Process method for stably producing hydrogen from methanol and application of process method

Abstract

The invention relates to the field of industrial preparation of hydrogen, in particular to a process method for stably producing hydrogen from methanol and application of the process method. According to the process method for stably producing hydrogen from methanol and the application of the process method, the yield, the purity, the service life, the stability and the environmental protection property of hydrogen are synchronously improved by constructing a whole-process parameter collaborative system of raw material configuration, reaction regulation and purification, and all the effects are mutually promoted. The limitation of single parameter adjustment in the prior art is broken through, and the high-load requirement of the AMS hydrogenation process is perfectly met.

Description

Technical Field

[0001] This invention relates to the field of hydrogen industrial preparation, specifically to a process for the stable preparation of high-purity hydrogen and its application. Background Technology

[0002] The AMS hydrogenation process is a crucial step in the fine chemical industry, demanding high-yield, high-purity, and low-fluctuation hydrogen. Current technologies primarily utilize methanol steam reforming (MSR) to supply hydrogen for the AMS hydrogenation process; however, these technologies suffer from the following key drawbacks: limited catalyst activity and selectivity, resulting in hydrogen production rates typically maintained at around 500 NM. 3 The current flow rate of methanol is around 0.00 h, which cannot meet the high-load operation requirements of the AMS hydrogenation process. The catalyst has a short lifespan and high replacement costs. Improper reaction temperature control or unreacted methanol residue can lead to catalyst poisoning, resulting in a shorter catalyst lifespan and frequent replacements, increasing equipment downtime and costs. The low precision of methanol and demineralized water flow control leads to large fluctuations in reaction pressure and temperature, causing significant fluctuations in hydrogen production and affecting the stability of the AMS hydrogenation reaction. Unreacted methanol residue after the catalytic reaction is discharged with the vacuum system drainage, resulting in a methanol content in the wastewater exceeding 0.5%, leading to large wastewater volumes and high treatment costs. Currently, no suitable solutions have been found for these problems. Therefore, it is essential to invent a stable and efficient hydrogen production process. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention aims to develop a stable process for producing high-purity hydrogen and its application. By constructing a synergistic parameter system encompassing raw material configuration, reaction control, and purification, this invention achieves simultaneous improvements in hydrogen yield, purity, lifespan, stability, and environmental friendliness, with each effect mutually reinforcing the others. It overcomes the limitations of existing technologies that rely on adjusting a single parameter, perfectly adapting to the high-load requirements of the AMS hydrogenation process.

[0004] This invention discloses a process for stabilizing methanol to produce hydrogen, comprising the following steps: S1 Raw Material Preparation and Transportation: Methanol is stably transported to the mixing pipe via a flow controller, while demineralized water is introduced simultaneously. The molar ratio of methanol to demineralized water is controlled to form a mixture, which is then pressurized by a raw material metering pump. S2 Heating, Vaporization, and Catalysis: The pressurized mixture obtained in step S1 is passed into a waste heat exchanger and heated to 180°C, and then passed into a heat transfer oil heater and heated to 260°C. The gaseous mixture is separated by a gas-liquid separator. The gaseous mixture is then passed into a vertical fixed-bed converter, which is filled with YL-98 copper-based catalyst. The flow rate of the mixed gas is adjusted by a temperature closed-loop controller to complete the methanol cracking and conversion reaction and control the converter outlet temperature to generate hydrogen-containing converted gas. S3 Cooling and Water Washing Purification: The converted gas obtained in step S2 is first cooled to 120°C by a waste heat exchanger, then enters the condenser and is cooled by 25°C circulating water. The condensate is separated by a gas-liquid separator. The cooled converted gas is then introduced from the bottom of the purification tower and sprayed with demineralized water from the top to perform countercurrent water washing. S4 PSA Purification and Product Collection: The converted gas after washing in step S3 is introduced into the PSA system for pressure swing adsorption, purification, and impurity removal to obtain hydrogen with a purity greater than 99%. Then, the inlet flow rate is adjusted by a flow meter to stabilize the hydrogen production. The purified converted gas waste gas is discharged to the tail gas pipeline network.

[0005] Preferably, in the S1 raw material preparation and conveying step, the molar ratio of methanol to deionized water is 1:1.

[0006] Preferably, in the raw material preparation and conveying step S1, the pressure of the pressurizing pump is increased to 1.6 MPa.

[0007] Preferably, in the S1 raw material preparation and conveying step, the flow rate of methanol is 235.3-240 kg / h.

[0008] Preferably, in the S1 raw material preparation and conveying step, the flow rate of the demineralized water is 378.7~386.4 kg / h.

[0009] Preferably, in the S3 cooling and water washing purification step, the circulating water is cooled to 40~44°C.

[0010] Preferably, in the S3 cooling and water washing purification step, the desalinated water flow rate of the countercurrent water washing is 100 kg / h.

[0011] Preferably, in the S3 cooling and water washing purification step, the countercurrent water washing time is greater than 30 seconds.

[0012] Preferably, in the S4 PSA purification and product collection step, the PSA system pressure swing adsorption cycle is 14.5 min.

[0013] Any of the methanol-stabilized hydrogen production processes described above can be applied to the AMS hydrogenation process system.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a process for the stable preparation of high-purity hydrogen, which has the following characteristics: (1) Significantly increased hydrogen production: By controlling the water-to-methanol ratio, pressure, staged temperature-controlled vaporization, and temperature-controlled catalysis, the hydrogen production was increased from the current 500 NM3 / h to 600~612.3 NM3 / h, which can meet the high-load requirements of the AMS hydrogenation process; this effect cannot be achieved by a single parameter. For example, if the reaction temperature is increased to 260℃, although the hydrogen production will increase by 5% in the short term, the catalyst activity will decrease by 15% after one month, and the hydrogen production will fall back to the original level.

[0015] (2) Catalyst life extended by 50%: The reaction temperature is controlled within the optimal activity range of the catalyst, and residual methanol is removed by water washing to avoid catalyst poisoning and sintering. The actual life of the catalyst is extended from 2 years to 3 years. When the catalyst activity is less than or equal to 70%, the catalyst needs to be replaced. According to accelerated experiments, the time for the catalyst activity to drop from the initial 90% to 70% has been increased from 16,000 hours to 24,000 hours, which corresponds to an extension of 1 year in the actual operating cycle.

[0016] (3) Minimal fluctuation in hydrogen production: The feedstock flow rate is stabilized through closed-loop control, and the reaction pressure and temperature are coordinated and stabilized. Combined with the PSA optimization cycle, the fluctuation range of hydrogen production is reduced from the current ±5% to 0.8%, ensuring the continuity and stability of the AMS hydrogenation reaction. Continuous 24-hour monitoring data shows that the difference between the maximum and minimum hydrogen production values ​​is ≤5.4 NM. 3 / h, far lower than ±12NM of the AMS process. 3 / h is the permissible fluctuation range.

[0017] (4) Reduced wastewater treatment costs: Water washing removes more than 90% of unreacted methanol, reducing the methanol content in wastewater from 0.5% to 0.07-0.09%. At the same time, water vapor condensation is sufficient, reducing the wastewater volume of the vacuum system from 105 kg / h to 79-82 kg / h.

[0018] (5) Balance between energy consumption and efficiency: By using the waste heat of the conversion gas to preheat the raw materials, the energy consumption of the heat transfer oil is reduced, while the short-cycle purification of PSA improves the processing efficiency and the hydrogen production per unit time is increased, thus achieving high efficiency and energy saving. Detailed Implementation

[0019] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0020] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0021] Example 1: A methanol-stabilized hydrogen production process, comprising the following steps: S1 Raw Material Preparation and Transportation: The flow rate of methanol is controlled at 235.3 kg / h and stably transported to the mixing pipe through the flow controller. At the same time, demineralized water is introduced through the demineralized water transfer pump, and the flow rate of demineralized water is controlled at 378.7 kg / h. The molar ratio of methanol to demineralized water is controlled at 1:1 to form a mixed liquid. The mixed liquid is pressurized to 1.6 MPa through the raw material metering pump.

[0022] S2 Heating, Vaporization, and Catalysis: The pressurized mixture obtained in step S1 is passed into a waste heat exchanger and heated to 180°C, then passed into a thermal oil heater and heated to 260°C. The gaseous mixture is separated by a gas-liquid separator. The gaseous mixture is then passed into a vertical fixed-bed converter, which is filled with YL-98 copper-based catalyst. The flow rate of the mixed gas is adjusted by a temperature closed-loop controller to complete the methanol cracking and conversion reaction. The converter outlet temperature is controlled at 253.6°C to generate converted gas containing hydrogen. S3 Cooling and Water Washing Purification: The converted gas obtained in step S2 is first cooled to 120°C by a waste heat exchanger, and then enters the condenser. 25°C circulating water is introduced to cool it to 40°C. The condensate is separated by a gas-liquid separator. The cooled converted gas is then introduced from the bottom of the purification tower, and demineralized water is sprayed from the top. The flow rate of demineralized water is controlled at 100 kg / h. The converted gas is then subjected to countercurrent water washing, and the countercurrent water washing time is controlled to be greater than 30 seconds. S4 PSA Purification and Product Collection: The converted gas after water washing in step S3 is introduced into the PSA system for pressure swing adsorption. The cycle of pressure swing adsorption is set to 14.5 min (i.e., adsorption 4 min, first average drop 30 s, second average drop 30 s, third average drop 30 s, reverse release 1 min, vacuuming 3 min, third average rise 30 s, second average rise 30 s, first average rise 30 s, final charge 3.5 min). After purification and impurity removal, hydrogen gas with a purity greater than 99% is obtained. Then, the inlet flow rate is adjusted by a flow meter to stabilize the hydrogen production. The purified converted gas waste gas is discharged to the tail gas pipeline network.

[0023] Example 2: Remove the waste heat exchanger from step S2 by heating it up, and directly heat it to 260°C in a thermal oil heater. Everything else is the same as in Example 1.

[0024] Example 3: The water washing process in step S3 is removed, and the rest is the same as in Example 1.

[0025] Example 4: The cycle of pressure swing adsorption in step S4 was changed to 16 minutes, and the rest was the same as in Example 1.

[0026] The experimental data for Examples 1-4 are shown in the table below:

[0027] The experimental data in the table above show that Example 1 yielded the best results, with a hydrogen production of 600.6 NM. 3 / h, which can meet the high load requirements of AMS, with hydrogen purity reaching 99.85% and fluctuation range of only ±0.8%, converter heat transfer oil outlet temperature of 253.6℃, ​​catalyst life of 24,000 hours (equivalent to 2.7 years in practice), and methanol content in wastewater of 0.08%; In Example 2, after removing waste heat and preheating, the mixture needs to be directly heated from room temperature to 260℃ using heat transfer oil, increasing the energy consumption of heat transfer oil (although the table shows a decrease in output of 5.4 NM compared to Example 1). 3 The heating uniformity decreased, leading to an increase in the converter heat transfer oil outlet temperature. In Example 3, without water washing, unreacted methanol directly entered the PSA system and circulated with the converter, causing methanol poisoning on the catalyst surface. The converter heat transfer oil outlet temperature increased from 253.6℃ to 256.7℃, and the catalyst lifespan plummeted from 24,000 hours to 16,000 hours (actual lifespan was only 1.83 years). The PSA system needed to adsorb methanol and impurities simultaneously, resulting in a decrease in purity from 99.85% to 99.50% (below the AMS requirement of ≥99.7%). The methanol content in the wastewater increased to 0.80%, increasing treatment costs. In Example 4, after extending the PSA cycle, the purity and lifespan were close to the baseline group, but the treatment efficiency decreased, and the yield decreased by 10.5 NM compared to Example 1. 3 / h. Experimental data from Examples 1-4 show that only coordinated adjustments to the entire process can produce hydrogen that meets the requirements of AMS, while increasing hydrogen production and reducing wastewater discharge while ensuring purity.

[0028] Example 5: The methanol flow rate in step S1 was screened (233.1 kg / h, 235.3 kg / h, 237.7 kg / h, 240 kg / h, 242.5 kg / h), and the rest were the same as in Example 1. The experimental data are shown in the table below.

[0029]

[0030] The experimental data in the table above show that when the methanol flow rate is between 235.3 and 240 kg / h, the output remains at 600 to 608.5 NM3 / h. When the flow rate exceeds 240 kg / h, although the hydrogen output increases slightly, the excess methanol leads to increased residue, the outlet temperature of the converter heat transfer oil increases from 253.6℃ to 256.1℃, and the catalyst life is shortened to 23,000 hours. Therefore, it can be seen that simply increasing the flow rate cannot continuously increase the output.

[0031] Example 6: The demineralized water flow rate in step S1 was screened (373.1 kg / h, 378.7 kg / h, 282.7 kg / h, 386.4 kg / h / h, 390.5 kg / h), and the rest were the same as in Example 1. The experimental data are shown in the table below.

[0032]

[0033] The experimental data in the table above show that the optimal demineralized water flow rate is between 378.7 and 386.4 kg / h; above 390.5 kg / h, excessive water dilutes the raw material, the reaction rate decreases, and the yield drops to 598.2 NM. 3 The flow rate is 83 kg / h, and the wastewater volume increases to 83 kg / h, so more water does not necessarily mean a higher conversion rate.

[0034] Example 7: The molar ratio of methanol to deionized water in step S1 was screened (1:0.8, 1:1.0, 1:1.2, 1:1.6, 1:2), and the rest were the same as in Example 1. The experimental data are shown in the table below.

[0035]

[0036] The experimental data in the table above show that when the molar ratio of methanol to deionized water is 1:1, the yield is 600.6 NM. 3 The converter's heat transfer oil outlet temperature is 253.6℃, ​​and the catalyst life is 24,000 hours. When the methanol to demineralized water molar ratio is 1:0.8 (methanol in excess), the converter's heat transfer oil outlet temperature increases to 257.3℃, and residual methanol reduces the life to 21,000 hours. When the methanol to demineralized water molar ratio is 1:1.2 (water in excess), feedstock dilution reduces the yield to 592.3 NM. 3 / h and below.

[0037] Example 8: The pressure of pressurizing the mixture in step S1 was screened (1.2MPa, 1.4MPa, 1.6MPa, 1.8MPa, 2.0MPa), and the rest were the same as in Example 1. The experimental data are shown in the table below.

[0038]

[0039] The experimental data in the table above show that when the pressure is 1.6 MPa, the mixture completely vaporizes at 260℃, with a yield of 600.6 NM. 3 / h, fluctuation ±0.8%; when the pressure is below 1.4MPa, vaporization is insufficient, and the output is ≤582.5NM 3 / h, fluctuation ≥1.5%; when the pressure is higher than 1.8MPa, energy consumption increases but output increase is limited (only 602.3NM). 3 Therefore, simply increasing the pressure ( / h) is not very effective.

[0040] Example 9: The cooling temperatures in step S3 were screened (38℃, 40℃, 42℃, 44℃, 46℃), and the rest were the same as in Example 1. The experimental data are shown in the table below.

[0041]

[0042] The experimental data in the table above show that when the cooling temperature is 40~44℃, water vapor is fully condensed and methanol is in a gaseous state, making it easy to remove by water washing, with a yield ≥600.6 NM. 3 / h, methanol in wastewater ≤0.08%; when the condensation temperature is below 40℃ or above 44℃, the data indicators will decrease. Therefore, single temperature control cannot take into account both water removal and methanol removal.

[0043] In summary, based on the experimental data from Examples 1 to 9, it can be seen that the effect of the present invention is not due to a single parameter, but rather to the synergistic effect of parameters throughout the entire process, including raw materials, reaction, purification, and refining. Specifically: (1) The increase in hydrogen production is the result of the synergistic effect of parameters throughout the entire process. Relying solely on a single parameter (such as increasing methanol flow rate or raising temperature) may result in a slight increase in production in the short term, but it cannot be kept stable at 600 NM for a long period. 3 / h or more; only through coordinated regulation as in Example 1 can the output be stably maintained at 600NM. 3(1) The catalyst life is extended by 50% due to the synergistic effect of temperature and water washing. Temperature control at 253.6℃ avoids sintering, and water washing removes 90% of residual methanol to avoid poisoning. The synergistic effect of the two extends the catalyst life from 2 years (16,000 hours) to 3 years (24,000 hours), which cannot be achieved by temperature control alone or water washing alone. (2) The hydrogen fluctuation is minimal due to the synergistic control of flow rate, pressure and temperature. Closed-loop control of raw material flow rate, 1.6MPa pressure stabilization, and 253.6℃ temperature stabilization, combined with the 8-minute cycle of the PSA system, reduces the fluctuation from ±5% to ±0.7%~0.9%, which is far lower than the ±2% requirement of AMS. Pressure control alone or temperature control alone cannot stabilize the fluctuation. (4) Reduced wastewater costs: Cooling and washing work together: Cooling at 40℃ causes water vapor to condense, and washing removes methanol. The two work together to reduce the wastewater volume from 105kg / h to 79~82kg / h and the methanol content from 0.5% to 0.07%~0.09%, effectively reducing treatment costs.

[0044] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A process for stabilizing methanol to produce hydrogen, characterized in that, Includes the following steps: S1 Raw Material Preparation and Transportation: Methanol is stably transported to the mixing pipe via a flow controller, while demineralized water is introduced simultaneously. The molar ratio of methanol to demineralized water is controlled to form a mixture, which is then pressurized by a raw material metering pump. S2 Heating, Vaporization, and Catalysis: The pressurized mixture obtained in step S1 is passed into a heat exchanger and heated to 180°C, and then passed into a heat transfer oil heater and heated to 260°C. The gaseous mixture is separated by a gas-liquid separator. The gaseous mixture is then passed into a vertical fixed-bed converter, which is filled with YL-98 copper-based catalyst. By adjusting the flow rate of the mixed gas, the methanol cracking and conversion reaction is completed and the converter outlet temperature is controlled to generate converted gas containing hydrogen. S3 Cooling and Water Washing Purification: The converted gas obtained in step S2 is first cooled to 120°C by a heat exchanger, then enters the condenser and is cooled by 25°C circulating water. The cooled converted gas is then introduced from the bottom of the purification tower and sprayed with demineralized water from the top. The converted gas is then washed with countercurrent water and the condensate is separated by a gas-liquid separator. S4 PSA Purification and Product Collection: The converted gas after washing in step S3 is introduced into the PSA system for pressure swing adsorption, purification, and impurity removal to obtain hydrogen with a purity greater than 99%. Then, the inlet flow rate is adjusted by a flow meter to stabilize the hydrogen production. The purified converted gas waste gas is discharged to the tail gas pipeline network.

2. The methanol-to-hydrogen stabilization process according to claim 1, characterized in that, In the S1 raw material preparation and transportation step, the molar ratio of methanol to deionized water is 1:

1.

3. The methanol-to-hydrogen stabilization process according to claim 1, characterized in that, In the S1 raw material preparation and conveying step, the pressure of the pressurizing pump is increased to 1.6 MPa.

4. The methanol-to-hydrogen stabilization process according to claim 1, characterized in that, In the S1 raw material preparation and transportation step, the flow rate of methanol is 235.3-240 kg / h.

5. The methanol-to-hydrogen stabilization process according to claim 1, characterized in that, In the S1 raw material preparation and conveying step, the flow rate of the demineralized water is 378.7~386.4 kg / h.

6. The methanol-to-hydrogen stabilization process according to claim 1, characterized in that, In the S3 cooling and water washing purification step, the circulating water is cooled to 40~44℃.

7. The methanol-to-hydrogen stabilization process according to claim 1, characterized in that, In the S3 cooling and water washing purification step, the flow rate of the desalinated water in the countercurrent water washing is 100 kg / h.

8. The methanol-to-hydrogen stabilization process according to claim 1, characterized in that, In the S3 cooling and water washing purification step, the countercurrent water washing time is greater than 30 seconds.

9. The methanol-to-hydrogen stabilization process according to claim 1, characterized in that, In the S4 PSA purification and product collection steps, the PSA system pressure swing adsorption cycle is 14.5 min.

10. The methanol-stabilized hydrogen production process method according to any one of claims 1 to 9 can be applied to the AMS hydrogenation process system.

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