WO2023042228A1

WO2023042228A1 - A system and process for the production of nitric acid

Info

Publication number: WO2023042228A1
Application number: PCT/IN2022/050835
Authority: WO
Inventors: Anil Kumar Kruthiventi; Rahul Raju KANUMURU
Original assignee: Fertis India Pvt Ltd
Priority date: 2021-09-19
Filing date: 2022-09-19
Publication date: 2023-03-23

Abstract

The present invention relates to systems and methods for producing nitric acid, nitrates, salts thereof. The system comprises of a reverse vortex plasmatron configured for operating with a feed stream comprising of molecular oxygen and molecular nitrogen to create a reverse vortex flow in the reactor in which a plasma is formed; the plasma reactor configured to produce oxidized nitrogen species could be fluidically coupled through a conduit to a mixing chamber fed optionally with a oxidizing gas; the nitrates, nitrites produced in the mixing chamber; the outlet of the mixing chamber is fluidically coupled with an absorber comprising glass fibers with continuous circulation of water or alkaline medium to produce nitric acid or salts thereof in the receiver tank used for recirculating the water or alkaline medium. The systems and the associated method methods of the present invention allow producing nitric acid, nitrates, salts thereof with high efficiency. This invention also has several advantages of using plasma technology, in particular the one of not requiring catalysts or high reaction temperatures.

Description

A SYSTEM AND PROCESS FOR THE PRODUCTION OF NITRIC ACID

TECHNICAL FIELD

The present invention relates to systems and methods for the conversion of a feed stream comprising of molecular oxygen and molecular nitrogen into nitric acid, nitrates, salts thereof.

BACKGROUND OF THE INVENTION

Nitrogen is an essential nutrient crucial for crop growth and development. Approximately half the food produced now in the world is supported by the use of N fertilizer. One of the most important scientific discoveries of the 20th century is the Haber-Bosch process, which transforms atmospheric nitrogen into synthetic nitrogen for crop fertilization. The Haber-Bosch process utilizes hydrogen and atmospheric nitrogen under extremely high pressure and temperature in combination with a metal catalyst such as iron to produce liquid ammonia also known as anhydrous ammonia. In this process, natural gas is typically used as a hydrogen feedstock and as a source of energy to obtain the high pressure and temperature required for the reaction, and for this reason, natural gas and nitrogen fertilizer prices are closely related. The world food problem is increasing the demands for nitrogen fertilizer at a time when supplies of natural gas and other fuels used in their production are decreasing and becoming more expensive. One method to compensate for present and future shortages of nitrogen fertilizers is to produce nitrate fertilizer from air and water using plasma discharge in air processes.

Plasma reactors have been used in the past for the fixation of nitrogen for producing nitric acid. The Birkeland-Eyde process was used historically to produce nitric acid using an electric arc plasma process but was later replaced with the process for production of nitric oxide by the catalytic oxidation of ammonia by air in the presence of catalysts. The plasma process was abandoned due its low conversion efficiency.

CN 102583278 A entitled “process for producing nitric acid by dielectric barrier discharge nitrogen fixation” comprising a tooth-shaped stainless-steel cylinder, wherein an insulation tube is sheathed outside the tooth-shaped stainless-steel cylinder. The gap between the SS cylinder and the insulation tube is 3-30 mm. They reported maximum concentration of HNO₃ (0.072 m mol/L) by applying 15.64kV peak voltage, 5-20 kHz frequency and the amount of nitric acid produced for IkWh plasma power consumption is 2.36 grams.

WO 2016063302 A2 entitled “Process for combustion of nitrogen for fertilizer production” discloses materials, methods and system useful for conversion of nitrogen gas into nitrogen compounds that can be assimilated by plants. GB 915,771 generates a dielectric barrier discharge via radio frequency power which is ignited at low pressure. Concentrations of up to 5% NO in the process exhaust gas are detected, which is about 20 kWh/kg HNO₃ in the best case.

Kaoru Harada et al., carried out the reductive fixation of molecular nitrogen with water using glow discharge. It was found that ammonia and nitrate ions were formed in the aqueous solution. The amount of ammonia and nitrate ion found in the reaction mixture increased with the reaction time, and the concentrations of ammonia and nitrate ion were 0.45 mmol/20 ml and 0.38 mmol/20 ml, respectively after 24 hours.

Wenjuan Bian et al., used pulsed high voltage discharge for Nitrogen fixation into nitric acid. By applying pulsed high voltage discharge to a needle-mesh reactor that using seven acupuncture needles as discharge electrode and stainless-steel wire mesh as ground electrode. At the end of the 36 min discharge, the HNO3 concentration with bubbling air was 2.215 mmol/1 at an applied voltage of 25 kV, pulse repetition frequency of 140 Hz and ground electrode mesh of 20 x 20. The energy yield was about 1.22 g (HNO3) / kWh.

GB 2442990A discloses a process of using a microwave plasma apparatus with vortex gas flow that operates at relatively low temperatures and pressures.

US 2022/0055901 Al discloses a process for the production of nitrogen oxides using microwave plasma. This method uses high energy and operates above ambient pressure (5 Bar abs) making it not suitable for decentralized production.

On analysis of the processes reported in the art it is evident that none of the processes have been successful in the development of an efficient process that can compete with the established nonplasma methods of production. The reported methods so far have limitations such as reduced reaction zone, requiring higher pressures or temperature, requiring higher ratios of oxygen and nitrogen leading to reduced overall efficiency. Therefore, there remains a need in the art to provide a system and efficient process for production of nitric acid using atmospheric air to overcome the above problems.

OBJECTIVES OF THE INVENTION

The object of the present invention is to provide a system and methods for production of nitric acid, nitrates and salts thereof using a feed stream comprising of molecular oxygen and molecular nitrogen.

It is another object of the present invention to provide a system and method for producing highly concentrated nitrogen oxide products that can be readily used by plants for optimized growth and productivity. It is a further objective of the invention to provide a system and method that uses the nitrogen and oxygen from the atmospheric air to produce nitrogen products that are required by plants.

It is yet another object of the invention to provide a system and method for on-site conversion of irrigation water and air into highly valuable nitrogen products that can be used by plants readily for growth.

It is yet another object of the present invention to provide a system and method and that would be capable of high throughputs, energy efficient and a low-cost low-maintenance mobile system which would be affordable to small famers thereby reducing the dependence on large fertilizer manufacturers.

It is a further objective of the present invention to provide a system and method that would be sustainable and capable of operation with renewable solar power or other renewable power sources.

SUMMARY OF THE INVENTION:

The present invention fulfills the above and other objects by providing a system and method for producing nitrogen compounds and/or a product stream comprising such nitrogen compounds. The nitrogen compound produced by the system and method include oxides of nitrogen, nitrates, nitrites, nitric acid, salts thereof or a mixture thereof.

In one aspect, the present invention provides a system and method for the production of nitrogen compounds using air, water and electricity. In some embodiments the system can be operated with electricity generated by green source or renewable source enabling the system to be installed near the point of use.

In one aspect, the present invention relates to a system which includes a plasma reactor, a mixing chamber and an absorption system. The plasma reactor preferably consists of a reactor inlet port at the top of the reactor and an outlet port at the bottom of the reactor. According to certain aspects, the inlet port of the plasma reactor is configured for receiving the feed stream, comprising molecular oxygen and molecular nitrogen and a recycle stream comprising recycle gases. In some aspects, the plasma reactor may have one or more inlet ports which are connected tangentially to generate a reverse vortex flow of the gases from the feed and recycle stream in the plasma reactor or perpendicularly to the reactor wall and passed through a swirl plate which generate a reverse vortex flow of the gases from the feed and recycle stream in the plasma reactor. This reverse vortex flow allows for stable containment of the plasma and prevents the overheating of the reactor walls.

According to some aspects of the invention, the plasma reactor is configured to produce thermal or non-thermal plasma of oxygen, thermal or non-thermal plasma of nitrogen, or a mixture thereof. The plasma reactor may comprise of glow discharge electrodes, dielectric barrier discharge electrodes and/or gliding arc discharge electrodes. In some instances, the plasma reactor may comprise of microwave generator or radio frequency generator for electrode-less generation of plasma.

In some aspects of the present invention, the nitrogen oxide/s produced in the plasma reactor exit the reactor through the outlet port of the reactor. The outlet port of the reactor is connected a gas mixing unit through a conduit. The mixing unit consists of a port for addition of an oxidizing gas to the nitrogen oxides generated from the plasma reactor. According to some aspects of the invention, the oxidizing gas could be air or oxygen enriched air or ozone or their mixtures thereof. The outlet of the mixing unit comprises of gases that can readily absorbed in water or alkaline medium to produce nitrates, nitric acid or salt thereof. Additionally, the mixing unit could be configured to increase the mixing of the gases by providing suitable column internals or packings.

According to some aspects of the invention, the system includes an absorber which is connected to the outlet port of the plasma reactor or the outlet port of the mixing unit to receive an inlet stream of gases and produce nitrates, nitric acid and salts thereof. The absorber also comprises of an inlet port for receiving a recirculating fluid from a receiver tank. In some aspects, the recirculating fluid could be water or alkaline solution which absorb the inlet stream of gases and produce nitrates, nitric acid and salts thereof. Additionally, the absorber may be filled or consist of suitable material like glass fiber to selectively absorb certain oxides of nitrogen. In certain aspects of the invention, the recirculating fluid could be sprayed through a nozzle to generate fine droplets.

These and other aspects of the invention are detailed in the drawings and in the detailed description that follows.

BRIEF DESCRIPTION OF THE FIGURES

In the following detailed description, reference will be made to the attached drawings in which:

Fig. 1 illustrates a non-limiting, exemplary system for producing nitrogen compounds in accordance with aspects of the disclosure

DETAILED DESCRIPTION

The present invention relates to a system and method for producing nitrogen compounds and/or a product stream comprising such nitrogen compounds. The nitrogen compound produced by the system and method include oxides of nitrogen, nitrates, nitrites, nitric acid, salts thereof or a mixture thereof. In one aspect, the present invention provides a system and method for the production of nitrogen compounds using air, water and electricity. In some embodiments, the system can be operated with electricity generated by green source or renewable source enabling the system to be installed near the point of use.

With reference to Fig. 1, in one embodiment, a system is provided for producing nitrogen compounds using air, water and electricity. As a brief overview this system includes a plasma reactor 20, a mixing unit 31 and an absorption system 52.

The plasma reactor 20 is built to produce a plasma of nitrogen or plasma of oxygen or a combination thereof. For the generation of plasma, the plasma reactor 20 may include electrodes. High voltage between the electrodes is provided by the power source 1 and resistor 3. In some embodiments of the present invention, the plasma is generated by maintaining high voltage between two electrodes which are in a gliding arc configuration. In Fig.l, the electrodes are in a gliding arc configuration wherein an arc is formed between the reactor body (cathode potential) and outlet (anode), the outlet (anode) diameter is smaller than the reactor body (cathode) diameter.

Alternatively, the plasma reactor 20, according to some aspects of the invention, is built to produce thermal or non-thermal plasma of oxygen, thermal or non-thermal plasma of nitrogen, or a mixture thereof. The plasma reactor 20 may comprise of glow discharge electrodes, dielectric barrier discharge electrodes and/or gliding arc discharge electrodes. In some instances, the plasma reactor may comprise of microwave generator or radio frequency generator for electrode-less generation of plasma.

In some aspects of the present invention, the plasma reactor 20 has an inlet port 16. As in Fig.l the inlet port 16 is connected to the reverse vortex flow generator 23 of the plasma reactor 20. The inlet port 16 is fluidically connected to the conduit 10 which in turn is connected to the feed conduit 12 and a recycle conduit 54. The inlet port 16 is built to receive feed stream from the feed conduit 12 and gases from recycle stream from the recycle conduit 54. In some instances, the conduit 10 connected to the inlet port 16 is connected to the feed conduit 12 and recycle conduit 54 through a T-pipe connector or a venturi. The inlet port 16 has a structure and formed with a suitable material for receiving the inlet stream. The conduits 10, feed conduit 12 and recycle conduit 54 may be a pipe, tube or the like formed with material, such as metal, metal alloy, plastic, ceramic, or the like and have a structure based on the contents flowing therethrough, the pressure exerted and other operating parameters.

According to some aspects of the invention, as in Fig. 1, the system for producing nitrogen compounds may contain a device for generating the feed gas supply. The feed gas supply device 11 is built to produce the feed stream to the plasma reactor 20 or a component thereof. The feed gas supply device 11 is built to provide air or components thereof. The feed stream generated by the feed gas supply device 11 has a weight ratio of molecular nitrogen to molecular oxygen in the ratio of about 5: 1 to about 1:5. The feed gas supply device could be selected from a compressor, a blower, an air filtration unit, a membrane-based separator, oxygen concentrator, pressure swing absorber or a combination thereof. In one aspect the feed gas supply device produces ozone such that the feed stream contains ozone of about 1 to 35% based on the volume of the feed gas. In such instances the ozone is generated by corona discharge or VUV light.

In some aspects of the invention, the inlet port 16 connected to the reverse vortex generator 23 is perpendicular to the body of the reverse vortex generator 23. The reverse vortex generator 23 has a reactor body and outlet, the outlet (anode) diameter is smaller than the reactor body diameter. According to certain aspects of the invention, the inlet gases are directed to a swirl plate which has plurality of angled vanes that divert the flow of gases to the walls so the gases are first forced to move upwards in the reactor in a forward vortex flow. While the gases are moving, it loses rotational speed due to friction and inertia, and when it reaches the top part of the reverse vortex generator 23, it moves down in a smaller reverse vortex flow to the bottom where it can leave the reactor. Alternatively, the inlet port 16 may be connected tangential to reverse vortex generator 23, the inlet gases are directed to the walls so the gases are first forced to move upwards in the reactor in a forward vortex flow. While the gases are moving, it loses rotational speed due to friction and inertia, and when it reaches the top part of the reverse vortex generator 23, it moves down in a smaller reverse vortex flow to the bottom where it can leave the reactor.

In some embodiments of the present invention, the plasma is generated by maintaining high voltage between two electrodes which are in a gliding arc configuration. In Fig.l, the electrodes are in a gliding arc configuration wherein an arc is formed between the reactor body (cathode potential) and outlet (anode), the outlet (anode) diameter is smaller than the reactor body (cathode) diameter. The reverse vortex flow surrounded by the forward vortex flow of the inlet gases generated by the reverse vortex flow generator 23 stabilizes the arc plasma in the centre resulting in better thermal insulation, which reduces heat loss and prolongs the lifetime of the electrodes.

In some embodiments of the invention, the plasma reactor 20 is provided with a reactor outlet port 24. The reactor outlet port is connected to the elongated portion 26 of the plasma reactor 20. The reactor outlet port is connected to the mixing unit 31 through the reactor outlet conduit 28. The outlet stream of the plasma reactor 20 is connected to the mixing unit 31 through the reactor outlet port 24 and reactor outlet conduit 28. The outlet stream of the plasma reactor 20 may comprise of one or more oxidized nitrogen species. For instance, the reactor stream may comprise one or more of NO, NO₂, N₂O, and/or nitric acid. The reactor outlet port 24 has a structure and formed with a suitable material for outlet stream of the plasma reactor 20. The plasma reactor outlet conduit 28 may be a pipe, tube or the like formed with material, such as metal, metal alloy, plastic, ceramic, or the like and have a structure based on the contents flowing therethrough, the pressure exerted and other operating parameters.

According to certain embodiments of the present invention the mixing unit 31 receives the outlet stream from the plasma reactor 20 through the reactor outlet conduit 28. Additionally, the mixing unit is built to receive an oxidizing gas through the conduit 34. In one aspect of the invention, the oxidizing gas could be air or oxygen enriched air or ozone or their mixtures thereof. Additionally, the mixing unit 31 could be configmed to increase the mixing of the gases by providing suitable column internals or packings. According to some aspects of the invention, the mixing unit 31 could be a venturi ejector to mix and blend the outlet gases from the plasma reactor 20 with the oxidizing gas/gases. The mixing unit 31 has a structure and formed with a suitable material based on the contents flowing therethrough, the pressure exerted and other operating parameters. The outlet of the mixing unit comprises of gases that can readily absorbed in water or alkaline medium to produce nitrates, nitric acid or salt thereof.

The absorber is connected to the mixing unit outlet conduit 39 and is built to receive the outlet stream of the mixing unit 31. In some aspects of the present invention, the absorber is built to connect to the reactor outlet conduit 28 to receive the plasma reactor outlet stream. The mixing unit outlet conduit 39 and/or the plasma reactor outlet conduit 28 is connected to the absorber at the absorber gas inlet port 46. In Fig. 1, the absorber 52 is packed with a material that has differential adsorption capacity for the gases entering the absorber through the gas inlet port 46. In some embodiments of the present invention, this material is made of glass fiber. Alternatively, the absorber 52 may be selected from the types reported in the art for efficient gas absorption such as packed column, tray column, bubble column, film column, plate column or a spray tower. In some aspects of the present invention, the absorber 52 may include a diffuser for diffusing the gases entering through the gas intel port 46. In one embodiment, the diffuser is submerged in the liquid contained in the absorber and made of porous material suitable for generating fine microbubbles in the liquid. The absorber 52 is built to produce nitrates, nitrites, nitric acid and salts thereof in the liquid phase. The absorber 52 has a structure and formed with a suitable material based on the contents flowing therethrough, the pressure exerted and other operating parameters.

The liquid phase in some aspects of the present invention may be water or an aqueous solution. This liquid phase is continuously or intermittently recirculated into the absorber 52 from a receiver 70. The nitrates, nitrites, nitric acid and salts thereof in the liquid phase of the absorber 52 exit from the absorber outlet port 51. The outlet port 51 is connected to receiver 70 through the absorber outlet conduit 50. The liquid phase present in the absorber may be water or may contain an aqueous solution which may comprise one or more basic compounds. In some aspects of the invention, the basic compound is chosen from potassium carbonate, potassium hydroxide, calcium hydroxide, calcium carbonate, ammonium hydroxide and a mixture thereof.

The receiver 70 has an outlet port 73, this is connected to a recirculation pump 72 through the pump feed conduit. The liquid phase is connected to the liquid phase inlet port 53 of the absorber 52 through the liquid phase conduit 85. In some aspects the liquid phase is pumped through a heat exchanger device to reduce the temperature of the liquid phase stream. The temperature of the liquid phase entering the absorber may be maintained by cooling medium circulation in the heat exchanger. The receiver 70 has a structure and formed with a suitable material based on the contents flowing therethrough, the pressure exerted and other operating parameters.

The nitrates, nitrites, nitric acid and salts thereof are produced in the liquid phase of the absorber 52 by the absorption of the oxides of nitrogen. In general, part of the oxides of nitrogen are absorbed by the liquid phase in the absorber 52, the remaining oxides of nitrogen that are not absorbed by the liquid phase traverse the liquid phase and form the gas phase of the absorber 52. In some aspects, this gas phase forms the recycle stream. The absorber 52 has an recycle stream port 55 which connected to the plasma reactor feed conduit 10 through the recycle stream conduit 54. The incorporation of the recycle stream offers the advantage of converting the non-absorbed nitrogen oxides into desirable nitrogen oxides, thereby avoiding green-house gas emissions.

EXAMPLES

Experiment 1

Effect of flow rate on NOx production

The operation of the reactor was carried out at atmospheric pressure. The feed stream was generated by the compressor. The amount of NOx produced was studied using different air flow rates between 13.5 and 35 1/min. The flow rate of the feed stream was maintained by using high precision flow meters. The NOx generated from the plasma reactor were analyzed using an NOx analyzer. The data collected in show in table 1

Table 1

With increase in the flow rate of the feed stream NOx production rate was found to increase.

Experiment 2

Effect of different oxidizing gas

The effect of the different oxidizing gas used for the oxidation of NOx from the plasma reactor was studied.

The NOx produced from the plasma reactor at atmospheric pressure with different flow rates ranging between 13.5 and 35 1/min was mixed with different oxidizing gas in the mixing chamber. For the oxidation of NOx air, oxygen and ozone were evaluated. The ratio of oxidizing gas to the NOx were varied. The oxidized gas was sent to the glass fibre filter for absorption. The amount of NOx absorbed by the filter estimated by measuring the NOx at the inlet and outlet of the glass fibre filter. The data collected in show in table 2

Table 2

Among the oxidizing gases tested ozone resulted in maximum NOx absorption. The results indicate that even with lower NOx to ozone ratio and higher inlet flow to the absorber maximum NOx absorption was observed.

Experiment 3

Effect of flow rate on the production of nitric acid The effect of flow rate on the production of nitric acid was evaluated.

The operation of the reactor was carried out at atmospheric pressure. The feed stream was generated by the compressor. The amount of NOx produced was studied using different air flow rates between 13.5 and 35 1/min. The flow rate of the feed stream was maintained by using high precision flow meters. The NOx produced from the plasma reactor was mixed with ozone for oxidation. The ratio of ozone to the NOx was adjusted to avoid the NOx at the exit of the absorber. Water from the receiver was recirculated in the absorber at constant rate to result in nitric acid production.

Table 3

Maximum production of nitric acid was observed at a flow rate of 35 1/min

Claims

CLAIMS We claim,

1. A system for producing nitrates, nitric acid and salts thereof comprising of a) A plasma reactor (20) built to generate plasma comprising of a reverse vortex generator (23) which is connected to inlet feed stream (16) to produce a product stream comprising of one or more oxides of nitrogen at the reactor outlet conduit (28) present in the elongated portion of the plasma reactor; b) A mixing unit (31) connected to the plasma reactor outlet stream where the nitrogen oxides produced in the plasma reactor are mixed with an oxidizing gas to generate a mixture of gases that can readily absorbed in water or alkaline medium to produce nitrates, nitric acid or salt thereof; and c) An absorber (52) coupled with the outlet conduit of the mixing unit (39), the absorber is built to produce a liquid phase stream containing nitrates, nitric acid or salt thereof and gas phase stream which is coupled with the inlet conduit (46) of the plasma reactor (20).

2. The system of claim 1, further comprises of a feed gas supply device (11) built to supply the feed stream to the system.

3. The system of claim 2, wherein the feed stream supply device (11) provides molecular nitrogen and molecular oxygen in the ratio of about 5 : 1 to 1:5.

4. The system of claim 3, wherein the feed stream supply device (11) provides a feed stream enriched in oxygen or ozone.

5. The system of claim 1, wherein the feed stream is connected to the inlet port (16) of the reverse vortex flow generator (23).

6. The system of claim 5, wherein the inlet port (16) is perpendicular to the body of the reverse vortex generator (23).

7. The system of claim 6, wherein the gases in the feed stream are directed to a swirl plate comprising a plurality of vanes to direct the gases and generate a forward vortex and reverse vortex flow.

8. The system of claim 1, wherein the plasma reactor (20) comprises glow discharge electrodes, dielectric barrier discharge electrodes and/or gliding arc discharge electrodes.

9. The system of claim 8, wherein the plasma generated is stabilized by the forward and reverse vortex flow of gases.

10. The system of claim 1, wherein the gases from the reactor outlet conduit (28) are mixed with an oxidizing gas.

11. The system of claim 10, wherein the mixing unit (31) comprises of column internal or packings to increase the mixing of gases

12. The system of claim 11, wherein the mixing unit could be a venturi ejector. The system of claim 12, wherein the oxidizing gas is air, oxygen enriched air, ozone, hydrogen peroxide and/or mixture thereof. The system of claim 1, wherein the absorber (52) is a packed column, tray column, bubble column, film column, plate column or a spray tower. The system of claim 14, wherein the absorber (52) comprises a liquid phase containing nitrates, nitric acid or salt and a gas phase with recycled back to the feed stream. The system of claim 15, wherein the liquid phase is recirculated in the absorber (52) from a receiver (70). A method for producing nitrates, nitric acid and salts thereof, or a mixture thereof, the method comprising: a) Producing a plasma reactor product stream comprising one or more of oxides of nitrogen from a feed inlet stream comprising of molecular nitrogen and molecular oxygen using plasma reactor; b) Generating a mixture of gases that can readily absorbed in water or alkaline medium to produce nitrates, nitric acid or salt thereof by mixing the gases from the plasma reactor outlet with an oxidizing gas in the mixing unit; c) Producing a liquid phase and gas phase in an absorber, wherein the liquid phase comprises of the produced nitrates, nitric acid, salts thereof and mixture thereof; and d) Recycling the gas phase stream from the absorber back to the inlet feed stream to the plasma reactor. The method of claim 17, wherein molecular oxygen and molecular nitrogen in the feed stream are converted to oxides of nitrogen in the plasma reactor. The method of claim 18, wherein the plasma produced is non-thermal plasma of oxygen and nitrogen. The method of claim 19, wherein the inlet feed stream to the plasma reactor comprise nitrogen and oxygen in the ratio of about 5: 1 to about 1:5. The method of claim 17, wherein the oxidizing gas is selected from air, oxygen enriched air, ozone, hydrogen peroxide and/or mixture thereof. The method of claim 21, wherein the ratio of the plasma reactor outlet gas containing the oxides of nitrogen and the oxidizing gas is in the range of about 1 : 10 to 1: 1. The method of claim 22, wherein the ratio of the plasma reactor outlet gas containing the oxides of nitrogen and the oxidizing gas is in the range of 1 :7 to 1:4, more preferably in the range of 1 :3 to 1: 1. The method of claim 17, wherein the absorber absorbs a part of the oxides of nitrogen in the liquid phase. The method of claim 23, wherein the liquid phase comprises of one or more of water and a basic compound selected from potassium carbonate, potassium hydroxide, calcium carbonate, calcium hydroxide and a mixture thereof. The method of claim 17, wherein the recycle stream provides unabsorbed oxides of nitrogen to the plasma reactor.