BASICS
Devices that convert the chemical energy in the boiler fuel into heat energy are called Boilers. Prepared fuels (petroleum or coal) are pulverized with air and sprayed into the combustion chamber. The heat released as a result of combustion evaporates the water inside the boiler pipes. Remaining solid waste and slag falls into the water basin under the boiler, and from there they are thrown out with belts. The gases formed as a result of combustion are sent from the chimney at around 110–160 C after the heat is taken thoroughly. The steam produced in the boiler is directed to the turbine.
Steam production; It is the process of converting water into steam with the effect of heat. In the water source, the temperatures of water and steam are the same. This temperature is called the saturation temperature. At constant pressure, a heat must be supplied to induce evaporation in a liquid source. This heat is also called “latent heat” or “heat of evaporation”.
If the steam produced is at the boiling point and does not contain water, it is called “dry saturated steam” and if it contains water, it is called “wet steam”. If the steam is heated to a point above its boiling point, it is called superheated steam.
CLASSIFICATION OF BOILERS
1- According to the type of material used in the construction of the boiler;
– Cast section boilers
– Steel boilers
2- According to the type of fuel used;
– Gas fired boilers (Natural gas)
– Liquid fuel boilers (Engine, fuel oil)
– Solid fuel boilers (hard coal, wood, etc.)
3- According to the pressure of the combustion chamber;
– Back pressure boilers
– Boilers without backpressure
4- According to the type of heating fluid;
– Hot water boilers
– Boiling water boilers
– Steam boilers
5- In terms of the structural design of the boiler;
– Flame tube boilers
– Flame smoke tube boilers
– Smoke tube boilers
– Water tube boilers
6- In terms of the shape of the cauldron;
– Half cylindrical boilers
– Fully cylindrical boilers
– Prismatic package boilers
Boilers are generally used in two main types in petrochemicals and refineries. These are named as flame tube boiler and water tube boiler.
Flame Tube Boilers
In flame tube boilers, all heat transfer takes place with the help of pipes (tubes) surrounded by water, through which hot combustion gases pass. Water and steam are in the same section (in the hive part). The steam outlet exits above the drum. Examples of this type of boilers are locomotive and ship steam boilers and steam boilers in which hot gas or hot liquid product passes through the tube in the process units.
Water Tube Boilers
In water tube boilers, the combustion chamber is surrounded by tubes through which a mixture of water and steam circulates. This type of boilers are used much more commonly in refinery operations than those with flame tube. Their designs have shown significant improvements in recent times. Vertical or near-vertical oriented tubes are used efficiently in both radiation (combustion chamber) and convection (combustion gases) regions. In addition, with the use of economizers and air heaters, the waste heat of the hot flue gases is utilized to the maximum extent.
