阅读说明：本技术 一种利用空气直接实现从氮气到硝酸一步转化的方法 (Method for directly realizing one-step conversion from nitrogen to nitric acid by utilizing air ) 是由 赵林 金长浩 但勇 高波 李莉 何永 赵澎 赵顶 于 2021-07-22 设计创作，主要内容包括：本发明涉及一种利用空气直接实现从氮气到硝酸一步转化的方法,包括以下步骤：脱除空气中的酸性气体和水分,制得净化空气；将所述净化空气与外加氧气混合后压缩,制得压缩混合气；利用电弧法使所述压缩混合气反应,制得一氧化氮气体；将所述一氧化氮气体降温后与补入的氧气发生氧化反应,制得氮氧化物；将所述氮氧化物与水反应生成硝酸。本发明通过引入氧气,并与空气混合后一同加压,使氮气与氧气浓度成倍提高,同时利用电弧高温固氮合成氮氧化物,实现氮到硝酸一步高效转化的方法,具有极大的现实意义与经济价值。(The invention relates to a method for directly realizing one-step conversion from nitrogen to nitric acid by using air, which comprises the following steps of: removing acid gas and water in the air to prepare purified air; mixing the purified air with external oxygen and then compressing to prepare compressed mixed gas; making the compressed mixed gas react by using an electric arc method to prepare nitric oxide gas; cooling the nitric oxide gas, and then carrying out oxidation reaction on the nitric oxide gas and supplemented oxygen to prepare nitrogen oxide; the nitrogen oxides are reacted with water to produce nitric acid. The invention introduces oxygen, mixes the oxygen with air and pressurizes the mixture, so that the concentration of nitrogen and oxygen is improved by times, and simultaneously utilizes the arc high-temperature nitrogen fixation to synthesize nitrogen oxide, thereby realizing the method for realizing the one-step efficient conversion from nitrogen to nitric acid, and having great practical significance and economic value.)

1. A method for directly converting nitrogen into nitric acid by using air, which is characterized by comprising the following steps:

(1) removing acid gas and water in the air to prepare purified air;

(2) mixing the purified air with external oxygen and then compressing to prepare compressed mixed gas;

(3) making the compressed mixed gas react by using an electric arc method to prepare nitric oxide gas;

(4) cooling the nitric oxide gas, and then carrying out oxidation reaction on the nitric oxide gas and supplemented oxygen to prepare nitrogen oxide;

(5) the nitrogen oxides are reacted with water to produce nitric acid.

2. The process for the direct conversion of nitrogen to nitric acid using air as claimed in claim 1, wherein,

the acid gas comprises carbon dioxide and hydrogen sulfide.

3. The process for the direct conversion of nitrogen to nitric acid using air as claimed in claim 1, wherein,

in the step (2), the proportion of the purified air and the external oxygen is proportioned according to the theoretical amount of nitrogen and oxygen which react to generate nitric oxide.

4. The process for the direct conversion of nitrogen to nitric acid using air as claimed in claim 1, wherein,

the pressure value of the compressed mixed gas is 1.0-10 MPa.

5. The process for the direct conversion of nitrogen to nitric acid using air as claimed in claim 1, wherein,

in the step (3), the arc temperature in the arc method is more than 3000 ℃.

6. The process for the direct conversion of nitrogen to nitric acid using air as claimed in claim 1, wherein,

in the step (4), the temperature reduction refers to temperature reduction to 40-50 ℃.

7. The process for the direct conversion of nitrogen to nitric acid using air as claimed in claim 1, wherein,

in the step (4), the addition amount of the supplemented oxygen is 1-10 times of the theoretical amount required by the reaction of the nitric oxide and the oxygen to generate the nitrogen dioxide.

Technical Field

The invention relates to the technical field of preparing nitric acid by an arc high-temperature method, in particular to a method for directly realizing one-step conversion from nitrogen to nitric acid by using air.

Background

Nitrogen fixation is a process of converting free nitrogen in the air into chemical nitrogen. Nitrogen fixation can be divided into artificial nitrogen fixation, natural nitrogen fixation and biological nitrogen fixation.

Nitric acid is one of important products in the chemical industry, the world yield of the nitric acid is second to that of sulfuric acid in various acids, and the nitric acid and salts thereof have extremely important significance in national economy. Nitric acid can be used for preparing nitrogen fertilizers such as ammonium nitrate, sodium nitrate, potassium nitrate, calcium nitrate and the like, can be used as raw materials for blasting operation and manufacturing other explosives, can be used for manufacturing other nitrates such as barium nitrate, silver nitrate and the like, and is used for separating noble metals in the nonferrous metallurgy industry.

Common methods for producing nitric acid are the ammonia oxidation method and the electric arc method.

The ammonia oxidation method for producing nitric acid is the most widely applied method in modern times, the main raw materials for the reaction are nitrogen, hydrogen, air and water, and the method has high nitric acid production rate, but is technically complex, high in production cost and serious in environmental pollution. The process for producing the nitric acid by the ammonia oxidation method comprises the following four steps: the first step is as follows: generating ammonia by nitrogen and hydrogen at high temperature and high pressure in the presence of a catalyst; the second step is that: carrying out ammonia oxidation to generate nitric oxide; the third step: nitrogen monoxide is oxidized to generate nitrogen dioxide; the fourth step: the nitrogen dioxide water absorbs to generate nitric acid. The harsh reaction conditions and the complex production process determine the characteristics of large scale and high cost of the nitric acid production process equipment by the ammonia oxidation method, so that the nitric acid cannot be developed in remote areas with deficient conditions of land resources, energy sources and the like. The method has huge energy consumption and greenhouse gas emission problems, and is difficult to develop vigorously under the current low-carbon economic situation of carbon neutralization and carbon peak reaching. The method has large amount of waste water discharge and causes environmental pollution in the process of synthesizing ammonia.

Along with the development of world industry and agriculture, the demand of human beings on nitric acid is more and more, and industrial synthesis of ammonia needs to be carried out under the conditions of high temperature and high pressure, so that serious energy waste and environmental pollution are caused. In addition, although the research on arc nitrogen fixation has been successful to some extent, most of the research is still in the theoretical stage and cannot be applied to actual production. Therefore, the research on the technology for producing the nitric acid by fixing nitrogen by the arc method has very important significance.

The arc process is to directly pass air through an arc furnace at a high temperature of 3000 ℃ to directly synthesize nitric oxide from nitrogen and oxygen in the air. The main advantages of the arc method are that the raw material is taken from air and the equipment is simple. However, since the generated nitric oxide is extremely easily decomposed at high temperature and also decomposed during cooling, and the concentration of the finally obtained nitric oxide is very low, about 1.5% to 2%, it takes a long time to oxidize the nitric oxide having such a low concentration into nitrogen dioxide, and the reaction volume of the absorption apparatus needs to be increased, which increases the costs for equipment construction and maintenance, and thus, has not been greatly developed.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a method for directly realizing one-step conversion from nitrogen to nitric acid by using air. The invention introduces oxygen, mixes the oxygen with air and pressurizes the mixture, so that the concentration of nitrogen and oxygen is improved by times, and simultaneously utilizes the arc high-temperature nitrogen fixation to synthesize nitrogen oxide, thereby realizing the method for realizing the one-step efficient conversion from nitrogen to nitric acid, and having great practical significance and economic value.

One of the objects of the present invention is to provide a process for the direct conversion of nitrogen into nitric acid in one step using air, comprising the steps of:

(1) removing acid gas and water in the air to prepare purified air;

(2) mixing the purified air with external oxygen and then compressing to prepare compressed mixed gas;

(3) reacting the compressed mixed gas by using an electric arc method to obtain nitric oxide gas;

(4) cooling the nitric oxide gas, and then carrying out oxidation reaction on the nitric oxide gas and supplemented oxygen to prepare nitrogen oxide;

(5) the nitrogen oxides are reacted with water to produce nitric acid.

In the invention, the compressed mixed gas enters an electric arc reactor, and nitrogen and oxygen react at extremely high electric arc temperature to mainly synthesize nitric oxide gas.

The method for removing the acid gases such as carbon dioxide, hydrogen sulfide and the like in the air can adopt an adsorption separation method of introducing an alkaline medium in the prior art, and can also adopt an existing air separation device to separate the acid gases such as carbon dioxide, hydrogen sulfide and the like.

The air drying in the invention can be realized by adopting a common gas drying device in the prior art.

The compressed mixed gas in the invention can be obtained by adopting a gas compression device commonly used in the prior art.

The arc method of the present invention may be carried out using an arc furnace as is commonly used in the art.

Preferably, the first and second liquid crystal materials are,

the acid gas comprises carbon dioxide and hydrogen sulfide. The acid gas in the invention is not limited to carbon dioxide and hydrogen sulfide, but can also comprise other acid gases commonly seen in the air.

Preferably, the first and second liquid crystal materials are,

in the step (2), the proportion of the purified air and the external oxygen is proportioned according to the theoretical reaction amount of the nitrogen and the oxygen. (i.e. the ratio of the nitrogen in the purified air to the sum of the oxygen in the purified air and the external oxygen is the theoretical ratio required for the reaction of the nitrogen and the oxygen to generate the nitric oxide)

Preferably, the first and second liquid crystal materials are,

the pressure value of the compressed mixed gas is 1.0-10 MPa, namely, after the mixed gas is compressed by the compressor, the pressure of the mixed gas is increased to 1.0-10.0 MPa.

Preferably, the first and second liquid crystal materials are,

in the step (3), the arc temperature in the arc method is more than 3000 ℃.

Preferably, the first and second liquid crystal materials are,

in the step (4), the temperature reduction refers to temperature reduction to 40-50 ℃.

Preferably, the first and second liquid crystal materials are,

the addition amount of the supplemented oxygen is 1-10 times of the theoretical amount of nitrogen dioxide generated by the reaction of nitric oxide and oxygen.

The reaction process corresponding to the step (3) of the invention is as follows:

N₂+O₂＝2NO

the reaction process corresponding to the step (4) of the invention is as follows:

2NO+O₂＝2NO₂

the reaction process corresponding to the step (5) of the invention is as follows:

3NO₂+H₂O＝2HNO₃+NO

the invention utilizes air to directly realize the one-step conversion method from nitrogen to nitric acid, and the mass concentration of the prepared nitric acid product is 60 percent.

The preparation method is environment-friendly, free of waste water and waste gas emission, simple and efficient in process flow, low in investment and operation cost, high in yield and small in occupied area, and solves the problems that in the prior art, ammonia is synthesized first and then converted into a nitrogen source for producing nitric acid, and further nitric acid is produced again, cost is high, and a device is complex.

In conclusion, the invention has obvious economic benefit and social benefit.

Drawings

FIG. 1 is a schematic diagram of a production system of the present invention utilizing air to directly effect a one-step conversion of nitrogen to nitric acid.

The method comprises the following steps of 1-air purifier, 2-dryer, 3-first oxygen inlet pipeline, 4-blower, 5-pressure device, 6-arc reactor, 7-cooler, 8-second oxygen inlet pipeline and 9-nitric acid generator.

Detailed Description

While the present invention will be described in detail and with reference to the specific embodiments thereof, it should be understood that the following detailed description is only for illustrative purposes and is not intended to limit the scope of the present invention, as those skilled in the art will appreciate numerous insubstantial modifications and variations therefrom.

Example 1

The invention relates to a method for directly converting nitrogen into nitric acid by using air, which comprises the following steps:

a. removing acidic gases such as carbon dioxide and hydrogen sulfide in the air, and drying the purified air to remove moisture in the air to obtain the purified air. The method for removing the acid gases such as carbon dioxide, hydrogen sulfide and the like in the air can adopt an adsorption separation method of introducing an alkaline medium in the prior art, and can also adopt an existing air separation device to separate the acid gases such as carbon dioxide, hydrogen sulfide and the like.

b. Mixing air and oxygen (according to the theoretical amount of NO produced by the reaction of nitrogen and oxygen), sending the mixed gas to a compressor for compression, and boosting the pressure of the mixed gas to 1.0MPa after the mixed gas is compressed by the compressor to obtain the compressed mixed gas.

c. And c, enabling the compressed mixed gas obtained in the step b to enter an electric arc reactor, and enabling nitrogen and oxygen to react at the electric arc temperature of 3000 ℃ to generate NO gas.

d. Cooling the NO gas obtained in the step c to 40 ℃.

e. And d, reacting the nitric oxide obtained in the step d with externally added oxygen with the theoretical amount being 1 time to generate nitrogen dioxide, and obtaining nitrogen oxide, wherein the nitrogen dioxide is mainly generated nitrogen dioxide gas and a small amount of unreacted nitric oxide gas.

f. And e, enabling the nitrogen oxide obtained in the step e to enter an absorption tower to prepare a nitric acid product, wherein the mass concentration of the nitric acid product is 60%.

Example 2

The invention relates to a method for directly realizing one-step conversion from nitrogen to nitric acid by using air, which comprises the following detailed steps:

a. removing acidic gases such as carbon dioxide and hydrogen sulfide in the air, and drying the purified air to remove moisture in the air to obtain the purified air.

b. Mixing air and oxygen (according to the theoretical amount of NO produced by the reaction of nitrogen and oxygen), sending the mixed gas to a compressor for compression, and boosting the pressure of the mixed gas to 5.0MPa after the mixed gas is compressed by the compressor.

c. And c, feeding the compressed mixed gas obtained in the step b into an electric arc furnace, and reacting nitrogen and oxygen at the electric arc temperature of 3000 ℃ to generate nitric oxide gas.

d. And c, cooling the gas from the electric arc furnace obtained in the step c by a heat exchanger, and reducing the temperature of the gas to 40 ℃ after the gas passes through the heat exchanger.

e. And d, reacting the nitric oxide obtained in the step d with externally added oxygen with 2 times of theoretical amount to generate nitrogen dioxide, and obtaining nitrogen oxide.

f. And e, enabling the nitrogen oxide obtained in the step e to enter an absorption tower to prepare a nitric acid product, wherein the mass concentration of the nitric acid product is 61%.

Example 3

The invention relates to a method for directly realizing one-step conversion from nitrogen to nitric acid by using air, which comprises the following detailed steps:

a. removing acidic gases such as carbon dioxide and hydrogen sulfide in the air, and drying the purified air to remove moisture in the air to obtain the purified air.

b. Mixing air and oxygen (according to the theoretical amount of NO produced by the reaction of nitrogen and oxygen), sending the mixed gas to a compressor for compression, and boosting the pressure of the mixed gas to 10.0MPa after the mixed gas is compressed by the compressor.

c. And c, enabling the compressed mixed gas obtained in the step b to enter an electric arc reactor, and reacting nitrogen and oxygen at the electric arc temperature of 3000 ℃ to generate nitric oxide gas.

d. And c, cooling the gas discharged from the arc reactor obtained in the step c by a heat exchanger, and reducing the temperature of the gas to 50 ℃ after the gas passes through the heat exchanger.

e. And d, reacting the nitric oxide obtained in the step d with externally added oxygen with the theoretical amount being 3 times that of the nitric oxide to generate nitrogen dioxide, and obtaining nitrogen oxide.

f. And e, enabling the nitrogen oxide obtained in the step e to enter an absorption tower to prepare a nitric acid product, wherein the mass concentration of the nitric acid product is 63%.

Comparative example 1

The preparation method of comparative example 1 is the same as that of example 3 except that comparative example 1 is a method in which air is directly compressed without supplementing oxygen to form compressed air; the nitric acid product prepared in comparative example 1 had a mass concentration of 30%.

Through the comparison, the invention can be seen that the concentration of nitrogen and oxygen is improved by times by supplementing oxygen to form compressed mixed gas, and meanwhile, the method realizes the one-step efficient conversion of nitrogen to nitric acid by fixing nitrogen at high temperature by utilizing electric arc to synthesize nitrogen oxide, thereby having great practical significance and economic value.

Example 4

Fig. 1 shows a production system for directly converting nitrogen into nitric acid by one step by using air, which comprises: the device comprises an air purifier 1, a dryer 2, a first oxygen inlet pipeline 3, a pressurizing device 5, an arc reactor 6, a cooler 7, a second oxygen inlet pipeline 8 and a nitric acid generator 9;

the feed inlet of the dryer 2 is communicated with the discharge outlet of the air purifier 1;

the discharge hole of the dryer 2 is communicated with the feed inlet of the pressurizing device 5;

the discharge hole of the first oxygen inlet pipeline 3 is also communicated with the feed hole of the pressurizing device 5;

the discharge hole of the pressurizing device 5 is communicated with the feed inlet of the electric arc reactor 6;

the discharge hole of the electric arc reactor 6 is communicated with the feed hole of the cooler 7;

the discharge hole of the cooler 7 is communicated with the feed inlet of the nitric acid generator 9;

the discharge hole of the second oxygen inlet pipeline 8 is also communicated with the feed hole of the nitric acid generator 9.

The main flowing medium in the production system of the invention is gas, and the communication among the components can adopt a suitable communication mode in the prior art, preferably pipeline communication.

Preferably, the first and second liquid crystal materials are,

the production system further comprises a metering device which is installed in front of the feed inlet of the air purifier 1. The metering device is intended for metering air and any suitable device for metering gas known in the art may be used.

Preferably, the first and second liquid crystal materials are,

the production system further comprises a blower 4, wherein a feed port of the blower 4 is communicated with a discharge port of the dryer 2, and a discharge port of the blower 4 is communicated with a feed port of the pressurizing device 5.

Preferably, the first and second liquid crystal materials are,

the discharge hole of the first oxygen inlet pipeline 3 is communicated with the feed hole of the blower 4. One of the functions of the blower of the present invention is to feed the mixed gas into the pressurizing device, and other devices having a gas introducing function in the prior art can be adopted.

Preferably, the first and second liquid crystal materials are,

the pressurizing device 5 is a compressor. The purpose of the pressurizing device is to pressurize the mixed gas, and a compressor is preferable, and other devices having a gas pressurizing function in the prior art may be used.

Preferably, the first and second liquid crystal materials are,

the arc reactor 6 may be an arc furnace as is commonly used in the art. Such as an arc reactor like that disclosed in patent CN104961112A, etc.

Preferably, the first and second liquid crystal materials are,

the cooler 7 is a heat exchanger, and the purpose of the cooler is to cool the gas, and preferably, a heat exchanger, and other devices having a gas cooling function in the related art may be used.

Preferably, the first and second liquid crystal materials are,

the nitric acid generator 9 is an absorption tower. The purpose of the nitric acid generator is to react with water to produce nitric acid, preferably an absorption column, although other prior art devices for generating nitric acid containing water may also be used.

Preferably, the first and second liquid crystal materials are,

metering devices are further mounted on the first oxygen inlet pipeline 3 and the second oxygen inlet pipeline 8. The metering device is intended for metering oxygen and any suitable gas metering device known in the art may be used.

Preferably, the first and second liquid crystal materials are,

the production system also comprises a nitric acid discharging pipeline which is communicated with a discharging hole of the nitric acid generator 9.

The production method of the production system for directly realizing one-step conversion from nitrogen to nitric acid by utilizing air comprises the following steps:

the preferred production method of the production system for directly realizing the one-step conversion from nitrogen to nitric acid by using air in the embodiment 4 of the invention is as follows:

a. air enters the air purifier 1 through a metering device to remove acid gases such as carbon dioxide, hydrogen sulfide and the like in the air, the purified air enters the dryer 2 to remove moisture in the air, and oxygen input by the first oxygen inlet pipeline 3 is mixed with the air flowing out of the dryer 2 and enters the blower 4.

b. A mixed gas of air and oxygen (according to the theoretical amount of NO produced by the reaction of nitrogen and oxygen) is sent to a compressor 5 by a blower 4 for compression, and after the mixed gas is compressed by the compressor 5, the pressure of the mixed gas is increased to 8 MPa.

c. And c, enabling the compressed mixed gas obtained in the step b to enter an arc reactor 6, and reacting nitrogen and oxygen at the arc temperature of 3000 ℃ to generate nitric oxide gas.

d. And c, cooling the gas discharged from the arc reactor obtained in the step c by a heat exchanger 7, and reducing the temperature of the gas to 45 ℃ after the gas passes through the heat exchanger 7.

e. The nitric oxide obtained in step d is mixed with oxygen input by the second oxygen inlet line 8 to react to generate nitrogen dioxide, so as to obtain nitrogen oxides (mainly generated nitrogen dioxide gas and a small amount of unreacted nitric oxide gas), and the oxygen input by the second oxygen inlet line 8 is 6 times of the theoretical amount of nitrogen dioxide generated by the reaction of nitric oxide and oxygen.

f. And e, allowing the nitrogen oxide obtained in the step e to enter an absorption tower to prepare a nitric acid product, wherein the mass concentration of the nitric acid product discharged through a nitric acid discharge pipeline is 64%.