Lng Main Propulsion Device Selection And Dual-fuel Engine Of The Economy

Liquefied natural gas(LNG),is a kind of high quality fuel.It has high calorific value,and its products of combustion pollute the environment to only a small extent,thus.it's called clean fuel.With the development of human living standard and the raise of consciousness about environmental protection,the proportion of LNG consumption to all tends to be bigger and bigger.As a kind of important industrial and domestic clean fuel,the LNG,which has been indispensable energy source in the industrial production,construction.and human daily life in every country,plays a more and more important part in modern society. Nowadays,LNG carrier is the main means of LNG transportation between continents,and the important bridge connecting LNG sources and terminals.LNG carrier main propulsion system is one of the important factors affecting ship operating economy.Because the fuel cost makes up a large proportion of the ship operational cost,it has to be reduced if raising ship operating economy. Nowadays,the steam turbine plant is still in the majority in LNG carrier,however.it has fatal disadvantages-low thermal efficiency and high oil wear.Under the conditions that the international energy source price is apt to keep rising.the steam turbine plant is supposed to be replaced by other main propulsion systems. Selecting the main propulsion system for LNG carrier,the requirements on redundancy and reliability must be fulfilled besides the ship operating economy.In addition,the boil-off gas must be treated properly by installing the reliquefaction plant or burning it as fuel.Based on ship operating economy,this paper investigates the selecting of LNG carrier main propulsion system fulfilling the requirements on redundancy,reliability and maneuverability.This paper introduces several main propulsion systems,and illustrates their advantages and disadvantages. Furthermore,this paper qualitatively compares dual fuel electric propulsion plant with steam turbine plant on economical efficiency,reliability,environmental protection and so on,and quantificationally compares it with other main propulsion systems.The prime mover of dual fuel electric propulsion plant is dual-fuel engine,so its economical efficiency is based on the condition that the dual-fuel engine runs on natural gas more economically than it does on heavy oil.That's to say,only when it burns natural gas more economically than heavy oil,the dual fuel electric propulsion plant is competitive.Finally,this paper discusses the economical efficiency of dual-fuel engine.