Coiled reactors length

FIGURE 4.13 Schlieren signals recorded for different solutions with the same refractive index. Carrier stream = water coiled reactor length = 100 cm a. b, c, d = 2.0 mol L-1 HC1,11.2% (m/v) sucrose, 14% (m/v) glycerol, and 24.13% (m/v) ethanol respectively. Other conditions are as in Fig. 4.13. Reprinted from Anal. Chim. Acta 234 (1990) 153, E.A.G. Zagatto, M.A.Z. Arruda, A.O. Jacintho, I.L. Mattos, Compensation of the Schlieren effect in flow-injection analysis by using dual-wavelength spectrophotometry, with permission from Elsevier (Ref [28]). 

This very large length of more than 2 km, or about 1 mile and a quarter, can be divided into n connected tubes, each with a length of 2036.36/n m. In this case each tube section has the volumetric flow rate c/(per tube) = 0.003/n m3/(sec tube) and the number n can be 100 or 1000, for example, depending on the mechanical and locational factors. Alternatively the total length L = 2036 m can be achieved by a coiled reactor. The particular choice of apparatus is based on mechanical engineering factors. 

The pipe coil reactor is made of Inconel 625, 15 metres in length with an inner diameter (i.d.) of 8 mm and an outer diameter (o.d.) of 14.4 mm. It is submerged in a fluidised sand bath, which is electrically heated and acts as a thermostat. 

Sensitivity Analysis of Length-to-Diameter Ratio for the Helical Coil Reactor... 

The type of tubing used for constructing the manifold should always be specified but less emphasis should be given to manifold components outside of the analytical path. There are different types of reactor (see 6.2.3) and they should be specified. The coiled reactor is by far the most common, and no further information means that this kind of reactor is used. Length and inner diameter of the tubing, winding diameter of the coiled reactor and the presence of different accessories (mixing chambers, solid-phase mini-columns, immobilised enzymes and connectors) in the analytical path should be reported. 

The PFR is usually a long tube, straight or coiled, a set of straight tubes connected in series at their ends, or a bank of independent tubes. The diameter of the tube is usually not more than 4-5 cm. For the PFR assumption to be valid, the length-to-diameter ratio should be very high, at least 30. These reactors are conunon for solid catalyzed vapor-phase reactions. Where no solids are present, the reactor tube is sometimes coiled to acconunodate high residence times. An example of this is the coiled reactor for the production of ethylenediamine by reaction between ethylene dichloride and aqueous anunonia sketched in Figme 1.4 (Venkitakrishnan and Doraiswamy, 1982). 

A tubular reactor setup was developed for the synthesis of the above-mentioned model copolymer for acrylic binder materials. The tuhular reactor essentially consists of capillaries with an internal diameter of 3.8 mm and a length of either 4 or 8 m, which are wound up to a coil of 15 cm diameter. The two reactor lengths allow for adjusting residence times between 5.5 and 44 min. The maximum pressure of the setup is 500 hat at 200 Typically, a premixed solution containing the... 

In coil visbreaking, the inlet pressure is about 2.5 MPa, which is maintained at higher values to facilitate the transport of the feed. Due to the two-phase frictional pressure drop, the inlet pressure along the reactor length is reduced in about 1.7 MPa. 

Based on this model, the feed enters the reactor and separates into two phases, liquid and vapor, whose composition and flowrates are determined by flash calculations. Then, only the liquid goes to the reactor model, which calculates flowrates and compositions of visbroken liquid and gases, as well as reactor temperature. This mixture of produced liquid and gases is blended with the gases from the prior separation, and new flowrates, compositions, and temperature are determined. Finally, the new mixture enters the following step. This procedure of VLB calculation and reactor modeling is repeated until the length of the coil reactor is completed when it is simulated as PFR or when the number of reactors is achieved when simulation is performed as N CSTR in series. 

Figures 3.9-3.12 show the variations of all of these parameters as function of dimensionless length of the coil reactor. After the value of one, which indicates the end of the coil reactor, there are straight lines that represent the behavior of the soaker reactor. For the case of coil reactor, 10 equal-volume CSTR in series were found to reproduce the behavior of the PFR. In other words, each 10% of length of the coil reactor is represented by one CSTR.

The effect of VLE is unimportant in most of the length of the coil reactor (y/L 0 from 0% to 60% coil length), point at which a temperature of 395°C has been reached. This means that below this value, the amount of liquid is considerably higher than that of the vapor. Also, it is known that the cracking reaction usually does not become evident until transfer temperature crosses 400°C. 

In the last section of the coil reactor, which is from 60% to 100% of length, there is a difference in all of the parameters between modeling with and without VLE, although still minimal. In this section, the V/L ratio has increased up to 0.44, which indicates that the temperature increase in this section (397°C-439°C) causes firstly that more vapor is produced, and secondly that those reactions producing gases and light hydrocarbons are enhanced. 

A stirred reactor contains a batch of 700 kg reactants of specific heat 3.8 kJ/kg K initially at 290 K, which is heated by dry saturated steam at 170 kN/m2 fed to a helical coil. During the heating period the steam supply rate is constant at 0.1 kg/s and condensate leaves at the temperature of the steam. If heat losses arc neglected, calculate the true temperature of the reactants when a thermometer immersed in the material reads 360 K. The bulb of the thermometer is approximately cylindrical and is 100 mm long by 10 mm diameter with a water equivalent of 15 g, and the overall heat transfer coefficient to the thermometer is 300 W/m2 K. What would a thermometer with a similar bulb of half the length and half the heat capacity indicate under these conditions ... 

The reactor can consist of a short packed tube or a length of coiled tube. Open tubes can give very serious band dispersion as already discussed and, if a tube is used for the reactor, it should be constructed of low-dispersion tubing. Low dispersion tubing will not only reduce band dispersion but will also produce highly efficient mixing and thus accelerate the reaction. 

The work reported here used a tubular reactor of approx. 2.5 cm id and 150 meters in length. The reactor, lined with a fluorinated polymer, was coiled in a helical shape. The recipe employed standard concentrations of initiator and emulsifier. 

Here in Chapter 1 we make the additional assumptions that the fluid has constant density, that the cross-sectional area of the tube is constant, and that the walls of the tube are impenetrable (i.e., no transpiration through the walls), but these assumptions are not required in the general definition of piston flow. In the general case, it is possible for u, temperature, and pressure to vary as a function of z. The axis of the tube need not be straight. Helically coiled tubes sometimes approximate piston flow more closely than straight tubes. Reactors with square or triangular cross sections are occasionally used. However, in most of this book, we will assume that PFRs are circular tubes of length L and constant radius R. 

For fast reactions (i.e., < 1 min.), open tubular reactors are commonly used. They simply consist of a mixing device and a coiled stainless steel or Teflon capillary tube of narrow bore enclosed in a thermostat. The length of the capillary tube and the flow rate through it control the reaction time. Reagents such as fluorescamine and o-phthalaldehyde are frequently used in this type of system to determine primary amines, amino acids, indoles, hydrazines, etc., in biological and environmental samples. 

For very long, helically coiled steam generator tubes, and for conditions typical of liquid-metal fast breeder reactors (LMFBRs), where steam is generated on the tube side, an overall heat transfer correlation for the whole boiling length (from X = 0 to X = 1.0) has been deduced experimentally (Campolunghi et al., 1977b) ... 

What would be the effect on the resolution between two peaks in the chromatogram of increasing the length of the reactor coil ... 

An increase in the length of the reactor tube will increase the dispersion and so decrease the resolution between a given pair of solutes. In practice, the length of the reactor coil used will represent a compromise between detector response and resolution. 

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