description

Method and device for treating an Ablauqe

The invention relates to a method for treating a waste liquor from a liquor wash using an oxidation reactor and a corresponding plant and a corresponding oxidation reactor 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. Especially at high concentrations

Sulfur compounds, the caustic wash can also be combined 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 incoming steam must be at least as high as the reactor pressure, is the main reason for the steam addition mentioned

overheated steam in question. 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.

The aforementioned steam is added to the oxidation reactor typically via one or more nozzles or lance designs. The distribution of the steam should take place as evenly as possible over the area of ​​the reactor, since the

Oxidation reactor, as mentioned, typically flows through in one direction and cross-mixing is limited as a result. As explained below, a corresponding addition of steam cannot be controlled in conventional processes and systems, or only to a limited extent.

The object of the present invention is to provide a method for wet oxidation of a waste liquor which makes it possible to achieve optimum oxidation of the sulfur constituents of the waste liquor, in particular at an operating pressure of 20 to 40 bar and with a minimum residence time. At the same time, the process should have another

Be controllable operating range, in particular using very different amounts of steam. In the process, the peak operating temperature is to be reduced in order to minimize the corrosive attack on the reactor material, which is mainly dependent on the temperature. Another object of the present invention is to provide a system that can be operated accordingly.

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 and a corresponding oxidation reactor with the features of the respective independent claims. Refinements are the subject of the dependent claims and the following description.

Advantages of the invention

In the method according to the prior art, as mentioned several times, there is an optional preheating of the lye and air, which are then fed into a corresponding

Oxidation reactor are fed. Furthermore, superheated steam is introduced into the oxidation reactor or the waste liquor present there. This is typically kept constant in a mass flow regardless of the current operating situation. Therefore, in the corresponding conventional methods, the temperature in the reactor changes according to the amount of the liquor supplied. The temperature in the reactor can reach the temperature of the steam if no liquor is fed in.

In conventional methods of this type, the superheated steam is added via simple nozzles or lance designs. Using steam superheaters will reduce the likelihood of steam hammer in the steam system. This enables the use of simple perforated pipe constructions as distributors, which then allow sufficient mixing. By the use of

However, overheating steam cannot be excluded from local high peak temperatures on the metal. The location of the steam feed is the hottest point of a corresponding reactor, which makes it a critical point with regard to a corrosion attack.

Due to the construction of steam lances used in conventional processes, minimizing the amount of steam is difficult or impossible. In the optimal case, the smallest amount of steam fed in can be a minimum of 40%, in the real case a minimum of 60% of the normal load, but not less. This is due to the fact that, due to an uneven flow of air to all lance holes, steam blows through

For example, local condensation and incorrect distribution of the steam are to be expected.

When operating in the desired pressure and temperature range of, for example, approx. 30 bar and 200 T, the distance between the desired maximum material wall temperature and the operating temperature is small. The distance is typically only 20 to 50 ° C. The maximum desired operating temperature should not be exceeded. Therefore the temperature in the reactor has to be regulated. This temperature control is advantageously carried out via the amount of steam added. This should advantageously be adjustable from 0 to 100%, with sufficient

Even distribution of the steam should be guaranteed even with small steam operating quantities. It makes sense to use saturated steam or steam that is slightly superheated by 5 to 10 T in order to limit the peak material temperature.

To achieve these goals, the present invention proposes a method for treating a waste liquor from a liquor laundry using a

Oxidation reactor, where, as mentioned, the waste liquor is introduced into the oxidation reactor together with oxygen or an oxygen-containing gas mixture and furthermore steam is introduced into the oxidation reactor. According to the invention it is provided that the steam at least partially by means of a

Steam feed device is introduced, which has one or more cylindrical sections, each with a central axis and each with a wall, the central axis being aligned perpendicularly or being, with several in the wall

Groups of openings are formed, each of the groups each comprising a plurality of the openings and wherein the plurality of openings of each of the groups are arranged in one or more planes which are each oriented perpendicular to the central axis. A plurality of cylindrical sections can be provided in particular in larger reactors. For the sake of clarity, “a” cylindrical section is used below, but the explanations also relate to the case in which several cylindrical sections are provided.

The advantages explained above are achieved by using a corresponding method. Reference is made below to features and advantages of embodiments of methods according to the invention, relating to these systems or oxidation reactors according to the invention with corresponding steam feed devices

in the same way. The features of methods and devices according to the invention as well as corresponding variants are therefore explained together.

In the context of the present invention, in contrast to a horizontal pipeline provided in some known way with one or more rows of holes, steam is advantageously introduced into the reactor exclusively via the aforementioned cylindrical section of one or more corresponding steam feed devices and thus into the waste liquor or into a two-phase mixture introduced from waste liquor and air. The cylindrical section can be designed as a "pin" which, in particular in the middle, is arranged vertically in a corresponding reactor. A corresponding oxidation reactor is typically at least partially cylindrical for its part.

Because the cylindrical section is arranged vertically and in this several groups of openings are provided, which are arranged in several planes one above the other, condensate can collect in the cylindrical section due to condensation of the steam, which has a condensate level corresponding to the pressure conditions in the cylindrical Can train section. In other words, in the method according to the invention, steam is in the

Steam feed device or brought to condensation in its cylindrical section, with a condensate level being formed in the cylindrical section which depends in particular on the pressure of the steam fed in.

In the case of small steam volumes, the cylindrical section fills comparatively heavily with condensate and the steam only flows through those openings which are formed in planes arranged further above. In this way it can be ensured that the openings through which the flow passes are each optimally exposed to steam and that optimal flow conditions are established. In contrast, in

conventional arrangements always acted upon all openings with steam, but the individual openings viewed individually but flowed through less. A method proposed according to the invention therefore results in a uniform distribution of the steam with a low tendency towards steam hammer and pumping. With a higher load, ie with higher steam volumes, and thus a higher pressure in the cylindrical section, the cylindrical section is increasingly emptied of condensate and further openings, which are arranged in lower levels, are flowed through with steam until full load is reached.

If in the context of the present application it is mentioned that each of the groups comprises several of the openings and the several openings of each of the groups are arranged in one or more planes, this is understood to mean that each different groups can each have openings that are above and below a reference plane can be arranged. In this way, even when a corresponding reactor is slightly inclined or when there is turbulence in the condensate level in the cylindrical section, in particular due to the

Steam feed, a sufficient flow must be ensured. In the simplest case, ie when the several openings of each of the groups are arranged in one plane, several rows of holes are arranged one above the other, the openings of different rows of holes advantageously each standing on gaps so that particularly good vapor mixing can be ensured.

In each of the planes, the respective openings are advantageously arranged equidistantly distributed around a circumference defined by a line of intersection of the respective plane with the wall. In other words, each radial lines which emanate from the central axis in the corresponding plane and run through the respective openings enclose identical angles. In this way, especially in the case of a cylindrical design of the oxidation reactor, a uniform

Mixing must be ensured.

Advantageously, in the steam injection device used in a corresponding method, the openings of each of the groups are arranged in a plurality of planes and a maximum distance of the planes in which the openings of one of the groups lie is less than a minimum distance of the planes in which the openings are located two different groups. As already mentioned, the opening of each of the groups does not have to lie in exactly one plane, but can also be arranged in different planes, which, however, are closer to one another than the planes of two different groups.

Advantageously, two, three, four or more of the openings are arranged in each of the planes and, as mentioned, are distributed equidistantly along the wall around the circumference of the cylindrical section. This results in intermediate angles between the openings of 180 ° C, 120 ° C or 90 ° C. The number of openings per level can also be different. In particular, the number of openings can be minimized in a top level so that the lowest possible underload operation can be guaranteed.

Advantageously, the cylindrical portion of the steam feed device has a first end and a second end and is at the first end by a

Closing surface closed. The first end points downwards and ensures that the condensate can collect in the cylindrical section. In particular, at least one further opening can be formed in the closing surface, which ensures that condensate can drain out of the cylindrical section. Several openings can also be arranged in the end surface, the size and number of which can depend in particular on the amount of steam to be processed or fed in.

The cylindrical section is advantageously connected at the second end to a steam feed line and / or holder which extends from the second end of the cylindrical section to a wall of the oxidation reactor used. If a steam feed line is provided, this can in particular be cylindrical and have the same or different diameter as the cylindrical section of the steam feed device. In order to ensure simple production, the diameters are advantageously identical.

The openings in the cylindrical section are advantageously arranged in such a way that steam flows out of this in an outflow direction that is different from a direction in which the steam supply line and / or the brackets of the top view extend from the direction of the central axis. In other words, the openings are each arranged in such a way that steam flowing out through them is advantageously not directed at the feed line and / or holder in order to ensure the most free outflow possible.

Overall, the diameter of the openings can be 5 to 15 mm.

A distance between the second end and a first group of openings arranged closest to it is advantageously L, wherein L is> 15 mm, particularly preferably> 20 mm. Advantageously, the distance between at least some of the groups of openings is the same and is also L. Deviating from this, it can be provided in particular that a distance between the mentioned first group of openings, ie the group of

Openings that are closest to the holder or the steam supply line, and a second group of openings following this direction of the first end is 1.5 times L. With particular advantage, a distance between the first end of the cylindrical section, ie between the end at which it is closed with the closing surface, and a group of openings arranged closest to it is M, where M is in particular 1.5 times the diameter corresponds to the openings.

As mentioned, the holes or openings are arranged offset from one another in different groups, in particular placed in a gap with one another. As also mentioned, the openings are advantageously arranged in such a way that the steam jet that is formed is only slightly influenced by the feed line or the supports of the steam feed device. If, for example, three openings are used, the angle of the respective radial lines which extend through the openings starting from the center line is 120 °. A radial line which, starting from the center line, extends in the direction of one of the openings, is advantageously aligned 60 ° to the axis of a corresponding carrier or a supply line.

The openings are advantageously surrounded by steam guiding structures which can be designed as nozzles or simple bores in the wall. These define a direction of outflow for the steam from the corresponding openings. The outflow direction corresponds to a radial direction starting from the central axis in the respective plane or is inclined by up to 30 ° with respect to this.

If it is mentioned above that a steam feed line is used, this is advantageously closed on a side through which there is no flow or is advantageously provided with drain holes.

In contrast to the prior art, the speed of the steam in the steam supply line can correspond to the speed of the steam in the respective bores. In conventional devices, however, the former is always larger by a factor of more than five. In the context of the present invention, a steam speed can be used or set in the feed line which advantageously corresponds at least to the speed of the steam in the openings and is preferably more than a factor of 1.5 greater than this. In all cases, however, the steam speed in the feed line can be below 10 times, 5 times or 2 times the steam speed in the openings.

A further advantage of the measures proposed according to the invention is that the pressure loss of the supply line has a minimal influence on the flow through the openings, since the openings are arranged centrally and thus work practically at the same pre-pressure. With conventional longitudinal distributors (steam plants), a high pressure loss leads to a strong change in the flow through the nozzles over the length of the longitudinal distributor.

In the context of the present invention, the steam speed in the

Openings or the minimum speed can be determined via the so-called Froude number (Fr), a common criterion being Fr> 6. The maximal

Speed ​​is about the rate of erosion in terms of steam and

Lance material set. The target size in the mentioned operation is 10 to 65 meters per second, in particular 20 to 30 meters per second.

A plant and an oxidation reactor with corresponding features are also the subject of the present invention. For features and advantages of this plant and this oxidation reactor, refer to the above explanations and the

corresponding claims are expressly referred to.

The invention is explained in more detail below with reference to the accompanying drawings, which illustrate a preferred embodiment of the present invention.

Brief description of the drawings

Figure 1 illustrates an oxidation reactor for use in a plant according to an embodiment of the invention in a schematic partial representation.

FIG. 2A illustrates a steam feed device for use in a system according to an embodiment of the invention in a first embodiment.

FIG. 2B illustrates a steam feed device for use in a plant according to an embodiment of the present invention in a second embodiment.

In the figures, elements that correspond to one another functionally or structurally are each given with identical reference symbols. For the sake of clarity, these are not explained repeatedly.

Detailed description of the drawings

In FIG. 1, a section of an oxidation reactor for use in a plant according to an embodiment of the present invention is illustrated in a highly simplified schematic and denoted overall by 100. The oxidation reactor 100 has a wall 110 which encloses an interior 120 of the oxidation reactor 100. A waste liquor or a waste liquor-air mixture can be received in the interior space 120 and, for example, essentially in the direction here in each case with 130

illustrated arrows are guided.

As mentioned, in particular the oxidizing air and the waste liquor before the

Feed into the oxidation reactor 100 are heated. An additional

Heating can take place by means of a steam stream 140, which, as illustrated here, is introduced via a steam feed device 10 into the oxidation reactor 100 or into the waste liquor contained therein.

The steam feed device 10 comprises a cylindrical section 1 1, which has a central axis 12, which is in particular a central axis of the

Oxidation reactor 100 may correspond overall. The cylindrical section 11 comprises a wall 13. The central axis 12 is aligned vertically. A plurality of openings 14 are arranged in the wall 13, which are only partially provided with reference symbols. The openings 14 are arranged in a plurality of groups, each of the groups comprising a plurality of the openings 14 and being arranged in a plurality of openings of each of the groups in one or more planes, which are illustrated here by dashed lines and denoted by 15.

The planes 15 are each aligned perpendicular to the central axis 12. In other words, the central axis 12 intersects the planes 15 perpendicularly. In this way, within the scope of the present invention, several rows of openings 14 or rows of holes are formed, which allow condensate to accumulate in the cylindrical section 11 and only the openings 14 that remain free of steam in the interior 120 of the oxidation reactor 100 or in the waste liquor present there is introduced. In this way, a corresponding oxidation reactor 100 can be operated in an optimized manner, as explained several times above.

As explained, the openings 14 are provided in the different planes 15 in the same or different numbers, in particular in a plane 15 shown here above only a smaller number of openings can be provided in order to enable a minimum load. Regarding the distances l 0 and L of the individual planes 14 from one another and with regard to the cylindrical section 11, express reference is made to the above explanations.

At a lower end or first end, the cylindrical section 11 is closed by an end surface 16 in which at least one further opening 17 is arranged. At an opposite second end of the cylindrical

Section 11, this is connected to a steam supply line 18, which can have the same or different diameter to the cylindrical section. The row of openings 14 lying closest to the steam supply line 18 advantageously has the smallest number of openings 14. The design and orientation of the respective openings 14 have been explained in detail above. The

Steam supply line 18 is closed at one end by a closure or has one or more further openings 20.

In FIG. 2A, the steam feed device 10, which is already illustrated in FIG. 1 as part of the oxidation reactor 100, is shown in a different perspective, a plan view along the axis 12 according to FIG. 1 from below being shown here. As shown here, the openings 14 are arranged in the cylindrical section 11 in such a way that an outflow direction for steam defined by them deviates from a central axis of the steam supply line 18.

If, as shown in the example shown in FIG. 2A, three openings are illustrated in one plane, an intermediate angle between these is 120 ° C and these are inclined at the illustrated angle of 60 ° C with respect to a perpendicular to the central axis of the supply line 18.

FIG. 2B shows the corresponding relationships already shown in FIG. 2A for the case that four openings 14 are provided in a plane 15 of a corresponding cylindrical section 11.

Claims

1. A method for treating a waste liquor from a caustic wash using an oxidation reactor (100), wherein the waste liquor is introduced into the oxidation reactor (100) with oxygen or with an oxygen-containing gas mixture and steam is introduced into the oxidation reactor (100), characterized in that the steam is introduced at least partially by means of a steam feed device (10) which has one or more cylindrical sections (1 1) each with a central axis (12) and each with a wall (13), the central axis (12) being or being aligned vertically, in several groups of openings (14) are formed in the wall, each of the groups comprises several of the openings (14), and the several openings (14) of each of the groups are arranged in one or more planes (15),which is or are each aligned perpendicular to the central axis (12).

2. The method according to claim 1, wherein the openings (14) in each of the planes (15) are arranged distributed equidistantly around a circumference defined by a line of intersection of the respective plane (15) with the wall (13).

3. The method of claim 1 or claim 2, wherein the openings (14) in each of the groups are arranged in a plurality of the planes (15) and a maximum distance of the planes (15) in which the openings (14) of one of the groups lie, is less than a minimum distance between the planes (15) in which the openings (14) of two different groups are located.

4. The method according to any one of the preceding claims, wherein in each of

Levels (15) two, three, four or more of the openings (14) are arranged.

5. The method according to any one of the preceding claims, wherein the cylindrical portion (1 1) has a first end and a second end and is closed at the first end by a closure surface (16).

6. The method according to claim 5, wherein at least one further opening (17) is formed in the end surface (16).

7. The method according to claim 5 or 6, wherein the cylindrical portion is connected to the second end with a steam supply line (18) and / or holder, which extends from the second end of the cylindrical portion (1 1) to a wall ( 1 10) of the oxidation reactor (100) extends.

8. The method according to claim 7, wherein the openings (14) are arranged such that the steam flows out of these in an outflow direction that is different from a direction in which the steam supply line (18) and / or the holder is in Top view from the direction of the central axis (12) extends.

9. The method according to any one of claims 5 to 8, wherein a distance between the second end and a first group of openings (14) arranged closest thereto is L, L being greater than or equal to 15 mm.

10. The method of claim 9, wherein a distance between at least a part of the groups of openings is equal and is L.

1 1. The method according to claim 10, wherein a distance between the first group of openings and a second group of openings following this in the direction of the first end is 1.5 times L.

12. The method according to any one of the preceding claims, wherein a distance

between the first end and a group of openings (14) arranged closest thereto is larger than M, M being 1.5 times the diameter of the openings (14).

13. The method according to any one of the preceding claims, wherein the openings (14) are surrounded by vapor guide structures which define an outflow direction which corresponds to a radial direction starting from the central axis in the respective plane or is inclined by up to 30 ° with respect to this.

14. Plant for carrying out a method for treating a waste liquor from a caustic washing, with means which are set up for the waste liquor together with oxygen or with an oxygen-containing gas mixture in one

To feed the oxidation reactor (100) and with means which are set up to introduce steam into the oxidation reactor (100), characterized in that the means which are set up to introduce the steam into the oxidation reactor (100), a steam feed device (10) comprise, which has one or more cylindrical sections (1 1) each with a central axis (12) and each a wall (13), the central axis (12) being aligned vertically, in the wall several groups of openings (14) are formed , each of the groups comprises a plurality of the openings (14), and the plurality of openings (14) of each of the groups are arranged in one or more planes (15) which are each oriented perpendicular to the central axis (12).

15. Oxidation reactor (100) for use in a system for carrying out a

A method for treating a waste liquor from a caustic wash, wherein the system has means which are set up to feed the waste liquor together with oxygen or with an oxygen-containing gas mixture into the oxidation reactor (100) and having means which are set up to add steam to the

Initiate oxidation reactor (100), characterized in that the means which are set up to introduce the steam into the oxidation reactor (100) comprise a steam feed device (10) which has one or more cylindrical sections (1 1) each with a central axis ( 12) and each having a wall (13), the central axis (12) being aligned vertically, several groups of openings (14) being formed in the wall, each of the groups comprising several of the openings (14), and the several openings ( 14) each of the groups are arranged in one or more planes (15) which are each aligned perpendicular to the central axis (12).