Top Urea technology 2000 plusTM
 
Chemoprojekt is entitled to design the newest modern urea plants based on the Stamicarbon Urea 2000 plus(tm) technology. This new Urea process is an improved CO2 stripping technology, comprising application of pool condenser, pool reactor and a number of other significant improvements. Results of these improvements are mainly lower investment costs now required for the CO2 stripping synthesis section and generally a better reliability of the HP synthesis. Investment for the other downstream parts of the urea plant are by the new technology not affected.

The lowest possible consumption figures, better operation flexibility and lower operating costs are typical for this new technology as well. Stamicarbon improvements of the previous CO2 stripping technology can be realised in two ways. The first one, suitable for the debottlenecking of the old urea plants especially, is application of the HP pool condenser. Pool condensation is characterised by additional reaction volume, higher operating temperature, lower pressure drop, less cooling area, non sensitive behaviour to deviations of NH3/CO2 ratios and by the absence of inverse response phenomena. Pool condenser is installed in a horizontal position. LP steam is generated in the bundle and gases around the bundle are partially condensed and partially dehydrated to form urea and water. Additional reaction volume was achieved by this arrangement. Result of the horizontal position of the horizontal position of the condenser is that the height of Stamicarbon stripping plants has been substantially reduced.

The application of the HP pool reactor established a totally new concept for the whole HP synthesis. Besides the same advantages as for the HP, pool condenser further features concerning investment costs as well as technology arise. Basis for lower investment is the omission of costly HP vessel, HP ejector, far less HP piping in the synthesis section and lower steel and concrete structure. Pool reactor is installed in a horizontal position and in such a way the height of the plants has been immensely reduced.

Revamping processes

There are several revamping concepts developed by Stamicarbon for Urea technology. From these revamping concepts the following expectations about capacity increase are given:

Concept type Expected capacity increase
More in more out 10 – 25 %
In-line medium pressure recirculation 15 – 30 %
The medium press. recirculation add-on 30 – 45 %
The double stripper 35 – 45 %
The pool condenser 40 – > 100 %
The achievable plant capacity increase depends on the original used design
margins of the large capital equipment.
Pool reactor – headliness
 
The application of the HP pool reactor established a totally new concept for the whole HP synthesis. The arrangement of the HP pool reactor greatly simplified the original HP synthesis loop. In comparison with the former one, only the CO2 stripper was left unchanged to maintain all the technological advantages of CO2 stripping. However, the stripper off-gases are now condensed in a submerged condenser forming an intrinsic part of the urea reactor. In this way, two complete process steps were combined in one horizontal vessel. The combination of HP pool condenser and reactor is called HP pool reactor. Besides the same advantages as for the HP pool condenser further features
concerning investment costs as well as technology arise. Basis for Loir investment is the omission of costly HP vessel, HP ejector, far less HP piping in the synthesis section and lower steel and concrete structure. Pool reactor is installed in a horizontal position and in this way the height of the plants has been immensely reduced. The baffles in the reactor prevent backmixing, thus allowing the nearest approach to equilibrium in the urea reaction and, consequently, the highest conversion and most economical downstream equipment sizing.

More in more out concept
• The installation of the new high-efficiency trays (improvement of carbon dioxide conver.)
• Narrowing the design margins in the synthesis section
• Addition of heating and condensation capacity in the several process and utility sections

In-line medium pressure recirculation concept
• Minimizing of the recycled amount of water back to synthesis and increase of carbon efficiency of 3-4 %
• The medium pressure recirculation, operating at 18 bar and located in between the high-pressure stripper and low-pressure recirculation section
 
The double stripper concept
• Parallel operated high-pressure strippers added in the synthesis; the urea solution, leaving synthesis is partly sent to the existing stripper and partly to the new one
• Parallel evaporation and urea finishing section is a part of debottlenecking
• Limitation of this concept is the capacity of the HP carbamate condenser
 
The pool condenser concept
• Installation of the horizontal HP condenser increases capacity of reaction volume and HP-condensation as well
• Parallel operated high-pressure strippers similar to the double stripper concept
• This concept is available especially for debottlenecking of conventional plants (change to a stripping process brings a capacity increase and drastically utility consumption in decrease)
 
Rotation disc absorbers

In the process, the air is enriched with gaseous ammonia and fine urea powder. The rotation disc absorber is an apparatus designed for creating an intensive contact between a gas and a liquid. It makes efficient use of the entrainment of the liquid phase (when related to the total apparatus cross section) so that large volumes of gases can be processed in a single apparatus. The RDA apparatus has been so far the most successfully utilized in the control of emissions from prilling towers in the urea plant.
 
In view of the very low concentrations of ammonia at the gas entry, use of the “acid technology” was suggested, i.e. absorption of NH3 in an aqueous solution of ammonium sulphate and ammonium hydrogen sulphate (20% by weight, pH = 1 to 2) which produces the minimum amount of waste.

Stamicarbon granulation

Chemoprojekt is entitled to design and supply urea granulation units with Stamicarbon licence based on fluid granulation concept. The first, pilot unit with capacity 280 tonnes/ day was realized in 1996. Afterwards, the technology was improved for utilization in high-capacity urea units. Currently, the units with capacity from 1200 tonnes per day till 3600 tonnes per day are in operation in one production line. The process is characteristic for its solidity and resistance of the granules against abrasion, which implies high reliability of granulation unit. Other advantage is low emission of the dust particles, which attains the values amounting to 25mg/Nm3 of air. On one of the first installed units with capacity 2000 tonnes/day there was attained 100 day consecutive operation without necessity to clean the unit. To other significant attributes linked with the technology belong:
 
■ Low formaldehyde content, which is lower by 0,3% in comparison with similar technologies
■ Size of 90% granules is 2 – 4 mm
■ Stable operation of the unit
■ Essential savings of operational costs in comparison with other technologies

Advantages:
·         Proven reliability
·         Low investment costs
·         Low NOx tail gas content (up to 100 ppm after SCR)

2) Dual pressure process

Simplified process description:
Ammonia oxidation occurs at low pressure while high pressure improve absorption of the nitrous gases and process of an acid formation. Liquid ammonia imported to the Nitric acid plant is evaporated and mixed with air before oxidation in the burner at low pressure about 0,4 MPa. Maximum energy is recovered by steam generation and cooling of nitrous gases via cross exchange with tail gas. After further cooling of the low pressure nitrous gases with simultaneous weak acid condensation gases are compressed to above 1,1 MPa in the NOx compressor. The high pressure nitrous gases are then cooled by cross exchange with tail gas and further weak acid condensation before entering the absorption tower where they react with water to form nitric acid. The product acid is bleached with secondary air and cooled down before sending to battery limit. The tail gas from the absorption tower is heated in the tail gas heater and than mixed with ammonia and introduced to the selective catalytic reactor (SCR) for reduction of  N20 content. Nitric acid from absorber is stripped by hot air and cooled before dispatch to the store.

Advantages:
·         Proven reliability
·         Low investment costs
·         High ammonia conversion efficiency
·         High heat recovery
·         Low NOx tail gas content (up to 50 ppm after SCR)

3) Nitric acid for explosives and organic chemistry

High concentrated nitric acid (98% to 99% concentration) can be usually obtained by concentrating the weak nitric acid (30% to 70% concentration) using extractive distillation. The distillation must be carried out in the presence of a dehydrating agent.

Advantages:
·         Proven reliability
·         High heat recovery
·         NOx content up to 100 ppm

4) N2O Emission Reduction

Kyoto Protocol - the international treaty on climate change has come into force after it has been ratified by Russia at the end of 2004.
Until ratification of Kyoto Protocol very little concern has been paid to N2O comparing to NOx. N2O arises as an unwanted by-product of ammonia catalytic oxidation during HNO3 production in quantities ranging typically from 350 to 3500ppmv.
Considering one ton of N2O accounts for 310 tons of CO2 equivalent in terms of emissions trading, N2O reduction in tail gas has become high importance issue for HNO3 producers as well as for the entire governments.
N2O contrary to NOx cannot be absorbed from tail gas and therefore new catalytic processes shall be applied.
Nowadays, two feasible processes of N2O destruction exist and both can be provided by Chemoprojekt a.s.

- High temperature (880-930C) catalytic reduction just under platinum gauzes
- Middle temperature (380-450C) catalytic reduction – so called end of technology process