Bubble point method

BP Method for Distillation The bubble-point method for distillation, particularly when the components involved cover a relatively narrow range of volatihty, proceeds iteratively by the following steps, where k is the iteration index for the entire distillation column. 

Theiie-Geddes oriented (Including bubble-point) methods... 

BP (bubble-point) methods. Temperatures are corrected iteratively by determinations of bubblepoints. The method is satisfactory for mixtures with relatively narrow ranges of volatilities. The parent program of this type is that of Wang and Henke (1966) which is flowsketched on Figure 13.16 and described in the next section. The availability of a FORTRAN program was cited earlier in this section. 

Figure 13.16. Algorithm of the BP (bubble-point) method for distillation separations [Wang and Henke, Hydrocarbon Processing 45(5, 155-166 1963)) Seader and Henley, 1998].

The first three methods involve the measurement of structural-related parameters while the last one is a typical permeation-related teclmique. Both electron microscopy and AFM can provide qualitative measurement of membrane materials. Figure 7 shows the top surface of porous polymeric membrane observed by scaiming electron microscopy (SEM). The bubble point method and permeation measurement, on the other hand, provide quantitative information of membrane materials. 

Determined by the bubble point method W (adapted from ASTM Method F361). 

Pore size. The bubble point method (BCI Test Method 3-015) [10] is used to measure the maximum pore diameter. The maximum pore size and the pore-size distribution can be determined by means of the liquid porosimetry method which uses, for example, a Coulter porosimeter (BCI Test Method 3-017) [10]. 

At the turn of the century (1906), Bechhold produced graded pore sizes in collodion membranes and measured the pore size with the "bubble-point" method (to be described later). 

In a computer program for the Wang-Henke bubble-point method, 10100 storage locations are wastefully set aside for the four indexed coefficients of the tridiagonal matrix solution of the component material balances for a 100-stage distillation column. 

Rigorous multicomponent methods (Chapter 15) Bubble-point method (Wang-Henke)... 

Table 1 Relation Between Pressure and Pore Radius Using Water as the Wetting Medium in the Bubble-Point Method...

The apparatus employed for the investigation is based on a modified version of the dew and bubble-point method of phase-boundary determination. By altering the standard procedure, solid-liquid-vapor and solid-vapor equilibria data can be determined along with the vapor-liquid data in the same basic apparatus used for dew and bubble-point measurements. The method presented here is a slight variation of the method presented by Kurata and Kohn [ ] and similar to that of Donnelly and Katz p]. 

Thalla-Qeddes Oriented (Including Bubble-Point Methods)... 

Pore size and pore size distribution It is obvious that the pore size and the pore size distribution of the membrane affect membrane performance. A number of methods can be used to determine the pore size and the pore size distribution. Conventional methods include bubble point method, mercury porometry, thermporometry, permporometry, and gas adsorption. Transport data of gases and solutions with solute probes can also be used to determine the pore size and the pore size distribution. Pores can also be observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Atomic force microscope can observe the pores only on the membrane surface. 

Remember that convergence of the stage-by-stage distillation calculation is easy only when the NKs are all heavy or are all light. Both the dew-point and bubble-point methods can be solved with a spreadsheet (see the Appendix for Chapter 51. 

FI. A distillation column with two stages plus a partial reboiler and a partial condenser is separating benzene, toluene, and jgdene. Feed rate is 100 kmol/h, and feed is a saturated vapor introduced on the bottom stage of the column. Feed conpositions (mole fractions) are Zg = 0.35, Zj- = 0.40, z = 0.25. Reflux is a saturated liquid and p = 16 psia. A distillate flow rate of D = 30 kmol/h is desired. Assume K = VP/p. Do not assume constant relative volatility, but do assume CMO. Use the matrix approach to solve mass balances and the bubble-point method for tenperature... 

The methods described above require establishing equilibrium between the vapor and liquid phases and determining the compositions of one or both phases. With the use of dew and bubble point methods the couples of corresponding compositions in equilibrium are not measured, and instead only single (independent) points on the equilibrium curves are determined. 

Another advantage of the dew and bubble point methods consists in the small amount of components needed for input. Last but not least, the methods may be applied easily to high pressure systems. On the other hand, imperfections are the necessity of thorough degassing of the compounds and die low accuracy of the measurements. Moreover, these methods cannot be generally used for the determination of ternary and multicomponent systems. 

In summary, the bubble-point method is a very simple technique for characterising the largest pores in microfiltration membranes. Active pores are determined with this technique. A disadvantage is that different results are obtained when different liquids are used for charaaerisatiorL In addition, the rate of pressure increase and the pore length may influence the result. Pore size distributions can be obtained by performing this technique by a stepwise increase of the pressure. 

The bubble-point method gives only limited information and a another method was developed that combines the bubble-point concept with the measurement of the gas flow through the emptied pores. Here at first the gas flow is measured through a dry membrane as a function of the pressure and generally a straight line obtained (see figure IV - 8). Then... 

The mercury intrusion technique is a variation of the bubble-point method. In this technique, mercury is forced into a dr> membrane with the volume of mercury being determined at each pressure. Again, the relationship pressure and pore size is given by the Laplace equation. Because mercury does not wet the membrane (since its contact angle is greater than 90° and consequently cos 0 has a negative value), eq. IV. 1 is modified to ... 

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