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Heroes of Chemical Engineering (Part 6): Carl von Linde

[caption id="attachment_1110" align="alignright" width="231"]Carl von Linde in 1868 Carl von Linde in 1868[/caption]

This month’s Hero of Chemical Engineering connects the Lutheran Church, beer and liquefied air. He became a knight in 1897 and his invention won the Grand Prix at the 1990 World Exposition in Paris. His Name: Carl Paul Gottfried Linde (1842 – 1934).

The rebellious son of a preacher man

Linde was born in a village in northern Bavaria, Germany, in the summer of 1842. Carl’s father wanted for his son to follow his own footsteps and become a Lutheran minister. His interest lay elsewhere, though, and in 1861 he started studying engineering in Switzerland at the Eidgenössische Polytechnische Schule (today’s ETH Zurich). These were exciting times, both in technology as in society, and Linde was expelled from the university after participating in a student protest.

Very successful start of an engineering career

Even though he had not graduated, one of his professors, the father of kinematics, Franz Reuleaux, helped him find a job in the industry in Bavaria. Shortly after he moved to Berlin to work for the Borsig locomotive company. Working in a booming industry and proving his skills, he quickly was offered the position as head of the engineering department of the new Krauss locomotive factory in Munich. After moving there, he learned of the soon-to-be-opened University of Technology and applied as a lecturer. That was in 1868, so it happened that he instructed students only 4 years after he had been expelled from his own studies. He received a full Professorship of mechanical engineering 4 years later.

Here is where BEER comes into play

His research went mainly into the area of refrigeration and he designed refrigeration plants that were commercially successful. They revolutionized the brewing industry making it possible to produce Lager beer - with need to be fermented at 0 – 5°C - not only in winter but all year round. Linde’s research in heat theory led him to the invention of the first reliable and efficient compressed-ammonia refrigerator. Ice used to keep food cold was in many areas replaced by the machines from Linde’s Company Gesellschaft für Lindes Eismaschinen Aktiengesellschaft. It was founded after he gave up his professorship in 1879 to focus on his business activities and development of new cooling technologies.

Back to the drawing board

Business was good for Linde in the 1880s, by 1890 he had sold 747 machines to breweries, slaughterhouses and storage facilities throughout Europe. In the 1890s Linde went back to teaching in Munich and developing new refrigeration cycles. A driver for innovation was once more a beer company: The Irish brewery Guinness in 1892 was seeking a machine that could produce liquid CO2. Linde had never built a machine like that, but accepted the order nonetheless, developing a new process.

Linde's Liquid Air

During this development it occurred to him to exploit the Joule-Thomson-Effect to cool the gases. This effect describes the cooling of gases as they pass through a valve, reducing the pressure. Linde later recounted: Happy and excited, we watched the temperature drop according to the effect described by Thomson and Joule, even after we had far surpassed the limits within which those researchers had worked. It took three days for the apparatus to get cold enough, but when it finally reached that point, on 29 May 1895, von Linde was jubilant. With clouds rising all around it, the pretty bluish liquid was poured into a large metal bucket. The hourly yield was about 3 liters. For the first time on such a scale air had been liquefied, and using tools of amazing simplicity compared to what had been used before, he wrote. Linde was knighted in 1897, so he was Carl von Linde from then on.

Improvement and industrial use

The inventor soon improved his machine, reducing start-up time and increasing yield and efficiency. At the 1900 World Exposition in Paris, it won the Grand Prix. To separate the liquefied air into it’s components, Linde added a rectification column in 1903. That made him the first to produce relatively pure oxygen on an industrial scale. That paved the way for the invention of the oxyacetylene torch that revolutionized metal cutting and welding in the construction of ships and skyscrapers. The development of synthetic fertilizers by Fritz Haber and others also led to a great demand for nitrogen, the other product of air separation. Other areas of use for nitrogen soon became light bulb production and biology research that used liquid nitrogen to freeze samples.

The rest is history

Linde’s air separation was the right invention at the right time. His company thrived, survived the Great Depression and is today, as Linde AG, one of the big 4 companies dominating the world market for gases and processes that produce gases. The US branch of Linde, today called Praxair, separated from the main company after World War I and is one of the other one of those 4. Combined, today those two companies employ more than 90.000 people worldwide.

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22 January 2016