Advanced Efficiency Options - Increasing Electricity Generating Potential from Pulp Mills, 2004 International Chemical Recovery Conference

The pulp and paper industry faces new era. New environmental expectations have appeared. Cutting down air emissions is not enough. Pulp and paper mills need to maximize their bioenergy potential and minimize their electricity consumption to produce green electricity. Energy efficiency has increased both in generating and consumption so that the newest pulp lines produce a surplus of electricity without firing mill bark and wood residues. Reducing the heat consumption in the mill has reduced the back pressure power potential and more and more of the power generated is actually condensing power. Higher black liquor dry solids generates more steam. Today’s challenge is to have integrated pulp and paper mills that operate totally without auxiliary fuels producing a net surplus of electricity from 100 % biomass fuels.

The first Tomlinson recovery boilers started operating in Canada 70 years ago. Recovery technology developed from early inefficient chemical recovery to modern large plants. 2004 marks the year when the first Canadian commercial black liquor gasifier starts operation. Black liquor gasifiers pose a challenge to recovery boilers. The size of pulp lines has increased. In the largest lines we talk about utility sized recovery boiler power production (>100 MWe). Economics of scale means there are now new possibilities to increase the yield of bioenergy. At large boilers the electricity generation can be further increased with the adoption of utility type power plant connections.

Black liquor gasification promises higher electric power but requires additional investments compared to recovery boilers. How black liquor gasification will fare in our industry is not clear yet. A lot of costly development work needs to be done. Only time will tell whether higher electricity generation can overcome lower efficiency and higher installation cost.