The Thermo Scientific Flo-Cal online calorimeter continuously measures the gas heating value during feed forward control and high-speed gas blending operations and enables automatic control of auxiliary fuel additions during flare gas measurement. Capable of measuring in W obbe Index and Calorific V alue, this versatile instrument offers fast response and reliable operation, and is easy to maintain and calibrate. When installed in an enclosure, ambient temperature variations have a minimal effect on the system, and Modbus output capabilities ensure it integrates easily into plant control systems.
The flexible Flo-Cal has two basic modes of operation. The base system provides a Wobbe Index measurement (a meaningful measurement of the heating characteristics of the gas mixture) that takes into consideration the compositional changes within the gas mixture. To provide a Calorific V alue measurement, the base Wobbe Index unit must incorporate the Thermo Scientific Sarasota FD900 specific gravity (SG) meter , a highly accurate device that is based on the well accepted vibrating tube technology . It provides a continuous online SG measurement with accuracy to 0.1% of reading. This combination enables the Flo-Cal to reliably calculate Calorific Value, the heat value of the gas at standard conditions expressed as Net Heating Value, or the actual available heat value of the gas at standard conditions.
Sample gas and combustion air are metered and burned under closely controlled conditions. As the heating value of the sample gas changes, a constant exhaust temperature is maintained by precisely regulating the combustion air to the burner (i.e., air flow lower when heating value is higher; air flow higher when heating value is lower). These airflow variations are monitored and the intelligent pressure transmitter converts the pressure changes into the calculated output signals (4-20 mA and Modbus protocol) for the appropriate measurement range. Should the flame be extinguished due to a shortage of sample gas or combustion air , mechanical failure or electrical supply failure, a solenoid valve shuts off the sample gas supply. When all required conditions are established, the solenoid valve is opened and the burner is automatically ignited.