HK1159058B - Method and device for producing synthesis gas from gaseous hydrocarbons - Google Patents

Description

The invention relates to a process and device for the production of synthesis gas from gaseous hydrocarbons by means of allothermal steam reforming with catalysts.

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Allothermal gasification processes produce a particularly high-quality synthesis gas. Since it is an endothermal reaction, the necessary heat energy must be introduced into the reaction chamber by heat transfer. The necessary heat is generated by burning hydrocarbons with air or oxygen.

A typical device of this type consists of a chain-shaped furnace equipped with a variety of pipes filled with nickel-containing catalyst pellets. At the head of this furnace there are a variety of burner nozzles arranged between the pipes. To avoid local overheating, a large distance must be maintained from the burner flame to the pipes. Both the flue gases and the hydrocarbons to be gasified flow in the pipes in direct current from top to bottom.

The state-of-the-art equipment requires a large amount of space and always produces an exhaust gas which must be laboriously removed from air pollutants.

US 2005/0229 488 A1 reveals a process for the production of synthesis gas by allothermic steam reforming, where electrical energy is supplied by means of a heating coil embedded in the catalyst bed.

The purpose of the invention is to enable the production of synthesis gas in a compact device without exhaust gases.

The problem is solved according to the invention by a procedure as described in claim 1.

The above-mentioned task is further solved by a device as described in claim 5.

The following are further embodiments of the invention: when electrical energy is coupled to the process, it is transferred entirely to the synthesis gas, so no energy is lost. This is also true if some of the electrical energy is coupled to a preformator if the appreciable heat of the synthesis gas is not sufficient to heat up the input streams and meet the energy demand of the endothermic reaction. Preformers are operated at 400°C to 500°C to break down higher hydrocarbons into small molecules, without any soot pressure entering the main process. The main transformer is operated at a tensile pressure between 820°C and 920°C. Support for the main transformer is provided by various catalytic converters and is thus operated in a non-linear manner.

Gaseous hydrocarbons may also be understood as evaporative hydrocarbons.

If the steam reforming unit is part of a hydrogen system, the pressure should preferably be at least high enough to allow the hydrogen to be fed into medium pressure lines from 16 bar to 25 bar without condensation, so that the operating pressure in the steam reforming unit should preferably be at least 16 bar, preferably between 16 bar and 30 bar, and in particular between 16 bar and 25 bar.

If oxygen is available at a low cost, for example as a waste product from the electrolysis of water by solar power, it can be used temporarily or proportionally for an autothermal operation.

Electrical energy can be coupled into the process in a variety of ways, such as microwaves, plasma converters and electrically heated contact surfaces.

The allothermic steam reforming process involves the supply of energy by electrically heated contact surfaces, which then deliver heat energy via the contact surfaces to the gas to be reformed and the catalyst.

The steam reforming unit is operated as a vortex reactor according to the invention. To this end, the mixture of gas and steam is directed from below into a vortex bed consisting of particles of catalytically active material or of a mixture of catalytically active material and inert material such as sand. The grain size of the catalytically active particles may vary between 0.1 mm and 2 cm depending on the density. Large particles are however only suitable for a vortex layer if they are inserted together with an inert, fine-grained material and have a rough density. For sand, the grain size is preferably between 0.15 mm and 0.8 mm. When using only catalytically active particles, the grain size is in this range, if a similar dizziness is achieved in case of small particles, because they allow a particularly good electrical contact between the particles.

In order to keep abrasion in check, the backbone should be formed as a stationary backbone. Because of the extremely high heat transfer between the backbone and the electric heating system, this arrangement is extremely compact. This arrangement is orders of magnitude smaller than the state-of-the-art devices. This would allow high efficiency and efficiency even at higher electricity prices, in conjunction with zero-emission operation.

The contact surfaces are then the outer surfaces of an electrical resistor of the resistance heating. The contact surfaces may also be associated with an electric heater in thermal conductive contact with these.

The contact surfaces may be formed by plates, rods and/or tubes inserted into the backbone, where the plates, rods and/or tubes form the electrical resistance of an electrical resistance heater, as appropriate.

In the case of electric heating, it is easy to adjust the power to the actual requirements of the reaction progress. This can be done either by pre-calculation or by dynamic changes in operation. Thus, the energy supply at the beginning of the reaction zone can be designed to be larger than in the further course of the reaction zone. Also, the on and off of additional heating registers can be advantageous. If necessary, the energy supply over the height of the vortex layer can be adjusted to the actual need. This can be achieved very simply, for example, by changing the resistance of the heating resistance over the height of the vortex layer.

Alternatively or additionally, the specific contact area may be varied along the height or length of the catalyst discharge, in relation to the height or length of the catalyst discharge; in other words, a larger specific contact area may be provided in areas of the catalyst layer with increased heat demand than in areas with reduced heat demand; alternatively or additionally, the specific contact area may also be increased in areas of the catalyst layer where the temperature gradient between the contact areas and the catalyst pellets or catalyst particles is lower.

Preferably, the synthesis gas can be obtained from a methane-containing gas. The production of synthesis gas from methane-containing gases ultimately represents an efficient alternative to the motorised combustion of methane-containing gases, for example in so-called cogeneration plants. A particularly high overall efficiency in biomass use can be achieved when the methane-containing gas is a biogas, landfill gas and/or waste gas.

Biogas in this context is a gas produced by fermentation of biomass in biogas plants and has methane and carbon dioxide (CO2) as its main components in addition to water vapour. Landfill gas and wastewater gas are obtained, like biogas, from the anaerobic decomposition of biomass, called fermentation or decay, where the biomass has either been introduced into a landfill or accumulated during wastewater treatment.

At appropriate raw material prices, it may be alternative or additionally particularly cost-effective to produce the synthesis gas from natural gas and/or naphtha.

The small catalyst particles may be nickel-containing.

If necessary, in order to improve process management, it may be appropriate to perform reforming partly in a pre-reformer and partly in a main reformer. The pre-reformer or main reformer may have a catalyst pellet spill. Alternatively or additionally, the pre-reformer and/or main reformer may have a vortex layer of catalyst particles. This allows the process and device for producing synthesis gas to be well matched to the raw gases used.

In addition, the contact surfaces for the direct or indirect supply of electrical energy may be provided in the preformer and/or the main reformer. If the contact surfaces are provided in both the preformer and the main reformer, the processes taking place there can be very well regulated.

The contact surfaces for supplying energy for allothermal steam reforming may be arranged in a catalyst pellet cascade in the pre-reformer or main reforming; alternatively or additionally, the contact surfaces may also be arranged in the pre-reformer and/or main reforming in a vortex layer containing catalyst particles. It should be borne in mind that a regular catalyst pellet cascade is more convenient to operate technically and apparently. However, a regular vortex layer allows for better heat and matter exchange.

Hydrogen produced from biomethane (biogas) from synthesis gas can be part of a solar hydrogen economy driven by heat.

The invention is explained in more detail below by means of a drawing which is merely an example of an implementation.

The drawing shows Figure 1a device for the production of synthesis gas and Figure 2a device for the production of synthesis gas according to the invention.

In Fig. 1 a reactor 1 is shown to perform an endothermic transition of the gas to be reformed. The gas to be reformed is introduced through the opening 2 into a catalytic pellets cascade 4 . This cascade 4 is supported at the bottom by a sieve 5. In practice, such sieves are attached to boreholes that bear the load. Such a borehole can also be the minus 9 (earthing) of the electric heater 7. The upper limit 6 of the cascade 4 is located in the shown lead example outside the electric overhead heater 7. Often the uppermost position of the cascade 4 is captured as an inert overhead conductor layer. The current 7 of the reactor 1 consists of a variety of static or electrical appliances that are designed to be used as heat sinks.

The resistance heater 7 consists of a variety of rods or tubes which are in contact with the collecting rails 21 and 22 and are also held there mechanically. The rods or tubes are formed as loops which are twisted. This top layer again ensures the destruction of large bubbles in the column 19 and improves the heat mixing and transition of the raw fluids to the interconnected surfaces. To ensure the mechanical stability of the column 24 or 24 these rods or tubes must be placed under the column 24 or 24 to ensure that no mechanical heat can be generated within the column 23 or 24 when the raw fluids are in contact with each other.

If the twisted loops formed as resistance heating 7 are made of high-resistance materials at the bottom and low-resistance materials at the top, only the area of the loops, which, due to their high resistance, give a high thermal performance, needs to be covered by the spindle layer. In this case, the collector rails 21,22,23 should also be made of low-resistance material. Collector rails outside the spindle layer have less wear. Of course, the heating can also be carried out in the classic way with heated pipes inside. This requires a complex design and constant flushing of the pipes so that the heat is not diffused by a diffused hydrogen.

The invention allows for a significant reduction in investment costs and greater efficiency. In view of the ever-increasing overall efficiency in the generation of electricity and heat, the use of electricity for steam reforming is not a waste of energy but a contribution to the economical use of energy.

Claims (13)

1. Method for producing synthesis gas from gaseous hydrocarbons by means of allothermal steam reforming using catalysts,

   - in which energy is at least partly supplied by means of electrical energy,

   - in which the energy is supplied by means of electrically heated contact surfaces and

   - in which the energy is supplied by means of contact surfaces within a fluidised bed which at least partly consists of catalyst particles.
2. Method according to Claim 1, in which the contact surfaces are directly heated by applying an electrical voltage.
3. Method according to Claim 1 or 2, in which the synthesis gas is produced from a gas containing methane, preferably from a biogas, landfill gas and/or sewage gas.
4. Method according to any one of Claims 1 to 3, in which the synthesis gas is produced from natural gas and/or naphtha.
5. Apparatus for producing synthesis gas from gaseous hydrocarbons by means of allothermal steam reforming, preferably according to any one of Claims 1 to 5,

   - using catalysts,

   characterised

   - in that means for supplying energy at least partly by means of electrical energy are provided,

   - in that the means for supplying energy comprise electrically heated contact surfaces, and

   - in that the contact surfaces are arranged within a fluidised bed which at least partly consists of small catalyst particles.
6. Apparatus according to Claim 5, characterised in that the contact surfaces are formed by an electrical resistor of an electric resistance heater.
7. Apparatus according to Claim 5, characterised in that the contact surfaces are formed by plates, rods and/or tubes incorporated into the fluidised bed.
8. Apparatus according to Claim 7, characterised in that the plates, rods and/or tubes form the electrical resistor of an electric resistance heater.
9. Apparatus according to any one of Claims 5 to 8, characterised in that the small catalyst particles contain nickel.
10. Apparatus according to any one of Claims 5 to 8, characterised in that a pre-reformer and a main reformer, downstream from the pre-reformer, are provided.
11. Apparatus according to Claim 10, characterised in that the means for supplying energy comprise contact surfaces which are arranged in the pre-reformer and/or in the main reformer.
12. Apparatus according to Claim 11, characterised in that the contact surfaces are arranged in a fill consisting of catalyst pellets in the pre-reformer or in the main reformer.
13. Apparatus according to Claim 11 or 12, characterised in that the contact surfaces in the pre-reformer and/or in the main reformer are arranged in a fluidised bed which at least partly consists of small catalyst particles.