Test Method And Control Of Microstickies In Recycled PULP

With the increasing use of recycle paper, stickies problems have begun to receive more attention, stickies of wastepapers can be divided into macro stickies, microstickies and secondary stickies according to particle size. The current definition of microstickies is stickies particles that are smaller than 100 μm or 150 μm and larger than 5μm in size, and it could through the screen of 0.1 mm or 0.15 mm, thus most microstickies distributed in whitewater. With the circulation of whitewater, microstickies can block the wires, and form substances with tackiness, and bring inconvenience to production, even lead to production halts, increase the time and cost of production. Thus the microstickies problems should to be solved without delay, but there are no effective microstickies test methods.The object is to establish microstickies test method which is simple and good applicability for mill, and study effects on control stickies with enzymes. There are three parts in this paper:(1) Establish a microstickies test method; (2) Enzyme preparations of compound and controlling of stickies with it; (3) Completed the project of controlling of stickies with Novozymes in HUATAI PAPER INDUSTRY, and measured microstickies content in whitewater of actual producing with the test method which established in laboratory.First:Measuring microstickies content in whitewater by gravimetry. the main suspended solids in whitewater are mircostickies, fines and inorganic filler, DIP and OCC whitewater were treated by cellulase and cellobiase to hydrolyze fines, then the treated whitewater was filtered with quantitative paper (aperture is 1-3 μm), and inorganic filler content was obtained by measuring ash content. Meanwhile it is necessary to measure their contents in whitewater so as to confirm if ignoring errors, the formula be summarized to calculate microstickies content according to different compositions.The results showed:Analyzed optimal effects of cellulase and cellobiase through treated Bleached and Unbleached KP whitewater which contains only fines; the enzymatic hydrolysis rate is 96.43% and 96.24% respectively.(the calibration factor was determined to correct result deviation that caused by few fines which has not been hydrolyzed). DIP and OCC whitewater were treated with optimal dosage of enzymes, the percentage of inorganic filler is 30.71% from total solids in treated DIP whitewater, and it is 27.58% in treated OCC whitewater. The percentage of hemicellulose is 1.23% from solids without fines in DIP whitewater, it is 1.43% in OCC whitewater; the percentage of lignin is 2.14% from solids without fines in DIP whitewater, it is 2.53% in OCC whitewater. Thus lignin and hemicellulose can be ignored in measuring microstickies because of the low concentrations. Finally a formula was summarized to calculate microstickies content:(1-k) M*96%(k:the percentage of inorganic filler in total solids which treated whitewater %; M: solids content of be treated whitewater g/L), and microstickies content in DIP and OCC whitewater were figured 0.497 g/L and 0.587 g/L, respectively.Second:Enzyme preparations were made up with esterase and surfactant on the basis of proportion and conserved, OCC and DIP pulp were treated with enzyme preparation at different preservation time, detecting the removal efficiency of stickies and comparing it to the results that esterase and surfactant which was added separately. Macrostickies content was measured with TAPPI T277; and microstickies content was obtained according to new measurement method. The results showed that the removal efficiency of stickies by enzyme preparation which has different preservation time was improved, and there is no significant drop for the removal efficiency of stickies with increasing of preservation time. The removal rate of macrostickies in OCC pulp were improved by 11.45% and it was improved by 4.64% of microstickies; the removal rate of macrostickies in DIP pulp the removal rate of macrostickies improved by 20.28%, and it was improved by 6.57% of microstickies. In addition there are no obvious stratification and precipitation of enzyme preparation with the increasing of preservation time.Third:The completion of the project of control stickies with Novozymes in HUATAI PAPER INDUSTRY through prophase preparation. The add point of enzyme is:secondary disc mill. We took samples for measuring stickies from Bleaching tower, Medium consistency pump, DIP pulp tower and Former pool. During the plant trial, stickies problems were controlled with enzyme, cleaning period is significantly longer from seven days to thirty days, the quality of products and filtration of pulp was improved. Meanwhile, the test method was used measured microstickies content of whitewater from mill, the results showed that it is good applicability for mill and could as the basis for control microstickies problems.