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Changing in delta pressure of effluent heat exchanger

Changing in delta pressure of effluent heat exchanger

Changing in delta pressure of effluent heat exchanger

(OP)
I work in a petroleum refining company. We have faced a problem in the middle distillates hydrotreating unit.
the change in the delta pressure for the outlet tube side of the second effluent recycle heat exchanger ( U bend tube) after the unifining reactor increased gradually from 0.2 bar to 4 bar.
knowing that ,
1. the reactor with heat exchangers have not be maintained for 20 years.
2. When we increased the capacity of the unit ,the delta pressure increased and when we decreased the the capacity ,the delta pressure decreased.
Can anybody help, why the delta pressure through heat exchanger tubeside increased ?

RE: Changing in delta pressure of effluent heat exchanger

Increase in dp from 0.2 to 4bar for a TEMA U shell is a lot and cannot be ascribed to capacity increase alone, since (4/0.2)^0.5 > 4, which means capacity increase of > 300% - highly unlikely. It may be partly due to increase in throughput and/or change in viscosity of HDT product effluent or it may be due to reactor catalyst or some other foulant blocking the tubes. Time to take this HX offline and clean the tubes.

RE: Changing in delta pressure of effluent heat exchanger

Hi,
To me the answer is in the question, the equipment needs a cleaning (as suggested), lack of preventive maintenance.
"The reactor with heat exchangers has not been maintained for 20 years".
You should have a plan to clean the equipment during turn around activity.
My 2 cents,
Pierre

RE: Changing in delta pressure of effluent heat exchanger

(OP)
The question is why the first heat exchanger doesn't suffer from the fouling or clogged tubes similer as the second one.
Is the gravity play a role in this situation?

RE: Changing in delta pressure of effluent heat exchanger

First HX temperature is probably running a bit higher than #2.
20yrs without cleaning? Really?

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

RE: Changing in delta pressure of effluent heat exchanger

Engrania,

You provide virtually no technical information.

So please provide.
Original flow rate
New flow rate
Design flowrate
Temp at innet midpoint between the two HX and exit
Pressure at inlet, midpoint and outlet.

Is this HX designed to heat or cool the fluid?

What is the fluid?

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

RE: Changing in delta pressure of effluent heat exchanger

(OP)
Original flow rate 42 ton per hour
New flow rate 50 ton per hour
Design flow rate 60 ton per hour
- pressure at inlet and outlet is shown in the document attached above
-fluid in the tube side is effluent
- fluid in shell side hydrogen
The heat exchanger is used to heat the hydrogen

RE: Changing in delta pressure of effluent heat exchanger

Sorry but the diagram only has dimensions?

What about temperatures?

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

RE: Changing in delta pressure of effluent heat exchanger

Another reason for "high dp at E1-B" may be that there is a low point piping pocket between E1-B and E2-A. Solids escaping from R-1 may be collecting in this low point pocket, giving the impression that E1-B is the location of high dp ( assuming the pressure guage is location somewhere downstream of the low point pocket). Reactor catalyst fines may be breaking through the bottom of the RX. Check the internals of the RX. Also the RX catalyst may have disintegrated through long term use or some kind of misoperation. So the solids may have deposited on the bottom row of tubes in E1-B and / or the low point piping pocket between E1-B and E2-A.

RE: Changing in delta pressure of effluent heat exchanger

Based on the information supplied you have a serious blockage / restriction in the U tube of the second HX.

Removal and cleaning or replacement of the U tube section is required.

Only then can you see what substance is causing this blockage. You don't show the temperature in the d s side of the H Xs though.

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

RE: Changing in delta pressure of effluent heat exchanger

I though i replied - but heres my 2 cents. The faouling could be percipitating at a specific temperature. out of the first HX its still to hot to percipitatate (or stick) but in the 2. it gets cold enough.

--- Best regards, Morten Andersen

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