JPS59189925A - Selective removal of hydrogen sulfide - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for selectively removing sulfide (7J) from a gas stream containing carbon dioxide in addition to hydrogen sulfide. This invention relates to a method for selectively removing even small amounts of hydrogen sulfide by saponifying it with a polyvalent metal chelate solution and converting it into elemental sulfur. The present invention relates to the use of a special type of aeration flotation device to recover metal chelate from a metal chelate solution and regenerate (harden) the reduced metal chelate solution.

Vigorous chemical and industrial processes, such as wood pulping;
Removal of hydrogen sulfide from gas streams, such as waste gases generated during natural gas and crude oil production and oil refining processes, has become increasingly important to prevent air pollution. Hydrogen sulfide-containing gases are In addition to having a strong odor, these gases can harm plant growth, painted surfaces, and wildlife.
It also poses a serious threat to human health.

Government regulations are constantly imposing lower permissible values for the content of hydrogen sulfide released into the atmosphere, and are now under penalty of a complete ban on continuing operations such as plants producing gas streams containing hydrogen sulfide. Removal of virtually all hydrogen sulfide is an absolute necessity in many regions.

The amount of hydrogen sulfide in the process gas stream is not very high. US Patent No. 3.714'3J discloses that the flue gas obtained from the concentration of black liquor, which is the waste pulping liquid of the kraft pulping process, is 3-00~. xoo.

Contains ppm of hydrogen sulfide. However, the smell of hydrogen sulfide is detectable by humans at concentrations of about 0.0/ppm. Therefore, a highly efficient process for hydrogen sulfide is required to remove small amounts of harmful hydrogen sulfide from the process gas.

Carbon dioxide is also present along with sulfur and hydrogen as contaminants in the gas, such as gas from oil well drilling, flue gas, geothermal steam or tank steam. Not only is it desirable to remove H2S from such gases, it is also desirable to selectively remove hydrogen sulfide but not carbon dioxide. U.S. Patent No. 27ri19Aλ is sulfide 7
Describes a method for selectively removing hydrogen sulfide from an acid gas stream that also contains carbon dioxide using an alkaline solution, such as carbon dioxide, to remove acid gases such as CO2. Since the absorption of
. 07 to 0.01 seconds], absorption of 002 is prevented. However, the disadvantage of this method is that the alkaline solution
．． When regenerated by heating to 2°C (-!70'F), HS is produced, so the problem of disposing of I-123 was not solved, but simply postponed.

Hydrogen sulfide is removed in a redox system by contacting the hydrogen sulfide-containing gas with a solution of polyvalent cations (e.g. iron) anchored with a chelating agent (e.g. ethyl diaminetetraacetic acid or its sodium salt). It is also known that

In such a process, iron in the trivalent state oxidizes hydrogen sulfide to liberate sulfur, the iron is reduced to the λ-valent state, and the chelate solution is regenerated by aeration to return the iron to the trivalent state. Sulfur is recycled from the bath overnight using the foam flotation method.

For example, US Patent No. 03 M9L! No. 1 involves reacting the fluid with oxygen in the presence of an amine-containing metal amino acid chelate to convert hydrogen sulfide to sulfur and alkyl mercaptans to dialkyl sulfides, and then separating these from the metal chelate aqueous solution. One method is disclosed for removing hydrogen sulfide and alkyl mercaptans, however, the presence of oxygen in the reactants is disadvantageous because it converts sulfur to sulfate and thiomensulfate.

Furthermore, the reaction described above requires a relatively long contact time between the metal chelate solution and the hydrogen sulfide-containing gas stream, and if carbon dioxide is present in the gas stream, the contact time required for the above reaction will not produce much carbon dioxide. Carbon is absorbed into the reaction solution, lowering the pH of the solution and reducing reaction efficiency.

U.S. Pat. Disclosed below is a method for the removal of hydrogen sulfide and alkyl mercaptans from a gas stream which consists of oxidizing hydrogen sulfide to sulfur without substantially producing sulfur oxides. Alkyl mercaptans are oxidized to dialkyl sulfides under the same conditions.

In the invention of US Pat. No. 57, an attempt was made to prevent hydrogen sulfide from being oxidized to sulfur oxides by adding the above-mentioned acid salts. Muhly recognizes that sulfur oxides are formed by such reaction mixtures by reacting a hydrogen sulfide-containing gas stream with oxygen, so metal chelates tm
Addition of an acid salt to the medium solution is necessary. Furthermore, the patented process described above requires relatively long contact times for oxidation, and therefore sulfur<L
The presence of carbon dioxide in the hydrogen-containing gas stream also results in the absorption of 002 at relatively long contact times, resulting in an increase in the p of the solution.
H decreases and the efficiency of the system decreases.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an improved method for selectively removing hydrogen sulfide from a gas stream that also contains carbon dioxide together with the hydrogen sulfide.

SUMMARY OF THE INVENTION Hydrogen sulfide is oxidized to elemental sulfur by bringing it into contact with a metal chelate solution for an extremely short time of 0.0 g seconds or less, without allowing the metal chelate solution to absorb a significant amount of carbon dioxide. Methods exist for selectively removing hydrogen sulfide from streams.

Industrial N9 foam flotation conventionally used to separate the reduced metal chelate solution containing the exhaust gases and sulfur particles from the process of this invention to recover the sulfur from the solution and simultaneously separate the oil from the water. The reduced metal chelate is regenerated (oxidized) by bubbling oxygen or an oxygen-containing gas into the solution using a process device. The solid sulfur obtained is of high purity and can be sold after being separated from the solution (even without further chemical treatment).

The polyvalent metal chelate solution used in the method of this invention has the following general formula: % formula %) () (where n is a number from / to 3, ■ is selected from the class consisting of acetic acid groups and propionic acid groups, An amino acid represented by is selected from the class consisting of acetic acid groups or propionic acid groups, zero to one of the X groups is selected from the class consisting of Ω-hydroxyethyl groups, co-hydroxybrobyl groups, and R is ethylene, propylene or propylene, or cyclohexane or benzene in which two hydrogen atoms are substituted by nitrogen at the /1.2-position) and a polyvalent metal form a chelate. Preferably, it is a coordination pyramid.

As polyvalent metals, polyvalent metals in more than seven oxidation stages can be used, but iron, copper and manganese are preferred, with iron being particularly preferred. Polyvalent metals can reduce hydrogen sulfide to sulfur in a typical redox reaction, and at the same time the metal itself is reduced from a high valence state to a low valence state,
It must then be able to be oxidized by oxygen from a low valence state to a high valence state. Other polyvalent metals that can be used include lead, mercury, palladium, platinum, tungsten,
These include nickel, chromium, kohar), ram, titanium, tantalum, silconium, molybdenum, and tin.

Polyvalent metal chelates can be easily prepared by reacting a suitable salt, oxide or hydroxide of a polyvalent metal with a chelating agent in the acid form or its alkali metal or ammonium salt form in an aqueous solution. . Examples of chelating agents include ammonium chloride, amine acids derived from Ω-hydroxyalkylamines, such as glycine, diglycine (
aminodiacetic acid), trilotriacetic acid in NTA; Acetic acid such as EDTA
(ethylenecyaminetetraacetic acid), HEDTA (,2
= human a bovine diethylenediamine triacetic acid), DETPA
(diethylenetriaminepentaacetic acid); cyclic/, amine acetic acid derivatives of cordiamine, such as /, -monodiaminocyclohexane-N,N-tetraacetic acid; and U.S. Patent No. 3!rg0
There is an amide of polyaminoacetic acid disclosed in No. 9sO.

Since the reaction proceeds quantitatively at room temperature, it is not necessary to use a temperature higher than room temperature, but a temperature higher than room temperature may be used if desired. For example, if you are careful not to lose moisture through evaporation, you can treat it with high-temperature gas. Metal chelate solutions are stable up to approximately
Therefore, the reaction can be carried out at elevated temperatures up to at least about /θ0'C.

The pH of the system should be within the range of about 7 to about //. p
The upper limit for H is that metal chelate solutions generally have // higher pH
It exists only because it is not stable. But p
Since the oxidation of H2S to sulfur is more efficient when H is // higher, such metals can be used if the metal chelate is stable at higher pH than //. The most efficient range for a given combination of conditions is about g゛ to about /0. ! ;
CD pH. If the chelate solution is acidic, add an alkali metal hydroxide such as sodium hydroxide, an alkali metal, or ammonium carbonate or ammonium bicarbonate or ammonium hydroxide to the chelate solution to bring the solution into an appropriate 4-ji range. It is necessary to adjust the pH.

A gas-liquid contact system can be used that ensures good contact between the hydrogen sulfide-containing gas phase and the metal chelate-containing liquid phase. Any of a continuous flow system, an intermittent flow system, a parallel flow system, a countercurrent flow system, and a cross flow system can be used. A preferred gas-liquid contact system is a static mixer with internally fixed baffles, no external power required other than that necessary to create flow, and no moving members. A special baffle design allows mixing or dispersion of all flowing substances with a predetermined precision. Many static mixers of this type are commercially available. The contact time between the gas and liquid phases of the static mixer can be adjusted by adjusting the flow rate and the length of the static mixer.

The method of the invention is applicable to hydrogen sulfide-containing gas streams of any concentration, and even to very low concentrations of hydrogen sulfide-containing gas streams of a few ppm@degrees. The process of this invention is particularly useful when high concentrations (greater than 75 mulberry by weight) of carbon dioxide are present in the hydrogen sulfide-containing gas stream. Examples of gas streams containing hydrogen sulfide and carbon dioxide are sour gas and waste gas from petroleum refining, oil and tar sands processing, coal liquefaction waste gas, gas recovered during crude oil and natural gas production, cellulose pulp housing. effluent gases from sewage treatment plants, exhaust gases from Claus process equipment and hydrogen sulfide exhaust gases from other chemical and industrial processes.

The following equation describes the reaction when iron chelate is used as a catalyst to convert hydrogen sulfide to elemental sulfur: Absorption: H2S+, 20H-)S+, 2H20 Oxidation: u(Fe(X) )""+S--+S'-), 2[Fe(
X), :l” Reproduction: ,2[Fe-(X):)”10'/,2 o2+,2H+
−+, 2[: Fe(X):]””10H20 Total net reaction: H2S+/u○2−+ S' + H,0 In the above formula, X is a chelating agent.

The invention will be explained in more detail below with reference to the figures.

Referring now to the figures, it will be understood that the present invention is most applicable to a circulation system for removing hydrogen sulfide from a gas stream as illustrated in FIG. It is particularly useful in selectively removing hydrogen sulfide from a hydrogen sulfide-containing gas stream that also contains hydrogen sulfide. lI, /A and 7g.Each static mixer separator connection immediately follows the static mixer O1 (comprising a gas-liquid separator, 2.2.J) Ferrous Φ rate solutions above H7 are static mixer separated Device connection device/G,/
Flow uQ enters each of l and/or. The contact time between the gas phase and liquid phase in each static mixer 2θ is: , is maintained at 7 seconds or less, preferably 70 to 70 g Omi IJ seconds. This contact time is adjusted by adjusting the flow rates of gas and liquid streams into each individual static mixer, 2o, of constant length and internal diameter. In the contact zone of the static mixer, 2o, the hydrogen sulfide in the introduced gas is instantaneously oxidized to elemental sulfur by the iron-in-rate solution. Solid sulfur precipitates as a slurry in the processing solution. , the exhaust gas from stream 2A is taken off at the top of the separator, 2.2, of each static mixer separator linkage and sent to the first static mixer separator linkage-g, JO and 32, respectively. Each of these static mixer separator articulations 2g, 30r3- has a static mixer and separator structure equal to the first static mixer separator articulation device /A, 7g static mixer, 20 and separator, 22. . The gas from stream 26 is contacted with the metal chelate solution from stream 2 in each first static mixer separator connection preferably for about 10-g0 milliseconds. 2g each static mixer separator connection device.

, 30 and the exhaust gas taken out from the top of the three separators leaves each separator as flow 3, which becomes stream J6,
Sent to incinerator. Stream 3g is a bypass flow of Stream 3g which supplies exhaust gas 3g to the feed stream/co as needed on an ad hoc basis to provide the required residence time in the static mixer.

Often, the feed gas stream/2 is not of the correct volumetric flow rate to provide the desired residence time in the static mixer to selectively remove H7S.

Static mixer/9. /A and 7g in parallel to provide the required gas flow through each mixer by splitting the feed stream. Ben/ ? + / 5 H /? adjusts the feed gas flow to the desired static mixer.

The liquid and solid sulfur containing reduced metal ions from each separator 22 in the first and second static mixer separator connections passes through conduit 0 to conduit q, 2, which The liquid and solid sulfur are fed to a pair of tanks <z<< and 4" 4. This tank <z<z and 6 is generally referred to as the regeneration stage of the process of this invention. In the regeneration stage hydrogen sulfide is converted to sulfur. During oxidation, the reduced iron is regenerated (oxidized) to a highly oxidized state, and the sulfur particles suspended in a slurry are separated by foam flotation.The liquid enters tanks ++ and 'IA from conduits f, 2. The chelated iron contained in it is about 60% by weight of ferric chelate and DaO
It consists of ferrous chelate. Tanks ++ and 414 consist of a number of flotation tanks, preferably the 'WEMcOJ tanks sold by Envirotech Corp. In each type, an oxygen-containing gas such as air is carried into the liquid by the reduced pressure created during the movement of a rotor within the liquid. The oxygen-containing gas is dispersed into small bubbles that carry the suspended sulfur to the various tops and oxidize the reduced iron.

The regenerated solution is transferred from the tank DAG and 'IA' through conduits yg and SO, respectively, and to the surge tank s by conduit SΩ.
Sent to ti. The regenerated solution is returned to the static mixer separator connection via conduit, 21I.

Sulfur and residual metal chelate from tanks DAG and 4tA are transported to sulfur melter 36 via conduits sg and 10, respectively. The molten sulfur is extracted as flowing λ,
Any remaining iron chelate solution is returned to the surge tank sp via conduit 5.2. The solution for replenishing the iron chelate solution and the solution for pH adjustment are placed in tanks 611 and 6.
-・゛ -Maki Hiromoto As mentioned earlier, the preferred playback device used in this invention is the WEMC! This is a commercially available flotation tank sold under the trade name O. Such devices have been used to separate oil from oil and water mixtures. WEMC with now! It has been found that the O floating reactor works very efficiently as a reactor for gas-liquid phase chemical reactants, and can further separate solids present before and after the completion of the reaction. The preferred regeneration system, shown as tanks 6 in FIG. 1, consists of a number of flotation wash tanks, seven of which are shown as 70 in FIG. Mabuhi U.S. Patent No. 3 disclosing this floating method device, 'I? /, gzaO and 3.61I, o6? Please refer to the issue. Each floating phase has a tank 72 with an inwardly sloping lower sidewall 7
4'.

Each @7θ rotor 76 and a dispersion plate 7g surrounding at least the upper part of the rotor 76 and provided at a distance from the rotor periphery are provided. The distribution plate 7g is provided with a large number of fluid passage holes go drilled at uniform intervals along substantially the entire peripheral surface of the distribution plate 7g. The rotor 7A is fixed to the bottom of the shaft get and rotates about a substantially vertical axis.
For this purpose, it is supported at a distance above the bottom wall of tank λ. The rotor 76 is moved by a pulley g! by a motor gg supported above the top of the tank 7.2. It is rotated many times by the belt 6 and the belt gti. Standpipe 90 (ri shaft g,
rotor 760 from above the liquid level of the tank
It forms a conduit for air into the interior of the nearby tank 7.2.

Nine air intake holes are formed in the standpipe 90 above the liquid level of the tank 72, and the perforated dispersion plate hood? The dispersion plate 7g is attached to the upper end of the dispersion plate 7g and extends downward and outward.

A ferrous chelate solution containing suspended sulfur particles is placed in seven tanks of a 70-liter tank.

As the rotor 76 rotates, the rotational motion creates a swirl, forcing water to pass through the holes 30 in the distribution plate 7g,
In this way, reduced pressure is generated in the standpipe 90. Due to this reduced pressure, the air is drawn through the air intake I-hole and descends the standpipe 90 to be dispersed in the iron chelate solution, and the gas (air) is well mixed with the solution. As the gas-liquid mixture moves through the dispersion plate 7g at high speed, shear forces are applied and the gas is drawn out to form small bubbles. As small air bubbles float through the metal chelate solution, sulfur particles are carried with them to the surface of the bath 700. Bubble plate 96 removes sulfur particles concentrated on the surface of the metal chelate solution. Additionally, the iron chelate can be regenerated since air or other oxygen-containing gas oxidizes the ferrous ions to ferric ions, and this regenerated iron chelate solution is recycled to the static mixer for oxidation of the sulfide chloride. used.

The WEMOO flotation tank was found to be extremely effective in oxidizing ferrous chelate ions to ferric chelate ions. FIG. 31 illustrates the time required to regenerate (oxidize) substantially all of the ferrous ions for three types of regenerators: bubbling tanks, packed columns, and IMOOs. In the figure, the X marks are the values obtained from the bubble bubbling tank, the ○ marks are the values obtained from the packed tower (continuous blowing type), and the openings are the values obtained from VIEMOO. The WE114CO is operated at /20 Orpm and air is used as the oxygen-containing gas and dispersed in the solution. As can be seen from Figure 3, the WEMCO flotation tank regenerates the first chelate solution in 7 minutes to λ minutes, but the bubble bubbling tank oxidizes and regenerates all iron ions gqfy into ferric ions. It takes 50 minutes. For ordinary oil field gas, y-
Used for regeneration of solution from ferrous state. The packed column regeneration test is conducted in a flow system (continuous system), and various regeneration times can be achieved by changing the amount of liquid retained in the column. The ferrous ion concentration entering the packed tower was maintained at 70%. With a residence time of 70 minutes, the packed column absorbs 70% of the iron ions.
was regenerated to ferric state.

wgt, gco #play tank operates with maximum regeneration efficiency and has distinct advantages over other regeneration equipment.

If a WEMCO tank is used, an air blower is not required.

The reason for this is that the air is dispersed into the melt bed by the low-pressure swirl created in the standpipe by the rotor's oral flow. In addition, the WBMCO flotation device is used to reduce the percentage of solution that must be filtered as the yellow is concentrated by the bubbling action and the action of the gas flow sucked into the liquid and the shearing of the gas-liquid mixture through the dispersion plate. action and (d) result in highly efficient regeneration (oxidation) of the reduced metal chelate.

An aerator that creates an air flow through the liquid without the gas-liquid shearing effect of MEMOO (F2MOO is not very efficient at regenerating the reduced metal chelate. An example of an aeration device for oxidizing hydrogen sulfide in liquids such as US Pat.
It is described in No. 2gs.

As mentioned with respect to Figure 2, sulfur is
It is collected from the surface of each solution of the floating method 44M 70 that constitutes ZA. The sulfur particles and residual metal chelate solution are then heat treated at about 732°C (2'10°F) to melt the sulfur. Metal is especially HE! It is advantageous to use an excess of chelating agent when the iron is chelated with DTA. Excess amounts of chelating agent of 6% or more keep the iron stable in solution during gas-liquid contact, regeneration reactions, and sulfur melting to prevent it from precipitating as hydroxide. found. Loss of iron is thus prevented. HED
When using TA as a chelating agent, an excess of 6 molar is sufficient if the pH of the regenerated chelate solution is approximately g-, g, since an increase in OPH will reduce the stability of this iron chelate solution, p' A large excess of chelate solution as H increases is desirable. The amount in excess depends on the chelating agent used. Therefore, other iron chelates require some excess chelate to keep the iron stable under operating conditions. The molten sulfur has a density of 1,000 g Ogg/ca, which is approximately 9 times greater than the density of the residual chelate solution, so the molten sulfur sinks to the bottom of the melting vessel. The recovered sulfur (d Akane pure) can be recovered from the container and sold directly in the container. good.

Ferrous chelate solution chemistry. In addition to the iron chelate solution, oxidation co-agents including dihydroxybenzenes (hydroquinones), anthraquinones, and naphthoquinones (which represent an intermediate step between hydroquinone and dihydroxybenzene) are added to the metal chelate to further accelerate the formation rate. Can be added to solutions. Since anthraquinone is water-insoluble, it is used by partially sulfonating it to make it water-soluble. To speed up the oxidation rate of the reduced metal chelate, 7
-Anthraquinone disulfone p74 disodium (AD
Preference is given to using A).

Of course, various isomers of anthoshiquinone disulfone can be used. As shown in the first batch, jj! /The regeneration (oxidation) rate of iron ions is accelerated by the addition of ADA. The ADA is then oxidized by the it22))-containing scum of the regeneration stage. ADA also reacts with hydrogen sulfide to produce primary sulfur. However, it has been found that the presence of ADA in the gas-liquid contact zone of the stop mixer produces undesirable sulfur compounds.

Effect of ADA on regeneration of chelated iron solution *0
．． 39 to, 2 5 and 0.
+2j j ff /, 0
Left θ3, o s s /, 2
s so t, o
,5-,J yugθ,2! ;
G? +! ,0'
, 1-30 g 3 g,,
t/2θ, KoS 7za
g, θ/63, θ wog j,,?
210,! ,2
j, 3 29θ+2A; 7g
7.0 3g *The equipment used is a packed column. No V elements should be present in the contact area between the polyvalent metal chelate and the hydrogen sulfide-containing gas stream to prevent the formation of sulfates, thiosulfates and sulfur oxides. is important. This can be advantageously done by keeping the regeneration (oxidation) of the reduced iron chelate to 100% droplets so that there is no excess electrolyte in the regeneration solution.

The invention will be explained below with reference to examples.

-''- The method of the invention was used to selectively remove hydrogen sulfide from waste gas produced and drained in an oil field.

The hydrogen sulfide-containing gas stream under test was approximately 2% hydrogen sulfide, g g carbon dioxide, s % nitrogen, s g hydrocarbons, expressed as a volume factor.
It is of the composition of

The metal chelate solution tested is a mixture of ferric chloride and EDTA (ethylenediaminetetraacetic acid).

The mixture composition of the iron chelate solution used in the experiment is shown in Table λ. The pH of the solution was varied using sodium carbonate, sodium bicarbonate and sodium hydroxide.

/1 nhi / 3/6 g1.
1g #, 2 2ri 7--7J.

122,? /6'I&:b 1g /10
．． 297 90 u,? 3,4t 3/4
4ggb 1g '10 30 80 1J.

4tj-, A 3/64#A 1g, 20
j3;0 80 g, A! 7'3N,
11g6/g/, 2j---g, 7AA
i 3.27 30Arg 717 -- --
Lt B**9 -1 -------
-----g! RiA 10 3/!
, 'Igb 1g /i
---1 ter2'IB**//, /2
−− −− −− −− −− −−10
, 1* The carbonate addition procedure affected the pH.

**Not a fresh solution - Na20 to raise pH
03 was added.

/ / k41/C7+1' (J j pounds) oil field waste gas is passed through the 1st 7 pipes to collect the condensate, and then passed through the pressure regulator to reduce the pressure to ? kg/C-
rIL' (b pounds). The condensate formed due to the pressure drop in the pressure regulator was collected by passing through a second tramp and then the dried saturated gas was fed to the stationary mixer, and the metal chelate solution was also fed to the correction mixer.

Optimum required for selective absorption of hydrogen sulfide by varying the gas-liquid fusion time for absorption in a static mixer from po, oob seconds to o, o g seconds by varying the gas flow rate. The residence time was determined.

In order to observe the effect of pH on hydrogen absorption,
0o,b crt changed from 7.75 to lθ,2
t (/ /la inch) diameter and two lengths tcm (
, 2 inches) and 10 crn (3 inches)] were used in the experiment. Finally, the concentration of 2 keyaki (0,04j N
and o, t 3Nj iron chelate solution was used. Third
The table shows the combinations of these variables that were tested.

Table 3 to, oa rm(,2)
q, r t r o, o
bss O, o2 sCI! L(,2g,b
the law of nature ! 〃6ヲ,? o, oy
5cra(s) g, bq 2. ! r o,
obrq o, ol/, 10CIIL(+) g
-b7s o, obss o, og
1ocI! L(a)t, 72
2. s O,0bsA 0.0'l/
θCm('I) g, 7.2! ; 0.06! ;
7 0.011 10ctrt(Q) L! ;
j O,130g O,0:), ! ;c
rl(2) tJ,tO,/309
0, o, 2scm (2)? , o s O
, /30/, o o, os, tm(x) 5
1. ．． 2 5 o, obs/io o, Oa
5crrt(a) 10-a s O,o
bs/, 2 01) 04 jcm (J 10.2.
g,,30. θ6j The results of the above experiment are shown in graphs in FIGS. 4 to 6.

As can be seen from Figure 4 (iron concentration 0.OA s1+),
Hydrogen sulfide absorption increased for corresponding gas/liquid ratios as pH increased, indicating that the hydrogen sulfide absorption rate was primarily limited by the human tetraxyl ion concentration. At high pI (and high gas/liquid ratios), all ferric ions are instantaneously converted to ferric ions, explaining that the conversion of sulfur ions to sulfur is also instantaneous.

From Figure 3 (pH 2 g, s), the iron chelate concentration is 2
It can be seen that even if the amount of hydrogen sulfide is doubled, the amount of hydrogen sulfide removed from the gas stream will not be doubled. The higher the humidity of the iron chelate solution, the more hydrogen sulfide is removed, but the conversion (S removal) efficiency of the high iron chelate concentration solution is low, and dilute solutions are not economical. To determine an economical iron ion chelate solution concentration, pumping costs as well as chemical costs must be balanced against hydrogen sulfide absorption efficiency.

The liquid-gas contact time was varied to determine the optimal residence time in the static mixer required to selectively absorb hydrogen sulfide with minimal carbon dioxide absorption, and the results were analyzed in the sixth column.
Shown in the figure. In the figure, the Δ mark indicates an iron concentration of 0.01. ! ;N,
Solution of pHg,k, the seal indicates iron concentration 0.73N, pH
In the case of S solution, the circle mark indicates an iron concentration of 0. Ob! ;M, p1
'110. Data are shown for solutions of . FIG. 6 illustrates the dependence of carbon dioxide on the residence time of the three different solutions mentioned above. At pH 10.2, the maximum residence time required for selective absorption of hydrogen sulfide without absorption of carbon dioxide is 10-20 milliseconds (marked with a circle), whereas at the same iron concentration, at pHg. In the case of solution (△ mark), IIo-t
ro milliseconds. Both solutions are identical except that more sodium carbonate is added to the higher pH solution to obtain the higher pH. Figure 6 is 't: pH
g, 3; other solutions with − times the iron chelate concentration (n
CO by mark).

It also shows the absorption of For this solution, the maximum residence time for selective absorption of hydrogen sulfide without appreciable absorption of carbon dioxide is ~30 milliseconds. This latter solution contains different amounts of sodium carbonate. Iron chelate concentration has little or no effect on the absorption of carbon dioxide.
The dependence of carbon dioxide absorption on residence time is based on the carbonate concentration in this solution. - Using sodium hydroxide to adjust pH reduces solution stability. When sodium hydroxide is added to the iron chelate solution in any form, the pm locally increases and iron hydroxide precipitates. Iron hydroxide is difficult to dissolve in the iron chelate solution C used, and returns to the solution very slowly and returns to the chelate complex.

Study of mixing characteristics to determine complete mixing or force S achieved in the shorter mixer by doubling the static mixer length (pH of iron chelate solution =, L? & concentration is 0) .obskJ) was performed. Figure 7 shows that even if the length of the mixer is doubled, there is no difference in the absorption of sulfuric acid and hydrogen.
It is explained that complete mixing was achieved with an Ocm (Coinci) mixer.

Hydrogen sulfide removal rate is a function of the amount of liquid in contact with the gas, ie, the gas/liquid ratio. From FIG. 6, the removal of hydrogen sulfide (H2El removal) from the gas stream is an exponential function when the pH of the solution is 10%. Thus p
At H10 or above, a more economical gas/liquid ratio can maintain sufficient hydrogen sulfide absorption.Hydrogen sulfide-containing oilfield gas is separated into a diameter S, θ (2 inches) and a length 53 crrt (2/inch). I tried it using a static mixer. At a flow rate of 22 k MOFD of oilfield gas, the residence time in the static mixer was /S milliseconds. The iron chelate solution tested was supplied by Dow Chemical Company. This iron chelate solution contains iron I (R7DTA
(N-Hydroxyethylethylenediami/triacetic acid) chelate. This chelate solution contained 2.5% by weight of button. The iron chelate solution was transported into a static mixer at a rate of lot, l (2 g gallons) per minute.
This flow rate gives a gas supply rate of 2.2, t MOFD and a contact time of /S milliseconds at a gas/liquid ratio SO:/.

Sufficient sodium carbonate solution was added to the iron chelate solution to bring the pH to 7.6. As shown in Table 2, 2.
After 7 hours of use, the pH of the solution decreased to g, s. Additional carbonate was added to bring the pH back to 9.0, and after 77 hours of use the solution stabilized at pH g, g, while a 4s removal rate of qgt% from the gas stream was achieved. The effect of pH on hydrogen sulfide removal rate is summarized and shown graphically in Figure 9. ,A g,9 wa6. Gu Gu, O Wa, Ri g, g 9 Otsu, 'l 3. t, 7
7.0g, g g, co qs, o gt,
! ig, st, 9 L2 9/, g 'gu j,
7 9JL9 L/ q/, “l!
L7 1/Jg, 9g-79! ;J 3g, 2
I3. ri g, g 7J 9 11.
．． 4',! ;3-//! ;Jg
,! s-7,5g ll-,041g,'/ /
A, SgJ 7J g'1.0 '/'/
J 17g, l, 7. Og destination 0 gu/, gu/7. j-g,s? , A gb:s
Tiq,q ig,! 7.3
I6. ．． 3: Da/, 7 I9. A-g, 4
t 7.3 gg, g evening/, 7 I
2゜, 5 -q, o g, s qt,, s
Ta/, 7/wa, θ g+da 9! r, 6'j
O,g 2ri,o g,! r ---
G 7.7 39, OgJ q7. A
3g, da gua, θ gJ I
7. A I3.5 3.
za, j tabbJ Jg, ko
6g, 9g,! ;? ? J 3L'
/ 7za, do g, ko 96. o da7. - gza, g g, θ 9A, g
Gua, 2qza, g g, 0 97+, 2
! 0+, 2 10g, g Lo 9g, θ
Hiroko+s, //As can be seen from the foregoing, the present invention combines a gas stream containing even a large proportion of carbon dioxide together with hydrogen sulfide into a polyvalent metal chelate solution without appreciable absorption of Co2. Hydrogen sulfide can be selectively removed from the gas stream by contacting for a period sufficient to absorb the hydrogen sulfide. CO2
This is disadvantageous because it lowers the absorption pH. Fourth
As can be seen from the figure, even if the pH of the polyvalent metal chelate solution is slightly lowered, the absorption of hydrogen sulfide is significantly reduced. The efficiency of the method of this invention decreases significantly with decreasing pH.

The contact time between the hydrogen sulfide-containing gas and the polyvalent metal chelate solution is preferably limited to less than about g o milliseconds (θ, where θ is seconds). Otherwise, absorption of carbon dioxide by the chelating solution will lower the pH of the chelating solution.

[Brief explanation of drawings]

Figure 1 is a schematic explanatory diagram of the process for removing hydrogen monoxide from a gas stream according to the method of the present invention/embodiment, and Figure 2 is a partial longitudinal section of a regenerator used in the process shown in Figure 1. Figure 3 shows a comparison graph of the relationship between the regeneration rate (a) to trivalent iron and the regeneration time when the regeneration equipment shown in Figure 2 is compared with other types of regeneration equipment. is the pH of the iron chelate solution
Figure 5 shows a graph illustrating the change in hydrogen sulfide removal rate (%) from a gas flow;
Figure 44 is a graph illustrating the influence of the residence time of the gas flow in the static mixer on the biliquefied carbon absorption rate when using an iron chelate solution, and Figure 7 shows the effect of hydrogen sulfide removal over the length of the static mixer. a diagram showing a graph illustrating the impact on rates;
Figure 7 is a graph explaining the effect of gas-liquid ratio on hydrogen sulfide removal rate, and Figure 7 is a graph explaining the effect of pH change on hydrogen sulfide cleaning removal rate (not as effective as rust). Yes ◇ In the diagram: l Yu...Hydrogen sulfide-containing gas flow (preparation gas flow)/I6,7g... (1st) static mixer separator connection device, 20...static mixer, here...gas liquid annex,
Moss... Stream or conduit (of ferrous chelate solution) 1
．． 26. Stream [from (7th) static mixer separator linkage] 2 g. 30.32...(2nd) static mixer separator connection device, 3'l...2nd static mixer separator connection device Exhaust gas from the separator, 36...Flow sent to the incinerator of the exhaust gas 3 g, 3 g・・Bypass flow of exhaust gas 31/-, yo,
p: l... (reduced metal ion-containing liquid and solid sulfur transport) conduit, l. Hiro6 tank (regeneration stage) lIg, so... (regeneration solution) conduit, S2... conduit, Sg... surge tank, S6
...Sulfur melting equipment, sg, to... (sulfur + residual chelate transport) conduit, 6.2...flow of molten sulfur, 6 da...tank for replenishing iron chelate solution, 66...p solution tank for PI adjustment , 70...flotation tank (flotation washing tank or tank), 7
:t...tank, 7 pieces...1 side wall part, 76...rotor, 7g...dispersion plate, 1go/one hole, g2...shaft,
gti, exposed belt, gs, gb, pulley, gg, motor, qo, standpipe, 9yu, air intake hole, q17, hood, q6, foam board. F +a, 4 11"7/31 Shibabekita 100"F,G,, h"x/liquid ratio 100 [90 0 0

Claims (1)

[Claims] l A gas stream containing carbon dioxide in addition to hydrogen sulfide is combined with a polyvalent metal chelate solution and the polyvalent metal chelate solution is sufficient to oxidize the hydrogen sulfide to elemental sulfur. A method for selectively removing hydrogen sulfide from a gas stream containing carbon dioxide in addition to hydrogen sulfide by contacting the gas for an absorbing amount of carbon dioxide. The method according to claim 1, wherein the polyvalent metal is iron. 3. The method according to claim 1 or 1, wherein the chelate is ethylenediaminetetraacetic acid. 3. The method according to claim 1 or 2, wherein the chelate is N-hydroxyethyl-ethylenediaminetriacetic acid. 5 The contact time between the gas flow and the metal chelate is approximately o,oot
A method according to any one of claims 1-g, wherein the time period is from 1.0 seconds to about 0.03 seconds. 6. The method according to any one of claims 1 to 5, wherein the polyvalent metal chelate solution has a pH of 7 to 1/l. 7. The method according to any one of claims 1 to 3, characterized in that the polyvalent metal chelate is produced by passing an oxygen-containing gas through the polyvalent metal chelate solution after oxidation of hydrogen sulfide. 8. The method of claim 7, wherein an oxygen-containing gas is bubbled into the clam solution, and the sulfur particles are carried to the surface of the solution by the bubbles. 7 Patent for dispersing gas into a polyvalent metal chelate solution by passing an acid-containing gas through the solution by forming a low-pressure zone below the surface of the solution and inducing an oxygen-containing gas into the low-pressure zone. Claim 7 or 3
The method described in section. 10. Patent for separating sulfur particles from a solution, melting the sulfur particles, and separating molten yellow from the remaining solution;
The method described in Section g. //The method according to any one of claims 7 to 9, wherein an oxidation aid is added to the solution in order to increase the regeneration efficiency of polyvalent gold iron gyrate. 2. The process according to claim 1, wherein the e-forming mJ agent is a C-forming agent different from the group consisting of hydroquinone, anti-quinone, naphthoyanone and mixtures thereof.