Cellhouse capacity

To simplify the discussion, a plant of fixed capacity is assumed. Because cellhouse capacity depends directly on certain fundamental design criteria it is useful to keep in mind the cellhouse capacity correlation ... 

Operation of the Kidd electrolytic zinc plant commenced in 1972 with a cellhouse capacity of 105,000 tonnes of zinc cathode. The original cellhouse layout consisted of 42 parallel rows for a total of 588 cells. As leaching capacity increased, the cellhouse was expanded to 630 cells. Zinc cathode was manually stripped from plant start-up until the development of a mobile automated stripping system in 1994. Machine development continued until a second unit was placed in production in 1996, from which point, 60 % of the cellhouse was being stripped with the automated system. The final phase of the project was implemented in 1999 with the commissioning of two more automated strippers. This paper describes the implementation of the automated stripping system and its impact on cellhouse productivity. 

The cellhouse is equipped with 528 cells having a capacity of about 2.5 m each in cascade-lines. Each cell is equipped with 30 cathodes and 31 Pb-Ag anodes and two water coolers. Inlet water at a temperature 286 K is delivered from a local mine. The cells are grouped in two units. Each unit with 22 double cascades of six cells in each cascade-line. Electric current goes to the electrodes through copper bus bars. Each cascade is connected inseries, and the electrodes in the cells are in parallel. The dimensions of the electrodes are the following for the A1 cathodes 1080 x 620 x 6 mm, and for the Pb-l%Ag anodes 1000 x 580 x 6 mm. Neutral electrolyte is fed to each cell, and the overflow from the upper cell flows through the lower cells of the cascades. From the lowest cell, it finally flows to the spent electrolyte tank... 

The motivations for replacement of an old cellhouse are nearly always the same reduce manpower for manual cathode stripping, improve workplace conditions for the employees, and reduce power costs. The need to expand capacity or improve product purity can be factors as well. It is also frequently the case that an old manually stripped cellhouse has high maintenance costs and may need major repairs to stay in operation. 

Construction of a new cellhouse to add to existing capacity is a less common situation. Unless the existing cellhouse is reasonably new, the owner usually gives serious consideration to moving all the production to the new cellhouse for the reasons given above. As a minimum, the new facility is usually designed to allow expansion to full production capacity at a later date. 

The electrical supply equipment is the second biggest equipment package after the mechanical equipment. The package includes the transformer/rectifier (T/R) sets and bus bars for providing DC power to the cells, the associated power factor correction equipment and harmonics filtration equipment, and the service transformers and circuitry. This equipment will typically comprise about 15 - 25 % of the cellhouse cost. The cost is heavily influenced by whether or not an electrical substation is included, and by the redundancy requirements for the T/R sets. A plant can choose to have no spare T/R capacity, partial redundancy, or full redundancy. Such cost savings must be weighed against the cost of lost production when a T/R set fails. 

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