Temperature Profile of Side fire furnace convection section

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MJA
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Temperature Profile of Side fire furnace convection section

Post by MJA » Wed May 03, 2017 7:15 pm

Hi,
I want to know about the temperature profile of side fire furnace convection section.
My question is " At our plant (Halder Topsoe), the top temperature (bridge wall temperature) of convection section is 1125 C while as this gas travelled towards the 1st convection section exchanger (Process gas pre-heater) E-201, the temperature at its up stream decreased itself to almost 1015C. We have three fertilizer plants and the temperature profile is almost the same. Although there is no source of heat transfer between these two temperature indications and the total distance of gases is almost 13ft.

Please share your experience.

chinh
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Re: Temperature Profile of Side fire furnace convection section

Post by chinh » Fri May 05, 2017 6:44 am

Dear Mr MJA.
The same my plant (Holder Topsoe). The top temp of convection 1110C, but up stream E201 about 900C. We have not found root cause. May be, leaking from false air dampers or thermalwell (at up stream E201) is so shot. We have plan to check it in the upcoming stop.
BRgd!

rajneesh_jauhari
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Re: Temperature Profile of Side fire furnace convection section

Post by rajneesh_jauhari » Sat May 06, 2017 3:37 pm

Diverging flue gas temperatures of Side Fired Furnace are seldom reliable. The only really reliable temperature is the stack temperature due to well mixing with flue gas blower. We can say, the process gas side temperatures are more reliable and accurate. You may calculate them on the basis of the process side conditions, the stack temperature and an estimated flue gas flow based on the excess O2 level at Stack and Reformer furnace dog house top sample point.

AshishMoon

Re: Temperature Profile of Side fire furnace convection section

Post by AshishMoon » Sun Jun 25, 2017 12:23 pm

MJA wrote:
Wed May 03, 2017 7:15 pm
Hi,
I want to know about the temperature profile of side fire furnace convection section.
My question is " At our plant (Halder Topsoe), the top temperature (bridge wall temperature) of convection section is 1125 C while as this gas travelled towards the 1st convection section exchanger (Process gas pre-heater) E-201, the temperature at its up stream decreased itself to almost 1015C. We have three fertilizer plants and the temperature profile is almost the same. Although there is no source of heat transfer between these two temperature indications and the total distance of gases is almost 13ft.

Please share your experience.
Hi,
We are getting (topsoe technology-Side fire burners) temp of 1050 oC at E201 upstream and around same at top temp of convection section. Some times at upstream of E201 temp may be on higher side due to post combustion.
As there is no heat exchange in between convection top section to upstream of E201, temp should not decrease to that extent. We have two thermocuples at upstream of E201 and readings are matching. In your case process calculations on Primary reformer can give you the expected temp at upstream of E201.

cstevenlancaster
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Re: Temperature Profile of Side fire furnace convection section

Post by cstevenlancaster » Thu Aug 03, 2017 10:24 pm

I don't know the specifics of your furnace, or where the thermocouples are located, but there is a phenomenon where bare wire thermocouples often register lower than the actual temperature, depending upon where they're located. If there is a cold heat sink in the area, the fluegas temperature can fall significantly due to reradiation from the thermocouple - the thermocouple never actually heats up to the actual fluegas temperature before this reradiation, so the temperature reads low. This difference can easily be up to 100 deg C.

There are a couple ways to figure out what's going on. One would be to use a velocity thermocouple to get a more accurate measurement. This may be difficult. Or, another way would be to close a heat and material balance around the furnace so you can calculate what the temperature really is at those points.

MJA
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Re: Temperature Profile of Side fire furnace convection section

Post by MJA » Tue Jan 01, 2019 6:30 pm

Thanks to all for sharing your valuable views.

bedmonds
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Re: Temperature Profile of Side fire furnace convection section

Post by bedmonds » Sun Jan 06, 2019 11:16 pm

Hi MJA,
One factor is what the thermocouples "view". I presume in the H-T design the bridgewall T/C's see the primarily
refractory that is at 1100 deg + while upstream of the mixed feed coil they see refractory on one side and the MF coil at perhaps 550 deg C on the other. and the flue gas sees both surfaces as well. A rough calculation of heat flux both radiant and convective produces temperatures close to your findings but my figures are quite rough.

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