Thermal Energy Requirements
The BeneVap units are extremely energy efficient consuming 2.9-3.1 MJ of energy per litre of water evaporated (10,400-11,100 BTU/gal). The smaller BV150 units require half the energy input at approximately 3.04 GJ/h (2.88 MBTU/h) to evaporate 25 kL/d (design capacity, 6,604 gal/d) and the larger BV300 units require approximately 6.08 GJ/h (5.76 MBTU/h) to evaporate 50 kL/d (design capacity, 13,208 gal/d). These values will vary according to operating conditions and wastewater concentrate quality and density, as well as over the concentration batch cycle time. The design of the combustion chamber, concentration vessel, the turbulent vessel environment and stack design all play a role in the heat transfer and energy efficiencies achieved with the BV units.
The BeneVap units can operate on a number of gaseous and liquid fuels including natural gas, biogas, landfill gas (LFG), liquefied petroleum gas (LPG) and fuel oil (diesel #2), as well as with a combination of these fuels. The BeneVap units can operate on LPG or be supplemented with LPG if the LFG energy value and volumes are insufficient to achieve the desired evaporation rates. LPG has a much higher calorific value than natural gas, approximately 2.4 times more energy per standard cubic metre depending on the particular mixture of propane and butane. As a result, the gas flow rates are reduced when operating on LPG with the energy flow rates being maintained to achieve design evaporation rates.
The electrical requirements for the BeneVap units vary between models and if the gas supply pressure is insufficient, such as in landfills, a gas blower skid is required to boost the pressure and this draws additional electrical power. All equipment operates on three phase voltage provided either by electrical mains or through a generator. The BV300 has a full load amp power draw of 63 kW with a maximum run load power draw of 52 kW. The BV150 has a full load power draw of 45 kW with a maximum run load power draw of 39 kW. The gas blower skid for landfill gas (typically 50% methane) has a full load power draw of 24 kW, with a maximum run load amp draw of 19 kW.