symmetrical dual shaft) to provide higher retention times and improved mixing efficiencies. This in turn encourages thermal transfer and liquid absorption. The shafts are parallel and counter-rotating, and the paddles intermesh for improved mixing capability.
This “true paddle” design features a thin, narrow blade intended to provide excellent mixing without promoting product build-up on its surface. With the proper speed management, this design offers the best conveying and level management within the preconditioner, creating higher efficiency.
When ETI removed the forward pitch from its preconditioner, several different areas become easily capitalized. The most important improvement was retention time and residence time distribution (RTD), both of which are vital to efficient operation. Retention time directly correlates to cook (thermal transfer) and liquid absorption. Another major advantage of the advanced configuration is the improved clean-out efficiency.
A good RTD will ensure that each specific quantity of feed receives the same amount of thermal energy, mechanical energy and absorption of any injections. This will ensure the extruder receives a flow of raw materials that has been consistently and precisely prepared for further processing.
Figure 2 demonstrates that as the fill level of the preconditioner is managed at higher levels, the percentage of starch gelatinization also increases. The concept is to maintain the highest level of energy transfer in the preconditioner as possible. Limitations to be considered include product specifications, thermal energy costs and the effective working capacity of the preconditioner. The return on this type of paradigm shift in moving the energy transfer from the
Figure 2: Fill level vs. gelatinization
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Preconditioner Fill Level
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By maintaining the highest level of energy transfer in the preconditioner, you can reduce consumption of electrical energy and its environmental impact.
extruder to the preconditioner can be substantial, especially when considering the reduction of electrical energy consumed and its impact on the environment.
Our research comparing processing parameters of identical formulations on identical equipment configurations revealed that proper preconditioning using the advanced techniques mentioned above will reduce electrical consumption by 10%–15% (based on production environment of 15 tons/hr., 16 hrs./ day, 340 days/yr.). This in turn will reduce your greenhouse gas emission contribution by more than 600,000 lbs. per annum (Cleaner and Greener, www.
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