Regeneration of Molecular sieve bed of dehydration unit 1

[IngGasP]

Hi!

We have a LPG plant where regeneration(Heating phase) of Molecular sieve bed of dehydration unit is performed by heated gas in mineral oil Shell-tube heat exchanger. However, a new LPG plant where construction is underway and the regeneration of the Molecular sieve bed is performed by the gas heated in Furnace(Heater)in intermittant way (Furnace works only in Reneration (Heating phase)).
If somebody has experience with this new way for me, could give me information.

Thanks

 

[ChemEngMKH]

we have the same system at our plant, what do you need to know exactly.
also the heater is on all the time what changes is its firing rate through controlling fuel gas flow.

 

[IngGasP]

Hi!

the heater is on all the time what changes is its firing rate through controlling fuel gas flow.
So, What about Thermal stress on the concrete of isolation(swinging from hot to cold or vice versa) beacuse in our old plant the working of the heater in intermittant way causes us damages on isolation layers which made of concrete(Concrete pieces damaged the burners by falling on) .
Please could you give me the working pressure value and the temperature out of this gas.Because in our new plant, our working pressure is 95barg @ 270°C out.
So, what about this high pressure in the heater because I've never seen such process.

Thanks

 

[IngGasP]

Hi!

the heater is on all the time what changes is its firing rate through controlling fuel gas flow.
So, What about Thermal stress on the concrete of isolation(swinging from hot to cold or vice versa) beacuse in our old plant the working of the heater in intermittant way causes us damages on isolation layers which made of concrete(Concrete pieces damaged the burners by falling on) .
Please could you give me the working pressure value and the temperature out of this gas.Because in our new plant, our working pressure is 95barg @ 270°C out.
So, what about this high pressure in the heater because I've never seen such process.

Thanks

 

[ports394]

I'd imagine the hot gas under pressure does a good job of scouring the bed as it expands through it. Just a guess.

 

[ChemEngMKH]

our pressure is 50 Barg with same temprature as yours.
frankly i don't know about the concrete, all i know is that we had some sort of problem with the thermal isolation for the heater and the inside of it

 

[IngGasP]

Hi ChemEngMKH!

Could you tell us What sort of problem with the thermal isolation for the heater and the inside of it?

Thanks for your professional replies

 

[ChemEngMKH]

as far as i know they had a problem with thermal stresses leading to cracking in the insulation

 

[rhylsta]

IngGasP,

We also have a Dew pointing plant that has molecular sieve beds as dehydrator. Our regeneration is similarly done through heated gas from a fired heater. I once looked through the heater and all i saw was some woolly insulation materials and not a concreted material. This fired heater has been in operation for 2 years and no problem of any sort has yet been reported. I guess this is the kind of heating system your new project might be getting.

kind regards,

 

[dcasto]

wow, at 95 barg it will take a huge amount of lpg and energy to regenerate the beds. Thats why others use 50 barg and lower.

I've never seen a heater left on like that. Typically we will turn the burner completely off and let the lpg run through the heater during the cool cycle, We did that because did not want anyway for flow to stop going through the heater when it is firing.