Development activities

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Runnability boxes for the Paper and Board Machines

Increasing the speed of paper and board machines is often restricted by web flutter, wrinkles, quality defects, web breaks and problems with tail threading. The runnability problems are typically tried to be compensated by unnecessarily high draws which lead to an increase in web breaks, therefore reducing the efficiency and productivity of the machine.

Recent development work for runnability has concentrated in minimizing the fan power consumption of runnability devices and at the same time achieving excellent sheet stability.

Improvement of the Heat transfer at impingement drying in Tissue Machines

The paper industry is highly energy intensive. Increasing requirements for higher paper production rates will have a direct impact on the energy economy and the development of new and more efficient drying systems. Also, increased quality expectations even at very high paper machine speeds have set new demands for paper machine manufacturers. Today, the importance of impingement drying in the paper making process has increased significantly.

Accurate design of the impingement drying process equipment at Tissue and Paper Machines depends on precise determination of different process parameters that influence drying. The most important of the air impingement paper drying related parameters in this respect is a convective heat transfer coefficient.

Based on the earlier studies the most common empirical correlations in the literature predict the impingement heat transfer coefficients rather well at low (close to 100 °C) temperatures but get inaccurate at higher temperatures. Impingement temperatures used in paper drying applications are typically 300 to 700 °C, and there has been a need to improve the existing heat transfer correlations at high temperature area.

 

Heat recovery at Paper, Board and Tissue Machines

It is a well-known fact that a large part of energy required to produce paper or board is consumed in the dryer section, primarily as fresh steam in the cylinders. As most of the of this energy leaves the dryer section with the exhaust air, which carries away evaporated water, it is economically profitable to recover energy from this flow. In a modern PM up to 25-30 MW of heat energy can be recovered with good heat recovery systems and used for different purposes at the paper machine. Heat recovery provides substantial savings in energy, the payback time of heat recovery investment is usually less than one year. Therefore, energy management and conditions in which the drying occurs play an important role in identifying and improving the existing situation at paper and board machines.

Active Cooling tower

Nowadays when the use of fresh water supply for a cooling purpose is becoming both expensive and environmentally unacceptable, cooling tower is becoming more common equipment in the pulp and paper industry. Cooling towers can provide an answer to the growing need to save water and energy and help to protect the environment. Instead of using fresh water for cooling, warm water can be recycled back to the process if it is first cooled down to a sufficiently low temperature. Cooling tower provides a simple and cost-effective means for this purpose. Fresh water consumption can be reduced even by 95 %.

Evaporative cooling towers are based upon a very simple principle where energy is removed from the hot water in a direct contact with relatively cool and dry air. In a counterflow cooling tower the process consist of gas phase (air) flowing upwards, a liquid phase (water film) flowing downwards, and a large interface between these two phases. The key factors required for intensive heat and mass transfer in the cooling tower are large air to water interfacial contact area and high heat transfer coefficient.  The main objectiveof the research is to determine the heat and mass transfer coefficients and the pressure drop of the different filling materials, and further how these depend on air and mass flow.

High Temperature Cylinder Drying

One of the weak points of multi-cylinder dryers is the low rate of heat transfer from steam to paper. Behind this are several natural, technical and economic aspects. At high rotational speeds, a layer of condensate forms on the inner surface of the cylinder, which dramatically reduces the rate of heat transfer from the steam to the cylinder shell. A cast iron dryer 30-45 mm thick is another barrier to heat transfer. Furthermore, significant resistance to heat flow occurs at the contact surface between the cylinder and the paper surface.The focus of the research is the analysis of improvements in heat transfer in drying cylinders by different cylinder interior design and high cylinder surface temperatures.

Influence of fabric Structure on the drying rate and cylinder-paper contact heat transfer coefficient

In a paper machine, drying fabrics are used to support the web as it passes through the dryer section. The main purpose of the fabric is to ensure a good thermal contact between the paper web and dryer surface and to maintain sufficient web tension in machine and cross directions.

The objective of the  study is determination of the influence of dryer fabric’s structure and tension on the drying rate and contact heat transfer coefficient.