Production of ammonium sulfate granules using a vacuum absorption process.

About

Anaerobic digestion is increasingly applied to various organic wastes to stabilize organic matter and recover energy from biogas. Ammonia is often accumulated to a level that inhibits methanogenesis (i.e. the last step of anaerobic digestions), especially in anaerobic digestion of protein-rich substrates such as dairy manure and food waste. Moreover, disposal and treatment of digest effluent with high concentrations of ammonia presents an economic challenge and environmental risks. The present technology is a vacuum thermal stripping—acid absorption system that includes a stripping vessel and a gas absorption column. The coupling of vacuum thermal stripping with acid absorption allows for recovery of ammonia from digestate. When the ammonia recovery process is installed in a recirculation line of anaerobic digestion, ammonia inhibition to methanogenesis is prevented or the digesters can be loaded at higher rates of organic feedstock. Further, the technology provides for the combination of optimal parameters of boiling temperature and vacuum pressure that is critical to the efficiency and performance of the process. Meanwhile, ammonia in digestate is recovered as a commodity in the form of ammonium sulfate granules. Patent: U.S. 10,053,369 SUNY-ESF-2009

Key Benefits

(1) Digester heating can be eliminated providing minimal additional energy cost. (2) Enhancement of hydrolysis and prevention from ammonia inhibition, thus increasing methane production of anaerobic digestion. (3) Improvement of dewaterability of digester effluent. (4) No need for liquid/solid separation. (5) Process is lower cost, and simple operation with modular design and less occupational safety concerns.

Applications

Soil fertilizer

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