Oxidized pellet production process and system using chain grate-rotary kiln system

Abstract

The invention discloses an oxidized pellet production process using a chain grate-rotary kiln system, which comprises the following steps: (1) green pellets are dried, preheated and oxidized through achain grate, then materials passing through the chain grate are conveyed to the rotary kiln to be roasted and then conveyed to an annular cooler to be cooled, and pellet ore is obtained; 2) hot air exhausted from the first circular cooling section is conveyed to the rotary kiln, the hot air exhausted from the rotary kiln is conveyed to a second preheating section, and the hot air exhausted from the second preheating section is conveyed to an air draft drying section in an air draft manner; 3) hot air exhausted from the second annular cooling section is conveyed to the first preheating sectionin an air blowing manner; and 4) the hot air exhausted from the third annular cooling section is conveyed to an air blast drying section in an air blast manner. According to the scheme, hot air is blown into the first preheating section, so that the air pressure in the first preheating section is greater than that of the second preheating section, and gas in the first preheating section does notneed to be denitrified; and meanwhile, a stable hot air area is formed in the first preheating section, and the preheating effect of upper-layer and lower-layer pellets is guaranteed.

Description

technical field [0001] The invention relates to a preheating process, in particular to a production process for oxidizing pellets using a grate-rotary kiln system, and belongs to the technical field of pellets; the invention relates to a grate-rotary kiln system. Background technique [0002] Pellets are the main iron-containing charge produced by blast furnace ironmaking in my country. In 2015, the output of pellets in my country was 128 million tons. Compared with sinter, due to the low energy consumption and relatively friendly environment of the pellet production process, and the product has the advantages of good strength, high grade, and good metallurgical properties, it can increase production and save coke when applied to blast furnace smelting, and improve ironmaking technology and economy Indicators, reducing the cost of pig iron, and improving economic benefits, so pellets have been vigorously developed in my country in recent years. [0003] my country's pellet p...

AI Technical Summary

Problems solved by technology

[0004] Although pelletizing enterprises have done a lot of work in environmental protection, dust removal and desulfurization have been effectively controlled, and can meet the emission requirements, but at present, due to the high cost of NOx removal and complicated process, in the environment of sluggish steel form, this poses a threat to pelletizing. The industry has brought new challenges. Some enterprises have to reduce production in large quantities due to excessive NOx, and even face shutdown

Judging from the current production situation of most pellets, in order to meet the new emission requirements, the terminal denitrification device is added after desulfurization, resulting in a substantial increase in investment costs and operating costs

In addition, the recycling of hot air in the hot air system of the grate-rotary kiln-ring cooler pelletizing process plays a very important role in the production and quality of pellets, as well as in energy saving and emission reduction. Under the existing hot air system , the two stages of preheating are preheated by exhaust air, which not only causes the flue gas of the second stage of preheating to flow into the first stage of preheating, causing the NOx of the preheating stage to exceed the standard, but also causes large differences in the strength and oxidation degree of the upper and lower layers of pellets due to uneven preheating affect the quality of its products

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