Batch Powder Mixer discharge time / emptying time
How to optimize emptying duration of a dry mixer
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Powder Mixing (main page)
# Types of mixers
# Mixing mechanisms
# Mixing time
# Mixing speed
# Mixing volume
# Mixing power
#Mixer loading # Discharge time
# Froude Number
# Coefficient of Variation
# Segregation / demixing
# Tip speed
# ATEX speed
# Mixer Bearing seals
# Mixer discharge valve
1. Discharge time
The discharging time of a bulk solids mixer is the time needed to empty it to the point it is ready for another batch. It is important to remark that the definition does not precise to "empty totally", indeed it is not always necessary to totally discharge a mixer working in batch.
2. Powder mixer discharged weight as function of time
Graph 1 :Discharge time
The weight discharged increases sharply at the beginning of the discharge, but then follows an asymptote, thus the last kg to be removed from the mixer takes proportionally longer than the rest of the batch.
3. Optimization discharge time batch powder mixers
To optimize the cycle time, it can be interesting to decide to stop the discharge while few kg of product are still remaining in the mixer. If it is sufficiently low, it is likely the remaining product will not affect the next mix homogeneity, but this will help to gain several seconds that will translate in additional capacity. The discharge can be governed according to a timer, but it is better to verify it through weight as well by having the discharge hopper or IBC on load cells.
The mixer should be run at low speed, below ATEX speed, to promote the discharge. An optimum is to be found as running too quick may in the contrary slow down the end of the discharge.
Bomb doors will give the quicker discharge time. For applications where bomb doors are not applicable, the discharging valve can be doubled to allow more flow.
4. Orders of magnitude discharge time mixers
For a 1000 l mixer
Table 1 : Usual discharge
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