A Contra Rotating Mixer, Contrablend or Contramix as they are also known are process vessels used the manufacturing of highly viscous products in the pharmaceutical, cosmetics, toiletries and food industries.
Typically, a contra rotating mixer consists of a hemispherical stainless steel vessel with a jacket and a top mounted double mixer arrangement. The vessel is jacketed to allow heating by means of steam and cooling by means of water. This does not preclude the use of other heating or cooling medias such as thermal fluid or chilled water. The vessel is clad with polished stainless steel and the interspace between the jacket and cladding is insulated with either mineral wool or foam. The vessel can be supported on tubular stainless steel legs or fitted with side supports so it can be incorporated into a support structure. Vessels are either built for atmospheric pressure or pressure vacuum conditions. For pressure models the lid is flanged and secured to the vessel by means of clamps or bolts and for atmospheric vessels the top is flat with hinged segmental lids.
The mixer comprises of two main assemblies which are contra-rotating and axially inclined up to 45deg to promote flow down the sides of the vessel and up the centre. The outer mixing mechanism comprises of an anchor assembly. Onto the anchor assembly are welded pairs of 45deg axial flow blades, which intermesh with the inner mixing blade configuration. Also secured to the outer anchor are PTFE hinged scraper blades, to maintain a clean heat transfer surface. The centre mixing mechanism is a shaft, with blades welded directly to the shaft, intermeshing with the outer anchor paddles.
The drive comprises of a double gearbox of worm type, which is of very robust construction. The units are flanged together by means of bolted registered flanges, to ensure precision location. Electric motors are coupled to the drive gearboxes via flexible couplings and are in the horizontal position. Often due to the complexity and range of products produced in a contra rotating mixer, variable speed is normally required. This is normally achieved using electronic frequency inverters which are inbuilt to the control panel.
A contra rotating mixer is regarded a low shear type mixer, and many circumstances occur in multi-purpose mixing where high shear mixing is require for a period of time during the processing of a batch. This can be achieved through the use of a high shear emulsifier/homogeniser. There are two types of high shear mixer that can be used, either with an inline high shear mixer externally connected to the vessel with interconnecting pipework or alternatively by the incorporation of an integral high shear mixer to the bottom dish of the vessel.
Contra rotating mixers are extremely versatile, enabling a variety of products to be mixed within them, particularly highly viscous products such as gels, emulsions and pastes.
3Di Process Equipment buy and sell used contra rotating mixers and stock both atmospheric and pressure vacuum units. Please visit our mixing vessels page on our website to view of current stock.