Dust removal and desulfurization of FCC exhaust gas

• US 10,471,383 B2
• Filed: 06/03/2019
• Issued: 11/12/2019
• Est. Priority Date: 05/25/2017
• Status: Active Grant

• Current Assignee: Jiangnan Environmental Protection Group Inc.
• Original Assignee: Jiangnan Environmental Protection Group Inc.
• Inventors: Luo, Jing, Zhang, Jun, Luo, Yongying, Tan, Qiang, Xu, Xiangjun
• Primary Examiner(s): Vanoy, Timothy C
• Application Number:
  US16/429,418
• Publication Number:
  US 20190282957A1
• Time in Patent Office: 162 Days
• CPC Class Codes: B01D 2252/102 Ammonia
• CPC Class Codes: B01D 2257/302 Sulfur oxides
• CPC Class Codes: B01D 2257/404 Nitrogen oxides other than dinitrogen oxide
• CPC Class Codes: B01D 2258/0283 Flue gases
• CPC Class Codes: B01D 47/06 Spray cleaning
• CPC Class Codes: B01D 53/343 Heat recovery
• CPC Class Codes: B01D 53/50 Sulfur oxides B01D53/60 takes precedence
• CPC Class Codes: B01D 53/501 by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
• CPC Class Codes: B01D 53/502 characterised by a specific solution or suspension
• CPC Class Codes: B01D 53/56 Nitrogen oxides B01D53/60 takes precedence
• CPC Class Codes: B01D 53/75 Multi-step processes
• CPC Class Codes: B01D 53/78 with gas-liquid contact
• CPC Class Codes: B01D 53/8625 Nitrogen oxides
• CPC Class Codes: B01D 53/8628 Processes characterised by a specific catalyst
• CPC Class Codes: B01D 53/96 Regeneration, reactivation or recycling of reactants
• CPC Class Codes: C10G 11/18 according to the "fluidised-bed" technique
• CPC Class Codes: C10G 2300/405 Limiting CO, NOx or SOx emissions
• CPC Class Codes: Y02P 70/10 Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

Abstract

Apparatus and methods for denitrification and desulfurization of and dust removal from an FCC tail gas by ammonia-based process. The apparatus may include a first-stage waste heat recovery system a denitrification system, a dust removal and desulfurization system, a tail gas, exhaust system, and an ammonium sulfate post-processing system. The dust removal and desulfurization system may include as deducting tower and an absorption tower disposed separately. The top and the bottom of the absorption tower may be connected respectively to the tail gas exhaust system and the ammonium sulfate post-processing system. The absorption tower may include sequentially, from bottom to top, an oxidation section, an absorption section, and a fine particulate control section. The methods may be implemented with the apparatus.

Claims

1. A method of using ammonia to treat fluid catalytic cracking tail-gas, the method comprising:

recovering in an indirect-contact heat exchanger heat from a flow that includes the tail-gas so that the temperature of the flow is reduced to 250-350°

C.;

then removing dust from the flow in a first vessel;

then removing sulfur dioxide from the flow in a second vessel, the removing including treating the flow, in the second vessel, with ammonia to produce ammonium sulfate; and

,

after the recovering heat, and before the removing dust;

removing nitrogen oxides from the flow;

then recovering eat from the flow; and

producing from the other heat;

low-pressure steam; and

preheated soft water.

2. The method of claim 1 further comprising, after the removing sulfur dioxide:

first washing the flow by spraying recycled dilute ammonium sulfate solution against the flow at a first location;

again washing the flow by spraying recycled dilute ammonium sulfate solution against the flow at a second location downstream from the first location;

first demisting the flow at a third location downstream from the second location;

again demisting the flow at a fourth location downstream from the third location.

3. The method of claim 2 wherein the first washing provides a ratio of sprayed solution to flow gas in a region between the first and second location that is not less than 1.1 L/m³.

4. The method of claim 3 wherein the first washing produces a spray coverage rate not less than 120%.

5. The method of claim 4 wherein the first washing produces a spray coverage rate not less than 300%.

6. The method of claim 1 wherein the removing dust comprises removing no less than 80% of dust that enters the first vessel in the flow.

7. The method of claim 1 further comprising:

adding heat o the ammonium sulfate with an evaporator to thicken the ammonium sulfate; and

collecting the ammonium sulfate that is produced, by the treating.

8. The method of claim 1 further comprising, at an inlet to the first vessel, receiving the flow when the flow has a temperature in the range 250-350°

C.

9. The method of claim 1 further comprising, at an inlet to the first vessel, receiving the flow when the flow has a temperature in the range 140 to 220°

C.

10. The method of claim 1 further including, prior to the recovering heat, receiving the flow in a state in which the flow has a temperature in the range 580 to 950°

C.

11. The method of claim 1 further including, prior to the recovering heat, receiving the flow in a state in which the flow has a NO_x concentration in the range 100 to 1200 mg/Nm³.

12. The method of claim 1 further including, prior to the recovering heat, receiving the flow in a state in which the flow has an SO₂ concentration in the range 200 to 30,000 mg/Nm³.

13. The method of claim 1 further comprising, after the recovering other heat, and before the removing dust, discharging the flow from a second-stage waste heat recovery system.

14. The method of claim 13 wherein discharged flow is in a state in which the flow has a temperature in the range 140 to 220°

C.

15. The method of claim 1 wherein the steam is in the range 0.3 to 0.8 MPa.

16. A method of using ammonia to treat fluid catalytic cracking tail-gas, the method comprising:

receiving a flow, which includes the tail-gas, in a state in which the flow has a dust level in the range 50 to 10,000 mg/Nm³;

recovering in an indirect-contact heat exchanger heat from the flow so that the temperature of the flow is reduced to 250-350°

C.;

removing dust from the flow in a first vessel, wherein the removing dust comprises removing no less than 80% of dust that enters the first vessel in the flow; and

removing sulfur dioxide from the flow in a second vessel, the removing including treating the flow, in the second vessel, with ammonia to produce ammonium sulfate.

17. The method of claim 16 further comprising, after the removing sulfur dioxide:

first washing the flow by spraying recycled dilute ammonium sulfate solution against the flow at a first location;

again washing the flow by spraying recycled dilute ammonium sulfate solution against the flow at a second location downstream from the first location;

first demisting the flow at a third location downstream from the second location;

again demisting the flow at a fourth location downstream from the third location.

18. The method of claim 17 wherein the first washing provides a ratio of sprayed solution to flow gas in a region between the first and second location that is not less than 1.1 L/m³.

19. The method of claim 18 wherein the first washing produces a spray coverage rate not less than 120%.

20. The method of claim 19 wherein the first washing produces a spray coverage rate not less than 300%.

21. The method of claim 16 further comprising:

adding heat to the ammonium sulfate with an evaporator to thicken the ammonium sulfate; and

collecting the ammonium sulfate that is produced by the treating.

22. The method of claim 16 further comprising, at an inlet to the first vessel, receiving the flow when the flow has a temperature in the range 250-350°

C.

23. The method of claim 16 further comprising, at an inlet to the first vessel, receiving the flow when the flow has a temperature in the range 140 to 220°

C.

24. The method of claim 16 further comprising after the recovering heat, and before the removing dust, removing nitrogen oxides from the flow.

25. The method of claim 24 further comprising, after the removing nitrogen oxides, recovering other heat from the flow.

26. The method of claim 25 further comprising, after the recovering other heat, and before the removing dust:

discharging the flow from a second-stage waste heat recovery system; and

producing from the other heat;

low-pressure steam; and

preheated soft water.

27. The method of claim 26 wherein:

the flow discharged from the second-stage waste heat recovery system is in a state in which the flow has a temperature in the range 140 to 220°

C.; and

the steam is in the range 0.3 to 0.8 MPa.

28. The method of claim 16 further including, prior to the recovering heat, receiving the flow in a state in which the flow has a temperature in the range 580 to 950°

C.

29. The method of claim 16 further including, prior to the recovering heat, receiving the flow in a state in which the flow has a NO_x concentration in the range 100 to 1200 mg/Nm³.

30. The method of claim 16 further including, prior to the recovering heat, receiving the flow in a state in which the flow has an SO₂ concentration in the range 200 to 30,000 mg/Nm³.