Project points to reduced process costs

Unitec Ceramics used a Powdermatrix SPARK project to ask Ceram to identify methods to improve the morphology of granulates.

Unitec Ceramics is one of the world's most significant producers of fused zirconia, selling thousands of tonnes each year around the world.

Its vast product range varies from monoclinic zirconia through to products partially or fully stabilised with a variety of oxides, to more specialised compositions with tailored properties.

Unitec Ceramics currently produces zirconia granulates for use by advanced ceramic component manufacturers using spray-dry atomisation of aqueous slurry.

However, the company needed to improve granulate quality to increase sales.

It used a Powdermatrix SPARK project to ask Ceram to identify methods to improve the morphology of granulates.

Ceram suggested increasing the solid loading of suspension prior to spray drying to deliver an improved granulate and reduce process costs.

The first step was to characterise the rheological behaviour of current zirconia suspension prior to entering the spray dryer.

Ceram then went on to investigate the influence of different combinations of dispersants and binders in order to lower the viscosity of suspension prepared.

Then, by using the optimal combination dispersant/binder Ceram supplied Unitec with suspensions having similar viscosity to the present suspension but with a higher solids loading for spray drying.

The suspension optimisation tasks identified a new binder that enabled the increasing of the solid loading of the YSZ from 59 to 62% by weight for a given viscosity and, although the rheology study did not improve the granulate spray drying process, the results did indicate that there may be possible improvements to the existing system and formulation by increasing the solid loading with their current binder from 59 to 60% by weight without blocking the nozzle.

Although only relatively small, the 1% increase in solids loading will improve efficiency through reduced process time and energy saving.

Granulate output can be potentially increased by 4.25% and the lower water content means less energy is needed to dry the product.

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