Two-Stage Liquid Mixer for High Viscosity De-aeration
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Solution Overview
Problem
Existing inline mixers, particularly high-shear mixers, experience reduced pumping ability and efficiency when dealing with high viscosity liquids, limiting their use to low viscous fluids due to cavitation and loss of sub-pressure below -0.6 bar, which restricts their application in food processing.
Innovation Solution
A two-stage mixing unit with a de-aeration vessel and a self-priming pumping device, such as a twin screw pump, is used to introduce additives downstream of the de-aeration vessel, allowing for adjustable mixing intensity and efficient pumping of high-viscous products, while a bypass valve and vacuum pump control ensure versatile operation and effective air removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If centrifugal principle-based inline mixers are used for high viscosity liquids, then mixing capability is reduced, but pumping ability is completely lost at viscosities above 1000 cP
Solution Approach 1:
The mixing system is divided into multiple mixing zones with different shear intensities. A first mixing zone provides high shear mixing for initial blending, while a second mixing zone provides lower shear mixing for final homogenization. This segmentation allows the system to handle high viscosity liquids effectively without losing pumping capability, as each zone is optimized for its specific function rather than relying on a single centrifugal mechanism.
Solution Approach 2:
The system changes the mixing parameters by providing different shear rates in different zones. The first mixing zone operates at high shear rates for initial mixing, while the second zone operates at lower shear rates. This parameter variation allows effective mixing of high viscosity liquids while maintaining pumping ability, as the lower shear zone does not create the cavitation conditions that limit centrifugal pumps at viscosities above 1000 cP.
2Ease of operation
If additives are introduced in the de-aeration vessel, then bulk circulation is required to draw down powders, but this results in inadequate mixing and lump formation on the liquid surface
Solution Approach 1:
Additives are introduced into the liquid stream before it enters the de-aeration vessel, rather than into the vessel itself. This preliminary action allows the additives to be incorporated into the flowing liquid where bulk circulation naturally draws them down, preventing lump formation on the liquid surface while avoiding the need for additional mixing interventions during de-aeration.
Solution Approach 2:
The liquid stream itself acts as an intermediary medium for additive introduction. By injecting additives into the flowing liquid rather than directly into the de-aeration vessel, the system uses the liquid flow as a carrier to distribute additives uniformly, preventing lump formation while maintaining ease of operation.
3Manufacturing precision
If high mixing intensity is applied to prevent lump formation, then mixing efficiency improves, but this causes extensive in-mixing of air and foam generation
Solution Approach 1:
The mixing process is segmented into two distinct zones: a first high-shear mixing zone that provides intense mixing for lump prevention, and a second low-shear mixing zone that completes the mixing process with minimal air incorporation. This segmentation allows the system to achieve thorough mixing without the continuous high-intensity mixing that would cause extensive foam generation in a single-zone system.
Solution Approach 2:
The mixing intensity is varied periodically through the two-zone system, with high shear applied in the first zone and lower shear in the second zone. This periodic variation in mixing intensity achieves effective lump prevention while allowing periods of lower intensity that reduce air in-mixing and foam generation compared to continuous high-intensity mixing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables efficient mixing of high-viscous liquids by maintaining pumping performance across a wide viscosity range, preventing lump formation and foam generation, and allowing for the use of inline mixers in applications previously limited by high viscosity.
Implementation Method 1
the pumping performance of existing in-line mixers that operates according to the centrifugal principle is lost when the suction pressure is reduced below -0.6 bar due to cavitation inside the mixer
Implementation Method 2
a de-aeration vessel, whereby solid and/or liquid additives are introduced downstream of the de-aeration vessel
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
A liquid processing mixer is provided, comprising a mixing unit (112) and a de- aeration vessel (106), said mixing unit (112) being separated from said de-aeration vessel (106) and in fluid connection with said de-aeration vessel (106), and wherein said liquid processing mixer (100) further comprises at least one additive inlet (114, 16) arranged between said de-aeration vessel (106) and a high shear mixing device (130) of said mixing unit (112) for introducing said additive downstream of said de- aeration vessel (106).