The synthesis gas is converted into methanol in a Linde isothermal reactor.
Methanol Synthesis in an Isothermal Reactor
Linde utilizes its own isothermal reactor for methanol synthesis. This is a fixed bed reactor cooled by coiled pipes. Its catalyst filling is cooled and maintained at optimum operating temperature through steam production in the pipe interiors.
The Linde isothermal reactor represents one of the most effective and successful developments of the recent past. The objective of the development was the creation of a reactor that offers at least the benefits of a pipe reactor, however avoids the head storage problems of a straight-pipe reactor. The catalyst conducts the reaction heat to a cooling pipe bundle embedded in the catalyst embankment, making it possible for the process to operate at optimum temperature. This results in higher performance, lower quantities of catalyst, fewer by-products as well as the efficient reclamation of reactor heat with lower reactor costs.
The design of the Linde isothermal reactor is based on the long familiar construction principle of the spirally wound heat exchanger, such as the ones used for decades as heat exchangers in cryogenic high-pressure applications and RECTISOL® washes. This type of heat exchanger is produced on our own shop floor and has acquired great technological and commercial significance in the recent past in applications for natural gas liquefaction units in base load plants. This is why there are reference applications and manufacturing facilities for a considerable spectrum of reactor sizes.
The Linde isothermal reactor has thus far been used in nineteen plants world-wide, among them eight methanol plants.
Linde has been a licensee of ICI (today: Johnson Matthey) for its low-pressure methanol synthesis and distillation processes since 1984. The ICI methanol technology is the market leader and, in combination with the isothermal reactor, represents an ideal system for methanol synthesis and distillation.
Gas-Heated Reformer
Some of the methanol plants built by Linde procure raw gas through integration with other synthesis gas plants. Because Linde also builds plants for CO production, our customers acquire from a single supplier the feedstocks of an acetic acid plant thanks to the simultaneous integration of methanol synthesis and CO production.
Large-scale methanol plants, however, call for an independent synthesis gas production based on the requirements of a methanol plant. This solves the machine drive concept while simultaneously producing an ideally composed synthesis gas. A "green field" methanol plant of this kind ideally has access to two-stage synthesis gas production, the second stage of which uses oxygen for the production of synthesis gas. Only the use of oxygen can generate an advantageous H2/CO ratio, which limits the loss of purge gas.
In principle, either a steam reformer or a gas-heated reformer is suitable for the first step of synthesis gas production. The combination of a secondary reformer with oxygen and a gas-heated reformer is called a Tandem reformer and provides very low energy consumption. In this case the machine drives are powered by electric motors and imported electricity.