Combustion of wood chips and grain residues for process heat supply in the largest bakery in Switzerland
Case study on how biomass can be used to produce industrial heat
The Coop Group is Switzerland’s largest retail and Europe’s second largest wholesale company. In 2015, Coop built a new production and distribution centre in Schafisheim in the Swiss midlands. The building complex incorporates a high-bay freezer warehouse and Switzerland’s largest bakery and confectioner with an annual production of 60 000 tons of baked goods.
In order to substitute fossil fuels, a biomass combustion plant was realized to provide process heat for the bakery by thermal oil. Since the treatment of the raw materials for the bakery causes residues in the up-stream milling process, the vision to use milling residues as energy for the bakery arose. The potential and technical opportunities were evaluated and a concept of co-firing wood chips and grain residues was developed. Swissmill, the largest mill of Switzerland located in Zurich and owned by Coop, was involved to provide fractions of grain residues, which are of low value for other purposes. To ascertain a flexible operation of the bakery, the decision was taken to implement a concept which enables a variable energy production by 50 % wood chips and 50 % grain residues with the opportunity to switch to 100 % wood chips. Consequently, a combustion system was designed, that enables the use of forestry wood chips from a respective silo with addition of pellets from grain residues from a separate storage compartment. The thermal oil boiler and the flue gas cleaning were adopted to comply with the challenges of increased slagging and fouling and with increased NOx emissions due to the high ash and nitrogen content of grain residues. To cover the rapid load changes of the bakery process, a gas fired peak boiler complements the heat production.
Full report:
CS5_T32_Biomass-combustion-for-process-heat-in-a-bakery
The case study was recently presented at the IEA Bioenergy 2021 conference. Presentation available here: https://www.ieabioenergyconference2021.org/wp-content/uploads/2021/12/11-02_NUSSBAUMER.pdf
This case study is the 5th of a series of case studies on how biomass can be used to produce industrial heat. Other case studies available here: https://itp-hightemperatureheat.ieabioenergy.com/iea-publications/
