ANDRITZ/UPM Schongau Industry News

didn’t treat every meeting as an excuse to charge a little more. We had a very good relationship.”

Air time The boiler now not only beats the new emissions targets, it also enjoys more stable operation – regardless of the fuel mix. Further benefits include reduced consumption of make- up sand and extended lifetime of pressure parts and main components. All of which mean lower costs, in the long run. Hohenwarter notes that every part of the emission-reduction package was necessary to deliver the promised performance, but he nevertheless points to the main highlights, which were the secondary air system, the FGR system, and the bed ash system. In this case, both the primary and

UPM’s newsprint and supercalendered magazine paper mill in Schongau, Bavaria, Germany.

shifts 24/7 to stay on schedule.” He explains that because the boiler is so important for getting rid of the waste – bark and fibre-containing sludge from Schongau itself, as well as from UPM’s nearby Augsburg and Ettringen mills – downtime had to be strictly minimised. As a result, the planned timescale was “very optimistic,” he says. And yet, “ANDRITZ planned it through side-by-side with us. The detailed engineering and implementation were very good. They supervised the work every day and we managed it.” From first contact to handing over

responsibility to the customer, ANDRITZ and UPM put in two and a half years of hard work. From ANDRITZ’S point of view, that meant the design, delivery, erection, and commissioning of all of the areas. As part of this process, Frömmrich appreciated that “ANDRITZ

secondary air systems, as well as the FGR system, were modernized to bring the air staging up to the very latest technology. The aim was to ensure even distribution of combustion air in the combustion chamber and recirculation of the flue gas to control the amount of oxygen available to react with the flame. The right air flow is also one of the factors necessary for proper bed fluidization, which is also necessary to ensure the correct pressure drop, otherwise non-uniform burning can create hot spots or dead spots. All of this helps to regulate the flame and

As a result, the planned timescale was very optimistic. And yet, Andritz planned it through side-by-side with us. The detailed engineering and implementation were very good. They supervised the work every day and we managed it

bed temperatures, which optimizes combustion, thereby limiting CO levels and NOx emissions. The rebuilt secondary air system

now has more optimally laid-out air blowers to feed air in from the side walls, and optimally-designed air nozzles now cover the complete cross area of the combustion chamber. Frömmrich points out that “the new system can handle a higher volume of air at higher pressure. Nothing now goes into the boiler that we can’t control.”

In the primary air system, the modernization raised the primary air temperature from 160 to 200°C, which helped to keep the bed temperature high even with low- calorific fuel mixtures. The improved air staging also

meant a big improvement in boiler temperature control. This resulted in a lower combustion chamber outlet temperature and the avoidance of temperature spikes and the related NOx and CO issues. The upgraded FGR system now also

feeds the rebuilt primary air system and the two new ignition burners, too. It also helps to keep the boiler bed fluidized, as well as simplifying temperature control, meaning – yet again – more uniform combustion. It is clear that this was a common theme throughout - as Frömmrich says, “Like with the secondary air system, we now have much more control. We can now control a higher volume of air in more individual stages.” All of this means more stable,

reliable steam generation, which means lower emissions, lower costs, and longer parts life.

We got what we wanted Another key part of the project was the modification of the bed ash system, including the wind screen with ash separator. The upgraded system at Schongau not only removes impurities from the bed material, but

New secondary air layer for advanced air staging to reduce NOx emissions. Summer 2019 Forest Bioenergy Review 15

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