Paper Technology International 2020 - Journal - Page 92

PAPERTECHNOLOGYINTERNATIONAL
Combustion and tissue drying verified at demo plant in Sweden
Interest from the tissue industry and the report, ”Fossil free
tissue drying” (Energiforsk, report 2016:231), which investigated
the effects of replacing LPG with syngas using mathematical
models became the starting point to look deeper into the possibility
of replacing the fossil gas with Meva Energy’s stable renewable
gas in the tissue drying hoods. Some questions remained: could
a low-calorific gas be used in a suitable gas burner and generate
stable sufficient heat without resulting in imperfections such
as smoothness, smell or similar on the tissue? How could the
availability of the paper machines be ensured? What needs to be
upgraded in the existing infrastructure of the mill and what effect
could it have on the whole tissue drying system?
Figure 6: Burner trials with renewable syngas showing full
combustability of the low-calorific gas.
The first step to answer these questions was to give the
research institute RISE ETC (Research Institute of Sweden, Energy
Technology Center) the task to evaluate the suitability and further
sort out the uncertainties.
Figure 5: Combustion trials at Meva’s plant in Sweden where a
mini-yankee was used to dry tissue paper.
A major test campaign was pursued, where syngas from
Meva Energy’s full-scale biomass gasification plant were burnt in a
combustion chamber and the combustion gases then analysed in
terms of particle content and combustion. RISE also investigated
tissue drying with a mini-yankee cylinder, whereupon the tissue
paper samples were analysed in terms of odor and visual damages.
The result showed:
•
No odor or visual damages at all
•
Sufficient heating value
•
Low level of particles in the exhaust gases
•
Stable and even combustion without any need to enrich
the biogas
These tests were conducted with a swirl type of burner and
followed up by commercial burner manufacturers testing the gas in
more conventional burners for tissue drying hoods, accepting multi
fuels.
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These tests concluded:
•
Works in both duct and corner burners
•
Possible to co-fire LPG/NG and renewable syngas in
same burner
•
No need to redesign or expand existing burner
chambers
These results mean that the transition from a fossil solution
to a renewable gas can be done simply. Hence, keep the existing
infrastructure as a redundancy and only exchange the burners to
multi-fuel types.
Renewable gas and burner system developed together with
ANDRITZ
The combustion and tissue drying tests revealed another
opportunity: by optimizing the gasification and burner solution the
gasification system could be simplified, compared to the solution
Meva Energy had developed for gas engines, which requires more
purified gas then an industrial burner. If the burner accepts a higher
moisture content and lower calorific value in the gas, it means that
more low-cost biomass can be utilized as well as the gas cleaning
system being simplified, giving a more robust and simple system.

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