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Mill it well, mill it fine

Micropulva can draw on over 20 years of experience in developing and manufacturing micronising technology, and has generated a number of patents and new applications in the field over that time.
Micropulva Oy Ltd.

Micropulva is an expert in the grinding, micronisation, classification, and fractionation of a variety of wet and dry materials, and has developed some of the most efficient technologies in the field.

Micropulva has over 20 years of experience in developing and manufacturing micronising technology. This FP5 opposed jet mill can handle between 1,000 kb/h to 3,000 kb/h, depending on the application.

The company’s Pulva FP fine grinding technology, based on kinetic energy, can deliver an over 50% saving in energy compared to conventional jet milling processes, which gives it a substantial competitive advantage.

This low energy consumption and high efficiency have opened up new applications for the technology in a number of industries. Fine grinding and micronising systems based on Pulva FP technology have been supplied to projects around the world – for use in areas such as milling mineral pigments in the paper industry and processing other pigments, industrial minerals, construction materials, mineral ores, and food ingredients.

Micropulva is committed to continuing to develop pro-environmental, low-energy technology and applications into the future.

The technology

Micropulva’s Pulva FP jet mills are based on a twophase stream process. Raw material is fed into the work gas, which is typically air, through a twin-valve feeder and equalised in a special balancing tank. The particles are then accelerated to their optimum speed by oil-free, pressured gas in two atomizers, where they collide and are ground by their own internal momentum.

Fly ash from power plants processed using Micropulva technology can be transformed into a useful resource for producing concrete.

After milling, the energy contained in the work gas is recovered and used in mechanical classifiers. The end-product and gas are separated from each other in a filter unit, with a centrifugal blower providing the pressure differential needed. Where appropriate, the process can be fully automated and operated from a remote control unit.

The advantages

Compared to conventional single-phase or freeflowing technologies, the Micropulva approach offers energy savings of over 50%, as well as substantially lower capital costs. A Pulva jet mill also has higher milling capacity and can produce finer particles, as well as provide more particle distribution control.

As the pressure of the work gas is low, normally 3.5 bar, it can be generated by a simple compressor, with no after-cooling. This yields enhanced energy efficiency, and enables energy to be used for drying the material to be milled.

These benefits are most valuable when dealing with hard and aggressive raw materials and when end-products need to be free of contamination, or when selective milling is called for in dry concentration applications. They are also useful when producing ultra-fine, nano-level products.

For laboratory and research purposes, Micropulva offers the PulvaRex unit.

Applications benefiting from Micropulva technology

Industrial minerals

Bentonite, ilmenite, quartz, wollastonite, zircon silicate

Mineral pigments used by the paper and plastic industry

Talc, kaolin

Construction industry materials

Cement, pigments, furnace slag, clinker, glass


Titanium dioxide, ferrous oxide, carbon pigments, cobalt pigments

Ore minerals

Gold, platinum, nickel, cobalt

Food industry

Sugar, soy bean etc.

Fine chemistry, pharmaceuticals



Transforming fly ash into a resource

Fly ash is formed in coal-fired power plants when the inorganic minerals, such as sand and clay, contained in the fuel melt in the furnace and solidify before exiting a plant’s electrostatic precipitator. As it reacts with calcium hydroxide to form solid cement stone, good-quality fly ash can be used to replace up to 40% of Portland cement by weight in concrete.

The varying quality of fly ash makes using it as a substitute for cement quite problematic, however. Carbon content is the main limiting factor here, as fly ash often contains unburned carbon.

This problem can be overcome using Micropulva technology, as it enables the problematic unburned carbon to be removed and the resulting clean fly ash optimised for the end-use application. The resulting fly ash can be used on a one-for-one basis by weight to replace Portland cement.

> Jouko Niemi
(Published in HighTech Finland 2009)