EA022555B1 - Integrated process for treating refinery waste water, containing ammonia and hydrogen sulphide, and refinery exhaust acid gas containing hydrogen sulphide - Google Patents

Abstract

The invention relates to a process for treating refinery waste water mainly containing hydrogen sulphide and ammonia in addition to acid gases effluent mainly containing hydrogen sulphide, said process comprising the following steps: a) stripping in the stripping tower (100) said waste water (1) at a pressure ranging from 8 to 20 bar g (from 8 to 20 atm) in order to produce a gaseous overhead stream (2) essentially containing hydrogen sulphide and water and a liquid bottom stream (4) essentially containing aqueous ammonia; b) stripping in a second stripping tower (110) the stream (4) at 1-3 bar g (1-3 atm) in order to produce a gaseous overhead stream (5-11) of ammonia essentially pure on dry basis and a liquid bottom stream (6) containing less than 1 ppm of hydrogen sulphide and less than 5 ppm of ammonia, said water composition having the requirements to be discharged into the sewer; c) oxidation on oxidizer deficiency to nitrogen and water of the ammonia contained in the stream (11) in the thermal oxidation unit (170), to produce an outlet stream (12) containing 50-150 ppm in volume of ammonia and 80-200 ppm in volume of nitrogen oxides; d) thermal oxidation of the stream (12) in the thermal oxidiser unit (160).

Description

The present disclosure discloses an integrated method for treating wastewater of an oil refinery, mainly containing ammonia and hydrogen sulfide, and at the same time an acid gas, also from an oil refinery, mainly containing hydrogen sulfide, and this method allows the quantitative removal of ammonia and hydrogen sulfide contained in the above streams, therefore obtaining purified water having a residual ammonia content equal to or less than 5 ppm (parts per million) and a residual hydrogen sulfide content equal to or less than 1 h / nH, and wherein the withdrawn gas contains less than 1500 hr. / gD ₂ million by volume, less than 150 mg / Nm ³ ΝΟ _Χ and less than 1.3 mg / Nm ³ of ammonia.

Hydrodesulfurization and catalytic cracking methods are common methods for the refinery, converting organic compounds containing sulfur into hydrogen sulfide, which is then separated from the fuel by solvent scrubber cleaning and regeneration of which gives off-gases (acidic) having a high content of hydrogen sulfide. Before these wastes are discharged into the atmosphere, hydrogen sulfide is converted to elemental sulfur, which is removed mainly in the form of a liquid.

Moreover, the hydrodesulfurization method, in addition to the conversion of hydrogen sulfide, produces ammonia from nitrogen-containing organic compounds contained in oil fractions. The ammonia thus obtained is accumulated in water for wet purification of hydrocarbons, from which it is removed by low pressure steam. According to current industrial practice, the streams in the aforementioned removal methods, usually produced by steam, are sent to Klaus plants to provide at the same time partial oxidation of both Η ₂ δ and ΝΗ ₃ .

However, acid gas streams and ammonia-containing streams can enter sulfur recovery plants only if the mixture composition ΝΗ ₃ / δ ₂ δ in the total stream formed from mixing the above two streams is equal to or less than the 35/65 molar ratio.

Streams with a content of ΝΗ ₃ greater than 35 mol.% Entail the risk of an excessive increase in the working temperature of the Claus thermal reactor, which, as a result, causes damage to the reactor jacket or deposition of ammonium salts on the relatively cold parts of the installation, so the installation is stopped and further production is not allowed .

The increasing diffusion of oil having a high content of nitrogen-based products causes an inevitable increase in the ratio ΝΗ ₃ / Η ₂ δ above the limits allowed for the proper operation of the Klaus installation.

In addition, the growing sensitivity to environmental issues is forcing local authorities to impose even stricter restrictions on waste emissions. If we consider, in particular, wastewater, it often requires an ammonia content of less than 5 ppm and a hydrogen sulfide content of less than 1 ppm. As for gas emissions, they require less than 1,500 ppmv for §O ₂ , less than 150 mg / Nm ³ ΝΟΧ and less than 1.3 mg / Nm ³ ammonia. It should be pointed out that a sulfur recovery efficiency of more than 99.8% is required to obtain this §O2 value.

Currently, a method for treating wastewater from an oil refinery, mainly containing hydrogen sulfide and ammonia, acid gases, mainly containing hydrogen sulfide, but often also ammonia, has been found, and this method is able to overcome the aforementioned disadvantages.

The present invention consists in an integrated method, providing:

(ί) sulfur recovery efficiency greater than 99.8%;

(ΐΐ) the quantitative removal of ammonia and hydrogen sulfide from the acidic waters of the refinery in order to obtain purified water having an ammonia content of not more than 5 ppm and a hydrogen sulfide content of not more than 1 ppm;

(ΐΐΐ) removal of excess gaseous ammonia, taking into account the amount allowed by the Klaus installation, by thermal oxidation in the incinerator, can provide a content of ΝΟ _Χ less than 150 mg / N-m ³ in the exhaust gases emitted into the atmosphere.

For a better understanding of the present invention, reference is made to FIG. 1 related to the prior art method, and FIG. 2-4 related to the method in accordance with the present invention. A simple comparison between the two technologies allows a better and deeper understanding of the present invention.

Description of FIG. 1 and the related prior art method.

In FIG. 1 are shown:

200 - distillation column;

210 - installation of Klaus to convert hydrogen sulfide into sulfur;

220 - apparatus for extracting mainly δ and §O ₂ from the exhaust gases from the Claus plant through the catalytic reduction of sulfur-containing products in them;

230 - apparatus for thermal oxidation;

240 - pipe for the release of exhaust gases into the atmosphere.

In the installation shown in FIG. 1, wastewater (1), mainly containing ammonia and hydrogen sulfide, is introduced into the distillation column (200) operating under pressure from 0.7 to 1.2 bar (from 0.7 to 1.2 bar)

- 1 022555 g., Where the lower water stream of purified water (3) and the gas stream (2) are formed. The acid gas stream (4) and gas stream (2) are supplied to the Claus unit (210) together with the recirculated exhaust gas stream (5) from the apparatus (220) used to process the exhaust gases of the Claus unit. The Klaus plant turns most of the hydrogen sulfide into a stream of liquid sulfur (6).

The stream (8) from the apparatus (220) mainly contains Ν ₂ , СО ₂ , Н ₂ О, §О _2, and traces of unreformed Н ₂ §. The specified stream is supplied to a thermal oxidation apparatus (230), which converts the residual hydrogen sulfide into §O ₂ . The stream (9) from the thermal oxidation apparatus (230) has almost the same composition as the stream (8), except that it does not contain hydrogen sulfide. Then the specified stream is fed into the apparatus (240), forming a gas stream (10), which is discharged into the atmosphere.

This installation is a viable technical solution only if the molar ratio ΝΗ ₃ / Η ₂ δ in the final stream resulting from mixing the stream (2) and the stream (3) of acid gases and fed into the Claus reactor (20) is equal to or less than 35/65 .

Description of FIG. 2 (configuration A) and the operation of the corresponding installation according to the invention.

In FIG. 2 are shown:

100 - the first distillation column operating under high pressure and not described in the prior art,

110 is a second distillation column operating at low pressure, as described in the prior art;

120 - protective column, also not described in the prior art,

140 is equivalent to installing Klaus 210 in FIG. one,

150 is equivalent to apparatus 220 in FIG. one,

160 is equivalent to apparatus 230 of FIG. one,

170 - apparatus not disclosed in the prior art and consisting of apparatus for thermal oxidation ΝΗ ₃ ,

180 is equivalent to pipe 240 in FIG. one.

The present invention provides two more configurations (FIG. 3, configuration B and FIG. 4, configuration C), wherein these configurations are various embodiments of the basic configuration of FIG. 2.

All of these configurations will be discussed below.

The present invention relates to a method for treating wastewater from an oil refinery containing mainly hydrogen sulfide and ammonia, and furthermore, acidic gases from the oil refinery containing mainly hydrogen sulfide (sometimes also containing ammonia), said method comprising the following steps:

a) distillation in a distant column (100) of said wastewater (1) under a pressure of from 8 to 20 bar (from 8 to 20 atm) g., preferably at 15 bar (at 15 atm) g. to obtain a gas overhead stream ( 2), essentially containing hydrogen sulfide and water, and a liquid lower stream (4), essentially containing aqueous ammonia;

b) distillation in a second distant column (110) of stream (4) at a pressure of 1 to 3 bar (1 to 3 atm) g., preferably at 1 bar (at 1 atm) g. to obtain a gas overhead stream (5 -11) ammonia, substantially pure on a dry basis, and the lower liquid stream (6) containing less than 1 ppm of mass, hydrogen sulfide and less than 5 ppm of ammonia, while the requirements for the specified water stream (6), so that it is removed to the sewage system;

c) oxidizing, when the oxidizing agent is deficient, to ammonia nitrogen and water contained in the stream (11) in the thermal oxidation apparatus (170), to obtain an exit stream (12) containing 50-150 ppmv ammonia and 80-200 ppm. / million volume nitrogen oxides;

b) thermal oxidation of the stream (12) in the apparatus 160 thermal oxidation.

In a preferred embodiment of the invention (FIG. 2, configuration A), the gas stream (5) of pure and dry ammonia is supplied to a protective column (120), where slightly alkaline water (pH 7.5-9) is continuously recycled. The purpose of this column is to retain hydrogen sulfide, possibly present in the stream (5), in order to thus prevent its release into the atmosphere by means of exhaust gases (8). A small amount of demineralized water, stream (9), is fed to the top of the protective column to keep the pH constant, while part of the recycle stream (10) is recycled to the high pressure column to ensure complete removal of hydrogen sulfide. At the outlet of the protective column (120), a gas stream of ammonia (1) is obtained, which is essentially pure in terms of dry matter, which is then fed to the ammonia thermal oxidation apparatus (170).

As for the composition of the streams being cleaned, the liquid water stream (1) usually has an ammonia concentration of from 2.1 to 4.22 mol% and a H ₂ concentration of 1.1 to 3.3 mol% and it is supplemented mainly up to 100 mainly water.

Stream (3) is called acid gas. This term is used in the meaning of a gas stream, the main component of which is H ₂ §, possibly mixed with CO ₂ . However, acid gases may also contain ΝΗ _3, especially from 2 to 15 vol.%. As an exception, acid gases can contain ΝΗ ₃ in an amount of up to 20%, as can be noted in an experimental example based on real data. Typically, stream (3) contains Η ₂ δ in an amount of from 80 to 95 mol% on a dry basis and CO ₂ from 3 to 18 mol% on a dry basis. Stream (3) may also contain hydrocarbons in an amount usually less than 2 mol%.

It should be emphasized that both acid gas (3) and liquid stream (1) have the same origin, i.e. hydrodesulfurization and / or catalytic cracking. The composition of the above flows depends on various factors, in particular on the type of refinery and on its working conditions. However, the important parameter is not the composition of the separate stream (1) and (3), but the molar ratio ΝΗ ₃ / Η ₂ δ of the mixture of streams (2) and (3), while this mixture is obtained in the Klaus burner block. Indeed, the Klaus burner mixes flows (2) and (3) before they enter the Klaus reactor. As mentioned above, the present invention particularly solves the problem when the molar ratio ΝΗ ₃ / Η ₂ δ in the mixture of streams (2) and (3) is greater than 35/65. However, the method of the present invention may also work when the molar ratio ΝΗ ₃ / Η ₂ δ is less than 35/65 due to the flexibility of the method in accordance with the present invention.

Now, as shown in FIG. 2, configuration A, the flow in accordance with the present invention operates as follows.

Wastewater from the refinery containing ammonia and hydrogen sulfide is fed through line (1) to the first distillation column (100) operating at a pressure of 8 to 20 bar (8 to 20 atm) gratis, preferably at about 15 bar (about 15 atm) huts, where hydrogen sulfide is separated from an aqueous solution. From the upper part of this distillation column, stream (2) is discharged at a temperature of from 120 to 200 ° C., preferably at about 140 ° C., said stream containing substantially hydrogen sulfide and water. The upper stream (2) is suitable for processing in a Claus unit (140), which is also capable of receiving acid gas (3) from various apparatuses of the refinery, for example, apparatus for wet cleaning of the amine. The aqueous solution (4), discharged from the bottom of the column (100) and containing almost all ammonia, is supplied after depressurization by means of a suitable distribution valve to the second distillation column (110), placed after the first column, but operating at a pressure of 1 to 3 bar (from 1 to 3 atm) h., preferably at about 1 bar (about 1 atm) h.

Ammonia is separated and removed from the top of the second column in the form of a stream (5) at a temperature of from 100 to 150 ° C, preferably at about 120 ° C, and is fed to the above-described protective column (120). From the bottom of the column (110), a water stream (6) is discharged containing hydrogen sulfide in an amount of less than 1 ppm and ammonia in an amount of less than 5 ppm. Therefore, said water stream is suitable for discharge into surface waters.

The indicated very low level of contaminant products can be obtained by means of a column (100) operating as follows:

heat is supplied to the boiler, equal to 50-100 kcal for each kg of injected solution, preferably 72 kcal / kg;

reflux into the column from 5 to 20 kg / m ^{3 of the} injected solution, preferably 11 kg / m ³ ; at least 30 separation steps are carried out.

In the second column (110), the preferred operating conditions are as follows: heat is supplied to the boiler equal to 60-120 kcal for each kg of solution supplied to the apparatus, preferably 90 kg / m ³ ;

reflux into the column from 140 to 250 kg / m ³ , preferably 225 kg / m ³ ; at least 35 separation steps are carried out.

It should be noted that the multiple distillation apparatus, i.e. (100) + (110), can also work as a single distillation apparatus if the amount of ammonia removed from the wastewater is small, while stream (1) is supplied lower from the distribution valve, as stream (19) in FIG. 3, configuration B, to column (110), excluding columns (100) and (120) from operation. In this case, a single gas stream is obtained from the stripping apparatus, said stream consisting of a wet mixture of hydrogen sulfide and ammonia, which can be sent directly to the Claus apparatus.

As again shown in FIG. 2, configuration A, the stream (5) from the top of the low pressure column (110) contains about 84 vol.% Ammonia and 16 vol.% Water at a temperature of preferably 120 ° C. In a preferred embodiment of the invention, said stream (5) is fed into a protective column (120), where a stream of slightly alkaline water (pH 7.5-9) is continuously recycled. The purpose of this column (120) is to retain hydrogen sulfide, possibly present in the stream (5), so as to prevent its discharge into the atmosphere along with the exhaust gases (8). A small amount of demineralized water, stream (9), is supplied from the top of the protective column (120) to keep the pH of the solution constant, while part of the recycle stream (10) is recycled to the high pressure column (100) to provide full recovery of hydrogen sulfide.

In another embodiment (see FIG. 4, configuration C), especially for reasons related to operational flexibility, stream (5) can be divided into two streams, i.e. a stream (19) supplied to the protective column (120), and a stream (20), which, when combined with the ammonia stream (2), forms an ammonia stream (21) supplied to the Claus apparatus (140). The stream (20) is controlled so that the molar ratio ΝΗ ₃ / Η ₂ δ in the final stream (obtained from all the supplied streams) introduced into the Claus apparatus (140) is less than 35/65,

- 3 022555 while, with an excess of ammonia, the stream (19) is directed to the thermal oxidation apparatus (170).

FIG. 2 and 3 shown below are equivalent. The ammonia stream (11) discharged from the protective column (120) is substantially pure on a dry basis, and this stream is removed after the conversion of ammonia to nitrogen and water in accordance with the following reaction (I):

2ΝΗ _? ι-3 / 2Ο- ·> Ν _; -3Η; Ο (I)

The above partial oxidation reaction (I) proceeds in a corresponding thermal oxidation apparatus, wherein the oxidizing agent is air. If necessary, pure oxygen or enriched air can also be used.

The oxidation reaction (I) is carried out with a small deficiency of the oxidizing agent (for example, using a molar ratio of Ο ₂ / ΝΗ _{3 of} 0.75 / 1 or slightly less than this ratio), then under reducing conditions to obtain in stream (12) exiting thermal apparatus (170), residual ammonia in an amount of from 50 to 150 ppmv volume and the content of nitrogen oxides from 80 to 200 ppmv volume. Reaction (I) is carried out at a temperature of from 1350 to 1500 ° C., preferably at 1500 ° C., with a value of 1350 ° C. being the lowest temperature at which ammonia is converted at a suitable rate.

Then, the stream (12) is supplied to the apparatus for the thermal oxidation of exhaust gases from the sulfur recovery unit (160) operating at a temperature of 850 to 950 ° C, preferably at about 900 ° C, with a small excess of oxygen, say, under oxidation conditions in order to ensure the largest conversion in the denitrification reaction (II), shown by the example of nitric monoxide, but valid for each nitric oxide:

4ΝΗ3 + 2ΝΟ + 2Ο ₂ -3Ν _£ + 6Η ₂ Ο (II)

The above denitrification (II) reaction is widely used in selective non-catalytic reduction (INEC) methods. This reaction allows to reduce both residual ammonia and ΝΟ _Χ until exhaust gas (stream 8) removed into the atmosphere has ΝΟ _Χ less than 150 mg / N-m ³ , residual ammonia is less than 1.3 mg / N-m ³ and 3Ο ₂ less than 1500 ppm The exhaust gas from the apparatus (160) is supplied as a stream (18) to the pipe (180) and then released into the atmosphere as a stream (8).

Sour gas (3) is supplied to the Klaus apparatus (3) from the refinery in the form of a stream (2), and an exhaust gas stream (15) is discharged from the apparatus to the Klaus installation (150). The above stream (15) usually consists of Ν ₂ , H ₂ O and Η ₂ 3, with the latter containing a maximum of 3 vol.%. In another embodiment (FIG. 4, configuration C), in the case of separation of stream (5), acid gas (3) of the refinery, stream (21) and recycling (15) are supplied to the Claus apparatus. The operating conditions of the Klaus installation are well known to specialists in this field, while this method allows the conversion of hydrogen sulfide to liquid sulfur. The extraction efficiency in the Klaus apparatus is about 95% if it consists of two reactors connected in series, or about 97.5% if it consists of three reactors connected in series. Then the exhaust gases from Klaus’s apparatus (140), say, stream (16), will include noticeable amounts of hydrogen sulfide, as well as Ν ₂ , Η ₂ Ο, Η ₂ 3, 3Ο ₂ , POPs. C3 ₂ and H ₂ . To increase the recovery efficiency of sulfur and up to 99.5%, sulfur products having a high oxidation number (3Ο ₂ and 3) and contained in the exhaust gas system (140) are reduced to hydrogen sulfide way catalytic reduction conducted in the apparatus (150). The hydrogen sulfide thus obtained is recycled to the Claus plant (140) for further conversion as a stream (15). At the outlet of the apparatus (150), a stream (17) is obtained, wherein said stream consists essentially of Ν ₂ , CΟ ₂ , Η ₂ Ο, H ₂ Z (usually from 200 to 350 ppm) and 3Ο ₂ typically 20 to 50 ppm Then, the above stream (17) is supplied to the apparatus (160) of thermal oxidation.

In the method in accordance with the present invention, the output streams are:

liquid sulfur (14);

purified water (6);

gas (8) after cleaning in a scrubber.

As for the ammonia stream (11), said ammonia can be separated from the water and stored or used at said refinery. However, this is not always allowed due to several reasons, for example, an oil refinery cannot store ammonia and cannot use it in such quantities.

The integrated method in accordance with the present invention allows you to comply with more and more stringent requirements for the removal of ammonia and hydrogen sulfide from liquid and / or gas streams and to ensure the need for a flexible oil refinery, receiving, on the one hand, the quality of the processed more and more raw oil and, on the other hand, satisfying the increasing demand for diesel fuel with a very low sulfur content.

- 4 022555

In order to provide more detailed data on prior art operations, a number of links are provided below:

S1aik p1ayk + TSSI: 1. Rakdiop, S., Sisggsp. Ρτίηείρί бе11а СЫш1еа 1Ыикайт1е, νοί. 3, Νβΐοάί άί keratasupe e п ripsa / jupe e 1st arrP / acupe ap'nIyk / pa sysh1sa e reI'oPGega, glad. 353 sneakers .; C1ir, 1895, A. Ko11, K. Noekep, Sak ripPsiop, Si1G RiNKYpd Sotrapu, 1997: N.S. Racca11, kA. Batek, Bi1r1shg Reso \ 'egu, Bi1r1shg Exreyk (\ Uek1egp Kekeagsy). This link also contains a chapter related to the Claus plant incinerator.

1stega1ogk; S.E. Vaika1, T1e 21pk SotBikyop Napbok, SKS Rgekk, 2001.

The following example is provided for a better understanding of the present invention.

Example.

The refinery should treat 60 m ³ / h of water contaminated with ammonia (1.20 wt.%) And hydrogen sulfide (1.70 wt.%). Due to the fact that this water is in excess with respect to the overall balance of the refinery, it must be cleaned before being discharged into surface water so that it has a residual ammonia of less than 5 ppm and a residual hydrogen sulfide of less than 1 h ./mln mass.

In addition, it is necessary to remove sulfur from the gas stream (acid gas) of about 1040 Nm ³ / h, containing about 62 vol.% Hydrogen sulfide and 20 vol.% Ammonia from the fluid cracking apparatus and the hydrocracking apparatus. The total ammonia content (summation of the values from the gas stream and from the acid gas) makes it impossible to process these two streams by well-known methods.

And finally, in order to comply with current standards for air emissions, the refinery must extract 99.8% of the sulfur contained in both liquid emissions and exhaust gas streams and provide a ΝΟ _Χ level in pipe fumes of not more than 100 mg / Nm ³ .

Due to this reason, it is necessary to achieve a high degree of purity of the treated water and remove ammonia by means of a specially designed incinerator.

In this case, the molar ratio of ammonia / hydrogen sulfide in the total flow supplied to the Claus apparatus will be about 87 mol.%; then the well-known sulfur recovery unit will not be able to receive the specified stream.

This problem is solved by a two-stage separation of ammonia from hydrogen sulfide and their separation from the waters of the refinery in accordance with the above configuration; the wet pure hydrogen sulfide stream is fed to the Claus plant through a high-pressure stage to convert the hydrogen sulfide into elemental sulfur recovered by condensation. Instead, ammonia is fed into a two-stage thermal oxidation apparatus (incinerator) to turn it into nitrogen and water, and thus reduce the amount of ΝΟ _Χ to 100 mg / N-m ³ .

99.8% sulfur recovery is provided by placing the Klaus plant downstream of the exhaust gas treatment apparatus based on the catalytic reduction of sulfur-containing products contained in the exhaust gases.

Claims (6)

1. A method of treating wastewater from a refinery, mainly containing hydrogen sulfide and ammonia, as well as waste acid gases containing hydrogen sulfide, comprising the following steps, in which: a) distillation column (100) of said wastewater (1) is distilled off at a pressure in the range of 8 to 20 bar (8 to 20 atm) g. to obtain an upper gas stream (2) containing essentially hydrogen sulfide and water and a liquid lower stream (4) containing essentially aqueous ammonia; b) carry out the distillation in the second distillation column (110) of the stream (4) at a pressure of 1 to 3 bar (1 to 3 atm) gage to obtain a substantially pure gas overhead stream calculated on a dry matter basis (5, 11) ammonia and a liquid lower stream (6) containing less than 1 ppm of hydrogen sulfide and less than 5 ppm of ammonia, wherein said liquid lower stream (6) meets the requirements for discharging it into the sewer; c) oxidize the ammonia contained in stream (11) when the oxidizing agent is deficient in nitrogen and water in the thermal oxidation apparatus (170) to obtain an output stream (12) containing 50-150 ppm (volume) ammonia and 80-200 ppm (volumetric) of nitrogen oxides, where the temperature is maintained in the range from 1350 to 1500 ° C with a ratio of Ο ₂ / ΝΗ ₃ 0.75 / 1; ά) conduct thermal oxidation of the stream (12) in the apparatus (160) for thermal oxidation. 2. The method in accordance with claim 1, in which the distillation in step (a) is carried out at 15 bar (at 15 atm) huts. and temperature 140 ° С. 3. The method in accordance with claim 1, in which the distillation in step (b) is carried out at 1 bar (at 1 atm) huts. and a temperature of 120 ° C. 4. The method in accordance with claim 1, in which the stream (1) has the following composition: ammonia - 2.1-4.22 mol%; hydrogen sulfide - 1.1-3.3 mol.%, while the rest is mainly water; and stream (3) in - 5 022555 in terms of dry matter has the following composition: hydrogen sulfide - 80-95 mol.%, Carbon dioxide - 3-18 mol.%; hydrocarbons - less than 2 mol.%; ammonia - 0-20 vol.%. 5. The method according to claim 1, in which the upper stream (5) of the stripping column (110) is sent to the protective column (120) before it is fed as stream (11) to the apparatus (170) for thermal oxidation of ammonia. 6. The method according to claim 5, in which the stream (5) is divided into two streams, for example, a stream (19) supplied to the protective column (120), and a stream (20), which is mixed with the stream (2) to form a stream (21) supplied to the Claus apparatus (140), wherein the speed of the specified stream (20) is controlled so that the molar ratio of ammonia to hydrogen sulfide in the combined supply to the Claus apparatus (140) is less than 35/65 with an excess of ammonia, with this stream (19, 11) is sent to the apparatus (170) for thermal oxidation. FIG. 1 (prior art) Configurations according to the invention (Configuration A) FIG. 2 - 6 022555 Configurations of the Invention (Configuration B) FIG. 3 Configuration according to the invention (Configuration C) FIG. 4