Case Study – Bottom ash (Jet Pump) & Fly ash (Vacuum & Positive Pressure) Handling system for PF Boiler

 Jet Pump System : Bottom ash (Jet Pump) & Fly ash (Vacuum & Positive Pressure) Handling system for PF Boiler.

Jet Pump System-

PROJECT SYNOPSIS

BOTTOM ASH HANDLING SYSTEM ( JET PUMP SYSTEM ):

Macawber Beekay successfully installed lean slurry conveying system using combination of Jet pumps or jet pump system,  Ash Slurry Pumps along with HP / LP water Pumps and ash conveying pipes.

Furnace (bottom) ash is collected for each unit, via a refractory lined steel construction bottom ash hopper installed below furnace. The furnace seal plate dips into seal trough filled with water around top periphery of bottom ash hopper for the sealing of furnace.  The necessary clearance is provided between seal plate and seal trough bottom to take care of expansion of furnace.

Spray nozzles are provided in the bottom ash hopper for quenching of ash and seal trough flushing pipe and cleaning of inspection window. Economizer ash also flows into respective Bottom Ash Hopper for further disposal.

The Ash is Collected in bottom ash slurry sump, this ash in Slurry Sump is further disposed to slurry pond using Ash Slurry Pumps.

HP and LP water pumps are provided to meet the water requirement of the system.

Ash water recovery system is provided to collect and pump back clear water from ash pond.

FLY ASH HANDLING SYSTEM:

System consists of combination of Vacuum fly ash collection from ESP hoppers into Intermediate Surge (buffer) Hoppers and Positive Pressure Pneumatic Conveying System for transfer of fly ash to main silos, provided near boundary wall of the power plant.

Brief write-up for System at ESP:

There are eight fields in ESP with four passes. Each pass shall have 32 Hoppers.

Beneath each ESP hopper, an Ash Intake Valve (Dome Valve) &Unloading T along with necessary Instruments and Fluidizing Padshas been provided.Each Row is connected in series with Single pipe for each Pass. That means there is one fly ash conveying pipeline for one Pass of ESP. Total 4 sets of fly ash conveying pipes have been provided for handling ESP ash for each boiler.

The Ash from ESP is either conveyed to Collector Tank OR to Three Cell Ash Collection Bag Filters. Suitable Vacuum Pumps are used to create vacuum in conveying pipes below ESP, which helps in the evacuation of material from ESP.

The Ash coming from ESP in Collector Tanks is mixed with water using wetting head above ash collector tank. This provision is provided to handle fly ash in slurry form to Ash Slurry Sump for further disposal using conveying pipes.

In the other route, Fly Ash below Bag Filter Hopper is collected in Suitable Buffer Hopper and conveyed to FA Silos using compressed Air and Ash Conveying Vessels with Conveying Pipeline. 2 sets of Conveying Pipelines is provided for each Boiler.Conveying air requirement for both the units is met from a common bank of CA compressors. Separate Instrument Air compressors have also been provided dedicated to fly ash handling system.

System at Fly Ash Silo:

Total of 2 sets of fly ash silos have been provided for collection of fly ash from two boilers.

At conical portion of fly ash silos, Fluidizing pads have been provided.3 Nos. (2W+1S) Roots Blower and 3 Nos. heaters are provided for fluidization of set of two fly ash silos.

The FA Silo 1 & Silo 2 have three outlet points. First and second outlet point are provided with fly ash unloading spouts for unloading of fly ash into closed tankers. The third outlet is provided with ash conditioners for moist fly ash disposal into open trucks, the fourth outlet is provided with just isolation valve for any emergency unloading of fly ash.