Sulfuric acid-containing sour gas sulfur recovery method and system

Abstract

The present invention belongs to the field of chemical engineering technology, and provides a method and a system for sulfur recovery from sulfuric acid-containing sour gas. The method includes reacting the sulfuric acid-containing sour gas with an oxygen-containing gas to obtain a first reactant, cooling the first reactant to obtain liquid sulfur and a first separated gas; after removing gases such as nitrogen and carbon dioxide from the first separated gas, heating it up, and performing a complete hydrogenation reaction with hydrogen in the presence of a hydrogenation catalyst to obtain a second reactant; after cooling the second reactant, removing water vapor, and then returning it to be combined with a low-sulfur raw gas to form sulfuric acid-containing sour gas for cyclic treatment. The system of the present invention is a system for implementing the method of the present invention. The method and system of the present invention are applicable to a wide range of conversion rates of catalytic oxidants, and are more applicable to the working conditions where the concentration of the low-sulfur raw gas is <2% and the conversion rate of the catalyst is low. It can achieve complete recovery of sulfur in the sour gas, and the present invention can achieve near-zero emissions of sulfur-containing tail gas under various working conditions.

Description

Technical Field

[0001] The present invention belongs to the field of chemical engineering technology and relates to sulfur recovery and low-sulfur gas emissions. Background Art

[0002] During the production processes of coal chemical industry and petrochemical industry, a part of the sulfur contained in the raw materials will form H2S, which is included in the sour gas as a conventional by-product or tail gas. Generally, this sour gas will be treated through a sulfur recovery process to recover more sulfur in the form of elemental sulfur and minimize the sulfur content in the exhaust gas as much as possible.

[0003] Currently, sulfur recovery processes applicable to sour gas with a low H2S content of <5% include the Clinsulf-Do process, the BSR / Hi-Activity process, the Selectox process, the TDA method, the ADA method, etc. However, these processes all have the problem that they cannot recover the sulfur-containing gas into elemental sulfur by 100%, and the tail gas after sulfur production fails to meet the environmental protection emission requirements.

[0004] The selective catalytic oxidation method can directly generate elemental sulfur from H2S. However, due to problems such as low catalyst conversion rate (about 60% - 70%), side reactions still occur. So far, it has not been possible to achieve 100% sulfur production from the sulfur-containing gas, and the tail gas cannot meet the emission standards. Although high-conversion catalysts can improve the sulfur production rate to a certain extent, this requires very high requirements for the catalyst and raw materials, resulting in a significant increase in cost, and the final tail gas still cannot meet the standards by 100%. Summary of the Invention

[0005] Based on the above problems, the present invention provides a sulfur production technology based on the selective catalytic oxidation method. After treatment, the hydrogen sulfide content in the tail gas discharged from the hydrogen sulfide electrolytic cell under various conditions is <0.1 kg / min, achieving the environmental protection goal of near-zero emissions.

[0006] In the first aspect, the present invention provides a method for sulfur recovery from sulfur-containing sour gas. The above method includes the following steps:

[0007] 1) In the presence of a low-temperature oxidation catalyst, the sulfur-containing sour gas reacts with an oxygen-containing gas to obtain a first reaction product; wherein, the volume concentration of hydrogen sulfide in the sulfur-containing sour gas is less than 13%.

[0008] 2) Cool the first reaction product to obtain liquid sulfur and a first separated gas. The liquid sulfur enters the liquid sulfur pool for recovery, and the first separated gas enters the first degassing tower to separate gases such as nitrogen and carbon dioxide, obtaining a degassed first separated gas composed of sulfur dioxide and water vapor.

[0009] 3) Heat up the degassed first separated gas, and in the presence of a hydrogenation catalyst, conduct a complete hydrogenation reaction with hydrogen to obtain a second reaction product.

[0010] 4) After the second reactant is cooled down, it enters the second stripping column to remove water vapor, and then returns to step 1) to be combined with the low-sulfur raw gas to form sulfur-containing acidic gas, which is processed cyclically.

[0011] Preferably, in step 1), the low-temperature catalytic oxidant is applicable to sulfur-containing acidic gas containing hydrocarbons, and its conversion rate is 5% to 55%.

[0012] In a preferred embodiment, the low-temperature catalytic oxidant is a ceramic-based catalyst (Fe2O3 / Pt-Pd-SiC), with a specific surface area of 148 m 2 / g to 168 m 2 / g, a bulk density of 0.62 g / m 3 to 0.92 g / m 3 , a pore volume of 0.47 ml / g to 0.67 ml / g, 42% to 62% of silicon carbide, and a size of Φ2×9 mm to Φ3×9 mm.

[0013] In a preferred embodiment, the low-temperature catalytic oxidant contains the following components by mass: 20% to 31% of iron oxide, preferably 25% to 30%; 42% to 62% of silicon carbide, preferably 45 to 58%; the balance is an auxiliary agent containing platinum and palladium noble metals; in a preferred embodiment, the specific surface area of the low-temperature catalytic oxidant is 168 (m 2 / g), the bulk density is 0.92 (g / m 3 ), the pore volume is 0.67 (ml / g), and the carrier is ceramic SiC.

[0014] Preferably, in step 1), the sulfur-containing acidic gas includes low-sulfur raw gas and recycled hydrogen sulfide; wherein, the low-sulfur raw gas is the tail gas from coal chemical industry or petrochemical industry. In a preferred embodiment, the low-sulfur raw gas contains the following components by volume ratio: 0.1% to 6% of hydrogen sulfide, 30% to 35% of nitrogen, 50% to 60% of carbon dioxide, 1% to 2% of methane, 1% to 2% of carbon monoxide, hydrogen, etc., and other impurity gases.

[0015] In one embodiment, the relationship between the low-temperature catalytic oxidant in step 1) and the low-sulfur raw gas is as follows: when the sulfur content of the low-sulfur raw gas is 0.1% to 2%, its conversion rate is 5% to 55%, preferably 5% to 55%; when the sulfur content of the low-sulfur raw gas is 2% to 3%, its conversion rate is 5% to 55%, preferably 7% to 55%; when the sulfur content of the low-sulfur raw gas is 3% to 4%, its conversion rate is 5% to 55%, preferably 15% to 55%; when the sulfur content of the low-sulfur raw gas is 4% to 5%, its conversion rate is 5% to 55%, preferably 26% to 55%; when the sulfur content of the low-sulfur raw gas is 5% to 6%, its conversion rate is 5% to 55%, preferably 34% to 55%.

[0016] Preferably, in step 1), the oxygen-containing gas is air, 28% oxygen-enriched gas or pure oxygen, preferably 28% oxygen-enriched gas, which enters the pipeline mixer through an ejector from the feed pipeline for sufficient mixing; the method of the present invention detects the composition of the first reactant, including detecting the oxygen content using an O2 instrument, and matching the amount of the oxygen-containing gas fed according to the detection range of the O2 instrument for the first reactant being 0 ppm to 0.5 ppm.

[0017] Preferably, in step 1), the pressure of the reaction feed is 0.3 Mpa to 0.6 Mpa, preferably 0.5 Mpa to 0.6 Mpa.

[0018] Preferably, in step 1), the sulfuric acid-containing gas is heated to 130 °C to 140 °C and then enters the catalytic oxidation reactor to start the low-temperature oxidation exothermic reaction.

[0019] Preferably, in step 1), the reaction temperature is 200 °C to 240 °C, preferably 200 °C to 220 °C; the pressure is 0.4 Mpa to 0.6 Mpa, preferably 0.5 Mpa to 0.6 Mpa; the space velocity is 300 to 500 h -1 ; the flow rate ≤ 9738 m 3 / h.

[0020] Preferably, in step 1), due to the low conversion rate of the catalyst and incomplete reaction, a certain amount of SO2 is associated. Therefore, the H2S and O2 contents of the first reactant are detected to judge the reaction situation of the selective catalytic reactor and the feed material ratio, so that the detection range of the O2 instrument is 0 ppm to 0.5 ppm.

[0021] Preferably, in step 2), the first reactant is cooled to 120 °C to 160 °C.

[0022] Preferably, in step 2), the cooling treatment of the first reactant uses a condensing heat exchanger. The low-sulfur raw gas in the sulfuric acid-containing gas exchanges heat with the first reactant, so that the low-sulfur raw gas rises from 80 °C to 130 °C to 140 °C, the first reactant drops from 220 °C to 120 °C to 160 °C, sulfur elemental precipitates into the liquid sulfur pool, and the first separated gas enters the first degassing tower to separate nitrogen, carbon dioxide, etc., to obtain the degassed first separated gas.

[0023] The tail gas in the liquid sulfur pool enters the buffer gas cabinet and can be returned to the front end to be mixed with the low-sulfur raw gas to adjust the sulfur content in the sulfuric acid-containing gas fed, so that it is stabilized at a certain concentration.

[0024] Preferably, in step 3), the degassed first separated gas is heated to 190 °C to 210 °C, preferably 200 °C, for hydrogenation reaction.

[0025] Preferably, in step 3), the hydrogenation reaction catalyst is CT6-11A, with a specific surface area > 234 (m 2 / g), a bulk density of 0.78 - 0.89 (g / m 3 ), a pore volume > 0.36 (ml / g), an Al2O3 content of 82%, a size of Φ2 × 10 mm, a brown appearance, and an active promoter metal cobalt > 13% and molybdenum > 3.3%.

[0026] Preferably, in step 3), the hydrogenation reaction temperature is 200°C - 240°C; the pressure is 0.05 Mpa - 0.5 Mpa, preferably 0.3 Mpa - 0.4 Mpa.

[0027] Preferably, in step 3), the SO2 content of the second reactant is detected, and the hydrogenation amount is automatically adjusted based on the SO2 content, such that the detected SO2 is in the range of 0 ppm - 0.5 ppm.

[0028] Preferably, in step 4), the second reactant is cooled to 190°C - 210°C, preferably 200°C, and then enters the second stripping tower for dehydration.

[0029] Preferably, the adsorbent in the first degassing tower is 4A molecular sieve. Among them, the lower layer preferably uses A-AS adsorbent to adsorb mechanical impurities and moisture; the upper layer preferably uses HX4A-98H adsorbent to adsorb gas components such as nitrogen, carbon dioxide, methane, carbon monoxide, and hydrogen in the first reactant. The temperature in the first degassing tower is 110°C - 160°C, preferably 110°C - 130°C; the pressure is 0.2 MPa - 0.6 MPa, preferably 0.4 MPa - 0.5 MPa, so that the first reactant becomes a degassed first separated gas composed of sulfur dioxide and water vapor.

[0030] The second stripping tower preferably uses a TiO2-SiO2 mesoporous adsorbent, with a reaction temperature of 140°C - 210°C, preferably 180°C - 200°C; the pressure is 0.2 MPa - 0.5 MPa, preferably 0.2 MPa - 0.3 MPa, and it can adsorb 99.3% of water vapor.

[0031] Preferably, the tail gas of the second stripping tower is directly used as the return to the front end to adjust the low-sulfur raw gas concentration under the natural circulation method working condition; under the fluctuating or differential circulation method working condition, it enters the buffer gas holder through the balance discharge valve, converges with the tail gas of the liquid sulfur pool, and returns to the front end to be mixed with the low-sulfur raw gas when needed to adjust the sulfur content in the feed acid gas, so that the volume concentration of hydrogen sulfide is less than 13%.

[0032] In the preferred embodiment, the formula for the concentration k of hydrogen sulfide returned to the front end is:

[0033]

[0034] The functional relationship is as follows:

[0035] where x is the hydrogen sulfide content of the low-sulfur feed gas, and y is the hydrogen sulfide conversion rate (%) in the sulfuric acid-containing sour gas;

[0036] wherein,

[0037]

[0038] n is the number of cycles.

[0039] Under normal and stable operating conditions, when the sulfur content of the low-sulfur feed gas is 0.1% - 2%, its conversion rate is 5% - 55%; when the sulfur content of the low-sulfur feed gas is 2% - 3%, its conversion rate is 15% - 55%; when the sulfur content of the low-sulfur feed gas is 3% - 4%, its conversion rate is 25% - 55%; when the sulfur content of the low-sulfur feed gas is 4% - 5%, its conversion rate is 33% - 55%; when the sulfur content of the low-sulfur feed gas is 5% - 6%, its conversion rate is 47% - 55%; in these cases, the low-sulfur feed gas can reach the natural equilibrium point value after several cycles without discharging to the buffer gas holder. This is the natural circulation method operating condition.

[0040] The formula for the equilibrium point value is

[0041] Taking the low-sulfur feed gas containing 4% hydrogen sulfide and a conversion rate of 50% as an example, the natural equilibrium point value cycle starts after the 21st cycle, that is, the natural circulation method.

[0042]

[0043]

[0044] Therefore, under normal operating conditions, the method and system of the present invention can completely handle the recovery of all low-sulfur feed gases within the natural circulation method range of hydrogen sulfide content from 0.1% to 6%, that is, within the range of 0.1% - 2% and within the natural circulation method corresponding to hydrogen sulfide content from 2% to 6% (including 2%), without any emissions, that is, achieving zero emissions.

[0045] When the hydrogen sulfide content is in the range of 2% - 6% (including 2%) and the differential circulation method is used for low-sulfur raw gas (under the condition that the hydrogen sulfide in the sulfur-containing acid gas exceeds 13%), that is, when the sulfur content of the low-sulfur raw gas is 2% - 3%, the conversion rate is 7% - 15%; when the sulfur content of the low-sulfur raw gas is 3% - 4%, the conversion rate is 15% - 25%; when the sulfur content of the low-sulfur raw gas is 4% - 5%, the conversion rate is 26% - 33%; when the sulfur content of the low-sulfur raw gas is 5% - 6%, the conversion rate is 34% - 47%, it is necessary to control by continuously discharging the difference between two adjacent equilibrium values through the balance discharge valve. The difference is discharged into the buffer gas cabinet for temporary storage, and the hydrogen sulfide electrolytic cell electrolyzes the hydrogen sulfide stored in the buffer gas cabinet to achieve zero emission under normal conditions for the differential circulation method.

[0046] Control the differential discharge according to the functional relationship. Among them,

[0047] The concentration difference of the differential method is: f(k n ) - f(k n-1 ) = ΔK

[0048] The discharge amount each time for the differential method is:

[0049]

[0050] Among them, ρ: the density of hydrogen sulfide gas.

[0051] For example: when the sulfur content in the low-sulfur raw gas is 5% and the conversion rate is 33%, after the 7th cycle, the return concentration reaches 8.043%, then the sulfur content in the sulfur-containing acid gas for feeding is 13.043%. After the 6th cycle, the return concentration reaches 7.96%, and the mixed concentration of the sulfur content in the sulfur-containing acid gas for feeding is 12.96%. At this time, the concentration difference between the 7th and 6th times is 0.083%. That is, the balance discharge valve discharges 0.083% (1 + k7)Vρ to the buffer gas cabinet to achieve the continuous cycle balance of the 6th time, and starts to achieve the cycle of the 7th differential balance point value, that is, the differential circulation method.

[0052]

[0053] During the fluctuating working condition, the tail gas of the second stripping tower and the liquid sulfur pool is stored in the buffer gas cabinet to prevent disorderly discharge. When the hydrogen sulfide content in the sulfur-containing acid gas for feeding is < 4%, increasing the return amount of the buffer gas cabinet can achieve nearly zero emission with the hydrogen sulfide discharge of the hydrogen sulfide electrolytic cell being less than 0.1 kg / min under the fluctuating working condition.

[0054] Further preferably, the hydrogen sulfide that is not returned in the buffer gas holder is converted into a hydrogen sulfide solution in the buffer gas holder and treated by electrolysis. Within the range of the cell load being < 2.8 kg / min, hydrogen sulfide under various working conditions is treated to achieve zero emissions. The sulfur generated after electrolysis is recycled, and the generated hydrogen is returned to the hydrogenation reactor for use.

[0055] In a second aspect, a sulfuric acid-containing sour gas recovery system is provided, which includes a catalytic oxidation reactor, a condensation heat exchanger, a first degassing tower, a hydrogenation reactor, and a second stripping tower connected in sequence according to the reaction sequence of the hydrogen sulfide logistics. Among them, the condensation heat exchanger includes a low-temperature logistics area and a high-temperature logistics area. The low-temperature logistics area flows through the low-sulfur raw gas in the sulfuric acid-containing sour gas, and the high-temperature logistics area flows through the first reactant. The high-temperature logistics area has a gas outlet and a liquid outlet. The gas outlet is communicated with the first degassing tower, and the liquid outlet is communicated with the liquid sulfur pool. The gas outlet of the second stripping tower is communicated with the material inlet of the catalytic oxidation reactor.

[0056] Preferably, the catalytic oxidation reactor and the hydrogenation reactor are integrated equipment.

[0057] Preferably, the system further includes a buffer gas holder. The second stripping tower and the liquid sulfur pool are respectively communicated with the inlet of the buffer gas holder, and the outlet of the buffer gas holder is communicated with the material inlet of the catalytic oxidation reactor. Preferably, the outlet of the buffer gas holder is communicated with a hydrogen sulfide electrolytic cell.

[0058] Preferably, a hydrogen gas pipeline is provided between the hydrogen sulfide electrolytic cell and the hydrogenation reactor.

[0059] Preferably, both the first degassing tower and the second stripping tower are composed of three towers combined. Both are in operation with two towers, and one tower is used for regeneration. The first degassing tower and the second stripping tower are both connected to a separation tank through a regeneration gas pipeline. The separation tank is used to store the regeneration gas used when stripping the degassing tower. Preferably, when the second stripping tower is regenerated, it is purged with nitrogen at 90 °C and 0.2 Mpa to 0.4 Mpa; the regeneration gas of the first degassing tower uses saturated steam at 0.2 MPa to 0.4 MPa, preferably 0.2 MPa to 0.3 Mpa.

[0060] Preferably, a heat exchanger and an air cooler are provided on the regeneration gas pipeline. Among them, the heat exchanger is used for heat exchange between the regeneration gas after leaving the stripping tower and the low-sulfur raw gas before entering the condensation heat exchanger.

[0061] Preferably, the system is further provided with four hydrogen sulfide content detectors and an integrated control module. The four hydrogen sulfide content detectors are respectively connected to the integrated control module, which monitors in real time and transmits data to the integrated control module for dynamic tracking and calculation of four variables, so as to obtain the conversion rate at a certain hydrogen sulfide content of low-sulfur raw gas and the balance point values of the natural circulation method and the differential circulation method corresponding thereto. The acquisition of each balance point value requires circulating the low-sulfur raw gas concentration n times. When the sulfuric acid-containing sour gas concentration is <13%, it determines the discharge amount of the balance valve.

[0062] The system is provided with a H2S content detector 1, which is arranged in front of the inlet of the catalytic oxidation reactor.

[0063] The system is further provided with a H2S content detector 2, which is arranged at the outlet of the reactants of the catalytic oxidation reactor.

[0064] The system is further provided with a H2S content detector 3, which is arranged at the outlet of the second stripping tower; the opening amount of the hydrogen sulfide detector 3 is adjusted according to k, which is the amount discharged from the second stripping tower to the buffer gas holder. The hydrogen sulfide detector 3 comes into play after reaching the balance point value. In the differential circulation method, the difference amount between two adjacent balance point values is discharged to the buffer gas holder.

[0065] The system is further provided with a H2S content detector 4, which is arranged at the outlet of the buffer gas holder to control the sulfur content concentration after returning to the inlet of the feed and matching the mixture.

[0066] Preferably, the system is further provided with SO2 and O2 content detectors, which are arranged at the outlet of the reactants of the catalytic oxidation reactor and are connected to the integrated control module.

[0067] Preferably, the system is further provided with a SO2 content detector, which is arranged at the outlet of the reactants of the hydrogenation reactor and is connected to the integrated control module.

[0068] Preferably, a balance discharge valve connected to the integrated control module is further arranged on the connecting pipeline between the second stripping tower and the buffer gas holder for controlling the excessive hydrogen sulfide in the differential circulation method.

[0069] A crossover line is arranged between the low-sulfur raw gas feed line and the buffer gas holder. At the same time, a fault discharge line is arranged at the top of the hydrogen sulfide electrolytic cell for fault discharge in case of faults, such as overload of the hydrogen sulfide electrolytic cell, faults in the low-sulfur raw gas pipeline, and equipment overload.

[0070] The conversion rate range of the catalytic oxidant applicable to the method of the present invention is wide, and it is more applicable to the working conditions of low sulfur feed gas concentration < 2% and low catalyst conversion rate. It can achieve the full recovery of sulfur in the acid gas, and the present invention can achieve near-zero emissions of sulfur-containing tail gas under various working conditions. It can achieve the emission of sulfur compounds in the tail gas < 0.1 kg / min. Under normal working conditions, the sulfur compounds in the tail gas are zero; and it has sensitive operation and low cost.

[0071] The method and equipment of the present invention are particularly applicable to the case where the hydrogen sulfide content in the feed gas is lower than 13%. As is known in the art, when the hydrogen sulfide content is higher than 13%, there are already established methods to treat such tail gas; but when the hydrogen sulfide content is lower than 13%, due to the low hydrogen sulfide content, there is currently no effective method to solve it. And the method of the present invention is precisely aimed at the situation where the hydrogen sulfide content is lower than 13%. The entire process also ensures the hydrogen sulfide content in the feed gas, enabling the method to be fully realized. Brief Description of the Drawings

[0072] Figure 1 It is the technical flow chart of the present invention. Detailed Embodiments

[0073] The present invention will be described below through specific embodiments, but the content of the present invention is not limited thereto.

[0074] In the following embodiments, unless otherwise specified, the instruments and reagents used are conventional and can be obtained through commercial purchase; the usage methods of each instrument are also conventional methods, and those skilled in the art can undoubtedly confirm how to operate each instrument according to the prior art and achieve the purpose of the present invention according to the method described in the present invention.

[0075] In the present invention, the fluctuating working condition refers to the range other than the natural circulation method and the differential circulation method within the conversion rate range of 5% - 55%, and within the range where the system has not reached the fault working condition. Therefore, like the differential circulation method, the fluctuating working condition discharges and stores to the buffer gas cabinet through the balance discharge valve.

[0076] The fault working condition refers to the working condition when each technical module is overloaded or when the equipment, pipelines fail, or the equipment is overloaded.

[0077] The technical solution of the present invention can be described as follows:

[0078] As Figure 1As shown in the figure, the sulfuric acid-containing sour gas recovery system of the present invention includes a catalytic oxidation reactor, a condensation heat exchanger, a first degassing tower, a hydrogenation reactor, and a second stripping tower connected in sequence according to the reaction sequence of the hydrogen sulfide logistics. Among them, the condensation heat exchanger includes a low-temperature logistics area and a high-temperature logistics area. The low-temperature logistics area flows through the low-sulfur feed gas in the sulfuric acid-containing sour gas, and the high-temperature logistics area flows through the first reactant. The high-temperature logistics area has a gas outlet and a liquid outlet. The gas outlet is connected to the first degassing tower, and the liquid outlet is connected to the liquid sulfur tank. The gas outlet of the second stripping tower is connected to the material inlet of the catalytic oxidation reactor.

[0079] The system of the present invention further includes a buffer gas holder. The tail gas outlets of the second stripping tower and the liquid sulfur tank are respectively connected to the gas inlet of the buffer gas holder. The gas outlet of the buffer gas holder is connected to the material inlet of the catalytic oxidation reactor, and another outlet of the buffer gas holder is connected to the hydrogen sulfide electrolytic cell. The hydrogen sulfide stored in the buffer gas holder is treated by electrolysis. A hydrogen pipeline is provided between the hydrogen sulfide electrolytic cell and the hydrogenation reactor, so that the hydrogen generated by the hydrogen sulfide electrolytic cell enters the hydrogenation reactor for reaction.

[0080] The sulfuric acid-containing sour gas includes low-sulfur feed gas and recycled hydrogen sulfide. Before entering the material inlet end of the catalytic oxidation reactor, the low-sulfur feed gas first exchanges heat with the regenerated gas from the first degassing tower and the second stripping tower, and then enters the condensation heat exchanger to exchange heat with the first reactant.

[0081] A cross-line is provided between the low-sulfur feed gas feed line and the buffer gas holder. At the same time, a fault discharge line is provided at the top of the hydrogen sulfide electrolytic cell for fault discharge under fault conditions, such as when the hydrogen sulfide electrolytic cell is overloaded or the raw material gas pipeline fails and the equipment is overloaded.

[0082] The material flow can be described as follows: The low-sulfur feed gas containing low-concentration (0.1% - 6%, V%) H2S from the upstream desulfurization and decarbonization unit first exchanges heat with the regenerated gas, and then exchanges heat with the first reactant generated later in the condensation heat exchanger, and is heated to 130°C - 140°C. It is mixed with the recycled hydrogen sulfide, and then enters the catalytic oxidation reactor together with the preheated oxygen-containing gas to carry out the selective catalytic oxidation sulfur production reaction of 2H2S + O2 → 2S + 2H2O + Q. The reaction temperature is 200°C - 240°C, the pressure is 0.4 Mpa - 0.6 Mpa, and the space velocity is 300 - 500 h -1 , and the flow rate ≤ 9738 m 3 / h; The conversion rate of the low-temperature catalytic oxidant used is 5% - 55%, and the reaction is incomplete. There is an accompanying reaction of S + O2 → SO2 + Q, and a certain amount of SO2 is still accompanied. The first reactant (gas-phase mixed gas) at the outlet of the catalytic oxidation reactor is detected by an H2S and O2 on-line analyzer to judge the reaction situation of the catalytic oxidation reactor and the air volume ratio. The first reactant enters the condensation heat exchanger and exchanges heat with the low-sulfur raw gas to obtain liquid sulfur and the first separated gas at a temperature of 120°C - 160°C. The elemental sulfur flows into the liquid sulfur pool from the bottom of the condensation heat exchanger, and the first separated gas separated from the top enters the first degassing tower to separate nitrogen, carbon dioxide, etc., to obtain the degassed first separated gas composed of sulfur dioxide and water vapor. Then it enters the heat exchanger and exchanges heat with the second reactant obtained later to 190°C - 210°C, and enters the hydrogenation reactor for the reaction 2H2 + SO2 → H2S + 2H2O + Q. The catalyst for the hydrogenation reaction is CT6-11A catalyst, the temperature is 200°C - 240°C, and the pressure is 0.05 Mpa - 0.5 Mpa. The complete reaction of SO2 is controlled by the hydrogenation amount to obtain the second reactant. The outlet of the hydrogenation reactor is detected by an SO2 on-line analyzer to judge the hydrogen ratio of the hydrogenation reaction, and the outlet SO2 is controlled within the range of 0 ppm - 0.5 ppm. The second reactant enters the heat exchanger and exchanges heat with the degassed first separated gas to 190°C - 210°C, and then enters the second stripping tower to remove the accompanying water vapor. After the water vapor is removed, the hydrogen sulfide flows back to the feed end and merges with the low-sulfur raw gas to form sour gas containing sulfuric acid, so that the hydrogen sulfide content in the sour gas containing sulfuric acid is not higher than 13%, and then re-enters the catalytic oxidation reactor for reaction.

[0083] Both the first degassing tower and the second stripping tower are composed of three towers, and both operate with two towers and one tower for regeneration. During regeneration, the regenerated gas of the first degassing tower is regenerated with steam at 0.2 Mpa - 0.4 Mpa, and the second stripping tower is blown and regenerated with nitrogen at 90°C, 0.2 Mpa - 0.4 Mpa. The blown regenerated gas exchanges heat with the low-sulfur raw gas and then is cooled to 80°C by air cooling and enters the liquid separation tank. The separated nitrogen goes to the nitrogen production unit, and the condensate goes to sewage stripping treatment.

[0084] The tail gas of the liquid sulfur pool enters the buffer gas cabinet.

[0085] Under normal operating conditions, for the natural circulation method within the range of 0.1% to 6% hydrogen sulfide content, the tail gas of the second stripping tower is directly returned to the front end to adjust the hydrogen sulfide concentration in the low-sulfur feed gas. For the differential circulation method under fluctuating operating conditions and within the range of 0.1% to 6% hydrogen sulfide content in the low-sulfur feed gas, it needs to be controlled by continuously discharging the difference between two adjacent equilibrium values through the balance discharge valve. The difference value is discharged and temporarily stored in the buffer gas holder. When the hydrogen sulfide content in the feed acid gas is <4%, the return amount of the buffer gas holder is increased so that the hydrogen sulfide content in the feed acid gas is <13%. The hydrogen sulfide electrolytic cell electrolyzes the hydrogen sulfide temporarily stored in the buffer gas holder. At the same time, a fault discharge line is set at the top of the hydrogen sulfide electrolytic cell to discharge the tail gas in the buffer gas holder under fault conditions.

[0086] A hydrogen sulfide content detector is set at each of the inlet and outlet of the catalytic oxidation reactor to calculate the conversion rate of hydrogen sulfide. Among them, the concentration of the low-sulfur feed gas is known, and the hydrogen sulfide concentration of the acid gas containing sulfur is detected at the inlet of the catalytic oxidation reactor. According to the formula calculation, the amount of hydrogen sulfide returned each time is obtained, so that the hydrogen sulfide content in the feed acid gas containing sulfur is lower than 13%. The natural circulation method is adopted; if it exceeds 13%, when the differential circulation method or fluctuating operating conditions are adopted, the excess amount is discharged through the balance discharge valve to make the system reach a new balance.

[0087] The present invention will be described below through specific embodiments.

[0088] Example 1:

[0089] In the system described in Example 1, according to the low-temperature catalytic oxidation of the technical solution of the present invention as shown in Figure 1 wherein, the low-sulfur feed gas contains the following components by volume ratio: hydrogen sulfide 4%, nitrogen 35%, carbon dioxide 57%, methane 2%, carbon monoxide, hydrogen, etc. 1.8%, and the balance is impurity gas. The impurity gas does not contain organic sulfur components such as CS2 and COS; the hydrogen sulfide content in the feed acid gas containing sulfur is 4%, and the low-temperature catalytic oxidant is 25% iron trioxide and 48% silicon carbide; the balance is the auxiliary agent, containing precious metals such as platinum and palladium, with a specific surface area of 168 (m 2 / g), a bulk density of 0.92 (g / m 3 ), a pore volume of 0.67 (ml / g), and the carrier is ceramic. The temperature is 200°C to 220°C; the pressure is 0.5 Mpa; the space velocity is 500 h -1Hydrogenation catalyst: CT6-11A, a conventional catalyst, with a hydrogenation catalytic reaction temperature of 220°C and a pressure of 0.3 Mpa. The bottom layer of the first degassing tower uses A-AS adsorbent to adsorb mechanical impurities and moisture; the upper layer uses HX4A-98H adsorbent, with a reaction temperature of 130°C and a pressure of 0.4 MPa; the second stripping tower uses TiO2-SiO2 mesoporous adsorbent, with a temperature of 180°C. The tail gas (hydrogen sulfide) from the second stripping tower is returned to the inlet end of the low-temperature catalytic reaction, and the buffer gas holder is used to recover the liquid sulfur pool and the tail gas not returned from the second stripping tower.

[0090] The return amount of hydrogen sulfide is calculated according to the formula as follows,

[0091] where x is the hydrogen sulfide content in the low-sulfur feed gas and y is the conversion rate of hydrogen sulfide in the sulfur-containing sour gas in %. This example achieves the natural circulation method, without discharging to the buffer gas holder, realizing zero emission.

[0092] The calculation data is as follows:

[0093] Taking the low-sulfur feed gas containing 4% hydrogen sulfide and a conversion rate of 50% as an example, after the 21st cycle, the natural equilibrium point value cycle starts, that is, the natural circulation method.

[0094]

[0095]

[0096] Example 2: In the system described in Example 2, according to the system described in Example 1, that is Figure 1 the technology of the present invention shown. The difference is that the sulfur content in the feed is 1%, the conversion rate of the low-temperature catalytic oxidant is 5%, and the sulfur content in the feed fluctuates within the range of 1% to 6%. The system does not reach the fault condition for comparison.

[0097] This example achieves that under fluctuating conditions, it is necessary to discharge and buffer to the buffer gas holder, and the hydrogen sulfide emission from the hydrogen sulfide electrolytic cell is less than 0.1 kg / min, realizing near-zero emission.

[0098] Example 3: In the system described in Example 3, according to the system described in Example 1, that is Figure 1 the technology of the present invention shown. The difference is that the sulfur content in the feed is 5%, and the conversion rate of the low-temperature catalytic oxidant is 33% for comparison.

[0099] This example achieves that the difference between two adjacent equilibrium values is discharged to the buffer gas holder. Under the functions of the buffer gas holder returning to the front-end mixing and the hydrogen sulfide electrolytic cell decomposing, the hydrogen sulfide electrolytic cell does not need to discharge to the atmosphere, realizing zero emission of the system.

[0100] Calculation of the difference value: f(k n ) - f(kn-1 ) = ΔK (concentration difference);

[0101]

[0102] Among them, ΔK is the emission amount to the buffer gas holder, and ρ is the density of hydrogen sulfide gas.

[0103] The decomposition amount of the hydrogen sulfide electrolytic cell is 0 - 2.8 kg / min.

[0104] The specific calculation data is as follows:

[0105] When the sulfur content in the low-sulfur feed gas is 5% and the conversion rate is 33%, after the 7th cycle, the return concentration reaches 8.043%. Then, the sulfur content in the feed acid gas is 13.043%. After the 6th cycle, the return concentration reaches 7.96%, and the mixed concentration of the sulfur content in the feed acid gas is 12.96%. At this time, the concentration difference between the 7th and 6th times is 0.083%. That is, the equilibrium discharge valve discharges 0.083% (1 + k7)Vρ to the buffer gas holder to achieve the continuous cycle balance of the 6th time, and starts to achieve the cycle of the 7th difference balance point value, that is, the difference cycle method.

[0106]

[0107] Example 4:

[0108] In the system described in Example 4, operate according to the method described in Example 1, except that the first degassing tower is not set for comparison. This example can also be regarded as a comparison when the first degassing tower fails.

[0109] Example 5:

[0110] In the system described in Example 5, operate according to the method described in Example 1, except that the second stripping tower is not set for comparison. This example can also be regarded as a comparison when the second stripping tower fails.

[0111] Example 6:

[0112] In the system described in Example 6, operate according to the method described in Example 1, except that the buffer gas holder is not set for comparison. Cross lines are respectively set from the liquid sulfur pool and the second stripping tower to the hydrogen sulfide electrolytic cell, and the tail gas is directly sent to the hydrogen sulfide electrolytic cell for electrolysis treatment through these two cross lines.

[0113] Comparative Example 1:

[0114] In the system described in Comparative Example 1, the operation was carried out according to the method described in Example 1, except that the low-temperature catalytic oxidation catalyst CN111498812A "Method and System for Near-Zero Emission of Sulfur Recovery", the catalyst was purchased from Zibo Haichuan Fine Chemical Co., Ltd. with the brand number HS-31, the TiO2 content was 92-95% by weight, the conversion rate was 60%, and the catalytic oxidation reaction was carried out under the conditions of a temperature of 260°C to 280°C and a pressure of 0.4 MPa to 0.5 MPa for comparison.

[0115] Comparative Example 2:

[0116] In the system described in Comparative Example 2, the operation was carried out according to the method of CN111498812A "Method and System for Near-Zero Emission of Sulfur Recovery", except that the low-temperature catalytic oxidation catalyst in the present technical solution was used, with 25% iron(III) oxide and 48% silicon carbide; the balance was additives, containing precious metals such as platinum and palladium, the specific surface area was 168 (m 2 / g), the bulk density was 0.92 (g / m 3 ), the pore volume was 0.67 (ml / g), and the carrier was ceramic. The temperature was 200°C to 220°C; the pressure was 0.5 Mpa; the space velocity was 500 h -1 , and the comparison was carried out under the condition that the conversion rate was 55%.

[0117] Table 1

[0118]

[0119] * The calculation formula is:

Claims

1. A sulfur recovery method for sulfuric acid-containing sour gas, comprising the following steps: 1) In the presence of a low-temperature oxidation catalyst, the sulfuric acid-containing sour gas reacts with an oxygen-containing gas to obtain a first reactant; wherein, the volume concentration of hydrogen sulfide in the sulfuric acid-containing sour gas is less than 13%; 2) Cool the first reactant to obtain liquid sulfur and a first separated gas. The liquid sulfur enters the liquid sulfur pool for recovery, and the first separated gas enters the first degassing tower to separate nitrogen and carbon dioxide, obtaining a degassed first separated gas composed of sulfur dioxide and water vapor; 3) Heat up the degassed first separated gas, and in the presence of a hydrogenation catalyst, perform a complete hydrogenation reaction with hydrogen to obtain a second reactant; 4) After the second reactant is cooled, it enters the second stripping tower to remove water vapor, and then returns to step 1) to be combined with the low-sulfur raw gas to form sulfuric acid-containing sour gas for cyclic treatment; In step 1), the low-temperature catalytic oxidant is applicable to sulfuric acid-containing gas containing hydrocarbons, and the conversion rate is 5% to 55%; the low-temperature catalytic oxidant is a ceramic-based catalyst Fe2O3 / Pt-Pd-SiC, with a specific surface area of 148 m 2 / g to 168 m 2 / g, the bulk density is 0.62 g / m 3 to 0.92 g / m 3 , the pore volume is 0.47 ml / g to 0.67 ml / g, the silicon carbide is 42% to 62%, and the size is Φ2×9 mm to Φ3×9 mm; the low-temperature catalytic oxidant contains the following components by mass: iron oxide 20% to 31%; silicon carbide 42% to 62%; the balance is an auxiliary agent containing platinum and palladium noble metals; In step 1), the sulfuric acid-containing sour gas includes a low-sulfur raw gas and recycled hydrogen sulfide; wherein, the low-sulfur raw gas is the tail gas from coal chemical or petrochemical industry; In step 1), the oxygen-containing gas is air, 28% oxygen-enriched gas or pure oxygen, and the amount of the oxygen-containing gas is matched according to the detection range of 0 ppm to 0.5 ppm of the O2 instrument for detecting the first reactant; In step 1), the pressure of the reaction feed is 0.3 Mpa to 0.6 Mpa. The sulfuric acid-containing sour gas is heated to 130°C to 140°C and then enters the catalytic oxidation reactor to start the low-temperature oxidation exothermic reaction. The reaction temperature is 200°C to 240°C, the pressure is 0.4 Mpa to 0.6 Mpa, the space velocity is 300 to 500 h -1 ; the flow rate is ≤ 9738 m 3 / h; In step 4), under the condition of fluctuating or differential circulation method, the tail gas of the second stripping tower enters the buffer gas holder, which is used to return to the front end to adjust the sulfur content in the sulfuric acid-containing sour gas blended with the low-sulfur raw gas, so that the hydrogen sulfide concentration in the sulfuric acid-containing sour gas is maintained below 13%.

2. The method according to claim 1, wherein In step 1), the specific surface area of the low-temperature catalytic oxidant is 168 m 2 / g, the bulk density is 0.92 g / m 3 , the pore volume is 0.67 ml / g, and the carrier is ceramic SiC.

3. The method according to claim 1, wherein In step 1), the pressure of the reaction feed is 0.5 Mpa to 0.6 Mpa; the reaction temperature is 200 °C to 220 °C; the pressure is 0.5 Mpa to 0.6 Mpa.

4. The method according to claim 1, wherein In step 1), the low-sulfur raw gas contains the following components by volume ratio: hydrogen sulfide 0.1% to 6%, nitrogen 30% to 35%, carbon dioxide 50% to 60%, methane 1% to 2%, carbon monoxide, hydrogen: 1% to 2%, and other impurity gases.

5. The method according to claim 1, wherein In step 2), the first reactant is cooled to 120 °C to 160 °C.

6. The method according to claim 1, wherein, In step 2), the adsorbent in the first degassing tower uses 4A molecular sieve, the temperature of the first degassing tower is 110 °C to 160 °C; the pressure is 0.2 MPa to 0.6 MPa.

7. The method according to claim 6, wherein, The lower layer of the first degassing tower uses A-AS adsorbent, and the upper layer uses HX4A-98H adsorbent.

8. The method according to claim 1, wherein In step 3), the degassed first separated gas is heated up to 190 °C to 210 °C for hydrogenation reaction; the hydrogenation reaction temperature is 200 °C to 240 °C; Pressure: 0.05 Mpa to 0.5 Mpa.

9. The method according to claim 1, wherein, In step 3), the hydrogenation reaction catalyst is CT6-11A, with a specific surface area > 234 m 2 / g, a bulk density of 0.78 - 0.89 g / m 3 , a pore volume > 0.36 ml / g, an Al2O3 content of 82%, a size of Φ2 × 10 mm, a brown appearance, and an active promoter metal cobalt > 13% and molybdenum > 3.3%.

10. The method according to claim 1, wherein In step 4), the second reactant is cooled to 190 °C to 210 °C and then enters the second stripping tower for dehydration.

11. The method according to claim 1, wherein In step 4), the second stripping tower uses TiO2-SiO2 mesoporous adsorbent, the reaction temperature is 140 °C to 210 °C; the pressure is 0.2 MPa to 0.5 MPa.

12. The method according to claim 1, wherein, In step 4), the formula for the concentration k of the recycled hydrogen sulfide is: where x is the hydrogen sulfide content of the low-sulfur feed gas, and y is the hydrogen sulfide conversion rate % in the sulfur-containing sour gas, where n is the number of cycles.

13. The method according to any one of claims 1 to 12, wherein, The tail gas of the liquid sulfur pool enters the buffer gas holder; The hydrogen sulfide not returned in the buffer gas holder is converted into a hydrogen sulfide solution and treated by electrolysis; The sulfur produced after electrolysis is recycled, and the hydrogen produced is returned to the hydrogenation reactor for use.

14. A sulfuric acid-containing sour gas recovery system for the method according to any one of claims 1 to 13, comprising a catalytic oxidation reactor, a condensation heat exchanger, a first degassing tower, a hydrogenation reactor, and a second stripping tower connected in sequence according to the reaction sequence of the hydrogen sulfide stream, wherein, The condensation heat exchanger includes a low-temperature logistics area and a high-temperature logistics area. The low-temperature logistics area flows through the low-sulfur raw gas in the sulfuric acid-containing sour gas, and the high-temperature logistics area flows through the first reactant. The high-temperature logistics area has a gas outlet and a liquid outlet. The gas outlet is connected to the first degassing tower, and the liquid outlet is connected to the liquid sulfur pool. The gas outlet of the second stripping tower is connected to the material inlet of the catalytic oxidation reactor.

15. The system according to claim 14, wherein The catalytic oxidation reactor and the hydrogenation reactor are integrated equipment.

16. The system according to claim 14, wherein The system further includes a buffer gas holder. The second stripping tower and the liquid sulfur pool are respectively connected to the inlet of the buffer gas holder, and the outlet of the buffer gas holder is connected to the material inlet of the catalytic oxidation reactor.

17. The system according to any one of claims 14 to 16, wherein, Both the first degassing tower and the second stripping tower are composed of three towers combined. Two towers are in operation, and one tower is used for regeneration. Both the first degassing tower and the second stripping tower are connected to the liquid separation tank through a regeneration gas pipeline. The liquid separation tank is used to store the regeneration gas used when stripping the tower.

18. The system according to claim 17, wherein, A heat exchanger and an air cooler are arranged on the regeneration gas pipeline. Among them, the heat exchanger is used for heat exchange between the regeneration gas after leaving the stripping tower and the low-sulfur raw gas before entering the condensation heat exchanger.

19. The system according to any one of claims 14 to 16, wherein, The system is also provided with four hydrogen sulfide content detectors and an integrated control module. The four hydrogen sulfide content detectors are respectively connected to the integrated control module. Among them, the H2S content detector 1 is arranged in front of the inlet of the catalytic oxidation reactor, the H2S content detector 2 is arranged at the reactant outlet of the catalytic oxidation reactor, the H2S content detector 3 is arranged at the outlet of the second stripping tower; the H2S content detector 4 is arranged at the outlet of the buffer gas holder.

20. The system according to claim 19, wherein, The system is also provided with an O2 content detector, which is arranged at the reactant outlet of the catalytic oxidation reactor and is connected to the integrated control module; the system is also provided with an SO2 content detector, which is arranged at the reactant outlet of the hydrogenation reactor and is connected to the integrated control module.

21. The system according to claim 20, wherein, A balance discharge valve connected to the integrated control module is also arranged on the pipeline connecting the second stripping tower and the buffer gas holder, which is used to control the excessive hydrogen sulfide in the discharge difference cycle balance; and A cross line is arranged between the low-sulfur raw gas feed line and the buffer gas holder, and a fault discharge line is arranged at the top of the hydrogen sulfide electrolytic cell.

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