Vacuum Freeze-Drying Nozzle Velocity Control
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Solution Overview
Problem
Conventional vacuum freeze-drying methods require larger apparatus sizes due to higher injection initial velocities, low vacuum evacuation in freezing tanks, and solvents with dropped freezing points, leading to increased costs and reduced production efficiency.
Innovation Solution
A vacuum freeze-drying method that injects a raw material liquid into a vacuum chamber at an initial velocity of 6 m/s to 33 m/s, maintaining a cooling velocity of 20°C to -25°C, and using an injection nozzle with a contact angle configuration to generate frozen particles of 200 μm or less, reducing the travel distance and apparatus size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the injection initial velocity is increased to freeze droplets faster, then the freezing speed is improved, but the apparatus size increases
Solution Approach 1:
The invention changes the parameters of the raw material liquid (using a solvent with a lowered freezing point) and controls the injection initial velocity within a specific range (6-33 m/s) to achieve fast freezing without requiring excessive apparatus size. By adjusting these parameters, the droplets freeze quickly while traveling a shorter distance, thus reducing the needed apparatus volume.
Solution Approach 2:
The invention transitions from conventional vertical freezing approaches to a horizontal injection method where droplets are injected horizontally into the vacuum chamber. This dimensional change allows the droplets to freeze during their horizontal travel, utilizing the vacuum environment's low pressure to achieve rapid freezing without requiring a tall freezing tank, thereby reducing apparatus size.
2Reliability
If the freezing tank height is increased to accommodate slower freezing, then the freezing completeness is improved, but the apparatus size increases
Solution Approach 1:
The invention performs preliminary vacuum evacuation of the chamber before injection, creating a low-pressure environment that promotes rapid freezing. This preliminary action ensures that when droplets are injected, they freeze quickly and completely during their travel, eliminating the need for a tall freezing tank and reducing apparatus size while maintaining freezing completeness.
Solution Approach 2:
The invention exploits the phase transition from liquid to solid during vacuum conditions. The low pressure in the vacuum chamber causes the solvent to freeze at lower temperatures, enabling rapid phase transition. This phase transition mechanism allows complete freezing within a short travel distance, reducing the needed apparatus height without sacrificing freezing reliability.
3Productivity
If the injection flow rate is increased to improve production efficiency, then the productivity is improved, but the apparatus size increases
Solution Approach 1:
The invention optimizes the injection flow rate within a specific range (corresponding to injection initial velocities of 6-33 m/s) to balance production efficiency with apparatus size. By controlling the flow rate to produce droplets of appropriate size and velocity, the system achieves high productivity while maintaining a compact apparatus design, as the droplets freeze quickly during their travel without requiring excessive chamber volume.
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
This approach allows for the efficient freezing of raw material droplets in a shorter distance without deteriorating solutes or dispersoids, resulting in a compact and cost-effective vacuum freeze-drying apparatus capable of producing high-quality powders.
Implementation Method 1
generates frozen particles by self-freezing using evaporation of moisture
Implementation Method 2
generates frozen particles by self-freezing
Implementation Method 3
drying is performed by subliming ice
Data Source
AI summary
[Object] To freeze droplets of a raw material liquid in a shorter drop distance while maintaining a cooling velocity, which is a super high speed, without deteriorating a solute or dispersoid.[Solving Means] A vacuum freeze-drying method according to an embodiment of the present invention is a vacuum freeze-drying method that includes steps of injecting a raw material liquid from an injection nozzle inside a vacuum chamber, generating frozen particles by self-freezing of the raw material liquid, and drying the generated frozen particles to thereby produce a dry powder, including: injecting the raw material liquid from the injection nozzle in a state in which the vacuum chamber is maintained at water vapor partial pressure corresponding to a self-freezing temperature of the raw material liquid, such that an injection initial velocity of the raw material liquid from the injection nozzle is 6 m/s or more and 33 m/s or less; and adjusting, when the maximum diameter of the generated frozen particle exceeds a predetermined value or droplets of the raw material liquid are unfrozen, an injection flow rate of the raw material liquid from the injection nozzle or properties of the injection nozzle such that frozen particles having a maximum diameter equal to or smaller than the predetermined value are generated.