DE1645842A1 - Process for the production of combustible gases - Google Patents

Description

Pate nt application

for

The Gas Council, 4-5 Grosvenor Place, London, S.W.1, England

concerning

Process for the production of "combustible gases"

The invention "relates to a process for the production of" combustible gases, particularly to a method for the manufacture development of a gas containing hydrogen, methane, oxides of carbon, and optionally contains nitrogen, methane, including _e of a gas that is suitable for distribution as a city gas .

It is known, for this purpose, cyclic steam heforraierverfahren apply, in which a bed of a catalyst alternates through the hot products of combustion a fuel is heated with air and then used for the endothermic steam reforming stage. Gas generation is necessarily discontinuous.

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The catalytic converter must be robust to withstand the high temperatures to which it is exposed during the heating phase and the temperature changes which are caused by the discontinuous operation to be able to withstand. That's why such a Catalyst has a limited activity, and a large volume of catalyst is required for a certain gas throughput.

The applicant's British patent specification 1 043 377 describes a method for reforming methane, in which a continuous operation is provided without direct heating of the catalyst vessel, whereby temperature fluctuations be avoided. Here, the heat consumed in the conversions is used as sensible heat (sensible heat) fed to the preheated reactants entering the catalyst vessel. With this procedure "will the required heat, for example with the help of a heated tubular preheater on the gases via « wear.

In contrast, the invention relates to a method for generating a gas containing hydrogen, methane, oxides of carbon and optionally contains nitrogen, by reforming

of methane with water vapor, in which a mixture containing methane and water vapor in a preheating stage, the contains at least one cyclically operated regenerator,

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is heated. The regenerator is made by passing the hot gaseous products of a suitable combustible Material heated and in the preheating of the reformed Mixture cooled to the desired value, whereupon the mixture under such conditions with a Steam reforming catalyst is brought into contact that the methane content of the mixture to the desired Value is decreased. For heating the cyclically operated Regenerators can expediently use the combustion products of methane. The preheater can be useful provide most or all of the heat necessary to sustain the endothermic steam reforming reaction is required. A suitable source of methane is natural gas, which has a greater proportion of Xthane and less May contain amounts of higher gaseous hydrocarbons. If these are available, they participate in a similar way like methane in the implementation, however, it can then be advisable to use a higher proportion of water vapor per unit weight than with methane alone.

In the normal execution of the method according to the invention is usually heated methane and water vapor-containing mixture to such an extent that its temperature in the range of 600 - is 800 ⁰ G, before it enters the catalyst bed} usually occurs have the emerging from the catalyst bed gases a Temperature of about 450 - 550 ⁰ C.

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According to a further aspect of the invention, the A gaseous reaction consisting of methane and water vapor is mixed in with air, for example by the density and thus also to regulate the Wobbe number of the gas produced. The air can be added before the preheated Reaction mixture of methane and steam reaches the reforming catalyst. This previous addition of Air can take place before or after the reaction mixture is passed through the regenerative preheater.

However, a second catalytic reforming stage can also be used be used, on which the gaseous products emerging from the first reforming stage are drawn in air. is set, and the heat of reaction of the second reforming stage is then by oxidation of some of the gases generated over the catalyst bed.

The gases generated by the method according to the invention

can be further treated in a manner known per se after leaving the first or, if appropriate, the second stage. The carbon monoxide is converted into carbon dioxide and hydrogen, the carbon dioxide is partially or completely removed and the gas is cooled. , The level of carbon monoxide conversion are 550- ⁰ C - in the production of town gas, in certain cases in which the final temperature at which over the second stage catalyst, the equilibrium is reached in the range of 500

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~ 5

not required, furthermore the composition of the the gas generated by the method according to the invention meet normal town gas requirements without the need to remove carbon dioxide.

When carrying out the method according to the invention using a regenerator, of course, the supply is the Reactants for the catalyst stage or stages discontinuous. If you want a continuous supply of the reactants to a maximum To achieve throughput through the catalyst stage or stages, "you need at least two regenerators» It is usually not necessary to use more than two regenerators. These are preferably like this arranged and "operated that" when heating a regenerator the other provides the necessary preheating for the mixture containing methane and water vapor to be reformed »

The pressure "at which the procedure can be carried out, is limited by the cyclical operation of the regenerators to atmospheric pressure or pressures of a few atmospheres ", which, for example, are not significantly above 5 ata.

A particular embodiment of the invention is in the following Description and the accompanying drawings explain

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tert, in which a process is shown schematically, in which methane and water vapor are reformed using two cyclically operated regenerators to produce a Preheat mixture of steam and methane, whereupon these gases are reformed in two catalyst vessels.

Reference is now made to the drawings. During the operation in which the regenerator 12 is heated, are the combustion products of methane and air introduced into the regenerator 12 at 11? the cooled gases leave the regenerator at 13 and are passed through the chimney 25 into the atmosphere. Similarly, when the regenerator 12 is heated, the hot products of combustion of methane and air at 11 'enter the regenerator 12 ^? and the gases from which the heat has been withdrawn leave the regenerator at 13 'and are discharged through chimney 25. A mixture of steam and methane is heated by being alternately passed through the regenerators 12 and 12 · so that the preheated mixture of methane and water vapor over 18 and 18 · at a temperature of 750-800 ⁰ C continuously first into the catalyst vessel is passed, which contains a nickel-containing steam reforming catalyst.

The water vapor and methane are reformed in vessel 19

Water vapor, mated, with a mixture of methane / hydrogen off and the Oxides of carbon are produced. This product gas will

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then mixed with the air introduced at 20, whereby some of the gases in the catalyst vessel 21 are oxidized so that an effective steam heating temperature is maintained. The gases emerging from the catalyst vessel 21, which ^{adhere to a temperature between 500 and 550 0} C, are passed into the waste heat boiler 22 and then into a cooler 23, in which the water vapor condenses into water and out of the. System is removed.

The gas formed, which leaves the system at 24, can be used as town gas.

Suitably, it is ensured that the temperature of the refractory filling material of the regenerators is not excessively high, so that exceed at any stage of the cyclic operation, the temperature of the preheated reactants 800 ⁰ C. Operation is preferably also carried out in such a way that during that phase of a cycle in which the preheated steam-methane mixture emerges from a specific regenerator, its temperature is subject to as little fluctuations as possible and, above all, there is no significant tendency for the preheating to occur. Regenerator supplies a preheated steam-methane mixture, the temperature of which is lower at the end of the phase than at the beginning of the phase. This condition is best met by first ensuring that practically the

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entire refractory filling compound is brought to a uniform temperature of little more than 800 ⁰ C, and secondly by the fact that the Waeserdampf-Methane mixture to be preheated is passed through so that practically the entire mixture is preheated to near this temperature, so that at the beginning During the next heating phase of the regenerator, almost the entire refractory mass in the regenerator has the inlet temperature of the methane-water vapor mixture (or is close to it) before it arrives at the preheater.

The heating of the regenerators can be done by controlling the temperature the combustion products of methane and air fed to the regenerators during the heating phase, e.g. by excess air is used; however, it is more effective to reduce the products of combustion that result from their Passing through the regenerator is cooled. have to lead back and to mix with the incoming combustion products. During the cycle in which the regenerator 12 is heated, the products of combustion of the methane and the air flowing through the pipe 11 are admixed of gases which have given up part of their sensible heat to the regenerator 12, flowed through the pipe 13 and have been sucked in through H and pumped through 16 with the aid of the fan 17, cooled to a suitable temperature. The part of the gas stream which flows through I3 and which is not returned is via the chimney 25 into the Atmosphere derived, and the temperature control takes place

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As a result, that the components of the current flowing through 13 split between 14 and 25.

The regenerator 12 'is heated in a corresponding manner Way, whereby it is expedient to have a single fan 15 between the two heating systems for the regenerators use.

The method described above, taking into account the drawing, has the advantage over the usual cyclic reforming _¥ mierverfahren that the catalyst of the steam reforming stage can work without being exposed to a rapidly changing oxidizing and reducing atmosphere or temperature fluctuations or temperatures above 800 ^{0 O.} is. The temperature fluctuations in the catalyst bed that occur when a single regenerator is operated are also insignificant. Furthermore, the embodiment of the process in which two regenerators are used, as has been described in connection with the drawing, allows the process to be operated continuously with a maximum throughput through the catalyst vessel under very uniform conditions.

Of course, the invention is not restricted to the embodiment described and explained above .

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The following examples serve to further illustrate the process according to the invention.

example 1

Algerian natural gas made from sulphurous compounds "was freed, was in a device whose operation corresponded to that of the cyclic regenerator according to the description, mixed with steam, preheated and without the admixture of air through a bed of steam reforming catalyst, which was enclosed in an isolated vessel, passed through.

Pressure, ata

Composition of natural gas,
Vol .- $ i

CH ₄ C ₂ H ₆ C ₃ H ₈ C ₄ H ₁₀ C ₅ H ₁₂ 85.9 10.3 2.4 '1.25 0.15

Weight ratio water vapor / natural gas 3 J

* Try Fr. 1 2 3

Preheating temperature of the

Natural gas steam

mixed, ⁰ C 650 700 750

Temperature of the mixture
"when leaving the reforming vessel, ⁰ C 482 502 527>

Composition of
generated gas, vol.
co ₂ 12.3 12.7 12.1 CO 0.5 0.9 1.1 ^H 2 35.8 37.1 44.0 CH ₄ 51.4 49.3 42.8 1CX) ₁ O 100.0 100.0

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Calorific value of the grass,

kcal / m ^ (BTu / cu.ft.) 5560 (625) 5440 (610) 505O (568)

Example 2

Water steam and methane were in the weight ratio 2.0: mixed and pre-heated so that a continuous flow of the mixture occurred at a temperature of 760-780 ⁰ C in the first catalyst bed. The pressure was Z ata.

The reactions in the bed gave a gas stream which, after leaving the first catalyst stage, had the following composition (in Vol .- #) had:

CO ₂ 6.0

CO 0.6

H ₂ 26.0

CH ₄ 24.5

H ₂ O 42.9

100.0 The temperature of the mixture was 480 - 485 ° C

About 247 liters of air per kilogram used for heating foethane (3.95 cu.ft. air / lb. methane) were the ones from the first Stage gases were added and the mixture was passed through the second stage catalyst. The gases left

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this stage "at 500 ⁰ C and had the following composition (in VoI .- #):

C0 "6.7

C. r

CO 1.0

H ₂ 28.0 OH ₄ 21.3

N ₂ 3.8

H ₂ O 39.2

100.0

The water vapor was condensed and the dry gas had the following composition (in Vol .- #):

CO ₂ 11.1

CO T, 6

H ₂ 46.1

CH ₄ 35.0

N ₂ 6.2

100.0

The gas was suitable for distribution as town gas and had a calorific value of about 4450 kcal / m · ^ (500 "btu / cu.ft.), a specific gravity (compared to air = 1) of 0.469 and a Wo "b" be number of 730.

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Example 3

Natural gas freed from sulfur-containing compounds was used in a device whose mode of operation corresponded to that of the cyclic regenerator as described, mixed with water vapor, preheated and passed through a first bed of steam reforming catalyst. The one from the first Exhaust gases were mixed with air and passed through a second bed of steam reforming catalyst3 directed. The exiting from the reformer Gases were cooled, with undecomposed water vapor being condensed.

Composition of natural gas before sulfur removal, vol -7 $:

CH ₄ O ₂ H ₆ C ₃ H ₈ .C ₄ H ₁₀ C ₅ H ₁₂ N _g

80.5 13.3 5.65 0.3 0.1 0.15

Weight ratio

Steam / natural gas 3.18

Temperature of the in the first

Entering catalyst bed

Mixture, ⁰ C.

Pressure at the entrance to the first

Catalyst bed, atmospheric (p.s.i.g.) 4.5 (64)

Composition of the gas at

Exit from the first catalytic converter stage, #

CO H _n CH, N

2 .4 "2 2

6.35 0.75 20.7 17.4 0.1 54.7 00982 8/0566

Temperature of the first

Exiting catalyst stage

Gas, ⁰ C * "526

Air addition after the first

Catalyst level, liters per kg

(cu.ft./ib.) natural gas for reforming 17.9 (2.87)

Temperature of the gases at the outlet of the

second catalyst stage, ⁰ C 520

Composition of the gas at the outlet
the second catalyst stage, Vl $

CO ₂ CO H ₂ CH ₄ N ₂ H ₂ O

6.4 0.8 20.45 16.5 2.3 53.55

Properties of the gas at the outlet of the second catalyst stage after the cooling and condensation of water vapor:
Composition, vol .- ^:

CO ₂ CO H ₂ CH ₄ N ₂

13.8 1.7 44.0 35.65 4.95

Calorific value, kcal / m ³ (Btu / cu.ft.) 4430. (498)

Specific weight (air = 1) 0.500

Wobbe number 705

Example 4

! Algerian natural gas freed from sulfur-containing compounds was mixed with steam and air at a total of 5 atmospheres pressure in a device whose operation ^{corresponded to that of the cyclic regenerator 1} according to the description, preheated and over a single stage one

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commercial Reformierkatalyaators, which drove autothermally was directed. The gas emerging from the reformer was cooled, with undecomposed water vapor condensing became.

Composition of the natural gas,

^CH 4 ° 2 ^H 6 ^C 3 ^H 8 ^σ 4 ^Η 1Ο ^G 5 ^H 12 85.9 10.3 2.4 1.25 0.15

Weight ratio water vapor / natural gas

Experiment number 1 2 3

Air addition, parts by weight

per part by weight of natural gas 0.25 0.3 0.3

Temperatures, ⁰ C

Input of the reforming catalyst 65Ο 710 78Ο

Reforming catalyst outlet 500 522 542

Tail gas composition,
VoI, .. £ 1

GO ₂

σο ^H 2

N ₂

Calorific value, kcal / nr *

(Btu / cu.ft.) 4800 (540) 4640 (521) 4980 (503)

Wobbe number 746 725 720

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13.3 12th ,8th 12, 15th 0.85 1 , 3 1, 1 38.15 39 , 95 44, 05 41.95 39 , 35 36, 25th 5.75 6th , 6 6, 45

Experiment No. 3 specifically illustrates the production of common town gas by suitable selection of the preheating temperature temperature and the ratio between the air added to the water vapor {and

The catalyst used in the above examples was a standard brand of one commercially available for high temperatures suitable steam reforming catalyst made of nickel and alumina. Of course, in the method according to According to the invention, other steam reforming catalysts which are stable at high temperatures can also be used.

- patent claims -

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Claims (12)

~ ¹⁷ Patent claims: \ A process for the production of hydrogen, methane and oxides of carbon and optionally nitrogen-containing gases by reforming methane with water vapor, characterized in that the mixture containing methane and water vapor is in a preheating stage which contains at least one cyclically operated regenerator which is passed through heated gaseous products of a suitable fuel and which is cooled to a certain value when the mixture to be reformed is preheated, and the mixture is brought into contact with a steam reforming catalyst under such conditions that the methane content of the mixture is reduced to the desired value. 2. The method according to claim 1, characterized in that natural gas is used as the methane source. 3. The method according to claim 1 or 2, characterized in that the methane and water vapor-containing mixture to a temperature in the range of 600 - 800 ⁰ C preheated. 4. The method according to claim 1 to 3 »characterized in that the temperature of the gases emerging from the catalyst bed is set to the range from 450 to 55 ° ° ^G. 009828/0566 5. The method according to claim 1 to 4, characterized in that that one mixes the mixture of methane and water vapor with air before the preheated reaction mixture from Methane and water vapor enter the reforming catalyst. 6. The method according to claim 5, characterized in that air is added to the mixture of methane and water vapor, before the reaction mixture passes through the regenerative preheater fc is directed. 7. The method according to claim 5, characterized in that air is added to the mixture of methane and water vapor after the reaction mixture has passed through the regenerative Preheater was passed. 8. The method according to claim 1 to 4, characterized in that when using two catalytic reformers adding air to the gaseous products emerging from the first catalytic reformer before the reaction mixture is passed through the second catalytic reformer. 9 # Method according to Claims 1 to 8, characterized in / that two cyclically operated regenerators are used in the preheating stage. 009828/0566 10. The method according to claim 1 to 9, characterized in that the reforming catalyst is only driven with the heat, which is provided by the preheated reaction mixture entering the reforming catalyst. 11. The method according to claim 1 to 10, characterized in that the operating pressure is not significantly above 5 ata. 12. Hydrogen, methane, oxides of carbon and optionally Nitrogen-containing gas, characterized in that, according to the method according to Claims 1 to 11 manufactured i ~ t. 009828/0566 Blank page