提出了一种基于塔总组合曲线(column grand composite curve,CGCC)确定分馏塔合理进料位置的方法——将分馏塔分别视为精馏塔与提馏塔进行物料与能量衡算,构造出与CGCC部分重合的两条相交的全塔精馏线和全塔提馏线,通过分析CGCC进料点与两曲线交点的位置关系,或定量比较两曲线上各塔板焓差大小,可以判断进料位置的合理性。研究发现,与非进料塔板相比,若CGCC进料点最靠近两曲线交点以及两曲线上进料塔板焓差取得最小值,则该进料位置最佳。两个二组分塔和一个多组分塔的应用实例表明,本文给出方法确定的分馏塔合理进料位置,与其它基于节能考虑确定分馏塔合理进料位置的方法和技术得到的计算结果基本相同。
Delayed coking is an important process in refinery to convert heavy residue oils from crude distillation units (CDUs) and fluid catalytic cracking units (FCCUs) into dry gas, liquefied petroleum gas (LPG), gasoline, diesel, gas oils and cokes. The main fractionator, separating superheating reaction vapors from the coke drums into lighter oil products, involves a de-superheating section and a rectifying section, and couldn't be simulated as a whole column directly because of non-equilibrium in the de-superheating section. It is very important to correctly simulate the main fractionator for operational parameter and energy-use optimization of delayed cokers. This paper discusses the principle of de-superheating processes, and then proposes a new simulation strategy. Some key issues such as composition prediction of the reaction vapors, selection of thermodynamic methods, estimation of tray efficiency, etc. are discussed. The proposed simulation approach is applied to two industrial delayed cokers with typical technological processes in a Chinese refinery by using PRO/Ⅱ. The simulation results obtained are well consistent with the actual operation data, which indicates that the presented approach is suitable to simulate the main fractionators of delayed cokers or other distillation columns consisting of de-superheating sections and rectifying sections.
