Runtech Systems Ltd. is a Finnish, privately held, company that develops, designs and supplies equipment to the paper, tissue and pulp mills. Hundreds of paper, tissue, board and pulp mills benefit from our dewatering meters, vacuum systems, tail threading equipment and doctoring solutions.
Years of hands-on paper-making know-how differentiates Runtech from traditional hardware suppliers. Our ì customers benefit from integrated solutions that result in significant operational cost savings, improved machine runnability and product quality.
Vacuum at a paper machine
Vacuum at a paper machine is used for a variety of reasons. Dewatering the paper sheet is the obvious, holding and controlling the route the sheet takes through the press section and conditioning the press felts are other key uses of vacuum in a paper machine. Vacuum is also used to hold and control the water jet at a suction roll. Early paper machine designs did not use vacuum at all, but relied on gravity and press nips to dewater paper. This we refer to as nip-dewatering.
Machine speeds were then much slower than what we today are accustomed to. Today it is hard to imagine a paper machine without a vacuum system, and felt-dewatering is today still the most common way to dewater the paper in a press section.
The vacuum levels at a paper machine are typically between 5 and 70 kPa, which is relatively low compared to other vacuum applications in, for instance, the chemical industry. The air flows, though, are very high due to the large open areas we see in a paper machine. Vacuum, which is a result of air being pulled through a restriction, is an expensive tool; it is one of the top three energy consumers in a paper mill. Historically it has been made available in abundance, and often used in excess.
Today we face increasing cost of energy. Paper mills are demanding reduced operational costs to stay competitive. Therefore, it makes sense to review air flow demands and, when suitable, apply old school thinking, i.e. nip-dewatering rather than felt dewatering.
Runtech engineers have done thousands of vacuum system audits and dewatering studies at paper mills over the last 20 years
The primary function of a wire- and press section in a paper machine is to remove water from the paper sheet. In order to understand the effectiveness of individual elements (such as save-all pans and suction boxes) of a wire- and press section, dewatering rate must be measured. Without this, critical air flow (i.e. vacuum level) review and consequent optimization cannot be successfully carried out.
Water that is removed from the paper sheet contains air, and is often subject to foaming. Traditional magnetic liquid flow meters demand a homogenous flow and will not be able to provide accurate data. Ecoflow™ meters are designed to measure water flow across a mechanical restriction and are not sensitive to entrained air or foaming. These devices are used both under vacuum (in a separator drop leg) and in atmospheric conditions.
The most economical method of water removal in a press section is nip dewatering, as opposed to felt dewatering which requires energy demanding air flow. Nip dewatering is facilitated by allowing felts to run wet in combination with suitable doctoring and save-all equipment.
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.
Dewatering and doctoring are not only related to energy consumption, but also plays a big role in paper machine runnability, efficiency and profitability, as well as paper profiles. Therefore, a well designed and operated dewatering and doctoring system is the key to a well performing and energy efficient press section. Runtech is one of the leading suppliers for the improved dewatering and doctoring solutions for the all kinds of pulp, paper, board and tissue machines.
In many cases, Runtech’s solutions lead to a 1-3% increase in dryness after press section which saves considerable amount of energy in the dryer section (4-12% less steam).
Ecopump Turbo blowers
Vacuum is created as a result of moving air across a restriction. Fans, turbo blowers and liquid ring pumps can be used to achieve this. Often paper mills use a combination of these.
Turbo blowers have the benefit of being an inherently efficient way of compressing air for the modest compression ratios (less than 3,5) we face at a paper machine.A turbo blower is, for a given rotational speed and impeller design, a constant compression ratio device as opposed to a liquid ring pump which is a constant displacement machine.
The power consumption of a turbo blower is a function of the air flow that is being compressed to satisfy the pre-determined compression ratio. A constant speed turbo blower has a limited range of efficient operation since paper machine vacuum adjustment outside of the designed level requires throttling.
Each vacuum element in the machine, such as suction box and suction roll, need a certain amount of air flow to operate at an ideal vacuum level. The needed capacity is depending on felt life and type, paper grades, basis weights, machine speed etc. Traditional liquid ring pumps and fixed speed blowers cannot cater for these dynamic vacuum and flow needs, resulting in, often significant, waste of energy.
Ecopump turbo blowers are designed to operate efficiently across a wide range of vacuum levels and air flows to allow paper mills to optimize vacuum levels while taking advantage of the higher efficiency a blower has over a traditional liquid ring pump device. High speed motors developed driven by frequency converters allows a typical RunEco blower to provide paper machine vacuum levels between 30 and 70 kPa.
Wide range impeller designs allow high efficient levels across the operating range. This means that the amount and the usage of throttling valves can be reduced to a very minimum. The result is 30 to 70% energy savings compared with traditional vacuum systems. Further, Ecopump turbo blowers operate without the need for sealant liquid (water) so contribute to water savings in a paper mill plant.
Vacuum system and dewatering audits
As we know, vacuum demand varies with different paper grades, felts and machine speeds, therefore a tailor-made solution with flexible and variable capacity can balance the supply and demand, resulting in both optimized dewatering and minimized power consumption.
For those reasons Runtech is performing professional vacuum system and dewatering audits, prior to a rebuild project, for its customers. Runtech engineers have done thousands of vacuum system audits and dewatering studies at paper mills over the last 20 years. Those studies and audits enables Runtech to benchmark the effectiveness of existing vacuum systems, dewatering equipment, suction elements, fabrics and felts. These pieces of information come together in a, often stepwise, rebuild and upgrade plan that will result in minimized operational expense coupled with production increase and runnability improvements.
Ipek Kagit, Turkey
Ipek Kagit is a Turkish tissue paper producer. Runtech replaced the existing vacuum system (3 liquid ring pumps) of TM3 with a single Ecopump turbo blower in 2015.
An EcoFlow™ system was installed at the same time allowing the mill to optimize the vacuum levels without sacrificing dewatering efficiency. The result was 50% savings in energy and significant reduction in water consumption.