Wet-to-Dry Conversions

Overview

Public and Governmental environmental concerns and regulations have changed the operation of coal-fired power generating stations.

Switching to lower-sulfur coals with elevated calcium content necessitated a change in the fly ash systems to eliminate water as the conveying medium.

Increased utilization of fly ash in cement manufacturing and concrete products and the use of fly ash to stabilize the byproducts produced by wet scrubbers were major drivers in the conversion of many fly ash systems to dry collection.

The ELG and CCR regulations implemented as a result of issues with ash storage ponds are requiring that all remaining fly ash systems eliminate using water from the conveying process. Changes in plant design and operation related to handling bottom ash are also required by the new regulations.

UCC has assisted many utilities and their consulting engineers in evaluating the power stations and implementing solutions for the specific needs of that installation.

Multiple options for addressing the plant needs and correctly sizing those systems for the different types of ash produced are available from UCC.

Extensive testing of ashes have identified that fuel switching and boiler modifications result in ash characteristics significantly different than experienced when the plants were originally designed.

The need to modify the plant design to address the wet-to-dry requirements, provides the customer an opportunity to address performance and maintenance issues they have experienced.

Wet-To-Dry System Options

Fly Ash

• Convert existing wet vacuum System to a dry NUVEYOR® Vacuum conveyor system.
  • Reuse Existing Hopper Valves and piping
  • Convey directly to silo within ~ 1,000 ft.
• Extend conveying distance or increase capacity with Vacuum/Pressure Transfer system
  Two Options for Pressure Transfer system:
  • NUVA FEEDER® Pressure System 
    • Long Distance Conveying
    • Easily accommodates Economizer Ash
  • DEPAC®  Pressure System
    • Long Distance Conveying
    • Dense Phase – Low Velocity
    • Easily handles high density ash

Bottom Ash

• Modify existing bottom ash hopper and install a Submerged Flight Conveyor (SFC™) below the hopper. SFC easily accommodates economizer ash and mill rejects (Pyrites).

• Remove entire existing bottom ash hopper and install a SFC. Applicable if existing ash system hopper is near the end of its service life.

• Install remote SFCs with clarifiers or Closed-loop Dewatering and Recirculation System (CDR™). Retains existing bottom ash hopper sluice system and has the shortest outage time required for implementation. Especially suitable for multi-unit installations.

• Replace existing bottom ash hoppers with new dry hoppers and incorporate Pneumatic Ash eXtraction (PAX™) technology system.