JP2002255506A - Production method for high purity hydrogen from heavy hydrocarbon fuel and its apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method and an apparatus therefor which manufacture high purity hydrogen easily and certainly from a heavy hydrocarbon fuel. SOLUTION: A first stage steam reforming part 1 carries out a steam reforming reaction by adding steam to a desulfurized heavy hydrocarbon fuel with a first reforming catalyst 2, and the generated gas which is generated in the first stage steam reforming part 1 comes to an equilibrium state with a shift reaction and a methanation reaction having a second reforming catalyst 6 and a hydrogen selective permeable membrane 7, and in this state, only hydrogen is extracted from the reaction field, and a second stage reforming part 5 depresses a hydrogen partial pressure by adding steam to the side of this extracted hydrogen, and a vapor-liquid separator 10 removes the steam added to the extracted hydrogen by cooling. The high purity hydrogen can be manufactured from the heavy hydrocarbon fuel by the second stage reforming, easily and on a large scale, and it is easily used for fuel cells, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing hydrogen from a heavy hydrocarbon fuel by a steam reforming reaction, and more particularly to a method for producing high-purity hydrogen from a heavy hydrocarbon fuel such as kerosene, naphtha and gasoline. The present invention relates to a method and an apparatus for producing with high yield.

[0002]

2. Description of the Related Art Conventionally, in this kind, FIG.
As shown in FIG. 2, a desulfurized heavy hydrocarbon fuel and steam are supplied to a reforming unit 102 having a nickel-based or noble metal-based catalyst and being heated to 650 ° C. to 850 ° C. by receiving heat supply from a combustion unit 101. After steam reforming is performed here, the generated gas generated by the steam reforming is temporarily cooled to 200 ° C. to 30 ° C.
After cooling to 0 ° C., CO and H 2 O are converted into H 2 and CO 2 by passing through a copper-zinc catalyst in the CO shift unit 103, and then cooled to 100 ° C. to 150 ° C. to oxidize CO. In the unit 104, the remaining CO is further converted to CO2 by passing through a catalyst such as a noble metal system, and supplied to the hydrogen utilization unit 105 such as a fuel cell in a state where hydrogen and each gas are mixed. .

[0003] Table 1 below shows an example of the production of this conventional example. However, for the sake of simplicity, in these calculations, it is assumed that the fuel conversion rate in the reforming section is 100%, heat loss other than exhaust heat from combustion exhaust gas is ignored, and the heat exchange rate in heat recovery is 100%.

[Table 1]

On the other hand, for example, Japanese Patent Laid-Open No. 4-321
As disclosed in JP-B-502, a reformer having a hydrogen selective permeable membrane of a palladium alloy is used to perform an equilibrium reaction while supplying an inert gas such as steam downstream of the permeable membrane.
Some produced hydrogen from hydrocarbons such as city gas.

[0005]

By the way, first, in the former shown in FIG. 2, hydrogen is partially oxidized in the CO oxidizing section 104, thereby lowering the yield of hydrogen.
In addition, not only hydrogen but also other gases are supplied to the hydrogen utilization unit 105, and a special device is required to remove the gas. Also, particularly when CO is mixed, the electrode portion is not used in the polymer electrolyte fuel cell. Was a cause of poisoning.

[0006] In the latter, the above-mentioned disadvantages are solved, but this configuration does not limit the fuel to hydrocarbons, but mainly considers city gas, which is directly used for kerosene or the like. There are many problems when applied to heavy hydrocarbon fuels. For example, in steam reforming of kerosene, if hydrogen is removed during reforming, the hydrogen partial pressure in the reformed gas will decrease, and the dehydrogenation reaction of the fuel will be excessively promoted, which will easily cause carbon deposition and reforming. This leads to catalyst deterioration. Further, when the methane conversion rate is reduced for the same reason, there is a problem that hydrocarbon components other than methane are adsorbed on the surface of the hydrogen selective permeable membrane made of a palladium alloy, causing deterioration of the hydrogen permeable performance. Was.

[0007]

In order to solve the above-mentioned problems, the present invention focuses on this point. In particular, the present invention is directed to a method of adding a plurality of heavy hydrocarbon fuels by adding steam to a desulfurized heavy hydrocarbon fuel. A steam reforming step of performing a steam reforming reaction to decompose into a gas, and a gas produced by the steam reforming step is subjected to a shift reaction and a methanation reaction to be in an equilibrium state, and only hydrogen is removed from the reaction field in this state, An equilibrium reaction step of adding water vapor to the withdrawn hydrogen side to lower the hydrogen partial pressure;
A cooling step of removing steam added to the extracted hydrogen, and performing a two-stage reforming.

[0008] Further, a first-stage reforming section for performing steam reforming reaction by adding steam to a desulfurized heavy hydrocarbon fuel having a first reforming catalyst, and a product gas generated in the first-stage reforming section, Second
It has a reforming catalyst and a hydrogen selective permeable membrane, and performs a shift reaction and a methanation reaction to make an equilibrium state. In this state, only hydrogen is extracted from the reaction field, and steam is added to the extracted hydrogen side to reduce the hydrogen partial pressure. It is provided with a reforming two-stage section and a gas-liquid separator that cools and removes the steam added to the extracted hydrogen, and performs two-step reforming.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A desulfurized heavy hydrocarbon fuel, for example, kerosene and steam are introduced into a system by a pressure pump 4 and steam-reformed in a first-stage reforming section 1 having a first reforming catalyst 2. A shift reaction of converting the generated gas into a second reforming section 5 having a second reforming catalyst 7 and a hydrogen selective permeable membrane 8 to convert carbon monoxide and water into carbon dioxide and hydrogen; Equilibrate with the methanation reaction to convert methane and water to carbon monoxide and hydrogen, separate only hydrogen from this high pressure reaction field by hydrogen selective permeable membrane 8, and further convert water vapor to the separated downstream hydrogen. By adding and lowering the partial pressure of hydrogen, hydrogen can be more easily released. Finally, by cooling with a gas-liquid separator to remove the added water vapor, only hydrogen can be obtained in high yield, and high-purity hydrogen can be obtained. 8 can be supplied to a hydrogen utilization unit 11 such as a fuel cell. The impermeable gas from which most of the hydrogen has been removed is directly supplied to the combustion unit 3 and used as fuel for heating the reforming first-stage unit 1 and the reforming second-stage unit 5. .

Therefore, the reforming is divided into two stages, namely, steam reforming and equilibrium reforming in which an equilibrium reaction is performed while removing hydrogen, and the partial pressure of hydrogen is reduced by adding steam to hydrogen on the permeation side. This makes it possible to relatively easily produce only a large amount of high-purity hydrogen from a heavy hydrocarbon fuel with a high yield. There are no problems such as poor performance.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydrogen production apparatus according to the present invention will be described with reference to an embodiment shown in FIG. Reference numeral 1 denotes a first-stage reforming section for performing a steam reforming step, which is filled with a nickel-based or noble metal-based first reforming catalyst 2 and receives heat supply from a combustion section 3 to reach 400 ° C. to 600 ° C. The fuel is heated to a desulfurized heavy hydrocarbon fuel, and here kerosene vapor is supplied, and high-temperature steam is supplied. The pressurized pump 4 pressurizes the system to about 3 to 20 atm. The reforming is performed to obtain mainly H2, CO, CO2, H2O, and CH4 product gases.

Reference numeral 5 denotes a reforming two-stage section for performing an equilibrium reaction step. The generated gas generated in the reforming first-stage section 1 is allowed to flow while maintaining a high pressure and further maintaining a temperature. And a hydrogen selective permeable membrane 7 mainly composed of an inorganic thin film such as a palladium alloy is inserted into the second reforming catalyst 6 to convert carbon monoxide and water into carbon dioxide. Equilibrium between the shift reaction to convert carbon and hydrogen and the methanation reaction to convert methane and water to carbon monoxide and hydrogen. In these equilibrium states, only hydrogen is permeated and separated from the high-pressure reaction field, resulting in high purity. This is for extracting hydrogen 8.

Reference numeral 9 denotes a water circulation circuit, which includes a circulation pump 11 for circulating water in a gas-liquid separator 10 for performing a cooling process, and a water evaporator 12 for receiving a supply of water from the circulation pump 11.
Receiving heat supply from the outside, the circulating water is converted into steam by the heat, and steam is ejected from the steam ejection section 13 on the downstream side of the hydrogen selective permeable membrane 7 of the second reforming section 5, and passed through the first cooling section 14. The cooling is performed in order to return to the gas-liquid separator 10. When the combustion gas energy from the combustion unit 3 is excessive in the process design, the heat may be used.

The hydrogen permeated through the hydrogen selective permeable membrane 7 is reduced in hydrogen partial pressure by the addition of water vapor, so that a large amount of hydrogen can pass through the hydrogen selective permeable membrane 7 from the pressurized upstream. Finally, only the water vapor is cooled and returned to the gas-liquid separator 10, and the high-purity hydrogen 8 is supplied to a hydrogen utilization unit 15 such as a fuel cell.

Reference numeral 16 denotes a supply path for supplying the non-permeate gas remaining in the second reforming section 5 to the combustion section 3 and burning it as fuel.

Reference numeral 17 denotes a second cooling unit for cooling the exhaust gas discharged from the combustion unit 1 to lower the exhaust gas temperature. First,
The second cooling units 14 and 17 not only cool the main gas, but also utilize the exchanged heat to contribute to the vaporization of water and fuel used in each unit, prevent wasteful heat radiation, and improve heat efficiency. It is a good device.

Next, the operation of the embodiment of the present invention will be described. By supplying the desulfurized kerosene steam and steam to the reforming first-stage unit 1 and performing steam reforming,

(Equation 1) Are produced, and the produced gas is supplied to the reforming two-stage section 5 while maintaining the temperature and the pressure.

Further, in the second reforming section 5, below the second reforming catalyst 6,

(Equation 2) Is predominant, but by pressurizing the entire upstream side of the hydrogen selective permeable membrane 7, hydrogen is extracted from the reforming two-stage section 5, and the upper equilibrium reaction shifts to the right, and hydrogen generation is promoted. You.

The extracted hydrogen is added to the water evaporator 12.
Of the water circulation circuit 9 generated in
, The partial pressure of hydrogen is reduced, and hydrogen is easily released from the upstream side of the hydrogen selective permeable membrane 7 under pressure, so that a large amount of hydrogen is obtained. Further, the hydrogen added with the steam is cooled in the first cooling unit 14 and also cooled in the gas-liquid separator 10 to liquefy and remove only the steam, and the high-purity hydrogen 8 is used in the hydrogen using unit 15. Things.

Further, the impervious gas from which most of the hydrogen has been removed is supplied to the combustion section 3 via the supply path 16 as it is, and the steam reforming in the first reforming section 1 and the second reforming section 5 is performed. It is used as a part of fuel for heat supply for quality.

The chemical equilibrium gas composition at the outlet of the first reforming stage 1 has, for example, an equilibrium conversion at 550 ° C. of only about 56% under the conditions shown in FIG. However, even with a gas having such a composition, chemical equilibrium shifts to the hydrogen generation side by removing only hydrogen from the reaction field by the hydrogen selective permeable membrane 7 as shown in the reforming second-stage section 5, and FIG. As shown, 550
When the hydrogen of about 1.8 times the equilibrium flow rate of hydrogen at that temperature is removed from the equilibrium state while reducing the hydrogen partial pressure on the downstream side of the permeable membrane 7, the conversion can be improved to 91%. The yield is 70% as pure hydrogen. This conversion corresponds to a temperature exceeding 700 ° C. in light of the equilibrium conversion in FIG. Therefore, in this case, the reforming temperature can be reduced by 150 ° C. or more, and the situation in which a high-cost heat-resistant material has to be used due to the conventional high-temperature reforming process can be greatly improved. The cost of the entire porcelain can be reduced and a more reliable design can be achieved.

Here, in FIG. 3, the equilibrium conversion is calculated based on the assumption that the hydrocarbon content in kerosene is decomposed to 100% methane, and the conversion for methane is calculated.
The amount of hydrogen that is the target of the hydrogen yield is based on the equilibrium flow rate itself without using the hydrogen selective permeable membrane 7 and the like. I have. The conversion rate in FIG.
The calculation for methane in the non-permeate gas at the outlet, the hydrogen for which the target of hydrogen yield is pure hydrogen obtained through the hydrogen selective permeable membrane 7, And different. The hydrogen removal amount on the horizontal axis is a dimensionless flow based on the equilibrium flow at 550 ° C.

Table 2 below shows a production example of this embodiment. Although the reforming heat efficiency is 0.77, which is not much different from the conventional example of 0.76, this example has a high purity hydrogen. Which is greatly different from the hybrid gas of the conventional example. Further, the reforming temperature can be greatly reduced as compared with the conventional example, and the thermal restriction of the constituent members can be greatly reduced. The assumptions in the calculation are the same as in Table 1.

[Table 2]

The reason why the first reforming section 1 is not heated to a high temperature as in the conventional example is that it is sufficient if the hydrocarbon fuel can be decomposed into methane by steam reforming. Two-stage reformer 5
This is because the effect of the hydrogen selective permeable membrane 7 can promote the production of hydrogen using methane as a raw material.

Therefore, in the two-stage reforming of steam reforming and equilibrium reforming in which an equilibrium reaction is performed while removing hydrogen, it is relatively easy to obtain only high-purity hydrogen from heavy hydrocarbon fuel by dividing reforming. Can be produced in good yield, and by adding steam to permeated hydrogen, a large amount of hydrogen can be obtained efficiently by lowering the hydrogen partial pressure. The permeated gas is used directly as fuel, and its combustion heat is used as a heating source for steam reforming, so energy loss is suppressed and efficiency is improved. There is no one.

In this embodiment, kerosene has been described as an example. However, the present invention is not limited to this, and high-purity hydrogen can be similarly obtained with naphtha, gasoline and the like. Further, in this embodiment, since the reforming first-stage portion 1 and the reforming second-stage portion 5 are formed in one device, there is an effect that the entire device can be made compact. However, the present invention is not limited to this. However, the effect of the present invention does not change, and the configuration is not limited to this embodiment.

[0027]

As described above, according to the present invention, two-stage reforming of steam reforming and equilibrium reforming in which an equilibrium reaction is carried out while removing hydrogen is performed. Hydrogen can be produced relatively easily and in large quantities, and the generated hydrogen does not contain impurities such as CO. Therefore, it is possible to reduce the cost of, for example, the electrodes of a fuel cell, and it is more inexpensive and obtainable. Since hydrogen is easily produced from an easy fuel, the future development of hydrogen utilization equipment such as a fuel cell can be expected.

Further, due to the effect of hydrogen separation by the hydrogen selective permeable membrane, the reforming temperature can be lowered by 150 ° C. to 300 ° C. as compared with the prior art, and the cost of various heat-resistant materials can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a hydrogen production apparatus to which an embodiment of the present invention is applied.

FIG. 2 is a schematic configuration diagram of the conventional example.

FIG. 3 is a diagram showing temperature characteristics of general equilibrium conversion and hydrogen yield.

FIG. 4 is a diagram showing a hydrogen removal characteristic of a conversion rate and a hydrogen yield by a reaction using the hydrogen selective permeable membrane of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reforming first-stage section 2 first reforming catalyst 5 reforming 2-stage section 6 second reforming catalyst 7 hydrogen selective permeable membrane 10 gas-liquid separator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA41 JA02C MA03 MB04 MC02 MC02X PA01 PB18 PB62 PB63 PB64 PB65 PB67 PB68 PC80 4G040 EA04 EA06 EB01 EB18 EB31 EB32 FA02 FB02 FC01 FE01 4G140 EA04 EB01 EB01 5H027 BA05

Claims (2)

[Claims] 1. A steam reforming step of adding steam to a desulfurized heavy hydrocarbon fuel to perform a steam reforming reaction for decomposing the heavy hydrocarbon fuel into a plurality of gases; The gas is subjected to a shift reaction and a methanation reaction to obtain an equilibrium state. In this state, only hydrogen is extracted from the reaction field, and steam is added to the extracted hydrogen side to reduce the hydrogen partial pressure. A method for producing high-purity hydrogen from heavy hydrocarbon fuel, comprising a cooling step of removing steam added to hydrogen, and performing a two-stage reforming. 2. A reforming one-stage section in which steam is added to a desulfurized heavy hydrocarbon fuel having a first reforming catalyst to perform a steam reforming reaction, and a product gas generated in the reforming one-stage section is formed. , Second
It has a reforming catalyst and a hydrogen selective permeable membrane, and makes the shift reaction and the methanation reaction in an equilibrium state. In this state, only hydrogen is extracted from the reaction field, and steam is added to the extracted hydrogen side to reduce the hydrogen partial pressure. A reforming two-stage section, and a gas-liquid separator that cools and removes steam added to the extracted hydrogen,
An apparatus for producing high-purity hydrogen from heavy hydrocarbon fuel characterized by performing two-stage reforming.