Short process claus desulfurization and sulfur recovery process coupled with low temperature catalytic oxidation

Abstract

The application discloses a short-process Claus desulfurization and sulfur recovery process coupled with low-temperature catalytic oxidation. After a waste gas containing H2S passes through a first-stage Claus conversion reactor and a condenser, the waste gas directly enters a catalytic oxidation reactor with carbon material or carbon-supported metal as a catalyst. The low-temperature catalytic oxidation activity of the carbon material or the carbon-supported metal is utilized to completely convert low-concentration H2S into sulfur at a low temperature and recover the sulfur. Compared with a traditional Claus process, the process route only needs a first-stage Claus reaction and a low-temperature catalytic oxidation reaction, and does not need multiple Claus conversion reactors and multiple reheating-condensation cycles, so that complete removal of H2S in the sulfur-containing waste gas and sulfur recovery can be realized, and the process route has the advantages of short process, low system complexity and low energy consumption.

Description

Technical Field

[0001] This invention relates to a process for purifying H2S-containing waste gas, specifically a short-process Claus desulfurization and sulfur recovery process coupled with low-temperature catalytic oxidation. Background Technology

[0002] Sulfur and hydrogen are fundamental elements in nature, and the gas they form, H2S, is widely present in industrial gases such as petroleum cracking gas, natural gas, biogas, blast furnace gas, coke oven gas, and converter gas. H2S is highly toxic and corrosive, posing a serious threat not only to human health and the ecological environment but also severely corroding production equipment and gas transmission pipelines. With rapid industrial development, the development of efficient hydrogen sulfide removal technologies has gradually become an important issue of concern in the energy and environmental fields.

[0003] The Claus process is currently the most commonly used and classic H2S removal and resource recovery process. In the Claus process, waste gas containing a high concentration of H2S first enters the combustion furnace, where approximately one-third of the H2S is converted into SO2 (H2S + O2 → SO2 + H2O). Then, through a normalization reaction between H2S and SO2, H2S is selectively converted into elemental sulfur (H2S + SO2 → S). x +H2O). However, the Claus reaction is exothermic, and due to thermodynamic equilibrium and sulfur recovery dew point limitations, the conversion rate of a single-stage Claus reaction is relatively low (60-70%). Therefore, practical Claus processes often involve multi-stage Claus converters and sulfur condensers, in which H2S undergoes multiple reaction-condensation-reheat cycles, resulting in a long process and high energy consumption. Moreover, to meet ultra-low emission requirements, conventional Claus processes also require tail gas incineration and absorption devices, further increasing system energy consumption and cost.

[0004] Low-temperature selective catalytic oxidation of H2S is a technology suitable for the resource conversion of low-concentration H2S. Unlike the Claus reaction, the low-temperature catalytic oxidation of H2S (H2S + O2 → S) x H2S (+H2O) is not limited by thermodynamic equilibrium and theoretically can be converted into sulfur with a 100% conversion rate. Researchers have attempted to combine H2S catalytic oxidation with the Claus process to efficiently convert the low-concentration tail gas from the Claus reactor outlet into sulfur. However, current H2S catalytic oxidation technologies used in conjunction with the Claus process employ Fe-based and TiO2-based catalysts, which are highly susceptible to sulfation and deactivation by SO2. To avoid this problem, current H2S catalytic oxidation technologies applied to the Claus process often require the integration of a high-temperature hydrogenation reduction unit, resulting in a complex system that consumes a large amount of additional energy. Moreover, current Claus systems coupled with H2S catalytic oxidation still require two to three stages of Claus conversion reactors, failing to address the issues of long process flow and high energy consumption inherent in the current Claus process. Summary of the Invention

[0005] To address the problems of long process flow, complex system, and high energy consumption in traditional Claus desulfurization and sulfur recovery processes, this invention provides a short-process Claus desulfurization and sulfur recovery process coupled with low-temperature catalytic oxidation. This simplifies the traditional Claus reaction process and achieves low-energy conversion of H2S into sulfur. Compared to the traditional Claus process, this process route achieves complete removal of H2S and sulfur recovery from sulfur-containing waste gas through only a single-stage Claus reaction and low-temperature catalytic oxidation reaction, eliminating the need for multi-stage Claus conversion reactors and multiple reheat-condensation cycles. It offers advantages such as a shorter process flow, lower system complexity, and lower energy consumption.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A short-process Claus desulfurization and sulfur recovery process coupled with low-temperature catalytic oxidation involves passing H2S-containing waste gas through a primary Claus conversion reactor and condenser, followed directly into a catalytic oxidation reactor using carbon materials or carbon-supported metals as catalysts. Utilizing the low-temperature catalytic oxidation activity of the carbon materials or carbon-supported metals, the low-concentration H2S is completely converted into sulfur and recovered under low-temperature conditions. The process includes the following steps:

[0008] Step 1: After being mixed, the waste gas containing H2S enters the sulfur production combustion furnace and the sulfur production waste heat boiler in sequence, where some H2S is converted to SO2 and Claus reaction occurs. The concentration of H2S in the waste gas entering the sulfur production combustion furnace after mixing is 15-30%.

[0009] Step 2: After the furnace gas is cooled, it enters the first-stage condenser. At a temperature not exceeding 160°C, the condensed sulfur is separated from the process gas, and the obtained liquid sulfur is recovered.

[0010] Step 3: The process gas at the outlet of the first-stage condenser is reheated to 240-300°C and enters the first-stage Claus converter, where a Claus reaction occurs under the action of a sulfur-producing catalyst. The sulfur-producing catalyst is one or a combination of natural bauxite, activated alumina, and TiO2 catalysts.

[0011] Step 4: After the process gas from the outlet of the first-stage Claus converter is cooled, it enters the second-stage condenser and is cooled to below 160°C. The condensed liquid sulfur is separated from the process gas, and the obtained liquid sulfur is recovered.

[0012] Step 5: The process gas from the outlet of the secondary condenser is mixed with air, cooled, and then enters the catalytic oxidation reactor. Under the action of a carbon-based catalyst or a carbon-supported catalyst, a catalytic oxidation reaction occurs, converting H2S into sulfur. Specifically: after air mixing, the H2S concentration in the exhaust gas entering the catalytic oxidation reactor does not exceed 5%; the carbon-based catalyst is one or a combination of activated carbon, carbon nanotubes, and porous graphene; for carbon-supported catalysts, the carbon support is one or a combination of activated carbon, carbon nanotubes, and porous graphene, and the carbon-supported catalyst is one or a combination of catalyst materials selected from Fe, Cu, Ce, Al2O3, TiO2, SiC, MgO, and MnO2; the temperature range of the catalytic oxidation reaction is 20–160℃.

[0013] Step 6: After the catalyst in the catalytic oxidation reactor is saturated, it is cleaned with an organic solvent to recover sulfur, a product of H2S catalytic oxidation. The organic solvent used to recover sulfur is one or a combination of benzene, acetone, and carbon tetrachloride.

[0014] Step 7: The catalyst, after being cleaned and regenerated with organic solvent, is further regenerated by water washing to recover trace amounts of sulfuric acid, a product of SO2 catalytic oxidation.

[0015] Compared with the traditional Claus process, the present invention has the following advantages:

[0016] (1) From the perspective of the overall process route, compared with the traditional Claus process, the present invention achieves short-process H2S removal and sulfur recovery with low system complexity: Due to the thermodynamic equilibrium limitation of the Claus reaction, the traditional Claus process requires multi-stage Claus conversion reactors and condensers, and needs to be coupled with tail gas incineration and absorption systems, resulting in a long process and complex system. The process route proposed in this invention utilizes catalytic oxidation to directly and completely convert the process gas formed by the first-stage Claus converter, simplifying the multi-stage Claus conversion reactor and significantly reducing system complexity and cost.

[0017] (2) From the perspective of system energy consumption, compared with the traditional Claus process, the present invention does not require multiple reaction-condensation-reheat cycles, resulting in lower energy consumption: In the traditional Claus process, the Claus reaction temperature range does not match the sulfur condensation and recovery temperature range, requiring multiple reaction-condensation-reheat cycles, which leads to high energy consumption. In the process route of the present invention, the process gas after the first-stage Claus reaction is condensed and directly enters the catalytic oxidation reactor, where H2S in the process gas is converted into sulfur under low-temperature conditions, eliminating the need for multiple reaction-condensation-reheat cycles and significantly reducing system energy consumption.

[0018] (3) This invention achieves near-zero emissions of sulfur-containing pollutants without a complex tail gas treatment system: In the traditional Claus process, the tail gas contains a certain proportion of SO2. To achieve near-zero emissions of pollutants and avoid deactivation of the catalytic oxidation catalyst, SO2 needs to be treated by chemical absorption or high-temperature hydrogenation reduction while removing H2S, making the system complex. The process route of this invention uses carbon-based materials as catalysts for the catalytic oxidation of H2S. Since carbon materials have low-temperature catalytic oxidation activity for both H2S and SO2, the removal and resource recovery of H2S and SO2 can be achieved simultaneously, without the need for additional tail gas treatment processes, resulting in low system complexity. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0020] Example 1:

[0021] Step 1: Pass the waste gas with an H2S concentration of 20% into the sulfur production combustion furnace and the sulfur production waste heat boiler at a temperature of 320℃, where part of the H2S is converted into SO2 and the Claus reaction occurs.

[0022] Step 2: After the furnace gas is cooled, it enters the primary condenser and is used to recover sulfur at a temperature of 160°C.

[0023] Step 3: The process gas discharged from the primary condenser is reheated with steam to 240°C and then enters the primary Claus converter to carry out the Claus reaction using activated alumina as a catalyst.

[0024] Step 4: The process gas from the outlet of the first-stage Claus converter is cooled and then enters the second-stage condenser to be cooled to 160°C to recover liquid sulfur.

[0025] Step 5: The process gas discharged from the secondary condenser is mixed with air to adjust the H2S concentration to 3%. After cooling to room temperature, the adjusted process gas enters the low-temperature catalytic oxidation reactor with a nitrogen content of 8% and a specific surface area of ​​1200 m². 2 g -1 Nitrogen-doped hierarchical porous carbon with a pore volume ratio of 40% is used as a catalyst to carry out catalytic oxidation reaction, converting H2S into sulfur.

[0026] Step 6: After 50 hours of reaction, the catalyst reaches saturation. The reactor is then switched to a regeneration reactor, where the catalyst is washed with acetone and water in sequence to recover sulfur and sulfuric acid.

[0027] During the 50-hour catalytic oxidation process, both SO2 and H2S emissions reached near-zero levels, and the sulfur capacity calculated based on the recovered sulfur was 2.2 g. -1 .

[0028] Example 2:

[0029] Step 1: Pass the waste gas with an H2S concentration of 20% into the sulfur production combustion furnace and the sulfur production waste heat boiler at a temperature of 320℃, where part of the H2S is converted into SO2 and the Claus reaction occurs.

[0030] Step 2: After the furnace gas is cooled, it enters the primary condenser and is used to recover sulfur at a temperature of 160°C.

[0031] Step 3: The process gas discharged from the primary condenser is reheated with steam to 240°C and then enters the primary Claus converter to carry out the Claus reaction using activated alumina as a catalyst.

[0032] Step 4: After the process gas from the outlet of the first-stage Claus converter is cooled, it enters the second-stage condenser and is cooled to 160°C to recover liquid sulfur.

[0033] Step 5: The process gas discharged from the secondary condenser is mixed with air to adjust the H2S concentration to 1%. After being cooled to room temperature, the process gas enters the low-temperature catalytic oxidation reactor with a specific surface area of ​​900 m². 2 g -1 Hierarchical porous carbon with a pore volume ratio of 40% (mesopores and macropores) is used as a support, and 10% MgO is loaded as a catalyst to carry out a catalytic oxidation reaction to convert H2S into sulfur.

[0034] Step 6: After 60 hours of reaction, the catalyst reaches saturation. The reactor is then switched to a regeneration reactor, where the catalyst is washed with acetone and water in sequence to recover sulfur and sulfuric acid.

[0035] During the 60-hour catalytic oxidation process, both SO2 and H2S emissions reached near-zero levels, and the sulfur capacity calculated based on the recovered sulfur was 2.5 g / kg. -1 .

Claims

1. A short-process Claus desulfurization and sulfur recovery process coupled with low-temperature catalytic oxidation, characterized in that... The process includes the following steps: Step 1: After being mixed, the waste gas containing H2S enters the sulfur production combustion furnace and the sulfur production waste heat boiler in sequence, where some H2S is converted to SO2 and Claus reaction occurs. The concentration of H2S in the waste gas entering the sulfur production combustion furnace after mixing is 15-30%. Step 2: After the furnace gas is cooled, it enters the first-stage condenser. At a temperature not exceeding 160°C, the condensed sulfur is separated from the process gas, and the obtained liquid sulfur is recovered. Step 3: The process gas at the outlet of the first-stage condenser is reheated to 240-300°C and enters the first-stage Claus converter, where it undergoes a Claus reaction under the action of a sulfur-producing catalyst. Step 4: After the process gas from the outlet of the first-stage Claus converter is cooled, it enters the second-stage condenser and is cooled to below 160°C. The condensed liquid sulfur is separated from the process gas, and the obtained liquid sulfur is recovered. Step 5: The process gas from the outlet of the secondary condenser is mixed with air and cooled before entering the catalytic oxidation reactor. Under the action of a carbon-based catalyst or a catalyst with carbon as a support, a catalytic oxidation reaction is carried out to convert H2S into sulfur. The H2S concentration in the exhaust gas entering the catalytic oxidation reactor after air mixing does not exceed 5%. Step 6: After the catalyst in the catalytic oxidation reactor is saturated, it is cleaned with an organic solvent to recover sulfur, a product of H2S catalytic oxidation. Step 7: The catalyst, after being cleaned and regenerated with organic solvent, is further regenerated by water washing to recover trace amounts of sulfuric acid, a product of SO2 catalytic oxidation.

2. The short-process Claus desulfurization and sulfur recovery process coupled with low-temperature catalytic oxidation as described in claim 1, characterized in that... The sulfur-producing catalyst is one or a combination of natural bauxite, activated alumina, and TiO2 catalysts.

3. The short-process Claus desulfurization and sulfur recovery process coupled with low-temperature catalytic oxidation as described in claim 1, characterized in that... The carbon-based catalyst is one or a combination of activated carbon, carbon nanotubes, and porous graphene.

4. The short-process Claus desulfurization and sulfur recovery process coupled with low-temperature catalytic oxidation according to claim 1, characterized in that... In the carbon-supported catalyst, the carbon support is one or a combination of activated carbon, carbon nanotubes, and porous graphene, and the carbon-supported catalyst is one or a combination of catalyst materials selected from Fe, Cu, Ce, Al2O3, TiO2, SiC, MgO, and MnO2.

5. The short-process Claus desulfurization and sulfur recovery process coupled with low-temperature catalytic oxidation according to claim 1, characterized in that... The temperature range for the catalytic oxidation reaction is 20–160 °C.

6. The short-process Claus desulfurization and sulfur recovery process coupled with low-temperature catalytic oxidation according to claim 1, characterized in that... The organic solvent is one or a combination of benzene, acetone, and carbon tetrachloride.