Advanced technical solutions for mid-scale LNG production

Augusto Bulte's picture
Augusto Bulte, Director Gas Monetisation / LNG, Amec Foster Wheeler
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Over the last 50 years, LNG has become a feasible and technically proven way of transferring natural gas from production locations to consumers, with this development being driven by economies of scale and substantial advances in technology. The competitive dynamics in today’s LNG market require projects to be capable of producing low cost LNG and to reduce the construction schedules and the investment costs through innovative technologies.

Mid-scale LNG plants up to 3.0 MTPA are forecasted to be the preferred solution to monetise stranded gas reserves at a minimized investment cost. It is through that breadth of current experience that the mid-scale technology combined with modularised design provides optimised process efficiency, scalability, and plot efficiency at an attractive capital cost. In addition, one of the trends in the current LNG industry is the flexibility that exporters need to achieve in terms of LNG production.

A proposed solution consists of an engineered modular approach to provide between 0.5 MTPA to 1.5 MTPA of LNG. Such solution is based on a liquefaction “train” which may contain from one to three liquefaction modules operating in a parallel. The train would allow the flexibility to isolate any one of the modules to perform maintenance work on the system. This also allows the operator to scale their production based on gas supply or market needs by adjusting modules in operation. The flexibility of this train design also allows for the utility systems to be optimally sized based on the number of modules/trains.

Due to the targeted production capacity of each module a single-cycle mixed refrigerant (SMR) process is considered. The SMR process is mature and proven process that uses a custom mix of nitrogen and hydrocarbons that cool the natural gas until it condenses. This process provides LNG producers with the optimum combination of liquefaction cycle efficiency and CAPEX for mid-scale LNG projects. As well as this, it provides the flexibility to be scaled and, using Braised Aluminium Heat Exchanger (BAHX), it can be modularised for nominal LNG unit sizes in the mentioned range of production.

Such modular solution allows to increment production in different execution phases and is suitable for in-land operations as well as for FLNG applications.

A single gas pre-treatment unit, to remove Mercury (Hg), Hydrogen Sulfide (H2S), Carbon Dioxide (CO2) and Water (H2O), will serve for all the liquefaction units in the train and when needed. This gas pre-treatment unit can operate in a turndown mode feeding only one or two liquefaction units.

The compression system for the liquefaction train can be coupled either with aero derivative gas turbines or electric motors. The selection depends on the utilities availability and costs of the same.

The plant availability, with this proposed solution, could be over 95.5%, which indicates that such design is robust and consistent with industry standards for LNG facilities.

In comparison with a stick built solution, since this is a modular approach, the manufacturing and assembly processes are improved, as well as their schedule, by substantially limiting the amount of field installation work required to commission the facility. In addition potential savings are expected due to the lower need skilled labor at the site and also the reduction of use of heavy equipment on the field.

This solution is positioned as a simple, low capital cost and energy efficient process in the mid-scale capacity. The significant reduction in complexity and cost is achieved with a quite limited sacrifice of energy efficiency compared to existing base load plants.

The technology is also an excellent fit for expansions at existing LNG production facilities looking for a low cost, small footprint and short schedule project to take advantage of an existing surplus of gas processing capacity.

Share your insights & join the conversation: What would you identify as another stand-out innovative technology for reducing costs? Leave your comment below.

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Image courtesy of Amec Foster Wheeler