Dynamic Simulation of Natural Gas Filter Separator Depressurization
127
3.2 Calculation of Discharge Temperature by Standard Method
The calculation formula for the gas discharge amount when exposed to open fire given
in API 521–2014 can be used to calculate the operating temperature when the natural
gas filter separator reaches the safety valve set pressure. The calculation formula is
T 1 =
P 1
P n
× T n
(1)
T 1 is the corresponding relief temperature at the relief pressure, K; T N is the normal
operating temperature, taken to be 293.15 K; P N is the absolute pressure under normal
operation, taken to be 1401.325kPa; P 1 is the absolute pressure when the safety valve
is opened, 1801.325 kPa. The discharge temperature of the filter safety valve in the
discharge state can be calculated by using the above data in Formula (1), resulting in a
value of 103.7 °C.
3.3 Calculation of Discharge Temperature by Dynamic Simulation
The basic assumptions for calculating the discharge temperature of the natural gas filter
separator using the dynamic simulation method are as follows:
a) The environment starts to catch fire at 0s. When the pressure reaches 1700 kPaG,
the safety valve opens to relieve the system pressure.
b) According to API 521–2014, the external surface temperature of vessel wall after
fire is considered to be 593 °C.
Fig. 3. Pressure and temperature curves of natural gas filter separator
It can be seen from Fig. 3 that when the operation time is 219 s (about 3.6 min), the
operating pressure of the system reaches 1700 kPaG, and the operating temperature of
the system is 98.0 °C.
127
3.2 Calculation of Discharge Temperature by Standard Method
The calculation formula for the gas discharge amount when exposed to open fire given
in API 521–2014 can be used to calculate the operating temperature when the natural
gas filter separator reaches the safety valve set pressure. The calculation formula is
T 1 =
P 1
P n
× T n
(1)
T 1 is the corresponding relief temperature at the relief pressure, K; T N is the normal
operating temperature, taken to be 293.15 K; P N is the absolute pressure under normal
operation, taken to be 1401.325kPa; P 1 is the absolute pressure when the safety valve
is opened, 1801.325 kPa. The discharge temperature of the filter safety valve in the
discharge state can be calculated by using the above data in Formula (1), resulting in a
value of 103.7 °C.
3.3 Calculation of Discharge Temperature by Dynamic Simulation
The basic assumptions for calculating the discharge temperature of the natural gas filter
separator using the dynamic simulation method are as follows:
a) The environment starts to catch fire at 0s. When the pressure reaches 1700 kPaG,
the safety valve opens to relieve the system pressure.
b) According to API 521–2014, the external surface temperature of vessel wall after
fire is considered to be 593 °C.
Fig. 3. Pressure and temperature curves of natural gas filter separator
It can be seen from Fig. 3 that when the operation time is 219 s (about 3.6 min), the
operating pressure of the system reaches 1700 kPaG, and the operating temperature of
the system is 98.0 °C.