Toscotec has developed key energy efficient solutions for the primary water recovery system, stock approach line, and headbox, which deliver substantial energy savings and process optimization results.
The performances of the majority of these solutions have been consolidated in several installations and have become part of Toscotec’s standard design.
Toscotec’s technical and R&D departments continuously upgrade their technology with the aim to achieve:
• sustainable production capacity increase
• final paper quality improvement
• reduction of maintenance or grade-change downtime
• reduction of energy demand for the same output.
Primary water recovery system and Headbox Stock approach line
Toscotec’s deaerator unit on the primary water recovery line is designed to reduce the air entrained in the water recovered from the forming roll’s save-all water pan. Internally, the deaerator is designed without any movable parts, which guarantees consistent performance and virtually maintenance-free operations. The flume, which is installed immediately after the deaerator unit, is designed to extend the effect of air removal before the water is fed back to the fan pump. The total air content measured at the fan pump suction point can be as low as 0,2%.
The flume is connected to the fan pump through a stand pipe which replaces the traditional large-dimension silo.
Toscotec introduced the TT Mix unit on the stock line in order to deliver efficient hydraulic mixing of fibers with low pressure losses, and entirely eliminate the installation of an intermediate mixing chest with its agitator and discharge pump. The key advantages of TT Mix include:
• important reduction of energy per ton: compared to previous solutions with a mixing chest, this solution saves up to 10% of the total energy required for the approach flow system
• reduction of space required in the mill layout
• reduction of buffer volumes on the line for easier and faster cleaning and grade and/or color changes
• reduction of chemicals usage.
The design solution complete with TT Mix, TT De-aerator, TT Flume and TT Stand Pipe determines an overall 35% – 40% reduction in required space if compared with previous solutions.
The elimination of the mixing tank and the silo has also led to a reduction of approximately 50% in excavation activities for a single floor machine installation.
In addition, Toscotec’s complete solution for stock mixing and primary water recovery depicted above has led to an overall reduction of storage volumes in the approach system of up to 75%, which corresponds to faster and more flexible cleaning and grade-change operations.
Toscotec has also recently included a Double Dilution System as a standard feature on its approach lines to the headbox. The idea underling the new double dilution system is that any contaminant that might enter the system comes from the stock preparation line. The double dilution is designed so initially the dense stock flow is only diluted to only approximately 1% consistency before passing through the pressure screen, then it is diluted to desired consistency for the fan pump and headbox. This solution reduces energy consumptions due to the reduction of the flow passing through the screen. In particular, the system achieves a flow reduction of 85 – 90 % at the screen, which leads to substantial energy savings, up to 15 kWhr/ton.
The removal of the screening unit from the headbox dilution system approach line for crescent former and C-wrap former configurations has now become a standard solution for Toscotec. Screening on the dilution system line is traditionally only a coarse filtration, like a rough mechanical barrier on a line which is naturally clean and where build-up of fiber slings is not an issue. Toscotec’s solution saves more energy by eliminating losses in the screen and the motor normally installed on the unit.
The removal of the Basis weight control valve from the high-consistency stock line has also been introduced. The main advantages are that the control of the stock flow becomes easier without affecting the stability of its dosing, and the losses through the thick stock valve are eliminated with subsequent energy savings.
There is an upgrade of the thick stock injection line ahead of the fan pump with a new in-line concentric injection design protruding inside the stand pipe line and with a specially designed nozzle at the end to boost fiber mixing into the main stream flow. Toscotec used CFD (Computerized Fluid Dynamics) simulation and several FFT (Fast Fourier Transform) analysis of scanner readings in fixed position to identify the best design for the injection system, in terms of optimal velocity ratio between stock and white water speeds, location of the injection versus fan pump suction, and geometry of the nozzle at the end of stock feeding pipe in order to avoid MD disturbances of the paper weight due to poor fiber mixing in that area.
TT Headbox: a unique design for top efficiency
Toscotec reviewed the fluid dynamics inside TT Headbox with the aim to guarantee superior final paper properties by operating at the highest possible consistency level. This review has led to a reduction of approximately 10% of fan pump electric power consumption.
The reduction of TT Headbox recirculation rate – now less than 3% of the incoming headbox flow – has delivered further reduction of energy use.
Synergies inside Voith Group
Following the acquisition of Toscotec by Voith Group, Toscotec has had the opportunity to further review and upgrade the design of the components in the stock preparation, approach line and water treatment with improvements in mill layout. Synergies within the Voith Group have further increased the company’s know-how allowing the upgrade of consolidated products by achieving energy benefits or process optimization and the increase of their production capacity. Finally, thanks to these intergroup synergies, important new products have also been added to Toscotec’s Fiber System portfolio.