Closure process design for conversion of

green power to products of nitric acid

Jiahua ZHU, Jing GE and Sulan XIA

Sichuan University, Chengdu, China

Closure process for green-power to nitric acid

• Definition of “closure process” for P2N

• Contributions of P2N expected to sustainable

chemical & renewable power industries

• Competitiveness of P2N by “closure process”

• Feasibility of P2N based on innovative technology

• Summary

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• Definition of “closure process” for P2N

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Overall reactions for NA production:

NH3 + 2O2 → HNO3 + H2O

1 kmol

Air

10 kmol

NH3

HNO3

1 kmol

7.9 kmol

Waste

CO2

emission

N2 + 3H2 → 2NH3

Fossil fuels

Closure process (CP) for P2N with

Electrolysis: 2H2O → 2H2 + O2

Air separation: Air → N2 + O2

Green NA

from AS

Conventional

process

• Contributions expected to sustainable

chemical & renewable power industries

A heavy chemical industry sector with 60 Mt/a (100% NA) global production

and 510 kt/a N2O

32.5 Mt/a CO2

Emissions worldwide

P2N expected to play an important role in

reduction of global GHG 158 Mt/a CO2-eq

(N2O has 310 times the Global Warming Potential of CO2 )

and save fossil resource of 30 Mt/a (C-eq)

• Contributions expected to sustainable

chemical & renewable power industries

P2N is a value added production system adaptable to renewable power supplies

N2 + 3H2

→ 2NH3

NH3 + 2O2 →

HNO3 + H2O

2H2O →

2H2 + O2

Air →

N2 + O2

NH3

storage

ASPEM

N2

NA

NH3 + 2O2 → HNO3 + H2OStrong exothermic

reaction: ΔGo= -17674.4 MJ/t-NH3

Power compensation

net output: W = 833 kWh/t-NH3

W = 833 kWh/t-NH3

• Competitiveness of P2N by innovative

“CPS”

( NH3+2O2→HNO3+H2O )(N2+3H2 →2NH3 ) &

Gap of 5.2%

• Taking N2 supply for NH3

synthesis, free of cost as by-

product of O2 generation (AS)

• Supplying O2 for NH3 oxidation,

increasing gain from by-

product of H2 generation (PEM)

• Increasing mass conversion efficiency by

stopping tail gas emission

• Increasing energy conversion efficiency by CP

Comparing to conventional tech.,

competitiveness of P2N coming from

W = 833 kWh/t-NH3

: Cost of NA product well in the line of market

Dual benefits to P2A:

• Feasibility of P2N based on

innovative technologies

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(263K,53MPa) (338K,53MPa)

Isobaric heating

Isentropic expanding

From air separation →

→ back to the air (288K,130kPa)(163K,130kPa)

Δh7=110 kJ/kg

Δh17=85 kJ/kg

Δh18=350 kJ/kg

Multi-stage regenerative thermodynamic cycle

( J.H. Zhu, J. Ge,. J. Li, et al. 2018, Pat. CN 201811478267.6.)

From residual heat recovery,

produce power W = 833 kWh/t-NH3

Summary

Table 1- Energy analysis for a closure process system of 150 kt/a (20 t/h) P2N

items amount specific weq Win(-) or Wout(+)

kWh

note

H2 from PEM 1040 kg/h 51.5 kWh/kg -53560 SIEMENS

O2 by-product 8330 kg/h / /

O2 from AS 13880 kg/h 0.42 kWh/kg -5830 AIR LIQUIDE

N2 by-product 45696 kg/h / /

Widea,compressor 3200 kWh 0.83 weq/widea -3855

Wcryogenic. -5830 Auxiliary

ΔHidea,expander, 11206 kWh 0.88 Δhidea/weq 9861

Steam, 4MPa 17 t/h 0.267 kWh/kg 4533

Total -54681

Power consumption = 54681/20 = 2734 kWh/t-NA(100%)

Total cost = Power cost = 2734/1000×38 = 104 €/t-NA(100%)

The total cost of P2N is well below the item-cost of NH3

consumed in conventional open process of NA:

NH3 cost = 0.28 (t)×450 (€/t) = 126 €/t-NA(100%)

P2N could be well beneficial

environmentally and economically,

worth to develop commercially.

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