Paper360 - March/April 2012 - (Page 48)

STICKIES TECHLINK PROCESS CONTROL for STICKIES A PEERS conference panel takes on a tacky topic MAHENDRA DOSHI D uring the TAPPI PEERS conference held in October 2011 in Portland, Ore., a panel focused on the problem of stickies. Panel members included: Gilles Dorris, FPInnovations, Canada; Shisei Goto, Nippon Paper Industries, Japan; R. Daniel Haynes, Eka Chemicals, USA; and Jean Morin, Cascades Canada. Each has more than ten years experience dealing with stickies. CHALLENGING AND FRUSTRATING According to Dorris, those who have dealt with stickies in the laboratory or in the mill will agree that getting a handle on them is challenging and often frustrating. He reviewed some of the methods developed at FPInnovations for measuring macro and microstickies. He also mentioned that they are working on measuring wet and dry tackiness of stickies at different temperatures. Lessons learned include: • Online ana lyzers like t he one FPInnovations developed for macrostickies,1 are necessary for research as well as for mills, as a large number of samples need to be evaluated. • Fine screens are necessary for the removal of macrostickies. • Properly tuned forward and reverse cleaners (or throughflow cleaners or rotating body cleaners) may also be helpful. Emphasis here is on the phrase "properly tuned." Many mills have installed these cleaners but they are either plugged, shut off or have poor stickies removal efficiency. • Froth flotation is not very effective in removing macrostickies but could be useful in removing microstickies. • Microstickies in the size range of 5 μm to 150 μm account for 50% to 80% of stickies population after the stock has gone through screening, cleaning and flotation treatment. • The best approach is to screen macrostickies and float microstickies. STICKIES BEHAVIOR Goto relied on his previous two presentations at the Research Forum on Recycling 2,3 to describe the behavior of stickies once deinked pulp (DIP) and thermomechanical pulp (TMP) reach the paper machine. He used photomicrographs of stickies deposited on the surface of quartz crystal to drive home some important points, including: • Deposits from paper machine and paper using deinked pulp, consist of fines, fillers and adhesive. Contrary to what one would think, Goto observed that fines and fillers are the major components of deposits. Adhesive is only a minor component of deposits on crystal surface. • Stickies end up as deposits on various parts of the paper machine or in the finished paper. • Goto observed a large number of small particles in deposits from DIP as opposed to a smaller number of larger particles in deposits from a headbox sample of a newsprint machine, concluding that stickies morphology changed during the papermaking process. It appears that the accumulation of stickies in circulated white water leads to agglomeration. • The examination of deposits in a sweetener stock, wire pit overflow, recovered fiber stock and cloudy filtrate, shown in Figure 1, revealed that agglomerated stickies are retained in the recovered stock. The wire pit overflow clearly contains larger stickies than the sweetener stock and these larger stickies end up in the recovered fiber stock and not in the cloudy filtrate. • The retention of microstickies along with the pacification of stickies using enzymes and/or inorganic additives is key to prevent the deposition of stickies.3 USING INGEDE METHOD 17 Haynes essentially agreed with Dorris that the majority of stickies population after fine screening is smaller than 150 μm. He reviewed some of the work done using Total Organic Figure 1. Photomicrographs of the quartz crystal microbalance (QCM) sensor surfaces after measurements of the samples from the sweetener, wire pit overflow, recovered fiber, and cloudy filtrate in the white water and the fiber recovery system in the newsprint paper machine in Mill B. 48 Paper360º MARCH/APRIL 2012

Table of Contents for the Digital Edition of Paper360 - March/April 2012

Over the Wire . . . News Summary
Asian Innovation on the Rise
SPECIAL FEATURE: Tissue Industry
North America Shifts to Specialization
A Measured Success
Aligning Rolls in a Paper Machine Winder
Understanding Lightweighting
Sappi Biberist Tests a New Inline Sensor to Control OBAs and Colors
Process Control for Stickies
An Innovative Yankee Coating Program
Biopolymers in Papermaking
Best Practices in Product Development
Employee Work Restrictions Challenge Human Resources
Paper360° Online Exclusives
Association News

Paper360 - March/April 2012