Pulp Paper & Logistics


ANDRITZ 23


opportunity to create happy customers,” Silventoinen says. “The quest for better performance, higher reliability, lower maintenance costs are all sound reasons for building a better bark press.”


Sound starting point “We made solid technical gains in all the main technologies in a wood processing plant: debarking, chipping, screening, rejects handling, stacking/reclaiming,” Hannimäki says. “Our goal is to systematically go through every process to make it better. Bark pressing, while not critical to the mainstream processes, has taken on higher importance as


mills replace their outside energy purchases and fossil fuels with their own in-house biofuels. That is one of the primary reasons our design team set out to develop a new-generation bark press.” “We took a look at our past


to see what we should retain and what we had to change,” Hannimäki says. “Our past experience re-affirmed that there are several ‘principles of pressing’ which are still sound. Only the execution of these principles needed to change.” The principles of pressing are: ● The bark should be pressed during one rotation of a drum – not going round and round. ● The pressing time (retention


The HQ-Press is the most economical way of draining bark, delivering bark with approximately 5 per cent unit higher dry solids content than any competitive unit. This can increase the net green energy value of the bark by up to 15 per cent


time on the drum) should be as long as possible.


● Higher pressure is more effective in achieving higher dry solids.


The Andritz HQ-Press provides a robust, reliable process for handling bark in any timber yard or biomass- handling operation


● Water removal is more effective when pressed out in multiple directions. Development work started in 2014. From this came some important design decisions: two- stage pressing; a large-diameter drum (around three metres) and a very slow speed (to encourage adequate pressing time; higher nip pressure to extract the most water; and removal of water through both the screen drum and the press drum. After proof-of-concept and


prototyping was completed, Andritz began talking about the new product with interested customers in Nordic countries. The ideas resonated quickly with pulp mills experiencing frustration with their existing bark press operations.


Good upside potential Metsä Fibre was approached by Andritz about being the first to try the new bark press for the Äänekoski project. Merikallio recalls: “Andritz has


a good track record in developing products with us and we have worked together for years. The presented design concept looked like Andritz had eliminated the problem areas. To be honest,


September/October 2017


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