Lean carbonate solution tank V-3 venting study

This is the process parameter study to control opening of vent, leading to loss of vapour.

1. Study on Venting of V-3 Tank

2. CONTENT Objective E-8 Design Simulation PFD After Debottleneck E-8 Design Simulation data Existing Data E-8 Existing Simulation PFD E-8 Existing Simulation data Results from Step-2 Other reasons of Overpressure Recommendations & Results Suggestion Simulation PFD, data and Outcomes

3. OBJECTIVE The main focus to find the root cause behind frequent V-3 venting was on E-8 exchanger performance. Hence the performance of E-8 exchanger has been carried out. The initial simulation was based on design conditions in order to determine the Overall heat transfer coefficient. The heat transfer area of E-8 is 255.9 m2.

4. CONTINUE …. In the first simulation of E-8 using design conditions, the cooling water flow was unknown as per MB sheet, so it was calculated using I/L & O/L temperatures of both the streams & flow rate of process fluid stream. The O.H.T.C & CW flow rate came out to be:- U=403.7 Kcal/h-m2-C & Qcw = 323.49 m3/ hr Before Debottleneck O.H.T.C was 355.8 kcal/h-m2-C & cooling water flow was 287 m3/hr.

5. E-8 Design Simulation PFD After Debottleneck

6. E-8 Design Simulation Data

7. EXISTING DATA As there were no Flow meters In both stream, we took the help of NPC to determine the flow rate of Cooling water using Ultra sonic flow meter, which came out to be 1220 m3/hr. Considering the above flow and actual temperatures, we eventually calculated the process side fluid flow i.e. 27500 kg/hr. As the value was coming very much high as compared to the design values, it was required to calculate the O.H.T.C again which results because of the change in flow rates & fouling. (U=520.9 Kcal/h-m2-C)

8. E-8 Simulation Existing

9. E-8 Existing Simulation Data

10. RESULT FROM STEP-2 In the inlet Process Stream, the vapour mass fraction was around 0.19 & after simulation, the vapour mass fraction of O/L process stream becomes zero. That means all the vapour part in the inlet stream gets condensed.

11. Other Reasons of Increase in Pressure The Exchanger performance is up to the mark as per simulation but practically there was a problem of increase in pressure in V-3 which could be because of:- High concentration of Ammonia at the inlet stream. The performance will get affected above NH3 conc. Of 48.5 wt.% Because of heavy fouling which results in vapour at O/l stream but for that to happen, the O.H.T.C value should be around 255 kcal/h-m2-C which is highly unlikely.

12. Recommendations & Results So the sample analysis of E-8 process inlet stream of both the unit were carried out and it was found after the analysis that the stream contains

13. Suggestion Simulation PFD, Data & Outcomes It was suggested to add the C-3 bottom stream into the inlet stream of E-8, so as to condense the vapour & eventually decrease the uncondensed vapour quantity as well as heat load on exchanger, For this suggestion it was considered that the exchanger performance is not up to the mark because of some unknown reasons(other than the reasons mentioned in earlier slides).

14. E-8 Simulation with C-3 stream Mixing

15. Mixer-1 Simulation Data

16. Mixer-2 Simulation Data

17. E-8 Simulation Data After C-3 Stream Mixing

18. Outcomes The motive behind this suggestion was to avoid addition of water in to the system as well as save the pumping cost of p-7 pump( C-3 bottom pump). But the vapour load is increasing a bit after adding C-3 bottom in E-8 inlet stream which is not required as increase in vapour load will further increase more problems. Also to achieve the required o/L temperature, the increase in CW flow rate is required which is already very high & is going to increase the heat load as well.

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