The objective of this project was to develop a method by which the Holston Army Ammonium Plant (HSAAP) Ammonium Nitrate Solution (ANSOL) waste could be processed to recover the dissolved ammonium nitrate and allow for its reuse to make fresh hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). This would be achieved through the concentration of the ANSOL material, recrystallization of the crude ammonium nitrate solids, and using the purified ammonium nitrate in RDX and HMX reactions.

The first task was to identify an efficient and robust process for isolating pure solid ammonium nitrate from HSAAP ANSOL. The purification of the ammonium nitrate from ANSOL built upon previously conducted research that identified viable purification options in order to yield pure, solid ammonium nitrate for reuse. The second objective was to evaluate the utility of this ammonium nitrate in the RDX and HMX synthesis processes that are currently used in production at HSAAP. To complete this task, the ammonium nitrate was used directly in laboratory scale syntheses reactions designed to mimic the production scale process. The synthesized nitramines were purified via recrystallization and evaluated per their respective military specifications (excluding particle size).

The isolation of ammonium nitrate from ANSOL was achieved using a three-step process: (1) filtration of the ANSOL material to remove suspended solids; (2) concentration of filtered sample to crystallize crude ammonium nitrate solids from solution; and (3) purification of crude ammonium nitrate by recrystallization and solvent washing. Final ammonium nitrate solids having a purity of >99.5 wt% ammonium nitrate were isolated using the process. The recovered ammonium nitrate solids were then used to produce the nitration reagent used to make RDX and HMX. Multiple adjustments of this solution were required to meet the desired chemical composition. Once the nitration reagent was generated successfully, it was used to synthesize both RDX and HMX. Characterization of the final solids showed that both RDX and HMX were produced which met their respective MIL-SPEC requirements. Extrapolating the designed process to full scale, it was estimated that the entire ANSOL waste stream could be consumed, allowing for a significant improvement in the environmental impact of operating the HSAAP facility.

The successful isolation of ammonium nitrate from ANSOL waste, and its subsequent use in the synthesis of RDX and HMX represents a promising solution to environmental and economic challenges associated with the disposal of ANSOL waste. The isolation and purification of ammonium nitrate from ANSOL Final Sludge using the method described in this study is a simple and cost-effective approach that can be easily scaled. Additional work will be required in a Phase II effort to improve ammonium nitrate yields, optimize preparation of the nitric acid/ammonium nitrate reagent, and further improve the process waste profile.