Electrolyser stream

The heart of an electrolysis plant is its electrolysers. The factors that improve the Rol are features such as low energy consumption and high on-stream factors, flexibility of plant load, high current densities and short electrolyser downtime periods for maintenance. 

All these modifications lead to the fulfilment of all aspects for an improvement of the Rol by KU single element technology and high efficiency of the latest cell design, such as low energy consumption with a high on-stream factor for the plant, simple and rapid maintenance of the electrolysers, plant load flexibility and high current densities. 

Production of hypochlorite takes place in a two-step absorption unit in which 23% caustic solution is fed counter-currently to the chlorine feed-stream. In the first step -the liquid jet-loop reactor - about 90% of the chlorine is converted to hypochlorite. In step two - a packed column - a very efficient absorption [1-3] is carried out in which the chlorine concentration in the off-gas is reduced to <1 ppm. The operating window of this apparatus with respect to chlorine load is quite large and varies from 100 to 6000 kg h-1 of chlorine. This high capacity is necessary for the consumption of peak loads from the electrolysis plant during short time periods. During start-up or shutdown of one electrolyser the total chlorine peak load can vary from 100 to 300 kg in just a few minutes. 

The denominator in this efficiency definition quantifies all of the net thermal energy that is consumed in the process, either directly or indirectly. For a thermochemical process, the majority of the high-temperature heat from the reactor is supplied directly to the process as heat. For HTE, the majority of the high-temperature heat is supplied directly to the power cycle and indirectly to the HTE process as electrical work. Therefore, the summation in the denominator of Eq. (1) includes the direct nuclear process heat as well as the thermal equivalent of any electrically driven components such as pumps, compressors, HTE units, etc. The thermal equivalent of any electrical power consumed in the process is the power divided by the thermal efficiency of the power cycle. For an electrolysis process, the summation in the denominator of Eq. (1) includes the thermal equivalent of the primary electrical energy input to the electrolyser and the secondary contributions from smaller components such as pumps and compressors. In additional, any direct thermal inputs are also included. Direct thermal inputs include any net (not recuperated) heat required to heat the process streams up to the electrolyser operating temperature and any direct heating of the electrolyser itself required for isothermal operation. 

Note that the heat exchangers are partially imbedded in the insulation thickness. The top portion of each heat exchanger is exposed to the hot zone radiant environment, which helps to insure that the inlet gas streams achieve the desired electrolyser operating temperature prior to entering the stacks. The temperature at the bottom of each heat exchanger will be close to the inlet stream temperature, minimising the thermal load on the hot zone base plate in the vicinity of the tubing penetrations. 

Another electrolyser is provided with a rotating cylindrical cathode that operates at high current densities causing deposition of metals in the form of a powder, which is removed by a brush and carried away by the streaming electrolyte. The metal powder is separated from the liguid by means of a filter. An industrial type of this equipment is known under the ncune ECO CELL. 

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