JPS6018602B2 - Method for producing high temperature reducing gas from light hydrocarbons - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-temperature reducing gas from light hydrocarbons, and more specifically, the present invention relates to a method for producing high-temperature reducing gas from light hydrocarbons. The present invention relates to a method for producing high-temperature reducing gas with high thermal efficiency and high quality.

In general, when steam-cooking is performed using vertical hydrocarbons equivalent to gas and naphtha fractions as raw materials to directly produce high-temperature reducing gas for steelmaking, the carbon content of vertical hydrocarbons of ethane and higher is higher than that of methane. Since the hydrogen ratio (atomic ratio) is high, from the viewpoint of catalyst performance, unless the amount of steam introduced is increased and steam reforming is performed under conditions with a high oxygen-to-carbon ratio (atomic ratio), carbon precipitation in the study soot tube may occur. Problems will occur.

Therefore, conventionally, as shown in Fig. 1, light hydrocarbons and steam as raw materials are first introduced into a steam reformer 1 at a high oxygen to carbon ratio (atomic ratio), and steam reforming is performed at a high temperature of 700 to 850 oo. This gas is then rapidly cooled in a waste heat boiler 2, and further in a carbon monoxide shift reactor 3, carbon monoxide in the gas is reacted with steam to convert it into carbon gas and hydrogen. After that, it is cooled in a cooler 4 and then introduced into a gas-liquid separator 5 to remove moisture, and then carbon dioxide is removed in a carbon dioxide removal device 6 to produce a reducing gas with a desired composition, which is then heated. A high-temperature reducing gas was produced by raising the temperature in vessel 7.

However, in the above-mentioned conventional method, a large amount of steam is produced as a by-product because the high-temperature gas emitted from the steam conditioning device 1 is cooled down to room temperature in each subsequent process, and the resulting reducing gas is used for steel manufacturing, etc. In order to use it, it was necessary to reheat it in the heater 7 from 800 to 950 o'clock.

As described above, the conventional method involves cooling the high-temperature reducing gas and then heating it again, which is an extremely inefficient method of thermal efficiency, and measures had to be taken to deal with the large amount of steam generated. Furthermore, within the reheater, problems include carbon precipitation due to the disproportionation reaction of carbon monoxide (the following OZC020C↓) and carbon precipitation due to the thermal decomposition reaction of methane.

Therefore, the present inventors have conducted extensive research in order to develop a method that can overcome the drawbacks of the above-mentioned conventional methods and produce a large amount of high-quality, high-temperature reducing gas with high thermal efficiency.

As a result, they found that the above object could be achieved by carrying out steam reforming in two stages and carrying out the steam reforming in the first stage at a relatively low temperature, thus completing the present invention. That is, the present invention provides a method for producing high-temperature reducing gas using light hydrocarbons as a raw material, in which the first stage steam reforming is carried out at 450 to 550 oo, normal pressure to 50 k9/G,
It is carried out under conditions where the oxygen to carbon ratio (atomic ratio) is 2 to 5,
Next, after the reformed gas obtained in the first stage steam reforming is dehydrated and decarbonated, the second stage steam reforming is carried out at 800 to 950 pm at normal pressure to 10 k9/g. ,
The present invention provides a method for producing a high-temperature reducing gas, characterized in that the process is carried out under conditions where the oxygen to carbon ratio (atomic ratio) is 1.1 to 1.5.

An example of the method of the present invention will be described below with reference to FIG.

First, the raw materials, vertical hydrocarbons, and steam are converted into a steam reformer 8.
The first stage of water vapor treatment is carried out. The steam reforming performed here is performed under lower temperature conditions than in the conventional method. Although there are no particular restrictions on this temperature condition, a range of 450 to 550 oo is generally suitable. Furthermore, there is no particular restriction on the introduction ratio of vertical hydrocarbons and steam;
Usually, it is selected so that the oxygen to carbon ratio (atomic ratio) is 2 to 5. In addition, the reactions that proceed in this steam reforming are mainly the following (1}, ■, and (3}.CmHm+N
H20→nCO10 (n+m/2) day 2 (endothermic reaction)
・・・・・・【11CO+day 2
0 ko CQ + day 2 (exothermic reaction) ・・・・・・■ CO 10 ga 2 ko CH 4 10 days 20 (exothermic reaction) ・・・・・・'3
'Since the first stage steam reforming in the method of the present invention is carried out at a lower temperature than in the conventional method, the above '21 and '3}
The reaction proceeds to the right, and as a result, the reformed gas exiting the Tsuruga apparatus 8 contains a large amount of hydrogen and methane gas, while the content of carbon monoxide is extremely small. In addition, when using the secondary method, the content of methane gas is too large under the above-mentioned low temperature conditions and is inappropriate as a reducing gas.
In the method of the present invention, even if the content of methane gas is large, since steam reforming is performed again in a later step, the reducing gas finally obtained contains almost no methane gas. The steam instructing device 8 used in the first stage steam reforming may be either an external heating type or an adiabatic type reactor.

In addition, when using an external heating type reactor, the reaction is not only carried out in the neck of the heating furnace as in the conventional method, but also because the temperature condition for the reaction is low at 450 to 550 qo and the required amount of heat is small. Waste heat from the second stage steam reformer 12, which is the process, can also be used as a heat source. Further, the pressure conditions during this first stage steam reforming are generally preferably normal pressure to 50 k9/mass G. Next, in the method of the present invention, the second stage steam reforming may be carried out immediately after the first stage steam reforming, but normally the reformed gas obtained by the first stage steam reforming is First, the degree of oxidation is adjusted by a conventional method.

That is, the reformed gas exiting the first-stage steam reformer 8 is guided to the waste heat boiler 9 and cooled to remove steam from the gas, and then the gas-liquid separator 10, the carbon dioxide removal device 11, and the necessary Depending on the situation, water and carbon dioxide are sufficiently removed using a water-cooled cooler, boiler water preheater, etc., and water vapor is added to keep the oxygen to carbon ratio (atomic ratio) in the reformed gas within an appropriate range. adjust. The reformed gas subjected to such adjustment is usually cooled to a temperature of about 100 to 250 oC before being introduced into the second steam reformer 12. In addition, in the method of the present invention, in adjusting the water content and carbon dioxide gas in the reformed gas, the above-mentioned apparatuses may be used in appropriate combinations depending on the desired high-temperature reducing gas conditions. Furthermore, as described above, the reformed gas obtained by the first stage steam reforming has a lower carbon monoxide content than in the case of the conventional method, so there is no need to use a carbon monoxide shift reactor. A part of the reformed gas produced in the first-stage steam reformer 8 is directly introduced into the second-stage steam-gas reformer 12 (described later), and the remainder is transferred to the aforementioned waste heat boiler 9, gas-liquid. It is also effective to introduce the gas into a series of devices such as the separator 10 and the carbon dioxide removal device 11 to obtain a high-temperature reducing gas having the overall desired composition. In the method of the present invention, water and carbon dioxide are removed through the above-mentioned steps, and the 100% carbon dioxide containing a large amount of methane and hydrogen is adjusted to achieve the desired degree of oxidation.
~25,000 of reformed gas is introduced into the Sariko second stage steam reformer 12 to perform second stage steam reforming.

Here, as mentioned above, the components of the waste gas introduced into the steam reformer 12 are mainly methane and hydrogen, and also contain carbon monoxide, carbon dioxide, steam, etc., and the number of carbon atoms is Hydrocarbons of two or more are almost never present. Therefore, even if steam reforming is performed under conditions where the oxygen to carbon ratio (atomic ratio) is relatively low, the problem of carbon precipitation does not occur. The ratio of the reformed gas and hydroxyl gas to be introduced in this second stage steam reforming varies depending on the composition, temperature, pressure, and other conditions of the desired high-temperature oxidation gas, but generally speaking, the ratio of oxygen to carbon Ratio (atomic ratio) of 1.1 to ZI. It is preferable to set it within the range of 5. If it is less than 1.1, the problem of carbon deposition occurs and the catalyst activity rapidly decreases, making it impractical.

On the other hand, if it exceeds 1.5, the degree of oxidation of the resulting reducing gas becomes high, which makes it unsuitable for the reduction reaction, which is not preferable. Furthermore, as for the pressure conditions for this water vapor regime, lower pressures are generally more desirable. That is, in the case of low pressure, methane is reduced due to the equilibrium relationship of the methane reforming reaction (the leg of the reaction equation described above), and along with this, water vapor and carbon dioxide gas are reduced, resulting in a high-quality reducing gas rich in hydrogen gas. Therefore, normal pressure ~ 10
Perform steam reforming at k9/KuG. Furthermore, regarding the temperature conditions, as can be seen from the above-mentioned reaction equations (1) and {3', the higher the temperature, the less methane, water vapor, and carbon dioxide gas, and the more hydrogen and carbon monoxide, resulting in a high-quality reducing gas.
Therefore, it should be selected appropriately taking into consideration the temperature conditions of the second stage steam reforming of the present invention, the composition of the desired reducing gas, the amount of heat contained, and the pressure conditions of the reaction.
It is preferably in the range of 0 to 950 qo. As described above, the second stage steam reforming is performed under higher temperature conditions than the first stage, and therefore, the second stage steam reformer 12 used is an external heating type reactor. As mentioned above, the reducing gas obtained by the method of the present invention is of good quality and already has a
It has an extremely high temperature of 50 qo, and can be directly introduced into a reduction iron manufacturing apparatus such as a shaft furnace.
As mentioned above, in the conventional method, the outlet temperature of the steam reformer is extremely high, but in order to avoid carbon deposition on the catalyst, the oxygen to carbon ratio (atomic ratio) during the reforming reaction is increased. Moreover, the resulting reformed gas has a composition inappropriate for use as a reducing gas, and therefore has to be cooled to a low temperature near room temperature and then subjected to decarbonation and dehydration steps. Moreover, since the Tsuruga gas was heated to a high temperature of around 80,000 ℃ and then cooled, the capacity of the waste heat boiler had to be increased, resulting in a large amount of steam and extremely poor thermal efficiency. On the other hand, according to the present invention, the outlet temperature of the first stage steam reformer is 45
Because the temperature is low (000 to 550 qo), the capacity of the waste heat boiler can be reduced, and by using a packaged boiler, it is also possible to self-balance the steam in the entire system, which improves thermal efficiency. It is excellent in terms of In addition, in the method of the present invention, various devices such as cooling and decarbonization equipment that should be installed after the first stage steam formation can be combined in various ways, so that the composition of the high temperature reducing gas finally produced can be changed. It is possible to select the degree of oxidation, etc. over a wide range, thus increasing operational flexibility. Furthermore, the composition of the resulting high-temperature reducing gas has a higher hydrogen content than that obtained by conventional methods, and is a high-quality reducing gas suitable for reduction reactions. This is clear from the following example.

That is, n-hexane is used as the raw material hydrocarbon, and the conditions for the first stage steam reforming are inlet temperature 450 qo, outlet temperature 50,000, and pressure 5k9/lump G, while the conditions for the second stage steam reforming are outlet temperature 95,000. , and the pressure was set at 2k9/g, and under these conditions, the mixing ratio of the steam and raw material hydrocarbon in the first and second stages, that is, the oxygen to carbon ratio (atomic ratio), was varied variously. The R value of the high temperature reducing gas obtained by this operation is (hydrogen gas carbon 11 oxide)/
(carbon dioxide gas and water vapor) (molar ratio) is shown in Figure 3. The conditions and results are shown in Tables 1 and 2. In the figure, A is the oxygen to carbon ratio (atomic ratio) of the second stage steam reforming.
is 1.1, B is 1.2. In addition, C was obtained by the conventional one-stage steam reforming method conducted under the same conditions as the second stage steam reforming method except for the oxygen to carbon ratio (atomic ratio). The conditions were set as shown in the numerical values on the horizontal axis of the graph in FIG. As can be seen from FIG. 3, according to the method of the present invention, the R value of the reducing gas obtained is higher and of better quality than when using the conventional method. As described above, according to the method of the present invention, a desired high-temperature reducing gas can be produced efficiently* even when light hydrocarbons with a large number of carbon atoms are used as raw materials.

Table 1 (For external heating type) Note) The numbers in parentheses are percentages (molarity) of the total flow rate.
shows.

Table 2 (Insulated type) Note) The numbers in parentheses indicate the percentage (mole) of the total flow rate.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of a conventional high-temperature reducing gas generation process, and FIG. 2 is a flowchart showing one embodiment of the method of the present invention. FIG. 3 is a graph showing the relationship between the oxygen to carbon ratio (atomic ratio) and the resulting R value. In the figure, 1 is a steam reformer, 2 is a waste heat boiler, 3 is a carbon monoxide shift reactor, 4 is a cooler, 5 is a gas-liquid separator, 6 is a carbon dioxide removal device, 7 is a heater, and 8 is a The first stage steam reformer, 9 is a waste heat boiler, 1
0 is a gas-liquid separator, 11 is a carbon dioxide removal device, and 12 is a second stage steam reformer. In addition, A and B in FIG. 3 show the relationship between the R value and the oxygen to carbon ratio (atomic ratio) of the reducing gas obtained when using the method of the present invention, and C shows the relationship between the reducing gas obtained when using the conventional method. The relationship between the R value and the oxygen to carbon ratio (atomic ratio) is shown. Figure - Figure 2 Figure 3

Claims (1)

[Claims] 1 In a method for producing high-temperature reducing gas using light hydrocarbon as a raw material, the first stage steam reforming is carried out at 450 to 550°C.
, normal pressure to 50 kg/cm^2G, and an oxygen to carbon ratio (atomic ratio) of 2 to 5. Then, the reformed gas obtained in the first stage steam reforming is dehydrated and decarboxylated. After gas treatment, the second stage steam reforming is carried out at 800~9
50℃, normal pressure ~ 10kg/cm^2G, oxygen to carbon ratio (
1. A method for producing a high-temperature reducing gas, characterized in that the method is carried out under conditions in which the atomic ratio (atomic ratio) is 1.1 to 1.5.