The simulation model of the exhaust flue gas cooler in 300MW oxy-coal fired boiler

Abstract

The exhaust flue gas cooler in a 300MW oxy-coal fired boiler is taken as an object of study. The simulation model of the cooler was established by the method of lumped parameter. The change rule of the exhaust flue gas cooler parameters and the flue gas thermal physical property parameters were analyzed by the disturbance of the coal feeder speed. It is found that, the simulation model of exhaust flue gas cooler was established basing on the conservation laws of mass and energy. The simulation experiment results show that the change rules of main operational parameters and the flue gas thermal physical property parameters in the exhaust flue gas cooler can be reasonably presented by the model with the speed disturbance of coal feeder, which can be the reference for the design and the operation control of the flue gas coolers. Introduction The oxy-coal fired mode is one of the most promising and research valuable technologies of CO2 emission reduction. In this way it can be used to eliminate CO2 emissions in pulverized coal fired boiler unit. Shown as Fig.1, after cooled and dehydrated, a part of exhaust flue gas is used as primary recycle gas, which is essential for the needs of the pulverized coal drying and conveying; On the other hand, the rest of the flue gas is sent to flue gas compression system. In the flue gas compression system, pressure of the flue gas is increased and most moisture of the flue gas is dehydrated by multistage compression and cooling, which are beneficial for further purification and recovery of flue gas. The gas cooler has been widely used in the oxy-coal fired boiler unit and its performance has influence on the dryness of pulverized coal and the safe and economy operation of the flue gas compressor. When the exhaust flue gas cooler has the working performance degradation, the moisture of the recycle flue gas increases following with the drop of its drying ability of pulverized coal, which is harmful to the furnace combustion. What is more, when the flue gas cooler in the compression system has the working performance degradation, the increase of its outlet temperature or water vapor fraction is not conducive to the economic and security operation of flue gas compressor. It is better to obtain the change rules of main parameters of gas cooler with external disturbance, which has principle significance to ensure the economic and safe operation of the unit. With the establishment of simulation model of the flue gas compression system in a 300MW oxy-coal fired boiler unit with the method of lumped parameter, the change rules of the gas cooler parameters is studied with the coal feeder speed disturbance, which provides the reference for the improvement of the design and the control of these flue gas coolers. 5th International Conference on Information Engineering for Mechanics and Materials (ICIMM 2015) © 2015. The authors Published by Atlantis Press 1060 The exhaust flue gas