Raschig analysis

J. Saien, M. Asgari, A.R. Soleymani, N.Taghavinia, Photocatalytic decomposition of direct red 16 and kinetics analysis in a conic body packed bed reactor with nanostructure titania coated Raschig rings , Chemical Engineering Journal, 151, 295-301, (2009). 

Analysis for the hydroxylamine content is effected by the Raschig method. The recommended procedure is a modification of the method given by Scott. Approximately 0.1 g. of sample is dissolved in 75 ml. of water in an Erlen-meyer flask and 30 ml. of a saturated solution of iron(III) ammonium sulfate is added, followed by 10 ml. of 50 per cent sulfuric acid. The solution is boiled for 10 minutes, treated with approximately 5 to 10 ml. of phosphoric acid to reduce the color, then diluted with 200 ml. of water and titrated immediately with standard permanganate solution. 

Two more tanks were added in 1977, for use with solutions. Reasons for installing slab tanks instead of Raschig-ring-filled tanks, include spatial constraints, the need to mlnirnize surface holdup, the need to handle a wider range of concentrations, and location of the neutron poison material out of contact with the solution. Due to great improvements in calculafional analysis tools less conservatism was... 

Two adsorption vessels packed with molecular sieves constitute the initial part of the apparatns, where gas saturation takes place. The main absorption column is packed with Raschig rings and is operated batchwise to assess the absorption capacity of the desiccant fluid. Four collection points were inserted along the main column and secured with rubber rings. Samples are collected in glass syringes with stainless steel needles and taken for analysis in laboratory. 

Example 8.1.4 Sherwood and Holloway (1940) determined the mass-transfer behavior in O2 desorption from water from a series of Raschig rings of sizes 0.5", 1.0", 1.5" and 2" in a column of diameter 20" at 25 °C. Sherwood et al. (1975), have considered a particular example from this study for 2" Raschig rings, wherein, at superficial liquid and gas velocities of = 0.542 cm/s, (vi ) = 26.3 cm/s and a packed height of 15.5 cm, the values of Hocp and Notp were found to be 29.26 cm and 0.529, respectively. We employ this worked example from Sherwood et al. (1975) to illustrate the application of the axial dispersion analysis just provided. Determine the true values of Hd and Not for this case, given the Henry s law constant for O2 and water at 20 °C and 30 °C to be 4.01 X 10 and 4.75 x lO atm/mole fraction, respectively. You are given that (A.eft.r) = 0.0148 ft Vs. 

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