A ribbon blender consists of a horizontal U-shaped trough containing a rotating double helical ribbon agitator inside. The horizontal agitator shaft is located in the center of the trough on which the helical ribbons are provided. A sealing arrangement is provided for the area where the shaft exits the container to ensure that material does not travel from the container to the outside and vice versa. The blender assembly along with the drive system components such as the motor, gearbox, couplings and bearing supports are mounted on a supporting frame.

Ribbon Blender Assembly

Double Helical Ribbon Flights

Consisting of a combination of inner and outer helical ribbons, the ribbon agitator is referred to as the "double" helical ribbon agitator. The external ribbon flights move the material from the ends to the center during the blending operation, while the inner ribbon flights move the material from the center to the ends. Because of the rotational motion of the ribbons, radial mixing is accomplished. Axial movement of the material along the horizontal axis of the blender stems from the disparity in peripheral velocities of the outer and inner ribbons. As a consequence of the radial and counter-current axial motion, homogeneous blending with 90 to 95 percent or better homogeneity is achieved within 15 to 20 minutes of start-up. The biggest effect on the mixing efficiency of the ribbon blender is the solid particle size and its bulk density. As compared to ingredients with variance in these properties, ingredients with similar particle size and bulk densities tend to blend faster.

The material loading in the blender normally takes place by means of nozzles or feed-hoppers located on the blender 's top cover. The ribbon blender 's working capacity ranges from 40 to 70 percent of its total volumetric capacity. The product is discharged from a discharge valve located at the bottom of the trough after blending. Depending on the size of the blender, more than one discharge valve may be provided. The valve operation may be manual or pneumatically actuated. In the ribbon blender, obtaining 100 percent discharge is practically difficult. The amount of hold up after discharge in the blender depends on the material properties, the clearance between the ribbon flight's outer edge and the blender container's inside wall. Depending on the application, a clearance of 3 mm to 6 mm is usually maintained.

Pneumatically Operated Knife Gate Valve for Product Discharge

Ribbon blenders can also be provided with integral screw conveyor located in the bottom portion of the container. The integrated screw conveyor can be used to discharge the product for packing or further process at a controlled rate of discharge.

Ribbon Blender with Integral Screw Conveyor for Product Discharge

The ribbon blender is suited for free flowing and cohesive products. The flexibility of the ribbon blender for mixing solids coupled with its ability to perform heating , cooling, coating, and other procedures make it a common blender. It is widely used in the food, chemicals, animal feed, pharmaceutical industries.

Powder Sampling Valve for Online Sampling of Blenders

Ribbon blenders can be designed to operate in both batch and continuous modes. Batch type blenders of up to 50 m3 size can be constructed. For 1000 kg of product mass to be blended, they are typically powered by 10 horsepower to 15 horsepower motors. Depending on the products to be blended, the specific power can vary from 5 to 12 kW / m3.

Double Helical Ribbon Blender Video Gallery