Side stream mixing

C is the DSR side-stream mixing concentration. Vectors zi i, zl, . .., are iterated Lie brackets as described earlier, given by... 

Rate constants have already been substituted into the rate expressions for convenience (they are kj = 1 s kj = 1 s, and kj = 10 L/(mol.s)). Determine an expression for the critical a policy if the DSR side-stream mixing composition is given by C° = [l,0,0]Tmol/L. 

The mixed oxidation products are fed to a stiU where the pelargonic and other low boiling acids are removed as overhead while the heavy material, esters and dimer acids, are removed as residue. The side-stream contains predominately azelaic acid along with minor amounts of other dibasic acids and palmitic and stearic acids. The side-stream is then washed with hot water that dissolves the azelaic acid, and separation can then be made from the water-insoluble acids, palmitic and stearic acids. Water is removed from the aqueous solution by evaporators or through crystallization (44,45). 

After leaving the reactor the reaction mixture is passed to a settling tank where the denser HF is deposited in the lower phase. The organic phase is mixed gently with HF the HF phase contains tar components and traces of benzene. From the HF phase a side stream is refined. This side stream is heated in a preheater, partially vaporized, and separated into two components in a distillation column HF and benzene are distilled over the top while tar components are taken away at bottom. The top product is condensed, cooled, and collected in a settle tank. The bottom product is neutralized using potassium... 

The flow rate of a hot coal/oil slurry in a pipeline is measured by injecting a small side stream of cool oil and measuring the resulting temperature change downstream in the pipeline. The slurry is initially at 300°F and has a density of 1.2 g/cm3 and a specific heat of 0.7 Btu/(lbm °F). With no side stream injected, the temperature downstream of the mixing point is 298°F. With a side stream at 60°F and a flow rate of 1 lbm/s, the temperature at this point is 295°F. The side stream has a density of 0.8 g/cm3 and a cp of 0.6 Btu/(lbm °F). What is the mass flow rate of the slurry ... 

If AW AW the process of finding a linear-mixture basis can be tedious. Fortunately, however, in practical applications Nm is usually not greater than 2 or 3, and thus it is rarely necessary to search for more than one or two combinations of linearly independent columns for each reference vector. In the rare cases where A m > 3, the linear mixtures are often easy to identify. For example, in a tubular reactor with multiple side-injection streams, the side streams might all have the same inlet concentrations so that c(2) = = c(iVin). The stationary flow calculation would then require only AW = 1 mixture-fraction components to describe mixing between inlet 1 and the Nm — I side streams. In summary, as illustrated in Fig. 5.7, a turbulent reacting flow for which a linear-mixture basis exists can be completely described in terms of a transformed composition vector ipm( defined by... 

T on the tubeside, T on the shellside. i = input, o = output, (a) One pass on shellside, any multiple of two passes on tubeside, (b) Two passes on shell side, any multiple of four on tubeside, (c) Cross flow, both streams unmixed laterally, (d) Cross flow, one stream mixed laterally, (e) Cross flow, both streams mixed laterally, (f) Effectiveness and number of transfer units in parallel and countercurrent flows, (g) Three shell passes, multiples of six on tubeside, (h) Four shell passes, multiples of eight on tubeside, (i) Five shell passes, multiples of ten on tubeside, (j) Six shell passes, multiples of 12 on tubeside. 

In contrast to segregated flow, in which the mixing occurs only after each side stream leaves the vessel, under maximum mixedness flow, mixing of all molecules having a certain life expectancy occurs at the time of introduction of fresh material. These two mixing extremes—as late as possible and as soon as possible, both having the same RTD— correspond to extremes of reactor performance. 

Each zone of the tubular reactor is simulated as a sequence of N perfectly mixed elementary volumes, as shown in Figure 2. Each volume can receive a feed side-stream, and exchanges heat with a corresponding volume in the oil jacket. For volume i and chemical species j (either initiator, oxygen, radicals or monomer) the mass balance is written as ... 

For a completely homogeneous mixture, sc = 0 and thus v=0. Usually, two partial flows are combined in a mixing process. The volumetric flow ratio of the side stream with respect to the main stream is defined as ... 

One method of determining the mixing quality is to use optical evaluation. A suitable set-up is shown in Fig. 9.19. Here, the main stream being fed to the extruder is a clear oil. A side stream containing a tracer is introduced at some arbitrary position along the screw. This approach allows the length available for mixing to be varied. The extruder can be equipped... 

I m not talidng about fun you can have at an amusement park, but CRE fun. Now that we have an understanding on how to solve for the exit concentrations of multiple reactions in a CSTR and how to plot the species concentration down the length of a PER or PER, we can address one of the most important and fun areas of chemical reaction engineering. This area, discussed in Section 6.1, is learning how to maximize the desired product and minimize the undesired product. It is this area that can make or break a chemical process financially. It is also an area that requires creativity in designing the reactor schemes and feed conditions that will maximize profits. Here you can mix and match reactors, feed steams, and side streams as well as vary the ratios of feed concentration in order to maximize or minimize the selectivity of a particular species. Problems of this type are what I call digital-age problems - because... 

Pipeline Mixers used as Reactors for Fast C/C Reactions. Taylor (1996) and colleagues (1998) conducted a study to determine scale-up procedures for fast C/C reactions in pipeline mixers. They used the fourth Bourne reaction, which is the acid catalyzed hydrolysis of dimethoxypropane (DMP) to acetone and methanol. This is an extremely rapid reaction when catalyzed by HCl. The competitive reaction scheme, which is a unique one, is one in which NaOH reacts practically instantaneously with the HCl to remove the catalyst for the hydrolysis reaction. A water/ethanol solution of NaOH and DMP was fed as a main stream to a Kenics helical element mixer and an aqueous side stream containing slightly greater (abour 5% greater) than equimolar amount of NaOH was fed as the side stream. The product was analyzed by GC for methanol and acetone. For extremely rapid mixing, essentially no hydrolysis occurred however, for slow mixing, essentially all the DMP is hydrolyzed because acidic conditions cause very rapid hydrolysis of the DMP. 

The activity of the primary coolant may be controlled by side-stream demineralization (decontamination) across mixed beds (C) of... 

Dissolved air flotation (DAF) is the process of removing suspended solid, oils, and other contaminants via the use of air bubble flotation. Air is dissolved into water, mixed with the waste stream prior to being released from the solution and is in intimate contact with the contaminants. The small bubbles will attach to the floatable oils, increase their buoyancy, and reduce their specific gravity. In this system, a side stream of the oily waste is supersaturated under pressure with dissolved air so that the movement of the air bubbles will carry the floatables upward where they can be removed (46,51). 

Impinging jets, routinely used in the plastics industry, have been used to crystallize small particles with a narrow particle size distribution [27,28].The impinging jet crystallizer is a cylindrical chamber with two spray nozzles that enter from opposite sides of the chamber. A solution of the material to be crystallized is fed into one nozzle, and the agent to induce crystallization is fed into the other nozzle. The smaller the nozzle apertures, the faster the velocity of the solutions into the chamber, and the faster the two streams mix and reach a uniform environment. In this manner a stream of finasteride (Figure 11.10) in AcOH and water was fed into one nozzle, and a stream of water (the crystallizing agent) was fed into the other nozzle. Crystallized finasteride had an average particle size of 10-15 pun. 

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