Wood Chip Tunnel

Wood chip tunnels are used to convey chips from storage piles to the pulping area using conveyor systems. During rain or snowmelt, water collects in tunnel sumps, carrying fine wood particles, bark, and debris that must be pumped out to prevent flooding and maintain safe operation.

Challenges:
Tunnel sumps accumulate fibrous, stringy material that entangles impellers and reduces flow. The mixture of organic solids and debris makes clogging common, while restricted access in tunnels complicates maintenance. Pumps must handle large solids, operate reliably in confined spaces, and resist wear from wood fiber abrasion.

Solution:
Hevvy/Toyo’s agitator-equipped submersible pumps are ideal for fibrous, debris-laden tunnel sumps. Their open impeller and large-passage designs allow wood chips and fibers to pass without clogging. With durable construction, simple servicing, and continuous-duty performance, they keep tunnels clear, safe, and free of overflow even in heavy runoff conditions.

Bark Ash and Boiler Ash

Bark ash and boiler ash are waste products from burning wood waste and black liquor in mill boilers. The resulting ash slurry — a mix of fine solids, water, and chemicals — must be collected, transported, or dewatered to maintain boiler efficiency and meet environmental compliance.

Challenges:
Ash slurries are highly abrasive and sometimes caustic, quickly wearing out impellers, casings, and liners. Solids tend to settle in sumps and piping, causing frequent clogs and requiring manual cleaning. Standard dewatering and transfer pumps often fail prematurely under these abrasive conditions.

Solution:
Hevvy/Toyo submersible slurry pumps are built to handle abrasive ash slurries with minimal wear. Their high-chrome construction, heavy-duty bearings, and agitator systems keep solids suspended and prevent buildup. These pumps deliver superior reliability, reduced downtime, and longer component life in ash handling applications across pulp and paper facilities.

Black Liquor

Black liquor is a by-product of the kraft pulping process, containing lignin, chemicals, and dissolved wood materials. It is a highly alkaline, viscous fluid that is concentrated and burned in recovery boilers to reclaim energy and chemicals for reuse in the mill.

Challenges:
Black liquor is both corrosive and sticky, with high viscosity that increases as it cools. It can cause scaling, crystallization, and deposits that clog standard pumps and piping. The chemical composition also leads to corrosion and mechanical seal wear, making reliability difficult to maintain in high-temperature service.

Solution:
Hevvy/Toyo’s pumps for black liquor service feature corrosion-resistant alloys, mechanical seal protection, and high-temperature capability. Their open and recessed impellers handle viscous fluids without clogging, and optional heating jackets or material upgrades ensure steady, reliable operation. These features extend equipment life and reduce unplanned maintenance in harsh liquor handling circuits.

Digester Sumps

Digesters break down wood chips into pulp using heat, pressure, and chemicals such as sodium hydroxide and sodium sulfide. Digester sumps collect residual slurry, wash water, and fibers from the process for recirculation, cleaning, or disposal. Maintaining flow from these sumps is essential to prevent downtime and ensure stable pulp production.

Challenges:
The slurry in digester sumps is hot, fibrous, and chemically aggressive. Fibers tend to bind and form mats that clog conventional pumps, while high temperatures and caustic chemicals accelerate corrosion and seal degradation. Downtime for cleaning or repairs can disrupt continuous operations and reduce plant efficiency.

Solution:
Hevvy/Toyo pumps are purpose-built to handle hot, fibrous, and caustic slurries. Their recessed impellers and agitator options prevent fiber buildup and maintain consistent flow, even with high solids content. Available in stainless steel and elastomer-lined configurations, they resist corrosion and provide long service life under the extreme conditions found in digester sumps.