In an oil refinery, crude oil is heated to 360-370°C before entering adistillation columnoperating at atmospheric pressure where the gas fraction andseveral liquid fractions withdifferent boiling points (e.g. gasoline, kerosene,diesel, gas oil, heavy gas oil) are separated off.The crude oil is heated in twostages. The preheat train - a series of heat exchangers - heats itfrom ambienttemperature to about 270°C when it enters the furnace, known as the coilinlettemperature. The furnace then heats the oil to the temperature required fordistillation.The purpose of the preheat train is to recover heat from the liquidproducts extracted in thedistillation column. Without this, 2-3% of the crudeoil throughput would be used for heating thefurnace; with the preheat train upto 70% of the required heat is recovered. It also serves tocool the refinedproducts: further cooling normally uses air or water.Over time, fouling reduces the performance of the heat exchangers, increasingthe amount ofenergy that has to be supplied. It is possible to bypass units toallow them to be cleaned, withan associated cost and temporary loss ofperformance. The cleaning schedule thus has animpact on the overall efficiency,cost of operation and emissions.The group at the Department of Chemical Engineering and Biotechnology atCambridgedeveloped a scheduling algorithm for this non-linear optimisationproblem. It yields a good,though not-necessarily optimal, schedule and canhandle additional constraints, such as thepresence of desalters with specifictemperature requirements within the preheat train. This isnow being developedinto a commercial software product.Data from two refineries - one operated by Repsol YPF in Argentina and the EssoFawleyRefinery in the UK - were used to model the systems and test thealgorithm.For the Repsol YPF refinery, when compared with current practice and including aconstrainton the desalter inlet temperature, the most conservative estimate ofthe emissions reductionwas 773 t CO2/year. This assumed a furnace efficiency of90%. The emissions reductionincreased to 927 t CO2/year at 75% efficiency and1730 t CO2/year at 40%. These were basedon a stoichiometric estimate of theemissions from the furnace. Using a standard emissionfactor increased them by7.4%.For Esso Fawley, the estimated emission reduction compared to no maintenancewas1435 t CO2/year at 90% furnace efficiency. This increased to 1725 t CO2/yearat 75% and3225 t CO2/year at 40% efficienc
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机译：在炼油厂中，将原油加热到360-370°C，然后进入在大气压下运行的蒸馏塔，在该塔中，将馏分不同的气体馏分和几种液体馏分（例如汽油，煤油，柴油，瓦斯油，重瓦斯油）分离出来原油分两个阶段加热。预热机组（一系列的热交换器）在进入炉子时将其从环境温度加热到大约270°C，即盘管入口温度。然后，炉子将油加热到蒸馏所需的温度。预热机组的目的是从蒸馏塔中提取的液体产物中回收热量。否则，将有2-3％的原油产量用于加热炉。使用预热机，可回收高达70％的所需热量。它还可以冷却精制产品：通常使用空气或水进行进一步冷却。随着时间的流逝，结垢会降低热交换器的性能，从而增加必须提供的能量。可能会绕过设备以允许对其进行清洁，同时带来相关成本和性能暂时损失。因此，清洁时间表会影响整体效率，运营成本和排放。剑桥大学化学工程与生物技术系的小组针对这种非线性优化问题开发了一种时间表算法。它产生了一个良好的（尽管不是最佳的）时间表，并可以处理其他限制，例如在预热机组中是否存在具有特定温度要求的脱盐器。现在已将其开发为商业软件产品。来自两个炼油厂的数据（分别由阿根廷的Repsol YPF和英国的EssoFawleyRefinery运营）用于对系统进行建模和测试算法。包括限制淡水入口温度在内，最保守的减排量估计为773吨二氧化碳/年。假设炉效率为90％。效率为75％时，减排量增加到927吨二氧化碳/年，而40％时，减少排放量为1730吨二氧化碳/年。这些是基于炉子排放的化学计量估算得出的。使用标准排放因子可使排放量增加7.4％。对于Esso Fawley，在90％的窑炉效率下，与不进行维护相比，估计的减排量为1435 t CO2 /年。在效率达到40％的情况下，这增加到1725吨二氧化碳/年，在3225吨二氧化碳/年
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