Porous granular low carbon lime and production method thereof

Abstract

The invention relates to porous granular low carbon lime and a production method thereof. The method comprises the following steps: selecting high-quality limestone particles with the particle size of 5-10 mm, washing and drying the selected particles, then coating the particle surface with ferrous chloride or iron chloride, putting the coated particles in a heat-resisting alloy pot in a horizontal or vertical type gas sintering furnace, carrying out external indirect heating at normal pressure, carrying out low-vacuum degree calcining and decomposition, and then carrying out air quenching atnormal pressure to obtain a finished product. The lime product produced by the invention has the characteristics of fine crystal particles, large porosity, low carbon content, and high activity in the early stage, and can be used in molten steel pretreatment desulphurization and deep desulfurization of external refining when smelting ultra low carbon steel.

Description

technical field [0001] The invention relates to a lime, in particular to a lime used for desulfurization in the iron and steel smelting process. The lime of the invention is used for the pretreatment desulfurization of molten steel and the deep desulfurization of refining outside the furnace during ultra-low carbon steel smelting. technical background [0002] Lime (CaO) is made from limestone (CaCO 3 ) is decomposed by high-temperature calcination, and is one of the raw materials for molten iron and molten steel desulfurization slagging agents commonly used in the iron and steel metallurgy industry (often used in conjunction with fluorite). However, regardless of the metallurgical industry standard (YB / T 042-2004) or the actual quality of lime produced by various existing processes and equipment, there are problems of high carbon content and low reactivity (see Table 1). Lime products produced by the existing technology can be used in general metallurgical processes and b...

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Problems solved by technology

[0014] 1) Vacuum internal heating electric furnace is used, which has low production capacity and high operating cost; and the charging and discharging of material tanks is very cumbersome and the efficiency is too low. It is impossible for this device to realize large-scale industrial production;

[0015] 2) The calcination process system of first vacuuming and then heating is unreasonable, which is not conducive to the heat transfer between limestone particles at the initial stage of charging, which will inevitably result in prolonged heating time and affect the output of finished products;

[0016] 3) The calcination temperature is low. Even if it is calcined in vacuum at 750-900°C, the decomposition rate of limestone is very slow, and the physical yield is low. Moreover, the porosity and activity of limestone calcined at this low temperature are too large and the activity is too high. If Without passivation measures, it is very easy to interact with moisture and CO in the air during the cooling stage 2 reaction, the stability of the finished lime is poor, and it is difficult to store, pack and transport;

[0017] 4) The initial vacuum degree (below 100Pa) is too low, not only the energy consumption is too high, but also the low vacuum degree is not conducive to the heat transfer between limestone particles

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