Wet Ash Handling Systems
Fly Ash is the major constituent of the ash generated from Pulverized and Fluidized bed Coalfired boilers. The Fly ash gets collected at various points, with most of it in ESP hoppers. One of the methods for handling Fly Ash is Wet system in which the ash is mixed with water to form slurry which is pumped to slurry pit.
The Fly Ash collected in various hoppers is at temperatures more than 100°C. The Hopper outlets are provided with isolation slide plate valves which can be remote operated (pneumatic or motorized) preceded by manual operated slide plate valve. The down flow spout is fitted with Expansion Joint which is followed by Feeder Ejector. A 100 NB water connection from side of Feeder Ejector supplies medium pressure water which mixes with Fly ash to form slurry of concentration upto 35%. This slurry flows out of the Ventury tail piece of the Feeder Ejector by gravity through open sluice trenches or closed pipes and collected at a central point from where centrifugal slurry pumps or Hyjector are used to pump it at the designated slurry pit / main slurry tank for further disposal. The unique DEMECH design of Feeder Ejector ensures that the steam / water vapours generated during mixing of hot Fly ash with water do not rise back to the hopper and clog the hopper outlet.
This is essentially an intermittent operating system with ash removal capacity at a rate of 30 to 60 TPH per Feeder Ejector. Number of Feeder Ejectors operated simultaneously decides the overall ash handling rate and thus the hopper evacuation time and its cycle is computed.
Wet system for handling Fly ash for large boilers where the quantity of ash produced is large. The need for such a system becomes important when the Fly ash cannot be utilized further and the disposal pits / ash ponds are located far away from the plant. The water requirement in this system can be reduced by installing water recovery systems to reuse the water back in handling Fly ash.