Development of Vapor-Phase Catalytic Ammonia Removal System

A report describes recent accomplishments of a continuing effort to develop the vapor-phase catalytic ammonia removal (VPCAR) process for recycling wastewater for consumption by humans aboard a spacecraft in transit to Mars. The VPCAR process is implemented by a system of highly integrated design in which some power consumption is accepted as a cost of minimizing the volume and mass of a wastewater-processing system and eliminating the need to resupply water. The core of the system is a wiped-film rotating-disk (WFRD) evaporator, which removes inorganic salts and nonvolatile organic compounds from the wastewater stream and concentrates these contaminants into a recycle-and-bleed stream. The WFRD evaporator is also part of a subsystem that distills water from the wastewater stream. This subsystem operates in a vacuum-vapor/compression distillation configuration in the temperature range from 20 to 65 °C. Volatile organic compounds and ammonia, distilled along with water, are oxidized to CO2, H2O, and N2O in a packed-bed, high-temperature catalytic reactor placed at the outlet of the vapor-phase compressor of the distillation subsystem. A VPCAR engineering demonstration unit is expected to be included in a human-rated simulation of a mission to Mars.