Pig iron productions

Introduction :

Pig iron is the intermediate product which is obtained during the smelting of iron ore with coke, in this process limestone is used as flux. Pig iron has maximum carbon content, it is around 3.5–4.5% which improves the brittleness of iron. In olden days, the Chinese Zhou dynasty were making pig iron in Europe. The plant used for the pig iron production is sinter plant.There will be use of two furnaces for the pig iron production. The word pig iron comes from old casting blast furnace iron method into moulds which are arranged on the beds of sand.

Pig iron production:

Blast furnace used for pig iron production:

Pig iron production is done by blast furnace method which involves the smelting of iron ore like hematite, i.e.
Fe₂O₃ + 3CO → 2Fe + 3CO₂

A blast of preheated air is blown through the furnace which reacts with carbon which is in the form of coke to produce carbon monoxide and also a large amount of heat is produced. The produced carbon monoxide reacts with the iron ore to form molten iron and carbon dioxide. Unreacted carbon monoxide, nitrogen which is present in the blown air and hot carbon dioxide are fed into the reaction zone as a fresh feed so that there will be preheating of fresh feed using counter current gases and also there will be the decomposition of limestone to calcium oxide and carbon dioxide and starts to reduce iron oxide in the solid state. So formed calcium oxide reacts with some of the acidic impurities which are present in iron which form a slag called calcium silicate. The reactions involved in the pig iron production are

C + O₂ → CO₂
CO₂ + C → 2CO
CaCO₃ → CaO + CO₂
SiO₂ + CaO → CaSiO₃(slag)

The pig iron obtained by this method has high carbon content so which increases the brittleness by that it has limited commercial applications. If there is a need to reduce the carbon content, pig iron undergoes further processes.

Applications of Pig iron:

• Pig iron sometimes used to produce cast iron and Gray iron which is achieved by smelting the pig iron.
• Pig iron is used to produce steel metal.

Iron Steel Manufacturing

Introduction :
Iron produced in the blast furnace is known as pig iron or cast iron.  Pig iron is the iron which contains 4% of carbon and some other impurities.

Carbon contents present in pig iron are reduced by burning off carbon as carbon monoxide and carbon dioxide. Impurities present as sulphur, manganese etc are oxidised as their oxides. There are three methods of burning carbon for production of steel.

(i) Bessemer Process
(ii) Open Hearth Process
(iii) Electric Furnace Process

Bessemer Process of Manufacturing:

This was the first process for the mass-production of steel from molten iron. Henry Bessemer invented this process in 1855.

Principle: Removal of impurities from iron by oxidation is the key principle of this process. The oxidation also raises the temperature and hence melts the iron.

Process: In this process, burning takes place in a pear shaped furnace called Bessemer Converter. This furnace is coated with basic mixture of calcium oxide or magnesium oxide (CaO / MgO). Hot air is introduced through holes. The temperature of furnace is maintained at 1873K. Manganese in the iron is removed as manganese silicate, (which is called as slag).

2Mn + O₂ ----------> 2MnO

Si + O₂ -----------> SiO₂

MnO + SiO₂ -----------> MnSiO₂

Phosphorus present as impurity is removed by formation of slag. This slag is called Thomas slag. Thomas slag is very useful fertilizer.

4P + 5O₂ -----------> 2P₂O₅

3CaO + P₂O₅ -----------> (Ca)₃(PO4)₂    Thomas Slag

Open hearth process of manufacturing:

This process can be used for rapid manufacture of large quantities of steel. The steel producd by this process can be used for the construction of the high buildings. This process complemented the Bessemer process to produce steel. It is easier to control because it is a slow process.
In this process, cast iron, iron scrap, haematite and lime is taken in open hearth furnace. This furnace is heated at temperature of 1873 K. This furnace is heated with (CO+N₂). (CO+N₂) is called producer gas. Impurities are removed by oxidation with haematite.

Fe₂CO₃ + 3C ----------> 2Fe + 3CO

2Fe₂O₃ + 3S -----------> 4Fe + 3SO₂

5Fe₂O₃ + 6P ------------> 10Fe + 3P₂O₅

2Fe₂O₃ + 3Si ------------> 4Fe + 3SiO₂

3CaO + P₂O₅ ------------> Ca₃(PO4)₂ (Slag)

Electric Arc Furnace

 In this method, iron is heated electrically. Normally thesedays, steel is prepared by open hearth process. About 39% of the steel manufactured in US is produced from the electric furnace. The stel produced by this process is not very pure or of high quality.

Energy Consumption: An electric arc furnace consumes an energy of 350 - 700 kWh/ton of steel produced. We can reduce the energy consumption to 425 kWh/ton by using oxy-fuel burners.
This process is used for the electric production of steel. It is used for remelting of steel scrap. This process is useful for those markets where the quality of steel is not critical.

Air speed

Introduction :
It is the speed of an air related to the aircraft among them the qualifying airspeed are Calibrated airspeed, Indicated aircraft, Equivalent air speed, true airspeed and finally the density airspeed. This aircraft speed is measured by the airspeed indicator which is shortly and popularly known as ASI. These are connected to the pitot static system. Types of the airspeed are Indicated airspeed, Calibrated airspeed, Equivalent airspeed, True airspeed. In this article we will know types of articles and how to calculate the airspeed.

Air speed Types

Indicated airspeed is abbreviated as IAS. This indicator reads directly form the airspeed indicator by the pitot static system on the aircraft. This is the airspeed related to the CAS that is calibrated airspeed it is corrected for the installation errors and the instrument.

These IAS are very much important for the pilots for the various purposes like calculation of the limited speeds and so on. This plays an important role in the airspeed.

Calibrated air speed is for the instrument errors and position errors and the installation errors. This equation shows the installation and the minus position.
Where, Vc is the calibrated airspeed
qc is the impact pressure
Po is static air pressure. Measures 29.92126 inches Hg at sea level.
ao is speed of sound. Measures 661.4788 knots at standard sea level.

Equivalent & True airspeed

Equivalent airspeed: This produces dynamic pressure as the true speed at the altitude where the vehicle is flying. It is forward to the flight for the effects of compressibility. Compressible impact pressure makes a function of calibrated airspeed. At standard sea level equivalent airspeed and calibrated airspeed are equal.

True airspeed is also called as TAS, it is the physical speed of the aircraft. The relation between true airspped and speed is Vg.
Vt = Vg - Vw
Where Vw is the wind speed vector.
To compute true airspeed using a function of mach number
V_{t =} a_o.M`sqrt(T/(To))`
Where:
a_o= Speed of sound(661.4788 knots) at standard sea level
M = Mach number
T = Temperature in kelvins
T_o= (288.15 kelvins)Standard sea level temperature

Speed of Light and Sound

Introduction :

Light and sound are the essential part of our life and with an absence of one; we will not be able to communicate or to detect properly as we can do with help of these two. Light and sound both are the sensations produced by energetic particles with the help of which we will be able to see or listen. 

Difference between Speed of Light and Sound :

Regarding the speed of light and sound we can say the following points

1. Speed of light is much faster than the speed of sound in air.
2. Light do not require the medium to travel with its speed while the sound require medium to propagate.  
3. Speed of light is much less in transparent than what it had in vacuum.  While the speed of sound is much, fast in solid medium such as steel then in air.

Speed of light and sound : Conclusion

Why speed of sound Differ in different mediums means solid, liquid and air?

Explanation:
Since sound require medium particles to propagate properly, hence the medium having particles much closer will enhance the movement (speed) of sound wave rather than the medium which have a long gap between the particles. Since, the molecules spacing for solid, liquids, and gases are different in that gas molecules are more spread apart & free to move, liquids are a little more structured, and solids are very compact.             

The other reason for the different speed in different mediums is the elasticity of the medium. More the elasticity in the medium more will be the speeds of sound as we can understand with ball, more the elasticity of the ball more will it jump. Since steel is more elastic than air, so sound travels 19 times much faster in steel than its speed in air. E.g. if we put your ear on rail track we can hear the vibration of the train movement in the track much before than the whistle of the train which travels through air.

Aircraft speed of sound

Introduction :
Air crafts with propellers in the initial stages were not able to perform well when they approached the speed of sound. This problem resulted into deep research into jet engines conducted mainly by Frank White of England and Hans van Ohain of Germany. They carried out this research in their respective countries.

Breaking Sound Barriers

Various sources claimed to have broken the sound barriers. Claims were made that air crafts ran smoothly at the speed of sound without any turbulence but there were many disputes against these claims. These claims were made as early as 1945. Man has attempted to break the sound barriers since the time the first plane was invented by the Wright Brothers. Bell X-1 was the first flight to travel faster than the speed of sound and this happened on 14^th October, 1947 under Captain Charles Yeager.

Speed of Sound

The exact speed of sound is not known but it is considered that it varies according to the height above sea level or what we call as altitude. It is 761 mph at sea level and at 20000 feet above it is 660 mph.

Modern Aircrafts and their speed

Today there are several air crafts like fighter jets that travel at speeds faster than the speed of sound regularly. When the aircraft reaches close to the speed of sound what happens is quite interesting in respect of the movement of air around the wings of the plane. It is called the Prandtl-Glauert singularity and it is quite photogenic.

Conclusion to aircraft speed of sound

In two decades ranging from 1947 to 1967 there were appreciable efforts by man to reach the speed of sound and there are crafts that are unmanned and cross the speed of sound easily and that is quite a remarkable achievement. There will be further developments and we all have to wait and watch how fast air crafts will become.

Orbital Speed

The orbital speed of a celestial body measures its speed around another object’s center of gravity. This can be its speed at a given time and place in its path or may be its average speed. Depending upon the eccentricity of heavenly body's orbit the orbital speed changes as a satellite or moon gets closer to its center of gravity or further away. The two regions where speeds can change the most are pericenter and apocenter.

A satellite in orbit moves faster (pericenter) when it is close to the planet or other body that it orbits and slower (apocenter) when it is farther away. A satellite moving in a circular orbit has a constant speed which depends only on the mass of the planet and the distance between the satellite and the center of the planet.

Calculating the Orbital Speed

The speed (v) of a satellite in circular orbit is:

`v = sqrt((GM)/r)`

Where, `G` is the universal gravitational constant and the value is `6.6726 xx 10^-11 N m^2 kg^-2`,
`M`  is the mass of the combined planet-satellite system, in case Earth's mass is `5.972 xx 10^24 kg`, and we can ignore the satellite's mass, in case for smaller man made satellites.
and `r` is the radius of the orbit measured from the planet's center.
The period `P` of a satellite in circular orbit is the orbit's circumference divided by the satellite's speed:

`P = (2*pi*r)/v`

Kepler's Law for Orbital Speed:

Kepler's second law is illustrates that the line joining the Sun and planet sweeps out equal areas in equal times, this means the planet moves faster when it is nearer the Sun (perihelion). Henceforth, a planet executes elliptical motion with constantly changing angular speed as it moves about its orbit. The point of nearest distance of the planet to the Sun is known as perihelion; the point of greatest separation is known as aphelion. Therefore, by Kepler's second law, the planet moves fastest when it is near perihelion and slowest when it is near aphelion.

Arrhenius theory acid

Introduction :
According to Arrhenius an acid  is any substance that dissociates   to give  a H+ ion  in aqueous solution.

Thus an aqueous solution of hydrochloric acid will  show the presence of H+ ions and Cl- ions.
 Later it was found that the H+ ions have no free existence in water or in aqueous solution but exist in the solvated state as hydronium ion as H₃O^+.

  Thus according to Arrhenius definition of an acid,  any substance that will increase the concentration of H+ ions in water is said to be an acid.

  General Representation:  An Arrhenius acid  is generally represented by the formula with a H in the begining as HCl , H₂SO4 , HNO_3. All  acids that can donate a proton in aqueous solution or  can increase the concentration of H₃O⁺ ions in solution  are called Arrhenius acids.The dissociation of an acid in water can be represented by the equation a follows:
 If HCl be the acid then the dissociation is given as
HCl((g)  +  H₂O(l)    ---> H₃O⁺  + Cl^-

The advantage of the Arrhenius definition of an acid.

1) All protic acids that can dissociate in aqueous solution to increase the H+ ione concentration show similar properties such as :

Reaction with bases result in neutralisation of the acid and formation of water and a salt
example: HCl + NaOH----------> NaCl + H₂O
                  HNO₃ + KOH --------> KNO₃ + H₂O      

2)  The basicity of the acids depends upon number of H+ ions, an acid can releas in aqueous solution

3) The pH of any substance depends upon the number of H+ ions the substance can release in solution

Limitation of Arrhenius definition of acid>

1) Arrhenius definition of acid holds good only for acids in aqueous solution. For example
HCl (aq) ----------> H⁺(aq)  + Cl^- (aq)
      H⁺ (aq) + H₂O (l) ---------> H₃O⁺ (aq)
    But HCl in gaseous state is neither acidic nor basic.

2) Acid not dissolved in (aq) solution cannot dissociate into H+ ions. For example
     HNO3 (l) + 2H2SO4 (l) -----------> NO⁺⁺ (l) + H₃O⁺ (l) + 2HSO₄^-   (l)
Here HNO3 acts as a base

3) Arrhenius definition of acid cannot account for the acidic character of AlCl₃