WO2018157972A1

WO2018157972A1 - Process and plant for partial oxidation

Info

Publication number: WO2018157972A1
Application number: PCT/EP2018/025035
Authority: WO
Inventors: Karsten Covella; Matthias Riße; Matthias Müller-Hagedorn
Original assignee: L'Air Liquide, Société Anonyme pour l'Etude et l'Exploitation des Procédés Georges Claude
Priority date: 2017-02-28
Filing date: 2018-02-09
Publication date: 2018-09-07
Also published as: EP3366640A1

Abstract

Process and plant for partial oxidation for generating a carbon monoxide- and hydrogen-containing synthesis gas from hydrocarbon-containing reactant material, wherein the reforming reactions are supported by enhancing the turbulence in the process gas.

Description

Process and plant for partial oxidation

Field of the invention

The invention relates to a partial oxidation process for generating a carbon monoxide- and hydrogen-containing synthesis gas from hydrocarbon-containing reactant material, wherein the following process steps are performed: - providing the reactants comprising a hydrocarbon-containing material, an oxygen-containing gas and optionally steam,

- providing a reactor comprising a vertical, refractory material-lined reactor vessel having a reaction chamber situated therein, an opening situated at the upper end of the vessel for introducing the reactant mixture and an opening situated at the lower end for discharg- ing the synthesis gas as product gas and a connecting conduit to a gas cooler joined thereto and a mixer/burner for generating a mixture from the reactants, wherein the mixer/burner is mounted to the upper opening of the reactor vessel such that the reactant mixture may be introduced into the reactor vessel via said mixer/burner,

- introducing the reactants via the mixer/burner into the reaction chamber of the reactor vessel at the temperatures and pressures required for the chemical conversion reactions of partial oxidation,

- converting the reactant mixture into synthesis gas inside the reaction chamber, - discharging the synthesis gas through the connecting conduit out of the reactor vessel for further treatment in a gas cooler.

The invention likewise relates to a plant for performing the partial oxidation process.

Prior art

Partial oxidation processes for converting hydrocarbon-containing gas into a carbon monoxide- and hydrogen-containing synthesis gas are known per se. Of practical importance are for example the Shell and Texaco processes which are outlined for example in Ullmanns Encyklopadie der technischen Chemie, 4th Edition (1973), volume 3, pages 340 - 341 .

The hydrocarbon-containing gas that is converted by partial oxidation may be obtained from coal, residues from crude oil processing or heavy oil. The hydrocarbon-containing gas, optionally mixed with steam, is supplied together with oxygen as a reactant mixture via a mixer/burner to the reaction chamber of a reactor in which at temperatures between 1200°C and 1500°C and pressures of 20 to 120 bar the gasification reactions take place. A portion of the hydrocarbons is burned to obtain the heat energy necessary for the gasification reactions. This takes place in the flame zone which forms at the mixer/burner outlet. Following said flame zone is the so-called reforming zone which occupies the remainder of the reactor chamber. Partial oxidation does not empoly a catalyst so that even hydrocarbons having a high content of impurities, such as sulfur, may be processed.

The mixture of reactants and products generated in the reaction chamber in the course of the partial oxidation process, the synthesis gas-product gas, is alternatively also referred to as process gas hereinbelow.

Patent document GB 1 342 1 16 describes a reaction apparatus for performing partial oxidation. This comprises a vertical reactor with a mixer/burner through which the reactant gases are conducted into the refractorily-lined reactor chamber of the reactor such that good mixing of the reacting gases and very largely complete progress of the chemical reactions in the reactor chamber are ensured. At the lower end of the reactor, the generated synthesis gas is discharged from the reactor chamber and subsequently supplied to a heat exchanger via a transfer conduit. The heat exchanger serves to utilize the tangible heat present in the synthesis gas for steam generation.

Due to the absence of a catalyst, it is in principle difficult to achieve a sufficient conversion of the employed hydrocarbons and thus a low residual methane content in the product gas. The process parameters temperature, quality of gas commixing and residence time of the gas in the reactor chamber are available for optimizing conversion.

With increasing temperature, an increase in the reaction rates between the gases is achieved but the enhanced reaction rates also result in an enhanced oxygen demand for the process and in an enhanced steam and carbon dioxide content in the product gas. In addition, the stress on the materials used for construction of the reaction apparatus in- creases with temperature.

Through suitable construction of the mixer/burner and, in concert therewith, through suitable construction of the reaction chamber, the quality of gas commixing, the flow path and the residence time of the gas in the reactor chamber may be influenced. Residence time is subject to narrow limits as a result of the size of the reaction chamber and the associated construction costs. Finding a suitable design for optimal gas commixing and flow management is very complex, especially since the flow paths may be altered greatly upon upscaling or downscaling of the apparatuses, thus requiring that the design of the components be revised.

The present invention accordingly has for its object to provide a process where the disadvantages of the prior art are encountered to a lesser extent.

Description of the invention

The problem is solved by a process according to the features of Claim 1 and by a plant according to the features of Claim 13. Commixing of the gases is improved when in accordance with the invention the process gases traverse commixing-enhancing or flow-directing internals that act as static mixing means and/or a layer of shaped bodies that likewise acts as a mixing means. The shaped bodies may have any shape which promotes commixing of the process gas and in partic- ular enhances the turbulence in the gas flow when flowing through the shaped body layer. A shaped body layer is preferably employed in the reactor chamber and the commixing- enhancing internals are preferably employed in the connecting conduit between the reactor vessel and the gas cooler. As a result of these measures according to the invention, commixing, in particular the turbulence in the process gas, is enhanced and commixing of the gas components is thus improved. This enhances the chance of reaction-ready gas molecules colliding, thus increasing the rate of the chemical reactions proceeding in the reactor. This simplifies the demands on the design of the mixer/burner or of the reactor chamber for achieving optimal flow management in terms of gas commixing or residence time. It is a further advantage of the invention that it is possible to reduce process temperature while reaction conversion remains unchanged.

Preferred embodiments of the invention

A preferred embodiment of the invention is characterized in that the commixing-enhancing internals are static mixers. Static mixers are long proven in process engineering and available in numerous versions.

A further preferred embodiment of the invention is characterized in that the commixing- enhancing internals are structured packings. Structured packings are easy to install into the reaction space. They provide an exactly defined flow result that is readily reproducible even on replacement of the packing.

A further preferred embodiment of the invention is characterized in that the shaped bodies are spheres. A commercially available product is then concerned. Through choice of the suitable sphere diameter, the mixing efficacy and the pressure drop of the process gas over the dumped bed may be adjusted. Preference is given in particular to spheres made of ceramic materials, for example based on AI2O3, since they exhibit the necessary mechanical and thermal stability and are chemically inert.

A further preferred embodiment of the invention is characterized in that the static mixing means or the shaped bodies of the dumped bed are made of ceramic foam. These are characterized by high thermal stability at low specific mass.

A further preferred embodiment of the invention is characterized in that the mixing means or the shaped bodies are made of AI2O3. This material is inert toward the chemical reac- tions proceeding in the process gas. The material is furthermore thermally stable and commercially customary.

A further preferred embodiment of the invention is characterized in that the mixing means or the shaped bodies occupy between 1 % and 50% by volume, preferably between 20% and 40% by volume, of the reaction chamber. In this range sufficient free volume is present for a uniform distribution of the gas in the reactor chamber while simultaneously sufficient mixing elements, such as shaped bodies or internals, are present to achieve a good mixing efficacy. A further preferred embodiment of the invention is characterized in that the process is performed at a pressure between 10 and 100 bar in the reactor chamber. This range allows a useful compromise between high throughput at compact dimensions and an equilibrium position which allows sufficient conversion. A further preferred embodiment of the invention is characterized in that the process is performed at a temperature between 900°C and 1500°C, preferably between 1200°C and 1400°C, in the reactor chamber. This represents a useful compromise between sufficient conversion, limited oxygen demand and thermal stability of the materials.

A further preferred embodiment of the invention is characterized in that the process is performed with a molar ratio of steam / carbon in the reactant gas mixture between 0 and 0.6. This allows the hydrogen/carbon monoxide ratio in the synthesis gas to be adjusted. A further preferred embodiment of the invention is characterized in that the process is performed with a molar ratio of oxygen / carbon in the reactant gas mixture between 0.5 and 0.8 in order to achieve the abovementioned temperature range.

Working examples

Developments, advantages and possible uses of the invention are also apparent from the description of non-limiting working and numerical examples and of the drawings which follows. All the features described and/or shown in images, alone or in any combination, form the invention, irrespective of the way in which they are combined in the claims or the dependency references therein.

The invention shall be more particularly elucidated hereinbelow with reference to the drawing and with reference to experimental data and results of simulation calculations.

Fig. 1 shows a section through a reactor according to the invention having a dumped bed of shaped bodies in the reaction chamber,

Fig. 2 shows a section through a reactor according to the invention having internals in the reaction chamber and in the connecting conduit,

Fig. 3 shows a section through a reactor according to the invention having a dumped bed of shaped bodies in the reaction chamber and internals in the connecting conduit.

Fig. 1 shows a section through an inventive reactor. The reactor 1 comprises the reactor vessel 2 having the refractory lining 3. Situated in the reactor 1 is the reactor chamber 4. Fitted to the upper opening 5 of the reactor chamber 4 is the mixer/burner 6. The mixer/burner 6 generates the reactant gas mixture 9 from the reactants hydrocarbon 7 and oxygen/steam 8. The reactants 7 and 8 are supplied to the mixer/burner 6 so that at the outlet from the mixer/burner 9 into the reactor chamber 4 a stable flame zone 10 can form. In the lower region of the reactor chamber, the flame zone transitions into the reforming zone in which a layer of shaped bodies 1 1 is arranged. After flowing through the reforming zone, the reactant gases have largely been converted into product gas, i.e. synthesis gas 12. The product gas 12 exits the reactor chamber 4 through the lower opening 13 and is supplied via the connecting conduit 14 to a gas cooler which is not depicted.

Fig. 2 shows a section through an inventive reactor of the same type as shown in fig. 1 . In a departure from fig. 1 , commixing-enhancing internals 15 are here installed in the re- actor chamber 4 and also in the connecting conduit 14.

Fig. 3 shows a section through an inventive reactor of the same type as shown in fig. 1 and fig. 2. As in fig. 1 , a layer of shaped bodies 1 1 is arranged in the reactor chamber here and, as in fig. 2, commixing-enhancing internals 15 are installed in the connecting conduit 14 here.

Also forming part of the invention are the not-depicted embodiments where either only the reactor chamber but not the connecting conduit, or only the connecting conduit but not the reactor chamber, are fitted with commixing-enhancing internals.

Numerical examples Experiments

To test the efficacy of a dumped bed of shaped bodies in the reactor chamber of a partial oxidation reactor, two experiments at 50 and at 60 bar of pressure in the reactor chamber above the mixing means were performed, each with and without mixing means. In the first phase A, the partial oxidation was performed according to the current prior art with an empty reactor chamber and then, in the second phase B, with a reaction chamber con- taining a dumped bed of shaped bodies but otherwise identical conditions. The mixing means used in the reactor chamber was a layer of spherical shaped bodies. The diameter of the layer, corresponding to the internal diameter of the reactor chamber, was 500 mm, the thickness of the layer was 900 mm and the diameter of the spheres was 20 mm. The spheres were made of AI2O3. The experimental results are summarized in the two tables which follow.

Experiment V02 VNG V H2+co/ VNG V H2+CO, dry CH4, syngas, dry Treactor 1

50 bar [Nm³/Nm³] [Nm³/Nm³] [Nm³/h] [mol%] [°C]

Phase A^*) 0.76 2.53 859 0.15 1420

Phase B^**) 0.76 2.69 904 0.1 1 1400

^*) without mixing means

*^*) with mixing means

In these experiments the reactant gases employed were natural gas and oxygen. In ex- periment phase B in which a dumped bed of shaped bodies was present in the reactor chamber, an enhanced volume ratio of hydrogen and carbon monoxide in the product gas to the employed natural gas NG was obtained. Furthermore, a lower residual CH₄ content in the synthesis gas, dry, was achieved. These positive results were achieved at lower process temperature in the reactor.

Simulation calculations

A first calculation simulated the efficacy of a mixing means in the reactor chamber at an oxygen amount in the reactant gas that was identical in both phases. The results of these simulation calculations are likewise summarized in tabular form. Calculation 1 O2, reactant Treactor Synthesis CH4, syngas, dry

gas

[kg/h] [°C] [kmol/h] [mol%]

Phase A^*) 450 1403 52.68 0.50

Phase B^**) 450 1387 53.24 0.25

^*) without mixing means

*^*) with mixing means

This first calculation shows that the mixing means reduces the residual methane content in the synthesis gas even at reduced process temperature.

A second calculation simulated the efficacy of a mixing means in the reactor chamber at a residual methane content in the synthesis gas, based on the dry state of the synthesis gas, that was identical in both phases.

^*) without mixing means

*^*) with mixing means

This second calculation shows that the mixing means can reduce the amount of employed oxygen/the process temperature while nonetheless increasing synthesis gas yield. By using the process according to the invention, it is thus possible at identical residual methane content in the synthesis gas and compared to operation of the partial oxidation according to the prior art to potentially reduce the oxygen demand by up to 3%. In addition, the temperature may be markedly reduced by around 70 K. Accordingly, a higher methane conversion may be achieved at identical oxygen feed rate. Moreover, compared to partial oxidation according to the prior art, the produced amount of synthesis gas is between 1 .07 mol% and 1 .3 mol% higher in both simulation scenarios. Industrial applicability

The invention provides an improved process and an improved apparatus for generating synthesis gas by partial oxidation and is accordingly industrially applicable.

List of reference numerals

1 inventive plant for partial oxidation

2 reactor

3 refractory lining

4 reaction chamber

5 opening for introduction of the reactant gas mixture

6 mixer/burner

7 hydrocarbon-containing reactant stream

8 oxygen- and optionally steam-containing reactant stream

9 reactant gas mixture

10 flame

1 1 layer of shaped bodies

12 product synthesis gas

13 opening for discharging the product synthesis gas

14 connecting conduit

15 commixing-enhancing internals

Claims

Claims:

1. Partial oxidation process for generating a carbon monoxide- and hydrogen-contain- ing synthesis gas from hydrocarbon-containing reactant material, wherein the following process steps are performed:

a) providing the reactants comprising a hydrocarbon-containing material, an oxygen-containing gas and optionally steam,

b) providing a reactor comprising a vertical, refractory material-lined reactor vessel having a reaction chamber situated therein, an opening situated at the upper end of the vessel for introducing the reactant mixture and an opening situated at the lower end for discharging the synthesis gas as product gas and a connecting conduit to a gas cooler joined thereto and a mixer/burner for generating a mixture from the reactants, wherein the mixer/burner is mounted to the upper opening of the reactor vessel such that the reactant mixture may be introduced into the reactor vessel via said mixer/burner,

c) introducing the reactants via the mixer/burner into the reaction chamber of the reactor vessel at the temperatures and pressures required for the chemical conversion reactions of partial oxidation,

d) converting the reactant mixture into synthesis gas inside the reaction chamber, e) discharging the synthesis gas product gas through the connecting conduit out of the reactor vessel for further treatment in a gas cooler,

characterized in that

f) the commixing of the synthesis gas product gas in the reaction chamber and/or in the connecting conduit to the gas cooler is enhanced by installing commixing-enhancing in- ternals and/or a layer of shaped bodies there.

2. Process according to Claim 1 , characterized in that the commixing-enhancing internals are static mixers.

3. Process according to Claim 1 , characterized in that the commixing-enhancing internals are structured packings.

4. Process according to Claim 1 , characterized in that the shaped bodies are spheres.

5. Process according to Claim 1 , characterized in that the static mixing means or the shaped bodies of the dumped bed are made of ceramic foam.

6. Process according to any of the preceding claims, characterized in that the mixing means or the shaped bodies are made of AI2O3.

7. Process according to any of the preceding claims, characterized in that the mixing means or the shaped bodies occupy between 1 % and 50% by volume, preferably between 20% and 40% by volume, of the reaction chamber.

8. Process according to any of the preceding claims, characterized in that the process is performed at a pressure between 10 and 100 bar in the reactor chamber.

9. Process according to any of the preceding claims, characterized in that the process is performed at a temperature between 900°C and 1500°C in the reactor chamber.

10. Process according to any of Claims 1 to 6, characterized in that the process is performed at a temperature between 1200°C and 1400°C in the reactor chamber.

1 1 . Process according to any of the preceding claims, characterized in that the process is performed with a molar ratio of steam / carbon in the reactant gas mixture between 0 and 0.6.

12. Process according to any of the preceding claims, characterized in that the process is performed with a molar ratio of oxygen / carbon in the reactant gas mixture between 0.5 and 0.8.

13. Plant for performing the partial oxidation process according to any of the preceding claims, comprising

- a reactor comprising a vertical, refractory material-lined reactor vessel having a reaction chamber situated therein, an opening situated at the upper end of the vessel for introducing the reactant mixture and an opening situated at the lower end for discharging the synthesis gas as product gas,

- a connecting conduit to a gas cooler joined to the opening of the reactor vessel for dis- charging the synthesis gas,

- a mixer/burner for generating a mixture from the reactants, wherein the mixer/burner is mounted to the upper opening of the reactor vessel such that the reactant mixture may be introduced into the reactor vessel via said mixer/burner,

characterized in that the reaction chamber and/or the connecting conduit to the gas cooler are fitted with commixing-enhancing internals and/or a layer of shaped bodies for traversal by the process gases.