BOG I believe everyone is familiar with, due to the low temperature liquefied natural gas (LNG) tank (about -160 DEG) by the intrusion of external environment heat, LNG tank liquid pump mechanical energy into heat, which will make the tank LNG flash steam gasification, the flash steam is BOG gas.
With the development of LNG industry, LNG station, L-CNG station, LNG station and L-CNG system have appeared, in addition to the three major oil companies, private enterprises are also active in LNG gas station construction field staking, the company's investment in gas station construction is also increasing. At the same time, the problems in operation of LNG filling stations have been exposed. The first thing to worry about is the large volume of emission. How to solve the problem of emission has become one of the key issues for companies to save costs and reduce losses. The following will be made from the design, operation, management and utilization of the process pipeline to reduce the rate of release, and put forward some opinions.
The cause of the release
In general, the reasons for the release can be attributed to the following factors:
First, equipment manufacturing factors.
LNG vacuum insulation tank, vacuum pump pool and other equipment can not achieve absolute vacuum insulation state at the current level of technology. Therefore, these devices will undergo slow heat exchange with outside to form BOG gas.
Second. Human factors.
Because the LNG filling industry is still at the initial stage in China, the LNG volume and operation procedure are not standardized, which results in the increase of BOG.
Third. Design factors.
To ensure the normal operation of the pump, LNG submersible pump pool and LNG plunger pump head into the liquid pipeline fully, if the design is not reasonable, will cause the liquid inlet and return air resistance increased, then you need to ensure that the manual air return port from the liquid inlet velocity, the discharge would have been produced in the running process of the equipment in emissions is considerable. Therefore, the correct grasp of the rationality of the process design will be the most effective way to reduce the discharge at the present stage. This is also the focus of this article.
Fourth, other external factors.
In addition, at the beginning of the operation of many gas stations, the air volume of the aerated vehicle is too small to reach the design scale, which leads to the long storage time of the LNG and the emission of the gas.
How to control the amount of BOG
Through the analysis of the causes of BOG, the production of BOG can be controlled from the following aspects:
Because of the current vacuum equipment manufacturing technology conditions, the equipment can not reach the absolute vacuum state. This problem is unavoidable. We must take measures to control as much as possible.
First, the equipment should be used as much as possible with good insulation, such as a vacuum wound tank instead of a LNG storage tank filled with pearlite. Of course, it needs to be calculated from funds and car sources.
Secondly, the maximum working pressure of LNG pipeline is generally 1.6MPa, and the maximum working pressure of storage tank is 0.8MPa. The maximum working pressure of storage tank is increased to 1.2MPa, which increases the storage time of storage tank, and also reduces the emission of BOG.
Finally, the vacuum degree of the vacuum equipment and the vacuum pipeline should be checked regularly, and the vacuum is re pumped when it is not qualified, so that the equipment is in the best working condition.