An excellent in-depth article! Safety design measures for high-temperature storage tanks!

I. Definition of high-temperature storage tanks: Expansion: Storage tanks are classified according to their design temperature. Low-temperature storage tanks: Design temperature below -40°C, such as LNG storage tanks. Semi-frozen storage tanks: Design temperature between -40°C and -20°C, such as ethylene spheres. Normal-temperature storage tanks: Design temperature between -20°C and 90°C, such as gasoline storage tanks. High-temperature storage tanks: Design temperature between 120°C and 250°C, such as wax storage tanks. Applications of high-temperature storage tanks: 1) High-temperature Fischer-Tropsch wax storage tanks in coal-to-oil plants. High-temperature Fischer-Tropsch wax with a temperature of around 180°C is transferred from the Fischer-Tropsch synthesis unit in the coal-to-oil plant to the high-temperature Fischer-Tropsch wax storage tanks in the intermediate storage area, where it settles and becomes homogeneous before being sent to the hydroprocessing unit for further processing of the oil product. The design temperature of these storage tanks is 200°C, which classifies them as high-temperature storage tanks. 2) Reducing line oil tanks in refineries: Oil at a temperature of around 150°C from the atmospheric and vacuum distillation units of the refinery is transferred to the reducing line oil tanks in the intermediate tank area, where it stays there to be homogenized before being sent to the high-pressure hydrogenation unit for further processing. This ensures stable liquid levels and temperature conditions in the reactors of that unit. The design temperature for these storage tanks is 180°C, meaning they are high-temperature storage tanks.

There are safety hazards: 1) Boiling over of the storage tank leading to pressure-induced rupture. The high-temperature Fischer-Tropsch wax, with a temperature of around 180°C and containing a small amount of water, is contained within oil and stored in high-temperature tanks. High-temperature storage tanks function like \"little suns,\" transferring heat to their surrounding environment, which results in a loss of heat from the tanks themselves. When the temperature of the high-temperature Fischer-Tropsch wax drops to 120°C, water accumulates at the bottom of the tank, forming free water. Under such operating conditions, if the temperature of the oil supplied from the upstream unit exceeds 120°C, the heat wave effect causes heat exchange with the free water at the bottom of the tank. As a result, the free water vaporizes, its volume increases significantly, and the pressure inside the tank rises sharply. This pressure can exceed the tank’s design limit, leading to overpressure boiling and tank rupture, which threatens the safety of the tank.

This post was last edited by Desert Fish on 2024-6-5 at 10:15. 1) Boiling over in the storage tank led to overpressure and rupture; it involved high-temperature Fischer-Tropsch wax at a temperature of around 180°C, containing a small amount of water, enclosed within oil and stored in a high-temperature tank. High-temperature storage tanks function like \"little suns,\" transferring heat to their surrounding environment, which results in a loss of heat from the tanks themselves. When the temperature of the high-temperature Fischer-Tropsch wax drops to 120°C, water accumulates at the bottom of the tank, forming free water. Under such operating conditions, if the temperature of the oil supplied from the upstream unit exceeds 120°C, the heat wave effect causes heat exchange with the free water at the bottom of the tank. As a result, the free water vaporizes, its volume increases significantly, and the pressure inside the tank rises sharply. This pressure can exceed the tank’s design limit, leading to overpressure boiling and tank rupture, which threatens the safety of the tank. 2) Large amounts of high-temperature oil and gas are released, leading to fires and explosions. Due to factors such as the separation efficiency of the stripping tower, high-temperature Fischer-Tropsch waxes inevitably contain small amounts of light oil components. When stored in a high-temperature tank, they will volatilize into the gas phase space of the tank; if the pressure in this gas phase exceeds the set pressure of the breathing valve, the gases will be released into the atmosphere. These highly flammable and explosive gases can easily cause fires and explosions in the atmosphere. A fire and explosion occurred due to the high-temperature oil and gas emitted from a factory’s storage tank, causing the tank to collapse and leading to a spreading fire

III. Safety design measures for high-temperature storage tanks 1) Safety design measures for tank operations Choosing the appropriate type of storage tank based on the properties of the oil being stored is a fundamental requirement for the safe design of liquid storage tanks, and it represents an important measure for controlling risks associated with such tanks. The saturated vapor pressure of the high-temperature Fischer-Tropsch wax is 5.2 KPa at OT 180°C, and its flash point is above 160°C; it should be classified as a Class B liquid. The selection of high-temperature storage tanks shall meet the requirements of the following standards and specifications: \"Code for Fire Protection Design of Petrochemical Enterprises\" (GB50160-2008 (2018 edition), clauses 2.0.27–2.0.29): Storage tanks with a design pressure of less than or equal to 6.9 KPa (gauge pressure at the tank top) are considered atmospheric pressure tanks ； Clause 4.2.6 of the \"Code for Design of Storage Tanks in Petrochemical Storage and Transportation Systems\" (SH/T 3007-2014): For storing Class B and Class C liquids, floating roof tanks, internal floating roof tanks, fixed-roof tanks, or horizontal tanks can be used. Articles C.1.1 and C.1.2 of the \"Code for Design of Vertical Cylindrical Welded Steel Oil Tanks\" (GB50341-2014): This appendix applies to oil tanks whose design temperature is greater than 90°C and not exceeding 250°C. This appendix does not apply to floating roof tanks and internal floating roof tanks. For high-temperature Fischer-Tropsch wax tanks, atmospheric pressure dome tanks suitable for Appendix C of GB50341 should be selected.