Continuous crystallization of energetic materials

COBC Technology Overview

COBC/R systems combine baffled and jacketed serpentine pipework with an oscillator system to provide uniform mixing, leading to very efficient heat and mass transfer. The net flow rate is independent of the high fluid velocity and excellent mixing created by the oscillation, allowing extended residence times under plug flow conditions.

Energetics materials with NiTech continuous oscillatory baffled crystalliser (COBC)


The combination of orifice baffles and oscillated process fluid flow create eddies between the baffles, providing a uniquely efficient mixing environment that enhances heat and mass transfer rates. The efficient heat and mass transfer speed up the process and ensure a consistent processing environment, while the jacketed pipework provides a large surface area for heat transfer to the process medium. For a typical cooling crystallization process, temperature zones are set up along the length of the COBC, starting from high temperature (at the start of the COBC) through to low temperature (at the end of the COBC). The modular nature of the serpentine pipework means there is a high degree of flexibility in configuring temperature zones for both crystallizations and reactions.

This is the essence of the NiTech Solutions COBC/R system: optimal heat transfer combined with uniform mixing, ensuring you can make right product first time, every time, allowing kinetic (theoretical) reaction times obtained in labs to be delivered at pilot and full scale.

Application overview

Historically, batch processing has been the preferred way to perform crystallization operations. Many established industries are burdened with legacy batch process equipment as a result.

Batch processing of energetics not only has the same processing issues as for other compounds (temperature and concentration gradients), but carries additional safety concerns due to the explosive and sensitive nature of the compounds concerned. Having large quantities of energetic material along with solvent in-process presents an opportunity for any safety incident to become catastrophic.


Energetic materials – batch manufacturing issues and COBR benefits


An increased focus on process safety and flexible manufacturing in the energetics sector has led to reinvestment in production facilities to modernise the industry.

Continuous crystallization using NiTech COBC technology tackles many of the issues associated with batch processing by offering a platform that is significantly smaller in footprint and reactor volume, as well as providing enhanced heat and mass transfer and uniform processing conditions. The reduction in size and volume improves process safety by ensuring only a small quantity of energetic material is in-process at any given time. The superior heat and mass transfer conditions give potential for the production of crystals with higher purity and more consistent particle size, ultimately leading to enhanced end-use performance of the energetic materials produced.

Equipment for continuous crystallization of energetic materials

NiTech can design processing solutions across a range of scales for the continuous crystallization of energetics.

Energetics manufacture with NiTech Solutions DN15 Lite

The DN15 range offers a range of opportunities for small-scale process development work on safer compounds and chemistries.

Energetics manufacture with NiTech Solutions DN15 MAX Series

For more hazardous compounds and processes, the DN15 MAX Series provides a DN15 crystallizer with the required ancillary equipment (pumps, valves, heaters, etc.) and a single interface control system capable of remote operation.

Results from small-scale equipment can be used to design bespoke units for pilot- or production-scale with the ability to produce in the tonne/day range.

Example processes

NiTech Solutions COBC technology has proven capability to crystallize both solid oxidisers and explosives. For both material types the processing conditions were adjusted to manipulate the product properties – specifically particle size and particle size distribution. For best results the crystallizations require seeding to provide an additional level of control over the product particle size and distribution.

In the case of solid oxidiser, the product particle size can be manipulated through seed size and or seed loading. Seed size has shown the largest impact on particle size manipulation, the use of small seeds giving a smaller product and large seeds giving a larger product. Seed loading was utilised to ensure controlled growth and maintain narrow particle size distributions, a property which is valuable for the formulation and mixing of solid rocket propellants.



Crystallization of a high explosive has been validated and it has been demonstrated that product properties can be manipulated by seed size, seed loading and cooling rate. As with the solid oxidiser crystallization, seed size can be used to control and manipulate product properties, with small seeds giving smaller crystals and large seeds producing large product crystals. Seed loading was also used to manipulate the product particle size and distribution. When using a high seed loading, seed growth was limited, giving product with a consistent size and regular particle shape. Low seed loading leads to higher growth and larger particle size with less consistent particle shapes.



Continuous flow crystallization allows for the use of processing conditions that cannot be practically implemented at scale in batch processing. One of these conditions is fast cooling, which can be easily implemented in a NiTech Solutions COBC due to the exceptional heat transfer. In the case of a high explosive processed using a rapid cooling rate, it was observed that unique particle shapes with advantageous properties for energetics (safer handling, reduced sensitivity, etc.) were produced.

Features and Benefits of COBC for energetics manufacture


Low crystallizer volume

Small system footprint

High production rates

Optimal yields (~95% of theoretical yield)

Consistent product quality (particle size and purity)

Particle engineering of crystal size and shape

Modular crystallizer design

Simple linear scale-up to larger throughputs

C1D1/ATEX-certified units available


Smaller and safer manufacturing facilities

Distributed or mobile manufacturing

Produce kilos to multi-tonnes of energetic material per day

Maximising manufacturing efficiency

No batch-to-batch variability

Remove downstream particle processing such as grinding

Flexible configuration of production systems

Lower development costs

Rated for use in hazardous environments