Washing calculations

A5. How does the solid enter into washing calculations Where does solids flow rate inplicitly appear in Figure 14-1 ... 

In some cases when the washing pressure is significantly higher than the pres-sure(s) previously used in a cycle and/or the cake is particularly compressible, then additional cake compression may occur at the start of (or throughout) a displacement washing process. While it is generally difficult to account for such instances, equations (6.4) and (6.5) can be used to recalculate and C y such that the resultant values are used in equation (6.49) and hence the subsequent washing calculations. For the majority of cases, however, such corrections are unnecessary and simply over-complicate calculation procedures. 

Tomiak A., 1994. Pulp Washing Calculation Manual, Canadian Pulp and Paper Association, Montreal. 

Tomiak, A., Application of Norden s efficiency factor method for pulp washing calculations... 

The acetylations may alternatively be performed in 100 ml. conical flasks, and the contents after dilution and hydrolysis with water can then be carefully washed into 250 ml. beakers for the titration with alkali. The calculation is precisely similar to that of the first method. Excellent results are r>btalned. 

The method is generally applicable when other modes of esterification are either slow, inefficient, or likely to cause isomerisation it is, however, time-consuming and expensive. Small quantities of acid impurities are sometimes produced, hence it is advisable to wash the ester with saturated sodium bicarbonate solution. The silver salt can usually be prepared by dissolving the acid in the calculated quantity of standard ammonium hydroxide solution and... 

Preparation of silver maleate. Dissolve 65 g. of pure maleic acid (Section 111,143) in the calculated quantity of carefully standardised 3-5N aqueous ammonia solution in a 1-htre beaker and add, whilst stirring mechanically, a solution of 204 g. of silver nitrate in 200 ml. of water. Filter oflf the precipitated silver maleate at the pump, wash it with distilled water, and press well with the back of a large flat glass stopper. Dry in an electric oven at 50-60° to constant weight. The yield of the dry silver salt is 150 g. Store in a vacuum desiccator in the dark. 

Concentrate the combined filtrate and washings (W) to about half the original volume, and pour it into sUghtly more than the calculated amount of dilute hydrochloric acid (use a mixture of 30 ml. of concentrated hydrochloric acid and 30 ml. of ice-water) then add about 300 ml. of water. Collect the active aec.-octyl hydrogen phthalate (crude lA) as above (5). The weight of the air-dried ester is about half that of the dl-ester originally used (7). 

The sodium carbonate content may be deterrnined on the same sample after a slight excess of silver nitrate has been added. An excess of barium chloride solution is added and, after the barium carbonate has setded, it is filtered, washed, and decomposed by boiling with an excess of standard hydrochloric acid. The excess of acid is then titrated with standard sodium hydroxide solution, using methyl red as indicator, and the sodium carbonate content is calculated. 

A number of excellent studies have used a variety of radiolabeled sods to iavestigate the removal of small amounts of colorless sods such as ods (102—104). By proper use of different radiolabels (such as and " C), the preferential removal of various components ia a sod mixture can be followed. In these cases ia particular, detergency can also be calculated from measurements of the amount of radioactivity that is removed from the fabric and is found ia the wash Hquor. 

The actual yield may be obtained from algebraic calculations or trial-and-error calculations when the heat effects in the process and any resultant evaporation are used to correc t the initial assumptions on calculated yield. When calculations are made by hand, it is generally preferable to use the trial-and-error system, since it permits easy adjustments for relatively small deviations found in practice, such as the addition of wash water, or instrument and purge water additions. The following calculations are typical of an evaporative ciy/staUizer precipitating a hydrated salt, if SI units are desired, kilograms = pounds X 0.454 K = (°F 459.7)/I.8. 

If the cake is washed with solnte-free liquid, percent remaining is readily calculated by dividing the solute concentration in the hqnid remaining in the washed cake by the solute concentration in the liquid in the original feed. 

Scale-Up on Rate Filtration rates calculated from bench-scale data shouldbe multiplied by a factor of 0.8 for all types of commercial units which do not employ continuous washing of the filter medium and on which there is a possibility of filter-medium bhnding. For those units which employ continuous filter-medium washing, belt-type drum and horizontal units, the scale-up fac tor maybe increased to 0.9. The use of this scale-up fac tor assumes the following ... 

Alternatively, the acid (5g) is refluxed for 2h with 15mL of MeOH and 2mL of 98% H2SO4 (cool when mixing this soln). Pour into 10 volumes of H2O and extract with the minimum volume of CHCI3 to give clear separation of phases. The extract is washed with H2O and dried (CaCl2) and distd. The methyl ester is collected at 77-79°/ mm, m 38-39°. The ester is hydrolysed with the calculated amount of N KOH and refluxed until clear. Acidification with HCl provides the pure acid with 90% recovery. [Org Synth 4 1 1964.] The amide crysts from cyclohexane, m 189°. [Chem Ber 62 1629 1959.]... 

Calculate the total filtration time of both steps and the volumes of filtrate, cake and separated slurry. Assume for these calculations that the operation is performed without any washing and dewatering stages. 

For the conditions in the above question, calculate the NaCl concentration in the wash water after 50 min. of washing. 

In the WASH-1400 analyses of nuclear power accidents, it was calculated that it is possible to overpressure and rupture the containment. Discuss whether this is better or worse than a pressure relief that releases radioactivity but prevents the pressure from exceeding the rupture... 

Refinements have been made on the source term calculational methods since WASH-1400. The general trend has been toward source term reduction (e.g., the iodine release for the large LOCA) as compared with the RSS results. In cases such as Station Blackout, the RSS underestimated the tellurium and barium compared with results from the BMI-2104 suite. 

In these cases, the product is reslurried with pure liquor or fresh solvent if the solubility is not too high, and refiltered. In order to meet the required product impurity level, several such washings may take place in series. See Coulson and Richardson (1991) and Mullin (2001) for design guides and examples calculations. It is noted that impurities retained within liquid occlusions are particularly difficult to remove without first crushing the crystals. 

The quality of the packed bed may also be determined by frontal analysis where the sample is applied until it reaches a plateau to give the residence time function and then the solution is momentarily switched to wash to give the washout function. The latter is used to calculate the plate height of the column... 

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