Successful stickies and tackies program implemented at Australian Paper Shoalhaven giving reduced machine production costs

摘要

It was decided that a survey of AP Shoalhaven should be conducted to determine if the current downtime and associated problems with stickies could possibly be improved. Although the performance of the current contaminant control program was previously perceived as adequate, some machine downtime was still being caused by stickies. The incumbent program consisted of a detackifying agent and a coagulant. The detackifier was dosed after the disperser and the coagulant into 4% stock before high density storage. It was also recognised that over time the number of stickies coming into the mill would certainly increase. The survey consisted of recording stock temperature, total hardness, pH, and mechanical shear throughout the stock approach system. The survey identified possible sticky agglomeration sites, which were then monitored carefully during the trial. Also the efficiency of mechanical processes was investigated to pinpoint where mechanical improvements to the process might be made before the addition of chemicals. Once the background data was collected a trial was conducted to determine if the machine downtime and therefore production costs could be decreased. The trial centred mainly on AP Shoalhaven number 1 machine (Sl) as Sl is the major consumer of waste furnish at the mill. The waste at Shoalhaven is classed as white ledger. It has a relatively low stickies content in comparison with recycled board or newsprint mills. The trial consisted of dosing a dispersant to the inlet of the disperser and a cationic coagulant to the thick stock storage chest and to Sl's machine chest. It was also recognised that stickies retention was important to ensure that stickies did not cycle up in the backwater system and reduce the program effectiveness. Many different parameters including machine runnability, machine downtime, filtered turbidity, winder efficiency, system cationic demand, microscopic stickies counts and stickies area on handsheets were all investigated. A new Tappi standard (10) method for reverse staining handsheets was also considered but discounted due to the nature of stickies at Shoalhaven and the time required to process the sample. The outcome of the trial was that many of the variables mentioned above showed encouraging signs. For example cationic demand and turbidity were reduced however the most conclusive evidence was the improvement in sticky related machine downtime which was reduced by 95%. This paper will discuss in detail all of the elements of stickies management with the aim of giving superior paper machine performance at a reduced machine production cost.