Metal contaminants in pulp processing

Mechanical breakdowns and damaged products were plaguing Ahlstrom Corporation’s Mt. Holly Springs, Pennsylvania facility, which produces paper products for liquid filtration. During the process of converting timber products into a fine pulp slurry, small bits of ferrous metal were getting in the flow. Metal contamination in paper processing can come from anywhere — a nail in a tree, baling wire or pieces of metal fence, so equipment to remove contaminants is located at nearly every stage of the paper-making process.

When Ahlstrom’s maintenance team discovered that the culprit was metal caught in the refiners during the manufacturing process, the need for new separation equipment became critical. The contaminants caught in refiners were damaging the refiner bars. In addition to the unnecessary, unscheduled and costly maintenance, the fine ferrous contamination could also result in the production of an off-quality product.

Ahlstrom Corporation’s addition of Eriez magnetic traps to its wood pulp processing operations has virtually eliminated damage to refiners from metal contaminants in the flow.

This happened as often as once a month. Looking to decrease those occurrences, Ahlstrom turned to Model T Magnetic Traps from Eriez Magnetics in Erie, Pennsylvania.

Before contacting Eriez, Ahlstrom removed metallic contaminants further downstream with a nearly identical magnet. Before the magnet would pick out the metal, damage was done to the refiners, or metal would get caught in the refiners resulting in the production of the sub par products.

Eriez suggested a T6 magnetic trap for its paper stock application. The Model T is available for 6- to 36-inch pipelines, and is primarily for upright installation in horizontal lines but can also be mounted sideways or in inclined or vertical lines. It is used to reduce damage and maintenance to filters, pumps, refiners and other processing machinery handling paper, chemical slurries and other liquid materials – just what Ahlstrom was looking for.

“We have trapped a lot of metallic product before going to the refiners, which has cut down on damage to the equipment,” says, Paul Wheeler, paper machine superintendent. “We are also less susceptible to off-quality product. The issue we would see was a once per month occurrence, and now has only happened once in the last seven months.” Item 125

This article appeared in the June/July 2007 issue of MRO Today magazine. Copyright 2007.

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