BRACE Microsphere Processes and LNF Process are both well established industrial standard processes to convert liquids into frozen particles. However, there are major difference in the processes, as the product quality, droplet generation, the solidification, the particle collection and the energy costs.

BRACE Microsphere Process is a patented vibrating nozzle technology (jetting with vibrating nozzle), with a precise control over the droplet formation in a high flow rate. The droplets are solidified in the case of a Fusion Process in a controlled low-temperature tower, which used liquid nitrogen as cooling medium, or were liquid nitrogen is not readily available industrial compressor refrigeration system. In this process, a narrow, monomodal size distribution of very round particles is generated, that are automatically and continuously collected at the end of the process for further treatment like freeze drying, packing etc.

These processes are known to work with a wide variety of materials, from low to high viscosity, mixtures and even emulsions and suspensions with high solid contents of 60% and more can be used easily. Additionally the process can be extended with easy to produce real core-shell Microcapsules to produce a total new class of encapsulated materials. Typical application are microbiological suspensions, instant products, food additives, nutrients, feed nutrients, cosmetic, pharmaceutics, but also metals, catalysts, or other high tech applications.

LNF is a variation of historically well know gravity dripping processes widespread for various applications from bullet prill towers to more recent applications. In such processes the liquid has a lower flow rate and the droplets are formed by surface tension forces slowly with little control over the size. The resulting droplets are collected in a liquid nitrogen bath in a container, out of which they are transported via a screw feed and rotary flap vanes to further treatment. Due to the nature of the process, capacity of the units are limited.

These processes prefer solutions, or low solid content suspensions and medium viscosity. High viscous materials as high sugar or high fat formulations have to be diluted, what reduces the energy efficiency of the process.

Process Comparison

BRACE Microsphere Process The nature of the process leads to highly controllable diameters with very spherical particles. Very small particles (“Satellites”) or agglomerates are typically absent. As the droplets are solidified in a gas phase, they do not coagulate in the process or agglomerate, as they only touch each other when they are completely solidified. A screening at the end of the process is technically not necessary.

As the particle size can be precisely selected, the diameter range of ca. 50 µm up to more than 5 mm can be easily selected and adjusted by the process parameters.

LNF In the historically well known (gravity) dripping processes, the droplets are formed under gravity and their own weight and then enter the liquid nitrogen bath. Here not only the hard liquid-liquid impact on the surface leads to misshaped particles, but also the high temperature difference between the droplet and the liquid nitrogen. The Leidenfrost effect forms a turbulent vapor layer around the droplet that acts as layer of low heat transfer, so the solidification of the droplet is slow and changing permanently the shape. Due to the turbulent conditions, coagulation and agglomeration occurs frequently and rapidly. Low viscous feed tend to be destroyed and broken up uncontrollable into different sizes, while higher viscosity feeds lead to strings. Regular spherical particles form only a subgroup of various shaped product with many different sizes. According to literature the particle range achievable is ca. 2-4 mm, however this does not take into account the frequent disruption of the particles or the agglomeration. Screening at the end of the process is mandatory.

Downstream Processing

BRACE Microsphere Process Drying in a cooling tower not only guarantees a fixed time for the solidification under always identical conditions, but also the particle size is very narrow and no fines or agglomerates exist, so that tray filling or even fully continuous freeze drying is simple and economical to be implemented. As the particles have well known shape and size, the freeze drying process can be cut short and additionally some other particle properties like hardness, porosity and color of the particles can be controlled in this optimized drying process. In comparison to liquid filled trays, the cost savings in freeze drying can reach 50%.

LNF Produces particles in a liquid nitrogen bath, where they have to be removed from by mechanical means, such as a screw feeder. Especially fines or large agglomerates that are produced here naturally are difficult to removed from the bath and form a “sump” over time. Their freezing residence time is affected by the liquid level and flow rate, making precise control difficult. Differences in rapid-freezing duration between particles may produce uneven internal ice crystal structures and batch-to-batch variations in the finished product. Due to the agglomerates and fines produced in this process, the freeze drying process is significantly more difficult to control. As the maximum size of the agglomerates is unknown, the drying process has to run long and may even vary from load to load. Drying of e.g. high sugar containing material becomes uncontrollable and uneconomical.

Other Benefits

BRACE Microsphere Process These processes offer far more possibilities than simply making round particles. The full package includes an integrated solution covering equipment, formulation, process development and pilot testing and scale-up. Customizable encapsulation process packages are also available to address surface crust formation and pore blockage in high-solids materials.

As the technology offers a simple path to real core-shell Microcapsules in the same equipment, it is easy and simple to create new and unheard of products, products the market does not know yet how much it wants them!

Operating Costs Comparison

BRACE Microsphere Process uses a controlled cryogenic drop tower without evaporative losses associated with open liquid nitrogen baths and improve liquid nitrogen energy utilization. Reference liquid nitrogen consumption is approximately 1.2 kg/kg of wet feed. When then unit is temporarily stopped, little or no liquid nitrogen is used for maintaing the state.

Table 1 BRACE Microsphere Process Throughput and Liquid Nitrogen Consumption

Model	Capacity kg/h	Size	Liquid nitrogen use kg/h
Spherisator M2 Lab	50	Ø400	~100
Spherisator M2 Pro	200	Ø690	~380
Pilot Unit	500	Ø1000	~750
Production Unit	2000	Ø1400	~2400

LNF uses an open liquid nitrogen bath that continuously boils and evaporates. Liquid nitrogen must be replenished to maintain a stable liquid level and low-temperature environment, increasing operating consumption. According to the LNF model data, liquid nitrogen consumption is on or above 4.0 kg/kg of wet feed.

Table 2 LNF Series Throughput and Liquid Nitrogen Consumption

Model	Capacity kg/h	Size	Liquid nitrogen use kg/h
LNF-100	100	Ø500	400
LNF-220	220	Ø640	900
LNF-500	500	Ø900	2,000

Liquid Nitrogen Consumption at Equal Wet Feed Throughput

The comparison assumes a wet feed throughput of 500 kg/h for both systems, using 4.0 kg/kg for the LNF-500 and approximately 1.2 kg/kg for BRACE Fusion.

Table 3 Liquid Nitrogen Consumption at Equal Wet Feed Throughput

Parameter	BRACE Fusion	LNF-500
Wet feed throughput kg/h	500	500
Specific liquid nitrogen use kg/kg wet feed	Approx. 1.2	4.0
Liquid nitrogen use kg/h	Approx. 600	2,000
Liquid nitrogen savings kg/h	Approx. 1,400	—
Liquid nitrogen use reduction	Approx. 70%	—

Note: Approximately 70% refers to the reduction in liquid nitrogen consumption under these reference operating conditions. It does not represent the reduction in energy consumption across the entire production line.