• Master of Science in Mechanical Engineering (MSME) from an accredited educational establishment.
• Minimum 3 years experience in engineering aspect of rotating machinery and auxiliaries design and manufacture.
• Versatility in the application of cryogenic technology in the design and development of pump auxiliary components.
• Proven Good communication discipline to carry out assigned tasks with little supervision and proven “Team Player.”
• Company offers company paid benefits including medical, prescription, dental, vision, LTD and life insurance. Also a 401(k)

Please email your resume to hr@ebaraintl.com. Please reference the title of the Job Posting you are interested in in your email. We look forward to working with you soon.

Please email your resume to hr@ebaraintl.com. Please reference the title of the Job Posting you are interested in in your email. We look forward to working with you soon.

Benefit package includes Medical, Dental, Vision, Prescription, Life/STD/LTD and a 401(k)

Send Resume or apply in person, No Phone calls accepted.

Please email your resume to hr@ebaraintl.com. Please reference the title of the Job Posting you are interested in in your email. We look forward to working with you soon.

The annual Appreciation Dinner for Ebara Cryodynamics & Hood EIC, LLC.’s employees was held this last weekend on Saturday January 28, 2012. Welcoming over 250 employees and their guests, the annual “Ebara Prom” was a fantastic soirée, filled with beautiful atmosphere, fun, dancing and dining. With fun new additions such as a fun-photo booth, the entire experience, venue and associate camaraderie came together to deliver a tremendous success.

Thank you to all of the committee members who made the evening so wonderful, with special thanks to Sara Grunstead & Sarah Finley, who co-chaired the planning and coordination of the event, no small undertaking to be sure!

Looking forward to next year!

London ExCEL center, October 8-11, 2012.

Gastech 2012 London will bring together thousands of commercial and technical industry professionals for unrivalled networking, new business opportunities, the exchange of ideas and to showcase the latest innovations, technologies and developments across the gas value chain.

For more information, visit our Gastech Exhibitor Page: http://www.gastech.co.uk/exhibitor/ebara-international-corporation/

Fox Business Network (FBN)’s “Manufacturing Marvels” program will feature Ebara International’s Cryodynamics Division at 5:35pm PST (8:35 EST) November 2nd. These 2 minute company profiles spotlight American manufacturers, their products, as well as the companies’ processes and customers.

Ebara Cryodynamics is proud to be recognized as the foremost producer of submersible pumps and turbine expanders for the ever – growing LNG and liquefied gas industries. Recently exceeding 5600 units installed aboard LNG Carriers and land based installations, Ebara is represented at the vast majority of LNG operations in liquefaction, marine transport and re-gasification applications.

If you would more information about this topic or about Ebara International in General, please call +1-775-356-2796 and request to speak with Rachel Clerico (Marketing Dept.).

Ebara International Corporation, Cryodynamics division announces the release of their newly enhanced website, set to go live at 12:01am, Nov 1 2011. The new website includes a more thorough review of Ebara’s cryogenic pump line including more detailed visuals and descriptions of their revolutionary machines and an expanded company outline.

The new website can be viewed at the same url: www.ebaraintl.com

Ebara Cryodynamics is proud to be recognized as the foremost producer of submersible pumps and turbine expanders for the ever – growing LNG and liquefied gas industries. Recently exceeding 5600 units installed aboard LNG Carriers and land based installations, Ebara is represented at the vast majority of LNG operations in liquefaction, marine transport and re-gasification applications.

If you would like more information about this topic or about Ebara International in General, please call +1-775-356-2796 and request to speak with Rachel Clerico (Marketing Dept.).

Introduction

Cryogenic liquid expanders come in a variety of forms. Though relatively small at just over 100 units, the fleet of installed expanders features variable geometry wicket gates, variable speed operation, external air-cooled generators, submerged generators, downward flow and two-phase operation.

Previously we discussed several of the benefits of the latest configuration; an upward flow liquid expander (“On the Up” July 2010). In part two, we will take a closer look at the relations between the standard downward flow liquid expander and the two-phase expander, along with how the upward flow configuration bridges the gap between the two.

Review

An upward flow cryogenic liquid expander is, in essence, a standard submerged generator liquefied gas expander oriented in the opposite direction. Process liquid through the machine enters from the bottom and expands as it travels upward out the top, rather than the typical downward direction. This upward orientation has many benefits over the standard downward flow expander installed in today’s LNG liquefaction plants.

Upward flow allows liquid expansion to occur in its natural direction, not unlike a tea kettle or a champagne bottle. That is, the natural pressure gradient within the machine is properly aligned with gravity. Any vapor bubbles formed do not collapse under cavitation as the pressure gradient is always decreasing in the flow direction. Upward flow configuration also aids the thrust balance mechanism as the rotating assembly weight acts opposite to the thrust forces. Another benefit is the fact that the expander’s containment pressure vessel accepts the incoming flow prior to the expander inlet. This inhibits any debris in the fluid from entering the tight clearance and high velocity areas of the machine, thus protecting it from potential mechanical damage.

Finally, an upward flow expander can take advantage of operating at a lower outlet pressure, thereby providing greater liquid expansion. It is here that the opportunity of two-phase liquid expansion exists. Existing two-phase liquid expanders utilize the upward flow configuration, and by understanding how they work, a comparison to a single-phase upward expander can be viewed.

The Two-Phase Liquid Expander

In an LNG liquefaction train, liquid expanders are installed downstream of the main cryogenic heat exchanger (MCHE) to reduce the high pressure liquid gas to near atmospheric pressure for storage. This process is a near isentropic expansion which produces less residual vapor than a Joule-Thomson valve and also cools the resulting liquid. As opposed to a Joule-Thomson valve, an expander reduces the enthalpy of the liquid; exporting the removed energy as electrical power through a generator.

For the two-phase expander, the liquid pressure is allowed to expand to a pressure less than the bubble point; that is, to within the two-phase liquid-vapor region. By doing so, the greater pressure drop across the machine allows for more energy to be removed from the liquid. Before the liquid exits the machine, the majority of vapor is condensed to result in increased liquid production when compared to an equivalent Joule-Thompson expansion. Figure 1 will help to illustrate this concept.

Liquid exits the MCHE at high pressure, P2. For expansion across a Joule-Thomson valve, no work is performed on the liquid and enthalpy remains constant. The pressure is reduced to P2 (red line) within the two-phase liquid-vapor region under the vapor dome. The quality of the liquid is X2. By comparison, the pressure within the two-phase expander is allowed to reduce to pressure P1 (blue line), which is less than the desired outlet pressure P2. Energy is removed from the liquid, the enthalpy reducing from H2 to H1. Before exiting the machine, the liquid is compressed at constant enthalpy to the desired outlet pressure P2. When compared to the Joule-Thomson valve, the two-phase expander has produced the same expansion (P3 to P2), but has produced power (H2 to H1) and has condensed more liquid, the liquid quality now being at X1. Two-phase expanders produce more liquid condensate for a given mass flow, and generate usable electrical power by recovering the energy in the compressed liquid.

So just how is this accomplished? Two major components unique to the two-phase version of the cryogenic liquid expander work in harmony to produce the actions described above; the Jet Exducer and the Condensation Cone. See Figure 2.

The Jet Exducer is a rotating radial outflow turbine. The liquid enters the exducer axially (i.e. with no angular momentum) and begins to vaporize at the inlet to the exducer. As the volume of the now two-phase liquid increases, the velocity of the fluid increases resulting in a drop in pressure. The two-phase liquid exits the exducer at high velocity and at a tangential angle to the shaft thus imparting torque to the shaft. Additionally, the rotating fluid has a large kinetic energy.

This kinetic energy can be converted to static pressure in much the same way as a diffuser converts kinetic energy to pressure energy in a pump. The Condensation Cone is a static device of gradually increasing area which straightens the flow and allows diffusion to occur to the desired outlet pressure. In the case of two-phase flow, this increase in pressure results in a lower quality fluid closer to the saturated liquid side of the vapor dome.

Power Recovery

The aim of liquid all expanders, be they single- or two-phase, is to increase the economic benefit of the process train. This is accomplished by increasing the efficiency of the process by means of increasing the LNG production for a given feed gas mass. 15 years of operational history has proven that this efficiency increase is from 3-5%.

The power generated by a liquid expander is proportional to the product of the mass flow and differential pressure across the inlet and outlet of the machine.

P = Q Δp η

where,

P = power

Q = mass flow

Δp = differential pressure

η = expander efficiency

Power can be increased by increasing the differential pressure drop across the expander. An increase in power results in greater energy being extracted from the gas stream, allowing for reduced boil-off and increased LNG production.

Single phase cryogenic liquid expanders are limited in their ability to extract energy. This is due to the necessity to maintain a margin between the outlet pressure of the expander and the vapor pressure of the liquid. Typically, this margin is in the range of 4-6 bar. Two-phase expanders, by definition, do not require this margin as they operate within the two-phase region. Thus, they can accommodate a larger pressure drop and extract more energy from the liquid.

Upward Flow Expanders

The pressure margin required by standard downward flow liquid expanders is a source of unused available potential energy. If this pressure can be reduced through the expander rather than across a downstream control valve, the energy can be extracted as usable electrical power.

An upward flow expander is able to access this potential pressure energy by means of allowing a lower outlet pressure than an equivalent downward flow expander. The lower outlet pressure is possible due to the fact that the hydraulic components are positioned above the main bearings and generator. As a submerged machine, these components require a portion of the process flow for cooling and lubrication. As the pressure within the machine approaches the vapor pressure, bubble formation is formed above the main bearings and generator and drawn away from them. The natural pressure gradient of the upward flow expander works positively to allow lower outlet pressures.

By doing so, a larger portion of the total desired process expansion occurs within the expander rather than the downstream valve. Since an expander can produce more liquid condensate for a given expansion than a valve, the efficiency of the overall process is increased.

Figure 3 illustrates this concept. A standard downward flow expander reduces the pressure of the process liquid from P3 to P2 (red line). The outlet pressure P2 is some margin above the vapor pressure for the necessary protection of the machine. The total enthalpy reduction is from H3 to H2. An equivalent upward flow expander is able to operate with less margin to the bubble point, so can continue to expand the liquid to pressure P1 (blue line). The enthalpy reduction is greater (H3 to H1).

Bridging the Gap

When considering single-phase and two-phase liquid expanders, plant process conditions often dictate one type of machine over the other. Cryogenic distillation processes, such as nitrogen rejection, naturally require two-phase operation and the associated two-phase expander. Conversely, it may be necessary in an LNG process to maintain higher outlet pressures in order to feed storage tanks where run-down product pumps are not available. Here, the standard downward flow single-phase expander is traditionally used. But where process conditions vary, efficiencies are to be maximized and debottlenecking is required, the upward flow expander offers great flexibility encompassing features of both machines.

Single-phase and two-phase expanders are not radically different machines. They share most of their mechanical design features. The rotating assembly design, generator, balance mechanism and other details are common. It is in the hydraulic components of the Jet Exducer and Condensation Cone at the exit of the machine that differentiate the two-phase expander from its single-phase cousin.

Mechanically, the upward flow expander is a variation of each machine. It is a traditional expander mounted in an upward configuration; a configuration pioneered in the two-phase expander. This provides the opportunity to accommodate the two-phase Jet Exducer and Condensation Cone, if desired. These components can be retrofitted into the upward flow expander should future process conditions require.

Summary

Both types of machine, the downward flow expander and the two-phase expander have several years of successful operating history. Each has found its niche in the industry. But they are not separate and diverse machines; rather they are variations along the same expander evolutionary path. The upward flow expander fits in to this continuum to bridge the gap between traditional downward flow single-phase expander and the two-phase expander.

Figures

FIGURE 1 – Pressure-enthalpy diagram comparing a Joule-Thomson valve (red) to a two-phase cryogenic liquid expander (blue).

FIGURE 2 – Hydraulic components of a two-phase liquid expander.

FIGURE 3 – Pressure-enthalpy diagram comparing a traditional downward flow expander (red) to an upward flow expander (blue).

All figures courtesy of Ebara International Corporation.

References

1. CORDS, M., ‘On the Up”, Hydrocarbon Engineering, July 2010.

2. CHIU, C. et al, ‘Two-Phase LNG Expanders Replace Two-Phase Joule-Thomson Valves’, AIChE Spring National Meeting, 2004.

3. KIMMEL, H., ‘Two-Phase Expansion’, Hydrocarbon Engineering, December 2010.

Author

Michael Cords
Senior Mechanical Engineer
Ebara International Corporation
Tel: 775-412-6235
Fax: 775-356-2884
E-mail: mcords@ebaraintl.com

Hans E. Kimmel
Executive Director R&D
Ebara International Corp.
Sparks, Nevada USA
hkimmel@ebaraintl.com

Abstract

Floating Storage Regasification Units, FSRU, Floating Production, Storage and Offloading Units, FPSO, and Floating Drilling, Production, Storage and Offloading Units, FDPSO are floating vessels used by the offshore industry for the drilling, processing, storage and transportation of LNG or oil [Appendix]. In those used for offloading the LNG cargo to the destination in gaseous form, the LNG is vaporized in a regasification unit on board the vessel, usually using ocean water as the heat source. Due to the large temperature difference between the LNG and the environment, a substantial power recovery is available. This paper proposes and describes a two-phase fluid Rankine Cycle to efficiently recover power from the floating regasification plant. The power recovery is achieved using field proven rotating and non-rotating equipment.

Introduction

The offshore regasification process is similar to the onshore process [1], although, the design of an offshore plant shows some significant differences. Every square meter of an offshore footprint is relatively expensive since it requires the support of an offshore structure. The design has to be compact to keep the surface area as small as possible. Due to the limited space, additional risk mitigation measures [2] and HAZOP assessments are required.

The continuous motion of the vessel impacts the design of the process equipment for operation under these dynamic conditions. Rotating equipment has to be designed to withstand the additional gyroscopic forces caused by the vessel movements. The design of any equipment requires that the centre of gravity is as low as possible to increase the stability of the vessel.

The conventional regasification process for onshore and offshore plants incorporates two major elements:

• High-pressure send-out pumps to bring the LNG from storage pressure through the vaporizer to pipe line pressure.
• The vaporizer to transform the LNG into gaseous natural gas

The proposed regasification process incorporates a third element:

• The power recovery system to partially regain the input energy used in the overall process.

Figure 1 and Figure 2 show the cryogenic high-pressure LNG pump for pressurizing the fluid up to the high pipe line pressure while it is still in the liquid state.

Typical dimensions for these pumps are 4 meters in height and 1 meter in diameter, with 12 centrifugal pump impeller stages each of 300 mm diameter.

There are particular design features shown in Figure 3 for high-pressure centrifugal LNG pumps:

• The single piece rotating shaft with integrally mounted multi-stage pump hydraulics and electrical induction motor.
• The thrust balancing mechanism to eliminate high axial thrust forces on the bearings.
• The electrical induction motor is submerged in and cooled by LNG.
• The ball bearings are lubricated and cooled by LNG.

Figure 4 summarizes the general high-pressure pump design criteria.

Click here to veiw full technical paper

Ebara International has recently shipped the highest head pumps for the LNG Industry. At 13 stages, these pumps produce rated head of 3260m. These pumps will be applied to vaporizer feed service at a major LNG regasification facility soon to finish construction.

Ebara Cryodynamics is proud to be recognized as the foremost producer of submersible pumps and expanders for the ever-growing LNG and liquefied gas industries. Recently exceeding 5600 units installed aboard LNG Carriers and land based installations, Ebara is represented at the vast majority of LNG operations in liquefaction, marine transport and regasification applications.

If you would like more information about this topic or about Ebara International in General, please call +1-775-356-2796 and request to speak with Rachel Clerico (Marketing Dept.).