Electrolyzers designs

As was discussed in detail in Chapter 1, Section 1.5.4, passing electricity through an aqueous electrolyte solution generates hydrogen at the negative electrode (cathode) and 02 at the positive electrode (anode). There are a number of electrolyzer designs on the market, and they all are made up of parallel cells. Each cell is split in two by a diaphragm, and in each half there is an electrode an anode in one half and a cathode in the other. One popular... 

Two cases were examined for the production of water electrolysis. Data were taken from Reference (1) and adjusted to mid-1979 levels in accordance with Table 1. The costs of "current technology" electrolysis were averaged in Reference (1) from information provided by Lurgi, Electrolyser Corp., General Electric, and Teledyne Isotopes. An advanced electrolyzer design, based upon the General Electric Solid Polymer Electrolyte (SPE) design, was also addressed as the second case. 

Electrode Materials and Fabrication Separator Materials Pressurized Cell Performance Electrolyzer Design Optimization Scale-Up Tests... 

Electrolyzer design Membrane separates anode and cathode No membrane... 

Galvanic compatibility is of most concern in electrolyzer design where a conductive KOH solution is used, and a variety of metals are used as electrodes, fasteners and containment vessels. It is also a concern for coupling I dissimilar metal fittings. 

The Hybrid Sulfur (HyS) thermochemical cycle task addresses the key technology issues involved in the development of a hybrid sulfur hydrogen production system - including the SO2 - H2O electrolyzer design, SO2/O2 separation, and the unique materials and process issues associated with the acid decomposition section. An electrolyser is being developed that can be used in conjunction with the sulfuric acid decomposition section being developed for the S-I cycle in a Hybrid Sulfur Integrated Laboratory-Scale Experiment. 

Experiments with a variety of materials led to the conclusion that monel is a perfect choice for electrodes in an electrolyzer designed for intermittent power supplies. It has an electrical resistance of about 42 micro ohms-cen-timeters at 20°C. This is much higher than, for instance, nickel, which has a resistance of 11. With higher resistance, more heat is generated as the current passes through the electrodes and electrolyte solution. 

Electrolyzer designs historically have emerged from particular industries. Their design parameters and requirements are quite different than what is needed to produce hydrogen from renewable energy sources. That said, there is a lot that can be learned from electrolyzer development over the years, but there is plenty of room for electrolyzer innovation, especially for those designed to operate with renewable energy power sources. 

The year 1995 saw the debut in Germany of an advanced pressurized filter-press electrolyzer designed by the Gesellschaft fur Hochleistungs-elektrolyseure, a joint venture of Daimler-Benz Aerospace Airbus, Hamburgische Electricitatswerke, and Norsk Hydro Electrolysers. 

Some plants "solar cell + electrolyzer" designed and constructed during the last decade, and their characteristics are listed in Table 1. 

INEOS BICHLOR Electrolyzers NaCi, Hp, electricity Production of chlorine, hydrogen and 32% NaOH solution by electrolysis of NaCi solution. 97%+ efficiency, very low-power consumption due to zero-gap electode design and modular design provides low-maintenance cost. Bipolar electrolyzer design 33 2009... 

Since then, several membrane-cell technologies were developed in Japan, as a pollution-free chlor-alkali process. Japanese contributions include composite membranes and several electrolyzer designs. Japan was the first major chlorine producing country to convert entirely to membrane cell technology. As of January 2003, 35% of world production of chlorine is by membrane-cell technology, generating 52,000 metric tons caustic/day. 

S.2. Effects of Operating Conditions Membranes function over a wide range of conditions, allowing chlor-alkali producers to select electrolyzer designs and process conditions. However, if membranes are operated outside the reconunended ranges, their performance may be adversely affected. The effects of the electrolyzer, anolyte, and catholyte operating conditions on membrane performance are addressed here. 

The following section addresses the actual electrolyzer designs of the suppliers. 

Control of electrolyte flows is just one aspect of proper distribution across the entire electrode surface in the cell room. Achieving the desired total flow and the proper flow to each electrolyzer is part of process design. The steps taken to ensure good distribution internally are part of electrolyzer design, discussed in Chapter 5. 

Fitting methods depend on the electrolyzer design. Some examples follow ... 

The k-factor is very dependent upon the electrolyzer design and type of membrane used. Older monopolar electrolyzers using robust membranes may have a k-factor in the range 0.2S-0.3, while the most modem bipolar electrolyzers using low-voltage membranes may operate with k-factors of 0.12-0.15. 

In reply. Dr Dell remarked that in the written text there is an acknowledgement of the extensive work done by the European Community or hydrogen production. It is an excellent example of international co-operation. He did not support the concept of thermochemical cycles and doubted whether the investment in R and D in that field had been worth while. In contrast, the researches into electrolyzer design seemed to have been a good investment. ... 

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