Uhdenora S.p.A.

In the chlor alkali industry, energy saving is of paramount importance.
With fuel cells technologies, energy saving goes hand in hand with environmental protection, since it is possible to use the hydrogen co produced during the salt electrolysis to produce electricity, without any polluting emission.
A fuel cell is a static device for converting directly the chemical energy of hydrogen and oxygen present in the air into direct current electricity, water and heat.
In practical terms, a fuel cell reverses the process of electrolysis in which the electric current breaks down water into its constituent oxygen and hydrogen gases.
Chlor alkali plants releases enormous amounts of high purity hydrogen during their operation, and the production of clean electricity using such hydrogen to feed a fuel cell system is an efficient way to decrease electrolysis power consumption or to boost plant productivity.
Early adopters for fuel cells are plants where the hydrogen has not an appreciable value, and the cost of electricity is high.
Today, two technologies are suitable for stationary power generation: Proton Exchange Membrane (PEM) and Phosphoric Acid (PAFC) fuel cells.

Schematic of fuel cells operating principles. Electrolyte for PEM is a proton exchange membrane, while for PAFC is a concentrated solution of phosphoric acid.

Technology maturity, experience in real life conditions and economical considerations are at the basis of this selection for the industrial application of fuel cells in electrochemical plants.
Proton Exchange Membrane (PEM) fuel cells consist of two electrodes – an anode and a cathode – separated by a thin polymeric membrane enclosed in-between. To obtain a fuel cell stack, multiple fuel cells and bipolar plates are sequentially assembled in series in a modular configuration.
Hydrogen is fed to the anode (negative pole), and air to the cathode (positive pole). The catalyst on the anode breaks down hydrogen molecules into hydrogen ions (H+) and electrons; the hydrogen ions migrate through the membrane to the cathode, where the cathode catalyst causes the combination of the hydrogen ions, electrons, and oxygen to produce water. The electrons travel through an external circuit, resulting in the flow of electricity.
Two bipolar plates are positioned against this backing, one on each side of the membrane. Function of the bipolar plates is the mechanical separation from different cells, the transmission of electric current through the elementary cells and support the release of heat to the external environment.
PEM fuel cells operating temperature is in the range of 65 °C – 80 °C.
Phosphoric acid fuel cells (PAFC) differs from PEM in the electrolyte medium between the anode and the cathode, that is composed by a concentrated solution of phosphoric acid that is bond in a gel matrix.
PAFC operates in the temperature range from 200 to 220 °C, and the high valuable heat can be recovered within the plant.

Schematic of fuel cells system integration into chlor alkali plants.

Experience: in June 2006 Uhdenora, Nuvera Fuel Cells (US) and Caffaro (Italy) announced the successful start up of the 125 kW PEM fuel cell system fully integrated into Caffaro's chlorate production plant in Brescia (Italy).
This represents one of the world’s first successful installation of fuel cells in an electrochemical plant: installation and maintenance was done with no interference with chlorate production, while all the electricity produced was used to reduce the electrolysis power consumption by direct electrical connection to the bus bars of electrolyzers.
As fuel cell system integrator, Uhdenora is today designing the MW size fuel cell system with the objective of first installations on membrane plants where the technology costs are in line with industry expectations.
Contact person for information about fuel cells in Uhdenora:

Alessandro Delfrate
Marketing Manager
(alessandro.delfrate@uhdenora.com)