CN101372314A - Method and device for producing high-purity hydrogen from hydrogen-containing synthesis gas using palladium membrane - Google Patents

Abstract

The invention relates to a method which adopts a palladium membrane to produce high-purity hydrogen from hydrogen-containing synthetic gas and a device. In the method, synthetic gas which contains water vapor and hydrogen and is produced by an upstream hydrogen making reactor is firstly sent to a cooler, the cooled synthetic gas enters a gas-liquid separator, after dehydration, the synthetic gas enters a primary heater and is heated in the heater, the heated synthetic gas enters a secondary heater and heated to the temperature of 450-600 DEG C, the heated synthetic gas enters a palladium membrane separator, and most of hydrogen in the synthetic gas permeates the palladium membrane separator to become the high-purity finished hydrogen. A pipeline of the device which connects a heat exchanger and the palladium membrane separator is sequentially provided with the gas-liquid separator, the primary heater and the secondary heater, the palladium membrane separator is connected with a burner by the primary heater, and the burner is also connected with the secondary heater. The invention has simple design and high hydrogen separation efficiency of the palladium membrane and provides a new technical method for efficient production of high-purity hydrogen.

Description

Method and device for producing high-purity hydrogen from hydrogen-containing synthesis gas using palladium membrane

Technical field:

The invention relates to a process for producing high-purity hydrogen from hydrogen-containing synthesis gas, in particular to a method and device for preparing high-purity hydrogen by using palladium membrane separation.

Background technique

At present, 90% of the hydrogen in the world comes from the reforming of hydrocarbons (natural gas, coal, biomass, etc.), purification after chemical processes such as gasification or cracking, 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, palladium membrane separation can produce high-purity hydrogen containing only ppb-level impurities, which is especially suitable for fuel cells; in addition, the palladium membrane separation device occupies a small area and 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.

There are two main methods of using palladium membrane separation to produce hydrogen: A) The membrane module is coupled with the hydrogen production reactor to form a membrane reactor, and the reactor is used to react and separate the raw material gas to obtain high-purity hydrogen in one step. . The coupling of membrane separation and reaction process can break the thermodynamic balance of the reaction, making the reaction favor the direction of hydrogen production. However, due to the addition of membrane separation components in the reactor, the structure of the reactor is complex, the palladium membrane is in direct contact with the reaction medium and the catalyst, the operating conditions are relatively harsh, and the life of the palladium membrane is short. B) Palladium membrane separation is separated from the hydrogen production reactor. The hydrogen production reactor produces hydrogen-containing synthesis gas, and its downstream adopts palladium membrane separation to obtain high-purity hydrogen. This method is simple in process and convenient in operation and maintenance. In the process of steam reforming of hydrocarbons widely used in industry to produce synthesis gas, in order to prevent carbon deposition on the catalyst and improve the conversion rate of hydrocarbons, the water vapor is often in excess, resulting in the synthesis gas containing more than 30% steam. According to Sievert's Law of palladium membrane separation, the power of palladium membrane separation mainly comes from the difference of hydrogen partial pressure inside and outside the membrane, and when the total pressure of synthesis gas remains unchanged, the existence of a large amount of water vapor in the synthesis gas greatly reduces The partial pressure of hydrogen in the synthesis gas is reduced, thereby reducing the efficiency of membrane separation to produce hydrogen. As shown in Figure 2, in the traditional direct membrane separation process, the synthesis gas generated by the upstream hydrogen production reactor directly enters the heat exchanger 1 through the pipeline P21 to exchange heat to the working temperature of the membrane separator (450-600°C); from the heat exchange The output from device 1 enters the membrane separator 5 through pipeline P22, the product hydrogen is transported downstream through pipeline P23, the tail gas is transported to burner 6 through pipeline P24 for combustion, and the generated flue gas is transported upstream through pipeline 26 to generate water vapor. There are two problems in this process. One is that the water vapor content in the mixed gas is high, which reduces the separation efficiency of the palladium membrane. The second is that the heat energy cannot be effectively utilized and the energy consumption is high.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a high-efficiency hydrogen separation and energy-saving method for producing high-purity hydrogen from hydrogen-containing synthesis gas using a palladium membrane.

Another object of the present invention is to provide a device for realizing the above-mentioned method for producing high-purity hydrogen from hydrogen-containing synthesis gas by utilizing palladium membrane.

The purpose of the present invention is achieved through the following technical solutions:

A method for producing high-purity hydrogen from hydrogen-containing synthesis gas by using a palladium membrane, comprising the steps of:

(1) The synthesis gas containing water vapor and hydrogen produced from the upstream hydrogen production reactor first enters the cooler and is lowered to 75-85°C. The cooled synthesis gas enters the gas-liquid separator to realize the condensation of water vapor and the synthesis gas separation;

(2) The syngas after water removal enters the primary heater, and the syngas is heated to 250-350°C in the heater. The heating medium of the heater is the high-temperature tail gas after the hydrogen is separated through the palladium membrane; the heated syngas Entering the secondary heater, the syngas is heated to 450-600°C, and the heating medium is the flue gas formed by the combustion of the tail gas passing through the primary heater;

(3) The heated synthesis gas enters the palladium membrane separator, and most of the hydrogen in the synthesis gas passes through the palladium membrane separator to become high-purity product hydrogen; the high-temperature tail gas enters the primary heater to heat the synthesis gas after water removal.

The heat exchange medium in the step (1) is cold water, and the cold water becomes water vapor after heat exchange, which is used as process water vapor for upstream hydrocarbon reforming.

A device for producing high-purity hydrogen from hydrogen-containing synthesis gas using a palladium membrane, comprising a heat exchanger, a palladium membrane separator, and a burner, the heat exchanger is connected to the palladium membrane separator, and the palladium membrane separator is connected to the burner, It is characterized in that: the pipeline connecting the heat exchanger and the palladium membrane separator is sequentially provided with a gas-liquid separator, a primary heater and a secondary heater, and the palladium membrane separator is connected to the burner through the primary heater, The burner is also connected to a secondary heater.

The invention aims at the situation that a large amount of water vapor in the synthesis gas reduces the separation efficiency of the palladium membrane when the palladium membrane separator is used alone to produce high-purity hydrogen from the hydrogen-containing synthesis gas, and a heat exchanger is used to reduce the temperature of the synthesis gas, thereby reducing the temperature of the synthesis gas. In order to reduce the water vapor content in the reactor, the dewatered synthesis gas is reheated into the palladium membrane separator to produce high-purity hydrogen. The invention has simple design, high hydrogen separation efficiency of the palladium membrane, and provides a new process method for efficient production of high-purity hydrogen.

Compared with the existing membrane separation technology for producing hydrogen, the present invention has the following advantages:

(1) Before the hydrogen-containing synthesis gas enters the membrane separator, a large amount of water vapor contained in the synthesis gas is removed, which improves the efficiency of membrane separation. Compared with the traditional process, under the same hydrogen production rate, the membrane area required for separation can be reduced and the cost can be saved.

(2) The present invention adopts the mode of energy integration when removing the water vapor in the synthesis gas, utilizes the high-temperature synthesis gas to produce the water vapor required in the upstream hydrogen production process, and utilizes the sensible heat and combustion heat of the tail gas of the palladium membrane separator to generate The synthesis gas after water removal is heated to improve the energy utilization efficiency.

Description of drawings

Figure 1 is a schematic diagram of a device for producing high-purity hydrogen from hydrogen-containing synthesis gas using a palladium membrane.

Figure 2 is a schematic diagram of a conventional device for producing high-purity hydrogen directly by palladium membrane separation.

Detailed ways

In order to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with the examples and accompanying drawings. It should be noted that the examples are not intended to limit the protection scope of the present invention.

As shown in Figure 1, the device for producing high-purity hydrogen from hydrogen-containing synthesis gas using a palladium membrane includes a cooler 1, a gas-liquid separator 2, a primary heater 3, a secondary heater 4, a palladium membrane separator 5 and burner6. The pipelines P01, P02, P04, and P06 that circulate the hydrogen-containing synthesis gas are sequentially connected to the cooler 1, the gas-liquid separator 2, the primary heater 3, the secondary heater 4, and the palladium membrane separator 5; the cooling water of the cooler 1 It enters through pipeline P13 and flows out through pipeline P14. The condensed water separated in the gas-liquid separator 2 is discharged through the pipeline P03. The high-purity hydrogen gas produced by the palladium membrane separator 5 is drawn out through the pipeline P07, and the tail gas is connected to the primary heater 3 and the burner 6 in sequence through the pipelines P08 and P09. The pipeline P10 introduces the air required for the combustion of the burner 6, and the high-temperature flue gas generated by the combustion of the burner 6 is introduced into the secondary heater 4 through the pipeline P11, and is connected to the downstream through the pipeline P12 for reuse.

The cooler 1 , the primary heater 3 and the secondary heater 4 of the present invention can all adopt sleeve-and-tube heat exchangers, and also can adopt plate-type, shell-and-tube, and shell-and-tube heat exchangers. The gas-liquid separator is a pressure vessel, which is a general-purpose gas-liquid separator that meets the process requirements (pressure, temperature). The palladium membrane separator 5 is a pressure vessel containing a palladium membrane module for separating hydrogen. The design of the membrane module is detailed in patent application 200710031743.5. The burner 6 is an atmospheric burner or a flameless burner.

Example: Separation and purification of hydrogen in kilowatt-level fuel cell hydrogen supply system

The hydrogen source of the proton exchange membrane fuel cell requires high purity hydrogen, especially for the content of CO. Pure hydrogen with impurities at the ppb level can be obtained by palladium membrane separation, and the palladium membrane separation volume is small, which is suitable for application Small home fuel cell power station.

Synthesis gas is produced by steam reforming of natural gas, and the reactor can be a conventional fixed-bed reactor, a new fluidized-bed reactor, a microchannel reactor, etc. The syngas composition is the composition of the gas when the reaction reaches equilibrium. The reaction raw gas flow rate is as follows: natural gas (according to methane): 0.280kg/h, water vapor: 0.944kg/h, reaction temperature: 700°C; reaction pressure: 1.1MPa; then its outlet (P01) synthesis gas molar composition is as follows : CH4: 7.9%; H ₂ O: 39.5%; H ₂ : 41.2%; CO: 4.5%; CO ₂ : 69%; it can be seen that the syngas contains about 40% water vapor by volume, and the hydrogen partial pressure is 0.453MPa .

The hydrogen separation process shown in Figure 1 is adopted. ASPEN Plus software was used to simulate and calculate the process data of the medium in each pipe section in Figure 1, such as temperature and pressure, as shown in Table 1.

In this example, in order to reduce the water vapor content and increase the hydrogen partial pressure, the synthesis gas in the pipeline P01 is first passed into the cooler 1 . Under the action of the cooler 1, the temperature of the syngas is reduced to 83°C. The heat-exchanging medium is cold water, and the cold water becomes water vapor after being heated, which is used as process water vapor for steam reforming reaction of natural gas upstream. The cooler adopts a tube-and-tube heat exchanger, the synthesis gas enters the shell side, and the cooling water goes through the tube side. The heat exchange area is 0.0027m ² and the heat exchange capacity is 0.62kw.

The cooled synthesis gas enters the gas-liquid separator 2 through the pipeline P02, 90% of the water in the synthesis gas is separated from the gas-liquid separator, and the condensed water is discharged through the pipeline P03. The gas-liquid separator is a pressure vessel, the material is 316L stainless steel, the design pressure is 1.2MPa, the design temperature is 100°C, and automatic drainage facilities are installed.

The volume content of hydrogen in the syngas after water removal increases from 41.2% to 65.0%, and the partial pressure increases from 0.453MPa to 0.715MPa. The syngas enters the primary heater 3 through the pipeline P04, and the syngas is heated to 324°C. The heating medium of the heater is the high-temperature tail gas after the hydrogen is separated through the palladium membrane, and the temperature of the tail gas is reduced from 600 °C to 180 °C. The primary heater 3 adopts a sleeve-type heat exchanger, the synthesis gas enters the shell side, and the high-temperature exhaust gas goes through the tube side, with a heat transfer area of 0.009m ² and a heat transfer capacity of 0.128kw.

The syngas leaving the primary heater 3 enters the secondary heater 4 through line P05, where the syngas is heated to 600°C. The heating medium of the heater is the flue gas formed by the combustion of the tail gas passing through the primary heater 3, and the temperature of the flue gas is reduced from 1000°C to 765°C. The heater 4 adopts a sleeve-type heat exchanger, the synthesis gas enters the shell side, and the high-temperature flue gas goes through the tube side, with a heat exchange area of 0.00043m ² .

The hydrogen-containing synthesis gas heated to 600°C enters the palladium membrane separator 5 through the pipeline P06. Here, most of the hydrogen in the synthesis gas passes through a palladium membrane separator into high-purity product hydrogen. The palladium membrane separator 5 is a pressure vessel containing a palladium membrane module (as introduced in Chinese invention patent application 200710031743.5), with a design pressure of 1.2MPa and a design temperature of 650°C. The palladium membrane in the palladium membrane module adopts palladium (75%) silver (25%) alloy membrane, the membrane thickness is 25μm, the membrane area is 0.018m ² , the hydrogen output is 0.06kg/h, and the hydrogen recovery rate is 80%.

The tail gas from which most of the hydrogen is removed in the palladium membrane separator 5 enters the primary heater 3 through the pipeline P08, the temperature drops to 180°C, and enters the burner 6 through the pipeline P09 for combustion. The high-temperature flue gas after combustion enters the secondary heater 4 through the pipeline P11 to heat the hydrogen-containing synthesis gas, and the temperature drops from 1000°C to 765°C. The low-temperature flue gas is sent to the upstream hydrogen production system through the pipeline P12, which can be used for the hydrogen production reaction The appliance provides heat.

If the traditional direct membrane separation process as shown in Figure 2 is adopted, the synthesis gas generated by the upstream hydrogen production reactor directly enters the cooler 1 through the pipeline P21 and is cooled to the optimum working temperature of the membrane separator of 450-600°C; 1 comes out and enters the membrane separator 5 through the pipeline P22, the hydrogen is transported to the downstream by the pipeline P23, the tail gas is transported to the burner 6 by the pipeline P24 for combustion, and the flue gas produced is transported to the upstream through the pipeline 26 to generate water vapor. The pipe P25 introduces the air required for the combustion of the burner 6 . If the composition of the synthesis gas in the pipeline P21 is the same as that in P01 in Figure 1, then to achieve the same hydrogen production of 0.06kg/h as in the above example, the required total membrane area is 0.046m ² , which is different from the traditional Compared with the membrane separation process, the invention can reduce the area of the palladium membrane to 39% of the original.

From the above comparison, it can be seen that by cooling the synthesis gas entering the membrane separator, the water component in the synthesis gas can be effectively removed, the partial pressure of hydrogen in the synthesis gas can be increased, and the efficiency of membrane separation can be improved.

Claims (7)

1. a method utilizing palladium membrane to produce high-purity hydrogen from hydrogen-containing synthesis gas, is characterized in that comprising the steps: (1) The synthesis gas containing water vapor and hydrogen produced from the upstream hydrogen production reactor first enters the cooler and is lowered to 75-85°C. The cooled synthesis gas enters the gas-liquid separator, and the water vapor is condensed and separated from the synthesis gas ; (2) The syngas after water removal enters the primary heater, and the syngas is heated to 250-350°C in the heater. The heating medium of the heater is the high-temperature tail gas after the hydrogen is separated through the palladium membrane; the heated syngas Entering the secondary heater, the syngas is heated to 450-600°C, and the heating medium is the flue gas formed by the combustion of the tail gas passing through the primary heater; (3) The heated synthesis gas enters the palladium membrane separator, and most of the hydrogen in the synthesis gas passes through the palladium membrane separator to become high-purity product hydrogen; the high-temperature tail gas enters the primary heater to heat the synthesis gas after water removal. 2. the method for utilizing palladium membrane to produce high-purity hydrogen from hydrogen-containing synthesis gas according to claim 1, is characterized in that: the medium of described step (1) heat exchange is cold water, and cold water becomes steam after heat exchange , as process steam for upstream hydrocarbon reforming. 3. the device that realizes the utilization palladium membrane of method described in claim 1 to produce high-purity hydrogen from hydrogen-containing synthesis gas comprises heat exchanger, palladium membrane separator, burner, and described heat exchanger is connected with palladium membrane separator , the palladium membrane separator is connected with the burner, and it is characterized in that: the pipeline connecting the heat exchanger and the palladium membrane separator is successively provided with a gas-liquid separator, a primary heater and a secondary heater, and the palladium membrane separates The burner is connected to the burner through the primary heater, and the burner is also connected to the secondary heater. 4. The device for producing high-purity hydrogen from hydrogen-containing synthesis gas using palladium membrane according to claim 3, characterized in that: the cooler is a sleeve-type, plate-type, tube-and-tube or shell-and-tube heat exchange device. 5. The device for producing high-purity hydrogen from hydrogen-containing synthesis gas by using palladium membrane according to claim 3, characterized in that: the primary heater is a casing type, a plate type, a shell-and-tube type or a shell-and-tube type. heater. 6. The device for producing high-purity hydrogen from hydrogen-containing synthesis gas using palladium membrane according to claim 3, characterized in that: the secondary heater is a casing type, a plate type, a shell-and-tube type or a shell-and-tube type Heat Exchanger. 7. The device for producing high-purity hydrogen from hydrogen-containing synthesis gas by using palladium membrane according to claim 3, characterized in that: the burner is an atmospheric burner or a flameless burner.

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