On the gas side the ongoing energy transition discussion towards a CO2 neutral economy mainly deals with the following gases: Natural Gas (CH4 methane), carbon dioxide (CO2) and Hydrogen (H2).
Methane is the simplest carbon hydrate available in abundance. Carbon dioxide is the main product of every combustion process. In addition, hydrogen is one of the most important energy sources for the energy transition.
In all the discussion on alternative energy sources and energy carriers as fuels it becomes obvious that at least for a transition period of around 20 years there are many applications which still require liquid fuels. Liquid fuels with their high volumetric energy density are especially required in energy demanding applications such as heavy transportation on land (trucks) and sea (cargo ships) and, also due to certification reasons, in aviation (airliners).
The three gases mentioned before offer possibilities to generate synthetic fuels and materials from. Depending on the educts and products, these processes are commonly called Power-to-Liquids, Power-to-Plastics, Gas-to-Liquids or Power-to-Gas.
The core of all these synthesis processes is a reactor. The feedstock and the desired product determine the mixing ratio, the operating pressure and temperature, and, most important the suitable catalyst(s). Catalysts are elements which lower the required activation energy for chemical reactions. Solid catalysts are preferred, as they are much easier to separate from the product stream than fluid ones. They often belong to the group of metals, e.g. copper - zinc oxide - aluminum oxide catalysts for methanol production or cobalt, ruthenium and iron for the Fischer-Tropsch process.
The latter process was developed to industrial maturity in the 1920s, with Mülheim in the coal rich Ruhr Area and the founder of nowadays NEUMAN & ESSER member “Andreas Hofer Hochdrucktechnik” playing an important role in the process. Originally intended to lower the dependency of coal rich countries from foreign oil supply (Coal-to-Liquids) this process now offers an excellent basis for the production of long- and short-chained hydrocarbons from non-fossil sources. The reactor feedstock, the so-called syngas (synthesis gas) consists mainly of H2 and CO in a mixing ratio of around 2. The multi-step reactions to carbon hydrates themselves are exothermal, so temperature control of the process by cooling is important to ensure the desired product distribution. Typical products of the process are fuels like gasoline, kerosene as well as solid waxes and paraffins, all of them of very high purity. This allows the production of tailor-made fuels free from Sulphur or other contaminants with the possibility to insert special additives for an improved combustion behavior, e.g. lowering the smoke spot number or NOx emissions. For plastics production the obtained carbon hydrates can be polymerized or combined with other elements.
To achieve carbon neutrality or even a carbon capturing effect it is important to use feedstocks from renewable resources. Green hydrogen can be combined with captured CO2 e.g. from flue gas. Biomass forms an especially suitable basis. In a biogas or biomethane plant, a mixture of mainly CH4 and CO2 is produced in the fermenters. Apart from the original use for either power and heat generation in a CHP (Combined Heat and Power) or gas grid feed in they can be used for syngas generation by steam methane reforming (CH4 + H2O (Steam) => 3H2 + CO) or CO-Electrolysis (CO2 + H2O in solid oxide electrolyzers forming CO+H2). For both processes we need energy, which can be taken from the cooling steam in the Fischer-Tropsch Reactor and e.g. from the CHP. This circular approach both for CO2 and energy increases the efficiency and the carbon reduction effect of these applications.
All the abovementioned reforming and reactor processes require pressure, mostly in the range of 10 to 100 bar. As the flows can be highly volatile and must be quickly adjusted for an optimized process quality, piston compressors are ideally suited for these applications.
NEUMAN & ESSER has supplied several compressors for synthetic fuel production, from Methanol, Coal-to-Liquids, over Methanation of H2 with CO2 stripped from Biogas up to Biomass-to-Liquids production. All the gases in the process, be it CO-rich mix gases, CO2, Steam and of course H2 can be compressed reliably with NEUMAN & ESSER´s compressor portfolio.