If there is no requirement to lower NOx emissions, the N2O decomposition catalyst described above can be used on its own. The catalyst achieves high N2O abatement performance up to temperatures of about 600°C, substantially increasing the range of nitric acid plants which can be equipped with N2O abatement. In such plants a NOx abatement unit can also be installed if necessary, provided an appropriate tail gas temperature level between about 200°C and 500°C is available.
Conclusion
The EnviNOx® process for the combined abatement of NOx and N2O emissions from nitric acid plants has proven itself in installations around the world which are now operating at temperatures between 340°C and 510°C. Typically, N2O emissions are reduced by ~98% – 99% while NOX emission levels of 1 to ~25 ppmv are achieved, depending on the process variant.
The EnviNOx® process can be applied in nitric acid plants with tail gas temperatures between about 340°C and 600°C covering an estimated 70% – 80% of all nitric acid production worldwide. For many of the nitric acid plants with tail gas temperatures outside this range, relatively simple plant modifications are possible to enable a nitrous oxide abatement system to be installed.
The EnviNOx® process can thus make a useful contribution to lowering greenhouse gas emissions.
EnviNOx® is an “operator friendly” technology since the EnviNOx® catalysts are easy to handle, environmentally uncontroversial materials with a long operating lifetime.
Furthermore as an end-of-pipe process EnviNOx® does not interact in any way with the plant product or its precursors.
140
Conclusion
In conclusion, setting up 100000 tons per year of nitric acid production plant in Saudi Arabia is very feasible and attractive in order to meet high demand of ammonia in this region. Ras Alkhair industrial city is identified as the most ideal location for the new petrochemical plant. All the desired criteria for the construction of the plant in Ras Alkhair are met and the necessary facilities for plant expansion are also available.
In order to produce the required capacity 100000 tons per year of nitric acid while the amount of ammonia required 2335.88 kg/hr while the amount of air needed 43537.52 kg/hr.
Designing and sizing for equipment used are prepared in Equipment Specification Sheet which provide the design and size estimation for chosen equipment.
A highly integrated process control system is also included to the proposed plant.
Control systems are essential to ensure the plant operates in safe manner and achieves the desired production. The control system proposed are all feedback and cascade model, which can correct the error continuously to serve better control objectives. All equipment has been covered and proper control strategy and design have been proposed.
In designing the proposed plant, various safety factors and procedures such as Hazard and Operability Studies (HAZOP), plant start up and shut down procedures, maintenance and inspection of each equipment as well as control system design were taken into consideration. However, it is recommended that further studies in this area is needed unceasingly to ensure operational safety of the plant. Safety aspects are also been considered in recommending the plant layout.
In responding to the environmental obligation, the plant has been designed to achieve the target of waste minimization while achieving cost minimization at the same time.
From our economic and cost estimation analysis, the expected payback period is (3.43) years. The economic analysis of the process flowsheet indicated that the ROI is about 20.5%. The project is worth investing.
Finally, it can be concluded that the construction of a 100,000 tons per year of nitric acid production plant in Ras Alkhair is technically feasible and economically attractive.
Encouragement from the Saudi government investment with various incentives offered serves as another factor that contribute to the feasibility of the plant.
142
References
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3- R. Perry and C. Chilton,"Perry's Chemical Engineer's Hand Book", 7th Ed.,Mcgra W-Hill, 1997 4- Vincent Sauchelli, "Fertilizer Nitrogen its Chemistry and Technology", Rinhold Publishing
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7- J. M. Coulson J. Richardson, "Chemical Engineering Design", Vol.6, 3rd Ed., Pergamon Press,1983 8- P.J.C. Kaasenbrood, "Chemical Reaction Engineering", Pergamon Press, 1968
9- Richard Turton, Richard C. Bailie, Wallace B. Whiting, Joseph A. Shaeiwitz, " Analysis, Synthesis, and Design of Chemical Processes ",3rd Edition, Prentice-Hall, 2009
10- W. Dekker, E. Snoeck and H. Kramers, "Chemical Engineering Science", 1959
11- (2012, january 15). Retrieved december 1, 2013, from Saudi Presidency of Meteorology and Enviroment: Http://www.pme.gov.sa
12- (2009, may 27). Retrieved December 1, 2013, from Vermont Safty Information Resources, Inc. : Http://www.siri.org
13- Richard M. Felder, Ronald W. Rousseau, " Elementary Principles of Chemical Processes ", Third edition,2005
14- Fritz Ullmann, “ Ullmann’s Encyclopedia of Industrial Chemistry “,John Wiley and Sons, 1999 15- Neil S. Chlager, Jayne Weisblatt, and David E. Newton, “Chemical Compounds”, 2001
16- Max. S. Peters, Klans D. Timmerhans, "Plan Design and Econmics for chemical Engineering 3-rd Ed, McGraw-Hill, 1990.
17- Christie J. Geankoplis, “ Transport Processes and Separation Process Principles “, 5th Edition, Prentice Hall, 2003
18- J. M. Smith, H. C. Van Ness, M. M. Abbott, "Introduction to Chemical Engineering Thermodynamics", 7th Edition, McCraw-Hill,2005
19- W. S. Norman, "Absorption, Distillation and Cooling Tower", Longmans,1962
Appendix A (12)
(Material Safety Data)
144
146
148
150
Appendix B (13)
(Physical Properties Data)
152
154
156
158
160
162
Appendix C
(Detailed Mass Balance Calculation)
Overall Material Balance NH3 + 2O2 HNO3 + H2O Conversion: 95%
HNO3:
𝐹𝑜𝑢𝑡 = 7500
63 = 119.048 𝐾𝑚𝑜𝑙/ℎ NH3:
𝐹𝑜𝑢𝑡 = 137.405 − 1
1 (119.048) = 18.357 𝐾𝑚𝑜𝑙/ℎ O2:
0 = 𝐹𝑖𝑛 − 2 (119.048) => 238.096 = 𝐹𝑖𝑛 Excess 20 %
𝐹𝑖𝑛 = 285.715 𝐾𝑚𝑜𝑙/ℎ
𝐹𝑜𝑢𝑡 = 285.715 − 238.096 = 47.619𝐾𝑚𝑜𝑙/ℎ N2:
𝐹𝑜𝑢𝑡 =285.715 × 32 × 0.79
28 × 0.21 = 1228.38 𝐾𝑚𝑜𝑙/ℎ H2O:
0.05𝐹𝑖𝑛 + 277.778 = 𝐹𝑖𝑛 +1
1(119.048) 𝐹𝑖𝑛 = 167.084 𝐾𝑚𝑜𝑙/ℎ
164 Reactor Material Balance
1) 4NH3 + 5O2 4NO + 6H2O Conversion: 95%
𝐸1 = 0.95 × 137.405 = 130.535 2) 4NH3 + 3O2 2N2 + 6H2O
Conversion: 5%
𝐸2 = 0.05 × 137.405 = 6.87 NH3:
𝐹𝑜𝑢𝑡 = 137.405 −4
4(130.535) −4
4(6.87) = 0 O2:
𝐹𝑜𝑢𝑡 = 285.715 −5
4(130.535) −3
4(6.87) = 117.393 𝐾𝑚𝑜𝑙/ℎ N2:
𝐹𝑜𝑢𝑡 = 1228.38 +2
4(6.87) = 1231.815 𝐾𝑚𝑜𝑙/ℎ NO:
𝐹𝑜𝑢𝑡 = 0 +4
4(130.535) = 130.535 𝐾𝑚𝑜𝑙/ℎ H2O:
𝐹𝑜𝑢𝑡 = 0 +6
4(130.535) +6
4(6.87) = 206.107 𝐾𝑚𝑜𝑙/ℎ
Oxidation Material Balance 2NO + O2 2NO2
Conversion: 96%
𝐸 = 0.96 × 130.535 = 125.313 NO:
𝐹𝑜𝑢𝑡 = 130.535 −2
2(125.313) = 5.222 𝐾𝑚𝑜𝑙/ℎ NO2:
𝐹𝑜𝑢𝑡 = 0 + 125.313 = 125.313 𝐾𝑚𝑜𝑙/ℎ O2:
𝐹𝑜𝑢𝑡 = 117.393 −1
2(125.313) = 54.736 𝐾𝑚𝑜𝑙/ℎ H2O:
𝐹𝑜𝑢𝑡 = 206.107 𝐾𝑚𝑜𝑙/ℎ N2:
𝐹𝑜𝑢𝑡 = 1231.815 𝐾𝑚𝑜𝑙/ℎ
166 Absorber Material Balance
2NO2 + H2O + ½ O2 2HNO3
Conversion = 95%
𝐸 = 0.95 × 125.313 = 119.048 𝑘𝑚𝑜𝑙/ℎ No2:
𝐹𝑜𝑢𝑡 = 125.313 – 2 2⁄ × (119.048) = 6.265 𝐾𝑚𝑜𝑙/ℎ HNO3:
𝐹𝑜𝑢𝑡 = 0 + 119.0475 = 119.0475 𝑘𝑚𝑜𝑙/ℎ H2O:
𝐹𝑜𝑢𝑡 = 373.191 − 1 2⁄ × (119.0475) = 313.667 𝐾𝑚𝑜𝑙/ℎ NO:
𝐹𝑜𝑢𝑡 = 5.222 𝑘𝑚𝑜𝑙/ℎ O2:
𝐹𝑜𝑢𝑡 = 54.736 − 0.5 2⁄ × (119.0475) = 24.974 𝐾𝑚𝑜𝑙/ℎ N2:
𝐹𝑜𝑢𝑡 = 1231.815 𝐾𝑚𝑜𝑙/ℎ
Appendix D
(Detailed Energy Balance Calculation)
168
Compressor Energy Balance
C-101
S 1 S 3
For S1: Air at 101 kPa and S3: Air at 1090 kPa
𝑊 = 𝑃1 𝑄1 ln𝑃2 𝑃1 𝑊 = 𝑃1 𝑚(𝑎𝑖𝑟) ln𝑃2
𝑃1 𝑊 = 101 (36000
1.178) ln1090 101 𝑊 = 8879734.37 kJ/h
𝑊 = 8879734.37 kJ/h (This is the mechanical energy required by the compressor)
170 Superheater Energy Balance
E-102
S 5 S 6
For S5: NH3 at 35 oC and S6: NH3 at 177 oC
𝑄 = ∑𝑛 𝐻𝑜𝑢𝑡 − ∑𝑛 𝐻𝑖𝑛 𝐻 = ∫ 𝐶𝑝 𝑑𝑇𝑇2
𝑇1
∫ 𝐶𝑝 𝑑𝑇
𝑇2 𝑇1
= 𝑎(𝑇2− 𝑇1) +𝑏
2(𝑇22− 𝑇12) +𝑐
3(𝑇23− 𝑇13) +𝑑
4(𝑇24− 𝑇14) Tref = 35 ○C
𝐻𝑖𝑛 = 𝑍𝑒𝑟𝑜
𝐻𝑜𝑢𝑡 = 137.405 × 1000 × 5.442 = 747758.01 𝐾𝐽/ℎ
𝑄 = 𝐻𝑜𝑢𝑡 – 𝑧𝑒𝑟𝑜 = 747758.01 𝐾𝐽/ℎ
Mixer Energy Balance
M-101 S 3
S 6
S 7
For S3: NH3 at 177 oC, S6: Air at 262 oC and S7: NH3+Air at ?
𝑄 = 0 (𝐴𝑑𝑖𝑎𝑏𝑎𝑡𝑖𝑐)
Energy required to heat ammonia = Energy lost by air 𝑚𝐶𝑝(𝑇𝑜𝑢𝑡 − 𝑇𝑖𝑛) = 𝑚𝐶𝑝(𝑇𝑜𝑢𝑡 − 𝑇𝑖𝑛)
𝐶𝑝 (𝑁𝐻3) = 2.38 𝐾𝐽/𝐾𝑔. 𝐶𝑜 𝐶𝑝(𝐴𝑖𝑟) = 1.05 𝐾𝐽/𝐾𝑔. 𝐶𝑜
2335.88 × 2.38 × (𝑇𝑜𝑢𝑡 − 177) = 43537.52 × 1.05 × (262 − 𝑇𝑜𝑢𝑡) 𝑇𝑜𝑢𝑡 = 250𝐶
172
Tref = 25oC
Component Input S7
(kJ/mol)
Output S8 (kJ/mol)
H (Air) 6.654 19
H (NH3) 8.84 -
H (NO) - 19.744
H (H2O) - 23
𝑄 = 21192906.91 + 𝐹(𝑁𝑂)𝑜𝑢𝑡. 𝛥𝐻𝑟1 + 𝐹(𝐻2𝑂)𝑜𝑢𝑡. 𝛥𝐻𝑟2 𝑄 = −51820729.07 𝑘𝐽/ℎ
174 Heat Exchanger Energy Balance (1st Cooler)
E-201
Oxidation Energy Balance
176 Heat Exchanger Energy Balance (2nd cooler)
E-202
For NO
𝐻 = ∫ 𝐶𝑝 𝑑𝑇 = 2.4230𝑘𝐽/𝑚𝑜𝑙
140
60
For NO2
𝐻 = ∫ 𝐶𝑝 𝑑𝑇 = 3.1796
140
60
kJ/mol 𝑄 = −3911927.94 𝐾𝐽/ℎ
178 Absorber Energy Balance
T-201
S 11 S 12
S 13 S 14
Basis: Tref = 25oC
For S11: Air+NO+H2O+NO2 at 60 oC, S14: H2O at 20 oC, S12: Air+NO+H2O at 30 oC and S13:
HNO3+H2O at 30 oC
3NO2+H2O + 1
2 O2 2HNO3
Conversion =95%
𝛥𝐻𝑟 = 𝛴(𝐹𝛥𝐻𝑓)𝑃𝑟𝑜𝑑𝑢𝑐𝑡 − 𝛴(𝐹𝛥𝐻𝑓)𝑅𝑒𝑎𝑐𝑡𝑎𝑛𝑡
𝛥𝐻𝑟 = −435.6 𝑘𝐽/𝑚𝑜𝑙 Based on (HNO3):
𝛥𝐻𝑟 = −435.6/2 = −217.8 𝑘𝐽/𝑚𝑜𝑙
𝑄 = 𝛴(𝐹𝐻)𝑜𝑢𝑡 − 𝛴(𝐹𝐻)𝑖𝑛 + 𝑛𝑃𝑟𝑜𝑑𝑢𝑐𝑡 𝛥𝐻𝑟 𝐻 = ∫ 𝐶𝑝 𝑑𝑇
𝑇2 𝑇1
𝐻 = 𝑎𝑇 +𝑏
2𝑇2 +𝑐
3𝑇3+𝑑 4𝑇4
Tref = 25oC
Component Input S11 (kJ/mol)
Input S14 (kJ/mol)
Output S12 (kJ/mol)
Output S13 (kJ/mol)
H (H2O) (g) 1.18 - 0.166 -
H (H2O) (L) - -0.375 - 0.375
H (Air) 1.02 - 0.145 -
H (NO) 1.044 - 0.149 -
H (NO2) 1.32 - - -
H (HNO3) - - - 0.55
𝑄 = −29876241 𝐾𝐽/ℎ
180
Appendix E
(Equipment Design References)
Table A: Typical overall coefficients