Large Electrolysis Systems in Chemical Industry Challenges with the advent of Green Hydrogen Production

Electrolysis processes are a key factor in the chemical industry, initially for producing caustic soda (NaCl) with chlorine as a byproduct. With hydrogen production by electrolysis on the rise, this technology is attracting increasing attention.Currently, the predominant rectifier technology in the high current area is based on thyristor controlled 3 phase bridges which has been a mature technology for decades but creates challenges regarding harmonics and power factor control, especially under constantly changing operating conditions like fluctuating availability of green energy.New technologies based on IGBT semiconductors in active frontend or chopper designs line up to take over. These technologies provide solutions for the challenges of the pure restriction on the use of green energy only, the type of these green grids and the power quality issues that come with the operation of large rectifier systems.The paper will describe some aspects as they were faced and tackled during the execution of a large project in the range of 2600MW electrolysis load. A hypothetical hydrogen supply for green steel production is sketched.Additional challenges in the downstream production of Ammonia and/or Methanol due to replacement of steam turbines by large electrical drive systems are addressed.