INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY # 161

1.   Headline:  Use of Acid Purification Unit on Concentrated
     High Temperature Pickling Liquor Reduces Iron
     Concentration

2.   Background:  See below.

3.   Cleaner Production Principle:  new technology and process
     modification

4.   Description of Cleaner Production Application:  This
     technology involves the use of an acid purification unit
     (APU) consisting of filters and an ion exchanger to reduce
     iron content of the pickle acid.

     Case Study Summary

     Process and Waste Information:  In the original pickling
     process, no purification of the acidic liquor was
     undertaken.  The liquid was discarded in a continuous
     "bleeding" process after the "bleed" was neutralized with
     lime.

     The new process involves use of equipment consisting of
     three basic pieces and one optional piece: an Eco-Tec Acid
     Purification Unit AP30-24 HT cartridge filter and ion
     exchanger, a feed pump, an Eco-Tec sand filter and an
     optional 400 gallon (1100 liter) water supply tank.  The
     pickle acid is pumped from the reservoir tank through a
     media filter to remove dirt and oil particles.  The acid
     then passes through a second filter (0.5 m) to remove very
     fine particulate and filter media from  reaching the resin
     bed in an ion exchange unit.  The following stage contains
     three steps per cycle: the water displacement stage, the
     byproduct (iron) removal stage, and the produce (acid)
     return stage.

     The water displacement phase allows the pickle acid into
     the resin bed, displacing the water from the previous
     cycle.  This water can be reused by sending it to the
     water supply tank, or sent to drain.  This stage lasts
     approximately one minute.

     The by product stage allows the pickle acid to continue
     its flow through the resin bed trapping the sulfate ions
     and allowing the iron to pass through and sent to drain.
     This phase also takes about one minute.

     The product return phase stops the flow of acid from the
     reservoir and starts a counterflow of water from a
     pressurized source (main water line or water supply tank
     pump).  The water picks up the sulfate ions and returns
     them to the tank of sulfuric acid.  This stage takes about
     two minutes.

     This three phase cycle continues automatically until the
     dirt build-up in the media filter causes the process to
     automatically shut down.  A back flush procedure is
     necessary to clean the filter before restarting the
     system again.  Backflushing time is approximately one
     hour.


     Using the new process results in the reduction of the iron
     content of the acid solution from an initial 7.7% to a
     steady 2-3% during the latter half of the test period.  An
     89% decrease in use of sulfuric acid and lime also
     resulted.  No new materials are introduced in the process.
     Since pickling uniformity is a product quality
     improvement, product quality is at least as good as before
     using the APU, but this was not quantified.

     Stage of Development:  The installation is fully
     implemented.  Data are derived from the last month of
     testing.

     Level of Commercialization:  The installation is fully
     commercially available.  The vendor seems well equipped
     and experienced in construction and maintenance of the
     equipment.

     Material/Energy Balances and Substitutions:

   Material Category       Quantity Before             Quantity
After

Waste Generation:           N/A                         N/A
Feedstock Use:

Sulfuric acid               629,089                     67,558
(lbs/yr)
Lime (tons/yr)                  252                         28
(Computed)

Water Use:                         N/A
N/A        Energy Use:                        N/A
N/A

5.   Economics

     Investment Costs:  Investment costs were as follows:

     Design and supply of equipment
     $84,000.00 Equipment installation
     $10,000.00 Start-up, supplies, etc.
     $ 2,500.00

     Total
     $94,000.00
     These costs do not include the test program or the
     management personnel costs for the project.

     Operational & Maintenance Costs:  These costs are
     estimated at $2500/yr.

     Payback Time:  Payback time was calculated as 2.33 years.
     Annual savings on chemicals were calculated as $43,937.
     Not included in the calculations are an estimated $8,000
     saved annually on sludge hauling.

6.   Advantages:  Annual savings on chemicals were $25,942 for
     sulfuric acid and $17,995 for lime, or a total of $43,937.
     An estimated $8,000 were saved on sludge hauling.  The
     project demonstrated that sulfuric acid used in preparing
     steel strip for electrogalvanizing could be reclaimed for
     continuous use.

7.   Constraints:  Except for some start-up problems, no other
     problems seem to have been encountered.

8.   Contacts

     Name & Location of Company

              Metal Koting
              Continuous Colour Coat Ltd.
              1430 Martin Grove Road
              Rexdale Ontario M9W 4Y1
              Canada
              TEL 1 416 743-7980

              Mr. M. Schulz
              Head Training Section
              Environment Canada
              3439 River Road South
              Ottawa, Ontario K1 OH3
              Canada
              TEL: 1 613 991-1954
              FAX: 1 613 991-1635

9.   Keywords:  Canada, metal, iron and steel, pickling, new
     technology, acid purification, ion exchange, pickle acid,
     sulfate, acid.

10.  Reviewer's Comments:  This case study was originally
     compiled by the UNEP IE Working Group on Metal Finishing.
     It underwent a UNEP IE funded technical review in 1994 for
     quality and completeness.  It was edited for the ICPIC
     diskette in July 1995.

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