Tailor-made solution for emission reductions

Metsä Fibre’s Joutseno pulp mill is located in south east Finland next to lake Saimaa. The mill produces some 690,000 t/a softwood pulp, as well as biochemicals and bioenergy. It operates without fossil fuels, and thus it does not produce any fossil CO₂ emissions during normal operation.

When the mill switched from burning natural gas in its lime kiln to gasifying bark to use as a biofuel, it encountered a challenge with increased emissions going into the atmosphere. The mill’s requirement was to lower the emissions to a target below the BAT (Best Available Technology) emission levels. With only a limited amount of room for expansion, it needed a tailor-made solution to solve the challenge, and in a short space of time. Pertti Kaikkonen, ANDRITZ, Sales and Marketing Manager, White Liquor Plant Services explains, “When switching from natural gas to biofuels, and particularly when using bark as a fuel in the gasifier, there is a lot of fine dust that is created which the usual electrostatic precipitator is not capable of fully and successfully handle.

“The Joutseno mill had three options to solve the challenge; adding new fields to its existing precipitator, building a new precipitator with added capacity, or the third option, installing an alternative technology that would solve the challenge.

Adding new fields to the existing precipitator, as well as installing a new precipitator were options that were simply out of the question due to the limited space at the mill, as well as time constraints on such a large project.

A TAILOR-MADE SOLUTION

After consultations with ANDRITZ, it was proposed that a MicroMist Scrubber™ from the US company EnviroCare International would be the perfect solution. The scrubbers offer very efficient cleaning, water recycling and a low load to the treatment plant and have been specifically designed to collect minute particles at very high efficiencies with low energy input. The technology has been implemented at US mills and has shown major successes when reaching tight emission regulations.

“Metsä Fibre and the ANDRITZ Sales Team visited a mill in Arkansas in the US which had the MicroMist technology installed and were impressed with the design, layout and results being obtained by the scrubber. At that time there were no installations in Europe of the technology,” adds Kaikkonen.

ANDRITZ received an order for the installation of a Scrubber in October 2019, and work began on engineering to fit the scrubber into a limited amount of space. “One of the real advantages of this scrubber is its small footprint,” says Jere Lehtinen, ANDRITZ Project Manager. “But still we had a very tight space and basically we had to shoehorn the scrubber in to the best possible position.”

One of the added advantages of the project was ANDRITZ’s knowledge of the lime kiln process, so it was able to design and supply all the infrastructure and equipment the new scrubber needed, at the same time as take responsibility for the commissioning and start-up of the project. The scope of supply from ANDRITZ included all equipment, design layout, piping and platforms, as well as pump station, dampers and booster fan.

Lehtinen adds, “ANDRITZ carried out the whole project, from providing the specific dimensions needed for the scrubber to designing, building, erecting, installing and starting up the equipment. We also installed all of the automation and electrification needed for the project.”

The installation work was finalized in October 2020 and the final connection of the scrubber took just five days during the Joutseno mill’s annual shut down.

EMISSIONS DOWN – ALL SYSTEMS GO

Start-up of the Scrubber, the first of its kind in Europe, took place in mid-October 2020 with the result being a dramatic reduction in emissions from the lime kiln. Kaikkonen says, “We more than reached the target Metsä Fibre requested of below BAT emission levels. The new scrubber now operates smoothly and efficiently and emissions have been measured at just 10–15 mg/Nm3, solving the mills’ challenge with a tailor-made solution.”

The MicroMist Scrubber solution can be installed in greenfield projects or retrofitted to existing operations. The technology can also replace old technologies in existing scrubber bodies.