DILUTION OF OXYGEN CONCENTRATION IN AMBIENT TEMPERATURE ROCK-BED UNDERGROUND STORAGE TANK

摘要

PURPOSE:To lower the concentration of oxygen in a rock bed underground storage tank, by burning a combustible substance using the air in the ambient temp. rock bed underground storage tank storing liquid fuel. CONSTITUTION:A burner 2 is mounted to the leading end of the fuel pipe 11 arranged in a rock bed underground storage tank 1 and ignited by an igniter 3. Ignition is confirmed on the ground by a flame detector 4. The rise in pressure and rise in temp. within the rock bed underground storage tank 1 by the combustion of the fuel are monitored on the ground by a pressure gauge 6 and a thermometer 8. Since the rock bed underground storage tank 1 is in a hermetically closed state, the lowering in the concentration of oxygen in the storage tank by combustion with the elapse of time is similarly monitored on the ground by a gas analyser 10. When the pressure and temp. in the rock bed underground storage tank 1 reach prescribed values or more, the combustion of the fuel is interrupted and, after it is confirmed that the pressure and temp. lower to the prescribed values or less by natural cooling, the fuel is again burnt on the basis of the above mentioned procedure. This operation is repeatedly performed to lower the concentration of oxygen in the rock bed underground storage tank 1 to the initially set concn. safe to the storage of the liquid fuel to be stored.