Wet-to-Dry Conversion

Recent high-profile incidents surrounding ash pond failures are forcing coal power plants to re-evaluate wet ash handling practices. Utility companies still using ash retention ponds to store ash by-product have important choices as they look to replace wet systems with dry solutions. Over the past few decades United Conveyor Corporation (UCC) has assisted many utilities in converting from wet fly ash handling to dry systems based on these market trends and factors:

•The Powder River Basin fuel-switching initiatives

• The reuse and sale of fly ash to concrete suppliers

• Extend pond life for bottom ash storage of capacity-constrained ponds

As of 2008, nearly 67% of plants with ash ponds have converted to dry fly ash systems, while only 10% of bottom ash systems are dry.

Public scrutiny, environmental concerns and pending government regulations may further shift the industry to dry or reduced water consumption alternatives. Increased focus on converting wet bottom ash systems is expected to eliminate legacy ash ponds. State-of-the-art ash handling systems from UCC offer greater equipment reliability and the broadest range of customized solutions to better serve removal operations.

United Conveyor recently had an article on Wet-To-Dry Conversions in CoalPower magazine.

Click here to read it.

Fly Ash Systems

Dry fly ash conveying has become the standard for new installations and retrofits over the last few decades. Since 1920, UCC has engineered thousands of fly ash handling installations in over 50 countries. Retrofitting an existing wet HYDROVEYOR® system into a dry fly ash system is completed with the addition of a few system components.

Using our technical experience, breadth of systems and products, UCC works directly with customers to find the right solution to address current and future environmental regulation requirements. The options include the NUVEYOR® Vacuum System, Combination Vacuum/Pressure System (NUVA FEEDER® for medium phase or DEPAC® for dense phase materials) or Pressure System.

Bottom Ash Systems

United Conveyor offers the broadest range of state-of-the-art dry bottom ash handling solutions. Four different system types – Hydraulic, Mechanical, Pneumatic and Vibratory – have been developed to address the particular characteristics of each individual power plant. With hundreds of installations and nearly 90 years of experience, UCC provides the confidence and peace of mind our customers demand. All of the below options eliminate the need for ash storage ponds.

Fly Ash

NUVEYOR® Vacuum System

- Reuse Existing Vacuum System

- Ease of Retrofit in Limited Space

NUVA FEEDER® Pressure System

- Ability to Convey Long Distances

- Can Handle Economizer Ash

DEPAC® Pressure System and MultiDAC™ Pressure System

- Dense Phase – Low Velocity

- DEPAC Conveys Long Distances

Bottom Ash

Recirculation System

- Shortest Outage Time for Conversion

- Continued use of Existing Bottom Ash Hoppers

- Easily Incorporates Mill Rejects

Submerged Flight Conveyor (SFC™)

- Continuous Removal of Ash

- Lower Power Consumption

- Easily Incorporates Mill Rejects

Pneumatic Ash Extractor (PAX™)

- Easily Retrofitted Around Structural Barriers

- Provides Improved Heat Recovery and Boiler Efficiency

- Does Not Require Water

Vibratory Ash Extractor (VAX™)

- Proven Technology

- Highest Heat Recovery

- Lower Operating Cost

Wet-To-Dry Thought Leadership Article
This article discusses all of the UCC wet-to-dry conversion options along with a decision analysis to help narrow down the options.
  1. Question 1[+]
    Answer 1
Vacuum Systems

The NUVEYOR® Vacuum System is an industry standard for efficient, reliable ash removal and is capable of conveying up to 80 TPH and distances of 1500 ft (450m).

Vacuum-Pressure Transfer System

UCC's Vacuum/Pressure Transfer systems combine the simplicity and lower headroom requirements of a vacuum system under the hoppers with the high capacity and long distance conveying capability of a positive pressure system.

NUVA FEEDER Dilute Phase Pressure System

The NUVA FEEDER® pressure system is optimal where conveying capacity requirements exceed the limits of a vacuum system. 

DEPAC Dense Phase Pressure System

DEPAC® is a dense phase system for conveying large quantity of material at low velocity over very long distances. 

 

Recirculation

Ideal for converting wet sluice systems into a “dry” ash system without change to the existing bottom ash hoppers.

 

Submerged Flight Conveyor

The Submerged Flight Conveyor (SFC) is a proven bottom ash system and the most cost-effective compared with other alternatives.

 

Pneumatic Systems

UCC pioneered the first dry bottom ash system using pneumatic technology in 1920. The PAX Pneumatic Ash Extractor added new technology to this time-proven vacuum system design and offers many benefits over wet bottom ash systems.

Vibratory Systems

The VAX system is the latest evolution in dry bottom ash technology which delivers superior heat recovery, lower installed cost, higher reliability and less maintenance compared with conventional moving belt designs.