Inside the Dahmes ThermaShear™ Nozzle

A technical look for engineers and operations leaders 

In the first post, we introduced the Dahmes ThermaShear™ Nozzle as a way to do more spray drying in less space, with lower pump pressure and better tolerance for tough feeds. This one is for the people who'll eventually live with the design: process engineers, plant managers, and operations leaders who want to know how it actually works. 

Let's open it up. 

Quick refresher: three ways to atomize 

Most spray dryers use one of three atomization methods. 

High-pressure nozzles. A high-pressure pump forces liquid through a small orifice; a swirl insert adds rotation and shapes the spray. Flexible and widely used, but they need expensive high-pressure pumps and are sensitive to wear and particulates. 

Rotary atomizers. Liquid is fed onto a disc spinning around 20,000 RPM and thrown into the chamber by centrifugal force. Once common in milk dryers, now less favored because of maintenance complexity, limited flexibility, and mechanical risk at those speeds. 

Two-fluid nozzles. Lower-pressure liquid meets compressed air inside the nozzle, and the air provides the shearing force. Usually that air is near room temperature and adds no meaningful heat for drying. 

The ThermaShear Nozzle is closest to a two-fluid nozzle, with one important difference. 

What makes the ThermaShear Nozzle different 

The ThermaShear Nozzle uses three elements: 

• A central liquid passage for your product feed 

• An annular stream of hot compressed air that both atomizes and heats 

• A cooling jacket that keeps the product from cooking in the lance before it sprays 

  
  

In operation, the hot air starts around 500°F and can be pushed toward 1,000°F; systems

built on the same principle have run as high as 2,000°F. That hot, high-velocity air exits the nozzle, shears the product into droplets, and delivers heat right in the spray zone. 

In a standard two-fluid nozzle, the compressed air is just a mechanical tool. In the ThermaShear Nozzle, the air is both a mechanical and a thermal tool. 

The energy balance: temperature vs. airflow 

Drying comes down to transferring enough energy into the liquid to evaporate its water. Two factors drive that energy input: airflow (the mass of air) and air temperature. 

Traditional dryers run moderate temperatures and higher airflows; a high-pressure system might cap its throat temperature around 500°F. The ThermaShear Nozzle inverts that pattern: higher air temperatures (500–1,000°F) and lower airflow for the same evaporation duty. 

Because airflow strongly influences dryer size, that creates two design payoffs: 

• Achieve the same water removal in a smaller chamber, or 

• Get more water removal out of an existing chamber without touching the vessel. 

  
  

On a full-scale dryer at the Dahmes R&D Center, a standard high-pressure nozzle removes about 100 lbs of water per hour. With the ThermaShear Nozzle on that same dryer, we remove at least double that, with no change to the chamber. 

For new projects, that translates directly into smaller chambers, shorter buildings, and lower steel, concrete, and construction costs. 

Pumping: 4,000 psi vs. 200 psi 

Conventional high-pressure systems need large piston pumps running around 4,000 psi. Those pumps are expensive (often around $50,000 even for small dryers), demand real maintenance and spares, and sit on the critical path for production. 

The ThermaShear Nozzle typically runs at about 200 psi liquid pressure. That buys you simpler pumps, often an order of magnitude cheaper (around $5,000 on small systems), with less mechanical stress, easier service, and less specialized spare inventory. 

Orifice size, wear, and particulates 

Because the ThermaShear Nozzle leans on air velocity rather than extreme liquid pressure to atomize, the liquid orifice can be relatively large. That helps in three ways: 

• Less orifice wear. You're not water-jetting the orifice at 4,000 psi. 

• Less clogging. Bone fragments, undissolved solids, and the occasional chunk are less likely to block it. 

• Better with abrasive products. Less erosion than a small high-pressure orifice. 

  
  

For meat slurries, breaker eggs, and other particulate-heavy feeds, that's a real, practical advantage. 

High-viscosity capability and upstream efficiency 

Viscosity is a hard limit in both evaporation and spray drying. Push a product too thick and it won't pump at high pressure or atomize cleanly with a conventional nozzle. 

Take skim milk. In the glass it's about 9% solids. The industry typically evaporates it to 50–55% solids, roughly a custard consistency, before spray drying, which is about the ceiling for high-pressure atomization. With the ThermaShear Nozzle, you can potentially carry that same skim milk to 60–70% solids and still spray dry it. 

Why does that matter? Spray drying is the least efficient way to remove water; evaporators do it far more cheaply. Every point of solids you add upstream is water the dryer never has to handle. That means lower dryer energy use, smaller dryers for the same output, and better process economics. This technology gives you more viscosity headroom, and with it more room to optimize upstream. 

Tradeoffs and engineering considerations 

Like any real solution, the ThermaShear Nozzle comes with tradeoffs worth understanding up front. 

Flexibility. High-pressure systems flex easily: change the swirl and orifice to shift capacity and particle size, and turn down to half or quarter speed. The ThermaShear Nozzle is more locked in. It doesn't offer that range of atomization control or fine particle-size tuning, so it fits best where the duty and product specs are stable and well understood. 

Higher exhaust dew point. By doing more evaporation with less air, the exhaust can leave at the same temperature (say 190°F) but carry a higher dew point, 120–130°F instead of closer to 100°F. That raises the risk of condensation on cold surfaces, which can lead to product buildup, hygiene problems (a petri-dish effect), and caking on filter bags or in ductwork. It's manageable with better insulation, careful air-handling design, and conditioned dilution air, the same tools already used to protect fabric filters on permeate dryers. 

Product positioning. The ThermaShear Nozzle is less suited to high-value, highly engineered powders that need agglomeration, precise particle structure, and wide operating flexibility. It's at its best delivering dependable, repeatable, high-throughput drying of utility or lower-value products. 

The proof is in the powder 

Before anything gets bolted down in your plant, let's prove it in ours: 

• Run your product through the ThermaShear Nozzle at the Dahmes R&D Center 

• Measure capacity, dew points, and exhaust behavior 

• Check powder characteristics and downstream handling 

• Use that data to design a system around your real operating conditions 

  
  

In the next post, we'll leave the equations behind and look at where the ThermaShear Nozzle fits best in practice: breaker eggs, permeate, meat, wastewater, and more. 

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