DE1255641B - Process for the production of hydrogen - Google Patents

Description

GERMAN

GERMANY

PATENT OFFICE Int. CL:

COIb

EDITORIAL

German class: 12 i- 1/18

Number: 1 255 641,

File number: M 55903 IV a / 12 i

Registration date: February 26th, 19.6.3.

Opened on: December 7, 1967

The invention relates to an improved process for the production of technical grade hydrogen gas through the catalytic conversion of hydrocarbons with water vapor.

The currently common process for the production of technical hydrogen gas consists of

a) a catalytic conversion of hydrocarbons with water vapor at pressures im Range from about 7 to about 10.5 atmospheres,

b) Conversion of the product of this first implementation to convert most of the carbon monoxide into carbon dioxide,,

c) Removal of CO ₂ from the crude hydrogen gas and. .

d) removing the CO from the hydrogen by conversion into methane or by absorption by copper (I) salt solutions, to be performed with the hydrogen hydrogenation provided by the presence of carbon monoxide is adversely affected _ao.

In the first step of this conventional process, the hydrocarbons are converted to about 90 ° / ₀ hydrogen.

A large number of plants for the production of hydrogen around the world use the process of catalytic reforming of hydrocarbons with water vapor at elevated temperatures. Most of them are operated under such conditions that in this process step a very high conversion of the hydrocarbons of, for example, over 90 ° / ₀ and thus also the greatest possible formation of hydrogen results, since an admixture of inert gases such as methane, the The usability of the hydrogen is impaired. In a hydrogenation process, e.g. B. in the high pressure hydrogenation of carbon-containing materials, contamination of the hydrogen by an inert gas, such as methane, causes a significant impairment of the efficiency of the operation. In many hydrogenations it is necessary to maintain a hydrogen concentration of approximately 90% in the gas phase. Under these circumstances, the introduction of 1 part by volume of an inert hydrocarbon with the gas to be reacted requires the simultaneous addition of more than 9 parts by volume of hydrogen, of which 9 parts are lost to the system, since every mole of methane admitted, 9 moles of hydrogen are practically ineffective power.

It is known that the reforming of hydrocarbons at elevated pressure is certain economic processes for the production of hydrogen

Applicant:

Walton H. Marshall Jr.,

Downings, Va. (V. St. A.)

Representative:

Dr.-Ing. E. Maier, patent attorney,

Stuttgart i, Werastr. 24

Named as inventor:
Walton H. Marshall Jr.,
Downings, Va. (V. St. A.)

Claimed priority:

V. St. v. America 28 February 1962 (176 362)

liche advantages, since the expenses for the Compression of the gas is reduced and a better recovery of the heat is made possible. On the On the other hand, it is also known that the application of higher pressure will reduce the conversion of the hydrocarbon slowed down. The reaction that usually takes place as the main reaction can e.g. B. can be expressed by the following equation:

CH ₄ + H ₂ O - * CO + 3H ₂

On the basis of this equation it follows from the law of mass action that the deceleration the response proportional to that. Is the square of the absolute pressure in the system. Accordingly, a compromise must be made in the construction of a hydrogen generation plant between the specific advantages that result from the use of higher pressures on the one side and the associated disadvantage of a less extensive conversion of the hydrocarbon to be found on the other side. In current industrial practice, Hydrogen is produced at a pressure of about 8.75 atmospheres or less with a conversion in the process of the hydrocarbon up to about 90% and more. This applies to immediate education of hydrogen; after cleaning the raw gas and converting the carbon monoxide into methane the hydrogen reaches degrees of purity of 96% and higher. In some plants for the extraction of Ammonia synthesis gas is known to be higher

709 707/526

3 4

Pressures are applied, but according to this drawing, a hydrocarbon is used in this process

introduced in a second reforming step air, or a mixture of hydrocarbons and

causing a rise in temperature, water vapor in the convection zone of a reformer

which the retarding effect of the increased pressure mierungsofens 1 on a temperature of about

rebalances. 5 400 ⁰ C preheated, whereupon the from the mentioned

Contrary to all expectations and for a person skilled in the art, two-component mixture in not

It was found, completely surprising, that the tubes prepared were filled with the catalyst

position of hydrogen by conversion of is conducted, which is in the radiant heat zone of the

Hydrocarbons are significantly affected by steam in the reforming furnace 1. The pressure of the

improves and also from an economic point of view far io reforming furnace entering gases is approximately

Can be carried out more profitably if according to the invention, and the ratio of water vapor to

according to a water vapor carbon (ratio of the number of oxygen atoms

Carbon ratio from about 3.0 to about in the water vapor to the number of carbon atoms in the

7.0 and a pressure-from about 21 to about ... hydrocarbon) is in. The specified gas-

50 ATA is observed, and that of the formed 15 mixture is set to 4.0. The gases that the

Hydrogen the unconverted hydrocarbons reforming furnace 1 with a temperature of un-

separated by freezing. about 805 ⁰ C, contained due to the

Preferably, a water vapor-carbon reaction with the water vapor occurs approximately

Ratio of about 4 and a pressure of about 35 ata 65% of the given carbon in the form of

applied. 20 oxides of carbon. The remaining coal

In a particularly preferred embodiment, hydrogen material consists largely of methane,

of the process according to the invention, this becomes heavier in the case of the but small amounts can also be used

Conversion obtained condensate evaporates and hydrocarbons are present, provided that they are in the

returned to the reforming zone. It contained starting gas. In a usual

If a steam-coal 25 waste heat steam boiler 7 is used, heat is used to generate it

substance ratio of about 3 to 7 pressures of about excess steam between the combustion

21 to 50 ata preferred, while when using the first reforming gas and water out-

a water vapor to carbon ratio of about exchanges.

3.5 pressures of about 25 to 42 ata are particularly the gases leaving the reforming furnace 1

have proven beneficial. 30 is cooled ^{to approximately 370 °} C. in a steam boiler 8

Another advantage of the inventive supply and then supplied to the converter 2, in

driving lies in the fact that the pre-cleaned gases in front of which the main part of the carbon monoxide is in

the low-temperature separation further amounts of carbon dioxide is transferred, with additional

Hydrogen of low purity added forms hydrogen. That in the steam boiler 8 to

can be. 35 evaporating water can be of any origin;

The improved method according to the invention for it is, however, particularly advantageous for this purpose of hydrogen consists in a catalyzed mix of condensates from the process itself Conversion of hydrocarbons, such as turning that deposited after the conversion Methane, pentane, or heavy hydrocarbons are used, and the contaminated steam in the reformite Water vapor can be traced back to 40 mierofen 1, which is unusual for this purpose, as detailed below To press. This results in an extremely licher is presented.

low conversion of the hydrocarbons in the conversion in the practical range of about 50 to about 85% and implementation of the inventive improved Very preferably in the range between 60 and 75 ° / ₀ , so that a number of variations can be applied to the resulting drive Unusually 45 hydrogen is about the use of two or more lesser degrees of purity and when working with different catalysts at different temperatures, the preferred conversion is 27.5 to 14%. Of the reaction gases that the converter 2 contains of unconverted hydrocarbons. can be left, as indicated by a steam boiler 9 and in order to make this less pure hydrogen suitable for industrial use, a heat exchanger 10, after which waste heat will be recovered. The gas flow in the present process in the series of process steps then arrives at the hot side of a device 11 following a process step to thermochemical heat recovery, where it was not previously necessary. This condensing excess steam, the energy for the process step, is the separation of hydrogen, the regeneration, which takes place in a known manner, and hydrocarbon by deep freezing, whereby 55 of used cleaning solutions, such as the purity of the hydrogen gas, preferably to aqueous solutions of monoethanolamine and potassium to contents of 97.5 up to 99% is increased. It has shown carbonate, which for the removal of carbon dioxide from itself - completely unexpectedly - that in one of which hydrogen is used provides
The hot condensate separates with approximately the material used hydrocarbon in 60 127 ° C in the separator 3, whereupon the gas flow in connection with a separation by freezing a heat exchanger 12 almost to room temperature considerable economic advantages over the temperature is cooled; practically the conventional process for the production of water - the total amount of still remaining water vapor can be achieved. brought to condensation. After removing the

The drawing shows a preferred embodiment 65 of the cooling of the condensate formed in the separator 4

again and should serve to ensure that the crude hydrogen gas according _{to the invention reaches the CO 2 exhaust}

Procedure and the separators achieved in its implementation 5. After the removal of the CO ₂ is the

Explain advantages in more detail. Hydrocarbon content of hydrogen unusual

5 6

borrowed high; it is about 12 ° / _0, while in hydrogen per day is reduced upon application

the usual way produced hydrogen on that of the improved process with a pressure of

Only add 2 to 3 per _cent. Or less of hydrocarbons to about 35 atmospheres in the reforming reaction

contains substances. The hydrogen obtained in this way is the energy required to compress the water

consequently for hydrogenation reactions not yet ₅ substance by about 1215 PS, compared with that

suitable. corresponding energy demand that is required,

To remove the inert hydrocarbons when the reforming reaction is at about 8.75 atm

the partially purified gas is made in the device 6. If one draws the energy

subjected to a deep-freeze process, in which the requirement of approximately 507 HP for the gas purification

Hydrogen and the hydrocarbons at a ₁₀ by freezing off, so there is a real one

Temperature from about -168 to about -179 ^° C. Savings of about 708 hp. Also supplies

be separated from one another in a known manner. one according to the present process with one

This deep-freezing process requires the supply of energy at a pressure of about 35 atmospheres during the reforming process.

outside, the system operating in the waste heat steam boiler through the reaction supplied through the feed line 13

compressed refrigerant occurs, which corresponds to ₁₅ of the reforming as much water vapor as a by

stretched state through line 14 again product that thus the compressors of the system

is discharged. That can be operated by freezing at approximately, even if the hydrogen

-173 ⁰ C obtained technical hydrogen gas then for a high pressure hydrogenation at un-

holds approximately 98.5 ° / ₀ hydrogen and is now atm for ferry 210 or higher is used. Will be in a

Suitable for hydrogenation processes. From the hydrogen from ₂₀ plant of the same size the reforming in

The separated hydrocarbon is released from the freezer at a pressure of approximately 8.75 atmospheres

plant under a relatively low pressure with extensive conversion of the reactants

withdrawn through a line 15. carried out, then results in the water vapor

An additional advantage of the present process creates a deficit so that all of the energy is used for

is that the compressors are additionally expended in the freezing plant also carbon _a5

monoxide can be deposited, so that must.

Carbon monoxide content in the hydrogen produced here. The present improved process is further reduced to 0.1 per thousand or even less. In the following points of the previously usual procedure, there is no need to think wisely:
Hydrogen used for hydrogenation processes _{Qn N} ".... ....,"",. .,,

which should work with a catalytic converter, ^{3 a} > g ^{5 glbt u} ^ ^{efahr 50} / » ^{wemger exhaust gas from the}

who is sensitive to carbon monoxide, in a hydration system,

special process for transferring the carbon b) it delivers hydrogen that is less than 0.1 per mille

to further purify monoxides in methane. Contains carbon monoxide, and

Another benefit of the improved process _{35 c) allows the} hydrogen to be concentrated

there is darm that there is also to be the simultaneous _{from the exhaust gases and the} use of

Processing of otherwise generated hydrogen, _{little pure} hydrogen of foreign origin

low degree of purity or to freshen up _{as part of the charge to the} hydrogenation plant. Exhaust gases or circulated gases from

Hydrogenation plants are suitable. In the figure it is shown ₄₀ In order to take advantage of the present procedure in

In order for these gases to reach the system to the full extent through a line 16, the following must be observed

upstream of the CO ₂ separator 5 so that working conditions are met:

any acidic constituents present such as CO ₂ or i. When reforming, the conversion of the

H ₂ S are removed. Contains the otherwise produced hydrocarbons in hydrogen and oxides of the

However, no such impurities hydrogen, carbon ₄₅ between about 50 and about 85 ° / ₀

so it can be fed directly to the freezing process _and preferably kept between 60 and 75 ° / ₀

will. will. If the conversion drops below 50%,

According to the calculations carried out which is _so j _{w ll} in the deep-freezing is a hydrocarbon gas

Working according to the present improved ver _m ; _t generated too little pressure, which has the consequence,

driving under the above conditions considerably _since ß ₅₀ at which then the necessary compression for

borrowed as the operation of a conven- _d j _e recirculation of the resulting economic low pressure

nelle plant which with a pressure of about gas most of the benefits of the present process

8.75 atm works. be nullified. In the preferred area

In the case of a plant for the production of technical equipment, that corresponds to that in the case of deep-freezing with low pressure

Hydrogen with a daily production of about ₅₅ resulting amount of hydrocarbon gas about

325 000 Nm ³ required the purification of the gas by _the fuel required for the reforming or is

Deep freezing requires _slightly less energy than this; as a result, there is practically

about 507 hp to compress the coolant and _t [ _sc ^ j ^ ine need to re-add this gas

• Compress a capital investment of one million US dollars as it comes with the low pressure of

for the creation of the freezer system. With the new _5o whoever it is immediately available as

like improved method of heating the present fuel. of the reforming furnace

Invention, however, less extensive inputs can be used. When the conversion

directions for compressing the hydrogen _{exceeds about 85 ° / 0} , then the

needed; In addition, the pressure applied in the steam boilers can be reduced to such an extent that

absorb the waste heat of the reforming reaction, g ₅ until the savings return the additional effort

sufficient steam are produced as by-product, to compensate f _{or d} j _e freezing,

to operate all compressors in the system. 2. The pressure in reforming should be between

For a plant producing 325,000 Nm ³ approximately 20 and approximately 50 ata and preferably

i 255 641

between about 25 and about 42 ata! These limits for printing are determined by the thermal peculiarity of hydrocarbon conversion determined and are in a certain, not immediate relationship to the above Limits of the conversion and the limits of the water vapor to carbon ratio described below.

3. That. The atomic ratio of oxygen (from water vapor) to carbon (from hydrocarbon) should in the case of reforming, between about 3.0 and about 7, Q and preferably between 3.5 and 6.0 being held. These limits are determined by the equilibrium conditions that apply to the gas at the exit from the reforming furnace, if the degree of conversion and the pressure is kept within the specified limits.

4, the temperatures in the freezing should be selected so that the hydrocarbon content of withdrawing from the .Tiefkühlanlage hydrogen to a value between about 0.5 and about 4 ° / ₀ and preferably between 1 and 2.5% lower. If the purity of the hydrogen is to be increased above 99.5%, the installation of the deep-freeze system becomes too complicated and the costs for its installation become too high for the technical production of hydrogen. With degrees of purity below 96%, there are only insignificant advantages over the currently used processes for the production of hydrogen with high degrees of conversion, since the amount of exhaust gases is then no longer reduced in the subsequent hydrogenation. Within the preferred range of hydrogen purity of 99 to 97.5%, the freezer, which uses a nitrogen cycle for cooling, is relatively simple. Within this range, the exhaust gas losses during the hydrogenation are kept within moderate limits.

Under certain circumstances, namely when high pressure hydrogenation is to be carried out, can it should be indicated to use the gas before the freezer cleaning to compress. In such a case, the working pressure in the freezer can be between about 45 and about 105 ata. Normally, however, the separation is done by freezing Pressures between about 17.5 and about 45 ata and preferably applied between 20 and about 39 ata.

The condensates produced in the process after the conversion of the gases, which are indicated in the figure as outlets 17 and 18 at the bottom of the separators 3 and 4, contain impurities, primarily dissolved CO ₂ , H ₂ and hydrocarbons. If the condensate is discharged, these contaminants can lead to pollution problems in the forefluid. In order to avoid such pollution, the condensate is usually subjected to an extensive degassing treatment in order to remove the pollutants. It has now been found that this can be avoided by steaming the contaminated condensate and returning it to the reforming zone. Within the specified ranges, the operating conditions of the present process, the majority of the contaminated condensate can be evaporated and recycled in this way; If the preferred conditions are observed, even the entire amount of the contaminated condensate can be evaporated and returned to the reforming zone. The primary heat source for re-evaporation of the condensate may be the reformate which contains a substantial amount of high efficiency heat for evaporation of the condensate or other water. Another source of heat

ίο can be the conversion product. If the preferred conditions of the present process are met and if the total amount of the contaminated condensate is evaporated again and the reforming zone is to be fed, so the larger part of the condensate preferably by heat exchange with the reformed product and the smaller part by heat exchange with the conversion product, e.g. B. in the in the figure reproduced steam boilers 8 and 9, for

ao vaping brought. This possibility of pollution Avoiding the receiving water or saving the costs of the aforementioned degassing is another Advantage of the method according to the invention.

Claims (6)

Patent claims: 1. Process for the production of hydrogen from hydrocarbons by catalytic reforming these hydrocarbons with water vapor and conversion of the resulting Gas mixture, characterized in that the reforming has a water vapor-carbon ratio from about 3.0 to about 7.0 and a pressure of about 21 to about 50 ata is maintained and that of the hydrogen formed, the unconverted hydrocarbons are separated by deep freezing will. 2. The method according to claim 1, characterized in that a water vapor-carbon ratio during the reforming of about 4 and a pressure of about 35 ata is applied. 3. The method according to claim 1, characterized in that the obtained in the conversion Condensate is evaporated and returned to the reforming zone. 4. The method according to claims 1 and 3, characterized in that during the reforming a water vapor to carbon ratio of about 3 to 7 and a pressure of about 21 to 50 ata is applied. 5. The method according to claims 1 and 3, characterized in that during the reforming a water vapor to carbon ratio of about 3.5 to about 6 and a pressure of about 25 to about 42 ata is applied. 6. The method according to claims 1 to 5, characterized in that the pre-cleaned Reaction gases before the low temperature separation further amounts of hydrogen of low purity to be added. Considered publications:
German Patent No. 745 069;
French Patent No. 1158 617;
British Patent No. 635,493;
U.S. Patent Nos. 1,904,592, 1,957,744. 1 sheet of drawings