Continuous Flow-stirred Reactor Research Articles

Quantitative Estimation of Segregation Indices in CSTR—Effects of Feed Stream and Output Port

We quantitatively estimate the segregation indices in a continuous-flow stirred reactor (CSTR) on the basis of a unique parallel competing reaction scheme proposed by Villermaux and co-workers. Although the feed stream flow rate is much less than the circulation rate in the tank, the feed stream still markedly affects the micromixing efficiency.

Influence of ozone air pollution on plant-herbivore interactions. Part 1: Biochemical changes in ornamental milkweed ( Asclepias curassavica L.; asclepiadaceae) induced by ozone

A series of fumigation experiments was conducted with bloodflower ( Asclepias curassavica L.) in continuous-flow stirred reactors (CSTRs) to elucidate the effects of ozone on foliar concentrations of several primary and secondary plant metabolites relevant to herbivores. Plants 8 weeks of age were subjected to different ozone levels ranging from 0 to 134 nl liter −1 for exposure periods up to 16 days. Leaves were analyzed for concentration of soluble carbohydrates, starch, free amino acids, soluble protein, total phenolics, and total cardenolides. Significant interactions between the linear effects of ozone concentration and exposure time were found for soluble carbohydrates, amino acids, cardenolides and phenolics. No significant treatment effects could be observed on foliar starch and protein concentration. The metabolic responses of plants to fumigation appeared to be altered by overall plant nutrition. It is possible that the metabolic changes observed in the host plant represent important changes in nutritional quality to insects.

Polymer crosslinking in continuous flow stirred reactors

The effect that tetrafunctional crosslinking of polymers has on molecular weight and molecular weight distribution in a continuous flow stirred reactor (CFSR) is calculated. If all mers have equal likelihood of coupling it is found that steady state operation of the reactor becomes impossible at a degree of crosslinking equal to only 1 4 that which causes gelation in a batch reactor. In steady state operation the ratio of weight to number average degrees of polymerization in the product cannot exceed 2 D w 0/ D n 0- 1 4 , the superscripts signifying initial values of degree of polymerization. Unlike in batch reactors, where D w diverges simultaneously with D z and higher averages, averages higher than D w can diverge while D w remains finite. Thus, significant differences exist when tetrafunctional branching occurs in a CFSR rather than a batch reactor. The relationship of these results to the behavior in polymerizations with branching by polymer transfer is also discussed.

High nitrate denitrification in continuous flow-stirred reactors

Continuous flow stirred reactors were used to evaluate the maximum denitrification specific removal rates for influent solutions made from NH 4NO 3, CaNO 3, KNO 3 and UO 2 fuel fabrication waste water. Nitrate substrate concentrations ranged from 0.01 to 20 kg NO 3/m 3. Values for U max (maximum specific substrate removal rate per unit mass of microorganisms per unit time, days −1) were determined using graphical solutions to the Lineweaver-Burk equations. For NH 4NO 3 solutions at nitrate substrate concentrations <6 kg NO 3/m 3 the value for U max was found to be 1.73 days −1. At nitrate substrate concentrations >6 kg NO 3/m 3 a nonlinear relationship was observed in the Lineweaver-Burk plots indicating nitrate substrate inhibition. Specific removal rates at nitrate concentrations >6 kg NO 3/m 3 averaged <1.0 days −1. Ammonia toxicity may also have occurred as the pH of the mixed liquor was near 8. Methanol concentrations as high as 11.6 kg CH 3OH/m 3 did not inhibit denitrification rates. The highest specific removal rates recorded (3.13 ± 0.56 days −1) were with influents made from UO 2 fuel fabrication waste water.

Nitrate reduction by denitrifying bacteria in single and two stage continuous flow reactors

Denitrification by a mixed bacterial population of medium containing 1000 mg NO3−-N1−1 and acetate as carbon source was studied in batch, a single stage continuous flow stirred reactor (CFSTR) and a two stage CFSTR at 30°C. The optimum pH for denitrification, nitratase, nitrite reductase activities and growth was found to be 7.5 in batch culture. A single stage CFSTR growth limited by nitrate had an optimum denitrification rate of 0.13 mg NO3−-N mg−1 cells h at a residence time of 8 h. The experimentally observed carbon to nitrate ratio (mg CH3 COO−-C mg−1 NO3−-N)was 1.7 for the dilution rates of 0.02–0.18 h−1. For the second stage CFSTR, bacteria growing at the maximum rate of 0.25 h−1 and not limited by nitrate had a denitrification rate of 0.24 mg NO3−-N mg−1 h. Dissolved oxygen (up to 9.5 mg 1−1) did not effect denitrification rates in the second stage CFSTR. As the second stage CFSTR runs progressed extensive wall growth occurred and concurrently the output gas contained increasing quantities of nitrous oxide. A development from this study would be a two stage CFSTR with wall growth in the second stage which would make an efficient nitrate removal process.