JPS592535B2 - Solid catalyst arrangement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for arranging solid catalysts, and more particularly, to
The present invention relates to a method of arranging a large number of solid catalysts in a cross section of a reactant flow path in a reaction vessel.

Generally, in heterogeneous gas phase reactions using solid catalysts,
In order to obtain maximum catalytic activity using the minimum amount of catalyst,
The following matters need to be considered.

1) Increase the activity per apparent surface area of the catalyst.

2) Increase the apparent surface area per unit weight of catalyst.

As a method, 1) Improve the shape.

11) Make the typical diameter of the catalyst as small as possible.

3) Make sure that all the apparent surface of the catalyst is used effectively.

Of these three important matters, 1) concerns the catalyst itself and its basic characteristics, while 2) and 3) concern how to use such catalysts effectively. This is particularly important when using catalysts industrially.

Conventionally, in a heterogeneous gas phase reaction, for example, in a sulfur dioxide converter in a sulfuric acid production process, the above 2)-i
Emphasizing the matter i), the solid catalyst has a diameter of 5 yr + m,
Pellets with a relatively small particle size of about 10 mm in length are used.

However, in the case of degrinding of thermal combustion exhaust gas, especially in the case of dry catalytic reduction, a large amount of dust (hereinafter referred to as "dust") is introduced, so it is not possible to use a catalyst with a small particle size as described above. This causes problems such as masking of the catalyst surface and clogging of the catalyst packed bed.

For this reason, the reactor itself has been modified to a moving bed type, parallel contact type, etc., but this has the disadvantage that the equipment becomes more complex and the equipment cost increases.

In recent years, in order to solve the above-mentioned problem of clogging of the catalyst layer due to dust, molded catalysts with a typical diameter of a dog or two have begun to be used.

For example, large Raschig ring type catalysts are currently used as solid catalysts for exhaust gas denitrification, especially for dry catalytic reduction systems, but their dimensions range from several tens to several hundred in cylinder diameter and several tens to hundreds in height. It is of a certain degree.

A large number of such large Raschig ring type catalysts are regularly stacked in a cross-section of a gas flow path in a reaction vessel so that their cylindrical axes coincide with the gas flow direction.

Specific methods for arranging such Raschig ring type catalysts include square stacking (Utility Model Publication No. 10455/1983) and diamond stacking, and these are usually stacked concentrically.

These cross-sectional views are shown in FIGS. 1 and 2, respectively.

Figure 1 shows the case of square stacking, and Figure 2 shows the case of diamond stacking.

In the figure, 1 is the Raschig ring. These arrangement methods are
(1) 1. Strong dust resistance, (2) Effective use of the apparent surface area of the catalyst and high reaction rate, (3) High linear velocity (
L, V, ) can be used, the pressure loss is small, and the diameter of the reactor can be made extremely small. (4) It is an industrially excellent arrangement method, as it has advantages such as extremely easy loading of the catalyst.

However, according to the studies of the present inventors, in these arrangements, the flow path passing inside the Raschig ring (in the figure, S
i) and a flow path (Se or Se' in the figure) that passes through the outside of the Raschig ring, and the flow rate ratios of these are significantly different, which has led to various problems.

In other words, if the outer diameter of the Raschig ring is Do, then the equivalent circular diameter of the flow path created by the outer circumference is 0.2 in the case of Suffini stacking.
In the case of 7Do1 diamond stacking, it is 0.10Do.

The term "equivalent circular diameter" as used herein refers to the diameter of a circle having the same area as a cross section having a non-circular cross-sectional shape.

In other words, the equivalent circular diameter represents the equivalent diameter of a circle with a cross-sectional shape that is not circular.
The following formula % formula % In other words, in a cylinder, if the diameter of the circle is Di, then when looking at the arrangement of solid catalysts, four times the cross-sectional area of the flow path formed by the solid catalyst is the immersion length (around the cross-sectional area). defined as the value divided by the length).

Incidentally, the equivalent circular diameter 4RHe in the case of square stacking is calculated as follows.

According to the knowledge of fluid mechanics, inside the Raschig ring cylinder qj' The outside flow rate ratio is given by the following equation.

se In the above formula, 0.5 (m (2,01Si and Se are the flow path cross-sectional areas inside and outside the Raschig ring, Vi and Ve
are the gas flow rates inside and outside the Raschig ring, Di is the inner diameter of the Raschig ring, and 4RHe is the equivalent circular diameter of the cross section of the flow path formed by the Raschig ring outer cylinder.

As mentioned above, in the case of square stacking, 4RHe=0.2
Since 7Do, Qsi)Qse=: This tendency becomes more remarkable as the thickness of the Raschig ring becomes thinner.

Considering that a heterogeneous gas phase reaction occurs on the catalyst surface, comparing the amount of passing gas with respect to the catalyst surface area of the inner and outer channels, the gas flow rate per catalyst surface area is Q s i / A
s i or Qse/Ase is given by the following equation.

Here, t is the height of the catalyst packed bed, and Asi and Ase are the catalyst surface areas of the inner and outer channels of the Raschig ring, respectively.

Here, it is clear that Ase)Asi, so Q s i
/A s i >> Qs e /A s e, and there is a large difference in the gas flow rate per unit surface of the catalyst between the inside and outside of the Raschig ring, and especially the flow rate outside the Raschig ring is extremely small. It became clear that the outer surface was not being used effectively.

Therefore, in situations where the flow rate ratio of Si and Se is a problem, that is, when exhaust gas with a significantly high dust load is being treated and the Raschig ring catalyst used is not very active, in order to avoid masking of the catalyst by dust, It is necessary to increase the typical diameter of the Raschig ring, but on the other hand, in order to maintain a high reaction rate (removal rate), it is necessary to use the catalyst surface more effectively, and for this purpose, the catalyst surface area per catalyst filling volume and the catalyst unit weight It is advantageous to take a method of increasing the surface area of the catalyst, that is, making the typical diameter of the Raschig ring catalyst as small as possible.

However, the representative diameter required to avoid masking blockage of the catalyst due to dust is determined based on the flow path formed by the outer cylinder, since the flow path formed by the outer cylinder is smaller than that formed by the cylinder.

That is, consideration must be given to making the flow path formed by the outer cylinder large enough to prevent dust from clogging it.

In this case, the flow path formed by the cylinder has a size that is larger than necessary in terms of dust resistance, and the overall demand for reducing the representative diameter of the catalyst as small as possible cannot be met.

The purpose of the present invention is to keep the above points in mind, to rationally define the internal and external flow paths of the solid catalyst, to effectively utilize not only the internal surface of the cylindrical solid catalyst, but also the external surface, and to fill the catalyst as a whole. The object of the present invention is to provide a method for arranging catalysts that can reduce weight and packing capacity.

In order to achieve the above object, the present invention provides a method of arranging a large number of solid catalysts in a cross-section of a flow path of a reactant in a reaction vessel so as to partition the flow path, the cylindrical portion being made of the same material,
and the finned Raschig ring catalysts formed along the axial direction of the cylindrical part are arranged so that the equivalent circular diameters of the cross sections of the reactant flow paths inside the cylindrical part of the catalyst and outside the cylindrical part are approximately equal. It is characterized by this.

The solid catalyst used in the present invention is shown in FIG. 3A.

A finned Raschig ring having a cross-sectional shape as shown in FIGS. 4B and 4A and 4B is preferably used.

These finned Raschig rings are arranged in a square shape or a diamond shape through the fins, respectively, as shown in FIGS. 3C and 4C.

The length of the fins of the Raschig ring is determined so that the equivalent circular diameters of the passage cross section S1 inside the cylinder of the Raschig ring and the passage cross section Se formed outside the cylinder of the Raschig ring are approximately equal.

Here, a method for calculating the equivalent circular diameter in the arrangement state of the solid catalyst shown in FIG. 3 will be explained based on FIGS. 5 and 6.

Figure 5 For a ship, the length of the fin is Xl, the thickness of the fin is tl, and the length of the straight line connecting the center point in the cylinder is X+D.

It is. The outer diameter and inner diameter of the Raschig ring are Do and Di, respectively, and the fin's thickness t1 is m-7--.

Here, the equivalent circular diameter inside the cylinder of the Raschig ring is as shown in the upper equation.

On the other hand, the area of the cross-section of the flow path outside the cylinder of the Raschig ring (the area shown with diagonal lines in FIG. 5) is calculated from the area of the part (quadrangular) surrounded by the straight line connecting the center points inside the cylinder, 1/4 circular part 6A,
Total area of 6B, 6C, 6D and fin portions 6E, 6
It is obtained by subtracting the total area of F, 6G, and 6H.

Further, the circumferential length of the cross-section of the flow path outside the cylinder of the Raschig ring is shown by a thick line in FIG.

Therefore, the cross-sectional area of the flow path outside the inner cylinder of the Raschig ring in the sphere arrangement is (X+D o)2-! LD62-x Yu1x4,
The perimeter is πDo+4t1.

Therefore, the equivalent circular diameter of the cross section of the flow path outside the cylinder of the Raschig ring is 4R.
He is determined as follows.

Next, when the equivalent circular diameters of the flow path cross sections inside and outside the cylindrical tube of the Raschig ring are equal, the equation (2) holds true.

The length X of the fin at which the equivalent diameters of Si and Se are equal is:
It varies depending on the wall thickness as shown in the table below.

In general, considering dust resistance, X is 0〈X〉OD
selected from the range of i.

When such a fin length X is selected, the flow velocities in the inner and outer channels become equal.

At this time, the gas flow rate with respect to the catalyst surface area of the inner and outer flow paths is as follows.

Flow rate of inner flow path, 7D I V I Catalyst surface area of inner flow path: πDi7 Gas flow rate relative to catalyst surface area: 'D i2V i/ π
D i 1. = -D i Ve/14 On the other hand, the flow rate of the outer surface flow path: ((Do+X)2 'D□''-4x
” ) Ve2 Catalyst surface area of external channel: (πDo + 4X, 4
tl) is the gas flow rate relative to the catalyst surface area: ((D
o +X)2”D o2-4 Xsu)Ve/(πD o
+4X-41,) t Therefore, the gas flow rate with respect to the catalyst surface area of the inner and outer flow paths becomes equal.

As a result, the reaction conversion rates of the inner and outer channels become equal.

Next, a method for calculating the equivalent circular diameter in the arrangement state of the solid catalyst shown in FIG. 4 will be explained based on FIGS. 7 and 8.

In Figure 7, the length of the fin is Y, and the thickness of the fin is t.
2. The length of the straight line connecting the center points in the cylinder is Y + Do.

Note that the outer diameter and inner diameter of the Raschig ring are Do and Di, respectively, and the thickness t of the fin is D and -Di.

The area of the cross section of the flow path outside the cylinder of the Raschig ring (the shaded area in Fig. 7) is calculated from the area of the part (triangle) surrounded by the straight line connecting the center points inside the cylinder, 1/6 of the circular part 8A,
Total area of 8B, 8C and fin portions 8D, 8E,
It is calculated by subtracting the total area of 8F.

Further, the circumferential length of the cross-section of the flow path outside the cylinder of the Raschig ring is shown by a thick line in FIG.

Therefore, the cross-sectional area of the flow path outside the cylinder of the Raschig ring in the diamond-shaped arrangement is as follows, and the circumferential length is T7rDo, +3 Y -3t2.

Therefore, the equivalent circular diameter of the cross section of the flow path outside the cylinder of the Raschig ring is 4R.
He is determined as follows.

Next, when the equivalent circular diameters of the flow path cross sections inside and outside the cylindrical tube of the Raschig ring are equal, neck 1)=equation (3) holds true.

The length Y of the fin at which the equivalent circular diameters of Si and Se are equal varies depending on the wall thickness l as shown in Table 2.

Y is generally o<y<20Di when considering dust resistance.
selected from the range.

If the arrangement method described above is adopted, the flow velocity of the inner and outer channels and the gas flow rate relative to the catalyst surface area are equal, and the reaction conversion rates of each are also equal, as in the case of the square arrangement described above.

In the present invention, examples of preferable dimensions that can be used for the Raschig ring are as follows.

10mm<D o <200rran 2m<Dl<200rrrm 5 groups x 1000 0.4 (D i / D □ (1,0 In the case of a square arrangement, the length of the fin of the Raschig ring
If the value is greater than 0 and smaller than 1.90 Di, the catalyst packing weight can be made smaller than in the case of close packing of Raschig rings without fins.

In the case of a diamond arrangement, the length Y of the fins can be made larger than 0 and smaller than 3.7D1 (f), which can be made smaller than the catalyst filling weight compared to the case of close packing of Raschig rings without fins.

Raschig rings having fin lengths within the above range include those having fin lengths that deviate from the optimum value of equal equivalent circular diameters, but all are treated as having substantially equal equivalent circular diameters in the present invention.

A particularly preferable fin length is 0.9 to 1.1 times Di when the equivalent circular diameters are equal.

In the present invention, the constituent materials of the catalyst are appropriately selected depending on the type of reaction.

In addition, in order to fill the reaction vessel with catalysts having the above shape, it is sufficient to stack them one after another so as to form the above-mentioned flow path cross section in the vessel, and if necessary, the catalysts may be fixed to each other or a suitable method may be used. It may be supported with a support.

An example in which a dry denitrification experiment of exhaust gas using ammonia was conducted using the catalyst arrangement described above will be described below.

A schematic flow sheet of the experimental equipment used is shown in FIG.

In the figure, exhaust gas containing nitrogen oxides flowing through a flue 6 is sucked in by a blower 5 and heated to a predetermined temperature by a heater 2.

After raising the temperature, a predetermined amount of ammonia is blown into the gas,
It is then sent to the catalytic reactor 3.

The amount of suction gas is automatically controlled to a predetermined amount by the FRC and the blower suction damper 4, and the exhaust gas outlet temperature of the heater 2 is also automatically controlled by the TRC.

The catalytic reactor 3 is filled with solid catalysts having the shapes shown in Table 3 in various arrangements.

The reaction conditions were set as follows.

Ammonia addition ratio: 1:1 (mole ratio) to the inlet NOx amount The catalysts used in each experiment and their arrangement methods are shown in Table 3.

The experimental results are shown in Tables 4 and 5.

That is, Tables 4 and 5 show the results of Experiments 1 and 2, respectively.

Further, in the case of a finned Raschig ring catalyst, the relationship between the catalyst filling weight and the catalyst filling volume with respect to the fin length is shown in FIGS. 10 and 11, respectively.

From the above experimental results (particularly Figures 10 and 11), the optimal values (unit: wrL) of the fin lengths X and Y of the finned Raschig ring catalyst are as follows: In the case of a square arrangement, X = 6.0 to 8.0 diamonds. It is clear that Y=16.0 to 18.0 for the type array.

This corresponds to the theoretical interval at which the equivalent circular diameters of the inner and outer flow passage cross sections of the Raschig ring cylinder are equal: In the case of a square arrangement, X = 6.6, and in the case of a diamond arrangement, Y = 15.8. It has been experimentally confirmed that if the catalysts are arranged so that their diameters are approximately equal, both the catalyst loading weight and the loading capacity can be minimized.

In addition, in the case of a square arrangement, the fin length X is 0 < x
< 1.90 D i allows the catalyst loading weight to be smaller than in the case of close packing of Raschig rings without fins (X=O), and similarly in the case of a diamond-shaped arrangement, the fin The length Y of is 0 (Y(
It is clear that by setting the value within the range of 3.7D i, the catalyst filling weight can be similarly reduced.

The present invention achieves the following excellent effects through the above-described structural functions.

(1) Regarding duct resistance, since the flow path of the solid catalyst with a small equivalent circular diameter that becomes a bottleneck becomes narrower, the representative diameter of the catalyst can be selected rationally according to the quality and quantity of dust in the exhaust gas. can.

That is, it is possible to rationally determine the cross-sectional areas of the internal and external flow paths of the solid catalyst and select the minimum necessary representative diameter of the solid catalyst.

(2) Since the inner and outer surfaces of the catalyst are equally utilized, the degree of utilization of the catalyst surface as a whole of the catalyst layer is greatly improved.

the result i) Catalyst loading weight can be reduced.

il) The catalyst packing volume can be reduced.

1] 1) As a ripple effect, when the utilization of the catalyst surface becomes equal, changes over time in each part of the catalyst become the same, and an appropriate initial filling amount can be achieved.

The above effects are achieved by reducing the construction costs and running costs of exhaust gas denitrification plants, especially those using the dry catalytic reduction method, since catalyst costs and catalytic reaction vessel costs account for a large portion of the cost. This is important in that it allows for

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing conventional arrangement methods in which Raschig ring type catalysts are arranged in a square shape and a diamond shape, respectively, and FIGS. 3A and 3B. C and FIGS. 4A, B, and C are cross-sectional views for explaining the arrangement method of the present invention in which finned Raschig ring catalysts are arranged in a square shape and a diamond shape, respectively.
Figures 7 and 6 are explanatory diagrams showing how to calculate the equivalent circle diameter in a square-shaped array, Figures 7 and 8 are explanatory diagrams to show how to calculate the equivalent circle diameter in a diamond-shaped array, and Figure 9 is an explanatory diagram to show how to calculate the equivalent circle diameter in a diamond-shaped array. 10 is a graph showing the relationship between the fin length of the Raschig ring catalyst and the catalyst filling weight. FIG. 11 is a graph showing the relationship between the fin length of the Raschig ring catalyst and the catalyst loading weight. It is a graph showing the relationship with filling volume. 1... Raschig ring, 3... Catalyst reaction vessel, 6... Exhaust gas flue, Si... In-cylinder flow path, Se... External flow path.

Claims (1)

[Scope of Claims] 1. In a method of arranging a large number of solid catalysts in a cross section of a reactant flow path in a reaction vessel so as to partition the flow path, a solid catalyst is made of the same material as the cylindrical portion and is arranged along the axial direction of the cylindrical portion. A solid catalyst characterized in that the finned Raschig ring catalysts formed by the finned Raschig ring catalyst are arranged so that the equivalent circular diameters of the cross sections of the reactant flow paths inside the cylindrical part of the catalyst and outside the cylindrical part are approximately equal. Array method. 2. A solid catalyst arrangement method according to claim 1, characterized in that the finned Raschig ring catalysts are arranged in a square shape via the fins. 3. A method of arranging solid catalysts according to claim 1, characterized in that the finned Raschig ring catalyst is arranged in a diamond shape through the fins. 4. has length 0
A method for arranging a solid catalyst characterized by having a larger diameter (a value smaller than 1,90 Di (however, Di indicates the contents of the Raschig ring). 5. In claim 3, the fin length is A solid catalyst arrangement method characterized in that the diameter is greater than 0 and smaller than 3.7Di (where Dl indicates the inner diameter of the Raschig ring).