安全阀计算实例讨论 设计数据 （1）容器数据： 设计压力：1.0 MPa G 设计温度：80 C 外壁不保温 安全阀定压：1.0 MPa G 直径：2000mm 切线长度：6500mm 椭圆型封头 （2）介质 10％NaOH溶液（物性按照水计算） （3）安全阀计算工况：火灾；按有合适的消防设施和良好的下水系统计算；设备允许超压按10%计 计算 1 按照《石油化工设计手册》第四卷P421页公式 (1) 选用计算公式 按照《石油化工设计手册》第四卷P421页公式 G=155400FA^0.82/L 其中 G——火灾工况时安全阀所需的排放量，kg/h F——容器外壁校正系数，此处取 1 A——容器湿表面积，m2 L——容器在泄压工况时的气化前热，kJ/kg （2）所需泄放量的计算 A=π *2.0*6.5+2.61*2.0^2 =51.26 m2 安全阀泄放时的入口压力1.0*1.1=1.1 MPa G；对应水的气化潜热 L=1987.7kj/kg G=155400FA^0.82/L =155400*1*51.26^0.82/1987.7 =1973.7kg/h 2 用chemCAD算 Device type = Relief valve Valve type = Balanced valve Vent model = HEM (Homogeneous Equilibrium Model) Vessel model = Bubbly model Design model = API-520/521 Design, Pressure vessels. Short cut method used for design case. API 520-521, Adequate firefighting and drainage facilities exist. Horizontal vessel Head type = Ellipsoidal Head K factor (dpth / R)=0.5 Vapor Z factor=0.91599 Cp/Cv=1.4177 Vapor MW=18.015 Liquid heat capacity kcal/kmol-C =19.43 Latent heat kJ/kg =1966.3 Relief device analysis: Set pressureMPa =1.2 Back pressureMPa =0.1 % Overpressure=10 TemperatureC =192.03 Discharge coefficient=0.953 C0 radial distribution parameter=1.2 Kb Backpressure correction factor =1 Exposed aream2 =49.245 Environmental factor=1 Heat ratekJ/h =3.7971e+006 Calculated nozzle aream2 =0.0038775 (For heat model 1) The following calculation is base on vent area 0.0038775 m2. Calculated vent ratekg/h =1.0208e+005 Calc criticalrate kg/h =1.0208e+005 Calc critical press MPa =1.1477 Nozzle inlet vapor mass fraction= 7.6261e-008 Device inlet densitykg/m3 = 873.54 ...
