A steam boiler is composed of 2 basic systems as shown in Figure 1. One basic boiler system is the water-steam system which is known as boiler waterside.
In waterside of boiler, water is heated and released by movement via water tubes, then water is transformed to steam, and also it retains as steam in the system.
Figure 1: Basic Boiler System Diagram
(Source: Book-Boiler Control System Engineering-G.F Gilman)
Steam boiler need to manage chemical stability. The method where this is performed could interact to control system of feedwater. The quantity of blowdown should be regarded in the control design of feedwater, particularly when the blowdown is continually performed.
Frequently, the flow of blowdown is separated by content level ratio of the flow of feedwater. The popular method pertaining to managing the chemical content level is continuous blowdown.
On big scale boiler this could possibly be performed automatically by way of measuring conductivity of boiler water to regulate blowdownn rate.
Mixing ratio control of blowdown with conductivity and comparing feedwater flow to blowdown is carried out to get blowdown rate.
Blowdown is usually obtained and conductivity is measured manually in utility plants. This is needed on a regular schedule or maybe any time the conductivity becomes very high.
The other basic boiler system is the fuel-flue gas-air system. This system is as well-known as the boiler fireside. This specific system supplies heat which is transferred into boiler fireside system.
Fuel is the input for this system and to perform combustion or firing needs air and ignition system. The combustion air and fuel is as well-known as wind box. Ash and gas will be the output of this system.