Simulation Of Lignite Drying And Thermal Economy Analysis Based On Cogeneration

China is rich in coal resources,The energy structure of our country is still taking coal as the main body and hard to change according to the current situation of China's resources and the proportion of coal in energy production and consumption structure.The high-quality kinds of coal including bituminous coal,anthracite,have been fully utilized with the rapid development of China's economy.Consequently,the development and utilization of lignite and other low rank coal has come into the public horizon.However,because of its low rank characteristics,such as high moisture content,high volatile matter,low calorific value,high porosity,easy spontaneous combustion oxidation and other typical characteristics which make it detrimental to long-distance transport and storage,as well as combustion efficiency and greenhouse gas emissions.So how to develop and utilize lignite efficiently and economically is a problem that needs to be solved and improved urgently at present..This paper aims at the lignite.The application status on lignite drying was global widely analyzed.The analysis shows that the domestic research has not made great progress.Based on the analysis of existing drying equipment,including rotary steam dryer,fluid bed dryer and pneumatic drying,this paper selected pneumatic dryer as the objective dryer for the reason of simple structure,large processing capacity and high drying efficiency.And superheated steam drying has safe,energy-saving,environmental protection,and many other advantages.The combination of the two points become the stand point and innovation in this paper.Based on the equations of fluid dynamics and Euler multiphase flow theory,this paper develop a basic CFD model after the analysis of the two-phase flow of lignite particles and superheated steam in the pneumatic drying tube.Through the establishment of physical model,proper meshing,and determine the import conditions,export conditions and boundary conditions and solving and control conditions,to simulate the gas-solid two-phase flow.The velocity field,temperature field,pressure field and change of moisture content have been obtained,which lay a theoretical foundation for engineering application of lignite drying and upgrading.This topic is based on the low-temperature upgrading of lignite in the background of cogeneration.In order to realize the coupling between the lignite drying system and the power station,an extraction steam pre-drying lignite power generation system was established.Then the paper analyze and calculate the extraction steam pre-drying lignite power system of a 600MW steam turbine.The results show that the lignite after pre-drying have obvious energy-saving effect.What's more,it can reduce the coal consumption in power generation,It is of great significance to the realization of energy saving and emission reduction in power plant.