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Why should we set up two sets of water circulation with different pressures?
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Why should we set up two sets of water circulation with different pressures?

Views: 1889     Author: Site Editor     Publish Time: 2023-04-21      Origin: Site

Steady state design theory to ensure various performances. The steady state design theory provides a theoretical basis for the structural design and performance calculation of the boiler. After the design according to the steady state theory, the layout of heating surfaces at all levels of the boiler is more reasonable, the combustion is more complete, the temperature field is more uniform, and the operating parameters are highly consistent with the design parameters.

A dual pressure boiler is a boiler that has two sets of water cycles with different working pressures, producing two different types of new steam, hence it is called a dual pressure boiler. Dual pressure boilers are commonly used as waste heat boilers, with the advantage of improving the equivalent thermal efficiency of the waste heat boiler.

This is because waste heat boilers usually do not have air preheaters that recover low-temperature heat energy from flue gas, so the exhaust temperature mainly depends on the temperature when flowing through the feedwater heater.

The highest temperature of flue gas in a waste heat boiler is lower than that of a regular boiler, which leads to a smaller steam flow rate that can be generated by the waste heat boiler under the same flue gas flow rate, which is also known as a smaller steam to gas ratio.

There are node temperature differences and proximity point temperature differences in steam boilers. So a small steam to gas ratio will result in a slow decrease in flue gas temperature in the feedwater heater section after the evaporator, resulting in a higher exhaust gas temperature of the boiler.

In order to improve the thermal efficiency of waste heat boilers, dual pressure boilers have emerged. Adding another set of water circulation with lower temperature and pressure in a dual pressure boiler can effectively reduce the emission temperature of flue gas and improve the thermal efficiency of the boiler due to its low evaporation temperature.

Compared with single pressure waste heat boilers, the disadvantage is that the system is a bit complex.

In some cases where higher thermal efficiency is required, there are also three pressure waste heat boilers. The equivalent thermal efficiency is higher (although the improvement is not as significant as from single pressure to dual pressure), and of course, the system is also more complex.


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