Bulk Freeze-Drying With Vibrating Shelves for Powder Uniformity
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Solution Overview
Problem
Conventional freeze drying systems for bulk products face challenges in handling large masses, leading to agglomeration, irregular heat transfer, long cycle times, and difficulty in maintaining aseptic conditions due to metal-to-metal contact, which complicates sterilization and results in product handling losses.
Innovation Solution
A nozzle system for a freeze drying system that generates uniform fluid product drops using a setpoint pressure, combined with a freezing vessel that forms frozen particles in a controlled freezing zone, followed by a drying chamber with sloped shelves and vibration elements to promote sublimation and prevent agglomeration, ensuring aseptic conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bulk product is placed in trays for freeze drying, then aseptic conditions can be maintained, but handling difficulty and product handling loss increase
Solution Approach 1:
The bulk product is divided into individual particles through spray freezing, eliminating the need for tray handling. Each particle is frozen separately as it falls through the freezing zone, converting a single large mass into many small, easily handled particles that maintain aseptic conditions without requiring manual tray manipulation.
Solution Approach 2:
The mechanical tray handling system is replaced with a gravity-based particle delivery system. Particles are conveyed from the freezing chamber to the drying chamber through gravity flow, eliminating the need for manual tray loading and unloading while maintaining aseptic conditions.
2Reliability
If bulk product is placed in trays for freeze drying, then aseptic conditions can be maintained, but cycle times become longer
Solution Approach 1:
Dividing the bulk product into small particles increases the surface area to volume ratio, dramatically improving heat transfer efficiency during both freezing and drying phases. This segmentation allows much faster processing cycles while maintaining aseptic conditions, as each particle can be rapidly frozen and dried individually.
Solution Approach 2:
The product form is changed from large bulk mass to small particles, fundamentally altering the thermal and mass transfer parameters. This parameter change enables rapid heat penetration and moisture removal, reducing cycle times from hours to minutes while preserving aseptic conditions.
3Productivity
If heating is applied to bulk product in trays, then sublimation can occur, but heat transfer irregularities and agglomeration occur
Solution Approach 1:
The product is segmented into small particles before drying, ensuring uniform heat distribution across all particles. This prevents agglomeration that occurs with bulk products, as each particle maintains consistent thermal contact with the drying surface, resulting in uniform particle size and improved sublimation efficiency.
Solution Approach 2:
Vibration is applied to the drying surface to prevent particle agglomeration and ensure uniform heat transfer. The mechanical vibration keeps particles separated and in constant contact with the heating surface, eliminating heat transfer irregularities and maintaining consistent particle size throughout the drying process.
4Strength
If metal-to-metal contact is used in freeze drying equipment, then structural integrity is maintained, but sterilization difficulty increases
Solution Approach 1:
The system uses pneumatic conveying and fluid-based particle handling instead of metal-to-metal contact mechanisms. Particles are transported through gravity flow and pneumatic systems with minimal mechanical contact, eliminating the sterilization problems associated with complex metal mechanisms while maintaining structural integrity through simple, cleanable surfaces.
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 system efficiently produces freeze-dried products in powder form while maintaining aseptic quality, reducing handling losses and cycle times, and ensuring uniform particle size and heat transfer efficiency.
Implementation Method 1
The nozzle is operated at a setpoint nozzle pressure to generate fluid product drops having a size suitable for freeze drying
Implementation Method 2
a cooling fluid flows through the cavity inlet, cavity and cavity outlet to form a freezing zone
Implementation Method 3
a heating element is associated with each shelf that heats the frozen particles to promote sublimation
Implementation Method 4
a plurality of vibration elements located outside the drying chamber vibrate the shelves in a horizontal direction to cause the frozen particles to advance relative to an associated shelf
Data Source
AI summary
A freeze drying system (200) having a nozzle (30) operated at a setpoint pressure to generate fluid product drops (242) for freezing in a freezing chamber (244) of a freezing vessel (228). The freezing chamber includes an inner wall (250) that defines a cavity (254) and an outer wall (252) having an inlet (260) that extends from a location on the outer wall that is lower than an outlet (262). A cooling fluid flows through the inlet, cavity and outlet to form a freezing zone (280). A drying chamber (304) having sloped shelves (352) receives frozen particles (282) from the freezing chamber. A heating element (418) is associated with each shelf that heats the frozen particles to promote sublimation. Vibration elements (396, 398, 400, 402) located outside the drying chamber vibrate the shelves causing the frozen particles to move from shelf to shelf to form freeze dried product (284).