A filter for filtration: reducing water consumption in a papermaking plant

Water is not only essential for human life, but also essential in many industrial production processes. Companies are looking for ways to clean and recycle used water to minimize consumption and ensure that water is used responsibly. The production of filter plates is a water intensive process. Eaton has developed its own automatic tubular backwash filter that dramatically reduces fresh water consumption in papermaking.

Context: filter sheets for life science applications

The 17 United Nations Global Sustainable Development Goals state that making safe drinking water easily accessible to all is one of humanity’s most crucial goals. Businesses play a central role in this effort, as energy management specialist Eaton has demonstrated. Eaton has reduced its worldwide water use by 87 million gallons since 2015. The company sees reducing water use as essential, both now and in the future.

The importance of reducing consumption is particularly relevant in areas where a relatively large amount of water is required, such as the Eaton factory in Langenlonsheim, Germany. Eaton manufactures a range of products in Langenlonsheim, including filter sheets for the food and beverage markets and the pharmaceutical industry. Filter sheets that are 0.08 to 0.2 inches thick can be much bulkier than paper, but they are produced in the same way.

The first step in the manufacture of filter sheets is to create a specific fibrous suspension during the preparation of the paste. This suspension has a maximum water content of 99% and passes through a Fourdrinier wire, where gravity forces and a vacuum generated by a pump drain the water. After undergoing various processing steps, the final product has a water content of less than 1%.

The challenge: process water containing particles must be filtered

Both the manufacture of the fiber slurry and the continuous conditioning of the Fourdrinier yarn require enormous amounts of fresh water. It was the responsibility of Eaton’s production managers to help the company achieve its global sustainability goals. So they started looking for ways to filter and save process water.

If the treated water is of a sufficiently high quality, it can be reused in other production processes. This reduces the consumption of fresh water, reduces costs and decreases the environmental impact. The objective was therefore to separate the particles from the excess process water and to reuse the filtered water in the cleaning processes.

The solution: Low maintenance tubular backwash filter

Filtration experts have finally found what they were looking for near them: In the F-Series, Eaton offers a powerful automatic tubular backwash filter that is well established in the paper industry.

“We supply both international paper machine manufacturers and special applications in paper mills,” said Ulrich Latz, technical sales engineer in Eaton’s Filtration division. “Our filters have been used in this field for decades and are the subject of continuous development.

For the paper industry, low maintenance filtration systems provide a valuable service in reducing the concentration of particles in process water. In Langenlonsheim, excess water from the Fourdrinier section is filtered through the F-Series tubular backwash filter. The filtered water can then be reused for cleaning or in other treatment areas.

The F-series is a modular filter system that can be adapted to process-related changes with the help of extensions. The system can be designed to accommodate from 2 to 20 filtration stations and therefore suitable for different volume flow rates, allowing it to clean up to 3000 gallons of water per minute. The automated system requires no operator and uses differential pressure measurement to sense when the filter elements need cleaning. This process is based on the principle of tubular backwashing: one station after another is backwashed with a high volumetric flow.

“Incoming water flows into the filter through the lower manifold and is distributed to individual filter stations,” Latz said.

Four stations are in operation at the Eaton site in Langenlonsheim, each with a split wedge wire element. Clean water flows through the filter element to the outlet and into the collector; dirt remains on the outside of the filter element. A ball valve switches the flow during backwashing. One filtration station after another is rinsed with a partial flow of the already filtered water.

“This process only takes five to 10 seconds per station,” Latz said. “During this time, the filtered water continues to flow without interruption and the filtration is continuous.”

Backwashing using low solids external rinse water is also possible when the flow rate or pressure of the water to be filtered is too low for backwashing or to avoid kickstrokes. ram in the system. In this case, a fourth header is used. This manifold is supplied with an external flushing fluid and delivers it to the station for backwashing via automatic ball valves. Since the entire flushing process takes only a few seconds for all stations, only a small amount of water is used.

“The use of the F-series in the production of filter plates at the Langenlonsheim site was not straightforward at first,” said Latz.

In the conventional paper industry, process water requires cleaning solids ranging from 150 to 230 microns. However, in the manufacture of the special filters in Langenlonsheim, much smaller particles measuring as small as 25 micrometers must be separated.

“The fact that filter sheets are manufactured at relatively low flow rates is an advantage and the particles differ significantly in size from those used in papermaking,” said Latz.

Changing the split corner wire element to a mesh size of 25 microns produced the desired result.

The result: high savings with even greater potential

It was easy to match the automatic tubular backwashing filter to the production specifications of the filter plates. Since using the backwash filter in this way, filtered water has been used in the production process for cleaning purposes.

“With just four filtration stations, in total, we have saved over 2.6 million gallons of water per year since installing the F-Series,” said Eaton’s production manager in Langenlonsheim.

He considers the low-maintenance operation of the automatic tubular backflow filter during long production runs as particularly important.

“The water filtration works exactly as we expected,” he added. “This has allowed us to further optimize our production environment by using our own in-house developed technology.”

This success does not mean that no further action will be taken to reduce water consumption. The system will be expanded next year with the aim of saving up to five times the current volume. This will allow even more filtered process water to be used for cleaning purposes and in the future in other process areas as well. This is another step towards creating a sustainable production process and responsible use of natural resources.

Ulrich Latz is a Technical Sales Engineer at Eaton and based in Nettersheim, Germany. He specializes in self-cleaning filtration systems and has over 10 years of experience in various industrial filtration applications.