A low-temperature plasma ammonia synthesis reaction and diagnostic device

Abstract

The application provides a low-temperature plasma ammonia synthesis reaction and diagnosis device, which comprises a reactor; the reactor comprises a quartz glass tube, a stainless steel threaded hollow rod and a stainless steel threaded rod are respectively arranged at the upper and lower ends of the quartz glass tube, and both are fixed by polytetrafluoroethylene sealing; a hollow stainless steel needle is arranged at the lower end of the stainless steel threaded hollow rod; a solid stainless steel needle is arranged at the upper end of the stainless steel threaded rod; the quartz glass tube is further provided with a quartz tube branch; the quartz tube branch is connected with a hydrogen gas cylinder through a mass flow controller; the stainless steel threaded hollow rod is connected with a nitrogen gas cylinder through a mass flow controller; the stainless steel threaded hollow rod is provided with a high-pressure probe, and the stainless steel threaded rod is provided with a current probe; the quartz glass tube is provided with an optical fiber probe and a gas chromatograph. The two gases are separately introduced in a way that the gases can directly pass through the plasma discharge area, so that the conversion can be better promoted.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of application of plasma technology, and particularly relates to a low-temperature plasma ammonia synthesis reaction and diagnosis device, and can utilize electrical diagnosis and optical diagnosis to study the micro-mechanism of the ammonia synthesis process, and utilize a product analysis system to perform qualitative and quantitative detection and analysis of products. TECHNICAL BACKGROUND

[0002] Ammonia (NH3) is an important chemical raw material for the production of fertilizers, pesticides and many other chemicals. In addition, due to the unique characteristics of NH3, such as high energy density, clean combustion, convenient storage and transportation, etc., in the future, NH3 is also considered to be a very promising alternative clean and sustainable energy storage carrier. At present, the traditional method of industrial-scale NH3 synthesis, i.e. the Haber-Bosch (HB) process, requires high pressure (20-40 MPa) and high temperature (400-600℃) in the presence of iron-based catalysts. Therefore, the HB process consumes 2% of the global primary energy supply, and produces about 300 million tons of carbon dioxide per year. There have been great efforts to develop more environmentally friendly and more sustainable alternatives for producing ammonia at lower pressures and temperatures, including biochemical and electrochemical processes. Recently, the potential application of ammonia production using small-scale devices has attracted increasing interest, as the process can be driven by renewable energy sources such as wind and solar energy.

[0003] In recent years, non-thermal plasma (NTP) assisted ammonia synthesis has become a research hotspot. The energy consumption of plasma synthesis of ammonia is expected to be lower than that of conventional ammonia synthesis. Through the exploration of the NTP ammonia synthesis process, the effective mechanism of electric field and particle interaction for improving the efficiency of ammonia synthesis is revealed. Plasma species, such as electrons, atoms, ions and radicals, can undergo various chemical reactions at room temperature and atmospheric pressure. The type of plasma discharge, the applied voltage waveform, the operating parameters of the power supply (i.e. the applied voltage, frequency and power input), the reactor design, the composition of the reactants, the gas flow, the reactant gas ratio and other parameters will affect the results of the synthesis process. Different discharges driven by different power sources, such as pulse power, microwave power, alternating current power and direct current power, can be used for ammonia synthesis. In order to better understand the potential mechanisms of ammonia synthesis, it is essential to understand the mechanism of NTP ammonia synthesis. And in the synthesis of ammonia reaction, due to the decomposition of the product ammonia, resulting in low conversion rate, low product selectivity, low energy efficiency, which is a great obstacle encountered in the synthesis of ammonia technology.

[0004] The present application mainly designs and builds a set of low-temperature plasma ammonia synthesis reaction device, which can utilize electrical diagnosis and optical diagnosis to study the micro-mechanism of the ammonia synthesis reaction process, and can perform qualitative and quantitative detection of products through a product analysis system. High selectivity and energy efficiency of products under atmospheric pressure and low temperature conditions are achieved. SUMMARY

[0005] In order to solve the problems of high energy consumption and low energy efficiency in ammonia synthesis technology, the application provides a low-temperature plasma ammonia synthesis device, which can realize high selectivity and energy efficiency of products, and can study the micro-mechanism of the reforming reaction through electrical and optical diagnostic techniques.

[0006] The specific technical solutions are as follows:

[0007] A low-temperature plasma ammonia synthesis reaction and diagnosis device, comprising a reactor;

[0008] The reactor comprises a quartz glass tube, and a stainless steel threaded hollow rod and a stainless steel threaded rod are respectively arranged at the upper and lower ends of the quartz glass tube, and both are fixed by polytetrafluoroethylene sealing;

[0009] The lower end of the stainless steel threaded hollow rod is provided with a hollow stainless steel needle, and the upper end of the stainless steel threaded rod is provided with a solid stainless steel needle;

[0010] The quartz glass tube is also provided with a quartz tube branch; the quartz tube branch is connected to a hydrogen gas cylinder through a first mass flow controller, and hydrogen gas enters the reactor through the quartz tube branch from the hydrogen gas cylinder through the first mass flow controller;

[0011] The stainless steel threaded hollow rod is connected to a nitrogen gas cylinder through a second mass flow controller, and nitrogen gas enters the reactor through the stainless steel threaded hollow rod after passing through the second mass flow controller; plasma is generated between the two electrodes.

[0012] The reactor is energized by a bipolar nanosecond pulse power supply;

[0013] The stainless steel threaded hollow rod is provided with a high-voltage probe, and the stainless steel threaded rod is provided with a current probe; the high-voltage probe and the current probe are connected to an oscilloscope; the discharge parameters such as discharge power, SEI, and energy efficiency can be calculated according to the voltage and current waveform diagram, and the electric energy consumption can be calculated.

[0014] An optical fiber probe is arranged on the quartz glass tube, and the optical fiber probe, ICCD, spectrometer, and computer are connected in sequence; the optical fiber probe faces the discharge area, the optical signal is transmitted to the spectrometer and ICCD through the optical fiber, the optical signal is converted into an electrical signal, and then the computer outputs a spectrum image; the particles in the discharge process are diagnosed by using the emission spectrum method, and the micro-mechanism of the ammonia synthesis reaction process can be explored.

[0015] The quartz glass tube is also connected to a gas chromatograph, and the gas chromatograph is connected to a computer; the gas chromatograph is equipped with a hydrogen flame ionization detector (FID) and a thermal conductivity detector (TCD). The carrier gas is argon. The reactants and products can be qualitatively and quantitatively detected according to the online spectrum, and the sample needs to be calibrated before detection.

[0016] The stainless steel threaded hollow rod, the hollow stainless steel needle, the stainless steel threaded rod and the solid stainless steel needle form at least one group.

[0017] The present application has the following beneficial effects: The present application provides an experimental device capable of realizing needle-needle discharge structure for synthesizing ammonia under atmospheric pressure and low temperature conditions, and the two gas separation and input mode can directly pass through the plasma discharge area to better promote the conversion. A set of conversion, diagnosis and product detection system is built, and the electrical and optical diagnosis can study the micro mechanism of the conversion process, which provides necessary theoretical basis for regulating the reaction process and product selection. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the schematic diagram of the experimental device for low-temperature plasma ammonia synthesis experiment and diagnosis in the present application.

[0019] Figure 2 is the schematic diagram of the main structure of the reactor. DETAILED DESCRIPTION

[0020] The specific embodiments of the present application will be further described in combination with the drawings and technical solutions.

[0021] As shown in Figure 1 and Figure 2 , a low-temperature plasma ammonia synthesis reaction and diagnosis device, comprising a reactor;

[0022] The reactor comprises a quartz glass tube 18, and a stainless steel threaded hollow rod 12 and a stainless steel threaded rod 17 are respectively installed on the upper and lower ports of the quartz glass tube 18, and both are fixed by polytetrafluoroethylene sealing 13;

[0023] The lower end of the stainless steel threaded hollow rod 12 is provided with a hollow stainless steel needle 15, and the upper end of the stainless steel threaded rod 17 is provided with a solid stainless steel needle 16;

[0024] The quartz glass tube 18 is also provided with a quartz tube branch 14; the quartz tube branch 14 is connected to a hydrogen gas cylinder 31 through a first mass flow controller 21, and hydrogen gas enters the reactor through the quartz tube branch 14 from the hydrogen gas cylinder 31 through the first mass flow controller 21;

[0025] The stainless steel threaded hollow rod 12 is connected to a nitrogen gas cylinder 3 through a second mass flow controller 2, and nitrogen gas enters the reactor through the stainless steel threaded hollow rod 12 after passing through the second mass flow controller 2 from the nitrogen gas cylinder 3; plasma is generated between the two electrodes

[0026] The reactor is energized by a bipolar nanosecond pulse power supply 1;

[0027] The stainless steel threaded hollow rod 12 is provided with a high-voltage probe 4, and the stainless steel threaded rod 17 is provided with a current probe 11; the high-voltage probe 4 and the current probe 11 are connected with an oscilloscope 5; the discharge parameters such as discharge power, SEI and energy efficiency can be calculated according to the voltage and current waveform diagram, and the electric energy consumption can be calculated.

[0028] The quartz glass tube 18 is provided with an optical fiber probe 6, the optical fiber probe 6, the ICCD 7, the spectrometer 8 and the computer 10 are sequentially connected; the optical fiber probe 6 is directly opposite the discharge area, the optical signal is transmitted to the spectrometer 8 and the ICCD 7 through the optical fiber, the optical signal is converted into an electrical signal, and then the spectral image is output by the computer 10; the particles in the discharge process are diagnosed by using the emission spectrum method, and the micro-mechanism of the synthesis ammonia reaction process can be explored.

[0029] The quartz glass tube 18 is also connected with a gas chromatograph 9, and the gas chromatograph 9 is connected with the computer 10; the gas chromatograph 9 is provided with a hydrogen flame ionization detector FID and a thermal conductivity detector TCD. The carrier gas is argon. The reactants and products can be qualitatively and quantitatively detected according to the online spectrum, and the sample needs to be calibrated before being detected.

[0030] The stainless steel threaded hollow rod 12, the hollow stainless steel needle 15, the stainless steel threaded rod 17 and the solid stainless steel needle 16 are at least one group.

[0031] As shown in Figure 2 The plasma is generated between the two electrodes, i.e. the hollow stainless steel needle 15 and the solid stainless steel needle 16, and the number of the two electrodes can be increased as needed.

[0032] Example 1

[0033] The parameters selected in this embodiment are as follows: the rising edge of the pulse voltage is 20 ns, the falling edge of the pulse voltage is 20 ns, the total pulse duration is about 90 ns, the pulse peak voltage is 26 kV, the pulse repetition frequency is 140 Hz, the flow rate ratio of N2 and H2 is 1:1, the total flow rate is maintained at 40 mL / min, and the discharge gap is 4 mm. H2 is introduced from the left side of the reactor, N2 passes through the stainless steel threaded hollow rod 12 and the hollow stainless steel needle 15 from above the reactor to directly reach the discharge area, the pulse peak voltage is 32 kV, and the average value of each quantity is taken three times. Each result is detected online by the gas chromatograph, and the active particles in the synthesis of ammonia are diagnosed by the spectrometer 8 and the ICCD 7.

[0034] The specific experimental analysis is as follows:

[0035] 1. Product component analysis

[0036] The gases used are N2 and H2, the products are detected online by gas chromatograph 9, and the ammonia can be qualitatively and quantitatively analyzed.

[0037] 2. Electrical diagnostic analysis

[0038] The electrical diagnostic system is mainly composed of experimental device diagram Figure 1 High-voltage probe 4, oscilloscope 5, current probe 11 and other parts. According to the voltage and current waveform diagram, the discharge power, SEI, energy efficiency and other discharge parameters are calculated.

[0039] 3. Optical diagnostic analysis

[0040] The optical diagnostic system is mainly composed of optical fiber probe 6, ICCD high-speed camera 7, spectrometer 8 and computer 10. Through the optical diagnostic system, the external trigger mode is adopted, the gain is 1000, the gate width is set to 5 ns, the delay opening time is 5 ns, the exposure time is 0.1 second, the accumulation number is set to 1, 20 pictures are continuously taken, and the discharge image is taken by ICCD. The discharge channel is composed of a large number of fast pulse current filaments, each current filament is irregularly distributed in space and time. The discharge channel presents a radial shape, the streamer extends from the ground electrode to the high-voltage electrode, the intensity inside the current filament is the strongest, the discharge filament diverges to the surrounding until it is annihilated. The appearance characteristics of this discharge are close to white light.

[0041] 4. Ammonia synthesis experimental results

[0042] The conversion rates of N2 and H2 are 18.50% and 15.54% respectively. The highest yield of ammonia can reach 13.00%, and the highest selectivity of ammonia can reach 57.92%. The energy efficiency of this device can reach 1.31 mmol / kJ at a power of 3.45 W.

[0043] Example 2

[0044] The parameters selected in this example are as follows:

[0045] Except that the pulse repetition frequency is 180 Hz, the other conditions are the same as in Example 1.

[0046] Ammonia synthesis experimental results:

[0047] The conversion rates of N2 and H2 are 15.64% and 13.07% respectively. The highest yield of ammonia can reach 33.70%, and the highest selectivity of ammonia can reach 34.72%.

Claims

1. A low-temperature plasma ammonia synthesis reaction and diagnostic device, characterized in that, Including reactors; The reactor includes a quartz glass tube (18), with stainless steel threaded hollow rods (12) and stainless steel threaded rods (17) installed at the upper and lower ends of the quartz glass tube (18), and both are fixed with polytetrafluoroethylene seals (13). The lower end of the stainless steel threaded hollow rod (12) is provided with a hollow stainless steel needle (15); the upper end of the stainless steel threaded rod (17) is provided with a solid stainless steel needle (16). The quartz glass tube (18) is also provided with a quartz tube branch (14); the quartz tube branch (14) is connected to the hydrogen cylinder (31) through the No. 1 mass flow controller (21), and the hydrogen enters the reactor from the hydrogen cylinder (31) through the No. 1 mass flow controller (21) and the quartz tube branch (14); The stainless steel threaded hollow rod (12) is connected to the nitrogen cylinder (3) through the second mass flow controller (2). Nitrogen gas enters the reactor from the nitrogen cylinder (3) through the second mass flow controller (2) and then through the stainless steel threaded hollow rod (12). The reactor receives energy input via a bipolar nanosecond pulse power supply (1); The stainless steel threaded hollow rod (12) is equipped with a high voltage probe (4), and the stainless steel threaded rod (17) is equipped with a current probe (11); both the high voltage probe (4) and the current probe (11) are connected to the oscilloscope (5). A fiber optic probe (6) is provided on a quartz glass tube (18). The fiber optic probe (6), ICCD (7), spectrometer (8) and computer (10) are connected in sequence. The fiber optic probe (6) is facing the discharge area. The optical signal is transmitted to the spectrometer (8) and ICCD (7) through the optical fiber. The optical signal is converted into an electrical signal and then the computer (10) outputs the spectral image. The quartz glass tube (18) is also connected to the gas chromatograph (9), which is connected to the computer (10).

2. The low-temperature plasma ammonia synthesis reaction and diagnostic device according to claim 1, characterized in that, The stainless steel threaded hollow rod (12), hollow stainless steel needle (15), stainless steel threaded rod (17), and solid stainless steel needle (16) are at least one set.

3. The low-temperature plasma ammonia synthesis reaction and diagnostic device according to claim 1, characterized in that, The gas chromatograph (9) is equipped with a flame ionization detector and a thermal conductivity detector.

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