The Extreme Rotary Valve Advantage: Superior Multiclone Sealing in High-Temp Pulp & Paper Operations

In the Pulp & Paper industry, reliability is the currency of operation. Nowhere is this more evident than in the power and recovery islands of a mill, where equipment is subjected to punishing environments. While Multiclones (multi-cyclone dust collectors) are the industry standard for rugged, first-stage filtration, their efficiency relies heavily on one critical, often overlooked component: the rotary airlock valve at the hopper outlet.

For mills struggling with valve failure due to abrasive hog fuel ash and high temperatures, the Delta Ducon Extreme Rotary Valve offers a purpose-built solution, featuring the revolutionary P-33 high nickel chrome alloy rotor-to-shaft seal.

The Critical Role of the Airlock in Multiclones

As described in standard mill operations, Multiclones are the "unsung workhorses" of the industry. Whether situated after a Hog Fuel (Biomass) Boiler to capture silica-laden fly ash or downstream of a Lime Kiln or Recovery Boiler, the multiclone’s job is to spin gas streams to separate particulates.

However, a multiclone is only as effective as the seal at its bottom. The rotary valve must perform two conflicting tasks simultaneously:

·         Discharge Material: Continuously remove the hot, abrasive sand, char, and ash collected in the hopper.

·         Maintain Pressure: Act as an airlock to prevent air leakage. If the seal fails, air leaks into the negative-pressure environment of the cyclone, disrupting the vortex and causing the particulate to re-entrain into the gas stream—defeating the purpose of the collector.

The Problem: Abrasion and Heat

In applications like Hog Fuel Boilers, the ash contains silica (sand) absorbed by trees during logging. This material is not just hot; it is essentially an abrasive grinding compound. Standard rotary valves often fail because this grit works its way into the shaft seals, destroying them, causing leaks, and seizing the rotor. Furthermore, flue gas temperatures can spike, warping standard metal components.

The Solution: Delta Ducon Extreme Series

Delta Ducon has engineered the Extreme Rotary Valve specifically for these severe-duty applications. It is designed to withstand the abrasive effect of pulp mill fly ash while maintaining a tight seal under thermal stress.

The P-33 Advantage: Cast Solid, 550+ BHN Hardness, Fully Field Adjustable and Replaceable

The standout feature of the Delta Ducon Extreme Valve—and the primary reason for its longevity in paper mills—is the P-33 high nickel chrome alloy rotor-to- wear shoe seal.

Unlike standard rotary valves that wear out quickly and require significant downtime to service, the Extreme Rotary Valve is engineered for resilience and ease of maintenance:

·         High Nickel Chrome Alloy: The P-33 material is exceptionally hard and resistant to the corrosion and abrasion common in biomass combustion byproducts. It resists the "grooving" caused by silica ash that typically destroys rotors and housings.

·         Fully Field Adjustable: Maintenance teams know that pulling a valve off a hot hopper is a difficult, dangerous, and time-consuming task. The P-33 seal is designed to be adjusted externally without removing the valve from the line. This allows operators to tighten the seal and stop leaks in the field, keeping the multiclone at peak efficiency.

·         Replaceable: When the rotor and wear shoe eventually reaches the end of its service life, it can be replaced in the field. This modular approach significantly lowers the Total Cost of Ownership (TCO) compared to valves that require complete refurbishment or replacement upon seal failure.

High-Temperature Performance

Recovery boilers and lime kilns generate exhaust gases that far exceed the limits of standard manufacturing components. The Delta Ducon Extreme Rotary Valve is available in high-temperature models rated up to 800°F (427°C).

This thermal resistance is crucial for preventing rotor-to-housing contact. In lower-quality valves, thermal expansion can cause the rotor to expand faster than the housing, leading to catastrophic seizing. The Extreme Series utilizes proper metallurgy and clearances to ensure the valve keeps turning, even when handling hot lime dust or unburned carbon char.

Application Summary

By upgrading multiclone outlets to Delta Ducon Extreme Rotary Valves, Pulp & Paper mills can address specific pain points in their process:

Hog Fuel Boilers: The P-33 seal creates a barrier against the highly abrasive silica sand and fly ash, protecting the ID fan downstream from particulate carryover caused by airlock leaks.

Lime Kilns: The 800°F temperature rating ensures the valve survives the intense heat of the kiln exhaust while handling fine, pervasive lime dust.

Recovery Boilers: Provides a reliable seal for salt cake removal, ensuring the initial separation phase operates efficiently before gases reach the ESP.

For maintenance planners and mill engineers, the move to Delta Ducon represents a shift from constant "fire-fighting" and valve replacement to a strategy of long-term reliability and field maintainability.

For more information on specifications and sizing for your mill, visit www.DeltaDucon.com