JP2007175595A - Exhaust gas treatment facility and exhaust gas treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treatment facility and an exhaust gas treatment method capable of simultaneously removing harmful substances and odorant in cement exhaust gas with a simple configuration. <P>SOLUTION: This exhaust gas treatment facility 1 is an activated carbon storage column 4 in which activated carbons 2 are stored, and is provided with: the activated carbon storage column for applying a catalytic reaction to nitrogen oxides and adsorbing the odorant by passing the exhaust gas containing nitrogen oxides and organic odorant through the activated carbon; and an ammonia gas adding apparatus 5 for adding ammonia gas to the exhaust gas supplied to the activated carbon storage column. In this exhaust gas treatment facility 1, the temperature of the exhaust gas supplied to the activated carbon storage column is defined as 90-120°C, and a space velocity in the column is defined as 250-1,000 l/h. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas treatment facility for suitably treating exhaust gas generated during cement production and a method for treating exhaust gas.

In recent years, waste has been used as a raw material or part of fuel in the manufacture of cement. In this case, the exhaust gas generated by cement production (hereinafter referred to as “cement exhaust gas”) contains harmful substances such as NO _x generated by combustion, organic odor substances such as acetaldehyde, and the like. Therefore, in the treatment of cement exhaust gas, not only the removal of harmful substances but also the removal of the odorous substances are required.

Generally, as an apparatus for removing harmful substances (NO _{x and the} like) from exhaust gas and an apparatus for removing odorous substances (acetaldehyde and the like), there are apparatuses using activated carbon. For example, in the apparatus described in Patent Document 1, after ammonia gas is added to the exhaust gas, it is passed through activated carbon in an adsorption tower (activated carbon storage tower). Thereby, harmful substances (for example, NO _x ) contained in the exhaust gas are removed by catalytic reaction.
JP 2003-286020 A

Incidentally, in the case of removing the odorous substances when removing toxic substances such as NO _x, the temperature of the exhaust gas through the activated carbon is different. That is, when removing harmful substances, the temperature of the exhaust gas needs to be 110 ° or more, whereas when removing odorous substances, the temperature of the exhaust gas is normal temperature (for example, 50 ° C. or less).

  Therefore, for example, when the exhaust gas treatment facility described in Patent Document 1 is used to treat cement exhaust gas, it is necessary to further provide an adsorption tower for removing odorous substances in the preceding stage of the adsorption tower (activated carbon storage tower). And the device configuration was complicated.

  Accordingly, an object of the present invention is to provide an exhaust gas treatment facility and an exhaust gas treatment method that can remove harmful substances and odorous substances in cement exhaust gas with a simple configuration.

  In order to solve the above problems, the present inventors have conducted intensive research, and if the temperature and space velocity (SV) of the exhaust gas to be introduced into the activated carbon containing tower satisfy predetermined conditions, the exhaust gas can be exhausted using activated carbon. It was found that odorous substances and nitrogen oxides can be removed together.

  That is, the exhaust gas treatment facility according to the present invention is an activated carbon containing tower having activated carbon therein, and the exhaust gas containing nitrogen oxides and organic odorous substances is passed through the activated carbon to cause a catalytic reaction to the nitrogen oxides. An activated carbon storage tower that adsorbs odorous substances to the activated carbon and an ammonia gas addition device that adds ammonia gas to the exhaust gas supplied to the activated carbon storage tower, and the temperature of the exhaust gas supplied to the activated carbon storage tower is 90 The space velocity in the activated carbon containing tower is 250 (1 / h) to 1000 (1 / h).

  In the said structure, ammonia gas is added to the waste gas supplied to an activated carbon accommodation tower by an ammonia gas addition apparatus. Thus, the activated carbon containing tower is supplied with exhaust gas containing ammonia and having a temperature of 90 ° C. to 120 ° C. to the activated carbon containing tower. Then, the exhaust gas supplied to the activated carbon storage tower is passed through the activated carbon at a space velocity of 250 (1 / h) to 1000 (1 / h).

  When the temperature of the exhaust gas is low, it is difficult to cause a catalytic reaction with nitrogen oxides, and when the temperature is high, odorous substances tend to be difficult to adsorb on the activated carbon. Further, when the space velocity increases, it becomes difficult to cause a catalytic reaction with nitrogen oxides, and it becomes difficult to adsorb odorous substances to the activated carbon, and when the space velocity is low, the equipment tends to increase. On the other hand, by passing exhaust gas that satisfies the above conditions through activated carbon, it is possible to cause a catalytic reaction to nitrogen oxides contained in the exhaust gas with a simple configuration and to adsorb odorous substances to the activated carbon more efficiently and more reliably. Is possible.

  The space velocity is preferably 250 (1 / h) to 800 (1 / h), and more preferably 250 (1 / h) to 500 (l / h).

  In addition, the exhaust gas treatment method according to the present invention includes a temperature adjustment step of adjusting the temperature of exhaust gas containing nitrogen oxides and an organic odor substance to 90 ° C. to 120 ° C., and an addition step of adding ammonia gas to the exhaust gas. And by passing the exhaust gas after passing through the temperature adjustment step and the addition step through activated carbon disposed in the activated carbon housing tower at a space velocity of 250 (1 / h) to 1000 (1 / h), nitrogen oxides And a removing step of causing the activated carbon to adsorb the odorous substance.

  In the said structure, ammonia gas is added and the waste gas whose temperature is 90 to 120 degreeC is introduce | transduced into an activated carbon accommodation tower. Then, the exhaust gas introduced into the activated carbon storage tower is passed through the activated carbon at a space velocity of 250 (1 / h) to 1000 (1 / h). When the temperature of the exhaust gas is low, it is difficult for the catalyst to react with nitrogen oxides, and when the temperature is high, odorous substances tend not to be adsorbed on the activated carbon. Further, when the space velocity increases, it becomes difficult to cause a catalytic reaction with nitrogen oxides, and it becomes difficult to adsorb odorous substances to the activated carbon, and when the space velocity is low, the equipment tends to increase. On the other hand, by passing exhaust gas that satisfies the above conditions through activated carbon, it is possible to cause a catalytic reaction to nitrogen oxides contained in the exhaust gas with a simple configuration and to adsorb odorous substances to the activated carbon more efficiently and more reliably. Is possible.

  In this exhaust gas treatment method, the space velocity is preferably 250 (1 / h) to 800 (1 / h), and the space velocity is more preferably 250 (1 / h) to 500 (1 / h). .

  In the exhaust gas treatment facility and the exhaust gas treatment method of the present invention, nitrogen oxides and odorous substances in cement exhaust gas can be removed together with a simple configuration.

  Hereinafter, preferred embodiments of an exhaust gas treatment facility and an exhaust gas treatment method according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an embodiment of an exhaust gas treatment facility according to the present invention. The exhaust gas treatment facility 1 uses activated carbon 2 to treat exhaust gas generated by producing cement using waste as part of the raw material or fuel.

In the present specification, exhaust gas generated by cement production and containing at least nitrogen oxide (NO _x ) and an organic odor substance is referred to as cement exhaust gas. Examples of organic odor substances contained in the cement exhaust gas include acetaldehyde, formaldehyde, and benzene. Further, as cement exhaust gas, moisture: 10-20%, oxygen concentration: 8-15%, dust: 0-50 mg / m ³ N, SO ₂ : 0-100 ppm, NO _x : 200-500 ppm, HCl: 0 _{^{10mg / m 3 N, NH 3}} : 0~60ppm, acetaldehyde: also exemplified those containing 0～20Ppm.

The exhaust gas treatment facility 1 adjusts the temperature of the cement exhaust gas that passes through the activated carbon 2 (hereinafter also referred to as exhaust gas temperature) and the space velocity (SV), thereby toxic substances containing NO _x contained in the cement exhaust gas. And organic odorous substances are removed together.

The exhaust gas treatment facility 1 includes a temperature adjustment device 3 that adjusts the temperature of the cement exhaust gas. The temperature adjusting device 3 is connected to the exhaust gas line L1. High-temperature cement exhaust gas from a plant for producing cement is introduced into the temperature adjusting device 3 through the exhaust gas line L1. The temperature adjusting device 3 cools the introduced cement exhaust gas to a predetermined temperature. Examples of the temperature adjusting device 3 include an air intake type and a water spray type. In addition, a heat exchanger or the like can be used for the temperature adjusting device 3. The temperature adjusting device 3 introduces the cooled cement exhaust gas into the activated carbon containing tower 4 through the exhaust gas line L2. An ammonia gas addition device (hereinafter simply referred to as “addition device”) 5 is connected to the exhaust gas line L2, and the addition device 5 adds NH ₃ gas to the exhaust gas. As a result, cement exhaust gas to which NH ₃ gas has been added is introduced into the activated carbon containing tower 4.

The activated carbon accommodating tower 4 accommodates the activated carbon 2 and causes the catalytic exhaust gas to pass through the activated carbon 2 to cause a catalytic reaction to harmful substances contained in the cement exhaust gas, and to adsorb and remove the odorous substances on the activated carbon 2. This activated carbon 2 has a bulk specific gravity of 650 ± 50 kg / m ³ (650 ± 50 g / l) and an SO ₂ adsorption amount of 90 mg · in order to remove harmful substances (NO _x, etc.) and odorous substances together. It is preferably SO ₂ / gAC or more.

  The activated carbon storage tower 4 is a so-called cross-flow type moving bed type in which the activated carbon 2 is moved in the vertical direction while flowing the cement exhaust gas in the horizontal direction to bring the activated carbon 2 into contact with the cement exhaust gas. The configuration of the activated carbon containing tower 4 will be described more specifically.

  An exhaust gas inlet 4a connected to the exhaust gas line L2 is provided on one side of the activated carbon containing tower 4, and an exhaust gas outlet 4b for discharging the exhaust gas that has passed through the activated carbon 2 is provided on the side opposite to the exhaust gas inlet 4a. Is provided. The exhaust gas outlet 4b is connected to the chimney 6 by an exhaust gas line L3. Thereby, the exhaust gas discharged from the exhaust gas outlet 4b is released to the outside through the chimney 6.

  In addition, a valve 4 c for introducing activated carbon 2 regenerated by a desorption / regeneration tower 7, which will be described later, into the activated carbon storage tower 4 is provided at the upper part of the activated carbon storage tower 4. Is provided with a valve 4 d for discharging the used activated carbon 2. In the activated carbon accommodating tower 4, the activated carbon 2 is accommodated so as to be movable from the valve 4c side toward the valve 4d side.

  In the exhaust gas treatment facility 1, the space velocity (SV) in the activated carbon storage tower 4 is set to 250 (1 / h) to 1000 (1 / h) from the viewpoint of adsorbing harmful substances and odorous substances to the activated carbon 2 together. It is said. The SV is more preferably 250 (1 / h) to 800 (1 / h), and more preferably 250 (1 / h) to 500 (1 / h).

SV is obtained by dividing the amount of cement exhaust gas (m ³ N / h) flowing through the activated carbon 2 per hour by the effective activated carbon capacity (m ³ ). The amount of cement exhaust gas flowing per hour is the effective activated carbon capacity. It shows whether it is double. This effective activated carbon capacity is the capacity of the activated carbon 2 in contact with the cement exhaust gas. In other words, the capacity of the activated carbon 2 located on the cement exhaust gas flow path from the exhaust gas inlet 4a toward the exhaust gas outlet 4b. For example, in the activated carbon housing tower 4 of FIG. 1, the activated carbon 2 in the region surrounded by the dashed line Capacity. As is clear from the above definition, the SV can be adjusted by adjusting the amount of cement exhaust gas introduced into the activated carbon containing tower 4 or changing the effective activated carbon capacity.

  The exhaust gas treatment facility 1 includes a desorption / regeneration tower 7 for regenerating the activated carbon 2 used in the activated carbon containing tower 4.

  The desorption / regeneration tower 7 includes a valve 7a and a valve 7b arranged at the upper part and the lower part. The valve 7a is connected to the valve 4d by an activated carbon transport line L4 that transports the activated carbon 2, and the valve 7b is connected to the valve 4c by an activated carbon transport line L5. The activated carbon transport lines L4 and L5 are, for example, belt conveyors. The desorption / regeneration tower 7 heats the activated carbon 2 introduced through the valve 7a in an inert gas (for example, nitrogen gas) atmosphere to desorb and decompose the substance adsorbed on the activated carbon 2. Reproduce. Then, after the regenerated activated carbon 2 is cooled, the activated carbon 2 is discharged through the valve 7b and conveyed to the activated carbon containing tower 4 through the activated carbon conveyance line L5.

  Next, a method for treating cement exhaust gas using the exhaust gas treatment facility 1 will be described.

Cement exhaust gas generated in a cement manufacturing plant is introduced into the temperature adjusting device 3 through an exhaust gas line L1. Then, after being cooled to 90 ° C. to 120 ° C. by the temperature adjusting device 3 (temperature adjusting step), it is introduced into the activated carbon containing tower 4 through the exhaust gas line L2 and the exhaust gas inlet 4a. When the cement exhaust gas flows through the exhaust gas line L2, NH ₃ gas is added to the cement exhaust gas by the adding device 5 (addition process). As a result, cement exhaust gas having a temperature of 90 to 120 ° C. to which NH ₃ gas has been added is introduced into the activated carbon containing tower 4.

  The cement exhaust gas introduced into the activated carbon containing tower 4 has an SV of any value of 250 (1 / h) to 1000 (1 / h), preferably 250 (1 / h) to 800 (1 / h). It passes through the activated carbon 2 at any value, more preferably any value from 250 (1 / h) to 500 (1 / h). Thereby, a catalytic reaction occurs in the harmful substance in the cement exhaust gas, and the odorous substance is adsorbed on the activated carbon 2 (removal step). The exhaust gas that has passed through the activated carbon 2 is discharged from the chimney 6 through the discharge line L3.

  Further, the activated carbon 2 on which the odorous substance or the like is adsorbed in the activated carbon storage tower 4 is discharged through the valve 4d and is transported to the desorption / regeneration tower 7 through the activated carbon transport line L4. The activated carbon 2 introduced into the desorption / regeneration tower 7 through the valve 7a is heated in an inert gas atmosphere so that the substance adsorbed on the activated carbon 2 is desorbed, decomposed and regenerated, and then cooled. The And it is conveyed to the activated carbon accommodation tower 4 by the valve | bulb 7b and activated carbon conveyance line L5, and is introduce | transduced in the activated carbon accommodation tower 4 again through the valve 4c.

Here, the experimental result shows that harmful substances and odorous substances can be removed together by setting the exhaust gas temperature to 90 ° C. to 120 ° C. and SV to 250 (1 / h) to 1000 (1 / h). This will be explained based on. In this experiment, NO _x always contained in the cement exhaust gas was used as the harmful substance.

As Example 1, the exhaust gas treatment facility 1 was used to treat the cement exhaust gas. The activated carbon 2 used is activated carbon for cement exhaust gas (manufactured by Sumitomo Heavy Industries, Ltd.). The activated carbon 2 has a bulk specific gravity of 650 ± 50 kg / m ³ (650 ± 50 g / l) and an SO ₂ adsorption amount of 90 mg · SO ₂ / g AC or more. In Example 1, first, the cement exhaust gas flowing through the exhaust gas line L1 was cooled to 110 ° C. by the temperature adjusting device 3. Next, the same amount of NH ₃ gas as NO _x was added to the cement exhaust gas flowing through the exhaust gas line L 2 by the addition device 5, and then the cement exhaust gas was treated by passing it through the activated carbon 2 in the activated carbon storage tower 4. As shown in Table 1, SV of cement exhaust gas in the activated carbon containing tower 4 was 300 (1 / h).

Then, the odor removal rate and the NO _x removal rate were calculated using the odor concentration and the NO _x concentration contained in the cement exhaust gas before and after passing through the activated carbon 2, more specifically, before and after the activated carbon containing tower 4. . As a result, as shown in Table 1, odor removal rate was 76.29%, NO _x removal rate was 51.46%.

Further, as Example 2 and Example 3, the exhaust gas treatment facility 1 was the same as in Example 1 except that the temperature and SV of the cement exhaust gas were changed from the conditions of Example 1 as shown in Table 1. Cement exhaust gas was treated using The odor removal rate and the NO _x removal rate in Example 2 and Example 3 are as shown in Table 1.

Further, as Comparative Example 1, Comparative Example 2 and Comparative Example 3, except that the temperature and SV of the cement exhaust gas were changed as shown in Table 1 from the conditions of Example 1, under the same conditions as in Example 1, The exhaust gas treatment facility 1 was used to treat the cement exhaust gas. In Comparative Example 1 and Comparative Example 2, the NO _x removal rate was calculated in the same manner as in Example 1. The calculation results are as shown in Table 1. In Comparative Example 3, the odor removal rate and the NO _x removal rate were calculated in the same manner as in Example 1. The odor removal rate and NO _x removal rate of Comparative Example 3 are as shown in Table 1.

FIG. 2 is a graph showing the odor removal rate with respect to SV. In FIG. 2, the horizontal axis represents the SV (1 / h) of the cement exhaust gas, and the vertical axis represents the odor removal rate (%). FIG. 2 shows the results of Examples 1 to 3 and Comparative Example 3. FIG. 3 is a graph showing the NOx removal rate with respect to SV. In FIG. 3, the horizontal axis represents SV (1 / h) of cement exhaust gas, and the vertical axis represents the NOx removal rate (%). 3 shows the results of Examples 1 to 3 and Comparative Example 3 as in FIG. FIG. 4 is a graph showing changes in the NO _x removal rate with respect to the exhaust gas temperature. The horizontal axis indicates the temperature (° C.) of the cement exhaust gas, and the vertical axis indicates the NO _x removal rate (%). In FIG. 4, the experimental result of Example 1 and Comparative Examples 1 and 2 is shown.

  As shown in FIG. 2 and Table 1, when SV is changed, the odor removal rate is higher in Examples 1 to 3 than in Comparative Example 3, and more odorous substances can be removed. Yes. Moreover, it can be seen from the experimental results shown in FIG. 2 that the odorous substance can be adsorbed and removed by the activated carbon 2 even when the exhaust gas temperature is 110 ° C. by adjusting the SV.

Further, as shown in FIG. 3 and Table 1, even when the exhaust gas temperature was 110 ° C., when the SV was 1200 (1 / h), the NO _x removal rate was less than 30%. On the other hand, the NO _x removal rate in Examples 1 to 3 exceeds 40%, and Examples 1 to 3 can remove more NO _x than Comparative Example 3.

Further, as shown in FIG. 4 and Table 1, NO _x removal rate in the case of Example 1 the exhaust gas temperature is 110 ° C. is over 50%. On the other hand, when the exhaust gas temperature was 75 ° C. (in the case of Comparative Example 1 and Comparative Example 2), the NO _x removal rate was less than 30%. Thus, it can be seen that the higher temperature of Example 1 can remove more NO _x than the cases of Comparative Example 1 and Comparative Example 2. In Comparative Example 1 and Comparative Example 2, as shown in Table 1, SV is 300 (1 / h) within a range of 250 (1 / h) to 1000 (1 / h).

By the way, from the viewpoint of removing odorous substances with activated carbon, the exhaust gas temperature has conventionally been considered to be about room temperature. However, as shown in FIG. 4, the temperature of the cement exhaust gas is preferably higher than 75 ° C. from the viewpoint of removing NO _x . As shown in FIG. 2, the present inventors have found that by adjusting SV, deodorization can be performed while removing NO _x even at around 110 ° C., which is higher than normal temperature.

Thus, since the odorous substance can be adsorbed on the activated carbon 2 at 110 ° C., if the exhaust gas temperature is lower than 110 ° C., more odorous substance can be adsorbed on the activated carbon 2. And considering the point that high temperature is preferable from the viewpoint of NO _x removal, the temperature of the cement exhaust gas needs to be 90 ° C. to 120 ° C. in order to remove NO _x and odorous substances together.

Further, as understood from FIGS. 2 and 3, SV is 1200 although (1 / h) better than smaller tends to be removed more odor substances and NO _x, SV is 250 (1 / h) more smaller, they tend to not be expected further improvement of the removal performance of the odor substances and nO _x. Therefore, in order to adsorb on the activated carbon 2 and odorant and NO _x together, considering the trend, SV should be 250 (1 / h) ~1000 ( 1 / h). Then, as shown in FIGS. 2 and 3, from the viewpoint of more remove odorous substances and NO _x, SV is more preferably from 250 (1 / h) ~800 ( 1 / h), 250 ( 1 / h) to 500 (1 / h) are more preferable.

As described above, when SV is a value in the range of 250 to 1000 (1 / h) and the exhaust gas temperature is a value in the range of 90 ° C. to 120 ° C., a catalytic reaction occurs in NO _x. And the odorous substance can be adsorbed on the activated carbon 2. And, in fact, in Examples 1 to 3 satisfy the above range, a large removal rate than Comparative Examples 1 to 3, which can be removed and odorant and NO _x together. Here, the removal rate of NO _x contained in cement exhaust gas as an example of harmful substances has been described. However, the conditions for removing harmful substances (for example, SO _x ) other than NO _x contained in cement exhaust gas are NO _x. Is almost the same. Therefore, toxic substances other than NO _x in the above temperature condition and SV condition can also be removed.

Conventionally, by using activated carbon, when removing harmful substances such as NO _x from exhaust gas and when removing odorous substances, the temperature of exhaust gas passing through activated carbon differs, so activated carbon for removing harmful substances It was thought that a storage tower and an activated carbon storage tower for removing odorous substances had to be prepared respectively.

In contrast, in the exhaust gas treatment system 1, by adjusting the SV and the exhaust gas temperature, by utilizing one activated carbon housing tower 4, you can remove the harmful substances and odorous substances of the NO _x or the like contained in the cement exhaust gas It is. This exhaust gas treatment facility 1 has a simple configuration because it is not necessary to use two activated carbon storage towers as in the prior art. As a result, the manufacturing cost of the exhaust gas treatment facility 1 can be reduced.

Although the preferred embodiments of the exhaust gas treatment facility and the exhaust gas treatment method according to the present invention have been described in detail above, the present invention is not limited to the above embodiments. The activated carbon uses carbon and may be any material that can adsorb odorous substances and nitrogen oxides (NO _x ).

It is a block diagram which shows the structure of one Embodiment of the waste gas processing equipment which concerns on this invention. It is a graph which shows the odor removal rate with respect to space velocity (SV). Is a graph showing the NO _x removal rate for the space velocity (SV). Is a graph showing the NO _x removal rate for the exhaust gas temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Exhaust gas treatment equipment, 2 ... Activated carbon, 3 ... Temperature control apparatus, 4 ... Activated carbon storage tower, 4a ... Exhaust gas inlet, 4b ... Exhaust gas outlet, 4c ... Valve, 4d ... Valve, 5 ... Ammonia gas addition device, 6 ... Chimney 7 ... Desorption / regeneration tower, 7a ... Valve, 7b ... Valve, L1, L2, L3 ... Exhaust gas line, L4, L5 ... Activated carbon transport line.

Claims (6)

An activated carbon containing tower having activated carbon inside, wherein an exhaust gas containing nitrogen oxide and an organic odor substance is passed through the activated carbon to cause a catalytic reaction in the nitrogen oxide, and the odor substance is converted into the activated carbon. Activated carbon containing tower to be adsorbed on
An ammonia gas addition device for adding ammonia gas to the exhaust gas supplied to the activated carbon housing tower;
The temperature of the exhaust gas supplied to the activated carbon containing tower is 90 ° C to 120 ° C,
An exhaust gas treatment facility characterized in that a space velocity in the activated carbon containing tower is 250 (1 / h) to 1000 (1 / h).   The exhaust gas treatment facility according to claim 1, wherein the space velocity is 250 (1 / h) to 800 (1 / h).   The exhaust gas treatment facility according to claim 1, wherein the space velocity is 250 (1 / h) to 500 (l / h). A temperature adjustment step of adjusting the temperature of the exhaust gas containing nitrogen oxides and organic odorous substances to 90 ° C. to 120 ° C .;
An addition step of adding ammonia gas to the exhaust gas;
By passing the exhaust gas after passing through the temperature adjustment step and the addition step through activated carbon disposed in an activated carbon storage tower at a space velocity of 250 (1 / h) to 1000 (1 / h), the nitrogen A removal step of causing a catalytic reaction on the oxide and adsorbing the odorous substance on the activated carbon;
An exhaust gas treatment method comprising:   The exhaust gas processing method according to claim 4, wherein the space velocity is 250 (1 / h) to 800 (1 / h).   The exhaust gas treatment method according to claim 4, wherein the space velocity is 250 (1 / h) to 500 (1 / h).

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