Power Recovery in LNG Regasification Plants

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1 Power Recovery in LNG Regasification Plants Harry K. Clever Director of Sales Hans E. Kimmel Executive Director R&D Ebara International Corporation Sparks, Nevada, USA 2010 INTERNATIONAL LNG WEEK ON EMERGING TECHNOLOGIES AND PROJECTS THE 16 TH GLOBAL ENERGY DIALOGUE ON , SHANGHAI, CHINA

2 Harry K. Clever is Director of Sales at Ebara International Corporation. Mr. Clever is an experienced and successful global business manager in the field of energy equipment and technologies. He is the connecting link between manufacturer and customer. EBARA International Corporation Cryodynamics Division Hans E. Kimmel is Executive Director for Research and Development at Ebara International Corporation. He holds a Master Degree in Mechanical and Process Engineering and a PhD from Munich, Germany. His main contributions are primarily in the LNG technology.

3 EBARA International Corporation Cryodynamics Division Company Profile Established in 1973 Manufacturer of custom engineered liquefied gas pumps and expanders Located in Sparks, Nevada, USA Division of Ebara Corporation of Japan 7500 m² factory with a modern, dedicated liquefied gas test facility ISO 9001 Certified

4 Company Profile Headquarters and Factory, Sparks, Nevada, USA

5 Headquarters and Factory, Nevada, USA

6 Ebara LNG Test Facility in Nevada

7 Ebara LNG Test Facility in Nevada

8 Experience Over 5500 submerged motor liquefied gas pumps and expanders built to date Leader in all three levels of the LNG industry: Liquefaction Process pumps Loading pumps Liquid expanders Two-phase expanders Transport Cargo pumps Emergency pumps Regasification High-pressure send-out pumps Circulation pumps

9 LNG Regasification Process Liquid Natural Gas is unloaded from LNG vessels at the receiving terminal and stored in insulated tanks at atmospheric pressure and a temperature of 111 Kelvin. For regasification and distribution the LNG is pumped to high pressure and then heated to vaporize into its gaseous state. The heat to regasify the LNG is provided by sea water using the heat naturally stored in the sea or by other heat sources.

10 Cryogenic high-pressure LNG pumps pressurize the fluid while it is still in the liquid state

11 Pump General Design Criteria Liquid Model LNG 6ECC-1212 Pump Design Pressure [bara] Lowest Design Temperature [ C] -168 Operating Temperature [ C] -147 Rated Flow [m³/hr] 287 Rated Differential Head [m] 2396 Design Specific Gravity.417 Maximum Specific Gravity.451

12 Typical dimensions for high-pressure LNG pumps: 4 meters in height 1 meter in diameter 12 pump stages with 300 mm impeller diameter

13 Particular design features for high-pressure LNG pumps: Single piece rotating shaft with integrally mounted multi-stage pump hydraulics and electrical induction motor Thrust balancing mechanism to eliminate high axial thrust forces on the bearings Electrical induction motor is submerged in and cooled by LNG Ball bearings are lubricated and cooled by LNG

14 Power Recovery LNG re-gasification plants are large heat sinks and require also large heat sources. The differences in temperatures between the heat sources and the heat sinks are in the range of 170 Celsius providing the pre-conditions for an efficient power recovery. The Rankine Cycle is a thermodynamic cycle which converts heat into work. The heat is supplied externally to a closed loop with a particular working fluid, and requires also a heat sink. This cycle generates about 80% of all global electric power.

15 Power Recovery using a Rankine Power Cycle The ideal Rankine Cycle consists of the following four processes: 1 2 Isentropic compression to high pressure in a pump 2 3 Constant high pressure heat addition in a boiler 3 4 Isentropic expansion in a turbine expander to low pressure 4 1 Constant low pressure heat rejection in a condenser

16 Rankine Power Cycle with vapour expansion

17 Rankine Cycle with liquid-vapour two-phase expansion

18 Thermodynamic Efficiency of the Rankine Power Cycle Specific work input to pump: w in = h 2 h 1 Specific work output from expander: w out = h 3 h 4 Specific heat input from 2 to 3: q in = h 3 h 2 Net power output: w net = w out w in The thermodynamic efficiency of the ideal cycle is the ratio of net power output to heat input. η therm = w net /q in η therm = 1 (h 4 h 1 )/(h 3 h 2 )

19 Schematic of Rankine Cycle with two-phase expansion

20 Schematic for Power Recovery Using a Cryogenic Working Fluid with a Pump Two-Phase Expander Generator For the power recovery in LNG re-gasification plants the proposed cryogenic working fluid for the Rankine cycle is liquefied propane gas. To achieve a higher efficiency the liquefied propane gas is passed through two heat exchangers and one set of a pump two-phase expander generator, a compact assembly of a pump, a two-phase expander and an induction generator integrally mounted on one rotating shaft.

21 Schematic Description with Rankine Power Cycle 1 2 With work input, the pump pressurizes the liquid single phase working fluid from low pressure to high pressure 2 3 The pressurized working fluid is heated by passing through the generator and the heat exchanger with the heat provided by sea water or other heat sources 3 4 The pressurized and heated working fluid expands from high pressure to low pressure across the two-phase expander generating a work output 4 1 The low pressure working fluid passes through a heat exchanger with the heat sink, the LNG for re-gasification. The working fluid condenses from liquid-vapor two-phase to liquid single phase.

22 The compact assembly of a Pump Two-Phase Expander Generator consists of a pump, a two-phase expander, and an induction generator integrally mounted on one rotating shaft.

23 Pump Two-Phase Expander Generator Working fluid enters the pump at the lower inlet nozzle, exits the pump to the side and passes through the generator housing cooling the generator, thus recovering the heat losses of the generator. After passing through the heat exchanger with the heat source, the working fluid expands across the two-phase expander generating work driving the pump and the induction generator

24 Pump Two-Phase Expander Generator In this modified design, the pressurized fluid passes directly from the pump through the generator housing cooling the generator, then exit to the side and passing through the heat exchanger. In both designs, the leakage through the seal and the thrust is minimized due to equal pressure on both sides of the seal and opposing directions of the thrust forces.

25 Advantages of the compact assembly The expander work output is larger than the pump work input and the difference in work is converted by the generator into electrical energy The losses of a separate pump motor are eliminated The losses of the induction generator are recovered and used as heat source to heat the working fluid in addition to the heat from sea water and other heat sources Any leakage of the working fluid is within a closed loop and occurs only between pump and expander

26 Advantages continued Any leakage of the working fluid is minimized due to equal pressure on both sides of the seal, and small leakages are within a closed loop and occur only between pump, expander and generator. The axial thrust is minimized due to opposing directions of the thrust forces decreasing the bearing friction and increasing the bearing life.

27 Existing Field Proven Two-Phase Expanders Cross section of a Two-Phase Liquefied Gas Expander inside pressurized containment vessel with lower inlet and upper outlet nozzle Rankine power cycle 3 4 Isentropic two-phase expansion to a lower pressure

28 Two-Phase hydraulic assembly with nozzle ring (red), turbine runner (yellow), jet exducer (green) and two-phase draft tube (metallic) 3 4 Isentropic two-phase expansion to a lower pressure

29 Nozzle Ring with converging nozzles generates high-velocity vortex flow

30 Reaction turbine runner converts angular fluid momentum into shaft torque

31 Jet Exducer A radial outflow turbine for power generation by isentropic two-phase expansion to lower pressure

32 Two-Phase Expander Draft Tube for pressure recovery

33 Power Generation with Ideal Liquids The generated theoretical maximum mechanical specific power per mass P max of expanders driven by ideal liquids is equal to the product of specific volumetric flow per second v s and the pressure difference Δp between expander inlet and outlet. P max [J/(kg s] = v s [m 3 /(kg s)] Δp[Pa] 33 Thermo-Fluid Dynamics of Two-phase Expanders

34 Power Generation with Real Fluids For expanders driven by real fluids, like compressible liquids, gases, and liquid-vapour mixtures, the specific volume v in m 3 /kg is not constant and changes with the momentary pressure p and the enthalpy h. v = v[h,p] 34

35 The theoretical maximum differential enthalpy dh for a small differential expansion pressure dp is described by the following differential equation dh = v [h,p] dp The generated theoretical maximum specific power is then calculated by integrating this differential equation for Δh = h[p]. The corresponding power output in kj/s is Δh in kj/kg multiplied by the mass flow in kg/s. Thermo-Fluid Dynamics of Two-phase Expanders

36 Field Experience with Liquefied Gas Two-Phase Expanders Two-phase rich liquid feed expanders installed in 2003 are operating successfully at PGNiG, Odalanów, Poland. Additional two-phase expanders are installed in the feed to the lower column during Field Experience

37 Two-Phase Liquefied Gas Expander at Ebara Manufacturing

38 The presented Rankine Power Cycle, incorporating a compact design consisting of a pump, a two-phase liquefied gas expander and an induction generator, integrally mounted on one single rotating shaft, offers an efficient and economical power recovery for LNG re-gasification plants

39 Thank You