In the operation of gas-fired steam/hot water boiler, it need continuous water supply to ensure the water volume in the drum. Once water shortage occurs, it will cause the boiler dry burning problem, which will further result in the boiler failure and other problems.
The combustion air preheater is definitely one of heat exchanger applications. Based on Figure 1 below, flue gas simply leaves steam boiler and passes via air preheater. The combustion air is passed through this equipment too to increase its temperature before being combined with boiler fuel.
Because the temperature of combustion air is lower than the temperature of flue gas, combustion air receive heat transfer from flue gas through combustion air preheater in the process of convection heat transfer. The heat transfer make temperature of flue gas lower and consequently minimizes its heat loss and also decreases the air temperature to stack.
Evaporation phase occurs in water wall tubes. Evaporation is the process to convert water into steam. Therefore water wall tubes should be designed and constructed to provide high heat absorption, minimum excess air level and highest boiler efficiency. Construction of water wall tubes should be also constructed to prevent air leakage into steam boiler, eliminate amount of heat losses and permit high heat release and combustion rate in the furnace.
Construction of water wall tubes must provide high quality of the supporting component such as tubes, casing, refractory, lagging, tile, fin, and so on. Best construction will reduce heat loss and maintenance. Construction of water wall tubes can be classified into four types such as:
Industrial boilers are welded from sturdy steel plates that are engineered to withstand intense heat and pressure - as a result of this thick steel, boilers can sometimes weigh as much as 165 tons! The construction of hot water boilers and steam boilers is very similar. They both feature a cylinder tube, otherwise known as the pressure vessel. The pressure vessel contains something called a flame tube, which is fired through a burner and a reversing chamber that feeds flue gases back through a second smoke tube. These flue gases are reversed again via an external reversing chamber. This reversing chamber sends the flue gases to the end of the boiler, in the third smoke tube pass. A major difference between hot water industrial boilers and the steam versions? Hot water boilers, as their name implies, are usually completely filled with hot water during their operation, while steam boilers are filled with water only until the ¾ mark, with the top fourth of the boiler reserved for steam.
One of the most important accessories you can have for your steam boiler is a water softener, which serves several purposes and plays a crucial role in helping your boiler avoid malfunctions and run more efficiently. Let's go back to the basics and walk through how water softeners are used in steam boilers.
In a water tube steam boiler, unlike a fire tube, water circulates inside the tubes. The heat that is generated and the combustion gases that surround the tubes heat the water that circulates inside them. Many water-tube boilers operate according to the principle of natural water circulation.
The capacity of this type of boiler can be enhanced by increasing the number of tubes in the boiler.
In superheated industrial water boilers, the water is pressurized and boiled to 100°C producing steam. These boilers are pyrotubular, with a high volume of water and a large temperature exchange zone. The designs can adapt to temperatures and pressures according to needs.
The pressure of the steam is directly related to its temperature. So process temperature will require steam used to be at a specified pressure. For example, a process requires that needs temperatures at 150°C will require steam delivered at 6 Kg/cm2 or higher.
