Defining Storage Requirements
Before selecting an ethylene storage tank, it's crucial to define the basic storage requirements, including the storage volume, temperature, operating pressure, and operating environment. Ethylene is a cryogenic liquefied gas with a boiling point of -103.7℃ at atmospheric pressure; therefore, storage tanks typically need insulation and pressure maintenance capabilities. Based on the size of each storage operation, a preliminary judgment can be made regarding whether an atmospheric pressure tank or a pressure tank is suitable. Generally, pressure tanks are suitable for small-scale storage, while cryogenic atmospheric pressure tanks are more commonly used for large-scale storage.
Tank Type Selection
Ethylene storage tanks are mainly divided into two categories: pressure tanks and cryogenic atmospheric pressure tanks. Pressure tanks are suitable for small to medium-scale storage, and the tank body can withstand higher internal pressures. Common types include horizontal or vertical pressure vessels. Cryogenic atmospheric pressure tanks are typically large, double-walled structures. The inner tank is made of cryogenic material, while the outer tank provides protection and insulation, with an insulation layer in between. They are suitable for large-scale, long-term storage. The selection should be based on the actual storage scale, turnover frequency, and site conditions.
Material Selection Considerations
The materials used in tank selection directly affect service life and safety. The inner tank material must possess good low-temperature toughness and corrosion resistance; common choices include low-temperature nickel steel, stainless steel, or aluminum alloy. The outer tank is mostly made of carbon steel, but requires anti-corrosion treatment. The selection of insulation materials is also crucial; commonly used materials include perlite, foam glass, or polyurethane, requiring comprehensive consideration of insulation performance, fire resistance rating, and cost.
Insulation System Design
The insulation system of ethylene storage tanks is particularly important for maintaining low temperatures and reducing evaporation losses. In addition to selecting suitable insulation materials, attention must be paid to the insulation layer thickness and construction process. Large atmospheric pressure storage tanks typically use powder vacuum insulation or multi-layer winding insulation, while pressure tanks can have an external cold insulation layer added. Cooling losses should be calculated reasonably to control costs while ensuring effectiveness.
Safety Devices and Monitoring Systems
Storage tanks must be equipped with comprehensive safety facilities, including pressure relief devices, level gauges, temperature sensors, and gas leak detectors. For large storage tanks, overfill prevention systems, emergency shut-off valves, and fire-fighting cooling devices must also be considered. The monitoring system should be able to display liquid level, pressure and temperature data in real time, and be equipped with alarm functions to ensure that operators can respond to abnormal situations in a timely manner.