ENERGY RECOVERY FROM REGASIFICATION OF LNG

Abstract

The international forecasts on energy consumption in the next future show an increasing trend due also to growing markets, and among this the leading emerging economies connected to BRICS countries (Brazil, Russia, India, China and South Africa). We need more and more energy. On the other side the environmental problem is arising and the climate change is a more and more pressing emergency. The latest environmental disasters, as the oil spill in the Gulf of Mexico in 2010 and the earthquake with the following tsunami in Japan in 2011, struck the public opinion and so, as in many European countries, the nuclear program is under a deep revision or even stopped. So it is necessary to utilize as well as possible all energy resources. Among these resources, natural gas is undoubtedly one of the most used. A lot of gas pipelines were build, and many others are under construction or in project. At the same time many countries utilizing gas are far from production countries, for example Japan that actually is reconverting the national energy plan pushing up on natural gas. Therefore the only way to utilize gas in this countries, is to achieve it by transportation with ships, and the better way is in liquid state, so it is possible to maximize mass per unit volume. The transport of natural gas is made by gas pipeline from gas field to the harbour where are located the gasification terminal. In these industrial sites the gasification process takes place with consumption of the natural gas itself, i.e. an huge amount of energy is used in order to liquefy the gas. At the terminal of arrival, the regasification process of LNG returns it back to gas state before its transport in the pipeline network. Again energy consumption is required and, moreover, a huge amount of cold is produced. The recovery of cold may be of capital interest because it has a relevant environmental impact, usually on the sea near the regasification site, and, by an energetic point of view, it is not a suitable operation to waste a lot of energy. So it is possible to consider both the production of electrical energy recovering the energy available as cold, using the cryogenic stream of LNG during regasification as cold source in an improved CHP Plant (Combined Heat and Power), and to utilize directly cold in some suitable process where cold is need. This paper, after a survey of the natural gas market, deals with some feasible process utilizing waste cold from regasification of LNG, showing an application in order to produce electric energy and another case study which reutilize cold directly.