ESP Startup and Shutdown

A specific startup and shutdown procedure should be supplied by the ESP vendor. Improper

startup and shutdown can damage the collector. It is imperative for the operator (source) to

have a copy of these procedures. Review agency engineers may want to assure that these procedures exist at the sites and that the operators follow the procedures or document reasons for

deviations.

Startup

Startup of an electrostatic precipitator is generally a routine operation. It involves heating

a number of components such as support insulators and hoppers. If possible, the ESP

should not be turned on until the process reaches steady-state conditions. As described in

Lesson 5, this is particularly important for ESPs used on cement kilns burning coal as fuel.

The internal arcing of the ESP could cause a fire or an explosion. When ESPs are used on

oil-burning boilers, the boiler should be started with gas or #2 fuel oil. Heavy oil (#6 fuel

oil) is not a good fuel for startup because tarry particulate emissions can coat collection

plates and be difficult to remove. If an ESP is used on a coal-fired boiler, the ESP should

not be started until coal firing can be verified. This will help prevent combustible gases

from accumulating in the unit and causing explosive conditions. A typical startup procedure

for an ESP used on a boiler is given below

Startup (preoperational checks - at least 2 hours prior to gas load):

1. Complete all maintenance/inspection items.

2. Remove all debris from ESP.

3. Safety interlocks should be operational and all keys accounted for.

4. No personnel should be in ESP.

5. Lock out ESP and insert keys in transfer blocks.

Prestart (at least one hour prior to gas load):

6. Check hoppers.

a. Level-indicating system should be operational.

b. Ash-handling system operating and sequence check - leave in operational mode.

c. Hopper heaters should be on.

7. Check top housing seal-air system.

a. Check operation of seal-air fan—leave running.

b. Bushing heaters should be on.

8. Check rappers.

a. Energize control, run rapid sequence, ensure that all rappers are operational.

b. Set cycle time and intensity adjustments, using installed instrumentation—leave rappers operating.

9. Check T-R sets.

a. Check half-wave/full-wave operation (half-wave operation is recommended for filtering fly ash when lignite is burned and a cold-side ESP is used.)

b. Keys should be in all breakers.

c. Test-energize all T-R sets and check local control alarm functions.

d. Set power levels and de-energize all T-R controls.

e. Lamp and function-test all local and remote alarms.

Gas load:

10. After gas at temperature of 200°F has entered ESP for 2 hours -

a. Energize T-R sets.

b. Check for normal operation of T-R control.

c. Check all alarm functions in local and remote.

d. Within 2 hours, check proper operation of ash removal system.

e. De-energize bushing heaters after 2 hours (hopper heaters optional).

Cold start (when it is not possible to admit flue gas at 200°F for 2 hours prior to energizing controls), proceed as follows:

1. Perform steps 1-9 above. Increase rapping intensity 50%.

2. Energize T-R sets, starting with inlet field, setting Powertrac voltage to a point just below sparking.

3. Successively energize successive field as load picks up to maintain opacity, keeping voltage below normal sparking (less than 10 flashes/min on spark indicator).

4. Perform step 10d above.

5. After flue gas at 200°F has entered ESP for 2 hours, perform steps 

       10b, c, d, and e above.

       Set normal rapping.

Shutdown

When an industrial process is shut down temporarily, the ESP system should be de-energized

to save energy. The shutdown of the ESP is usually done by reversing the order of

the startup steps. Begin with de-energizing the ESP fields starting with the inlet field to

maintain appropriate opacity levels from the stack. The rappers should be run for a short

time after the ESP is de-energized so that accumulated dust from the collection plates and

discharge wires can be removed. All hoppers should be emptied completely before bringing

the unit back on line. A typical shutdown and emergency shutdown procedure for

ESPs used on industrial sources is given below

Typical shutdown

1. When boiler load drops and total ash quantity diminishes:

a. De-energize ESP by field, starting with inlet field to maintain opacity limit.

b. De-energize outlet field when all fuel flow ceases and combustion air flow falls below 30% of rated flow.

c. Leave rappers, ash removal system, seal-air system, and hopper heaters operational.

d. Four hours after boiler shutdown, de-energize seal-air system and hopper heaters. Secure ash removal system.

e. Eight hours after boiler shutdown, de-energize rappers.

Note: Normal shutdown is a convenient time to check operation of alarms.

Emergency shutdown

1. De-energize all T-R sets.

2. Follow steps 1c, d, and e above (shutdown).