Industry Coal Biomass Boiler Economizer Industry boiler parts function of boiler
Coal Biomass Boiler Economizer Introduction
1. To obtain an acceptable degree of efficiency and reduce fuel consumption as much as possible by introducing further heat recovery surface so that the gas temperature at the funnel may be as low as practicable, the gas temperature leaving a boiler cannot be reduced much below 30oC above the saturation temperature.
2. In radiant types a much higher exit gas temperature is usually found. To carry out this further heat exchange, surfaces such as economizers and air heaters are commonly used.
3. In many radiant boiler types, economizers are also found arranged integrally within the boiler unit. In this location they consist of a number of multi-loop elements of plain tubes connected at their ends to inlet and outlet headers.
4. Since are situated in a hot gas temperature zone and are required to perform a considerable heat exchange duty, a portion of the water pumped through them may be converted into steam. These steaming economizers are arranged so that water enters the lower header and the steam and water mixture leaves from the top header to the steam drum where the steam and water separate.
Economizers are used externally to boilers for further heat recovery. Economizers are found in the cooler gas zone and are fed with water temperatures around 116oC or 185oC depending upon whether the feed cycle includes high pressure feed heaters after the de-aerator.
The function of Boiler Economiser
1. The Economizer in Boiler works on the principle of Heat Transfer. Heat transfer usually takes place from high temperature to low temperature.
In the case of Boilers, flue gases or exhaust from the boiler outlet are at high temperature and water that needs to be preheated is at low temperature.
2. So, this temperature difference between water and flue gases helps to increase the feed water temperature.
3. Depending on the type of operations, design of Economisers can be smoke tube type or water tube type.
4. In smoke tube type flue gases are inside the tubes and water is on the shell side while in the water tube type, water is in the tube and flue gases are on the shell side.
Boiler Economiser and Waste Heat Recovery Concept
1. Boilers are generally designed to produce steam from water. Water is converted to steam by transferring both sensible and latent heat.
2. Sensible heat is the amount of heat required to increase the temperature of water at constant pressure without changing its liquid state, while Latent heat is the amount of heat required to change the state from Liquid to Vapor at constant temperature and pressure.
3. The exhaust from the boilers is generally in the temperature range of 200°C – 250°C, so there are a huge amount of losses from the boiler if any heat recovery devices are not installed after it.
4. If the exhaust gases which are leaving the Boiler at such high temperature is made to pass through the Economiser in order to provide the required sensible heat to the water by increasing its temperature, it will reduce the heat load on the boiler to the greater extent.