Exhaust gas temperature is a key indicator of a boiler’s economic operation. A high exhaust gas temperature means reduced heat exchange efficiency in the boiler, which, over time, can decrease the economic performance of the operation. This is a common issue in boiler systems. According to related formulas, every 10-15°C increase in exhaust gas temperature results in a roughly 1% decrease in boiler thermal efficiency, meaning exhaust gas heat loss increases by 1%.
The main reasons for high exhaust temperature are:
- Severe air leakage
Air leakage occurs when air escapes from the furnace, flue, or other areas due to poor welding quality or other factors, which is a significant contributor to elevated exhaust temperatures in boilers. Specifically, furnace air leakage typically happens at the furnace top seal, the fire viewing port, the manhole door, and the sealing water tank at the bottom of the furnace. Flue air leakage happens when external air enters through gaps in the furnace wall or flue during negative pressure operation, with the most significant effect being from air leakage at the furnace bottom. This air leakage increases the exhaust volume, consequently leading to higher heat loss during exhaust.
- Excessive Excess Air Coefficient
The air coefficient greatly impacts boiler combustion and thermal efficiency. A high air coefficient increases the exhaust gas emissions, leading to more heat loss. This also raises the power consumption of the induced draft fan and blower, reducing thermal efficiency. Choosing the right air coefficient minimizes energy losses and boosts boiler efficiency, ensuring safe operation. When the load changes, adjust the fuel and air supply to modify the combustion conditions accordingly.
- High Moisture Content in Fuel
Moisture in fuel makes ignition difficult and lowers the combustion zone’s temperature. This can prevent the fuel from burning completely. For every 5% increase in moisture, heat loss decreases boiler efficiency by around 0.5%.
- Scaling, Ash Deposition, and Slagging on the Heating Surface
Poor water quality or high fuel moisture can cause scaling, ash deposition, or slagging on the boiler’s heating surface. These issues reduce heat transfer efficiency between the heating surface and exhaust gas. As a result, the exhaust gas cannot cool down properly, raising the exhaust temperature.
To solve this problem, Shandong Bokk Tech designed an elliptical tube air preheater. This design is different from traditional round tubes. After some time in operation, tests showed that elliptical tubes have better external flow characteristics, lower drag resistance, and a longer heat transfer perimeter. The heat exchanger structure is also more compact, leading to much better heat exchange performance.
About Us
Shandong Bokk Tech is dedicated to solve the problem such as ash blockage, corrosion and excessive exhaust gas temperature in the tubular air preheater of small and medium-sized boilers. We primarily manufacture automatic cleaning devices for tubular air preheaters and corrosion-resistant heat pipes. Our products are widely used in the thermal power plants, chemical plants, new energy sector, etc.
We offer customized services to customers around the world, allowing us to adjust product dimensions and other specifications based on your specific needs, to improve air preheater heat efficiency.
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