P.C. Dell'Orco’s research while affiliated with Los Alamos National Laboratory and other places

In this work, we present model-based control and estimation algorithms developed to control the effluent composition for a hydrothermal oxidation reactor. The reactor is used to oxidize the organic compounds present in the hydrolysate solutions obtained from the destruction of HMX-based high explosives by base hydrolysis. The objective of the model-based control is to minimize the total amount of aqueous nitrogen compounds in the effluent of the reactor while maintaining the desired excess oxygen concentration in the reactor to ensure the complete destruction of the organic carbon compounds. A novel aspect of the controller design for this reactor is that the total aqueous nitrogen effluent concentration is locally uncontrollable at the desired optimal operating conditions. The controller uses a plug-flow reactor model with a reduced kinetic model describing the oxidation - reduction reactions in the hydrothermal oxidation reactor. Simulation and reactor implementation results are used to verify the closed-loop control algorithm.

Sodium carbonate (Na2CO3) is identified as a hydrolysis reagent for decomposing HMX and HMX-based explosives to water-soluble, nonenergetic products. The reaction kinetics of Na2CO3 hydrolysis are examined, and a reaction rate model is developed. Greater than 99% of the explosive at an initial concentration of 10 wt % PBX 9404 was destroyed in less than 5 min at 150 °C. The primary products from Na2CO3 hydrolysis were nitrite (NO2), formate (HCOO-), nitrate (NO3-), and acetate (CH3COO-) ions, hexamethylenetetramine, (hexamine:  C6H12N4), nitrogen gas (N2), nitrous oxide (N2O), and ammonia (NH3). The rate of hydrolysis was characterized for HMX powder and PBX 9404 molding powder from 110 to 150 °C. The rate was found to be dependent on both the chemical kinetics and the mass transfer resistance. Since the HMX particles are nonporous and external mass transfer dominates, gas−liquid film theory for fast chemical kinetics was used to model the reaction rate.

This paper describes the model-based control algorithm developed for a hydrothermal oxidation reactor at the Pantex Department of Energy facility in Amarillo, Texas. The combination of base hydrolysis and hydrothermal oxidation is used for the disposal of PBX 9404 high explosive at Pantex. The reactor oxidizes the organic compounds in the hydrolysate solutions obtained from the base hydrolysis process. The objective of the model predictive controller is to minimize the total aqueous nitrogen compounds in the effluent of the reactor. The controller also maintains a desired excess oxygen concentration in the reactor effluent to ensure the complete destruction of the organic carbon compounds in the hydrolysate