Development of an Ammonia Generator for Demonstration Tests

Exhausts gases from industries and agriculture mainly contain water, carbon dioxide, and ammonia. Several studies have focused on the recovery and effective utilization of low concentrations of ammonia from these exhaust gases to reduce the environmental impact of nitrogen compounds. To effectively study the recovery and utilization of ammonia from exhaust gases, it is important to simulate these gases in the laboratory. In this study, an apparatus was developed that generated ammonia, water, and carbon dioxide at low concentrations by volatilizing an aqueous ammonium bicarbonate solution. The concentration of ammonia produced was evaluated by varying the concentration, pH, temperature, and contact area between the gas and the aqueous ammonium bicarbonate solution. A linear relationship between the concentration of free ammonia in the ammonium bicarbonate solution and that generated in a low-concentration range. In the laboratory experiment, when the concentration of free ammonia was 7.0 mmol/L, generated ammonia volatilized at 0.0028 mL/min per cm2 of the contact area. Furthermore, the volatilization of ammonia and carbon dioxide converged at a pH of ∼8.6, and the concentration of volatilized ammonia stabilized. Based on these results, an apparatus was developed to generate approximately 40 ppmv ammonia at an airflow rate of 700 m3/h. Furthermore, the ammonia adsorbent developed was tested for adsorption. Consequently, the experiment was able to continuously generate ammonia for 120 h., and the adsorbent could adsorb approximately 1.8 mmol of ammonia per gram in the presence of water vapor and carbon dioxide.