RU2320399C1 - Method of removing hydrogen sulfide from gas - Google Patents

Abstract

FIELD: purification of gases.

SUBSTANCE: method comprises mixing hydrogen sulfide containing gas with a water oxidizing absorbing solution based on the bischofite having chromate of alkaline earth metal or its mixture with chromate of alkaline metal. The mixing is carried out at a Ph value of at least 7 in the temperature interval from the freezing point of the solution to +60°C. The exhaust absorbing solution is regenerated by air at a temperature above +25°C or active oxygen in the temperature interval from the freezing temperature of the solution to +25°C.

EFFECT: expanded functional capabilities.

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Description

The invention relates to the purification of gases, mainly hydrocarbon, and in particular to oxidative-liquid processes for the purification of gases from sulfur compounds to obtain elemental sulfur, and can be used in gas, oil, oil refining, chemical and other industries.

A known method of purifying gas from hydrogen sulfide, which consists in neutralizing hydrogen sulfide by mixing sulfur-containing gas with a liquid absorption solution containing ferric compounds as an oxidizing agent, and subsequent regeneration of the spent solution by mixing the latter with air (AS USSR No. 645687, B01D 53/14, 1977) (1).

The disadvantage of this method is the low speed of the processes of neutralization and regeneration, and, as a result, low economic efficiency and productivity, especially in field conditions.

Closest to the proposed invention is a method of purifying gas from hydrogen sulfide, in which, in addition to the above (1), bischofite is present in the absorption solution as a catalyst (RF Patent No. 2116121. Cl. B01D 53/14, 1998) ( 2).

The disadvantages of this invention are also: insufficiently high efficiency of neutralization of hydrogen sulfide and regeneration of spent sorbents; limited use for cleaning small volumes of gas with a low hydrogen sulfide content.

The technical task of the invention is to increase the rate of neutralization of sulfur compounds and the regeneration of spent sorbent, increasing the degree of purification of sulfur-containing gas at any content of sulfur compounds in the source gas, with minimal energy and other costs.

The problem is solved in that in a method for purifying gas from hydrogen sulfide, including mixing a hydrogen sulfide-containing gas with an aqueous oxidative absorption solution based on bischofite and subsequent regeneration of the spent absorption solution, it is new in that the aqueous absorption solution based on bischofite contains alkaline-earth chromate metal or its mixture with alkali metal chromate, mixing hydrogen sulfide-containing gas with an aqueous oxidative absorption solution is carried out at a pH of less than 7 units . in the temperature range from the freezing point of the solution to + 60 ° C, and the regeneration of the spent absorption solution is carried out with air at temperatures above + 25 ° C or active oxygen in the temperature range from the freezing point of the solution to + 25 ° C.

Thus, according to the invention, alkali and / or alkaline earth chromates are proposed as the main oxidizing agent of hydrogen sulfide. Aqueous solutions of chromates have strong oxidizing properties, which allows them to be used for the effective extraction of hydrogen sulfide from hydrocarbon gases. Chromate solutions have advantages over solutions in which other hydrogen sulfide oxidizing agents are used (iron hydroxide, iron chelate, etc.), namely:

- high reactivity to hydrogen sulfide;

- the absence of a solid phase in the initial solutions, which improves the operation of the pumps;

- solutions of chromates make it possible to partially extract carbon dioxide from the gas along with hydrogen sulfide, which eliminates the increase in alkalinity of the spent solutions;

- used solutions do not cause corrosion of equipment, since chromates are simultaneously highly effective inhibitors of corrosion processes;

- the use of aqueous solutions of chromates in a bischofite medium, which, at the same time, is a catalyst, helps to accelerate and increase the efficiency of the neutralization and regeneration reaction and, as a result, increases the efficiency of the entire cleaning process as a whole.

Bischofite is simultaneously an antifreeze agent, which allows the cleaning process to be carried out at any ambient temperature, from the freezing point of the solution (from minus 40 ° C) to + 60 ° C, which greatly expands the technological capabilities of the method.

The use of heated air (over + 25 ° C) or active oxygen (ozone or ionized oxygen) for regeneration significantly activates the sorbent recovery reaction, which, in turn, increases the efficiency of the method. At the same time, active oxygen is used at ambient temperature (from the freezing temperature of the solution to + 25 ° C), which simplifies and reduces the cost of the process.

The proposed method of purification of gas from hydrogen sulfide is as follows.

A bischofite-based aqueous absorption solution containing alkali and / or alkaline-earth metal chromate as the main oxidizing agent is mixed with a hydrogen sulfide-containing gas, in which case a gas-liquid dispersed mixture forms and the following main reactions with hydrogen sulfide:

In this case, the process of oxidation of hydrogen sulfide proceeds with the production of elemental sulfur and the formation of non-aggressive, non-toxic chromium hydroxide Cr (OH) ₃ , which precipitates in the form of an insoluble finely divided gray precipitate.

The chemistry of the neutralization reaction of sulfur compounds with chromate solutions shows that the presence of water-soluble chromates makes it possible to simultaneously extract not only hydrogen sulfide, but also partially carbon dioxide (carbon dioxide) from the processed gas, the amount of which depends directly on the amount of neutralized hydrogen sulfide and does not lead to additional chemical costs.

The process of neutralizing hydrogen sulfide in the presence of carbon dioxide by chromates will look as follows:

The gas purified from hydrogen sulfide is removed, and the spent absorption solution is restored by mixing it with heated atmospheric air or with active oxygen, which is used as ozone or ionized oxygen, and the spent sorbent is regenerated with oxygen according to the equation;

Thus, dispersed (water-insoluble) chromium hydroxide is regenerated to a soluble chromate salt, i.e. before the formation of the initial sorbent. The gas purification process proceeds with the release of elemental sulfur in the form of water pulp.

The total reactions of the process of gas purification from hydrogen sulfide (and partially from carbon dioxide) with a complex chromate-bischofite sorbent with the production of elemental sulfur and the release of carbon dioxide are expressed by the equations:

Thus, the developed gas purification process consists of two separate and sequential operations: neutralization of hydrogen sulfide with an oxidizing absorption solution and regeneration of the absorption solution with atmospheric oxygen and / or active oxygen, while the operation of neutralizing hydrogen sulfide is carried out at ambient temperature, i.e. from the freezing point, which, due to the presence of bischofite, is reduced to minus 40 ° C and to + 60 ° C, at a pH of less than 7 units. (to the point of transition to dichromates), since the processes of oxidation of hydrogen sulfide by chromates and the oxidation of spent sorbent (chromium hydroxide) are active in an acidic environment, and the lower the pH and the higher the temperature, the more efficient.

The spent sorbent is regenerated with heated air at temperatures above + 25 ° C or cold with active oxygen, from the freezing point to + 25 ° C.

The main physicochemical and technical parameters of the oxidative absorption solution are given below.

Density at 20 ° С, kg / m ³ 1100-1180 Dynamic viscosity at 20 ° С, MPa · s 1.5-2.8 pH less than 7 Freezing temperature, ° С, - (15 ÷ 40) Boiling point, ° С + 108-114 Corrosion activity to steel at 25 ° С, mm / year 0.002-0.02 The temperature regime of the neutralization process, ° C -40 ÷ + 60

Regeneration process temperature, ° С

- heated air above +25 - active oxygen below +25

The table shows specific examples of the method.

Table Values Options Options BUT B AT 1. Neutralization of hydrogen sulfide: a) reagents: - an aqueous solution of bischofite, density, kg / m ³ 1100 1150 1180 - chromates of alkali and / or alkaline earth metal, wt.% 12 9 7 b) the temperature of the solution, ° C from -15 to +60 from -30 to +60 from -40 to +60 c) the pH of the solution, units 6.5-6.9 6.2-6.6 5.8-6.4 2. Regeneration of the absorption solution a) air temperature + (25-90) + (35-90) + (45-90) b) temperature of active oxygen from -15 to +24 from -30 to +24 from -40 to +24

Claims (1)

A method of purifying gas from hydrogen sulfide, comprising mixing hydrogen sulfide gas with an aqueous oxidative absorption solution based on bischofite and subsequent regeneration of the spent absorption solution, characterized in that the aqueous absorption solution based on bischofite contains alkaline earth metal chromate or a mixture thereof with alkali metal chromate, mixing hydrogen sulfide-containing gas with an aqueous oxidizing absorption solution is carried out at a pH of less than 7 units. in the temperature range from the freezing point of the solution to 60 ° C, the regeneration of the spent absorption solution is carried out with air at temperatures above 25 ° C or active oxygen in the temperature range from the freezing point of the solution to 25 ° C.