Solids concentration sampler

Thin L-shaped probes are commonly used to measure solids concentration profile in slurry pipelines (28-33), However, serious sampling errors arise as a result of particle inertia. To illustrate the effect of particle inertia on the performance of L-shaped probes, consider the fiuid streamlines ahead (upstream) of a sampling probe located at the center of a pipe, as shown in Figure 2. The probe has zero thickness, and its axis coincides with that of the pipe. The fluid ahead of the sampler contains particles of different sizes and densities. Figure 2A shows the fluid streamlines for sampling with a velocity equal to the upstream local velocity (isokinetic sampling). Of course, the probe does not disturb the flow field ahead of the sampler, and consequently, sample solids concentration and composition equal those upstream of the probe. 

The results discussed so far indicate that the sampling efficiency of a side-wall sampler from a vertical pipeline is always less than unity. One way to increase sample solids concentration is by using a side-wall sampler with a projection see Figure ID). Nasr-El-Din et al. 40) examined the performance of such sampling devices. They found that the projection increased the sample solids concentration. However, the variation of the sampling efficiency with the velocity ratio was different from that obtained with a... 

C solids concentration in the sampler, volume fraction Cb average solids concentration over the pipe cross section, volume fraction... 

The asstanption in this simplified equation is that an effective collection medium is used and the concentration of the analyte at the sortent surface is zero. For solid sorbent samplers, this is not always true for the more volatile compoimtk and becomes a problem for the weakly retained species, when peak exposures are followed by no or low exposure or when samples are stored for a long period of time before analysis. A more exact Eq. substitutes the quantity (C—Co) for C in Eq. (9). Where Co is the concentration at the surface of the adsorbing layer. 

Normally when dissolved solids concentrations exceed about 2 mg/L, depending on the specific matrix of the sample, it can be anticipated that potential stability problems will be encountered. Several solutions to solving this problem can be employed. Perhaps the simplest is to dilute the samples so that matrix concentrations are below levels that encourage the buildup of salts on the sampler cone. This approach can be used effectively because of the high sensitivity enjoyed by the ICP-MS methodology, thereby maintaining suitable detectability of analyte species. 

The laboratory scale plant is shown in Fig. /. The reactor consists of a stainless steel tube, 90 mm inner diameter and 230 mm length, placed inside a concentric furnace. The particles of solid black liquor were placed in a tray of 40 pm mesh inside the reactor. Downstream the reactor exit, two ice traps and a cotton filter were installed to collect tars. Gas samplers and a CO/CO2 I.R- analyser, permitted to follow the exit gas conposition during the experiments. 

Figure 4.1.6 Comparison of TWA concentrations (jug L-1) of (a) Cd, and (b) Zn obtained using the DGT OP, and Chemcatcher passive sampling devices deployed in the River Meuse (Eijsden, Netherlands) along side spot sampling with measurements of total ( ) and filtered (0.45 jLtm) (o) fractions. DGT OP samplers (dashed line) were exposed for overlapping period of 7, 14, 14, and 28 days. Chemcatcher samplers (solid line) were exposed for 21 days...

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