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US 2019/0126222 A1Published application
Methods of mixing impeller sensing
AssigneeSartorius Stedim Biotech GmbH
InventorsLars Boettcher, Jonathan E. Cutting, Sharon D. West, Martin Oschwald
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Abstract
A method is provided for monitoring a flow behavior of mixed components without requiring additional instrumentation or sampling. The method is carried out by determining ratios of the power required to rotate a mixing impeller at different rotational speeds and then comparing the ratios. Characteristics about the mixed components are determined based on differences between the ratios.
Claims6
A control system for monitoring a flow behaviour of mixed components, comprising:
- a memory for storing a relationship between a Reynolds number NRe and a Power number Np for at least one used mixing system geometry;
- an input means adapted to receive data regarding at least one of the speed N of the mixing impeller and the power P required to rotate the mixing impeller;
- a speed control means which is adapted to control the speed of the mixing impeller;
- a determining means which is adapted to:
- determine a quantity
- P
- i
- N
- i
- 3
- at various speeds Ni of the mixing impeller and compare two subsequently calculated quantities in order to determine whether the difference is within a specified range to determine whether the flow of the components in the mixing vessel is a turbulent flow, wherein Ni is the speed at which the mixing impeller rotates and Pi is the power required to rotate the mixing impeller at the speed Ni;
- determine the density ρ of the mixed components based on at least one speed Ni for which the flow is determined to be turbulent by the following formula:
- ρ
- =
- P
- i
- N
- P
- ,
- constant
-
- N
- i
- 3
-
- D
- 5
- wherein ρ is the density, Pi is the power required to turn the mixing impeller at the speed Ni, NP,constant is the Power number for a used mixing system configuration, Ni is the speed at which the mixing impeller rotates and D is the diameter of the mixing impeller;
- determine the Power number NP,variable for at least one detected speed Nj at which the flow is determined to be non-turbulent by the following formula:
- N
- P
- ,
- variable
- =
- P
- j
- ρ
-
-
- N
- j
- 3
-
- D
- 5
- wherein Pj is the power required to rotate the mixing impeller at the speed Nj, ρ is the density previously determined based on NP,constant, Nj is the speed at which the mixing impeller rotates, and D is the diameter of the mixing impeller;
- and
- to determine the dynamic viscosity μ of the mixed components by the following formula:
- μ
- =
- ρ
- 2
-
- N
- j
- 5
-
- D
- 6
- x
- T
-
- P
- j
- wherein ρ is the calculated density, Nj is the speed at which the mixing impeller rotates, D is the diameter of the mixing impeller, Pj is the power required to rotate the mixing impeller at the speed Nj and xT corresponds to a specified relationship between the Reynolds number for the used mixing system configuration and the determined Power number NP,variable.
62 more elements
A method for detecting settled solids at a mixing impeller, comprising:
- providing the mixing impeller in a mixing vessel;
- accommodating components to be mixed in the mixing vessel;
- rotating the mixing impeller at a speed Nstart for a time tstart, wherein the speed Nstart is lower than the speed at which the mixing impeller is mixing components;
- detecting whether an overload of a motor driving the mixing impeller applies during timestart;
- detecting a torque required to rotate the mixing impeller at the speed Nstart and comparing the detected torque with a known torque required to rotate the mixing impeller in the absence of solids;
- determining that the mixing impeller is blocked by solids if at least one of overload or a higher torque is detected.
3 more elements
A method for detecting settled solids at a mixing impeller, comprising:
- providing the mixing impeller in a mixing vessel, wherein the mixing impeller comprises a mixing impeller housing which houses at least one magnet and at least one mixing blade attached to the mixing impeller housing, wherein the mixing impeller housing is at least partly arranged in a mounting depression in a side wall of the mixing vessel, wherein the at least one magnet is magnetically connected to a motor to be driven;
- accommodating components to be mixed in the mixing vessel;
- rotating the mixing impeller such that mixing impeller housing is levitating in the mounting depression;
- moving the mixing impeller in a direction having a movement component substantially perpendicular to a rotation axis of the mixing impeller so that a gap between the mixing impeller housing and the mounting depression reduces;
- and
- determining that mixing impeller is blocked by solids if the mixing impeller has not moved the specified distance.
3 more elements
Dependencies are inferred from the claim text.