To increase its ability to deliver quality tissue at the highest efficiency at its Hokkaido mill, the decision was taken by Doh-Ei in June 2011 to upgrade its drying line. This included the installation of an AndritzPrimeDry Steel Yankee with a diameter of
3.7 m and shell length of 4.3 m to help produce its 19,000 tonnes/yr of high quality output.
The machine itself, PM 1, has a working width of 4 m and a machine speed of 830 m/min for18 g/m² tissue and 900 m/min for 12.5 g/m² tissue. Production is around 55 tonnes/day.
Masashi Kobayashi, CEO of Doh-Ei says: "I first saw a lecture on the Andritz steel Yankee at a technology fair and was taken by its ability over a cast iron one to improve on drying efficiency. Also, it is a fact the cast iron dryer used a lot of energy, and we had to make a change. The steel Yankee has more contact drying which meant a reduction in drying energy."
A PrimeDry steel Yankee installed in Japan is showing favorable results
Production, energy savings and speed
The work was carried out on the drying line, the new Yankee was installed and the machine started up in May this year, and by all accounts it is winning favor with the management at Doh-Ei. Kobayashi says: The installation went smoothly and without any problems and it took us only an hour or two after start up before we had quality product. The unit is compact and easy to operate, we have already reached the design speed of the machine. In fact production speed has increased by 7-9% and the 135-mm wider dryer shell length allows much better drying of the sheet edges and as a consequence decreases sheet breaks by half. Drying efficiency has greatly improved compared to the cast iron Yankee with LPG usage for the dryer hood being reduced by 30-50% and the power for the dryer fan has been reduced by 10%."
And what about the crucial factor of quality? "Sheets are more evenly dried and the tissue quality has improved especially in terms of softness," says Kobayashi.
What other effect has the installation of the PrimeSteel Yankee had on Doh-Ei: "Well, since there are no Japanese suppliers that can produce a similar sized Yankee dryer, ours attracts a lot of interest in our industry here, mainly due to the energy saving factors. But as far as we are concerned, we are studying the future possibilities of introducing steel Yankees across the whole group".