CN201301224Y - Palladium membrane module applied for small-scale passage heat exchange and ceramics heat insulation - Google Patents

Abstract

The utility model discloses a palladium membrane assembly using small-scale channels for heat exchange and ceramic heat insulation. Porous metal support sheets and palladium membranes are sequentially arranged on both sides of the membrane support frame from inside to outside. Purify the hydrogen gas flow channel and the small-scale channel. The small-scale channel is a heating gas circulation channel passing through the membrane support frame, and its cross section is rectangular. The hydrogen gas flow channel of the supporting frame is a combination of two symmetrical rectangular teeth in the center of the supporting frame of the membrane, and a ceramic heat insulating layer is provided on the outside of the two palladium membranes. The component utilizes the high or low temperature in the small-scale channel, the flow heat transfer of the fluid and the heat insulation effect of the ceramic layer, so that the operating temperature of the membrane is different from the working temperature of the medium outside the component, so as to ensure that the membrane operates at its best It operates at a temperature (generally 450-600°C), and makes the hydrogen production process outside the module at its optimum temperature.

Description

A palladium membrane module using small-scale channel heat exchange and ceramic heat insulation

technical field

The utility model relates to a high-purity hydrogen production technology, in particular to a palladium membrane assembly using a small-scale channel for heat exchange and ceramic heat insulation. The assembly can be coupled to the hydrocarbon hydrogen production process in application, but the operation of the palladium membrane The temperature may be different from the reaction temperature of the hydrocarbon to produce hydrogen.

Background technique

At present, 90% of the hydrogen in the world comes from chemical processes such as reforming, gasification or cracking of hydrocarbons (natural gas, coal, biomass, etc.), and the purification of synthesis gas is one of the key processes. Available purification techniques include: pressure swing adsorption, polymer membrane separation, palladium membrane separation, low temperature separation, etc. Compared with other separation technologies, the operating temperature of palladium membrane separation is higher (450-600°C), which can be coupled with the synthesis gas production process, thereby breaking the reaction equilibrium conversion rate, increasing the hydrogen production rate, shortening the process flow, and reducing production equipment ; Palladium membrane can produce high-purity hydrogen containing only ppb-level impurities, especially suitable for fuel cells; in addition, palladium membrane separation is easier to miniaturize than other separation methods.

The transfer of hydrogen in the palladium membrane obeys the so-called "solution-diffusion" (Solution-diffusion) mechanism, which includes the following processes: hydrogen diffuses from the boundary layer to the surface of the palladium membrane; hydrogen decomposes into hydrogen atoms on the membrane surface; Atoms are dissolved by the palladium membrane; hydrogen atoms diffuse from the high pressure side to the low pressure side in the palladium membrane; hydrogen atoms recombine into hydrogen molecules on the low pressure side of the palladium membrane; hydrogen gas diffuses away from the membrane surface. According to the above theory, the penetration rate of hydrogen in the palladium membrane is related to the temperature, thickness, alloy composition of the membrane, and the partial pressure of hydrogen on both sides of the membrane, and can be expressed by Sievert's law:

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;E</span>}}{\mathrm{<span\; class="notranslate">\; RT</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>$

In the formula:

R: Gas constant; T: Temperature; A _: Membrane area; L: Membrane thickness; _E : Activation energy; Coefficient before function; M: transmittance.

Chinese utility model patent (application number: 200720060238.9) discloses a quick-start palladium membrane module using small-scale channels for heat transfer, including a membrane support frame, a porous metal support piece and a palladium alloy membrane, two porous metal support pieces and a palladium alloy membrane They are respectively located on both sides of the supporting frame containing the membrane, and it is characterized in that the supporting frame of the membrane contains the purified hydrogen gas flow channel and the small-scale channel, and the small-scale channel is a heating gas passing through the supporting frame of the membrane. The flow channel of the flow channel has a rectangular cross-section, and the cross-sectional size is 0.2-1.0 mm × 0.2-1.0 mm. The channel inlet and outlet connecting the small-scale channels are set on the support frame containing the membrane; The outlet is arranged on the upper end of the support frame and communicates with the airflow channel. The width of the rectangular toothed hydrogen flow channel is 3-5 mm, the width of the membrane support frame between the channels is 3-5 mm, and the support frame 1 is made of stainless steel; the support frame 1 and the sintered metal support sheet 4 are welded For connection, the palladium alloy film adopts a palladium-silver alloy film, and the thickness of the film is 10-50 microns. The alloy membrane, the metal support frame and the sintered metal support sheet are sealed and connected together by means of metal diffusion, or the edge of the palladium alloy membrane and the metal support frame are sealed together by pressure through a flange.

The suitable operating temperature of the palladium membrane is generally 450-600°C. If the temperature is too low, the transmittance of the palladium membrane will be low; if the temperature is too high, the life of the membrane will be affected. The optimum temperature for hydrogen production from hydrocarbons is often different from the optimum operating temperature for palladium membranes. For example, the typical operating temperature of hydrogen production by steam reforming of natural gas is 800-900°C. Therefore, in the current process of coupling hydrogen separation with palladium membrane to the reforming process of natural gas to produce high-purity hydrogen in one step, if the above-mentioned patented technology is used for processing Since the membrane module is directly exposed to the reaction environment of natural gas reforming hydrogen production without any heat insulation layer on the membrane surface, the temperature of the membrane must be the same as the reaction temperature of hydrogen production. In order to ensure the hydrogen permeability and lifetime of the membrane, the temperature of natural gas reforming must be lowered below 600°C, at the cost of a decrease in the equilibrium conversion rate of natural gas reforming. Another example is methanol reforming for hydrogen production. The typical operating temperature is 200-300°C, which is lower than the suitable working temperature of palladium membrane. If the membrane module processed by the above patented technology is used, the operating temperature for methanol reforming for hydrogen production must be raised. The suitable operating temperature of the membrane is above 450°C, so there is no report on the coupling of methanol reforming hydrogen production and palladium membrane separation process.

Utility model content

In the current application of palladium membrane for hydrogen separation, when it is coupled with hydrogen production process, the reaction temperature of hydrogen-containing synthesis gas production must be the same as the operating temperature of palladium membrane, which greatly limits the application range of palladium membrane. In order to overcome the defects of the application of the above palladium membrane, the utility model provides a palladium membrane module with a membrane operating temperature that can be different from the synthesis gas production reaction temperature and which uses small-scale channel heat exchange and ceramic heat insulation.

The utility model proposes a new palladium membrane application concept: add a layer of porous ceramic plate on the outside of the palladium membrane module as a heat insulation layer, when the reaction temperature on the hydrogen production side is higher than the suitable operating temperature of the palladium membrane (450-600°C) At this time, the reaction temperature of hydrogen production does not have to be lowered to the appropriate operating temperature range of the membrane, but the low-temperature gas is introduced into the small-scale channel of the membrane module to take away the heat transferred from the bed and maintain the operating temperature of the membrane within its appropriate range. . When the reaction temperature on the hydrogen production side is lower than the suitable operating temperature (450-600°C) of the palladium membrane, the reaction temperature of the hydrogen production is maintained at its suitable temperature range, and the high-temperature fluid is passed into the small-scale channel of the membrane module, both Heat is transferred to the bed to maintain the endothermic reaction while maintaining the operating temperature of the membrane within its optimum range.

The utility model purpose is realized through the following technical solutions:

A palladium membrane module using small-scale channel heat exchange and ceramic heat insulation, including a membrane support frame, a porous metal support sheet and a palladium membrane, and porous metal support sheets and palladium membranes are sequentially arranged on both sides of the membrane support frame from inside to outside. Membrane, the membrane support frame contains purified hydrogen gas flow channels and small-scale channels, the small-scale channel is a heating gas circulation channel passing through the membrane support frame, its cross-section is rectangular, and the cross-sectional size is 0.2-1.0 mm ×0.2-1.0 mm, the channel inlet and outlet connecting the small-scale channels are set on the support frame containing the membrane; the hydrogen gas flow channel of the membrane support frame is a combination of two symmetrical rectangular teeth located in the center of the membrane support frame, and the channel width is 3-5 mm, the width of the membrane support frame between the channels is 3-5 mm, the gas outlet is set on the upper end of the support frame, and communicates with the air flow channel; ceramic heat insulation layers are respectively provided on the outer sides of the two palladium membranes.

To further realize the purpose of the utility model, the ceramic heat insulation layer covers the palladium membrane and is fixed on the membrane support frame by bolts. There are four bolts, which are respectively arranged on the four corners of the membrane support frame and the ceramic heat insulation layer. The length and width of the ceramic heat insulation layer are the same as that of the membrane support frame.

The length and width of the ceramic heat insulation layer are the same as that of the membrane supporting frame, and the thickness is 0.5-2 mm. Corresponding to the positions of the round holes around the support frame, there are round holes and long holes near the four corners of the heat insulation layer, which are used to fix the ceramic heat insulation layer on the membrane module with bolts. The long holes can make the ceramic insulation layer have a certain degree of expansion and contraction in the length direction, so as to prevent the thermal expansion and contraction of the ceramics from destroying its structure.

Compared with the prior art, the utility model has the following advantages:

(1) Utilizing the high or low temperature (relative to the temperature of the medium outside the component) fluid flow heat transfer in the small-scale channel and the heat insulation effect of the ceramic layer, the operating temperature of the membrane can be different from the working temperature of the medium outside the component, so that It is ensured that both the membrane operates at its optimal operating temperature and the hydrogen production process outside the module reacts at its optimal temperature.

(2) When the membrane module is started, the temperature of the palladium membrane module can be quickly raised to the required working temperature (generally 450-600°C) by using the flow heat transfer of the thermal fluid in the small-scale channel;

(2) The existence of small-scale heat exchange channels reduces the metal content of the palladium membrane module, further reducing material consumption and heat capacity of the membrane module;

(3) Using a palladium membrane with a thickness as low as 10 microns, high-purity hydrogen can be purified and separated, and the hydrogen permeability is high.

The palladium film described in the utility model refers to palladium and its alloy film, such as palladium-silver alloy film, palladium-copper alloy film and the like.

Description of drawings

Figure 1 is a schematic diagram of the structure of a palladium membrane module using small-scale channel heat exchange and ceramic heat insulation;

Fig. 2 is A-A direction sectional view in Fig. 1;

Fig. 3 is B-B direction sectional view in Fig. 1;

Figure 4 is a schematic cross-sectional view of the supporting frame

5 is a schematic diagram of the connection between the sintered metal support sheet and the support frame;

Fig. 6 is the position schematic diagram of palladium film on support frame;

Fig. 7 is the schematic diagram of ceramic insulation layer;

Fig. 8 is a sectional view along line C-C in Fig. 7 .

Detailed ways

Below in conjunction with accompanying drawing and specific example the utility model is described further. It should be noted that the examples cited are only used to further illustrate the technical features of the utility model, rather than to limit the utility model.

As shown in Figure 1-6, a palladium membrane module using small-scale channel heat exchange and ceramic heat insulation is composed of the following parts from the inside to the outside: membrane support frame 1, porous metal support sheet 4 (quantity: 2 pieces) , palladium film 5 (quantity: 2 pieces), ceramic heat insulation layer 9 (quantity: 2 pieces). Membrane support frame 1 is a stainless steel frame, and its main functions include: A) providing a circulation channel 2 for hydrogen passing through palladium membrane 5 and sintered metal sheet 4; B) providing support for sintered metal sheet 4 to withstand synthesis The gas high pressure on the gas side (generally 1-3MPa); C) contains a small-scale channel 3, and the high-temperature or low-temperature (relative to the temperature of the synthesis gas outside the palladium membrane module) fluid flowing in the channel 3 is used to control the temperature of the palladium membrane. Its optimum operating temperature provides a source of heat or cooling. The small-scale channel 3 is a heating or cooling gas circulation channel that runs through the entire membrane support frame 1. Its cross-section is rectangular, and the cross-sectional size is 0.2-1.0 mm×0.2-1.0 mm. It connects the channel inlet 6 and the outlet of the small-scale channel 3 7 is located on the left and right sides of the upper end of the membrane support frame 1; the hydrogen gas flow channel 2 of the membrane support frame 1 is a combination of two symmetrical rectangular teeth in the center of the membrane support frame 1, the width of the channel is 3-5 mm, and the membrane support between the channels The width of the frame is 3-5 mm, and the gas outlet 8 is arranged on the upper end of the support frame 1 and communicates with the air flow channel 2 . The support frame 1 has round holes 10 near the four corners, which are used to fix the ceramic heat insulation layer 9 on the outside of the membrane module with bolts.

The porous metal support sheet 4 is sintered metal stainless steel, and its function is: A) the pores in the sintered metal sheet provide a passage for the hydrogen passing through the palladium membrane 5 to flow to the channel 2; B) provide support for the palladium membrane 5 on it , withstand the high pressure of the gas on the side of the syngas (generally 1-3MPa). The support frame 1 and the sintered metal support sheet 4 are connected by welding.

The palladium film 5 adopts palladium and its alloy film, and the thickness of the film is 10-50 microns. The palladium film 5, the metal support frame 1 and the sintered metal support sheet 4 can be sealed and connected together by metal diffusion. Molecules diffused with each other, so that the palladium membrane and the supporting frame were closely attached together.

The structure of the ceramic heat insulating layer 9 is shown in Fig. 7-8. Its length and width are the same as the membrane support frame, and its thickness is 0.5-2mm. Corresponding to the positions of the round holes 10 around the support frame 1, there are round holes 11 and long holes 12 around the ceramic heat insulating layer 9, which are used to fix the ceramic heat insulating layer 9 on the membrane module with bolts. The long holes 12 can make the ceramic insulation layer have a certain degree of expansion and contraction in the length direction, so as to prevent the thermal expansion and contraction of ceramics from destroying its structure.

When preheating the membrane module, the high-temperature gas is introduced into the small-scale channel 3 through the small-scale channel inlet 6, and the heat transfer of the high-temperature gas in the small-scale channel 3 is used to transfer heat to the support frame 1 to raise the temperature, and the heat transfer of the high-temperature gas is completed Finally, the small-scale channel 3 flows out through the outlet 7. When the membrane module is coupled to a hydrogen production reactor to produce high-purity hydrogen in one step, if the suitable temperature of the hydrogen production reaction is higher than the suitable operating temperature of the membrane (450-600°C), such as the steam reforming process of natural gas, it is suitable The reaction temperature is 700-800°C. At this time, low-temperature water vapor can be introduced into the small-scale channel 3. Since the ceramic heat-insulating layer 9 has a low thermal conductivity, a relatively small space is formed on both sides of the ceramic heat-insulating layer 9. The large temperature gradient makes the outer side (near the reforming reaction side) 700-800°C suitable for reforming reaction, while the inner side (closer to the palladium membrane side) is 450-600°C suitable for membrane separation, so as to ensure that the palladium membrane 5 The operating temperature is still maintained at 450-600°C. If the suitable temperature of the hydrogen production reaction is lower than the suitable operating temperature (450-600°C) of the membrane, such as the steam reforming process of methanol, the suitable reaction temperature is 200-300°C, at this time, the small-scale channel 3 can be passed through Inject high-temperature fluid, because the ceramic insulation layer 9 has a lower thermal conductivity, a larger temperature gradient is formed on both sides of the ceramic insulation layer 9, so that the inner side (near the palladium membrane side) is a 450 °C suitable for membrane separation. -600°C, the outer side (near the reforming reaction side) is 200-300°C suitable for reforming reaction, to ensure that the operating temperature at the palladium membrane 5 is still maintained at 450-600°C, on the other hand, it can also absorb heat to the The reaction provides part of the heat.

Claims (6)

1. A palladium membrane module using small-scale channel heat exchange and ceramic heat insulation, including a membrane support frame, a porous metal support sheet and a palladium membrane, and porous metal support sheets are sequentially arranged on both sides of the membrane support frame from inside to outside and a palladium membrane, the membrane supporting frame contains a purified hydrogen gas flow channel and a small-scale channel, and the small-scale channel is a heating gas circulation channel passing through the inside of the membrane supporting frame, and its cross-section is rectangular, with a cross-sectional size of 0.2- 1.0 mm × 0.2-1.0 mm, the channel inlet and outlet connecting the small-scale channels are set on the support frame containing the membrane; the hydrogen gas flow channel of the membrane support frame is a combination of two symmetrical rectangular teeth located in the center of the membrane support frame, and the channel width is 3 -5 mm, the width of the membrane support frame between the channels is 3-5 mm, the gas outlet is set on the upper end of the support frame, and communicates with the air flow channel; it is characterized in that ceramic heat insulation layers are respectively provided on the outer sides of the two palladium membranes. 2. A palladium membrane module using small-scale channel heat exchange and ceramic heat insulation according to claim 1, characterized in that: the ceramic heat insulation layer covers the palladium membrane and is fixed on the membrane support frame by bolts. 3. A palladium membrane module using small-scale channel heat exchange and ceramic heat insulation according to claim 2, characterized in that: there are four bolts, which are respectively arranged on the four sides of the membrane support frame and the ceramic heat insulation layer. on a corner. 4. A palladium membrane module using small-scale channel heat exchange and ceramic heat insulation according to claim 1, characterized in that: the length and width of the ceramic heat insulation layer are the same as the membrane support frame. 5. A palladium membrane module using small-scale channel heat exchange and ceramic heat insulation according to any one of claims 1-4, characterized in that the thickness of the ceramic heat insulation layer is 0.5-2 mm. 6. A palladium membrane module using small-scale channel heat exchange and ceramic heat insulation according to claim 1, characterized in that: the upper and lower ends of the ceramic heat insulation layer near the four corners are respectively provided with circles holes and slots.

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