Method for determining optimal oxygen-carbon ratio of hydrogen production technology by reforming fuel with low-temperature plasma

Abstract

The present invention discloses a method for determining the optimal oxygen-to-carbon ratio in the low-temperature plasma reforming fuel hydrogen production technology. The optimal oxygen-to-carbon ratio in the low-temperature plasma reforming fuel hydrogen production technology is determined in the order of decreasing oxygen-to-carbon ratio. By adjusting the order of the oxygen-to-carbon ratio, the present invention reduces the influence of carbon deposition in the early stage of the experiment on the subsequent low-temperature plasma reforming hydrogen production effect, promotes the conversion of methane and oxygen, and improves the selectivity of H2 and CO. At the same time, compared with the optimal oxygen-to-carbon ratio determined by the existing method, the optimal oxygen-to-carbon ratio determined by the method of the present invention further improves the selectivity of H2 and CO.

Description

Technical Field

[0001] The present invention belongs to the technical field of atmospheric pressure low-temperature plasma energy conversion, and particularly relates to a method for determining the optimal oxygen-carbon ratio of a low-temperature plasma reforming fuel hydrogen production technology. Background Art

[0002] Low-temperature plasma is a conductive fluid containing a large number of active particles and being overall electrically neutral. Most of the energy in low-temperature plasma is mainly used to generate high-energy electrons and active particles, rather than heating the gas, and the overall temperature can be as low as room temperature. Compared with the catalytic reforming hydrogen production technology, the plasma hydrogen production technology has the characteristics of simple reaction device structure, quick start and stop, low investment and operation costs, high energy density, etc., and has received a lot of attention in recent years. However, the existing low-temperature plasma reforming fuel hydrogen production technology has low selectivities for H2 and CO. Summary of the Invention

[0003] The present invention has conducted research on the reasons for the low selectivities of H2 and CO, and it has been found that carbon deposition in the early stage of the experiment is an important factor affecting the selectivities of H2 and CO. The reason for carbon deposition in the early stage of the experiment is that currently, the optimal oxygen-carbon ratio of the low-temperature plasma reforming fuel hydrogen production technology is usually determined in the order of increasing oxygen-carbon ratio. The carbon deposition caused by this method in the early stage of the experiment, on the one hand, affects the subsequent low-temperature plasma reforming hydrogen production effect, resulting in low selectivities of H2 and CO, and on the other hand, also affects the determination of the optimal oxygen-carbon ratio during the experiment.

[0004] In view of the above technical problems, the present invention provides a method for improving the selectivities of H2 and CO. The technical solution of the present invention is as follows:

[0005] The present invention adjusts the order of the oxygen-carbon ratio, and determines the optimal oxygen-carbon ratio of the low-temperature plasma reforming fuel hydrogen production technology in the order of decreasing oxygen-carbon ratio, so as to reduce the influence of carbon deposition in the early stage of the experiment on the subsequent low-temperature plasma reforming hydrogen production effect, promote the conversion of methane and oxygen, and improve the selectivities of H2 and CO.

[0006] Based on the above technical solution, preferably, the oxygen-carbon ratio gradually decreases from 1.8 to 0.5, and decreases in a gradient of 0.1 - 0.2.

[0007] Based on the above technical solution, preferably, the oxygen-carbon ratio gradually decreases from 1.4 to 0.8, and decreases in a gradient of 0.1.

[0008] Based on the above technical solution, preferably, the raw materials of the reforming fuel hydrogen production technology include air, fuel and water, and the fuel includes one or more of methanol, ethanol, diesel, gasoline, methane, n-heptane.

[0009] Based on the above technical solutions, preferably, the power supply discharge frequency is 0.1 - 40 kHz, the peak value of the power supply current is 100 - 330 mA, and the effective value of the current remains almost unchanged during the discharge process.

[0010] Beneficial effects

[0011] (1) The present invention has discovered an important factor that leads to low selectivity of H2 and CO in the low-temperature plasma reforming fuel hydrogen production technology, and proposes a solution, that is, by adjusting the order of the oxygen-carbon ratio, the influence of carbon deposition in the early stage of the experiment on the subsequent low-temperature plasma reforming hydrogen production effect is reduced, the conversion of methane and oxygen is promoted, and the selectivity of H2 and CO is improved.

[0012] (2) By adjusting the order of the oxygen-carbon ratio, the present invention avoids the influence of carbon deposition in the early stage of the experiment on the determination of the optimal oxygen-carbon ratio. The optimal oxygen-carbon ratio determined by the method of the present invention further improves the selectivity of H2 and CO under the same conditions compared with the optimal oxygen-carbon ratio determined by the existing method. Description of the drawings

[0013] Figure 1 is the low-temperature plasma reforming fuel hydrogen production system used in the embodiments and comparative examples of the present invention;

[0014] Figure 2 is the experimental result under different oxygen-carbon ratios of Example 1 and Comparative Example 1. In the figure, Scheme1 represents Example 1, and Scheme2 represents Comparative Example 1;

[0015] Figure 3 is the experimental result under the optimal oxygen-carbon ratio of Example 1 and Comparative Example 1;

[0016] Figure 1 Among them, 1, blade electrode; 2, constant current - AC power supply; 3, polytetrafluoroethylene insulating base; 4, quartz glass cover; 5, sampling resistor; 6, flame arrester; 7, one-way valve; 8, fuel gas source; 9, air source; 10, gas outlet, 11, gas chromatograph analyzer, 12, digital oscilloscope, 13, high-voltage probe, 14, low-voltage probe. Detailed implementation manners

[0017] The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0018] The experimental system used in the present invention is as Figure 1As shown in the figure, it includes a gas distribution device, a discharge device, an electrical property detection device, a constant current - AC power supply, and a product analysis device; the gas distribution device includes an air source 9 and a fuel gas source 8. After the vaporized fuel passes through a one - way valve 7, it mixes with air and enters a sliding arc plasma reactor (i.e., the discharge device); the discharge device includes a quartz glass cover 4, a blade electrode 1, and a polytetrafluoroethylene insulating base 3; the electrical property detection device includes a high - voltage probe 13, a low - voltage probe 14, and a digital oscilloscope 12. The low - voltage probe 14 further obtains the discharge current by measuring the voltage across a resistor; the product analysis device includes a gas chromatograph analyzer 11 and a computer, and the computer is directly connected to the gas chromatograph analyzer.

[0019] The experimental process using the above - mentioned system is as follows: When a mixture of air and vaporized fuel (methanol, ethanol, diesel, gasoline, methane, n - heptane) passes through the narrowest gap distance between two metal electrodes with a strong electric field and a blade - like appearance, breakdown occurs, forming an arc. The arc slides downstream under the push of the gas flow, thus forming a sliding arc plasma. After the sliding arc discharge is formed, the parameters of the constant current - AC power supply and the total gas flow rate remain unchanged, and two groups of experiments are carried out respectively, namely Example 1 and Comparative Example 1.

[0020] Example 1

[0021] Adjust the oxygen - to - carbon ratio in the order of decreasing oxygen - to - carbon ratio; the specific experimental process is as follows:

[0022] The peak value of the power supply current is set to 250 mA, the discharge frequency is set to 40 kHz, and the total gas flow rate of the methane - air mixture is controlled to 9.2 L / min. First, investigate the hydrogen production effect when O / C = 1.4. Set the methane gas flow rate to 2.1 L / min, the air flow rate to 7. i L / min, and the discharge time to about 5 min. After the reactor temperature stabilizes, detect the composition of the reformed gas at this time; after the detection is completed, directly adjust the flow rates of methane and air, control O / C = 1.3, and the discharge time is about 5 min. After the reactor temperature stabilizes, detect the composition of the reformed gas at this time; in the same way, successively investigate the composition of the reformed gas when O / C = 1.2, O / C = 1.1, O / C = 1.0, O / C = 0.9, and O / C = 0.8.

[0023] Comparative Example 1

[0024] Adjust the oxygen - to - carbon ratio in the order of increasing oxygen - to - carbon ratio.

[0025] The peak value of the power supply current is set to 250 mA, the discharge frequency is set to 40 kHz, and the total gas flow rate of the methane-air mixture is controlled to 9.2 L / min. First, the hydrogen production effect at O / C = 0.8 is investigated. The methane gas flow rate is set to 2.1 L / min, the air flow rate is set to 7.1 L / min, and the discharge time is about 5 min. After the reactor temperature stabilizes, the composition of the reformed gas is detected. After the detection is completed, the flow rates of methane and air are directly adjusted to control O / C = 0.9, and the discharge time is about 5 min. After the reactor temperature stabilizes, the composition of the reformed gas is detected. In the same way, the composition of the reformed gas at O / C = 1.0, O / C = 1.1, O / C = 1.2, O / C = 1.3, and O / C = 1.4 is investigated in turn.

[0026] The reformed gas under different oxygen-carbon ratios in Example 1 and Comparative Example 1 is collected respectively and the gas components are analyzed.

[0027] Among them, during the above experimental process, the optimal oxygen-carbon ratios determined in Example 1 and Comparative Example 1 are as Figure 2 shown. The optimal oxygen-carbon ratio determined in Example 1 is 1.0, while the optimal oxygen-carbon ratio determined in Comparative Example 1 is 1.3.

[0028] Experiments are carried out at the respective optimal oxygen-carbon ratios of Example 1 and Comparative Example 1. The experimental results are as Figure 3 shown. The experimental results show that under the same power supply parameters and total gas flow rate, the H2 selectivity, CO selectivity, and energy efficiency of Example 1 are all higher than those of Comparative Example 1. This is mainly because Example 1 reduces the influence of carbon deposition in the early stage of the experiment on the subsequent low-temperature plasma reforming hydrogen production effect, and determines a more optimal oxygen-carbon ratio compared to Comparative Example 1. Therefore, the H2 selectivity, CO selectivity, and energy efficiency are all higher than those of Comparative Example 1. Therefore, taking the decreasing order of the oxygen-carbon ratio as the method for determining the optimal oxygen-carbon ratio of future low-temperature plasma reforming fuels (methanol, ethanol, diesel, gasoline, methane, n-heptane) hydrogen production technology is an important way to improve the H2 selectivity and CO selectivity.

Claims

1. A method for determining the optimal oxygen-carbon ratio in the low-temperature plasma reforming fuel hydrogen production technology, characterized in that, The method is as follows: the total gas flow rate remains unchanged, and the optimal oxygen-carbon ratio of the raw materials in the low-temperature plasma reforming fuel hydrogen production technology is determined in the order of decreasing oxygen-carbon ratio; the oxygen-carbon ratio gradually decreases from 1.8 to 0.5, and decreases according to a gradient of 0.1-0.

2.

2. The method according to claim 1, characterized in that, The oxygen-carbon ratio gradually decreases from 1.4 to 0.8, and decreases according to a gradient of 0.

1.

3. The method according to claim 1, wherein The raw materials of the reforming fuel hydrogen production technology include air, fuel and water, and the fuel includes one or more of methanol, ethanol, diesel, gasoline, methane, and n-heptane.

4. The method according to claim 1, wherein The power supply discharge frequency is 0.1-40 kHz, the peak value of the power supply current is 100-330 mA, and the effective value of the current remains unchanged during the discharge process.

Images