Energy Tab: Dry Ash system : 500 MW

Dry Ash system : 500 MW

Ash is oxidised form of the mineral matters present in coal
Typical ash composition : SiO2, Al2O3, Fe2O3, CaO, MgO etc
Coal with more SiO2 & Al2O3, Ash MP > 1400ºC
Coal with more Fe2O3, CaO & MgO, Ash MP < 1100ºC
Ash content of Indian coal used in power station is about 30 to 40 %.
A typical 2000 MW station produce around 9000T to 12000T of ash per day
FA is collected from Air heater hopper, Eco hopper and ESP hopper
In Flushing apparatus system ash is allowed to fall in flushing apparatus under gravitation.
Water jet in flushing apparatus carries away the ash to FA trench
High pressure jets further carries it to FA sump.

In Dry Ash Mode: Vacuum pumps are used to convey ash from the ESP hoppers to Bag Filter and CTT
In Bag Filter Dry ash is separated out from the air
Through Transfer Hopper ash is transferred to Buffer Hopper
Blower are connected to the bottom of buffer hopper for fluidized air supply
From buffer hopper, it is transferred to Transporter.
From Transporter, Dry ash is conveyed through Pipe lines (Pneumatic Conveying). For pass A & B the line is AB similarly for pass C & D the line is CD
Modes of conveying: a) Dilute phase: If the material is conveyed in suspension in the air through the pipeline it is referred to as dilute phase conveying.b) Dense phase: If the material is conveyed at low velocity in a non suspension mode, through all or part of the pipeline, it is referred to as dense phase conveying.
In dense phase conveying two modes of flow are recognized.
Moving Bed Flow: Moving bed flow is only possible in a conventional conveying system if the material to be conveyed has good air retention characteristics.
Plug Type Flow: Plug type flow is only in a conventional conveying system if the material has good permeability. This type of flow is typically limited to the materials that are essentially mono-sized, since these allow the air to pass readily through the interstices between the particles.

Vacuum pump is use to convey the Fly Ash from ESP hoppers to the CTT (for wet system) and bag filter (for Dry system).
Type of pump :Water Ring Vacuum Pump
Total No. of pumps : 8 Nos.
Capacity : 4200M3/Hr
Shut-off Vacuum : 500 mm of Hg
Machine speed : 460 RPM
Electric Motor : 90 Kw at 1440 RPM
Seal water req. : 65 LPM
Seal water pressure : 1 Kg/cm2
Seal water Temp. : 300C