Flue gas treatment method for catalytic cracking device
By adjusting the process parameters in the catalytic cracking device, controlling the iron content, reaction temperature, alkali injection and water replenishment of the desulfurization tower, optimizing the role of the sulfur transfer agent, the problem of blue smoke tailing in the catalytic cracking device is solved, and effective flue gas treatment is achieved.
Patent Information
- Application Number
- CN202510478066.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-16
- Publication Date
- 2025-06-27
AI Technical Summary
In the catalytic cracking device, even though sulfur transfer agent is added, it is still impossible to effectively solve the problem of blue smoke tailing in the flue gas.
By adjusting the process parameters of the catalytic cracking device, the iron content in the raw oil should not exceed 2 μg/g, the reactor temperature should be controlled between 527℃-535℃, and the alkali injection amount and water replenishment amount should be adjusted in the desulfurization tower to optimize the effect of the sulfur transfer agent.
It effectively reduces the SO3 content in the flue gas, reduces the tailing and blueness of the flue gas, and solves the problem that the addition of sulfur transfer agents cannot effectively control the flue gas.
Smart Images
Figure CN120204910A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of flue gas treatment, and particularly relates to a method for treating the flue gas of a fluid catalytic cracking unit. Background Art
[0002] The fluid catalytic cracking unit is the most rapidly developed oil refining unit in the past half century. It is also the most important production unit in the current oil refinery and an important unit for producing liquefied gas, gasoline, and diesel in the refinery, making a great contribution to the efficiency of the refinery. Therefore, the operation of the catalytic unit is a favorable guarantee for the efficiency of the oil refinery. In recent years, with the increasing proportion of imported crude oil, the properties of catalytic feedstocks have become increasingly heavy, and the sulfur and nitrogen contents in the feedstocks have gradually increased. Therefore, the problem of flue gas quality emissions from catalytic cracking has become the focus of attention of environmental protection departments.
[0003] In the fluid catalytic cracking process, thiophene and benzothiophene in the total sulfur of the catalytic feedstock partially enter the coke. After regeneration and burning, they are phase-converted into SO2 and SO3 in the regenerator. The sulfur oxides enter the desulfurization tower of the flue gas desulfurization device after passing through the boiler in the flue gas. After passing through the slurry circulation section and the filtration module section of the desulfurization tower, most of the sulfur oxides have been removed. A small amount of SO3 forms an aerosol together with salts, catalyst dust, and slurry, and is discharged into the atmosphere with the purified flue gas. Excessive SO3 content will form a large amount of aerosol, causing the purified flue gas to have a tail and form a blue plume.
[0004] The sulfur transfer agent is an environmental protection catalytic additive that reduces the SO x emission by changing the proportion of sulfur elements in the various products of the fluid catalytic cracking unit. Adding a sulfur transfer agent to the regenerator of the fluid catalytic cracking unit can effectively capture SO3 in the regenerated flue gas and significantly reduce the SO2 concentration. Although it can alleviate the problem of the blue plume in the desulfurization tower to a certain extent, it still cannot effectively solve the problem of blue smoke trailing. Therefore, it is of great significance to develop a new method for treating the flue gas of the fluid catalytic cracking unit. Summary of the Invention
[0005] The purpose of the present invention is to overcome the problems existing in the above-mentioned prior art and provide a method for treating the flue gas of a fluid catalytic cracking unit.
[0006] The present invention is realized through the following technical solutions:
[0007] A method for treating the flue gas of a fluid catalytic cracking unit provided by the present invention includes the following steps:
[0008] (1) Pass the feedstock oil into the reactor of the fluid catalytic cracking unit, and the iron content in the feedstock oil is not higher than 2 μg / g;
[0009] (2) Adjust the reaction temperature at the outlet of the first reaction zone of the riser reactor of the fluid catalytic cracking unit to 527°C - 535°C;
[0010] (3) Adjust the bottom alkali injection amount of the desulfurization tower to no higher than 700 kg / h, and adjust the makeup water amount of the desulfurization tower to 50 t / h - 80 t / h.
[0011] In some refineries under the original operating conditions, there is a problem that even if a sulfur transfer agent is added, it is still impossible to control the serious blue smoke trailing of the flue gas. Without adjusting the addition amount of the sulfur transfer agent and changing the type of the sulfur transfer agent, the present invention effectively improves the blue smoke trailing problem of the flue gas through the process adjustment of the fluid catalytic cracking unit. The present invention controls the iron content in the fluid catalytic cracking feedstock oil not to exceed 2 μg / g, avoiding the reaction of iron with decomposed H2S in the riser to generate FeS, which is then brought back to the regenerator to generate SO X ; and control the reactor temperature at 527°C - 535°C. The following reactions occur for the sulfur transfer agent in the reactor: MSO4 + 4H2 → MS + 4H2O, MSO4 + 4H2 → MO + H2S + 3H2O, MS + H2O → MO + H2S; the sulfur transfer agent undergoes a reduction reaction in the reactor. At this reaction temperature, it is beneficial to the reduction of the active metal in the sulfur transfer agent, and only after the active metal resumes its activity can it better exert the desulfurization effect. The alkali injection amount in the desulfurization tower is controlled not to exceed 700 kg / h because a large alkali injection amount will cause the salt content in the circulating slurry to increase. The temperature of the flue gas entering the desulfurization tower is about 180°C, and a large amount of water vapor will evaporate. The salts in the circulating slurry will precipitate into the flue gas, and the increase in the salt content will cause an increase in aerosols, forming blue smoke trailing; the makeup water amount of the desulfurization tower is adjusted within the range of 50 t / h - 80 t / h, which can reduce the salt content at the bottom of the desulfurization tower. At the same time, too large a makeup water amount of the desulfurization tower will increase the energy consumption of the device, so the makeup water amount should not be too large. In the treatment method of the present invention, by adjusting specific process parameters, the content of SO3 in the flue gas can be effectively reduced, the flue gas trailing and the bluing of the flue gas can be effectively alleviated, and the problem that the addition of a sulfur transfer agent still cannot effectively treat the flue gas is solved.
[0012] As a preferred embodiment of the treatment method of the flue gas of the fluid catalytic cracking unit described in the present invention, in the fluid catalytic cracking unit, the addition amount of the sulfur transfer agent is 2.8% - 3.2% of the total catalyst inventory.
[0013] Preferably, the addition amount of the sulfur transfer agent in the fluid catalytic cracking unit is 3% of the total catalyst inventory.
[0014] Through the process adjustment of the fluid catalytic cracking unit, the present invention can effectively reduce the blue smoke trailing problem of the flue gas without adjusting the addition amount of the sulfur transfer agent and changing the type of the sulfur transfer agent, while maintaining the addition amount of the sulfur transfer agent at 2.8% - 3.2% of the total catalyst inventory.
[0015] As a preferred embodiment of the treatment method of the flue gas of the fluid catalytic cracking unit described in the present invention, the sulfur transfer agent includes an enhanced RFS sulfur transfer agent.
[0016] The treatment method of the present invention does not make special restrictions on the type of sulfur transfer agent, and can be applied to a variety of common sulfur transfer agents.
[0017] As a preferred embodiment of the treatment method of the flue gas of the fluid catalytic cracking unit of the present invention, in the step (3), the concentration of the suspended matter in the bottom slurry of the desulfurization tower does not exceed 2500 mg / L.
[0018] As a preferred embodiment of the treatment method of the flue gas of the fluid catalytic cracking unit of the present invention, in the step (3), the pH value at the bottom of the desulfurization tower is 6.4 - 6.6.
[0019] Preferably, in the step (3), the pH value at the bottom of the desulfurization tower is 6.5.
[0020] As a preferred embodiment of the treatment method of the flue gas of the fluid catalytic cracking unit of the present invention, the fluid catalytic cracking unit includes a reactor, a regenerator, a main blower, a compressor, a fractionating tower, an absorption tower, a stabilizing tower, an external heat exchanger, a waste heat boiler, and a desulfurization tower.
[0021] The treatment method of the present invention can be applied to common fluid catalytic cracking units. Under the process conditions of the present invention, the problem of blue smoke trailing can be effectively improved.
[0022] As a preferred embodiment of the treatment method of the flue gas of the fluid catalytic cracking unit of the present invention, in the step (3), the makeup water volume of the desulfurization tower is adjusted to 50 t / h - 70 t / h.
[0023] The present invention has the following beneficial effects: Without adjusting the addition amount of the sulfur transfer agent and changing the type of the sulfur transfer agent, the present invention effectively improves the problem of blue smoke trailing of the flue gas through the process adjustment of the fluid catalytic cracking unit. The present invention controls the iron content in the fluid catalytic cracking feedstock oil not to exceed 2 μg / g, avoiding the reaction of iron with decomposed H2S in the riser to generate FeS, which is then brought back to the regenerator to generate SO X The problem; and controlling the reactor temperature at 527°C - 535°C is beneficial to the reduction of the active metal in the sulfur transfer agent, and better plays the desulfurization effect. The alkali injection amount in the desulfurization tower is controlled not to exceed 700 kg / h, avoiding the increase of aerosol and forming blue smoke trailing. The makeup water volume of the desulfurization tower is adjusted within the range of 50 t / h - 80 t / h, which can not only reduce the salt content in the bottom slurry of the desulfurization tower, but also avoid excessive energy consumption of the device. Through adjusting specific process parameters in the treatment method of the present invention, the content of SO3 in the flue gas can be effectively reduced, effectively reducing the flue gas trailing and the blue color of the flue gas, and solving the problem that the addition of the sulfur transfer agent still cannot effectively treat the flue gas. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is the flue gas state after the treatment method of Example 1;
[0025] Figure 2 Flue gas state after treatment by the treatment method of Example 2;
[0026] Figure 3 Flue gas state after treatment by the treatment method of Comparative Example 1;
[0027] Figure 4 Flue gas state after treatment by the treatment method of Comparative Example 2;
[0028] Figure 5 Flue gas state after treatment by the treatment method of Comparative Example 3. Detailed implementation manners
[0029] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0030] Unless otherwise specified, the test methods used in the examples are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial channels.
[0031] Unless otherwise specified, the component raw materials used in each embodiment and comparative example of the present invention are all commercially available raw materials, and the component raw materials and instrument devices used in each parallel experiment are all of the same kind.
[0032] The sulfur transfer agent described in the examples and comparative examples is the enhanced RFS sulfur transfer agent produced by Qilu Branch of Sinopec Catalyst Co., Ltd.; the fluid catalytic cracking unit used includes a reactor, a regenerator, a main blower, a compressor, a fractionating tower, an absorber, a stabilizer, an external heat exchanger, a waste heat boiler, and a desulfurization tower; the process parameters are set as reaction pressure 0.27 MPa, regeneration pressure 0.3 MPa, regeneration temperature 690 °C, catalyst circulation rate 3000 t / h, feed rate 470 t / h, main air volume 8900 Nm 3 / min.
[0033] Example 1
[0034] A method for treating flue gas of a fluid catalytic cracking unit, comprising the following steps:
[0035] (1) Feed the feedstock oil into the reactor of the fluid catalytic cracking unit, and the iron content in the feedstock oil is not higher than 2 μg / g;
[0036] (2) Adjust the reaction temperature at the outlet of the first stage of the riser reactor of the fluid catalytic cracking unit to 527 °C - 535 °C;
[0037] (3) Adjust the bottom alkali injection amount of the desulfurization tower to no higher than 700 kg / h, control the pH value at the bottom of the desulfurization tower to 6.5, adjust the makeup water amount of the desulfurization tower to 60 t / h, and control the suspended solids in the bottom slurry of the desulfurization tower below 2500 mg / L.
[0038] During the operation of the fluid catalytic cracking unit, maintain the addition amount of the sulfur transfer agent at 3% of the total catalyst inventory.
[0039] After the conventional process flow, detect the flue gas conditions. After the adjustment of the treatment method of this embodiment, the SO3 content in the flue gas of the fluid catalytic cracking unit is reduced to 20 mg / m 3 Below, at the same time, along with the reduction of the salt content in the flue gas, the blue smoke trailing of the flue gas is significantly improved, and the flue gas state is as Figure 1 shown, there is almost no flue gas trailing, and the blue color of the flue gas is also improved.
[0040] Example 2
[0041] A treatment method for the flue gas of a fluid catalytic cracking unit includes the following steps:
[0042] (1) Feed the feedstock oil into the reactor of the fluid catalytic cracking unit, and the iron content in the feedstock oil is no higher than 2 μg / g;
[0043] (2) Adjust the reaction temperature at the outlet of the first reactor of the fluid catalytic cracking riser reactor to 527 °C - 535 °C;
[0044] (3) Adjust the bottom alkali injection amount of the desulfurization tower to no higher than 700 kg / h, control the pH value at the bottom of the desulfurization tower to 6.5, increase the makeup water amount of the desulfurization tower to 80 t / h, and control the suspended solids in the bottom slurry of the desulfurization tower below 2500 mg / L.
[0045] During the operation of the fluid catalytic cracking unit, maintain the addition amount of the sulfur transfer agent at 3% of the total catalyst inventory.
[0046] That is, the difference between the treatment method of this embodiment and that of Example 1 is only that the makeup water amount of the desulfurization tower is 80 t / h. The flue gas state of this embodiment is as Figure 2 shown, there is almost no flue gas trailing, but the makeup water amount of 80 t / h will increase the energy consumption of the unit and cause energy waste. It is more preferable to adjust the makeup water amount to 50 t / h - 70 t / h.
[0047] Example 3
[0048] A treatment method for the flue gas of a fluid catalytic cracking unit includes the following steps:
[0049] (1) Feed the feedstock oil into the reactor of the fluid catalytic cracking unit, and the iron content in the feedstock oil is no higher than 2 μg / g;
[0050] (2) Adjust the reaction temperature at the outlet of the first reaction zone of the catalytic cracking riser reactor to 527 °C - 535 °C;
[0051] (3) Adjust the alkali injection amount at the bottom of the desulfurization tower to no higher than 700 kg / h, control the pH value at the bottom of the desulfurization tower to 6.5, adjust the makeup water amount of the desulfurization tower to 50 t / h, and control the suspended solids in the slurry at the bottom of the desulfurization tower below 2500 mg / L.
[0052] During the operation of the catalytic cracking unit, maintain the addition amount of the sulfur transfer agent at 3% of the total catalyst inventory.
[0053] After the conventional process flow, detect the flue gas situation. After adjustment by the treatment method of this example, the SO3 content in the flue gas of the catalytic cracking unit is reduced to 20 mg / m 3 Below, and at the same time, along with the reduction of the salt content in the flue gas, the blue smoke trailing situation of the flue gas is similar to that in Example 1.
[0054] Comparative Example 1
[0055] A method for treating the flue gas of a catalytic cracking unit, comprising the following steps:
[0056] (1) Feed the feedstock oil into the reactor of the catalytic cracking unit, and the iron content in the feedstock oil is 3.5 μg / g;
[0057] (2) The reaction temperature at the outlet of the first reaction zone of the catalytic cracking riser reactor is 520 °C - 525 °C;
[0058] (3) The alkali injection amount at the bottom of the desulfurization tower is 1200 kg / h, the pH value at the bottom of the desulfurization tower is 7, the makeup water amount of the desulfurization tower is 30 t / h, and the suspended solids in the slurry at the bottom of the desulfurization tower is 3400 mg / L.
[0059] During the operation of the catalytic cracking unit, maintain the addition amount of the sulfur transfer agent at 3% of the total catalyst inventory.
[0060] Under this operating condition, the flue gas discharged from the catalytic flue gas desulfurization tower is as Figure 3 shown, with obvious blue smoke plume and trailing. After detection, the SO3 content in the flue gas is above 30 mg / m 3 Above, SO3 is easy to form aerosol with water, salts and catalysts, causing flue gas trailing and forming a blue smoke plume.
[0061] Comparative Example 2
[0062] A method for treating the flue gas of a catalytic cracking unit, comprising the following steps:
[0063] (1) Feed the feedstock oil into the reactor of the catalytic cracking unit, and the iron content in the feedstock oil is not higher than 2 μg / g;
[0064] (2) Adjust the reaction temperature at the outlet of the first reaction zone of the catalytic cracking riser reactor to 520°C - 525°C;
[0065] (3) Adjust the alkali injection amount at the bottom of the desulfurization tower to no higher than 700 kg / h, control the pH value at the bottom of the desulfurization tower to 6.5, adjust the makeup water amount of the desulfurization tower to 60 t / h, and control the suspended solids in the slurry at the bottom of the desulfurization tower below 2500 mg / L.
[0066] During the operation of the catalytic cracking unit, maintain the addition amount of the sulfur transfer agent at 3% of the total catalyst inventory.
[0067] That is, the difference between the treatment method of this comparative example and that of Example 1 is only that the reaction temperature at the outlet of the first reaction zone of the catalytic cracking riser reactor is 520°C - 525°C. However, due to the too low reaction temperature, the desulfurization activity of the sulfur transfer agent will be weakened, the sulfur oxide content in the flue gas will increase, resulting in flue gas tailing. The flue gas state of this comparative example is as Figure 4 shown, and there is a little flue gas tailing.
[0068] Comparative Example 3
[0069] A method for treating flue gas of a catalytic cracking unit, comprising the following steps:
[0070] (1) Feed the feedstock oil into the reactor of the catalytic cracking unit, and the iron content in the feedstock oil is no higher than 2 μg / g;
[0071] (2) Adjust the reaction temperature at the outlet of the first reaction zone of the catalytic cracking riser reactor to 527°C - 535°C;
[0072] (3) Control the alkali injection amount at the bottom of the desulfurization tower at 800 kg / h - 900 kg / h, control the pH value at the bottom of the desulfurization tower to 6.5, adjust the makeup water amount of the desulfurization tower to 60 t / h, and control the suspended solids in the slurry at the bottom of the desulfurization tower below 2500 mg / L.
[0073] During the operation of the catalytic cracking unit, maintain the addition amount of the sulfur transfer agent at 3% of the total catalyst inventory.
[0074] That is, the difference between the treatment method of this comparative example and that of Example 1 is only that the alkali injection amount at the bottom of the desulfurization tower is 800 kg / h - 900 kg / h. However, the sodium salts brought about by the increase in the alkali injection amount have a certain impact on the formation of aerosols, resulting in a slight flue gas tailing situation. The flue gas state of this comparative example is as Figure 5 shown.
[0075] There has long been a situation of blue smoke trailing in the flue gas discharged from the FCC unit of a refinery. To prevent the phenomenon of blue smoke trailing, a sulfur transfer agent is specially added to the FCC unit. The inventory of the sulfur transfer agent accounts for 3% of the total catalyst inventory, but the blue smoke trailing in the flue gas discharged from the FCC unit is still serious. Comparative Example 1 shows the control of relevant parameters of the FCC unit of this refinery, and under this operating condition, the flue gas trailing and blue smoke are relatively serious. However, the present invention effectively treats the flue gas discharged by adjusting process parameters. It can be seen from the examples and comparative examples that in the treatment method of the present invention, by adjusting specific process parameters, the content of SO3 in the flue gas can be effectively reduced, the flue gas trailing and the bluing of the flue gas can be effectively alleviated, and the problem that the addition of a sulfur transfer agent still cannot effectively treat the flue gas is solved.
[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for treating flue gas from a catalytic cracking unit, characterized in that: The following steps are involved: (1) introducing a feedstock oil into a reactor of a catalytic cracking unit, wherein the iron content of the feedstock oil is not higher than 2 μg / g; (2) adjusting the reaction temperature at the outlet of the first reactor of the catalytic cracking riser reactor to 527° C.-535° C.; (3) Adjust the alkali injection rate at the bottom of the desulfurization tower to no more than 700 kg / h, and adjust the water replenishment rate of the desulfurization tower to 50 t / h-80 t / h.
2. The method for treating flue gas from a catalytic cracking unit according to claim 1, characterized in that: In the catalytic cracking unit, the added amount of sulfur transfer agent is 2.8%-3.2% of the total catalyst reserve.
3. The method for treating flue gas from a catalytic cracking unit according to claim 2, characterized in that: The amount of sulfur transfer agent added to the catalytic cracking unit is 3% of the total catalyst storage.
4. The method for treating flue gas from a catalytic cracking unit according to claim 1, characterized in that: In the step (3), the concentration of suspended matter in the desulfurization tower bottom slurry does not exceed 2500 mg / L.
5. The method for treating flue gas from a catalytic cracking unit according to claim 1, characterized in that: In the step (3), the pH value of the desulfurization tower bottom is 6.4-6.
6.
6. The method for treating flue gas from a catalytic cracking unit according to claim 5, characterized in that: In the step (3), the pH value of the desulfurization tower bottom is 6.
5.
7. The method for treating flue gas from a catalytic cracking unit according to claim 5, characterized in that: In the step (3), the water replenishment rate of the desulfurization tower is adjusted to 50 t / h-70 t / h.
8. The method for treating flue gas from a catalytic cracking unit according to claim 5, characterized in that: The catalytic cracking device comprises a reactor, a regenerator, a main fan, an air compressor, a fractionating tower, an absorption tower, a stabilizing tower, an external heat exchanger, a waste heat boiler, and a desulfurization tower.
9. The method for treating flue gas from a catalytic cracking unit according to claim 1, characterized in that: The sulfur transfer agent includes an enhanced RFS sulfur transfer agent.