The mixer plays a vital role in the feed production process, with efficient mixing being the key to good feed production. In fact, only the perfect mixing of the feed ingredients will ensure uniform distribution of nutrients, vitamins and minerals, which will result in a homogeneous nutrient content in each feed pellet. Further, it will ensure optimum growth of the animals.
Particle size may be the most important factor in causing this phenomenon. In general, the smaller and the more uniformly sized the ingredients are prepared, the more nearly they will approach random distribution during mixing. In many formulae a decrease in particle size is necessary to attain a sufficient number of particles of an essential additive (vitamin, mineral, medication) for dispersion in each daily feed unit. This may require the particle size to be the diameter of dust, from 10 to 50 microns.
The result of mixing dry solid ingredients may be a definite pattern of particle segregation. This is due to differences in the physical properties of ingredients and the shape and surface characteristics of the mixer. Segregation or poor blending can have many implications, including: rejected product, variable color, look or taste, excessive blend times, customer complaints, erratic dosage, product or process delays, inconsistent particle size, poor quality control.
Batch process means discontinuous. Venting spigot must always be open to vent air in a filter, preferably slightly under pressure; filling through the product inlet, with the unloading door closed: mixing, with unloading door closed, product inlet closed or open only if connected with a closed feeding hopper; emptying of the mixed product through the unloading door. Batch mixing can be done on an open flat surface with shovels or in containers shaped as cylinders, half-cylinders, cones or twin-cones with fixed baffles or moving augers, spirals, or paddles.
In the continuous process the machine is an open system. The production sequence consists in a flow of product that enters from the loading inlet, than it is mixed and exits from the unloading outlet. Both inlet and outlet doors are always open. Therefore, it’s important to remember that the final product quality depends on the permanence inside the mixing chamber and on the volume of product in the processing phase.
Continuous mixing proportions by weight or volume, is a technique best suited for formula feeds with few ingredients and minimal changes and no (or minimum) liquids addition.
Depending on the different products to be mixed, you can use one the following mixing tools:
- Ploughshare: are composed by two symmetrical plough-shaped faces. The space between the two faces is closed with a specially shaped metal sheet to prevent the wedging of the product. This tool works on the principle of mechanical fluidisation obtains excellent mixing quality in a very short time.
- Mix paddle: require a longer mixing time than ploughshare, but are easier to clean. Paddles are normally used with pastes and moist or sticky products.
- Screw: the fourfold screw ribbon is used for non intensive and gentle mixing or to keep the product agitated to avoid lumps. It’s used also to homogenise different batches obtained with ploughshare or paddle intensive mixers in a single batch.
Talking about mixers, speed and quality are two qualities customers prioritise. Furthermore, a good mixer should be easy to clean and maintain.
Mixing is very important and it’s essential to know what the feed formulation is and that all the ingredients remain intact during the process. The formula has to be mixed properly, so the animals get exactly the ingredients they need to grow.
A good mixer must meet the following specifications:
- Homogeneity after as short a time as possible
- Careful treatment of mixed material
- No residues remaining in the mixer
- Possibility to add liquids
- Short filling and discharge time
- Variable rate of admission