Liquefaction Process Evaluation

Liquefaction Process Evaluation

Introduction from LNG12 (1998) presented

by Mr. Vink of SIOP

entitled as

“COMPARISON OF BASELOADLIQUEFACTION PROCESSES”

Feb 2008

1. Study Premises

1) 3-4 MTPA LNG Production Capacity with Two Trains2) Compare 5 Processes, i.e. C3 MR, Cascade, Dual MR, Single MR, and

Nitrogen Expansion, including Capex view3) Including Pretreating, common Fractionation and Utilities4) LNG Storage and Loading outside of study scope5) Located at onshore and tropical area6) Feed gas at 60 bara and 25 deg.C, and following composition:

N2 1.5 mol%CO2 2.2C1 85.1C2 6.5C3 3.0C4 1.2C5+ 0.5

7) Air Cooling and ambient temperature 27 deg.C8) LPGs reinjection to LNG

2.1 Schematic Flow of C3 MR

2.2 Schematic Flow of Cascade

2.3 Schematic Flow of Dual MR

2.4 Schematic Flow of Single MR

2.5 Schematic Flow of Nitrogen Expansion

Tem

per

atu

re (°C

)

Enthalpy difference (kcal/mol)

-100

-40

20

-60

-80

-20

0

-120

-140

-160

1000 2000 3000

Natural Gas

C3 Cycle

MR Cycle

3.1 Cooling Curve of C3 MR Process

Te

mp

era

ture

(°C

)

Enthalpy difference (kcal/mol)

1000 2000 3000

-100

-40

20

-60

-80

-20

0

-120

-140

-160

Natural Gas

Propane

Ethylene

Methane

3.2 Cooling Curve of Cascade Process

4.1 Main Rotating Equipment

4.2 Main Heat Exchanger

4.3 Power Generation (excluding spare)

5. 1 LNG Production (t/day/train)

5.2 Specific Power (kW/t/day-LNG)

5.3 Efficiency

6.1 Indexed Capex

6.2 Availability and Annual Capacity (two trains)

6.3 Indexed Specific Costs

7. Conclusion

The Propane/MR process appears to be the best choice within the premises of this comparison study, viz. large capacity LNG trains, employing air cooling in a tropical climate. Other promising processes are the Dual Mixed Refrigerant process and the Single Mixed refrigerant process. Shell is further investigating several variations of these three processes.

The Cascade process appears to be relatively expensive, partly disadvantaged as it is by the study premises. Under colder conditions (arctic, water cooling) the capacity comes closer to the C3/MR capacity.

The pre-cooled Nitrogen Expansion process is not an economic choice for a large, onshore application. It may be an alternative for smaller scale offshore applications (absence of hydrocarbon refrigerants).