co2 compressor new
TRANSCRIPT
-
7/29/2019 Co2 Compressor New
1/6
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.
-
7/29/2019 Co2 Compressor New
2/6
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
-
7/29/2019 Co2 Compressor New
3/6
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
-
7/29/2019 Co2 Compressor New
4/6
-
7/29/2019 Co2 Compressor New
5/6
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.
-
7/29/2019 Co2 Compressor New
6/6