3 replies to this topic

[TS1979]

Hello all,

 

The process is for naphtha heating system. Two naphtha heaters are in parallel. The steam to the heaters is controlled by the naphtha outlet temperature. The condensate is collected in the condensate collection drum through a Spirax Thermo float ball steam trap. The steam collection drum opens to atmosphere to remove any uncondensed steam. From the condensate collection drum, two pitbull pumps are used to drive the condensate to the condensate drum. Pitbull pump is a simple vessel with some sensors installed. When the vessel is full, the air is turned on and pushes the condensate to the condensate drum. The pitbull pumps have not been working and condensate has been dumped to sewer with a flow rate about 60 gpm for many years!

We are trying to fix the problem. We are discussing to install a new pitbull pump system. Because of the previous experience with pitbull pumps, we are not confidence that the new pump system will work.

My questions are:

Is the pitbull pump system really needed?

 Can the condensate be directly sent to the condensate drum from the steam trap based on the pressure drop analysis, steam supply pressure, DP through the control valve, and pressure drop through the piping? What will be the potential issue if we arrange the condensate system that way?

If you need more information, please let me know.

Thanks advance for your comments.

Attached Files

•  63FV-18 datasheet.pdf   352.38KB   36 downloads
•  6-3 Naphtha Heater.xls   438KB   24 downloads

[breizh]

http://www.tlv.com/g...e-recovery.html

 

Consider this resource .

 

You may also consult Armstrong or similar vendors to support you.

 

Breizh

[Neelakantan]

let me recall my first "real" engineering work; three/four months after college and working in an oil-processing unit, my first activity was to find a solution for avoiding continuous dumping of the the steam condensate;

we have four trains of oil stabilization units each with a crude-oil pre-heater;  the heating medium was steam ; duty was to heat the crude oil from 30 deg c to 60 deg C. the heating route was simple: steam header to FCV/TCV to exchanger to condensate flashdrum to LCV to condensate header;

as per the design, the exchanger was expected to operate at 3.0 kg/cm2-g and the condensate flash drum was expected to operate at 2.5 kg/cm2-g and the header at 2.0 kg/cm2-g. but in reality the exchanger worked only when the condensate is dumped to atmosphere keeping the condensate flash drum close to atm pressure.

 

Culprit?

 

overdesign of the exchanger area and location of the exchanger in relation to the condensate flash drum. to explain more:

the exchanger was designed with low U and high delT and the original design calculations expected the steam to condense at ~145 deg C (giving a huge del T) and ~3 bar-g; but actual U is quite high and resulted in stem condensing close to 75 deg C. This resulted in the steam condensation pressure close to atmospheric and required dumping the condensate!

 

solution:

 

we looked at reducing the area of condensation /heat transfer; this was achieved by moving the condensate drum at level with the exchanger so that when the  part of the tubes are immersed in the hot condensate resulting in reduced heat transfer and increasing the del T.  Definitely not an optimal solution, but a workable one

 

regards

neelakantan

Attached Files

•  e201 original.png   34.41KB   1 downloads
•  e201 modified .png   34.77KB   1 downloads

[Supriyo Mukherjee]

Dear TS1979,

 

With my very little steam condensate experience, what I understand is you basic query is whether the steam condensate ex-steam trap can be directly dumped into sewers via pipeline an d control valve.

 

I can find no issues with that from process point of view if we have pressure drop in our hand.

On the other hand if we see what for the condensate collection drum is provided and the pump at downstream of it??

 

What I feel we are dealing with saturated steam here. Although there is a steam trap always there is a chance of uncondensed steam passing through the trap and that is why a collection drum  is being provided. Which is kept open to atmosphere so that there is no probability of two phase flow in downstream pipeline and valves.

 

I am not so so sure about control valve functioning(the valve you spoke about ex-steam trap to route to sewers) when there is two phase flow at inlet. We generally avoid them in our processes. Also once you throttle the saturated water to a lower pressure in a valve there will be two phase flow at downstream of the valve and there will be steam hammering. So in lieu of the above difficulties we may face we should go for a system that involves minimum two phase flow.

 

Regards,

 

Supriyo Mukherjee