Incineration of Residues

In recovered paper processing paper mills without deinking (e.g. Testliner, Wellenstoff, carton board or folding boxboard) around 4 to 10% of input material becomes residues arising primarily from the pulper disposal system, rejects from various screening and cleaning stages from the stock preparation plant, and sludge from waste water treatment. Most of these fractions are not suitable for material recycling (although compost can be produced from rejects from final cleaning and screening stages of paper machine loop). However, as they have a heating value of around 22 - 24 MJ/kg dry matter, their incineration appears as a feasible waste management option.

Similarly, in RCF paper mills with deinking (DIP) additionally produce high amounts of deinking sludge and sludge from process water clarification. The generated rejects and sludge amount to about 15 to 40 %, dependent on the input of raw material. In DIP plants, the deinking sludge, containing mainly short fibres, coatings, fillers and ink particles, is the crucial waste fraction to be handled.  Incineration of this fraction, together with sludge together with the sludge from waste water treatment, is also seen as an attractive waste management option. 

Incineration of these fractions. with power and process heat generation presents an environmentally sound option. For the incineration of these fractions, the following options can be considered for energy recovery:

  • Incineration in an in-mill reject incineration plant (rejects and sludge from a DIP plant in a fluidised bed boiler is a more widely used option in European paper mills)
  • Co-combustion in an in-mill coal fired power plant;
  • Co-combustion in cement kilns;

To obtain a high surface and good ignition behavior, a pretreatment comprised mainly of crushing, screening and secondary crushing is necessary.

Development Status Products
Commercial

Incineration of ResiduesCosts & Benefits

Parent Process: Recovered Fiber Pulping
Energy Savings Potential

One ton of rejects (from mills without de-inking) with about 45% water content can substitute 0.7 tons of brown coal in the boiler. in a German plant with 370 000 t/year production capacity, incineration of rejects in a hearth combustion (with a capacity of 28 000 t/year) that is integrated in the power plant of the mill, fossil fuel usage corresponding to 66 000 MWh was reduced.

CO2 Emission Reduction Potential

Because the rejects help substitute coal, and about 50% of solid matter in the rejects are CO2 natural substances, CO2 emissions are reduced.

Costs

The investment cost for a co-incineration plant including facilities for reject pretreatment, drying and the gasification chamber for a reject volume flow rate of maximum 3 t/hour is estimated to be around €2.5 million. In Europe, these can provide annual annual savings of €0.6 million, assuming costs for landfilling of €50/t. An additional EUR 0.3 million/yr can be saved through the substitution of brown coal.

Incineration of Residues Publications