Estimating the Impact on Makeup and the Liquor Loop of Environmental Modifications - A Graphical Method, 1991 Pulping Conference Proceedings

Environmental demands have forced numerous process changes in pulp mills in recent years. Modifications made or planned will have an impact on the liquor loop, changing the makeup chemical requirements in sometimes unexpected ways. In addition, the continual tightening up of the liquor loop may force mills to go to alternative makeup chemicals, while finding other uses for waste streams currently used as makeup, such as spent acid from Cl02 and tall oil plants. Proper analysis of the impact of these environmental modifications should include effects on the liquor loop.

A method is presented for estimating the effects on the liquor system of various environmentally oriented modifications. The calculations are based on numerous applications in mill situations, and typical ranges are given for data that can be difficult to measure. The results are displayed in an intuitive graphical form, which clarifies the way different variables interact and allows back-of-the-envelope, “what if” types of analyses. Simple methods for estimating changes in makeup requirements and sulfidity are given.

This method is applied to several case studies, in which the effects of modernizing the bleach plant in combination with other simultaneous changes were analyzed. In these studies changes in chemical makeup requirements were estimated, and these estimates provided each mill a basis for evaluating among several alternative options.