Can the temperature of natural gas flue gas be reduced to below 100°C for use?
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Friends, when natural gas is used as a fuel for heat exchange, due to process-related reasons, the flue gas temperature remains around 230°C, which results in significant waste when it is discharged. Could it be considered to use the residual heat in the flue gas to heat the air, thereby reducing the amount of natural gas used? After all, natural gas is a very clean fuel; there is basically no SO2 in the flue gas, so there is no risk of corrosion of materials due to low-temperature SO2 condensation. Please discuss whether the flue gas temperature can be kept below 100°C and what the economic implications would be Has it been implemented before? Please share your experience in this regard. If it drops below 100 degrees, condensation water will form – will this increase the heat transfer coefficient? This post was last edited by zhyl1129 on 2009-3-31 19:25.]
If your natural gas is very clean, I think it’s feasible. As for whether condensation water will form, that would depend on the partial pressure of water vapor. The effect of the heat transfer coefficient needs to be analyzed comprehensively; the formation of water vapor increases the heat transfer coefficient, but I can’t say by how much.
The natural gas flue gas can be reduced to below 80 without any problem.
I’ve never tried reducing the flue gas temperature below 100 degrees; the lowest temperature achieved was 170 degrees. I think the economic efficiency in such a scenario would be poor, as the average logarithmic temperature difference decreases by several times, which means the area required would have to increase significantly. But you still need to count it yourself in detail. Even with condensate water, the heat transfer coefficient does not increase; the amount of water is so small that it hardly flows at all, and the heat transfer coefficient of water is still lower than that of steel.
1. Reducing it to 100 degrees poses no major problems from a theoretical or practical standpoint, but the economic efficiency will be very poor, as the gas-to-gas heat transfer coefficient is too low. 2 If there is condensate, it will increase the heat transfer coefficient; however, condensation also increases the heat exchange amount, so the effect is more or less the same. Condensation can be ignored in calculations. 3 It is recommended to first use a finned heat exchanger to transfer heat from the flue gas to water, and then use water to transfer that heat to the air; alternatively, a plate-fin heat exchanger can be used directly.
As for the method to be used for heat transfer, this is an issue that needs to be discussed; using heat pipes to enhance heat exchange is one option, as the efficiency of gas-to-gas heat exchange is indeed too low.
Using a heat pipe heat exchanger is a good choice. Especially in cases of gas-to-gas heat exchange at low temperatures
There should be no major issues if the flue gas temperature is reduced below 100 degrees, but economic considerations need to be taken into account when deciding whether to use existing equipment or invest in new one.
It can be kept below 100 degrees; energy should be utilized properly without being wasted, as it has many applications. There are also various types of such devices available, such as tubular heat exchangers and plate heat exchangers that can be welded together