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Calculation of expansion of hot material cooling in tank

Calculation of expansion of hot material cooling in tank

Calculation of expansion of hot material cooling in tank

(OP)
Hi

I need some urgent help on the following.

We have a 18m3 7bar/full vac rated vessel that has a spring PRV of set pressure 125 psi and 175 l/min rated discharge.

What I need advice on is calculating required discharge rate i.e. is our PRV correct.

Material is introduced into the vessel via vacuum. The main problem comes from the two streams we have, one is vac'ed material that is ambient temperature, the other is vac'ed at ~150 deg c.

I need to check who the pressure will alter as the material cools and can the PRV cope?

I guess worste case senerio would be, when tank is nearly full of ambeint temp material i.e 15m3, we then vac in 3m3 of 150deg c material.

Vac turned off and materials mix and cool and expand.

Thanks

RE: Calculation of expansion of hot material cooling in tank

More details required;- what material would expand in the tank/vessel that much, to set off the PRV's 125 psi, starting from vacuum or 0 psig?? Obviously, you are handling an existing system, hence this is not an academic question from you;- but it is still unclear, what are you discharging at 125 psi from the 100% full vessel, gas, liquid, polymer foam, fluid butter garlic flavoured?
Please advise..
cheers,
gr2vessels

RE: Calculation of expansion of hot material cooling in tank

(OP)
Hi

I wish it was garlic flavoured butter!

We reprocess and distill all wastes containing solvents, from paints printing inks, vinaly products etc etc.

So receive drums,IBC tankers of MIXED materials.

Stream A is drums vaced into Vessel X. at ambient temp.
Stream B is still base residue x distialtion of mixed material @ ~150 deg C.

You could say that everything below toluene should have been removed.

Above streams (one at a time) are vacced into vessel X, by appying vacuum to vessel X.

We normaly then pressurise vessel x with nitrogen to trasfer to another part of the plant.

But the question is what and when could we lift the PRV.

One thought would be is we have vessel X full nearly full of material at ambient, and then we filled it to 100% with 150 deg c material.

Vacuum is then removed, but we do not trasfer it straight away.

Material cools and expands, will prv blow?

Vessel is ~18m3 3m x 3.5m.

I have already done some calcs, to verify that the current area of the PRV is more than twice required, as per API520

see below cals

Relief Area Calculation to API RP520 (2000) Appendix D                        
                        
                        
Input Data                        
                        
Case                Toluene        
                        
Relief Device Set Pressure                125    psi g    
Overpressure permitted                10    %    
Proportion of vessel filled                100    %    
                        
Vapour MW                92        
?                1.2        
Temperature                100    oC    
Heat input rate                50    kW    
Latent heat                351    kJ/kg    
Liquid density                867    kg/m3    
                        
Two Phase Discharge Rate                        
                        
Derived Parameters                        
                        
Mass flow rate of vapour                512.8    kg/hr    
?v                31.13    kg/m3    
Volumetric discharge rate                16.5    m3/hr    
Relieving pressure, Po                1,049,655    N/m2    
                        
?o                836.19    kg/m3    
vo                0.00120    m3/kg    
vvo                0.03213    m3/kg    
xo                0.00000        
cpl                2647.7    J/kg K    
vvlo                0.03097    m3/kg    
                        
Omega Value and Critical Mass Flux                        
                        
Two phase mass flow for relief                13,777    kg/hr    
?                6.8        Eqn. D.2
?c                0.91        Figure D.1
GC                10374.58    kg/m2 s    
                        
                        
Relief Area                        
                        
Relief area                0.0003689    m2    
                0.57    in2    
                        
Bursting disc diameter                22    mm    
                0.85    in    
                        
                        

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