The Numerical Simulation Of Small Scale Natural Gas Liquefaction Process With Nitrogen Expander And Design Expander And Design Of Boosted Turbine Expander

Liquid natural gas (LNG) has obvious advantages in storing and transporting natural gas. Compared to LNG technology in western nations, the LNG technology in China which is a new technology and developing rapidly have a shorter history and a big technology gap. There are lots of scattered and remote natural gas resources in China, which haven't been utilized for limits of kinds of conditions, and our purpose of researching small plants of gas liquefaction is no other than to utilize these natural gas resources. Based on thermodynamics, here the simulation and optimization of the process of nitrogen expander cycle for small scale gas liquefaction plants have been researched.In this thesis first the history and trends of LNG technology in the world is presented, and the principle of liquefaction technology is introduced. Based on the investigation of different liquefaction technology chosen by plants of natural gas liquefaction over the world, the choosing principles for liquefaction process are presented here too. The author chooses the PR equation to calculate the phase equilibrium properties of LNG liquefaction, and builds mathematic models for equipment modules in the liquefaction cycle, which consists of compressor,multi-flow heat exchanger, expander and throttle valve. Considering the characteristics of natural gas resource, the author presents three flow process of nitrogen expander cycle for small scale gas liquefaction plants, simulates and analyses the whole process based on the two steps before. Finally, the author chooses the process of one-nitrogen expander cycle with propane precooling.In this thesis the thermodynamic analyze of one-nitrogen expander cycle with propane precooling has been discussed. The author especially analyses the influence on process parameters from the factors including: the pressure, temperature and methane fraction of natural gas, the inlet-temperature, outlet-pressure, storing pressure and the inlet-pressure of boosted turbine expander. The author optimizes the process, using the minimum power consumption of the compressor as the aim function.In this thesis, the design calculation and the structural design of pass part of the boosted turbine expander which is important equipment in the liquefaction process...