The temperature of the available heat sink, often air or seawater, affects performance in many industrial processes. Low temperature processes, such as natural gas liquefaction, are particularly affected. Industrial development in the Arctic presents many challenges but has the benefit of access to a low temperature heat sink. Although several studies have considered the impact ambient temperature has on the performance of natural gas liquefaction, there is little agreement about the scale of the benefit. The present study focuses on the modeling and optimization of several different liquefaction processes. The results show that the energy consumption of any optimized gas liquefaction process will be 20–26% higher in the Middle East or Northern Australia than in an Arctic climate such as that found in Northern Norway, equivalent to a 0.8–1.3% reduction in CO2 emissions for the full gas to power chain. The performance data are also combined with worldwide sea temperature to illustrate variation by geographic location.

Carbon capture and sequestration (CCS) is a technology that can help reduce CO 2 emissions and thereby mitigate global warming. The temperature of the available cooling medium effects many of the processes relevant to CCS and in particular, low ambient temperature helps reduce the power consumed by compression and liquefaction processes needed to prepare CO 2 for transportation, e.g., in pipelines or tanker ships. The aim of this paper is to look at energy usage in different geographic locations and identify the benefits of preparing CO 2 for transportation in a cold climate. The main finding is that the pipeline alternative consumes 10−15% more energy in the Middle East than in Northern Norway and 25− 30% more if the CO 2 is liquefied. Lower temperature also offers an opportunity to simplify CO 2 compressor design. The most efficient refrigerant for CO 2 liquefaction is NH 3 (R717), but CO 2 (R744) is a practical alternative for cold climates.

Liquefaction of natural gas is an energy-intensive process in which the energy efficiency depends on the number of compressors stages and the heat integration scheme. The aim of the study is to systematically evaluate process performance of pure component cascade processes, present optimized designs for all relevant numbers of compression stages and compare energy consumption between processes with differing levels of complexity. An original method for the evaluation of process performance is developed that utilizes as little human interaction as possible, making it suitable for optimization. This study shows that a pure-component cascade process using the three refrigerants R290, R1150 and R50 must have at least 11 stages to equal the energy efficiency of the best mixed refrigerant process. An optimized configuration for an 11-stage process scheme operating at 20 • C ambient temperature is described in detail.

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