Lesson 4: Fly Ash System Unit 2 &3

Question 1

1. Draw a one line diagram of the fly ash flow.

Answer 1

Economizer hopper-Ductwork-Bag House Compartment-Hopper-Vacuum Line-Primary Collector-Secondary Collector-Silo

Question 2

2. Describe the operation of the vacuum pumps.

Answer 2

The vacuum pumps pull ash through the system for collection in the silos. They use water and centrifugal force to create a seal inside the pump which in turn creates a vacuum on the lines.

Question 3

3. Explain the theory of operation of a bag house.

Answer 3

Ash and flue gases pass through the bags and the ash is collected there while the gases continue out the stack.

Question 4

4. What is the purpose of the shaker mechanism?

Answer 4

The shaker shakes the bags during a compartment cleaning cycle to release the ash from the bags to be collected in the hoppers.

Question 5

5. Why are the bags deflated during a cleaning cycle?

Answer 5

Better ash release from the bags and to reduce tearing of the bags.

Question 6

6. Why is it important to check the bag house differential pressure on a regular basis?

Answer 6

To see how well the compartments are being cleaned.

Question 7

7. How can you tell if a hopper heater is working?

Answer 7

Amperage on the gauge and a green light on the breaker.

Question 8

8. Why are vacuum leaks on the fly ash lines such a problem?

Answer 8

Vacuum leaks cause a decrease in ash collection. Hoppers and legs also tend to get plugged up easier.