JP2655800B2 - Gas desulfurizing agent and desulfurization method for hydrogen sulfide-containing gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a desulfurizing agent and a desulfurizing method for removing hydrogen sulfide contained in a gas containing hydrogen sulfide at a high temperature.

[0002]

2. Description of the Related Art In order to use coal energy with high efficiency, technological developments such as coal gasification combined cycle power generation and coal gasification fuel cell power generation have been promoted. In these techniques, it is necessary to remove hydrogen sulfide contained in coal gasified gas in order to prevent air pollution and extend the life of components such as gas turbines and fuel cells. Also,
When hydrogen sulfide is contained as an impurity in fuel gas other than coal gas, desulfurization treatment is often indispensable prior to its use.

As a gas desulfurization method, there is a wet desulfurization method in which a gas is washed with a solvent having high solubility in hydrogen sulfide, and many processes have already been used in the chemical industry and the like. However, since the desulfurization temperature is as low as room temperature to 120 ° C. in the wet desulfurization method, a cooling operation is required to treat a high-temperature gas, and when applied to coal gasification power generation or the like, a large energy loss is involved.

[0004] In order to solve this drawback, development of a high-temperature dry desulfurization method for desulfurization at a temperature of about 500 ° C or higher has been advanced. The most important issue in this technology is the development of high-performance desulfurizing agents. Research and development of honeycomb-type iron oxide-based desulfurizing agents, copper oxide-based and zinc oxide-based desulfurizing agents already supported on iron ore, titania, silica, etc. Has been done. Among these, iron oxide-based desulfurizing agents such as iron ore are advantageous in terms of desulfurization speed, performance stability in repeated use of desulfurization-regeneration, and price, and are regarded as one of the most promising desulfurizing agents. .

[0005]

However, the iron oxide-based desulfurizing agents developed so far have a problem that when the fuel gas contains steam, the desulfurization capacity is remarkably reduced (Central Research Institute of Electric Power Industry). Research report: 284005, August 1984). Further, even in the desulfurization of fuel gas containing no water vapor, the desulfurization capacity is not always sufficient (Ishikawajima Harima Technical Report, Vol. 21, pages 274 to 27).
8. 1981, Research Report of Central Research Institute of Electric Power Industry: 2850
30, March 1986). Here, the desulfurization capacity is a term used when performing desulfurization in a fixed-bed type reactor, and is usually defined as follows. That is, the amount of hydrogen sulfide absorbed and removed until the concentration of hydrogen sulfide at the reactor outlet reaches a predetermined value (breakthrough concentration) is determined by the weight of the desulfurizing agent charged in the reactor or the weight of iron oxide contained in the desulfurizing agent. Is defined as the divided value. Generally, the desulfurization agent having a higher desulfurization reaction rate has a larger desulfurization capacity.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors focused on various iron oxide-based minerals produced naturally, compared their desulfurization capacities, and determined pore distribution and the like. The relationship with physical properties was examined. As a result, they found that the potter's clay had a desulfurization capacity remarkably superior to iron ore or the like, and completed the present invention. That is, according to the present invention, there is provided a desulfurizing agent comprising a potter's clay fired at 400 to 1000 ° C. as a desulfurizing active component. Further, according to the present invention, there is provided a method for desulfurizing a hydrogen sulfide-containing gas, comprising contacting a hydrogen sulfide-containing gas with a desulfurizing agent at 300 to 700 ° C.

The desulfurizing agent prepared from the red clay of the present invention and its performance will be described in detail below. Red clay is a natural mineral found in Guangxi, China. Its main component is iron oxide (Fe ₂ O ₃ : hematite) (see Table 1 below) and is a clay-like substance composed of fine particles of about 10 μm or less.

[0008] Since the hydrated red clay is soft and rich in plasticity, molded articles of various shapes can be obtained by utilizing this property. For example, a pottery clay having a water content of 5 to 30 wt%, preferably 10 to 15 wt% is prepared as a molding material, formed into a required shape, and then dried at room temperature to 100 ° C, preferably 40 to 80 ° C. Thus, a molded article can be obtained. The dry compact obtained in this way has considerable compressive strength by itself. When a molded body is obtained as described above, a binder and another desulfurizing agent can be added to the molding material as needed. As the binder, inorganic and organic binders can be used. Examples of the inorganic binder include kaolin, bentonite, zeolite, and alumina hydrate. Examples of the organic binder include, in addition to cellulose derivatives such as hydroxypropylcellulose, methylcellulose and carboxymethylcellulose, various water-soluble polymers such as sodium alginate, polyvinyl alcohol, polyvinylpyrrolidone and starch paste, and molasses. . The amount of the binder added is 5
-40 wt%, preferably 5-20 wt%. The shape of the molded body can be any shape such as a granular shape, a pellet shape, a spherical shape, a cylindrical shape, and a column shape. The desulfurizing agent of the present invention,
It can also be obtained by using paste-like hydrous red clay as a coating material, and applying and drying this on a support such as a honeycomb support. In this case, a binder or another desulfurizing agent can be appropriately added to the coating material as needed.

In the desulfurizing agent of the present invention, the red clay is 400 to 1000 ° C., preferably 500 to 900 ° C.
It is a fired product fired in. In order to obtain a molded body in which red clay is a fired product, it can be obtained by firing the dried molded body obtained as described above. And refired if necessary. Further, the desulfurizing agent in which the fired red clay is supported on the support can be obtained by firing the dried red clay supported on the support, or by adding an appropriate amount of water and a binder to the fired fine particles of the red clay. It can be obtained by applying a paste-like coating material on a support, drying and refiring as necessary. The granular desulfurizing agent according to the present invention can be obtained by the above-mentioned molding method, and further crushes a lump dry molded body,
It can be obtained by classifying and firing if necessary, or can be obtained by pulverizing and classifying a massive fired molded body. Further, the desulfurizing agent of the present invention can be a powder. The powder desulfurizing agent can be obtained by drying red clay and firing it if necessary.

In a granular desulfurizing agent, its pore distribution and pore volume are important factors affecting the desulfurization capacity. Generally, in a high-temperature gas desulfurization reaction, intraparticle diffusion often becomes a limiting factor of the reaction. Therefore, in order to increase the gas diffusion rate in the particles and enable the desulfurization active component (iron oxide in the case of red clay) contained in the desulfurization agent to efficiently react with hydrogen sulfide, the macropores of the desulfurization agent are required. It is desirable to increase the volume. This is particularly important in the case of desulfurization of fuel gas without water vapor. Since red clay is a substance consisting of fine particles, it is possible to change the pore distribution, particularly the volume of macropores, over a wide range by devising the desulfurizing agent preparation conditions. An excellent desulfurizing agent having a large desulfurization capacity can be obtained. In the case of the desulfurizing agent of the present invention, the peak of the pore volume is 5
Although the pore diameter is in the range of 0 to 100 mm, in order to enhance the desulfurization effect, the macropore volume having a diameter of 100 nm or more is reduced to 10% or more, preferably 20%, based on the total pore volume.
It is better to specify the above range. The upper limit of the ratio of the macropore volume to the total fine volume is not particularly limited,
Generally, it is about 40%. As a method of increasing the macropore volume of the desulfurizing agent, it is possible to adopt a method in which a high-boiling liquid organic substance or a solid organic substance is added and mixed in advance to a molding material made of hydrous red clay, and then molded and fired. it can. Examples of the high boiling liquid organic substance include those having a boiling point of 200 ° C. or higher, such as glycerin, polyethylene glycol, and polypropylene glycol. Examples of solid organic substances include glucose, lactose, sugar, dextrin, starch, cellulose, and the like, and the above-mentioned various polymer substances shown as binders. These organic substances decompose into gaseous substances upon firing, creating macropores. The content of the organic substance in the molding material is appropriately determined according to the content of the desired macropores.
0 wt%, preferably 3 to 15 wt%.

As described above, the hydrogen sulfide desulfurization capacity of an iron oxide-based desulfurizing agent often decreases significantly when gas contains water vapor. However, in the desulfurizing agent obtained from red clay, even if the gas contains water vapor, the desulfurization capacity does not decrease unless the concentration is too high, and usually does not exceed 20 vol%. It should be further noted that when the water vapor concentration is about 15 vol% or less, a unique phenomenon has been found that the desulfurization capacity is increased as compared with the case where no water vapor is contained.
This is a phenomenon peculiar to the potter's clay, and the reason for it has not been elucidated. However, since such a phenomenon is not observed in the loess, it may be due to the specificity of the microscopic structure such as the crystal structure of iron oxide contained in the red clay.

To remove hydrogen sulfide in a gas using the desulfurizing agent of the present invention, a gas containing hydrogen sulfide is brought into contact with the desulfurizing agent. The contact temperature is not particularly limited.
To 700 ° C, preferably 400 to 600 ° C. As the contact device, a packed tower filled with a desulfurizing agent or the like can be used. The gas to be subjected to the desulfurization treatment may be any gas containing hydrogen sulfide and containing a reducing gas such as hydrogen and carbon monoxide. Examples of the gas include a fuel gas obtained by gasification of coal, And the like.

The desulfurizing agent of the present invention exhibits excellent desulfurizing activity even in the presence of steam and has a large desulfurizing capacity, and is used for separating and removing hydrogen sulfide from various hydrogen sulfide-containing gases.

[0014]

Next, specific examples of the desulfurizing agent prepared from the red clay of the present invention will be described in comparison with other desulfurizing agents.

[0015] The desulfurizing agent used for comparison was prepared from loess (from Niwasaka, Fukushima Prefecture) and iron ore (from Newman, Australia). These are iron oxide natural minerals like red clay. Table 1 shows the elemental composition of each mineral.
In each case, iron oxide (hematite) is a main component, and silica (quartz) and alumina are contained in small amounts. Also, loess has a high calcium content, and according to X-ray diffraction analysis, most of it is calcium sulfate.

[0016]

[Table 1]

The desulfurizing agent was prepared as follows. For red clay and loess, after adding water to the powdery raw material and granulating,
Fired in air. In the case of red clay, two types of desulfurizing agents having different macropore volumes: red clay-P and red clay-A
5 was prepared. The latter is prepared by adding 5% by weight of Avicel (crystalline cellulose powder) to red clay when granulating with water. The Avicel burns and disappears during firing, but plays a role in imparting macropores to the desulfurizing agent. For iron ore, the ore was crushed into small blocks before firing. Each desulfurizing agent has a particle size of 0.59 to 0.84 m.
m were sieved to an experiment.

FIG. 1 shows the results of measuring the pore distribution of the desulfurizing agent prepared as described above using a mercury porosimeter. In FIG. 1, the loess (Niwazaka) “」 ”indicates a product baked at 900 ° C.,
"△" indicates a product baked at 600 ° C, red clay-A5 "▲" indicates 900
° C baked products, iron ore (Newman) “□” indicate 900 ° C baked products. When comparing the total pore volume, loess> red clay-
A5> Red clay-P> Iron ore. On the other hand, the volume of macropores (pores having a pore diameter of 100 to 200 nm or more) which is considered to govern the diffusion rate of the reaction gas in the pores is as follows:
Loess> Red Pottery-A5> Iron Ore ≧ Red Pottery-P In addition, in the red clay desulfurizing agent, the pore diameter is 50 to 10
It is characterized by a large content of pore volume in the range of 0 nm (about 10 to 40% based on the total pore volume).

Example 1 An experiment on desulfurization of hydrogen sulfide from a reaction gas containing no steam was carried out as follows. As the reaction apparatus, a flow-type fixed-bed reaction apparatus to which a quartz reaction tube having an inner diameter of 6 mm was connected was used.
0.85 ml (bed height: 3 cm) of a desulfurizing agent (particle diameter: 0.59 to 0.84 mm) was charged into a reaction tube, and the reaction temperature was set to 500.
° C, GHSV 10,000h ^-1 , pressure 1.4kg / cm
^A 0.5% H ₂ S-20% H ₂ —N ₂ mixed gas is circulated under the conditions of ² , and the point when the hydrogen sulfide concentration at the outlet of the reaction tube reaches 300 ppm is defined as breakthrough, and the flow of the reaction gas is defined. Stopped. The concentration of hydrogen sulfide in the gas at the outlet of the reaction tube was measured at 4-minute intervals by a gas chromatograph equipped with an automatic sampling valve. FIG. 2 is a breakthrough curve of the obtained hydrogen sulfide. From this figure, it can be seen that loess and red clay-A5 have a long breakthrough time and a large desulfurization capacity. The reason for this is that these two have a large macropore volume and a high diffusion rate of the reaction gas into the desulfurizing agent particles, and this point has been clarified by the present inventors' previous studies. By the way.

Example 2 A reaction gas containing water vapor, that is, 0.5% H ₂ S-10
Example 1 using a 20% H ₂ O-20% H ₂ —N ₂ mixed gas
The experiment was performed under the same reaction conditions as described above. FIG. 3 shows the result. As can be seen from a comparison between FIG. 3 and FIG. 2, when steam is contained in the reaction gas, the breakthrough time is remarkably shortened in the loess, and is slightly shortened in the iron ore. On the other hand, red clay-A5 shows almost the same breakthrough time, and red clay-P has remarkably improved. That is,
The red clay desulfurizing agent does not decrease the desulfurization capacity even when desulfurizing a gas containing water vapor, and may even improve it. Note that FIG.
, The concentration of hydrogen sulfide at the reaction tube outlet before the breakthrough was 100
ppm, which is higher than that in the absence of water vapor (FIG. 2), due to the thermodynamic equilibrium restriction in the desulfurization reaction by iron oxide as described below. 3Fe ₂ O ₃ + H ₂ → 2Fe ₃ O ₄ + H ₂ O (1) Fe ₃ O ₄ + 3H ₂ S + H ₂ → 3FeS + 4H ₂ O (2)

Example 3 The effect of the concentration of water vapor contained in the reaction gas was investigated using loess as a desulfurizing agent. The reaction conditions are the same as in Example 1 except for the concentration of water vapor in the reaction gas. FIG. 4 shows the results. Looking at the results in FIG. 4, the breakthrough time is significantly shorter as the water vapor concentration increases. That is, in the case of a desulfurizing agent prepared from loess, the desulfurization capacity of hydrogen sulfide is significantly reduced by an increase in the steam concentration.

Example 4 The effect of water vapor concentration was examined under the same reaction conditions as in Example 3 using red clay-P as a desulfurizing agent. FIG. 5 shows the result, but there is a remarkable difference as compared with FIG. That is, in the case of red clay, the desulfurization capacity is remarkably improved when the steam concentration is 10% or less than when the steam concentration is 0%. Such a result was not observed with the conventional desulfurizing agent, and is considered to be a phenomenon peculiar to red clay. Water vapor concentration is 2
When it reaches 0%, the breakthrough concentration becomes 30 in a short time of about 0.3 hour.
It has reached 0 ppm and the desulfurization capacity has been extremely reduced. However, this is considered to be mainly due to the high thermodynamic equilibrium concentration of hydrogen sulfide in the above reaction formula of iron oxide and hydrogen sulfide, and can be said to be an inevitable phenomenon.

Based on the results of the desulfurization experiments from Example 1 to Example 4, the average degree of sulfuration of each desulfurizing agent at the time of breakthrough was determined. The values are shown in Table 2 together with the surface area and pore volume of the desulfurizing agent before the reaction. Here, the average sulfidity is
The amount of hydrogen sulfide (A) required to convert all iron oxide contained in the desulfurizing agent (the amount filled in the reaction tube) into iron sulfide (FeS), and the amount actually absorbed by the time of breakthrough after the start of the desulfurization reaction Ratio to total hydrogen sulfide (a) (a / A × 100
%), And the value of a can be calculated from FIG. 2 and FIG. As can be seen from this definition, the average degree of sulfuration is an index indicating the hydrogen sulfide absorption capacity per unit amount of iron oxide, that is, the desulfurization capacity.

[0024]

[Table 2] 1) Desulfurization reaction of 0.5% hydrogen sulfide-20% hydrogen-nitrogen (balance) gas 2) Desulfurization reaction of 0.5% hydrogen sulfide-10% steam-20% hydrogen-nitrogen (balance) gas

From this table, it can be seen that, in the case of loess, when the water vapor concentration in the reaction gas is 0%, the average sulfidity is as high as 91%, but when the water vapor concentration is 10%, it is significantly reduced to 16%. You can see that On the other hand, Red Pottery-P
It is greatly improved from 2% to 74%.
However, it is only slightly reduced. The average sulfidity of iron ore (Newman) is low and, like loess, is considerably reduced in the presence of water vapor. Thus, it is clear that the red clay desulfurizing agent has a large desulfurization capacity even for gas containing steam.

[0026]

The desulfurizing agent of the present invention has a large desulfurizing capacity,
It is a desulfurizing agent that is not easily affected by water vapor contained in the fuel gas, and can effectively remove hydrogen sulfide in the fuel gas. Since red clay used as a desulfurizing agent base material is a substance composed of fine particles, it can be easily formed into a desired shape. INDUSTRIAL APPLICABILITY The desulfurizing agent of the present invention in various shapes can be used in a fixed-bed type or fluidized-bed type desulfurization apparatus. It is also suitable for use in a system in which fine powder is blown into fuel gas as it is.

[Brief description of the drawings]

FIG. 1 shows a pore distribution curve of each desulfurizing agent used in Examples 1 to 4.

FIG. 2 shows a breakthrough curve of hydrogen sulfide in a desulfurization reaction of hydrogen sulfide from a 0.5% H ₂ S-20% H ₂ —N ₂ mixed gas.

FIG. 3 0.5% H ₂ S-10% H ₂ O-20% H ₂ -N ₂
4 shows a breakthrough curve of hydrogen sulfide in a desulfurization reaction of hydrogen sulfide from a mixed gas.

FIG. 4 is a diagram showing the results of examining the effect of the concentration of water vapor contained in a reaction gas using loess as a desulfurizing agent.

FIG. 5 is a view showing the results of examining the effect of the concentration of water vapor contained in a reaction gas using red clay-P as a desulfurizing agent.

[Explanation of symbols]

 ○ Loess (Niwazaka) (fired at 900 ° C) △ Red clay-P (fired at 600 ° C) ▲ Red clay-5A (fired at 900 ° C) □ Iron ore (Newman) (fired at 900 ° C)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mamoru Kaiho 16-3 Onogawa Tsukuba City, Ibaraki Pref. National Institute of Advanced Industrial Science and Technology (72) Inventor Takuo Kigoshi 17-chome Minami 9-Jo Nishi, Chuo-ku, Sapporo, Hokkaido No. 1-12 (56) References JP-A-3-284350 (JP, A)

Claims (3)

(57) [Claims] 1. A desulfurizing agent comprising a potter's clay fired at 400 to 1000 ° C. as a desulfurizing active component. 2. The desulfurizing agent according to claim 1, wherein the desulfurizing agent is at 300 to 700 ° C.
A method for desulfurizing a hydrogen sulfide-containing gas, comprising contacting with a hydrogen sulfide-containing gas under the following conditions. 3. The method according to claim 2, wherein the hydrogen sulfide-containing gas is a fuel gas containing 0 to 20 vol% water vapor.