Direct steaming

The Vepex process developed in Hungary (Table 9) involves disintegration of plant materials followed by double screw pressing to maximize juice production. Green chloroplastic protein is removed by direct steam-injection heat treatment at 82°C with the addition of flocculents and centrifugation. The white protein fraction is separated from the chlorophyU-free process juice by direct steam injection at 80°C, followed by centrifugation and drying (94). 

The critical parameters of steam sterilization are temperature, time, air elimination, steam quaUty, and the absence of superheating. Temperature and time are interrelated, as shown in equation 8. The success of steam sterilization is dependent on direct steam contact which can be prevented by the presence of air in the chamber. The abiUty of steam to heat a surface to a given temperature is considerably reduced by the presence of air. Air elimination, therefore, is regarded as an absolute parameter. If the required amount of air has not been eliminated from the chamber and the load, no combination of time and temperature results in complete sterilization. 

Dutt, S. (1996). Safe Design of Direct Steam Injection Heaters. 5th World Congress of Chemical Engineering, July 14-18, 1996, San Diego, CA, Paper 52c. New York American Institute of Chemical Engineers. 

Ofen-trocknung, /. kiln (or oven or stove) drying. -tlir, -tiire, /. door (esp., the fire door) of a furnace, oven, kiln or stove (Ceram.) wicket, -verkokung, /. coking in ovens, -ziegcl, m. fire brick stove tile, -zug, m. furnace (or oven or kiln) draft, offen, a. open (of sound) hollow clear, clever, frank. — offener Dampf, direct steam, live steam. 

Direct steam piston direct connected to liquid piston or plunger through piston rod. 

Ellerbee [127, 128] provides an excellent summary of steam distillation basics. The theory of direct steam distillation evolves around the partial pressures of the immiscible organics/petroleum/petroleum component and the presence of direct open steam in the system. The system may consist of the organic immiscible plus steam (vapor and/or liquid). Each hquid exerts its otvn vapor pressure independent of the other. Thus, the total pressure of the system is the sum of the individual vapor pressures of the two liquids (assuming the liquids do not dissolve in each other). An important use of this approach is to separate a volatile organic from non-organic impurities. 

This system requires direct steam injection into the still with the liquid, all the steam leaves overhead with the boiled-up vapors (no internal condensation) in a steady-state operation, and system at its dew point. Steam is assumed immiscible with the organics. Steam distillation is usually applied in systems of high boiling organics, or heat sensitive materials which require separation at vacuum conditions. 

Figure 10-163. Constant flow direct steam heater (variable flow also available.) (Used by permission Cat. CF-5924 P. Pick " Heaters, Inc.)...

Figure 10-164. Direct steam heating of liquids with internal temperature control using variable orifice steam nozzle. (Used by permission Bui. H 150. Hydro-Thermal Corp.)...

Pick, A. E., Consider Direct Steam Injection for Heating Liquids, Chem. Eng, p. 87, June 28, (1982). 

Empty vessel, sterilisation of vessel and piping using direct steam injection... 

Traps should be fitted to steam heated tracing lines, rather than allowing them to blow to the atmosphere (as is common), to avoid a direct steam loss. 

The use of direct steam injection into air is a common method of increasing humidity levels for both commercial and industrial applications. The process kills most types of bacteria and similar organisms that may contribute to fouling, health, or other indoor air quality (IAQ) problems. Where amines are present in the steam, however, even small concentrations can be detected by their odor and may be objectionable, even though they may be well under guidelines for concentrations in air. 

In certain direct steam-contact process applications (such as in food and beverage processing or pharmaceutical preparations) the use of amine-based products in steam and condensate systems is subject to legal restrictions. Also, the use of ammonia or amines may be dependent on the materials of construction employed or technical limitations (such as the risk of copper alloy corrosion). 

Phase changes can go in either direction Steam condenses upon cooling, and liquid water freezes at low temperature. Each of these is exothermic because each is the reverse of an endothermic phase change. That is, heat is released as a gas condenses to a liquid and as a liquid freezes to a solid. To make ice cubes, for instance, water... 

Figure 11.17 Substitute some (or all) of the reboiling with direct steam injection and introduce intermediate condensation.

Recrystallizer A process for reciystallizing sodium chloride from brine. Rock salt is dissolved in brine heated with direct steam. The solution is then partially evaporated under reduced pressure. Invented in 1945 by C. M. Hopper and R. B. Richards at the International Salt Company, Scranton, PA. See also Alberger. 

When stepping off the theoretical stages, the bottom step should start at y = 0, x = xw. In this way, the use of direct steam, although eliminating the still, dilutes the bottom material, and so increases the number of stages required in the lower part of the column. 

---