PROCESS AND APPARATUS FOR STEAM REFORMING

Abstract

A process and an apparatus for generating a hydrogen- and/or carbon monoxide-comprising gas product, wherein a hydrocarbon feed formed from a hydrocarbons-containing starting material is supplied together with superheated steam to a steam reforming proceeding at elevated pressure to obtain a hydrogen- and carbon monoxide-containing crude synthesis gas from which the gas product is derived are disclosed. The boiler feed water is supplied at a pressure higher than its critical pressure with heat to obtain supercritical water of which subsequently at least a portion is employed as propelling medium in a steam jet ejector by means of which the hydrocarbon feed and/or a substance employed for the formation thereof are compressed.

Claims

1. A process for generating a hydrogen- and/or carbon monoxide-comprising gas product, wherein a hydrocarbon feed formed from a hydrocarbons-containing starting material is supplied together with superheated steam to a steam reforming proceeding at elevated pressure to obtain a hydrogen- and carbon monoxide-containing crude synthesis gas from which the gas product is derived, characterized in that boiler feed water is supplied at a pressure higher than its critical pressure with heat to obtain supercritical water of which subsequently at least a portion is employed as propelling medium in a steam jet ejector by means of which the hydrocarbon feed and/or a substance employed for the formation thereof are compressed.

2. The process according to claim 1, characterized in that during compression of the hydrocarbon feed in the steam jet ejector a substance mixture is formed which meets the requirements of steam reforming on account of its composition and/or has a pressure allowing supply to the steam reforming without further compression.

3. The process according to claim 1, characterized in that the boiler feed water is heated in indirect heat exchange against flue gas from which heat is removed beforehand for the steam reforming.

4. The process according to claim 1, characterized in that the substance mixture formed during compression of the hydrocarbon feed in the steam jet ejector is heated in indirect heat exchange against flue gas from which heat is removed beforehand for the steam reforming reaction.

5. The process according to claim 1, characterized in that supercritical water is generated at a pressure not more than 20 bar higher than the critical pressure of the boiler feed water.

6. The process according to claim 1, characterized in that a portion of the supercritical water not required as propelling medium for the steam jet ejector is exported and used for a process selected from the group consisting of generating electrical power, for heating purposes, for performing chemical reactions, as an extractant, and for destroying toxic substances.

7. The process according to claim 6, characterized in that before export the portion of the supercritical water not required as propelling medium for a steam jet ejector is heated further against flue gas that is to be cooled.

8. The process according to claim 1, characterized in that natural gas or vaporized liquefied gas or vaporized naphtha is used as the hydrocarbons-containing starting material.

9. An apparatus for generating a hydrogen- and/or carbon monoxide-comprising gas product from a hydrocarbon feed formed from a hydrocarbons-containing starting material, comprising a steam reformer and a system for process steam generation from boiler feed water, characterized in that the system for process steam generation comprises a once-through boiler operable in the supercritical range whose superheater is connected via a throttling means to a steam jet ejector so that supercritical water generable in the superheater can be used as propelling medium in the steam jet ejector for compressing the hydrocarbon feed and/or a substance employed for the formation thereof.

10. The apparatus according to claim 9, characterized in that the once-through boiler is arranged in the flue gas channel of the steam reformer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention is to be more particularly elucidated hereinafter with reference to a working example shown in schematic form in the FIGURE.

[0025] The FIGURE shows a plant in which pure hydrogen is derived as a gas product from a hydrocarbons-containing starting material by steam reforming.

DETAILED DESCRIPTION OF THE INVENTION

[0026] A hydrocarbons-containing starting material 1, for example natural gas, vaporized liquefied gas or naphtha, is divided into a first substream 2 and a second substream 3. While the first substream 2 is supplied as fuel to the steam reformer D for heating the firebox F the second substream 3 is mixed with recycled hydrogen 4 and introduced into the treatment means B to remove substances such as sulfur compounds which would result in failures in the downstream plant parts and to provide a hydrocarbon feed 5 for the steam reformer D. Since the pressure of the hydrocarbon feed 5 is too low for direct introduction into the steam reformer D operated at about 20-30 bar(a) it is supplied to the steam jet ejector V to increase the pressure.

[0027] To generate process steam demineralized water 6 is passed into the treatment means C to be degassed and treated to afford boiler feed water 7. The boiler feed water 7 which is under slight positive pressure is subsequently brought by means of the boiler feed water pump P to a pressure up to 20 bar above its critical pressure and via conduit 8 supplied to the heat exchanger E1 arranged in the flue gas channel A of the steam reformer D where in indirect heat exchange with hot flue gas 9 supercritical water 10 is formed. A portion 11 of the supercritical water 10 is exported and may be utilized for example for power generation in a steam turbine (not shown). By contrast, the remainder 12 of the supercritical water 10 is decompressed via the throttling means a to form superheated steam 13 which is employed as propelling medium in the steam jet ejector V to bring the hydrocarbon feed 5 to the pressure required for steam reforming while simultaneously effecting intensive mixing thereof with the propelling medium which serves as process steam. The supercritical water 10 is preferably generated at a pressure and a temperature which make it possible to supply the superheated steam 13 to the steam jet ejector P with the entirety of the process steam required for the steam reforming so that the material stream 14 leaving the steam jet ejector V without any further alteration of its composition and merely after superheating against hot flue gas 15 in the second heat exchanger E2 arranged upstream of the first heat exchanger E1 may be introduced as superheated feed 16 into the reformer tubes R of the steam reformer D.

[0028] From the hydrogen-rich crude synthesis gas 17 generated in the reformer tubes R by steam reforming, in the purification means G by removal in particular of water and carbon monoxide a synthesis gas 18 consisting largely of hydrogen and carbon monoxide is generated which in the pressure swing adsorber W is resolved into pure hydrogen 19 and a residual gas 20 consisting predominantly of carbon monoxide. While the residual gas 20 is burned in the firebox F of the steam reformer D to provide energy for the reforming reaction the larger part of the pure hydrogen 19 is discharged as gas product 21 and the smaller part 4 is recycled upstream of the treatment means B into the second substream 3 of the starting material 1.