Ethylene storage issues
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I would like to ask why spherical tanks are chosen for ethylene storage? What issues should be considered when working with stored procedures?
At present, most of the steel plates used for low-temperature ethylene spheres in China are still imported from abroad. Although some large-scale ethylene spheres have begun to use domestically produced plates in recent years, the number is still small. In the past, due to the lack of suitable materials for manufacturing ethylene spheres in China, the vast majority of such spheres were imported from abroad. These spheres were made from steel with low sensitivity to welding cracks, which not only possesses good weldability but also excellent low-temperature toughness. Strict requirements apply in cases such as the replacement, pre-cooling, and emptying of spherical tanks, especially when these processes get out of control or fail to comply with the specified operating procedures (operating pressure: 16–20 Kgf/cm2, operating temperature: -40 degrees).
This post was last edited by sjjyyy on 2009-6-9 at 16:37. Spherical tanks are used because the ethylene stored is in liquid form; they ensure that the stress is distributed evenly throughout the tank. During storage, attention must be paid to the tank’s pressure and temperature – the pressure is generally in the range of 1450–1670 Kpa, while the temperature should be below -36 degrees. To maintain such a low temperature, ammonia refrigeration is required.
Pressured spherical tanks are generally used for this purpose; the storage pressure for ethylene is usually around 20 kg/m2, with a temperature of around -38 degrees Celsius. I won’t say anything else; when emptying and replacing ethylene storage tanks, it’s essential to prevent low pressures, as this can easily lead to low temperatures. During another maintenance session carried out by a reputable company, the tank was depressurized, and an operational error resulted in low pressures, causing the temperature to drop below -100 degrees, which ultimately led to the destruction of the tank. The loss is too great.
Although our facility has ethylene, for the raw materials used in another workshop, I haven’t paid attention to this issue: L. But it doesn’t seem to be spherical
The storage requirements for ethylene spherical tanks are very strict. Let me talk about the fire protection measures: there are water spray systems on the top of the tanks, and temperature-based fuse contacts are installed in the middle part of the tanks. The tank bottom is equipped with a solenoid valve interlock, and the tank top has two safety valves: one for atmospheric pressure and one for the flare.
It is common practice to use spherical tanks as storage vessels for ethylene, but in recent years, atmospheric-pressure cryogenic ethylene/propane tanks have been put into use in China (at Yangzi and Fuli refineries), achieving good economic benefits. These storage tanks have a cylindrical vault-shaped exterior, include a insulation layer, contain perlite in their interior, and are equipped with BOG compressors to recover evaporated gases. It offers significant advantages over conventional spherical tank storage, representing the future direction for ethylene/propane storage!
8# freedom_wj: Since ethylene is highly sensitive to external temperatures, which causes changes in the atmospheric pressure inside, a breathing valve must be installed on the spherical tank to maintain a constant pressure within it.
It depends on the storage volume; if it is below 100 m3, horizontal tanks can also be used. If the volume is too large, the only option for pressure storage is spherical tanks.