Many fixed speed mixers, irrespective of type, are limited when required to mix viscous or glutinous materials.
When batching and mixing a blend of solid and viscous liquids, much of the batching and mixing sequence may utilise only a fraction of the available power required to mix the viscous liquid with the solids. As a consequence smaller batches are produced and through put is reduced. In addition the mixing of solids may require a low shear mixing action changing to high shear when viscous or glutinous materials are added.
An offshoot from Neilson's mobile concrete batching plants has been a demand for systems capable of processing clay rich soils / trench arising's with lime and cement. The resultant "concrete" is then used to back fill the trench in wet or dry form with the confidence that the ultimate strength of the resultant mix meets stringent industry specifications.
Mixing clay in a pan mixer results in "balling", thus a high shear is required to cut through
the clay enabling the lime and cement to produce a friable material. The problem is exacerbated in that solids have varying clay content and may vary within the same batch.
The problem will be mirrored in other applications and industries where materials, recipes
and quantities are often changed to suit demand but mixers capable of blending such a
wide range of materials are not available.
Neilson's solution has drawn on their expertise with hydraulics and their experience mixing
a range of concretes, screeds and mortars. The new planetary mixer is a hydraulically
driven, main drive being via high torque, low speed, planetary gearbox and twin planetary drives (50 to 400 rpm) via rotary union. All three mixed motors are independently driven
and speeds are reduced as load increases whilst maintaining constant power to the mixer,
all controlled via a Sauer Danfoss PLUS+1™ electro-hydraulic control system.
The benefit of this arrangement being that as the mixer is loaded with clay, glutinous animal feeds or viscous liquid, the Sauer Danfoss PLUS+1™ system automatically reacts to the consequent increase in hydraulic pressure, reduces the oil flow and thus mixer speed, whilst maintaining power to
the mixer overall. This in turn minimises the risk of the mixer stalling whilst awaiting the next ingredient.
The above system coupled with Neilson's batch controller provides a system which may be programmed to automatically batch and mix a number of solid and liquid ingredients.
Multiple repeatable recipes can be called up, based on industry standards or company standards, software ensures batch will not complete in event if exhausted hopper/silo/tank which means that operator error and wastage is reduced. Batch computer ensures that constituents are within 1-2% by weight.