JP3029861B2 - Pressure swing type H lower 2 S removal method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for removing H ₂ S in a gas, and more particularly to a method for removing H ₂ S from a process gas of a petroleum refining plant, and a method of removing H ₂ S from a gas produced by a coal gasification plant. H ₂ S removal, relates to a method which can be advantageously applied to H ₂ S removal from various fluids such as H ₂ S removal from a geothermal power plant off-gas.

[Conventional technology]

Poisoning of catalyst during process included in various process fluids,
H ₂ S causes corrosion of equipment and air pollution after release to the environment
Various processes have been proposed for the removal of water. Typical methods are (i) a method using a solid oxide type desulfurizing agent, and (ii) a liquid phase absorption using an H ₂ S absorbent. The method will be described.

(I) Solid desulfurizing agent method When H ₂ S is brought into contact with metal oxides such as zinc oxide and iron oxide at a high temperature of 100 ° C or higher, the metal is represented by Me, and the sulfurization reaction of MeO + H ₂ S → MeS + H ₂ O The S component is fixed.

When the H ₂ S concentration in the exhaust gas is low, the solid desulfurizing agent often adopts a disposable method without regeneration. On the other hand, when the H ₂ S concentration in the exhaust gas is high, the obtained sulfide is further subjected to high-temperature air conditions. Is removed as SO ₂ by the above reaction, and the metal is regenerated in the form of a metal oxide.

That is, in a steam reforming furnace, sulfides are recovered using metal oxides such as ZnO and FeO, and the used adsorbent is discarded after use without being regenerated. On the other hand, in coal gasification, a large amount of waste adsorbent is used. Therefore, S is removed as SO ₂ by an oxidation reaction using high-temperature air and reused.

(Ii) Liquid phase absorption method In the liquid phase absorption method, removal is performed using an absorbing solution having selectivity for H ₂ S such as triethanolamine. This method is further divided into chemical absorption method and physical absorption method.In the physical absorption method, after absorbing at a high pressure, the pressure is reduced to atmospheric pressure to release H ₂ S, and after absorbing at a low temperature in the chemical absorption method, H ₂ S is released at high temperature to regenerate the absorbing solution. This method has been used for desulfurization of process fluids in petroleum refineries.

[Problems to be solved by the invention]

Since H ₂ S is rich in reactivity and extremely harmful, its treatment is complicated. However, since the problems differ depending on the process, the above-mentioned (i) solid desulfurizing agent method and (ii) liquid phase absorption method Will be described separately.

(I) Solid desulfurizing agent method This method always requires operation at a high temperature. Normally, in the case of petroleum refining, steam reforming, coal gasification, etc., there is no thermal loss because the process fluid is hot, but when applied to low-temperature gas such as geothermal off-gas, a large amount of heat such as temperature rise of the process fluid is required. I need.

Also, when applied to the above high temperature process fluid, low concentration
In the case of H ₂ S, it is extremely expensive because it is disposable, and in the case of high concentration H ₂ S, the filler repeats the sulfurization reaction during treatment and the oxidation reaction during regeneration in a cycle of several hours,
The strength is significantly reduced.

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

Usually, the absorbing liquid shows alkalinity, and it is difficult to selectively absorb H ₂ S when the process fluid contains an acidic gas such as CO ₂ .

Further, the absorption liquid is expensive, and it is necessary to replenish the absorption liquid for a certain amount due to deterioration of the absorption liquid in the desulfurization step, scattering of the absorption liquid to the downstream side, and the like.

The present invention has been made in view of the above-mentioned state of the art, and aims to provide an H ₂ S removal method free from defects as in the related art.

[Means for solving the problem]

The present inventors have conducted intensive studies to solve the above problems,
After the gas containing H ₂ S is contacted with γ-alumina under relatively pressurized conditions and adsorbed and removed, the adsorbent is continuously regenerated by releasing the adsorbed H ₂ S under relatively reduced pressure conditions In this method, a small amount of H ₂ S was precipitated as a solid S component in the adsorbent during H ₂ S adsorption,
The adsorbent is deteriorated by continuous operation for about 4,000 hours, but it has been confirmed that the adsorbent can be removed and regenerated as gaseous S by raising the temperature of the adsorbent to 220 ° C or higher. Operation was confirmed.

The present invention has been completed based on the above findings,
The present invention relates to (1) a method in which a gas containing H ₂ S
- is contacted with alumina H ₂ S removed by adsorption, relatively decompression condition pressure swing H ₂ S removal process to regenerate the adsorbent and leave the H ₂ S adsorbed by (2) claim (1) In the long-term pressure swing type H ₂ S removal method in the step of, after the γ-alumina in which the S component is gradually accumulated is heated to a temperature of 220 ° C. or more to release the S component, the temperature is lowered and the long-term pressure swing H ₂ S removal process over a pressure swing H ₂ S removal process in combination with thermal regeneration to implement.

In other words, the present invention is based on the high-efficiency H ₂ S removal by the pressure swing adsorption method, and sublimates and removes the S component precipitated at a temperature rise once every several thousand hours, so that the adsorbent is not replenished for a considerably long time. Can be set.

This is an advantage of selecting γ-alumina as the adsorbent. As other adsorbents, for example, with a zeolite-based adsorbent, the adsorbed H ₂ S is difficult to be released in the decompression step, and furthermore, the removal of S content by raising the temperature Requires higher temperature and is not usable due to poor heat resistance. Activated carbon is also the same as zeolite as another adsorbent.

It is a kind of silica gel and zeolite, but almost 100w
At room temperature, silicalite, which is a t% silica compound, can be expected to have almost the same performance as γ-alumina at room temperature as an adsorbent for pressure swing adsorption. It is not suitable for extremely high temperature process fluids.

[Action]

In the present invention, after the H ₂ S-containing gas is adsorbed and removed at 0 to 400 ° C. at an adsorption pressure of at least atmospheric pressure using γ-alumina as an adsorbent, the regeneration pressure is reduced to less than atmospheric pressure for regeneration. Thus, H ₂ S can be continuously separated and removed. Between about setting of the suction pressure Pa and the regeneration pressure Pd, as Skarstrom in advocate pressure swing method for efficient separation is submitted, the purge gas amount G _P, the inlet gas amount G ₀ so It is natural that.

In addition, under a relatively reduced pressure condition, for example, a vacuum evacuation condition, a purge gas is introduced into the adsorption tower from the outside of the system by passing air or a purified gas so that the flow is countercurrent to that during the adsorption, and flows through the adsorption tower. This is a gas for rapidly reducing the partial pressure of H ₂ S in the adsorption tower to easily separate H ₂ S from the adsorbent. Assuming that the amount of gas at the inlet of the adsorption tower is G ₀ , the amount of H ₂ S removal gas is G ₁ , and the amount of purge gas is _GP , the purge rate R is Is defined by

Normally, since the purpose is to reduce the purge gas to concentrate H ₂ S at a high concentration, it is preferable to reduce _GP so that Pa / Pd ≧ 5 or more, and it is desirable to concentrate at least 5 times or more.

According to the method of the present invention, continuous regeneration for at least about 4,000 hours is possible, but the S component is gradually precipitated on the adsorbent, and the amount of adsorption is reduced, so that further operation becomes impossible. In the pressure swing method, since the cost of variation is extremely small, the adsorbent may be disposable. However, the present inventors have made an improvement in this regard as follows. It has been confirmed that the pressure swing operation can be further performed for several thousand hours after the temperature is lowered.

As described above, according to the present invention, the adsorbent which can be obtained for a considerably long time by repeating (i) the operation for 4,000 hours by the pressure swing adsorption method, (ii) the sublimation removal of S by the temperature rise of 220 ° C. or more and the subsequent temperature decrease. so that the H ₂ S removal technique no replenishment is provided.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG.

The main plant 1 generates a fluid containing 5,000 ppm of H ₂ S, and the fluid coexists with N ₂ : 90 vol% and CO ₂ : 9.5 vol%. The fluid exiting the main plant 1 is compressed from the passage 2 by the compressor 3 in a range of 1.2 atm. To 40 atm. The compressed fluid is filled with γ-alumina (boehmite) 6 from the passage 4 through the valve 5a. To the absorbed adsorption tower 7a.

In the adsorption tower 7a, H ₂ S is removed by the filled γ-alumina 6, and the purified gas is discharged from the valve 8a through the flow path 9 to the outside of the system.

At this time, the adsorption tower 7b is in a state in which the γ-alumina 6 is saturated with H ₂ S, the valves 5b and 8b are closed, and the gas is discharged from the valve 10b and the flow path 11 from the flow path 12 for regeneration at a pressure higher than the atmospheric pressure. ,
Under a reduced pressure by a vacuum pump 13 is reproduced below atmospheric pressure H ₂
S removal is measured.

At this time, when a part of the purified gas flows through the pressure reducing valve 15, the valve 16 and the valve 14b to the adsorption tower 7b under the countercurrent depressurization condition (that is, purge), the partial pressure of H ₂ S in the adsorption tower 7b rapidly increases. H ₂ S desorbs efficiently as it decreases.

Set the purge gas flow rate to G _P (Nm ³ / h) and the inlet gas flow to G ₀ (Nm ³
/ h), operating the adsorption pressure Pa (atm), if the regeneration pressure Pd (atm), the Skarstrom law, but _{G P ≧ Pd / Pa × G} 0 is a measure of 20% more of the values on the right side of the equation The actual purge amount at the time was used.

The desorbed H ₂ S gas that has passed through the flow path 12 and the vacuum pump 13
8 H ₂ S partial oxidation of a typical fixation of H ₂ S from the guided Klaus reactor 19, the solid S by Nachi Suwa _{H 2 S + 1 / 2O 2} → S ↓ + H 2 O. In this case, since the H ₂ S concentration of the gas at the inlet of the adsorption tower is reduced to 5 vol% or more with respect to the H ₂ S concentration of 5,000 ppm, the treatment cost is greatly reduced.

Thereafter, the purified gas from which H ₂ S has been removed is discharged from the flow path 20 to the outside of the system.

When this operation is continued, the surface of γ-alumina 6 gradually becomes S
Γ-alumina, which has been degraded by the S component, is passed through the valve 17 and the heater 18 to the adsorption tower 7c.
Let the purified gas of ℃ or more flow. By doing so, the S component on the surface of γ-alumina 6 is sublimated. This operation may be performed about once every 4,000 hours.

When the regeneration is completed, the heater 18 is turned off to flow the low-temperature gas to cool the adsorption tower 7c, and the γ-alumina of the other adsorption towers 7a and 7b is deteriorated, and the operation is required to wait until the above operation is necessary. .

In order to confirm the effect of the above embodiment, 3,000 Nm ³ / h
In order to remove H ₂ S from the process fluid gas containing H ₂ S gas, the pressure swing method according to the present invention uses 1.5 tons (0.5 tons / tower × 3 towers) of the adsorbent to raise the temperature and S sublimation. The test was carried out by attaching a device using the method.

In advance, in addition to γ-alumina as an adsorbent, Na-X type zeolite, activated carbon, silicalite, the S content accumulation of silica gel was examined, but Na-X type zeolite and activated carbon precipitate S component in a very short time, 300 ° C even when removing S content by heating
The above high-temperature regeneration was necessary. For this reason, it was judged to be inferior to γ-alumina, silicalite, and silica gel, and γ-alumina and silica gel were used as candidates for the examination with the above apparatus.

FIG. 2 shows the relationship between the temperature of the adsorption tower (x-axis) and the desulfurization rate (y-axis) under the pressure swing conditions at an adsorption pressure of 1.2 atm. And a regeneration pressure of 0.5 atm. The desulfurization rate is Defined. In the figure, γ-alumina is indicated by ○ and silica gel is indicated by ●.

γ-alumina exhibits nearly 100% desulfurization in a wide temperature range of 0 to 300 ° C. On the other hand, silica gel shows a high desulfurization rate comparable to that of γ-alumina at 60 ° C. or lower, but rapidly decreases at high temperatures.

FIG. 3 shows the relationship between the adsorption pressure (x-axis) of γ-alumina and the desulfurization rate (y-axis) at a temperature of 25 ° C., a purge rate of 10%, and a regeneration pressure of 1 atm.

The desulfurization rate reaches 100% at high pressure of 10atm.
It can be seen that _GP / G ₀ = 0.1 ≧ Pd / Pa = 0.1 was almost satisfied, indicating that H ₂ S was separated well in the high pressure range.

Fig. 4 shows the regeneration pressure of γ-alumina at 25 ° C, adsorption pressure of 1.2atm., Purge rate of 20% for regeneration pressure of 0.1atm. Or higher and purge rate of 0 for 0.1atm. Or lower (x-axis).
It shows the relationship between and the desulfurization rate (y-axis). When the adsorption pressure is set near atmospheric pressure, the desulfurization rate reaches 100% at a desorption pressure of 0.2 atm. Or less. 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 by sufficient vacuum regeneration.

〔The invention's effect〕

High desulfurization rates are achieved with very little power consumption with little replenishment of adsorbent.

[Brief description of the drawings]

FIG. 1 is a schematic view of the flow sheet of the present invention, FIG. 2 is a chart showing the relationship between the adsorption tower temperature and the desulfurization rate, FIG. 3 is a chart showing the relationship between the adsorption pressure and the desulfurization rate, and FIG. 3 is a table showing the relationship between the ratio and the desulfurization rate.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Araki 1-1, Akunoura-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Kazuaki Oshima 1-1, Akunoura-cho, Nagasaki-shi, Nagasaki (56) References JP-A-2-126936 (JP, A) JP-A-2-119921 (JP, A) JP-A-62-1110744 (JP, A) JP-A-59 -203625 (JP, A) JP-B 51-23470 (JP, B2) JP-B 48-20102 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 53/02- 53/053 B01D 53/34-53/72 B01J 20/08

Claims (2)

(57) [Claims] 1. A H ₂ S is contacted with relatively pressurized with pressure conditions γ- alumina gas containing by H ₂ S was adsorbed and removed, leaving the H ₂ S adsorbed at relatively reduced pressure condition A pressure swing type H ₂ S removal method, wherein γ-alumina is regenerated. 2. The γ-alumina in which the S content is gradually accumulated by the long-term pressure swing type H ₂ S removal method in the step (1) is heated to a temperature of 220 ° C. or more to release the S content. after, pressure swing H ₂ S removal method in combination with heat regeneration which comprises carrying out the re prolonged pressure swing H ₂ S removal method and cooled.