[link Point to another website Only the registered members can access] We have commissioned diesel hydrotreating unit in June-2017 with capacity of 150 m3/hr EURO-4 diesel product specification.

At start of run we run the unit at design throughput 150 m3/hr. Right now the throughput is dropped to 80 m3/hr and its is decreasing day by day. We have identified the pressure profile in feed pre-heat section is disturbed (hindrance in flow). Feed pre-heat section consist of a flow controller, filter, two heat exchanger (one with two shell and one with 3 shell) in series and at last feed vessel with operating pressure of 3.5 bar. PFD is attached for better understanding. The feed pump is building pressure/head as per its performance curve but flow is restricted in feed circuit.

At start of run feed pump develop pressure of 20 bar and 150 m3/hr flow. Flow controller drop pressure from 20 to 8 bar at 50% opening. Pressure drop across filter is 2 bar and rest of the pressure drop is between exchanger and feed vessel.

Right now pump is producing 23 bar pressure and 80 m3/hr (also matching pump curve), control valve is fully open 100% (its by pass valve is also 100% open). Pressure drop across filter is 2 bar and pressure drop across first exchanger is 1 bar. So the pressure at inlet of second exchanger is 20 bar but we dont have any provision to measure the pressure at outlet of second exchanger. So it is assumed all the pressure drop is now between second exchanger and its outlet piping to feed vessel (20 to 3.5 bar main reason for decrease in flow). We have cleaned all the exchanger but no increase in flow was observed.

Kindly suggest the solution for this problem. Also suggest if all the pressure drop is across outlet piping of exchanger to feed vessel the how we can check for blockage in line (Any recommended practice) and also how to depluge line if such a huge blocka.


Muhammad Farhan
Process Engineer

See More: Diesel Hydrotreating Unit Plant Throughput Reduction