Method and apparatus for processing hydrogen sulphide-containing gas mixtures

Abstract

The invention pertains to processes for processing hydrogen sulphide-containing gas mixtures to obtain elemental sulphur. The invention relates to an apparatus and a method for the gas phase catalytic oxidation of hydrogen sulphide by oxygen in a fluidized bed. The apparatus comprises an ejector, a feed line for feeding oxygen-containing gas into the lower part of a reactor, a feed line for feeding inert gas into the ejector, a reactor for the direct oxidation of hydrogen sulphide having a gas distribution tray in the lower part thereof for a catalyst, a heat exchanger, a combined unit comprising an interconnected condenser and bubbler for condensing and coagulating sulphur, and a sulphur trap for discharging sulphur. The method is carried out using a spherical catalyst mixed with an inert material. To regulate the O2 / H2S ratio in the reactor, oxygen-containing gas is fed to the ejector and via an additional line into the lower part of the reactor, or a stream of inert gas is fed to the ejector and all of the oxygen-containing gas is fed into the lower part of the reactor via the additional line. The technical result is that of maintaining an optimal oxygen / hydrogen sulphide ratio in the reactor, reducing the catalyst charge, increasing the specific yield of sulphur obtained, reducing the specific metal intensity of the apparatus and improving both the environmental soundness and the safety thereof.

Description

[0001] METHOD AND INSTALLATION FOR PROCESSING HYDROGEN SULFIDE-CONTAINING GASEOUS MIXTURES

[0002] The invention relates to processes for processing hydrogen sulfide-containing gas mixtures to obtain elemental sulfur and can be used to utilize hydrogen sulfide by its gas-phase oxidation.

[0003] State of the art.

[0004] A method for direct catalytic oxidation of H2S to elemental sulfur is known (US Patent 4507274, C 01 B 17 / 02, B 01 J 8 / 02, published 26.05.1985), which was used as the basis for the industrial Catasulf process by BASF. The method involves passing a gas mixture containing H2S and an oxygen-containing gas mixture through a tubular reactor filled with a catalyst, removing the heat of reaction using water or an organic coolant located in a jacket space around the reactor tubes, passing the gaseous reaction mixture after the reactor through a condensation stage, and separating sulfur from the reaction mixture at the condensation stage. Several options have been proposed for processing the gas obtained after the condensation stage, based on the absorption of hydrogenated or oxidized residual sulfur compounds by a solvent or a solid sorbent.

[0005] In addition to the Catasulf process, there are other industrial processes based on the reaction of direct oxidation of hydrogen sulfide (Superclaus, BSR / Selectox, MODOP) [S. Khairulin, M. Kerzhentsev, A. Salnikov, ZR Ismagilov. Direct Selective Oxidation of Hydrogen Sulfide: Laboratory, Pilot and Industrial Tests and Catalysts. - 2021. - Vol. 11. - P. 1109; Mazgarov AM Technologies for cleaning associated petroleum gas from hydrogen sulfide / AM Mazgarov, OM Kornetova. - Kazan: Kazan, University, 2015. - 70 p.]. However, these processes are aimed exclusively at cleaning hydrogen sulfide-containing gas streams from other sulfur production processes.

[0006] A method for producing elemental sulfur from hydrogen sulfide is known, described in Russian patent No. 2709374 (B 01 D 53 / 52, published on 12 / 17 / 2019), which includes passing the initial hydrogen sulfide-containing gas through a fixed bed of a solid granular chemisorbent capable of adsorbing hydrogen sulfide to form hydrogen and solid sulfur-containing compounds on the surface of the chemisorbent, releasing hydrogen from the resulting gas stream and periodically regenerating the chemisorbent by decomposing the adsorbed sulfur-containing compounds and releasing elemental sulfur vapor at an elevated temperature, followed by condensation of the sulfur vapor at a reduced temperature. The method is carried out in at least two parallel reactors containing layers of the said chemisorbent, wherein in each of the reactors the chemisorption mode is alternated with the regeneration mode, making the transition from the chemisorption mode to the regeneration mode when the temperature of the chemisorbent decreases below a specified value.

[0007] A method is known for extracting sulfur from gases containing up to 50 vol.% hydrogen sulfide, with sulfur absent in the exhaust gases (RU Patent No. 1723761, C 01 B 17 / 04, published on 20.03.1995). The method is carried out by heterogeneous catalytic oxidation of hydrogen sulfide in two stages. The first oxidation stage takes place in a reactor with a fluidized catalyst bed at a temperature of 250-300°C and an oxygen: hydrogen sulfide ratio of 0.5-0.51. At the second stage, a block catalyst with a honeycomb structure is used, reducing the temperature from 140-155°C at the beginning of the bed to 110-120°C at the end of the bed.

[0008] A method for producing sulfur by heterogeneous catalytic oxidation of hydrogen sulfide with oxygen in a suspended bed reactor at temperatures of 150 - 350°C is known (RU Patent No. 2041163, C 01 B 17 / 04, published 09.08.1995), with water being introduced directly into the reactor. The degree of conversion of H2S is 97 - 99%. High conversion of hydrogen sulfide and, accordingly, sulfur yield are achieved in this invention due to explosive boiling of water on catalyst particles, which prevents the deposition and accumulation of sulfur on the catalyst.

[0009] A method for obtaining sulfur from hydrogen sulfide contained in hydrocarbon gases is known, which is carried out in two stages (RU Patent No. 1695612 C 01 B 17 / 04, published 20.03.1995): Stage 1 (heterogeneous catalytic oxidation of hydrogen sulfide) takes place in a reactor with a fluidized bed of catalyst at 240 - 270 ° C and an oxygen : hydrogen sulfide ratio of 0.55 - 0.7; Stage 2 (heterogeneous catalytic reduction of sulfur dioxide formed in stage 1 by hydrocarbons of the original natural gas) occurs at 420 - 500 ° C. The catalysts are mixed oxide systems on an AI2O3 carrier. The degree of sulfur extraction is 99.99%, the space velocity of the gas is 5000 h ' 1 .

[0010] A method for producing elemental sulfur by gas-phase oxidation of hydrogen sulfide with oxygen to produce elemental sulfur and a device for implementing it are described in patent No. 2136585 (C01B 17 / 04, published 10.09.1999). In this method, heated air is fed to the lower layers of the catalyst poured onto the gas distribution grid of the reactor. Hydrogen sulfide-containing gas is fed under the grid. The reaction zone is cooled with a coolant fed to the coils. The gaseous products of the reaction with dispersed sulfur are cooled at the reactor outlet to 127-158°C by introducing water. Then they are bubbled through a bubble grid in the sulfur collector through liquid sulfur having the same temperature. The level of liquid sulfur in the sulfur collector is maintained by removing liquid sulfur. The gas phase of the reaction products enters the zone "above the bubbling layer" through a drip collector. It is cleaned of sulfur droplets of 1000 µm in size and discharged.The method ensures high efficiency with stable characteristics of the initial gas flow (flow rate, hydrogen sulfide content). However, the method of separate supply of purified hydrogen sulfide-containing gas and oxygen-containing gas (air) does not ensure effective mixing due to the difference in flow pressure, especially in the initial period of the unit start-up, which leads to the absence of a fluidization state, uncontrolled heating of the catalyst bed, a decrease in the cleaning efficiency, and overheating of the catalyst. When the unit switches to a steady-state mode, part of the catalyst bed (up to 20%) operates as a mixing device.

[0011] The closest in technical essence to the proposed invention are the installation for processing hydrogen sulfide-containing gases to obtain elemental sulfur and the method for obtaining elemental sulfur using this installation, described in Russian Federation Patent No. 149826 (C 01 B 17 / 04, published on 28.01.2015). The installation contains an ejector device, a direct hydrogen sulfide oxidation reactor, which is a cylindrical apparatus, in the lower part of which there is a gas distribution grid on which a granulated spherical catalyst is placed, above the grid in the catalyst layer there is a heat exchanger for removing heat from the exothermic reaction of hydrogen sulfide oxidation. After the reactor there is a sulfur condenser and a bubbler filled with liquid sulfur.The ejector device used in this installation is characterized by a narrow range of working fluid (oxygen-containing mixture) flow rate variation - ± 5%, which limits the possibility of promptly changing the amount of air and maintaining the required O2 / H2S ratio in the range of 0.5 - 0.6. In addition, due to the need for contact between the fluidized catalyst bed and the entire surface of the heat exchange devices, the entire reaction space of the reactor is loaded with catalyst, which is irrational from the point of view of using a catalyst that can provide the target process indicators with lower loads. Also, in the described installation, sulfur condensation and gas flow bubbling to capture fine sulfur particles are carried out in separate devices, which leads to the need to equip the installation with an additional device to prevent sulfur "slippage" into the gas tract (sulfur trap).

[0012] Disclosure of the essence of the invention.

[0013] The problem that the invention is aimed at solving is the continuous effective purification of gas flows from hydrogen sulfide with the production of elemental sulfur.

[0014] The technical result is maintaining an optimal oxygen / hydrogen sulfide ratio in the reactor with sharp changes in the flow rate or content of hydrogen sulfide in the incoming gas stream, reducing the catalyst loading, increasing the specific yield of produced sulfur per unit weight of loaded catalyst (kg of produced S per hour / kg of catalyst), reducing the specific metal consumption - tons of equipment / kg of produced sulfur per hour and, as a consequence, increasing the environmental reliability and safety of the plant.

[0015] The technical result of the proposed invention is achieved by the design of the plant units, the method of feeding the reaction flows and the dilution of the highly active catalyst with an inert material.

[0016] The installation for processing hydrogen sulfide-containing gases includes an ejector, lines for feeding and releasing gas agents, a reactor for direct oxidation of hydrogen sulfide, which is a cylindrical apparatus, in the lower part of which a gas distribution grid is located for placing a spherical catalyst or a spherical catalyst mixed with an inert material, a heat exchanger located above the gas distribution grid, an additional line for feeding oxygen-containing gas into the reactor (wherein the inlet of this line into the reactor is located in its lower part above the gas distribution grid), an additional line for feeding inert gas into the ejector, a combined unit for condensing and coagulating sulfur, including a condenser and a bubbler directly connected to each other, and a sulfur trap for removing sulfur, connected to the combined unit.

[0017] The method for processing hydrogen sulfide-containing gas mixtures to obtain elemental sulfur by gas-phase catalytic oxidation of hydrogen sulfide with oxygen in a fluidized bed is carried out on the claimed unit using a spherical catalyst or a spherical catalyst diluted with an inert material, wherein in order to maintain the stoichiometric ratio of reagents in the reactor with a sharp change in the composition of the supplied gas mixture, the O2 / H2S ratio is regulated by feeding oxygen-containing gas into the lower part of the reactor; the reaction products from the reactor enter a combined unit for condensation and coagulation of sulfur for sequential cooling of the gas flow containing sulfur vapor and trapping finely dispersed particles in a layer of liquid sulfur with continuous discharge of the liquid sulfur flow through a sulfur trap.

[0018] Reducing the catalyst consumption by diluting it with an inert material allows maintaining a fluidized mode of operation of the catalyst bed and a high degree of purification of the gas flow, while increasing the specific yield of sulfur.

[0019] With a sharp increase in the hydrogen sulfide content in the gas mixture fed to the reactor, in order to maintain the stoichiometric O2 / H2S ratio in the reactor, in addition to the oxygen-containing gas supplied through the ejector, it is supplied to the lower part of the reactor through an additional line. With a sharp decrease in the hydrogen sulfide content in the gas mixture fed to the reactor, a flow of inert gas is supplied to the ejector, and all the oxygen-containing gas is supplied to the lower part of the reactor through an additional line.

[0020] Combining the process of condensation and coagulation (capturing fine particles) of sulfur in a single unit allows the use of one sulfur trap in the installation, thereby increasing its safety and reducing the specific metal consumption.

[0021] The installation and process for processing hydrogen sulphide-containing gas mixtures to obtain elemental sulphur are shown in Figs. 1 and 2.

[0022] Fig. 1 shows the installation diagram. Fig. 2 shows the combined unit for condensation and coagulation of sulfur.

[0023] The installation (Fig. 1) for the processes of processing hydrogen sulfide-containing gas flows comprises: an ejector (1) for mixing hydrogen sulfide-containing gas with a flow of oxygen-containing gas (air) or inert gas; a cylindrical reactor (2) with an ascending flow; a gas distribution grid (3) located in the lower part of the reactor (2) for placing a catalyst (4) and an inert material; a heat exchanger located above the gas distribution grid (3) for removing heat from the exothermic reaction of hydrogen sulfide oxidation (in Fig.1 not specified); a feed line (5) for hydrogen sulphide-containing gas; a feed line (6) for oxygen-containing gas (air); a feed line (7) for inert gas (nitrogen); an additional feed line (8) for oxygen-containing gas, the inlet of which into the reactor is located in its lower part above the gas distribution grid (3); a temperature sensor (9) located in the middle part of the reactor (2); a discharge line (10) from the reactor (2) for a gas stream containing sulphur vapor; a combined unit (I) for condensation and coagulation of sulphur; a sulphur trap 12 for removing sulphur and preventing gas from entering the sulphur storage tank.

[0024] The combined block (11) includes a condensation zone (condenser) (Pa), a coagulation zone (bubbler) (116), a tube bundle (13), an intertube space (14), a collector with a tube sheet (15).

[0025] Implementation of the invention.

[0026] Preheated oxygen-containing gas (air) is fed through line (6) into the lower part of the reactor (2), loaded with a spherical catalyst (4) or a mixture of a spherical catalyst (4) and a spherical inert material taken in a volume ratio of 1:3 to 2:1.

[0027] Spherical aluminum or silicon oxides of a bulk density and fractional composition close to the catalyst can be used as an inert material. Permissible deviations of the fractional composition and bulk density of the inert material from the fractional composition and bulk density of the catalyst should not exceed 20 and 10%, respectively.

[0028] When the temperature in the catalyst bed reaches 180-200°C, hydrogen sulphide-containing gas begins to flow through the feed line (5) to the ejector (1), where it mixes with air. Then the gas mixture flows into the lower part of the reactor (2) under the gas distribution grid (3). In the reactor (2), when the gas mixture comes into contact with the catalyst granules (4), an exothermic reaction of selective oxidation of hydrogen sulphide occurs. The temperature of the working (catalytic) zone is controlled by a temperature sensor (9), located in the middle part of the reactor (2), and is automatically maintained at 280 - 320°C by varying the flow rate of the heat-removing agent into the heat exchanger.

[0029] A sharp decrease in the hydrogen sulfide content in the feed gas leads to a drop in the selectivity of the process of obtaining elemental sulfur by converting it into sulfur dioxide, which is associated with the O2 / H2S ratio exceeding the value of 0.5, which is necessary for the selective course of reaction (1).

[0030] H2S + 0.5 O2 => S r + H2O + Q (1)

[0031] In this case, in order to maintain high selectivity of the process of converting hydrogen sulfide into sulfur, the air flow to the ejector (1) is reduced, and fine regulation of the O2 / H2S ratio is carried out by additionally supplying air to the lower part of the reactor (2) along line (8), the entrance to the reactor of which is located above the gas distribution grid (3).

[0032] An increase in the hydrogen sulphide content in the feed gas leads to its incomplete conversion in the reactor due to an insufficient amount of oxygen. In this case, to maintain the stoichiometric ratio of the reagents (see reaction (1)) an additional air supply is also used via line (8).

[0033] In case of an extreme drop in the initial gas flow rate (more than 2 times), it is envisaged to use a gas inert to the oxidation process (for example, nitrogen or natural gas) as the working fluid of the ejector. In this case, such gas is fed to the ejector (1) through line (7) instead of air, and air is fed to the reactor only through line (8).

[0034] The reaction products from the upper part of the reactor (2) through line (10) enter the combined unit (11) for condensation and coagulation of sulfur, where after passing through the tube bundle (13) of the condensation section (11a), where sulfur passes into a liquid state during cooling of the steam-gas flow, the mixture enters through a branch pipe into the coagulation section (Pb), and then through a collector with a tube sheet (15) enters a layer of liquid sulfur, where droplet sulfur is captured. Liquid sulfur is continuously discharged through a sulfur trap (12), and the purified gas flow exits through a branch pipe located in the upper part of the coagulation section (116).

[0035] The essence of the invention is illustrated by the following examples.

[0036] Example 1.

[0037] Experiments to test the method were carried out at a pilot plant at the Bavlinsky sulfur purification site of the Tatneftegazpererabotka Directorate of PJSC TATNEFT.

[0038] In a direct oxidation reactor of hydrogen sulfide with a free live cross-section of 0.147 m 2 , pre-loaded with spherical catalyst (fraction 1.2 1.6 mm., bulk density 1.05 kg / dm3 3 ) and spherical aluminum oxide (fraction 1.2 1.6 mm., bulk density 1.0 kg / dm3 3 ), taken in a volume ratio of 1:1, at a speed of 225 nm 3 / h preheated air was supplied. When the temperature in the catalyst bed reached 180-200°C, through the ejector at a speed of 210 nm 3 / h, the regeneration gas of the amine purification unit containing 45% vol. of hydrogen sulfide was started to be supplied. When the gas mixture containing hydrogen sulfide and oxygen came into contact with the catalyst, the temperature in the catalyst bed increased and was maintained at 325±5°C by pumping the heat-removing agent through the heat exchanger. The steam-gas mixture after the reactor entered the combined unit for condensation and coagulation of sulfur, after passing through which the liquid sulfur was removed through the sulfur trap, and the exhaust gas after the combined unit entered the afterburning furnace. The following parameters were calculated during the direct oxidation of hydrogen sulfide: selectivity of hydrogen sulfide oxidation to sulfur, degree of purification of regeneration gas from H2S, degree of sulfur capture, specific sulfur yield. The specific metal consumption was estimated taking into account the calculated total weight of the hardware units obtained during the design with 3-D modeling.

[0039] The analysis of the initial gas raw material and gas products of purification was carried out by gas chromatography. The quality of the obtained sulfur was assessed in the accredited gas analysis laboratory of the Tatneftegazpererabotka Department of PJSC TATNEFT. The gravimetric method was used to analyze the sulfur content in the exhaust gases.

[0040] The conditions for carrying out the process of direct oxidation of hydrogen sulfide and the indicators achieved in the process are given in Table 1.

[0041] Example 2.

[0042] The process was carried out similarly to example 1, except that the hydrogen sulfide content in the regeneration gas of the amine purification unit was 32% by volume, and the temperature of the catalyst bed during the reaction was maintained at 315±5°C. Unlike example 1, air was supplied in two streams: 160 nm 3 / h (70%) - to the ejector and 62 nm 3 / h (30%) - via an additional line to the lower part of the reactor.

[0043] Example 3.

[0044] The process was carried out similarly to Example 1, except that the hydrogen sulfide content in the regeneration gas of the amine purification unit was 66% by volume, and the temperature of the catalyst bed during the reaction was maintained at 315±5°C. As in Example 2, air was supplied in two streams: 225 nm 3 / h (67%) - to the ejector and 100 nm 3 / h (33%) - via an additional line to the lower part of the reactor.

[0045] Example 4.

[0046] The process was carried out similarly to example 1, except that the regeneration gas from the amine purification unit with a hydrogen sulfide content of 45% by volume was fed at a rate of 104 nm. 3 / h, the temperature of the catalyst bed during the reaction was maintained at 316±5°C. Unlike all previous examples, all air was fed into the reactor through an additional line at a rate of 110 nm 3 / h, and nitrogen was supplied to the ejector at a rate of 115 nm. 3 / h.

[0047] The results of tests carried out using the method described in the prototype (RU Patent No. 149826) are given in Table 1 under numbers 1 / 1, 2 / 1, 3 / 1, 4 / 1.

[0048] Table 1.

[0049] 1 low degree of purification due to H2S “breakthrough”;

[0050] 2 the purity of sulfur does not comply with GOST R 56249-2014 in terms of the mass fraction of acids in terms of sulfuric acid; nitrogen is supplied to the ejector instead of air;

[0051] 5 4 uncontrolled heating of the catalyst bed due to the fact that the catalyst bed is not in a state of fluidization and there is no effective removal of heat from the exothermic reaction of hydrogen sulfide oxidation.

Claims

Formula 1. An installation for processing hydrogen sulfide-containing gas mixtures to obtain elemental sulfur, comprising an ejector, lines for feeding and discharging gas agents, a reactor for direct oxidation of hydrogen sulfide, which is a cylindrical apparatus, in the lower part of which a gas distribution grid is located for placing a catalyst, a heat exchanger located above the gas distribution grid, a sulfur trap for removing sulfur, characterized in that it contains an additional line for feeding oxygen-containing gas to the lower part of the reactor, an additional line for feeding inert gas to the ejector, a combined unit for condensing and coagulating sulfur, connected to the reactor by a discharge line, including a condenser and a bubbler directly connected to each other.

2. The installation according to paragraph 1, characterized in that the input of the additional line for supplying oxygen-containing gas to the reactor is located in its lower part above the gas distribution grid.

3. A method for processing hydrogen sulfide-containing gas mixtures to obtain elemental sulfur by gas-phase catalytic oxidation of hydrogen sulfide with oxygen in a fluidized bed, characterized in that the processing is carried out in the installation described in paragraph 1, using a spherical catalyst and an inert material taken in a volume ratio of from 1:3 to 2:1, wherein in order to regulate the O2 / H2S ratio in the reactor, oxygen-containing gas is fed to the ejector and to the lower part of the reactor through an additional line, or a stream of inert gas is fed to the ejector, and all the oxygen-containing gas is fed to the lower part of the reactor through an additional line; a gas stream containing sulfur vapor from the reactor enters a combined unit for condensation and coagulation of sulfur for sequential cooling of the gas stream containing sulfur vapor and trapping finely dispersed particles in a layer of liquid sulfur with continuous discharge of liquid sulfur through a sulfur trap.

4. The method according to paragraph 3, characterized in that spherical aluminum oxide or silicon oxide of similar bulk density and fractional composition to the catalyst is used as the inert material.

5. The method according to paragraph 3, characterized in that, when the hydrogen sulfide content in the gas mixture fed to the reactor sharply increases, oxygen-containing gas is fed both through the ejector and into the lower part of the reactor through an additional line.

6. The method according to paragraph 3, characterized in that, when the hydrogen sulfide content in the gas mixture fed to the reactor sharply decreases, a flow of inert gas is fed to the ejector, and all the oxygen-containing gas is fed into the lower part of the reactor through an additional line.

7. The method according to paragraph 6, characterized in that nitrogen is used as the inert gas.