Cold slurry flow

Using lots of slurry, particularly if the slurry is not recycled, but discarded, is not only expensive, but the lower temperature reduces the rate at which silicon is removed from the wafer. However, using a very low slurry flow to increase the temperature and therefore the chemical attack rate runs the risk of developing so much heat that the slurry dries, and the silica particles aggregate into scratch-producing sediments. Therefore, as with Goldilocks and the Three Bears one flow is too hot, one is too cold and one is just right . 

The pilot-scale SBCR unit with cross-flow filtration module is schematically represented in Figure 15.5. The SBCR has a 5.08 cm diameter and 2 m height with an effective reactor volume of 3.7 L. The synthesis gas passes continuously through the reactor and is distributed by a sparger near the bottom of the reactor vessel. The product gas and slurry exit at the top of the reactor and pass through an overhead gas/liquid separator, where the slurry is disengaged from the gas phase. Vapor products and unreacted syngas exit the gas/liquid separator and enter a warm trap (373 K) followed by a cold trap (273 K). A dry flow meter downstream of the cold trap measures the exit gas flow rate. 

S. Rio Segade and J. F. Tyson, Determination of methylmercury and inorganic mercury in water samples by slurry sampling cold vapor atomic absorption spectrometry in a flow injection system after preconcentration on silica C18 modified, Talanta, 71(4), 2007, 1696-1702. 

To a chromatographic column, packed with 6.67 g of charcoal ("Nuchar C") with layers of sea sand at either end, 75 ml of acetone was added to wet the carbon. The column was heated to 40°C, and 25 ml of acetone was drained off. A solution of 20 g of dry crude dehydrocholic acid in 500 ml of acetone was poured into a reservoir atop the column and maintained in this reservoir at 40°C. This solution was then allowed to drop through the column at a constant rate over a 3-hour period. The column was then washed with 250 ml of acetone flowing through the column at a constant rate over a 1-hour-period at 40°C. The column effluent and wash acetone were combined and concentrated to a residual volume of about 100 ml which resulted in the formation of a thick slurry. The slurry was cooled with stirring at 0° to 5°C and aged for 30 min at this temperature. The slurry was filtered and the filter cake washed with cold acetone. The filter cake of U.S.P. dehydrocholic acid was sucked partially dry on the filter and then dried at 110°C for 3 hours. 

Analyzer Q = quadrupole, CC = collision cell, DRC = dynamic reaction cell, MC = multicollector, SF = sector field. Analytical details CV = cold vapor, ETV = electro-thermal vaporization, FI = flow injection, HG = hydride generation, ID = isotope dilution, LA = laser ablation, UN = ultrasonic nebulization. Sample introduction in liquid or slurry (si) form. 

S. R. Segade, J. F. Tyson, Evaluation of two flow injection systems for mercury speciation analysis in fish tissue samples by slurry sampling cold vapor atomic absorption spectrometry, J. Anal. Atom. Spectrom., 18 (2003), 268-273. 

In most spray towers, the air flow rate and the temperature are adjusted at the inlet ports to maintain balanced air/temperature patterns. When the atomized slurry is sprayed into the drying chamber, the air flow pattern is disturbed and becomes very turbulent. This effect can cause localized temperature gradients (hot or cold spots) and affect the particle drying characteristics. It is possible to have... 

As part of the work undertaken by APCI under contract to the DOE, to develop a slurry phase Fischer-Tropsch process to produce selectively transportation fuels, a study of the hydrodynamics of three phase bubble column reactors was begun using cold flow modelling techniques (l ). Part of this study includes the measurement of solid concentration profiles over a range of independent column operating values. 

Ultrasonic slurry formation has been frequently used prior to cold-vapour and hydride generation. Both procedures usually involve a drastic treatment of the slurry to ensure complete transfer of the target species to the liquid phase for subsequent formation of the gas phase — after a normally long standing time — which is the only phase reaching the atomizer in the case of hydride generation and the detection point in the case of mercury vapour formation. The gaseous analytes or their hydrides are most often obtained in a commercial or laboratory-made dynamic flow injection manifold. 

Exelus has developed a novel structured catalytic system that allows one to meet all four criteria in a single catalytic system Hydrodynamic tests reveal that the HyperCat has similar gas hold-up as a slurry bubble column reactor but with a much lower liquid axial-dispersion coefficient. Cold-flow studies appear to indicate that the heat-transfer coefficient of this new system is similar to a bubble column reactor. Catalyst performance tests reveal that the performance of the HyperCat is similar to that of a powder catalyst when used in a plug-flow reactor. 

As in any slurry based process, complex hydrodynamic behavior complicates the scale up to a commercial size unit. Therefore, computational modeling supported by cold flow x-ray mapping tests on a pilot reactor prototype has been used to assist the reactor development efforts. Operation of a 2 bpd Fischer Tropsch pilot plant began in 2003 and has continued through 2004 at the BP Chemicals Saltend site. 

Other methods are based on polymer blends of two immiscible polymers, a water-soluble matrix [e.g., poly(vinyl alcohol)] and an insoluble fiber-forming component [e.g., poly(ethylene terephthalate)]. Upon exfrusion, the streamlined flow characteristics produce a fibrillary morphology. The matrix is extracted after cold drawing. The resulting foamed slurry is then filtered off and spun into microfibers with a diameter of 0.1-10 pm. Using this method, ultrasuperfine fibers with counts of 10 " dtex are obtained for use as filter material [81]. 

The CARPT—CT techniques have been introduced at CREL to provide cold flow modeling information on slurry bubble column flows operated in chum turbulent regime needed for gas-to-Hquid conversion processes (Degaleesan, 1997 Degaleesan and Dudukovic, 1998 Degaleesan et al.. 

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