摘要
人口增长，能源危机，是当今世界的两大主题，节能降耗已是大势所趋。石油化工企业是用能大户，而原油常减压装置又是其中之最，约占整个炼油厂炼油用能量的20％-30％。因此，优化换热网络结构，最大限度的回收热量，意义重大。
本文围绕这一主题，以某一炼油厂常减压蒸馏装置为工艺背景，开展了如下工作：
1．利用夹点技术，对整个系统进行用能诊断，发现系统的夹点温度低，传热温差大，且有穿越夹点换热的流股，根据夹点理论，在夹点上方引入冷却公用工程负荷、在夹点下方引入加热公用工程负荷及存在穿越夹点换热的流股，会造成系统加热和冷却公用工程负荷的双重损失。同时，现场操作的系统热回收温差较原设计的大，有效能损失较大，现场操作情况下的系统用能不合理，应改善夹点附近的流股匹配点，减少穿越夹点的热流量，以减少系统的热公用工程的消耗量。
2．石油物系的组成十分复杂，包含的化合物种类数以万计，确切组成难以确定，本文利用大型化工模拟软件ASPEN PLUS对整个常减压蒸馏装置进行了模拟，确定了现场两个工况的原油组成、物流流率等数据，为现场换热网络的优化奠定了基础，同时模拟了350万吨／年四个工况的基本数据，为扩能改造提供了基础。
3．针对在用能诊断过程中发现的问题，利用Simsci公司的软件Hextran对该装置现场的换热网络进行了模拟、优化，提出了两种优化方案；同时基于扩能改造的需要，优化生成了350万吨／年四个工况的换热网络。
4．对优化后的换热网络进行用能分析，做出了过程的组合曲线和总组合曲线，结果发现夹点温度有所提高，冷热公用工程用量降低了很多，原油预热终温提高了，证明优化后的换热网络在一定程度上达到了最优。
Population overflow and energy crisis are two topics of today's world, and energy conservation is of the tendency. Chemical enterprises of petroleum are consumers of enormous energy, among which, with 20-30 percent of the total energy consumption, atmosphere-vacuum plant is of the utmost consumer. So, optimizing the heat exchanger network and maximizing the energy-saved are of great importance .
Surrounding this subject, according to the background of a certain atmosphere-vacuum plant, such work has been done:
1. Using pinch technology to diagnose the energy-used conditions of the whole system, the results showed that the pinch temperature is low, temperature difference is big and heat flow through the pinch. According to pinch technology, cold utility loads above pinch and hot utility loads below pinch will make double waste of the utility loads. At the same time, the temperature difference of the locale is bigger than of the original design, the waste of virtual energy is huge and the usage of energy is irrational. Therefore it is necessary to improve the matches of the streams neighboring the pinch and diminish the heat quantity flowing through the pinch in order to reduce the hot utility consumption of the system.
2. The petroleum system is very complicated, which includes thousands of compounds, and its exact components are difficult to define. So the simulation software of ASPEN PLUS was applied to simulate the whole atmosphere-vacuum distillation process in order to make certain the petroleum components N streams flow rate etc. of the tow conditions of the locale , which established the foundation of the optimization of the locale heat exchanger network. Simultaneously, the basic data of the four conditions of 350 X 104 ton per year were simulated to settle the base of capacity-augment retrofit.
3.Aiming at the problems found in energy diagnosis process, the HEXTRAN software of Simsci corporation was used to simulate and optimize the heat exchanger network of the locale, which obtained two optimal schemes; considering the need of retrofit, optimal heat exchanger networks of four conditions of 350 X 104 ton per year were produced.
4.After diagnosing the energy-used of the heat exchanger networks of optimization, hot-cold curves and grand curves were obtained. The results indicates that pinch temperature is improved, utility quantity is much reduced, and final temperature of the preheated crude oil is increased, which proves the optimal heat exchanger networks are the most optimal ones to
some extent.
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