JPH04187207A - Pressure swinging-type h2s removing method - Google Patents

Abstract

PURPOSE:To obtain high desulfurization efficiency with slight consumption of power by bringing a gas contg. H2S into contact with gamma-alumina under pressure to adsorb H2S, and desorbing the adsorbed H2S under reduced pressure to regenerate the gamma-alumina. CONSTITUTION:A gas contg. H2S is brought into contact with the gamma-alumina 6 packed in adsorption towers 7a-7c under pressure to adsorb the H2S and the adsorbed H2S is desorbed under reduced pressure to regenerate the gamma-alumina. The gamma-alumina 6, on which S is gradually deposited in the pressure swinging- type H2S removal process over a long period, is heated to a high temp. to release the S and then cooled, and the pressure swinging-type H2S removal is again performed over a long period. As a result, the adsorbent is hardly replaced, and high desulfurization efficiency is attained with slight consumption of power.

Description

[Detailed Description of the Invention] [Industrial Application Field] □The present invention relates to a method for removing ll2S from gas, and in particular, H2S removal from process gas of an oil refinery plant, H2S removal from coal gasification plant gas, 1 from various fluids such as H2S removal from geothermal power plant off-gas
The present invention relates to a method that can be advantageously applied to 428 removal.

[Conventional technology]

H□S is contained in various process fluids and causes poisoning of catalysts during processes, corrosion of equipment materials, and air pollution after release into the environment.
Various processes have been proposed for the removal of H2S, but the representative methods include (i) a method using a solid oxide desulfurization agent, and (ii) a liquid phase absorption method using an H2S absorbent. explain.

(i) Solid desulfurization agent method When a metal oxide such as zinc oxide or iron oxide is brought into contact with H2S at a high temperature of 100°C or higher, a sulfidation reaction of Men + H2S- + MeS 1820 takes place in 8 minutes, where the metal is represented by Me. is fixed.

When the concentration of 825m degrees in the exhaust gas is low, the solid desulfurization agent is often discarded without being regenerated. On the other hand, when the H2S concentration in the exhaust gas is high, a method is adopted in which the obtained sulfide is removed as S02 by further reaction under high temperature air conditions, and the metal is regenerated in the form of metal oxide. There is.

That is, in a steam reforming furnace, metal oxides such as ZnO and Pen are used to recover sulfides, and the adsorbents used are discarded after use without being regenerated. On the other hand, in coal gasification, a large amount of waste adsorbent is produced, so 8 minutes is removed as 802 by an oxidation reaction using high-temperature air and reused.

(ii) Liquid phase absorption method In liquid phase absorption method, +23
It is removed using an absorption liquid that is selective to This method is further divided into chemical absorption method and physical absorption method. In the physical absorption method, H2S is absorbed by high pressure and then reduced to atmospheric pressure.
In the chemical absorption method, after absorbing at low temperature, H is released at high temperature.
2S is released to regenerate the absorption liquid. This method is used for desulfurization of process fluids in petroleum refinery plants.

[Problem to be solved by the invention]

Since 82S is highly reactive and extremely harmful, its treatment is complicated, but since the challenges differ depending on the process, the methods described above (i) solid desulfurization agent method and (ii) liquid phase absorption method are recommended. I will explain it separately.

(i) Solid desulfurization agent method This method requires constant operation at high temperatures.

Normally, in oil refining, steam reforming, coal gasification, etc., the process fluid must be at a high temperature and there is no heat loss. However, when applied to low-temperature gas such as geothermal off-gas, a large amount of heat is generated by raising the temperature of the process fluid. Requires.

Also, when applied to the above-mentioned high-temperature process fluid, low concentration H
2S is usually disposable and therefore extremely expensive, and with high concentration H2S, the filler undergoes a sulfurization reaction during treatment and an oxidation reaction during regeneration over a cycle of several hours, resulting in a significant decrease in its strength.

(ii) Liquid phase absorption method Since this method requires operation at low temperatures, the above-mentioned high-temperature process fluid requires temperature-lowering operation by heat exchange, and if high-temperature operation is required downstream of the desulfurization process, Heat loss is a problem.

Normally, the absorption liquid exhibits alkalinity, and selective absorption of H2S is difficult when the process fluid contains an acidic gas such as CO2.

In addition, the absorption liquid is expensive, and deterioration of the absorption liquid during the desulfurization process,
A certain amount of absorption liquid needs to be replenished due to the absorption liquid scattering to the downstream.

In view of the above-mentioned state of the art, the present invention seeks to provide a H2S removal method that does not have the problems encountered in the prior art.

[Means to solve the problem]

As a result of intensive research to solve the above problems, the present inventors found that H.
We discovered a method to continuously regenerate the adsorbent by bringing a gas containing 2S into contact with T-alumina under relatively pressurized conditions to adsorb and remove it, and then removing the adsorbed H2S under relatively reduced pressure conditions. , Furthermore, with this method, H2
During S adsorption, a part of H2S is precipitated on the adsorbent as a solid state, and the adsorbent deteriorates after approximately 4,000 hours of continuous operation. It was confirmed that the adsorbent could be removed and regenerated within 8 minutes, and it was confirmed that the operation could be carried out without replenishing the adsorbent for a considerable period of time.

The present invention was completed based on the above findings, and the present invention consists of (1) bringing a gas containing H2S into contact with T-alumina under relatively pressurized conditions to adsorb and remove H2S; Pressure swing 2 H2S removal method (2) in which the adsorbed H2S is released under reduced pressure conditions to regenerate the adsorbent (2) In the pressure swing 2 H2S removal method that takes a long time in the process of claim (1), the method gradually removes the adsorbed H2S in 8 minutes. The accumulated T-alumina is heated to a relatively high temperature to release the S component, and then the temperature is lowered and the long-term pressure swing H2S removal method is carried out again.This is a pressure swing H2S removal method that combines thermal regeneration. be.

In other words, the present invention is based on highly efficient H2S removal using the pressure swing adsorption method, and by sublimating and removing the precipitated S by increasing the temperature once every several thousand hours, the adsorbent is not refilled for a considerable period of time. It was made to last.

This is an advantage of selecting γ-alumina as an adsorbent. When using other adsorbents, such as zeolite-based adsorbents, the adsorbed H and S are released during the depressurization process. Removal of the S content requires a higher temperature, and the heat resistance is poor, making it unusable. The same applies to activated carbon as another adsorbent.

It is a type of silica gel and zeolite, but about 10
Regarding silicalite, which is a 0wt% silica compound,
At room temperature, as an adsorbent for pressure swing adsorption, it can be expected to have almost the same performance as T-alumina for temperature raised regeneration, but the adsorption amount decreases significantly at temperatures above 50°C, making it unsuitable for use in high-temperature process fluids.

[Effect]

In the present invention, r-alumina is used as an adsorbent to adsorb and remove H2S-containing gas at a temperature of 0 to 400°C at an adsorption pressure above atmospheric pressure, and then the regeneration pressure is reduced to below atmospheric pressure for continuous regeneration. It is possible to separate and remove H2S. Regarding the setting of adsorption pressure Pa and regeneration pressure Pd, in order to efficiently separate the adsorption pressure, pressure swing method advocate Ska et al.
As submitted by rs-trom, purge gas amount G
, d Inlet gas amount G. Gp≧□ ・Go is 1 between
7. Ah. 2" Note that purge gas refers to air or purified gas that is introduced into the adsorption tower from outside the system under relatively reduced pressure conditions, such as vacuum exhaust conditions, so that the flow is countercurrent to that during adsorption. This gas is used to rapidly reduce the H2S partial pressure in the adsorption tower and facilitate the removal of 12S from the adsorbent.

The amount of gas at the inlet of the adsorption tower was 6°, the amount of H,S removal gas was 61,
Since the purpose is to concentrate the liquid, the smaller the amount, the better.
It would be desirable to set a/Pd≧5 and concentrate it at least five times.

Although continuous regeneration for at least 4,000 hours is possible with the method of the present invention, S content gradually precipitates on the adsorbent and the amount of adsorption decreases, making further operation impossible. □In the pressure swing method, the variable cost is extremely low, so the adsorbent can be used as a disposable material.However, as an improvement on this point, the present inventors proposed that the S content precipitated on the adsorbent at a high temperature of 220°C or higher is desorbed by sublimation. It has been confirmed that after the temperature has been lowered, pressure swing operation can be performed for several thousand hours.

As described above, according to the present invention, (i) operation for 4,000 hours by pressure swing adsorption method, (ii) sublimation removal of S by increasing temperature to 220°C or higher, and cooling after 9'. An adsorbent replenishment technique that can be repeated over a fairly long period of time will be provided.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to FIG.

Main plant 1 generates a fluid containing 5.000 p'pm of H2S, which contains 1% N2:90'VO, CO
2:9, 5 vo1% coexists. The fluid exiting the main plant 1 is compressed by the compressor 3 from the flow path 2 to a range of 2 atm to 40 atm, and the compressed fluid passes from the flow path 4 to the valve 5 a' and is converted into r-alumina (
The adsorption tower 7a is filled with boehmite) 6.

Adsorption tower? , in a, from 6 filled γ-alumina tanks l
'123 is removed, and the purified gas is then discharged from the lube 8a through the channel 9 to the outside of the system.

At this time, the adsorption tower 7b is saturated with alumina 6 with H2S, and the valves 5t) and 8b are closed, and the flow path 12 is opened from the valve 10b and the flow path H in the case of regeneration above atmospheric pressure.
During regeneration below atmospheric pressure, H28 is removed under reduced pressure conditions using a vacuum pump 13.

At this time, a part of the purified gas is passed through the pressure reducing valve 15, valve 16, and valve 14b to the adsorption tower 7b under countercurrent pressure reduction conditions (
That is, when purging), the partial pressure of 2S in the adsorption tower 7b rapidly decreases, and H2S is efficiently adsorbed.

Purge gas flow rate is Gp (Nrn3/h), inlet gas amount is Go (Nm3/h), adsorption pressure Pa (at+n
), regeneration pressure Pd (atm), Skarst
According to the ROM rule, G, ≧ Pd/Pa

The desorbed H2S gas that has passed through the flow path 12 and the vacuum pump 13 is transferred from the flow path 18 to the Claus reactor 19 where it is converted into solid S by partial oxidation of H2S, which is a typical fixation method for H2S, that is, ■2s+z02→S↓+H20. be guided. In this case, since the H2S concentration of the adsorption column inlet gas is 5.000 ppm, the volume is reduced and concentrated to 5 vol. 1% or more, and the processing cost is significantly reduced.

Thereafter, the purified gas from which H2S has been removed is discharged from the flow path 20 to the outside of the system.

If this operation is continued, 8 minutes will gradually precipitate on the surface of the T-alumina 6, so the purified gas at 220°C or higher will pass through the valve 17 and heater 18 to the adsorption tower 7c filled with the deteriorated T-alumina. to flow through. By doing this, 80% of the surface of the γ-alumina 6 is sublimated. This operation is 4. It suffices to do this about once every 00 hours.

When the regeneration is completed, the heater 18 is turned off and the low temperature gas is passed through to cool the adsorption tower 7c, until the time when the r-alumina in the other adsorption towers 7a and 7b deteriorates and the above operation becomes necessary. .

In order to confirm the effect of the above embodiment, 3.00Nm
In order to remove H2S from a process fluid gas containing H2S gas at The experiment was carried out using an apparatus that also uses a sublimation method at elevated temperatures for 8 minutes.

In addition to T-alumina, we previously tested the 8-minute accumulation ability of Na-X type zeolite, activated carbon, silicalite, and silica gel as adsorbents, but Na-X type zeolite and activated carbon are extremely difficult to accumulate in 8 minutes. Precipitation, 8 minutes removal by temperature increase is 30%
High temperature regeneration of 0°C or higher was required. Therefore, T-alumina and silica gel were judged to be inferior to r-alumina, silicalite, and silica gel, and T-alumina and silica gel were used as candidates for the study using the above device.

Figure 2 shows the adsorption pressure 1.2 atm, and the regeneration pressure Kani Q.
, 5 at+n, shows the relationship between adsorption tower temperature (X axis) and desulfurization rate (y axis) under pressure swing conditions. The desulfurization rate was defined as In the figure, r-alumina is indicated by a circle, and silica gel is indicated by a symbol.

γ-Alumina is 100% in a wide temperature range from 0 to 300℃
Shows similar desulfurization properties. On the other hand, silica gel exhibits a high desulfurization rate comparable to r-alumina at temperatures below 60°C, but the desulfurization rate rapidly decreases at high temperatures.

Figure 3 shows a temperature of 25°C, a purge rate of 10%, and a regeneration pressure of l a
T-alumina adsorption pressure (X axis) and desulfurization rate (
y-axis).

The desulfurization rate reaches 100% at high pressures of 10 atm or more, and S
Karstrom's law Gp/Go=0.1≧Pd/Pa
= 0.1, and it can be seen that the separation of 1''2S is performed well in the high pressure region.

Figure 4 shows a temperature of 25°C, an adsorption pressure of 12 atm, a purge rate of regeneration pressure of 0.1 atm, and a purge rate of 20.
%, 0.1 atm.The following shows the relationship between fresh alumina regeneration pressure (X-axis) and desulfurization rate (y-axis) with a purge rate of 0. When the adsorption pressure is set near atmospheric pressure, the desulfurization rate is 100% at desorption pressures below Q, 2 atm.
has reached. That is, it can be seen from FIG. 4 that if the fluid pressure is near atmospheric pressure, a high desulfurization rate can be obtained with sufficient vacuum regeneration.

〔Effect of the invention〕

High desulfurization efficiency is achieved with very little power consumption and almost no adsorbent replenishment.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the flow sheet of the present invention, Fig. 2 is a chart showing the relationship between adsorption tower temperature and desulfurization rate, Fig. 3 is a chart showing the relationship between adsorption pressure and desulfurization rate, and Fig. 4 is a chart showing the regeneration pressure. It is a chart showing the relationship between and desulfurization rate.

Claims (2)

[Claims] (1) A gas containing H_2S is brought into contact with γ-alumina under relatively pressurized conditions to adsorb and remove H_2S, and the adsorbed H_2S is removed under relatively reduced pressure conditions to regenerate γ-alumina. Pressure swing type H_2 characterized by
S removal method. (2) The γ-alumina that has gradually accumulated S content in the long-term pressure swing type H_2S removal method in the process of claim (1) is heated to a relatively high temperature to remove the S content, and then the temperature is lowered. A pressure swing type H_2S removal method using thermal regeneration, characterized in that the pressure swing type H_2S removal method is carried out again over a long period of time.