摘要
为解决流化催化裂化(FCC)外取热器的取热负荷不足问题,提出了一种新型折流式外取热器,即在工业常用的下流式外取热器的基础上,沿催化剂流动方向增设若干折流板。通过大型冷模实验分别测量了下流式和折流式外取热器密相区和稀相区的传热系数,结果表明:在密相区和稀相区,折流式外取热器的传热系数均大于下流式外取热器,其中密相区和稀相区的传热系数的相对增长量分别为26.9%~267.9%和31.6%~152.5%。在折流式外取热器的密相区,传热系数得到强化,主要是因为颗粒径向流动的增加、密相床层的轴向混合的增强和气泡尺寸的变小;在稀相区,主要是由于颗粒流沿折流板以"折流"形式流动,增长了颗粒的过流路径,同时折流板上的开孔使催化剂分布更加均匀,提高了颗粒与换热管的接触分率。由于下流式和折流式外取热器内密相区传热系数均远大于稀相区,因此密相区为主要换热区域。建立了2种外取热器的密相区传热系数关联式,其计算值与预测值间相对误差小于20%。
A new type of baffle catalyst cooler was proposed to solve the problem of low cooling capacity in fluid catalytic cracking(FCC)external catalyst cooler through installing several baffles at the downflow catalyst cooler in current commercial design.A large scale cold model experimental device was built to measure heat transfer coefficients in both dense and dilute regions of the two coolers.Experimental results show that heat transfer coefficients in the baffle catalyst cooler are higher than those in the downflow catalyst cooler,either in dense or dilute regions.Heat transfer coefficients relatively increase 26.9%-267.9%and 31.6%-152.5%in dense and dilute region,respectively.In dense region,the intensification effect mainly results to more particle radial movement,enhance particle axial mixture and smaller bubble size.In dilute region,particles from top inlet flow along the baffle and this could extend particle flow path.Especially,the pores in baffles distribute particles more uniformly in the bed,thus could increase the particle contact time fraction with tube surface.Mathematical correlations are proposed to predict heat transfer coefficients in dense regions of the two coolers with relative errors less than 20%.
作者
刘璐
姚秀颖
李建涛
卢春喜
LIU Lu;YAO Xiuying;LI Jiantao;LU Chunxi(The State Key Laboratory of Heavy Oil,China University of Petroleum,Beijing 102249,China)
出处
《石油学报（石油加工）》
EI
CAS
CSCD
北大核心
2021年第1期32-43,共12页
Acta Petrolei Sinica(Petroleum Processing Section)
基金
国家自然科学基金项目(21706280,U1862202)
中国石油大学(北京)科研基金项目(2462017YJRC011)资助。
关键词
外取热器
传热系数
折流板
流化催化裂化(FCC)
external catalyst cooler
heat-transfer coefficient
baffle
fluid catalytic cracking(FCC)
