| Foamed ceramic is a kind of high porosity,low density and closed cell porcelain thermal insulation material formed by using general industrial solid waste as the main raw material,adopting fine control foaming technology and roasting at 1200 ℃.Tunnel kiln is the main firing kiln.In the process of ceramic quenching,product fracture and uneven cooling often occur,which seriously affects the output and phase of products.In this paper,taking the six section kiln in the quench section of the three-layer foamed ceramic tunnel kiln as the prototype,the structure of the actual kiln is simplified and modeled,and the polyhedron mesh is divided by withfluent software.The boundary condition setting is determined by using the measured parameters in the enterprise,and the numerical simulation calculation of the model is carried out by fluent.Through the analysis of the simulated cloud diagram,the changes of the internal temperature field,flow field and ceramic cooling rate of the three-layer foamed ceramic quench section with time are analyzed,so as to determine the best working condition in line with the three-layer foamed ceramic quench,that is,the speed and temperature of quench air and the layout of air duct.It provides theoretical basis and technical guidance for relevant kiln enterprises to determine reasonable quenching conditions and improve the quality of ceramic quenching in the quenching section of three-layer foamed ceramic tunnel kiln.Through the numerical simulation calculation results,the following four main conclusions are obtained:（1）Under standard conditions,compared with 10 m / s and 11 m / s quench wind speed,12 m / s quench wind has better quench effect on three-layer foamed ceramics.In the early stage of quench,the ceramic surface temperature drops rapidly,the surrounding temperature field changes obviously,and the internal heat conduction of ceramics is obvious in the middle and later stage of quench.Under the condition of opening the nozzle with 12 m / s wind speed,the temperature field and flow field in the kiln are more uniform,the internal thermal stress of ceramics is small,and the cooling quality of foamed ceramics is better.（2）25 ℃ quench air is selected for the same wind speed,which is better than 20 ℃,60 ℃ and 100 ℃.25 ℃ quench air is blown directly.From about 1450 s of quench,the temperature difference inside and outside the ceramics increases.At the same time,the fluidity of the main flow area of the cold air increases,and the temperature difference between the top and bottom of the kiln in the first and third layers decreases.It is more suitable for evenly cooling the three layers of foamed ceramics.Combined with the actual situation of kiln enterprises,25 ℃ normal temperature quench air is easy to obtain.（3）For the six section kiln in the quench section,the arrangement of one closing and one closing of the spray air duct of the adjacent two sections of kiln is better than the fully open arrangement.The foamed ceramics are cooled quickly when the air jet pipe section is opened and slowed down when the air jet pipe section is closed,so that the temperature gradient on the outer surface and inside of the ceramics can be alleviated,so as to reduce the damage of thermal stress to the ceramics.At the same time,the pressure of the quench section is reduced to avoid excessive cold air flowing into the firing belt,resulting in under burning of the products.（4）Through orthogonal cross method,it is determined that the best ideal working condition of rapid cooling of three-layer foamed ceramics is that the speed is 12 m / s,the temperature is 25 ℃,and the air jet pipe is arranged as two adjacent kilns,one opening and one closing.At this time,the temperature field and flow field in the quench section kiln are uniform,the energy consumption of the quench fan is reduced,and the cooling quality of foamed ceramics is improved. |
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