Attachment 1 

Seminole Dry Conveyor Bottom Ash Handling System Summary Description and Diagram 
THE BOTTOM ASH SYSTEM DESIGN: 

The primary ash removal conveyor is mounted beneath the boiler, fully sealed to the combustion 

chamber. The negative pressure inside the boiler draws in air in a controlled manner through the 

primary conveyor. The incoming ambient air travels along the conveyor, counter to the ash flow 

direction, over the surface of the ash contained on the conveyor pans. This causes a re-burning 

process of the glowing ash, which reduces the unburned carbon level and frees up additional thermal 

energy. Therefore, the air is preheated before it enters the combustion chamber of the boiler. 

THE ARRANGEMENT 

Underneath the combustion chamber of the boiler, a hopper is installed and supported from the floor 

by means of a steel structure. The transition chute or hopper is lined with special refractory and 

insulation on the inside to withstand the radiation from the combustion chamber of the boiler. A heat 

resistant fabric compensator (expansion joint) is installed between the boiler/hopper outlet and the 

primary conveyor inlet, to compensate for the movement between the cold and hot conditions of the 

boiler. Large slag agglomerations are broken down by jaw crushers in order to ensure they are an 

appropriate size to be cooled and conveyed. These jaw crushers are hydraulic operated. In the full 

closed position, they will provide isolation of the primary conveyor from the boiler hopper. 

THE REST OF THE SYSTEM 

In addition to collecting the bottom ash in a dry condition, Seminole also collects its economizer ash 

in a dry condition. The ash is collected from the boiler economizer area in 6 hoppers that discharge to 

a series of drag chain conveyors that transport the ash onto the primary conveyor where it is added to 

the bottom ash. 

Once the bottom ash and economizer ash are removed from the boiler by the primary conveyor, it is 

transported up to the transfer tower where the ash then passes though a double roll grinder to reduce 

the particle size to below 3 inches. The crushed ash will fall onto a secondary transfer conveyor that 

is very similar in design to primary conveyor. The ash will travel up the secondary conveyor where it 

passes through another set of single roll crushers where it is reduced to 3⁄4 inches in size and is then 

discharged into the storage silo. The ash is stored in a dry condition. Seminole has the capability of 

offloading the ash in either a dry or a wet condition. The Pug mill wet unloading system adds 

sufficient quantities of water to condition the ash to prevent dusting in open top trucks. The dry 

unloading system utilizes a retractable loading spout that is attached directly to specialized trucks 

designed to receive dry material. 
Seminole Dry Conveyor Bottom Ash Handling System Summary Diagram Removed - CBI
Attachment 2 

Seminole Plant Water Diagram 
EVAP

957 GPM

EVAP

20 GPM

EVAP

1032 GPM 1020 GPM 

1632 GPM

55 GPM

1750 GPM 1750 GPM

Demin Regen NH3 TO SCR Polisher Regen 

Water Water

UREA

COMMON FGD

SYSTEM

SUPERN

T

FGD Effluent

BLOWDOW

SOLID WASTE 

DISPOSAL

FGD Recirc

UREASLUDGE 4

61 GPM 0.3 TPD

61 GPM

50 GPM

55 GPM

BOILER MAKEUP 

61 GPM 25 GPM 52 GPM 

1032 GPM

8000 TONS, 1X/YR

25GPM

FIRE PROTECTION SYSTEM BASIN 

61 GPM SLUDGE

191 GPM 

BOTTOM ASHSLUDGE

195 TPD 113 GPM

191 GPM 548 GPM

14 GPM

PRETREATMENT BLOWDOWN/SLUDGE

POTABLE WATER SYSTEM 133 GPM

QUENCH WATER

85 GPM 85 GPM

110 GPM

PURG

TREATM

WASTEWATER

TREATMENT SYSTEM Bottom Ash System

Common Plant

Services 

(Unit 1 and Unit 2)

PRETREATMENT

SYSTEM

DEMINERALIZER

SYSTEM

NEUTRALIZATION

RAW

WATER 

WELLS

INTAKE

UREA TO AMMONIA

SYSTEM

LANDF

BOILER

BLOWDOWN

SOLD

FDW

110 GPM

RAINFALL

525,000 GPD, 4D/YR 4 GPM EVAP 2 GPM

EVAP 2 GPM EVAP

RAINFALL RAINFALL

8050 GPM 6 GPM 133 GPM

1117 GPM Solids 480 TONS, 1X/YR

RIVER 11051 GPM 11341 GPM 3291 GPMWATERINTAKE

COAL PILE RUNOFF 

PONDS

COOLING

TOWERS

Percolation Ponds

Air Heater

LANDFILL