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Long-term investment in resilient mills

Due to excessive wear and tear, the chemicals group Yara has replaced its existing mills with NEA PM 30 pendulum mills and achieved a considerable increase in production.

After experiencing significant mill wear and tear, Norwegian fertiliser, urea, nitrate and ammonia manufacturer, Yara International, was left searching for a new pendulum mill provider.

After working with pendulum mills from a French manufacturer at its fertiliser works in Poppendorf, close to Rostock in Germany, Yara International approached NEUMAN & ESSER, part of the NEA Group, which produces wear resistant pendulum mills, with components that are easy to exchange.

Large quantities of dolomite are pulverised at the Rostock works to be used as fertiliser carriers. The previous mills displayed massive wear and tear, both on the base of the mill housing and on the main vertical shaft. The shovel shaft and the shovels were only designed as a welded sheet steel construction.

A further weakness in the highly abrasive environment was that the pendulum purge air was fed using rubber hoses. 

Wear resistant mills for top requirements

NEA pendulum mills incorporate 80 years’ experience, both in construction materials and design. For example, the four-part ground wear plate can be replaced quickly. The shovel shaft and shovel carrier are made of robust cast steel and the shovels themselves are made of high strength sheet steel.

In contrast to the current mill, the PM 30 does not use any rubber tubes for the purge air. The pendulum purge air is fed through the rotor and the spigot trunnion. It is a well-designed, long-term, non-wearing solution.

Wolfgang Palm, sales manager after sales at NEUMAN & ESSER Mahl- und Sichtsysteme, was responsible for the new installation of the PM 30 mills at Yara. 

“The special feature of this project was its many ambitious specifications. For example, it involved a very tight time frame. We had to conclude all of the assembly work within only three weeks,” he explained.

This is precisely the period of time which Yara schedules for the annual servicing of the entire fertiliser works. Also, the space available for the 42-tonne heavy lower mill housing was extremely tight. 

For the installation of the cast housing with the dimensions 4,900 x 4,400 x 1,100mm, the access space was very limited.

“To the left and right of the housing, we had no more than a hand’s width of space,” Palm said.

Yara stipulated that the mill gear, mill drive and upper mill housing, including the feeder from the existing pendulum mill, had to be reused. NEA incorporated all of these components into the complete system design. 

Ambitious project mastered with routine

Following the successful mill assembly, the NEA experts installed a new inverted cone classifier and incorporated the product and hot gas ducts into the system design. The pulverising system was operable again with-in the specified period of only three weeks.

“YARA is now perfectly equipped for dolomite grinding. Apart from the very tight space available, this is really a routine project for us. The dolomite has very little wear effect on the lower mill housing and the vertical main shaft any longer. The mill now consists of very solid components,” Palm said.

Yara Rostock project manager, Wolfgang Wolff, added: “The newly installed pendulum mills mean a huge improvement for me and not only with regard to their wear and tear behaviour. The new mills are considerably quieter and enable higher throughput. The first PM 30 installed by NEUMAN & ESSER already improved throughput by 15% to 34,500kg/h. We now even manage 37,500kg/h with the new filter. Moreover, we can adapt the fineness better to our requirements.”

After the installation of the first PM 30 and its reliable functioning since then, Yara has also replaced the second mill with a PM 30 from NEUMAN & ESSER. It was installed in September last year and has been grinding kieserite and anhydrite since the beginning of October.

Although these are the first NEA mills for Yara, the companies have worked together in the past. Four MAFA Wurzen compressors have been in use at these works for over 30 years. MAFA was taken over by NEA Holding in 1991 and these compressors have been serviced since then by the company group service provider, NEAC Compressor Service.