JP2000042348A - Desulfurizing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently desulfurize by an easy method with a simple device event at a rather low temp. by introducing gas to be treated containing sulfur compds. into plasma to bring the gas into contact with a catalyst. SOLUTION: A reactor 1 consists of a plasma producing part 11 and a catalyst contact part 12 formed in a cylindrical quartz tube of specified dimension. In a process to introducing gas into the plasma, the reactivity of sulfur compds. such as H2S, SO2 and SO3 present in the gas to be treated is increased by imparting energy by the plasma. Further, these compds. are efficiently oxidized by various kinds of radicals, ions or the like having high activity in the plasma. In a catalyst contact process, the activation energy is decreased by a catalyst and the oxidation of the sulfur compds. is caused even at a low temp. Therefore, by combining the two processes above described, the sulfur compds. can be efficiently oxidized at a low temp. and easily desulfurized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a desulfurization method. More specifically, the present invention relates to a desulfurization method capable of efficiently oxidizing a sulfur compound contained in a gas to be treated, in particular, SO ₂ into SO ₃ which can be more easily treated at a low temperature in a short time with a simple apparatus.

[0002]

2. Description of the Related Art In recent years, many methods for recovering SO _x , particularly SO ₂ , from fossil fuel combustion gas have been developed in order to alleviate the serious problem of acid rain.
Many of them required large-scale equipment, equipment capable of withstanding high heat, large amounts of water, and the like. There are also problems such as high cost and complicated operation.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a desulfurization method which does not require a large-scale apparatus, is simple, and can efficiently desulfurize even at a relatively low temperature with a simple apparatus.

[0004]

The desulfurization method of the first invention comprises:
The method is characterized by comprising a step of introducing a gas to be treated containing a sulfur compound into plasma and a step of bringing the gas into contact with a catalyst.

The above-mentioned "gas to be treated" containing a sulfur compound is an exhaust gas generated when fossil fuels such as coal, petroleum and natural gas are burned, and a waste gas discharged during chemical synthesis. It is a gas containing sulfur compounds such as H ₂ S, SO ₂ and SO ₃ . Of these sulfur compounds, SO ₂ , one of the causative substances causing acid rain, is difficult to recover as it is. Thus, SO ₂ is oxidized to SO _3, further this SO ₃ becomes possible to recover by changing the compound such as sulfuric acid or ammonium sulfate. The above-mentioned "plasma" may be plasma generated from any of heating to a high temperature, supplying energy by light, and performing electric discharge, but plasma generated by electric discharge is used because a simple device can be used. Is preferred. As the above “catalyst”, TiO ₂ , V
_{In addition to 2} O ₅ , Mn ₂ O _{3 and the} like, a multi-element catalyst obtained by mixing these catalysts can be used. In addition, these catalysts may have any shape, but because the contact area is large,
It is preferable to have a smaller pellet shape, a shape having irregularities, a porous shape, or the like.

The above-mentioned "step of introducing a gas to be treated into plasma" (hereinafter, also simply referred to as "plasma introducing step").
Then, H ₂ S, SO ₂ and SO ₃ present in the gas to be treated
And the like, the reactivity of the sulfur compound is increased by the application of energy by the plasma. Further, it is efficiently oxidized by various highly active radicals and ions existing in the plasma. In particular, when using plasma by electric discharge, the reaction can be easily performed even at room temperature. Similarly, in the "step of bringing the gas to be treated into contact with the catalyst" (hereinafter, also simply referred to as "catalyst contact step"), the activation energy is reduced by the catalyst, and the oxidation reaction of the sulfur compound occurs even at a low temperature. Therefore, by combining these two steps, at low temperature,
The sulfur compound can be more efficiently oxidized and desulfurized easily.

Either of the plasma introducing step and the catalyst contacting step may be performed first. However, as in the second invention, the plasma introducing step and the catalyst contacting step are performed simultaneously. It is preferred to do so. That is, desulfurization can be performed more efficiently by performing the catalyst contacting step in plasma. In addition, the reactor can be made smaller, and the reactor itself can be made smaller. As described later, the smaller the reactor, the better.

Further, as in the third invention, H radicals, OH radicals, O radicals, N radicals, H ⁺ ions, OH ^- ions and O ^-2 ions (hereinafter simply referred to as "components in the plasma") are contained in the plasma. ) Is preferably contained. In addition, the catalyst
As in the third invention, H ₂ O, H ₂ O ₂ , H radical, OH
Radical, O radical, N radical, H ⁺ ion, OH ⁻
It is preferable that at least one of an ion and an O ^-2 ion (hereinafter, also simply referred to as a "component in a catalyst") is adsorbed.

As described above, in order to recover the sulfur compound as sulfuric acid or ammonium sulfate, it is preferable that the above-mentioned various components in the plasma and the components in the catalyst which can efficiently cause various reactions are present. Among them, it is particularly preferable that OH radicals and O radicals are present. In addition to these OH radicals and O radicals being able to effectively cause a chain reaction, OH radicals have a relatively long life, so that they can particularly promote the oxidation reaction more than other radicals and ions.
Of these, OH radicals have a large tendency, and therefore it is more preferable that at least OH radicals be adsorbed on the catalyst as in the eighth invention.

It is preferable that both the plasma introducing step and the catalyst contacting step are performed as in the first invention. However, as in the fourth invention, the gas to be treated is introduced into the plasma containing the components in the plasma. The desulfurization can be performed only by performing the step of bringing the gas to be treated into contact with the catalyst on which the components in the catalyst are adsorbed, as in the sixth invention.

Further, in the case of the catalyst contacting step, as described above, the components in the catalyst capable of accelerating the oxidation reaction include:
It is formed from H ₂ O and H ₂ O ₂ etc. adsorbed on the catalyst.
However, in order to further promote this oxidation reaction, it is preferable to supply these radicals and ions from the outside in addition to the OH radicals and O radicals generated by the catalyst. That is, these are separately supplied directly onto the catalyst and adsorbed on the catalyst, whereby more radicals and ions can be brought into contact with SO ₂ or the like on the catalyst surface.

Further, among the components in the catalyst contained in the catalyst,
It is preferable that the radicals and ions are generated and supplied by a plasma generator as in the seventh invention. As described above, during the oxidation reaction, these radicals and ions are also generated from the catalyst and are present on the surface. Is preferably raised. Therefore, it is preferable to generate these radicals and ions by a plasma generator capable of generating them instantaneously and supply them to the catalyst surface.

Further, as in the fifth invention, it is preferable that the gas to be treated is further brought into contact with the catalyst on which the components in the catalyst have been adsorbed after the plasma introducing step. In this way, the radicals and ions generated in the plasma can be supplied to the catalyst contacting step as excess catalyst components after the oxidation reaction of the sulfur compound occurs in the plasma introduction step, More radicals and ions can be present on the surface. That is,
Simultaneously performing the plasma introduction step and the catalyst contacting step,
It is particularly preferable to perform the catalyst contacting step after the plasma introduction step.

The radicals and ions contained in the above-mentioned components in the plasma and the radicals and ions etc. adsorbed as the components in the catalyst may be those generated from water vapor, oxygen, nitrogen, etc. existing in the air. H ₂ O, H ₂ for high density generation, especially in plasma
A compound having a hydroxyl group, a hydroperoxyl group, a methoxyl group, an ethoxyl group, a carbonyl group, a carboxylate group, a methoxycarbonyl group, and an acyl group in addition to O ₂ , alcohols, oxygen and nitrogen, is separately supplied into the plasma. Is preferred. The supply amount depends on the state of the plasma and the substance to be supplied, but when supplying H ₂ O ₂ , which is a particularly preferable substance, all the sulfur compounds are converted to SO _2.
In terms of, preferably from 0.1 to 5 times the molar amount of SO _2, and more preferably 0.5 to 2 times.
In addition, when plasma is generated by electric discharge, it is preferable to use a high voltage. As a result, plasma containing a high concentration of radicals and ions can be generated, and the probability of occurrence of an oxidation reaction also increases.

Further, both the plasma introducing step and the catalyst contacting step include a closed reactor, a reactor open to the atmosphere, a separate reactor connected by a pipe or the like, and a separate reaction not connected to each other. It can be performed with a vessel or the like. However, in order to further increase the efficiency of the reaction, that is, to make the sulfur compound more contact with the components in the plasma and the components in the catalyst, the reactor is a closed reactor and a reactor having a small internal volume. It is preferable to carry out the reaction in a reactor or the like capable of producing a higher pressure state. Thus, even a short-lived radical or the like can be brought into contact with the sulfur compound with a higher probability, and the oxidation reaction is more likely to occur. The volume inside the reactor is preferably 10 to 10 ⁶ cm ³ , more preferably 10 ^{2 to} 5 × 10 ⁵ cm ³ . Further, the pressure is preferably 10 ^{3 to} 2 × 10 ⁶ Pa, and more preferably 10 ⁴ to 10 ⁵ Pa.

Further, the temperature varies depending on various conditions of both processes, but when desulfurization is carried out only by the plasma introduction process containing the components in the plasma, the temperature is preferably from 20 to 800 ° C, more preferably from 200 to 400 ° C. More preferred. Supplies of H ₂ O from the outside, is preferably twenty-five to eight hundred ° C. When catalyst component performs desulfurization only the catalyst contacting step adsorbed, and more preferably 100 to 400 ° C.. Supplying H ₂ O ₂ from the outside, it is preferable that catalyst component is twenty to nine hundred ° C. When performing desulfurization only the catalyst contacting step adsorbed, and more preferably 400 to 800 ° C.. 20 to 800 when desulfurization is performed by supplying H ₂ O from the outside and performing both of the plasma introduction step including the plasma component and the catalyst contacting step in which the catalyst component is adsorbed.
C., more preferably 100 to 500C. ₂₀ to 900 ° C. when desulfurization is performed by supplying H ₂ O ₂ from the outside and performing both the plasma introduction step including the components in the plasma and the catalyst contacting step including the components in the catalyst
And more preferably 200 to 600 ° C.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to examples. (1) Reactor used in Examples Reactor As shown in FIG. 1, a reactor 1, a cylinder 2 filled with SO ₂ , a cylinder 3 filled with air, and a cylinder 4 filled with nitrogen. , A container 5 containing liquid H ₂ O or liquid H ₂ O ₂ , a sulfur compound recovery device 6 (H ₂ O, H ₂ O _2, etc. can be recovered at the same time), and a detector 7.

Reactor The reactor 1 comprises a plasma generating part 11 and a catalyst contact part 12 formed in a cylindrical quartz tube having an inner diameter of 15 mm and a length of 100 cm. The plasma generation unit 11 is formed at a position 20 to 30 cm from one end of the reactor 1.
The catalyst contact part 12 is 3 to 10 cm from the plasma generation part 11.
It is formed at a remote site. When the catalyst contact step is performed, a spherical T
10 g of iO ₂ pellet 121 is sealed. This pellet has a total surface area of 112 cm ² with a weight of 10 g. The pellets were replaced for each experimental example, and were further heated in advance at 300 ° C. for 2 hours to remove the contained H ₂ O and the like, and then used. By adding H ₂ O and NH ₃ to the gas to be treated that has passed through the reactor 1, it is recovered as sulfuric acid and ammonium sulfate in the sulfur compound recovery device 6.

Plasma Generator The plasma generator has the circuit shown in FIG. 2, and has a discharge side electrode 111 and a power receiving side electrode 112 as shown in FIG. A discharge-side electrode 111 made of a metal (nickel and stainless steel) and formed of a cylinder having an outer diameter of 3 mm and a length of 10 cm is inserted from the center of the cross section of the quartz tube toward the center of the quartz tube. On the other hand, the power-receiving-side electrode 112 made of a copper foil having a thickness of 0.2 mm has a length of 10 c so as to face the discharge-side electrode.
m and is attached to the outer peripheral surface of the reactor 1. Detector Detector 7 is an SO _x meter (“SO
A-7000 ”), and the concentration of SO ₂ is detected.
When the plasma introducing step and the catalyst contacting step are performed at the same time, they can be performed by a reactor as shown in FIG.

(2) Method and conditions for Examples 1 to 5 and Comparative Examples 1 to 3 The temperature in the reactor 1 was set to 15, 100, 200, 300, 4
The temperature is kept at 00, 500, 600, 700 and 800 ° C. for 1 to 6 hours, respectively. Further, from the cylinder 3 filled with air, 0.1 liter / minute of air is filled with SO _2. SO ₂ was supplied at 0.9 L / min from the cylinder 2 and N ₂ was supplied at a required supply rate from the cylinder 4 filled with N ₂ . As a result, the gas supplied into the reactor 1 becomes S with respect to the total gas volume supplied.
O ₂ is 906 ppm (based on nitrogen), and O ₂ is 2.1% by volume.

As shown in FIG. 2, the supplied air is passed through a container 5 containing liquid H ₂ O or liquid H ₂ O ₂ , or is directly blown into the reactor 1. , With respect to the total volume of gas supplied to the reactor 1, H ₂ O
0.1% by volume or 0.055% by volume of H ₂ O ₂ . The container 5 containing H ₂ O or H ₂ O ₂
Can control the temperature. The value indicating the effect of desulfurization was calculated as a desulfurization rate. The desulfurization rate was calculated by the following equation. Desulfurization rate (%) = {(molar amount of SO ₂ was fed into the reactor 1) - (molar amount of SO ₂ which is detected by the detector 7)} /
(Molar amount of SO ₂ supplied into reactor 1) × 100

Example 1 Desulfurization was carried out in both the plasma introduction step and the catalyst contact step while supplying air that did not pass through the vessel 5 containing H ₂ O and H ₂ O ₂ . The desulfurization rate of SO ₂ is shown in Table 1, and the graph is shown in FIG.

Example 2 Without generating plasma in a plasma generator, H ₂
Desulfurization was performed only by the catalyst contacting step while supplying air having 0.1% by volume of O. In this example, 300 ° C.
Tested at temperatures up to Table 1 shows the desulfurization rate of SO ₂ ,
The graph is shown in FIG.

Example 3 Without generating plasma in a plasma generator, H ₂
Desulfurization was performed only by the catalyst contacting step while supplying air having 0.055% by volume of O ₂ . The test at a temperature of 800 ° C. was not performed. The desulfurization rate of SO ₂ is shown in Table 1, and the graph is shown in FIG.

Example 4 While supplying air containing 0.1% by volume of H ₂ O, desulfurization was performed by both the plasma introduction step and the catalyst contact step.
In this example, the test was performed at temperatures up to 300 ° C. S
The desulfurization rate of O ₂ is shown in Table 1, and the graph is shown in FIG.

Example 5 While supplying air having 0.055% by volume of H ₂ O ₂ ,
Desulfurization was performed in both the plasma introduction step and the catalyst contact step. The test at a temperature of 800 ° C. was not performed. S
The desulfurization rate of O ₂ is shown in Table 1, and the graph is shown in FIG.

Comparative Example 1 A plasma was not generated in a plasma generator, and
The effect of desulfurization was evaluated when the catalyst was not put in the reactor and the temperature and gas supply amount and the concentration of the mixed gas supplied to the reactor were the same as those described above. The desulfurization rate of SO ₂ is shown in Table 1, and the graph is shown in FIG.

Comparative Example 2 While supplying air that does not pass through the container 5 containing H ₂ O and H ₂ O ₂ , only the plasma introducing step was performed to desulfurize.
The desulfurization rate of SO ₂ is shown in Table 1, and the graph is shown in FIG.

Comparative Example 3 While supplying air that does not pass through the container 5 containing H ₂ O and H ₂ O ₂ , only the catalyst contacting step was performed to desulfurize. SO
Table ₂ shows the desulfurization rate of No. ₂ , and the graph is shown in FIG.

[0030]

[Table 1]

Effects of Examples From Comparative Examples 1 to 3, even when the reaction temperature was set to 600 ° C. or higher, S
While the desulfurization rate of O ₂ is only about 5%, in Example 1, both steps of the plasma introduction step and the catalyst contacting step are performed without separately supplying H ₂ O and H ₂ O ₂ . Even if only performed, a desulfurization rate of 6.2% can already be achieved at a temperature of 15 ° C. which does not require heating. Further, Example 2
From Tables 4 and 4, by performing the catalyst contacting step in which H ₂ O was separately supplied, a desulfurization rate of 22.4% was obtained at a temperature of 200 ° C.
It can be seen that a desulfurization rate of 34.3% is obtained at 0 ° C. Further, from Examples 3 and 5, by performing the catalyst contacting step in which H ₂ O ₂ was separately supplied, a desulfurization rate of 67.2% was obtained at a temperature of 600 ° C., and by adding a plasma introduction step to this. At a temperature of 600 ° C. and a desulfurization rate of 92.6%. It is considered that these effects can be further improved by adjusting the temperature, pressure, components to be supplied, and the like.

The present invention is not limited to the specific embodiments described above, but may be variously modified within the scope of the present invention according to the purpose and application. That is, the supply amount of the components to be supplied into the reactor, the reaction temperature, the pressure, and the like can be appropriately adjusted. In addition, a reactor,
Appropriate reactors and the like can be used. In particular, it can be an excellent denitration method by performing plasma doping process and / or catalyst contacting step of the present invention with respect to NO _x. Further, a method of simultaneously performing desulfurization and denitration may be adopted.

[0033]

According to the desulfurization method of the present invention, the step of introducing the gas to be treated into the plasma containing various radicals and ions, and the step of adsorbing H ₂ O, H ₂ O ₂ , various radicals and ions, etc. By performing the step of contacting with a catalyst, a remarkable desulfurization effect can be obtained even at a relatively low temperature of 400 ° C. or lower. In addition, since conditions such as high pressure, high temperature, and a large reactor are not required, desulfurization can be performed with a simple and small apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic view of a reaction apparatus used in Examples.

FIG. 2 is an electric circuit diagram of the plasma generator used in the embodiment.

FIG. 3 is a graph showing the SO ₂ desulfurization rate at each temperature of Comparative Examples 1 and 2.

FIG. 4 shows SO ₂ at each temperature of Comparative Example 3 and Example 1.
3 is a graph showing the desulfurization rate of the steel.

FIG. 5 is a graph showing the SO ₂ desulfurization rate at each temperature in Examples 2 and 4.

FIG. 6 is a graph showing the SO ₂ desulfurization rate at each temperature in Examples 3 and 5.

FIG. 7 is a schematic view showing one embodiment of a reaction apparatus when a plasma introducing step and a catalyst contacting step are performed simultaneously.

[Description of Signs] 1; reactor, 11; plasma generation unit, 111; discharge side electrode, 112; power receiving side electrode, 12; catalyst contact unit, 121;
TiO ₂ pellets, 2; a cylinder filled with SO ₂ ,
3; a cylinder filled with air, 4; a cylinder filled with nitrogen, 5; a container containing H ₂ O or H ₂ O ₂ ,
6; sulfur compound recovery device, 7; detector.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D002 AA01 AA02 AA03 BA02 BA05 BA07 BA20 DA07 DA11 DA19 DA21 DA24 DA31 DA35 DA52 EA02 EA03 FA08 4D048 AA02 AB01 BA07Y BA13Y BA23Y BA28Y BA41Y BB01 BB04 EA03

Claims (8)

[Claims] 1. A desulfurization method comprising: a step of introducing a gas to be treated containing a sulfur compound into plasma; and a step of bringing the gas into contact with a catalyst. 2. The desulfurization method according to claim 1, wherein the step of introducing into the plasma and the step of contacting with the catalyst are performed simultaneously. 3. The plasma contains H radicals, OH
Radical, O radical, N radical, H ⁺ ion, OH ⁻
And at least one of O ² ions and H ₂ O, H ₂ O ₂ , H radical, OH radical, O radical, N radical, H ⁺ ion, OH ^At least one of-ions and O ^-2 ions
The desulfurization method according to claim 1 or 2, wherein the seed is adsorbed. 4. A gas to be treated containing a sulfur compound is introduced into a plasma containing at least one of H radical, OH radical, O radical, N radical, H ⁺ ion, OH ^- ion and O ^-2 ion. A desulfurization method, comprising the step of: 5. The method according to claim 5, wherein the gas to be treated is further mixed with H ₂ O, H ₂ O
The desulfurization method according to claim 4, wherein at least one of ₂ , ₂ , H radical, OH radical, O radical, N radical, H ⁺ ion, OH ^- ion and O ^-2 ion is brought into contact with the adsorbed catalyst. 6. The process gas containing a sulfur compound is converted to H
A step of bringing at least one of ₂ O, H ₂ O ₂ , H radical, OH radical, O radical, N radical, H ⁺ ion, OH ^- ion and O ^-2 ion into contact with the adsorbed catalyst; A desulfurization method characterized by the following. 7. The plasma generator generates the H radical, the OH radical, the O radical, the N radical, the H ⁺ ion, the OH ⁻ ion, and the O ⁻² ion adsorbed on the catalyst. The desulfurization method according to at least one of claims 3, 5 and 6, wherein the method is supplied and supplied. 8. The desulfurization method according to claim 1, wherein at least OH radicals are adsorbed on the catalyst.