Slurry concentration measurements

Means should be provided for measuring and varying the slurry concentration in the contacting zone up to 50 % by volume. 

Table I shows the size ranges and concentrations of the slurries of silica and iron oxide in isoparaffin and water, that were utilized in the tests. From the stirred, baffled reservoir tank, which was approximately the same volume as the columns, slurry was pumped with a diaphragm pump, using a tranquilizer to even out the flow, into the bottom of the 12.7 cm column, and above the distributor for the 30.5 cm column. In the 12.7 cm column, therefore, slurry passed with the gas through the distributor plate for V- >0. At the top of the column, the slurry was separated from the gas, and returned by gravity to either the reservoir tank, or to a calibrated volume used for slurry flow measurement.

Research various particle-size distribution and chemical concentration measurement technologies and related instrumentation. Create a list of their capabilities and limitations, measurement ranges, and accuracy and repeatability. Evaluate the applicability of these in the CMP slurry measurements. Discuss the possibilities of zeta-potential changes as a result... 

The originators of the Penn Kem system claim that it is capable of measuring particle size distributions in the size range 0.01 to 100 pm for slurry concentrations at volume concentrations as high as 50%. They report experimental work with an on-line system using titanium dioxide at volume concentrations from 3.5% to 42.3%. Quantitative comparison of data was carried out at eighteen frequencies and eleven concentrations by volume [248,249]. Theoretical work resulted in the development of a unified coupled phase model which successfully predicted the experimental data for suspensions, emulsions and aerosols [250]. 

Figure 31 shows the resistivity measured by the conductivity probe and the local concentration measured by the isokinetic sampling method. Measurements were made for slurries of polystyrene particles of 1.4-mm mean diameter at the pipe center and at radial positions of R = 0.8. Good agreement with calibration results is seen in these tests. Because the particles used in these experiments were large, no samples could be withdrawn from the center of the pipe at concentrations higher than 35%. Also, no voltage measurements could be taken closer to the pipe wall because particles tended to be trapped between the probe and the wall. 

At the end of the digestion time the plutonium peroxide slurry was transferred to the Filterometer. The volume of the slurry was measured to the nearest milliliter and the time required for filtration to the nearest second. The volume of the filtrate was also measured to the nearest milliliter and then diluted with an equal volume of concentrated HNO3. This HNO3 dissolved any plutonium peroxide present and prevented any post precipitation. The filtrate was then analyzed coulometrically for plutonium. From the filtration time, slurry volume, and the plutonium analysis data, the relative filtration time and the... 

To examine dentifrice abrasivity, the most widely used methods are the radiotracer [13, 14] and profilometry methods [15, 16], In the radiotracer technique [14], samples of either enamel or dentine from extracted human teeth are exposed to a radiation source. The radioactive samples are then brushed with a slurry of the test dentifrice in a brushing simulator under defined conditions of loading, slurry concentration and number of cycles. The abrasion is measured by assessing the radioactivity of the resulting slurry following the test, which therefore gives a measure of the amount of material abraded from the enamel or dentine surface. A standard reference abrasive (usually calcium pyrophosphate or calcium carbonate) is also tested using the same conditions and the abrasivity... 

To estimate the amount of ultrasonic energy required to run in the scaled-up crystallizer, a study was carried out measuring crystal dismption by elutriation from a glass flow unit. As shown in Table 7-6, breakage was essentially first-order with sonication power and slurry concentration. This also implies that the main mechanism for crystal breakage is individual crystal breakage in the... 

It is desirable to measure the fluidization behavior of the particular solids in the column, ideally in actual mother liquors. A typical set of curves is shown in Fig. 1 l-22a. Each particle size is a relatively monosized sieve fraction. The x-intercept of each curve is the terminal settling velocity (slurry concentration 0 gm/liter), but it is more accurate to measure the tenninal settling velocity separately with a stopwatch and a graduated cylinder. Such a data set is shown in Fig. ll-22b. 

When scaling up column geometry, it is desirable to know the localized slurry concentrations within the crystallizer. Excessively high concentrations can result in sluggish fluidization and possible agglomeration, and excessively low concentrations decrease productivity. These local concentrations can be calculated, assuming a classified bed (largest particles on the bottom), and either a measured or estimated size distribution. 

Figure 20. A conductivity probe for local solids concentration measurement in slurry pipelines. (Reproduced with permission from reference 27. Copyright 1987.)...

The development status of process control instrumentation lags that of the quality control instruments significantly Nuclear density gauges function in the coal preparation plant environment The slurry concentration meter has application in the intermediate and fine sized coal cleaning circuits and needs to be tested in a preparation plant Other devices, such as ash monitors to control the operation of heavy media baths or jigs are not available and instruments developed for other process industries are not suitable for use in coal preparation plants Modeling studies of the various unit operations are required in order to ascertain the fundamental parameters required to automate the control of these systems Primary process control instrument needs include ash, sulfur, and moisture monitors secondary needs include an on-line washability and ash fusion measurement ... 

Quantitative rate data on the catalytic reduction of nitrates in drinkable water are relatively scarce. One of the first works concerning kinetics is that of Tacke and Vorlop who employed a Pd-Cu bimetallic catalyst containing 5wt.% of Pt and 1.25 wt.% of Cu in a slurry reactor. Measurements of the initial rates resulted in a power-law rate expression. They reported a power of 0.7 with respect to the nitrate concentration, and an independency on the hydrogen partial pressure providing this pressure exceeded 1 bar. Pintar efa/. reported a complete kinetic model of the Langmuir-Hinshelwood type written in the form... 

By advancing clear liquor and adjusting the feed rate to the centrifuge and returning clear liquor, sluny concentration can be controlled over wide ranges. It should be noted that slurry concentration is difficult to measure, and samples of crystallizer contents usually are extracted manually and analyzed for solids content. 

In another case, dissolution of crystalline and amorphous ciclesonide was studied (Feth et al. 2008). Crystalline and amorphous ciclesonide exhibit the same saturation solubility (Feth et al. 2008). For the crystalline ciclesonide, within the first 60 min of dissolution, the concentration measured (50 mg/L) was significantly lower than its saturation solubility (90.1 2.2 mg/L). On the contrary, for the amorphous form, concentration increased almost instantaneously to values up to four times higher than the saturation solubility determined for amorphous ciclesonide (91.6 5.2 mg/L). After 24 h, for both forms, concentrations were approaching the saturation concentration. It was suggested that the amorphous ciclesonide was able to form a stable supersaturated solution in water for at least 60 min due to the absence of inoculation crystals in the amorphous phase. On the other hand, in crystalline ciclesonide, the crystal itself acts as crystallization seed in the slurry which speeds up the process. 

Difficulties in reliable temperature measurement preclude automatic control. The maximum temperature is limited by the wear rate of the refractory and the minimum temperature by the carbon conversion [70]. Typically, temperature is adjusted using the O/C ratio, which is highly sensitive to the coal rank, slurry concentration, and the quantity and composition of the recycled solids. However, an on-line measurement of the latter parameters is often not possible. Pyrometers lack optical access because of slag deposition [70]. The temperature can be measured indirectly using the CH4 yield or CO/CO2 ratio [71]. Finally, thermocouples immersed in the refractory must be used these indicate temperatures, which are lower than is actually the case, and are sensitive to the insulating effects of the slag film [70]. 

The abrasive wear of a series of four semi-crystalline polymers was investigated with a micro-scale abrasive wear tester. The wear of four semi-crystalline polymers PA6.6, PBT, POM and PTFE was measured under specific test conditions. The silicon carbide slurry concentration and the load were varied. The wear coefiBcients of the polymers were compared with the (mechanical) properties. 

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