DE1815137C3 - Process for leaching acidic components and organic sulfur compounds from fuel and synthesis gases - Google Patents

Description

ι alcohol.

2. The method according to claim 1, characterized in that the absorption solution 0.01 to 0.2 mol per liter of an acid with a pK value of 7 to 11 can be added.

permanent gases CO, H

temperatures down to about -50 °

10 ata washed out. These are especially swine

hydrogen sulphide and organic sulfur compounds

3 'verfahraTnäch claim 2, Ge characterized * o carbon dioxide, and unsaturated hydrocarbons d denotes the ⁿ Abso'rptionsiösung ate phenol, Suitable absorbents own ^ ^ Methanol * Ati boric acid or arsenic trioxide or mixtures thereof nol, acetone, toluene, xylene, heptane _and a_ In emen, ₇ " _OP Q _P t7t u / prripn such a process, the total load of the absorption

associated. acidic gases are usually considerably larger

than the total load of 25 to 30 NnV CO, + H ₂ SZnV that can be achieved with chemical gas scrubbing

Washing solution. As a result, the detergent circulation is often smaller even with physical washing than with a chemical wash.

Attempts have therefore already been made to combine the advantages of a physical wash with those of a chemical wash Combine laundry by adding the acidic gases to the physically dissolving absorbent chemically binding component, e.g. B. an amine,

The invention relates to a method for washing out acidic components, in particular Hydrogen sulfide and carbon dioxide, as well as from

organic sulfur compounds from fuel and 35 sets. Has as a physically dissolving basic component Synthesis gases. one z. B. Diethylene glycol used, so a highly

Such gases are e.g. B. Natural gases, which consist mainly of methane with small proportions of other hydrocarbons exist and next to it, depending on the pre-boiling solvent. Such a mix that may also contain water, but must be heated to temperatures above 100 ° C, z. B. on

men different proportions of CO ₂ and / or H ₂ S 40 120 to 140 ⁰ C of H ₂ S and CO _{2 are} freed.

This requires steam with a pressure of at least 2 atmospheres, but usually 4 to 6 atmospheres, which is a Has a temperature of 160 ° C and higher. Due to this relatively high temperature, the basic component, z. B. Glycol, already somewhat decomposed, with corrosive decomposition products in the detergent arise and enrich. Because of the high boiling point of diethylene glycol (244.5 ° C) is the processing of the so contaminated washing solution

Wash out bases. From the laden neutralizer, distillation is troublesome and time-consuming.
th solutions can absorb the carbon dioxide From DT-PS 9 36 715 is known from gases

acidic components and sulfur compounds by washing under pressure using aliphatic Remove alcohols and the loaded absorption solution to relax and regenerate. The disadvantage, however, is that a freezing of the too cleaning gases is required, whereby the temperature is below 30 ° C.

Os is also known a method whereby the total pressure of the gas is almost independent. You will ⁶ ° gases with water, the small amounts of an Ethanol, preferably to wash out medium and amine as well as a polybasic mineral acid to low carbon dioxide concentrations are washed to high purity (DT-AS 11 45 740). grades, ie as so-called delicates and for the US-PS 6 64 677 relates to a gas scrubbing

Cleaning of non-compressed or slightly compressed gases with alcohol with amine added, but only with one

such amine that with the organic sulfur

contain. Gases rich in carbon dioxide are also produced during the gasification of solid or liquid fuels or in the catalytic cleavage of liquid hydrocarbons with water vapor and optionally Oxygen.

It is known to remove carbon dioxide and hydrogen sulfide from gases by means of alkaline solutions of alkali salts of weak inorganic or organic acids or with liquid organic acids

be driven out again by heating and blowing out with steam or air, with which the solution regenerated and can be used again as an absorbent after cooling.

In these as chemical gas scrubbing or neutralization scrubbing The loading capacity of the washing solution is essentially subject to these processes the stoichiometric laws and is therefore dated

used.

For leaching acidic components from compressed gases, which are compressed to 10 ata or higher, for example, and which can react chemically to a comparatively high level of Anverbindeii, e.g. B. with carbon disulfide CS., With formation of H ₂ S, which must be removed ^{on other Wc: sc.} This

: ethanol with

Washing alone does not result in complete de-monoethanolamine in methanol with 10% sulfurization by weight. In addition, the amine solution is not regenerated a cent of water. Curve B applies to a solution of 3 mol / l

According to a further known process, monoethanolamine in methanol with 10% by weight is pro-acid Components from gases by washing with 5 cent water.

a solution of an amine in a mixture of these two curves it can be seen that a

Water, benzyl alcohol or tetrahydrofurfuryl alcohol - high addition of base by no means high absorption

hol removed (US-PS 24 45 463). tion speed means.

It has been found that absorbents which The curve D applies to a solution with 3 mol / l

simple oxygen-containing, water-soluble organic io monoethanolamine in anhydrous methanol. In the

Compounds, especially the lower alcohols anhydrous solution, the absorption speed

Methane oil, ethanol, propanol, isopropanol and that is the greatest. The presence of water

However, water-miscible butanols or the lower ones reduce the simultaneous absorption of

water-soluble ether with an addition of 0.2 to methane and causes the hydrolysis of COS to the

4 mol / l of one or more organic bases, in particular easily absorbable substances H ₂ S and CO ₂ .

special of simple alkanolamines ^ contain, surprisingly it was found that the ab-

are particularly effective. They are characterized by a rate of sorption of the solution according to curve B.

rapid absorption of acidic gas components and one in a start-up time of a few days, i.e. after

easy to regenerate up to minimal residual - repeated regeneration of the solution, still increasing

concentrations of acidic gas components. The 20 and then constant to the course of curve A correspond to

low-boiling physically dissolving components speaks. This effect is not on top, and it is

this mixture offers the advantage that the ab- not yet fully elucidated. It has only been proven so far

sorption solution already by heating to temperature- its reproducibility. He was found at

temperatures up to about 100 ⁰ C can be regenerated, attempts to known weakly acidic corrosive

ie by heating with cheap exhaust steam and without as sion inhibitors, such as V ₂ O ₅ , by other weak ones

replace the risk of thermal decomposition of waste acids, in particular organic acids,

sorbent components. In these experiments it was found that the solution

The invention accordingly relates to a method of 3 mol monoethanolamine in methanol with for washing out acidic components and 10 percent by weight of water from the beginning the inorganic sulfur compounds from fuel gases 3 ° sorption rate according to curve A and synthesis gases by absorption with a weight, if it additionally contains 0.01 to 0.2 mol / l of a mixture of a primary aliphatic alcohol, acid with a pK value of 7 to 11. (As ethanolamines and water at temperatures between the pK value is the negative logarithm of the dissociants 0 and 100 "C and regeneration of the absorption constants of the acid - in the case of polybasic ionic solution by decompression and heating to 35 acids in the first dissociation stage - in aqueous boiling temperature. The process is labeled as a solution at 25 ° C.) Such additives can improve the regenerability of an absorption solution 4 mol per liter of solution by an ethanolamine concentration of 0.2 to NEN and by using them as a low-volatility acid that of methanol as primary Aliphatic alcohol, expulsion of the last remains of the volatile acids

The absorption solution will preferably deliver 0.01 to 40 components.

0.2 moles per liter of an acid with a pK value Acids with a pK value above 12 are relative

from 7 to 11 added. a complete regeneration of the solution from to

According to a further development of the invention, the effect will be less.

the absorption solution phenol, boric acid or arsenic acids with a pK value below 7 make this more difficult

trioxide or mixtures thereof added. 45 Acid Gas Absorption.

In comparison tests with solutions that contained the entrained portions of the absorbent, different amounts of different weak acids can be removed from these gases by small rewashes with a high-boiling and acid-free standard solution, it was found that the the latter continuously improved its absorption rate and speed by distilling over from this solvent, and that the initial values are recovered. Suitable solution values for this, which correspond to curve B , mean in a few days are z. B. diethylene glycol or triethylene values according to curve A reached glycol. This effect can be seen on the basis of diagram 2 when the cleaned gas does not purify to be dry.

the leaching of the absorption 55 In this diagram the course of the potentio-

medium vapors from the pure gas and the regenerative titration of a regenerated absorption

tion exhaust gas can also be carried out by means of water. solution containing 3 moles per liter of monoethanolamine in

The base addition to the physically dissolving tha.iol contains 10 percent by weight of water,

Component in the amount of 0.2 to 4 mol / l is provided. The abscissa is the acid consumption in ml

critical than when the base ^{concentration} is outside 6o, the voltage of the contact on the ordinate

of these limits is the absorption speed centering chain in mV. The titration was carried out with

will wrestler. a glass electrode as a measuring electrode and a cable

In the diagram of FIG. 1 is the absorption lomel electrode as a reference electrode. Have been titrated

speed of some solutions shown graphically. four taken every 2 hours

The time in minutes is plotted as the abscissa. ⁶ 5 samples of up to a specified residual load

The ordinate indicates the load is an absorption _{erierten A} Bsor tion _P ^ solution with hydrochloric acid.

Solution in Nm ¹ CO ₂ per m> of solution applied. ^{eh b} 10

Curve C applies to a solution of 5 mol / l. All show in the area of higher acid consumption

four titration curves show the two potential jumps A methanol recovered during regeneration

and B, the conversion of carbonate to Bi- is recycled to the top of the absorber

carbonate and the conversion of bicarbonate to the other absorbent components from the

Chloride. In this area, keep all clean gas away.

four titration curves follow the same course and fall 5 in the A b b. 3 is the flow diagram of a plant

accordingly together. for carrying out the method according to the invention

In the area of low acid consumption, i.e. shown on for example. The plant consists of At the beginning of the titration, the four curves run from washing tower 1 with post-washer 2 and distillation differentials, As can be seen from the dashed curves, apparatus 3, the regenerator 4 with backwashing part 5 is visible. Soon after the lioio and still 6 and still 7 were put into operation, Solution shows the curve before the carbonate decomposition also the expansion tank 8, the coolers 9, a potential jump 7 ",. With increasing operating 10, 11 and 12, the container 13 and the separation time In the solution, this potential jump moves in the 14th

Direction of decreasing acid consumption ordinatenanfangspunkt The gas to be purified passes through line IS for co-, so that the cam 15 finally into the scrubber. 1 Through the line 16, a linear increase in absorption solution with a mixture of methanol is shown up to the potential jump A. The potential jumps T ₂ , Τ _Ά , T ₄ show this 10 weight percent water content and 3 mol / l mono shift with increasing operating time. abandoned ethanolamine. This solution removes CO ₂ ,

The occurrence of these potential jumps shows that H ₂ S and COS are out of the gas. The purified gas,

the CO ₂ absorption is preceded by another reaction which is exited from the scrubber through the line 17

device, the reaction product of which occurs as it progresses, now still contains some evaporated methanol,

Operating time disappears. which in the washing pipe 2 (post-washer) by di-

If the titration is washed out of line 18 under otherwise identical conditions,

The purified methanol-free gas passes through the

Contains drawn addition of a weak acid, as line 19, the separator 14 and the line 20

then the potential jumps T ₁ to T _{4 are} not formed for further use. The methanol-containing di-

off, and the titration curve runs from the beginning, ethylene glycol from the wash tube and the separator

like the solid curve. which is through the lines 21 and 22 of a distillery

The water content of the absorbent is supplied from the lierkolonne 3, in order to use it with the methanol

of particular importance when washing out sa'irer 30 with the help of heating 23 to drive off again. By

Gases from gases containing hydrocarbons, in particular the line 24 withdrawing methanol vapors

those made from natural gas. It was found that the precipitated in the cooler 11 and collect in the

water-based solvents with 10 percent by weight container 13. From here a part passes through the

Water even at a high pressure of 53.8 ata in line 25 as reflux to the distillation column 3,

30 ⁰ C only dissolves 0.10 Nm ³ methane / m ³ , while 35 while the methane washed back from the gas

without the addition of water, more than three times the amount taken up through the line 26 back to the head

men will. Correspondingly, the coals of the washer 1 are also tapered. This avoids

hydrogen losses are considerably lower and that, in addition to methanol, volatile bases are also removed from the

Washed acidic gases are far less released into the exiting gas by methanol containing carbon.

oil contaminated. 40 long and thus lost.

The water content of the solvent is also _{important. The detergent loaded with CO 2} , H ₂ S and COS is important in the washing out of hydrolysable substances through line 27 into the expansion tank for organic sulfur compounds such as carbon oxides 8. Here is part of the absorbed sulfide and carbon disulfide. Particularly when gases are released due to relaxation and due to the presence of moncethanolamine in the detergent 45, line 28 exits. These gases can be completely washed out of the gas device29 together with the relaxed scrubbing solution through the release of these compounds. It can, however, be introduced into the regenerator 4. This is also heated to a certain extent, non-regenerable dissolved sump 30, as a result of which the dissolved gases form from by-products, the formation of which are driven off by the detergent. The rain-presence of water is pushed back. Denied detergent is returned to the washer 1 through the line 16 after cooling in the cooler 9 after non-regenerable byproducts that have still been created can be passed back to the washer 1 in a simple manner by distilling off the. The expelled gases are expelled by the volatile constituents of the solvent. Line 31 is passed into the post-washer S, where they are separated. by washing with water from line 32 of Me-

In the case of gases rich in hydrogen sulphide - some 55 are released from ethanol before passing through line 43 Natural gases contain over 10% H ₂ S - it can be diverted purposefully as exhaust gas or for further use

be moderate, the bulk of the hydrogen sulfide will be out

the gas at temperatures from -10 to + 3O ⁰ C The 'methanol-containing water from the post

to be washed selectively with methanol and the gas scrubber 5 is passed through line 33 to the distillation

then passed through a wash with 60 lierkolonne 6 in the circuit. Here, by means of the heating

led base-containing methanol is driven off by CO ,, residue 34 the methanol, while the

Lichem H ^ and organic sulfur compounds water is discharged through line 35. the

πι free. The purified gas from the exiting methanol vapors are through line 36 a

Approved methanol is expediently fed through a condenser 12. This will be the case

your washing with injected polyalcohol, pre-6 ₅ condensate partly through the line 37 as a return

Roughly dietary glycol, washed out, which on the distillation column 6, partly through the line 38

abandoned by heating and desbJIating the methanol at the top of the regeneration column 4,

is not regenerated and circulated. The order of the \ n between the washer 1 and the Reee-

nerator 4 to keep circulating base-containing methanol as free as possible from non-regenerable by-products, can a partial flow of the regenerated detergent through the line 39 a stripper? are fed. The distillable components are evaporated by means of the heater 40 and fed to the regenerator 4 through the line 41, the residue that cannot be distilled is drained off through the line 42 .

If the quantities of acidic gases to be washed out are large, the heat of reaction in the absorber 1 can be so significant that cooling of the detergent is required. This can be either by correspondingly deep pre-cooling in the cooler 9 before entering the absorber 1 or by intermediate cooling take place during the washout in absorber I.

Example!

Hin natural gas is to be used as town gas for the long-distance gas supply. It consists of

T3.14 volume percent CH ,,

0.5 percent by volume C ₂ H ₀ ,

0.04 volume percent C _n H ,.
22.1 volume percent CO. ,,

4.2 percent by volume H ₃ S,

0.02 percent by volume CÖS.

The gas is dry, has a temperature of 2 "! C. and is under a pressure of 56 atmospheres. The sulfur compounds should be removed to less than: 0ppm, the CO .." to a maximum of 1 percent by volume. For this purpose, a system is used which, according to the method according to the invention, operates as follows (A bb 3):

^ O 000 Nm ' ¹ h of the gas to be scrubbed enters the absorber 1 through line 15. CH .γ ₁ Zh washed ■, ^{; Jas by ■ from 16 Leitune discontinued detergents are ms the gas fo 900 Nm "CO _n Zh 2100 Nm- H, S..h Kt Nm ¹ cosh and 920 ^Nm..!.. ate 36 070 Nm ^{: i} Gash with 0.39 percent by volume 0.1, 1.5 mg H ₁ SNm ' ¹ and 5 ppm COS from the Ab-M.rher 1 through the line 17 with a temperature ■ •' in 2VC . This gas has recorded a total of h üS2 kg of methanol, which in Nachvascher 2 by 2 m · ¹ hour turned overspray Diäthylenjivko "! to be washed up again. The clean gas exiting through line 19, separator 14 and line 20 at a pressure of 55 atmospheres and a temperature of 24 ⁿ C is dry and free of methanol and can be fed to the remote gas supply.

The detergent applied to the washer 1 contains 3.0 mol of diethanolamine per liter of methanol a water content of 10 percent by weight.

Of this, 255 ms / h are circulated between absorber I and regenerator 4. In absorber 1,> 0 * »*» »l £ OJT £ 2100 Nm ⁸ HJS / h, 920 Nm» CH ₄ / h and 9.8 are converted from the gas Nm * COS added. The detergent entering the absorber 1 through the line 16 m initially has a temperature of 28 ° C., but warms up to 74 ° C. as a result of the absorption of CO ₂ and H _{2 S. The CO 2} -, H ₂ S reaches this temperature - and COS-containing detergent in the expansion tank 8, here it is relaxed to 3 atmospheres and cools down to 53 ° C. The partially expanded detergent passes through line 29 together with the expanded CO. into the regenerator 4, where it is expanded to the operating pressure of the regenerator of about 1 ata. Indirect heating in the sump of the re-

In the generator, the detergent is heated to 80 ° C and brought to the boil and practically completely freed _{from CO 2} and H _{2 S.} The COS taken up in the Absorbei is completely _{hydrolyzed to H 2} S and CO ₂ and also expelled. The regenerated detergent! fed to a cooler 9, cooled to 28 ° C. and returned to the washing tower I. The arr head of the regenerator 4 through the line 31 contains vapors except 10 909 Nm ^!

;> o CO ₂ Zh, 2110 Nm ¹ H ₂ SZh and 920 Nm "CH ₄ Zh nor methanoi. Therefore, 6 m ^{3 of} water / h are applied to the post-washer ί through line 32 and the methanol is washed back Gas escapes through line 43. It contains

:> 5 15 percent by volume H ₂ S and is suitable for processing on sulfur in a Claus plant. The water-containing methanol is distilled in the column 6, the methanol condensing in the condenser 12 and partly as reflux to the column 6,

3: 0 is partly abandoned through the line 38 to the head of the regenerator 4. This prevents the organic base, in addition to methanol, from reaching the post-washer 5 and then being lost through the line 35 together with the waste water from the column 6.

In a similar way, the methanol washed back from the gas in the post-washer 2 by means of circulating diethylene glycol is recovered by heating the methanol-containing glycol draining through line 21 in column 3, with methanol being driven off and liquefied again in condenser 11. This recovered methanol gets partly as reflux to the column 3, partly through the line 26 to the top of the absorber 1. This also prevents the escape of organic base or acid from the detergent.

In the procedure described, the detergent in the regenerator 4 only needs to be heated to 98 ° C. Indirect heating with cheap exhaust steam of 0.2 atmospheres and 104 ° C is sufficient for this, so that there is no need to recover heat and thus to install expensive heat exchangers.

If the system is operated with the absorption solution described above, about 2 days pass until the optimum operating values specified in this example are achieved.

However, this solution still has an addition

of 0.03 mol of boric acid or vanadic acid, then these optimal values are already in the first hours of operation.

Sheet character

<0963T / 102

Claims (1)

Patent claims: 1. Process for washing out acidic components and organic sulfur compounds from fuel gases and synthesis gases by absorption with a mixture of a primary aliphatic alcohol, ethanolamines and water at temperatures between 0 and 100 ° C Relaxation and heating to boiling temperature, characterized by an ethanolamine part of acidic components, so-called physical washes are advantageous in which the gas components to be washed out are dissolved but not chemically bound The solubility of the gases and thus the loading of the absorbent increases with it k and with falling temperature. The regeneration of the physical absorption center is preferably carried out by relaxing to ambient pressure or even lower pressure, given possibly with warming. According to a well-known process, the following are produced: