Toscotec has recently introduced TT Defender, a leading-edge patented innovation that provides Yankee dryers with an effective internal protection coating against corrosive steam. Toscotec has successfully tested TT Defender at Lucart Group’s Diecimo tissue mill in Italy on a TT SYD that came online in February 2020.
Additional protection for Yankee
Since steel Yankee dryers have outperformed cast iron Yankees and replaced them as the new technological standard of the tissue industry, more pressure has been put on paper mills to more frequently check steam quality. In order to maintain steam parameters such as pH and conductivity within the correct range, increased monitoring and expertise has become a “best practice”. TT Defender is Toscotec’s pioneering solution: an extremely uniform layer ensuring excellent resistance to highly corrosive conditions. It prevents the risk of chemical corrosion and related problems including mechanical abrasion, erosion, and straw pipes plugging that can lead to an uneven humidity profile.
Increase plant performance
By virtue of its extremely low thickness, TT Defender does not affect the high drying efficiency of TT SYD. Instead, it increases its O.E.E. (Overall Equipment Efficiency) by greatly reducing the risk of unplanned maintenance stops due to soda straw plugging or internal corrosion issues and reducing time needed for regular internal inspection. This all leads to a greater plant performance.
Increase operation stability
Simone Pieruccini, Toscotec’s Pressure Vessel Technical Manager, says: “TT Defender represents an additional guarantee of TT SYD’s operation stability. The positive results we achieved on Lucart’s PM5 fully validate the theoretical study carried out by Toscotec’s R&D. The advantages of TT Defender apply to steel and cast-iron Yankees alike: excellent resistance to highly corrosive conditions, more stable operations, and higher flexibility in the continuous monitoring and chemical treatment of the steam and condensate system.”
Lucart’s point of view
Danilo Calamari, Lucart’s Paper Mill senior engineer&cogeneration plants manager, is the technical expert who closely followed the project in Lucart. In this interview, he shares Lucart’s experience with TT Defender and his professional views on the results they achieved so far.
The TT SYD installed on your PM5 in Diecimo is fitted with TT Defender. During the regular checks you performed 6 months after start-up, you personally entered inside the Yankee. Which conditions did you find?
I was pleasantly surprised at how good the Yankee looked inside. During our regular Yankee checks, we often find some magnetite deposits and soda straw blockage. Instead, the TT SYD on PM5 appeared as if it were new, or even better: the entire internal surface and all the straw pipes were perfectly clean. Evidently, during its six months of operation, no magnetite deposits had formed inside the Yankee. This result validated our decision to participate in this project. To be honest, at the beginning when Toscotec suggested they test this new technology on our TT SYD, we were not entirely convinced. Finally, we decided to get on board, because we have had a very good cooperation with them for many years, and we trust their professionalism and reliability as a supplier.
Mill technicians know very well that in the ordinary operation of the steam and condensate system, it is quite common to go through transitory phases or issues that cause some of the chemical and physical values under control to fall short of the requirements for the proper functioning of the plant. Does TT Defender represent an additional security in this regard? Do you think that it allows your Yankee to have a greater tolerance to these kind of normal variations?
Yes, we do. TT Defender allows us to overcome some possibly critical issues in the chemical treatment of the steam and condensate system of PM5 without consequences. We can now successfully manage these phases that are completely normal throughout the year.
Before the TT SYD with TT Defender, Toscotec had installed another TT SYD on your PM6, which is right next to PM5 and shares the same steam and condensate system. In terms of drying performances, did you find that the drying capacity of the steel Yankee with TT Defender was any different from the other?
Apart from TT Defender, the two TT SYDs installed on PM5 and PM6 have the same characteristics, so we could easily compare their performances under various operating conditions. We did not find any limitation in the drying capacity of the TT SYD with TT Defender. Before the application, one might wonder if TT Defender could hinder the heat exchange between the Yankee’s internal and external surface on which its drying capacity is based upon. The actual result is that TT Defender does not affect the Yankee’s thermal efficiency in any way. In one year of operations, we found that the two TT SYDs on PM5 and PM6 perform equally well.
Do you think that TT Defender allows you to eliminate the risk of longer maintenance stops due to the obstruction of soda straws?
At Lucart, we perform one regular internal Yankee inspection per year. We will check PM5’s TT SYD this summer, but what we can say now is that we are not experiencing any issues with tissue quality that could point to soda straw blockage. The paper we are producing on PM5 is high quality and has a very uniform cross-direction moisture profile. This suggests that when we will open up the Yankee later this year, we will most likely do just a quick check, without allocating extra personnel and extend the downtime in order to clean or replace soda straws. With TT Defender, we expect to find a Yankee that is always clean, and allows us to realize the best production efficiency in terms of both quality and quantity.