PMI Ammonia Removal and Recovery Technology
|Above: PMI Ammonia Removal and Recovery schematic.|
A major challenge that impacts the ash industry is ammonium sulfate deposition in fly ash. Whether from ammonia slip from NOx control devices (SCR, SNCR), or from use to increase the efficiency of electrostatic precipitators, or most recently, from efforts to control blue plume, higher levels of ammonium sulfate is ending up on the fly ash. This ammonia does not affect the performance of the fly ash in concrete. However, fly ash with high ammonium sulfate levels, when mixed with Portland cement and water in the concrete mix, can release substantial quantities of gaseous ammonia which, in some cases – especially in enclosed areas, can reach dangerous concentrations.
|Above: PMI Ammonia Removal and Recovery Pilot Plant.|
To bring the process to commercial-ready status, PMI built a pilot plant at the Crystal River Power Plant facility. The pilot plant confirmed the earlier data and process design, at a scale which allowed reasonable scale up to a commercial size. It also allowed optimization of the key temperature and residence time parameters. Finally, pilot plant stack gas testing was performed to confirm the composition of the gas being returned to the power plant.
PMI’s Carbon-Burn Out technology effectively handles ammonia for higher LOI fly ashes. However, for fly ashes with low carbon content and high levels of ammonia, development of another technology was needed. Using the lessons learned during the CBO development and other small scale testing, PMI engineers developed and patented such a process. This process is based on the fact that the ammonium sulfate can be made to release the ammonia in gaseous form by exposing the ash to a suitable temperature for a suitable residence time.
Additionally, a substantial portion of the ammonia can be recovered and reinjected into the boiler gas stream for reuse of the ammonia. Additionally, the heat required for the process is minimal, less than 0.25 percent from the power plant.
|Above: PMI Ammonia Removal and Recovery Commercial Plant.|
Using data generated from the pilot plant, a preliminary design was developed to provide layout, interface and other technical data as well as a preliminary design level capital cost estimate for full scale commercial facility. PMI is actively looking for candidates for the first commercial facility.
For more information on the technology and its development, please contact us.