Numerical Simulation And Structure Optimization Research On Three-dimensional Heat Transfer Characteristic Of Calciner Cooling Water Jacket

The cooling process of high temperature calcined petroleum coke in water jacket is a key part of petroleum coke calcination technology,however,the cooling effect of traditional cooling water jacket on high temperature calcined coke is poor.On the one hand,the internal heat of hot material is difficult to transfer,so the temperature of cooled calcined petroleum coke remains high,the coke is easily oxidized,which would adversely affect the quality of calcined coke and subsequent production processes;On the other hand,the water velocity in hollow jacket is extremely low and distributed unevenly,there is whirlpool and even water-vapour,which impacts the heat transfer performance of water jacket,therefore,in order to improve the heat transfer performance,the research of heat transfer characteristic of water jacket is imminent.Firstly,in this paper,the geometric model of pot calciner cooling water jacket is built and the grid of the geometric model is divided by using GAMBIT software,the numerical simulation of high-temperature coke is completed by respectively using Mixture Model and Porous Medium Model of FLUENT software.The calculation model is validated through comparing the numerical simulation and experimental results,the good agreement between them reveals that these two models can yield good results on the temperature field.Secondly,the heat transfer characteristic of pot calciner cooling water jacket whose single tank productivity is 80kg/h is researched,regarding the exit coke temperature and cooling efficiency as evaluation indicators,the disadvantages of water jacket is analysed by the evolvement rule of water velocity field,water temperature field,coke temperature field,exit temperature of water and coke.Based on the water jacket simulation,the exit average temperature of coke only reduces 1.33K when the water flow is stiffened to double its original one,which demonstrates that the increase of water flow can't help to improve the water jacket cooling efficiency.The effect of coke mass flow rate and coke porosity on water jacket heat transfer performance are studied simultaneously,the results show that:the exit average temperature and exit maximum temperature of coke monotonously increase with the increase of coke flow,and the increase slope gradually dwindle,the exit average temperature of coke increases from 552K to 777.89K with the coke flow increasing from 40kg/h to 130kg/h;The exit average temperature of coke decreases rarely with the increase of coke porosity.Lastly,the structure optimization scheme of water jacket is proposed according to the heat transfer analysis on water side and coke side,the numerical calculation research of heat transfer performance on optimized water jacket is completed.Spiral deflectors and vertical deflectors are arranged respectively in the water side,the results prove that:the water flows smoothly and water velocity rises substantially in optimized water jacket,particularly,for spiral deflectors scheme,there is no whirlpool and local high temperature zone,the vaporization of cooling water could be avoided with the more uniformly distributed flow field and temperature field,the water vapor could be discharged in time even though the occurrence of vaporization under slow water entrance velocity,nevertheless,the coke temperature of central areas basically remains unchanged.Heat exchanger bundle is arranged in the coke side,firstly,the heat transfer characteristic of water jacket with single heat exchange tube is calculated and analyzed,the results show that,the heat transfer performance of optimized water jacket has been greatly improved,the coke exit average temperature reduces by 103.59K and the cooling efficiency raises 19.58%compared with un-optimized jacket,furthermore,the coke exit average temperature decreases monotonously and the reduced slope keeps almost unchanged along with the increase of heat exchanger tube height;Regard water jacket with single heat exchange tube as research object,changes of heat transfer performance of water jacket,whose water entrance velocity of internal heat exchange tube is 0.08?0.4m/s,is discussed,the coke exit average temperature only decreases 0.77K within the calculated water velocity,which indicates that the increase of water speed couldn't significantly improve the cooling capacity of water jacket.Finally,the optimization arrangement scheme for heat exchange tube bundle is confirmed according to the temperature field and temperature distribution curves of coke.Comparing with the un-optimized scheme,the coke exit average temperature decreases from 721.95K to 428.06K,the exit uneven temperature coefficient decreases from 0.24 to 0.135.The cooling efficiency increases from 55.51%to 86.35%.The conclusion could provide guidance for the structure optimization of calcinator cooling water jacket and could lay a theoretical foundation for the following engineering application.