Clive Butler, A.Celli, Italy
STEAM SYSTEMS, BACK TO BASICS
Over the years, the engineers at Beloit, then Sandusky, and now PMT, have learned a lot about Yankee dryers. One of the fundamental systems we rely upon for smooth operations of our Yankee cylinder is the steam system. Steam systems can be a source of process variability if not properly controlled. With a focus on blow-through control, this session will get us back to the basics of stable steam system operations.
William Bonis, application engineer, SKF, USA
LUBRICATION FOR YANKEE BEARINGS
Bearings for Yankee cylinders are oversized from a load point of view. The requested basic calculated rating life, L10h, is above 200 000 hours. This means that 90% of the bearings should operate more for than 23 years and that 50% of the bearings should operate for more than 115 years without any flaking (subsurface fatigue micro cracks reaching the surface and metal particles being liberated).
The real average service life of Yankee cylinder bearings is below what could be expected. The reason is that many parameters such as bearing storage, handling, mounting, the lubrication and the lubricant characteristics etc. influence service life.
Furthermore, many tissue machines get speeded up with steam pressures increased. Often, they then operate above original design speed. Inadequate bearing lubrication is a principal cause of lower than expected service life.
Al Coons, Clearwater Paper
MANAGING YANKEE METALLIZATION
Yankee thermal coatings, or metallizations, have been around since the 1980’s. However, new technologies are increasing the share of Yankees which are metallized. One of the most significant shifts is the acceptance of steel Yankee dryers in the marketplace, all of which must be metalized. Even on cast iron, thermal coatings are now thought of as Yankee performance improvement projects versus just asset life extension.
As accepted as these coatings are, there is little information regarding how to specify a project, how is final quality determined, and how to care for the coating over the years to ensure the best return in investment? The paper will cover practical application examples and provide ideas regarding project management and long term surface care.
Oscar Lopez, R&D Manager, Brunnschweiler
NEW TECHNIQUES FOR INTEGRATION OF WATER RECOVERY IN HUMID FLUE GASES FROM YANKEE HOODS
Paper drying equipment generates large amounts of heat release through humid flue gases stacks, together also with huge quantities of water losses to the ambient air. Water amounts released to the atmosphere are of the order of magnitude of the total water evaporation in the dryer section. This large amount of water can produce highly visible plumes under some environmental circumstances that can be undesirable.
On the other hand, several pollutants and corrosive chemical compounds are contained both in the gases and in the water delivered and contribute to overall contamination impact of the plant. Traditional solutions of heat recovery and plume removal do not guarantee an efficient recovery of the water at the same time. A high performing traditional water recovery system involved the consumption of lots of energy. The integration of a new method proposed for an efficient water recovery with no external use of energy is discussed, together with its optimization. Energy and water losses are efficiently reduced together with contamination (both chemical and thermal pollution).
The method (patent pending) include the use of conventional equipment that conveniently sized and combined, cooperate to get a water recovery yield higher than 90% with no use of external energy, and without negatively affecting other heat recovery purposes. Alternative solutions integrating full energy recovery, partial water recovery and plume removal are also presented.
Fatos Anil, Tissue Paper R&D Manager, Hayat Chemicals
A STUDY ON INCREASING THE ABSORPTION CAPACITY OF TISSUE PAPER: THE EFFECT OF SOFTWOOD/HARDWOOD BALANCE
“Tissue paper products require a balance of several effects including tensile strength, absorbency and softness. Of these three parameters, the strength of the sheet and its corresponding softness are interrelated. It is a well-known fact that while improving one of these properties often harms the other such as mechanical treatments that enhance softness also decrease tensile strength. For tissue products water absorbency is considered the most important property. In order to improve the water absorbency, the optimization between pulp furnish and chemical additives is generally required.
Softwood and hardwood fibres can be blended into a single paper to achieve a desired combination of strength, softness and absorbency. Softwood fibres that produce long, thick and strong fibres are obtained from coniferous trees. These qualities give strength to tissue. Whereas, hardwood fibres are from deciduous trees and give smoothness and softness to tissue paper products since the fibres are shorter and finer. Using various fibre combinations helps to optimize the required characteristics of the tissue paper.”
Clayton Campbell, Sr. Manager Global Business Development, Kemira
UTILIZING NOVEL TEMPORARY WET STRENGTH FOR THE AWAY FROM HOME (AFH) TOWEL MARKET
Polyamidamine epichlorohydrin (PAE) resins are widely used to provide permanent wet tensile strength sheet properties in the Away From Home (AFH) towel market. However, high PAE wet strength usage can cause operation problems, reducing machine’s operational equipment efficiency (% OEE). In addition, towel producers and consumers occasionally report issues with poor fiber repulpability, septic system operation problems due to poor dispersability, and environmental disposal.
In most Away From Home towel applications, having long term wet strength “permanence” is not necessary. The end user requires only a short period of wet strength performance. The expanding use of “hands free” automated dispensing units’ further supports the reduced need for wet strength permanence. Temporary wet strength is actually more desirable as it meets consumers’ product performance needs from the Away From Home towel and can address the manufacturers’ concerns with using PAE chemistries.
New novel temporary wet strength utilizing modified glyoxyalated polyacrylamide (GPAM) technology offer the AFH towel manufacturers a variety of benefits, including significantly reducing the use of permanent wet strength (PAE) chemistries, optimizing wet end chemical costs, and improving overall machine productivity and profitability. As outlined in a Kemira patent, there is synergistic performance when GPAM and PAE products are co-mixed and fed in line together to the papermaking system.
This technical paper focuses on improving wet end strength performance efficiency, reviewing permanent – vs. – temporary wet strength requirements and process factors that can affect wet strength performance. Case studies will be presented to illustrate how utilizing temporary wet strength can provide significant beneficial impacts on both sheet quality and machine overall operating efficiency.
To read a summary of talks at Tissue World Americas, see the next issue of Tissue World magazine (May/June) and website.