Co2 Compressor New

7/29/2019 Co2 Compressor New

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My Duration Time at Urea-2 was from 11th July To 1st August, During

this I gone through general equipment details according to giving

schedule and these are as follows

CO2 COMPRESSOR

Multistage Centrifugal Compressor

Two compressor are installed with different dia of impeller

One is L.p and 2nd is HP

Driven by steam driven condensable turbine

Which gives 7110 rpm to compressor

Compressor has Lubricants Which are cooled by cooling water

Steam of turbine is condensed in condensate tank

CO2 compressed gas is then passed through inter cooler to make the process

isothermal

Passivation air is given to inhabitate the corrosion process

Compressors Are Used For Gases

Pressure gauges and temperature indicators are also installed

Surging of compressor that is due to back pressure may happen

H.P having vertical casing while LP has horizontal casing

After compression T=117 c and pressure 159 kg/cm

Urea reactor

Reactor is made of carbon steel with internal lining of carbon ,nickel, molybedim

43 m height

NH3 is introduced at high pressure which passed through ejector and also take

carbamate solution

Where it react with CO2 coming from compressor

In reactor 15 trays are employed which increases contact area

In reactor residence time is 45 mint

There are 500 holes per tray with 8 mm hole Trays are employed to prevent carbamate not to come below and to prevent the

escape of CO2

At start up it is heated with steam at temperature 160c which is required to meet

the operating conditions.

First ammonium carbamate is formed.

2nd decomposition of ammonium carbamate to urea.


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Ammonium carbamate formation is exothermic reaction

While decomposition reaction is endothermic reaction.

The Reaction is as follow:

2NH3 + CO2 NH2 CO2 NH4 H = -

37.6 KCal

NH2 COO NH4 CO (NH2)2 + H2O H = +

6.KCal.

The efficiency of reactor can be enhanced by

By increasing pressure and removal of water.

Rate of urea formation also depends on

Rate of formation of ammonium carbamate which is favorable at high pressure

and low temperature

Temperature and pressure

Residense time

By increasing resedense time biuret formation will be increased

Conversion of carbamate to urea which is favorable at high temperature

NH3 is taken in excess to facilitate the stripping of CO2 and to reduce the

formation of biuret.

While weep holes are provide to detect leackage of reactor.

Stripper

The removal of gases at the reactor pressure and the boiling point of solution is

called stripping.

Stripper is made of carbon steel vessel

It operate at slightly low pressure than reactor and high temperature

The solution is allowed to fall through ferrule in to tubes. which are like falling

film type heat exchanger where the partial pressure of carbamate is reduced while

solution comes down in falling film tubes.

The required heat is supplied in the shell side of stripper by hs steam which is at219c.

There are 2585 tubes and 2582 ferrules.

Carbamate condenser


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The effluent high pressure vapors from stripper are absorbed in carbonate solution

in carbamate condenser.

The condensation reaction is exothermic heat is which is used to generate steam at

4.5atm.

The solution inlet ,outlet ,condensate inlet ,outlet are employed Psv connection

and temperature indicators are also employed. There are 1483 tubes and weir ring are used to control water level it has also

vapour collector .

Carbamate ejector

Ejector work on the principle of venture.

Two fluid are necessary one is driving fluid known as driving fluid and second is

moving fluid.

Liquid ammonia under high pressure is used as driving fluid while carbamate is

moving fluid.

The suction capacity is controlled by varying the motive fluid flow through a

nozzle needle which is moved by pneumatic actuator.

MP SECTION DECOMPOSER

It consist of a vessel and shell and tube heat exchanger

Solution enter in the top of mp at 17kg/cm2

Vessel is for the expension of fluid to minimize the pressure Pressure of complete loop is controlled by blow down valve.

The purpose of heat exchanger is to decompose the solution into NH3,CO2.

The vapour of composer are mixed with aquas carbonate solution coming from lp

section.

There is also Ls and HS circuit.

There is another decomposer in the mp section which is buble cap tray type.

LP SECTION

In This Section There Is One Decomposer

At low pressure the remaining CO2 and NH3 are removed.

The vapor at the top of vessel are mixed with the vapor coming from pct.

Vacuum section


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Instrument air

Instruement air is passed through filter to remove dust particles and moisture.

Then it passed to two activated alumina filled bed.

And this dry air is send to plant.

N2 genaration plant

Air at 35 c is passed through refrigeration unit cooled by chilled water .

It comes out at 14c and passed through knock out drum.

Molecular sieves unit also installed . where 10 Ao sieve size made of sodium

aluminum silicate as absorbate Here co2 and hydro carbon are absorbed and N2

goes out.

Adsorption conditions are low temperature and high pressure.

Then it passes through cold box N2 is separated under cryogenic process and sent

to ammonia section.

PCT SECTION

Vapor from vacuum section along with NH3 and CO2 is condensed in T-4107

Then this solution is passed through heat exchanger with the help of pump.

In pct there is fractionating column there are 55 trays and where chimney trays are

at 35 positioned . Solution is showered from the top and passed through trays and co2 and NH3 is

stripped out while the solution from upper section is passed through hydrolyser

where further gases are removed and again send to lower of chimney trays. At

chimney trays solution level is maintained and gase from lower solution s strippedout through chimney.

Absorption chiller

Absorber

Absorption chiller has four parts Concentrator

Condenser

Evaporator

Absorber

And there are also absorber pump, refrigerant pump and concentrated pump.

In absorption chiller lithium bromide solution is used.


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Co2 Compressor New