Improved LNG Production Using Process Controlled Two-Phase LNG Expanders

Transcription

1 Improved LNG Production Using Process Controlled Two-Phase LNG Expanders KBR Paper 2260 China International LNG Conference June 2011 Beijing, China

2 Gilbert LGM Habets Consultancy & Engineering Services C&ESWA Subiaco, WA 6008, Australia David W. Cameron Vice President Business Development Ebara International Corporation Sparks, Nevada, USA Coauthors Chen-Hwa Chiu Senior Technology Advisor Chevron Energy Technology Company Houston, Texas, USA LNGCHINA Speakers Arindom Goswami Senior Principal Engineer KBR UK Ltd. Greenford, Middlesex, U.K Hans E. Kimmel Research and Development Ebara International Corporation Sparks, Nevada, USA

3 The liquefaction of Natural Gas requires a significant amount of energy for the refrigeration process

4 Cryogenic LNG Expanders reduce this amount of energy for the liquefaction process by replacing the Joule-Thomson throttling valve with a near isentropic expansion across a cryogenic liquid expander

5 Large 2.6 MW Cryogenic LNG Expander for Algeria, Skikda, at the Ebara Test Stand in Sparks, Nevada, USA

6 In existing older LNG plants with a liquefaction capacity of 100% the pressurized condensed LNG is passed across a J-T throttling valve reducing the pressure to storage conditions

7 The pressure reduction across the J-T valve produces 10% undesirable LNG vapour and only 90% of the liquid LNG is delivered to the storage tank

8 Liquefaction Process without LNG Expander for Existing Older Plants

9 By replacing the J-T valve with a cryogenic LNG expander the amount of undesirable LNG vapour is reduced from 10% to only 5%, and in existing older plants 95% of the liquid LNG is delivered to the storage tank

10 Liquefaction Process with Retrofitted LNG Expander in an Existing Older Plant

11 In a projected new LNG plant with a contractual delivery capacity of 100% LNG, the entire liquefaction plant has to be sized for 110% capacity if the LNG pressure reduction occurs across a J-T valve

12 Projected New LNG Plant with J-T valve Requires 110% Liquefaction Capacity to achieve 100% LNG Delivery

13 If in a projected new plant the LNG pressure reduction occurs across a cryogenic LNG Expander, the entire liquefaction plant has to be sized only for 105% capacity for a delivery of 100% LNG

14 Projected New Plant with LNG Expander Requires only 105% Liquefaction Capacity to achieve 100% LNG Delivery

15 Cryogenic LNG Expanders have been in operation for more than 15 years LNG Expanders remove energy from the LNG stream by converting the pressure into electrical energy decreasing the total power consumption

16 There are three basic designs of LNG expanders Single phase liquid expanders in downward flow Single phase liquid expanders in upward flow Two-phase liquid-vapour expanders in upward flow

17 Expander design in downward flow Generator Rotor Generator Stator Thrust Equalization Mechanism (TEM) Fixed Geometry Inlet Guide Vanes Runners

18 Expander designs in upward flow for liquid single phase LNG for liquid-vapour two-phase LNG

19 There are three basic control options for LNG expanders Variable speed with fixed guide vanes Adjustable guide vanes with fixed speed Variable speed with adjustable guide vanes

20 The performance of LNG expanders under the three different control options is shown in the following flow / head graphs The curves N are the no-load curves for the de-energized generator mode The curves L are the locked-rotor curves The curves T are the typical turbine performance curves for constant speed

21 Typical performance for variable speed with fixed guide vanes

22 Typical performance for adjustable guide vanes with fixed speed

23 Typical performance for variable speed with adjustable guide vanes

24 Control Summary Variable speed control moves the operation points in vertical direction Adjustable guide vane control moves the operation points in horizontal direction Variable speed control combined with adjustable guide vane control increases the operational field in all directions

25 LNG expanders with combined variable speed and adjustable guide vanes optimize the performance within a wide range of flows and differential heads, and are called Process Controlled LNG Expanders

26 Outlet Condensation Cone Exducer Fixed Nozzle Vanes Runners Adjustable Nozzle Vanes Thrust Equalization Mechanism Generator Inlet

27 Fixed Axial Nozzles Return Vanes Runner Adjustable Nozzle Vanes with Actuator Inlet Thrust Equalizing Mechanism Adjustable guide vanes at the inlet

28 The adjustable guide vanes are located at the inlet of the first expander stage. They are remotely controlled by an actuator

29 Cryogenic actuator for adjustable guide vanes

30 Process Controlled Two-Phase LNG Expanders reduce the enthalpy of the pressurized condensed LNG by expansion close to an ideal isentropic process. Two-phase expanders reduce the portion of the LNG vapor and increase the production of the liquid LNG directly proportional to the removed power.

31 This additional amount of condensed LNG depends on the interaction between the momentary process data and the process controlled operation of the two-phase expander

32 Hydraulic Assembly for Two-Phase Expanders

33 Process Controlled Two-Phase LNG Expanders increase the production of LNG directly proportional to the generated power. Each Megawatt of generated power increases the production by 60,000 tons/year.

34 Thank you for your attention! Gilbert LGM Habets Chen-Hwa Chiu Arindom Goswami David W. Cameron Hans E. Kimmel