Improved dust extraction not to be sneezed at

The fume arms New Zealand Duct & Flex installed at Pyrotek.

The fume arms New Zealand Duct & Flex installed at Pyrotek.

New Zealand Duct & Flex from Otahuhu, Auckland, recently installed two 160mm diameter fume arms, each with 3m reach, at the Auckland branch of global industrial ceramic giant Pyrotek. The fume arms are employed to eliminate dust in the company’s metal zinc recovery department.

Pyrotek manufactures ceramics and other consumables for the hot metal and glass container industries. One of these consumables is metal zinc, which Pyrotek recovers from galvaniser skimmings sourced from outside the company.

Zinc demand is high and raw resource costs are increasing, however recovering and recycling it is a fairly simple process. Around 75 percent of the zinc consumed worldwide originates from mined ores and 25 percent from recycled zinc. Metal zinc is used in a variety of applications including die casting and brass manufacturing, but the largest consumer of zinc is the hot-dip galvanising of steel – about 50 percent of the annual zinc tonnage used in the world.

On the one hand, zinc-coated steel and other zinc containing products are slow to enter the recycling circuit, as the zinc optimises their durability – zinc coated steel poles placed in the Australian outback a hundred years ago are reportedly still in excellent condition. On the other hand, recoverable zinc from galvanising skimmings may be as much as 90 percent with an average of about 70 percent by weight.

The Metaullics Zinc Recovery (MZR) system, patented in the 1990s, is an easy, low-cost technology to recover zinc from skimmings. The European Commission Integrated Pollution Prevention and Control (IPPC) recognises the MZR system as the best available technique for zinc dross waste management. Based in Cryers Road, East Tamaki, Pyrotek Auckland uses the MZR-750 to recover zinc though MZR technology.

At the heart of MZR technology is a thermo-mechanical device that can separate free zinc from material mixtures, top drosses, and skimmings. Staff use a fork hoist to decant skimmings, which arrive in 210l containers, into the device’s drum, which can process a nominal 750kg at a time. The device rotates the drum at a specified rotational velocity within a temperature controlled chamber.

In the course of the processing time, which is around three hours, the process stratifies the dross inside the heated drum, with the zinc pooling at the bottom. An operator then decants the liquid zinc into a custom made mould. When solidified the zinc is returned to the galvanising plant for reuse in their process.

The 210l containers are then also tipped into bulk bags to decant the last residue of the skimmings. Both skimmings tipping processes create a dusty environment which lowers staff comfort levels significantly. Pyrotek production manager Graham Greenhorn says in earlier years the Pyrotek team addressed the dust problem by scheduling decanting during times when the rest of the staff was not working, such as during breaks and, notably, through an extra morning shift which started at 4am.

“It was inconvenient for our staff doing the early shift, uncomfortable for everybody to work in an environment that had a dust problem. So we thought, there has to be a better way to do things. We researched the matter on the Internet, and found a few companies, including NZ Duct & Flex, which promised to eliminate dust problems. NZ Duct & Flex looked the most suitable, and turned out to provide us with the most professional quote and the best price,” Mr Greenhorn recalls. “And by the way they did the installation and the results we’ve seen, that promise and professional image are well-founded.”

Alison Campbell, marketing manager at NZ Duct & Flex, says the system installed at Pyrotek has proved its mettle on numerous occasions. “Two features of the system stand out. In the first instance, the arms are connected to galvanised modular ducting with pneumatic blast gates to shut off the fume arms when not needed, which allows the suction to be utilised fully to the rest of the plant.

“In the second instance the arms have external hinging. That means the moving hinge parts are on the outside so the arm is easier to maintain – if the hinging is on inside like most companies would do it, then all the muck passes over the hinge and they get damaged or jam up and the user has to undo them to clean them. And, in addition, we provide metal rather than plastic hoods, the hoods have an all-round grab handle and dampener, and we only use quality powder-coated steel made in Europe for our products. These seemingly small refinements make a huge difference,” she says.

Ms Campbell says NZ Duct & Flex having its own install employees and engineering manager instead of using contractors saves the customer time. “We can organise our jobs to suit the customer. The customer has access to our full warehouse of stock as, despite carefully prepared quotes and pre-inspections, specs more often than not change slightly on site. For instance, people forget that there’s a beam in the way or the exit through the wall has to move,” she comments.

With the fume arms installed in an optimum spot to capture dust from both skimmings decanting processes, Mr Greenhorn says the area has been cleaned up, the extra shift has been cancelled, and all staff work and have breaks at the same time. “The dust has been reduced significantly and everybody’s comfort levels have increased dramatically,” he says.

Ms Campbell says NZ Duct & Flex receive similar feedback all the time. “Here we see proof that dealing with dust issues where the dust is generated really does sort out the environmental quality for the staff who work there,” she adds.