Pulse dryer

Because the atomization in a pulse dryer is achieved with little mechanical shear, the encapsulating sheath is largely unaffected, leaving the core intact. As described in the following, a measure for encapsulate integrity is free core —the lower, the better. Pulsed drying can produce low levels of free core. 

The equipment used in a pulse dryer is the same as that used in a conventional taU-form, pressure-... 

Pulse dryers in operation in industry range in evaporative capacity between 30 pounds of water per hour and 2000 pounds per hour. 

Material Conditions Spray Dryer Pulse Dryer... 

Figure 14.10 Basic configuration of the Pulse-Dryer. (Courtesy of Pulse Drying Systems, Inc., Portland, Oregon.)...

Table 14.4 Characteristics of Pulse-Dryer for Industrial Plating Waste...

Table 14.5 Characteristics of Pulse Dryer for Sewage Sludge Processing...

Dryer characteristics PCS Pulse Dryer Spray dryer (nozzle Spray dryer (disk... 

The average energy consumption of the Pulse-Dryer has been claimed to be about 3370 kj kg of water evaporated, but it may be as low as 2950 kj kg for finely dispersed materials with mostly surface water, such as kaolin clay, metal oxides or calcium carbonate (Duncan, 2012). Because the residence time in the... 

Convection heat transfer is dependent largely on the relative velocity between the warm gas and the drying surface. Interest in pulse combustion heat sources anticipates that high frequency reversals of gas flow direction relative to wet material in dispersed-particle dryers can maintain higher gas velocities around the particles for longer periods than possible ia simple cocurrent dryers. This technique is thus expected to enhance heat- and mass-transfer performance. This is apart from the concept that mechanical stresses iaduced ia material by rapid directional reversals of gas flow promote particle deagglomeration, dispersion, and Hquid stream breakup iato fine droplets. Commercial appHcations are needed to confirm the economic value of pulse combustion for drying. 

The Cello pulse combustion burner system is an ex sitn technology for the enhancement of combustion devices. Cello pulse combustion can be incorporated into the constrnction of most new combustion devices or can be retrofit to most existing incinerators, boilers, and dryers. The system can be used to treat any material typically treated in a conventional incinerator, including soils, sludges, medical wastes, and liquids contaminated with volatile organic compounds (VOCs) or semivolatile organic componnds (SVOCs). The CeUo system has been installed in commercial systems and is commercially available. 

Noise Noise analysis and abatement is a very speciahzed area. Generally, the issue with dryers is associated with the fans, particularly for systems requiring fans that develop very high pressures. Noise is a very big issue that needs to be addressed with pulse combustion dryers and can be an issue with very large dryers such as rotary dryers and kilns. 

Fig. 7.82 SEM photographs of some typical product from dryers with PCS pulse combustion atomizers (courtesy Pulse Combustion Systems, San Rafael, CA, USA), (a) non-fat dry milk, 200x (b) non-fat dry milk, 2,000x (c) sodium alkene sulfonate, 350x (d) sodium alkene sulfonate, 2,000x (e) soy sauce, 2,000x (f) silica alumina,...

Stream composition, humidity, and temperature Paper mills, brownstock washer ventilation stream Wood processing plants, strandboard press ventilation stream Wood processing plants, strandboard dryer ventilation stream Range of parameters, tested in pulsed corona plasma treatment... 

FIGURE 23.2 A demonstration pulse combustion dryer installed in the Arizonaplant of PCS. 

Results from microcapsule spray drying runs on PCS pulsed combustion dryer will serve as the basis for this discussion. The rationale behind showing the different data sets is simply to illustrate the many variables to consider while drying microcapsule slurries with the pulsed combustion dryer technology. These data sets also show that different products tend to behave differently. The encapsulated material presented in this chapter is primarily fragrance based. 

The data, chart, and discussion points presented in this application section are based on several trials conducted at the PCS plant in Payson, AZ, ntilizing their pulsed combustion spray dryer technology. The trials were not specifically designed for this documentation, so some definitive protocols cannot be provided. However, we investigated how several parameters such as contact and exit temperatures (components of the dryer operating envelope), flow aid level, and percentage of feed solids affected capsule integrity as measured analytically and presented as % free core. 

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