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1、案例分析报告课程名称 数据、模型与决策 案例名称 埃克森公司的应对方案 Case 2： Exxons Response to the RegulationsAs a result of several major studies conducted by the Environmental Protection Agency, the federal government has issued regulations mandating a gradual phase out of tetraethyl lead (TEL) for gasoline sold in the United St
2、ates. Separate legislation developed by the state of California provided even stiffer limits for the TEL content of gasoline. For years refiners had used TEL as an addition to gasoline as a cheap and convenient way to improve the octane rating of the gasoline, thus reducing the potential for harm to
3、 motor vehicle engines. In the absence of TEL, a refinery must reprocess some of the low-octane components of gasoline to increase their octane ratings. This can be accomplished either by breaking apart the hydrocarbon chains, through processes known in the trade as “cat cracking” or “hydrocracking
4、,” or by rearranging the bonding in the chains through processes called reforming or alkylation. All four processes are very costly and efficient but provide more variability in results than the simple addition of TEL to improve the octane rating of a blend. Faced with the dual impact of federal reg
5、ulations on TEL and the more stringent California limits, officials at Exxons Benicia, California, refinery initiated a crash program to determine the most efficient means of addressing the new requirements. Experiments were undertaken using each of the four known methods of increasing octane rating
6、s without exceeding mandated limits on the use of TEL . In their study gasoline from Exxons Benicia refinery was reprocessed in a way such that costs were equalized by using each experimental procedure. The data in the table show the octane ratings resulting from the application of the four reproces
7、sing procedures to gasoline derived from each of eight storage tanks. Octane Rating When Reprocessing byStorage Tank Cat Cracking Hydrocracking Reforming Alkylation 1 89.4 88.6 95.5 89.6 2 88.3 91.3 94.0 90.2 3 87.2 88.2 86.7 90.0 4 89.8 89.0 87.5 88.9 5 90.1 88.9 90.7 90.2 6 87.7 88.8 94.8 92.5 7 8
8、4.6 86.0 87.3 87.1 8 88.3 89.1 91.5 92.0 1. Do these data suggest that a difference exists in the ability of the four reprocessing procedures to increase octane ratings? 2. Does a difference exist between the octane efficiency of processes that break apart the hydrocarbon chains (cat cracking and hy
9、drocracking) and processes that rearrange the bonding in chains (reforming and alkylation)? 3. If you were advising Exxon, which reprocessing procedure would you recommend for increasing octane ratings? (Hint: Consider the variability of octane rating when using each reprocessing procedure.)数据、模型与决策
10、案例二：埃克森公司的应对方案基于环保局的几项重大研究成果，联邦政府已经颁布法令要求逐渐停止在美国销售的汽油中使用四乙铅。加利福利亚州则单独立法对汽油中的四乙铅含量予以更加苛刻的限制。多年来，精炼厂以使用四乙铅作为汽油添加剂这种廉价、方便的方法来增加汽油的辛烷值，从而减少对发动机的潜在伤害。如果不用四乙铅，精炼厂必须对汽油中一些低辛烷成分再生以提高辛烷值，这可以通过两种方式来得以实现，一是通过炼化业俗称的“催化裂化” 或“氢化裂解”方法阻断烃链分离，二是通过叫做重整或烷基化方法对烃链连接重排。这四种程加工方法花费非常昂贵但非常有效，但结果比在汽油中使用四乙铅这种单一的添加剂以提高辛烷值会带来更多
11、的可变性。面对联邦政府对四乙铅使用的规定和加州更严厉限令的双重压力，加州 Exxons Benicia官员、精炼厂实施一项紧急计划以确定一种最有效率的方法来选定新的炼化设备。实验采用以上四种加工方法来增加辛烷值，而不超过法规限定的四乙铅用量。在研究中，来自 Exxons Benicia 精炼厂的汽油以相同的花费使用每一种加工方法进行再生。下表中的数据显示了对分别取自 8 个储油罐汽油使用四种不同加工方法再生所得到的辛烷值。四种方法再生汽油的辛烷值油罐 催化裂化 氢化裂解 重整 烷基化1 89.4 88.6 95.5 89.6 2 88.3 91.3 94.0 90.2 3 87.2 88.2
12、86.7 90.0 4 89.8 89.0 87.5 88.9 5 90.1 88.9 90.7 90.2 6 87.7 88.8 94.8 92.5 7 84.6 86.0 87.3 87.1 8 88.3 89.1 91.5 92.0 1、这些数据是否可以说明这四种再生方法对提高辛烷值的效果不同？2、阻断烃链分离加工法（催化裂化、氢化裂解）与烃链连接重排加工法（重整、烷基化）对提高辛烷率是否存在差异？3、如果让你向 Exxon 建议，你会推荐哪种提高辛烷值的再生方法?（提示：考虑使用每种再生方法辛烷值的差异性）一、案例背景分析1 、社会及行业背景汽油主要是沸点在 80200之间的液体碳氢化
13、合物，含有直链烷烃或支链烷烃，环烷烃，烯烃等。直接分馏和催化裂化产生的汽油成分有些差异，催化裂化产生的汽油中支链烃、烯烃的含量相对较多。无论用何种方式从石油中提炼出来的汽油都是不含任何添加剂的，但这样的汽油性能一般都很不好。作为用于发动机使用的汽油，抗爆震性是最主要的指标，辛烷值就是用来间接反映抗暴性能的一个参数，一次表征汽油的标号。选定异辛烷和正庚烷为标准物分别定为 100 和 0，将汽油抗爆震性与不同比例的两种物质混合液比较，其中异辛烷含量体积百分数便是该汽油的辛烷值。刚提炼出来的汽油辛烷值一般只有 5060，只有早期汽车发动机压缩比较低时（低于 6：1）才可直接使用。现在，汽车发动机的压缩比均在 8：1 以上，要求使用的汽油辛烷值一般都在 90 以上，所以必须通过各种方法来提高汽油的辛烷值。一般来说，用催化裂化的方法获得的汽油由于含有较多的支链烃，辛烷值较高，而要提高直馏汽油的辛烷值，工业上的一个办法就是对汽油进行化学重整，让更多的烃分子在催化剂作用下进行分子的结构重排，产生更多的支链烃、环烷烃，进一步脱氢成芳烃，这样的汽油的
