To produce direct reduced iron (sponge iron) by using tunnel oven canning process is first used for producing direct reduced iron (sponge iron) by Swede in 1911. With years' improvement, this process became efficient for producing direct reduced iron (sponge iron).Beijing Ruizhi Feiteng Co,. Ltd.developed new process of producing direct reduced iron (sponge iron) through technological improvement and innovation in 1992.Developed a new type of tunnel kiln direct reduction iron (DRI) production. Created a tunnel kiln in China's use of a new era in the production of sponge iron。Through continuous improvement and perfection，Formed in terms of Series of sponge iron production process no matter investment size and Automation level.It can meet a variety of environment, the various regions, the requirements of the various investment groups, Beijing Ruizhi Feiteng Co,. Ltd. was far ahead in Ratio of investment or investment returns, Products or raw material costs requirements, Product quality or process maturity, equipment reliability, stability, Energy conservation or environmental protection and so on .They put refined ore powder, coal powder and limestone powder into reducing pot with a certain proportion and way of charging and discharging, and lay the pots on the tank truck, then push it into long narrow tunnel oven or ring rotary oven. After preheating, heating roasting on 1150℃ and cooling, the refined ore powder is reduced into direct reduced iron (sponge iron).
Scores of production lines of direct reduced iron (sponge iron) by using tunnel oven have been built and put into production. When the content of the iron in the refined ore powder is more than 67%, the analysis of the products is C≥0.04%, S<0.01%, P<0.02%, SiO2<3%, MFe≥86%, TFe≥92% M≥94%.
Characteristics of tunnel oven process and wheel oven process:
Raw material, reducer and fuel are easy to be purchased
The raw material of this method is refined ore powder or Grade≥60% haematite or limonite, it is more easy to use than enriched iron ore. It needn't to change the refined ore powder into oxidation ball, and the cost is low. Reducers used in this method are anthracite powder or coal powder. Blast furnace gas, coke gas, rotary oven gas, mixed gas, petroleum gas, generator gas and heavy oil also can be used as pyrogen.
When we used high-quality refined iron ore for blast furnace smelting, the advantages can not be exerted, and it brings disadvantages too. It is unsuitable in technology and economy.
Production technology is easy to master, production process is easy to control
Tunnel oven process adopts heating of coal, coal gas, heavy oil or coal powder. Burner port is on the wall of the two sides along the length direction or on the head of the oven. To adjust the gas consumption by heating curve of the oven, the temperature inside the oven should be controlled within the specific limits. The normal temperature of the oven's top is 950-1180. For long narrow tunnel oven, roasting pots are put into the oven in succession, through preheating, reducing, heat preservation and slow-cooling, the reduced reaction finished, and then enters into the discharge process. For ring oven, roasting pots finished the reduced reaction under the alternating action of heating coal powder nozzles, and through preheating, reducing, heat preservation and slow-cooling. It is easy to control the proportion of refined ore powder and coal. The temperature and time of roasting is also easy to achieve. So tunnel oven process and rotary oven process is easy to control.
Equipments run steadily, products' quality is uniform
There is little process and simple equipments for direct reduced iron (sponge iron) by using tunnel oven. The special structure of long narrow tunnel oven makes it reliable to work. Ring rotary oven needn't tank trucks inside the oven. The life of tunnel oven is long under the roasting temperature above. There is almost no trouble. Under the same condition, every pot through preheating, reducing, heat preservation and slow-cooling in the same time, it must produce the products with certain metallization rate in the condition with a certain roasting temperature and time. Products' quality must be uniform. Production practices have already verified this.
Little investment on fixed asset
The investment for per ton of direct reduced iron (sponge iron) with annual output 20000 tons is only 300-400 Yuan. It is cheaper than to build one small blast furnace, the scale is bigger but the investment is fewer.
Low cost
The price of direct reduced iron (sponge) that imported from Malaysia, Australia, South Africa, and India to our factory is above 4000 Yuan/ton. In 1993, the cost of direct reduced iron (sponge) in Tianjin Seamless Steel Tube Company with annual output 300,000 tons is 4,500 Yuan/ton. The cost of other factories by using simple rotary oven is also above 3,200 Yuan/ton. If the factory was built near to refined ore powder plant, the cost of direct reduced iron (sponge) is between 1,600-1,900 Yuan by using rotary oven process.
Flexible Layout Method
For direct reduced iron (sponge iron) process by using tunnel oven, two rotary ovens are in a group, each group can produce 20,000-150,000 tons of direct reduced iron (sponge iron), one factory can build one or many groups at the same time. When the fund is temporarily tight, you can only build one tunnel oven with annual output of 10,000 tons, the investment is about 4 million Yuan, and the scale is flexible. The investment and cost are not changed because the change of the scale.
More extensive application potentiality
Direct reduced iron (sponge iron) which was produced by more than 67% (the content of the iron) of the refined ore powder, can be used as raw material for electric stove of steel making. Direct reduced iron (sponge iron) which was produced by more than 71.5% (the content of the iron) of the refined ore powder, can be used for powder metallurgy.
Pollution-free
To roast the reduced free iron in tunnel oven by refined ore powder is a chemical reaction under high temperature. The reducing material is mainly CO2 and iron. There are no water pollution and noise pollution. After sedimentation in the oven, dust that produced by coal firing discharges by the chimney. It doesn't pollute the environment.
We adopted the patent of our company to produce briquetting of direct reduced iron (sponge iron). We can produce various shape and weight of cold briquetting according to customers' different demands. Products can meet different demands, thus the extent of supply is expanded in the market.
Simple equipments
Rotary oven process is only composed with reducing stove, bogie, transition car, thruster, temperature meter, chimney, and other simple equipments.
Go into operation fast and construction period is short
Construction period of production line with annual output 20,000 tons of direct reduced iron (sponge iron) is only 2 months.
According to the data and analysis above, direct reduced iron (sponge iron) process by using tunnel oven is more outstanding with low cost, little investment, and steady running. So we Should develop direct reduced iron (sponge iron) process by using tunnel oven in the place where has refined ore powder.
Production process
burnt powder/coal powder + refined ore powder + limestone powder — putting into the pot — roasting in the stove — cooling — inspection of the finished products — putting in storage. Refined ore powder, burnt powder or coal powder and limestone powder are put into the pot by a certain proportion, put on the bogies by hand, and then thrust into the stove by propeller. After heating, heat preservation, cooling and inspection, the quality products are put in storage. Pots and bogies can be recycled. A production line can produce 34 tons per day by self-ignite and adding the coal artificially. Under the normal situation, the annual output of one production is 10,000 tons, two production lines are in one group, and the annual output of one group is 20,000 tons.
Main Equipments: Tune Oven, Bogie, propeller, Chimney, Panel
Auxiliary Project:
Direct reduced iron (sponge iron) production line with annual output 10000 tons occupies an area that the length is 120M and width is 24M.
The workshop adopts the simple awning, does not have the crown block. The length is 120M, the width is 24M, and the construction area is 2880M 2 . The annual output of two production lines is 20,000 tons, the length is 120M and the width is 36M.
Electric Power:
Power capacity of direct reduced iron (sponge iron) production line with annual output 10000 tons is 120Kv.A, it mainly used for using the propellers and workshop lighting. The whole installed capacity of two production lines is 160Kv.A.
Water Supply: this project doesn't use water, so just consider living water. Consumption is very small
Investment Estimation
Not considering the land and electricity expansion, construction investment of direct reduced iron (sponge iron) production line with annual output 10,000 tons is 3.5 million Yuan (according to the different price of raw material in local place, the actual price can be varying.)
Economic Evaluation and Cost Estimation
Employment : a production line of tunnel oven needs 70 staff (including all the workers and management.)
Cost estimation: the cost of direct reduced iron (sponge iron) of per ton is 1,600-1,900 Yuan according to the general price. Materials or other costs vary based on local circumstances.
Economic Profit Analysis
Annual output of direct reduced iron (sponge iron) is 10,000 tons, construction period is two months, put-into-production within 2 months, and product' price is 2,500Yuan/ton.
10,000 tons×2,500Yuan/ton , annual production value is 25 million Yuan, and tax is 1.50 million Yuan ( tax rate is 6%)
Yearly Profit: 35-50 million yuan.
The investment will be refunded within one year based on above calculation.
Based on actual condition, the investment can be refunded within months.
If annual output reaches 20,000 tons, construction period is two months, and products' price is 2,500Yuan/ton.
Annual production value is 50 million Yuan, and tax is 3.00 million Yuan ( tax rate is 6%)
Yearly profit: 7-10 million Yuan
To calculate by above-mentioned, it can regain all investment in half a year.
Explanation
To use tunnel oven – solid carbon reduced process, the productivity will double increased by adding activator into carbon reducer.
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