CN101177240B - An integrated dimethyl ether steam reforming hydrogen production device and method - Google Patents

Abstract

The invention discloses an integrated dimethyl ether steam reforming hydrogen-production device and a method, belonging to the hydrogen-production equipment and the method. The invention utilizes a dual-jacketed membrane reactor to realize the coupling of an exothermic reaction and an endothermic reaction and the coupling of a catalytic reaction and a product separation. The invention is characterized in that the central tube of the double cannula is a hydrogen permeation membrane made of palladium silver alloy for in-situ separation of H2, the product of the reaction system; two reforming catalysts are filled in a jacket of the double cannula and the dimethyl ether steam reforming hydrogen production is carried out in the jacket of the tube side; a combustion supporting catalyst is filledin the shell side out of the double cannula to supply heat for the dimethyl ether steam reforming reaction. The invention has the advantages of greatly promoting the steam reforming reaction rate ofthe dimethyl ether, the heat utilization rate and the product purity. The invention obtains high purity hydrogen at lower reaction temperature and pressure, in which the conversion of dimethyl ether canreach 80%, the hydrogen recovery rate 85%, the hydrogen production rate 0.05 to 0.6 m<3>/h, the hydrogen purity 99.5% and the thermal efficiency of the system is above 80%.

Description

An integrated dimethyl ether steam reforming hydrogen production device and method

technical field

The invention relates to a device and method for producing hydrogen by using dimethyl ether as a raw material, in particular to an integrated hydrogen production device and method for steam reforming of dimethyl ether.

Background technique

Hydrogen energy is regarded as the energy source with the most development potential in this century because of its cleanliness, high efficiency, and renewability. At present, it is still an ideal low-pollution or zero-pollution vehicle energy source. At present, the research and development of the mobile hydrogen production process based on chemical processes from liquid hydrocarbons (such as methanol) has become one of the hot topics in the field of fuel cells. Using methanol as fuel can solve storage and transportation problems, but the specific energy density of methanol is still not ideal, and it is highly toxic. Once leaked, it will cause great harm to the human body and the environment. In addition, the infrastructure used for fueling needs to be re-established .

In recent years, the research on the hydrogen production process by steam reforming of dimethyl ether (DME SR) has attracted the attention of researchers. DME is a clean, high-energy-density hydrogen carrier that can be easily compressed into a liquid (0.5 MPa). The physical properties are similar to liquefied petroleum gas (LPG), and it has the advantages of high hydrogen content, high calorific value, easy storage and transportation, etc. The pollution of the environment after combustion is far less than that of various existing fuels. Compared with other hydrogen production methods, dimethyl ether has the advantages of easy availability of raw materials, high hydrogen content, convenient storage and transportation, and mild hydrogen production conditions, and is suitable for mobile hydrogen production.

Dimethyl ether and water vapor are reformed to produce hydrogen under the action of a catalyst, and the reaction formula is as follows:

CH ₃ OCH ₃ +H ₂ O = 2CH ₃ OH ΔH ₂₉₈ =+37kJ/mol (1)

CH ₃ OH + H ₂ O = 3H ₂ + CO ₂ ΔH ₂₉₈ = +49kJ/mol (2)

The overall response is:

CH ₃ OCH ₃ +3H ₂ O=6H ₂ +2CO ₂ ΔH ₂₉₈ =+135kJ/mol (3)

The steam reforming reaction of dimethyl ether produces hydrogen with high hydrogen content, and the reaction conditions are mild. The disadvantage is that the steam reforming reaction of dimethyl ether is a strong endothermic reaction, and the reaction itself and the vaporization of raw material water need absorption. When producing hydrogen, part of the fuel needs to be burned to provide heat.

Japanese patent (Zhao 63-295402) proposed a method of producing hydrogen with a porous glass-Pd-Cu composite membrane reactor. This method uses a membrane reactor to make the reaction and separation proceed simultaneously, breaking the chemical equilibrium limit and making the conversion However, in order to obtain high hydrogen yield, the method adopts higher operating temperature, high energy consumption, and the method has low gas yield, and the direct product is a mixture of hydrogen and argon instead of pure hydrogen, which is difficult separate. There are related patents on the method and system of steam reforming of dimethyl ether, such as CN1126709C, CN1044896C and CN1123530C. Patents CN1126709C and CN1044896C propose a method for catalyzing hydrogen production by dimethyl ether in the presence of steam. In this patent, dimethyl ether is first hydrolyzed to produce a mixture containing carbon oxides and hydrogen, and then the reaction product is subjected to a water gas change reaction to make a large amount of carbon monoxide Converted into carbon dioxide, and the product is rich in carbon monoxide, which makes the hydrogen production process of dimethyl ether complicated and high in energy consumption; although the patent CN1123530C proposes a method of generating rich hydrogen by steam reforming dimethyl ether and using part of the hydrogen to oxidize for heat , but the patent preferably uses a fluidized bed reactor, the reaction operating pressure is high, the gas components in the reaction product are complex, and it is difficult to obtain relatively high-purity hydrogen. The above-mentioned patents are not suitable for mobile hydrogen production or hydrogen production from small-scale hydrogen sources. Therefore, it is necessary to design a more reasonable structure, give full play to the characteristics of dimethyl ether energy and the advantages of dimethyl ether hydrogen production, to realize hydrogen production by steam reforming of dimethyl ether, which is suitable for mobile hydrogen production or small hydrogen source production hydrogen.

Contents of the invention

Aiming at the deficiencies and defects of the prior art, the present invention proposes an integrated dimethyl ether steam reforming hydrogen production device and method, so that the invention integrates fuel heating, steam reforming reaction and hydrogen-rich gas separation and purification Designed as an integration, realize the coupling of exothermic reaction and endothermic reaction, as well as the coupling of catalytic reaction and product separation process, and obtain high-purity hydrogen at lower reaction temperature and pressure, which is suitable for mobile hydrogen production or small hydrogen source Hydrogen production.

Technical scheme of the present invention is as follows:

An integrated dimethyl ether steam reforming hydrogen production device, characterized in that the device contains a reactor body, and multiple sets of double-pipe hydrogen permeable components are uniformly arranged in the reactor body, and each set of double-pipe hydrogen permeable components It is composed of a central tube and an outer tube. The central tube is made of a palladium alloy film or a composite palladium film. The reforming catalyst is filled in the jacket of the double tube, and the combustion-supporting catalyst is filled in the shell side outside the double tube. At the bottom of the outer tube A porous end cap is provided to allow the tail gas of the reforming reaction to pass through; the upper part of the reactor is provided with a release gas outlet and a raw material gas inlet in sequence, and a hydrogen outlet is provided at the top of the reactor; an ignition device is provided at the lower part of the reactor. There are air inlets and catalyst loading and unloading ports at the bottom respectively.

The central tube adopts a palladium-silver alloy film, and the mass percentage of palladium and silver in the palladium-silver alloy film is 2.3-9:1. Preferably it is 3:1.

The present invention also provides a method using the integrated dimethyl ether steam reforming hydrogen production device, which is characterized in that the method is carried out as follows:

1) After water and dimethyl ether are mixed, they enter the double-pipe jacket from the feed gas inlet, and flow from top to bottom in the double-pipe jacket, and the steam reforming reaction of dimethyl ether occurs under the action of the reforming catalyst , the reforming reaction temperature is 200-300°C, and the reaction pressure is 0.1-0.5MPa; the reforming catalyst is a composite bifunctional catalyst composed of solid acid and metal catalyst, and the weight ratio of solid acid to metal catalyst is 1:5-5: 1;

2) The hydrogen obtained from the steam reforming reaction of dimethyl ether is separated by the double-pipe hydrogen permeable component, enters the upper part of the reactor through the center pipe, and is discharged from the hydrogen outlet at the top of the reactor; the tail gas of the steam reforming reaction of dimethyl ether And unseparated hydrogen enters the bottom of the reactor through the porous end cap; the pressure in the central tube is normal pressure;

3) The reaction tail gas and unseparated hydrogen entering the bottom of the reactor are mixed with air, and after being heated by the ignition device, under the action of the combustion-supporting catalyst, they are gradually burned from bottom to top in the shell side outside the double casing, forming two The steam reforming reaction of methyl ether supplies heat; the tail gas of the combustion reaction is discharged from the reactor through the release gas outlet; the combustion-supporting catalyst adopts a supported noble metal catalyst.

In the above method, the reforming catalyst is preferably a mixture of molecular sieve catalyst ZSM-5 and copper-based catalyst, and the weight ratio of molecular sieve ZSM-5 to copper-based catalyst is 1:2-2:1. The combustion-supporting catalyst is preferably a Pd/Al ₂ O ₃ noble metal catalyst.

Compared with the prior art, the present invention has the following advantages and outstanding effects: the invention utilizes the selective permeability of the palladium alloy film or the composite palladium film to hydrogen, and promptly removes the hydrogen generated by the steam reforming reaction of dimethyl ether from the product In order to improve the conversion rate of the reaction, high-purity hydrogen can be obtained at a lower reaction temperature and pressure; the dual-functional catalyst is used to couple the hydrolysis reaction of dimethyl ether and the steam reforming reaction of methanol to increase the yield of dimethyl ether. Conversion rate and hydrogen yield; use electric heating wire to preheat the reactants to the initial reaction temperature, after the dimethyl ether steam reforming reaction starts, burn the unreacted dimethyl ether and unseparated hydrogen in the reaction tail gas, Provide heat for the reaction and make full use of energy; the device integrates fuel heat supply, steam reforming reaction and hydrogen-rich gas separation and purification to realize the coupling of exothermic reaction and endothermic reaction and the separation of catalytic reaction and product process coupling.

Description of drawings

Figure 1 is a schematic diagram of a typical structure of a hydrogen production plant by steam reforming of dimethyl ether.

Fig. 2 is a flow chart of hydrogen production by steam reforming of dimethyl ether.

In the figure: 1. Air inlet; 2. Head; 3. Porous end cap; 4. Cylinder; 5. Combustion catalyst; 6. Reforming catalyst; 7. Release gas outlet; 8. Feed gas inlet; Exit; 10. Hydrogen permeable tube flower plate; 11. Porous flower plate; 12. Outer tube flower plate; 13. Central tube; 14. Outer tube; 15. Support flower stand; 16. Air distributor; 18. Ignition device; 19. Dimethyl ether gas cylinder; 20. Pump; 21. Air gas cylinder; 22. Pressure reducing valve; 23. Mass flow meter; 24. Reactor; 25. Constant temperature box; 26. Cold trap; 27. Liquid collection tank; 28. Back pressure valve; 29. Wet flow meter; 30. Gas chromatograph; 31. Main control system.

Detailed ways

The structure, principle and technological process of the present invention will be further described in conjunction with the accompanying drawings.

Figure 1 is a schematic diagram of a typical structure of a hydrogen production plant by steam reforming of dimethyl ether. The device contains a reactor body, and multiple sets of double-sleeve hydrogen permeation components are evenly arranged in the reactor body. Each set of double-sleeve hydrogen permeation components is composed of a central tube 13 and an outer sleeve 14. The porous end cap 3 through which the tail gas of the reforming reaction passes; the central tube adopts a palladium alloy membrane or a composite palladium membrane, and the inner wall of the central tube constitutes a permeation cavity for in-situ separation of the product H ₂ of the reaction system. The dimethyl ether steam reforming catalyst 6 is filled in the jacket of the double jacket, and the dimethyl ether reforming catalytic hydrogen production reaction is carried out in the jacket of the double jacket; the combustion-supporting catalyst 5 is filled in the shell side outside the double jacket for Catalytic combustion of dimethyl ether steam reforming reaction tail gas and unseparated hydrogen; the upper part of the reactor is provided with a release gas outlet 7 and a raw gas inlet 8 in sequence. A hydrogen gas outlet 9 is provided at the top of the reactor, and the hydrogen gas separated by the steam reforming reaction of dimethyl ether is discharged out of the reactor through the hydrogen gas outlet 9 . An ignition device 18 is provided at the lower part of the reactor for heating the fuel. The bottom of the reactor is respectively provided with an air inlet 1 and a loading and unloading port 17 for the catalyst. The air inlet 1 is a passage for the air in the reactor, and the loading and unloading port 17 for the catalyst is a passage for loading and unloading the catalyst.

The raw material gas dimethyl ether enters the double-tube jacket from the raw material gas inlet 8 on the upper part of the reactor. The dimethyl ether flows from top to bottom in the double-tube jacket and enters the bottom of the reactor from the porous end cap 3. The air inlet 1 enters the bottom of the reactor, the ignition device 18 heats the mixture of air and dimethyl ether, and the combustion-supporting catalyst 5 in the shell side outside the double casing adopts a supported noble metal catalyst, preferably a Pd/Al ₂ O ₃ noble metal catalyst , the loading amount of the combustion-supporting catalyst can be determined according to actual needs. Under the action of the combustion-supporting catalyst 5, dimethyl ether and air are gradually combusted from bottom to top on the shell side outside the double casing, and the heat is transferred from the shell side outside the double casing to the jacket of the double casing, making the double casing The temperature inside the pipe jacket rises gradually, and the combustion reaction tail gas is discharged from the reactor through the release gas outlet 7. When the temperature in the double-pipe jacket rises to the dimethyl ether steam reforming reaction temperature, the pump 20 is started, and after water and dimethyl ether are evenly mixed, they enter the double-pipe jacket from the feed gas inlet 8, and the reforming The dimethyl ether steam reforming reaction occurs under the action of catalyst 6. The dimethyl ether steam reforming catalyst adopts a composite bifunctional catalyst composed of a solid acid and a metal catalyst, and the weight ratio of the solid acid to the metal catalyst is 1:5-5 : 1;, preferably the catalyst that the molecular sieve catalyst ZSM-5 and the copper-based catalyst physically mix, the weight ratio of the molecular sieve catalyst ZSM-5 and the copper-based catalyst is combined in a weight ratio between 1: 2～2: 1, and the reforming catalyst The amount of filling can be determined according to actual needs. The molar ratio of raw material water to dimethyl ether is 3:1-6:1, the reaction temperature is 200°C-300°C, the reaction pressure is 0.1-0.5MPa, and the internal pressure of the hydrogen permeable tube assembly is normal pressure. The hydrogen gas obtained from the steam reforming reaction of dimethyl ether is separated by the hydrogen permeable component and enters the upper part of the reactor through the central pipe 13, and is discharged from the hydrogen outlet 9 at the top of the reactor. 20mm, film thickness 0.06mm, hydrogen production scale 0.02-0.3m ³ /h. DME steam reforming reaction tail gas and unseparated hydrogen enter the bottom of the reactor through the porous end cap 3, mix with air and burn to provide heat for DME steam reforming reaction to maintain DME steam reforming The heat required for the reaction keeps the reaction temperature of the dimethyl ether steam reforming part constant, and the dimethyl ether reforming reactants flow countercurrently with the fuel, and the heat transfer efficiency is high. At the same time, according to the demand of actual hydrogen production, the structural size of the double-tube hydrogen permeation module and the loading amount of catalyst can be adjusted accordingly according to this structure.

The outlet of the reactor is a constant temperature box 25, which maintains a high temperature so that all reactants and products continue to maintain a gas state. A high temperature resistant six-way valve is provided in the constant temperature box, and the gas at the reactor outlet can be collected online and entered into the chromatogram for component analysis. analyze. The tail gas enters the cold trap 26 after coming out of the constant temperature box for gas-liquid separation. The gas phase is reduced to normal pressure after passing through the back pressure valve 28, and is measured by the wet flow meter 29. Composition was also analyzed using gas chromatography 30 . The measurement and control process is realized by computer with the main control system 31 .

Calculated as follows:

It can be seen that the integrated dimethyl ether steam reforming hydrogen production device in the present invention performs a catalytic combustion reaction on the tail gas of the dimethyl ether steam reforming reaction while performing the dimethyl ether steam reforming reaction, which is two The steam reforming reaction of methyl ether supplies heat, and the device does not require additional heat exchange equipment. In addition, since the reforming system adopts countercurrent heat exchange (the flow direction of the heat transfer medium is opposite to that of the dimethyl ether steam reforming raw material, and the heat transfer driving force is large), the heat transfer efficiency can also be improved.

Because the present invention adopts palladium-silver alloy film tube, it can separate pure hydrogen at a low temperature of 200°C to 300°C, making the hydrogen production device compact in structure, miniaturized and easy to carry, and at the same time, the catalyst is not easy to wear, and it is easy to add or update the catalyst. The system can realize self-heating, and can be used for small hydrogen sources and vehicle-mounted hydrogen production. This integrated dimethyl ether steam reforming hydrogen plant can handle a variety of fuels, including gasoline, methanol, ethanol and other hydrocarbon fuels.

Using the integrated dimethyl ether steam reforming hydrogen production device in the present invention, the dimethyl ether conversion rate is 60% to 80%, the hydrogen recovery rate is 85%, the hydrogen purity reaches 99.5%, and the hydrogen production scale of the reaction is 0.02 to 0.3m ³ /h, the thermal efficiency of the system is 80%. When the hydrogen recovery rate is 80%, the whole dimethyl ether steam reforming hydrogen production unit can reach self-heating equilibrium. The reaction temperature is low, the energy consumption is low, the reaction and separation are synchronized, the operation is convenient, and the equipment investment is small.

Embodiments of the present invention are as follows:

Example 1

0.02m ³ /h dimethyl ether hydrogen production plant

The reaction device is constructed as shown in Figure 2, a membrane reactor is used, the reaction temperature is 200 ° C, the reaction pressure is 0.1 MPa, the central tube adopts palladium-silver alloy, the mass percentage of palladium and silver is 3: 1, and the internal pressure of the central tube is normal pressure. The feeding amount of ether is 500ml/min, and the molar ratio of water and dimethyl ether is 3: 1; The reforming catalyst adopts the mixture of molecular sieve ZSM-5 and copper-based catalyst to be 10g altogether, the mixture of molecular sieve catalyst ZSM-5 and copper-based catalyst The weight ratio is 1:1, the combustion-supporting catalyst adopts 5g of Pd/Al ₂ O ₃ precious metal catalyst, the tube length of the central tube assembly is 300mm, the tube diameter is 10mm, the film thickness is 0.06mm, and there are 5 central tubes, the conversion rate of dimethyl ether is 60 %, the hydrogen production scale is 0.02m ³ /h, the hydrogen recovery rate is 82%, the hydrogen purity reaches 99.5%, and the system thermal efficiency is 80%.

Example 2

0.03m ³ /h dimethyl ether hydrogen production plant

The reaction device is constructed as shown in Figure 2, using the membrane reactor of Example 1, the reaction temperature is 300 ° C, the reaction pressure is 0.1 MPa, the center tube adopts palladium-silver alloy, and the mass percentage of palladium and silver is 9: 1. The pressure in the center tube is normal pressure , the feed rate of dimethyl ether is 500ml/min, the molar ratio of water and dimethyl ether is 3: 1, the reforming catalyst adopts the mixture of molecular sieve catalyst ZSM-5 and copper-based catalyst to be totally 10g, molecular sieve ZSM-5 and copper The weight ratio of the base catalyst is 2:1, the combustion-supporting catalyst adopts 5g of Pd/A1 ₂ O ₃ precious metal catalyst, the tube length of the central tube assembly is 300mm, the tube diameter is 10mm, the film thickness is 0.06mm, and there are 5 central tubes to obtain the conversion of dimethyl ether The hydrogen production rate is 80%, the hydrogen production scale is 0.03m ³ /h, the hydrogen recovery rate is 80%, the hydrogen purity reaches 99.5%, and the system thermal efficiency is 80%.

Example 3

0.3m ³ /h dimethyl ether hydrogen production plant

The reaction device is constructed as shown in Figure 2, using the membrane reactor of Example 1, the reaction temperature is 300 ° C, the reaction pressure is 0.5 MPa, the central tube adopts a composite palladium membrane, the internal pressure of the central tube is normal pressure, and the feed amount of dimethyl ether is 5000 ml /min, the mol ratio of water and dimethyl ether is 6: 1, and catalyzer is to adopt the mixture of solid acid Al ₂ O ₃ and noble metal platinum catalyst altogether 100g, the weight ratio of solid acid Al ₂ O ₃ and noble metal platinum catalyst is 5: 1. The combustion-supporting catalyst uses 50g of Pd/Al ₂ O ₃ noble metal catalyst, the central tube assembly has a tube length of 300mm, a tube diameter of 20mm, a film thickness of 0.01mm, and 15 central tubes. The conversion rate of dimethyl ether is 80%, and the scale of hydrogen production is 0.3m ³ /h, the recovery rate of hydrogen is 83%, the purity of hydrogen is 99.5%, and the thermal efficiency of the system is 85%.

Claims (6)

1. An integrated dimethyl ether steam reforming hydrogen production device, characterized in that: the device contains a reactor body, and multiple groups of double casing hydrogen permeable components are uniformly arranged in the reactor body, and each group of double casing permeable hydrogen The hydrogen assembly consists of a central tube (13) and an outer tube (14). The central tube is made of a palladium alloy film or a composite palladium film. The double-tube jacket is filled with a reforming catalyst (6). The combustion-supporting catalyst (5) is filled in the process, and a porous end cap (3) is provided at the bottom of the outer casing (14) to allow the tail gas of the reforming reaction to pass through; the upper part of the reactor is sequentially provided with a release gas outlet (7) and a feed gas An inlet (8), a hydrogen outlet (9) is provided at the top of the reactor; an ignition device (18) is provided at the bottom of the reactor, and an air inlet (1) and a catalyst loading and unloading port (17) are respectively provided at the bottom of the reactor . 2. according to the integrated dimethyl ether steam reforming hydrogen production device described in claim 1, it is characterized in that: described center tube adopts palladium-silver alloy film, and the mass percent of palladium and silver in the palladium-silver alloy film is 2.3～9:1. 3. The integrated dimethyl ether steam reforming hydrogen production device according to claim 2, wherein the mass percentage of palladium and silver in the palladium-silver alloy film is 3:1. 4. A method for producing hydrogen by the integrated dimethyl ether steam reforming of the device as claimed in claim 1 is characterized in that the method is carried out as follows: 1) After mixing water and dimethyl ether, it enters the double-pipe jacket from the feed gas inlet (8), flows from top to bottom in the double-pipe jacket, and generates dimethyl ether water vapor under the action of the reforming catalyst Reforming reaction, the reforming reaction temperature is 200-300 ° C, the reaction pressure is 0.1-0.5 MPa; the reforming catalyst is a composite bifunctional catalyst composed of solid acid and metal catalyst, and the weight ratio of solid acid and metal catalyst is 1:5 ~5:1; the reforming catalyst is a mixture of molecular sieve ZSM-5 and copper-based catalyst; 2) The hydrogen gas obtained from the steam reforming reaction of dimethyl ether is separated by the double-tube hydrogen permeable component, enters the upper part of the reactor through the central pipe (13), and is discharged from the hydrogen outlet (9) at the top of the reactor; the dimethyl ether water The tail gas of the steam reforming reaction and the unseparated hydrogen enter the bottom of the reactor through the porous end cap (3); the pressure in the central tube is normal pressure; 3) The reaction tail gas and unseparated hydrogen entering the bottom of the reactor are mixed with air, and after being heated by the ignition device (18), under the action of the combustion-supporting catalyst (5), it gradually flows from bottom to top in the shell side outside the double casing. Combustion above provides heat for the steam reforming reaction of dimethyl ether; the tail gas of the combustion reaction is discharged from the reactor through the release gas outlet (7); the combustion-supporting catalyst adopts a supported noble metal catalyst. 5. The method for producing hydrogen by integrated dimethyl ether steam reforming according to claim 4, characterized in that the weight ratio of the molecular sieve catalyst ZSM-5 to the copper-based catalyst is 1:2 to 2:1. 6. The method for producing hydrogen by integrated dimethyl ether steam reforming according to claim 4, characterized in that: the combustion-supporting catalyst is a Pd/Al ₂ O ₃ noble metal catalyst.

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