Research On Heavy Gas Dispersal Behaviors Of Large Lng Tank Leakage Accident And Layout Optimization Of Detectors

LNG is Colorless, tasteless, non-toxic and takes a role on modern industry which is more and more important, however, it is hazardous in production and transportation with its low temperature and combustibility. LNG may lead to disaster especially when it leaks out at the process of storage and transportation. So it is important to study LNG leakage behaviors from tank.This paper uses FLACS to study dispersal behaviors of combustible substance leaking from large LNG tank. It establishes mass&heat transfer equations and describes the characteristic of the pool and heavy gas cloud. The main work consists of:1、Change wind speed, leakage and solar radiation flux in spacious space. Investigate the influence to LNG dispersion by analyzing height, width and distance of the cloud. It is favorable to form a big heavy gas cloud and a big flammable area, when the wind speed is low and stable, the leakage is large, and the solar radiation flux is strong.2、 Add an obstacle under the wind and change the height of the obstacle. Investigate the influence to LNG dispersal behaviors. Heavy gas cloud can bypass the obstacle by climbing and shunting. When the height is low and the cloud can climb the obstacle, which take a lot of energy, heavy gas will climb as well as shunt. When the height is high and the cloud can not climb the obstacle, heavy gas will just shunt.3、 Change the position of the obstacle to upper drift and investigate the influence to LNG dispersal behaviors. It turns out that the heavy gas cloud will not climb the obstacle but has a short dispersion distance. Not direct contact with the wind, the area near the obstacle has a higher FMOLE.4、Build a160000m3LNG tank model, and simulate LNG dispersal behaviors at the two situation:with a cofferdam and without a cofferdam. It turns out that cofferdam built by standard can obviously accumulate heavy gas and make cloud disperse at vertical orientation with higher FMOLE.5、Relying on the vote arrangement in ISA84and the distribution of FMOLE optimize the site layout of detectors. Reduce the number of detectors and the cost effectively. At the same time, reduce the probability of false alarm.