C2762 - Pacific Wire Ltd - Wire Manufacturers - Auckland Region

Summary
The total annual savings resulting from CP options implemented to date are estimated as well over $0.5 million per year with a payback period for each option implemented varying from immediate to less than one year. The adjustment of the raking procedure alone saved the company several $100,000s per year and increased product throughput.

Business Profile
Pacific Wire manufactures galvanised and bright wire for various applications such as fencing, nails, steel mesh, armoured wire for cables. Processes include the mechanical drawing of wire from steel rods, wire cleaning and galvanising. The company employs 80 staff.

Type of Project
Cardboard and paper recycling, boiler shutdown during non-production hours, installation of a central power switch and daylight sensors, reuse of steam condensate from cleaning baths, recovery of bath dragout, regeneration of sulphuric acid, caustic soda regeneration, and raking adjustment to prevent lumps on wires.

Reasons for Project
Waste reduction is part of an operational excellence (OPEX) programme. OPEX is Pacific Wire's continual improvement programme which has an objective of enhancing operational effectiveness through energy savings and minimising waste to bring benefit to the company. Management are also committed to producing products in an environmentally responsible way.

The Project

Cardboard and paper recycling

Details	Since September 1996 Pacific Wire has segregated cardboard and paper for recycling. Approximately 85 kg of loose office waste paper is collected per month or 1 tonne per year. Approximately 25 kg of cardboard is collected per month or 300 kg per year.
Economics	Cardboard collection costs $5/month bin rental and $7.50 per bin pickup = $150/year. Paper collection costs are $2.50/week per bin for 8 bins and no costs for pickup = $960/year. Bin purchase will eliminate rental costs and is being investigated. Savings include reduced disposal costs of $90 per year ($69/tonne) and reduced pickup costs of $600 per year ($50 per monthly pickup). Annual costs for recycling are therefore $270, but will quickly become savings when bins are purchased.
Benefits	Reduced paper and cardboard waste of 1.3 tonne per year.

Boiler shutdown during non-production hours

Details	The production hours at Pacific Wire are 120 hours/week or 5 continuous days. Previously the boiler operated for 142 hours/week. The boiler is now shut down during weekends and now operates 128 hours/week (the 8 hour additional hours are required to start up the boiler before production begins on Monday mornings). As a result, gas for heat the water, electricity for the water circulation pump, and chemicals used to reduce water hardness have been reduced.
Economics	Gas savings are $ 4800 per year. The payback period is immediate.
Benefits	Reduced gas, electricity and chemical consumption and costs.

METAL CLEANING PROCESS

Reuse steam condensate for cleaning baths

Details	Steam condensate from heated borax and metasilicate tanks is collected and used to fill and heat the rinsing tank. Approximately 5.4 m3 water per day or 1,971 m3 per year is saved. Also, 144,000 kWh is saved per year because the rinsing tank requires less heating. The condensate was collected from the steam traps and was transported into the tanks. The work undertaken by maintenance staff to install hot water recycle pipelines and material costs were nominal.
Economics	Water savings are $1,080 per year and energy savings are approximately $3,000 per year. The payback period is immediate.
Benefits	Reduced water and energy consumption and costs.

Recovery of bath dragout

Details	Pacific Wire have a series of five cleaning tanks. Rubber sheets were placed between the different cleaning tanks to prevent dragout spillages caused by moving objects from one tank into the next. As a result, chemical consumption and trade waste discharges were reduced.
Economics	Six rubber sheets cost $360 ($60 each). Savings have not been determined.
Benefits	Reduced chemical consumption, including acids and sulphates. Reduced wastewater stream.

Regeneration of sulphuric acid

Details	The first stage of making wire is the pickling of the rod steel. This is done in pickling baths of dilute sulphuric acid which removes rod scales, rust and dirt. The acid requires replacement when the iron level reaches 12%. Use acid from the pickling baths is recycled by an acid recovery process (see diagram). The liquid is cooled to 0°C where iron salts crystallise and precipitates to the bottom of the cooling tank. The weak acid which is free of iron is syphoned back to the pickling tank for reuse. The crystals are removed via draining bins into hoppers. They are then sold as "ferrous sulphate heptahydrate" (ferrosulphate) for fertiliser blending. Each year approximately 4,000 tonnes of diluted (= 200 tonnes of undiluted) sulphuric acid is recycled and approximately 500 tonnes of ferrosulphate is produced for sale.
Economics	The existing system is overhauled which costs $50,000. Annual savings are $231,000 including: - $126,000 ($630/tonne) from reduced sulphuric acid consumption; - $50,000 ($100/tonne) from ferrosulphate revenue; - $55,000 reduced trade waste costs through reduced disposal of spent sulphuric acid.
Benefits	Reduced wastewater stream, sulphuric acid consumption and associated costs. Income from selling ferrosulphate as fertiliser.

Caustic soda regeneration

Details	Caustic soda is used in one of the cleaning tanks and becomes contaminated with boron from the previous cleaning tank. By cooling the caustic soda, the contaminants form a gel which is subsequently separated from the weak caustic soda solution by filtration in a filter bag. Following treatment the gel is landfilled. The clean caustic soda is reused in the cleaning tank. Each year 20,000 L of caustic soda is recycled rather than discharged into the sewer. Water consumption has also been reduced by approximately 300 m3/year.
Economics	The system cost $17,000 to install and $18,000 a year to operate. Total savings are $56,000 and include: - reduced caustic soda consumption of 20,000 L per year - reduced disposal of caustic soda solution of 46,000 per year - reduced trade waste costs associated with caustic soda disposal. - reduced water costs of $192 per year. The payback period is 6 months.
Benefits	Reduced caustic soda consumption, disposal and costs. Reduced water consumption and costs.

METAL FINISHING PROCESSES

Raking adjustment to prevent lumps on wires

Details	Following the galvanising process, hot zinc wires are passed through gravel to remove any zinc dross formed during the process of galvanising. Employees use a stick or rake to loosen the gravel, but where they touch the wires lumps are formed which need to be cut out losing valuable product and labour time. A modified tool was made and employees were instructed how to rake the gravel without touching the wires. Wire waste was reduced by 1,000 kg per day or 300 tonnes per year.
Economics	No costs were involved in modifying the rake. Savings through reduced raw material consumption have not been fully costed but are estimated as several $100,000s per year. The payback period was immediate.
Benefits	Reduced zinc dross and production loss estimated at several $100,000/year. Improved product quality. Increased productivity through increased throughout as fewer stoppages.

For additional information contact:
Shiu Singh,
Pacific Wire Ltd,
PO Box 22198,
Otahuhu,
Auckland
Ph 09-2704249
Fax 09-276576

For further information about Cleaner Production in the Metal Industry see:

Opus International Consultants (September 1997): Cleaner Production Guide for the Metal Industry- Minimising waste, reducing costs and caring for the environment.