WO2016070989A1

WO2016070989A1 - Process for producing synthesis gas

Info

Publication number: WO2016070989A1
Application number: PCT/EP2015/002206
Authority: WO
Inventors: Josef Sporer; Rachid Mabrouk
Original assignee: Linde Aktiengesellschaft
Priority date: 2014-11-05
Filing date: 2015-11-04
Publication date: 2016-05-12
Also published as: DE102014016407A1

Abstract

The invention relates to a process for the production of synthesis gas, wherein, in a first process step, a high-temperature gasification is carried out in a reactor, in which thermal energy is released, the released thermal energy being used for the additional production of synthesis gas in a second process step which is carried out inside or outside of the reactor.

Description

description

Process for the production of synthesis gas

The invention relates to a process for the production of synthesis gas, wherein as a first process step in a reactor, a high-temperature gasification is performed, is released in the heat energy.

Process for the production of synthesis gas from various solid and

gaseous raw materials are already known.

Solid raw materials are advantageously converted into H ₂ and CO in so-called gasification processes. Particularly suitable for this purpose are biological raw materials, such as used and residual wood, energy wood or agricultural residues such as straw or peat.

Processes and plants for the at least partial gasification of solid, organic feedstock are known, for example, from EP 0 745 1 14 B1, DE 41 39 512 A1 and DE 42 09 549 A1. The present application relates in particular to such processes or plants which use a low-temperature gasifier and a

Have high temperature carburetor, as explained below. Compared to other methods, these enable u.a. a lower consumption of feed and have a higher cold gas efficiency.

In a low-temperature carburetor, the feedstock, for example

Biomass, by partial gasification with a gasification agent at temperatures between about 300 ° C and 600 ° C to coke (so-called in the case of biomass

Biokoks) and Schwelgas implemented. The carbonization gas is then in a

Combustion chamber of Hochtemperaturvergasers transferred and there with a

oxygen-containing gas, for example with more or less pure oxygen, but also with air and / or oxygen-containing exhaust gases, e.g. from gas turbines or

Internal combustion engines, partially oxidized. By this oxidation released heat causes a temperature increase to 1200 ° C to 2000 ° C, for example 1 .400 ° C. Under such conditions, aromatics, tars and oxo compounds contained in the carbonization gas are completely decomposed. This forms a synthesis gas that consists essentially of carbon monoxide, hydrogen, carbon dioxide and water vapor consists. In a further stage, for example in one in the

High temperature carburetor integrated or downstream of this

Quencheinheit, the synthesis gas thus produced with coke from the

Low temperature carburetor brought into contact. The coke can previously be treated separately (eg by grinding and sifting) and then introduced into the quench unit. By endothermic reactions between coke and syngas, the latter is cooled to about 900 ° C. This causes partial conversion of the carbon dioxide to carbon monoxide. The CO and C0 ₂ rich synthesis gas thus produced can

then be further conditioned. The conditioning includes, for example, a further cooling, a dedusting, a desulfurization, CO to CO 2

Conversion, a compression and / or the separation of residual carbon dioxide.

Synthesis gas resulting from such gasification typically has a relatively low 0.8 / 1 H ₂ / CO ratio. The heat produced by the cooling of the synthesis gas stream to about 200 ° C, is converted in most cases by the generation of steam and stored. The steam can be heated only to a maximum of 400 ° C in the rule, the material costs, especially for the heat exchanger and

Keep storage facilities in an economically reasonable context. However, higher quality energy is converted into less valuable (with less exergy content, i.e. it can do less work). The steam produced in this way is usually not completely needed for the biomass gasification itself, so that for the excess generated steam more customers must be found or this even has to be discarded. Also, the heat transfer to others

Intermediate media, such as heat transfer oils, has similar disadvantages.

Synthesis gas can also be produced via the reforming of gaseous and solid substances. For this purpose, in particular a steam reforming of methane-rich gases is customary. In this case, biogas or natural gas with steam is usually reacted on a heterogeneous catalyst to synthesis gas. This usually produces a H ₂ / CO ratio of about 3: 1.

For many production processes that start from synthesis gas, in particular for the synthesis of methanol, the Fischer-Tropsch synthesis or the dimethyl ether synthesis, a very specific H ₂ to CO ratio is necessary to achieve the highest possible To achieve sales and a high selectivity for the desired products. The necessary H ₂ to CO ratio is achieved by various methods. On the one hand, the CO and C0 ₂ rich synthesis gas from the gasification device, for example, H ₂ can be mixed from an electrolysis (for example, known from EP2166064 A1). Disadvantages arise, however, from the fact that the electrolysis only at very low electricity prices, for example in excess electricity

regenerative sources, can be carried out economically. On the other hand, the H ₂ rich synthesis gas stream from a reformer and the CO and C0 ₂ rich synthesis gas stream from a parallel operated carburetor can be mixed in the required ratio.

In another variant of the process, part of the CO can be reacted with H ₂ O in a water gas shift reaction to CO ₂ and H ₂ until, for example, an H ₂ / CO ratio of about 2: 1 is reached. A disadvantage is considered that in this case also resulting C0 ₂ for many subsequent processes, for example, for the provision of liquid hydrocarbons, is not usable, and thus lost for such processes. In particular, in the synthesis of methanol, the C0 _2, in the absence of separation, to the formation of water, which must be separated from the methanol consuming. Object of the present invention is to provide a method of the type mentioned in such a way that an improved heat utilization is achieved.

This object is achieved in that the released heat energy for

additional production of synthesis gas is used in a second process step, which is carried out inside or outside the reactor.

The method previously used to use the released thermal energy for the production of water vapor or a transfer of energy to others

Heat transfer fluid always requires further use of heat for other processes. Furthermore, the previously practiced production of steam with a

Although temperatures of 200-400 ° C do not lead to energy losses, the proportion of usable high-temperature energy decreases as entropy increases, which means that the available energy is not optimally utilized. Temperatures of 1000 ° C usually do not fall as waste heat, but must usually be generated by combustion of chemical energy sources such as hydrocarbons. It is therefore important to use this high temperature of waste heat as beneficial as possible. In the heat transfer shown here has the advantage that the yield of the desired product, in this case the synthesis gas, can be directly increased and the heat is used directly at a high level. A particular advantage also results if the production of the additional synthesis gas in a second process step internally, within the same

Reactor is carried out via a conversion of natural gas or biogas, which is added to the hot synthesis gas of the first process step.

So can be fed in particular at the upper end of the high-temperature gasifier natural gas or biogas. The temperature is still so high that it is sufficient for the direct conversion of the gas to synthesis gas. Optionally, the reactor length can be extended to achieve a sufficient residence time. In order to improve the reaction rate and the yield, it is additionally possible to incorporate a preferably monolithic catalyst. In addition to the better use of heat, there are two more advantages. On the one hand done by

Adding the colder gas and the endothermic reaction the necessary cooling for further processing of the synthesis gas. On the other hand, the H ₂ content in the

Synthesis gas increases, as in the conversion of natural gas or biogas, more H _{2 is formed} as CO.

Another preferred embodiment results if the production of the additional synthesis gas in a second process step is carried out externally, in a second reactor, in particular by means of steam reforming. The released thermal energy can be used directly for a further reaction by not being first transferred to steam, but being used directly. In addition, the resulting synthesis gas from the first step can be mixed in whole or in part with the synthesis gas from the second step. This also allows the stoichiometric ratio of H ₂ and CO to be varied. Conveniently, the resulting synthesis gas can additionally with H ₂

be enriched, which is produced in particular by electrolysis. This results in an even better flexibility with respect to the stoichiometric

Ratio of H ₂ and CO. The process is particularly preferred when the resulting synthesis gas is further processed, in particular in a process for the synthesis of methanol and / or dimethyl ether or for Fischer-Tropsch synthesis. In particular, for these processes, a H ₂ / CO ratio of 0.8: 1, resulting from a

Gasification device usually not high enough, so that additional H _{2 is} necessary.

A further preferred embodiment is when in the second process step, in addition to the waste heat of the hot synthesis gas, further energy is fed in, in particular regenerative electrical energy. By using a favorable excess flow, more natural gas or biogas can be converted in this reactor in order to achieve an optimum H ₂ / CO ratio of 2: 1. This is an energetically meaningful combination of waste heat and surplus electricity, especially with favorable electrical energy from regenerative sources. The energy can be introduced via at least one electrode. In case of

Using a metallic monolithic catalyst for steam reforming, this metal structure itself can be used as an electrode. By the

Using a plurality of electrodes, which may also have different lengths, or by the subdivision of the monolithic catalyst, certain zones can be heated differently and thus specifically the temperatures can be set in certain reactor zones. The use of electric current also ensures a short claim time to change the

Temperatures. The advantages of the invention result in particular from the possibility of optimally utilizing the heat produced during the cooling of the synthesis gas streams, since no intermediate medium is used any longer. Even with the external arrangement of the second reaction step, the hot synthesis gas of the first reaction step is used directly for the transfer. By the cooling of the second

Synthesis gas stream can continue to be used for heat transfer steam. In addition, the H ₂ / CO ratio can be optimally adjusted for subsequent production processes. If the reforming of the methane-rich gas is integrated into the upper part of the carburetor, an external steam reformer can be saved. The additional use of surplus electricity from renewable energy, in particular from wind turbines and photovoltaic systems, can also contribute to a Stabilization of the power grids are added and the surplus energy is chemically stored.

The invention is suitable for all processes of syngas production via

Gasification processes regardless of which raw materials are used. Both biological and fossil raw materials or waste can be used. Likewise, not only natural gas and biogas can be used for the reforming, but also other hydrocarbon-rich gases, in particular exhaust gases (overhead gases) from further processing processes. Depending on the H ₂ / CO ratio of the synthesis gas stream, numerous further processing steps for the synthesis gas are also possible. These include, in particular, the synthesis of methanol, of dimethyl ether, of ammonia, fermentations or the Fischer-Tropsch synthesis

In the following, the invention will be explained in more detail with reference to embodiments schematically illustrated in the figures:

Show it

Figure 1 is a schematic view of a high-temperature gasifier with internal second reaction stage

Figure 2 is a schematic view of a plant for the production of synthesis gas with external second reaction stage Figure 3 is a schematic view of a plant for the production of synthesis gas with external second reaction stage with additional heating electrodes

In Figure 1, the section of a plant is shown schematically, which combines two different syngas production methods and thus effectively uses the resulting heat. The product stream 101 from a high temperature gasifier is fed to a quench portion of the gasifier 104 at 1400 ° C. In the lower part of the reactor 104 coke 102 is usually added, which is also converted to CO and at the same time ensures a certain cooling. In the upper part of the reactor 104 is now additionally methane-rich gas 103 is added, which also at the correspondingly high temperatures of about 1000 ° C to synthesis gas is implemented. The additional metering of methane-rich gas 103 effectively utilizes the heat in the upper part of the reactor. In addition, the H ₂ content of the entire synthesis gas 105 is increased. Following is the entire

Synthesis gas 105, in which it is further cooled in particular, desulfurized, dedusted and cleaned. To improve the

Reaction rate and yield, in addition, a monolithic catalyst in the upper part of the reactor 104 can be installed.

FIG. 2 schematically shows a system which produces synthesis gas in two separate stages, the heat for the second stage operation being taken directly from the product stream of the first stage. The CO and C0 ₂ rich synthesis gas 203 originating from the gasification 201 generally has a temperature of> 900 ° C. This is used directly as a heat medium for a steam reformer 204, which is usually operated at about 500 to 850 ° C. The cooled synthesis gas 208 can subsequently be prepared by, in particular, being further cooled, desulfurized, dedusted and cleaned. The steam reformer 204 is usually operated with a mixture of methane-rich gas and water vapor 202, which is supplied in the case described here via a preheating stage in the steam reformer 204. However, the steam can also be added only after the preheating stage. The resulting H ₂ -rich synthesis gas 205 is first used to preheat the mixture 202 and then may also be treated similarly to the syngas stream 208. The workup of the

Synthesis gas streams can be separated or shared. Further processing of the conditioned synthesis gas stream takes place in particular in one

Methanol synthesis, dimethyl ether synthesis or Fischer-Tropsch synthesis.

FIG. 3 shows the plant already shown in FIG. In addition to heating by the hot synthesis gas stream 203, the steam reformer 204 is heated with electrical electrodes 301. As a result, favorable surplus stream can be used for heating and the sales can be increased. The electrodes can be inserted in different numbers and lengths in the catalyst bed. When using a metallic monolithic catalyst, these too

Metal structure can be used directly as an electrode. Table 1 shows a comparison of a method from the prior art with the two embodiments, in the event that methanol is to be produced from the synthesis gas obtained. Table 1: Comparison of the method used so far and the two

Embodiments.

It can be clearly seen in Table 1 that more methanol could be obtained by the two-stage embodiment, in particular the external example with constant energy input. The reason for this is the energy-neutral improvement of the H ₂ / CO ratio in the direction of the optimal synthesis gas composition of 2: 1 instead of 0.8: 1, as it arises in a conventional gasification process.

Claims

claims

1. A process for the production of synthesis gas, wherein as a first process step in a reactor, a high-temperature gasification (201) is performed, is released in the heat energy, characterized in that the released heat energy for the additional production of synthesis gas is used in a second process step, within (104) or outside (204) of the reactor.

2. The method according to claim 1, characterized in that the production of the additional synthesis gas in a second process step internally, within the same reactor (104) via a reaction of natural gas or biogas (103) is performed, which the hot synthesis gas of the first

Process step is added.

3. The method according to claim 1, characterized in that the production of the additional synthesis gas (207) in a second process step externally, in a second reactor, in particular by means of a steam reforming (204) is performed.

4. The method according to claim 3, characterized in that in the second

Process step, in addition to the waste heat of the hot synthesis gas (203), a further energy (301) is fed, in particular by means of regenerative electrical energy.

5. The method according to any one of claims 1 to 4, characterized in that the resulting synthesis gas is additionally enriched with H ₂ , which is produced in particular by electrolysis.

6. The method according to any one of claims 1 to 5, characterized in that the resulting synthesis gas is further processed, in particular in a process for the synthesis of methanol and / or dimethyl ether or for Fischer-Tropsch synthesis.