Crystallization of RDX by Drowning-Out Combined with Fines Dissolution and Cooling Process

Abstract

A new process of drowning-out combined with fines dissolution and cooling crystallization (the DFC process) was proposed to recover 1,3,5-trinitro-1,3,5-triazinane (RDX) from RDX/γ-butyrolactone solution with relatively large crystal size and high yield. In this process, fine crystals induced by drowning-out are dissolved into the solution by heating so that the dissolved solute can contribute to grow seed crystals by cooling. The DFC process is repeated to reach the desired yield. Estimation of the amount of antisolvent for drowning-out is made by a simple mass balance model in which the mass of fine particles produced by drowning-out equals to that dissolved. Considering dissolution of seeds at the fines dissolution stage, an empirical parameter α which is smaller than 1 was employed for the estimation of the optimum amount of antisolvent added. α = 1 indicates that effect of dissolution of seeds is negligible. In the present work, initial seeds were prepared by rapid injection of 15 g of water into a saturated RDX/γ-butyrolactone solution of 30 °C. Heating temperature for fines dissolution and cooling temperature for further crystal growth were 40 and 20 °C, respectively. In those operating conditions with α = 0.8, the average crystal size of RDX with the yield of 90% was 67.6 μm, which was a remarkably improved result when compared with that of 40.4 μm by drowning-out only.

Preparation of PbS nano‐microcrystals with different morphologies and their optical properties

“…Recently, great efforts have been devoted to the morphological control and assembly of semiconductor nanocrystals of metal sulfides [2].…”

Study on crystallization kinetics and the crystal internal defects of HMX

“…M T can be calculated as M T = ( m 2 − m 1 )/ V ( m 1 , m 2 , V are, respectively, the weight of filter cake, the weight of filter, and the sampling volume). In the present work, k V = 0.11 was obtained by the method reported previously 17.…”

Evaluation of nucleation rate by in‐situ focused beam reflectance measurement in an unseeded batch cooling crystallization

“…The average crystal size was calculated by measuring the characteristic lengths of more than 500 crystals from the optical micrographs (OPTIPHOT2‐POL, Nikon, Japan). The total number of crystal per unit volume of solution N T was calculated by the following equation where V S is the volume of solution in a batch crystallizer, M T is the total mass of crystals in one batch, f V and ρ c are the volume shape factor (0.38 in this experiment) and the crystal density (1.82 × 10 6 g m −3 ), respectively. The volume shape factor is defined as f V = M /( ρ c L 3 ), where M and L are the mass and the characteristic length of a crystal, respectively.…”

“…Solution crystallization processes are widely used to control the physical properties of solid products in many fields of science and technology such as pharmaceutics, agricultural chemistry, food science, pigments or energetic materials . In the unseeded crystallization, crystals induced by primary nucleation become the first source of solid body that grows, and secondary nucleation affects the population density of crystal during the growth stage . Kinetics of nucleation is also responsible for morphology and defects of growing crystals because the total surface area of growing crystals is proportional to the total number of crystals .…”