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History of Natural Gas Liquefaction

History shows us how the present circumstances have evolved; every new development builds on previous situations. The demand for gas has developed with the demand for energy in general. Technical progress led to the development of the liquefaction of gases, and after this process had been realised for various gases, so it became possible to liquefy natural gas, too. That was followed by the development of storage and transport methods for the liquefied natural gas (LNG), which in turn evolved into a global LNG market. The history of LNG outlined in sections 2.1 to 2.4 below is essentially based on the book by Matthias Heymann: Engineers, markets and visions - The turbulent history of natural-gas liquefaction [1].

2.1 Industrialisation and Energy Demand

The process of the industrialisation of the production of energy, iron and steel, which began in England and reached the rest of Europe in the early 19th century, required a transition from wood-fired ovens and waterwheels to coal and oil as the energy sources. The start of the 20th century saw another considerable rise in the demand for oil and gas; oil was used as a fuel for many different means of transport, as a fuel for heating and as a raw material for the petrochemicals industry. The widespread use of natural gas did not come about until pipeline technology had been established, which then led to an increase in gas consumption in the USA during the 1930s and in Europe after 1945.

At first, gas was used for lighting only. The destructive distillation of coal produced gas and coke. This synthetic gas was therefore known as coal gas or, indicating its usage, town gas. It gave off a much brighter light and brought about a considerable change to people's living and working conditions, as they were no longer reliant on daylight alone. The operation of gas lighting was, in many respects, unchartered territory. It called for a complex infrastructure that was linked with high costs, a restriction to just one supplier for a defined area, political approvals and also society's acceptance of this new form of energy. Economic operations required the signing of long-term contracts so that the costly investments could be recouped. Municipal or national bodies were set up in order to prevent monopolies from being abused.

The first gasworks were built in Europe in 1812 (London and Amsterdam) and in the USA in 1816 (Baltimore); the first German gasworks followed in 1826 (Berlin and Hannover). During the second half of the 19th century, competition for the gasworks appeared in the form of petroleum and electric lighting, to which the gasworks responded by creating new usage options such as heating, cooking and the provision of hot water. As the type of usage shifted from lighting to heating, so very pronounced fluctuations in consumption appeared between summer and winter (which exceeded a factor of five). In the 1920s a new welding method enabled the use of seamless pipes for pipelines, meaning that it was now possible to transport natural gas over greater distances. Pipeline networks were built in the USA which connected the gasfields of Texas and Louisiana with the centres of population in the north-east of the country.

Gas consumption in the former West Germany increased from 2 billion m3 in 1964 to 16 billion m3 in 1970. This rise is connected with the changeover (or "conversion") from town gas to natural gas. Matthias Heymann [1] calls this a "complex systemic change", because it involved much more than just changing the type of gas. Instead of small, local gas networks run by the municipalities, there was now a supraregional network with new pipelines that joined the local networks together. These new networks also needed high-pressure pipelines to bring the gas from the supplying countries and intermediate compressor stations to generate the pressure gradient. And last but not least, the appliances of the end consumers had to be converted or renewed. Conversion work in the former West Germany was carried out between 1967 and 1972.

The reasons for changing over to natural gas were its better gross calorific value (roughly twice that of town gas) and its much cleaner combustion with fewer pollutants and less carbon dioxide. During this process of growth and industrialisation, two opposing requirements emerged for operators aiming to guarantee availability: base load and peak load. The base load problem was that consumption was growing faster than new sources of gas could be brought online or pipelines laid. However, this disparity eased over time. The peak load problem arose due to the use of gas primarily for heating and the associated, very distinct, seasonal fluctuations. Suppliers had to expand their existing and create new storage capacities. One option was to liquefy the gas and store it in the form of LNG.

2.2 The Beginnings of Gas Liquefaction

We have to go back a few centuries to find the beginnings of gas liquefaction. By the end of the 18th century it had become possible to convert gases into their liquid state through a combination of pressure and cooling. In the first half of the 19th century, all known gases - with the exception of oxygen, hydrogen, nitrogen, nitrous oxide, carbon monoxide and methane - could be liquefied. Around 1860, the prevailing view was that a gas could only be liquefied when its temperature dropped below a temperature specific to that gas - its boiling point. The liquefaction of oxygen was first achieved in 1877 by Louis Cailletet in France and Raoul Pictet in Switzerland working independently of each other. Cailletet discovered a physical phenomenon of gases which we call expansion. This means that the temperature of a gas subjected to a high pressure drops considerably when its volume is increased and hence the pressure is suddenly reduced. It was already generally known that gases heat up when subjected to high pressure.

If the two methods were now combined, i.e. first pressurising the gas, then waiting until the gas had cooled to the ambient temperature and, in a third step, increasing its volume, the gas could be cooled below the ambient temperature. The cooling achieved is proportional to the pressure applied. Cailletet's method was based on the fact that by controlling the magnitude of the pressure, it was possible to achieve the cooling required for the particular type of gas. Using this method it was possible to liquefy small amounts of oxygen at -183°C and nitrogen at -196°C. Pictet's method was based on the same physical principles. His idea was to arrange the cooling processes in series, as a cascade. In doing so, he made use of the different boiling points of different gases. In the first stage, a combination of pressure, cooling and expansion was used to liquefy sulphur dioxide. This liquid sulphur dioxide was then used as a coolant for carbon dioxide, which was subsequently expanded and hence liquefied. In the following cascade stage, the carbon dioxide was used as a coolant to liquefy oxygen. Although Pictet's method required different coolants, it worked with a lower pressure. Over the coming years, no further methods were developed, instead industrial usage and applications were improved. The precursors to Linde AG and Air Liquide were founded.

Natural gas, the main constituent of which is methane, was first liquefied by Godfrey Cabot in the USA in 1915. However, natural gas consists of other constituents apart from methane which liquefy or solidify at temperatures much higher than the boiling point of methane (-162°C). Therefore, natural gas liquefaction plants require various stages to purify the gas by removing these constituents, which would otherwise impair the liquefaction process and clog the plant. It was many years before natural gas liquefaction could be operated on an industrial scale.

In 1937 H. C. Cooper, president of the Hope Natural Gas Company, initiated studies of the liquefaction, storage and regasification of natural gas. A small pilot plant was built in Cornwell, West Virginia, to test the method. A cascade process was chosen, with water, ammonium and ethylene as the coolants. Trial operations began in early 1940 and continued uninterrupted for four months without any problems. At the same time, north-eastern USA experienced a very cold winter, which presented many suppliers with difficulties in trying to cover the peak load. Therefore, the East Ohio Gas Company, a subsidiary of Hope Natural Gas, decided to build a natural gas liquefaction plant, storage tanks and a regasification plant in Cleveland, Ohio. Three double-wall spherical tanks, with cork as insulation, were built to store the gas; each tank was 17 m in diameter and thus had a capacity of 2500 m3. The Cleveland plant had a total capacity of 41 million m3 of natural gas and was therefore the first large natural gas liquefaction plant in the world; it went into operation at the start of February 1941. At times of low gas demand, LNG was produced and stored, and when demand increased, the LNG was regasified and fed into the network. No malfunctions occurred during the first year of operation and so it was decided to increase the total capacity by building a further tank. The new tank No. 4 was planned with a capacity of 4500 m3, which would increase the capacity of the plant by 80%. A spherical tank was seen as unsuitable for a tank of this size, and so a 23 m dia. x 12 m high double-wall, cylindrical, flat-bottom tank was designed. Like the spherical tanks, the inner container of...