New Jet Pump Technology for Wood Drying Kilns

Kilns for drying wood effectively draw moisture from lumber, allowing for better wood quality. Standard kilns typically use hydraulic systems, which sometimes lead to reduced efficiency and fluctuations in temperature and pressure. However, new regulated water jet pump technology is available for drying wood, enhancing kiln control while reducing energy and investment costs. Learn more about drying kilns, the benefits of jet pump technology in wood drying, and how Baelz North America can help.

How Wood Drying Kilns Work

Green lumber holds a substantial amount of moisture, which can lead to warping, buckling, and related deformations. Carefully lowering the moisture content in wood within a controlled environment helps produce strong, straight lumber. With the traditional kiln drying process, lumber transfers from lathes to pre-heated, thermally insulated wood drying ovens.

These ventilated enclosures allow operators to control temperature, airflow, and humidity. Hot water, steam, or fuel oil typically generate the heat for this process, and users can set the internal temperature to between 40° and 90° C by modifying control valves on the register. The optimal temperature for the oven depends on the wood type, and that heat triggers moisture evaporation within the wood. The rate at which the evaporation occurs is based on the particular oven, the type of wood, and the humidity and temperature levels in the kiln.

Issues With Hydraulic Systems

Traditional wood drying kilns utilize hydraulic systems, which achieve temperature control through a return mixture from the circulation pump and a three-way valve. During maintenance, these systems often experience issues with the thermal supply. When this occurs, its effects on system efficiency grow exponentially with the size and number of ovens.

When using multiple drying ovens set at the maximum energy requirements, this strains the hydraulic system after the first few days of drying. Cost is another issue. Drying operations often choose not to utilize flow limiters or differential pressure controllers on corresponding ovens to save on operational costs. Without these components, the other drying ovens receive an insufficient amount of supply flow from the high-consumption mixing pumps.

Fluctuations in temperature and differential pressures create undesirable conditions inside affected kilns. The differential pressure fluctuations can cover a range of 3 to 35 mWS or more. Providing reduced control over the conditions within the kiln, fluctuations negatively impact efficiency, raise costs and energy consumption, and extend drying time. All of these problems in hydraulic systems can result in lumber of lesser quality.

How Jet Pump Technology Works in Wood Drying Kilns

Jet pumps are not new to heating systems, and the three-way injector valve fitting has been available for decades. However, when combining the two for a regulated jet pump, kiln operators benefit from improved ventilation and heating technology. Ultimately, rather than depending upon a single valve, burner, or pump, jet pump systems with three-way injector valves form an efficient chain from heat generation to heat consumers.

Jet pumps follow Bernoulli’s equation, which is that adding dynamic pressure to static pressure equals the total pressure. The equation evaluates constant fluid flow in relation to pressure and fluid speed. When a jet pump uses a narrower driving nozzle, the static pressure of flowing fluid is less than that of the adjacent motionless fluid, thereby creating a suction effect that increases the speed of fluid flow. Operators can use a spindle to adjust the nozzle’s cross-section, modifying the conveyed driving flow. Higher flow rates reduce the pressure prior to the driving nozzle to draw in a portion of the return fluid.

Advantages of Jet Pumps for Wood Drying Kilns

These pumps offer numerous benefits for wood drying kiln operations, including:

  • Fewer components for fewer points of potential failure. Jet pumps eliminate the need for certain components, such as mixing pumps, pump pressure gauges, compensators, differential pressure controllers, circulation pump control systems and electrical cables, flow limiters, and shut-off, non-return, and heating control valves. They utilize a single frequency-controlled main pump for higher efficiency.
  • Improved performance and consistency. Jet pumps help regulate fluctuating pressures and thermal conditions. They also lower peaks in the drying process given the absence of external influences. These systems can process all actuating signals that would normally be available for efficient operation. Corresponding operation/faults data points to override the control technology, however, aren’t necessary.
  • Safer operation. With their optimized designs and ability to reliably stabilize temperature and pressure, jet pump systems improve overall safety across kiln operations.
  • Reduced costs. With fewer, non-rotating components and connections as well as increased efficiency rates in the jet pump, this equipment can reduce maintenance and energy costs. Also, briefly after completing kiln modifications with jet pump technology, operations amortize the equipment costs.

Learn More With Baelz NA

At Baelz NA, our process heating and cooling solutions help lower costs while enabling consistent, reliable, and easily controlled conditions in equipment like wood drying kilns. We manufacture and supply quality two- and three-way control valves as well as controllers, controllable ejectors, actuators, engineered systems, and more to enhance efficiency, lower energy consumption, and optimize operations.

Contact us to learn more about our products, or request a quote for incorporating our high-performance components into your kiln and jet pump equipment.

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