柴油加氢裂化装置分馏系统模拟分析

Simulation Analysis of Fractionation System in Diesel Hydrocracking Unit

摘要: 以柴油加氢裂化装置分馏系统为研究对象，以PROII模拟软件为平台，从物料平衡、能量平衡角度出发，考察分馏塔中段回流抽出位置、侧线重石脑油塔底油抽出量占比对分馏系统的影响以及采用分馏塔底油作为重沸器热源的投资成本优势。计算结果表明，随着分馏塔中段回流抽出位置的下移，分馏塔和侧线白油塔能耗会小幅增加，在满足温位匹配的情况下，抽出位置尽量靠近塔的上部可以节省能耗。增加侧线重石脑油塔底油流量占重石脑产品总量的比例，不会影响重石脑油产品指标和分馏系统总冷热负荷的大小，可以综合考虑设备投资大小和温位匹配来确定侧线重石脑油塔底油抽出量；若分馏塔顶为冷回流，重石脑油塔底油抽出量受分馏塔顶气出口温度的限制而不能无限增大。采用分馏塔底油作为重沸器热源的投资费用在装置投产的第一年内已小于采用过热蒸汽作为重沸器热源的投资费用，分馏塔底油作为重沸器热源在固定投资成本方面具有优势。

Abstract: Taking the fractionation system of a diesel hydrocracking unit as the research object and PROII simulation software as the calculation platform, this paper investigates the influences of the draw-off position of the middle pumparound of the fractionator and the proportion of heavy naphtha column bottom draw-off flowrate on the fractionation system from the perspectives of material balance and energy balance. It also analyzes the capital cost advantages of utilizing fractionator bottom oil as the heat source for reboilers. The calculation results show that moving the draw-off position of the fractionator’s middle pumparound downward leads to a slight rise in the energy consumption of the fractionator and the side-stream white oil column. To reduce energy consumption under the premise of proper temperature level matching, the draw-off position should be arranged as close to the upper section of the column as possible. Increasing the ratio of heavy naphtha column bottom flowrate to the total heavy naphtha product output exerts no adverse impacts on heavy naphtha product specifications or the overall heating and cooling duty of the fractionation system. The draw-off flowrate of heavy naphtha column bottom can be determined by comprehensively balancing equipment capital investment and temperature level matching. When cold reflux is adopted at the fractionator overhead, the draw-off rate of heavy naphtha column bottom cannot be infinitely increased due to the limitation imposed by the outlet temperature of overhead vapor from the fractionator. The capital expenditure for adopting fractionator bottom oil as the reboiler heat source becomes lower than that of using superheated steam within the first year after unit startup, which demonstrates prominent advantages of fractionator bottom oil as reboiler heat source in terms of fixed capital investment.