Catalyst Mixer Temeperature Control 1

[Instr13]

Hi,
For preparing catalyst we are using a 7' ID by 9' T/T Carbon Steel mixing tank with agitator at around 30 % height of the vesssel from the bottom. Vessel is vertical. We are going to install temperature element to measure and control the fluid (mixed) temperature at 25 (±5) deg C. A 4" flange available on the head.
1- Do we need thermowell? or stilling well.
2- What type of sensor (RTD fast response or thermocouple)? and how many?
3- Should we look into multipoint temperature measurement for this 9' high vessel.
Any suggestion is appreciated. Thanks

 

[m777182]

The response speed depends on heat transfer from liquid to the RTD. There are layers of different materials that resist the transfer: a stagnant layer of the liquid around the well, the wall resistance of the well, resistance of the liquid or air in the well, the wall of the metal sheath around the sensor, the ceramics around final RTD winding or whatever.It is good practice to apply a thermowell from the side of the vessel:you can change the probe even if the vessel is full, it is mechanically protected and you can fit the material of the well if there is a problem with corrosion. For good dynamics you should provide good Reynolds number around the well.For good heat transfer the well should be filled with some liquid or grease with excellent heat transfer properties.When choosing the RTD look for the one with small time constant.With good aggitation temperature in the vessel will be more or less homogeniously distributed. With additional sensors you will be confused with differences in readings that cannot be assigned to real diferences in temperature. A volume of a liquid like that cannot change its temperature very quickly unless we talk about runaway or ...explosion.
M777182