Steam Generators - Chapter 10

Components

Design Criteria

Boiler types

Representative firetube boilers

Representative water-tube boilers

Water walls

Boiler installation

Furnace

Superheat

Boiler accessories and trim

Combustion equipment

Spreader stoker

Conveyor stoker

Underfeed stoker

Coal burners

Gas and oil burners

Operation and performance

Heat balance of a steam generator



Some important points under development


Components

Design Criteria

Boiler types

Representative firetube boilers

Representative water-tube boilers

Water walls

Boiler installation

Furnace


Furnace Heat Release Rates


Many types of furnace walls are in use;

1. Solid masonry

2. Air cooled masonry walls

3. Partially water cooled walls

4. Water jacketed furnace


Materials chiefly used are fire clay, silica, kaolin, diaspore, alumina, and certain products of the electric furnace.

Fire clay bricks are preferred because of their low cost whenever they give satisfactory results.

Ordinarily optical thermometers used with furnaces give wall temperatures.

Superheat

Boiler accessories and trim

Combustion equipment



Spreader stoker

Conveyor stoker

Underfeed stoker

Coal burners

Functions of a burner

1. There is stability of ignition.
2. 2. Effective adjustment for control of point of ignition and resulting flame shape.
3. Complete combustion
4. Heat unformly developed in flame
5. Adequate protection against overheating, internal fires, and excessive abrasive wear.


Pulverised coal burners are classified as long-flame, short-flame (or turbulent), and tangential burners.


Cyclone burner

Gas and oil burners

Operation and performance

Operation of the boiler consists in ascertaining that equipment is following the load and functioning normally, but also in making secondary adjustments which refine the thermal efficiency beyond the normal abilities of the usual complement of automatic equipment. Automatic equipment must be watched through instruments for periodic inspections, load shifts between multiple units made, critical points for  pressure, temperature, etc., inspected from time to time and other precautionary actions taken.

In most plants, especially, central stations, part of the supervision is "taking log", ie the record of flows, pressures, material quantities, and other physical data. These are supplemented by samples of coal, water, etc., for testing in the plant laboratory. Performance of the plant as a whole, or parts of it are computed at intervals from such data. Then there is always a certain amount of maintenance and repair. In larger installations, there are specialized groups such as operations, tests, plant improvement, maintenance, repair etc.


Heat balance of a steam generator