A major breakthrough at tunnel kiln industrial-scale reduction of technical problems

 - Large tunnel kilns and automatic loading machine come out one after another

Wang Shouping Wang Lixin

（Tangshan Outstanding science and technology CO.LTD 063020）

As its well-known, there are two technical problems in the field of direct reduced iron tunnel kiln coal-based reduction method, one is tunnel kiln capacity, low level automation, environmental pollution, high energy consumption; the second is loading and unloading system which cannot meet the needs of large-scale industrial production. For these two problems, our company has made considerable efforts in recent years, and has achieved remarkable success and has made significant breakthroughs in the tunnel kiln construction, and laid a solid foundation for the development of the tunnel kiln in the field of DRI, and opened up broad prospects.

First, The large tunnel kiln put into operation set a solid foundation for the tunnel kiln reduction process on an industrial scale.

Our company designed and built production capacity up to 50,000 tons of 260 meters large gas tunnel kiln for Jiangsu Liantai Science and Technology Co., Ltd in July 2008 ， which is a  mark for large tunnel kiln in the field of direct reduced iron and had a good beginning.

The industrial symbols of large-scale gas tunnel kiln are as follows

- Single kiln production capacity is 50,000 tons.

-The production line can achieve automatic control and automatic operation, including PLC interlocking kiln car automatically, the fan interlock automatic PLC control, PID intelligent automatic temperature control, pressure PLC automatic frequency regulation.

- Achieve environment protect friendly, emissions, dust meet national environmental standards, no waste water and solid waste.                                

- All above industrialized mark the traditional industrial modernization tunnel kiln realized towards reducing equipment.

Second, automatic loading machine be put into market opens up prospects for the industrial scale development of tunnel kiln reduction process

Large tunnel kiln be successfully put into operation can only solve the tunnel kiln native capacity issue, however if the loading system can’t meet the process requirement, the tunnel kiln reduction process still can’t have a good development in industrial scale.

Technology background is: for the conventional loading process, people often first take the mold into the reaction container, and then load the iron powders and reducer into the container separately, at last take out of the mold from the container. This method has a certain degree of mechanization, but this process have four defects: the first is that when the mold be put onto the kiln car, it is difficult to accurately locate; the second is due to different material properties, particle size, moisture, it is difficult to fill the material into the container smoothly and uniform; The third is that when the mold be taken out of the container, the material maybe come out with the mold; the fourth is that during the material loading and mold removing will generate a great of dust which cause environmental pollution. Using this process takes a long time, low labor efficiency, dust pollution is serious, not only hinder the development of tunnel kiln direct reduction iron-scale industrial production, but also not in compliance with the basic national policy of environmental protection standard.

After two years of painstaking research our scientific and technical personnel finally developed a new concept of loading machine (Patent No. 200920302346.1), the loading machine has been successfully be used in Kunming Iron and Steel Group Co., Ltd. 100,000 tons of reduced iron production line. The loading machine consists of loading mold positioning parts, the loading section, mold remove parts and dust cleaning parts. Its biggest advantage is:

- Charging efficiency is greatly improved, the conventional device each shift can only be loading 5 cars, but now each shift can load 32 cars, which improve the efficiency more than 6 times.

- Automatic level. The conventional device need operating workers for 32 people, and now the operating workers is 12 people; The workers reduced by 20 people, and reduces production costs.

- The effect of dedusting is greatly improved. When loading, the conventional device generated a lot of dust which pollute the environment, dust concentration over 500mg / ng3, now the dust concentration less than 10mg / ng3, decreased by 50 times.

Third, the prospect for reduction process on an industrial scale tunnel kiln

we have solves two major obstacles in the field of tunnel kiln DRI process; tunnel kiln reduction process on an industrial scale will embark on the path of healthy development, which is consistent with China's national conditions. Because: tunnel kiln mature process and reliable technology is its biggest advantage, its high stability product quality is the biggest advantage. if overcome its shortcomings, continue to enhance innovation capability, in a certain historical period, the tunnel kiln as the main force in the field of direct reduced iron is undoubted, it is the task of China's technology research people in the tunnel kiln technology.

Our company's goal is:

Single kiln capacity: According to advanced modern furnace design concept, wide-body light, energy conservation, two kiln as a combination unit, single kiln 75,000 tons kiln combination up to 150,000 tons in two years, single kiln 100,000 tons kiln combination up to 200,000 tons in three years, single kiln 150,000 tons kiln combination up to 30,000 tons in five years, three kilns combination up to 50 tons.

Loading machine: single capacity in the series of 10 tons, 150,000 tons, 200,000 tons, 250,000 tons, meet the objectives of three combination kilns can produce more than 500,000 tons

 (This article was published in the "2009 China International DRI market Symposium ")