Bioproduct mill gets massive support from stainless steel

Wood is a way of life in Äänekoski town in central Finland and a new mill for Metsä Fibre, part of Metsä Group, will enhance an already strong history of forestry in the town. It will also bring added value to Finland, as exports are expected to increase by half a billion euros thanks to the added output.

With an annual pulp production capacity of 1.3 million tonnes, the mill will source from mainly Finnish raw materials as it produces a range of bioproducts for use in Europe and Asia. Tall oil, turpentine, lignin products and wood fuel are all products of the industrial processes as is bioelectricity seeing that the mill will produce much more electricity than it will use.

Construction logistics for large loads

As of mid-summer 2016, construction is in full-swing and all of the elements of the next generation mill are being put into place in anticipation of a scheduled completion in autumn 2017. Alongside the mill's pulp towers, the building site includes four pressurized reactors and two storage tanks for the fiberline and evaporation plant, which are being supplied by the pipe and tank construction company, Althammer, in cooperation with Outokumpu.

Outokumpu has thus far delivered some 140 tonnes of Outokumpu Forta LDX 2101 (EN 1.4162) and Forta DX 2205 (EN 1.4462) stainless steel plates for this project from Outokumpu's mill in Degerfors, Sweden. Duplex stainless steel was chosen due to its corrosion resistance against chloride, and the steel has gone into two oxygen reactors, an oxygen blow tank and an EOP reactor in addition to both a heavy liquor storage tank and a firing liquor storage tank designed to withstand temperatures of up to 165°Celsius.

Installation feat

These reactors and tanks are massive structures - the recovery boiler, for example, will reach a height of 80 meters - posing unique challenges during the construction and installation process. The mill is going up in an area with five fully operational pulp mills. With approximately 5,000 truckloads delivered to the mill, logistics for the installation are planned to the minute to ensure there is room to maneuver when the large structures are delivered.

The sheer number of wide and heavy loads being delivered – at least 1,500, with the heaviest load weighing 175 tonnes – is a testament to the essential infrastructure going into this unique project. Though not yet complete, the bioproduct mill has already proven itself an architectural marvel during construction and installation.