FCC液化气碱精制后碱渣中碱的再生

REGENERATION OF SPENT CAUSTIC FROM LPG CAUSTIC WASHING

针对现有液化气碱渣处理工艺效果不理想且未利用液化气碱渣中的硫化物、小分子烃类及残余游离碱等资源的现状,利用活性组分MO与LPG碱渣中的无机硫化物及小分子硫醇钠生成NaOH的反应特性,采用浸渍法制备了活性组分负载量不同的再生剂,并对液化气碱精制后碱渣进行了静、动态再生研究。研究结果表明,LPG碱精制后碱渣中碱的再生是一个化学反应与物理吸附共同作用的过程,当MO负载量为46.19%、n(MO)∶n(S)=1.3、反应时间5.0h、反应温度为40℃时,碱液中游离碱质量浓度由0提高到46.09g/L,无机硫和COD的脱除率分别为80.97%和65.47%。再生实验结果表明,失活再生剂适宜的再生条件为:400～450℃,灼烧50～70min。经5次再生后的再生剂,其游离碱的再生活性比新鲜再生剂下降约10%。

The current treatment of spent caustic from caustic washing process of FCC LPG was not satisfied and was partly due to low utilization of components in the spent caustic such as sulfides, hydrocarbons and free-alkali. Since sodium hydroxide could be formed by the reaction of metal oxides （MO） with inorganic sulfides and some low molecular weight sodium thiolates in the spent caustic, regeneration agents with different MO loading were prepared by impregnation method to study the possibility of regenerating the spent caustic. Static and dynamic regeneration experiments using the prepared regeneration agents were conducted. The test results showed that the regeneration of caustic was a process combining physical adsorption and chemical reaction. Using a regeneration agent loaded with 46.19% of active MO, under the reaction conditions of a molar ratio of metal oxide to sulfur in spent caustic of 1.3, a reaction time of 5h and a reaction temperature of 40℃, the free sodium hydroxide content increased from 0 to 46.09g/L, the removal rates of inorganic sulfides and COD were 80.97% and 65. 74%, respectively. The results also showed that when the regeneration agent was deactivation, it could be regenerated under 400-450℃ for 50-0min. The activity of the regenerated agent after 5 cycle of deactivation-regeneration was only 10% lower than that of the fresh regeneration agent.