Pulse atomization spray drying differs from conventional spray drying in atomization method, residence time and exhaust oxygen content, and those differences are measurable in the powders it produces. This page describes the practical performance benefits and the limitations of pulse drying.

    Successful Materials

    We have experience with over 200 different materials in our dryer, and have obtained very favorable results on minerals, specialty chemicals, foods and nutraceuticals.

    For foods and nutraceuticals, our powders are generally superior in:

    • flavor
    • texture
    • pigmentation
    • protein viability
    • surface characteristics
    • flowability
    • reconstitution properties
    • particle size distribution

    The low degradation in the pulse drying process contributes to better taste and color of food products. This also produces similar benefits in other sensitive products.

    There are four reasons for this:

    1. The liquid is evaporated very rapidly by using high temperatures for a very short time. The heat transfer in the atomizing zone of the dryer is very high, and evaporative cooling protects the feed material. We have dried egg whites and other delicate proteins at inlet temperatures of 1000 °F with measurably lower degradation than conventional spray drying, and with functional properties — including foaming and gelling — preserved. Comparative particle size distributions, SEM images and DSC data are reported in US Patent 9,809,619 B2, “Pulse combustion drying of proteins” (Rehkopf and Mirko, granted November 7, 2017), and independently in Wu, Z., Yue, L., Li, Z. et al., “Pulse Combustion Spray Drying of Egg White: Energy Efficiency and Product Quality,” Food and Bioprocess Technology 8, 148–157 (2015), available in our Download Center.
    2. No mechanical shear is applied to the liquid. The PCS Dryer does not use high-pressure pumps, nozzles or rotary disks. Nothing in the feed line or at the atomizer restricts the feed path, so there is no feed pressure specification — whatever pressure exists comes only from the height of the dryer and the viscosity of the feed. A peristaltic pump delivers feed to the atomizer, but plays no part in atomization. Atomization is gas dynamic: it occurs in the exhaust jet of the pulse atomization burner, where the velocity differential between the process air (approximately 250 mph) and the liquid drop (approximately 1 metre per minute) breaks the drop apart.
    3. The pulse dryer is capable of very low dryer exhaust temperatures, which, when combined with very rapid drying, produces freeze-dry quality powders.
    4. The high-velocity combustor exhaust that comes into direct contact with the liquid contains less oxygen than a conventional spray dryer’s heated air.

    For minerals, our powders are generally superior to spray dried powders in:

    • particle surface characteristics
    • mean particle size
    • particle size distribution
    • flowability

    Concentration of Feeds Yields Lower Costs

    For most materials currently spray dried, the PCS Dryer can handle the same feed in a higher concentration of solids. This yields higher powder production rates and lower processing costs per finished pound. It also means that a smaller, less-expensive pulse dryer can handle the same throughput as a larger, more-expensive conventional spray dryer. In one recent dryer sale, we were able to cut the number of dryers required in half.

    Special Materials

    Due to our unique atomization method and very large operating envelope, we have made successful powders with many difficult or ‘un-dryable’ materials.

    Problem Materials

    While we are adding to our list of successful tests on often a weekly basis, we’ve also discovered a few materials that do not perform well in our pulse atomization spray dryer.

    These are products that have:

    • High elastomeric viscosity,
    • High levels of low-melting-point sugars, such as orange juice, or
    • High levels of unencapsulated fat.

    Demonstrated Expertise

    Pulse Drying Systems has conducted a series of drying product development trials on algae produced for biofuel (https://en.wikipedia.org/wiki/Algae_fuel) and for food and nutraceutical use. The trials were conducted for one of the leading algal companies, and covered several different end uses.

    The pulse dryer produces a fine, free-flowing powder with minimal degradation, and easily handles high-viscosity concentrations of algae. The dryer handles algal slurries with intact cell walls as well as those that have been ruptured to release the oil.

    Other methods of drying algal slurries are freeze drying, spray drying, and drum drying. Each involves a trade-off between product quality, throughput and cost. Freeze drying, for instance, makes a low-degradation product, but is an expensive batch process that often requires post-drying milling to make a fine powder. Spray drying is efficient, but can rupture intact cells in its high-pressure atomization process, and generally imparts unacceptable degradation due to time/temperature considerations. Drum drying exposes the algal slurry to long periods of elevated temperatures, and produces a flake that must be milled to obtain a fine powder. By comparison, the pulse dryer makes a fine powder like the spray dryer, and, due to very rapid drying, also delivers the low-degradation characteristic of freeze drying. In short, pulse drying delivers a fine, free-flowing algal powder at continuous-process throughput, without the batch cycle and post-drying milling that freeze drying requires.

    Pulse Drying Systems is eager to demonstrate its technology for customers producing algal slurries that must be dried for stability, end use, extraction, or other processing. A summary of our development and commercialization processes can be found on our Getting Started page.

    The best way to start evaluating pulse drying is to send an email to James A. Rehkopf, Pulse’s president, at jrehkopf@pulsedry.com. We look forward to working with you.

    For more information contact:
    James A. Rehkopf, President
    (415) 726-3536

    PDS built and successfully demonstrated “prilling” operations by making minor changes to its standard pulse combustion spray dryer. The new system, created through product development processes, uses all of the existing “spray dryer” elements, and adds some special equipment for feed preparation and transportation.

    Thus, customers can order from PDS a Pulse Atomization Spray Dryer, a Pulse Priller, or a “Combination Unit” that can switch from drying to prilling at the push of a button. The Combination Unit costs only about 25% more than either of the separate units.

    PDS also demonstrated previously unseen small mean particle sizes for prills, allowing customers to develop new products around the tiny prills.

    For more information, contact:
    James A. Rehkopf at jrehkopf@pulsedry.com or (415) 726-3536.

    Pulse Drying Systems has extensive experience and success in drying lithium slurries for today’s high-tech batteries.  In particular, PDS has produced over 120 metric tons of lithium dihydrogen phosphate powder for one manufacturer, and has sold two dryers for lithium battery powder production to Altair Nanotechnologies in Reno, Nevada.

    In addition to practical experience, PDS has discovered some unique characteristics through product development testing and trials that are only available through pulse drying, and has applied for a patent covering these advantages.

    The success in lithium slurries is an outgrowth of the generally excellent results from the pulse-drying of minerals and metals.  The PDS dryer is highly efficient, delivers powders with uniform surface characteristics and tight particle size distributions, and is impervious to abrasion and chemical attack.  This resistance to chemical attack and abrasion is due to the pulse dryer’s unique low-pressure “gas-dynamic” atomization method that completely avoids high-pressure pumps, spray nozzles, and rotary disks.  Maintenance costs, therefore, are extremely low.  An overview of how the dryer works can be seen on our Pulse Technology page.

    Pulse Drying Systems is eager to demonstrate its technology for customers who are manufacturing battery materials.  A summary of our demonstration, development and commercialization processes can be found on our Getting Started page.

    The best way to start evaluating pulse drying is to send an email to James A. Rehkopf, Pulse’s President, at jrehkopf@pulsedry.com.  We look forward to working with you.

    For more information contact:
    James A. Rehkopf, President
    (415) 726-3536

    In response to a customer request, Pulse Drying Systems (PDS) developed and prototyped an “indirectly-heated” version of its Pulse Atomization Dryer. Instead of burning fuel in a combustion chamber, this new dryer employs either an electric heating element or a heat exchanger to heat the drying gas. Thus, the drying gas can be pure air (or CO2, or N2), with no combustion byproducts, and no potential for flame contact with the products to be dried.

    This new dryer model allows PDS to:

    • Dry products with extreme purity requirements,
    • Dry any product that is sensitive to combustion byproducts,
    • Meet regulatory requirements that may prohibit “direct contact” heating of the drying air, and
    • Handle any feed material containing flammable solvents.

    PDS prototyped the new dryer design by converting its existing Pilot Dryer to use air heated by an electric coil. (A conventional heat exchanger could also be used.) The prototype worked perfectly, and the new dryer retained all the other great attributes of pulse drying – gas-dynamic atomization and rapid drying, minimal product degradation, consistent particle size, and high efficiency, all controlled by PDS’s advanced dryer control system.

    Based on the excellent Pilot Dryer results, PDS was fortunate to receive an order from Orbite Aluminae, Inc. for the first Indirect Pulse Dryer. Orbite will use the new Pulse Dryer in the production of High Purity (.9999) Alumina. The Dryer is almost complete, with commissioning expected in January 2013.

    The company’s Indirect Pulse Dryer Prototype is available for Pilot Trials of customer products.

    For more information contact:
    James A. Rehkopf, President
    (415) 726-3536
    jrehkopf@pulsedry.com

    Pulse Drying Systems has conducted a series of drying trials on cyclodextrins (https://en.wikipedia.org/wiki/Cyclodextrin) and cyclodextrin complexes, and has proven that pulse technology produces a dry powder that is far better than what can be produced in a conventional spray dryer, and creates a powder quality that rivals that produced by freeze drying.  (Freeze drying is a capital-intensive “batch” process which is much more expensive than pulse drying.  Pulse drying, like spray drying, is a continuous process requiring a minimum of labor.)

    The drying trials were so successful that we have prepared a patent application with respect to the pulse drying of cyclodextrins and cyclodextrin complexes.

    As for all other products, Pulse Drying Systems is prepared to conduct product development activities for customers interested in cyclodextrins and cyclodextrin complexes.  Our first such development round was for NanoSonic Products, Inc. A summary of our development and commercialization processes can be found on our Getting Started page.

    The best way to get started on this process is to send an email to James A. Rehkopf, Pulse’s President, at jrehkopf@pulsedry.com.  We look forward to working with you.

    For more information contact:
    James A. Rehkopf, President
    (415) 726-3536

    Pulse Drying Systems (PDS) has been developing expertise in drying certain components of Hydraulic Fracturing Fluid that need to be delivered in a dry form to the oil and natural gas fields. These additives are designed to enhance the output and longevity of each well by performing specific functions in the well.

    PDS was contacted by companies working in this fast-growing market. They were looking for quick development of the drying parameters, toll-drying to enable instant marketplace entry, and fast delivery of modular dryers to remote sites. PDS provides all three.

    The PDS pulse atomization dryer is perfect for this application, because it is efficient, highly resistant to abrasion and corrosion, and able to handle a wide variety of liquid inputs, including those with solid particles – called ‘proppants.’

    The PDS Dryer is also perfect for remote locations, because it runs on a variety of fuels, is extremely reliable, and requires almost no maintenance.

    PDS welcomes customer inquiries, and is ready to conduct Pilot Trials on customer products on short notice.

    For more information contact:
    James A. Rehkopf, President
    (415) 726-3536
    jrehkopf@pulsedry.com

    In response to requests from companies working in the industry, Pulse Drying Systems (PDS) has developed and implemented a new high-temperature drying system.

    Certain processes require elevated temperatures in the drying chamber while spray drying, and these are very hard to obtain in conventional spray drying.

    PDS’s pulse dryers can produce combustion air at up to 2,000 degrees F, at very high volume, which can heat up a drying chamber quickly, and allow “normal” spray drying functions at dryer outlet temperatures as high as 600F.

    PDS welcomes customer inquiries, and is ready to conduct Pilot Trials on customer products on short notice.

    For more information contact:
    James A. Rehkopf, President
    (415) 726-3536
    jrehkopf@pulsedry.com

    Pulse Drying Systems (PDS) has recently developed, fabricated, and implemented a new Fluid Bed section for use in its Pilot Dryer.

    The Fluid Bed is mounted at the bottom center of the spray dry chamber, and powder produced in the upper section of the drying chamber falls into the bed by gravity as the drying air is extracted from the top of the dryer.

    The Fluid Bed is fitted with an under-bed air inlet system. The pressure of the air is controllable (thus influencing bed height and agitation), and the temperature of the air can be changed to either heat or cool the powder.

    The Fluid Bed gives PDS the ability to impart more residence time, and also to introduce other elements such as flow agents or agglomeration aids.

    PDS welcomes customer inquiries, and is looking for additional customer trial opportunities.

    For more information contact:
    James A. Rehkopf, President
    (415) 726-3536
    jrehkopf@pulsedry.com

    Pulse Drying Systems (PDS) has purchased a homogenizer for use in preparing emulsions and other products containing fats (such as whole milk) for pulse drying. The homogenizer’s output will match the input of the PDS Pilot Dryer.

    The PDS Pulse Dryer has always done a great job on emulsions and other products containing lipids, but will now be able to turn out even better powders. Pulse drying tends to preserve lipids to a far greater extent than conventional spray drying.

    PDS welcomes customer inquiries about lipid-containing products, and looks forward to conducting Pilot Trials for customers.

    For more information contact:
    James A. Rehkopf, President
    (415) 726-3536
    jrehkopf@pulsedry.com

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