Will different production processes influence the off-gassing and self-ignition behaviour of wood pellets? Prof. Dr.

Transcription

1 Will different production processes influence the off-gassing and self-ignition behaviour of wood pellets? Prof. Dr. Werner Sitzmann Amandus Kahl GmbH & Co. KG Reinbek, Germany

2 Contents - Kahl-Group - Energy saving pan grinder mill - How to influence autoxidation - Conclusions

3 KAHL - Group Each company of the KAHL - Group has been successful in its own markets and offers worldwide solutions, plants and machines for the following industries: Recycling industry Green coffee Rice and grain Systems for the (tyres, waste, sludge, warehousing and processing industry food industry: biomass and wood) Chemical industry Food and sugar industry Feed industry Petfood industry processing centre Coffee roasting plants Roasting technology for nuts and kernels Particle technology (cereals, legumes) Edible oil industry Hydrothermal treatment Spice and tea processing industry Pasteurisation Fermentation Cooling Freezing Edible oil industry

4 Facility Amandus Kahl

5 A Global Player HEINEN Freezing Varel, Germany NEUHAUS NEOTEC Ganderkesee, Germany AMANDUS KAHL Reinbek/Hamburg, Germany SCHULE Reinbek/Hamburg, Germany AMANDUS KAHL Benelux AMANDUS KAHL France Moscow, Russia AMANDUS KAHL USA Corp., USA AMANDUS KAHL Ibérica Kuala Lumpur, Malaysia Cairo, Egypt Amman, Jordan COMPANY SUBSIDIARY AGENCY

6 10 x 6 mt/h pine USA (Enviva) Jan. 2018: New machine type : ~ 7 mt/h

7 Two types of pelletizers material flat die pellet mill ring die pellet mill

8 Product inlet Product distribution Adjusting nut for roller gap, hydraulic Flexible ring Pan grinder roller Pan grinder head Scraper Die Cutting device Main shaft Design and function of the flat die pelleting press

9 Wood pellet production from wood chips Wood chips Wet grinding Drying Dry grinding Pelleting - Domestic fuel - Pellet post-grinding - Industrial pellets (dust firing in power plant)

10 Pan grinder mill Shearing and cutting forces combined in one system Hammer mill Hitting forces by hammers.

11 Wet grinding using the pan grinder mill Shearing and cutting effect due to the variation of pan grinder rollers (width, surface, diameter) and die (shape, depth and arrangement of holes)

12 Hammermill (left) and pan grinder mill (right) ground wood chips predetermined breaking points

13 Energy-minimised production of wood pellets b) wet grinding with pan grinder mill dry grinding with hammermill Hammer mill a) wet and dry grinding with hammermill particle size reduction Hammer hammermill mill Pan pan grinder grinder mill mill dry grinding step specific energy input, % % %

14 Chemical composition of different wood types, weight - % sawdust spruce pine larch cellulose hemicelluloses lignin extractive matters resins, waxes, fats phenolic ingredients polysaccha rides components

15 Structural formula of fat & autoxidation of fatty acids fat = triglyceride Fatty acid (FA) Fatty acid (FA) FA radical radical Chain forming FA peroxide radical FA hydroperoxide Aldehyde formation Alcohols, ketones, CO - formation etc. etc. = unsaturated binding Hexanal as main product Landesinstitut f. Schulentwicklung, Baden-Württemberg

16 Autoxidation of fats and oils is a very complex, exothermal chain reaction that requires - oxygen - radicals (caused by H 2 O 2 for example) - unsaturated chemical bindings - time - temperature (heat) is found by different research groups to be the main reason for off-gassing and self-ignition of wood pellets!

17 Kinetics of autoxidation of fats/oils degree of oxidation O 2 binding peroxides hexanal volatiles Induction phase start of rancidity time Heiss, Eichner: Haltbarmachen von Lebensmitteln, 1990

18 Thesis of this study Will it be possible to influence autoxidation during pellet production by - changing the grinding processes (surfaces, mass transfer), - adding radicals (increasing the reaction rate) and/or - increasing residence time by increasing the storage period between dry grinding and pelleting after radical-addition? Target: Autoxidize defined as many as possible of wood containing unsaturated chemical compounds during the pellet production process to prevent offgassing and self-ignition later on! Forming of hexanal characterizes the degree of autoxidation

19 Target: Acceleration of autoxidation degree of oxidation O 2 binding peroxides hexanal volatiles start of rancidity time Heiss, Eichner: Haltbarmachen von Lebensmitteln, 1990

20 Wood pellet production from wood chips Wood chips hammermill OR pan grinder mill Wet grinding Drying Dry grinding hammermill OR pan grinder mill H 2 O 2 as radical donator + time Pelleting - Domestic fuel - Industrial pellets - Pellet post-grinding (dust firing in power plant)

21 Analytics Prüfverfahren µ-chamber Small samples (up to 6 in parallel) Bulk-/Cell-mode Temperature: RT C Air Flow: ml min-1 Adsorption tubes with Tenax -TA Analysis by TD-GC-MS Dr. Ohlmeyer, v. Thünen Institut, Hamburg

22 Hexanal [µg/kg/h] Significant different autoxidation behaviour 5000 All parameter combinations

23 Hexanal [µg/kg/h] Influence of grinding process Pan grinder mill Hammer mill Emission rate of hexanal per 1 kg of pellets

24 Hexanal [µg/kg/h] Influence of H 2 O 2 addition in the conditioner Emission rate of hexanal after per 1 kg of pellets 5000 H 2 O H 2 O

25 Hexanal [µg/kg/h] Influence of residence time after H 2 O 2 - addition Emission rate of hexanal (four hours reaction time after conditioning) per 1 kg of pellets time

26 Conclusions First qualitative studies showed that autoxidation can be influenced by - changing the grinding process - increasing the reaction rate by adding radicals - applying additional residence times during pellet production after addition of radicals Make autoxidation happen within the pellet production line!

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28 Thank you very much!