Abelló Linde Centenary Book

The discoveries were always the consequence of the succession of a series
of scientific discoveries. In 1895 Linde improved on Dewar’s system and offered
the possibility of making industrial use of his discovery by reducing its cost, and
the capability of multiplying production. In order to give more stability to the liquid
gas and permit a continued process of liquefaction of the air, he resorted to
continued isenthalpic expansion (the Joule-Thomson effect), i.e., to a system that
kept the liquid air obtained impenetrable to heat, without doing any exterior work,
and which continued to produce it.
According to the Linde process, the atmospheric air was compressed to 200
atmospheres and was cooled with an external agent – ammonia. This cold air was
deposited in a copper coil with a narrow tube, from where it passed to a second,
wider coil around the first. The compressed air reached lower temperatures due to
its free expansion upon passing to a wider tube. In this way the compressed air
turned liquid when it reached a temperature of –190 degrees. Part of the cooled
air was allowed to escape through a third coil, with which its cooling was
accentuated. To compensate for the lost air, and the lower volume, which was
produced when it liquefied, there was a compressor with two cylinders that
absorbed more air from the atmosphere, compressed it to 200 atmospheres and
restarted the process.
Liquid air is a transparent substance, pale blue in colour with a density
similar to that of water. In itself it had no special use, although it was used in
medicine as a refrigerant and an anaesthetic. The main application of liquid air
was the obtainment, by fractioning, of oxygen and nitrogen, its chief components.
This system was based on the fact that each of these elements had its own
temperature for liquefaction.
The Linde procedures soon reached Barcelona, a city well tuned to what
was happening in Europe. The machines and devices of the German engineer had
been presented in December 1900, at the same time as Doctor Eugenio
Mascareñas Hernández, Professor of Chemical Science at the University of
Barcelona, was giving a lecture on liquid air at the Academy of Science and Arts in
Barcelona. That month, in fact, Wagner’s opera Siegfried opened at the Gran
Teatre del Liceu, proof that German science and culture went hand in hand and
were well received in Barcelona.
In 1902 Linde published the paper The manufacture of oxygen through the
vaporization of liquid air, in which he explained the system that his company
would be using. In 1905 the first air separator was set up in Höllriegelskreuth
(Section B) using the genius’s work on oxygen, according to his patents. Once the
liquid air had been achieved, they proceeded to the separation of the components
in a rectification column.
As the liquid air evaporates, the proportion of oxygen increases, until it
represents an overall majority. When the recommended degree of purity has been
reached – 97 or 98% oxygen – the gas is sent to compressors that do the job of
filling the containers destined for consumption. They are steel bottles, able to
withstand high pressures.
Isidro Abelló and the German genius. The oxygen industry 35