Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size
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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 1

Crystallization monitoring Inline analytical technology for: ·· saturation degree ·· supersaturation ·· crystal content ·· metastable range ·· particle size

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 3

quality, saving resources: LiquiSonic®. h-value, innovative sensor technology. curate, user-friendly. LiquiSonic® is an inline analytical system, that detects the concentration in a liquid directly in the process and without any time lag. The device is based on the accurate measurement of sonic velocity and temperature and enables so the monitoring of processes and complex reactions. Benefits for the user include: · optimal plant control through online information about the state of the process · maximum efficiency of processes · increasing of the product quality · reduction of costs for...

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 4

Inline process analysis

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 5

3.4 Supersaturation decreasing and crystal growth kinetics 14

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 7

Sonic velocity measurement is used to determine crystallization parameters and to control crystallization processes. This measuring method enables the detection of the nucleation and saturation point and thus the metastable range. During the crystallization, it is possible to measure the difference to the saturation (degree of saturation), the degree of supersaturation or the crystal content, using as a control variable for influencing the crystallization. When a solid substance is dissolved in a liquid, the liquid is absorptive up to a certain concentration. If further substance is added...

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 9

Crystallization processes in continuous as well as in batch processes can be monitored by measuring the sonic velocity with the LiquiSonic® system. In case of failures or deviations from the process flow, it can easily be reacted to achieve the required product quality. By using typical analogue or digital interfaces, minor deviations from the ideal course are provided to the user or the process control, for example, to steer the crystallization via temperature control into the ideal course. The following diagram includes the evaluation of three different process flows concerning...

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 11

Crystallization parameters Sonic velocity and temperature are measured during cooling and heating the solution to establish the relevant parameters within the process. The sonic velocity presented as a function of the temperature, important crystallisation parameters, such as saturation temperature, nucleation temperature, and the position in the metastable range can be directly determined. The following diagram describes crystallization characteristics like ammonium sulphate with 42.6 w% during heating and cooling at different temperatures. Consequently, it is possible to determine the...

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 12

Then, a spontaneous nucleation occurs on the nucleation curve. Online measurement of the degree of saturation is based on saturation concentrations varying at different temperatures.The following diagram shows exemplary the saturation behaviour of a large crystallization process stored in the LiquiSonic® 50 system. The range between saturation and nucleation is called the metastable (supersaturated) range. The supersaturation is the indicator for the perfect seeding point within the controlled nucleation. The current concentration is determined by sonic velocity and temperature measurement,...

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 13

The degree of supersaturation can also be determined by sonic velocity, as a function of the temperature. As shown in the figure below the degree of supersaturation reflects a specific point within the metastable range. The closer this point is to the nucleation curve, the higher is the degree of supersaturation. By measuring the sonic velocity and the temperature of the mother solution during crystallization, an optimization of the crystallization process control within the metastable range can be realized. This enables an direct influence on growth and so on the morphology of crystals....

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 14

Supersaturation decreasing and crystal growth kinetics The degree to which supersaturation is decreasing during crystallization can be represented as a function of time (supersaturation decline curve). The following diagram shows different crystal growth kinetics which were detected by decreasing of sonic velocity as well as by supersaturation The crystal growth kinetics can be determined from the supersaturation decline curve. This variable indicates how fast the crystals grow in the mother solution and is therefore an important variable for designing and dimensioning crystallizers. It is...

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 15

Crystal content Each suspension is characterised by a specific sonic velocity behaviour depending on temperature and concentration. The corresponding characteristic curves are also stored in the LiquiSonic® system. This enables the direct inline measurement of the solid concentration respectively crystal content or dry matter content. It is possible to monitor and control the separation in continuous crystallization processes by determining the crystal content. In batch processes the end point of crystallization and the crystal growth can be determined and monitored. Sonic velocity...

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 17

LiquiSonic® 50 can be configured for reaction monitoring (fingerprint) or for crystallization monitoring (crystallization). The controller processes the sensor data and is the interface to the operator by displaying the concentrationvalues. The controller is equipped with a high sophisticated microprocessor, even handles complex concentration calculations. LiquiSonic® 50 detects and evaluates all relevant process parameters and is thus an efficient tool for characterization, visualization and control of crystallization processes of all types. For example, the saturation and the nucleation...

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Inline analytical technology for crystallization monitoring: saturation degree, supersaturation, crystal content, metastable range and particle size - 18

temperature (X) concentration (Y) back to main view Y-axis concentration nucleationline saturationline difference to base line Chart view with current position of the process state In most cases, different process parameters, which lead to an optimal course of reaction and endproduct, were determined by preliminary investigations. This so-called “Golden Batch” can be implemented in the controller flexibly. Diverse analog, digital outputs as well as BUS connections to the control system provide the user with little deviations from the ideal process. So, the user has the opportunity to...

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