Solids-containing feeds

Adsorption Isotherms. The adsorption isotherms were determined using the serum-replacement adsorption or desorption methods (7). For the adsorption method, the latex samples (50 or 100 cm 2% solids) containing varying amounts of PVA were equilibrated for 36 hours at 25°C, placed in the serum replacement cell equipped with a Nuclepore membrane of the appropriate pore size, and pressurized to separate a small sample of the serum from the latex. For the desorption method, the latex samples (250 cm 2.5% solids) were equilibrated for 36 hours at 25°C and subjected to serum replacement with DDI water at a constant 9-10 cm /hour. The exit stream was monitored using a differential refractometer. The mean residence time of the feed stream was ca. 25 hours. It was assumed that equilibrium between the adsorbed and solute PVA was maintained throughout the serum replacement. For both methods, the PVA concentration was determined using a An-C calibration curve. 

The reaction mixture is filtered. The solids containing K2Mn04 are leached, filtered, and the filtrate composition adjusted for electrolysis. The solids are gangue. The Cams Chemical Co. electrolyzes a solution containing 120—150 g/L KOH and 50—60 g/L K MnO The cells are bipolar (68). The anode side is monel and the cathode mild steel. The cathode consists of small protrusions from the bipolar unit. The base of the cathode is coated with a corrosion-resistant plastic such that the ratio of active cathode area to anode area is about 1 to 140. Cells operate at 1.2—1.4 kA. Anode and cathode current densities are about 85—100 A/m2 and 13—15 kA/m2, respectively. The small cathode areas and large anode areas are used to minimize the reduction of permanganate at the cathode (69). Potassium permanganate is continuously crystallized from cell liquors. The caustic mother liquors are evaporated and returned to the cell feed preparation system. 

A small, but important, variation of NaCl electrolysis substitutes KC1 as the feed. Both mercury cells and membrane cells are used for producing chlorine and KOH (caustic potash). The KOH is concentrated for sale as a 45 percent solution or as a solid containing 88 to 92 percent KOH. A big use for KOH is in the manufacture of liquid soaps and detergents. The analogous sodium soaps and detergents are generally solids. Approximately 1.5 percent of chlorine production results from the electrolysis of KC1.36... 

For a steady-state crystallizer receiving solids-free feed and containing a well-mixed suspension of crystals experiencing neghgible breakage, a material-balance statement degenerates to a particle balance (the Randolph-Larson general-population balance) in turn, it simplifies to... 

The basic concept of a H2 PSA process is relatively simple. The impurities from the H2-containing feed gas mixture are selectively adsorbed on a micro- and meso-porous solid adsorbent (zeolites, activated carbons, silica and alumina gels) at a relatively high pressure by contacting the feed gas with the solid in a packed column of... 

The simplest gas-solid containment systems conceptually are the direct adsorption ones. These accomplish adsorption on solids such as activated carbon, or alkalized alumina at relatively low temperatures and ordinary pressures [46]. In a separate unit a more concentrated sulfur dioxide stream is produced when the saturated absorbent is regenerated by heating. This is a more economically attractive feed to an acid plant or for liquefaction or sulfur generation. 

CONCENTRATION PATTERNS IN FIXED BEDS. In fixed-bed adsorption, the concentrations in the fluid phase and the solid phase change with time as well as with position in the bed. At first, most of the mass transfer takes place near the inlet of the bed, where the fluid first contacts the adsorbent. If the solid contains no adsorbate at the start, the concentration in the fluid drops exponentially with distance essentially to zero before the end of the bed is reached. This concentration profile is shown by curve in Fig. 25.5a, where c/cq is the concentration in the fluid relative to that in the feed. After a few minutes, the solid near the inlet is nearly saturated, and most of the mass transfer takes place further from the inlet, The concentration gradient becomes S shaped, as shown by curve /j- The region where most of the change in concentration occurs is called the mass-transfer zone, and the limits are often taken as c/cq values of 0.95 to 0.05. 

RO is used to treat 1.31 m3/s of seawater at 293 K containing 3.5 wt% dissolved solids to produce 0.44 m3/s of potable water with 500 ppm of dissolved solids. The feed-side pressure is 138 bar, while the permeate pressure is 3.4 bar. A single stage of spiral-wound membrane is used that approximates crossflow. If the total membrane area is 0.10 km2, estimate the permeance for water and the salt rejection. Assume that the densities of the seawater and of the brine are approximately equal to the density of pure water. 

In the French Oil Machinery Co. stationary basket extractor (Fig. 10.3-5), extract percolates through beds of solids contained in a circular array of sector-shaped compartments with perforated bottoms and drains into sumps positioned below the beds. Unlike crossflow extractors, the solids do not move." Instead, the solid feed spout and solids discharge zone rotate about the circle and the extract feed and discharge connections are switched periodically. These extractors are like automated diffusion batteries in which downflow is used but, because extract backmixes in each sump, the extract concentration leaving a stage is somewhat different from that entering the next stage. 

FIGURE 18.4 Profiles of fed-batch fermentation of Candida tropicalis ATCC 13803 in a 3.5-L fermentor containing 1 L of YP medium (10 g/L yeast extract, 20 g/L bactopeptone), in which 105 g/L xylose and 32 g/L glucose were added initially. Fermentation environments were fixed at 30°C, pH 6, 500 rpm, and 1 vvm., dry cell mass , glucose A, xylose O, xylitol solid line, feeding of a concentrated xylose solution arrow, shift of dissolved oxygen content. 

Upstream of the roaster, the run-of-mine sulphide ore is milled and then concentrated in froth flotation cells. The 75 wt% solids roaster feed slurry contains approximately 40% copper and 4% cobalt (dry basis). 

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