WO2012095328A2

WO2012095328A2 - Method for treating a carbon dioxide-containing waste gas

Info

Publication number: WO2012095328A2
Application number: PCT/EP2012/050015
Authority: WO
Inventors: Manfred Baldauf; Thomas Matschullat
Original assignee: Siemens Aktiengesellschaft
Priority date: 2011-01-13
Filing date: 2012-01-02
Publication date: 2012-07-19
Also published as: EP2659185A2; DE102011002612A1; WO2012095328A3; RU2013137756A; RU2569105C2; KR20140020846A; BR112013017844A2; US20140013665A1; CN103547863A

Abstract

The invention relates to a method for treating a carbon dioxide-containing waste gas (2), in which a hydrocarbon-containing gas (5) is guided to the waste gas and the carbon dioxide of the waste gas is at least partially converted into carbon monoxide and hydrogen when reacted with hydrocarbon and said waste gas is used with the carbon monoxide hydrogen mixture (9) for an additional combustion process.

Description

description

The invention relates to a process for the treatment of a carbon dioxide-containing exhaust gas according to claim 1.

In industrial processes, in particular in the Stahlerzeu ^¬ supply, often hot exhaust gases, which have a high proportion of CO ₂ . This occurs (= Oxygen Blast Furnage BOF), for example, when operating ei ^¬ nes so-called converter. This hot exhaust gases escape at a temperature of about 1700 ° C. The waste heat is partly ge uses ^¬ in a steam boiler. The rest is cooled by an evaporative cooler. Subsequently, the exhaust gases are freed of dust particles by filtering. For the passage through the filter system, the exhaust gas may not exceed a temperature of more than 180 ° C. The resulting exhaust gas, particularly in converters contains many process sections a large amount of carbon dioxide (CO ₂₎ · promotes This carbon dioxide when it ge into the environment ^¬ reached, the so-called greenhouse effect. The object of the invention is therefore to provide a method for the treatment of a carbon dioxide-containing exhaust gas, by which the proportion of carbon dioxide entering the free atmosphere is reduced. The solution of the problem consists in a method with the features of claim 1.

According to the inventive method for the treatment of a carbon dioxide-containing exhaust gas, a hydrocarbon-containing gas is supplied to the exhaust gas. This hydrocarbon-containing gas reacts with the carbon dioxide of the exhaust gas in a reaction ^¬ at least partially to the reaction products Kohlenmo- noxid (CO) and hydrogen (H ₂ ). The exhaust gas that causes the coal contains n-oxide-hydrogen mixture in a suitable concentration is used in a further combustion process. In this case, it may be temporarily stored beforehand. This further combustion process may, but need not necessarily be part of the process in which the stated ^¬ be acted incurred.

The carbon monoxide-hydrogen mixture (hereinafter referred to simply as fuel gas) in a preferred embodiment ^¬ form a higher calorific value than the introduced hydrocarbon-containing gas (hereinafter called reforming). This in turn means that the reaction between the reforming gas and the carbon dioxide takes place, is an endothermic Re ^¬ action, so a reaction that deprives their environment heat.

Thus, a significant proportion of the environmentally harmful carbon dioxide is removed from the exhaust gas by the invention and it can in converted form as fuel gas another

Be supplied combustion process. In this case, therefore, the heat energy of the exhaust gas is converted into chemical energy of the produced fuel gas.

It has proven to be expedient to use methane, in particular in the form of natural gas, for the hydrocarbon-containing reforming gas. Here, sets a strong for the return ^¬ recovery of carbon dioxide endothermic reaction leading to the formation of carbon monoxide and hydrogen.

Advantageously, the inventive method is used in steel production, as occurs in steelmaking often highly gas containing carbon dioxide with high tempera ^¬ ren. In particular, the exhaust gas of a converter in the steelmaking is suitable to be treated by the method according to the invention. A converter in the production of steel is used to reduce the carbon content in ge ^¬ schmolzenem iron. In one embodiment of the invention, in addition to the reforming gas, the exhaust gases may also be added with water, preferably in a vaporous form. By adding additional water, the ratio of carbon monoxide to hydrogen is changed, which is useful in various applications as fuel gas.

Since the carbon content of the exhaust gas is not constant at any point in the process, it is useful to control the exhaust gas. In particular, by the introduction of a gas sensor of the carbon dioxide content of the exhaust may be monitored over ^¬ and the insertion of the reformate gas are entspre ^¬ accordingly controlled.

It may be appropriate also to introduce a parking ^¬ ring the converter is already present in many conventional systems and reduces the intake of false air, so unwanted ambient air, thus, no additional ^¬ Liche reaction between oxygen and the reforming gas can take place.

The fuel gas can be stored further in a (preferred) already existing gas container. The fuel gas may also be applied in various other processes, especially in the steel industry. It can ^¬ example, be used to generate electricity in a power plant or process steam (optionally in combination with a power generation). Furthermore, the fuel gas for slab, billet and Vorblockvorwärmung be used in Hubherdöfen or pusher or in burners. This applies, for example, for pan drying and heating, for heating stations or for distributors in continuous casting plants.

Further advantageous embodiments and features of the invention will be explained in more detail with reference to the following figures. Show

FIG. 1 shows a schematic representation of the individual method steps in the treatment of exhaust gases from a converter,

Figure 2 shows the original treatment of an exhaust gas in the

Steel industry according to the prior art and

Figure 3 is a block diagram of the process of Figure 2 with additional Abgasreformierung.

In the following, the process for treating exhaust gas will be explained using the example of a converter used in steel production according to FIG. The converter 4 serves a molten iron from excess carbon to Exempt ^¬ s. For this purpose, oxygen is passed into the iron, and the carbon is in the molten iron, oxidized to Koh ^¬ dioxide. For this reason, an exhaust gas 2 of the converter 4 contains a considerable proportion of carbon dioxide.

The carbon dioxide content of the converter exhaust gas depends on its operating parameters. Depending on the oxygen supply and operating temperature, the proportion of carbon dioxide in relation to carbon monoxide in the exhaust gas 2 fluctuates. The exhaust gas 2 flows into an exhaust gas duct and is there checked by a probe 3 for its carbon dioxide content. If the carbon dioxide ^{portion is} above a preset threshold value, then reforming gas 5 is conducted into the exhaust gas channel 11 via a reforming gas ^feed 6. The reformate gas 6, for example, earth ^¬ gas can be used with a high methane content, rea ^¬ yaws with the carbon dioxide of the exhaust gas at least partly according to the following reaction equation (dry reforming 7, see. Fig. 3).

CH ₄ + C0 ₂ -> 2CO + 2H ₂ ΔΗ = +250 kJ / mol

This reaction is endothermic, 250 kJ heat energy of the environment, ie the exhaust gas 2, are withdrawn per mole. In this way, heat energy is converted by the reaction, the in the formed fuel gas 7 (CO + H _2, also synthesis gas ge ^¬ Nannt) is stored as chemical energy. Accordingly, therefore, thermal energy into chemical energy is converted, since the fuel gas 9 formed according to Equation 1 has a higher calorific value than the Refor ^¬ minimizing gas originally used (methane).

The individual calorific values of the educts and products are:

CH ₄ : 55.5 MJ / kg = 888 MJ / kmol

CO: 10.1 MJ / kg = 283 MJ / kmol

H ₂ : 143 MJ / kg = 286 MJ / kmol

The calorific value of a mixture of 2 moles of carbon monoxide and 2 moles of H ₂ is higher than the calorific value of a mole of CH ₄ (methane) from which the fuel gas 7 is produced by the abovementioned reaction enthalpy of 250 kJ / mol. The increase in calorific value thus amounts to 28% of the introduced calorific value of methane (250 kJ / mol: 888 kJ / mol).

Depending on the use of the fuel gas 7, it may be useful to the CO ^ ratio in favor of hydrogen to various ^¬ ben. In this case, water (preferably in vapor form) may optionally also be introduced at the reforming gas feed 6. Thus, an exothermic CO shift reaction he ^¬ allows, after which

H ₂ 0 + CO -> C0 ₂ + H ₂ ΔΗ = H-42 kJ / mol the ratio of H ₂ to CO is changed. Characterized less heat although is stored (as it here is a exother ^¬ me reaction), but there is obtained ₂ content in the combustion gas 7, a higher H, which is advantageous in some combustion processes. This is the case in particular when, in these combustion processes, the heat transport is by radiation and not by convection. From the combustion results in the exhaust gas, a higher content of water, the be ^¬ favored by its broad radiation band heat transport.

In the present example of a converter, in particular in a converter with a control ring 13, these can be Reformierbehandlung ^¬ sets with the CO ₂ of the exhaust gas 2 at two Various ^¬ NEN process conditions of the reforming process is useful. On the one hand this is the case with so genann ^¬ th arrival and Abfahrphasen in which the exhaust gas is so far therefore not used because of the C0 ₂ content of the exhaust gas is too high and the CO content is too low. The described tro ^¬ ckene reforming a useful fuel gas according sliding ^¬ chung 1 is obtained with sufficient calorific value, which will be described in more relative to the further process sequence and can be stored in a gas store.

On the other hand, the dry reforming can also be used to further increase the calorific value of CO rich gas, which is already collected in the prior art, if this fuel-rich gas is to be mixed with lean gases from other steelworks parts and the mixture for more combustion processes does not have the energy value the sufficient ^¬.

The application of an actuating ring 13 is advantageous to the on ^¬ sucking of false air to avoid that would result in the combustion of methane or natural gas, so the reforming 7, rather than to carry out the reforming according to Equation 1 described above. In addition, the high nitrogen content of the air would lead to dilution of the converter gas and the fuel gas.

After the reforming process, the exhaust gas is cooled in a steam ^¬ boiler 8, where steam is generated there, which in turn ^¬ can be used for power generation.

This is followed by a coarse dedusting 10 of the exhaust gas 2, which is further ^{¬ passed} into an evaporative cooler 12. This evaporative cooler 12 is necessary because for a following Tro Ckenelektrofilterung 14, in which the residual particulate matter is removed from the exhaust gas 2, the exhaust gas must not be hotter than 180 ° C. After the fine dust has been separated off, the exhaust gas 2 is either flared off via a flare chimney 18 via a blower 10 or, after further cooling in a gas cooler 20, is fed to a gas container 22.

The question whether the combustible components in the exhaust gas 2 are burned over ei ^¬ NEN flare tower or whether the high calorie exhaust gas ₂ mixture is stored as a fuel gas 9 in the gas container 22 with a CO-H, depends on the carbon dioxide content of the exhaust gas. 2 The described reforming of the exhaust gas 2 with the Re ^¬ forming gas methane leads to a suitable control of reforming, for example via a sensor 3 to the fact that the proportion of CO-H ₂ mixture in the exhaust gas after filtering is so high that the majority of the Exhaust gas or the carbon monoxide and the hydrogen stored in the gas container 22 who ^¬ can and can be used again as a fuel gas 9. The flaring of the exhaust gas in the torch tower 18 is reduced to a very small proportion by this measure compared to the prior art.

In Figures 2 and 3, the difference between the prior art for the exhaust gas treatment process of converter ^¬ exhaust gases and the methods described herein is once more shown schematically with reference to a block diagram representation.

At the far left is a C0 ₂ exhaust-producing process step, shown here using the example of a converter 4, in which exhaust gas 2 is formed. The carbon dioxide-containing exhaust gas 2 is cooled in a steam boiler 8, resulting in steam for further use. Furthermore, now follows an evaporative cooler 12, in the waste heat Ql arises, which is not used in this case. The following is a dry electrostatic precipitator 14, wherein ßend subse- depending on the carbon dioxide content of the exhaust gas 2 that is flared on ei ^¬ NEN flare tower 18 or stored as a fuel gas 9 in a gas tank 22 for further use. The method described here differs according to Fi ^¬ gur 3 from the method according to Figure 2 according to the prior art, characterized in that between the converter 4 and the steam generator 8, a reforming process 7 takes the form of a dry reforming, via a Reformiergaszuführung 6 reforming 5 the process is supplied and as described in equation 1, the exhaust gas 2 is treated.

The two methods are different in addition to this loading signed insertion of the dry reforming 7 further characterized in that the amount of heat Q2 is removed from the evaporative cooler 12, is smaller than the quantity of heat Q of the evaporation ^¬ evaporation cooler 12 of Figure 2 and that the amount m2 of the gas 2 flared at the torch tower 18 is smaller than the amount ml flared at the torch tower 18 'according to the prior art.

Since the fuel gas mixture can be reused in suitable installations of the steelworks, the production phases in which post-combustion in the flare 18 is carried out according to the prior art can be reduced or shortened. In this way, the energy content of the combustible components of the exhaust gas is used together with the combustible gas formed under SpeI ^¬ assurance of waste heat in advantageous manner. By shortening the torch operating times, the gas collection time is increased and the carbon dioxide emissions of the converter system or the torch are reduced.

Claims

claims

A method for treating a carbon dioxide-containing exhaust gas (2), wherein the exhaust gas, a hydrocarbon-containing gas (5) is supplied and the carbon dioxide of the exhaust gas is at least partially converted into carbon monoxide and hydrogen in a reaction and the carbon monoxide-hydrogen mixture (9) another combustion process is used.

2. The method according to claim 1, characterized in that the carbon dioxide in the exhaust gas with the hydrocarbon-containing gas (7) enters into an endothermic reaction and the exhaust gas (2) is cooled by this reaction.

3. The method according to claim 1 or 2, characterized in that the hydrocarbon-containing gas (5) contains methane.

4. The method according to any one of the preceding claims, characterized in that the exhaust gas (2) is obtained in a process of steelmaking.

5. The method according to any one of the preceding claims, characterized in that the exhaust gas (2) in a converter (4) for Re ^¬ production of carbon content in molten iron occurs.

6. The method according to any one of the preceding claims, characterized in that the exhaust gas (2) in addition to the hydrocarbon-containing gas (5) water is added.

7. The method according to any one of the preceding claims, characterized in that the carbon dioxide content of the exhaust gas for controlling the supply of the hydrocarbon-containing gas (5) is monitored by a gas sensor.

8. The method according to any one of claims 5 to 7, characterized in that the converter (4) is provided a collar to prevent the suction of false air.

9. The method according to any one of the preceding claims, dadur characterized in that the carbon monoxide-hydrogen mixture (9) is stored in a gas tank between.

10. The method according to any one of the preceding claims, characterized in that the carbon monoxide-hydrogen mixture (9) is used as the fuel gas.

11. The method according to any one of the preceding claims, characterized in that the hydrocarbon-containing gas in egg nem start-up process and / or Abfahrprozess a converter z is performed.