BERG, A.; KARNA, N.; FUENTEALBA, C.:
Proceeding 5th Nordic Wood Biorefinery Conference Stockholm, Sweden, 25-27 March 2014.
Delignification of wheat straw in concentrated carboxylic acetic acid solutions was reported during the 3rd Nordic Wood Biorefinery Conference, 2011. Cellulose fibers with a Kappa number of 14 could be obtained digesting the biomass with 87% (w/w) acetic acid solution at 160°C for 120 min. Alternatively it was also possible to operate at atmospheric pressure, replacing a part of acetic acid with formic acid.
The paper being presented reports the advances in the development of the process to date, particularly with respect to its technological scaling up. It should be noted the change of the delignification process in batch mode to a continuous operation, to decrease the required liquid / solid ratio. The batch pilot plant was operated periodically over the past two years, while the continuous plant is in its initial operating phase.
In addition, progress has been made in the design of a complete process that includes both delignification of biomass, separation of the dissolved lignin and hemicelluloses, liquor evaporation and fractional distillation of dilute acetic acid. The two determinant variables in energy requierments are: (1) The liquid flows required in the digestion, separation of dissolved lignin and hemicelluloses, and washing acetic pulp with water, and (2) the amount of water to be fed to the distillation column. Consistent with this, various technological options were evaluated to optimize the process.