Home >  Working for the Promotion of New Technology of DRI Kiln ���������� Chen Zhengdong[1] Experts and colleagues, my dear friends: ������� Hello everyone

Working for the Promotion of New Technology of DRI Kiln ���������� Chen Zhengdong[1] Experts and colleagues, my dear friends: ������� Hello everyone

Working for the Promotion of New

Technology of DRI Kiln

���������� Chen Zhengdong[1]

Experts and colleagues, my dear friends:

������� Hello everyone!

My name is Chen Zhengdong, General Manager of Hubei Huanggang Zhongji Kiln Co., Ltd (HZK) China. I’m honored to have this opportunity to make a speech in such an important meeting. My topic is: Working for the promotion of new technology of DRI kiln. With the help of this meeting, I would like to share unique achievements of ours with guests from various countries.

As a director unit of DRI Professional Committee of China Association of Metal Scrap Utilization, HZK is one of the largest DRI tunnel kiln manufacturing enterprises in China. The company has National second-level kiln construction qualification and safety qualification, also has a number of DRI technology patents and DRI utility model patents. HZK has strong technical strength, provide scientific research design, machinery manufacturing, installation, commissioning, technical advice integrated services.

HZK conduct extensive exchanges and cooperation with Chinese universities and well-known experts, DRI tunnel kilns designed and manufactured by us is throughout China's 28 provinces, cities, and autonomous regions. Quality of more than 100 DRI tunnel kiln production lines which have been built by experts are highly recognized. Having summed up these tunnel kiln production line equipment technology then I make a brief introduction here for you right now.

Ⅰ.DRI tunnel kiln equipment characteristics

Short process,simple process, easy operation.

It is of high efficiency, large output, energy saving and environment protection.

Suitable for use with low added value of coal and iron ore powder.

Less labor, a high degree of mechanization, low labor intensity.

Tunnel kiln belongs to a un-high altitude, un-high temperature and un-high pressure. The production process is safe.

It is of low investment, more suitable for large and medium-sized enterprises in construction project.

This process is suitable for mining iron powder; in general requirements for iron ore grade is up to TFe65%~70%, as well as requirements for oxidation of iron grade is about TFe72%, it will be able to produce direct reduction sponge iron.

A combination of the above materials, the factory area, investment scale and other factors, it will be decided to invest in DRI tunnel kiln production line.

The length of the kiln made by above process depends on the output size, kiln trolley size, reduction time, raw material types, thermal system stability, easy operation and energy saving shall also be considered.

Domestic and foreign manufacturers could select DRI kiln devices suitable for your own development.

Ⅱ.DRI Process parameters and cost analysis

Next I take 20,000T/Y & 30,000T/Y as example and list representation, it helps investors to enhance the understanding of DRI tunnel kiln production line then recognize it.

Table 1.DRI tunnel kiln section parameter



20,000 T tunnel kiln

30,000 T� tunnel kiln



The length of the kiln




Inner width




Loading height




Fuel type: Producer gas or other gas


Combustion-supporting air preheated temperature is 350 ℃(can save the producer gas 600Nm3/h)

Table 2.DRI Tunnel kiln main equipments



Device configuration(includes)


Raw materials processing

Iron ore powder dryer、reducing agent drier、Conveying equipment and so on


Tunnel kiln equipment

tunnel kiln steel structure parts、kiln trolley transport system、combustion system、fan system、trolley care system、transportation system of out of kiln and electrical control system and so on


Loading system

Loading and mold transporter、raw material conveying、feeding system transmission line equipment and so on


Unloading system

Unloading sand cleaning equipment、dust suction recovery system、the cover、cover position equipment and so on


Broken cold pressing system

Multi roll reversible conveyor、cutting machine、storage bin、raw materials delivery machine、briquetting machine


Gas generating station

20,000T/Y & 30,000T/Y DRI tunnel kiln, each is equipped with a gas furnace, diameter is respectively 2.6 meters and 3 meters

Table 3.Main cost structure of 1ton sponge iron (TFe65%Iron ore powder as an example)


the main cost form item

tons of consumption


ore fine



producer gas



power consumption



anthracite coal(reducing agent)



limestone(reducing agent)



Si C� tank

12kg(according to the cycle number allocation)

Ⅲ.DRI material balance

1、For example,iron ore powder in 65%, 67%, 70% three magnetite and sponge iron physicochemical index after roasting reduction:



TFe(Total iron)

Impurity (Si、S、P and so on)













Iron ore powder TFe65% of 2% moisture content as an example:

①With an annual output of 20,000 tons of DRI, it needs 28,000 tons of iron ore powder and 13,000 tons of reducing agent.

②With an annual output of 30,000 tons of DRI, it needs 42,000 tons of iron ore powder and 19,500 tons of reducing agent.

③After reduction, the reducing agent could be used one or two times according to the carbon content.

2、Physical properties

The raw material that tunnel kiln produce reducing sponge iron is used ore powder, using silicon carbide tank canning, with good reducing atmosphere and high metallization rate, quality of DRI is good and stable. After being broken DRI particles or powder will be pressed block then density will be increased to more than 4.0t/m3, it can be used for steelmaking.

3、Coal raw material and Calcium oxide index

As a reducing agent and fuel, it is request for the coal such as the volatile, calorific value, ash melting point. Higher index of coal is in favor of energy saving and consumption reducing, is good for reducing the equipment failure rate. Anthracite composition: ash is less than 20%, volatile matter is less than 15%, fixed carbon is greater than 60%, and sulfur is less than 0.5%, ash melting point is greater than 1250℃. Limestone composition: calcium oxide is greater than 50%.

Ⅳ.DRI production process flowchart

��������� ��� ���

The picture of rod shape sponge iron products� ��������������� the picture of cold press sponge iron products

Ⅴ.A group of drawings below are some detail drawings of tunnel kiln process equipment designed by HZK

Tunnel kiln production process plane layout

The front of the tunnel kiln side (From right to left)

� The rear of the tunnel kiln side (From right to left)

Tunnel kiln profile

�� Canning structure profile �

Ⅵ.A group of pictures below are some production and construction pictures�������������������������������

�������������� ������

Two 136.8 m tunnel kiln� ������������������� Two 161.12m tunnel kiln

Two 190m tunnel kiln����������������� loading and unloading system

� ���������������������

����� Broken cold pressing system����������� ���� Construction site

Ⅶ.Brief description of new technology about DRI tunnel kiln

①Efficient energy-saving heat exchanger

On the top of preheating section of kiln flue heat exchanger is arranged and in the middle of cooling section rapid cooling /heating exchanger is arranged, hot air which temperature is 300℃~350℃ degrees out from cooling /heating exchanger can be used for combustion-supporting directly, it can save fuel 20%~25%, at the same time it reduces both waste gas temperature and the temperature of cooling section.

②Rational layout of the combustion system

Gas burner with multi points by small flow arrangement in the roasting section are "goods" – type distribution which are in upper and lower dislocation,so, combustion gas injected into the kiln can also stir air, let reduction temperature in a kiln reaches unanimity, the maximum temperature difference is no more than plus or minus 10 degrees.

③Comprehensive utilization of circulating water system

In the rear of cooling section circulating water cooling system is arranged. For further reduce the temperature in the kiln, meanwhile the output of the hot water can meet the various needs of the factories such as heating or bath hot water and so on.�

④Safe and stable trolley foot structure

Trolley foot, made by radiation type big wheel with high temperature resistant bearing,coupled with kiln trolley frame body connected with a bearing seat, run safely and steadily.

⑤Automated material load& unload system

It has such characteristics as simple operation, low amount of repair, a high degree of mechanization. It improves the labor intensity of workers and operating environment and increase the economic benefit of enterprises.

⑥Automatic control

The electrical appliance control equipment and switch are centralized installed in the control cabinet. In the both ends of the tunnel kiln, including the back trolley line, video surveillance system is equipped.

Following the social economic development, it always accompanied by people’s new technology and new process innovation. A mature innovation process should be from simple to complex, from complexity to simplicity,the company's innovative series tunnel kilns have such characteristics. Welcome friends to choose the coal based tunnel kiln equipment suitable for your own development. It will bring investors great economic benefit and social benefit to construct DRI tunnel kiln production line which is low investment and quick returns.

Welcome you to visit HZK!

Thank you!

[1] The speaker is HZK General Manager & Senior Engineer.

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