The fate of nitrogen in the chemical recovery process in a kraft pulp mill.: Part III:: The effect of some process variables

In this work, the effects of some process variables on the fate of nitrogen in the chemical recovery cycle were studied, The general picture of the relative flows of wood nitrogen in the cycle was the same for both hardwood and softwood. The wood species, however was of significance for the nitrogen concentrations in the cycle as well as for the level of NOx emissions from the boiler. The different ways to handle secondary condensates caused some minor changes in the routes of nitrogen in the cycle. The addition of biosludge (about 0.5 wt% of black liquor solids) to black liquor in the middle of the evaporation plant increased the nitrogen content of liquor by about 30%. This addition and the feed of the high-concentration, low-volume gases and methanol to the recovery, boiler did not result, however in any change in the share of the smelt nitrogen of the liquor nitrogen or in any increase in the levels of NOx emissions in the boiler.