January 16, 2024 ​

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​The ETC is seeking companies interested in providing better understanding of applicability of kinetic models and their use in predicting solvent content over time to support process modelling. 

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An accurate kinetic model is required as the basis for any drying model. Different models exist in literature, including terms for heat transfer, mass transfer, and uniformity through the drying cake over the course of the drying process. During development of API processes, many of the terms within these models are unknown, making selecting the most appropriate model a challenge. In some scenarios, de-solvation and dehydration can occur and incorporating the kinetics of these into process models adds to the complexity. Not knowing which model terms are required for different scenarios and which terms are most influential in predicting solvent content over time prohibits drying modelling use more widely in development and optimization. It is expected that further advances in these areas are required that will further support the development of a more robust drying model, which will allow for process optimization as well as technical transfer across different scales and equipment types.

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Download the Request for Proposal and submit your response.

RFP ISSUED:  January 16, 2024

QUESTIONS on RFP DUE to ETC:  February 5, 2024

RFP RESPONSES DUE to ETC:  February 23, 2024

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Q&A - Note see FAQ document for answers to common questions​​​ (Answers updated Feb 12, 2024)

• Do you intend to add the convective model onto the Schlünder and/or Murru model or is a completely new model (could be first principles or data-driven) preferred?

  • ANSWER: A model capable of being transferable between scales of equipment and across equipment types is desired. Whether a convective model is built into the Shlünder / Murru models may depend on the accuracy of these models themselves, or whether a more accurate estimation is achieved through an alternative approach.  A model capable of being transferable between scales of equipment and across equipment types is desired. Whether a convective model is built into the Shlünder / Murru models may depend on the accuracy of these models themselves, or whether a more accurate estimation is achieved through an alternative approach. 

• Will we have access to Dynochem to do an initial comparison on the Schlünder and Murru models?

  • ANSWER: We will not be able to provide access to DynoChem for a comparison.

• What is the preferred programming language to develop an enhanced agitated filter dryer model?

  • ANSWER: A common programming language (e.g. Python, Matlab) should be used

• Are we investigating different morphologies and particle size distributions?

  • ANSWER: We would like a model that is applicable for all particle shapes and sizes.

• Do we have flexibility on the wash solvent or is it imposed?

  • ANSWER: We would ideally like a model that can incorporate any solvent properties that are likely to impact drying rate so these can be used to predict solvent content over time. This would allow us to assess drying performance by comparing different wash solvents and be transferrable across scenarios.

• Is wet Nitrogen drying out of scope?

  • ANSWER: Understanding the kinetics using ‘dry’ nitrogen drying is the priority of this project. Expansion to ‘wet’ nitrogen drying is of interest, but not a critical deliverable for this project.

• What is the final expectation in terms of deliverables? Does it include a user interface with integrated workflow (experimental data for parameter estimation and then validation)?

  • ANSWER: The final model should be delivered in a format that allows scientists to apply it to new cases. This should include any parameter estimation / calibration, optimisation and validation. Instructions on how to use the model and complete these activities are required and should be delivered with a user interface.

• Is the intent of the deliverable to be used for development or filing (QbD such as design space) or both?

  • ANSWER: We intend to use this to support development by providing process understanding and optimisation. 

• Can you confirm that the modelling of PSD evolution during agitated drying is out of scope?

  • ANSWER: We would like to concentrate on solvent content rather than evolution of PSD through attrition or agglomeration in this project.

• How critical is the requirement “Ability to predict impact of agitation regime and speed on drying time and spatial variation of solvent content ”? (Section 2.3) Are there specific published research/approaches the ETC members would like to explore through this project? Would both intermittent and/or continuous agitation be considered in scope?

  • ANSWER: Beyond the approximations used in the Schlünder model, we are not aware of any research that is routinely used to assess impact of agitation regime, etc, on solvent content, however an ability to predict this will greatly improve the accuracy of any model and increase the scope of its applicability.

• Are there specific dryer types/geometries which should be considered, or are there particular equipment types of specific interest, such as agitated filter dryers?

  • ANSWER: Ultimately, we would like to be able to understand and model drying performance in all types of dryers. An agitated filter dryer is one of the most common would be a sensible place to start with any models. If proposals are to focus on a single type of equipment, a filter dryer would be the preference.

• For the requirements in section 2 of 2.3, on model accuracy for desolvation/dehydration, will this involve the usage of solid form phase maps as a function of solvent/water composition and temperature, which can be used to guide drying design spaces?

  • ANSWER: Incorporating any phase maps would be ideal and would help providing more accurate design space, however this could be considered a nice-to-have as these may not always be known.

• For the requirement “Develop simple methods to measure terms required for an accurate model, i.e., the parameters identified as key in the sensitivity analysis.”, are the ETC members willing to provide access to such measurement equipment/techniques, if required, if not available/accessible to the vendor?

  • ANSWER: ETC member companies should not be relied on to provide access to measurement equipment. Please highlight if you do not have access, but would be willing to collaborate and have any proposed partners. We appreciate that this project requires both data generation and model development that may require collaboration.   

• Is the ability to model/consider combined vacuum contact and convective drying also a requirement of a modelling tool? Or would vacuum contact and convective drying/nitrogen blowdown steps be modelled separately?

  • ANSWER: Combining both vacuum contact and convective drying in a single model may be a long term goal. Having this available may make the models applicable in different dryers, but may not be a short term goal.

• Are the ETC members able/willing to provide or generate suitable data sets to support the project activities, if a vendor unable to do so via external  collaborators/third parties?

  • ANSWER: ETC members will not be able to generate data due to the challenges with committing time to generate data sets using generic materials and the restrictions with sharing any data based on development / commercial compounds. Please highlight if you do not have ability to generate data sets but would be willing to collaborate and have any proposed partners. We appreciate that this project requires both data generation and model development that may require collaboration.   

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