JPH0244001A - Fuel reformer - Google Patents

Abstract

PURPOSE:To reduce the amt. of a preheated gaseous mixture, to miniaturize a preheater, and to decrease the power consumption by providing plural combustion catalyst beds along the passage for the combustion gas and air, and furnishing a premixed gas supply pipe on the upstream side of each catalyst bed. CONSTITUTION:Air is supplied from an air supply pipe 42, measured by a flowmeter 43, preheated by a gas preheater 44, and premixed with the natural gas from a natural gas supply pipe 45. The premixed gas is supplied to the first combustion catalyst bed 31 from a premixed gas supply pipe 37. The premixed gas of natural gas and air is blown into the combustion gas from a premixed gas supply pipe 38, the heating gas and oxygen are sufficiently mixed, and the temp. is uniformized. The process is repeated, natural gas is supplied to the combustion gas obtained from the fourth combustion catalyst bed 34, from a fuel diffusion pipe 41 made of alumina, and the natural gas is burned along the wall surface through an alumina grain-packed bed 35 and a honeycomb plate 36. The hot air from a hot air generating part 30 is supplied to a reaction tower 20, and a hydrogen-rich reformed gas is obtained from the natural gas and steam supplied to a reaction tube 3.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel reformer for producing hydrogen through the reaction of hydrocarbons and steam.

(Prior Art) Various fuel reformers of this type are known, and FIG. 5 shows an example of the fuel reformer described in Japanese Utility Model Application Publication No. 143742/1983.

The illustrated fuel reformer 1 consists of an upper head A, an intermediate reaction section B, and a lower combustion section C. The head A is provided with a raw material supply pipe 2, and the reaction section B has a double structure inside. The reaction tube 3 is filled with a reforming catalyst 4, and the combustion section C is provided with a fuel supply pipe 5 and an air supply pipe 6.

The raw material hydrocarbon (for example, LNG) and steam are preheated from 170°C to 400°C in a raw material preheating device (not shown), and then supplied to the head A in the upper part of the fuel reformer 1 from the raw material supply pipe 2. be done. The raw material supplied from the raw material supply pipe 2 enters the reaction outer tube 3a of the reaction tube 3, and the temperature inside the tube is approximately 800°C.
It reacts in the presence of the reforming catalyst layer 4 and is reformed into hydrogen-rich gas, passes through the reaction tube vent 7 and the reaction inner tube 3b, is collected in the gas collecting tube 8 in the upper head A, and is generated from the gas extraction tube 9. Hydrogen is extracted. At this time, the reaction tube 3 is heated with the combustion gas from the combustion FfBc.

In the combustion section C, fuel is supplied to a premixing chamber 10 through a fuel supply pipe 5 and air through an air supply pipe 6, and is combusted in a combustion chamber having a combustion catalyst layer 12 held by a ceramic tray 11 to produce high-temperature gas. The combustion gas becomes combustion gas, which externally heats a large number of reaction tubes 3 in the heating section 13, and is exhausted from the combustion gas exhaust pipe 14 provided on the side of the reaction section.

However, since the steam reforming reaction of hydrocarbons is an endothermic reaction, it is necessary to transfer heat from the outside of the reaction tube 3 to the reforming catalyst layer 4 inside the reaction tube. A method is adopted in which a combustion section C having a layer 12 is provided to heat the reforming catalyst layer 4.

This combustion section C is connected to the air from the air supply pipe 6 and the fuel supply pipe 5.
is mixed with the fuel from the combustion catalyst layer 12 in the premixing chamber lO.
The reforming catalyst layer 4 is heated to a constant temperature of 800°C by catalytic combustion and generating hot air at about 1000'C to 1200°C.
to hold.

Now, the combustion start temperature in catalytic combustion differs depending on the fuel, but in general, hydrogen and methanol are at room temperature, and propane is at room temperature.
It is known that the combustion start temperature of lower saturated hydrocarbons is higher than 00°C, methane is 370-380°C.

Figure 6 shows the results of an experiment to investigate the combustion conditions for low-concentration methane in catalytic combustion. From this figure, it is clear that premixing of air and methane at the inlet of the combustion catalyst layer is necessary for stable catalytic combustion of methane. Is it necessary to maintain the preheating temperature of the gas above 360'C?
In the case of C, it burns in the initial stage, but the combustion is unstable, and after about 40 minutes the temperature drops, and it can be seen that the flame eventually goes out. This preheating temperature of 360°C is close to the catalytic combustion start temperature of 370 to 380°C. When natural gas (LNG) is used as fuel, the main component is methane, so in order to continue stable catalytic combustion, the temperature of the LNG-air premixed gas in the combustion catalyst layer must be adjusted to the combustion start temperature of methane. Is there a need to maintain this at all times?

For this reason, conventional fuel reformers are generally equipped with an air preheater to preheat the air to a temperature above the catalyst starting temperature of the fuel, and then premix the fuel with the air preheater for safety reasons.

In the conventional fuel reformer as described above, it is necessary to preheat the entire amount of air necessary for combustion to a predetermined temperature, especially at startup, which places a heavy burden on the air preheater, especially at startup. Power consumption is large. For example, in order to generate 35 Nm'/h of hydrogen, a fuel reformer (for 50 kW fuel cell) that uses LNG as raw material generates 11
00°C hot air or 15ONrn'/h is required,
With an electric heater type air preheater, it is necessary to preheat air at 5°C to 380°C at a rate of 15ONrn'/h. Even if the thermal efficiency of the electric heater is 90%, it will require a power consumption of 22KWh as estimated below, and when used as a reformer for a 50kW fuel cell, 44% of the power generated will be consumed by the air inside the plant. The power must be used for the power consumption of the preheater, which poses problems both in terms of performance and economy.

150 x 0112 x (380-Is)/(86
0' x O,9) = 22kWh (22150) X1
00=40% Here, the mature air purity is 0.312k Cal/N m
J/h°C1 The supply air temperature was 15°C and the electric heater was 90%.

In addition, in order to downsize the fuel reformer, it is advantageous to use combustion gas with a temperature as high as possible after considering the allowable heat resistance temperature of the reaction tube material. Conventionally, a method is known in which secondary fuel is directly blown into the catalytic combustion outlet gas to obtain hot gas. But 2
Next, since a flame is formed at the tip of the fuel injection pipe, there may be problems such as the need to enlarge the combustion space to prevent the flame from coming into contact with the opposite wall, or an increase in the amount of NOx generated from the flame section, which becomes hot. Ta.

(Objective and Structure of the Invention) The present invention has been made in view of the above-mentioned points. In order to achieve this goal, we installed multiple stages of combustion catalyst layers along the fuel gas flow path of the hot air generation section for heating the reaction tubes of the fuel reformer. A premixed gas supply pipe for supplying a mixed gas of combustion gas and air is provided upstream of each combustion catalyst layer except for the uppermost combustion catalyst layer.

(Example) The present invention will be explained below based on the drawings.

FIG. 1 is a schematic diagram of an embodiment of a fuel reformer according to the present invention.

The fuel reformer shown in Figure 1 uses natural gas (main component methane) as a raw material, and head A has a raw material supply pipe for supplying the raw material natural gas and steam, and a gas pipe for taking out the reformed gas. The reaction section B includes a reaction column 20 lined with a heat insulating material 16 to prevent heat loss, and a reaction column 20 filled with a nickel-alumina reforming catalyst layer 4. 3 or more are provided, and a heating section 13 outside the reaction tube 3 is provided.
is filled with heat transfer particles 17 made of alumina and held by a perforated plate 18 made of heat-resistant metal. Further, the reaction section B is provided with a combustion gas discharge pipe 14 passing through the reaction tower 20.

The combustion section C includes a hot air generating section 30 for heating the reaction tube 3.
is provided.

This hot air generating section 30 has first to fourth sections inside a cylindrical body 30a communicating with a space 19 formed at the bottom of the reaction tower 20.
The four stages of lanthanum beta alumina combustion catalyst layers 31, 32, 33° 34 are arranged at a distance from each other, and an alumina particle packed bed 35 and a honeycomb plate 36 are further arranged on the downstream side thereof. A premixed gas supply pipe 37 for introducing a premixed gas of preheated air and natural gas is connected to the upstream side of the first stage combustion catalyst layer 31. A premixed gas supply pipe 38 for introducing a mixed gas of unpreheated air and natural gas is connected between the second stage combustion catalyst layer 32 and the second stage combustion catalyst layer 3.
A premixed gas supply pipe 39 for introducing a mixed gas of unpreheated air and natural gas is connected between the combustion catalyst layer 33 of the third stage and the combustion catalyst layer 33 of the third stage. A premixed gas supply pipe 40 for introducing a mixed gas of unpreheated air and natural gas is connected between the four stages of combustion catalyst layers 34. Furthermore, an alumina fuel dispersion tube 41 is introduced into the alumina particle packed bed 35.

Air to each premixed gas supply pipe 37.38, 39.40 is supplied from an air supply pipe 42 via a flow meter 43, and only air to the premixed gas supply pipe 37 is heated by a gas preheater 44. .

On the other hand, natural gas to each premixed gas supply pipe 37, 38, 39° 40 is supplied via a flow meter 46 from a natural gas supply v45.

The above is the schematic configuration of the fuel reformer according to the present invention,
An example of an actual specification is as follows.

Reaction column 20: Column diameter 70 ports + mm, height 3000 mm Reaction tube 3: Diameter 1100 II x length 1800 II 1 m
(7 pieces) Reforming catalyst 7: 50mm Heat transfer particles 17: Alumina particles with a diameter of 10mm 120M Hot air generation part diameter cylinder 30: Diameter 200 + sm Height 100
0i11 Combustion catalyst: diameter 100mm, length 50cm ~ 1501m
Next, a fuel reforming experiment conducted using the above fuel reformer will be explained.

Air at 15°C is sent from the air supply pipe 42, measured by the flow meter 43, and the 3ONm'/h of air is preheated to 400°C by the gas preheater 44, and natural gas from the natural gas supply pipe 45 is The premixed gas is premixed by 0.56 Nm'/h and supplied to the first stage combustion catalyst layer 31 from the premixed gas supply pipe 37.
A combustion gas of 30.6 Nrn'/h at 00°C was obtained. This combustion gas is supplied with air 3 at 15°C from the premixed gas supply pipe 38.
ONm'/h and natural gas 0.94Nm''/h were injected into the premixed gas in a swirling flow to sufficiently mix the heated gas and oxygen to achieve a uniform temperature.The gas temperature after mixing The temperature was about 390°C.The second stage combustion catalyst layer 3
From No. 2, 61.5 Nrn'/h of combustion gas at 800°C was obtained. By repeating the same operation, 247.2 Nrn'/h of combustion gas (temperature 800°C) obtained from the fourth stage combustion catalyst layer 34 was obtained.
3.81N of natural gas from the alumina acid fuel dispersion pipe 41.
m''/h was supplied and burned along the wall surface using the alumina particle packed bed 35 and the honeycomb plate 36 to obtain 251.2 Nm'/h of combustion gas at 1200°C. Almost no flame was generated, and the temperature distribution was is uniform, so NaX in the combustion gas
At 6 degrees Celsius, the concentration was extremely low at 12 ppm.

The hot air thus obtained in the hot air generating section 30 is supplied to the reaction tower 20 through the space 19 of the combustion section C, and as a result, 21.9 N m'/h of natural gas and 37 kg of steam are supplied to the reaction tube 3. /h to hydrogen-rich reformed gas (
Hydrogen 70 Nrn'/h, carbon dioxide 1ONm'
/h, - carbon oxide 11 Nm'/h), and the reforming catalyst outlet temperature was maintained at 800°C.

A summary of the above experiments is summarized in a separate table.

In this table, the thermal efficiency is estimated from the temperature of the combustion gas purified at each part of the hot air generation part, and each part shows 90% or more, and the heat loss from the cylinder 30a is small, and the hot air generation part is efficiently It worked.

According to this embodiment, in order to obtain 251.2 Nrn'/h of combustion gas, the amount of air preheated by the gas preheater 44 is 3ONm'/h, which is about 1/8 of the combustion gas.
capacity and heater power consumption using the conventional method (single-stage catalytic combustion method)
has become significantly smaller compared to Furthermore, by adopting a method of burning along the wall surface, the No.
. We were able to reduce the concentration to a fraction of that of conventional methods and generate clean hot air.

FIG. 2 shows a schematic configuration of a fuel cell power generation system incorporating a fuel reformer according to the present invention.

In the figure, numeral 1 represents a fuel reformer according to the present invention, and numeral 100 represents a fuel cell.

Natural gas NG and steam W, which are raw materials for reforming, were adjusted to have a steam/carbon (molar ratio) value of 3.5 and supplied to the fuel reformer 1, where they were reformed into hydrogen-rich gas. After the reformed gas is introduced into shift converters 50 and 51 to convert carbon monoxide in the reformed gas into carbon dioxide, the gas is cooled with a cooler 52, and condensed water is separated with a steam/water separator 53. The reformed gas was introduced into the anode 1ooa of the fuel cell 100. Approximately 80% of the hydrogen in the anode "C reformed gas has been consumed, and the anode exhaust gas supply pipe 1oob containing unreacted hydrogen is connected to the natural gas supply pipe 45 (see FIG. 1) of the hot air generation section 30. , anode exhaust gas was used as fuel.
Since the anode exhaust gas could not be used when starting up the fuel reformer I, hot air was generated using natural gas as a fuel in accordance with the operating procedure of Example 1, and the reformer was started up.

On the other hand, the air from the air compressor 54 is supplied to the cathode 100c of the fuel cell 100, where the supply pipe 55 of the cathode exhaust gas in which 50% of oxygen has been consumed is guided to the hot air generation section 30 of the reformer 1, and the air is It was connected to a supply pipe 42 (see FIG. 1) to serve as an oxygen source.

The anode exhaust gas and cathode exhaust gas from the fuel cell 100 pass through the heat exchanger 57 and the steam/water separator 58 to reach the hot air generator 30, so the gas temperature is equal to the fuel cell outlet temperature 2.
In both cases, the temperature had dropped from 00°C to about 40°C. 1/8 (approximately 25 N m'/h) of the cathode exhaust gas is preheated to 150°C, and a part of the anode exhaust gas is premixed with this to bring the temperature of the first stage combustion catalyst layer 31 to 500°C. The mixed rate of anode exhaust gas amount was adjusted as follows. An equal amount of premixed gas is blown into this combustion gas from the premixed gas supply pipe 38 in a swirling flow, and the mixture is combusted in the next second stage combustion catalyst layer 32. Similarly, the combustion gas at 500°C is Obtained. This operation was repeated, and finally the remaining anode exhaust gas and the auxiliary fuel methane gas were combusted along the wall to generate combustion gas at 1150° C., which was used to heat the reforming reaction tube 3.

From the fuel reformer l, hydrogen-rich reformed gas (water J7ONm'/h, carbon dioxide 1ONm'
/h, -carbon oxide 11 Nrn'/h) was obtained.

The stable catalytic combustion initiation temperature of hydrogen in the premixed gas was 90°C, lower than that of methane at 380°C.

Fig. 3 shows the actually measured combustion start temperatures in comparison with other fuels.

Since the combustion catalyst inlet gas temperature was 250°C in all cases, the catalytic combustion reaction continued stably. Note that only the temperature of the final combustion catalyst layer 34 is 750°C higher than the other catalyst layers by 250'C.
'C. This is the gas phase combustion temperature of the fuel (hydrogen 580
(°C) or above, in order to smoothly advance combustion along the subsequent wall surface.

According to this embodiment, the anode exhaust gas (approximately 100 kcal/N m'
) is stably combusted using Kanto exhaust gas, which is a low-oxygen gas (m element concentration 10%), and the amount of gas initially preheated is reduced to approximately 1/8 of the amount of combustion gas finally obtained. This has the effect of reducing the capacity of the device and the amount of power consumed by the heater.

FIG. 4 shows another embodiment of the hot air generating section of the fuel reformer according to the present invention, and shows the hot air generating section for better mixing the premixed gas into the combustion gas obtained from the combustion catalyst layer. The schematic structure of

In the figure, the same reference numerals as in FIG. 1 indicate constituent parts.

The hot air generating section in this embodiment is different from the hot air generating section shown in FIG.
A fixed bed 47 is formed by filling alumina particles with a particle size of 6 cm between each catalyst layer.
A fuel distribution tube 41a is a heat-resistant alumina tube with ten 1ms holes.

This is the point where 41b and 41c are inserted, respectively. When such a hot air generating section was operated in substantially the same manner as in Example 1, combustion gas similar to the operation results described below was obtained.

Since the method of supplying the premixed gas is simpler than the swirl blowing method of Example 1, and the temperature distribution of the combustion catalyst layer is more uniform, the mixing of the combustion gas and the premixed gas is even better. The effects of this experiment were seen.

In all of the above embodiments, four stages of combustion catalyst layers are provided in the heat R generating section, but in the present invention, a certain effect can be obtained by providing two or more stages of combustion catalyst layers.

(Effects of the Invention) As explained above, in the present invention, two or more combustion catalyst layers are provided along the flow path of combustion gas and air in the hot air generation section for heating the reaction tube of the fuel reformer, Since a premixed gas supply pipe was installed on the upstream side of each combustion catalyst layer,
By repeating the operation of mixing unpreheated premixed gas with the gas obtained from each combustion catalyst layer and combusting it in the downstream combustion catalyst layer, the amount of preheated mixed gas required in the first stage combustion catalyst layer is reduced. There are some effects that can be done. In addition, by inserting a fuel distribution pipe into a fixed bed made of heat-resistant granular or honeycomb-like materials provided downstream of the final combustion catalyst layer and burning it along the wall surface, clean hot air with a temperature higher than the heat-resistant temperature of the combustion catalyst can be produced. This has the effect of generating heat in the reaction tube.

[Brief explanation of the drawing]

FIG. 1 is a condyle diagram of an embodiment of the fuel reformer according to the present invention, FIG. 2 is a condyle diagram of a fuel cell system incorporating the fuel reformer d according to the present invention, and FIG. Fig. 1 is an actual measurement diagram showing the combustion start temperature of natural gas according to the embodiment shown in comparison with other fuels, and Fig. 4 is a schematic diagram of the main part of another embodiment of the hot air generating section of the fuel reformer according to the present invention. 5 is a cross-sectional view of an example of a conventional fuel reformer, and FIG. 6 is a graph 7 showing the relationship between methane combustion conditions and catalyst temperature in the conventional fuel reformer. l...Fuel aeration device, 2...Raw material supply pipe, 3...
・Reaction tube, 4... Reforming catalyst, 9... Gas extraction pipe, 2
0... Reaction tower, 30... Hot air generation section, 31, 32,
33.34... Combustion catalyst layer, 37.38, 39.40
... Premixed gas supply pipe, 35 ... Alumina particle packed bed, 36 ... Honeycomb plate, 42 ... Air supply pipe, 4
5...Natural gas supply pipe

Claims (2)

[Claims] (1) having a hot air generating section and heating a reaction tube filled with a reforming catalyst using the hot air generated by the hot air generating section;
In the fuel reformer that generates hydrogen-rich gas by reforming the raw material gas introduced into the reaction tube by the action of the reforming catalyst, the hot air generation section includes a preheater that preheats the air for hot air, and a preheater that preheats the hot air. A multi-stage combustion catalyst layer is arranged along the flow path of a mixed gas of air and fuel gas, and a combustion catalyst layer is arranged upstream of each combustion catalyst layer except for the uppermost combustion catalyst layer. A fuel reformer comprising a premixed gas supply pipe for supplying mixed gas. (2) On the downstream side of the final stage combustion catalyst layer of the hot air generation section,
2. The fuel reformer according to claim 1, further comprising a fixed bed having a granular or honeycomb structure, and a fuel dispersion pipe for introducing fuel into the fixed bed. (3) The fuel reformer according to claim 1, wherein particles of a heat-resistant material are filled between the combustion catalyst layers of the hot air generating section to form a fixed bed, and a fuel dispersion pipe for introducing fuel is provided in the fixed bed. quality equipment.