VX Cycle - Frequently Asked Questions

Why is the VX Cycle more efficient than other LNG production systems?
The VX Cycle is a Methane Expansion Cycle, which can operate with a single compressor, which pressurizes the “product” NG as well as the “refrigerant” NG. By contrast, Nitrogen Expansion or Mixed Refrigerant cycles require two compressors, one for the NG and one for the refrigerant. The single compressor in VX will always be more efficient than two separate compressors in other cycles.

Also, the “liquefier” in the VX Cycle is a methane-to-methane heat exchanger, which results in closer “approach temperatures” than the methane-to-refrigerant heat exchangers in other cycles.

Does VX need access to reliable grid power?
No, VX can operate with its entire kW need provided by a small portion of the feed NG, including off-gases from the front-end clean up system. In most cases, that internal power production feature will yield lower cost and more reliable power than power purchased from the grid.

What is the highest efficiency of the Cycle?
The VX Cycle will yield more than 82% LNG from the feed NG, with less than 18% used to run the plant. Under some conditions, the Cycle can yield more than 85% product with less than 15% of the feed NG used as fuel. Beyond that, under some circumstances, as much as 90% of the feed NG can be converted to product, with less than 10% used to fuel the plant.

Is the VX Cycle sensitive to high ambient temperatures?
No, VX is much less sensitive than other options to high ambient temperatures. For example, unlike Mixed Refrigerant cycles, VX will not lose efficiency during hot summer days.

Why is the VX Cycle less costly than other options?
The single compressor in VX will always be less expensive than the two compressors required in other cycles. Also, at no point in the VX Cycle does any system need to operate at pressures above, say, 400 psi. By contrast, all other cycles require some portions of the process to operate at much higher pressures, requiring more expensive heat exchangers, piping and valves.

Additionally, the higher efficiency of VX will yield a lower CAPEX/unit of LNG, even if the absolute CAPEX was the same as another cycle’s.

Does the VX Cycle need make-up fluids?
No, VX does not need any consequential make-up fluids, such as refrigerants, because the Cycle uses NG as both the refrigerant stream and product stream. Any minor seal losses are made up from the feed NG. VX avoids the need for the purchase and periodic delivery of fluids and the need for on-site fluids storage.

Can the VX Cycle be deployed at low-pressure sites, such as at flares?
Yes, the single compressor design of the VX Cycle can handle feed NG at any pressure, including atmospheric pressures at flares.

Must the feed NG to VX be “pipeline quality?
Low-CO2, pipeline quality NG is the best feed NG for VX and for other system. However, the VX Cycle front-end clean up system can handle high-CO2 feed NG.

Also, if the feed NG contains a significant amount of heavier hydrocarbons (such as propane, butane, etc.), VX can produce two separate streams, an LNG stream that contains mostly methane and some heavier hydrocarbons as well as an NGL stream that contains mostly heavier hydrocarbons and some methane.

Which is better economically, an NG pipeline extension or a VX Cycle deployment that sends product by truck to off-pipeline customers?
In almost every case, if the pipeline extension needed to serve one or more new customers is more than 20 km long, the VX Cycle will yield a much better Internal Rate of Return (IRR) and a shorter payback period than a pipeline extension.

At more than $3,000,000 / km, a 20 km pipeline extension will cost more than $60,000,000, which is unsupportable unless the extension serves a large-enough customer base. By contrast, a much smaller capacity VX Cycle, serving one or two customers with relatively modest NG needs, can be built for a fraction of the cost of a pipeline extension, in a quicker time frame.

How clean is the VX Cycle LNG production process?
The VX Cycle will always have a lower emission profile (on a per unit of LNG basis) than any other cycle because VX is more efficient.

Additionally, the CO2 removed from the feed gas during pre-treatment and the CO2 emitted by the on-site power production system are both suitable for Expansion Energy’s patented VCCS technology, which converts CO2 into carbonates. Those carbonates can produce additional revenues,

With European carbon avoidance credits above $100/metric ton, the cost of producing LNG with VX + VCCS, yielding zero CO2 emissions, is becoming economically viable.

What is the smallest practical VX Cycle deployment?
The VX Cycle can be cost effective at feed gas flow rates of as little as 300,000 standard cubic feet per day (SCFD).

What is the largest practical VX Cycle deployment?
VX can be built at any scale. However, most deployments will benefit from multiple, modular production trains, with each portion processing, say, 10,000,000 SCFD of feed NG.

How much storage capacity is recommended at each VX Cycle deployment?
The need for on-site storage will vary, project by project. Two-days worth of production may be adequate storage capacity for some projects, but three-days or more may be needed where the LNG is “critical” from the customer’s point of view and/or where the feed gas flow may, on occasion, be disrupted.