Evaluation of tunable diode laser absorption spectroscopy for in‐process water vapor mass flux measurements during freeze drying

Gieseler, Henning; Kessler, William J.; Finson, Michael L.; Davis, Steven J.; Mulhall, Phillip A.; Bons, Vincent; Debo, David J.; Pikal, Michael J.

doi:10.1002/jps.20827

Cited by 133 publications

(74 citation statements)

References 10 publications

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“…The Doppler-shifted near-infrared absorption spectroscopy is used for measuring the water vapour concentration and gas flow velocity in the duct (that connects drying and condenser chamber). At this point, these variables can be used, known the cross-sectional area of the duct, to estimate the vapour flow rate (Kessler et al, 2006;Gieseler et al, 2007). It must be remarked that TDLAS does not measure directly the mass flow, but only the gas flow velocity in a limited number of points; therefore, the reliability of the vapour flow rate estimation depends on how well the velocity profile is known.…”

Section: Experimental Methods For K V Measurementmentioning

confidence: 99%

Heat Transfer in Freeze-Drying Apparatus

Pisano¹,

Fissore²,

Barresi³

2011

Developments in Heat Transfer

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Section: Experimental Methods For K V Measurementmentioning

confidence: 99%

Heat Transfer in Freeze-Drying Apparatus

Pisano¹,

Fissore²,

Barresi³

2011

Developments in Heat Transfer

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“…The easiest way to measure the mass flow rate at the choke point is by tunable diode laser absorption spectroscopy (10) or TDLAS (see discussion below). Where TDLAS is not available, the mass flow rate corresponding to choked flow can be measured gravimetrically after stopping the process at a point where most of the initial ice load remains.…”

Section: The Capacitance Manometermentioning

confidence: 99%

Recommended Best Practices for Process Monitoring Instrumentation in Pharmaceutical Freeze Drying—2017

et al. 2017

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Abstract.Recommended best practices in monitoring of product status during pharmaceutical freeze drying are presented, focusing on methods that apply to both laboratory and production scale. With respect to product temperature measurement, sources of uncertainty associated with any type of measurement probe are discussed, as well as important differences between the two most common types of temperature-measuring instruments-thermocouples and resistance temperature detectors (RTD). Two types of pressure transducers are discussed-thermal conductivity-type gauges and capacitance manometers, with the Pirani gauge being the thermal conductivity-type gauge of choice. It is recommended that both types of pressure gauge be used on both the product chamber and the condenser for freeze dryers with an external condenser, and the reasoning for this recommendation is discussed. Developing technology for process monitoring worthy of further investigation is also briefly reviewed, including wireless product temperature monitoring, tunable diode laser absorption spectroscopy at manufacturing scale, heat flux measurement, and mass spectrometry as process monitoring tools.KEY WORDS: heat flux measurement; mass spectrometry; pressure measurement; process analytical technology; temperature measurement; tunable diode laser absorption spectroscopy.

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“…Then, model parameters (Kv and Rp), as well as other variables like product temperature and the residual amount of ice, are estimated looking for the best fit between the values of chamber pressure measured and those calculated using a mathematical model of the process [22][23][24][25][26][27]. As an alternative to this method, it is possible to use Tunable Diode Laser Absorption Spectroscopy (TDLAS) to estimate Kv and Rp, beside product temperature and the residual amount of ice [28][29][30]. Moreover, a soft-sensor based on the measurement of product temperature, on a mathematical model of the process and on the Extended Kalman Filter algorithm was also proposed to get the values of Kv and Rp [31][32][33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

Computer-Aided Framework for the Design of Freeze-Drying Cycles: Optimization of the Operating Conditions of the Primary Drying Stage

Fissore

Pisano

2015

Processes

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This paper deals with the freeze-drying process and, in particular, with the optimization of the operating conditions of the primary drying stage. When designing a freeze-drying cycle, process control aims at obtaining the values of the operating conditions (temperature of the heating fluid and pressure in the drying chamber) resulting in a product temperature lower than the limit value of the product, and in the shortest drying time. This is particularly challenging, mainly due to the intrinsic nonlinearity of the system. In this framework, deep process knowledge is required for deriving a suitable process dynamic model that can be used to calculate the design space for the primary drying stage. The design space can then be used to properly design (and optimize) the process, preserving product quality. The case of a product whose dried layer resistance, one of the key model parameters, is affected by the operating conditions is addressed in this paper, and a simple and effective method to calculate the design space in this case is presented and discussed.

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Evaluation of tunable diode laser absorption spectroscopy for in‐process water vapor mass flux measurements during freeze drying

Cited by 133 publications

References 10 publications

Heat Transfer in Freeze-Drying Apparatus

Heat Transfer in Freeze-Drying Apparatus

Recommended Best Practices for Process Monitoring Instrumentation in Pharmaceutical Freeze Drying—2017

Computer-Aided Framework for the Design of Freeze-Drying Cycles: Optimization of the Operating Conditions of the Primary Drying Stage

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