JP2000265185A - Suppression of foaming of amine solution in amine treating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a substance causing foaming, suppress foaming of an amine solution and carry out stable operation of whole purification apparatus by treating an alkanolamine solution after chemical absorption treatment with an anion exchange resin before recycling the alkanolamine solution to hydrogen sulfide treating process. SOLUTION: When removing hydrogen sulfide from a gas (sour gas) containing hydrogen sulfide generated in petroleum purification process or LPG gas containing hydrogen sulfide by chemical absorption with a solution of an alkanol amine such as monoethanolamine, the alkanolamine solution after chemical absorption treatment is treated with an anion exchange resin such as a resin having a basic group such as a (substituted) amino group before recycling the alkanolamine solution after chemical absorption treatment to a hydrogen sulfide treating process. Furthermore, it is preferably to provide a process for treating the alkanolamine solution with the anion exchange resin in a recycle line of process for removing hydrogen sulfide by chemical absorption or in its bypass line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the chemical absorption of hydrogen sulfide from a gas containing hydrogen sulfide (sour gas) or LPG gas containing hydrogen sulfide generated in a petroleum refinery using an alkanolamine (aqueous solution). The present invention relates to a method for treating an amine by removing a foaming causative substance or a foam causative substance precursor from the amine solution to suppress foaming.

[0002]

2. Description of the Related Art In petroleum refining, sulfur in oil is generally removed in the form of hydrogen sulfide by hydrodesulfurization. The hydrogen gas containing hydrogen sulfide discharged from the desulfurization device is chemically absorbed and removed from the hydrogen sulfide in the amine treatment device, and is recycled to the reactor again. Further, since hydrogen sulfide is also contained in the fuel gas discharged from a distillation apparatus, a catalytic cracking apparatus, or the like, hydrogen sulfide is removed in an amine treatment apparatus. These refinery gases containing hydrogen sulfide are called sour gas, and must be treated with an amine treatment device in order to prevent corrosion and pollution. Further LPG
Also contains hydrogen sulfide, and hydrogen sulfide is removed in an amine treatment device to be commercialized.

[0003] The amine treatment apparatus is an apparatus for removing hydrogen sulfide in sour gas or LPG by chemical absorption into the amine solution by countercurrent contact of sour gas or LPG with the amine solution.

The amine solution is subjected to an absorption step of absorbing hydrogen sulfide or the like (a weakly alkaline amine solution such as methyldiethanolamine and hydrogen sulfide or carbon dioxide form a salt by an exothermic reaction, that is, under low temperature and high pressure. Process)
And a regeneration process to dissipate absorbed hydrogen sulfide
Step of promoting the amine regeneration reaction at low pressure: Specifically,
The reboiler steam heats the column at about 100 to 110 ° C. and at the bottom of about 120 to 130 ° C. ) Is repeatedly used. (The outline and operation management of the amine treatment device are described in “PETROTECH,
Vol. 8, No. 2 (1985), pages 152 to 157, "Acid Gas Removal Device". ).

[0005] However, the circulating amine solution may cause foaming in the amine treatment apparatus. The foaming of the amine solution not only cannot maintain the stable operation of the equipment, but also affects downstream equipment such as sulfur recovery equipment due to entrainment of the amine solution into the cleaning gas or the cleaning LPG caused by the foaming in the countercurrent contact absorption tower. It is feared that the operation may become unstable and the product may be out of specification.

In order to suppress the foaming of the amine solution, at present, a measure is taken by adding a trace amount of a higher alcohol-based or silicone-based antifoaming agent to the circulating amine solution.

[0007] However, addition of the defoaming agent requires not only labor and cost but also, if not performed properly, may affect the operation of an upstream device that generates sour gas or LPG.

Further, excessive addition of an antifoaming agent may cause foaming of an amine solution caused by a degraded antifoaming agent (above, a review of operational problems and countermeasures of an amine treatment apparatus is given below). "HYDROCARBON
PROCESSING, April 1995 p41
~ 50 "Amin plant troubleshoes
Otting and optimization ". )).

[0009]

The substances causing foaming of the amine solution include corrosive substances such as iron sulfide generated by corrosion of the apparatus by hydrogen sulfide, in addition to those caused by the above-mentioned defoaming agent. A heat-stable amine salt (HSAS :) which cannot be regenerated in a regeneration step generated by the reaction of an amine solution with impurities such as an organic acid or SOx brought in from a purification device such as a fluid catalytic cracking device (hereinafter, FCC).
Heat Stable Amine Salts),
Light oils brought in from the distillation apparatus can be considered.
At present, as a method for removing these substances, a mechanical filter made of chemical fiber is used for impurities such as iron sulfide, and an activated carbon filter is used for oil. A small amount of a neutralizing agent (a strong alkaline aqueous solution) is added to HSAS to control the HSAS concentration in the amine solution. However, the HSAS concentration management requires labor such as maintenance as in the case of the above-described antifoaming agent. The problem to be solved by the present invention is to solve the above-mentioned drawbacks of the prior art and to reduce the foaming causing substances in the amine solution by HS.
It is an object of the present invention to provide a method for effectively removing an anionic substance such as an organic acid and the like, which is a cause substance of AS, and suppressing foaming of an amine solution.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the circulating amine solution was passed through a container filled with an anion-exchange resin to form a foam-causing substance or foam. By removing the causative precursor,
The inventors have invented an epoch-making method for suppressing foaming of an amine solution in which foaming of the amine solution can be suppressed.

[0011] Among the causative substances in the amine solution, HSAS, which cannot be regenerated in the regenerating step, is generated by a reaction between the amine solution and impurities having a high acidity. Organic acids, SOx, and the like can be cited as impurities having a high acidity as a precursor of a foaming substance. These include off-gas from an FCC device and LP.
There are many in G.

These foam-causing substances and foam-causing substance precursors are trace components in the amine solution, and it is difficult to grasp the detailed structure. However, it is believed that these substances become anions at a significant rate in the amine solution.

As a method of applying the present invention to an amine treatment method or apparatus in a refinery, an amine exchange resin filling tank is provided in a circulation line of a regenerated amine solution to treat the amine solution.
In addition to adsorbing and removing the foam-causing substance or foam-causing substance precursor and reusing it, part of the amine solution bypassed from the recycled amine solution circulation line is treated by installing an anion exchange resin filling tank in the bypass line. Then, a method of adsorbing and removing the foaming causative substance or the foaming causative substance precursor and returning the foaming causative substance to the circulation line again is considered. Preferably, a method of removing contaminants and oils with a mechanical filter or an activated carbon filter, removing an anionic substance such as an organic acid in a container filled with an anion exchange resin, and then returning the mixture to the circulation line again is preferable.

The amine treatment apparatus employed in the present invention can be applied to all apparatuses generally used in the petroleum refining industry. In general, various amine solutions are used in an amine treatment apparatus, for example, monoethanolamine (MEA), diglycolamine (DGA), diethanolamine (D
EA), diisopropanolamine (DIPA), triethanolamine (TEA), methyldiethanolamine (MDEA) and the like are used, but the present invention is applicable to any amine solution. Normally, the initial concentration of the circulating amine aqueous solution depends on the operating conditions and the type of alkanolamine to be used, but is about 25% to 55% by weight. Since problems such as a decrease in heat transfer efficiency and an increase in pump load occur, the amine solution is replenished so as to maintain the initial circulating concentration suitable for each device.

As the anion exchange resin used in the present invention, a resin having a basic group such as an amino group, a substituted amino group, and a quaternary ammonium group, which are generally used, can be used. However, the amine solution must contain oil,
In consideration of acidity and acidity, it is preferable to use one having high durability against acids and organic solvents. For example, those having a quaternary ammonium group are the most basic, and those having a polystyrene base as a base are preferable in that they have durability against acids and organic solvents.

The conditions for the adsorption treatment with an anion exchange resin are preferably a temperature of 20 to 60 ° C. and a pressure of 0.2 MPa or less. Optimal adsorption treatment conditions are determined by the usable temperature range of the anion exchange resin to be used, the operating conditions of the amine treatment apparatus to be adopted, and the like.

[0017]

EXAMPLES The present invention will be described in more detail with reference to Examples. (Example 1) As an amine solution, an amine solution (300 ml) circulated and used in an amine treatment device at a refinery was used. The amine solution was obtained by diluting an alkanolamine containing MDEA as a main component with pure water.
% By weight. Anion exchange resin (strongly basic ion exchange resin having polystyrene-based quaternary ammonium group:
(Amberlite IRA-900 manufactured by Organo)
Is activated with a 1 mol / l aqueous sodium hydroxide solution,
The wastewater was washed with ultrapure water until neutral. The amine solution was filtered with a 5 μm filter paper to remove impurities. The mixture was placed in a container so that the volume ratio of the amine solution to the anion exchange resin was 2: 3, and the mixture was stirred for 30 minutes. The amine solution separated from the anion exchange resin was further filtered through a 5 μm filter paper to remove impurities. The amine concentration of the amine solution treated with the ion exchange resin was 23% by weight. 200 of this amine solution
The foaming property and the defoaming property were evaluated using the foaming test apparatus shown in FIG. As a result, the foam amount 620
ml and the defoaming time was 10 seconds.

The foaming and defoaming test methods for the amine solution are not specified in JIS or the like. Therefore, JIS
K 2518 (petroleum products-lubricating oil-foaming test method),
Known "Testing method for foaming and defoaming" [Oil Chemistry No. 42, No. 10
No. (1993) p. 737 to 745].
The following measurement method was determined (see FIG. 1). (1) 1000m containing 200ml (1) of amine solution
1. Place the graduated cylinder (2) in the thermostat (3) so that the amine solution is kept at 50 ° C. (2) A diffuser stone (4) is installed at the center of the bottom of the measuring cylinder, and air is supplied at a pressure of 0.6 kg / cm ² G at 3 L / min. (3) After about 5 minutes, confirm that the foam height is kept constant, and measure the foam volume. The foam volume is a value obtained by subtracting the amine solution volume of 200 ml from the scale reading (→ foamability). (4) Remove the diffuser stone from the graduated cylinder and measure the time taken for the foam to disappear and the surface of the amine solution to be seen (antifoaming property).

(Example 2) The amine solution treated with the anion exchange resin in Example 1 was treated again with a new anion exchange resin (corresponding to an increase in the length of the treatment tower). The amine concentration was 12% by weight.) Was evaluated for foaming and defoaming properties. As a result, the foaming amount was 450 ml and the defoaming time was 7 seconds.

(Comparative Example 1) Using the circulating amine solution before the anion exchange resin treatment of Example 1, foaming and defoaming properties were evaluated. As a result, the foaming amount was 950 ml, and the defoaming time was 19 seconds.

(Comparative Example 2) When an unused amine solution containing no foam-causing substance was used (Comparative Example 3 examined the case where a foam-causing substance was included), the amine concentration was reduced by the amine concentration. In order to confirm that the decrease was not caused by the decrease in the amine solution, an unused amine solution before dilution (equivalent to before the use of the treatment step; amine concentration: 95% by weight) was diluted with ultrapure water (amine concentration: 49% by weight). %) (Corresponding to the use of the treatment step), and the diluted amine solution is treated with an anion exchange resin. The foaming and defoaming properties of the amine solution before use and the amine solution after use were evaluated. as a result,
Before the treatment, the foaming amount was 650 ml and the defoaming time was 15 seconds, and after the treatment, the foaming amount was 650 ml and the defoaming time was 11 seconds. That is,
If the amine concentration is low in the amine solution that does not contain the foam-causing substance (assuming the concentration is low and the amine has been consumed in the processing step), the amine solution is treated with an anion exchange resin. However, it was confirmed that there was no change in the foaming and defoaming properties as compared with the unused amine solution.

Comparative Example 3 In Examples 1 and 2, the amine concentration of the amine solution was reduced from 41% by weight of circulating amine to 23% by weight of Example 1 and 12% by weight of Example 2. Therefore, even in the case where the foaming agent is contained, the circulating amine solution (including the foaming agent) is added to ultra-pure water at 23% by weight in order to confirm that the decrease in the foaming property of the amine solution is not caused by the decrease in the amine concentration. And the amine solution diluted to 12% by weight was used to evaluate the foaming and defoaming properties. As a result, the foaming amount was 880 ml and 9 respectively.
20 ml and the defoaming time was 15 seconds and 21 seconds.

From these results, it was confirmed that the treatment with the anion exchange resin was effective only for the circulating amine, and that the amine concentration did not affect the foamability and foam stability. Therefore,
It is considered that the foaming cause substance or the foaming cause substance precursor in the circulating amine solution was adsorbed by the anion exchange resin treatment, and foaming was suppressed.

[0024]

The foaming of the amine solution can be suppressed by removing the foaming causative substance or the foaming causative substance precursor by treating the amine solution containing the foaming causative substance or the foaming causative substance precursor with an anion exchange resin. Without injection of a defoamer, stable operation of not only the amine treatment unit but also the entire refinery unit at the refinery can be expected.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a foaming tester.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Amine solution 200ml 2 ... 1,000ml measuring cylinder 3 ... Constant temperature bath 4 ... Diffuser stone 5 ... Dry gas meter 6 ... Flow meter 7 ... Pressure gauge 8 ... Valve

Claims (2)

[Claims] 1. A gas (sour gas) containing hydrogen sulfide generated in a petroleum refining process or an LPG containing hydrogen sulfide
A method for chemically absorbing and removing hydrogen sulfide from a gas using an alkanolamine solution, comprising a step of treating the amine solution after the chemical absorption treatment with an anion exchange resin before circulating the amine solution in a hydrogen sulfide treatment step. 2. The method according to claim 1, wherein the step of treating with an anion exchange resin is provided in a circulation line or a bypass line of the step of chemically absorbing and removing hydrogen sulfide with an alkanolamine solution.