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This paper discusses complexities and challenges of managing boil off gas (BOG) in liquefied natural gas (LNG) liquefaction plants. Most publications in the past have focused on regasification terminals and have not addressed the area of liquefaction plants. The paper discusses the generation and management of BOG and the associated networks and machinery to manage it. BOG options available for both Greenfield plants and in debottlenecking situations are covered. The advantages and disadvantages of different options and compressor systems are covered and the concept of dynamic simulation as an analysis tool is addressed.

This paper discusses complexities and challenges of managing boil off gas (BOG) in LNG liquefaction plants. Most publications in the past have focused on regasification terminals and have not addressed the area of liquefaction plants. The paper discusses the generation and management of BOG and the associated networks and machinery to manage it. BOG Options available for both greenfield plants and in debottlenecking situations are covered. The advantages and disadvantages of different options and compressor systems are covered and the concept of dynamic simulation as an analysis tool is addressed.

High thermal efficiency of LNG liquefaction plants is of importance to minimize feed usage and to reduce CO2 emissions. The need for high efficiency becomes important in gas constrained situations where any savings in fuel auto consumption of the plant for liquefaction chilling and power generation can be converted into LNG production. The Darwin LNG Facility was the world’s first liquefaction facility to utilize high efficiency aeroderivatives and its successful operation for close to four years has increased the interest in aeroderivative based liquefaction plants. The application of aeroderivative engines allows a significantly lower CO2 footprint of about 30% compared to the use of simple cycle industrial industrial engines. Aeroderivative engines offer very attractive efficiencies where steam systems are not viable or desired by the customer. When steam systems are acceptable, a cogeneration type liquefaction facility can be attractive. Cogeneration concepts can also be used to augment the already high efficiency of aeroderivative engines. This paper will cover concepts relating to cogeneration options for LNG facilities using both aeroderivative engines and industrial engines.

In designing propane quenching systems, a number of concerns arise with the specific fluids properties, thermal, and structural behavior of the system. In this work, the fluid-based loading on a quenched piping system is examined using computational fluid dynamics (CFD). Fluids loading is assessed during an event when a propane line is liquid quenched prior to a recycle valve opening event. During the event, hot vaporous propane is quickly exhausted into the quenched pipe. The CFD studies suggest that the loading in such an event is much larger than a similar event where the line is not quenched. Several aspects of the quench are shown to increase the loads with respect to the non-quench line, and appear to be associated with two mechanisms. The first load amplifying mechanism is the reduction of sound speed in a liquid/vapor mixture. This effect impacts the axial load in the pipe, and increases it multiple orders of magnitude as compared to a pure vapor flow. The second load increasing mechanism observed was due to slug formation. It was found that when considering quench stream droplets, stratification layers are likely to develop eventually within long pipes as the velocity from the nozzles is dissipated in the large line. In the pipe investigated, the hot, high-speed vapor blows the stratified liquid into a slug. When the slug makes turns through elbows, the pipe axial load increased even more. Simultaneously, a similar scale, perpendicular load was also observed. The overall results suggest that these loading events are not small and should be considered in the structural design and layout of a quenching system. The series of results also indicates that CFD provides a valuable tool for assessing complex two phase fluid issues, in particular for the loading on a pipe.