Lesson 4: Fly Ash System Flashcards
- What is the function of the precipitator and how does it work?
The precipitator sprays chemical onto the fly ash to give it an electrical charge. The ash then sticks to electrically charged plates and wires. Then a rapper knocks the ash off the plates and wires, down into a hopper while the flue gases continue out the stack.
- List the pumps that are associated with Unit #1 Fly ash system.
Vacuum Pumps A and B
- Draw a one-line diagram of the fly ash system from the hoppers to the separator. Label all lines and equipment.
Hopper-Valve-Vacuum Lines-Silo-Primary-Secondary-Tertiary Collectors-Vacuum Line-Inline Filter-Vacuum Pump
- How do the collectors on top of the silo operate?
Unit #1: Ash is drawn into the primary collector via the vacuum pumps. There are upper and lower dump gates in the primary. Every 15 minutes the vacuum on the system is broken and the dump gates open allowing ash to fall into the silo. The secondary collector follows the same schedule, it just dumps into the lower portion of the primary before falling into the silo. Any leftover ash flows into the Tertiary collector where a dump gate opens to dump ash into the silo too.
Unit #2: Ash is drawn into the primary upper collector, then an equalization valve opens, equalizing the pressure between the upper and lower collectors. The upper dump gate opens and the ash falls into the lower collector. Upper dump gate closes. Then an equalization valve opens and equalizes the pressure between the lower collector and the silo. The lower dump gate opens, dumping ash into the silo.
Unit #3: Ash is drawn into a primary and secondary collector, both have upper and lower sections. Equalization valves open, equalizing pressure between the upper and lower sections and a dump gate opens allowing ash to fall into the lower section of the collectors. Dump gate close, EQ valve closes. Then another equalization valve opens, equalizing pressure between the lower sections and the silo. Lower dump gates open, dumping the ash into the silo.
- What are your responsibilities as an operator on the fly ash system?
Monitor ash equipment and trends to keep fly ash flowing through the system.
- What steps would you take if a hopper was plugged or rat-holing? How would you determine if the hopper was doing this?
Watch the ash trend and see how much vacuum was pulled on the hopper. Clear line that leg and go out to the hopper and manually operate the solenoid to open the valve. Then poke or use air to clear the hopper.
- What should be checked on the vacuum pumps before starting? After starting?
Starting Vacuum Pump:
Breaker Racked in Safe Run in Run Grounding Strap Seal Water valved in Air to Seal Water solenoid Solid Lines clear Oil Levels and Leaks Belts in working condition
Post Start Vacuum Pump: Heat/Vibration of motor Oil Level Seal Water Flow Solid Lines Clear Water packing leak off Belt Conditions Oil/Water Leaks
- Why does going from gas to coal as main fuel affect the fly ash system?
Burning gas produces moisture which can negatively impact the fly ash collection system. Fly ash becomes clumped when wet.
- Why is it necessary to have heaters in the fly ash hoppers?
Hopper heaters keep the ash hot to allow better flow through the system.
- What are the safety precautions that should be used when moving fly ash?
Proper PPE and watch for hot ash.
- What electrical buses supply the precipitator and related equipment?
J&K, R&S
- What percent of ash is removed by the precipitator?
95%
- What is the purpose of the rappers?
Rappers knock the ash off the plates and wires
- What different kind of rappers do we have?
- Plates and Wires
- What do you check on the rappers?
Power supply Leaning/ not upright Rapper Boot Rapper Sleeve Grounding Strap Is it operational?
