Date of Award
Bachelor of Science
Paper Science and Engineering
Microorganisms can cause many problems during the papermaking process. These problems include slime deposits, corrosion, felt plugging, holes, and additive contamination. An effective biocide program can reduce the numbers of microorganisms resulting in a reduction of these associated problems. This study focuses on the control of microorganisms on the paper machine and the relevant sources of water. Observation of the paper machine began with bleach being pumped into the headboxes, AES screen rotating shower water system and Bel-Bond showers. There was approximately 250 ml/min of bleach being pumped into each of these systems. The amount of bleach being pumped into each system then changed to 250 ml/min (175 ppm) into the Bel-Bond showers and 1000 ml/min (175 ppm) into the AES water system. The moving of the bleach resulted in a 39- 67%, 70-75%, and 69% reduction in microorganisms in the headboxes, machine chests, and whitewater respectively. Throughout this time approximately 75 ppm of sulfone-based biocide was pumped into each of the machine chest. The experiment began by utilizing a bromobutane based biocide in conjunction with sodium hypochlorite. The biocide was fed on a "slug" basis to a concentration of 98 ppm. The sodium hypochlorite was added to the Bel-Bond showers and the AES water systems at the beginning of the experiment in the same amounts as was previously used. Later in the experiment, bleach was added to these two systems along with the dirty whitewater at a rate of approximately 600 ml/min (50 ppm). A change in the number of microorganisms was not readily apparent between these two methods of addition. It was found that the number of microorganisms was decreased an additional 76-80%, 63-74%, and 83% in the headboxes, machine chests and whitewater respectively. This is the amount of additional reduction based on the already lowered amount of microorganisms. The final goal of this experiment was to reduce holes and breaks on the machine which would result in increased production. It was found that the number of wet-end breaks decreased which caused an increase in production. An additional benefit was that the defoamer usage was cut in half.
Taube, Josh, "Optimizing Biocides to Control Microorganisms" (1997). Paper Engineering Senior Theses. 536.