Steelmaking

Steel is The Iron that contain the Carbon lower than 1,7%, as figure 1.

Steel is very important for our life, more than 95% of the equipment is made of steel. In line with the increasing demand for steel, the main raw material requirements and support: Alloy, Refractory, Flux, Spare Parts, Energy etc. will also increase.

The material requirements for steelmaking can be seen as figure 2.

Figure 2. The Material Requirements of Steelmaking

 

 

 

The continous process of steelmaking can be seen as figure 3.

 

 



Figure 3. The Process of Steelmaking

 

 

The most important processes in the manufacture of steel is how to maintain the properties of steel produced. So, maintaining the composition by adjusting the impurity content is very important. Impurities are usually controlled, Sulfur, Phosphor, Silicon, as well as gas and other alloy material if used.

  

 

 

Desulfurization

 

In absence of carbon, silicon and aluminium in metal, the desulphurization reaction can be written as:

 

[S] + [Fe] + (CaO) = (CaS) + (FeO)

 

 

Sulphur distribution ratio will be higher if:

 

aCaO is high (higher basicity)

aFeO is low (reducing slag)

k‘ is high (higher temperature)

 

Figure 4. Melt and Slag in The Laddle ( From Dr. Ing. Zulfiadi Zulhan)

 

Figure 5. Bottom stirring of Desulphurization Process

 

 



Desiliconization

Silicon in metal is oxidized to SiO2, the reaction taking place is:

[Si] + 2[O] = (SiO2)

The partitioning between slag and metal will depend upond the activities of silicon and oxygen in metal and on the the activity of silica in slag

[Si] + 2[O] = (SiO2)

 

Dephosphorization

 

Phosphor in metal is oxidized to P2O5, the reaction taking place is:

2[P] + 5[O] = (P2O5)

The partitioning between slag and metal will depend upond the activities of Phosphorus Pentoxide and oxygen in metal and on the the activity of Phospor in slag

2[P] + 5[O] = (P2O5)

 

Desulphurization need Reductive Environment, but the Desiliconization and Dephosphorization need Oxidative Environment. Degassing is done with vacuum condition.

 

 



 





Cast Irons

Cast irons contain much higher carbon and silicon levels than steels, theoretically higher than 1.8 wt.% but typically 3 to 5 wt.% Fe and 1 to 3 wt.% Si. These comprise another category of ferrous materials that are intended to be cast from the liquid state to the final desired shape. Various types of cast irons are widely used in industry, especially for valves, pumps, pipes, filters, and certain mechanical parts. Cast iron can be considered a ternary Fe-Si-C alloy. The carbon concentration is between 1.7 and 4.5%, most of which is present in insoluble form (e.g., graphite flakes or nodules). Such material is, however, normally called unalloyed cast iron and exists in four main types:

(i) white iron, which is brittle and glass hard;

(ii) unalloyed gray iron, which is soft but still brittle and which is the most common form of unalloyed cast iron;
(iii) the more ductile malleable iron;

(iv) nodular or ductile cast iron, the best modern form of cast iron, which has superior mechanical properties and equivalent corrosion resistance.
 

In addition, there are a number of alloy cast irons, many of which have improved corrosion resistance and substantially modified mechanical and physical properties. Generally, cast iron is not a particularly strong or tough structural material. Nevertheless, it is one of the most economical and is widely used in industry. Its annual production is surpassed only by steel. Iron castings are used in many items of equipment in the chemical-process industry, but its main use is in mechanical engineering applications: automobile and machine tools. Some of the best known classes, listed below, include the high-silicon and nickel cast irons. 

• gray cast iron

• white cast iron• chilled iron (duplex) • malleable cast irons
• ductile or nodular cast irons

• alloy cast irons

• high-silicon cast irons
• nickel cast irons

Gray Cast Iron or Graphitic Iron
 

Gray cast irons contain 1.7 to 4.5 wt.% of C and other alloying elements such as Si, Mn, and Fe. Due to the slow cooling rate during casting, the carbon is precipitated as thin flakes of graphite dispersed throughout the metal. Therefore, gray cast irons are relatively brittle. Gray cast iron is the least expensive material, is quite soft, has excellent machinability, and is easy to cast into intricate shapes. Various strengths are produced by varying the size, amount, and distribution of the graphite. For instance, ultimate tensile strength typically ranges from 155 to 400 MPa and the Vickers hardness from 130 to 300 HV. Gray iron has excellent wear resistance and damping properties. However, it is both thermal and mechanical shock sensitive. Gray iron castings can be welded with proper techniques and adequate preheating of the components.
 

 

White Cast Iron

White cast iron is made by controlling the chemical composition (i.e., low Si, high Mn) and rate of solidification of the iron melt. Rapid cooling leads to an alloy that has practically all its carbon retained as dissolved cementite that is hard and devoid of ductility. The resulting cast is hard, brittle, and virtually unmachinable, and finishing must be achieved by grinding. Typically, the Vickers hardness ranges from 400 to 600 HV. Its main use is for wear- or abrasion-resistant applications. In this respect white irons are superior to manganese steel, unless deformation or shock resistance is required. The major applications of cast irons include pump impellers, slurry pumps, and crushing and grinding equipment.



Malleable Cast Irons

Malleable iron exhibits a typical carbon content of 2.5 wt.% C. It is made from white cast iron by prolonged heating of the casting. This causes the carbides to decompose, and graphite aggregates are produced in the form of dispersed compact rosettes (i.e., no flakes). This gives a tough, relatively ductile material. There are two main types of malleable iron, standard and pearlitic. The latter contains both combined carbon and graphite nodules. Standard malleable irons are easily machined. This is less so for pearlitic iron. All malleable cast irons withstand cold working and bending without cracking. 


Ductile (Nodular) Cast Irons 

This is the best modern form of cast iron as it has superior mechanical properties and equivalent corrosion resistance. Ductility is much improved and may approach that of steel. Ductile iron is sometimes also called nodular cast iron or spheroidal graphite cast iron, as the graphite particles are approximately spherical in shape, in contrast to the graphite flakes in gray cast iron. Ductile cast iron exhibits a typical microstructure. This is achieved by the addition of a small amount of nickel-magnesium alloy or by inoculating the molten metal with magnesium or cerium. Furthermore, composition is about the same as gray iron, with some nickel, and with more carbon (3.7 wt.% C) than malleable iron. There are a number of grades of ductile iron. Some have maximum machinability and toughness, others have maximum oxidation resistance. Ductile iron castings can also be produced to have improved low-temperature impact properties. This is achieved by adequate thermal treatment, by control of the phosphorus and silicon content, and by various alloying processes.

 
High-Silicon Cast Irons
Cast irons with a high silicon level (i.e., 13 to 16 wt.% Si), which are called Duriron, exhibit,  for all concentrations of H2SO4, even up to the boiling point, a constant corrosion rate of  130 μm/year (i.e., 5 mpy). For these reasons, it is widely used in sulfuric acid service. Duriron is a cheap material that does not contain any amount of strategic metal. Nevertheless, it is very hard and brittle and thermal shock sensitive, so it is not readily machined or welded.

 

 

 

  

The Iron-Carbon (Fe-C) and Iron-Cementite (Fe-Fe3C) Systems

Because carbon is a ubiquitous element in both iron- and steelmaking processes due to its essential use as a reductant during the extractive process of iron from its ores, carbon has   a predominant role in  siderurgy  (i.e., the metallurgy of iron and its alloys). Although other  alloying elements may be added to produce steels for special purposes, usually the structure of iron and steels is determined first by the content of carbon, secondly by the type of other alloying elements, and finally by the rate of cooling from the molten state. For all the above reasons, a solid grasp of the iron-carbon system is a mandatory step for understanding iron and iron alloys (i.e., steels and cast irons). As for the phase diagram of pure iron, the major phases occuring in the Fe-C phase diagram (Figure 1) can be accurately characterized by means of X-ray diffraction, thermal analysis, and dilatometry techniques. In practice, the iron-carbon phase diagram is a graphical plot of phases existing in thermodynamic equilibrium as a function of temperature versus the mass fraction of total carbon in the iron. The diagram depicted in this book is only a detail of the entire diagram. Actually, the phase diagram extends on the abscissa axis at left from pure iron free of carbon to a content of total carbon reaching 6.70 wt.% C that corresponds to the theoretical composition of iron carbide or cementite (Fe3C), while temperatures range from 200°C to 1600°C, the temperature at  which the system is fully liquid. The binary phase diagram exhibits, in addition to the four  critical points of the allotropes of pure iron, three other important characteristics:

 

(i) a eutectic point at 4.30 wt.% C and 1148°C;

(ii) a eutectoid point at 0.77 wt.% C and 727°C;

(iii) a peritectic transformation occurring at 1495°C.

 

 

 

Moreover, experimentally the following solid phases were identified.

 

Alpha-ferrite (α-ferrite, bcc). Sensu stricto and historically, ferrite consists of a solid solution of carbon inside a body-centered cubic crystal lattice in alpha-iron. The solubility of carbon in alpha-iron is extremely low, ca. 0.01 wt.% C at ambient temperature, and reaches only 0.025 wt.% C at 723oC. Therefore, at room temperature under conditions of equilibrium, any carbon present in excess of that small amount will exsolute in the form of cementite. Due to this low carbon content, some textbooks treat the ferrite phase substantially as pure iron, but this view must be discontinued to avoid confusion.  Usually, the ferrite of an alloyed steel may contain in solid solution appreciable amounts of other elements; ab extenso, any solid solution of which alpha-iron is the solvent is called ferrite (i.e., a solid solution of any element in alpha-iron). Alloying elements that stabilize ferrite are listed in Table 1.
 

 

 

Beta-ferrite (b-ferrite, bcc). Like alpha-ferrite, beta-ferrite consists of a solid solution of  any element in body-centered cubic beta iron.

Delta-ferrite (δ-ferrite, bcc).
Like alpha-ferrite, delta-ferrite consists of a solid solution of  any element in body-centered cubic delta iron. In the case of carbon, its maximum solubility in delta-iron is only 0.1 wt.% at 1487°C.
Gamma-austenite (g-austenite, fcc). Austenite is a solid insertion solution of carbon into the crystal lattice of face-centered cubic gamma-iron. It has been definitively established that the carbon atoms in austenite occupy interstitial positions in the face-centered cubic space lattice causing the lattice parameter to increase progressively with the carbon content. Cementite. Cementite is an iron carbide with the chemical formula Fe3 C. At room temperature,   cementite is a hard, brittle, and ferromagnetic material with a Curie temperature of   210°C. It is formed by chemical reaction between iron and excess carbon. Three distinct origins must, however, be distinguished:

(i) primary cementite resulting from the separation during solidification of liquid iron with carbon content ranging between 4.3 wt.% and 6.69 wt.% C;

(ii) secondary cementite formed after demixion of carbon as a result of a decrease in miscibility during the cooling of ferrite;

(iii) tertiary cementite resulting from demixion during the cooling of austenite. Actually, at

room temperature under conditions of equilibrium, any carbon present in excess of that small amount must exist in a form other than that of a solute in a solid solution.

Perlite. A biphasic eutectoidic constituent that consists of an interlamellar growth of ferrite and cementite. Perlite is formed during the transformation of austenite with a eutectoid composition (i.e., 0.77 wt.% C).

 

Ledeburite. A biphasic eutectic constituent resulting from the solidification of a molten metal having a eutectic composition. Hence it consists of an austenite containing 1.7 wt.% C in solid solution and cementite.

 

In the phase diagrams in Figures 2.1 and 2.2, the transition temperatures or critical points   previously identified for the four iron allotropes must now be replaced by two temperature  limits or points. Actually, due to hysteresis phenomena occurring upon heating and cooling, the equilibrium curves are greatly influenced by the rate of cooling and heating, and they form distinct plots. The various temperatures at which pauses occur in the rise or fall of  temperatures when iron or steel is heated from room temperature or cooled from the molten  state are called arrest points, denoted by uppercase letter A. Due to the previously mentioned hysteresis behavior during heating and cooling, the arrest points obtained on heating   are denoted Ac and those obtained on cooling are denoted Ar,  while arrest points at equilibrium are denoted Ae. Historically, the subscripts c , r, and e were derived from the first letters  of the French words chauffage (heating), refroidissement (cooling), and équilibre (equilibrium),  respectively. These arrest points are described in detail in Table 2.

 

 

From the iron-carbon phase diagram several important characteristics regarding the classification   of iron and iron alloys can be seen. Iron alloys are classified according to their total content of carbon. Steel are particular iron alloys having a carbon content below 2.1 wt.% C.  Above this limit, we have cast irons up to a practical limit of 3.75 wt.% C. A steel containing  0.77 wt.% C is called a eutectoid steel.  Eutectoid steel consists of an intimate mixture of alpha- ferrite and cementite forming an intergrowth of thin plates or lamellae known as perlite.  Therefore, a steel having a carbon content below 0.77 wt.% C is called a hypotectoid steel. Its  structure consists of a small amount of pearlite with an excess of alpha-ferrite, which collectsat the grain boundaries. Hypotectoid steels are hence softer and more ductile than eutectoid steels. On the other hand, a steel with more than 0.77 wt.% C is called a hypertectoid steel. Its   structure consists of pearlite with an excess of cementite. Hypertectoid steels are harder,  more brittle, and les ductile than eutectoid steels. Above 2.11 wt.% C, molten iron solidifies   always below 1350°C and the resulting low liquidus temperature iron alloys are called cast irons due to their ease of melting. The eutectic point in the Fe-C diagram is located at  4.3 wt.% C. At this composition, when the alloy solidifies, it forms a mixture of austenite  with 1.7 wt.% C in solid solution and cementite; this eutectic structure is called ledeburite. In  practice, cast irons exhibit a carbon content ranging between 2.11 and 3.75 wt.%. Upon cooling, cast irons exhibit a mixture of pearlite and cementite.

 

 

 

The iron-carbon phase diagram only applies to alloys that contain only iron and carbon. But because other desired or undesired alloying elements are usually originally present from the ironmaking process (e.g., O, C, Si, P, Mn, V) or are added intentionally (e.g., Ni, Cr, Mo), during steelmaking the iron-carbon phase diagram cannot show accurately the conditions that apply to actual steels. Hence it has to be modified appropriately to take into account the effect of the elements. These additional elements impact both the arrest points and equilibrium lines, and they also determine the existence or not of certain phases. Alloying elements with their related impact on iron-carbon phases are listed in Table 3.

 

 

Iron Making

The blast furnace

Ironmaking consists in winning iron metal from iron chemically combined with oxygen. The blast-furnace process, which consists in the carbothermic reduction of iron oxides, is industrially the most efficient process. From a chemical engineering point of view, the blast furnace can be described as a countercurrent heat and oxygen exchanger in which rising combustion gas loses most of its heat on the way up, leaving the furnace at a temperature of about 200°C, while descending iron oxides are reduced to metallic iron. The blast furnace is a tall, vertical steel reactor lined internally with refractory ceramics such as high-alumina firebrick (45 to 63 wt.% Al2O3) and graphite. Five sections can be clearly identified:

 

(i) At the bottom is a parallel-sided hearth where liquid metal and slag collect. This is surmounted by 

(ii) an inverted truncated cone known as the bosh. Air is blown into the furnace through

(iii) tuyeres, i.e., water-cooled copper nozzles, mounted at the top of the hearth close to its  junction with the bosh.

(iv) A short vertical section called the bosh parallel, or the barrel, connects the bosh to the truncated upright cone that is the stack.

(v) Finally, the fifth and top section, through which the charge is fed into the furnace, is the throat.

The lining in the bosh and hearth, where the highest temperatures occur, is usually made of carbon bricks, which are manufactured by pressing and baking a mixture of coke, anthracite, and pitch. Actually, carbon exhibits excellent corrosion resistance to molten iron and slag in comparison with the aluminosilicate firebricks used for the remainder of the lining.

 

 

The Processing of Blast Furnace

 

 

 

Figure 1. The Process of Blast Furnace

 

 

 

Iron oxides can come to the blast furnace plant in the form of raw ore, pellets or sinter. The raw ore is removed from the earth and sized into pieces that range from 0.5 to 1.5 inches. This ore is either Hematite (Fe₂O₃) or Magnetite (Fe₃O₄) and the iron content ranges from 50% to 70%. This iron rich ore can be charged directly into a blast furnace without any further processing. Iron ore that contains a lower iron content must be processed or beneficiated to increase its iron content. Pellets are produced from this lower iron content ore. This ore is crushed and ground into a powder so the waste material called gangue can be removed. The remaining iron-rich powder is rolled into balls and fired in a furnace to produce strong, marble-sized pellets that contain 60% to 65% iron. Sinter is produced from fine raw ore, small coke, sand-sized limestone and numerous other steel plant waste materials that contain some iron. These fine materials are proportioned to obtain a desired product chemistry then mixed together. This raw material mix is then placed on a sintering strand, which is similar to a steel conveyor belt, where it is ignited by gas fired furnace and fused by the heat from the coke fines into larger size pieces that are from 0.5 to 2.0 inches. The iron ore, pellets and sinter then become the liquid iron produced in the blast furnace with any of their remaining impurities going to the liquid slag.

 

 

The coke is produced from a mixture of coals. The coal is crushed and ground into a powder and then charged into an oven. As the oven is heated the coal is cooked so most of the volatile matter such as oil and tar are removed. The cooked coal, called coke, is removed from the oven after 18 to 24 hours of reaction time. The coke is cooled and screened into pieces ranging from one inch to four inches. The coke contains 90 to 93% carbon, some ash and sulfur but compared to raw coal is very strong. The strong pieces of coke with a high energy value provide permeability, heat and gases which are required to reduce and melt the iron ore, pellets and sinter.

The final raw material in the ironmaking process in limestone. The limestone is removed from the earth by blasting with explosives. It is then crushed and screened to a size that ranges from 0.5 inch to 1.5 inch to become blast furnace flux . This flux can be pure high calcium limestone, dolomitic limestone containing magnesia or a blend of the two types of limestone.

Since the limestone is melted to become the slag which removes sulfur and other impurities, the blast furnace operator may blend the different stones to produce the desired slag chemistry and create optimum slag properties such as a low melting point and a high fluidity.

All of the raw materials are stored in an ore field and transferred to the stockhouse before charging. Once these materials are charged into the furnace top, they go through numerous chemical and physical reactions while descending to the bottom of the furnace.

The iron ore, pellets and sinter are reduced which simply means the oxygen in the iron oxides is removed by a series of chemical reactions. These reactions occur as follows:

 

1) 3 Fe2O3 + CO = CO2 + 2 Fe3O4	Begins at 455° C
2) Fe3O4 + CO = CO2 + 3 FeO	Begins at 595° C
3) FeO + CO = CO2 + Fe     or     FeO + C = CO + Fe	Begins at 705° C

At the same time the iron oxides are going through these purifying reactions, they are also beginning to soften then melt and finally trickle as liquid iron through the coke to the bottom of the furnace.

The coke descends to the bottom of the furnace to the level where the preheated air or hot blast enters the blast furnace. The coke is ignited by this hot blast and immediately reacts to generate heat as follows:

C + O₂ = CO₂ + Heat

Since the reaction takes place in the presence of excess carbon at a high temperature the carbon dioxide is reduced to carbon monoxide as follows:

CO₂+ C = 2CO

The product of this reaction, carbon monoxide, is necessary to reduce the iron ore as seen in the previous iron oxide reactions.
The limestone descends in the blast furnace and remains a solid while going through its first reaction as follows:

CaCO₃ = CaO + CO₂

This reaction requires energy and starts at about 870°C. The CaO formed from this reaction is used to remove sulfur from the iron which is necessary before the hot metal becomes steel. This sulfur removing reaction is:

FeS + CaO + C = CaS + FeO + CO

The CaS becomes part of the slag. The slag is also formed from any remaining Silica (SiO₂), Alumina (Al₂O₃), Magnesia (MgO) or Calcia (CaO) that entered with the iron ore, pellets, sinter or coke. The liquid slag then trickles through the coke bed to the bottom of the furnace where it floats on top of the liquid iron since it is less dense.
 

Another product of the ironmaking process, in addition to molten iron and slag, is hot dirty gases. These gases exit the top of the blast furnace and proceed through gas cleaning equipment where particulate matter is removed from the gas and the gas is cooled. This gas has a considerable energy value so it is burned as a fuel in the "hot blast stoves" which are used to preheat the air entering the blast furnace to become "hot blast". Any of the gas not burned in the stoves is sent to the boiler house and is used to generate steam which turns a turbo blower that generates the compressed air known as "cold blast" that comes to the stoves.

During the blast-furnace process, the solid charge (i.e., mixture of iron ore, limestone, and coke) is loaded either by operated skips or by conveyor belts at the top of the furnace at temperatures ranging from 150 to 200°C, while preheated air (i.e., 900 to 1350°C) in hot-blast stoves, sometimes enriched up to 25 vol.% O, is blown into the furnace through the tuyeres. During the process, the coke serves both as fuel and reducing agent, and a fraction combines with iron. The limestone acts as a fluxing agent, i.e., it reacts with both silica gangue materials and traces of sulfur to form a slag. Sometimes fluorspar is also used as fluxing agent. During the carbothermic reduction, the ascending carbon monoxide (CO) resulting from the exothermic combustion of coke at the tuyere entrance begins to react with the descending charge, partially reducing the ore to ferrous oxide (FeO). At the same time the CO is cooled by the descending charge and reacts, forming carbon dioxide (CO2) and carbon black (soot). 

 

This soot is dissolved in the iron, forming a eutectic, and hence decreases the melting temperature. At this stage, the temperature is sufficiently high to decompose the limestone into lime (CaO) and CO2. Carbon dioxide reacts with the coke to give off CO, and the free lime combines with silica gangue to form a molten silicate slag floating upon molten iron. Slag is removed from the furnace by the same taphole as the iron, and it exhibits the following chemical composition: 30 to 40 wt.% SiO2, 5 to 15 wt.% Al2O3,  reduction of ferrous oxide into iron is completed and the main product, called molten pig iron (i.e., hot metal or blast-furnace iron), is tapped from the bottom of the furnace at regular intervals. The gas exiting at the top of the furnace is composed mainly of 23 vol.% CO, 22 vol.% CO2, 3 vol.% H2O, and 49 vol.% N2, and after the dust particles have been removed using dust collectors, it is mixed with coke oven gas and burned in hot-blast stoves to heat  the air blown in through the tuyeres. It is important to note that during the process, traces of   aluminum, manganese, and silicon from the gangue are oxidized and recovered into the slag, while phosphorus and sulfur dissolve into the molten iron.

 In summary, the blast furnace is a counter-current realtor where solids descend and gases ascend. In this reactor there are numerous chemical and physical reactions that produce the desired final product which is hot metal. A typical hot metal chemistry follows:

Iron (Fe)	= 93.5 - 95.0%
Silicon (Si)	= 0.30 - 0.90%
Sulfur (S)	= 0.025 - 0.050%
Manganese (Mn)	= 0.55 - 0.75%
Phosphorus (P)	= 0.03 - 0.09%
Titanium (Ti)	= 0.02 - 0.06%
Carbon (C)	= 4.1 - 4.4%

Figure 2. The Blast Furnace Plant

Direct reduction iron

The blast-furnace process is strongly dependent on the commercial availability of coke. For that reason, numerous substitute processes have been investigated since the 1950s to produce a prereduced product for crude steelmaking based on iron ore reduction without using coke as a reductant and to avoid operation of a capital-intensive coke oven plant. These technologies have been especially attractive in countries suffering a coke supply deficit, and hence they are used in Central and South America, India, and  Africa. These processes are grouped under the term direct reduction and smelting reduction.  Direct reduction processes produce solid direct reduced iron (DRI) or hot briquetted iron  (HBI), while smelting reduction processes produce liquid hot metal. However, despite their great promise, these technologies have never superseded the blast furnace, especially in industrialized countries, for the following reasons:

 

(i) Direct reduction is attractive at locations where cheap energy and particularly cheap natural gas is available.

(ii) The development of a market for steel scrap as a raw material acts against direct reduction. Direct reduction can be divided according to the type of reductant used (i.e., natural gas, coal) or the screen size of iron ore (i.e., coarse, fines).

 

 

Table 1. Processes For Direct Reduction

 

 

 

Table 2. Pure Iron Grades

 

Sponge Iron Making

The process of sponge iron manufacturing involves removal of oxygen from iron ore. When that happens, the departing oxygen causes micro pores in the ore body, turning it porous. When the eventual product is observed under a microscope, it resembles a honeycomb structure, which looks spongy in texture. Hence the name sponge iron.
 

The Main Raw Material are Primary ore Secondary Iron Ore (Magnetite or Hematite),  Iron sand also can be used but it should be a Pellet first. Beside that Non Cooking Coal for reduction and sometimes dolomite or Lime is needed to fix the Sulfur and or bacisity.

Fig 1. Example for Specification of Iron Ore

 

 

Fig 2. Rotary Kiln Cross Section

 

Coal based Direct reduction process is classified based on the reducing agent namely solid. Most solid reduction process use non-coking coal as reducing agent due to abundantly available non-coking coal. The process proposed to be adopted is the rotary kiln proposes using Non-coking coal and iron ore. Iron are undergoes the following reduction reaction in all the processes.

 

Based on Fig 3. seen that the reaction start at Temperature around 700 oC with 60% of CO at 1 atm. But Normally, the process is done at temperature 900-1100 oC.

 

Fig 3. Iron and Boudouard reaction Diagram

 

 

After processed in rotary kiln, the product sponge iron come to the water cooled cooler where its temperature reaches to 80 to 100°C. The Product is conveyed to the product separation and storage building.

 

 

 

Fig 4. Example of Spong Iron Specification

 

 



The Example of the Complete Flowsheet can be seen as figure 5.

 

 

Fig. 5 Process Flowsheet