Mixer Performance Data from Pilot Plants.

Abstract

Figure 1. Water-Jacketed Vessel Refitted for Gas-Liquid Contacting with a Disperser MIXER PERFORMANCE DATA MIXING is an operation that is utilized at some point in almost all chemical processes.Yet there is no well defined or universally accepted measure of mixing (5). The application of mechanical mixing devices is still an art and will remain so until sufficient performance data are accumulated to permit a clear understanding of the relations between the chemical reaction, the physical properties of the materials, the impeller, and the geometry of the system. The intent of this paper is to point out how mixing affects chemical reactions and, in view of present knowledge, what specific data should be obtained on pilot plant scale to give the most useful information for engineering design of unit process mixing equipment.Pilot plant equipment is usually smaller than that used for manufacturing; it can also be modified so that control variables can be studied, and more temperature, pressure, and other physical measurements can be taken than would be practical in large scale operations. From pilot plant operations it should be possible to evaluate four important considerations: (1) the feasibility of the process with respect to yield of principal product; (2) the proper conditions of temperature, pressure, concentrations, etc., for optimum yield; (3) the operational costs in terms of heat, power, and life of equipment; and (4) the possibilities for scaling up the equipment for larger installations. Equilibrium and reaction rate data form the bases for evaluating all the considerations mentioned. Equilibrium data will enable one to estimate maximum yields and, together with rate data, will allow estimation of equipment size and operational costs. The evaluation of mixer performance in terms of the particular chemical reaction involved will then be of immediate usefulness.

Effect of agitation on selectivity in the hydrogenation of soybean oil

“…Under these conditions a high degree of selectivity with regard to removal of linoleic and linolenic acids may be obtained. The conclusion that batch size has a larger effect than agitator speed in determining the course of the reaction emphasizes the importance of the relationship between the physical dimensions of the system and the manner in which agitation influences the chemical changes involved (14). Although this observation justifies the decision that was made to carry out the experiments in the pilot plant, it also implies that the situation may even be changed again when hydrogenations are carried out on a commercial scale.…”

“…If, as has been suggested previously, the use of the dispersion agitator leads to better dispersion of the gas and greater interfacial area for the gas-oil mixture, it is then evident that selective removal of linoleic and linolenic acids is better accomplished by providing for intimate mixtures of gas and oil than by attempting to obtain better agitation for the catalyst in the oil. If, in contrast, a high speed of agitation provides for a high rate of interchange of reactants at the catalyst surface, an increased interchange does not appreciably affect the relative rates of reaction of the various component acids but within certain limits may affect the rate of hydrogen uptake of the mixture (10,14).…”

“…The results of preliminary experiments in the laboratory were promising, but the decision to carry out more complete experiments in the pilot plant was made for two other reasons. First, physical dimensions were believed to exert a significant influence on the manner in which various other factors affect the course of the reaction (14). Thus study of hydrogenations conducted in the pilot plant should furnish more valid estimates of the effect of agitation than experiments on a smaller scale.…”

Hydrogenation and Hydrogenolysis

“…In the United States there appears to be a trend toward the use of simpler hydrogenation equipment (17,19). The development of special turbine-type agitators has eliminated need for complicated circulating systems for oil and hydrogen and permits the use of less complicated and expensive auxiliary equipment (17,19,77,184,165,211,280). Commercial hydrogenators have a capacity of 5 to 20 tons of oil per batch, are usually made from carbon steel, and can withstand 100 to 150 pounds' pressure and full vacuum.…”

Strahlenkonservierung anstelle von Zusatzstoffen

“…Dehydratation vor allem zur Beseitigung der Restfeuchtigkeit bereits vorgetrockneter Produkte [22], wobei eine Trocknung ohne Hartung der aul3eren Schichten moglich ist. In Verbindung mit der Vakuumtrocknung bedeutet die Anwendung von Hochfrequenzenergie eine erhebliche Zeiteinsparung [23], das gleiche gilt auch fur die Sublimationsgeschwindigkeit bei der Gefriertrocknung [24].…”