Edmister method

The accuracy depends on the fraction distilled it deviates particularly when determining the initial and final boiling points the average error can exceed 10°C. When calculating the ASTM D 86 curve for gasoline, it is better to use the Edmister (1948) relations. The Riazi and Edmister methods lead to very close results when they are applied to ASTM D 86 calculations for products such as gas oils and kerosene. 

Edmister Method (1947). Briefly, the Edmister absorption method (1947) with a known rich gas going to a fixed tower is as follows ... 

Edmister Method (1957). Edmister has developed an improved procedure that features equations combining absorption and stripping functions as follows ... 

The Edmister method for absorption use factors for overall stripping and absorption built up by combining column top and bottom factors. 

Hines and Maddox (1985) found that the Edmister method gives a close approximation to observed or rigorously computed concentration gradients in many multicomponent absorbers. 

The Lee-Erbar-Edmister method is of the same type, but uses different expressions for the fugacity and activity coefficients. The vapor phase equation of state is a three-parameter expression, and binary interaction corrections are included. The liquid phase activity and fugacity coefficient expressions were derived to extend the method to lower temperatures and to improve accuracy. Binary interaction terms were included in the liquid activity coefficient equation. 

Estimating the unknown but required starting values of conditions and compositions is an important and sensitive part of these calculations. The composition of the feed is always known, as is the composition of one of the two phases in bubble and dew point calculations. With the Chao-Seader, Grayson-Streed, and Lee-Erbar-Edmister methods, it is possible to assume that both phases have the composition of the feed for the first trial. This assumption leads to trouble with the Soave-Redlich-Kwong, the Peng-Robinson and the Lee-Kesler-Ploecker... 

Multicomponent distillation, 393 absorption factor method, 398 azeotropic, 420-426 bubblepoint (BP) method, 406-409 computer program references. 404 concentration profiles, 394 distribution of non-kevs. 395 Edmister method, 398,399 extractive, 412, 417-422 feed tray location, 397 free variables, number of 395 Lewis-Matheson method 404 MESH eauations. 405-407 molecular, 425-427 nomenclature, 405 number of theoretical trays, 397 packed towers, 433-439 petroleum, 411-415 reflux, minimum, 397 reflux, operating, 397 SC (simultaneous correction) method, 408-411... 

Kremser-Brown-Sherwood Method — No Heat of Absoip-tion, 108 Absorption — Determine Component Absorption in Fixed Tray Tower, 108 Absorption — Determine Number of Trays for Specified Product Absorption, 109 Stripping— Determine Theoretical Trays and Stripping or Gas Rate for a Component Recovery, 110 Stripping — Determine Stripping-Medium Rate for Fixed Recovery, 111 Absorption — Edmister Method, 112 Example 833 Absorption of Hydrocarbons with Lean Oil, 114 Intercooling for Absorbers, 116 Absorption and Stripping Efficiency, 118 Example 834 Determine Number of Trays for Specified Product Absorption, 118 Example 835 Determine Component Absorption in Fixed-Tray Tower, 119 Nomenclature for Part 2, 121... 

FIGURE 13.10 Nomenclature for use of the Edmister method for determining stages in absorbers and strippers. In order to maintain similarity of equations for absorption and stripping, the stages are numbered up from the bottom of the stripper. 

For the more concentrated feed liquids, such as those found in petroleum refinery stripping operations, the Edmister method [Equations (13.15) through (13.20)] are modified as follows (see Figure 13.10) ... 

The Edmister method predicts ethane and propane recoveries of 98.5% and 97.7%, respectively, compared to values of 98.8% and 98.1% by the exact method. 

Edmister method Estimate the top-tray temperature tj = 26 C (to be checked). The results of the preliminary calculations then give the following approximate results ... 

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