24-09-2013, 12:40 PM
UREA PLANT
[attachment=58243]
Introduction
• Urea (identified 1773), the first organic compound prepared
by inorganic synthesis (1828 Wohler)
NH3 + HCNO → CO(NH2)2
• Commercial production started in 1922 – Germany, 1932 –
USA and 1935 – UK.
• Urea has been considered as slow – release fertilizer since it
must undergo two transportation
1. Hydrolysis:
2. Nitrification: NH3 → Nitrite or Nitrate (Microbes, moist and warm soil )
• Biuret is the impurity in urea.
• More than 50 M tons is produced annually
Uses of Urea
• Main N2 fertilizer, specially for the flooded region.
• Cattle feed supplement where it is cheap.
• Feed material for melamine plastics and various
glues (Urea – Formaldehye, urea – melamine –
formaldehyde)
• Use: Prill or microprill (0.2-0.4 mm), liquid mixture of
urea (±75% solution), molasses, phosphoric acid.
Optimum Conditions
• Maximize the production of urea per unit time with
due regard to cost of recycling unreacted NH3 and
CO2, the cost increase of reactor size, corrosion
difficulties. NOT to increase the percentage of
conversion.
Partial Recycle Process
• Part of the off – gas is recycled back to the reactor.
• The amount of ammonia is reduced to 15% to that of once
through that must be used in other processes.
• Investment cost is somewhat lower than the total recycle
process, this advantage apparently does not compensate the
inflexibility arising from the necessity to operate a co-product
plant with mutual interdependency problems. However it
finds application in UAN co-product plants.
The general design objectives are:
• Maximize the heat recovery
• Minimize the amount of carbamate solution recycled (smaller
pumps and less power) and amount of water returned to the
reactor (better conversion).
• Minimize power requirement
• Maximize ammonia recovery (lowering operating cost and less
pollution)
• Other important requirement is of-course minimizing
investment. The problem is finding the best balance between
the utility consumption and maintenance on one hand and
investment on the other hand.
Stripping Process Based Plants
• In 1966 Stamicarbon of Netherland introduced CO2 stripping
→ Snamprogetti built a plant using NH3 as stripping process
(requires high NH3:CO2 ratio) later switched to thermal
stripping → Toyo Engineering Corpora on (TEC) Japan
utilized CO2 stripping.
• Three licensors have different approaches and have improved
their technology throughout the years.
Closely stoichiometric amount of raw material consumption
Reduced steam consumption to an apparently economic level
Avenues available for improvements in reduction of capital cost,
improved reliability and efficiency of mechanical improvements and
advances in metallurgical advances.
[attachment=58243]
Introduction
• Urea (identified 1773), the first organic compound prepared
by inorganic synthesis (1828 Wohler)
NH3 + HCNO → CO(NH2)2
• Commercial production started in 1922 – Germany, 1932 –
USA and 1935 – UK.
• Urea has been considered as slow – release fertilizer since it
must undergo two transportation
1. Hydrolysis:
2. Nitrification: NH3 → Nitrite or Nitrate (Microbes, moist and warm soil )
• Biuret is the impurity in urea.
• More than 50 M tons is produced annually
Uses of Urea
• Main N2 fertilizer, specially for the flooded region.
• Cattle feed supplement where it is cheap.
• Feed material for melamine plastics and various
glues (Urea – Formaldehye, urea – melamine –
formaldehyde)
• Use: Prill or microprill (0.2-0.4 mm), liquid mixture of
urea (±75% solution), molasses, phosphoric acid.
Optimum Conditions
• Maximize the production of urea per unit time with
due regard to cost of recycling unreacted NH3 and
CO2, the cost increase of reactor size, corrosion
difficulties. NOT to increase the percentage of
conversion.
Partial Recycle Process
• Part of the off – gas is recycled back to the reactor.
• The amount of ammonia is reduced to 15% to that of once
through that must be used in other processes.
• Investment cost is somewhat lower than the total recycle
process, this advantage apparently does not compensate the
inflexibility arising from the necessity to operate a co-product
plant with mutual interdependency problems. However it
finds application in UAN co-product plants.
The general design objectives are:
• Maximize the heat recovery
• Minimize the amount of carbamate solution recycled (smaller
pumps and less power) and amount of water returned to the
reactor (better conversion).
• Minimize power requirement
• Maximize ammonia recovery (lowering operating cost and less
pollution)
• Other important requirement is of-course minimizing
investment. The problem is finding the best balance between
the utility consumption and maintenance on one hand and
investment on the other hand.
Stripping Process Based Plants
• In 1966 Stamicarbon of Netherland introduced CO2 stripping
→ Snamprogetti built a plant using NH3 as stripping process
(requires high NH3:CO2 ratio) later switched to thermal
stripping → Toyo Engineering Corpora on (TEC) Japan
utilized CO2 stripping.
• Three licensors have different approaches and have improved
their technology throughout the years.
Closely stoichiometric amount of raw material consumption
Reduced steam consumption to an apparently economic level
Avenues available for improvements in reduction of capital cost,
improved reliability and efficiency of mechanical improvements and
advances in metallurgical advances.