WO2009124666A2

WO2009124666A2 - Method and device for producing hydrogen and/or carbon monoxide from coke

Info

Publication number: WO2009124666A2
Application number: PCT/EP2009/002267
Authority: WO
Inventors: Stefano Innocenzi; Christian Freitag
Original assignee: Linde Aktiengesellschaft
Priority date: 2008-04-08
Filing date: 2009-03-27
Publication date: 2009-10-15
Also published as: WO2009124666A3; DE102008017820A1

Abstract

The invention relates to a method and a device for obtaining hydrogen (19) and/or carbon monoxide (17) from coke (1), the coke (1) being converted by partial oxidation (V) at pressures of between 2 and 8 bar and temperatures of between 500 and 1,000 °C into a gas (waste gas) (20) containing carbon monoxide and carbon dioxide. An oxidant (2) consisting of water vapour (4) and/or oxygen (3) and carbon dioxide (5) is used to convert the coke (1).

Description

description

Process and apparatus for producing hydrogen and / or carbon monoxide from coke

The invention relates to a process for the production of hydrogen (H ₂ ) and / or carbon monoxide (CO) from coke, wherein the coke by partial oxidation at pressures between 2 and 15 bar and temperatures between 500 and 1000 ° C in a carbon monoxide and carbon dioxide ( CO ₂ ) containing gas (exhaust gas) is reacted.

The term coke refers predominantly to carbon solids, such as those incurred in refineries as residues.

A method in which coke is produced, for. As the catalytic cracking (fluid catalytic cracking or FCC) of crude oil distillates. The coke (FCC coke) settles on the catalyst used for the cleavage and impairs its effectiveness. It is therefore necessary to regenerate the catalyst material at intervals by thermal treatment (burnout), wherein the coke is reacted with atmospheric oxygen and gasified. In order to avoid damage to the catalyst material by excessive temperatures, the regeneration is carried out under oxygen deficiency, whereby the coke does not react completely to CO ₂ , but partly only to CO. That at the

Catalyst regeneration produced exhaust gas (FCC exhaust) therefore contains CO in a significant concentration, which is small compared to the concentrations of nitrogen, which is fed together with the oxygen in the air regeneration process, but also to that of carbon dioxide.

Long-chain residues that are not directly usable in a refinery (eg vacuum residues) are often converted into short-chain hydrocarbons by so-called integrated fluid coking gasification (IFCG). An example of such a method is the Flexicoking ^® process of Exxon. This process also produces coke (IFCG coke), which is gasified at low temperatures, low pressure and under oxygen deficiency with air and water vapor. The use of air rather than oxygen, as is common in other gasification processes, makes it easier to achieve the desired low gasification temperatures and to control. In addition, it makes the purchase of an expensive air separator for oxygen production superfluous.

The water formed during the gasification of the coke-IFCG exhaust gas (IFCG exhaust gas) is cleaned of dust, water and sulfur compounds, and then has approximately the following composition in the case of flexi ^® process:

Nitrogen 50Vol%

Carbon monoxide 24Vol% Hydrogen 18Vol%

Carbon dioxide 7Vol%

Methane 1% by volume

Hydrogen and carbon monoxide are sought-after in the chemical and petrochemical industry for a variety of applications and therefore valuable raw materials. Because of their comparatively low concentrations and the relatively low gas pressure of 2-3 bar, it is not possible in the prior art to separate H ₂ and / or CO from FCC and IFCG exhaust gas in an economical manner in product quality. In particular, the CO separation is problematic because carbon monoxide and nitrogen have very similar boiling points. So far, such exhaust gases are therefore used for Unterfeuerung, for example in steam generators, where they substitute other energy sources (eg natural gas). The disadvantage here, however, that the facilities to be heated because of the large nitrogen ballast with significantly larger heating surfaces, and thus more expensive, must be performed, as is the case with a natural gas fired.

The object of the invention is therefore to provide a method of the type described above and a device for its implementation, by which an exhaust gas is generated from which at least hydrogen and / or carbon monoxide can be separated in an economical manner with product quality.

The stated object is achieved in that for the implementation of the coke from water vapor and / or oxygen and carbon dioxide existing oxidant is used. The carbon dioxide contained in the oxidizing agent is inert under the conditions of the coke gasification according to the invention and therefore performs the same tasks that the atmospheric nitrogen in the coke gasification of the prior art fulfills: it absorbs a part of the heat released during the gasification and simplifies it, to achieve and control the desired low gasification temperatures.

The inventive use of a nitrogen-free oxidizing agent results in the coke gasification of a nitrogen-free, hydrogen and / or carbon monoxide containing exhaust gas, which consists to a large extent of carbon dioxide. Such an exhaust gas can be treated with relatively little effort and processed into commercially useful products.

The exhaust gas produced in coke gasification may contain, in addition to gaseous ones, also solid components, such as soot and dust, which are troublesome in gas separation and recovery of products. An embodiment of the method according to the invention provides that the exhaust gas is purified of solids in a purification step before it is subjected to further treatment steps. Conveniently, the solids are separated by water washing and / or filtering and / or inertial separation.

Depending on the composition of the solids-free exhaust gas and the nature and proportions of the products to be produced (carbon monoxide and / or hydrogen), different treatment steps are necessary to produce the desired products. However, always a treatment step is required in which CO _{2 is} separated. If the gas to be treated by CO ₂ separation also contains sulfur components (eg H ₂ S, COS), these are expediently separated from the gas together with CO ₂ .

For CO ₂ separation, it is advisable to subject the gas to be treated a chemical gas scrubbing, as known in the art and the skilled person for a long time. Such gas washes can be operated economically at pressures only slightly higher than the pressure of an FCC or IFCG exhaust. A preferred embodiment of the method according to the invention therefore provides that the solids-free exhaust gas or a CO ₂ -containing gas generated from the exhaust gas is compressed and at a pressure between 4 and 15 and is preferably between 4 and 8 bar, for the separation of sulfur components and / or carbon dioxide is supplied to a chemical gas scrubber. Particularly preferably, the carbon dioxide in the gas scrubbing is recovered independently of the sulfur components and in product purity.

If, in addition to carbon dioxide, the gas to be treated by CO ₂ separation contains only hydrogen which is to be recovered as product, then a variant of the process according to the invention provides that the gas to be treated is at a pressure of between 4 and 15, but preferably between 5 and 5 and 1 0bar, fed to a pressure swing adsorption (PSA) device and there is decomposed adsorptively into a hydrogen and a carbon dioxide-rich gas stream.

Further developing the method according to the invention, it is proposed that at least part of the carbon dioxide separated off from the exhaust gas or from a gas generated from the exhaust gas be compressed, returned and together with

Water vapor and / or oxygen is mixed to an oxidizing agent, which is used for the partial oxidation of the coke. If carbon dioxide with product quality is separated from the exhaust gas, excess carbon dioxide, which is not required for the production of the oxidizing agent, can be released as product at the plant boundaries.

Often, the demand for hydrogen product is higher than for carbon monoxide. For example, in refineries where coke is gasified at low temperatures and pressures as described above, there is a need for hydrogen that is used for hydrogenation purposes. On the other hand, carbon monoxide would have to be exported to an external customer with economic losses because there is often no need for pure CO within the refinery. A further embodiment of the method according to the invention therefore provides that at least a subset of the solids-free exhaust gas or a H ₂ - and / or CO-containing gas stream generated from the solids-free exhaust gas to increase the H ₂ / CO ratio of a water gas shift reaction at which is subjected to a high-temperature shift and / or a medium-temperature shift and / or a low-temperature shift and / or an isothermal shift. The water gas shift reaction is carried out according to the invention before or after a compression step. So that enough water molecules are available as reactants, the becomes treated gas stream expediently enriched with water vapor before the water gas shift reaction.

The treated by water gas shift gas stream is cooled to a temperature lying below the water dew point and, after separation of the condensed water, the CO ₂ separation supplied. Optionally, the treated by water gas shift gas stream is supplied together with a non-treated by water gas shift partial stream of the solids-free exhaust gas of CO ₂ - separation. A variant of the method according to the invention provides that the two gas streams are fed independently of CO ₂ separation.

After CO ₂ separation, the gas streams (synthesis gas) consist almost completely of carbon monoxide and / or hydrogen. If only one hydrogen product is to be obtained, it is advisable to use a synthesis gas

To separate pressure swing adsorption (PSA) into a hydrogen product and a residual gas. If, on the other hand, a carbon monoxide and a hydrogen product are to be obtained from a synthesis gas, the synthesis gas is decomposed according to the invention by cryogenic gas separation, which is preferably a condensation process, and / or in a membrane process and / or by vacuum PSA. In the event that such a generated H ₂ -rich gas stream has no hydrogen product purity, a hydrogen product is advantageously generated from the H ₂ -rich gas stream by pressure swing adsorption or in a membrane process.

An expedient embodiment of the method according to the invention provides that a stream (exhaust gas or a gas stream generated from the exhaust gas) having a temperature that makes subsequent treatment in a treatment step impossible or at least uneconomical, as far as heated or cooled until its Temperature assumes a value that allows an economical treatment of the material flow in this treatment step.

The inventive method is particularly suitable for the gasification of FCC coke, as it results in the cleavage of heavy (long-chain) hydrocarbons by means of fluid catalytic cracking (FCC) or of IFCG coke, as he, for example, in a flexicoking process. Preferred embodiments of the method according to the invention therefore provide that it is used for the gasification of FCC and / or IFCG coke.

The invention further relates to an apparatus for gasification of coke, comprising a gasification reactor in which the coke by partial oxidation at pressures between 2 and 8 bar and temperatures between 500 and 1000 ° C in a carbon monoxide and carbon dioxide-containing gas (exhaust gas) can be implemented ,

On the device side, this object is achieved by providing a

In which a gas mixture consisting of water vapor and / or oxygen and carbon dioxide can be produced and a feed device, via which the gas mixture from the mixing device can be fed to the gasification reactor as oxidizing agent.

A preferred variant of the device according to the invention provides that mixing device and feeding device form a functional unit, which is designed as a pipeline. Another preferred variant provides that mixing device and feed device form a separate functional unit, wherein the mixing device, for example by the installation of static mixers, is designed so that the gases to be mixed are rapidly and completely miscible before they enter the feed device.

Contains the exhaust gas in addition to the gaseous and solid components, such as soot and dust, so provides an expedient embodiment of the device according to the invention a device in which the exhaust gas by separation of solids, such as soot and / or dust, is convertible into a solids-free exhaust. These devices are preferably water washes and / or inertia separators and / or filters.

In a preferred embodiment, the device according to the invention comprises a device for the separation of sulfur components (eg H ₂ S, COS) and / or CO ₂ from the exhaust gas or from a gas generated from the exhaust gas, such as a chemical gas scrubbing and / or a pressure swing adsorber. Preferably, carbon dioxide is independent of the sulfur components in the separator separated from the exhaust gas, so that a CO ₂ stream is formed, which particularly preferably has product quality.

Appropriately, the device for separating CO ₂ via a return device is connected to the mixing device such that at least a portion of the separated CO _{2 can be introduced} into the mixing device.

A variant of the device according to the invention comprises a device for carrying out a water gas shift reaction (shift reactor), in which at least a subset of the solids-free exhaust gas of a water gas shift reaction is unterziehbar, wherein it is a high temperature at the shift reactor Shift reactor and / or a medium-temperature shift reactor and / or a low-temperature shift reactor and / or an isothermal shift reactor. The shift reactor is expediently arranged upstream of the device for separating off sulfur components (eg H ₂ S, COS) and / or CO ₂ .

If the gas to be treated by CO ₂ separation contains not only carbon dioxide but also hydrogen which is to be recovered as product, a variant of the device according to the invention provides a pressure swing adsorber in which the gas to be treated is at a pressure of between 4 and 15 and preferably is between 4 and 1 bar, adsorptively into a hydrogen and a carbon dioxide-rich gas stream can be dismantled. In the event that the hydrogen-rich gas stream has no hydrogen product purity, the pressure swing adsorber expediently downstream of a further pressure swing adsorber or a membrane reactor in which from the H ₂ -rich gas stream, a hydrogen product can be generated.

After CO ₂ separation, there is a gas (synthesis gas) which consists almost completely of carbon monoxide and / or hydrogen. If only one hydrogen product is to be recovered, the invention provides a pressure swing adsorber in which synthesis gas is separable into a hydrogen product and a residual gas. If, on the other hand, a carbon monoxide and a hydrogen product are to be obtained from synthesis gas, according to the invention a cryogenic gas separation device, which is preferably a device operating in the condensation process, and / or a membrane system and / or a vacuum pressure swing adsorber are provided. In the event that one in the cryogenic gas separation and / or the Membrane system and / or the vacuum pressure swing adsorber generated H ₂ -rich gas stream has no hydrogen product purity, the H ₂ -rich gas stream is advantageously fed to a hydrogen purification device in which it can be converted by pressure swing adsorption or in a membrane process in a hydrogen product.

In order to ensure that the gas streams to be treated always flow at a suitable temperature into one of the partial devices of the device according to the invention, an embodiment of this device provides devices for cooling or heating the gas streams.

In addition, the device according to the invention comprises devices in which preferably CO ₂ -free gas can be compressed to a pressure which is sufficiently high to be able to introduce the gas into subsequent sub-devices.

The device according to the invention is particularly suitable for the gasification of FCC coke, as it results in the cleavage of heavy (long-chain) hydrocarbons by means of fluid catalytic cracking (FCC) or IFCG coke, as obtained for example in a Flexicoking ^® process. Preferred embodiments of the device according to the invention therefore provide that it can be used for the gasification of FCC and / or IFCG coke.

In the following, the invention will be explained in more detail with reference to an embodiment schematically shown in the figure. In the exemplary embodiment, coke, which is obtained for example in the utilization of vacuum residues in refineries, converted in a gasification reactor by partial oxidation in a carbon monoxide and hydrogen-containing gas (exhaust gas), which is subsequently decomposed into commercially useful products.

Via line 1 coke is introduced into the gasification reactor V, at the same time via line 2 from an oxygen 3, water vapor 4 and carbon dioxide 5 existing and generated in the mixing device M oxidant is supplied. In the gasification reactor V, the coke 1 is partially or completely gasified by partial oxidation at a temperature of between 500 and 1000 ⁰ C and a pressure between 2 and 15 bar. The gas produced in the coke gasification (exhaust gas) 20, the next Hydrogen, carbon monoxide and carbon dioxide also sulfur components (H ₂ S, COS) and soot and dust is cooled in the heat recovery device WR and introduced via line 6 in the cleaning device R, where it is cleaned of the solids. In order to increase the hydrogen content, the purified of solids exhaust gas 7 is divided into two parts 8 and 9, the first of which is bypassed to the shift reactor S, while the second warmed up (not shown), enriched with water vapor 10 and in the shift reactor S is initiated. In the shift reactor S, the carbon dioxide contained in the partial stream 9 reacts catalytically supported with water to hydrogen and carbon dioxide. In the gas cooler C, the water contained in the shifted gas stream 11 is condensed out by cooling down to below the water drop point and removed. The gas stream 12 is then introduced together with the bypass stream 8 in the chemical gas scrubbing W, are selectively separated in the carbon dioxide 13 and sulfur components 14. The sulfur components 14 are withdrawn from the chemical scrubbing W and fed to a means (not shown) for obtaining sulfur, while the separated carbon dioxide 13 is compressed in the compressor P1 and returned via line 5 in the mixing device M. Via line 15, a virtually only consisting of hydrogen and carbon monoxide synthesis gas in the compressor P2 is compressed to a pressure between 10 and 40 bar and then introduced via line 16 into the cryogenic gas separator K, where he in a

Carbon monoxide product stream 17 and a hydrogen-rich gas stream 18 is decomposed. Since the hydrogen-rich gas stream 18 still has no product purity, it is fed to the hydrogen purification device HC and converted into a hydrogen product 19.

Claims

claims

1. A process for the production of hydrogen (19) and / or carbon monoxide (17) from coke (1), wherein the coke (1) by partial oxidation (V) at pressures between 2 and 8 bar and temperatures between 500 and 1000 ⁰ C. in a carbon monoxide and carbon dioxide-containing gas (exhaust gas) (20) is reacted, characterized in that for the implementation of the coke (1) consisting of water vapor (4) and / or oxygen (3) and carbon dioxide (5) existing oxidizing agent (2) is used.

2. The method according to claim 1, characterized in that carbon dioxide (13) separated from the exhaust gas or from a gas generated from the exhaust gas (12) and mixed with water vapor (4) and / or oxygen (3) to the oxidizing agent (2) becomes.

3. The method according to any one of claims 1 or 2, characterized in that from the exhaust gas or from a gas generated from the exhaust gas (12) carbon dioxide (13) by chemical gas scrubbing (W) and / or by adsorption is separated.

4. The method according to any one of claims 1 to 3, characterized in that the exhaust gas or the gas generated from the exhaust gas (12) before the carbon dioxide separation (W) of soot and / or dust cleaned (R) is.

5. Device for gasification of coke (1), comprising a gasification reactor (V) ₁ in which the coke (1) by partial oxidation at pressures between 2 and 8bar and temperatures between 500 and 1000 ⁰ C in a carbon monoxide and carbon dioxide-containing gas ( Exhaust gas) (20) is convertible, characterized in that it comprises a mixing device (M) in which a water vapor (4) and / or oxygen (3) and carbon dioxide (5) existing gas mixture can be produced and a feed device (2) about which the

Gas mixture from the mixing device (M) as an oxidizing agent to the gasification reactor (V) can be fed.

6. Apparatus according to claim 5, characterized in that it comprises a device (W) for the separation of carbon dioxide from the exhaust gas or from a gas obtained from the exhaust gas (12) and a return device (13, P1, 5), via the at least part of the separated carbon dioxide (13) can be introduced into the mixing device (M).

7. Device according to one of claims 5 or 6, characterized in that it is the device (W) for the separation of carbon dioxide is a chemical gas scrubber and / or a pressure swing adsorber.

8. Device according to one of claims 5 to 7, characterized in that it comprises means (R) for the separation of soot and / or dust from the exhaust gas, which is designed as a centrifugal separator and / or filter and / or water washing.