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Pulp Paper & Logistics


at nearly twice its original 600 t/d rated capacity. Because of this, very little washing is done in the digester itself. That is why the fibreline includes a pressure diffuser, two brownstock washers, a pre-oxygen washer, and two wash presses. “Even with this, we run a high COD load into our bleach plant,” Parfitt says. High COD carryover requires significant chlorine dioxide just to neutralize it before the bleaching can take place. “We looked at different options across the fibreline to reduce bleaching costs,” Parfitt explains. “We also knew we could reduce our

effluent load. So, there are many benefits to running cleaner pulp into the bleach plant.”

Investing in what we have A company of Canfor’s size certainly has the money to replace a press or two. “We don’t just throw out equipment to buy something new,” Parfitt says. “We push our equipment reasonably hard and we are always looking for ways to make our existing equipment operate better and at a lower cost. That is our job.” Canfor’s focus honed in on the

wash presses since they were the last stage before bleaching.

“Improving the wash presses should also help our oxygen delignification process, since we have been holding back on caustic to reduce soda carryover to the bleach plant.” With the goal of improving the existing presses, Parfitt and a colleague started speaking to vendors. “Their options were limited,” Parfitt says, “either in the benefit or very high in capital cost. For example, one option was to go to a medium-consistency screw feed with a medium-consistency downpipe and pump. That is a huge capital cost.” Faced with the currently

Greg Hallas, ANDRITZ product manager for Twin Roll Press Services (left), with Kelly Parfitt, Canfor project engineer, standing on post-oxygen wash press #1 that received the Mult- E-Nip upgrade.

available options – and not being happy with any of them – Canfor gave the challenge to ANDRITZ.

A new design Greg Hallas has worked around wash presses for about 20 years. He knows the designs, the strengths, and the limitations well. “There are twin roll displacement press

4 May/June 2015

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