延迟焦化混合喷雾冷焦新工艺数值研究

NUMERICAL SIMULATION OF NEW HYBRID ATOMIZATION PROCESS FOR COKE COOLING IN DELAYED COKER

通过建立包含多孔介质模型、"等效流体"模型、二维轴对称焦炭塔流固耦合模型,对延迟焦化大吹汽阶段新老工艺冷焦过程进行了数值模拟。计算得出了传统纯蒸汽冷焦工艺条件下焦炭塔温度分布并进行现场数据验证,预测了水汽喷雾冷焦新工艺下焦炭塔瞬态温度分布,分析了液态水含量对冷焦效果的影响及其规律,对新工艺的经济性进行了定量评价。结果表明:水汽喷雾冷焦新工艺下喷雾流量一定时,焦层冷焦效果随水汽喷雾的液态水含量的提高先显著改善后趋于稳定再受到抑制;在压力为0.3 MPa、水汽喷雾流量为7.5t/h的条件下,液态水质量分数分别为0.4,0.5,0.6,0.7,0.8,0.9时,相对传统蒸汽冷焦工艺,节约蒸汽量分别为36%,53%,64%,71%,79%,84%;使用513K的过热蒸汽与353K的液态水通过雾化喷嘴进行混合的条件下,当液态水质量分数为0.8时,冷焦效果达到最优,年增经济效益76.14万元。

A two-dimensional axisymmetric fluid-solid coupled model containing the equations of momentum and mass transfer in porous media as well as the equivalent fluid model is developed and used to simulate both traditional pure steam spray and new water-steam spray coke cooling method in big flow stage of delayed coking. The temperature distribution in coking drum using traditional steam cooling method was obtained and verified on-site. The transient temperature field in coke drum using new spray method was calculated. The influence of water content on the coke drum cooling effect and its regularity was analyzed. The economical efficiency of new method was evaluated quantitatively. The research results indicate that at a fixed water^steam flow rate, the cooling effect is first quickly improved then slowed down and final restrained with increasing liquid water in the mixture. The optimum water fraction is 0.8 to realize the best cooling effect. At the conditions of 0.3 MPa and 7.5 t/h mass rate of spray flow, the steam saving is 36%-84% when the liquid water fraction are 0.4--0.9 respectively, relative to the traditional method.