Biomass pre-treatment for bioenergy – Case study 4: The steam explosion process technology

This case study is concerned with the upgrade of low-grade biomass feedstocks through steam explosion followed by densification to produce a fuel pellet. By comparing the current state of technology with conventional wood pellet production the economic potential is examined. Based on an actual user case, consultation with users and consultation with a producer, the properties and opportunities of steam explosion pellets are further explored.
From the case study, it can be concluded that the steam explosion technology:
• Is a technology that is known from other applications in the past
• Works in a batch-wise configuration, as per current state-of-the-art
• In a batch-wise configuration the reactor technology and process control are relatively simple
• Requires size reduction and drying before the biomass is fed in the steam explosion vessel
• At present has only few developers with operational producing plants
• Needs to be proven at scale for non-woody biomass types.

The steam exploded product:
• Can be stored outdoors for a longer duration with no significant impact on mechanical durability
• Requires measures for dust prevention
• Has a calorific value slightly higher than that of wood pellets but below that of torrefied pellets
The calculations presented in this report show that the production costs of steam explosion pellets are higher than those of wood pellets. This requires specific applications for the steam explosion pellets, such as peaking power plants where outdoor storage is permitted and the cost differentiation between wood pellets and steam explosion pellets can be balanced, e.g. by savings on handling equipment.

Authors:
Patrick Wolbers (DNV GL), Marcel Cremers (DNV GL), Travis Robinson (NRCan), Sebnem Madrali (NRCan), Guy Tourigny (NRCan)

Acknowledgements:
Rob Mager (Ontario Power Generation), Rune Brusletto (Arbaflame)

Download the report here: CS4 – Steam explosion