Carryover reduction

The explicit aims of boiler and feed-water treatment are to minimise corrosion, deposit formation, and carryover of boiler water solutes in steam. Corrosion control is sought primarily by adjustment of the pH and dissolved oxygen concentrations. Thus, the cathodic half-cell reactions of the two common corrosion processes are hindered. The pH is brought to a compromise value, usually just above 9 (at 25°C), so that the tendency for metal dissolution is at a practical minimum for both steel and copper alloys. Similarly, by the removal of dissolved oxygen, by a combination of mechanical and chemical means, the scope for the reduction of oxygen to hydroxyl is severely constrained. 

Any action or operating condition that reduces effective steam-water separation leads to some level of BW carryover and a consequential reduction in steam purity and increase in the water content. 

Sudden reductions in steam pressure. Soot blowing or sudden, very high process steam demands can cause carryover. 

A complete dose-response analysis was generated for PCP for doses from 0.625 to 20 mg/kg IP (data not shown). PCP exhibited dose-related anticonvulsant action when day one minus day three differ ence scores were compared for all doses tested. When retested with saline only on day five, no reduction in convulsant sever it or super-sensitive response was observed (day one minus day five), indicating no carryover drug effect 48 hours after dosing. At behavioral ly equivalent doses, all compounds assayed were clearly anticonvulsant (table 3). TCP was most potent at the doses tested. PCA was the most efficacious, and reduced convulsant severity by 2.58 points. As with PCP, none of the other phencycli-noids had any carryover effects 48 hours after dosing (day one minus day five). 

Flooding is an excessive accumulation of liquid inside a column. Flood symptoms include a rapid rise in pressure drop (the accumulating liquid increases the liquid head on the trays), liquid carryover from the column top, reduction in bottom flow rate (the accumulating liquid does not reach the tower bottom), and instability (accumulation is non-steady-state). This liquid accumulation is generally induced by one of the following mechanisms. 

Sample preparation Sample handling, carryover in instruments Dilutions, homogenization, size reduction Glassware and instrument Ambient contamination... 

Hydrazine (N2H ) was found to be an effective scavenger of N02 ions and thus a promising holding reductant. Production scale tests at Hanford in 1968 with hydrazine-stabilized ferrous nitrate were plagued by problems associated with the carryover of nitrite, though the soundness of this method was demonstrated (3). 3+... 

The UV-Visible detector is the universal detector used in analytical and preparative CCC. It does not destroy solutes. It is used to detect organic molecules with a chromophore moiety or mineral species after formation of a complex (for instance, the rare earth elements with Arsenazo III ). Several problems can occur in direct UV detection, as has already been described by Oka and Ito 1) carryover of the stationary phase due to improper choice of operating conditions, with appearance of stationary phase droplets in the effluent of the column 2) overloading of the sample, vibrations, or fluctuations of the revolution speed 3) turbidity of the mobile phase due to difference in temperature between the column and the detection cell or 4) gas bubbling after reduction of effluent pressure. Some of these problems can be solved by optimization of the operating conditions, better control of the temperature of the mobile phase, and addition of some length of capillary tubing or a narrow-bore tube at the outlet of the column before the detector to stabilize the effluent flow and to prevent bubble formation. The problem of stationary phase carryover (especially encountered with hydrodynamic mode CCC devices) can be solved by the addition between the column outlet and UV detector of a solvent that is miscible with both stationary and mobile phases and that allows one to obtain a monophasic liquid in the cell of the detector (a common example is isopropanol). 

For example, a high MW hindered amine (eg, CYASORB UV-3346 Light Stabilizer) combined with CYASORB UV-2908 provides synergistic performance in PP slit tape applications during Xenon ARC WOM exposure (Fig. 11) (64). The use of this combination also allows improved processability in production of the slit tapes because of reduction in water carryover compared with HALS alone. It has also been demonstrated that, in thick section PP, long-term stability can be dramatically improved with CYASORB UV-3346 combined with CYASORB UV-2908. 

New columns require a period of running-in before maximum reduction is achieved, although this normally does not require more than about 1 hr. Be on guard during this period for the carryover of a little copper dust which may settle in the colorimeter cell and require removing. 

The capital cost of a THERMAL DeNO, system includes the costs of ammonia and carrier gas systems, injectors, instrumentation and controls, installation, engineering, licensing fees, and, for a retrofit, the cost of any nnodifications. Retrofit applications usually involve neither major modifications nor excessive downtime. The capital cost is application specific and depends on the initial NO, concentration, the size of the boiler, the NO, reduction required, the load following capability, and the ammonia carryover limitations. 

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