JPH0790139B2 - Method for dry removal of organic sulfur compounds in gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a dry type gas such as a coke oven, a blast furnace gas in the iron manufacturing industry, various generated gases in the oil refining industry, and a flue gas in various industries. And a method for removing organic sulfur compounds.

<Prior Art> Methods for removing organic sulfur compounds in gas such as coke oven gas include a dry method and a wet method.

As a wet method, there is US Pat. No. 2,490,840 as a method suitable for practical use. In this method, a solution containing amine is countercurrently contacted with a gas to remove sulfur compounds in the gas. However, when carbon dioxide is contained in the gas, a secondary product is obtained from a reaction product with carbon dioxide. Acid and alkali aqueous solutions are also required to recover amines. Therefore, if the concentration of secondary amines in the absorbing solution is increased for the purpose of improving the removal rate of organic sulfur compounds, the acid and alkali consumption will increase according to the carbon dioxide absorption amount. There is a drawback that the amount also increases.

As a method for improving this, there is JP-B-58-43132.

According to this method, the secondary amine is recovered without using the acid and the alkaline aqueous solution for the treatment of the absorption reaction solution. In any case, these wet methods have complicated processes and are very economically disadvantageous.

In the dry method, metal sulfides, metal oxides, molecular sieves, etc. are used for direct absorption or removal, or hydrogen, water vapor, oxygen, etc. in the gas are converted into compounds that can be easily removed before absorption / adsorption removal. However, this method requires a treatment at a relatively high temperature or a pressure of about 100 to 450 ° C., the influence of coexisting gas is large, complete adsorption and regeneration of the absorbent are difficult, and the absorption amount is large. There is a big problem that there are few.

Among these dry methods, a relatively good method is disclosed in JP-A-49-
There is a 22375 publication. This method involves the use of a porous carrier with a second
It is proposed that the organic sulfur compound be removed by using a substance carrying a primary amine or an organic solvent solution thereof as an absorbent. Looking at the absorption amount of the organic sulfur compound using the activated carbon of the Example, the life of the absorbent is short in practical use, and when treating a gas mainly containing carbon disulfide and carbonyl sulfide, the There is a problem that carbon disulfide having good reactivity is preferentially absorbed and removed, and the absorption life of carbonyl sulfide is very short.

<Problems to be Solved by the Invention> In the above-mentioned Japanese Patent Application Laid-Open No. 49-22375, an organic sulfur compound is prepared by using a porous amine carrier carrying a secondary amine or an organic solvent solution thereof as an absorbent. When it is removed, its absorption amount is small, so it has a short life, and when treating a gas that mainly contains carbon disulfide or carbonyl sulfide, carbon disulfide with good reactivity with amine takes precedence. However, there is a problem that the absorption life of carbonyl sulfide is very short.

The present invention is intended to solve the above-mentioned problems of the prior art. First, by using an absorbent in which a secondary amine is impregnated in a porous carrier, carbon disulfide is removed by a dry method. Then, by using an absorbent impregnated with a primary carrier, diglycolamine, which is a primary amine, dry carbonyl sulfide is decomposed and absorbed, and further hydrogen sulfide generated by decomposition of carbonyl sulfide is used. To provide a method of absorbing the.

<Means for Solving the Problems> The present inventor has proposed a method for treating a gas mainly containing carbon disulfide and carbonyl sulfide as an organic sulfur compound in a gas with an absorbent to remove the organic sulfur compound. The present invention has been made paying attention to the preferential absorption of carbon disulfide having good reactivity with amines.

That is, the present invention, in the method of treating the gas mainly containing carbon disulfide, carbonyl sulfide as the organic sulfur compound, with an absorbent to remove the organic sulfur compound,
First step of absorbing and removing by using an absorbent comprising a secondary amine supported on a porous carrier, decomposing residual carbonyl sulfide by using a catalyst comprising a diglycolamine supported on a porous carrier A dry removal method of an organic sulfur compound in a gas, comprising: a second step; and a third step of absorbing and removing hydrogen sulfide generated when carbonyl sulfide is decomposed in the second step. provide.

Further, in a method of treating a gas mainly containing carbon disulfide or carbonyl sulfide as an organic sulfur compound with an absorbent to remove the organic sulfur compound, a secondary carrier is supported on a porous carrier. It includes each step of a first step of absorbing and removing with an absorbent, and a second step of absorbing and removing residual carbonyl sulfide with an absorbent obtained by supporting diglycolamine on a porous carrier. A method of dry-removing an organic sulfur compound in a gas is provided.

Further, in a method of treating a gas mainly containing carbon disulfide or carbonyl sulfide as an organic sulfur compound with an absorbent to remove the organic sulfur compound, a secondary carrier is supported on a porous carrier. In the first step of absorbing and removing with an absorbent, the second step of decomposing and absorbing and removing the residual carbonyl sulfide with an absorbent obtained by supporting diglycolamine on a porous carrier, and the second step Provided is a method for dry-removing an organic sulfur compound in a gas, which comprises each step of a third step of absorbing and removing hydrogen sulfide generated and remaining when carbonyl sulfide is decomposed.

In addition, in a method of treating a gas mainly containing carbon disulfide or carbonyl sulfide as an organic sulfur compound with an absorbent to remove the organic sulfur compound, the second carrier is used as a porous carrier.
First step of absorbing and removing using an absorbent supporting a primary amine, second step of decomposing and absorbing remaining carbonyl sulfide by using an absorbent supporting a diglycolamine on a porous carrier The method for dry-removing an organic sulfur compound in a gas is characterized by including each step of

Further, it is preferable that the material supporting diglycolamine used in the second step absorbs hydrogen sulfide.

Hereinafter, the present invention will be described in detail.

As the absorbent used in the first step of absorbing and removing carbon disulfide in the gas of the present invention, a secondary amine is supported on a porous carrier. As this absorbent, in order to maintain the absorption life for a long time, it is preferable to use the carrier described in Japanese Patent Application No. 62-282517. For this carrier, the pore volume
0.3cc / g or more, average pore size 0.02μm or more and solid acid amount
It is preferable to use a property having a property of 0.2 mmol / g or less.

The large pore volume leads to the possibility of absorbing a large amount of secondary amine having an activity of reacting and absorbing the organic sulfur compound in the gas.

In other words, having a high liquid absorbing property may increase the absorption amount of the organic sulfur compound, thus leading to a longer life.

The pore volume is preferably 0.3 cc / g or more. 0.3cc / g
If the amount is less than the above, naturally the amount of the amine, which is the active substance, is reduced, and the theoretical amount of the organic sulfur compound absorbed is also reduced, which is disadvantageous.

Next, it is considered that the average pore size is not small, and if the pore size is small, it is difficult for the secondary amine, which is an active substance, to be supported in the pores.

Further, even if it is supported, it is considered that the diffusion rate becomes slow when the organic sulfur compound diffuses into the pores having a small pore diameter, and the active substance does not easily react with the organic sulfur compound effectively.

The average pore size is 0.02 μm or more, preferably 0.05 μm
It is m or more. If it is less than 0.02 μm, as described above, not only the amount of amine carried becomes small, but also the reactivity with the organic sulfur compound becomes low.

Finally, the fact that the amount of solid acid (solid acidity) is not large means
Since the secondary amine that is an active substance is basic, if the amount of acid (acidity) of the carrier to be supported is large, it will react with the carrier when the active amine is supported, and the dispersed state in the pores Is also non-uniform and, as a result, the reactivity with the organic sulfur compound may significantly decrease. Therefore, it is important that the solid acid amount (solid acidity) of the carrier is not large.

The solid acid amount (solid acidity) is 0.2 mmol / g or less. If it is more than 0.2 mmol / g, the reactivity between the carrier and the amine becomes strong as described above, and the tendency becomes stronger as the solid acid amount becomes larger, and the reactivity with the organic sulfur compound decreases on the contrary. .

Here, the amount of solid acid (solid acidity) means a value measured under the following conditions or a value corresponding thereto.

(1) Measuring device: Tokyo Riko multi-purpose calorimeter (2) Measuring method: NH ₃ adsorption heat measurement (3) Pretreatment condition: Exhaust treatment 400 ° C (7 hours) Treatment vacuum degree 1.0 × 10 ^-4 Torr (4 ) Definition of acid point: The point showing the heat of adsorption of 80 kJ / mol or more is defined as the acid point. (5) Acid amount: The amount showing the heat of adsorption of 80 kJ / mol or more in (4) above is defined as the acid amount (mmol / g). Represent.

The carrier used in the present invention may be any carrier as long as it satisfies the above conditions, but it is preferable to select a carrier satisfying the above conditions among calcium silicate, magnesium silicate, silica and the like.

In addition, the second carrier supported on the porous carrier as described above.
Examples of the primary amine include piperidine, morpholine, pyrrolidine, hexamethyleneimine, N-methylaminoethanol, N-aminoethylhyperazine, N- (2-aminoethyl) -1,3-propanediamine, diethanolamine and diisopropanolamine. , Dibutylamine, diphenylamine, diisobutylamine, dibenzylamine and the like.

These secondary amines are preferably 0.1 to 70% by weight of the total weight.
%, Directly or as a solvent solution is added to a porous carrier to impregnate and carry it.

Examples of the solvent that can be dissolved include creosote liquid, hydrocarbon liquid such as benzol and naphtha, and aliphatic, alicyclic or aromatic alcohols and ketones having about 1 to 10 carbon atoms.

The dose is appropriately about 1 to 10 times the volume of the carrier.

The reaction when the organic sulfur compound in the gas is absorbed / desorbed by the absorbent containing the secondary amine is considered to be the following reaction.

<Absorption reaction> <Regeneration reaction> The form of the amine after decomposition is unknown, but it is considered to be a secondary or tertiary amine containing a part of S.

It also decomposes or absorbs carbonyl sulfide in gas,
Alternatively, the absorbent (catalyst) used in the second step of decomposing / absorbing is a primary amine, in which diglycolamine is supported on a porous carrier. The following two points can be considered as the reaction form at this time.

(1) Carbonyl sulfide in gas is absorbed and removed by the diglycolamine carried on the carrier.

(2) The carbonyl sulfide in the gas is decomposed by the following reaction by the glycolamine carried on the carrier.

DGA: Diglycolamine BHEEU: (N, N-Bis (hydroxyethoxyethyl) urea The above two reactions (1) and (2) may occur at the same time or both may or may not occur depending on the carrier material used. When the decomposition reaction of (2) above occurs, a third step of absorbing and removing the produced hydrogen sulfide is necessary, and therefore (1) above.
If only the reaction occurs, the third step becomes unnecessary and the step is facilitated. Therefore, a carrier may be selected so that the reaction (1) occurs.

However, by using the catalytic reaction of (2) above, it is less expensive to use diglycolamine, because carbonyl sulfide is changed to hydrogen sulfide and hydrogen sulfide is absorbed and removed by the solid absorbent.
Therefore, the carrier can be absorbed and removed with a long life.

Even when the reaction of the above (2) occurs, by using the hydrogen sulfide solid absorbent that can be used in the third step as the carrier used in the second step, the generated hydrogen sulfide is internally absorbed and the third step It is also possible to adopt a method in which the function of is added to the carrier in the second step.

Further, as a carrier used in the second step, a specific surface area (B.
A porous substance having an ET method of 5 m ² / g or more and a pore volume of 0.1 ml / g or more is used. When the specific surface area is less than 5 m ² / g or the pore volume is less than 0.1 ml / g, the amount of amine as an active substance supported is small, and the theoretical absorption amount of organic sulfur compound is also small. is not.

As the carrier satisfying this condition and in which the reaction (2) above easily occurs, alumina, silica-alumina, zeolite,
A substance having a relatively strong solid acid such as titania or zirconia is selected.

Examples of the method of supporting diglycolamine on these carriers include a method of impregnating a stock solution or an aqueous solution thereof or an organic solvent solution thereof. Examples of the organic solvent include hydrocarbon oils such as benzene and alcohols. And ketones are used, and the dose is appropriately 1 to 20 times the volume of the carrier. This is because if it exceeds 20 times the volume, diglycolamine becomes excessive and there is no effect.

A known method is used in the third step of removing the generated hydrogen sulfide.

For example, it is a method using a solid absorbent of iron oxide, iron hydroxide, iron oxide hydroxide, zinc oxide, copper oxide, activated carbon.

The reaction temperature in each step is preferably room temperature to 100 ° C. If the temperature exceeds 100 ° C, the vapor pressure of the supported primary amine, diglycolamine, or the secondary amine will increase, and the vapor will be released from the carrier, resulting in a very short catalyst life.

The pressure can be increased, but it is practical because it can be used at normal pressure.

Next, a process for carrying out the present invention will be specifically described with reference to the drawings. That is, FIG. 1 is a process diagram showing an embodiment of the present invention. A gas 1 containing a sulfur compound (mainly carbon disulfide and carbonyl sulfide) appropriately passes through a heater 2 used when it is desired to heat the gas, and a first step of absorbing and removing carbon disulfide in a packed tower 3 is performed. . Next, the gas passes through a heater 4 that appropriately heats the gas, and enters a packed tower 5 that performs the second step of decomposing and absorbing carbonyl sulfide in the residual gas. Further, when it is necessary to absorb and remove hydrogen sulfide, the purified gas 7 is generated by entering the packed column 6 in which the third step is performed.

<Examples> The following examples will more specifically describe.

(Example 1 and Comparative Example) Example in which CS ₂ is absorbed and removed in the first step, COS is decomposed and absorbed in the second step, and H ₂ S generated during decomposition is simultaneously absorbed and removed in the second step. Describe.

First, the first step was performed under the following conditions.

(1) Absorber: 50 wt% diethanolamine impregnated calcium silicate (2) Average particle size: 5 mm (3) Filling amount: 100 ml (4) Gas treatment amount: 1.67 / min (5) Concentration of CS ₂ and COS in inlet gas CS ₂ ; 50 mg / Nm ³ , COS; 50 mg / Nm ³ (6) SV (space velocity): 1000H ^-1 (7) Temperature: 40 ° C (8) Pressure: normal pressure As a result of treating the gas under the above conditions, as shown in Fig. 2, It was found that CS _{2 in} the gas is selectively absorbed and removed by using the absorbent in which the secondary carrier is impregnated in the porous carrier.

Next, an example of the second step will be described below.

COS in the gas was removed by using an absorbent obtained by impregnating a primary carrier with diglycolamine as a primary amine. The test conditions were as follows, and the results are shown in FIG.

(1) Absorbent: 2 wt% diglycolamine impregnated iron oxide (2) Temperature: Enter in Fig. 3 (3) All other conditions are the same as the above example.

For comparison, the blot of (1) in FIG. 3 does not pass the first step, and when CS ₂ and COS coexist in the gas, the plot of (2) shows the first plot in this example. The absorption performance is shown when only 50 mg / Nm ³ COS is present in the gas after passing through the process.

From the figure, in the system coexisting with CS ₂ and COS, CS ₂ has a higher removal rate than COS, but neither shows a stable removal rate. Next, judging the removal performance of COS only with the same absorbent from the plot of (2), it is clear that the absorption and removal performance of COS is clearly high. It can be seen that when the reaction temperature is 60 ° C., the activity is considerably high. It can also be said that a more stable removal rate can be obtained.

As described above, in the method for removing an organic compound in a gas according to the present invention, after removing CS _{2 in} the first step, COS is used as the second step.
It was confirmed that the removal of COS was more efficient in removing COS.

(Example 2) An example in which CS ₂ is absorbed and removed in the first step, COS is decomposed and absorbed in the second step, and H ₂ S generated during decomposition is absorbed and removed in the third step will be described.

First, in the first step, CS ₂ was removed under the same conditions as in Example 1.

Next, the second step is described below. By using a catalyst in which a primary carrier, diglycolamine, is impregnated in a porous carrier, reactivity with respect to carbonyl sulfide (COS), which is an organic sulfur compound in gas, is obtained. The test was conducted.

The test conditions were as follows, and the results are shown in FIG.

(1) Catalyst: diglycolamine-impregnated zeolite Impregnation rate 7 wt% (2) Filling amount: 100 ml (3) Particle shape: 1.5 mmφ × 10 mmL (cylindrical) (4) Gas treatment rate: 1.67 / min (5) Inlet COS concentration in gas: See Fig. 4 (6) SV (space velocity): 1000H ^-1 (7) Temperature: 60 ° C (8) Pressure: normal pressure As is clear from Fig. 4, COS has high activity. Is decomposed H
_It can be seen that it has been converted to ₂ S. In the figure, the outlet H ₂ S concentration increases with time and then tends to be stable.
It is considered that an absorption reaction occurs between diglycolamine and COS in the initial stage.

In the third step, the H ₂ S generated in the second step was removed by a known H ₂ S absorbent, so that the following steps were performed.

(1) Catalyst: Iron oxide (2) Filling amount: 500 ml (3) Particle shape: 8 mmφ × 10 mmL (cylindrical) (4) Gas treatment amount: 1.67 / min (5) SV (space velocity): 200H ^-1 (6) Temperature: 25 ° C (7) Pressure: normal pressure Under the above conditions, H ₂ S generated in the 2nd process became a trace in the 3rd process.

(Example 3) CS ₂ is absorbed and removed in the first step, COS is decomposed in the second step,
An example of absorbing and removing H ₂ S generated during decomposition in the third step will be described.

First, in the first step, CS ₂ was removed under the same conditions as in Example 1.

Next, the second step will be described below.

In this example, a reactivity test using alumina as a carrier was conducted. The test conditions were as follows, and the results are shown in FIG.

(1) Catalyst: diglycolamine-impregnated alumina Impregnation rate 5 wt% (2) Filling amount, gas treatment amount, SV value, temperature and pressure are the same as in Example 2.

(3) Average particle size: 5 mm As can be seen from Fig. 5, the catalyst used in this example has COS of H
_It can be seen that it decomposes into ₂ S and its activity is stable.

Next, in the third step, the H ₂ S generated in the second step is converted into known H
_{Since it} was removed by the ₂ S absorbent, the same catalyst and conditions as in the third step of Example 2 were used, and H ₂ S in the outlet gas became a trace.

(Example 4) An example in which CS ₂ is absorbed and removed in the first step and COS is absorbed in the second step will be described.

First, in the first step, CS ₂ was removed under the same conditions as in Example 1.

Next, in the second step, a reaction test using calcium silicate as a carrier was performed. The test conditions were as follows, and the results are shown in FIG.

(1) Catalyst: diglycolamine-impregnated calcium silicate Impregnation rate 60 wt% (2) Filling amount, gas treatment amount, SV amount, temperature, pressure and average particle size are the same as in Example 2.

As can be seen from FIG. 6, the catalyst used in this example is COS.
Is absorbed and removed, and it can be seen from the SV value of this test condition that the activity is quite high.

<Effects of the Invention> According to the method for dry-removing the organic sulfur compound in the gas of the present invention, first, the first method using the absorbent carrying the secondary amine
By the process, mainly carbon disulfide is absorbed and removed at a low temperature with a long carrier life, and the carbonyl sulfide remaining in the second process is efficiently decomposed and absorbed at a low temperature by a decomposition / adsorbent carrying diglycolamine. Further, if necessary, the step of absorbing hydrogen sulfide is carried out in the third step, which is a dry method, is economically excellent, and can easily remove the organic sulfur compound in the gas.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention. FIG. 2 is a graph showing the absorption performance of CS ₂ and COS by the secondary amine impregnated material. FIG. 3 is a graph showing the absorption performance of CS ₂ and COS by the diglycolamine-impregnated material. Figure 4 shows COS with diglycolamine-impregnated zeolite.
3 is a graph showing the decomposition and absorption activity of the. FIG. 5 is a graph showing the decomposition activity of COS by diglycolamine-impregnated alumina. FIG. 6 is a graph showing the absorption of COS by diglycolamine-impregnated calcium silicate. Explanation of symbols 1 ... Gas impregnated with sulfur compound, 2 ... Heater, 3 ... Packing tower (first step), 4 ... Heater, 5 ... Packing tower (second step), 6 ... Packed tower (3rd step), 7 ... Purified gas

Claims (5)

[Claims] 1. A gas mainly containing carbon disulfide and carbonyl sulfide as an organic sulfur compound is treated with an absorbent,
In the method for removing the organic sulfur compound, a first step of mainly absorbing and removing carbon disulfide by using an absorbent obtained by supporting a secondary amine on a porous carrier, and diglycolamine on the porous carrier. Each step of the second step of decomposing the remaining carbonyl sulfide by using the catalyst supporting the catalyst and the third step of absorbing and removing the hydrogen sulfide produced when decomposing the carbonyl sulfide in the second step are included. A method for dry-removing an organic sulfur compound in a gas, comprising: 2. A gas mainly containing carbon disulfide and carbonyl sulfide as an organic sulfur compound is treated with an absorbent,
In the method for removing the organic sulfur compound, a first step of mainly absorbing and removing carbon disulfide by using an absorbent obtained by supporting a secondary amine on a porous carrier, and diglycol on the porous carrier A method for dry-removing an organic sulfur compound in a gas, comprising each step of a second step of absorbing and removing residual carbonyl sulfide by using an absorbent supporting an amine. 3. A gas mainly containing carbon disulfide and carbonyl sulfide as an organic sulfur compound is treated with an absorbent,
In the method for removing the organic sulfur compound, a first step of mainly absorbing and removing carbon disulfide by using an absorbent obtained by supporting a secondary amine on a porous carrier, and diglycolamine on the porous carrier. A second step of decomposing and absorbing and removing residual carbonyl sulfide by using an absorbing material supporting carbon; and a second step of absorbing and removing residual hydrogen sulfide generated during decomposition of carbonyl sulfide in the second step. A dry removal method of an organic sulfur compound in a gas, which comprises each of three steps. 4. A gas mainly containing carbon disulfide and carbonyl sulfide as an organic sulfur compound is treated with an absorbent,
In the method for removing the organic sulfur compound, a first step of mainly absorbing and removing carbon disulfide by using an absorbent obtained by supporting a secondary amine on a porous carrier, and diglycol on the porous carrier A method for dry-removing an organic sulfur compound in a gas, which comprises each step of a second step of decomposing and absorbing and removing residual carbonyl sulfide by using an absorbent supporting an amine. 5. The method for dry-removing an organic sulfur compound in a gas according to claim 4, wherein the porous carrier supporting diglycolamine used in the second step absorbs hydrogen sulfide.