重油催化裂化装置旋风分离器器壁上的结焦过程研究

针对取自重油催化裂化装置（RFCCU）沉降器旋风分离器器壁4个不同区域的结焦样品，利用扫描电子显微镜（SEM）对其微观结构和性能进行了分析，并以此对结焦过程进行了研究。研究结果表明，结焦是流动油气混合物中夹带的一些重质非挥发性油滴由于重力沉降或湍流扩散作用沉积在在旋风分离器器壁上，然后逐渐凝脱氢缩合反应形成的。同时，一些较细的催化剂颗粒也沉积在结焦中。根据结焦的性质、成分和微观结构，可分为硬焦和软焦。在油气混合物的滞留区域中，油滴和催化剂颗粒自由沉降在器壁上，形成软焦。软焦非常松散，含有大量的催化剂颗粒。在油气混合物的流动区域中，油滴和催化剂颗粒扩散到壁面上，形成了硬焦。这种硬焦致密，坚硬，含有少量的催化剂微粒。因此，流动油气混合物不仅携带油滴和催化剂颗粒，而且影响其在器壁上的沉积，从而影响沉积结焦的组成和特性。

Investigation of the Different Cokes on the Cyclone Walls from a Commercial RFCC Reactor

The microstructures and properties of the coke samples collected from the 4 different wall regions of the cyclone in the reactor of a Residue Fluid Catalytic Cracking unit (RFCCU) were analyzed by using scanning-electron microscope (SEM), and the possible coke formation processes were investigated as well. The results show that some of the heavy nonvolatile oil droplets carried in the flowing oil and gas mixture are possibly deposited or collided on the walls by gravity settlement or turbulence diffusion, and then gradually carbonized into solid coke by condensing and polymerization with dehydrogenation. Meanwhile some of fine catalyst particles are deposited and integrate into the solid coke. The coke can be classified into two types, namely, hard coke and soft coke, according to the property, composition and microstructure. The soft coke is formed in the oil and gas mixtures stagnant region where the oil droplets and catalyst particles are free settling on the wall. The soft coke appears loose and contains lots of large catalyst particles. However, the hard coke is formed in the oil and gas mixtures flowing region where the oil droplets and catalyst particles are diffused on the wall. This kind of coke is nonporous and very hard, containing a few fine catalyst particles. Therefore, it is clear that the oil and gas mixtures not only carries the oil droplets and catalyst particles, but also has the effects on the deposition on the wall, which turns to influence the composition and characteristics of deposited coke.