Ammonia-adding system for ammonia-based desulfurization device

• US 10,099,170 B1
• Filed: 07/27/2017
• Issued: 10/16/2018
• Est. Priority Date: 06/14/2017
• Status: Active Grant

• Current Assignee: Jiangnan Environmental Protection Group Inc.
• Original Assignee: Jiangnan Environmental Protection Group Inc.
• Inventors: Luo, Jing, Wang, Jinyong
• Primary Examiner(s): Holecek, Cabrena
• Application Number:
  US15/661,186
• Time in Patent Office: 446 Days
• CPC Class Codes: B01D 2252/102 Ammonia
• CPC Class Codes: B01D 2252/103 Water
• CPC Class Codes: B01D 53/1412 Controlling the absorption process
• CPC Class Codes: B01D 53/1481 Removing sulfur dioxide or sulfur trioxide
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: B01D 53/346 Controlling the process
• CPC Class Codes: B01D 53/50 Sulfur oxides B01D53/60 takes precedence
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

Ammonia-adding apparatus and methods for ammonia-based desulfurization use multi-stage control, calculate a theoretical amount of ammonia based on gas amounts provided by an inlet continuous emission monitoring system (CEMS) and an outlet CEMS of the ammonia-based desulfurization device or associated gas amounts, a SO₂ concentration provided by the inlet CEMS, and a predetermined SO₂ concentration of the outlet CEMS. The apparatus and methods calculate a corrected theoretical amount of ammonia using half of the ratio of the actual amount of added ammonia to the actual amount of removed sulfur dioxide as a correction coefficient for the theoretical amount of ammonia; add an ammonia absorbent equivalent to the corrected theoretical amount of ammonia to the ammonia-based desulfurization device through an ammonia metering means and an ammonia control valve, and automatically control the actual ammonia flow rate based on the actual SO₂ concentration and a change trend provided by the outlet CEMS.

Claims

1. A method for adding ammonia to an absorption solution in a flue-gas desulfurization system, the method comprising:

adding ammonia to the absorption solution at a base rate that is proportional to;

a) a target sulfur dioxide removal rate; and

b) a correction coefficient that includes a ratio of cumulative ammonia added to cumulative sulfur dioxide removed; and

,

then, controlling ammonia addition to the absorption solution to a second rate based on a measured output sulfur dioxide characteristic.

2. The method of claim 1 wherein the controlling comprises:

receiving at a distributed control system (“

DCS”

) a sulfur dioxide concentration at an outlet of the desulfurization system; and

changing the correction coefficient in response to the sulfur dioxide concentration.

3. The method of claim 1 wherein the controlling includes dispensing ammonia through an auxiliary valve at a rate that is the base rate minus a rate at which ammonia is dispensed through a main ammonia dispensing valve.

4. The method of claim 3 wherein the controlling further includes changing the rate of dispensing through the auxiliary ammonia dispensing valve based on the measured output sulfur dioxide characteristic.

5. The method of claim 4 wherein:

the measured sulfur dioxide characteristic is a rate of change of sulfur dioxide emission rate at an outlet of the system; and

the changing is based on a predefined relationship between;

the rate of change of sulfur dioxide emission at the outlet; and

a fine adjustment value.

6. The method of claim 5 wherein:

the adding includes;

passing ammonia through the main ammonia dispensing valve; and

controlling the main ammonia dispensing valve with coarse control; and

the controlling includes;

passing ammonia through the auxiliary valve; and

controlling the auxiliary valve with fine control.

7. The method of claim 6 further comprising:

measuring only one of;

a gas flow rate corresponding to an inlet of the system; and

a gas flow rate corresponding to the outlet of the system; and

evaluating the other one as the measured one.

8. The method of claim 7 further comprising:

receiving at a distributed control system (“

DCS”

) a flue gas flow characteristic; and

correcting the other one based on the flow characteristic.

9. The method of claim 8 wherein the flow characteristic is temperature.

10. The method of claim 8 wherein the flow characteristic is pressure.

11. The method of claim 8 wherein the flow characteristic is water content.

12. The method of claim 1 wherein, in the adding, the target sulfur dioxide removal rate is defined as a difference between:

a) a product of;

a gas flow rate corresponding to an inlet of the system and an inlet SO₂ concentration; and

b) a product of;

a gas flow rate corresponding to an outlet of the system and a predetermined SO₂ outlet concentration.

13. The method of claim 12 further comprising:

receiving at a distributed control system (“

DCS”

) a steam generation rate from a boiler that produces the flue gas; and

evaluating the gas flow rate corresponding to the inlet as the steam generation rate.

14. The method of claim 12 further comprising:

receiving at a distributed control system (“

DCS”

) a steam generation rate from a boiler that produces the flue gas; and

evaluating the gas flow rate corresponding to the outlet as the steam generation rate.

15. The method of claim 12 further comprising:

receiving at a distributed control system (“

DCS”

) a boiler combustion airflow intake rate from a boiler that produces the flue gas; and

evaluating the gas flow rate corresponding to the inlet as the boiler combustion airflow intake rate.

16. The method of claim 12 further comprising:

receiving at a distributed control system (“

DCS”

) a boiler combustion airflow intake rate from a boiler that produces the flue gas; and

evaluating the gas flow rate corresponding to the outlet as the boiler combustion airflow intake rate.

17. The method of claim 12 further comprising:

receiving at a distributed control system (“

DCS”

), from a continuous emission monitoring system, a flue gas inlet flow rate corresponding to an inlet of the desulfurization system; and

evaluating the gas flow rate corresponding to the inlet as the flue gas inlet flow rate.

18. The method of claim 17 further comprising measuring the flue gas inlet flow rate.

19. The method of claim 12 further comprising:

receiving at a distributed control system (“

DCS”

), from a continuous emission monitoring system, a flue gas outlet flow rate corresponding to the outlet of the desulfurization system; and

evaluating the gas flow rate corresponding to the outlet as the flue gas outlet flow rate.

20. The method of claim 19 further comprising measuring the flue gas outlet flow rate.

21. The method of claim 1 wherein, in the adding, the correction coefficient is defined as:

one half of;

a ratio of actual molar number of added ammonia to actual molar number of removed sulfur dioxide.

22. The method of claim 21 wherein the adding comprises regulating the base rate to be:

no less than 90% of a product of;

ammonia stoichiometrically required by the target sulfur dioxide removal rate and the correction coefficient; and

no more than 110% of the product.

23. The method of claim 22 wherein:

the targeted sulfur dioxide removal rate depends on a preset outlet sulfur dioxide concentration; and

the ammonia stoichiometrically required is;

24. The method of claim 23 further comprising receiving, at a distributed control system (“

DCS”

), from an inlet continuous electronic monitoring instrument, the gas flow rate corresponding to the inlet of the desulfurization system.

25. The method of claim 23 further comprising receiving, at a distributed control system (“

DCS”

), from an inlet continuous electronic monitoring instrument, the SO₂ concentration at the inlet of the desulfurization system.

26. The method of claim 23 further comprising receiving, at a distributed control system (“

DCS”

), from an outlet continuous electronic monitoring instrument, the gas flow rate corresponding to the outlet of the desulfurization system.