[From Chisato Horiuchi in Tokyo, Japan]
"Metanation" Next-generation technology competition Osaka Gas and Tokyo Gas
Competition for the development of next-generation technology has begun for "methanation," which synthesizes methane, a raw material for city gas, from hydrogen and carbon dioxide (CO2). By increasing the energy conversion efficiency compared to the conventional type, the production cost of methane is reduced. Aim for early technological development to achieve the government's goal of reducing greenhouse gas emissions to virtually zero by 2050.
New SOIC single cell developed by Osaka Gas = provided by the company
Metanation is a technology that produces methane, which is the main component of city gas, from CO2 recovered from factories and hydrogen produced from electricity generated from renewable energy. Since the emitted CO2 is used as a raw material, city gas produced by metanation is considered to be "carbon-free" that does not emit CO2.
The Japan Gas Association (Tokyo, Minato) has set a goal of putting metanation into practical use by 30 years. The first aim is the conventional method based on the "Sabatier reaction". Hydrogen is produced from electric power derived from renewable energy, and then hydrogen and CO2 are reacted with a dedicated device to synthesize methane.
However, since a lot of heat loss occurs in the reaction process, the energy conversion efficiency is generally about 55 to 60%. There is a problem that it is difficult to make it large and it is difficult to improve efficiency.
The current price of methane is about 40 to 50 yen per 1 N cubic meter (normal lube = volume of gas under standard conditions). It costs about 350 yen to manufacture with Metanation. For this reason, major city gas companies are embarking on the development of next-generation technologies to reduce costs.
"SOEC Metanation Technology" is being developed by Osaka Gas. Water is electrolyzed together with CO2 in a solid oxide fuel cell (SOEC), and methane is produced from the produced hydrogen and carbon monoxide (CO).
The exhaust heat generated by the methane synthesis reaction is effectively used for the endothermic reaction when electrolyzing water and CO2. It has the advantage of suppressing heat loss compared to the conventional method, and the conversion efficiency can be increased to 85 to 90%.
In January 2009, Osaka Gas announced that it had prototyped a SOIC suitable for upsizing. Ceramics have been used so far, but the ability to withstand impact has been enhanced by using metal as a substrate and covering the surface with a thin ceramic layer. The technology will be established around 30 years, aiming for full-scale introduction from the 1940s.
Tokyo Gas has also begun developing multiple next-generation technologies. One of them is a method called "hybrid sabatier". From electrolysis of water to methane synthesis will be carried out in an integrated manner. In addition, the policy is to proceed with technical verification and development, including methods that utilize microorganisms.
Although the conventional method of metanation has not been commercialized, many people expect it as a decarbonization technology. If it becomes widespread in the future, the existing gas supply network can be used as it is even in a carbon-free society, and capital investment can be suppressed. The focus for commercialization is how much the cost can be reduced by technological development. (Shuhei Ochiai)
