Preparation of Ultrafine Nitroguanidine by One-Step Crystallization in an Impinging Stream-Rotating Packed Bed

Abstract

To solve the problems of the traditional production process of ultrafine nitroguanidine (NQ), such as a long process and easy pollution caused by recrystallization, the ultrafine NQ (2−6 μm) was prepared by the one-step crystallization in an impinging stream-rotating packed bed (IS-RPB). The influence of operation parameters on the size of the NQ crystal was discussed through various particle size characterization methods. Results show that the size of ultrafine NQ prepared in the IS-RPB was 2.0−3.0 μm, which was smaller than that of market products and conformed to the military standard. Simultaneously, the crystal morphology tended to reduce the length, meeting the target requirement of "shorter and thicker" high-end products. The role of high dispersion and strong mixing in the IS-RPB was the key to continuous and one-step nucleation and crystallization of NQ. One-step crystallization in the IS-RPB is a push flow operation process, where abundant accumulation of the raw material will be avoided effectively, and the safety of energetic material processing will be enhanced greatly. Ultrafine NQ can be prepared without recrystallization, which greatly reduces the energy consumption and the pollution of organic impurities to the product and the environment, providing a new way for the continuous production of ultrafine NQ.

Effect of particle size distribution on the cryogenic mechanical properties of triple‐base propellants

“…In the case of NQ, significant progress has been made in the preparation of spherical, controllable, and densely packed low-sensitive NQ through solvent recrystallization. 37 Furthermore, from a theoretical standpoint, reducing the particle size and achieving a spherical morphology can potentially mitigate internal defects within NQ crystals, as well as minimize the formation of stress concentrations and voids at the interfaces when combined with the matrix. Extensive research has been conducted on the thermal properties of NQ with different particle sizes, as well as the combustion performance of triple-based propellants.…”

“…Nanosizing methods for high‐energy explosives encompass a wide range of techniques, including ball milling, 35 electrostatic spraying, 36 etc. In the case of NQ, significant progress has been made in the preparation of spherical, controllable, and densely packed low‐sensitive NQ through solvent recrystallization 37 . Furthermore, from a theoretical standpoint, reducing the particle size and achieving a spherical morphology can potentially mitigate internal defects within NQ crystals, as well as minimize the formation of stress concentrations and voids at the interfaces when combined with the matrix.…”

Preparation and Characterization of Ultrafine Nitroguanidine with Different Aspect Ratios

“…In recent years, the main ways to improve the mechanical properties and thermodynamic stability of NQ have been through physical and chemical methods, with ultrasonic pulverization, grinding refinement, and impact crushing refinement as the main physical methods and solvent–nonsolvent recrystallization refinement and microemulsification refinement as the main chemical methods. − The use of physical methods for pulverization suffers from the shortcomings of safety, energy consumption, and the difficulty of controlling the crystal size distribution and the regularity of the crystal shape. The recrystallization of NQ by chemical methods increases the unsafe factor due to the volatility and combustion of organic solvents such as DMF, NMP, and acetone, as well as the consumption and recycling costs of solvents and new sources of pollution.…”