58989 - On Small Scale Lng Concepts 

The ubiquitous availability of inexpensive natural gas has spawned a large number of LNG plants. Besides plants in the multi Mtpa size, there is also an opportunity for much smaller LNG plants. These, so called small scale LNG plants. These plants typically support mining or fracking operations, truck fleets, or ships. The economics of such small scale plants are very different , as they compete with liquid fuels, like Diesel; the added advantage is in the lower emissions from LNG fuels compared to Diesel.

The different economics put more emphasis on capital expenses over process efficiency, and thus favors simpler refrigeration cycles. We typically find reverse Brayton cycles, or SMR (Single mixed refrigerant) cycles. These cycles have specific requirements to the compression equipment, and typically have smaller drivers, either electric drives or gas turbines. The relationship between output, driver size, and process preferences is explained. The type of compressors, and expanders needed are discussed, together with thoughts and the driver preferences. This includes the different control methods that can be used, both for the cycle adaptation, as well as the related control of the compressors, expanders, valves and drivers. Compressor performance maps are created to highlight required different operating conditions. This leads to typical optimization discussions.