METHOD AND INSTALLATION FOR OBTAINING HYDROGEN

Abstract

The invention relates to a process for recovering hydrogen (b) from crude gas (a) from a coke oven (110) in which the crude gas (a) produced in the coke oven (110) is initially compressed and in which impurities are subsequently removed from the crude gas (a) by pressure swing adsorption, wherein oxygen is depleted from the crude gas (a) using nonthermal plasma prior to the pressure swing adsorption, and to a plant for recovering hydrogen from crude gas.

Claims

1. A process for recovering hydrogen (b) from crude gas (a) from a coke oven (110) in which the crude gas (a) produced in the coke oven (110) is initially compressed and in which impurities are subsequently removed from the crude gas (a) by pressure swing adsorption characterized in that oxygen is depleted from the crude gas (a) using nonthermal plasma prior to the pressure swing adsorption.

2. The process as claimed in claim 1, wherein oxygen is depleted from the crude gas (a) by using the thermal plasma to activate a catalytic oxygen removal.

3. The process as claimed in claim 2, wherein the catalytic oxygen removal may be performed using in particular platinum and/or palladium and/or copper and/or zinc, in particular on aluminum or aluminum oxide.

4. The process as claimed in claim 2, wherein the catalytic oxygen removal is performed using at least one catalyst (151) arranged in a plasma field of the thermal plasma or downstream of a plasma field with respect to a stream of the crude gas (a).

5. The process as claimed in claim 1, wherein the nonthermal plasma is produced by dielectric barrier discharge or using microwaves.

6. The process as claimed in claim 1, wherein the crude gas (a) is pretreated before the pressure swing adsorption and after the crude gas (a) is compressed, in particular by adsorptive or catalytic means and/or regeneratively or nonregeneratively and/or using a pressure swing adsorption/membrane hybrid process.

7. The process as claimed in claim 6, wherein oxygen is depleted from the crude gas (a) using the nonthermal plasma before or after the crude gas (a) is pretreated before the pressure swing adsorption.

8. The process as claimed in claim 1, wherein oxygen is depleted from the crude gas (a) using the nonthermal plasma after the crude gas (a) is compressed.

9. The process as claimed in claim 1, wherein oxygen is depleted from the crude gas (a) using the nonthermal plasma before the crude gas (a) is compressed.

10. A plant (200, 300, 400, 500) for recovering hydrogen (b) from crude gas (a) comprises a coke oven (110) in which the crude gas (a) is producible, a compression means (120) to which the crude gas from the coke oven (110) is suppliable and which is adapted for compressing the crude gas (a) and a pressure swing adsorber (140) to which the crude gas (a) is suppliable after exiting the compression means (120) and which is adapted for removing impurities from the crude gas (a) and providing hydrogen (b), characterized by a plasma generator (150) which is arranged upstream of the pressure swing adsorber (140) and is adapted for producing nonthermal plasma in the crude gas (a).

11. The plant (200, 300, 400, 500) as claimed in claim 10 further comprising at least one catalyst (151) for removal of oxygen from the crude gas (a) arranged in a plasma field of the nonthermal plasma producible by the plasma generator (150) or downstream of the plasma field with respect to a stream of the crude gas (a).

12. The plant (300, 400, 500) as claimed in claim 10 further comprising a pretreatment means (130) through which the crude gas (a) is conductible before it is supplied to the pressure swing adsorber (140).

Description

BRIEF DESCRIPTION OF THE DRAWING

[0024] FIG. 1 shows a noninventive plant for recovering hydrogen in the form of a schematic process flow diagram.

[0025] FIG. 2 shows a preferred embodiment of an inventive plant in the form of a schematic process flow diagram.

[0026] FIG. 3 shows a further preferred embodiment of an inventive plant in the form of a schematic process flow diagram.

[0027] FIG. 4 shows a further preferred embodiment of an inventive plant in the form of a schematic process flow diagram.

[0028] FIG. 5 shows a further preferred embodiment of an inventive plant in the form of a schematic process flow diagram.

DETAILED DESCRIPTION OF THE DRAWING

[0029] FIG. 1 is a schematic diagram of a plant 100 for obtaining hydrogen (H.sub.2) from crude gas by means of which the process for recovering hydrogen on which the invention is based shall initially be elucidated.

[0030] Produced in a coke oven 110 which may also be a so-called coke oven battery is not only coke but also coke oven gas/crude gas which via a pipeline 115 is supplied as stream a to a compression means 120 which may be a compressor for example. This crude gas may comprise for example about 60% to 65% hydrogen, about 20% to 25% methane and smaller proportions of inter alia nitrogen, carbon monoxide, carbon dioxide, oxygen and heavy hydrocarbons. The precise composition may vary depending on how the coke oven is operated and the coal is employed.

[0031] While the crude gas from the coke oven 110 is generally provided at a slight negative pressure, the pressure swing absorber requires a pressure of for example between 5 and 10 bar and in some cases more, which is produced by the compression means. Once the crude gas has been compressed in the compression means 120, i.e. once the pressure has been increased, the crude gas is supplied to the pressure swing adsorber 140.

[0032] The pressure swing adsorber 140 removes impurities from the crude gas by pressure swing adsorption. Impurities are to be understood as meaning in particular those constituents in the crude gas (which is a gas mixture) that are undesired, i.e. in the present case all fractions save hydrogen. It will be appreciated that the pressure swing adsorption cannot completely remove all impurities. Typical values for the purity of the hydrogen which may be provided by the pressure swing adsorber 140 as stream b are for example at least 98 mol % or higher.

[0033] The gas/the fractions (residual gas) removed in the pressure swing adsorber 140 are supplied to pipeline 115 as stream d and may then be sent for downstream use as heating gas for example.

[0034] For a detailed description of the process described here and in particular of the pressure swing adsorption, reference is hereby made for example to the technical literature recited at the outset.

[0035] As mentioned, the crude gas (stream a) may have an oxygen proportion of 0.6 mol % or higher which may result in particular from leaks in the coke oven 110 and the ambient air aspirated as a result.

[0036] FIGS. 2 to 5 are schematic diagrams of various preferred embodiments of a plant according to the invention by means of which the present invention shall be more particularly elucidated. To a large extent, in particular in terms of the basic components and the corresponding process steps, the plants shown in FIGS. 2 to 5 correspond to the plant 100 of FIG. 1. Reference is thus also made to the above description, identical components being designated with identical reference numerals.

[0037] FIG. 2 shows a plant 200 in whichcompared to plant 100 of FIG. 1a plasma generator 150 and a catalyst 151 are provided between the pipeline 115 and the compression means 120.

[0038] The plasma generator 150 may be for example an apparatus comprising two electrodes to which an alternating voltage may be applied and between which a dielectric material has been introduced. This makes it possible to produce a nonthermal plasma in the crude gas (stream a).

[0039] The catalyst 151 may be for example a catalyst comprising palladium, platinum, copper or zinc on an aluminum surface. Also conceivable is a combination of a plurality of these materials/a plurality of catalysts each comprising one of these materials.

[0040] The catalyst 151 may be arranged in a plasma field formed upon production of the nonthermal plasma. In the case of dielectric barrier discharge the catalyst 151 may thus be arranged for example between the dielectric material and a corresponding electrode. However, it is also conceivable for the catalyst 151 to be arranged downstream of the plasma generator 150 with respect to the stream a and its flow direction.

[0041] Production of the nonthermal plasma then makes it possible to carry out the catalytic oxygen removal/the depletion of oxygen from the crude gas particularly efficiently and in particular at comparatively low temperatures. The crude gas is thus already heavily depleted of oxygen in the subsequent compression and in the pressure swing adsorption 140 so that an ignitable mixture is no longer present and a safe removal of further impurities is possible.

[0042] Typical values for the purity of the hydrogen which may then be provided by the pressure swing adsorber 140 as stream b are for example at least 99 mol % or higher while a value of 99.9999 mol % is in particular also conceivable.

[0043] FIG. 3 shows a plant 300 in whichcompared to plant 200 of FIG. 2a pretreatment means 130 is provided between the compression means 120 and the pressure swing adsorber 140.

[0044] The pretreatment means 130 may for example comprise a membrane which allows for removal of impurities even before the pressure swing adsorption. The membrane thus provides together with the pressure swing adsorber 140 a two-stage pressure swing adsorption/membrane hybrid process for removal of impurities.

[0045] FIG. 4 shows a plant 400 in whichcompared to plant 300 of FIG. 3the plasma generator 150 and the catalyst 151 are provided not between the pipeline 115 and the compression means 120 but between the compression means 120 and the pretreatment means 130.

[0046] FIG. 5 shows a plant 500 in whichcompared to plant 400 of FIG. 4the plasma generator 150 and the catalyst 151 are provided not between the compression means 120 and the pretreatment means 130 but between the pretreatment means 130 and the pressure swing adsorber 140.

[0047] The variants shown in FIGS. 4 and 5 may allow more efficient removal of oxygen compared to the variant from FIG. 3 depending on the available plant/options.

[0048] It will be appreciated that further variants are also conceivable. Thus for example in a plant without a pretreatment means, as is shown for example in FIG. 2, the plasma generator 150 and the catalyst 151 may also be provided between the compression means and the pressure swing adsorber.