MXPA97001646A - Procedure and device of craqueo odesintegracion of ammonia present in a gas containing acid sulfhidr - Google Patents

Abstract

The present invention relates to a process for the catalytic cracking of ammonia present in a fluid containing hydrogen sulphide, in which the fluid is introduced into a reactor comprising an appropriate catalyst, and a catalytic cracking effluent is recovered. The temperature of the reaction zone is from 1000 to 1400 ° C, and the reactor for the application of the process comprises at least one heating chamber (3,4) and at least one catalysis chamber (11) in which the ammonia is cracked without cracking the hydrogen sulfide. According to another variant, the reactor can comprise at least one catalyst in the spaces defined between the heating elements.

Description

PROCEDURE AND DEVICE FOR CRACKING OR DISINTEGRATION OF AMMONIA PRESENT IN A GAS CONTAINING SULF HYDRIC ACID DESCRIPTION OF THE INVENTION The present invention concerns a process and a device for catalytic cracking of ammonia contained in a gaseous or liquid fluid, comprising hydrogen sulfide. The invention also concerns its use in a process or device for the removal of hydrogen sulfide. It is well known that petroleum may contain nitrogenous indole or pyridine type molecules. During hydrotreating operations, the nitrogen contained in these molecules is transformed into ammonia (NH3). This ammonia is removed by washing with water which, as a consequence of the presence of hydrogen sulfide (H2S), provides an aqueous solution of ammonium sulphide. Until now, the aqueous solution, after having been concentrated in H2S and NH3 by steam drag, was sent to incineration. This is not currently admitted, for reasons that affect the environment (pollution by SO2). Currently, the refineries send this product to the thermal zone of a Claus unit. If the ammonia is badly incinerated, which is often the case, solid salts such as sulphides or ammonium sulphites are formed, and blockages occur in the colder parts of the Claus unit, particularly in the condensers. sulfur. To burn well the REF: 24199 ammonia, requires a homogeneous mixture of ammonia with air, and a high flame temperature. However, the formation of nitrogen oxides that favors the oxidation of sulfur dioxide (SO2) in sulfuric anhydride (S03) is observed. The Claus catalyst is then sulfated, and corrosion is observed on the cold parts of the unit. Improvements have been made by the use of more complex combustion systems, such as a single burner with derivation of one part of H2S, or two burners, one for H2S and the other for the gas containing the ammonia. These innovations present the disadvantage of a high cost, and of a greater difficulty in regulating an H2S / SO2 ratio equal to 2, necessary to achieve a high performance of the Claus unit. On the other hand, the combustion of ammonia has a direct effect on the conversion of the Claus unit: - dilution effect due to the increase in the amount of air injected; -Unfavorable effect on the thermodynamic equilibrium due to the production of water vapor. Thus, the presence of 18.7% by volume of ammonia in the charge (H2S) of a Claus unit produces an increase in the production of returned gas (most of the nitrogen) of 53.7%, and an increase in the emission of sulfur-containing products. of 47.8% in relation to the operation of the unit in the presence of the same amount of H2S free of ammonia (BG Goar Hydrocarbon, Processing, July 1974, page 129 to page 132).

To avoid these disadvantages, a more interesting route has been studied, which consists of cracking the ammonia in nitrogen and hydrogen. For example, US patents 4273748 and 4273749 describe the use of iron-based or nickel-based catalysts to decompose the ammonia from coal gasification. However, the sulfhydric acid present poisons the catalyst. This makes it necessary to work in two stages: -in a first stage, the gas is passed over a catalyst at a temperature of 450 to 700 ° C, in order to remove substantially all the hydrogen sulfide; the catalyst having been sulfided must be regenerated by oxidation; -in a second stage, the purified gas is released from all the ammonia, passing over a catalyst at a temperature that reaches 900 ° C. Patent US4374105 describes the use of zinc oxide to decompose the ammonia in the presence of H2S . This catalyst does not allow a total conversion of NH3 and on the other hand, it also needs a regeneration step by oxidation. Finally, the German patent DE 320 9858 describes a process in which the catalytic dissociation of ammonia in the presence of hydrogen sulfide on a nickel-based catalyst is carried out at temperatures between 1000 and 1200 ° C.

According to this patent, the obtaining of these high temperatures is achieved by reducing combustion of the gas to be treated with the aid of combustible gas. The fact of mixing the gas to be treated containing the ammonia with fuel gas and air and then effecting a reductive combustion of the assembly offers serious disadvantages from the point of view of the treatment of the residual hydrogen sulfide below the catalytic dissociation stage of the ammonia: - The combustion of the fuel gas produces large amounts of water, which means that all the gas leaving the ammonia dissociation reactor can not be admitted as such to the Claus unit. In the German patent, about two thirds of this gas must be cooled to allow the condensation of this combustion water in the distribution column. In addition, the water produced in this way by condensation may contain certain impurities (traces of undissociated ammonia, traces of hydrogen sulfide ...) that make it impossible to return to the environment without prior treatment; -combusting combustible gas (usually made up of methane and other light hydrocarbons) produces large quantities of carbon dioxide, which will react with hydrogen sulfide to form carbon oxysulfide and carbon disulfide in significant quantities, taking take into account the conditions prevailing at the level of the catalysis zone of ammonia dissociation (elevated temperature and partial pressure of hydrogen sulphide). Or, it is well known that these products are particularly difficult to subsequently hydrolyze at the level of the catalytic beds of the Claus unit; -Finally, the presence of comburent in the combustion causes the presence of nitrogen, which can not condense and which contributes to dilute the gas mixture. One of the objects of the invention is to remedy the drawbacks of the prior art. Another object is to return as little as possible of toxic pollutants to the atmosphere. Another object is to keep the catalyst in good working condition as long as possible, avoiding its regeneration. Another object concerns the use of catalytic thermal ovens, of ceramic material, specially adapted for the catalytic cracking of the ammonia contained in a gas comprising hydrogen sulfide.

More precisely, the invention concerns a catalytic cracking process of the ammonia present in a fluid containing hydrochloric acid, into which the fluid is introduced into a reaction zone comprising an appropriate catalyst, and a catalytic cracking effluent is recovered. The temperature of the reaction zone is generally between 1000 and 1400 ° C, and is obtained by means of heating or heat exchange, contained within the reaction zone. In no case will there be a mixture of the gas to be treated with a fluid that provides the heat necessary for the dissociation reactions.

The method according to the invention, in which only the fluid is introduced into the reaction zone needs a simple equipment, and allows the direct shipment to the Claus unit of all the gas leaving the ammonia dissociation reactor without dilution of the gas, contrary to the patent DE 320 9858. This contributes to improve the performance of the conversion. Preferably, the temperature of the reaction zone is 1150 to 1250 ° C. According to another characteristic, the pressure in the reaction zone is usually that of the fluid entering it, and that it is brought into contact with the catalyst . Advantageously, this pressure can be comprised between 1.07 and 5.095 kg / cm2 (1.05 and 5 absolute bars). According to another characteristic of the invention, the fluid can be injected at a flow rate such that the residence time in the catalytic reaction zone is between 0.1 and 100 seconds, and preferably between 0. 5 and 10 seconds. The residence time is shorter because the final temperature is higher. Under these operating conditions, the ammonia conversion ratio is greater than 99.5%, and still remains greater than 99.5% over a longer period of time, for example for at least 2000 hours.

The conversion ratio of hydrogen sulphide is and generally remains less than 10%, advantageously less than 4%, and preferably less than 2%. The treated loads can be liquid or gas. In general, they are in aqueous form, containing NH4OH and H2S, or in gaseous form, containing H2S, NH3, and eventually water vapor. These fillers can be at least one effluent selected from the group consisting of head effluents from a steam stripping device of refinery wastewater, coal gasification effluents, and biogas. The effluents from the manufacture of coke (coke-making gas), which also contain hydrocyanic acid, can also be treated according to the process and the device of the present invention. In the presence of water vapor, the dissociation of hydrocyanic acid leads, according to known reactions, to the formation of nitrogen, hydrogen and carbon monoxide, and then carbon dioxide. The hydrogen obtained can contribute to improving the conversion performance of the Claus unit, below. After removal of the ammonia, the sulfuric acid can then be destroyed in a conventional manner. For example, in the case of the treatment of a head effluent from a steam stripping device of a refinery wastewater, the gas after cracking can be sent very naturally to the thermal zone of a Claus unit. In the case where there is no Claus unit available, any method of purifying the gas containing H2S can be used, for example by chemical absorption. The catalyst used can be selected from the group consisting of at least one noble metal of group VIII, at least one metal of group VII, at least one metal of group VII, mixed with at least one metal of group VII, at least one metal of group VIII, at least one metal of group VI B, at least one non-noble metal of group VIII in admixture with at least one metal of group VI B and at least one non-noble metal of group VIII with at least one noble metal of group VIII. Preferably, cobalt or nickel may be used in a mixture with molybdenum or tungsten. Among the metals of the group V B, the Rhenium alone or associated with the noble metals of group VIII are preferred: Ru, Rh, Pd, Os, Ir, Pt, advantageously Re-Pt. Other catalysts can be used, such as those described in EP-A-27069, incorporated by reference, which also contain cerium. The catalysts can be in the metallic form (filament of W, Mo or Pt for example) supported (alumina, silica, silicas-aluminas, titanium oxide, cordierite), made pellets or extruded (oxides or sulfides of Co-Mo for example) ).

According to a first embodiment, the reaction zone is usually a reactor that contains a catalyst that allows to reach very high temperatures, preferably a reactor of ceramic material, heated by means of heating or heat exchange substantially perpendicular to the axis of the reactor , but in the direction of the exit of the fluids. More precisely, the invention concerns a catalytic reactor of elongated shape according to an axis, comprising at a first end at least one means of feeding in at least one load, at the opposite end at least one means of evacuation of the effluents produced, the reactor comprises heating means disposed in substantially parallel layers that determine cross sections substantially perpendicular to the axis of the reactor, in such a way that define between the means and / or the layers formed by these means, spaces or passages for the circulation of the load and / or effluents, the reactor is characterized, according to a first embodiment, because it comprises at least one elementary reaction zone (Zj) containing, according to the axis, in the direction of the output of the load and / or the effluents, a heating chamber containing the heating means, followed by a catalysis chamber containing at least one catalyst. The alternating circulation of the gases in a heating zone and then in a catalytic zone makes it possible to dissociate the ammonia in an almost isothermal manner and thus obtain a better ammonia conversion ratio than in the case of the adiabatic reactor described according to the German patent DE 3209858 The reactor may contain no more than a single elementary reaction zone Z comprising a heating chamber communicated to the charge feeding means, and below this, a catalysis chamber connected to the effluent evacuation means, particularly when The treated load is very diluted in ammonia. According to another variant, the reactor can comprise a plurality of elementary reaction zones Z i, i is advantageously comprised between 1 and 10, arranged in series along the axis, the catalytic chamber of the zone Zn above is adjacent to the heating chamber from this zone Z below. The temperature of the heating chamber of this zone Zj is advantageously greater than that of the zone ZM above, which in turn is higher than that of the zone Zμ2, more still above, and so on. The catalyst can also be introduced in at least part of the spaces defined between the heating means of the heating chamber, preferably between those with a temperature at least equal to 600 ° C. The length of the zones, as well as their number, depend on the ammonia concentration of the load, and on the selected conversion ratio.

According to a second embodiment of the device, the catalytic reactor can comprise heating means arranged in substantially parallel layers, which determine cross sections substantially perpendicular to the axis of the reactor, in such a way that they define between the means and / or the layers formed by these means, spaces or passages for the circulation of cargo or effluents. These spaces are filled with at least one catalyst. According to these two embodiments of the device, each heating cross section may comprise at least one heating or heat exchange means. They can be filled with catalyst over the entire length of the reactor, but since there is no conversion to a low temperature, it is advantageous that only the spaces that are in a temperature range at least equal to 600 ° C contain the catalyst. Preferably, the spaces at a temperature higher than 900 ° C will be full of catalyst. Thus a substantial economy is realized. According to the second embodiment, there is no longer an adiabatic zone of catalysis, contrary to the first mode. The temperature profile can be increasing, with or without plateaus. It may be advantageous to provide at least one partition of refractory material substantially parallel to the axis of the reactor, in such a way that the flow is divided. Thus, this partition participates in the radiative exchange.

Thus, at least two substantially parallel channels are defined, in which the elementary reaction zones, or the heating means, are arranged when the space between these heating means contains the catalyst. The heating means generally constitute, in the spaces or passages, successive transverse strata, independent and substantially perpendicular to the axis of the reactor. According to a characteristic of the reactor, the heating means may comprise conduits, in which electrical resistances are arranged. This embodiment is for example that described in French patent FR2662158, incorporated herein by reference. According to this same patent, in the interior space between the conduits and the electrical resistances, a gas containing hydrogen, nitrogen, water vapor or a mixture of these products can circulate at a pressure generally higher than the gas pressure of the gas. reaction inside the reactor. According to another variant, the heating means can be at least one heat exchange medium comprising a tube, formed of at least one cover, connected to a gas supply means or a mixture of heat exchange gas, adapted for exchange heat with the reagent (s) (effluents) that circulate outside the heat exchange medium. The latter generally comprises at least one evacuation means to the outside of the reactor of the gas or mixture of gases that have exchanged heat with the effluent (s). Advantageously, this heat exchange means is communicated with a gas burner connected to fuel gas and combustion gas supply means, as described in patents FR2616518, FR2616520 and FR2715583, incorporated by reference. Means for feedback and modulation of electrical heating or by means of hot gas are generally connected to the heating chamber of each elementary zone, more generally to each heating cross-section whose fluid circulation spaces contain the catalyst. According to one of the features of the invention, the heating chambers are independently powered by electric energy or hot gas, either separately, either by transverse rows, or also by small groups, so as to define heating sections along the heating chambers, and in order to be able to modulate the amount of energy supplied throughout this zone. The modulation of these heating sections can be done in a classical manner; the heating elements, in the case of electric heating, correspond to the sections mentioned above are generally supplied by thyristor modulator assemblies. The transformers allow to eventually adapt the voltages a priori, when the modulators allow the fine and continuous adjustment of the injected energy.

In order to allow the regulation of the assembly, each heating section can be provided with a thermoelectric pyrometric pair adapted to the temperature level; these pairs are arranged in the spaces where the load circulates, the information is transmitted to the regulator that drives the thyristor modulator in the case of electric heating. The temperature profile in each heating zone is generally increasing, while the catalytic zone is substantially adiabatic.

In the case where the spaces between the heating sections contain catalyst, the temperature profile may be increasing with or without plateaus, and there is no adiabatic zone. The electrical energy supplied to this first heating chamber is such that it generates a strong temperature gradient, which allows an average temperature of the load, on the heating chamber considered relatively high, which is favorable to the conversion reaction. The invention tconcerns the use of a catalytic reactor according to the invention in an integrated process for the removal of hydrogen sulphide and ammonia contained in a gas, the latter of which may contain hydrocyanic acid. A unit of the Claus type for eliminating the sulfur is known, comprising a burner (B) receiving the charge containing the hydrogen sulfide and air, and disposed at the entrance of the combustion chamber (CC) of the Claus unit. Below the chamber, a boiler (Ch) is located to recover the stored energy of combustion. The effluents from the boiler are cooled in a sulfur condenser Ci, and the sulfur is recovered. The gaseous effluents of the condenser are introduced into at least one device (Di), which comprises a heater (Ri) of the effluent followed by a catalytic bed Claus (CRi) followed in turn by a condenser (Ci) of sulfur, recovering the sulfur solid of the effluent released from the sulfur. This last effluent can be sent finally to a TGT tail gas treatment unit of Claus. According to the invention, the gas to be treated containing H2S, NH3 and N2O, optionally liberated from the water contained in a separator or distiller S and previously heated with steam, is introduced into the catalytic (F) cracking reactor (dissociation) according to the invention. The cracked gaseous effluent, substantially released from the ammonia and at a very high temperature, can be introduced at least in part: 1-either to the burner supply (B) of the Claus unit .. This solution makes it possible to limit the eventual aid fuel gas while recovering the heat released by the reactor F to the level of the boiler (Ch); 2 - either at the output of the CC combustion chamber of the Claus unit.

This solution allows to recover the heat released by the reactor F at the level of the boiler Ch and above all to avoid the combustion of the hydrogen produced by the dissociation of the ammonia, and tlimit the dilution of the gas that feeds the catalytic beds Claus (CRi), that improves the sulfur performance of these beds; 3- either at the level of the heaters (Ri) of the devices (Di), at the entrance of the catalytic beds (CRi). This solution allows to reduce the operating costs of the Claus unit, and simplify its conception (the heater can then be replaced by a simple mixture with the hot gas). It allows, like the previous one, to avoid the combustion of hydrogen produced by the dissociation of ammonia.

The hot effluent from the dissociation reactor F can also be introduced, once cooled, to the inlet of the Claus tail gas treatment unit (TGT). This solution, as well as solutions 2 and 3 allow, when the TGT is a procedure that incorporates a stage of hydrogenation (SCOT procedure for example) simplify this stage and reduce the consumption of fuel gas necessary for the production of hydrogen, because it uses the produced by the dissociation of ammonia. They are made possible by the fact that hydrocarbons, usually present in traces (-1% by volume) SE, have been reduced in H2, CO, CO2 in the catalytic F furnace of dissociation.

The invention will be better understood in view of the figures schematically illustrating the method and device, among which: - Figures 1 and 2 represent a longitudinal section of a reactor along the axis of the ducts, - Figure 3 illustrates a embodiment detail of the heating chamber, which is fed on the other hand by a guide gas, and - figures 4 and 5 illustrate another embodiment of the device, in which the spaces between the transverse heating elements contain catalyst. In figure 1, according to an embodiment, there is represented a reactor (1) of ceramic material, vertical, elongated and rectangular section, comprising a distributor (2) that allows to feed through an entrance hole ( 5) the reactor with a reaction gas mixture. The latter, which contains a mixture of water vapor, S02 and NH3, has been previously heated in a conventional preheating zone, not shown in the figure, preferably by convection. The reactor comprises two elementary reaction zones Zi and Z2 in series, each of them comprising a heating chamber and a catalytic chamber whose length may vary from one elementary reaction zone to the other. Each heating chamber of the reactor comprises a plurality of electrical heating means (3) surrounded by ducts (4) arranged in parallel layers, and forming in a plane (plane of the figure) a beam with square pitch. These strata define transverse heating sections substantially perpendicular to the axis of the reactor defined according to the direction of exit of the load, each of the cross sections of heating comprises at least one heating means. These heating sections are powered by electric power, independently, thanks to a pair of electrodes not shown, and pyrometric thermocouple probes (7) are housed in the spaces where the load flows between the ducts (4) and allow automatic adjustment the temperature of each heating section, by a classical regulation and modulation device not shown in the figure. In the first heating chamber, the ducts are heated in such a way that the temperature of the load passes quickly from 150-300 ° C (pre-heating temperature) to around 1100 ° C. The parallel strata can form in a plane ( figure plane) a square passage beam, as shown in figure 1. In this figure 1, 6 parallel heating layers are shown, which define 4 transversal heating sections. These numbers may vary depending on the concentration and especially the gas flows to be treated. Following the first heating chamber of the first elementary reaction zone which allows the load to be heated, for example up to 110 ° C, a first catalytic chamber (11) containing, for example, a catalyst in the form of a honeycomb is provided. as that described in the patent EP27069, between two grids (12) crossed by holes through which the heated load is introduced at 1100 ° C in the catalytic zone. The temperature then falls to 1000 ° C after the crossing of the first catalysis chamber. A second heating chamber, corresponding to the second elementary reaction zone Z2 adjacent to the first catalysis chamber, allows the effluent to be brought to a temperature of approximately 1250 ° C. This temperature drops to 1200 ° C at the outlet of the second catalysis chamber. The recovered effluent, which does not substantially contain ammonia, is collected in the lower part (8) of the reactor (1) and evacuated through an exit orifice (10). The effluent contains essentially hydrogen sulfide, hydrogen and nitrogen. In figure 2, according to another embodiment, there is represented a reactor (1) of elongated shape and rectangular section, with the same references as those of figure 1. It comprises ducts (4) arranged in parallel layers, which define cross sections to the axis of the reactor, and form in a plane (plane of the figure) a square passage beam. Several layers are separated by a wall (22) of ceramic material, substantially parallel to the axis that defines in that precise case two channels. These walls have a shape, adapted to create turbulence, comprises alveoli at the level of each conduit (4). The walls of the reactor can on the other hand comprise cells as indicated in the figure. Figure 3 represents for the reactor the same elements as those described in connection with figure 1 or 2; FIG. 3 shows a protective box (30) comprising at one end a hole (31) through which the gas G containing nitrogen, for example, is introduced. Another hole, provided with a valve not shown at the other end, allows regulating the flow of this gas G. This box (30) is fixed on the metallic frame of the reactor (1) and surrounds the set of electrical resistances and the conduits that contain, with the exception of the end of the electrical resistors where the power supply is made. The resistances (3), in relief, are placed in the ducts (4) with the help of washers (18), for example ceramic fiber, comprising passages (23) that allow the gas G, for example nitrogen, to penetrate into space (24) included between the reistepcias and the conduits. The gas G circulates with a slight overpressure with respect to the pressure of the reaction gas that is inside the reactor, thus ensuring a perfectly controlled atmosphere and a better diffusion of this gas G towards the circulation space of the reaction gases . The absolute pressure difference between the space of the resistors and the space of circulation of the reaction gases, or overpressure, will preferably be such that the pressure in the space of the resistors is greater than at least 0.1%, and most of the times at least 1% at the pressure in the reaction space. It is not necessary to have a very high overpressure, and most of the time the pressure in the space of the resistors remains less than 2 times the pressure in the circulation space of the reaction gases. Figure 3 also represents a detail of an embodiment of the heating zone according to the invention. Cylindrical resistances (3) are used as electric heating means. These resistances comprise in each of their ends cold zones, and a part of the central zone which is the hot zone represent for example approximately 68% of the total length. A reactor of rectangular section is realized, whose walls are constituted of insulating refractory concrete (14) and by a metal frame (15). A circular hole is drilled in two opposite side walls, in which a duct (4), for example of ceramic, of double diameter of that of the electrical resistance (3) is passed. The duct (4) is located by means of a press-tow system (16) that acts in a groove at the level of the metal frame on a lining of refractory material (17), for example a lining of ceramic material. The location of the resistance (3) in the duct (4) is effected by means of washers (18), for example of ceramic fiber, comprising the. orifices (23) that allow the passage of the gas G, which contains for example nitrogen, introduced into the box (30) by the conduit (31) in the space (24) of the resistors. The hot zone of the resistance (3) fed by a pair of electrodes (6) whose ends protrude from the box (30), and positioned so that it does not penetrate the passage through the insulating concrete wall. It is not essential to use a lining (17) at the level of the press-tow since it has, within the framework of the invention, the role of positioning means, and whose main objective is not to ensure a hermetic seal as perfect as possible between the inside and outside of the reactor. This tow-press can, on the other hand, advantageously be replaced by a simpler means for positioning the ducts, such as, for example, simple washers made of refractory material. A certain number of heating resistors placed in conduits in the walls, for example of ceramic material, are thus arranged by successive horizontal rows, these rows are preferably aligned so that, on the side walls of the furnace, form a square or rectangular path. The box (30), from which only the ends of the resistors and / or its power supply (6) protrude, is traversed by the gas stream G containing, for example, nitrogen which thus circulates inside the ducts. According to FIG. 4, which corresponds to the second embodiment of the device, the reactor comprises the same heating elements, with the same references as those of FIG. 1, with the difference that only all the spaces included between the various conduits which is released to the load and the effluents contain at least one catalyst supported by grids 12. Figure 5 returns to take the same heating elements as Figure 2, with a division of the flow by a partition 22. Instead, the catalyst is arranged in the spaces between the heating ducts 4, and supported by grids 12. Only the part of the heating zone, at a temperature higher than 600 ° C for example, contains catalyst with an increasing temperature profile from the high towards the base. The following examples illustrate the invention. Example 1: A horizontal reactor of rectangular section having the following internal dimensions is used: 0.5 m x 1 m, and whose length is 4.3 meters. The heating means of this reactor are constituted by electrical resistances in relief, of molybdenum bisilicide (MoSi2); these resistors are surrounded by ceramic conduits, arranged concentrically in relation to the center of the circle that includes the resistors. These conduits are made of silicon carbide. Each duct, closed at one end, surrounds 2 resistances in relief. These conduits, substantially parallel to each other, are arranged perpendicularly to the direction of circulation of the load. The length of each branch of the relief of the electrical resistance is 90 cm, and the diameter of the resistance is 9 mm. The ceramic ducts have a length of 100 cm, an outside diameter of32 cm, and a lower diameter of 30 cm. The reactor comprises three elementary reaction zones: the first heating chamber comprises four cross-sections, independently regulated, each comprising a heating conduit containing nitrogen as a guide gas. The length of this heating chamber is 1.8 m. The temperature is brought to 1100 ° C; The first catalyst chamber, of a length equal to 0.3 m, contains a catalyst prepared according to EP27069 (example 2), of the following weight composition: platinum: 0.09%; rhodium: 0.009%, iron: 1% and cerium: 3.5%. The temperature of the effluent that comes out is 1000 ° C. - The second heating chamber contains only one heating duct, and has a length of 0.6 m. The temperature goes back to 1180 ° C. - The second catalyst chamber contains the same catalyst, and has a length of 0.3 m. The temperature of the effluent that comes out is 1100 ° C; -The third heating chamber contains no more than a single heating duct, and has a length of 0.6 m. The final temperature is 1240 ° C.

-The third catalysis chamber contains the same catalyst, and has a length of 0.7 m. The temperature of the effluent leaving the reactor is 1200 ° C. The total length of the catalysis chambers is 1.3 m. The residence time is determined from the total volume of the catalysis chambers. A charge comprising 56.4% by weight of hydrogen sulfide, 18.2% by weight of ammonia, and 25.4% by weight of water, is introduced at a flow rate of 241 kg / hr, so that the residence time at the temperature and at the Operating pressure of 0.11 MPa is 2 seconds. The results of the catalytic cracking of the ammonia at 1200 ° C according to the invention and at 900 ° C for comparative purposes are presented in the table below. T 1200 ° C T 900 ° C Times% cracking% cracking% cracking% cracking d? NH3 of H2S of NH3 of H2S min 99.65 1% 99.5 1% 90 min 99.65 1% 50 1% 5 hours 99.65 1% 1% 2000 hours 99.65 1% The comparison of the results shows that the catalyst continues to operate completely normally. It does not need to be regenerated.

Example 2 The reactor with the following internal dimensions: 1.2 m x 1 m, and of length 3.5 m comprises the same conduits as those of example 1, but arranged in two rows between the walls. The reactor comprises two zones: the first zone, which is the preheating chamber, comprises six heating ducts, regulated two by two, each heating duct containing nitrogen as a guide gas. The length of this heating chamber is 1.5 m. The temperature is brought to 950 ° C; -the second zone, of length equal to 2 m, delimited by two grids, comprises six heating ducts, regulated two by two. In the sense of width, the difference between conduits and between conduit and wall is 18.7 cm, and in the direction of length, the difference between conduits, and between conduits and gratings is 26 cm. These differences have been selected so that the residence time at the temperature and the operating pressure of 0.11 MPa is 2 seconds. Before placing the reactor vault, cobalt and molybdenum-based catalyst is placed between the grids, so as to fill the empty spaces. A filler is introduced, comprising 56.4% by weight of hydrogen sulfide, 18.2% by weight of ammonia, and 25.4% by weight of water, at a flow rate of 482 kg / hr, so that the residence time at the temperature and The operating pressure of 0.11 MPa is 2 seconds. The temperature of the effluent leaving the reactor is 1220 ° C. The results of the catalytic cracking of the ammonia at 1220 ° C according to the invention and at 900 ° C for comparative purposes are presented in the table below. T 1220 ° C T 900 ° C Times% of cracking% of cracking% of cracking% of cracking of NH3 of H2S of NH3 of H2S min 99.85 1% 99.5 1% 90 min 99.85 1% 50 1% hours 99.85 1% 1% 2000 hours 99.85 1% The comparison of the results shows that the catalyst continues to operate completely normal. It does not need to be regenerated, according to this variant. The gaseous effluent obtained in this way can be introduced into a Claus unit.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (22)

1. CLAIMS 1. Catalytic cracking process of the ammonia present in a fluid containing hydrogen sulfide, in which the fluid is introduced in a reaction zone heated to between 1000 to 1400 ° C comprising an appropriate catalyst, and an effluent is recovered from Catalytic cracking, the process is characterized in that the reaction zone is heated by means of heating or heat exchange, arranged inside the reaction zone.
2. 2. Method according to claim 1, characterized in that the temperature of the reaction zone is 1150 to 1250 ° C.
3. 3. Method according to claim 1 or 2, characterized in that the pressure in the reaction zone is appreciably that of the fluid entering the zone, preferably comprised between 1.07 and 5.095 kg / cm2 (1.05 and 5 absolute bars), and the injection rate is such that the residence time in the catalytic reaction zone is comprised between 0.1 and 100 seconds, and preferably between 0.5 and 10 seconds.
4. 4. Method according to any of claims 1 to 3, characterized in that the fluid is a gas.
5. 5. Method according to any of claims 1 to 3, characterized in that the fluid contains water.
6. Method according to any one of claims 1 to 5, characterized in that the fluid is at least one effluent selected from the group consisting of the head effluents of a steam stripping device of a refinery wastewater, the gasification effluents of coal, effluents from the manufacture of coke and biogas.
7. Method according to any of claims 1 to 6, characterized in that the catalyst is selected from the group consisting of at least one noble metal of group VIII, at least one metal of group VII, at least one metal of group VII in admixture with at least one metal of group VIII, at least one metal of group VIII, at least one metal of group VI B, at least one non-noble metal of group VIII in admixture with at least one metal of group VI B and minus a non-noble metal of group VIII with at least one noble metal of group VIII.
8. 8. Method according to any of claims 1 to 7, characterized in that a reaction zone of ceramic material is used.
9. 9. Procedure according to any of the claims 1 to 8, characterized in that the reaction zone comprises heating means arranged in substantially parallel layers, which determine cross sections substantially perpendicular to the axis of the reaction zone, so that they define between the means and / or the layers formed by these means spaces or passages for the circulation of cargo or effluents, the spaces are in a temperature range at least equal to 600 ° C, preferably higher than 900 ° C, which contains the catalyst.
10. 10. Method according to any of claims 1 to 8, characterized in that the reaction zone comprises at least one elementary zone Z, of reaction in the direction of the fluid outlet containing a fluid heating chamber, followed by a chamber of catalysis of the heated fluid.
11. Method according to claim 10, characterized in that the reaction zone comprises a plurality of elementary reaction zones Z,, the temperature of the heating chamber of the zone Z, lower is preferably higher than that of the chamber of heating zone Z,.? higher.
12. Method according to any of claims 1 to 11, characterized in that at least one partition substantially parallel to the axis defines at least two channels in which the heating means defining the spaces or passages are arranged.
13. 13. Catalytic reactor for the application of the method according to any of claims 1 to 12, of refractory material, of elongated shape according to an axis, comprising at a first end at least one means of feeding in at least one load, at the opposite end at least one means for evacuation of the produced effluents, the reactor comprises means of heating arranged in substantially parallel layers, which determine cross sections substantially perpendicular to the axis of the reactor, in such a way that they define between the means and / or the strata formed by the means, spaces or passages for the circulation of the load and / or the effluents , the reactor is characterized in that it comprises at least one elementary reaction zone (Zj) containing, according to the axis, in the direction of the outlet of the charge and / or the effluents, a heating chamber containing the heating means , followed by a catalysis chamber containing at least one catalyst.
14. 14. Reactor according to claim 13, characterized in that a plurality of elementary reaction zones Z1 are disposed along the axis, the catalytic chamber of the ZM zone above is adjacent to the heating chamber of zone Z? below.
15. 15. Catalytic reactor according to any of claims 13 to 14, characterized in that the catalyst chamber comprises heating means.
16. 16. Reactor according to any of claims 13 to 15, characterized in that the means for feedback and modulation of the heating are connected to the heating means.
17. 17. Reactor according to any of claims 13 to 16, characterized in that the heating means comprise conduits, in which electrical resistances are arranged.
18. Reactor according to any one of claims 13 to 16, characterized in that the heating means consist of heat exchange means supplied with gas or a mixture of heat exchange gas.
19. Reactor according to any one of claims 13 to 17, characterized in that the conduits contain a guide gas.
20. 20. Reactor according to any of claims 15 to 19, characterized in that the spaces between the heating means in the heating chamber contain the catalyst.
21. 21. Reactor according to any of claims 13 to 20, characterized in that at least one partition substantially parallel to the axis defines at least two channels in which the heating means and / or the catalyst are arranged.
22. 22. The use of the reactor according to any of claims 13 to 21, the use is characterized in that it is in an integrated process of elimination of hydrogen sulfide, ammonia and possibly hydrocyanic acid contained in a gas.