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SAFINA
CHEMOPROJEKT
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Contractor for UREA Stamicarbon process
In the year of 1969 Chemoprojekt and Stamicarbon concluded a licence and know-how agreement, enabling Chemoprojekt to design and construct urea plants on the basis of the modern Stamicarbon CO2 stripping technology.
Chemoprojekt has been successful from the first beginning in design and start-up of a number of urea plants. Already in the year of 1970 first two contracts for the fertiliser factory VEB Stickstoffwerk Piesteritz in the East Germany were concluded. The first three units with the capacity of 1050 tpd each were designed and successfully put into operation. Further on a row of the other urea plants followed. Up to the present time Chemoprojekt has designed together 19 units ever since based on the Stamicarbon urea process.
Chemoprojekt is one of the selected Stamicarbon's contractors for urea. The total units capacity, designed by Chemoprojekt, represents altogether 19 920 tpd of urea. This production quantity represents about 15 % of the total units number in the whole world, designed on the basis of the Stamicarbon stripping technology.
The single units capacities, designed by Chemoprojekt, range from 1000 up to 1670 tpd. Six of the plants were designed for production of urea with low biuret content using the technology of crystallisation and melt prilling. The other units are usual processes with evaporation and melt prilling, producing urea with standard biuret content.
Top Urea technology 2000 plus TM
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 characteristic 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.
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 lower investment is the omission of costly HP vessel, HP ejector, far less HP ping 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.
The baffles in the reactor prevent backmixing, so affording the nearest approach to equilibrium in the urea reaction and, consequently, the highest conversion and most economical downstream equipment sizing.
Pool reactor – headlines
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 lower investment is the omission of costly HP vessel, HP ejector, far less HP ping 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.
The baffles in the reactor prevent backmixing, so affording the nearest approach to equilibrium in the urea reaction and, consequently, the highest conversion and most economical downstream equipment sizing.
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 Percentage of expected capacity increase
- More in more out 10 - 25
- In-line medium pressure recirculation 15 - 30
- The medium pressure 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.
More in more out concept
The principle of this concept is based on the following improvements:
- The installation of the new high-efficiency trays (improvement of carbon dioxide conversion)
- 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
Base of this concept:
- Minimising 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
Base of this 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
Base of this 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 for debottlenecking of conventional plants especially (change to a stripping process brings a capacity increase and drastically utility consumption decrease)
- Activities in Urea Plant emissions decreasing
Ecology activities are aimed to reduce ammonia and carbon dioxide emissions from the urea plants to the atmosphere. Parallel to these improvements consumption figures of ammonia and carbon dioxide decrease down to the possible minimum.
The modifications concern mainly LP absorption arranged downstream synthesis section and ATM absorption in the recirculation. All ammonia and carbon dioxide off-gases, i.e. mainly from HP Scrubber, Urea Solution Tank, NH3 Water Tank, Level Tank of the LP Carbamate Condenser, Level Tank of the Reflux Condenser, Final Condenser of Evaporation, Centrifuges, Screw Conveyors etc. are treated in the absorption system.
Installation of the effective absorption system enables the achievement of very low consumption figures coming near to the theoretical ones. The highest emissions standards can be achieved. Ammonia quantity lower than 0.5 kg/hour, measured at the outlet from the LP absorber, downstream synthesis loop and 0.5 kg/hour at the outlet of the ATM absorber in the LP recirculation.
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