Material selection and system process of propane full tank

Material selection of main vessel and secondary vessel: according to the basic design requirements of bimetal full tank operation conditions, a537cl2 steel plate is selected for main vessel and secondary vessel.

Material selection of low temperature pipe fittings: low temperature liquid phase and gas phase pipes of the equipment (from the hanging roof to the junction point, including the inlet and outlet pipes of nitrogen purging in the interlayer space, etc.), all materials are low temperature seamless steel pipes, and the material is 09mnd.

Selection of materials for normal temperature pipes and fittings of equipment: carbon steel pipes and fittings at normal temperature are made of grade 20, and the executive standard is GB / t8163-2018 seamless steel pipes for fluid transmission. Pipe fittings are made of grade 20, and the executive standard is GB / t12459-2017 steel butt welded seamless pipe fittings.

System process overview

◆ The liquid propane from propane unloading platform is sent to propane full capacity tank for storage through low temperature cold insulation pipe. The liquid propane is output by propane submerged pump, the flash gas (bog) generated by propane storage tank is recovered by bog system, and the gas after safety valve enters into flare through EAG system.

Liquid inlet and purging system

◆ Liquid inlet system: liquid propane from propane liquefaction unit or unloading platform is sent to 85000m through low temperature process pipeline ³ Propane can be stored in the tank through the top liquid inlet pipeline or the bottom liquid inlet pipeline. The top liquid inlet pipeline and the bottom liquid inlet pipeline need to be equipped with remote control emergency shut-off valve.

◆Purging system: the normal temperature and low pressure nitrogen from the process unit area enters the main vessel through the purging ring pipeline set in the main vessel, enters the bottom insulation layer of the storage tank through the nitrogen purging pipeline of the bottom insulation layer, and enters the pump well of the submerged pump through the submerged pump purging pipeline, so as to ensure the air replacement at all corners of the storage tank and the drying of the internal insulation materials, In addition, a nitrogen purge and exhaust pipeline is arranged at the top of the secondary vessel, a purge and exhaust pipe is arranged at the bottom insulation layer, and an annular exhaust pipe is arranged in the interlayer space to discharge the replacement air during purging.

Tank discharge and return system

◆Liquid out of storage tank (gasification or loading): the storage tank is equipped with two submerged pumps. The discharge pipes of the submerged pumps are equipped with remote low-temperature shut-off valve, propane orifice flowmeter, and return pipeline after the pump. After the discharge pipes of each pump column are led out, check valve and root stop valve are installed respectively, and then the discharge pipes are summarized (one orifice flowmeter and one low-temperature shut-off valve are installed on the discharge pipe).

◆The submersible pump is equipped with a return pipeline after the pump, and a low-temperature regulating valve is set on the return main pipeline after the pump. This pipeline is used as the start-up pipeline of the submersible pump, and it can prevent the tank from rolling, so it can start the pipeline to circulate the low-temperature liquid inside the tank.

Bog recovery system

◆ When the gas phase pressure in the storage tank rises to 10-13kpa (which can be adjusted according to the process package), the low temperature automatic control valve will be opened and the gas will be discharged into the bog heater or low pressure flare to balance the pressure in the storage tank; When the gas-phase pressure in the tank drops to 10KPA (which can be adjusted according to the process package), the low-temperature regulating valve is closed to maintain the tank pressure within the safe range.

Air supply system

◆If the gas phase pressure in the storage tank drops to 2KPa, the low temperature automatic control valve on the gas replenishment pipeline will be opened. When the pressure of the storage tank rises to 5kpa, the gas replenishment will be stopped (fine adjustment can be made according to the liquefaction process package) to keep the pressure of the storage tank in a safe range.

EAG to torch

◆ When the gas phase pressure in the storage tank is higher than 14kpa, the regulating valve to the flare is opened, and the gas inside the storage tank is discharged into the low pressure flare system to ensure the safety of the storage tank.

Safety control pipeline

◆The pressure and vacuum relief valve is an integral part of the tank. Two sets of safety vent pipelines are set at the top of the storage tank, and two sets of pressure relief valves are equipped, one for use and one for standby. There is always a set of pressure relief valve in operation. When the gas phase pressure of the storage tank reaches 17kpa, the pressure relief valve will be opened to exhaust and depressurize.

◆ Three sets of vacuum suction valves are set on the top of the storage tank, one for use and the other for standby. There are always two sets of suction valves in operation. When the gas phase pressure of the storage tank reaches -0.22kpa, the suction valve opens to make the gas phase pressure in the storage tank rise.