What
is a ammonia cracker?
Also known as ammonia cracking units, ammonia crackers are widely used in
gas plants, especially in hydrogen and nitrogen plants, for the production
of pure hydrogen or pure nitrogen. An ammonia cracker is actually a furnace
consisting of a catalyst that breaks up ammonia gas into nitrogen and
hydrogen (synthesis gas). The main purpose of an ammonia cracker is to
decompose ammonia gas (NH
3) thereby producing 75% hydrogen and
25% nitrogen which is done by using anhydrous ammonia from the cylinders.
The gas thus produced is very dry and free from oxygen.
The Process
Ammonia cracking unit usually makes use of nickel catalyst to crack or
break ammonia into a mixture of hydrogen and nitrogen under endothermic
reaction. Raw material for ammonia cracker is ammonia gas and this gas is
easily available in cylinders. When ammonia is passed over the catalyst, the
cracking takes place at 8500 degree C temperature and it cracks to N
2
+ H
2 mixture containing 75% hydrogen and the remaining 25% is
nitrogen. The cracked ammonia gas consists of approximately 80 PPM
un-cracked ammonia impurities and its dew point is only (-) 300 degree C.
There is a special tank surrounding the cracker where the nitrogen and
hydrogen are separated. Since hydrogen is 14 times lighter than nitrogen, it
rises to the top of the tank, while a special relief valve at the bottom of
the tank allows the nitrogen at the base of the tank.
Uses of ammonia crackers
- Ammonia crackers are widely used in industries for small generation
of hydrogen gas.
- The cracking of ammonia gas in the ammonia cracker saves on the
expensive gas clean-up needed with hydrocarbon reformers.
- Ammonia cracker is mostly used for heat treatment furnace.
- Cracked ammonia is used as an alternate to hydrogen plant for the
purpose of catalytic purification of nitrogen gas having oxygen as an
impurity.
- Ammonia cracker is a cost effective alternative for hydrogen
production by electrolysis process and has wide acceptance.
- Ammonia cracking units are key components of ammonia-hydrogen
exchange plants used mainly for the production of heavy water.
- It helps in the removal of oxygen impurity to PPM level from nitrogen
gas.
Features of ammonia crackers
The most notable features of ammonia crackers are as follows:
- They are fully automatic.
- They are usually skid mounted and ready to install at very close to
PSA nitrogen generation equipment.
- Ammonia crackers are very simple and easy to operate.
- Raw material used here is ammonia gas, which is easily available in
cylinders.
- Ammonia cracking surface usually has an efficient ceramic fiber
insulation.
- These units are designed in such a way that they virtually require
negligible maintenance.
- They have a compact body.
Typical appearance of ammonia crackers
Also known as ammonia-cracking furnaces, ammonia crackers are similar in
appearance to catalytic reformer furnaces. The catalyst is inside the tubes
within the furnace. The catalyst tubes have greater wall thickness and may
be used in ammonia crackers to permit operation at pressures up to 15 MPa.
These furnaces are rectangular in shape and typically 6 to 9 m high, with a
footprint of around 6 by 9 m, but may also be larger. Multiple ammonia
crackers used in a heavy water production facility are of varying sizes. The
catalyst may be iron oxide, with a mixture of calcium (Ca), aluminum (Al)
and potassium (K). It can also be nickel based.
Packaging of ammonia crackers
The components needed in ammonia crackers are likely to be shipped
separately and erected at the fields at the plant site. Large sub assemblies
of the cracking units may be shipped as a unit by barge or rail. Catalyst
and furnace internals be shipped separately. The catalyst is normally
shipped in drums.
Buyer's Guide
Specifications to consider for purchasing ammonia crackers are as follows:
- Tank size
- Material of construction
- Weight
- Input ammonia
- Output
|
- Capacity
- Power supply
- Catalyst load
- Power consumption
- Heat exchanger
|
Ammonia
Crackers
Ammonia
Crackers