Optimization Of Shoe Presses For Paper Machines, Where To Start

Everyone in the paper industry knows: "Each 1% increase in dryness in the press section can save about 4% of heat energy." This is for continuous production without changing the speed of the paper machine. If converted into kWh / t, it means that for every 10% increase in the dryness of the press section, about 60kWh / t of thermal energy will be saved. The shoe press can increase the dryness after the press section by 4%, which can save more. energy.

Due to different crushing boundary conditions, different customers have different evaluations. Customers also have very different costs for steam and electricity. In addition, from steam hoods to high-temperature hot air hoods, from small-diameter cast iron Yankee cylinders to large-diameter high-performance steel Yankee cylinders, paper machine installations are also different in heat recovery systems or systems that use waste heat to generate electricity. In addition, the investment recovery rate of a large paper machine is superior to that of a small paper machine. The return on investment of shoe presses is about one and a half to two years.

Shoe presses are more commonly installed on new tissue machines. This installation includes the design of the vacuum system and the installation of the drive system, which is performed on the entire system components in order to form the largest sheet covering area on the Yankee cylinder (such as the suction roller, shoe press roller and Yankee dryer). Optimized installation, implementation of the hydraulic system and embedding shoe presses into the control system.

If shoe presses are added to existing tissue paper machines, some of the previously mentioned systems need to be adjusted. Therefore, the investment in repositioning shoe presses on paper machines is much higher than the cost of deploying shoe presses on new paper machines. In the past, ANDRITZ had a shoe press with a particularly small diameter for tissue paper. It is ideal to configure this shoe press on an existing paper machine, but in the actual market, more attention is paid to the use of new paper machine shoes. Press.

Based on the concept of a crescent shaper, the paper sheet is formed on a saturated web of felt, so shoe presses are specifically used to produce tissue paper, which requires an appropriate vacuum condition upstream of the felt in the nip. In addition, the Yankee cylinder is not the optimal back roller of the press roll. Therefore, the shoe pressure roller must compensate the surface condition of the non-ideal Yankee cylinder by adjusting the elasticity of the shoe cover and the side pressure control force. In order to operate effectively, the entire system, including the design of the vacuum system, the felt and conveyor section, and the shoe press, must be well set up.

All automated retrofits are part of a shoe press installation. The operating mechanism and logic of the shoe press will be fully integrated into the DCS of the paper machine. This way, no extra effort is required in production.