Research On Cold Energy Utilization Of Liquefied Natural Gas

Liquefied natural gas (abbr.LNG) has many advantages such as low pressure on the environment, higher calorific value, and good availability…LNG is then becoming more and more popular in many countries. These countries import each year tons of LNG. Since 2005 China has imported a great amount of LNG; the quantity of Chinese import of LNG is expected to grow each year and it's predicted that China will import more than 4200 ton of LNG in 2015. LNG is a kind of low temperature high-pressure liquid which is made from natural gas by mechanical refrigeration. The whole process consumes a great amount of power and this knowing that LNG will be gasified for further use. According to the first law of thermodynamics, LNG releases a great quantity of cold energy during gasification. Recycling the cold energy released during transformation is becoming a worldwide topic. This dissertation aims to study the cold energy utilization of LNG. The main contents are as follows:First of all, based on the study of Chinese and foreign researches about LNG cold energy utilization; the use of the second law of thermodynamics exergy as evaluation standard is proposed. From the available usable energy(exergy) viewpoint, this thesis analyses how to use the LNG cold energy in the most economical way. The present thesis also puts forward the matters needing attention during the process of recycling LNG cold energy.Secondly, an evaluation of the recycling effect of various methods of LNG cold energy utilization is presented; summing up the main problems encountered during this process. A new style of LNG cold energy utilization is proposed on the basis of previous studies. This new method combines cascade utilization and cold storage technology, which is the main innovation of this study. Then, combining the current actual situation of LNG industry in China: this thesis sums up the main problems in the construction of LNG cold utilization projects in our country and proposes corresponding solutions.Finally, this thesis mainly focuses on LNG cold energy for desalination technology and puts forward two processes including intermediate refrigerant with phase changing and another process with no phase changing. Then, this paper simulates the two processes using a simulation software: compares, analyzes their advantages and disadvantages and carries out corresponding conclusions.