(BAT) Reference Document for the Production of Chlor-alkali ...

Chapter 6
Achieved environmental benefits
The achieved environmental benefit of this technique is a reduction of energy consumption.
Environmental performance and operational data
At the AkzoNobel chlor-alkali plant in Delfzijl (Netherlands), a 70 kW PEMFC power plant
was put into operation in 2007. The rated electrical peak power of the unit is 120 kW, but to
extend the lifetime and to attain a high conversion efficiency, the unit operates at partial load.
At a load of 50 kW, a total of 12 stacks comprising a total of 900 cells (cell area of 200 cm 2 ) are
connected in series, generating 630 V direct current at 80 A. An inverter converts the direct
current to 400 V alternating current which is fed into the local electricity grid. Although the
chlor-alkali plant uses direct power, it was more economical to feed to the grid than to feed to
the electrolysers. The conversion efficiency of the fuel cells is 55 %, but the balance of the plant
including the inverters reduces the overall efficiency to 45 % (on the basis of the lower heating
value of hydrogen). The PEMFC system was reported to be very reliable. In April 2011 it had
been 20 000 h on the grid and the stack lifetime in real life was reported to be higher than
8000 h with an average cell voltage loss of 3 ZV/h. However, a drawback of the design with the
serial connection of the stacks is that the whole unit stops when the voltage of a single cell falls
below a threshold [ 109, Verhage et al. 2010 ], [ 110, Verhage 2011 ].
At the Solvin chlor-alkali plant in Antwerp-Lillo (Belgium), a 1 MW PEMFC power plant is
expected to be put into operation in 2011. It will be the world's largest PEMFC power plant. At
1 MW, it is expected that the balance-of-plant can be reduced so as to raise the overall
conversion efficiency to 50 % (on the basis of the lower heating value of hydrogen). The
problem of non-availability of a PEMFC power plant due to cell failure is expected to be solved
by switching 12 power modules of 85 kW in parallel. Failure of a cell in a module will trip one
module but the other 11 will compensate for the loss by automatically raising the current. Stack
replacement is designed to be rapid and restoration of the original situation should occur within
1 h [ 109, Verhage et al. 2010 ], [ 110, Verhage 2011 ].
In the United States, the company K2 expects to put into operation a new bleach production
plant by 2012 in Pittsburg, California. The co-produced hydrogen will be converted to
electricity in a 163 kW fuel cell generator [ 111, Ballard 2010 ].
PEMFCs can also be used for the hydrogen generated during the electrolytic production of
sodium chlorate. A 120 kW pilot plant ran unattended for approximately 2500 h at the Caffaro
chlorate plant in Brescia (Italy) from September to December 2006 [ 112, Santorelli et al.
2007 ].
Cross-media effects
Some raw materials and energy are consumed for the manufacture of the fuel cells. One
equipment provider reports that all materials used in their fuel cells are easy to recycle and
allow for the reuse of the major components. The scarce and valuable platinum can be recycled
to an extent of approximately 98 % [ 108, Nedstack 2011 ].
Technical considerations relevant to applicability
If the fuel cell power plant is run with purified hydrogen and feeds alternating current to the
WORKING DRAFT IN PROGRESS
grid, there are generally no technical restrictions to its use in new or existing chlor-alkali
installations. In 2011, however, there is only one fuel cell plant to be put into operation with a
rated power equal to or greater than 1 MW and practical experience with this plant size needs
yet be gained. In addition, if the fuel cell system is to be completely embedded in the
electrolysis process, installed inside or close to the cell room, more information is needed, such
as on performance in the presence of specific contaminants and on durability under the typical
operating conditions of a chlor-alkali plant [ 114, Delfrate and Schmitt 2010 ].
Economics
From an economic point of view, it is ideal to use fuel cells for hydrogen which is otherwise
emitted. The hydrogen used as a chemical will never be accessible for other uses, while the
296 December 2011 TB/EIPPCB/CAK_Draft_1