7/30/2019 III sem ICT (5)

1/22

MANUFACTURE OF AMMONIA

7/30/2019 III sem ICT (5)

2/22

Purified

NH3

Synthesis

Gas

Oil

Filter

1 mol N2

3 mol H2

Feed

Guard

Converter

Recycle GasSmall purge stream

to preventaccumulation of

diluents such as Ar

Gas

Liquid-15C

NH3

Refrigerant Spherical tankStorage

Cooling Water

Water Chiller

Spent cooling water

Centrifugal

Recirculator

Reactor

Co

ldGas

500-600C

100-1000atms

Separato

r

7/30/2019 III sem ICT (5)

3/22

INTRODUCTION

At the beginning of the 20th century there was a shortage of

naturally occurring, nitrogen-rich fertilizers, such as Chilesaltpetre, which prompted the German Chemist Fritz Haber,and others, to look for ways of combining the nitrogen in theair with hydrogen to form ammonia, which is a convenientstarting point in the manufacture of fertilizers.

This process was also of interest to the German chemicalindustry as Germany was preparing for World War I andnitrogen compounds were needed for explosives.

The hydrogen for the ammonia synthesis was made by thewater-gas process (a Carl Bosch invention) which involvesblowing steam through a bed of red hot coke resulting in theseparation of hydrogen from oxygen.

The nitrogen was obtained by distillation of liquid air, then bycooling and compressing air.

In ammonia production, the hydrogen and nitrogen are mixedtogether in ratio of 3:1by volume and compressed to around200 times atmospheric pressure.

7/30/2019 III sem ICT (5)

4/22

PHYSICAL PROPERTIES

Molecular formula NH3

Molar mass 17.036gm/mL

Appearance

Colorless gas with

pungent odour

Density

0.6942g/cm3

Melting point

-77.73C

Boiling point -33.34C

Solubility 89.9g/100mL at 100C

Molecular shape Trigonal pyramid

7/30/2019 III sem ICT (5)

5/22

TYPES OF PROCESS

All process for synthetic ammonia are based on

the pressure, catalytic reactions of nitrogen,

hydrogen.The main classification of the ammonia process

are 1.Haber process

2.Haber-Bosch process

7/30/2019 III sem ICT (5)

6/22

7/30/2019 III sem ICT (5)

7/22

CHEMICAL REACTION

N2+3H2>2NH3

7/30/2019 III sem ICT (5)

8/22

HABER PROCESS

The Haber Process combines nitrogen from the

air with hydrogen derived mainly from natural gas

(methane) into ammonia. The reaction is reversible

and the production of ammonia is exothermic.

7/30/2019 III sem ICT (5)

9/22

LE CHETALIERS PRINCIPLEByLe Chetalier's Principle:

increasing the pressure causes the equilibrium position tomove to the right resulting in a higher yeild of ammonia sincethere are more gas molecules on the left hand side of theequation (4 in total) than there are on the right hand side ofthe equation (2). Increasing the pressure means the systemadjusts to reduce the effect of the change, that is, to reduce the

pressure by having fewer gas molecules. decreasing the temperature causes the equilibrium position to

move to the right resulting in a higher yield of ammonia sincethe reaction is exothermic (releases heat). Reducing thetemperature means the system will adjust to minimise the

effect of the change, that is, it will produce more heat sinceenergy is a product of the reaction, and will therefore producemore ammonia gas as well

However, the rate of the reaction at lower temperatures isextremely slow, so a higher temperature must be used to speed

up the reaction which results in a lower yield of ammonia.

http://www.ausetute.com.au/lechatsp.htmlhttp://www.ausetute.com.au/lechatsp.html

7/30/2019 III sem ICT (5)

10/22

SOME NOTES ON THE CONDITIONS

Temperature

Pressure

Catalyst

7/30/2019 III sem ICT (5)

11/22

TEMPERATURE

Equilibrium considerations The forward reaction (the production of ammonia) is

exothermic.

According to Le Chatelier's Principle, this will befavoured if you lower the temperature. The system will

respond by moving the position of equilibrium tocounteract this - in other words by producing more heat.

In order to get as much ammonia as possible in theequilibrium mixture, you need as low a temperature as

possible. However, 400 - 450C isn't a low temperature!

The compromise

400 - 450C is a compromise temperature producing areasonably high proportion of ammonia in theequilibrium mixture (even if it is only 15%), but in a very

short time.

7/30/2019 III sem ICT (5)

12/22

PRESSURE

Equilibrium considerations

Notice that there are 4 molecules on the left-hand side of theequation, but only 2 on the right.

According to Le Chatelier's Principle, if you increase the

pressure the system will respond by favouring the reactionwhich produces fewer molecules. That will cause the pressureto fall again.

In order to get as much ammonia as possible in theequilibrium mixture, you need as high a pressure as possible.200 atmospheres is a high pressure, but not amazingly high.

The compromise

200 atmospheres is a compromise pressure chosen oneconomic grounds. If the pressure used is too high, the cost ofgenerating it exceeds the price you can get for the extraammonia produced.

7/30/2019 III sem ICT (5)

13/22

CATALYST

Equilibrium considerations

The catalyst has no effect whatsoever on the position of theequilibrium. Adding a catalyst doesn't produce any greater

percentage of ammonia in the equilibrium mixture. Its only

function is to speed up the reaction.Rate considerations

In the absence of a catalyst the reaction is so slow thatvirtually no reaction happens in any sensible time. Thecatalyst ensures that the reaction is fast enough for a dynamicequilibrium to be set up within the very short time that thegases are actually in the reactor.

7/30/2019 III sem ICT (5)

14/22

VARIOUS STEPS INVOLVED

Synthesis gas

Filtration

Feed guard converter Reaction

Separation

7/30/2019 III sem ICT (5)

15/22

1.SYNTHESIS GAS

Synthesis gas contains 1 mole of pure N2 from

the air and 3 moles of H2 from the natural gas.

Synthesis gas is compressed to the operating

pressure(100-1000 atm) depending on

conversion required.

7/30/2019 III sem ICT (5)

16/22

2.FILTRATION

Compressed gas is sent to a filter to

remove compression oil.

7/30/2019 III sem ICT (5)

17/22

3.FEED GUARD CONVERTER

Feed guard converter converts CO and CO2 to

CH4 and removes traces of H2O, H2S,

phosphorous.

7/30/2019 III sem ICT (5)

18/22

4.REACTION

The relatively cool gas is added along the

outside of converter tube to provide cooling so

that carbon steel can be used for the thick wall

pressure vessel and internal tubes. The

preheated gas flows through the inside of the

tubes which contains promoted porous iron

catalyst at 500-550C.Conversion of NH3 is 8-30%.

7/30/2019 III sem ICT (5)

19/22

5.SEPARATION

Ammonia vapours is removed by

condensation first with water cooling and then

NH3 refrigerator. The unconverted N2 and H2mixture is recirculated to allow an 85-90%

yield.

7/30/2019 III sem ICT (5)

20/22

APPLICATIONS

Industry Use

Fertilser production of:

ammonium sulfate, (NH4)2SO4

ammonium phosphate, (NH4)3PO4

ammonium nitrate, NH4NO3

Urea.

Explosives ammonium nitrate, NH4NO3

Fibres & Plastics nylon, -[(CH2)4-CO-NH-(CH2)6-NH-CO]-,and other

polyamidesRefrigeration used for making ice, large scale refrigeration plants,

air-conditioning units in buildings and plants

Pulp & Paper ammonium hydrogen sulfite, NH4HSO3, enables some

hardwoods to be used

7/30/2019 III sem ICT (5)

21/22

Chemicals synthesis of:

nitric acid, HNO3, which is used in making explosives

such as TNT (2,4,6-trinitrotoluene), nitroglycerine which

is also used as a vasodilator (a substance that dilatesblood vessels) and PETN (pentaerythritol nitrate).

sodium hydrogen carbonate (sodium bicarbonate),

NaHCO3

sodium carbonate, Na2CO3

hydrogen cyanide (hydrocyanic acid), HCN

hydrazine, N2H4 (used in rocket propulsion systems)

Pharmaceuticals used in the manufacture of drugs such as sulfonamide which

inhibit the growth and multiplication of bacteria that require p-

aminobenzoic acid (PABA) for the biosynthesis of folic acids,

anti-malarials and vitamins such as the B vitamins nicotinamide(niacinamide) and thiamine.

Cleaning ammonia in solution is used as a cleaning agent such as in

'cloudy ammonia'

7/30/2019 III sem ICT (5)

22/22

A PRESENTATION BY

DEEPTHI.R

BAGHYA LAKSHMI.M

BALAJI.R

DINESHKUMAR.S

DINESHKUMAR.M

ESSAKIRAJ

EZHILARASAN

GURUNATHAN HARISH

HARIRAMAKRISHNAN