Repack averaging

Samples that are in a dry form require tumbling or thorough mixing to minimize the effects of repack error. Repack error is an effect that is demonstrated for a given sample as the differences between sample spectral measurements of several aliquots of a sample. If this effect is not minimized, the correlation between the optical data and the reference chemical information is drastically reduced and the sensitivity of NIR for any particular application is reduced. Repack averaging, or compression, and other methods of reducing these effects have been demonstrated in the literature [66]. 

A key step in the application of rapid analysis methods is the collection of high quality NIR spectra. To minimize the effect of water in the biomass spectra, each sample was air-dried to less than 10 percent moisture prior to NIR spectroscopic analysis. Spectroscopic techniques were used that enable a high quality, reproducible, and representative NIR reflectance spectrum to be obtained. For each sample, a total of 35 spectra were collected and averaged to compensate for sample heterogeneity. Each calibration sample was subsampled three times. Sample cells were emptied and repacked between subsamples. Instrument reproducibility tests demonstrated that the reproducibility limits of the NIR spectrometer contributed less than 0.1 percent to the absolute prediction errors in the rapid analysis method. 

Average S02 removal for Run 907-1A was 97.5 percent at 2,350 ppm average inlet SO2 concentration. The SO2 removal stayed within a narrow range of 96 to 99 percent throughout almost the entire run. This was a significant improvement over the 57 percent S02 removal for the base case run, Run 901-1A, at 9.4 ft/sec spray tower gas velocity under similar conditions. On October 19 and on October 27, SO2 removal dropped briefly to less than 90 percent when the pump which supplied the slurry to the top two spray headers was brought offstream for repacking, and the spray tower slurry flow rate was cut in half to 800 gpm. At the reduced slurry recirculation rate, SO2 removal was 82 to 87 percent. 

Considering the fact, that the procedure of washing and repacking could be completed in about 1 h from the overall average decay of catalytic activity indicated, by the broken line a catalytic half-life of could be determined. 

Non-uniformity of the column packing does affect the retention volume because of the pressure variation along the column. Measurements must therefore be made on both forward and reversed columns and the average taken, if this effect is to be eliminated. If the difference between the activity coefficients from the two sets of measurements is large the column must be repacked. 

Miscible displacement experiments were conducted on repacked sediments to determine relevant transport parameters (retardation coefficients) for U(VI) and SrEDTA in the absence of the effects of sedimentary stmcture and unsaturated flow. The erq)eriments were conducted in a glass column 1 cm in diameter and 4.5 cm in lengtii (U(VI)) or 10 cm in length (SrEDTA ). The influent solutions consisted of NaNOa or NaCl matrix, nomeactive Br tracer (2x 10 M), and the highest concentration of U and Sr utilized in the equilibrium batch e qteriments. A medical punq> was used to deliver solution to the bottom of the column at an average pore water velocity of 2.1 cm hr for... 

Improve mixing guidelines Improve grinding procedures Average replicate repacks Rotate sample cup... 

Pulverize sample to less than 40-/t particle size Average multiple repacks... 

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