Clean Up To Twelve Rolls or Dryers at Once with the BCS Roll Cleaning System
If you are a paper machine operator you are likely familiar with contamination and buildup on dryer cans and the associated problems that occur with increased web breaks, sheet deformation, and increased utility costs. But why does buildup on dryer cylinders occur in the first place? And why does it form where it does in the machine? In part 1 of this post, we explore some of the root causes to problems associated with dryer can buildup on paper machines and discuss some mechanical cleaning solutions to the problem.
During the initial steps in the papermaking process when water and wood chips are sent to the digester, contaminants can be introduced to the process at the same time. This is especially true for recycled paper machines that are reprocessing gums and adhesives in the recycle material. However, even in virgin or fine papermaking applications, various additives that aid in the breakdown of the pulp can also precipitate out. These contaminants often drop out of solution in the press section and the beginning of the drying section resulting in significant buildup on rollers. Because the contamination often has a tacky component, it starts to “pick” on the paper web which can increase the risk of sheet breaks. Studies have shown that as the sheet dries, there is stronger sheet cohesion, which consequently inhibits adhesion of fibers to the surface of the cylinder. Therefore, peak picking often occurs at the intermediate temperatures in the first several dryer cylinders. To avoid this problem, machine operators often stage temperatures across the dryer section by lowering initial temperatures. While this can reduce the number of sheet breaks, it also has the detrimental side effect of forcing a slowdown in production rates.
Additionally, as contaminants build up on the dryer cylinder surface, the heat transfer rate and uniformity from the dryer cylinder to the sheet are decreased as well. While heat transfer rates lead directly to an increase in steam consumption to maintain target drying temperature, the non-uniformity of temperatures across the face of the dryer cylinder often lead to an increased risk in sheet deformation and lower product quality. Studies have also shown that by improving temperature uniformity profiles across the face of the dryer can directly leads to a decreased incidence rate of sheet deformation and improved product quality .
Dryer Cylinder Contamination – Mechanical Solutions
While problems associated with dryer cylinder contamination are well known, some of the solutions to the problem are not. This results in many papermakers living with the associated costs and downtime caused by contaminated dryer cans. Some of the more proactive paper machine maintenance supervisors and machine superintendents look for mechanical solutions to resurface their dryer cylinders during an outage using mechanical means. Available options range from soda blast cleaning, dry ice blasting, laser cleaning, or hydro blasting with contaminant removing chemicals. However, in addition to the relatively high cost of these methods, a significant downside is often in the time and duration to set up equipment and perform the cleaning. This typically limits cleaning cycles to an annual outage even if the paper machine operators want to resurface even a small number of dryer cylinders.
Fluoron engineers have worked around this issue by designing the Fluoron BCS cleaning system, the fastest cleaning system in the world. This system was designed to be set up quickly and fit neatly in the “pocket” between cylinders such that one setup could clean multiple cans without the need to remove the dryer felts. With our unique setup, the service can typically be performed in place on up to six rollers simultaneously, and we can often complete multiple cleanings in a single shift during a regular monthly maintenance outage.
Our customers who utilize our BCS dryer cylinder cleaning service quickly recognize the benefits of decreased steam cost, higher throughput, even temperature distribution and lower incidents of deformation and sheet breaks. This gives our cleaning service one of the highest return on investment projects in the paper mill with payback rates typically measured in less than one month and sometimes in as few as 10 days! One of these case studies is presented below:
BCS Roll Cleaning Service Case Study:
Improve Production by 36 MTPD With Better Product Quality
Juha Jarvinen of TOLKO Manitoba Kraft Papers was running at capacity and his machine was dryer limited. Fluoron Inc. was contracted to utilize our BCS roll cleaning system to clean 16 dryer cans in less than 30 hours. The benefits of the cleaning greatly exceeded expectations. Mr. Jarvinen reported that “The dryer cans are performing very well since the cleaning job. We have gained approximately 36 metric tons/day. in drying capacity at peak rates and have realized significant energy savings when running at lower rates due to improved heat transfer. We are also experiencing a much “cleaner” sheet that is free of surface markings since the cleaning.
To quickly check to see how our BCS cleaning service can fit in your tight production window, and improve your machine performance contact us today and see how we can get you running clean tomorrow!
Call Us Today at 800-785-4491
 Investigation of paper dryer picking, web transfer and quality issues using a new web adhesion and drying simulator. F. Ahrens*; T. Patterson; S. Mueller; B. Hojjatie. Georgia Institute of Technology, Institute of Paper Science and Technology