Industries

N2O and Nitric Acid Manufacture

MGM Innova is one of the most experienced companies in the field of nitrous oxide (N2O) abatement. One of the three methodologies in use today (AM0034: Catalytic Reduction of N2O inside the ammonia burner of nitric acid plants) was developed by MGM Innova, and we are currently working on 15 N2O abatement projects in Latin America, North America, Africa and Eastern Europe.

N2O is a powerful greenhouse gas with a high Global Warming Potential (310 times greater than that of carbon dioxide - CO2). It is produced by both natural and human-related sources. The main human-related sources of N2O are agricultural soil management, animal waste management, sewage treatment, mobile and stationary combustion of fossil fuel, adipic acid production, and nitric acid production.

N2O is also produced naturally from a wide variety of biological sources in soil and water, particularly microbial action in wet tropical forests.

Primary sources of N2O emissions

Nitric acid is an inorganic compound used primarily as a feedstock for synthetic commercial fertilizer. It is also a major component in the production of adipic acid and explosives. Virtually all of the nitric acid produced is manufactured by the catalytic oxidation of ammonia in which N2O is formed as a by-product and is released from reactor vents into the atmosphere. Over a suitable catalyst, a maximum 98% (typically 92-96%) of the fed ammonia is converted to nitric oxide (NO). The remainder participates in undesirable side reactions that lead to the production of N2O, among other compounds.

Available N2O abatement technologies

Primary: N2O is prevented from forming in the oxidation gauzes.

Secondary: Once formed, N2O is eliminated anywhere between the outlet of the ammonia oxidation gauzes and the inlet of the absorption tower (normally inside the oxidation reactor).

Tertiary: N2O is removed at the tail gas, after the absorption tower and previous to the expansion turbine. Available tertiary approaches include the NSCR and the EnviNOx® (Uhde) process; both act on N2O and acidic species (NOx). Both consume reducing agents (fuels and/or ammonia) to attain N2O abatement.

Quaternary: N2O is removed following the expansion turbine, before or at the stack.

N2O abatement benefits

  • Reduce N2O emissions
  • Improve environmental conditions
  • Obtain additional income through the sale of emission reductions in the carbon market
  • Contribute to sustainable development through technology transfer

HFCs

Hydrofluorocarbons (HFCs) are man-made chemicals, many of which have been developed as alternatives to ozone-depleting substances for industrial, commercial, and consumer products. The HFCs with the largest measured atmospheric abundances are (in order), HFC-23 (CHF3), HFC-134a (CF3CH2F), and HFC-152a (CH3CHF2).

Trifluoromethane (HFC-23 or CHF3) has a 100-year global warming potential (GWP) that is 11,700 times greater than the GWP of CO2 over the same period. HFC-23 is generated as a by-product during the production of chlorodifluoromethane (HCFC-22), currently used in refrigeration and air-conditioning systems and as a chemical feedstock for manufacturing synthetic polymers.

Current and potential applications for HCFC-22 include:

  • Aerosol propellants, as alternatives to CFC-12 in a few permitted uses.
  • Foam blowing, as an alternative to CFC-12 in polyurethane foams and in polystyrene extruded boardstock and billet.
  • Refrigeration, as an alternative to R-502 (a blend of CFC-115 and HCFC-22) in most cooling systems, air-conditioning systems, heat pumps, and in blends to replace other CFCs in various cooling systems.
  • Tetrafluoroethylene manufacture, as a feedstock used in tetrafluoroethylene production.
How can HFC-23 emissions in HCFC-22 production be reduced?

In non-Annex I countries (developing countries) under the Kyoto Protocol, most HFC-23 emissions are vented to the atmosphere. However, two options have been identified as technically viable measures to reduce HFC-23 emissions from HCFC-22 production: (1) manufacturing process optimization, and (2) the destruction of HFC-23 by thermal oxidation.

Process Optimization

Process optimization and modifying production equipment can both optimize HCFC-22 production and reduce HFC-23 emissions. Process optimization is relatively inexpensive and is likely to be most effective in reducing the emissions from plants that are generating HFC-23 at a rate of 3-4%.

Thermal Oxidation

Thermal oxidation (the process of oxidizing HFC-23 to CO2, hydrogen fluoride, and water) is a demonstrated technology for the destruction of halogenated organic compounds. For example, destruction of more than 99% of HFC-23 can be achieved under optimal conditions (i.e., a relatively concentrated HFC-23 vent stream with a low flow rate). In practice, units will experience some downtime based on the extreme corrosivity and high temperatures required for complete destruction. Although typical incinerators that burn only HFC-23 produce six pounds of CO2 for every pound of HFC-23 burned, scrubbers in the smokestack prevent almost all of the CO2 produced from entering the atmosphere. This reduction in CO2 emissions occurs while scrubbing to remove hydrogen fluoride (HF) from the waste stream.

For CDM/JI projects the primary activity is to reduce HFC-23 emissions by recovering and decomposing it. This gas is currently released to the atmosphere. This activity allows the client to reduce HFC-23 emissions, improve environmental conditions and obtain additional income through the sale of Certified Emission Reductions (CERs)/Emission Reduction Units (ERUs) in the carbon market.

CDM project activities also contribute to the sustainable development of the host country through industrial technology transfer (technology from an Annex I country to a non-Annex I country).

Related Projects

  • Nitrous Oxide Abatement Project
    Donau Chem
    Romania
  • PFC Emission Reductions at ALBRAS
    Alumínio Brasileiro
    Brazil
  • Abatement of N2O Emissions from Nitric Acid Production
    CJSC Severodonetsk Azot Association
    Ukraine