Development and Latest Research in New Spray Drying Technology

As the mechanisms of spray drying continue to be studied and the technology finds widespread application across various industries, this article reviews recent research achievements in spray drying both domestically and internationally.

1. Spray Freeze Drying Technology

Since the introduction of spray freeze drying by Werly et al. in 1964, this technique has advanced rapidly across various fields. Spray freeze drying combines spray technology with freezing techniques. Initially, droplets are frozen into ice particles using cooling media like liquid nitrogen, followed by drying to dehydrate these frozen particles into a powder.

Particles obtained through spray freeze drying have superior morphology compared to those from traditional spray drying or freeze drying. This method produces droplets with a well-distributed size, and the moisture in the solution leaves tiny channels within the particles during the freeze-drying process. This micro-porous structure increases the specific surface area, significantly enhancing the wettability and solubility of the product. Because it operates at low temperatures, it is particularly suitable for drying heat-sensitive materials and has been widely adopted in food and pharmaceutical research.

To improve the solubility and bioavailability of azithromycin, Adeli et al. used spray freeze drying to prepare solid dispersions of the drug. Their analysis showed that the dissolution rate of azithromycin produced by this method was higher than that of azithromycin produced by conventional spray drying, with an improvement in dissolution rate by 8.9 times.

Jae-Young Her et al. employed spray freeze drying to create a probiotic powder with a survival rate of up to 97.7%, which also exhibited a large specific surface area.

S. PadmaIshwarya et al. evaluated the physicochemical properties and aroma quality of soluble coffee processed by spray freeze drying. Their results indicated that coffee processed by this method retained the aroma of low-boiling aromatic compounds, providing good flowability and instant solubility, thus giving it a significant competitive advantage over similarly processed products.

2. Superheated Steam Spray Drying Technology

Superheated steam spray drying utilizes superheated steam at temperatures above the corresponding saturation temperature at a given pressure to directly contact and dry materials. Compared to traditional hot air drying, superheated steam has a higher specific heat capacity, requires less quantity, and dries materials faster. This method boasts high thermal efficiency, good drying quality, no risk of oxidation or explosion, and significant energy savings.

Zhang Zhihui et al. prepared powders using both hot air and superheated steam drying methods, finding that the powders produced with superheated steam exhibited numerous uniform micro-pores on the rubber surface, with relatively stable molecular weights.

V. V. Sidorchuk et al. used hot air and superheated steam spray drying to create microspherical aerosols. They discovered that the superheated steam method yielded particles with more uniform sizes compared to hot air spray drying.

Yonggun Park et al. evaluated the energy-saving effects of combining hot air and superheated steam drying, revealing that hot air spray drying achieved energy savings of 46% to 51%, while the combined method improved savings to 77% to 82%.

3. Nano Spray Drying Technology

Nano spray drying technology is primarily applied in the preparation of nanoparticles for pharmaceuticals. Compared to micrometer-sized particles, nanoparticles have a larger specific surface area, resulting in higher drug dissolution rates and bioavailability, making this technique particularly suitable for the production of poorly soluble drugs.

The B90 nano spray dryer developed by Swiss company Buchi can directly produce drug particles sized between 0.3 to 0.5 μm. The equipment includes a high-frequency vibrating atomizer, laminar flow heater, and high-pressure electrostatic collector.

In the nano spray dryer, liquid passes through an electrically driven vibrating mesh atomizer, forming fine droplets that are dried in a drying chamber to produce solid particles, which are then collected by an electrostatic dry powder collector.

Traditional spray drying generally employs pressure atomizers to spray liquid into hot air, followed by cyclone separation to collect solid particles, achieving yields of about 30% to 50%. In contrast, nano spray dryers use high-pressure electrostatic collectors to gather solid particles, achieving yields of over 90%.

Zhou Yang et al. used nano spray drying to prepare a micro powder of fresh rehmannia oligosaccharides with a drug loading of 30%, a yield of 89%, and good moisture absorption properties.

Taoran Wan et al. applied nano spray drying technology to produce solid lipid nanoparticles and nanostructured lipid carriers, successfully transforming the resulting lipid colloidal particles into solid powders that were aggregated, with small, uniform spherical particles.