Towards energy-efficient and economical Tissue production with RunEco solution

Vacuum is an expensive tool and often excessively used; one of the top three energy consumers in a paper mill. With increasing cost of energy and environmental awareness, paper mills are demanding reduced specific energy levels and operational costs to help with their competitiveness. Runtech RunEco vacuum system is developed especially to take into account the challenges and demands related to the dewatering and runnability.
Traditional method of increasing vacuum levels is replaced with speed adjustable turbo blowers, optimal doctoring and save-all systems with online dewatering measurements.
By using only the needed vacuum in the critical consumers, mills can fully benefit from the more efficient nip dewatering strategy and save energy.

RunEco solution – operating principles

EP turbo blowers are designed to operate efficiently across a wide range of vacuum levels and air flows. It allows mills to optimize vacuum levels whilst taking advantage of the higher efficiency a blower has over a traditional liquid ring pump device. High speed motors, driven by frequency converters, allow a typical RunEco blower to provide paper machine vacuum levels between 30 and 70 kPa. A wider range of impeller designs allows highly efficient levels across the operating range. This means that the amount and the usage of throttling valves can be reduced to a minimum. The result is energy savings of 30% to 70% when compared with traditional vacuum systems.

Reliable dewatering – the basis for runnability

Each vacuum element in the machine requires a certain amount of air flow to operate at an ideal vacuum level i.e. at the minimum to maximize the energy efficiency while maintaining the runnability and dewatering capacity. The needed capacity is dependent on felt life and type, paper grade, basis weight, machine speed etc. To achieve this challenging goal we need reliable dewatering measurements. Runtech EcoFlow™ meters are designed to measure water flow across a mechanical restriction and are not sensitive to entrained air or foaming.

Dewatering and doctoring are not only related to energy consumption, but also play a major role in paper machine runnability (profiles), efficiency (dirt and breaks) and profitability. Therefore, a well-designed and operated dewatering and doctoring system is one of the key issues to a well-performing and energy-efficient machine. The most economical method of water removal in a press section is nip dewatering. Fit-for-purpose doctoring and save-all equipment allows the felts to run wet collecting water in the pans enabling higher dewatering, higher felt lifetime and better moisture profiles to improve runnability. Suction rolls are often equipped with double doctors to prevent re-wetting and maximize void volume to allow best water removal. Save-all pans should be designed to manage the water that is removed from the nips, and engineered to be rigid enough to accommodate doctor holders.

Runtech is one of the leading suppliers for the improved dewatering and doctoring solutions for all kinds of paper machines. In many cases, Runtech’s solutions have led to a 1-3% increase in dryness after the press section which saves considerable amount of energy in the dryer section (4-12% less steam).

Tailor-made RunEco solutions – no compromises

Depending on Tissue machine design and width the most efficient operation sometimes requires one and sometimes two Turbo blowers. The specified air flow capacity is typically quite high consisting of overall safety margin, felt life and type margin and with liquid ring pumps e.g. pump wear and seal water temperature variation margins. In normal operating conditions the needed air flow capacity is ~40-50% lower than the specified capacity. Regardless of the situation, RunEco system with a fully speed-controlled turbo blower provides high operating efficiency at all times. During normal operation one single-stage turbo blower typically provides sufficient capacity. However, a system with two turbo units allows even higher operational flexibility, controllability and energy efficiency. Table 1 shows a typical calculation, comparing the costs of a single turbo unit and two turbo unit RunEco system to a traditional vacuum system with liquid ring pumps.

The absolute difference is naturally related to the local energy price. However, the table highlights the fundamental differences in the running method, controllability and
losses between the systems.

With years of hands-on papermaking know-how, Runtech develops, designs and supplies equipment and related services for paper, tissue and pulp mills. Hundreds of delivered systems, such as dewatering meters, vacuum systems, tail threading equipment and doctoring solutions benefit our customers by enabling energy-efficient and economical production. The integrated solutions result in significant operational cost savings, improved machine runnability and product quality, giving a competitive edge for the customers in the market.

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