Rising energy prices and growing environmental awareness are behind a boom in sales of TURBAIR® vacuum systems, which are developed and constructed by MAN Diesel & Turbo at its Zurich plant. The systems can offer substantial energy and water savings. In the last twelve months alone, the company delivered and installed more than 25 of the vacuum blowers, the performance of which has been proven and developed continuously for over 60 years.
"Our vacuum systems are now in use in a large number of new installations of cardboard, paper and tissue machinery," says Manfred Dobler, head of Paper Industry. "In recent months we have also noticed a pleasing trend towards an increasing number of revamps. In these orders we are replacing existing water ring pumps with our high-efficiency TURBAIR® vacuum system, which enables our customers around the world to increase the energy efficiency of their paper machines drastically."
Vacuum systems play a central role in the paper production process. They are deployed at the point in the production process at which the installation dewaters the paper. This is done by vacuum. TURBAIR® systems from MAN Diesel & Turbo (mandieselturbo.com) handle volume flow rates of 300 up to 3000 m³/min (cubic meters per minute).
They achieve this high level of energy efficiency thanks to several factors. Constructed using radial flow impellers, the vacuum blowers manufactured by the Zurich turbomachinery specialists generally have an absorbed energy consumption that is up to 40 percent lower than conventional water ring pumps. They don't even require any fresh water. Another advantage: They have no wearing parts and are especially easy to service. This also saves resources and cuts costs. "Even vacuum blowers of the same basic design that we installed over 50 years ago are still in operation at many customers' mills," Dobler reports.
Various control and instrumentation systems assume another important role, as these enable the TURBAIR® system to react optimally and flexibly to the paper machine. The single-stage integrally geared blower, type RT, adapts its power consumption to the required volume by using this as a correcting variable to regulate its emission. Paper manufacturers can thus run a very wide range of grammages on their production machinery, because the TURBAIR® vacuum system always delivers the right vacuum and volume flexibly.
Depending on which type of paper the production machine is producing, it requires different amounts of vacuum and volume. The RT models can supply between 30 and 100 percent of the maximum volume requirement flexibly, while at the same time only needing between 30 and 100 percent of their maximum power consumption. This superb partial load capability and flexibility make them the first-choice blower for revamps in particular.
The type RC vacuum blower with its four intake manifolds also adapts itself flexibly to the requirements of the paper machine. It is chiefly in demand for new installations for graphic papers, cardboard or chemical pulp. These require a high vacuum of around 75 kPa (kilopascals), which the type RC blower supplies reliably, thanks to its multistage centrifugal design. It can replace entire water ring pump systems.
If the two RT and RC blower types are also driven with frequency control, all the ultra-modern control systems available today are at the customer's disposal.
"In combination, these technologies result in a simple 'return-on-investment' calculation for our customers: the amortization time of a TURBAIR® system of this kind, installed in an existing paper production mill, isn't even two years," Manfred Dobler explains. First the specialists at MAN Diesel & Turbo obtain a precise picture of the existing production facility on site. Then they put together a made-to-measure quotation. TURBAIR® vacuum systems are constructed individually, but on the basis of a proven system of modular components. A downtime of just two days is normally required before the customer can start up the paper machine again.
The possibilities for energy and cost savings are far from exhausted, however. "By using a one- to three-stage heat exchanger, we can additionally recover 70 percent of the absorbed power from the 140 °C exhaust air of our vacuum system," Dobler explains. In a first stage, an air-air heat exchanger additionally heats the dry section of the paper machine. A second stage transfers heat from the air to the process water. An optional third stage can remove the remaining residual thermal energy from the exhaust air for heating premises. The result: the entire procurement costs of a TURBAIR® vacuum system are amortized within a year, depending on the installation.