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Benefits of Automating Shear in Starch Cooking with Hydro-Thermal Jetcooker™ Autopilot


The Hydro-Thermal Jetcooker™ is a critical component and the first step of the liquefaction process. A pump feeds into the Jetcooker, where it heats thoroughly, uniformly, and optimally. The Autopilot is an additional component to the Jetcooker that automatically, without local operator intervention, adjusts the product flow path as process conditions change to maintain a constant pressure drop across the unit. This results in optimized shear, mixing characteristics, and more effective starch conversion.

Maintaining a constant pressure drop across the Jetcooker will optimize shear. Adjustments can be made to keep the optimal pressure drop during operation, even as process conditions change. This is done by adjusting the gap between the combining tube (CT) and nozzle (see illustration 1). As the gap is widened or opened, the pressure drop is decreased (lower shear). As the gap is narrowed or closed, the pressure drop is increased (higher shear).

Manually adjusting the gap can be done by turning the drive nut, which rotates the drive shaft, moving the combining tube stud, and CT laterally.

 illustration 1 01


Maintain constant pressure with Automation and the Autopilot.

The Autopilot can be added to the Jetcooker to automatically adjust the combining tube's (CT) position to maintain the desired pressure drop.

The control panel receives signals representing differential pressure setpoints and signals from pressure transmitters in the slurry inlet and discharge. Compared to the target setpoints and signals, pressure measurements are sent to the pneumatic package to adjust the CT position.

From a digital control system (DCS) or another control package, the Autopilot receives analog 4-20mA signals representing actual differential pressure and the differential pressure setpoint. It then automatically adjusts the CT's position, as needed, to maintain a constant product pressure drop. The outputs to the DCS are the measured pressure drop and the CT position.


Why is Optimum Position Important?

If the CT and nozzle gap is too large, there is low shear and low-pressure drop. This results in an incomplete starch conversion, which is a loss of efficiency.

If the gap is too small, there is high shear and excessive pressure drop. The result is excessive wear to the internals of the Jetcooker and increased pumping cost (see illustration 2).

Illustration 2 01 


Theoretically, by optimizing the CT position, the plant could reach the optimal differential pressure. An optimal CT position can be established by testing for the minimum pressure drop, which produces optimal starch hydrolysis. Many factors will come into play, such as incoming viscosity, flow rate, CT diameter, size of the Jetcooker, temperature, and slurry makeup conditions.



When producing starch with the Jetcooker, it's just that simple. If the CT and nozzle gap is too big, the starch stream is too thick for the steam to penetrate (penetration of the starch is only 50-75%). When the gap is narrowed, the velocity is increased to a point where the starch stream is thinner, and therefore the steam can penetrate 100%. This allows for an efficient and instantaneous way of mixing steam and the starch molecules resulting in instant hydrolysis and complete starch conversion with the Jetcooker. 


Click here to learn more about our application experience in starch cooking

Contact us at 800-952-0121 or This email address is being protected from spambots. You need JavaScript enabled to view it. today to get a free evaluation from our application experts. We can provide tips on how to optimize your heating system(s).




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Hydro-Thermal is the global leader in the development and manufacturing of Hydroheaters. Through our vast global channel partners, we support hydro heating in six continents and all industrialized areas. We create heating systems for a variety of industries including: pulp, paper, chemical, ethanol, food & beverage, metal, & more!

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