Bachelor’s Thesis
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Design case study for catalytic ammonia converter for 1200 tonnes/day capacity production plant, in collaboration with Johnson Matthey Catalysts, UK.
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Bachelor’s Thesis
- 1. GROUP 10 Abdullah Ahmad, Andrew Cole, Arani Elanganathan, Chun − Heng Huang, Jen – Yueh Hu, Joseph I. Ogun, Mohamad Raihaan, Olajumoke Shonubi, Sara Al − Jebari Supervised by Prof. Colin Webb Ammonia Production (1200 TPD Capacity)
- 2. DESIGN PHILOSOPHY To maximise energy recovery from exothermic reactions in the process Worst case scenario assumed Overdesign of equipments to compensate for uncertainty of design parameters and allow for additional capacity Inherently safe design features and BAT employed
- 3. PRESENTATION OUTLINE Process Outline Justifying the Omission of a Pre–reformer Unit features that are unique to our plant Plant Layout Environmental Sustainability Safety Considerations Energy Efficiency Control System Economic Analysis
- 4. R-1 S-1 R-3 R-4 S-6 S-4 S-8 S-9 S-12 Desulphurisation R-5 R-6 S-17 R-7 R-9 S-22 S-13 E-4 S-15 S-18 E-6 S-20 Primary Reformer Secondary - Reformer High Shift Reactor Low Shift Reactor BFW E-1 S-3 R-2 S-5 S-11 R-8 S-21 Absorber Stripper Methanation Ammonia Synthesis Flow Sheet – Group 10 Carbon dioxide Mixer S = Stream R = Reactor E = Heat Exchanger F = Flash Drum X = Surge Tank BFW = Boiling Feed Water C-1 S-10 S-14 E-5 S-16 Carbon dioxide Removal Hydrogen Natural Gas S-2 Air S-19 R-10 R-11 E-10 F-2 F-1 C-2 C-3 C-4 F-3 F-4 C-5 C-6 S-26 S-27 S-28 S-24 S-29 S-31 S-32 S-33 S-35 S-37 S-39 S-36 S-40 S-46 S-43 S-41 S-42 S-44 F-5 S-45 F-6 S-47 S-49 X-1 S-52 S-30 S-50 Purge S-51 Pure Ammonia S-48 S-38 E-8 Mixer Splitter Mixer Ammonia Converter Separation Unit S-7 E-2 S-6A E-3 S-23 E-7 S-25 E-9 S-34 Boiler H2O PROCESS FLOW SHEET Desulphuriser Reformers Ammonia converters CO2 removal Methanator Compression Refrigeration Shift reactors
- 5. JUSTIFYING THE OMISSION OF A PRE - REFORMER Used mostly in plants with heavy gas feeds To reduce carbon formation reformer tubes To use up remaining heat energy in flue gas to promote reforming reaction Flue gas heat used instead for : Combustion air preheat Steam duties No appreciable improvement in overall energy consumption
- 6. PRIMARY REFORMER Uhde cold outlet manifold system Prevents premature failure of the tubes None required replacement from 1968 – 1994 (McKetta, 1994) Recommendation Explore potential rate of carbon formation Lower S/C ratio – reduced operating cost 300 600 900 Skin Temperature (°C)
- 7. HAZOP ON PRIMARY REFORMER Some highlighted plant modifications Furnace fuel inlet Fail close and pressure relief valves Fuel composition analyser Control loops Combustion air inlet Oxygen analyser
- 8. SECONDARY REFORMER In the event of controlled relief response being triggered Quenching chamber containing water to neutralise unreacted reactants Pipes from combustion zone to quenching chamber Sprinklers and relief vents
- 9. AMMONIA SYNTHESIS P&ID Split into two reactors
- 10. AMMONIA SYNTHESIS LOOP Minimise wastage of synthesis gas in purge Minimise energy required to recycle synthesis gas Minimise duty required for refrigeration
- 11. SYNTHESIS LOOP PFD Surge tank Variable operating conditions Usage of leftover methane/hydrogen stream
- 12. LAYOUT OF PLANT Tank 1 Tank 2 Tank 3 Tank 5 Tank 4 Tank 1 Tank 3 D-2 PR SR LS Canteens Change House, Gym and Social Rooms ABS STP MET HS FD D-1 C-1 C-2 C-3 AC-2 REF AC-1 Offices CCR (Centre of Control Room) Laboratory Maintenance Room Fire Station Medical Centre Garden Waste Treatment Tanks Tank 2 Storage Tanks Plant Warehouse for Product Storage and for Other Purpose Car Park Security Loading/Unloading Area STK
- 13. ENVIRONMENT/SUSTAINABILITY Ammonia production generates some environmental impact Impacts can be minimised Gaseous emissions: Desulphuriser: H2S, ZnS, SO2 Primary Reformer: CO2, Nox , SO2, CO Secondary Reformer: CO2 & CH4 High & Low Temperature Shift: FeCr Catalyst, Cu, CO,CO2 Carbon dioxide Removal: CO2 and MDEA solvent Methanation: CO Ammonia Synthesis and Recycle Loop: CH4, NH3, H2, N2 ,Ar
- 14. TO MINIMISE OR REDUCE THE ACID GAS Wet scrubber low Nox burners Electrostatic precipitator
- 15. AMMONIA PLANT LIQUID EFFLUENT Ammonia liquid emissions can be limited by applying good management practices Stripping to reduce ammonia in purge effluent Other effluents include Boiler blowdown Cooling water blowdown. These effluents are recycled and reused Limits amount requiring treatment
- 16. SAFETY CONSIDERATIONS Personal Protective Equipment (PPE) COSHH Hydrogen Sulphide and Nickel Carbonyl - Toxic Natural gas and Hydrogen – Potentially explosive MDEA – Irritant Flammability limits Flammability limits calculated at exit of each major section Overpressure Control valves
- 17. HEAT EXCHANGER NETWORK Process integration saves ~£24M yr-1 heating costs Excess energy of 179 MW used to raise steam 783 783 600 613 443 313 490 288 P3 P1 c P2 640 P4 - C5 C4 C1 C3 C2 C S6A S5 S22 S48 S13 S17 S17 S33 S34 333 683 383 - 456 1262 616 450 689 490 - H 32333 5628 11511 44778 56306 14985 40250 68611 93056 H1 Heat Exchanger Network Design Ammonia Synthesis Plant kW kW K K
- 18. CONTROL ROOM & SOFTWARE USED 6 operators to work in plant; 3 shifts per day; Proposed control system: Honeywell’s Profit Controller (Robust Multivariable Predictive Controller) Real time system to calculate current output Perturbed Normal Operation Upset Shut Down Control System Operator Intervention ESD X X X X X X X = Alarm X X X X X X X Image from: Brown, D., & O'Donnell, M. (199?). Too much of a good thing? Alarm management experience in BP oil. Part 1: Generic Problems with DCS Alarm Systems. BP .
- 19. ECONOMIC ANALYSIS - PROFITABILITY Total Capital Investment needed ≈ £134 million Pre-tax Profit ≈ £38 million The plant can achieve an internal rate of return of 20%
- 20. CONCLUSION Extra ~42 TPD capacity from 588 TPD natural gas Achieve IRR of 20% over 10 year operating period Excess energy of ~ 179 MW Environmentally sustainable, surpassing UK & Welsh legislation requirements Safe operating conditions Plant layout takes into account minimum safe distances
- 21. THANK YOU FOR LISTENING. ANY QUESTIONS?
- 22. IMPORTANT CONTROL LOOPS The temperature of the stream entering the tubes of the primary reformer; The ammonia reactor temperature of the outlet gas after each compression
- 23. ECONOMIC ANALYSIS - PROFITABILITY
Editor's Notes
- Made of carbon steel, there are no high-alloy pig tails or outlet manifolds which work at creep condition Prevents premature failure of the components due to creep and embrittlement therefore there are no thermal expansion problems it has an almost unlimited service life (Uhde, 2007) with no maintenance required other than painting The potential rate of carbon formation in the proposed primary reformer should be explored. This is recommended because the sensitivity studies carried out indicate that an increase of the S/C ratio to 4 gives a 10% increase in the amount of energy required for the reaction and a decrease to 2, gives a 10% reduction in the required energy. There may be a potential here for reduction in operating costs and hence increased profitability if further investigation suggests that a lower S/C ratio than that proposed in this design (3.1) can be operated at without compromising the reformer tube life.
- Some of the highlighted plant modifications Furnace fuel Fail close valves for fuel flow, control loops monitoring temperature of reformer tubes, flue gas composition and fuel to air ratio. Install pressure relief valve to furnace fuel pipe, S1, to direct the fuel to a large reserve tank Install a fuel composition analyser to enable control of fuel flow rate and air flow rate, to give the heat required and complete combustion respectively Install a nitrogen blanket on the fuel tank Combustion air Install a pressure controller on the combustion air line. Pressure relief valve to atmosphere. Install an oxygen analyser on the inlet air flow line to monitor air flow in terms of oxygen flow rate.
- Acid gas that might escape during the process are (say for each process) are: (refer to Process in slide) Table each of gas emission and impact (refer to table): H2S – if hydrogen sulphide reacts with atmospheric water and oxygen it will produce sulphuric acid. The impact of hydrogen sulphide is acid rain and it will lower the pH of soil and freshwater in the ground. ZnS – zinc sulphide is very toxic to human. CO2 – Carbon dioxide is considered as first important gas in greenhouse gasses (GHGs) which leads to global warming. This gas is potentially having a major effect on climate change in atmosphere. Nox – Nitrogen oxides also contributes to the acid rain and depletion of the ozone. It is also one of major greenhouse gasses (GHGs). If Nitrogen dioxide goes to the air, it will can react with organic peroxy radicals (formed from the breakdown of Volatile Organic Compounds in the air) to form PANs (peroxyacetyl nitrates) (The Environment Agency, 2010). SO2 – Sulphur dioxide is one of chemical gas that caused acid rain. This gas can dissolves in water droplets in clouds and potentially will make the rain more acidic. CO – Carbon monoxide is man-made gas which reacts with other acid gases to produce ground level ozone. This gas has a direct impact to the human health. CH4 – Methane is considered as second important gas in greenhouse gasses (GHGs) after carbon dioxide which leads to global warming.
- These gasses can be minimise or reduce by some common methods. Those methods are like flue gas recirculation, wet scrubber, cyclone separators, baghouse, low Nox burners, selective and non-selective catalytic reduction (SCR and NSCR) and electrostatic precipitator (ESP). These gasses can be minimise or reduce by some common methods. Those methods are like flue gas recirculation, wet scrubber, cyclone separators, baghouse, low Nox burners, selective and non-selective catalytic reduction (SCR and NSCR) and electrostatic precipitator (ESP). These gasses can be minimise or reduce by some common methods. Those methods are like flue gas recirculation, wet scrubber, cyclone separators, baghouse, low Nox burners, selective and non-selective catalytic reduction (SCR and NSCR) and electrostatic precipitator (ESP).