Kenics mixer pressure drop

Motionless inline mixers obtain energy for mixing and dispersion from the pressure drops developed as the phases flow at high velocity through an array of baffles or packing in a tube. Performance data on the Kenics (132) and Sul2er (133) types of motionless mixer have been reported. 

The pressure drop in the Kenics mixer of the same length and diameter as an empty pipe can be determined from... 

Add (T+1/8) inch per flange up to a maximum of 3/8 inch per flange when ordering with flanges (T= wall thickness of housing) (1/8 inch = 3.18 mm, 3/8 inch = 9.53 mm). Mod. Length is based on Model 6. (Source Chen, S.J. Pressure Drop in the Kenics Mixer, Kenics Technical data KTEK-2, 1978). 

Because there are no moving parts in the Kenics mixer, only the processed materials are in motion. Therefore, the only energy required for the mixer is the energy required to overcome the pressure drop (AP). The general equation for calculating the pressure drop in an empty pipe for isothermal incompressible fluids is given by... 

What Kenics Mixer model of 3-in. Schedule 40 is required to process a Newtonian fluid with a viscosity of 150,000 cP, a density of 60 Ib/ft, and a flowrate of 650 Ib/hr What is the pressure drop (AP) and theoretical horsepower ... 

A liquid-gas mixture is to flow in a 3-in. Schedule 40 Kenics mixer. Estimate the pressure drop of the unit. The system conditions and physical properties are ... 

Source Chen, S J. Pressure Drop in the Kenics Mixer, Kenics Technical data KTEK-2, 1978). 

The Lockhart and Martinelli [32] correlation is employed to estimate the two-phase pressure drop in the Kenics mixer. The pressure drop... 

Multiply K by the empty-pipe pressure drop to obtain the pressure drop caused by the Kenics mixer model installation. The theoretical horsepower required by the Kenics mixer is determined by... 

Most manufacturers of static mixers have published (either in sales literature or in the technical literature) design methods for pressure drop. The pressure drop design methods, from Myers et al. (1997) for the Kenics HEM and Kenics HEV mixers are presented. The Darcy friction factor for the standard HEV mixer, Ntr = 2, L/D = 1, (with X/D = 3 downstream pipe) is presented in Figure 10.31. The friction factor is not given below Nrc = 1,000 because the HEV mixer should not be used for Nrc < 3,000. 

The constant has the numeric value of 64 for empty pipe, as is well known. The following numerical values apply for the static mixers whose characteristics are given in Fig. 8.5 Kenics 450 SMX (LP) 640 SMX (standard) 4000 and SMV 5600 Ross-ISG mixer 1.2 x IO. The pressure drop of these mixers is, in the laminar flow range, thus about a factor of 7 10 60 90 or 200 higher than in an empty pipe [416]. 

The process characteristic of the Sulzer SMX-L mixer is for the 5% CMC solution identical to that for the Kenics mixer for L/D> 30, see expression (8.19). The value for glycerine lies about 20% above that for PAA. The viscoelastic viscosity behavior affected heat transfer negatively. The pressure drop characteristic Cf Re — const (for Re < 1 X lO ) has been confirmed for SMX-L, the constant being about a factor of 10 higher than for an empty pipe. 

This, however, says nothing about whether more heat is removed than is added due to the increase in pressure drop. Kalbritz and Bohnet [254] answered this question. They investigated different static mixers (Kenics Fix-Mix Ross LLDP Sulzer SMX and SMXL) in the range Re = 1.8-4 x 10 and found for the heat transfer ... 

The evaluation of diazotization reactions [41], which were carried out in Kenics and Sulzer SMXL mixers, provide a possible access to this parameter determination. For small throughputs and high viscosities the yield of the desired product was determined by micro-mixing. The power dissipation of 85-90% in both mixers indicated, that the engulfment model for micro-mixing prevailed. Faster micro- and meso-mixing was achieved in the Sulzer mixers, because larger pressure drops were also present in them, see Fig. 8.11 and 8.12. 

Azer et al. [188] reported data for condensation in tubes with Kenics static mixer inserts. Substantial improvements in heat transfer coefficients were reported however, the increases in pressure drop were very large. A subsequent paper [189] presents a surface renewal model for the condensing heat transfer coefficient. With one experimentally determined constant, the correlation derived from this model is in good agreement with the experimental data. 

The enhanced heat transfer coefncient is due to the increase in radial mixing compared with the empty tube and possibly a contribution due to the fin effect associated with the presence of the metal element— particularly if there is good contact between element and tube wall. It is difflcult to relate the heat transfer characteristics of static mixers to empty pipes but low pressure drop mixers (e.g. Kenics, SM X) give increases in heat transfer coefficient of the order of 300% for an increase of pressure drop of the order of 700%. Some simple correlations have been presented for the Kenics mixer ... 

Data are also described in terms of the relationship between pressure drop in the static mixer and the equivalent pressure loss in an empty tube. For the Kenics mixer ° the relationship ... 

Kenics-type static mixers have been used as inserts in tubular reactors. Compared to an open tube operated at the same pressure drop, the static mixer gives about 40% more heat transfer. Stand-alone mixer reactors of the Koch or Sultzer SMR type have been used as post-reactors and devolatilization preheaters. The polymer flows through the shell side of the SMR and the heat transfer fluid flows inside tubes that have been strategically placed to promote radial mixing of the polymer. One bulk polystyrene process used the SMR as in a recycle loop as the first reactor, but the capital cost is high compared to alternatives such as a boiling CSTR or a proprietary stirred-tube reactor. 

The flow twisting arrangement of the Ross ISG mixer is completely different in that it uses two sets of crossing tubular ducts within each element to provide the redistribution, but this mechanism has a relatively high pressure drop compared with other mixers [1 ]. The Ross ISG and Kenics mixers and their mixing mechanisms have been described in some detail by Tadmor and Gogos [3]. 

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