JPS5946554B2 - How to remove hydrogen sulfide - Google Patents

Description

[Detailed Description of the Invention] The present invention deals with hydrogen, methane, and
A method of absorbing and removing hydrogen sulfide contained in the ethane fraction (hereinafter referred to as the hydrogen fraction) and the propane/butane fraction (hereinafter referred to as the P, G, fractions) using an aqueous IJ solution. By adopting a two-stage absorption method and adjusting the make-up amount of sodium hydroxide and dilution water, the concentration of unreacted sodium hydroxide and produced sodium sulfide can be adjusted, saving sodium hydroxide and The present invention relates to a method for making a waste soda solution after absorbing hydrogen sulfide into a composition suitable for waste soda treatment using a wet oxidation method.

In the process of producing aromatic hydrocarbons through the hydrogenation reforming reaction of naphtha, various light gases are generally produced as by-products.

Of these, the hydrogen fraction, L, P, and G fractions are all available (each is separated and recovered).

However, this fraction contains hydrogen sulfide,
If this is not removed, the utility value for industrial and commercial purposes will decrease, which is not preferable.

In particular, since hydrogen fractions are often used as reaction raw materials in the petrochemical industry, the current standards are particularly strict, requiring a hydrogen sulfide content of 1 mol ppm or less.

On the other hand, the standards for P, G, and fractions are less strict than those for hydrogen fractions, and the hydrogen sulfide content is regulated at around 100 m/Ltpm.

Conventionally, hydrogen sulfide in such a light gas has been removed by bringing an alkaline aqueous solution into contact with the light gas to absorb hydrogen sulfide.

Moreover, as mentioned above, since the standards for hydrogen sulfide content are strict, it is necessary to increase the alkali content in the alkaline aqueous solution in excess and to ensure safe operation by bringing each gas fraction into contact with a fresh alkali aqueous solution.

As a result, not only is the operating cost soaring due to excess alkali, which is not only uneconomical, but also
The waste soda solution containing excess alkali causes soda cracking of melt-resistant materials such as 5US-306 in waste soda processing equipment using the wet oxidation method.

Furthermore, if excess alkali is saved, not only the hydrogen fraction, aliquots, P, G, and fractions are likely to be out of specification, but also problems will occur in the treated waste soda liquid.

In other words, when sodium hydroxide is used as the alkali, the hydrogen sulfide absorption reaction is 2NaOH + H2S- + Na2
There are reactions that follow the reaction formula of S+2H20 (A) and reactions that follow the reaction formula of Na S + H2S-+ 2 NaH8 (B), and since the alpha reaction is preferential, if there is not enough NaOH (dynamic A reaction will occur resulting in the formation of NaH8 in the waste soda.

When waste soda containing more NaH8 is treated by the wet oxidation method, NaH8 generates H2SO4 according to the reaction formula 2NaH8+402→Na2SO4+H2SO4@, which has the drawback of easily corroding equipment in the process.
absorption must be prevented.

Furthermore, if the Na2S content in the waste sorter becomes large, crystals tend to precipitate due to the low solubility of the substance, which may clog pipes in the process, which is not preferable.

The present invention solves all of the above-mentioned drawbacks, and its gist is to remove hydrogen sulfide contained in the hydrogen fraction and propane fraction, respectively, which are produced as by-products in the hydrogenation reforming reaction of naphtha. In the method, hydrogen sulfide in the hydrogen fraction is first absorbed with an aqueous sodium hydroxide solution to form a waste soda solution (■), and then the hydrogen sulfide in the propane fraction is absorbed using the waste soda solution (■) to form a waste soda solution (■). consecutive 2
A method using a stage absorption method, in which (1) hydrogen sulfide in the second stage propane fraction is removed using 2 Na
It follows the reaction formula of OH + H2S- + Na 2S + 2 H20 (A) and was prepared in an amount that satisfies the conditions to substantially prevent the reaction from proceeding to the reaction of Na 2S + H2S- + 2 NaH8 (B). Using an aqueous sodium hydroxide solution, remove hydrogen sulfide from the hydrogen production in the first stage according to the Hiroki reaction formula, and (2) reduce the amount of produced sodium sulfide contained in waste soda solution ■ and waste soda solution ■ by 7 weight each. % or less, and by carrying out the present invention, there will be no piping blockage due to Na2S, which is a conventional drawback, and no corrosion will occur in the treatment of waste soda liquid ( At the same time, it is possible to reduce operating costs by saving soda.

The present invention will be described in detail below with reference to the drawings, but the present invention is not limited to the method shown in the drawings.

In the figure, the hydrogen fraction is supplied to the soda washing tower 1 from the supply line 3, and after contacting the sodium hydroxide aqueous solution newly supplied from the supply line 8 and the circulating sodium hydroxide aqueous solution 9 in the tower, it is washed with water. It passes through column 2 and is recovered from line 4 as a purified hydrogen fraction.

On the other hand, the L, P, and G fractions are supplied from the supply line 6 to the lower stage of the soda washing tower 5, and are passed through the soda washing tower 5 within the tower.
After coming into contact with the soda liquid passing through the line 16 from the upper stage, it moves to the upper stage of the soda washing tower 5, where it comes into contact with the waste soda liquid ■, which is the bottom product of the tower 1 supplied from the tower 10, and is purified through the line 7. P, G, and fractions are recovered, and waste soda solution (2) flows out from the bottom of the column through line 12.

The sodium hydroxide in the aqueous sodium hydroxide solution supplied from the supply line 8 absorbs hydrogen fractions and P, G, and hydrogen sulfide contained in the fractions in the soda washing tower 1 and the soda washing tower 5. In addition, an amount sufficient to absorb P, G, and hydrogen sulfide in the fraction of the waste soda solution (2) is required.

In other words, the required sodium hydroxide must be supplied from 8 to satisfy this requirement.

In order to save excess sodium hydroxide here (
It is preferable that 0 balls be □.

That is, a safety factor of 50% or less for excess sodium hydroxide is sufficient.

If the condition (C) is satisfied, the H2S absorption reaction in each of the soda washing towers 1 and 5 follows the reaction formula (4), (the dynamic reaction is suppressed and NaH8 is substantially It will not be generated.

On the other hand, waste noda liquid I that absorbed hydrogen sulfide in the hydrogen fraction,
That is, in the figure, lines 9 and 10, P, G, waste soda liquid that has absorbed hydrogen sulfide in the fraction,
In other words, in line 12 in the figure, the amount of generated sodium sulfide contained in each waste soda liquid must be 7% by weight or less, and if it is thicker than this value, sodium sulfide crystals will precipitate in each waste soda. , lines 9, 10, 12
There is a high possibility that pipes such as 15 and 16 will be blocked.

There are no particular limitations on how to reduce the amount to 7% by weight or less, but (1)
(2) When the sodium hydroxide aqueous solution used has a high concentration, a method such as adding dilution water from the supply lines 13 and 14 as shown in the figure is used. is more preferable.

Hereinafter, the present invention will be specifically described by showing comparative examples and examples, but the present invention is not limited thereto.

Comparative Examples 1 to 2 and Example 1 Hydrogen fraction (
H2) 2T/H () 77 hours), L, P, G.

Fraction 3T/H was separated and collected.

Each fraction contained about 2000.1500 ppm of hydrogen sulfide.

The contained hydrogen sulfide was absorbed and removed using a 20% by weight aqueous sodium hydroxide solution in the apparatus shown in the figure.

In Comparative Example 1, sodium hydroxide aqueous solution and dilution water were each added at 80%
．． 0, Okg/H1 Comparative example 2 is the same (120, 0, Ok
g/H, Example 1 is 120.150.200 kg/H
It was used under the following conditions.

The composition and amount of waste nodal fluids I and (2) on each side are shown in the table.

In Comparative Example 1, the amount of sodium hydroxide aqueous solution added was as small as 80 kg/H (the value in formula 0 was 0.7, which was smaller than 1.0, so NaH8 was generated in the waste soda solution). .

On the other hand, in Comparative Example 2 and Example 1, (the value of equation 0 is 1.4
Therefore, NaH8 is not generated.

On the other hand, in Comparative Example 1.2, the generated Na2S contained in waste soda solutions (1) and (2) were both 7% or more, whereas in Example 1, it was 7% or less due to dilution.

Desulfurization operation was attempted for a long time (approximately one month) under these conditions, and as a result of treating the waste soda solution ■ with the wet oxidation method, in Comparative Example 1.2, Na2S crystals precipitated in the process and desulfurization operation was interrupted. was not possible for a long time, and in addition, in Comparative Example 1, the wet oxidizer was severely corroded.

On the other hand, in Example 1, there were no abnormalities in both the desulfurization process and the wet oxidation process, and long-term operation was possible.

It is necessary to satisfy this requirement by supplying the necessary sodium hydroxide from 8.

In order to save excess sodium hydroxide here (
It is preferable that CX be □.

That is, a safety factor of 50% or less for excess sodium hydroxide is sufficient.

If the condition (C) is satisfied, the H2S absorption reaction in each of the soda washing towers 1 and 5 follows the trapping reaction formula (the dynamic reaction is suppressed and NaH8 is not substantially produced). It turns out.

On the other hand, waste soda liquid that absorbed hydrogen sulfide in the hydrogen fraction■,
That is, in the figure, lines 9 and 10, P, G, waste soda liquid that has absorbed hydrogen sulfide in the fraction,
In other words, in line 12 in the figure, the amount of generated sodium sulfide contained in each waste soda liquid must be 7% by weight or less, and if it is thicker than this value, sodium sulfide crystals will precipitate in each waste soda. , lines 9, 10, 12
There is a high possibility that pipes such as 15 and 16 will be blocked.

There are no particular limitations on how to reduce the amount to 7% by weight or less, but (1)
(2) When the sodium hydroxide aqueous solution used has a high concentration, a method such as adding dilution water from the supply line 13.14 as shown in the figure is used. is more preferable.

Hereinafter, the present invention will be specifically described by showing comparative examples and examples, but the present invention is not limited thereto.

Comparative Examples 1 to 2 and Example 1 Hydrogen fraction (
H2) 2T/H () 77 hours), L, P, G - fraction 3T
/H was separated and collected.

Each fraction contained about 2000.1500 ppm of hydrogen sulfide.

The contained hydrogen sulfide was absorbed and removed using a 20% by weight aqueous sodium hydroxide solution in the apparatus shown in the figure.

In Comparative Example 1, the IJum aqueous solution and dilution water were each 80.0, and in Comparative Example 2, the same was 120 and 0.0.
0kg/H1 Example 1 is 12o, 150.200kMH
It was used under the following conditions.

The composition and amount of waste soda solution I and (2) on each side are shown in the table.

In Comparative Example 1, the amount of sodium hydroxide aqueous solution added was as small as 80 kg/H (the value in equation 0 was 0.7, which was smaller than 1.0, so NaH8 was not produced in the waste soda solution). Ta.

On the other hand, in Comparative Example 2 and Example 1, (the value of equation 0 is 1.4
Therefore, NaH8 is not generated.

On the other hand, in Comparative Example 1.2, the generated Na2S contained in waste soda solutions (1) and (2) were both 7% or more, whereas in Example 1, it was 7% or less due to dilution.

Desulfurization operation was attempted for a long time (approximately one month) under these conditions, and as a result of treating the waste soda solution ■ with the wet oxidation method, in Comparative Example 1.2, Na2S crystals precipitated in the process and desulfurization operation was interrupted. was not possible for a long time, and in addition, in Comparative Example 1, the wet oxidizer was severely corroded.

On the other hand, in Example 1, there were no abnormalities in both the desulfurization process and the wet oxidation process (long-time operation was possible).

Claims (1)

[Claims] 1. In a method for removing hydrogen sulfide contained in a hydrogen fraction and a propane fraction, which are by-produced by a naphtha hydrogenation reforming reaction, hydrogen sulfide in a hydrogen fraction is first removed with an aqueous sodium hydroxide solution. This method uses a continuous two-stage absorption method in which hydrogen sulfide in the propane fraction is absorbed using the waste soda liquid ■ to form a waste soda liquid ■, and (1) the second stage is used. Removal of hydrogen sulfide in propane fraction is 2NaO
H+H2S-)Na2S+2H20 (A), and the first step is carried out using an aqueous sodium hydroxide solution prepared in an amount that satisfies the conditions to substantially prevent the reaction from proceeding to Na2S+H2S→2NaH8(B). The removal of hydrogen sulfide in the hydrogen fraction of (
A method for removing hydrogen sulfide, which is carried out according to the reaction formula (4), and is characterized in that (2) the amount of generated sodium sulfide contained in the waste soda liquid (1) and the waste soda (2) is each 7% by weight or less.