ECONOMIC FUNDAMENTALS OF OZONE BLEACHING, 2018 PEERS

The combination of ozone and chlorine dioxide in Z-ECF bleaching has been expanding quickly recently with 5 new installations contracted since end of 2016. Ozone bleached pulp capacity is passing above 10 million tons per year in 2018 and accounts for 10% of global bleached chemical pulp capacity.  There are several reasons for that growth when comparing Z-ECF bleaching sequences with conventional ECF ones:

- Similar or better strength properties - Higher brightness stability
- Significantly lower extractive content - Significantly lower organic halogens (OX) content in the pulp
- Significantly lower COD, AOX and color load in the effluent discharge

There are a few publications dealing with operating costs of Z-ECF bleaching. However there is little, if any, public information about the impact of ozone bleaching on capital costs. The present article intends to address the case of a 1,200 adt/d bleach plant and compare capital and operating expenditures of the conventional ECF bleaching sequence D-Eop-D-D with two Z-ECF ones: Z/D-Eop-D with a medium consistency Z-stage and Ze-D-D with a high consistency Z-stage. 

The Capex calculation is simplified by not considering unchanged bleaching stages, civil work, automation, piping, etc. but assumes cost of these elements remains unchanged with or without ozone bleaching. On the Opex side, Authors will review energy requirements for ozone production, ozone generation, chlorine dioxide production and chlorine dioxide pre-heating to assess impacts of a Z-ECF bleaching sequence on electricity, steam and chemicals consumptions. 

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