INTRODUCTION

Start of urea production : October 29,1987

Process Licensors : M.KELLOG (Ammonia)

TEC –MTC ‘D’ Improved

General Contractor : Toyo Engineering Corp(TEC) JAPAN

Project Life : 20 years

Project Area : Plant site 135.41 Acres, Others 396.92 acres

Neareast Seaport : Chittagong 00K

Neareast Airport : Chittagong 05 km (app.)

Neareast Railway Station : Chittagong 20 km (app.)

RAW MATERIAL UTILITY

Natural Gas : 53000Nm/Hr
Raw Water from : 1000MT/Hr.(max)
River Karnaphuli about 30km
Upstream
Stream 40 kg/cm(square)G :160MT/Hr
Stream 105 kg/cm(square)G : 230 MT/Hr
Electric power (normal load) : 6.5 MWH

RAW MATERIALS FOR PRODUCTION OF UREA

  1. Ammonia , NH3
  2. Carbondioxide , CO2

RAW MATERIALS FOR PRODUCTION OF AMMONIA

  1. Natural Gas

  2. Steam

  3. Fresh air

  4. Ni Catalyst

Chemical Reaction Changes in the Process

PRODUCTION OF AMMONIA

The natural gas received is metered and then divided into two flows, one as the raw material and
the other as fuel. The raw material gas enters the pre- treatment process where sulfur is removed.
The pre- treated gas is mixed with stream and passed through the catalyst-filled tubes of the
primary reformer where steam reacts with the gas to produce hydrogen, carbon monoxide,
&carbon dioxide.
From the primary reformer the gas flows through a secondary reformer where it is mixed with air
in a quantity required to reform the remaining unconverted hydrocarbons and provide the required
amount of nitrogen to produce ammonia. Leaving the secondary reformer, the process gas flows
through catalyst beds where the remaining steam reacts with carbon monoxide to produce
additional hydrogen & nitrogen, carbon dioxide, methane & argon, is scrubbed with an activated
potassium carbonate solution to remove the carbon dioxide. The remaining carbon dioxide,
carbon monoxide are removed from the process reconversion to methane by reaction with
hydrogen and in the presence of a catalyst. The final synthesis gas contains hydrogen and nitrogen
in the ratio of 3 to 1 which is compressed to about 150kg/cm2G and recirculated through a
converter where the hydrogen and nitrogen react to produce ammonia.

PRODUCTION OF UREA

Ammonia and carbon dioxide produced in ammonia unit are reacted in the synthesis reactor at
pressure of about 210kg/cm2G and temperature, 180-190oC to produce ammonium carbonate
which is subsequently dehydrated to form urea. The reactor effluent solution is composed of urea,
ammonium carbonate water and free ammonia. The ammonium carbonate is decomposed into
ammonia and carbon dioxide in decomposers operated under successively reduced pressure. The
ammonia and carbon dioxide are then recovered as carbonate solution which is recycled back to
the reactor through mixer where low pressure steam is generated by utilizing the heat of reactions.
The purified urea solution is concentrated vacuum concentrator and then it is further concentrated
to form molten urea in air swept type evaporator. The molten urea is sprayed from the prilling
urea to form prilled urea. The prills are finally conveyed as product urea to either bulk storage or
bagging unit.

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