description

Method and installation for the treatment of a lukewarm wash

The invention relates to a method for treating a waste liquor from a liquor wash using an oxidation reactor and a corresponding system according to the respective preambles of the independent claims.

State of the art

Olefins such as ethylene or propylene, but also diolefins such as butadiene and aromatics can be produced from paraffins by steam cracking. Corresponding processes have been known for a long time. For details, refer to specialist literature such as the article "Ethylene" in Ullmann's Encyclopedia of Industrial Chemistry,

Online edition, April 15, 2007, DOI 10.1002 / 14356007. a10_045.pub2, referenced.

During steam cracking, what is known as cracked gas is obtained which, in addition to the target products, contains unconverted hydrocarbons and undesired by-products. In known processes, this cracked gas is first subjected to processing before it is fractionated for recovery

different hydrocarbons or hydrocarbon fractions is fed. Details are described in the cited article, in particular in Section 5.3.2.1, "Front-End Section" and 5.3.2.2., "Hydrocarbon Fractionation Section".

A corresponding preparation includes in particular what is known as

Sour gas removal, in which components such as carbon dioxide, hydrogen sulfide and mercaptans are separated from the cracked gas. The cracked gas is typically compressed before and after an appropriate treatment. For example, the cracked gas can be taken from a so-called raw gas compressor at an intermediate pressure level, subjected to the acid gas removal, and then in the

Raw gas compressor can be further compressed.

The acid gas removal can in particular include a so-called lye washing using sodium hydroxide solution. Particularly with high concentrations of sulfur compounds, the caustic wash can also be carried out with an amine wash,

for example using ethanolamine. The waste liquor obtained in the caustic washing, which has sulfide and carbonate in a content of a few percent, is typically oxidized in a waste liquor treatment and, if necessary, neutralized before it can be subjected to biological waste water treatment. The oxidation serves to remove toxic components and to reduce the biological oxygen demand. The waste liquor oxidation is typically carried out in the form of a wet chemical oxidation of the sulfide with oxygen in solution.

Several different methods are known from the prior art

Known wet oxidation of spent waste liquors. For example, see the article by CB Maugans and C. Alice, "Wet Air Oxidation: A Review of Commercial Sub-critical Hydrothermal Treatment", IT3Ό2 Conference, May 13-17, 2002, New Orleans, Louisiana, or US Pat. No. 5,082,571 A referenced.

The spent liquor can be used in such processes to the desired

Reaction pressure brought and heated in countercurrent with the oxidized waste liquor. The heated, used waste liquor can then be fed into an oxidation reactor with the addition of oxygen and oxidized. The oxygen required for the reaction is added either in the form of air or as pure oxygen. An additional, in other process variants also the exclusive, heating of the spent waste liquor can be carried out by introducing hot steam into the oxidation reactor.

After a typical dwell time of around one hour (depending on the selected temperature and pressure), the oxidized waste liquor is mixed with the

associated exhaust gas is cooled by a heat exchanger while heating the used waste liquor. After a pressure check, a subsequent

Separation tank separates the exhaust gas from the liquid. The liquid oxidized waste liquor can then be fed into a process for biological waste water treatment with optional adjustment of the pH value (neutralization).

Further processes and process variants are from DE 10 2006 030 855 A1, US 4,350,599 A and the article by CE Ellis, "Wet Air Oxidation of Refinery Spent Caustic", Environmental Progress, Volume 17, No. 1, 1998, pages 28- 30 described.

The oxidation of the sulfur-containing compounds in the spent waste liquor normally takes place in two different steps. The oxidation of sulfides produces sulfite, sulfate and thiosulfate in parallel. While sulfite is oxidized further to sulfate very quickly, the further reaction of thiosulfate is comparatively slow. The main reactions are as follows:

The state of the art in the oxidation of waste liquor is an operating pressure of 6 to 40 bar and an operating temperature of over 200 O, for example up to 210 O. The higher the temperature selected in the reactor, the higher the pressure must be set, since the steam pressure increases significantly the temperature rises. The residence time in the reactor required for substantial conversion drops from the order of 12 hours at 6 bar to 10% of the stated residence time at 30 bar.

According to the prior art, the waste liquor is fed into the oxidation reactor. An oxygen carrier, usually air, is placed anywhere, usually in front of the

actual reactor, mixed with the lye. The waste liquor or the waste liquor-oxygen carrier mixture can be preheated in a heat exchanger.

According to the prior art, the waste liquor can thus be preheated in the

Oxidation reactor are abandoned. However, this is not absolutely necessary. Further heating (or the only heating) often takes place by adding steam, which can either be added to the inflowing waste liquor or directly into the reactor, and generally also through the enthalpy of reaction or exothermicity of the oxidation reactions. As mentioned, the waste liquor to the reactor can also be preheated against the product from the reactor in appropriate processes.

Since the pressure of the gas phase consists of the vapor pressure and the pressure of the

Oxidation air is added and the pressure of the inflowing steam must be at least as high as the reactor pressure, superheated steam in particular comes into consideration for the steam addition mentioned. This partially condenses and in this way supplies the additional heat.

An oxidation reactor used for the oxidation of waste liquor is constructed according to the prior art in such a way that a directed flow is formed in the reactor and thereby a greater reaction rate and a higher conversion are possible. For this purpose, fixtures in the form of perforated floors can be used.

Processes of the type explained above are known, for example, from DE 10 2010 049 445 A1, in which a pressure of more than 60 bar is used in a corresponding reaction reactor, and from DE 10 2006 030 855 A1.

Reactors for the oxidation of waste caustic are made of high-quality materials such as nickel-based alloys or nickel due to the extreme stresses involved. Such materials, however, can also be attacked by high sulfide concentrations at elevated temperatures.

In particular, the treatment of a component mixture emerging from or withdrawn from a corresponding oxidation reactor has conventionally proven to be expensive or processes and devices are conventionally used for this for the reasons explained below

unsatisfactory. The present invention therefore has the object of specifying improved measures for the treatment of corresponding component mixtures.

A corresponding system should, in particular, have a lower cost of materials for a comparable service life or for the same cost of materials to increase

Lead life of corresponding system components.

Disclosure of the invention

Against this background, the present invention proposes a method for

Treatment of a waste liquor of a caustic wash using a

Oxidation reactor and a corresponding system according to the respective

The preambles of the independent claims. Refinements of the present invention are each the subject of the dependent claims and the description below.

Advantages of the invention

One emerging from an oxidation reactor of the type described

The component mixture is typically three-phase and comprises gas, aqueous liquid (lye) and solids in the form of organic components (oligomers, polymers) and inorganic components (salts).

According to the prior art, this three-phase component mixture is cooled in one or more heat exchangers at the outlet from the oxidation reactor, the components that can still be condensed being condensed out. The gas phase and the liquid phase and the solid phase are separated from one another in a corresponding heat exchanger or in a container connected downstream of this. The correspondingly separated and cooled media are each passed separately via valves, relaxed to almost ambient pressure and fed to further post-treatment.

In the explained treatment of the three-phase component mixture removed from the oxidation reactor, it is particularly disadvantageous that the heat exchanger used comes into contact with hot reaction products. Due to the aggressiveness of the media (lye and abrasive solids) and the constantly changing wetting surfaces, the service life of a corresponding heat exchanger is short and in any case limited to significantly less than 20 years, even when using higher quality materials such as alloy 600 or nickel. It should be noted here that a corresponding heat exchanger must withstand a high operating pressure of 20 to 40 bar when using the process variants described at the beginning and therefore corresponding material thicknesses are required.

A further disadvantage is that the separated liquid phase with the particles contained therein is expanded at process pressure and residual gases dissolved in the liquid outgas ("flash"). As a result, the valve used for expansion is again flowed through with a three-phase mixture, with the outgassing resulting in extremely high flow velocities. The existing particles lead to strong mechanical or abrasive loads. As a rule, the residual gas that forms must be separated from the liquid again downstream of a corresponding valve and discharged separately from this, for example together with the gas phase that has already been separated off upstream.

Due to the solids content of the liquid in the valve and the small flow through seats compared to gas (control) valves

Liquid (control) valves, these valves, which are typically designed as nozzle valves, tend to blockage and leakage due to the particles in question in the form of the polymers and salts.

These disadvantages can be overcome by using the measures proposed in the context of the present invention. In particular, there is a significant increase in the service life of a heat exchanger used and post-treatment or storage of the liquid is simplified by a low content of outgassing components. Overall, the use of the present invention increases the availability of a corresponding method or a corresponding plant.

Overall, the present invention proposes a method for treating a waste liquor from a caustic wash of the type explained above, in which the waste liquor with oxygen or an oxygen-containing gas mixture is fed to an oxidation unit and in this for a reaction period on a first

Temperature level and a first pressure level is subjected to wet oxidation. The oxidation unit can, in particular, have one or more of the oxidation reactors explained above, as well as apparatuses assigned to them, for example.

Include heaters, steam systems, and the like. The wet oxidation in the oxidation unit is carried out as explained in detail above.

As also mentioned, a three-phase component mixture, which comprises a gas phase, a liquid phase and solid particles, is removed from the oxidation unit, and thus also within the scope of the present invention, and subjected to cooling and phase separation. This is conventionally carried out, as also explained again with reference to the attached FIG

Component mixture is first subjected to cooling without relaxation and then to phase separation. The phases formed then relax. In this case, the problems explained above can arise, which consist in particular in a strong mechanical load on the expansion valves used with a corresponding expansion.

In order to overcome the problems explained, the present invention proposes, in contrast, to subject at least part of the three-phase component mixture initially to a relaxation from the first pressure level to a second pressure level in unchanged composition and thereby to cool it to a second temperature level. To avoid confusion, it should be emphasized that the "unchanged composition" relates in particular to the respective contents of the gaseous liquid and solid phase upstream of the expansion. Downstream of the expansion, it can become relative, in particular due to outgassing

The gas phase increases and the liquid phase decreases. The "unchanged composition" does not exclude that upstream of the expansion, a portion with likewise unchanged composition is discharged and only the remainder with unchanged composition is fed to the expansion.

Such relaxation has proven to be particularly advantageous in the context of the present invention. The present invention makes use of the fact that the temperature of a corresponding three-phase

Component mixture that contains outgassing components, for example, from a temperature level of about 200 T to a temperature level of well below 170 T, if this pressure level of 30 to 40 bar from the typically used in a corresponding reactor to a pressure level of 1 to 10 bar (both absolute pressures) is released. A temperature level that sets in when the pressure is released to 7 bar is, for example, approx. 150 TD. This advantageous physical behavior of the relaxed medium, ie the three-phase

Component mixture, is used in the context of the present invention.

In the context of the present invention, the three-phase, which is relaxed to the second pressure level and cooled to the second temperature level, is also used

Component mixture is then at least partially subjected to further cooling to a third temperature level and then subjected to phase separation. This further cooling can take place in particular in one or more heat exchangers

which, however, are burdened to a lesser extent due to the cooling and relaxation that have already taken place and due to other advantages that are achieved within the scope of the present invention and can therefore be produced more cost-effectively or a longer service life when using the same materials as before exhibit. During the subsequent phase separation, there is less outgassing due to the significant pressure reduction that has already been carried out, which makes a renewed phase separation unnecessary. The method proposed according to the invention therefore manages with a smaller number of apparatuses, regulating devices and the like, which can also be produced more cost-effectively within the scope of the present invention.

In particular, within the scope of the present invention, the peak temperature at the one for cooling decreases from the second temperature level to the third

Temperature level used heat exchanger or in several corresponding heat exchangers. This makes the use of inexpensive materials (e.g.

Austenitic stainless steel or comparable) possible with reduced service life.

Alternatively, in the context of the present invention, when using corresponding higher quality materials such as Alloy 600 or nickel-based alloys or nickel, a significant increase in the heat exchanger life can be achieved, which in this way can be in the range of a typical system life. A premature exchange of corresponding heat exchangers is therefore not necessary when using the method proposed according to the invention.

As a result of the relaxation from the first pressure level to the second pressure level, a corresponding heat exchanger is also subjected to a lower pressure.

The same applies to the supply lines and other devices that use the

lead three-phase component mixture. Due to the lower operating pressure, the required wall thickness of the pipes involved and the whole decreases

Heat exchanger. This reduces the thermal mass and inertia. In addition, the use of the present invention also results in lower material costs in this area.

Another advantage achieved by the method according to the invention is that the heat exchanger (s) that is or will be used for cooling from the second to the third temperature level has a lower liquid content flowing through it at the respective inlet. This is the case because, as a result of the expansion from the first pressure level to the second pressure level, some of the gases dissolved in the liquid of the three-phase component mixture outgas and thus increase the proportion of gas or the proportion of the gas phase. Due to the lower proportion of liquid, an even distribution of the multiphase current or the three-phase current can be achieved within the scope of the present invention

Component mixture can be accomplished more easily in one or more corresponding heat exchangers. In this way, the local risk is reduced

Phase changes and thus the risk of increased local corrosion.

As mentioned, the one to cool off from the second to the third

Temperature level used heat exchanger is or are operated at the lower pressure level of the downstream systems, there is practically no flash (outgassing) in the context of the present invention when the liquid phase is discharged. A corresponding flash can be brought about centrally downstream of the heat exchanger or heat exchangers if the operating pressure of the heat exchanger or heat exchangers is close to the operating pressure of the downstream system. A second flash container or phase separator, which is used in the context of conventional methods, as illustrated in FIG. 1, can therefore be omitted.

In the context of the present invention, there is also an advantageous process control that is not possible in the prior art. So far such a

Prozessregelung als nicht möglich angesehen. Nach Stand der Technik werden Gas bzw. Dampf einerseits und Flüssigkeit und Feststoffe andererseits voneinander auf gleichem Druckniveau beispielsweise in einem Separator getrennt und die beiden sich bildenden Ströme werden separat abgeführt. Der Gas- bzw. Dampfstrom dient der Druckregelung des Systems und der Flüssigkeitsstrom wird direkt abgeführt. Durch die im Vergleich zum Gas- bzw. Dampfventil kleine Ventilgröße des Flüssigkeits- und Feststoffventils neigt dieses zur Blockade. In der vorliegenden Erfindung durchströmen hingegen alle Phasen zusammen ein geeignetes Ventil. Durch dessen größere Ausführung werden die Nebeneffekte Blockade und Ablagerung minimiert.

For further advantages that can be achieved by the method proposed according to the invention, express reference is made to the above explanations.

The relaxation is advantageously reduced to the second pressure level

Using a valve assembly carried out the one or more

Have expansion valves each with at least two flow-through sealing edges and a maximum valve cross-section of at least 80% each. In other words, within the scope of the present invention, valves with at least two flow-through sealing edges with the simultaneous possibility of releasing the almost maximum free flow are advantageously used as expansion valves

Flow cross section preferred. In particular, ball valves or modified ball valves with improved control characteristics can be used in this context. The use of at least two sealing edges reduces the susceptibility to erosion, increases the service life of the valves and at the same time ensures good sealing properties. The possibility of opening almost 100% (this can be, for example, 80, 85, 90 or 95% opening or corresponding intermediate values) reduces the susceptibility to blockages due to accumulation and deposition of particles or solids.

According to a particularly preferred embodiment of the present invention, two or more expansion valves arranged in parallel can be in one

corresponding valve arrangement are used, which enable improved controllability of a corresponding system and / or redundant operation with maintainability without interrupting operation.

The first temperature level is advantageously 150 to 220 T, in particular 185 to 210 TD. The second temperature level, so the temperature level that is achieved by the relaxation from the first pressure level to the second pressure level, is typically 120 to 180 TD, in particular 150 to 175 TD and at the same time at least 5 TD below of the first temperature level. By reducing the temperature accordingly, the load on heat exchangers and other devices in one

Device used according to the invention can be significantly reduced in contrast to the prior art, as explained.

The third temperature level is within the scope of the present invention

advantageously at ambient temperature up to 100 ° C., in particular below the boiling point of water. In this way there can be condensation of all

causes condensable components and thus a technically complete

Phase separation can be ensured.

Advantageously, within the scope of the invention, the first pressure level is at an absolute pressure of 10 to 50 bar, in particular 30 to 40 bar, and the second pressure level is an absolute pressure of 1 to 10 bar, in particular 4 to 7 bar.

In the context of the present invention it can be provided that the three-phase component mixture, which has been expanded to the second pressure level and cooled to the second temperature level, is subjected to a first portion of further cooling to the third temperature level and then to phase separation and a second portion without further cooling is subjected to the third temperature level of phase separation. Such a measure can be used to set a mixed temperature that results from the temperatures of the first (further cooled) and the second (not further cooled) portion.

A corresponding measure can, in particular, also include regulating the temperature by adjusting the first and second components to one another

Be set according to a temperature control.

In particular, in this context, the further cooling of the first portion can be carried out using a heat exchange unit with one or more heat exchangers, at which or which the second portion is at least partially passed. For example, within the scope of the present invention, a plurality of heat exchangers can also be used in series, which can be bypassed partially or entirely in accordance with temperature regulation by means of a bypass line.

Advantageously, the phase separation in the context of the present invention includes the use of a phase separation unit, with one in the phase separation

Gas phase and two-phase component mixture, which comprises a liquid phase and solid particles, are formed. As explained, the formation of the liquid phase takes place within the scope of the present invention without significant further outgassing of dissolved gaseous components, so that a repeated

Phase separation can be dispensed with. This is especially true if the

Phase separation unit at a pressure level of 1 to 10 bar absolute pressure,

is preferably operated between 4 and 7 bar absolute pressure. The pressure level of the phase separation unit can also be 1 to 2 bar absolute pressure.

Particular advantages can be achieved in the method according to the invention if a volume fraction of the gas phase in the three-phase component mixture is more than 25% and, for example, up to 75% or 50%. In this case, a particularly advantageous pressure control can be carried out in connection with the measures explained below.

It is particularly advantageous if the three-phase component mixture is removed from the oxidation unit at a first geodetic level, at a second geodetic level of at least partial relaxation from the first

Pressure level is fed to the second pressure level, and is subjected to a third geodetic height of cooling to the second temperature level, the second geodetic height being below the first geodetic height and the third geodetic height being below the second geodetic height. In other words, the exit from the oxidation unit, ie from one or more oxidation reactors, is a high point is or are used on the second pressure level, connected to one or more first lines and the relief valve (s), that is or are used for expansion from the first to the second pressure level are connected to the one or more heat exchangers that are used for further cooling to the third temperature level with one or more second lines. The one or more first and the one or more second lines are in particular laid in a continuously falling manner.

The present invention also extends to an installation for the treatment of waste liquor from a liquor laundry, with respect to which reference is made to the corresponding independent patent claim. A corresponding system is advantageously set up for carrying out a method as previously different

Refinements has been explained, and has appropriate means for this. The features and advantages of a system provided according to the invention should therefore

express reference is made to the above explanations of the method according to the invention and its configurations.

The invention is explained below with reference to the accompanying drawings compared to the prior art.

Brief description of the drawings

Figure 1 illustrates a method for treating a waste liquor according to an embodiment not according to the invention in a simplified representation.

FIG. 2 illustrates a method for treating a waste liquor according to an embodiment of the invention in a simplified representation.

Detailed description of the drawings

In FIG. 1, a method according to an embodiment not according to the invention for treating a waste liquor is illustrated in the form of a greatly simplified process flow diagram.

In the method illustrated in FIG. 1, an oxidation unit 1, which is illustrated here in a very simplified manner, and one or more

Oxidation reactors can include a wet oxidation of a waste liquor carried out. For this purpose, waste liquor is fed to the oxidation unit together with steam and oxygen or an oxygen-containing gas mixture and is subjected to wet oxidation in the oxidation unit for a reaction period at a first temperature level and a first pressure level. The pressures and used here

Temperatures, express reference is made to the explanations above.

In the method illustrated in FIG. 1, a three-phase component mixture, which is illustrated here in the form of a substance flow 101, is removed from the oxidation unit 1 and cooled in a heat exchange unit 110 to the pressure and temperature level at which it was removed from the oxidation unit 1. The heat exchange unit 1 10 is using a

Tempering medium operated, which is illustrated here in the form of a pre-flow stream 1 1 1 and a follow-up stream 1 12.

A three-phase component mixture cooled in this way is fed in the process illustrated in FIG. In the container 121, a liquid phase with particles separates out on the sump side

Two-phase mixture, from. This can be drawn off in the form of a material flow 103 via a valve 122 in accordance with an early level check LC and transferred to a second phase separation unit 130. This is necessary here because when the two-component mixture is expanded, gases dissolved out of the first phase separation unit 120 outgas (flash). In the second phase separation unit 130, which again comprises a container 131, a two-phase unit is therefore again separated

Component mixture in the sump.

A gas phase in the form of a stream 104 is drawn off from the head of the first phase separation unit 120 via a valve 123 in accordance with a pressure control PC. This can be done with a gas phase in the form of a gas phase withdrawn from the phase separation unit 130 via a valve 133 in accordance with a pressure control PC

Material flow 106 are combined to form a collective flow 107.

By means of the method according to the prior art illustrated in FIG. 1, the second phase separation unit 130 can ultimately be used in accordance with a

Level control LC, a liquid flow with particles, that is to say a two-phase flow 105, can be provided via a valve 132, which can be fed to storage or further processing, for example.

In FIG. 2, a method according to an embodiment of the present invention is illustrated in the form of a greatly simplified process flow diagram. Here, too, an oxidation unit 1 is used, with respect to which reference can be made to the explanations relating to FIG. 1 and the explanations given in the introduction.

A three-phase component mixture 201, which comprises a gas phase, a liquid phase and solid particles, is generated from the oxidation unit 1 at the pressure level at which the oxidation unit 1 is operated and at a corresponding pressure level

Temperature level, deducted. In contrast to the method illustrated in FIG. 1, however, this is now initially relaxed by means of a relaxation unit 2. The relaxation takes place from a first pressure level to a second pressure level. Regarding the pressure levels, express reference is made to the explanations above. Due to the existing physical laws, the relaxation results in a cooling of the three-phase

Component mixture 201 and a partial outgassing of dissolved gaseous components. A correspondingly formed, also three-phase

Component mixture is denoted by 202.

The relaxation unit 2 can, as is the case in the embodiment of the present invention illustrated in FIG. 2, two arranged in parallel

Relief valves, 21, 22 comprise, which can be designed in the manner explained above. At least one of these expansion valves 21, 22 can be operated on the basis of a pressure control PC. Instead of providing several expansion valves 21, 22 in parallel, however, valves can be arranged in series or one valve can be arranged individually. In the example shown, in particular switching valves 23 or shut-off valves are upstream or downstream of the expansion valves 21, 22.

downstream.

In the embodiment of the present invention illustrated in FIG. 2, the three-phase component mixture 202, after which it is in the

Relaxation device 2 was relaxed from the first pressure level to the second pressure level, divided into two substreams 203 and 204. However, this is not absolutely necessary. Only one treatment of the entire three-phase component mixture 202 in the manner of the material flow 203 can also be provided. The material flow 204 is not formed in such a case.

In the example shown, the partial flow 203 is fed to a heat exchanger 31 in the heat exchange unit 3, which, as already before with regard to the

Explained heat exchanger according to Figure 1, can be flowed through with a refrigerant. This is shown here in the form of a lead 11 1 and a lag 1 12, as illustrated in FIG. Due to the different cooling requirement here, however, in particular a different refrigerant than in the method illustrated in FIG. 1 can be used. The three-phase component mixture 203 is in

the heat exchanger 31 from the second temperature level to a third

Temperature level further cooled.

In parallel to this, in the embodiment illustrated in FIG. 2, the partial flow 204 is optionally guided past the heat exchanger 31 via a valve 32 in accordance with a temperature control TC and combined with the partial flow 203 cooled there to form a collective flow 205. In this way, a temperature of the

Collective stream 205 can be set.

In the example shown, the collective flow 205 is fed into a phase separation unit 4 which has a container 41. This is provided with valves 42 and 43, which can be controlled via an early level control LC or a pressure control TC. In this way, by means of the phase separation unit 4 or the container 41, a two-phase mixture 206, which represents a liquid phase with particles, and a gas phase 207 can be formed.

In contrast to the embodiment according to the prior art illustrated in FIG. 1, the liquid phase 206 does not need to be subjected to any further phase separation according to this embodiment of the invention, since it has a lower proportion of outgassed components.

Claims

1. A method for the treatment of a waste liquor of a caustic wash, in which the

Waste liquor with oxygen or an oxygen-containing gas mixture and steam is fed to an oxidation unit (1) and in this for a reaction period at a first temperature level and a first pressure level

Wet oxidation is subjected, the oxidation unit (1) being a three-phase component mixture, which is a gas phase, a liquid phase and

Comprises solid particles, is removed and subjected to cooling and phase separation, characterized in that at least part of the three-phase component mixture in an unchanged composition is initially relieved from the first pressure level to a second

Pressure level is supplied and thereby cooled to a second temperature level, and that the three-phase component mixture relaxed to the second pressure level and cooled to the second temperature level is then at least partially subjected to further cooling to a third temperature level and then phase separation.

2. The method according to claim 1, in which the expansion to the second pressure level is carried out using a valve arrangement (2) which has one or more expansion valves (21, 22) each with at least two

have through-flow sealing edges and a maximum valve cross-section of at least 80% each.

3. The method according to claim 2, wherein the relief valve or valves (21, 22) are designed as one or more ball valves.

4. The method according to claim 2 or 3, wherein the valve arrangement (2) comprises two or more expansion valves (21, 22) arranged in parallel.

5. The method according to any one of the preceding claims, wherein the first

Temperature level at 180 to 220 O and the second temperature level at 120 to 180 T and at least 5 T below the first s temperature level.

6. The method according to any one of the preceding claims, wherein the third

Temperature level at ambient temperature up to 100 T.

7. The method according to any one of the preceding claims, wherein the first

Pressure level at an absolute pressure of 20 to 50 bar and the second

Pressure level is at an absolute pressure of 1 to 10 bar.

8. The method according to any one of the preceding claims, wherein the three-phase component mixture relaxed to the second pressure level and cooled to the second temperature level is subjected to a first portion of the further cooling to the third temperature level and then the phase separation and to a second portion without the further Cooling off to the third

Temperature level of the phase separation is subjected.

9. The method according to claim 8, in which the first and the second component are adjusted to one another in accordance with a temperature control.

10. The method according to claim 8 or 9, wherein the further cooling of the first portion is carried out using a heat exchange unit (3) with one or more heat exchangers (31), which or which the second portion is at least partially bypassed.

1 1. Method according to one of the preceding claims, in which the phase separation is carried out using a phase separation unit (4) and in which a gas phase and a two-phase component mixture comprising a liquid phase and solid particles are formed in the phase separation.

12. The method of claim 1 1, wherein the phase separation unit (4) on a

Pressure level of 1 to 10 bar absolute pressure is operated.

13. The method according to any one of the preceding claims, in which a volume fraction of the gas phase in the three-phase component mixture is more than 25%.

14. The method according to any one of the preceding claims, wherein the three-phase component mixture at a first geodetic height of the

Oxidation unit (1) is removed, is supplied at a second geodetic height of at least partial relaxation from the first pressure level to the second pressure level, and at a third geodetic height of the

Is subjected to cooling to the second temperature level, the second geodetic height being below the first geodetic height and the third geodetic height being below the second geodetic height.

15. Plant for the treatment of a waste liquor from a caustic wash, with means which are set up to feed the waste liquor with oxygen or an oxygen-containing gas mixture and steam to an oxidation unit (1) and in this for a reaction period at a first temperature level and a first pressure level of wet oxidation to subject, and means, which are set up, the oxidation unit (1) a three-phase

Component mixture, which is a gas phase, a liquid phase and

Includes solid particles, to be removed and a cooling and

To subject phase separation, characterized in that means are provided which are set up to initially relax at least part of the three-phase component mixture in unchanged composition from the first pressure level to a second pressure level and thereby cool down to a second temperature level, and that means are provided that are set up for the three-phase, which is relaxed to the second pressure level and cooled to the second temperature level

Component mixture then, at least in part, further cooling to a third temperature level and then phase separation

subject.