Performance return cleaning

If return occurs during the bromination of cw-stilbenes and rotation around the C-C bond is faster than collapse of the intermediates to dibromides, this process will lead to fra j-stilbene (Scheme 9). We used this test to check the possibility of return in the bromination of unsubstimted, 4-methyl, 4-trifluoromethyl-, and 4,4 -bis(trifluoromethyl)-stilbenes in DCE (ref. 24). All these olefins gave clean third-order rate constants spanning 7 powers of 10. For each cis-trans couple the cis olefin was brominated 3.5 to 5.5 times faster than the trans isomer. Reactions for products analysis were performed at initial molar ratios of Br2 to olefin of 1 to 2, so that products arose only from the cis olefin, the trans isomer being accumulated in the reaction medium. 

Between analyses, and at the end of each day, the HPLC analytical column should be reequilibrated with the appropriate initial gradient conditions until system pressure returns to initial operating conditions. However, on occasion, the analytical column may require a more rigorous cleaning procedure as described below in order to ensure continued optimal performance. Examples of conditions where this may be required are listed in Table F4.4.6. 

If a system was returned from inspection, external exercise, or maintenance at the manufacturer, an additional test for cleanness (entrance control) is performed. Three different blank injections with solvent, BSTFA, and DMT are performed and evaluated using an on-site target library containing all MS spectra from the OCAD. Absence of any identification ensures that the system components are free from scheduled chemicals and their degradation products. The same blank injection tests are performed if a system in waiting status was used internally for injections other than check mixture. The on-site target library used in the test of cleanness is removed from the hard disk before issuing the system for a mission. 

Note that performance fo the RO unit may be different after a high pH cleaning. Specifically, the flux may be higher and the rejection may be lower. This is a result of the membrane "loosening" at high pH and is a temporary condition. Performance should return to nominal within a couple of days. 

What Should Be Done if Cleaning Does Not Return Performance to Baseline ... 

To determine the cost of ownership of a single cleaning alternative or to compare the cost of two or more alternatives, it is necessary to determine the appropriate capital cost, the operating cost and the company s financial costs and performance criteria. The financial costs include the company s cost of money, depreciation rates, desired rates of return and performance hurdle rates. 

Filter the solution through Whatman 40 dry filter paper into clean and dry beakers. Perform a blank without soil (if the filtrate is not clear, return it to the conical flask containing the sample, add more charcoal, shake quickly and filter again). 

The membrane separation plant is tubular ultraflltration (UF) and the pilot-plant operation was on a batch basis with a volume reduction factor approaching 40. The UF membrane had a maximum permeate flux of around 300 L/m hr at maximum 6 kg/cm inlet pressure and 3.8 m/s fluid velocity with a clean membrane. The flux typically dropped and approached 80 L/m hr at the end of a day s operation. The retentate from UF separation was returned to the feed tank whereas the permeate was routed to the sewer. Design of a full-scale plant was performed using a flux value of 40 L/m hr and volume reduction of 20x. 

A recent U.S. Army study (performed by Battelle) identified, described, and evaluated technologies to facilitate remediation of oversize ex-plosives-contaminated debris. During composting of explosives-contaminated soil at military installations, such debris interferes with the operation of the flail-type windrow equipment used to turn and aerate the composting soil. The study examined size reduction and return of the crushed debris to the compost pile and removal of the contaminants from the debris followed by disposal of the cleaned debris. If the debris is to be returned to the compost pile, the particle size must be less than V2-inch diameter. For removal, the explosives contaminants level must be reduced to below 30 mg/kg. 

A sufficient liquid level in a reboiler used to supply steam to the column is important from a performance and safety standpoint. The reboiler is under a slight pressure and therefore must be a pressure vessel. It usually has a gasketed and bolted lid. Welded steam outlet and stillage return lines connect the reboiler to the column. The liquid return enters the reboiler below the desired liquid level. The outflow of bottoms can be controlled by regulating the back-pressure in the bottoms line, in turn controlling the level of liquid in the pot. The pot must be designed so it can be completely drained to ease clean-out. 

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