INCREASING THE CAPACITY OF NGL RECOVERY TRAINS. Stéphane MESPOULHES XVI CONVENCIÓN INTERNACIONAL DE GAS Caracas de Mayo de 2004

Transcription

1 INCREASING THE CAPACITY OF NGL RECOVERY TRAINS Stéphane MESPOULHES XVI CONVENCIÓN INTERNACIONAL DE GAS Caracas

2 WHO IS TECHNIP? 2 World Class Engineering & Construction Group in Oil & Gas Public Company listed in New York and Paris Revenues: Billion in 2003 Staff: Worldwide Engineering Centers,, Yards, Plants and Ships

3 DIVERSIFIED MIX OF BUSINESS WORLDWIDE 3 % of Revenues 2003 ( 4.711( Billion ) Onshore + Downstream Offshore Americas 30 % 27 % Europe, Russia Central Asia 44 % 47 % 9 % Asia Pacific 10 % 33 % Africa, Middle East Industries

4 TECHNIP WORKFORCE 4 USA United Kingdom France Iberian Peninsula 290 Scandinavia Benelux 450 Germany Italy Qatar 100 Russia 100 Abu Dhabi 550 India 670 Asia-Pacific Colombia 150 Venezuela 300 Africa 150 Brazil Australia 190 OFFSHORE: 50 % ONSHORE/DOWNSTREAM: 45 % INDUSTRIES: 5 %

5 CONTENTS 5 Introduction Definition Reference projects Methodology Case studies NGL recovery train Sweetening unit Drying NGL recovery unit Propane refrigeration cycle NGL fractionation Conclusion

6 1. INTRODUCTION Commonly used method. Reduction of production costs, Step wise investment, Easy decisions and financing. 1.2 Quantitative analysis. Powerful tool to locate bottlenecks, Modeling in rating mode and CFD, 1.3 Use of new technologies. Trays and packing, Separation vessels internals, Filters and coalescers, Heat exchangers.

7 2. DEFINITION Maintaining the nominal capacity. Plant is operating successfully, Modification of feed composition, New marketing objectives, Improvement of control and operation. 2.2 Restoring the full capacity after capacity reduction. Plant starts up, Feed composition is different from design, Capacity has to be reduced, Capacity is restored or improved. 2.3 Increase the production with a stable well known feed. Targets : 20 to 30% of increase, Step wise capacity increase feasibility is established, Modifications are implemented.

8 3. REFERENCE PROJECTS OGD1, Emirates, Habshan Design capacity: Sales gas: 1060 MMSCFD NGL production: 5780 t/d Condensate production: bpd Increase of capacity: 110%

9 3. REFERENCE PROJECTS OGD2, Emirates, Habshan Design capacity: Sales gas: 1000 MMSCFD NGL production: 490 t/d Condensate production: bpd Increase of capacity: 120%

10 3. REFERENCE PROJECT GASCO, Emirates, Ruwais NGL Fractionation Design capacity: Inlet NGL capacity: T/D C2 production: 2600 T/D C3 production: 5400 T/D C4 production: 6700 T/D Condensate production: 7800 T/D Increase of capacity: Inlet NGL capacity: +6% C2 production: +23% C3 production: +38% C4 production: +33% Condensate production: -50%

11 3. REFERENCE PROJECTS PDVSA, Venezuela, ACCRO I&II Sales gas: 2 x 400 MMSCFD NGL production: 2 x 2500 t/d in ethane rejection

12 3. REFERENCE PROJECTS QGPC, Qatar, NGL3 Increase of capacity: 800 MMSCFD to 1000 MMsfcd

13 4. METHODOLOGY Basis of study. Detailed composition of hydrocarbons, Heavy end chemical structure, Impurities:Hg,Sulfur,Salts,Chemicals. Utilities: cooling water,steam, Climatic conditions. 4.2 Tests at normal and full capacity. Performances of units to tune the simulation, Pressure profiles of main circuits, Performance tests of compressors, Thermal and hydraulic tests of exchangers. 4.3 Simulation of units in rating mode. Compressors with head vs volume curves, Towers taking into account efficiencies, Non ideality of L-V separations.

14 4. METHODOLOGY CFD studies of separation vessels and towers. Detection of root causes of poor hydraulic behavior, Check new design of internals, Improve pressure drop profile. 4.5 Solutions proposed. Processing scheme without modification, Modified processing scheme, Detailed study of the proposed solutions, Comparison of the proposed solutions.

15 5. CASE STUDY 15 NGL recovery train Sweetening unit Dehydration unit NGL recovery unit Propane refrigeration NGL fractionation unit Common facilities Upstream separation Stabilization Sales gas compression Sulfur recovery units Utilities Steam or heating medium Cooling water or air cooling Electricity

16 5.2. SWEETENING UNIT General consideration : Foaming, H2S-CO2 selectivity Case study : 640 mmscfd MDEA sweetening from 80% to 105% Gas composition different from design composition : more H2S less CO2 : cold amine solution in absorber bottom. Heavy ends contamination of the amine absorber : Poor efficiency of vane pack, Poor efficiency of coalescer, Heat leaks, retrograde condensation. Design upgrade : Modified Vane pack installation, Insulation of lines, Installation of HC skimming facilities, Installation of a new separator with vane distributor and efficient mist eliminator, Modification of absorber bottom internals, Installation of higher capacity trays.

17 5.2. SWEETENING UNIT case study Figure 1-1 : Amine Unit, Initial installation LT LT LT LT V1 Separator F1 A/B/C Filter / Coalescers V2 Absorber

18 5.2. SWEETENING UNIT Case study Figure 1-2 : A m ine U nit, M odified installation Insulation and H eat Tracing Insulation High efficiency Mesh Pad Vane distributor MVG trays Chimney tray Pipe downcom ers LT LT LT LT LT Gas box V1 Separator F1 A/B/C Filter / Coalescers V3 New Separator V2 Absorber Skimming Pot

19 5.3. DRYING UNIT General consideration High water content lead to hydrates formation and plugging, Absorption in TEG (few ppm) or on Mol. Sieves (<1ppm) Case study : capacity increase by 25% Case study : Gas pretreating facilities : Gas sweetening unit, Drying with TEG followed by Mol. Sieves. Operating problems : Loss of TEG. Foaming by contamination of TEG by MDEA entrained from upstream unit. Design upgrade : Amine unit sweet gas KO drum: Vane type distributor and high efficiency mesh pad installation to avoid MDEA carry-over, Glycol contactor: Trays replaced by high efficiency structured packing & TEG high efficiency liquid distributor installation, Addition of a new vertical filter coalescer d/s TEG Contactor, to avoid loss of TEG and d/s dryers contamination, Addition of a new dryer in parallel to the existing ones, to limit pressure drop and keep regeneration flowrate and temperature.

20 5.3. DRYING UNIT Case study Figure 2-1 : G as treatm ent, Initial schem e C1 Lean TEG R1 R2 R3 R4 V1 Sweet gas Lean amine Rich TEG Treated dry gas Sour gas Rich amine Am ine treating unit Glycol dehydration M olecular Sieves dehydration

21 5.3. DRYING UNIT Case study Figure 2-2 : Gas treatment, Modified scheme F1 C1 V1 Sweet gas Lean TEG RS R1 R2 R3 R4 Lean amine Rich TEG Treated dry gas Sour gas Rich amine Amine treating unit Glycol dehydration Molecular Sieves dehydration

22 5.4. NGL RECOVERY UNIT General consideration Ethane recovery in addition to propane recovery Increase of capacity to satisfy markets NGL and NG Case study : Capacity increase by 25% Propane recovery scheme with C2 reflux modified to Ethane recovery and LNG reflux Addition of 2 heat exchangers : 304L Shell and tube : To condense NG and produce LNG reflux to the DC1 To precool NG and limit pressure drop on Treated gas Modification of the turbo expanders for increased flow rate Modification of DC1 trays in upper part Design chosen to minimize number of tie-ins and shut downs

23 5.4. NGL RECOVERY UNIT Case study Figure 3-1 : NGL recovery, Initial scheme C2 to C2= plant To sales gas compression E5 A1 K2 M X1 K1 E6 Dry Feed gas E1 Ethane reflux PR T1 T2 E2 E4 E7 C3+ to fractionation E3

24 5.4. NGL RECOVERY UNIT Case study Figure 3-2 : NGL recovery, Increased capacity C2 to C2= plant To sales gas com pression E5 A1 K2 M Dry Feed gas E12 E1 X1 K1 E11 NNF Modified Trays Ethane reflux E6 PR T1 T2 E2 E4 E7 C3+ to fractionation E3

25 5.5. PROPANE REFRIGERATION CYCLES General consideration on propane refrigeration cycles The main parameters that limit a propane refrigeration loop are the following: The capacity of the compressor or the available power on the driver, gas turbine, electric motor or even steam turbine, The capacity of the propane condenser: air cooled or water cooled exchanger, The surface of the propane vaporizers and the size of the kettle. The propane compressor is simulated in rating mode: design curves supplied by the vendor are used; these curves are sometimes corrected after shop tests. The performances of the compressor measured on site are then compared to the predicted values. It may be necessary to adjust the curves to obtain a better fit to the actual data. This can only be done with a detailed procedure.

26 5.5. PROPANE REFRIGERATION CYCLES Case study

27 5.5. PROPANE REFRIGERATION CYCLES Case study Main advantages of the selected solution: In case of shut down of the additional compressor, the unit can still run at reduced capacity. No significant increase of sea water flowrate for the existing compressor condenser (additional loop condenser is an air-cooler). Only two tie-in are required to the existing propane refrigeration loop. The new compressor and air-cooled condenser are installed outside the unit.

28 5.6. NGL FRACTIONATION General consideration on NGL fractionation units The most attractive way to debottleneck those units is to replace the trays by high efficiency trays, or high efficiency packing for the deethanizer. It is very often necessary to add surface to the condensers and reboilers. The retubing of exchangers with extended surface tubes is the more cost efficient. When the diameters of the columns are to small for the capacity increase the addition of a prefractionation column upstream of the fractionation column can be a good choice especially for the deethaniser, if it allows not to modify the propane cycle, in all other cases the addition of a new train is necessary.

29 5.6. NGL FRACTIONATION 29 In the case presented the capacity was increased by 20%. The composition of the NGL was different from the NGL composition of the one used for the initial design. The following modifications were implemented: Deethaniser: As a consequence of the increase of the ethane contained in the NGL, the condenser was retubed with extended surface tubes. The impellers of the reflux pumps were changed. The electric motor driving the pump was also replaced. high capacity trays replaced the conventional trays. Depropaniser: Condenser: a third shell was added in parallel to the other 2.The seawater flow rate was increased by 50%. high capacity trays replaced the conventional trays. Reboiler: The reboiler is a fired heater. The chimney height was increased by 5m and the air intake to the burners was modified to increase the natural draft. The burners were modified to increase their duty.

30 CONCLUSION 30 Success factors Solutions : efficient / robust / innovative Minimum production losses Schedule precisely established and exactly followed New technologies available Necessity of a Methodology Detailed analysis of Actual operation Collaboration between Client-Contractor-Suppliers When the goals are reached and difficulties surmounted, Knowledge gained, Progresses made.