| Quench boiler is one of the key equipment in the ethylene production,and its safe and stable operation has important significance for the stable operation of ethylene plant and increasing the yield of ethylene.When the first quench boiler of an ethylene plant are running on site in Daqing Petrochemical Plant,it is found that inner tube of multiple furnace tubes appears instability phenomenon in close to the water supply region of boiler.Because of its high temperature and high pressure operating conditions,at present people are not fully understood the flow inside the quench boiler and the boiling heat transfer characteristics.This paper uses the CFD software for numerical simulation study on the distribution of boiler feed water flow in each furnace heat load evenly and a single furnace tube ring space fluid flow and heat transfer characteristics.Combined with the results of the analysis and strength evaluation of the inner tube material,comprehensive analysis of the main reason for the instability of quench boiler furnace tube,and provide the technical basis for the upgrading of the quench boiler.Through overall three-dimensional simulation of a single heat exchanger unit of the quench boiler,it shows that under the same conditions,the flow at both ends of the furnace tube is small,while the flow at the middle six furnace tube is greater than the average flow and the flow deviation between each furnace tube is very small.After getting the law of the distribution of the boiler feed water flow between each furnace tube,to further study the furnace tube of the flow field and temperature field characteristics,this paper made a numerical simulation study about high-pressure water flow and boiling process in double sleeve of quench boiler using the CFD software on the basis of two-phase flow Mixture model.After getting the law of the velocity field,temperature field and the gas-liquid distribution of Single furnace tube,we are sure that close to the boiler feed water export areas are most likely to occur heat transfer deterioration.Combination of numerical simulation results,the furnace tube materials on-site analysis of data and strength assessment calculations,the reason for furnace tube instability can be got by comprehensive analyzing.There are uneven flow distribution in quench boiler,the normal water cycle fluctuations in operating conditions deteriorate,so that part of the furnace tube boiler feed water exit of the heat transfer deterioration occurs,leading to the sharp decline of the inner tube over-temperature material properties,external pressure instability.The furnace tube prone to instability and the main failure parts,which are calculated by the numerical simulation,are basically consistent with the actual situation. |
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