Liquefaction

Exergy Exergy efficiency Comparison criteria a b s t r a c t In a hydrogen liquefier the pre-compression of feed gas has generally higher stand-alone exergy efficiency than the cooling and liquefaction sub-process. Direct comparison of liquefiers based on overall exergy efficiency and specific power consumption will favour those with a higher portion of pre-compression. A methodology for comparing hydrogen liquefaction processes that compensates for non-uniformity in feed specifications has been developed and applied to three different hydrogen liquefiers. The processes in consideration have been modified to have equal hydrogen feed pressure, resulting in a more consistent comparison. Decreased feed pressure results in generally higher power consumption but also higher exergy efficiency, and vice versa. This approach can be adapted to the boundary conditions that the liquefaction process will be subject to in a real energy system. ª

In 2013, over 500 million metric tons of Iron Ore Fines (IOF) were transported around the world using bulk carriers. Under certain conditions IOF, while being transported, can possibly undergo liquefaction. Since 2006, there has been eight reported bulk carrier casualties possibly caused by the liquefaction of IOF. The objective of this study is to evaluate, compare and verify the limitations and relevance of the Proctor/Fagerberg, Flow Table and Penetration test methods that are used to determine the Transportable Moisture Limit (TML) of IOF. The TML is the maximum gross water content that bulk cargoes, including IOF, may contain while being transported at sea without being at risk of liquefying. A thorough literature review, along with laboratory research, was carried out to compare the TML results from the three leading test methods to determine whether they produce reliable results when testing IOF. The study concludes that the three test methods, as stated in the 2012 International Maritime Solid Bulk Cargoes Code, are unverified and therefore not appropriate for testing IOF. This is due to the variation in the results produced by the three test methods and also due to the difference in the physical properties of IOF when compared with the materials that were originally intended for testing. It is noted that the TML alone may not control the potential liquefaction of IOF and further studies, regarding the physical properties and system variables, which cause the material to liquefy, are required to determine the liquefaction potential of IOF.

Earthquake excitations often cause an increase in pore water pressure in contractive sands resulting in liquefaction, which can lead to catastrophic consequences. Therefore, it is imperative to assess the earthquake-induced excess pore water pressure and deformations to evaluate the post-earthquake serviceability of the important structures such as earthen dams. The analyses are usually performed using the equivalent linear method or the non-linear method. The purpose of this research is to evaluate and compare the excess pore water pressure and associated deformations predicted using these two methods of analyses. Two numerical models of a typical zoned earthen dam were subjected to two earthquake time-history data with significantly different frequency contents to comprehend the differences in the outcome. The analyses results are similar for dams with dense sand shells when subjected to low-intensity earthquake excitations with the predominant frequency significantly different from the first natural frequency of the structure.

A number of countries have recently discovered and are developing oil and gas reserves. Policy makers in such countries are anxious to obtain the greatest benefits for their economies from the extraction of these exhaustible resources by designing appropriate policies to achieve desired goals. One important theme of such policies is the so-called local content created by the sector—the extent to which the output of the extractive industry sector generates further benefits to the economy beyond the direct contribution of its value-added, through its links to other sectors. The use of industrial policy in the petroleum sector to support broad-based economic growth is hardly a new trend in the oil and gas sector. Local content policies (LCPs) were first introduced in the North Sea in the early 1970s and ranged from restrictions on imports to direct state intervention in the oil sector. Over time the aim of LCPs has evolved from creating backward links (that is, supplying input to the local economy through transfer of technology, the generation of value-added in domestic supply sectors, the creation of local employment opportunities, and increasing local ownership and control) to creating forward links link (that is, processing the sector’s output prior to export through, for example, the establishment of refineries, petrochemical industry, and the production of fertilizers). While LCPs have the potential to stimulate broad-based economic development, which is necessary to alleviate poverty and achieve the United Nation’s Millennium Development Goals (MDGs), their application in petroleum-rich countries has achieved mixed results. The use of specialized inputs and the technological complexity of the petroleum sector often limit the possibility of developing backward and forward links into the local economy. An economy that is very limited can hardly be expected to quickly supply services (let alone build forward links). A fast-growing petroleum sector coupled with too ambitious local content targets may exacerbate supply bottlenecks arising from increased aggregate final demand. This would ultimately affect employment and output trends in other sectors of the economy, create distortions and inefficiencies, and in some cases even promote corruption. Furthermore, the size and location of petroleum projects also affect the type of potential links, and the speed at which they can efficiently develop. The use of LCPs raises a number of questions:

What exactly is “local content”?
What is the extent of local content in the oil and gas sectors?
Why is increasing local content good for development?
What types of policies can be used to encourage an increase in local content?
What are the costs and benefits of introducing such policies?
How can the implementation of such policies be monitored and how can their impacts be measured?
What are the lessons to be learned from oil- and gas-producing countries that have implemented policies to increase local content?
This study serves to introduce the topic by describing policies and practices meant to foster the development of economic links from the petroleum sector, as adopted by a number of petroleum-producing countries both in and outside the Organisation for Economic Co-operation and Development (OECD).