Improved LNG Production Using Process Controlled Two-Phase LNG Expanders KBR Paper 2260 China International LNG Conference 28-30 June 2011 Beijing, China
Gilbert LGM Habets Consultancy & Engineering Services information@ceswau.com C&ESWA Subiaco, WA 6008, Australia David W. Cameron Vice President Business Development dcameron@ebaraintl.com Ebara International Corporation Sparks, Nevada, USA Coauthors Chen-Hwa Chiu Senior Technology Advisor chen-hwa.chiu@chevron.com Chevron Energy Technology Company Houston, Texas, USA LNGCHINA Speakers Arindom Goswami Senior Principal Engineer arindom.goswami@kbr.com KBR UK Ltd. Greenford, Middlesex, U.K Hans E. Kimmel Research and Development hkimmel@ebaraintl.com Ebara International Corporation Sparks, Nevada, USA
The liquefaction of Natural Gas requires a significant amount of energy for the refrigeration process
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
Large 2.6 MW Cryogenic LNG Expander for Algeria, Skikda, at the Ebara Test Stand in Sparks, Nevada, USA
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
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
Liquefaction Process without LNG Expander for Existing Older Plants
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
Liquefaction Process with Retrofitted LNG Expander in an Existing Older Plant
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
Projected New LNG Plant with J-T valve Requires 110% Liquefaction Capacity to achieve 100% LNG Delivery
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
Projected New Plant with LNG Expander Requires only 105% Liquefaction Capacity to achieve 100% LNG Delivery
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
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
Expander design in downward flow Generator Rotor Generator Stator Thrust Equalization Mechanism (TEM) Fixed Geometry Inlet Guide Vanes Runners
Expander designs in upward flow for liquid single phase LNG for liquid-vapour two-phase LNG
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
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
Typical performance for variable speed with fixed guide vanes
Typical performance for adjustable guide vanes with fixed speed
Typical performance for variable speed with adjustable guide vanes
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
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
Outlet Condensation Cone Exducer Fixed Nozzle Vanes Runners Adjustable Nozzle Vanes Thrust Equalization Mechanism Generator Inlet
Fixed Axial Nozzles Return Vanes Runner Adjustable Nozzle Vanes with Actuator Inlet Thrust Equalizing Mechanism Adjustable guide vanes at the inlet
The adjustable guide vanes are located at the inlet of the first expander stage. They are remotely controlled by an actuator
Cryogenic actuator for adjustable guide vanes
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.
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
Hydraulic Assembly for Two-Phase Expanders
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.
Thank you for your attention! Gilbert LGM Habets Chen-Hwa Chiu Arindom Goswami David W. Cameron Hans E. Kimmel