Storage tank temperature maintenance 3

[Vishal Kumar]

Hello all ,
Can you guide me how to know utility flow rate for maintaining temperature of a storage tank at 80-85C.

Storage tank is storing a product of melting point 65C , inlet lines are electrical traced & coming at 80 C. How to do energy balance for storage tank to maintain that temperature through saturated steam at 3.5kg/cm2(g) and provided in limpet. I understand that heat loss will be through tank wall (MOC-SS316L). Please guide me.. tank size is 100 KL. Limpet or internal coil we are still working on. But sizing part need to understand. We need to unload in liquid phase to tanker for sale.

 

[EdStainless]

Is the tank insulated?
What is your worst case (lowest) ambient temperature?
Calculate your estimated heat loss, most all will be through the side walls though there will be some from the top.
Remember the wind, this is forced convection on the outside.
I would assume that the outside has the lowest heat transfer and will therefore be the limiting case.

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P.E. Metallurgy, consulting work welcomed

 

[georgeverghese]

Is this a road tanker ? Does it have on board heating to keep the liquid warm during transport? Or do you have to heat up the liquid some more with an export heat exchanger to say 100degC or so, to account for cooling during transport ?
Insulation thickness at this 100kL tank should be based on economics - use say a payout time of 3years for insulation.
Since tank MOC is SS316L and outside wall temp > 60degC, this tank would be prone to chloride induced pitting if installed outdoors if this plant is some where near the sea coast. Else use a TSA coat ( thermal sprayed aluminum coat) and cellular glass insulation to reduce the risk of pitting corrosion.

 

[Vishal Kumar]

Jacketed road tanker it will be transported in solid and melted on reaching destination

 

[shvet]

https://checalc.com/solved/tankcoil.html

https://www.chesolver.com/tank-heat-loss/

for info
dT 15°C might become not enough for unloading because of high viscosity of liquid.

 

[LittleInch]

Well 100 m3 isn't that big a tank. What are your dimensions? What type of tank? vertical, horizontal? Closed roof? floating roof?

80C is a high temperature so it becomes a hazard to personnel, never mind a waste of energy.

Depending on the size and shape of the tank, the roof and flow could be a large percent of the heat loss.

Usually sizing is dominated by the heat up of the contents if they have been allowed to cool down within a certain amount of time. The choice of that time period is crucial. The SS heating load then depends on external temps, wind, amount of insulation etc. Should be easy to calculate that.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Vishal Kumar]

It is a fixed roof tank, and i understand the concern but we have to find a way so that it never solidifies and also have a plan B which will work in case it solidifies. No agitation possible so I don't have much experience apart from limpeting or internal coil. I have considered heating 80 to 85 in an hour. What factors should I think of more?

 

[LittleInch]

You need to work out how much heat is getting lost and how much heat it is going to take to heat up your 100m3 of mysterious substance.

One hour is going to be three or four times or more the ongoing heat loss IME.

Internal coils should give you better circulation of heat, but how viscous is this stuff when heated?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

Is there any volumetric change on cooling and solidification?
This can be rough on internal coils.
But they are still my favorite for this type of application.
For transport containers it is common to very heavily insulate them, and before filling preheat them (hot air blowers) to a temp well above your product temperature. If it won't damage or boil the product I would preheat the tank to 100C so that there is no heat loss when you fill.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[MJCronin]

LittleInch ...

You should know by now that you will never get the information that you (or anyone else) needs to properly evaluate this problem...

You will never get the identity or specific heat of the liquid .... because the 18 year old OP does not understand the concept

You will never get the dimensions or tank configurations that you need because the OP doesn't really think that they are necessary .... (and that it is an extreme bother for the OP to get them)

Tell Vishna anything so that he can show his boss an answer ....

You need a flowrate Vish ?..... I say 100 gpm .... How is that, old buddy ?

MJCronin
Sr. Process Engineer

 

[LittleInch]

MJC, it always raises a smile with me when you respond and tells me you're not dead yet...



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

In bitumen tanks, in addition to the horizontal floor spiral heating coils, 1 or 2 vertical coils, extending up beyond LAH are also installed. This is to allow for heating when tank contents have frozen up. The vertical coils will create a liquid phase rat hole through which expanded hot liquid at the base of the tank ( where the main heating coils are) can escape out above LAH so the tank base doesnt bulge out and explode with the thermal expansion of the molten liquid at the tank floor. You may want to do the same for this tank.
This may be a small tank, but local cold spots are possible. The floor coils may be some 6-8inches above the floor, so the liquid below may be cooler than 80degC, given this liquid's viscosity. Do not under estimate the heat loss through the floor.
This must be some corrosive liquid. Beware of trace contaminants that may make even SS316L unsuitable.

 

[pierreick]

Hi,
Study the document attached.

https://www.chesolver.com/tank-heat-loss/

Note: MJC is right with his comments. Too often lack of basic data, little or no work from OP before asking.
Get a copy of Kern Process Heat transfer and or a copy of Perry to support your work.
Pierre

 

[pierreick]

Another document,
You should be able to translate the document.
Pierre

 

[pierreick]

last one,
Good luck.
Pierre

 

[Vishal Kumar]

Mr MJC think what you want it doesn't matter , i wanted to understand the method and not have a exact calculated answer with the data , I also didn't hide anything intentionally. You can chose not to respond instead of acting smart.

 

[Vishal Kumar]

Thank you everyone else , i will share maximum possible available data with me for next question, but please understand it was a genuine attempt because many times experience teaches a lot so i thought in this forum someone can say me things which me/team in my company may not think of at the start but come to know later. This was my thinking, and my boss already knows I ask in forums, nothing to hide and impress anyone. It's not a race which i answer will get promoted. More sense to someone who thinks so.

 

[Vishal Kumar]

We are moving ahead with thermic fluid circulation in limpet & tank inserted electrical heater bundle.

Thermic fluid already we are using as utility for a melt crystalliser, adding to the capacity.

 

[LittleInch]

Interesting mix.

I assume the limpet keeps it warm in normal operation and the electric is there for re-heat?

Otherwise seems like double the cost for the same effect?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Vishal Kumar]

Yes heater for the re-heat only. We submitted various scenarios with costing but this was accepted.