JPH0841470A - Alternative natural gas manufacturing method - Google Patents

Abstract

(57) [Summary] [Structure] In a method for producing an alternative natural gas from a raw material hydrocarbon by a steam reforming reaction, ruthenium is supported on an activated alumina composite support containing an oxide of a metal such as a group IIa, and then Using a steam reforming catalyst obtained by reduction treatment, using a raw material with a sulfur content of 0.5 ppm or less,
The S / C ratio is set to 0.7 to 0.8, the desulfurization reactor and the recycle gas compressor are not included in the process constitution, and the desulfurization catalyst is used for deep desulfurization, and then the above steam reforming catalyst is used. A method for producing an alternative natural gas, wherein steam reforming is performed at an S / C ratio of 0.5 to 0.7. [Effect] SNG can be manufactured at low cost by using a steam reforming catalyst having carbon resistance and sulfur resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inexpensively producing alternative natural gas (hereinafter sometimes referred to as SNG) from a raw material hydrocarbon such as LPG or naphtha.

[0002]

2. Description of the Related Art An alternative natural gas is a high calorie content with a high methane content produced from coal, heavy oil, naphtha, LPG, etc., by using a reforming reaction or a methanation reaction of synthesis gas. It refers to gas and is mainly used as city gas.

The flow of the SNG manufacturing process generally used conventionally is shown in FIG. Raw material is LPG
Using naphtha or naphtha, the hydrogen-containing gas at the outlet of the steam reforming reactor is partially recycled to hydrodesulfurize the raw material. In this hydrodesulfurization section, at a reaction temperature of about 380 ° C., the nickel-molybdenum-based or cobalt-molybdenum-based hydrodesulfurization catalyst converts the sulfur content in the raw material into hydrogen sulfide, which is then oxidized. Adsorbed on a zinc-based catalyst. In this desulfurization process, the sulfur content in the raw material gas is up to about 0.2 ppm or less when a nickel-based catalyst is used as the next steam reforming catalyst, and about 0.05 ppm or less when a ruthenium-based catalyst is used. It is necessary to desulfurize to the following. Next, the desulfurized raw material gas undergoes a steam reforming reaction in a reforming reactor (usually composed of two stages) filled with a nickel-based or ruthenium-based steam reforming catalyst to produce a gas rich in methane components. Is generated. At this time, the reaction temperature is 400 to 550 ° C., the reaction pressure is 9 to 25 kg / cm ² G, and the total steam / carbon ratio is 0.
It is 8 to 1.7 (mol / atom). The carbon monoxide gas remaining in the produced gas flowing out from the reforming reactor is transformed into methane gas (CO + 3H ₂ → CH ₄ + H ₂ O) at a reaction temperature of about 350 ° C. by the methanation catalyst. Furthermore,
The product gas with an increased methane concentration is transferred to the decarbonation step, where carbon dioxide gas in the product gas is removed, and then the heat quantity is adjusted by adding LPG in the heat quantity adjusting section to produce the product SNG.

Further, as a steam reforming catalyst in recent SNG production, a ruthenium-based catalyst having a high methane synthesis activity is used.

[0005]

However, according to the conventional method,
In both nickel-based and ruthenium-based catalysts used for steam reforming, the sulfur content is a catalyst poison, so in order to maintain its catalytic activity, the desulfurization depth can be increased to produce the sulfur content in the raw material. It had to be removed as long as possible.

[0006] Further, since the steam basic unit (amount of steam used per product unit amount) occupies a large proportion in the operating cost of the SNG manufacturing process, in order to reduce the SNG manufacturing cost, the total steam / carbon ratio should be set. Need to reduce. Here, the overall steam / carbon ratio refers to the ratio of the number of moles of the total steam injected into the reforming reaction system to the number of carbon atoms in the raw material, and the individual steam / carbon for each reforming reactor. The ratios may differ slightly.

However, when the overall steam / carbon ratio is lowered, carbon produced as a result of the reforming reaction adheres to the catalyst, not only lowering the catalytic activity but also blocking the catalyst layer, which makes it impossible to continue the operation. There was a problem of becoming.

Therefore, an object of the present invention is to reduce the catalytic activity even if carbon is attached, and to prevent the activity from degrading even if the sulfur content in the raw material remains to some extent, that is, carbon resistance, It is intended to provide a steam reforming catalyst having a sulfur property, and thereby to provide a method for inexpensively producing SNG.

[0009]

Therefore, as a result of various studies to achieve the above object, the present inventor has developed a new steam reforming catalyst excellent in sulfur resistance and carbon resistance. By using, the desulfurization reactor and the recycle gas compressor, which are part of the components of the conventional process, can be omitted, SNG can be produced at a lower cost, and even if the sulfur content in the raw material is relatively high, The present invention has been completed by finding that an energy-saving type process can be constructed as compared with the conventional process by using the specific steam reforming catalyst and the specific deep desulfurization catalyst in combination.

Therefore, the present invention provides a method for producing an alternative natural gas from a raw material hydrocarbon by a steam reforming reaction, which comprises (1) a group IIa, a group IIIa and / or an activated alumina composite containing an oxide of a lanthanoid metal. Using a steam reforming catalyst obtained by supporting ruthenium on a carrier and then carrying out a reduction treatment, (2) using a raw material having a sulfur content of 0.5 ppm or less, and (3) an overall steam / carbon ratio of 0.7. ~
The present invention provides a method for producing an alternative natural gas, which has a range of 0.8 and (4) does not include a desulfurization reactor and a recycle gas compressor in the process configuration.

Furthermore, the present invention provides a desulfurization catalyst in which nickel or nickel oxide is supported on zinc oxide, iron oxide or a composite oxide thereof in a method for producing an alternative natural gas from a raw material hydrocarbon by a steam reforming reaction. Using a steam reforming catalyst obtained by deep desulfurization using, then supporting ruthenium on an activated alumina composite support containing an oxide of IIa group, IIIa group and / or lanthanoid metal, followed by reduction treatment, Overall steam / carbon ratio 0.5-
The present invention provides a method for producing an alternative natural gas, which comprises performing steam reforming in a range of 0.7.

The steam reforming catalyst used in the present invention is obtained by supporting ruthenium on an activated alumina composite carrier and then subjecting it to a reduction treatment.
IIa group and / or lanthanoid metal oxide 5 to 30
A composite carrier containing 50% by weight and having a specific surface area of 60 m ^2.
/ G or more and a pore volume of 0.2 to 0.5 ml / g, to which 0.5 to 5% by weight of ruthenium is loaded, and then subjected to a reduction treatment to form carbon monoxide (hereinafter referred to as CO. It is preferable that the adsorption amount is 2 ml / g or more.

In the steam reforming catalyst of the present invention, beryllium, magnesium, calcium, strontium, barium, and radium can be used as the Group IIa metal, but magnesium and barium are particularly preferable.

As the group IIIa metal, scandium, yttrium or the like can be used, but yttrium is particularly preferable.

As the lanthanoid metal, lanthanum, cerium, praseodymium, neodymium, promethium, samarium and the like can be used, but lanthanum and cerium are particularly preferable.

As the Group IIa metal oxide, the Group IIIa metal oxide, and the lanthanoid metal oxide, chlorides, nitrates, and the like of precursors can be used in addition to the oxides.

As the alumina, an alkoxide such as aluminum isopropoxide can be used as a precursor.

Group IIa metal oxides in composite supports, III
The amount of group a metal oxide and lanthanoid metal oxide is 5 to
30% by weight is preferable. If this amount is less than 5% by weight, a sufficient effect cannot be obtained with respect to sulfur resistance, and therefore a sufficient life extension of the catalyst cannot be expected. That is, a sulfur compound such as hydrogen sulfide in the source gas is a Group IIa metal oxide, III
Since it is adsorbed and absorbed by the a-group metal oxides and lanthanoid metal oxides, ruthenium, which is the active ingredient, is less likely to be poisoned, and the life is considered to be extended. If the amount of the Group IIa metal oxide exceeds 30% by weight, the amount of alumina is relatively decreased, which is not preferable. That is, alumina is effective in improving the specific surface area and mechanical strength, and therefore, if the content is extremely small, these improving effects cannot be expected.

The specific surface area of the composite carrier is 60 m ² / g or more,
The pore volume is preferably 0.2 to 0.5 ml / g, and when the specific surface area of the carrier or the pore volume is smaller than this, the dispersibility of the ruthenium to be supported becomes poor and the activity during SNG production is impaired. Further, in such a case, the carrier component is not sufficiently exposed on the surface, so that not only the effect of sulfur resistance is lowered but also a predetermined amount of the active component cannot be supported. On the contrary, when the specific surface area is extremely increased, the dispersibility effect and the sulfur resistance effect are improved, but there is a problem that sufficient carrier strength cannot be obtained.

The composite carrier is prepared by dispersing the metal oxide in a solvent such as water, methanol, ethanol or acetone and kneading the mixture, followed by firing or by adjusting the pH of a mixed solution of the metal chloride and nitrate. It can be prepared by firing the coprecipitate. Alternatively, oxides may be simply mechanically mixed and fired. The order of mixing alumina and the metal oxide is not particularly limited. For example, a mixture of an aluminum compound and one of the group IIa metal oxides may be further mixed with a group IIIa metal oxide and / or a lanthanoid metal oxide.

As a method for supporting ruthenium on the above composite carrier, a known method such as an impregnation method can be used. As the active ingredient ruthenium, precursors such as ruthenium trichloride anhydride, ruthenium trichloride hydrate and ruthenium nitrate can be used, but ruthenium trichloride monohydrate is particularly preferable from the viewpoint of solubility.

The amount of ruthenium supported is 0.5 to 5% by weight,
It is preferably 0.5 to 3% by weight. If the supported amount is less than this, the amount of active sites will be small, and if it is greater than this, the activity will not be improved and the dispersibility will be decreased, which is not preferable.

As a method of supporting ruthenium on the carrier, first, the carrier is weighed, and water is gradually added dropwise to the carrier so that water is sufficiently absorbed inside the carrier. This water absorption is preferably performed until it is saturated inside the carrier. In this way, the saturated water absorption amount is obtained in advance. Here, a solution in which a predetermined amount of ruthenium trichloride monohydrate is dissolved is absorbed by the carrier in an amount equal to the saturated water absorption. Then 10-15
An excess of volume% aqueous ammonia was added dropwise to the ruthenium concentration, and the formula RuCl ₃ + 3NH ₄ OH → Ru (OH) _{3 was} added.
Chloride is converted to hydroxide such as + NH ₄ Cl (1) to make it insoluble and fixed.

At this time, since the chlorine anion becomes water-soluble ammonium chloride as shown in the formula (1), dechlorination can be performed in the washing process. The carrier on which ruthenium is immobilized is dried at 100 ° C. or lower under reduced pressure or atmospheric pressure.
If this temperature is too high, some of the hydroxide will change to oxide. To reduce the carrier mixed with oxides, 2
Since a temperature of 00 ° C. or higher is required, the dispersibility of ruthenium after the reduction treatment becomes worse due to the higher reduction temperature. From this point as well, it is preferable to avoid the presence of oxides during drying. Further, if the drying temperature is too low, the drying time becomes extremely long, which is not preferable.

In addition to ammonia water, an aqueous solution of a base such as sodium hydrogen carbonate, sodium carbonate, caustic soda, and caustic potash can be used for immobilization. However, in the case of sodium salts and potassium salts, there is a risk that alkali metal cations will remain during cleaning, so ammonia water is the easiest to handle.

In order to improve the dispersibility of the supported metal, the reduction of the supported ruthenium catalyst is preferably carried out at a temperature of 100 to 150 ° C. so that the metal does not aggregate.
Pure hydrogen, hydrogen / steam, and carbon monoxide can be used as the reducing gas. Among these, it is preferable to use hydrogen gas or hydrogen / steam gas, and it is particularly preferable to use hydrogen gas.

The method of the present invention is carried out as follows using the steam reforming catalyst obtained as described above.

Since the catalyst of the present invention is excellent in sulfur resistance, it is sufficient that the content of sulfur in the raw material hydrocarbon is 0.5 ppm or less, and the desulfurization step and the recycling performed prior to the conventional steam reforming reaction. The gas step can be omitted.

Since this catalyst is excellent in carbon resistance, it can be operated with a total steam / carbon ratio in the range of 0.7 to 0.8, that is, with a smaller amount of steam than in the conventional method. If the overall steam / carbon ratio is less than 0.7, the effect of carbon deposition becomes large, which causes adverse effects such as shortening of catalyst life, which is not preferable.

The reaction temperature of the steam reforming reaction is 350 to 50.
0 ℃, preferably 400-450 ℃, pressure is 20kg / cm
² G or less, preferably atmospheric pressure to 15 kg / cm ² G, particularly preferably 8 to 10 kg / cm ² G, and GHSV of 600 to 120.
0h ^-1 is preferred.

Further, according to the present invention, by using the nickel oxide / zinc oxide-based deep desulfurization catalyst and the ruthenium-based steam reforming catalyst, the overall steam / carbon ratio is in the range of 0.5 to 0.7. That is, it can be operated with a smaller amount of water vapor than the conventional process.

First, with respect to the raw material hydrocarbon, in the presence of a gas containing hydrogen, nickel or nickel oxide is supported on zinc oxide, iron oxide or a composite oxide thereof in an amount of less than 40% by weight in terms of metal, and in the reaction temperature range. Desulfurization is performed using a catalyst having a nitric oxide adsorption capacity of 0.02 cc / m ² or more per unit area of the catalyst surface area.

The catalyst used here is less than 40% by weight of nickel or nickel oxide (hereinafter, simply referred to as Ni for convenience of description) in terms of metal, zinc oxide, iron oxide or a composite oxide thereof (hereinafter, described). For convenience of description, it is supported on ZnO, etc.) and has a nitric oxide adsorption capacity (hereinafter simply referred to as NO adsorption capacity) of 0.02 cc / m ² or more per unit area of the catalyst area in the reaction temperature range. Is to have. The amount of Ni supported on ZnO is 1% by weight.
The amount is not particularly limited as long as it is at least 40% by weight, preferably 2 to 30% by weight. If it is less than 1% by weight, the desulfurization effect due to Ni is not sufficient, and if it is 40% by weight or more, the desulfurization effect is saturated, a methanation reaction occurs, heat is generated, and it becomes difficult to control the reaction temperature.

The specific surface area of the present catalyst is not particularly limited,
If the specific surface area is about 2 m ² / g or more, a sufficiently high reaction rate can be obtained. On the other hand, when the specific surface area is too large, the catalyst filling amount per unit catalyst bed volume decreases, and the hydrogen sulfide adsorption amount per unit catalyst bed volume decreases, so that the catalyst life may decrease. Accordingly, preferred specific surface area of the catalyst is about 2~150m ² / g, more preferably from about 3~110m ² / g.

The present catalyst is produced as follows when zinc oxide is used, for example. That is, in the impregnation method, first, a predetermined amount of zinc oxide is weighed, and water is gradually added dropwise with stirring so that the zinc oxide absorbs water. This water absorption is preferably performed until the inside of the zinc oxide is saturated, and the necessary Ni amount is calculated from this saturated water absorption amount and the known amount of zinc oxide. Next, this Ni
An aqueous solution of Ni salt such as nitrate, acetate or chloride adjusted to an appropriate concentration based on the amount is gradually added dropwise to a weighed predetermined amount of zinc oxide while stirring, as in the case of water. Saturated water may be absorbed, dried and fired. In the coprecipitation method, an aqueous solution of zinc acetate, nitrate, etc., and N 2
An aqueous alkali solution is added to a mixture of the aqueous solution of nitrate salt, acetate salt, etc. of i to form a precipitate, and the precipitate is filtered and washed.
It may be dried and baked. In the above impregnation method, if it is desired to increase the amount of Ni supported, the above impregnation operation may be repeated. Further, when iron oxide such as Fe ₂ O ₃ is used as a carrier, it can be similarly prepared.

By using this catalyst, the sulfur content of 0.
It is possible to obtain less than 05 ppm, and thereby the catalytic activity of the steam reforming catalyst can be maximized. The desulfurization reaction is carried out at a temperature of 180 to 440 ° C., preferably 2
80-440 ° C., pressure 30 kg / cm ² G or less, preferably 1
-10 kg / cm ² G, GHSV 600-3000 h ^-1 .

When the steam reforming reaction is carried out as described above on the raw material hydrocarbon thus deeply desulfurized,
The overall steam / carbon ratio is less than 0.8, preferably 0.
It can be set to 5 to 0.7, and the alternative natural gas can be efficiently obtained with a small amount of water vapor. If the total steam / carbon ratio is less than 0.5, the effect of carbon precipitation becomes large, which is not preferable.

[0038]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to these.

Example 1 (i) Preparation of Steam Reforming Catalyst 19.8 g of cerium oxide (manufactured by Wako Pure Chemical Industries) powder and 82.2 g of activated alumina powder (aluminum oxide 90 type I, manufactured by Merck) were sufficiently used in a mortar. About 40 after mixing
The mixture was further kneaded by adding ml of water. 2.7 kPa (approx. 20 mmHg) of the pasty mixture on a rotary evaporator
Under vacuum, the mixture was heated to 60 to 70 ° C. with an infrared hot plate to remove water. This was pre-dried in a constant temperature dryer kept at 105 ° C, and then calcined at 500 ° C for 3 hours in an electric furnace to obtain a composite carrier. The specific surface area at this time is 8
It was 2.5 m ² / g and the pore volume was 0.4 ml / g. 15.4 g of ruthenium trichloride monohydrate (manufactured by Kanto Chemical Co., Inc.) was dissolved in 37 ml of water to immerse 25.4 g of the composite powder for 1 hour, and after removing the residual liquid, about 2 using a rotary evaporator. Water was removed by heating to 40 to 45 ° C. on an infrared hot plate under a vacuum of about 0.7 kPa. Add this to 10-15% by volume ammonia water and
Keep ruthenium insoluble and immobilized by stirring for 2 hours.
Dried at 40-45 ° C. for 8 hours using a Buchner funnel, ruthenium 1.8% by weight, cerium oxide 21.6% by weight,
A catalyst was prepared with the balance consisting of alumina and
The particles were sized into a mesh. Furthermore, 10 mg of this catalyst is pressure 8 kg
/ Cm ² G, reduction temperature 150 ° C, GHSV 3000h ^-1 8
Hydrogen reduction was carried out for a period of time to obtain a steam reforming catalyst. The amount of CO adsorbed on the catalyst after the reduction treatment was 3.8 to 4.0 ml / g (S
TP).

(Ii) Manufacture of SNG The process shown in FIG. 2 was constructed by removing the desulfurization process and the recycle gas process from the conventional SNG manufacturing process, and the steam reforming reactors ((2-2) and (3-2 )) Was filled with the steam reforming catalyst prepared in (i) above, and SNG was produced as follows. After the raw material LPG or naphtha is preheated to 300 ° C. by heat exchange with the product gas at the outlet of the methanation reactor (6-2) and the outlet gas of the second stage steam reforming reactor (3-2) Branch off. One of the source gases branched here (about 60% of the source) is
The first-stage steam reforming reactor after merging with the reforming steam at the inlet of the heating furnace (1-2) and raising the temperature required for the steam reforming reaction to 450 ° C. in the heating furnace (1-2). In (2-2), the steam reforming reaction is performed. In this reactor, a reaction pressure of 8.7 kg / cm ² G and a steam / carbon ratio of about 1.2 are exothermic reactions. On the other hand, the raw material gas (about 40% of the raw material) branched before the heating furnace merges with the outlet gas of the first-stage steam reforming reactor at the inlet of the second-stage steam reforming reactor (3-2), The temperature is raised to ℃, enters the second stage steam reforming reactor (3-2), and further reforming reaction is performed. In this reactor, the reaction pressure was 8.6 kg / cm ² G, steam /
It is an exothermic reaction with a carbon ratio of about 1.1. Then, the outlet gas of the second stage steam reforming reactor (3-2) is cooled to 310 ° C. by heat exchange with the raw material gas (4-2) and heat exchange with pure water (5-2). After that, it enters the methanation reactor (6-2). Here, a methanation reaction in which residual carbon monoxide is converted into methane is performed. Then, the outlet gas of the methanation reactor (6-2) in which the remaining carbon monoxide concentration becomes 1% or less condenses the heat exchanger (7-2) for preheating the raw material and the generated steam. After the condensed water is separated through a cooling device (8-2) for the purpose, a decarbonation step (9-2) and a heat quantity adjusting step (10-2), which are the same as those in the conventional method, are performed, and finally a product SNG is obtained. Become. The composition of the gas at each stage of this process is shown in FIG. In this case, the product SNG amount is 1
It was 86 kg-mol / h (100,000 Nm ³ / day).
Further, S / C = 0.8 in FIG. 5 indicates that the total steam / carbon ratio is 0.8.

Example 2 (i) Preparation of deep desulfurization catalyst 53 g of zinc acetate and 19 g of nickel nitrate were dissolved in 600 ml of water to prepare a mixed solution of both, and 22 g of ammonium carbonate was dissolved in 200 ml of water to form carbonic acid. An ammonium aqueous solution and 15% aqueous ammonia were added to form a precipitate of zinc carbonate and basic nickel carbonate, and the mixture was left for about 12 hours. The precipitate is filtered, washed with water, dried at 120 ° C. for 12 hours, and while being blown with air, the temperature is 200 ° C. for 1 hour and 300 ° C.
2 hours, 400 ° C. for 1 hour, 510 ° C. for 16 hours, and the amount of nickel oxide supported on zinc oxide is 15.4% by weight.
The catalyst was obtained. The amount of NO adsorbed on the catalyst is 0.348cc /
It was m ² . The specific surface area of the catalyst was 4.7 m ² / g.

(Ii) Production of SNG In the SNG production process shown in FIG. 3, the deep desulfurization catalyst prepared in (i) above was added to the desulfurization reactor (11-3).
The steam reforming reactors ((2-3) and (3-3)) were filled with the steam reforming catalyst prepared in (i) of Example 1,
SNG was manufactured as follows. After the raw material LPG or naphtha is preheated to 460 ° C. by heat exchange with the product gas at the outlet of the methanation reactor (6-3) and the outlet gas of the second stage steam reforming reactor (3-3), The recycled gas compressor (12-3) joins the hydrogen-containing gas (about 90% of the raw material) at the outlet of the second-stage steam reforming reactor (3-3), the fluid temperature becomes 380 ° C. Then, after entering the desulfurization reactor (11-3), the sulfur content in the raw material was desulfurized to 0.05 ppm or less, and then branched.
One of the gases branched here (about 60% of the raw material) merges with the reforming steam at the inlet of the heating furnace (1-3), and the heating furnace (1
After the temperature is raised to 450 ° C. required for the steam reforming reaction in (3), the steam reforming reaction is performed in the first stage steam reforming reactor (2-3). In this reactor, a reaction pressure of 8.7 kg / cm ² G and a steam / carbon ratio of about 1.0 are exothermic reactions. On the other hand, the raw material gas branched before the heating furnace (about 40% of the raw material) is the second stage steam reforming reactor (3-3).
At the inlet, it joins with the outlet gas of the first-stage steam reforming reactor (2-3) and, after being heated to 450 ° C., enters into the second-stage steam reforming reactor (3-3) to carry out the reforming reaction. Is done. In this reactor, a reaction pressure of 8.6 kg / cm ² G and a steam / carbon ratio of about 0.8 are an exothermic reaction. The outlet gas of the second-stage steam reforming reactor (3-3) is 310 due to heat exchange with the source gas (4-3) and heat exchange with pure water (5-3).
After the temperature was lowered to ℃, the methanation reactor (6-
3) Enter. Here, a methanation reaction for converting the remaining carbon monoxide into methane is performed. Then, the outlet gas of the methanation reactor (6-3) in which the remaining carbon monoxide concentration becomes 1% or less condenses the heat exchanger (7-3) for preheating the raw material and the generated steam. After passing through the cooling device (8-3) for separating the condensed water, the same decarboxylation step (9-3) as in the conventional method and the calorie adjusting step (10-
After 3), it finally becomes a product SNG. The gas composition at each stage of this process is shown in FIG. The product SNG amount is constant at 186 kg-mol / h (1
It was set to 0,000 Nm ³ / day). Also, in FIG.
The expression /C=0.6 indicates that the overall steam / carbon ratio is 0.6.

Comparative Example 1 (Production of SNG) Using the conventional SNG production process shown in FIG.
The desulfurization reactor (11-1 ′) was equipped with a commercially available desulfurization catalyst (NiS-
MoS ₂ / Al ₂ O ₃ ) and further desulfurization reactor (11-1)
To a commercially available desulfurization catalyst (ZnO), and the steam reforming reactors ((2-1) and (3-1)) to a commercially available ruthenium-based steam reforming catalyst (Ru / Al ₂ O ₃ ). Then, SNG was manufactured as follows. After the raw material LPG or naphtha is preheated to 460 ° C. by heat exchange with the product gas at the outlet of the methanation reactor (6-1) and the outlet gas of the second stage steam reforming reactor (3-1), The second boosted pressure by the recycled gas compressor (12-1)
The hydrogen-containing gas (about 90% of the raw material) at the outlet of the stage steam reforming reactor (3-1) merges, and the fluid temperature becomes 380 ° C.
Then, the desulfurization reactors ((11-1) and (11-
1 ')), the sulfur content in the raw material is desulfurized to 0.2 ppm or less, and then branched, and one of the branched gases (about 60% of the raw material) enters the heating furnace (1-1) at the inlet. After joining the reforming steam and raising the temperature to 450 ° C. necessary for the steam reforming reaction in the heating furnace (1-1), the steam enters the first stage steam reforming reactor (2-1). A quality reaction takes place. In this reactor, a reaction pressure of 8.7 kg / cm ² G and a steam / carbon ratio of about 1.3 are exothermic reactions. On the other hand, the raw material gas branched before the heating furnace (about 40% of the raw material) is the outlet gas of the first-stage steam reforming reactor (2-1) at the inlet of the second-stage steam reforming reactor (3-1). And the temperature is raised to 450 ° C., the second stage steam reforming reactor (3-1) enters and the reforming reaction is performed. In this reactor, the reaction pressure is 8.
Exothermic reaction at 6 kg / cm ² G and steam / carbon ratio of about 1.0. The temperature of the outlet gas of the second stage steam reforming reactor (3-1) can be lowered to 310 ° C. by heat exchange with the raw material gas (4-1) or heat exchange with pure water (5-1). After that, it enters the methanation reactor (6-1). Here, a methanation reaction for converting the remaining carbon monoxide into methane is performed. Then, the outlet gas of the methanation reactor (6-1) in which the remaining carbon monoxide concentration becomes 1% or less condenses the heat exchanger (7-1) for preheating the raw material and the generated steam. After passing through the cooling device (8-1) for separating the condensed water, the product SNG is finally obtained through the decarbonation step (9-1) and the heat quantity adjusting step (10-1). The composition of the gas at each stage of this process is shown in FIG. Note that the product SNG amount is constant at 186
kg-mol / h (100,000 Nm ³ / day). Also,
In FIG. 4, S / C = 0.8 indicates that the total steam / carbon ratio is 0.8.

When the sulfur content in the raw material is 0.5 ppm or less,
In Example 1, as compared with Comparative Example 1, the operating cost can be reduced by several%, and the construction cost can be reduced by about 10% by omitting the desulfurization process and the recycled gas process. When the sulfur content in the raw material exceeds 0.5 ppm, when Example 2 is selected and carried out, the overall steam / carbon ratio is 0.1 to 0 as compared with Comparative Example 1 when the catalyst life is constant. It can be reduced by about 3 and as a result, operating costs can be reduced by several percent.

[0045]

According to the present invention, by using the steam reforming catalyst of the present invention, the sulfur content in the raw material gas is about 0.
If it is 5 ppm or less, the desulfurization process and the recycle gas process can be omitted, and the heating furnace, the steam reforming reactor and the methanation reactor can be downsized, and the power of the recycle gas compressor becomes unnecessary. Therefore, operating costs can be reduced. Further, even if the sulfur content in the raw material is about 0.5 ppm or more, the overall steam / carbon ratio can be lowered by using the steam reforming catalyst of the present invention and the high-performance hydrodesulfurization adsorption catalyst in combination. Therefore, it is possible to reduce the operating cost associated with this.

[Brief description of drawings]

FIG. 1 is a diagram showing a flow of an SNG manufacturing process of Comparative Example 1.

FIG. 2 is a diagram showing a flow of an SNG manufacturing process of Example 1.

FIG. 3 is a diagram showing a flow of an SNG manufacturing process of Example 2.

FIG. 4 is a diagram showing a gas composition at each stage of the SNG manufacturing process of Comparative Example 1.

5 is a diagram showing a gas composition at each stage of the SNG manufacturing process of Example 1. FIG.

FIG. 6 is a diagram showing a gas composition at each stage of the SNG manufacturing process of Example 2.

Claims (3)

[Claims] 1. A method for producing an alternative natural gas from a raw material hydrocarbon by a steam reforming reaction, which comprises (1) Group IIa, I
Using a steam reforming catalyst obtained by supporting ruthenium on an activated alumina composite support containing an oxide of a IIa group and / or a lanthanoid metal, and then performing a reduction treatment (2)
A raw material having a sulfur content of 0.5 ppm or less is used, and (3) the total steam / carbon ratio is set in the range of 0.7 to 0.8,
(4) A method for producing an alternative natural gas, characterized in that the desulfurization reactor and the recycle gas compressor are not included in the process constitution. 2. A steam reforming catalyst is an activated alumina composite containing 5 to 30% by weight of an oxide of a IIa group, a IIIa group and / or a lanthanoid metal and having a specific surface area of 60 m ² /
0.5 to 5% by weight of ruthenium is supported on a carrier having a pore volume of 0.2 to 0.5 ml / g and a reduction amount of 2 ml / g or more. The method for producing alternative natural gas according to claim 1, wherein 3. A method for producing an alternative natural gas from a raw material hydrocarbon by a steam reforming reaction, using a desulfurization catalyst in which nickel or nickel oxide is supported on zinc oxide, iron oxide or a composite oxide thereof, and deep desulfurization is performed. Then IIa
Ruthenium is supported on an activated alumina composite carrier containing an oxide of a genus, a group IIIa and / or a lanthanoid metal,
Next, using a steam reforming catalyst obtained by reduction treatment,
A method for producing an alternative natural gas, characterized in that steam reforming is carried out at a steam / carbon ratio of 0.5 to 0.7.