Distillation analyzers

Mixed with NaOH solution and distilled distillate analyzed for ammonia by titration, colorimetry, or electrode method (see Ammonia and Ammonium chloride). Bromide portion of NH4Br in aqueous solution may be analyzed by ion chromatography, or by the colorimetry method in which red to violet color is produced upon treatment with chloramine-T, and phenol red at pH 4.5. The colorimetry test for bromide is subject to interference from oxidizing and reducing agents, chloride, and bicarbonate. NH4Br may then be determined stoichiometrically. 

Table IV details the characteristics of the middle distillate (400-650 F) charge stocks utilized in this study. The sulfur level of the coal liquid is low at 371-ppm sulfur, while the petroleum liquid shows 3500 ppm and the shale middle distillate analyzed at 7400-ppm sulfur. Nitrogen contents were 1800 ppm for the coal material, 11,400 ppm in the shale liquid, and 31 ppm for the petroleum. Also to be noted for the charge stocks is the wide range of gravities for similar boiling fractions. As was the case with the naphtha charges, these middle distillates contained 1.6-2.6-ppm total metals. The middle distillate charges of coal and shale contained greater than 50% of their nitrogen in the basic form.

The heavy gas oils were processed at 1300 psig, 3000 SCF H2/bbl, 1 LHSV, and at temperatures of 625°, 675°, and 725°F. Desulfurization eflBciency of the coal heavy distillate was greater than that for the petroleum. Results show that at 725°F the coal heavy distillate was 91% desulfurized, the petroleum fraction was 83% at 725°F, and the shale heavy distillate analyzed at 61% sulfur removal. Here again, the nitrogen compounds proved very diflBcult to remove. At 725°F the petroleum fraction underwent 69% nitrogen removal, the shale cut revealed a 56% denitrogenation, and the coal heavy distillate exhibited 17% introgen removal. 

Percent Esterification. Ethanol-insoluble powder (200 mg) was suspended in 10 ml 0.5 N NaOH containing ethanol as internal standard. After 1 hr, the suspensions were filtered, distilled under vacuum until 5 ml were collected, and the distillate analyzed for methanol using gas chromatography on a column of Super Q (Alltech) operated at 160°C. 

In this example, the specification on distillate purity was not severe. In many towers, though, extreme purity is demanded of the products, and narrow span analyzers are used. If the span of the distillate analyzer in this case were 0.01, the proportional band would need to be 1,430... 

Application Note 9701, "Characterization of Vacuum Gas Oils by the AC Heavy Distillates Analyzer," AC—Analytical Controls Inc., Bensalem, PA. 

Distillation simulated by gas chromatography is a reproducible method for analyzing a petroleum cut it is appiicabie for mixtures whose end point is less than 500°C and the boiling range is greater than 50°C. The results of this test are presented in the form of a curve showing temperature as a function of the weight per cent distilled equivalent to an atmospheric TBP. 

A f.OO-mL sample of sea water is placed in a 500-mL volumetric flask and diluted to volume with distilled water. When injected into the flow injection analyzer, an absorbance of 0.3f7 is measured. What is the concentration of Ck in the sample ... 

In the use of temperature measurement for control of the separation in a distillation column, repeatability is crucial but accuracy is not. Composition control for the overhead product would be based on a measurement of the temperature on one of the trays in the rectifying section. A target would be provided for this temperature. However, at periodic intervals, a sample of the overhead product is analyzed in the laboratory and the information provided to the process operator. Should this analysis be outside acceptable limits, the operator would adjust the set point for the temperature. This procedure effectively compensates for an inaccurate temperature measurement however, the success of this approach requires good repeatability from the temperature measurement. 

Example 3 Calculation of TG Method The TG method will he demonstrated hy using the same example problem that was used above for the approximate methods. The example column was analyzed previously and found to have C -I- 2N + 9 design variables. The specifications to be used in this example were also hstedat that time and included the total number of stages (N = 10), the feed-plate location (M = 5), the reflux temperature (corresponding to saturated liquid), the distillate rate (D = 48.9), and the top vapor rate (V = 175). As before, the pressure is uniform at 827 kPa (120 psia), but a pressure gradient could be easily handled if desired. 

Verneuil et al. (Verneuil, V.S., P. Yan, and F. Madron, Banish Bad Plant Data, Chemical Engineering Progress, October 1992, 45-51) emphasize the importance of proper model development. Systematic errors result not only from the measurements but also from the model used to analyze the measurements. Advanced methods of measurement processing will not substitute for accurate measurements. If highly nonlinear models (e.g., Cropley s kinetic model or typical distillation models) are used to analyze unit measurements and estimate parameters, the Hkelihood for arriving at erroneous models increases. Consequently, resultant models should be treated as approximations. 

A simple ealibration eurve based on distilled water is suitable for tungsten determination (linearity range is 1-50 mg/dm of W), no interferenee from Fe, Co, Cr, Ni was found. The aeeuraey of the method is eonfirmedby analysis of eertified referenee materials of high alloy steels and niekel based alloys (in range of 0.3 to 15 % W). The analyzed values are agreeing well with the eertified values. 

In this study in order to eompare the green and yellow leaves of plant they were separately eolleeted and their essential oils were extraeted by water-distillation method and analyzed by GC and GC/MS. The main eonstituents were separated and analyzed by TLC, IR, NMR and UV methods. 

The general reaction procedure and apparatus used are exactly as described in Procedure 2. Ammonia (465 ml) is distilled into a 2-liter reaction flask and to this is added 165mlofisopropylalcoholandasolutionof30g(0.195 mole) of 17/ -estradiol 3-methyl ether (mp 118.5-120°) in 180 ml of tetrahydrofuran. The steroid is only partially soluble in the mixture. A 5 g portion of sodium (26 g, 1.13 g-atoms total) is added to the stirred mixture and the solid dissolves in the light blue solution within several min. As additional metal is added, the mixture becomes dark blue and a solid (matted needles) separates. Stirring is inefficient for a few minutes until the mass of crystals breaks down. All of the sodium is consumed after 1 hr and 120 ml of methanol is then added to the mixture with care. The product is isolated as in Procedure 4h 2. After being air-dried, the solid weighs 32.5 g (ca. 100% for a monohydrate). A sample of the material is dried for analysis and analyzed as described in Procedure 2 enol ether, 91% unreduced aromatics, 0.3%. The crude product may be crystallized from acetone-water or preferably from hexane. 

Into a mixture of 1.6 g of 2-amino-4-methylpyrlmidine with 10 ml of glacial acetic acid is slowly added 2.13 g of concentrated sulfuric acid. A mixture of 2.4 g of 2-formyl-1-methyl-5-nitroimidazole in 20 ml of glacial acetic acid is slowly added to the mixture of the pyrimidine under stirring. The reaction mixture is maintained at a temperature of about 55°C for 4 hours. The resultant mixture is then diluted with 200 ml of distilled water and neutralized with a saturated aqueous solution of sodium bicarbonate. A brownish-yellow precipitate (MP 232° to 235°C) is formed and recovered. The product is analyzed by infrared spectroscopy and is found to conform to 2-amino-4-[2-(1-methyl-5-nitro-2-imidazolyI)vinyl] pyrimidine. 

The residue from the distillation was evaporated to dryness in a vacuum oven at 50°C and the resulting product analyzed. The product weighing 105.5 parts by weight, 0.488 equivalent, was obtained which is a 98% yield of the technical calcium cyclohexylsulfamate dIhydrate. 

The frequency and method of testing feed streams varies from one refiner to another. Some refiners analyze daily, others two or three times a week, and some once a week. The frequency depends on how the distillation results are applied, the variation in crude slates, and the availability of lab personnel. 

Additional analyzers should be considered. Temperature and pressure are no longer adequate to control distillation columns to tight specifications. Consider chromatographs on the overhead streams. One chromatograph with multiple sample streams can be adequate for most services. Ensure that qualified service is available locally. 

The product is analyzed by vapor phase chromatography using a 6-ft., f-in. O.D. copper tube, packed with 5% Bentone-34 (Wilkins Instrument Co.) and 0.5% XF-1150 (General Electric Silicone Products) on Diatoport-S (80-100 mesh) (F and M Co.) flow rate of helium 60 ml./min., oven temperature 85°. This column separates m-cymene (retention time 12 minutes) from />-cymene (retention time 10 minutes) but does not resolve the ortho isomer. The purity of the distilled w-cymene is above 98%. 

On evaporating the alcoholic solution under reduced pressure from a water bath held at 50-60° (Note 6) the residue weighs about 540 g. A mixture of 600 cc. of absolute alcohol and 10 cc. of concentrated sulfuric acid (Note 7) is then added. The mixture is then heated on the water bath under a reflux condenser for three hours. The excess of alcohol and some of the water formed are removed by distillation under reduced pressure and the residue again heated for two hours with 300 cc. of absolute alcohol and an additional 4 cc. of concentrated sulfuric acid. The alcohol is removed by distillation under reduced pressure, and when the ester has cooled to room temperature, the sulfuric acid is neutralized with a concentrated solution of sodium carbonate the ester (upper layer) is separated, and the aqueous solution extracted with ether, or preferably benzene about one-tenth of the yield is in the extract. The combined products are placed in a i-l. distilling flask and distilled under reduced pressure after the solvent and alcohol and water have been removed. The ester is collected at 94-990, chiefly at 97-98°/x6 mm. (Note 8). The yield of a product analyzing about 97-98 per cent ethyl cyanoacetate amounts to 474-492 g. (77-80 per cent of the theoretical amount) (Note 9). 

Using the same technique employed in the previous model study, a series of experiments have been carried out by mixing 15 ml 0.1 M 4 and 15 ml 1.0 M MejAl in CH2C12 at 22° for 15 min at —20° for 10 min and at —50° for 5,10,20, and 60 min. The reactions were terminated by slowly adding prechilled methanol. The products were washed with ice-cold 0.5 N HC1 and distilled water, separated, dried over MgS04, solvent removed under vacuum, and analyzed by H1 NMR and IR spectroscopies. 

PUCI3, and MgCl2 to form a 50/50 mole % NaCl-CaCl salt phase and a molten Am-Pu-Mg-Ca alloy which is immiscible in the above salt(lO). After cooling, the metal phase is cleaved away from the salt phase and the salt phase is analyzed. Little, if any, Am or Pu remains in the salt phase and the salt residues can be discarded to waste. Metal recovery begins by evaporating magnesium and calcium from the residual metal button at about 800°C in vacuum. The americium can then be distilled away from the plutonium in a vacuum still operated at 1200°C, using yttria ceramic vessels to contain the molten metal fraction. The bottoms fraction contains the plutonium which is recycled back into the main plutonium stream. 

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