Feed viscosity

EmpiricalEfficieny Prediction Methods. Numerous empirical methods for predicting plate efficiency have been proposed. Probably the most widely used method correlates overall column efficiency as a function of feed viscosity and relative volatiHty (64). A statistical correlation of efficiency and system variables has been developed from numerous plate efficiency data (65). 

Due to the abrasive character of the CEB together with its high viscosity, spraying of CEB is possible only if a suitable atomiser is applied in combination with an appropriate CEB pun i. Various atomisers and oil pumps were tested for this purpose, after a first selection on basis of the physical properties of the feed (viscosity, density, solids content, moisture, surface tension, etc.), and the required spray characteristics (droplet size and its size distribution, spray angle, spatial distribution, power consumption, etc.). 

FIGURE 7 Impact of twin-fluid atomizer ALR and feed viscosity on dro plet size. Abbreviation ALR. air-to-liquid. 

Table 12-43 shows the variety of process parameters used in practical apphcations of spray drying. The air temperatures are traditionally estabhshed through experiments and test work. The inlet temperatures reflect the heat sensitivity of the different products, and the outlet temperatures the willingness of the products to release moisture. The percent water in feed parameter is an indication of feed viscosity... 

To avoid concentration polarization, an improved mass transfer should be realized in the feed compartment. Determining parameters are feed flow velocity (modified through the hydraulic diameter of the feed cell or the pump characteristics), solute diffusion (changed via the feed temperature), feed viscosity (idem), shape and dimensions of the module (introduction of turbulence promoters, use of pulsating flows to break the boundary layer, increased Reynolds numbers,...). 

Pressure nozzles are usually operated with a feed pressure of 30-200 bar and lead to a certain flow velocity at the orifice of the nozzle. The feed is forced into rotation in a swirl chamber within the nozzle resnlting in a cone-shaped spray at the nozzle orifice. It readily integrates into a spray as it is unstable. An increase in the feed rate leads to a less homogeneous and coarse spray with an increase in the width of the droplet size distribution. The mean size of droplets is indirectly proportional to pressnre up to 690 bar (680 atm) and directly proportional to feed rate and feed viscosity. Working with pressure nozzles results in a particle size diameter between 50 and 500 pm. °... 

It is recommended that feed viscosity is lower than 500 mPas. Higher viscosities may be possible, but only with appropriate nozzle design. 

Pig. 8.15 a Feed solution characterization regarding the impact of Cfeed and Tfced on feed viscosity and b simulation of four nozzles MFP (maximum free passage) SK series SprayDry nozzles from Spraying Systems the core/orifice codes are -80/16, -70/20, -65/21, and -65/17... 

Cfeed is a critical parameter which impacts the process viability and product quality in several manners, viz. process throughput, particle/powder density, or feed viscosity. Economic considerations of the process favor high Cfeed, but concentrations close to the saturation point should be further studied to minimize the risk of product precipitation. Further, the use of high concentrations may lead to highly viscous feeds which may be difficult to atomize (Fig. 8.15a illustrates a typical relationship between feed concentration and temperature with feed viscosity). Tfeed is rarely manipulated to obtain target powder properties. Nevertheless, it may affect solution stability and also influences viscosity and solubility. A strict control of Tfeed is required, namely when operating close to solubility limits. 

The JBGLTS code provides a convenient way to check the operating line method. -Isothermal operation is generated by assigning Kjyj=0, f=0, and and computing results for several feed temperatures. The results are shown in Figure 9 for the reference case, the solution being a feed viscosity of 10.0 cP at a temperature of 30.6 C. 

The two methods give remarkably similar overall results. Variable temperature JBGLTS calculations indicate a somewhat higher c and 4. The power parameter j, which is based on feed viscosity Petroff power consumption, is high for the operating line method since a high inlet temperature has been assumed. 

The second derived by O Connell (Figure 12-22) correlates efficiency with the product of relative volatility times the feed viscosity (at average column temperature). 

Stable, P., Gaukel, V., Schuchmann, H. P. (2015). Influence of feed viscosity on the two-phase flow inside the exit orifice of an effervescent atomizer and on resulting spray characteristics. Food Research International, 77, 55-62. 

Equation (10.2) applies for both steady-state and unsteady-state conditions. The key feature is how the mode of operation controls the magnitude of deposit resistance, Rd- One other point of interest from Eqs. (10.1) and (10.2) is the role of permeate (filtrate) viscosity, nri, which can have a strong influence on production. For example, the effect of temperature on water viscosity would mean at 10°C the flux would only be about 60% of that at 30°C for the same TMP. It is important to note that ti refers to permeate and not feed viscosity, which can be much higher than water, as found in a typical membrane bioreactor. 

New reaction condition to achieve a target increase in conversion The maximum conversion to produce stable visbroken products The maximum reduction of feed viscosity without significantly affecting the fuel stability... 

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