JPS5912602B2 - Claus sulfur recovery equipment tail gas processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing sulfur compounds contained in Claus sulfur recovery apparatus tail gas.

More specifically, as a catalyst for producing sulfur by reacting hydrogen sulfide and sulfur dioxide in the Claus sulfur recovery equipment tail gas, titanium oxide is used as the first active component, and iron, cobalt, nickel, and copper are used as the second active components. The present invention relates to a method for treating tail gas of a Claus sulfur recovery apparatus, characterized in that the present invention uses at least one type of oxides added thereto.

Currently, Claus sulfur recovery equipment is used to treat gases containing high concentrations of hydrogen sulfide.

In the Claus sulfur recovery equipment, hydrogen sulfide is partially oxidized to form elemental sulfur, and the reaction is generally expressed by the following formula.

HO+-0=802+H20(1) 22 2 H2S +802= -Sx +2 H2O(2)
From equations (1) and 2), the overall Claus reaction is 3 3 HS+-〇 =-8x+3HO(3)2 22 x
It can be expressed as 2.

Reaction (2), which produces sulfur from hydrogen sulfide and sulfur dioxide, proceeds to the right at low temperatures in terms of chemical equilibrium.

Therefore, the lower the temperature in the Claus reaction, the higher the rate of sulfur production.

However, since the Claus reaction as a whole is a large exothermic reaction, the reaction is usually carried out in two or three stages, with a cooling step in the middle to remove sulfur and cool the gas.

In the Claus sulfur recovery equipment, the Claus reaction is carried out by 2 to 3
Even when the stage is reached, the tail gas normally contains 0.2 to 4% hydrogen sulfide and 0.1 to 2.0% sulfur dioxide.
, and small amounts of carbon disulfide, carbonyl sulfide, and sulfur.

Emission of tail gas containing these sulfur compounds into the atmosphere is naturally undesirable because it causes air pollution.

Various methods have been developed or proposed for processing the tail gas of Claus sulfur recovery equipment.

One is to contact the tail gas with hydrogen at high temperature to convert the sulfur compounds in the tail gas to hydrogen sulfide, and then oxidize the hydrogen sulfide in a solution or remove it by absorption into a renewable solution. Bebon Law (Special Public Interest Act 1977-1)
1142, JP-A-48-55896), the Scott method (JP-A-47-2908, 47-6254), and the like are known.

Other methods for treating tail gas include oxidizing the sulfur compounds in the tail gas to produce sulfur dioxide, and then converting the sulfur dioxide into general flue gas desulfurization (a well-known method is to fix sulfur dioxide as gypsum). There is something to process.

In contrast to the treatment method including the reduction or oxidation step described above, there is a treatment method in which a Claus reaction is performed at a low temperature to increase the removal rate of sulfur compounds.

As mentioned earlier, the Claus reaction (Equation (2)) is carried out at a lower temperature, the higher the removal rate of sulfur compounds, but since the dew point of sulfur is 150 to 250°C, it is difficult to remove sulfur compounds at temperatures below the dew point of sulfur. When the Claus reaction is carried out, the sulfur produced accumulates on the catalyst.

A method using alumina (Japanese Patent Publication No. 48-20999.50-21439, 5
A method using activated carbon (Japanese Patent Publication No. 46-22728) is already known.

In the low-temperature Claus process, sulfur adsorbed on the catalyst is desorbed using regeneration gas.

If the desorbed gas is circulated to the Claus sulfur recovery unit, the tail gas treatment unit will be closed, which is a major feature and advantage of the low-temperature Claus process.

The present inventors studied the activity of the above-mentioned alumina, activated carbon, and various catalysts for the Claus reaction over a wide temperature range, and found that titanium oxide was the first active component, and iron, cobalt, nickel, and The present invention was achieved by discovering that a catalyst containing at least one type of copper oxide has excellent performance.

The catalyst of the present invention (Ti-Fe, Co, Ni, Cu catalyst) not only has excellent activity for Claus reaction, but also
It also shows extremely excellent performance in attachment and detachment.

It is an object of the present invention to provide a method for economically reducing sulfur compounds in Claus sulfur recovery unit tail gas.

Another object of the present invention is to provide a novel catalyst for achieving the above object.

To treat Claus sulfur recovery apparatus tail gas in accordance with the present invention, the tail gas is treated with a catalyst comprising titanium oxide as an active first component and at least one of oxides of iron, cobalt, nickel, and copper as a second component. at least one of the sulfur produced by the reaction (hole 2))
part is adsorbed onto the catalyst.

The temperature at which this adsorption step is carried out is preferably 80 to 200°C, and 120 to 170°C from the viewpoint of catalyst activity and sulfur vapor pressure.
C is particularly preferred.

The space velocity of the tail gas in the adsorption step (converted to standard conditions) is preferably 200 to IQ, ooov/v/h, and 200 to 5,000/v/h from the viewpoint of economical catalyst usage and removal efficiency of sulfur compounds. h is particularly preferred.

When sulfur is adsorbed on the catalyst and reaches a certain value or more,
The removal rate of sulfur compounds begins to decrease.

Therefore, if the removal rate of sulfur compounds becomes lower than the desired value, the catalyst that has desorbed the sulfur on the catalyst must be regenerated.

In order to desorb sulfur from the catalyst and regenerate the catalyst, 2.
There are different methods.

In one method, an oxygen-containing gas is used as a regeneration gas to oxidize the adsorbed sulfur and desorb it as sulfur dioxide.

Another method uses a hot inert gas as a regeneration gas to evaporate and desorb sulfur at temperatures above the sulfur dew point.

When adsorbed sulfur is desorbed with oxygen-containing gas, reaction (4) occurs.

S+0□=SO□ Δ, H= -70K cal /
mole (4) Ti-Fe, Co, Ni of the present invention
) When a Cu catalyst is used, reaction (4) proceeds at a sufficiently practical rate at a temperature of 100° C. or higher.

Since reaction (4) is a very exothermic reaction of 70 Kcal/mole, the desorption gas reaches a very high temperature.

For example, when air is used as the regeneration gas, the desorption gas contains about 20 °C of sulfur dioxide, but the temperature is 1,00 °C.
Exceeds 0℃.

At such high temperatures, Ti-Fe, Co,
Ni.

Since the Cu catalyst loses its activity, either the oxygen concentration in the regeneration gas is lowered, or the desorbed gas is cooled and then mixed with the regeneration gas and circulated to the catalyst layer.

This method of circulating the desorption gas is advantageous because it allows the concentration of sulfur dioxide in the desorption gas to be increased.

If air is used as the regeneration gas, a desorption gas containing about 20% sulfur dioxide can be obtained, and if oxygen gas is used as the regeneration gas, a gas containing almost 100% sulfur dioxide can be obtained.

The circulation rate of the desorption gas (ratio of the desorption gas circulated to the total desorption gas) can be selected by considering the heat resistance of the catalyst, but the Ti-Fe, Co, Ni of the present invention
, When using a Cu catalyst, the temperature of the catalyst layer is about 6
Decide the circulation rate to keep it below 00℃.

For example, when air is used as the regeneration gas, the circulation rate may be approximately 75% or more.

The supply rate or space velocity of the regeneration gas in this desorption step may be approximately the same as that in the adsorption step.

By appropriately selecting the supply rate of the regeneration gas in this manner, the oxygen concentration in the desorption gas can be reduced to a trace level.

When an oxygen-containing gas is used as the regeneration gas as described above, a desorption gas containing a relatively high concentration of sulfur dioxide (and sulfur vaporized at high temperature) is obtained.

This desorption gas containing sulfur dioxide may be treated by a known dry or wet flue gas desulfurization method or a process for producing sulfuric acid, or may be circulated to a Claus sulfur recovery device.

When circulating the desorption gas to the Claus sulfur recovery device,
This is particularly preferred since the tail gas treatment becomes a closed system.

The present invention is characterized by the use of Ti-Fe, which is highly active at low temperatures, as a catalyst that promotes the reaction between hydrogen sulfide and sulfur dioxide.

Co, Ni, Cu catalysts may be used,
Another feature of the invention is that the regeneration of the sulfur-adsorbed catalyst can be carried out with an oxygen-containing gas and that it can be
This means that it can be done at a very low temperature of C.

As is known in the art, when activated carbon is used as a catalyst for low-temperature Claus reactions, oxygen-containing gas cannot be used for regeneration.

This is because some of the activated carbon reacts with oxygen and is lost.

When alumina is used as a catalyst, oxygen-containing gas can be used as a regeneration gas, but the reaction of the alumina catalyst (
The activity against 4) is low, and in our tests, 200
It will not progress unless the temperature reaches ℃ or higher.

Another method for regenerating the catalyst is to use a high temperature inert gas.

Examples of the inert gas include nitrogen, water vapor, Claus recovery device tail gas, etc. In this case, these regeneration gases may be passed through the catalyst layer at a temperature equal to or higher than the dew point of sulfur.

The desorbed gas may be cooled to condense out the sulfur or recycled to the Claus reactor.

In the treatment of the Claus recovery apparatus tail gas of the present invention, a catalyst is used which comprises titanium oxide as the active first component and at least one of oxides of iron, cobalt, nickel, and copper as the second component.

From the viewpoint of catalytic activity and cost, the ratio of these active components is such that the atomic ratio of the metal components of the first component and the second component is 50:
50-99:1 is preferred, especially 70:30-98:2
It is preferable that

Titanium raw materials for obtaining the catalyst of the present invention include various titanium oxides, titanic acids, titanium tetrachloride, titanium sulfate,
Titanyl sulfate and the like may be used.

Raw materials for iron include various iron oxides, as well as various organic and inorganic iron salts such as hydrated iron oxide, iron nitrate, iron sulfate, iron chloride, iron acetate, and iron oxalate, which produce iron oxide when heated. Can be used.

It is also preferable to precipitate an aqueous solution of the above-mentioned various iron salts with aqueous ammonia, alkali carbonate, alkali carbonate, urea, etc., which is commonly used as a catalyst preparation method, and generate iron oxide by thermal decomposition.

As a raw material for cobalt, various cobalt oxides, cobalt hydroxide which produces cobalt oxide by heating, and various other organic and inorganic cobalt salts can be used.

Also preferred is a method in which cobalt oxide is produced by adding a precipitant to an aqueous solution of various cobalt salts and thermally decomposing the produced hydroxide.

As raw materials for nickel, nickel oxide, nickel hydroxide which produces nickel oxide when heated, and various other organic and inorganic nickel salts can be used.

Also preferred is a method in which nickel oxide is produced by adding a precipitant to an aqueous solution of various nickel salts and thermally decomposing the produced hydroxide.

As a raw material for copper, copper oxide, copper hydroxide which produces copper oxide upon heating, and various other organic and inorganic copper salts can be used.

It is also a good method to obtain oxidized steel by adding a precipitant to an aqueous solution of these copper salts and thermally decomposing the generated hydroxide.

Further, in order to produce the catalyst of the present invention, any of the tableting method, extrusion molding, transfer granulation method, etc. commonly used in the production of catalysts can be used.

It should be noted that the present invention is not limited only to the treatment of Clarastail gas, but can also be applied to various gases similar to this by making modifications to the extent of ordinary design changes.

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example-1 500 g of titanium tetrachloride (T t C14) solution was added to 11 parts of water.
dissolve in

Ferrous sulfate (FeSO4・7H20) 811
Add and dissolve.

When this mixed solution is gradually dropped into aqueous ammonia, a coprecipitate of titanic acid and hydrated iron oxide is generated.

In this case, ammonia water is added as appropriate so that the pH of the ammonia solution does not become 7 or less.

The resulting precipitate is thoroughly washed with distilled water by decantation, filtered, and dried at 120°C for one day and night.

Add 3 weights of graphite to the dried powder, mix thoroughly, and set the molding pressure to 500 to 9/cI? Compress and mold into a L size with a diameter of 6 mrn and a thickness of 6 mm.

The obtained molded product is fired at 5000C for 4 hours.

The catalyst thus obtained had an atomic ratio of Ti:Fe=9
: It has a composition of 1.

The catalyst performance test was conducted as follows.

The reaction tube was made of quartz and had an inner diameter of 17 mm, and contained therein a thermocouple protection tube made of quartz and had an outer diameter of 5 mm.

This reaction tube is heated in an electric furnace to set the reaction temperature.

The center of the reaction tube was filled with 8 d of catalyst crushed into 10 to 20 meshes, and a gas having the following composition was flowed at a flow rate of 801/h (space velocity 10,000 h-'').

gas composition H2S 1.0±0.05% S02 0.5±0.025% N2 remainder The results obtained are shown in Table 1.

Comparative example-1 Aluminum nitrate (AA(NOs)3.9H20) 50
0g and 41g of ferrous sulfate are dissolved in 11g of water.

If this mixed solution is gradually dropped into aqueous ammonia, a coprecipitate of alumina sol and hydrated iron oxide is generated.

A 1203 was prepared in the same manner as shown in Example-1.
-Fe203 catalyst (Al:Fe=9:1, atomic ratio) was prepared.

The performance of the obtained catalyst was measured under the same experimental conditions as shown in Example-1, and the results shown in Table 1 were obtained.

Comparative Example-2 Using a commercially available alumina catalyst for Claus reaction, Example-
Performance was measured under the same experimental conditions as shown in Table 1, and the results shown in Table 1 were obtained.

Example-2 Example 1 except that the ratio of titanium oxide and iron oxide was changed
A catalyst containing Ti2Fe in a ratio of 9.8:0.2°8:2, 7:3 was prepared using the same method as above.

The performance of these catalysts was measured under the same experimental conditions as shown in Example-1, and the results shown in Table 2 were obtained.

Example-3 A Ti02-Co0 catalyst was prepared in the same manner as in Example-1 except that cobalt nitrate was used instead of ferrous sulfate.

In this case, a Na 2 C03 solution was used as a precipitant.

The composition of the catalyst was varied and its performance was measured under the same experimental conditions as shown in Example 1, and the results shown in Table 3 were obtained.

Example-4 A T 102 N t O catalyst was prepared in the same manner as in Example-1 except that nickel nitrate was used instead of ferrous sulfate.

In this case, a Na2CO3 solution was used as a precipitant.

The composition of the catalyst was varied and its performance was measured under the same experimental conditions as shown in Example-1, and the results shown in Table 4 were obtained.

Example-5 Example-1 except that copper nitrate was used instead of ferrous sulfate
A T 102 Cu O catalyst was prepared in a similar manner.

In this case, a Na 2 C03 solution was used as a precipitant.

The composition of the catalyst was varied and its performance was measured under the same experimental conditions as shown in Example 1, and the results shown in Table 5 were obtained.

Example-6 In this example, the performance of a three-residue catalyst will be described.

Take 500 g of metatitanic acid slurry (150.!i' as TiO2) and add 25.2.9 g of copper nitrate and 8.3 g of iron oxide.

Furthermore, 5001 rLl of water was added, and the mixture was thoroughly kneaded in a kneader.

After preliminarily calcining the resulting paste-like mixture at 300° C. for 5 hours, 3 weights of graphite are added and the mixture is compressed into tablets with a diameter of 6 and a thickness of 6 at a molding pressure of about 500 fQ9/crA.

The obtained molded product was fired at 500° C. for 4 hours.

The catalyst thus obtained has an atomic ratio of Ti:Fe:
It has a composition of Cu=9:0.5:0.5.

Its performance was measured under the same experimental conditions as shown in Example-1, and the results shown in Table 6 were obtained.

Example 7 In this example, the results of an adsorption step and a regeneration step using the catalyst of Example 1 will be described.

(a) Adsorption step: Reaction gas (E(,,S 1.0±0.05%, 502
0.5±0.025%, N2020%, N2 remainder) gas was passed through the tube at a space velocity of 2,000 h-1 for 3 hours.

(b) Regeneration process: Regeneration gas (024%, remaining N2) at a space velocity of 1,
000 h-''.

The following results were obtained.

When the adsorption process was carried out at 130°C, H2S and SO2
The removal rate was 95% or more for all three hours.

When the regeneration step was also carried out at a catalyst bed inlet temperature of 130°C, the desorption gas contained 4% S02.

It was observed that when the sulfur on the catalyst was oxidized to SO2, the temperature at the center of the catalyst layer rose to a maximum of 430°C due to the heat of reaction.

It was confirmed by observing that sulfur adhered to the lower part of the reaction tube that as a result of the temperature increase, some of the sulfur adsorbed on the catalyst evaporated and was desorbed.

Although the above adsorption-regeneration step was repeated 10 times, there was no deterioration in the performance of the catalyst.

Comparative Example 3 Using the alumina catalyst shown in Comparative Example 2, an experiment similar to Example 7 was conducted, and the following results were obtained.

When the adsorption step was carried out at 130° C., the removal rate of H2S and S02 was 95% or more for 3 hours.

The regeneration process was attempted at 130, 150, and 170°G, but the oxidation reaction of sulfur to SO2 did not proceed, and the desorption gas contained SO2.
was not included.

Claims (1)

[Claims] 1. A gas containing at least hydrogen sulfide and sulfur dioxide, with titanium oxide as the first component and at least one of iron, cobalt, nickel, and copper oxides as the second component. in contact with a catalyst containing as an active ingredient,
A method for treating till gas from a Claus sulfur recovery apparatus, comprising the steps of: adsorbing generated sulfur onto the catalyst; and desorbing sulfur from the catalyst that has adsorbed sulfur. 2. A method for treating tail gas from a Claus sulfur recovery apparatus according to claim 1, in which an oxygen-containing gas is used in the attaching and detaching step. 3. A method for treating tail gas from a Claus sulfur recovery apparatus according to claim 1, wherein in the attachment/desorption step, an inert gas is passed through the catalyst layer at a temperature equal to or higher than the dew point of sulfur. 4. A method for treating tail gas from a Claus sulfur recovery device according to claim 1, wherein the adsorption step is carried out at 80 to 200°C. 5. The method for treating tail gas of a KRAKS sulfur recovery device according to claim 1, wherein the composition ratio of the first component and the second component of the catalyst is 99:1 to 50:50 in terms of atomic ratio of metal components.