Two-Stage Dilution System

For the two-stage dilution apparatus, the agent carrier gas (1) for the first dilution is supplied from a nitrogen tank and is controlled by a flow meter equipped with a 

However, if the concentration of the vapor source is very high and the target concentration is very low — for example, when a parts-per-billion level of CI2 vapor is generated with 99.99% CI2 gas — a multiple-stage dilution system may have to be used. A portion of the sample from the mixer of the first-stage dilution system is used as the source of the next stage of dilution and mixes with the second-stage 

Therefore, the required dilution flow is 1 ml/min less than 10 m /min. Such a large amount of flow, greatly in excess of detector needs, creates undesirable side effects. Because CWAs or TICs are highly toxic, their release into the atmosphere should, if possible, be kept to a minimum to avoid excessive contamination. Therefore, the excess exhaust from the generation process must be contained via trapping or filtering through an activated charcoal filter to capture toxic material from the stream before it is exhausted. 

When a two-stage dilution system is used, the concentration is first reduced to, for example, the 3-ppm level by using 1-ml/min source vapor and 2999-ml/min dilution air  

We can, then, take 1 ml/min of this diluted vapor and dilute it with again with 3000 ml/min of dilution air to reach the desired 1 ppb second-stage concentration in a total flow of 3 1. 

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Figure 4.10 is an example of a two-stage dilution system. An air generator (6) provides the clean and dried air used for the carrier stream. This pressurized air is split into five streams, each controlled by flow meters equipped with appropriate needle valves (7, 11, 12, 19, and 20). Flow meters (11), (12), (19), and (20) control the two parallel humidity dilution streams. These are identical for ease of operation. The flow meter (7) is used to provide a dry airstream for the first-stage dilution. 

Figure 4.15 Two-stage dilution system with gas dispersion bottle as interference source.

Fig. 3—in the two stage desalting system, dilution waier is injected between stages. 9reatly reducing the amount ol dilution water required. Further reductions may be achieved by adding the second stage recycle pump... 

FIGURE 22 Two-step, two-stage membrane system to produce pure nitrogen and a concentrated propylene stream from a dilute feed gas. (Membrane Technology and Research, Inc.) [Baker, R. W., et al. (1998). J. Membrane Sci. 159, 55-62.]... 

In practice, the ratios and flow rates through the chambers are chosen according to sampling needs, and the exhaust rate is determined by solving the equation for Qe. This expression is somewhat more complicated for more than a two-stage dilution, but can easily be set up and worked out. The system in use for the... 

Figure 1.50 is a schematic of a two-stage desalting system with dilution water recycling capability. This system is similar to the dehydrator and desalter system described in the previous section. The only difference is that the water removed in the second stage is pumped back to the first stage. The addition of this recycle provides for some... 

Froth from the hot-water process may be mixed with a hydrocarbon diluent, eg, coker naphtha, and centrifuged. The Suncor process employs a two-stage centrifuging operation, and each stage consists of multiple centrifuges of conventional design installed in parallel. The bitumen product contains 1—2 wt % mineral (dry bitumen basis) and 5—15 wt % water (wet diluted basis). Syncmde also utilizes a centrifuge system with naphtha diluent. 

The reconcentration of dilute (50—60%) sulfuric acid is one of the more costly operations in the manufacture of ethanol by this process. An acid reboiler, followed by a two-stage vacuum evaporation system, raises acid concentration to about 90%. The 90% acid is then brought to 96—98% strength by fortification with 103% oleum (fuming sulfuric acid). 

There are two other mixing systems that should be considered as having progressed beyond the development stage and will likely be instituted as production systems for the manufacture of composite propellant. The first is a proprietary system developed by Rocketdyne and referred to as the Quickmix system (10). Here the solid ingredients, such as oxidizer and fuel additives, are placed in a dilute slurry with low viscosity, volatile, and immiscible carrier. These slurries, a minimum of two, and the fluid polymer and curing agent streams are metered to a continuous fluid mixer. The effluent from the mixer then flows to a separator and... 

Dilution water calculations for a two stage system using recycle are slightly more complicated than for a single stage or two stage without recycle. These problems are better suited tn a computer, as hand calculations require several entries of dilution water variables in order to zero in on the proper balance. 

Figure 9.8 The use of permeate vapor fractional condensation systems to improve the separation achieved in pervaporation of dilute ethanol solutions (a) Two-stage fractional condensation [40] and (b) Dephlegmator condensation [39]...

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