Mesatorrhalt

Sammanfattning: Abstract Degree thesis Solid content in Lime Mud By Andre Flodin Process operator program – Umeå University 17/6 – 2014 Pages: 21 A thesis was made on Billerudkorsnäs production unit in Karlsborg where lime kiln in the causticising department of chemical recovery plant does not meet the required production. Causticising department is the final step in the chemical recycling unit. There, the filtered green liquor is mixed with lime to recover the cooking chemicals used in the pulp factory. The cooking liquid is called white liquor. As a residue from the recycling of the white liquor you get lime mud, calcium carbonate. Calcium carbonate is recovered in the lime recycling department to reduce the need to buy lime to the factory, thus saving money. By first washing the lime mud in the lime filter and then burning it in the lime kiln. In order to increase production through the furnace better washed lime mud which means higher solid content and so little residual alkali as possible is sought. In order to increase the dry content and reduce the residual alkali in the lime mud examinations are made on one of the lime filters by means of multivariate experimental design. This is a great tool for examining whether there are interaction effects between different factors in an effective manner. The experimental design on the lime filter examines three different parameters, density of incoming lime mud flow, speed of the filter and wash water flow to the filter. Through the variation of these three variables in a calculated pattern an optimum can be obtained. There are other factors that will affect the dry matter content and residual alkali but these are not considered to affect as much. Two attempts were made, a test experiment and a main experiment. The test experiment was made to check how well the sampling and analytical methods work. Smaller version of the experimental design was used and the results are not considered to be reliable enough to be used for optimizing the process. It was however discovered some problems. The wash water flow to the filter was not stable and no compensation was made on the lime mud flow in relation to density. For the main experiment, the design CCF - Central Composite Face Centered with three center points was used, to determine the variation between samples. Before the trial started a second wash water pump was started and during the experiment compensation was made to the lime mud flow against density. With the obtained results on the center points, the variation between them made the experiment unreliable. This may be due to several reasons. When the results are not considered reliable, it is hard to make any conclusions about how the filter should be set for maximum dryness or residual alkali. But it is possible to discern that certain factors influence more than others, wash water flow and speed of the filter seems to affect the dry matter content the most.