Optimering av kalkcykeln på Iggesunds bruk med avseende på specifik energianvändning

Abstract: Iggesund Mill is an integrated pulp and paperboard mill that makes kraft pulp and solid bleached board. In the pulp process, white liquor is used to make pulp. The white liquor is recovered in the recovery process. One step of the recovery process is the lime kiln where calcium oxide is made by heating up the residue, calcium carbonate, to 1,200 °C. In this master thesis two proposals are examined to lower the specific energy consumption in the lime kiln. The two proposals are: to raise the height of the dam in the lime kiln and to bleed out dust from the electrostatic precipitator. The goal is to clarify if it is economically feasible to bleed out dust from the electrostatic precipitator and to recommend an optimal height of the dam in the lime kiln.During the work a mapping of lime kilns in other Swedish kraft pulping mills has been made and meetings with the lime kiln manufacturer and a lime kiln consultant have been held. Samples of the lime, lime mud and dust from the electrostatic precipitator have been taken and sent for analyses to find out the chemical compositions. Simulations and calculations have been made in MATLAB. The result shows that a higher dam will lower the specific energy consumption with approximate 200 MJ/ton produced lime. The other proposal, to bleed out dust from the electrostatic precipitator, will lower the energy consumption as well. The optimal amount to lower the energy consumption is to bleed out 2.7 kg/ton produced lime and will lower the specific energy consumption with approximate 45 MJ/ton produced lime. This will save 200,000–260,000 SEK per year for an investment cost of 350,000–400,000 SEK. The conclusion is that the recommended dam height for the lime kiln in Iggesund Mill is 72–80 cm. The optimal amount of dust from the electrostatic precipitator to bleed out is 2.7 kg/ton produced lime.