Seminar Topics: Boiler control instrumentation

THREE ELEMENT CONTROL

FIG. 4 THREE ELEMENT BOILER CONTROL

FIVE ELEMENT CONTROL

Additional elements can be added to a feedwater control system to improve response accuracy. A five element feedwater control system is essentially a three element configuration in which the steam flow measurement is temperature compensated and drum level measurement is pressure compensated

FIG. 5 FIVE ELEMENT BOILER CONTROL

SEVEN ELEMENT CONTROL

Transmitters for blow down flow and sootblower flow could be added to five element control to make up seven element feedwater control.

Types of steam

Here we are using two types of steam i.e, saturated steam and super heated steam. Steam obtained while heating is called saturated steam. It is called wet steam since moisture content is also present. Super heated steam is obtained when saturated steam is further heated above 220 degrees. It is also called dry steam.

ADVANTAGES

1. Multiple element feedwater control can help:
i. Faster response of systems.
ii. More accurate control.
iii. Maximum system stability.

2. Metering control system maintains combustion efficiency over wide. load changes and over long period of time.

3. Parallel combustion control can be used in any size of boilers.

DISADVANTAGES

1. Boilers require quick responding controls.
2. Level of the water in the boiler must be kept above 50% of height.

FUTURE DIRECTIONS

Microcontrollers & PLC are used as controllers.

CONCLUSIONS

The various goals of boiler control includes:

1. To minimize excess air
2. To minimize blowdown
3. To minimize steam pressure
4. To measure efficiency
5. To find when to perform maintenance

Bibliography

1. Instrumentation Controls Journal - July 2001
Boiler Instrumentation, R. Ramamoorthy
2. Instrument Engineers’ Hand Book
Process Control – Bela G. Liptak
3. Process Control Instrmentation
- C.D. Johnson