Nickel iron production has become a major industry in China due to the large number of nickel smelting factories, and the need for nickel is growing rapidly worldwide. The process involves turning laterite ore, using electric furnaces, into nickel. The nickel is smelted into nickel ingots, and the iron is converted to steel through the blast furnace or direct reduction processes. The steel is then processed into different products through rolling, cutting, sizing, bending and casting.
The main method of nickel iron smelting uses the nickel powder-foam technique. Nickel is mixed with e.g. Polyurethane particles that coat the surface are packed together, heated above 700 degrees and then melted. This method can be more cost effective than the conventional methods for nickel smelting.
However the problem of evolution of hydrogen and oxygen gas is very severe with this method. It is a more severe problem than the lead acid, NiMH and NiCad batteries because of their higher gas production. The evolution of these gasses can lead to the explosion of batteries in some cases, while other times they are unable to be used.
To reduce the risk associated with using the nickel powder-foam technique, a number of precautions were incorporated into manufacturing. These include improving the quality of the polyurethane foam, increasing the thickness of the coating, and adding anti-corrosive additives to the coated flittings. The quality of the nickel can also be improved by soaking electrodes and coatings in a hot solution of sodium hydroxide to convert the nitrates to hydroxides, followed by high-temperature baking.
The electrodes should also be carefully monitored for excessive current density and the parameters adjusted accordingly to prevent overloading. An activator such as magnesium sulfur or elemental sulfur can speed up the sintering. These activated additives make the flittings more conductive and reduce the rate of oxygen evolution, thus increasing battery life.
The electrode can become overly stressed if the sintering procedure is not done quickly enough. This may cause local darkening at the tip of the electrode or cracks. This problem can be caused by water that leaks from the top of the furnace. It is important to ensure the surface of your electrode is free of excessive cooling.
Material instability: Instabilities within the refractory of the rotary kiln can lead to frequent shutdowns, and fluctuation in the supply sand. This can then cause significant changes in power levels needed for sintering. It can lead to a rapid power recovery following a shutdown of the furnace, which could cause the electrode temperature to rise too quickly. This could cause the metal at the sintering area, such as the electrode, delaminate and fracture. The cracks caused by this can decrease the mechanical strength of an electrode, or even cause it to break.
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