DE1260676B - Process for removing soot and carbon oxysulphide from hot gases obtained by incomplete combustion of carbon-containing combustible substances - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

ClOk

German KL: 26 d - 8/50

Number: 1260 676

File number: S 94141IV c / 26 d

Filing date: November 11, 1964

Open date: February 8, 1968

The invention relates to a method for removing soot and carbon oxysulphide (COS) from hot, gases obtained from incomplete combustion of carbon-containing combustible substances.

The term "carbonaceous flammable substances" means anything, incineration accessible material that contains chemically bound and / or free carbon, such as coke, Coal, natural gas, crude oil and crude or refined petroleum fractions.

It is known per se, e.g. B. from British Patent 780120 that by the incomplete Combustion of carbonaceous flammable substances can be obtained, which are hydrogen and carbon monoxide. As the combustion entertaining agent, air can be used Oxygen-enriched air or pure oxygen can be used, and the combustion is more frequent carried out in the presence of added steam and / or carbon dioxide. The incomplete combustion often occurs at superatmospheric pressures.

The crude combustion gases contain relatively large proportions of hydrogen and carbon monoxide. Depending on the reaction conditions used, the type and proportions of the reaction components fed to the combustion zone, however, also smaller or larger proportions of nitrogen, oxygen, water vapor, carbon dioxide and optionally other components are present in the gases. In addition, they contain in cases where sulfur-containing raw materials are used, but also sulfur-containing impurities, such as hydrogen sulfide and COS. The level of COS in such crude combustion gases is generally relatively large and in most cases the gas contains 2 to 10% of the total sulfur in the form of COS. The raw combustion gases also contain a certain amount of soot (carbon and ash).

In accordance with normal practice, a greater proportion of the soot is removed from the raw combustion gases removed by washing with water. This can be done in a variety of ways, for example under Use of the device described in British patent specification 826 209 and that described at the same time Procedure.

However, the gases usually have to be cleaned further after such a washing treatment in order to remove most of the hydrogen sulfide and COS therefrom, which may be necessary in particular so that the gases are suitable for subsequent further processing steps, for example for processes for removing soot and
Carbon oxysulphide from hot, through
incomplete combustion of
carbonaceous flammable substances
obtained gases

Applicant:

Shell International

Research Maatschappij N.V., The Hague

Representative:

Dr. E. Jung, patent attorney,

8000 Munich 23, Siegesstr. 26th

Named as inventor:

Wilhelmus Marinus Johannes Ruedisulj, The Hague

Claimed priority:

Great Britain 13 November 1963 (44 856)

the conversion of the carbon monoxide present in the gas in the presence of steam and a suitable catalyst into hydrogen and CO ₂ .

It is already known to then pass the scrubbed gases over a catalyst which converts the COS into hydrogen sulfide and then _{to treat the gas mixture obtained in this way with an agent for the removal of H 2} S and possibly of COS (cf. USA patent 3,074,783).

However, these measures have the disadvantage that the scrubbed gases, which with the catalyst in Must be brought into contact, have quite low temperatures, so that the conversion rate of the COS is quite low, while the alternative is a heating up of the gases higher temperatures prior to contacting the conversion catalyst is not very beneficial since the gases then have to be cooled again, so that these measures are quite cumbersome and are also expensive.

It has now been found, surprisingly, that these disadvantages are very simple and practical Way can be fixed.

Accordingly, the invention provides a method for removing soot and carbon oxysulfide from hot, from incomplete combustion

809 507/521

3 4

carbonaceous flammable substances obtained another heat exchange device conducts, however

Gases, which is characterized in that the cooling can also take place directly, for example

Gas in the absence of water via a COS bypass by spraying in water. This optional

Conversion catalyst is passed, that subsequently carried out cooling takes place with or without gezur Saturation of the gas with water vapor and to 5 wanted pressure change of the combustion gases,

Simultaneous cooling of the gas to a temperature. The combustion gases are in the pre-cooled or

temperature below the dew point of the gas sufficiently not pre-cooled state with the COS conversion

Water is added, which brings most of the ventilation catalyst into contact, which in any-

Soot deposited in the form of an aqueous suspension may be present in a suitable arrangement, for example

and that the gas after separation of this io way in the form of a fixed bed, a moving one

aqueous carbon black suspension with at least one per se fluidized bed or a fluidized bed. The COS Um-

known means for removing sulfur water conversion catalyst can also be added if desired

substance and possibly COS is treated. together with one or more catalysts of this

In the present description refers to the type used.

Print out "COS conversion catalyst" on every 15 While the gases come into contact with the COS

any catalyst, at least one of the post-conversion catalyst reacts to the COS present

catalyzes standing reactions: with the hydrogen and / or the water vapor,

COS + H ₂ O (water vapor) -► H ₂ S + CO ₂ ^wel f ^ei usually in relatively large proportions

COS + H - * ■ HS 4- CO is present because the incomplete combustion in general

^{2 2} ao mean in the presence of added steam

Such catalysts are known per se, and is carried out, and during this contact the

suitable representatives are e.g. B. aluminum oxide, bauxite, COS at least partially converted into hydrogen sulfide

activated carbon, aluminum phosphate, thorium oxide. This conversion should preferably be up to

and magnesium chloride. to such an extent that the

In practice, it is customary to use a correspondingly low level of oxides or oxide-containing gases

Materials to use, and preferably is to have content of COS, then its percentage

For this purpose a catalyst is used which is no longer harmful or which is economical

Consists of or contains aluminum oxide. then removed or decomposed in a justifiable manner

It is sometimes beneficial to convert to a COS.

treatment catalyst to be used, which is a particular 30 Preferably at least 50% of the original

has pronounced hydrogenation activity, because it is the COS originally present in the combustion

through it becomes possible that the catalyst not only converts the gassing into hydrogen sulfide and carbon dioxide.

Carbon oxysulphide decomposes, but also a hydride converted. While in contact with the catalyst

tion or hydrogenation conversion of certain Sator, the temperature is usually between 100

other impurities is achieved that in the 35 and 1000 ⁰ C, preferably between 100 and 500 ⁰ C.

treating gases may be present. Taking into account and in particular between 200 and 35O ⁰ C. It is

In view of this point of view, the COS advises that the application of a

Conversion catalyst preferably at least a low temperature has the advantage that

Metal from groups VI and / or VIII of the periodic impurities, such as hydrocyanic acid, are better decomposed

system of elements, either as 40 den. The pressure is preferably the same as in FIG

such or in chemically bound form. One from burn zone without being deliberately degraded

Cobalt and / or Molybdenum on an aluminum dignity. The space velocities used

Oxide-supported catalyst has usually been found to be in the range from 1000 to 20,000 Nm ³

proved to be particularly suitable. Gas per cubic meter of catalyst per hour, whereby

It is known per se that water vapor and 45 space velocities between 2000 and 6000 Nm ^{3 /}

Carbon monoxide many hydrogenation catalysts are preferred for ^{m 3 · h.} The volume ratio of

activate, including the aforementioned water vapor to COS in the gas mixture, which with

Cobalt-molybdate-aluminum oxide catalyst, and the COS conversion catalyst in contact

that solid substances, such as soot, are also brought in as catalysts, is preferably between 100 and

Deactivate by removing the active surface from the 50 1000. If desired, a little steam can also be used

clog the same. Surprisingly, was now added to the total concentration am

found that practically no or only a very long water vapor can be adjusted to the desired value,

Loss of activity in COS conversion The desired level of COS conversion can be

Catalysts occurs when the by incomplete easily by regulating the space velocity

Combustion obtained gases, which a relative 55 can be adjusted.

high proportion of carbon monoxide and, if necessary, surprisingly, it was found that a

Contain water vapor, according to the invention, an extraordinarily sharp drop in the activity of the treated

delt even if it also enters considerable catalyst if during contact

Contain soot. of the gas with the conversion catalyst is liquid

If the temperature of the combustion zone is 60 water present. For this reason, the letting hot combustion gases must be very high, so the COS conversion catalyst come into contact with this initially brought the gas to a temperature in the range practically from 100 to 500 ⁰ C and preferably especially in the table free of liquid water be. Preferably cooled in the range from 200 to 350 ⁰ C, before it has the gas to a temperature which at least COS conversion catalyst are passed. 65 is 5 ° C above the dew point.

This partial cooling can be caused indirectly by the strong deactivation of the COS heat exchange done by using the combustion conversion catalyst, which is caused by the annealing gases for example caused by a heater or essence of liquid water,

is essentially reversible because it has been found that a deactivated catalyst is its original Recovers activity very quickly when treating gases at temperatures slightly above their dew point will.

Subsequent to this conversion step, the gas is subjected to a treatment to remove soot. For this purpose, such an amount of water, if desired partly also in the form of cold steam, added that a simultaneous saturation and cooling of the gas takes place until the The dew point is reached, whereupon the gas is cooled further. This is at least the main part of the soot originally contained in the gas is deposited in the form of a suspension in the aqueous phase.

The bringing of gases into contact with water is well known per se, and it can be in any suitable manner Way to be carried out. For example, the water can be sprayed into the gas, while this passes through at least one washing tower or through pipes. It is very much like that convenient to spray the water into the hot gas via a number of spray nozzles arranged one behind the other, while this passes through an inclined pipeline (cf. the first washing stage of the in British Patent 826 209).

The gas is usually brought into contact with water in such a way that it is up to a temperature does not cool too far below the dew point, for example to a temperature that is no more than 40 ° C below the dew point. This has the advantage that a relatively concentrated aqueous Carbon black suspension is obtained.

The so scrubbed gases typically have a temperature between 75 and 250 ° C, which temperatures are preferably in the range of 120 to 200 ⁰ C. In most cases, more than 90 percent by weight of the soot originally contained in the crude combustion gases is found in the form of the separated aqueous suspension. Preferably, however, 99 percent by weight or more of the carbon black originally present should be separated off in this form.

The aqueous carbon black suspension is separated from the gas in any desired manner, e.g. B. by mixing the mixture from gas and aqueous suspension through at least one vapor-liquid separator (cyclone) passes through. If the hot gases are countercurrent to the water in a vertical tower in Brings contact, it is also possible to draw off practically liquid-free gases at the top of the tower and to discard the aqueous suspension obtained at the bottom of the tower. Subsequent to the separation of aqueous soot suspension and gas, it may be desirable in some cases to add some steam in to introduce the gases (see British patent specification 851 655).

After the gases have been washed and the aqueous carbon black suspension has been separated from them, it is generally desirable to carry out a second washing treatment in order to completely remove the last traces of soot from the gas and at the same time to cool it to the temperature required for the subsequent removal of the Sulfur-hydrogen is required. For this purpose, cooling down to a temperature in the range from 10 to 70 ^° C. is generally desired.

The second washing treatment can be carried out in any manner. So the water can go into that Gas are injected during this through at least one scrubbing tower, such as a packed column, or at least one pipe passes through it.

If the gases contain practically no soot after the first scrubbing treatment, this can be used if desired Instead of the second washing treatment, an indirect heat exchange takes place around the gases to cool that temperature, which for the subsequent treatment for the purpose of removal of Hydrogen sulfide is desirable.

The gases thus obtained are then treated with an agent to produce hydrogen sulfide and remove any remaining COS if necessary. In the case of gases that do not undergo a treatment according to the invention have been subjected to the conversion of COS, but in which only the soot contained therein was removed by a washing treatment with water, absorption liquids which are conventional per se could not be used as treatment agents will. Some of these absorption liquids react in an irreversible manner with what is present COS, making such treatment at high COS concentrations out of economic Reasons is intolerable. This applies in particular to aqueous solutions of monoethanolamine. Other Absorbents, such as aqueous solutions of potassium phosphate or "alkazide" solutions, remove the present COS only slightly, so the gases ultimately obtained still have an intolerably high level Have content of COS. Still other absorption liquids, for example aqueous solutions of Diethanolamine, and especially dipropanolamines, remove both hydrogen sulfide as well as COS, however, they are used at high COS concentrations because of the long contact times required too expensive because then very narrow columns have to be used and at the same time with such long contact times an absorption of carbon dioxide cannot be avoided.

In the method according to the invention, however, the gas has to be treated for the purpose of removal must be subjected to hydrogen sulfide and possibly COS, an already reduced COS content, which makes it much more suitable for such treatment with absorbent liquids. Indeed, a large number of liquid absorbents are now useful.

In all cases where the gas to be treated has such a low content of COS that it is in this Any treatment agent can be used if the conditions to be met by the end gas are already met which is suitable for removing hydrogen sulfide, regardless of whether it is Able to remove COS. In these cases, all absorption liquids can be used are known in the art for the removal of hydrogen sulfide from gases. For this purpose, z. B. aqueous solutions of alkanolamines ^ such as monoethanolamine, diethanolamine, di-n-propanolamine and / or diisopropanolamine; aqueous solutions of potassium sulfate, sodium hydroxide and mixtures of cyclotetramethylene sulfone or a derivative of this compound with alkanolamines A very suitable one Absorption liquid consisting of cyclotetramethylene sulfone, an alkanolamine and optionally Water is contained in the British patent

972140 described. Other suitable treatment agents, for example mixtures that contain iron oxide and are used to purify town gas, can also be used.

If an absorption liquid is to be used which is capable of removing both hydrogen sulfide as well as COS from a gas which without the treatment to convert COS According to the invention such a high content of COS leave the heat exchanger 6 and are in the Vessel 7 filled with catalyst is initiated. In this vessel is at least one bed of COS conversion catalyst arranged at which the conversion of COS into hydrogen sulfide takes place. The gases being drawn off first pass through a washing zone, which consists of an inclined pipe 8 consists. This pipeline 8 is over its entire length with a series of z. B. six spray cans 9 provided,

would show that the removal up to the point where each finely dispersed water is economically sprayed into the desired low concentration, so that the gases flowing through would be unsustainable, the conversion of the COS needs to be cooled and saturated _{with H 2 O at the same time} . the

according to the invention but not to take place to such an extent that the desired for the end gas COS content is already achieved in the conversion stage. This is due to the fact that in the subsequent treatment of the gases with such absorption liquids under conditions those for the removal of hydrogen sulfide in gases are sprayed with such amounts of water, that their temperature drops below the dew point. The inclined line 8 opens with its lower end in a vapor-liquid separator 10 of conventional design, for example in a Centrifugal separator (cyclone) or in a defogger, which has baffle plates

are still economical to deposit practically all liquid present at the same time.

a significant amount of COS is also removed. It is particularly advantageous for this purpose to be aqueous Use solutions of diethanolamine or dipropanolamines because the COS is special with these Amines does not react in an irreversible manner. Aqueous solutions of dipropanolamines, in particular of diisopropanolamines, are preferred over solutions of diethanolamine because they are better Removal of hydrogen sulfide and COS from soot and water easily separate from that flowing gas in the form of an aqueous soot suspension, which from the separator 10 via a line 11 is deducted.

The gases leave the head end of the separator 10 via a line 12 which is fed into a second washing zone in Form of a washing tower 13 leads, in which the gases in countercurrent to that supplied via line 14 Water rise. Remaining traces of soot

enable lower steam consumption. When 30 are separated from the gases by the water.

the remaining amounts of COS to be removed relative The cooled gases leave the scrubbing tower 13 on

are small, it is sometimes economically feasible to also use such absorbent liquids, which the COS by means of an irreversible reaction

remove, with which then a consumption of absorption 35 absorption column 17 are treated, for example means because a complete regeneration with an aqueous solution of diisopropanol

Head end via a line 15, while the water at the bottom is drawn off via a line 16. If so desired can this gas then still in a

tion of the latter is practically impossible. An example of such an absorption liquid is an aqueous one Solution of monoethanolamine.

In some cases it is advantageous to use two or more different treatment agents in succession apply.

With reference to the drawing, two preferred embodiments of the invention are shown below Procedure explained.

In the drawing, FIGS. 1 and 2 two flow charts for incomplete combustion systems of hydrocarbons again, including plants for the purification of the crude gases produced in this way the method of operation according to the invention.

In the case of the installation according to FIG. 1 is a suitable hydrocarbon material via line 1 into the Combustion chamber 2 of a gas generator 3 introduced. In the combustion chamber 2, the hydrocarbon intimately with a gaseous oxidizing agent, for example with a line 4 added oxygen, mixed and then incompletely burned. If desired, the Line 4 is also supplied with steam. The amm, which is supplied via a line 18, so to remove all hydrogen sulphide and possibly COS still present in the gas. The enriched Absorption solution is drawn off via a line 19 for the purpose of regeneration. The pure gas is taken at the head end via a line 20. The in F i g. 2 plant shown works in whole in a corresponding manner, but it has no heat exchanger or steam generator 6. The the combustion chamber 3 exiting hot gases are here by quenching with liquid water, which is fed via a line 21, directly cooled. However, the amounts of water used here should be kept so low that the gas mixture introduced into the catalyst vessel does not contain liquid water contains.

The invention is explained in more detail by the exemplary embodiment that now follows.

Embodiment

A gas obtained from the incomplete combustion of a heavy fuel oil with oxygen and steam

Combustion gases consist mainly of 60 mixing was initially caused by indirect heat

of carbon monoxide and hydrogen, and they also contain a small amount of soot. The hot gases leave the gas generator 3 via a line 5 which opens into a heat exchanger 6, which can be a steam generator in combination with a steam superheater. Here the hot gases are up to an intermediate temperature of z. B. 225 to 275 ° C cooled. The gases cooled in this way are cooled down to a temperature of about 250 ° C. The gas mixture with the composition given in the table below was then introduced in an amount of 10,000 Nm ³ / h into a catalyst vessel which contained a layer of a cobalt molybdate catalyst on an aluminum oxide support. The temperature in this catalyst vessel was 25O ⁰ C, and there was a pressure

ίο

of 31.7 kg / cm ² abs. The gas was passed over the catalyst at a space velocity of 3500 Nm ³ per cubic meter of catalyst per hour. The effluent gas contained 0.006 percent by volume COS and 0.61 percent by volume hydrogen sulfide. It was first introduced into a first washing zone, into which water was sprayed by means of nozzles. The gas mixture cooled thereby to a temperature of 128 ° C., was the 7 ⁰ C below the dew point. During this cooling, an aqueous suspension of carbon black was formed which contained about 99 percent by weight of the carbon black originally present in the gas mixture. The gas mixture was separated from the carbon black suspension in a cyclone and then passed into a second scrubbing zone in the form of a tower, in which the gas was treated in countercurrent with water. The gas left this washing tower at a temperature of 40 ^° C. and had the composition given in the table below. It was then passed into an absorption column, where it was ^{treated with 21 / Nm 3 of} a solution containing 45 percent by weight of diisopropanolamine, 40 percent by weight of an aqueous suspension of tetramethylene sulfone and 15 percent by weight of water.

lo held.

As confirmed by the numerical values in the table, that was purified leaving the absorption column Gas practically free from COS and hydrogen sulfide. In addition, his salary was up Carbon dioxide extremely low.

Composition of the gas in percent by volume

Gas behind the Gas after Gas after Gas after Gas before catalyst first wash second wash Absorption catalyst vessel zone after Zone column vessel Removal of 43.56 Soot suspension 48.29 50.64 43.56 41.40 43.79 45.89 48.20 41.40 3.69 41.61 4.08 0.02 3.68 0.61 3.70 0.66 0.0002 0.60 0.006 0.60 0.0056 0.0003 0.02 0.56 0.0058 0.62 0.65 0.56 9.99 0.57 0.26 0.28 10.00 0.18 9.55 0.20 0.21 0.18 9000 0.18 1 1 9000 250 100 40 40 250 31.7 128 30.4 30.3 31.8 31.2

CO

H ₂ .

CO ₂

H ₂ S

COS

N ₂ (+ A etc.)

H ₂ O

CH ₄

Soot content, mg / Nm ³

Temperature, ⁰ C

Total pressure, kg / cm ² · abs.

Claims (7)

Patent claims: 1. Process for removing soot and carbon oxysulfide from hot, incomplete Combustion of gases obtained from carbon-containing combustible substances, characterized in that that the gas in the absence of water over a COS conversion catalyst that is then passed to saturation of the gas with water vapor and simultaneous cooling of the gas to a temperature below the dew point, sufficient water is added to the gas is, whereby most of the soot is deposited in the form of an aqueous suspension is, and that the gas after separation of this aqueous carbon black suspension with at least one known agents for removing hydrogen sulfide and optionally COS treated will. 2. The method according to claim 1, characterized in that the gas is cooled ^{to a temperature of 100 to 500 0} C, preferably from 200 to 350 ^{0 C, before it is passed over the COS conversion catalyst.} 3. The method according to claim 2, characterized in that the cooling of the gas without intentional Pressure change is carried out. 4. The method according to claim 1, characterized in that the gas is passed at a space velocity of 1000 to 20 000 Nm ³ gas per cubic meter of catalyst per hour over the COS conversion catalyst. 5. The method according to claim 1, characterized in that following the separation of the aqueous soot suspension is introduced into the gas vapor. 6. The method according to claim 1, characterized in that the gas after separation of the aqueous Soot suspension is treated with water. 7. The method according to claim 1, characterized in that the gas is cooled to a temperature of 10 to 7O ⁰ C after the separation of the aqueous carbon black suspension. 1 sheet of drawings 809 507/521 1.68 © Bundesdruckerei Berlin