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前言：多数人在使用Google搜索的过程是非常低效和无谓的，如果你只是输入几个关键词，然后按搜索按钮，你将是那些无法得到Google全部信息的用户，在这篇文章中，Google搜索专家迈克尔.米勒将向您展示如何更智能、更高效地进行Google的系列搜索。
Google是一个非常精密成熟的搜索引擎，但大多数的用户都没有能完全地利用到它的能力。一般人就是在Google的搜索框中输入一两个关键 字，然后点击“搜索”按钮，等着Google显示出它第一页的搜索结果。这是一个相当简单模式匹配算法的搜索，不幸的是，通常此时出现的大部分都是并不需要的结果。
其实，还是有更好的方式能够让搜索产生一些更少、更为准确的结果。你所需要做的事只是学习一些简单的技巧，你就能很快得到更多更好的Google搜索结果。
技巧一：使用正确的方法
无论你是使用一个简单或是高级的Google搜索，在此都存在你应该使用的某种可靠的方法。遵循适当的方法你就能获得非常准确的结果；要是忽略这条建议的话，你也许就会看到大量不相关的结果或是缺乏你想要的相关结果。
虽然有很多不同（且同样有效的）方法用于网络搜索，我保证这个特别的方法将能带来最棒的结果。这是一个分六步骤的过程，如下：
1、首先，想好你想要寻找什么。哪些词能够最好地描述你要寻找的信息或者概念？哪些词是你能够用来替换的？有没有那些词是可以不必包括在你想要搜索的更好定义你的需求之内？
2、构建你的搜索要求。使用尽可能多你所需要的关键词；越多越好。如果皆存在可能的话，试着用适当的搜索操作来使你的搜索更精炼——或者，如果你愿意的话，可以使用高级搜索页面。
3、点击“搜索”按钮进行搜索。
4、评估一下搜索结果页面上的匹配程度。如果一开始的结果与你想要的不一致，再精炼你的搜索要求并重新搜索——或转向更合适的搜索站点再进行搜索。
5、选择你想要查看的匹配的页面，点击进行浏览。
6、保存这些最符合你需求的信息。
换言之，这需要你在搜索之前思考清楚，接着在获得最初结果后精炼你的搜索。这些多做的努力都是轻微的，但确实很值得。
技巧二：合理利用一个“与/或”的搜索
大多数的用户都没有意识到，Google会自动假定一次搜索要求中所有的词之间都是一种“和”的关系。也就是，如果你输入两个词，它就会假定你所寻找的页面是包含这两个词的。它不会反馈给你仅包含其中一个词的页面。
这就使得你无须在输入搜索要求时输入一个“和”。如果你想要搜索的包括“Bob”和“Ted”，你所需要做的就是输入bob ted即可。Google会自己假定一个“和”，并自动地将它包括在内部的索引搜索内。
这与在所要求的词之间假定“或”是不同的。例如，对比输入的要求“bob ted”（记得，这个实际上是bob和ted）与“bob或ted”。根据第一个要求所得的结果所包含的页面会共同提到Bob和Ted.而后者，结果所包 含的页面会只单独提到Bob，也有些页面是单独提到Ted，还有一些是共同提到他们二者的。这是一个微妙的差异，但却是很重要的。
因此，如果你想要一个“与/或”的搜索——搜索包括一个或另一个词的页面，但不一定是都包括二者——你必须在两个关键词之间插入一个带有“或 者”功能的操作。当你输入这个“OR”的表示“或者”操作时，请确保所输入的要大写，否则Google会将它忽视为一个忽略的单词（stop word）——也我们接下去将要讲到的。
技巧三：你的搜索中包括或不包括的词
关于这些“and”和“or”的词，Google会自动地将这些在你输入的搜索要求中的不重要的、普通的词忽略掉。这些被称作是“忽略的单 词”，包括“and”、“the，”、“where”、“how”、“what”、“or”（所有字母皆为小写，还有其它一些类似的词——包括一些单独的 数字或单独的字母（例如 “a”）。
在搜索中包含忽略的单词并没有什么大碍，不过会使搜索速度有些下降，这就是Google将它们剔 除的原因。举一个例子，你想要搜索的是“how a toaster works”（烤箱如何工作），Google会移除“how”和“a”两个词，并自行按新的更短的关键词“toaster works”进行搜索。
如果你想要让这些一般的词包含在你的搜索要求内，你可以通过让Google必须在搜索中包含这些特定的词，使它不去排除“忽略的单词”。想要做 到这点，你可以在你确实需要的词之前加上一个“+”符号。例如，要在搜索要求中包含“how”，你应该输入“+how”。请确保在+符号之前有一个空格 符，而不是在它之后。
从另一方面来说，有时你会想要通过排除一些包含特定词的页面来精炼你的搜索结果。你可以通过使用一个“-”号来 去掉搜索结果中不想要包括在内的 词；在你的搜索要求中任何之前加上了“-”符号的词都会自动地排除在搜索结果之外。同样地，也请记住在“-”符号之前留一个空格符。
例如，如果你想要搜索“bass”，你所得到的页面可能会包括男歌手一类的或是关于鱼的一类的。如果你仅向搜索的是歌手这类的页面，输入搜索要求时应如下：“bass -fish”。
技巧四：搜索近似的词
幸运的是，Google能够让你搜索近似的词——叫做同义词——通过使用“~”符号。只要在想要搜索的词之前加上“~”符号，Google就会搜索所有包括这个词以及合适的近义词的页面。
例如，要搜索类似“elderly”的词，输入“~elderly”，所得到的页面就会不仅是包括“elderly”这个词，还会有包括“senior”、“older”、“aged”等等词的页面。
在此还有个额外的技巧：如果要只是列出近义词的页面，而不需要给出许多原先输入的那个词的页面，可以用“-”符号来连接“~”操作，例如 “~keyword -keyword”。这样就能在近义词所得的结果中排除原先输入的词。在先前的例子中，要得到仅有“elderly”近义词的搜索结果，就输入 “~elderly -elderly”即可。
技巧五：搜索特定的词组
当你搜索一个特定词组时，如果你只是简单地输入词组中所有的词你是无法得到最好的结果的。Google也许能够反馈出包含这个词组的结果，但它也会列出包含你所输入所有词的结果，却未必让这些词按照正确的顺序。
如果你要搜索一个特定的词组，你应该将整个词组放在一个引号内。这样就能让Google搜索规定顺序的精确的关键词。
例如，如果你要搜索“Monty Python”，你可以输入monty python作为你的搜索要求，接着你也许会获得可接受的结果；这些结果中会包含有着“monty”和“python”两个词的页面。但这些结果并不仅是 包含了关于英国喜剧团体的页面，还包括了名叫Monty的蛇以及名叫Monty的家伙，他养了蛇来当宠物，还有其它一些包括了“monty”和 “python”的词的页面，即使它们之间看起来似乎毫无关联。
为了将搜索结果限定在只关于Monty Python喜剧团之内，也就是你想要搜索的页面是按规定的顺序，将这两个词作为一个词组包含在内的，你就应该在输入搜索要求时输入”monty python”——确保这个词组在引号之内。这样的话，如果没有按照规定的顺序将这两个次匹配为一个精确的词组，这个页面就不会被列在搜索结果当中。
技巧六：列出相似的页面
你是否有发现过一个网页是你确实很喜欢的，又想知道是否还有与它类似的其它网页呢？不需要再疑虑地思考了；你可以使用Google的相关来寻 找：这个操作算符所显示的页面会与特定的页面在某些方面是相似的。例如，如果你很喜欢InformIT上的文章，你可以通过输入“related: http://www.informit.com”来寻找类似的页面。
技巧七：通过其它的操作算符调整你的搜索
使用相关操作算符只是众多你可用来调整Google搜索结果的方法之一。所有的这些输入的操作算符都是以相同的方式工作的，将这些算符作为你搜 索请求的一部分输入，再将变量紧接在这些输入的操作算符之后的冒号之后（而不是空格），就像这样：“‘操作算符’:‘变量’”。
有哪些搜索的操作算符是你可以利用的呢？以下是一个简短的清单：
算符 用途 用法
allinanchor: 限制搜索的词语是网页中链接内包含的关键词（可使用多个关键词） allinanchor:keyword1 keyword2
allintext: 限制搜索的词语是网页内文包含的关键词（可使用多个关键词） allintext:keyword1 keyword2
allintitle: 限制搜索的词语是网页标题中包含的关键词（可使用多个关键词） allintitle:keyword1 keyword2
allinurl: 限制搜索的词语是网页网址中包含的关键词（可使用多个关键词） inurl:keyword1 keyword2
filetype: 限制所搜索的文件一个特定的格式 filetype:extension
inanchor: 限制搜索的词语是网页中链接内包含的关键词 inanchor:keyword
intext: 限制搜索的词语是网页内文包含的关键词 intext:keyword
intitle: 限制搜索的词语是网页标题中包含的关键词 intitle:keyword
inurl: 限制搜索的网页的地址 inurl:keyword
site: 限制所进行的搜索在指定的域名或网站内 site:domain
技巧八：搜索特定的事实
如果你要搜索一些客观事实，Google也许能够帮得上忙。是的，Google总是能够反馈给你一个匹配你指定的搜索要求的清单，但只要你能够 正确地描述了你的搜索要求，且接着搜索的事实是Google已经预先鉴定了额，你就能在搜索结果页面的最顶端得到你所需要的精确信息。
我们在此谈到的有哪些类型的信息呢？是一些事实性的信息，例如诞生日、诞生地、人口等等。你所需要做的就是输入你想要知道的描述事实的搜索要求。例如：
要查询圣弗朗西斯科的人口，则输入“人口 圣弗朗西斯科”。
要查询马克·吐温在哪里出生，则输入“出生地 马克吐温”。
要查询总统比尔·克林顿什么时候出生，则输入“生日 比尔克林顿”。
要查询雷蒙德·钱德勒什么时候去世，则输入“去世 雷蒙德·钱德勒”。
要查询谁是德国总统，则输入“总统 德国”。
这些问题的答案就会显示在搜索结果页面的顶部。你能够获根据关联的网站得应对你的疑问的正确答案。点击相关的链接还能从这个资源里获悉更多的东西。
技巧九：搜索Google Directory
Google在它的搜索数据库中将成千上万的网页索引化——这就能使得不会产生压倒性数量的搜索结果。量确实已经够了，但有时你也许会更愿意得到一些高质量的结果。
由于质量较数量更为重要，就可以绕过主要的Google搜索引擎而使用Google Directory来代替。Google Directory是一个网页清单相对较小的数据库，它们都是通过一个人工编辑团队手动精心挑选的。Google Directory是有被注释和组织到相关的话题类目下的。你可以通过类目来浏览网页目录，或是搜索指定的项目。
Google Directory是一个可用来搜索大量Google网页索引实用选择。Google Directory的结果比起你在更大的搜索索引范围中的搜索结果更为集中且高质，也能够帮助你在任何给定的类目下更好地认识什么是可用的信息。另外，如 果你喜欢，你也可以利用浏览类目来替代搜索。
要进入Google Directory，点击Google主页上的“更多”链接，在接下来的页面中选择类别。当然，你也可以直接进入Google的Directory，只要在浏览器中输入directory.google.com即可。
技巧十：使用Google的其它专业搜索
Google Directory不仅仅是Google所提供的除了主搜索引擎之外的唯一选择。根据你所做的搜索类型，你也可以通过使用其中Google更为专业的搜索站点之一来得到更好的结果。它们包括：
Froogle可以用来搜索那些有着最低价格的特定商品的在线购物网站。
Google Answers所提供的服务是直接让你的搜索需求面向专业人员的小组，大多数都是用于当你有着更为复杂的问题，而无法通过简单的搜索来解答的时候。
Google Apple Macintosh Search主要是在apple.com域名中以及和其它与苹果相关的站点进行搜索。
Google Blog Search是用来搜索博客和博客文章的。
Google Book Search可以搜索成千上万的小说和非小说类图书的全文。
Google BSD UNIX Search可以搜索到大量专门为BSD版本的UNIX操作系统专业化的站点。
Google GroUPS可以搜索到Google Groups档案的相关文章。
Google Linux Search用来搜索大量与Linux相关的网站。
Google Microsoft Search可以搜索主要是microsoft.com域名中的内容以及其它微软相关的站点。
Google News可用来搜索大量有最新新闻和头条的新闻网站，也能够搜索历史的新闻资料，一直可以追溯到两个世纪之前。
Google Scholar在一个有着学术杂志、文章、报纸、论文和书籍的数据库中进行搜索，也能够选择大学或研究书库。
Google U.S. Government Search是用来搜索那些美国政府的网站——这是一个最好的用来搜索官方性政府举措、信息、报告等等的地方。
Google University Search能在一个有着超过600所大学网站的数据库中进行搜索——能够用来查询课程安排、入学资料等等。
Sunday, February 22, 2009
论坛收集—aspenplus 60 问（炼油方向）
本文章转自海川论坛，原文链接http://bbs.hcbbs.com/thread-369198-1-11.html
aspenplus 60 问（炼油方向）
1. Aspen Plus does not generate distillation curves for a stream containing 4 pseudo-components. Why?
To generate a distillation curve, a stream must contain at least 5 pseudo-components of non-zero flow to generate distinctive data points at 10%, 30%, 50%, 70, 90%.
2. For streams with significant amount of light components, the calculated Reid vapor pressure is usually off. Why is that? Are there any guidelines for using Reid vapor pressure?
Reid vapor pressure is the absolute pressure exerted by a mixture (in pounds per square inch)
determined at 100 F and at a vapor-to-liquid volume ratio of 4 (ASTM Method D 323. RVP is intended for
characterizing the volatility of gasoline and crude oil, with a typical range of 1 to 20 psia. Out of this range,
the accuracy may be poor. Therefore, RDV should not be applied to very light or very heavy streams.
3. How is the Reid vapor pressure calculated in ASPEN PLUS?
The Reid vapor pressure is vapor pressure of liquid at 100 F, as measured according to ASTM D-323procedures. Aspen Plus simulates these procedures by a series of flash as follows:
i. Check if N2 or O2 is present; if so, determine their index values.
ii. Setup to the ideal gas option-set (sysop0).
iii. Calculate volume for AIR at 32 and 100 Degree F, 1 atm.
iv. Determine bubble point pressure of the liquid stream at 100 F.
v. Saturate the liquid with air at 32 degree F.
vi. Mix liquid with 4 vol% equivalent of air and flash at 100 F under constant volume.
vii. If calculated Reid vapor pres. is greater than 26 psi repeat w/o air saturation.
The Reid vapor pressure as measured by the ASTM D-323 differs from the true vapor pressure of the sample due to some small sample vaporization and the presence of water vapor and air. Reid vapor pressure is often used to determine the appropriate type of storage tank (cone roof or floating roof) for petroleum stocks with undefined components.
4. What is the difference between Prop-Set REIDVP, RVP-ASTM, and RVP?
The Prop-sets REIDVP and RVP-ASTM are identical. Both are kept for upward compatibility, and can be requested like any other Prop-set. RVP, however, is available only if you define a petroleum property curve for the Reid vapor pressure in the ASSAY.PROP-Curve form, by providing a table of Mid-Percent distilled vs. Reid vapor pressure values.
5. Aspen calculated API gravity is quite different from that of PRO II in some cases. What is the
method used in Aspen Plus and what are the assumptions/limitations?
The API Liquid Volume model implemented in Aspen Plus uses the following eqution:
Vm = Xp Vp + Xr Vr
Where
V = liquid molar volume
X = liquid mole fraction
m = mixture
p = pseudocomponents
r = real components
Vp (for pseudocomponent liquid mixture) is calculated using a correlation based on API Figure
6A3.5 (API Technical Data Book, 4th edition).
Vr (for real component liquid mixture) is caculated by the mixture Rachett model.
The variations in petroleum liquid density results are often caused by the number of cuts generated.
Increasing the number of cuts or reducing the cut temperature intervals may improve the accuracy. Refer to Solution 103736 for more details.
When multiple assays are present, the way they are blended could also affect the liquid density
calculation. The choices include generating:
one common pseudocomponent set for all assays
one pseudocomponent set for each assay
some combinations of assays and blends
Refer to Solution 103921 for more about one versus multiple pseudocomponent sets.
6. How is assay broken into pseudo-components?
Assay is broken into pseudo-components based on the number of cuts on the True Boiling Point (TBP) curve. The middle point of each cut is used as the boiling point of that cut.By default, Aspen Plus generates 40 pseudo-components using the following cut temperatures:
TBP Range (F) No. of Cuts Increments (F)
100 - 800 28 25
800 - 1200 8 50
1200 - 1600 4 100
User can change the default settings under Components, ADA Characterization, Generation.
7. Can users access Aspen Plus generated pseudo-components like real components? Users would like to access pseudo-component properties, such as Tc, Pc, Vc, API gravity, SG, and MW. Currently they are listed in the external report file.
No. Only a limited number of pseudo-component property parameters are reported as results in GUI.
User cannot alter what to report. To access and change pseudo-component property parameters, use user property model subroutines.
8. How does Aspen handle petroleum properties among pseudo-components? For example, if only bulk sulfur content is given, how does Aspen distribute it to pseudo-components?
Petroleum properties are treated as component attributes and attached to pseudo-components. When a property curve is given, the distribution of the property is based on the curve. When only a bulk property
is given, it is evenly distributed among all pseudo-components.
9. How does Aspen Plus calculate motor and research octane number?
Octane number is calculated from the Octane curve entered with the assay. There are four (4)property-sets for Octane number:
i. MOC-NO - Motor octane number
ii. MOCNCRC - Motor octane number curve
iii. ROC-NO - Research octane number
iv. ROCNCRV - Research octane number curve
10. What is the difference between match and not-match light ends?
Light-ends (gases) are typically analyzed separately from the liquid fractions. The distillation curves from
the lab normally exclude the light-ends. To generate a distillation curve reflecting the full distillation range of an assay, you need to use Match Light-ends. Match light-ends uses the boiling points of the light-ends components to determine the curve in the range from 0 to lt% where lt% is the percentage of the light-ends in the assay. The default is not match light-ends.
11. How does Aspen Plus match light ends?
When Match Light-ends is selected, the TBP curve, from the light-end fraction and blow, will be represented by the boiling points and concentrations of the light-end components. For example, given the light-end fraction = 0.05, the boiling point of the heaviest lights = 64 F, the original TBP curve at 0.05 = 68 F. After matching light-ends, the final TBP curve will be 64 F at 0.05. And, from 0 to 0.05, the curve will be calculated from the light-ends. The original TBP curve in the range from 0 to 0.05 is not used.
12. When using match light ends, sometime I receive a warning message saying the temperature
difference is too large. Under what conditions will Aspen Plus not perform matching light ends?
Match light-ends works only when the boiling point of the heaviest component in the light-ends falls within
10 F on the TBP curve at the light-end fraction. In the above example, if the original TBP curve at 0.05 is below 54 F or above 74 F, Aspen Plus will give an error message and not perform matching light-ends.
To avoid this error, user has to make sure that the light-ends analysis is accurate and the fraction of light-ends in the assay is accurate. To force matching light-ends when the temperature difference is > 10F, you can：
a. Add or remove the heavy components in the light-end analysis.
b. Change light-end fraction.
13. Can one enter viscosity data for a stream? For heavy petroleum fractions, the API methods do not cope well. If two viscosity points are available, 2800 cp @275 F and 600 cp @325 F can they be used in the simulation?
You cannot enter the data directly either in Assay input or stream input. The current procedure is to substitute MUL2USR for the mixture viscosity model. Write a Fortran subroutine for doing interpolation
based on these two points. The subroutine fits a model of the type:
ln(mulmx) = aa + bb/T
14. How is pseudo-component specific gravity calculated?
Liquid molar volume is based on the Rackett or Cavett model. The default is Rackett. Refer to the Aspen Plus on-line help.
15. How is pseudo-component MW calculated?
There are nine (9) models for calculating pseudo-component molecular weight. Refer to the Aspen Plus on-line help.
16. How is gross/net heating value calculated for a petroleum stream? Is the method the same for pure components and pseudo-components?
Heating value is also called heat of combustion. The heat of combustion of a substance is the change in enthalpy when that substance is converted to its final oxidation products by means of molecular oxygen. The beginning and ending states are:
standard heat of combustion: 77 F and 1 atm
gross heat of combustion: 60 F and 1 atm
The normal state for the water formed by the reaction is liquid in both cases. Since the sensible heat of water from 60 to 77 F is usually negligible in comparison with the heat of combustion, the gross and standard heats of combustion are approximately equal. The net heat of combustion is the heat evolved in combustion beginning and ending at 60 F with product water in gaseous phase. Therefore, the net heat of combustion is less than the gross heat of combustion by the heat of vaporization of the water product.
Net/Gross heating value can be reported in Dry/Wet basis for a stream:
Dry basis - excludes water already present in the stream before combustion,
Wet basis - includes water already present in the stream before combustion.
The methods for calculating pure component and petroleum fractions heating value are different.
Petroleum Fractions: The method is based on API Procedure 14A1.3, 4th Edition (1983). The heating value is a function of API gravity corrected for impurity concentrations of H2O, S and other inert. Pure components Net Heating Value = -HCOM from pure component databank
17. How does ASPEN PLUS extrapolate values between 0% and the first distillation point and between the end point and 100% point for the True Boiling Point curve?
Suppose that the first point is at 10% and the last at 90%. Aspen Plus extrapolates between 0 - 10% and 90 - 100% using two methods: Probabilistic and Quadratic. The default is Probabilistic, which assumes a normal distribution of boiling points and uses the last point provided to extrapolate to the initial and end point. Quadratic was introduced in Aspen Plus Release 9.1-3
18. What is the difference between Probabilistic and Quadratic methods?
19. How does initial (default = 0.5%) and final (default = 99%) boiling points setting affect extrapolation?
The setting determines at what percentage the end points are reported. For example, with final point set at 0.99%, the temperature corresponding to 99% in the extrapolation is reported as the 100% temperatures. They may be adjusted to match end points.
20. For viscosity the API formula is limited to temperatures of below 400 C (750 F) and component MW of not greater than 7000. How does the program handle very heavy crudes or residues beyond these limits?
The procedure uses linear extrapolation for Watson K and API based the chart on 11-31 API Data Book, Fourth Edition.
21. How can Aspen Plus cope with downstream refinery products that are higher in olefinic components than the original crude does? For flosheets with reactors, there should be 2 sets of pseudo-components, one set for the streams before the reactor block and another set after the reactor. Each set of pseudo-components should have its own ssay data characterization. The reactor model will need to determine the flows of each pseudo-component for the reactor effluent.
22. How to use a SEP block to separate pseudo-components?
SEP block can only access pseudo-components entered in the Component.Main form or generated with Naming Option = LIST. It cannot access pseudo-components generated with the default Naming Option (NBP). You can set the Naming Option in pseudo-component Generation form to LIST. The steps are:
Run the simulation once to obtain the pseudo-component break-down.
Go to the pseudo-component Generation (PC-Calc) form and change the naming option from
NBP to LIST. Enter the names of all the pseudo-components in the LIST fields.
Now the pseudo-components become accessible in the SEP block.
23. What is the procedure of using pseudo-component components in a reactor model (eg. RYIELD)?
To do this, it is necessary to associate pseudo-components that are generated during an ADA/PCS run with components on the Components.Main form. These components can then be used in a reactor
model.
Steps:
Perform an ADA/PCS run.
Create a component id for each ADA/PCS fraction that you want to include in the reactor.
Go to 'Components.Main' form
Enter a user-specified Comp Id of type 'Pseudo' for each component.
Enter the required properties for each of the above components.
The component IDS now can be accessed in the reactor model.
24. If pseudo-components are used in RSTOIC, would atom balance be a problem since
pseudo-component MW's are estimated from correlation?
25. What is the difference of the five Naming Options in Pseudo-Component Generation?
NBP - use the normal boiling points to name each cut
LIST - use the IDs in the ID-LIST fields to name the cuts
NUMBERED - use integer numbers to name the cuts
ROUND-UP - use the upper temperature of the cut as its name
ROUND-DOWN - use the lower temperature of the cut as its name
For example, if a cut has an average T=215.4 F and the cut temperature specification is 200, 250, . . . F,
the cut will be named as
Naming Option Cut Name (ID)
BNP PC215F
ROUND-DOWN PC200F
ROUND-UP PC250F
25. Can I generate cuts at specified normal boiling temperatures?
No. You cannot specify a set of normal boiling temperatures (NBP) to generate cuts. What you can specify is the cut temperatures, such as 200, 225, 250, 275, 300, ... Aspen Plus will generate cuts at these temperatures and calculate the normal boiling point for each cut. With Naming Option = BNP, the cut names in the results or report file will not match the cut temperatures in the specification, although the
actual cuts are generated at the temperatures specified by user. Cut temperature and cut name are not to be confused. The specified cut temperatures are used to generate cuts at specific temperature points, and the cut name is as component ID for a pseudo-component. In the ADA/PCS.PC-Calc form, you can specify both
1. Cut Temperatures - used to generate the cuts.
2. Naming Option - used to name the cuts.
The specified cut temperatures overwrite the default values (see online HELP). There are five ways to name the cuts: NBP, LIST, NUMBERED, ROUND-UP and ROUND-DOWN.
26. How is the Pour Point calculated in Aspen Plus?
When a liquid petroleum product is cooled a point can be reached at which the oil ceases to flow in a standard test. The pour point is defined as the temperature 5 F above that point.
The user can input a pour point curve by supplying temperature values for the pour point at different mid-percent distilled points. Four such data points are required to define a property curve.
The value of pour point may be accessed by two different prop-set properties. Prop-set property 'POURPT' calculates the pour point of a stream based on the pour point property curve entered with the
assay. Prop-set property 'PRPT-API' calculates the pour point based on API procedure 2B8.1, a function of molecular weight, specific gravity and kinematic viscosity.
27. Does Aspen Plus estimate DHFORM and DGFORM for pseudo-components?
Yes. Both are by the Edmister method. Refer to the online help.
28. What are the limitations of the COSTALD method for calculating mole-volume? Can it be
applied to pseudo-components of high MW? How does it compare to API or Rackett?
Costald is an empirical correlation that computes mole-volume from Tb, MW and SG. For very heavy components, the calculated liquid density may be abnormally high. This method should not be used for pseudo components of high MW. For example, set up a system that has 1 pseudo component. MW = 980, GRAV=0.894 NBP=750.
COSTALD: density = 2790 kg/m3
API or Racket: density = 890 kg/m3
29. For a single component stream, the purecomp and mixture densities differ much.
RHO prop-set uses DNLDIP(DIPPR model)and that RHOMX uses the Rackett model even if the ThermoSwitch is set to use DIPPR. Aspen Plus uses DIPPR model for pure component and Rachett model for mixture. VL2RKT (mixture model) does not calculate mixture volume by mole-fraction average of pure component volume. It is a corresponding-state method in which the parameters are mixed (there are mixing rules for TC, RKTZRA, etc.). The pure-component model, on the other hand allows both the Rackett and the DIPPR model.
30. Why is the end point of a D86 curve higher than the boiling point of the heaviest component in a mixture?
The end point (100%) is extrapolated from the last percentage point (such as 95%). Therefore, it can be higher than the boiling point of the heaviest component.
31. Why does the distillation curve reported for an assay sometimes differ from the input curve?
This may be due to the presence of light-ends or curve fitting.
32. What value does Aspen Plus use for the endpoint and IBP of an assay? SimSci uses the 98% point as the endpoint and the 2% as the IBP, by default.
By default Aspen Plus use 0.5% and 99% for the initial and end points, respectively. The setting can be modified by user.
33. How can I change the number of pseudo-components generated?
This is under Components, Petro Characterization, Generation, Cuts.
33. Should I enter my light-end analysis in the stream input form or in the assay input form? Which is better?
In general light-end analysis is entered with assay in the assay input form. In that form, you can also enter specific gravity and molecular weight for each component. To enter light-end analysis in the stream
input form, the flow rate of each light-end component must be entered according to its concentration in the assay feed.
34. How many pseudo components should I generate for a given assay? The Getting Started
Guide shows how to do this but does not explain how to set the numbers.
As a Rule-of-Thumb, you should generate smaller (more) cuts at lower temperatures and larger (less)
cuts at higher temperatures. The idea is to generate more cuts in the temperature range of high interest
and less cuts in the temperature range of low interest. Cut temperature smaller than 5 F likely will not have much effect and larger than 25 F should be used with reason. The default cut setting is good for most applications.
35. How is the "Weight Factor" used in pseudo-component generation (PC-Calc)?
The Weight-Factor determines how pseudo-component parameters (Tc, Pc, ...) are linearly averaged of the assays/blends. The default is 1.0. For example, given a cut of 100 - 120 C
Assay-1 Assay-2
Weight-factor 0.4 0.6
Tc, C 500 550
Average Tc = 0.4 x 500 + 0.6 x 550 = 530 C
36. How are pseudo-components generated when multi assays/blends are entered?
Generation under Components, Petro Characterization (PC-Calc in R9) controls pseudo-component set generation.
When Generation is not specified (default), Aspen Plus will generate one common set of pseudo-components for all assays and blends, averaged with Weight Factor = 1.0. All assays/blends will be accessible in the feed stream input form. When Generation is specified, Aspen Plus will generate one set of pseudo-components for each ID created under Generation, where one ID may contain several assays, blends or combination of both. In this case only assays/blends included in Generation will show in the feed stream form. Those not included will be treated as not used in simulation and, therefore, become not accessible in the feed input form.
For example, if there are four assays A1, A2, A3 and A4. Under Generation, two Ids are created:
G-1, contains A1 and A2 with Weight Factor = 1.0 G-2, contains A3 only
Aspen will generate the first set of pseudo-components for G-1 and the second set for G-2. A1, A2 and
A3 will show in the feed input. No pseudo-component will be generated for A4, and it will not show in the
feed input form.
37. How are the following petroleum properties calculated?
ANIL-API
CETANENO
FLPT-API
MABP-API
PHYDRATE
THYDRATE
38. Do we have a correlation for calculating Cloudpt?
No.
39. What is the difference between the Harwell spline fitting method and the Hermite method?
When should I use the new method?
40. There are a number of different distillation curve conversion methods. Which one should I use?
The question applies to both the ASTM D2287 and ASTM D86 conversions.
API94 is the latest and recommended. The default is Edmister for D86 and API87 for D2287.
41. When should I change the Blend Options for a property?
If you have an in-house blending correlation and you know that gives better results.
42. Which option of SOLU-WATER should be used?
Option 3 is recommended for most applications. Option 2 is the default for petroleum applications when Free-Water = YES.
43. What is the plan for future versions with the crude library? (update or expansion)
Currently there is no plan to update/expand the assay library. Aspen Plus does have an interface to the Phillips Petroleum Assay Library which contains up to 500 assays.
44. How can we use in-house correlation for properties like assay viscosity?
Substitute user subroutines for assay parameter models under Components, Petro Characterization, Property.
45. Are there plans to improve the petroleum properties as REIDVP, hydrate formation temperature and pressure.
No. There is no such plan.
46. What does "Apply cracking correction" do when the distillation curve type is ASTM D86?
ASTM D86 distillation is carried out at atmospheric pressure. When heated sufficiently hot, heavy fractions undergo thermal cracking before vaporization. The amount and severity of thermal cracking
increases with increasing boiling point, contact time, pressure and temperature. Early editions of API included a correction for cracking for observed ASTM D86 temperatures above 475 F. No correction for cracking is now recommended.
47. Is D2887 on volume or weight basis?
D2887 is always on weight basis.
48. The final boiling points (TBP, D86 and other curves) generated by Aspen Plus for the bottom product and the feed differ up to 70 C. I would expect that the final boiling points be close together because they contain about the same amount of heavies.
The discrepancy is caused by end point extrapolation. Many users think that the initial and end points should be corresponding to the boiling points of the lightest and the heaviest component or pseudocomponent in the assay. That is NOT true. As a matter of
fact, TBPs of an assay are a function of component distribution. For two streams containing the same components but with different distribution, their TBP curves will differ. TBPs are defined by the "cumulative mid-point mass fractions" and the boiling temperature of components (pure or pseudo) in the mixture. The cumulative mid-point mass fraction is the sum of all the mass fractions of the components lighter than the component plus 1/2 of the mass fraction of the component.
Example:
Fraction Cumulative Frac
Pseudo Feed Residue Feed Residue Tb,C
PC242C 0.004045 4.97E-06 0.002023 2.48E-06 242
PC253C 0.007435 1.08E-05 0.007763 1.04E-05 253
PC267C 0.008231 1.5E-05 0.015596 2.33E-05 267
PC281C 0.00921 2.12E-05 0.024316 4.14E-05 281
PC295C 0.010555 3.11E-05 0.034199 6.76E-05 295
PC309C 0.012675 4.83E-05 0.045813 0.000107 309
PC323C 0.018611 8.98E-05 0.061456 0.000176 323
PC336C 0.023724 0.000148 0.082624 0.000295 336
PC351C 0.025983 0.000215 0.107478 0.000477 351
PC365C 0.036273 0.0004 0.138605 0.000784 365
PC379C 0.057014 0.000845 0.185249 0.001406 379
PC392C 0.067484 0.001328 0.247497 0.002493 392
PC406C 0.058821 0.001595 0.31065 0.003954 406
PC420C 0.067442 0.002511 0.373781 0.006008 420
PC440C 0.134319 0.008157 0.474662 0.011342 440
PC468C 0.125365 0.014943 0.604504 0.022892 468
PC496C 0.087523 0.021416 0.710947 0.041071 496
PC524C 0.085013 0.044097 0.797215 0.073828 524
PC548C 0.059187 0.058576 0.869315 0.125164 548
PC579C 0.016588 0.037357 0.907203 0.173131 579
PC607C 0.015729 0.068538 0.923362 0.226078 607
PC635C 0.01623 0.118288 0.939341 0.319491 635
PC677C 0.033627 0.375979 0.964269 0.566625 677
PC720C 0.018917 0.245386 0.990541 0.877307 720
If Tb vs cumulative fraction is plotted for the two streams, the curve will look differently.
Notice the ends at the cumulative mid-point mass fraction of the heaviest component. It is 0.99 for Feed and 0.877 for Residue. This means that points above 88%wt (90%, 95% and end point) for for Residue have to be extrapolated. The extrapolation may well generate an end point higher than the boiling temperature of the heaviest component. The fact that the highest mass fraction for Feed is 99% explains why its TBPCRV end point is much closer to the boiling temperature of the heaviest component. The extent of extrapolation is controlled by the Assay Procedure in R10:I
Initial boiling point =
Final boiling point =
The specified values determine at what percentage the 0% and 100% points are reported. To improve
end point calculation:
a. Increase the number of cuts.
b. Change the initial/final boiling points settings.
c. Use a different extrapolation method.
49. How to apply user correlation for assay physical property parameter (MW, Tc, Pc, . . .)
calculation in Aspen Plus.
Aspen has a suite of user routines for these property parameters. Currently they are not documented but can be obtained from Aspen Customer Support on an as-needed basis and used as templates for writing user models. Aspen plans to document and deliver these user models in future product release.
50. How is D86 curve converted to TBP curve? Aspen Plus and Pro II give different end points.
There are three (3) procedures for converting D86 data to TBP:
i. Edmister
ii. Edmister-Okamoto
iii. API procedure 3A1.1 Vol 1. 1994
As far as the end-point difference from Aspen Plus and Pro II, it has to do with the difference in curving fitting technique, which is standardized by API.
Test results from Release 9.3 are given below for conversion of D86 TO TBP - D86 data taken from API 5th Edition (1992):
%Dist D86 (F) API94 (F) ED-OK (F) EDMISTER (F)
0 303.404785 241.655090 248.901810 236.724243
5 336.359467 295.528229 302.408966 290.206329
10 350.000000 316.537140 325.531799 313.357819
30 380.000000 372.577423 376.742188 365.252502
50 404.000000 411.190308 415.087708 404.005188
70 433.000000 451.185425 456.328430 445.771851
90 469.000000 496.695404 501.794098 491.966125
95 486.264587 511.385498 521.353027 510.775635
100 503.529144 538.973938 540.911987 529.585205
Conversion by API94 matches exactly the example in API 5th Edition (1992).
51. How can I obtain the results of pumparound flows and side-stripper stage flows in PetroFrac?
In PetroFrac Pumparounds and Sidestripers have their own psuedostream forms. You can attach pseudo-streams to pumparound and side-strippers. For pumparounds, you can specify whether the
pseudo-stream is connected to the inlet or outlet. For side-strippers, you can specify the stage and phase of the pseudo-stream.
52. MultiFrac and PetroFrac report the liquid flow rates around the condenser with their own convention ( different from RADFRAC ) that may cause confusion for users. For instance, column profile seems to indicate that the liquid flow coming off the top stage is higher than the column liquid product rate, and reported RR seems to be inconsistent with the reported flow rates. What is the convention?
The source of the confusion is the way that the liquid flow rates around the top of the tower are reported:
The liquid product rate reported in column profiles includes the free water (it is wet) The top stage liquid flow rate is water free. The subcooled liquid flow rate includes hydrocarbon liquid product.
The following definitions should resolve the confusions:
a. Distillate liquid product (DL) in stream report:
o DL = total liquid product - water decant
b. Stage-1 liquid flow rate (L1) in the column profile:
o L1 = vapor from stage-2 (V2) - vapor product (V1)
c. Liquid return to the column (LR):
o LR = stage-1 liquid flow (L1) - DL
d. Reflux Ratio (RR):
o RR = LR / ( DL + DV )
53. How is the Flash Point calculated in Aspen Plus?
Flash Point is a measure of the volatility and the inflammability of liquid petroleum mixtures. It is the lowest temperature at which a liquid will give off enough vapor to form an flammable mixture with air. The value of the flash point may be accessed by prop-set properties:
FLPT-API, the API method for determining flash point (ASTM-D86)
FLPT-PM, the Pensky-Martens method (ASTM-D93)
FLPT-TAG, the Tag method (ASTM-D56)
FLASHPT and FLASHCRV, user specified assay property data for petroleum mixtures
For more information see Solution 115183.
54. If a stream contains significant amount of light components (vapor fraction), distillation curves, such as D86 curve will not be generated. What is the upper limit of vapor fraction above
which distillation curves are not generated?
1. D86T is not calculated if the related stream contains less than four(4) components of significant mole fraction (i.e., a mole fraction of greater than 1.D-2).
2. D86T is not calculated for streams that contain a lot of light end (>0.8) or are hydrogen rich(>0.01).
These limits were set to ensure the quality of simulation results.
55. What is free-water?
Free water is a term used in 3-phase (VLL) separation, referring to liquid that contains mainly water and little hydrocarbon. In such a case, the amount of hydrocarbon in the phase is so low that it is insignificant to simulation. Free-water assumption is often used in petroleum separation.
56. How is water solubility calculated and how to select water solubility option codes in 3-phase calculation?
There are several models for calculating water solubility in the organic phase in a 3-phase (VLL) equilibrium system. The water solubility option codes (0, 1, 2 and 3) determine which model to use for the simulation. The default:
Solu-water=2, Free-water=YES for petroleum application, Solu-water=3, Free-water=NO for all other applications.
When Free-water=NO, solu-water=3 is internally selected and what entered in the GUI is ignored. Choosing a water solubility option code is similar to selecting a property option set. It depends on the
system. In the past, codes 0 and 1 were widely used in refining applications with free-water = YES. However, code 3 is the most rigorous approach in dealing with 3-phase. Code 2 is somewhere between 1 and 3.
Aspen Plus calculates water k-value as follows:
k = gamma *(water fugacity coeff in organic phase)/(water fugacity coeff in vapor phase)
where, Water fugacity coeff in organic: free water option set (solu-water = 0,1,2,3)
Water fugacity coeff in vapor: the primary option set (solu-water = 1,2,3) and free water option set (solu-water = 0)
Gamma: 1/(mole fraction of water saturated in organic) (solu-water = 0,1)
ln (gamma) = G(1 - x)^2 (solu-water = 2): primary option set (solu-water = 3)
Mole fraction of water saturated in organic = calc from databank parameters A,B,C
ln (x) = A + B/T + CT
G is determined from gamma = 1/(mole frac of water saturated in organic)
1. Solu-water = 0 and 1 works OK when free water is ALWAYS present. When water is not saturated in organic, the results will be off.
2. Solu-water = 2 and 3 give more accurate results.
3. Solu-water = 3 is rigorous and recommended.
Water solubility increases exponentially with temperature. A saturated system at normal temperatures may well become unsaturated at higher temperatures.
57. I have the distillation curves of the products but not the curve of the feed. How can I set up my simulation?
Enter the product distillation curves as assay input and the gas products as light-ends. Blend them to create the feed.
58. What is the definition of "mid-percent distilled" in assay property input?
Mid-percent-distilled refers to a cut. A cut between 5% - 10% has a mid-percent-distilled point of 7.5%. The property entered should be the property of the cut, not the accumulative of the distilled or the heavy left in the pot.
59. What is the furnace feed convention in Petrofrac?
Stage duty on feed stage: similar to "on-stage" feed convention, specified furnace duty added to the feed stage. Single stage flash: similar to "above-stage" feed convention. Single state flash with liquid runback: similar to "above-stage" feed convention with the liquid runback from the stage above the feed stage sent to the furnace instead of the feed stage.
60. What is "liquid runback" in Petrofrac?
Liquid runback is the liquid flow from one stage to the stage below. Runback differs from stage liquid flow that includes side- draws (products or pumparounds). The RunbackSpec is usually used to set column liquid flow rates and prevent dry stage
aspenplus 60 问（炼油方向）
1. Aspen Plus does not generate distillation curves for a stream containing 4 pseudo-components. Why?
To generate a distillation curve, a stream must contain at least 5 pseudo-components of non-zero flow to generate distinctive data points at 10%, 30%, 50%, 70, 90%.
2. For streams with significant amount of light components, the calculated Reid vapor pressure is usually off. Why is that? Are there any guidelines for using Reid vapor pressure?
Reid vapor pressure is the absolute pressure exerted by a mixture (in pounds per square inch)
determined at 100 F and at a vapor-to-liquid volume ratio of 4 (ASTM Method D 323. RVP is intended for
characterizing the volatility of gasoline and crude oil, with a typical range of 1 to 20 psia. Out of this range,
the accuracy may be poor. Therefore, RDV should not be applied to very light or very heavy streams.
3. How is the Reid vapor pressure calculated in ASPEN PLUS?
The Reid vapor pressure is vapor pressure of liquid at 100 F, as measured according to ASTM D-323procedures. Aspen Plus simulates these procedures by a series of flash as follows:
i. Check if N2 or O2 is present; if so, determine their index values.
ii. Setup to the ideal gas option-set (sysop0).
iii. Calculate volume for AIR at 32 and 100 Degree F, 1 atm.
iv. Determine bubble point pressure of the liquid stream at 100 F.
v. Saturate the liquid with air at 32 degree F.
vi. Mix liquid with 4 vol% equivalent of air and flash at 100 F under constant volume.
vii. If calculated Reid vapor pres. is greater than 26 psi repeat w/o air saturation.
The Reid vapor pressure as measured by the ASTM D-323 differs from the true vapor pressure of the sample due to some small sample vaporization and the presence of water vapor and air. Reid vapor pressure is often used to determine the appropriate type of storage tank (cone roof or floating roof) for petroleum stocks with undefined components.
4. What is the difference between Prop-Set REIDVP, RVP-ASTM, and RVP?
The Prop-sets REIDVP and RVP-ASTM are identical. Both are kept for upward compatibility, and can be requested like any other Prop-set. RVP, however, is available only if you define a petroleum property curve for the Reid vapor pressure in the ASSAY.PROP-Curve form, by providing a table of Mid-Percent distilled vs. Reid vapor pressure values.
5. Aspen calculated API gravity is quite different from that of PRO II in some cases. What is the
method used in Aspen Plus and what are the assumptions/limitations?
The API Liquid Volume model implemented in Aspen Plus uses the following eqution:
Vm = Xp Vp + Xr Vr
Where
V = liquid molar volume
X = liquid mole fraction
m = mixture
p = pseudocomponents
r = real components
Vp (for pseudocomponent liquid mixture) is calculated using a correlation based on API Figure
6A3.5 (API Technical Data Book, 4th edition).
Vr (for real component liquid mixture) is caculated by the mixture Rachett model.
The variations in petroleum liquid density results are often caused by the number of cuts generated.
Increasing the number of cuts or reducing the cut temperature intervals may improve the accuracy. Refer to Solution 103736 for more details.
When multiple assays are present, the way they are blended could also affect the liquid density
calculation. The choices include generating:
one common pseudocomponent set for all assays
one pseudocomponent set for each assay
some combinations of assays and blends
Refer to Solution 103921 for more about one versus multiple pseudocomponent sets.
6. How is assay broken into pseudo-components?
Assay is broken into pseudo-components based on the number of cuts on the True Boiling Point (TBP) curve. The middle point of each cut is used as the boiling point of that cut.By default, Aspen Plus generates 40 pseudo-components using the following cut temperatures:
TBP Range (F) No. of Cuts Increments (F)
100 - 800 28 25
800 - 1200 8 50
1200 - 1600 4 100
User can change the default settings under Components, ADA Characterization, Generation.
7. Can users access Aspen Plus generated pseudo-components like real components? Users would like to access pseudo-component properties, such as Tc, Pc, Vc, API gravity, SG, and MW. Currently they are listed in the external report file.
No. Only a limited number of pseudo-component property parameters are reported as results in GUI.
User cannot alter what to report. To access and change pseudo-component property parameters, use user property model subroutines.
8. How does Aspen handle petroleum properties among pseudo-components? For example, if only bulk sulfur content is given, how does Aspen distribute it to pseudo-components?
Petroleum properties are treated as component attributes and attached to pseudo-components. When a property curve is given, the distribution of the property is based on the curve. When only a bulk property
is given, it is evenly distributed among all pseudo-components.
9. How does Aspen Plus calculate motor and research octane number?
Octane number is calculated from the Octane curve entered with the assay. There are four (4)property-sets for Octane number:
i. MOC-NO - Motor octane number
ii. MOCNCRC - Motor octane number curve
iii. ROC-NO - Research octane number
iv. ROCNCRV - Research octane number curve
10. What is the difference between match and not-match light ends?
Light-ends (gases) are typically analyzed separately from the liquid fractions. The distillation curves from
the lab normally exclude the light-ends. To generate a distillation curve reflecting the full distillation range of an assay, you need to use Match Light-ends. Match light-ends uses the boiling points of the light-ends components to determine the curve in the range from 0 to lt% where lt% is the percentage of the light-ends in the assay. The default is not match light-ends.
11. How does Aspen Plus match light ends?
When Match Light-ends is selected, the TBP curve, from the light-end fraction and blow, will be represented by the boiling points and concentrations of the light-end components. For example, given the light-end fraction = 0.05, the boiling point of the heaviest lights = 64 F, the original TBP curve at 0.05 = 68 F. After matching light-ends, the final TBP curve will be 64 F at 0.05. And, from 0 to 0.05, the curve will be calculated from the light-ends. The original TBP curve in the range from 0 to 0.05 is not used.
12. When using match light ends, sometime I receive a warning message saying the temperature
difference is too large. Under what conditions will Aspen Plus not perform matching light ends?
Match light-ends works only when the boiling point of the heaviest component in the light-ends falls within
10 F on the TBP curve at the light-end fraction. In the above example, if the original TBP curve at 0.05 is below 54 F or above 74 F, Aspen Plus will give an error message and not perform matching light-ends.
To avoid this error, user has to make sure that the light-ends analysis is accurate and the fraction of light-ends in the assay is accurate. To force matching light-ends when the temperature difference is > 10F, you can：
a. Add or remove the heavy components in the light-end analysis.
b. Change light-end fraction.
13. Can one enter viscosity data for a stream? For heavy petroleum fractions, the API methods do not cope well. If two viscosity points are available, 2800 cp @275 F and 600 cp @325 F can they be used in the simulation?
You cannot enter the data directly either in Assay input or stream input. The current procedure is to substitute MUL2USR for the mixture viscosity model. Write a Fortran subroutine for doing interpolation
based on these two points. The subroutine fits a model of the type:
ln(mulmx) = aa + bb/T
14. How is pseudo-component specific gravity calculated?
Liquid molar volume is based on the Rackett or Cavett model. The default is Rackett. Refer to the Aspen Plus on-line help.
15. How is pseudo-component MW calculated?
There are nine (9) models for calculating pseudo-component molecular weight. Refer to the Aspen Plus on-line help.
16. How is gross/net heating value calculated for a petroleum stream? Is the method the same for pure components and pseudo-components?
Heating value is also called heat of combustion. The heat of combustion of a substance is the change in enthalpy when that substance is converted to its final oxidation products by means of molecular oxygen. The beginning and ending states are:
standard heat of combustion: 77 F and 1 atm
gross heat of combustion: 60 F and 1 atm
The normal state for the water formed by the reaction is liquid in both cases. Since the sensible heat of water from 60 to 77 F is usually negligible in comparison with the heat of combustion, the gross and standard heats of combustion are approximately equal. The net heat of combustion is the heat evolved in combustion beginning and ending at 60 F with product water in gaseous phase. Therefore, the net heat of combustion is less than the gross heat of combustion by the heat of vaporization of the water product.
Net/Gross heating value can be reported in Dry/Wet basis for a stream:
Dry basis - excludes water already present in the stream before combustion,
Wet basis - includes water already present in the stream before combustion.
The methods for calculating pure component and petroleum fractions heating value are different.
Petroleum Fractions: The method is based on API Procedure 14A1.3, 4th Edition (1983). The heating value is a function of API gravity corrected for impurity concentrations of H2O, S and other inert. Pure components Net Heating Value = -HCOM from pure component databank
17. How does ASPEN PLUS extrapolate values between 0% and the first distillation point and between the end point and 100% point for the True Boiling Point curve?
Suppose that the first point is at 10% and the last at 90%. Aspen Plus extrapolates between 0 - 10% and 90 - 100% using two methods: Probabilistic and Quadratic. The default is Probabilistic, which assumes a normal distribution of boiling points and uses the last point provided to extrapolate to the initial and end point. Quadratic was introduced in Aspen Plus Release 9.1-3
18. What is the difference between Probabilistic and Quadratic methods?
19. How does initial (default = 0.5%) and final (default = 99%) boiling points setting affect extrapolation?
The setting determines at what percentage the end points are reported. For example, with final point set at 0.99%, the temperature corresponding to 99% in the extrapolation is reported as the 100% temperatures. They may be adjusted to match end points.
20. For viscosity the API formula is limited to temperatures of below 400 C (750 F) and component MW of not greater than 7000. How does the program handle very heavy crudes or residues beyond these limits?
The procedure uses linear extrapolation for Watson K and API based the chart on 11-31 API Data Book, Fourth Edition.
21. How can Aspen Plus cope with downstream refinery products that are higher in olefinic components than the original crude does? For flosheets with reactors, there should be 2 sets of pseudo-components, one set for the streams before the reactor block and another set after the reactor. Each set of pseudo-components should have its own ssay data characterization. The reactor model will need to determine the flows of each pseudo-component for the reactor effluent.
22. How to use a SEP block to separate pseudo-components?
SEP block can only access pseudo-components entered in the Component.Main form or generated with Naming Option = LIST. It cannot access pseudo-components generated with the default Naming Option (NBP). You can set the Naming Option in pseudo-component Generation form to LIST. The steps are:
Run the simulation once to obtain the pseudo-component break-down.
Go to the pseudo-component Generation (PC-Calc) form and change the naming option from
NBP to LIST. Enter the names of all the pseudo-components in the LIST fields.
Now the pseudo-components become accessible in the SEP block.
23. What is the procedure of using pseudo-component components in a reactor model (eg. RYIELD)?
To do this, it is necessary to associate pseudo-components that are generated during an ADA/PCS run with components on the Components.Main form. These components can then be used in a reactor
model.
Steps:
Perform an ADA/PCS run.
Create a component id for each ADA/PCS fraction that you want to include in the reactor.
Go to 'Components.Main' form
Enter a user-specified Comp Id of type 'Pseudo' for each component.
Enter the required properties for each of the above components.
The component IDS now can be accessed in the reactor model.
24. If pseudo-components are used in RSTOIC, would atom balance be a problem since
pseudo-component MW's are estimated from correlation?
25. What is the difference of the five Naming Options in Pseudo-Component Generation?
NBP - use the normal boiling points to name each cut
LIST - use the IDs in the ID-LIST fields to name the cuts
NUMBERED - use integer numbers to name the cuts
ROUND-UP - use the upper temperature of the cut as its name
ROUND-DOWN - use the lower temperature of the cut as its name
For example, if a cut has an average T=215.4 F and the cut temperature specification is 200, 250, . . . F,
the cut will be named as
Naming Option Cut Name (ID)
BNP PC215F
ROUND-DOWN PC200F
ROUND-UP PC250F
25. Can I generate cuts at specified normal boiling temperatures?
No. You cannot specify a set of normal boiling temperatures (NBP) to generate cuts. What you can specify is the cut temperatures, such as 200, 225, 250, 275, 300, ... Aspen Plus will generate cuts at these temperatures and calculate the normal boiling point for each cut. With Naming Option = BNP, the cut names in the results or report file will not match the cut temperatures in the specification, although the
actual cuts are generated at the temperatures specified by user. Cut temperature and cut name are not to be confused. The specified cut temperatures are used to generate cuts at specific temperature points, and the cut name is as component ID for a pseudo-component. In the ADA/PCS.PC-Calc form, you can specify both
1. Cut Temperatures - used to generate the cuts.
2. Naming Option - used to name the cuts.
The specified cut temperatures overwrite the default values (see online HELP). There are five ways to name the cuts: NBP, LIST, NUMBERED, ROUND-UP and ROUND-DOWN.
26. How is the Pour Point calculated in Aspen Plus?
When a liquid petroleum product is cooled a point can be reached at which the oil ceases to flow in a standard test. The pour point is defined as the temperature 5 F above that point.
The user can input a pour point curve by supplying temperature values for the pour point at different mid-percent distilled points. Four such data points are required to define a property curve.
The value of pour point may be accessed by two different prop-set properties. Prop-set property 'POURPT' calculates the pour point of a stream based on the pour point property curve entered with the
assay. Prop-set property 'PRPT-API' calculates the pour point based on API procedure 2B8.1, a function of molecular weight, specific gravity and kinematic viscosity.
27. Does Aspen Plus estimate DHFORM and DGFORM for pseudo-components?
Yes. Both are by the Edmister method. Refer to the online help.
28. What are the limitations of the COSTALD method for calculating mole-volume? Can it be
applied to pseudo-components of high MW? How does it compare to API or Rackett?
Costald is an empirical correlation that computes mole-volume from Tb, MW and SG. For very heavy components, the calculated liquid density may be abnormally high. This method should not be used for pseudo components of high MW. For example, set up a system that has 1 pseudo component. MW = 980, GRAV=0.894 NBP=750.
COSTALD: density = 2790 kg/m3
API or Racket: density = 890 kg/m3
29. For a single component stream, the purecomp and mixture densities differ much.
RHO prop-set uses DNLDIP(DIPPR model)and that RHOMX uses the Rackett model even if the ThermoSwitch is set to use DIPPR. Aspen Plus uses DIPPR model for pure component and Rachett model for mixture. VL2RKT (mixture model) does not calculate mixture volume by mole-fraction average of pure component volume. It is a corresponding-state method in which the parameters are mixed (there are mixing rules for TC, RKTZRA, etc.). The pure-component model, on the other hand allows both the Rackett and the DIPPR model.
30. Why is the end point of a D86 curve higher than the boiling point of the heaviest component in a mixture?
The end point (100%) is extrapolated from the last percentage point (such as 95%). Therefore, it can be higher than the boiling point of the heaviest component.
31. Why does the distillation curve reported for an assay sometimes differ from the input curve?
This may be due to the presence of light-ends or curve fitting.
32. What value does Aspen Plus use for the endpoint and IBP of an assay? SimSci uses the 98% point as the endpoint and the 2% as the IBP, by default.
By default Aspen Plus use 0.5% and 99% for the initial and end points, respectively. The setting can be modified by user.
33. How can I change the number of pseudo-components generated?
This is under Components, Petro Characterization, Generation, Cuts.
33. Should I enter my light-end analysis in the stream input form or in the assay input form? Which is better?
In general light-end analysis is entered with assay in the assay input form. In that form, you can also enter specific gravity and molecular weight for each component. To enter light-end analysis in the stream
input form, the flow rate of each light-end component must be entered according to its concentration in the assay feed.
34. How many pseudo components should I generate for a given assay? The Getting Started
Guide shows how to do this but does not explain how to set the numbers.
As a Rule-of-Thumb, you should generate smaller (more) cuts at lower temperatures and larger (less)
cuts at higher temperatures. The idea is to generate more cuts in the temperature range of high interest
and less cuts in the temperature range of low interest. Cut temperature smaller than 5 F likely will not have much effect and larger than 25 F should be used with reason. The default cut setting is good for most applications.
35. How is the "Weight Factor" used in pseudo-component generation (PC-Calc)?
The Weight-Factor determines how pseudo-component parameters (Tc, Pc, ...) are linearly averaged of the assays/blends. The default is 1.0. For example, given a cut of 100 - 120 C
Assay-1 Assay-2
Weight-factor 0.4 0.6
Tc, C 500 550
Average Tc = 0.4 x 500 + 0.6 x 550 = 530 C
36. How are pseudo-components generated when multi assays/blends are entered?
Generation under Components, Petro Characterization (PC-Calc in R9) controls pseudo-component set generation.
When Generation is not specified (default), Aspen Plus will generate one common set of pseudo-components for all assays and blends, averaged with Weight Factor = 1.0. All assays/blends will be accessible in the feed stream input form. When Generation is specified, Aspen Plus will generate one set of pseudo-components for each ID created under Generation, where one ID may contain several assays, blends or combination of both. In this case only assays/blends included in Generation will show in the feed stream form. Those not included will be treated as not used in simulation and, therefore, become not accessible in the feed input form.
For example, if there are four assays A1, A2, A3 and A4. Under Generation, two Ids are created:
G-1, contains A1 and A2 with Weight Factor = 1.0 G-2, contains A3 only
Aspen will generate the first set of pseudo-components for G-1 and the second set for G-2. A1, A2 and
A3 will show in the feed input. No pseudo-component will be generated for A4, and it will not show in the
feed input form.
37. How are the following petroleum properties calculated?
ANIL-API
CETANENO
FLPT-API
MABP-API
PHYDRATE
THYDRATE
38. Do we have a correlation for calculating Cloudpt?
No.
39. What is the difference between the Harwell spline fitting method and the Hermite method?
When should I use the new method?
40. There are a number of different distillation curve conversion methods. Which one should I use?
The question applies to both the ASTM D2287 and ASTM D86 conversions.
API94 is the latest and recommended. The default is Edmister for D86 and API87 for D2287.
41. When should I change the Blend Options for a property?
If you have an in-house blending correlation and you know that gives better results.
42. Which option of SOLU-WATER should be used?
Option 3 is recommended for most applications. Option 2 is the default for petroleum applications when Free-Water = YES.
43. What is the plan for future versions with the crude library? (update or expansion)
Currently there is no plan to update/expand the assay library. Aspen Plus does have an interface to the Phillips Petroleum Assay Library which contains up to 500 assays.
44. How can we use in-house correlation for properties like assay viscosity?
Substitute user subroutines for assay parameter models under Components, Petro Characterization, Property.
45. Are there plans to improve the petroleum properties as REIDVP, hydrate formation temperature and pressure.
No. There is no such plan.
46. What does "Apply cracking correction" do when the distillation curve type is ASTM D86?
ASTM D86 distillation is carried out at atmospheric pressure. When heated sufficiently hot, heavy fractions undergo thermal cracking before vaporization. The amount and severity of thermal cracking
increases with increasing boiling point, contact time, pressure and temperature. Early editions of API included a correction for cracking for observed ASTM D86 temperatures above 475 F. No correction for cracking is now recommended.
47. Is D2887 on volume or weight basis?
D2887 is always on weight basis.
48. The final boiling points (TBP, D86 and other curves) generated by Aspen Plus for the bottom product and the feed differ up to 70 C. I would expect that the final boiling points be close together because they contain about the same amount of heavies.
The discrepancy is caused by end point extrapolation. Many users think that the initial and end points should be corresponding to the boiling points of the lightest and the heaviest component or pseudocomponent in the assay. That is NOT true. As a matter of
fact, TBPs of an assay are a function of component distribution. For two streams containing the same components but with different distribution, their TBP curves will differ. TBPs are defined by the "cumulative mid-point mass fractions" and the boiling temperature of components (pure or pseudo) in the mixture. The cumulative mid-point mass fraction is the sum of all the mass fractions of the components lighter than the component plus 1/2 of the mass fraction of the component.
Example:
Fraction Cumulative Frac
Pseudo Feed Residue Feed Residue Tb,C
PC242C 0.004045 4.97E-06 0.002023 2.48E-06 242
PC253C 0.007435 1.08E-05 0.007763 1.04E-05 253
PC267C 0.008231 1.5E-05 0.015596 2.33E-05 267
PC281C 0.00921 2.12E-05 0.024316 4.14E-05 281
PC295C 0.010555 3.11E-05 0.034199 6.76E-05 295
PC309C 0.012675 4.83E-05 0.045813 0.000107 309
PC323C 0.018611 8.98E-05 0.061456 0.000176 323
PC336C 0.023724 0.000148 0.082624 0.000295 336
PC351C 0.025983 0.000215 0.107478 0.000477 351
PC365C 0.036273 0.0004 0.138605 0.000784 365
PC379C 0.057014 0.000845 0.185249 0.001406 379
PC392C 0.067484 0.001328 0.247497 0.002493 392
PC406C 0.058821 0.001595 0.31065 0.003954 406
PC420C 0.067442 0.002511 0.373781 0.006008 420
PC440C 0.134319 0.008157 0.474662 0.011342 440
PC468C 0.125365 0.014943 0.604504 0.022892 468
PC496C 0.087523 0.021416 0.710947 0.041071 496
PC524C 0.085013 0.044097 0.797215 0.073828 524
PC548C 0.059187 0.058576 0.869315 0.125164 548
PC579C 0.016588 0.037357 0.907203 0.173131 579
PC607C 0.015729 0.068538 0.923362 0.226078 607
PC635C 0.01623 0.118288 0.939341 0.319491 635
PC677C 0.033627 0.375979 0.964269 0.566625 677
PC720C 0.018917 0.245386 0.990541 0.877307 720
If Tb vs cumulative fraction is plotted for the two streams, the curve will look differently.
Notice the ends at the cumulative mid-point mass fraction of the heaviest component. It is 0.99 for Feed and 0.877 for Residue. This means that points above 88%wt (90%, 95% and end point) for for Residue have to be extrapolated. The extrapolation may well generate an end point higher than the boiling temperature of the heaviest component. The fact that the highest mass fraction for Feed is 99% explains why its TBPCRV end point is much closer to the boiling temperature of the heaviest component. The extent of extrapolation is controlled by the Assay Procedure in R10:I
Initial boiling point =
Final boiling point =
The specified values determine at what percentage the 0% and 100% points are reported. To improve
end point calculation:
a. Increase the number of cuts.
b. Change the initial/final boiling points settings.
c. Use a different extrapolation method.
49. How to apply user correlation for assay physical property parameter (MW, Tc, Pc, . . .)
calculation in Aspen Plus.
Aspen has a suite of user routines for these property parameters. Currently they are not documented but can be obtained from Aspen Customer Support on an as-needed basis and used as templates for writing user models. Aspen plans to document and deliver these user models in future product release.
50. How is D86 curve converted to TBP curve? Aspen Plus and Pro II give different end points.
There are three (3) procedures for converting D86 data to TBP:
i. Edmister
ii. Edmister-Okamoto
iii. API procedure 3A1.1 Vol 1. 1994
As far as the end-point difference from Aspen Plus and Pro II, it has to do with the difference in curving fitting technique, which is standardized by API.
Test results from Release 9.3 are given below for conversion of D86 TO TBP - D86 data taken from API 5th Edition (1992):
%Dist D86 (F) API94 (F) ED-OK (F) EDMISTER (F)
0 303.404785 241.655090 248.901810 236.724243
5 336.359467 295.528229 302.408966 290.206329
10 350.000000 316.537140 325.531799 313.357819
30 380.000000 372.577423 376.742188 365.252502
50 404.000000 411.190308 415.087708 404.005188
70 433.000000 451.185425 456.328430 445.771851
90 469.000000 496.695404 501.794098 491.966125
95 486.264587 511.385498 521.353027 510.775635
100 503.529144 538.973938 540.911987 529.585205
Conversion by API94 matches exactly the example in API 5th Edition (1992).
51. How can I obtain the results of pumparound flows and side-stripper stage flows in PetroFrac?
In PetroFrac Pumparounds and Sidestripers have their own psuedostream forms. You can attach pseudo-streams to pumparound and side-strippers. For pumparounds, you can specify whether the
pseudo-stream is connected to the inlet or outlet. For side-strippers, you can specify the stage and phase of the pseudo-stream.
52. MultiFrac and PetroFrac report the liquid flow rates around the condenser with their own convention ( different from RADFRAC ) that may cause confusion for users. For instance, column profile seems to indicate that the liquid flow coming off the top stage is higher than the column liquid product rate, and reported RR seems to be inconsistent with the reported flow rates. What is the convention?
The source of the confusion is the way that the liquid flow rates around the top of the tower are reported:
The liquid product rate reported in column profiles includes the free water (it is wet) The top stage liquid flow rate is water free. The subcooled liquid flow rate includes hydrocarbon liquid product.
The following definitions should resolve the confusions:
a. Distillate liquid product (DL) in stream report:
o DL = total liquid product - water decant
b. Stage-1 liquid flow rate (L1) in the column profile:
o L1 = vapor from stage-2 (V2) - vapor product (V1)
c. Liquid return to the column (LR):
o LR = stage-1 liquid flow (L1) - DL
d. Reflux Ratio (RR):
o RR = LR / ( DL + DV )
53. How is the Flash Point calculated in Aspen Plus?
Flash Point is a measure of the volatility and the inflammability of liquid petroleum mixtures. It is the lowest temperature at which a liquid will give off enough vapor to form an flammable mixture with air. The value of the flash point may be accessed by prop-set properties:
FLPT-API, the API method for determining flash point (ASTM-D86)
FLPT-PM, the Pensky-Martens method (ASTM-D93)
FLPT-TAG, the Tag method (ASTM-D56)
FLASHPT and FLASHCRV, user specified assay property data for petroleum mixtures
For more information see Solution 115183.
54. If a stream contains significant amount of light components (vapor fraction), distillation curves, such as D86 curve will not be generated. What is the upper limit of vapor fraction above
which distillation curves are not generated?
1. D86T is not calculated if the related stream contains less than four(4) components of significant mole fraction (i.e., a mole fraction of greater than 1.D-2).
2. D86T is not calculated for streams that contain a lot of light end (>0.8) or are hydrogen rich(>0.01).
These limits were set to ensure the quality of simulation results.
55. What is free-water?
Free water is a term used in 3-phase (VLL) separation, referring to liquid that contains mainly water and little hydrocarbon. In such a case, the amount of hydrocarbon in the phase is so low that it is insignificant to simulation. Free-water assumption is often used in petroleum separation.
56. How is water solubility calculated and how to select water solubility option codes in 3-phase calculation?
There are several models for calculating water solubility in the organic phase in a 3-phase (VLL) equilibrium system. The water solubility option codes (0, 1, 2 and 3) determine which model to use for the simulation. The default:
Solu-water=2, Free-water=YES for petroleum application, Solu-water=3, Free-water=NO for all other applications.
When Free-water=NO, solu-water=3 is internally selected and what entered in the GUI is ignored. Choosing a water solubility option code is similar to selecting a property option set. It depends on the
system. In the past, codes 0 and 1 were widely used in refining applications with free-water = YES. However, code 3 is the most rigorous approach in dealing with 3-phase. Code 2 is somewhere between 1 and 3.
Aspen Plus calculates water k-value as follows:
k = gamma *(water fugacity coeff in organic phase)/(water fugacity coeff in vapor phase)
where, Water fugacity coeff in organic: free water option set (solu-water = 0,1,2,3)
Water fugacity coeff in vapor: the primary option set (solu-water = 1,2,3) and free water option set (solu-water = 0)
Gamma: 1/(mole fraction of water saturated in organic) (solu-water = 0,1)
ln (gamma) = G(1 - x)^2 (solu-water = 2): primary option set (solu-water = 3)
Mole fraction of water saturated in organic = calc from databank parameters A,B,C
ln (x) = A + B/T + CT
G is determined from gamma = 1/(mole frac of water saturated in organic)
1. Solu-water = 0 and 1 works OK when free water is ALWAYS present. When water is not saturated in organic, the results will be off.
2. Solu-water = 2 and 3 give more accurate results.
3. Solu-water = 3 is rigorous and recommended.
Water solubility increases exponentially with temperature. A saturated system at normal temperatures may well become unsaturated at higher temperatures.
57. I have the distillation curves of the products but not the curve of the feed. How can I set up my simulation?
Enter the product distillation curves as assay input and the gas products as light-ends. Blend them to create the feed.
58. What is the definition of "mid-percent distilled" in assay property input?
Mid-percent-distilled refers to a cut. A cut between 5% - 10% has a mid-percent-distilled point of 7.5%. The property entered should be the property of the cut, not the accumulative of the distilled or the heavy left in the pot.
59. What is the furnace feed convention in Petrofrac?
Stage duty on feed stage: similar to "on-stage" feed convention, specified furnace duty added to the feed stage. Single stage flash: similar to "above-stage" feed convention. Single state flash with liquid runback: similar to "above-stage" feed convention with the liquid runback from the stage above the feed stage sent to the furnace instead of the feed stage.
60. What is "liquid runback" in Petrofrac?
Liquid runback is the liquid flow from one stage to the stage below. Runback differs from stage liquid flow that includes side- draws (products or pumparounds). The RunbackSpec is usually used to set column liquid flow rates and prevent dry stage
Saturday, February 21, 2009
坐在杯边，焦急的等待
相对漫长的寒假终于结束，也许这是我人生中的最后一次寒假，也许不是。一年一度的研招考试过去一个多月了，但是离公布分数还有很久。这期间让人面临两难的尴尬，找工作？等着上学？也许两者都是火坑，只是哪个烧的快点而已。就像四年前要上大学一样，满心以为要踏入天堂了，上了大学才知道好多人宁可选择下地狱也不想再上了。现在的心情就像一只坐在杯子边的蚂蚁，一边是水，一边是悬崖，往哪边跳？就看你是会飞还是会游，其实事情就这么简单。
如何撰写论文综述
综 述
一、综述概述
1．什么是综述：综述，又称文献综述，英文名为review。它是利用已发表的文献资料为原始素材撰写的论文。
综述包括“综”与“述”两个方面。所谓综就是指作者必须对占有的大量素材进行归纳整理、综合分析，而使材料更加精炼、更加明确、更加层次分明、更有逻辑性。所谓述就是评述，是对所写专题的比较全面、深人、系统的论述。因而，综述是对某一专题、某一领域的历史背景、前人工作、争论焦点、研究现状与发展前景等方面，以作者自己的观点写成的严谨而系统的评论性、资料性科技论文。
综述反映出某一专题、某一领域在一定时期内的研究工作进展情况。可以把该专题、该领域及其分支学科的最新进展、新发现、新趋势、新水平、新原理和新技术比较全面地介绍给读者，使读者尤其从事该专题、该领域研究工作的读者获益匪浅。因此，综述是教学、科研以及生产的重要参考资料。
2．综述的类型：根据搜集的原始文献资料数量、提炼加工程度、组织写作形式以及学术水平的高低，综述可分为归纳性、普通性和评论性三类。
(1)归纳性综述：归纳性综述是作者将搜集到的文献资料进行整理归纳，并按一定顺序进行分类排列，使它们互相关联，前后连贯，而撰写的具有条理性、系统性和逻辑性的学术论文。它能在一定程度上反映出某一专题、某一领域的当前研究进展，但很少有作者自己的见解和观点。
(2)普通性综述：普通性综述系具有一定学术水平的作者，在搜集较多资料的基础上撰写的系统性和逻辑性都较强的学术论文，文中能表达出作者的观点或倾向性。因而论文对从事该专题、该领域工作的读者有一定的指导意义和参考价值。
(3)评论性综述：评述性综述系有较高学术水平、在该领域有较高造诣的作者。在搜集大量资料的基础上．对原始素材归纳整理、综合分析、撰写的反映当前该领域研究进展和发展前景的评论性学术论文。因论文的逻辑性强，有较多作者的见解和评论。故对读者有普遍的指导意义，并对读者的研究工作具有导向意义。
二、综述的书写格式
综述与一般科技论文不同。科技论文注重研究方法的科学性和结果的可信性，特别强调阳性结果。而综述要写出主题(某一专题、某一领域)的详细情报资料，不仅要指出发展背景和工作意义，而且还应有作者的评论性意见，指出研究成败的原因；不仅要指出目前研究的热点和争论焦点，而且还应指出有待于进一步探索和研究的处女领域：不仅要介绍主题的研究动态与最新进展，而且还应在评述的基础上，预测发展趋势和应用前景。因此，综述的书写格式比较多样化，除了题目、署名、摘要、关键词(这四部分与一般科技论文相同)以外，一般还包括前言、主体、总结和参考文献四部分，其中前三部分系综述的正文，后一部分是撰写综述的基础。
1。前言：与一般科技论文一样，前言又称引言，是将读者导人论文主题的部分，主要叙述综述的目的和作用，概述主题的有关概念和定义，简述所选择主题的历史背景、发展过程、现状、争论焦点、应用价值和实践意义，同时还可限定综述的范围．使读者对综述的主题有一个初步的印象。这部分约200～300字。
2．主体部分：综述主体部分的篇幅范围特别大，短者5000字左右，长者可达几万字，其叙述方式灵活多样，没有必须遵循的同定模式，常由作者根据综述的内容，自行设计创造。一般可根据主体部分的内容多寡分成几个大部分，每部分标上简短而醒目的小标题。部分的区分标准也多种多样，有的按年代，有的按问题，有的按不同论点，有的按发展阶段。然而，不管采用何种方式，都应该包括历史发展、现状评述和发展前景预测三方面的内容。
(1)历史发展：按时间顺序，简述该主题的来龙去脉，发展概况及各阶段的研究水平。
(2)现状评述：重点是论述当前国内外的研究现状，着重评述哪些问题已经解决，哪些问题还没有解决，提出可能的解决途径；目前存在的争论焦点，比较各种观点的异同并作出理论解释，亮明作者的观点；详细介绍有创造性和发展前途的理论和假说，并引出论据，指出可能的发展趋势。
(3)发展前景预测：通过纵横对比，肯定该主题的研究水平，指出存在的问题，提出可能的发展趋势，指明研究方向，提示研究的捷径。
3．总结部分：总结部分又称为结论、小结或结语。书写总结时，可以根据主体部分的论述，提出几条语言简明、含义确切的意见和建议；也可以对主体部分的主要内容作出扼要的概括，并提出作者自己的见解，表明作者赞成什么，反对什么；对于篇幅较小的综述，可以不单独列出总结，仅在主体各部分内容论述完后，用几句话对全文进行高度概括。
4．参考文献：参考文献是综述的原始素材．也是综述的基础，因此，拥有并列出足够的参考文献显得格外重要。它除了表示尊重被引证作者的劳动及表明引用的资料有其科学依据以外，更重要的是为读者深入探讨该主题提供查找有关文献的线索。
三、综述的写作步骤和注意事项
1．综述的写作步骤。
(1)选题：综述的选题应遵循以下几个原则：
①选择的专题或领域：应是近年来进展甚快、内容新颖、知识尚未普及而研究报告积累甚多的主题；或研究结论不一致有争论的主题或是新发现和新技术在我国有应用价值的主题。
②选题与作者的关系：应选择与作者从事的专业密切相关的主题；或是与作者从事专业交叉的边缘学科的主题；或是作者即将进行探索与研究的主题；或是与作者从事专业关系不大，但乐于探索的主题；或是科学情报工作者作为研究成果的主题。
③题目要具体、明确，范围不宜过大．切忌无的放矢，泛泛而谈。
④选题必须有所创新，具有实用价值。
(2)搜集文献：题目确定后．需要查阅和积累有关文献资料．这是写好综述的基础。因而，要求搜集的文献越多、越全越好。常用的方法是通过文摘、索引期刊等检索工具书查阅文献。也可以采用微机联网检索等先进的查阅文献方法。
(3)阅读和整理文献：阅读文献是写好综述的重要步骤。因此，在阅读文献时，必须领会文献的主要论点和论据，做好“读书笔记”，并制作文献摘录卡片，用自己的语言写下阅读时所得到的启示、体会和想法，摘录文献精髓，为撰写综述积累最佳的原始素材。阅读文献、制作卡片的过程，实际上是消化和吸收文献精髓的过程。制作的卡片和笔记便于加工处理．可以按综述的主题要求进行整理、分类编排，使之系列化和条理化。最终对分类整理好的资料进行科学分析，结合作者的实践经验，写出体会，提出自己的观点。
(4)撰写成文：撰写综述之前，应先拟定写作大纲，然后写出初稿，待“创作热”冷却后进行修改。
2．撰写综述的注意事项。
(1)综述内容应是前人未曾写过的。如已有人发表过类似综述，一般不宜重复，更不能以他人综述之内容作为自己综述的素材。
(2)对于某些新知识领域、新技术，写作时可以追溯该主题的发展过程，适当增加一些基础知识内容，以便读者理解。对于人所共知或知之甚多的主题，应只写其新进展、新动向、新发展，不重复别人已综述过的前一阶段的研究状况。
(3)综述的素材来自前人的研究报告，必须忠实原文，不可断章取义，阉割或歪曲前人的观点。
(4)综述的撰写者必须对所写主题的基础知识、历史与发展过程、最新进展全面了解，或者作者本身也从事该主题的研究工作，是该主题的“专家”，否则容易出大错、闹笑话。
(5)撰写综述时，搜集的文献资料尽可能齐全，切忌随便收集一些文献就动手撰写，更忌讳阅读了几篇中文资料，便拼凑成一篇所谓的综述。
(6)综述的原始素材应体现出一个“新”字，亦即必须有最近最新发表的文献，一般不将教科书、专著列为参考文献。
(本文转自百度知道)
一、综述概述
1．什么是综述：综述，又称文献综述，英文名为review。它是利用已发表的文献资料为原始素材撰写的论文。
综述包括“综”与“述”两个方面。所谓综就是指作者必须对占有的大量素材进行归纳整理、综合分析，而使材料更加精炼、更加明确、更加层次分明、更有逻辑性。所谓述就是评述，是对所写专题的比较全面、深人、系统的论述。因而，综述是对某一专题、某一领域的历史背景、前人工作、争论焦点、研究现状与发展前景等方面，以作者自己的观点写成的严谨而系统的评论性、资料性科技论文。
综述反映出某一专题、某一领域在一定时期内的研究工作进展情况。可以把该专题、该领域及其分支学科的最新进展、新发现、新趋势、新水平、新原理和新技术比较全面地介绍给读者，使读者尤其从事该专题、该领域研究工作的读者获益匪浅。因此，综述是教学、科研以及生产的重要参考资料。
2．综述的类型：根据搜集的原始文献资料数量、提炼加工程度、组织写作形式以及学术水平的高低，综述可分为归纳性、普通性和评论性三类。
(1)归纳性综述：归纳性综述是作者将搜集到的文献资料进行整理归纳，并按一定顺序进行分类排列，使它们互相关联，前后连贯，而撰写的具有条理性、系统性和逻辑性的学术论文。它能在一定程度上反映出某一专题、某一领域的当前研究进展，但很少有作者自己的见解和观点。
(2)普通性综述：普通性综述系具有一定学术水平的作者，在搜集较多资料的基础上撰写的系统性和逻辑性都较强的学术论文，文中能表达出作者的观点或倾向性。因而论文对从事该专题、该领域工作的读者有一定的指导意义和参考价值。
(3)评论性综述：评述性综述系有较高学术水平、在该领域有较高造诣的作者。在搜集大量资料的基础上．对原始素材归纳整理、综合分析、撰写的反映当前该领域研究进展和发展前景的评论性学术论文。因论文的逻辑性强，有较多作者的见解和评论。故对读者有普遍的指导意义，并对读者的研究工作具有导向意义。
二、综述的书写格式
综述与一般科技论文不同。科技论文注重研究方法的科学性和结果的可信性，特别强调阳性结果。而综述要写出主题(某一专题、某一领域)的详细情报资料，不仅要指出发展背景和工作意义，而且还应有作者的评论性意见，指出研究成败的原因；不仅要指出目前研究的热点和争论焦点，而且还应指出有待于进一步探索和研究的处女领域：不仅要介绍主题的研究动态与最新进展，而且还应在评述的基础上，预测发展趋势和应用前景。因此，综述的书写格式比较多样化，除了题目、署名、摘要、关键词(这四部分与一般科技论文相同)以外，一般还包括前言、主体、总结和参考文献四部分，其中前三部分系综述的正文，后一部分是撰写综述的基础。
1。前言：与一般科技论文一样，前言又称引言，是将读者导人论文主题的部分，主要叙述综述的目的和作用，概述主题的有关概念和定义，简述所选择主题的历史背景、发展过程、现状、争论焦点、应用价值和实践意义，同时还可限定综述的范围．使读者对综述的主题有一个初步的印象。这部分约200～300字。
2．主体部分：综述主体部分的篇幅范围特别大，短者5000字左右，长者可达几万字，其叙述方式灵活多样，没有必须遵循的同定模式，常由作者根据综述的内容，自行设计创造。一般可根据主体部分的内容多寡分成几个大部分，每部分标上简短而醒目的小标题。部分的区分标准也多种多样，有的按年代，有的按问题，有的按不同论点，有的按发展阶段。然而，不管采用何种方式，都应该包括历史发展、现状评述和发展前景预测三方面的内容。
(1)历史发展：按时间顺序，简述该主题的来龙去脉，发展概况及各阶段的研究水平。
(2)现状评述：重点是论述当前国内外的研究现状，着重评述哪些问题已经解决，哪些问题还没有解决，提出可能的解决途径；目前存在的争论焦点，比较各种观点的异同并作出理论解释，亮明作者的观点；详细介绍有创造性和发展前途的理论和假说，并引出论据，指出可能的发展趋势。
(3)发展前景预测：通过纵横对比，肯定该主题的研究水平，指出存在的问题，提出可能的发展趋势，指明研究方向，提示研究的捷径。
3．总结部分：总结部分又称为结论、小结或结语。书写总结时，可以根据主体部分的论述，提出几条语言简明、含义确切的意见和建议；也可以对主体部分的主要内容作出扼要的概括，并提出作者自己的见解，表明作者赞成什么，反对什么；对于篇幅较小的综述，可以不单独列出总结，仅在主体各部分内容论述完后，用几句话对全文进行高度概括。
4．参考文献：参考文献是综述的原始素材．也是综述的基础，因此，拥有并列出足够的参考文献显得格外重要。它除了表示尊重被引证作者的劳动及表明引用的资料有其科学依据以外，更重要的是为读者深入探讨该主题提供查找有关文献的线索。
三、综述的写作步骤和注意事项
1．综述的写作步骤。
(1)选题：综述的选题应遵循以下几个原则：
①选择的专题或领域：应是近年来进展甚快、内容新颖、知识尚未普及而研究报告积累甚多的主题；或研究结论不一致有争论的主题或是新发现和新技术在我国有应用价值的主题。
②选题与作者的关系：应选择与作者从事的专业密切相关的主题；或是与作者从事专业交叉的边缘学科的主题；或是作者即将进行探索与研究的主题；或是与作者从事专业关系不大，但乐于探索的主题；或是科学情报工作者作为研究成果的主题。
③题目要具体、明确，范围不宜过大．切忌无的放矢，泛泛而谈。
④选题必须有所创新，具有实用价值。
(2)搜集文献：题目确定后．需要查阅和积累有关文献资料．这是写好综述的基础。因而，要求搜集的文献越多、越全越好。常用的方法是通过文摘、索引期刊等检索工具书查阅文献。也可以采用微机联网检索等先进的查阅文献方法。
(3)阅读和整理文献：阅读文献是写好综述的重要步骤。因此，在阅读文献时，必须领会文献的主要论点和论据，做好“读书笔记”，并制作文献摘录卡片，用自己的语言写下阅读时所得到的启示、体会和想法，摘录文献精髓，为撰写综述积累最佳的原始素材。阅读文献、制作卡片的过程，实际上是消化和吸收文献精髓的过程。制作的卡片和笔记便于加工处理．可以按综述的主题要求进行整理、分类编排，使之系列化和条理化。最终对分类整理好的资料进行科学分析，结合作者的实践经验，写出体会，提出自己的观点。
(4)撰写成文：撰写综述之前，应先拟定写作大纲，然后写出初稿，待“创作热”冷却后进行修改。
2．撰写综述的注意事项。
(1)综述内容应是前人未曾写过的。如已有人发表过类似综述，一般不宜重复，更不能以他人综述之内容作为自己综述的素材。
(2)对于某些新知识领域、新技术，写作时可以追溯该主题的发展过程，适当增加一些基础知识内容，以便读者理解。对于人所共知或知之甚多的主题，应只写其新进展、新动向、新发展，不重复别人已综述过的前一阶段的研究状况。
(3)综述的素材来自前人的研究报告，必须忠实原文，不可断章取义，阉割或歪曲前人的观点。
(4)综述的撰写者必须对所写主题的基础知识、历史与发展过程、最新进展全面了解，或者作者本身也从事该主题的研究工作，是该主题的“专家”，否则容易出大错、闹笑话。
(5)撰写综述时，搜集的文献资料尽可能齐全，切忌随便收集一些文献就动手撰写，更忌讳阅读了几篇中文资料，便拼凑成一篇所谓的综述。
(6)综述的原始素材应体现出一个“新”字，亦即必须有最近最新发表的文献，一般不将教科书、专著列为参考文献。
(本文转自百度知道)
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