Need help with furnace technology?
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The preheating and recovery system for the heaters in our hydrogenation unit is an air preheater. At present, the temperature of the heated exhaust gas is around 135°C; however, at this temperature, condensate water still flows out from the bottom of the air preheater, on a continuous basis, with a pH value of around 3-4. What’s going on here? Theoretically, there shouldn’t be any water at 135°C, right?
This has happened to us before as well, but in our case it was due to corrosion and leakage in the wind preheater, which caused cool air to reach the bottom of the air preheater and cool the carbon dioxide and water present in the hot flue gases, thereby leading to further corrosion. We replaced the air preheater
Verify whether this exhaust gas temperature is before or after the air preheater If the exhaust temperature at the air preheater outlet can be maintained at this level, the probability of condensate formation should be relatively low. The key is to see what the flue gas temperature at the exit of the air preheater is In winter, the air temperature is relatively low; after the flue gas undergoes heat exchange in the air preheater, its temperature drops significantly, which results in the formation of condensate. If the fuel contains a high amount of sulfur, condensation will occur even at this temperature; the SOX in the flue gases raises the dew point temperature of those gases.
It is very likely that continuous water condensation was caused by structural issues with the heat exchanger of the air preheater. First, it is necessary to check whether the structure of the air preheater heat exchanger results in excessive energy loss; when the temperature rises above 135°C, water begins to evaporate and condense, and the pH value of the condensed water is lower than 3-4. To solve this problem, the heat exchanger tubes should be replaced with a structure that prevents water from flowing out before heating the hydrogenation unit. Please like it; it’s even better if you give money. God bless
1. The flue gas exhaust temperature is adjusted based on the dew point temperature of the flue gas, and the dew point temperature of the flue gas is closely related to the sulfur content in the fuel gas; therefore, it is necessary to calculate whether the dew point temperature is appropriate according to the sulfur content in the fuel gas. 2. Is the furnace operating at a low load? 3. Check whether the preheater cross-line is tightly closed.
You can try raising the flue gas temperature; there is a high possibility of leakage in the preheater. Also, check whether there are any leaks in the steam pipelines in the convection section.
The measurement point for the flue gas temperature is at the inlet of the exhaust fan, behind the preheater
Without steam, it is heat exchange between flue gas and cold air, which is divided into a high-temperature section and a low-temperature section. The air first exchanges heat with the flue gas in the high-temperature section, and then exchanges heat in the low-temperature section. If there’s a leak, how can it leak?
If there is a leak, it’s probably a leak in the air pipe, right? In that case, air gets into the flue gas, which increases the oxygen content in the flue gas – is that correct? But the oxygen content in our flue gas is not high, around 3%
This temperature is the temperature at the inlet of the induced draft fan. It is the temperature after the air preheater