Claus sulfur recovery method

Abstract

The invention discloses a Claus sulfur recovery method which comprises the following steps: enabling acid gas generated by an upstream device and air from a main fan to enter an acid gas combustion furnace together for combustion; high-temperature process gas discharged from an acid gas combustion furnace is cooled by a waste heat boiler and then mixed with SO2 returned by a tail gas device, the mixture is subjected to first sulfur separation and remixed and then enters a first-stage reactor, the inlet temperature of the first-stage reactor is 220 DEG C, and the temperature of a catalyst bed layer of the first-stage reactor is 250-300 DEG C; the process gas discharged from the first-stage reactor is subjected to heat exchange, secondary sulfur separation and remixing and then enters a second-stage reactor, the inlet temperature of the second-stage reactor is 170 DEG C, and the temperature of a catalyst bed layer of the first-stage reactor is 160-200 DEG C. According to the method, heat loss caused by heat exchange of conventional Claus can be effectively reduced, the technological process is reduced, so that energy consumption loss is reduced, temperature control is simplified, it is guaranteed that the sulfur yield reaches 95% or above, and meanwhile it is guaranteed that SO2 reaches the standard and is discharged.

Description

Technical Field

[0001] The present invention relates to a Claus sulfur recovery method, belonging to the technical field of sulfur recovery. Background Art

[0002] During the processes of petroleum refining and natural gas processing, a large amount of H 2 S gas is generated. In order to protect the environment and recover elemental sulfur, industrially, acid gas containing H 2 S is usually treated through a sulfur recovery unit, and the by-product is sulfur. The Claus sulfur recovery process is the main sulfur recovery method currently, and its principle is as follows:

[0003] The Claus sulfur recovery process is the main sulfur recovery method currently. Its reaction equations are as follows:

[0004] H 2 S + 3 / 2 O 2 → SO 2 + H 2 O (1)

[0005] 2H 2 S + SO 2 → 3 / X Sx +2H 2 O (2)

[0006] Among them, reactions (1) and (2) are carried out in a high-temperature reaction furnace. In the catalytic reaction zone (below 538 °C), in addition to reaction (2), the following hydrolysis reactions (3) and (4) of organic sulfides also occur:

[0007] CS 2 + H 2 O → COS + H 2 S (3)

[0008] COS + H 2 O → H 2 S + CO 2 (4)

[0009] Specifically: The conversion of H 2 S in the acid gas into elemental sulfur is jointly completed in the high-temperature reaction of the acid gas in the reaction furnace and the low-temperature catalytic reaction in the reactor. The high-temperature thermal reaction of H 2 S oxidation into elemental sulfur in the reaction furnace is carried out in two steps. Among them, 1 / 3 of H 2 S burns with stoichiometric air between 900 and 1300 °C. After partial oxidation through the free flame, H 2 S is converted into SO 2 and H 2 O; The remaining 2 / 3 of H2 S reacts with SO 2 to carry out the second reaction to generate sulfur and water. Under high-temperature thermal reaction conditions, sulfur elements basically exist in the forms of S l and S 2 . The sulfur-containing mixture after combustion enters the waste heat boiler and is cooled to about 350°C; the mixed gas coming out of the waste heat boiler enters the first-stage condenser and is cooled to 150 - 160°C, and the liquid sulfur produced enters the liquid sulfur storage tank in the forms of S 8 and S 6 . The reheated process gas then enters two to three adiabatic reactors for catalytic reaction. The operating temperature of the first reactor bed is generally controlled at about 330°C, the operating temperature of the second reactor bed is roughly controlled at about 250°C, and if there is a third reactor, the temperature is controlled at about 220°C. The prior art mostly adopts the aforementioned method of gradually decreasing the temperature to force the reaction to proceed in the direction favorable for sulfur production, and at the same time, the method of condensation is used between reactors to continuously recover liquid sulfur.

[0010] Industrial practice shows that at the high temperature that the reaction furnace can reach, the conversion rate of H 2 S in the furnace can reach 60 - 75%. If a two-stage Claus process device is adopted, the total sulfur conversion rate is about 92 - 95%, and the three-stage Claus process can reach up to 98% at most.

[0011] During the actual operation of the Claus sulfur recovery process, it is necessary to control the ratio of H 2 S to SO 2 in the tail gas of the recovery device at 2:1 to ensure the favorable progress of the Claus reaction. At the same time, it is necessary to strengthen the control of the temperatures before the first, second, and third reactors and before the Super Claus. Generally, the temperature before the first reactor is controlled at 220 - 235°C, and the bed temperature is 330 - 340°C. The temperature before the second reactor is controlled between 210 - 220°C, and the bed temperature is 240 - 250°C. The temperature before the third reactor is controlled between 210 - 220°C, and the bed temperature is controlled between 210 - 230°C. The temperature before the Super Claus reactor is controlled at 205 - 210°C, and the bed temperature is controlled at 220 - 242°C.

[0012] However, in actual production, due to process operations, upstream gas, etc., it is difficult to operate with a stoichiometric ratio of 2:1. Moreover, the high-temperature solution is likely to cause thermal aging of the catalyst, and the low-temperature sulfur vapor is condensed into liquid sulfur and adheres to the surface of the catalyst, resulting in catalyst deactivation. Therefore, during the Claus reaction, it is also necessary to monitor the bed temperature in real time to avoid over-temperature or low-temperature situations. At the same time, when the acid gas volume or the H 2 S content in the acid gas is very low, its combustion is not sufficient to maintain the furnace temperature, and the device cannot operate normally. Therefore, the liquid-phase direct oxidation-reduction process is often adopted.

[0013] Furthermore, when sulfur recovery has gas quality fluctuations, it is easy to cause system fluctuations, resulting in a decrease in sulfur yield and even causing tail gas SO 2 Exceeding the emission standard. Therefore, it is necessary to ensure that the exhaust gas SO 2 Qualified emissions cannot be achieved by relying solely on conventional Claus and Super Claus processes. The exhaust gas needs to be treated again with an exhaust device to achieve qualified emissions. Summary of the invention

[0014] The present invention provides a Claus sulfur recovery method, which solves the technical problem that the Claus sulfur recovery process in the prior art needs to strictly control the air distribution ratio and the bed temperature.

[0015] To achieve the above object, the technical solution adopted by the present invention is: a Claus sulfur recovery method, comprising the following steps: the acid gas generated by the upstream device and the air from the main fan are both fed into the acid gas combustion furnace for combustion; the high-temperature process gas from the acid gas combustion furnace is cooled by the waste heat boiler and then mixed with the SO 2 After mixing, the first sulfur separation is carried out, and after the first sulfur separation, it enters the primary reactor, the inlet temperature of the primary reactor is 220°C, and the temperature of the catalyst bed of the primary reactor is 250-300°C; after heat exchange, the process gas coming out of the primary reactor undergoes the second sulfur separation and re-mixes before entering the secondary reactor, the inlet temperature of the secondary reactor is 170°C, and the temperature of the catalyst bed of the primary reactor is 160-200°C.

[0016] Furthermore, the temperature of the acid gas combustion furnace is controlled at 900-1000°C.

[0017] Furthermore, the first sulfur separation and remixing enters the primary reactor, specifically including the following steps: the high-temperature process gas from the acid gas combustion furnace is cooled by the waste heat boiler, 70% of the process gas is cooled to 200°C by the second channel of the waste heat boiler and mixed with the SO returned from the tail gas device. 2 After mixing, it enters the primary condenser and is cooled to about 130°C. About 30% of the process gas is mixed with the process gas after liquid sulfur is separated from the primary condenser through a channel of the waste heat boiler and then enters the primary reactor.

[0018] Furthermore, a gas-to-gas heat exchanger is used to exchange heat for the process gas coming out of the primary reactor.

[0019] Furthermore, the second sulfur separation and remixing before entering the secondary reactor specifically includes the following steps: the process gas coming out of the primary reactor enters the secondary condenser and is cooled to 130° C. after passing through the tube side of the gas-gas heat exchanger; the process gas coming out of the secondary condenser enters the secondary reactor after heat exchange with the process gas coming out of the primary reactor through the shell side of the gas-gas heat exchanger.

[0020] Further, the liquid sulfur separated by the primary condenser and the secondary condenser respectively enters the corresponding liquid sulfur seals at each level, and the liquid sulfur flowing through the liquid sulfur seals at each level flows into the liquid sulfur tank by itself, and the H in the liquid sulfur in the liquid sulfur tank is removed. 2 After S, it is then sent to the sulfur forming unit by a liquid sulfur pump.

[0021] Further, the process gas of the secondary reactor is cooled to 130 °C by a tertiary sulfur condenser, the sulfur vapor is condensed and separated, and then enters the tail gas treatment device; the process gas treated by the tail gas treatment device returns to the waste heat boiler for cooling.

[0022] Further, the tail gas treatment device is used to convert various forms of sulfur-containing compounds in the tail gas into SO 2 .

[0023] The present invention adopts an inaccurate control of the air distribution ratio and optimizes the temperatures of the primary reactor and the secondary reactor, so that the system temperature operates between conventional Claus and low-temperature Claus to ensure the stable progress of the Claus reaction, effectively reduce the heat loss caused by heat exchange in conventional Claus, reduce the process flow to reduce the loss of energy consumption and simplify the temperature control, so that the outlet temperature of the process gas of the reactor can reach 300 °C and the system temperature can reach 200 °C, and the sulfur recovery rate can still reach more than 95%. At the same time, it ensures that SO 2 meets the discharge standards, broadens the treatment range of the Claus process, and realizes the safe and environmentally friendly operation of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of a Claus sulfur recovery method provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] In order to enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be further described below with reference to the drawings and embodiments.

[0026] The present invention provides a Claus sulfur recovery method, which is particularly suitable for Claus sulfur recovery with a latent sulfur content of less than 3 t, and includes the following steps:

[0027] S1. The acid gas generated by the upstream device and the air from the main blower are jointly introduced into the acid gas combustion furnace for combustion, and the temperature of the acid gas combustion furnace is controlled at 900-1000 °C. In this step, part of the H 2 S is converted into elemental sulfur.

[0028] The fuel gas blending combustion method is adopted to increase the furnace temperature, control the temperature at 900-1000 °C, and ensure the conversion rate of hydrogen sulfide in the main combustion furnace. In order to make the hydrocarbons in the acid gas burn completely, an excess air operation is adopted and combined with the SO returned from the tail gas device 2Widen the air distribution ratio control range to 1.2 - 1.8:1, so as to non-precisely control the H 2 S and SO 2 ratio, which can reduce the operation difficulty.

[0029] S2. The high-temperature process gas coming out of the acid gas combustion furnace is cooled by the waste heat boiler.

[0030] The process gas cooled by the waste heat boiler is mixed with the SO 2 returned from the tail gas device and then undergoes the first sulfur separation: 70% of the process gas is cooled to 200°C through the second channel of the waste heat boiler and mixed with the SO 2 returned from the tail gas device, and then enters the primary condenser to be cooled to about 130°C. About 30% of the process gas is mixed with the process gas after the liquid sulfur is separated from the primary condenser through the first channel of the waste heat boiler and then enters the primary reactor at about 220°C. The Claus reaction occurs on the catalyst bed to generate elemental sulfur, and the temperature of the catalyst bed is 250 - 300°C. This step can be without setting up a fuel gas reheating furnace reheating system.

[0031] S3. The process gas coming out of the primary reactor undergoes the second sulfur separation after passing through the gas-gas heat exchanger and then is remixed and enters the secondary reactor.

[0032] The process gas coming out of the primary reactor enters the secondary condenser through the tube side of the gas-gas heat exchanger and is cooled to 130°C, and part of the condensed liquid sulfur is separated. The process gas coming out of the secondary condenser is then heated through the shell side of the gas-gas heat exchanger with the process gas coming out of the primary reactor and enters the secondary reactor at about 170°C, and continues to react on the catalyst bed to generate elemental sulfur, and the reaction temperature is 160 - 200°C.

[0033] S4. The process gas of the secondary reactor is cooled to 130°C by the tertiary sulfur condenser, and most of the sulfur vapor is condensed and separated, and then enters the tail gas treatment device. The tail gas treatment device converts various forms of sulfur-containing compounds in the tail gas into SO 2 After that, the SO 2 gas returns to step S2 to continue recovering elemental sulfur.

[0034] The liquid sulfur separated by each stage of condenser enters each stage of liquid sulfur seal respectively, and the liquid sulfur passing through each stage of liquid sulfur seal flows into the liquid sulfur tank by itself. After removing H 2 S in the liquid sulfur, it is then sent to the sulfur forming unit by a liquid sulfur pump. The low-pressure saturated steam generated by the waste heat boiler and each stage of condenser can provide heat preservation and tracing steam for this device, and the remaining steam enters the whole plant low-pressure steam system pipe network for other devices to use.

[0035] Adopting the method of the present invention, the tail gas emission standard complies with the "Emission Standard of Air Pollutants for Onshore Oil and Gas Exploitation Industry (GB 39728 - 2020)".

[0036] The first-stage Claus reactor of the present invention conducts reactions at a reaction temperature of 250 - 300 °C; the second-stage Claus reactor conducts reactions at a reaction temperature of 160 - 200 °C, enabling the system temperature to operate between that of conventional Claus and low-temperature Claus, ensuring the stable progress of the Claus reaction with a latent sulfur content of 3 t or less. This can effectively reduce the heat loss caused by heat exchange in conventional Claus, reduce the process flow to lower energy consumption losses, and simplify temperature control. Even when the outlet temperature of the process gas from the reactor is 300 °C and the system temperature is 200 °C, the sulfur recovery rate can reach over 95%, while ensuring that SO 2 meets the emission standards, broadens the treatment range of the Claus process, and realizes the safe and environmentally friendly operation of the device.

[0037] Example 1

[0038] In a purification plant, when the treatment volume decreased, the designed treatment volume decreased from 1.2×10⁶ m 3 / d to 0.25×10⁶ m 3 / d, the designed latent sulfur content was broadened from 11 t / d to 3 t / d, the tail gas met the standards, and the total sulfur recovery rate was over 99%. The SO 2 in the tail gas met the emission standards.

[0039] The present invention effectively broadens the lower limit of the treatment range of the conventional Claus process, solves the problem that the Claus sulfur recovery cannot operate normally with a latent sulfur content of 3 t or less. At the same time, it can effectively extend the service life of the equipment, save the costs of equipment replacement, overhaul construction, and material consumption, and save the costs of equipment replacement at different stages of the device. Moreover, it can more effectively guide the optimization and adjustment of the device, reduce costs and increase efficiency, significantly reduce the SO₂ emissions, and has good effects after being promoted and tested.

[0040] The above are only examples of the present invention. Specific structures and common knowledge such as characteristics well-known in the art are not described in detail herein. Those of ordinary skill in the art know all the common general technical knowledge in the technical field to which the invention belongs before the application date or priority date, can know all the existing technologies in this field, and have the ability to apply the conventional experimental means before this date. Those of ordinary skill in the art can, under the inspiration given in this application, improve and implement this solution in combination with their own abilities. Some typical well-known structures or well-known methods should not become obstacles for those of ordinary skill in the art to implement this application. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent.

Claims

1. A Claus sulfur recovery method, characterized in that, it comprises the following steps: The acid gas generated by the upstream device and the air from the main blower enter the acid gas combustion furnace for combustion together; the high-temperature process gas coming out of the acid gas combustion furnace is cooled by the waste heat boiler and then mixed with the SO 2 returned from the tail gas device. After the first sulfur separation, it enters the first-stage reactor. The inlet temperature of the first-stage reactor is 220°C, and the temperature of the catalyst bed of the first-stage reactor is 250-300°C; The process gas coming out of the first-stage reactor is heat-exchanged and then undergoes secondary sulfur separation and re-mixing before entering the second-stage reactor. The inlet temperature of the second-stage reactor is 170 °C, and the temperature of the catalyst bed of the first-stage reactor is 160 - 200 °C.

2. The Claus sulfur recovery method according to claim 1, characterized in that: The temperature of the acid gas combustion furnace is controlled at 900 - 1000 °C.

3. The Claus sulfur recovery method according to claim 1, characterized in that, After the first-stage splitting and remixing, it enters the first-stage reactor, which specifically includes the following steps: The high-temperature process gas coming out of the acid gas combustion furnace is cooled by the waste heat boiler. After 70% of the process gas is cooled to 200 °C through the second channel of the waste heat boiler, it is mixed with the SO 2 returned from the tail gas unit, enters the first-stage condenser and is cooled to about 130 °C. About 30% of the process gas is mixed with the process gas after the liquid sulfur is separated from the first-stage condenser through the first channel of the waste heat boiler and then enters the first-stage reactor.

4. The Claus sulfur recovery method according to claim 3, characterized in that: A gas-gas heat exchanger is used to heat-exchange the process gas coming out of the first-stage reactor.

5. The Claus sulfur recovery method according to claim 4, characterized in that, After the secondary sulfur separation and re-mixing, it enters the second-stage reactor, which specifically includes the following steps: The process gas coming out of the first-stage reactor enters the second-stage condenser through the tube side of the gas-gas heat exchanger and is cooled to 130 °C; the process gas coming out of the second-stage condenser then enters the shell side of the gas-gas heat exchanger to exchange heat with the process gas coming out of the first-stage reactor and then enters the second-stage reactor.

6. The Claus sulfur recovery method according to claim 5, characterized in that: The liquid sulfur separated by the primary condenser and the secondary condenser respectively enters the corresponding liquid sulfur seals at each level, and the liquid sulfur passing through the liquid sulfur seals at each level flows into the liquid sulfur tank by gravity. After removing H 2 S from the liquid sulfur in the liquid sulfur tank, it is then sent to the sulfur forming unit by a liquid sulfur pump.

7. The Claus sulfur recovery method according to claim 1, characterized in that: The process gas of the second-stage reactor is cooled to 130 °C by a third-stage sulfur condenser, the sulfur vapor is condensed and separated, and then enters the tail gas treatment device; the process gas treated by the tail gas treatment device returns to the waste heat boiler.

8. The Claus sulfur recovery method according to claim 7, characterized in that: The exhaust gas treatment device is used to convert various forms of sulfur-containing compounds in the exhaust gas into SO 2 .

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