Two energy conservation schemes in Ammonia Plant

ID :FE-5[1]	Title of the measure Installation of a new LT Shift Guard Reactor BFW Preheater to reduce the CO slippage and to control the gas inlet temperature to the LT Shift Converter							Sector: 12( Fertilisers)
Year:2006								Technology:  LT Shift Guard Reactor & BFW Preheater
Two energy conservation schemes have been installed  under Energy Saving Project (Phase-I) as detailed below: A)      LTS Guard Reactor & BFW Preheater In the Ammonia-Urea manufacturing Complex at IFFCO Aonla, ammonia is manufactured by steam reforming of Natural Gas/ Naphtha. During the process, carbon monoxide (CO) is formed in the gaseous mixture, which is converted to carbon dioxide in shift conversion section where carbon monoxide reacts with steam to form carbon dioxide and hydrogen. Original System : The reformed gas from Reforming Section flows to HT Shift Convertor after cooling in HP Waste Heat Boiler from 9880C to 3800C.  The carbon monoxide content of the process gas is reduced from 12.96% to 3.46% in HT Shift Converter through shift reaction which takes place in the reactor in presence of Iron-chromia catalyst.  Process gas temperature of around 4440C at the outlet of HT Shift Convector is reduced to around 2100C by heat recovery in a Waste Heat Boiler and Boiler Feed Water Preheater.  The carbon monoxide (CO) content of 3.46% in the process gas in further reduced to 0.37% in LT Shift Convertor through shift reaction which takes place in the reactor in presence of chromium based & copper zinc catalysts.
Description of the Scheme / Modification: A new LT Shift Guard Reactor has been installed before LT Shift Coverter   in order to reduce the CO slippage from the Shift Conversion Section.  The CO slip after LT Shift Converter, with the LT Shift Guard in line has become lower i.e 0.10 - 0.16% as against 0.25-0.37% without LT Shift Guard Reactor.  Lower CO slip, in turn, results in additional Ammonia production due to reduction in the consumption of hydrogen in Methanator.  A new BFW Preheater has been installed at down stream of the new LT Shift Guard Reactor for controling the process gas inlet temperature to the LT Shift Converter.
B) Conversion of Single Stage GV System to 2-Stage GV System for CO2 Removal In Ammonia Plant-I   Ammonia is manufactured by steam reforming of natural gas. During the process, CO2 is formed in the gaseous mixture and the same is removed from the  gaseous mixture in the CO2 Removal Section designed by M/s. Giammarco Vetrocoke (GV) of Italy. Original system In the original system, the process gas containing CO2 enters at the bottom of GV absorber. GV solution enters the Absorber at the top and absorbs CO2 from the process gas while flowing down though the packed beds. CO2 free gas comes out from the top of Absorber and sent down to Methanator for further processing. Rich GV solution containing CO2 is sent to Regenerator operating at around 1.0 kg/cm2g. Here dissolved CO2 is separated from the solution by flashing. CO2 is further removed from the cascading solution, by stripping action of rising steam/vapors. The lean GV solution collects at the bottom of Regenerator. From the Regenerator bottom lean GV solution goes to a Flash Drum operating at 0.6 kg/cm2g. Here again, any dissolved CO2 in the solution is separated. The separated CO2 is fed to Regenerator from the Flash Drum with the help of LP steam ejectors. The lean GV solution is pumped from Flash Drum to GV Absorber. The separated CO2 comes out from Regenerator top and is cooled in coolers. After cooling and separation of condensate, CO2 is sent to Urea Plant.  The schematic diagram of original system is as given below: Modified System The main features of the modified 2-stage GV process are (1) Absorption by lean & semi lean solutions (2) High pressure & low-pressure stripping. The features result in better absorption of CO2 in Absorber and lower energy consumption for regeneration of the solution in Regenerators. In the modified system, the process gas containing CO2 enters at the bottom of GV Absorber. Lean GV solution enters the Absorber at the top and absorbs CO2 from the process gas while flowing down though packed beds. CO2 free gas comes out from the top of Absorber and is sent down to Methanator for further processing. Semi lean solution enters at the middle of Absorber above the second bed and absorbs CO2 from the process gas. When the GV solution reaches the bottom of Absorber, it becomes rich in absorbed CO2. The rich GV solution containing CO2 is sent to HP Regenerator operating at around 1.0 kg/cm2g. Here, part of dissolved CO2 is separated from the solution by flashing. First part of GV solution is sent from HP Regenerator top take off tray to LP Regenerator top operating at around 0.1 kg/cm2g. Second part of GV solution is sent from HP Regenerator semi lean draw off pan (located below two packed beds) to LP Regenerator semi lean solution sump. Balance GV solution in HP Regenerator is reboiled in GV Reboilers. Vapors from Reboilers again enter the HP Regenerator bottom for stripping the GV solution. Live LP steam is also injected into HP Regenerator for stripping the GV solution. Solution from Reboilers is sent to HP Regenerator bottom. Lean solution from HP Regenerator bottom is sent to LP Regenerator bottom. Semi lean solution from LP Regenerator draw off pan, is pumped to GV Absorber and enters above the top of second bed for absorption of CO2. Lean solution from the bottom of LP regenerator is cooled in a heat exchanger with DM Water and pumped to GV Absorber top. CO2 from LP regenerator is boosted upto HP regenerator pressure with a CO2 Blower and sent to Urea plant alongwith CO2 from HP regenerator. Schematic diagram of the modofied system is given below: Benefits of the modification Major benefits of the modification are: 1.          Reduction of CO2 slip through Absorber by around 600 ppm, which has resulted in: ·         Higher availability of CO2 for urea production ·         Decrease in hydrogen consumption in Methanation Section 2.       Decrease in LP steam consumption in CO2 Removal System from 38 MT/hr to 15 MT/hr.
Picture/sketch/drawing after modification
Agency that executed the project (with complete address and email): Basic Engineering M/s HTAS A/s NYMOLLEVES 55, P. O. BOX 213, DK-2800 LYNBY DENMARK FAX:45272999 Email : techservice@topsoe.dk Detailed Engineering M/s PDIL, PDIL BHAWAN, A-14, SECTOR-1, NOIDA-201301 DISTT: GAUTAM BUDH NAGAR (U. P.)
Total investment, Rs. : 3104 Lakh					Year of implementation: 2005-06
First year energy cost savings,Rs.: 2955 Lakh
First year other savings, Rs.:
On annual basis			Gcal/MT urea
Reduction in energy consumption			0.24
Energy tariff, Rs/Gcal			2475.55
Company complete address: IFFCO Aonla-I P. O. IFFCO Township Bareilly (U. P.) . Contact person who could be contracted for more information: N. C. Nigam, Senior General Manager Email:  ncnigam@iffco.nic.in										We authorise Bureau to use this information for dissemination Signature Date :14.10.2006