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Woodyard Best Practices: Increasing Wood Yield

How to Choose the Right Equipment to Ensure Quality Chip Processing

Two key factors are particularly important to drive the success of chip thickness screening operations: the right equipment and proper maintenance of this equipment. TerraSource Global partners with our customers to customize their chip thickness screening system to meet specific product needs and expectations, delivered at the highest levels of performance, durability and quality in the market.

And the support does not stop there. Throughout the lifetime of the machine, our exceptional team of engineers, field service technicians, and customer service professionals works to ensure your system continues to run at its peak capacity by setting up regular maintenance visits and ensuring new OEM wear-parts are available when you need them most.

Importance of Chip Thickness Screening

Significant yield increase can be attained by pulping only properly sized chips. While undersized chips pulp quickly, they negatively impact yield. Likewise, oversized chips produce a high amount of rejects. Target chip thickness for most kraft pulp mills is between 2-8 mm.

Additional benefits to pulping only properly sized chips include: lower alkali consumption, more uniform pulp, and lower shives. For these reasons, kraft pulp mills must include a properly selected and well-maintained chip thickness screening system at the early stages of the pulp sizing process.

Key Screening Principles: Precise open area is key to quality chip screening

DynaGage Bar Screen

The two most critical components of any screen are its perforation size and the total open area between screen slots. The perforation size is the size and type of an individual opening, which combine to limit what will pass through the screen. In thickness screens, the perforation is called “IFO” (interfacial opening) and is a slot opening through which chips can pass. The IFO should be slightly smaller than the desired maximum acceptable chip thickness.

Open area is the total area on the screen that material can pass through. In a Dynagage bar screen, the open area is the summation of all slot areas. A screen’s capacity is limited by its open area. As the open area increases, so does the screen’s maximum capacity. Properly sized thickness screens have the correct IFO to remove overthick chips and enough open area for the woodyard’s maximum capacity.

Raderwave Fines Screen

Jeffrey Rader DynaGage bar screens are ideal thickness screens because they have the largest open area of any thickness screen on the market. As any thickness screen wears, the IFO increases and so does the size of accepted chips. In a DynaGage bar screen, this process can take many years. Screen feed, accepts, and rejects samples should be regularly tested to assess screening quality. The cost of pulping a high level of overthick chips significantly outweighs the cost of replacing screen wear surfaces. Chip thickness quality should be a determining factor for changing screen wear surfaces.

Machines for Overthick Chip Processing

Jeffrey Rader Chip-Sizer

After overthick chips have been separated, they need to be re-sized before going to the digester. TerraSource’s Jeffrey Rader brand offers three machines to process overs: Chip Slicers, Chip Conditioners, and Chip-Sizers. Chip Sizers are quickly becoming the industry standard for overthick processing because of their high recovery rate, low capital cost and easy maintenance.

Mills that are disposing of overs or sending them to the boiler have an opportunity to increase their wood yield by processing them with a Chip Sizer. For these machines, payback periods have been less than one year and in some cases as short as 3-6 months, even when replacing existing equipment. Interested customers can evaluate Chip Sizers at TerraSource’s Testing and Demonstration Center in Duncan, South Carolina.

DynaYeld II Chip Conditioner

Conclusion

Key takeaways and best practices for wood yards looking to increase yield:

Pulping only properly sized chips can increase digester yield ~2%.
Proper screen type and regular maintenance will improve digester yield.
As screens wear, large chips will be accepted.
Chip thickness quality should be a determining factor for changing screen wear surfaces.
If overthick chips are sent to the boiler or removed from the process, pulping plants should consider processing them with a Chip Sizer to increase wood yield.

If you are looking for ways to enhance your current woodyard operational productivity or performance, feel free to reach out to me directly or contact us through the website at https://terrasource.com/contact-us-2/. We can set up a meeting assess your specific application needs through a custom ROI assessment .

By : Caldwell Reed

Strategic Account Manager – TerraSource Global

Caldwell.reed@terrasource.com