# Optimization of Droplet Granulation Process for HNS-IV Explosives Utilizing Pulsed Air-Jet Shear Technology

## TL;DR

This study introduces a pulsed air-jet shearing method to precisely control the granulation of HNS-IV explosives, resulting in safer and more efficient production.

## Contribution

A novel pulsed air-jet shearing strategy for precise control of HNS-IV granulation with reduced solvent accumulation.

## Key findings

- Median particle sizes of 375.84 μm, 444.45 μm, and 504.22 μm were achieved by adjusting suspension flow rate.
- Increased calcium alginate content improved particle sphericity but altered thermal decomposition behavior.
- The method reduces volatile solvent accumulation and allows for easy management of non-toxic aqueous solutions.

## Abstract

To achieve precise control over droplet size and generation frequency in the granulation process of HNS-IV, this study introduces a novel droplet granulation strategy that utilizes pulsed air-jet shearing technology. This approach enables independent and precise regulation of droplet injection frequency (fg) and volume (V) through systematic adjustments of air pressure (P), frequency (fp), duty cycle (η), and liquid flow rate (Q). By controlling the suspension flow rate (Q), we successfully achieved primary particle size control, obtaining median particle sizes (D50) of 375.84 μm, 444.45 μm, and 504.22 μm in ascending order. Furthermore, we systematically investigated the influence of calcium alginate (CA) concentration on both the sphericity of the resultant particles and the thermal decomposition characteristics of HNS microspheres. Our findings demonstrate that while increased CA content enhances particle sphericity, it simultaneously affects the thermal decomposition behavior of the microspheres. The proposed pulsed air-jet shearing method offers significant advantages by significantly reducing the accumulation of volatile organic solvents typical of liquid–liquid biphasic systems. Furthermore, the residual non-toxic aqueous solutions can be easily managed, establishing a greener, safer, and highly controllable approach for HNS-IV granulation. This methodology presents a valuable reference for achieving precise and controllable granulation of various energetic materials.