By-products are common to most industries. Some are harmless, some dangerous and others useless. Others are simply under-utilized. VTT Technical Research Centre of Finland is using hydrogen generated as a by-product of the sodium chlorate production process in its pilot-scale power plant to produce electricity.
Sodium chlorate is a white crystalline powder predominantly used for bleaching paper, with several hundred million tons of the compound produced annually using an energy intensive electrolysis process that also produces hydrogen gas at the cathode as a by-product.
Stored hydrogen is a clean, zero-emissions energy source, but pure hydrogen is not a naturally occurring element. Other methods of generating then storing hydrogen have been explored by various methods of artificial photosynthesis, but making use of hydrogen already produced as a by-product of an existing industrial process seems like a no-brainer.
The 50 kW pilot plant runs at a total electrical efficiency of 44 percent, with VTT claiming that, if scaled up from pilot to commercial size, the power plant would reduce energy consumption of the electrolysis process during sodium chlorate production by 10 to 20 percent by utilizing the hydrogen by-product in fuel cells.
The fuel cells in question are PEMs (proton exchange membrane/polymer electrolyte membrane), a type that is considered promising for use in fuel cell vehicles. While other types of cells may use the combustion of hydrogen and oxygen to produce thermal energy, PEMs utilize the electrochemical reaction of hydrogen and oxygen to produce electrical energy.
The fuel cells operate at a relatively low 60º C (140º F) – PEM cells typically range in temperature from 50 to 100º C (122 to 212º F) – however, with further improvements the VTT team says waste heat may be better utilized.
The pilot project is aimed at gaining some real world experience of operating such a fuel cell in an industrial environment, which will allow any unresolved problems or bugs to be ironed out now rather than during or after commercial implementation. The project also provides developers with information on how industrial-quality hydrogen may work with PEM cells.
The pilot plant, which has been in operation since January of this year, is the first of this kind in a Nordic nation, though similar plants have been built in both North America and the Netherlands.
Source: VTT Technical Research Centre
