Analysis Optimization And Application Of Gas Inerting In LNG Tank

In recent years,the world's demand for clean energy has shown a strong trend of growth.Compared with other basic energy sources,liquefied natural gas(LNG)is environmentally friendly and efficient.However,the distribution of its demand and supply places around the world is uneven,so it needs to be transported.LNG shipping is the most economical way for long distance transportation.The safety of LNG tank is particularly important during loading and transportation.In order to avoid the potential risks of LNG entering the tank and mixing with oxygen-containing gas,such as explosion and ice blocking,the average volume fraction of oxygen in the tank should be reduced to less than2%.At present,studies on the inert gas inerting process of LNG tank are mostly focused on the upward or downward upward entryway,which has low inerting efficiency.In particular,due to the small expansion Angle of the direct entryway,the inerting rate of large volume storage tank is usually lower.In addition,the existing inerting methods also have a large area of inert dead Angle,inerting is very difficult.Therefore,this paper analyzes the characteristics of gas inerting process of c-type independent cargo tank of small and medium-sized LNG ships,optimizes the inerting process,and improves the economy of engineering inerting operation.The main contents of the paper are as follows:?.Change above into bottom out or into the air inlet,C on the LNG carrier independent type of tank inerting of lateral air inlet was proposed,and design the direct jet,rotary jet and mix jet of three different inlet structure,by comparing the numerical simulation and post-processing,combined with gas convection diffusion mechanism,analysis the influence of different inlet structure of inerting process,it is concluded that rotary jet air intake structure is better than the other two structure.?.Three different intake structures are proposed for the lateral intake,and the influence of different intake methods on the inerting process is analyzed by comparing the simulation calculation and post-treatment,and combining with the convective diffusionmechanism of gas.1.For direct jet,and rotary jet mix jet mechanism analysis after three air inlet was simulated,get three jet in the passage of rotary jet type inerting effect is best.2.Through the mechanism analysis of the oxygen volume fraction curve of the simulation results of three air intake methods,the inflection point of the curve is taken as the turning point to obtain the following results.In the middle stage,nitrogen goes directly into the storage tank under the direct jet,and the inlet expansion Angle is very small,leaving a dead Angle of inerting,which slows down the process of inerting.However,the volume fraction of oxygen in the rotary jet and the mix jet decreases rapidly,basically presenting a progressive inerting.In the later stage,the volume fraction of the rotary jet decreased faster,and the slotting inerting effect was the best,which greatly reduced the consumption of nitrogen and saved time.3.In the scale ratio model,rotary jet is better than direct jet and mix jet and has better economy.Compared with the direct jet scheme,the rotary jet can reduce the amount of nitrogen by 40.4% and shorten the inerting time by up to 40.4%.Compared with the mix jet scheme,the nitrogen consumption can be reduced by up to 26.1%.For mix jet,compared with the direct jet scheme,the nitrogen amount and inerting time can be saved by 19.4%.?.Through numerical simulation and mechanism analysis of three different inerting modes in LNG tank,the advantages of rotary jet are obtained,and then the inerting mode of rotary jet is further optimized according to the swirl strength and put forward the optimization plan.Finally,according to the optimization results,the simulation analysis of the actual project(full-size tank)program is carried out,and it is found that the rotary jet can save 36.3% of the nitrogen amount and time compared with the direct jet,and 43.2%of the nitrogen amount and time compared with the mix jet.It is of great significance to the practical engineering operation.