PERED ® DIRECT REDUCTION PROCESS

1. Brief description of the PERED ® Direct Reduction Process

There are several processes to derive Iron from Iron oxide without converting

their physical form. The PERED® Direct Reduction Process is the latest

invention in this. The process has been invented & developed by the experts

having rich experience in every field of Direct Reduction process, which has

ensured that all the flaws of other processes are taken care in this process &

provides the optimum & efficient results to the buyer.

The technology is patented at Germany & Iran and process to obtain the

patent for Europe is being carried out.

The PERED® Direct Reduction Process converts iron oxides, in the form of

pellets or lump ore, to highly reduced product suitable for steel making. To

accomplish this, the reduction process utilizes a continuous flow of reducing

gas to chemically extract oxygen from the iron oxide and to carburize the

reduced product.

The reduction process is carried out below the fusion temperature of the feed

material. The reducing gas, a mixture of hydrogen, carbon monoxide and

other components is produced in the reformer and introduced into the

reduction furnace at controlled analysis and temperature. The reducing gas

flows up the furnace, heating the descending iron oxide to reduction

temperatures. The hydrogen and carbon monoxide extract the oxygen from

the iron oxide yielding a highly reduced product.

Output from The PERED® Direct Reduction plants can be in any form, viz.

Cold DRI, Hot Briquetted Iron (HBI), or combination of Cold DRI / HBI, Hot DRI/

Hot Briquetted Iron (HBI) or Cold DRI/Hot DRI combination.

The most significant features of the PERED® Direct Reduction Process are:

• A continuous system utilizing an uninterrupted flow of reducing gases for

the removal of oxygen from the iron oxide feed material and for

carburizing the reduced iron;

• Minimum fuel consumption by recycling the top gas from the shaft furnace

into the process;

• The specially designed gas reforming system which uses carbon dioxide

and steam, produced during the reduction of the iron oxide, for the

catalytic conversion of the natural gas without formation of soot. This

obviates the necessity of an external source of oxygen for the partial

oxidation of methane.

• The speciality of PERED Reformer is the control of steam percentage which

is produced from the waste heat from the flue gas.

• Maximum heat recovery by preheating the main air, natural gas and feed

gas & production of steam through flue gas.

PERED® DR-plant is operating at wide range of reduction temperatures. The

reduction temperature employed depends on the type of oxide feed. The

flexibility of the PERED® DR-process is further demonstrated by the fact that

variety of material can be used effectively & a range of desired degree of

metallization of product can be achieved to suit the requirements of steel

making.

The difference between the chemical analyses of the raw material and the

metallized material is related to the oxygen removal, in proportion to the

metallizing percentage, and the formation of carbon. The shape of the oxide

material is not changed during the reduction. The metallized material is

highly porous, as oxygen is removed from the ore, and tends to reoxidation.

Therefore, the hot metallized material must be cooled before exposure to the

atmosphere to prevent reoxidation before discharging the DRI to the storage

bins.

2. Basic Flow sheet of the PERED ® Direct Reduction Process

A simplified process flow diagram is shown on figure 1.

Fig I

3. Major equipments of PERED ® DR plant

The two principal equipments of a PERED® DR-plant are the Reactor as a

shaft furnace in which the reduction process takes place and the Gas

Reformer for the production of the reducing gases.

3.1 Vertical Shaft Furnace

The shaft type metallizing furnace utilizes a continuous process flow at

highest known efficiencies. Within the furnace, the pellets descend by gravity

and will be metallized by direct counter current contact with reducing gasses

in the reduction zone.

In the shaft furnace the iron oxide material is fed from charge hopper by

gravity through a dynamic gas seal into distribution pipes, which feed the

material into the reduction furnace. The oxide distribution pipes are designed

specially to deliver the material on the periphery & at centre thereby

maintaining a uniform profile of material in the furnace & to increase the

reduction zone volume. The feed rate to the charge hopper is controlled by

the discharge rate of the product from the bottom of the furnace.

The shaft furnace is divided in three zones with separate gas system, the

upper zone for reduction, transition zone for carburizing & In-situ reforming

and the lower zone for cooling.

A, Reduction zone

The reduction zone in PERED reactor is specially designed to increase the

efficiency, to eliminate fines generation & to take care of swelling of pellet

during reduction process. The bustle ports, installed in two levels at the

bottom of the reduction zone, are of special shape to have better penetration

of gas to the burden & for better maintainability. The position of Top Gas

offtake reduces fines carry over & improves height / diameter ratio.

The reformed gas, containing hydrogen and carbon monoxide at a controlled

temperature and ratio, is introduced into the descending burden through a

series of ports arranged in two levels around the bottom periphery of the

reduction zone. In PERED® process the composition & temperature of the

Bustle gas can be adjusted independently, if required.

The ascending gases heat the oxide material by counter flow contact up to

the reduction temperature whereby H2 and CO reacts with the iron oxide to

form water vapour and CO2 and leave metallic iron in the product.

The basic reactions taking place in the reduction zone are as follows:

A . Hematite reduced to magnetite

3Fe2O3 + CO 2Fe3O4 + CO2

3Fe2O3 + H2 2Fe3O4 + H2O

B . Magnetite reduced to iron Wustite

Fe3O4 + CO 3FeO + CO2

Fe3O4 + H2 3FeO + H2O

C . Wustite reduced to metallic iron

Fe O + CO Fe + CO2

Fe O + H2 Fe + H2O

The carburizing potential of the reducing gas is controlled to achieve to a certain extent – the desired level of carbon in the reduced iron. The majority

of carbon contained in PERED direct reduced iron is in the form of iron carbide (Fe3C) which favours subsequent melting. The basic carburizing reactions taking place are as follows:

D. Metallic iron to Cementite

3Fe + 2CO Fe3C + CO2

3Fe +CO + H2 Fe3C + H2O

3Fe + CH4 Fe3C + 2H2

B, Transition zone

Material flowing thro the reduction zone passes into a transition zone prior to entering the cooling zone. This transition zone has sufficient height to isolate the reduction zone and cooling zone gas circuits from each other and to allow independent control.

In PERED process the transition zone is utilized for Insitu reforming by injecting natural gas at higher and controlled flow rate.

In –situ reforming has several beneficial functions:

• It carburizes & cools the metallic iron

• It uses sensible heat in the metallic iron to heat and reform the natural

gas into additional reducing gas thus increases productivity & overall energy consumption.

Elimination of water cooled burden feeder reduces fines generation, drop in burden temperature & chances of cluster formation in this region .

In this zone there is a specially designed easy flow device called “China hat” to regulate uniform material flow inside the furnace.

C, Cooling zone

In PERED process the cooling gas is introduced circumferentially through a specially designed nozzles in the lower part of the shaft furnace. This modified arrangement reduces cooling zone height and improves proper distribution of the gas along the burden, which in turn improves efficiency of cooling zone.

At the top of the cooling zone, hot cooling gas is sucked through four off take channels specially designed for uniform utilization of cooling zone and to reduce fines carryover.

The hot gas from the furnace is then scrubbed, compressed and recycled after conditioning with NG. PERED operates with very high cooling gas CH4

content to optimize the cooling zone efficiency.

The material flow at this zone is regularised by two series of burden feeders which rotates 360 degree and can be controlled independently for speed, direction and degree of rotation. These burden feeders are advantageous to regularise the material flow and during trouble shooting.

The reduction furnace operates at moderate pressure with the reduction gas remaining within the furnace system by means of dynamic seals at both, top and bottom of the reduction furnace. The raw material entering and the product discharged through the seal legs provide a resistance to gas flow. Inert seal gas generated during firing of the reformer is introduced at elevated pressure into the seal legs. Small volumes of inert gases are vented from the reduction furnace discharge and/or the furnace charge hopper.

The DRI produced is discharged from the furnace bottom via a conveyor system into the storage bins for passivation before being consumed in the EAF or sent to further storage for shipment.

The hot, dust laden top gas from furnace is sent to the top gas scrubber where it is cooled, cleaned and its water vapour content reduced. Upon leaving the top gas scrubber, the gas stream is split. Approximately 2/3 of gas is used as process gas, while the remaining 1/3 of the gas is utilized as combustion fuel to heat the reformer.

Unlike other processes, the water content is minimised from the top gas in top gas scrubber. This in turn reduces the load on Process gas compressors as it has to circulate less process gas flow.

3.2 Reformer

PERED Reformer generates reduction gases by reforming natural gas in presence of specially designed catalyst, named “PERFORMEX”.

The required water content for reforming is achieved by adding steam which is produced from the waste heat of the flue gas from the reformer a controlled flow rate.

The process gas is enriched with preheated natural gas and water in the form of steam to obtain the proper feed gas mixture for reforming. After enrichment, this gas is called feed gas. The feed gas is then heated up to approximately 550°C by waste process heat.

The preheated feed gas then flows through the reformer and is reformed in multiple heat-resisting alloy tubes containing specially designed flower type “Performex” catalysts developed to reform methane with CO2 and H2O with up to 10 ppm (vol.) sulphur present in the feed gas, according to the following fundamental chemical reactions:

1) CH4 + CO2 2CO + 2H2

2) CH4 + H2O CO + 3H2

The reformed gas analysis and the temperature of the reformer are automatically controlled. The PERED reformer produces reducing gases with higher H2/CO ratio than MIDREX reformer, which provides a safe operation of reformer & furnace. The reformed gas temperature is adjusted before entering the reduction furnace as per oxide mix ratio and oxygen availability.

The reformer is fired by multiple burners using preheated air and burning a mixture of top gas fuel recycled from furnace top gas / spent gas and natural gas. The flue gas from the reformer is used to preheat combustion air, feed gas and natural gas and generate steam in the heat recovery system thereby minimizing the energy consumption of the DR-Plant. The flue gas is exhausted to the atmosphere by a ID fan. A small portion of the reformer flue gas is cooled and is then compressed and used as inert gas throughout the DR-Plant at various points.

4. Salient features of the PERED ® Direct Reduction Process:

• Moderate operating pressure in reactor compared to MIDREX & HYL

processes to improve the reaction rate and to keep the process simplified.

• Higher H2/CO ratio to reduce the risk of clustering inside the reactor

furnace and safer operation of reformer.

• Top gas scrubber with single outlet composition with less moisture

content reduce the load of process gas compressor.

• Steam generation from waste heat recovery to reduce the energy

consumption & environmental impacts.

• Separate steam addition to control the H2/CO ratio precisely and thus

stabilise the reduction gas quality and in turn the product quality.

• Safe reformer operation with high H2/CO ratio.

• Specially designed Performex catalyst with improved efficiency to

produce high quality reducing gases.

• Heat recovery system of high efficiency with inverted tube bundles.

• Maximum heat recovery by preheating the main air, natural gas and

feed gas & production of steam from flue gas and thus Low flue gas temperature to the atmosphere.

• Double bustle gas injection ports with provision for injecting reducing

gases with two different composition and temperature.

• Simplified design of bustle port to have better flow pattern & easy

maintenance.

• Oxide distributor feed legs specially designed for uniform distribution

of oxide particle size & increase the reduction zone volume.

• Ultra thin Tapered refractory construction in reactor to take care of DRI

swelling

• Specially designed top gas off take to improve the efficiency of the

furnace & to minimize the fines carryover.

• No water cooled burden feeders in 800 series plant.

• Specially designed rotating burden feeders, which can be controlled

independently for speed, direction & degree of rotation, to improve the flow pattern & to perform better as cluster breaker in case of cluster formation in side the furnace.

• Specially designed china hat for uniform material flow inside the

furnace.

• Circumferential cooling gas injection to optimize the cooling zone

efficiency.

• Specially designed cross shaped cooling gas off take to optimize the

cooling efficiency & to minimize the fines carryover.

• Less furnace height.

• Less capital, operating & maintenance cost.