Showing papers in "Industrial & Engineering Chemistry Process Design and Development in 1978"

Product Composition and Kinetics of Lignite Pyrolysis

Abstract: Previous research at M.I.T. on coal pyrolysis in inert gas and in hydrogen was based on the measurement of coal weight loss, referred to as volatiles yield. The work is now being extended to include volatiles composition measurements and elemental analysis of the char for the same ranges of experimental conditions covered in the previous study. To this end, the previous apparatus has been modified to permit the collection and analysis of volatiles. This paper presents the first set of composition data, for lignite pyrolysis, and some initial interpretations of pyrolysis behavior in the light of the products formed. The pyrolysis of pulverized Montana lignite by time-resolved measurement of the yields and compositions of products formed under controlled temperature-time histories was studied in a captive sample apparatus. The yields of water, carbon monoxide, carbon dioxide, hydrogen, and hydrocarbon gases and light liquids were determined by gas chromatography. The yields of all the volatile products increase monotonically with temperature and approach asymptotic values at the higher temperatures.

Representation of NH3-H2S-H2O, NH3-CO2-H2O, and NH3-SO2-H2O Vapor-Liquid Equilibria

Abstract: A new method of calculation of vapor-liquid equilibria for ammonia/hydrogen sulfide/water and ammonia/carbon dioxide/water at 0/sup 0/-100/sup 0/C at the concentrations encountered in refinery sour water strippers and for ammonia/sulfur dioxide/water as found in gas cleaning systems was developed. The model was based on the Edwards et al. thermodynamic approach.

Multiple Hydrodynamic States in Cocurrent Two-Phase Downflow through Packed Beds

Abstract: Evidence for the existence of multiple hydrodynamic states in trickle bed reactors with small particles is produced. These states are characterized by significantly different pressure gradients and different liquid holdups for identical gas and liquid flowrates. The determining factor is the maximum gas flowrate to which the packed bed has been subjected.

A Modified Soave Equation of State for Phase Equilibrium Calculations. 2. Systems Containing CO2, H2S, N2, and CO

Abstract: K values for the light hydrocarbons were calculated and compared with those reported by Solomon. The author reported no K values for the absorber oil as it was essentially nonvolatile. The results are summarized in Table XI. For the paraffinic and naphthenic oils consisting of the gas oil, hexadecane, and dicyclohexyl, the results are generally in good agreement with experiment and similar to those obtained for binary systems. For the highly aromatic oils, the Soave procedure gives larger errors in all K values and tends always to underpredict the light component volatilities. This suggests that the procedure as applied to highly aromatic liquids might require an interaction coefficient to optimize the equilibrium phase predictions. There is, however, insufficient information on such systems to show that the need for an interaction coefficient is generally true. The results, however, more clearly indicate that the Soave procedure in its present form may be applied to heavier hydrocarbon systems.

Bed Expansion in Three-Phase Fluidization

Abstract: Bed expansion in three-phase fluidization was determined for three sizes of commercial cobalt-molybdate extrudate catalyst and n-heptane and nitrogen in 12.70 and 15.24 cm diameter Lucite tubes at 0-25.9 cm/sec gas velocity and 0.86-9.40 cm/sec liquid velocity. The catalyst bed contracted measurably on gas injection for the smallest (0.0635 cm dia) catalyst but not at all for the largest (0.1600 cm dia) catalyst. Correlations were developed for the effect of gas velocity on bed expansion, based on particle Reynolds numbers, sphericity of the particle, and the liquid-to-gas velocity ratio. For a given catalyst, a chart is readily prepared for catalyst expansion as a function of liquid and gas velocities. Three-phase fluidization is used in hydrodesulfurization processes such as H-Oil and H-Coal. Graphs and table.

Simultaneous Absorption of SO2 and NO2 in Aqueous Solutions of NaOH and Na2SO3

Abstract: Experiments on the absorption of sulfur dioxide and/or nitrogen dioxide diluted with nitrogen into aqueous solutions of sodium hydroxide and sodium sulfite with a plane interface were carried out at 1 atm and 25/sup 0/C in an agitated vessel (15 cm high, 10 cm ID). From a mixture with nitrogen oxides and nitrogen, the rate of nitrogen dioxide absorption into aqueous sodium hydroxide solution was enhanced by the presence of the sulfur dioxide, but into aqueous sodium sulfite solution, the rate was reduced. Such absorption behavior arose from the change of sulfite concentration at the gas-liquid interface. Therefore, the rate of nitrogen dioxide absorption with sulfur dioxide can be predicted according to the previously proposed mechanism of competitive reactions of nitrogen dioxide with sulfite and water. These results suggest that it may be possible to develop an economical process for removing sulfur dioxide and nitrogen oxides simultaneously from stack gases by an alkaline solution, especially at high sulfur dioxide concentrations.

Decontamination of Alkaline Radioactive Waste by Ion Exchange

Abstract: An ion-exchange process was developed to remove cesium-137, strontium-90, and plutonium from alkaline salt solutions. About 20 million gal of alkaline salt cake and supernatant solution from processing nuclear fuels and materials for defense programs are presently stored at the Savannah River Plant. Ion exchange may be used to decontaminate this radioactive waste during a proposed waste solidification program. In development tests 100-L quantities of liquid waste were decontaminated. Decontamination factors were 4 x 10/sup 5/ for /sup 137/Cs, 5 x 10/sup 3/ for /sup 90/Sr, and 300 for Pu. The separated radionuclides were concentrated by a factor of 1500 and immobilized by adsorption onto zeolite. Residual /sup 137/Cs, /sup 90/Sr, and Pu activity in the decontaminated product was about 6 nCi/g. /sup 106/Ru, the most hazardous radionuclide remaining after /sup 137/Cs removal, will decay to 6 nCi/g about 10 years after the waste is processed.