Recovery Process Alternatives for Sulfur-Free Pulping, 2004 International Chemical Recovery Conference

The research project EFPRO funded by the European Community under the Fifth Framework Program aimed to increased production of green electricity by adopting a sulfur-free chemical pulping process. A competitive pulp production by the IDE process has to be secured to study the potentials of chemical recovery and energy generation in order to provide a suitable overall mill concept.

The technical properties of fine paper made from birch IDE pulp and those anisotropic handsheets made from birch and eucalyptus IDE pulp were identical to properties of papers made from Kraft reference pulp. Two alternative recovery processes were outlined for the sulfur-free pulping: based on advanced recovery boiler and based on pressurized gasification of spent liquor. The chemical and physical properties of IDE spent liquor were more favorable than those of Kraft liquor, which enabled to utilize higher steam parameters in the advanced boiler resulting in an increase of total efficiency of more than 10 % units.

A pressurized gasifier can be outlined to operate at favorable conditions for sulfur-free pulping, but there are several details in gasifier and gas cooling, which were identified as clear targets for challenging future research and development. Existing gas turbine already proven for this kind of syngas applications can be used to achieve high gross power output of more than 220 MW with pulp production of 1.000.000 t pulp/year.

The economics for a new IDE pulp mill compared to Kraft will be good, payback periods of less than 5 years can be achieved. Retrofitting will not be an alternative today since too high investment costs necessary and likely no smaller pulp mills will be equipped by IGCC.