recovery of sulfur from the
     concentrate for use in sulfuric acid production,
     eliminating SO2 emissions to the environment. Slag
     cleaning reduces copper content from 24% to <0.6% prior to
     disposal, eliminating liquid run-off from granulation pond

     IMPACT: The main advantages of the Outokumpu process are
     the high sulphur recovery, the efficient energy
     utilization, and the flexible process in terms of
     accepting a varied feed material.

7.   Constraints:  No information provided.

8.   CITATION/PAGE: Compendium on Low and Non-waste Technology,
     United Nations Economic and Social Counsel,  "Primary
     Copper Production Using the Outokumpu Flash Furnace",
     Monograph ENV/WP.2/5/Add.115

9.   Keywords:  metal, copper, copper smelting, new technology,
     sulfur, heating, sulfuric acid, oxygen-enriched air,
     energy saving, fuel, ISIC 3720.

10.  Reviewers Comments:  This case study was originally
     abstracted for the US EPA Pollution Prevention Information
     Clearinghouse.  It underwent a UNEP IE funded technical
     review in 1994 for quality and completeness. It was edited
     for the ICPIC diskette in July 1995.

 ( DOCNO: 400-115-A-328 )