In the CALORIX™ system, biogas is burnt at near atmospheric pressure in a combustion chamber, which is mounted in the center of a stainless steel tank and suspended from the roof. A burner on the roof of the tank projects a downward flame into the combustion chamber. The tank is partially filled with wastewater, with the hot flame tip staying just above the water’s surface.
Hot exhaust gases are deflected by the water surface to the annular space around the central combustion chamber. Wastewater is sprayed around this vast, annular headspace for heating, thereby cooling the combustion chamber from the outside and cooling and washing the exhaust gases. The wastewater is circulated from the bottom of the tank to the headspace by a centrifugal pump and a set of non-clog spraying nozzles.
Freshly-screened, cold wastewater continuously enters the tank. It is heated within minutes and flows out of the tank by gravity over a constant level weir. Virtually all the combustion heat is transferred from the exhaust gas to the wastewater. Extra heat is recovered through water condensation, resulting in more than 100% efficiency (expressed as a lower heating value). Dust particles, NOx and SO2, are also primarily absorbed and dissolved in the water, making the CALORIX™ unit an exceptionally clean heating system, and allowing it to avoid much of the permitting issues associated with large boilers.
The cooled exhaust gas (40-60°C) can be discharged into the air or into the wastewater treatment plant’s foul air collection system for odor control.
The CALORIX™ unit operates fully automatically, with programmed start, stop, and emergency stop sequences. The burner is a modulating type, taking a continuous flow of biogas over a wide capacity range (25-100%). The combustion air flow is controlled as a function of the variable biogas flow, so as to give a constant air to biogas ratio. Natural gas or propane can be fired as an alternative fuel as well, e.g. during plant start-up, when no biogas is available yet.
Industries and applications: as an anaerobic treatment of the various industry wastewater streams, including breweries, soft drinks & other beverages production, paper mills, starch production, and many more.