U and Q will be much lower with PSV on tubeside inlet, since the flow path to the PSV almost completely does not pass through HX. As you said, flow in HX will be almost stagnant - it will be in natural convection mode.
a) If this LPG remains in liquid phase at relieving pressure, then design duty can be used as heat input
b) If the PSV is located on the LPG exit side of this HX, and given that Cp of LPG liquid will remain the same at relieving pressure, it is likely that LPG exit temp to the PSV will still be...
Rather than work out what T_isen will be at 360bar with a constant Cp/Cv or gamma value, given the large compression ratio, it would be better to read off what T2 will be with a T-S diagram for O2 - see fig 2-15 on page 2-263 in the 7th edn of Perry. So you dont have to worry about Cp/Cv and Z...
Its probably safest to use the lowest operating steam pressure that will enable gentle heating with less risk of thermal decomposition on the inside heating surface, and that will keep batch heating time just about acceptable.
Steam pressure at the jacket will also influence the safety relief...
There are 2 or 3 requirements for such ROs':
1) As other have pointed out, it acts to limit the gas blowby rate to be no more than the vapor handling capacity of the downstream vessel. Check if there is a possibility that 2 dump valves may be in operation at the same time.
2) It also slows...
In steam heated heat exchangers where steam temp is lower than process fluid temp, there is a risk of migration of the higher pressure process fluid into steam due to corrosion / pinhole leaks on tubes and seepage through tube to tubesheet joints. De aeration / degassing helps to vent off these...
If the skin temp on the reactor side of the jacket is too hot, you may have thermal decomposition of the reactor fluid. If this concern is valid for your application, adjust the steam temp to be below what corresponds to this limiting skin temp. Calculation of this skin temp may be complicated...
Google says typical suction lift for a gear / lobe pump is about 8m, and you wont need a foot valve in the suction line. Ask the pump vendor if the pump can dry for say a minute or so until the pump casing is filled with liquid.
As shown, this pump will work as intended only if the suction line is fully primed with liquid. Only then will it be able to lift this liquid from 40cm below. Some types of pumps in this service have auxiliary positive displacement pump that operate for a short while on startup to pull this...
You normally dont use the PSV for this emergency "dumping". Use a dedicated depressuring valve which is forced full open through the plant's safety controls. The emergency flow through this path is constrained by a restriction orifice or by selecting a globe type valve as the depressure valve...
Given the viscosity of asphalt, its better to set up a feed spreader to cover the cross section of the tank. This will also improve mixing and reduce the time for homogenisation.
The thermal designer may have picked on a higher tubeside velocity at design flow here so that at turndown, phase stratification in the tubes is still not indicated.
For a pump to "stay at a good operating point", it must be operating at constant differential pressure. This then gives you constant flow. Presume this is what you are aiming for ?
Given that you have a varying level in the source tank, the simplest way to enable constant diff pressure is to...
That foot valve is a necessity in this case, but in the long run, it will turn out to be the weak link in this priming setup. If it is stuck / jammed in some intermediate position, the suction line will not prime. Foot valves fail to work as intended due to corrosion and or bio fouling.
Tube side material should resist corrosion from condensing liquid. With such materials, velocity at 18m/sec should be okay, provided there are no erosive solids suspended in the feedgas. Overall U in this case will be constrained by shellside htc, but watch out for tubeside pressure drop.
For thermal design of and pressure drop on tubeside in partial condensors, pls refer to page 11-12 in Perry Chem Engg Handbook 7th edn. You can do a manual check of the Aspen output with these correlations.
