BioRegional MiniMill technology - report on UK industrial scale trials of novel black liquor gasification and energy and chemical recovery system

This paper will report on the first findings of a UK industrial scale trial of the BioRegional MiniMill black liquor gasification process which is projected to operate cost effectively at the scale of 10,000-30,000TPA of pulp production. It is expected that the process could be used for either incremental capacity at wood pulp mills or small-scale non-wood pulp mills. Two types of black liquor have been tested at the plant at the time of writing and results are reported in this paper. Black liquor from straw pulped using NaOH was processed, demonstrating that a calorific gas can be produced sufficient to result in a significant increase in temperature at the afterburner and therefore ultimately capable of operating in conjunction with a heat recovery boiler. Black liquor from abaca pulped using a sulphite process was tested, demonstrating that sulphite liquor can be processed in this system without problems associated with reduced sulphur gases (eg H2S). Although the abaca black liquor trialled has a low calorific value, the process itself is projected to be autothermal with the added benefit of steam generation from the afterburner off-gas. Chemical recovery has also been investigated with a projected recovery rate of 88% of available sodium in the ash.