Method of estimating gas emission amount

A method of estimating a gas emission amount from a storage tank for storing a liquid containing volatile compounds therein, the method comprising:

• a first step of setting preconditions relating to:
• (a) a tank shape of the storage tank of fixed roof type including a relief valve;
• (b) a working pressure of the relief valve;
• (c) thermodynamic physical properties of the liquid inside the storage tank;
• and (d) thermodynamic physical properties of a gas inside the storage tank;
• a second step of setting initial conditions for a storage volume, a temperature, and a pressure for each of the liquid and the gas inside the storage tank;
• a third step of obtaining a mass transfer amount between the liquid and the gas by determining an inflow heat quantity to or an outflow heat quantity from the liquid and the gas through a partition wall of the storage tank and calculating a change in temperature of the liquid and a change in temperature of the gas and a change in vapor-liquid equilibrium condition through computational fluid dynamics analysis;
• and
• a fourth step of obtaining a pressure change of the gas based on the mass transfer amount so as to obtain the gas emission amount vented through the relief valve when a pressure of the gas after the pressure change exceeds a working pressure of the relief valve.