碳化硅-六铝酸钙复合材料的抗渣机制:煤气化用无铬耐火材料新探索

Slag Resistance Mechanism of SiC-CA_(6)Composites:New Exploration of Chrome-free Refractories for Coal Gasification

高铬耐火材料具有优异的抗侵蚀性,虽存在铬危害,但长期以来作为水煤浆气化炉炉衬仍无可取代。为探索煤气化用耐火材料的无铬化,本研究采用碳化硅颗粒和六铝酸钙细粉为主要原料,经混料、压制成坯、高温烧成制备了碳化硅-六铝酸钙复合耐火材料(SiC-CA_(6),SCA),以气化炉煤灰渣为试验渣,分别采用静态坩埚法和回转抗渣法于1500℃下进行抗渣试验,并与高铬材料进行平行对比,测量试样的侵蚀厚度、渗透厚度,观察裂纹,采用SEM、EDS、XRD等分析了抗渣试验前后耐火材料及渣的化学成分、相组成、微观结构等变化,以探究SCA的抗煤渣侵蚀机理。结果表明,SCA具有比高铬材料更优的抗渣渗透性和抗热震性,熔渣仅在SCA材料表面发生侵蚀反应,抗渣试验后试样内部无熔渣和裂纹。SCA的抗渣机制为:耐火材料中的SiC、六铝酸钙与熔渣在界面处反应形成了高黏度的Al_(2)O_(3)-SiO_(2)-CaO玻璃相,封堵了表面气孔,并在耐火材料表面形成了结构致密的保护膜,阻止了熔渣向材料内部的渗透;该玻璃相与熔渣成分相近,向渣中扩散溶解缓慢,具有耐侵蚀性。SCA综合性能优异,具有应用于水煤浆气化炉的潜力。

High chromium refractory has been used as the lining of coal water slurry gasifier for a long time because of its excellent corrosion resistance.It has been a problem for many years to replace it with chrome free refractories.Silicon carbide and calcium hexaaluminate composite refractories(SiC-CA_(6),SCA)were prepared by pressing and burning the mixture of silicon carbide particles and calcium hexaaluminate powders.The slag resistance tests with gasifier slag for high chromium refractory and SCA were carried out at 1500℃by crucible method and rotary slag resis-tance method,respectively.The erosion depth and penetration depth of the samples after slag tests were measured,and cracks were observed.The chemical compositions,phase compositions and microstructure of refractories and slags before and after slag tests were analyzed by SEM,EDS and XRD.The slag corrosion behavior and slag resistance mechanism of the new chrome-free refractory were explored.The results show that SCA has better slag penetration resistance and thermal shock resistance than high chromium refractory.The corrosion of SCA with slag is very weak because their reaction is only in the contact area.Once the slag infiltrates from the refractory surface,a kind of glass phase with high viscosity,whose components are mainly Al_(2)O_(3),SiO_(2)and CaO,will be formed by the reaction of slag and refractory at the interface.And then the glass phase fills the pores and makes the dense microstructure.A shield with the similar chemical composition of slag is formed at the interface between slag and SCA,which effectively prevents the erosion and penetration of slag.SCA has the potential to be used in coal water slurry gasi-fier because of its excellent comprehensive properties.