Process equipment and method for high-temperature nitrogen-free sintered magnesia

Abstract

The invention discloses process equipment and method for high-temperature nitrogen-free sintered magnesia, and belongs to the technical field of high-temperature combustion of industrial kilns, and the process equipment is composed of a calcining kiln, a bag-type dust collector, an induced draft fan, a gas cooler, a gas mixer, a liquid oxygen storage tank, a gasifier, PLC control equipment and a high-pressure fan. The oxygen content in the mixed gas is controlled to be 21-25%, artificial nitrogen-free combustion-supporting air is obtained to replace air to complete sintering of magnesia, air is not used, 79% of nitrogen components in the air are prevented from entering a combustion system, discharged tail gas is reduced by more than 2 / 3, heat loss in smoke is reduced, nitrogen oxide is not generated, catalytic reduction denitration is not needed, and the production cost is reduced. As the flue gas does not need to be heated, the energy consumption cost is saved. The concentration of carbon dioxide in discharged flue gas can reach more than 90%, liquid carbon dioxide is prepared through pressurization, and waste is turned into wealth.

Description

Technical Field

[0001] The invention belongs to the technical field of high-temperature combustion of industrial kilns, and in particular relates to a process equipment and method for high-temperature nitrogen-free sintering of magnesia. Background Art

[0002] Dead-burned magnesia is the main high-temperature refractory material with a wide range of uses.

[0003] At present, the production process of high-grade heavy-burned magnesia is: calcining magnesia ore into light-burned magnesia, then pressing it into apricot-shaped pellets, sending it into a high-temperature calcining furnace, using natural gas or heavy oil as fuel, sintering and melting at 1800~1900℃, blowing cold air from the bottom of the furnace to cool and shrink the sintered material out of the furnace, and then processing it into magnesia products. Cold air is blown in from the bottom of the furnace and contacts the sintered material to cool it down. The cold air is preheated into combustion-supporting air, mixed with natural gas (or heavy oil) in proportion and burned to produce high-temperature flames, completing the sintering of magnesia. The high-temperature flue gas ascends to preheat the magnesium balls from top to bottom, and the flue gas is discharged from the top of the furnace after cooling.

[0004] The flue gas discharged from the top of the furnace enters the bag filter for dust removal. The purified flue gas is heated to 320℃ by natural gas combustion and sent to the SCR denitrifier. Concentrated ammonia water is used for catalytic reduction and denitrification. The flue gas after denitrification enters the wet desulfurization and is discharged after meeting the standards.

[0005] This process is mature, has low energy consumption, and produces high-quality magnesia products. It is the mainstream production process for high-quality dead-burned magnesia in my country. However, the main disadvantage of this process is that when sintering at a high temperature of 1800~1900℃, the nitrogen and oxygen in the air entering the sintering furnace begin to undergo an obvious oxidation reaction at high temperature (1300℃) to generate nitrogen oxides, which the environmental protection industry calls "thermal" NO X As the temperature rises, especially above 1300℃, the generation rate of nitrogen oxides increases exponentially. In the actual production process, when the temperature rises to 1800~1900℃, the NO in the flue gas emitted by the sintering furnace X The concentration is between 5000~7000mg / M 3 ,Denitrification of flue gas with such high nitrogen oxide content is difficult and costly.

[0006] High-concentration nitrogen oxide flue gas generally uses SCR ammonia reduction catalytic denitrification, and the flue gas can meet the emission requirements. However, the use of the SCR process has the following four disadvantages: First, the flue gas needs to be heated to above 320°C, and natural gas is used as the energy source for heating, which results in high energy consumption.

[0007] Secondly, the catalyst needs to be replaced regularly, especially at the end of its use. The decline in denitrification capacity can easily lead to a decrease in the denitrification rate and excessive nitrogen oxides in the flue gas.

[0008] Third, the large-scale use of ammonia (generally 18% concentrated ammonia water) is costly and can easily cause ammonia escape.

[0009] Fourth, the operating costs are relatively high. Generally, a magnesia furnace with a daily output of 150 tons requires 6 to 7 tons of concentrated ammonia water per day. The operating cost of out-of-stock conditions is more than 100 yuan per ton, causing an economic burden of 15,000 yuan per day.

[0010] In summary, the traditional nitrogen sintering industry, especially the production process and equipment of dead-burned magnesia products, have the burden of high energy consumption and high operating costs caused by the treatment of high-concentration nitrogen oxide flue gas. In addition, there are serious environmental risks due to excessive nitrogen oxides and ammonia escape.

[0011] Therefore, in light of the characteristics of the high-temperature combustion industry, it is imperative to innovate high-temperature combustion process equipment and methods that are safe, reliable, have low operating costs and meet environmental protection standards in order to achieve significant progress in existing technologies. Summary of the invention

[0012] The purpose of the present invention is to provide a process equipment and method for high-temperature nitrogen-free sintering of magnesia, wherein artificial nitrogen-free combustion-supporting wind is used to replace air as combustion-supporting wind and is sent into a calcining kiln to complete the sintering of magnesia.

[0013] Firstly, the purpose of the present invention is to provide a process equipment for high-temperature nitrogen-free sintering of magnesia, which can synthesize artificial nitrogen-free combustion-supporting air to replace air as combustion-supporting air and send it into the calcining kiln to complete the sintering of magnesia.

[0014] In order to achieve the above-mentioned invention object, the present invention provides a process equipment for high-temperature nitrogen-free sintering of magnesia, which is composed of a calcining kiln, a bag dust collector, an induced draft fan, a gas cooler, a gas mixer, a liquid oxygen storage tank, a gasifier, a PLC control equipment and a high-pressure blower. The calcining kiln comprises an artificial nitrogen-free combustion air inlet, a flue gas outlet, a natural gas inlet, a raw material inlet and a magnesia outlet, wherein the artificial nitrogen-free combustion air inlet is matched and connected with the high-pressure blower outlet, and the flue gas outlet is matched and connected with the flue gas inlet of the bag filter; The bag filter comprises a flue gas inlet, a clean flue gas outlet and a discharge port, wherein the flue gas inlet is matched and connected with the flue gas outlet of the calcining kiln, and the clean flue gas outlet is matched and connected with the gas cooler inlet and the flue gas inlet of the desulfurization system respectively; The induced draft fan comprises a clean flue gas inlet and a clean flue gas outlet, wherein the clean flue gas inlet is matched and connected with the clean flue gas outlet of the bag filter, and the clean flue gas outlet is matched and connected with the clean flue gas inlet of the gas cooler and the inlet of the desulfurization system respectively; The high-pressure blower comprises an artificial nitrogen-free combustion-supporting air inlet and an artificial nitrogen-free combustion-supporting air outlet, wherein the artificial nitrogen-free combustion-supporting air inlet is matched and connected with the artificial nitrogen-free combustion-supporting air outlet of the gas mixer, and the artificial nitrogen-free combustion-supporting air outlet is matched and connected with the artificial nitrogen-free combustion-supporting air inlet of the calcining kiln; Different from the traditional nitrogen calcination, The gas cooler comprises a clean smoke inlet, a cooling clean smoke outlet, a cooling water inlet and a cooling water outlet, wherein the clean smoke inlet is matched and connected with the clean smoke outlet of the induced draft fan, and the cooling clean smoke outlet is matched and connected with the cooling clean smoke inlet of the gas mixer; The liquid oxygen storage tank comprises a liquid oxygen inlet and a liquid oxygen outlet, and the liquid oxygen outlet is matched and connected with the vaporizer inlet; The gasifier also includes an oxygen outlet, which is matched and connected with the oxygen inlet of the gas mixer; The gas mixer also includes a PLC action command interface and an artificial nitrogen-free combustion-supporting air outlet, wherein the PLC action command interface controls the flow rate of the oxygen outlet of the gasifier, and the artificial nitrogen-free combustion-supporting air outlet is matched and connected with the artificial nitrogen-free combustion-supporting air inlet of the high-pressure blower; The PLC control equipment comprises a gas mixer detection signal terminal and a PLC action command interface, wherein the gas mixer detection signal terminal is inserted into the inner shell of the gas mixer, and the PLC action command interface is matched with the oxygen outlet of the gasifier.

[0015] Preferably, the gas mixer (4) further comprises a PLC action command interface and an artificial nitrogen-free combustion-supporting air outlet, wherein the PLC action command interface controls the cooling clean flue gas inlet of the gas cooler (3) and the oxygen outlet of the gasifier (6), respectively, and the artificial nitrogen-free combustion-supporting air outlet is matched and connected with the artificial nitrogen-free combustion-supporting air inlet of the high-pressure blower (8); Preferably, the PLC control equipment includes a gas mixer detection signal terminal and a PLC action command interface, wherein the gas mixer detection signal terminal extends into the inner shell of the gas mixer, and the PLC action command interface matches the cooling clean flue gas outlet of the gas cooler and the oxygen outlet of the gasifier respectively.

[0016] Preferably, the calcining kiln is an internal combustion vertical calcining furnace.

[0017] In order to better achieve the above-mentioned invention object, the present invention provides a process for high-temperature nitrogen-free sintering of magnesia, comprising the following steps: Step 1: Process preparation - prepare a set of high-temperature nitrogen-free sintered magnesia process equipment, including calcining kiln, bag dust collector, induced draft fan, gas cooler, gas mixer, liquid oxygen storage tank, gasifier, PLC control equipment and high-pressure fan, and connect them in sequence according to the properties of their equipment units; Step 2: Preparation of cooled clean flue gas - The flue gas discharged from the calcining kiln is first introduced into a bag filter (1) to filter and remove particulate matter in the flue gas to obtain clean flue gas, and then the flue gas is split by an induced draft fan, with one part sent to desulfurization and then discharged, and the other part sent to a gas cooler for water-cooled indirect heat exchange to cool the flue gas and obtain cooled clean flue gas below 30°C; Step 3: Liquid oxygen to oxygen - The liquid oxygen in the liquid oxygen storage tank is vaporized by the vaporizer, and the air heat energy is used to vaporize the liquid oxygen into O 2 Get oxygen; Step 4: Prepare artificial nitrogen-free combustion-supporting air - respectively send the obtained cooled clean flue gas below 30°C and oxygen into the gas mixer in proportion, measure and control the oxygen content in the mixed gas through the PLC control equipment, and automatically control the oxygen feed amount through the PLC to control the oxygen content in the mixed gas to 21-25%, to prepare a mixed gas of artificial synthetic air, and obtain artificial nitrogen-free combustion-supporting air; Step 5: Replace the air with artificial nitrogen-free combustion-supporting air and send it into the calcining kiln through a high-pressure blower to be used as cooling air and combustion-supporting air to complete the magnesia product production process.

[0018] Preferably, the calcining kiln is an internal combustion vertical calcining furnace.

[0019] Preferably, in step 4, the oxygen and cooling clean flue gas feed amounts are automatically controlled by PLC, so that the oxygen content in the mixed gas is controlled at 21-25%, and a mixed gas of artificial synthetic air is produced to obtain artificial nitrogen-free combustion-supporting air.

[0020] The main components of the mixed gas are carbon dioxide and oxygen. Carbon dioxide does not participate in the reaction, and the oxygen in the gas reacts with natural gas (or heavy oil) to release heat through oxidation combustion. The high-temperature calcination of magnesia is completed. The gas mixed with oxygen after water cooling can reach room temperature, complete the cooling and quenching of the sintered molten material of magnesia, and recover its heat to become combustion-supporting air without changing the working state of the calcining kiln. The main component of the discharged kiln gas is carbon dioxide. Part of it is returned to make artificial nitrogen-free combustion-supporting air, and the other part is sent to the desulfurization system to complete flue gas desulfurization.

[0021] In this way, air is not used as combustion-supporting air, and there is no nitrogen in the calcination process, so no nitrogen oxides are produced. Therefore, there is no need to use ammonia for catalytic reduction and denitrification, and the hidden danger of ammonia escape is eliminated. Since there is no need to heat the flue gas, the energy cost of natural gas is saved. The carbon dioxide concentration in the exhaust flue gas can reach more than 90%, which can be pressurized to make liquid carbon dioxide and sold as a commodity, turning waste into treasure.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a process equipment and method for high-temperature nitrogen-free sintering of magnesia. The sintering of magnesia is completed by replacing air with artificial nitrogen-free combustion-supporting wind. Since air is not used, 79% of nitrogen components in the air are prevented from entering the combustion system, and the exhaust gas discharged will be reduced by more than 2 / 3. Since the exhaust gas emission is reduced, the heat energy loss in the flue gas is also reduced, and the total amount of impurities is also significantly reduced compared to the total emission. Since no nitrogen oxides are produced, there is no need for catalytic reduction denitrification, thereby eliminating the hidden danger of ammonia escape. Since there is no need to heat the flue gas, the energy consumption cost of natural gas is saved. The carbon dioxide concentration in the discharged flue gas can reach more than 90%, which can be made into liquid carbon dioxide by pressurization and sold as a commodity, turning waste into treasure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] FIG1 is a schematic diagram of a process equipment for high-temperature nitrogen-free sintering of magnesia provided by the present invention.

[0025] In the attached figure 1-Bag dust collector, 2-Induced draft fan, 3-Gas cooler, 4-Gas mixer, 5-Liquid oxygen storage tank, 6-Gasifier, 7-PLC controller, 8-High pressure fan, 9-Internal combustion vertical calcining furnace. DETAILED DESCRIPTION

[0026] Example 1: Figure 1 As shown, the present invention provides a process equipment for high-temperature nitrogen-free sintering of magnesia. It is composed of a bag filter (1), an induced draft fan (2), a gas cooler (3), a gas mixer (4), a liquid oxygen storage tank (5), a gasifier (6), a PLC control device (7), a high-pressure fan (8) and an internal combustion vertical calcining furnace (9). The internal combustion vertical calcining furnace (9) comprises an artificial nitrogen-free combustion air inlet, a flue gas outlet, a natural gas inlet, an apricot pellet inlet and a magnesia sand outlet, wherein the artificial nitrogen-free combustion air inlet is matched and connected with the outlet of the high-pressure blower (8), and the flue gas outlet is matched and connected with the flue gas inlet of the bag filter (1); The bag filter (1) comprises a flue gas inlet, a clean flue gas outlet and a discharge port, wherein the flue gas inlet is matched and connected with the flue gas outlet of the internal combustion vertical calcining furnace (9), and the clean flue gas outlet is matched and connected with the inlet of the gas cooler (3) and the flue gas inlet of the desulfurization system respectively; The induced draft fan (2) comprises a clean smoke inlet and a clean smoke outlet, wherein the clean smoke inlet is matched and connected to the clean smoke outlet of the bag filter (1), and the clean smoke outlet is matched and connected to the clean smoke inlet of the gas cooler (3); The gas cooler (3) comprises a clean smoke inlet, a cooling clean smoke outlet, a cooling water inlet and a cooling water outlet, wherein the clean smoke inlet is matched and connected with the clean smoke outlet of the induced draft fan (2), and the cooling clean smoke outlet is matched and connected with the cooling clean smoke inlet of the gas mixer (4); The liquid oxygen storage tank (5) comprises a liquid oxygen inlet and a liquid oxygen outlet, and the liquid oxygen outlet is matched and connected with the inlet of the vaporizer (6); The gasifier (6) further comprises an oxygen outlet, which is matched and connected with the oxygen inlet of the gas mixer (4); The gas mixer (4) further comprises a PLC action command interface and an artificial nitrogen-free combustion-supporting air outlet, wherein the PLC action command interface controls the cooling clean flue gas outlet of the gas cooler (3) and the oxygen outlet of the gasifier respectively, and the artificial nitrogen-free combustion-supporting air outlet is matched and connected with the artificial nitrogen-free combustion-supporting air inlet of the high-pressure blower (8); The high-pressure blower (8) comprises an artificial nitrogen-free combustion-supporting air inlet and an artificial nitrogen-free combustion-supporting air outlet, wherein the artificial nitrogen-free combustion-supporting air inlet is matched and connected with the artificial nitrogen-free combustion-supporting air outlet of the gas mixer (4), and the artificial nitrogen-free combustion-supporting air outlet is matched and connected with the artificial nitrogen-free combustion-supporting air inlet of the internal combustion vertical calcining furnace (9); The PLC control equipment (7) comprises a gas mixer (4) detection signal terminal and a PLC action command interface, wherein the gas mixer (4) detection signal terminal is inserted into the inner shell of the gas mixer (4), and the PLC action command interface is matched with the oxygen outlet of the gasifier (6) and the cooling clean flue gas outlet of the gas cooler (3) respectively.

[0027] Example 2: Reference Figure 1 As shown, the present invention provides a process for high-temperature nitrogen-free sintering of magnesia, comprising the following steps: Step 1: Process preparation - prepare a set of high-temperature nitrogen-free sintered magnesia process equipment, including an internal combustion vertical calcining furnace (9), a bag filter (1), an induced draft fan (2), a gas cooler (3), a gas mixer (4), a liquid oxygen storage tank (5), a gasifier (6), a PLC control equipment (7) and a high-pressure fan (8), and connect them in sequence according to the properties of the equipment units; Step 2: preparing cooled clean flue gas - the flue gas discharged from the internal combustion vertical calcining furnace (9) is first introduced into a bag filter (1) to filter and remove particulate matter in the flue gas to obtain clean flue gas, and then the flue gas is split by an induced draft fan (2), with one part being sent to desulfurization and then discharged, and the other part being sent to a gas cooler (3) for water-cooled indirect heat exchange to cool the flue gas and obtain cooled clean flue gas below 30°C; Step 3: Liquid oxygen production: The liquid oxygen in the liquid oxygen storage tank (5) is vaporized by the vaporizer (6), and the liquid oxygen is vaporized into O by heat exchange with air. 2 Get oxygen; Step 4: preparing artificial nitrogen-free combustion-supporting air - respectively feeding the obtained cooled clean flue gas below 30°C and oxygen into a gas mixer (4) in proportion, measuring and controlling the oxygen content in the gas mixer through a PLC control device (7), and automatically controlling the oxygen feed amount through the PLC so that the oxygen content in the mixed gas is controlled at 23%, thereby preparing a mixed gas of artificial synthetic air and obtaining artificial nitrogen-free combustion-supporting air; Step 5: Replace the air with artificial nitrogen-free combustion-supporting air and send it into the internal combustion vertical calcining furnace through the high-pressure blower (8) to be used as cooling air and combustion-supporting air, thereby completing the magnesia product production process.

Claims

1. A process equipment for high-temperature nitrogen-free sintering of magnesia, comprising a calcining kiln (9), a bag filter (1), an induced draft fan (2), a gas cooler (3), a gas mixer (4), a liquid oxygen storage tank (5), a gasifier (6), a PLC control device (7) and a high-pressure fan (8), The calcining kiln (9) comprises an artificial nitrogen-free combustion-supporting air inlet, a flue gas outlet, a natural gas inlet, a raw material inlet and a magnesia outlet, wherein the artificial nitrogen-free combustion-supporting air inlet is matched and connected with the outlet of the high-pressure blower (8), and the flue gas outlet is matched and connected with the flue gas inlet of the bag filter (1); The bag filter (1) comprises a flue gas inlet, a clean flue gas outlet and a discharge port, wherein the flue gas inlet is matched and connected with the flue gas outlet of the calcining kiln (9), and the clean flue gas outlet is matched and connected with the inlet of the gas cooler (3) and the flue gas inlet of the desulfurization system respectively; The induced draft fan (2) comprises a clean flue gas inlet and a clean flue gas outlet, wherein the clean flue gas inlet is matched and connected with the clean flue gas outlet of the bag filter (1), and the clean flue gas outlet is matched and connected with the clean flue gas inlet of the gas cooler (3) and the inlet of the desulfurization system respectively; The high-pressure blower (8) comprises an artificial nitrogen-free combustion-supporting air inlet and an artificial nitrogen-free combustion-supporting air outlet, wherein the artificial nitrogen-free combustion-supporting air inlet is matched and connected with the artificial nitrogen-free combustion-supporting air outlet of the gas mixer (4), and the artificial nitrogen-free combustion-supporting air outlet is matched and connected with the artificial nitrogen-free combustion-supporting air inlet of the calcining kiln (9); Features: The gas cooler (3) comprises a clean smoke inlet, a cooling clean smoke outlet, a cooling water inlet and a cooling water outlet, wherein the clean smoke inlet is matched and connected with the clean smoke outlet of the induced draft fan (2), and the cooling clean smoke outlet is matched and connected with the cooling clean smoke inlet of the gas mixer (4); The liquid oxygen storage tank (5) comprises a liquid oxygen inlet and a liquid oxygen outlet, and the liquid oxygen outlet is matched and connected with the inlet of the vaporizer (6); The gasifier (6) further comprises an oxygen outlet, which is matched and connected with the oxygen inlet of the gas mixer (4); The gas mixer (4) further comprises a PLC action command interface and an artificial nitrogen-free combustion-supporting air outlet, wherein the PLC action command interface controls the flow rate of the oxygen gas outlet of the gasifier (6), and the artificial nitrogen-free combustion-supporting air outlet is matched and connected with the artificial nitrogen-free combustion-supporting air inlet of the high-pressure blower (8); The PLC control equipment (7) includes a gas mixer (4) detection signal terminal and a PLC action command interface. The gas mixer (4) detection signal terminal is inserted into the inner shell of the gas mixer (4), and the PLC action command interface matches the oxygen gas outlet of the cold gasifier.

2. The process equipment for high temperature nitrogen-free sintering of magnesia according to claim 1, characterized in that: The gas mixer (4) also includes a PLC action command interface and an artificial nitrogen-free combustion-supporting air outlet, wherein the PLC action command interface controls the cooling clean flue gas outlet of the gas cooler (3) and the oxygen gas outlet of the gasifier (6) respectively, and the artificial nitrogen-free combustion-supporting air outlet is matched and connected with the artificial nitrogen-free combustion-supporting air inlet of the high-pressure blower (8).

3. The process equipment for high-temperature nitrogen-free sintering of magnesia according to claim 1, characterized in that: The PLC control equipment (7) comprises a gas mixer (4) detection signal terminal and a PLC action command interface, wherein the gas mixer (4) detection signal terminal is inserted into the inner shell of the gas mixer (4), and the PLC action command interface is matched with the cooling clean flue gas outlet of the gas cooler (3) and the oxygen gas outlet of the gasifier (6) respectively.

4. A process equipment for high temperature nitrogen-free sintering of magnesia according to claim 1, 2 or 3, characterized in that: The calcining kiln (9) is an internal combustion vertical calcining furnace.

5. A process for high temperature nitrogen-free sintering of magnesia, comprising the following steps, characterized in that: Step 1: Process preparation - prepare a set of high-temperature nitrogen-free sintered magnesia process equipment, including calcining kiln, bag dust collector, induced draft fan, gas cooler, gas mixer, liquid oxygen storage tank, gasifier, PLC control equipment and high-pressure fan, and connect them in sequence according to the properties of their equipment units; Step 2: Preparation of cooled clean flue gas - The flue gas discharged from the calcining kiln is first introduced into a bag filter (1) to filter and remove particulate matter in the flue gas to obtain clean flue gas, and then the flue gas is split by an induced draft fan, with one part sent to desulfurization and then discharged, and the other part sent to a gas cooler for water-cooled indirect heat exchange to cool the flue gas and obtain cooled clean flue gas below 30°C; Step 3: Liquid oxygen production - The liquid oxygen in the liquid oxygen storage tank is vaporized by the vaporizer, and the air heat energy is used to vaporize the liquid oxygen into O2 to obtain oxygen; Step 4: Prepare artificial nitrogen-free combustion-supporting air - respectively send the obtained cooled clean flue gas below 30°C and oxygen into the gas mixer in proportion, measure and control the oxygen content in the mixed gas through the PLC control equipment, and automatically control the oxygen feed amount through the PLC to control the oxygen content in the mixed gas to 21-25%, to prepare a mixed gas of artificial synthetic air, and obtain artificial nitrogen-free combustion-supporting air; Step 5: Replace the air with artificial nitrogen-free combustion-supporting air and send it into the calcining kiln through a high-pressure blower to be used as cooling air and combustion-supporting air to complete the magnesia product production process.

6. A process for high temperature nitrogen-free sintering magnesia according to claim 5, characterized in that: The calcining kiln is an internal combustion vertical calcining furnace.

7. The process for high temperature nitrogen-free sintering of magnesia according to claim 5, characterized in that: In the step 4, the oxygen and cooling clean flue gas feed amounts are automatically controlled by PLC, so that the oxygen content in the mixed gas is controlled at 21-25%, and a mixed gas of artificial synthetic air is produced to obtain artificial nitrogen-free combustion-supporting air.

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