Regarding furnace temperature
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I work in a hydrogen production facility. Some time ago, our furnace encountered a problem that puzzled everyone. Under normal conditions, the temperature inside the furnace chamber is around 1000 degrees; the furnace tubes run through this chamber, and it is there that methane and water vapor react to produce hydrogen and carbon dioxide – it’s an endothermic reaction. On that day, the calorific value of the fuel gas used in the furnace changed, causing the furnace temperature to rise by about 50 degrees. Strangely enough, however, the temperature at the furnace outlet continued to drop, and this decline lasted for around 50 minutes. The furnace outlet temperature is certainly supposed to rise as the furnace temperature increases. Although our furnace is large and there is some lag, it doesn’t exceed 10 minutes; the opposite situation never occurs, which is quite incredible. At that time, the amount of water vapor increased for a short period of time; an increase in water vapor would cause the temperature at the furnace inlet to drop. However, the rise in the furnace temperature was sufficient to counteract this effect. Moreover, and most importantly, the outlet temperature moved in the opposite direction to the furnace temperature for 50 minutes! I hope everyone can help me figure out what’s going on; those who are aware of the circumstances at that time can share their insights. Looking forward eagerly
The calorific value of the fuel gas generally does not change; factors such as the atmosphere of reactants and products inside the furnace need to be taken into consideration
The furnace outlet temperature is influenced not only by the amount of fuel gas and the furnace temperature, but also by the amount of feedstock, that is, the quantity and type of hydrocarbon feed, as well as the temperature of the mixed feed gas entering the furnace. It is recommended to check the feed temperature and hydrogen production volume at that time; this will help identify the cause
The feed rate remains unchanged. I have also considered the possibility of changes in the composition of the feed, but we use products from upstream facilities as raw materials; if there were any changes in their composition, they would inform us promptly, so this option is essentially ruled out.
1. The amount of feed steam increases and the composition of the raw materials changes. 2. The instrument readings are inaccurate; check for changes in the water-to-carbon ratio as well as the oxygen content in the furnace. 3. Observe any changes in the steam production volume and check whether there is any internal leakage in the heat exchanger. 4. An increase in furnace temperature indicates an increase in the amount of fuel gas or a decrease in the feed material entering the furnace tubes; fewer methanation reactions occur due to a lower amount of reactants, which may result in a decrease in temperature. Examine the amount and composition of the exhaust gases at that time for further analysis
I’ve never worked on a conversion furnace, so I’m just making guesses: aside from the reasons analyzed by the friend mentioned above, could it be that there was some kind of tube interference near the thermometer used to measure the furnace temperature, or could secondary combustion have occurred around the thermometer, resulting in localized high temperatures? Also, since the steam volume increased at that time, could there have been an issue with the steam’s dryness, leading to water being carried along with it? It is unknown whether the wall temperature of the furnace tubes changes when the furnace temperature is high.