21-07-2012, 12:30 PM
NATIONAL FERTILIZER
LIMITED
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National Fertilizers Limited is a major Indian producer of
Inorganic and organic fertilizers and industrial chemicals.
Established in 1974. it operates 5 major plants across India.
NFL was established in 1974, as a public-sector
Undertaking of the Government of India. The company
Operates under the administrative controls of the
Department of Fertilizers in the ministry of chemicals and
Fertilizers.
Manufacturing process of Ammonia
A typical modern ammonia-producing plant first converts natural gas (i.e., methane) or LPG (liquified petroleum gases such as propane and butane) or petroleum naphtha into gaseous hydrogen. The method for producing hydrogen from
Hydrocarbons is referred to as "Steam Reforming". The hydrogen is then combined with nitrogen to produce ammonia. Starting with a natural gas feedstock, the processes used in producing the hydrogen are:
The first step in the process is to remove sulfhur compounds from the feedstock because sulfur deactivates the catalysts used in subsequent steps. Sulfhur removal requires catalytic hydrogenation to convert sulfur compounds in the feedstock to gaseous hydrogen sulfide:
H2 + RSH → RH + H2S(gas)
The gaseous hydrogen sulfide is then absorbed and removed by passing it through beds of zinc -oxide where it is converted to solid zinc sulfide:
The advantages of this process are
compactness, simplicity in case of converter design since under high pressure gases have smaller volume. 2. Elimination of expensive heat exchanger required in processes operated at low pressure.3. Removal of ammonia with water cooling alone.Against these are the disadvantages:1. Shorter life of converters.2. High apparatus upkeep in the high pressure operation.3. Efficiency loss in approximately 20% of making up gas,
which is unconverted.
SIGNAL CONDITIONING+HART MANAGEMENT:
In the marshalling cabinets the isolators supply 24V DC power to the field transmitters and receive 4-20mA signals and a FSK digital signal from the field transmitters. Then this 4-20mA is fed to the HART card ( TB-16 cards) where this 4-20mA signal is converted to 1-5 V DC signal Through 250 ohm resistance and these signals are transmitted to the input card, which is located in the I/O nest 0f EFCD.