The feed water temperature plays a crucial role in the overall performance of an industrial boiler. Optimal management of this temperature can significantly improve energy efficiency while reducing the risk of corrosion.
Water Temperature Effect on Boiler Efficiency
The colder the feed water, the more it acts as a heat sink to cool the exhaust gases. This characteristic can enhance the boiler’s efficiency by lowering the temperature of the escaping gases. See the technical bulletin on combustion efficiency as a function of exhaust gas temperature.
Risks Associated with Water That Is Too Cold
Despite the benefits of cold water, it has a major drawback: a higher level of dissolved oxygen. When this water is heated in the boiler, the dissolved oxygen is released as gas, which can accelerate internal corrosion processes.
Oxygen penetrates the spaces between water molecules without altering their molecular bonds. However, as the temperature increases, these bonds weaken, allowing the dissolved oxygen to escape. This process exposes the internal surfaces of the boiler to an increased risk of corrosion, potentially reducing the equipment’s lifespan and leading to additional maintenance costs.
Optimal Feed Water Temperature
To minimize the risks of corrosion while enhancing boiler efficiency, it is crucial to maintain an optimal feed water temperature. This involves balancing the reduction of exhaust gas temperature with the limitation of dissolved oxygen in the water.
Moreover, a temperature too close to saturation may cause cavitation in the feed pump. In general, the optimal feed water temperature for the boiler is 180°F.
Deaerator Role
Devices such as degassers can be used to remove dissolved oxygen before the water enters the boiler. Degassing is carried out mechanically and thermally within the equipment. The feed water temperature at the degasser outlet is typically 227°F.
Prevention of Pressure and Water Level Losses
If too large a volume of water enters the boiler at an excessively low temperature, there is a risk of interrupting boiling, which results in a loss of pressure. This sudden cooling can also cause a sharp drop in the water level, potentially triggering safety alarms and shutting down the boiler, thereby exacerbating the issue.