Design And Analysis Of Waste Heat Recovery Device On The Surface Of Cement Rotary Kiln

At present,China's economy is developing rapidly.Economic development has driven the development of all walks of life,resulting in increasing energy consumption.According to relevant statistics,it is very important to implement energy conservation and emission reduction measures in the cement industry because of industrial energy consumption accounts for 70% of total social energy consumption.The energy consumption of building materials industry accounts for a large proportion of all industrial energy consumption,and the most energy-consuming in the building materials industry is the cement industry.The study found that a large amount of waste heat resources in cement production can be utilized.These heat sources mainly come from the low-temperature exhaust gas discharged from the kiln head cooler and the kiln tail preheater,and the heat radiated from the surface of the rotary kiln cylinder to the air.Domestic and foreign research on the utilization technology of kiln head and kiln exhaust gas is relatively mature,which is mainly used to generate electricity and preheat raw materials.However,the heat on the surface of the rotary kiln cylinder cannot be recycled well,resulting in waste of resources.In order to improve the radiant heat recovery efficiency of cement rotary kiln cylinder surface,a new waste heat recovery device which is based on vacuum technology is designed.The main part of this novel waste heat recovery device is a collector with vacuum space.By comparing the heat recovery process of the new waste heat recovery device with the existing two waste heat recovery devices,it can be found that the heat exchange process between the new waste heat recovery device and the outside air is less.Furthermore,structural strength analysis,structural stability analysis and thermal-structural coupling analysis are carried out by using ANSYS software,which can reveal the mechanical properties and heat transfer characteristics of the new waste heat recovery device.Under the condition of gravity and an atmospheric pressure,the structural strength analysis results show that the maximum stress is located at the bending position of the support collector bracket.Considering that the collector is an external pressure vessel,the thin-walled component is examined according to the strength check standard of the pressure vessel,and the results show that the strength meets the design requirements.The external pressure vessel requires not only a strength check but also a stability check.The stability analysis of the collector structure shows that no instability occurs under working conditions.The thermal-structural coupling analysis shows that the thermal load had a greater influence on the structural strength of the device than the mechanical load,and the maximum stress is distributed in the place where the components of the collector are connected.Based on heat transfer theory,the parameters of the new waste heat recovery device are set.Besides,the relationship between the parameters of the hot water collecting pipe and the heat recovery amount of the collector is also researched.The different heat recovery of the collector is calculated by adjusting the parameters of the hot water collector.The results show that the measures of increasing the length of pipe and increasing the diameter of pipe and reducing the wall thickness of pipe are beneficial to improving the heat recovery of the collector within a certain range.However they may cause some problems such as a decrease in the water temperature of outlet and a decrease in the strength of pipe.Therefore,the influence of different factors should be considered in determining the size parameters of heat collector pipe.